title: Identification of distinct activation pathways of the human neutrophil NADPH-oxidase.
abstract: The stimulation of the human neutrophil NADPH-oxidase is initiated by a variety of agonists, which appear to utilize more than one activation pathway. We have discerned that opsonized zymosan (OZ) stimulates O2- release by a mechanism distinct from that of phorbol myristate acetate (PMA). PMA differs from OZ stimulation in its susceptibility to H-7 (a protein kinase inhibitor) inhibition of O2- release and the lack of PMA-initiated release of radiolabeled arachidonic acid ([3H]AA) from prelabeled cells. That AA release was linked to O2- generation in OZ-stimulated cells was suggested by the finding that mepacrine, a phospholipase inhibitor, exhibits parallel dose response inhibition for both O2- generation and [3H]AA release, whereas mepacrine did not significantly inhibit the O2- generation induced by PMA. The specific involvement of phospholipase A2 (PLA2) in the release of AA was indicated by the lack of release of [3H]oleate, which is not released by PLA2 in intact cells; [3H]AA released from phosphatidylinositol and phosphatidylcholine and not accompanied by the formation of [3H]-arachidonyl phosphatidic acid, thus eliminating the involvement of phospholipase C; and the inhibition of [3H]AA release by p-bromophenacyl bromide, a specific PLA2 inhibitor. The reduction of O2- formation by inhibitors of AA metabolism (BW755C, acetylsalicylic acid, and indomethacin) further supports a linkage between AA release and O2- generation. That [3H]AA release, like O2- generation, in OZ-stimulated cells was calcium dependent further differentiates OZ from calcium-independent PMA activation. These studies in toto suggest that OZ stimulation of the NADPH-oxidase differs from PMA, in that the particulate stimulus is PLA2 mediated and independent of protein kinase C.
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D015772:4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001241:Aspirin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D019255:NADPH Oxidases; D009504:Neutrophils / Q000201:enzymology*; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011796:Quinacrine / Q000494:pharmacology; D013481:Superoxides / Q000096:biosynthesis; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015054:Zymosan
chemical_list: D001095:Arachidonic Acids; D007546:Isoquinolines; D010743:Phospholipids; D010879:Piperazines; D011720:Pyrazoles; D013481:Superoxides; D016718:Arachidonic Acid; D015772:4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D015054:Zymosan; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D010741:Phospholipases A; D054467:Phospholipases A2; D011796:Quinacrine; D013755:Tetradecanoylphorbol Acetate; D001241:Aspirin; D002118:Calcium; D007213:Indomethacin