TREM-2-NLRP3炎性小体通路在铜绿假单胞菌肺炎中的保护作用研究

Pseudomonas aeruginosa is one of the most common pathogenic bacteria and opportunistic infectious bacteria in sepsis. The mortality of Pseudomonas aeruginosa induced infection is high, and the current treatment is struggling. Triggering receptor expressed on myeloid cells 2 (TREM-2) is a phagocytic receptor expressed in macrophage. The biologic function of TREM-2 in phagocytosis of bacteria may be completely different because of the different sources of the cells expressing TREM-2 and the different types of bacteria infected. However, the role of TREM-2 in Pseudomonas aeruginosa pneumonia remains unknown. Of previous work, we found that in Pseudomonas aeruginosa pneumonia, the expression of TREM-2 in alveolar macrophage was deeply inhibited. The ability of TREM-2 overexpressing alveolar macrophage to phagocytose and kill pseudomonas aeruginosa was enhanced, and subsequently, ROS and activated caspase-1 levels were increased. Thus, we speculated that TREM-2 plays a protective role in pseudomonas aeruginosa pneumonia by activating NLRP3 inflammasome to eliminate invading bacteria. On this basis, using genetic animal and cell models, the current project will first clear the role of TREM-2 in pseudomonas aeruginosa pneumonia, and then elaborate the mechanisms of TREM-2 mediated activation of NLRP3 inflammasome in fighting against pseudomonas aeruginosa. Furthermore, the protection role of TREM-2-NLRP3 inflammasome pathway in pseudomonas aeruginosa pneumonia will be confirmed in vivo mice model. In addition, the project will also explore the potential therapeutic value of TREM-2 in pseudomonas aeruginosa pneumonia and pseudomonas aeruginosa pneumonia complicated by sepsis.

铜绿假单胞菌是脓毒症最常见的病原菌和机会感染菌之一，致死率高，目前治疗举步维艰。TREM-2是表达于巨噬细胞的吞噬受体，对细菌的吞噬作用因其表达细胞来源和细菌种类不同而大相径庭，但其在铜绿假单胞菌肺炎中的作用尚未见报道。我们前期工作发现，铜绿假单胞菌肺炎中肺泡巨噬细胞TREM-2表达明显抑制；TREM-2高表达肺泡巨噬细胞吞噬清除铜绿假单胞菌的能力明显增强，ROS和活化caspase-1水平明显增加。因而推测TREM-2通过激活NLRP3炎性小体在铜绿假单胞菌肺炎中起保护作用。本项目将在此基础上，利用遗传动物和细胞模型，明确TREM-2在铜绿假单胞菌肺炎发病中的作用，阐述NLRP3炎性小体在TREM-2介导的清除铜绿假单胞菌中的重要地位，在体证实TREM-2-NLRP3炎性小体通路在铜绿假单胞菌肺炎中的保护作用，探索TREM-2在铜绿假单胞菌肺炎和脓毒症并发铜绿假单胞菌肺炎中的防治价值。

肺炎是世界上最常见的感染性疾病，严重威胁人类的生命健康。细菌性肺炎是常见的肺炎类型，总病死率居高不下。目前临床上对细菌性肺炎的治疗除应用抗菌药物和辅助治疗外，尚无特异有效的手段，原因在于其发病机制尚未完全明确。TREM-2是一类属于免疫球蛋白超家族的细胞表面受体，是固有免疫的重要组分。前期研究发现，在盲肠结扎穿孔（CLP）诱导的脓毒症小鼠模型中，回输高表达TREM-2腺病毒的BMDM能明显减轻小鼠体内的细菌负荷，改善脓毒症小鼠的预后,但其具体杀菌机制尚不明确。本项目采用基因敲除、电子显微镜和过继回输等技术手段，在整体、细胞、分子水平上探讨TREM-2/caspase-1炎性小体在E.coli肺炎中的保护作用和机制：①发现TREM-2在不同感染模型（E.coli肺炎和E.coli腹膜炎）中的作用不同，提示巨噬细胞TREM-2的作用可能与其组织来源密切相关；②在体证实回输TREM-2高表达的骨髓来源巨噬细胞（BMDM）对E.coli肺炎有保护作用，显著增强肺部细菌清除；明确TREM-2高表达BMDM对E.coli的杀菌作用依赖于NOX2途径产生的ROS；③发现TREM-2高表达BMDM E.coli感染后线粒体ROS产生较少，细胞焦亡减轻；在caspase-1基因敲除的BMDM中低表达TREM-2对E.coli肺炎有保护作用，表明TREM-2对E.coli肺炎的保护作用与抑制caspase-1炎性体介导的细胞焦亡密切相关。此外，项目组还发现，TREM-2高表达巨噬细胞对老年小鼠脓毒症的发生发展有重要的保护作用，其机制与TREM-2的杀菌作用不相关。本项目阐明了TREM-2 在巨噬细胞杀菌中的重要作用和机制，为TREM-2的免疫防御作用提供新的见解。本项目已发表SCI论文1篇；培养在读博士研究生1名；参加国内外学术会议各1次；项目部分内容获浙江省医药卫生科技奖特等奖。