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Role of SIRT1 in vasoprotection

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Oxidative stress plays a key role in vascular impairment during aging. The goal of the present proposal is to identify novel mechanisms that act as regulators of vascular redox homeostasis and thus suppress oxidative stress-induced inflammatory processes in aging. Previous studies indicate that caloric restriction (CR) attenuates the age- related increase in oxidative stress and increases lifespan. Importantly, the age-related effects of CR appear to be dependent on the NAD+ dependent protein deacetylase SIRT1. SIRT1 is expressed in the vasculature and regulates multifaceted vasoprotective pathways. In the proposed studies, we hypothesize that induction of SIRT1- dependent pathways by CR or by pharmacological activators of the enzyme conveys vasoprotective effects in aging. NF-E2-related factor 2 (Nrf2) is a transcription factor, that regulates the expression of numerous ROS detoxifying and antioxidant genes. We have recently demonstrated that caloric restriction exhibits a protective action against tumorigenesis in mice by upregulation of Nrf2. Our preliminary data suggest that Nrf2 plays a similar role in vasoprotection by CR in aging. A major downstream effector of the Nrf2/ARE pathway is the NAD(P)H:quinone oxidoreductase (NQO1) -dependent trans-plasma membrane antioxidant redox system. Although NQO1 is up-regulated by CR, its protection against oxidative stress in endothelial cells is completely unknown. The overall goal of the proposed project is to test the hypothesis that caloric restriction protects the vasculature from the deleterious effects of oxidative stress associated with aging, via activation of SIRT1 and induction of the Nrf2- regulated ROS detoxification systems (including NQO1). We posit that pharmacological activation of this pathway in endothelial cells mimics the effects of caloric restriction, which contributes significantly to an intervention strategy for vasoprotection during aging. The following aims are proposed: 1/a: Determine whether caloric restriction, via activating SIRT1, exerts vasoprotective effects in aging animals by attenuating mitochondrial oxidative stress and inhibiting vascular inflammation. 1/b: Define the efficacy of treatment with pharmacological activators of SIRT1 on age-related vascular impairment. 2/a: Determine whether induction of the Nrf2/ARE pathway mediates the vasoprotective effects of caloric restriction in aging. 2/b: Determine whether up-regulation of the NQO1-dependent trans-plasma membrane antioxidant redox system confers vasoprotection in aging. The proposed studies will provide the first comprehensive analysis on the effects and potential mechanisms through which caloric restriction contributes to preventing the age-related decline in vascular function. These experiments will provide novel and definitive information on the actions of SIRT1 and the Nrf2/ARE pathway during biological aging and will resolve significant controversies related to the effects of antioxidant systems on the genesis and modulation of cardiovascular function and age- related pathology.
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