Influence of the peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist, rosiglitazone and antagonist, biphenol-A-diglicydyl ether (BADGE) on the course of inflammation in the experimental model of colitis in rats.

PPAR-γ plays a role in the development of immune response, particularly in inflammation. The inflammatory reaction may be stimulated or suppressed by the presence of PPAR ligands. Some researchers suggest positive influence of the PPAR-γ agonist on suppression of the intestinal inflammatory process, yet there has not been much evidence showing that the antagonist of PPAR-γ can affect the inflammatory process. The aim of the present study was to define the mechanism by which PPAR-γ ligands affect the course of experimentally induced colitis in rats. Colitis was induced in rats by rectal administration of TNBS (trinitrobenzene sulfonate). Rosiglitazone was administrated to animals at the dose of 8 mg/kg four times via an intra-gastric probe. Biphenol-A-diglicydyl ether (BADGE) was administrated intraperitoneally at the dose of 120 mg/kg, three times every second day. One group of animals received rosiglitazone together with BADGE before the induction of inflammation. Histological and ELISA examinations of large intestine samples were performed. Levels of IL-1β, IL-6, TNF-α cytokines were determined in serum and homogenates. Rats exposed to rosiglitazone had higher body weight yet lower large intestine weight. Histological findings showed less ulceration, lower expression of crypts' loss and smaller oedema. Animals, which did not receive rosiglitazone, and those receiving it together with BADGE, developed more severe inflammatory changes. Rosiglitazone decreased the expression of inflammatory cytokines, such as IL-6 and TNF-α, both in serum and in intestinal homogenates. BADGE used with TNBS did not increase the expression of inflammatory cytokines; however, applied together with rosiglitazone, it caused inflammation similar to that observed among rats with experimentally induced colitis. Rosiglitazone reduces inflammation by decreasing the expression of IL-6 and TNF-α. BADGE administered with rosiglitazone blocks the activity of PPAR-γ and abolishes the protective effects of PPAR-γ agonist.