Effect of PPARγ agonists on IL-1β-induced prostaglandins levels, COX-2 and mPGES-1 mRNAs. After 4 hours of pretreatment with 10 μM 15-deoxy-Δ12,14prostaglandin J2 (15d-PGJ2) or rosiglitazone, chondrocytes were incubated with 10 ng/ml IL-1β for 12 or 24 hours. (a) PGE2 and 6-keto-PGF1α levels assayed by ELISA in culture supernatant; (b) relative abundances of cyclo-oxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1) mRNAs, analysed by real-time PCR and normalized to S29 mRNA (c) COX-2 and mPGES-1 protein levels assessed by western blotting and normalized to β-actin level. Results are expressed as means ± SD for at least three independent experiments. Statistically significant differences (P < 0.05): *, comparison with non-stimulated controls; #, comparison with IL-1β-stimulated cells.