转录辅激活子MED1在动脉粥样硬化发生中的作用及机制研究

Atherosclerosis is a leading cause of death worldwide, and severely endangers human health. As we know, atherogenesis is a complicated pathological process which is considered to be affected by multiple factors. However, the molecular mechanism of atherosclerotic pathogenesis remains unclear. The purpose of this study is to investigate the contribution of transcription coactivator Mediator 1 (MED1) on atherosclerosis. We propose a hypothesis that macrophage MED1 has an antiatherogenic role in atherosclerotic lesion development. We will focus on lipid accumulation and inflammatory responses which are contributed to the development of atherosclerosis. Since disruption of MED1 gene causes embryonic lethality due to placental dysfunction, we will generate macrophage MED1 conditional knockout (MacMED1KO) mouse. The generated LDLR and macrophage MED1 double knockout (LDLR-/-/MacMED1KO) mice will be used as animal model. The effects of MED1 on foam cell formation, the development of atherosclerotic plaque, macrophage cholesterol efflux, PPARs and inflammatory signaling pathways will be studied in vivo and invitro using pathological histology, peritoneal macrophage culture and gene expression analysis, etc. This study will provide a theoretic and experimental basis for understanding molecular mechanism of atherosclerosis, and developing MED1 as a potential therapeutic target for atherosclerosis.

动脉粥样硬化引起的心脑血管病已成为全球第一位死亡原因，严重危害人类健康。研究表明，动脉粥样硬化的发病是一个多因素共同作用的复杂病理过程，其机制至今不清楚。本课题以转录辅激活子Mediator 1（MED1）为研究对象，假设巨噬细胞MED1具有抗动脉粥样硬化作用，从动脉粥样硬化发病的脂质沉积和炎症反应学说入手，通过制作巨噬细胞MED1特异性敲除（MacMED1KO）小鼠和LDLR/MED1双敲除（LDLR-/-/MacMED1KO）小鼠模型，利用病理组织学、巨噬细胞培养及基因表达分析等技术，从体内和体外两个层面，重点研究巨噬细胞MED1缺失对泡沫细胞和动脉粥样斑块形成、胆固醇流出、PPARs及炎症通路的影响，阐明MED1调控动脉粥样硬化发生发展的作用及分子机制。本研究将为深入探讨动脉粥样硬化发病机理，进一步开发MED1作为治疗动脉粥样硬化的潜在新靶点提供理论依据和实验基础。

动脉粥样硬化引起的心脑血管病已成为全球第一位死亡原因，严重危害人类健康。研究发现，转录辅激活子Mediator 1（MED1）在PPARs调控的脂质代谢中发挥重要作用。然而，MED1如何调控动脉粥样硬化的发病过程及其机制至今不清楚。本项目中，通过构建巨噬细胞MED1特异性敲除（MED1ΔMac）小鼠和ApoE/MED1双敲除（ApoE-/-/ MED1ΔMac）小鼠模型，利用病理组织学、骨髓移植、巨噬细胞培养及基因表达分析等技术，研究了巨噬细胞MED1缺失对泡沫细胞和粥样斑块形成、胆固醇流出、PPARs及炎症通路基因表达的影响。研究结果表明，西方饮食饲喂MED1fl/fl/ApoE-/-和MED1ΔMac/ApoE-/-小鼠12周，无论在正常饮食或西方饮食下，与对照组小鼠相比，MED1ΔMac/ApoE-/-小鼠整个主动脉树和主动脉根部的斑块病变面积显著增加。将MED1ΔMac小鼠骨髓移植到LDLR-/-小鼠，用西方饮食诱导动脉粥样硬化病变， 与MED1fl/fl→LDLR-/-对照小鼠相比，MED1ΔMac→LDLR-/-雄性或雌性小鼠主动脉树和主动脉根部的斑块都有增加。从MED1ΔMac/ApoE-/-和对照小鼠腹腔提取巨噬细胞，Real time RT-PCR结果表明，与对照组相比，MED1ΔMac/ApoE-/-小鼠巨噬细胞M1标志基因IL-1β、IL6、COX2、iNOS、Gro1、MCP1和TNFα等mRNA表达显著上升，而M2标志基因Arg1、Mrc1、Retnla、Chi3l3、PPARγ和 IL10表达明显下降。MED1fl/fl/ApoE-/-小鼠巨噬细胞高表达MED1能够显著地抑制M1型炎症基因的表达，MED1ΔMac/ApoE-/-小鼠巨噬细胞恢复MED1表达后，M1炎症基因表达下降。基因表达谱和PCR芯片结果进一步证实，MED1ΔMac小鼠巨噬细胞中M1型基因表达显著升高，M2型基因表达降低，提示MED1可能是通过炎症通路来发挥抗动脉粥样硬化的作用。本研究为深入探讨动脉粥样硬化发病机理，进一步开发MED1作为治疗动脉粥样硬化的潜在新靶点提供了理论依据和实验基础。