CRF Induces Intestinal Epithelial Barrier Injury via the Release of Mast Cell Proteases and TNF-α

Elizabeth L Overman,Adam J Moeser,Jean E Rivier,Jörn Karhausen

doi:10.1371/journal.pone.0039935

Elizabeth L Overman, Adam J Moeser + Show 2 more

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https://doi.org/10.1371/journal.pone.0039935

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Abstract

Background and AimsPsychological 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.MethodologyIleum 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.ResultsExposure 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 CRF1/2 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.ConclusionThese 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.

Highlights

The gastrointestinal barrier, consisting primarily of intestinal epithelial cells, mucus layer, and sub-epithelial immune cells, selectively controls the access of the immense luminal load of antigens and resident microorganism to the underlying lamina propria immune tissues [1]
Blocking the deleterious effects of corticotropin releasing factor (CRF) may address the enteric signaling of mast cell degranulation, TNFa release, and protease secretion, hallmarks of irritable bowel syndrome (IBS) and inflammatory bowel diseases (IBD)
Mast cells are capable of releasing a variety of proinflammatory mediators, including de novo synthesized mediators such as prostaglandins, leukotrienes, and cytokines or preformed granule-housed mediators including histamine, serine proteases, tryptase, chymase, and cytokines [18], which profoundly influence intestinal epithelial barrier function; the mast cell mediators and signaling pathways that are responsible for CRF-mediated intestinal barrier dysfunction have not been fully elucidated

Summary

Introduction

The gastrointestinal barrier, consisting primarily of intestinal epithelial cells, mucus layer, and sub-epithelial immune cells, selectively controls the access of the immense luminal load of antigens and resident microorganism to the underlying lamina propria immune tissues [1] It is well-known that intestinal barrier function can be adversely affected by acute or chronic psychological stress, resulting in increased intestinal permeability [2,3,4,5,6], a critical event in the onset of clinical symptoms of GI disorders including irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) [7,8,9,10]. 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

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