thromboplastin and Thrombocythemia--Essential

Thrombotic complications in patients with hematologic malignancies are as frequent as in those with solid tumors and significantly affect morbidity and mortality. In acute leukemia, thrombosis and bleeding manifestations may occur concomitantly as a part of the same thrombo-hemorrhagic syndrome. In patients with Philadelphia chromosome-negative chronic myeloproliferative disorders (i.e., essential thrombocythemia [ET] and polycythemia vera [PV]), a thrombosis rate as high as 40% has been recorded. A hypercoagulable state is present in virtually all of these patients, even without clinical manifestations. In this review, we focus on the pathogenic mechanisms underlying the hypercoagulable state of these two hematologic malignancies. Although the pathogenesis of hypercoagulability is complex, a central role is played by the fundamental molecular changes of both the leukemic cells and of the progeny arising from the hematopoietic progenitor cells that have undergone clonal rearrangement. These cells overexpress procoagulant factors, as well as adhesion molecules and cytokines capable of inducing procoagulant changes in the vascular wall and stimulating increased cellular interactions. Recent molecular studies in experimental models of human tumors have demonstrated for the first time that oncogene- and repressor gene-mediated neoplastic transformation induces activation of blood coagulation. Similarly, in cells from patients with acute promyelocytic leukemia, the T15-17 translocation induces hyperexpression of tissue factor (TF) and renders the patient hypercoagulable. Furthermore, in blood cells from patients with PV or ET, the presence of the JAK2V617F mutation translates into activation of hemostasis, with increased expression of platelet-associated TF microparticles and the formation of increased platelet/neutrophil aggregates. Understanding the pathophysiology of hypercoagulability is critical to the design of appropriate measures for intervention in these hematologic disorders to prevent thromboembolic complications.

Topics: Hematologic Neoplasms; Hemostasis; Humans; Leukemia, Promyelocytic, Acute; Myeloproliferative Disorders; Neovascularization, Pathologic; Polycythemia Vera; Thrombocythemia, Essential; Thrombophilia; Thromboplastin; Up-Regulation

Topics: Blood Coagulation Disorders; Blood Coagulation Factors; Blood Platelets; Cell Membrane Permeability; Fibrinogen; Fibrinolysis; Hemorrhagic Disorders; Humans; Leukemia, Myeloid; Leukemia, Myeloid, Acute; Thrombocythemia, Essential; Thrombocytopenia; Thromboplastin

Topics: Blood Coagulation; Blood Platelets; Feedback, Physiological; Female; Humans; Leukocytes; Lipoproteins; Male; Middle Aged; Neovascularization, Pathologic; Signal Transduction; Statistics, Nonparametric; Thrombocythemia, Essential; Thromboplastin; Thrombosis; Vascular Endothelial Growth Factor A

Thrombotic complications may occur in 7.6-29.4% of patients with essential thrombocythemia. According to the cellular theory, tissue factor (TF) activating extrinsic blood coagulation pathway is essential for the activation of blood clotting. The aim of the study was to evaluate the activation of the TF-dependent extrinsic pathway in patients with essential thrombocythemia, depending on the presence or absence of the Janus kinase 2 (JAK2) V617F mutation. The study included 74 newly diagnosed patients (F/M: 47/27; mean age 61 years) with essential thrombocythemia (Tefferi and Vardiman, Leukemia 2008; 22(1):14-22). Patients were diagnosed in the Department of Clinical Hematology and Hematological Malignancies University Hospital No. 2, Bydgoszcz, Poland. The control group consisted of 30 healthy volunteers (F/M: 17/13; mean age 49 years). The concentration and activity of TF and TF pathway inhibitor (TFPI) were measured using ELISA method. In patients with essential thrombocythemia, we observed a higher concentration of TF [median (Me) = 686.90 vs 164.28 pg/ml] and over 10-fold higher activity of TF (Me = 46.05 vs 4.01 pmol/l) when compared with the control group. We also reported significantly higher activity of TFPI compared with the control group (Me = 1.93 vs 1.78 U/ml). Moreover, a concentration of TFPI was significantly lower in patients with essential thrombocythemia with JAK2 V617F mutation as compared with patients without the mutation (Me = 1.90 vs 2.16 U/ml; P = 0.039639). Increased TF activity and concentration is responsible for higher procoagulant potential in patients with essential thrombocythemia. Reduced activity of TFPI in patients with essential thrombocythemia with JAK2 V617F mutation indicates an increased prothrombotic risk in this group of patients.

Topics: Adult; Aged; Aged, 80 and over; Female; Humans; Janus Kinase 2; Lipoproteins; Male; Middle Aged; Mutation; Thrombocythemia, Essential; Thromboplastin; Young Adult

This study evaluates the functional procoagulant features of plasma microparticle (MP) to explore the MP contribution to the hypercoagulable state of patients with essential thrombocythemia (ET). Platelet-free plasma samples were obtained from 73 ET patients (37 positive for the JAK2V617F mutation) and 72 control subjects. The calibrated automated thrombogram (CAT) was performed in plasma samples to determine thrombin generation of MP-associated tissue factor (TF) and procoagulant phospholipid (PPL) activity, and the STA Procoag PPL assay to measure MP-PPL activity only. Both thrombin generation and PPL procoagulant activities were found significantly elevated in ET patients compared to controls, and were associated to significantly higher levels of TF antigen and FVIIa/AT complex. Thrombin generation was significantly greater in JAK2-V617F positive compared to JAK2-V617F negative patients and normal subjects. Significant correlations were found between the PPL-assay and the different parameters of the CAT assay. No difference was seen between the thrombosis and no thrombosis group. Prospective studies are needed to test whether MP-associated thrombin generation and procoagulant activity may predict for thrombosis in these patients.

Topics: Adult; Aged; Aged, 80 and over; Blood Coagulation; Case-Control Studies; Cell-Derived Microparticles; Factor VIIa; Female; Humans; Janus Kinase 2; Male; Middle Aged; Mutation; Phospholipids; Thrombin; Thrombocythemia, Essential; Thromboplastin; Young Adult

The clinical courses of polycythemia vera (PV) and essential thrombocythemia (ET) are characterized by thrombohemorrhagic diathesis. Several groups have suggested an association between JAK2V617F mutation and thrombosis. We hypothesized a relationship between JAK2V617F allele burden, cellular activation parameters, and thrombosis. We evaluated a group of PV and ET patients using flow cytometry: platelet CD62P, CD63, and dense granules, platelet-leukocyte aggregates (PLA), leukocyte CD11b and monocyte tissue factor (TF) expression. All patients had increased baseline platelet CD62P and CD63 expression (p < 0.05); 71 % of PV and 47 % of ET presented with a storage pool disease. Leukocyte CD11b, TF, and PLA were elevated in all patients. TF was higher in PV compared to ET (p < 0.05) and platelet-neutrophil [polymorphonuclear (PMN)] aggregates were increased in ET versus PV (p < 0.05). In ET, PLA were correlated with platelet numbers (p < 0.05). In all patients, JAK2V617F allele burden was directly correlated with monocyte CD11b. Patients with JAK2V617F allele burden >50 % presented higher levels of leukocyte activation. In ET, thrombosis was associated with JAK2V617F mutation (p < 0.05, χ (2) = 5.2), increased monocyte CD11b (p < 0.05) and with platelet-PMN aggregates (p < 0.05). In ET patients, hydroxyurea does not significantly reduce the activation parameters. Our data demonstrate that JAK2V617F allele burden is directly correlated with activation parameters that drive mechanisms that favor thrombosis.

Topics: Adult; Aged; Aged, 80 and over; Alleles; Blood Platelets; Case-Control Studies; CD11b Antigen; Codon; Female; Hemorrhage; Humans; Janus Kinase 2; Male; Middle Aged; Monocytes; Mutation; Neutrophils; Platelet Activation; Platelet Aggregation; Polycythemia Vera; Quinacrine; Thrombocythemia, Essential; Thromboplastin; Thrombosis; Young Adult

Recently, the asymmetric distribution of phospholipids in eukaryotic cell membranes has been appreciated and been found to be dependent on the activity of a number of enzymes. The expression of phosphatidylserine (PS), a negatively charged phospholipid, on the platelets of patients with polycythemia vera (P vera) and essential thrombocythemia (ET) was compared to that in normal individuals. The effect of platelet aggregation on PS expression was determined. Exposure of PS on platelets obtained from patients with P vera and ET and from age- and sex-matched healthy volunteers was measured by fluorescein-labeled Annexin V binding to platelets and by the platelets' thrombin-generating capacity determined by the prothrombinase assay. PLatelet prothrombinase activity (mean +/- standard deviation [SD]), as measured by thrombin generation, was 2.32+/-2.2 micro/mL in the P vera group and 1.55+/-1.0 micro/mL in the control group (p=0.3). PS expression as measured by Annexin V binding (mean +/- SD) was 2.6+/-2.4 % in the P vera group versus 1.55+/-1.2% among controls (p=0.03). In the ET group, prothrombinase activity (mean +/- SD) was 1.0+/-0.6 micro/mL and 2.1+/-0.9 micro/mL in the control group (p=0.006). Annexin V binding (mean +/- SD) was 4.8+/-4.2% in the ET group and 2.77+/-2.1% among control subjects (p=0.09). When the prothrombinase assay was performed after addition of adenosine diphosphate (ADP) to the platelets, there was a significant increase in thrombin generation in the myeloproliferative disorder (MPD) group (3.1+/-2.0 micro/mL) compared to the thrombin generated by unstimulated myeloproliferative disorder platelets (2.07+/-1.69 micro/mL) (p=0.0006). An increase in thrombin generation was seen in the ADP-stimulated platelet samples in all ten paired samples studied. Likewise, the addition of ADP to control platelets increased thrombin generation from 2.0+/-1.0 micro/mL in unstimulated platelets to 4.3+/-1.6 micro/mL in ADP-treated platelets (p=0.0006). Thrombin generation increased in all of the ADP-stimulated platelet samples compared to the untreated platelets. There was however, no difference in the increased thrombin generation when ADP-stimulated platelets from MPD patient and control subjects were compared (p=0.3). Results indicate that some patients with MPDs may show increased PS expression on platelet surface. When analyzed overall, there was a tendency toward greater PS expression in the P vera and ET patient groups; however, the increase d

Topics: Adenosine Diphosphate; Annexin A5; Blood Platelets; Enzyme Activation; Female; Humans; Male; Membrane Lipids; Phosphatidylserines; Platelet Aggregation; Polycythemia Vera; Prothrombin; Thrombin; Thrombocythemia, Essential; Thromboplastin

Both the basal and the collagen plus thrombin-stimulated prothrombinase activities have been measured in platelets from eight patients with essential thrombocythaemia (ET). On a mean basis these activities were significantly lower than the values recorded for a group of age and sex matched control subjects. When the Ca2+ ionophore A23187 was substituted for the agonist mixture the induced expression of prothrombinase activity was essentially the same for the patient and control groups. It is suggested that the defect in prothrombinase expression seen with ET platelets may reside in either membrane signal transduction processes concerned with Ca2+ mobilization or in Ca2+ sensitive cytoskeletal control of membrane phospholipid topography.

Topics: Adult; Aged; Blood Platelets; Collagen; Female; Humans; In Vitro Techniques; Male; Middle Aged; Platelet Count; Reference Values; Thrombocythemia, Essential; Thromboplastin

Bernard-Soulier syndrome (BSS) was described in 1948 as a constitutional platelet disorder characterized by giant sized platelets, a prolonged bleeding time, and a defect in prothrombin consumption. The accurate mechanisms of these abnormalities remain unexplained, especially the defect in prothrombin consumption on which we focus in this paper. Several hypotheses are proposed: firstly, a defective reaction between the platelet membrane, where the phospholipid composition is abnormal, and the proteins which initiate thromboplastin generation such as collagen, factor XI; secondly, an abnormal reaction between thrombin, whose synthesis is increased, and its receptor, possibly glycoprotein V, which is defective; lastly, as factor VIII/vW binding is diminished, an abnormal dissociation of the complex VIII/vW-VIIIc at the site of the platelet membrane, which leads to an inactivation of factor VIIIc.

Topics: Binding Sites; Blood Coagulation Disorders; Blood Platelets; Cell Membrane; Collagen; Factor V; Factor VIII; Factor XI; Glycoproteins; Humans; Membrane Proteins; Platelet Factor 3; Platelet Membrane Glycoproteins; Thrombin; Thrombocythemia, Essential; Thrombocytopenia; Thromboplastin

Topics: Adult; Aged; Blood Coagulation Tests; Blood Platelets; Female; Humans; Male; Middle Aged; Thrombocythemia, Essential; Thromboplastin

Topics: Blood Platelet Disorders; Blood Platelets; Busulfan; Hemorrhagic Disorders; Humans; Phospholipids; Research; Thrombocythemia, Essential; Thrombocytosis; Thromboplastin; Uracil