Oxidant-mediated AA release from astrocytes involves cPLA(2) and iPLA(2).
Excessive generation of reactive oxygen species (ROS) in the central nervous system (CNS) is a leading cause of neuronal injury. Despite yet unknown mechanisms, oxidant compounds such as H(2)O(2) have been shown to stimulate the release of arachidonic acid (AA) in a number of cell systems. In this study, H(2)O(2) and menadione, a compound known to release H(2)O(2) intracellularly, were used to examine the phospholipases A(2) (PLA(2)) responsible for AA release from primary murine astrocytes. Both H(2)O(2) and menadione dose-dependently stimulated AA release, and the release mediated by H(2)O(2) was completely inhibited by catalase. H(2)O(2) also stimulated phosphorylation of extracellular signal-regulated kinases (ERK1/2) and cytosolic phospholipase A(2) (cPLA(2)). However, complete inhibition of cPLA(2) phosphorylation by U0126, an inhibitor for mitogen-activated protein kinase kinase (MEK) and GF109203x, a nonselective PKC inhibitor preferring the conventional and novel isoforms, only reduced H(2)O(2)-stimulated AA release by 50%. MAFP, a selective, active, site-directed, irreversible inhibitor of both cPLA(2) and the Ca(2+)-independent iPLA(2), nearly completely inhibited H(2)O(2)-mediated AA release; but, HELSS, a potent irreversible inhibitor of iPLA(2), only inhibited H(2)O(2)-mediated AA release by 40%. Along with the observation that H(2)O(2)-mediated AA release was only partially inhibited upon chelating intracellular Ca(2+) by BAPTA, these results indicate the involvement of both cPLA(2) and iPLA(2) in H(2)O(2)-mediated AA release in murine astrocytes.
Xu
Jianfeng
J
Department of Biochemistry, University of Missouri, Columbia, MO 65212, USA.
Yu
Sue
S
Sun
Albert Y
AY
Sun
Grace Y
GY
D000818:Animals; D000933:Antifibrinolytic Agents / Q000494:pharmacology; D016718:Arachidonic Acid / Q000378:metabolism*; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D054513:Group IV Phospholipases A2; D054522:Group VI Phospholipases A2; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D020935:MAP Kinase Signaling System; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000494:pharmacology; D024483:Vitamin K 3 / Q000494:pharmacology
D000933:Antifibrinolytic Agents; D004791:Enzyme Inhibitors; D016877:Oxidants; D016718:Arachidonic Acid; D024483:Vitamin K 3; D006861:Hydrogen Peroxide; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D054513:Group IV Phospholipases A2; D054522:Group VI Phospholipases A2; C516476:Pla2g6 protein, mouse; D002118:Calcium