The effects of the phospholipase A2 inhibitors aristolochic acid and PGBx on A23187-stimulated mobilization of arachidonate in human neutrophils are overcome by diacylglycerol or phorbol ester.
Aristolochic acid and PGBx, two structurally unrelated, protein-targeted inhibitors of isolated phospholipases A2, are effective antagonists of calcium ionophore A23187-stimulated mobilization of [3H]arachidonate from human neutrophils. We now report that preincubation of neutrophils with oleoylacetylglycerol (OAG, 15 microM) substantially reverses the inhibitory effect of 200 microM aristolochic acid (from 70 to 24% inhibition). Similarly, OAG increases the IC50 for PGBx from 2.5 to greater than 20 microM. The effects of OAG on inhibition by either aristolochic acid or PGBx are dose-dependent, with an ED50 of 2.5 microM. Protection against inhibition by either aristolochic acid or PGBx is also observed with phorbol myristate acetate (PMA, ED50 3 nM), but not 4-alpha-phorbol didecanoate. Aristolochic acid and PGBx do not inhibit PMA-stimulated superoxide generation, and are thus not protein kinase C inhibitors. Furthermore, neither aristolochic acid nor PGBx inhibit diglyceride generation through the phospholipase D/phosphatidate phosphohydrolase pathway. A23187-stimulated [3H]arachidonate mobilization is increased by 20-50% when neutrophils are preincubated with OAG or PMA. The present results indicate that OAG and PMA also modulate the A23187-stimulated [3H]arachidonate mobilization so as to render it less sensitive to inhibitors of phospholipase A2.
Rosenthal
M D
MD
Department of Biochemistry, Eastern Virginia Medical School, Norfolk 23501.
Lattanzio
K S
KS
Franson
R C
RC
D016718:Arachidonic Acid / Q000378:metabolism*; D034341:Aristolochic Acids; D000001:Calcimycin / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology; D006801:Humans; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010616:Phenanthrenes / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010711:Phosphatidate Phosphatase / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors*; D054467:Phospholipases A2; D011108:Polymers / Q000494:pharmacology*; D011456:Prostaglandins B / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D013110:Sphingosine / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D034341:Aristolochic Acids; D004075:Diglycerides; D010616:Phenanthrenes; D011108:Polymers; D011456:Prostaglandins B; D013481:Superoxides; D016718:Arachidonic Acid; D000001:Calcimycin; C024303:prostaglandin Bx; D009240:N-Formylmethionine Leucyl-Phenylalanine; C038237:1-oleoyl-2-acetylglycerol; C000228:aristolochic acid I; D010741:Phospholipases A; D054467:Phospholipases A2; D010711:Phosphatidate Phosphatase; D010739:Phospholipase D; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate