HDL介导的胆固醇流出在调控应激状态脾脏单核细胞分化及动员的作用及机制探讨

Resent studies indicate that myocardial infarction (MI) promotes the progression of atherosclerosis due to lesional accumulation of inflammatory monocytes (Ly-6Chigh ), which originate mainly from spleen. Our preliminary observation in acute coronary syndrome (ACS) patients found that the potential of cholesterol efflux of high-density lipoprotein (HDL) was inversely correlated with the proportion of inflammatory monocytes in circulation. Also supplementation with recombinant HDL (rHDL) may reverse the quantitative increase in circulating inflammatory monocytes after myocardial infarction. Thus we hypothesize that HDL impacts on the differentiation and mobilization of splenic monocytes by enhancing cellular cholesterol efflux. This study is going to assess the effect of recombinant HDLs with distinct functionalities (which was developed by our lab) on splenic monocytosis and monocyte mobilization after MI. The mobilization of splenic monocyte will be visualized by CFSE staining. Nuclear factor NR4A1 and chemokine receptor CCR2 were found to regulate the differentiation and mobilization of monocytes. Therefore, this study is to further investigate whether HDL-mediated cholesterol efflux could influence the expression of NR4A1 and CCR2, with the aim to delineate the molecular mechanisms by which HDL regulate splenic monocytosis and monocyte mobilization. This study will help to expand new target for HDL to treat atherosclerosis. This study will help to understand the anti-atherosclerotic effect of HDL from a new perspective. It will also provide a new strategy for reducing post-MI cardiovascular events.

最近的研究提示心肌梗死相关的应激刺激可促进动脉粥样硬化进展，其机制与促炎型（Ly-6Chigh）单核细胞进入动脉粥样硬化斑块有关，而应激状态下促炎型单核细胞主要来源于脾脏。我们的初步研究发现急性冠脉综合征患者促炎型单核细胞比例显著增加，且与HDL的胆固醇流出功能呈负相关，同时注射重组HDL能减少心梗诱导的小鼠外周促炎型单核细胞增加。据此，我们假设：HDL通过介导胆固醇流出影响心梗诱导的脾脏单核细胞分化及动员。本研究将采用自行开发的具有不同功能状态apoAI重组的HDL干预, 利用脾细胞示踪技术，观察其对心肌梗死小鼠脾脏单核细胞分化和动员的影响。已知核因子NR4A1和趋化因子受体CCR2分别调控单核细胞的分化和动员，本研究将进一步探讨HDL介导的细胞内胆固醇流出是否影响NR4A1及CCR2的表达调控，从而明确HDL调节脾脏单核细胞分化及动员的分子机制。

最近的研究提示，应激状态下来自脾脏的促炎型（Ly-6Chigh）单核细胞可进入动脉粥样硬化斑块，加重动脉粥样硬化甚至心肌梗死进展。我们的研究结果证实了载脂蛋白A1（apoA1）具有抗炎、促进胆固醇流出的作用，这些作用与apoA1的结构相关，对apoA1进行分子结构改造（亮氨酸代替色氨酸）后，apoA1的抗炎、促胆固醇流出功能消失；同时从信号途径研究表明，apoA1的抗炎、促进胆固醇流出通过JAK2/STAT3信号通路起作用。接着，我们根据前期的研究探索发现的问题，脾脏细胞流式细胞仪分选后的单核细胞生长慢，不能有效观察HDL刺激后的反应。因此，我们调整了部分研究方案，重点探讨HDL的功能，观察了载脂蛋白C3（apoC3）对HDL功能的影响，发现冠心病患者HDL中的apoCIII水平明显高于非冠心病对照组，且冠心病患者HDL中的apoCIII水平和胆固醇流出呈负相关关系，从而确定了冠心病患者的apoCIII比值是HDL介导的胆固醇流出能力的独立作用因素。由于HDL胆固醇流出功能比HDL-C水平更能预测冠心病风险，因此我们研究将阐明apoC3掺入HDL影响胆固醇流出的机制，为改善HDL功能提供新思路。最后，我们还发现冠心病患者血清PCSK9水平升高，血清Sortilin水平升高但受他汀药物影响，且Sortilin对PCSK9存在独立影响，提示Sortilin可能参与了PCSK9的调节。这些结果对本课题组进行下一步有关血脂代谢异常的机制研究提供了理论依据及实验数据支持。