title: CRF induces intestinal epithelial barrier injury via the release of mast cell proteases and TNF-α.
abstract: OBJECTIVE
  Psychological stress is a predisposing factor in the onset and exacerbation of important gastrointestinal diseases including irritable bowel syndrome (IBS) and the inflammatory bowel diseases (IBD). The pathophysiology of stress-induced intestinal disturbances is known to be mediated by corticotropin releasing factor (CRF) but the precise signaling pathways remain poorly understood. Utilizing a porcine ex vivo intestinal model, the aim of this study was to investigate the mechanisms by which CRF mediates intestinal epithelial barrier disturbances.
  
  
  METHODS
  Ileum was harvested from 6-8 week-old pigs, mounted on Ussing Chambers, and exposed to CRF in the presence or absence of various pharmacologic inhibitors of CRF-mediated signaling pathways. Mucosal-to-serosal flux of 4 kDa-FITC dextran (FD4) and transepithelial electrical resistance (TER) were recorded as indices of intestinal epithelial barrier function.
  
  
  RESULTS
  Exposure of porcine ileum to 0.05-0.5 µM CRF increased (p<0.05) paracellular flux compared with vehicle controls. CRF treatment had no deleterious effects on ileal TER. The effects of CRF on FD4 flux were inhibited with pre-treatment of tissue with the non-selective CRF(1/2) receptor antagonist Astressin B and the mast cell stabilizer sodium cromolyn (10(-4) M). Furthermore, anti-TNF-α neutralizing antibody (p<0.01), protease inhibitors (p<0.01) and the neural blocker tetrodotoxin (TTX) inhibited CRF-mediated intestinal barrier dysfunction.
  
  
  CONCLUSIONS
  These data demonstrate that CRF triggers increases in intestinal paracellular permeability via mast cell dependent release of TNF-α and proteases. Furthermore, CRF-mast cell signaling pathways and increases in intestinal permeability require critical input from the enteric nervous system. Therefore, blocking the deleterious effects of CRF may address the enteric signaling of mast cell degranulation, TNFα release, and protease secretion, hallmarks of IBS and IBD.
authors: College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, United States of America.
authors: Elizabeth L
authors: EL
authors: Overman
authors: Jean E
authors: JE
authors: Rivier
authors: Adam J
authors: AJ
authors: Moeser
mesh_terms: D000818:Animals; D015550:Cell Degranulation / Q000187:drug effects; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology*; D003911:Dextrans; D017615:Enteric Nervous System / Q000187:drug effects / Q000473:pathology; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives; D007082:Ileum / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000293:injuries* / Q000473:pathology / Q000503:physiopathology; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D008970:Molecular Weight; D009500:Neutralization Tests; D062793:Occludin / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D010447:Peptide Hydrolases / Q000378:metabolism; D010539:Permeability / Q000187:drug effects; D011480:Protease Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D034421:Sus scrofa; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D003911:Dextrans; D062793:Occludin; D010446:Peptide Fragments; D011480:Protease Inhibitors; D014409:Tumor Necrosis Factor-alpha; C120841:astressin B; C015219:fluorescein isothiocyanate dextran; D003346:Corticotropin-Releasing Hormone; D010447:Peptide Hydrolases; D016650:Fluorescein-5-isothiocyanate