TITLE-KININS ROLE IN MESANGIAL CELL FIBROSIS The risk factors and pathophysiology for diabetic glomerulosclerosis are not fully defined. Although inherent susceptibility seems to influence the rate at which complications develop, the abnormal milieu of the diabetic state (hyperglycemia) is the primary driving force for cellular damage. These deleterious effects of the diabetic state are mediated via a myriad of cellular signals that alter cell structure and function. The overall goals of this project are to elucidate the cellular and molecular basis for activation and expression of glomerular kinin receptors and their contribution to the development of glomerular injury in diabetes. Among the mediators that are being studied, our data strongly supports a key role for kinins in promoting mesangial cell fibrosis. In this regard, our preliminary data demonstrate that kinins through activation of B1-and/or B2-receptors stimulate key signaling pathways that participate in the development of diabetic glomerular fibrosis. First, B1- and B2-kinin receptors are induced in glomeruli isolated from diabetic rats, and hyperglycemia can increase both B1- and B2-kinin receptor expression in mesangial cells. Second, bradykinin (BK) acting on B2-receptors, induce activation and membrane translocation of Rho family GTPases (RhoA, cdc42 and Rac1) in mesangial cells. Third, BK and/or des-Arg9-BK, acting on B1-receptors, stimulate MAPK (p42mapk and p44mapk) activation and c-fos mRNA expression in mesangial cells. Fourth, BK stimulates the mRNA levels of collagen I, and transforming growth factor-beta1 (TGF-beta) in mesangial cells. This induction of collagen I mRNA levels by BK is mediated via autocrine activation of TGF-beta. Fifth, the induction of TGF-B mRNA levels by BK in mesangial cells is mediated via activation of the MAPK pathway, thus providing a link between proliferative and fibrotic pathways. Finally, our recent findings in Type-1 diabetic patients demonstrate that patients with increased kallikrein activity display an increase in albumin excretion rate. We hypothesize that activation of glomerular B1-and/or B2-kinin receptors by the diabetic state plays a key role in the initiation and progression of diabetic glomerulorsclerosis. This hypothesis will be evaluated by addressing the following specific aims 1) To establish the role of diabetes and hyperglycemia on activation of glomerular kinin receptors and their functional significance. 2) To determine the role and contribution of kinins to induce mediators of mesangial cell fibrosis under normal and hyperglycemic conditions. 3) To determine the contribution of kinin receptor activation and blockade on the development of diabetic glomerulosclerosis in moderate hyperglycemic diabetic rats. These experiments will result in a comprehensive and critical assessment of the contribution of kinins to the development of diabetic glomerulopathy and will also provide a detailed understanding of the cellular mechanisms through which kinin receptor activation alters glomerular structure and function.
