title: Enterohaemorrhagic, but not enteropathogenic, Escherichia coli infection of epithelial cells disrupts signalling responses to tumour necrosis factor-alpha.
abstract: Enterohaemorrhagic Escherichia coli (EHEC), serotype O157 : H7 is a non-invasive, pathogenic bacterium that employs a type III secretion system (T3SS) to inject effector proteins into infected cells. In this study, we demonstrate that EHEC blocks tumour necrosis factor-alpha (TNFα)-induced NF-κB signalling in infected epithelial cells. HEK293T and INT407 epithelial cells were challenged with EHEC prior to stimulation with TNFα. Using complementary techniques, stimulation with TNFα caused activation of NF-κB, as determined by luciferase reporter assay (increase in gene expression), Western blotting (phosphorylation of IκBα), immunofluorescence (p65 nuclear translocation) and immunoassay (CXCL-8 secretion), and each was blocked by EHEC O157 : H7 infection. In contrast, subversion of host cell signalling was not observed following exposure to either enteropathogenic E. coli, strain E2348/69 (O127 : H6) or the laboratory E. coli strain HB101. Heat-killed EHEC had no effect on NF-κB activation by TNFα. Inhibition was mediated, at least in part, by Shiga toxins and by the O157 plasmid, but not by the T3SS or flagellin, as demonstrated by using isogenic mutant strains. These findings indicate the potential for developing novel therapeutic targets to interrupt the infectious process.
authors.affiliation: Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
authors.forename: Mélanie G
authors.initials: MG
authors.lastname: Gareau
authors.affiliation: Department of Laboratory Medicine and Pathobiology University of Toronto, Medical Sciences Building, 1 King's College Circle, University of Toronto, Toronto, ON M5S 1A8, Canada.|Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
authors.forename: Nathan K
authors.initials: NK
authors.lastname: Ho
authors.affiliation: Campbell Family Cancer Research Institute, Princess Margaret Hospital, 620 University Avenue, Toronto, ON M5G 2C1, Canada.
authors.forename: Dirk
authors.initials: D
authors.lastname: Brenner
authors.affiliation: Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Sousa
authors.affiliation: Department of Immunology, Medical Sciences Building, 1 King's College Circle, University of Toronto, Toronto, ON M5S 1A8, Canada.
authors.forename: Lionel
authors.initials: L
authors.lastname: LeBourhis
authors.affiliation: Campbell Family Cancer Research Institute, Princess Margaret Hospital, 620 University Avenue, Toronto, ON M5G 2C1, Canada.
authors.forename: Tak W
authors.initials: TW
authors.lastname: Mak
authors.affiliation: Department of Laboratory Medicine and Pathobiology University of Toronto, Medical Sciences Building, 1 King's College Circle, University of Toronto, Toronto, ON M5S 1A8, Canada.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Girardin
authors.affiliation: Department of Immunology, Medical Sciences Building, 1 King's College Circle, University of Toronto, Toronto, ON M5S 1A8, Canada.
authors.forename: Dana J
authors.initials: DJ
authors.lastname: Philpott
authors.affiliation: Department of Laboratory Medicine and Pathobiology University of Toronto, Medical Sciences Building, 1 King's College Circle, University of Toronto, Toronto, ON M5S 1A8, Canada.|Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
authors.forename: Philip M
authors.initials: PM
authors.lastname: Sherman
mesh_terms: D002460:Cell Line / Q000382:microbiology*; D054324:Enterohemorrhagic Escherichia coli / Q000235:genetics / Q000502:physiology*; D004847:Epithelial Cells / Q000378:metabolism* / Q000382:microbiology; D004927:Escherichia coli Infections / Q000378:metabolism* / Q000382:microbiology; D019453:Escherichia coli O157 / Q000235:genetics / Q000502:physiology*; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha