Peroxisome proliferator-activated receptor gamma activation promotes intestinal barrier function by improving mucus and tight junctions in a mouse colitis model.

BACKGROUND AND AIMS: Defects in mucus and intestinal epithelia can lead to intestinal inflammation in colitis. Reduced peroxisome proliferator-activated receptor gamma (PPARγ ) in the mucosa may contribute to inflammation. However, the roles of PPARγ in the intestinal barrier remain poorly understood.

METHODS: Chronic colitis was induced in C57BL/6 mice by administration of dextran sulfate sodium (DSS) for 27 days. Three days before DSS treatment, mice were treated with the PPARγ agonist rosiglitazone (Ro) orally at 20 mg kg-1  day-1 .

RESULTS: The colitis based on disease activity index and colonic histopathology was significantly ameliorated in the DSS + Ro group. Additionally, mice in the DSS + Ro group had a thicker mucous layer than those in DSS + NS group, and muc2 mRNA expression was elevated significantly along with the mouse atonal homolog, SAM-pointed domain-containing Ets-like factor, and anterior gradient 2 genes. Moreover, tight junctions were up-regulated, whereas long myosin light chain kinase and phosphorylation of the myosin II light chain were lower in DSS + Ro mice. Similarly, after HT-29 and Caco-2 cells were treated by LPS or LPS + Ro, PPARγ activation by Ro could effectively improve the intestinal barrier, including intestinal mucus and tight junctions.

CONCLUSIONS: Our results demonstrate that activated PPARγ could effectively promote intestinal mucus integrity by increasing the number of goblet cells, the glycosylation of mucins, and tight junctions via an MLCK-dependent mechanism.