Probiotika erhalten die epitheliale Barrierefunktion in der akuten DSS-Kolitis der Maus

Abstract

Background: In inflammatory bowel diseases (IBD) intestinal permeability is increased. The effect of VSL#3, a mixture of 8 probiotic bacteria, on the epithelial barrier was studied in a murine model of colitis. Material and Methods: Three groups, each with 14 balb/c mice, were studied: healthy controls, acute colitis + placebo, and acute colitis + 15 mg VSL#3 daily (induction of colitis with Dextrane-Sodium-Sulphate (DSS) 3.5 % in drinking water for 7 days; placebo/VSL#3 via gastric tube once daily). The inflammation was assessed by a daily disease activity index (DAI) and a histological inflammation score. Colonic permeability to Evans Blue in vivo was measured (extinction/gram colonic tissue). Epithelial apoptotic ratio was assessed by immunofluorescence for cleaved caspase 3. The expression of epithelial tight junction and adherens junction proteins was studied by immunofluorescence and Western blot. Results: VSL#3 reduced the DAI on days 5–7 vs. placebo (day 7: healthy controls 0 ± 0, DSS + placebo 8.4 ± 0.4, DSS + VSL#3 5.4 ± 0.9; p = 0.012), and histological inflammation scores (healthy controls 0.9 ± 0.3, DSS + placebo 14.6 ± 2.5, DSS + VSL#3 8.4 ± 1.8; p = 0.011). In DSS colitis + placebo, colonic permeability was increased compared to controls (5.7 ± 1.7 vs. 0.4 ± 0.1; p < 0.001), whereas this increase was prevented by VSL#3 (0.3 ± 0.1; p = 0.003 vs. DSS + placebo, N.S. vs. healthy controls). VSL#3 prevented the DSS induced increase of epithelial apoptotic ratio (healthy controls 1.58 ± 0.01/1000 cells, DSS + placebo 13.35 ± 1.29/1000 cells, DSS + VSL#3 1.67 ± 0.10/1000 cells; p = 0.012 vs. DSS + placebo, N.S. vs. controls). In DSS colitis + placebo, immunofluorescence revealed a reduced apical expression of tight junction proteins occludin, ZO-1, claudin-1, and -5, whereas VSL#3 therapy preserved the physiological expression pattern. No changes were observed for claudin-3, and for adherens junction proteins β-catenin and E-cadherin in the three groups. Western blots showed a quantitatively reduced expression of occludin, claudin-1, -2 and -4 for DSS + placebo. VSL#3 prevented this decrease in expression. Conclusion: The probiotic mixture VSL#3 preserves the epithelial barrier by preventing the redistribution and the decrease in expression of tight junction proteins, and by reducing the epithelial apoptotic ratio. This may lead to the anti-inflammatory effect observed in this IBD model.