Genomic analysis of sulfasalazine effect in experimental colitis is consistent primarily with the modulation of NF-kappaB but not PPAR-gamma signaling.

OBJECTIVE: Sulfasalazine (SAZ) is a widely used drug in inflammatory bowel disease patients but its mechanism of action is incompletely understood. The objective of our study was to further characterize SAZ mechanism by studying its effect on the colonic transcriptome in a suitable preclinical model of inflammatory bowel disease.
METHODS: The trinitrobenzenesulfonic acid model of colitis in rats was used. The effect of SAZ on mRNA expression was assessed with Affymetrix Rat Expression 230 2.0 arrays used in triplicate (sextuplicate for controls), validated in separate samples with quantitative reverse-time PCR analysis. Some nongenomic experiments were also carried out.
RESULTS: SAZ (500 mg/kg) had a marked anti-inflammatory effect as expected, which was correlated with a dramatic impact on colonic gene expression. In addition to immune/inflammatory genes, SAZ responsive genes were involved in distinct metabolic and signaling pathways. The effect of sulfasalazine was generally of normalization of colitis-modulated genes to control levels, with very few exceptions. Postgenomic validation showed an excellent correlation with microarray data and seemed to be slightly more sensitive. SAZ generally modulated the expression of nuclear factor-kappaB-driven genes. SAZ was also shown to inhibit IkappaB-alpha phosphorylation in rat primary splenocytes and in HT29 and IEC18 cells. In contrast, SAZ had only a modest effect on peroxisome proliferator-activated receptor (PPAR)-gamma-regulated genes and it was confirmed to induce PPAR-gamma in enterocytes but not splenocytes.
CONCLUSION: Mechanistically, our data are consistent primarily with nuclear factor-kappaB inhibition, and there is little evidence of a prominent role of activation of PPAR-gamma receptors or antioxidative actions.