Regulation of Factor VIII Expression and Activity by von Willebrand Factor

1999 ◽  
Vol 82 (08) ◽  
pp. 201-208 ◽  
Author(s):  
Steven Pipe ◽  
Randal Kaufman
Keyword(s):  
Factor Viii ◽  
Thrombin Generation ◽  
Platelet Adhesion ◽  
Hemophilia A ◽  
Factor Viia ◽  
Factor Xa ◽  
Factor X ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
Von Willebrand

IntroductionHemostasis requires a cascade of proteolytic reactions that occurs on the surfaces of damaged or activated cells, such as platelets, white blood cells, and endothelial cells. Initial damage to a blood vessel results in platelet adhesion to the subendothelium mediated by von Willebrand factor (vWF). Subsequently, platelet activation and aggregation occur. Protease complexes assemble on the surface of activated cells and are converted sequentially to their proteolytically active forms to result in a localized burst of thrombin generation and the conversion of soluble fibrinogen to insoluble fibrin. Activation of the extrinsic coagulation pathway occurs to form a factor VIIa—tissue factor complex on activated or damaged endothelial cells. In turn, factor VIIa activates the intrinsic pathway of blood coagulation by activating factor IXa, which in turn interacts with activated factor VIIIa, in the presence of calcium and negatively-charged phospholipids, to convert factor X to factor Xa. Factor Xa then acts with its cofactor factor Va, in the presence of calcium and negatively-charged phospholipids, to convert prothrombin to thrombin. Initial factor Xa and thrombin generation feeds back to activate cofactors VIII and V. Activation of these cofactors in the intrinsic pathway serves to amplify thrombin generation. The importance of this cascade in hemostasis is evident from the characterization of individuals who are defective in proteins that function in this cascade. The most common of these disorders, a deficiency of factor VIII that results in hemophilia A, was documented more than 1,700 years ago in the Talmud.1 The genetics of hemophilia A was described in the early 1800s, and transfusion of whole blood was shown to successfully treat a hemophilia A-associated bleeding episode by 1840.2,3 Although the presence of factor VIII in plasma was demonstrated in 19114 and its role in hemostasis was described in 1937,5 a detailed biochemical and structural characterization of factor VIII was achieved only within the last 20 years. Prior to 1980, the relationship between hemophilia A and von Willebrand’s disease generated a great deal of confusion because the autosomally-inherited von Willebrand’s disease is associated with some degree of factor VIII deficiency, although hemophilia is an X-linked disease. In addition, early preparations of antihemophilia factor not only corrected the clotting time of hemophilic plasma, but also restored platelet adhesion and aggregation defects in the plasma of patients with von Willebrand’s disease. It is now appreciated that factor VIII and vWF are two separate proteins that exist as a complex in plasma. They are under separate genetic control, have distinct biochemical and immunological properties, and have unique and essential physiological functions (Table 1). Factor VIII is the X-linked gene product that accelerates the factor IXa-mediated activation of factor X by four orders of magnitude. vWF is an autosomal gene product that is essential for platelet adhesion to the subendothelium and for ristocetin-induced platelet aggregation. In addition, vWF plays a critical role in the regulation of factor VIII activity by 1) stabilizing factor VIII on secretion from the cell;6,7 2) requiring the survival of factor VIII in plasma,8,9 3) protecting factor VIII from activation by factor Xa and inactivation by activated protein C;10,11 and 4) preventing factor VIII from binding to phospholipids and activated platelets.3,12 It is likely that vWF mediates its inhibitory properties on factor VIII by preventing factor VIII from binding to phospholipids, an interaction required for both factor Xa- and APC-mediated cleavage of factor VIII. Because vWF and factor VIII are found in plasma as a complex and vWF stabilizes factor VIII and regulates its activity, the activities of these two proteins are intimately intertwined.

scholarly journals In Hemophilia Α Plasma Treated with Emicizumab, Factor IX Activation By Factor VIIa Drives Thrombin Generation

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 17-17
Author(s):  
Dougald Monroe ◽  
Mirella Ezban ◽  
Maureane Hoffman
Keyword(s):  
Factor Viii ◽  
Tissue Factor ◽  
Plasma Levels ◽  
Thrombin Generation ◽  
Hemophilia A ◽  
Factor Viia ◽  
Factor Ix ◽  
Factor X ◽  
Dose Dependent

Background.Recently a novel bifunctional antibody (emicizumab) that binds both factor IXa (FIXa) and factor X (FX) has been used to treat hemophilia A. Emicizumab has proven remarkably effective as a prophylactic treatment for hemophilia A; however there are patients that still experience bleeding. An approach to safely and effectively treating this bleeding in hemophilia A patients with inhibitors is recombinant factor VIIa (rFVIIa). When given at therapeutic levels, rFVIIa can enhance tissue factor (TF) dependent activation of FX as well as activating FX independently of TF. At therapeutic levels rFVIIa can also activate FIX. The goal of this study was to assess the role of the FIXa activated by rFVIIa when emicizumab is added to hemophilia A plasma. Methods. Thrombin generation assays were done in plasma using 100 µM lipid and 420 µM Z-Gly-Gly-Arg-AMC with or without emicizumab at 55 µg/mL which is the clinical steady state level. The reactions were initiated with low (1 pM) tissue factor (TF). rFVIIa was added at concentrations of 25-100 nM with 25 nM corresponding to the plasma levels achieved by a single clinical dose of 90 µg/mL. To study to the role of factor IX in the absence of factor VIII, it was necessary to create a double deficient plasma (factors VIII and IX deficient). This was done by taking antigen negative hemophilia B plasma and adding a neutralizing antibody to factor VIII (Haematologic Technologies, Essex Junction, VT, USA). Now varying concentrations of factor IX could be reconstituted into the plasma to give hemophilia A plasma. Results. As expected, in the double deficient plasma with low TF there was essentially no thrombin generation. Also as expected from previous studies, addition of rFVIIa to double deficient plasma gave a dose dependent increase in thrombin generation through activation of FX. Interestingly addition of plasma levels of FIX to the rFVIIa did not increase thrombin generation. Starting from double deficient plasma, as expected emicizumab did not increase thrombin generation since no factor IX was present. Also, in double deficient plasma with rFVIIa, emicizumab did not increase thrombin generation. But in double deficient plasma with FIX and rFVIIa, emicizumab significantly increased thrombin generation. The levels of thrombin generation increased in a dose dependent fashion with higher concentrations of rFVIIa giving higher levels of thrombin generation. Conclusion. Since addition of FIX to the double deficient plasma with rFVIIa did not increase thrombin generation, it suggests that rFVIIa activation of FX is the only source of the FXa needed for thrombin generation. So in the absence of factor VIII (or emicizumab) FIX activation does not contribute to thrombin generation. However, in the presence of emicizumab, while rFVIIa can still activate FX, FIXa formed by rFVIIa can complex with emicizumab to provide an additional source of FX activation. Thus rFVIIa activation of FIX explains the synergistic effect in thrombin generation observed when combining rFVIIa with emicizumab. The generation of FIXa at a site of injury is consistent with the safety profile observed in clinical use. Disclosures Monroe: Novo Nordisk:Research Funding.Ezban:Novo Nordisk:Current Employment.Hoffman:Novo Nordisk:Research Funding.

Inhibition of thrombin generation by the zymogen factor VII: implications for the treatment of hemophilia A by factor VIIa

Blood ◽  
2000 ◽  
Vol 95 (4) ◽  
pp. 1330-1335 ◽  
Author(s):  
Cornelis van 't Veer ◽  
Neal J. Golden ◽  
Kenneth G. Mann
Keyword(s):  
Factor Viii ◽  
Tissue Factor ◽  
Thrombin Generation ◽  
Hemophilia A ◽  
Factor Viia ◽  
Plasma Concentrations ◽  
Factor Xa ◽  
Factor Vii ◽  
Lag Phase ◽  
Single Chain

Factor VII circulates as a single chain inactive zymogen (10 nmol/L) and a trace (∼10-100 pmol/L) circulates as the 2-chain form, factor VIIa. Factor VII and factor VIIa were studied in a coagulation model using plasma concentrations of purified coagulation factors with reactions initiated with relipidated tissue factor (TF). Factor VII (10 nmol/L) extended the lag phase of thrombin generation initiated by 100 pmol/L factor VIIa and low TF. With the coagulation inhibitors TFPI and AT-III present, factor VII both extended the lag phase of the reaction and depressed the rate of thrombin generation. The inhibition of factor Xa generation by factor VII is consistent with its competition with factor VIIa for TF. Thrombin generation with TF concentrations >100 pmol/L was not inhibited by factor VII. At low tissue factor concentrations (<25 pmol/L) thrombin generation becomes sensitive to the absence of factor VIII. In the absence of factor VIII, factor VII significantly inhibits TF-initiated thrombin generation by 100 pmol/L factor VIIa. In this hemophilia A model, approximately 2 nmol/L factor VIIa is needed to overcome the inhibition of physiologic (10 nmol/L) factor VII. At 10 nmol/L, factor VIIa provided a thrombin generation response in the hemophilia model (0% factor VIII, 10 nmol/L factor VII) equivalent to that observed with normal plasma, (100% factor VIII, 10 nmol/L factor VII, 100 pmol/L factor VIIa). These results suggest that the therapeutic efficacy of factor VIIa in the medical treatment of hemophiliacs with inhibitors is, in part, based on overcoming the factor VII inhibitory effect.

Current Knowledge of the AHF-Like Antigen

1975 ◽  
Author(s):  
Dominique Meyer
Keyword(s):  
Molecular Weight ◽  
Factor Viii ◽  
Von Willebrand Factor ◽  
Hemophilia A ◽  
Factor Activity ◽  
Factor Viii Activity ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
Von Willebrand ◽  
Willebrand Factor

Factor VIII and von Willebrand Factor activities are associated with a high molecular weight protein which can be isolated from plasma and may be studied by immunological methods. Homologous antibodies to Factor VIII are directed towards the active site of the Factor VIII molecule; they do not neutralize Willebrand Factor activity and do not precipitate with normal plasma. The use of such antibodies has allowed the distinction between Hemophilia A+ and A-. Specific precipitation of Factor VIII antibodies using polyethylene glycol will be reported, allowing typing of heavy and light chains of purified antibodies. Heterologous antisera prepared in rabbits against purified human Factor VIII complex neutralize Factor VIII and von Willebrand Factor activities and precipitate with AHF-like antigen. Estimation of this antigen in plasma has allowed (1) the differenciation of the molecular abnormalities in Hemophilia A and classical von Willebrand’s disease; (2) the comparison between normal and Hemophilic AHF-like antigen; (3) the detection of carriers of Hemophilia A; (4) the study of variants of von Willebrand’s disease; (5) the demonstration of this antigen in platelets and in endothelial cells. Factor VIII activity and AHF-like antigen are probably separate entities, circulating as a complex in normal plasma, as suggested by the following experiments: transfusion studies in von Willebrand’s disease; immuno-adsorption studies; comparison of Factor VIII complex in cryoprecipitate and supernatant; and dissociation in high salt buffer, demonstrating that Factor VIII includes two biologically linked but distinct fragments, of high (HMW) and low (LMW) molecular weight. The non functional HMW subunit, controlled by an autosomal locus, is identified by the presence of AHF-like antigen and Willebrand Factor activity. The LMW subunit, product of an X-chromosome locus, does not contain AHF-like antigen, but it carries Factor VIII activity, as demonstrated by the following facts: inactivation by both human and rabbit antibodies to Factor VIII; transient activation by thrombin; obtention of antisera which specifically inactivate Factor VIII.

A Simple Enzyme-Immunoassay (EIA) Test for Factor VIII-Related Antigen (VIIIAGN)

1979 ◽  
Vol 42 (03) ◽  
pp. 848-854 ◽  
Author(s):  
Paul M Ness ◽  
Herbert A Perkins
Keyword(s):  
Factor Viii ◽  
Enzyme Immunoassay ◽  
Hemophilia A ◽  
Single Sample ◽  
Healthy Controls ◽  
Von Willebrand's Disease ◽  
Factor Viii Related Antigen ◽  
Von Willebrand’S Disease ◽  
Increased Sensitivity

SummaryAn enzyme immunoassay (EIA) system has been developed to measure factor VIII- related antigen (VIIIAGN). This assay gives similar results to the commonly used Laurell electroimmunodiffusion (EID) assay for VIIIAGN as shown by comparison of both techniques with samples from healthy controls, patients with hemophilia A, and patients with von Willebrand’s disease. The assay also has a greater precision than the EID technique as demonstrated by multiple assays of aliquots of a single sample. The use of this EIA test for VIIIAGN is simple and employs inexpensive reagents and equipment. The use of expensive antisera is minimized. EIA for VIIIAGN has the advantage of increased sensitivity compared to Laurell EIA.

scholarly journals Characterization of the defect of the factor VIII/von Willebrand factor protein in von Willebrand's disease

Blood ◽  
1982 ◽  
Vol 59 (3) ◽  
pp. 542-548 ◽  
Author(s):  
HR Gralnick ◽  
MC Cregger ◽  
SB Williams
Keyword(s):  
Sialic Acid ◽  
Factor Viii ◽  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Molecular Forms ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
Platelet Receptor ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract The factor VIII/von Willebrand factor (f.VIII/vWf) protein was purified from the plasma of a patient with von Willebrand's disease (vWd). The patient had all of the classic laboratory findings of vWd except for the ristocetin-induced platelet aggregation of his own platelet-rich plasma. The disease has been documented in three generations. Comparison of the purified normal and vWd f.VIIi/vWf protein revealed several abnormalities, including decreased concentration of f.VIII/vWf antigen; decreased specific vWf activity; absence of the larger molecular forms of the f.VIII/vWf protein; carbohydrate deficiencies affecting the sialic acid, penultimate galactose and N- acetylglucosamine moieties; and decreased binding of the f.VIII/vWf protein to its platelet receptor. These studies indicate the multiplicity of biochemical and functional abnormalities associated with the f.VIII/vWf protein in vWd. f.VIII/vWf protein to normal f.VIII/vWf protein that had been treated with 2-mercaptoethanol (2-ME) to reduce the multimer size and then treated with specific exoglycosidases to remove the sialic acid and penultimate galactose residues revealed similar biologic properties.

Effect Of DDAVP In Patients With Von Willebrand’s Disease And Hemophilia A

1981 ◽  
Author(s):  
A I Warrier ◽  
C Hillman ◽  
J M Lusher
Keyword(s):  
Side Effects ◽  
Factor Viii ◽  
Hemophilia A ◽  
Blood Components ◽  
Excessive Bleeding ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
Crossed Immunoelectrophoresis ◽  
Transient Improvement ◽  
The U.S

European investigators have reported on the efficacy of l-deamino-9-D-arginine vasopressin (DDAVP) in von Willebrand’s disease (vWD) and mild hemophilia A. We have thus evaluated the effects of a single intranasal dose of DDAVP (200ugm of the more dilute form available in the U.S.), in 12 individuals with vWD and in 4 with moderate hemophilia A. Crossed immunoelectrophoresis of VIII: RAg demonstrated normal electrophoretic mobility in each of the vWD subjects. Components of the factor VIII system (VIII: C, VIII: RAg, VIII: R Cof.) were assayed pre - and 90 and 180 minutes post- DDAVP. Each of 11 subjects with mild or moderate vWD had an increase in VIII: C activity (avg. 2X increase), 8 of 11 had an increase in VIII: R Cof, and 9 of 11 had an increase in VIII: RAg. The twelfth vWD subject, who had severe vWD, had no rise in any of these components. Of 4 vWD subjects who had pre- and post-DDAVP template bleeding times (BT) performed, the only one who had a prolonged baseline BT showed a normal BT 90 minutes post-DDAVP. One vWD subject, in whom we had documented an increase in all F. VIII components after DDAVP, later underwent dental extractions 90 minutes after DDAVP. No excessive bleeding was noted. Four individuals with moderate hemophilia A (baseline VIII: C values of 0.02-0.10 u/ml) were also studied. Three had a rise in all components of the factor VIII system post-DDAVP while the fourth did not. No undesirable side effects were noted in any of the 16 subjects who received DDAVP. We conclude that even the more dilute form of DDAVP available in the U.S., when given intranasally, results in transient improvement in selected individuals with vWD or moderate hemophilia A. This drug thus warrants further study as an alternative to blood components in the management of vWD, as well as in mild and moderate hemophilia A.

scholarly journals DDAVP in type IIa von Willebrand's disease

Blood ◽  
1986 ◽  
Vol 67 (2) ◽  
pp. 465-468 ◽  
Author(s):  
HR Gralnick ◽  
SB Williams ◽  
LP McKeown ◽  
ME Rick ◽  
P Maisonneuve ◽  
...  
Keyword(s):  
Factor Viii ◽  
Protease Inhibitors ◽  
Von Willebrand Factor ◽  
Bleeding Time ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
Time Period ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Ristocetin Cofactor

Abstract 1-D-Amino(8-D-arginine)-vasopressin (DDAVP) infusion in three patients with type IIa von Willebrand's disease (vWD) resulted in a normalization of the factor VIII coagulant, factor VIII-related antigen, and von Willebrand factor (vWF) (ristocetin cofactor) activities and the bleeding time. The normalization of these hemostatic parameters persisted for four hours. Over the same time period there was a marked increase in the quantity of the vWF multimers when blood was collected in the presence of protease inhibitors. The vWF multimers present were even larger than the normal. When blood was collected in the absence of protease inhibitors, a smaller increase in the plasma vWF multimers was observed and fewer of the intermediate and larger vWF multimers were seen; multimers larger than those present in normal plasma were not visualized. The platelet vWF multimers and activities did not change with or without inhibitors. These studies suggest that there is a subgroup of patients with type IIa vWD who respond to DDAVP with complete normalization of their hemostatic abnormalities and whose vWF is sensitive to proteolysis.

scholarly journals Multimeric composition of factor VIII/von Willebrand factor following administration of DDAVP: implications for pathophysiology and therapy of von Willebrand's disease subtypes

Blood ◽  
1982 ◽  
Vol 59 (6) ◽  
pp. 1272-1278 ◽  
Author(s):  
ZM Ruggeri ◽  
PM Mannucci ◽  
R Lombardi ◽  
AB Federici ◽  
TS Zimmerman
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Resting State ◽  
Bleeding Time ◽  
Type I ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
Plasma Factor ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract We have studied the modifications in the multimeric composition of plasma factor VIII/von Willebrand factor and the bleeding time response following administration of 1-Deamino-[8-D-arginine]-Vasopressin (DDAVP) to patients with different subtypes of von Willebrand's disease. In type I, all multimers were present in plasma in the resting state, though they were decreased in concentration. Administration of DDAVP resulted in an increased concentration of these forms as well as the appearance of larger forms than were previously present. There was concomitant correction of the bleeding time. In type IIA, large multimers were absent in the resting state, and although DDAVP induced an average threefold increase in the plasma concentration of factor VIII/von Willebrand factor, the larger multimers did not appear and the bleeding time, although shortened, was not corrected. In contrast, the larger multimers that were also absent from type IIB plasma in the resting state rapidly appeared following DDAVP administration. However, their appearance was transitory and the bleeding time, as in IIA patients, was shortened but not corrected. The characteristic multimeric composition of platelet factor VIII/von Willebrand factor in given subtypes predicted the alteration in plasma factor VIII/von Willebrand factor induced by DDAVP. These studies provide evidence that the different subtypes of von Willebrand's disease represent distinct abnormalities of factor VIII/von Willebrand factor. They also suggest that complete hemostatic correction following DDAVP can be routinely expected only in type I von Willebrand's disease, and only if factor VIII/von Willebrand factor can be raised to normal levels.

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