Purpose: The goal of this study was to identify the mechanisms by which 15-deoxy-Delta(12,14)-prostaglandin J(2) (dPGJ(2)) protects RPE cells from oxidative injury.
Methods: Cell viability was determined by MTT assay. Protein expression and activation of signaling molecules were detected by Western blot. Reduced glutathione (GSH) was determined by a colorimetric assay kit. PPARgamma expression was knockdown by small interfering (si)RNA technique.
Results: dPGJ(2) protected ARPE19 cells from oxidative injury, whereas the synthetic PPARgamma agonists AGN195037 and rosiglitazone had no effect. PPARgamma knockdown also did not affect dPGJ(2)'s protective activity. dPGJ(2) upregulated GSH synthesis via induction of glutamylcysteine ligase. GSH depletion sensitized cells to oxidative stress and completely reversed the protective effect of dPGJ(2). dPGJ(2) activated ERK, JNK, and p38; GSH induction by dPGJ(2) depended partially on JNK and p38. In addition, dPGJ(2) significantly extended hydrogen peroxide-induced activation of JNK and p38, but not of Akt. Inhibition of MEK, JNK, and p38 abolished dPGJ(2)'s protection of ARPE19 cells from oxidative injury, whereas inhibiting PI3K/Akt pathway failed to affect dPGJ(2)'s protective effect. Heme oxygenase-1 was strongly induced by dPGJ(2) but was not associated with protection.
Conclusions: Independent of its PPARgamma activity, dPGJ(2) protected cells from oxidative stress by elevating GSH and enhancing MAPK activation. Thus, dPGJ(2) may delay the development of dry-type age-related macular degeneration.