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Recombinant fragment of von Willebrand factor AR545C inhibits platelet binding to thrombin and platelet adhesion to thrombin‐treated endothelial cells
Author(s) -
Dardik Rima,
Varon David,
Eskaraev Regina,
Tamarin Ilya,
Inbal Aida
Publication year - 2000
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1046/j.1365-2141.2000.02094.x
Subject(s) - thrombin , platelet , chemistry , hirudin , adhesion , glycoprotein ib , von willebrand factor , ristocetin , platelet activation , platelet membrane glycoprotein , p selectin , biophysics , medicine , endocrinology , pharmacology , microbiology and biotechnology , biology , organic chemistry
Activated, but not resting, platelets are capable of adhering to intact endothelial cells (ECs). We evaluated the effect of a recombinant von Willebrand factor (VWF) fragment AR545C, which inhibits glycoprotein Ib (GPIb)/VWF binding, on platelet adhesion to human ECs under static or flow conditions. Incubation of resting platelets with intact endothelium under flow conditions (350/s) resulted in minimal platelet adhesion. The adhesion was enhanced two‐ to threefold after either platelet activation by thrombin receptor agonist peptide (TRAP) or EC pretreatment with thrombin. The enhancing effect of thrombin was abolished by addition of either hirudin (10 u/ml) or PGE 1 (1 µg/ml). Preincubation of resting platelets with increasing concentrations of AR545C under static or flow conditions resulted in a dose‐dependent inhibition of thrombin‐induced enhanced adhesion to ECs. AR545C (0·3 µ m ) completely abolished the effect of thrombin, reducing platelet adhesion to the control level observed with non‐treated ECs. In contrast, the same concentration of AR545C had no effect on the adhesion of TRAP‐activated platelets to ECs. AR545C also inhibited thrombin‐induced platelet aggregation and binding in a dose‐dependent manner. In addition, 0·3 µ m of AR545C reduced thrombin‐induced serotonin release by 57%, whereas monoclonal antibody AN51, which inhibits ristocetin‐induced platelet aggregation, had no effect on either thrombin‐induced platelet aggregation or binding or on serotonin release. Similarly, AR545C had no effect on TRAP‐induced serotonin release. These findings suggest that (i) AR545C inhibits platelet activation mediated by thrombin and this inhibition occurs through blocking the high‐affinity thrombin binding sites on the GPIb/IX complex and (ii) AR545C has no effect on the moderate affinity thrombin receptor (seven transmembrane domain thrombin receptor; STDR).