Impact of Thrombophilia on the Risk of Hypoxic-Ischemic Encephalopathy in Term Neonates.

BACKGROUND: The incidence of neonatal hypoxic-ischemic encephalopathy (HIE) is reportedly high in countries with limited resources. Its pathogenesis is multifactorial. A role for thrombophilia has been described in different patterns of preterm and full-term perinatal brain injury. AIM: This study aims to identify risk factors associated with neonatal HIE and also to determine the contributions of genetic thrombophilia in the development of neonatal HIE. METHODS: Sixty-seven neonates with HIE and 67 controls were enrolled in the study. Clinical history and examination were undertaken. Patients and controls were tested for the presence of factor V G1691A and prothrombin G20210A mutations. In addition, protein S, protein C, and antithrombin III levels were assessed. RESULTS: Parental consanguinity and performing emergency cesarean section (CS) were significant risk factors for neonatal HIE (odds ratio [OR] 6.5, 95% confidence interval [CI] 2.6-15.3, P < .001, OR 12.6, 95% CI 2.52-63.3, P = .002, respectively). No significant difference was found regarding maternal age and parity. About 33% of cases and 6% of controls were found to have at least 1 thrombophilic factor ( P < .001). Factor V G1691A mutation significantly increased the risk of neonatal HIE (OR 4.5, 95% CI 1.4-14.5, P = .012), while prothrombin G 20210A mutation and protein C deficiency were not. CONCLUSION: Parental consanguinity, emergency CS, and factor V mutation may contribute to the higher risk of developing neonatal HIE.

Discoidin Domains as Emerging Therapeutic Targets.

Discoidin (DS) domains are found in eukaryotic and prokaryotic extracellular and transmembrane multidomain proteins. These small domains play different functional roles and can interact with phospholipids, glycans, and proteins, including collagens. DS domain-containing proteins are often involved in cellular adhesion, migration, proliferation, and matrix-remodeling events, while some play a major role in blood coagulation. Mutations in DS domains have been associated with various disease conditions. This review provides an update on the structure, function, and modulation of the DS domains, with a special emphasis on two circulating blood coagulation cofactors, factor V and factor VIII, and the transmembrane neuropilin receptors that have been targeted for inhibition by biologics and small chemical compounds.

Pro- and anticoagulant properties of factor V in pathogenesis of thrombosis and bleeding disorders.

Factor V (FV) serves an important role in the regulation of blood coagulation, having both pro- and anticoagulant properties. The circulating high molecular weight single-chain FV molecule undergoes a series of proteolytic cleavages during both activation of coagulation and during anticoagulant regulation of coagulation by activated protein C (APC). It is noteworthy that mutations in the factor V gene (F5) either cause thrombosis or bleeding. New insights into the importance and complexity of FV functions have been generated from elucidation of the pathogenic mechanisms of two familial mutations in the F5 gene. The first mutation was identified as a result of the discovery of APC resistance as the most common risk factor for venous thrombosis. The mutation (FV Leiden) predicts the Arg(506) Gln replacement, which impairs the normal regulation of FVa by APC, as the Arg506 site is an important APC cleavage site. In addition, elucidation of APC resistance resulted in the discovery of the anticoagulant APC cofactor activity of FV. The second FV mutation (FV(A2440G) ), identified in a family with an autosomal dominant bleeding disorder, has led to the discovery of an alternative splicing generating a previously unidentified FV isoform (FV-Short), which inhibits coagulation via an unexpected and intriguing mechanism involving the coagulation inhibitor TFPI-α. These are naturally occurring mutations in the F5 gene that have generated new knowledge on the role of FV in regulation of coagulation and the importance of genetic risk factors for thrombosis and bleeding.

2013 scientific sessions Sol Sherry distinguished lecture in thrombosis: polyphosphate: a novel modulator of hemostasis and thrombosis.

Polyphosphate is a highly anionic, linear polymer of inorganic phosphates that is found throughout biology, including in many infectious microorganisms. Recently, polyphosphate was discovered to be stored in a subset of the secretory granules of human platelets and mast cells, and to be secreted on activation of these cells. Work from our laboratory and others has now shown that polyphosphate is a novel, potent modulator of the blood clotting and complement systems that likely plays roles in hemostasis, thrombosis, inflammation, and host responses to pathogens. Therapeutics targeting polyphosphate may have the potential to limit thrombosis with fewer hemorrhagic complications than conventional anticoagulant drugs that target essential proteases of the blood clotting cascade.

Decrease in factor V activity in patients treated with azathioprine or 6-mercaptopurine.

BACKGROUND AND OBJECTIVE: A decrease in factor V activity has been reported in some patients treated with azathioprine or 6-mercaptopurine. This may lead to unnecessary treatment discontinuation in otherwise asymptomatic patients. Our aim was to review spontaneously reported cases of decreased factor V activity associated with both drugs and to identify the possible impact on patient care. METHODS: Cases of decrease in prothrombin (PT) or factor V activity involving purine analogs were extracted from the French pharmacovigilance database. Reports with evidence of disseminated intravascular coagulation, signs of acute hepatocellular failure, liver cirrhosis or concomitant vitamin K antagonist treatment were excluded. RESULTS: Twenty-four cases (azathioprine: 13 and 6-mercaptopurine: 11) were retained. Therapeutic indications were inflammatory bowel diseases in 11 patients, acute leukemia in eight, and other autoimmune diseases in five. PT activity before treatment was normal in all nine tested patients. The decrease in PT or factor V activity occurs after a median of 10 weeks of treatment and all patients were asymptomatic. The median PT and factor V activities values were 51.5% and 36.4%, respectively. Other coagulation factors were inconsistently decreased. Full recovery was observed within 3-60 days following purine analogs discontinuation. In four patients, drug rechallenge was associated with recurrence of the coagulation disorders. CONCLUSIONS: Although the mechanism remains unknown, this series that includes cases with positive drug reintroduction strongly suggests the causative role of these drugs. As all patients remained asymptomatic, treatment discontinuation should be carefully considered in patients who clearly benefits from this treatment.

Evolution of Factor V Leiden.

Factor V Leiden is a procoagulant mutation associated with venous and arterial thrombosis and pregnancy complications. Its high prevalence of 5% in Caucasians suggests that there are evolutionary benefits as well. Carriers are indeed reported to have various advantageous phenotypes related to haemostasis, inflammation and fertility: less acute blood loss; less menstrual blood loss; decreased risk of intracranial haemorrhage; milder phenotypes of haemophilia; higher survival in and lower susceptibility to severe sepsis; higher survival in acute respiratory distress syndrome; less severe diabetic nephropathy and higher fecundity in both men and women. Not all these associations come from high quality adequately powered studies and many have not been confirmed by further research. The evolutionary influence of the alleged associations varies and is difficult to establish, partly due to a shift over time in risk factors of the diseases concerned. For most of the phenotypes possible mechanistic explanations can be provided. The procoagulant phenotype and perhaps also certain pregnancy complications follow from activated protein C (APC) resistance. Elevated APC levels possibly mediate anti-inflammatory effects. Higher sperm counts and more successful embryo implantation seem to play a role in the increased fecundity.

Umbilical artery Doppler in relation to placental pathology and FV Leiden in pregnant women and their offspring.

OBJECTIVE: Abnormal umbilical artery blood flow has been implicated in pregnancy complications and fetal demise. Its relation to histopathological changes in the placenta and to maternal or fetal thrombophilia is less well understood. The aim of this study was to evaluate the relation between umbilical artery Doppler findings, placental histopathology, and maternal and fetal coagulation factor V Leiden (FVL) status. METHODS: Two previous studies on FVL in pregnancy made the placentas of 25 women with maternal FVL carriership and 43 randomly selected non-carriers available for a histopathological examination. Umbilical artery Doppler velocimetry was performed on 54 women in late pregnancy. RESULTS: Abnormal umbilical artery Doppler velocimetry was associated with an approximately sevenfold increased risk of fetoplacental thrombotic vasculopathy (odds ratio [OR]: 7.5, 95% confidence intervals [CI]: 1.3-44.3), ischemic lesions (OR: 7.5, 95% CI: 1.2-46.1) and fetal carriership of FVL (OR: 8.2, 95% CI: 1.5-43.5), but not maternal FVL. Fetal FVL carriership was also associated with a sevenfold increased risk of ischemic lesions (OR: 6.7, 95% CI: 1.3-35). CONCLUSIONS: Our results indicate that the fetal - not the maternal - FVL carriership matters regarding the umbilical artery blood flow and placental pathology, which might explain some of the heterogeneity of studies.

Heparin--not only thinning the blood.

In this issue of Blood, An et al(1) report that thrombotic disorders such as factor V Leiden are often treated with drugs like low molecular weight heparin (LMWH) to prevent placental failure and recurrent pregnancy loss. To date, the involvement of thrombotic mechanisms in this process is highly debated. An et al(1) have identified a new mechanism by which LMWH improves pregnancy outcome in a murine model of factor V Leiden that is unrelated to its anticoagulation capabilities.

Heparin rescues factor V Leiden-associated placental failure independent of anticoagulation in a murine high-risk pregnancy model.

Low molecular weight heparin (LMWH) is being tested as an experimental drug for improving pregnancy outcome in women with inherited thrombophilia and placenta-mediated pregnancy complications, such as recurrent pregnancy loss. The role of thrombotic processes in these disorders remains unproven, and the issue of antithrombotic prophylaxis is intensely debated. Using a murine model of factor V Leiden-associated placental failure, we show that treatment of the mother with LMWH allows placental development to proceed and affords significant protection from fetal loss. Nonetheless, the therapeutic effect of LMWH is not replicated by anticoagulation; fondaparinux and a direct Xa inhibitor, C921-78, achieve anticoagulation similar to LMWH but produce little or no improvement in pregnancy outcome. Genetic attenuation of maternal platelet aggregation is similarly ineffective. In contrast, even a partial loss of thrombin sensitivity of maternal platelets protects pregnancies. Neonates born from these pregnancies are growth retarded, suggesting that placental function is only partially restored. The placentae are smaller but do not reveal any evidence of thrombosis. Our data demonstrate an anticoagulation-independent role of LMWH in protecting pregnancies and provide evidence against the involvement of thrombotic processes in thrombophilia-associated placental failure. Importantly, thrombin-mediated maternal platelet activation remains central in the mechanism of placental failure.

Co-occurrence of cardiovascular and prothrombotic risk factors in women with a history of preeclampsia.

OBJECTIVE: Formerly preeclamptic women are at increased risk for remote cardiovascular and thrombotic diseases. We studied co-occurrence of cardiovascular and prothrombotic risk factors within a cohort of formerly preeclamptic women and tested if prevalence of these risk profiles related to onset of preeclampsia in previous pregnancy. METHODS: We evaluated 1,297 nonpregnant formerly preeclamptic women (6-12 months postpartum) for the presence of four risk profiles: circulatory risk profile (hypertension or latent hypertension [low plasma volume, increased vascular resistance, or both]; metabolic syndrome (World Health Organization criteria); thrombophilia (factor V Leiden, prothrombin mutation, or protein C or S deficiency); and hyperhomocysteinemia. Trends between prevalence of these four profiles and onset of preeclampsia were studied using linear regression analysis. RESULTS: After exclusion of 63 women (4.9%) because of incomplete data, 1,234 women were included. One or more risk profiles were detected in 958 of 1,234 (77.6%) formerly preeclamptic women. Circulatory risk profile was more prevalent (66.1%) than hyperhomocysteinemia (18.7%), metabolic syndrome (15.4%), or thrombophilia (10.8%). Prevalence of circulatory risk profile, metabolic syndrome, and hyperhomocysteinemia decreased significantly with gestational age at delivery, whereas thrombophilia did not (P=.22). There was minimal overlap (less than 2%) between metabolic syndrome, thrombophilic profile, and hyperhomocysteinemia. CONCLUSION: Circulatory risk profile is present in two thirds of formerly preeclamptic women. Metabolic syndrome, thrombophilia, and hyperhomocysteinemia are prevalent in 10-20%. There is considerable overlap between circulatory risk profile and other profiles, but not among the three other profiles. Prevalence of these risk factors, except thrombophilia, decreases with gestational age at delivery in preceding pregnancy. LEVEL OF EVIDENCE: : II.

Thrombomodulin-dependent effect of factor V Leiden mutation on the cross-linking of α2-plasmin inhibitor to fibrin and its consequences on fibrinolysis.

INTRODUCTION: It has been shown that thrombomodulin (TM) considerably delays factor XIII (FXIII) activation and this effect is abrogated by Factor V Leiden (FV(Leiden)) mutation. The aim of the study was to explore the effect of TM on the cross-linking of α(2)-plasmin inhibitor (α(2)-PI) to fibrin in plasma samples of different FV genotypes and how this effect is related to the impaired fibrinolysis of FV(Leiden) carriers. METHODS: In the plasma samples of fifteen individuals with different FV genotypes and in FV deficient plasma supplemented with wild type FV or FV(Leiden) coagulation was initiated by recombinant human tissue factor and phospholipids with or without recombinant human TM (rhTM). In the recovered clots the extent of α(2)-PI-fibrin cross-linking was evaluated by Western blotting and quantitative densitometry. The effect of rhTM on tissue plasminogen activator (tPA) induced clot lysis was measured by turbidimetric method. RESULTS: rhTM significantly delayed the formation of α(2)-PI-fibrin α-chain heterodimers/oligomers in plasma samples containing wild type FV. This effect of rhTM was impaired in the presence of FV(Leiden). rhTM delayed tPA-induced clot lysis and this effect of rhTM was more pronounced in plasma containing FV(Leiden). When TAFIa was inhibited by potato carboxypeptidase inhibitor, rhTM accelerated clot lysis in the presence of wild type FV, which is explained by the delayed α(2)-PI-fibrin cross-linking. This effect of rhTM did not prevail in the presence of FV(Leiden). CONCLUSION: FV(Leiden) abrogates the delaying effect of rhTM on α(2)-PI-fibrin cross-linking, which contributes to the impaired fibrinolysis observed in FV(Leiden) carriers.

Broadening the factor V Leiden paradox: pulmonary embolism and deep-vein thrombosis as 2 sides of the spectrum.

Risk factors for deep-vein thrombosis have been shown not to be always the same as for pulmonary embolism. A well-known example is the factor V Leiden (FVL) paradox: the FVL mutation poses a clearly higher risk for deep-vein thrombosis (DVT) than for pulmonary embolism. We aimed to expand this paradox and therefore present risk estimates for several established risk factors for DVT and pulmonary embolism separately. When such separate risk estimates could not be retrieved from the literature, we calculated these risks in our own data, a large population-based case-control study on venous thrombosis (the MEGA study). Our results showed that the FVL paradox can be broadened (ie, the risk factors oral contraceptive use, pregnancy, puerperium, minor leg injuries, and obesity have an effect comparable with FVL). Furthermore, we found that pulmonary conditions, such as chronic obstructive pulmonary disease, pneumonia, and sickle cell disease, were risk factors with an opposite effect: a higher risk of pulmonary embolism, but little or no effect on DVT. These findings suggest that pulmonary embolism and DVT may not always have the same etiology, and encourage unraveling this phenomenon in further studies.

Vascular behcet and mutations in thrombogenic genes: methylene tetrahydrofolate reductase, factor V, and prothrombin.

Vasculitis, thrombophlebitis, arterial aneurysms, and occlusions occur in about 25% of patients with Behçet's disease (BD). The common inherited gene defects, factor V (FV) 1691A (Leiden), methylene tetrahydrofolate reductase (MTHFR) 677T, and prothrombin 20210A, are known risk factors for thrombosis. The aim of the study was to evaluate the contribution of these mutations to thrombosis in Israeli patients with BD. Fifty-four patients with BD (n=54; 27 men and 27 women) underwent clinical and genetic evaluation. Most patients (n=43; 79.6%) were of Arab descent (31 sporadic and 12 familial cases from 4 families), and 11 patients (20.4%) were of Jewish descent (all sporadic cases). The FV Leiden mutation was identified in five patients (9.2%), and eight patients were MTHFR 677TT homozygotes (14.8%). None had the 20210A mutant prothrombin allele. No statistical differences between carriers and noncarriers with regards to demographic and disease manifestations were calculated. Arabs were diagnosed earlier than Jewish patients (25.8±11.6 compared with 37.2±10.7, p=0.01, respectively), but Jewish patients had, respectively, more events of deep vein thrombosis (DVT) compared with Arabs (3 of 11, 27.3% and 3 of 43, 7%, p=0.09). Thrombotic events in our patients with BD were not associated with variations in thrombophilic genes.

Impact of the factor V Leiden mutation on the outcome of pneumococcal pneumonia: a controlled laboratory study.

INTRODUCTION: Streptococcus (S.) pneumoniae is the most common cause of community-acquired pneumonia. The factor V Leiden (FVL) mutation results in resistance of activated FV to inactivation by activated protein C and thereby in a prothrombotic phenotype. Human heterozygous FVL carriers have been reported to be relatively protected against sepsis-related mortality. We here determined the effect of the FVL mutation on coagulation, inflammation, bacterial outgrowth and outcome in murine pneumococcal pneumonia. METHODS: Wild-type mice and mice heterozygous or homozygous for the FVL mutation were infected intranasally with 2*106 colony forming units of viable S. pneumoniae. Mice were euthanized after 24 or 48 hours or observed in a survival study. In separate experiments mice were treated with ceftriaxone intraperitoneally 24 hours after infection and euthanized after 48 hours or observed in a survival study. RESULTS: The FVL mutation had no consistent effect on activation of coagulation in either the presence or absence of ceftriaxone therapy, as reflected by comparable lung and plasma levels of thrombin-antithrombin complexes and fibrin degradation products. Moreover, the FVL mutation had no effect on lung histopathology, neutrophil influx, cytokine and chemokine levels or bacterial outgrowth. Remarkably, homozygous FVL mice were strongly protected against death due to pneumococcal pneumonia when treated with ceftriaxone, which was associated with more pronounced FXIII depletion; this protective effect was not observed in the absence of antibiotic therapy. CONCLUSIONS: Homozygosity for the FVL mutation protects against lethality due to pneumococcal pneumonia in mice treated with antibiotics.

Plasmin-induced procoagulant effects in the blood coagulation: a crucial role of coagulation factors V and VIII.

Plasminogen activators provide effective treatment for patients with acute myocardial infarction. However, paradoxical elevation of thrombin activity associated with failure of clot lysis and recurrent thrombosis has been reported. Generation of thrombin in these circumstances appears to be owing to plasmin (Plm)-induced activation of factor (F) XII. Plm catalyzes proteolysis of several coagulant factors, but the roles of these factors on Plm-mediated procoagulant activity remain to be determined. Recently developed global coagulation assays were used in this investigation. Rotational thromboelastometry using whole blood, clot waveform analysis and thrombin generation tests using plasma, showed that Plm (> or =125 nmol/l) shortened the clotting times in similar dose-dependent manners. In particular, the thrombin generation test, which was unaffected by products of fibrinolysis, revealed the enhanced coagulation with an approximately two-fold increase of peak level of thrombin generation. Studies using alpha2-antiplasmin-deficient plasma revealed that much lower dose of Plm (> or =16 nmol/l) actually contributed to enhancing thrombin generation. The shortening of clotting time could be observed even in the presence of corn trypsin inhibitor, supporting that Plm exerted the procoagulant activity independently of FXII. In addition, using specific coagulation-deficient plasmas, the clot waveform analysis showed that Plm did not shorten the clotting time in only FV-deficient or FVIII-deficient plasma in prothrombin time-based or activated partial thromboplastin time-based assay, respectively. Our results indicated that Plm did possess procoagulant activity in the blood coagulation, and this effect was likely attributed by multicoagulation factors, dependent on FV and/or FVIII.

Risk of myocardial infarction related to factor V Leiden mutation: a meta-analysis.

BACKGROUND: Myocardial infarction (MI) can be due to inherited thrombophilia caused by resistance to activated protein C resulting from factor V Leiden (FVL) mutation. OBJECTIVES: The objectives of this study were to estimate the frequency of FVL mutation among MI cases in various populations and calculate the overall risk related to it. SUBJECTS AND METHODS: Subjects comprised 7790 cases with MI and 19,276 healthy controls collected from 41 relevant studies in the search databases. The resulting frequency of FVL mutation among cases and the odds ratio were compared and integrated in a meta-analysis format. RESULTS: Although there was marked variation of the frequency of FVL mutation among different populations including MI and healthy controls, most studies reported a positive risk related to it. Compilation of analyzed studies resulted in an overall frequency of FVL mutation of 6.791% among MI cases, which was significantly higher than that among controls (1.304%, p = 0.0) with an overall odds ratio of 1.608 (95% confidence interval, 1.98-4.44). CONCLUSION: There is a definite risk related to the carriage of FVL mutation among MI cases. This should have a potential impact on the genetic counseling of family members of affected cases for proper prophylaxis.

Factor V Leiden mutation enhances fibrin formation and dissolution in vivo in a human endotoxemia model.

Disseminated intravascular coagulation in sepsis is associated with microvascular thrombosis and organ dysfunction. It was expected that prothrombotic disposition such as factor V Leiden (FVL) mutation would worsen clinical outcome. Astonishingly, clinical trial and animal experimental data indicate that FVL can be associated with improved survival. This study investigated the effect of FVL on the response to endotoxin of the coagulation and fibrinolytic system in humans. Fourteen healthy male subjects without FVL and 15 healthy males with heterozygous FVL received an intravenous bolus dose of endotoxin, 2 ng/kg of body weight. Blood samples were drawn before and 1, 2, 4, 6, and 24 hours after administration of the endotoxin. Injection of endotoxin led to a more pronounced increase in soluble fibrin in patients with FVL than in controls. Patients with FVL displayed a more sustained increase in plasmin-plasmin inhibitor complex after 4, 6, and 24 hours. Patients with FVL mutation also displayed higher levels of D-dimer and fibrinogen-fibrin degradation products in plasma after 24 hours. Patients with FVL generate higher levels of soluble fibrin, which may serve as cofactor in tissue plasminogen activator-induced plasminogen activation, leading to a more sustained activation of fibrinolysis with production of more fibrinogen- and fibrin-degradation products.