Interactions of heparin and a covalently-linked antithrombin-heparin complex with components of the fibrinolytic system

Ankush Chander; Helen M. Atkinson; Ivan Stevic; Leslie R. Berry; Paul Y. Kim; Anthony K. C. Chan

doi:10.1160/TH13-04-0290

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 2013; 110(06): 1180-1188
DOI: 10.1160/TH13-04-0290

Blood Coagulation, Fibrinolysis and Cellular Haemostasis

Schattauer GmbH

Interactions of heparin and a covalently-linked antithrombin-heparin complex with components of the fibrinolytic system

Authors

Ankush Chander

¹Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada

²Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
Helen M. Atkinson

¹Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada

²Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
Ivan Stevic

¹Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada

²Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
Leslie R. Berry

¹Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada

²Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
Paul Y. Kim

¹Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
Anthony K. C. Chan

¹Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada

²Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada

Abstract

Summary

Unfractionated heparin (UFH) is used as an adjunct during thrombolytic therapy. However, its use is associated with limitations, such as the inability to inhibit surface bound coagulation factors. We have developed a covalent conjugate of antithrombin (AT) and heparin (ATH) with superior anticoagulant properties compared with UFH. Advantages of ATH include enhanced inhibition of surface-bound coagulation enzymes and the ability to reduce the overall size and mass of clots in vivo. The interactions of UFH or ATH with the components of the fibrinolytic pathway are not well understood. Our study utilised discontinuous second order rate constant (k₂ ) assays to compare the rates of inhibition of free and fibrin-associated plasmin by AT+UFH vs ATH. Additionally, we evaluated the effects of AT+UFH and ATH on plasmin generation in the presence of fibrin. The k₂ values for inhibition of plasmin were 5.74 ± 0.28 x 10⁶ M^-1 min^-1 and 6.39 ± 0.59 x 10⁶ M^-1 min^-1 for AT+UFH and ATH, respectively. In the presence of fibrin, the k₂ values decreased to 1.45 ± 0.10 x 10⁶ M^-1 min¹ and 3.07 ± 0.19 x 10⁶ M^-1 min^-1 for AT+UFH and ATH, respectively. Therefore, protection of plasmin by fibrin was observed for both inhibitors; however, ATH demonstrated superior inhibition of fibrin-associated plasmin. Rates of plasmin generation were also decreased by both inhibitors, with ATH causing the greatest reduction (approx. 38-fold). Nonetheless, rates of plasmin inhibition were 2–3 orders of magnitude lower than for thrombin, and in a plasma-based clot lysis assay ATH significantly inhibited clot formation but had little impact on clot lysis. Cumulatively, these data may indicate that, relative to coagulant enzymes, the fibrinolytic system is spared from inhibition by both AT+UFH and ATH, limiting reduction in fibrinolytic potential during anticoagulant therapy.

Keywords

Fibrinolysis - plasmin generation - antithrombin - heparin - antithrombin-heparin covalent complex

Full Text

References

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