title: Enterohemorrhagic Escherichia coli specific enterohemolysin induced IL-1β in human macrophages and EHEC-induced IL-1β required activation of NLRP3 inflammasome.
abstract: Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a major foodborne pathogen causing hemorrhagic colitis and hemolytic-uremic syndrome. The role of EHEC O157:H7-enterohemolysin (Ehx) in the pathogenesis of infections remains poorly defined. In this study, we used gene deletion and complement methods to confirm its putative functions. Results demonstrated that, in THP-1 cells, EHEC O157:H7-Ehx is associated with greater production of extracellular interleukin (IL)-1β than other cytokines. The data also showed that EHEC O157:H7-Ehx contributed to cytotoxicity in THP-1 cells, causing the release of lactate dehydrogenase (LDH). Although we observed a positive correlation between IL-1β production and cytotoxicity in THP-1 cells infected with different EHEC O157:H7 strains, our immunoblot results showed that the majority of IL-1β in the supernatant was mature IL-1β and not the pro-IL-1β that can be released after cell death. However, EHEC O157:H7-Ehx had no detectable effect on biologically inactive pro-IL-1β at the mRNA or protein synthesis levels. Neither did it affect the expression of apoptosis-associated speck-like protein containing a CARD (ASC), caspase-1, or NOD-like receptor family pyrin domain containing 3 (NLRP3). RNA interference experiments showed that EHEC O157:H7-induced IL-1β production required the involvement of ASC, caspase-1, and NLRP3 expression in THP-1 cells. Our results demonstrate that Ehx plays a crucial role in EHEC O157:H7-induced IL-1β production and its cytotoxicity to THP-1 cells. NLRP3 inflammasome activation is also involved in EHEC O157:H7-stimulated IL-1β release.
authors.affiliation: National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, State Key Laboratory for Infectious Disease Prevention and Control, Changping, Beijing, China.
authors.forename: Xiaoai
authors.initials: X
authors.lastname: Zhang
authors.forename: Yuli
authors.initials: Y
authors.lastname: Cheng
authors.forename: Yanwen
authors.initials: Y
authors.lastname: Xiong
authors.forename: Changyun
authors.initials: C
authors.lastname: Ye
authors.forename: Han
authors.initials: H
authors.lastname: Zheng
authors.forename: Hui
authors.initials: H
authors.lastname: Sun
authors.forename: Hongqing
authors.initials: H
authors.lastname: Zhao
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Ren
authors.forename: Jianguo
authors.initials: J
authors.lastname: Xu
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism*; D020170:Caspase 1 / Q000378:metabolism; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D054324:Enterohemorrhagic Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D017353:Gene Deletion; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007249:Inflammation; D053583:Interleukin-1beta / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D008954:Models, Biological; D009000:Monocytes / Q000166:cytology; D009154:Mutation; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D010957:Plasmids / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D014774:Virulence
chemical_list: D002352:Carrier Proteins; D016207:Cytokines; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; D053583:Interleukin-1beta; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; D012333:RNA, Messenger; C066219:enterohemolysin; D007770:L-Lactate Dehydrogenase; D020170:Caspase 1