Effects of oxidative stress on phospholipid signaling in rat cultured astrocytes and brain slices

Although reactive oxygen species (ROS) are conventionally viewed as toxic b y-products of cellular metabolism, a growing body of evidence suggests that they may act as signaling molecules. We have studied the effects of hydrog en peroxide (H2O2)-induced oxidative stress on phospholipid signaling in cu ltured rat cortical astrocytes. H2O2 stimulated the formation of phosphatid ic acid and the accumulation of phosphatidylbutanol, a product of the phosp holipase D (PLD)-catalyzed transphosphatidylation reaction. The effect of e xogenous H2O2 on the PLD response was mimicked by menadione-induced product ion of endogenous H2O2. Oxidative stress also elicited inositol phosphate a ccumulation resulting from phosphoinositide phospholipase C (PLC) activatio n. The PLD response to H2O2 was totally suppressed by chelation of both ext racellular and cytosolic Ca2+ with EGTA and BAPTA/AM, respectively. Further more. H2O2-induced PLD stimulation was completely abolished by the protein kinase C (PKC) inhibitors bisindolylmaleimide and chelerythrine and by PKC down-regulation. Activation of PLD by H2O2 was also inhibited by the protei n-tyrosine kinase inhibitor genistein. Finally, H2O2 also stimulated both P LC and PLD in rat brain cortical slices. These results show for the first t ime that oxidative stress elicits phospholipid breakdown by both PLC and PL D in rat cultured astrocytes and brain slices.