Resveratrol addiction: to die or not to die

Resveratrol, sirtuins, and the promise of a DR mimetic

Dietary restriction (DR) delays or prevents age-related diseases and extends lifespan in species ranging from yeast to primates. Although the applicability of this regimen to humans remains uncertain, a proportional response would add more healthy years to the average life than even a cure for cancer or heart disease. Because it is unlikely that many would be willing or able to maintain a DR lifestyle, there has been intense interest in mimicking its beneficial effects on health, and potentially longevity, with drugs. To date, such efforts have been hindered primarily by our lack of mechanistic understanding of how DR works. Sirtuins, NAD(+)-dependent deacetylases and ADP-ribosyltransferases that influence lifespan in lower organisms, have been proposed to be key mediators of DR, and based on this model, the sirtuin activator resveratrol has been proposed as a candidate DR mimetic. Indeed, resveratrol extends lifespan in yeast, worms, flies, and a short-lived species of fish. In rodents, resveratrol improves health, and prevents the early mortality associated with obesity, but its precise mechanism of action remains a subject of debate, and extension of normal lifespan has not been observed. This review summarizes recent work on resveratrol, sirtuins, and their potential to mimic beneficial effects of DR.

Resveratrol, a natural polyphenolic compound, inhibits cholera toxin-induced cyclic AMP accumulation in Vero cells

Resveratrol (3,4',5-trihydroxystilbene), a natural polyphenol found in red grapes, berries and peanuts, exhibits anti-inflammatory, cell-growth modulatory, and anticarcinogenic effects. In this report, we show that resveratrol inhibited cholera toxin (CT)-induced cyclic AMP accumulation in Vero cells. Resveratrol suppressed the CT activity by suppressing the internalization of CT and traffic to the Golgi apparatus without affecting CT binding to cells. Further, resveratrol partially precipitated CT from solution, and suppressed CT ADP-ribosyltransferase activity. These data suggest that resveratrol may inhibit CT-induced activity directly by associating with CT and suppressing its enzymatic activity, and indirectly by inhibiting CT endocytosis into cells.

Multidrug resistance proteins restrain the intestinal absorption of trans-resveratrol in rats

trans-Resveratrol, a natural antioxidant, has been described as a nutraceutic compound with important beneficial effects on health, but its low oral bioavailability hinders its therapeutic activity. Here, we studied the mechanisms of apical transport of trans-resveratrol in enterocytes and the role of ATP-binding cassette (ABC) transporters in the secretion of resveratrol glucuronide and sulfate resulting from the rapid intracellular metabolism. An intestinal perfusion method with recirculation in vivo was used in rats. Jejunal loops were perfused with increasing concentrations of trans-resveratrol and results showed that its uptake occurs by simple diffusion without the participation of a mediated transport. The apparent diffusion constant was 8.1 +/- 0.3 microL/(5 min.mg dry weight). The glycoprotein-P (Pgp, ABCB1), multidrug resistance-associated protein 2 (MRP2, ABCC2), and breast cancer resistance protein (BCRP, ABCG2) located in the apical membrane of enterocytes were investigated using specific inhibitors. The Pgp inhibitors verapamil (5 micromol/L) and cyclosporin A (5 micromol/L) did not affect the efflux of trans-resveratrol and its conjugates. The MRP2 inhibitors probenecid (2 mmol/L) and MK571 (10 micromol/L) reduced the efflux of glucuronide by 61 and 55%, respectively, and of sulfate by 43 and 28%, respectively. The BCRP inhibitor Ko143 (0.5 micromol/L) decreased the secretion of glucuronide by 64% and of sulfate by 46%. Our experiments identify MRP2 and BCRP as the 2 apical transporters involved in the efflux of resveratrol conjugates.

Dietary supplementation of resveratrol attenuates chronic colonic inflammation in mice

Ulcerative colitis is a nonspecific inflammatory disorder characterized by oxidative and nitrosative stress, leucocyte infiltration and upregulation of inflammatory mediators. Resveratrol is a polyphenolic compound found in grapes and wine, with multiple pharmacological actions, mainly anti-inflammatory, antioxidant, antitumour and immunomodulatory activities. The aim of this study was to investigate the effect of dietary resveratrol on chronic dextran sulphate sodium (DSS)-induced colitis. Six-week-old mice were randomized into two dietary groups: one standard diet and the other enriched with resveratrol at 20mg/kg of diet. After 30days, mice were exposed to 3% DSS for 5days developing acute colitis that progressed to severe chronic inflammation after 21days of water. Our results demonstrated that resveratrol group significantly attenuated the clinical signs such as loss of body weight, diarrhea and rectal bleeding improving results from disease activity index and inflammatory score. Moreover, the totality of resveratrol-fed animals survived and finished the treatment while animals fed with standard diet showed a mortality of 40%. Three weeks after DSS removal, the polyphenol caused substantial reductions of the rise of pro-inflammatory cytokines, TNF-alpha and IL-1beta and an increase of the anti-inflammatory cytokine IL-10. Also resveratrol reduced prostaglandin E synthase-1 (PGES-1), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) proteins expression, via downregulation of p38, a mitogen-activated protein kinases (MAPK) signal pathway. We conclude that resveratrol diet represents a novel approach to the treatment of chronic intestinal inflammation.

Resveratrol reduces glutamate-mediated monocyte chemotactic protein-1 expression via inhibition of extracellular signal-regulated kinase 1/2 pathway in rat hippocampal slice cultures

Published evidence has linked glutamate with the pathogenesis of Alzheimer's disease (AD) and the up-regulation of a variety of chemokines, including monocyte chemotactic protein-1 (MCP-1)/chemokine ligand 2, with AD-associated pathological changes. In this study, we assessed the potential molecular basis for the role of glutamate in hippocampal inflammation by determining its effects on MCP-1 induction. We also attempted to identify the mechanism by which resveratrol (trans-3,5,4'-trihydroxystilbene), a polyphenolic phytostilbene, modulates the expression of MCP-1 in the glutamate-stimulated hippocampus. An ex vivo study using rat hippocampal slices demonstrated a time- and dose-dependent increase in MCP-1 release from glutamate-exposed hippocampus. This increase was accompanied by enhanced MCP-1 gene expression via the activation of the MEK/extracellular signal-regulated kinase (ERK) pathway and interleukin-1beta (IL-1beta) expression. The inhibition of the MEK/ERK pathway with SL327, which is capable of crossing the blood-brain barrier, nearly abolished the observed glutamate-induced effects. Furthermore, anti-IL-1beta antibodies suppressed the glutamate-induced expression of MCP-1 mRNA and protein, whereas an isotype-matched antibody exerted only minimal effects. It is worthy of note that resveratrol, to a similar degree as SL327, down-regulated glutamate-induced IL-1beta expression and reduced the expression of MCP-1 mRNA and protein release via the inactivation of ERK1/2. These results indicate that the activation of the MEK/ERK pathway and the consequent IL-1beta expression are essential for glutamate-stimulated MCP-1 production in the hippocampus. Additionally, our data reveal an anti-inflammatory mechanism of resveratrol involving the inactivation of the ERK1/2 pathway in the hippocampus, which is linked principally to AD-associated cognitive dysfunction.

Resveratrol in the chemoprevention and treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers and lethal diseases in the world. Although the majority of HCC cases occur in developing countries of Asia and Africa, the prevalence of liver cancer has risen considerably in Japan, Western Europe as well as the United States. HCC most commonly develops in patients with chronic liver disease, the etiology of which includes viral hepatitis (B and C), alcohol, obesity, iron overload and dietary carcinogens, including aflatoxins and nitrosamines. The current treatment modalities, including surgical resection and liver transplantation, have been found to be mostly ineffective. Hence, there is an obvious critical need to develop alternative strategies for the chemoprevention and treatment of HCC. Oxidative stress as well as inflammation has been implicated in the development and progression of hepatic neoplasia. Using naturally occurring phytochemicals and dietary compounds endowed with potent antioxidant and antiinflammatory properties is a novel approach to prevent and control HCC. One such compound, resveratrol, present in grapes, berries, peanuts as well as red wine, has emerged as a promising molecule that inhibits carcinogenesis with a pleiotropic mode of action. This review examines the current knowledge on mechanism-based in vitro and in vivo studies on the chemopreventive and chemotherapeutic potential of resveratrol in liver cancer. Pre-clinical and clinical toxicity studies as well as pharmacokinetic data of resveratrol have also been highlighted in this review. Future directions and challenges involved in the use of resveratrol for the prevention and treatment of HCC are also discussed.

Curcumin, resveratrol and flavonoids as anti-inflammatory, cyto- and DNA-protective dietary compounds

Numerous dietary compounds, ubiquitous in fruits, vegetables and spices have been isolated and evaluated during recent years for their therapeutic potential. These compounds include flavonoid and non-flavonoid polyphenols, which describe beneficial effects against a variety of ailments. The notion that these plant products have health promoting effects emerged because their intake was related to a reduced incidence of cancer, cardiovascular, neurological, respiratory, and age-related diseases. Exposure of the body to a stressful environment challenges cell survival and increases the risk of chronic disease developing. The polyphenols afford protection against various stress-induced toxicities through modulating intercellular cascades which inhibit inflammatory molecule synthesis, the formation of free radicals, nuclear damage and induce antioxidant enzyme expression. These responses have the potential to increase life expectancy. The present review article focuses on curcumin, resveratrol, and flavonoids and seeks to summarize their anti-inflammatory, cytoprotective and DNA-protective properties.

Biochemical effects of SIRT1 activators

SIRT1 is the closest mammalian homologue of enzymes that extend life in lower organisms. Its role in mammals is incompletely understood, but includes modulation of at least 34 distinct targets through its nicotinamide adenine dinucleotide (NAD(+))-dependent deacetylase activity. Recent experiments using small molecule activators and genetically engineered mice have provided new insight into the role of this enzyme in mammalian biology and helped to highlight some of the potentially relevant targets. The most widely employed activator is resveratrol, a small polyphenol that improves insulin sensitivity and vascular function, boosts endurance, inhibits tumor formation, and ameliorates the early mortality associated with obesity in mice. Many of these effects are consistent with modulation of SIRT1 targets, such as PGC1alpha and NFkappaB, however, resveratrol can also activate AMPK, inhibit cyclooxygenases, and influence a variety of other enzymes. A novel activator, SRT1720, as well as various methods to manipulate NAD(+) metabolism, are emerging as alternative methods to increase SIRT1 activity, and in many cases recapitulate effects of resveratrol. At present, further studies are needed to more directly test the role of SIRT1 in mediating beneficial effects of resveratrol, to evaluate other strategies for SIRT1 activation, and to confirm the specific targets of SIRT1 that are relevant in vivo. These efforts are especially important in light of the fact that SIRT1 activators are entering clinical trials in humans, and "nutraceutical" formulations containing resveratrol are already widely available.

Soluble polyphenols: synthesis and bioavailability of 3,4',5-tri(alpha-D-glucose-3-O-succinyl) resveratrol

We report the development of a chemical modification method of general applicability to polyphenols, which increases solubility to influence absorption. Glucosyl groups were added to the resveratrol kernel via a succinate linker, yielding 3,4',5-tri-(alpha-D-glucose-3-O-succinyl) resveratrol. The construct was only slowly hydrolyzed in acid and at pH 6.8, but it was destroyed by blood esterases in less than 1h. In rats its administration resulted in a blood concentration versus time curve shifted to longer times in comparison to resveratrol, a useful modulation of pharmacokinetics. The area-under-curve parameter and the metabolite mix were similar to those of resveratrol. The method may be advantageously employed to solubilize other polyphenols and to make them more palatable.

Resveratrol: cellular actions of a potent natural chemical that confers a diversity of health benefits

Resveratrol is a polyphenolic flavonoid with potent antioxidant activity. It is found in a diversity of plants, notably berry fruit, and is attracting increased attention due to its health benefits, especially in common age-related diseases such as cancer, type 2 diabetes, cardiovascular disease, and neurological conditions. Resveratrol has positive effects on metabolism and can increase the lifespan of various organisms. Its effects arise from its capacity to interact with multiple molecular targets involved in diverse intracellular pathways. Most well known is the ability of resveratrol to activate sirtuins, a class of NAD(+)-dependent deacetylases that affect multiple transcription factors and other protein targets. More potent sirtuin activators have now been discovered by large-scale screening programs. Resveratrol and the new compounds are the subject of clinical trials to determine their consumer safety and suitability for the prevention and treatment of most common diseases of aging.

NF-kappaB signaling in the aging process

INTRODUCTION

The aging process represents a progressive decline in cellular and organism function. Explaining the aging process has given rise to a cornucopia for different theories in which the basic difference has been the question whether aging is genetically regulated or an entropic degeneration process.

DISCUSSION

Different screening techniques have revealed that mammalian aging is associated with the activation of NF-kappaB transcription factor system. The NF-kappaB system is an ancient host defense system concerned with immune responses and different external and internal dangers, such as oxidative and genotoxic stress. NF-kappaB signaling is not only the master regulator of inflammatory responses but can also regulate several homeostatic responses such as apoptosis, autophagy, and tissue atrophy. We will describe how chronic activation of NF-kappaB signaling has the capacity to induce the senescent phenotype associated with aging. Interestingly, several longevity genes such as SIRT1, SIRT6, and FoxOs can clearly suppress NF-kappaB signaling and in this way delay the aging process and extend lifespan.

CONCLUSION

It seems that the aging process is an entropic degeneration process driven by NF-kappaB signaling. This process can be regulated by a variety of longevity genes along with a plethora of other factors such as genetic polymorphism, immune and dietary aspects, and environmental insults.