Enterohemorrhagic Escherichia coli specific enterohemolysin induced IL-1β in human macrophages and EHEC-induced IL-1β required activation of NLRP3 inflammasome

• Published in: PloS one Vol. 7; no. 11; p. e50288
• Main Authors: Zhang, Xiaoai, Cheng, Yuli, Xiong, Yanwen, Ye, Changyun, Zheng, Han, Sun, Hui, Zhao, Hongqing, Ren, Zhihong, Xu, Jianguo
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 27.11.2012; Public Library of Science (PLoS)
• Subjects: Apoptosis; Biological effects; Biology; Carrier Proteins - metabolism; Caspase; Caspase 1 - metabolism; Caspase-1; Cell activation; Cell death; Cell Line; Clonal deletion; Colitis; Cytokines; Cytokines - metabolism; Cytotoxicity; Disease control; Disease prevention; E coli; Enterohemolysin; Enterohemorrhagic Escherichia coli - metabolism; Escherichia coli; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - metabolism; Foodborne pathogens; Gene Deletion; Gene expression; Genes; Hemolysin Proteins - chemistry; Hemolysin Proteins - metabolism; Hemorrhage; Humans; IL-1β; Infectious diseases; Inflammasomes; Inflammation; Interleukin-1beta - metabolism; Interleukins; L-Lactate dehydrogenase; L-Lactate Dehydrogenase - metabolism; Laboratories; Lactate dehydrogenase; Lactic acid; Macrophages; Macrophages - metabolism; Models, Biological; Monocytes - cytology; mRNA; Mutation; NLR Family, Pyrin Domain-Containing 3 Protein; Pathogenesis; Plasmids; Plasmids - metabolism; Protein biosynthesis; Protein synthesis; Pyrin protein; Ribonucleic acid; RNA; RNA Interference; RNA, Messenger - metabolism; RNA-mediated interference; Rodents; Staphylococcus aureus; Time Factors; Toxicity; Transcription; Tumor necrosis factor-TNF; Virulence; Beijing China; China
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0050288

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.