Phospholipase D2 activity suppresses hydrogen peroxide-induced apoptosis in PC12 cells

Phospholipase D (PLD) plays an important role as an effector in the membrane lipid-mediated signal transduction. However, the precise physiological functions of PLD are not yet well understood. In this study, we examined the role of PLD activity in hydrogen peroxide (H₂O₂)-induced apoptosis in rat pheochromocytoma (PC12) cells. Treatment of PC12 cells with H₂O₂ resulted in induction of apoptosis in these cells, which is accompanied by the activation of PLD. This H₂O₂-induced apoptosis was enhanced remarkably when phosphatidic acid production by PLD was selectively inhibited by pre-treating the PC12 cells with 1-butanol. Expression of PLD2, but not of PLD1, correlated with increased H₂O₂-induced PLD activity in a concentration- and time-dependent manner. Concomitant with PLD activation, the PLD2 activity suppressed H₂O₂-induced apoptosis in PC12 cells. Expression of PLD2 lipase-inactive mutant (K758R) had no effect on either PLD activity or apoptosis. PLD2 activity also suppressed H₂O₂-induced cleavage and activation of caspase-3. Taken together, the results suggest that PLD2 activity is specifically up-regulated by H₂O₂ in PC12 cells and that it plays a suppressive role in H₂O₂-induced apoptosis.