Platelet activation by a novel solid‐phase agonist: effects of VWF immobilized on polystyrene beads

Stewart, Michael W.; Etches, Wai S.; Boshkov, Lynn K.; Mant, Michael J.; Gordon, Philip A.; Shaw, Andrew

doi:10.1046/j.1365-2141.1997.372681.x

Cited by 7 publications

(6 citation statements)

References 22 publications

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“…The objective of our investigation was to study TCIPA in the presence of sVWF, a novel solid‐phase agonist (Stewart et al ., 1997). As VWF is a major adhesion protein contributing to the interactions between platelets and the vascular wall (Ruggeri et al ., 1999), the use of sVWF added yet another dimension to studies on TCIPA that have considered until now only the platelet – tumour cell relationship (Honn et al ., 1981; Radomski et al ., 1991; Jurasz et al ., 2001).…”

Section: Discussionmentioning

confidence: 99%

“…PAC‐1 FITC monoclonal mouse anti‐platelet GPIIb/IIIa antibodies were obtained from Becton Dickinson (San José, CA, U.S.A.). Von Willebrand factor coated polystyrene beads (Stewart et al ., 1997) were provided by Thrombotics Inc (Edmonton, AB, Canada). The beads were washed and resuspended in equivalent volume of saline and used for the experiments.…”

Section: Methodsmentioning

confidence: 99%

“…Recently, Stewart et al . (1997) reported that VWF when immobilized on polystyrene beads acts as a novel solid‐phase agonist (sVWF) in human platelet‐rich plasma.…”

Section: Introductionmentioning

confidence: 99%

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Role of von Willebrand factor in tumour cell‐induced platelet aggregation: differential regulation by NO and prostacyclin

Jurasz

Stewart²,

Radomski

et al. 2001

British J Pharmacology

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1 We have studied the e ects of a novel agonist, solid-phase von Willebrand Factor (sVWF), on tumour cell-induced platelet aggregation (TCIPA). 2 Washed platelet suspensions were obtained from human blood and the e ects of HT-1080 human ®brosarcoma cells and sVWF on platelets were studied using aggregometry, phase-contrast microscopy, and¯ow cytometry. 3 Incubation of platelets with sVWF (1.2 mg ml 71 ) and HT-1080 cells (5610 3 ml 71 ) resulted in a two-phased reaction characterized ®rst by the adhesion of platelets to sVWF, then by aggregation. 4 TCIPA in the presence of sVWF was inhibited by S-nitroso-glutathione (GSNO, 100 mM) and prostacyclin (PGI 2 , 30 nM). 5 Platelet activation in the presence of tumour cells and sVWF resulted in the decreased surface expression of platelet glycoprotein (GP)Ib and up-regulation of GPIIb/IIIa receptors. 6 Pre-incubation of platelets with PGI 2 (30 nM) resulted in inhibition of sVWF-tumour cellstimulated platelet surface expression of GPIIb/IIIa as measured by¯ow cytometry using antibodies directed against both non-activated and activated receptor. In contrast, GSNO (100 mM) did not a ect sVWF-tumour cell-stimulated platelet surface expression of GPIIb/IIIa. 7 Flow cytometry performed with PAC-1 antibodies that bind only to the activated GPIIb/IIIa revealed that GSNO (100 mM) caused inhibition of activation of GPIIb/IIIa. 8 The inhibitors exerted no signi®cant e ects on TCIPA-mediated changes in GPIb. 9 Thus, sVWF potentiates the platelet-aggregatory activity of HT-1080 cells and these e ects appear to be mediated via up-regulation of platelet GPIIb/IIIa. 10 Prostacyclin and NO inhibit TCIPA-sVWF-mediated platelet aggregation. The mechanisms of inhibition of this aggregation by PGI 2 di er from those of NO.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Role of von Willebrand factor in tumour cell‐induced platelet aggregation: differential regulation by NO and prostacyclin

Jurasz

Stewart²,

Radomski

et al. 2001

British J Pharmacology

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“…Because of its large molecular size it has been difficult to study the effects of vWF on platelets using conventional methods such as aggregometry. Recently, Stewart et al . (1997) immobilized vWF on polystyrene beads generating a solid‐phase preparation (svWF).…”

Section: Introductionmentioning

confidence: 99%

Pharmacological characteristics of solid‐phase von Willebrand factor in human platelets

Radomski

Stewart²,

Jurasz

et al. 2001

British J Pharmacology

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1 The pharmacological characteristics of solid-phase von Willebrand factor (svWF), a novel platelet agonist, were studied. 2 Washed platelet suspensions were obtained from human blood and the eects of svWF on platelets were measured using aggregometry, phase-contrast microscopy,¯ow cytometry and zymography. 3 Incubation of platelets with svWF (0.2 ± 1.2 mg ml 71 ) resulted in their adhesion to the ligand, while co-incubations of svWF with subthreshold concentrations of ADP, collagen and thrombin resulted in aggregation. 4 6B4 inhibitory anti-glycoprotein (GP)Ib antibodies abolished platelet adhesion stimulated by svWF, while aggregation was reduced in the presence of 6B4 and N-Acetyl-Pen-Arg-Gly-Asp-Cys, an antagonist of GPIIb/IIIa. 5 Platelet adhesion stimulated with svWF was associated with a concentration-dependent increase in expression of GPIb, but not of GPIIb/IIIa. 6 In contrast, collagen (0.5 ± 10.0 mg ml 71) caused down-regulation of GPIb and up-regulation of GPIIb/IIIa in platelets. 7 Solid-phase vWF (1.2 mg ml 71 ) resulted in the release of MMP-2 from platelets. 8 Inhibition of MMP-2 with phenanthroline (10 mM), but not with aspirin or apyrase, inhibited platelet adhesion stimulated with svWF. 9 In contrast, human recombinant MMP-2 potentiated both the eects of svWF on adhesion and up-regulation of GPIb. 10 Platelet adhesion and aggregation stimulated with svWF were reduced by S-nitroso-n-acetylpenicillamine, an NO donor, and prostacyclin. 11 Thus, stimulation of human platelets with svWF leads to adhesion and aggregation that are mediated via activation of GPIb and GPIIb/IIIa, respectively. 12 Mechanisms of activation of GPIb by svWF involve the release of MMP-2, and are regulated by NO and prostacyclin.

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“…Non-magnetic ligand-coated beads have been used for platelet function testing, with detection by flow cytometry [11,12], bioluminescence, electron microscopy [13], and agglutination [1,14]. Magnetic beads have been used to study platelet glycoprotein deficiency [15] and to extract platelet specific proteins from whole blood [16].…”

Section: Introductionmentioning

confidence: 99%

Measurement of platelet responsiveness using antibody-coated magnetic beads for lab-on-a-chip applications

Zijp¹,

Schot²,

Jong³

et al. 2012

Platelets

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We investigate novel methods for the quantification of platelet responsiveness that are suited for implementation in lab-on-a-chip devices. Magnetic beads are convenient carriers for rapid capture and manipulation of biological cells in a miniaturized system. In this article, we demonstrate that antibody-coated magnetic beads can be used to quantify platelet responsiveness. We use anti-CD62P coated beads to capture activated platelets from samples stimulated with a PAR-1 specific agonist SFLLRN, also known as thrombin receptor activator peptide. The responsiveness of the platelets is analyzed via the remaining unbound platelets in the solution and compared to a reference method in which the number of activated platelets is analyzed via fluorescent labeling. The effective concentrations for platelet activation are in agreement for the two assay types, proving that platelet responsiveness can be quantified using antibody-coated magnetic beads. We discuss the outlook for application in lab-on-a-chip devices.

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Platelet activation by a novel solid‐phase agonist: effects of VWF immobilized on polystyrene beads

Cited by 7 publications

References 22 publications

Role of von Willebrand factor in tumour cell‐induced platelet aggregation: differential regulation by NO and prostacyclin

Role of von Willebrand factor in tumour cell‐induced platelet aggregation: differential regulation by NO and prostacyclin

Pharmacological characteristics of solid‐phase von Willebrand factor in human platelets

Measurement of platelet responsiveness using antibody-coated magnetic beads for lab-on-a-chip applications

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