SIRT6调控血管平滑肌细胞RUNX2及其下游BMP-2-BMP受体信号通路抑制肾衰血管钙化的机制研究

核去乙酰化酶Sirt6与能量代谢和细胞表型转化有关。肾衰血管钙化的核心机制是VSMCs摄取磷、凋亡和成骨表型转化。我们已发现SIRT6保护缺血心脏，但尚不清楚其对血管钙化的作用。预实验显示SIRT6敲低加重肾衰高磷诱导的血管钙化，为明确SIRT6的具体作用和机制，我们构建Sirt6+/-ApoE-/-小鼠和血管VSMCs特异敲除Sirt6的小鼠，以肾脏5/6切除加高磷饮食诱导血管钙化，高磷诱导Sirt6敲低和RESCUE/过表达的VSMCs钙化，探究Sirt6拮抗肾衰血管钙化的保护作用；利用IP/coIP、EMSA及ChIP等实验研究Sirt6与RUNX2的相互作用，阐明RUNX2招募Sirt6至其下游关键性的促异位钙化因子BMP-2及其受体基因的启动子区，减低H3K9的乙酰化状态，抑制这些基因的转录和受体后的促钙化信号转导，缓解VSMCs的钙化病变，拮抗肾衰血管钙化的创新性负性调控机制。

Sirt6, a nuclear deacetylase, plays an important role in regulation of metabolism and cellular phenotypic transformation. The main pathological changes of vascular calcification in renal failure are phosphate uptake, apoptosis, and osteogenic phenotypic transformation of vascular smooth muscle cells (VSMCs). We have cognized the protection of SIRT6 agaisnt ischemic hearts, but it is little known about the role of SIRT6 in vascular calcification. The results of our tentative experiments indicated that SIRT6 knockdown aggravated vascular calcification induced by renal failure and high phosphorus diet. To investigate the specific ptotective function and the underlying mechanisms of SIRT6 in the regulation of vascular calcification indued by renal failure, we generated SIRT6 +/- ApoE-/- mice as well as SMC-specific SIRT6 conditional knockout mice, and further induced vascular calcification in them by using 5/6 kidney excision together with a high phosphorus diet. We also induced calcification in VSMCs with SIRT6 gene knockdown or RESCUE/overexpression by high phosphate exposure. We further explore the interaction between Sirt6 and RUNX2 in VSMCsby using IP/coIP, EMSA and ChIP methods, to reveal how RUNX2 recruits Sirt6 to the promoter regions of its downstream proteins, including BMP-2, a key ectopic calcification inducer, as well as the receptors of BMP-2, BMPR1A, BMPR1B and BMPRII, and then reducing H3K9 acetylation levels to suppress the transcription and expression of BMP-2 and its receptors. And then the pro-calcification signal transductions mediated by BMPRs are weakened, and the calcification in VSMCs is alleviated. Our study will reveal a new negative regulation mechanism mediated by SIRT6 against vascular calcification in renal failure.