ARACHIDONIC-ACID RELEASE AND PLATELET-ACTIVATING-FACTOR FORMATION BY STAUROSPORINE IN HUMAN NEUTROPHILS CHALLENGED WITH N-FORMYL PEPTIDE

Staurosporine, a putative protein kinase C (PKC) inhibitor, increased the release of [C-14]arachidonic acid dose dependently between 100 nM and 1000 nM in human neutrophils challenged with 100 nM N-formyl-methionine-leucine-phenylalanine (FMLP). Staurosporine also increased the formation of leukotriene B4 (LTB4) and platelet-activating factor (PAF) in a dose-dependent manner. In addition, exogenously added lyso-PAF further augmented [H-3]PAF formation in staurosporine-pretreated human neutrophils stimulated by FMLP, thus suggesting an activation of acetyl-CoA: lyso-PAF acetyltransferase by staurosporine. The potentiation of [C-14]arachidonic acid release and [H-3]PAF formation by staurosporine was further enhanced in the presence of 100 nM phorbol 12-myristate 13-acetate (PMA), which pinpoints a mechanism other than the modulation of PKC in this process, inasmuch as staurosporine antagonizes PMA-induced O2- production and [H-3]PAF formation. Additional studies with other putative PKC inhibitors also revealed the potentiating effects of 1-(5-isoquinolinsulfonyl)-2-methylpiperazine (H-7, 20-mu-M) and sphingosine (2.5-mu-M) on FMLP-induced [C-14]arachidonic acid release and [H-3]PAF formation. We therefore conjecture that staurosporine-sensitive protein kinases including PKC are not involved in the activation of phospholipase A2 and acetyl-CoA: lyso-PAF acetyltransferase.