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 B 4 , 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 v -nitro-L-arginine) altered FMLP-or IL-8 -elicited neutrophil chemotaxis (P ú .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 Å .03) or by S-nitrosoglutathione (P Å .004). NO-augmented IL-8 release was not reproduced by treating neutrophils with dibutyryl-cGMP. Upregulation of IL-8 release by NO was associated with increased IL-8 mRNA levels (P Å .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.

No abstract

We studied the effect of nitric oxide on LPS-induced TNF-alpha production by human neutrophils. Human neutrophils exposed to LPS and IFN-gamma did not show measurable increases in intracellular cyclic GMP (cGMP). However, cGMP increased upto 30-fold (p < 0.01) in neutrophils incubated with both sodium nitroprusside (SNP), an exogenous source of nitric oxide, and N-acetylcysteine (NAC), which increases the bioavailability of nitric oxide; this increase indicates that neutrophils contain a nitric oxide-sensitive guanylate cyclase. SNP, with or without NAC, did not increase TNF-alpha production in human neutrophils cultured in medium alone. However, LPS-dependent TNF-alpha production was increased by exposure to SNP (p < 0.05); this effect was further increased by the addition of NAC (p < 0.02). IFN-gamma greatly increased LPS-mediated TNF-alpha production by human neutrophils (p < 0.01), and SNP plus NAC was found to further augment this production (p < 0.01). The up-regulation of TNF-alpha production by nitric oxide was not associated with increased amounts of LPS-induced TNF-alpha mRNA, and was not reproduced by exposing neutrophils to cGMP analogues. These data suggest that nitric oxide released by endothelial and vascular smooth muscle cells may exert a paracrine effect on human neutrophils and augment the inflammatory response in sepsis by increasing the production of cytokines. Although the mechanism of this effect remains unknown, it does not seem to be dependent on cGMP or increased levels of TNF-alpha mRNA.

No abstract

The 42 kDa saliva-binding region (SBR) of Streptococcus mutans AgI/II adhesin, like most soluble protein antigens, is a poor mucosal immunogen when administered alone. However, by genetically linking SBR to the targeting A2/B subunits of cholera toxin (CT), good mucosal salivary IgA