KININS ROLE IN MESANGIAL CELL FIBROSIS

标题-激肽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确定。 虽然固有的易感性似乎影响并发症的发生率，但糖尿病状态（高血糖症）的异常环境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改变细胞结构和功能的无数细胞信号介导的。 本项目的总体目标是阐明肾小球激肽受体激活和表达的细胞和分子基础及其在糖尿病肾小球损伤发展中的作用。在正在研究的介质中，我们的数据强烈支持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，激肽通过激活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，B1-和B2-激肽受体诱导分离自糖尿病大鼠的肾小球，和高血糖症可以增加B1-和B2-激肽受体在系膜细胞的表达。 第二，缓激肽（BK）作用于B2受体，诱导系膜细胞Rho家族GTP酶（RhoA、cdc 42和Rac 1）活化和膜转位。 第三，BK和/或des-Arg 9-BK作用于B1受体，刺激系膜细胞MAPK（p42 mapk和p44 mapk）活化和c-fos mRNA表达。 第四，BK刺激肾小球系膜细胞中I型胶原和转化生长因子β 1（TGF-β）的mRNA水平。 BK对I型胶原mRNA水平的诱导是通过TGF-β的自分泌激活介导的。 第五，系膜细胞中BK对TGF-β mRNA水平的诱导是通过活化MAPK途径介导的，从而提供了增殖和纤维化途径之间的联系。 最后，我们最近在1型糖尿病患者中的发现表明，具有增加的激肽释放酶活性的患者显示白蛋白排泄率增加。 我们推测糖尿病状态下肾小球B1和/或B2激肽受体的激活在糖尿病肾小球硬化的发生和发展中起关键作用。 这一假说将通过解决以下具体目标进行评估：1）确定糖尿病和高血糖症对肾小球激肽受体激活的作用及其功能意义。2)确定激肽在正常和高血糖状态下诱导肾小球系膜细胞纤维化介质中的作用和贡献。3)在中度高血糖糖尿病大鼠中，确定激肽受体激活和阻断在糖尿病肾小球硬化发展中的作用。这些实验将导致一个全面的和关键的评估，激肽的糖尿病肾小球病变的发展的贡献，也将提供一个详细的了解细胞机制，通过激肽受体活化改变肾小球结构和功能。

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.