基于p38/MAPK信号转导通路的多粘菌素E(Colistin)免疫调节机制研究

Rapid rise of antibiotic resistance and slowly development of antimicrobials has driven anti-infective research into a new era characterized by combination of antibacterial activity and immunomodulatory. Polymyxin E (Colistin) is the “last resort” of severe infections caused by multi-drug resistant Gram-negative pathogen. Our previous findings indicated that colistin can activate innate immunity via p38/PMK-1 signaling pathway and enhance the defense capability during the infection in a simple animal model C. elegans. Considering both of protective effects after immune activation and hypersensitivity caused by excessive activation, we propose the idea of antimicrobials combination regimen based on immune-enhancing activity of colistin and hypothesis of inflammatory response is one of the mechanisms of colistin nephrotoxicity. We designed experiments from the molecular, cellular and whole animal to analyze the mechanisms of colistin effect on the mammalian innate immune system and to evaluate the feasibility of antimicrobial combination regimen based on immunomodulatory activity of colistin. Hypothesis of colistin caused inflammation-induced renal injury through p38/MAPK pathway is verified by inflammatory cytokines analysis, histopathology observation and p38 inhibitors effect evaluation in a rat nephrotoxicity model. These series of studies will provide solid theoretical foundation for the new use of colistin besides antibacterial activity and reduce the risk of nephrotoxicity.

细菌耐药性的快速攀升与抗菌药物研发滞缓的现状，驱使抗感染治疗进入活性抗菌与免疫调节双管齐下的新时代。多粘菌素E（Colistin）是治疗多药耐药革兰氏阴性杆菌所致严重感染的“最后防线”，课题组基于前期关于colistin通过p38/PMK-1信号转导通路激活低等模式生物C. elegans先天免疫提高抗感染能力的发现，从激活保护和过敏危害双向入手，首次提出“colistin免疫增强活性应用设想”以及“colistin肾毒性的炎性反应机制假说”，从分子、细胞和整体动物三个层面解析colistin对哺乳动物先天免疫系统作用机制，评价基于colistin免疫增强活性的抗菌药物联用方案的可行性，并通过炎性因子、组织病理以及p38抑制剂效果分析，验证colistin通过诱发炎症反应致肾损伤的假说，为开拓colistin除抗菌活性外的新用途、寻找降低colistin肾毒性的新策略奠定坚实的理论基础。

多黏菌素E (colistin)是多药耐药革兰阴性菌感染的最后防线，本项目前期关于colistin能够提高低等动物线虫先天免疫并抵御感染的发现以及其作用机制研究基础上，进一步研究了colistin对高等哺乳动物的免疫调节作用。研究发现5、10和20μg/ ml colistin能显着增加TNF-α的分泌，而20和5μg/ mlcolistin分别显着增加IL-1β和IL-6的水平；colistin能增强巨噬细胞对荧光微球和金黄色葡萄球菌的吞噬，该现象可被p38抑制剂（SB203580）阻断；colistin作用后的磷酸化p38蛋白水平以剂量依赖性方式增加，炎症反应、MAPK通路、T细胞、B细胞调节、部分白细胞介素的信号转导等通路被显著改变，其中MAPK通路与许多炎症反应、免疫反应通路相互影响，且MAPK通路处于整个相互作用网络下游，因此可能是colistin产生免疫调节作用的关键通路之一。大鼠肺部金葡菌感染模型提示短时小剂量colistin能够提高大鼠白细胞和中性粒细胞水平，调节部分促炎细胞因子，激活大鼠自身免疫功能清除病原体，改善MRSA导致的肺组织损伤。但SB203580的抑制作用在动物实验中并不明显，提示在高等动物体内p38/MAPK可能不是唯一的影响通路。本研究首次证明colistin对哺乳动物巨噬细胞具有免疫调节作用，而p38 / MAPK通路是参与该调节功能的关键通路之一，为开拓colistin在免疫调节方面的应用提供实验依据。