scholarly journals Antithrombotic effect of a monoclonal antibody to the platelet glycoprotein IIb/IIIa receptor in an experimental animal model

Blood ◽  
1986 ◽  
Vol 68 (3) ◽  
pp. 783-786 ◽  
Author(s):  
BS Coller ◽  
JD Folts ◽  
LE Scudder ◽  
SR Smith
Keyword(s):  
Monoclonal Antibody ◽  
Animal Model ◽  
Platelet Aggregation ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Platelet Glycoprotein ◽  
Antithrombotic Effect ◽  
Antithrombotic Agent ◽  
Antithrombotic Effects ◽  
Platelet Thrombus

Abstract A murine monoclonal antibody directed at the platelet glycoprotein IIb/IIIa complex, which blocks platelet aggregation ex vivo, was tested for its antithrombotic effects in an established animal model of acute platelet thrombus formation in partially stenosed arteries. Infusion of 0.7 to 0.8 mg/kg of the F(ab')2 fragment of the antibody completely blocked new thrombus formation despite multiple provocations, making it the most potent antithrombotic agent tested in this model.

scholarly journals Antithrombotic effect of a monoclonal antibody to the platelet glycoprotein IIb/IIIa receptor in an experimental animal model

Blood ◽  
1986 ◽  
Vol 68 (3) ◽  
pp. 783-786 ◽  
Author(s):  
BS Coller ◽  
JD Folts ◽  
LE Scudder ◽  
SR Smith
Keyword(s):  
Monoclonal Antibody ◽  
Animal Model ◽  
Platelet Aggregation ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Platelet Glycoprotein ◽  
Antithrombotic Effect ◽  
Antithrombotic Agent ◽  
Antithrombotic Effects ◽  
Platelet Thrombus

A murine monoclonal antibody directed at the platelet glycoprotein IIb/IIIa complex, which blocks platelet aggregation ex vivo, was tested for its antithrombotic effects in an established animal model of acute platelet thrombus formation in partially stenosed arteries. Infusion of 0.7 to 0.8 mg/kg of the F(ab')2 fragment of the antibody completely blocked new thrombus formation despite multiple provocations, making it the most potent antithrombotic agent tested in this model.

scholarly journals GPVI inhibition by glenzocimab synergistically inhibits atherosclerotic plaque-induced platelet activation when combined with conventional dual antiplatelet therapy

2021 ◽  
Vol 42 (Supplement_1) ◽  
Author(s):  
F O Alenazy ◽  
M H Harbi ◽  
D P Kavanagh ◽  
J Price ◽  
P Brady ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Animal Model ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Atherosclerotic Plaque ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Microvascular Thrombosis ◽  
Antithrombotic Effects ◽  
St Elevation

Abstract Introduction Aspirin and a potent platelet P2Y12 inhibitor, such as prasugrel or ticagrelor, are not always sufficient to prevent thrombus formation in patients with ST-elevation MI (STEMI), leading to “slow flow” or “no reflow” effects after stenting. GPIIb/IIIa inhibitors, such as eptifibatide, may help in this setting, but are not used routinely due to their bleeding risk. GPVI has critical roles in thrombosis and a minimal role in haemostasis. Here we tested whether depletion of GPVI has effects on thrombus formation after MI in an animal model and investigated the effects of a novel platelet GPVI inhibitor, glenzocimab (a Fab fragment of a monoclonal antibody), on platelet activation and thrombus formation when combined with aspirin and ticagrelor. Methods We used intravital microscopy in a murine model of ST-elevation myocardial infarction and ischaemia-reperfusion injury to investigate microvascular thrombosis. We investigated the antithrombotic effects of adding glenzocimab (previously known as ACT017) to blood from healthy donors and 20 patients with ACS treated with aspirin and ticagrelor. We compared the effect of glenzocimab with the GPIIb/IIIa inhibitor eptifibatide ex-vivo. We stimulated platelets with collagen and atherosclerotic plaque material that was sourced from patients undergoing carotid endarterectomy. We investigated effects on platelet aggregation, spreading, signalling, adhesion, thrombin generation, thrombus formation and clot stability ex vivo. Results Genetic depletion of GPVI in an animal model of myocardial infarction reduced microvascular thrombosis. Ex vivo, aspirin and ticagrelor partially inhibited atherosclerotic plaque-induced platelet aggregation (assessed by multiple electrode aggregometry) by 48% compared to control (34±3 vs. 65±4 U; P<0.001; Figure 1). Atherosclerotic plaque-induced platelet aggregation, adhesion, secretion and activation were critically dependent on platelet GPVI activation and were potently inhibited by glenzocimab. Glenzocimab alone reduced atherosclerotic plaque-induced platelet aggregation by 75% compared to control (16±4 vs. 65±4 U; P<0.001; Figure 1) and by over 95% when combined with aspirin and ticagrelor (3±1 vs 65±4 U; P<0.001; Figure 1). Furthermore, glenzocimab provided multiple synergistic antithrombotic effects when added to the blood of aspirin and ticagrelor-treated patients with ACS ex vivo. Glenzocimab and the GPIIb/IIIa inhibitor, eptifibatide, had many similar antithrombotic effects but glenzocimab had less effect on mechanisms of general haemostasis compared to eptifibatide, as assessed by ROTEM (Figure 2). Conclusions The addition of glenzocimab to aspirin and ticagrelor provides synergistic inhibition of multiple critical mechanisms of atherothrombosis. Glenzocimab and the GPIIb/IIIa inhibitor, eptifibatide, share many similar antithrombotic effects, although glenzocimab has less impact on mechanisms involved in haemostasis compared to eptifibatide. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Academy of Medical Sciences UK Clinical Lecturer Starter GrantRoyal Embassy of Saudi Arabia

Antiplatelet and Antithrombotic Effects of YM337, the Fab Fragment of a Humanized Anti-GPIIb/IIIa Monoclonal Antibody in Monkeys

1996 ◽  
Vol 75 (04) ◽  
pp. 679-684 ◽  
Author(s):  
Seiji Kaku ◽  
Tomihisa Kawasaki ◽  
Nami Hisamichi ◽  
Yumiko Sakai ◽  
Yuta Taniuchi ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Bleeding Time ◽  
Bolus Injection ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Fab Fragment ◽  
Inhibition Of Platelet Aggregation ◽  
Antithrombotic Effects

SummaryThe antiplatelet and antithrombotic effects of the Fab fragment of the humanized antiplatelet glycoprotein (GP) IIb/IIIa monoclonal antibody C4G1 (YM337) were investigated in monkeys. First, the relationship between the inhibition of platelet aggregation and the prolongation of bleeding time was studied in rhesus monkeys. YM337 dose-dependently inhibited ex vivo platelet aggregation, with complete inhibition at doses higher than 0.25 mg/kg intravenous injection or 1.5 μg/kg/min infusion. At 0.25 mg/kg bolus injection followed by 1.5 μg/kg/min infusion, YM337 immediately and continuously inhibited platelet aggregation during the 6-h infusion period with platelet aggregation rapidly returning to over 50% of baseline within 1 h after the cessation of infusion. Template-bleeding time was significantly prolonged during the period of complete inhibition of platelet aggregation.Second, the antithrombotic effects of YM337 were investigated in a photochemically-induced thrombosis model in squirrel monkeys. YM337 at a dose of 1 mg/kg intravenous injection followed by 6 μg/kg/min infusion for 60 min prevented occlusive thrombus formation in all 4 monkeys. In contrast, time to occlusive thrombus formation did not change on intravenous bolus injection of aspirin 17 mg/kg (11.3 ± 5.2 min) or sodium ozagrel (9.4 ± 3.0 min) compared with saline (13.3 ± 4.0 min). YM337 but not aspirin or sodium ozagrel significantly inhibited ex vivo ADP-induced platelet aggregation, while all drugs completely inhibited arachidonic acid-induced platelet aggregation. However, while aspirin and sodium ozagrel inhibited the thromboxane B2 generation accompanying arachidonic acid-induced platelet aggregation, YM337 had no effect on this variable. Platelet counts and bleeding time showed no significant change in any group in this squirrel monkey model.These results indicate that YM337, with a short half-life, may be a useful therapeutic agent in patients with thrombotic disorders.

scholarly journals Relative antithrombotic effects of monoclonal antibodies targeting different platelet glycoprotein-adhesive molecule interactions in nonhuman primates

Blood ◽  
1994 ◽  
Vol 83 (11) ◽  
pp. 3218-3224 ◽  
Author(s):  
Y Cadroy ◽  
SR Hanson ◽  
AB Kelly ◽  
UM Marzec ◽  
BL Evatt ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Platelet Glycoprotein ◽  
Venous Flow ◽  
Shear Rates ◽  
Platelet Deposition ◽  
Antithrombotic Effects ◽  
Induced Aggregation

Abstract The relative antithrombotic effectiveness of targeting glycoprotein (GP) Ib-dependent versus GPIIb-IIIa-dependent platelet interactions has been determined in baboons by measuring thrombus formation after infusing comparable antihemostatic doses of anti-von Willebrand factor (vWF) monoclonal antibody (MoAb) BB3-BD5, anti-GPIb MoAb AP1, and anti- GPIIb-IIIa MoAb LJ-CP8 under conditions of arterial and venous flow (shear rates of 750 to 1,000 seconds-1 and 100 seconds-1, respectively). Thrombus formation was quantified as 111In-platelet deposition and 125I-fibrin accumulation on segments of collagen-coated tubing interposed in chronic exteriorized arteriovenous (AV) shunts for 40 minutes. In vitro, anti-vWF MoAb BB3 BD5 (IgG) and anti-GPIb MoAb AP1 [IgG or F(ab)2 fragments] inhibited ristocetin-induced platelet aggregation (IC50 50 nmol/L and 1 mumol/L, respectively), but neither of these MoAbs blocked platelet aggregation induced by adenosine diphosphate (ADP) (P > .5). Conversely, anti-GPIIb-IIIa MoAb LJ-CP8 inhibited platelet aggregation induced by ADP (IC50 1 mumol/L, but failed to block ristocetin-induced platelet aggregation (P > .5). In vivo, the intravenous infusion of anti-vWF MoAb BB3 BD5 or anti-GPIIb- IIIa MoAb LJ-CP8 into baboons at doses that abolished corresponding agonist-induced aggregation ex vivo (bolus injections of 0.5 mg/kg and 10 mg/kg, respectively) prolonged template bleeding times from baseline values of 4.0 +/- 0.3 minutes to > 27 +/- 4 minutes, and to > 26 +/- 4 minutes, respectively (P 3 .001 in both cases), without affecting the peripheral platelet count (P > .5). However, injection of anti-GPIb MoAb AP1 [10 mg/kg as IgG or 1 mg/kg as F(ab)2 fragments] produced immediate irreversible thrombocytopenia (< 40,000 platelets/microL). Anti-GPIIb-IIIa MoAb LJ-CP8 abolished platelet deposition and fibrin accumulation on collagen segments under both arterial and venous flow conditions (P < .01 in all cases), whereas MoAb BB3 BD5 produced minimal inhibition of platelet deposition and no decrease in fibrin accumulation at arterial shear rates and undetectable antithrombotic outcomes at low shear. Thus, inhibiting GPIIb-IIIa-dependent platelet recruitment abrogates both thrombus formation and platelet hemostatic function at both venous and arterial shear rates. By contrast, interfering with GPIb-vWF-dependent platelet interactions abolishes platelet hemostatic function without producing corresponding antithrombotic effects.

scholarly journals Relative antithrombotic effects of monoclonal antibodies targeting different platelet glycoprotein-adhesive molecule interactions in nonhuman primates

Blood ◽  
1994 ◽  
Vol 83 (11) ◽  
pp. 3218-3224 ◽  
Author(s):  
Y Cadroy ◽  
SR Hanson ◽  
AB Kelly ◽  
UM Marzec ◽  
BL Evatt ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Platelet Glycoprotein ◽  
Venous Flow ◽  
Shear Rates ◽  
Platelet Deposition ◽  
Antithrombotic Effects ◽  
Induced Aggregation

The relative antithrombotic effectiveness of targeting glycoprotein (GP) Ib-dependent versus GPIIb-IIIa-dependent platelet interactions has been determined in baboons by measuring thrombus formation after infusing comparable antihemostatic doses of anti-von Willebrand factor (vWF) monoclonal antibody (MoAb) BB3-BD5, anti-GPIb MoAb AP1, and anti- GPIIb-IIIa MoAb LJ-CP8 under conditions of arterial and venous flow (shear rates of 750 to 1,000 seconds-1 and 100 seconds-1, respectively). Thrombus formation was quantified as 111In-platelet deposition and 125I-fibrin accumulation on segments of collagen-coated tubing interposed in chronic exteriorized arteriovenous (AV) shunts for 40 minutes. In vitro, anti-vWF MoAb BB3 BD5 (IgG) and anti-GPIb MoAb AP1 [IgG or F(ab)2 fragments] inhibited ristocetin-induced platelet aggregation (IC50 50 nmol/L and 1 mumol/L, respectively), but neither of these MoAbs blocked platelet aggregation induced by adenosine diphosphate (ADP) (P > .5). Conversely, anti-GPIIb-IIIa MoAb LJ-CP8 inhibited platelet aggregation induced by ADP (IC50 1 mumol/L, but failed to block ristocetin-induced platelet aggregation (P > .5). In vivo, the intravenous infusion of anti-vWF MoAb BB3 BD5 or anti-GPIIb- IIIa MoAb LJ-CP8 into baboons at doses that abolished corresponding agonist-induced aggregation ex vivo (bolus injections of 0.5 mg/kg and 10 mg/kg, respectively) prolonged template bleeding times from baseline values of 4.0 +/- 0.3 minutes to > 27 +/- 4 minutes, and to > 26 +/- 4 minutes, respectively (P 3 .001 in both cases), without affecting the peripheral platelet count (P > .5). However, injection of anti-GPIb MoAb AP1 [10 mg/kg as IgG or 1 mg/kg as F(ab)2 fragments] produced immediate irreversible thrombocytopenia (< 40,000 platelets/microL). Anti-GPIIb-IIIa MoAb LJ-CP8 abolished platelet deposition and fibrin accumulation on collagen segments under both arterial and venous flow conditions (P < .01 in all cases), whereas MoAb BB3 BD5 produced minimal inhibition of platelet deposition and no decrease in fibrin accumulation at arterial shear rates and undetectable antithrombotic outcomes at low shear. Thus, inhibiting GPIIb-IIIa-dependent platelet recruitment abrogates both thrombus formation and platelet hemostatic function at both venous and arterial shear rates. By contrast, interfering with GPIb-vWF-dependent platelet interactions abolishes platelet hemostatic function without producing corresponding antithrombotic effects.

Antithrombotic Effects and Bleeding Time Prolongation with Synthetic Platelet GPIIb/llla Inhibitors in Animal Models of Platelet-Mediated Thrombosis

1994 ◽  
Vol 71 (01) ◽  
pp. 095-102 ◽  
Author(s):  
Désiré Collen ◽  
Hua Rong Lu ◽  
Jean-Marie Stassen ◽  
Ingrid Vreys ◽  
Tsunehiro Yasuda ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Bolus Injection ◽  
Cell Injury ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Femoral Vein ◽  
Thrombotic Occlusion ◽  
Antithrombotic Effects

SummaryCyclic Arg-Gly-Asp (RGD) containing synthetic peptides such as L-cysteine, N-(mercaptoacetyl)-D-tyrosyl-L-arginylglycyl-L-a-aspartyl-cyclic (1→5)-sulfide, 5-oxide (G4120) and acetyl-L-cysteinyl-L-asparaginyl-L-prolyl-L-arginyl-glycyl-L-α-aspartyl-[0-methyltyrosyl]-L-arginyl-L-cysteinamide, cyclic 1→9-sulfide (TP9201) bind with high affinity to the platelet GPIIb/IIIa receptor.The relationship between antithrombotic effect, ex vivo platelet aggregation and bleeding time prolongation with both agents was studied in hamsters with a standardized femoral vein endothelial cell injury predisposing to platelet-rich mural thrombosis, and in dogs with a carotid arterial eversion graft inserted in the femoral artery. Intravenous administration of G4120 in hamsters inhibited in vivo thrombus formation with a 50% inhibitory bolus dose (ID50) of approximately 20 μg/kg, ex vivo ADP-induccd platelet aggregation with ID50 of 10 μg/kg, and bolus injection of 1 mg/kg prolonged the bleeding time from 38 ± 9 to 1,100 ± 330 s. Administration of TP9201 in hamsters inhibited in vivo thrombus formation with ID50 of 30 μg/kg, ex vivo platelet aggregation with an ID50 of 50 μg/kg and bolus injection of 1 mg/kg did not prolong the template bleeding time. In the dog eversion graft model, infusion of 100 μg/kg of G4120 over 60 min did not fully inhibit platelet-mediated thrombotic occlusion but was associated with inhibition of ADP-induccd ex vivo platelet aggregation and with prolongation of the template bleeding time from 1.3 ± 0.4 to 12 ± 2 min. Infusion of 300 μg/kg of TP9201 over 60 min completely prevented thrombotic occlusion, inhibited ex vivo platelet aggregation, but was not associated with prolongation of the template bleeding time.TP9201, unlike G4120, inhibits in vivo platelet-mediated thrombus formation without associated prolongation of the template bleeding time.

scholarly journals Sex differences in the antithrombotic effects of aspirin

Blood ◽  
1978 ◽  
Vol 52 (5) ◽  
pp. 1073-1076 ◽  
Author(s):  
JG Kelton ◽  
J Hirsh ◽  
CJ Carter ◽  
MR Buchanan
Keyword(s):  
Clinical Trials ◽  
Animal Model ◽  
Arterial Thrombosis ◽  
Sodium Salicylate ◽  
Inhibitory Effect ◽  
Prostaglandin Synthesis ◽  
Antithrombotic Effect ◽  
Antithrombotic Agent ◽  
Male And Female ◽  
Antithrombotic Effects

Abstract Aspirin inhibits platelet function by acetylating platelet cyclooxygenase. Recent clinical trials indicate that aspirin is a promising antithrombotic agent against both venous and arterial thrombosis, but somewhat surprisingly this protective effect appears to be limited to males. To examine the potential sex-related differences in response to aspirin, we developed an animal model for quantitating fibrin accretion into an injury-induced thrombus and used it to study the effects of aspirin on thrombus size in male and female rabbits. Platelet prostaglandin synthesis was estimated by assay of platelet malondialdehyde and was significantly decreased in both male and female rabbits following treatment with 10 mg/kg aspirin (p less than 0.001). This inhibitory effect was not different for platelets from male and female rabbits. Thrombus size was significantly decreased in aspirin- treated male rabbits when compared to controls (p less than 0.05), but this aspirin effect was not apparent in female rabbits or rabbits of either sex treated with 10 mg/kg sodium salicylate. These findings support the results of clinical trials that were obtained by retrospective subgroup analysis. The reason for the sex difference is not known, but the findings raise an important issue in relationship to this mechanism of the antithrombotic effect of aspirin.

A Double-Blind Randomized Comparison of Combined Aspirin and Ticlopidine Therapy Versus Aspirin or Ticlopidine Alone on Experimental Arterial Thrombogenesis in Humans

Blood ◽  
1998 ◽  
Vol 92 (5) ◽  
pp. 1518-1525 ◽  
Author(s):  
Jean-Pierre Bossavy ◽  
Claire Thalamas ◽  
Luc Sagnard ◽  
André Barret ◽  
Kjell Sakariassen ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Thrombus Formation ◽  
Randomized Study ◽  
Combined Treatment ◽  
Antithrombotic Effect ◽  
Ex Vivo Model ◽  
Double Blind ◽  
Thrombotic Complications ◽  
Platelet Thrombus ◽  
American Society

Abstract No randomized study comparing the effect of combined ticlopidine and aspirin therapy versus each drug alone in reducing poststenting thrombotic complications has been performed. To compare these three antiplatelet regimens versus placebo, we conducted a double-blind randomized study using an ex vivo model of thrombosis. Sixteen healthy male volunteers were assigned to receive for 8 days the following four regimens separated by a 1-month period: aspirin 325 mg/d, ticlopidine 500 mg/d, aspirin 325 mg/d + ticlopidine 500 mg/d, and placebo. At the end of each treatment period, native nonanticoagulated blood was drawn directly from an antecubital vein over collagen- or tissue factor (TF)-coated coverslips positioned in a parallel-plate perfusion chamber at an arterial wall shear rate (2,600 s−1 ) for 3 minutes. Thrombus, which formed on collagen in volunteers treated by placebo, were rich in platelets and poor in fibrin. As compared with placebo, aspirin and ticlopidine alone reduced platelet thrombus formation by only 29% and 15%, respectively (P &gt; .2). In contrast, platelet thrombus formation was blocked by more than 90% in volunteers treated by aspirin + ticlopidine (P &lt; .01v placebo or each treatment alone). Furthermore, the effect of the drug combination therapy was significantly larger than the sum of the two active treatments (P &lt; .05). Thrombus, which formed on TF-coated coverslips in volunteers treated by placebo, were rich in fibrin and platelets. Neither of the three antiplatelet treatments significantly inhibited fibrin deposition and platelet thrombus formation on this surface (P &gt; .2). Thus, the present study shows that combined aspirin and ticlopidine therapy dramatically potentiates the antithrombotic effect of each drug alone, but that the antithrombotic effect of the combined treatment depends on the nature of the thrombogenic surface. © 1998 by The American Society of Hematology.

Endotoxin enhances microvascular thrombosis in mouse cremaster venules via a TLR4-dependent, neutrophil-independent mechanism

2006 ◽  
Vol 290 (4) ◽  
pp. H1671-H1679 ◽  
Author(s):  
Rolando E. Rumbaut ◽  
Ricardo V. Bellera ◽  
Jaspreet K. Randhawa ◽  
Corie N. Shrimpton ◽  
Swapan K. Dasgupta ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Adhesion ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Mouse Strains ◽  
Microvascular Endothelium ◽  
Microvascular Thrombosis ◽  
Platelet Thrombus ◽  
Adhesive Interactions

Endotoxemia promotes adhesive interactions between platelets and microvascular endothelium in vivo. We sought to determine whether endotoxin (lipopolysaccharide, LPS) modified platelet thrombus formation in mouse cremaster venules and whether Toll-like receptor 4 (TLR4) and neutrophils were involved in the response. Intravital videomicroscopy was performed in the cremaster microcirculation of pentobarbital-anesthetized mice; venular platelet thrombi were induced with a light/dye endothelial injury model. C57BL/6 mice treated with Escherichia coli endotoxin had enhanced rates of venular platelet thrombus formation: the time to microvessel occlusion was reduced by ∼50% ( P < 0.005) compared with saline-treated animals. Enhanced microvascular thrombosis was evident as early as 2 h after LPS administration. LPS had no effect on thrombosis in either of two mouse strains with altered TLR4 signaling (C57BL/10ScNJ or C3H/HeJ), whereas it enhanced thrombosis in the control strains (C57BL/10J and C3H/HeN). LPS also enhanced platelet adhesion to endothelium in the absence of light/dye injury. Platelet adhesion, but not enhanced thrombosis, was inhibited by depletion of circulating neutrophils. LPS failed to enhance platelet aggregation ex vivo and did not influence platelet P-selectin expression, a marker of platelet activation. These findings support the notion that endotoxemia promotes platelet thrombus formation independent of neutrophils and without enhancement of platelet aggregation, via a TLR4-dependent mechanism.

Antithrombotic Effect of a Recombinant von Willebrand Factor, VCL, on Nitrogen Laser-Induced Thrombus Formation in Guinea Pig Mesenteric Arteries

1995 ◽  
Vol 73 (02) ◽  
pp. 318-323 ◽  
Author(s):  
K Azzam ◽  
L I Garfinkel ◽  
C Bal dit Sollier ◽  
M Cisse Thiam ◽  
L Drouet
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Mesenteric Arteries ◽  
Antithrombotic Effects ◽  
Von Willebrand ◽  
Willebrand Factor

SummaryTo assess the antithrombotic effectiveness of blocking the platelet glycoprotein (GP) Ib/IX receptor for von Willebrand factor (vWF), the antiaggregating and antithrombotic effects were studied in guinea pigs using a recombinant fragment of vWF, Leu 504-Lys 728 with a single intrachain disulfide bond linking residues Cys 509-Cys 695. The inhibitory effect of this peptide, named VCL, was tested in vitro on ristocetin- and botrocetin-induced platelet aggregation and compared to the ADP-induced platelet aggregation. In vivo, the antithrombotic effect of VCL was tested in a model of laser-injured mesentery small arteries and correlated to the ex vivo ristocetin-induced platelet aggregation. In this model of laser-induced thrombus formation, five mesenteric arteries were studied in each animal, and the number of recurrent thrombi during 15 min, the time to visualization and time to formation of first thrombus were recorded.In vitro, VCL totally abolished ristocetin- and botrocetin-induced platelet aggregation, but had no effect on ADP-induced platelet aggregation. Ex vivo, VCL (0.5 to 2 mg/kg) administered as a bolus i. v. injection inhibits ristocetin-induced platelet aggregation with a duration of action exceeding 1 h. The maximum inhibition was observed 5 min after injection of VCL and was dose related. The same doses of VCL had no significant effect on platelet count and bleeding time. In vivo, VCL (0.5 to 2 mg/kg) had no effect on the appearance of the thrombi formed but produced dose-dependent inhibition of the mean number of recurrent thrombi (the maximal effect was obtained at 5 min following i. v. injection of the highest dose: 0.8 ± 0.2 thrombi versus 4 ± 0.4 thrombi in controls). The three doses of VCL increased the time in which the first thrombus in a concentration-dependent manner was formed. However, the time to visualize the first thrombus was only prolonged in the higher dose-treated group.These in-vivo studies confirm that VCL induces immediate, potent, and transient antithrombotic effects. Most importantly, this inhibition was achieved without inducing thrombocytopenia nor prolongation of the bleeding time.

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