Mechanisms of Resveratrol and Estrogen in Cardioprotective Function

The antioxidant resveratrol is a polyphenolic compound that is found in grapes, berries, and peanuts, with the highest concentration of 50-100 µg in the grapes’ skin. Resveratrol induces nitric oxide synthetase (eNOS) in cultured endothelial cells, and thus plays a cardio-protective role by increasing NO levels. The mechanism for the activation of eNOS is unknown. It was hypothesized that resveratrol, like estradiol (E2), activated membrane estrogen receptor (ER), which in turn activated eNOS through the MAPK and/or PI3K signaling pathways in endothelial cells. Cell extracts of bovine aortic endothelial cells (BAEC) were treated with resveratrol, E2, and other compounds and were analyzed by Western blots probed with antibodies against MAPK and P-MAPK. Activities of eNOS were determined by an enzymatic reaction measuring the conversion of 14C-arginine to 14C-citrulline. Results indicated that resveratrol and E2 both increased MAPK activity in a concentration-dependent manner as observed by Western blot analysis. The increase in MAPK activity was abolished with the ER antagonist, ICI 182,780, suggesting that resveratrol and E2 both activate MAPK via direct interaction with ER-alpha and ER-beta. Both resveratrol and E2 induced eNOS activity in BAEC through a mechanism that involved MAPK and PI3K signaling pathways since the selective inhibitors PD 98059 and LY 294002, respectively, inhibited E2 and resveratrolinduced eNOS activity. These data provide preliminary evidence that mechanism of action of resveratrol in BAEC is similar to that of E2, is mediated by ER, and may provide better understanding on the mechanism of cardio-protection by these two ligands.