CHARACTERIZATION OF PLATELET-ACTIVATING-FACTOR INDUCED SUPEROXIDE ANION GENERATION BY GUINEA-PIG ALVEOLAR MACROPHAGES

Guinea-pig alveolar macrophages (AM) exhibited a concentration dependent superoxide anion (.O2-) generation as measured by means of lucigenin-chemiluminescence (CL) in response to platelet-activating factor (PAF) in the range of 1 nM to 100 nM. PAF effects on .O2--generation were specific to the form of PAF that is biologically active in most systems; lyso-PAF had no effect. The CL-response was inhibited following incubation with EDTA (IC50: 859-mu-M), the intracellular Ca2+-antagonist TMB-8 (IC50: 73-mu-M), or the calmodulin antagonists W-7 (IC50: 13-mu-M) and trifluoperazine (IC50: 14-mu-M) indicating the involvement of Ca2+ in the signal transduction pathway. Increasing the intracellular cAMP-levels by PGE2 or forskolin resulted in an inhibition of the CL-response, whereas the beta-adrenoceptor agonist salbutamol showed no effect. On the other hand phosphodiesterase inhibition by IBMX (10-mu-M: 25%) or zardaverine (10-mu-M: 29%) also resulted in a transient inhibition of the CL-response. Protein kinase C (PKC) seemed not to be involved in the signal transduction, since the PKC-inhibitors staurosporine, H-7 and D-sphingosine were inactive. In contrast, the PAF receptor antagonists WEB-2086 (IC50: 700 nM) and WEB-2170 (IC50: 176 nM) exerted a strong inhibitory activity. The antiallergic/antiasthmatic drug azelastine also reduced the PAF induced CL-response (IC50: 12-mu-M), whereas the other antiallergic/antiasthamtic compounds showed almost no inhibition.