SIRT1通过转录因子IRF8调控巨噬细胞极化介导脓毒症早期炎症反应的分子机制研究

Sepsis is still the leading cause of death in severe injuries and critical disease by far. Macrophage polarization, a kind of the most immune events, is involved in the pathogenesis of sepsis, which represents an uncontrolled inflammatory response. Previous studies have shown that in the early stage of sepsis, the expression of SIRT1 was significantly decreased while the IRF8 expression was upregulated, which resulted in increase of inflammatory cytokines by macrophages; Inhibited SIRT1 expression induced higher expression, acetylation level of IRF8 and more production of cytokines by the macrophages. However, whether SIRT1 has an effect on macrophage plastics is unclear. Accordingly, based on previous research, we intend to clarify the effects of IRF8 epigenetic modification on the macrophage function in the early stage of sepsis through bioinformatics, gene knockout and molecular biology methods. It is critical to clarify interaction mechanisms of SIRT1 and IRF8 in regulating inflammatory response at the acute phase of sepsis, therefore to provide a theoretical basis for clinical control the inflammation of sepsis.

脓毒症迄今仍是烧创伤和各种危重病的主要死因；早期巨噬细胞的过度激活导致机体免疫失衡是重要发病机制。巨噬细胞极化与脓毒症疾病进程密切相关。项目组前期研究结果显示：脓毒症发生早期，SIRT1表达显著下调，转录因子IRF8表达上调，M1型巨噬细胞过度活化；抑制SIRT1可以显著增加IRF8表达及乙酰化水平，巨噬细胞炎症因子表达进一步增加，加剧脓毒症小鼠的脏器损伤。然而，脓毒症早期巨噬细胞SIRT1与IRF8的具体调控机制，及两者的调控应答对巨噬细胞极化的作用尚不明确。本课题拟在前期研究基础上，从调节巨噬细胞极化着手，通过生物信息学，基因敲除，定点突变等生物学方法，深入探讨SIRT1调控IRF8的分子机制及其在巨噬细胞炎症反应中的功能意义，并重点阐述脓毒症早期巨噬细胞极化对疾病进程的调控机理，从而拓宽脓毒症研究的临床科研思路，为脓毒症的治疗提供新的理论基础及治疗靶点。

脓毒症迄今仍是烧创伤和各种危重病的主要死因；早期巨噬细胞的过度激活导致机体免疫失衡是重要的发病机制。巨噬细胞极化与脓毒症疾病进程密切相关。在脓毒症发生早期，转录因子IRF8表达上调，SIRT1表达下调，M1型巨噬细胞过度活化；但是脓毒症早期巨噬细胞SIRT1与IRF8的调控关系及两者的调控应答对巨噬细胞极化的作用尚不明确。因此本研究主要围绕IRF8转录活性的调控机制及其在巨噬细胞极化中作用，通过质谱分析，染色体免疫共沉淀，慢病毒转导等实验技术深入探讨了SIRT1对IRF8的调控机制，调控IRF8的转录活性在脓毒症疾病发生发展中的作用。首先明确了LPS刺激巨噬细胞，诱导IRF8乙酰化水平增加；过表达IRF8促进iNOS的表达，而过表达IRF8乙酰化位点突变体，则抑制iNOS的表达，表明了乙酰化修饰影响IRF8的转录活性，IRF8去乙酰化抑制iNOS的表达；将过表达乙酰化位点缺失的IRF8突变体的巨噬细胞转移到已清除巨噬细胞的小鼠体内，可使脓毒症小鼠病情加重。IRF8去乙酰化促进SIRT1与iNOS的启动子区域结合抑制iNOS的转录。相较于野生型脓毒症小鼠，髓系单核细胞Sirt1特异性敲除的小鼠中，iNOS的表达更高，脏器损伤更严重。本研究关于IRF8-SIRT1的相互作用调控iNOS的表达发现可能为脓毒症等炎性疾病提供新的治疗策略。