Oxidative stress and aortic valve disease

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DESCRIPTION (provided by applicant): Replacement of the aortic valve is the primary treatment for patients with symptomatic, calcific aortic valve stenosis (AVS), and is the most common valvular surgical procedure performed (> 250,000 performed annually). Stenotic valves are histologically similar to atherosclerotic lesions, and the applicant's laboratory has shown significant increases in superoxide in atherosclerotic lesions and stenotic valves in hypercholesterolemic mice (ldlr-/-/ApoB100/100). However, while superoxide in atherosclerotic lesions is increased due to increased NAD(P)H oxidase activity, the applicant's preliminary data suggest that mechanisms contributing to increased superoxide in stenotic valves are fundamentally different, and are likely due to reductions in superoxide dismutase (SOD) enzyme activity and uncoupling of nitric oxide synthase. The applicant has developed echocardiographic and magnetic resonance imaging methods to evaluate the changes in aortic valve function in hypercholesterolemic mice over time, and confocal microscopy and laser capture microdissection to examine molecular mechanisms underlying these changes. The applicant proposes two main goals: 1) to examine the effects of treating hypercholesterolemia on the progression of aortic valve disease, and 2) to identify molecular mechanisms contributing to the pathogenesis of aortic valve disease. During the K99/Mentored phase of the grant, the applicant will examine the effects of aggressive lipid lowering on the progression of valve disease in hyperlipidemic mice, using a "genetic switch" to normalize cholesterol levels (using Ldlr-/-/Apob100/100/ Mttpfl/fl/Mx1Cre+/+ mice, also called "Reversa" mice). During the R00/lndependent phase of the grant, the applicant will examine mechanisms that predispose to the development of aortic valve stenosis. In the first portion of the R00 phase, the applicant will determine the role of mitochondria-derived oxidative stress on the progression of AVS using hyperlipidemic MnSOD-deficient and hyperlipidemic MnSOD-overexpressing mice. In the second portion of the ROD phase, the applicant will determine the role of nitric oxide synthase (NOS) cofactor depletion and the endogenous NOS inhibitor asymmetric dimethylarginine (ADMA) on oxidative stress in normal and stenotic human valves ex vivo. The applicant will also examine the role of DDAH1 (an enzyme involved in ADMA degradation) in the progression of AVS using hyperlipidemic DDAH1-deficient and hyperlipidemic DDAH1-overexpressing mice. Collectively, these studies will lend novel insights into the pathophysiology of AVS as well as the effects of treatment of hypercholesterolemia, and thus will lead to new approaches to prevent and treat AVS.