Electron Transfer Flavoprotein (ETF) α Controls Blood Vessel Development by Regulating Endothelial Mitochondrial Bioenergetics and Oxygen Consumption.

While impairment of vascular homeostasis induced by hypercholesterolemia is the first step of cardiovascular diseases, the molecular mechanism behind such impairment is not well known. Here, we reported that high-cholesterol diet (HCD) induced defective vessel sprouting in zebrafish larvae. Electron transfer flavoprotein subunit α (ETFα) (encoded by the ETFA gene), a protein that mediates transfer of electrons from a series of mitochondrial flavoenzymes to the respiratory chain, was downregulated in HCD-fed zebrafish and in endothelial cells treated with oxidized low-density lipoprotein. Knockdown of ETFα with morpholino antisense oligonucleotides reproduced vascular sprouting defects in zebrafish larvae, while replenishing with exogeneous ETFA mRNA could successfully rescue these defects. ETFA knockdown in endothelial cells reduces cell migration, proliferation, and tube formation in vitro. Finally, knockdown of ETFA in endothelial cells also reduced fatty acid oxidation, oxygen consumption rate, and hypoxia-inducible factor-1α (HIF1α) protein levels. Taken together, we demonstrate that downregulation of ETFα is involved in hypercholesterolemia-induced defective vessel sprouting in zebrafish larvae via inhibition of endothelial proliferation and migration. The molecular mechanism behind this phenomenon is the decrease of HIF1α induced by downregulation of ETFα in endothelial cells. This work suggests that disturbance of ETFα-mediated oxygen homeostasis is one of the mechanisms behind hypercholesterolemia-induced vascular dysfunction.

虽然高胆固醇血症诱导的血管内稳态受损是心血管疾病的第一步，但这种受损背后的分子机制尚不清楚。在此，我们报道高胆固醇饮食（HCD）在斑马鱼幼鱼中诱导了血管出芽缺陷。电子传递黄素蛋白亚基α（ETFα）（由ETFA基因编码），一种介导电子从一系列线粒体黄素酶向呼吸链传递的蛋白质，在喂食HCD的斑马鱼以及用氧化低密度脂蛋白处理的内皮细胞中表达下调。用吗啉反义寡核苷酸敲低ETFα在斑马鱼幼鱼中重现了血管出芽缺陷，而补充外源性ETFA mRNA能够成功挽救这些缺陷。在内皮细胞中敲低ETFA会降低细胞在体外的迁移、增殖和管形成。最后，在内皮细胞中敲低ETFA还降低了脂肪酸氧化、耗氧率以及缺氧诱导因子 - 1α（HIF1α）蛋白水平。综上所述，我们证明ETFα的下调通过抑制内皮细胞的增殖和迁移参与了高胆固醇血症诱导的斑马鱼幼鱼血管出芽缺陷。这一现象背后的分子机制是内皮细胞中ETFα下调导致的HIF1α减少。这项工作表明，ETFα介导的氧稳态紊乱是高胆固醇血症诱导的血管功能障碍背后的机制之一。