RESUMO
Antithrombin deficiency, the most severe congenital thrombophilia, might be underestimated, as some pathogenic variants are not detected by routine functional methods. We have identified 2 new SERPINC1 variants, p.Glu227Lys and p.Asn224His, in 4 unrelated thrombophilic patients with early and recurrent thrombosis that had normal antithrombin activity. In one case, the mutation was identified by whole genome sequencing, while in the 3 remaining cases, the mutation was identified by sequencing SERPINC1 based on a single functional positive finding supporting deficiency. The 2 variants shared a common functional defect, an impaired or null N-glycosylation of Asn224 according to a eukaryotic expression model. Carriers had normal anti-FXa or anti-FIIa activities but impaired anti-FVIIa activity and a detectable loss of inhibitory function when incubating the plasma for 1 hour at 41°C. Moreover, the ß glycoform of the variants, lacking 2 N-glycans, had reduced secretion, increased heparin affinity, no inhibitory activity, and a potential dominant-negative effect. These results explain the increased thrombin generation observed in carriers. Mutation experiments reflected the role that Lysine residues close to the N-glycosylation sequon have in impairing the efficacy of N-glycosylation. Our study shows new elements involved in the regulation of N-glycosylation, a key posttranslational modification that, according to our results, affects folding, secretion, and function, providing new evidence of the pathogenic consequence of an incorrect N-glycosylation of antithrombin. This study supports that antithrombin deficiency is underestimated and encourages the development of new functional and genetic tests to diagnose this severe thrombophilia.
Assuntos
Deficiência de Antitrombina III , Antitrombina III , Antitrombina III/genética , Antitrombina III/metabolismo , Deficiência de Antitrombina III/diagnóstico , Deficiência de Antitrombina III/genética , Variação Genética , Glicosilação , Heparina/metabolismo , HumanosRESUMO
Multiplex ligation-dependent probe amplification (MLPA) identifies genetic structural variants in SERPINC1 in 5% of cases with antithrombin deficiency (ATD), the most severe congenital thrombophilia. Our aim was to unravel the utility and limitations of MLPA in a large cohort of unrelated patients with ATD (N = 341). MLPA identified 22 structural variants (SVs) causing ATD (6.5%). MLPA did not detect SVs affecting introns (four cases), and the diagnosis was inaccurate in two cases according to long-range PCR or nanopore sequencing. MLPA was used to detect possible hidden SVs in 61 cases with type I deficiency with single nucleotide variations (SNVs) or small insertion/deletion (INDEL). One case had a false deletion of exon 7, as the 29-bp deletion affected an MLPA probe. We evaluated 32 variants affecting MLPA probes: 27 SNVs and 5 small INDELs. In three cases, MLPA gave false-positive results, all diagnosed as deletions of the affected exon: a small INDEL complex, and two SNVs affecting MLPA probes. Our study confirms the utility of MLPA to detect SVs in ATD, but also shows some limitations in detecting intronic SVs. MLPA renders imprecise and false-positive results for genetic defects which affect MLPA probes. Our results encourage the validation of MLPA results.
Assuntos
Trombofilia , Humanos , Trombofilia/genética , Éxons , Reação em Cadeia da Polimerase Multiplex/métodos , Íntrons , Nucleotídeos , AntitrombinasRESUMO
Antiphospholipid syndrome (APS) is a thromboinflammatory disorder caused by circulating antiphospholipid autoantibodies (aPL) and characterized by an increased risk of thrombotic events. The pathogenic mechanisms of these antibodies are complex and not fully understood, but disturbances in coagulation and fibrinolysis have been proposed to contribute to the thrombophilic state. This study aims to evaluate the role of an emerging hemostatic molecule, FXI, in the thrombotic risk of patients with aPL. Cross-sectional and observational study of 194 consecutive and unrelated cases with aPL recruited in a single center: 82 asymptomatic (AaPL) and 112 with primary antiphospholipid syndrome (APS). Clinical and epidemiological variables were collected. The profile of aPL was determined. Plasma FXI was evaluated by Western blotting and two coagulation assays (FXI:C). In cases with low FXI, molecular analysis of the F11 gene was performed. FXI:C levels were significantly higher in patients with APS than in patients with AaPL (122.8 ± 33.4 vs. 104.5 ± 27.5; p < 0.001). Multivariate analysis showed a significant association between symptomatic patients with aPL (APS) and high FXI (>150%) (OR = 11.57; 95% CI: 1.47-90.96; p = 0.020). In contrast, low FXI (<70%), mostly caused by inhibitors, was less frequent in the group of patients with APS compared to AaPL (OR = 0.17; 95%CI: 0.36-0.86; p = 0.032). This study suggests that FXI levels may play a causal role in the prothrombotic state induced by aPLs and holds the promise of complementary treatments in APS patients by targeting FXI.
Assuntos
Síndrome Antifosfolipídica , Trombose , Humanos , Fator XI , Estudos Transversais , Anticorpos Antifosfolipídeos , Trombose/etiologiaRESUMO
Antithrombin deficiency, the most severe thrombophilia, might be underestimated, since it is only investigated in cases with consistent functional deficiency or family history. We have analyzed 444 consecutive, unrelated cases, from 1998 to 2021, with functional results supporting antithrombin deficiency in at least one sample. Plasma antithrombin was evaluated by functional and biochemical methods in at least two samples. SERPINC1 gene was analyzed by sequencing and MPLA. Hypoglycosylation was studied by electrophoresis and high-performance liquid chromatography (HPLC). In 260 of 305 cases (85.2%) with constitutive deficiency (activity < 80% in all samples), a SERPINC1 (N = 250), or N-glycosylation defect (N = 10) was observed, while 45 remained undetermined. The other 139 cases had normal antithrombin activity (≥ 80%) in at least one sample, what we called transient deficiency. Sixty-one of these cases (43.9%) had molecular defects: 48 had SERPINC1 variants, with two recurrent mutations (p.Ala416Ser[Cambridge II], N = 15; p.Val30Glu[Dublin], N = 12), and 13 hypoglycosylation. Thrombotic complications occurred in transient deficiency, but were less frequent, latter-onset, and had a higher proportion of arterial events than in constitutive deficiency. Two mechanisms explained transient deficiency: The limitation of functional methods to detect some variants and the influence of external factors on the pathogenic consequences of these mutations. Our study reveals a molecular defect in a significant proportion of cases with transient antithrombin deficiency, and changes the paradigm of thrombophilia, as the pathogenic effect of some mutations might depend on external factors and be present only at certain timepoints. Antithrombin deficiency is underestimated, and molecular screening might be appropriate in cases with fluctuating laboratory findings.
Assuntos
Deficiência de Antitrombina III/diagnóstico , Trombofilia/congênito , Adulto , Antitrombina III/genética , Deficiência de Antitrombina III/genética , Feminino , Variação Genética , Humanos , Masculino , Pessoa de Meia-Idade , Trombofilia/genéticaRESUMO
Atresia of inferior vena cava (IVC) is a rare congenital malformation associated with high risk of venous thrombosis that still has unknown etiology, although intrauterine IVC thrombosis has been suggested to be involved. The identification of IVC atresia in a case with early idiopathic venous thrombosis and antithrombin deficiency caused by the homozygous SERPINC1 c.391C > T variant (p.Leu131Phe; antithrombin Budapest 3) encouraged us to evaluate the role of this severe thrombophilia in this vascular abnormality. We have done a cross-sectional study in previously identified cohorts of patients homozygous for the Budapest 3 variant (N = 61) selected from 1118 patients with congenital antithrombin deficiency identified in two different populations: Spain (N = 692) and Hungary (N = 426). Image analysis included computed tomography and phlebography. Atresia of the IVC system was observed in 17/24 cases (70.8%, 95% confidence interval [CI]: 48.9%-87.3%) homozygous for antithrombin Budapest 3 with available computed tomography (5/8 and 12/16 in the Spanish and Hungarian cohorts, respectively), 16 had an absence of infrarenal IVC and one had atresia of the left common iliac vein. All cases with vascular defects had compensatory mechanisms, azygos-hemiazygos continuation or double IVC, and seven also had other congenital anomalies. Short tandem repeat analysis supported the specific association of the IVC system atresia with SERPINC1. We show the first evidence of the association of a severe thrombophilia with IVC system atresia, supporting the possibility that a thrombosis in the developing fetal vessels is the reason for this anomaly. Our hypothesis-generating results encourage further studies to investigate severe thrombophilic states in patients with atresia of IVC.
Assuntos
Antitrombina III/genética , Trombofilia/genética , Doenças Vasculares/genética , Veia Cava Inferior/patologia , Adulto , Idoso , Estudos Transversais , Feminino , Homozigoto , Humanos , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único , Trombofilia/patologia , Doenças Vasculares/patologia , Adulto JovemRESUMO
BACKGROUND AND AIMS: Splanchnic vein thromboses (SVT) are a rare condition that can be life-threatening. The most severe thrombophilia associated to SVT is antithrombin (AT) deficiency, usually caused by SERPINC1 mutations. Although transitory AT deficiencies and congenital disorders of the N-glycosylation pathways (CDG) have been recently reported as causes of AT deficiency, the current AT clinical screening still only includes anti-FXa activity. This study aims to (a) improve the detection of AT deficiency in SVT and (b) characterize the features of AT deficiency associated with SVT. METHODS: The study was performed in 2 cohorts: (a) 89 SVT patients with different underlying etiologies but in whom AT deficiency had been ruled out by classical diagnostic methods; and (b) 271 unrelated patients with confirmed AT deficiency and venous thrombosis. AT was evaluated by functional (anti-FXa and anti-FIIa) and immunological methods (ELISA, crossed immunoelectrophoresis, western blot), and SERPINC1 sequencing was performed. RESULTS: In 4/89 patients (4.5%) additional alterations in AT were found (two had SERPINC1 mutations, one had a specific variant causing transient AT deficiency and one patient had CDG). In 11 of the 271 patients (4.1%) with AT deficiency and thrombosis, thrombosis was located at the splanchnic venous territory. CONCLUSIONS: Antithrombin deficiency may be underdiagnosed by current clinical screening techniques. Therefore, a comprehensive AT evaluation should be considered in cases of rethrombosis or doubtful interpretation of anti-FXa activity levels. SVT is a relatively common localization of the thrombotic event in patients with congenital AT deficiency.
Assuntos
Deficiência de Antitrombina III , Trombofilia , Trombose , Trombose Venosa , Deficiência de Antitrombina III/complicações , Deficiência de Antitrombina III/genética , Antitrombinas , Humanos , Circulação Esplâncnica , Trombose Venosa/genéticaRESUMO
Patients with multirefractory immune thrombocytopenia (ITP) have limited treatment options. Recent data suggest that specific anti-platelet antibodies may cause destruction of platelets by favoring platelet loss of sialic acid. In this multicenter study 35 patients with ITP, including 16 with multirefractory disease, were analyzed for antiplatelet-antibodies, thrombopoietin (TPO) levels, and platelet desialylation. In selected cases, responses to a novel treatment strategy using oseltamivir were tested. We found that antibodies against GPIbα were overrepresented in multirefractory patients compared to responders (n = 19). In contrast to conventional ITP patients, multirefractory patients exhibited a significant increased platelet activation state (granule secretion) and desialylation (RCA-1 binding) (p < 0.05), and a trend toward higher plasma TPO concentrations. The decreased sialic acid content seemed to be restricted to platelet glycoproteins, since other plasma proteins were not hypoglycosylated. A total of 10 patients with multirefractory ITP having remarkable loss of platelet terminal sialic acids were given oseltamivir phosphate. When the antiviral drug was combined with TPO receptor agonists (TPO-RAs) or with immunosuppressant drugs, platelet responses were observed in 66.7% of patients. All responding patients presented with antibodies reactive only against GPIbα. These findings suggest that desialylation may play a key pathogenic role in some multirefractory ITP patients, and provide diagnostic tools for the identification of such patients. Furthermore, we show that sialidase inhibitor treatment in combination with therapies that help to increase platelet production can induce sustained platelet responses in some patients with anti-GPIbα -mediated thrombocytopenia that have failed previous therapies.
Assuntos
Ácido N-Acetilneuramínico/metabolismo , Púrpura Trombocitopênica Idiopática , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Adulto JovemAssuntos
Antitrombinas , Efeito Fundador , Humanos , Polônia , Antitrombina III , Mutação , AnticoagulantesRESUMO
BackgroundFetal alcohol syndrome (FAS) is caused by maternal alcohol consumption during pregnancy; although additional factors might be involved, as development and severity are not directly related to alcohol intake. The abnormal glycosylation caused by alcohol might play a role in FAS according to the clinical similarities shared with congenital disorders of glycosylation (CDG). Thus, mutations underlying CDG, affecting genes involved in glycosylation, could also be involved in FAS.MethodsA panel of 74 genes involved in N-glycosylation was sequenced in 25 FAS patients and 20 controls with prenatal alcohol exposure. Transferrin glycoforms were evaluated by HPLC.ResultsRare (minor allele frequency<0.009) missense/splice site variants were more frequent in FAS than controls (84% vs. 50%; P=0.034, odds ratio: 5.25, 95% confidence interval: 1.3-20.9). Remarkably, three patients, but no controls, carried variants with functional effects identified in CDG patients. Moreover, the patient with the most severe clinical phenotype was the only one carrying two variants with functional effects. Family studies support that the combination of a genetic defect and alcohol consumption during pregnancy might have a role in FAS development.ConclusionsOur study supports that the rare variants of genes involved in N-glycosylation could play a role in the development and severity of FAS under prenatal alcohol exposure.
Assuntos
Defeitos Congênitos da Glicosilação/genética , Transtornos do Espectro Alcoólico Fetal/genética , Predisposição Genética para Doença , Mutação , Adolescente , Adulto , Alelos , Estudos de Casos e Controles , Criança , Pré-Escolar , Cromatografia Líquida de Alta Pressão , Defeitos Congênitos da Glicosilação/complicações , Feminino , Variação Genética , Glicosilação , Humanos , Lactente , Masculino , Exposição Materna , Pessoa de Meia-Idade , Mães , Razão de Chances , Gravidez , Estudos Retrospectivos , Análise de Sequência de DNA , Transferrina/químicaAssuntos
COVID-19/sangue , Trombofilia/sangue , Trombose/sangue , Adulto , Idoso , Antitrombina III/genética , Deficiência de Antitrombina III/sangue , Deficiência de Antitrombina III/complicações , Deficiência de Antitrombina III/genética , COVID-19/complicações , COVID-19/fisiopatologia , Estudos de Coortes , Deficiência do Fator V/sangue , Deficiência do Fator V/complicações , Deficiência do Fator V/genética , Feminino , Produtos de Degradação da Fibrina e do Fibrinogênio , Humanos , Hipoprotrombinemias/sangue , Hipoprotrombinemias/complicações , Hipoprotrombinemias/genética , Unidades de Terapia Intensiva/estatística & dados numéricos , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Mortalidade , Projetos Piloto , Proteína C/genética , Deficiência de Proteína C/sangue , Deficiência de Proteína C/complicações , Deficiência de Proteína C/genética , Proteína S/genética , Deficiência de Proteína S/sangue , Deficiência de Proteína S/complicações , Deficiência de Proteína S/genética , Síndrome do Desconforto Respiratório/sangue , Síndrome do Desconforto Respiratório/fisiopatologia , SARS-CoV-2 , Índice de Gravidade de Doença , Trombofilia/complicações , Trombofilia/genética , Trombofilia/fisiopatologia , Trombose/fisiopatologiaAssuntos
Ciclo-Oxigenase 1/genética , Transtornos Hemorrágicos/genética , Mutação com Perda de Função , Mutação de Sentido Incorreto , Ativação Plaquetária/genética , Processamento de Proteína Pós-Traducional/genética , Adolescente , Povo Asiático/genética , Ciclo-Oxigenase 1/deficiência , Ciclo-Oxigenase 1/metabolismo , Feminino , Genes Dominantes , Glicosilação , Células HEK293 , Transtornos Hemorrágicos/sangue , Heterozigoto , Humanos , Fenótipo , Ativação Plaquetária/fisiologiaRESUMO
The balance between actions of procoagulant and anticoagulant factors protects organisms from bleeding and thrombosis. Thus, antithrombin deficiency increases the risk of thrombosis, and complete quantitative deficiency results in intrauterine lethality. However, patients homozygous for L99F or R47C antithrombin mutations are viable. These mutations do not modify the folding or secretion of the protein, but abolish the glycosaminoglycan-induced activation of antithrombin by affecting the heparin-binding domain. We speculated that the natural ß-glycoform of antithrombin might compensate for the effect of heparin-binding mutations. We purified α- and ß-antithrombin glycoforms from plasma of 2 homozygous L99F patients. Heparin affinity chromatography and intrinsic fluorescence kinetic analyses demonstrated that the reduced heparin affinity of the α-L99F glycoform (K(D), 107.9 ± 3nM) was restored in the ß-L99F glycoform (K(D), 53.9 ± 5nM) to values close to the activity of α-wild type (K(D), 43.9 ± 0.4nM). Accordingly, the ß-L99F glycoform was fully activated by heparin. Similar results were observed for recombinant R47C and P41L, other heparin-binding antithrombin mutants. In conclusion, we identified a new type of mosaicism associated with mutations causing heparin-binding defects in antithrombin. The presence of a fully functional ß-glycoform together with the activity retained by these variants helps to explain the viability of homozygous and the milder thrombotic risk of heterozygous patients with these specific antithrombin mutations.
Assuntos
Deficiência de Antitrombina III/genética , Antitrombina III/genética , Antitrombina III/metabolismo , Heparina/metabolismo , Mutação/genética , Processamento de Proteína Pós-Traducional , Trombose/genética , Sítios de Ligação , Cromatografia de Afinidade , DNA/genética , Heterozigoto , Homozigoto , Humanos , Cinética , Masculino , Mosaicismo , Linhagem , Reação em Cadeia da Polimerase , Ligação Proteica , Conformação Proteica , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Trombose/metabolismo , Trombose/patologiaAssuntos
Antitrombinas/sangue , Defeitos Congênitos da Glicosilação/diagnóstico , Defeitos Congênitos da Glicosilação/genética , Manose-6-Fosfato Isomerase/genética , Mutação , Fenótipo , Alelos , Biópsia , Defeitos Congênitos da Glicosilação/terapia , Análise Mutacional de DNA , Feminino , Estudos de Associação Genética , Predisposição Genética para Doença , Glicosilação , Humanos , Intestinos/patologia , Masculino , Pessoa de Meia-Idade , LinhagemRESUMO
BACKGROUND: Developmental haemostatic studies may help identifying new elements involved in the control of key haemostatic proteins like antithrombin, the most relevant endogenous anticoagulant. RESULTS: In this study, we showed a significant reduction of sialic acid content in neonatal antithrombin compared with adult antithrombin in mice. mRNA levels of St3gal3 and St3gal4, two sialyltransferases potentially involved in antithrombin sialylation, were 85% lower in neonates in comparison with adults. In silico analysis of miRNAs overexpressed in neonates revealed that mir-200a might target these sialyltransferases. Moreover, in vitro studies in murine primary hepatocytes sustain this potential control. CONCLUSIONS: These data suggest that in addition to the direct protein regulation, microRNAs may also modulate qualitative traits of selected proteins by an indirect control of post-translational processes.
Assuntos
Antitrombinas/metabolismo , MicroRNAs/metabolismo , Processamento de Proteína Pós-Traducional , Fatores Etários , Animais , Animais Recém-Nascidos , Perfilação da Expressão Gênica , Hepatócitos/metabolismo , Camundongos , MicroRNAs/genética , Ácido N-Acetilneuramínico/metabolismo , RNA Mensageiro/metabolismo , Sialiltransferases/genética , Sialiltransferases/metabolismo , beta-Galactosídeo alfa-2,3-SialiltransferaseRESUMO
BACKGROUND: Congenital factor XI (FXI) deficiency is a probably underestimated coagulopathy that confers antithrombotic protection. Characterization of genetic defects in F11 is mainly focused on the identification of single-nucleotide variants and small insertion/deletions because they represent up to 99% of the alterations accounting for factor deficiency, with only 3 gross gene defects of structural variants (SVs) having been described. OBJECTIVES: To identify and characterize the SVs affecting F11. METHODS: The study was performed in 93 unrelated subjects with FXI deficiency recruited in Spanish hospitals over a period of 25 years (1997-2022). F11 was analyzed by next-generation sequencing, multiplex ligand probe amplification, and long-read sequencing. RESULTS: Our study identified 30 different genetic variants. Interestingly, we found 3 SVs, all heterozygous: a complex duplication affecting exons 8 and 9, a tandem duplication of exon 14, and a large deletion affecting the whole gene. Nucleotide resolution obtained by long-read sequencing revealed Alu repetitive elements involved in all breakpoints. The large deletion was probably generated de novo in the paternal allele during gametogenesis, and despite affecting 30 additional genes, no syndromic features were described. CONCLUSION: SVs may account for a high proportion of F11 genetic defects implicated in the molecular pathology of congenital FXI deficiency. These SVs, likely caused by a nonallelic homologous recombination involving repetitive elements, are heterogeneous in both type and length and may be de novo. These data support the inclusion of methods to detect SVs in this disorder, with long-read-based methods being the most appropriate because they detect all SVs and achieve adequate nucleotide resolution.
Assuntos
Deficiência do Fator XI , Fator XI , Humanos , Éxons , Fator XI/genética , Deficiência do Fator XI/diagnóstico , Deficiência do Fator XI/genética , Heterozigoto , NucleotídeosRESUMO
Mutations affecting mobile domains of antithrombin induce conformational instability resulting in protein polymerization that associates with a severe clinical phenotype, probably by an unknown gain of function. By homology with other conformational diseases, we speculated that these variants might infect wild-type (WT) monomers reducing the anticoagulant capacity. Infective polymerization of WT polymers and different P1 mutants (p.R425del, p.R425C and p.R425H) were evaluated by using native gels and radiolabeled WT monomers and functional assays. Human embryonic kidney cells expressing the Epstein-Barr nuclear antigen 1 (HEK-EBNA) cells expressing inducible (p.R425del) or two novel constitutive (p.F271S and p.M370T) conformational variants were used to evaluate intracellular and secreted antithrombin under mild stress (pH 6.5 and 39°C for 5 h). We demonstrated the conformational sensitivity of antithrombin London (p.R425del) to form polymers under mild heating. Under these conditions purified antithrombin London recruited WT monomers into growing polymers, reducing the anticoagulant activity. This process was also observed in the plasma of patients with p.R425del, p.R425C and p.R425H mutations. Under moderate stress, coexpression of WT and conformational variants in HEK-EBNA cells increased the intracellular retention of antithrombin and the formation of disulfide-linked polymers, which correlated with impaired secretion and reduction of anticoagulant activity in the medium. Therefore, mutations inducing conformational instability in antithrombin allow its polymerization with the subsequent loss of function, which under stress could sequestrate WT monomers, resulting in a new prothrombotic gain of function, particularly relevant for intracellular antithrombin. The in vitro results suggest a temporal and severe plasma antithrombin deficiency that may contribute to the development of the thrombotic event and to the clinical severity of these mutations.
Assuntos
Deficiência de Antitrombina III/metabolismo , Proteínas Antitrombina/química , Proteínas Antitrombina/metabolismo , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Proteínas Antitrombina/genética , Linhagem Celular , Humanos , Conformação Proteica , Multimerização Proteica , Estabilidade Proteica , Estresse FisiológicoRESUMO
Antithrombin, a major endogenous anticoagulant, is a serine protease inhibitor (serpin). We characterized the biological and clinical impact of variants involving C-terminal antithrombin. We performed comprehensive molecular, cellular, and clinical characterization of patients with C-terminal antithrombin variants from a cohort of 444 unrelated individuals with confirmed antithrombin deficiency. We identified 17 patients carrying 12 C-terminal variants, 5 of whom had the p.Arg445Serfs*17 deletion. Five missense variants caused qualitative deficiency, and 7, including 4 insertion-deletion variants, induced severe quantitative deficiency, particularly p.Arg445Serfs*17 (antithrombin <40%). This +1 frameshift variant had a molecular size similar to that of WT antithrombin but possessed a different C-terminus. Morphologic and cotransfection experiments showed that recombinant p.Arg445Serfs*17 was retained at the endoplasmic reticulum and had a dominant-negative effect on WT antithrombin. Characterization of different 1+ frameshift, aberrant C-terminal variants revealed that protein secretion was determined by frameshift site. The introduction of Pro441 in the aberrant C-terminus, shared by 5 efficiently secreted variants, partially rescued p.Arg445Serfs*17 secretion. C-terminal antithrombin mutants have notable heterogeneity, related to variant type and localization. Aberrant C-terminal variants caused by 1+ frameshift, with similar size as WT antithrombin, may be secreted or not, depending on frameshift site. The severe clinical phenotypes of these genetic changes are consistent with their dominant-negative effects.
Assuntos
Antitrombinas , Serpinas , Antitrombina III/genética , Antitrombina III/metabolismo , Antitrombinas/metabolismo , Retículo Endoplasmático/genética , Retículo Endoplasmático/metabolismo , Inibidores de Serina Proteinase , Serpinas/genéticaRESUMO
Background: Aortic valve replacement is the gold standard treatment for severe symptomatic aortic stenosis, but thrombosis of bioprosthetic valves (PVT) remains a concern. Objective: To analyze the factors involved in the contact pathway during aortic valve replacement and to assess their impact on the development of thromboembolic complications. Methods: The study was conducted in 232 consecutive patients who underwent: transcatheter aortic valve replacement (TAVR, N = 155), and surgical valve replacement (SAVR, N = 77) (MUVITAVI project). Demographic and clinical data, outcomes including a combined end point (CEP) of thrombotic events, and imaging controls were recruited. Samples were collected 24 h before and 48 h after valve replacement. FXII, FXI and (pre)kallikrein were evaluated by Western Blot and specific ELISA with nanobodies. Results: The CEP of thrombotic events was reached by 19 patients: 13 patients presented systemic embolic events and 6 patients subclinical PVT. Valve replacement did not cause FXII activation or generation of kallikrein. There was a significant reduction of FXI levels associated with the procedure, which was statistically more pronounced in SAVR than in TAVR. Cases with reductions of FXI below 80% of basal values had a lower incidence of embolic events during the procedure than patients in whom FXI increased above 150%: 2.7 vs. 16.7%; p: 0.04. Conclusion: TAVR or SAVR did not significantly activate the contact pathway. A significant reduction of FXI, was observed, particularly in SAVR, associated with lower incidence of thrombotic events. These results encourage evaluating the usefulness and safety of FXI-directed antithrombotic treatments in these patients.