Recent studies have indicated that several anti-hypertensive drugs may delay the development and progression of Alzheimer’s disease (AD). However, the relationships among AD, hypertension, and oxidative stress remain to be elucidated. Here, we aimed to determine whether reactive oxygen species (ROS) reduction by resveratrol in the brain leads to cognitive impairment reduction in rats with angiotensin II (Ang-II)-induced early AD. Male Wistar Kyoto (WKY) rats with Ang-II-induced AD were treated with losartan or resveratrol for two weeks. Our results show decreased blood pressure, increased hippocampal brain-derived neurotrophic factor (BDNF) level, and decreased nucleus tractus solitarius (NTS) ROS production in the Ang-II groups with losartan (10 mg/kg), or resveratrol (10 mg/kg/day) treatment. Furthermore, losartan inhibition of hippocampal Tau^T231 phosphorylation activated Akt^S473 phosphorylation, and significantly abolished Ang-II-induced Aβ precursors, active caspase 3, and glycogen synthase kinase 3β (GSK-3β)^Y216 expressions. Consistently, resveratrol showed similar effects compared to losartan. Both losartan and resveratrol restored hippocampal-dependent contextual memory by NADPH oxidase 2 (NOX2) deletion and superoxide dismutase 2 (SOD2) elevation. Our results suggest that both losartan and resveratrol exert neuroprotective effects against memory impairment and hippocampal damage by oxidative stress reduction in early stage AD rat model. These novel findings indicate that resveratrol may represent a pharmacological option similar to losartan for patients with hypertension at risk of AD during old age.

Purpose: Cataracts in patients with diabetes mellitus (DM) are a major cause of blindness in developed and developing countries. This study aims to examine whether the generation of reactive oxygen species (ROS) via the increased expression of glucose transporters (GLUTs) and the receptor for advanced glycation end products (RAGE) influences the cataract development in DM. Methods: Lens epithelial cells (LECs) were isolated during cataract surgery from patients without DM or with DM, but without diabetic retinopathy. In a rat model, fructose (10% fructose, 8 or 12 weeks) with or without dapagliflozin (1.2 mg/day, 2 weeks) treatment did induce DM, as verified by blood pressure and serum parameter measurements. Immunofluorescence stainings and immunoblottings were used to quantify the protein levels. Endogenous O₂˙¯ production in the LECs was determined in vivo with dihydroethidium stainings. Results: We investigated that GLUT levels in LECs differed significantly, thus leading to the direct enhancement of RAGE-associated superoxide generation in DM patients with cataracts. Superoxide production was significantly higher in LECs from rats with fructose-induced type 2 DM, whereas treatment with the sodium-glucose cotransporter 2 (SGLT2) inhibitor dapagliflozin prevented this effect in fructose-fed rats. Protein expression levels of the sodium/glucose cotransporter 2 (SGLT2), GLUT1, GLUT5, the nicotinamide adenine dinucleotide phosphate reduced form (NADPH) oxidase subunit p67-phox, NOX2/4 and RAGE were upregulated in fructose-fed animals, whereas dapagliflozin treatment reversed these effects. Conclusions: In rats with fructose-induced DM, dapagliflozin downregulates RAGE-induced NADPH oxidase expression in LECs via the inactivation of GLUTs and a reduction in ROS generation. These novel findings suggest that the SGLT2 inhibitor dapagliflozin may be a candidate for the pharmacological prevention of cataracts in patients with DM.

Background and Purpose: μ‐Opioid receptors, pro‐opiomelanocortin and pro‐enkephalin are highly expressed in the nucleus tractus solitarii (NTS) and μ receptor agonists given to the NTS dose‐dependently increased BP. However, the molecular mechanisms of this process remain unclear. In vitro, μ receptors heterodimerize with α_2A‐adrenoceptors. We hypothesized that α_2A‐adrenoceptor agonists would lose their depressor effects when their receptors heterodimerize in the NTS with μ receptors.Experimental Approach: We microinjected μ‐opioid agonists and antagonists into the NTS of rats and measured changes in BP. Formation of μ receptor/α_2A‐adrenoceptor heterodimers was assessed with immunofluorescence and co‐immunoprecipitation methods, along with proximity ligation assays.Key Results: Immunofluorescence staining revealed colocalization of α_2A‐adrenoceptors and μ receptors in NTS neurons. Co‐immunoprecipitation revealed interactions between α_2A‐adrenoceptors and μ receptors. In situ proximity ligation assays confirmed the presence of μ receptor/α_2A‐adrenoceptor heterodimers in the NTS. Higher levels of endogenous endomorphin‐1 and μ receptor/α_2A‐adrenoceptor heterodimers were found in the NTS of hypertensive rats, than in normotensive rats. Microinjection of the μ receptor agonist [D‐Ala², MePhe⁴, Gly⁵‐ol]‐enkephalin (DAMGO), but not that of the α_2A‐adrenoceptor agonist guanfacine, into the NTS of normotensive rats increased μ receptor/α_2A‐adrenoceptor heterodimer formation and BP elevation. The NO‐dependent BP‐lowering effect of α_2A‐adrenoceptor agonists was blunted following increased formation of μ receptor/α_2A‐adrenoceptor heterodimers in the NTS of hypertensive rats and DAMGO‐treated normotensive rats.Conclusions and Implications: Increases in endogenous μ receptor agonists in the NTS induced μ receptor/α_2A‐adrenoceptor heterodimer formation and reduced the NO‐dependent depressor effect of α_2A‐adrenoceptor agonists. This process could contribute to the pathogenesis of hypertension.

Chronic hyperglycemia triggers an abnormal rise in reactive oxygen species (ROS) that leads to blindness in patients with diabetes mellitus (DM) and cataracts. In this study, the effects of dapagliflozin, metformin and resveratrol on ROS production were investigated in lens epithelial cells (LECs) of animals with fructose-induced DM. LECs were isolated from patients without DM, or with DM devoid of diabetic retinopathy. Animals were treated with 10% fructose for 8 weeks to induce DM, which was verified by monitoring blood pressure and serum parameters. For drug treatments, 1.2 mg/day of dapagliflozin was given for 2 weeks, 500 mg/kg/day of metformin was given, and 10 mg/kg/day of resveratrol was given. Dihydroethidium was used to stain endogenous O₂˙⁻ production in vivo of the LECs. Superoxide production was expressed in the cataract of DM, or patients without DM. Sodium–glucose cotransporter 2 (SGLT2), glucose transporter 1 (GLUT1), GLUT5, the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47/p67-phox, NOX4 and RAGE were significantly increased in LECs with DM. In addition, the dapagliflozin treatment reduced GLUT5, p47/p67-phox, NADPH oxidase 4 (NOX4) and receptor for advanced glycation end products (RAGE) expressions. On the contrary, metformin or resveratrol inhibited p47-phox, GLUT5, and SGLT2 expressions, but not nuclear factor erythroid 2–related factor 2 (NRF2). In summary, dapagliflozin, metformin or resveratrol down-regulated p47-phox expression through SGLT2 inactivation and ROS reduction. These important findings imply that SGLT2 can be blocked to ameliorate oxidative stress in the cataracts of DM patients.