title: Loss of GM-CSF signalling in non-haematopoietic cells increases NSAID ileal injury.
abstract: BACKGROUND
  Administration of granulocyte-macrophage colony stimulating factor (GM-CSF) relieves symptoms in Crohn's disease (CD). It has been reported that reduced GM-CSF bioactivity is associated with more aggressive ileal behaviour and that GM-CSF-null mice exhibit ileal barrier dysfunction and develop a transmural ileitis following exposure to non-steroidal anti-inflammatory drugs (NSAIDs). STAT5 signalling is central to GM-CSF action. It was therefore hypothesised that GM-CSF signalling in non-haematopoietic cells is required for ileal homeostasis.
  
  
  METHODS
  Bone marrow (BM) chimeras were generated by reconstituting irradiated GM-CSF receptor (gm-csfr) beta chain or GM-CSF (gm-csf) deficient mice with wild type BM (WTBM-->GMRKO and WTBM-->GMKO). Intestinal barrier function and the response to NSAID-induced ileal injury were examined. Expression of gm-csf, gm-csfr or stat5 in Caco-2 and HT-29 intestinal epithelial cell (IEC) lines was knocked down and the effect of GM-CSF signalling on IEC survival and proliferation was determined.
  
  
  RESULTS
  Elevated levels of GM-CSF autoantibodies in ileal CD were found to be associated with dysregulation of IEC survival and proliferation. GM-CSF receptor-deficient mice and WTBM-->GMRKO chimeras exhibited ileal hyperpermeability. NSAID exposure induced a transmural ileitis in GM-CSF receptor-deficient mice and WTBM-->GMRKO chimeras. Transplantation of wild type BM into GM-CSF-deficient mice prevented NSAID ileal injury and restored ileal barrier function. Ileal crypt IEC proliferation was reduced in WTBM-->GMRKO chimeras, while STAT5 activation in ileal IEC following NSAID exposure was abrogated in WTBM-->GMRKO chimeras. Following knock down of gm-csf, gm-csfr alpha or beta chain or stat5a/b expression in Caco-2 cells, basal proliferation was suppressed. GM-CSF normalised proliferation of Caco-2 cells exposed to NSAID, which was blocked by stat5a/b RNA interference.
  
  
  CONCLUSIONS
  Loss of GM-CSF signalling in non-haematopoietic cells increases NSAID ileal injury; furthermore, GM-CSF signalling in non-haematopoietic cells regulates ileal epithelial homeostasis via the STAT5 pathway. The therapeutic use of GM-CSF may therefore be beneficial in chronic ileitis associated with CD.
authors.affiliation: Division of Gastroenterology, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, MLC 2010, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA. xiaonan.han@cchmc.org
authors.forename: Xiaonan
authors.initials: X
authors.lastname: Han
authors.forename: Shila
authors.initials: S
authors.lastname: Gilbert
authors.forename: Katherine
authors.initials: K
authors.lastname: Groschwitz
authors.forename: Simon
authors.initials: S
authors.lastname: Hogan
authors.forename: Ingrid
authors.initials: I
authors.lastname: Jurickova
authors.forename: Bruce
authors.initials: B
authors.lastname: Trapnell
authors.forename: Charles
authors.initials: C
authors.lastname: Samson
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gully
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal; D016026:Bone Marrow Transplantation; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004198:Disease Susceptibility; D004847:Epithelial Cells / Q000473:pathology; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000172:deficiency / Q000276:immunology / Q000494:pharmacology / Q000502:physiology*; D007079:Ileitis / Q000139:chemically induced / Q000276:immunology / Q000473:pathology*; D007413:Intestinal Mucosa / Q000473:pathology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D011994:Recombinant Proteins / Q000494:pharmacology; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D011994:Recombinant Proteins; D050799:STAT5 Transcription Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor