NITRIC-OXIDE MODULATES THE EXPRESSION OF MONOCYTE CHEMOATTRACTANT PROTEIN-1 IN CULTURED HUMAN ENDOTHELIAL-CELLS

The recruitment of monocytes into the arterial wall is one of the earl iest events in the pathogenesis of atherosclerosis. Since monocyte che moattractant protein 1 (MCP-1) plays a key role in the subendothelial recruitment of monocytes, we tested whether nitric oxide (NO) modulate s the expression of MCP-1 in cultured human endothelial cells. Inhibit ion of basal NO production by N-G-nitro-L-arginine (L-NAG) upregulates endothelial MCP-1 mRNA expression (250+/-20%) and protein secretion. Exogenous addition of NO dose-dependently decreased MCP-1. mRNA expres sion and secretion. Changes in MCP-1 mRNA expression and protein secre tion were paralleled by corresponding changes in chemotactic activity of cell-conditioned media for monocytes. An MCP-1 antibody reduced mon ocyte chemotactic activity by 85% and completely abolished the increas ed monocyte chemotactic activity induced by the inhibition of NO produ ction. Elevation of endothelial cGMP levels had no significant effect on MCP-1 mRNA expression. Inhibition of basal endothelial NO productio n by L-NAG increased binding activity of a nuclear factor kappa B (NF- kappa B)-like transcriptional regulatory factor, whereas exogenous add ition of NO decreased NF-kappa B-like binding activity during stimulat ion with tumor necrosis factor-alpha. Thus, NO modulates MCP-1 express ion and monocyte chemotactic activity secreted by human umbilical vein endothelial cells (HUVECs) in culture. The activation of NF-kappa B-l ike transcriptional regulatory proteins by inhibition of NO suggests a molecular link between an oxidant sensitive transcriptional regulator y mechanism and NO synthesis in HUVECs.