Stress-induced disruption of colonic epithelial barrier: role of interferon-γ and myosin light chain kinase in mice

Abstract

Background & Aims : Stressful life events are supposed to be involved in various diseases such as inflammatory bowel diseases and irritable bowel syndrome. Impairment of the intestinal epithelial barrier function is a suspected consequence of stress, but the underlying mechanisms remain unclear. This study aimed to determine the mechanisms through which stress modulates the colonic epithelial barrier. Methods : Cytokine messenger RNA (mRNA) expression was evaluated in murine colon, liver, and spleen by competitive reverse-transcription polymerase chain reaction after 1–4 days of daily 2-hour stress sessions. Colonic paracellular permeability was measured as the in vivo lumen-to-blood ratio of 51Cr-ethylenediaminetetraacetic acid. The effect of a myosin light chain (MLC) kinase inhibitor (ML-7) was assessed on stress-induced interferon (IFN)-γ mRNA expression and colonic epithelial barrier impairment, and MLC phosphorylation was determined by immunoblot. Finally, the incidence of repeated stress sessions on bacterial translocation was determined. Results : Repeated stress induced an overexpression of colonic IFN-γ. In the liver, higher levels of IFN-γ, interleukin (IL)-4, and IL-10 mRNAs were detected and were associated with bacterial translocation, inflammation, and apoptosis. Stress increased colonic permeability of control mice, but not of SCID and IFN-γ-deficient mice. ML-7 inhibited the stress-induced increased permeability, bacterial translocation, and cytokine overexpression in the liver and restored a normal histology. Larger amounts of phosphorylated MLC were detected in stressed animals. Conclusions : Repeated stress sessions drive organ-specific cytokine expression patterns and alter colonic mucosal barrier functions associated with bacterial translocation. This effect depends on the presence of CD4 + T cells and requires IFN-γ production and MLC phosphorylation.