Role of Cyclooxygenase Stimulated Neovascularization in Diabetic Nephropathy

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DESCRIPTION (provided by applicant): Diabetic nephropathy (DN) is the major single cause of end stage renal disease in the United States. DN is associated with vascular disease, including retinopathy, impaired wound healing and neuropathy. Although less recognized, increased glomerular neovascularization has also been observed in type 1 diabetes. However, at present it is not clear which molecular pathway/s control glomerular angiogenesis in diabetes. Cyclooxygenases (COX) 1 and 2 are key enzymes involved in the generation of prostaglandin E2 (PGE2). Notably, COX-2 is over-expressed in both renal cortex and medulla of diabetic mice. The observation that treatment of diabetic mice with COX-2 inhibitors reduces the expression of pro-angiogenesis molecules as well as albuminuria, strongly suggest a role for COX-derived prostanoids in DN. As i) increased COX expression is observed in diabetic kidneys, ii) PGE2 stimulates angiogenesis, iii) PGE2 increases endothelial permeability, and iv) the PGE2 EP4 receptor is highly expressed in glomeruli, we hypothesize that a functional prostaglandin dependent pathway is activated in diabetic kidney disease and promotes glomerular angiogenesis. To test this hypothesis we will assess 1) the contribution of COX-1 versus COX-2 derived prostanoids to the progression of neovascularization in mouse models of type I diabetes; 2) the role of a microsomal prostaglandin E2 synthase in the production of PGE2 and consequent glomerular neovascularization in type I diabetes and 3) the role of the glomerular endothelial and podocytes EP4 in the progression of diabetic. This study will enable us not only to define how COXs, PGE2 and its receptors alter glomerular microvascular angiogenesis in the setting of type 1 diabetes, but also to define whether preventing PGE2 synthesis and/or EP receptor activation might provide a specific therapeutic strategy to the treatment for altered angiogenesis in DN. This work will be a joint effort between Drs. Breyer and Pozzi. Dr. Breyer's group has been studying the roles of renal cyclooxygenase and PGE2 for over 15 years and has generated several of the transgenic mouse models used to study prostanoid function. His group also has substantial experience phenotyping mouse models of diabetic nephropathy. Dr. Pozzi studies the role of integrin (1(1, a major collagen binding receptor, in the control of endothelial cell biology and collagen homeostasis, two relevant aspects in DN. Recently she has examined the contribution of COX-2-derived PGE2 and its receptor EP4 in the control of tumor angiogenesis. Moreover, Drs. Pozzi and Breyer published in JBC an article on the role of COX-2 in the renal medullary interstitial cell survival. We believe the present proposal provides synergy between Dr. Pozzi's expertise in angiogenesis and Dr. Breyer's expertise in mouse models of diabetic nephropathy, and draws on their common interest in the prostanoid pathway in cell differentiation and survival.