FAM172A调控血管平滑肌细胞表型转化在糖尿病动脉粥样硬化中的作用及机制

High glucose-inducing phenotype switching of vascular smooth muscle cells (VSMCs) participates in the pathogenesis of atherosclerosis. However，its mechanism has not been completely elucidated. FAM172A is a novel protein confirmed by our group for the first time in the world, which can regulate histone methylation. Our studies found that high glucose increased the H3K9 methylation levels in promoter region of VSMCs-specific contractile genes SMA-α and SM22α, and stimulated VSMCs switching to "synthetic" phenotype. However, chaetocin, a specific inhibitor of H3K9 methylation, inhibited VSMCs switching to "synthetic" phenotype. Intraperitoneal injection of chaetocin in Apoe-knockout mice inhibited VSMCs switching to "synthetic" phenotype and alleviated the aortic atherosclerotic lesions in mice. High glucose upregulated the expression of FAM172A in VSMCs. Overexpression of FAM172A downregulated the expression of Myocardin and SRF (transcription factors related to VSMCs phenotype switching) and significantly promoted VSMCs switching to "synthetic" phenotype. We have successfully obtained Fam172a-knockout mice model. We will verify and explore a novel pathway and mechanism of diabetes atherosclerosis- “High glucose → FAM172A → H3K9 methylation, Myocardin and SRF →Vascular smooth muscle cells phenotype switching→ Diabetic atherosclerosis”.

高糖诱导血管平滑肌细胞(VSMCs)表型转化参与动脉粥样硬化（AS）发病的机制目前尚未彻底阐明。FAM172A是我们在国际上首次证实的可调控组蛋白甲基化的新蛋白。研究发现：高糖上调VSMCs特异性收缩蛋白SMA-α、SM22α启动子区H3K9甲基化而刺激VSMCs向合成表型转化；而H3K9甲基化特异性阻断剂Chaetocin抑制VSMCs向合成表型转化，Apoe-/-基因敲除小鼠腹腔注射Chaetocin抑制VSMCs向合成表型转化而减轻小鼠AS病变；高糖上调VSMCs中FAM172A表达，过表达FAM172A可下调VSMCs表型转化调控因子Myocardin、SRF的表达并促进VSMCs向合成表型转化；目前已成功获得Fam172a-/-基因敲除小鼠，我们将验证并探索“高糖→FAM172A→H3K9甲基化、Myocardin、SRF→VSMCs表型转化→糖尿病AS”这一新致病途径及机制。

背景:血管平滑肌细胞（VSMCs）在动脉粥样硬化的发病中起着关键作用。FAM172A是一个新蛋白，其在动脉粥样硬化中的作用迄今尚未被探索。我们的目的是研究FAM172A是否通过VSMCs影响动脉粥样硬化以及可能的机制。课题组使用CRISPR/Cas9技术产生Fam172a-/-小鼠。Fam172a-/-和Apoe-/-双基因敲除（Fam172a-/-/Apoe-/-）小鼠和它们的同窝对照（Fam172a+/+/Apoe-/-）用西方饮食喂养18周，诱发晚期动脉硬化病变。通过体内和体外实验，深入研究了Fam172a在VSMCs表型转换、增殖和迁移中的作用和机制。研究发现：与Fam172a+/+/Apoe/-小鼠相比，Fam172a-/-/Apoe/-小鼠动脉粥样硬化病变更加严重，和斑块稳定性减弱，如坏死核心面积增加和纤维沉积减少等。此外，Fam172a的敲除促进了CD68和KLF4的表达，减少了α-SMA和SM22α在动脉粥样硬化病变中的表达。另外，Fam172a过表达促进了Movas细胞的增殖和迁移，增加了α-SMA和SM22α的表达，减少了KLF4的表达，而在Movas细胞中敲除Fam172a和Fam172a-/Apoe-/-小鼠的VSMCs中表现出相反的表型。在人类主动脉平滑肌细胞中也观察到类似的表型。结论：我们的结果证明Fam172a通过增加动脉粥样硬化斑块的稳定性和抑制VSMCs从收缩型到合成型的转变，在晚期动脉粥样硬化中具有保护作用，这可能是通过KLF4依赖性的途径发挥作用的。