Antithrombin-independent thrombin inhibitors, but not direct factor Xa inhibitors, enhance thrombin generation in plasma through inhibition of thrombin-thrombomodulin-protein C system

Summary

There is increasing concern that some anticoagulants can paradoxically increase thrombogenesis under certain circumstances. Previously, we demonstrated that at certain doses a direct thrombin inhibitor, melag-atran, worsens the coagulation status induced by tissue factor (TF) in-jection in a rat model. We utilised an in vitro thrombin generation (TG) assay to determine if direct thrombin inhibitors could enhance TG in human plasma, and whether inhibition of the negative-feedback sys-tem [thrombin-thrombomodulin (TM)-protein C] contributed to the TG enhancement. TG in human plasma was assayed by means of the cali-brated automated thrombography. In this assay, direct factor Xa (FXa) inhibitors such as edoxaban and antithrombin (AT)-dependent anti-coagulants such as heparin did not increase, but simply suppressed TG. AT-independent thrombin inhibitors (melagatran, lepirudin, and active site blocked thrombin (IIai)) increased peak levels of TG (2.0, 1.6, and 2.2-fold, respectively) in the presence of 12 nM recombinant human soluble TM (rhsTM). Melagatran and lepirudin at higher concentrations began to suppress TG. In the absence of rhsTM, the enhancement of peak TG by melagatran decreased to 1.2-fold. Furthermore, in protein C-deficient plasma, AT-independent thrombin inhibitors failed to enhance TG. In addition, a human protein C neutralising antibody increased the peak height of TG in the presence of rhsTM. These results suggest that AT-independent thrombin inhibitors may activate throm-bogenesis by suppression of the thrombin-induced negative-feedback system through inhibition of protein C activation. In contrast, direct FXa inhibitors are more useful than AT-independent thrombin inhibitors in terms of lower possibility of activation of the coagulation pathway.

Keywords

Thrombin inhibitor - factor Xa inhibitor - protein C - thrombomodulin - negative-feedback system

• References

• 1 Kontny F. Reactivation of the coagulation system: rationale for long-term antithrombotic treatment. Am J Cardiol 1997; 80: 55E-60E.
• 2 Watkins MW, Luetmer PA, Schneider DJ. et al. Determinants of rebound thrombin activity after cessation of heparin in patients undergoing coronary interventions. Cathet Cardiovasc Diagn 1998; 44: 257-264.
• 3 FDA. Integrated executive summary of FDA review for NDA 21-686 Exanta (Ximelagatran). Washington (DC): Food and Drug Administration 2004;
• 4 Connolly SJ, Ezekowitz MD, Yusuf S. et al. Dabigatran versus warfarin in patients with atrial fibrillation. N Engl J Med 2009; 361: 1139-1151.
• 5 Furugohri T, Shiozaki Y, Muramatsu S. et al. Different antithrombotic properties of factor Xa inhibitor and thrombin inhibitor in rat thrombosis models. Eur J Pharmacol 2005; 514: 35-42.
• 6 Lind SE. The hemostatic system. In Handin RI, Stossel TP, Lux SE. eds Blood: Principles and Practice of Hematology. Philadelphia: Lippincott; 1995. pp 949-973.
• 7 Becker RC. Factor Xa: a pleuripotential protease. J Thromb Thrombolysis 2003; 15: 5-9.
• 8 Dahlback B, Villoutreix BO. Molecular recognition in the protein C anticoagulant pathway. J Thromb Haemost 2003; 1: 1525-1534.
• 9 Esmon CT. The protein C pathway. Chest 2003; 124: 26S-32S.
• 10 Mattsson C, Menschik-Lundin A, Nylander S. et al. Effect of different types of thrombin inhibitors on thrombin/thrombomodulin modulated activation of protein C in vitro. Thromb Res 2001; 104: 475-486.
• 11 Furugohri T, Isobe K, Honda Y. et al. DU-176b, a potent and orally active factor Xa inhibitor: in vitro and in vivo pharmacological profiles. J Thromb Haemost 2008; 6: 1542-1549.
• 12 Hara T, Yokoyama A, Ishihara H. et al. DX-9065a, a new synthetic, potent anticoagulant and selective inhibitor for factor Xa. Thromb Haemost 1994; 71: 314-319.
• 13 Hron G, Kollars M, Binder BR. et al. Identification of patients at low risk for recurrent venous thromboembolism by measuring thrombin generation. J Am Med Assoc 2006; 296: 397-402.
• 14 Brandts A, van Hylckama Vlieg A, Rosing J. et al. The risk of venous thrombosis associated with a high endogenous thrombin potential in the absence and presence of activated protein C. J Thromb Haemost 2007; 5: 416-418.
• 15 Tripodi A, Martinelli I, Chantarangkul V. et al. The endogenous thrombin potential and the risk of venous thromboembolism. Thromb Res 2007; 121: 353-359.
• 16 Castoldi E, Govers-Riemslag JW, Pinotti M. et al. Coinheritance of Factor V (FV) Leiden enhances thrombin formation and is associated with a mild bleeding phenotype in patients homozygous for the FVII 9726 + 5G>A (FVII Lazio) mutation. Blood 2003; 102: 4014-4020.
• 17 Dargaud Y, Dargaud S, Lienhart A. et al. Evaluation of thrombin generating capacity in plasma from patients with haemophilia A and B. Thromb Haemost 2005; 93: 475-480.
• 18 Hemker HC, Giesen P, AlDieri R. et al. The calibrated automated thrombogram (CAT): a universal routine test for hyper- and hypocoagulability. Pathophysiol Haemost Thromb 2002; 32: 249-253.
• 19 Hemker HC, AlDieri R, De Smedt E. et al. Thrombin generation, a function test of the haemostatic-thrombotic system. Thromb Haemost 2006; 96: 553-561.
• 20 Esmon CT. The protein C pathway. Chest 2003; 124: 26S-32S.
• 21 Linder R, Frebelius S, Jansson K. et al. Inhibition of endothelial cell-mediated generation of activated protein C by direct and antithrombin-dependent thrombin inhibitors. Blood Coagul Fibrinolysis 2003; 14: 139-146.
• 22 Wagenvoord RJ, Deinum J, Elg M. et al. The paradoxical stimulation by a reversible thrombin inhibitor of thrombin generation in plasma measured with thrombinography is caused by a2-macroglobulin-thrombin. J Thromb Haemost 2010; 8: 1281-1289.
• 23 Wagenvoord RJ and Hemker C. The action mechanism of direct thrombin inhibitors during coagulation. J Thromb Haemost 2011; 9 (Suppl. S2) 573
• 24 He R, Xiong S, He X. et al. The role of factor XI in a dilute thromboplastin assay of extrinsic coagulation pathway. Thromb Haemost 2001; 85: 1055-1059.
• 25 Mattsson C, Menschik-Lundin A, Nylander S. et al. Effect of different types of thrombin inhibitors on thrombin/thrombomodulin modulated activation of protein C in vitro. Thromb Res 2001; 104: 475-486.
• 26 Grutter MG, Priestle JP, Rahuel J. et al. Crystal structure of the thrombin-hirudin complex: a novel mode of serine protease inhibition. EMBO J 1990; 9: 2361-2365.