THROMBOSPONDIN IN GLUCOSE-MEDIATED TGFB UPREGULATION

高血糖及由此产生的晚期糖基化终末产物 产物(AGEs)是糖尿病发病机制中的主要因素 肾病。促纤维化生长因子，转化生长因子-b，是 转化生长因子-β在糖尿病肾小球硬化中的作用 刺激基质蛋白合成和基质组装。氧化 应激与蛋白激酶C(PKC)活性对高密度脂蛋白的响应 葡萄糖/AGEs刺激转化生长因子-b的表达。现在有令人信服的 高血糖和AGEs与自分泌上调有关的证据 然而，转化生长因子-b的活性，调节激活的分子机制 关于转化生长因子-β的潜在前体形式尚不清楚。我们之前 证实了血小板和基质分子TSP结合和 激活潜伏的转化生长因子-β，并显示TSP依赖的转化生长因子-β的激活 发生在生理环境中。凝血酶敏感蛋白可能参与了 肾小球系膜细胞表达TSP1与糖尿病肾病的发病机制 细胞受高糖上调，TSP是早期 糖尿病肾脏的纤维化。在此基础上，我们提出葡萄糖 氧化机制的调节通过UP-1诱导肾小球硬化 凝血酶敏感蛋白刺激的转化生长因子-b激活的调节。具体的 目的是：1)确定TSP是否参与葡萄糖介导的 对系膜细胞转化生长因子-β活性的刺激；2)测定 TSP依赖的转化生长因子-β是否参与氧化机制 激活受高糖和/或AGEs的调节。初步数据显示 TSP拮抗肽阻断葡萄糖刺激的自分泌转化生长因子-β 肾小球系膜细胞的活性，提示TSP的作用。这些多肽 拮抗剂为我们提供了一种独特的工具来研究TSP在 转化生长因子-β在糖尿病肾病中的激活我们建议将其描述为 TSP在急性和慢性转化生长因子-β调节中的作用 条件，b)基质合成和组装的调节，c)系膜 细胞增殖，以及d)葡萄糖/AGEs和PKC在 TSP表达和转化生长因子-β活性的调节及其分布 在糖尿病大鼠的肾脏中。我们还建议研究以下因素的影响 一氧化氮(NO)供体对高血压病患者TSP mRNA、蛋白及转化生长因子-β的影响 葡萄糖；确定TSP是否不涉及PKC的调节，并 评估细胞内氧化还原平衡在TSP和转化生长因子-β中的作用 监管。一个长期的目标是发展这些TSP 拮抗剂作为干预关键步骤的治疗工具 激活转化生长因子-β，以减轻纤维化。这些研究是 了解分子机制的更大倡议的一部分 与纤维化有关。

Hyperglycemia and the resultant generation of advanced glycosylation end products (AGEs) are major factors in the pathogenesis of diabetic nephropathy. The pro-fibrotic growth factor, TGF-b, is key to the development of diabetic glomerulosclerosis due to TGF-b's role in the stimulation of matrix protein synthesis and matrix assembly. Oxidative stress and protein kinase C (PKC) activity in response to high glucose/AGEs stimulates TGF-b expression. There is now compelling evidence linking hyperglycemia and AGEs to up-regulation of autocrine TGF-b activity, however, the molecular mechanisms regulating activation of the latent precursor form of TGF-b are not clear. We previously established that the platelet and matrix molecule, TSP, binds and activates latent TGF-b and showed that TSP-dependent activation of TGF-b occurs in physiologic situations. Thrombospondin may be involved in the pathogenesis of diabetic nephropathy, since TSP1 expression by mesangial cells is up-regulated by high glucose and TSP is a marker of early fibrosis in diabetic kidneys. On this basis, we propose that glucose regulation of oxidative mechanisms induce glomerulosclerosis via up- regulation of thrombospondin-stimulated TGF-b activation. The specific aims are: 1) to determine whether TSP is involved in glucose-mediated stimulation of TGF-b activity in mesangial cells; and 2) to determine whether oxidative mechanisms are involved in TSP-dependent TGF-b activation regulated by high glucose and/or AGEs. Preliminary data show that TSP antagonist peptides block glucose stimulated autocrine TGF-b activity in mesangial cells, suggesting a role for TSP. These peptides antagonists provide us with a unique tool to study the role of TSP in activation of TGF-b in diabetic nephropathy. We propose to characterize the role of TSP in a) TGF-b regulation in both acute and chronic conditions, b) regulation of matrix synthesis and assembly, c) mesangial cell proliferation, and d) the role of glucose/AGEs and PKC in regulation of TSP expression and TGF-b activity, and TSP's distribution in diabetic rat kidneys. We also propose to examine the effects of nitric oxide (NO) donors on TSP mRNA, protein, and TGF-b in high glucose; to determine whether NO regulation of TSP involves PKC, and to assess the role of intracellular redox balance in TSP and TGF-b regulation. A long-term goal is the development of these TSP antagonists as a therapeutic tool to intervene in the critical step of TGF-b activation in order to ameliorate fibrosis. These studies are part of a larger initiative to understand the molecular mechanisms involved in fibrosis.