A high level of total cholesterol is associated with several lipid metabolism disorders, including atherosclerosis and cardiovascular diseases. ATP-binding cassette (ABC) transporter A1 (ABCA1) and miR-33-5p play crucial roles in atherosclerosis by controlling cholesterol efflux. While citrate is a precursor metabolite for lipid and cholesterol synthesis, little is known about the association between citrate synthase (CS) and cholesterol efflux. This study investigated the role of the miR-33-5p/ABCA1/CS axis in regulating cholesterol efflux in vascular endothelial cells (VECs). VECs were treated with oxidized low-density lipoprotein cholesterol (ox-LDL), or pretreated with plasmids overexpressing CS, ABCA1, siRNAs against CS and ABCA1, and an miR-33-5p inhibitor. Cell apoptosis, cellular senescence-associated β-galactosidase activity, inflammation, and cholesterol efflux were detected. Treatment with ox-LDL decreased ABCA1 and CS levels and increased miR-33-5p expression and apoptosis in dose-dependent manners. In contrast, treatment with the miR-33-5p inhibitor and ABCA1 and CS overexpression plasmids inhibited the above-mentioned ox-LDL-induced changes. In addition, treatment with ox-LDL decreased cholesterol efflux, induced aging, and promoted the production of inflammatory cytokines (i.e., IL-6 and tumor necrosis factor TNF-α), as well as the expression of Bax and Caspase 3 proteins in VECs. All these changes were rescued by miR-33-5p inhibition and ABCA1 and CS overexpression. The inhibition of ABCA1 and CS by siRNAs eliminated the effects mediated by the miR-33-5p inhibitor, and knockdown of CS eliminated the effects of ABCA1 on VECs. This study demonstrated the crucial roles played by the miR-33-5p/ABCA1/CS axis in regulating cholesterol efflux, inflammation, apoptosis, and aging in VECs, and also suggested the axis as a target for managing lipid metabolism disorders.

中文翻译：

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MicroRNA-33-5p 通过调节柠檬酸合酶和 ATP 结合盒转运蛋白 A1 抑制血管内皮细胞中的胆固醇流出

高水平的总胆固醇与几种脂质代谢紊乱有关，包括动脉粥样硬化和心血管疾病。ATP 结合盒 (ABC) 转运蛋白 A1 (ABCA1) 和 miR-33-5p 通过控制胆固醇流出在动脉粥样硬化中起关键作用。虽然柠檬酸盐是脂质和胆固醇合成的前体代谢物，但对柠檬酸合酶 (CS) 和胆固醇流出之间的关联知之甚少。本研究调查了 miR-33-5p/ABCA1/CS 轴在调节血管内皮细胞 (VEC) 中胆固醇流出中的作用。VEC 用氧化的低密度脂蛋白胆固醇 (ox-LDL) 处理，或用过表达 CS、ABCA1、针对 CS 和 ABCA1 的 siRNA 和 miR-33-5p 抑制剂的质粒预处理。细胞凋亡、细胞衰老相关的 β-半乳糖苷酶活性、炎症、并检测到胆固醇流出。ox-LDL 治疗以剂量依赖性方式降低了 ABCA1 和 CS 水平，并增加了 miR-33-5p 表达和细胞凋亡。相反，用 miR-33-5p 抑制剂和 ABCA1 和 CS 过表达质粒处理抑制了上述 ox-LDL 诱导的变化。此外，ox-LDL 治疗可减少胆固醇流出，诱导衰老，并促进炎性细胞因子（即 IL-6 和肿瘤坏死因子 TNF-α）的产生，以及 VEC 中 Bax 和 Caspase 3 蛋白的表达. 所有这些变化都被 miR-33-5p 抑制和 ABCA1 和 CS 过表达所挽救。siRNA对ABCA1和CS的抑制消除了miR-33-5p抑制剂介导的作用，而CS的敲低消除了ABCA1对VECs的作用。