W‐7, a calmodulin antagonist, primes the stimulation of human neutrophil respiratory burst by formyl peptides and platelet‐activating factor

Abstract

Low concentrations of the calmodulin antagonist W-7 (1-1μM) enhanced the respiratory burst (RB) of human polymorphonuclear leukocytes (PMN) stimulated by N-formyl-methionyl-leucyl-phenylalanine, whereas high drug concentrations (above 20 μM) depressed it. The maximal increase obtained with 5–10μM W-7 affected both initial rate (50%) and total Superoxide anion production (150%). W-7 also primed both parameters of the RB mediated by platelet-activating factor, although higher drug concentrations were required (15–50 μM). By contrast, W-7 depressed the RB induced by the calcium ionophore A23187 and by a protein kinase C activator, phorbol myristate acetate, with an 1C₅₀ of approximately 20 and 8 μM, respectively. These data show the enhancing effect of W-7 on chemoattractant-mediated RB and suggest that RB priming may involve calmodulindependent regulation of chemoattractant-mediated early signalling events.