15-Deoxy-δ12,14-prostaglandin J2 protects PC12 cells from LPS-induced Cell death through Nrf2 pathway in PPAR-γ dependent manner

Introduction: The inflammatory response requires a coordinated integration of various signaling pathway including cyclooxygenase (COX). COX catalyzes the formation of prostaglandins from arachidonic acid. Among prostaglandins, 15-Deoxy-D12, 14-prostaglandin J2 (15d-PGJ2), an endogenous ligand of Peroxisome proliferator-activated receptor-gamma (PPAR-γ), has been demonstrated to have anti-inflammatory actions. In this study, we investigated whether 15d-PGJ2 as a PPAR-γ ligand could exert neuroprotective effects in rat pheochromocytoma (PC 12) cells in PPAR-γ dependent manner. Methods: In our experiment, using PC12 cells, the levels of NF-KB, Nr£2, γ-glutamylcysteine synthetase (γ-GCS), hemeoxygenase (HO-1) and apoptosis factors were determined using Western blot in different groups. Also cell viability was determined by the conventional MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide) reduction assay and two staining involved Hoechst staining and Acridine Ordange/Ethidiume Bromide staining respectively. Results: Our results show that NS-398, a selective COX-2 inhibitor and 15d-PGJ2, a natural potent ligand of PPAR-γ, were neuroprotective through modulation of at least three different, but related pathways and molecules, including NF-KB and Nrf2 signaling pathway. Our data showed that 15d-PGJ2 and NS-398 induced Nrf2 signaling pathway and its downstream factors such as HO-1 and γ-GCS, while 15d-PGJ2 and NS-398 decreased NF-KB level. Interestingly, the observed protective effects were mediated through PPAR-γ-dependent mechanisms, as they reversed by GW9662, an irreversible antagonist of PPAR-γ receptor. Discussion: Thus we conclude that 15d-PGJ2 as well as NS-398 exert anti cell death effect in a PPAR-y dependent mechanisms.