Genetic lifespan regulation has been studied extensively in the nematode roundworm Caenorhabditis elegans (C-elegans) since the 1980s.  Hundreds of research papers have been written on this topic.  And I have generated a number of blog entries on longevity pathways known through nematode-based research, including calorie restriction, FOXO/DAF-16, IGF-1, SIRT1, and mTOR.  And important new studies adding to the knowledge in this area are continuing to appear in the literature.  One showed up only two days ago.  As a result of this collective research, genetic interventions are now known that can extend the lifespans of nematodes by a factor of about seven.  If this were true for people, we could live to the age of 570. 

This blog entry reports on recent findings not discussed in this blog  before related to the ETS and PDEF transcription factors, the AGE protein, TUBBY, WWP-1, and GATA activation factors.  A follow-up blog entry will deal with why nematode life extension has gotten so far during the last 20 years while, during the same period, there has been virtually no progress in creating significant life extension in humans. 

Before I get into the newer findings, I need to review what has been discovered over the years about nematode longevity as related to well-studied pathways.  In the process I will note a few benchmark points relating to life extension in C-elegans.   

AGE-1 

Back in 1988 it was noticed that there is a gene called AGE-1 that, when mutated, extends the life of C-elegans by around 50% and longer in hermaphrodite worms.   As described in the publication A Mutation in the age-1 Gene in Caenorhabditis elegans Lengthens Life and Reduces Hermaphrodite Fertility,  “age-1(hx546) is a recessive mutant allele in Caenorhabditis elegans that results in an increase in mean life span averaging 40% and in maximal life span averaging 60% at 20{deg}; at 25{deg} age-1(hx546) averages a 65% increase in mean life span (25.3 days vs. 15.0 days) and a 110% increase in maximum life span (46.2 days vs. 22.0 days for wild-type hermaphrodites).” 

FOXO/DAF-16/IGF-1 pathway, insulin-like signaling  

A subsequent benchmark for radical life extension in C-elegans was telegraphed in a 1993 publication A C. elegans mutant that lives twice as long as wild type.  This time the FOXO/DAF-16/IGF-1 pathway was involved.  The FOXO transcription-factor protein DAF-16 is an important regulator of longevity that I have discussed in a number of previous blog postings and specifically in the April 2010 post Another piece of DAF-16 research.  According to the 1993 publication, “We have found that mutations in the gene daf-2 can cause fertile, active, adult Caenorhabditis elegans hermaphrodites to live more than twice as long as wild type. This lifespan extension, the largest yet reported in any organism, requires the activity of a second gene, daf-16. Both genes also regulate formation of the dauer larva, a developmentally arrested larval form that is induced by crowding and starvation and is very long-lived. Our findings raise the possibility that the longevity of the dauer is not simply a consequence of its arrested growth, but instead results from a regulated lifespan extension mechanism that can be uncoupled from other aspects of dauer formation.  Daf-2 and daf-16 provide entry points into understanding how lifespan can be extended.” 

It did not take researchers very long to figure out how to go from doubling nematode lifespans to nearly quadrupling it based on Daf mutations and associated modifications in insulin-like signaling.  The 1995 publication Genes that regulate both development and longevity in Caenorhabditis elegans reported: “The increased life spans are suppressed completely by a daf-16 mutation and partially in a daf-2; daf-18 double mutant. A genetic pathway for determination of adult life span is presented based on the same strains and growth conditions used to characterize Daf phenotypes. Both dauer larva formation and adult life span are affected in daf-2; daf-12 double mutants in an allele-specific manner. Mutations in daf-12 do not extend adult life span, but certain combinations of daf-2 and daf-12 mutant alleles nearly quadruple it. This synergistic effect, which does not equivalently extend the fertile period, is the largest genetic extension of life span yet observed in a metazoan.” 

As further outlined in the 2006 publication Worming pathways to and from DAF-16/FOXO “In Caenorhabditis elegans, the insulin/IGF-1 signaling pathway controls many biological processes such as life span, fat storage, dauer diapause, reproduction and stress response.  This pathway is comprised of many genes including the insulin/IGF-1 receptor (DAF-2) that signals through a conserved PI 3-kinase/AKT pathway and ultimately down-regulates DAF-16, a forkhead transcription factor (FOXO).”   See the publications An insulin-like signaling pathway affects both longevity and reproduction in Caenorhabditis elegans (1998),  Regulation of C. elegans life-span by insulinlike signaling in the nervous system(2000), and Insulin-like signaling, metabolism, stress resistance and aging in Caenorhabditis elegans(2001).   

MicroRNAs and EGF signaling 

The list of microRNAs and pathways implicated in C-elegans lifespans appears to be ever increasing(ref)(ref).  The August 2010 paper Novel EGF pathway regulators modulate C. elegans healthspan and lifespan via EGF receptor, PLC-gamma, and IP3R activation  reports “Further analysis revealed a potent role of EGF signaling, acting via downstream phospholipase C-gammaplc-3 and inositol-3-phosphate receptor itr-1, to promote healthy aging associated with low lipofuscin levels, enhanced physical performance, and extended lifespan. This study identifies HPA-1 and HPA-2 as novel negative regulators of EGF signaling and constitutes the first report of EGF signaling as a major pathway for healthy aging. Our data raise the possibility that EGF family members should be investigated for similar activities in higher organisms.” 

TUBBY 

The TUBBY gene tub-1 is another that seems to play a critical role in nematode aging as described in the 2005 paper C. elegans tubby regulates life span and fat storage by two independent mechanisms.  “Here, we show that mutation in tub-1 also leads to life span extension dependent on daf-16/FOXO. Interestingly, function of tub-1 in fat storage is independent of daf-16. –. Taken together, we define a role for tub-1 in regulation of life span and show that tub-1 regulates life span and fat storage by two independent mechanisms.”  

GATA 

The 2008 publication An elt-3/elt-5/elt-6 GATA Transcription Circuit Guides Aging in C. elegans identifies another piece of transcriptional circuitry and begins to clarify some of the major issues involved in nematode aging. “To define the C. elegans aging process at the molecular level, we used DNA microarray experiments to identify a set of 1294 age-regulated genes and found that the GATA transcription factors ELT-3, ELT-5, and ELT-6 are responsible for age regulation of a large fraction of these genes. Expression of elt-5 and elt-6 increases during normal aging, and both of these GATA factors repress expression of elt-3, which shows a corresponding decrease in expression in old worms. elt-3 regulates a large number of downstream genes that change expression in old age, including ugt-9, col-144, and sod-3. elt-5(RNAi) and elt-6(RNAi) worms have extended longevity, indicating that elt-3, elt-5, and elt-6 play an important functional role in the aging process. These results identify a transcriptional circuit that guides the rapid aging process in C. elegans and indicate that this circuit is driven by drift of developmental pathways rather than accumulation of damage.”  

WWP-1 

There appears to be no end to discovery of critical new genes in nematodes that play a role in aging.  The 2010 publication WWP-1 is a novel modulator of the DAF-2 insulin-like signaling network involved in pore-forming toxin cellular defenses in Caenorhabditis elegans relates “Here we reveal that reduction of the DAF-2 insulin-like pathway confers the resistance of Caenorhabditis elegans to cytolitic crystal (Cry) PFTs produced by Bacillus thuringiensis. In contrast to the canonical DAF-2 insulin-like signaling pathway previously defined for aging and pathogenesis, the PFT response pathway diverges at 3-phosphoinositide-dependent kinase 1 (PDK-1) and appears to feed into a novel insulin-like pathway signal arm defined by the WW domain Protein 1 (WWP-1). In addition, we also find that WWP-1 not only plays an important role in the intrinsic cellular defense (INCED) against PFTs but also is involved in innate immunity against pathogenic bacteria Pseudomonas aeruginosa and in lifespan regulation. Taken together, our data suggest that WWP-1 and DAF-16 function in parallel within the fundamental DAF-2 insulin/IGF-1 signaling network to regulate fundamental cellular responses in C. elegans.”  Here we see an example of an important point:  the same pathway that confers longevity confers bacterial resistance and health. 

ETS/PDEF 

A very new publication, Sept 23 2010, ETS-4 is a Transcriptional Regulator of Life Span in Caenorhabditis elegans, points to yet another important set of transcription factors affecting nematode longevity. “Animal life span is regulated in response to developmental and environmental inputs through coordinate changes in gene expression. Thus, longevity determinants include DNA-binding proteins that regulate gene expression by controlling transcription. Here, we explored the physiological role of the transcriptional regulator, ETS-4, in the roundworm Caenorhabditis elegans. Our data showed that worms that lack ETS-4 lived significantly longer, revealing ETS-4s role in the transcription network that regulates life span. We identified 70 genes whose expression was modulated by ETS-4 that function in lipid transport, lipid metabolism and innate immunity. Some of the ETS-4-regulated genes were also controlled by two other regulators of aging, the FOXO and GATA factors. We concluded that a common set of transcriptional targets orchestrate the network of physiological factors that affect aging. ETS-4 is closely related to the human ETS protein SPDEF that exhibits aberrant expression in breast and prostate tumors. Because the genetic pathways that regulate aging are well conserved in other organisms, including humans, our findings could lead to a better understanding of SPDEF function and longevity regulation in mammals.”

The human ortholog of ETS-4 is SPDEF, quite possibly also a longevity determinant in us humans.  Interestingly, SPDEF may play an important role in preventing/treating cancers.  See PDEF is a negative regulator of colon cancer cell growth and migration, Prostate-derived Ets transcription factor (PDEF) downregulates survivin expression and inhibits breast cancer cell growth in vitro and xenograft tumor formation in vivo, Prostate-derived Ets transcription factor as a favorable prognostic marker in ovarian cancer patients and the 2010 paper PDEF and PDEF-induced proteins as candidate tumor antigens for T cell and antibody-mediated immunotherapy of breast cancer.   

I cannot begin here to cover the hundreds of additional papers on factors affecting C-elegans longevity.  Some researchers have been responsible for multiple discoveries related to nematode longevity over the years.  In particular, Cynthia Kenyon of the University of California, a lead author of the 1993 paper describing a doubling of nematode lifespans, has authored or co-authored some 80 relevant papers including these most-recent ones:

·         The somatic reproductive tissues of c. elegans promote longevity through steroid hormone signaling.

·         A pathway that links reproductive status to lifespan in Caenorhabditis elegans.

·         Widespread protein aggregation as an inherent part of aging in C. elegans. 

·         Insulin/IGF-1 signaling mutants reprogram ER stress response regulators to promote longevity.

·         Glucose shortens the life span of C. elegans by downregulating DAF-16/FOXO activity and aquaporin gene expression.

·         A transcription elongation factor that links signals from the reproductive system to lifespan extension in Caenorhabditis elegans.

·         Stimulation of movement in a quiescent, hibernation-like form of Caenorhabditis elegans by dopamine signaling

·         Regulation of the longevity response to temperature by thermosensory neurons in Caenorhabditis elegans.

·         A regulated response to impaired respiration slows behavioral rates and increases lifespan in Caenorhabditis elegans.

·         A role for autophagy in the extension of lifespan by dietary restriction in C. elegans.

·         Distinct activities of the germline and somatic reproductive tissues in the regulation of Caenorhabditis elegans’ longevity.

·         Tissue entrainment by feedback regulation of insulin gene expression in the endoderm of Caenorhabditis elegans.

·         DAF-16/FOXO targets genes that regulate tumor growth in Caenorhabditis elegans.

·         On why decreasing protein synthesis can increase lifespan.

·         Lifespan extension by conditions that inhibit translation in Caenorhabditis elegans.

·         A steroid hormone that extends the lifespan of Caenorhabditis elegans.

·         My adventures with genes from the fountain of youth.

·         Mutations that increase the life span of C. elegans inhibit tumor growth.

·         Worming pathways to and from DAF-16/FOXO.

·         Enrichment of regulatory motifs upstream of predicted DAF-16 targets. 

A list of many additional nematode-related publications coming from the Kenyon lab can be found here.  And oh yes, some of the nematodes living in Dr. Kenyon’s lab are now capable of living seven times as long as their normal wild-type counterparts.   From the Kenyon lab website  – Quicktime movie of two active 144 day old worms. [normal life span 21 days]. 

Some lessons from the nematode

·        Very significant lifespan extension is possible in genetically complex organisms that share many common gene activation pathways with humans.

·        Well over a thousand genes affect aging or are age-regulated in nematodes and probably a larger number in humans.

·        Nematode studies strongly supports the hypothesis that aging is an extremely complex process involving the interactions of multiple pathways  and an immense number of genes and is not the result of accumulated damage, oxidative damage or other damage.  [My own theory is that the two smoking guns implicated in aging are accumulated epigenetic changes (e.g. in DNA methylation and histone acetylation) and exhaustion of the stem cell supply chain.  See my presentation Towards a Systems Theory of Aging offered at the 2009 American Aging Society meeting.]

·        C-elegans provides an excellent working model for examining how a limited number of transcriptional regulators can mediate to influence downstream aging  lifespan effector genes.

·        After twenty years of research, the job of studying longevity in nematodes is hardly complete.  Important new transcription factors, pathways and genes are still being identified.  In this blog entry I have been able to cover only highly-selected topics in the nematode research domain.

·        Metabolic regulation is essential for life extension.  The 2010 publication Regulation of metabolism in Caenorhabditis elegans longevity, reports “The nematode Caenorhabditis elegans is a favorite model for the study of aging. A wealth of genetic and genomic studies show that metabolic regulation is a hallmark of life-span modulation. A recent study in BMC Biology identifying metabolic signatures for longevity suggests that amino-acid pools may be important in longevity.”

·        There appear to be certain proteins that both extend longevity in nematodes and combat cancers in humans, ETS-3 and its human homolog SPDEF being a good example.  In general, factors that increase longevity do so by increasing healthspan.

·        In terms of regulation of aging-related genes, some genes act upstream of others, and downstream genes can be regulated by several different upstream pathways.  For example, the FOXO, GATA and Ets-4 transcription factors all regulate common genes.  In fact, it appears that Ets-4 functions in parallel to the insulin/IGF-1 receptor, daf-2 and akt-1/2 kinases. Many pathways impact on many genes to slow down/accelerate aging.  This explains why a similar pattern of age postponement (or acceleration) can be generated by quite different upstream interventions such as calorie restriction, feeding rapamycin, and knocking out of various gene combinations.

There is incredibly good life extension news, if you are happen to be a nematode. The following blog entry will examine why we have not been able to make similar progress with human life extension.

The October 2009 blog entry Klotho anti-aging gene in the news describes how the Klotho protein exhibits anti-aging effects in mice when over-expressed and accelerates aging when under-expressed, Klotho’s role with respect to the vitamin D receptor (VDR),  and how defects in Klotho expression is correlated with a number of disease processes.  I said “As to how Klotho may impact on longevity: a) I have already mentioned its actions in averting tissue glycation, b) the IGF-1 pathway (affected by Klotho) has long been known to be associated with longevity and is that affected by calorie restriction, and c) Klotho promotes the body’s antioxidant defenses.”  Research published in the last year reveals an important new link of Klotho to longevity involving phosphate clearance.  I discuss that link and possible implications for consummate drinkers of cola drinks in this blog entry.  Also, increasing evidence exists that Klotho functions as tumor suppressor, and I also discuss that topic. 

Defects in Klotho expression can lead to underexpression of FGF23 and accumulation of phosphates 

The 2010 paper Klotho introduces the main topic of this blog entry: “The klotho gene was identified as an “aging-suppressor” gene in mice that accelerates aging when disrupted and extends life span when overexpressed. It encodes a single-pass transmembrane protein and is expressed primarily in renal tubules. The extracellular domain of Klotho protein is secreted into blood and urine by ectodomain shedding. The two forms of Klotho protein, membrane Klotho and secreted Klotho, exert distinct functions. Membrane Klotho forms a complex with fibroblast growth factor (FGF) receptors and functions as an obligate co-receptor for FGF23, a bone-derived hormone that induces phosphate excretion into urine. Mice lacking Klotho or FGF23 not only exhibit phosphate retention but also display a premature-aging syndrome, revealing an unexpected link between phosphate metabolism and aging.” 

The link between Klotho, phosphate retention and aging was telegraphed in the October 2009 paper Klotho and aging.  “The klotho gene encodes a single-pass transmembrane protein that forms a complex with multiple fibroblast growth factor (FGF) receptors and functions as an obligatory co-receptor for FGF23, a bone-derived hormone that induces negative phosphate balance. Defects in either Klotho or Fgf23 gene expression cause not only phosphate retention but also a premature-aging syndrome in mice, unveiling a potential link between phosphate metabolism and aging.” 

The 2010 review Klotho as a regulator of fibroblast growth factor signaling and phosphate/calcium metabolism also describes the situation.  “PURPOSE OF REVIEW: This review summarizes the most recent findings on Klotho in the regulation of fibroblast growth factor-23 (FGF23) signaling and phosphate/calcium homeostasis.  — RECENT FINDINGS: The klotho gene encodes a single-pass transmembrane protein and functions as an aging-suppressor gene, which extends life span when overexpressed and accelerates the development of aging-like phenotypes when disrupted in mice. FGF23 is a hormone that suppresses phosphate reabsorption in renal proximal tubules. Recent studies have shown that Klotho mice and Fgf23 mice exhibit identical phenotypes including hyperphosphatemia and hypercalcemia in addition to the aging-like syndrome. This may be explained by the fact that Klotho binds to multiple FGF receptors and increases their affinity to FGF23.”

The mechanism of operation of Klotho with respect to FGF23 is further detailed in the 2010 publication Regulation of ion channels by secreted Klotho: mechanisms and implications.  “Klotho is an anti-aging protein predominantly expressed in the kidney, parathyroid glands, and choroid plexus of the brain. It is a single-pass transmembrane protein with a large extracellular domain. The extracellular domain of Klotho is cleaved and released into extracellular fluid, including blood, urine, and cerebrospinal fluid. The membrane-bound full-length Klotho and secreted extracellular domain of Klotho have distinct functions. Membrane Klotho interacts with fibroblast growth factor (FGF) receptors to form high-affinity receptors for FGF23. Secreted Klotho functions as a humoral factor that regulates several ion channels and transporters, and other processes, including insulin and insulin-like growth factor signaling.”

FGF23 and its relationship to Klotho are linked to a number of bone and joint diseases, such as described in the 2010 publication [Bone and joint diseases in children. Phosphaturic hormone, FGF23, and bone metabolism].   “Fibroblast growth factor 23 (FGF23) belongs to FGF19 subfamily, whose members function like endocrine factors, and has a phosphaturic effect, leading to hypophosphatemia associated with rickets or osteomalacia when its concentration in blood is elevated. FGF23 is involved in the pathogenesis in many forms of hypophosphatemia including the autosomal dominant and recessive types, the X-linked type and the tumor-induced type. Alpha klotho, originally discovered as an anti-aging factor, along with the FGF receptor type 1 makes a specific receptor for FGF23.”

 Accumulated phosphates can accelerate aging

The link between accumulated phosphates and aging is detailed in the 2010 publication Dietary and genetic evidence for phosphate toxicity accelerating mammalian aging. “Identifying factors that accelerate the aging process can provide important therapeutic targets for slowing down this process. Misregulation of phosphate homeostasis has been noted in various skeletal, cardiac, and renal diseases, but the exact role of phosphate toxicity in mammalian aging is not clearly defined. Phosphate is widely distributed in the body and is involved in cell signaling, energy metabolism, nucleic acid synthesis, and the maintenance of acid-base balance by urinary buffering. In this study, we used an in vivo genetic approach to determine the role of phosphate toxicity in mammalian aging. Klotho-knockout mice (klotho(-/-)) have a short life span and show numerous physical, biochemical, and morphological features consistent with premature aging, including kyphosis, uncoordinated movement, hypogonadism, infertility, severe skeletal muscle wasting, emphysema, and osteopenia, as well as generalized atrophy of the skin, intestine, thymus, and spleen. Molecular and biochemical analyses suggest that increased renal activity of sodium-phosphate cotransporters (NaPi2a) leads to severe hyperphosphatemia in klotho(-/-) mice. Genetically reducing serum phosphate levels in klotho(-/-) mice by generating a NaPi2a and klotho double-knockout (NaPi2a(-/-)/klotho(-/-)) strain resulted in amelioration of premature aging-like features. The NaPi2a(-/-)/klotho(-/-) double-knockout mice regained reproductive ability, recovered their body weight, reduced their organ atrophy, and suppressed ectopic calcifications, with the resulting effect being prolonged survival. More important, when hyperphosphatemia was induced in NaPi2a(-/-)/klotho(-/-) mice by feeding with a high-phosphate diet, premature aging-like features reappeared, clearly suggesting that phosphate toxicity is the main cause of premature aging in klotho(-/-) mice. The results of our dietary and genetic manipulation studies provide in vivo evidence for phosphate toxicity accelerating the aging process and suggest a novel role for phosphate in mammalian aging.”

Other effects of Klotho 

Of course Klotho does other things beyond binding to FGF23 as outlined in my earlier blog entry and in the 2008 paper Klotho as a regulator of oxidative stress and senescence.  “The klotho gene encodes a single-pass transmembrane protein that binds to multiple fibroblast growth factor (FGF) receptors and functions as a co-receptor for FGF23, a bone-derived hormone that suppresses phosphate reabsorption and vitamin D biosynthesis in the kidney. In addition, the extracellular domain of Klotho protein is shed and secreted, potentially functioning as a humoral factor. The secreted Klotho protein can regulate multiple growth factor signaling pathways, including insulin/IGF-1 and Wnt, and the activity of multiple ion channels. Klotho protein also protects cells and tissues from oxidative stress, yet the precise mechanism underlying these activities remains to be determined. Thus, understanding of Klotho protein function is expected to provide new insights into the molecular basis for aging, phosphate/vitamin D metabolism, cancer and stem cell biology.” 

Klotho and cancer processes

The 2010 publication Klotho inhibits growth and promotes apoptosis in human lung cancer cell line is one of several dealing with the anti-cancer properties of Klotho.  “Recently, published studies suggest that klotho can also serve as a potential tumor suppressor. The aim of this study is to investigate the effects and possible mechanisms of action of klotho in human lung cancer cell line A549. — CONCLUSIONS: Klotho can inhibit proliferation and increase apoptosis of A549 cells, this may be partly due to the inhibition of IGF-1/insulin pathways and involving regulating the expression of the apoptosis-related g nes bax/bcl-2. Thus, klotho can serve as a potential tumor suppressor in A549 cells.” 

The 2010 publication The anti-aging gene KLOTHO is a novel target for epigenetic silencing in human cervical carcinoma suggests that turning the Klotho gene off by means of epigenetic silencing may be an important survival strategy used by certain cancers.  “Recently, KLOTHO was reported to function as a secreted Wnt antagonist and as a tumor suppressor. Epigenetic gene silencing of secreted Wnt antagonists is considered a common event in a wide range of human malignancies. Abnormal activation of the canonical Wnt pathway due to epigenetic deregulation of Wnt antagonists is thought to play a crucial role in cervical tumorigenesis. In this study, we examined epigenetic silencing of KLOTHO in human cervical carcinoma. — Methylation-specific PCR and bisulfite genomic sequencing analysis of the promoter region of KLOTHO revealed CpG hypermethylation in non-KLOTHO-expressing cervical cancer cell lines and in 41% (9/22) of invasive carcinoma cases. Histone deacetylation was also found to be the major epigenetic silencing mechanism for KLOTHO in the SiHa cell line. — CONCLUSIONS: Epigenetic silencing of KLOTHO may occur during the late phase of cervical tumorigenesis, and consequent functional loss of KLOTHO as the secreted Wnt antagonist may contribute to aberrant activation of the canonical Wnt pathway in cervical carcinoma.”

Statins promote expression of Klotho

Finally, I hearken back to a 2004 publication which suggests that use of statins promotes Klotho expression, HMG-CoA reductase inhibitors up-regulate anti-aging klotho mRNA via RhoA inactivation in IMCD3 cells.  The conclusion is “Statins inactivate the RhoA pathway, resulting in overexpression of klotho mRNA, which may contribute to the novel pleiotropic effects of statins towards vascular protection.” Other substances may also activate the expression of Klotho, but discovering them will take more research on my part.

Soft drinks, phosphoric acid and aging

Sixteen years ago, I would head down the corridor in my software company twice or three times a day to the vending machine for a diet coke.  I loved the stuff and I still like its taste and short-term impact on me.  And I love diet Dr. Pepper for the same reason too.  Back then, little did I think I might be pursuing a pro-aging strategy.  These and some other soft drinks are strong sources of phosphoric acid, a species of phosphates.  If the above-described research is correct, and if I did not have strong Klotho expression to activate FGF23 to clear the phosphates out, accelerated aging could well have been a consequence of my soft drink addiction. 

There has been serious questions posed as to whether consistent consumption of diet colas leads to osteoporosis(ref). “New research indicates that there may be more to the soda and osteoporosis connection than simply replacing the good stuff with the useless stuff. — Researchers at Tufts University, studying several thousand men and women, found that women who regularly drank cola-based sodas — three or more a day — had almost 4% lower bone mineral density in the hip, even though researchers controlled for calcium and vitamin D intake. But women who drank non-cola soft drinks, like Sprite or Mountain Dew, didn’t appear to have lower bone density. Soda and Osteoporosis: Possible Culprits. — Phosphoric acid, a major component in most sodas, may be to blame, according to lead study author Katherine Tucker, PhD. — Phosphorus itself is an important bone mineral. But if you’re getting a disproportionate amount of phosphorus compared to the amount of calcium you’re getting, that could lead to bone loss.” 

Now to that concern I add another based on the research cited here.  Is loading up on phosphoric acid due to frequent drinking of cola sodas robbing of longevity?  And If there is a life-shortening effect due to chronic ingestion of drinks containing phosphoric acid, does it apply to everybody or only to people with defective Klotho or FGF23 expression?

Smurf2 is a fascinating gene and enzyme that plays a number of key roles throughout life in people, ranging from roles in embryonic development and stem cell differentiation to ones relating to cell senescence and accelerated (or delayed) aging.  It is also implicated in cancers and osteoarthritis.   I strive here to summarize some of the key properties of this substance and point out why it is particularly interesting from the viewpoint of aging. I was made aware of the importance of this substances by a presentation by Hong Zhang at the recent Ellison Medical Foundation’s Colloquium on the Biology of Aging.  Zhang is a researcher at the University of Massachusetts Medical School

What is Smurf2?

The biochemical activities and genetic activation pathway related to Smurf2 are very complex.  In super-simplified terms, Smurf2 has a lot to do with key processes that go in cells including cell reproduction, apoptosis and differentiation.    Smurf2 stands for SMAD specific E3 ubiquitin protein ligase 2, an enzyme that in humans is encoded by the SMURF2 gene.  One of the first documents discussing Smurf2, published in 2000, was Smurf2 is a ubiquitin E3 ligase mediating proteasome-dependent degradation of Smad2 in transforming growth factor-beta signaling. Decoded, this means that Smurf2 links up with ubiquitin (a small regulatory protein found in almost all cells with nuclei that directs proteins for breakdown and recycling) for breakdown of Smad2  in the proteasomes (large protein complexes in cells that break down and recycle unwanted proteins) as part of transforming growth factor-beta  (a protein that controls proliferation, cellular differentiation, and other functions in most cells) signaling.  “SMAD2 mediates the signal of the transforming growth factor (TGF)-beta, and thus regulates multiple cellular processes, such as cell proliferation, apoptosis, and differentiation(ref)” Whew! 

The 2001 document Regulation of Smad degradation and activity by Smurf2, an E3 ubiquitin ligase expands further on the early understanding of the actions of Smurf2.  “Smad proteins are key intracellular signaling effectors for the transforming growth factor-beta superfamily of peptide growth factors. Following receptor-induced activation, Smads move into the nucleus to activate transcription of a select set of target genes. The activity of Smad proteins must be tightly regulated to exert the biological effects of different ligands in a timely manner. Here, we report the identification of Smurf2, a new member of the Hect family of E3 ubiquitin ligases.  Smurf2 selectively interacts with receptor-regulated Smads and preferentially targets Smad1 for ubiquitination and proteasome-mediated degradation.”       

Telomere length attrition, Smurf2 and cell senescence

There are a number of publications further detailing actions of Smurf2, but I am focusing this discussion on longevity-related issues so I move now to a December 2004 publication co-authored by Zhang Smurf2 up-regulation activates telomere-dependent senescence.  “Progressive telomere shortening activates replicative senescence, which prevents somatic cells from being propagated indefinitely in culture. The limitation of proliferative capacity imposed by replicative senescence is thought to contribute to both organismal aging and the prevention of tumor development. Here we report that up-regulation of Smurf2, an E3 ubiquitin ligase previously implicated in TGF-β signaling, is a specific consequence of telomere attrition in human fibroblasts and that such up-regulation is sufficient to produce the senescence phenotype.”  In other words, telomere attrition leads to upregulation of Smurf2 which in turn drives the cell into senescence.  Smurf2 upregulation is an intermediary between telomere attrition and cell senescence.

Telomere attrition can be due to DNA damage, oxidative stress, oncogenic activation or aging.  Continuing to quote from the same 2004 article, “We show that the senescence-inducing actions of Smurf2 occur in the absence of detectable DNA damage or stress response, that Smurf2’s effects require a novel function distinct from its E3 activity, that Smurf2 recruits the Rb and p53 pathways for senescence induction, and that while p21 is elevated by Smurf2, Smurf2-mediated senescence is independent of p21. Smurf2 is the first gene found to be both up-regulated by telomere attrition and sufficient to induce senescence.”   

Expression of Smurf2 in fibroblasts appears to depend on telomere attrition, not on how many times a cell reproduces.  “Importantly, fibroblasts immortalized by adventitious expression of hTERT and analyzed after multiple passages in culture showed no increase in Smurf2 expression (Fig. 1C), indicating that up-regulation of Smurf2 is not the result of extended cell passage per se but, rather, is a consequence of telomere shortening.”  And exposing immortalized fibroblasts with long and stable telomeres to Smurf2 drives them directly into a senescent state.  “Smurf2 expression produces senescence in hTERT-immortalized cells —  Expression of hTERT in primary cultures of human fibroblasts precludes the progressive shortening of telomeres that activates events leading to senescence, resulting in the immortalization of cell populations (Bodnar et al. 1998; Vaziri and Benchimol 1998; Dickson et al. 2000). In strong support of the conclusion that Smurf2 expression is sufficient to produce the senescence phenotype, we found that adventitious expression of Smurf2 to the level normally observed during replicative senescence induced by telomere attrition (cf. Figs. ​Figs.5A5A and ​and1B) reversed hTERT-mediated immortalization of human fibroblasts. — Collectively, our findings support the argument that Smurf2 up-regulation mediates one of the multiple cellular pathways that have been proposed to lead to senescence (Pereira-Smith and Smith 1988).” 

These findings are clearly relevant to the 12^th theory of aging laid out in my treatise Telomere Shortening and Damage.   Long telomeres and even extraordinary expression of telomerase cannot protect a cell from senescence if Smurf2 is also strongly present in that cell. 

Zhang has been concerned with the overall process of cell senescence as well as with the specific role of Smurf2 and has generated a number of publications  on the topic including a comprehensive 2007review paper Molecular signaling and genetic pathways of senescence: Its role in tumorigenesis and aging.  His discussions in that paper of senescence and aging, senescence as a tumor suppression mechanism, and senescence and tissue microenvironment are worth reading though there has been much relevant subsequent research.   

The 2008 paper Suppression of human tumor cell proliferation by Smurf2-induced senescence, again co-authored by Zhang, continues to tell the story, this time extending the research from fibroblasts cells to a wide variety of cell types including cancer cells.    “Here we report that Smurf2 up-regulation induced senescence in a wide variety of human cell types, including highly neoplastic cell lines. Consistent with our previous findings, the ability of Smurf2 to arrest cell proliferation did not require its ubiquitin ligase activity. Furthermore, expression of the cyclin-dependent kinase inhibitor p21 was increased in tumor cells undergoing Smurf2-induced senescence, and such increase occurred independently of the transactivation function of p53. Our results, which reveal a previously unsuspected tumor suppression function for Smurf2-induced senescence, suggest that modulation of Smurf2 action may be a useful strategy for inhibition of cancer cell growth.”   

From an evolutionary viewpoint, it appears that one role of Smurf2 is protection against cancers.  Cells experiencing telomere attrition are driven into senescence by Smurf2 rather than being exposed to the possibility of oncogenesis due to DNA damage that could be incurred in further cycles of replication.  The upside of cell senescence is limiting the accumulation of additional DNA mutations and limiting the population of cells at risk for neoplastic transformation.  The downside is limiting the renewal capacity of stem and progenitor cells and negative changes in gene expression and cell secretions.  Senescent cells make bad neighbors and contribute to organismal aging.  Quoting from my treatise  “It appears that cellular senescence initiates a self-amplifying cycle between mitochondrial and telomeric DNA damage.  The telomere shortening theory of aging suggests that when a substantial number of cells in an organ approach the Hayflick limit and cell senescence, integrity of that organ can no longer be assured and that virtually all of the conditions and diseases of old age are thus traceable to cell senescence.” 

At his presentation at the Ellison colloquium, Zhang described another round of Smurf2 research, this time based on breeding a new strain of Smurf2-knockout mice.  In culture, the cells in these mice generally survived longer with more population doublings,  and were more prone to turning cancerous when compared with similar cells from  normal; “wild type” mice. The Smurf2 knockout mice showed a significant increase in B cell proliferation.  Conclusions of the slide presentation were “1.  Smurf2-deficient MEFs exhibit delayed senescence and enhanced potential to immortalize in culture, 2.  Smurf2 deficient mice develop tumors including lymphomas, soft tissue sarcomas, small intestine andocarcinomas and hepatocellular carcinomas, suggesting that Smurf2 is a tumor suppressor, and 3. Smurf2 deficient mice have increased bone marrow and LT-HSC populations, suggesting a beneficial effect of Smurf2 deficiency during aging.”   

So, we have another example of a familiar story, in aging Smurf2 is strongly protective against cancers but at a cost of limiting stem and progenitor cell differentiation and the increased life span that would result from this.  Smurf2 is similar to P16/Ink4a in this regard.  As I said in my treatise, “Unfortunately there is a paradox in that the same mechanisms that promote neurogenesis, like expression of Bcl-2 and NF-kappaB, can also promote carcinogenesis(ref)., The Ink4a proteins which are increasingly active with age suppress those mechanisms leading to increased protection against cancers with age, but at the cost of decreased neurogenesis and decreased proliferation of other somatic stem cell types. Sorting out the differences between the biomolecular programs that promote stem cell expression and the programs that promote cancers, assuming there are some differences, is a major challenge that must be overcome if substantial life extension is to be made possible.”  Smurf2 is another Dr Jekyll and Mr. Hyde protein. 

Smurf2 and cancers 

A number of past and relatively recent papers point out ugly things Smurf2 does in cancers, like the 2002 publication High-level expression of the Smad ubiquitin ligase Smurf2 correlates with poor prognosis in patients with esophageal squamous cell carcinoma.  The 2009 publication Smad ubiquitination regulatory factor 2 promotes metastasis of breast cancer cells by enhancing migration and invasiveness states “Overexpression of Smurf2 promotes metastasis in a nude mouse model and increases migration and invasion of breast cancer cells. Moreover, expression of Smurf2CG, an E3 ligase-defective mutant of Smurf2, suppresses the above metastatic behaviors. These results establish an important role for Smurf2 in breast cancer progression and indicate that Smurf2 is a novel regulator of breast cancer cell migration and invasion.” 

Not all actions of Smurf2 are negative with respect to cancers, however.  The 2008 publication Smurf2 induces ubiquitin-dependent degradation of Smurf1 to prevent migration of breast cancer cells states “In the present study, we show the post-translational regulation of Smurf1 by Smurf2 and the functional differences between Smurf1 and Smurf2 in the progression of breast cancer cells. Smurf2 interacted with Smurf1 and induced its ubiquitination and degradation, whereas Smurf1 failed to induce degradation of Smurf2. Knockdown of Smurf2 in human breast cancer MDA-MB-231 cells resulted in increases in the levels of Smurf1 protein, and enhancement of cell migration in vitro and bone metastasis in vivo. — These results indicate that two related E3 ubiquitin ligases, Smurf1 and Smurf2, act in the same direction in TGF-beta family signaling but play opposite roles in cell migration.” 

Smurf2 and Osteoarthritis 

Smurf2 also plays a negative role in certain other age-related disease processes, specifically, osteoarthritis.  The 2009 publication Smurf2 induces degradation of GSK-3beta and upregulates beta-catenin in chondrocytes: a potential mechanism for Smurf2-induced degeneration of articular cartilage has to say: “We have previously demonstrated that Smurf2 is highly expressed in human osteoarthritis (OA) tissue, and overexpression of Smurf2 under the control of the type II collagen promoter (Col2a1) induces an OA-like phenotype in aged Col2a1-Smurf2 transgenic mice, suggesting that Smurf2 is located upstream of a signal cascade which initiates OA development. — Furthermore, we discovered that ectopically expressed Smurf2 interacted with GSK-3beta and induced its ubiquitination and subsequent proteasomal degradation, and hence upregulated beta-catenin in Col2a1-Smurf2 transgenic chondrocytes ex vivo. It is therefore likely that Smurf2-mediated upregulation of beta-catenin through induction of proteasomal degradation of GSK-beta in chondrocytes may activate articular chondrocyte maturation and associated alteration of gene expression, the early events of OA.”  The 2010 publication β-catenin, cartilage, and osteoarthritis states flatly “Overexpression of Smurf2, an E3 ubiquitin ligase, also induces an OA-like phenotype through upregulation of β-catenin signaling.” 

From the Arthritis Foundation’s website:  “A new clinical trial seeks to predict who is most likely to experience osteoarthritis, and to test whether an experimental treatment can prevent it altogether. Physicians are setting their sights on people who sustain a knee injury, seeking to understand why nearly half of them will later go on to develop osteoarthritis. — Initial research has shown an enzyme that controls the response of cells to growth factors may in fact be a major cause of osteoarthritis. The enzymes are called “Smad Ubiquitination Regulatory Factors,” or smurfs; but unlike the small, loveable blue cartoon characters, researchers believe that a particular form of these regulatory enzymes, smurf2, might be responsible for America’s leading cause of disability. — We believe that smurf2 controls whether or not a cartilage cell matures and calcifies into hard bone, which is a very good thing when ‘turned on’ in those areas of the body where we are supposed to have hard bone,” said Randy Rosier, MD, PhD, professor of Orthopaedics and director of Research Translation in Orthopaedics at the University of Rochester Medical Center in New York. “But when smurf2 is active in joint cartilage, it may set off a chain reaction that leads to the steady deterioration of the smooth gliding surface tissue, or cartilage, which comprises the joint surface. When this occurs, the cartilage breaks down and severely damages the weight-bearing surface of a joint. Or, put another way, activation of smurf2 in the joint cartilage appears to significantly contribute to the onset of osteoarthritis.”  The clinical trial referenced is entitled Chondrocyte Maturation and Cartilage Loss Following Meniscal Injury and is currently recruiting participants. 

Smurf2 is another odd-shaped piece of the longevity and health jigsaw puzzle with possible future implications both for treatment of diseases of the aged and pro-longevity interventions. 

The July 2010 blog entry HSP70 to the rescue describes how heat shock protein 70 (HSP70) works to promote survival of cells under stress and provides examples of the positive hormetic effects of this chaperone protein.  For example HSP70 is neuroprotection in case of cerebral ischemia.  HSP-70 is also protective of cancer cells which gives it its good-guy – bad-guy characteristics.   This blog entry briefly reviews the actions of HSP70 again, its role in cancer cells, and research efforts aimed at turning it off in cancer cells.

Roles of HSP70 in cells

One of HSP70’s key job is to act as a cell’s protein-folding officer, detecting unfolded or improperly folded proteins, refolding them properly if possible and, if a protein can’t be folded properly, signaling the cell to commit apoptosis.  Unfolded or improperly folded proteins can lead to dysfunctional cells and a number of disorders.  In my treatise I have discussed incorrect protein folding as a theory of aging. To protect themselves against folded proteins, cells have evolved what is known as the unfolded protein response (UPR).  The UPR process is described in the review paper Signal integration in the endoplasmic reticulum unfolded protein response. “The endoplasmic reticulum (ER) responds to the accumulation of unfolded proteins in its lumen (ER stress) by activating intracellular signal transduction pathways — cumulatively called the unfolded protein response (UPR). Together, at least three mechanistically distinct arms of the UPR regulate the expression of numerous genes that function within the secretory pathway but also affect broad aspects of cell fate and the metabolism of proteins, amino acids and lipids. The arms of the UPR are integrated to provide a response that remodels the secretory apparatus and aligns cellular physiology to the demands imposed by ER stress.” 

“Hsp70 proteins are central components of the cellular network of molecular chaperones and folding catalysts. They assist a large variety of protein folding processes in the cell by transient association of their substrate binding domain with short hydrophobic peptide segments within their substrate proteins. — Additional co-chaperones fine-tune this chaperone cycle. For specific tasks the Hsp70 cycle is coupled to the action of other chaperones, such as Hsp90 and Hsp100(ref).” 

So, HSP70 keep cells alive by refolding badly-folded proteins and preventing excess aggregation of proteins in cells.  And it helps transportation of proteins to their proper intracellular locations.    HSP70 also keeps cells alive by other means.  “In addition to the well-studied role of Hsp70 as a molecular chaperone assisting in correct protein folding, several new mechanisms by which Hsp70 can prevent cell death have been described. Hsp70 is now known to regulate apoptotic cell death both directly by interfering with the function of several proteins that induce apoptotic cell death as well as indirectly by increasing levels of the anti-death protein bcl-2(ref).”

HSP70 family members and other heat shock proteins are thought to play a role in delaying aging.  Widespread protein aggregation in cells is thought to play a prominent role in aging, at least in lower species and quite possibly in humans(ref).  The 2009 publication The shock of aging: molecular chaperones and the heat shock response in longevity and aging–a mini-review concludes “Molecular chaperones play an important role in the deterrence of protein damage during aging and their expression is required for longevity. Chemical stimulation of HSP synthesis might therefore be a significant strategy in future design of antiaging pharmaceuticals.”  The previous blog post Valproic acid – The phoenix drug arises again pointed out that valproic acid appears to induce HSP70 in cortical neurons and this may be responsible for some of the neuroprotective and therapeutic effects of valproic acid.

A more complete discussion of HSP70’s protective roles can be found in the blog entry HSP70 to the rescue. 

HSP70 in cancer cells

Recently, awareness has been developing that the same mechanisms that make HSP70 protective of normal stressed cells makes it protective of cancer cells. 

For some time it has been known that HSP70 is highly expressed in certain cancer cells, although its exact role was unknown.  The 2000 paper Hsp70 plasma membrane expression on primary tumor biopsy material and bone marrow of leukemic patients stated “With the exception of mammary carcinomas, an Hsp70 plasma membrane expression was found on freshly isolated human biopsy material of colorectal, lung, neuronal, and pancreas carcinomas, liver metastases, and leukemic blasts of patients with acute myelogenous leukemia.  Since normal tissues and bone marrow of healthy human individuals do not express Hsp70 on the cell surface, Hsp70 can be considered as a tumor-selective structure in vivo.”

The 2004 article Heat shock protein 70 promotes cancer cell viability by safeguarding lysosomal integrity started to zoom in on the cancer-specific cell-protective effects of HSP70.  “The major heat-inducible Hsp70 is a potent survival protein that confers cytoprotection against numerous death-inducing stimuli and increases the tumorigenicity of rodent cells. The depletion of Hsp70 by adenovirus-mediated transfer of antisense cDNA induces caspase-independent death of tumorigenic cells while non-tumorigenic cells are unaffected, suggesting that Hsp70 has cancer-specific function(s). We have recently demonstrated that the depletion of Hsp70 in cancer cells results in a cysteine cathepsin-dependent death, which is preceded by lysosomal destabilization and release of lysosomal constituents to the cytosol. In line with this, Hsp70 localizes to the membranes of lysosomes in human colon carcinoma cells and immortalized murine embryonic fibroblasts (MEFs) and prevents lysosomal membrane permeabilization and cell death induced by tumor necrosis factor (TNF), etoposide and H2O2. These findings identify Hsp70 as the first survival protein that functions by stabilizing the lysosomal membrane.”

It is increasingly clear that mobilization of HSP70 as well as other heat shock proteins is a survival strategy employed in several cancer lines.  The 2010 publication Heat shock proteins in breast cancer progression – A suitable case for treatment?  reports “Heat shock proteins (HSP) and heat shock factor 1 (HSF1), key factors in the heat shock response (HSR) have been implicated in the etiology of breast cancer. At least two members of the HSP family, Hsp27 and Hsp70 undergo significant increases in cellular concentration during the transformation of mammary cells. These changes result in HSP-mediated inhibition of tumour cell inactivation through blockade of the apoptosis and replicative senescence pathways. The increases in HSP thus mediate two of the common hallmarks of cancer and favour cell birth over cell death.”

“The cancer microenvironment exposes malignant cells to a variety of stressful conditions that promote protein misfolding. HSP70 helps cancer cells deal with this stress. Unlike normal cells, which typically express little, if any, of HSP70, cancer cells contain high levels of this protein all of the time. Indeed, HSP70 has been termed a cancer-critical survival factor, since cancer cells probably require the actions of this protein to survive the protein-altering adverse conditions(ref).”

A July 2010 report in Science Daily states “Professor Afshin Samali, lead author of the study and head of the Department of Biochemistry at NUI Galway, and his team have discovered that under cell stress conditions Hsp70 interacts with a receptor in the cell, activating survival mechanisms and preventing apoptosis, the normal cell death mechanism. — Professor Samali states: “Our results have identified a novel protein-protein interaction that helps cancer cells to survive stressful growth conditions. By interfering with this interaction we hope to develop a new class of anticancer drugs.”  The source publication for the study mentioned in this quote deals with the mechanism of action of HSP72: “Here, we report that Hsp72, a stress-inducible cytosolic molecular chaperone, can bind to and enhance the RNase activity of IRE1α, providing an important molecular link between the heat shock response and the ER stress response. Importantly, increased production of active XBP-1 was necessary for Hsp72 to exert its prosurvival effect under conditions of ER stress. Our results suggest a mechanism whereby Hsp72 overexpression helps cells adapt to long-term ER stress in vivo by enhancing the pro-survival effects of the IRE1α/XBP1 branch of the UPR.”  HSP72 is the same as HSP70 as related to the HSPA1A gene.

Inhibiting HSP70 in cancer cells

The growing awareness of the importance of HSP70 as a survival factor in cancers has motivated a search for new molecules that can inhibit the expression of HSP70.

HSP70 inhibition via anti-sense Hsp70 cDNA

A page from the Sloan-Kettering Institute web site discusses inhibitors of HSP70 expression.  One of those is anti-sense Hsp70 cDNA.  “It is documented that inhibition of Hsp70 expression by anti-sense Hsp70 cDNA resulted in inhibition of tumor cell proliferation and induction of apoptosis. Depletion of Hsp70 by Ad.asHsp70 led to massive cell death of all tumorigenic cell lines tested (carcinomas of breast, colon, prostate and liver as well as glioblastoma). In spite of an effective depletion of Hsp70, Ad.asHsp70 had no effect on the survival or growth of fetal fibroblasts or non-tumorigenic epithelial cells of breast or prostate.”

HSP70 inhibition via quercetin

The same Sloan-Kettering web page mentions use of quercetin as a HSP70 inhibitor.  “Inhibition of hsp70 gene expression has been documented after pharmacological intervention with the flavanoid quercetin. The agent induced apoptosis in several tumor cell lines. In addition, inhibition of hsp70 accumulation by quercetin made cells more susceptible to apoptotic inducers. Quercetin also sensitized cells to hyperthermia, chemotherapy and radiation. Inhibition of hsp70 synthesis as well as induction of apoptosis by treatment with quercetin combined with hyperthermia was reported to be confined to leukemic cells, and not to normal hematopoietic progenitor cells.”  The ability of quercetin to kill tumor cells via a mechanism involving HSP70 has been known for some time.  The 1994 paper Induction of Apoptosis by Quercetin: Involvement of Heat Shock Protein stated “Quercetin, a widely distributed bioflavonoid, inhibits the growth of tumor cells. The present study was designed to investigate the possible involvement of apoptosis and heat shock protein in the antitumor activity of quercetin. — These results suggest that quercetin displays antitumor activity by triggering apoptosis and that HSP70 may affect quercetin-induced apoptosis.”

The same Sloan-Kettering web page goes on to say “In spite of its evident utility in cancer treatment, quercetin is not potent enough to grant its clinical use. Since the introduction of anti-sense mRNA or siRNAs into humans will be problematic because the extent of inhibition cannot be modulated, and the effects of quercetin are likely pleiotropic, small molecules that directly compromise but not completely inhibit the activities of Hsp70 chaperones will prove clinically valuable to combat cancer. In addition, the above data suggest that an Hsp70 inhibitor concentration can be identified that will not be toxic to healthy cells. To date, however, Hsp70 inhibitors have not been tested in cell or animal cancer models, and very few Hsp70 inhibitors have been identified. — We are interested in identifying both inhibitors of Hsp70 activity and expression and efforts in this regard are currently underway.”

HSP70 inhibition via PES

Late last year there was a report of a possibly promising substance, PES.  The October 2009 publication A Small Molecule Inhibitor of Inducible Heat Shock Protein 70 reports “The multifunctional, stress-inducible molecular chaperone HSP70 has important roles in aiding protein folding and maintaining protein homeostasis. HSP70 expression is elevated in many cancers, contributing to tumor cell survival and resistance to therapy. We have determined that a small molecule called 2-phenylethynesulfonamide (PES) interacts selectively with HSP70 and leads to a disruption of the association between HSP70 and several of its cochaperones and substrate proteins. Treatment of cultured tumor cells with PES promotes cell death that is associated with protein aggregation, impaired autophagy, and inhibition of lysosomal function. Moreover, this small molecule is able to suppress tumor development and enhance survival in a mouse model of Myc-induced lymphomagenesis. The data demonstrate that PES disrupts actions of HSP70 in multiple cell signaling pathways, offering an opportunity to better understand the diverse functions of this molecular chaperone and also to aid in the development of new cancer therapies.”

According to a November 2009 Science Daily article on this research Inhibitor Of Heat Shock Protein Is A Potential Anticancer Drug, Study Finds,  “The inhibitor, called PES, interferes with the HSP70 activities that the cancer cell needs to survive, so by targeting HSP70, one can target the cancer cell. — The investigators showed that PES interacts with HSP70 by blocking its stress-relieving functions. It also induces HSP70-dependent cell death by disrupting the cell’s ability to remove damaged components. Paradoxically for a compound first identified for blocking the cell-death pathway of apoptosis, PES does kill cells, but by a different mechanism. — PES seems to be specifically targeting HSP70, a protein that is differentially expressed in normal versus cancerous cells, and “one that the cancer cell seems to require to survive” says George. “It’s still early days — we don’t know what it will do in a human. But, the exciting part is that this is a pathway and a protein target that clearly is important for cancer cells. — Given the extreme heterogeneity of cancer cells, simultaneously disabling networks of signaling pathways may be important. Indeed, PES was more or less equally effective in every type of cancer cell tested, she says, “which is unusual and supports the idea that it is targeting a protein that is required for the functioning of multiple pathways.”

The article goes on “”We found several known HSP70-interacting proteins that were no longer interacting properly when the cells were exposed to the small molecule,” Leu notes. — Among those were proteins that help HSP70 refold misfolded proteins and proteins that abet its protein trafficking functions. — When they then studied the effect that loss of those functions had on the cell, the team discovered that PES blocks the cell’s ability to get rid of the proteins damaged by cellular stress in a process called autophagy, a process in which cells were basically eating themselves to death. In mice, Murphy and her students Julia Pimkina and Amanda Frank found that PES could inhibit tumor formation and significantly extend survival. — “That was one of the highlights from our perspective, because PES has potential to be developed as a therapeutic,” says Murphy.’

Wrapping it up:

·        HSP70 assures proper folding of proteins in cells and, via this and other mechanisms, is strongly protective of cells under stress and possibly plays a positive role with respect to longevity.

·        HSP70 also plays a major role in protecting cancer cells, setting off a search for substances that can inhibit HSP70 expression in cancer cells.

·        Quercetin, a substance in the anti-aging firewalls regimen, inhibits the expression of HSP70 in cancer cells, but its effects may be too weak for its use as a clinical therapy.

·        A substance called PES shows promise as a possible drug candidate for inhibiting HSP70 expression in cancer cells.

·        The research in this area still involves experimentation with laboratory animals and may or may not lead to clinical trials in humans.

The chemical valproic acid has been around for a very long time.  It was first synthesized in 1882 and for a great many years it seemed to be not very useful. However, over its 128 year history valproic acid has periodically risen in importance from the ashes like the phoenix bird* as new properties of it were discovered and new important applications found for it.  In 1962 it was found to be a powerful anticonvulsant and it soon evolved to become a favorite mood stabilizer. Currently valproic acid seems to have strong potential applications for treating cancers and Alzheimer’s disease, and for guiding stem cell regeneration of nerves in cases of spinal cord injuries.    This blog entry briefly covers the history of valproic acid and its major traditional applications and then focuses on important newfound properties of this substance and potential new applications for it.

History of valproic acid

Valerian (Valeriana officinalis) is a perennial plant of European and Asian origin.  Dietary supplements have traditionally been made from its roots and have been used as a sedative for dealing with insomnia(ref).  My wife tells me that back in the 60s valerian was often found in hippy cookbooks, and has been thought to have magical powers.  “Its magical reputation is Evil and Protective, and it is used to Force Love. It is burned in Black Arts Incense for hexing, but added to Uncrossing Incense to destroy jinxes if burned with a yellow candle(ref).”  Magic apart, research in the 1990s suggests that valerian achieves its effects through acting on the GABAA (gamma-aminobutyric acid) receptor, promoting the expression of GABA(ref).  “In conclusion, our data show that the extent of GABAA receptor modulation by Valerian extracts is related to the content of valeric acid(ref).” Valproic acid (also known as valproate and abbreviated VPA)  is a synthetic substance, not present in the valerian plant.  “Valproic  acid (by its official name 2-propylvaleric acid) was first synthesized in 1882 by Burton as an analogue of valeric acid, found naturally in valerian.^[1] (ref)”  As we shall see, VPA too is a strong modulator of the GABA receptor.  Although mostly not known to be evil, it is also strongly protective. 

For the first 88 years of its history valproic acid did not seem to be good for very much except as a laboratory solvent.  “In 1962, the French researcher Pierre Eymard serendipitously discovered the anticonvulsant properties of valproic acid while using it as a vehicle for a number of other compounds that were being screened for anti-seizure activity. He found that it prevented pentylenetetrazol-induced convulsions in rodents.^[2] It was approved as an antiepileptic drug in 1967 in France and has become the most widely prescribed antiepileptic drug worldwide(ref).³” By 2005, research showed that “Its pharmacological effects involve a variety of mechanisms, including increased gamma-aminobutyric acid (GABA)-ergic transmission, reduced release and/or effects of excitatory amino acids, blockade of voltage-gated sodium channels and modulation of dopaminergic and serotoninergic transmission(ref).” As described in a 2005 review paper, Valproate, a simple chemical with so much to offer, “Valproate is generally regarded as a first-choice agent for most forms of idiopathic and symptomatic generalized epilepsies.”

Soon after VPA started to be used to control seizures in the late 60s and early 70s, research was initiated on possible use of VPA for treatment of bipolar disorders,.  By 1989 VPA’s role in treating psychiatric disorders was becoming well established.  The 1989 publication Valproate in psychiatric disorders: literature review and clinical guidelines reported “A growing literature suggests that the anticonvulsant medication valproate may be effective and well tolerated in the acute and prophylactic treatment of some mood and psychotic disorders, particularly the manic phase of bipolar disorder and schizoaffective disorder. Valproate may sometimes be effective even in those patients who have not responded to conventional somatic therapies.”  Approved by the FDA for the treatment of manic or mixed episodes, with or without psychotic features , valproic acid is currently marketed as a mood stabilizer under various trade names such as Depakote and Depakene.  “Besides its clinical use as an anticonvulsant and mood-stabilizing drug [9], VPA presents beneficial effects in clinical depression [10], absence seizures [11, 12], tonic-clonic seizures, complex partial seizures [13], juvenile myoclonic epilepsy [14], seizures associated with Lennox-Gastaut syndrome [15], migraine headaches, and schizophrenia(ref).”  There are ten different branded valproic acid products sold by ten different pharma companies or their branches worldwide.

Additional potential applications of valproic acid

As time has progressed, one after another potential new medical application  of valproic acid has emerged, and that process has been continuing until today.  For example a July 2910 report indicates Valproic acid shown to halt vision loss in patients with retinitis pigmentosa.  “WORCESTER, MASS. – Researchers at the University of Massachusetts Medical School (UMMS) believe they may have found a new treatment for retinitis pigmentosa (RP), a severe neurodegenerative disease of the retina that ultimately results in blindness.  One of the more common retinal degenerative diseases, RP is caused by the death of photoreceptor cells and affects 1 in 4,000 people in the United States. RP typically manifests in young adulthood as night blindness or a loss of peripheral vision and in many cases progresses to legal blindness by age 40. — In the July 20 online edition of the British Journal of Ophthalmology, Shalesh Kaushal, MD, PhD, chair of ophthalmology and associate professor of ophthalmology and cell biology at UMMS, and his team, describe a potential new therapeutic link between valproic acid and RP, which could have tremendous benefits for patients suffering from the disease. In a retrospective study, valproic acid – approved by the FDA to reduce seizures, treat migraines and manage bipolar disorder – appeared to have an effect in halting vision loss in patients with RP and in many cases resulted in an improved field of vision. Results from this study, in conjunction with prior in vitro data, suggest valproic acid may be an effective treatment for photoreceptor loss associated with RP. — UMass Medical School will be the coordinating site for a $2.1 million, three-year clinical trial funded by the Foundation Fighting Blindness/National Neurovision Research Institute quantifying the potential of valproic acid as a treatment for RP.”  The August 2010 paper in the British Journal of Ophthalmology Therapeutic potential of valproic acid for retinitis pigmentosa concludes “Treatment with VPA (valproic acid)_is suggestive of a therapeutic benefit to patients with RP. A placebo-controlled clinical trial will be necessary to assess the efficacy and safety of VPA for RP rigorously.” 

In a quite different dimension, VPA might be very useful for treating Alzheimer’s Disease.  The 2008 paper Valproic acid inhibits Aβ production, neuritic plaque formation, and behavioral deficits in Alzheimer’s disease mouse models relates to another action of the versatile substance. “Neuritic plaques in the brains are one of the pathological hallmarks of Alzheimer’s disease (AD). Amyloid β-protein (Aβ), the central component of neuritic plaques, is derived from β-amyloid precursor protein (APP) after β- and γ-secretase cleavage. The molecular mechanism underlying the pathogenesis of AD is not yet well defined, and there has been no effective treatment for AD. Valproic acid (VPA) is one of the most widely used anticonvulsant and mood-stabilizing agents for treating epilepsy and bipolar disorder. We found that VPA decreased Aβ production by inhibiting GSK-3β–mediated γ-secretase cleavage of APP both in vitro and in vivo. VPA treatment significantly reduced neuritic plaque formation and improved memory deficits in transgenic AD model mice. We also found that early application of VPA was important for alleviating memory deficits of AD model mice. Our study suggests that VPA may be beneficial in the prevention and treatment of AD.”

The 2010 review article Valproic acid as a promising agent to combat Alzheimer’s disease furthers the advocacy of valproic acid as a treatment for AD, and provides an explanation of its actions that are highly relevant for treatment of AD.  “Alzheimer’s disease (AD) is one of the most threatening diseases to the elderly population at present. However, there is no yet efficient therapeutic method to AD. Recently, accumulating evidence indicates that valproic acid (VPA), a widely used mood stabilizer and antiepileptic drug, has neuroprotective potential relevant to AD. Moreover, VPA can induce neurogenesis of neural progenitor/stem cells both in vitro and in vivo via multiple signaling pathways. Therefore, it is suggested that VPA is a promising agent to combat AD.” The operant word here that I will return to is “neurogenesis,” the birth of new neurons through differentiation of neural progenitor cells.

Molecular biology, genetic and epigenetic properties of VPA 

So what is going on with valproic acid?  Starting out with a sleep-helping plant extract going on to control of seizures and then on to mood stabilization and to possible control of retinitis pigmentosa and further to  possible control of Alzheimer’s Disease – what else can it do?  What else it can do as we will see includes possible treatment of Parkinson’s Disease and multiple cancers and assistance in regenerating damaged spinal cords through promoting the proper kind of stem cell differentiation.  But first I want to discuss a few of the more newly-discovered biochemical properties of valproic acid that gives it such versatile pluripotency.

The major properties of valproic acid that make it interesting to today’s researchers were not known to exist more than 10 to 30 years ago.  They are: a) valproic acid increases the activity of the neurotransmitter Gamma Amino Butyrate (GABA through several mechanisms, b) VPA is a histone deacetylase inhibitor, c) VPA induces the mobilization of heat shock proteins, HSP70 in particular , and d) VPA promotes the selective differentiation of certain stem and progenitor cells.
 

a)        GABA

I introduced GABA in the blog entry GABA, beta-alanine, carnosine, homocarnosine and gabapentin and have mentioned it in a number of others. GABA “is the chief inhibitory neurotransmitter in the mammalian central nervous system. It plays a role in regulating neuronal excitability throughout the nervous system. In humans, GABA is also directly responsible for the regulation of muscle tone.^[1] (ref)” 

Discussions of the GABA-promoting and the HDAC–inhibiting properties of valproic acid are given in the July 2010 publication Molecular and Therapeutic Potential and Toxicity of Valproic Acid.  “In the human brain, VPA alters the activity of the neurotransmitter Gamma Amino Butyrate (GABA) by potentialising the inhibitory activity of GABA through several mechanisms, including inhibition of GABA degradation, inhibition of GABA Transaminobutyratre (ABAT), increased GABA synthesis, and decreased turnover [5]. Moreover, VPA attenuates N-Methyl-D-Aspartate-mediated excitation [6, 7] and blocks Na+ channels, Ca2+ channels (voltage-dependent L type CACNA1 type C, D, N, and F), and voltage-gated K+ channels (SCN) [8].” 

b)        HDAC inhibition

The blog entry Histone acetylase and deacetylase inhibitors provides an introduction to what histone deacetylase inhibitors (HDAC inhibitors) basically are, how they work and why they are relevant. Basically a HDAC inhibitor keeps a histone, a spindle around which DNA is wrapped, acetylated – which is in an unfolded state that allows relatively unimpeded gene activation.  Inhibition of HDAC promotes decondensed chromatin formation, thereby promoting the expression of genes and consequently modulating processes such as cell growth, differentiation and apoptosis(ref)(ref).  I also touch on the relationship of HDAC inhibition to aging in that blog entry.  Certain substances I have featured in recent blog posts, curcumin in particular(ref), are also powerful HDAC inhibitors, (ref)(ref).

“VPA, as well as other HDAC inhibitors (HDACi), is able to alter expression of many genes. Corresponding proteins were described to play important roles in cellular activity and could influence several important pathways such as cell cycle control, differentiation, DNA repair, and apoptosis [16–19].  — VPA specifically targets 2 of the 4 classes of HDACs: class I, subclasses Ia and Ib, and class II, subclass IIa. Within subclass IIa, HDAC9 is an exception to this modulation, being activated by VPA, which is also true for HDAC11 [20]. HDAC 6, 8, and 10 are not modulated. It is interesting to mention that HDAC classes I and II have been reported to be strongly implicated in neuronal function, which could partially explain the action of VPA in neural pathologies(ref).”   

c)         HSP70

The 2009 paper 2009 Valproic acid induces functional heat-shock protein 70 via Class I histone deacetylase inhibition in cortical neurons: a potential role of Sp1 acetylation relates the actions of valproic acid to our old friend HSP 70, a heat-shock protein involved in hormesis.  “Taken together, the data suggest that the phosphatidylinositol 3-kinase/Akt pathway and Sp1 are likely involved in HSP70 induction by HDAC inhibitors, and induction of HSP70 by VPA in cortical neurons may contribute to its neuroprotective and therapeutic effects.” See the blog entry HSP70 to the rescue.

d) VPA and neural stem cell differentiation

I have introduced the topic of neurogenesis in the in my treatise in the section on the Neurological degeneration theory of aging and in the recent blog entry Neurogenesis, curcumin and longevity. “Increasing research evidence suggests that maintaining a sufficient and consistent rate of neurogenesis in the brain, particularly in the hippocampus, is important for the maintenance of cognitive health. Insufficient or irregular neurogenesis is thought to be a causative factor in bipolar disease and other mood disorders.”  Neurogenesis is also critical as an ongoing process in other nervous tissue such as in the spinal column, and for effective repair of certain spinal cord injuries. 

The capability of VPA to induce neural differentiation has been known for some time, at least for certain cancer cells. The 1996 publication Antitumor activity of sodium valproate in cultures of human neuroblastoma cells concluded “The results indicate that VPA, at non-toxic pharmacological concentrations, arrests the growth, induces differentiation and increases immunogenicity of NB cells through non-toxic mechanisms.”  The 2008 online publication Valproic acid induces differentiation and inhibition of proliferation in neural progenitor cells via the beta-catenin-Ras-ERK-p21Cip/WAF1 pathway describes the mechanism.  “We report here that 1 mM VPA simultaneously induces differentiation and reduces proliferation of basic fibroblast growth factor (bFGF)-treated embryonic day 14 (E14) rat cerebral cortex neural progenitor cells (NPCs). The effects of VPA on the regulation of differentiation and inhibition of proliferation occur via the ERK-p21Cip/WAF1 pathway. — We propose that this mechanism of VPA action may contribute to an explanation of its anti-tumor and neuroprotective effects, as well as elucidate its role in the independent regulation of differentiation and inhibition of proliferation in the cerebral cortex of developing rat embryos.” 

Valproic acid as a cancer treatment 

Valproic acid’s capabilities as a HDAC inhibitor motivate a great deal of the scientific interest in this drug as a potential cancer treatment.  One mechanism involved is explained in the 2006 paper Valproic acid and butyrate induce apoptosis in human cancer cells through inhibition of gene expression of Akt/protein kinase B.  “RESULTS: Here, we report that a key determinant for the susceptibility of cancer cells to histone deacetylase inhibitors is their ability to maintain cellular Akt activity in response to the treatment. Also known as protein kinase B, Akt is an essential pro-survival factor in cell proliferation and is often deregulated during tumorigenesis. We show that histone deacetylase inhibitors, such as valproic acid and butyrate, impede Akt1 and Akt2 expression, which leads to Akt deactivation and apoptotic cell death. In addition, valproic acid and butyrate induce apoptosis through the caspase-dependent pathway. The activity of caspase-9 is robustly activated upon valproic acid or butyrate treatment. Constitutively active Akt is able to block the caspase activation and rescues cells from butyrate-induced apoptotic cell death.  – CONCLUSION: Our study demonstrates that although the primary target of histone deacetylase inhibitors is transcription, it is the capacity of cells to maintain cellular survival networks that determines their fate of survival.” 

It should be pointed out that valproic acid may play a special therapeutic role for some cancers since not all HDAC inhibitors produce the same results. The July 2010 paper Histone deacetylase inhibition modulates cell fate decisions during myeloid differentiation concludes  “Individual histone deacetylase inhibitors had specific effects on cell fate decisions during myeloid development. These data provide novel insights into the effects of histone deacetylase inhibitors on the regulation of normal hematopoiesis, which is of importance when considering utilizing these compounds for the treatment of myeloid malignancies and bone marrow failure syndromes.”Another of the multiple actions of VPA related to  cancers is described in the 2007 publication Downregulation of c-Myc is critical for valproic acid-induced growth arrest and myeloid differentiation of acute myeloid leukemia.  “VPA also downregulated c-Myc levels, and induced apoptosis and myeloid differentiation of primary AML cells, leading to decreased colony-forming ability.  Given the role of c-Myc in leukemogenesis, our study suggests that VPA might be a potential therapeutic agent for AML.”

Here is a selection from the many publications relating to VPA as a potential cancer treatment, in  some cases with selected quotes.  Note that the major interest started less than 10 years ago.

2005 Natural killer cell-mediated lysis of hepatoma cells via specific induction of NKG2D ligands by the histone deacetylase inhibitor sodium valproate.  “Taken together, our data show that the HDAC-I VPA mediates specific priming of malignant cells for innate immune effector mechanisms. These results suggest the clinical evaluation of HDAC-I in solid tumors such as hepatocellular carcinoma, especially in combination with immunotherapy approaches employing adoptive NK cell transfer.”

2005 Results of a phase 2 study of valproic acid alone or in combination with all-trans retinoic acid in 75 patients with myelodysplastic syndrome and relapsed or refractory acute myeloid leukemia.  “We conclude that VPA is clinically useful in low-risk MDS. For patients with high-risk MDS, VPA may be combined with chemotherapy or demethylating drugs.”

2006 Valproic acid induces apoptosis in prostate carcinoma cell lines by activation of multiple death pathways “Our data indicate that the use of valproic acid may be a suitable therapeutic agent in the control of prostate cancer progression and its action appears particularly relevant in the control of refractory stages of prostate cancer.”

2006 The histone deacetylase (HDAC) inhibitor valproic acid as monotherapy or in combination with all-trans retinoic acid in patients with acute myeloid leukemia.  “We used VPA in 58 patients with acute myeloid leukemia (AML) who were too old and/or medically unfit to receive intensive chemotherapy.”  The study showed some improvement in the patients involved due to VPA but VPA did not provide a cure. “ CONCLUSIONS: Future trials should combine VPA with chemotherapy or demethylating agents.”

2006 Histone deacetylase inhibition by valproic acid down-regulates c-FLIP/CASH and sensitizes hepatoma cells towards CD95- and TRAIL receptor-mediated apoptosis and chemotherapy   This cell-level study concludes “These findings provide a rationale for the development of VA and Apo2L/TRAIL combination as a novel molecular therapeutic for thoracic cancers.”

2007 Valproic acid for the treatment of myeloid malignancies  “When it was used as monotherapy or in combination with all-trans retinoic acid, which synergizes in vitro, VPA achieved hematologic improvement in a subset of patients. Similar to other inhibitors of histone deacetylases, complete or partial remissions rarely were observed.”

2007 Valproic acid induces p21 and topoisomerase-II (alpha/beta) expression and synergistically enhances etoposide cytotoxicity in human glioblastoma cell lines.  This cell-level study is of particular interest because glioblastoma cells are particularly refractory to treatment and the disease is a certain and rapid killer. “CONCLUSION: Our study demonstrates that VPA sensitizes U87, U251, and LN18 cells to the cytotoxic effects of etoposide in vitro by inducing differentiation and up-regulating the expression of p21/WAF1 and both isoforms of topoisomerase-II.”  As pointed out in the recent blog entry, Curcumin, cancer and longevity, curcumin, another HDAC inhibitor, is also toxic to glioblastoma cells.

2008  Valproic acid activates Notch1 signaling and induces apoptosis in medullary thyroid cancer cells. CONCLUSIONS: VPA activates Notch1 signaling in MTC cells and inhibits their growth by inducing apoptosis. As the safety of VPA in human beings is well established, a clinical trial using this drug to treat patients with advanced MTC could be initiated in the near future.”

2010 Cell type-specific anti-cancer properties of valproic acid: independent effects on HDAC activity and Erk1/2 phosphorylation Shows that more than inhibition of HDAC is involved in anti-cancer activities of valproic acid.  “These results suggest that VPA can modulate the degree of Erk1/2 phosphorylation in a manner unrelated to HDAC inhibition and emphasize that changes in the degree of Erk1/2 phosphorylation are also important for the anti-cancer properties of VPA.”

Research on VPA appears to be accelerating exponentially.  A search in pubmed.org on valproate and cancer revealed 47 new 2010 publications.  I list only a few of these highly selectively for flavor.

2010 Phase I Pharmacokinetic and Pharmacodynamic Evaluation of Combined Valproic Acid/Doxorubicin Treatment in Dogs with Spontaneous Cancer.

2010 Cell type-specific anti-cancer properties of valproic acid: independent effects on HDAC activity and Erk1/2 phosphorylation.

2010 Enhancement of radiation response in osteosarcoma and rhabdomyosarcoma cell lines by histone deacetylase inhibition.

2010 HDAC inhibitor, valproic acid, induces p53-dependent radiosensitization of colon cancer cells.

2010  Histone deacetylase inhibitor valproic acid inhibits cancer cell proliferation via down-regulation of the Alzheimer amyloid precursor protein.

2010 A combined pretreatment of 1,25-dihydroxyvitamin D3 and sodium valproate enhances the damaging effect of ionizing radiation on prostate cancer cells.

Valproic acid and Parkinson’s Disease

The 2005 publication Valproate pretreatment protects dopaminergic neurons from LPS-induced neurotoxicity in rat primary midbrain cultures: role of microglia  suggests a potential role for VPA in treatment of Parkinson’s Disease.  “Parkinson’s disease is a neurodegenerative disorder characterized by progressive degeneration of dopaminergic (DA) neurons in the substantia nigra. Accumulating evidence supports the notion that neuroinflammation is involved in the pathogenesis of this disease. Valproate (VPA) has long been used for the treatment of seizures and bipolar mood disorder. In vivo and in vitro studies have demonstrated that VPA has neuroprotective and neurotrophic actions. In this study, using primary neuron-glia cultures from rat midbrain, we demonstrated that VPA is a potent neuroprotective agent against lipopolysaccharide (LPS)-induced neurotoxicity. Results showed that pretreatment with 0.6 mM VPA for 48 h robustly attenuated LPS-induced degeneration of dopaminergic neurons as determined by [(3)H] dopamine uptake and counting of the number of TH-ir neurons. The neuroprotective effect of VPA was concentration-dependent and was mediated, at least in part, through a decrease in levels of pro-inflammatory factors released from activated microglia. Specifically, LPS-induced increase in the release of TNFa, NO, and intracellular reactive oxygen species was markedly reduced in cultures pretreated with VPA. These anti-inflammatory effects of VPA were time and concentration-dependent correlated with a decrease in the number of microglia. Thus, our results demonstrate that protracted VPA pretreatment protects dopaminergic neurons from LPS-induced neurotoxicity through a reduction in levels of released pro-inflammatory factors, and further suggest that these anti-inflammatory effects may be contributed by VPA-induced reduction of microglia cell number. Taken together, our study reinforces the view that VPA may have utility in treating Parkinson’s disease.”

The 2006 study Valproate protects dopaminergic neurons in midbrain neuron/glia cultures by stimulating the release of neurotrophic factors from astrocytes reports “Our study identifies astrocyte as a novel target for VPA to induce neurotrophic and neuroprotective actions in rat midbrain and shows a potential new role of cellular interactions between DA neurons and astrocytes. The neurotrophic and neuroprotective effects of VPA also suggest a utility of this drug for treating neurodegenerative disorders including Parkinson’s disease. Moreover, the neurotrophic effects of VPA may contribute to the therapeutic action of this drug in treating bipolar mood disorder that involves a loss of neurons and glia in discrete brain areas.”

The 2007 publication Valproic acid and other histone deacetylase inhibitors induce microglial apoptosis and attenuate lipopolysaccharide-induced dopaminergic neurotoxicity  reports “The aim of this study was to determine the mechanism underlying VPA-induced attenuation of microglia over-activation using rodent primary neuron/glia or enriched glia cultures. — We found that VPA induced apoptosis of microglia cells in a time- and concentration-dependent manner. VPA-treated microglial cells showed typical apoptotic hallmarks including phosphatidylserine externalization, chromatin condensation and DNA fragmentation. — Taken together, our results shed light on a novel mechanism whereby HDACIs induce neuroprotection and underscore the potential utility of HDACIs in preventing inflammation-related neurodegenerative disorders such as Parkinson’s disease.”

The 2008 publication Histone deacetylase inhibitors up-regulate astrocyte GDNF and BDNF gene transcription and protect dopaminergic neurons relates:  “Parkinson’s disease (PD) is characterized by the selective and progressive loss of dopaminergic (DA) neurons in the midbrain substantia nigra. Currently, available treatment is unable to alter PD progression. Previously, we demonstrated that valproic acid (VPA), a mood stabilizer, anticonvulsant and histone deacetylase (HDAC) inhibitor, increases the expression of glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) in astrocytes to protect DA neurons in midbrain neuron-glia cultures. The present study investigated whether these effects are due to HDAC inhibition and histone acetylation. — This study indicates that astrocytes may be a critical neuroprotective mechanism of HDAC inhibitors, revealing a novel target for the treatment of psychiatric and neurodegenerative diseases.” 

The 2009 publication Valproic acid is neuroprotective in the rotenone rat model of Parkinson’s disease: involvement of α-synuclein reports:  “The decrease of the dopaminergic marker tyrosine hydroxylase in substantia nigra and striatum caused by 7 days toxin administration was prevented in VPA-fed rats. VPA treatment also significantly counteracted the death of nigral neurons and the 50% drop of striatal dopamine levels caused by rotenone administration. The PD-marker protein alpha-synuclein decreased, in its native form, in substantia nigra and striatum of rotenone-treated rats, while monoubiquitinated alpha-synuclein increased in the same regions. VPA treatment counteracted both these alpha-synuclein alterations. Furthermore, monoubiquitinated alpha-synuclein increased its localization in nuclei isolated from substantia nigra of rotenone-treated rats, an effect also prevented by VPA treatment.”

More on valproic acid and Alzheimer’s  Disease

The 2010 publication Valproic acid enhances microglial phagocytosis of amyloid-beta(1-42)  reports: “BV-2 cells treated with the neuroactive drug valproic acid (VPA) showed greatly enhanced phagocytic activity for both latex beads and Abeta. VPA also reduced microglial viability by inducing apoptosis, as previously reported. The relevance of these in vitro results to the treatment of AD is unclear but further investigation into the effects of VPA on the clearance of Abeta through enhanced microglial phagocytosis is warranted.”

The 2010 publication Valproic acid stimulates clusterin expression in human astrocytes: Implications for Alzheimer’s disease reports “We have observed earlier that histone deacetylase (HDAC) inhibitors can induce the expression of clusterin in several neuroblastoma and glioma cell lines. Recent studies have revealed that valproic acid, a common and well-tolerated drug for epilepsy and bipolar disorders, is a potent HDAC inhibitor. In this study, we examined whether valproic acid can induce the expression of clusterin in human astrocytes. Our results demonstrated that valproic acid is a potent inducer of clusterin expression and secretion in human astrocytes at the therapeutical concentrations.”

Spinal Muscular Atrophy

The 2009 publication The emerging role of epigenetic modifications and chromatin remodeling in spinal muscular atrophy states: “As the leading genetic cause for infantile death, Spinal Muscular Atrophy (SMA) has been extensively studied since its first description in the early 1890s. Though today much is known about the cause of the disease, a cure or effective treatment is not currently available. Recently the short chain fatty acid valproic acid, a drug used for decades in the management of epilepsy and migraine therapy, has been shown to elevate the levels of the essential survival motor neuron protein in cultured cells. In SMA mice, valproic acid diminished the severity of the disease phenotype. This effect was linked to the ability of the short chain fatty acid to suppress histone deacetylase activity and activate gene transcription. Since then, the study of different histone deacetylase inhibitors and their epigenetic modifying capabilities has been of high interest in an attempt to find potential candidates for effective treatment of SMA.”

Valproic acid and repairing spinal cord injury

The final topic I am going to take up here relates to breaking news reported in August 2010.  According to a Science Daily article, Repairing Spinal Cord Injury With Manipulated Neural Stem Cells, “One of the most common causes of disability in young adults is spinal cord injury. Currently, there is no proven reparative treatment. Hope that neural stem cells (NSCs) might be of benefit to individuals with severe spinal cord injury has now been provided by the work of a team of researchers, led by Kinichi Nakashima, at Nara Institute of Science and Technology, Japan, in a mouse model of this devastating condition. — In the study, mice with severe spinal cord injury were transplanted with NSCs and administered a drug known as valproic acid, which is used in the treatment of epilepsy. The valproic acid promoted the transplanted NSCs to generate nerve cells, rather than other brain cell types, and the combination therapy resulted in impressive restoration of hind limb function. The authors hope that this approach, whereby the fate of transplanted NSCs is manipulated, for example by administration of valproic acid, could be developed as an effective treatment for severe spinal cord injury.”

The e-publication of the aforementioned research dated Sept  1 2010 is Neurons derived from transplanted neural stem cells restore disrupted neuronal circuitry in a mouse model of spinal cord injury.  “The body’s capacity to restore damaged neural networks in the injured CNS is severely limited. Although various treatment regimens can partially alleviate spinal cord injury (SCI), the mechanisms responsible for symptomatic improvement remain elusive. Here, using a mouse model of SCI, we have shown that transplantation of neural stem cells (NSCs) together with administration of valproic acid (VPA), a known antiepileptic and histone deacetylase inhibitor, dramatically enhanced the restoration of hind limb function. VPA treatment promoted the differentiation of transplanted NSCs into neurons rather than glial cells. Transsynaptic anterograde corticospinal tract tracing revealed that transplant-derived neurons reconstructed broken neuronal circuits, and electron microscopic analysis revealed that the transplant-derived neurons both received and sent synaptic connections to endogenous neurons. Ablation of the transplanted cells abolished the recovery of hind limb motor function, confirming that NSC transplantation directly contributed to restored motor function.  These findings raise the possibility that epigenetic status in transplanted NSCs can be manipulated to provide effective treatment for SCI.”  The body of the article contains much interesting discussion, for example” In the present study, we adopted what we believe is a novel approach for the treatment of SCI: manipulation of transplanted NSC fate by an epigenetic reagent. A combined treatment involving NSC transplantation and administration of the HDAC inhibitor VPA led to a marked functional recovery. We will refer below to this dual treatment as the HINT (HDAC inhibitor and NSC transplantation) method. Immunohistochemical analysis revealed that VPA administration promoted the neuronal differentiation of transplanted NSCs. We examined extensively the roles of the neurons responsible for reconstruction of broken neuronal networks using 2 neuronal tracers, immunoelectron microscopy, and 2 cell-ablation methods. These results revealed that transplant-derived neurons received projections from endogenous neurons and that their extended processes made synapses with endogenous neurons in the ventral horn.”

Clinical trials of valproic acid

A search of clinicaltrials.gov using the term “valproic acid” retrieves 249 trials worldwide.  The list is worth perusing for it indicates the acute interest of pharmaceutical companies in valproic acid and where bets are being placed.  In general, with exceptions it can be noted that:

·        Most of the trials, including many the completed Phase III trials, relate to the traditional applications of valproic acid such as seizure control and psychiatric applications, and there are many new trials relating to these applications.

·        A number of trials for cancer treatments, usually involving VPA in combination with other substances, are in early phases or just being started up

·        A few trials relate to additional medical conditions beyond those mentioned here, such as autism(ref) and withdrawal from opiates.

·        Some cutting-edge applications such as assisting in spinal cord regeneration as mentioned here are not yet in clinical trials.

The evil side of valproic acid

Remember the magic superstition that valerian was protective but also had capability to do evil?  Well, medication with VPA can also on rare occasions induce dementia and Parkinson’s Disease symptoms as reported in this, this and this publication.  Also VPA has been reported to induce delirium in a demented patient in this publication. 

Wrapping it up

·        Valproic acid is a 128 year-old chemical but initial understanding of its biomolecular and epigenetic properties has only emerged recently and there is probably still a lot to be learned about it.

·        The major properties of valproic acid that make VPA interesting to today’s researchers involve distinctions that did not exist until relatively recently.  They are: a) VPA increases the activity of the neurotransmitter Gamma Amino Butyrate (GABA), b) VPA is a histone deacetylase inhibitor, c) VPA induces the mobilization of heat shock proteins, HSP70 in particular , and d) VPA promotes the directed differentiation of certain stem and progenitor cells.

·        Drug applications of VPA traditionally have been focused on control of epilepsy  and psychiatric disorders but intense research and clinical trials suggest that VPA will soon be included in combined treatments for multiple cancers, Parkinson’s Disease, Alzheimer’s Disease and probably a number of other conditions.  I do not think VPA by itself will cure such diseases but will be embodied in more-powerful treatment regimens.

·        VPA can act as an epigenetic switch for stem cell differentiation fate with possibly important implications for regenerative medicine.———————————————–

*          “The legend of the Phoenix has been around for centuries. There are a few variations, but the basic idea is this: The Phoenix is a supernatural creature, living for 1000 years. Once that time is over, it builds its own funeral pyre, and throws itself into the flames. As it dies, it is reborn anew, and rises from the ashes to live another 1000 years. Alternatively, it lays an egg in the burning coals of the fire which hatches into a new Phoenix, and the life cycle repeats(ref).”  In its earliest reincarnation, VPA’s herbal ancestor promoted peaceful sleep.  In its latest reincarnation VPA is an epigenetic modifier necessary for directed stem cell differentiation.  I don’t know how many other cycles of reincarnation it will have.

Most times when I meet old friends who I have not seen for a long time, the old magic comes back.  There is new vitality in our new context of relationship.  With certain other people met again after many years, memory of the original relationship sees to be the only thing we still have in common.  That person usually seems to me to have gone nowhere with his or her life and is not visibly going anywhere now.  He or she comes across to me now as having lost all vitality, and now we seem to have little in common except stale memories.  Our interaction is flat and listless and I usually don’t want to see that person again. 

 My relationship with the antagonistic pleiotropy theory of the cause of aging falls in the second category.  The theory has an impressive name to throw around in publications and cocktail parties, but that seems to be the main thing going for it.  I see it as a fuzzy obsolete theory of the impact of evolution on aging that is no longer particularly informative.  I expand on this theme in this blog entry and describe what I see to be the actual impact of evolution – genetic, epigenetic and social – on longevity.

What is antagonistic pleiotropy, anyway?

“The antagonistic pleiotropy hypothesis was first proposed by George C. Williams in 1957 as an explanation for senescence.^[1] Pleiotropy is the phenomenon where one gene controls for more than one phenotypic trait in an organism.^[2] Antagonistic Pleiotropy is when one gene controls for more than one trait where at least one of these traits is beneficial to the organism’s fitness and at least one is detrimental to the organism’s fitness.^[3] The theme of G.C. William’s idea about antagonistic pleiotropy was that if a gene caused both increased reproduction in early life and aging in later life, then senescence would be adaptive in evolution(ref).”

Here are some of the problems I have with Antagonistic Pleiotropy as it was formulated by Williams in ‘57

:a.      There are few if any genes that cause both increased reproduction in early life and aging in later life.  Multiple papers have been written on genes purported to exhibit Antagonistic Pleiotropy, P53 being among the favorites(ref)(ref).  The arguments in those papers tend to befuddle me.  Actually the FRAP1 gene involved in activation of the mTOR pathway is probably a better example(ref)(ref).  According to the 2010 paper Revisiting the antagonistic pleiotropy theory of aging: TOR-driven program and quasi-program: “A half century ago, the antagonistic pleiotropy (AP) theory had solved a mystery of aging, by postulating genes beneficial early in life at the cost of aging. Recently it was argued however that there are very few clear-cut examples of antagonistically pleiotropic (AP) genes other than p53. In contrast, here I discuss that p53 is not a clear-cut example of AP genes but is rather an aging-suppressor (gerosuppressor). In contrast, clear-cut examples of AP genes are genes that encode the TOR (target of rapamycin) pathway. TOR itself is the ultimate example of AP gene because its deletion is lethal in embryogenesis. Early in life the TOR pathway drives developmental program, which persists later in life as an aimless quasi-program of aging and age-related diseases.”

 b.     But how TOR operates later in life is highly variable involving many genes and a pathway that is still not fully understood.  The idea that any one gene “controls”an important aspect of normal aging is unsubstantiated although we know that mutations in certain genes like WRN can generate abnormal aging phenotypes(ref).  Single genes often influence multiple phenotypic traits of an organism, and most-commonly such traits are influenced by multiple genes.  One-to-one relationships between genes and complex traits such as are involved in normal aging are rare to nonexistent. 

 c.      The phenotypic traits resulting in part from the activation of any gene is strongly influenced by the state of the pathway the gene is in, and the degree of activation of other genes in that and other pathways having to do with the traits.  Whether activation occurs is affected by the epigenetic state of the cell concerned. Age of the organism is only one of multiple factors that determines whether gene activation occurs or its consequences.  

So, it makes no sense to hang “causation” of increased reproduction in early life or aging in later life on individual genes.  

Antagonistic Pleiotropy as formulated by Williams is too blunt and obsolete a way of looking at aging to be useful. I agree with the author of the 2004 paper Reflections on an unsolved problem of biology: the evolution of senescence and death who wrote  “It is suggested that the evolutionary theory of senescence should be focused on those evolutionary principles that have been validated experimentally, and that the notion of antagonistic pleiotropy–which cannot be experimentally validated–be dropped from our thinking about the evolution of senescence.”

A new look at what Antagonistic Pleiotropy was tryng to get at

The above having been said, I do think that something like a reformulation of the Antagonistic Pleiotropy hypothesis could be useful.  Here is how it would go:

1.     Genetic evolution, has operated in most species so as to such as to favor health of the young (animals who bear or still care for offsprings) over health of animals beyond the age where they care for their young.  (This says little more than that evolution favors the young over the aged, something we already know). 

2.     In humans at least, evolution viewed more broadly (genetic, social and epigenomic evolution) is changing the balance between health ­for-young vs health-for-old, maintaining health of humans in advanced societies for more years and leading to ever-longer life spans.

I articulated this theme in earlier blog posts, particularly in Social ethics of longevity and in Ever-increasing longevity– is epigenomics involved?   I repeat a few key passages from those blog entries regarding social evolution and epigenomic evolution.  And I show how this reformulation leads to very different conclusions than did the original theory.

Social evolution impacting longevity

‘The argument from evolution — goes like this:  Each species, humans included, has evolved characteristic life-spans designed to optimize the survival of that species taking into account resource limitations, a need for protection against predators and diseases, and environmental conditions.  Scarce resources need to be devoted to providing for the young and raising new generations and fighting off predators and diseases during the years of rearing the young.  According to this argument, need for individual survival diminishes after child-rearing years.  Younger animals are stronger and can better fight off predators and diseases than older ones. From the viewpoint of the human species, then, resources are better devoted to raising and protecting children than to keeping old people around, people who are no longer part of the reproductive-child-rearing cycle.  According to this argument, extending the lives of old people leads to a misallocation of resources that is counter to survival of the species.” 

“The problem with this argument is that it takes biological evolution into account but not social evolution.  The argument  does not take into account the ever-increasing complexity of our society, the ever-increasing requirement for education that is necessary to function well in society, the ever-increasing cost of rearing young including education, the increase in the time required for young people to become fully functional in society, and the need for people to spend more years working to cover the ever-growing costs for educating their young.  As social evolution advances at an exponentially increasing rate and society continues to become more complex, there is an ever-increasing need for people to draw on vast resources of information, deep knowledge and wisdom to survive and advance the society.  The time required for basic education continues to grow and continuing education becomes a lifelong necessity.   Longer life spans therefore serve the need of social evolution by increasing mobilization of knowledge and wisdom. 

In fact, social evolution has been working hard to extend our longevity in recent times.  A few hundred years ago people typically died before 40.  Now, life expectancy has roughly doubled, to about 78 for US males and 80 for females.  All the other typical age-marking numbers have also roughly doubled.  Once young males could join their fathers as hunters or warriors or farmers or artisans at the age of 15 and start fully contributing to society shortly thereafter.  About twice as much time (30 years) is now required in an advanced society for a male to become a doctor or lawyer or physicist, to become fully engaged in his profession, to get married and have children.  Females used to start having babies when they were biologically capable, around 15.  Now for educated Western women, the age is roughly 30.  The investment required for rearing a child has become enormous – $300,000 – $500,000 or more for a thirty year period when including the cost of preparatory education.  All this change has happened in less than 400 years.  The key thing to focus on is that the number of productive years – the years between completion of education and retirement – has doubled too. Instead of 20 good working years now the average is more like 40. 

So, social evolution requires longer life spans because people have to become ever more sophisticated to accommodate to ever more-complex social conditions.  Now as social evolution continues to accelerate at an exponential pace, it is appropriate that life spans also become extended at an accelerating rate.  That is what my work is about.

My main point is this:  as society becomes exponentially more complex, so a need arises for exponential growth in life expectancy.  Life extension is not about older people surviving unproductively longer in retirement communities in Florida or nursing homes.  It is about keeping an increasingly complex society workable.”

So, how does social evolution work to increase longevity? The answer is easier than it might seem.  All the things we do to increase health and longevity are part of our social evolution.  It is useful to recall that in 1850 the streets of London were ladened with fecal matter from horses and dogs and had open ditches running with human sewage.  Sanitation as we know it was nonexistent.  Wood fires in hundreds of thousands of fireplaces contributed mightily to air pollution. Syphylis was common as Victorian morals led to widespread prostitution. No wonder people died young!  All that is behind us now.  The second half of the 19^th century saw the recognition of the germ theory of disease and the building of the first sewage systems and water treatment plans.  The last 40 years saw a turning against cigarette smoking in advanced countries and thrusts for world-wide vaccinations against multiple killer diseases.  These and countless other developments contributed significantly to overall longevity.  Also contributing are improved diets, food safety laws, cleaning up remaining air pollution, seat belt laws, safer cars, elimination of lead paint, modern medicine and antibiotics.  And, in its own small way, this blog contributes to the distribution of knowledge making for greater health and longevity.  My writing and your reading and comments are part of that social evolution.

Epigenomic evolution affecting longevity

The entire field of gene regulation is new and existed in only very crude form when Williams formulated the original Antagonistic Pleiotropy theory.  But, gene regulation is all-important.  The same genes exist in your brain neuron cells, your red and white blood cells, in your heart, and in your toe muscle cells.  The difference between these cells are due to regulation of gene expression, not due to the genes themselves.  The same genes exist in the cells of an ambryo, the resultant child at the age of 2, the young adult of 22 and the same person at an old an of 90.  The resulting age phenotypes have also to do with gene regulation.  And an important determinant of gene regulation is the epigenetic/epigenomic state of the cell, including histone acetylation and DNA methylation patterns and other chromatin modifications.  These changes are present in our DNA but not in the genes themselves, result from the experience of the cell, typically vary with age, and are to some extent heritable.  For background, see the blog post Epigenetics, Epigenomics and Aging, and Histone acetylase and deacetylase inhibitors.   Clearly, epigenetic states have a great deal to do with disease suscptibility and aging.  See the blog post Epigenetics, inflammation, cancer, immune system, neurological and cardiovascular disease and aging. Regarding the heritability of epigenetic changes, you can check out the references in this list.

So, my hypothesis is that inheritable epigenomic changes are happening in our DNA that are leading to greater longevity.  I first put this suggestion forward in the blog entry Ever-increasing longevity– is epigenomics involved? which cites astounding increases in longevity throughout the developed world. 

Insofar as epigenomic modifications are heritable, they are subject to evolution just as genomic modifications are.  The important factor to emphasize in this discussion is that epigenomic evolution and social evolution happen on a much shorter time scale than genetic evolution.  Our genome is pretty much the same as it was millions of years ago but our social habits affecting longevity have changed drastically in the last 200 years and are continuing to evolve rapidly.  And epigenomic changes can be inherited from one generation to the next.  Why are kids who grow up in developing countries where there is newfound prosperity 6 inches to a foot taller than their parents?  The answer lies in social and epigenomic evolution.  For fun reading, see also my blog post Longevity Genes and Two Fantasies

Wrapping it up

If you accept the reformulation of Antagonistic Pleiotropy that I suggest above including consideration of social and epigenomic evolution, you come out with quite a different perspective consistent with what we experience:

·      Human physical evolution did not stop 2 million years ago; it appears to be accelerating.

·      Most of the new evolution results from social evolution and evoution in the epigenome, not in our genes

.·      The evolutionary process has been leading to altered bodytypes and longer lifespans in developed countries.

·      We can affect the evolutionary process individually and collectively through social activism and applying knowledge of health and longevity.

None of these statements are true for the original theory of Antagonistic Pleiotropy.  That is why I say we should stop torturing ourselves about this outdated conjecture and let it rest in its crypt in history where it belongs.

This blog entry is a companion and sequel to the previous one Neurogenesis, curcumin and longevity.  I focus here on the extensive research related to the anti-cancer properties of curcumin and go further into an issue raised in the last blog entry: does curcumin inhibit the mTOR pathway in humans and, if so, is curcumin a life extending substance due to mTOR in inhibition?

The research literature on curcumin and cancers

The research literature relating to curcumin and cancer is truly vast.  A search in the National Library of medicine database pubmed.org on the terms curcumin and cancer returns 1311 research abstracts of published literature.  Researchers in the field have little to no doubt as to the probable clinical usefulness of curcumin for preventing and treating cancers.  The new (Aug 19 2010) e-publication Curcumin in Cancer Chemoprevention: Molecular Targets, Pharmacokinetics, Bioavailability, and Clinical Trials makes the case very succinctly: “Curcumin (diferuloylmethane), a derivative of turmeric is one of the most commonly used and highly researched phytochemicals. Abundant sources provide interesting insights into the multiple mechanisms by which curcumin may mediate chemotherapy and chemopreventive effects on cancer. The pleiotropic role of this dietary compound includes the inhibition of several cell signaling pathways at multiple levels, such as transcription factors (NF-kappaB and AP-1), enzymes (COX-2, MMPs), cell cycle arrest (cyclin D1), proliferation (EGFR and Akt), survival pathways (beta-catenin and adhesion molecules), and TNF. Curcumin up-regulates caspase family proteins and down-regulates anti-apoptotic genes (Bcl-2 and Bcl-X(L)). In addition, cDNA microarrays analysis adds a new dimension for molecular responses of cancer cells to curcumin at the genomic level. Although, curcumin’s poor absorption and low systemic bioavailability limits the access of adequate concentrations for pharmacological effects in certain tissues, active levels in the gastrointestinal tract have been found in animal and human pharmacokinetic studies. Currently, sufficient data has been shown to advocate phase II and phase III clinical trials of curcumin for a variety of cancer conditions including multiple myeloma, pancreatic, and colon cancer.”

How much is known about the molecular mechanisms through which curcumin prevents or stops cancers?  The answer is the same as the answer to many questions relating to cancers and other critical diseases:  not enough to provide a complete answer, but actually quite a bit.  An excellent summary of the state of knowledge about a year ago is provided in the September 2009 publication Curcumin and Cancer Cells: How Many Ways Can Curry Kill Tumor Cells Selectively? “Cancer is a hyperproliferative disorder that is usually treated by chemotherapeutic agents that are toxic not only to tumor cells but also to normal cells, so these agents produce major side effects. In addition, these agents are highly expensive and thus not affordable for most. Moreover, such agents cannot be used for cancer prevention. Traditional medicines are generally free of the deleterious side effects and usually inexpensive. Curcumin, a component of turmeric (Curcuma longa), is one such agent that is safe, affordable, and efficacious. How curcumin kills tumor cells is the focus of this review. We show that curcumin modulates growth of tumor cells through regulation of multiple cell signaling pathways including cell proliferation pathway (cyclin D1, c-myc), cell survival pathway (Bcl-2, Bcl-xL, cFLIP, XIAP, c-IAP1), caspase activation pathway (caspase-8, 3, 9), tumor suppressor pathway (p53, p21) death receptor pathway (DR4, DR5), mitochondrial pathways, and protein kinase pathway (JNK, Akt, and AMPK). How curcumin selectively kills tumor cells, and not normal cells, is also described in detail.”

The above-mentioned paper is worth reading in detail for it summarizes a great deal of the knowledge available only piecewise in hundreds of other publications.  I quote further only highly selectively.  “Curcumin has a diverse range of molecular targets, supporting the concept that it acts upon numerous biochemical and molecular cascades. Curcumin physically binds to as many as 33 different proteins, including thioredoxin reductase, cyclooxygenase-2, (COX2), protein kinase C, 5-lipoxygenase (5-LOX), and tubulin. Various molecular targets modulated by this agent include transcription factors, growth factors and their receptors, cytokines, enzymes, and genes regulating cell proliferation, and apoptosis (6). Curcumin has been shown to inhibit the proliferation and survival of almost all types of tumor cells. Accumulating evidence suggests that the mode of curcumin-induced cell death is mediated both by the activation of cell death pathways and by the inhibition of growth/proliferation pathways (Table I; Refs. 28–173). Many studies indicate the selective role of curcumin towards cancer cells than normal cells (Table II). We could identify more than 40 biomolecules that are involved in cell death induced by curcumin (Fig. 1).  The mechanistic relationship among different signal transduction pathways, whether acting alone or together, leading to apoptosis is described. Because curcumin mediates its effect through multiple cell signaling pathways, the likelihood of developing resistance to it is less.” How these interrelated pathways are activated by curcumin is explained in the publication.

Curcumin and specific cancers

Interestingly, curcumin is active in killing cells of certain deadly cancers for which there are few or no known existing treatments.  One example is glioblastoma.  The August 2010 publication The anti-cancer efficacy of curcumin scrutinized through core signaling pathways in glioblastoma reports “Curcumin exhibits superior cytotoxicity on glioblastoma in a dose- and time-dependent manner in the MTT assay. In the core signaling pathways of glioblastoma, curcumin either significantly influences the p53 pathway by enhancing p53 and p21 and suppressing cdc2 or significantly inhibits the RB pathway by enhancing CDKN2A/p16 and suppressing phosphorylated RB. In the apoptotic pathway, the Bax and caspase 3 are significantly suppressed by curcumin and the Giemsa stain elucidates apoptotic features of DBTRG cells as well. In conclusion, curcumin appears to be an effective anti-glioblastoma drug through inhibition of the two core signaling pathways and promotion of the apoptotic pathway.”  Curcumin apart, there is no known cure for this disease which usually kills humans in less than a year after diagnosis.

Another cancer having cells that are killed by curcumin is Acute lymphoblastic leukemia (ALL), a disease that affects children as well as adults and is sure to be deadly unless treated with a complex and toxic chemotherapy regimen.  The 2008 publication Curcumin inhibits proliferation and induces apoptosis of leukemic cells expressing wild-type or T315I-BCR-ABL and prolongs survival of mice with acute lymphoblastic leukemia reports “Curcumin decreased c-Abl levels in cells expressing the wild, but not the mutant, BCR-ABL oncogene. Curcumin treatment resulted in a statistically significant improved survival in diseased mice along with decreasing white blood and GFP cell counts. — CONCLUSIONS: Curcumin is effective against leukemic cells expressing p210 BCR-ABL and T315I BCR-ABL and holds promise in treating BCR-ABL-induced B-ALL.”

Other publications relating curcumin to leukemias include:

–         (2006) Inhibitory effect of curcumin on MDR1 gene expression in patient leukemic cells. “In summary, curcumin decreased MDR1 mRNA level in patient leukemic cells, especially in high level of MDR1 gene groups. Thus, curcumin treatment may provide a lead for clinical treatment of leukemia patients in the future.”

–         (2006) Curcumin induces apoptosis via inhibition of PI3′-kinase/AKT pathway in acute T cell leukemias. “Taken together, our finding suggest that curcumin suppresses constitutively activated targets of PI3′-kinase (AKT, FOXO and GSK3) in T cells leading to the inhibition of proliferation and induction of caspase-dependent apoptosis.”

–         (2006) Inhibitory effect of curcumin on WT1 gene expression in patient leukemic cells. “In summary, curcumin decreased WT1 mRNA in patient leukemic cells. Thus, curcumin treatment may provide a lead for clinical treatment in leukemic patients in the future.”

–         (2004) Nitric oxide is synthesized in acute leukemia cells after exposure to phenolic antioxidants and initially protects against mitochondrial membrane depolarization.

Curcumin has been tested against a large number of cancer types.  For example, curcumin offers promise for preventing prostate cancer.  The 2010 publication Chemopreventive potential of curcumin in prostate cancer reports “The long latency and high incidence of prostate carcinogenesis provides the opportunity to intervene with chemoprevention in order to prevent or eradicate prostate malignancies. We present here an overview of the chemopreventive potential of curcumin (diferuloylmethane), a well-known natural compound that exhibits therapeutic promise for prostate cancer. In fact, it interferes with prostate cancer proliferation and metastasis development through the down-regulation of androgen receptor and epidermal growth factor receptor, but also through the induction of cell cycle arrest. It regulates the inflammatory response through the inhibition of pro-inflammatory mediators and the NF-kappaB signaling pathway. These results are consistent with this compound’s ability to up-induce pro-apoptotic proteins and to down-regulate the anti-apoptotic counterparts. Alone or in combination with TRAIL-mediated immunotherapy or radiotherapy, curcumin is also reported to be a good inducer of prostate cancer cell death by apoptosis. Curcumin appears thus as a non-toxic alternative for prostate cancer prevention, treatment or co-treatment.”

A search in pubmed.org using the terms “curcumin” and “breast cancer” surfaces 144 research citations.  The blog posts On Cancer stem cells and Update on cancer stem cells suggests the importance of cancer stem cells and the need to target such cells if a cancer therapy is to be effective.  The August 2010 publication Targeting breast stem cells with the cancer preventive compounds curcumin and piperine reports “The cancer stem cell hypothesis asserts that malignancies arise in tissue stem and/or progenitor cells through the dysregulation or acquisition of self-renewal. In order to determine whether the dietary polyphenols, curcumin, and piperine are able to modulate the self-renewal of normal and malignant breast stem cells, we examined the effects of these compounds on mammosphere formation, expression of the breast stem cell marker aldehyde dehydrogenase (ALDH), and Wnt signaling. Mammosphere formation assays were performed after curcumin, piperine, and control treatment in unsorted normal breast epithelial cells and normal stem and early progenitor cells, selected by ALDH positivity. Wnt signaling was examined using a Topflash assay. Both curcumin and piperine inhibited mammosphere formation, serial passaging, and percent of ALDH+ cells by 50% at 5 microM and completely at 10 microM concentration in normal and malignant breast cells. There was no effect on cellular differentiation. Wnt signaling was inhibited by both curcumin and piperine by 50% at 5 microM and completely at 10 microM. Curcumin and piperine separately, and in combination, inhibit breast stem cell self-renewal but do not cause toxicity to differentiated cells. These compounds could be potential cancer preventive agents.”  Piperine is a compound derived from black pepper commonly added to commercial curcumin supplements to enhance their bioavailability. It is what gives black pepper its zing.

Curcumin analogs and curcumin nanoparticles

Pharmaceutical companies have been investigating the therapeutic values of curcumin analogs as cancer treatments.  Viewed positively, such analogs might be engineered to be more powerful and bioavailable than curcumin itself.  Viewed cynically, drug companies are interested in analogs because there is no money for them to be made from curcumin itself because it is so commonly available, cheap, and not patentable.  One such analog molecule is the subject of the 2010 research report The small molecule curcumin analog FLLL32 induces apoptosis in melanoma cells via STAT3 inhibition and retains the cellular response to cytokines with anti-tumor activity.  “CONCLUSIONS: These data suggest that FLLL32 represents a lead compound that could serve as a platform for further optimization to develop improved STAT3 specific inhibitors for melanoma therapy.”  Other curcumin analogs being explored are PAC and a number of heterocyclic cyclohexanone analogues.   Other approaches drug companies are exploring to add-value to curcumin for treating cancers includes use of curcumin-containing nanoparticles and microparticles(ref)(ref)(ref).  I am not clear how much additional value for patients or ordinary people the analogs or nanoparticle formulations provide beyond that in plain curcumin, if any.  Obviously, since the analogs and nanoparticle formulations are proprietary, they could be very valuable to the pharmaceutical companies that own them if they could be made popular in the medical community.

Hundreds of additional current publications can be found relating curcumin to other specific types of cancer.  Titles of some representative 2010 publications include:

–         Nicotine-induced survival signaling in lung cancer cells is dependent on their p53 status while its down-regulation by curcumin is independent.

–         Apoptosis of human lung cancer cells by curcumin mediated through up-regulation of “growth arrest and DNA damage inducible genes 45 and 153”. 

–         [Curcumin promoted the apoptosis of cisplain-resistant human lung carcinoma cells A549/DDP through down-regulating miR-186*]

–         Curcumin induces apoptosis in human non-small cell lung cancer NCI-H460 cells through ER stress and caspase cascade- and mitochondria-dependent pathways. 

–         Curcumin promotes apoptosis in A549/DDP multidrug-resistant human lung adenocarcinoma cells through an miRNA signaling pathway.

–         Curcumin enhances dasatinib-induced inhibition of growth and transformation of colon cancer cells.

–         Epigenetic therapy of lymphoma using histone deacetylase inhibitors.

–         Curcumin selectively induces apoptosis in cutaneous T-cell lymphoma cell lines and patients’ PBMCs: potential role for STAT-3 and NF-kappaB signaling. 

–         Systemic administration of polymeric nanoparticle-encapsulated curcumin (NanoCurc) blocks tumor growth and metastases in preclinical models of pancreatic cancer 

–         Development of curcumin as an epigenetic agent.

–         Inhibition of NFkappaB and pancreatic cancer cell and tumor growth by curcumin is dependent on specificity protein down-regulation. 

–         Chemoprevention strategies for pancreatic cancer.

–         Safety and pharmacokinetics of a solid lipid curcumin particle formulation in osteosarcoma patients and healthy volunteers.

–         Reversal of multidrug resistance by curcumin through FA/BRCA pathway in multiple myeloma cell line MOLP-2/R. 

–         Thioredoxin reductase-1 mediates curcumin-induced radiosensitization of squamous carcinoma cells. 

–         Therapeutic efficacy evaluation of curcumin on human oral squamous cell carcinoma xenograft using multimodalities of molecular imaging

–         Colon targeted curcumin delivery using guar gum 

–         Possible action mechanism for curcumin in pre-cancerous lesions based on serum and salivary markers of oxidative stress.

I could go on and list many more relevant 2010 publications.  The simple point is that there is a great deal of current research relating to curcumin as a preventative of or treatment for cancers and a large accumulated body of research knowledge in these areas. 

Clinical trials of curcumin related to cancers

The government database of clinical trials responded to the query “curcumin cancer” with 25 trials.  The list of trials that was retrieved is here.  Looking over the list, I remark that few of the trials head-on address the effectiveness of the substance against a cancer, like the Trial of Curcumin in Advanced Pancreatic Cancer (in the recruiting phase).  Several of the trials look at the effectiveness of curcumin in combination with other substances or drugs, like the trial Phase III Trial of Gemcitabine, Curcumin and Celebrex in Patients With Metastatic Colon Cancer (not yet recruiting), And most of the completed trials are either initial safety/dosage studies or remain not-yet reported in the literature.

More on curcumin, mTOR and life extension

In the past blog entries Longevity genes, mTOR and lifespan, Viva mTOR! Caveat mTOR! and More mTOR links to aging theories and in my treatise, I described how the mTOR pathways appears to be highly conserved across species and how in primitive species as well as mice, inhibition of mTOR signaling is an effective strategy for extending longevity as well as addressing many disease processes.  In my treatise one of the advanced “candidate” aging theories is Increasing mTOR signaling which happens with aging.

I have discussed mTOR in those documents at some length and have speculated on the question of whether human longevity might be extended by somehow chemically inhibiting the mTOR pathway.  mTOR stands for mammalian target of rapamycin and the drug rapamycin inhibits the pathway and can extend the lives of mice.  Rapamycin has certain toxicities however, making it unsuitable for sustained human consumption.  In the most-recent blog post Neurogenesis, curcumin and longevity I reported on how a key researcher of curcumin’s neurological effects thought that curcumin might inhibit the mTOR pathway and I quoted from a research report that indicates that this is indeed the case.

Additional credence to the concept that curcumin inhibits mTOR signaling can be found in other publications.  I came across a relevant passage in the 2009 publication mentioned above Curcumin and Cancer Cells: How Many Ways Can Curry Kill Tumor Cells Selectively? “mTOR regulates Akt activity, a crucial downstream effector in the PI-3K–PTEN pathway, which controls cell proliferation and survival. Targeting this function of mTOR may also have therapeutic potential. For example, curcumin was shown to inhibit the Akt/mammalian target of rapamycin/p70 ribosomal protein S6 kinase pathway and activate the extracellular-signal-regulated kinases (ERK) 1/2, thereby inducing autophagy (118).”  The reference is to the 2007 publication Roles of the Akt/mTOR/p70S6K and ERK1/2 signaling pathways in curcumin-induced autophagy.  “We previously demonstrated that curcumin induced non-apoptotic autophagic cell death in malignant glioma cells in vitro and in vivo. This compound inhibited the Akt/mammalian target of rapamycin/p70 ribosomal protein S6 kinase pathway and activated the extracellular signal-regulated kinases 1/2 thereby inducing autophagy.”

A relevant July 2010 publication is Curcumin Extends Life Span, Improves Health Span, and Modulates the Expression of Age-Associated Aging Genes in Drosophila melanogaster.  “Results: We report that curcumin extended the life span of two different strains of D. melanogaster (fruit flies), an effect that was accompanied by protection against oxidative stress, improvement in locomotion, and chemopreventive effects. Life span extension was gender and genotype specific. Curcumin also modulated the expression of several aging-related genes, including mth, thor, InR, and JNK. — Conclusions: The observed positive effects of curcumin on life span and health span in two different D. melanogaster strains demonstrate a potential applicability of curcumin treatment in mammals. The ability of curcumin to mitigate the expression levels of age-associated genes in young flies suggests that the action of curcumin on these genes is a cause, rather than an effect, of its life span–extending effects.”

Going beyond fruit flies, rapamycin fed late in life to genetically heterogeneous mice increases both their median and maximal lifespans, by an average of 14% for females and 9% for males(ref).  If curcumin happens to be doing the same for me by controlling mTOR expression as well as by keeping cancers and neurological deterioration at bay, I would be grateful for the additional 7-8 years due to taking this one supplement alone.  Of course I am also taking a lot of other supplements and pursuing an anti-aging lifestyle program, so the results are likely to be synergistic though far too complex to allow prediction of how long I may live .

Wrapping it up

A group of researchers with Indian-sounding names at the University of Texas were perhaps expressing frustration with Western Medicine when they wrote in the 2008 publication Curcumin and cancer: an “old-age” disease with an “age-old” solution: “Cancer is primarily a disease of old age, and that life style plays a major role in the development of most cancers is now well recognized. While plant-based formulations have been used to treat cancer for centuries, current treatments usually involve poisonous mustard gas, chemotherapy, radiation, and targeted therapies. While traditional plant-derived medicines are safe, what are the active principles in them and how do they mediate their effects against cancer is perhaps best illustrated by curcumin, a derivative of turmeric used for centuries to treat a wide variety of inflammatory conditions. Curcumin is a diferuloylmethane derived from the Indian spice, turmeric (popularly called “curry powder”) that has been shown to interfere with multiple cell signaling pathways, including cell cycle (cyclin D1 and cyclin E), apoptosis (activation of caspases and down-regulation of antiapoptotic gene products), proliferation (HER-2, EGFR, and AP-1), survival (PI3K/AKT pathway), invasion (MMP-9 and adhesion molecules), angiogenesis (VEGF), metastasis (CXCR-4) and inflammation (NF-kappaB, TNF, IL-6, IL-1, COX-2, and 5-LOX). The activity of curcumin reported against leukemia and lymphoma, gastrointestinal cancers, genitourinary cancers, breast cancer, ovarian cancer, head and neck squamous cell carcinoma, lung cancer, melanoma, neurological cancers, and sarcoma reflects its ability to affect multiple targets. Thus an “old-age” disease such as cancer requires an “age-old” treatment.”

A funny thing happens to curcumin on its way to the clinic

Wrapping it up, curcumin is non-toxic and without side effects at reasonable doses, inexpensive and easily available.  The complex biomolecular pathways through which it exercises its anti-cancer effects are fairly well understood and being further explored in many laboratories.  It kills multiple types of cancer cells.  Its anti-cancer actions appear to be preventative as well as therapeutic.  Because it operates through many parallel biological channels, cancers cannot readily evolve to neutralize its effects.  It has been used as a traditional medicine for centuries and the countries in which it is heavily consumed have low rates of cancer.  And the research case for basing cancer therapies on curcumin appears to becoming ever-stronger as time progresses.  Perhaps curcumin is even life-extending if regularly taken by humans.

For years, researcher after researcher has declared that cancer therapies can likely be designed based on use of curcumin.  Yet, this substance has not entered mainline clinical practice and probably most oncologists don’t know about it or would not think of prescribing it.  The journals oncologists read may talk about complex, expensive and toxic chemotherapy regimens, but will likely not discuss curcumin which is still regarded by many to be a “folk remedy.” This is the situation despite the vast amounts of solid research on the substance using the most contemporary approaches of molecular biology, genomics and the other “omics.”  One reason for this situation appears to be lack of large-scale clinical trial evidence for curcumin’s anti-cancer efficacy.  This in turn is strongly correlated with the fact that drug companies won’t sponsor clinical trials of plain curcumin because they can’t make any money from selling it. 

Yet, awareness of the potentials of curcumin is slowly expanding.  It took the medical community some 40 years to acknowledge the pluripotent health activities of Vitamin D and embrace its use.   Hopefully, recognition of the health and longevity values of curcumin will happen a lot faster than that.

MEDICAL DISCLAIMER

FROM TIME TO TIME, THIS BLOG DISCUSSES DISEASE PROCESSES.  THE INTENTION OF THOSE DISCUSSIONS IS TO CONVEY CURRENT RESEARCH FINDINGS AND OPINIONS, NOT TO GIVE MEDICAL ADVICE.  THE INFORMATION IN POSTS IN THIS BLOG IS NOT A SUBSTITUTE FOR A LICENSED PHYSICIAN’S MEDICAL ADVICE. IF ANY ADVICE, OPINIONS, OR INSTRUCTIONS HEREIN CONFLICT WITH THAT OF A TREATING LICENSED PHYSICIAN, DEFER TO THE OPINION OF THE PHYSICIAN. THIS INFORMATION IS INTENDED FOR PEOPLE IN GOOD HEALTH.  IT IS THE READER’S RESPONSIBILITY TO KNOW HIS OR HER MEDICAL HISTORY AND ENSURE THAT ACTIONS OR SUPPLEMENTS HE OR SHE TAKES DO NOT CREATE AN ADVERSE REACTION.

I have discussed both neurogenesis and curcumin in my treatise and in numerous blog entries but have never examined their relationship.  This blog entry is about the actions of curcumin in promoting neurogenesis in the hippocampus and highly-likely mental-health implications of taking curcumin supplements.  Finally, I touch on something else that is new – on how curcumin might possibly contribute to longevity by inhibiting mTOR pathway signaling.

Background on neurogenesis and curcumin

Prior to 1999, scientific dogma said that the adult supply of brain cells could not be replenished.  Once brain cells died they were irrevocably lost. Then in 1999 researchers at Princeton University reported in the Oct. 15 issue of Science that in adultprimates “the formation of new neurons or nerve cells — neurogenesis — takes place in several regions of the cerebral cortex that are crucial for cognitive and perceptual functions(ref).” 

An introductory discussion of neurogenesis can be found in my treatise in the section on the Neurological degeneration theory of aging. “Increasing research evidence suggests that maintaining a sufficient and consistent rate of neurogenesis in the brain, particularly in the hippocampus, is important for the maintenance of cognitive health. Insufficient or irregular neurogenesis is thought to be a causative factor in bipolar disease and other mood disorders. Neurogenesis takes place throughout the life of a mammal in two major brain structures: the dentate gyrus of the hippocampus and the subventricular zone of the forebrain. In these regions neural progenitor cells continuously divide and give birth to new neurons and glial cells. In the mammalian brain neural progenitor cells are multipotent. They can differentiate into neurons, astrocytes or oligodendrocytes, though the factors that determine differentiation are poorly understood. The rate of neurogenesis tends to decline with advancing age in old mammals, as well as the does the number of functional neurons.”

Also, see the discussion of neurogenesis with respect to lifestyle and diet in the Neurological Degeneration Firewall section and in the blog posts Mental exercise and dementia in the news again and Brain fitness, Google and comprehending longevity. Finally, a blog post relevant to the actions of curcumin discussed below is BDNF gene – personality, mental balance, dementia, aging and epigenomic imprinting.

If you do a search in this blog or in my treatise for curcumin, you will see that it long has been one of the favorite substances in my anti-aging firewall regimen for good reasons: it is anti-inflammatory, it is known to combat numerous cancers, it inhibits the expression of NF-kappaB, it can help regulate P53, P21, CASP9 and other genes which control apoptosis, inhibition of cell growth and cell cycle arrest so as to maintain a line of cells in a healthy state, it is a COX-2 enzyme inhibitor, it protects against bone loss, it chelates heavy metals – and the list goes on and on.  The actions of this substance are complex.  For example, it appears that curcumin acts to control the proliferation of neurogliaoma cells by modulating gene expression related to at least four different pathways: oxidative stress, cell cycle control, and DNA transcription and metabolism(ref).  

Quoting from the 2007 publication Curcumin: the Indian solid gold “Curcumin exhibits activities similar to recently discovered tumor necrosis factor blockers (e.g., HUMIRA, REMICADE, and ENBREL), a vascular endothelial cell growth factor blocker (e.g., AVASTIN), human epidermal growth factor receptor blockers (e.g., ERBITUX, ERLOTINIB, and GEFTINIB), and a HER2 blocker (e.g., HERCEPTIN). Considering the recent scientific bandwagon that multitargeted therapy is better than monotargeted therapy for most diseases, curcumin can be considered an ideal “Spice for Life”.”

Neuroprotective effects of curcumin

The 2005 publication Dietary curcumin counteracts the outcome of traumatic brain injury on oxidative stress, synaptic plasticity, and cognition relates to the effects of but not the process of neurogenesis in rat’s brains.  “Here, we evaluated the capacity of the powerful antioxidant curry spice curcumin ingested in the diet to counteract the oxidative damage encountered in the injured brain. In addition, we have examined the possibility that dietary curcumin may favor the injured brain by interacting with molecular mechanisms that maintain synaptic plasticity and cognition. The analysis was focused on the BDNF system based on its action on synaptic plasticity and cognition by modulating synapsin I and CREB. Rats were exposed to a regular diet or a diet high in saturated fat, with or without 500 ppm curcumin for 4 weeks (n = 8/group), before a mild fluid percussion injury (FPI) was performed. The high-fat diet has been shown to exacerbate the effects of TBI on synaptic plasticity and cognitive function. Supplementation of curcumin in the diet dramatically reduced oxidative damage and normalized levels of BDNF, synapsin I, and CREB that had been altered after TBI. Furthermore, curcumin supplementation counteracted the cognitive impairment caused by TBI. These results are in agreement with previous evidence, showing that oxidative stress can affect the injured brain by acting through the BDNF system to affect synaptic plasticity and cognition.”

The 2007 publication NEUROPROTECTIVE EFFECTS OF CURCUMIN elaborates further. “Neurodegenerative diseases result in the loss of functional neurons and synapses. Although future stem cell therapies offer some hope, current treatments for most of these diseases are less than adequate and our best hope is to prevent these devastating diseases. Neuroprotective approaches work best prior to the initiation of damage, suggesting that some safe and effective prophylaxis would be highly desirable. Curcumin has an outstanding safety profile and a number of pleiotropic actions with potential for neuroprotective efficacy, including anti-inflammatory, antioxidant, and anti-protein-aggregate activities. These can be achieved at sub-micromolar levels. Curcumin’s dose–response curves are strongly dose dependent and often biphasic so that in vitro data need to be cautiously interpreted; many effects might not be achievable in target tissues in vivo with oral dosing. However, despite concerns about poor oral bioavailability, curcumin has at least 10 known neuroprotective actions and many of these might be realized in vivo. Indeed, accumulating cell culture and animal model data show that dietary curcumin is a strong candidate for use in the prevention or treatment of major disabling age-related neurodegenerative diseases like Alzheimer’s, Parkinson’s, and stroke.” The 2009 publication Neuroprotective effects of curcumin (with the same title but by different authors) carries the same message forward. 

The 2009 publication Protective effect of curcumin against intracerebral streptozotocin induced impairment in memory and cerebral blood flow relates: “AIMS: The aim of the present study is to investigate the effect of curcumin on cerebral blood flow (CBF), memory impairment, oxidative stress and cholinergic dysfunction in intracerebral (IC) streptozotocin (STZ) induced memory impairment in mice.  MAIN METHODS: Memory impairment was induced by STZ (0.5mg/kg, IC) administered twice with an interval of 48h in mice. Memory function was assessed by Morris water maze and passive avoidance test. CBF was measured by Laser Doppler Flowmetry (LDF). To study the preventive effect, curcumin (10, 20 and 50mg/kg, PO) was administered for 21days starting from the first dose of STZ. In another set of experiment, curcumin was administered for 7days from 19th day after confirming STZ induced dementia to observe its therapeutic effect. Biochemical parameters of oxidative stress and cholinergic function were estimated in brain on day 21.  KEY FINDINGS: The major finding of this study is that STZ (IC) caused a significant reduction in CBF along with memory impairment, cholinergic dysfunction and enhanced oxidative stress. Curcumin dose dependently improved CBF in STZ treated mice together with amelioration of memory impairment both in preventive and therapeutic manner.  SIGNIFICANCE: The present study clearly demonstrates the beneficial effects of curcumin, the dietary staple of India, on CBF, memory and oxidative stress which can be exploited for dementia associated with age related vascular and neurodegenerative disorders.”

Neurogenesis and curcumin

The researchers back in 1999 used a chemical BrdU as a marker of neurogenesis.  “When cells are exposed to BrdU during cell division, the chemical becomes incorporated into the DNA of newly formed cells. The researchers injected BrdU into rhesus monkeys, whose brain structure is fundamentally similar to that of humans. Then, at intervals ranging from two hours to seven weeks, they looked for evidence of the chemical in neurons in the cerebral cortex. In all cases, there were neurons with BrdU in their DNA, which showed that those cells had to have been formed after the BrdU injection(ref).”  Similarly BrdU measurements have been used to establish that chronic intake of curcumin promotes neurogenesis in the hippocampus of rat’s brains.   

The 2007 research report Curcumin reverses impaired hippocampal neurogenesis and increases serotonin receptor 1A mRNA and brain-derived neurotrophic factor expression in chronically stressed rats  reports “The aim of this study was to investigate the effects of curcumin on hippocampal neurogenesis in chronically stressed rats. We used an unpredictable chronic stress paradigm (20 days) to determine whether chronic curcumin treatment with the effective doses for behavioral responses (5, 10 and 20 mg/kg, p.o.), could alleviate or reverse the effects of stress on adult hippocampal neurogenesis. Our results suggested that curcumin administration (10 and 20 mg/kg, p.o.) increased hippocampal neurogenesis in chronically stressed rats, similar to classic antidepressant imipramine treatment (10 mg/kg, i.p.). Our results further demonstrated that these new cells mature and become neurons, as determined by triple labeling for BrdU and neuronal- or glial-specific markers. In addition, curcumin significantly prevented the stress-induced decrease in 5-HT1A mRNA and BDNF protein levels in the hippocampal subfields, two molecules involved in hippocampal neurogenesis. These results raise the possibility that increased cell proliferation and neuronal populations may be a mechanism by which curcumin treatment overcomes the stress-induced behavioral abnormalities and hippocampal neuronal damage. Moreover, curcumin treatment, via up-regulation of 5-HT1A receptors and BDNF, may reverse or protect hippocampal neurons from further damage in response to chronic stress, which may underlie the therapeutic actions of curcumin.” 

One of the authors of this paper is William Ogle who made a presentation on curcumin and neurogenesis at the Ellison Medical Foundation’s Colloquium on the Biology of Aging at Woods Hole which I attended the week before last.  His slides indicate:

·        Triple labeling indicated that the BrdU-positive cells observed after curcumin administration to stressed rats indeed matured into neurons.

·        “Neurogenesis in the adult hippocampus is regulated by chronic stress.  Curcumin regulated the stress-induced decrease in progenitor cell differentiation, indicating that it can increase hippocampal neurogenesis in stressed rats.”

·        “Curcumin significantly prevented the stress-induced decrease in 5HT1A mRNA and bdnf protein levels in the hippocampus, two molecules implicated in neurogenesis.”

·        The degree of improvement of water-maze learning curves of restraint-stressed rats fed curcumin appears to be dose-dependent.  Trials were conducted after stressed animals were fed curcumin for 21 days.  Dose-dependent performance improvements were also observed in the latency time required to reach the maze platform and the number of platform crossings.  Best results were obtained at a dose of 20mg/kilogram.

·        Similarly, the corticosterol levels in stressed rats was reduced by curcumin administration, also in a dose-dependent manner.  (Corticosterol is the steroid hormone hydrocortisone which is released in response to stress.  It suppresses the immune system and its frequent activation is thought to be life-shortening.)  At the highest level of curcumin administration, the corticosterol level was reduced by more than half.

·        Curcumin also has an effect on reducing corticosterol-induced death in hippocampal neurons, although dose-dependency is not so striking.

·        Curcumin also has a striking dose-dependent effect in reducing CaMKII and pCaMKII expression in corticosterol-treated hippocampal neurons.  The same can be said for reducing NMDA-R2B mRNA expression.

·        Curcumin-driven neurogenesis in can be seen visibly in representative Golgi-impregnated pyramidal cells for rats from each of the groups taken from the hippocampal CA3 region.·        “Curcumin reduces impaired spatial memory under conditions of chronic stress.”

·        “Curcumin prevents dendritic hippocampal remodeling under conditions of chronic stress.”

·        “Curcumin blocks corticosterone-induced toxicity in primary hippocampal neurons.”

·        “Corticosterone-induced phosphorylation of CaMKII is blocked by curcumin in primary hippocampal neurons.”

·        “ Curcumin prevents corticosterone-induced increase in NMDA-R mRNA expression in primary hippocampal regions. 

Curcumin’s effect on stress are mediated in part by the 5-HT1 and 5-HT2 receptors as discussed in the 2008 paper The antidepressant effects of curcumin in the forced swimming test involve 5-HT1 and 5-HT2 receptors and the 210 paper Differential involvement of 5-HT(1A) and 5-HT(1B/1D) receptors in human interferon-alpha-induced immobility in the mouse forced swimming test.

Curcumin – an inhibitor of mTOR signaling?

Finally, in his presentation at Woods Hole, Ogle speculated that curcumin could possibly act as a mimetic of rapamycin and thus inhibit expression of mTOR.  The speculation is based on the molecular structure similarity of the two substances as well as on the health-producing effects of curcumin.  Inhibition of mTOR signaling is one of the very few approaches known to provide significant life extension.  See the blog entries Longevity genes, mTOR and lifespan, Viva mTOR! Caveat mTOR! and More mTOR links to aging theories. 

Considerable weight is given to the speculation by the research reported in the 2010 publication Curcumin Disrupts the Mammalian Target of Rapamycin-Raptor Complex. “Recently, we have shown that curcumin inhibits phosphorylation of p70 S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1), two downstream effector molecules of the mammalian target of rapamycin complex 1 (mTORC1) in numerous cancer cell lines. This study was designed to elucidate the underlying mechanism. We observed that curcumin inhibited mTORC1 signaling not by inhibition of the upstream kinases, such as insulin-like growth factor 1 receptor (IGF-IR) and phosphoinositide-dependent kinase 1 (PDK1). Further, we found that curcumin inhibited mTORC1 signaling independently of protein phosphatase 2A (PP2A) or AMP-activated protein kinase AMPK-tuberous sclerosis complex (TSC). This is evidenced by the findings that curcumin was able to inhibit phosphorylation of S6K1 and 4E-BP1 in the cells pretreated with PP2A inhibitor (okadaic acid) or AMPK inhibitor (compound C), or in the cells expressing dominant-negative (dn) PP2A, shRNA to PP2A-A subunit, or dn-AMPKα. Curcumin did not alter the TSC1/2 interaction. Knockout of TSC2 did not affect curcumin inhibition of mTOR signaling. Finally, we identified that curcumin was able to dissociate raptor from mTOR, leading to inhibition of mTORC1 activity. Therefore, our data indicate that curcumin may represent a new class of mTOR inhibitor.”  This research is based on working with cancer cells but the conclusions are likely to apply to normal cells as well.

I would certainly like it if curcumin is indeed an mTOR inhibitor in normal cells and therefore a major contributor to my longevity.  In any event, the research reported here says it is highly likely that curcumin contributes to neurogenesis and maintenance of mental acuity in older people like me.  Curcumin remains a central component of my anti-aging firewalls combined supplement regimen.  

You can probably expect to hear a lot about PGC-1-alpha as time goes on because this remarkable substance is turning out to have a lot to do with health and longevity.  It appears to be the mediator of the health benefits produced by exercise. This blog post is about PGC-1-alpha, about its relationship to exercise, and about efforts to stimulate it with various substances, in essence seeing if it is possible to provide “exercise in a pill.”

PGC-1-alpha and the PPARG gene

PGC-1-alpha is a gene co-activator, necessary to turn on the PPARG gene and essential in the metabolic process.  PGC-1-alpha (Peroxisome proliferator-activated receptor gamma coactivator 1-alpha)  “is a protein that in humans is encoded by the PPARGC1A gene.^[1] The protein encoded by this gene is a transcriptional coactivator that regulates the genes involved in energy metabolism. This protein interacts with the nuclear receptor PPAR-gamma, which permits the interaction of this protein with multiple transcription factors. This protein can interact with, and regulate the activities of, cAMP response element binding protein (CREB) and nuclear respiratory factors (NRFs). It provides a direct link between external physiological stimuli and the regulation of mitochondrial biogenesis, and is a major factor that regulates muscle fiber type determination. This protein may be also involved in controlling blood pressure, regulating cellular cholesterol homoeostasis, and the development of obesity(ref).^[2]”

The nuclear receptor PPAR-gamma “is a regulator of adipocyte differentiation.  — PPAR-gamma has been implicated in the pathology of numerous diseases including obesity, diabetes, atherosclerosis and cancer. PPAR-gamma agonists have been used in the treatment of dyslipidaemia and hyperglycemia.^[7] PPAR-gamma decreases the inflammatory response of many cardiovascular cells, particularly endothelial cells.^[8] PPAR-gamma activates the PON1 gene, increasing synthesis and release of paraoxonase 1 from the liver, reducing atherosclerosis ^[9] (ref).”

Exercise increases PGC-1-alpha expression

In the April 2010 blog entry AMPK and longevity, I touched on the role of AMPK in exercise and quoted the 2009 publication Brief intense interval exercise activates AMPK and p38 MAPK signaling and increases the expression of PGC-1alpha in human skeletal muscle reports “We tested the hypothesis that an acute session of intense intermittent cycle exercise would activate signaling cascades linked to mitochondrial biogenesis in human skeletal muscle — We conclude that signaling through AMPK and p38 MAPK to PGC-1-alpha may explain in part the metabolic remodeling induced by low-volume intense interval exercise, including mitochondrial biogenesis and an increased capacity for glucose and fatty acid oxidation.”

Production of PGC-1-alpha in cells is stimulated by physical activity and exercise, the presence of cold, glucagon and reactive oxygen species.  So, a swim I had last night in the cool waters of Lake Winnipesaukee had a double or triple effect both in making me feel good and rejuvenating my mitochondria with PGC-1-alpha.

PGC-1-alpha in white fat and brown fat

The difference between white fat, based on white adipocytes, and brown fat, based on brown adipocytes, was introduced in the blog entry Getting skinny from brown fat.  I said “Brown fat, long known to exist plentifully in babies and rodents, is rich in turned-on mitochondria and blood vessels.  Unlike white fat, brown fat burns energy at a ferocious rate.  In adults, however, it tends to be scarce and concentrated around the neck and has been traditionally thought to play a relatively minor role in adult human metabolism.  The newer research suggests a different picture.  Brown fat can be very important for metabolism.”  In general, white adipocytes store energy, have few mitochondria, are pro-inflammatory , and manifest in obesity.  While brown adipocytes dissipate energy, are dense in mitochondria and function to prevent or reduce obesity.  Further,  the mitochondria in brown fat contain UCP-1 while those in white fat do not(Note 1). UCP-1 “is an uncoupling protein found in the mitochondria of brown adipose tissue (BAT). It is used to generate heat by non-shivering thermogenesis. Non-shivering thermogenesis is the primary means of heat generation in hibernating mammals and in human infants(ref).” 

PGC-1-alpha seems to play important roles in the metabolism of both white and white and brown fat.   The 2005 publication PGC-1-alpha, a transcriptional coactivator involved in metabolism states “PPARgamma coactivator-1-alpha (PGC-1-alpha), in cooperation with several transcription factors, has emerged as a key regulator of several aspects of mammalian energy metabolism including mitochondrial biogenesis, adaptive thermogenesis in brown adipose tissue, glucose uptake, fiber type-switching in skeletal muscle, gluconeogenesis in liver and insulin secretion from pancreas. Recent studies have shown a reduced expression of PGC-1-alpha in skeletal muscle of diabetic and prediabetic humans. Moreover, expression of PGC-1-alpha in white fat cells activates a broad program of adaptive thermogenesis characteristic of brown fat cells.”

PGC-1-alpha turns on the biogenesis of mitochondria primarily in brown fat, working through NRF1, NRF2 and ERRalpha.  It promotes fatty acid oxidation working through the PPARs and RXRs, NRF1 and NRF2, combats ROS and promotes glucose utilization, promotes oxidative phosphorylation working via NRF2 and ERRalpha, promotes angiogenesis working through ERRalpha, and contributes to fiber-type switching(Note1).

Effects of elevating the expression of PGC-1-alpha

PGC-1-alpha protects against denervation-induced muscle wasting such as induced by BF-kappaB activation(ref)(note1).  Muscle PGC-1alpha blocks age-related obesity and age-related sarcopenia.  The 2009 publication Increased muscle PGC-1-alpha expression protects from sarcopenia and metabolic disease during aging highlights the significance of maintaining PGC1-alpha levels for general health and longevity.  “Here, we analyzed the effect of mildly increased PGC-1-alpha expression in skeletal muscle during aging. We found that transgenic MCK-PGC-1-alpha animals had preserved mitochondrial function, neuromuscular junctions, and muscle integrity during aging. Increased PGC-1-alpha levels in skeletal muscle prevented muscle wasting by reducing apoptosis, autophagy, and proteasome degradation. The preservation of muscle integrity and function in MCK-PGC-1-alpha animals resulted in significantly improved whole-body health; both the loss of bone mineral density and the increase of systemic chronic inflammation, observed during normal aging, were prevented. Importantly, MCK-PGC-1-alpha animals also showed improved metabolic responses as evident by increased insulin sensitivity and insulin signaling in aged mice. Our results highlight the importance of intact muscle function and metabolism for whole-body homeostasis and indicate that modulation of PGC-1-alpha levels in skeletal muscle presents an avenue for the prevention and treatment of a group of age-related disorders.” Of course, for us non-transgenic humans, the way to maintain the higher PGC1alpha level is exercise.

The 2009 publication PGC-1-alpha protects skeletal muscle from atrophy by suppressing FoxO3 action and atrophy-specific gene transcription relates “Maintaining muscle size and fiber composition requires contractile activity. Increased activity stimulates expression of the transcriptional coactivator PGC-1-alpha –, which promotes fiber-type switching from glycolytic toward more oxidative fibers. In response to disuse or denervation, but also in fasting and many systemic diseases, muscles undergo marked atrophy through a common set of transcriptional changes. — Increased expression of PGC-1-alpha also increased mRNA for several genes involved in energy metabolism whose expression decreases during atrophy. Transfection of PGC-1-alpha into adult fibers reduced the capacity of FoxO3 to cause fiber atrophy and to bind to and transcribe from the atrogin-1 promoter. Thus, the high levels of PGC-1-alpha in dark and exercising muscles can explain their resistance to atrophy, and the rapid fall in PGC-1-alpha during atrophy should enhance the FoxO-dependent loss of muscle mass.”

PGC-1-alpha and muscle fiber type switching

Muscle fibers fall into different type categories which have different properties with respect to mitochondrial content and exercise endurance, and different susceptibilities to obesity and diabetes.  Selectively, expression of PGC-1-alpha can influence switching of muscle fibers from one type to another.  According to the 2004 publication Regulation of Muscle Fiber Type and Running Endurance by PPARδ, “Endurance exercise training can promote an adaptive muscle fiber transformation and an increase of mitochondrial biogenesis by triggering scripted changes in gene expression. However, no transcription factor has yet been identified that can direct this process. We describe the engineering of a mouse capable of continuous running of up to twice the distance of a wild-type littermate. This was achieved by targeted expression of an activated form of peroxisome proliferator-activated receptor -delta(PPAR-delta) in skeletal muscle, which induces a switch to form increased numbers of type I muscle fibers. Treatment of wild-type mice with PPAR-delta agonist elicits a similar type I fiber gene expression profile in muscle. Moreover, these genetically generated fibers confer resistance to obesity with improved metabolic profiles, even in the absence of exercise. These results demonstrate that complex physiologic properties such as fatigue, endurance, and running capacity can be molecularly analyzed and manipulated.”

Further, “Muscle fiber specification appears to be associated with obesity and diabetes. For instance, rodents that gain the most weight on high-fat diets possess fewer type I fibers (Abou et al. 1992). In obese patients, skeletal muscle has been observed to have reduced oxidative capacity, increased glycolytic capacity, and a decreased percentage of type I fibers (Hickey et al. 1995; Tanner et al. 2002). Similar observations have been made in type 2 diabetic patients (Lillioja et al. 1987; Hickey et al. 1995). Recently, it has been shown that increasing oxidative fibers can lead to improved insulin action and reduced adipocyte size (Luquet et al. 2003; Ryder et al. 2003). — Adult skeletal muscle shows plasticity and can undergo conversion between different fiber types in response to exercise training or modulation of motoneuron activity (Booth and Thomason 1991, Jarvis et al. 1996; Pette 1998; Olson and Williams 2000; Hood 2001). This conversion of muscle fiber from type IIb to type IIa and type I is likely to be mediated by a calcium signaling pathway that involves calcineurin, calmodulin-dependent kinase, and the transcriptional cofactor Peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) (Naya et al. 2000; Olson and Williams 2000; Lin et al. 2002; Wu et al. 2002)(ref).”

Muscle PGC-1-alpha protects against oxidative damage in aging muscle and PGC-1-alpha prevents age-related loss of endurance running capacity(Note 1).

PGC-1-alpha, insulin resistance and diabetes

Feeding rats a high-fat diet results in the production of more mitochondria, so lack of mitochondria is not responsible for insulin-resistance in this instance.  Expression of PGC-1-alpha is responsible for the effect.  “It has been hypothesized that insulin resistance is mediated by a deficiency of mitochondria in skeletal muscle. In keeping with this hypothesis, high-fat diets that cause insulin resistance have been reported to result in a decrease in muscle mitochondria. In contrast, we found that feeding rats high-fat diets that cause muscle insulin resistance results in a concomitant gradual increase in muscle mitochondria. This adaptation appears to be mediated by activation of peroxisome proliferator-activated receptor (PPAR)delta by fatty acids, which results in a gradual, posttranscriptionally regulated increase in PPAR gamma coactivator 1alpha (PGC-1-alpha) protein expression. Similarly, overexpression of PPARdelta results in a large increase in PGC-1-alpha protein in the absence of any increase in PGC-1-alpha mRNA. We interpret our findings as evidence that raising free fatty acids results in an increase in mitochondria by activating PPARdelta, which mediates a posttranscriptional increase in PGC-1-alpha. Our findings argue against the concept that insulin resistance is mediated by a deficiency of muscle mitochondria(ref).”

The discussion in the blog entry Diabetes Part 2: Lifestyle, dietary and supplement interventions relates exercise to the control of diabetes.

Exercise-induced expression of PGC-1-alpha appears to enhance insulin sensitivity, according to the 2010 publication PGC-1-alpharegulation by exercise training and its influences on muscle function and insulin sensitivity. “In contrast, a modest (25%) upregulation of PGC-1, within physiological limits, does improve mitochondrial biogenesis, fatty acid oxidation, and insulin sensitivity in healthy and insulin-resistant skeletal muscle. Taken altogether, there is substantial evidence that the p38MAPK-PGC-1alpharegulatory axis is critical for exercise-induced metabolic adaptations in skeletal muscle, and strategies that upregulate PGC-1-alpha, within physiological limits, have revealed its insulin-sensitizing effects.”  Thus, it is likely that maintenance of upregulated levels of PGC-1-alpha-is protective against diabetes.

PGC-1-alpha-appears to regulate hundreds of transcription factors.  Spiegelman has identified over 120 of them (Note 1).

So, we have a venerable body of conventional wisdom and large population studies supporting the health and longevity effects of regular exercise and now, starting with PGC-1-alpha, an explanation of the molecular and biological mechanisms that produce those health and longevity effects.  See the blog entries Exercise, telomerase and telomeres, and On the conventional wisdom of exercise.

(Note 1: a number of the statements in this blog were presented on slides by Bruce L Spiegelman in his presentation last week Control of Aging and Muscle Atrophy by the PGC1 Coactivators at the Ellison Medical Foundation’s Colloquium on the Biology of Aging.  Spiegelman has been researching PGC1 coactivators for some time and has contributed to an impressive list of publications related to them.  Listening to Spiegelman’s talk inspired me to generate this blog entry.)

Negative effects of PGC-1-beta

I have focused on PGC-1-alpha, but it is worth mentioning that PGC-1-beta is a quite different matter.  It appears that consuming saturated fats increases the expression of PGC-1-beta resulting in harmful effects.  See for example the 2006 Heartwire item Researchers identify protein that triggers the harmful effects of saturated and trans fatty acids.  “Boston, MA – Researchers have identified the molecular mechanism in which the dietary intake of saturated and trans fatty acids results in the elevation of total cholesterol and triglycerides. The target of both saturated and trans fatty acids is PGC-1-beta, a coactivator that alters liver metabolism through a cascade of biochemical signals.[1] — “What we showed was that when you put PGC-1-betainto the liver of an animal, it elevates the secretion of the VLDL particles containing triglycerides and cholesterol,” senior author Dr Bruce Spiegelman (Dana Farber Cancer Institute, Boston, MA) told Heartwire.”

Looking for PGC-1alpha activators

The incredible health-inducing properties of PGC-1-alphahave led to a search for substances that could promote its expression in humans, the idea being to develop a pill that has the positive effects of exercise.  Spiegelman reports that his lab at the Dana-Farber Cancer Institute has screened 4,600 bioactive compounds for their ability to induce PGC1alpha in mytotubes.  The screen surfaced 36 primary candidates including crinamine, an antibacterial alkaloid present in the crinum asiaticum plant which significantly increased PGc1alpha expression.  The candidates screened so far, including crimamine, appeared to be bioactive in other ways and to some extent toxic.  Next steps include 1. experiments in aging and mdx mice to see if is possible to activate PGC-1 target genes in-vivo and determine appropriate dosing regimens, 2. screening a larger 54,000 compound library for PGC-1-alpha activators, working with the Broad Institute and 3.  collaborating with a large pharmaceutical company to screen additional substances on a very large scale(Note 1).

Meanwhile, my personal response is to continue to exercise, my current target continuing to be a minimum of 47 minutes a day of swimming, treadmilling or hard work like mowing lawns and moving lumber.  Having a collection of old buildings on my lake property and a big primary home offers me no end of opportunities for physical work.  Viva la PGC-1alpha!

I have covered much of the “low hanging fruit” of the longevity sciences in the 304 existing blog entries written over the last two years.  Yet, developing a comprehensive understanding of the key aspects of aging requires harvesting fruit from ever-higher in the research-knowledge tree, from areas of science more complex and arcane.  Many of the new topics being covered in this blog are fruit higher-up on the tree of longevity sciences, sometimes delicious fruit but fruit more difficult to harvest.  More research and learning is required to deal with those topics on my part so it is taking me longer to crank out blog entries for them.  My new blog entries have therefore been coming less frequently.  At the same time, many of my more-recent postings are tending to be more comprehensive in their depth of coverage. 

Also, I have been attending major conferences related to longevity sciences – four of them so far this year.  These conferences enable me to be aware of yet-unpublished research and to interact directly with some of the key researchers involved.  I have just returned from a 3-day Colloquium on the Biology of Aging held at the Marine Biological Laboratory in Woods Hole on Cape Cod.  And I am still working on digesting the information from 41 rapid-fire presentations on the latest aging research sponsored by the Ellison Medical Foundation.  Some 1,300 slides were flashed on the screen in the course of the presentations, many shown for only a few seconds but full of technical details.  I managed to photograph most of these slides and am now going through the images for additional insights.  Though there were several topics surfaced at the colloquium that I want to look into further, this knowledge-digesting process has also slowed down my writing productivity. 

Here are some of the blog entries I am currently working on or planning for the near future. I have been thinking about some of these for a long time, at least one was pointed out by a blog reader in a comment, and others surfaced in the Woods Hole conference.

1.    About Acute Lymphoblastic Leukemia – an interesting rapidly-acting form of leukemia that affects young children as well as older adults and about what we might learn from this disease relating to malignant disease processes. 

2.    PGC-1alpha and exercise- about a transcriptional co-activator protein involved in the regulation of mitochondrial biogenesis and many other body processes and that appears to be the mediator of the health-producing effects of exercise.

3.    Curcumin and neurogenesis – additional properties of this remarkable herb and its potential for helping to maintain mental acuity and preventing/treating dementia. 

4.    The dendritic function of tau protein – based on recently-reported ground-breaking research that could possibly, this time for real, lead before long to a cure for Alzheimer’s disease. 

5.    The unfolded protein response – multiple mechanisms cells use to protect themselves against improperly folded proteins, an essential form of genomic quality control.

6.    Another look at antagonistic pleiotropy – there seems to be good evidence for the operation of this classical theory (evolution favors protecting the young and does not care about the old), but there is also good emerging evidence that we may be able to selectively engineer our way around it.

7.    A further look at klotho, WNT signaling and aging – key pathways relevant to accelerated cellular senescence, stem cell differentiation, and the aging process.

8.    The dynamic balance between DNA damage and repair – how genomic mutations and epigenomic changes occur much more frequently than once thought and the various strategies used by cells for error and problem detection, quality control and damage repair.

9.    Great news for curing diseases and longevity – if you are a mouse – how our knowledge of what goes on in mouse models is running way ahead of what we know about humans. 

These are in various stages of development and, as of the present, I can’t say for sure which ones will be available when.  Items 1 and 2 are in the pipeline now but items 3 and 4 are much simpler and I might green-light them for sooner publication.  In any event, I expect the next substantive blog entry will be available in a day or two.  Also, I want to respond to a number of thoughtful comments posted by readers in the course of the last week.  I welcome suggestions from readers as to setting priorities or other topics of interest.