Platelets and Phospholipids in Tissue Factor-initiated Thrombin Generation

Butenas, Saulius; Branda, Richard F.; Veer, Cornelis van ’t; Cawthern, Kevin M.; Mann, Kenneth G.

doi:10.1055/s-0037-1616110

Cited by 84 publications

(86 citation statements)

References 49 publications

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“…Figure 1A (f) shows thrombin generation in the presence of 2 M PCPS (1-2 M PCPS is equivalent to 2 ϫ 10 8 /mL platelets in supporting thrombin generation 50 ) initiated by 25 pM TF with factor VIIa at a physiologic concentration (0.1 nM). The initiation phase lasted approximately 3 minutes, and maximum levels of thrombin (ϳ 390 nM) were achieved 7 minutes after initiation of the reaction.…”

Section: Factor Viia and Tf In Normal Bloodmentioning

confidence: 80%

Mechanism of factor VIIa–dependent coagulation in hemophilia blood

Butenas

Brummel

Branda

et al. 2002

Blood

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188

163

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The ability of factor VIIa to initiate thrombin generation and clot formation in blood from healthy donors, blood from patients with hemophilia A, and in anti-factor IX antibody-induced ("acquired") hemophilia B blood was investigated. In normal blood, both factor VIIa-tissue factor (TF) complex and factor VIIa alone initiated thrombin generation. The efficiency of factor VIIa was about 0.0001 that of the factor VIIa-TF complex. In congenital hemophilia A blood and "acquired" hemophilia B blood in vitro, addition of 10 to 50 nM factor VIIa (pharmacologic concentrations) corrected the clotting time at all TF concentrations tested (0-100 pM) but had little effect on thrombin generation. Fibrinopeptide release and insoluble clot formation were only marginally influenced by addition of factor VIIa. TF alone had a more pronounced effect on thrombin generation; an increase in TF from 0 to 100 pM increased the maximum thrombin level in "acquired" hemophilia B blood from 120 to 480 nM. Platelet activation was considerably enhanced by addition of factor VIIa to both hemophilia A blood and "acquired" hemophilia B blood. Thus, pharmacologic concentrations of factor VIIa cannot restore normal thrombin generation in hemophilia A and hemophilia B blood in vitro. The efficacy of factor VIIa (10-50 nM) in hemophilia blood is dependent on TF. IntroductionThe blood-coagulation cascade is initiated when cryptic tissue factor (TF) is expressed and exposed to circulating blood and binds plasma factor VIIa. The resulting factor VIIa-TF complex activates the serine protease zymogens factor IX and factor X. The factor Xa that is initially produced generates picomolar amounts of thrombin, which activates platelets and cleaves procofactors factors V and VIII. Factor VIIIa forms a complex on a membrane surface with serine protease factor IXa and activates factor X at a 50-to 100-fold higher rate than the factor VIIa-TF complex. The factor Xa produced, in complex with its cofactor, factor Va, and an appropriate membrane surface forms the prothrombinase complex, which is the primary activator of prothrombin. The thrombin produced amplifies its own generation by activating factor XI and completing the activation of platelets and procofactors. Thrombin cleaves fibrinogen and activates factor XIII to form the insoluble isopeptide cross-linked fibrin clot. The coagulation cascade is down-regulated by the stoichiometric inhibitors antithrombin III (AT-III) and tissue factor pathway inhibitor (TFPI) and by the dynamic protein C system. 1 Genetic and acquired deficiencies in coagulation proteins lead to hemorrhagic syndromes. [2][3][4][5][6] The most common bleeding disorders result from deficiencies of factor VIII (hemophilia A) or factor IX (hemophilia B) coagulant activity. In the past, the principal treatments for hemophilia relied on partially purified concentrates of coagulation factors. 7,8 These concentrates, however, have been associated with thromboembolic complications and viral infections. 9-11 During the past decade, plasma-derived, ...

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Section: Factor Viia and Tf In Normal Bloodmentioning

confidence: 80%

Mechanism of factor VIIa–dependent coagulation in hemophilia blood

Butenas

Brummel

Branda

et al. 2002

Blood

Self Cite

188

163

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“…66 Similarly, reductions in platelet counts (Ͻ10 000/mm 3 ) elicit dependence on platelet concentration. 64 The end point used in evaluating hemostasis in most bioassays is the generation of a fibrin clot. As illustrated in Figure 4, the formation of a fibrin clot occurs at 10 to 30 nmol/L thrombin or Ϸ3% of the total amount of thrombin produced during the reaction, which is provided by only Ϸ7 pmol/L prothrombinase.…”

Section: Mann Et Al Dynamics Of Thrombin Formation 19mentioning

confidence: 99%

“…These have included the following: (1) synthetic plasma, in which mixtures prepared from purified procoagulants and anticoagulants and a natural or synthetic membrane source are induced to react by the addition of lipid reconstituted tissue factor 9,10,41,55-60 ; (2) paravivo studies of coagulation, in which whole, contact pathway-suppressed blood obtained by phlebotomy and maintained at 37°is induced to clot by addition of a fixed amount of membrane reconstituted tissue factor 42,[61][62][63][64][65][66][67][68] ; (3) numerical (computer) models of the coagulation system, which are based on the ensemble of published (and estimated) rate constants and concentrations of procoagulants and stoichiometric inhibitors and the mechanisms of their interactions 69 -71 (also referred to as "in silico" simulations); and (4) in vivo studies of the hemostatic reaction, in which whole blood exuding from a microvascular wound is sequentially sampled for relevant product formation. [72][73][74][75] Each of the model systems used has specific benefits and limitations.…”

Section: Models Of the Blood Coagulation Reactionmentioning

confidence: 99%

“…61 However, under conditions of congenital deficiency, thrombocytopenia, platelet pathology, or pharmacologic intervention, the tissue factor initiated reaction can become sensitive to factor V or platelets. 64,66,74 In studies to assess the influence of preactivation of platelets, we used the thrombin receptor activation peptide to provide for the preexpression of complex binding sites on the platelet surface. 66 Preactivation of the platelets did not change the rate of thrombin generation.…”

Section: Mann Et Al Dynamics Of Thrombin Formationmentioning

confidence: 99%

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The Dynamics of Thrombin Formation

Mann

Butenas

Brummel

2003

ATVB

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476

394

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Abstract-The central event of the hemostatic process is the generation of thrombin through the tissue factor pathway. This is a highly regulated, dynamic process in which thrombin itself plays many roles, positively and negatively its production and destruction. The hemostatic process is essential to normal physiology and is also the Achilles heel of our aging population. The inappropriate generation of thrombin may lead to vascular occlusion with the consequence of myocardial infarction, stroke, pulmonary embolism, or venous thrombosis. In this review, we summarize our present views regarding the tissue factor pathway by which thrombin is generated and the roles played by extrinsic and intrinsic factor Xa generating complexes in hemostasis and the roles of the stoichiometric and dynamic inhibitors that regulate thrombin generation. Key Words: coagulation Ⅲ fibrinogen Ⅲ aggregation Ⅲ coagulation inhibitors T he inventory of molecular components and the presumed physiology of the hemostatic process and its regulation have been established on the basis of plasma abundance, hemorrhagic or thrombotic pathology, in vitro tests, and chemical signatures. Two in vitro plasma tests, the prothrombin time and the activated partial thromboplastin time, were prominent in the development of the inventory. The former test relies on the addition of an extrinsic tissue factor source (thromboplastin), whereas the latter is based on the introduction of a foreign surface to initiate coagulation using only this surface contact and the biological constituents intrinsic to plasma. Both tests rely on a fibrin formation (clotting) end point. These assays permitted identification of connectivity between the component activities identified as required for plasma coagulation and defined the concept of intrinsic and extrinsic coagulation pathways, which converge at the step of formation of the prothrombinase complex. However, the mechanisms established by in vitro tests are not always mirrored in human pathology associated with bleeding or thrombosis. The primary pathway leading to hemostatic and thrombotic pathologies is associated with the tissue factorinitiated extrinsic coagulation pathway, whereas components unique to the intrinsic or contact pathway (factor XI, factor XII, prekallikrein, HMW kininogen) may have accessory roles in the process. Therefore, in this review, we focus on the dynamics of the reactions associated with the introduction of tissue factor to blood, leading to the formation of thrombin.An evaluation of the reactions involved in the formation of thrombin leads to the conclusion that the physiologically relevant hemostatic mechanism is composed of 3 procoagulant vitamin K-dependent enzyme complexes (which use the proteases factor IXa, factor Xa, and factor VIIa) and one anticoagulant vitamin K-dependent complex. 1 Each complex involves a vitamin K-dependent serine protease and a cofactor protein with the protein-protein complex assembled on a membrane surface provided by activated or damaged cells. The same hemostati...

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“…In vitro studies primarily utilize artificial phospholipid vesicles (PCPS) as a surrogate membrane surface to study the process of blood coagulation. It has been demonstrated that PCPS at 1 to 2 g.mol/L is equivalent to platelets at physiological concentrations (2 x 10 8 /mL) in supporting thrombin generation [25]. However, platelets (and phospholipid) at physiological concentrations do not saturate the reactions of blood coagulation [26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Testing of Intravenous Hemostatic Agents in a Novel Swine Model of Bleeding: Preliminary Results With FXa-PCPs

Ryan¹,

Dorfman²,

Jenny³

et al. 2005

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Platelets and Phospholipids in Tissue Factor-initiated Thrombin Generation

Cited by 84 publications

References 49 publications

Mechanism of factor VIIa–dependent coagulation in hemophilia blood

Mechanism of factor VIIa–dependent coagulation in hemophilia blood

The Dynamics of Thrombin Formation

Testing of Intravenous Hemostatic Agents in a Novel Swine Model of Bleeding: Preliminary Results With FXa-PCPs

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