SMAD SIGNALING IN ANGIOTENSIN II-MEDIATED RENAL FIBROSIS

说明(申请人提供)：血管紧张素转换酶II在终末期肾脏疾病的发展中起着关键作用。已知Ang II通过刺激转化生长因子-β介导肾纤维化。然而，我们的初步研究表明，Ang II诱导的肾脏纤维化可能需要一个额外的信号通路。我们发现Ang II能够激活转化生长因子-b信号通路Smad2和Smads。这种反应通过两种机制导致胶原生成的增加：1)通过激活ERK/p38 MAP激酶的急性途径(5-30分钟)；2)通过自分泌的转化生长因子-b作用并导致纤维化的晚期机制(24小时)。此外，我们还发现，Smad2基因缺失的小鼠对肾脏纤维化有保护作用，而Smad2基因缺失的小鼠则增强了Smads信号转导和肾纤维化对Ang II的反应。因此，我们假设Smad信号是Ang II反应的肾纤维化发生的关键。我们计划验证这一假说，并通过追求三个特定目标来确定Ang Il-Smad信号通路在肾纤维化中的新作用。在目标1中，我们将研究Ang II通过急性(5-30分钟)ERK/p38 MAPK依赖和晚期(20小时)经典的依赖于转化生长因子-b的途径激活Smads。在目标2中，我们将剖析依赖和独立的Smad信号通路在AngⅡ诱导的肾纤维化中的功能作用，在表达或不表达转化生长因子-b或TbRII的系膜细胞(MC)和肾小管上皮细胞(TEC)中，以及在条件性TbRII KO小鼠中。在目标3中，我们将剖析Smad2或Smads在AngⅡ介导的肾纤维化中的具体作用。这将在表达或不表达Smad2和Smads的小鼠胚胎成纤维细胞、MC和TEC以及Smads KO和条件性Smad2 KO小鼠中进行检测。我们期望这项研究的结果将支持中心假说，并为AngⅡ介导的肾纤维化的发病机制提供新的见解，并为通过靶向Smad信号来对抗肾纤维化的新的治疗策略的发展提供有价值的信息。

DESCRIPTION (provided by applicant): Ang II plays a pivotal role in the development of end-stage renal disease. It is known that Ang II acts by stimulating TGF-b to mediate renal fibrosis. However, our preliminary studies showed an additional signaling pathway that may be required for renal fibrosis induced by Ang II. We found that Ang II is able to activate the TGF-b signaling pathway, Smad2 and SmadS. This response leads to increased collagen production by two mechanisms: 1) an acute pathway (5-30 minutes) via activation of the ERK/p38 MAP kinases; and 2) a late mechanism (24 hours) that acts through autocrine TGF-b and leads to fibrosis. Furthermore, we also find that mice null for SmadS are protected against renal fibrosis, while mice that are conditionally deleted for Smad2 enhance SmadS signaling and renal fibrosis in response to Ang II. Thus, we hypothesize that Smad signaling is a key to the development of renal fibrosis in response to Ang II. We plan to test this hypothesis and to determine the new role for the Ang Il-Smad signaling pathway in renal fibrosis by pursuing three specific aims. In Aim 1, we will study that Ang II activates Smads via an acute (5-30 mins) ERK/p38 MAPKdependent and a late (20 hrs) classic TGF-b-dependent pathways. In Aim 2, we will dissect the functional role of TGF-b-dependent and independent Smad signaling pathways in Ang ll-induced renal fibrosis in mesangial cells (MC) and tubular epithelial cells (TEC) that do or do not express TGF-b or TbRII, and in conditional TbRII KO mice. In Aim 3, we will dissect the specific role of Smad2 or SmadS in Ang ll-mediated renal fibrosis. This will be examined in mouse embryonic fibroblasts, MC, and TEC that do or do not express Smad2 and SmadS and in SmadS KO and conditional Smad2 KO mice. We expect that the outcomes obtained from this study will support the central hypothesis and provide new insights into the pathogenesis of Ang ll-mediated renal fibrosis and valuable information for the development of new therapeutic strategies to combat renal fibrosis by targeting Smad signaling.