自噬促进宿主抵抗力和耐受力对脓毒症的保护效应及其机制研究

严重感染所致脓毒症发病机制及其防治策略是亟待解决的重大难题。研究发现，宿主可通过抵抗力和耐受力两种策略抵抗病原菌感染。我们前期研究结果显示：自噬缺失小鼠对病原菌感染和脓毒症更加易感，自噬的体内诱导能够提高CLP脓毒症动物存活率，并且促进了对细菌的清除以及减轻组织和器官的损伤。进一步体外实验显示，诱导自噬后，巨噬细胞的吞噬作用和杀菌活性显著增强，内皮细胞对细胞损伤的耐受力提高。提示自噬可通过促进宿主对细菌感染的抵抗力和耐受力两种机制发挥保护作用，但确切机制尚待研究。本项目拟利用临床标本及动物模型进一步明确自噬对脓毒症感染的作用，并通过条件性基因敲除小鼠，证明自噬对脓毒症小鼠的保护作用有赖于自噬所促进的宿主抵抗力和耐受力，同时进一步探讨自噬增强宿主抗细菌感染抵抗力和耐受力的确切分子机制。自噬通过促进宿主抵抗力和耐受力对脓毒症的保护作用机制的阐明，将为脓毒症的免疫防治提供新的策略。

The prevention and treatment of microbial sepsis continue to be a major clinical challenge, particularly in intensive care units. Upon bacterial infection, resistance and tolerance are the two distinct defense strategies that the host can employ to protect itself against microbial threats. Our previous work has shown that LC3b-deficient mice were more susceptible to CLP-induced polymicrobial sepsis; the induction of autophagy in vivo affords strong protection against CLP-induced polymicrobial sepsis, which is closely associated with accelerated bacterial clearance and attenuated tissue and organ damage. We further revealed that induction of autophagy in macrophages by C2250 strongly augmented their bacterial phagocytosis and intracellular bacterial killing；and induction of autophagy in endothelial cells by C2250 leads to increased tolerance to LPS-induced cell apoptosis and damage in endothelial monolayer integrity. However, the precise molecular mechanism involved is still unclear. In this proposed research project, we will use clinical samples and in vivo animal model to investigate the protection of autophagy against microbial sepsis. We will also use the Atg16L1fl/fl-LyzCre and Atg16L1fl/fl-Tie2Cre mice to clarify the autophagy inducer-afforded protection against sepsis-associated lethality is predominantly dependent on autophagy-augmented host resistance and/or tolerance. Finally, we will use the in vitro experiments to verify the underlying mechanism responsible for autophagy-augmented resistance and tolerance of the host to microbial infection. By identifying the significance of autophagy confers protection against microbial sepsis by promoting both resistance and tolerance of the host to bacterial infection, this study will help us to clarify a new immuno-therapeutic strategies for prevention and treatment of microbial sepsis.