Pregnane X receptor activation ameliorates DSS-induced inflammatory bowel disease via inhibition of NF-kappaB target gene expression.

Pregnane X receptor (PXR) expression was shown to be protective in inflammatory bowel disease (IBD). However, the mechanism by which PXR provides protection remains unclear. Wild-type and Pxr-null mice were treated with the PXR agonist pregnenolone-16alpha-carbonitrile or vehicle and administered 2.5% dextran sulfate sodium (DSS) in drinking water to induce IBD. Typical clinical symptoms were evaluated on a daily basis. In vivo intestinal permeability assays and proinflammatory cytokine analysis were performed. PXR agonist-treated mice were protected from DSS-induced colitis compared with vehicle-treated mice, as defined by body weight loss, diarrhea, rectal bleeding, colon length, and histology. Pregnenolone-16alpha-carbonitrile did not decrease the severity of IBD in Pxr-null mice. PXR agonist treatment did not increase epithelial barrier function but did decrease mRNA expression of several NF-kappaB target genes in a PXR-dependent manner. The present study clearly demonstrates a protective role for PXR agonist in DSS-induced IBD. The data suggest that PXR-mediated repression of NF-kappaB target genes in the colon is a critical mechanism by which PXR activation decreases the susceptibility of mice to DSS-induced IBD.