Abstract：
Vascular smooth muscle cells (VSMCs) are considered to be a crucial source of foam cells in atherosclerosis due to their low expression level of cholesterol exporter ATP-binding cassette transporter A1 (ABCA1) intrinsically. While the definite regulatory mechanisms are complicated and have not yet been fully elucidated, we previously reported that Dickkopf-1 (DKK1) mediates endothelial cell (EC) dysfunction, thereby aggravating atherosclerosis. However, the role of smooth muscle cell (SMC) DKK1 in atherosclerosis and foam cell formation remains unknown. In this study, we established SMC-specific DKK1-knockout (DKK1SMKO ) mice by crossbreeding DKK1flox/flox mice with TAGLN-Cre mice. Then, DKK1SMKO mice were crossed with APOE-/- mice to generate DKK1SMKO /APOE-/- mice, which exhibited milder atherosclerotic burden and fewer SMC foam cells. In vitro loss- and gain-of-function studies of DKK1 in primary human aortic smooth muscle cells (HASMCs) have proven that DKK1 prevented oxidized lipid-induced ABCA1 upregulation and cholesterol efflux and promoted SMC foam cell formation. Mechanistically, RNA-sequencing (RNA-seq) analysis of HASMCs as well as chromatin immunoprecipitation (ChIP) experiments showed that DKK1 mediates the binding of transcription factor CCAAT/enhancer-binding protein delta (C/EBPδ) to the promoter of cytochrome P450 epoxygenase 4A11 (CYP4A11) to regulate its expression. In addition, CYP4A11 as well as its metabolite 20-HETE-promoted activation of transcription factor sterol regulatory element-binding protein 2 (SREBP2) mediated the DKK1 regulation of ABCA1 in SMC. Furthermore, HET0016, the antagonist of CYP4A11, has also shown an alleviating effect on atherosclerosis. In conclusion, our results demonstrate that DKK1 promotes SMC foam cell formation during atherosclerosis via a reduction in CYP4A11-20-HETE/SREBP2-mediated ABCA1 expression.
摘要：
血管平滑肌细胞（VSMC）被认为是动脉粥样硬化中泡沫细胞的重要来源，因为其固有的胆固醇输出者ATP结合盒转运蛋白A1（ABCA1）的表达水平较低。虽然明确的调控机制比较复杂,尚未完全阐明,我们先前报道Dickkopf-1（DKK1）介导内皮细胞（EC）功能障碍，从而加重动脉粥样硬化。然而,平滑肌细胞（SMC）DKK1在动脉粥样硬化和泡沫细胞形成中的作用尚不清楚。在这项研究中,我们通过将DKK1flox/flox小鼠与TAGLN-Cre小鼠杂交，建立了SMC特异性DKK1基因敲除（DKK1SMKO）小鼠。然后，DKK1SMKO小鼠与APOE-/-小鼠杂交以产生DKK1SMKO/APOE-/-小鼠，表现出更温和的动脉粥样硬化负担和更少的SMC泡沫细胞。原代人主动脉平滑肌细胞（HASMC）中DKK1的体外功能丧失和获得研究证明，DKK1可防止氧化脂质诱导的ABCA1上调和胆固醇流出，并促进SMC泡沫细胞形成。机械上,HASMC的RNA测序（RNA-seq）分析以及染色质免疫沉淀（ChIP）实验表明，DKK1介导转录因子CCAAT/增强子结合蛋白δ（C/EBPδ）与细胞色素P450环氧合酶4A11（CYP4A11）启动子的结合，以调节其表达。此外,CYP4A11及其代谢物20-HETE促进转录因子固醇调节元件结合蛋白2（SREBP2）的激活，介导了SMC中ABCA1的DKK1调节。此外，CYP4A11的拮抗剂HET0016也显示出对动脉粥样硬化的缓解作用。总之,我们的结果表明,DKK1通过降低CYP4A11-20-HETE/SREBP2介导的ABCA1表达促进动脉粥样硬化期间SMC泡沫细胞的形成.
