Reaction products of 1-naphthol with reactive oxygen species prevent NADPH oxidase activation in activated human neutrophils, but leave phagocytosis intact

Activation of human neutrophils with opsonized particles in the presence of a nontoxic dose of 1-naphthol resulted in inhibition of superoxide anion production but not of the phagocytotic activity of the cells. In this study we have investigated the mechanism of action of 1-naphthol. The inhibition is not at the level of cellular activation since the FMLP-induced rise of intracellular free calcium was unaffected. Our results show that the (metabolic) activation of 1-naphthol to 1,4-naphthoquinone by reaction with H2O2 from the oxidative burst is a necessary event for the inhibition to occur. The study provides evidence that by its reactivity with essential thiol groups 1,4-naphthoquinone (1,4-NQ) prevents the assembly of a functional NADPH-oxidase in the neutrophil membrane.