title: Characterization of epithelial IL-8 response to inflammatory bowel disease mucosal E. coli and its inhibition by mesalamine.
abstract: BACKGROUND
  Mucosally adherent E. coli are found in inflammatory bowel disease (IBD) and colon cancer. They promote release of the proinflammatory cytokine interleukin-8 (IL-8). We explored mechanisms for this release and its inhibition by drugs.
  
  
  METHODS
  IL-8 release from colon epithelial cells in response to mucosal E. coli isolates from IBD, colon cancer, and controls was characterized at the cellular and molecular level.
  
  
  RESULTS
  IL-8 response of HT29 cells was greater with Crohn's disease (689 +/- 298 [mean +/- SD] pg IL-8/mL at 4 hours, n = 7) and colon cancer isolates (532 +/- 415 pg/mL, n = 14) than with ulcerative colitis (236 +/- 58 pg/mL, n = 6) or control isolates (236 +/- 100 pg/mL, n = 6, P < 0.0001). Bacterial supernatants contained shed flagellin that triggered IL-8 release. For whole bacteria the IL-8 response to E. coli that agglutinate red blood cells (548 +/- 428 pg IL-8/mL, n = 16), a function that correlates with epithelial invasion, was greater than for nonhemagglutinators (281 +/- 253 pg/mL, n = 17; P < 0.0001). This was particularly marked among E. coli that, although flagellate, could not release IL-8 from TLR5-transfected HEK293 cells. IL-8 release was mediated by extracellular-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) and inhibited by mesalamine, but not hydrocortisone, at therapeutic concentrations.
  
  
  CONCLUSIONS
  Mucosa-associated E. coli shed flagellin that elicits epithelial IL-8 release but this may only become relevant when the mucosal barrier is weakened to expose basolateral TLR5. Adherent and invasive IBD and colon cancer E. coli isolates also elicit a flagellin-independent IL-8 response that may be relevant when the mucosal barrier is intact. The IL-8 release is MAPK-dependent and inhibited by mesalamine.
authors.affiliation: Division of Gastroenterology, University School of Clinical Science, Liverpool, UK.
authors.forename: Sreedhar
authors.initials: S
authors.lastname: Subramanian
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Rhodes
authors.forename: C Anthony
authors.initials: CA
authors.lastname: Hart
authors.forename: Ben
authors.initials: B
authors.lastname: Tam
authors.forename: Carol L
authors.initials: CL
authors.lastname: Roberts
authors.forename: Shirley L
authors.initials: SL
authors.lastname: Smith
authors.forename: John E
authors.initials: JE
authors.lastname: Corkill
authors.forename: Craig
authors.initials: C
authors.lastname: Winstanley
authors.forename: Mumtaz
authors.initials: M
authors.lastname: Virji
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Campbell
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D016022:Case-Control Studies; D002478:Cells, Cultured; D003110:Colonic Neoplasms / Q000276:immunology / Q000382:microbiology; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D005408:Flagellin / Q000235:genetics / Q000276:immunology; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000276:immunology* / Q000382:microbiology*; D016209:Interleukin-8 / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology; D020935:MAP Kinase Signaling System; D019804:Mesalamine / Q000494:pharmacology*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D016209:Interleukin-8; D005408:Flagellin; D019804:Mesalamine