Sirt6调控血管平滑肌细胞表型转化在腹主动脉瘤中的作用及机制研究

The phenotypic switching of vascular smooth muscle cell (VSMC) plays an important role in the development of abdominal aortic aneurysm (AAA). Activation of KLF4 is a key mechanism for the phenotypic switching of VSMC in AAA. The histone deacetylase Sirt6 has been shown to be powerfully cardioprotective, but its role in AAA remains unclear. We have found that the expression of Sirt6 in AAA tissues and Ang II-stimulated VSMC was significantly reduced. Knockdown of Sirt6 enhanced the promoter activity and expression of KLF4, accompanied by obvious VSMC phenotypic switching. Thus, we hypothesized that Sirt6 deficiency might aggravate the development of Ang II-induced abdominal aortic aneurysm through activating KLF4 gene transcription by increasing the acetylation level of histone H3K9 and promoting the phenotypic transformation of VSMC. The present study is designed to explore the role of Sirt6 in AAA by means of several biological techniques in vitro and in vivo. Our results will reveal an essential role of Sirt6 in AAA and provide a potential therapeutic target for the treatment of AAA.

血管平滑肌细胞（VSMC）表型转化是腹主动脉瘤（AAA）发生发展的关键环节，KLF4的激活是引起AAA中VSMC表型转化的重要机制。组蛋白去乙酰化酶Sirt6具有广泛的心血管保护作用，但其在AAA中的作用尚无报道。申请者前期研究发现，AAA组织及血管紧张素II刺激的VSMC中Sirt6的表达均显著减少。Sirt6的敲减能够上调KLF4启动子的活性，促进KLF4的表达，促进VSMC表型转化。据此，提出如下科学假说“Sirt6的缺失可通过增加组蛋白H3K9位点的乙酰化水平，靶向激活KLF4基因转录，促进血管平滑肌细胞表型转化，加剧AngII诱导的腹主动脉瘤的发生发展”。本课题拟运用多种实验方法，体内外研究相结合，研究Sirt6在AAA中的作用及分子机制。本研究将为临床防治AAA提供新靶点，也为从表观遗传学方面防治AAA提供新思路。

血管平滑肌细胞（VSMC）表型转化是腹主动脉瘤（AAA）发生发展的关键环节，KLF4的激活是引起AAA中VSMC表型转化的重要机制。组蛋白去乙酰化酶Sirt6具有广泛的心血管保护作用，但其在AAA中的作用尚无报道。项目组主要研究了Sirt6通过抑制KLF4的表达继而调控血管平滑肌细胞表型转化，从而抑制AngII诱导的腹主动脉瘤的发生发展。项目组构建平滑肌特异性Sirt6敲除小鼠并建立腹主动脉瘤模型，利用染色质免疫共沉淀实验、质粒共转染、双荧光素酶报告基因检测技术，发现1）Sirt6在AAA瘤体组织中的表达显著降低，Ang II刺激下平滑肌细胞中Sirt6的表达显著减少；2）敲减Sirt6能够上调KLF4的表达、促进血管平滑肌细胞表型转化；3）敲减Sirt6能够上调血管平滑肌细胞中组蛋白H3K9乙酰化水平、增加KLF4的启动子活性；4）平滑肌特异性Sirt6敲除能够加剧腹主动脉瘤的发生发展。我们的研究表明Sirt6/KLF4轴驱动的血管平滑肌细胞表型转化是腹主动脉瘤进展的重要因素，为腹主动脉瘤提供了新的治疗靶点。