Affiliations: Laboratoire de Physiopathologie et Pharmacologie Articulaires, UMR 7561 CNRS-UHP, Nancy, France
Note: [] Address for correspondence: Jean-Yves Jouzeau, PharmD, PhD, Laboratoire de Physiopathologie et Pharmacologie Articulaires, UMR 7561 CNRS-UHP, Avenue de la forêt de Haye, BP 184, 54505 Vandœ uvre-Lès-Nancy, France. Tel.: +33 3 83 68 39 50; Fax: +33 3 83 68 39 59; E-mail: [email protected].
Abstract: In response to inflammatory cytokines, chondrocytes and synovial fibroblasts produce high amounts of prostaglandins (PG) which self-perpetuate locally the inflammatory reaction. Prostaglandins act primarily through membrane receptors coupled to G proteins but also bind to nuclear Peroxisome Proliferator-Activated Receptors (PPARs). Amongst fatty acids, the cyclopentenone metabolite of PGD2, 15-deoxy-$\Delta\tsup{12,14}$PGJ2 (15d-PGJ2), was shown to be a potent ligand of the PPARγ isotype prone to inhibit the production of inflammatory mediators. As the stimulated synthesis of PGE2 originates from the preferential coupling of inducible enzymes, cyclooxygenase-2 (COX-2) and membrane PGE synthase-1 (mPGES-1), we investigated the potency of 15d-PGJ2 to regulate prostaglandins synthesis in rat chondrocytes stimulated with interleukin-1β (IL-1β). We demonstrated that 15d-PGJ2, but not the high-affinity PPARγ ligand rosiglitazone, decreased almost completely PGE2 synthesis and mPGES-1 expression. The inhibitory potency of 15d-PGJ2 was unaffected by changes in PPARγ expression and resulted from inhibition of NF-κB nuclear binding and IκBα sparing, secondary to reduced phosphorylation of IKKβ. Consistently with 15d-PGJ2 being a putative endogenous regulator of the inflammatory reaction if synthesized in sufficient amounts, the present data confirm the variable PPARγ-dependency of its effects in joint cells while underlining possible species and cell types specificities.
