Resveratrol recruits rat muscle microvasculature via a nitric oxide-dependent mechanism that is blocked by TNFα

Abstract

Resveratrol, a polyphenol found in many plants, has antioxidant and anti-inflammatory actions. It also improves endothelial function and may be cardioprotective. Tumor necrosis factor-α (TNFα) causes oxidative stress and microvascular endothelial dysfunction. Whether resveratrol affects microvascular function in vivo and, if so, whether inflammatory cytokines antagonize its microvascular action are not clear. In cultured bovine aortic endothelial cells (BAECs), resveratrol (100 nM) increased the phosphorylation of protein kinase B (Akt), endothelial nitric oxide (NO) synthase (eNOS), and ERK1/2 within 15 min by more than twofold, and this effect lasted for at least 2 h. Treatment of BAECs with TNFα (10 ng/ml) significantly increased the NADPH oxidase activity and the production of hydrogen peroxide and superoxide. Pretreatment of cells with resveratrol (100 nM) prevented each of these. Injection (ip) of resveratrol in rats potently increased muscle microvascular blood volume (MBV; P = 0.007) and flow (MBF; P < 0.02) within 30 min, and this was sustained for at least 2 h. The phosphorylation of Akt in liver or muscle was unchanged. Superimposed systemic infusion of L-NAME (NOS inhibitor) completely abolished resveratrol-induced increases in MBV and MBF. Similarly, systemic infusion of TNFα prevented resveratrol-induced muscle microvascular recruitment. In conclusion, resveratrol activates eNOS and increases muscle microvascular recruitment via an NO-dependent mechanism. Despite the potent antioxidant effect of resveratrol, TNFα at concentrations that block insulin-mediated muscle microvascular recruitment completely neutralized resveratrol's microvascular action. Thus, chronic inflammation, as seen in type 2 diabetes, may limit resveratrol's vasodilatory actions on muscle microvasculature.

Figures

Fig. 1.

Effects of resveratrol on the phosphorylation of Akt, endothelial nitric oxide synthase (eNOS), and ERK1/2 in cultured endothelial cells. A: representative gel of dose response study. B: representative gel of time course study. C: quantification of protein phosphorylation. Con, control; Ins, insulin vs. Con. *P < 0.01; **P < 0.04; #P < 0.004; ##P < 0.001; ♦P < 0.004; ♦♦P < 0.03.

Fig. 2.

Effects of resveratrol on TNFα-induced oxidative stress in cultured endothelial cells. *P < 0.02 and **P < 0.004 vs. control. Res, resveratrol; RLU, relative light units.

Fig. 3.

Effects of resveratrol on muscle microvascular parameters in vivo. Resveratrol significantly increased microvascular blood volume (MBV; P = 0.007, ANOVA) and microvascular blood flow (MBF; P < 0.02, ANOVA) vs. basal. *P < 0.05. MFV, microvascular flow velocity; l-NAME, Nω-nitro-l-arginine methyl ester.

Fig. 4.

Effects of resveratrol on Akt phosphorylation in liver and muscle in vivo. A: representative gels. L1 and L2, liver samples 1 and 2, respectively; M1 and M2, muscle samples 1 and 2, respectively. B: quantification of Akt phosphorylation.