SAH在ApoE-/-小鼠动脉粥样硬化形成中的作用机制及甜菜碱干预研究

Atherosclerosis (AS) is an important disease harmful to human health, and the mechanism of pathogenesis is unclear. Recently several studies have shown that S-adenosylhomocysteine (SAH) the metabolic precursor of homocysteine may play an important role in the development of AS. In our previous study we found that increased plasma SAH levels could independently predict the risk of cardiovascular disease and aggravated AS formation in ApoE-deficient mice by promoting the proliferation and migration of vascular smooth muscle cells through inducing oxidative stress. However, the mechanism of SAH-induced AS and the causal relationship between SAH and AS remain unclear. Based on our previous study the present project will establish the high SAH model by employing SAH hydrolase inhibitor and shRNA interference in ApoE-deficient mice and vascular endothelial cells, and explore the effect of increased SAH level on early and advanced AS plaque area and vascular endothelial dysfunction in ApoE-deficient mice. We will further explore the possible mechanism of SAH-aggravated AS from the perspective of apoptosis and inflammation of vascular endothelial cells. And then in order to demonstrate the causal relationship between SAH and AS, we will further conduct an intervention study with use of betaine to lower plasma SAH level, and observe whether lowering SAH level could reduce the severity of AS and restore the damage of endothelial function. This study will provide experimental basis for further clarifying the relationship between SAH and AS, and provide a new theoretical foundation for the effective prevention and treatment of cardiovascular disease.

动脉粥样硬化（AS）是危害人类健康的重要疾病，其发病机制尚不明确。近年来研究显示同型半胱氨酸的代谢前体S-腺苷同型半胱氨酸（SAH）在AS发展过程中可能发挥着重要作用。我们前面研究发现血浆SAH水平能独立预测心血管疾病的发病风险，并且通过诱导氧化应激促进平滑肌细胞增殖和迁移加重AS的严重性。但SAH致AS的作用机制以及与AS的因果关系仍不清楚。现在的课题在前面研究的基础上拟采用SAH水解酶抑制剂和shRNA干扰在ApoE基因敲除小鼠和血管内皮细胞中建立高SAH模型，观察血浆SAH升高对ApoE基因敲除小鼠AS不同阶段斑块大小和血管内皮功能损伤的影响，并且从内皮细胞凋亡和炎症反应的角度探讨SAH致AS形成的可能机制，进一步采用甜菜碱干预降低SAH水平，观察能否减轻AS的严重性和恢复内皮功能的损伤。本研究为进一步阐明SAH与AS之间的关系提供实验依据，并为心血管疾病有效防治提供新的理论基础。

动脉粥样硬化（AS）是心血管疾病的病理基础，其发病机制非常复杂。S-腺苷同型半胱氨酸（SAH）是心血管疾病的一个新的危险因素，但是其在AS中的作用及致病机制仍不清楚。本研究通过采用SAH水解酶抑制剂ADA和shRNA干扰建立高SAH动物和细胞模型，在此模型上观察到血浆SAH水平的升高加重AS的中期进展，在高SAH模型基础上添加不同剂量的甜菜碱进行干预实验，结果表明中、高剂量的甜菜碱能有效地降低血浆SAH水平，并且有效地降低SAH增加的AS斑块面积。机制研究发现SAH水平升高加剧AS中期进展与诱导GRP78和CHOP的表达有关，进一步研究表明SAH水平升高与3meH3K9和组蛋白甲基转移酶表达降低有关，且3meH3K9与GRP78和CHOP基因启动子的结合在高SAH小鼠体内也降低。另外从炎性反应的角度探讨SAH诱导AS形成的机制，结果表明SAH水平升高增加内皮细胞凋亡和促进单核-内皮细胞粘附，增加内皮细胞VCAM-1和ICAM-1的蛋白表达，进一步研究发现SAH增加p65、Caspase-8、Caspase-3的蛋白表达，采用NF-κB、Caspase-8、Caspase-3酶的抑制剂抑制SAH诱导炎性反应。总之，本课题揭示了SAH水平升高加剧AS中期进展与诱导ER stress和炎性反应相关，甜菜碱干预对SAH诱导的AS严重性起到保护作用，该项目为阐明SAH和AS之间的关系提供了实验依据，为AS的防治提供了理论基础。