KININS ROLE IN MESANGIAL CELL FIBROSIS

KINS在系膜细胞纤维化中的作用糖尿病肾小球硬化的危险因素和病理生理学尚未完全明确。虽然固有的易感性似乎影响并发症的发展速度，但糖尿病状态的异常环境(高血糖)是细胞损伤的主要驱动力。糖尿病状态的这些有害影响是通过无数改变细胞结构和功能的细胞信号来调节的。该项目的总体目标是阐明肾小球激动素受体激活和表达的细胞和分子基础，以及它们在糖尿病肾小球损伤发展中的作用。在正在研究的介质中，我们的数据有力地支持了激肽在促进系膜细胞纤维化中的关键作用。在这方面，我们的初步数据表明，激动素通过激活B1和/或B2受体刺激参与糖尿病肾小球纤维化发展的关键信号通路。首先，糖尿病大鼠肾小球上皮细胞可诱导B1和B2激动素受体的表达，高血糖可增加系膜细胞B1和B2激动素受体的表达。第二，缓激肽(BK)作用于B_2受体，诱导系膜细胞Rho家族GTP酶(RhoA、CDC42和rac1)的激活和膜转位。第三，BK和/或DES-Arg9-BK作用于B1受体，刺激系膜细胞MAPK(p42mapk和p44mapk)激活和c-fos基因表达。第四，BK可刺激系膜细胞I型胶原和转化生长因子-β1(TGF-β)的mRNA水平。BK对I型胶原mRNA水平的诱导是通过自分泌激活转化生长因子-β来实现的。第五，BK诱导系膜细胞表达转化生长因子-β是通过激活MAPK途径实现的，从而在增殖和纤维化途径之间建立了联系。最后，我们最近在1型糖尿病患者中的发现表明，激肽释放酶活性增加的患者白蛋白排泄率增加。我们推测糖尿病状态下肾小球B1和/或B2激动素受体的激活在糖尿病肾小球硬化的发生和发展中起着关键作用。这一假说将通过以下具体目标进行评估：1)确定糖尿病和高血糖对肾小球激动素受体激活的作用及其功能意义。2)探讨激肽在正常和高血糖条件下诱导系膜细胞纤维化中的作用和贡献。3)探讨激动素受体的激活和阻断在中度高血糖糖尿病大鼠糖尿病肾小球硬化形成中的作用。这些实验将导致对激肽在糖尿病肾小球病变发展中的作用进行全面和关键的评估，并将提供对激肽受体激活改变肾小球结构和功能的细胞机制的详细了解。

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.