IFI204促进NETs形成以限制金葡菌增殖的研究

Staphylococcus aureus infection is recognized one of the most challenging issues perplexing the development of breeding industry and endangering human health. With the emergence of drug-resistant Staphylococcus aureus and drug resistance spectrum expanding, the demand for new drugs is even more pressing. Innate immune acts as the first line of defense against pathogenic infections. Research on anti-bacterial innate immune response to identify intervention target is beneficial for disease prevention and control. Our preliminary results showed that interferon-activated gene 204 (IFI204) restricts the proliferation of methicillin-resistant Staphylococcus aureus (MRSA). IFI204 deficiency inhibits bacteria-induced KC and IFN-β production, and impairs the activation of NF-κB and STING-IRF3 pathways in vivo and in vitro. However, the administration of exogenous recombinant KC or IFN-β proteins could not prevent bacterial proliferation. IFI204 does not affect phagocytosis and clearance of bacteria by macrophages. Interestingly, we found that IFI204 inhibits bacterial extracellular growth, maybe through an extracellular traps-dependent manner. Thus, the roles of IFI204 in anti-infection and neutrophil extracellular traps (NETs) formation, whether NETs mediating the protective effect of IFI204, the mechanism of IFI204 promoting NETs formation, and IFI204-NETs signaling in bovine and human neutrophils will be studied. Hopefully, these studies will lead to the identification of intervention target and establish a basis for the follow-up drug screening and the therapy of Staphylococcus infectious diseases such as bovine mastitis.

金葡菌感染是困扰养殖业发展和危害人类健康的问题之一。随着金葡菌耐药株出现和耐药谱扩大，对新型药物的需求更为紧迫。天然免疫是防御病原感染的第一道防线，研究抗菌天然免疫反应，找到干预靶标，有利于疾病防控。我们前期发现模式识别受体IFI204限制金葡菌增殖。体内外实验表明IFI204缺失抑制细胞因子KC和IFN-β分泌，以及NF-κB和STING-IRF3通路活化，但回补重组细胞因子并不能抑制体内细菌增殖。进而发现IFI204不影响巨噬细胞对金葡菌的吞噬和胞内清除，却限制其胞外增殖，初步揭示可能依赖于胞外陷阱。因此，本项目拟从IFI204抗感染和调节NETs形成、NETs介导IFI204的保护作用、IFI204促进NETs形成的机制、IFI204-NETs信号在牛和人嗜中性粒细胞中的验证进行系统研究，找到金葡菌感染的新干预靶标，为后续干预药物的筛选和奶牛乳房炎等金葡菌感染性疾病的治疗奠定基础。

金黄色葡萄球菌是重要的人兽共患病病原，严重危害养殖业发展和人类健康。宿主天然免疫在识别和清除致病微生物中起着重要作用，金葡菌与天然免疫互作机制的研究，有助于开发新的干预靶标和防治策略。基于前期的预实验数据，我们提出核酸识别受体IFI204可能促进胞外诱捕网ETs的形成以限制金葡菌增殖的假设。在国家自然科学基金资助下，本项目组围绕总体研究目标，完成了研究任务和计划，揭示了IFI204通过PAD4信号促进ETs形成，增强天然免疫细胞对金葡菌的胞外杀菌力，从而在金葡菌全身性感染或呼吸道感染中促进宿主防御的重要作用，为靶向IFI204信号的抗金葡菌感染药物的研发提供实验依据。随着研究的深入，项目组也开展了IFI204核酸识别信号分子STING、IFI204炎性体信号分子GSDMD在抗金葡菌感染中的作用及机制研究，以及探讨了金葡菌毒力因子OatA对ETs形成的影响和机制。项目组发现STING一方面抑制MLKL介导巨噬细胞坏死性凋亡，同时通过ROS-ERK信号促进ETs胞外杀菌效应，从而在抗金葡菌呼吸道感染起重要作用；发现GSDMD不依赖于炎性体活化，而是通过抑制Cxcl1–Cxcr2轴促进宿主抵抗金葡菌表皮感染；也发现了金葡菌借助于毒力因子OatA抑制ETs形成，从而达到逃逸ETs抗菌免疫反应，OatA不依赖于IFI204，而是通过阻止GSDMD活化以抑制ETs的形成。这些研究结果为后续研发金葡菌感染性疾病的干预药物提供了靶标或策略，如IFI204、STING、GSDMD的激动剂，以及Cxcl1–Cxcr2抑制剂在金葡菌感染和炎症治疗中具有一定研发价值。

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