Clinical relevance of decreased free protein S levels: results from a retrospective family cohort study involving 1143 relatives

The impact of PROS1 mutation position on thrombotic risk in protein S-deficient patients

Background

Inherited protein S deficiency is a thrombophilic risk factor associated with venous thromboembolism. However, there is not much data on the impact of mutation position on thrombotic risk.

Objectives

The aim of this study was to evaluate the risk of thrombosis due to mutations located in the sex hormone-binding globulin (SHBG)-like region as opposed to the rest of the protein.

Methods

Genetic analysis of PROS1 was performed in 76 patients with suspected inherited protein S deficiency, and the effect of missense mutations present in the SHBG region on thrombosis risk was analyzed by statistical methods.

Results

We found 30 unique mutations (13 of them novel), of which 17 were missense mutations, in 70 patients. Patients with missense mutations were then divided into 2 groups: the "SHBG-region" mutation group (27 patients) and the "non-SHBG" group (24 patients). The multivariable binary logistic regression analysis showed that mutation position in the SHBG region of protein S is an independent risk factor for thrombosis in deficient patients (OR, 5.17; 95% CI, 1.29-20.65; P = .02). The patients with a mutation in the SHBG-like region also developed a thrombotic event at a younger age compared to the "non-SHBG" group in the Kaplan-Meier analysis (median thrombosis-free survival of 33 vs 47 years, respectively; P = .018).

Conclusion

Our findings show that a missense mutation located in the SHBG-like region may contribute to higher thrombotic risk rather than a missense mutation located elsewhere in the protein. However, as our cohort was relatively small, these findings should be taken with this limitation.

Clinical and imaging risk factors for the persistence of thromboembolism following acute pulmonary embolism

Background

Predicting the progression of acute pulmonary embolism to chronic pulmonary thromboembolism (CPTE) disease is essential to monitoring and improving the long-term prognosis of pulmonary embolism. We explored the risk factors for chronic persistence of thromboembolism after acute pulmonary embolism.

Methods

Cases with newly onset acute pulmonary embolism in the China-Japan Friendship Hospital from November 2016 to November 2019 were retrospectively analyzed. The clinical characteristics, serological examination results, and treatment strategies of acute pulmonary embolism patients were obtained through the electronic medical record system (Goodwill E-Health Info Co., Ltd.). Imaging parameters on computed tomography pulmonary angiography (CTPA) images at the onset of the acute pulmonary embolism were measured and counted. Notably, we propose a new parameter based on CTPA images: the ratio of S_d (sum of residual segmental pulmonary artery diameter) to MPA_d (the main pulmonary artery diameter) (S_d/MPA_d). After 3 months of regular treatment for acute pulmonary embolism, patients were classified into a CPTE group or a non-CPTE group based on the presence of residual embolus. All data were compared between the CPTE group and non-CPTE group. Furthermore, logistic regression analysis was used to investigate risk factors for the progression of acute pulmonary embolism to CPTE.

Results

A total of 77 cases (male:female = 1:1.26) were included in the study. There were 43 cases (55.84%) in the CPTE group and 34 cases in the non-CPTE group (44.16%). The results of univariate analysis showed that there were statistically significant differences between the 2 groups in risk stratification (χ²=8.043; P=0.005), protein S activity (χ²=5.551; P=0.018), the ratio of sum of residual segmental pulmonary artery diameter to the main pulmonary artery diameter (S_d/MPA_d; t=–2.103; P=0.039), Mastora score (U=362.500; P<0.001), and embolus location (χ²=16.969; P<0.001). However, there were no statistically significant differences between the 2 groups in treatment options (P=0.381). According to multivariate logistic-regression analysis, protein S activity <55% (P=0.025), S_d/MPA_d ≥1.97 (P=0.011), and an embolus being located in the central pulmonary artery (P<0.001) were independent risk factors for chronic persistence of thromboembolism following acute pulmonary embolism.

Conclusions

The protein S activity, location of the embolus, and S_d/MPA_d on CTPA at the onset of acute pulmonary embolism may suggest the progression of acute pulmonary embolism to CPTE.

Protein S Deficiency and the Risk of Venous Thromboembolism in the Han Chinese Population

Plasma levels of the anticoagulant cofactor protein S and PROS1 mutation are reported to impart increased risk of thromboembolism in European and south east Asian populations, but the relationship is not yet documented in Han Chinese in population-based study. Therefore, we undertook a case-control study of this relationship among patients with venous thromboembolism, and probed the genetic factors contributing to low protein S deficiency. Among the 603 consecutively recruited venous thromboembolism patients, 51 (8.5%) proved to be deficient in free protein S antigen (lower than 38.6 U/dl), among whom 30 cases were identified to have a causative mutation by direct sequencing. In contrast, six cases (1.0%) of the 584 healthy controls had low free antigen levels, among whom direct sequencing confirmed disease-causing gene mutations in four controls (0.7%). After adjusting for age and gender, the odds ratio of developing venous thromboembolism in individuals with protein S deficiency based on free protein S tests was 8.1 (95% CI = 3.6–19.9, P < 0.001). Gene sequencing yielded 24 different heterozygous mutations in the 34 participants, of which 13 were newly described. 17 (50%) of the 34 mutations in our study cohort occurred in exons 12 and 13, indicating the LGR2 domain to be a hotspot mutation region for the protein. These findings are conducive to the clinical application of protein S assays for the molecular diagnosis of thrombophilia.

Atypical presentation of pulmonary embolism and deep vein thrombosis due to protein S deficiency in a young female with chest pain

Venous thromboembolism has many risk factors including protein S deficiency, which poses a significant diagnostic challenge as it presents with atypical complaints. A treatable yet potentially fatal condition, acute pulmonary embolism, is currently third most common cause of cardiovascular death. Clinicians should include pulmonary embolism as differential diagnosis in young adults with atypical symptoms with 2 D ECHO findings of the dilated right atrium, right ventricle, and elevated pulmonary artery pressure, and diagnosis is confirmed by computed tomography pulmonary angiography (CTPA). Anticoagulants including NOACs should be initiated promptly to improve the outcome for patients.

Kallikrein augments the anticoagulant function of the protein C system in thrombin generation

BACKGROUND

Genetics play a significant role in coagulation phenotype and venous thromboembolism risk. Resistance to the anticoagulant activated protein C (APC) is an established risk for thrombosis. Herein, we explored the genetic determinants of thrombin generation (TG) and thrombomodulin (TM)-modulated TG using plasma from the Human Functional Genomics Project.

METHODS

Calibrated TG was measured both in absence and presence of TM using tissue factor as trigger. Genetic determinants of TG parameters and protein C pathway function were assessed using genome-wide single-nucleotide polymorphism (SNP) genotyping. Plasma samples were supplemented with purified apolipoprotein A-IV, prekallikrein, or kallikrein to test their influence on the anticoagulant function of TM and APC in TG.

RESULTS

Thrombin generation data from 392 individuals were analyzed. Genotyping showed that the KLKB1 gene (top SNP: rs4241819) on chromosome 4 was associated with the normalized sensitivity ratio of endogenous thrombin potential to TM at genome-wide level (nETP-TMsr, P = 4.27 × 10-8 ). In vitro supplementation of kallikrein, but not prekallikrein or apolipoprotein A-IV, into plasma dose-dependently augmented the anticoagulant effect of TM and APC in TG. Variations of rs4241819 was not associated with the plasma concentration of prekallikrein. Association between rs4241819 and nETP-TMsr was absent when TG was measured in presence of a contact pathway inhibitor corn trypsin inhibitor.

CONCLUSIONS

Our results suggest that kallikrein plays a role in the regulation of the anticoagulant protein C pathway in TG, which may provide a novel mechanism for the previously observed association between the KLKB1 gene and venous thrombosis.

Derangement of protein S and C4b-binding protein levels as acquired thrombophilia in HIV-infected adult Nigerians

BACKGROUND

HIV is a chronic inflammatory state with the production of many acute-phase-reactant proteins. Some of these proteins have procoagulant activities that predispose HIV-infected patients to thrombosis.

OBJECTIVES

The aim of the study was to evaluate the effects of HIV infection on the serum levels of C4b-binding protein (C4BP) and protein S as markers of predisposition to thrombosis in HIV-infected adults.

METHODS

The study population comprised of 61 HIV-infected adults on antiretroviral treatment (ART) who had achieved virological suppression, 58 HIV-infected adults not yet on ART and 59 HIV-negative healthy controls. The serum levels of free protein S, C4BP and the euglobulin clot lysis time (ECLT) were determined.

RESULTS

The mean plasma-free protein S level of HIV-infected patients on ART (86.9% ± 25.8%) was significantly higher than that of treatment-naïve HIV-infected patients (75.7% ± 27.3%) (p = 0.005). Conversely, there was no statistically significant difference between the protein S levels of the HIV-infected subjects on ART (86.9% ± 25.8%) and those of the controls (94.9% ± 7.9%) (p = 0.119). The mean C4BP was significantly higher in the treatment-naïve HIV-infected subjects (36.7 ± 1.7 ng/dL) than that in those on ART (30.7 ± 2.6 ng/dL) and that in the controls (22.4 ± 2.4 ng/dL) (p < 0.0001). Protein S deficiency was more prevalent among the subjects with elevated C4BP (p = 0.023). The mean ECLT was significantly more prolonged in the treatment-naïve HIV-infected subjects (241.9 ± 34.7 s) than controls (189.5 ± 40.7 s) (p < 0.0001).

CONCLUSION

HIV infection causes elevated levels of C4BP and diminishes the serum levels of free protein S. We infer that the risk of thrombosis (as measured by these biomarkers) decreases with the use of antiretroviral drugs.

Platelet protein S limits venous but not arterial thrombosis propensity by controlling coagulation in the thrombus

Anticoagulant protein S (PS) in platelets (PSplt) resembles plasma PS and is released on platelet activation, but its role in thrombosis has not been elucidated. Here we report that inactivation of PSplt expression using the Platelet factor 4 (Pf4)-Cre transgene (Pros1lox/loxPf4-Cre+) in mice promotes thrombus propensity in the vena cava, where shear rates are low, but not in the carotid artery, where shear rates are high. At a low shear rate, PSplt functions as a cofactor for both activated protein C and tissue factor pathway inhibitor, thereby limiting factor X activation and thrombin generation within the growing thrombus and ensuring that highly activated platelets and fibrin remain localized at the injury site. In the presence of high thrombin concentrations, clots from Pros1lox/loxPf4-Cre- mice contract, but not clots from Pros1lox/loxPf4-Cre+ mice, because of highly dense fibrin networks. Thus, PSplt controls platelet activation as well as coagulation in thrombi in large veins, but not in large arteries.

A novel rare c.-39C>T mutation in the PROS1 5'UTR causing PS deficiency by creating a new upstream translation initiation codon

Autosomal dominant inherited Protein S deficiency (PSD) (MIM 612336) is a rare disorder caused by rare mutations, mainly located in the coding sequence of the structural PROS1 gene, and associated with an increased risk of venous thromboembolism. To identify the molecular defect underlying PSD observed in an extended French pedigree with seven PSD affected members in whom no candidate deleterious PROS1 mutation was detected by Sanger sequencing of PROS1 exons and their flanking intronic regions or via an multiplex ligation-dependent probe amplification (MLPA) approach, a whole genome sequencing strategy was adopted. This led to the identification of a never reported C to T substitution at c.-39 from the natural ATG codon of the PROS1 gene that completely segregates with PSD in the whole family. This substitution ACG→ATG creates a new start codon upstream of the main ATG. We experimentally demonstrated in HeLa cells that the variant generates a novel overlapping upstream open reading frame (uORF) and inhibits the translation of the wild-type PS. This work describes the first example of 5'UTR PROS1 mutation causing PSD through the creation of an uORF, a mutation that is not predicted to be deleterious by standard annotation softwares, and emphasizes the need for better exploration of such type of non-coding variations in clinical genomics.

Compound heterozygous mutations identified in severe type I protein S deficiency impaired the secretion of protein S

AIMS

Hereditary protein S (PS) deficiency is one of the natural anticoagulant deficiencies causing thrombophilia. We herein described a young male with recurrent deep venous thrombosis, who was diagnosed as type I PS deficiency with compound heterozygous mutations of PROS1 gene. We aimed to analyse the relationship between the genotype and phenotype detection and investigate the pathological mechanisms of PROS1 mutations causing PS deficiency.

METHODS

Genetic analysis of PROS1 gene was carried out by direct sequencing. Thrombin generation potential and the inhibition function of thrombin generation by plasma PS were detected by thrombin generation test (TGT). The mRNA transcription level of mutant PS in vitro was measured by real-time PCR, while the protein level was evaluated by western blot and ELISA. Cellular distribution of the protein was further analysed by immunofluorescence.

RESULTS

Compound heterozygous mutations (PROS1 c.1551_1552delinsG, p.Thr518Argfs*39 and PROS1 c.1681C>T, p.Arg561Trp) were identified in the propositus, and the former one was a novel small indel mutation. TGT results showed impaired inhibition of thrombin generation with the addition of activated protein C in his parents with certain heterozygous mutations. In vitro expression study, p.Thr518Argfs*39 mutant produced truncated protein retained in the cytoplasm, while p.Arg561Trp mutant partially affected the secretion of PS. Both mutations are located in C-terminal sex hormone-binding globulin (SHBG)-like domain of PS.

CONCLUSIONS

Compound heterozygous mutations identified in the study have strong detrimental effect, causing severe type I PS deficiency in the propositus. SHBG-like domain of PS might play an important role in PS secretion system.

Pulmonary deregulation of expression of miR-155 and two of its putative target genes; PROS1 and TP53INP1 associated with gold nanoparticles (AuNPs) administration in rat

Background: Gold nanoparticles (AuNPs) have been considered as an ideal candidate in various biomedical applications due to their ease of tailoring into different size, shape, and decorations with different functionalities. The current study was conducted to investigate the epigenetic alteration in the lung in response to AuNPs administration regarding microRNA-155 (miR-155) gene which can be involved in AuNP-induced lung pathogenesis. Methods: Thirty-two Wister rats were divided into two equal groups, control group and AuNPs treated group which received a single intravenous (IV) injection of plain spherical AuNPs (0.015 mg/kg body wt) with an average diameter size of 25±3 nm. Lung samples were collected from both the control and injected groups at one day, one week, one month and two months post-injection. The alteration of relative expression of miR-155 gene and two of its putative target genes; tumor protein 53 inducible nuclear protein 1 (TP53INP1) and protein S (PROS1) was investigated by real time PCR and protein S (PS) expression was analyzed by Western blotting technique. Results: The obtained results revealed that AuNPs administration significantly increases the expression level of miR-155 and reduce relative mRNA expression of TP53INP1 and PROS1 genes at one day post-injection. In contrast, a significant down-regulation of miR-155 level of expression concurrent with up-regulation of expression level of TP53INP1 and PROS1 genes were shown at one week, one month and two months post-injection. PS levels were mirrored to their PROS1 mRNA levels except for two month post-injection time point. Conclusions: These findings indicate epigenetic modulation in the lung in response to AuNPs administration regarding the miR-155 gene which can be involved in AuNP-induced lung pathogenesis.

Risk of Recurrent Venous Thromboembolism After an Initial Episode: Risk Stratification and Implications for Long-term Treatment

PURPOSE OF REVIEW

Venous thromboembolism (VTE) is a common condition with significant associated morbidity and mortality. Recurrent VTE after an initial episode is a preventable medical condition. The following review discusses data supporting recurrence risk estimates after an initial VTE episode as well as treatment strategies to mitigate risk of recurrent VTE.

RECENT FINDINGS

This review particularly highlights methods for stratifying the risk of recurrent VTE and recent studies that have evaluated direct oral anticoagulants for the prevention of recurrent VTE. Risk assessment for VTE recurrence should guide anticoagulation duration. In patients who present with unprovoked VTE events, there remains a high risk of recurrence that is significantly mitigated with extended duration anticoagulation with either a vitamin K antagonist or direct oral anticoagulant.

Preventative management against thromboembolism using fresh frozen plasma in a coronary artery bypass graft patient with protein S deficiency: a case report

Protein S deficiency patient is characterized by recurrent thrombosis, and its risk is higher intraoperatively, especially in cardiac surgery involving cardiopulmonary bypass. Two heparin cessation periods are defined in cardiac surgery. One is the period between the cessation of heparin 4 to 5 h before surgery and the heparinization prior to cardiopulmonary bypass. The other is the period between protamine administration and resumption of heparin postoperatively. Because the risk of thromboembolism is high during the period of heparin cessation, other anticoagulants are necessary. Although fresh frozen plasma, rich in protein S, is often used in cardiac surgery for protein S deficiency patients, the most appropriate times and volume of its administration to prevent thromboembolism remain poorly understood. We herein report a case of on-pump coronary artery bypass grafting in a patient with protein S deficiency who received fresh frozen plasma targeting the two heparin cessation periods. Some qualitative measurements to identify the effect of fresh frozen plasma on the protein S level are desirable to evaluate whether our present administration strategy has any beneficial effects on protein S deficiency patients.

Differential haemostatic risk factors for pregnancy-related deep-vein thrombosis and pulmonary embolism

Limited data exist on thrombophilia and the risk of venous thrombosis (VT) during pregnancy and postpartum. The objectives of the present study were to investigate the role of haemostatic risk factors for pregnancy-related VT and their phenotypic expression in deep-vein thrombosis (DVT) and pulmonary embolism (PE). Total 313 cases with objectively verified first time VT and 353 controls were selected from a source population of 377,155 women with 613,232 pregnancies. The adjusted odds ratio (aOR) for pregnancy-related VT was 1.7 (95% confidence interval [CI] 1.1–2.8) for women with factor VIII >90th percentile. The aOR for VT for endogenous thrombin potential and D-dimer values >90thpercentiles were 1.8 (95% CI 1.1–3.0) and 2.1 (95% CI 1.3–3.3), respectively. Factor IX >90thpercentile or free protein S ≤the 5th percentile increased the risk for PE, and the aORs were 2.4 (95% CI 1.1–5.0) and 3.1 (95% CI 1.3–7.2), respectively. Women carrying the factor V Leiden (F5 rs6025) polymorphism, or who had reduced sensitivity to activated protein C (aPC) in the absence of F5 rs6025, had increased risk for DVT, with unadjusted ORs 7.7 (95% CI 4.7–12.7) and 3.5 (95% CI 2.2–5.4), respectively. Women with a history of pregnancy-related VT showed activation of coagulation and had elevated factor VIII. Furthermore, high levels of factor IX and low levels of free protein S were associated with increased risk for PE, whereas aPC resistance and F5 rs6025 were risk factors for DVT and not PE.

New functional assays to selectively quantify the activated protein C- and tissue factor pathway inhibitor-cofactor activities of protein S in plasma

Essentials Protein S is a cofactor of activated protein C (APC) and tissue factor pathway inhibitor (TFPI). There are no assays to quantify separate APC and TFPI cofactor activities of protein S in plasma. We developed assays to measure the APC- and TFPI-cofactor activities of protein S in plasma. The assays were sensitive to protein S deficiency, and not affected by the Factor V Leiden mutation.

SUMMARY

Background Protein S plays an important role in the down-regulation of coagulation as cofactor for activated protein C (APC) and tissue factor pathway inhibitor (TFPI). Aim To develop functional assays to quantify the APC- and TFPI-cofactor activities of protein S in plasma. Methods APC- and TFPI-cofactor activities of protein S in plasma were measured using calibrated automated thrombography in protein S-depleted plasma supplemented with a small amount of sample plasma either in the presence of anti-TFPI antibodies and APC (APC-cofactor activity) or at excess full-length TFPI without APC (TFPI-cofactor activity). Total and free protein S levels in plasma were measured by ELISAs. Results Average APC-cofactor activities of protein S were 113%, 108% and 89% in plasma from normal individuals (n = 15), FV Leiden heterozygotes (n = 14) and FV Leiden homozygotes (n = 7), respectively, whereas the average APC-cofactor activity of protein S in plasma from heterozygous protein S-deficient individuals (n = 21) was significantly lower (55%). Similar trends were observed for the TFPI-cofactor activity of protein S, with averages of 109%, 115% and 124% in plasma from individuals with normal protein S levels and different FV Leiden genotypes, and 64% in plasma from protein S-deficient patients. APC-cofactor activities of protein S correlated significantly with free and total protein S antigen levels, whereas TFPI-cofactor activities correlated less with protein S antigen levels. Conclusion We have developed functional protein S assays that measure both the APC- and TFPI-cofactor activities of protein S in plasma, which are hardly if at all affected by the FV Leiden mutation.

An Overview of Thrombophilia and Associated Laboratory Testing

Venous thromboembolism, usually entailing deep vein thrombosis, pulmonary embolism, or both, is a complex and multifactorial disorder, in which a number of putative conditions interplay and finally contribute to propel the individual risk over a certain degree, so ultimately culminating in the development of venous occlusive disorders. Thrombophilia is commonly defined as a propensity to develop venous thromboembolism on the basis of an underlying hypercoagulable state attributable to inherited or acquired disorders of blood coagulation or fibrinolysis. The thrombophilic conditions are conventionally classified as inherited (or genetically determined) and acquired. The former include deficiencies of natural anticoagulants such as antithrombin, protein C, protein S, increased values of clotting factors (especially factor VIII), as well as prothrombotic polymorphisms in genes encoding for factor V (i.e., factor V Leiden) and prothrombin. The latter conditions mainly entail antiphospholipid antibody syndrome, malignancy, acquired elevations of coagulation factors or acquired reduction of natural inhibitors, or hyperhomocysteinemia. Deepened knowledge of all potential risk factors, as well as the clear understanding of their role in the pathophysiology of venous thrombosis, are both essential to help achieve a faster and more efficient diagnosis of this condition as well as a more effective prophylaxis of patients at higher risk and treatment of those with manifest disease.

Comparative biochemical studies of fresh frozen plasma and pooled solvent/detergent-treated plasma (octaplasLG® ) with focus on protein S and its impact in different thrombin generation assay set-ups

BACKGROUND AND OBJECTIVES

The solvent/detergent treatment enables effective and robust inactivation of all lipid-enveloped viruses, but also inactivates partly sensitive plasma proteins such as protein S. The aim of this study was to investigate the thrombin generation capacity of octaplasLG^® , in particular focusing on the function of protein S in thrombin generation assay and the impact of assay settings.

MATERIALS AND METHODS

Sixteen octaplasLG^® batches and 32 units of single donor fresh frozen plasma (FFP) were investigated. For protein S, both functional activity and free antigen levels were measured. Thrombin generation assay was performed using two fluorogenic tests with different triggers. Finally, rotational thromboelastometry was performed.

RESULTS

Mean protein S levels were lower in octaplasLG^® , but a wider range of values was found for FFP. Clotting parameters and thrombin generation capacities overlapped between the two plasma groups as demonstrated using both thrombin generation assays and different triggers. Spiking studies with protein S-depleted plasma, human purified protein S or antibodies against protein S confirmed a correlation between protein S and thrombin generation capacity under specific assay conditions, especially in an assay with low tissue factor concentration.

CONCLUSION

Correlation between protein S and thrombin generation capacity was demonstrated in the TGA. Due to higher variability in protein S content in the FFP group, overlapping haemostatic potentials of the two plasma groups were found.

Diagnostic implications of computed tomography pulmonary angiography in patients with pulmonary embolism

INTRODUCTION:

Pulmonary embolism (PE) is a serious cardiovascular and pulmonary complication worldwide. We aimed to assess the implications of different computed tomography pulmonary angiography (CTPA) parameters in patients with acute PE.

METHODS:

A retrospective observational study to include patients presented with clinical suspicious of PE who underwent CTPA was conducted. Patients' demographics, clinical presentation, risk factors, laboratory investigations, management, and outcome were analyzed. Computed tomography findings included clot burden (Qanadli score [QS]) and right ventricular dysfunction (RVD) parameters.

RESULTS:

A total of 45 patients with radiologically confirmed diagnosis of PE were included in the study; of these patients, 8 (17.8%) died during the hospital course. Patients who died were 13 years older than those who survived, and the mortality rate was significantly higher in patients with cancer. The two groups were comparable for cardiovascular parameters. The mean clot burden (QS) was 19.5 ± 11.3 points and 53% of patients had QS >18 points. Obesity (52.4% vs. 12.5%; P = 0.01), hypertension (54.4% vs. 23.8%; P = 0.03), and median D-dimer levels (7.8 vs. 3.4; P = 0.03) were significantly higher in patients with QS >18. Among right ventricular (RV) dysfunction parameters, only higher RV/left ventricular (LV) ratio (P = 0.001) and bowing of interventricular septum (P = 0.001) were associated with higher QS. A significant positive correlation was found between RV short axis (r = 0.499, P = 0.001), RV/LV ratio (r = 0.592, P = 0.001), and pulmonary artery (PA) diameter (r = 0.301, P = 0.04) with the PA clot burden. Receiver operating characteristic curve for clot burden showed a cutoff value of 17.5 points to accurately predict RV dysfunction.

CONCLUSIONS:

Clot burden >18 is associated with RV dysfunction in patients with acute PE. Echocardiography and RVD parameters showed no correlation with in-hospital deaths. CTPA has clinicoradiological implications for risk stratification in PE patients. As the sample size is small, our findings warrant further larger prospective studies.

PROS1 genotype phenotype relationships in a large cohort of adults with suspicion of inherited quantitative protein S deficiency

Inherited protein S deficiency (PSD) is an established risk factor for venous thromboembolism (VTE). However, data are conflicting concerning risk of VTE associated with decreased free PS level (FPS) and information on PROS1 genotype-phenotype relationship is sparse. In a retrospective cohort of 579 patients with inherited type I/III deficiency suspicion, PROS1 genotyping was performed and the effect of genotype on FPS and on VTE risk was investigated. We found 116 (including 65 novel) detrimental mutations (DM) in 222 (type I/III in 194, type II in 28), PS Heerlen in 74, possibly non DM in 38 and no mutation in 245 subjects. Among DMs, type I/IIIDMs only were found in subjects with FPS< 30 %. Prevalence of type I/III DM decreased with increasing FPS level. Risk of VT associated with FPS level and genotype was studied in the 467 subjects with personal or family history of thrombosis. Only type I/IIIDM carriers presented with an increased risk of VTE [1.41 (95 %CI (1.05-1.89)] compared to subjects with no mutation. Among the group of type I/IIIDM heterozygotes and subjects with no mutation, the optimal FPS cut-off point for identifying subjects at increased VTE risk was searched for. We found that only subjects with FPS< 30 % and type I/IIIDM presented with an increased risk [1.48 (95 %CI 1.08-2.04)]. Our findings confirm the value of a cut-off FPS level for identifying subjects at increased VTE risk far below the lower limit of the normal range and suggest a place for PROS1 genotyping in PSD diagnosis strategy.

Understanding the functional difference between growth arrest-specific protein 6 and protein S: an evolutionary approach

Although protein S (PROS1) and growth arrest-specific protein 6 (GAS6) proteins are homologous with a high degree of structural similarity, they are functionally different. The objectives of this study were to identify the evolutionary origins from which these functional differences arose. Bioinformatics methods were used to estimate the evolutionary divergence time and to detect the amino acid residues under functional divergence between GAS6 and PROS1. The properties of these residues were analysed in the light of their three-dimensional structures, such as their stability effects, the identification of electrostatic patches and the identification potential protein-protein interaction. The divergence between GAS6 and PROS1 probably occurred during the whole-genome duplications in vertebrates. A total of 78 amino acid sites were identified to be under functional divergence. One of these sites, Asn463, is involved in N-glycosylation in GAS6, but is mutated in PROS1, preventing this post-translational modification. Sites experiencing functional divergence tend to express a greater diversity of stabilizing/destabilizing effects than sites that do not experience such functional divergence. Three electrostatic patches in the LG1/LG2 domains were found to differ between GAS6 and PROS1. Finally, a surface responsible for protein-protein interactions was identified. These results may help researchers to analyse disease-causing mutations in the light of evolutionary and structural constraints, and link genetic pathology to clinical phenotypes.

Natural anticoagulants deficiency and the risk of venous thromboembolism: a meta-analysis of observational studies

INTRODUCTION

Natural anticoagulants deficiency (antithrombin [AT], protein C [PC], protein S [PS]) is a rare, but potent risk factor for venous thromboembolism (VTE). We performed a meta-analysis of observational studies evaluating the impact of inherited natural anticoagulants deficiency on VTE risk.

MATERIALS AND METHODS

Case-control and cohort studies evaluating the association of these abnormalities with VTE were systematically searched in the PubMed, Web of Science, Scopus and EMBASE databases.

RESULTS

Twenty-one studies were included in the analysis. Thirteen studies (3,452 cases and 11,562 controls) showed an increased risk of first VTE in AT deficient subjects compared to controls (OR: 16.26, 95%CI:9.90-26.70; P<0.00001). An increased risk of first VTE was also found in PC (11 studies, 2,554 cases and 9,355 controls; OR: 7.51, 95%CI:3.21-17.52; P<0.00001) and PS deficient patients (14 studies, 4,955 cases and 9,267 controls; OR: 5.37; 95%CI:2.70-10.67; P<0.00001) compared to controls. Evaluating the risk of VTE recurrence, we found a significant association with AT (4 studies, 142 cases and 1,927 controls; OR: 3.61; 95%CI:1.46-8.95; P=0.006) and with PC (2 studies, 80 cases and 546 controls; OR: 2.94; 95%CI:1.43-6.04; P=0.03), but not with PS deficiency (2 studies, 57 cases and 589 controls; OR: 2.52; 95%CI:0.89-7.16; P=0.08). Sensitivity and subgroup analyses confirmed these results. The association among natural anticoagulants deficiency and VTE was maximal for patients with unprovoked events.

CONCLUSION

The VTE risk is increased in patients with natural anticoagulants deficiency, but additional studies are warranted to better assess the risk of VTE recurrence.

Protein S levels and the risk of venous thrombosis: results from the MEGA case-control study

Low free protein S and low total protein S levels could not identify subjects at risk for venous thrombosis in a population-based study. Protein S testing and subsequent testing on PROS1 mutations should not be considered in unselected patients with venous thrombosis.

Molecular basis of protein S deficiency in China

Protein S (ProS) is a physiological inhibitor of coagulation with an important function in the down-regulation of thrombin generation. ProS deficiency is a major risk factor for venous thrombosis. This study enrolled 40 ProS-deficient probands to investigate the molecular basis of hereditary ProS deficiency in Chinese patients. A mutation analysis was performed by resequencing the PROS1 gene. Large deletions were identified by multiplex ligation-dependent probe amplification (MLPA) analysis. A total of 20 different mutations, including 15 novel mutations, were identified in 21 of the 40 index probands. Small mutations were detected in 18 (45.0%) probands, and large deletions were found in 3 (7.5%) probands, leaving 19 (47.5%) patients without causative variants. To evaluate the functional consequences of 2 novel missense variants, ex vivo thrombin-generation assays, bioinformatics tools, and in vitro expression studies were employed. The p.Asn365Lys ProS variant was found to have moderately impaired secretion and reduced activated protein C cofactor activity. In contrast, the p.Pro410His mutant appeared to have severely impaired secretion but full anticoagulant activity. This study is the largest investigation of ProS deficiency in China and the first investigation of the influence of Type I ProS missense mutations on the global level of coagulation function. The p.K196E mutation, which is common in the neighboring Japanese population, was not found in our Chinese population, and null mutations were common in our Chinese population but not common in Japan. Further genetic analysis is warranted to understand the causes of ProS deficiency in patients without a genetic explanation.

Postintervention duration of anticoagulation in venous surgery

For a substantial proportion of patients with deep venous thrombosis (DVT), current treatment strategies are suboptimal and new treatment options are needed. Especially for the group of patients who are at the highest risk for post-thrombotic syndrome, new treatment modalities such as catheter-directed thrombolysis and additional stenting are being investigated. With current clinical studies addressing new technical options, the medical management of patients following these interventions deserves attention. The duration of anticoagulant treatment following surgical or radiological interventions for DVT seems not to be influenced by the presence of a venous stent. According to recent ACCP 2012 guidelines the anticoagulant management in patients who have had any method of thrombus removal performed, the same intensity and duration of anticoagulant therapy as in comparable patients who do not undergo thrombosis removal is recommended (Grade 1B). In the acute phase of thrombosis, irrespective of the technique and whether or not stenting is applied, immediate anticoagulation following the procedure is pertinent to reduce the risk of recurrent thrombosis and thrombus propagation. The long-term treatment duration after venous interventions therefore may be tailored based on common risk factors for recurrent thrombosis and the individual risk for bleeding. Selected thrombophilia factors, d-dimer assessment and residual venous thrombosis provide markers for recurrent DVT. Currently, vitamin K antagonists) provide the main anticoagulants for (prolonged) anticoagulation, while the new oral anticoagulants emerge as promising alternatives. In case prolonged anticoagulation after unprovoked DVT is not indicated, cardiovascular risk management is warranted because of an increased rate of arterial thrombotic events after DVT; aspirin may be indicated as secondary prevention against recurrent thrombosis (while providing primary prevention against arterial thrombosis).

Deficiencies of antithrombin, protein C and protein S - practical experience in genetic analysis of a large patient cohort

Deficiencies of natural anticoagulant proteins including antithrombin (AT), protein C (PC) and protein S (PS) are important causes of inherited thrombophilia. This study aimed to report on the practical experience gained in performing genetic analyses of a large cohort of patients with AT, PC and PS deficiencies and to relate this knowledge to clinical application. We genotyped a large cohort of 709 unrelated patients with AT (231), PC (234) and PS (244) deficiencies referred to us by physicians throughout Germany. Mutations were detected by direct sequencing and multiplex ligation-dependent probe amplification (MLPA). The highest mutation detection rate (MDR) was found for the SERPINC1 gene (83.5%), followed by the PROC (69%) and PROS1 (43%) genes. Even at AT activities close to the normal range (75%), the MDR was 70%. Contrastingly, for PC and PS deficiencies, the MDR dropped significantly and mildly lowered to subnormal values. At PS activities >55% for PS no mutations were detected. Mutation profiles of all three genes were similar with the highest prevalence for missense mutations (63-78%), followed by nonsense (7-11%), splice-site mutations (7-13%), small deletions (1-8%), small insertions/duplications (1-4%) and large deletions (3-6%). In conclusion, genetic testing is a useful diagnostic tool for diagnosing thrombophilia. Based on our data, genetic analysis for patients with AT deficiency is indicated for all subnormal activities. In contrast, genotyping is not advisable for PC activities >70% and for PS activities >55%.

The induction of epigenetic regulation of PROS1 gene in lung fibroblasts by gold nanoparticles and implications for potential lung injury

Advances in nanotechnology have given rise to the rapid development of novel applications in biomedicine. However, our understanding in the risks and health safety of nanomaterials is still not complete and various investigations are ongoing. Here, we show that gold nanoparticles (AuNPs) significantly altered the expression of 19 genes in human fetal lung fibroblasts (using the Affymetrix Human Gene 1.0 ST Array). Among the differentially expressed genes, up-regulation of microRNA-155 (miR-155) was observed concomitant with down-regulation of the PROS1 gene. Silencing of miR-155 established PROS1 as its possible target gene. DNA methylation profiling analysis of the PROS1 gene revealed no changes in the methylation status of this gene in AuNP-treated fibroblasts. At the ultrastructural level, chromatin condensation and reorganization was observed in the nucleus of fibroblasts exposed to AuNPs. The findings provide further insights into the molecular mechanisms underlying toxicity of AuNPs and their impact on epigenetic processes.

Protein S abnormalities: a diagnostic nightmare

Heterozygous deficiency of Protein S (PS) increases the risk for developing thrombosis. Many acquired conditions alter plasma PS levels. These complex interactions of PS in plasma make it imperative that clinical PS assay limitations are understood so that the assays are reliable, reproducible and specific to diagnose true genetic abnormalities based on plasma phenotype alone. Unfortunately, the diagnosis of PS deficiency is difficult and complicated. Three basic assays can be utilized for assessing PS in plasma: PS activity assay, Free PS antigen assay, and Total PS antigen assay. This article will review these clinical assays and their associated problems. We also discuss the confounding and interfering factors that make it difficult to obtain an accurate diagnosis of PS deficiency.

C4BPB/C4BPA is a new susceptibility locus for venous thrombosis with unknown protein S-independent mechanism: results from genome-wide association and gene expression analyses followed by case-control studies

Through its binding with protein S (PS), a key element of the coagulation/fibrinolysis cascade, the C4b-binding protein (C4BP) has been hypothesized to be involved in the susceptibility to venous thrombosis (VT). To identify genetic factors that may influence the plasma levels of the 3 C4BP existing isoforms, alpha(7)beta(1), alpha(6)beta(1), and alpha(7)beta(0), we conducted a genome-wide association study by analyzing 283 437 single nucleotide polymorphisms (SNPs) in the Genetic Analysis of Idiopathic Thrombophilia (GAIT) study composed of 352 persons. Three SNPs at the C4BPB/C4BPA locus were found genome-wide significantly associated with alpha(7)beta(0) levels. One of these SNPs was further found to explain approximately 11% of the variability of mRNA C4BPA expression in the Gutenberg Heart Study composed of 1490 persons, with no effect on C4BPB mRNA expression. The allele associated with increased alpha(7)beta(0) plasma levels and increased C4BPA expression was further found associated with increased risk of VT (odds ratio [OR] = 1.24 [1.03-1.53]) in 2 independent case-control studies (MARseille THrombosis Association study [MARTHA] and FActeurs de RIsque et de récidives de la maladie thromboembolique VEineuse [FARIVE]) gathering 1706 cases and 1379 controls. This SNP was not associated with free PS or total PS. In conclusion, we observed strong evidence that the C4BPB/C4BPA locus is a new susceptibility locus for VT through a PS-independent mechanism that remains to be elucidated.

Selective testing for thrombophilia in patients with first venous thrombosis: results from a retrospective family cohort study on absolute thrombotic risk for currently known thrombophilic defects in 2479 relatives

Thrombophilia screening is controversial. In a retrospective family cohort, where probands had thrombosis and a thrombophilic defect, 2479 relatives were tested for thrombophilia. In antithrombin-, protein C–, and protein S–deficient relatives, annual incidences of venous thrombosis were 1.77% (95% CI, 1.14-2.60), 1.52% (95% CI, 1.06-2.11), and 1.90% (95% CI, 1.32-2.64), respectively, at a median age of 29 years and a positive family history of more than 20% symptomatic relatives. In relatives with factor V (FV) Leiden, prothrombin 20210G>A, or high FVIII levels, these were 0.49% (95% CI, 0.39-0.60), 0.34% (95% CI, 0.22-0.49), and 0.49% (95% CI, 0.41-0.51), respectively. High FIX, FXI, and TAFI, and hyperhomocysteinemia were not independent risk factors. Annual incidence of major bleeding in antithrombin-, protein C–, or protein S–deficient relatives on anticoagulants was 0.29% (95% CI, 0.03-1.04). Cumulative recurrence rates in relatives with antithrombin, protein C, or protein S deficiency were 19% at 2 years, 40% at 5 years, and 55% at 10 years. In relatives with FV Leiden, prothrombin 20210G>A, or high levels FVIII, these were 7%, 11%, and 25%, respectively. Considering its clinical implications, thrombophilia testing should address hereditary deficiencies of antithrombin, protein C, and protein S in patients with first venous thrombosis at young age and/or a strong family history of venous thrombosis.