ROLE OF RELEASED ADP IN THE STABILIZATION OF PLATELET AGGREGATES: STUDIES IN PATIENTS WITH DEFICIENCY IN AMINE STORAGE GRANULES CONTENTS

1987 ◽  
Author(s):  
M Cattaneo ◽  
M T Canciani ◽  
J F Mustard
Keyword(s):  
Von Willebrand Factor ◽  
Human Platelets ◽  
Small Extent ◽  
Amine Storage ◽  
Storage Granules ◽  
Platelet Aggregates ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Amine Storage Granules

Human platelets aggregated by thrombin (T) under conditions in which the release reaction (RR) occurs to only a small extent can be deaggregated by agents that dissociate 125I-fibrinogen bound to platelets. In contrast, when platelets undergo the RR, they cannot be reading deaggregated even though combinations of inhibitors cause 125I-fibrinogen to dissociate. Therefore, material released from platelet granules seems to stabilize aggregates. T-induced aggregates of washed platelets deficient in fibrinogen or von Willebrand factor cannot be deaggregated readily by deaggregating agents, implying that released fibrinogen or von Willebrand factor do not have a major role in stabilizing aggregates. To examine the role of platelet (δ-granule contents in stabilizing platelet aggregates, aggregation and deaggregation were studied with platelets from patients with (δ- Storage Pool Deficiency (δ- SPD). Platelet aggregation and the release ofβ-TG in response to T (1 U/ml) were similar for platelets from patients and controls. Platelets from patients (but not from controls) could be deaggregated by PGE1 (10 uM) plus chymotrypsin (10 U/ml), with hirudin (5 U/ml) added to block further effects of T. Addition of ADP (20 uM) to the (5-SPD platelets 5 sec after T abolished the ability of this combination of inhibitors to deaggregate the platelets. The addition of serotonin (2 uM) 5 sec after T did not prevent inhibitors from deaggregating δ-SPD platelets. When apyrase was added to normal platelets immediately before they were aggregated by T, the combination of inhibitors readily deaggregated the platelets. Therefore, released ADP may stabilize platelet aggregates through a mechanism that could be independent of released fibrinogen and von Willebrand factor.

scholarly journals Flow studies on human GPVI-deficient blood under coagulating and noncoagulating conditions

2020 ◽  
Vol 4 (13) ◽  
pp. 2953-2961 ◽  
Author(s):  
Magdolna Nagy ◽  
Gina Perrella ◽  
Amanda Dalby ◽  
M. Francisca Becerra ◽  
Lourdes Garcia Quintanilla ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Transmembrane Domain ◽  
Stop Codon ◽  
Premature Stop Codon ◽  
Glycoprotein Vi ◽  
Heterozygous Variant ◽  
Platelet Aggregates ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract The role of glycoprotein VI (GPVI) in platelets was investigated in 3 families bearing an insertion within the GP6 gene that introduces a premature stop codon prior to the transmembrane domain, leading to expression of a truncated protein in the cytoplasm devoid of the transmembrane region. Western blotting and flow cytometry of GP6hom (homozygous) platelets confirmed loss of the full protein. The level of the Fc receptor γ-chain, which associates with GPVI in the membrane, was partially reduced, but expression of other receptors and signaling proteins was not altered. Spreading of platelets on collagen and von Willebrand factor (which supports partial spreading) was abolished in GP6hom platelets, and spreading on uncoated glass was reduced. Anticoagulated whole blood flowed over immobilized collagen or a mixture of von Willebrand factor, laminin, and rhodocytin (noncollagen surface) generated stable platelet aggregates that express phosphatidylserine (PS). Both responses were blocked on the 2 surfaces in GP6hom individuals, but adhesion was not altered. Thrombin generation was partially reduced in GP6hom blood. The frequency of the GP6het (heterozygous) variant in a representative sample of the Chilean population (1212 donors) is 2.9%, indicating that there are ∼4000 GP6hom individuals in Chile. These results demonstrate that GPVI supports aggregation and PS exposure under flow on collagen and noncollagen surfaces, but not adhesion. The retention of adhesion may contribute to the mild bleeding diathesis of GP6hom patients and account for why so few of the estimated 4000 GP6hom individuals in Chile have been identified.

Microfibrils (MF) Platelet Interaction: Requirement Of Von Willebrand Factor In Platelet Adhesion To A Placenta Microfibrillar Component (PMC)

1981 ◽  
Author(s):  
F Fauvel ◽  
Y J Legrand ◽  
N Gutman ◽  
J P Muh ◽  
G Tobelem ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Adhesion ◽  
Human Platelets ◽  
Human Artery ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Adhesion Of Platelets ◽  
Aggregation Of Platelets

It has been shown that collagenase resistant arterial microfibrils (MF) are able to interact with platelets and therefore represents, besides collagen, a second thrombogenic structure in the vessel wall. In vitro observation using a PMC purified from the villosities of human placenta by a mechanical non denaturing procedure confirm this interaction between platelets and MF. PMC was homogenous under electron microscope (feltwork of MF with a mean diameter of 120 – 130 A) and was glycoproteic in nature. PMC were able to induce an aggregation of human platelets only if the platelets were in plasma. The role of Von Willebrand factor (F VIII/WF) as a cofactor of the aggregation of platelets by MF has been postulated from the fact that twice washed platelets from normal subject resuspended in PPP obtained from a severe Von Willebrand deficient patient were not aggregated by the PMC. Furthermore, aggregation was restored after resuspension of the same platelets in the PPP of the same patient 30 and 120 minutes after perfusion of cryoprecipitate (40 units F VIII/RA per kg).F VIII/WF mediates platelet adhesion after binding to subendothelium of human artery. Our observation strongly supports the idea that MF are the subendothelial components to which F VIII/WF binds, thus promoting an adhesion of platelets.

Interaction between von Willebrand factor and glycoprotein Ib activates Src kinase in human platelets: role of phosphoinositide 3–kinase

Blood ◽  
2003 ◽  
Vol 101 (9) ◽  
pp. 3469-3476 ◽  
Author(s):  
Yi Wu ◽  
Naoki Asazuma ◽  
Kaneo Satoh ◽  
Yutaka Yatomi ◽  
Toshiro Takafuta ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Kinase Inhibitor ◽  
Signal Transduction Pathway ◽  
Human Platelets ◽  
Glutathione S Transferase ◽  
Phosphoinositide 3 Kinase ◽  
A1 Domain ◽  
Von Willebrand ◽  
Willebrand Factor

The binding of von Willebrand factor (VWF) to glycoprotein (GP) Ib-IX-V stimulates transmembrane signaling events that lead to platelet adhesion and aggregation. Recent studies have implied that activation of Src family kinases is involved in GPIb-mediated platelet activation, although the related signal transduction pathway remains poorly defined. This study presents evidence for an important role of Src and GPIb association. In platelet lysates containing Complete, a broad-spectrum protease inhibitor mixture, Src and Lyn dynamically associated with GPIb on VWF-botrocetin stimulation. Cytochalasin D, which inhibits translocation of Src kinases to the cytoskeleton, further increased Src and GPIb association. Similar results were obtained with botrocetin and monomeric A1 domain, instead of intact VWF, with induction of both Src activation and association between GPIb and Src. These findings suggest that ligand binding of GPIb, without receptor clustering, is sufficient to activate Src. Immunoprecipitation studies demonstrated that Src, phosphoinositide 3– kinase (PI 3–kinase), and GPIb form a complex in GPIb-stimulated platelets. When the p85 subunit of PI 3–kinase was immunodepleted, association of Src with GPIb was abrogated. However, wortmannin, a specific PI 3–kinase inhibitor, failed to block complex formation between Src and GPIb. The Src-SH3 domain as a glutathione S-transferase (GST)–fusion protein coprecipitated the p85 subunit of PI 3–kinase and GPIb. These findings taken together suggest that the p85 subunit of PI 3–kinase mediates GPIb-related activation signals and activates Src independently of the enzymatic activity of PI 3– kinase.

Lack of Stability of Aggregates after Thrombin-Induced Reaggregation of Thrombin-Degranulated Platelets

1992 ◽  
Vol 67 (04) ◽  
pp. 453-457 ◽  
Author(s):  
Raelene L Kinlough-Rathbone ◽  
Marian A Packham ◽  
Dennis W Perry ◽  
J Fraser Mustard ◽  
Marco Cattaneo
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Aggregate Stability ◽  
Relative Importance ◽  
Platelet Aggregates ◽  
The Stability ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

SummaryThe stability of platelet aggregates is influenced by the extent of the release of granule contents; if release is extensive and aggregation is prolonged, deaggregation is difficult to achieve. The relative importance of the contributions of released substances to aggregate stability are not known, although stable thrombin-induced aggregates form in platelet-rich plasma from patients with barely detectable plasma or platelet fibrinogen, and ADP stabilizes thrombin-induced aggregates of platelets from patients with delta storage pool deficiency which otherwise deaggregate more readily than normal platelets. We degranulated platelets with thrombin (0.9 U/ml caused greater than 90% loss of delta and alpha granule contents) and recovered them as individual platelets in fresh medium. The degranulated platelets were reaggregated by thrombin (2 U/ml). To prevent continuing effects of thrombin, FPRCH2C1 was added when thrombin-induced aggregation of thrombin-degranulated platelets reached its maximum. EDTA (5 mM) or EGTA (5 mM) added at maximum aggregation did not deaggregate these platelets, indicating that the stability of these aggregates does not depend on Ca2+ in the medium. Whereas with control platelets a combination of PGE1 (10 μM) and chymotrypsin(10 U/ml) was required for deaggregation, with thrombin-degranulated platelets either PGE1 or chymo-trypsin alone caused extensive deaggregation. The rate and extent of deaggregation of thrombin-degranulated platelets by a combination of PGE1 and chymotrypsin was greater than with control platelets.Electron microscope gold immunocytochemistry using antihuman fibrinogen IgG, anti-von Willebrand factor and anti-fibronectin showed a) that fibrinogen in the vacuoles of degranulated platelets was visible at focal points of platelet contact in the aggregates, but that large areas of platelet contact had no fibrinogen detectable between them; and b) in comparison to fibrinogen, little fibronectin or von Willebrand factor (vWf) was detectable in the platelets.Since the linkages between thrombin-degranulated platelets reaggregated by thrombin can be disrupted either by raising cAMP (thus making glycoprotein IIb/IIIa unavailable) or by proteolysis, these linkages are less stable than those formed between normal platelets. It might therefore be expected that platelets that take part in thrombus formation and then recirculate are likely to form less stable thrombi than platelets that have not released their granule contents.

Interactions of Purified Rat Factor VIII/von Willebrand Factor with Rat and Human Platelets – Effect of Albumin and Ristocetin

1984 ◽  
Vol 52 (01) ◽  
pp. 057-059 ◽  
Author(s):  
E Dejana ◽  
M Furlan ◽  
B Barbieri ◽  
M B Donati ◽  
E A Beck
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Rat Plasma ◽  
Human Platelets ◽  
High Concentrations ◽  
Low Sensitivity ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor ◽  
Rat Platelets

SummaryRat platelets do not respond to ristocetin in their own plasma nor do they aggregate in the presence of bovine or porcine factor VIII von Willebrand factor (F VIII R:WF) or human F VIII R:WF in presence of ristocetin. However, rat plasma supports ristocetin induced aggregation of washed human platelets. In this study we report on purification of rat F VIII R:WF from cryoprecipitate. Similarly to porcine or bovine material, purified rat F VIII R:WF induced aggregation of human washed fixed platelets. This effect was enhanced by addition of ristocetin and was not modified by addition of albumin. Rat washed platelets were aggregated by ristocetin in the presence of rat or human F VIII R:WF provided that high concentrations of ristocetin are added in a system essentially free of extraneous proteins. Increasing concentrations of albumin dramatically reduced the ability of ristocetin to aggregate rat platelets while human platelet aggregation by human or rat F VIII R:WF was only moderately affected.These studies show that rat F VIII R:WF can interact with rat and human platelets. The lack of response of rat platelets to ristocetin in their own plasma is most likely due to a low sensitivity of rat platelets to this drug and to an inhibitory activity of plasma proteins on this reaction.

scholarly journals The role of von Willebrand factor in breast cancer metastasis

2021 ◽  
Vol 14 (4) ◽  
pp. 101033
Author(s):  
Chia Yin Goh ◽  
Sean Patmore ◽  
Albert Smolenski ◽  
Jane Howard ◽  
Shane Evans ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Von Willebrand Factor ◽  
Cancer Metastasis ◽  
Breast Cancer Metastasis ◽  
Von Willebrand ◽  
Willebrand Factor

Role of Platelet Membrane Glycoproteins and Von Willebrand Factor in Adhesion of Platelets to Subendothelium and Collagen

1987 ◽  
Vol 516 (1 Blood in Cont) ◽  
pp. 52-65 ◽  
Author(s):  
KJELL S. SAKARIASSEN ◽  
EDITH FRESSINAUD ◽  
JEAN-PIERRE GIRMA ◽  
DOMINIQUE MEYER ◽  
HANS R. BAUMGARTNER
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Membrane ◽  
Membrane Glycoproteins ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Adhesion Of Platelets
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