REGULATION OF P-SELECTIN EXPRESSION IN HUMAN ENDOTHELIAL-CELLS BY NITRIC-OXIDE

P-selectin translocation to the surface of endothelial cells is increa sed after exposure to the nitric oxide (NO) synthase inhibitor N-G-nit ro-L-arginine methyl ester (L-NAME), resulting in increased endothelia l adhesiveness. L-NAME (3 mM) was added to human cultured iliac vein e ndothelial cells for 1, 2, 4, and 6 h, and P-selectin mRNA expression was quantified by a ribonuclease protection assay. In parallel experim ents, the NO donor, SPM-5185 (10 mu M), was added to human iliac venou s endothelial cells, and P-selectin mRNA expression quantified. P-sele ctin protein synthesis was quantified by Western blot analysis. L-NAME caused increased expression of P-selectin RNA at 2-4 h, whereas D-NAM E, the stereoisomer lacking NO synthase-inhibitory activity, had no ef fect. The stimulatory effect of L-NAME was reversed by addition of 3 m M L-arginine. SPM-5185 decreased P-selectin mRNA over the same time pe riod (P < 0.02). The increased P-selectin mRNA expression induced by L -NAME was paralleled by an increase in P-selectin protein synthesis. T he effects of SPM-5185 and L-arginine were also paralleled by decrease s in P-selectin protein synthesis and in decreased adherence of human neutrophils to human iliac venous endothelial cells. The peak effect o f inhibition of NO synthesis or addition of exogenous NO occurred at 2 -4 h. These results suggest a regulatory effect of NO on endothelial P -selectin expression that modulates early leukocyte-endothelial cell i nteractions to preserve vascular homeostasis.