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Gresele P, Momi S. Inhibitors of the interaction between von Willebrand factor and platelet GPIb/IX/V. Handb Exp Pharmacol 2012:287-309. [PMID: 22918736 DOI: 10.1007/978-3-642-29423-5_12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The formation of platelet-rich thrombi, a critical step in the pathogenesis of atherothrombotic events, is a multistep process involving several components, among which von Willebrand Factor (VWF) plays a central role. Ruptured atherosclerotic plaques expose subendothelial matrix proteins which bind VWF that represents a bridge between the injured blood vessel and activated platelets, playing a crucial role in platelet adhesion and aggregation, especially in conditions of high-shear rate. Due to these peculiarities, the binding of VWF to GPIbα is an attractive drug target. Here we summarize the present knowledge on the different classes of drugs targeting the VWF-GPIb interaction and we give an account of their level of clinical development. In particular, the following compounds are discussed: AJW200, an IgG4 humanized monoclonal antibody against VWF-A1; 82D6A3, a monoclonal antibody against VWF-A3; ALX-0081 and ALX-0681, bivalent humanized nanobodies targeting the VWF-A1 domain; ARC1779 and its advanced formulation ARC15105, second-generation aptamers that bind the VWF-A1 domain; h6B4-Fab, a murine monoclonal antibody, and GPG-290, a recombinant chimeric protein, both directed against GPIbα.
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Affiliation(s)
- Paolo Gresele
- Division of Internal and Cardiovascular Medicine, Department of Internal Medicine, University of Perugia, Via E. dal Pozzo, 06126, Perugia, Italy.
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Oney S, Nimjee SM, Layzer J, Que-Gewirth N, Ginsburg D, Becker RC, Arepally G, Sullenger BA. Antidote-controlled platelet inhibition targeting von Willebrand factor with aptamers. Oligonucleotides 2007; 17:265-74. [PMID: 17854267 DOI: 10.1089/oli.2007.0089] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Thrombus formation is initiated by platelets and leads to cardiovascular, cerebrovascular, and peripheral vascular disease, the leading causes of morbidity and mortality in the Western world. A number of antiplatelet drugs have improved clinical outcomes for thrombosis patients. However, their expanded use, especially in surgery, is limited by hemorrhage. Here, we describe an antiplatelet agent that can have its activity controlled by a matched antidote. We demonstrate that an RNA aptamer targeting von Willebrand factor (VWF) can potently inhibit VWF-mediated platelet adhesion and aggregation. By targeting this important adhesion step, we show that the aptamer molecule can inhibit platelet aggregation in PFA-100 and ristocetin-induced platelet aggregation assays. Furthermore, we show that a rationally designed antidote molecule can reverse the effects of the aptamer molecule, restoring platelet function quickly and effectively over a clinically relevant period. This aptamer-antidote pair represents a reversible antiplatelet agent inhibiting a platelet specific pathway. Furthermore, it is an important step towards creating safer drugs in clinics through the utilization of an antidote molecule.
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Affiliation(s)
- S Oney
- Duke Translational Research Institute, Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA
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Matsuno H, Ishisaki A, Nakajima K, Kato K, Kozawa O. A peptide isolated from alpha B-crystallin is a novel and potent inhibitor of platelet aggregation via dual prevention of PAR-1 and GPIb/V/IX. J Thromb Haemost 2003; 1:2636-42. [PMID: 14750503 DOI: 10.1111/j.1538-7836.2003.00502.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND The ability of low-molecular-weight heat shock protein (HSP) to modulate thrombin-induced platelet aggregation has been investigated. OBJECTIVES We examined the inhibitory effects on platelet aggregation of nine amino acid sequences isolated from HSP20 or alpha B-crystallin and their various derivatives. METHODS AND RESULTS Platelet aggregation induced by various agonists was performed. These findings indicated that a peptide (Trp-Ile-Arg-Arg-Pro-Phe-Phe-Pro-Phe) from alpha B-crystallin significantly inhibits platelet aggregation induced by thrombin, TRAP (a protease activated receptor-1 agonist) and botrocetin, ristocetin (a stimulator of the platelet glycoprotein Ib/V/IX-von Willebrand factor axis), but not a protease-activated receptor-4 agonist, collagen and ADP. The inhibitory activity against thrombin or botrocetin is mainly linked to Arg-Arg-Pro-Phe or Trp-Ile-Arg-Arg-Pro, respectively, among nine amino acids. Additionally, during in vivo experiments, Trp-Ile-Arg-Arg-Pro-Phe-Phe-Pro-Phe shows a significant antithrombotic effect without marked bleeding. CONCLUSION Our results provide the basis for a potential new aspect of antiplatelet compound for the therapy of thrombosis and cardiovascular disease.
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Affiliation(s)
- H Matsuno
- Department of Pharmacology, Gifu University School of Medicine, Japan.
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5
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Wu D, Vanhoorelbeke K, Cauwenberghs N, Meiring M, Depraetere H, Kotze HF, Deckmyn H. Inhibition of the von Willebrand (VWF)-collagen interaction by an antihuman VWF monoclonal antibody results in abolition of in vivo arterial platelet thrombus formation in baboons. Blood 2002; 99:3623-8. [PMID: 11986216 DOI: 10.1182/blood.v99.10.3623] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The interaction between collagen, von Willebrand factor (VWF), and glycoprotein Ib is the first step in hemostasis and thrombosis especially under high shear conditions. We studied the inhibition of the VWF-collagen interaction by using an antihuman VWF monoclonal antibody 82D6A3 to prevent arterial thrombosis in baboons to develop a new kind of antithrombotic strategy and determine for the first time experimental in vivo data concerning the importance of the collagen-VWF interaction. We used a modified Folts model to study the antithrombotic efficacy of 82D6A3, where cyclic flow reductions (CFRs) were measured in the femoral artery. Administering a dose of 100, 300, and 600 microg/kg resulted in a 58.3%, 100%, and 100% reduction in the CFRs, respectively. When 100 microg/kg 82D6A3 was infused into the baboons, 80% of VWF-A3 domain was occupied, corresponding to 30% to 36% ex vivo inhibition of VWF binding to collagen, with no prolongation of the bleeding time. The bleeding time was also not significantly prolonged when the CFRs were abolished at doses of 300 microg/kg and 600 microg/kg. At these doses 100% of VWF was occupied by the antibody and 100% ex vivo inhibition of the VWF-collagen binding was observed. 82D6A3 has a high affinity for VWF; after 48 hours still 68% VWF (300 microg/kg) was occupied with a pharmacologic effect up to 5 hours after administration (80%-100% occupancy). In conclusion, these results clearly indicate that the VWF-collagen interaction is important in vivo in thrombosis under high shear conditions and thus might be a new target for preventing arterial thrombosis.
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Affiliation(s)
- Dongmei Wu
- Laboratory for Thrombosis Research, Interdisciplinary Research Center, K U Leuven Campus Kortrijk, Kortrijk, Belgium
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6
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Abstract
Advancement in the understanding of the mechanisms of platelet activation, as well as the development of new techniques for studying platelet function, have led to the availability of new classes of platelet inhibiting drugs. Initially, characterization of arachidonic acid metabolism in platelets furthered an understanding of the utility of cyclooxygenase inhibitors, most notably aspirin. The discovery and characterization of platelet receptors such as the adenosine diphosphate (ADP) receptor and glycoprotein IIb/IIIa has been associated with the development of novel classes of anti-platelet drug, such as thienopyridine derivatives and glycoprotein IIb/IIIa receptor antagonists, respectively. Future development in receptor pathway inhibitors also includes glycoprotein Ib/IX as well as the potential use of platelet signaling pathway inhibitors.
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Affiliation(s)
- P Clutton
- Departments of Pharmacology and Medicine, Georgetown University Medical Center, Washington, DC, USA
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Matsuno H, Kozawa O, Ueshima S, Matsuo O, Collen D, Uematsu T. The interaction between components of the fibrinolytic system and GPIb/V/IX of platelets thrombus formation in mice. Br J Pharmacol 2000; 131:858-64. [PMID: 11030738 PMCID: PMC1572395 DOI: 10.1038/sj.bjp.0703639] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The interaction of fibrinolytic components with GPIb/V/IX of platelets on thrombus formation, was investigated in mice deficient in tissue type (tPA-/-), urokinase type plasminogen activator (uPA-/-) or plasminogen activator inhibitor-1 (PAI-1-/-) and in their wild type control (tPA+/+, uPA+/+, PAI-1+/+). A thrombus was induced in the murine carotid artery using a photochemical reaction. The times to occlusion after the initiation of endothelial injury in all wild type mice was within 12 min, and no significant changes in occlusion delay were observed in uPA-/- and tPA-/- mice compared to wild type mice, whereas that of PAI-1 mice were significantly prolonged (16.9+/-2.9 min, P<0.05). When high molecular weight aurintricarboxylic acid (ATA), an inhibitor of platelet glycoprotein Ib/V/IX, was administered, the time to occlusion was prolonged in a dose-dependent manner in all types of mice. However, when this compound was injected in tPA-/- mice, the most significant changes were observed: i.e. the estimated ED(50) was 20.2 times higher than that in tPA+/+ mice, but the estimated ED(50) in uPA-/- mice was not changed as compared with that of wild type mice. On the other hand, when ATA was injected in PAI-1-/- mice, the estimated ED(50) was significantly decreased (P<0.05). Platelet aggregation induced by botrocetin was not significantly different among all types of mice. The bleeding time was prolonged in a dose dependent-manner when ATA was injected in all types of mice. In conclusion, the antithrombotic effect of inhibition of platelet GPIb/V/IX is severely affected by the absence or presence of tPA-production on thrombus formation and the inhibition of PAI-1 could enhance this antithrombotic effect.
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Affiliation(s)
- Hiroyuki Matsuno
- Department of Pharmacology, Gifu University School of Medicine, Tsukasa-machi 40, Gifu 500, Japan
- Department of Physiology, Kinki University School of Medicine, Osakasayama City, Japan
- Author for correspondence:
| | - Osamu Kozawa
- Department of Pharmacology, Gifu University School of Medicine, Tsukasa-machi 40, Gifu 500, Japan
| | - Shigeru Ueshima
- Department of Physiology, Kinki University School of Medicine, Osakasayama City, Japan
| | - Osamu Matsuo
- Department of Physiology, Kinki University School of Medicine, Osakasayama City, Japan
| | - Désiré Collen
- Center for Transgene Technology and Gene Therapy, Flanders Interuniversity Institute for Biotechnology, Leuven, Belgium
| | - Toshihiko Uematsu
- Department of Pharmacology, Gifu University School of Medicine, Tsukasa-machi 40, Gifu 500, Japan
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Affiliation(s)
- J I Weitz
- Hamilton Civic Hospitals Research Centre, ON, Canada
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Poletti LF, Bird K, Harris RB, Marques D, Sobel M. Prevention of arterial thrombosis using a novel heparin with enhanced antiplatelet activity and reduced anticoagulant activity. J Vasc Surg 1997; 26:366-72. [PMID: 9308582 DOI: 10.1016/s0741-5214(97)70029-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
PURPOSE Thrombosis after arterial injury is often initiated by von Willebrand factor (vWF)-dependent platelet accumulation. A promising antithrombotic strategy is the interruption of platelet/vWF interactions. Previously, we demonstrated how chemical and affinity modification can enhance heparin's anti-vWF activity while reducing conventional anticoagulation. Here, we investigated whether a modified heparin can block platelet-dominated arterial thrombosis. METHODS Standard heparin was oxidized with periodate, refined to have high vWF affinity and inhibitory potency, and tested in a guinea pig model of platelet-dependent arterial thrombosis. In this model, a controlled mechanical arterial injury yields cyclic flow variations (CFVs) caused by recurrent accumulation of platelet thrombi. RESULTS All six control animals developed CFVs (mean, 10.4 +/- 2.6 CFVs), and six of seven animals treated with standard heparin also developed CFVs (mean, 7.6 +/- 4.6). Only one of six animals treated with the anti-vWF heparin and one of six treated with AJvW-2 (an anti-vWF antibody) developed CFVs (mean, 2.0 +/- 4.9 and 0.5 +/- 1.2, respectively). Thus both the modified heparin and AJvW-2 were more effective than standard heparin (p < 0.03). Bleeding times and platelet counts were unaffected. A modified activated partial thromboplastin time was less prolonged by the modified high-affinity heparin (91 +/- 17) seconds) than by standard heparin (144 +/- 30 seconds; p < 0.01). CONCLUSIONS The modified heparin with high vWF affinity was a more effective arterial antithrombotic agent, with fewer conventional anticoagulant effects than standard heparin. Interruption of the vWF/platelet interaction is a promising antithrombotic strategy that may be met by novel heparin-based antithrombotic drugs.
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Affiliation(s)
- L F Poletti
- Division of Vascular Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond, USA
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ten Cate H, Nurmohamed MT, ten Cate JW. Developments in antithrombotic therapy: state of the art anno 1996. PHARMACY WORLD & SCIENCE : PWS 1996; 18:195-203. [PMID: 9010882 DOI: 10.1007/bf00735960] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This review aims to discuss recent developments in antithrombotic therapy. New and specific inhibitors of platelet dependent thrombosis appear to moderately improve the outcome in coronary vascular disease. Further studies will need to address the cost-benefit ratio of this additional intervention. Hirudin and analogues are potent inhibitors of thrombin, and are clinically efficious, but at current dosage levels still complicated by bleeding. Low molecular weight heparin have markedly improved the efficacy of prevention and treatment of venous thromboembolism.
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Affiliation(s)
- H ten Cate
- Dept of Internal Medicine, Slotervaart Hospital, Amsterdam, The Netherlands
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André P, Hamaud P, Bal dit Sollier C, Drouet V, Garfinkel LI, Uzan A, Caen JP, Drouet LO. Guinea pig blood: a model for the pharmacologic modulation of the GPIb/IX-vWF axis. Thromb Res 1996; 83:127-36. [PMID: 8837311 DOI: 10.1016/0049-3848(96)00113-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Antithrombotic activity of two recombinant GPIb-binding fragments of vWF, RG12986 (residues 445-733), and VCL (residues 504-728), were assessed in an ex vivo capillary perfusion chamber exposing human type III collagen to native nonanticoagulated guinea pig blood. Platelet adhesion and thrombus formation were evaluated by computer assisted morphometry for two shear rates (650 and 1800 s-1) and for two perfusion times (1.5 and 4 min). At 1800 s-1 and 4 min of perfusion, platelet adhesion decreased from 63 +/- 7% for control, to 46 +/- 4% for 20 mg/kg RG12986, and to 29 +/- 5% for 4 mg/kg VCL, and the mean thrombus height dropped from 40 +/- 8 microns to 24 +/- 3 microns and 7.5 +/- 1 microns, respectively. The two doses did not change bleeding time values. Our results suggest that guinea pig blood and the circular perfusion chamber represent a good model for the evaluation of limited amount of GPIb/IX-vWF axis inhibitors.
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Bal dit Sollier C, Drouet L, Pignaud G, Chevallier C, Caen J, Fiat AM, Izquierdo C, Jolles P. Effect of kappa-casein split peptides on platelet aggregation and on thrombus formation in the guinea-pig. Thromb Res 1996; 81:427-37. [PMID: 8907292 DOI: 10.1016/0049-3848(96)00015-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
An undecapeptide (residues 106-116 of cow kappa-casein) is known to inhibit human platelet aggregation and fibrinogen binding through inhibition of the interaction between the fibrinogen gamma-chain C-terminus and alphaIIbbeta3. This was due to structural homologies with the fibrinogen gamma-chain C-terminal dodecapeptide. We have therefore compared in this work the in vitro anti-aggregating activity of kappa-casein split peptides and their in vivo potential antithrombotic activity in a model of arterial thrombosis triggered by laser-induced intimal injury in the guinea-pig. Caseinoglycopeptide (residues 106-169), the undecapeptide (residues 106-116) and the pentapeptide KNQDK (residues 112-116) from cow kappa-casein, were anti-aggregating peptides and exerted a significant antithrombotic activity in the guinea-pig. Caseinoglycopeptides from three species (cow, ewe and human) were also antithrombotic and the most potent being the human one. The antithrombotic activity was achieved in vivo for doses less than the one suspected from in vitro data and for which, ex vivo platelet aggregation was not decreased. In conclusion, the relative involvement of the fibrinogen gamma-chain C-terminal dodecapeptide could be much more important in in vivo thrombosis process than in in vitro platelet aggregation. Its specificity and activity in vivo unveiled an interesting potential way for inhibition of arterial thrombosis if alternative molecular presentation (i.e. peptidomimetics) and alternative route (i.e. per os) can be developed.
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Affiliation(s)
- C Bal dit Sollier
- Institut des Vaisseaux et du Sang, Hopital Lariboisiere, Paris, France
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Affiliation(s)
- J I Weitz
- Hamilton Civic Hospitals Research Center, Ontario, Canada
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Abstract
Platelet activation plays a critical role in thromboembolic disorders, and aspirin remains a keystone in preventive strategies. This remarkable efficacy is rather unexpected, as aspirin selectively inhibits platelet aggregation mediated through activation of the arachidonic-thromboxane pathway, but not platelet aggregation induced by adenosine diphosphate (ADP), collagen and low levels of thrombin. This apparent paradox has stimulated investigations on the effect of aspirin on eicosanoid-independent effects of aspirin on cellular signalling. It has also fostered the search for antiplatelet drugs inhibiting platelet aggregation at other levels than the acetylation of platelet cyclo-oxygenase, such as thromboxane synthase inhibitors and thromboxane receptor antagonists. The final step of all platelet agonists is the functional expression of glycoprotein (GP) IIb/IIIa on the platelet surface, which ligates fibrinogen to link platelets together as part of the aggregation process. Agents that interact between GPIIb/IIIa and fibrinogen have been developed, which block GPIIb/IIIa, such as monoclonal antibodies to GPIIb/IIIa, and natural and synthetic peptides (disintegrins) containing the Arg-Gly-Asp (RGD) recognition sequence in fibrinogen and other adhesion macromolecules. Also, some non-peptide RGD mimetics have been developed which are orally active prodrugs. Stable analogues of prostacyclin, some of which are orally active, are also available. Thrombin has a pivotal role in both platelet activation and fibrin generation. In addition to natural and recombinant human antithrombin III, direct antithrombin III-independent thrombin inhibitors have been developed as recombinant hirudin, hirulog, argatroban, boroarginine derivatives and single stranded DNA oligonucleotides (aptanes). Direct thrombin inhibitors do not affect thrombin generation and may leave some 'escaping' thrombin molecules unaffected. Inhibition of factor Xa can prevent thrombin generation and disrupt the thrombin feedback loop that amplifies thrombin production.
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Affiliation(s)
- M Verstraete
- Center for Molecular and Vascular Biology, University of Leuven, Belgium
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Fressinaud E, Federici AB, Castaman G, Rothschild C, Rodeghiero F, Baumgartner HR, Mannucci PM, Meyer D. The role of platelet von Willebrand factor in platelet adhesion and thrombus formation: a study of 34 patients with various subtypes of type I von Willebrand disease. Br J Haematol 1994; 86:327-32. [PMID: 8199022 DOI: 10.1111/j.1365-2141.1994.tb04734.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In order to investigate the respective role of plasma and platelet von Willebrand factor (vWF) in mediating platelet adhesion and thrombus formation, we performed ex vivo perfusion studies with native blood from patients with various subtypes of type I von Willebrand disease (vWD). We studied 34 patients with type I vWD (19 'platelet normal', five 'platelet low', two 'platelet discordant', eight 'Vicenza'). Parallel studies were carried out on nine patients with severe vWD (type III). At high shear rate (2600 s-1) we found that the defect in platelet-vessel wall interactions in patients having a normal platelet vWF content ('platelet normal' and 'Vicenza') involved thrombus formation, whereas platelet adhesion was normal. At this high shear rate, platelet adhesion and thrombus volume were significantly decreased in patients with subtypes 'platelet low' and 'platelet discordant', i.e. when platelet vWF is either low or dysfunctional. These results indicate that platelet vWF may substitute for plasma vWF to promote platelet adhesion, emphasizing the important role of platelet vWF. They also confirm the role of vWF in thrombus formation at high shear rate because an abnormal thrombus volume was observed in all patients, even when platelet adhesion was normal.
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Abstract
Platelet-dependent thrombosis and subsequent embolization are major causes of cerebral ischaemia. Beside aspirin which irreversibly blocks platelet cyclo-oxygenase, several other substances interfere in different platelet metabolic pathways and block platelet adhesion and aggregation. We found in an experimental model using non-human primates that a specific peptide inhibitor blocking GP IIb/IIIa platelet receptor which binds fibrinogen completely, prevents the retention of embolized platelet aggregates in the cerebral circulation. As thrombin may play a key role for platelet activation in vivo leech-derived hirudin, a direct thrombin inhibitor as well as activated protein C which limits thrombin production and also prevents platelet dependent thrombus formation very effective. We demonstrated in the same non-human primate model of platelet embolization that the amount of retention of platelet emboli in the vascular bed depends on the nature of the vasculature. For example, platelet emboli were cleared very quickly from brain microcirculation, whereas platelet embolization into the lower limb via the femoral artery caused a significantly longer retention of the embolized material. Such specific mechanisms may be caused by different levels of local vasodilators as PGI2 or EDRF.
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Affiliation(s)
- C M Kessler
- Department of Neurology, Ernst-Moritz-Arndt-University, Greifswald, Germany
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Abstract
The evidence in support of the safety and efficacy of aspirin in the secondary prevention of platelet dependent vascular occlusion is compelling. The utility of this drug has stalled the development of potential competitors, such as thromboxane antagonists. The emergence of glycoprotein IIb/IIIa antagonists as the most promising competitors for aspirin has focused attention on the possibility of delivering these drugs at an effective dose safely.
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Affiliation(s)
- G A Fitzgerald
- Department of Medicine and Experimental Therapeutics, University College, Dublin, Ireland
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Abstract
Life-threatening thrombo-occlusive events producing heart attacks and strokes develop in patients at sites of atherosclerotic arterial stenoses when plaques rupture, a process resistant to both aspirin and heparin. Resistant thrombotic complications are also troublesome during therapeutic thrombolytic or mechanical interventions for symptomatic atherosclerotic vascular disease, including angioplasty, various types of atherectomies, endarterectomy, endovascular stent deployment, or implanted small caliber vascular grafts. In this review therapeutic strategies for more effective management of these resistant, platelet-dependent, occlusive thrombi are discussed, including: a) inhibition of platelet recruitment by anti-GPIIb/IIIa monoclonal antibodies, naturally occurring peptides containing RGD sequences, or synthetic competitive analogs; b) direct inactivation of thrombin bound to thrombus by natural or synthetic antithrombin peptides; c) interruption of thrombin's production by natural or synthetic antagonists of Factor Xa or extrinsic and intrinsic coagulation pathways; and d) elimination of thrombogenicity at sites of vascular injury by immediately restoring confluent endothelium or prior therapy with dietary n-3 fatty acids. However, antagonists of both GPIIb/IIIa- and thrombin-dependent platelet recruitment produce equivalent inhibition of thrombus formation and platelet hemostatic function. Interestingly, hemostasis is spared by therapies that inhibit thrombin's production. Recommendations for development strategies are related to the relative hemostatic risks and antithrombotic benefits.
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Affiliation(s)
- L A Harker
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322
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