The Th17:Treg Ratio: A Limitation of Immunosuppressive Pharmaceutical Drugs
The ratio of a particularly aggressive sub-class of T-cells, called Th17 cells, to Treg cells is highly reflective of the tendency of the immune system to react aggressively towards transplanted tissue.
It is known that Treg cells have anti-inflammatory properties and cause quiescence of an over-aggressive immune response and prolongation of transplant function. Furthermore, Th17 cells are pro-inflammatory and can exacerbate the immune response in transplant rejection (Ma, 2010; Afzali, 2007; Kimura, 2010).
In October, 2010, researchers confirmed that decreasing the Th17:Treg resulted in increased allograft survival in an animal model. The team administered TGFβ directly to mice that had received transplants of pancreatic islet cells. Administering TGFβ resulted in a decrease in IL-6 activity and number of Th17 cells in circulation, and an increase in circulating Treg cells, prolonging allograft survival time. The researchers concluded that targeting IL-6 activity and lowering the Th17:Treg ratio “provides a promising approach for inducing transplant tolerance…” (Zhang, 2010).
Incorporating this recent understanding of immune tolerance and inflammatory pathology, researchers examined the impact of calcineurin inhibitors (CNIs) on the level of allograft protecting Treg cells circulating in 32 liver transplant recipients. Their study revealed that CNIs significantly reduced the level of Treg cells in circulation, compared to healthy control patients not receiving a CNI. The data lead the team to conclude that CNIs hampered progression towards a tolerance inducing Th17:Treg profile (Chu, 2010).
These new findings demonstrate that the most commonly prescribed immunosuppressive drugs in transplant patients fail to address an important underlying cause of transplant rejection – insufficient levels of protective Treg cells.
Grape Seed Extract Favorably Alters the Th17:Treg Ratio
An October, 2010 study revealed that a proanthocyanidin-rich grape seed extract is highly effective in reducing the ratio of Th17:Treg and modulating an over-aggressive immune response. Researchers observed that grape seed extract favorably altered the Th17:Treg ratio in both animal (murine) and human cell lines (Park, 2010).
In taking their research a step further, the scientists examined the effect of grape seed extract on the clinical symptoms of mice with collagen-induced arthritis, a model highly sensitive to the Th17:Treg ratio. They found that grape seed extract effectively attenuated clinical symptoms, confirming that the extract was a potent immunomodulator. The authors concluded that “by potently regulating inflammatory T-cell differentiation, grape seed extract may serve as a possible novel therapeutic agent for inflammatory and autoimmune diseases.”
Another study showed that dietary supplementation with blueberry extract (also high in proanthocyanidins) was highly effective in prolonging the survival of transplanted dopamine neurons, which are exceptionally delicate, in an animal model of Parkinson’s disease. The researchers also noted that the mice receiving blueberry extract exhibited better mobility and coordination than did the control group, which was not receiving blueberry extract (McGuire, 2006).
Targeting Residual Effects of Organ Transplantation and Side Effects of Immunosuppressive Pharmaceutical Drugs
Avoiding tissue rejection is not the only challenge facing transplant recipients. Many other complications frequently arise as a result of receiving a transplant and taking immunosuppressive drugs.
In nearly all transplant cases, the vasculature of the transplanted organ functions less optimally than that of the host’s native tissue. This often leads to cardiovascular complications, such as blood clots and hypertension (Vandergheynst, 2010; Vrochides, 2010). It is vitally important that the health and function of the endothelial cells (cells that line the inside of blood vessels) in recipients of an organ transplant be maintained.
Maintaining a low level of homocysteine is very important for transplant patients. Homocysteine is an amino acid derivative that damages endothelial cells and contributes to the pathogenesis of atherosclerosis.
A study published in October, 2010 found that higher homocysteine was a predictor of death from any cause in 378 renal transplant recipients, even after the researchers adjusted for multiple confounding factors. Subjects with the lowest one-third homocysteine level (<13.1 µmol/L) were much more likely to be alive 3,000 days post-transplant than those with the highest one-third homocysteine levels (>18.5 µmol/L). The researchers also noted that subjects taking a CNI had higher levels of homocysteine than subjects not taking a CNI (mean 16.3 µol/L vs. 14.3 µmol/L), suggesting that CNIs, like cyclosporine, might raise homocysteine (Connolly, 2010).
Fortunately, there are several nutraceutical ingredients that have been shown to effectively control homocysteine in transplant patients.
B6, B12 and 5-Methyltetrahydrofolate
In evaluating 98 renal transplant patients, researchers found that, not only were high levels of homocysteine correlated with chronic allograft dysfunction, but intake of vitamin B6, as well as higher blood levels of the active form of folate, 5-methyltetrahydrofolate, were associated with lower levels of homocysteine and improved vascular health. The researchers noted that “increased folate and vitamin B6 intakes seem to reduce homocysteine concentrations among transplant patients…and could contribute to reducing the risk of chronic allograft dysfunction” (Biselli, 2007).
In 56 renal transplant recipients, the combination of 50 mg B6, 400 mcg B12 and 5 mg folic acid daily, for six months, was found to significantly reduce levels of homocysteine (from 21.8 µmol/L to 9.3 µmol/L vs. no change in the placebo group) and carotid intima-media thickness, a marker of atherosclerosis (from 0.95 mm to 0.64 mm, average 32% reduction) while the placebo group showed a marked increase in carotid intima-media thickness (from 0.71 mm to 0.87 mm) over the trial period (Marcuzzi, 2003).
A study of 730 renal transplant patients provided unique insight into the importance of vitamin B12 and active folate in this population. Researchers in this study noted that higher levels of plasma B12 and active folate are likely associated with a survival advantage seen in kidney transplant patients who have a genetic predisposition to having higher levels of these vitamins in circulation (Winkelmayer, 2005).
The antioxidant N-acetyl cysteine, especially in combination with B vitamins, has been shown to lower homocysteine levels and improve endothelial function (Yilmaz, 2007).
In 12 children who received liver transplants, intravenous infusions of N-acetyl cysteine (70 mg/kg), in combination with prostaglandin-E1, were administered daily for six days starting immediately post-operation. The combination reduced the severity of rejection episodes within the first three months after the transplant, compared to a control group who did not receive infusions (Bucuvalas, 2001).
Intravenous N-acetyl cysteine (5 grams over four hours) was shown to dramatically reduce levels of homocysteine (from 15.5 µmol/L to 3.36 µmol/L) in 11 renal transplant patients with healthy levels of B12 and folate. The team reported no adverse effects attributable to N-acetyl cysteine. This study highlights both the safety and efficacy of N-acetyl cysteine in renal transplant patients (Rymarz, 2009).
An animal model of cyclosporine induced kidney toxicity found that N-acetyl cysteine was protective against the nephrotoxic effects of cyclosporine. Animals receiving cyclosporine alone showed significant increases in oxidative stress, as measured by levels of the reactive species nitric oxide and malondialdehyde, significant decreases in superoxide dismutase and glutathione peroxidase activity and notable kidney morphological changes, while animals receiving N-acetyl cysteine with cyclosporine did not manifest these changes (Duru, 2008).
In an in vitro study conducted on cells taken from lung transplant recipients, N-acetyl cysteine was able to reduce the genetic expression of the inflammatory cytokine TNFα, which contributes to transplant rejection. The authors concluded that “the therapeutic use of antioxidant compounds could, therefore, be of interest in conditions such as lung transplantation, in which oxidative stress and inflammation can contribute significantly to the loss of allograft function” (Hulten, 1998).
Cocoa and Pomegranate Polyphenols
Researchers, in double-blind placebo controlled fashion, examined the impact of polyphenols derived from cocoa on the vascular health of 22 heart transplant recipients. Researchers evaluated endothelial function, as measured by endothelium-dependent coronary vasomotion and coronary artery diameter, two hours after subjects consumed 40 grams of dark chocolate, providing 15.6 mg of polyphenols. Cocoa polyphenols were found to significantly increase coronary artery diameter (from 2.36 to 2.51 mm) and improve coronary vasomotion (+4.5% vs. -4.3% in placebo group). Furthermore, the researchers also saw a significant reduction in platelet adhesion in the polyphenol group (from 4.9% to 3.8%), compared to no change in the placebo group, indicating a decreased risk of blood clot formation and hypertension (Flammer, 2007).
Polyphenols from pomegranate, also known to support endothelial function (de Nigris, 2006), were administered to animals at a dose equivalent to ~500 mg for a 60 kg human for 21 days. Researchers found that pomegranate polyphenols significantly reduced cyclosporine-induced hepatic oxidative stress, as measured by levels of thiobarbituric acid reactive substances and activity of the antioxidative enzymes glutathione-S-transferase, superoxide dismutase and catalase. The team concluded that “the results of this study indicate that [pomegranate polyphenols] might play an important role in protecting [against] cyclosporine-induced oxidative damage in the liver” (Pari, 2008).
Daily supplementation with 90 mg of CoQ10 for four weeks resulted in significant improvements in cardiovascular health, as measured by HDL, LDL and total cholesterol levels, in 11 renal transplant patients. Furthermore, the researchers found that CoQ10 did not adversely affect blood levels of cyclosporine, highlighting the safety of CoQ10 in transplant patients taking cyclosporine (Dlugosz, 2004). This data suggests that CoQ10 could safely combat the side effects of cyclosporine, which is known to cause oxidative damage and unfavorably alter cholesterol levels (van den Dorpel, 1997).
Vitamins C and E
A double-blind trial examining the effect of supplementation with a combination of 500 mg vitamin C and 400 IU vitamin E, twice daily, showed that the vitamins slowed the progression of coronary arteriosclerosis in heart transplant patients. Over a period of one year, patients receiving vitamins C and E (n=19) experienced no increase in average intima-media index, while patients receiving a placebo (n=21) saw an 8% increase (Fang, 2002).
In a randomized, placebo controlled fashion, researchers studied the effects of 2,000 mg of vitamin C on the vascular function of 13 renal transplant patients. They found that vitamin C significantly improved endothelium-dependent dilation (from 1.6% to 4.5%), and also enhanced the antioxidant capacity of the subject’s blood, as measured by the time required to oxidize lipids in vitro (Williams, 2001).
The widely prescribed immunosuppressive drug, cyclosporine, is known to cause oxidative damage, and is associated with an unhealthy lipid profile (van den Dorpel, 1997). Vitamin E was effective in reducing cyclosporine-induced mitochondrial damage to porcine renal endothelial cells (de Arriba, 2009) and, in combination with quercetin, was shown to be protective against hepatotoxicity caused by cyclosporine, as measured by the level of thiobarbituric acid-reacting substances, and activity of glutathione peroxidase and catalase, in an animal model (Mostafavi-Pour, 2008).
It is important to note that, in at least one study, the combination of vitamins C and E was shown to reduce blood levels of cyclosporine by roughly 30% in heart transplant recipients who were taking 500 mg vitamin C twice daily and 400 IU vitamin E twice daily. These researchers went on to state that “although more detailed pharmacokinetic analysis is necessary to clarify the exact mechanism of this interaction, physicians who take care of transplant recipients should be aware that more frequent cyclosporine concentration monitoring is warranted after initiating these anti-oxidant agents” (Lake, 2005).
The amino acid L-arginine has been shown in multiple studies to improve the function of endothelial cells (Ou, 2010; Orea-Tejeda, 2010).
A 2010 study of 22 heart transplant patients found that supplemental L-arginine, six grams twice daily, improved endothelial function, as measured by the nitric oxide/endothelin ratio, and increased sub-maximal exercise capacity, as measured by a six minute walk test (distance walked increased from 525 m to 580 m). Significantly, the researchers also noted that supplemental L-arginine improved subjects overall quality of life score, as measured by standardized questionnaire (Doutreleau, 2010).
A study of 777 liver transplant recipients found that surgical site infection occurred in 37.8% of patients. These infections resulted in, on average, roughly 24 additional days of hospital stay, $159,967 in extra expenses and a 10% increase in mortality (Hollenbeak, 2001). Furthermore, post-operative infections have been associated with a significantly higher incidence of graft loss due to rejection (Cainelli, 2002).
A randomized placebo controlled trial of 95 liver transplant recipients examined the effects of probiotics (10 billion colony forming units), in combination with fiber, on post-operative infection rates. The researchers found that infection occurred in only 13% of the patients receiving probiotics and fiber, while in the control group 48% of patients developed infections (Rayes, 2002).
In order to duplicate these impressive results, the same lead researcher conducted another similar study shortly thereafter. This time the team studied the effect of probiotics, in combination with fiber, against fiber alone, on post-operative infection rates in 66 liver transplant recipients. The group receiving the combination of probiotics and fiber had an infection rate of only 3%, while, in the group receiving solely fiber, post-operative infection occurred in 48% of the patients (Rayes, 2005).
Magnesium wasting is common in transplant patients, especially those who receive a transplanted kidney (Mazzaferro, 2002). Low levels of magnesium have been shown to potentiate the toxic effects of cyclosporine and reduce allograft survival (Holzmacher, 2005).
In a study of 14 hypomagnesemic renal transplant patients, magnesium supplementation at a dose of 400 to 1,200 mg daily, for three months, was shown to significantly improve total and LDL cholesterol levels, glucose metabolism, and restore levels of magnesium. The researchers concluded that magnesium replenishment was effective for combating magnesium wasting and important for maintaining the health of renal transplant patients (Gupta, 1999).
What You Need To Know
Organ transplantation offers individuals with critically injured or failing organs a means to improve the quality of their lives and extend their lifespan. However, receiving a transplanted organ comes with many challenges.
Because a donated organ does not contain the DNA of the tissue recipient, the immune system of the host recognizes the transplanted organ as pathological and attempts to eliminate it. This ongoing battle between the donated tissue and the host’s immune system ultimately results in the destruction of the transplanted tissue. Thus, recipients of a transplant must take side-effect laden immunosuppressive drugs in order to preserve the transplanted organ for as long as possible.
Life Extension has identified multiple nutraceuticals which, based on peer-reviewed scientific evidence, target specific aspects of the immune response involved in tissue rejection, as well as help combat side effects of immunosuppressive drugs.
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