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Blood Dec 1997Platelet activation and microthrombus formation are invariable features of xenograft rejection and the vascular injury observed when porcine organs are transplanted into...
Platelet activation and microthrombus formation are invariable features of xenograft rejection and the vascular injury observed when porcine organs are transplanted into primates. This pathological process could be mediated, at least in part, by aberrant interactions of von Willebrand Factor (vWF) associated with the donor vasculature with host platelets. Unlike human vWF, native porcine vWF (pvWF) interacts with human GPIb independently of shear stress or nonphysiological stimuli, eg, ristocetin. We therefore contrasted the potential of isolated human and porcine vWF-A1-domains to interact with human platelets in vitro. Both human and porcine vWF-A1-domains expressed as glycosyl phosphatidylinositol-linked FLAG fusion proteins on COS-7 cells induced GPIb-dependent aggregation and intracellular Ca++ uptake of platelets, independent of both the remainder of the vWF protein and additional modifying factors. Porcine A1-domains were more potent than human homologues, and in addition ristocetin could boost platelet aggregation only with the human A1-domain. Putative conformational changes in the porcine A1-domain could result in the heightened, ristocetin-independent interactions observed with human platelets and may be of importance for xenograft survival.
Topics: Amino Acid Sequence; Animals; Anti-Bacterial Agents; Binding Sites; Blood Platelets; COS Cells; Calcium; Cells, Cultured; Epitopes; Flow Cytometry; Humans; Macaca fascicularis; Molecular Sequence Data; Oligopeptides; Papio; Peptides; Platelet Activation; Platelet Glycoprotein GPIb-IX Complex; Ristocetin; Swine; von Willebrand Factor
PubMed: 9373253
DOI: No ID Found -
Thrombosis and Haemostasis Dec 2019Proteolytic cleavage of von Willebrand factor (VWF) by a plasma a disintegrin and metalloproteinase with a thrombospondin type 1 motifs, member 13 (ADAMTS13) is...
BACKGROUND
Proteolytic cleavage of von Willebrand factor (VWF) by a plasma a disintegrin and metalloproteinase with a thrombospondin type 1 motifs, member 13 (ADAMTS13) is regulated by shear stress and binding of coagulation factor VIII, platelets or platelet glycoprotein 1b, and ristocetin to VWF.
OBJECTIVE
Current study aims to identify novel VWF binding partners that may modulate VWF functions under physiological conditions.
METHODS
A deoxyribonucleic acid aptamer-based affinity purification of VWF, followed by tandem mass spectrometry, functional, and binding assays was employed.
RESULTS
Apolipoprotein B100/low-density lipoprotein (apoB100/LDL) was identified as a novel VWF-binding partner. Purified apoB100/LDL was able to accelerate the proteolytic cleavage of VWF by ADAMTS13 under shear in a concentration-dependent manner. This rate-enhancing activity was dramatically reduced when apoB100/LDL was oxidized. More interestingly, the oxidized apoB100/LDL appeared to compete with native apoB100/LDL for its enhancing activity on VWF proteolysis under shear. As a control, a purified apoA1/high-density lipoprotein (apoA1/HDL) or apoB48 exhibited a minimal or no activity enhancing VWF proteolysis by ADAMTS13 under the same conditions. Both VWF and ADAMTS13 were able to bind native or oxidized apoB100/LDL with high affinities. No binding interaction was detected between VWF (or ADAMTS13) and apoA1/HDL (or apoB48). Moreover, apoB100/LDL but not its oxidized products inhibited the adhesion of platelets to ultra large VWF released from endothelial cells under flow. Finally, significantly reduced ratios of high to low molecular weight of VWF multimers with increased levels of plasma VWF antigen were detected in mice fed with high cholesterol diet.
CONCLUSION
These results indicate that apoB100/LDL may be a novel physiological regulator for ADAMTS13-VWF functions.
Topics: ADAMTS13 Protein; Animals; Apolipoprotein B-100; Arteries; Blood Platelets; Endothelial Cells; Hemostasis; Lipoproteins, LDL; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microfluidics; Platelet Glycoprotein GPIb-IX Complex; Protein Binding; Proteolysis; Receptors, LDL; Ristocetin; Shear Strength; Stress, Mechanical; Tandem Mass Spectrometry; von Willebrand Factor
PubMed: 31493779
DOI: 10.1055/s-0039-1696713 -
Blood Nov 1981The clinical course and coagulation profile of a pregnant patient with variant von Willebrand's disease were followed from the second trimester through puerperium. The...
The clinical course and coagulation profile of a pregnant patient with variant von Willebrand's disease were followed from the second trimester through puerperium. The clinical course was characterized by a normal delivery and absence of abnormal bleeding or need for replacement therapy. The coagulation profile demonstrated an increase in factor VIII procoagulant activity, factor-VIII-related antigen, and platelet aggregation activity in response to ristocetin prior to delivery. Postpartum, these factors decreased to prepregnancy values with distinctly different patterns. Factor VIII procoagulant activity continued to rise for 5 days after delivery and then decreased with a half-life of approximately 6 days. Factor-VIII-related antigen began to decrease just prior to delivery, displaying a half-life or approximately 6 days. Ristocetin cofactor activity, however, dropped immediately postpartum and displayed a half-life of approximately 6 hr. The ristocetin cofactor activity was associated with factor-VIII-related antigen, which displayed a significantly smaller molecular weight than does normal factor-VIII-related antigen. Larger aggregates of factor-VIII-related antigen. Larger aggregates of factor-VIII-related antigen did not appear during the pregnancy, and ristocetin cofactor activity could not be demonstrated in fragments of less than 0,8 x 10(6).
Topics: Adult; Antigens; Bleeding Time; Estradiol; Factor VIII; Female; Genetic Variation; Humans; Partial Thromboplastin Time; Platelet Adhesiveness; Pregnancy; Pregnancy Complications, Hematologic; Prothrombin Time; von Willebrand Diseases; von Willebrand Factor
PubMed: 6794676
DOI: No ID Found -
The Journal of Antibiotics May 1985A new antibacterial antibiotic complex, aridicin, was produced by a new genus, Kibdelosporangium aridum (SK&F-AAD-216). The individual factors, aridicins A, B and C,...
A new antibacterial antibiotic complex, aridicin, was produced by a new genus, Kibdelosporangium aridum (SK&F-AAD-216). The individual factors, aridicins A, B and C, were isolated from the fermentation broth by an Amberlite XAD-7 resin extraction and purified by preparative reversed phase HPLC. The aridicins were found to be novel members of the glycopeptide class of antibiotics as exemplified by ristocetin and vancomycin, based on chemical and spectroscopic data, their molecular weights as determined by FAB mass spectrometry (1,786, 1,800 and 1,814), the detection of actinoidinic acid in their acid hydrolysates, and detailed TLC and HPLC comparisons with representative members of this class.
Topics: Actinomycetales; Amino Acids; Anti-Bacterial Agents; Chromatography, High Pressure Liquid; Glycopeptides; Molecular Weight; Protein Conformation; Vancomycin
PubMed: 4019308
DOI: 10.7164/antibiotics.38.561 -
The Journal of Biological Chemistry Oct 1983von Willebrand factor (VWF) functions in platelet aggregation, a form of cellular interaction. In vitro analysis of platelet aggregation, as measured by the platelet...
von Willebrand factor (VWF) functions in platelet aggregation, a form of cellular interaction. In vitro analysis of platelet aggregation, as measured by the platelet aggregometer, requires addition of a promoter such as the glycopeptide antibiotic ristocetin. Native multimeric VWF (Mr = 1-20 X 10(6)) can be reduced with sulfhydryl reagents to a monomeric state (Mr = 2 X 10(5)). In this study, the binding of bovine VWF and ristocetin to bovine platelets was investigated using fluorescence anisotropy of derivatized monomer protein and ristocetin and also by radioisotope methods using 125I-labeled monomer and native protein. Ristocetin bound to bovine platelets but not to VWF. VWF binding to formaldehyde-fixed platelets was dependent on the presence of a promoter such as ristocetin. The monomer and multimer VWF bound equally well in the presence of low ristocetin concentrations. Under these conditions, plots of VWF binding versus platelet concentration were sigmoidal, indicating positive cooperativity with respect to platelets. At higher (100 micrograms/ml) ristocetin concentrations, the binding curve was no longer sigmoidal. Ristocetin promoted the formation of small platelet aggregates, an effect that was amplified by the presence of VWF. In fact, all conditions which resulted in monomer or multimer VWF binding to platelets also caused formation of platelet aggregates observed by light microscopy. These combined results were consistent with VWF binding only to the interface between proximal platelets. High affinity binding could be provided by the presence of two cell surfaces and the resulting multiple binding interactions. Polycations, such as poly(L-lysine) and Polybrene, also promoted the formation of platelet aggregates and facilitated the binding of VWF to platelets. Physiological platelet activators such as thrombin, ADP, and collagen also facilitated VWF binding to native platelets and caused platelet aggregation. It appears possible that any process which causes the surface membranes of platelets to become spatially close will allow expression of VWF activity.
Topics: Animals; Blood Coagulation Factors; Blood Platelets; Cattle; Cell Membrane; Fibrinogen; Fluorescence Polarization; Kinetics; Platelet Aggregation; Ristocetin; von Willebrand Factor
PubMed: 6605342
DOI: No ID Found -
BioMed Research International 2013Platelet function analysis utilizing platelet-rich plasma and optical density based aggregometry fails to identify patients at risk for uremia associated complications.
BACKGROUND
Platelet function analysis utilizing platelet-rich plasma and optical density based aggregometry fails to identify patients at risk for uremia associated complications.
METHODS
We employed whole blood platelet aggregation analysis based on impedance as well as determination of ATP release from platelet granules detected by a chemiluminescence method. Ten chronic kidney disease (CKD) stage 4 or 5 predialysis patients underwent platelet evaluation. Our study aims to evaluate this platform in this patient population to determine if abnormalities could be detected.
RESULTS
Analysis revealed normal aggregation and ATP release to collagen, ADP, and high-dose ristocetin. ATP release had a low response to arachidonic acid (0.37 ± 0.26 nmoles, reference range: 0.6-1.4 nmoles). Platelet aggregation to low-dose ristocetin revealed an exaggerated response (20.9 ± 18.7 ohms, reference range: 0-5 ohms).
CONCLUSIONS
Whole blood platelet analysis detected platelet dysfunction which may be associated with bleeding and thrombotic risks in uremia. Diminished ATP release to arachidonic acid (an aspirin-like defect) in uremic patients may result in platelet associated bleeding. An increased aggregation response to low-dose ristocetin (a type IIb von Willebrand disease-like defect) is associated with thrombus formation. This platelet hyperreactivity may be associated with a thrombotic diathesis as seen in some uremic patients.
Topics: Adult; Aged; Dielectric Spectroscopy; Female; Humans; Luminescent Measurements; Male; Middle Aged; Platelet Aggregation; Platelet Function Tests; Renal Insufficiency, Chronic; Reproducibility of Results; Risk Assessment; Sensitivity and Specificity; Uremia
PubMed: 23878808
DOI: 10.1155/2013/486290 -
PloS One 2015An experimental model of endocardial thrombosis has not been developed and endocardial endothelial dysfunction in heart failure (HF) is understudied. We sought to...
OBJECTIVE
An experimental model of endocardial thrombosis has not been developed and endocardial endothelial dysfunction in heart failure (HF) is understudied. We sought to determine whether disruption of the endothelial anti-coagulant activated protein C (APC) pathway in CREBA133 HF mice promotes endocardial thrombosis in the acute decompensated phase of the disease, and whether alterations in von Willebrand factor (vWF) secretion from HF endocardium reduces thrombus formation as HF stabilizes.
APPROACH AND RESULTS
Echocardiography was used to follow HF development and to detect endocardial thrombi in CREBA133 mice. Endocardial thrombi incidence was confirmed with immunohistochemistry and histology. In early and acute decompensated phases of HF, CREBA133 mice had the highest incidence of endocardial thrombi and these mice also had a shorter tail-bleeding index consistent with a pro-thrombotic milieu. Both APC generation, and expression of receptors that promote APC function (thrombomodulin, endothelial protein C receptor, protein S), were suppressed in the endocardium of acute decompensated HF mice. However, in stable compensated HF mice, an attenuation occurred for vWF protein content and secretion from endocardial endothelial cells, vWF-dependent platelet agglutination (by ristocetin), and thrombin generation on the endocardial surface.
CONCLUSIONS
CREBA133 mice develop HF and endocardial endothelial dysfunction. Attenuation of the anti-coagulant APC pathway promotes endocardial thrombosis in early and acute decompensated phases of HF. However, in stable compensated HF mice, disruptions in endothelial vWF expression and extrusion may actually reduce the incidence of endocardial thrombosis.
Topics: Animals; Anticoagulants; Cyclic AMP Response Element-Binding Protein; Disease Models, Animal; Echocardiography; Endocardium; Endothelial Cells; Female; Heart Diseases; Heart Failure; Hemodynamics; Immunohistochemistry; Male; Mice; Mice, Transgenic; Phenotype; Platelet Aggregation; Protein C; Thrombin; Thrombosis; von Willebrand Factor
PubMed: 26565707
DOI: 10.1371/journal.pone.0142940 -
Journal of Thrombosis and Haemostasis :... Mar 2022Platelet-binding Von Willebrand Factor (VWF) strings assemble upon stimulated secretion from endothelial cells.
BACKGROUND
Platelet-binding Von Willebrand Factor (VWF) strings assemble upon stimulated secretion from endothelial cells.
OBJECTIVES
To investigate the efficiency of platelet binding to multi-molecular VWF bundles secreted from endothelial cells and to investigate the role of osteoprotegerin, a protein located in Weibel-Palade bodies that interacts with the VWF platelet binding domain.
METHODS
The nanobody VWF/AU-a11 that specifically binds to VWF in its active platelet-binding conformation was used to investigate the conformation of VWF.
RESULTS
Upon stimulated secretion from endothelial cells, VWF strings were only partially covered with platelets, while a VWD-type 2B mutation or ristocetin enhanced platelet binding by 2-3-fold. Osteoprotegrin, reduces platelet adhesion to VWF by 40% ± 18% in perfusion assays. siRNA-mediated down-regulation of endothelial osteoprotegerin expression resulted in a 1.8-fold increase in platelet adhesion to VWF strings. Upon viral infection, there is a concordant rise in VWF and osteoprotegerin plasma levels. Unexpectedly, no such increase was observed in plasma of desmopressin-treated hemophilia A-patients. In a mouse model, osteoprotegerin expression was low in liver endothelial cells of vehicle-treated mice, and concanavalin A-treatment increased VWF and osteoprotegerin expression 4- and 40-fold, respectively. This increase was translated in a 30-fold increased osteoprotegerin/VWF ratio in plasma.
CONCLUSIONS
Release of VWF from endothelial cells opens the platelet-binding site, irrespective of the presence of flow. However, not all available platelet-binding sites are being occupied, suggesting some extent of regulation. Part of this regulation involves endothelial proteins that are co-secreted with VWF, like osteoprotegerin. This regulatory mechanism may be of more relevance under inflammatory conditions.
Topics: Animals; Blood Platelets; Endothelial Cells; Humans; Mice; Osteoprotegerin; Platelet Adhesiveness; Ristocetin; von Willebrand Diseases; von Willebrand Factor
PubMed: 34816579
DOI: 10.1111/jth.15598 -
Clinical and Applied... Dec 2010This study was performed to investigate the platelet aggregation alterations in platelet-rich plasma (PRP) samples of children with Helicobacter pylori (H pylori)...
This study was performed to investigate the platelet aggregation alterations in platelet-rich plasma (PRP) samples of children with Helicobacter pylori (H pylori) infection. Platelet aggregation induced by adenosine diphosphate (ADP), collagen, ristocetin, or epinephrine was studied with photometric aggregometry in 30 patients before and after eradication therapy and in a control group including 15 children. The pretreatment mean maximum aggregation values and slope were significantly lower (P < .0001) in the study group at 10 μmol/L concentrations of ADP (ADP-like defect). The maximum aggregation values and slope revealed no significant differences (P > 0.05) between the study group after therapy and the control group. We concluded that H pylori infection may cause dysfunction of platelets in children and can be reversed by H pylori eradication therapy. Further studies should be carried out to determine the mechanisms of platelet dysfunction in children with H pylori infection.
Topics: Adenosine Diphosphate; Adolescent; Blood Platelets; Case-Control Studies; Child; Collagen; Epinephrine; Female; Helicobacter Infections; Helicobacter pylori; Humans; Male; Platelet Aggregation; Platelet-Rich Plasma; Ristocetin
PubMed: 19633022
DOI: 10.1177/1076029609339747 -
Blood Jan 2002Type Vicenza variant of von Willebrand disease (VWD) is characterized by a low plasma von Willebrand factor (VWF) level and supranormal VWF multimers. Two candidate...
Type Vicenza variant of von Willebrand disease (VWD) is characterized by a low plasma von Willebrand factor (VWF) level and supranormal VWF multimers. Two candidate mutations, G2470A and G3864A at exons 17 and 27, respectively, of the VWF gene were recently reported to be present in this disorder. Four additional families, originating from northeast Italy, with both mutations of type Vicenza VWD are now described. Like the original type Vicenza subjects, they showed a mild bleeding tendency and a significant decrease in plasma VWF antigen level and ristocetin cofactor activity but normal platelet VWF content. Unlike the original patients, ristocetin-induced platelet aggregation was found to be normal. Larger than normal VWF multimers were also demonstrated in the plasma. Desmopressin (DDAVP) administration increased factor VIII (FVIII) and VWF plasma levels, with the appearance of even larger multimers. However, these forms, and all VWF oligomers, disappeared rapidly from the circulation. The half-life of VWF antigen release and of elimination was significantly shorter than that in healthy counterparts, so that at 4 hours after DDAVP administration, VWF antigen levels were close to baseline. Similar behavior was demonstrated by VWF ristocetin cofactor activity and FVIII. According to these findings, it is presumed that the low plasma VWF levels of type Vicenza VWD are mainly attributed to reduced survival of the VWF molecule, which, on the other hand, is normally synthesized. In addition, because normal VWF-platelet GPIb interaction was observed before or after DDAVP administration, it is proposed that type Vicenza VWD not be considered a 2M subtype.
Topics: Blood Platelets; DNA Mutational Analysis; Deamino Arginine Vasopressin; Drug Stability; Factor VIII; Half-Life; Humans; Italy; Kinetics; Macromolecular Substances; Mutation; Platelet Aggregation; Ristocetin; von Willebrand Diseases; von Willebrand Factor
PubMed: 11756169
DOI: 10.1182/blood.v99.1.180