S-nitroso-N-acetylpenicillamine reduces leukocyte adhesion to type I collagen.

The initial step in the migration of neutrophils to the extravascular space is adhesion to the endothelium. We examined the effect of nitric oxide on this process by treating human neutrophils with S-nitroso-N-acetylpenicillamine (SNAP), a NO-producing compound. Since NO has been shown to increase the level of cGMP in other cell types, we used 8-Br-cGMP in order to mimic the effects of NO. Indeed, both these treatments resulted in a reduced adhesion of neutrophils to type I collagen coated surfaces. After a prolonged incubation with SNAP, the adhesion was the same as for untreated cells. SNAP incubation reduced the F-actin content in the cells whereas 8-Br-cGMP increased it, demonstrating different mechanisms of action on F-actin. These data suggest that endothelium-derived nitric oxide is an important endogenous modulator of neutrophil adhesion, but the effect is not mediated by a cGMP-dependent regulation of F-actin levels.