Effects and mechanism of anti-tumor necrosis factor-α on intestinal permeability in dextran sulfate sodium induced colitis mice

Objective To investigate the effect and mechanism of anti-tumor necrosis factor (TNF)-α on the intestinal mucosal permeability in dextran sulfate sodium (DSS) induced colitis mice.Methods Eighteen C57BL/6J mice were evenly divided into healthy control group,model group and anti-TNF-α treated group.The mice of model group and anti-TNF-α treated group were fed with 5％DSS solution for 7 days.The mice of anti-TNF-α treated group were injected anti-TNF-α (5 mg/kg)intraperitoneally on the first and fourth day; control group and model group were substituted with equal volume saline injection.The mice were sacrificed at 7 days after modeling.The disease activity index (DAI) score was evaluated everyday.The intestinal permeability was examined by Evan′s blue (EB) method and FITC-dextran (FITC-D) method.The colon tissue was collected for observation under microscope and histological index (HI).The small intestinal tissues were examined under electron microscope.The 10％ homogenate of colon and intestinal mucosa was prepared,the activity of myeloperoxidase (MPO),the content of TNF-α and epithelial myosin light chain kinase (MLCK) concentration were determined with kits respectively.The expression of MLCK in intestinal mucosa was tested by Western blot assay.Single factor of variance between groups were analyzed.Results Compared with control group,the DAI of model group increased daily.Compared with model group,the DAI of anti-TNF-α treated group improved.In model group,mice intestinal epithelial cells junctional complex shortened and widened and the cell gap expanded.In anti-TNF-α treated group,the connection structure of mice intestinal epithelial cells was tighter.The activity of HI and MPO and the content of TNF-α of model group were higher than those of control group (P ＝ 0.008,0.006 and 0.001,respectively),all of those of anti-TNF-α treated group were lower than those of model group (P=0.004,0.008 and 0.005,respectively).The F value of three groups was 131.98,218.28 and 58.93,respectively.The contents of EB in mice intestinal wall and serum FITC-D of model group were higher than those of control group (P=0.003 and 0.010),and those of anti-TNF-α treated group were lower model group (P＝0.001 and 0.009).The F value of three groups was 69.36 and 17.96.The MLCK concentration in mice intestinal mucosa of model group [(71.10± 7.52) ng/g] was higher than that of control group [(18.56±9.92) ng/g,P＜0.01],that of anti-TNF-α treated group [(37.56±15.84) ng/g] was lower than model group (P=0.008),and the difference among these three groups was statistically significant (F＝ 17.23).The Western blot results indicated the expression of MLCK in intestinal mucosa of model group was higher than that of control group,and that of anti-TNF-α treated group was lower than model group.Conclusions Anti-TNF-α play an important role in improving colitis,and the intestinal mucosal permeability.The mechanism may be related with the regulation of MLCK expression. Key words: Tumor necrosis factor-alpha; Antibodies; Colitis; Intestinal mucosa; Cell membrane permeability; Myosin-light-chain kinase