Potential utility of a multi-component coagulation factor panel to calculate MELD scores and assess the risk of portal vein thrombosis in chronic liver disease

BACKGROUND

Current quantitative approaches to assess chronic liver disease (CLD) severity have limitations. Further, portal vein thrombosis (PVT) pre-liver transplant (LT) is a major contributor to morbidity in CLD; the means of detecting and/or predicting PVT are limited. We sought to explore whether plasma coagulation factor activity levels can serve as a substitute for prothrombin time/international normalized ratio (PT/INR) in the Model for End-stage Liver Disease (MELD), and/or help assess the risk of PVT.

METHODS

Plasma activity levels of Factor V (FV), Factor VIII (FVIII), Protein C (PC), and Protein S (PS) and the concentrations of D-dimer, sP-selectin, and asTF were assessed in two cohorts of CLD patients (ambulatory, n = 42; LT, n = 43).

RESULTS

FV and PC activity levels strongly correlated with MELD scores, which enabled the development of a novel scoring system based on multiple linear regressions of the correlations of FV and PC activity with MELD-Na that substitutes PT/INR. Six-month and 1-year follow-up revealed that our novel approach was non-inferior to MELD-Na at predicting mortality. A significant inverse correlation between FVIII activity levels and PVT was found in the LT cohort (p = 0.010); FV and PS activity levels were in-trend (p = 0.069, p = 0.064). We developed a logistic regression-based compensation score to identify patients at risk of PVT.

CONCLUSIONS

We demonstrate that FV and PC activity levels may be used to replace PT/INR in MELD scoring. We also show the potential of using the combination of FV, FVIII, and PS activity levels to assess the risk of PVT in CLD.

DNA methylation changes and increased mRNA expression of coagulation proteins, factor V and thrombomodulin in Fuchs endothelial corneal dystrophy

Late-onset Fuchs endothelial corneal dystrophy (FECD) is a disease affecting the corneal endothelium (CE), associated with a cytosine-thymine-guanine repeat expansion at the CTG18.1 locus in the transcription factor 4 (TCF4) gene. It is unknown whether CTG18.1 expansions affect global methylation including TCF4 gene in CE or whether global CE methylation changes at advanced age. Using genome-wide DNA methylation array, we investigated methylation in CE from FECD patients with CTG18.1 expansions and studied the methylation in healthy CE at different ages. The most revealing DNA methylation findings were analyzed by gene expression and protein analysis. 3488 CpGs had significantly altered methylation pattern in FECD though no substantial changes were found in TCF4. The most hypermethylated site was in a predicted promoter of aquaporin 1 (AQP1) gene, and the most hypomethylated site was in a predicted promoter of coagulation factor V (F5 for gene, FV for protein). In FECD, AQP1 mRNA expression was variable, while F5 gene expression showed a ~ 23-fold increase. FV protein was present in both healthy and affected CE. Further gene expression analysis of coagulation factors interacting with FV revealed a ~ 34-fold increase of thrombomodulin (THBD). THBD protein was detected only in CE from FECD patients. Additionally, we observed an age-dependent hypomethylation in elderly healthy CE.Thus, tissue-specific genome-wide and gene-specific methylation changes associated with altered gene expression were discovered in FECD. TCF4 pathological methylation in FECD because of CTG18.1 expansion was ruled out.

[Elucidation of an altered anticoagulant function due to Factor V abnormality and development of a simple screening assay for thrombophilia]

Coagulation factor V (FV) is both procoagulant and anticoagulant functions. Congenital FV abnormality, which are caused by mutations in the FV gene, are characterized by a tendency to bleed. However, FV-R506Q (FVLeiden) is the most common FV abnormality that eliminates an activated protein C (APC) cleavage site, resulting in the occurrence of deep venous thrombosis (DVT). In Japan, the thrombotic predisposition caused by FVLeiden and FV molecular abnormalities was believed to be nonexistent. We did, however, report the first case in Japan of a young patient with FV abnormality-related thrombosis. The recurrent DVT in this case was caused by a novel mutation of FV-W1920R (FVNara), located in the C1 domain and far from the APC cleavage sites. We considered the possibility that there were cases of FV-related thrombotic predisposition that had gone undetected in Japan. We thoroughly examined FV-related anticoagulant function to understand the pathogenesis of thrombosis caused by FV abnormality. Furthermore, using recombinant thrombomodulin, we successfully developed a novel assay with clot waveform analysis for the rapid detection of FV deficiency with APC resistance. Other FV abnormality-related thrombosis has been reported in Japan in recent years, and we hope to further clarify the FV-related thrombotic predisposition in the future.

Assessing Factor V Antigen and Degradation Products in Burn and Trauma Patients

INTRODUCTION

Proposed mechanisms of acute traumatic coagulopathy (ATC) include decreased clotting potential due to factor consumption and proteolytic inactivation of factor V (FV) and activated factor V (FVa) by activated protein C (aPC). The role of FV/FVa depletion or inactivation in burn-induced coagulopathy is not well characterized. This study evaluates FV dynamics following burn and nonburn trauma.

METHODS

Burn and trauma patients were prospectively enrolled. Western blotting was performed on admission plasma to quantitate levels of FV antigen and to assess for aPC or other proteolytically derived FV/FVa degradation products. Statistical analysis was performed with Spearman's, Chi-square, Mann-Whitney U test, and logistic regression.

RESULTS

Burn (n = 60) and trauma (n = 136) cohorts showed similar degrees of FV consumption with median FV levels of 76% versus 73% (P = 0.65) of normal, respectively. Percent total body surface area (TBSA) was not correlated with FV, nor were significant differences in median FV levels observed between low and high TBSA groups. The injury severity score (ISS) in trauma patients was inversely correlated with FV (ρ = -0.26; P = 0.01) and ISS ≥ 25 was associated with a lower FV antigen level (64% versus. 93%; P = 0.009). The proportion of samples showing proteolysis-derived FV was greater in trauma than burn patients (42% versus. 16%; P = 0.0006).

CONCLUSIONS

Increasing traumatic injury severity is associated with decreased FV antigen levels, and a greater proportion of trauma patient samples exhibit proteolytically degraded FV fragments. These associations are not present in burns, suggesting that mechanisms underlying FV depletion in burn and nonburn trauma are not identical.

Rare Coagulation Factor Deficiencies (Factors VII, X, V, and II)

Although rare clotting factor deficiencies primarily referred to as rare bleeding disorders (RBD), including factors II, V, VII, and X, make up ∼5% of all inherited bleeding disorders worldwide, each of these clotting factors play a critical role in the coagulation cascade. Incomplete bleeding evaluation or misinterpretation of laboratory studies can result in delayed diagnoses that ultimately affect patient outcomes. Bleeding manifestations can range from mild to severe, but the most common are mucocutaneous bleeding. The ideal treatment in RBD is dedicated single-factor concentrates that can be used for acute bleeding events, surgical management, and prophylaxis.

Prevalence of thrombophilia-associated genetic risk factors in blood donors of a regional hospital in southern Brazil

Introduction

Thromboembolic events occur due to an imbalance in the hemostasis and some factors associated with this condition can be inherited. In order to evaluate the frequency of genotypes considered to be common hereditary risk factors for thrombophilia associated with venous thrombosis (g.1691G > A and g.20210G > A) and hyperhomocysteinemia (g.677C > T and g.1298A > C), samples from voluntary healthy blood donors at the Hospital de Clínicas de Porto Alegre were tested.

Methods

We examined 325 blood samples from blood donors collected from October 2017 to July 2018. Blood was collected on filter paper and the DNA was extracted for single nucleotide polymorphisms (SNPs) analysis using the qualitative real time polymerase chain reaction.

Results

The calculated frequencies of each genetic variant in heterozygosity were 4% for the FV gene (g.1691G > A), 4% for the F2 gene (g.20210G > A) and 42% and 39% for methylenetetrahydrofolate reductase (MTHFR), g.677C > T and g.1298A > C, respectively. Only the genetic variants of MTHFR were found in homozygosity, with frequencies of 14% and 6% (g.677C > T and g.1298A > C), respectively.

Discussion

Altogether, these results describe the frequencies of genetic variants associated with venous thrombosis and hyperhomocysteinemia in the analyzed group and are important to enhance our current knowledge about the genetic profiles of Brazilian blood donors.

Structure and function of factor X: properties, activation, and activity in prothrombinase. A retrospective in a historical context

The evolution of our understanding of the formation of thrombin from the postulated thrombokinase of Morawitz to activated Factor X and prothrombinase occurred during a period of nearly 100 years. During this time structure-function relationships have emerged and the roles of phospholipid surfaces, the accessory factor, Factor V and its activated form have been clarified. This paper summarizes this story with particular acknowledgement of the seminal contributions of Haskell Milstone.

Prothrombinase: the paradigm for membrane bound enzyme complexes; a memoir

This review is a brief summary of the history of the development of the Prothrombinase complex paradigm and its incorporation into the "extrinsic pathway". It summarizes my laboratory's research from 1968 to 2012 and identifies many of the key players in these efforts.

Factor VIII and Factor V Membrane Bound Complexes

The formation of membrane-bound complexes between specific coagulation factors at different cell surfaces is required for effective blood clotting. The most important of these complexes, the intrinsic Tenase and Prothrombinase complexes, are formed on the activated platelet surface during the propagation phase of coagulation. These two complexes are highly specific in their assembly mechanism and function modulated by anionic membranes, thus offering desirable targets for pharmaceutical interventions. Factor V (FV) and factor VIII (FVIII) are highly homologous non-enzymatic proteins. In their active state, FVa and FVIIIa serve as cofactors for the respective serine proteases factor Xa (FXa) and factor IXa (FIXa), significantly increasing their catalytic activity. This is achieved by forming well organized membrane-bound complexes at the phosphatidylserine rich activated platelet membrane in the presence of Ca²⁺ ions. The tenase (FVIIIa/FIXa) complex, catalyzes the proteolytic conversion of FX to FXa. Subsequently the prothrombinase (FVa/FXa) complex catalyzes the conversion of prothrombin to thrombin, required for efficient blood clotting. Although significant knowledge of FV and FVIII biochemistry and regulation has been achieved, the molecular mechanisms of their function are yet to be defined. Understanding the geometric assembly of the tenase and prothrombinase complexes is paramount in defining the structural basis of bleeding and thrombotic disorders. Such knowledge will enable the design of efficient pro- and anticoagulant therapies critical for regulating abnormal hemostasis. In this chapter, we will summarize the findings to date, showing our achievement in the field and outlining the future findings required to grasp the complexity of these proteins.

Characterisation of a novel thrombomodulin c.1487delC,p.(Pro496Argfs*10) variant and evaluation of therapeutic strategies to manage the rare bleeding phenotype

INTRODUCTION

A novel variant in the thrombomodulin (TM) gene, c.1487delC,p.(Pro496Argfs*10), referred to as Pro496Argfs*10, was identified in a family with an unexplained bleeding disorder. The Pro496Argfs*10 variant results in loss of the transmembrane and intracellular segments of TM and is associated with an increase in soluble TM (sTM) in the plasma. The aim of this study was to characterise the effect of elevated sTM on thrombin generation (TG) and fibrinolysis, and to evaluate therapeutic strategies to manage the patients.

METHODS

Plasma samples were obtained from two patients carrying the variant. TG was triggered using 5 pM tissue factor and measured using the Calibrated Automated Thrombogram. A turbidity clot lysis assay was used to monitor fibrinolysis. TM antigen was quantified by ELISA.

RESULTS

Patients with the Pro496Argfs*10 variant had significantly elevated plasma sTM compared to controls (372.6 vs. 6.0 ng/ml). TG potential was significantly lower in patients but was restored by inhibition of activated protein C (APC) or addition of activated Factor VII (FVIIa) or platelet concentrates. In vitro experiments suggested that activated prothrombin complex concentrates (APCC) posed a risk of thrombosis. The time to 50% lysis was significantly prolonged in patients compared to controls, 69.7 vs. 42.3 min. Clot lysis time was shortened by inhibition of activated thrombin activatable fibrinolysis inhibitor (TAFIa).

CONCLUSIONS

Our data demonstrate that increased sTM enhances APC generation and reduces TG. Simultaneously, the rate of fibrinolysis is delayed due to increased TAFI activation by sTM. Treatment with platelet or FVIIa concentrates may be beneficial to manage this rare bleeding disorder.

Novel single nucleotide mutations in exon-10 of human coagulation Factor V gene in patients with pulmonary thromboembolism

Introduction: Acute pulmonary thromboembolism (PTE) presents with wide spectrum and has variable prognosis. Factor V Leiden (FVL) is the most common inherited thrombophilia, with a prevalence of 3%-7% in the general US population, approximately 5% in Whites, 2.2% in Hispanics and 1.2% in Blacks. PTE most commonly originates from venous thrombosis. The occurrence of venous thromboembolism is a culmination of environmental and genetic risk factors. The current study was sought to identify the mutations in exon-10 of FV gene in patients with PTE.

Methods: Sixty cases diagnosed with PTE and 50 healthy controls were enrolled in the present study. Mutation studies in exon-10 of Factor V gene included PCR-DNA sequencing method.

Results: Of 60 patients, we found two novel transition type point mutations: c.1538 G>A and c.1601 G>A in exon-10 of Factor V which is responsible for the cleavage site for aPC. These point mutations resulted in single amino acid change in protein sequence at p.Arg513Lys and p.Arg534Gln respectively. These mutations prevent efficient inactivation of Factor V and Factor V remains active which facilitates over production of thrombin leading to generation of excess fibrin and excess coagulation which results in deep vein thrombosis and PTE.

Conclusion: We report two novel point mutations (c.1538 G>A and c.1601 G>A) in exon-10 of Factor V gene in Indian patients with PTE.

[Retinal artery occlusion and anterior ischemic optic neuropathy associated with factor V Leiden mutation: A case report]

Factor V is a pro-coagulant cofactor required for the transformation of prothrombin into thrombin. Thrombin activates factor V, which is then deactivated by protein C. A mutation in factor V is responsible for the formation of factor V Leiden, resistant to activated protein C. The association of this mutation with venous thromboses has been established. Its association with arterial occlusions is still controversial. We report the case of a central retinal artery occlusion associated with a non-arteritic anterior optic neuropathy associated with a Leiden mutation of factor V (FVL). The presence of FVL has been associated with lack of reperfusion and rapid progression to neovascularization. It seems that FVL intervenes mainly during the reperfusion phase after the occurrence of arterial thrombosis.

Simple Laboratory Test Utilization Interventions to Reduce Inappropriate Specialty Coagulation Testing

OBJECTIVES

The naming convention in coagulation may cause confusion in electronic ordering systems, leading to inappropriate test orders. We implemented test utilization efforts and studied utilization before and after interventions for two specialty coagulation assays.

METHODS

Two interventions were implemented: test names were changed from factor assay to activity, and residents reviewed all factor V and X requests. A retrospective review of factor V and X activity orders was performed for the period 1 year before and after interventions.

RESULTS

After interventions, factor V and X activity orders decreased by approximately 40%. Resulted tests decreased by 53.8% and 47.8%, corresponding to reductions of $2,493.05 and $1,867.80 per year in laboratory charges for factor V and factor X activity, respectively. Abnormal factor V activity results increased from 45% to 59%. Factor V activity orders from outpatient clinics decreased by 21.6%.

CONCLUSIONS

Simple interventions can reduce inappropriate specialty coagulation test orders and unnecessary costs.

Effects of factor v Leiden polymorphism on the pathogenesis and outcomes of preeclampsia

Background

Factor V Leiden polymorphism is a well-recognized genetic factor in the etiology of preeclampsia. Considering that Ghana is recording high incidence of preeclampsia, we examined if factor V Leiden is a contributory factor to its development and pregnancy outcomes.

Methods

STROBE consensus checklist was adopted to recruit eighty-one (81) consenting subjects after ethical clearance. Subjects were followed up till delivery to obtain outcomes of PE. Routine blood chemistry and proteinuria were done on all samples. Factor V Leiden was characterized by polymerase chain reaction and restriction fragment length polymorphism (RFLP). The data was captured as protected health information (PHI) and analyzed with SPSS version 22.

Results

Overall allelic frequencies found in FVL exon 10 were 0.67 and 0.33 for G and A alleles respectively. The FVL mutation was more in PE and hypertensive patients. Increased white blood cells, increased uric acid and a three – fold increment of AST / ALT ratio was observed in PE cases when stratified by FVL exons (exon 8 and 10). Significant differences were also observed between FVL and age, systolic blood pressure (SBP), diastolic blood pressure (DBP), liver enzymes, white blood cells (wbc), hemoglobin levels.

Conclusion

FVL mutation allele frequency was 0.33, a first report. The mutation was associated with increased uric acid, liver enzymes and blood cell indices suggestive of acute inflammation.

Common Variations in Prothrombotic Genes and Susceptibility to Ischemic Stroke in Young Patients: A Case-Control Study in Southeast Iran

Background and Objective: Evidence indicates that genetic factors may be involved in the risk of ischemic stroke (IS). The aim of this study was to assess the effect of genetic polymorphisms located in exons or untranslated regions of MTHFR as well as FV genes on ischemic stroke. Materials and Methods: In this case-control study, 106 patients with IS and 157 healthy volunteers (age <50 years) were genotyped for MTHFR C677T, A1298C, C2572A and C4869G, FVL, and prothrombin G20210A polymorphisms. Results: The MTHFR 677CT genotype was more frequent in patients and increased risk of IS with Odds Ratio = 1.9. The MTHFR A1298C and C2572A polymorphisms were not associated with IS in dominant and recessive models. Our findings showed a significant decrease in the MTHFR4869CG genotype in IS patients, and this variant was associated with a decreased risk of IS in the dominant model. The CAAT haplotype was associated with increased risk, and the GAAC haplotype was associated with decreased risk of IS compared to other haplotypes. There was no relation between FVL G1691A polymorphism and IS risk. Conclusions: The present study showed that the MTHFR 677CT genotype was more frequent and the MTHFR 4869CG genotype was less frequent in young IS patients.

Factor-V Leiden G1691A and prothrombin G20210A polymorphisms in Sudanese women with preeclampsia, a case -control study

Background

Preeclampsia can lead to adverse maternal and perinatal outcomes. There are few studies on the association of preeclampsia with thrombophilia in Africa including Sudan.

Methods

A case –controls study was conducted at Saad Abualila Hospital in Khartoum, Sudan during the period of February through November 2017. The cases were women with preeclampsia and healthy pregnant women were the controls (180 women in each arm of the study). Genotyping for Factor-V Leiden 1691G/A and Prothrombin gene variation 20210G/A was done by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP).

Results

There was no significant difference in the age, parity, body mass index (BMI) and the other characteristics between the cases and the controls. Genotypes distribution of Factor V Leiden 1691G/A and prothrombin gene 20210G/A in controls was in accordance with the Hardy–Weinberg equilibrium (P > 0.05). The factor V Leiden-variation was present in 9.6% of the cases compared with 0.6% of the controls, P < 0.001 (OR = 18.60, 95% CI = 2.38–136.1). Only 4 patients with severe preeclampsia had homozygous variation A/A and it was not detected in the controls. Prothrombin G20210A variations not detected neither in the cases nor in the controls group.

Conclusions

High prevalence of Factor V Leiden 1691G/A variation in preeclamptic patients compared to controls suggest an involvement of this variation in predisposing to preeclampsia in this setting.

Factor V levels and risk of venous thrombosis: The MEGA case-control study

BACKGROUND

Blood coagulation levels are associated with risk of venous thrombosis (VT). The role of factor (F)V is ambiguous since it plays a dual role in coagulation: it has a procoagulant role when it serves as a cofactor for the activation of thrombin and it has an anticoagulant role by enhancing the inactivation of activated FVIII.

OBJECTIVES

To elucidate the association of FV levels with risk of VT.

PATIENTS/METHODS

We analyzed FV antigen levels in 2377 patients with VT and 2943 controls from the MEGA study. FV levels were categorized according using the 1st, 2.5th, 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles of FV levels in controls as cut-off points. Odds ratios (ORs) were estimated using logistic regression models and adjusted for age and sex, liver disease, FVIII levels, FV Leiden, and TFPI.

RESULTS

The risk estimates were U-shaped with increased ORs for the lowest (<0.57 U/dL) levels (OR 1.46; 95% CI 0.87-2.43) as well as the highest (>1.22 U/dL) (OR 1.86; 95% CI 1.46-2.37) levels as compared with the reference group (25th-50th percentile). FVIII adjustment led to attenuation of the OR for high FV levels (OR 1.14; 95% CI 0.88-1.48), with little change for low FV levels (OR 1.68; 95% CI 0.97-2.91). Other adjustments had limited effects.

CONCLUSIONS

We found high FV levels to be associated with increased risk for VT, which was explained by concurrently raised FVIII levels. For low levels of factor V, the increased risk for VT could not be explained by the mechanisms we explored.

Interaction of factor V B-domain acidic region with its basic region and with TFPI/TFPI2: Structural insights from molecular modeling studies

BACKGROUND

Factor V (FV) B-domain contains an acidic region (FV-AR2) and a basic region (FV-BR), which interact with each other and maintain FV in a procofactor form; removal of either region via deletion/proteolysis results in an active FVa molecule. Tissue factor pathway inhibitor type-1 (TFPI) and type-2 (TFPI2) each contain a C-terminus basic segment homologous to FV-BR; this region in TFPI (and predicted in TFPI2) binds to FV-AR2 in platelet FVa (that lacks FV-BR) with high affinity and inhibits FVa function.

OBJECTIVES

To understand molecular interactions between FV-AR2 with FV-BR, TFPI-BR and TFPI2-BR.

METHODS

Circular dichroism (CD) and molecular modeling approaches.

RESULTS AND CONCLUSIONS

CD experiments reveal the presence of ∼20% helical content in both FV-AR2 and FV-BR but each lacks beta-sheet. Predicted structures of FV-AR2 and FV-BR, obtained using threading (I-TASSER), are consistent with the CD data and have compact folds with hydrophobic residues in the interior and charged residues on the surface. Scores from QMEAN and ModFOLD servers indicate a very high probability for each structure to be native. Predicted models of Kunitz domain-3 of TFPI and TFPI2 each with C-terminal basic tail are consistent with known homologous structures. Docking experiments using ClusPro indicate that the acidic groove of FV-AR2 has high shape complementarity to accommodate the conserved basic residues in FV-BR (1002-RKKKK-1006), TFPI-BR (256-RKRKK-260) or TFPI2-BR (191-KKKKK-195). Further, similar electrostatic interactions occur in each case. These models, in the absence of experimentally determined structures, provide a guiding point for proper mutagenesis studies in FV, TFPI and TFPI2.

Polymorphisms of the coagulation system and risk of cancer

Hypercoagulability is a frequently finding in patients with cancer, and is associated with an increased risk of venous thrombosis (VT). Cancer-associated VT is associated with poor prognosis and represents the leading non-cancer cause of death among these patients. Conversely, patients experiencing VT are at increased risk of subsequent cancer, suggesting an epidemiological bidirectional link between cancer and hemostasis, and indicating a role of the hemostatic system in cancer development. How the coagulation system relates to cancer etiology at the genetic level is largely unexplored. Data on the association of polymorphisms in genes involved in coagulation with cancer development is important to clarify the role of the coagulation system in cancer pathogenesis. Effects of coagulation-related gene polymorphisms on cancer risk may possibly be translated into novel treatment- and prevention strategies of cancer-associated thrombosis and the cancer itself. This article reviews the current knowledge of the relation between polymorphisms in genes involved in coagulation and cancer risk in solid tumors.

Polymorphisms at activated protein C cleavage sites of factor V: Are they important in the absence of factor V Leiden?

Background: Activated protein C (APC) inactivates factor V (FV) by cleavage of its heavy chain at Arg306, Arg506, Arg679, and Lys994. Mutational changes, which abolish APC cleavage sites, may predispose thrombosis by altering the inactivation process of FV. FV Leiden (FVL) (Arg506Glu) has been demonstrated as a strong risk factor for thrombosis. In the current study, we have studied whether mutations in the cleavage sites of FV for APC, not due to FVL, would have a role in presenting APC resistance (APCR) and initiation of a cerebral thrombotic event. Methods: A group of 22 patients with a history of cerebral venous thrombosis (CVT), who were not carriers of FVL enrolled in the study. The patients who had conditions associated with acquired APCR were excluded from the study. APCR test was performed on the remaining 16 patients, which showed APCR in 4 plasma samples. DNA sequencing was performed on four exons of FV of APCR patients, encoding Arg306, Arg506, Arg679, and Lys994. Results: Mutations were not found within nucleotides encoding the cleavage sites; neither was found within their close upstream and downstream sequences. Conclusion: Our results show that polymorphisms affecting cleavage sites of FV other than Arg506Glu it would be less likely to be the basis for APCR and its increased thrombosis susceptibility. In addition, it emphasizes on the importance of screening for APCR in the patients diagnosed with CVT.

Mechanistic insight into the procoagulant activity of tumor-derived apoptotic vesicles

BACKGROUND

Chemotherapy induces the release of apoptotic vesicles (ApoV) from the tumor plasma membrane. Tumor ApoV may enhance the risk of thrombotic events in cancer patients undergoing chemotherapy. However, the relative contribution of ApoV to coagulation and the pathways involved remain poorly characterized. In addition, this study sets out to compare the procoagulant activity of chemotherapy-induced ApoV with their cell of origin and to determine the mechanisms of ApoV-induced coagulation.

METHODS

We utilized human and murine cancer cell lines and chemotherapeutic agents to determine the requirement for the coagulation factors (tissue factor; TF, FII, FV, FVII, FVIII, FIX and phosphatidylserine) in the procoagulant activity of ApoV. The role of previously identified ApoV-associated FV was determined in a FV functional assay.

RESULTS

ApoV were significantly more procoagulant per microgram of protein compared to parental living or dying tumor cells. In the phase to peak fibrin generation, procoagulant activity was dependent on phosphatidylserine, TF expression, FVII and the prothrombinase complex. However, the intrinsic coagulation factors FIX and FVIII were dispensable. ApoV-associated FV could not support coagulation in the absence of supplied, exogenous FV.

CONCLUSIONS

ApoV are significantly more procoagulant than their parental tumor cells. ApoV require the extrinsic tenase and prothrombinase complex to activate the early phase of coagulation. Endogenous FV identified on tumor ApoV is serum-derived and functional, but is non-essential for ApoV-mediated fibrin generation.

GENERAL SIGNIFICANCE

This study clarifies the mechanisms of procoagulant activity of vesicles released from dying tumor cells.

H1299R in coagulation Factor V and Glu429Ala in MTHFR genes in recurrent pregnancy loss in Sari, Mazandaran

BACKGROUND

Recurrent pregnancy loss (RPL) is caused by different factors, including genetics and thrombophilia. Beside Factor V Leiden, another nucleotide change in a factor V (FV) gene (A4070G; His1299Arg) has been identified linking to hereditary thrombophilia. Also, two proposed MTHFR polymorphisms, C677T and A1298C (Glu429A) are linked with RPL.

OBJECTIVE

In this study, the effect of two factors, A4070G in FV and A1298C in MTHFR are evaluated in RPL patients from Mazandaran province, Iran.

MATERIALS AND METHODS

Sample population of 100 women with RPL and 100 controls with Mazandarani ethnics from northern Iran were consist. The factor V (A4070G) and MTHFR (A1298C) polymorphisms were genotyped by PCR-RFLP.

RESULTS

Molecular study showed 5 women from patients and 9 women from control group were heterozygous AG for A4070G. Frequency of "A" allele in patient and control groups was 97.5% (0.975) and 95.5% (0.955) respectively, and "G" allele frequency was 2.5% (0.025) and 4.5% (0.045) respectively. No significant association (p≤0.05) between FV A4070G genotype and RPL with an OR=1.88, CI 95%=0.6-5.82, was observed (p=0.4). Also, for A1298C, all patients and control individuals were AA genotype. "A" allele frequency in patients and control was 100% and "C" allele frequency was zero. There was no significant difference for A1298C between groups.

CONCLUSION

Our finding showed that A4070G and A1298C polymorphisms cannot be considered as a cause of PRL in women from Mazandaran province, northern Iran.

Efficacy of solvent/detergent plasma after storage at 2-8 °C for 5 days in comparison to other plasma products to improve factor V levels in factor V deficient plasma

OBJECTIVES

Factor V (FV) plays an important role in coagulation. As no purified concentrate is available to restore critical FV levels, the main blood product used to replace FV is plasma. The aim of the present in vitro study was to compare the efficacy of the different available plasma products on the reversal of moderate and severe FV deficiency as assessed by ROTEM® and FV levels.

METHODS

Five different plasma products (6 batches of each) were compared to determine their effectiveness in replacing FV in plasma moderately or severely deficient in FV. Effectiveness was measured using the ROTEM® EXTEM clotting time (CT) and a factor V assay.

RESULTS

FFP, plasma frozen within 24 hours (FP24), Octaplas (solvent/detergent treated pooled plasma), as well as Octaplas and FP24 thawed and stored for 5 days (Octaplas TP and TP), were all used for in vitro replacement of FV. TP was significantly less effective at reversing a prolonged EXTEM CT and FV levels in FV deficient plasma than other tested products. There were no significant differences in EXTEM CT between Octaplas and Octaplas TP, while factor V activity was significantly lower in the Octaplas TP. There was no significant difference between Octaplas and FFP for EXTEM CT or FV activity.

CONCLUSIONS

Octaplas and Octaplas TP appear to have an equivalent ability to improve the EXTEM CT and could be considered as a treatment alternative to FFP in patients with FV deficiency.

Acquired factor V inhibitor in a patient receiving venous-venous extracorporeal membrane oxygenation for Legionella pneumonia

We report a rare complication of factor V deficiency in a patient having Legionella pneumonia. This patient also had other complications like severe acute respiratory distress syndrome, acute kidney injury, and septic shock that required venous-venous extracorporeal membrane oxygenation support. This is the first reported case of acquired factor V deficiency in a patient receiving extracorporeal membrane oxygenation for Legionella pneumonia. With the combined use of intravenous immunoglobulin, rituximab and plasma exchange, we achieved rapid clearance of the factor V inhibitor within 1 week so as to allow safe decannulation of extracorporeal membrane oxygenation.

Improved coagulation and haemostasis in haemophilia with inhibitors by combinations of superFactor Va and Factor VIIa

Bypassing inhibitors in haemophilia patients is limited to activated (a) Factor(F)VII products. We introduced "FVa activity augmentation" as another bypassing strategy and studied effects of an engineered FVa variant designated superFVa. Procoagulant and clot stabilising properties of superFVa and recombinant human (rh)FVIIa, either alone or in combination, were studied in thrombin generation and clot lysis assays in normal human plasma (NHP) with or without anti-FVIII inhibitors, in haemophilia plasma, and in FVIII-deficient mice or in wild-type mice with anti-FVIII inhibitors. SuperFVa was as effective as rhFVIIa to improve thrombin generation or clot lysis. Furthermore, procoagulant effects were significantly enhanced when these compounds were combined. RhFVIIa at 40 nM (a therapeutic concentration) improved thrombin generation mildly, but markedly improved thrombin generation when combined with a low concentration (e. g. 3 nM) of superFVa. In clot lysis studies, the concentration of rhFVIIa to normalise clot lysis times could be reduced by 100-fold (e. g. from 40 nM to 0.4 nM) when combined with a low concentration (0.37 nM) of superFVa. In haemostasis studies of FVIII-deficient mice, blood loss was dose-dependently reduced by either superFVa or rhFVIIa. SuperFVa (200 U/kg) corrected mean blood loss indistinguishably from rhFVIII. Blood loss correction by rhFVIIa was greatly improved when combined with superFVa. Similar blood loss correction results were observed for therapies in wild-type mice after infusion with anti-FVIII inhibitors. Thus, superFVa may be an effective procoagulant agent in the setting of haemophilia with inhibitors and it merits further evaluation for new bypassing strategies.

Association of Factor V Secretion with Protein Kinase B Signaling in Platelets from Horses with Atypical Equine Thrombasthenia

Background

Two congenital bleeding diatheses have been identified in Thoroughbred horses: Glanzmann thrombasthenia (GT) and a second, novel diathesis associated with abnormal platelet function in response to collagen and thrombin stimulation.

Hypothesis/Objectives

Platelet dysfunction in horses with this second thrombasthenia results from a secretory defect.

Animals

Two affected and 6 clinically normal horses.

Methods

Ex vivo study. Washed platelets were examined for (1) expression of the αIIb‐β3 integrin; (2) fibrinogen binding capacity in response to ADP and thrombin; (3) secretion of dense and α‐granules; (4) activation of the mammalian target of rapamycin (mTOR)‐protein kinase B (AKT) signaling pathway; and (5) cellular distribution of phosphatidylinositol‐4‐phosphate‐3‐kinase, class 2B (PIK3C2B) and SH2 containing inositol‐5′‐phosphatase 1 (SHIP1).

Results

Platelets from affected horses expressed normal amounts of αIIb‐β3 integrin and bound fibrinogen normally in response to ADP, but bound 80% less fibrinogen in response to thrombin. α‐granules only released 50% as much Factor V as control platelets, but dense granules released their contents normally. Protein kinase B (AKT) phosphorylation was reduced after thrombin activation, but mTOR Complex 2 (mTORC2) and phosphoinositide‐dependent kinase 1 (PDK1) signaling were normal. SH2‐containing inositol‐5'‐phosphatase 1 (SHIP1) did not localize to the cytoskeleton of affected platelets and was decreased overall consistent with reduced AKT phosphorylation.

Conclusions and clinical significance

Defects in fibrinogen binding, granule secretion, and signal transduction are unique to this thrombasthenia, which we designate as atypical equine thrombasthenia.

Internal jugular vein thrombosis due to heterozygote methylene tetrahydrofolate reductase (MTHFR) 1298C and Factor V G1691A mutations after a minor trauma

Internal jugular vein thrombosis usually appears in central venous catheterization, distant malignancies, hypercoagulation, infections, or secondary to ovarian hyperstimulation syndrome. A 44-year-old female patient presented to us with sore throat, and pain and swelling on the right side of her neck. She had a history of simple neck trauma 10 days ago. Ultrasonography and computed tomography showed bilateral multiple lymphadenopathies and right internal jugular vein thrombosis. Patient was put on parenteral antibiotherapy and oral anticoagulant treatment. Genomic DNA tests for hypercoagulation revealed methylene tetrahydrofolate reductase 1298C heterozygote mutation and Factor V G1691A (Leiden) mutation. Patient has been under clinical control for 1 year and does not have any complaints. In this article, diagnosis, treatment, and the etiology of internal jugular vein thrombosis, which is a rare and potentially fatal condition, have been discussed through this case.

Comparative analysis of activity of coagulation Factors V and VIII and level of fibrinogen in fresh frozen plasma and frozen plasma

Background:

The aim of this study was to analyse and compare the activity of factor V, VIII and fibrinogen level in fresh frozen plasma and frozen plasma frozen after 8 hrs but within 24 hours after phlebotomy.

Materials and Methods:

Fresh frozen plasma separated from whole blood within 8 hours was compared with plasma separated within 24 hours after phlebotomy in terms of coagulation factors V and VIII and level of fibrinogen by standard methods using semi automated coagulometer sysmex CA50.

Results:

Longer storage of whole blood before processing resulted in significant decrease (18.4%) in activity of factor VIII but the fall in activity of factor V (6.52%) or level of fibrinogen (1.81%) was not significant.

Discussion:

These data suggest that there is good retention of coagulation factors in both types of plasma. Although there is significant fall in activity of factor VIII, but it is an acute phase reactant and raised in most of the diseases so it is suggested that frozen plasma would be an acceptable product for most patients requiring fresh frozen plasma.

Managing menorrhagia in a familial case of factor V deficiency

BACKGROUND

Factor V deficiency is a rare coagulation disorder. Excessive uterine bleeding is common in affected women. We describe a case of 2 siblings with Factor V deficiency and menorrhagia who achieved control of bleeding with differing treatments.

CASES

Patient 1 is a 16-year-old female with Factor V deficiency and menorrhagia which was previously controlled with oral contraceptives (OC). She developed heavy bleeding treated with fresh frozen plasma, anti-inhibitor coagulant complex (AICC), and OC taper. A levonorgestrel IUD was placed with good control of her menorrhagia. Patient 2 is the 12-year-old sister of Patient 1. She was treated with AICC, aminocaproic acid, and her menorrhagia was ultimately controlled with continuous OCs.

SUMMARY AND CONCLUSION

Factor V deficiency is a rare cause of menorrhagia. Various treatment modalities are available. In these adolescent sisters desiring future fertility, menorrhagia was managed with OCs and an IUD.

Anticoagulant factor V: factors affecting the integration of novel scientific discoveries into the broader framework

Since its initial discovery in the 1940s, factor V has long been viewed as an important procoagulant protein in the coagulation cascade. However, in the later part of the 20th century, two different scientists proposed novel anticoagulant roles for factor V. Philip Majerus proposed the first anticoagulant function for factor V in 1983, yet ultimately it was not widely accepted by the broader scientific community. In contrast, Björn Dahlbäck proposed a different anticoagulant role for factor V in 1994. While this role was initially contested, it was ultimately accepted and integrated into the scientific framework. In this paper, I present a detailed historical account of these two anticoagulant discoveries and propose three key reasons why Dahlbäck's anticoagulant role for factor V was accepted whereas Majerus' proposed role was largely overlooked. Perhaps most importantly, Dahlbäck's proposed anticoagulant role was of great clinical interest because the discovery involved the study of an important subset of patients with thrombophilia. Soon after Dahlbäck's 1994 work, this patient population was shown to possess the factor V Leiden mutation. Also key in the ultimate acceptance of the second proposed anticoagulant role was the persistence of the scientist who made the discovery and the interest in and ability of others to replicate and reinforce this work. This analysis of two different yet similar discoveries sheds light on factors that play an important role in how new discoveries are incorporated into the existing scientific framework.

Protein S and factor V in regulation of coagulation on platelet microparticles by activated protein C

INTRODUCTION

Platelets are the main source of microparticles in plasma and the concentration of microparticles is increased in many diseases. As microparticles expose negatively charged phospholipids, they can bind and assemble the procoagulant enzyme-cofactor complexes. Our aim was to elucidate possible regulation of these complexes on microparticles by the anticoagulant protein C system.

MATERIALS AND METHODS

Platelets were activated with thrombin ± collagen or the calcium ionophore A23187 ± thrombin to generate microparticles. The microparticles were analyzed using flow cytometry and functional coagulation assays to characterize parameters with importance for the activated protein C system.

RESULTS

Activation with A23187+thrombin was most efficient, fully converting the platelets to microparticle-like vesicles, characterized by high lactadherin and protein S binding capacity. Suppression of thrombin generation by activated protein C in plasma spiked with these microparticles was dependent on the presence of plasma protein S. Experiments with purified components showed that activated protein C inhibited both factor Va and factor VIIIa on the microparticle surface. Inhibition of factor Va was stimulated by, but not fully dependent on, the presence of protein S. In the factor VIIIa-degradation, activated protein C was dependent on the addition of protein S, and exogenous factor V further increased the efficiency.

CONCLUSIONS

Protein S is crucial for activated protein C-mediated inhibition of thrombin generation on platelet-derived microparticles in plasma. Moreover, protein S and factor V are synergistic cofactors in the inhibition of factor VIIIa. The results demonstrate that the activated protein C system has the capacity to counterbalance the procoagulant ability of microparticles.

Prevalence of thrombophilic gene polymorphisms in an azari population of iran

There is several evidence suggests that thrombophilic gene polymorphisms may influence susceptibility to thromboembolic events. The prevalence of these polymorphisms is different in various races and ethnics. Accordingly, we studied the prevalence of Factor V (G1691A and A4070G), prothrombin G20210A and PAI-1 4G/5G in healthy northwest population of Iran. In this prospective study, 500 healthy individuals, who had no history of both personal and family history of thromboembolic disorders, were selected as a sample of healthy population in northwestern Iran. Genotyping of these polymorphisms was performed using the amplification refractory mutation system-polymerase chain reaction method. No significant differences were detected between the expected and observed frequencies of FV G1691A and A4070G, prothrombin G20210A polymorphisms (P>0.05), while the expected frequency of 4G allele was significantly more than observed frequency in the studied population (P<0.01). These findings were compared with other reports from various populations. In conclusion, the allele frequency for FV G1691A and PAI-1 4G/5G polymorphisms showed relative consistency compared to those of previous studies, while the incidence pattern of FV A4070G polymorphism in Northwestern population of Iran showed conflicting results regarding other studied population. The prothrombin G20210A polymorphism was observed at a higher frequency than other studied populations.

Inherited genetic markers for thrombophilia in northeastern Iran (a clinical-based report)

BACKGROUND

Thrombophilia is a main predisposition to thrombosis due to a procoagulant state. Several point mutations play key roles in blood-clotting disorders, which are grouped under the term thrombophilia. These thrombophilic mutations are methylenetetrahydrofolate reductase (MTHFR, C677T, and A1298C), factor V Leiden (G1691A), prothrombin gene mutation (factor II, G20210A), and plasminogen activator inhibitor (PAI). In the present study, we assessed the prevalence of the above thrombophilia markers in patients with recurrent pregnancy loss or first and second trimester abortions, infertility, and failed in vitro fertilization (IVF).

METHODS

This study was conducted among 457 cases those were referred to detect the inherited genetic markers for thrombophilia. Markers for MTHFR, Factor II, and Factor V were assessed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP), and PAI was assessed by Amplification Refractory Mutation System (ARMS-PCR).

RESULTS

Two hundred sixty cases (56.89%) were diagnosed as having at least one thrombophilia marker, whereas 197 cases (43.11%) had no thrombophilia markers and were normal.

CONCLUSION

According to the current study, the pattern of abnormal genetic markers for thrombophilia in northeastern Iran demonstrates the importance of genetic evaluations in patients who show clinical abnormalities with recurrent spontaneous abortion (RSA) or other serious obstetric complications.

Erythrocytic phosphatidylserine exposure and hemostatic alterations in β-thalassemia intermediate patients

INTRODUCTION

Hypercoagulable state is one of the common findings in beta-thalassemia intermedia (β-TI), particularly in splenectomized patients, with infrequent blood transfusion. Abnormality of the red blood cells (RBC) membrane due to oxidative damage is suggestive of possible etiologies. Membrane lipid peroxidation increases the exposure of phosphatidylserine (PS) that plays a role in the activation of coagulation factors V and X, subsequently initiating thrombosis. Our aim of this study was to find the probable correlation of the alteration of the PS on the RBC outer membrane with the hypercoagulable state in the β-TI patients.

MATERIALS AND METHODS

Our cross-sectional study was conducted on 39 splenectomized β-TI patients and 38 age-matched healthy controls. The mean age was 37 years. Analysis of the PS exposure on the RBCs was performed by fluorescein isothiocyanate (FITC) conjugated AV protein. Measurement of the coagulation factors X, V and antithrombin III (AT-III) was performed. We also checked the D-dimer levels. Analysis was performed by SPSS16.

RESULTS

Fluorescence of FITC-Annexin V labeling on patients RBCs were higher than healthy controls; (2.8 ± 2.2%) of the patients versus (0.4 ± 0.18%) in the control group and was statistically significant (P < 0.05). Mean levels of factor X and AT-III of the patients as compared with the control group decreased and showed significant difference (P < 0.05).

CONCLUSIONS

Circulation of thalassemic RBCs, which abnormally possess PS on RBC membrane outer surface, suggests the possibility of the gradual consumption of the coagulation factors in the presence of a chronic coagulability state.

Combined genetic mutations have remarkable effect on deep venous thrombosis and/or pulmonary embolism occurence

PURPOSE

Although deep vein thrombosis and thromboembolic diseases differ among various races, they are still important in our day. The difficulties in treatment and following-up of these diseases are caused by secret genetic mutations rather than predisposing factors.

METHODS

Between January 2011 and May 2013, patients who were traced for deep vein thrombosis and/or pulmonary embolism were evaluated retrospectively. 84 patients (53.6% males and 46.4% females) were included in the study. Their family histories, predisposing factors and treatments were researched. Factor V Leiden (G 1691A), Factor II G20210A, Plasminogen Activator Inhibitor-Type 1 (4G/5G), and Methylene Tetrahydrofolate Reductase (C677T, A1298C) mutations were investigated from peripheral venous blood.

RESULTS

Among the genetic mutations we searched, the incidence of single mutation rate was observed at 11.9%, double mutation collocation at 44%, triple mutation collocation at 29.8%, quadruple mutation collocation at 13.1%, and finally, quintuplet mutation collocation at 1.2%. Our approximate mutation number was found as 2.47 ± 0.91.

CONCLUSION

We observed that multiple mutations were high in number compared to single genetic mutations. The patients who have multiple mutations should be more in the front line considering their diagnosis, treatment and following up, and also in terms of decreasing mortality, morbidity and recurrence.

Amino acid region 1000-1008 of factor V is a dynamic regulator for the emergence of procoagulant activity

Single chain factor V (fV) circulates as an M_r 330,000 quiescent pro-cofactor. Removal of the B domain and generation of factor Va (fVa) are vital for procoagulant activity. We investigated the role of the basic amino acid region 1000–1008 within the B domain of fV by constructing a recombinant mutant fV molecule with all activation cleavage sites (Arg⁷⁰⁹/Arg¹⁰¹⁸/Arg¹⁵⁴⁵) mutated to glutamine (fV^Q3), a mutant fV molecule with region 1000–1008 deleted (fV^ΔB9), and a mutant fV molecule containing the same deletion with activation cleavage sites changed to glutamine (fV^ΔB9/Q3). The recombinant molecules along with wild type fV (fV^WT) were transiently expressed in COS-7L cells, purified, and assessed for their ability to bind factor Xa (fXa) prior to and following incubation with thrombin. The data showed that fV^Q3 was severely impaired in its interaction with fXa before and after incubation with thrombin. In contrast, K_D(app) values for fV^ΔB9 (0.9 nm), fVa^ΔB9 (0.4 nm), and fV^ΔB9/Q3 (0.7 nm) were similar to the affinity of fVa^WT for fXa (0.3 nm). Two-stage clotting assays revealed that although fV^Q3 was deficient in its clotting activity, fV^ΔB9/Q3 had clotting activity comparable with fVa^WT. The k_cat value of prothrombinase assembled with fV^ΔB9/Q3 was minimally affected, whereas the K_m value of the reaction was increased 57-fold compared with the K_m value obtained with prothrombinase assembled with fVa^WT. These findings strongly suggest that amino acid region 1000–1008 of fV is a regulatory sequence protecting the organisms from spontaneous binding to fXa and unnecessary prothrombinase complex formation, which in turn results in catastrophic physiological consequences.

Restoring the procofactor state of factor Va-like variants by complementation with B-domain peptides

Coagulation factor V (FV) circulates as an inactive procofactor and is activated to FVa by proteolytic removal of a large inhibitory B-domain. Conserved basic and acidic sequences within the B-domain appear to play an important role in keeping FV as an inactive procofactor. Here, we utilized recombinant B-domain fragments to elucidate the mechanism of this FV autoinhibition. We show that a fragment encoding the basic region (BR) of the B-domain binds with high affinity to cofactor-like FV(a) variants that harbor an intact acidic region. Furthermore, the BR inhibits procoagulant function of the variants, thereby restoring the procofactor state. The BR competes with FXa for binding to FV(a), and limited proteolysis of the B-domain, specifically at Arg(1545), ablates BR binding to promote high affinity association between FVa and FXa. These results provide new insight into the mechanism by which the B-domain stabilizes FV as an inactive procofactor and reveal how limited proteolysis of FV progressively destabilizes key regulatory regions of the B-domain to produce an active form of the molecule.

Human platelets do not express tissue factor

BACKGROUND

The controversy about the expression of tissue factor (TF) in platelet after de novo synthesis prevail despite many groups recognize that platelet isolation, assays and reagents, particularly non-specific antibodies, may account for the diversity. In this study the potential of TF expression was evaluated using immune-purified human platelets and employing a very sensitive and highly specific TF activity assay.

METHODS

Isolated platelets in plasma anti-coagulated with Fragmin were subjected to stimulation by LPS plus PMA, IgG antibody or TRAP and tested for TF activity.

RESULTS

Platelets stimulated with LPS plus PMA for 4 hours expressed trace amounts of TF like activity (PCA), not inhibited by anti-TF antibody (0.2±0.1 mU/ml blood). Platelets, not immune-adsorbed to remove monocytes, showed significant TF activity (2.0±0.9 mU/ml blood) that was nearly abolished by anti-TF antibody. IgG antibody from patient with lupus anticoagulant failed to enhance the trace amount of PCA as compared to the control in contrast to high TF activity induced in monocytes (0.4±0.1 mU/ml blood versus 27.5±10.5 mU/10(6) cells) showing that activation of complement is not mediating TF expression. Platelet subjected to TRAP activation for 10 min possessed only trace amounts of PCA that was not inhibited by anti-TF antibody and slightly enhanced by anti-TFPI antibody.

CONCLUSIONS

It is concluded that platelets free of monocytes do not express TF activity when stimulated by LPS or activated complement factors, implying no role for Toll like receptor (TLR4) as suggested recently. There is no evidence of TF activity associated with platelets as a result of rapid and dynamic process.