Phospholipase A2 is involved in the mechanism of activation of neutrophils by polychlorinated biphenyls.
Aroclor 1242, a mixture of polychlorinated biphenyls (PCBs), activates neutrophils to produce superoxide anion (O2-) by a mechanism that involves phospholipase C-dependent hydrolysis of membrane phosphoinositides; however, subsequent signal transduction mechanisms are unknown. We undertook this study to determine whether phospholipase A2-dependent release of arachidonic acid is involved in PCB-induced O2- production. We measured O2- production in vitro in glycogen-elicited, rat neutrophils in the presence and absence of the inhibitors of phospholipase A2: quinacrine, 4-bromophenacyl bromide (BPB), and manoalide. All three agents significantly decreased the amount of O2- detected during stimulation of neutrophils with Aroclor 1242. Similar inhibition occurred when neutrophils were activated with the classical stimuli, formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol myristate acetate. The effects of BPB and manoalide were not a result of cytotoxicity or other nonspecific effects, although data suggest that quinacrine is an O2- scavenger. Significant release of 3H-arachidonic acid preceded O2- production in neutrophils stimulated with Aroclor 1242 or fMLP. Manoalide, at a concentration that abolished O2- production, also inhibited the release of 3H-arachidonate. Aspirin, zileuton, or WEB 2086 did not affect Aroclor 1242-induced O2- production, suggesting that eicosanoids and platelet-activating factor are not needed for neutrophil activation by PCBs. Activation of phospholipase A2 and O2- production do not appear to involve the Ah receptor because a congener with low affinity, but not one with high affinity for this receptor, stimulated the release of arachidonic acid and O2-. These data suggest that Aroclor 1242 stimulates neutrophils to produce O2- by a mechanism that involves phospholipase A2-dependent release of arachidonic acid.
Tithof
P K
PK
Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824, USA.
Schiamberg
E
E
Peters-Golden
M
M
Ganey
P E
PE
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001140:Aroclors / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D006918:Hydroxyurea / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D008297:Male; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D018375:Neutrophil Activation; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D011078:Polychlorinated Biphenyls / Q000494:pharmacology / Q000633:toxicity*; D011796:Quinacrine / Q000494:pharmacology; D051381:Rats; D013481:Superoxides / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D001140:Aroclors; D016861:Cyclooxygenase Inhibitors; D016859:Lipoxygenase Inhibitors; D013729:Terpenes; D013481:Superoxides; D016718:Arachidonic Acid; C027423:aroclor 1242; D009240:N-Formylmethionine Leucyl-Phenylalanine; D011078:Polychlorinated Biphenyls; C045673:manoalide; D010741:Phospholipases A; D054467:Phospholipases A2; D011796:Quinacrine; D013755:Tetradecanoylphorbol Acetate; D001241:Aspirin; C063449:zileuton; D006918:Hydroxyurea