组胺-STAT信号通路介导不成熟髓系细胞动员和分化及其在心肌梗死发展中的作用与机制

Innate immune cells comprise granulocytes and monocytes/macrophages that contribute to the atherosclerosis-related cardiovascular inflammation and progression of acute myocardial infarction(AMI). However, the mechanisms of proliferation,differentiaiton, and activation of immature myeloid cells in AMI remain largely unclear. Recent study indicated that AMI could activate immature myelid cells (IMCs) and monocytic precursors in the spleen in early stage. In our preliminary experiments, we identified marked decreasing of STAT4 and STAT6 mRNA expression in bone marrow derived IMCs of AMI mice by microarray screening. FACS data showed significant increasing of CD11b+Gr-1+ IMCs in the bone marrow and peripheral blood of histamine-deficience HDC knock out mice(Histidine Decarboxyasle,HDC). Furthermore, we detected great increasing of IMCs in the circulation of AMI mice and patients and in the infarcted myocardium of AMI mice. In addition, FACS data showed increasing of IMCs in the bone marrow and blood of STAT4 and STAT6 knock-out mice. These rsults help to propose the hypethesis that histamine and STAT4, STAT6 signaling pathway play criticle roles in the proliferation,activation, and differentiation of IMCs, contributing to apoptosis of myocardial cells and progression of AMI. To prove the hypothesis, we will construct AMI murine models with HDC-EGFP, HDC-KO, STAT4-KO, and STAT6-KO mice.We aim to investigate the mechanisms mediating the expression and regulation spleen and bone marrow-derived IMCs during AMI.The present study sheds light on the novel targets of fundamental study and clinic therapy of AMI related diseases.

巨噬细胞和中性粒细胞在急性心肌梗死(AMI)发生发展中有重要作用，但机理有待进一步阐明。研究发现AMI动员脾脏巨噬细胞及其前体细胞，促进心梗发展。我们前期研究发现AMI促进脾脏和骨髓CD11b+Gr-1+不成熟髓系细胞（IMC）动员和侵入梗死心肌，加重心肌损伤，但IMCs的作用机制不清楚。我们前期基因芯片扫描发现STAT4和STAT6在IMC表达降低；组胺缺失抑制单核细胞分化、促进IMC动员。流式分析发现STAT4和STAT6基因敲除小鼠骨髓和血中IMC动员增多。提示：组胺和STAT信号通路可能介导AMI后IMC动员和分化；IMC侵入心肌可分化成M1巨噬细胞，促进炎症反应，加重心肌损伤。本项目将采用组胺缺失小鼠和STAT4、STAT6基因敲除小鼠建立AMI模型，从分子、细胞到整体，探索组胺-STAT信号通路在AMI后IMC动员、巨噬细胞极化、心肌损伤和心室重塑中的作用，明确AMI的发病机理。

本项目应用HDC-EGFP可示踪HDC表达的髓系免疫细胞的转基因小鼠，阐明了AMI后CD11b+Gr-1+不成熟髓系细胞的骨髓内增殖、动员和向梗死心肌浸润的动态变化模式。首次阐明HDC+CD11b+髓系细胞是心梗后主要的组胺合成、释放细胞，而不是肥大细胞。进一步应用HDC-KO小鼠建立心梗模型，发现内源性组胺缺失促进不成熟髓系细胞动员、心肌细胞凋亡和心室重塑。机制研究发现STAT6信号途径在组胺调控不成熟髓系细胞，心肌损伤和心室纤维化中发挥了关键的的作用。我们在研究中也发现，内源组胺缺失加重缺血状态下心肌损伤，给予适当剂量外源组胺能够通过一定程度抑制缺血缺氧诱导的心肌细胞自噬活性来保护心肌细胞；其分子机制在于激活心肌细胞的H1R信号通路，上调miR-206的表达，从而抑制自噬形成关键基因Atg13的表达。为进一步开展AMI病人不成熟髓系细胞表达和相关因素的研究，我们完成了近200例AMI病人和年龄、性别匹配的正常体检对照人群的CD14-CD33+CD11b+不成熟髓系细胞的流式分析。对外周血免疫细胞亚群，尤其是不成熟髓系细胞的变化与心肌损伤酶学指标、 炎性因子、血脂、血糖、组胺和年龄等指标关联分析。本项目研究成果不仅完善了对于组胺参与的免疫反应在急性心梗中的作用的认识，提出了“内源性组胺可能在急性心梗后心肌损伤中起保护作用”的科学假设。而histamine/HR/STAT6信号轴也可能成为防治急性心梗后心衰发展的新的药物靶标。本研究实施期间，共发表标注有项目编号的英文文章6篇，中文核心期刊文章1篇,中文综述2篇，其中SCI收录文章6篇（第一标注2篇，5篇本项目负责人为通讯或并列通讯作者）。项目实施期间，培养博士研究生1名，硕士研究生2名。