目的:探究大肠埃希菌(Escherichia coli,E.coli)强毒力岛(high-pathogenicity island,HPI)对细胞焦亡及肠道炎症的影响.方法:用含HPI的E.coli株(HPI+)、HPI缺失的E.coli株(∆HPI)和脂多糖(lipopolysaccha-ride,LPS)分别处理昆明小鼠和IPEC-J2细胞(猪小肠上皮细胞).测定小鼠肠道乳酸脱氢酶(lactate dehydroge-nase,LDH)活性、超氧化物歧化酶(superoxide dismutase,SOD)活性、IgA表达和分泌性IgA(secretory IgA,SIgA)含量;HE和TUNEL染色观察肠道损伤;RT-qPCR、免疫组织化学染色和Western blot检测小鼠肠组织和IPEC-J2细胞中核苷酸结合寡聚化结构域样受体蛋白3(nucleotide-binding oligomerization domain-like receptor protein 3,NLRP3)/caspase-1信号通路关键调控点的表达;ELISA检测小鼠血清和IPEC-J2细胞培养上清液中白细胞介素1β(interleu-kin-1β,IL-1β)和IL-18含量;共聚焦显微镜观察NLRP3与caspase-1的共定位.siRNA沉默IPEC-J2细胞的NLRP3,验证NLRP3在E.coli HPI感染中的关键调控功能.结果:相对于∆HPI感染,E.coli HPI显著降低小鼠肠道SOD活性,增加IgA+B细胞,并促进LDH的释放和SIgA的分泌;ELISA、HE染色和TUNEL染色结果显示,E.coli HPI促进了小鼠肠道上皮细胞DNA断裂、组织损伤和炎症;Western blot结果显示,相对于∆HPI,E.coli HPI感染使得小鼠肠道消皮素D的N端片段(gasdermin D N-terminal fragment,GSDMD-N)蛋白水平显著升高;RT-qPCR和免疫组织化学染色结果显示,E.coli HPI显著促进了小鼠肠道和IPEC-J2细胞中NLRP3、含caspase募集结构域的凋亡相关斑点样蛋白(apoptosis-associated speck-like protein containing a caspase recruitment domain,ASC)、caspase-1、GSDMD、IL-1β和IL-18的mRNA和蛋白表达,IL-1β和IL-18分泌增加;共聚焦显微镜观察发现,相对于∆HPI感染,E.coli HPI显著促进了NLRP3炎症小体的组装,使得NLRP3与caspase-1发生共定位;此外,在NLRP3沉默的IPEC-J2细胞中观察到E.coli HPI诱导的细胞炎症、细胞损伤及NLRP3/caspase-1信号通路的激活被缓解.结论:HPI的存在增强了E.coli的毒力水平,促进肠道炎症;NLRP3/caspase-1信号通路调控的细胞焦亡参与了E.coli HPI诱导的肠道损伤.
E.coli HPI promotes enteritis by inducing pyroptosis through NLRP3/caspase-1 signaling pathway
AIM:This study aims to explore the impact of Escherichia coli(E.coli)high-pathogenicity island(HPI)on pyroptosis and intestinal inflammation.METHODS:Kunming mice and IPEC-J2 cells(porcine small intesti-nal epithelial cells)were treated with HPI-containing E.coli strain(HPI+),HPI-deleting E.coli strain(ΔHPI),or lipo-polysaccharide(LPS).The intestinal lactate dehydrogenase(LDH)activity,superoxide dismutase(SOD)activity,IgA expression and secretory IgA(SIgA)content were assessed in mice.The expression of key regulatory factors in the nucleo-tide-binding oligomerization domain-like receptor protein 3(NLRP3)/caspase-1 signaling pathway-related proteins in mouse intestinal tract and IPEC-J2 cells was analyzed by RT-qPCR,immunohistochemical staining and Western blot.The levels of interleukin-1β(IL-1β)and IL-18 in mouse serum and IPEC-J2 cell culture supernatants were measured by ELISA.The pivotal role of NLRP3 in HPI+infection was confirmed by silencing NLRP3 in IPEC-J2 cells using siRNA.RE-SULTS:The HPI+infection markedly decreased SOD activity,increased IgA+B cell count,and induced the LDH release and SIgA secretion in the mouse intestine compared with ΔHPI infection.The results of ELISA,HE staining and TUNEL staining indicated that E.coli HPI triggered DNA damage,tissue injury and inflammation in mouse intestinal epithelial cells.Western blot revealed an increase in intestinal gasdermin D N-terminal fragment(GSDMD-N)protein level with HPI+infection compared with ΔHPI infection.E.coli HPI significantly up-regulated mRNA and protein expression of NLRP3,apoptosis-associated speck-like protein containing a caspase recruitment domain(ASC),caspase-1,GSDMD,IL-1β and IL-18 in mouse intestinal tissues and IPEC-J2 cells,accompanied by the elevated secretion of IL-1β and IL-18.The confo-cal microscopy demonstrated an enhanced assembly of the NLRP3 inflammasome with HPI+infection compared with ΔHPI infection,leading to colocalization of NLRP3 and caspase-1.Furthermore,NLRP3 silencing in IPEC-J2 cells attenuated E.coli HPI-induced cell inflammation,damage,and NLRP3/caspase-1 signaling pathway activation.CONCLUSION:The presence of HPI enhances the virulence of E.coli and exacerbates intestinal inflammation.Moreover,pyroptosis,regu-lated by the NLRP3/caspase-1 signaling pathway,plays a pivotal role in the intestinal injury induced by E.coli HPI.
万方数据
维普
