SirT1 is a class III histone deacetylase that has beneficial roles in various diseases related to aging such as cancer, diabetes and neurodegenerative disease. Resveratrol is a natural compound that mimics most of the beneficial effects attributed to SirT1. Resveratrol has toxicity towards cancer cells and has been reported to be a direct activator of SirT1. Interestingly, SirT1 over-expression has also been reported to be toxic. We set out to determine if resveratrol toxicity is mediated through activation of SirT1. We have assessed resveratrol toxicity in embryonic stem cells and mouse embryonic fibroblast (MEFs) across different SirT1 genotypes. Our data indicates that SirT1 is not implicated in resveratrol toxicity in either normal or transformed MEFs. Thus, resveratrol toxicity does not appear to be mediated by SirT1.

SirT1 is a class III histone deacetylase that has beneficial roles in various diseases related to aging such as cancer, diabetes and neurodegenerative disease. Resveratrol is a natural compound that mimics most of the beneficial effects attributed to SirT1. Resveratrol has toxicity towards cancer cells and has been reported to be a direct activator of SirT1. Interestingly, SirT1 over-expression has also been reported to be toxic. We set out to determine if resveratrol toxicity is mediated through activation of SirT1. We have assessed resveratrol toxicity in embryonic stem cells and mouse embryonic fibroblast (MEFs) across different SirT1 genotypes. Our data indicates that SirT1 is not implicated in resveratrol toxicity in either normal or transformed MEFs. Thus, resveratrol toxicity does not appear to be mediated by SirT1.

Recent studies demonstrated that fructose intake can increase blood pressure in experimental animals. Oxidative stress has emerged as an important pathogenic factor in the development of hypertension. It has been reported that increased superoxide production in fructose-fed rat mediated through nicotinamide adenine dinucleotide phosphate NAD(P)H oxidase. Superoxide dismutase (SOD) is one of the most important enzymes against oxidative stress. However, the signaling mechanisms of fructose which induce hypertension through superoxide remain unclear. Nucleus tractus solitarii (NTS) is the integrative center for baroreflex. Our previous study had revealed that accumulation of superoxide in the NTS can induce hypertension. As an important antioxidant in red wine, resveratrol is likely to contribute to the potential of red wine to prevent cardiovascular disease. At pharmacological doses, resveratrol increases vascular nitric oxide (NO) levels and improves NO bioavailability in animal models. Resveratrol is a potent activator of AMPK in neuronal cell lines, primary neurons, and the brain. Recent reports have indicated that metformin targets AMPK which activates nNOS and eNOS. Therefore, we hypothesized that resveratrol causes blood pressure decrease through regulating nitric oxide and superoxide production in the NTS of fructose-fed rats. There were three specific aims: 1. To investigate whether fructose induce superoxide production and causes hypertension in the NTS. 2. To investigate which signaling pathway is involved in fructose-induced hypertension. 3. To investigate which signaling pathway is involved in resveratrol modulates blood pressure. Male Wistar Kyoto rats (WKY) were divided into two groups: control group and fed with 10% fructose water group for 1 week. After one-week treatment, the systolic blood pressure and superoxide production increased significantly and the nitrate level in the NTS was significantly decreased. Immunoblotting showed that administration of fructose significantly increased NADPH oxidase subunits p22-phox, p67-phox activity, RAGE activity and reduce SOD2 activity in the NTS. Based on our previous studies, male Wistar-Kyoto rats (WKY) were divided into five groups: Group I: Control group; Group II: fructose-fed rats (FFR) fed with 10% fructose for 4 weeks; Group III: Control + resveratrol (R) rats received a gavage of resveratrol; Group IV: FFR+ resveratrol (FR) fed with 10% fructose and resveratrol ; Group V: FFR + 2weeks resveratrol (F2R) fed with 10% fructose and received a gavage of resveratrol 2 weeks. We found that systolic blood pressure measured by tail-cuff method in F group rats and F2R group rats revealed a significantly increased than C group rats continuously through week 0 to week 2 but R group rats and FR group rats were no difference with C group. However, received a gavage of resveratrol (10 mg/kg/d) 2 weeks, F2R group revealed a significantly decrease in SBP than the F group continuously through week 2 to week 4. Fructose-induced hypertension increased NADPH oxidase activity and SOD2 activity related to inhibit the production of NO in the regulation of blood pressure. These results suggest that in the NTS, intake of fructose induces NADPH oxidase activity and reduces SOD2 activity to increase blood pressure. Resveratrol can not only reverse fructose-induced hypertension but also prevent fructose-induced hypertension.

Approximately two-thirds of US adults are overweight or obese, and obesity is also becoming more prevalent in children and adolescents. Similar to adults, obese children are at a higher risk of developing health problems due in part to dysfunctional immune surveillance. Obesity has been shown reduce the generation of new T-cells by accelerating thymic aging in an adult mouse. This study therefore aimed at determining whether similar diet induced obesity (DIO) changes can be induced in a young mouse. Comparisons made between lean and DIO C57Bl/6 mice showed a significant increase in thymic weight, decrease in thymic cellularity and thymic output, and impaired T-cell development at the double negative stage. We associate these alterations with changes in thymic architecture and accumulation of lipid droplets within the thymic cortex and medulla of the obese mice. The above observations indicate that DIO can induce fat accumulation and reduce thymic function at a young age. Resveratrol, a natural polyphenolic compound, was then used to regulate fat metabolism in an attempt to reduce these DIO changes we observed. Resveratrol induces fat oxidation via 5' adenosine monophosphate-activated protein kinase (AMPK), and its reciprocal regulation of glycerol-3-phosphate acyltransferase-1 (GPAT-1) and carnitine palmitoyltransferase-1 (CPT-1), the rate-limiting enzymes required for glycerophospholipid biosynthesis and oxidation, respectively. Through resveratrol feeding, we were able to prevent the effects of DIO on thymic architecture and thymic T-cell proliferation. This was achieved by manipulating AMPK into inhibiting GPAT-1 and enhancing CPT-1 activity. Since the expression of GPAT-1 was upregulated in the obese mice, we investigated whether deleting GPAT-1 altogether might prevent the thymic involution, by inhibiting synthesis of glycerophospholipids and triacylglycerol. Instead, we found that GPAT-1 deletion slowed thymic growth and reduced cellularity in young mice, which we associated with impaired thymic T-cell function and development, suggesting that the deleterious effects of GPAT-1 deficiency may be due to perturbations in thymic T-cell activation and signaling. These data provide a novel link between lipid metabolism and T-cell development, and identify the use of the naturally-occurring resveratrol to reduce lipid accumulation within the involution-prone thymus, thus providing a useful approach to preventing a decline in thymic function in childhood. / text

published_or_final_version / Anatomy / Master / Master of Philosophy

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Mitochondrial function declines with aging and obesity, and has been implicated in the development of many age-related diseases. Caloric restriction (CR) prevents aging and has been shown to induce mitochondrial biogenesis and improve mitochondrial function. These effects may involve increased activity of the \(NAD^+\)-dependent deacetylase SIRT1. Indeed, overexpression of SIRT1 reproduces many of the health benefits of CR including induction of mitochondrial biogenesis by deacetylation and activation of the transcriptional co-activator \(PGC-1\alpha\). Because mitochondria regulate cellular functions important for aging, including, cellular energy production, ROS generation, and apoptosis, determining why mitochondrial function declines with age will improve our understanding of the underlying forces that drive organismal aging. Resveratrol and other SIRT1 activators induce mitochondrial biogenesis and protect against metabolic decline, but whether SIRT1 mediates these benefits is still a matter of debate. To circumvent the developmental defects of germ-line SIRT1 knockouts, we have developed the first inducible system that permits whole-body deletion of SIRT1 in adult mice. Obese mice treated with a moderate dose of resveratrol showed increased mitochondrial biogenesis and function, AMPK activation, and increased \(NAD^+\) levels in skeletal muscle, whereas SIRT1 knockouts displayed none of these benefits. Overexpression of SIRT1 in mice mimicked these effects, demonstrating that SIRT1 is sufficient and necessary for resveratrol to increase mitochondrial function in obese animals, and indicating a central role for SIRT1 in mediating the benefits of this molecule on muscle. Loss of SIRT1 or aging causes mitochondrial dysfunction and decreased expression of mitochondrial-encoded electron transport chain (ETC) components. This decrease in mitochondrial-encoded, but not nuclear-encoded ETC components in SIRT1 knockouts, which we have termed “genome asynchrony”, is independent of \(PGC-1\alpha\). Elevating \(NAD^+\) levels by treatment with the \(NAD^+\) precursor NMN prevented genome asynchrony and mitochondrial dysfunction in aged animals, similar to effects seen with CR. Together these data demonstrate that SIRT1 plays an essential role in preventing genome asynchrony, and that maintaining \(NAD^+\) levels and SIRT1 activity with age may prevent mitochondrial dysfunction. Since SIRT1 is required for NMN or resveratrol to improve mitochondrial function, compounds that activate SIRT1 or elevate \(NAD^+\) may help treat or prevent age-related diseases caused by mitochondrial dysfunction.

Vascular endothelial cell activation and apoptosis (programmed cell death) are critical in inflammation and angiogenesis (the formation of new blood vessels). Tumor necrosis factor (TNF) is a pro-inflammatory cytokine known for its ability to induce endothelial cell activation and apoptosis. However, the ability of two death ligands in the TNF superfamily: TRAIL (TNF-Related Apoptosis-Inducing Ligand) and Fas ligand (FasL), to activate vascular endothelium is less well defined, and forms the basis of this work. We find that in the human endothelial cell line EA.hy926, TRAIL induces endothelial cell activation (activation of the transcription factor NF-?B with increased expression of the adhesion protein ICAM-1 and adhesion of human neutrophils) when it concurrently induces apoptosis. In addition, angiogenesis is implicated in diseases of the central nervous system, and its modulation represents an attractive therapeutic strategy. We investigated the modulatory potential of the two endogenous molecules TRAIL and FasL as well as an exogenous molecule resveratrol, a phytochemical present in red wine, in angiogenesis. We modeled cerebral angiogenesis with the human brain endothelial cell line hCMEC/D3 and primary bovine brain endothelial cells. Resveratrol inhibited several parameters of angiogenesis (proliferation, migration and tube formation) in human umbilical vein endothelial cells, however, neither TRAIL nor FasL had an effect on this model. By contrast, in hCMEC/D3 cells both resveratrol and TRAIL inhibited all parameters while FasL had minimal effects. Resveratrol did not induce apoptosis in hCMEC/D3 but arrested cell cycle progression to G2/M phase and inhibited phosphorylation of Akt/PKB, a key cell survival protein kinase. This leads to a reduction in cell growth, endothelial migration and tube formation, hence, inhibition of in vitro angiogenesis. TRAIL induced anti-angiogenic effects in hCMEC/D3 due to apoptosis. The data suggests that TRAIL primarily influences angiogenesis through induction of vascular endothelial apoptosis while resveratrol induces cell cycle arrest, both of which may lead to vessel regression. These are the first studies to report the modulation of different aspects of endothelial cell activation by TRAIL and resveratrol in several endothelial cell culture models, with a particular focus on the central nervous system.

Resveratrol has been reported as a potential anticancer agent but cannot be used as an antitumor drug due to its chemical and metabolic instability. We have designed and synthesized 184 novel compounds related to resveratrol in an attempt to produce more potent and drug-like molecules. We have identified a tetrazole analog of resveratrol, ST-145(a) as a lead anticancer agent from the resveratrol analog series of compounds with a GI50 value of less than 10nM against almost all the human cancer cell lines in the National Cancer Institute’s screening panel. In a separate study, we tested the hypothesis that the limited bioavailability of resveratrol, can be improved by synthesizing analogs which would be glucuronidated at a lower rate than resveratrol itself. We demonstrated that ST-05 and ST-12(a) exhibit lower glucuronidation profiles when compared to resveratrol and that these synthesized stilbenoids likely represent useful scaffolds for the design of efficacious resveratrol analogs. We have also initiated a new discovery program to identify selective CB1 and CB2 receptor ligands from a library of novel stilbene scaffolds structurally related to the resveratrol molecule. From the screened resveratrol analogs, two compounds were identified as selective CB2 and CB1 ligands. Compound ST-179 had 47-fold selectivity for CB2 (Ki = 284 nM) compared to CB1, while compound ST-160 was 2-fold selective for CB1 (Ki = 400 nM) compared to the CB2 receptor. These structural analogs have the potential for development as novel cannabinoid therapeutics for treatment of obesity and/or drug dependency. Combretastatin A4 (CA-4) is one of the most potent antiangiogenic and antimitotic agents of natural origin. However, CA-4 suffers from chemical instability due to cis-trans isomerism in solution. To circumvent this problem, we have developed a facile procedure for the synthesis of novel 4,5-diaryl-2H-1,2,3-triazoles as CA-4 analogs to constrain the molecule to its cis-configuration. Twenty three triazoles were prepared as CA-4 analogs and submitted for anticancer screening. Among these CA-4 analogs, ST-467 and ST-145(b) can be considered as lead anticancer agents from this series, and further investigation against various cancer cell types in vivo with this class of compound may provide novel therapeutic avenues for treatment.

SirT1 is a class III histone deacetylase that has beneficial roles in various diseases related to aging such as cancer, diabetes and neurodegenerative disease. Resveratrol is a natural compound that mimics most of the beneficial effects attributed to SirT1. Resveratrol has toxicity towards cancer cells and has been reported to be a direct activator of SirT1. Interestingly, SirT1 over-expression has also been reported to be toxic. We set out to determine if resveratrol toxicity is mediated through activation of SirT1. We have assessed resveratrol toxicity in embryonic stem cells and mouse embryonic fibroblast (MEFs) across different SirT1 genotypes. Our data indicates that SirT1 is not implicated in resveratrol toxicity in either normal or transformed MEFs. Thus, resveratrol toxicity does not appear to be mediated by SirT1.