title: Flagellin Induces β-Defensin 2 in Human Colonic Ex vivo Infection with Enterohemorrhagic Escherichia coli.
abstract: Enterohemorrhagic E.coli (EHEC) is an important foodborne pathogen in the developed world and can cause life-threatening disease particularly in children. EHEC persists in the human gut by adhering intimately to colonic epithelium and forming characteristic attaching/effacing lesions. In this study, we investigated the innate immune response to EHEC infection with particular focus on antimicrobial peptide and protein expression by colonic epithelium. Using a novel human colonic biopsy model and polarized T84 colon carcinoma cells, we found that EHEC infection induced expression of human β-defensin 2 (hBD2), whereas hBD1, hBD3, LL-37, and lysozyme remained unchanged. Infection with specific EHEC deletion mutants demonstrated that this was dependent on flagellin, and apical exposure to purified flagellin was sufficient to stimulate hBD2 and also interleukin (IL)-8 expression ex vivo and in vitro. Flagellin-mediated hBD2 induction was significantly reduced by inhibitors of NF-κB, MAP kinase p38 and JNK but not ERK1/2. Interestingly, IL-8 secretion by polarized T84 cells was vectorial depending on the side of stimulation, and apical exposure to EHEC or flagellin resulted in apical IL-8 release. Our results demonstrate that EHEC only induces a modest immune response in human colonic epithelium characterized by flagellin-dependent induction of hBD2 and low levels of IL-8.
authors.affiliation: Norwich Medical School, University of East AngliaNorwich, UK; Gut Health and Food Safety Programme, Institute of Food ResearchNorwich, UK.
authors.forename: Steven B
authors.initials: SB
authors.lastname: Lewis
authors.affiliation: Gastroenterology Department, Norfolk and Norwich University Hospital Norwich, UK.
authors.forename: Alison
authors.initials: A
authors.lastname: Prior
authors.affiliation: Norwich Medical School, University of East AngliaNorwich, UK; Gut Health and Food Safety Programme, Institute of Food ResearchNorwich, UK.
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Ellis
authors.affiliation: Gastroenterology Department, Norfolk and Norwich University Hospital Norwich, UK.
authors.forename: Vivienne
authors.initials: V
authors.lastname: Cook
authors.affiliation: Norwich Medical School, University of East AngliaNorwich, UK; Gastroenterology Department, Norfolk and Norwich University HospitalNorwich, UK.
authors.forename: Simon S M
authors.initials: SS
authors.lastname: Chan
authors.affiliation: Gastroenterology Department, Norfolk and Norwich University Hospital Norwich, UK.
authors.forename: William
authors.initials: W
authors.lastname: Gelson
authors.affiliation: Norwich Medical School, University of East AngliaNorwich, UK; Gut Health and Food Safety Programme, Institute of Food ResearchNorwich, UK.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Schüller
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism; D000890:Anti-Infective Agents / Q000494:pharmacology; D001422:Bacterial Adhesion; D001706:Biopsy; D045744:Cell Line, Tumor; D003106:Colon / Q000378:metabolism* / Q000382:microbiology; D003110:Colonic Neoplasms; D054324:Enterohemorrhagic Escherichia coli / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000276:immunology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005408:Flagellin / Q000235:genetics / Q000494:pharmacology*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007113:Immunity, Innate; D016209:Interleukin-8 / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism / Q000382:microbiology; D016328:NF-kappa B / Q000378:metabolism; D017384:Sequence Deletion; D023083:beta-Defensins / Q000187:drug effects*
chemical_list: D018829:Adhesins, Bacterial; D000890:Anti-Infective Agents; C508606:CXCL8 protein, human; C106641:DEFB4A protein, human; D029968:Escherichia coli Proteins; D016209:Interleukin-8; D016328:NF-kappa B; D023083:beta-Defensins; D005408:Flagellin
keywords: EHEC; colon; flagellin; inflammation; interleukin-8; β-defensin