S1PR3调控脓毒症发生发展中M2型巨噬细胞募集的作用及机制研究

Sepsis is recast as a systemic inflammatory response syndrome and assumed to be the result of the host’s invasion by pathogenic organisms. M2 macrophages contribute to alleviate inflammatory response and promote tissue repair during sepsis. S1PR3 regulates recruitment of M2 macrophage to inflammatory lesions, keeping the balance of the body’s immune system. In our pilot study, it was demonstrated that S1PR3 protected mice from sepsis by promoting macrophage recruitment and alleviating tissue damage. Chemokine CX3CL1 facilitates the accumulation of the anti-inflammatory monocytes in diverse tissues, which are the most important source of M2 macrophage. Therefore, we hypothesis that S1PR3 will be involved in the pathogenesis of sepsis via modulating the CX3CL1 expression and subsequent recruitment of M2 macrophage. The present project will, from the systemic, cellular and molecular levels, analyze the function of S1PR3 in M2 macrophage recruitment, to clarify the roles of S1PR3 in up-regulating CX3CL1 expression and subsequent tissue recruitment of anti-inflammatory monocytes during sepsis, and further to explore the signal pathway how S1PR3 mediates the tissue recruitment of M2 macrophage. This study will provide new ideas and targets in the prevention and management of sepsis.

脓毒症是病原微生物入侵机体后所致的全身炎症反应综合症。M2型巨噬细胞在下调炎症反应，促进组织修复中发挥重要作用。S1PR3参与调节M2型巨噬细胞向炎症病灶募集，维持机体免疫稳态。我们前期研究发现：S1PR3促进巨噬细胞募集，减轻脏器损伤，对脓毒症产生保护作用。文献报道趋化因子CX3CL1是介导血液中抗炎单核细胞向组织募集，并转变为M2型巨噬细胞的关键分子。因此，我们推测：S1PR3通过调节CX3CL1的表达，调控M2型巨噬细胞募集，介导脓毒症发生发展。本项目拟从整体、细胞和分子水平，观察S1PR3对脓毒症M2型巨噬细胞的募集作用；明确S1PR3通过上调CX3CL1表达促进血液抗炎单核细胞向组织募集并转化为M2型巨噬细胞，参与脓毒症发生发展；深入探讨S1PR3调控M2型巨噬细胞募集的分子机制，为脓毒症免疫防治提供新思路。

脓毒症系感染引起的机体反应异常导致危及生命的器官功能障碍，进一步可发展为脓毒症休克，死亡率高达40%，是危重病患者死亡的首要原因。目前国际上对脓毒症尚无特异、有效的治疗手段，其根本原因在于脓毒症的发病机理不明确。1-磷酸鞘氨醇受体3（Sphingosine 1-phosphate receptor 3, S1PR3）是七次跨膜G蛋白(G protien)偶联受体家族的其中一员，它的主要功能是与磷脂分子1-磷酸鞘氨醇(Sphingosine 1-phosphate, S1P)相结合，从而启动了细胞跨膜信号转导，调节细胞增殖，血管生成和炎症反应。我们的前期研究发现，S1PR3促进巨噬细胞募集，减轻脏器损伤，对脓毒症产生保护作用。本项目运用遗传动物模型、细胞生物学、分子生物学等多种技术，进一步在整体、细胞、分子子水平上探讨了S1PR3在脓毒症致器官损伤发生发展中的作用及其病理生理机制：①证实了S1PR3通过提高巨噬细胞杀菌能力对脓毒症具有保护作用；②明确了S1PR3通过促进Vps34在吞噬体上富集，进而上调吞噬体NOX2活性，同时加快吞噬体成熟进程，促进细菌清除，参与维持脓毒症免疫功能稳态的分子机制；③脓毒症患者的不良预后与其外周血单核巨噬细胞S1PR3 水平下降存在相关性，脓毒症患者 S1PR3 mRNA水平与外周血单核细胞的杀菌能力呈正相关。本项目阐明了S1PR3在脓毒症致多脏器损伤中的作用和机制，这不仅为系统阐述脓毒症的发病机理提供新的理论依据，而且对有效防治脓毒症，提供了新的分子靶标。