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

Abstract

Background and Aims 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. Methodology 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. Conclusion 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.

Mast Cells and Irritable Bowel Syndrome: From the Bench to the Bedside

“…62,84 Plenty of work has been done to verify the concept that MCs contribute to stress induced gut dysfunction. For example, MCs mediate stress induced intestinal barrier disruption [85][86][87] and visceral hypersensitivity 82,88,89 due to the release of tryptase, TNF-α, 86 and histamine. 82 Peripheral administration of H 1 R antagonists fexofenadine and ebastine are capable of reversing post stress visceral hypersensitivity in rats.…”

“…91 Recently, evidence supported that stress induced CRF, acting on the CRF1 and CRF2 receptors, should be the key factors in MCs degranulation. 62,85,86 Stress triggers the increase in intestinal paracellular permeability via mast cell dependent release of proteases, which could be reproduced by peripheral administration of CRF, and blocked by CRF 1/2 receptor antagonist, mast cell stabilizers, and protease inhibitors. 86 …”

Role of Corticotropin-releasing Factor in Gastrointestinal Permeability

“…Tumor necrosis factor- (TNF-) has been shown to increase intestinal permeability through nuclear factor-kappa B activation in association with nuclear factor-kappa B-dependent downregulation of zona occludens protein-1 expression and alteration in junctional localization in Caco-2 cells, 85 and through myosin light chain kinase phosphorylation. 86 More recently, using a porcine ex vivo intestinal model, Overman et al 87 found that CRF increased intestinal paracellular permeability via mast cell dependent release of TNF- and proteases. On the other hand, the tryptase released by mast cells upon activation has been shown to induce TJs disassembly through the activation of proteinase-activated receptor-2 of the epithelial cells.…”

Nerve growth factor and diarrhea-predominant irritable bowel syndrome (IBS-D): a potential therapeutic target?

“…2), psychophysiological stress (such as adverse life events, catching cold, and intestinal infection) activates the hypothalamic-pituitary-adrenal (HPA) axis (Mayer, 2000;Chang et al, 2009;Kennedy et al, 2014). The central and intestinal corticotropin releasing factor (CRF) increases and activates intestinal MCs (Barreau et al, 2007;Overman et al, 2012). Activated MCs degranulate and release mediators such as NGF and tryptase.…”