Anthocyanins attenuate endothelial dysfunction through regulation of uncoupling of nitric oxide synthase in aged rats

Endothelial dysfunction is one of the main age-related arterial phenotypes responsible for cardiovascular disease (CVD) in older adults. This endothelial dysfunction results from decreased bioavailability of nitric oxide (NO) arising downstream of endothelial oxidative stress. In this study, we investigated the protective effect of anthocyanins and the underlying mechanism in rat thoracic aorta and human vascular endothelial cells in aging models. In vitro, cyanidin-3-rutinoside (C-3-R) and cyanidin-3-glucoside (C-3-G) inhibited the d-galactose (d-gal)-induced senescence in human endothelial cells, as indicated by reduced senescence-associated-β-galactosidase activity, p21, and p16^INK4a . Anthocyanins blocked d-gal-induced reactive oxygen species (ROS) formation and NADPH oxidase activity. Anthocyanins reversed d-gal-mediated inhibition of endothelial nitric oxide synthase (eNOS) serine phosphorylation and SIRT1 expression, recovering NO level in endothelial cells. Also, SIRT1-mediated eNOS deacetylation was shown to be involved in anthocyanin-enhanced eNOS activity. In vivo, anthocyanin-rich mulberry extract was administered to aging rats for 8 weeks. In vivo, mulberry extract alleviated endothelial senescence and oxidative stress in the aorta of aging rats. Consistently, mulberry extract also raised serum NO levels, increased phosphorylation of eNOS, increased SIRT1 expression, and reduced nitrotyrosine in aortas. The eNOS acetylation was higher in the aging group and was restored by mulberry extract treatment. Similarly, SIRT1 level associated with eNOS decreased in the aging group and was restored in aging plus mulberry group. These findings indicate that anthocyanins protect against endothelial senescence through enhanced NO bioavailability by regulating ROS formation and reducing eNOS uncoupling.