Regulation of Platelet Factor Va-dependent Thrombin Generation by Activated Protein C at the Surface of Collagen-adherent Platelets

Briedé, Jacob J.; Tans, Guido; Willems, George M.; Hemker, H.C.; Lindhout, Théo

doi:10.1074/jbc.m009230200

Cited by 11 publications

(9 citation statements)

References 36 publications

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“…These results are consistent with the observations of Hockin et al 18 and Colucci et al 22 who showed that APC inactivation of factor Va on endothelial cells was similar to inactivation on lipids. These results differ from Briede et al, 21 but are consistent with the observations of Camire et al 15,20 who showed that on platelets, APC does not completely inactivate factor Va. However, while Camire et al concluded that platelet factor Va and plasma-derived factor Va differ in their resistance to cleavage by APC, 15,20 our studies using factor V-deficient platelets showed that platelet-derived and plasmaderived factor Va are inactivated identically (Figure 4).…”

Section: Discussioncontrasting

confidence: 55%

“…Previous studies have examined the ability of APC to cleave factors Va and VIIIa on lipid surfaces, 7,8,13,15,19,21 on endothelial cell surfaces, 9,18,38 and on platelet surfaces. 21 Some studies showed that factor Va on the platelet surface was relatively resistant to cleavage by APC. 15,16,20 The previous work has generally focused on factor Va inactivation as the endpoint of the study.…”

Section: Discussionmentioning

confidence: 99%

“…[1][2][3][4][5] Thrombin regulation results from inactivation of factors Va and VIIIa by activated protein C (APC) in the presence of its cofactor protein S. [6][7][8][9][10][11][12][13][14] The role of different surfaces in inactivation of factors Va and VIIIa by the APC system has been the subject of several studies. [7][8][9][15][16][17][18][19][20][21][22] Some of these studies have used assay systems incorporating lipid vesicles, 7,8,13,19 whereas others have used monocytes, 22 endothelial cells, 9,18 or platelets [15][16][17]20,21 as the surface for APC activity and the results have been somewhat different. Because the physiologic site of action of APC in inactivating factors Va and VIIIa is extremely important in terms of hemostasis and thrombosis, we have carried out experiments looking at the effect of APC on thrombin generation on a number of different surfaces.…”

Section: Introductionmentioning

confidence: 99%

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Activated protein C cleaves factor Va more efficiently on endothelium than on platelet surfaces

Oliver

Monroe

Church

et al. 2002

Blood

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The protein C/protein S system is known to regulate thrombin generation in vivo by cleaving factors Va and VIIIa. We have examined the activity of activated protein C in several tissue factor-initiated models of coagulation. We used 4 models: monocytes as the tissue factor source with platelets as the thrombin-generating surface; endothelial cells as the tissue factor source with platelets as the thrombin-generating surface; endothelial cells as both the tissue factor source and the thrombin-generating surface; and relipidated tissue factor with lipid vesicles providing the surface for thrombin generation. With the lipid surface, activated protein C dose-dependently reduced thrombin generation. Similarly, when endothelial cells provided the only surface for thrombin generation, activated protein C dosedependently decreased thrombin generation significantly. By contrast, whenever platelets were present, activated protein C only minimally affected the amount of thrombin generated. When endothelial cells were the tissue factor source with platelets providing the surface for thrombin generation, activated protein C did increase the time until the burst of thrombin generation but had minimal effects on the total amount of thrombin generated. Activated protein C had essentially no effect on thrombin generation when monocytes were the tissue factor source with platelets providing the surface for thrombin generation. From the studies reported here, we conclude that in vivo, despite the important role of the protein C system in regulating thrombosis, activated protein C does not serve as a primary regulator of platelet-dependent thrombin generation. (Blood. 2002;100: 539-546)

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Section: Discussioncontrasting

confidence: 55%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Activated protein C cleaves factor Va more efficiently on endothelium than on platelet surfaces

Oliver

Monroe

Church

et al. 2002

Blood

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“…12 There has been some confusion about whether FVa and FVIIIa are inactivated on the surface of the activated platelet or on endothelial cells or both. [13][14][15] In experiments in our cell-based model system, we find that when platelets are used for thrombin generation, APC has very little ability to inactivate FVa. 2 Conversely, in the presence of phospholipid surfaces, APC rapidly inactivates FVa.…”

Section: Resultsmentioning

confidence: 85%

A Cell-Based Model of Thrombin Generation

Roberts¹,

Hoffman²,

Monroe³

2006

Semin Thromb Hemost

226

163

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We have developed a cell-based model of thrombin generation using activated monocytes as a source of tissue factor (TF) and platelets serving as a surface for thrombin generation. Monocytes are activated by lipopolysaccharide and express cell-bound TF. To these are added physiologic (plasma) concentrations of all the plasma procoagulants as well as TF pathway inhibitor, antithrombin, and C1-esterase inhibitor. Coagulation takes place in microtiter wells and is initiated by factor VIIa (FVIIa) and calcium. At time intervals, aliquots are removed, platelet activation is measured by the expression of P-selectin, and thrombin generation is measured by chromogenic assay. In addition, one can measure the activation of FIX, FX, FVIII, FV, and FXI. Initial results reveal that the FVIIa-TF interaction results in the activation of FX to FXa and FIX to FIXa. FXa stays in the vicinity of the TF-bearing cell and, in the presence of FVa, converts a small amount of prothrombin to thrombin on the surface of the TF cell. This small amount of thrombin is not sufficient to clot fibrinogen, but is sufficient to activate platelets and FVIII, FV, and FXI. Following platelet activation, FVIIIa, FVa, and FXa occupy sites on the activated platelet surface. FIXa, activated by TF-FVIIa, does not remain on the TF cell, but converts FX to FXa on the platelet surface. FXIa acts to boost FIXa generation on the activated platelet, increasing FXa and subsequent thrombin generation. We have also shown that activated protein C does not inactivate Va on the platelet surface but rather on endothelial cell surfaces.

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“…Thrombin activity was measured using the chromogenic substrate S2238 as described. 16 Quantification of thrombin-antithrombin III complexes (TAT) and TXB 2 in the plasma from PCI patients obtained at baseline, 30 min after PCI, and 120 minutes after termination of bivalirudin infusion was performed by ELISA using commercially available kits (Affinity Biologicals, Cayman Chemicals, respectively) and following the manufacturer’s protocols. TAT and TXB 2 ELISAs used 20 μL of plasma and 80 μL of buffer per assay well.…”

Section: Methodsmentioning

confidence: 99%

Bivalirudin Is a Dual Inhibitor of Thrombin and Collagen-Dependent Platelet Activation in Patients Undergoing Percutaneous Coronary Intervention

Kimmelstiel

Zhang

Kapur

et al. 2011

Circ: Cardiovascular Interventions

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Background Bivalirudin, a direct thrombin inhibitor, is a widely used adjunctive therapy in patients undergoing percutaneous intervention (PCI). Thrombin is a highly potent agonist of platelets and activates the protease-activated receptors, PAR1 and PAR4, but it is not known whether bivalirudin exerts anti-platelet effects in PCI patients. We tested the hypothesis that bivalirudin acts as an anti-platelet agent in PCI patients by preventing activation of PARs on the platelet surface. Methods and Results The effect of bivalirudin on platelet function and systemic thrombin levels was assessed in patients undergoing elective PCI. Mean plasma levels of bivalirudin were 2.7 ± 0.5 μM during PCI which correlated with marked inhibition of thrombin-induced platelet aggregation and significantly inhibited cleavage of PAR1. Unexpectedly, bivalirudin also significantly inhibited collagen-platelet aggregation during PCI. Collagen induced a conversion of the platelet surface to a procoagulant state in a thrombin-dependent manner which was blocked by bivalirudin. Consistent with this result, bivalirudin reduced systemic thrombin levels by more than 50% during PCI. Termination of the bivalirudin infusion resulted in rapid clearance of the drug with a half-life of 29.3 minutes. Conclusions Bivalirudin effectively suppresses thrombin-dependent platelet activation via inhibition of PAR1 cleavage and inhibits collagen-induced platelet procoagulant activity as well as systemic thrombin levels in patients undergoing PCI.

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Regulation of Platelet Factor Va-dependent Thrombin Generation by Activated Protein C at the Surface of Collagen-adherent Platelets

Cited by 11 publications

References 36 publications

Activated protein C cleaves factor Va more efficiently on endothelium than on platelet surfaces

Activated protein C cleaves factor Va more efficiently on endothelium than on platelet surfaces

A Cell-Based Model of Thrombin Generation

Bivalirudin Is a Dual Inhibitor of Thrombin and Collagen-Dependent Platelet Activation in Patients Undergoing Percutaneous Coronary Intervention

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