An endogenous inhibitor of nitric oxide synthase regulates endothelial adhesiveness for monocytes

OBJECTIVES We sought to determine whether asymmetric dimethylarginine (ADMA ) inhibits nitric oxide (NO) elaboration in cultured human endothelial cell s and whether this is associated with the activation of oxidant-sensitive s ignaling mediating endothelial adhesiveness for monocytes. BACKGROUND Endothelial NO elaboration is impaired in hypercholesterolemia a nd atherosclerosis, which may be due to elevated concentrations of ADMA, an endogenous inhibitor of NO synthase. METHODS Human umbilical vein endothelial cells (ECV 304) and human monocyto id cells (THP-1) were studied in a functional binding assay. Nitric oxide a nd superoxide anion (O-2(-)) were measured by chemiluminescence; ADMA by hi gh pressure liquid chromatography, monocyte chemotactic protein-1 (MCP-1) b y:ELISA and NF-KB by electromobility gel shift assay. RESULTS Incubation of endothelial cells with ADMA (0.1 muM to 100 muM) inhi bited NO formation, which was reversed by coincubation with L-arginine (1 m M). The biologically inactive stereoisomer symmetric dimethylarginine did n ot inhibit NO release. Asymmetric dimethylarginine (10 muM) or native low-d ensity lipoprotein cholesterol (100 mg/dL) increased endothelial O-2(-) to the same degree. Asymmetric dimethylarginine also stimulated MCP-1 formatio n by endothelial cells. This effect was paralleled by activation of the red ox-sensitive transcription factor NF-kappaB. Preincubation of endothelial c ells with ADMA increased the adhesiveness of endothelial cells for THP-1 ce lls in a concentration-dependent manner. Asymmetric dimethylarginine-induce d monocyte binding was diminished by L-arginine or by a neutralizing anti-M CP-1 antibody. CONCLUSIONS We concluded that the endogenous NO synthase inhibitor ADMA is synthesized in human endothelial cells. Asymmetric dimethylarginine increas es endothelial oxidative stress and potentiates monocyte binding. Asymmetri c dimethylarginine may be an endogenous proatherogenic molecule. (C) 2000 b y the American College of Cardiology.