Effect of prothrombin Belgrade mutation, causing antithrombin resistance, on fibrin clot properties

INTRODUCTION

Prothrombin Belgrade mutation is the result of the c.1787G>A substitution in the prothrombin gene. It is located in the antithrombin and sodium binding site and leads to impaired inactivation of thrombin by antithrombin, resulting in antithrombin resistance and thrombotic disorders. However, it negatively affects sodium binding and may have hypocoagulant effects. Considering that prothrombin Belgrade mutation mechanism is still not fully elucidated and that sodium binding is important for thrombin affinity towards fibrinogen, our aim was to determine whether this mutation affects fibrin clot formation and lysis.

METHODS

Using HEK293T cell line, recombinant wild type and mutated prothrombin were generated by transient transfection. Samples that correspond to plasma of a non-carrier, heterozygous and homozygous carriers were reconstituted using prothrombin deficient plasma and recombinant proteins. Reconstituted samples were used in OHP assay (Overall Hemostasis Potential) to determine kinetic profiles of coagulation and fibrinolysis. Clot turbidity assay was performed to observe kinetics of clot formation and lysis more closely. Fibrin clots formed in reconstituted plasma samples were analyzed by confocal microscopy to determine density of fibrin network. Fibrin clots were additionally observed using electron microscopy to determine thickness of individual fibrin fibers.

RESULTS

No significant difference found in OHP, OCP, OFP, and fibrin network density between wild type, heterozygous, and homozygous carrier reconstituted plasma samples. There were significant differences between samples for slope and slope time parameters in kinetic profiles and fibrin fiber thickness.

CONCLUSIONS

Results indicate that prothrombin Belgrade mutation has no significant impact on fibrinolysis, however it may affect kinetics of clot formation and its architecture.

Prothrombin Knockdown Protects Podocytes and Reduces Proteinuria in Glomerular Disease

Chronic kidney disease (CKD) is a leading cause of death, and its progression is driven by glomerular podocyte injury and loss, manifesting as proteinuria. Proteinuria includes urinary loss of coagulation zymogens, cofactors, and inhibitors. Importantly, both CKD and proteinuria significantly increase the risk of thromboembolic disease. Prior studies demonstrated that anticoagulants reduced proteinuria in rats and that thrombin injured cultured podocytes. Herein we aimed to directly determine the influence of circulating prothrombin on glomerular pathobiology. We hypothesized that (pro)thrombin drives podocytopathy, podocytopenia, and proteinuria. Glomerular proteinuria was induced with puromycin aminonucleoside (PAN) in Wistar rats. Circulating prothrombin was either knocked down using a rat-specific antisense oligonucleotide or elevated by serial intravenous infusions of prothrombin protein, which are previously established methods to model hypo- (LoPT) and hyper-prothrombinemia (HiPT), respectively. After 10 days (peak proteinuria in this model) plasma prothrombin levels were determined, kidneys were examined for (pro)thrombin co-localization to podocytes, histology, and electron microscopy. Podocytopathy and podocytopenia were determined and proteinuria, and plasma albumin were measured. LoPT significantly reduced prothrombin colocalization to podocytes, podocytopathy, and proteinuria with improved plasma albumin. In contrast, HiPT significantly increased podocytopathy and proteinuria. Podocytopenia was significantly reduced in LoPT vs. HiPT rats. In summary, prothrombin knockdown ameliorated PAN-induced glomerular disease whereas hyper-prothrombinemia exacerbated disease. Thus, (pro)thrombin antagonism may be a viable strategy to simultaneously provide thromboprophylaxis and prevent podocytopathy-mediated CKD progression.

POS0923 EXTRACELLULAR VESICLES AS POTENTIAL BIOMARKERS OF EARLY DISEASE STAGE IN SYSTEMIC SCLEROSIS

Background

Extracellular vesicles (EVs) are membrane-coated vesicles most often generated from the vasculature and circulating blood cells upon cell activation and during the early phase of apoptosis (1).

Objectives

To evaluate the concentration of different subpopulations of EVs in plasma from patients with SSc in relation to the disease duration and to the markers of endothelial injury.

Methods

Our study included 59 SSc patients (36 limited (lSSc) and 23 diffuse cutaneous subset (dSSc)) and 46 healthy age and gender matched controls subjects. Disease duration less than 3 years in patients with dSSc and less than 5 years in those with lSSc was considered as early disease stage. Clinical evaluation of patients was performed. EVs were analysed with flow cytometry after staining platelet poor plasma with fluorescent cell-specific monoclonal antibodies. The concentration of following phosphatidylserine-positive EVs (PS+ EVs) were analyzed: total EVs, endothelial EVs (EEVs; CD144+), platelet EVs (PEVs; CD42b+), monocytes EVs (LEVs; CD14+), EVs expressing ICAM1 (CD54+), VCAM1 (CD106+) and P selectin (CD62p+). Serum levels of ICAM1, VCAM1 and P selectin were determined with ELISA.

Results

Median disease duration of our cohort was 4 (0-29) years (early lSSc [20/36]: 2.5 (0-4.5) years; early dSSc [11/23]: 10 (1-30) months). All types of investigated EVs were significantly elevated in SSc patients compared to controls (p<0.05). Patients with early disease stage had significantly increased levels of all PS+EVs compared to HC (p<0.05). Moreover, the levels of EVs expressing ICAM1 and VCAM1 showed good validity in identifying patients with early disease stage (AUC 0.7, p<0.01). PEVs were increased in early dSSc compared to early lSSc, but the difference did not reach statistical significance (p=0.07). There was a correlation between serum levels and the levels of EVs expressing specific adhesion molecules (ICAM1: r=0.7, p<0.01; VCAM1: r=0.7, p<0.01; P selectin: r=-0.7, p<0.01), only within the group with early dSSc subtype of the disease. Further correlations were detected between ICAM1+EVs with either mRSS (r=0.07, p< 0.01) or EUSTAR activity index (r=0.07, p= 0.02) among patients with early dSSc.

Conclusion

Increased levels of circulating EVs of different cell origin were present in patients with early SSc. EVs expressing either ICAM1 or VCAM1 could be novel biomarkers of early disease. EVs expressing ICAM1 showed association with severity of skin involvement and disease activity in patients with early dSSc giving insight into their role in the pathogenesis of SSc.

References

[1]J Colic, M Matucci-Cerinic, S Guiducci and N Damjanov. Review: Microparticles in systemic sclerosis, targets or tools to control fibrosis: This is the question!. Journal of Scleroderma and Related Disorders. 2019; 5(34):239719831985735

Disclosure of Interests

None declared

Impaired fibrinolysis is linked with digital vasculopathy and onset of new digital ulcers in systemic sclerosis

Objective

To assess thrombin generation, fibrin formation and structure together with the fibrinolytic status in patients with systemic sclerosis (SSc) in relation to the occurrence of digital ulcers (DUs) during the course of disease.

Methods

We studied parameters of endothelial dysfunction, thrombin generation, overall haemostatic potential and fibrin clot turbidity in plasma from 58 SSc patients (39 with DUs history and 19 DU naïve) and 46 matched healthy controls (HC). Fibrin structure was visualised using scanning electron microscopy (SEM). Finally, 39 patients with a history of DUs were followed for 1.5 years and the predictive value of all investigated markers for new DU onset was explored.

Results

Significantly enhanced endogenous thrombin potential (ETP) and prolonged clot lysis time (CLT) were found in patients with DUs compared to HC. CLT was prolonged in patients with DUs compared to those without, showing good validity in identifying DUs with an area under the curve of 0.7, 95% CI 0.6-0.8. The levels of ETP and Intercellular Adhesion Molecule (ICAM1) were independently associated with CLT. Over the follow-up period, 20 patients developed new DU. CLT was prolonged (p<0.001) in patients with new DU episodes, especially those with recurrent DUs. Regression analysis showed that VAS Raynaud and CLT were predictors of new DUs (OR 1.1, 95%CI1.02-1.1; OR 1.2, 95%CI1.1-1.3, respectively. SEM confirmed denser fibrin clots in patients with new DUs.

Conclusion

Our results implicate that impaired fibrinolysis might have an emerged role in the underlying digital vasculopathy and its progression in SSc.

Increased Expression of Extracellular Vesicles Is Associated With the Procoagulant State in Patients With Established Rheumatoid Arthritis

This study sought to identify different subpopulations of extracellular vesicles (EVs) in plasma from female patients with established rheumatoid arthritis (RA) in relation to the activation of coagulation and fibrin formation in these patients. Forty women were included in the study, 20 patients and 20 age-matched healthy controls. The mean disease duration in patients was 13.0 (5.0-25.0) years, with medium to high disease activity despite ongoing treatment with low-dose prednisolone and methotrexate. There were no differences between the investigated groups regarding the presence of traditional cardiovascular risk factors. The concentration of phosphatidylserine-positive (PS+) EVs; platelet (CD42a+), leucocyte (CD45+), monocyte (CD14+), and endothelial (CD144+)-derived EVs; and EVs-expressing tissue factor (CD142+), P-selectin (CD62P+), and E-selectin (CD62E+) were determined by flow cytometry analysis. Overall hemostasis potential (OHP) was assessed to follow the hemostatic disturbances, including the parameters for overall coagulation potential (OCP) and overall fibrinolytic potential (OFP). Fibrin clot turbidity was measured together with clot lysis time, and scanning electron microscopy was performed. Increased concentrations of PS+, CD42a+, CD142+, CD45+, CD14+, and CD62P+ EVs were found in plasma from patients with RA compared to healthy controls, and the concentrations of PS+, CD42a+, CD14+, and CD62P+ EVs were positively correlated with the inflammatory parameters in RA patients. Positive correlations were also found between the levels of PS+ and CD42a+ EVs and OCP as well as between the levels of PS+, CD42a+, and CD62P+EVs and OHP. The levels of PS+, CD42a+, CD14+, CD62P+, and CD62E+ EVs were negatively correlated with OFP. Elevated levels of circulating EVs of different cell origins were found in patients with established RA, in relation to the inflammatory burden and coagulation activation in the disease.

POS0874 CLOT LYSIS TIME PREDICTS RECURRENT DIGITAL ULCERS IN SYSTEMIC SCLEROSIS AFTER ONE YEAR OF FOLLOW-UP: A NESTED CASE-CONTROL STUDY

Background:

Digital ulcers (DU) are a common visible manifestation of vasculopathy in systemic sclerosis (SSc), which could be recurrent and associated with disability and mortality (1). Although vasculopathy is connected with impaired coagulation/fibrinolysis system and aberrant expression of adhesion molecules, there are few data about their role in developing recurrent DU.

Objectives:

To evaluate the possible role of Fibrin generation/Fibrinolysis parameters and adhesion molecules in the prediction of new ischaemic DU oncet during a 1-year follow-up and their impact on the time to new DU onset (TD).

Methods:

From 58 consecutive patients with SSc who fulfilled the 2013 ACR/EULAR SSc criteria and have never been treated with endothelin receptor antagonist, phosphodiesterase 5 inhibitors or prostanoids, a total of 38 patients with ever had DU, either active at inclusion or in past, were enrolled in a prospective cohort study. Each patient was given a “DU diary”. Demografic, clinical and serologycal data were recorded. The serum concentration of ICAM1 and E selectin were measured by ELISA. Haemostatic potential parameters: overall haemostasis (OHP), overall coagulation (OCP) and overall fibrinolysis (OFP) potential were assessed. Maximum absorbance (Cmax), reflects the fibrin clot density and clot lysis time (Lys50t0, time from initiation of clot formation to the time at which a 50% fall in absorbance from Cmax in the lysis assay), reflects fibrinolytic susceptibility, were calculated (2). Fibrin structure was visualised using scanning electron microscopy (SEM).

Results:

Over the follow-up period,18 patients (45.5%) developed new DU with the average TD of 7.4±2.9 months. There was no differance in ASA and CCB treatment among two groups (p>0.05). The OFP value was significantly decreased (p<0.01), Lys50t0 prolonged (p<0.05), while OHP was increased (p<0.05) in patients experienced new DU. Lys50t0 showed good validity in identifying patients with new DU oncet (AUC 0.683 95% CI 0.5 - 0.9). By multivariate analysis including clinical data in model the Lys50t0 (HR 1.2, 95% CI 1.1-1.3, p=0.018) and active DU at enrollment (HR 9.6, 95% CI 1.4-66.8, p=0.022) were identified as independent risk factors for the occurrence of new DU. TD was inversly correlated with ICAM1(p<0.001), E selectin (p<0.05), Cmax (p <0.05) and Lys50t0 (p<0.001). Model explaining 81.6% of the TD variability included Lys50t0 (β=- 0.55,p=0.003), E selectin (β=- 0.44,p=0.014) and fibrinogen (β=- 0.49,p=0.017). SEM revealed denser fibrin clots with thinner fibres in group experienced new DU compared to clots formed in plasma of patient without DU.

Conclusion:

Our results provide evidence that impaired fibrinolysis has critical role in the progression of microvascular disease, identifing clot lysis time as a strong predictor in the oncet of new digital ulcers in Systemic sclerosis. The higher level of E selectin and the longer lysis time are, the shorter is time until the onset of new digital ulcer. These results could be used in selection of patients at high risk of developing recurrent digital ulcer and therefore allow earlier therapeutic intervention.

References:

[1]Allanore Y, Distler O, Matucci-Cerinic M, Denton CP. Review: Defining a Unified Vascular Phenotype in Systemic Sclerosis. Arthritis Rheumatol. 2018 Feb;70(2):162-170

[2]Carter AM, et al. Heritability of clot formation, morphology, and lysis: the EuroCLOT study. Arterioscler Thromb Vasc Biol. 2007 Dec;27(12):2783-9.

Figure 1.

SEM images of fibrin network in 1 representative sample from a SSc patient with (A) and 1from patient without (B) new DU oncet

Disclosure of Interests:

None declared

Early-onset ischaemic stroke in patient with novel F2 c.1824C>T gene variant and PAI-1 4G/4G, MTHFR 677TT genotype

Background/Aim. Ischemic stroke is a heterogeneous disorder caused by several genetic and environmental risk factors. It was suggested that coagulation disorders cause 1-4% of cases with ischemic stroke, especially in patients with early-onset of ischemic stroke. Case report. Here, we describe a case of patient who developed an unprovoked ishemic stroke in young adult. Biochemical, immunological and thrombophilia screening, as well DNA sequencing were performed in order to reveal molecular pathology underlying stroke of patient. Thrombophilia testing showed that patient was homozygous carrier for PAI-1 4G/5G and MTHFR C677T mutations. Additional genetic analysis revealed the presence of recently reported FII c.1824C>T gene variant, which is located in the last exon of prothrombin gene and previously shown to cause hyperprothrombinemia, hypofibrinolysis and altered fibrin clot phenotype. Conclusion. Our results suggest that newly reported FII c.1824C>T gene variant might have synergistic effect with PAI 4G/4G and MTHFR 677TT genotype in formation of altered fibrin clot phenotype characterized by thin, densely packed fibrin fibers, which makes clot less susceptible to fibrinolysis and greatly increases the risk for early ischemic stroke onset.

Diagnostic Accuracy in Acute Venous Thromboembolism: Comparing D-Dimer, Thrombin Generation, Overall Hemostatic Potential, and Fibrin Monomers

Introduction  For acute venous thromboembolism (VTE), a biomarker with higher specificity than D-dimer would be of great clinical use. Thrombin generation and overall hemostatic potential (OHP) reflect the hemostatic balance by globally assessing multiple coagulation factors and inhibitors. These tests discriminate between healthy controls and patients with a prothrombotic tendency but have yet to be established as clinical biomarkers of VTE.

Objective  This study compares endogenous thrombin potential (ETP) and OHP to D-dimer and fibrin monomers (FM) in outpatients with suspected VTE.

Methods  A cross-sectional diagnostic study where 954 patients with suspected pulmonary embolism or deep venous thrombosis were recruited consecutively from the medical emergency department at Karolinska University Hospital. D-dimer, FM, OHP, and ETP were analyzed in a subpopulation of 60 patients with VTE and 98 matched controls without VTE. VTE was verified either by ultrasonography or computed tomography and clinical data were collected from medical records.

Results  Compared with healthy controls, both VTE and non-VTE patients displayed prothrombotic profiles in OHP and ETP. D-dimer, FM, ETP area under the curve (AUC), and ETP T _lag were significantly different between patients with VTE and non-VTE. The largest receiver-operating characteristic AUCs for discrimination between VTE and non-VTE, were found in D-dimer with 0.94, FM 0.77, and ETP AUC 0.65. No useful cutoff could be identified for the ETP or the OHP assay.

Conclusion  Compared with D-dimer, neither ETP nor OHP were clinically viable biomarkers of acute venous thrombosis. The data indicated that a large portion of the emergency patients with suspected VTE were in a prothrombotic state.

The Silence Speaks, but We Do Not Listen: Synonymous c.1824C>T Gene Variant in the Last Exon of the Prothrombin Gene as a New Prothrombotic Risk Factor

BACKGROUND

Thrombosis is a major global disease burden with almost 60% of cases related to underlying heredity and most cases still idiopathic. Synonymous single nucleotide polymorphisms (sSNPs) are considered silent and phenotypically neutral. Our previous study revealed a novel synonymous FII c.1824C>T variant as a potential risk factor for pregnancy loss, but it has not yet been associated with thrombotic diseases.

METHODS

To determine the frequency of the FII c.1824C>T variant we have sequenced patients' DNA. Prothrombin RNA expression was measured by quantitative PCR. Functional analyses included routine hemostasis tests, western blotting and ELISA to determine prothrombin levels in plasma, and global hemostasis assays for thrombin and fibrin generation in carriers of the FII c.1824C>T variant. Scanning electron microscopy was used to examine the structure of fibrin clots.

RESULTS

Frequency of the FII c.1824C>T variant was significantly increased in patients with venous thromboembolism and cerebrovascular insult. Examination in vitro demonstrated increased expression of prothrombin mRNA in FII c.1824T transfected cells. Our ex vivo study of FII c.1824C>T carriers showed that the presence of this variant was associated with hyperprothrombinemia, hypofibrinolysis, and formation of densely packed fibrin clots resistant to fibrinolysis.

CONCLUSION

Our data indicate that FII c.1824C>T, although a synonymous variant, leads to the development of a prothrombotic phenotype and could represent a new prothrombotic risk factor. As a silent variant, FII c.1824C>T would probably be overlooked during genetic screening, and our results show that it could not be detected in routine laboratory tests.

Synergistic Effect of Bypassing Agents and Sequence Identical Analogue of Emicizumab and Fibrin Clot Structure in the In Vitro Model of Hemophilia A

Development of inhibitors to factor VIII (FVIII) occurs in approximately 30% of severe hemophilia A (HA) patients. These patients are treated with bypassing agents (activated prothrombin complex concentrate [aPCC] and recombinant activated FVII-rFVIIa). Recently, a bispecific FIX/FIXa- and FX/FXa-directed antibody (emicizumab) has been approved for the treatment of HA patients with inhibitors. However, the data from clinical studies imply that coadministration of emicizumab and bypassing agents, especially aPCC, could have a thrombotic effect.

This study was aimed to address the question of potential hypercoagulability of emicizumab and bypassing agents' coadministration, we have investigated fibrin clot formation and structure in the in vitro model of severe HA after adding sequence-identical analogue (SIA) of emicizumab and bypassing agents.

Combined overall hemostasis potential (OHP) and fibrin clot turbidity assay was performed in FVIII-deficient plasma after addition of different concentrations of SIA, rFVIIa, and aPCC. Pooled normal plasma was used as control. The fibrin clots were analyzed by scanning electron microscopy (SEM).

OHP and turbidity parameters improved with the addition of aPCC, while therapeutic concentrations of rFVIIa did not show substantial improvement. SIA alone and in combination with rFVIIa or low aPCC concentration improved OHP and turbidity parameters and stabilized fibrin network, while in combination with higher concentrations of aPCC expressed hypercoagulable pattern and generated denser clots.

Our in vitro model suggests that combination of SIA and aPCC could potentially be prothrombotic, due to hypercoagulable changes in fibrin clot turbidity and morphology. Additionally, combination of SIA and rFVIIa leads to the formation of stable clots similar to normal fibrin clots.

FRI0232 ALTERED FIBRIN CLOT PROPERTIES IN PATIENTS WITH SYSTEMIC SCLEROSIS

Background:

Vasculopathy in Systemic sclerosis (SSc) is connected with the activation of coagulation. However, the fibrinolytic activity still remains unclear since the most preliminary evidences are discordant (1, 2).

Objectives:

To assess the haemostatic function, fibrin clot density and clot lysis time in SSc patients and healthy controls (HC) to determine their relation to disease findings.

Methods:

Patients who fulfilled the 2013 ACR/EULAR SSc criteria and have never been treated with endothelin receptor antagonist, phosphodiesterase 5 inhibitors or prostanoids were eligibile. Our study included 58 SSc patients [36 limited (lcSSc) and 22 diffuse cutaneous SSc (dcSSc)] and 46 sex/age-matched HC. Clinical evaluation of patients was performed, including high-resolution CT (HRCT), pulmonary function tests and the revised EUSTAR activity index. The interstitial lung disease (ILD) group (n = 15) was defined as moderate or severe changes on HRCT, with a forced vital capacity (FVC) < 85% predicted, without evidence of significant pulmonary arterial hypertension. The serum concentration of ICAM1 and von Willebrand factor antigen (VWF) were measured by ELISA. Haemostatic potential parameters; including overall haemostasis (OHP), overall coagulation (OCP) and overall fibrinolysis (OFP) potential, were assessed and endogenous thrombin potential (ETP) was determined. Maximum absorbance (Cmax), reflects the fibrin clot density and clot lysis time (Lys50t0), reflects fibrinolytic susceptibility, were calculated from OHP and OCP curves (3). Fibrin structure was visualised using scanning electron microscopy (SEM).

Results:

The OFP value was significantly decreased, Lys50t0 prolonged (p<0.05), while OHP and ETP were increased (p<0.05) in patients. In dSSc group ETP, OHP, Cmax and Lys50t0 were higher compared to HC (p<0.05). In SSc group, a positive association was found between coagulation parameters (OCP, OHP, Cmax) and the erythrocyte sedimentation rate (ESR), fibrinogen and ICAM1 (respectively p<0.05). Lys50t0 was positively correlated with ICAM1, ESR and VWF (respectively p<0.001, p<0.05, p<0.05). An inverse correlation was found between Cmax and both the diffusing capacity of the lungs for carbon monoxide (r=-0.408, p<0.01) and FVC (r=-0.318, p<0.01). Increased Cmax was found in ILD respect to HC (p<0.01). Denser plasma clot was associated with active disease (p<0.01). Longer Lys50t0 was observed in pitting scars group (p<0.01). Prolonged Lys50t0 was independently predicted by ICAM1 (OR 1.12, 95% CI 1.03–1.2, p<0.01).

Conclusion:

Our results provide evidences of denser plasma fibrin clot among patients with lung involvement and impaired fibrinolysis, selectively presented among SSc patients with piting scars. Thus, these patients might be at risk for thrombotic complications. Raised ICAM-1 levels could reflect impaired fibrinolysis, giving insight the important role of this molecule in endothelial homeostasis.

References:

[1]Cerinic MM, et al. Blood coagulation, fibrinolysis, and markers of endothelial dysfunction in systemic sclerosis. Semin Arthritis Rheum. 2003;32:285–95

[2]Lippi G, et al. Plasma D-dimer concentration in patients with systemic sclerosis.Thromb J. 2006;4:2.

[3]Carter AM, et al. Heritability of clot formation, morphology, and lysis: the EuroCLOT study. Arterioscler Thromb Vasc Biol. 2007 Dec;27(12):2783-9

Figure 1.

SEM images of fibrin network in 1 representative sample from a SSc (A) and 1from HC sample (B).

Disclosure of Interests:

Jelena Colic: None declared, Aleksandra Antovic: None declared, Iva Pruner: None declared, Jelena Vojinovic Consultant of: Roche, Abbvie, Pfizer, MSD, Speakers bureau: Roche, Abbvie, Pfizer, MSD, Mirjana Sefik Bukilica: None declared, Nemanja Damjanov Grant/research support from: from AbbVie, Pfizer, and Roche, Consultant of: AbbVie, Gedeon Richter, Merck, Novartis, Pfizer, and Roche, Speakers bureau: AbbVie, Gedeon Richter, Merck, Novartis, Pfizer, and Roche

Evaluation of global haemostatic assays and fibrin structure in patients with pre-eclampsia

INTRODUCTION

Haemostatic balance shifted towards hypercoagulability in normal pregnancy is even more pronounced in pre-eclampsia (P-EC). The aim of this study was to analyse haemostatic disturbances and fibrin clot properties in women with pre-eclampsia and to investigate their association with maternal and foetal outcomes.

METHODS

Forty-six pregnant women diagnosed with pre-eclampsia were included in the study, with blood sampling done on the morning following admission to hospital, as well as after delivery (mean duration 4.8 days). Two global haemostatic assays-endogenous thrombin potential (ETP) and assay of overall haemostatic potential (OHP)-were employed, including fibrin clot turbidity measurements and scanning electron microscopy (SEM) of representative samples.

RESULTS

Three thrombin generation parameters (ETP, t_lag and peak height) and OHP were significantly increased in pre-eclampsia compared with controls, whereas overall fibrinolytic potential (OFP-determined as a parameter of the OHP assay) had significantly lower values. Clot lysis time was significantly prolonged in patients with pre-eclampsia. In the pre-eclamptic group after delivery, we observed a significant elevation in the peak height and a reduction in the time to peak and OFP compared with values before delivery. Pre-eclamptic patients with renal complications had significantly higher values for ETP, peak height and D-dimer. Turbidity measurements and SEM revealed dense fibrin structure in patients with pre-eclampsia.

CONCLUSION

Patients with pre-eclampsia have enhanced coagulation and impaired fibrinolysis before, and even after, delivery. In particular, the presence of multi-organ dysfunction, such as renal dysfunction, may be associated with increased thrombin generation in pre-eclampsia.

Prothrombin 3'end Gene Variants in Patients With Sporadic Colon Adenocarcinoma

BACKGROUND/AIM

Thrombin plays significant roles in various types of cancer. However, the expression levels of prothrombin, the thrombin precursor, in cancer remain unclear. Variants of the 3'end of the prothrombin gene lead to increased prothrombin expression. This study aimed to analyze prothrombin 3'end gene variants in colon tumor and adjacent normal tissue samples.

MATERIALS AND METHODS

The study group consisted of 93 patients suffering from colon adenocarcinoma. The 3'end of the prothrombin gene was analyzed by DNA sequencing.

RESULTS

Three variants, all previously associated with increased prothrombin expression were detected. Frequency of the FII 19911G allele was 46.77% and 47.85% in tumor and normal tissue, respectively. For the FII 20210A allele, the detected frequencies were 2.15% and 1.61%, respectively. The frequency of the FII c.1824T allele was 0.54% in both tissues. Four patients showed different genotypes in tumor and normal tissue.

CONCLUSION

Prothrombin 3' end gene variants may play a role in colorectal cancer.

Assessment of hemostatic disturbances in women with established rheumatoid arthritis

OBJECTIVES

This study was aimed to assess hemostatic disturbances in female patients with established rheumatoid arthritis (RA) in relation to menopausal status and disease activity.

METHOD

Ninety women were included in the study, 42 patients and 48 age-matched healthy controls. There were no differences between the investigated groups regarding the presence of traditional cardiovascular risk factors. Two global hemostatic assays were employed, namely endogenous thrombin potential (ETP) and overall hemostasis potential (OHP). The parameters of the ETP assay (ETP, C-max, t-lag, t-max) and OHP assay (overall coagulation potential (OCP) and overall fibrinolytic potential (OFP)) were assessed. Moreover, the parameters of the fibrin clot (lag time, Max Abs, and slope) were measured by clot turbidity and scanning electron microscopy (SEM). Both patients and controls were divided into four subgroups according to menopause status.

RESULTS

The premenopausal controls differed significantly from all other subgroups in terms of diminished levels of ETP (p = 0.02), C-max (p = 0.01), OCP (p = 0.02), OHP (p = 0.001), and Max Abs (p = 0.008), while OFP (p = 0.0001) was increased. This tendency was not seen in the premenopausal RA patients compared with the postmenopausal RA patients. SEM images showed denser clots composed of thinner fibers in samples from RA patients. The disease activity measured by DAS28 correlated with OCP and OHP (r = 0.54; p = 0.001 and r = 0.44; p = 0.003, respectively) indicating persistent hypercoagulable condition in the whole group of RA patients.

CONCLUSIONS

Our results point towards coagulation activation in premenopausal women with established RA. The patients were well characterized, which enabled assessment in a real-life setting. Key Points • Extensive assessment points towards persistent coagulation activation in premenopausal women with established rheumatoid arthritis. • Impaired thrombin generation and fibrin formation are associated with menopause in healthy women, while rheumatoid arthritis closes the gap within patients regarding menopause. • Fibrin morphology is unfavorably altered and fibrinolysis is decreased in patients with established rheumatoid arthritis. • Increased activity of thrombin activatable fibrinolysis inhibitor (TAFI) may contribute to impaired fibrinolysis in patients with rheumatoid arthritis.

Clinical and biochemical characterization of the prothrombin Belgrade mutation in a large Serbian pedigree: new insights into the antithrombin resistance mechanism

Essentials Prothrombin Belgrade mutation leads to antithrombin resistance. Clinical and biochemical phenotypes in a large family with this mutation were investigated. In carriers, we detected decreased factor II activity and increased endogenous thrombin potential. Prothrombin Belgrade mutation represents a strong prothrombotic risk factor.

SUMMARY

Background The recently reported c.1787G>A mutation in the prothrombin gene leads to Arg596Gln replacement in the protein molecule (prothrombin Belgrade). This substitution impairs binding of antithrombin to thrombin and results in inherited thrombophilia, known as antithrombin resistance. Objectives We aimed to elucidate the clinical and biochemical characteristics of thrombophilia associated with antithrombin resistance in a large Serbian family with the prothrombin Belgrade mutation. Patients and methods Nineteen family members were investigated, among whom 10 were carriers of the c.1787G>A mutation. In all subjects the clinical phenotype was determined and laboratory investigations of hemostatic parameters were performed. Results Six out of the 10 mutation carriers developed thromboembolic events, mainly deep venous and mesenteric vein thrombosis. The median age of the first thrombotic event was 26.5 (12-41) years, whereas the incidence rate of first thrombosis was 2.2% per year. In all mutation carriers prothrombin activity was significantly decreased in comparison with non-carriers, clearly distinguishing each group. However, the presence of the mutation did not affect the prothrombin antigen level in plasma. The endogenous thrombin potential was significantly increased in all carriers in comparison with non-carriers, indicating the presence of blood hypercoagulability. Interestingly, levels of D-dimer and the F1+2 fragment were similar in both groups. Conclusions Although rare, the prothrombin Belgrade mutation represents strong thrombophilia with early onset of thrombosis in the investigated family. According to our results, decreased prothrombin activity may be a simple screening test for detection of this mutation in thrombotic patients.

[The effect of FII c.1787G>A (prothrombin Belgrade) mutation on prothrombin gene expression in vitro]

The FII c.1787G>A (prothrombin Belgrade) is a novel prothrombotic mutation which leads to impaired inhibition of thrombin by antithrombin (antithrombin resistance). So far, the mechanism of this variant has not been fully elucidated. To investigate the effect of FII c.1787G>A mutation on the prothrombin gene expression, its functional analysis was performed in vitro. By Real-Time PCR, expression levels of FII gene variants were evaluated in Cos-7 cells transiently transfected with c.1787G (wild-type) and c.1787A prothrombin expression vectors, with no differences observed. The relative quantification of prothrombin protein amounts was accomplished by Western blot analysis, also with no differences observed. Therefore, the mechanism of FII c.1787G>A mutation does not alter prothrombin expression profile.

Prothrombin 3'end gene variants in isolated pulmonary embolism--the first report of FIIc.*64_*66del and FIIc.*303T>C variants

OBJECTIVE

Pulmonary embolism is usually considered as a complication of deep vein thrombosis, but there are still a number of cases of isolated pulmonary embolism. We aimed to investigate whether prothrombin 3'end gene variants might play a significant role in the pathogenesis of isolated pulmonary embolism.

METHODS AND RESULTS

In this study 100 patients with isolated pulmonary embolism and 100 controls were screened by DNA sequencing. Screening included last intron, last exon, 3'UTR and part of the 3'FR region of the prothrombin gene. Our results have shown that heterozygous carriers of the FIi G2021 OA variant have a significantly higher risk of isolated pulmonary embolism (OR 4.83; 95% CI 1.33-17.52; P=0.02). Carriers of the Ili 19911GG genotype (OR 1.41; 95% CI 0.72-2.73; P=0.31) and FII 20068CT genotype (OR 3.06; 95% CI 0.31-29.95; P=0.34) were more frequent in patients with isolated pulmonary embolism compared to controls. We also detected the novel gene variants, FIIc.*64_*66del and FII c.*303T>C, in two patients.

CONCLUSIONS

Our results suggest that FII G20210A represents a significant risk factor for isolated pulmonary embolism. The FII G19911A and FII C20068T are potentially associated with an increased risk for the occurrence of isolated pulmonary embolism, but the results did not reach statistical significance. This is the first study in which the two novel 3'end prothrombin gene variants, FIIc.*64_*66del and FlI c.*303T>C, were reported.

Factor V Leiden mutation and high FVIII are associated with an increased risk of VTE in women with breast cancer during adjuvant tamoxifen - results from a prospective, single center, case control study

BACKGROUND

Estimates of the risk ratio of tamoxifen-associated venous thromboembolism (VTE) in breast cancer patients range from 2.4 to 7.1. The occurrence of thrombosis in patients with breast cancer complicates the clinical condition and causes a change of treatment. Our study was conducted in order to investigate the influence of patient-related risk factors for thrombosis development in breast cancer patients whose treatment included adjuvant tamoxifen.

METHODS

The prospective, single center, case control study included 150 breast cancer women, 50 whom developed venous thrombosis during adjuvant tamoxifen and 100 whom did not have thrombosis, as a control group. Patient-related risk factors such as: age, body mass index, previous VTE, varicose veins, concomitant diseases, the presence of prothrombotic mutations (FV Leiden, FII G20210A) and FVIII activity were evaluated in both groups.

RESULTS

In respect of prothrombotic mutations, the FV Leiden mutation was present in a higher number of women from the VTE group (10/50 vs 7/100; P=0.020). Additionally, FVIII activity was significantly higher in the VTE group; median (IQR), of 1.79 (0.69) vs 1.45 (0.55); P<0.001 and more women in this group (24/50 vs 34/100) had increased FVIII activity; P=0.020. In those women with FVIII>1.5IU/ml, who were carriers of prothrombotic mutations, an OR of 3.76 (CI 95% 1.276-11.096; P=0.016) was obtained for VTE.

CONCLUSION

The results of our study showed that the factor V Leiden mutation and high FVIII are associated with an increased risk of VTE in women with breast cancer during adjuvant tamoxifen.

The 3'end prothrombin gene variants in patients with different thrombotic events

BACKGROUND

Prothrombin (FII) A19911G and C20221T gene variants are associated with increased prothrombin levels and potentially represent thrombotic risk factors.

OBJECTIVE

To determine the frequency of A19911G and C20221T FII gene variants in patients with thrombotic disorders and in women who have experienced pregnancy loss (PL).

METHODS

We determined the frequency of these variants in 133 patients with deep venous thrombosis (DVT), 80 patients with isolated pulmonary embolism (PE), 101 patients with idiopathic PL, and 180 control individuals.

RESULTS

The FII A19911G variant was more prevalent in patients with DVT and with PL compared with controls; however, these differences were not statistically significant. The 19911GG genotype was associated with increased risk of PE (odds ratio, 1.91; 95% confidence interval, 1.04-3.51). We did not detect carriers of the FII C20221T gene variant in this study.

CONCLUSIONS

This is the first study, to our knowledge, that demonstrates the FII 19911GG genotype may represent a risk factor for isolated PE. Also, our results show that the FII C20221T is a rare variant in this population and therefore, routine thrombophilia screening should not include screening for this genotype.