Vol. 63, Issue 3, 607-616, March 2003

Activation of p38 Mitogen-Activated Protein Kinase and Activator Protein-1 during the Promotion of Neurite Extension of PC-12 Cells by 15-Deoxy-^12,14-prostaglandin J₂

Kyung Mi Jung, Ki Sook Park, Jae Ho Oh, Soo Youn Jung, Ki Hwa Yang, Youn Sook Song, Dong Ju Son, Young Hyun Park, Yeo Pyo Yun, Myung Koo Lee, Ki Wan Oh, and Jin Tae Hong

College of Pharmacy, Chungbuk National University, Chungbuk, Korea (Y.S.S., Y.P.Y., M.K.L., K.W.O., J.T.H.); National Institute of Toxicological Research, Korea Food and Drug Administration, Seoul, Korea (K.M.J., K.S.P., J.H.O., S.Y.J., K.H.Y.); and College of Natural Sciences, Soonchunhyang University, Chungnam, Korea (D.J.S., Y.H.P.)

15-Deoxy-^12,14-prostaglandin J₂ (15-deoxy-PGJ₂), a naturally occurring ligand, activates the peroxisome proliferator-activated receptor- (PPAR-). Activation of PPAR- has been found to induce cell differentiation in such cells as adipose cells and macrophages. Herein, we investigated whether 15-deoxy-PGJ₂ has neuronal cell differentiation and possible underlying molecular mechanisms. Dopaminergic differentiating PC-12 cells treated with 15-deoxy-PGJ₂ (0.2 to 1.6 µM) alone showed measurable neurite extension and expression of neurofilament, a marker of cell differentiation. However, a much greater extent of neurite extension and expression of neurofilament was observed in the presence of NGF (50 ng/ml). In parallel with its increasing effect on the neurite extension and expression of neurofilament, 15-deoxy-PGJ₂ enhanced NGF-induced p38 MAP kinase expression and its phosphorylation in addition to the activation of transcription factor AP-1 in a dose-dependent manner. Moreover, pretreatment of 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(pyridyl)1H-imidazole (SB203580), a specific inhibitor of p38 MAP kinase, inhibited the promoting effect of 15-deoxy-PGJ₂ (0.8 µM) on NGF-induced neurite extension. This inhibition correlated well with the ability of SB203580 to inhibit the enhancing effect of 15-deoxy-PGJ₂ on the expression of p38 MAP kinase and activation of AP-1. The promoting ability of 15-deoxy-PGJ₂ did not occur through PPAR- because synthetic PPAR- agonist and antagonist did not change the neurite-promoting effect of 15-deoxy-PGJ₂. In addition, contrast to other cells (embryonic midbrain and neuroblastoma SK-N-MC cells), PPAR- was not expressed in PC-12 cells. Other structure-related prostaglandins (PGD₂ and PGE₂) acting via a cell surface G-protein-coupled receptor (GPCR) did not increase basal or NGF-induced neurite extension. Moreover, GPCR (PGE₂ and PGD₂ receptors) antagonists did not alter the promoting effect of 15-deoxy-PGJ₂ on neurite extension and activation of p38 MAP kinase, suggesting that the promoting effect of 15-deoxy-PGJ₂ may not be mediated by GPCR either. These data demonstrate that activation of p38 MAP kinase in conjunction with AP-1 signal pathway may be important in the promoting activity of 15-deoxy-PGJ₂ on the differentiation of PC-12 cells.