Altered von Willebrand factor molecule in children with thrombosis following asparaginase-prednisone-vincristine therapy for leukemia.

1985 ◽  
Vol 3 (9) ◽  
pp. 1266-1272 ◽  
Author(s):  
C H Pui ◽  
C M Chesney ◽  
J Weed ◽  
C W Jackson
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Degradation Products ◽  
Thrombus Formation ◽  
Adenosine Diphosphate ◽  
Factor V ◽  
Fibrin Degradation Products ◽  
Thrombotic Complications ◽  
Von Willebrand ◽  
Willebrand Factor

Eleven consecutive leukemia patients with thrombosis induced by asparaginase-prednisone-vincristine therapy were studied to gain insight into the pathogenesis of this complication. Measurement of anti-thrombin III, plasminogen, factor V, and fibrin degradation products as well as platelet aggregation sensitivity to adenosine diphosphate disclosed no consistent abnormalities that would explain pathologic thrombus formation. A decrease in platelet counts observed in nine of 11 patients, prompted us to investigate the possible involvement of factor VIII in this disorder. Levels of factor VIII procoagulant activity, von Willebrand factor (vWF) and ristocetin cofactor were similar to findings for an identically treated comparison group who remained free of thrombotic complications. However, qualitative examination of vWF by crossed immunoelectrophoresis (CIE) revealed a distinct right shift of the immunoprecipitin lines in each of three thrombotic patients tested, whereas a normal profile was found in three similarly treated patients without the complication. This altered pattern had reverted to normal when CIE was repeated 2 to 7 months later. We postulate that the abnormal vWF is related to the development of thrombosis.

scholarly journals Studies of a Second Family With the Quebec Platelet Disorder: Evidence That the Degradation of the α-Granule Membrane and Its Soluble Contents Are Not Secondary to a Defect in Targeting Proteins to α-Granules

Blood ◽  
1997 ◽  
Vol 89 (4) ◽  
pp. 1243-1253 ◽  
Author(s):  
Catherine P.M. Hayward ◽  
Elisabeth M. Cramer ◽  
William H. Kane ◽  
Shilun Zheng ◽  
Madeleine Bouchard ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Autosomal Dominant ◽  
Degradation Products ◽  
Bleeding Disorder ◽  
Factor V ◽  
Platelet Counts ◽  
Normal Platelet ◽  
Platelet Disorder ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract We recently described a Quebec family with an autosomal dominant bleeding disorder characterized by mildly reduced-low normal platelet counts, an epinephrine aggregation defect, multimerin deficiency, and proteolytic degradation of several, soluble α-granular proteins. Similar clinical features led us to investigate a second family with an unexplained, autosomal dominant bleeding disorder. The affected individuals had reduced to normal platelet counts, absent platelet aggregation with epinephrine, and multimerin deficiency. Their platelet α-granular proteins factor V, thrombospondin, von Willebrand factor, fibrinogen, fibronectin, osteonectin, and P-selectin were proteolyzed and comigrated with the degradation products found in patients from the other family. However, their platelet albumin, IgG, external membrane glycoproteins, CD63 (a lysosomal and dense granular protein), calpain, and plasma von Willebrand factor were normal, indicating restriction in the proteins proteolyzed. Electron microscopy studies indicated preserved α-granular ultrastructure, despite degradation of soluble and membrane α-granular proteins. Immunoelectron microscopy studies of the patients' platelets indicated that fibrinogen, von Willebrand factor, P-selectin, multimerin, and factor V were within α-granules, with normal to reduced labeling for these proteins. Pathologic proteolysis of α-granular contents, rather than a defect in targeting proteins to α-granules, may be the cause of the protein degradation in the Quebec platelet disorder.

Distinct roles of ADP receptors in von Willebrand factor–mediated platelet signaling and activation under high flow

Blood ◽  
2004 ◽  
Vol 104 (10) ◽  
pp. 3221-3227 ◽  
Author(s):  
Mario Mazzucato ◽  
Maria Rita Cozzi ◽  
Paola Pradella ◽  
Zaverio M. Ruggeri ◽  
Luigi De Marco
Keyword(s):  
Shear Stress ◽  
Von Willebrand Factor ◽  
Platelet Adhesion ◽  
Thrombus Formation ◽  
Adenosine Diphosphate ◽  
Ion Concentration ◽  
Adp Receptors ◽  
Platelet Signaling ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract We have investigated the role of adenosine diphosphate (ADP) receptors in the adhesion, activation, and aggregation of platelets perfused over immobilized von Willebrand factor (VWF) under high shear stress. Blocking P2Y1 prevented stable platelet adhesion and aggregation, indicative of a complete inhibition of αIIbβ3 activation, and decreased the duration of transient arrests from 5.9 seconds ± 2.8 seconds to 1.2 seconds ± 0.8 seconds; in contrast, blocking P2Y12 inhibited only the formation of larger aggregates. Moreover, blocking P2Y1 decreased the proportion of platelets showing early intracytoplasmic Ca++ elevations (α/β peaks) from 20.6% ± 1.6% to 14.6% ± 1.5% (P < .01), and the corresponding peak ion concentration from 1543 nM ± 312 nM to 1037 nM ± 322 nM (P < .05); it also abolished the Ca++ elevations seen in firmly attached platelets (γ peaks). Blocking P2Y12 had no effect on these parameters, and did not enhance the effect of inhibiting P2Y1. Inhibition of phospholipase C had similar consequences as the blocking of P2Y1, whereas inhibition of Src family kinases abolished both type α/β and γ Ca++ oscillations, although the former effect required a higher inhibitor concentration. Our results demonstrate that, under elevated shear stress conditions, ADP signaling through P2Y1 may contribute to the initial stages of platelet adhesion and activation mediated by immobilized VWF, and through P2Y12 to sustained thrombus formation.

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.

Factor VIII Inhibitor Antibodies with C2 Domain Specificity Are Less inhibitory to Factor VIII Complexed with von Willebrand Factor

1996 ◽  
Vol 76 (05) ◽  
pp. 749-754 ◽  
Author(s):  
Suzuki Suzuki ◽  
Morio Arai ◽  
Kagehiro Amano ◽  
Kazuhiko Kagawa ◽  
Katsuyuki Fukutake
Keyword(s):  
Complex Formation ◽  
Factor Viii ◽  
Von Willebrand Factor ◽  
Domain Specificity ◽  
Factor Viii Inhibitor ◽  
C2 Domain ◽  
Recombinant Fviii ◽  
Von Willebrand ◽  
A2 Domain ◽  
Willebrand Factor

SummaryIn order to clarify the potential role of von Willebrand factor (vWf) in attenuating the inactivation of factor VIII (fVIII) by those antibodies with C2 domain specificity, we investigated a panel of 14 human antibodies to fVIII. Immunoblotting analysis localized light chain (C2 domain) epitopes for four cases, heavy chain (A2 domain) epitopes in five cases, while the remaining five cases were both light and heavy chains. The inhibitor titer was considerably higher for Kogenate, a recombinant fVIII concentrate, than for Haemate P, a fVIII/vWf complex concentrate, in all inhibitor plasmas that had C2 domain specificity. In five inhibitor plasmas with A2 domain specificity and in five with both A2 and C2 domain specificities, Kogenate gave titers similar to or lower than those with Haemate P. The inhibitory effect of IgG of each inhibitor plasma was then compared with recombinant fVIII and its complex with vWf. When compared to the other 10 inhibitor IgGs, IgG concentration, which inhibited 50% of fVIII activity (IC50), was remarkably higher for the fVIII/vWf complex than for fVIII in all the inhibitor IgGs that had C2 domain reactivity. Competition of inhibitor IgG and vWf for fVIII binding was observed in an ELISA system. In 10 inhibitors that had C2 domain reactivity, the dose dependent inhibition of fVIII-vWf complex formation was observed, while, in the group of inhibitors with A2 domain specificity, there was no inhibition of the complex formation except one case. We conclude that a subset of fVIII inhibitors, those that bind to C2 domain determinants, are less inhibitory to fVIII when it is complexed with vWf that binds to overlapping region in the C2 domain.

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