EPO促巨噬细胞吞噬杀菌介导细菌性炎症消退作用和机制研究

Acute inflammatory responses are critical for host survival from infection and injury. Inflammation resolution is an active rather than a passive process that activates by the beginning of the inflammation and promotes the clearance of pathogens and apoptotic cells. The failture of inflammation resolution will the persistent chronic inflammation and infection. Endogenous mechanisms leading to host protection and resolution of infections without immunosuppression are of wide interest. Erythropoietin (EPO) is critical for the formation of red blood cell and widely applied in clinic. Our recent data showed that EPO and EPO receptor (EPOR) were induced following E. coli-induced peritonitis, EPO promoted the phagocytosis of E. coli by macrophages and EPO played an important role in infection inflammation resolution. So EPO might be a potent immunoresolvent actions in host defense, host protection and antimicrobial defense. The project here aim to investigate the functions and mechanisms of EPO in infection inflammation resolution in E. coli-induced peritonitis by using conditional EPOR knockout mice. And we hope to elucidate following issues: 1. how E. coli infection induced EPO/EPOR and our investigation will focus on the HIF pathway; 2. how EPO promoted infection inflammation resolution and our study will focus on the E. coli clearance and inflammatory cytokine production; 3. how EPO promoted E. coli phagocytosis by macrophages and its contribution to EPO-induced inflammation resolution; 4. Therapeutic effects of EPO in high-dose E. coli infection inflammation; 5. The additive effects of EPO with antibiotics in infection regulation; 6. The effects of EPO in regulating Staphylococcus aureus-induced inflammation. Through this project we hope to indentified EPO as an endogenous immunoresolvent, reveal its actions and underlying mechanisms in host defense and host protection.

细菌性炎症消退(BIR) 是炎症自身反馈主动调控机制，起着终止炎症反应及促病原菌清除作用；促BIR分子清除病原菌机制不同于传统药物，随着细菌耐药的日益严重，可望成为抗生素的有益补充，因此发现新促BIR分子并阐明其机理具重要意义。已知巨噬细胞（MΦ）低炎症性吞噬清除病原菌在促BIR中起关键作用，我们研究首次发现促红细胞生成素（EPO）在促BIR和促MΦ吞噬病原菌中起重要作用，为新内源性促BIR分子，但其作用机制不清。本项目拟采用MΦ特异EPO受体敲除等小鼠，在大肠杆菌诱导腹膜炎等模型中，从正反角度，阐明细菌感染诱导内源性EPO途径，分析内外源性EPO促BIR作用，研究EPO促MΦ吞噬杀伤病原菌作用、机制及在促BIR中关键作用，检测EPO与抗生素合用对抗细菌性感染作用，并在金葡菌皮肤感染模型进一步验证。以提供促BIR新机制和新分子，为调控细菌性感染和减少抗生素使用提供候选新分子。

细菌感染是人类健康的重要威胁之一，虽然抗生素能有效杀灭细菌，但耐药菌的快速出现是抗生素应用的重大挑战，急需发展新的抗菌策略。不同于抗生素直接杀伤细菌的抗菌策略，免疫调控剂通过增强机体免疫系统的杀菌能力而清除感染机体的细菌，是抗生素的有益补充。虽然增强机体的抗菌炎症反应有利于清除细菌感染，但也同时会导致非特异性的组织损伤，不利于机体康复。而促感染性炎症消退分子，在促进病原菌清除同时，可促进局部组织修复，恢复组织稳态，是抗菌感染的新策略和现有抗菌药物的重要补充，因此发现新的促细菌性炎症消退分子具有重要意义。在上一个自然基金项目资助下我们发现在无菌性腹膜炎中，促红细胞生成素（EPO）通过增强巨噬细胞对凋亡细胞的清除而促进非感染性炎症消退，在本项目中我们通过采用巨噬细胞EPOR敲除小鼠和PPARγ敲除等小鼠，以大肠杆菌腹膜炎和金葡菌皮肤感染为模型，进一步研究了EPO在细菌感染性炎症中的作用。我们发现：细菌感染诱导了局部巨噬细胞EPO通路激活；巨噬细胞EPOR敲除恶化了细菌感染性炎症消退，而外源性EPO促进了细菌感染性炎症消退；机制上EPO通过诱导激活PPARγ的调控的CD36受体促进对细菌的吞噬清除而促进感染性炎症消退；外源性EPO可促进抗生素的作用；EPO对耐药性金葡菌感染也具有促消退作用。相关研究论文正在投稿中，专利在实质审核中。同时我们也研究发现EPO可促进肥胖相关炎症消退，并且EPO来源非促造血肽可促进自身免疫性炎症消退，相关研究论文已发表。 红景天苷可通过促进机体EPO生成，而促进感染性炎症消退，相关论文和专利在撰写中。通过本项目我们揭示了EPO了促细菌感染性炎症消退的作用和机制，为细菌感染，尤其是耐药菌感染干预提供了新策略和新靶标。