Complement Activation and Renal Ischemia/Reperfusion Injury

描述(由申请人提供)： 这笔R03赠款与K08 DK064790有关，题为“补体与缺血性急性肾功能衰竭”。在这笔赠款的前三年，我们探索了肾缺血/再灌注(I/R)后补体激活的机制，补体介导的肾脏损伤机制，并开发了一种新的替代补体途径的抑制剂。在完成该资助的特定目标1中概述的实验时，我们发现近端肾小管上皮细胞(PTECs)通过合成补体C3对缺血做出反应。PTECs表达的补体抑制蛋白通常也极化到细胞的基底外侧表面，这种极化在缺血后消失。这些变化有利于PTECs基底外侧表面替代补体途径的激活，并可能导致I/R后的小管间质损伤。最近的研究表明，甘露糖结合凝集素(MBL)系统也可能通过替代途径放大引起补体激活，这一观点最初并未基于先前公认的补体激活模型而被考虑。在这些发现的基础上，本提案中的实验检验了这些新的机制，通过这些新的机制，替代途径在受损的PTECs表面得到了极大的放大。这项资助的总体假设是：(1)MBL识别缺血的PTECs，启动补体的激活，(2)细胞表面补体抑制物的缺失足以允许替代补体途径的不受控制的放大。这些补体启动和放大的机制，以及我们先前证明的缺血PTECs主动合成C3的机制，解释了为什么替代途径在I/R后在肾脏被广泛激活。拟议的研究将利用缺血性急性肾功能衰竭模型和孤立替代途径介导的肾小管损伤的体内模型。体外模型也将被用来探索特定蛋白在低氧PTECs表面补体激活中的作用。这些研究将加深我们对缺血性急性肾功能衰竭的病理生理机制的理解，并将有助于揭示PTECs的局部无菌损伤转化为全身炎症反应的分子机制。通过这笔赠款提供的资金将通过提供一名全职技术员和帮助支付与这些研究有关的动物费用来帮助实现这些目标。。缺血性急性肾功能衰竭是一种常见疾病，与重症监护病房中50%以上的死亡率有关。许多补体抑制剂已经上市，包括我们实验室开发的替代途径的一种特定抑制剂。建议的研究将有助于阐明补体抑制作为治疗缺血性急性肾功能衰竭的益处和局限性，并扩大我们对补体激活作为肾小管损伤后炎症介质的理解。

DESCRIPTION (provided by applicant): This R03 grant is associated with K08 DK064790, entitled "Complement and Ischemic Acute Renal Failure". During the first three years of that grant we have explored the mechanisms of complement activation after renal ischemia/reperfusion (I/R), the mechanisms of complement mediated injury to the kidney, and we have developed a novel inhibitor of the alternative complement pathway. While completing the experiments outlined in Specific Aim 1 of that grant, we found that proximal tubular epithelial cells (PTECs) respond to ischemia by synthesizing complement C3. The complement inhibitory protein expressed by PTECs is also ordinarily polarized to the basolateral surface of the cells, and this polarity is lost after ischemia. These changes favor activation of the alternative complement pathway on the basolateral surface of PTECs, and likely contribute to tubulointerstitial injury after I/R. Recent work has revealed that the mannose binding lectin (MBL) system may also cause complement activation through alternative pathway amplification, an idea we had not initially considered based upon the previously accepted models of complement activation. Expanding upon these findings, the experiments in the current proposal examine these novel mechanisms by which the alternative pathway becomes greatly amplified on the surface of injured PTECs. The overall hypothesis of this grant is that (1) MBL recognizes ischemic PTECs, initiating the activation of complement, and (2) absent expression of cell surface complement inhibitors is sufficient to permit uncontrolled amplification of the alternative complement pathway. These mechanisms of complement initiation and amplification, and the active synthesis of C3 by ischemic PTECs that we have previously demonstrated, explain why the alternative pathway is extensively activated in the kidney after I/R. The proposed studies will utilize a model of ischemic acute renal failure and an in vivo model of isolated alternative pathway mediated injury to the tubules. An in vitro model will also be used to explore the roles of specific proteins in complement activation on the surface of hypoxic PTECs. The proposed studies will enhance our understanding of the pathophysiology of ischemic acute renal failure, and will help reveal the molecular mechanisms by which local aseptic injury to PTECs is transformed into a systemic inflammatory response. The funds made available through this grant will assist the completion of these aims by providing for a full-time technician and by assisting with the animal costs associated with these studies. . Ischemic acute renal failure is a common disease and is associated with a mortality rate of greater than 50% in the intensive care unit setting. A number of complement inhibitors have become available, including a specific inhibitor of the alternative pathway that has been developed by our laboratory. The proposed studies should help delineate the benefits and limitations of complement inhibition as a therapy for ischemic acute renal failure, as well as expand our understanding of complement activation as a mediator of inflammation after renal tubular injury.