Regulation of tissue factor expression in human microvascular endothelial cells by nitric oxide

Background-Tissue factor (TF) is a critical determinant of thrombin generation in normal hemostasis and in athepothrombotic disease. Nitric oxide has both antithrombotic and antiatherosclerotic actions in the vasculature, yet its role in the regulation of TF expression has not been examined. Methods and Results-To study the effect of endogenous endothelium-derived nitric oxide on TF expression and activity, we induced TF in human microvascular endothelial cells with lipopolysaccharide or interleukin-1 beta and observed a dose- and time-dependent increase in TF activity and expression by Northern and Western blotting. L-Arginine, the principal substrate for nitric oxide synthases, added to the media suppressed the induction of TF activity significantly (by 66% for lipopolysaccharide induction and by 59% for interleukin-1 beta induction) at 24 hours. These changes in activity were accompanied by correlative changes in TF protein and steady-state mRNA. D-Arginine had no effect, and inhibition of endogenous nitric oxide production failed to increase TF expression. Conclusions-These data suggest that enhanced production of endothelium-derived nitric oxide reduces endotoxin- and cytokine-induced expression of TF and, thereby, the prothrombotic phenotype of the endothelial cell.