Meprin A Metalloproteinase in Acute Kidney Injury

描述(申请人提供)：MEPRIPs是一种‘ASTIN’家族的细胞表面和分泌的寡聚体金属内肽酶，在肾脏近端小管的刷状缘膜上高度表达。MEPRIPS在急性肾损伤(AKI)中的具体作用尚不完全清楚。我们的研究证实，Meprin A是大鼠肾皮质中主要的基质降解酶，能够在体外降解细胞外基质(ECM)蛋白，包括IV型胶原、纤维连接蛋白、层粘连蛋白和Nidogen。我们最近发表的初步研究表明，MEPRIPs还能够从其非活性的ProForm中产生生物活性的促炎细胞因子IL-1-β，并对趋化细胞因子MCP-1进行蛋白水解性处理，这表明MEPRIPs在炎症中也是重要的。从外周血或肾组织中分离出的白细胞表达Meprinβ。此外，我们的研究表明，在缺血-再灌注和顺铂诱导的AKI之后，meprin A重新分布到近端小管的基底外侧。这些研究表明，在急性肾小管损伤中，在根尖刷状缘膜以外的位置改变meprin A的定位可能是有害的。初步研究表明，Meprin A的脱落可能涉及ADAM(一种去整合素和金属蛋白酶)家族的成员。利用顺铂和缺血再灌注诱导的AKI模型，我们证明了meprin A的有效抑制剂放线宁在体内抑制meprin A并改善急性肾损伤，meprin A缺陷小鼠对顺铂肾毒性具有抵抗力。有趣的是，我们观察到，在顺铂肾毒性过程中，在正常小鼠的尿液中检测不到的Nidogen和meprin-beta片段显著增加，而放线宁显著阻止Nidogen片段在尿中的排泄。因此，有一个独特的机会来进一步探讨meprin A在AKI中的作用和作用机制。我们推测，梅普林A具有巨大的破坏力，在急性肾损伤期间由于定位改变而对肾近端小管有害，了解其作用机制对于保护或减少急性肾损伤具有重要意义。我们将通过以下具体目标来检验这一假说：1.利用IR和顺铂肾毒性的实验模型，研究急性肾损伤期间梅普林A再分布、肾脏损伤、白细胞浸润和梅普林A脱落之间的时间关系。2.MEPRIN A介导的细胞外基质成分在IR和顺铂肾毒性过程中体内降解产物的鉴定3.应用meprin A抑制剂和meprin A基因缺陷小鼠，研究meprin A在AKI中的炎症作用机制及其功能意义。了解meprin A在AKI中的潜在作用将为预防急性肾损伤的特定治疗干预提供见解。

DESCRIPTION (provided by applicant): Meprins, cell-surface and secreted oligomeric metalloendopeptidases of the 'astacin' family, are highly expressed at the brush-border membranes of the kidney proximal tubules. The specific role of meprins during acute kidney injury (AKI) is not fully understood. Our studies identified that meprin A is the major matrix-degrading protease in the rat kidney cortex capable of degrading the extracellular matrix (ECM) proteins including collagen IV, fibronectin, laminin, and nidogen in vitro. Our recently published and preliminary studies demonstrated that meprins are also capable of producing biologically active proinflammatory cytokine interleukin 1-beta from its inactive proform and proteolytically processing chemotactic cytokine MCP-1, suggesting that meprins are also important in inflammation. Leukocytes isolated from the peripheral blood or the kidney tissue were found to express meprin beta. Furthermore, our studies demonstrate that, following ischemia-reperfusion- and cisplatin-induced AKI, meprin A is redistributed toward the basolateral side of the proximal tubule. These studies suggest that altered localization of meprin A in places other than the apical brush-border membranes may be deleterious in vivo in acute tubular injury. Preliminary studies suggest that meprin A shedding may involve a member of the ADAM (a disintegrin and metalloproteinase) family. Using in vivo models of cisplatin- and ischemia- reperfusion-induced AKI, we demonstrated that actinonin, a potent inhibitor of meprin A inhibits meprin A in vivo and ameliorates acute kidney injury and meprin A-deficient mice are resistant to cisplatin nephrotoxicity. Interestingly, we observed that nidogen and meprin-beta fragments, undetectable in the urine of normal mice, increased significantly during cisplatin nephrotoxicity and actinonin markedly prevented urinary excretion of nidogen fragments. Thus, a unique opportunity exists to further explore the role and mechanism of action of meprin A in AKI. We hypothesize that meprin A, with its enormous destructive potential, is detrimental to renal proximal tubules due to altered localization during AKI and that understanding its mechanism of action is important in protecting or reducing AKI. We will test the hypothesis through the following specific aims: The Specific Aims are: 1. Examine the temporal relationship between meprin A redistribution, renal injury, leukocyte infiltration, and meprin A shedding during AKI using experimental models of IR and cisplatin nephrotoxicity. 2. Identification of meprin A-mediated in vivo degradation products of the ECM components during IR and cisplatin nephrotoxicity. 3. Determine the mechanisms of meprin A-mediated inflammatory effects and functional significance of meprin A during AKI using a meprin inhibitor and meprin A-deficient mice. Understanding the underlying role of meprin A in AKI will provide insights for specific therapeutic interventions to prevent acute kidney injury.