Importance of the alternative complement pathway in nephrotic syndrome

补体替代途径在肾病综合征中的重要性

• 批准号: 457011590
• 负责人: Professor Dr. Ferruh Artunc
• 金额: --
• 依托单位: Innere Medizin IV: Endokrinologie und Diabetologie, Angiologie, Nephrologie und Klinische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/457011590?language=en
• 关键词: Importance; alternative; complement; pathway; nephrotic

The epithelial sodium channel (ENaC) is expressed in the late distal aldosterone-sensitive tubule and is of essential importance for the sodium homeostasis. Among the various regulatory mechanisms of ENaC, activation after proteolytic cleavage by intra- and extracellular serine proteases is a specific feature of ENaC. Nephrotic syndrome leads to sodium retention and edema formation and is mediated by increased ENaC activity due to aberrantly filtered serine proteases from the plasma which activate ENaC by proteolysis. The relevance of this mechanism was demonstrated in vivo by the applicant whereby the unselective serine protease inhibitor aprotinin protected nephrotic mice from sodium retention and edema formation. Since this pivotal finding, the applicant´s group – supported by DFG grants - focuses on the identification of the essential serine protease(s) from urine samples of mice and humans that might be involved in proteolytic ENaC activation. Using a proteomic approach several serine proteases were identified and tested for their pathophysiological relevance in nephrotic knockout mouse models. Currently, involvement of urokinase, plasmin, plasma kallikrein, coagulation factor XII, Factor VII-activating protease as well as prostasin was excluded. In addition, nephrotic urine samples contained the serine proteases complement factor D and B which are part of the alternative complement pathway and could also play a significant role. Moreover, there was evidence of activation of the alternative complement pathway in nephrotic samples from humans and mice. In accordance with a possible relevance of this pathway, the cleavage sequence of CFD at this physiological substrate CFB is identical with that of the γ-subunit of ENaC which was determined by own experiments with a substrate approach. In this project, the applicant aims to elucidate the role of the alternative complement pathway in sodium retention and edema formation in nephrotic syndrome. To this end, a comprehensive analysis of complement factors and activation will be established in nephrotic urine samples. The in vivo relevance will be investigated using nephrotic mouse models involving knockout mice with deletion of the essential components of the alternative complement pathway (CFD, CFB, C3, properdin). This identification of the alternative complement pathway as the cause of proteolytic ENaC activation may lay the foundation to develop a therapeutic strategy in nephrotic syndrome.

上皮钠通道（ENaC）在晚期远端醛固酮敏感性小管中表达，对钠稳态至关重要。在ENaC的各种调节机制中，通过细胞内和细胞外丝氨酸蛋白酶的蛋白水解切割后的活化是ENaC的特定特征。肾病综合征导致钠潴留和水肿形成，并由ENaC活性增加介导，ENaC活性增加是由于来自血浆的异常过滤的丝氨酸蛋白酶通过蛋白水解激活ENaC。申请人在体内证明了这种机制的相关性，其中非选择性丝氨酸蛋白酶抑制剂抑肽可以保护肾病小鼠免受钠潴留和水肿形成的影响。由于这一关键发现，申请人的小组-由DFG赠款支持-专注于从小鼠和人类尿样中鉴定可能参与蛋白水解ENaC激活的必需丝氨酸蛋白酶。使用蛋白质组学方法鉴定了几种丝氨酸蛋白酶，并在肾病敲除小鼠模型中测试了它们的病理生理学相关性。目前，排除了尿激酶、纤溶酶、血浆激肽释放酶、凝血因子XII、因子VII活化蛋白酶以及前列腺素的参与。此外，肾病尿液样本含有丝氨酸蛋白酶补体因子D和B，它们是补体旁路途径的一部分，也可能发挥重要作用。此外，有证据表明，在人类和小鼠的肾病样本中，补体旁路途径被激活。根据该途径的可能相关性，CFD在该生理底物CFB处的切割序列与ENaC的γ-亚基的切割序列相同，ENaC的γ-亚基的切割序列通过自己的实验用底物方法确定。在本项目中，申请人旨在阐明替代补体途径在肾病综合征钠潴留和水肿形成中的作用。为此，将在肾病尿液样本中建立补体因子和活化的综合分析。将使用肾病小鼠模型研究体内相关性，所述肾病小鼠模型涉及缺失旁路补体途径的基本组分（CFD、CFB、C3、备解素）的敲除小鼠。这种替代补体途径作为蛋白水解ENaC激活的原因的鉴定可能为开发肾病综合征的治疗策略奠定基础。