Inhibition of factor Xa suppresses the expression of tissue factor in human monocytes and lipopolysaccharide-induced endotoxemia in rats

Background. Activated factor X (FXa) is involved in hemostasis, thrombogenesis, inflammation, and cellular immune response. Tissue factor (TF) is an initiator of blood coagulation. We investigated whether FXa induces TF expression in human peripheral monocytes and whether treatment with FXa inhibitor reduces TF expression in an experimental model of rat endotoxemia. Methods. Human peripheral mononuclear cells were used to determine TF expression induced by FXa. Experimental rat endotoxemia was induced by intravenous bolus injection of lipopolysaccharide (LPS). A specific FXa inhibitor, DX-9065a, was administered subcutaneously immediately after LPS injection. Results. FXa induced TF expression in monocytes without intervention of thrombin and the expression was suppressed by FXa inhibitor. In the experimental model of rat endotoxemia, TF and TF mRNA expression levels in the liver were reduced by DX-9065a. Moreover, administration of DX-9065a suppressed the rise in plasma concentrations of thrombin-antithrombin III complex (TAT) and monocyte chemoattractant protein-1 (MCP-1). Conclusions. Our results indicated that FXa can induce TF expression in human peripheral monocytes and that inhibition of FXa reduces TF expression in the liver of rat endotoxemia. These results suggest that FXa is an important factor for TF expression in sepsis. (Surgery 2001;130:809-18.)