NERVE GROWTH-FACTOR TREATMENT PREVENTS THE INCREASE IN SUPEROXIDE PRODUCED BY EPIDERMAL GROWTH-FACTOR IN PC12 CELLS

Stimulation of pheochromocytoma (PC12) cells with the mitogen epiderma l growth factor (EGF) produced a rapid and robust accumulation of intr acellular reactive oxygen species (ROS), an accumulation which, in oth er systems, has been shown to be essential for mitogenesis, Brief pret reatment of the cells with nerve growth factor (NGF) suppressed the EG F-mediated ROS increase. EGF failed to produce elevations in ROS in a PC12 variant stably expressing a dominant-negative p2(ras) construct ( PC12-N17) or in cells pretreated with the MEK inhibitor PD098059, NGF failed to suppress the increase in ROS in the PC12 variant nnr5, which lacks p140(trk) receptors, The suppression of the increase in ROS by NGF was restored in nnr5 cells stably expressing p140(trk) (nnr5-trk), but NGF failed to prevent the increase in ROS in nnr cells expressing mutant p140(trk) receptors that lack binding sites for Shc and phosph olipase C gamma, Among several inhibitors of superoxide-generating enz ymes, only the lipoxygenase inhibitor, nordihydroguaiaretic acid reduc ed EGF-mediated ROS accumulation. The inhibitory action of NGF on ROS production was mimicked by the nitric oxide donor, sodium nitroprussid e, and was blocked by an inhibitor of nitric-oxide synthetase, L-nitro arginine methyl ester, These results suggest a novel mechanism for the rapid interruption of mitogenic signaling by the neurotrophin NGF.