TY - JOUR
T1 - Recombinant fragment of yon Willebrand factor AR545c inhibits platelet binding to thrombin and platelet adhesion to thrombin-treated endothelial cells
AU - Dardik, Rima
AU - Varon, David
AU - Eskaraev, Regina
AU - Tamarin, Ilya
AU - Inbal, Aida
PY - 2000
Y1 - 2000
N2 - 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 PGE1 (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 μM) 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 μM 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).
AB - 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 PGE1 (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 μM) 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 μM 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).
KW - AR545C
KW - Endothelial cells
KW - Platelet adhesion
KW - Thrombin receptor
UR - http://www.scopus.com/inward/record.url?scp=0033623790&partnerID=8YFLogxK
U2 - 10.1046/j.1365-2141.2000.02094.x
DO - 10.1046/j.1365-2141.2000.02094.x
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AN - SCOPUS:0033623790
SN - 0007-1048
VL - 109
SP - 512
EP - 518
JO - British Journal of Haematology
JF - British Journal of Haematology
IS - 3
ER -