Salmonella typhimurium translocates flagellin across intestinal epithelia, inducing a proinflammatory response.
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.
Gewirtz
A T
AT
Epithelial Pathobiology Division, Department of Pathology, Emory University School of Medicine, Atlanta, Georgia, USA. agewirt@emory.edu
Simon
P O
PO
Schmitt
C K
CK
Taylor
L J
LJ
Hagedorn
C H
CH
O'Brien
A D
AD
Neish
A S
AS
Madara
J L
JL
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
D018836:Inflammation Mediators; D016209:Interleukin-8; D005408:Flagellin