Possible involvement of cytosolic phospholipase A 2 in cell death induced by 1-methyl-4-phenylpyridinium ion, a dopaminergic neurotoxin, in GH3 cells

Abstract

Previously we reported that 1-methyl-4-phenylpyridinium ion (MPP +), a dopaminergic neurotoxin, induced apoptosis of GH3 cells established from rat anterior pituitary. In the present study, the role of MPP + along with that of other apoptotic factors such as Ca 2+ and H 2O 2 in cell death was examined. Ionomycin induced DNA fragmentation and lactate dehydrogenase (LDH) leakage in GH3 cells. H 2O 2 also induced LDH leakage. Co-addition of MPP +, in conditions where MPP + had no effect by itself, enhanced ionomycin- and H 2O 2-induced cell death. Because the stimulation of phospholipase A 2 (PLA 2) causing arachidonic acid (AA) release has been proposed to be involved in neuronal cell death, the effect of MPP + on AA release in GH3 cells was investigated. MPP + treatment for 8 h enhanced ionomycin- and H 2O 2-stimulated AA release mediated by activation of cytosolic PLA 2 in a concentration-dependent manner, although MPP + by itself had no effect on AA release. An inhibitor of cytosolic PLA 2 inhibited MPP +-induced cell death. These findings suggest a synergistic effect of MPP + on Ca 2+- and H 2O 2-induced cell death, and the involvement of cytosolic PLA 2 activation in MPP +-induced cell death in GH3 cells. Pretreatment with a caspase inhibitor or EGF did not modify the ionomycin- or H 2O 2-induced AA release, or enhancement by MPP +, but the pretreatment inhibited the cell death in the presence and absence of MPP +. The involvement of caspase(s) on activation of PLA 2 by MPP + was excluded, and EGF inhibited MPP +-induced cell death downstream of the AA release.