Resveratrol and Related Compounds as Antioxidants With an Allosteric Mechanism of Action in Epigenetic Drug Targets

SIRT3/6: an amazing challenge and opportunity in the fight against fibrosis and aging

Fibrosis is a typical aging-related pathological process involving almost all organs, including the heart, kidney, liver, lung, and skin. Fibrogenesis is a highly orchestrated process defined by sequences of cellular response and molecular signals mechanisms underlying the disease. In pathophysiologic conditions associated with organ fibrosis, a variety of injurious stimuli such as metabolic disorders, epigenetic changes, and aging may induce the progression of fibrosis. Sirtuins protein is a kind of deacetylase which can regulate cell metabolism and participate in a variety of cell physiological functions. In this review, we outline our current understanding of common principles of fibrogenic mechanisms and the functional role of SIRT3/6 in aging-related fibrosis. In addition, sequences of novel protective strategies have been identified directly or indirectly according to these mechanisms. Here, we highlight the role and biological function of SIRT3/6 focus on aging fibrosis, as well as their inhibitors and activators as novel preventative or therapeutic interventions for aging-related tissue fibrosis.

The Role of Sirtuin-1 (SIRT1) in the Physiology and Pathophysiology of the Human Placenta

Sirtuins, especially SIRT1, play a significant role in regulating inflammatory response, autophagy, and cell response to oxidative stress. Since their discovery, sirtuins have been regarded as anti-ageing and longevity-promoting enzymes. Sirtuin-regulated processes seem to participate in the most prevalent placental pathologies, such as pre-eclampsia. Furthermore, more and more research studies indicate that SIRT1 may prevent pre-eclampsia development or at least alleviate its manifestations. Having considered this, we reviewed recent studies on the role of sirtuins, especially SIRT1, in processes determining normal or abnormal development and functioning of the placenta.

In Silico Identification of Natural Product-Based Inhibitors Targeting IL-1β/IL-1R Protein-Protein Interface

IL-1β mediates inflammation and regulates immune responses, cell proliferation, and differentiation. Dysregulation of IL-1β is linked to inflammatory and autoimmune diseases. Elevated IL-1β levels are found in patients with severe COVID-19, indicating its excessive production may worsen the disease. Also, dry eye disease patients show high IL-1β levels in tears and conjunctival epithelium. Therefore, IL-1β signaling is a potential therapeutic targeting for COVID-19 and aforementioned diseases. No small-molecule IL-1β inhibitor is clinically approved despite efforts. Developing such inhibitors is highly desirable. Herein, a docking-based strategy was used to screen the TCM (Traditional Chinese Medicine) database to identify possible IL-1β inhibitors with desirable pharmacological characteristics by targeting the IL-1β/IL-1R interface. Primarily, the docking-based screening was performed by selecting the crucial residues of IL-1β interface to retrieve the potential compounds. Afterwards, the compounds were shortlisted on the basis of binding scores and significant interactions with the crucial residues of IL-1β. Further, to gain insights into the dynamic behavior of the protein-ligand interactions, MD simulations were performed. The analysis suggests that four selected compounds were stabilized in an IL-1β pocket, possibly blocking the formation of an IL-1β/IL-1R complex. This indicates their potential to interfere with the immune response, making them potential therapeutic agents to investigate further.

Differentiated modulation of signaling molecules AMPK and SIRT1 in experimentally drug-induced hepatocyte injury

AIM

Currently available medicines have little to offer in terms of supporting the regeneration of injured hepatic cells. Previous experimental studies have shown that resveratrol and metformin, less specific activators of AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1), can effectively attenuate acute liver injury. The aim of this experimental study was to elucidate whether modulation of AMPK and SIRT1 activity can modify drug/paracetamol (APAP)-induced hepatocyte damage in vitro.

METHODS

Primary rat hepatocytes were pretreated with mutual combinations of specific synthetic activators and inhibitors of SIRT1 and AMPK and followed by a toxic dose of APAP. At the end of cultivation, medium samples were collected for biochemical analysis of alanine-aminotransferase and nitrite levels. Hepatocyte viability, thiobarbituric reactive substances, SIRT1 and AMPK activity and protein expression were also assessed.

RESULTS

The harmful effect of APAP was associated with decreased AMPK and SIRT1 activity and protein expression alongside enhanced oxidative stress in hepatocytes. The addition of AMPK activator (AICAR) or SIRT1 activator (CAY10591) significantly attenuated the deleterious effects of AMPK inhibitor (Compound C) on the hepatotoxicity of APAP. Furthermore, CAY10591 but not AICAR markedly decreased the deleterious effect of APAP in combination with SIRT1 inhibitor (EX-527).

CONCLUSION

Our findings demonstrate that decreased AMPK activity is associated with the hepatotoxic effect of APAP which can be significantly attenuated by the administration of a SIRT1 activator. These findings suggest that differentiated modulation of AMPK and SIRT1 activity could therefore provide an interesting and novel therapeutic opportunity in the future to combat hepatocyte injury.

A Technique of Measurement of Gastrointestinal Luminal Nutrient Sensing and These Absorptions: Ussing Chamber (Short-Circuit Current) Technique

The gastrointestinal (GI) tract is a series of hollow organs that play roles in food digestion and nutrient absorption. To perform these functions, they should recognize the luminal environment and elicit adequate physiological responses, including digestive juice secretion, peristaltic movements, etc. The Ussing chamber technique is an electrophysiological method for measuring transepithelial ion transport and permeability as short-circuit current (I_sc) and transepithelial electrical tissue conductance (G_t) or resistance (TEER), respectively, in vitro. This technique can be applied for the measurement of luminal nutrient sensing and absorption. This article introduces practical methods for measuring luminal nutrient sensing and absorption using intestinal mucosa specimens isolated from humans and experimental animals.

High Sucrose Ingestion during a Critical Period of Vessel Development Promotes the Synthetic Phenotype of Vascular Smooth Muscle Cells and Modifies Vascular Contractility Leading to Hypertension in Adult Rats

Cardiometabolic diseases, including hypertension, may result from exposure to high sugar diets during critical periods of development. Here, we studied the effect of sucrose ingestion during a critical period (CP) between postnatal days 12 and 28 of the rat on blood pressure, aortic histology, vascular smooth muscle phenotype, expression of metalloproteinases 2 and 9, and vascular contractility in adult rats and compared it with those of adult rats that received sucrose for 6 months and developed metabolic syndrome (MS). Blood pressure increased to a similar level in CP and MS rats. The diameter of lumen, media, and adventitia of aortas from CP rats was decreased. Muscle fibers were discontinuous. There was a decrease in the expression of alpha-actin in CP and MS rat aortas, suggesting a change to the secretory phenotype in vascular smooth muscle. Metalloproteinases 2 and 9 were decreased in CP and MS rats, suggesting that phenotype remains in an altered steady stationary state with little interchange of the vessel matrix. Aortic contraction to norepinephrine did not change, but aortic relaxation was diminished in CP and MS aortas. In conclusion, high sugar diets during the CP increase predisposition to hypertension in adults.

Molecular Targets of Natural Compounds with Anti-Cancer Properties

Cancer is the second leading cause of death in humans. Despite rapid developments in diagnostic methods and therapies, metastasis and resistance to administrated drugs are the main obstacles to successful treatment. Therefore, the main challenge should be the diagnosis and design of optimal therapeutic strategies for patients to increase their chances of responding positively to treatment and increase their life expectancy. In many types of cancer, a deregulation of multiple pathways has been found. This includes disturbances in cellular metabolism, cell cycle, apoptosis, angiogenesis, or epigenetic modifications. Additionally, signals received from the microenvironment may significantly contribute to cancer development. Chemical agents obtained from natural sources seem to be very attractive alternatives to synthetic compounds. They can exhibit similar anti-cancer potential, usually with reduced side effects. It was reported that natural compounds obtained from fruits and vegetables, e.g., polyphenols, flavonoids, stilbenes, carotenoids and acetogenins, might be effective against cancer cells in vitro and in vivo. Several published results indicate the activity of natural compounds on protein expression by its influence on transcription factors. They could also be involved in alterations in cellular response, cell signaling and epigenetic modifications. Such natural components could be used in our diet for anti-cancer protection. In this review, the activities of natural compounds, including anti-cancer properties, are described. The influence of natural agents on cancer cell metabolism, proliferation, signal transduction and epigenetic modifications is highlighted.

Sirt1 inhibits kidney stones formation by attenuating calcium oxalate-induced cell injury

Cell injury is a necessary and critical event during CaOx kidney stone formation. Sirt1 exerts a number of pleiotropic effects, protecting against renal cell injury. This study aims to explore the relationship between Sirt1 and CaOx kidney stone formation and the underlying mechanism. Sirt1 expression in renal tissues or HK-2 cells was detected by Western blot, immunohistochemistry and immunofluorescence. Apoptosis in renal tissues was examined by TUNEL staining. Renal pathological changes and the crystals deposition were detected by hematoxylin-eosin and Von Kossa staining. Crystal-cell adhesion and cell injury in HK-2 cells were assessed by atomic absorption spectrometry and flow cytometry, respectively. Sirt1 expression in nephrolithiasis patients was downregulated and the level of apoptosis was increased. Further study found that Sirt1 expression was decreased in both in vivo and in vitro models. Interestingly, the levels of cell injury were elevated in vivo and in vitro models. Suppressing Sirt1 expression promoted COM-induced crystal-cell adhesion and exacerbated cell injury. In contrast, increasing the expression of Sirt1 by lentivirus transfection in vitro and resveratrol administration in vivo, alleviated crystal deposition and cell damage. Our findings suggest that Sirt1 could inhibit kidney stone formation, at least in part, through attenuating CaOx -induced cell injury.

Defective lysosomal storage in Fabry disease modifies mitochondrial structure, metabolism and turnover in renal epithelial cells

Fabry disease (FD) is an X-linked lysosomal storage disorder. Deficiency of the lysosomal enzyme alpha-galactosidase (GLA) leads to accumulation of potentially toxic globotriaosylceramide (Gb3) on a multisystem level. Cardiac and cerebrovascular abnormalities as well as progressive renal failure are severe, life-threatening long-term complications. The complete pathophysiology of chronic kidney disease (CKD) in FD and the role of tubular involvement for its progression are unclear. We established human renal tubular epithelial cell lines from the urine of male FD patients and male controls. The renal tubular system is rich in mitochondria and involved in transport processes at high-energy costs. Our studies revealed fragmented mitochondria with disrupted cristae structure in FD patient cells. Oxidative stress levels were elevated and oxidative phosphorylation was upregulated in FD pointing at enhanced energetic needs. Mitochondrial homeostasis and energy metabolism revealed major changes as evidenced by differences in mitochondrial number, energy production and fuel consumption. The changes were accompanied by activation of the autophagy machinery in FD. Sirtuin1, an important sensor of (renal) metabolic stress and modifier of different defense pathways, was highly expressed in FD. Our data show that lysosomal FD impairs mitochondrial function and results in severe disturbance of mitochondrial energy metabolism in renal cells. This insight on a tissue-specific level points to new therapeutic targets which might enhance treatment efficacy.

Hydrogen-rich water protects against liver injury in nonalcoholic steatohepatitis through HO-1 enhancement via IL-10 and Sirt 1 signaling

Nonalcoholic steatohepatitis (NASH) could progress to hepatic fibrosis in the absence of effective control. The purpose of our experiment was to investigate the protective effect of drinking water with a high concentration of hydrogen, namely, hydrogen-rich water (HRW), on mice with nonalcoholic fatty liver disease to elucidate the mechanism underlying the therapeutic action of molecular hydrogen. The choline-supplemented, l-amino acid-defined (CSAA) or the choline-deficient, l-amino acid-defined (CDAA) diet for 20 wk was used to induce NASH and fibrosis in the mice model and simultaneously treated with the high-concentration 7-ppm HRW for different periods (4 wk, 8  wk, and 20 wk). Primary hepatocytes were stimulated by palmitate to mimic liver lipid metabolism during fatty liver formation. Primary hepatocytes were cultured in a closed vessel filled with 21% O₂ + 5% CO₂ + 3.8% H₂ and N₂ as the base gas to verify the response of primary hepatocytes in a high concentration of hydrogen gas in vitro. Mice in the CSAA + HRW group had lower serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and milder histological damage. The inflammatory cytokines were expressed at lower levels in the HRW group than in the CSAA group. Importantly, HRW reversed hepatocyte fatty acid oxidation and lipogenesis as well as hepatic inflammation and fibrosis in preexisting hepatic fibrosis specimens. Molecular hydrogen inhibits the lipopolysaccharide-induced production of inflammation cytokines through increasing heme oxygenase-1 (HO-1) expression. Furthermore, HRW improved hepatic steatosis in the CSAA + HRW group. Sirtuin 1 (Sirt1) induction by molecular hydrogen via the HO-1/adenosine monophosphate activated protein kinase (AMPK)/peroxisome proliferator-activated receptor α (PPARα)/peroxisome proliferator-activated receptor γ (PPAR-γ) pathway suppresses palmitate-mediated abnormal fat metabolism. Orally administered HRW suppressed steatosis induced by CSAA and attenuated fibrosis induced by CDAA, possibly by reducing oxidative stress and the inflammation response.NEW & NOTEWORTHY The mRNA expression of inflammatory cytokines in the HRW group was lower than in the CSAA group. HRW reversed hepatocyte apoptosis as well as hepatic inflammation and fibrosis in NASH specimens. Molecular hydrogen inhibits LPS-induced inflammation via an HO-1/interleukin 10 (IL-10)-independent pathway. HRW improved hepatic steatosis in the CSAA + HRW group. Sirt1 induction by molecular hydrogen via the HO-1/AMPK/PPARα/PPARγ pathway suppresses palmitate-mediated abnormal fat metabolism.

Dietary Spray-Dried Porcine Plasma Prevents Cognitive Decline in Senescent Mice and Reduces Neuroinflammation and Oxidative Stress

BACKGROUND

Aging is characterized by chronic, low-grade inflammation that correlates with cognitive decline. Dietary supplementation with spray-dried porcine plasma (SDP) reduces immune activation in rodent models of inflammation and aging.

OBJECTIVE

We investigated whether the anti-inflammatory properties of SDP could ameliorate age-related cognitive deterioration and preserve brain homeostasis in an aging mouse model of senescence.

METHODS

Male senescence-accelerated prone 8 (SAMP8) mice were used. In Experiment 1, cognitive performance (n  = 10-14 mice/group) was analyzed by the novel object recognition test in 2-mo-old mice (2M group) and in mice fed a control diet or a diet supplemented with 8% SDP for 2 (4M-CTL and 4M-SDP groups) and 4 mo (6M-CTL and 6M-SDP groups). In Experiment 2, the permeability of the blood-brain barrier and junctional proteins in brain tissue was assessed, as well as synaptic density, oxidative stress markers, and inflammatory genes and proteins in mice from the 2M, 6M-CTL, and 6M-SDP groups ( n = 5-11). Statistical analyses included one-factor ANOVA followed by Fisher's posthoc test.

RESULTS

6M-SDP mice had better cognitive performance than 6M-CTL mice in both short-term (P = 0.024) and long-term (P = 0.017) memory tests. In brain tissue, 6M-SDP mice showed reduced brain capillary permeability (P = 0.034) and increased ZO1 and E-cadherin expression (both P <0.04) compared with 6M-CTL mice. SDP also prevented the NFκB activation observed in 6M-CTL mice (P = 0.002) and reduced Il6 expression and hydrogen peroxide concentration (both P <0.03) observed in 6M-CTL mice. SDP also increased the concentration of IL10 (P = 0.027), an anti-inflammatory cytokine correlated with memory preservation.

CONCLUSIONS

In senescent SAMP8 mice, dietary supplementation with SDP attenuated cognitive decline and prevented changes in brain markers of neuroinflammation and oxidative stress.

Effects of Polyphenol Compounds and Nitrogen Oxide Donors on Lipid Oxidation, Membrane-Skeletal Proteins, and Erythrocyte Structure under Hypoxia

This study shows that membrane-associated cytoskeletal protein structures and the erythrocyte morphology undergo profound changes during hypoxia. Hypoxia also intensified oxidative processes in the lipid phase of the bilayer of red blood cell membranes. Sodium nitroprusside impaired the morphology of red blood cells and altered quantitative and qualitative composition of membrane-skeletal proteins. The findings suggest that hypoxia causes changes at all levels of red blood cell organization, which can cause the functional disorders of hemoglobin oxygen-transporting properties and, eventually, the complete degradation of red blood cells. The use of flavonoids has a protective effect against hypoxia.

Epigenetic regulation of bone remodeling by natural compounds

Osteoporosis and osteopenia impact more than 54 million Americans, resulting in significant morbidity and mortality. Alterations in bone remodeling are the hallmarks for osteoporosis, and thus the development of novel treatments that will prevent or treat bone diseases would be clinically significant, and improve the quality of life for these patients. Bone remodeling involves the removal of old bone by osteoclasts and the formation of new bone by osteoblasts. This process is tightly coupled, and is essential for the maintenance of bone strength and integrity. Since the osteoclast is the only cell capable of bone resorption, the development of drugs to treat bone disorders has primarily focused on reducing osteoclast differentiation, maturation, and bone resorption mechanisms, and there are few treatments that actually increase bone formation. Evidence from observational, experimental, and clinical studies demonstrate a positive link between naturally occurring compounds and improved indices of bone health. While many natural extracts and compounds are reported to have beneficial effects on bone, only resveratrol, sulforaphane, specific phenolic acids and anthocyanins, have been shown to both increase bone formation and reduce resorption through their effects on the bone epigenome. Each of these compounds alters specific aspects of the bone epigenome to improve osteoblast differentiation, reduce osteoblast apoptosis, improve bone mineralization, and reduce osteoclast differentiation and function. This review focuses on these specific natural compounds and their epigenetic regulation of bone remodeling.

Resveratrol Treatment Ameliorates Leptin Resistance and Adiposity Programed by the Combined Effect of Maternal and Post-Weaning High-Fat Diet

SCOPE

Prenatal high-fat (HF) and postnatal HF diet are both associated with obesity and metabolic disturbances in adults. Leptin resistance induced by obesity limits its biological effects. The anti-obesity mechanism of resveratrol in visceral adiposity is investigated here.

METHODS AND RESULTS

During mating and lactation, Sprague-Dawley dams are fed either control or a HF diet. Subsequently, the offspring are fed chow or an HF diet. A fifth group that received maternal/postnatal HF diet and resveratrol after weaning (HHR) is used to study the effects of resveratrol treatment. Resveratrol treatment alleviates adiposity programed by maternal and postnatal HF diet by decreasing feed intake or inducing metabolic changes. Resveratrol treatment is also found to ameliorate the decrease in SIRT1 abundance observed in retroperitoneal adipose tissue, programed by maternal and postnatal HF diet. Moreover, resveratrol therapy decreases plasma leptin level and increases leptin receptor expression in retroperitoneal adipose tissue through DNA methylation modification.

CONCLUSION

These results suggest that resveratrol can alleviate peripheral leptin resistance programed by the combined effect of prenatal and postnatal HF diet through epigenetic regulation of genes coding leptin and its receptor. It provides insights into a novel mechanism explaining the beneficial effects of resveratrol in obesity management.

SIRT1 Modulators in Experimentally Induced Liver Injury

This article is directed at highlighting the involvement of the endogenous stress sensor SIRT1 (silent information regulator T1) as a possible factor involved in hepatoprotection. The selective SIRT1 modulators whether activators (STACs) or inhibitors are being tried experimentally and clinically. We discuss the modulation of SIRT1 on cytoprotection or even cytotoxicity in the liver chemically injured by hepatotoxic agents in rats, to shed light on the crosstalk between SIRT1 and its modulators. A combination of D-galactosamine and lipopolysaccharide (D-GalN/LPS) downregulated SIRT1 expression, while SIRT1 activators, SRT1720, resveratrol, and quercetin, upregulated SIRT1 and alleviated D-GalN/LPS-induced acute hepatotoxicity. Liver injury markers exhibited an inverse relationship with SIRT1 expression. However, under subchronic hepatotoxicity, quercetin decreased the significant increase in SIRT1 expression to lower levels which are still higher than normal ones and mitigated the liver-damaging effects of carbon tetrachloride. Each of these STACs was hepatoprotective and returned the conventional antioxidant enzymes to the baseline. Polyphenols tend to fine-tune SIRT1 expression towards normal in the liver of intoxicated rats in both acute and subchronic studies. Together, all these events give an impression that the cytoprotective effects of SIRT1 are exhibited within a definite range of expression. The catalytic activity of SIRT1 is important in the hepatoprotective effects of polyphenols where SIRT1 inhibitors block and the allosteric SIRT1 activators mimic the hepatoprotective effects of polyphenols. Our findings indicate that the pharmacologic modulation of SIRT1 could represent both an important move in alleviating hepatic insults and a future major step in the treatment of xenobiotic-induced hepatotoxicity.

Effect of Sucrose Ingestion at the End of a Critical Window that Increases Hypertension Susceptibility on Peripheral Mechanisms Regulating Blood Pressure in Rats. Role of Sirtuins 1 and 3

Susceptibility to develop hypertension may be established during early stages of life that include the intrauterine period, infancy and childhood. We recently showed that blood pressure increased when rats reached adulthood when sucrose was ingested for a short-term critical window from postnatal day 12 to 28 in the rat, which corresponds to days around weaning. Here, we studied several factors that might participate in the increased susceptibility to hypertension when adulthood is reached by analyzing the changes produced at the end of the sucrose ingestion during this critical period. Body weight of the rats at the end of the sucrose period was decreased even if there was an increased ingestion in Kcal. We found an increase in blood pressure accompanied by a decrease in endothelial nitric oxide synthase (eNOS) expression in the aorta. When insulin was administered to rats receiving sucrose, glucose in plasma diminished later than in controls and this slight insulin resistance may reduce nitric oxide synthase action. Oleic acid that modulates eNOS expression was increased, lipoperoxidation was elevated and total non-enzymatic anti-oxidant capacity was decreased. There was also a decrease in SOD2 expression. We also studied the expression of Sirt1, which regulates eNOS expression and Sirt3, which regulates SOD2 expression as possible epigenetic targets of enzyme expression involved in the long- term programming of hypertension. Sirt3 was decreased but we did not find an alteration in Sirt1 expression. We conclude that these changes may underpin the epigenetic programming of increased susceptibility to develop hypertension in the adults when there was exposure to high sucrose levels near weaning in rats.

Molecular hydrogen protects against ischemia-reperfusion injury in a mouse fatty liver model via regulating HO-1 and Sirt1 expression

Fatty liver has lower tolerance against ischemia-reperfusion (I/R) injury in liver operations, including liver transplantation. Seeking to ameliorate liver injury following I/R in fatty liver, we examined the protective effect of hydrogen (H₂) saline on I/R liver injury in a methionine and choline-deficient plus high fat (MCDHF) diet-induced fatty liver mouse model. Saline containing 7 ppm H₂ was administrated during the process of I/R. Livers were obtained and analyzed. Primary hepatocytes and Kupffer cells (KCs) were obtained from fatty liver and subjected to hypoxia/reoxygenation. Apoptosis-related proteins and components of the signaling pathway were analyzed after treatment with hydrogen gas. The MCDHF I/R group showed higher levels of AST and ALT in serum, TUNEL-positive apoptotic cells, F4/80 immunopositive cells, mRNA levels of inflammatory cytokines, constituents of the signaling pathway, pro-apoptotic molecules in liver, and KCs and/or primary hepatocytes, compared to the control group. In contrast, H₂ treatment significantly suppressed the signs of I/R injury in fatty liver. Moreover, the expression of Bcl-2, HO-1, and Sirt1 in liver, KCs, and hepatocytes by hydrogen gas were increased, whereas caspase activation, Bax, and acetylation of p53 were suppressed by hydrogen gas. These results demonstrated that H₂ treatment ameliorated I/R liver injury in a fatty liver model by reducing hepatocyte apoptosis, inhibiting macrophage activation and inflammatory cytokines, and inducing HO-1 and Sirt1 expression. Taken togather, treatment with H₂ saline may have a protective effect and safe therapeutic activity during I/R events, such as in liver transplantation with fatty liver.

The Roles of Natural Compounds in Epigenetics

Epigenetic modifications include DNA methylation, histone modification, microRNA and lncRNA regulations, and take part in many physiological and pathological processes. Recently, it has been found that natural compounds are essential in regulation of epigenetics. By influencing the expression and activities of genes related with epigenetics and altering the expression and functions of miRNAs, many natural compounds exhibit the biological and pharmaceutical activities in the prevention, diagnosis and treatment of many kinds of human diseases, such as cancer, diabetes and cardiovascular diseases. Here in this review, the effects of several natural compounds on epigenetics and the underlying mechanisms were summarized, providing a new insight into the role of natural compounds.

Short-Term Exposure to High Sucrose Levels near Weaning Has a Similar Long-Lasting Effect on Hypertension as a Long-Term Exposure in Rats

Adverse conditions during early developmental stages permanently modify the metabolic function of organisms through epigenetic changes. Exposure to high sugar diets during gestation and/or lactation affects susceptibility to metabolic syndrome or hypertension in adulthood. The effect of a high sugar diet for shorter time lapses remains unclear. Here we studied the effect of short-term sucrose ingestion near weaning (postnatal days 12 and 28) (STS) and its effect after long-term ingestion, for a period of seven months (LTS) in rats. Rats receiving sucrose for seven months develop metabolic syndrome (MS). The mechanisms underlying hypertension in this model and those that underlie the effects of short-term exposure have not been studied. We explore NO and endothelin-1 concentration, endothelial nitric oxide synthase (eNOS) expression, fatty acid participation and the involvement of oxidative stress (OS) after LTS and STS. Blood pressure increased to similar levels in adult rats that received sucrose during short- and long-term glucose exposure. The endothelin-1 concentration increased only in LTS rats. eNOS and SOD2 expression determined by Western blot and total antioxidant capacity were diminished in both groups. Saturated fatty acids and arachidonic acid were only decreased in LTS rats. In conclusion, a high-sugar diet during STS increases the hypertension predisposition in adulthood to as high a level as LTS, and the mechanisms involved have similarities (participation of OS and eNOS and SOD expression) and differences (fatty acids and arachidonic acid only participate in LTS and an elevated level of endothelin-1 was only found in LTS) in both conditions. Changes in the diet during short exposure times in early developmental stages have long-lasting effects in determining hypertension susceptibility.

Sirtuins in Renal Health and Disease

Sirtuins belong to an evolutionarily conserved family of NAD⁺-dependent deacetylases that share multiple cellular functions related to proliferation, DNA repair, mitochondrial energy homeostasis, and antioxidant activity. Mammalians express seven sirtuins (SIRT1-7) that are localized in different subcellular compartments. Changes in sirtuin expression are critical in several diseases, including metabolic syndrome, diabetes, cancer, and aging. In the kidney, the most widely studied sirtuin is SIRT1, which exerts cytoprotective effects by inhibiting cell apoptosis, inflammation, and fibrosis together with SIRT3, a crucial metabolic sensor that regulates ATP generation and mitochondrial adaptive response to stress. Here, we provide an overview of the biologic effects of sirtuins and the molecular targets thereof regulating renal physiology. This review also details progress made in understanding the effect of sirtuins in the pathophysiology of chronic and acute kidney diseases, highlighting the key role of SIRT1, SIRT3, and now SIRT6 as potential therapeutic targets. In this context, the current pharmacologic approaches to enhancing the activity of SIRT1 and SIRT3 will be discussed.

Potential of resveratrol in mitigating metabolic disturbances induced by ethanol

Alcohol abuse is associated with numerous health problems, including metabolic disturbances and liver damage. Therefore, different compounds are continuously being tested to evaluate their potential effectiveness in reducing these harmful changes. Animal studies clearly show that resveratrol is capable of ameliorating some consequences of ethanol ingestion. Resveratrol is a naturally occurring diphenolic compound having pleiotropic, health-promoting properties. Its beneficial action have been also demonstrated in animal models with ethanol-induced metabolic disturbances and liver injury. In ethanol treated animals, resveratrol effectively reduced liver lipid accumulation. Moreover, this compound diminished necrosis of hepatocytes, and also reduced liver fibrosis. The hepatoprotective action of resveratrol is largely associated with its ant-oxidant and anti-inflammatory properties, and also covers changes in activities of some enzymes. It is known that this compound upregulates the adiponectin-SIRT1-AMPK signaling pathway in the liver. Resveratrol was also found to positively affect blood lipids in animals exposed to ethanol. Moreover, administration of resveratrol to animals with ethanol-induced hypoinsulinemia and insulin resistance was shown to alleviate these disturbances. These outcomes clearly indicate that resveratrol holds great potential to reduce some consequences of ethanol ingestion. However, human studies are required to fully assess its therapeutic value.

Chemoprevention by resveratrol and pterostilbene: Targeting on epigenetic regulation

Epigenetic mechanisms are essential in regulating normal cellular functions and play an important role during the disease developmental stages. However, aberrant epigenetic mechanisms may lead to pathological consequences such as cancer, neurological disorders, bone and skeletal diseases, cardiovascular dysfunction, and metabolic syndrome. The molecular mechanisms of epigenetic modification include DNA methylation, histone modification (acetylation, methylation and phosphorylation), and microRNAs (miRNAs). Unlike genetic modifications, epigenetic states of genes are reversible and can be altered by certain intrinsic and extrinsic factors. In the past few decades, accumulated evidence shows that dietary phytochemicals with chemopreventive effects are also potent epigenetic regulators. Resveratrol and pterostilbene are stilbenoids, which have been reported to have anti-cancer, anti-inflammatory, anti-lipid, and anti-diabetic properties. Stilbenoids are also reported to improve cardiovascular disease. By altering DNA methylation and histone modification or by modulating miRNA expression, resveratrol, and pterostilbene become potent epigenetic modifiers. In this review, we summarize these studies and underlying mechanisms of resveratrol and pterostilbene and their influence on epigenetic mechanisms. © 2017 BioFactors, 44(1):26-35, 2018.

Epigenetic Regulatory Mechanisms Induced by Resveratrol

Resveratrol (RVT) is one of the main natural compounds studied worldwide due to its potential therapeutic use in the treatment of many diseases, including cancer, diabetes, cardiovascular diseases, neurodegenerative diseases and metabolic disorders. Nevertheless, the mechanism of action of RVT in all of these conditions is not completely understood, as it can modify not only biochemical pathways but also epigenetic mechanisms. In this paper, we analyze the biological activities exhibited by RVT with a focus on the epigenetic mechanisms, especially those related to DNA methyltransferase (DNMT), histone deacetylase (HDAC) and lysine-specific demethylase-1 (LSD1).

Sirtuin-Activating Compounds (STACs) Alleviate D-Galactosamine/Lipopolysaccharide-Induced Hepatotoxicity in Rats: Involvement of Sirtuin 1 and Heme Oxygenase 1

Sirtuin activating compounds (STACs) attenuate various type of liver insults through mechanisms which are not fully understood. In the present study, we investigated the ameliorative potential of quercetin (natural polyphenol) and SRT1720 (synthetic SIRT1 activator) against D-galactosamine/lipopolysaccharide-induced hepatotoxicity (an experimental model of acute liver failure). Moreover, we compared and contrasted the roles of stress responsive enzymes, sirtuin 1 (SIRT1) and heme oxygenase 1 (HO-1) in hepatoprotection/ hepatotoxicity. Liver injury was induced in male Wistar rats by intraperitoneal injection of D-galactosamine (400 mg/kg) and lipopolysaccharide (10 µg/kg). Some animals were pretreated with quercetin (50 mg/kg i.p.) or SRT1720 (5 mg/kg i.p.). Twenty-four hours later, the effects of these treatments were evaluated by biochemical studies and Western blot. D-GalN/LPS treatment upregulated HO-1 expression, downregulated SIRT1 expression, decreased AST:ALT ratio and markedly increased bilirubin, catalase and conjugated diene levels. Pretreatment of D-GalN/LPS rats with either quercetin or SRT1720 returned SIRT1 expression, HO-1 expression and all the aforementioned markers towards normal. Collectively, these findings suggest that elevated HO-1 and low SIRT1 expressions are involved in the pathogenesis of D-GalN/LPS-induced hepatotoxicity. Drugs that downregulate HO-1 and/or upregulate SIRT1 seem to have antihepatotoxic effects and need further exploration.

Metabolic Stress Induces Cognitive Disturbances and Inflammation in Aged Mice: Protective Role of Resveratrol

Inflammation and oxidative stress (OS) are key points in age progression. Both processes impact negatively in cognition and in brain functions. Resveratrol (RV) has been postulated as a potent antioxidant natural compound, with rejuvenating properties. Inducing a metabolic stress by high-fat (HF) diet in aged C56/BL6 (24 months) led to cognitive disturbances compared with control age mated and with young mice. These changes were prevented by RV. Molecular determinations demonstrated a significant increase in some inflammatory parameters (TNF-α, Cxcl10, IL-1, IL-6, and Ccl3) in old mice, but slight changes in OS machinery. RV mainly induced the recovery of the metabolically stressed animals. The study of key markers involved in senescence and rejuvenation (mitochondrial biogenesis and Sirt1-AMPK-PGC1-α) demonstrated that RV is also able to modulate the changes in these cellular metabolic pathways. Moreover, changes of epigenetic marks (methylation and acetylation) that are depending on OS were demonstrated. On the whole, results showed the importance of integrative role of different cellular mechanisms in the deleterious effects of age in cognition and the beneficial role of RV. The work presented in this study showed a wide range of processes modified in old age and by metabolic stress, weighting the importance of each one and the role of RV as a possible strategy for fighting against.

In Vitro and In Vivo Experimental Hepatotoxic Models in Liver Research: Applications to the Assessment of Potential Hepatoprotective Drugs

This mini-review highlights our and others’ experience about in vitro and in vivo models that are being used to follow up events of liver injuries under various hepatotoxic agents and potential hepatoprotective drugs. Due to limitations of the outcomes in each model, we focus primarily on two models. First, a developed perfusion method for isolated immobilized hepatocytes that improves the process of oxygenation and helps in end-product removal is of considerable value in improving cell maintenance. This cellular model is presented as a short-term research-scale laboratory bioreactor with various physiological, biochemical, molecular, toxicological and pharmacological applications. Second, the in vivo model of D-galactosamine and lipopolysaccharide (D-GalN/LPS) combination-induced liver damage is described with some details. Recently, we have revealed that resveratrol and other natural polyphenols attenuate D-GalN/LPS-induced hepatitis. Moreover, we reported that D-GalN/LPS down-regulates sirtuin 1 in rat liver. Therefore, we discuss here the role of sirtuin 1 modulation in hepatoprotection. A successful development of pharmacotherapy for liver diseases depends on the suitability of in vitro and in vivo hepatic injury systems. Several models are available to screen the hepatotoxic or hepatoprotective activity of any substance. It is important to combine different methods for confirmation of the findings.

Resveratrol alleviates ethanol-induced hormonal and metabolic disturbances in the rat

Resveratrol is a polyphenol found in different plant species and having numerous health-promoting properties in animals and humans. However, its protective action against deleterious effects of ethanol is poorly elucidated. In the present study, the influence of resveratrol (10 mg/kg/day) on some hormones and metabolic parameters was determined in rats ingesting 10 % ethanol solution for two weeks. Blood levels of insulin, glucagon and adiponectin were affected by ethanol, however, resveratrol partially ameliorated these changes. Moreover, in ethanol drinking rats, liver lipid accumulation was increased, whereas resveratrol was capable of reducing liver lipid content, probably due to decrease in fatty acid synthesis. Resveratrol decreased also blood levels of triglycerides and free fatty acids and reduced gamma-glutamyl transferase activity in animals ingesting ethanol. These results show that resveratrol, already at low dose, alleviates hormonal and metabolic changes induced by ethanol in the rat and may be useful in preventing and treating some consequences of alcohol consumption.

Effects of ε-viniferin, a dehydrodimer of resveratrol, on transepithelial active ion transport and ion permeability in the rat small and large intestinal mucosa

ε-Viniferin is a dehydrodimer of resveratrol, a polyphenol synthesized in many plants, including grapevine. The present study investigated the effects of ε-viniferin and resveratrol on epithelial secretory and barrier functions in isolated rat small and large intestinal mucosa. Mucosa-submucosa tissue preparations of various segments of the rat large and small intestines were mounted on Ussing chambers, and short-circuit current (Isc) and tissue conductance (Gt) were continuously measured. The mucosal addition of ε-viniferin (>10(-5) mol/L) and resveratrol (>10(-4) mol/L) to the cecal mucosa, which was the most sensitive region, induced an increase in Isc and a rapid phase decrease (P-1) followed by rapid (P-2) and broad (P-3) peak increases in Gt in concentration-dependent manners. Mucosal ε-viniferin (10(-4) mol/L), but not resveratrol (10(-4) mol/L), increased the permeability of FITC-conjugated dextran (4 kDa). The mucosal ε-viniferin-evoked changes in Isc (Cl(-) secretion), but not in Gt, were attenuated by a selective cyclooxygenase (COX)-1 inhibitor and a selective EP4 prostaglandin receptor. The mucosal ε-viniferin-evoked increase in Isc was partially attenuated, and P-2, but not P-1 or P-3, change in Gt was abolished by a transient receptor potential cation channel, subfamily A, member 1 (TRPA1) inhibitor. Moreover, the mucosal ε-viniferin concentration-dependently attenuated the mucosal propionate (1 mmol/L)-evoked increases in Isc and Gt Immunohistochemical studies revealed COX-1-immunoreactive epithelial cells in the cecal crypt. The present study showed that mucosal ε-viniferin modulated transepithelial ion transport and permeability, possibly by activating sensory epithelial cells expressing COX-1 and TRPA1. Moreover, mucosal ε-viniferin decreased mucosal sensitivity to other luminal molecules such as short-chain fatty acids. In conclusion, these results suggest that ε-viniferin modifies intestinal mucosal transport and barrier functions.

Sirtuin 1 Modulation in Rat Model of Acetaminophen-Induced Hepatotoxicity

Sirtuin 1 (SIRT1) is involved in important biological processes such as energy metabolism and regulatory functions of the cell cycle, apoptosis, and inflammation. Our previous studies have shown hepatoprotective effect of polyphenolic compound resveratrol, which is also an activator of SIRT1. Therefore, the aim of our present study was to clarify the role of SIRT1 in process of hepatoprotection in animal model of drug-induced liver damage. Male Wistar rats were used for both in vivo and in vitro studies. Hepatotoxicity was induced by single dose of acetaminophen (APAP). Some rats and hepatocytes were treated by resveratrol or synthetic selective activator of sirtuin 1 (CAY10591). The degree of hepatotoxicity, the activity and expression of the SIRT1 were determined by biochemical, histological and molecular-biological assessments of gained samples (plasma, liver tissue, culture media and hepatocytes). Resveratrol and CAY attenuated APAP-induced hepatotoxicity in vivo and in vitro. Moreover, both drugs enhanced APAP-reduced SIRT1 activity. Our results show that modulation of the SIRT1 activity plays a role in hepatoprotection. Synthetic activators of SIRT1 would help in understanding the role of SIRT1 and are therefore a major boost towards the search for specific treatment of liver disease.

Antioxidants in Translational Medicine

SIGNIFICANCE

It is generally accepted that reactive oxygen species (ROS) scavenging molecules or antioxidants exert health-promoting effects and thus their consumption as food additives and nutraceuticals has been greatly encouraged. Antioxidants may be beneficial in situations of subclinical deficiency and increased demand or acutely upon high-dose infusion. However, to date, there is little clinical evidence for the long-term benefit of most antioxidants. Alarmingly, recent evidence points even to health risks, in particular for supplements of lipophilic antioxidants.

RECENT ADVANCES

The biological impact of ROS depends not only on their quantities but also on their chemical nature, (sub)cellular and tissue location, and the rates of their formation and degradation. Moreover, ROS serve important physiological functions; thus, inappropriate removal of ROS may cause paradoxical reductive stress and thereby induce or promote disease.

CRITICAL ISSUES

Any recommendation on antioxidants must be based on solid clinical evidence and patient-relevant outcomes rather than surrogate parameters.

FUTURE DIRECTIONS

Such evidence-based use may include site-directed application, time-limited high dosing, (functional) pharmacological repair of oxidized biomolecules, and triggers of endogenous antioxidant response systems. Ideally, these approaches need guidance by patient stratification through predictive biomarkers and possibly imaging modalities.

Exercise Pills: At the Starting Line

Sedentary lifestyles, limited physical exercise, and prolonged inactivity undoubtedly increase chronic diseases, including obesity, type 2 diabetes, and cardiovascular diseases. It is widely acknowledged that exercise induces a number of physiological adaptations that have beneficial effects in the prevention and treatment of these chronic metabolic diseases. Unfortunately, exercise compliance is extremely low and often not possible. The development of exercise science and molecular techniques has increased our understanding of the molecular pathways responsive to exercise. Knowledge of these molecular targets has led to the development of chemical interventions that can mimic the beneficial effects of exercise without requiring actual muscle activity. This review focuses on the concept of 'exercise pills' and how they mimic the effects produced by physical exercise including oxidative fiber-type transformation, mitochondrial biogenesis, increased fat oxidation, angiogenesis, and improvement of exercise capacity. We also review candidate exercise pills, and contrast the beneficial effects and molecular mechanisms between physical exercise and exercise pills.

Exploiting the Pleiotropic Antioxidant Effects of Established Drugs in Cardiovascular Disease

Cardiovascular disease is a leading cause of death and reduced quality of life worldwide. Arterial vessels are a primary target for endothelial dysfunction and atherosclerosis, which is accompanied or even driven by increased oxidative stress. Recent research in this field identified different sources of reactive oxygen and nitrogen species contributing to the pathogenesis of endothelial dysfunction. According to lessons from the past, improvement of endothelial function and prevention of cardiovascular disease by systemic, unspecific, oral antioxidant therapy are obviously too simplistic an approach. Source- and cell organelle-specific antioxidants as well as activators of intrinsic antioxidant defense systems might be more promising. Since basic research demonstrated the contribution of different inflammatory cells to vascular oxidative stress and clinical trials identified chronic inflammatory disorders as risk factors for cardiovascular events, atherosclerosis and cardiovascular disease are closely associated with inflammation. Therefore, modulation of the inflammatory response is a new and promising approach in the therapy of cardiovascular disease. Classical anti-inflammatory therapeutic compounds, but also established drugs with pleiotropic immunomodulatory abilities, demonstrated protective effects in various models of cardiovascular disease. However, results from ongoing clinical trials are needed to further evaluate the value of immunomodulation for the treatment of cardiovascular disease.

Redox regulation of genome stability by effects on gene expression, epigenetic pathways and DNA damage/repair

Reactive oxygen and nitrogen species (e.g. H2O2, nitric oxide) confer redox regulation of essential cellular signaling pathways such as cell differentiation, proliferation, migration and apoptosis. In addition, classical regulation of gene expression or activity, including gene transcription to RNA followed by translation to the protein level, by transcription factors (e.g. NF-κB, HIF-1α) and mRNA binding proteins (e.g. GAPDH, HuR) is subject to redox regulation. This review will give an update of recent discoveries in this field, and specifically highlight the impact of reactive oxygen and nitrogen species on DNA repair systems that contribute to genomic stability. Emphasis will be placed on the emerging role of redox mechanisms regulating epigenetic pathways (e.g. miRNA, DNA methylation and histone modifications). By providing clinical correlations we discuss how oxidative stress can impact on gene regulation/activity and vise versa, how epigenetic processes, other gene regulatory mechanisms and DNA repair can influence the cellular redox state and contribute or prevent development or progression of disease.

A Resveratrol Analogue Promotes ERKMAPK-Dependent Stat3 Serine and Tyrosine Phosphorylation Alterations and Antitumor Effects In Vitro against Human Tumor Cells

(E)-4-(3,5-dimethoxystyryl)phenyl acetate (Cmpd1) is a resveratrol analog that preferentially inhibits glioma, breast, and pancreatic cancer cell growth, with IC50 values of 6-19 μM. Notably, the human U251MG glioblastoma tumor line is the most sensitive, with an IC50 of 6.7 μM, compared with normal fibroblasts, which have an IC50 > 20 μM. Treatment of U251MG cells that harbor aberrantly active signal transducer and activator of transcription (Stat) 3 with Cmpd1 suppresses Stat3 tyrosine705 phosphorylation in a dose-dependent manner in parallel with the induction of pserine727 Stat3 and extracellular signal-regulated kinase/mitogen-activated protein kinase 1/2 (pErk1/2(MAPK)). Inhibition of pErk1/2(MAPK) induction by the mitogen-activated protein/extracellular signal-regulated kinase kinase inhibitor PD98059 [2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one] blocked both the pserine727 Stat3 induction and ptyrosine705 Stat3 suppression by Cmpd1, indicating dependency on the mitogen-activated protein/extracellular signal-regulated kinase kinase-Erk1/2(MAPK) pathway for Cmpd1-induced modulation of Stat3 signaling. Cmpd1 also blocked epidermal growth factor-stimulated pStat1 induction, whereas upregulating pSrc, pAkt, p-p38, pHeat shock protein 27, and pmammalian target of rapamycin levels. However, pJanus kinase 2 and pEpidermal growth factor receptor levels were not significantly altered. Treatment of U251MG cells with Cmpd1 reduced in vitro colony formation, induced cell cycle arrest in the G2/M phase and cleavage of caspases 3, 8, and 9 and poly(ADP ribose) polymerase, and suppressed survivin, myeloid cell leukemia 1, Bcl-xL, cyclin D1, and cyclin B1 expression. Taken together, these data identify a novel mechanism for the inhibition of Stat3 signaling by a resveratrol analog and suggest that the preferential growth inhibitory effects of Cmp1 occur in part by Erk1/2(MAPK)-dependent modulation of constitutively active Stat3.

TSG (2,3,5,4'-Tetrahydroxystilbene-2-O- β -D-glucoside) from the Chinese Herb Polygonum multiflorum Increases Life Span and Stress Resistance of Caenorhabditis elegans

2,3,5,4'-Tetrahydroxystilbene-2-O-β-D-glucoside (TSG) was isolated from Polygonum multiflorum, a plant which is traditionally used as an anti-ageing drug. We have analysed ageing-related effects of TSG in the model organism C. elegans in comparison to resveratrol. TSG exerted a high antioxidative capacity both in a cell-free assay and in the nematode. The antioxidative capacity was even higher compared to resveratrol. Presumably due to its antioxidative effects, treatment with TSG decreased the juglone-mediated induction of the antioxidative enzyme SOD-3; the induction of the GST-4 by juglone was diminished slightly. TSG increased the resistance of C. elegans against lethal thermal stress more prominently than resveratrol (50 μM TSG increased mean survival by 22.2%). The level of the ageing pigment lipofuscin was decreased after incubation with the compound. TSG prolongs the mean, median, and maximum adult life span of C. elegans by 23.5%, 29.4%, and 7.2%, respectively, comparable to the effects of resveratrol. TSG-mediated extension of life span was not abolished in a DAF-16 loss-of-function mutant strain showing that this ageing-related transcription factor is not involved in the effects of TSG. Our data show that TSG possesses a potent antioxidative capacity, enhances the stress resistance, and increases the life span of the nematode C. elegans.

Reshaping faecal gut microbiota composition by the intake of trans-resveratrol and quercetin in high-fat sucrose diet-fed rats

Diet-induced obesity is associated to an imbalance in the normal gut microbiota composition. Resveratrol and quercetin, widely known for their health beneficial properties, have low bioavailability, and when they reach the colon, they are targets of the gut microbial ecosystem. Hence, the use of these molecules in obesity might be considered as a potential strategy to modulate intestinal bacterial composition. The purpose of this study was to determine whether trans-resveratrol and quercetin administration could counteract gut microbiota dysbiosis produced by high-fat sucrose diet (HFS) and, in turn, improve gut health. Wistar rats were randomised into four groups fed an HFS diet supplemented or not with trans-resveratrol [15 mg/kg body weight (BW)/day], quercetin (30 mg/kg BW/day) or a combination of both polyphenols at those doses. Administration of both polyphenols together prevented body weight gain and reduced serum insulin levels. Moreover, individual supplementation of trans-resveratrol and quercetin effectively reduced serum insulin levels and insulin resistance. Quercetin supplementation generated a great impact on gut microbiota composition at different taxonomic levels, attenuating Firmicutes/Bacteroidetes ratio and inhibiting the growth of bacterial species previously associated to diet-induced obesity (Erysipelotrichaceae, Bacillus, Eubacterium cylindroides). Overall, the administration of quercetin was found to be effective in lessening HFS-diet-induced gut microbiota dysbiosis. In contrast, trans-resveratrol supplementation alone or in combination with quercetin scarcely modified the profile of gut bacteria but acted at the intestinal level, altering the mRNA expression of tight-junction proteins and inflammation-associated genes.

Antiasthmatic effects of resveratrol in ovalbumin-induced asthma model mice involved in the upregulation of PTEN

Resveratrol, a natural polyphenolic compound known for its antioxidative and antiinflammatory effects, exerts antiasthmatic effects, although the mechanism underlying these effects remains elusive. The phosphatase and tensin homology deleted on chromosome ten gene (PTEN) is involved in the pathogenesis of asthma, and PTEN overexpression in asthmatic mice improved asthma symptoms. To investigate whether the antiasthmatic mechanisms of resveratrol correlated with the upregulation of PTEN expression, an ovalbumin (OVA)-induced murine asthma model was used to determine the effectiveness of resveratrol treatment. PTEN mRNA and protein expression was assessed with real-time polymerase chain reaction (PCR) and immunochemistry. To determine whether airway remodeling occurred, the inner airway wall, mucous layer, and smooth muscle areas were each determined using an image analysis system. The lung epithelial cell line 16HBE was used to study the regulation of PTEN expression levels by resveratrol in vitro. Our data demonstrated that resveratrol inhibited OVA-induced airway inflammation and airway remodeling in asthmatic mice. PTEN expression was decreased in the murine asthma model, although the expression of PTEN was restored following treatment with resveratrol. Correlation efficiency analysis showed that PTEN expression was associated with the degree of airway remodeling. Further in vitro studies demonstrated that the inhibition of Sirtuin 1 (SIRT1) activity by a SIRT1 inhibitor and RNA interference decreased PTEN protein expression, while resveratrol attenuated the decreases in PTEN expression induced by the SIRT1 inhibitor. These data suggest the mechanism of the antiasthmatic effects of resveratrol in an OVA-induced murine asthma model, which resulted in the upregulation of PTEN via SIRT1 activation.

D-Galactosamine/Lipopolysaccharide-Induced Hepatotoxicity Downregulates Sirtuin 1 in Rat Liver: Role of Sirtuin 1 Modulation in Hepatoprotection

D-Galactosamine/Lipopolysaccharide (D-GalN/LPS) is a well known model of hepatotoxicity that closely resembles acute liver failure (ALF) seen clinically. The role of sirtuin 1 in this model has not yet been documented. However, there have been a number of studies about the cytoprotective effects of resveratrol, a SIRT1 activator, in the liver. This study was aimed at elucidating the roles of SIRT1 protein expression or catalytic activity in D-GalN/LPS model of hepatotoxicity. ALF was induced in male Wistar rats by intraperitoneal injection of D-GalN and LPS. Some groups of animals were pretreated with resveratrol and/or EX-527 (SIRT1 inhibitor). The effects of these treatments were evaluated by biochemical and Western blot studies. D-GalN/LPS treatment was able to induce hepatotoxicity and significantly increase all markers of liver damage and lipid peroxidation. A dramatic decrease of SIRT1 levels in response to D-GalN/LPS treatment was also documented. Resveratrol pretreatment attenuated D-GalN/LPS-induced hepatotoxicity. EX-527 blocked the cytoprotective effects of resveratrol. However, both resveratrol and EX-527 pretreatments did not exhibit any significant effect on SIRT1 protein expression. Collectively, these results suggest that downregulation of SIRT1 expression is involved in the cytotoxic effects of D-GalN/LPS model and SIRT1 activity contributes to the cytoprotective effects of resveratrol in the liver.

Resveratrol and cardiovascular health--promising therapeutic or hopeless illusion?

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a natural polyphenolic compound that exists in Polygonum cuspidatum, grapes, peanuts and berries, as well as their manufactured products, especially red wine. Resveratrol is a pharmacologically active compound that interacts with multiple targets in a variety of cardiovascular disease models to exert protective effects or induce a reduction in cardiovascular risks parameters. This review attempts to primarily serve to summarize the current research findings regarding the putative cardioprotective effects of resveratrol and the molecular pathways underlying these effects. One intent is to hopefully provide a relatively comprehensive resource for clues that may prompt ideas for additional mechanistic studies which might further elucidate and strengthen the role of the stilbene family of compounds in cardiovascular disease and cardioprotection. Model systems that incorporate a significant functional association with tissues outside of the cardiovascular system proper, such as adipose (cell culture, obesity models) and pancreatic (diabetes) tissues, were reviewed, and the molecular pathways and/or targets related to these models and influenced by resveratrol are discussed. Because the body of work encompassing the stilbenes and other phytochemicals in the context of longevity and the ability to presumably mitigate a plethora of afflictions is replete with conflicting information and controversy, especially so with respect to the human response, we tried to remain as neutral as possible in compiling and presenting the more current data with minimal commentary, permitting the reader free reign to extract the knowledge most helpful to their own investigations.

Activators of AMPK: not just for Type II diabetes

Recent discoveries of AMPK activators point to the large number of therapeutic candidates that can be transformed to successful designs of novel drugs. AMPK is a universal energy sensor and influences almost all physiological processes in the cells. Thus, regulation of the cellular energy metabolism can be achieved in selective tissues via the artificial activation of AMPK by small molecules. Recently, special attention has been given to direct activators of AMPK that are regulated by several nonspecific upstream factors. The direct activation of AMPK, by definition, should lead to more specific biological activities and as a result minimize possible side effects.

Resveratrol promotes degradation of the human bile acid transporter ASBT (SLC10A2)

The sodium/bile acid co-transporter ASBT [apical sodium-dependent bile acid transporter; SLC10A2 (solute carrier family 10 member 2)] plays a key role in the enterohepatic recycling of the bile acids and indirectly contributes to cholesterol homoeostasis. ASBT inhibitors reportedly lower plasma triglyceride levels and increase HDL (high-density lipoprotein) cholesterol levels. RSV (resveratrol), a major constituent of red wine, is known to lower LDL (low-density lipoprotein) cholesterol levels, but its mechanism of action is still unclear. In the present study, we investigated the possible involvement of ASBT in RSV-mediated cholesterol-lowering effects. We demonstrate that RSV inhibits ASBT protein expression and function via a SIRT1 (sirtuin 1)-independent mechanism. The effect was specific to ASBT since other transporters involved in cholesterol homoeostasis, NTCP (SLC10A1), OSTα (SLC51A) and ABCG1 (ATP-binding cassette G1), remained unaffected. ASBT inhibition by RSV was reversed by proteasome inhibitors (MG-132 and lactacystin) and the ubiquitin inhibitor LDN57444, suggesting involvement of the ubiquitin-proteasome pathway. Immunoprecipitation revealed high levels of ubiquitinated ASBT after RSV treatment. Phosphorylation at Ser335 and Thr339 was shown previously to play a role in proteosomal degradation of rat ASBT. However, mutation at corresponding residues in rat ASBT revealed that phosphorylation does not contribute to RSV-mediated degradation of ASBT. Combined, our data indicate that RSV promotes ASBT degradation via the ubiquitin-proteasome pathway without requiring phosphorylation. We conclude that regulation of ASBT expression by RSV may have clinical relevance with regard to the observed cholesterol-lowering effects of RSV.

Adaptation and sensitization to proteotoxic stress

Although severe stress can elicit toxicity, mild stress often elicits adaptations. Here we review the literature on stress-induced adaptations versus stress sensitization in models of neurodegenerative diseases. We also describe our recent findings that chronic proteotoxic stress can elicit adaptations if the dose is low but that high-dose proteotoxic stress sensitizes cells to subsequent challenges. In these experiments, long-term, low-dose proteasome inhibition elicited protection in a superoxide dismutase-dependent manner. In contrast, acute, high-dose proteotoxic stress sensitized cells to subsequent proteotoxic challenges by eliciting catastrophic loss of glutathione. However, even in the latter model of synergistic toxicity, several defensive proteins were upregulated by severe proteotoxicity. This led us to wonder whether high-dose proteotoxic stress can elicit protection against subsequent challenges in astrocytes, a cell type well known for their resilience. In support of this new hypothesis, we found that the astrocytes that survived severe proteotoxicity became harder to kill. The adaptive mechanism was glutathione dependent. If these findings can be generalized to the human brain, similar endogenous adaptations may help explain why neurodegenerative diseases are so delayed in appearance and so slow to progress. In contrast, sensitization to severe stress may explain why defenses eventually collapse in vulnerable neurons.

The involvement of heme oxygenase 1 but not nitric oxide synthase 2 in a hepatoprotective action of quercetin in lipopolysaccharide-induced hepatotoxicity of D-galactosamine sensitized rats

The objective of this study was to evaluate potential hepatoprotective capabilities of quercetin in relation to its modulation of the HO-1 and NOS-2 activities in an experimental model of fulminant liver failure. Liver insult was induced by in vivo administration of D-galactosamine (d-GalN, 400 mg/kg, i.p.) and lipopolysaccharide (LPS, 10 μg/kg, i.p.). The effects of quercetin (50 mg/kg, i.p) on D-GalN toxicity was evaluated by standard biochemical, RT-PCR and Western blot methods. Administration of d-GalN/LPS combination resulted in significantly higher plasma levels of aminotransferases, as well as increased mRNA and protein expressions of both HO-1 and NOS-2 enzymes. Quercetin exhibited cytoprotective effects on the liver, as evidenced by decreased aminotransferase plasma levels. Additionally, quercetin treatment in D-GalN/LPS treated rats significantly increased HO-1 mRNA and its protein expressions. On the contrary, quercetin did not exhibit any significant effects on the levels of nitrites, and NOS-2 mRNA and protein expressions in D-GalN/LPS treated rats. Quercetin when given alone did not have any significant changes on liver enzymes nor HO-1 and NOS-2 mRNA and protein expressions. It can be concluded that the quercetin's induction of HO-1 and its byproducts, without concomitant NOS-2 activity reduction, is among mechanisms contributing to the hepatoprotective effect in D-GalN/LPS hepatotoxicity.