Possible involvement of cytosolic phospholipase A2 in cell death induced by 1-methyl-4-phenylpyridinium ion, a dopaminergic neurotoxin, in GH3 cells

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 Ca2+ and H2O2 in cell death was examined. Ionomycin induced DNA fragmentation and lactate dehydrogenase (LDH) leakage in GH3 cells. H2O2 also induced LDH leakage. Co-addition of MPP+, in conditions where MPP+ had no effect by itself, enhanced ionomycin- and H2O2-induced cell death. Because the stimulation of phospholipase A. (PLA.) 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 H2O2-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 Ca2+ and H2O2-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 H2O2-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, by MPP+ was excluded, and EGF inhibited MPP+-induced cell death downstream of the AA release. (C) 2000 Elsevier Science B.V. All rights reserved.