Stimulus-dependent inhibition of platelet aggregation by the protein kinase C inhibitors polymyxin B, H-7 and staurosporine

Abstract

The effects of various protein kinase C (PKC) inhibitors on NADPH oxidase (NO) activation by the phorbol ester PMA and by the chemotactic peptide FMLP were studied. H-7 reduced the effects of both stimuli in human neutrophils (HN) and HL-60 cells by 13-63%. Polymyxin B did not inhibit NO activation by PMA and FMLP in HN and reduced the effects of both stimuli in HL-60 cells by 27-55%. Retinal and retinoic acid enhanced the effects of PMA and FMLP in HL-60 cells and of FMLP in HN up to 4.5-fold. In contrast, retinoic acid inhibited the effect of PMA in HN, In the presence of cytochalasin B, retinal inhibited the effect of FMLP in HN, whereas retinoic acid inhibited NO activation by FMLP in both cell types. The dual PKC/calmodulin inhibitors trifluoperazine and W-7 abolished NO activation by PMA and FMLP in HN and HL-60 cells. Thus, the effects of PKC inhibitors on NO activation exhibit (I) cell type specificity, (2) stimulus dependency and (3) no correlation with in vitro inhibition of PKC. Our results suggest that studies with PKC inhibitors presently available cannot clarify the role of PKC in NO activation. ~1988Ac~d .... Press, Inc.Human neutrophils possess an NADPH oxidase which catalyzes 0 2" formation and can be activated by cell-permeable diacylglycerol and PMA via PKC [I,2] and by the chemotactic peptide, FMLP [3]. The mechanism by which FMLP activates 0 2 -formation is not known. There is a debate concerning the involvement of PKC in cellular activation by FMLP [3]. In recent studies, certain PKC

Protein kinase C is an important signaling mediator associated with motility of intact sea urchin spermatozoa

“…On the other hand, staurosporine, a broad-spectrum kinase inhibitor, was as effective as chelerythrine in blocking sea urchin sperm motility (Table·1) and the corresponding increase of phospho-PKC substrate phosphorylation (data not shown), while H-7 failed to do so. Considering that PKC appeared to be a central signaling molecule for the motility of intact sea urchin sperm, this discrepancy may be partly explained by the fact that staurosporine is at least 1000 times D. White, E. de Lamirande and C. Gagnon more efficient than H-7 as a PKC inhibitor (Table·1) (Schächtele et al, 1988). As a matter of fact, both chelerythrine and staurosporine are chemically related microbial alkaloids that directly exert their action on the catalytic domain of PKC (Herbert et al, 1990;Tamaoki et al, 1986).…”

Agonist‐induced desensitization of histamine Hi receptor‐mediated inositol phospholipid hydrolysis in human umbilical vein endothelial cells

“…Staurosporine is acknowledged to be a potent but rather non-selective inhibitor of protein kinase C (Ruegg & Burgess, 1989) and is in addition a relatively potent inhibitor of protein kinases A and G (Tamaoki et al, 1986;Schachtele et al, 1988;Tischler et al, 1990). Consequently, the lack of effect of both staurosporine and the similarly non-selective kinase inhibitor K-252a (1 JAM) (Kase et al, 1987;Ruegg & Burgess, 1989;Tischler et al, 1990) on histamine-induced desensitization supports the data obtained with forskolin and sodium nitroprusside, and appears to rule out a role for either cyclic AMP or cyclic GMP dependent kinases in this process.…”

Substrate‐dependent inhibition of protein kinase C by specific inhibitors

“…The mechanism of action of these in~bitors is quite variable, ranging from those like H7 that acts on the ATP catalytic site, to staurosporine that acts (mainly) on the regulatory domain [2]. Activation of PKC by phorbol esters or via enhancement of phosphoinositide turnover in response to agonist binding to membrane receptors may be prevented, in most cases, by incubating the cells with inhibitors such as H7 or staurospo~ne [2,19,20]. A major criticism of the use of these inhibitors is that its range of specificity in the inhibition of protein kinases is quite broad.…”