Regulation of tissue factor-induced coagulation and platelet aggregation in flowing whole blood

Kuijpers, Marijke J. E.; Nieuwenhuys, Cécile M. A.; Feijge, Marion A.H.; Kloots, Willem; Giesen, Peter; Jerling, Johann C.; Egbrink, Mirjam G.A. oude; Heemskerk, Johan W. M.

doi:10.1160/th04-02-0091

Cited by 11 publications

(16 citation statements)

References 25 publications

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“…The fibrin surface was verified to recruit platelets, and to trigger platelet spreading, pseudopod extension and formation of small aggregates, consistent with platelet activation. The combination of PGE 1 /aspirin partially inhibited the control and QPD platelet adhesion to fibrin, consistent with their known attenuating effects on platelet adhesion to fibrin [33,34]. We confirmed that QPD platelet recruitment to a fibrin surface was associated with an increased fibrin degradation, likely mediated, at least in part, by platelet delivered u‐PA, as platelet activation inhibitors reduced the fibrin degradation.…”

Section: Discussionsupporting

confidence: 84%

Insights into abnormal hemostasis in the Quebec platelet disorder from analyses of clot lysis

Diamandis

Adam

Kahr

et al. 2006

Journal of Thrombosis and Haemostasis

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Summary. Background: The Quebec platelet disorder (QPD) is inherited and characterized by delayed-onset bleeding following hemostatic challenge. Other characteristics include increased expression and storage of active urokinase-type plasminogen activator (u-PA) in platelets in the setting of normal to increased u-PA in plasma. There is also consumption of platelet plasminogen activator inhibitor-1 and increased generation of plasmin in platelets accompanied by proteolysis of stored a-granule proteins, including Factor V. Aims and Methods: Although fibrinolysis has been proposed to contribute to QPD bleeding, the effects of QPD blood and platelets on clot lysis have not been evaluated. We used thromboelastography Ò (TEG Ò ), biochemical evaluations of whole blood clot lysis, assessments of clot ultrastructure, and perfusion of blood over preformed fibrin to gain insights into the disturbed hemostasis in the QPD. Results: Thromboelastography was not sensitive to the increased u-PA in QPD blood. However, there was abnormal plasmin generation in QPD whole blood clots, generated at low shear, with biochemical evidence of increased fibrinolysis. The incorporation of QPD platelets into a forming clot led to progressive disruption of fibrin and platelet aggregates unless drugs were added to inhibit plasmin. In whole blood perfusion studies, QPD platelets showed normal adherence to fibrin, but their adhesion was followed by accelerated fibrinolysis. Conclusions: The QPD is associated with Ôgain-of-functionÕ abnormalities that increase the lysis of forming or preformed clots. These findings suggest accelerated fibrinolysis is an important contributor to QPD bleeding.

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Section: Discussionsupporting

confidence: 84%

Insights into abnormal hemostasis in the Quebec platelet disorder from analyses of clot lysis

Diamandis

Adam

Kahr

et al. 2006

Journal of Thrombosis and Haemostasis

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“…34 However, because this phosphorylation can be reversible as well, the relation between the integrin phosphorylation state and the presently studied delayed platelet disaggregation still needs to be established. This also holds for the cAMP/protein kinase A-mediated mechanism of integrin closure, which is likely to be distinct from the cAMP effect on Ca 2ϩ signal generation, 35 but is still unidentified.…”

Section: Discussionmentioning

confidence: 98%

Continuous signaling via PI3K isoforms β and γ is required for platelet ADP receptor function in dynamic thrombus stabilization

Cosemans¹,

Munnix²,

Wetzker³

et al. 2006

Blood

143

149

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Signaling from collagen and G proteincoupled receptors leads to platelet adhesion and subsequent thrombus formation. Paracrine agonists such as ADP, thromboxane, and Gas6 are required for platelet aggregate formation. We hypothesized that thrombi are intrinsically unstable structures and that their stabilization requires persistent paracrine activity and continuous signaling, maintaining integrin ␣ IIb ␤ 3 activation. Here, we studied the disassembly of human and murine thrombi formed on collagen under high shear conditions. Platelet aggregates rapidly disintegrated (1) in the absence of fibrinogen-containing plasma; (2) by blocking or inhibiting ␣ IIb ␤ 3 ; (3) by blocking P2Y 12 receptors; (4) by suppression of phosphoinositide 3-kinase (PI3K) ␤. In murine blood, absence of PI3K␥ led to formation of unstable thrombi, leading to dissociation of multiplatelet aggregates. In addition, blocking PI3K␤ delayed initial thrombus formation and reduced individual platelet-platelet contact. Similarly without flow, agonist-induced aggregation was reversed by late suppression of P2Y 12 or PI3K isoforms, resulting in single platelets that had inactivated ␣ IIb ␤ 3 and no longer bound fibrinogen. Together, the data indicate that continuous outside-in signaling via P2Y 12 and both PI3K␤ and PI3K␥ isoforms is required for perpetuated ␣ IIb IntroductionPlatelet plug formation at sites of vascular injury is considered to consist of 3 phases: initiation, propagation, and perpetuation. 1,2 The initiation phase involves platelet adhesion to von Willebrand factor (VWF) and to collagen exposed in the vessel wall. In the propagation phase, activated platelets secrete mediators such as ADP, thromboxane A 2 (TxA 2 ), and Gas6, which activate other platelets to form aggregates. In the perpetuation phase, fibrin formation and less well-understood postaggregation events are assumed to accomplish stabilization of the thrombus.At arterial shear rates, the thrombotic process is initiated by the tethering of platelets via glycoprotein (GP) Ib-IX-V to VWF, bound to collagen. 3 In human and murine platelets, 2 interacting collagen receptors, GPVI and integrin ␣ 2 ␤ 1 , mediate stable adhesion to collagen. [4][5][6][7] The signaling receptor GPVI triggers series of activation events, including integrin ␣ IIb ␤ 3 activation (providing binding sites, for example, for fibrinogen) and Ca 2ϩ mobilization and secretion, which all function to recruit other platelets. 8,9 During the propagation phase of thrombus formation, released ADP and TxA 2 in a paracrine way pursue the activation process, mediated by P2Y 1 , P2Y 12 , and TP␣ receptors. 8,10,11 The Gq-coupled P2Y 1 and TP␣ receptors evoke Ca 2ϩ mobilization and protein kinase C activity. The P2Y 12 signaling pathway involves Gimediated inhibition of adenylyl cyclase, which lowers cyclic AMP and indirectly enhances Ca 2ϩ signal generation. 12-14 P2Y 12 signaling via Gi also leads to activation of the phosphoinositide 3-kinase (PI3K) and protein kinase B signaling pathways. However, it is still unc...

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“…The perfusion protocol was such that coagulation occurred at physiological, millimolar Mg 2ϩ , and Ca 2ϩ concentrations. 21 With wild-type blood, perfusion in the presence of tissue factor resulted in PS exposure and the formation of platelet aggregates, which gradually transformed to clots trapping erythrocytes ( Figure II, available online at http://atvb.ahajournals.org). TPLSM analysis indicated that the thrombi contained extensive networks of fibrin and aggregated platelets, which were surrounded by single PSexposing platelets.…”

Section: Components Of the Gpvi Signaling Pathway Determining Platelementioning

confidence: 99%

The Glycoprotein VI-Phospholipase Cγ2 Signaling Pathway Controls Thrombus Formation Induced by Collagen and Tissue Factor In Vitro and In Vivo

Munnix

Strehl

Kuijpers

et al. 2005

ATVB

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Objective-Both collagen and tissue factor can be initiating factors in thrombus formation. We investigated the signaling pathway of collagen-induced platelet activation in interaction with tissue factor-triggered coagulation during the thrombus-forming process. Methods and Results-In murine blood flowing over collagen, platelet exposure of phosphatidylserine and procoagulant activity, but not adhesion, completely relied on each of the following signaling modules: glycoprotein VI (GPVI), FcR ␥-chain, Src kinases, adaptor protein LAT, and phospholipase C␥2 (PLC␥2). On flow in the presence of tissue factor, these signaling components were essential for platelet aggregation and greatly enhanced fibrin clot formation. Collagen-stimulated thrombin generation relied on the presence and activity of GPVI, FcR ␥-chain, Src kinase, LAT, and PLC␥2. The physiological importance of this GPVI pathway was shown in a FeCl 3 -induced in vivo murine thrombosis model. In both venules and arterioles, signaling through GPVI, FcR ␥-chain, and Src kinases enhanced the formation of phosphatidylserine-exposing and fibrin-rich thrombi. Key Words: glycoprotein VI Ⅲ LAT Ⅲ platelets Ⅲ Src kinase Ⅲ thrombin T hrombus formation can be initiated by both platelet-and coagulation-activating factors. Collagens in the extracellular matrix and other vascular layers are thought to act as principal platelet-activating components of the damaged vessel wall; they also provide a surface for von Willebrand factor adhesion. 1 Tissue factor, also exposed in damaged vessels, is a key trigger of the coagulation process. 2 Because of the proposed major role of platelets in arterial thrombosis and the importance of coagulation in venous thrombosis, the current understanding is that collagen/von Willebrand factor-mediated events are more important in arteries, whereas tissue factor plays a more prominent role in venous thrombus formation. Conclusions-TheFlow studies with human and mouse blood have established that the signaling receptor glycoprotein VI (GPVI) exclusively mediates collagen-induced platelet procoagulant activity, thus linking the processes of platelet activation and coagulation. [3][4][5] This procoagulant platelet response is mediated by a prolonged and potent rise in cytosolic [Ca 2ϩ ] i , which results in exposure of procoagulant phosphatidylserine (PS) at the platelet outer surface. 6 PS exposure is a key regulating factor in the coagulation process. For instance, PS-containing membrane surfaces dramatically increase the formation of factor Xa and thrombin. 7 However, several authors have argued that this platelet response has only an assistant role in coagulation and that, in vivo, other platelet reactions may play important roles as well. 2,8 Thus, although there is no doubt that platelets enhance thrombin generation (coagulation) in plasma or whole blood, the precise mechanism is still a matter of debate. The platelet immunoreceptor GPVI is coexpressed with the Fc receptor (FcR) ␥-chain, although the latter also interacts with other plat...

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Regulation of tissue factor-induced coagulation and platelet aggregation in flowing whole blood

Cited by 11 publications

References 25 publications

Insights into abnormal hemostasis in the Quebec platelet disorder from analyses of clot lysis

Insights into abnormal hemostasis in the Quebec platelet disorder from analyses of clot lysis

Continuous signaling via PI3K isoforms β and γ is required for platelet ADP receptor function in dynamic thrombus stabilization

The Glycoprotein VI-Phospholipase Cγ2 Signaling Pathway Controls Thrombus Formation Induced by Collagen and Tissue Factor In Vitro and In Vivo

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