Nitric oxide and prostacyclin. Divergence of inhibitory effects on monocyte chemotaxis and adhesion to endothelium in vitro.

Monocyte-endothelial interactions are of fundamental importance in determining the movement of monocytes from the blood stream into the vessel wall. This study reports that two endothelium-derived factors, nitric oxide and prostacyclin, alter in vitro monocyte behavior. Nitric oxide (greater than 10(-5) M) inhibited monocyte adhesion to porcine aortic endothelial cell monolayers, whereas prostacyclin (10(-9) to 10(-5) M) had no effect. Both nitric oxide and prostacyclin inhibited monocyte chemotaxis stimulated by N-formyl-methionyl-leucyl-phenylalanine and induced dose-dependent increases in intracellular cyclic guanosine monophosphate and cyclic adenosine monophosphate concentrations, respectively. The cell surface expression of the CD11b/CD18 adhesion receptor, a glycoprotein complex known to mediate monocyte intracellular adhesion, was not altered by either nitric oxide or by prostacyclin. Thus, endothelium-derived nitric oxide and prostacyclin may have a physiological role in modulating monocyte-vascular wall interactions. Alterations in this system may contribute to the increased monocyte emigration from the blood stream into the vessel wall observed in atherogenesis.