2型甲酰肽受体调控M2型巨噬细胞极化的分子机制及其在炎症反应中的作用

Macrophages play an important role in development and progression of inflammation.Macrophage significantly influences the quality, duration and magnitude of most inflammatory reactions in a polarized manner.The classically activated macrophages(M1) produce pro-inflammatory cytokines,e.g., IL-6,IL-12,IL-23,to elicit chronic inflammation, whereas alternatively activated macrophages(M2) produce anti-inflammatory cytokines,e.g.,IL-10,to resolve inflammation.However,mechanisms underlying macrophage polarization are incompletely understood.Our previous studies demonstrated a critical role of formyl peptide receptor 2(Fpr2) in M2 macrophage polarization.For instance,we found that Fpr2-/- macrophage had a diminished M2 macrophage polarization in IL-4 induced system，whereas Fpr2 overexpression enhanced M2 genes expression. The ligand ANXA1 expression was robustly induced in M2 macrophages and played an important role in regulating M2 macrophage polarization.However,mechanisms underlying the invovlement of Fpr2 in M2 macrophage polarization remain largely unknown.We propose that Fpr2 regulates M2 macrophage polarization through synergistic effect of ERK and Stat6-IRF4 pathway,thus providing an explanation to the observed anti-inflammatory effect of Fpr2 ligands.To test the hypothesis, macrophage cell lines and primary macrophages isolated from Fpr2 knock-out mice will be used to .to determine whether activation of ERK and Stat6-IRF4 pathway is required for Fpr2-dependent M2 macrophage polarization.In addition,peritonitis model will also be carried out to detect the regulatory function of Fpr2 on M2 macrophage polarization in vivo. Furthermore, anti-inflammatory cytokines secretion and efferocytosis of peritoneal macrophage in Fpr2 knock-out mice will also be studied for anti-inflammatory role of Fpr2 in regulating M2 macrophage polarization. In this study, real-time PCR, ELISA, flow cytometry, retrovirus infection，report gene assay will be used as the main approaches. The outcome of this study may provide new insights into the molecular mechanisms of M2 macrophage polarization and may lead to the development of novel anti-inflammatory drug target.

巨噬细胞（MΦ）在炎症发生、发展、转归上起重要作用。MΦ分为M1(致炎型)和M2（抗炎型）两种亚型。近来研究发现M2型MΦ在抑制炎症中发挥重要作用，但其诱导机制还不很清楚。前期研究发现，IL-4刺激下，2型甲酰肽受体（Fpr2）敲除小鼠原代MΦ向M2型极化明显降低；而过表达Fpr2，则明显上升。结果提示Fpr2对M2型MΦ极化起重要调控作用。但其作用机制有待进一步探讨。我们的假说是：Fpr2可能通过ERK与Stat6-IRF4协同作用促进M2型MΦ极化，起抗炎作用。为验证这一假说，我们将用Fpr2敲除小鼠原代MΦ，从分子、细胞水平探讨Fpr2调控M2型MΦ极化的机制。同时利用腹膜炎模型从整体动物水平明确Fpr2通过促进M2型MΦ极化增加抗炎细胞因子分泌，增强胞葬作用，而发挥抗炎功能。本研究将从新视角揭示Fpr2调控M2型MΦ极化的分子机制,为以Fpr2为靶点进行抗炎药物研发提供坚实的基础。

巨噬细胞是参与调控炎症及各类炎症性疾病的一类重要细胞。其主要通过分泌细胞因子，吞噬作用，抗原递呈等发挥作用，并在各类炎症性疾病中以不同的极化方式存在。鉴于其在调控感染，获得性免疫等方面的重要作用，其功能调控机制一直是当前的研究重点。甲酰肽受体（Fprs）是一类广泛表达于巨噬细胞，嗜中性粒细胞上的GPCR受体。一直以来，其对巨噬细胞功能的调控作用研究的还不是十分清楚。本课题主要是利用Fpr1， Fpr2的基因敲除小鼠，研究其对巨噬细胞分泌细胞因子，吞噬作用以及极化作用的影响。经过三年的研究工作，我们发现Fpr2受体参与调控巨噬细胞的极化。其配体血清淀粉样蛋白A可以通过诱导白介素33（IL-33）的表达，其作用机制是通过诱导和激活转录因子IRF7结合到IL-33的启动子区域，从而诱导IL-33。此外，我们还发现SAA可以诱导M2型巨噬细胞的特异性标记物，同时促进巨噬细胞对凋亡嗜中性粒细胞的胞葬作用。研究发现，SAA可以诱导转录因子IRF4 的表达和活化在调控M2型巨噬细胞标记物以及胞葬作用中发挥作用。进一步的我们还发现，SAA可以通过诱导去甲基化酶Jmjd3的表达，调控巨噬细胞细胞因子的产生，并在调控巨噬细胞泡沫化中发挥作用。这一系列的工作都是开创性的阐明了甲酰肽受体及其配体在调控巨噬细胞功能中的作用，并为进一步研究其在调控炎症性疾病中的作用提供了坚实的理论基础。