Effect of cetiedil on the superoxide-generating system of porcine neutrophils

Cetiedil, alpha-cyclohexyl-3-thiopheneacetic acid 2-(hexahydro-1H-azepin-1-yl)-ethyl ester, was found to inhibit the generation of superoxide (O2-) by porcine neutrophils exposed to various stimulators. The concentration of cetiedil required for 50% inhibition was about 45 microM when neutrophils were stimulated by phorbol myristate acetate. Cetiedil not only decreased the rate of generation of O2-, but prolonged the lag time prior to the production of O2-. The inhibitory effect of cetiedil on the O2(-)-generating activity of the NADPH oxidase in the membrane vesicles was less than that on whole cells; the concentration of cetiedil necessary for 50% inhibition was about 250 microM. To study the mechanism of cetiedil's effect on the membrane, the transmembrane potential of neutrophils and the intracellular free Ca2+ concentration were monitored by using fluorescence probes, diS-C3-(5), and quin-2, respectively. Cetiedil caused depolarization of the membrane potential and increased the intracellular free Ca2+. These results indicate that integrity of ionic distribution is necessary to activate the O2(-)-generating system of neutrophils.