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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

Ankush Chander
1   Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
2   Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
,
Helen M. Atkinson
1   Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
2   Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
,
Ivan Stevic
1   Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
2   Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
,
Leslie R. Berry
1   Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
2   Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
,
Paul Y. Kim
1   Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
,
Anthony K. C. Chan
1   Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
2   Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
› Author Affiliations
Further Information

Publication History

Received: 07 April 2013

Accepted after major revision: 19 August 2013

Publication Date:
30 November 2017 (online)

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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
 

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