Effects of nitric oxide on chemotaxis and endotoxin-induced interleukin-8 production in human neutrophils

The effects of nitric oxide (NO) on human neutrophil chemotactic responses and release of interleukin (IL)-8 was studied. Neutrophils exposed to chemoattractants (IL-8, FMLP, leukotriene B4, and C5a) failed to show increases in intracellular guanosine 3',5'-cyclic monophosphate (cGMP), an indicator of NO production. Although NO increased cGMP in neutrophils, neither of two NO donors (sodium nitroprusside and 3-morpholino-sydonimine) nor a NO synthase inhibitor (N omega-nitro-L-arginine) altered FMLP- or IL-8-elicited neutrophil chemotaxis (P > .25 for all). However, lipopolysaccharide-induced IL-8 production was increased in a dose-dependent manner by a combination of sodium nitroprusside and N-acetylcysteine (P = .03) or by S-nitrosoglutathione (P = .004). NO-augmented IL-8 release was not reproduced by treating neutrophils with dibutyryl-cGMP. Up-regulation of IL-8 release by NO was associated with increased IL-8 mRNA levels (P = .009). These data suggest that NO does not directly affect neutrophil chemotaxis but may indirectly alter chemotactic responses by increasing IL-8 production via a cGMP-independent pathway.