Antithrombin inhibits lipopolysaccharide-induced tissue factor and interleukin-6 production by mononuclear cells, human umbilical vein endothelial cells, and whole blood

Objective: To investigate the effects of antithrombin on lipopolysaccharide (LPS)-induced tissue factor and interleukin-6 (IL-6) production in three d ifferent in vitro cellular systems: whole blood, human umbilical vein endot helial cells, and mononuclear cells. Design and Setting: Laboratory in vitro study of the effects of antithrombi n on procoagulant activity and cytokine release by LPS-stimulated endotheli al and peripheral blood cells. Subjects: In vitro whole blood, isolated human umbilical vein endothelial c ell, and mononuclear cell cultures. Interventions: Addition of antithrombin to LPS-treated whole blood, human u mbilical vein endothelial cells, and mononuclear cells. Measurement and Main Results: Citrated whole blood, isolated human umbilica l vein endothelial cells, or mononuclear cells were stimulated with LPS for 4-6 hrs in the presence or absence of antithrombin. Tissue factor activity was estimated by a tissue factor-dependent clotting or chromogenic assay a nd IL-6 was measured by specific ELISA. Antithrombin was found to inhibit t issue factor and IL-6 production in all three systems in a dose-dependent m anner (0-40 IU/mL). Flow-through fractions of immunoadsorbed antithrombin c oncentrate were found to be ineffective. Five different batches of the same antithrombin concentrate were tested and the inhibitory activity was found to be consistent throughout all batches, Up to 40 muM of recombinant hirud in, a specific thrombin inhibitor, did not inhibit the production of tissue factor or IL-6 in either of the three cell systems, suggesting that the ob served inhibition by antithrombin was not due solely to its ability to inhi bit thrombin. Conclusions: Apart from the inhibition of thrombin and other activated clot ting factors, antithrombin may also down-regulate the cellular expression o f proinflammatory cytokines, Consequently, antithrombin concentrates may ha ve value in the treatment of sepsis-induced disseminated intravascular coag ulation.