乙醛脱氢酶2在动脉粥样硬化中对脂代谢的时空网络调控

ACKGROUND: Atherosclerosis is the major cause for cardiovascular diseases (CVD) and temproal and spatial regulation of lipid metabolism play a central role in atherosclerosis. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is a critical enzyme for detoxification of acetaldehyde from alcohol consumption and endogenous lipid aldehydes derived from lipid peroxidation. Around 50% of East Asian carrying a single nucleotide polymorphism (SNP) rs671 in ALDH2 have significantly increased incidence of CVD but the underlying molecular mechanisms are not well defined. Macrophage lipid metabolism is critical for the degradation of oxidized low-density lipoprotein (ox-LDL) and dysregulation of macrophage lipid metabolism may lead to foam cell formation, an early hallmark of atherosclerosis. Surprisingly, the role of ALDH2 in macrophage lipid metabolism and foam cell formation in atherosclerosis remains unexplored. .SPECIFIC AIMS：In this application, we propose to investigate the regulatory mechanisms of ALDH2 in lipid metabolism in hepatocytes and macrophage foam cell formation in the context of atherosclerosis..EXPERIMENTAL DESIGN: We propose to use various animal models, cell experiments, multiple omics techniques including transcriptomics, metabolomics, lipidomics, and proteomics, to investigate the roles of ALDH2 in regulating macrophage lipid metabolism and foam cell formation. In our preliminary studies, we used LDLR knockout (LDLR-/-), ALDH2 knockout (ALDH2-/-), ALDH2 and LDLR double knockout (ALDH2-/-LDLR-/-) fed with Western Diet and primary mouse macrophages to study the roles of ALDH2 in atherosclerosis. ALDH2-/-LDLR-/- mice had significantly decreased areas of atherosclerotic plaques comparing to LDLR-/- mice, suggesting an unexpected deleterious role of ALDH2 in atherosclerosis. Further studies demonstrated that macrophages from LDLR KO mice had decreased uptake of ox-LDL with activated AMPK, which phosphorylated ALDH2 and led to its nuclear translocation. Once in the nucleus, ALDH2 bound to HDAC3 and repressed the transcription of a lysosomal proton pump protein ATP6V0E2. On the other hand, LDLR blocked the nuclear translocation of mitochondrial ALDH2 and maintained a functional lysosome in macrophages. Furthermore, human ALDH2 SNP rs671 attenuated the inhibitory effects of LDLR and released ALDH2 to nucleus and the down-regulated ATP6V0E2 expression. .IMPLICATIONS AND IMPACT: Our preliminary experiments strongly suggest that LDLR prevents macrophage foam cell formation by blocking nuclear translocation of ALDH2 to regulate genes critical for lysosome function and LDL degradation. We propose to study this novel regulatory mechanism of LDLR in the pathogenesis of atherosclerosis through modulating macrophage foam cell formation by interaction with ALDH2 and AMPK. Successful completion of this application will provide novel insights into the spatial and temperal networks of lipid metabolism by which dysregulation of lipid metabolism contributes to foam cell formation in CVD.

巨噬细胞和肝细胞脂代谢时空网络调控对与动脉粥样硬化相关的心血管病极其重要。乙醛脱氢酶-2(ALDH2)的主要功能是代谢乙醛和脂质过氧化产生的活性醛类, 40%左右的东亚人携带 ALDH2SNPrs671,其心血管疾病的风险显著增加,但机制尚不清楚。我们长期研究脂质氧化与心血管疾病，前期结果显示AMPK磷酸化ALDH2促其从线粒体转移至细胞核, 抑制调控溶酶体功能的关键蛋白ATP6V0e2的表达和对吞噬的脂质在溶酶体降解而形成泡沫细胞；低密度脂蛋白受体LDLR抑制ALDH2的这种负面作用，但该抑制在ALDH2SNPrs671中显著减弱。本项目我们拟利用多种基因敲除小鼠和细胞模型，结合代谢组学和脂质组学等研究ALDH2与LDLR相互作用对肝细胞、巨噬细胞脂代谢时空网络的调控，该研究结果对动脉粥样硬化的发病机制将有全新的理解，并可能为心血管疾病的预防和治疗提供新思路。

胆固醇代谢失衡是动脉粥样硬化和心血管疾病的重要原因。乙醛脱氢酶 2（ALDH2）代谢饮酒产生的乙醛和脂质过氧化产生的活性醛类。大约8%世界人口和40%东亚人携带喝酒脸红基因ALDH2突变rs671,心血管疾病风险显著增加,但机制不明。本项目利用多种基因工程小鼠和细胞模型，结合代谢组学和脂质组学等发现了系列ALDH2在巨噬细胞和肝细胞中胆固醇代谢时空网络调控全新机制：.（1）ALDH2与LDLR和AMPK相互作用调控泡沫细胞形成：在ALDH2rs671巨噬细胞中，AMPK磷酸化ALDH2，减弱其与LDLR的相互作用，从线粒体转移至细胞核, 抑制调控溶酶体pH的ATP6V0e2的表达和对吞噬的脂质在溶酶体降解，促进形成泡沫细胞（Zhong et al, J. Clin. Invest., 2019）。JCI同期发表专评, 高度评价我们的工作，认为其对动脉粥样硬化的发病机制提供全新的理解，可能为心血管疾病的防治提供新思路 (Gibb et al, J. Clin. Invest. 2019)。.（2）肝脏ALDH2调控HMGCR的稳定性影响胆固醇合成: ALDH2促进HMGCR与Insig1/SCAP/gp78的互作，抑制胆固醇合成; ALDH2丢失或rs671突变时，HMGCR的蛋白稳定性增加从而促进胆固醇合成。该研究发现了胆固醇代谢调控的新机制，提示在ALDH2突变人群心血管疾病的风险增加与胆固醇代谢失调有关，临床降胆固醇药物他汀可以有效抑制突变人群胆固醇的升高　(Zhong et al, Redox Biol. 2021).（3）内源性胆固醇脂氧化物抑制肝细胞和巨噬细胞对胆固醇的摄取从而升高血液胆固醇水平，增加心血管疾病的风险。氧化胆固醇脂氧化产物可作为心血管疾病的分子标志物，为脂质氧化增加动脉硬化与心血管疾病的风险提供了新机制 (Guo et al, Redox Biol., 2019). 综上，本项目系统阐明了ALDH2调控胆固醇稳态代谢新机制，为动脉粥样硬化心血管疾病的诊治提供了新策略，有望对糖脂代谢领域产生重大影响。