Abstract
Intestinal epithelial barrier is affected by multiple factors, such as tumour necrosis factor-α (TNF-α). Plasma concentration of TNF-α is higher in patients with Crohn’s disease (CD) than healthy controls (HC) and correlates positively with disease activity. This study aimed to determine the effect of plasma from active, inactive CD patients on intestinal barrier function and to investigate the underlying mechanism. Plasma samples were collected from CD patients and HC. 3D Caco-2 cysts were treated with plasma or TNF-α, with or without pre-incubation of adalimumab (a monoclonal antibody that antagonizes TNF-α) or JNK inhibitor SP600125. The results demonstrated that exposure of the cysts to plasma from CD patients resulted in enhanced paracellular permeability in a disease activity-dependent manner. Compared to HC, active CD plasma decreased ZO-1 and OCCLUDIN expression on mRNA and protein levels, and led to an increased JNK phosphorylation. Pre-incubation with adalimumab or SP600125 ameliorated TJ disruption and barrier dysfunction induced by plasma from CD patients. These results indicate that plasma from CD patients is able to induce epithelial barrier disruption, in part through TNF-α induced TJs modulation. The data also demonstrate an involvement of MAPK pathway, in particular the JNK isoform, in CD patient plasma-induced barrier dysfunction.
Highlights
Permeability could predict Crohn’s disease (CD) disease course[6,12,13], while some even define IBD as an impaired intestinal barrier disease[14]
In the present study, using a 3D Caco-2 cell culture model, we evaluated the effects of plasma from patients with Crohn’s disease (CD) on epithelial barrier function
We demonstrated that plasma from active and inactive CD patients, compared to healthy controls, triggers a disruption of the epithelial tight junctions, which results in increased paracellular permeability, while the effect of plasma from inactive CD patients was less pronounced as compared to the active
Summary
Permeability could predict CD disease course[6,12,13], while some even define IBD as an impaired intestinal barrier disease[14]. In vitro studies using intestinal epithelial monolayers revealed that TNF-α induces barrier dysfunction through a mechanism that is primarily mediated by myosin light chain kinase (MLCK) activation[26]. This notion is further supported by in vivo studies demonstrating an improved intestinal permeability in patients responding to anti-TNF therapy[27,28]. The majority of previous research on the role of MAPK in CD has focused on its involvement in the inflammatory responses and cross-talk to other inflammatory pathways, such as NF-kB and Janus kinase/STAT signalling[29] Their function in mediating intestinal barrier defects has not been fully elucidated. A three-dimensional (3D) Caco-2 cell culture model was employed, which more accurately recreates the features of intestinal epithelium in vivo and offers a great promise to examine the responsiveness and underlying mechanisms of epithelial cells to pathophysiological stimuli
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