Identif ication of New Targets Used by 15-deoxy-delta-12 , 14-Prostaglandin J 2 to Stimulate Skeletal Muscle Cell Proliferation

Introduction: Clinical conduct can influence the healing of injured tissue. Eradication of inflammation seemed a promising strategy to promote musculoskeletal healing until studies showed a delayed/incomplete recovery from partial or complete elimination of inflammation. Endogenous lipid mediators biosynthesized from omega-3 and some from -6 fatty acids are molecules potentially playing important roles in the resolution of inflammation. Using such lipid mediators to treat injuries represents an attractive approach due to their anti-inflammatory and pro-resolving roles. Our goal was to identify the intracellular and/or extracellular targets used by 15-deoxy-delta-12,14Prostaglandin J2(15∆-PGJ2) to stimulate myoblast proliferation. Methods: Expression of D prostanoid (DP) 1 and 2 receptors was evaluated by western blotting. Proliferation of L6 myoblasts incubated with agonists and antagonists of prostaglandin (PG) D2 receptors DP1 and DP2 and of the peroxisome proliferator-activated receptor (PPAR) δ was assessed. Intracellular and extracellular concentrations of 15∆-PGJ2 following L6 cell activation with protease-activated receptor (PAR)-2 agonist were measured by liquid chromatography coupled to tandem mass spectrometry. Results: Both DP1 and DP2 receptors are present in myoblasts. DP1 agonist did not modulate L6 myoblast proliferation, but DP2 and PPARδ agonists induced an increase. DP1 and DP2 antagonists both significantly inhibited 15∆-PGJ2-induced stimulating effect of L6 cell proliferation (60% and 75%, respectively). 15∆-PGJ2was present in the intracellular and extracellular compartments under basal conditions, but was not modulated by PAR-2 receptor activation. Conclusion: L6 muscle cell can produce 15∆-PGJ2 and its effect on cell proliferation likely relies on both DP1 and DP2 receptor activation.