SRF/MRTF-A通路介导内源性二氧化硫对血管新生内膜形成中血管平滑肌细胞表型转化的调节作用及机制

Vascular smooth muscle cell (VSMC) phenotypic switching is a crucial process of vascular neointima formation. However, its mechanisms need to be clarified. The previous studies by the applicants showed that the endogenous sulfur dioxide (SO2) was an important signaling molecule in vascular regulation. Based on the previous findings, the applicants attempt to probe into the regulatory effect of SO2 on VSMC phenotypic switching in vascular neointima formation induced by carotid artery wire injury and the mechanisms in mice, targeting on the serum response factor (SRF)/myocardin-related transcription factor-A (MRTF-A). First, the endogenous SO2 pathway changes in vascular neointima formation are planned to be measured; the effect of SO2 on the SRF/MRTF-A activity and VSMC phenotypic switching is to be studied in mice with SO2 generating enzyme AAT-1 gene transfer or knockout, and VSMCs; the SRF/MRTF-A-mediated regulatory effect of SO2 on VSMC phenotypic switching is to be tested by over-expressing or knocking down MRTF-A or inhibiting its activity; and lastly, the oxidative modification of MRTF-A protein, its target site and the significance in the regulation of VSMC phenotypic switching by SO2 are to be elucidated. The above studies would help in clarifying a novel mechanism by which SO2 regulates vascular neointima formation and provide with new idea for intervening vascular injury diseases.

血管平滑肌细胞(VSMC)表型转化作为血管新生内膜形成的关键环节，其发生机制亟待阐明。本项目组前期发现内源性二氧化硫(SO2)是血管调节的重要信号分子。在此基础上，拟以血清反应因子/心肌素相关转录因子-A(SRF/MRTF-A)为靶点，探索SO2对小鼠颈动脉导丝损伤诱导血管新生内膜形成中VSMC表型转化的调控与机制。首先研究血管新生内膜形成中内源性SO2体系的变化；进一步在SO2生成酶AAT1转基因及敲除小鼠和VSMC中揭示内源性SO2对SRF/MRTF-A活性及VSMC表型转化的作用；通过过表达或敲低MRTF-A表达或抑制其活性，揭示SRF/MRTF-A介导SO2对VSMC表型转化的调控；通过对MRTF-A定点突变，发现SO2对MRTF-A蛋白的氧化修饰、作用位点及其在SO2调控VSMC表型转化中的意义。以期阐明内源性SO2调控血管新生内膜形成的新机制，为血管损伤性疾病的干预提供新思路。

表型转换是血管平滑肌细胞针对各种内外刺激因素的重要应答反应，也是血管损伤与修复的核心病理生理环节，因此揭示血管平滑肌细胞表型转换的分子机制对于深化血管损伤的发生机制及探索血管修复临床干预的新靶点具有重要意义。本课题组前期研究发现内源性二氧化硫是机体拮抗高血压、肺动脉高压等血管损伤性疾病的重要内源性防御体系。在本项目中拟以SRF/myocardin/Elk1通路为切入点，揭示内源性二氧化硫对血管平滑肌细胞表型转换的调控作用及分子机制。研究发现，新生内膜形成中内源性二氧化硫/AAT1体系显著下调，血管平滑肌细胞表型向合成表型转换；血管平滑肌细胞过表达AAT1可抑制血管平滑肌细胞收缩表型向合成表型转换，抑制小鼠颈动脉新生内膜形成；内源性二氧化硫通过促进SRF与共转录因子myocardin结合，抑制SRF与共转录因子Elk1结合，从而维持VSMC收缩表型；二氧化硫通过次磺化修饰SRF决定SRF与共转录因子myocardin/Elk1结合的偏向性选择，次磺化修饰的SRF与myocardin结合增强，促进收缩表型标志分子的表达。综上，本项目研究提示，内源性二氧化硫是维持血管平滑肌细胞生理表型的重要调控分子。研究成果有望为探索血管损伤与修复的临床干预策略提供新思路及靶点。围绕上述研究，共发表SCI论文8篇，在国内外学术会议特邀讲座、大会发言及会议交流6次，培养博士研究生4人。