髓样分化蛋白2在游离脂肪酸诱导的肾损伤和肥胖相关性肾病中的作用和机制研究

Obesity-induced renal chronic inflammation and fibrosis plays an important role in the development of obesity-related glomerulopathy (ORG). However, it is unclear how the hyperlipidemia / free fatty acid induce inflammation and renal injury. Myeloid differentiation protein 2 (MD2) is an important protein which mediates the acute inflammatory response induced by endotoxin and toll like receptor 4 (TLR4) pathway. Although the importance of TLR4 in FFA-induced inflammatory response has been reported, the role of MD2 in this process is yet unkown. Our previous studies showed that a MD2 specific inhibitor, L6H21, significantly inhibited the release of cytokines in FFA-stimulated cells. Furthermore, L6H21 markedly relieved renal injury in obese mice, accompanied with the inhibition against renal inflammation, and renal fibrosis. These data indicate that MD2 may mediate the pathogenesis of ORG. We hypothesize that, FFA directly binds to MD2, activating TLR4 signaling pathway, and then induces renal inflammtion and fibrosis. In this project, we are going to demonstrate how FFA directly binds to MD2 protein and activate MD2/TLR4-dependent pro-inflammatory signaling pathway, and how FFA induces renal fibrosis, at both molecular and cellular levels. Then, we will confirm the role of MD2 in the pathogensis of ORG in high fat diet-fed mice, and MD2-/- mice. Completion of this challenging project will provide the clear understanding on the mechanism by which FFA induced renal inflammation and fibrosis. In addition, these studies will provide novel target and strategy for the prevention and treatment of ORG.

肥胖导致的肾脏慢性炎症反应和纤维化与肥胖相关性肾病（ORG）的发生发展密切相关，但高血脂（游离脂肪酸FFA）诱导炎症反应和病变的分子机制尚不清晰。MD2是介导内毒素-TLR4急性炎症反应的重要蛋白，尽管TLR4在FFA炎症反应中的重要性已被报道，但MD2在FFA诱导的炎症反应和ORG中尚无报道。我们前期实验发现MD2小分子抑制剂L6H21可以抑制FFA诱导的炎症反应，显著缓解肥胖小鼠的肾脏损伤，并伴随着对肾脏炎症反应和纤维化的抑制，提示MD2介导了ORG的发生。本课题假设：FFA通过直接结合MD2，激活TLR4，导致肾炎症反应和纤维化，引起ORG的发生发展。本项目中，我们拟在分子和细胞层面确证FFA通过直接结合MD2激活TLR4炎症反应；在动物层面，利用高脂饮食和MD2-/-小鼠验证MD2在ORG中的作用。本项目将阐明FFA诱导肾炎症和肾纤维化的分子机制，为ORG的防治提供新的靶点。

肥胖是肾脏疾病的一个主要和独立的危险因素，同时也是一种慢性炎性疾病。肥胖相关肾损伤的致病机制已被认识至少涉及肾脏组织的高游离脂肪酸和促炎状态，但建立因果关系的具体机制仍然存在未知的。饱和脂肪酸在肥胖人群中升高，已知会引起肾脏的慢性炎症。髓样分化蛋白2是脂多糖诱导的先天性免疫应答和炎症反应中的重要蛋白。我们认为肥胖是相关的肾损伤受MD2调控，从而驱动炎症性肾损伤或过度自噬引起的肾损伤。本项目的实施阐明了MD2介导肥胖性肾病的药理机制，确证了MD2可以作为缓解肥胖性肾病的新靶点，L6H21也可能是缓解肥胖性肾病的候选药物。 . 同时我们还发现炎症反应和肾脏肾素-血管紧张素II-醛固酮（RAS）激活都是DN的重要病理通路和发病过程，但其中还有许多尚未清楚的调控机制。天然免疫中的重要介导蛋白髓样分化蛋白2（MD2）在糖尿病肾病小鼠的肾脏中显著高表达；高血糖激活的MD2不仅仅促进肾脏炎症反应的发生，更重要的是，MD2激活下游的MAPKs，而后者上调RAS系统的中ACE\AT1的表达，从而促使肾脏原位AngII的增加和肾脏RAS系统激活，导致肾脏纤维化和系列肾损伤。MD2基因敲除和特异性抑制剂可以通过抑制上述机制显著改善糖尿病肾病的发生发展，也预示着MD2可能是糖尿病肾病防治的有效靶点。