The flow of weekly news items related to telomeres and telomerase has grown from a trickle to a steady stream.  Here is a selection of some recent items. 

• Centenarian Ashkenazi Jews

A recent study of centenarian Ashkenazi Jews found that they and their descendents have a mutant gene which results in higher levels of telomerase, longer telomeres, greater health at old age and – well – and ability to live very long healthy lives.  The study looked at “blood samples from 86 very old, but generally healthy, people with an average age of 97; 175 of their offspring; and 93 other people who were the offspring of parents who had lived a normal lifespan and could therefore make up a control group, with which the results could be compared. — Yousin Suh, associate professor of medicine and genetics at Einstein and a lead author on the paper, said: “Our findings suggest that telomere length and variants of telomerase genes combine to help people live very long lives, perhaps by protecting them from the diseases of old age(ref).”  My own comment is “no kidding, that’s what we’ve been talking about for years now.”  Here is the original November 11 news release from the Albert Einstein College of medicine.  The story was picked up by dozens of publications worldwide.

·         Childhood emotional trauma

Another study reported in the press last Friday indicates that a history of childhood emotional trauma such as having been beaten or sexually abused is strongly correlated with shorter telomere lengths in grown adults(ref).  “– researchers Audrey Tyrka of Brown University in Providence, Rhode Island measured DNA extracted from blood samples of 31 18-to-64 year old adults, including 22 women and nine men. — They found more rapid shortening of telomeres only in those who said they had suffered severe mistreatment as children.”  Again, this tends to confirm what we already know about telomere lengths: they respond negatively to stress, apparently due to repeated over-expression of cortisol.   Again, the story was picked up widely in the press and an interview on the social ramifications of the study with Dr. Audrey R. Tyrka the team leader can be found here.

• The oyster fungus

For those of you who have a passionate interest in the oyster fungus (Pleurotus ostreatus), fungus of the month in October 1998, there is more telomerase news.  A Nov 21 news report describes a study that, interestingly enough, indicates that the ‘telomere sequence of P. ostreatus is identical to that of human telomeres.”  How fascinating that we and some mushrooms could enjoy this same genetic feature, and how indicative this is of how fundamental telomeres are to most life forms!  These oyster mushrooms (so-called because of their appearance), by the way, are good to eat and great for the environment “The oyster fungus, together with the common mushroom, is the fungus with the greatest production and consumption worldwide. Likewise this fungus is of great biotechnological interest for its capacity to produce enzymes and degrade industrial and agricultural waste(ref).”

·         The Arabidopsis weed

There is an October 28 report in ScienceDaily about a common weed (the Arabidopsis plant) and about what studies of its telomeres may mean for us. The story’s headline and lead lines are: “Common Weed Could Provide Clues On Aging And Cancer —— A common weed and human cancer cells could provide some very uncommon details about DNA structure and its relationship with telomeres and how they affect cellular aging and cancer, according to a team led by scientists from Texas A&M University and the University of Cincinnati (UC). — “We found that removal of the plant telomere proteins caused rampant end-to-end joining of chromosomes and dramatic defects in plant development,” explains Shippen.” — “The Cincinnati team then showed that removal of one of the human proteins from human cancer cells caused wide-spread DNA damage and complete loss of some telomeres.”Going back in history a slight bit, I found two recent stories relating to the protein structure and replication of telomeres. 

·         TRF1 and telomere fragility

The first, a July 2009 story deals with the protein makeup of telomeres.  A protein TRF1 that was discovered in 1995 plays a very important role in assuring the structural integrity of telomeres and protecting them from what otherwise would be fragility.  “Using a conditional mouse knockout, de Lange and Sfeir (Titia de Lange  and Agnel Sfeir, researchers at Rockerfeller University)  have now revealed that TRF1, which is part of a six-protein complex called shelterin, enables DNA replication to drive smoothly through telomeres with the aid of two other proteins. — Telomeric DNA has a repetitive sequence that can form unusual DNA structures when the DNA is unwound during DNA replication,” says de Lange. “Our data suggest that TRF1 brings in two proteins that can take out these structures in the telomeric DNA. In other words, TRF1 and its helpers remove the bumps in the road so that the replication fork can drive through. — Sfeir deleted TRF1 and saw that the telomeres resembled common fragile sites, suggesting that TRF1 protects telomeres from becoming fragile. Instead of a continuous string of DNA, the telomeres were broken into fragments of twos and threes. — the researchers observed the dynamics of replication across individual DNA molecules — the first time this technique has been used to study telomeres. In the absence of TRF1, the fork often stalled for a considerable amount of time.”

·         hRAP1 and telomere DNA breaks

The second story relating to the structure of telomeres, September 2009 is entitled “Protein Helps Distinguish Chromosome Ends From DNA Breaks.”  The lead line is “The Stowers Institute’s Baumann Lab has demonstrated how human cells protect chromosome ends from misguided repairs that can lead to cancer. The work, published in The EMBO Journal, a publication of the European Molecular Biology Organization, follows the team’s 2007 in vitro demonstration of the role of the hRAP1 protein in preventing chromosome ends from being fused to new DNA breaks.” – “—in this work, the team demonstrated that the human RAP1 protein plays a key role in preventing chromosome ends from being fused to new DNA breaks. Chromosome end fusions result in genomic instability, which can cause cancer. These findings suggest that RAP1 plays a critical role in cancer prevention in humans.”

There are also several recent stories related to development of anti-cancer drugs that work by inhibiting telomerase, b ut I won’t bother listing those.  It probably won’t be long before telomeres and telomerase – things once known only to a handful of distant researchers and geeky anti-aging aficionados – may be familiar to hundreds of millions.

If you are an old timer like me you may remember the World War I marching song: 

It’s a long way to Tipperary,

It’s a long way to go.

It’s a long way to Tipperary,

To the sweetest girl I know!

Goodbye Piccadilly, Farewell Leicester Square!

It’s a long long way to Tipperary,

But my heart’s right there.  

Last year at this time, I expected that by now, at least a Phase I clinical trial of Geron’s embryonic stem cell treatment for spinal injury would be well underway.  However, according to a Reuters press release on October 30 2009, “Geron Corporation (Nasdaq: GERN) today announced the company`s plan to advance clinical development of its human embryonic stem cell (hESC)-based product, GRNOPC1, for the treatment of spinal cord injury. The plan is expected to enable Geron to re-initiate the Phase I clinical trial of GRNOPC1 in patients with complete thoracic spinal cord injury and to support future expansion of the trial to patients with cervical injuries.” The company had plans to move the drug into Phase I clinical trials but put these on hold when preclinical trials produced cysts in some animals. “As announced previously, in one preclinical study, a higher frequency of animals developed cysts in the injury site than had been seen in numerous foregoing preclinical studies with clinical grade GRNOPC1.  These cysts are non-proliferative, confined to the injury site, smaller than the injury cavity,and were not associated with adverse effects on the animals. As part of ongoing work to optimize GRNOPC1 manufacturing and product release, the company developed new candidate markers and assays. Data from studies using the new markers were submitted to the FDA. The IND for spinal cord injury was placed on clinical hold pending FDA review of the data.”  In other words, back to the FDA drawing board for the new trial.

The news item goes on:  “Geron will complete a confirmatory preclinical study using GRNOPC1 that has been characterized by the new markers and assays, as agreed upon in discussions with the FDA. As part of the ongoing plan to advance clinical development to cervical patients, Geron had already initiated this preclinical study in an animal model of cervical injury. — In discussions with the company, the FDA has advised that it concurs with Geron that positive data from this study can be used to support both release of the clinical hold and expansion to cervical patients. Geron expects the data from this study to enable re-initiation of the clinical trial in the third quarter of 2010.” 

So the good news is that when, assuming there is a when a year or more from now, GRNOPC1 goes into human clinical trial it can possibly be for both thorasic and cervical spinal cord injuries.  In the meantime, there is yet-another preclinical study.  Learning about this 18 month delay, I composed this version of the Tipperary song:

It's a long way to stem cell treatment, 

It's a long way to go! 

It's a long way to stem cell treatment,

To the sweetest treatment we’ll  ever know!

Goodbye radiation, Farewell scalpel and chemo! 

It's a long long way to stem cell treatment, 

But my heart's with the new techno.  

Maria Blasco heads the Telomeres & Telomerase Group at the Spanish National Cancer Center in Madrid.  She and her group have produced a number of important papers over recent years contributing to our understanding of telomere/telomerase science. A November 2009 publication describes what I believe is a breakthrough result enhancing our understanding of both the Telomere Shortening and Damage and the Programmed Epigenomic Changes theories of aging and showing a way in which they fit together.

The publication, Telomere shortening relaxes X chromosome inactivation and forces global transcriptome alterations describes a new viewpoint on how telomere shortening contributes to aging.  The “classical” viewpoint is that telomere shortening results from cell division and that after a certain number of divisions the telomeres start to become too-short for further cell division to take place reliably.  At that point either apoptosis takes place and the cell dies, or the cell can become senescent, no longer reproducing but sending out noxious signals to neighboring cells.  The new viewpoint suggested in the Blasco paper goes much further.  It says that as telomeres become critically short, the gene expression in the cell changes so as to induce senescence and at the same time to affect the maintenance of epigenomic memory and nuclear organization, thereby contributing to organismal aging on the whole-animal level.  Critically short telomeres deregulate epigenomic control and alter gene expression so as to create the changes we know as “aging.”  Too-short telomeres is not just an issue of affected cells dying off or becoming senescent.  After all, these can be replaced by differentiating stem cells.  It is an issue of screwing up the body’s cellular control mechanisms in a way that creates aging. 

In my mind, this is an important finding and provides all the more reason to pursue telomerase activation as an anti-aging strategy.  I have stated before that telomerase activation may not make telomeres longer because of the complex feedback loops involved in telomere length regulation.  The key point is that telomerase activation might keep telomere lengths from getting critically shorter, and that would be enough to stave off cell senescence and deregulation of the epigenome and, perhaps even, much of what we know as aging.

Going to a further level of detail, the new publication summarizes the results: “Using telomerase-deficient TRF2-overexpressing mice (K5TRF2/Terc_/_) as a model for accelerated aging, we show that telomere shortening is paralleled by a gradual deregulation of the mammalian transcriptome leading to cumulative changes in a defined set of genes, including up-regulation of the mTOR and Akt survival pathways and down-regulation of cell cycle and DNA repair pathways. — Collectively, these findings suggest that critically short telomeres activate a persistent DNA damage response that alters gene expression programs in a nonstochastic manner toward cell cycle arrest and activation of survival pathways, as well as impacts the maintenance of epigenetic memory and nuclear organization, thereby contributing to organismal aging.”  We know that mTOR is involved in a number of disease and aging processes and that inhibition of mTOR confirms longevity.  Introductions to mTOR  signaling and its relationship to longevity can be found in my blog entries Longevity genes, mTOR and lifespan, More mTOR links to aging theories, and  Viva mTOR! Caveat mTOR!  As mentioned previously in this blog, the P13/Akt pathway is involved in cancer processes as well as cell survival and stem cell proliferation. 

The paper states “Dysfunctional, critically short telomeres elicit a DNA damage response (DDR) that triggers senescence or apoptosis in mammalian cells, two processes that are associated with organismal aging (1–9).” This has been known for some time.  “Mice with a targeted deletion of the RNA component of telomerase (Terc_/_) display accelerated telomere shortening, premature loss of tissue renewal, and decreased longevity (3, 7–9).”  Again, this is not surprising.    “DNA damage signals originating from critically short telomeres in these mice is in line with current models proposing a causative role for DNA damage in organismal aging (10–13. — Interestingly, epigenetic alterations at heterochromatic regions are proposed to lead to changes in gene expression associated with aging (14–16)..”  Here is where the discussion starts to get interesting.  

Going on, “In S. cerevisiae, induction of DNA double-strand breaks (DSBs) or cellular stress causes a dramatic redistribution of telomeric silentinformation regulator (Sir) proteins and yKU proteins (17–19), thus linking changes in telomere chromatin to global epigenetic alterations. “  This is interesting given the linkages of human Sir proteins to longevity.  Stimulating Sir1 is why people take resveratrol. Disturbing these proteins is likely to contribute to “shortivity.” “Sir complex relocalization is known to alter the expression of stress response genes, survival factors, and ribosomal biogenesis (20, 21). In functional analogy to yeast, mammalian SIRT1 is redistributed upon induction of DNA damage, causing broad alterations in global gene expression (22). Collectively, these findings suggest that aging-related DNA damage drives gene expression alterations that could promote the development of aging pathologies. – The point is restated several times throughout the paper: “These findings suggest that progressive telomere shortening and the accumulation of dysfunctional telomeres with age may constitute a unique source of DNA damage, sufficient to induce global alterations in genome regulation.” – “Using a mouse model system, we provide evidence that progressive telomere shortening in stratified epithelia, such as the skin, is linked to global deregulation of the mammalian transcriptome and loss of maintenance of epigenetic silencing mechanisms, exemplified by the re-expression of an Xi-linked transgene.”  

So, put simply, telomeric shortening at some point induces DNA damage which lets loose signaling which changes the epigenome disrupting epigenetic silencing and resulting in pro-aging global DNA expression.   

From the viewpoint of the Programmed Epigenomic Changes theory of aging, the paper says that telomere shortening is at least one of the drivers of the epigenomic aging program.  The paper goes into significantly more detail.  For those of you who can read such technical material, I suggest you do.  As for me, I popped my daily cycloastragenol telomerase-activator pill just a bit ago.  It is late and I will soon be going to bed.

An important approach to retarding aging that I have not discussed explicitly so far is hormesis, challenging cells and body systems by mild stress resulting in them becoming stronger and resistant to aging(ref).  The stress can be physical, chemical and even possibly psychological. Regular exercise is a familiar activity that produces hormetic effects.  I can assure you that mild stress is involved because I just got off my treadmill and am still sweating a bit.  And I expect this will help me live longer.  Also, many of the supplements in the combined anti-aging regimen likely exercise some of their positive effects via hormesis.   I review some of the science related to hormesis here, especially the roles of heat shock proteins and chaperones.  And I discuss how the phyto-substances featured in my anti-aging firewalls work through hormesis.
 

The anti-aging effects of hormesis have been observed experimentally.

In the 2004 paper Slowing down aging from within: mechanistic aspects of anti-aging hormetic effects of mild heat stress on human cells, the authors report:  “In a series of experimental studies, we have reported that repeated mild heat stress (RMHS) has anti-aging hormetic effects on growth and various cellular and biochemical characteristics of human skin fibroblasts undergoing aging in vitro. These beneficial effects of repeated challenge include the maintenance of stress protein profile, reduction in the accumulation of oxidatively and glycoxidatively damaged proteins, stimulation of the proteasomal activities for the degradation of abnormal proteins, improved cellular resistance to other stresses, and enhanced levels of cellular antioxidant ability. In order to elucidate the molecular mechanisms of hormetic effects of RMHS, we are now undertaking studies on signal transduction pathways, energy production and utilization kinetics, and the proteomic analysis of patterns of proteins synthesized and their posttranslational modifications in various types of human cells undergoing cellular aging in vitro.”   The Danish authors of this paper also see hormesis as a possible systematic anti-aging intervention.  “Human applications of hormesis include early intervention and modulation of the aging process to prevent or delay the onset of age-related conditions, such as sarcopenia, Alzheimer’s disease, Parkinson’s disease, cataracts and osteoporosis(ref).”

The 2009 paper Heat Stress and Hormetin-Induced Hormesis in Human Cells: Effects on Aging, Wound Healing, Angiogenesis, and Differentiation was generated by some of the same Danish authors and represents their continuing research.  This paper confirms the earlier observations and goes on to say “RMHS (repeated mild heat stress ) given to human cells increased the basal levels of various chaperones, reduced the accumulation of damaged proteins, stimulated proteasomal activities, increased the cellular resistance to other stresses, enhanced the levels of various antioxidant enzymes, enhanced the activity and amounts of sodium-potassium pump, and increased the phosphorylation-mediated activities of various stress kinases. We have now observed novel hormetic effects of mild heat stress on improving the wound healing capacity of skin fibroblasts and on enhancing the angiogenic ability of endothelial cells. We have also tested potential hormetins, such as curcumin and rosmarinic acid in bringing about their beneficial effects in human cells by inducing stress response pathways involving heat shock proteins and hemeoxygenase HO-1. These data further support the view that mild stress-induced hormesis can be applied for the modulation, intervention and prevention of aging and age-related impairments.” 

I have discussed curcumin repeatedly in my treatise and rosmarinic acid in the recent blog post with that name.  The concepts that these substances work by “inducing stress response pathways involving heat shock proteins and hemeoxygenase HO-1” is an interesting one that I have not explored before.

Hormesis can operate through the activation of  heat shock proteins

Heat shock proteins (HSPs) are produced by cells when the cells are exposed to elevated temperature or other stresses.  Their role is to protect cells and tissues which they do by regulating important cellular functions when they are expressed due to stress.  “Hsps are expressed in response to an array of stresses, including hyperthermia, oxygen radicals, heavy metals, ethanol, and amino acid analogues. In addition, the heat shock response is induced during clinically relevant situations such as ischemia/reperfusion and circulatory and hemorrhagic shock. All of the above stresses have in common that they disturb the tertiary structure of proteins and have adverse effects on cellular metabolism. Pretreatment of cells with a mild stress, sufficient to induce the expression of hsps, results in protection to subsequent insults. This phenomenon has been coined “stress tolerance” and is apparently caused by the resolubilization of proteins that were denatured during the stress(ref).”  Discovered in 1974, a large literature has been built up about heat shock proteins which appear to be evolutionary conserved and observed in a wide variety of organisms ranging from bacteria to humans(ref).  Many, but not all chaperone proteins are also HSPs, so in some discussions the terms “heat shock protein” and “chaperone protein” are incorrectly used interchangeably.

Hormesis theory of anti-aging

The hormesis theory of anti-aging is that by systematically introducing mild systematic stresses on body systems , heat shock proteins will be generated and molecular pathways will be activated that exercise protective effects on cells and consequently on entire organisms; the result will be delayed aging. 

Examples on the level of entire organisms are calorie restriction(ref) and exercise.  Hormesis is observed on multiple levels.  For example, confronting mental challenges preserves memory and cognitive capability(ref)(ref)(ref).  A study in Florida of 660 older people, aged aged 63 to 97, showed that people who kept driving were four to six times more likely to still be alive after a three-year period than their counterparts who stopped driving(ref).  Another example may be Polygamy which helps men live 12% longer according to research studies(ref).  One possibility is that polygamy extends life of men because “the challenge multiple wives pose requiring constant physical and mental activity.” I have written several times earlier on hormetic effects without using that name.  See my blog entry Stress and longevity for a further discussion of how moderate stresses confer longevity.

Too much stress, stress that overwhelms the body’s defenses can of course be dangerous or lethal and excess or the wrong kind of stress can further the progress on some diseases like melanoma(ref).  For many substances there is a response curve based on dose where there is a transition point beyond which the effect is no longer beneficial and is deleterious(ref).

Hormesis and dietary phytochemicals

The 2007 publication Dietary Factors, Hormesis and Health states “Some specific dietary components may also exert health benefits by inducing adaptive cellular stress responses. Indeed, recent findings suggest that several heavily studied phytochemicals exhibit biphasic dose responses on cells with low doses activating signaling pathways that result in increased expression of genes encoding cytoprotective proteins including antioxidant enzymes, protein chaperones, growth factors and mitochondrial proteins. Examples include: activation of the Nrf-2 – ARE pathway by sulforaphane and curcumin; activation of TRP ion channels by allicin and capsaicin; and activation of sirtuin-1 by resveratrol.”

The age-prolonging effects of phytochemicals, as pointed out in the 2008 publication Hormetic dietary phytochemicals.  “One general mechanism of action of phytochemicals that is emerging from recent studies is that they activate adaptive cellular stress response pathways. From an evolutionary perspective, the noxious properties of such phytochemicals play an important role in dissuading insects and other pests from eating the plants. However at the subtoxic doses ingested by humans that consume the plants, the phytochemicals induce mild cellular stress responses. This phenomenon has been widely observed in biology and medicine, and has been described as ‘preconditioning’ or ‘hormesis.’ Hormetic pathways activated by phytochemicals may involve kinases and transcription factors that induce the expression of genes that encode antioxidant enzymes, protein chaperones, phase-2 enzymes, neurotrophic factors, and other cytoprotective proteins. Specific examples of such pathways include the sirtuin-FOXO pathway, the NF-kappaB pathway, and the Nrf-2/ARE pathway.”

Specifically, my blog post Nrf2 and cancer chemoprevention by phytochemicals  discusses the signaling pathways involved in the hormetic process initiated by some phytochemicals , including the roles of the nuclear factor Nrf2 and the MAPK/ERK and PI3K/Akt pathways .  I have discussed these pathways and the sirtuin-FOXO and NF-kappaB pathways  before in this blog and in my treatise.   

Hormesis and the anti-aging firewalls

I have already mentioned how several of the suggestions in my lifestyle firewall regimen, like exercise and keeping mentally and socially active, tend to be life-extending by creating hormetic effects.

Several supplements in my anti-aging firewalls supplement regimen have been shown in-vitro to act via activation of heat shock proteins and hormesis.  The document Curcumin, a medicinal herbal compound capable of inducing the heat shock response, for example, concludes “Curcumin, a widely used medicinal compound, induces the heat shock response in vitro as measured by expression of heat shock protein 70. The mechanism of heat shock protein 70 induction depends on activation of heat shock factor-1. Examining known inhibitors of nuclear factor-KB for their ability to induce heat shock protein 70 may be a valid screening method to discover novel pharmacologic inducers of the heat shock response.” Thirty nine substances in my combined firewall regimen are known inhibitors of NF-kappaB and many if not most of these are likely to activate heat shock proteins. 

The home run reported this week was in a practice game in a minor league.  But nonetheless the results are impressive and lead to hope for those suffering from certain forms of congenital blindness and vision impairment.  The report leading to this optimism, Age-dependent effects of RPE65 gene therapy for Leber’s congenital amaurosis: a phase 1 dose-escalation trial, appeared in the November 7 edition of The Lancet.

The trial involved 12 patients (aged 8—44 years), all having  Leber’s congenital amaurosis (LCA), “a rare inherited eye disease that appears at birth or in the first few months of life, and affects around 1 in 80,000 of the population.”

People with this disease are born with impaired vision and their  vision deteriorates until they are totally blind, usually within 10-15 years. “Typically a baby with LCA will have very reduced vision at birth although the retina may appear normal when first examined. Within months, however, parents will usually notice nystagmus – an involuntary, rhythmical, repeated movement of the eyes. Children with LCA account for 10-18% of all cases of congenital blindness. Vision in individuals with LCA varies greatly from relatively mild acuity problems (20/70) to no light perception(ref).”  Up to this point, the disease has been incurable.

LCA is an autosomal recessive disorder, which means that if both parents are carriers of a defective gene as well as a good gene, there is a 1 in 4 chance the child will end up with two defective genes and manifest the disease.  The 12 patients in the recent trial had a variant of LCA caused a defect in the RPE65 gene(ref)(ref), a gene responsible for encoding the retinal pigment epithelium-specific 65 kDa protein. This protein “is located in the retinal pigment epithelium and is involved in the conversion of all-trans retinol to 11-cis retinal during phototransduction, which is then used in visual pigment regeneration in photoreceptor cells(ref).” 

The  therapy used in “home run” trial  is a simple one.   Each of the 12 patients were given one given one subretinal injection using a thin needle in the worst eye of a “defanged” adeno-associated virus (AAV) into which the RPE65 gene had been inserted.  “The engineered virus then invaded retinal cells and inserted the gene into the cells’ DNA. — Within two weeks, the treated eyes began to become more sensitive to light, and within a few more weeks, vision began to improve. The younger the patients were, the better they responded.  — By both objective and subjective measures, vision improved for all the patients. They were able to navigate obstacle courses, read eye charts and perform most of the tasks of daily living. The children who were treated “are now able to walk and play just like any normally sighted child —  The improvement has now persisted for as long as two years(ref).”  There appeared to be no safety issues or adverse effects involved.   

“The study “holds great promise for the future” and “is appealing because of its simplicity,” wrote researchers from the Nijmegen Medical Center in the Netherlands in an editorial accompanying the report –(ref).” The study had its limits of course.  The patients would like to have their other eye treated and optimum dosage of the adenovirus/RPE65 is not yet determined.  Yet the results lend hope to the other some 130,000 victims of LCA worldwide as well as to victims of other more common hereditary eye diseases such as Retinitis pigmentosa.

After many years of false starts and problematical trials, it appears that gene therapies may finally be getting off the ground.  See also the recent post ALD and lentivirus vectors for gene therapy.

Senesco is a small research-based company specializing in “genetic technologies designed to regulate cell death.”  A company that started out with focus on commercial agriculture, it has been exploring a proprietary gene, Factor 5A1, that might well also have a role in treating human diseases, particularly cancers.  The story of Senesco is interesting because it illustrates the serendipity that can lead to drug discovery, because it describes a research company that has no research labs, because it points to another gene that could be a key to curing certain cancers, and because after five years the possible cancer therapy is still in a preclinical stage tested only on small animals.

The trade publication Gen featured a story this week, Senesco Attempts to Exploit Cell Death, which tells the early history of the company.  “At the University of Waterloo, Ontario, John Thompson, Ph.D., now Senesco’s CSO, discovered that lipase is regulated by two genes that work together to control senescence in plants. Because the finding held promise for extending the life of plants, Sascha Fedyszyn co-founded Senesco in 1998 to explore agricultural applications. A few years later, company researchers learned that the same senescence cascade in plants operates in humans, too. “That was the start of our life science work,” says Fedyszyn, vp, corporate development. — Senesco scientists found that two genes—eukaryotic translation initiation Factor 5A and deoxyhypusine synthase (DHS)—are powerful regulators of programmed cell death, known as apoptosis in human cells and senescence in plant cells. Although cell death is a normal function, premature apoptosis leads to inflammatory conditions, cancer, and tumor growth.”

The company outsources its research.  “To take greatest advantage of our early stage discoveries, we have formed a highly focused and efficient R&D department headed by John Thompson, Ph.D., the inventor of our technology. This R&D takes place at several highly regarded academic institutions around North America. While most early-stage biotechnology companies spend millions on R&D, we are conducting top-notch research with relatively minimal cash burn by utilizing these institutions(ref).” 

The company maintains relationships with a number of agricultural product firms.  “Agricultural research and development programs continue through licensing and joint ventures with agricultural biotechnology companies such as Monsanto, Bayer Crop Science, and Scotts. Efforts are under way to improve corn, soybeans, rice, cotton, bananas, canola, turf grass, and ornamental plants(ref).”

Relating to the life sciences area, “Senesco’s technology is based on the discovery that Factor 5A1, one of two human genes encoding eucaryotic translation initiation Factor 5A, regulates apoptosis as well as certain execution genes, pro-inflammatory cytokines, receptors and transcription factors and therefore plays a key role in cell death and inflammation. We believe that Factor 5A1 is a novel and potentially powerful therapeutic target for a broad range of apoptotic diseases, including inflammatory/ischemic diseases and cancers(ref).” 

In plain language, the following from the company’s web site says that Factor 5A1 kills cancer cells without affecting normal cells.  “Factor 5A1 functions as a shuttle protein, selectively translocating mRNAs required for apoptosis and cytokine function from the nucleus to cytosolic ribosomes for translation. Our preclinical studies have shown that Factor 5A1 kills cancer cells through both the intrinsic (p53) and the extrinsic (cell death receptor) pathways. We have specifically shown that Factor 5A1 regulates the expression of p53, caspases, TNFR1 (TNFa receptor) and the IFN-gamma receptor, and that it also negatively regulates bcl-2 and telomerase. Our studies to date have shown that Factor 5A1 may be non-toxic to normal cells, presumably because of its function as a shuttle protein. Normal cells are not actively expressing mRNAs of cell death genes, and therefore the Factor 5A1 protein, even if present in normal cells, is non-functional(ref).”

According to the Gen article “The company’s first drug candidate based on this combination therapy, SNS-01, targets multiple myeloma. The cytokines IL-1, IL-6, and NF-kB are known to contribute to the proliferation of this disease. The design of SNS-01 “provides a perfect combination for killing multiple myeloma cells,” says Richard Dondero, Senesco’s vp of R&D. Multiple myeloma is not only a cancer, but also a disease of the immune system with a proinflammatory side. “Our technology lends itself to that,” Dondero says. — Collaborators at the Mayo Clinic tested SNS-01 in in-vitro experiments and on mice. Within two weeks of intravenous delivery of SNS-01, “tumor reduction was visible, and some multiple myeloma tumors were even completely eradicated within six weeks,” says Dondero. Senesco plans to file an IND application for SNS-01 in the treatment of multiple myeloma early in 2010.”

Promotion or inhibition of Factor 5A1 may also serve other therapeutic purposes and Senesco’s experiments with therapies  based on Factor 5A1  go back at least five years.   For example, according to a 2004 report Factor 5A1 may be useful for controlling glaucoma. “By inhibiting Factor 5A1, Senesco blocked TNF-alpha-induced apoptosis by 80% in lamina cribrosa cells of the human optic nerve head. — TNF-alpha is strongly upregulated in the optic nerve head of the glaucomatous eye, and TNF-alpha-induced apoptosis appears to be an important determinant of the progressive neurodegeneration characteristic of glaucoma. Thus, inhibition of TNF-alpha-induced apoptosis may reduce damage to the optic nerve during glaucoma.”  Another 2004 report indicated Proprietary gene Factor 5A1 induces atopsis in lung cancer tumors of mice. 

It will be interesting to see whether Senesco will be successful in moving treatments involving the targeting of Factor 5A1 into clinical trials and, if so, how long it will take for this to happen.

If you want to live a very long life and are tired of the highly technical stuff in this blog, you might want to appeal to one of the traditional longevity gods or goddesses.  Some of these gods and goddesses, courtesy of the Encyclopedia Mythica website are:

1.   Fukurokuju 

2.   Gama 

3.   Djambu Baros 

4.   Shou-xing 

5.   Atira 

6.   Peng-zi 

7.   San-xing 

8.   Shou-lao 

9.   Heammawihio 

10.       Pancaraksa 

Gene therapy – the substituting of inherited defective genes with good ones – does not have an outstanding success record but now is getting off the ground.  As pointed out in an editorial in the Nov 6 2009 issue of Science magazine, “Gene therapy has recently had some important successes in treating severe inherited diseases after years of skepticism from the scientific community and neglect by the pharmaceutical industry.  On page 818 in this issue, Cartier et al. (4) report another major advance—the successful first clinical testing of an HIV-derived vector in hematopoietic stem cell (HSC)–based gene therapy. The procedure was used to treat a severe neurodegenerative disease, X-linked adrenoleukodystrophy (ALD), and the results indicate stable expression of a therapeutic gene in a substantial fraction of patients’ hematopoietic cells, as well as clinical benefits.”  

ALD is a rare disease that typically affects boys between the ages of six and 10. Featured in the Hollywood film Lorenzo’s Oil, “ALD is a severe hereditary condition caused by a deficiency of a protein called ALD that is involved in fatty acid degradation. Sufferers steadily lose their myelin sheath, the protective layer that coats nerve fibers in the brain. Without myelin the nerves lose function, leading to increasing physical and mental disability in patients. X-linked ALD, the most common form of the disease, affects boys starting at age 6-8 years of age and death usually occurs before the patients reach adolescence(ref).”

The November 6 2009 research article Hematopoietic Stem Cell Gene Therapy with a Lentiviral Vector in X-Linked Adrenoleukodystrophy was reported widely in the press and describes successful treatment by a French team of two patients with ALD.  “X-linked adrenoleukodystrophy (ALD) is a severe brain demyelinating disease in boys that is caused by a deficiency in ALD protein, an adenosine triphosphate–binding cassette transporter encoded by the ABCD1 gene. ALD progression can be halted by allogeneic hematopoietic cell transplantation (HCT). We initiated a gene therapy trial in two ALD patients for whom there were no matched donors. Autologous CD34+ cells were removed from the patients, genetically corrected ex vivo with a lentiviral vector encoding wild-type ABCD1, and then re-infused into the patients after they had received myeloablative treatment. Over a span of 24 to 30 months of follow-up, we detected polyclonal reconstitution, with 9 to 14% of granulocytes, monocytes, and T and B lymphocytes expressing the ALD protein. These results strongly suggest that hematopoietic stem cells were transduced in the patients. Beginning 14 to 16 months after infusion of the genetically corrected cells, progressive cerebral demyelination in the two patients stopped, a clinical outcome comparable to that achieved by allogeneic HCT. Thus, lentiviral-mediated gene therapy of hematopoietic stem cells can provide clinical benefits in ALD.”

“The healthy ALD protein was expressed in about 15 percent of blood cells, yet surprisingly this low level was sufficient to slow brain disease in ALD. This percentage of correction will not be sufficient for all diseases,” warns Aubourg (Patrick Aubourg, co-author of the study). “There is a lot of work to be done to make this gene therapy vector more powerful, less complicated, and less expensive. This is only the beginning,” he said(ref).”

What  is particularly interesting in the study is use of a defanged version of the HIV virus as a delivery vector for getting the corrected genes into the hematopoietic stem cells extracted from the patients.  “In most gene therapy studies, a working gene is inserted into the genome to replace a dysfunctional, disease-causing gene. A carrier molecule called a vector is used to deliver the therapeutic gene into the patient’s cells. Vectors are typically the backbones of viruses that have been genetically altered to carry normal human DNA. Scientists have recently turned to vectors based on the lentivirus genus of retroviruses, which includes HIV. Lentiviral vectors are a type of retrovirus that can infect both dividing and nondividing cells, and are thought to provide long-term and stable gene expression, unlike other retroviruses(ref).” 

“Although studies with larger cohorts of patients are needed, these results suggest that gene therapy with lentiviral vectors, which are derived from disabled versions of human immunodeficiency virus (HIV), could potentially become instrumental in treating a broad range of human disorders(ref).”  A concern has been that the lentiviral DNA could integrate itself into the stem cells and their descendents and in time create mischief.  “Gene therapy is not without serious risks. Like other retrovirus vectors, the HIV-derived lentivirus vector is tasked with inserting the therapeutic gene in the chromosomes of the patients’ cells. In a worst case scenario, this action could disturb the biology of the cells and patients could end up with leukemia; this outcome has occurred in past gene therapy trials.  “The HIV-derived lentivirus vector basically has this same risk, although the design of the vector makes patients less prone to this side effect,” said Aubourg(ref).” It seems like the two boys are doing fine so far.

Falling is one of the major causes of debilitation and accelerated death among the elderly.  Older as well as recent research indicates that old folks in and out of nursing homes who take regular Vitamin D supplements fall a lot less than those who don’t.

The research literature on injuries and deaths in the elderly due to falling goes way back.  In 1985 it was written “Injuries are the sixth leading cause of death in the 75-and-over population, with falls the leading cause of injury-related deaths. Hospitals and residential centers for the elderly have high rates of falls and injuries. With increasing age, patients in nursing homes have a corresponding increase in the proportion of fatal falls.” My own mother fell and very seriously injured herself in her late 80s, contributing to her decline and death at age 93.  A 1996 report Epidemiology of hip fractures indicated “There were an estimated 1.66 million hip fractures world-wide in 1990. According to the epidemiologic projections, this worldwide annual number will rise to 6.26 million by the year 2050. This rise will be in great part due to the huge increase in the elderly population of the world.”  Over 90% of hip fractures result from falling. 

According to the CDC website on hip fractures,

• “In 2004, there were more than 320,000 hospital admissions for hip fractures, a 3% increase from the previous year.
• About one out of five hip fracture patients dies within a year of their injury.
• Most patients with hip fractures are hospitalized for about one week.
• Up to one in four adults who lived independently before their hip fracture has to stay in a nursing home for at least a year after their injury.
• In 1991, Medicare costs for hip fractures were estimated to be $2.9 billion.” (Imagine what the cost must be now!)

There is also a long history relating vitamin D to falling and hip fractures.  Citing data based on women living in nursing homes in France, in the 1996 paper Prevention of hip fractures by correcting calcium and vitamin D insufficiencies in elderly people the author state “We have shown in a 3-year controlled prospective study that the daily use of these supplements (1.2 g of calcium and 800 IU of vitamin D3) given in a large population of 3270 elderly ambulatory women living in nursing homes reduced of 23% (intention-to-treat analysis) the number of hip fractures and other non vertebral fractures.”

Another study report, published in 2008 was entitled A Higher Dose of Vitamin D Reduces the Risk of Falls in Nursing Home Residents: A Randomized, Multiple-Dose Study.  “PARTICIPANTS: One hundred twenty-four nursing home residents (average age 89). INTERVENTION: Participants were randomly assigned to receive one of four vitamin D supplement doses (200 IU, 400 IU, 600 IU, or 800 IU) or placebo daily for 5 months. MEASUREMENTS: Number of fallers and number of falls assessed using facility incident tracking database. RESULTS: —  Participants in the 800 IU group had a 72% lower adjusted-incidence rate ratio of falls than those taking placebo over the 5 months (rate ratio=0.28; 95% confidence interval=0.11-0.75). — CONCLUSION: Nursing home residents in the highest vitamin D group (800 IU) had a lower number of fallers and a lower incidence rate of falls over 5 months than those taking lower doses. Adequate vitamin D supplementation in elderly nursing home residents could reduce the number of falls experienced by this high falls risk group.”  A discussion of this study treating its limitations and comparing the results with those of other studies can be found here.

An October 2009 report Extended Physiotherapy and Vitamin D Protect Against Second Hip Fractures appears to describe the latest work on this topic. “Extended physiotherapy significantly reduced the rate of falls among patients with a prior hip fracture, and high-dose vitamin D significantly reduced the rate of hospital readmissions in a study of 173 patients. — A program of extended physiotherapy reduced the fall rate by 25%, compared with standard postfracture physiotherapy; high-dose vitamin D therapy reduced the hospital readmission rate by 39%, compared with a lower dose, the researchers found.”  Half of the patients had a severe vitamin D deficiency when they started the study and the mean age of the patients was 84 years.  Some patients were given 800 IU of vitamin D, others 2000 IU. “There was no difference in the fall rate for the two vitamin D groups, but high-dose vitamin D did reduce the rate of hospital readmission by 39%, which was significant. There was also a significant 60% reduction in fall-related injuries. “This was mainly driven by a nonsignificant reduction in repeat nonvertebral fractures by 52%,” said Dr. Bischoff-Ferrari of the Centre on Aging and Mobility at the University Hospital Zurich.”

Interestingly, I found one 2007 dissenting study Does Vitamin D Stop Inpatients Falling? A Randomised Controlled Trial.  “Objective: to determine whether routine supplementation with vitamin D plus calcium reduces numbers of fallers and falls in a cohort of hospital admissions while they are inpatients.  Design: randomised, double-blind, controlled study. Participants: two hundred and five acute admissions > 65 years to a geriatric medical unit. Methods: patients were randomised to intervention of daily vitamin D 800 IU plus calcium 1,200 mg or control group of daily calcium 1,200 mg, until discharge or death.  — Results: median age 84 years and a median length of stay = 30 days.   —  Although there were fewer fallers in the vitamin D cohort, this did not reach statistical significance –Conclusions: in a population of geriatric hospital inpatients, vitamin D did not reduce the number of fallers. Routine supplementation cannot be recommended to reduce falls in this group.”  I think the explanation is that the lengths of the hospital stays involved (30 days mean) were too short for the effects of vitamin D to be manifest and too short for many falls to happen (36 of those on vitamin D, 45 for those doing only calcium).  The other studies were longer and involved a lot more falls providing statistical significance.

So, it appears that Vitamin D works two ways to prevent fall-related injuries: 1. it reduces the number of falls, probably by a combination of muscle strengthening and improving coordination, and 2. it reduces the number of fractures in those who do fall, via bone strengthening.  Of course, preventing falls is only one of an impressive array of benefits due to vitamin D supplementation.

Chronic nagging back pain can result from spinal cord injury (SCI) and can lead to pain in other parts of the body that are in fact not injured.  It can be very difficult to diagnose and a person suffering from it can find their quality of life seriously compromised.  I know, for I have been suffering from such pain for three months now and only this week have I been able to put together a diagnosis and identify an effective treatment plan for myself.  There are two stories to be told here.  One is a science story about a new paradigm for viewing and treating chronic neuropathic pain and the other is a personal story about how I managed to connect the dots about my personal problem and arrive at insight as to what is going on in me.   I relate the science story here.

Neuropathic pain is pain “gone wild,” normally pain that was initiated by some injury to the nervous system but that assumes a life of its own and is out of proportion to the original injury and can show up in other locations. It creates “allodynia, meaning “other pain”, a pain due to a stimulus which does not normally provoke pain(ref).”   “As much as 7% to 8% of the population is affected by neuropathic pain and in 5% it may be severe(ref)(ref)(ref).”  Neuropathic pain may result from a variety of conditions including injuries to or disorders of the peripheral nervous system or the central nervous system (brain and spinal cord).

The traditional view of pain is that it is caused by firing of neurons which transmit signals up to the brain.  The conventional way to handle even persistent neuropathic pain has therefore been to block the neural signals.  This approach has a basic limitation.  Opiates like morphine are the most effective drugs for blocking acute pain.  But in the case of chronic pain opiates seem to become less and less effective in time requiring the use of higher doses leading to addiction. “Previous studies have shown opiates to be relatively ineffective for neuropathic pain in animals, and the animals typically develop tolerance over a short period of time, in that the drugs lose their ability to relieve pain(ref).”

In the mid-90s a new view of neuropathic pain started to emerge, which is to pay attention to the glial cells, the microglia and astrocyte cells which accompany and support  the neurons in nervous tissues in the spine.   Before pain is perceived in the brain, pain-producing signals must pass through stages of neural circuitry including ones that pass through the spine. There are more glia than neurons in the spinal cord and brain and they play essential functions like providing nourishment  to neurons, maintaining the chemical environment surrounding neurons and absorbing neurotransmitter molecules given off by them.  Glia listen carefully to signaling molecules from the neurons they accompany and respond with signaling molecules of their own.  This mutual molecular signaling process serves many important functions, including facilitating repair of damaged nerves.  However, it can get out of control and produce neuropathic pain.   

Quoting from a 2004 paper Glial activation: a driving force for pathological pain “Pain is classically viewed as being mediated solely by neurons, as are other sensory phenomena.   The discovery that spinal cord glia (microglia and astrocytes) amplify pain requires a change in this view. These glia express characteristics in common with immune cells in that they respond to viruses and bacteria, releasing proinflammatory cytokines, which create pathological pain. These spinal cord glia also become activated by certain sensory signals arriving from the periphery. Similar to spinal infection, these signals cause release of proinflammatory cytokines, thus creating pathological pain.  Taken together, these findings suggest a new, dramatically different approach to pain control, as all clinical therapies are focused exclusively on altering neuronal, rather than glial, function.”  An excellent and detailed explanation of this new view is in the article New Culprits in Chronic Pain in the November 2009 issue of Scientific American.  This 2009 paper further explains the molecular biology of how activated microglia creates pain without apparent cause (allodynia).

A simplified explanation is that neurons respond to an injury by firing rapidly to signal pain and releasing stress-related messenger molecules.  These changes are picked up by the microglia which begin emitting molecules that ease stress on the neurons and increase their sensitivity.  Among these molecules are proinflammatory cytokines like Interleukin-1, TNFα and IL-6, and TNFr, urgent messengers requesting mobilization of the body’s repair mechanisms.  The cytokines can greatly increase the sensitivity of the injured neurons as well as other neighboring neurons causing them to fire all the more.  This in turn leads to  additional production of cytokines by neighboring microglia, etc.   A vicious pro-inflammatory cycle ensues.  As this happens the pain is amplified.   Further, the cytokines fan out and affect other tissue systems leading them to give out their own pain signals.  The result is neuropathic pain – pain amplified in the nervous system. 

“Pathological pain has long been described as the result of dysfunctional neuronal activity.  While neuronal functioning is indeed altered, there is significant evidence showing that exaggerated pain is regulated by the activation of astrocytes and microglia. In exaggerated pain, astrocytes, and microglia are activated by neuronal signals including substance P, glutamate, and fractalkine. Activation of glia by these substances leads to the release of mediators that then act on other glia and neurons. These include a family of proteins called “proinflammatory cytokines” released from microglia and astrocytes. These cytokines have been shown to be critical mediators of exaggerated pain. Some patients with pathological pain also report “extra-territorial” and/or “mirror” image pain (Allodynia). That is, exaggerated pain is experienced not only in the area of trauma.  In extra-territorial pain, pain is also perceived as arising from neighboring healthy tissues outside of the site of trauma. In the rare cases of mirror-image pain, such pain is perceived as arising from the healthy, corresponding body part on the opposite side of the body. New data suggest that activation of astrocyte communication via gap junctions may mediate such spread of pain(ref).”

The paper Activated Microglia Contribute to the Maintenance of Chronic Pain after Spinal Cord Injury probably tells the central story of my own pain experience “Given that there are data supporting the involvement of microglia in pain after peripheral injury and work showing chronic post-SCI activation of microglia, we hypothesized that activated spinal microglia play a role in chronic central pain after SCI. Here, we report that thoracic SCI causes chronic activation of microglia in the lumbar spinal cord and that these activated microglia contribute to the maintenance of neuronal hyperresponsiveness and pain-related behaviors.”

The new view of pain also explains why opiates like morphine lose their pain-killing effectiveness in time(ref).  It turns out that since morphine or other opiates lowers the sensitivity of neurons to pain, the accompanying glia whose job is to maintain balance detect that fact and send out proinflammatory molecules that ratchet the neuron’s sensitivity back up again.  So, the blunting effect of the narcotic on pain is unblunted.  The agony of withdrawal experienced by a heroin addict who suddenly stops taking the drug is also explained.  While on the drug, the addicted person’s microglia have ratcheted up the pain sensitivity of the person’s neurons so that the person’s pain sensitivity is restored to near normal.  Suddenly withdrawing the drug leaves the person’s pain neurons super-sensitized without the blunting effect of the narcotic and it takes several days for them to calm back down.

The way to treat chronic pain according to this new perspective is to inhibit microglia from expressing cytokines, a story told by the title of the 2009 paper Early microglial inhibition preemptively mitigates chronic pain development after experimental spinal cord injury.  “These results suggest that inhibition of early neuroimmune events can have a powerful impact on the development of long-term pain phenomena following SCI and support the conclusion that modulation of microglial signaling may provide a new therapeutic strategy for patients suffering from post-SCI pain.”  One of the first substances identified that calm down microglia is the drug minocycline. “The current study examined the hypothesis that early administration of the microglial-inhibiting drug minocycline could ameliorate the development of pain after SCI. — Adult male Sprague-Dawley rats underwent SCI at the ninth thoracic spinal segment and received either vehicle or minocycline treatment for 5 days postinjury. Time course studies revealed that over 4 weeks post-SCI, microglial activation in vehicle-treated animals was progressively increased. Minocycline treatment resulted in reduction, but not prevention, of microglial activation over time. — These results suggest that inhibition of early neuroimmune events can have a powerful impact on the development of long-term pain phenomena following SCI and support the conclusion that modulation of microglial signaling may provide a new therapeutic strategy for patients suffering from post-SCI pain.”

The aforementioned Scientific American article mentions nine different of drugs being tested for their capability to quiet overactive glia, either in cell or animal tests and in some cases in clinical trials.  But that article says nothing about any drug that is available right now that quiets glia and is generally safe to use on a protracted basis for neuropathic pain.  Through serendipity I believe I have possibly identified such a substance, a familiar drug Gabapentin (Neurontin).  Indeed, I have been using this drug and in the course of four days it has brought my pain level down from 7-8 to 1-3 and greatly enhanced my comfort and functionality.

Gabapentin, is widely prescribed for chronic spinal pain and other pain conditions though its means for controlling pain have not been understood.   Gabapentin is approved by the FDA as an anti-convulsive drug and only for the Post-Therapeutic Neuralgia pain indication. Neurontin has an interesting history.  While several scientific studies and clinical trials support its use for pain management and a large percentage of the prescriptions for Neurontin are off-label, the company owning the rights to it, Pfizer, has gotten into trouble for promoting such uses.  “A division of Pfizer Inc., the world’s largest drug maker, has agreed to plead guilty to two felonies and pay $430 million in penalties to settle charges that it fraudulently promoted the drug Neurontin for a string of unapproved uses(ref).”  And there are still many unsettled lawsuits connected with such uses.  The key point here is that, strictly speaking, Gabapentin is an off-label treatment for neuropathic pain.  Moreover, the drug is now a low-cost generic so it is unlikely that Pfizer would ever want to incur the high costs of clinical trials for other indications.The 2003 review paper Gabapentin dosing for neuropathic pain: Evidence from randomized, placebo-controlled clinical trials concludes “At doses of 1800 to 3600 mg/d, Gabapentin was effective and well tolerated in the treatment of adults with neuropathic pain.”  The 2005 review paper Gabapentin in the treatment of neuropathic pain states:  “Clinically, several large randomized controlled trials have demonstrated its effectiveness in the treatment of a variety of neuropathic pain syndromes. Patients with neuropathic pain can expect a mean reduction in pain score of 2.05 points on an 11 point numerical rating scale compared with a reduction of 0.94 points if they had taken the placebo. Around 30% of patients can expect to achieve more than 50% pain relief and a similar number will also experience minor adverse events –.“  The 2004 paper Gabapentin is a first line drug for the treatment of neuropathic pain in spinal cord injury and the paper Gabapentin effect on neuropathic pain compared among patients with spinal cord injury and different durations of symptoms report on studies suggesting  that Gabapentin may be particularly effective for treating neuropathic pain associated with spinal cord injuries.

The paper I have found that suggests that Gabapentin moderates pain via the microglia is Gabapentin reverses microglial activation in the spinal cord of streptozotocin-induced diabetic rats.  “In addition, an attenuation of microglial activation correlated with reduced Allodynia following Gabapentin treatment, while Gabapentin had no effect on the number of astrocytes. Here we show a role of microglia in STZ-induced mechanical Allodynia and furthermore, that the anti-Allodynia effect of Gabapentin may be linked to a reduction of spinal microglial activation. Astrocytic activation in this model appears to be limited and is unaffected by Gabapentin treatment. Consequently, spinal microglial activation is a key mechanism underlying diabetic neuropathy. Furthermore, we suggest that Gabapentin may exert its anti-allodynic actions partially through alterations of microglial cell function.”

While this last conclusion is based on experiments with pain due to induced spinal injury in rats, I suspect strongly it also applies to spinal neuropathic pain in humans.  I have found a number of other papers suggesting possible molecular channels through which Gabapentin may inhibit pain, related to Gabapentin and cytokines and how Gabapentin inhibits the expression of NF-kappaB in certain cells, but none others that directly deal with the effects of Gabapentin on microglia.

I am on day 4 of Gabapentin treatment and the pain/discomfort level due to my spinal injury is running 1-3 in a scale of 1 to 10, down from a month or more of 6-8.  Time will tell whether I can maintain this comfort level and whether the original injury will heal.  So, I now have: 1.  a good working diagnosis of my condition; it is neuropathic pain created by a probably-minor spinal injury incurred while swimming, 2.  what so far is an effective therapeutic regimen, 3. a significantly enhanced personal state of comfort and functionality associated with pain reduction, and 4. an understanding of the basic mechanisms of the pain that was torturing me, as explained in this blog entry.