PROXIMAL TUBULE ANGIOTENSINS--HEMOLYTIC UREMIC SYNDROME

描述（改编自应用程序） 大多数关于溶血性尿毒症综合征（HUS）的研究，这是急性肾病的主要原因 儿童失败，重点关注血栓性微血管病的机制 和内皮损伤。然而，直到最近，人们才开始考虑肾功能 肾小管作为志贺样毒素 [Stx] 的主要损伤部位已在很大程度上被 切向。据报道，人类近曲小管细胞[PTCs] 对 Stx 造成的伤害极其敏感。许多关于发病机制的研究表明 Stx相关疾病会导致凝血因子异常， 剪切力增加、氧化损伤、血小板活化、红细胞损伤 多种细胞因子和血管活性物质的参与。虽然很多 人们的注意力集中在内皮素、NO和血管舒张物质的变化上， 人们对肾素-血管紧张素系统的潜在作用知之甚少 [RAS] 调节 HUS 的严重程度。近年来，互动 具有凝血因子和细胞因子的 RAS 已被认为是重要的 在正常和病理生理状态下。该应用程序将重点关注 PTC 组织 RAS 的独特作用，假设局部血管紧张素 放大 Stx 对 PTC 的影响，导致进一步的伤害。这样，我们将 定义局部近端肾小管 RAS 在 HUS 中的作用。我们假设 Stx 诱导的近端小管细胞 [PTC] 损伤引发一系列病理学 RAS 和凝血级联相互作用的事件如下： PTC 损伤导致 Ang II 生成增加。肾小球和肾小管改变 剪切力会导致管状流体流动受损、碎片堆积 红细胞和白细胞近乎停滞，甚至缺氧。血管紧张素在 这种环境中存在 Stx、白细胞和 PT 衍生细胞因子 [例如，IL-1、TNF]，有利于组织因子 [TF，存在于 PT 中] 的 PTC 表达， PAI-1 和其他促纤维化因子。此外，肾小管中的 TF 可能会变成 鉴于 PTC 因暴露于血液制品而进一步上调 肾小球损伤。中断这些相互作用可能会消除或减轻 Stx引起的损伤。该应用程序的具体目标是： 1. 证明 Stx 增强近端局部 RAS 的表达 肾小管细胞 [PTC]，以及肾小球内皮细胞和系膜细胞， 反过来，调节组织因子 PAI-1 和细胞因子的产生， 导致 HUS 中肾小管损伤。初步数据表明 Stx 增加血管紧张素原和血管紧张素转换酶（ACE）的生成 PTC，对 Stx 2 极其敏感。为了证明 Stx 诱导的 RAS 反过来又增加了局部 TF、PAI-1 和细胞因子的产生，有助于 HUS 中的肾小管损伤。我们假设 Stx 诱导的 PTC 损伤受到调节 通过 RAS、凝血途径和细胞因子相互作用，并影响 PT 功能。我们将单独和在静态和流动条件下检查 PTC 接近肾小球内皮细胞和系膜细胞；我们将同时 使用流变学研究 Stx 诱导的 HUS 狒狒模型的组织 技术和分子研究。 3. 证明 Stx 诱导的废除 通过阻断血管紧张素、志贺毒素和 凝血途径。使用相同的系统，RAS 的交互， 凝血因子和细胞因子将依次被特异性阻断 为了定义这些相互作用的机制。预计 特定的封锁可能会导致与临床相关的策略 可能预防或改善 HUS。

DESCRIPTION (adapted from the application) Most studies of hemolytic uremic syndrome (HUS), a leading cause of acute renal failure in children, have focused on mechanisms of thrombotic microangiopathy and endothelial injury. However, until recently, consideration of the renal tubule as a site for primary damage by shiga-like toxin [Stx] has been largely tangential. It has now been reported that human proximal tubule cells [PTCs] are exquisitely sensitive to damage by Stx. Much work on pathogenesis has shown that Stx-related disease leads to abnormalities in coagulation factors, increased shear forces, oxidant injury, platelet activation, rbc injury, with involvement of multiple cytokines and vasoactive substances. While much attention has focused on changes in endothelin, NO, and vasodilator substances, little has been paid to the potential role of the renin-angiotensin system [RAS] in modulating the severity of HUS. In recent years, the interaction of the RAS with coagulation factors and cytokines has been recognized as important in both normal and pathophysiologic states. This application will focus on the unique role of the PTC tissue RAS, hypothesizing that local angiotensins amplify the effects of Stx in PTC, resulting in further injury. Thus, we will define the roles of the local proximal tubular RAS in HUS. We hypothesize that Stx-induced proximal tubule cell [PTC] injury initiates a pathologic series of events in which the RAS and the coagulation cascade interact as follows: PTC injury results in heightened Ang II generation. Altered glomerular and tubular shear forces lead to impairment of tubular fluid flow, accumulation of debris with rbc and leukocytes with near stasis, and even hypoxia. Angiotensins in this milieu in the presence of Stx and leukocyte and PT-derived cytokines [e.g., IL-1, TNF], favor PTC expression of tissue factor [TF, present in PT], PAI-1 and other pro-fibrotic factors. Furthermore, TF in the tubule may become further upregulated in view of exposure of PTC to blood products due to glomerular injury. Interrupting these interactions may abrogate or mitigate Stx-induced damage. The specific aims of this application are: 1. To demonstrate that Stx enhances the expression of the local RAS in proximal tubule cells [PTC], as well as in glomerular endothelial and mesangial cells, which, in turn, modulates tissue factor PAI-1, and cytokine production, contributing to tubular damage in HUS. Preliminary data suggest that Stx increases angiotensinogen and angiotensin converting enzyme (ACE) generation in PTCs, which are exquisitely sensitive to Stx 2. To demonstrate that Stx-induced RAS, in turn increases local TF, PAI-1 and cytokine production, contributing to tubular damage in HUS. We hypothesize that Stx-induced PTC injury is modulated by RAS, coagulation pathway and cytokine interaction, and influences PT functions. We will examine PTC under static and flow conditions, alone and in proximity to glomerular endothelial and mesangial cells; we will concomitantly study tissues from the baboon model of Stx-induced HUS using rheologic techniques and molecular studies. 3. To demonstrate abrogation of Stx-induced injury in PTC by blocking the interaction of angiotensins, shiga toxin, and the coagulation pathway. Using the same systems, the interaction of the RAS, coagulation factors and cytokines will be blocked sequentially and specifically in order to define the mechanism of these interactions. It is anticipated that specific blockade may lead to strategies with clinical relevance for the possible prevention or amelioration of HUS.