Contrasting effects of peroxisome-proliferator-activated receptor (PPAR)γ agonists on membrane-associated prostaglandin E 2 synthase-1 in IL-1β-stimulated rat chondrocytes: evidence for PPARγ-independent inhibition by 15-deoxy-∆ 12,14 prostaglandin J 2

Arnaud Bianchi (1) , David Moulin (1) , Sylvie Sébillaud (1) , Meriem Koufany (1) , Marie-Madeleine Galteau (1) , Patrick Netter (1) , Bernard Terlain (1) , Jean-Yves Jouzeau (1)

1 PPIA - Physiopathologie, Pharmacologie et Ingénierie articulaires

Microsomal prostaglandin E synthase (mPGES)-1 is a newly identified inducible enzyme of the arachidonic acid cascade with a key function in prostaglandin (PG)E 2 synthesis. We investigated the kinetics of inducible cyclo-oxygenase (COX)-2 and mPGES-1 expression with respect to the production of 6-keto-PGF 1α and PGE 2 in rat chondrocytes stimulated with 10 ng/ml IL-1β, and compared their modulation by peroxisome-proliferator-activated receptor (PPAR)γ agonists. Real-time PCR analysis showed that IL-1β induced COX-2 expression maximally (37-fold) at 12 hours and mPGES-1 expression maximally (68-fold) at 24 hours. Levels of 6-keto-PGF 1α and PGE 2 peaked 24 hours after stimulation with IL-1β; the induction of PGE 2 was greater (11-fold versus 70-fold, respectively). The cyclopentenone 15-deoxy-∆ 12,14 prostaglandin J 2 (15d-PGJ 2) decreased prostaglandin synthesis in a dose-dependent manner (0.1 to 10 µM), with more potency on PGE 2 level than on 6-keto-PGF 1α level (-90% versus-66% at 10 µM). A high dose of 15d-PGJ 2 partly decreased COX-2 expression but decreased mPGES-1 expression almost completely at both the mRNA and protein levels. Rosiglitazone was poorly effective on these parameters even at 10 µM. Inhibitory effects of 10 µM 15d-PGJ 2 were neither reduced by PPARγ blockade with GW-9662 nor enhanced by PPARγ overexpression, supporting a PPARγ-independent mechanism. EMSA and TransAM ® analyses demonstrated that mutated IκBα almost completely suppressed the stimulating effect of IL-1β on mPGES-1 expression and PGE 2 production, whereas 15d-PGJ 2 inhibited NF-κB transactivation. These data demonstrate the following in IL-1-stimulated rat chondrocytes: first, mPGES-1 is rate limiting for PGE 2 synthesis; second, activation of the prostaglandin cascade requires NF-κB activation; third, 15d-PGJ 2 strongly inhibits the synthesis of prostaglandins, in contrast with rosiglitazone; fourth, inhibition by 15d-PGJ 2 occurs independently of PPARγ through inhibition of the NF-κB pathway; fifth, mPGES-1 is the main target of 15d-PGJ 2 .

Domaines: Rhumatologie et système ostéo-articulaire; Génomique, Transcriptomique et Protéomique [q-bio.GN]

Arnaud Bianchi, David Moulin, Sylvie Sébillaud, Meriem Koufany, Marie-Madeleine Galteau, et al.. Contrasting effects of peroxisome-proliferator-activated receptor (PPAR)γ agonists on membrane-associated prostaglandin E 2 synthase-1 in IL-1β-stimulated rat chondrocytes: evidence for PPARγ-independent inhibition by 15-deoxy-∆ 12,14 prostaglandin J 2. Arthritis Research and Therapy, 2005, 7 (6), pp.R1325-R1337. ⟨10.1186/ar1830⟩. ⟨hal-01715324⟩