scholarly journals Type IIB von Willebrand factor with normal sialic acid content induces platelet aggregation in the absence of ristocetin. Role of platelet activation, fibrinogen, and two distinct membrane receptors.

1987 ◽  
Vol 80 (2) ◽  
pp. 475-482 ◽  
Author(s):  
L De Marco ◽  
M Mazzuccato ◽  
M Grazia Del Ben ◽  
U Budde ◽  
A B Federici ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Membrane Receptors ◽  
Sialic Acid Content ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Distinct Membrane

An Essential Role of Factor VIII-Mediated Hemostasis in the Absence of von Willebrand Factor.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3101-3101
Author(s):  
Yoshihiko Sakurai ◽  
Midori Shima ◽  
Shogo Kasuda ◽  
Shoko Omura ◽  
Masahiro Takeyama ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Essential Role ◽  
Bolus Administration ◽  
Type 3 ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Background: The replacement therapy with plasma-derived factor VIII (FVIII)/von Willebrand factor (VWF) concentrates is the first line treatment for the patients with type 3 von Willebrand disease (VWD). However, development of anti-VWF alloantibodies (inhibitor) is a major problem since the inhibitor neutralizes the VWF activity and may cause anaphylactic reactions. As an alternative treatment, the usage of FVIII concentrates has been reported but the mechanism of the hemostatic effects remains to be elucidated. Objectives: The purpose of this study is to address the role of FVIII in the hemostatic mechanism in the absence of VWF by in vitro and ex vivo analysis in the treatment for type 3 VWD with recombinant FVIII (rFVIII). Patient/Methods: The patient is a 55-year-old male with type 3 VWD. Blood samples were obtained before and 30 min after bolus administration. Rotating thromboelastometry (ROTEM) assay was performed to examine global interactions in hemostasis. To elucidate the effect on platelet activation, α-thrombin- and shear-induced platelet aggregation studies were performed. Further, α-thrombin-induced [Ca2+]i rise was assessed using fura2-AM loaded platelets. Results and Implications: The patient underwent two surgical procedures of multiple teeth extractions successfully with minimal bleeding by bolus administration of rFVIII (50 IU/kg) before procedure and followed by continuous infusion at rate of 10 IU/kg/h for 15 hours. FVIII:C was elevated from 1.0% to 20~30% 30 min after bolus infusion and maintained ~15% after 12 h-continuous infusion. ROTEM analysis showed that infusion of rFVIII shortened clotting time (preinfusion 2083.8±784.3 sec vs. post-infusion 1022.0±191.5 sec) and clot formation time (pre 1267.3±455.4 sec vs. post 705.8±261.8 sec) and increased α (pre 8.5±7.4 degree vs. post 23.5±4.4 degree). The α value and CFT indicate the rate of increase of elastic shear modulus. Addition of rFVIII to preinfusion blood in vitro corrected ROTEM parameters and thrombin-induced aggregation dose-dependently. Infusion of FVIII enhanced thrombin-induced platelet aggregation (% maximal aggregation: pre 26.3% vs. post 98.2%) as well as low shear-induced platelet aggregation (% maximal aggregation: pre 18% vs. post 52%). Furthermore, infusion of rFVIII meliorated thrombin-induced intracellular calcium flux of washed platelets (thrombin 10 nM, Ca flux: pre 414.0 nM vs. post 620.6 nM). Recently, the cell-based model of hemostasis provides a solid foundation for the relation between platelet and coagulation. Although coagulation initiation occurs normally via the extrinsic pathway, amplification mediated by the intrinsic pathway is seriously disturbed in type 3 VWD due to the marked decrease in FVIII. Therefore, correction of FVIII could result in the improvement of hemostasis. Our data demonstrated the effectiveness of FVIII in the surgical treatment for type 3 VWD and further suggested that FVIII molecules are incorporated into platelet phospholipids to facilitate platelet activation as well as act directly to intrinsic pathways to normalize coagulation. Conclusions: Our observations suggested that FVIII plays an essential role in hemostasis in the absence of VWF and provided the rationale for the usage of rFVIII in the hemostatic management of type 3 VWD.

Decreased Sialic Acid Content of Plasma von Willebrand Factor in Precapillary Pulmonary Hypertension

2000 ◽  
Vol 83 (05) ◽  
pp. 683-687 ◽  
Author(s):  
Bruno de Souza ◽  
Nair Maeda ◽  
Antonio Lopes
Keyword(s):  
Pulmonary Hypertension ◽  
Sialic Acid ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Acid Content ◽  
Thiobarbituric Acid Reactive Substance ◽  
Sialic Acid Content ◽  
Reactive Substance ◽  
Von Willebrand ◽  
Willebrand Factor

SummaryIn pulmonary hypertension, defective von Willebrand factor protein (vWF) lacking large multimers is present in circulation. This is associated with evidence of chronic endogenous platelet activation. Since asialo vWF has been shown to promote platelet activation and aggregation, we decided to investigate possible changes in the sialic acid content of plasma vWF in patients with precapillary pulmonary hypertension. vWF-associated sialic acid was measured indirectly as a wheat germ agglutinin-reactive substance (WGA-RS, Western blotting), and directly, as a thiobarbituric acid-reactive substance (TBA-RS, spectrophotometric reading). In the sixteen patients we studied (ages 8–45 yr), circulating vWF concentration was 2.18 times normal (p <0.001). However, patient vWF subunit contained 19% (WGA-RS) to 24% (TBA-RS) less sialic acid than the normal protein (p <0.05 for both determinations). In five patients, vWF-associated sialic acid was below 50% normal. We conclude that circulating vWF is hyposialylated in precapillary pulmonary hypertension and speculate that this might influence its interaction with platelets in vivo in these patients.

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

2001 ◽  
Vol 134 (5) ◽  
pp. 1104-1112 ◽  
Author(s):  
Paul Jurasz ◽  
Michael W Stewart ◽  
Anna Radomski ◽  
Fadi Khadour ◽  
Marek Duszyk ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Von Willebrand Factor ◽  
Tumour Cell ◽  
Differential Regulation ◽  
Von Willebrand ◽  
Willebrand Factor

Filamin A binding to the cytoplasmic tail of glycoprotein Ibα regulates von Willebrand factor–induced platelet activation

Blood ◽  
2003 ◽  
Vol 102 (6) ◽  
pp. 2122-2129 ◽  
Author(s):  
Shuju Feng ◽  
Julio C. Reséndiz ◽  
Xin Lu ◽  
Michael H. Kroll
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Fusion Protein ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Cytoplasmic Tail ◽  
Cytoplasmic Domain ◽  
Filamin A ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract We examined the hypothesis that filamin A binding to the cytoplasmic tail of platelet glycoprotein Ibα (GpIbα) is regulated by pathologic shear stress and modulates von Willebrand factor (VWF)–induced platelet activation. To begin, we examined filamin binding to GpIbα in Chinese hamster ovary cells coexpressing mutant human GpIb-IX and wild-type human filamin A. We observed that many different deletions and truncations N-terminal to GpIbα's cytoplasmic domain residue 594 disrupted filamin A binding, but that binding was unaffected by 14 different point mutations in hydrophilic residues between amino acids 557 and 593. To try to narrow GpIbα's filamin A–binding domain, we next measured the effect of several cytoplasmic domain peptides on human filamin A binding to a GST-GpIbα cytoplasmic domain fusion protein. One peptide (residues 557-575; designated “A4 peptide”) inhibited filamin A binding to the GST-GpIbα cytoplasmic domain fusion protein and competed with GpIbα for binding to filamin A. When the A4 peptide was delivered to intact human platelets using a carrier peptide, we observed the dose-dependent inhibition of VWF-induced platelet aggregation in response to both ristocetin and shear stress. The effect of the A4 peptide on shear-induced platelet aggregation was accompanied by the attenuation of shear-induced filamin A binding to GpIbα and diminished shear-dependent protein tyrosine phosphorylation. These results suggest that shear-dependent VWF-induced platelet activation affects filamin A binding to GpIb-IX-V, and that filamin A binding to the cytoplasmic tail of GpIbα regulates proaggregatory tyrosine kinase signaling.

Adenovirus Induced Thrombocytopenia: The Role of P-Selectin and von Willebrand Factor in Virus- Mediated Platelet Clearance.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 222-222 ◽  
Author(s):  
Maha Othman ◽  
Andrea Labelle ◽  
Ian Mazzetti ◽  
David Lillicrap
Keyword(s):  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Critical Role ◽  
Flow Cytometric Analysis ◽  
Adhesive Proteins ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Acute thrombocytopenia has been consistently reported following IV administration of adenoviral vectors (Ad) but the mechanism responsible for this phenomenon has not been elucidated. Thrombocytopenia appears 24 hours after IV administration of Ad and is vector dose dependent. In this study, we have assessed the potential roles of the adhesive proteins P-selectin and von Willebrand Factor (VWF) on the aggregation and clearance of platelets following virus administration. We have addressed the question of whether the thrombocytopenia is due to a direct effect of the virus on platelets or an indirect effect related to interaction of platelets with other proteins or cells modified by the virus. We assessed platelet count in a group of Balb/c and C57Bl/6 mice over 1 week period following Ad administration and performed a detailed examination of the events within the first 24 h after Ad injection, the period that precedes the appearance of thrombocytopenia. We examined the effect of Ad on expression of the platelet activation marker P-selectin and the formation of platelet leukocyte aggregates (PLA) by means of flowcytometry after incubation of adenovirus with mouse platelets in vitro, and following Ad administration in vivo. To assess the role of VWF in Ad-induced thrombocytopenia we measured plasma VWF levels one hour after injection of Ad. Further investigations involved comparison of platelet counts, platelet activation, and the formation of PLA in a group of VWF KO mice. All studies have been performed with a replication deficient E1/E3-deleted Ad 1x 1011 viral particles/mouse. Our in vitro studies have shown that Ad directly activates mouse platelets as shown by increased expression of P-selectin. The average index of platelet activation for platelets stimulated by Ad was 2519.4 compared to 128.2 for resting platelets (n=5, p<0.02). Flow cytometric analysis of CD41 (platelets) and CD45 (leucocytes) double stained positive events indicated that Ad stimulation induced PLA when compared to the unstimulated samples. Our in vivo studies have confirmed the development of significant thrombocytopenia in both Balb/c as well as C57Bl/6 WT mice (n=8, p=0.00001, n= 6, p=0.002) 24 hours following Ad administration. Significant P-selectin expression was documented in both strains (n=4,p=0.0003; n=3, p=0.0008 respectively) as well as significant PLA one hour following Ad (n=4, p=0.01; n=3, p=0.007). The VWF KO mice showed non-significant thrombocytopenia (n= 6, p=0.063) at 24 hours following Ad, significant P-selectin expression (n=3, p=0.0003), but no significant PLA formation at one hour (n=3 p=0.12) relative to pre-injection levels. Plasma VWF levels were significantly elevated in both Balb/c and C57Bl/6 WT mice one hour following administration of the virus (n= 3, p=0.02; n= 3, p= 0.001). The average plasma VWF levels were 48.1 U/mL at 1h compared to 5.7 U/mL pre injection in Balb /c mice and 85.9 U/mL compared to 6.1 U/mL in C57Bl/6 mice. These studies have shown that Ad can act as an inducer of mouse platelet activation and as a promoter for platelet-leukocyte association both in vitro and in vivo. We have demonstrated a role for Ad in stimulating VWF release from the endothelium, and have shown that VWF has a critical role in platelet activation and clearance following Ad administration. We conclude that P-selectin and VWF proteins are directly involved in interactions between endothelial cells, platelets and leukocytes, a complex interaction that can explain at least in part the mechanisms underlying Ad-mediated thrombocytopenia.

scholarly journals Ibrutinib treatment affects collagen and von Willebrand factor-dependent platelet functions

Blood ◽  
2014 ◽  
Vol 124 (26) ◽  
pp. 3991-3995 ◽  
Author(s):  
Marie Levade ◽  
Elodie David ◽  
Cédric Garcia ◽  
Pierre-Alexandre Laurent ◽  
Sarah Cadot ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Shear Rate ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Bleeding Diathesis ◽  
Key Points ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Platelet Functions

Key Points Ibrutinib affects collagen and VWF-mediated platelet activation. The bleeding diathesis correlates with defects in collagen-induced platelet aggregation and firm adhesion on VWF at arterial shear rate.

scholarly journals The role of von Willebrand factor and fibrinogen in platelet aggregation under varying shear stress.

1991 ◽  
Vol 87 (4) ◽  
pp. 1234-1240 ◽  
Author(s):  
Y Ikeda ◽  
M Handa ◽  
K Kawano ◽  
T Kamata ◽  
M Murata ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Von Willebrand Factor ◽  
Von Willebrand ◽  
Willebrand Factor

Specific N- and O-Linked Carbohydrate Structures Mediate Von Willebrand Factor Interaction with Galectins -1 and -3

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2234-2234 ◽  
Author(s):  
Orla Rawley ◽  
Jamie O'Sullivan ◽  
Gudmundur Bergsson ◽  
Alain Chan ◽  
Rachel Therese McGrath ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Blood Group ◽  
Von Willebrand Factor ◽  
Blood Group Antigens ◽  
Terminal Galactose ◽  
Pngase F ◽  
Galectin 3 ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Abstract 2234 Von Willebrand Factor (VWF) is extensively glycosylated with both N- and O-linked carbohydrates. Moreover, these complex glycan structures influence VWF functional properties, including susceptibility to ADAMTS13 proteolysis, and plasma clearance. The molecular mechanisms through which VWF glycosylation (including ABO blood group antigens) act to influence VWF physiology remains unexplained. However, recent data suggest that VWF circulates in normal plasma bound to various carbohydrate-binding proteins, including specific members of the galectin family. In addition, galectin-3 binding has been reported to influence VWF cleavage by ADAMTS13. In this context, we sought to elucidate the role of specific VWF glycan determinants in modulating galectin interaction. VWF was purified from human plasma (pdVWF) by cryoprecipitation and gel filtration. VWF glycosylation was then modified using exoglycosidases and quantified by specific lectin ELISAs. Blood group specific VWF was also purified from pooled group AB, O, or Bombay plasmas. Galectins-1 and -3 were transiently expressed in competent E-coli cells with an N-terminal histidine tag, and purified by nickel chromatography. Finally, binding interactions were characterized via modified immunosorbant assay. In keeping with the previous report of Lenting et al, human pdVWF bound to both galectin-1 and galectin-3 in a dose-dependent manner. Enzymatic desialylation of pdVWF with α2-3,6,8,9 neuraminidase (Neu-VWF) markedly enhanced binding to galectin-1 (231±6%, p<0.0001). Similarly, removal of terminal sialic acid also increased binding to galectin-3, albeit to a lesser extent (136±6%, p<0.05). To further define the role of VWF glycans in regulating galectin binding, pdVWF was exposed to sequential neuraminidase and galactosidase digestions to remove terminal sialic acid and sub-terminal galactose residues (NeuGal-VWF). In contrast to the enhanced binding of Neu-VWF, binding of NeuGal-VWF to both galectin -1 and -3 was significantly reduced (51±5% and 52±6% compared to pdVWF; p<0.005). Cumulatively these findings suggest that loss of capping sialic acid and exposure of sub-terminal galactose critically regulates VWF-galectin binding. Treatment with PNGase F to completely remove N-linked carbohydrate structures (PNG-VWF) markedly decreased binding to galectin -1 and -3 (13±1% and 57±2%, p<0.001). Moreover, combined PNGase F and O-glycosidase digestions further attenuated galectin-3 binding (21±1%, p<0.001), suggesting that both the N- and O-linked glycans are involved in mediating the VWF-galectin interaction. ABO(H) blood group antigens are expressed on both the N-linked and O-linked glycans of human VWF. Moreover, ABO(H) determinants influence VWF susceptibility to ADAMTS13 proteolysis and plasma VWF half-life, through unknown mechanisms. Purified VWF from normal group AB individuals bound to both galectin-1 and galectin-3 significantly better than group O VWF (146±8% and 483±19%; p<0.01). Conversely, no significant difference in binding was observed between Group O and Bombay VWF. Consequently, although terminal A (GalNAc) and B (Gal) sugar moieties promote galectin binding, expression of terminal α1–2 fucose residues is not important. The glycosylation profile of platelet-VWF differs from that of pdVWF. In particular, platelet-VWF expresses reduced levels of both capping sialic acid and sub-terminal galactose residues (∼50%), and lacks AB blood group antigens. To characterize the effects of this differential sugar expression on galectin binding, platelet-derived VWF was isolated and purified (platelet freeze-thawing followed by immuno-affinity chromatography with monoclonal CLB-Rag20). In keeping with the reduction in Gal and AB blood group antigen expression, platelet VWF bound less well to galectin-1 and galectin-3 (72±6% and 67±7% versus pdVWF; p<0.05). These novel data demonstrate that both the N- and O-linked oligosaccharide structures of VWF are involved in mediating galectin binding. In particular, expression of terminal AB blood group antigens, and expression of sub-terminal galactose moieties following loss of capping sialic acid, both markedly enhance galectin binding affinity. Further studies will be required to define how galectin binding is involved in mediating the functional consequences of variation in VWF glycans. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Investigation of the role of von Willebrand factor in thrombotic thrombocytopenic purpura

Blood ◽  
1985 ◽  
Vol 66 (5) ◽  
pp. 1219-1221 ◽  
Author(s):  
EC Lian ◽  
FA Siddiqui
Keyword(s):  
Platelet Aggregation ◽  
Thrombotic Thrombocytopenic Purpura ◽  
Von Willebrand Factor ◽  
Platelet Glycoprotein ◽  
Plasma Samples ◽  
Thrombocytopenic Purpura ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

Abstract Von Willebrand factor (vWF) has been implicated to function as a cofactor in platelet aggregation induced by thrombotic thrombocytopenic purpura (TTP) plasma. To investigate further this role of vWF, we have used rabbit monospecific anti-FVIII/vWF antibodies and a monoclonal antibody to platelet glycoprotein Ib (GP Ib) that blocks the ristocetin- induced platelet aggregation. The monoclonal anti-platelet GP Ib antibody inhibited the platelet aggregation induced by ristocetin in the presence of normal plasma, but not that by any of the five TTP plasma samples. The TTP plasma samples from five patients were incubated with the monospecific antibodies to FVIII/vWF. In all of the samples, the FVIII/vWF:Ag was drastically reduced; however, there was almost no effect on the platelet-aggregating activity. Therefore, it is concluded that vWF is unlikely to play a major role in platelet aggregation induced by majority of TTP plasmas and that the site of platelet GP Ib, to which vWF binds in the presence of ristocetin, is not involved in TTP plasma-induced aggregation.

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