BACKGROUND AND PURPOSEOxidative stress is an important pathogenic factor in the development of hypertension. Resveratrol, the main antioxidant in red wine, improves NO bioavailability and prevents cardiovascular disease. The aim of this study was to examine whether resveratrol decreases the generation of reactive oxygen species (ROS), thereby reducing BP in rats with fructose-induced hypertension. EXPERIMENTAL APPROACHRats were fed 10% fructose with or without resveratrol (10 mg·kg ) for 1 week or for 4 weeks with resveratrol treatment beginning at week 2; systolic BP (SBP) was measured by tail-cuff method. Endogenous in vivo O2− production in the nucleus tractus solitarii (NTS) was determined with dihydroethidium. Real-time PCR and immunoblotting analyses were used to quantify RNA and protein expression levels. KEY RESULTSIn fructose-fed rats, ROS levels in the NTS were higher, whereas the NO level was significantly decreased. Also, RNA and protein levels of NADPH oxidase subunits (p67, p22-phox) were elevated, superoxide dismutase 2 (SOD2) reduced and AMP-activated PK (AMPK) T172 phosphorylation levels in the NTS were lower in fructose-fed rats. Treatment with the AMPK activator resveratrol decreased levels of NADPH oxidase subunits and ROS, and increased NO and SOD2 levels in the NTS of fructose-fed rats. Administration of resveratrol, in combination with fructose at week 0 and later at week 2, significantly reduced the SBP of fructose-fed rats. CONCLUSIONS AND IMPLICATIONSCollectively, resveratrol decreased BP through the phosphorylation of AMPK, Akt and neuronal NOS in fructose-fed rats. These novel findings suggest that resveratrol may be a potential pharmacological candidate for the treatment of hypertension. Abbreviations

535I n humans, the intake of sugar-sweetened beverages is correlated with the prevalence of type 2 diabetes mellitus and obesity.1 High fructose intake is used as a well-established animal model for insulin resistance.2 Some studies have shown that chronic fructose intake in normal rats induces hypertension in association with insulin resistance.2,3 However, insulin infusion was found to stimulate local vasodilation by enhancing the action of nitric oxide (NO). 4 The effect of insulin on the baroreceptor reflex in nucleus tractus solitarii (NTS) is probably mediated by a change in sympathetic nervous activity. 4,5 Furthermore, sympathectomy can prevent the development of fructose-induced hypertension in rats. 6 Recent studies suggest that fructose consumption increases superoxide generation and attenuates baroreflex response. 7,8 Interestingly, inhibition of superoxide generation in NTS can reduce blood pressure (BP) in stroke-prone hypertensive rats. 9 The NTS is located in the dorsal medulla of the brain stem, which is the primary integrating center for cardiovascular regulation and other autonomic functions of the central nervous system. Furthermore, NO has important modulatory functions in the NTS, including the modulation of arterial BP and sympathetic nerve activity. 10 In previous experiments, we demonstrated that insulin microinjected into the NTS induces a depressor effect and initiates an interaction between insulin and phosphatidylinositol 3-kinase Abstract-Recent clinical studies found that fructose intake leads to insulin resistance and hypertension. Fructose consumption promotes protein fructosylation and formation of superoxide. In a previous study, we revealed that inhibition of superoxide production in the nucleus tractus solitarii (NTS) reduces blood pressure. Caffeine displays significant antioxidant ability in protecting membranes against oxidative damage and can lower the risk of insulin resistance. However, the mechanism through which caffeine improves fructose-induced insulin resistance is unclear. The aim of this study was to investigate whether caffeine consumption can abolish superoxide generation to enhance insulin signaling in the NTS, thereby reducing blood pressure in rats with fructose-induced hypertension. Treatment with caffeine for 4 weeks decreased blood pressure, serum fasting glucose, insulin, homeostatic model assessment-insulin resistance, and triglyceride levels and increased the serum direct high-density lipoprotein level in fructose-fed rats but not in control rats. Caffeine treatment resulted in the recovery of fructose-induced decrease in nitric oxide production in the NTS. Immunoblotting and immunofluorescence analyses further showed that caffeine reduced the fructoseinduced phosphorylation of insulin receptor substrate 1 (IRS1 S307) and reversed Akt S473 and neuronal nitric oxide synthase phosphorylation. Similarly, caffeine was able to improve insulin sensitivity and decrease insulin levels in the NTS evoked by fructose. Caffeine intake also reduced the production o...

Background: Inflammation is a common pathophysiological trait found in both hypertension and cardiac vascular disease. Recent evidence indicates that fractalkine (FKN) and its receptor CX3CR1 have been linked to inflammatory response in the brain of hypertensive animal models. Here, we investigated the role of CX3CR1-microglia in nitric oxide (NO) generation during chronic inflammation and systemic blood pressure recovery in the nucleus tractus solitarii (NTS). Methods: The hypertensive rat model was used to study the role of CX3CR1-microglia in NTS inflammation following hypertension induction by oral administration of 10% fructose water. The systolic blood pressure was measured by tail-cuff method of non-invasive blood pressure. The CX3CR1 inhibitor AZD8797 was administered intracerebroventricularly (ICV) in the fructose-induced hypertensive rat. Using immunoblotting, we studied the nitric oxide synthase signaling pathway, NO concentration, and the levels of FKN and CX3CR1, and pro-inflammatory cytokines were analyzed by immunohistochemistry staining. Results: The level of pro-inflammatory cytokines IL-1β, IL-6, TNF-α, FKN, and CX3CR1 were elevated two weeks after fructose feeding. AZD8797 inhibited CX3CR1-microglia, which improved the regulation of systemic blood pressure and NO generation in the NTS. We also found that IL-1β, IL-6, and TNF-α levels were recovered by AZD8797 addition. Conclusion: We conclude that CX3CR1-microglia represses the nNOS signaling pathway and promotes chronic inflammation in fructose-induced hypertension. Collectively, our results reveal the role of chemokines such as IL-1β, IL-6, and TNF-α in NTS neuroinflammation with the involvement of FKN and CX3CR1.