Role of SIRT1 in vasoprotection
Description: PUBLIC HEALTH RELEVANCE: Oxidative stress and inflammation plays a central role in the pathophysiology of cardiovascular disease, which is the main cause of mortality among elderly Americans. The goal of this project is to identify novel molecular targets that can be activated pharmacologically to protect the blood vessels from free radical mediated injury and inflammation and thus to improve vascular function in elderly patients. We will test the hypotheses that in the vascular system a protein named SIRT1 mediates multifaceted vasoprotective effects. We posit that treatment with SIRT1-activating molecules, or inducing SIRT-1 by dietary restriction or overexpression of SIRT1 by genetic engineering can exert significant vasoprotective effect in aged mice. 7) Project Narrative Oxidative stress and inflammation plays a central role in the pathophysiology of cardiovascular disease, which is the main cause of mortality among elderly Americans. The goal of this project is to identify novel molecular targets that can be activated pharmacologically to protect the blood vessels from free radical mediated injury and inflammation and thus to improve vascular function in elderly patients. We will test the hypotheses that in the vascular system a protein named SIRT1 mediates multifaceted vasoprotective effects. We posit that treatment with SIRT1-activating molecules, or inducing SIRT-1 by dietary restriction or overexpression of SIRT1 by genetic engineering can exert significant vasoprotective effect in aged mice. __SpecificAimsTextDelimiter__ [2]. Specific Aims: There are over 35 million Americans 65 years of age or older and the vast majority will suffer from age- associated cardiovascular disease26-28. Therefore, there is an urgent need to develop novel interventional treatments for promotion of cardiovascular health in older persons. An extensive series of studies conducted over the past 60 years provides compelling data that caloric restriction (CR) can delay aging and extend lifespan in evolutionary distant organisms. The goal of the present proposal is to identify novel mechanisms induced by CR that act as regulators of vascular redox homeostasis and thus suppress oxidative stress and oxidative stress-induced inflammatory processes known to contribute to vascular aging and provide a pharmacological approach to promote vascular health in older individuals. Previous studies conducted in our lab and others have revealed that the NAD+ dependent protein deacetylase SIRT1 contributes to the anti-aging effects of CR29-34. SIRT1 is expressed in the vasculature and regulates multifaceted vasoprotective pathways35, 36. 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. Our recent publication strongly supports this hypothesis in that treatment with resveratrol, the most potent naturally occurring SIRT1- activating compound, reverses endothelial dysfunction, attenuates oxidative stress and inhibits vascular inflammation in vessels of aged mice37. NF-E2-related factor 2 (Nrf2) is a transcription factor, that regulates the expression of numerous ROS detoxifying and antioxidant genes in liver and other organs. Nrf2-dependent pathways are expressed and functional in endothelial cells in culture38-40. We have recently demonstrated that caloric restriction exhibits a protective action against tumorigenesis in mice by upregulation of Nrf21. Importantly, our preliminary data suggest that Nrf2 plays a similar role in vasoprotection by CR in aging. A major downstream effector of the Nrf2/ARE-induced cellular stress response is the NAD(P)H:quinone oxidoreductase (NQO1) -dependent transplasma membrane antioxidant redox system1,41,42. We have recently determined that CR in mice activates Nrf2 in the liver, that induces plasma membrane associated free radical detoxification systems, including NQO11. Although NQO1 is abundantly expressed in endothelial cells, its protective role in oxidative stress of endothelial cells is currently 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 (Figure 1). The following aims are proposed: Figure 1: Proposed mechanism by which CR confers vasoprotection. In aged vessels CR, via activating SIRT1, promotes mitochondrial biogeneis in endothelial cells restoring cellular energetics and attenuating mitochondrial oxidative stress by activating Nrf2. Nrf2 is translocated to the nucleus and binds to the antioxidant redox element (ARE), which up-regulates antioxidant enzymes, increasing glutathione synthesis (up-regulating GCLC) and inducing the NQO1-dependent transplasma-membrane associated redox system. The model predicts that SRT1720 and resveratrol (similar to CR) activate Nrf2- dependent ROS detoxification pathways, which will attenuate oxidative stress in the endothelial cells limiting NF-¿B activation and vascular inflammation in aging. Aim 1/a: Determine whether caloric restriction, via activating SIRT1, exerts vasoprotective effects in aging animals by attenuating mitochondrial oxidative stress and inhibiting vascular inflammation. Vascular mitochondrial oxidative stress, mitochondrial biogenesis, vascular NF-¿B activation, pro-inflammatory gene expression and endothelial activation will be assessed in mice with endothelium-specific deletion of SIRT1 and wild type controls, which are fed a standard or caloric restricted diet for 0,3,15 and 21 months beginning at 3 months of age. Subsequent studies using eNOS-/- mice will determine the role of eNOS in promoting vascular mitochondrial health in caloric restriction. Aim 1/b: Define the efficacy of treatment with pharmacological activators of SIRT1 on age-related vascular impairment. Vascular mitochondrial oxidative stress, mitochondrial biogenesis, vascular NF-¿B activation, pro-inflammatory gene expression and endothelial activation will be assessed in SIRT1-/- mice and wild type controls, which are treated with SRT1720 or resveratrol for 3 months beginning at 21 months of age. Aim 2/a: Determine whether induction of Nrf2/ARE pathway mediate the vasoprotective effects of caloric restriction in aging. Endothelial function and markers of cellular oxidative stress and vascular inflammation will be assessed in Nrf2-null mice and wild type controls, which are fed a standard diet and caloric restricted diet for 21 months beginning at 3 months of age. Subsequent studies will determine whether genetic depletion of Nrf2 abrogates vasoprotective action of SRT1720 and resveratrol. Aim 2/b: Determine whether up-regulation of the NQO1-dependent transplasma membrane antioxidant redox system confer vasoprotection in aging. Using NQO1-/- mice, it will be determined whether 1) genetic depletion of NQO1 exacerbates arterial dysfunction in aged animals, and/or 2) abrogates vasoprotection by CR and by resveratrol treatment. Additional studies using a NQO1 transgenic mouse strain will define whether overexpression of NQO1 confers vasoprotective effects in aging. The proposed studies will provide the first comprehensive analysis on the effects and potential mechanisms through which caloric restriction contribute 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.
Funding type: research
Funder scheme: R01
Start date: 2010-09-01
End date: 2016-08-31
Investigator: ZOLTAN ISTVAN UNGVARI
Institution: UNIVERSITY OF OKLAHOMA HLTH SCIENCES CTR
Subfield: Geriatrics and Gerontology
Field: Medicine
Domain: Health Sciences
Funded outputs count: 97
Funder award ID: R01AT006526
OpenAlex ID: G2012315927