| Balckground The intestinal mucosal barrier plays a important role in the body’s protectionagainst luminal pathogens and antigenic molecules.However, the barrier is frequentlydisrupted in inflammatory bowel disease (IBD) and this has been proposed to play a pivotalrole in disease pathogenesis and reactivation. Recent advances have shown that barrierdysfunction may precede clinical evidence of inflammatory bowel disease and may serve asa marker of impending disease reactivation. This barrier is mainly composed of intestinalepithelium which including the apical enterocyte membrane and the epithelial tight junction(TJ), however, TJ opening is the major limiting factor of the paracellular pathway, And TJopening is driven by myosin light chain (MLC) phosphorylation, which depends on MLCK activation.in addition，In vitro studies also show that cytokine-induced epithelial barrierdysfunction can be mediated by increased MLCK expression and subsequent MLCphosphorylation..Anti-TNF-α has been expected as a promising medicine for Crohn’sdisease.Furthermore,Infliximab has been approved for the therapy of ulcerativecolitis.Studies carried out in natural and experimental models of colitis have provided someevidence of pharmacological success with TNF-α mab in reducing diseaseseverity.Thus,The mechanisms of barrier dysfunction and MLCK-driven pathway havegreat potential for guiding the development of novel drugs for treatment of UC.For example,Infliximab (anti-TNF-α) has been used to treat UC. These agents significantly improve theinflammation in the intestine by decreasing the activation of MLCK both in vitro and vivo.However, the therapeutic effect of anti-tumor necrosis factor has never been estimated inUC patients. the aim of these studies, therefore, was to determine whether anti-tumornecrosis factor improving intestinal permeability to correction intestinal epithelial barrierdysfunction in colitis models, by inhibiting MLC phosphorylation to improve intestinalfunction.Aim To investigate the effect of anti-tumor necrosis factor(TNF) treatment on the intestinalmucosal permeability in dextran sulfate sodium (DSS)-induced colitis and to determine itsassociated mechanism.Methods Experimental colitis was induced in C57BL/6J mice by the administration of5%DSS. Anti-TNF-α was injected intraperitoneally at doses of5mg/kg on twice a week(thefirst day and the fourth day). The disease activity index (DAI) score was evaluated, and thecolon tissue was collected for the assessment of histological changes.The activity ofmyeloperoxidase (MPO),and the levels of TNF-α，interferon-γ(IFN-γ)， interleukin-13（IL-13） and interleukin-17（IL-17） in the colon were determined. The small intestinalmucosal was ultrastructurally examined with transmission electron microscopy, and theintestinal permeability was assayed using the amount of FITC-dextran(FD-4) permeating into blood and Evans blue(EB) permeating into the intestinal wall.As well as mucosa fromthe small intestine was collected to determine epithelial myosin light chain kinase (MLCK)protein expression and enzymatic activity.Results Anti-TNF-α was found effective in reducing the DAI score and the histologicalindex (HI) score, and decreasing the activity of MPOã€levels of TNF-α, IFN-γ, IL-13andIL-17in colitis mice.The small intestinal mucosal injury was ameliorated by anti-TNF-αand the amount of FD-4permeating into blood and EB permeating into the intestinal wallwere decreased by anti-TNF-α in colitis mice.Moreover the small intestinal epithelialMLCK protein expression and enzymatic activity were downregulated by anti-TNF-α.Conclusion Anti-TNF-α showed a significant anti-colitis effect in colitis mice.Themechanism of this effect is partly associated with immunoloregulation and inhibit theepithelial MLCK protein expression and enzymatic activity, which resulting in amelioratedintestinal mucosal permeability. |
