Antiplatelet-anticoagulant, APAC, a mimic of endogenous heparin, is an antithrombotic with von Willebrand factor-mediated characteristics
Annukka Jouppila a),b); Ilja Nevola b); Marja Lemponen c); Tomi Mattila b); Riitta Lassila b),d),e).
a) Clinical Research institute HUCH, Helsinki, Finland
b) Research Program Unit in Systems Oncology, Medical Faculty, University of Helsinki, Helsinki, Finland
c) HUS Diagnostic Center, Department of Clinical Chemistry and Hematology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
d) Coagulation Disorders Unit, Departments of Hematology and Clinical Chemistry (HUSLAB Laboratory Services), Comprehensive Cancer Center, Helsinki University Hospital, Helsinki, Finland
e) Aplagon Ltd., Helsinki, Finland
Abstract
Background
We have conjugated selected number of unfractionated heparin (UFH) chains to human albumin core to mimic mast-cell heparin proteoglycans (HEP-PG). Indeed, APAC, dual antiplatelet and anticoagulant, as HEP-PG, has inhibited collagen- (CIPA) and thrombin-induced platelet aggregation, being simultaneously an anticoagulant. In several animal models of arterial thrombosis, APAC has provided vascular-injury-associated local antithrombotic properties mediated by von Willebrand factor (VWF).
Aims
We compared the structure-function effects of APAC with those of UFH in vitro, and when supplemented in blood studied platelet and VWF-dependency and anticoagulation.
Methods
We assessed the total thrombosis formation analysis system (T-TAS) and coagulation (rotational thromboelastometry, ROTEM) in blood, and thrombin generation and aggregation in platelet-rich plasma. We studied aggregation responses of APAC to collagen, ristocetin, ADP, and potential synergism with cangrelor, P2Y12 receptor antagonist. Finally, heparin-neutralizing role of platelet factor 4 (PF4) on antiplatelet and anticoagulant functions of APAC was investigated.
Results
APAC concentration-dependently exceeded the anticoagulant and antithrombotic action of UFH in ROTEM, and platelet thrombus formation under arterial blood flow over collagen/tissue factor. APAC uniquely inhibited CIPA. While ADP- and ristocetin-induced aggregation were unaffected by APAC, we detected synergism with cangrelor for CIPA. Disruption of the tertiary structure of APAC reverted its mode of action to anticoagulation only, alike UFH. PF4 neutralized antithrombotic actions of APAC.
Conclusion
The structure-function of APAC conveys dual and unique antiplatelet and anticoagulant actions in flowing blood over collagen and beyond. Our studies confirmed the inhibitory role of APAC on VWF functions and fibrin formation.