Stimulation and inhibition of elastase release from human neutrophils dependent on the calcium messenger system

The neutral proteinase elastase is released from polymorphonuclear (PMN) leukocytes in various physiological and pathological conditions. Aim of the present study was to gain further insight into the mechanisms which govern the liberation of this proteinase. Therefore, the effects of the calcium ionophore A23187 and of the protein kinase-C activator phorbol myristate acetate (PMA) on neutrophils were investigated in human whole-blood samples. Furthermore, the inhibitory effects of the calcium channel blocker verapamil and of the calmodulin blocker trifluoperazine were followed. A23187 induced a release of elastase from neutrophils in a dose- and time-dependent manner. Complexation of extracellular calcium by ethylenediamine tetraacetate (EDTA) completely abolished the stimulatory effect of A23187. In a concentration of 10(-4) M verapamil was capable to attenuate (-49%) the A23187-induced secretion of PMN elastase. Beside the increase in intracellular calcium concentration, the activation of protein kinase C by PMA did also cause a release of neutrophil elastase. This release was strictly depending on the concentration of PMA and the time of incubation. In contrast to the stimulatory effect of A23187, the PMA-induced liberation of neutrophil elastase was attenuated, but not completely abolished, by complexation of extracellular calcium with EDTA. Both 10(-4) M verapamil (-43%) and 10(-5) M trifluoperazine (-42%) were able to reduce the PMA-induced release of neutrophil elastase. Based upon these data, we conclude that both the translocation of calcium intracellularly by A23187 and the activation of protein kinase C by PMA stimulate the release of neutrophil elastase. Verapamil and trifluoperazine were capable to suppress the stimulation of elastase release.