内源性硫化氢(H2S)是心血管调节的气体信号分子，本课题组前期研究发现H2S可抑制动脉粥样硬化，其作用可能与其调节肝细胞胆固醇代谢有关。为阐明H2S对高胆固醇血症的调节作用及机制，本项目将以前蛋白转化酶枯草溶菌素9(PCSK9)为靶点，研究内源性H2S对PCSK9/低密度脂蛋白受体(LDLR)通路的调控在大鼠高胆固醇血症发病中的意义。首先，在整体水平研究高脂饮食大鼠肝脏H2S及PCSK9/LDLR通路的变化；进一步通过过表达或敲低肝脏H2S生成酶CSE及CBS，揭示内源性H2S对高胆固醇血症及PCSK9/LDLR通路的调节作用；通过过表达或敲低PCSK9，阐明PCSK9是H2S调节肝细胞LDL代谢的分子靶点；采用质谱分析结合硫氢化修饰探针及定点突变，揭示H2S对PCSK9的硫氢化修饰是其抑制高胆固醇血症的分子机制。以期发现H2S调节高胆固醇血症的新机制，为动脉粥样硬化的临床防治提供新思路。

Endogenous hydrogen sulfide (H2S) is a cardiovascular regulatory gasotransmitter. Our previous studies showed that H2S inhibited the development of atherosclerosis possibly through controlling the cholesterol metabolism in hepatocyte. To investigate the effect of H2S on the hypercholesterolemia and its mechanisms, the present project will target on proprotein convertase subtilisin/kexin type 9 (PCSK9) and examine the significance of regulatory effect of H2S on the PCSK9/low density lipoprotein receptor (LDLR) pathway in the pathogenesis of hypercholesterolemia in rat. Firstly, the applicants shall detect the change of hepatic H2S pathway and PCSK9/LDLR pathway in high-fat diet rats. Secondly, the applicants shall explore the effect of endogenous H2S on hypercholesterolemia and hepatic PCSK9/LDLR pathway by upregulating or downregulating the expression of endogenous H2S generating enzymes cystathionine γ lyase (CSE) or cysthathionine β synthase (CBS) in rat liver. Thirdly, the researchers plan to investigate if PCSK9 is a target, on which H2S regulates hepatic LDL metabolism via overexpression or knockdown of PCSK9. Mechanistically, the applicants plan to use the mass spectrometry, the specific probe for protein sulfhydration and site-directed mutation to clarify if the sulfhydration modification of PCSK9 by H2S might be the molecular mechanism by which H2S inhibits hypercholesterolemia. Based on the abovementioned studies, it is expected to discover a novel regulatory mechanism by which H2S inhibits hypercholesterolemia and provide new idea for exploring the prevention and treatment strategy for atherosclerosis.