Dual Effect of Platelet Factor Four on the Activities of Factor Xa

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1034-1034
Author(s):  
Martine Marie Fiore ◽  
Ian J Mackie
Keyword(s):  
Factor Xa ◽  
Fold Increase ◽  
Peptide Hydrolysis ◽  
Dual Effect ◽  
Platelet Factor ◽  
Paradoxical Effects ◽  
Heparin Activity ◽  
High Concentrations ◽  
Prothrombin Activation

Abstract Platelet Factor 4 (PF4) is a cationic molecule that binds to heparin with high affinity and neutralises the activity of the latter. Our recent studies indicate that heparin can promote an interaction of fXa with PF4 since neutralization of heparin activity by PF4 was dependent on the concentration of protease. To examine the contribution of PF4 in protease function, fXa activity was determined in chromogenic assays. Upon preincubation with fXa and heparin, PF4 (at a concentration of 100 nM) decreased the kcat of S2765 peptide hydrolysis 4-fold and that of prothrombin activation about 2-fold. These results suggested an effect of PF4 on the primary specificity of the protease. In fact, PF4 exerted a mild effect (30 % decrease) on the Na+ dependence of fXa, consistent with linkage between Na+ and S1. PF4 preincubation with fXa also prevented the binding of the S1 probe p-aminobenzamidine (pAB) while simultaneous addition of PF4 and pAB diminished the contribution of PF4. In the presence of excess fVa (relative to fXa), kinetic parameters measuring fXa amidolytic activity in the presence of PF4 were restored to control values in the absence of PF4. Interestingly, high concentrations of PF4 (> 1 μM) totally restored fXa activity toward peptidyl substrate and strongly enhanced prothrombin activation, indicating a dual effect of PF4 on fXa activities. The inhibitory contribution of PF4 during prothrombin activation was due to a three-fold decreased affinity of fXa for fVa while enhancement of prothrombin activation was accompanied by a three-fold increase in fVa-dependent cofactor activity. Thus, the effects of PF4 possibly involved a region of the heparin/fVabinding exosite that is linked to the S1 and Na+ sites. These findings suggest that PF4 is a probe of fVa-dependent changes occurring in the active site of fXa and provide an explanation for the in vivo paradoxical effects of PF4 reported in the literature.

Induction of monocyte tissue factor expression by antibodies to heparin–platelet factor 4 complexes developed in heparin-induced thrombocytopenia

Blood ◽  
2001 ◽  
Vol 97 (10) ◽  
pp. 3300-3302 ◽  
Author(s):  
Claire Pouplard ◽  
Sophie Iochmann ◽  
Benoit Renard ◽  
Olivier Herault ◽  
Philippe Colombat ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Mononuclear Cells ◽  
Factor Xa ◽  
Platelet Factor 4 ◽  
Peripheral Blood Mononuclear ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Chromogenic Assay ◽  
High Concentrations

Abstract The pathogenesis of thrombosis in heparin-induced thrombocytopenia (HIT) was studied by investigating whether antibodies to heparin-platelet factor 4 (H-PF4) induced tissue factor (TF) synthesis by monocytes. Plasma from 5 patients with HIT containing IgG to H-PF4 was incubated with peripheral blood mononuclear cells without or with purified PF4 and heparin. Significant TF-dependent procoagulant activity (PCA) expressed by monocytes, measured with a factor Xa-based chromogenic assay, was induced after incubation of each HIT plasma sample. This monocyte PCA required the presence of PF4 and was inhibited by high concentrations of heparin. Furthermore, purified HIT IgG added to whole blood with PF4 and heparin also provoked significant synthesis of TF mRNA by monocytes, demonstrated by RT-PCR, and this effect was not observed with normal IgG. These findings strongly support the hypothesis that antibodies to PF4 developed in HIT trigger the production of tissue factor by monocytes, and this effect could account in vivo for hypercoagulability and thrombotic complications in affected patients.

scholarly journals Monitoring "mini-intensity" anticoagulation with warfarin: comparison of the prothrombin time using a sensitive thromboplastin with prothrombin fragment F1+2 levels

Blood ◽  
1992 ◽  
Vol 79 (8) ◽  
pp. 2034-2038 ◽  
Author(s):  
MM Millenson ◽  
KA Bauer ◽  
JP Kistler ◽  
S Barzegar ◽  
L Tulin ◽  
...  
Keyword(s):  
Prothrombin Time ◽  
Factor Xa ◽  
High Sensitivity ◽  
International Normalized Ratio ◽  
Target Range ◽  
Lower Sensitivity ◽  
Sensitivity Index ◽  
Plasma Samples ◽  
Prothrombin Activation

Treatment with warfarin using a target International Normalized Ratio (INR) range of 1.7 to 2.5 is efficacious for many clinical indications, but the minimal intensity of anticoagulation required for antithrombotic protection has yet to be determined. To evaluate whether patients could be reliably monitored with a less intense regimen, we anticoagulated patients with warfarin for several months using a target INR range of 1.3 to 1.6 as determined by prothrombin time (PT) using a sensitive thromboplastin (Dade IS, International Sensitivity Index [ISI] = 1.3). Plasma measurements of F1+2, a marker of factor Xa action on prothrombin in vivo, were also obtained to determine the suppressive effect of warfarin on hemostatic system activity. Overall, 20 of 21 patients with a history of cerebrovascular events (mean age, 61 years) could be reliably regulated with warfarin in the target INR range. F1+2 levels were significantly suppressed from baseline in all patients, with a mean reduction of 49% (range, 28% to 78%). We found a significant relationship between the extent of suppression of prothrombin activation levels and the baseline measurements. A mean reduction of 65% was observed for those patients with baseline F1+2 greater than or equal to 1.5 nmol/L, but only 38% for baseline F1+2 less than or equal to 0.5 nmol/L. Overall, 68% of plasma samples obtained during stable anticoagulation were within the target INR range. PTs were also determined on all plasma samples with two thromboplastins of lower sensitivity (C+, ISI = 2.09; and automated simplastin, ISI = 2.10). Only 47% and 35% of PT determinations, respectively, were within the target range with these reagents. We conclude that prothrombin activation can be significantly suppressed in vivo with use of warfarin in an INR range of 1.3 to 1.6. This level of anticoagulation can be reliably achieved by monitoring PTs with a thromboplastin of high sensitivity.

scholarly journals In vivo radiolabeling of platelet proteins: a new method with identification of platelet factor XIII

Blood ◽  
1980 ◽  
Vol 55 (4) ◽  
pp. 559-563 ◽  
Author(s):  
DM Rider ◽  
RP McDonagh ◽  
J McDonagh
Keyword(s):  
Gel Electrophoresis ◽  
Factor Xiii ◽  
Soluble Fraction ◽  
Polyacrylamide Gel Electrophoresis ◽  
Fold Increase ◽  
Platelet Factor ◽  
Intravenous Injections ◽  
Molecular Weights ◽  
The Third

Abstract A method for radiolabeling platelets in vivo was developed in which 3H- arginine was injected into the bone marrow of normal dogs. On the third day after injection, a maximum of 6%--7% of the radioactivity had been incorporated into the total platelet mass. This method of isotope administration resulted in a 50--60-fold increase in maximum uptake of radiolabel by platelets, as compared to values obtained by others using intravenous injections of various radioactive compounds. Tritium- labeled platelets were harvested from the animals and then were washed to remove unbound 3H-arginine. On polyacrylamide gel electrophoresis 7 labeled protein bands, with molecular weights ranging from 29,000to 132,000, were obtained from the platelet-soluble fraction. One 3H- containing protein with a molecular weight of 81,000 was identified immunologically and enzymatically as platelet factor XIII.

Measurement of factor Xa-antithrombin III in plasma: relationship to prothrombin activation in vivo

1995 ◽  
Vol 90 (3) ◽  
pp. 669-680 ◽  
Author(s):  
ISABELLE GOUIN-THIBAULT ◽  
LORI DEWAR ◽  
MYRON KULCZYCKY ◽  
MARION STERNBACH ◽  
FREDERICK A. OFOSU
Keyword(s):  
Antithrombin Iii ◽  
Factor Xa ◽  
Prothrombin Activation

scholarly journals Monitoring "mini-intensity" anticoagulation with warfarin: comparison of the prothrombin time using a sensitive thromboplastin with prothrombin fragment F1+2 levels

Blood ◽  
1992 ◽  
Vol 79 (8) ◽  
pp. 2034-2038 ◽  
Author(s):  
MM Millenson ◽  
KA Bauer ◽  
JP Kistler ◽  
S Barzegar ◽  
L Tulin ◽  
...  
Keyword(s):  
Prothrombin Time ◽  
Factor Xa ◽  
High Sensitivity ◽  
International Normalized Ratio ◽  
Target Range ◽  
Lower Sensitivity ◽  
Sensitivity Index ◽  
Plasma Samples ◽  
Prothrombin Activation

Abstract Treatment with warfarin using a target International Normalized Ratio (INR) range of 1.7 to 2.5 is efficacious for many clinical indications, but the minimal intensity of anticoagulation required for antithrombotic protection has yet to be determined. To evaluate whether patients could be reliably monitored with a less intense regimen, we anticoagulated patients with warfarin for several months using a target INR range of 1.3 to 1.6 as determined by prothrombin time (PT) using a sensitive thromboplastin (Dade IS, International Sensitivity Index [ISI] = 1.3). Plasma measurements of F1+2, a marker of factor Xa action on prothrombin in vivo, were also obtained to determine the suppressive effect of warfarin on hemostatic system activity. Overall, 20 of 21 patients with a history of cerebrovascular events (mean age, 61 years) could be reliably regulated with warfarin in the target INR range. F1+2 levels were significantly suppressed from baseline in all patients, with a mean reduction of 49% (range, 28% to 78%). We found a significant relationship between the extent of suppression of prothrombin activation levels and the baseline measurements. A mean reduction of 65% was observed for those patients with baseline F1+2 greater than or equal to 1.5 nmol/L, but only 38% for baseline F1+2 less than or equal to 0.5 nmol/L. Overall, 68% of plasma samples obtained during stable anticoagulation were within the target INR range. PTs were also determined on all plasma samples with two thromboplastins of lower sensitivity (C+, ISI = 2.09; and automated simplastin, ISI = 2.10). Only 47% and 35% of PT determinations, respectively, were within the target range with these reagents. We conclude that prothrombin activation can be significantly suppressed in vivo with use of warfarin in an INR range of 1.3 to 1.6. This level of anticoagulation can be reliably achieved by monitoring PTs with a thromboplastin of high sensitivity.

scholarly journals Platelet Factor 4 (PF4) and Protamine Neutralisation of Heparin in Plasma

1977 ◽  
Author(s):  
R. Michalski ◽  
D.A. Lane ◽  
D. Pepper ◽  
V.V. Kakkar
Keyword(s):  
Intravenous Injection ◽  
Factor Xa ◽  
Weight Basis ◽  
Platelet Factor 4 ◽  
Assay System ◽  
Platelet Factor ◽  
Protamine Sulphate ◽  
Heparin Activity ◽  
Plasma Heparin

The ability of PF4 and protamine sulphate to neutralise heparin in plasma has been studied using a specific anti-Factor Xa assay and a KCCT assay to measure residual heparin. When heparin is added to plasma in vitro PF4 and protamine neutralise almost equivalent amounts of heparin on a weight basis, 1.0 unit of heparin being neutralised by approximately 20 μg of PF4 and 15 μg of protamine. Similar results are obtained using either of the heparin assays. However, following intravenous injection of heparin only about one half of the circulating heparin could be neutralised in vitro by PF4 or protamine when it was measured by anti-Factor Xa assay. Total neutralisation was obtained with both neutralising agents in the KCCT assay system. These results demonstrate that the choice of assay is important when a protamine titration is used to measure plasma heparin levels, and that PF4 and protamine are unable to totally neutralise circulating antithrombotic heparin activity.

Identification of a blood-derived chemoattractant for neutrophils and lymphocytes as a novel CC chemokine, Regakine-1

Blood ◽  
2001 ◽  
Vol 97 (8) ◽  
pp. 2197-2204 ◽  
Author(s):  
Sofie Struyf ◽  
Paul Proost ◽  
Jean-Pierre Lenaerts ◽  
Griet Stoops ◽  
Anja Wuyts ◽  
...  
Keyword(s):  
Acute Infection ◽  
Large Family ◽  
Fold Increase ◽  
Cell Types ◽  
Platelet Factor ◽  
Cc Chemokine ◽  
Chemotactic Protein ◽  
Biologic Effects ◽  
Cc Chemokines ◽  
High Concentrations

Abstract Chemokines constitute a large family of chemotactic cytokines that selectively attract different blood cell types. Although most inflammatory chemoattractants are only induced and released in the circulation during acute infection, a restricted number of CXC and CC chemokines are constitutively present in normal plasma at high concentrations. Here, such a chemotactic protein was purified to homogeneity from serum and fully identified as a novel CC chemokine by mass spectrometry and amino acid sequence analysis. The protein, tentatively designated Regakine-1, shows less than 50% sequence identity with any known chemokine. This novel CC chemokine chemoattracts both neutrophils and lymphocytes but not monocytes or eosinophils. Its modest chemotactic potency but high blood concentration is similar to that of other chemokines present in the circulation, such as hemofiltrate CC chemokine-1, platelet factor-4, and β-thromboglobulin. Regakine-1 did not induce neutrophil chemokinesis. However, it synergized with the CXC chemokines interleukin-8 and granulocyte chemotactic protein-2, and the CC chemokine monocyte chemotactic protein-3, resulting in an at least a 2-fold increase of the neutrophil and lymphocyte chemotactic response, respectively. The biologic effects of homogeneous natural Regakine-1 were confirmed with chemically synthesized chemokine. Like other plasma chemokines, it is expected that Regakine-1 plays a unique role in the circulation during normal or pathologic conditions.

Elimination of Platelet Factor 4 (PF4) from Platelets Reduces Atherosclerosis and Increases HDL Cholesterol in C57Bl/6 and ApoE−/− Mice.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 418-418
Author(s):  
Bruce S. Sachais ◽  
Tiffany Turrentine ◽  
Jeanine M. Dawicki-McKenna ◽  
Daniel J. Rader ◽  
M. Anna Kowalska
Keyword(s):  
Atherosclerotic Lesion ◽  
Annexin V ◽  
Hdl Cholesterol ◽  
Fold Increase ◽  
Platelet Factor 4 ◽  
Spontaneous Bleeding ◽  
Platelet Factor ◽  
Cholesterol Levels ◽  
Fold Reduction

Abstract There is a presence of circulating, activated platelets in blood of patients with atherosclerosis, coronary disease and hypercholesterolemia. Upon activation, platelets release a large amount of platelet factor 4 (PF4), a platelet specific chemokine. Our laboratory has previously demonstrated several potentially proatherogenic properties of PF4 including alteration of LDL metabolism and cellular trafficking, and activation of NFkB, a proinflammatory transcription factor involved in atherosclerosis. We have also localized PF4 to human atherosclerotic lesions. However, to date, no direct in vivo evidence for the involvement of PF4 in atherogenesis. In the current study, we have bred PF4−/− mice onto two athero-susceptible backgrounds, WT-C57Bl/6(WT) and apoE−/−, to examine the importance of PF4 in atherogenesis. PF4−/− and PF4−/−apoE−/− (DKO) mice are viable and healthy, with no spontaneous bleeding disorders. In order to induce atherosclerosis, WT and PF4−/− mice were fed an atherogenic Paigen diet for 30 weeks (Study 1), while apoE−/− and DKO mice were fed a high fat Western style diet for 10 weeks (Study 2). Examination of lesions in the aortic roots of Study 1 animals demonstrated a 5-fold reduction in PF4−/− compared to WT mice (p = 0.008). Measurement of cholesterol levels demonstrated similar total and non-HDL cholesterol levels in WT and PF4−/− mice. However, HDL cholesterol was significantly increased in PF4−/− mice compared to WT (2.5-fold, p = 0.001). Examination of apoE−/− mice (Study 2) demonstrated similar changes, with DKO mice demonstrating a 2.7-fold reduction in aortic atherosclerosis (measured by the en face method; p = 0.03) and a 1.7-fold increase in HDL cholesterol (p = 0.02) compared to apoE−/− mice. Although platelet counts were increased by ~30% in mice lacking PF4, the activation state of the platelets in our mice at sacrifice (WT vs PF4−/− and apoE−/− vs DKO) were similar as measured by both p-selectin expression and annexin V binding. These data demonstrate, for the first time, that the platelet specific chemokine PF4 promotes atherosclerotic lesion development in vivo.

scholarly journals Thrombin generation is not increased in the blood of hemophilia B patients after the infusion of a purified factor IX concentrate

Blood ◽  
1990 ◽  
Vol 76 (12) ◽  
pp. 2540-2545 ◽  
Author(s):  
PM Mannucci ◽  
KA Bauer ◽  
A Gringeri ◽  
S Barzegar ◽  
B Bottasso ◽  
...  
Keyword(s):  
Significant Risk ◽  
Factor Xa ◽  
Factor Ix ◽  
Hemophilia B ◽  
Coagulation Cascade ◽  
Platelet Factor ◽  
Sensitive Index ◽  
Before And After ◽  
Fibrin Monomers

Abstract Prothrombin complex concentrates (PCC), licensed for the treatment of hemophilia B, are known to carry a significant risk of thromboembolic complications. Although the reasons for thrombogenicity are not completely understood, several manufacturers have developed purified factor IX concentrates that contain negligible amounts of the other vitamin K-dependent factors. To evaluate whether or not the infusion of such a factor IX concentrate is followed by lesser activation of the hemostatic system than by the infusion of a PCC, we performed a series of coagulation assays on 11 hemophilia B patients before and after the administration of these two types of concentrate using a randomized cross-over design. The levels of prothrombin fragment F1 + 2, a sensitive measure of the in vivo cleavage of prothrombin by factor Xa, was significantly increased in plasma after PCC, but not after factor IX concentrate. Plasma fibrinopeptide A, a sensitive index of the enzymatic activity of thrombin on fibrinogen, also increased significantly after PCC but not after factor IX concentrate. The fragment B beta 15–42, a sensitive index of the enzymatic action of plasmin on fibrin II, did not change after either concentrate. There were also no differences in less sensitive coagulation measurements, such as plasma fibrinogen, antithrombin III, and fibrin monomers, nor in indices of platelet activation, such as beta-thromboglobulin and platelet factor 4. These findings show that the infusion of a purified factor IX concentrate can result in substantially less activation of the coagulation cascade than may be seen with PCC.

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