Alteration of the activated responses in platelet-activating factor-stimulated neutrophils by protein kinase inhibitors

Abstract

Roles of protein kinase C and protein tyrosine kinase in the activation of neutrophil respiratory burst, degranulation and elevation of cytosolic Ca2+ in platelet-activating factor (PAF)-stimulated neutrophils were investigated. Superoxide and H2O2 production and myeloperoxidase and acid phosphatase release in PAF-stimulated neutrophils were inhibited by protein kinase C inhibitors, staurosporine and H-7 and protein tyrosine kinase inhibitors, genistein and tyrphostin. The PAF-induced elevation of [Ca2+](i) in neutrophils was inhibited by staurosporine, genistein and methyl-2,5-dihydroxycinnamate. Staurosporine inhibited both intracellular Ca2+ release and Mn2+ influx in PAF-stimulated neutrophils. Genistein and methyl-2,5-dihydroxycinnamate inhibited Mn2+ influx induced by PAF, whereas their effects on intracellular Ca2+ release were not detected. In neutrophils preactivated by PMA, the stimulatory effect of PAF on the elevation of [Ca2+](i) was reduced. Protein kinase C and protein tyrosine kinase may be involved in respiratory burst, lysosomal enzyme release and Ca2+ mobilization in PAF-stimulated neutrophils. The elevation of [Ca2+](i) appears to be accomplished by intracellular Ca2+ release and Ca2+ influx which are differently regulated by protein kinases. Preactivation of protein kinase C appears to attenuate the stimulatory action of PAF on intracellular Ca2+ mobilization.