脂质代谢紊乱中mtDNA-STING-NLRP3-Caspase-1 轴调节平滑肌细胞收缩的机制研究

Atherosclerotic cardiovascular disease is the leading cause of mortality worldwide. Atherosclerosis (AS) is a important feature of ischemic heart disease and smooth muscle cell (SMC) phenotype switch that leads to SMC contractile dysfunction is critical to this process. We previously observed significant SMC phenotype switch characterized by reduced expression of contractile proteins (SM22α, α-actin, MHC11 et al.) in palmitic acids treated SMCs, which can be blocked by STING inhibition. STING deficiency also significantly improved SMC contractile protein levels and phenotype switch in the aorta of the mice that challenged with high-fat diet and angiotensin II infusion. Earlier study in our lab showed that after activated by NLRP3 inflammasome, Caspase-1 directly cleaved and degraded contractile proteins, leading to SMCs contractile dysfunction. Interestingly, recent study showed that detection of cytosolic DNA by the cGAS-STING axis induces lysosomal release upstream of NLRP3, which indicated us that there might be a linkage between STING pathway and NLRP3-Caspase 1 inflammasome in palmitic acids treated SMCs. Thus, the aim of this project is to test the hypothesis that lipid metabolism disorder lead to SMC contractile dysfunction through mtDNA-cGAS-STING-NLRP3-Caspase 1 inflammasome axis and to explore whether we can improve atherosclerosis by inhibiting this axis.

动脉粥样硬化是一系列缺血性心脑病的重要病理基础，血管平滑肌细胞表型改变（尤其是收缩蛋白水平下降）是其进展中的重要环节。然而调节平滑肌细胞收缩蛋白水平的具体机制仍未明确。我们前期证明脂质代谢紊乱损伤线粒体，释放mtDNA并激活STING信号通路。下调平滑肌细胞内的STING蛋白水平，可以明显改善棕榈酸引起的收缩蛋白下调。同时，STING缺陷能够减少血管紧张素II+高脂饮食诱导的小鼠主动脉收缩蛋白水平下降。研究表明，平滑肌细胞内NLRP3炎症小体能够直接与平滑肌细胞收缩蛋白结合并促进其降解。有趣的是，最近研究表明STING信号通路识别胞浆DNA后，能够通过lysosomal激活NLRP3炎症小体。本课题主要研究目的就是证明脂质代谢紊乱可以通过mtDNA-STING-NLRP3炎症小体轴调节血管平滑肌细胞收缩蛋白水平；探索动物体内应用STING-NLRP3抑制剂延缓动脉粥样硬化进展的可行性。

心脑血管疾病是目前在世界上致死致畸的首要原因，动脉粥样硬化是冠心病、脑血管病和血栓栓塞性疾病等缺血性心血管疾病的主要病理基础，动脉粥样硬化及其并发症已经被公认为世界范围内致死致畸的重要因素。本课题通过游离脂肪酸刺激平滑肌细胞，证明脂质代谢紊乱可以引起细胞线粒体损伤，线粒体 DNA 释放入胞浆及细胞外，进而激活 cGAS-STING 信号通路，并促进细胞间信号转导；在此过程中STING 可直接调节 NLRP3 炎症小体形成，影响动脉粥样硬化进展。.同时通过生物信息学分析，发现严重动脉粥样硬化患者中内质网应激和线粒体损伤相关基因均处于上调状态，预示着晚期患者中内质网应激和线粒体损伤功能更加活跃。N6-甲基腺嘌呤（m6A）修饰是真核生物中最常见且最丰富的RNA修饰，已有研究显示m6A修饰在动脉粥样硬化发展中的作用，可用来寻找预防和治疗动脉粥样硬化的潜在靶点。我们查看了m6A调控因子在动脉粥样硬化早期和晚期的表达情况，结果发现，m6A相关的FTO (erasers)、METTL14 (writers)、YTHDF3 (readers)、ZC3H13 (writers)在早期表达显著高于晚期; IGF2BP2 (readers)、IGF2BP3 (readers)则是晚期表达显著高于早期。