NLRP3炎症小体在大肠杆菌血流感染免疫反应机制中的作用

The role of NLRP3 inflammasome in immune response mechanism of Escherichia coli bloodstream infection

目的探讨Nod样受体蛋白3(NLRP3)炎症小体在大肠杆菌(大肠埃希菌)血流感染中的免疫反应机制。方法对C57BL/6小鼠经尾静脉注射大肠杆菌作为感染组,经尾静脉注射磷酸盐缓冲液(PBS)作为对照组,感染组分别于24 h和48 h分别处死小鼠,对照组在实验开始时即处死小鼠,取各组小鼠的组织标本,分别通过ELISA法、实时荧光定量PCR(RT-q PCR)法、Western blot法、HE染色等各种方法检测各项指标的变化。结果大肠杆菌感染后24 h组和48h组小鼠组织HE染色可见大量炎症细胞浸润和组织坏死;在血流感染组中所有组织匀浆及血清中白介素1β(IL-1β)及白介素18(IL-18)等细胞因子增多;肝肺组织匀浆中NLRP3、含CRAD结构域的凋亡相关斑点样蛋白(ASC)、半胱氨酸天冬氨酸蛋白酶1(caspase-1)mRNA表达量在感染后24 h明显升高,而肾组织匀浆中NLRP3、ASC、caspase-1 mRNA在感染后48 h明显升高;肝、肺、肾组织中NLRP3蛋白、ASC蛋白在48 h组中表达量比在24 h组中表达量要明显升高,而pro-caspase-1在肝肾组织中3组表达量没有明显区别,caspase-1蛋白在肺肾组织中表达量随时间推移表达量上升。结论大肠杆菌血流感染与NLRP3炎症小体的激活有关,并且NLRP3炎症小体的表达水平与感染的严重程度有关,随着感染的加重,NLRP3炎症小体的表达量增加。此项研究结果可能为大肠杆菌血流感染导致的脓毒症的治疗提供一个新的思路。

Objective To investigate the immune reaction mechanism of NLRP3 inflammsome in the Escherichia coli bloodstream infection. Methods C57 BL/6 mouses were injected by caudal vein with Escherichia coli and phosphate buffer（ PBS） respectively as injected group and control group. The infected group mice were executed after 24 hours and 48 hours,and the control group mice were executed at the beginning of experiment,taking the tissue samples of the two groups and detecting the changes of each index. The changes of the indexes were detected by enzyme-linked immunosorbent assay（ ELISA）,real-time quantitative PCR（ RT-q PCR）,Western blot and HE staining. Results Significant inflammatory cell infiltration and tissue necrosis were observed by HE staining in 24 h and 48 h after infection with Escherichia coli. The IL-1β and IL-18 cytokines in tissue homogenate and serum of bloodstream infection group were all increased significantly. The mRNA expression of NLRP3,ASC and caspase-1 in liver and lung homogenate increased significantly at 24 h after infection,while NLRP3,ASC and caspase-1 mRNA in kidney homogenate increased significantly at 48 h after infection. The expression of NLRP3 protein and ASC protein in the liver,lung and kidney tissues of the 48 h group was significantly higher than that in the 24 h group,but there was no significant difference in pro-caspase-1 expression of liver and kidney tissues between three groups.The expression of NLRP3 protein and ASC protein in liver,lung and kidney tissues in 48 h group was significantly higher than that in 24 h group,the expression of pro-caspase-1 protein in liver and kidney tissue in three groups displayed no significant difference,the expression of caspase-1 protein in lung and kidney tissues was increased with time. Conclusion Escherichia coli bloodstream infection is associated with the activation of NLRP3 inflammatory,and the expression level of NLRP3 inflammasome was related to the severity of infection,with the increase of infection,NLRP3 inflammatory expression increased. The findings may provide a new idea for the treatment of sepsis caused by Escherichia coli bloodstream infection.