Low factor XIII levels and altered fibrinolysis in patients with multiple myeloma.

BACKGROUND: Acquired factor FXIII (FXIII) deficiency can be immune- or non-immune mediated and may cause severe bleeding symptoms. The incidence of acquired FXIII deficiency and its etiology in patients with multiple myeloma (MM) are poorly understood. OBJECTIVES: To assess FXIII levels and the balance of fibrinolysis in newly diagnosed, untreated MM and monoclonal gammopathy of undetermined significance (MGUS) patients. METHODS: FXIII activity, mixing studies, FXIII-A2B2 antigen, total FXIII-B antigen were measured in platelet-poor plasma from 17 untreated MM patients, 33 untreated MGUS patients, and 30 age and sex-matched healthy controls. Besides routine laboratory measurements, the balance of coagulation and fibrinolysis was evaluated using quantitative fibrin monomer (FM) test, thrombin-antithrombin assay, α2-antiplasmin activity, plasmin-α2-antiplasmin (PAP) complex, D-dimer, plasmin generation assay, clot lysis assay, and ClotPro-TPA test. RESULTS: FXIII-A2B2 levels were significantly lower in MM patients compared to controls [median (IQR):14.6 (11.2-19.4) vs. 21.8 (17.1-26.4) mg/L, p = 0.0015], whereas total FXIII-B did not differ between groups. Decrease in FXIII activity was parallel to the decrease in FXIII-A2B2. An immune-mediated inhibitory mechanism was ruled out. Free/total FXIII-B was significantly higher in MM patients compared to MGUS and healthy controls, suggesting an etiology of FXIII-A consumption. In MM and MGUS patients, FM, D-dimer, and PAP complex were significantly elevated compared to controls, indicating hypercoagulability and ongoing fibrinolysis. CONCLUSIONS: Low FXIII levels due to consumption were observed in MM patients at diagnosis. Hypercoagulability and ongoing fibrinolysis were detected in MM and MGUS, indicating that a disturbed hemostasis balance is already present in the latter benign condition.

Patients with multiple myeloma and monoclonal gammopathy of undetermined significance have variably increased thrombin generation and different sensitivity to the anticoagulant effect of activated protein C.

BACKGROUND: Patients with multiple myeloma (MM) are at high risk of thrombosis especially when receiving immunomodulatory therapy. Thrombotic risk in patients with monoclonal gammopathy of undetermined significance (MGUS) may also be increased. Although activated protein C (APC) resistance has been linked to an increased risk of thrombosis in MM, little is known about how APC influences thrombotic risk in MGUS. We compared thrombin generation (TG) in MM and MGUS patients to that of healthy controls (HCs) and investigated the exogenous effect of APC on TG in these groups. METHODS: Hemostasis tests including factor VIII (FVIII) and von Willebrand factor (vWF) levels were measured in platelet-poor plasma in 14 untreated MM patients, 34 MGUS patients, and 30 age and sex-matched HCs. TG assay was performed with or without the addition of APC. RESULTS: Peak thrombin and velocity index were significantly higher in MM and MGUS patients compared to HCs, while MM patients also had elevated endogenous thrombin potential (ETP). In MGUS cases, ETP and peak thrombin values significantly correlated with FVIII and vWF levels. In the presence of APC, peak thrombin and ETP were reduced in MGUS and control plasmas whereas lagtime and time to peak were significantly prolonged. In contrast, adding APC to MM plasma had no effect on any TG parameters. CONCLUSIONS: Hypercoagulability was observed in MM and even in MGUS cases with very low monoclonal protein concentration. In MM patients, APC had no effect on TG, but it attenuated TG in MGUS patients.

Ponatinib Exerts an Inhibitory Effect on Collagen-induced Platelet Aggregation and Generation of Coated-Platelets.

BACKGROUND/AIM: BCR-ABL tyrosine kinase inhibitors (TKIs) are exceptionally effective drugs in the treatment of chronic myeloid leukemia, nevertheless, TKIs have also an effect on platelets. We aimed to investigate the effect of a third-generation TKI, ponatinib on platelet functions. MATERIALS AND METHODS: Collagen-induced platelet aggregation and coated-platelet formation were examined using in vitro and in ex vivo samples of patients on ponatinib therapy. RESULTS: In platelet rich plasma of healthy volunteers, ponatinib at a supra-therapeutic concentration (1,000 nM) significantly impaired collagen induced platelet aggregation (p≤0.01) and reduced the formation of coated-platelets at 150 nM ponatinib concentration (p≤0.05). In addition, upon glycoprotein VI (GPVI) receptor activation, a significantly lower percentage of PAC1 binding platelets (p≤0.05) was observed at 1,000 nM final concentration of ponatinib. Platelets, isolated from patients on ponatinib therapy showed impaired collagen elicited aggregation response, already in pre-dose samples compared to healthy donors. CONCLUSION: The therapeutic concentration of ponatinib impairs platelet activation processes elicited by GPVI receptor agonists.

The Proteasome Inhibitor Bortezomib Induces Apoptosis and Activation in Gel-Filtered Human Platelets.

Bortezomib (BTZ) has demonstrated its efficacy in several hematological disorders and has been associated with thrombocytopenia. There is controversy about the effect of BTZ on human platelets, so we set out to determine its effect on various types of platelet samples. Human platelets were investigated in platelet-rich plasma (PRP) and as gel-filtered platelets (GFPs). Mitochondrial inner membrane potential depolarization and phosphatidylserine (PS) and P-selectin expression levels were studied by flow cytometry, while thrombin generation was measured by a fluorescent method. In PRP, BTZ caused negligible PS expression after 60 min of treatment. However, in GFPs, PS expression was dose- and time-dependently increased in the BTZ-treated groups, as was P-selectin. The percentage of depolarized cells was also higher after BTZ pretreatment at both time points. Peak thrombin and velocity index increased significantly even with the lowest BTZ concentration (p = 0.0019; p = 0.0032) whereas time to peak and start tail parameters decreased (p = 0.0007; p = 0.0034). The difference between PRP and GFP results can be attributed to the presence of plasma proteins in PRP, as the PS-stimulating effect of BTZ could be attenuated by supplementing GFPs with purified human albumin. Overall, BTZ induces a procoagulant platelet phenotype in an experimental setting devoid of plasma proteins.

Dasatinib inhibits coated-platelet generation in patients with chronic myeloid leukemia.

Since the introduction of tyrosine kinase inhibitors, the overall survival of patients with chronic myeloid leukemia has markedly improved. However long term use of these drugs results in various adverse events. Treatment with second generation dasatinib is often complicated by hemorrhagic events. Previous lumi-aggregometry studies have shown impaired platelet function in patients on dasatinib therapy. Dual agonist activated platelets (coated-platelets) are also sensitive indicators of platelet function. We hypothesized that dual activation with convulxin and thrombin of platelets in a flow cytometric assay could be a more sensitive method for detecting platelet dysfunction as compared to single agonist studies used in lumi-aggregometer. Platelets of healthy volunteers incubated with dasatinib as well as platelets from patients on dasatinib therapy were investigated. Low therapeutic plasma level dasatinib concentrations at which a considerable reduction in coated-platelet generation was observed in vitro, did not cause detectable change in platelet aggregation response. Coated-platelet assay and lumi-aggregometry were also investigated at 0, 1 and 4 hours after drug administration in dasatinib treated CML patients. Significant decrease was observed at 1 hour in maximal aggregation by collagen. Although the aggregation curves became normalized by 4 hours, coated-platelet generation was still inhibited in dasatinib treated patients. Nilotinib, another second generation tyrosine kinase inhibitor, had no effect on aggregation and on coated-platelet formation neither in vitro nor in ex vivo samples. At therapeutic plasma levels coated-platelet assay is more sensitive than lumi-aggregometry studies for the demonstration of the inhibitory effect of dasatinib on platelet function.

Laboratory characterization of leukemic cell procoagulants.

BACKGROUND: In acute myeloid leukemias, there is an increased chance to develop thrombotic disorders. We hypothesized that in addition to leukemic promyelocytes, monocytic leukemia cells may also have a higher procoagulant activity. METHODS: Fibrin formation was assessed by a one-stage clotting assay using a magnetic coagulometer. The thrombin generation test (TGT) of magnetically isolated normal human monocytes, intact leukemic cells and their isolated microparticles was performed by a fluorimetric assay. Phosphatidylserine (PS) expression of leukemic cells and microparticle number determinations were carried out by flow cytometry. RESULTS: All cell lines displayed a significant procoagulant potential compared to isolated normal human monocytes. In the TGT test, the mean of lagtime and the time to peak parameters were significantly shorter in leukemic cells (3.9-4.7 and 9.9-10.3 min) compared to monocytes (14.9 and 26.5 min). The mean of peak thrombin in various monocytic leukemia cell lines was 112.1-132.9 nM vs. 75.1 nM in monocytes; however, no significant difference was observed in the ETP parameter. Factor VII-deficient plasma abolished all procoagulant activity, whereas factor XII-deficient plasma did not affect the speed of fibrin formation and thrombin generation but modulated the amount of thrombin. Factor XI-deficient plasma affected the time to peak values in one leukemic cell line and also attenuated peak thrombin. Leukemia cell-derived microparticles from all three cell lines exerted a procoagulant effect by significantly shortening the lagtime in TGT; there was a nonsignificant difference in case of ETP parameter. CONCLUSIONS: All investigated monocytic leukemia cell lines exhibited significant thrombin generation. This phenomenon was achieved by the procoagulants on the surface of leukemic cells as well as by their microparticles.

Red blood cell and platelet parameters are sepsis predictors in an Escherichia coli induced lethal porcine model.

OBJECTIVE: In a fulminant porcine sepsis model, we determined the kinetics of hypoxia induced changes in relation to sepsis parameters and markers of organ damage. METHODS: Female pigs were challenged by live Escherichia coli and samples were analysed up to 4 hours. Bone marrow reactions were determined by analysing immature forms of peripheral blood cells by a hematology analyser and light microscopy. Platelet mitochondrial membrane depolarisation was determined by flow cytometry. RESULTS: Core temperature, modified shock index and lactate levels all became significantly elevated compared to baseline values at 4 hours in septic animals. At 2 hours already the reticulocyte count, nucleated red blood cell count and the absolute number of dysplastic platelets became significantly elevated. The platelet mitochondrial membrane depolarisation was significantly decreased by 2 hours in septic animals compared to the baseline values and to control animals. No massive organ damage was evident during the 4-hour observation period, but uric acid levels in septic animals became significantly elevated already by 2 hours. CONCLUSIONS: In this Escherichia coli induced porcine model, severe sepsis was evident by conventional criteria at 4 hours while several - mostly hypoxemia induced - biomarkers were already altered by 2 hours.

Integrity(®) bare-metal coronary stent-induced platelet and endothelial cell activation results in a higher risk of restenosis compared to Xience(®) everolimus-eluting stents in stable angina patients.

Drug-eluting stenting (DES) has become a reliable tool for coronary stenting; however, its direct effects on platelet and endothelium function differ from those of bare-metal stenting (BMS). This study involved a periprocedural analysis of various biomarkers of cellular activation after elective DES (Xience(®), Abbott Vascular, Santa Clara, CA, USA) or BMS (Integrity(®), Medtronic, Minneapolis, MI, USA). Forty-nine stable angina patients were recruited: 28 underwent BMS, and 21 received everolimus-eluting stents. Samples were collected (i) prior to stenting, (ii) at 24 hours after procedure, and (iii) after 1 month of dual antiplatelet therapy. Platelet activation was analyzed by surface P-selectin positivity in parallel with plasma levels of soluble P-selectin, CD40L and platelet-derived growth factor (PDGF). Endothelial cell (EC) activation was detected by measuring markers of early (von Willebrand factor) and delayed response (VCAM-1, ICAM-1, E-selectin). Patients were followed for 6 months for the occurrence of restenosis or stent thrombosis. Increased platelet activation was sustained regardless of stent type or antiplatelet medication. Concentrations of most EC markers were more elevated after BMS than after DES. No stent thrombosis was seen, but six BMS subjects displayed restenosis with significantly higher sCD40L (779 [397-899] vs. 381 [229-498] pg/mL; p = 0.032) and sICAM-1 (222 [181-272] vs. 162 [153-223] ng/mL; p = 0.046) levels than in those without complication, while DES patients exhibited significantly decreased PDGF (572 [428-626] vs. 244 [228-311] pg/mL; p = 0.004) after 1 month. Nonresponsiveness to antiplatelet drugs did not influence these changes. In conclusion, the degree of platelet and EC activation suggests that Xience(®) DES may be regarded a safer coronary intervention than Integrity(®) BMS, with a lower risk of in-stent restenosis.

Comparison of coated-platelet levels in patients with essential thrombocythemia with and without hydroxyurea treatment.

Essential thrombocythemia (ET) is an acquired myeloproliferative disorder with sustained increase of platelet count. This disease may be associated with thrombotic or bleeding complications due to the altered number and function of platelets. Coated-platelets produced by a simultaneous activation of collagen and thrombin represent a subpopulation of activated platelets with high prothombinase activity and the retention of several α-granule-derived coagulation factors on their surface. There is a growing body of evidence for a relationship between variable levels of coated-platelets and different hemostatic alterations. However, no data are available on coated-platelet formation in the pathogenesis of ET in the presence or absence of treatment. The levels of coated-platelets in 43 ET patients (15 non-treated and 28 hydroxyurea-treated) without known thrombotic or hemorrhagic complications were analyzed using flow cytometry. These results were compared with data of 31 healthy individuals. In addition, platelet function was analyzed with PFA-100 analysis, and P-selectin (CD62) positivity was also measured by flow cytometry. Increased P-selectin expression was detected with prolonged PFA-100 closure times in the ET group; however, significantly lower levels of coated-platelets were found in non-treated ET patients compared to controls (23.1 ± 8.8% vs. 37.6 ± 12.7%, p = 0.0008). This tendency was more evident in patients with JAK2-V617F mutation. Patients on hydroxyurea treatment had elevated coated-platelet levels (34.1 ± 12.3%) close to the normal value. In conclusion, lower than normal levels of coated-platelets were generated in ET, which were significantly (p = 0.0008) increased by hydroxyurea treatment. We suppose that abnormal coated-platelet level may also contribute to platelet dysfunction in ET.