Arterial calcification is a phenotype of vascular repair in atherosclerosis, diabetes, hyperphosphatemic renal failure, and aging that promotes mortality. Arterial calcification is an active and organized process, switched on by chondrocytic and osteoblastic differentiation of intra-arterial progenitors. Chondrogenesis is modulated by the metabolism of GSH. Vanin-1 pantetheinase suppresses GSH synthesis. Vanin-1 is induced by a variety of inflammatory stressors and promotes granuloma formation and intestinal inflammation. Vanin-1 suppresses PPARgamma expression and signaling, and vanin-1 thereby "licenses" pro-inflammatory cytokine expression. We observe increased chondrogenic potential of mesenchymal precursor cells linked with both PPi deficiency and driven by increased vanin-1 pantetheinase activity, cysteamine generation, and consequent GSH depletion. Vanin-1 knockout also blunts phosphate donor-induced chondrogenic differentiation and calcification in PPi-deficient arterial explants. PPARgamma suppresses bone formation and inhibits calcification by vascular cells. PPARgamma agonism also blunts experimental aortic media calcification. Our core hypothesis is that vanin-1 and modulation of PPARgamma are central and linked threads by which PPi/Pi imbalance, bone morphogens, and inflammation drive intra- arterial chondro-osseous differentiation and distinct phenotypes of primarily intimal or tunica media calcification. Here, we specifically aim to: 1. Define the core paracrine and autocrine mechanisms by which vanin-1 promotes switching on chondrogenic trans- differentiation in arterial SMCs. 2. Test the hypothesis that vanin-1 deficiency delays or prevents intra-arterial chondrogenesis and lethal artery media calcification in MGP deficient mice. 3. Test the hypothesis that SMC PPARgamma deficiency is sufficient to increase artery calcification in MGP deficient mice without primary dysregulation of vanin-1. 4. Test the hypothesis that generalized vanin-1 deficiency and SMC-specific PPARgamma deficiency exert opposite effects on atherosclerotic lesion calcification in chow-fed, aged apoE ko mice. Completion of these studies will provide novel insight and identification of vanin-1 as a potential new therapeutic target for arterial calcification.
Lay summary Arterial calcification is one of the potential outcomes of blood vessel repair in atherosclerosis, diabetes, chronic kidney disease, and aging. Artery calcification promotes mortality in these conditions and our objective is to identify new targets for therapies. In this project, we will define and test proposed mechanisms whereby linked changes in an enzyme (Vanin-1) involved in defense against oxidative stress, and the gene expression regulator PPARgamma, promote arterial calcification by switching on cartilage and bone formation in diseased arteries.
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