Nitric Oxide Modulates the Expression of Monocyte Chemoattractant Protein 1 in Cultured Human Endothelial Cells

Abstract

Abstract The recruitment of monocytes into the arterial wall is one of the earliest events in the pathogenesis of atherosclerosis. Since monocyte chemoattractant protein 1 (MCP-1) plays a key role in the subendothelial recruitment of monocytes, we tested whether nitric oxide (NO) modulates the expression of MCP-1 in cultured human endothelial cells. Inhibition 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 expression and secretion. Changes in MCP-1 mRNA expression and protein secretion were paralleled by corresponding changes in chemotactic activity of cell-conditioned media for monocytes. An MCP-1 antibody reduced monocyte chemotactic activity by 85% and completely abolished the increased monocyte chemotactic activity induced by the inhibition of NO production. Elevation of endothelial cGMP levels had no significant effect on MCP-1 mRNA expression. Inhibition of basal endothelial NO production by L-NAG increased binding activity of a nuclear factor κB (NF-κB)–like transcriptional regulatory factor, whereas exogenous addition of NO decreased NF-κB–like binding activity during stimulation with tumor necrosis factor-α. Thus, NO modulates MCP-1 expression and monocyte chemotactic activity secreted by human umbilical vein endothelial cells (HUVECs) in culture. The activation of NF-κB–like transcriptional regulatory proteins by inhibition of NO suggests a molecular link between an oxidant-sensitive transcriptional regulatory mechanism and NO synthesis in HUVECs.