Characteristics of the inhibition of NADPH oxidase activation in neutrophils by apocynin, a methoxy-substituted catechol.

Phagocytes are able to generate reactive oxygen species by an activatable NADPH oxidase system. We investigated the inhibition of NADPH oxidase activation by a methoxy-substituted catechol, apocynin. Oxygen uptake by neutrophils incubated with 300 microM apocynin was completely inhibited at 7 min after addition of serum-treated zymosan (STZ), with a lagtime of inhibition of 2 to 3 min. The lagtime of effect of apocynin in neutrophils relatively deficient of myeloperoxidase was about 50% longer when compared with normal cells. Inhibition of the STZ-induced respiratory burst by apocynin was also observed in human eosinophils but not in human alveolar macrophages. Immunoblots of neutrophil membranes, isolated at 2 and 7 min after STZ stimulation of neutrophils, demonstrated translocation of the cytosolic oxidase components p47-phox and p67-phox to the membrane fraction. Translocation at 7 min after STZ stimulation was markedly reduced when the neutrophils had been incubated with 300 microM apocynin, but tran...