Human polymorphonuclear neutrophil activation with arachidonic acid

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Abstract
1 The capacity of arachidonic acid (AA) to stimulate granule exocytosis from human polymorphonuclear neutrophils (PMNs) was investigated. 2 AA induced the selected extracellular release of azurophil (myeloperoxidase, lysozyme) and specific (lysozyme, vitamin B12 binding protein) granule constituents from human PMNs in a time-and concentration-dependent manner. 3 Cytochalasin B (CB) enhanced but was not required for PMN activation with AA. 4 Although extracellular calcium had no effect on granule exocytosis, AA did stimulate the mobilization of intracellular sequestered Ca2+ which resulted in an increase in cytosolic-free Ca2+ ([Ca2+]i) as reflected by increased fluorescence of Fura-2-treated cells. 5 AA stimulated Ca2+/phospholipid-dependent protein kinase C (PK-C) activity in PMNs. 6 4,4′-Diisothiocyano-2,2′-disulphonic acid stilbene (DIDS), an anion channel blocker, caused a concentration-dependent inhibition of granule enzyme release. 7 Activation of PMNs with AA was unaffected by the lipoxygenase/cyclo-oxygenase inhibitors, 5,8,11, 14-eicosatetraynoic acid (ETYA) and benoxaprofen, a lipoxygenase inhibitor, 6, 9, deepoxy-6,9-(phenylimino)-Δ6,8-prostaglandin 11 (piriprost potassium) or a pure cyclo-oxygenase inhibitor, flurbiprofen. 8 These data define the properties of AA as a secretory stimulus for human PMNs.

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