Joost C M Meijers

University of Amsterdam, Amsterdamo, North Holland, Netherlands

Are you Joost C M Meijers?

Claim your profile

Publications (388)2133.86 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Coagulation factor concentrates like factor IX (FIX) and prothrombin complex concentrate (PCC) can contain anticoagulant substances that may hamper their procoagulant effectiveness in the treatment of hemophilia B or reversal of oral anticoagulation, as well as the laboratory assessment thereof. The aim of the present study was to evaluate the influence of anticoagulant heparin supplement on the prohemostatic potential of different PCCs and FIX concentrates.
    No preview · Article · Jan 2016 · Thrombosis Research
  • [Show abstract] [Hide abstract]
    ABSTRACT: Corticosteroids have been associated with an increased risk for venous thromboembolism (VTE) in patients treated for inflammatory diseases. It is unclear whether the thrombotic risk is induced by the inflammation of the underlying inflammatory diseases or whether corticosteroids are prothrombotic as well. Considering the widespread use of corticosteroids in clinical practice, it is critical to know whether corticosteroids enhance coagulation. To investigate whether a 10-day prednisolone burst therapy activates haemostasis in healthy individuals. Healthy subjects received either 0.5 mg/kg/day of oral prednisolone or placebo. Venous blood was collected at baseline, day 1 and day 10 and tested for thrombin-antithrombin complexes (TATc), D-dimer, plasmin-alpha2-antiplasmin complexes (PAPc), plasminogen-activator inhibitor type-1 (PAI-1), von Willebrand factor (vWF) and thrombin generation (peak thrombin, velocity index and endogenous thrombin potential (ETP)). Fifteen subjects received prednisolone and 16 placebo (median age 29 vs. 22 years, female 33% vs. 56%, respectively). Peak thrombin and velocity index were higher in the placebo group at baseline. After 10 days of treatment, peak thrombin, velocity index, PAI-1 and vWF increased in the oral prednisolone group as compared to the placebo group (15.8 (SD 16.3) vs. -0.1 (SD 16.1); 41.2 (SD 41.3) vs. -2.3 (SD 42.7); 18.0 (IQR 8.0-37.0) vs. 0.5 (IQR -18.5–13.0); 4.0 (IQR -1.0–12.0) vs. 0.0 (IQR -2.5–1.5), respectively). No changes were observed for TATc, ETP, PAPc and D-dimer. Oral prednisolone induces a procoagulant state in healthy subjects, suggesting that corticosteroid treatment may increase thromboembolic risk in patients with inflammatory diseases. This article is protected by copyright. All rights reserved.
    No preview · Article · Jan 2016 · Journal of Thrombosis and Haemostasis
  • Tom Plug · Joost C.M. Meijers
    [Show abstract] [Hide abstract]
    ABSTRACT: Thrombin-activatable fibrinolysis inhibitor (TAFI) is an important regulator in the balance of coagulation and fibrinolysis. TAFI is a metallocarboxypeptidase that circulates in plasma as zymogen. Activated TAFI (TAFIa) cleaves C-terminal lysine or arginine residues from peptide substrates. The removal of C-terminal lysine residues from partially degraded fibrin leads to reduced plasmin formation and thus attenuation of fibrinolysis. TAFI also plays a role in inflammatory processes via the removal of C-terminal arginine or lysine residues from bradykinin, thrombin-cleaved osteopontin, C3a, C5a and chemerin. TAFI has been studied extensively over the past three decades and recent publications provide a wealth of information including crystal structures, mutants and structural data obtained with antibodies and peptides. In this review, we combined and compared available data on structure/function relationships of TAFI. This article is protected by copyright. All rights reserved.
    No preview · Article · Jan 2016 · Journal of Thrombosis and Haemostasis
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: Epidemiologic studies have shown that asthmatic patients, in particular those with severe disease, have increased risk of pulmonary embolism. It is unknown whether these patients have a prothrombotic state under stable conditions. Objective: We sought to compare coagulation and fibrinolysis parameters between healthy subjects and patients with mild, severe, and prednisolone-dependent asthma under stable conditions and to investigate whether hemostatic markers correlate with airway inflammation. Methods: In 126 adults (33 healthy control subjects, 31 patients with mild asthma, 32 patients with severe asthma, and 30 patients with prednisolone-dependent asthma) parameters of inflammation (peripheral blood eosinophils and neutrophils) and markers of hemostasis (endogenous thrombin potential [ETP], thrombin-antithrombin complex, plasmin-α2-antiplasmin complex, plasminogen activator inhibitor type 1 [PAI-1], D-dimer, and von Willebrand factor [vWF]) were measured in plasma. One-way ANOVA with the post hoc Bonferroni test was used for group comparison, and linear regression analysis was used for correlations. Results: We observed increased ETP (121% vs 99%, overall P < .01), plasmin-α2-antiplasmin complex (520 vs 409 μg/L, overall P = .04), PAI-1 (10 vs 7 ng/mL, overall P = .02), and vWF (142% vs 87%, overall P < .01) levels in asthmatic patients compared with healthy control subjects. ETP, PAI-1, and vWF levels increased with increasing asthma severity. In addition, we found a correlation between ETP and vWF with neutrophil but not eosinophil counts. Conclusion: Asthmatic patients have a prothrombotic state that increases with asthma severity. This might explain why patients with asthma, in particular those with severe disease, have an increased risk of venous thromboembolism.
    Full-text · Article · Dec 2015 · The Journal of allergy and clinical immunology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Introduction: ST-elevated myocardial infarction (STEMI) is most frequently caused by coronary occlusion due to formation of an intracoronary thrombus in reaction to rupture of atherosclerotic plaques. Little is known about kinetics of coagulation markers after STEMI in patients treated according to current guidelines. We aimed to investigate kinetics of important coagulation markers in percutaneous coronary intervention (PCI)-treated STEMI patients. Materials and methods: 60 consecutive PCI-treated STEMI patients were prospectively included. Blood samples were collected immediately after as well as 1, 4 and 7days following PCI. Samples collected 90days after PCI served as baseline values. ADAMTS13 activity, VWF (von Willebrand factor) activity, VWF antigen, VWF propeptide, fibrinogen antigen, D-dimer, alpha2-antiplasmin (α2AP), plasmin-alpha2-antiplasmin complex (PAP), prothrombin fragment F1+2 (F1+2), prothrombin time (PT), activated partial thromboplastin time (aPTT), and anti-factor Xa (anti-Xa) were measured. Cardiac magnetic resonance (CMR) was performed at 4-6 and 90days after PCI in 49 patients and left ventricular ejection fraction (LVEF), infarct size and microvascular injury (MVI) were determined. Results: Immediately after PCI, ADAMTS13 activity, fibrinogen antigen and α2AP levels were significantly decreased and VWF activity, VWF antigen and VWF propeptide levels were significantly elevated, compared to baseline. Individual coagulation markers and different combinations thereof were not related to LVEF or infarct size at 90days, or the occurrence of MVI at 4-6days after PCI. Conclusion: Coagulation parameters show a very dynamic profile in the early days after STEMI. However, individual coagulation parameters or combinations thereof do not predict CMR-defined LVEF, infarct size or MVI.
    Full-text · Article · Dec 2015 · Thrombosis Research
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: Epidemiologic studies have shown that patients with severe asthma have increased risk of pulmonary embolism, in particular patients with frequent asthma exacerbations. Therefore, we hypothesized that asthma exacerbations are associated with increased hemostatic activity. Objective: To investigate if induced loss of asthma control is associated with changes in coagulation and fibrinolytic parameters in peripheral blood. Methods: We performed a prospective, inhaled steroid-withdrawal study in 23 patients with moderate to moderately severe asthma, consisting of a baseline visit and a visit after loss of asthma control. During the visits we measured asthma control questionnaire (ACQ), atopy, lung function, inflammatory markers (eosinophils and neutrophils), and hemostatic parameters in plasma. Results: Complete cessation of inhaled corticosteroids led to a loss of asthma control in 22 out of 23 patients. We found increased asthma symptoms (ACQ 0.9 vs. 2.9, p<0.01), significantly reduced lung function (forced expiratory volume in 1 second (FEV1 ) 3.51L vs. 3.13L, p<0.01) and increased levels of eosinophils in plasma (0.26x10(E9) /L vs. 0.16x10(E9) /L, p=0.03) in patients after loss of asthma control. However, we observed no significant changes in the coagulation and fibrinolysis parameters. Conclusion: Loss of asthma control after cessation of inhaled corticosteroids does not lead to increased hemostatic activation in patients with moderate to moderately severe asthma. This suggests that more severe inflammation or additional risk factors are required for activation of coagulation or reduction of fibrinolysis in asthma. This article is protected by copyright. All rights reserved.
    Full-text · Article · Oct 2015 · Clinical & Experimental Allergy
  • Source
    Marisa L. R. Cunha · Joost C. M. Meijers · Saskia Middeldorp
    [Show abstract] [Hide abstract]
    ABSTRACT: Despite knowledge of various inherited risk factors associated with venous thromboembolism (VTE), no definite cause can be found in about 50% of patients. The application of data-driven searches such as GWAS has not been able to identify genetic variants with implications for clinical care, and unexplained heritability remains. In the past years, the development of several so-called next generation sequencing (NGS) platforms is offering the possibility of generating fast, inexpensive and accurate genomic information. However, so far their application to VTE has been very limited. Here we review basic concepts of NGS data analysis and explore the application of NGS technology to VTE. We provide both computational and biological viewpoints to discuss potentials and challenges of NGS-based studies.
    Full-text · Article · Oct 2015 · Thrombosis and Haemostasis
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Asthma patients show evidence of a procoagulant state in their airways, accompanied by an impaired function of the anticoagulant protein C system. We aimed to study the effect of recombinant human activated protein C (rhAPC) in allergic asthma patients.We conducted a randomised, double-blind, placebo-controlled, proof-of-concept study in house dust mite (HDM) allergic asthma patients. Patients were randomised to receive intravenous rhAPC (24 microg.kg-1.h-1; n=12) or placebo (n=12) for 11 h. 4 h after the start of infusion, a first bronchoscopy was performed to challenge one lung segment with saline (control) and a contralateral segment with a combination of HDM extract and lipopolysaccharide (HDM+LPS), thereby mimicking environmental house dust exposure. A second bronchoscopy was conducted 8 h after intrabronchial challenge to obtain bronchoalveolar lavage fluid (BALF).rhAPC did not influence HDM+LPS induced procoagulant changes in the lung. In contrast, rhAPC reduced BALF leukocyte counts by 43% relative to placebo, caused by an inhibitory effect on neutrophil influx (64% reduction), while leaving eosinophil influx unaltered. rhAPC also reduced neutrophil degranulation products in the airways.Intravenous rhAPC attenuates HDM+LPS-induced neutrophil migration and protein release in allergic asthma patients by an effect that does not rely on coagulation inhibition.
    Full-text · Article · Sep 2015 · European Respiratory Journal
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mortality and morbidity in bacterial meningitis results from the pro-inflammatory response and dysregulation of coagulation and fibrinolysis. Thrombin-activatable fibrinolysis inhibitor (TAFI) is activated (TAFIa) by free thrombin or in complex with thrombomodulin, plays an anti-fibrinolytic role during fibrin clot degradation, but also has an anti-inflammatory role by inactivating proinflammatory mediators, such as complement activation products. To assess the role of TAFI in pneumococcal meningitis. We performed a prospective nationwide genetic association study in patients with bacterial meningitis, determined TAFI and complement levels in CSF, and assessed the function of TAFI in a pneumococcal meningitis mouse model using Cpb2 (TAFI) knockout mice. polymorphisms (reference sequence: rs1926447 and rs3742264) in the CPB2 gene, coding for TAFI, were related with development of systemic complications in patients with pneumococcal meningitis. Higher protein levels of TAFI in CSF were significantly associated with CSF complement levels (C3a, iC3b and C5b-9) and with more systemic complications in patients with bacterial meningitis. The risk allele of rs1926447 (TT) was associated with higher levels of TAFI in CSF. In the murine model, consistent with the human data, Cpb2-deficient mice had decreased disease severity reflected by lower mortality, attenuated cytokine levels and bacterial outgrowth in the systemic compartment during disease, without differences in the brain compartment, as compared with wild-type mice. These findings suggest that TAFI plays an important role during pneumococcal meningitis, which is likely to be mediated through inhibition of the complement system, and influences the occurrence of systemic complications and inflammation. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Full-text · Article · Sep 2015 · Journal of Thrombosis and Haemostasis
  • Source
    Tom Plug · J. Arnoud Marquart · Pauline F. Marx · Joost C.M. Meijers
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Thrombin-activatable fibrinolysis inhibitor (TAFI) is a risk factor for coronary heart disease. TAFI is proteolytically activated by thrombin, the thrombin-thrombomodulin complex and plasmin. Once active, it dampens fibrinolysis and inflammation. The aim of this study was to generate TAFI-derived peptides that specifically modulate TAFI activation and activity.Methods34 overlapping TAFI peptides, and modifications thereof, were synthesized. The effects of these peptides on TAFI activation and TAFIa activity were determined. In addition, the binding of the peptides to thrombin were determined.ResultsFour peptides (peptides 2, 18, 19 and 34) inhibited TAFI activation and two peptides (peptides 14 and 24) inhibited TAFIa activity directly. Peptide 2 (Arg12-Glu28) and peptide 34 (Cys383-Val401) inhibited TAFI activation by the thrombin-thrombomodulin complex with IC50 values of 41.9±9.1 and 6.1±0.9 μM, respectively. However, no inhibition was observed in the absence of thrombomodulin. This suggests that the regions Arg12-Glu28 and Cys383-Val401 in TAFI are involved in thrombomodulin-mediated TAFI activation. Peptide 18 (Gly205-Ser221) and peptide 19 (Arg214-Asp232) inhibited TAFI activation by thrombin and the thrombin-thrombomodulin complex. Furthermore, these peptides bound to thrombin (KD: 1.5±0.4 and 0.52±0.07 μM for peptides 18 and 19 respectively), suggesting that Gly205-Asp232 of TAFI is involved in binding to thrombin. Peptide 14 (His159-His175) inhibited TAFIa activity. The inhibition was TAFIa specific, since no effect on the homologous enzyme carboxypeptidase B was observed.ConclusionsTAFI-derived peptides show promise as new tools to modulate TAFI activation and TAFIa activity. Furthermore, these peptides revealed potential binding sites on TAFI for thrombin and the thrombin-thrombomodulin complex.This article is protected by copyright. All rights reserved.
    Full-text · Article · Sep 2015 · Journal of Thrombosis and Haemostasis
  • [Show abstract] [Hide abstract]
    ABSTRACT: Introduction: Protein Z (PZ)-dependent protease inhibitor (ZPI) is a serine protease inhibitor that efficiently inhibits activated factor X when ZPI is in complex with PZ. We previously reported significantly higher concentrations of plasma ZPI (and PZ) in women during normal pregnancy than in non-pregnant women. Methods: We explored the possible contribution of estrogen to the ZPI levels in patients with or without bilateral oophorectomy (OVX), which induces artificial menopause where blood estrogen levels drastically decrease. One hundred ninety-one pre-menopausal Japanese women who underwent open hysterectomy owing to neoplasms participated in this study and were divided into two groups: 98 OVX and 93 Non-OVX cases. Plasma ZPI was measured by ELISA. Results and conclusion: Contrary to our working hypothesis, plasma ZPI levels increased significantly in the OVX group after surgery when compared with the pre-operation levels. When these patients were individually analyzed, their ZPI value also rose significantly from pre-operation to post-operation levels. In contrast, plasma PZ levels remained unchanged. The significantly increased ZPI and unchanged PZ levels were also observed in the Non-OVX group. The increased ZPI levels were not significantly related to 17β-estradiol, luteinizing hormone or follicular stimulating hormone levels, clearly indicating that estrogen did not contribute to the plasma ZPI concentrations. Typical acute phase reactants fibrinogen and C-reactive protein (CRP) were also significantly elevated after surgery in both OVX and Non-OVX groups. However, only weakly significant linear relationships were observed between ZPI and fibrinogen or CRP, indicating the presence of alternative regulatory mechanisms underlying their plasma concentrations.
    No preview · Article · Sep 2015 · Thrombosis Research
  • [Show abstract] [Hide abstract]
    ABSTRACT: Factor XIII(a) [FXIII(a)] stabilizes clots and increases resistance to fibrinolysis and mechanical disruption. FXIIIa also mediates red blood cell (RBC) retention in contracting clots and determines venous thrombus size, suggesting FXIII(a) is a potential target for reducing venous thrombosis. However, the mechanism by which FXIIIa retains RBCs in clots is unknown. We determined the effect of FXIII(a) on human and murine clot weight and composition. Real-time microscopy revealed extensive RBC loss from clots formed in the absence of FXIIIa activity, and RBCs exhibited transient deformation as they exited the clots. Fibrin band-shift assays and flow cytometry did not reveal crosslinking of fibrin or FXIIIa substrates to RBCs, suggesting FXIIIa does not crosslink RBCs directly to the clot. RBCs were retained in clots from mice deficient in α2-antiplasmin, thrombin-activatable fibrinolysis inhibitor, or fibronectin, indicating RBC retention does not depend on these FXIIIa substrates. RBC retention in clots was positively-correlated with fibrin network density; however, FXIIIa inhibition reduced RBC retention at all network densities. FXIIIa inhibition reduced RBC retention in clots formed with fibrinogen that lacks γ-chain crosslinking sites, but not in clots that lack α-chain crosslinking sites. Moreover, FXIIIa inhibitor concentrations that primarily block α-, but not γ-, chain crosslinking decreased RBC retention in clots. These data indicate FXIIIa-dependent retention of RBCs in clots is mediated by fibrin α-chain crosslinking. These findings expose a newly-recognized, essential role for fibrin crosslinking during whole blood clot formation and consolidation, and establish FXIIIa activity as a key determinant of venous thrombus composition and size. Copyright © 2015 American Society of Hematology.
    No preview · Article · Aug 2015 · Blood
  • [Show abstract] [Hide abstract]
    ABSTRACT: Asthma is a chronic disease of the airways; asthma patients are hampered by recurrent symptoms of dyspnoea and wheezing caused by bronchial obstruction. Most asthma patients suffer from chronic allergic lung inflammation triggered by allergens such as house dust mite (HDM). Coagulation activation in the pulmonary compartment is currently recognized as a feature of allergic lung inflammation and data suggests that coagulation proteases further drive inflammatory mechanisms. Here, we tested whether treatment with the oral thrombin inhibitor Dabigatran attenuates allergic lung inflammation in a recently developed HDM-based murine asthma model. Mice were fed Dabigatran (10mg/g) or placebo chow during a three-week HDM airway exposure model. Dabigatran treatment caused systemic thrombin inhibitory activity corresponding with Dabigatran levels reported in human trials. Surprisingly, Dabigatran did not lead to inhibition of HDM-evoked coagulation activation in the lung as measured by levels of thrombin-antithrombin complexes and D-dimer. Repeated HDM administration caused an influx of eosinophils and neutrophils into the lungs, mucus production in the airways, and a T helper 2 response, as reflected by a rise in bronchoalveolar IL-4 and IL-5 levels and a systemic rise in IgE and HDM-IgG1. Dabigatran modestly improved HDM-induced lung pathology (P<0.05) and decreased IL-4 levels (P<0.01), without influencing other HDM-induced responses. Considering the limited effects of Dabigatran in spite of adequate plasma levels, these results argue against clinical evaluation of Dabigatran in patients with asthma. Copyright © 2015, American Journal of Physiology - Lung Cellular and Molecular Physiology.
    No preview · Article · Aug 2015 · AJP Lung Cellular and Molecular Physiology
  • Cheung YW · Barco S · Hutten BA · J.C.M. Meijers · Middeldorp S · Coppens M.
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Four-factor prothrombin complex concentrate (PCC) (Cofact; Sanquin Blood Supply) 50 IU kg(-1) increased thrombin generation beyond baseline values in healthy, rivaroxaban-treated subjects. Objective To assess whether infusion with doses of 37.5 IU kg(-1) and 25 IU kg(-1) PCC reverses the anticoagulant effect of high-dose apixaban, another oral direct factor Xa inhibitor. Methods In a randomized, double-blind, placebo-controlled, crossover study, six healthy subjects received twice-daily apixaban 10 mg for 3.5 days followed by a single bolus of 37.5 IU kg(-1) PCC, 25 IU kg(-1) PCC, or placebo. The primary outcome was the effect of PCC 15 min after infusion on thrombin generation (endogenous thrombin potential [ETP]); secondary outcomes were the immediate effect of PCC on prothrombin time (PT) and the effect of PCC as compared with placebo over a period of 24 h on ETP and PT. ResultsFifteen minutes after infusion of 37.5 IU kg(-1) and 25 IU kg(-1) PCC, ETP increased from 41% 11% to 56% +/- 23% (P = 0.06) and from 44% +/- 12% to 51% +/- 15% (P = 0.03), respectively. ETP significantly differed over time between 37.5 IU kg(-1) PCC and placebo during 24 h after infusion (P < 0.01). Both PCC doses restored apixaban-induced PT prolongation after 15 min (P < 0.01), and this was sustained over a period of 24 h. Conclusion Both 37.5 IU kg(-1) PCC and 25 IU/kg PCC improved coagulation parameters in healthy subjects, suggesting partial reversal of the anticoagulant effect of apixaban. This implies that PCC might be considered in patients with apixaban-associated bleeding. However, ETP was not immediately restored to pre-apixaban levels, suggesting that these doses are too low to instantly and fully restore hemostasis at peak apixaban levels.
    No preview · Article · Aug 2015 · Journal of Thrombosis and Haemostasis
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Previous studies concluded that haemorrhage is one of the most accurate prognostic factors of mortality in leptospirosis. Therefore, endothelial cell activation was investigated in relation to disease severity in severe leptospirosis. Prospective cohort study of severe leptospirosis patients. Plasma levels of sE-selectin and Von Willebrand factor (VWF) were determined. Consequently, an in vitro endothelial cell model was used to assess endothelial activation after exposure to virulent Leptospira. Finally, immune activation, as a potential contributing factor to endothelial cell activation, was determined by soluble IL2-receptor (sIL-2r) and soluble Fas-ligand (sFasL) levels. Plasma levels of sE-selectin and VWF strongly increased in patients compared to healthy controls. Furthermore, sE-selectin was significantly elevated (203 ng/ml vs. 157 ng/ml, p < 0.05) in survivors compared to non-survivors. Endothelial cells exposed to virulent Leptospira showed increased VWF expression. E-selectin and ICAM-1 expression did not change. Immunohistochemistry revealed the presence of intracellular Leptospira and qPCR suggested replication. In vivo analysis showed that increased levels of sFasL and sIL-2r were both strongly associated with mortality. Furthermore sIL-2r levels were increased in patients that developed bleeding and significantly correlated to duration of hospital stay. Markers of endothelial activation and immune activation were associated with disease severity in leptospirosis patients. Copyright © 2015. Published by Elsevier Ltd.
    Full-text · Article · Jun 2015 · The Journal of infection
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Circulating microRNAs (miRNAs) have been reported as biomarkers for disease diagnosis. RT-qPCR is most commonly used to detect miRNAs; however, no consensus on the most appropriate method for data normalization exists. Via a standardized selection method, we aimed to determine separate miRNA normalization panels for RT-qPCR measurements on whole blood, platelets, and serum. Candidate miRNAs were selected from studies describing circulating miRNA microarray data in the Gene Expression Omnibus or ArrayExpress. miRNA expression data of healthy controls were retrieved from each study. For each sample type, we selected those miRNAs that were least variable and sufficiently highly expressed in multiple microarray experiments, performed on at least 2 different platforms. Stability of the candidate miRNAs was assessed using NormFinder and geNorm algorithms in a RT-qPCR cohort of 10 patients with coronary artery disease and 10 healthy controls. We selected miRNA normalization panels for RT-qPCR measurements on whole blood, platelets, and serum. As a validation, we assessed the precision of all 3 panels in 3 independent RT-qPCR cohorts and compared this with normalization for miR-16 or RNU6B. The proposed normalization panels for whole blood, platelets, and serum show better precision than normalization for miR-16 or RNU6B.-Kok, M. G. M., Halliani, A., Moerland, P. D., Meijers, J. C. M., Creemers, E. E., Pinto-Sietsma, S.-J. Normalization panels for the reliable quantification of circulating microRNAs by RT-qPCR. © FASEB.
    Full-text · Article · May 2015 · The FASEB Journal
  • [Show abstract] [Hide abstract]
    ABSTRACT: Activation of thrombin is a critical determinant in many physiological and pathological processes including haemostasis and inflammation. Under physiological conditions many of these functions are involved in wound healing or eradication of an invading pathogen. However, when activated systemically, thrombin can contribute to severe and life-threatening conditions by causing complications such as multiple multi-organ failure and disseminated intravascular coagulation. In the present study we investigated how the activity of thrombin is modulated when it is bound to the surface of Streptococcus pyogenes. Our data show that S. pyogenes bacteria become covered with a proteinaceous layer when incubated with human plasma, and that thrombin is a constituent of this layer. Though the coagulation factor is found attached to the bacteria with a functional active site, thrombin has lost its capacity to interact with its natural substrates and inhibitors. Thus, the interaction of bacteria with human plasma renders thrombin completely inoperable at the streptococcal surface. This could represent a host defense mechanism to avoid systemic activation of coagulation which could be otherwise induced when bacteria enter the circulation and cause systemic infection.
    No preview · Article · May 2015 · Thrombosis and Haemostasis
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Puumala virus (PUUV) infection causes over 5000 cases of hemorrhagic fever in Europe annually and can influence the hemostatic balance extensively. Infection might lead to hemorrhage, while a recent study showed an increased risk of myocardial infarction during or shortly after PUUV infection. The mechanism by which this hantavirus influences the coagulation system remains unknown. Therefore we aimed to elucidate mechanisms explaining alterations seen in primary and secondary hemostasis during PUUV infection. By using low passage PUUV isolates to infect primary human umbilical vein endothelial cells (HUVECs) we were able to show alterations in the regulation of primary- and secondary hemostasis and in the release of fibrinolysis regulators. Our main finding was an activation of secondary hemostasis due to increased tissue factor (TF) expression leading to increased thrombin generation in a functional assay. Furthermore, we showed that during infection platelets adhered to HUVEC and subsequently specifically to PUUV virus particles. Infection of HUVEC with PUUV did not result in increased von Willebrand factor while they produced more plasminogen activator inhibitor type-1 (PAI-1) compared to controls. The PAI-1 produced in this model formed complexes with vitronectin. This is the first report that reveals a potential mechanism behind the pro-coagulant changes in PUUV patients, which could be the result of increased thrombin generation due to an increased TF expression on endothelial cells during infection. Furthermore, we provide insight into the contribution of endothelial cell responses regarding hemostasis in PUUV pathogenesis.
    Full-text · Article · Apr 2015 · Frontiers in Microbiology
  • [Show abstract] [Hide abstract]
    ABSTRACT: An unbalance between the platelet-adhesive protein von Willebrand factor (VWF) and its cleaving protease ADAMTS13 is a risk factor for thrombosis. Here, we assessed levels and functionality of VWF and ADAMTS13 in patients undergoing off-pump lung transplantation. We analyzed plasma of 10 patients and distinguished lung transplantation-specific effects from those generally accompanying open-chest surgeries by comparing results with 11 patients undergoing off-pump coronary bypass graft (CABG) surgery. Forty healthy volunteers were included for reference values. VWF antigen levels as well as the VWF ristocetin cofactor activity/VWF antigen ratio increased during lung transplantation and after CABG surgery. An increase in VWF propeptide levels was paralleled by a decrease in ADAMTS13 activity. This was more pronounced during lung transplantation. Similarly, the capacity of plasma to support platelet aggregation under shear flow conditions in vitro was more increased during lung transplantation. The proportion of high molecular weight VWF multimers was elevated in both groups without evidence for ultra-large VWF. VWF's collagen binding activity remained unchanged. In conclusion, a hyperactive primary hemostatic system develops during lung transplantation resulting both from a pronounced (functional) increase of the VWF molecule and decrease of ADAMTS13. This may increase the risk of platelet thrombosis within the allograft. © Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.
    No preview · Article · Apr 2015 · American Journal of Transplantation
  • [Show abstract] [Hide abstract]
    ABSTRACT: Streptococcus (S.) pneumoniae is the most common causative pathogen in community-acquired pneumonia. Coagulation and inflammation interact in the host response to infection. Tissue factor pathway inhibitor (TFPI) is a natural anticoagulant protein that inhibits tissue factor (TF), the main activator of inflammation-induced coagulation. It was the objective of this study to investigate the effect of endogenous TFPI levels on coagulation, inflammation and bacterial growth during S. pneumoniae pneumonia in mice. The effect of low endogenous TFPI levels was studied by administration of a neutralising anti-TFPI antibody to wild-type mice, and by using genetically modified mice expressing low levels of TFPI, due to a genetic deletion of the first Kunitz domain of TFPI (TFPIK1(-/-)) rescued with a human TFPI transgene. Pneumonia was induced by intranasal inoculation with S. pneumoniae and samples were obtained at 6, 24 and 48 hours after infection. Anti-TFPI reduced TFPI activity by ~50 %. Homozygous lowTFPI mice and heterozygous controls had ~10 % and ~50 % of normal TFPI activity, respectively. TFPI levels did not influence bacterial growth or dissemination. Whereas lung pathology was unaffected in all groups, mice with ~10 % (but not with ~50 %) of TFPI levels displayed elevated lung cytokine and chemokine concentrations 24 hours after infection. None of the groups with low TFPI levels showed an altered procoagulant response in lungs or plasma during pneumonia. These data argue against an important role for endogenous TFPI in the antibacterial, inflammatory and procoagulant response during pneumococcal pneumonia.
    No preview · Article · Apr 2015 · Thrombosis and Haemostasis

Publication Stats

11k Citations
2,133.86 Total Impact Points

Institutions

  • 2004-2016
    • University of Amsterdam
      • • Faculty of Medicine AMC
      • • Laboratory of Experimental Internal Medicine
      Amsterdamo, North Holland, Netherlands
  • 2001-2016
    • Academisch Medisch Centrum Universiteit van Amsterdam
      • • Department of Internal Medicine
      • • Academic Medical Center
      • • Center for Infection and Immunity Amsterdam
      • • Department of Vascular Medicine
      Amsterdamo, North Holland, Netherlands
  • 2013
    • University of Groningen
      • Department of Surgery
      Groningen, Groningen, Netherlands
  • 1987-2011
    • University Medical Center Utrecht
      • • Department of Clinical Chemistry and Haematology
      • • Department of Hematology
      Utrecht, Utrecht, Netherlands
  • 2007-2009
    • Leiden University Medical Centre
      • Department of Clinical Epidemiology
      Leiden, South Holland, Netherlands
  • 2006
    • Academic Medical Center (AMC)
      Amsterdamo, North Holland, Netherlands
  • 2004-2006
    • The Scripps Research Institute
      • Department of Molecular and Experimental Medicine
      لا هویا, California, United States
  • 2000-2005
    • Leiden University
      Leyden, South Holland, Netherlands
  • 1987-2003
    • Utrecht University
      • • Institute of Biomembranes
      • • Department of Hematology
      Utrecht, Utrecht, Netherlands
  • 1990-1992
    • University of Washington Seattle
      • Department of Biochemistry
      Seattle, Washington, United States
  • 1988
    • Netherlands Institute for Space Research, Utrecht
      Utrecht, Utrecht, Netherlands