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

Previously we reported that 1-methyl-4-phenylpyridinium ion (MPP+), a dopam inergic neurotoxin, induced apoptosis of GH3 cells established from rat ant erior 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. I onomycin induced DNA fragmentation and lactate dehydrogenase (LDH) leakage in GH3 cells. H2O2 also induced LDH leakage. Co-addition of MPP+, in condit ions where MPP+ had no effect by itself, enhanced ionomycin- and H2O2-induc ed cell death. Because the stimulation of phospholipase A. (PLA.) causing a rachidonic acid (AA) release has been proposed to be involved in neuronal c ell 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 m ediated by activation of cytosolic PLA(2) in a concentration-dependent mann er, although MPP+ by itself had no effect on AA release. An inhibitor of cy tosolic PLA(2) inhibited MPP+ induced cell death. These findings suggest a synergistic effect of MPP+ on Ca2+ and H2O2-induced cell death, and the inv olvement of cytosolic PLA(2) activation in MPP+-induced cell death in GH3 c ells. Pretreatment with a caspase inhibitor or EGF did not modify the ionom ycin- or H2O2-induced AA release, or enhancement by MPP+, but the pretreatm ent inhibited the cell death in the presence and absence of MPP+. The invol vement of caspase(s) on activation of PLA, by MPP+ was excluded, and EGF in hibited MPP+-induced cell death downstream of the AA release. (C) 2000 Else vier Science B.V. All rights reserved.