title: Salmonella typhimurium translocates flagellin across intestinal epithelia, inducing a proinflammatory response.
abstract: This study investigated whether soluble paracrine factors mediated Salmonella-induced IL-8 expression in polarized model intestinal epithelia. We found that the basolateral media of model epithelia that had been apically infected with Salmonella typhimurium for a short period (10 minutes) could activate IL-8 secretion in virgin model epithelia, demonstrating that a proinflammatory factor (PIF) was indeed present. Initial characterization found that PIF was a heat-stable protein with a molecular mass of about 50 kDa that acts on the basolateral, but not apical, surface of model intestinal epithelia to elicit IL-8 secretion. PIF was not present in the media of model epithelia stimulated with other inducers of IL-8 secretion (TNF-alpha or carbachol) but was present in S. typhimurium supernatants, indicating PIF is of bacterial origin. PIF was purified from bacterial culture supernatants by anion/cation exchange chromatography and SDS-PAGE and found by using microsequencing to be the protein flagellin. In support of this finding, flagellin-deficient S. typhimurium mutants did not secrete detectable levels of PIF (i.e., a bioactivity that induced IL-8 secretion when placed basolaterally on model epithelia). Furthermore, viable flagellin-deficient mutant organisms (fliC/fljB and flhD) failed to elicit IL-8 secretion when added apically to model intestinal epithelia. These findings indicate that translocation of flagellin across epithelia, subsequent to apical epithelial-S. typhimurium interaction, is likely a major means of activating a mucosal inflammatory response.
authors.affiliation: Epithelial Pathobiology Division, Department of Pathology, Emory University School of Medicine, Atlanta, Georgia, USA. agewirt@emory.edu
authors.forename: A T
authors.initials: AT
authors.lastname: Gewirtz
authors.forename: P O
authors.initials: PO
authors.lastname: Simon
authors.forename: C K
authors.initials: CK
authors.lastname: Schmitt
authors.forename: L J
authors.initials: LJ
authors.lastname: Taylor
authors.forename: C H
authors.initials: CH
authors.lastname: Hagedorn
authors.forename: A D
authors.initials: AD
authors.lastname: O'Brien
authors.forename: A S
authors.initials: AS
authors.lastname: Neish
authors.forename: J L
authors.initials: JL
authors.lastname: Madara
mesh_terms: D002460:Cell Line; D004848:Epithelium / Q000276:immunology / Q000382:microbiology; D005408:Flagellin / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000209:etiology* / Q000276:immunology / Q000382:microbiology; D018836:Inflammation Mediators / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology*; D008954:Models, Biological; D009154:Mutation; D012486:Salmonella typhimurium / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology
chemical_list: D018836:Inflammation Mediators; D016209:Interleukin-8; D005408:Flagellin