探讨小窝蛋白1信号通路介导中期因子促进ARDS相关肺损伤与纤维化的机制与治疗手段

Our previous study found that mechanical stretch can induce an epithelial-mesenchymal transition mediated by the Midkine (MK)-Notch2-ACE signaling pathway, contributing to ARDS associated lung fibrosis. However, the underlying mechanism of upregulation of ACE by Notch2 remains unknown. Since Caveolin 1 is the key regulator of ACE expression, in the current study, we propose that "Caveolin1 can directly bind to Nothc2 on the cell membrane and is a key molecule in the regulation of ACE expression”. Previous studies have proved that the major source of MK is from immune cells; thus the endothelium are the first line cells to be effected by MK. In this grant we will firstly prove the direct binding of CAV1 and Notch2 and its regulation of ACE expression; Secondly, Recombinant MK induce the endothelial/epithelial- mesenchymal transition via Nothc2-Caveoin 1 signaling pathway; Thirdly, we will evaluate the therapeutic effects of MK inhibitor on a rat ARDS-associated lung fibrosis model. The current study will clarify the roles and mechanism of Caveolin1 in promoting mechanical ventilation associated lung injury and fibrosis in ARDS and provide potential therapeutic targets for ARDS treatment.

本课题组已证实机械通气上调中期因子（MK）表达，通过Notch2-ACE信号介导肺上皮细胞-间质转化造成ARDS机械通气相关肺纤维化。但由于两分子不直接结合，故Notch2如何调节ACE有待研究。由于小窝蛋白1（CAV1）可调节ACE表达，我们假设：MK刺激CAV1与Notch2胞膜结合而上调ACE。由于MK由免疫细胞分泌释放，故血管内皮是其作用的一线细胞。本项目将研究：1. CAV1与Notch2在血管内皮细胞是否直接结合并调控MK诱导ACE的表达；2. 重组MK是否通过Notch2-CAV1信号通路促进内皮-间质转化；3. MK抑制剂是否对大鼠ARDS机械通气相关肺纤维化有抑制作用。本研究将阐明CAV1在MK促进ARDS机械通气相关肺纤维化的关键作用。

本课题组前期研究已在急性呼吸窘迫综合征（ARDS）患者和动物模型中证实机械通气可上调中期因子（MK）表达，通过Notch2-ACE信号通路介导肺上皮细胞-间质转化造成ARDS机械通气相关肺纤维化。但由于Notch2和ACE不直接结合，因此Notch2上调ACE的分子机制有待研究，因此本项目主要研究内容为MK促进ARDS机械通气相关肺纤维化关键作用和机制。按照研究计划，我们证实1、CAV1可以与Notch2直接结合；但不与肺上皮细胞中的其他Notch同源物Notch1，Notch3和Notch4结合；2、CAV1是MK上调ACE表达、促进人肺上皮细胞转化发生EMT和内皮细胞发生EndoMT的关键分子；3、MK抑制剂（iMDK）可减轻盐酸-机械通气双重打击ARDS大鼠的肺纤维；4、间充质基质细胞（MSC）可减轻机械通气诱导的小鼠肺损伤和肺纤维化，而加重盐酸气管吸入、盐酸气管吸入加机械通气诱导的肺损伤和肺纤维化。本项目共发表SCI收录文章4篇，其中MSC的研究成果发表于American Journal of Respiratory and Critical Care Medicine杂志；发表中文核心期刊文章5篇。通过本项目的研究，我们阐明了CAV1在MK促进ARDS机械通气相关肺纤维化的关键作用和分子机制，并探索了MK抑制剂和MSC在ARDS机械通气相关肺纤维化的治疗作用，为ARDS相关肺纤维化治疗提供了全新的靶点和方法。