Endogenous NO blockade enhances tissue factor expression via increased Ca²⁺ influx through MCP-1 in endothelial cells by monocyte adhesion

Objective - Ca²⁺ plays an important role in tissue factor (TF) gene expression. We investigated the role of endogenous nitric oxide (NO) in the induction of TF expression in endothelial cells (ECs) by monocyte adhesion and the mechanisms of NO action. Methods and Results - Inhibition of endogenous NO by N^ω-nitro-L-arginine methyl ester (L-NAME) enhanced TF promoter activity and protein expression induced in human coronary ECs by monocyte adhesion, as well as EC surface TF activity. L-NAME also induced monocyte chemoattractant protein-1 (MCP-1) expression, which was blocked by an NO donor, NOC18. Exogenous MCP-1 enhanced TF expression induced by monocyte adhesion, whereas adenovirus-mediated expression of the mutant MCP-1, 7ND, abolished the L-NAME enhancement of TF expression induced by monocyte adhesion. Monocyte attachment to L-NAME-treated ECs increased Ca²⁺ influx, which was prevented by NOC18, anti-MCP-1 antibody or 7ND. These results indicate that the binding of increased MCP-1 induced by endogenous NO blockade to CCR2 mediated the enhancement of Ca²⁺ influx only when monocytes adhered to ECs, which upregulated TF expression in ECs triggered by monocyte adhesion. Conclusion - MCP-1/CCR2 may play a role in Ca²⁺ influx-dependent TF regulation in the monocyte-EC interaction in the impairment of NO synthesis.