Abstract:Hydrogen peroxide (H 202) is a potent stimulator of signal-responsive phospholipase A2 (PLA2) in vascular smooth muscle and cultured endothelial cells. We investigated whether H202 plays a similar regulatory role in neurons. H202 did not stimulate a release of arachidonic acid from cultured neurons when applied alone but strongly enhanced the liberation of arachidonic acid evoked by maximally effective concentrations of either glutamate, the glutamate receptor agonist N-methyl-Daspartate (NMDA), the muscarinic receptor agonist carbachol, the Na + -channel opener veratridine, or the Ca 2-ionophore ionomycin. The potentiating effects of H 202 were strongly inhibited in the presence of the PLA2 inhibitor mepacrine, suggesting that the site of action was within the signal responsive arachidonic acid cascade. The enhancing effect of H202 was not reversed by protein kinase C inhibitors (chelerythrine chloride or GF 1 09203X) nor was it mimicked by phorbol ester treatment. H202 alone strongly enhanced the levels of immunodetectable activated mitogen-activated protein kinase (activated MAP kinases ERK1 and ERK2) in a Ca 2~-dependent manner and this effect was additive with increases in the levels of activated MAP kinase evoked by glutamate. The enhanced release of arachidonic acid, however, was not clearly reversed by the MAP kinase kinase (MEK) inhibitor PD 98059, although this treatment effectively abolished H 202 activation of MAP kinase. Thus, MAP kinase activation and Ca 2~-dependent arachidonic acid release are regulated by oxidative stress in cultured striatal neurons.