Thrombin-induced platelet aggregation −effect of dabigatran using automated platelet aggregometry−

Abstract

Dabigatran, a direct oral thrombin inhibitor, has two therapeutic effects: anticoagulation; and antiplatelet activity. In the clinical field, evaluation of the effect of dabigatran on thrombin-induced platelet aggregation is difficult because of fibrin clot formation and platelet aggregation. The aim of this study was to establish a new platelet aggregation method and to investigate the effects of dabigatran on thrombin-induced platelet aggregation. Platelet aggregation with thrombin was performed with automated light transmission aggregometry (CS2400; Sysmex, Kobe, Japan) in 40 healthy subjects. Thrombin-induced platelet aggregation was performed using thrombin and platelet-rich plasma (PRP), and thrombin-induced fibrin polymerization was inhibited by adding the peptide Gly-Pro-Arg-Pro (GPRP). The effect of dabigatran was then evaluated using the above method. Thrombin at < 0.2 U/mL did not induce platelet aggregation in most normal subjects. Median maximum aggregation percent (MA%) (25th–75th percentile) with 0.5 and 1.0 U/mL of thrombin was 87.0% (79.3–90.8%), and 90.2% (86.5–92.2%), respectively. The anti-platelet effects of dabigatran were then evaluated with these concentrations of thrombin. Dabigatran (final concentration, 2.5–1000 nM) inhibited platelet aggregation by 0.2–1.0 U/mL of thrombin in a concentration-dependent manner in vitro. Dabigatran showed potent inhibitory effects against platelet aggregation induced by 0.5 and 1.0 U/mL thrombin with half maximal inhibitory concentrations of 10.5 and 40.4 nM, respectively. A standard for thrombin-induced platelet aggregation was developed using the CS2400 in healthy subjects, and dabigatran was confirmed to inhibit thrombin-induced platelet aggregation in vitro with PRP.

Keywords:

• Dabigatran
• platelet aggregation
• thrombin
• thrombin inhibitor

Acknowledgements

The authors would like to thank Mr. S Kitamura (Gene Techno Science Co., Ltd.) for comments and advice on this study. The invaluable assistance of Ms. S Hinata from the Department of Neurology and Gerontology, School of Medicine, Iwate Medical University is also gratefully acknowledged.

Additional information

Funding

This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors.