Peroxisome proliferator activated receptor gamma in colonic epithelial cells protects against experimental inflammatory bowel disease.

INTRODUCTION

Peroxisome proliferator activated receptor gamma (PPARgamma) is expressed in epithelial cells, macrophage, and T and B lymphocytes. Ligand induced activation of PPARgamma was reported to attenuate colitis activity but it is not clear whether this protection is mediated by epithelial or leucocyte PPARgamma.

METHODS

Mice with targeted disruption of the PPARgamma gene in intestinal epithelial cells, generated using a villin-Cre transgene and floxed PPARgamma allele and designated PPARgamma(DeltaIEpC), were compared with littermate mice having only the PPARgamma floxed allele with no Cre transgene that expressed PPARgamma in the gut, designated PPARgamma(F/F). Colitis was induced by administering dextran sodium sulphate (DSS) and the two mouse lines compared for typical symptoms of disease and expression of inflammatory cytokines.

RESULTS

PPARgamma(DeltaIEpC) mice displayed reduced expression of the PPARgamma target genes ADRP and FABP in the gut but were otherwise normal. Increased susceptibility to DSS induced colitis, as defined by body weight loss, colon length, diarrhoea, bleeding score, and altered histology, was found in PPARgamma(DeltaIEpC) mice in comparison with PPARgamma(F/F) mice. Interleukin (IL)-6, IL-1beta, and tumour necrosis factor alpha mRNA levels in colons of PPARgamma(DeltaIEpC) mice treated with DSS were higher than in similarly treated PPARgamma(F/F) mice. The PPARgamma ligand rosiglitazone decreased the severity of DSS induced colitis and suppressed cytokine production in both PPARgamma(F/F) and PPARgamma(DeltaIEpC) mice.

CONCLUSIONS

These studies reveal that PPARgamma expressed in the colonic epithelium has an endogenous role in protection against DSS induced colitis and that rosiglitazone may act through a PPARgamma independent pathway to suppress inflammation.