Hyperactive S6K1 Mediates Oxidative Stress and Endothelial Dysfunction in Aging: Inhibition by Resveratrol

Abstract

Mammalian target of rapamycin (mTOR)/S6K1 signalling emerges as a critical regulator of aging. Yet, a role of mTOR/S6K1 in aging-associated vascular endothelial dysfunction remains unknown. In this study, we investigated the role of S6K1 in aging-associated endothelial dysfunction and effects of the polyphenol resveratrol on S6K1 in aging endothelial cells. We show here that senescent endothelial cells displayed higher S6K1 activity, increased superoxide production and decreased bioactive nitric oxide (NO) levels than young endothelial cells, which is contributed by eNOS uncoupling. Silencing S6K1 in senescent cells reduced superoxide generation and enhanced NO production. Conversely, over-expression of a constitutively active S6K1 mutant in young endothelial cells mimicked endothelial dysfunction of the senescent cells through eNOS uncoupling and induced premature cellular senescence. Like the mTOR/S6K1 inhibitor rapamycin, resveratrol inhibited S6K1 signalling, resulting in decreased superoxide generation and enhanced NO levels in the senescent cells. Consistent with the data from cultured cells, an enhanced S6K1 activity, increased superoxide generation, and decreased bioactive NO levels associated with eNOS uncoupling were also detected in aortas of old WKY rats (aged 20–24 months) as compared to the young animals (1–3 months). Treatment of aortas of old rats with resveratrol or rapamycin inhibited S6K1 activity, oxidative stress, and improved endothelial NO production. Our data demonstrate a causal role of the hyperactive S6K1 in eNOS uncoupling leading to endothelial dysfunction and vascular aging. Resveratrol improves endothelial function in aging, at least in part, through inhibition of S6K1. Targeting S6K1 may thus represent a novel therapeutic approach for aging-associated vascular disease.

Mammalian Target of Rapamycin (mTOR) Inhibition with Rapamycin Improves Cardiac Function in Type 2 Diabetic Mice

“…It is interesting that the previous studies also documented the antioxidant-like effect of rapamycin in different organs. For instance, this drug protects the mitochondria against oxidative stress and apoptosis in a rat model of Parkinson disease (55), improves endothelial function (56) and vascular contractility (57), and protects human corneal endothelial cells (58) by reducing oxidative stress. The potent antioxidant-like effect of rapamycin in T2D hearts suggests that this drug may have complimentary benefit in addition to mTORC1 inhibition for protection against myocardial dysfunction in T2D mice.…”

The effects of resveratrol on aging vessels

“…Treatment of the cells for one hour with RV restored excess production of mitochondrial O2-and enhanced the synthesis of NO in response to acetylcholine (Rajapakse et al, 2011).…”

“…Over activation of this pathway leads to aging-related disorders including cardiovascular disease (Stanfel et al, 2009). The activity of S6K1 is higher in aortic rings of old rats and in cultured senescent human endothelial cells (Rajapakse et al, 2011). Related to this, there is a higher production of free radicals and a concomitant reduced synthesis of NO.…”

Mechanistic perspectives of calorie restriction on vascular homeostasis

“…The mTOR signaling pathway is involved in the regulation of vascular oxidative stress and inflammation as well. Silencing ribosomal S6 protein kinase 1 (S6K1), a component of mTOR signaling pathway, reduces oxidative stress and enhances NO production in senescent HUVECs [164]. In addition, knockdown or pharmacological attenuation of mTOR has been shown to prevent atherogenesis by inhibiting macrophage chemotaxis and the expression of inflammatory molecules in mice [165169].…”