Unsaturated fatty acids and lipoxygenase products regulate phagocytic NADPH oxidase activity by a nondetergent mechanism.

Neutrophils produce reactive oxygen species (superoxide anion [O2-]) via activation of reduced nicotinamide dinucleotide phosphate oxidase. In the intact neutrophil, this enzyme can be activated by increases in cytosolic calcium, protein kinase C, and unsaturated fatty acids such as arachidonic acid, all of which are produced on stimulation by chemotactic peptides like N-formyl-methionyl-leucyl-phenylalanine. Cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF) do not stimulate the respiratory burst but instead prime the cell for an enhanced response by an appropriate stimulus. We examined the role and potential mechanisms of free fatty acids in stimulating or priming neutrophil O2- production. Except for arachidonic acid, the ability of an unsaturated fatty acid to stimulate O2- production was not correlated with its critical micellar concentration, suggesting that detergent action was not the primary mechanism. Eicosatetraynoic acid, which blocks further arachidonate metabolism by the 5- and 15-lipoxygenases, inhibited O2- production by arachidonic acid. However, eicosatetraenoic acid did not inhibit other unsaturated fatty acid or phorbol ester-induced O2- production, suggesting that the effects of arachidonic acid were mediated at least in part by a metabolite. The same negatively charged, unsaturated fatty acids that directly stimulated O2- production when used in micromolar concentrations also primed neutrophils when added in nanomolar concentrations. The amount of a priming response was independent of chain length or number of double bonds. The magnitude of priming observed in GM-CSF-treated cells could be reconstituted with combinations of arachidonic acid and its lipoxygenase products.(ABSTRACT TRUNCATED AT 250 WORDS)