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Sillen M, Declerck PJ. Thrombin Activatable Fibrinolysis Inhibitor (TAFI): An Updated Narrative Review. Int J Mol Sci 2021; 22:ijms22073670. [PMID: 33916027 PMCID: PMC8036986 DOI: 10.3390/ijms22073670] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 03/26/2021] [Accepted: 03/29/2021] [Indexed: 01/02/2023] Open
Abstract
Thrombin activatable fibrinolysis inhibitor (TAFI), a proenzyme, is converted to a potent attenuator of the fibrinolytic system upon activation by thrombin, plasmin, or the thrombin/thrombomodulin complex. Since TAFI forms a molecular link between coagulation and fibrinolysis and plays a potential role in venous and arterial thrombotic diseases, much interest has been tied to the development of molecules that antagonize its function. This review aims at providing a general overview on the biochemical properties of TAFI, its (patho)physiologic function, and various strategies to stimulate the fibrinolytic system by interfering with (activated) TAFI functionality.
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2
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Claesen K, Mertens JC, Leenaerts D, Hendriks D. Carboxypeptidase U (CPU, TAFIa, CPB2) in Thromboembolic Disease: What Do We Know Three Decades after Its Discovery? Int J Mol Sci 2021; 22:ijms22020883. [PMID: 33477318 PMCID: PMC7830380 DOI: 10.3390/ijms22020883] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/12/2021] [Accepted: 01/13/2021] [Indexed: 02/01/2023] Open
Abstract
Procarboxypeptidase U (proCPU, TAFI, proCPB2) is a basic carboxypeptidase zymogen that is converted by thrombin(-thrombomodulin) or plasmin into the active carboxypeptidase U (CPU, TAFIa, CPB2), a potent attenuator of fibrinolysis. As CPU forms a molecular link between coagulation and fibrinolysis, the development of CPU inhibitors as profibrinolytic agents constitutes an attractive new concept to improve endogenous fibrinolysis or to increase the efficacy of thrombolytic therapy in thromboembolic diseases. Furthermore, extensive research has been conducted on the in vivo role of CPU in (the acute phase of) thromboembolic disease, as well as on the hypothesis that high proCPU levels and the Thr/Ile325 polymorphism may cause a thrombotic predisposition. In this paper, an overview is given of the methods available for measuring proCPU, CPU, and inactivated CPU (CPUi), together with a summary of the clinical data generated so far, ranging from the current knowledge on proCPU concentrations and polymorphisms as potential thromboembolic risk factors to the positioning of different CPU forms (proCPU, CPU, and CPUi) as diagnostic markers for thromboembolic disease, and the potential benefit of pharmacological inhibition of the CPU pathway.
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3
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Westbury SK, Whyte CS, Stephens J, Downes K, Turro E, Claesen K, Mertens JC, Hendriks D, Latif AL, Leishman EJ, Mutch NJ, Tait RC, Mumford AD. A new pedigree with thrombomodulin-associated coagulopathy in which delayed fibrinolysis is partially attenuated by co-inherited TAFI deficiency. J Thromb Haemost 2020; 18:2209-2214. [PMID: 32634856 DOI: 10.1111/jth.14990] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 06/10/2020] [Accepted: 06/15/2020] [Indexed: 01/27/2023]
Abstract
BACKGROUND Thrombomodulin-associated coagulopathy (TM-AC) is a rare bleeding disorder in which a single reported p.Cys537* variant in the thrombomodulin gene THBD causes high plasma thrombomodulin (TM) levels. High TM levels attenuate thrombin generation and delay fibrinolysis. OBJECTIVES To report the characteristics of pedigree with a novel THBD variant causing TM-AC, and co-inherited deficiency of thrombin-activatable fibrinolysis inhibitor (TAFI). PATIENTS/METHODS Identification of pathogenic variants in hemostasis genes by next-generation sequencing and case recall for deep phenotyping. RESULTS Pedigree members with a previously reported THBD variant predicting p.Pro496Argfs*10 and chain truncation in TM transmembrane domain had abnormal bleeding and greatly increased plasma TM levels. Affected cases had attenuated thrombin generation and delayed fibrinolysis similar to previous reported TM_AC cases with THBD p.Cys537*. Coincidentally, some pedigree members also harbored a stop-gain variant in CPB2 encoding TAFI. This reduced plasma TAFI levels but was asymptomatic. Pedigree members with TM-AC caused by the p.Pro496Argfs*10 THBD variant and also TAFI deficiency had a partially attenuated delay in fibrinolysis, but no change in the defective thrombin generation. CONCLUSIONS These data extend the reported genetic repertoire of TM-AC and establish a common molecular pathogenesis arising from high plasma levels of TM extra-cellular domain. The data further confirm that the delay in fibrinolysis associated with TM-AC is directly linked to increased TAFI activation. The combination of the rare variants in the pedigree members provides a unique genetic model to develop understanding of the thrombin-TM system and its regulation of TAFI.
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Affiliation(s)
- Sarah K Westbury
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - Claire S Whyte
- Aberdeen Cardiovascular and Diabetes Centre, Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen, UK
| | | | - Kate Downes
- Department of Haematology, University of Cambridge, Cambridge, UK
- East Midlands and East of England Genomic Laboratory Hub, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Ernest Turro
- Department of Haematology, University of Cambridge, Cambridge, UK
| | - Karen Claesen
- Laboratory of Medical Biochemistry, University of Antwerp, Antwerp, Belgium
| | - Joachim C Mertens
- Laboratory of Medical Biochemistry, University of Antwerp, Antwerp, Belgium
| | - Dirk Hendriks
- Laboratory of Medical Biochemistry, University of Antwerp, Antwerp, Belgium
| | | | - Emma J Leishman
- Department of Haematology, Glasgow Royal Infirmary, Glasgow, UK
| | - Nicola J Mutch
- Aberdeen Cardiovascular and Diabetes Centre, Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen, UK
| | - R Campbell Tait
- Department of Haematology, Glasgow Royal Infirmary, Glasgow, UK
| | - Andrew D Mumford
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
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4
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Rattanawan C, Komanasin N, Settasatian N, Settasatian C, Kukongviriyapan U, Intharapetch P, Senthong V. Association of TAFI gene polymorphisms with severity of coronary stenosis in stable coronary artery disease. Thromb Res 2018; 171:171-176. [PMID: 30321704 DOI: 10.1016/j.thromres.2018.10.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 09/26/2018] [Accepted: 10/01/2018] [Indexed: 01/29/2023]
Abstract
INTRODUCTION Coronary stenosis is a consequence of atherosclerotic plaque progression that is associated with impaired fibrinolysis. Thrombin-activatable fibrinolysis inhibitor (TAFI) and plasminogen activator inhibitor 1 (PAI-1) are fibrinolysis inhibitors whose levels are influenced by acquired conditions and by polymorphisms. This study therefore aimed to investigate the association of TAFI and PAI-1 gene polymorphisms with severity of coronary stenosis in subjects with stable coronary artery disease (CAD). MATERIALS AND METHODS A total of 327 subjects suspected with CAD who underwent a coronary angiogram were recruited. Gensini score was applied to stratify the severity of coronary stenosis. Based on the Gensini score, the subjects were categorized into low-medium (<20) or high (≥20) groups. The study polymorphisms included TAFI Ala147Thr (505G/A), Thr325Ile (1040C/T), +1542C/G, +1583T/A and PAI-1 -675 4G/5G. Most polymorphisms were genotyped by allele-specific polymerase chain reaction, except for TAFI Thr325Ile that was genotyped by polymerase chain reaction-restriction fragment length polymorphism. RESULTS A significant increase in the Gensini score was found in TAFI 505A and +1583A allele carriers. Binary regression analysis revealed the independent association of the TAFI 505G/A and +1583T/A polymorphisms with a high Gensini score [adjusted OR = 1.67 (95% CI: 1.03, 2.73) and 1.69 (95% CI: 1.04, 2.76), respectively]. Neither the homozygous PAI-1 -675 4G/4G nor the heterozygous 4G/5G was associated with a high Gensini score. CONCLUSIONS The results indicated the contribution of TAFI polymorphisms to atherosclerosis progression and severity of coronary stenosis in stable CAD.
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Affiliation(s)
- Chutima Rattanawan
- Biomedical Sciences Program, Graduate School, Khon Kaen University, Khon Kaen, Thailand; Cardiovascular Research Group, Khon Kaen University, Khon Kaen, Thailand
| | - Nantarat Komanasin
- Cardiovascular Research Group, Khon Kaen University, Khon Kaen, Thailand; Department of Clinical Microscopy, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand.
| | - Nongnuch Settasatian
- Cardiovascular Research Group, Khon Kaen University, Khon Kaen, Thailand; Department of Clinical Chemistry, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand
| | - Chatri Settasatian
- Cardiovascular Research Group, Khon Kaen University, Khon Kaen, Thailand; Department of Pathology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Upa Kukongviriyapan
- Cardiovascular Research Group, Khon Kaen University, Khon Kaen, Thailand; Department of Physiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Pongsak Intharapetch
- Cardiovascular Research Group, Khon Kaen University, Khon Kaen, Thailand; Queen Sirikit Heart Center of the Northeast, Khon Kaen University, Khon Kaen, Thailand
| | - Vichai Senthong
- Cardiovascular Research Group, Khon Kaen University, Khon Kaen, Thailand; Department of Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
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5
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Abstract
Development and standardization of fibrinolysis methods have progressed more slowly than coagulation testing and routine high-throughput screening tests for fibrinolysis are still lacking. In laboratory research, a variety of approaches are available and are applied to understand the regulation of fibrinolysis and its contribution to the hemostatic balance. Fibrinolysis in normal blood is slow to develop. For practical purposes plasminogen activators can be added to clotting plasma, or euglobulin prepared to reduce endogenous inhibitors, but results are complicated by these manipulations. Observational studies to identify a 'fibrinolysis deficit' have concluded that excess fibrinolysis inhibitors, plasminogen activator inhibitor 1 (PAI-1) or thrombin-activatable fibrinolysis inhibitor (TAFI), zymogen or active enzyme, may be associated with an increased risk of thrombosis. However, results are not always consistent and problems of adequate standardization are evident with these inhibitors and also for measurement of fibrin degradation products (D-dimer). Few methods are available to investigate fibrinolysis under flow, or in whole blood, but viscoelastic methods (VMs) such as ROTEM and TEG do permit the contribution of cells, and importantly platelets, to be explored. VMs are used to diagnose clinical hyperfibrinolysis, which is associated with high mortality. There is a debate on the usefulness of VMs as a point-of-care test method, particularly in trauma. Despite the difficulties of many fibrinolysis methods, research on the fibrinolysis system, taking in wider interactions with hemostasis proteins, is progressing so that in future we may have more complete models and better diagnostic methods and therapeutics.
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Affiliation(s)
- C. Longstaff
- Biotherapeutics DivisionNational Institute for Biological Standards and ControlSouth MimmsUK
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6
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Stanne TM, Olsson M, Lorentzen E, Pedersen A, Gummesson A, Gils A, Jood K, Engström G, Melander O, Declerck PJ, Jern C. A Genome-wide Study of Common and Rare Genetic Variants Associated with Circulating Thrombin Activatable Fibrinolysis Inhibitor. Thromb Haemost 2018; 118:298-308. [PMID: 29378355 PMCID: PMC6260132 DOI: 10.1160/th17-04-0249] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Thrombin-activatable fibrinolysis inhibitor (TAFI) plays a central role in haemostasis, and plasma TAFI concentrations are heritable. Candidate gene studies have identified several variants within the gene encoding TAFI,
CPB2
, that explain part of the estimated heritability. Here, we describe an exploratory genome-wide association study to identify novel variants within and outside of the
CPB2
locus that influence plasma concentrations of intact TAFI and/or the extent of TAFI activation (measured by released TAFI activation peptide, TAFI-AP) amongst 3,260 subjects from Southern Sweden. We also explored the role of rare variants on the HumanExome BeadChip. We confirmed the association with previously reported common variants in
CPB2
for both intact TAFI and TAFI-AP, and discovered novel associations with variants in putative
CPB2
enhancers. We identified a gene-based association with intact TAFI at
CPB2
(
PSKAT-O
= 2.8 × 10
−8
), driven by two novel rare nonsynonymous single nucleotide polymorphisms (SNPs; I420N and D177G). Carriers of the rare variant of D177G (rs140446990; MAF 0.2%) had lower intact TAFI and TAFI-AP concentrations compared with non-carriers (intact TAFI, geometric mean 53 vs. 78%,
PT-test
=
5 × 10
−7
; TAFI-AP 63 vs. 99%,
PT-test
= 7.2 × 10
−4
). For TAFI-AP, we identified a genome-wide significant association at an intergenic region of chromosome 3p14.1 and five gene-based associations (all
PSKAT-O
< 5 × 10
−6
). Using well-characterized assays together with a genome-wide association study and a rare-variant approach, we verified
CPB2
to be the primary determinant of TAFI concentrations and identified putative secondary loci (candidate variants and genes) associated with intact TAFI and TAFI-AP that require independent validation.
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Affiliation(s)
- Tara M Stanne
- Department of Pathology and Genetics, Institute of Biomedicine, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden
| | - Maja Olsson
- Department of Pathology and Genetics, Institute of Biomedicine, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden
| | - Erik Lorentzen
- Bioinformatics Core Facility, University of Gothenburg, Gothenburg, Sweden
| | - Annie Pedersen
- Department of Pathology and Genetics, Institute of Biomedicine, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden
| | - Anders Gummesson
- Department of Pathology and Genetics, Institute of Biomedicine, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden
| | - Ann Gils
- Laboratory for Therapeutic and Diagnostic Antibodies, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Brussels, Belgium
| | - Katarina Jood
- Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden
| | - Gunnar Engström
- Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Olle Melander
- Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Paul J Declerck
- Laboratory for Therapeutic and Diagnostic Antibodies, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Brussels, Belgium
| | - Christina Jern
- Department of Pathology and Genetics, Institute of Biomedicine, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden
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7
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Wu C, Stafford AR, Fredenburgh JC, Weitz JI, Gils A, Declerck PJ, Kim PY. Lys 42/43/44 and Arg 12 of thrombin-activable fibrinolysis inhibitor comprise a thrombomodulin exosite essential for its antifibrinolytic potential. Thromb Haemost 2017. [PMID: 28640323 DOI: 10.1160/th17-01-0054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The thrombin-thrombomodulin (TM) complex activates thrombin-activable fibrinolysis inhibitor (TAFI) more efficiently than thrombin alone. The exosite on TAFI required for its TM-dependent activation by thrombin has not been identified. Based on previous work by us and others, we generated TAFI variants with one or more of residues Lys 42, Lys 43, Lys 44 and Arg 12 within the activation peptide mutated to alanine. Mutation of one, two, or three Lys residues or the Arg residue alone decreased the catalytic efficiency of TAFI activation by thrombin-TM by 2.4-, 3.2-, 4.7-, and 15.0-fold, respectively, and increased the TAFI concentrations required for half-maximal prolongation of clot lysis times (K1/2) by 3-, 4,- 15-, and 24-fold, respectively. Mutation of all four residues decreased the catalytic efficiency of TAFI activation by 45.0-fold, increased the K1/2 by 130-fold, and abolished antifibrinolytic activity in a clot lysis assay at physiologic levels of TAFI. Similar trends in the antifibrinolytic activity of the TAFI variants were observed when plasma clots were formed using HUVECs as the source of TM. When thrombin was used as the activator, mutation of all four residues reduced the rate of activation by 1.1-fold compared with wild-type TAFI, suggesting that these mutations only impacted activation kinetics in the presence of TM. Surface plasmon resonance data suggest that mutation of the four residues abrogates TM binding with or without thrombin. Therefore, Lys 42, Lys 43, Lys 44 and Arg 12 are critical for the interaction of TAFI with the thrombin-TM complex, which modulates its antifibrinolytic potential.
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Affiliation(s)
| | | | | | | | | | | | - Paul Y Kim
- Paul Y. Kim, Thrombosis and Atherosclerosis Research Institute, 237 Barton St. East, Hamilton, Ontario, L8L 2X2, Canada, Tel.: +1 905 521 2100, Fax: +1 905 575 2646, E-mail:
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8
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Leirs K, Tewari Kumar P, Decrop D, Pérez-Ruiz E, Leblebici P, Van Kelst B, Compernolle G, Meeuws H, Van Wesenbeeck L, Lagatie O, Stuyver L, Gils A, Lammertyn J, Spasic D. Bioassay Development for Ultrasensitive Detection of Influenza A Nucleoprotein Using Digital ELISA. Anal Chem 2016; 88:8450-8. [DOI: 10.1021/acs.analchem.6b00502] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Karen Leirs
- BIOSYST-MeBioS, KU Leuven, 3001 Leuven, Belgium
| | | | | | | | | | | | - Griet Compernolle
- Laboratory
for Therapeutic and Diagnostic Antibodies, KU Leuven, 3000 Leuven, Belgium
| | | | | | | | | | - Ann Gils
- Laboratory
for Therapeutic and Diagnostic Antibodies, KU Leuven, 3000 Leuven, Belgium
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9
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Zhou X, Weeks SD, Ameloot P, Callewaert N, Strelkov SV, Declerck PJ. Elucidation of the molecular mechanisms of two nanobodies that inhibit thrombin-activatable fibrinolysis inhibitor activation and activated thrombin-activatable fibrinolysis inhibitor activity. J Thromb Haemost 2016; 14:1629-38. [PMID: 27279497 DOI: 10.1111/jth.13381] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Indexed: 11/30/2022]
Abstract
UNLABELLED Essentials Thrombin-activatable fibrinolysis inhibitor (TAFI) is a risk factor for cardiovascular disorders. TAFI inhibitory nanobodies represent a promising step in developing profibrinolytic therapeutics. We have solved three crystal structures of TAFI in complex with inhibitory nanobodies. Nanobodies inhibit TAFI through distinct mechanisms and represent novel profibrinolytic leads. SUMMARY Background Thrombin-activatable fibrinolysis inhibitor (TAFI) is converted to activated TAFI (TAFIa) by thrombin, plasmin, or the thrombin-thrombomodulin complex (T/TM). TAFIa is antifibrinolytic, and high levels of TAFIa are associated with an increased risk for cardiovascular disorders. TAFI-inhibitory nanobodies represent a promising approach for developing profibrinolytic therapeutics. Objective To elucidate the molecular mechanisms of inhibition of TAFI activation and TAFIa activity by nanobodies with the use of X-ray crystallography and biochemical characterization. Methods and results We selected two nanobodies for cocrystallization with TAFI. VHH-a204 interferes with all TAFI activation modes, whereas VHH-i83 interferes with T/TM-mediated activation and also inhibits TAFIa activity. The 3.05-Å-resolution crystal structure of TAFI-VHH-a204 reveals that the VHH-a204 epitope is localized to the catalytic moiety (CM) in close proximity to the TAFI activation site at Arg92, indicating that VHH-a204 inhibits TAFI activation by steric hindrance. The 2.85-Å-resolution crystal structure of TAFI-VHH-i83 reveals that the VHH-i83 epitope is located close to the presumptive thrombomodulin-binding site in the activation peptide (AP). The structure and supporting biochemical assays suggest that VHH-i83 inhibits TAFIa by bridging the AP to the CM following TAFI activation. In addition, the 3.00-Å-resolution crystal structure of the triple TAFI-VHH-a204-VHH-i83 complex demonstrates that the two nanobodies can simultaneously bind to TAFI. Conclusions This study provides detailed insights into the molecular mechanisms of TAFI inhibition, and reveals a novel mode of TAFIa inhibition. VHH-a204 and VHH-i83 merit further evaluation as potential profibrinolytic therapeutics.
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Affiliation(s)
- X Zhou
- Department of Pharmaceutical and Pharmacologic Sciences, Laboratory for Therapeutic and Diagnostic Antibodies, KU Leuven, Belgium
| | - S D Weeks
- Department of Pharmaceutical and Pharmacologic Sciences, Laboratory for Biocrystallography, KU Leuven, Belgium
| | - P Ameloot
- Flanders Institute for Biotechnology, Medical Biotechnology Center, Ghent, Belgium
- Department of Biochemistry and Microbiology, Laboratory for Protein Biochemistry and Biomolecular Engineering, Ghent University, Ghent, Belgium
| | - N Callewaert
- Flanders Institute for Biotechnology, Medical Biotechnology Center, Ghent, Belgium
- Department of Biochemistry and Microbiology, Laboratory for Protein Biochemistry and Biomolecular Engineering, Ghent University, Ghent, Belgium
| | - S V Strelkov
- Department of Pharmaceutical and Pharmacologic Sciences, Laboratory for Biocrystallography, KU Leuven, Belgium
| | - P J Declerck
- Department of Pharmaceutical and Pharmacologic Sciences, Laboratory for Therapeutic and Diagnostic Antibodies, KU Leuven, Belgium
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10
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Bouman AC, Cheung YW, Spronk HM, Schalkwijk CG, ten Cate H, ten Wolde M, ten Cate-Hoek AJ. Biomarkers for post thrombotic syndrome: a case-control study. Thromb Res 2014; 134:369-75. [PMID: 24975586 DOI: 10.1016/j.thromres.2014.06.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Revised: 06/06/2014] [Accepted: 06/06/2014] [Indexed: 01/08/2023]
Abstract
INTRODUCTION There is limited knowledge on the etiology of post thrombotic syndrome (PTS), although several mechanisms have been proposed. The objectives are to explore the role of different pathogenic mechanisms for PTS, through measurement of an elaborate panel of biomarkers in patients with and without PTS. MATERIALS AND METHODS Patients with a history of deep vein thrombosis (DVT) with PTS (cases) and without PTS after minimal 2years follow-up (controls), were selected from the outpatient clinic of two Dutch hospitals. As a reference to the normal population healthy individuals (HI) without a history of venous thromboembolism were invited to participate. The population consisted of: 26 cases, 27 controls, and 26 HI. A panel of predefined biomarkers was measured in venous blood. RESULTS D-dimer showed a decreasing trend from cases to controls to HI; p=0.010. Thrombin/antithrombin complex levels were significantly higher in cases than in controls; p=0.032, and HI; p=0.017. APC-ratio was significantly lower in cases compared to controls; p=0.032, and HI; p=0.011. A significant trend of increasing proTAFI from cases, to controls, and HI; p=0.002 was found. There were no differences in inflammatory markers (CRP, Interleukin-6, Interleukin-8). Thrombomodulin, tissue-plasminogen activator, and von Willebrand factor were higher in patients compared to HI. There was a significant trend of decreasing sVCAM, from cases, to controls, and HI; p=0.029. CONCLUSIONS Patients with PTS displayed increased coagulation activity, an altered pattern of fibrinolytic marker expression, and increased endothelial activation. We found no evidence of systemic inflammation in patients with PTS at 63months since the last DVT.
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Affiliation(s)
- A C Bouman
- Laboratory for Thrombosis and Hemostasis, Maastricht University Medical Centre, Universiteitssingel 50, Maastricht, the Netherlands; Department of Internal Medicine, Maastricht University Medical Centre, P.Debyelaan 25, Maastricht, the Netherlands.
| | - Y W Cheung
- Department of Internal Medicine, Flevohospital, Hospitaalweg 1, Almere, the Netherlands
| | - H M Spronk
- Laboratory for Thrombosis and Hemostasis, Maastricht University Medical Centre, Universiteitssingel 50, Maastricht, the Netherlands
| | - C G Schalkwijk
- Department of Internal Medicine, Maastricht University Medical Centre, P.Debyelaan 25, Maastricht, the Netherlands
| | - H ten Cate
- Laboratory for Thrombosis and Hemostasis, Maastricht University Medical Centre, Universiteitssingel 50, Maastricht, the Netherlands; Department of Internal Medicine, Maastricht University Medical Centre, P.Debyelaan 25, Maastricht, the Netherlands
| | - M ten Wolde
- Department of Internal Medicine, Flevohospital, Hospitaalweg 1, Almere, the Netherlands
| | - A J ten Cate-Hoek
- Laboratory for Thrombosis and Hemostasis, Maastricht University Medical Centre, Universiteitssingel 50, Maastricht, the Netherlands; Department of Internal Medicine, Maastricht University Medical Centre, P.Debyelaan 25, Maastricht, the Netherlands
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11
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Wyseure T, Declerck PJ. Novel or expanding current targets in fibrinolysis. Drug Discov Today 2014; 19:1476-82. [PMID: 24886765 DOI: 10.1016/j.drudis.2014.05.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 05/23/2014] [Indexed: 12/27/2022]
Abstract
Globally the leading cause of long-term disability and mortality stems from cardiovascular diseases, which creates an enormous economic burden. Currently available treatments for intravascular thrombosis consist of a large repertoire of antithrombotic agents targeting coagulation and platelet function. However, the only agents available to enhance fibrinolysis are recombinant or modified forms of plasminogen activators. Their clinical use is limited by low efficacy, life-threatening side-effects (primarily caused by the high systemic dose required) and the inapplicability for prophylactic use. This review provides an update on the latest advances in targeting the antifibrinolytic proteins, plasminogen activator inhibitor-1 and thrombin-activatable fibrinolysis inhibitor, and will highlight novel therapeutic avenues to enhance fibrinolysis.
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Affiliation(s)
- Tine Wyseure
- Laboratory for Therapeutic and Diagnostic Antibodies, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - Paul J Declerck
- Laboratory for Therapeutic and Diagnostic Antibodies, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium.
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12
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Semeraro F, Ammollo CT, Gils A, Declerck PJ, Colucci M. Monoclonal antibodies targeting the antifibrinolytic activity of activated thrombin-activatable fibrinolysis inhibitor but not the anti-inflammatory activity on osteopontin and C5a. J Thromb Haemost 2013; 11:2137-47. [PMID: 24134522 DOI: 10.1111/jth.12431] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Indexed: 11/29/2022]
Abstract
BACKGROUND Recently, anti-thrombin-activatable fibrinolysis inhibitor (TAFI) mAbs selectively inhibiting plasmin-mediated TAFI activation were shown to stimulate fibrinolysis in vitro and in vivo, suggesting, in contrast to other findings, that plasmin-mediated TAFI activation plays an important role in fibrinolysis regulation. OBJECTIVE To further characterize the effects of two plasmin-specific anti-TAFI mAbs (MA-TCK11A9 and MA-TCK26D6) on TAFI-dependent inhibition of fibrinolysis. METHODS AND RESULTS Both mAbs inhibited plasmin-mediated but not thrombin/thrombomodulin-mediated TAFI activation, whereas neither inhibited the cleavage of hippuryl-arginine by activated TAFI (TAFIa). They stimulated tissue-type plasminogen activator-induced fibrinolysis in different clot lysis models through a TAFI-dependent mechanism, especially in the presence of thrombomodulin (TM), a condition in which TAFI is largely activated by the thrombin-TM complex. In a fibrinolysis-based TAFIa activity assay, both mAbs inhibited TAFIa, whereas other mAbs targeting thrombin-TM-mediated TAFI activation did not. The inhibition of TAFIa activity, however, was substrate-specific, because neither mAb inhibited the cleavage of thrombin-activated osteopontin and C5a by TAFIa, thus sparing the anti-inflammatory activity of TAFIa. CONCLUSIONS Our anti-TAFI mAbs, by selectively inhibiting TAFIa activity on fibrin, may represent the prototype of a new class of TAFI inhibitors with improved pharmacologic activity.
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Affiliation(s)
- F Semeraro
- Department of Biomedical Sciences and Human Oncology, Section of General and Experimental Pathology, Aldo Moro University, Bari, Italy
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13
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Foley JH, Kim PY, Mutch NJ, Gils A. Insights into thrombin activatable fibrinolysis inhibitor function and regulation. J Thromb Haemost 2013; 11 Suppl 1:306-15. [PMID: 23809134 DOI: 10.1111/jth.12216] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Fibrinolysis is initiated when the zymogen plasminogen is converted to plasmin via the action of plasminogen activators. Proteolytic cleavage of fibrin by plasmin generates C-terminal lysine residues capable of binding both plasminogen and the plasminogen activator, thereby stimulating plasminogen activator-mediated plasminogen activation and propagating fibrinolysis. This positive feedback mechanism is regulated by activated thrombin activatable fibrinolysis inhibitor (TAFIa), which cleaves C-terminal lysine residues from the fibrin surface, thereby decreasing its cofactor activity. TAFI can be activated by thrombin alone, but the rate of activation is accelerated when in complex with thrombomodulin. Plasmin is also known to activate TAFI. TAFIa has no known physiologic inhibitors and consequently, its primary regulatory mechanism involves its intrinsic thermal instability. The rate of TAFI activation and stability of the active form, TAFIa, function in maintaining its concentration above the threshold value required to down-regulate fibrinolysis. Although all methods to quantify TAFI or TAFIa have their limitations, epidemiologic studies have indicated that elevated TAFI levels are correlated with an increased risk of venous thrombosis. Major efforts have been made to develop TAFI inhibitors that can either directly interfere with TAFIa activity or impair its activation. However, the anti-inflammatory properties of TAFIa might complicate the development and application of a TAFIa inhibitor that aims to increase the efficiency of thrombolytic therapy.
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Affiliation(s)
- J H Foley
- Centre for Blood Research, University of British Columbia, Vancouver, BC, Canada
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14
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Sasaki T, Yoshimoto N, Sugimoto K, Takada K, Murayama N, Yamazaki H, Yamamoto K, Ishii H. Intravenous and oral administrations of DD2 [7-Amino-2-(sulfanylmethyl)heptanoic acid] produce thrombolysis through inhibition of plasma TAFIa in rats with tissue factor-induced microthrombosis. Thromb Res 2012; 130:e222-8. [PMID: 22795218 DOI: 10.1016/j.thromres.2012.06.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 06/03/2012] [Accepted: 06/13/2012] [Indexed: 12/24/2022]
Abstract
Thrombin-activatable fibrinolysis inhibitor (TAFI) is a plasma zymogen that is activated by thrombin in plasma. In fibrinolytic processes, carboxy-terminal lysine (Lys) residues in partially degraded fibrin are important sites for plasminogen binding and activation, and an active form of TAFI (TAFIa) inhibits fibrinolysis by eliminating these residues proteolytically. We synthesized DD2 [7-Amino-2-(sulfanylmethyl)heptanoic acid], a Lys analogue containing sulfur, as an inhibitor of TAFIa and investigated its pharmacological profile and pathophysiological role in thrombolysis via in vitro and in vivo studies. DD2 specifically inhibited plasma TAFIa activity with an apparent IC(50) (50% inhibitory concentration) value of 3.4×10(-8)M under the present experimental condition and enhanced tissue plasminogen activator-mediated clot lysis in a concentration-dependent manner. In order to study tissue factor (TF)-induced microthrombosis in an animal model, rats were given intravenous injection (2.5mg/kg and higher) or oral administration (10mg/kg and higher) of DD2. This attenuated TF-induced glomerular fibrin deposition and increased the plasma levels of fibrin degradation products and D-dimer in a dose-dependent manner. A DD2 dose approximately 4X higher than the dose used in intravenous injections was required to achieve an equivalent thrombolytic effect to that seen following oral administration. Moreover, the oral absorption efficiency of DD2 into the vasculature was 29.8%. These results indicate that both intravenous and oral administration of DD2 enhanced endogenous fibrinolysis and reduced thrombi in a TF-induced microthrombosis model.
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Affiliation(s)
- Tomoyuki Sasaki
- High Technology Research Center, Showa Pharmaceutical University, 3-3165 Higashi Tamagawa Gakuen, Machida, Tokyo 194-8543, Japan
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15
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Van De Craen B, Scroyen I, Abdelnabi R, Brouwers E, Lijnen HR, Declerck PJ, Gils A. Characterization of a panel of monoclonal antibodies toward mouse PAI-1 that exert a significant profibrinolytic effect in vivo. Thromb Res 2011; 128:68-76. [DOI: 10.1016/j.thromres.2011.01.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 11/23/2010] [Accepted: 01/31/2011] [Indexed: 11/27/2022]
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16
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Declerck PJ. Thrombin activatable fibrinolysis inhibitor. Hamostaseologie 2011; 31:165-6, 168-73. [PMID: 21629966 DOI: 10.5482/ha-1155] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 05/26/2011] [Indexed: 12/14/2022] Open
Abstract
Thrombin activatable fibrinolysis inhibitor (TAFI) was discovered two decades ago as a consequence of the identification of an unstable carboxypeptidase (CPU), which was formed upon thrombin activation of the respective pro-enzyme (proCPU). The antifibrinolytic function of the activated form (TAFIa, CPU) is directly linked to its capacity to remove C-terminal lysines from the surface of the fibrin clot. No endogenous inhibitors have been identified, but TAFIa activity is regulated by its intrinsic temperature-dependent instability with a half-life of 8 to 15 min at 37 °C. A variety of studies have demonstrated a role for TAFI/TAFIa in venous and arterial diseases. In addition, a role in inflammation and cell migration has been shown. Since an elevated level of TAFIa it is a potential risk factor for thrombotic disorders, many inhibitors, both at the level of activation or at the level of activity, have been developed and were proven to exhibit a profibrinolytic effect in animal models. Pharmacologically active inhibitors of the TAFI/TAFIa system may open new ways for the prevention of thrombotic diseases or for the establishment of adjunctive treatments during thrombolytic therapy.
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Affiliation(s)
- P J Declerck
- Katholieke Universiteit Leuven, Campus Gasthuisberg, Herestraat 49, Leuven, Belgium.
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17
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Mishra N, Vercauteren E, Develter J, Bammens R, Declerck PJ, Gils A. Identification and characterisation of monoclonal antibodies that impair the activation of human thrombin activatable fibrinolysis inhibitor through different mechanisms. Thromb Haemost 2011; 106:90-101. [PMID: 21544309 DOI: 10.1160/th10-08-0546] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 03/18/2011] [Indexed: 11/05/2022]
Abstract
Thrombin activatable fibrinolysis inhibitor (TAFI) forms a molecular link between coagulation and fibrinolysis and is a putative target to develop profibrinolytic drugs. Out of a panel of monoclonal antibodies (MA) raised against TAFI-ACIIYQ, we selected MA-TCK11A9, MA-TCK22G2 and MA-TCK27A4, which revealed high affinity towards human TAFI-TI-wt. MA-TCK11A9 was able to inhibit mainly plasmin-mediated TAFI activation, MA-TCK22G2 inhibited plasmin- and thrombin-mediated TAFI activation and MA-TCK27A4 inhibited TAFI activation by plasmin, thrombin and thrombin/thrombomodulin (T/TM) in a dose-dependent manner. These MA did not interfere with TAFIa activity. Using an eight-fold molar excess of MA over TAFI, all three MA were able to reduce clot lysis time significantly, i.e. in the presence of exogenous TM, MA-TCK11A9, MA-TCK22G2 and MA-TCK27A4 reduced clot lysis time by 47 ± 9.1%, 80 ± 8.6% and 92 ± 14%, respectively, compared to PTCI. This effect was even more pronounced in the absence of TM i.e. MA-TCK11A9, MA-TCK22G2 and MA-TCK27A4 reduced clot lysis time by 90 ± 14%, 140 ± 12% and 147 ± 29%, respectively, compared to PTCI. Mutagenesis analysis revealed that residues at position 268, 272 and 276 are involved in the binding of MA-TCK11A9, residues 147 and 148 in the binding of MA-TCK22G2 and residue 113 in the binding of MA-TCK27A4. The present study identified three MA, with distinct epitopes, that impair the activation of human TAFI and demonstrated that MA-TCK11A9 which mainly impairs plasmin-mediated TAFI activation can also reduce significantly clot lysis time in vitro.
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Affiliation(s)
- Niraj Mishra
- Laboratory for Pharmaceutical Biology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, O&N II, Leuven, Belgium
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18
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Lin JHH, Garand M, Zagorac B, Schadinger SL, Scipione C, Koschinsky ML, Boffa MB. Identification of human thrombin-activatable fibrinolysis inhibitor in vascular and inflammatory cells. Thromb Haemost 2011; 105:999-1009. [PMID: 21505719 DOI: 10.1160/th10-06-0413] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Accepted: 03/10/2011] [Indexed: 11/05/2022]
Abstract
TAFI (thrombin-activatable fibrinolysis inhibitor) is a carboxypeptidase zymogen originally identified in plasma. The TAFI pathway helps to regulate the balance between the coagulation and fibrinolytic cascades. Activated TAFI (TAFIa) can also inactivate certain pro-inflammatory mediators, suggesting that the TAFI pathway may also regulate communication between coagulation and inflammation. Expression in the liver is considered to be the source of plasma TAFI. TAFI has also been identified in platelets and CPB2 (the gene encoding TAFI) mRNA has been detected in megakaryocytic cell lines as well as in endothelial cells. We have undertaken a quantitative analysis of CPB2 mRNA and TAFI protein in extrahepatic cell types relevant to vascular disease. Using RT-PCR and quantitative RT-PCR, we detected CPB2 mRNA in the human megakaryoblastic cell lines MEG-01 and Dami, the human monocytoid cell line THP-1 as well as THP-1 cells differentiated into a macrophage-like phenotype, and in primary human umbilical vein and coronary artery endothelial cells. CPB2 mRNA abundance in MEG-01, Dami, and THP-1 cells was modulated by the state of differentiation of these cells. Using a recently developed TAFIa assay, we detected TAFI protein in the lysates of the human hepatocellular carcinoma cell line HepG2 as well as in MEG-01 and Dami cells and in the conditioned medium of HepG2 cells, differentiated Dami cells, and THP-1 macrophages. We have obtained clear evidence for extrahepatic expression of TAFI, which has clear implications for the physiological and pathophysiological functions of the TAFI pathway.
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Affiliation(s)
- J H H Lin
- Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, Canada
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González FJ, Caturla JM, Fernández M, Carrasco R, Marco P, Sánchez J, Benlloch S. [Prognosis value of thrombin activatable fibrinolysis inhibitor concentration and C1040T polymorphism in acute myocardial infarction treated with fibrinolysis]. Med Intensiva 2011; 34:513-22. [PMID: 20627371 DOI: 10.1016/j.medin.2010.05.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 04/28/2010] [Accepted: 05/01/2010] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To analyze the prognostic value of thrombin activatable fibrinolysis inhibitor (TAFI) and C1040T polymorphism in acute myocardial infarction treated with fibrinolysis. To analyze C1040T polymorphism influence on its plasma level. DESIGN An observational, prospective study performed from November 2003 to November 2005 and with a 3 month follow-up. SETTING Intensive Medicine Service from a university-affiliated teaching hospital. PATIENTS A total of 53 patients with acute myocardial infarction with persistent ST segment elevation treated with the same fibrinolytic therapy. A control group of 53 biologically similar subjects was included. INTERVENTIONS None. MAIN MEASUREMENTS Baseline characteristics; frequency of wild-type genotype (Thr325Thr) and of those corresponding to the mutation (Thr325LLe and LLe325lle), TAFI levels at 6 h, 34 h and 3 months post-fibrinolysis; ejection fraction; Killip-Kimball; reperfusion; ischemic recurrence; death. RESULTS No relationship was found between biological features and TAFI concentration. The latter was significantly higher in infarct patients (p<0.01) and in the mutation group (p<0.01). The homozygotic mutation (Ile325Ile) was significantly higher in infarct patients (p<0.01). Reperfusion was significantly associated with lower body mass index (p=0.02. OR 0.22. 95% CI), ejection fraction (p=0.004. OR 0.91. 95% CI), triglyceride level (p=0.01. OR 1.02. 95% CI) and cholesterol levels (p=0.001. OR=0.84. 95% CI). Mutation was associated to a significant fall in post-fibrinolysis concentration TAFI antigen and functional TAFI (p=0.01) and (p=0.02), and lower frequency of reperfusion. Reperfusion was associated with a significant post-fibrinolysis reduction in the level of TAFI antigen (p=0.02). Recurrence was associated to a significantly higher post-fibrinolysis level (p=0.05. OR=0.84. 95% CI). This was more frequent in mutation. Post-fibrinolysis TAFI antigen concentration was significantly lower in non-recurrence patients (p=0.028. OR=1.03. 95% CI). CONCLUSIONS A higher concentration of TAFI is associated to a worse prognosis in reperfusion and recurrence in acute myocardial infarction treated with fibrinolysis. Homozygotic mutation was more frequent in myocardial infarction patients. Wild genotype is associated to a better prognosis. Mutation is associated to a higher expression of TAFI.
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Affiliation(s)
- F J González
- Servicio de Medicina Intensiva, Hospital General Universitario de Alicante, Alicante, España.
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20
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Martínez-Zamora MA, Creus M, Tassies D, Reverter JC, Civico S, Carmona F, Balasch J. Reduced plasma fibrinolytic potential in patients with recurrent implantation failure after IVF and embryo transfer. Hum Reprod 2011; 26:510-6. [PMID: 21216787 DOI: 10.1093/humrep/deq369] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Recurrent implantation failure (RIF) following embryo transfer (ET) is a major continuing problem in IVF. Women with haemostatic defects may be at increased risk of miscarriage and preclinical pregnancy loss. The fibrinolytic system is considered, at present, the key to new thrombotic pathogenic mechanisms. Patients with unexplained recurrent miscarriage have an impairment of fibrinolysis, as demonstrated by prolonged clot lysis time (CLT) in association with increased plasma levels of thrombin-activatable fibrinolysis inhibitor (TAFI). In this study, we investigated fibrinolytic potential in patients with RIF. METHODS Three groups of patients were studied: 30 women with RIF (RIF group), 60 patients undergoing a first successful IVF-ET cycle (IVF group) and 60 healthy fertile women (FER group). Plasma CLT was measured using a global fibrinolysis assay. TAFI antigen plasma levels and polymorphisms in the TAFI gene (+505A/G and +1542C/G) were analysed using enzyme-linked immunosorbent assay and allele-specific PCR, respectively. RESULTS CLT was significantly longer (P < 0.0001 and P < 0.0009, respectively) and TAFI antigen levels were significantly higher (both P < 0.0001) in the RIF versus the IVF and FER groups. A direct relationship between CLT and TAFI antigen levels (r = 0.40; P = 0.001) was detected in the whole study population. There were no differences in distribution of TAFI polymorphisms between groups. CONCLUSIONS Patients with RIF have reduced plasma fibrinolytic potential, as shown by a prolonged CLT, and this may be explained, at least in part, by increased TAFI antigen levels.
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Affiliation(s)
- M Angeles Martínez-Zamora
- Institut Clínic of Gynecology, Obstetrics and Neonatology, Hospital Clínic, Villarroel 170, 08036 Barcelona, Spain
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Schadinger SL, Lin JHH, Garand M, Boffa MB. Secretion and antifibrinolytic function of thrombin-activatable fibrinolysis inhibitor from human platelets. J Thromb Haemost 2010; 8:2523-9. [PMID: 20723026 DOI: 10.1111/j.1538-7836.2010.04024.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND The thrombin-activatable fibrinolysis inhibitor (TAFI) is a zymogen first characterized in human plasma that is activated through proteolytic cleavage by thrombin, thrombin in complex with thrombomodulin, or plasmin. Active TAFI attenuates fibrinolysis by removing C-terminal lysine residues from partially degraded fibrin, thereby inhibiting a potent positive feedback loop in the fibrinolytic cascade. The existence of a separate pool of TAFI within platelets has been described. OBJECTIVES AND METHODS We aimed to confirm the presence of TAFI in the medium of washed, thrombin-stimulated platelets and to evaluate the characteristics of platelet TAFI by western blot analysis and with a quantitative assay for activated TAFI. We also assessed the ability of platelet TAFI to inhibit fibrinolysis in vitro, using a platelet-rich thrombus lysis assay. RESULTS Our data are consistent with the presence of TAFI in the α-granules of resting platelets. In contrast to previous reports, platelet TAFI is very similar in electrophoretic mobility to plasma-derived TAFI. We also show, for the first time, that platelet-derived TAFI is capable of attenuating platelet-rich thrombus lysis in vitro independently of plasma TAFI. Moreover, we demonstrate additive effects on thrombolysis of platelet-derived TAFI and TAFI present in plasma. CONCLUSIONS Taken together, these observations indicate that the secretion of platelet-derived TAFI can augment the concentrations of TAFI already present in plasma to enhance attenuation of the fibrinolytic cascade. This could be significant in regions of vascular damage or pathologic thrombosis, where activated platelets are known to accumulate.
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Affiliation(s)
- S L Schadinger
- Department of Biochemistry, Queen's University, Kingston, ON, Canada
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22
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Martínez-Zamora MA, Tassies D, Carmona F, Espinosa G, Cervera R, Reverter JC, Balasch J. Clot lysis time and thrombin activatable fibrinolysis inhibitor in severe preeclampsia with or without associated antiphospholipid antibodies. J Reprod Immunol 2010; 86:133-40. [DOI: 10.1016/j.jri.2010.05.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2010] [Revised: 05/18/2010] [Accepted: 05/18/2010] [Indexed: 10/19/2022]
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23
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Martínez-Zamora MA, Creus M, Tassies D, Bové A, Reverter JC, Carmona F, Balasch J. Thrombin activatable fibrinolysis inhibitor and clot lysis time in women with recurrent miscarriage associated with the antiphospholipid syndrome. Fertil Steril 2010; 94:2437-40. [DOI: 10.1016/j.fertnstert.2010.02.032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 02/09/2010] [Accepted: 02/15/2010] [Indexed: 11/26/2022]
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Effect of obesity on TAFI in postmenopausal period. Obes Res Clin Pract 2010; 4:e247-342. [DOI: 10.1016/j.orcp.2010.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2009] [Revised: 05/18/2010] [Accepted: 05/27/2010] [Indexed: 11/22/2022]
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Martinez-Zamora MA, Tassies D, Carmona F, Espinosa G, Cervera R, Reverter JC, Balasch J. ORIGINAL ARTICLE: Thrombin Activatable Fibrinolysis Inhibitor and Clot Lysis Time in Pregnant Patients with Antiphospholipid Syndrome: Relationship with Pregnancy Outcome and Thrombosis. Am J Reprod Immunol 2009; 62:381-9. [DOI: 10.1111/j.1600-0897.2009.00751.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
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26
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Tàssies D, Roqué M, Monteagudo J, Martorell T, Sionis A, Arzamendi D, Heras M, Reverter JC. Thrombin-activatable fibrinolysis inhibitor genetic polymorphisms as markers of the type of acute coronary syndrome. Thromb Res 2009; 124:614-8. [PMID: 19699511 DOI: 10.1016/j.thromres.2009.07.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2009] [Revised: 07/01/2009] [Accepted: 07/06/2009] [Indexed: 11/30/2022]
Abstract
INTRODUCTION In patients with coronary disease at risk of acute coronary events it is unclear which biological factors could predict the type of acute coronary syndrome clinical presentation. The aim of the study was to investigate the role of genetic polymorphisms in key proteins in fibrinolysis in the type of acute coronary syndrome. MATERIALS AND METHODS 248 patients with acute coronary syndrome (unstable angina or myocardial infarction) (77% male, mean age 60.75 SD 13.30years) were prospectively recruited. PAI-1 (type-1 plasminogen activator inhibitor) 4G/5G and TAFI (thrombin-activatable fibrinolysis inhibitor) Ala147Thr, C+1542G, and Thr325Ile polymorphisms were determined by PCR. RESULTS 147 (59.3%) patients presented with ST-segment elevation acute coronary syndrome (all Q-wave myocardial infarction), and 101 (40.7%) with non-ST-elevation acute coronary syndrome (52 non-Q wave myocardial infarction, and 49 unstable angina). Homozygous TAFI +1542G and TAFI 325Ile genotypes were less prevalent in patients with ST elevation acute coronary syndrome (p<0.001, OR: 0.22, 95% CI 0.10-0.50 and p<0.001, OR: 0.25, 95% CI 0.11-0.55, respectively). There were no differences in TAFI Ala147Thr or PAI genotype distribution between ST elevation and non-ST elevation acute coronary syndrome. In the multivariate analysis including clinical variables, the best model for ST elevation acute coronary syndrome included TAFI +1542GG (p<0.001, OR: 0.17, 95% CI 0.07-0.30), age (in years, p<0.005, OR: 0.97, 95% CI 0.94-0.98) and dyslipidemia (p<0.005, OR: 2.33, 95% CI 1.42-3.80). CONCLUSION TAFI polymorphism C+1542G and Thr325/Ile are related to the type of acute coronary syndrome. Patients with coronary disease would benefit from individualized cardiovascular prophylaxis based on genetic risk.
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Affiliation(s)
- Dolors Tàssies
- Hemotherapy and Hemostasis Department, Hospital Clínic, Villarroel 170. 08036 Barcelona, Spain.
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27
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Meltzer ME, Doggen CJM, de Groot PG, Meijers JCM, Rosendaal FR, Lisman T. Low thrombin activatable fibrinolysis inhibitor activity levels are associated with an increased risk of a first myocardial infarction in men. Haematologica 2009; 94:811-8. [PMID: 19377074 DOI: 10.3324/haematol.2008.002386] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Studies on the relation between thrombin activatable fibrinolysis inhibitor (TAFI) and arterial thrombosis have produced conflicting results. TAFI regulates fibrinolysis, but other roles of this inhibitor, including anti-inflammatory properties, have also been demonstrated. DESIGN AND METHODS We investigated the association between TAFI activity and the risk of myocardial infarction. Additionally, we studied the association of common single nucleotide polymorphisms in the TAFI gene with levels of the TAFI protein and risk of myocardial infarction.We included 554 men under 70 years old with a first myocardial infarction and 643 controls participating in the Study of Myocardial Infarctions Leiden (SMILE), a case-control study. RESULTS We found odds ratios (95% confidence intervals) of a first myocardial infarction of 2.4 (1.6-3.6), 3.2 (2.1-4.7) and 3.4 (2.3-5.1) for subjects whose TAFI levels were in the third, second and first quartiles (lowest TAFI levels), respectively, compared with the fourth quartile, after adjusting for arterial disease risk factors. The rare -438A and 1040T alleles were associated with lower, and the rare 505G allele with higher TAFI levels than the common alleles. Carriers of the -438A allele had an increased risk of myocardial infarction (odds ratio 1.6 (1.0-2.5) for AA; odds ratio 1.2 (0.9-1.5) for AG compared with GG). The other single nucleotide polymorphisms were not associated with myocardial infarction. CONCLUSIONS Low TAFI activity levels are associated with increased risk of a first myocardial infarction in men. The results on the association between TAFI single nucleotide polymorphisms and myocardial infarction were inconsistent.
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Affiliation(s)
- Mirjam E Meltzer
- Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands
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28
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Miah MF, Boffa MB. Functional analysis of mutant variants of thrombin-activatable fibrinolysis inhibitor resistant to activation by thrombin or plasmin. J Thromb Haemost 2009; 7:665-72. [PMID: 19335449 DOI: 10.1111/j.1538-7836.2009.03311.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Thrombin-activatable fibrinolysis inhibitor (TAFI) defines a pathway that functionally links the coagulation and fibrinolytic cascades. TAFI is activated by proteolytic cleavage, a reaction that can be performed by thrombin and plasmin, but most efficiently by thrombin in complex with the endothelial cofactor thrombomodulin (TM). The respective roles of these activators in regulating the TAFI pathway are largely unknown. OBJECTIVE AND METHODS In the present study, we constructed and expressed mutant variants of TAFI that have key substitutions in the amino acids surrounding the scissile Arg92-Ala93 bond. RESULTS AND CONCLUSIONS We identified variants that showed patterns of resistance to specific activators. For example, the P91S, R92K and S90P variants exhibited specific impairment of activation by thrombin or thrombin-TM, thrombin alone, and thrombin alone or plasmin, respectively. The variants that we tested also showed antifibrinolytic potentials that can be rationalized in terms of which enzymes are capable of activating them. On the other hand, certain predictions from peptide studies of mutations that would be expected to interfere with plasmin cleavage were not satisfied by our data, indicating that protein context, as well as the identity of amino acids at protease cleavage sites, dictates protease specificity.
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Affiliation(s)
- M F Miah
- Department of Biochemistry, Queen's University, Kingston, ON, Canada
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Detecting Activated Thrombin Activatable Fibrinolysis Inhibitor (TAFIa) and Inactivated TAFIa (TAFIai) in Normal and Hemophilia A Plasmas. B KOREAN CHEM SOC 2009. [DOI: 10.5012/bkcs.2009.30.1.077] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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30
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Biswas A, Tiwari AK, Ranjan R, Meena A, Akhter MS, Yadav BK, Behari M, Saxena R. Thrombin activatable fibrinolysis inhibitor gene polymorphisms are associated with antigenic levels in the Asian-Indian population but may not be a risk for stroke. Br J Haematol 2009; 143:581-8. [PMID: 18986391 DOI: 10.1111/j.1365-2141.2008.07384.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thrombin activatable fibrinolysis inhibitor [carboxypeptidase B2 (plasma), CPB2] is a basic carboxypeptidase, which inhibits fibrinolysis by cleaving the C-terminal lysine residues on plasmin-modified partially degraded fibrin. Plasma CPB2 concentrations have been reported to be under the control of numerous single nucleotide polymorphisms located in the regulatory and coding regions of the gene encoding CPB2 (CPB2). High functional CPB2 levels have been found to be associated with an increased risk for ischemic stroke. The present study investigated CPB2 antigen levels and associated CPB2 polymorphisms in an acute onset non-cardioembolic stroke population compared with an age- and sex-matched healthy control population. This is, to the best of our knowledge, the first such study done in an Asian Indian population. CPB2 antigen levels were significantly associated with the disease phenotype (P < 0.001) and with CPB2 polymorphisms (P < 0.001). The haplotypes generated on analysis of the genotypic data accounted for 21% of the natural variation in the CPB2 antigenic levels. However none of the haplotype combinations generated showed any association with disease phenotype and therefore could not explain for the difference in CPB2 antigen levels between cases and controls.
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Affiliation(s)
- Arijit Biswas
- Department of Haematology, All India Institute of Medical Sciences, New Delhi, India
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Tregouet DA, Schnabel R, Alessi MC, Godefroy T, Declerck PJ, Nicaud V, Munzel T, Bickel C, Rupprecht HJ, Lubos E, Zeller T, Juhan-Vague I, Blankenberg S, Tiret L, Morange PE. Activated thrombin activatable fibrinolysis inhibitor levels are associated with the risk of cardiovascular death in patients with coronary artery disease: the AtheroGene study. J Thromb Haemost 2009; 7:49-57. [PMID: 19017260 DOI: 10.1111/j.1538-7836.2008.03221.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND Thrombin activatable fibrinolysis inhibitor (TAFI) attenuates fibrinolysis. Results on the association between TAFI levels and the risk of coronary artery disease (CAD) are inconsistent. OBJECTIVES We investigated the association between TAFI levels and the risk of cardiovascular events in CAD. PATIENTS/METHODS 1668 individuals with angiographically proven CAD at baseline were followed for a median of 2.3 years, as part of the prospective AtheroGene cohort. Fifty-six deaths from cardiovascular (CV) causes and 35 non-fatal CV events were observed. RESULTS At baseline, three TAFI measurements were available: one evaluating the total amount of TAFI (t-TAFI), one measuring the TAFIa/TAFIai amount, and the last the released activated peptide (TAFI-AP). TAFIa/TAFIai levels were associated with increased risk of CV death [hazard ratio (HR) for one tertile increase, 2.38 (1.56-3.63); P < 10(-4)]. This association remained significant after adjustment for conventional risk factors, CRP levels, white blood count and markers of thrombin generation and fibrinolysis [HR = 1.69 (1.07-2.67); P = 0.01]. In addition, CPB2 gene polymorphisms explained 12%, 6%, and 3% of t-TAFI, TAFIa/TAFIai and TAFI-AP levels, respectively, but none was associated with CV events. CONCLUSIONS The amount of activated TAFI, measured by TAFIa/TAFIai ELISA, but not of the t-TAFI is independently associated with the risk of CV death.
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Wu C, Kim PY, Manuel R, Seto M, Whitlow M, Nagashima M, Morser J, Gils A, Declerck P, Nesheim ME. The roles of selected arginine and lysine residues of TAFI (Pro-CPU) in its activation to TAFIa by the thrombin-thrombomodulin complex. J Biol Chem 2008; 284:7059-67. [PMID: 19074424 DOI: 10.1074/jbc.m804745200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thrombomodulin (TM) increases the catalytic efficiency of thrombin (IIa)-mediated activation of thrombin-activable fibrinolysis inhibitor (TAFI) 1250-fold. Negatively charged residues of the C-loop of TM-EGF-like domain 3 are required for TAFI activation. Molecular models suggested several positively charged residues of TAFI with which the C-loop residues could interact. Seven TAFI mutants were constructed to determine if these residues are required for efficient TAFI activation. TAFI wild-type or mutants were activated in the presence or absence of TM and the kinetic parameters of TAFI activation were determined. When the three consecutive lysine residues in the activation peptide of TAFI were substituted with alanine (K42/43/44A), the catalytic efficiencies for TAFI activation with TM decreased 8-fold. When other positively charged surface residues of TAFI (Lys-133, Lys-211, Lys-212, Arg-220, Lys-240, or Arg-275) were mutated to alanine, the catalytic efficiencies for TAFI activation with TM decreased by 1.7-2.7-fold. All decreases were highly statistically significant. In the absence of TM, catalytic efficiencies ranged from 2.8-fold lower to 1.24-fold higher than wild-type. None of these, except the 2.8-fold lower value, was statistically significant. The average half-life of the TAFIa mutants was 8.1+/-0.6 min, and that of wild type was 8.4+/-0.3 min at 37 degrees C. Our data show that these residues are important in the activation of TAFI by IIa, especially in the presence of TM. Whether the mutated residues promote a TAFI-TM or TAFI-IIa interaction remains to be determined. In addition, these residues do not influence spontaneous inactivation of TAFIa.
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Affiliation(s)
- Chengliang Wu
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
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Develter J, Booth NA, Declerck PJ, Gils A. Bispecific targeting of thrombin activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 by a heterodimer diabody. J Thromb Haemost 2008; 6:1884-91. [PMID: 18752580 DOI: 10.1111/j.1538-7836.2008.03137.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND AND OBJECTIVES Thrombin activatable fibrinolysis inhibitor (TAFI) and plasminogen activator inhibitor-1 (PAI-1) play important roles in fibrinolysis. Both reduce plasmin generation, but they exert their antifibrinolytic effects via different mechanisms. This study reports the cloning and characterization of a heterodimer diabody that inhibits TAFI and PAI-1 simultaneously. METHODS AND RESULTS The diabody was derived from two inhibiting monoclonal antibodies, i.e. MA-33H1F7, an anti-PAI-1 antibody that induces non-inhibitory substrate behavior of PAI-1, and MA-T12D11, an anti-TAFI antibody that inhibits activation of TAFI by the thrombin-thrombomodulin complex. A single-chain variable fragment (scFv) was derived from MA-T12D11 that displayed slightly reduced binding and inhibitory properties as compared to MA-T12D11. Characterization of the diabody revealed a similar affinity for TAFI and PAI-1 as that of the parental antibodies. Furthermore, the inhibitory properties of MA-33H1F7 and MA-T12D11 were fully preserved in the diabody format. In platelet-free plasma (PFP) clots, addition of the diabody had a stronger effect in shortening lysis times than either MA-T12D11 or MA-33H1F7. A similar reduction in clot lysis time was observed in platelet-rich plasma (PRP) clots. The same effect on clot lysis times in PFP and PRP was also achieved by the combined addition of MA-T12D11 and MA-33H1F7. The lysis rate of human model thrombi, made from whole blood, was approximately doubled after addition of the diabody. Moreover, this effect was significantly better than after the combined addition of the individual antibodies. CONCLUSIONS These observations demonstrate that simultaneous inhibition of TAFI and PAI-1 results in faster lysis of the formed thrombus.
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Affiliation(s)
- J Develter
- Laboratory for Pharmaceutical Biology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
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Hillmayer K, Brouwers E, León-Tamariz F, Meijers JCM, Marx PF, Declerck PJ, Gils A. Development of sandwich-type ELISAs for the quantification of rat and murine thrombin activatable fibrinolysis inhibitor in plasma. J Thromb Haemost 2008; 6:132-8. [PMID: 17922808 DOI: 10.1111/j.1538-7836.2007.02789.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Altered plasma levels of thrombin activatable fibrinolysis inhibitor (TAFI) are associated with a large number of pathologies. Rat and murine models are frequently used to study the pathophysiological role of TAFI in vivo but immunological tools to quantify rat and murine TAFI are lacking. OBJECTIVE The production of monoclonal antibodies (mAb) towards rat TAFI and the development of an ELISA for the quantification of rat and murine TAFI in plasma. METHODS AND RESULTS Monoclonal antibodies were raised in TAFI-deficient mice towards (activated) recombinant rat TAFI. Pair-wise testing of the mAb revealed three suitable ELISA combinations, namely RT36A3F5/RT30D8-HRP, RT36A3F5/RT82F12-HRP and RT82F12/RT36A3F5-HRP. All three ELISAs are highly specific for rat and murine TAFI. TAFI concentrations in the lower ng mL(-1) range can be determined in plasma samples with a high reproducibility. Comparing TAFI antigen levels measured by these ELISAs with TAFIa activity values determined by activity based assays revealed excellent correlations (R(2) > 0.98). The average antigen levels of 20 individual rat plasma samples were 16 +/- 2 microg mL(-1) using the RT36A3F5-RT30D8-HRP, 12 +/- 2 microg mL(-1) using the RT36A3F5-RT82F12-HRP and 21 +/- 2 microg mL(-1) using the RT82F12-RT36A3F5-HRP ELISA. The determined antigen levels in rat plasma are similar to the levels reported for human plasma. CONCLUSIONS We developed three highly specific and extremely sensitive sandwich-type ELISAs for the quantification of rat and murine TAFI in plasma. The described ELISAs will facilitate in vivo investigation on the pathophysiological role of TAFI.
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Affiliation(s)
- K Hillmayer
- Laboratory for Pharmaceutical Biology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
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Buelens K, Hillmayer K, Compernolle G, Declerck PJ, Gils A. Biochemical importance of glycosylation in thrombin activatable fibrinolysis inhibitor. Circ Res 2007; 102:295-301. [PMID: 18063813 DOI: 10.1161/circresaha.107.157099] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Activated Thrombin Activatable Fibrinolysis Inhibitor (TAFIa) exerts an antifibrinolytic effect by removing C-terminal lysines from partially degraded fibrin. These lysines are essential for a rapid conversion of plasminogen to plasmin by tissue type plasminogen activator. TAFI is heavily glycosylated at Asn22, Asn51, Asn63, and Asn86. Although the glycans occurring at the glycosylation sites have previously been identified, the biochemical role of these glycans is not known yet. Therefore, we have determined the biochemical importance of the glycosylation in TAFI. Four single, 6 double, 4 triple, and 1 quadruple mutant, in which asparagine was replaced by glutamine, were constructed and transfected into HEK293T cells. Based on the determination of antigen and activity levels on conditioned medium, 4 single and 1 triple mutant were purified and their biochemical properties were determined. The glycosylation knockout mutants did neither reveal an altered fragmentation pattern nor differences in TAFIa stability, but TAFI-N51Q, TAFI-N63Q, and TAFI-N22Q-N51Q-N63Q revealed a decreased TAFIa activity, an increased intrinsic catalytic activity of the zymogen, and a decreased antifibrinolytic potential compared with TAFI-wild-type, whereas TAFI-N22Q and TAFI-N86Q revealed an increased antifibrinolytic potential probably because of an increased catalytic efficiency toward the physiological substrate. From these data it can be concluded that mainly the glycosylation at Asn86 contributes to the biochemical characteristics of TAFI. Furthermore we provide evidence that the activation peptide stays in close proximity to the TAFIa moiety after activation.
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Affiliation(s)
- Karlien Buelens
- Laboratory for Pharmaceutical Biology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Campus Gasthuisberg, O&N2, PB 824, Herestraat 49, B-3000 Leuven, Belgium
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36
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Ceresa E, De Maeyer M, Jonckheer A, Peeters M, Engelborghs Y, Declerck PJ, Gils A. Comparative evaluation of stable TAFIa variants: importance of alpha-helix 9 and beta-sheet 11 for TAFIa (in)stability. J Thromb Haemost 2007; 5:2105-12. [PMID: 17666015 DOI: 10.1111/j.1538-7836.2007.02720.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Activated thrombin activatable fibrinolysis inhibitor (TAFIa) plays a pivotal role in fibrinolysis. TAFIa activity is regulated by a temperature-dependent instability. This instability has not only complicated the study of structure-function relationships of TAFIa but has also prevented the crystallization of TAFIa. Furthermore, the TAFIa instability has severely compromised the development of activity inhibiting monoclonal antibodies. Recently, we combined all known stabilizing mutations (i.e. S305C, T325I, T329I, H333Y and H335Q) resulting in a synergistic (one hundred and eightyfold) stabilization of TAFIa at 37 degrees C. All these residues are located in an amino acid region (AA297-335) consisting of alpha-helix 9 and beta-sheet 11. OBJECTIVES To provide a comparative evaluation of the characteristics of a panel of stable TAFIa mutants and an energy-minimized model of the most stable TAFI variant. RESULTS The catalytic efficiency for activation of TAFI by thrombin/thrombomodulin was higher for all TAFI mutants compared with TAFI-wild type (wt). Except for TAFI variants carrying T325I-T329I, S305C-T325I or S305C-T325I-T329I mutations, the catalytic efficiency for Hip-Arg hydrolysis by TAFIa was similar for the TAFI mutants compared with the wild type. All TAFIa variants were equally well inhibited by potato tuber carboxypeptidase inhibitor (PTCI) and showed a significantly increased antifibrinolytic potential in accordance with their increased stability. Based on the intrinsic fluorescence decay of TAFIa, two independent structural transitions were found to be associated with the loss of functional activity. CONCLUSIONS Using molecular dynamic calculations on both TAFI-wt and TAFI-S305C-T325I-T329I-H333Y-H335Q models, we were able to identify the molecular interactions that contribute to the increased stability of the mutants.
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Affiliation(s)
- E Ceresa
- Laboratory for Pharmaceutical Biology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
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Boffa MB, Maret D, Hamill JD, Bastajian N, Crainich P, Jenny NS, Tang Z, Macy EM, Tracy RP, Franco RF, Nesheim ME, Koschinsky ML. Effect of single nucleotide polymorphisms on expression of the gene encoding thrombin-activatable fibrinolysis inhibitor: a functional analysis. Blood 2007; 111:183-9. [PMID: 17855631 DOI: 10.1182/blood-2007-03-078543] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Thrombin-activable fibrinolysis inhibitor (TAFI) is a plasma zymogen that acts as a molecular link between coagulation and fibrinolysis. Numerous single nucleotide polymorphisms (SNPs) have been identified in CPB2, the gene encoding TAFI, and are located in the 5'-flanking region, in the coding sequences, and in the 3'-untranslated region (UTR) of the CPB2 mRNA transcript. Associations between CPB2 SNPs and variation in plasma TAFI antigen concentrations have been described, but the identity of SNPs that are causally linked to this variation is not known. In the current study, we investigated the effect of the SNPs in the 5'-flanking region on CPB2 promoter activity and SNPs in the 3'-UTR on CPB2 mRNA stability. Whereas the 5'-flanking region SNPs (with 2 exceptions) did not have a significant effect on promoter activity, either alone or in haplotypic combinations seen in the human population, all of the 3'-UTR SNPs substantially affected mRNA stability. We speculate that these SNPs, in part, contribute to variation in plasma TAFI concentrations via modulation of CPB2 gene expression through an effect on mRNA stability.
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Affiliation(s)
- Michael B Boffa
- Department of Biochemistry, Queen's University, Kingston, ON, Canada.
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38
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Walker JB, Bajzar L. Complete inhibition of fibrinolysis by sustained carboxypeptidase B activity: the role and requirement of plasmin inhibitors. J Thromb Haemost 2007; 5:1257-64. [PMID: 17389009 DOI: 10.1111/j.1538-7836.2007.02541.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The antifibrinolytic effect of activated thrombin-activatable fibrinolysis inhibitor (TAFIa) and carboxypeptidase B (CPB) displays threshold behavior. When CPB was used to simulate conditions mimicking continuous TAFIa activity, it affected the lysis of plasma clots differently to clots formed from a minimal fibrinolytic system comprising fibrinogen, plasminogen and alpha(2)-antiplasmin. Whereas CPB saturably prolonged clot lysis in the purified system, the effect of CPB did not appear saturable in plasma clots. METHODS To rationalize this difference, we investigated the effects of alpha(2)-antiplasmin, alpha(2)-macroglobulin, antithrombin and aprotinin on CPB-mediated antifibrinolysis. RESULTS CPB alone prolonged fibrinolysis in a saturable manner and the efficacy of CPB increased with decreasing tissue-type plasminogen activator (t-PA) concentration. The inhibitors by themselves did not halt fibrinolysis and the potency of each inhibitor in the absence of CPB mirrored their solution-phase plasmin inhibitory potentials: alpha(2)-antiplasmin approximately equal to aprotinin >> alpha(2)-macroglobulin >> antithrombin. With both CPB and inhibitor present, a synergistic effect was observed. The antifibrinolytic sensitivity to CPB was related to the plasmin inhibitory potential of the inhibitor. CONCLUSIONS Fibrinolysis could be completely inhibited by alpha(2)-antiplasmin, alpha(2)-macroglobulin and antithrombin, but not aprotinin, in the presence of CPB, and occurred only when the irreversible inhibitor or pool of inhibitors were in excess of plasminogen. Western blot analysis indicated that the CPB-mediated shutdown of fibrinolysis was a result of plasminogen consumption prior to clot lysis. The CPB concentration required for fibrinolytic shutdown was dependent on t-PA concentration and the inhibitory potential of the irreversible inhibitor pool.
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Affiliation(s)
- J B Walker
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
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Meltzer ME, Doggen CJM, de Groot PG, Rosendaal FR, Lisman T. Fibrinolysis and the risk of venous and arterial thrombosis. Curr Opin Hematol 2007; 14:242-8. [PMID: 17414214 DOI: 10.1097/moh.0b013e3280dce557] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW The fibrinolytic system is often regarded as just an innocent bystander in the pathogenesis of venous and arterial thrombosis, while (hyper)coagulation as a risk factor has been studied extensively. In this review, we evaluated studies that investigated the association between fibrinolysis and thrombosis. RECENT FINDINGS There is some evidence for an association between impaired overall fibrinolytic activity and increased risk of venous or arterial thrombosis. Plasminogen levels were found not to be related to thrombosis. Plasma levels of tissue-type plasminogen activator were related to arterial thrombosis in a number of studies but not to venous thrombosis. Thrombin activatable fibrinolysis inhibitor levels appeared to be associated with venous thrombosis. Studies on the association between thrombin activatable fibrinolysis inhibitor or plasminogen activator inhibitor-1 and arterial thrombosis had conflicting results. SUMMARY Current evidence on an association between fibrinolysis and thrombosis is inconclusive. Although overall assays point to an association, not all individual factors have an association with thrombosis. Most importantly, plasminogen deficiency is not related to thrombosis, which suggests that the fibrinolytic system as a whole is unimportant in the occurrence of thrombosis. Certain components of the fibrinolytic system, however, appear to be involved in processes unrelated to fibrin degradation but related to other processes important in the development of thrombosis.
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Affiliation(s)
- Mirjam E Meltzer
- Department of Clinical Chemistry and Hematology, University Medical Center Utrecht, Utrecht, The Netherlands
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Willemse JL, Matus V, Heylen E, Mezzano D, Hendriks DF. Influence of the Thr325Ile polymorphism on procarboxypeptidase U (thrombin-activable fibrinolysis inhibitor) activity-based assays. J Thromb Haemost 2007; 5:872-5. [PMID: 17408417 DOI: 10.1111/j.1538-7836.2007.02396.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Ladenvall C, Gils A, Jood K, Blomstrand C, Declerck PJ, Jern C. Thrombin activatable fibrinolysis inhibitor activation peptide shows association with all major subtypes of ischemic stroke and with TAFI gene variation. Arterioscler Thromb Vasc Biol 2007; 27:955-62. [PMID: 17272741 DOI: 10.1161/01.atv.0000259354.93789.a6] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Thrombin activatable fibrinolysis inhibitor (TAFI) attenuates fibrinolysis. The aim of the present study was to investigate the possible association between TAFI and overall ischemic stroke and ischemic stroke subtypes. METHODS AND RESULTS The Sahlgrenska Academy Study on Ischemic Stroke (SAHLSIS) comprises 600 cases (18 to 69 years) and 600 matched population controls. Stroke subtype was defined by the Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification. TAFI was investigated at the protein level, by analyzing plasma levels of intact TAFI and released activation peptide [AP], and at the genetic level, by genotyping a selection of eleven single nucleotide polymorphisms. After adjustment for traditional risk factors, both TAFI measurements showed association with overall ischemic stroke (AP: odds ratio, 2.22; 95% confidence interval, 1.89 to 2.61; intact TAFI: odds ratio, 1.21; 95% confidence interval, 1.06 to 1.38; for 1-SD increase in AP and intact TAFI, respectively). AP showed associations with all 4 major subtypes of ischemic stroke and intact TAFI to large vessel disease and cryptogenic stroke. TAFI genotypes and haplotypes showed significant associations with both TAFI measurements. In contrast, no association was observed between genetic variants and overall ischemic stroke. CONCLUSION TAFI levels show independent association with overall ischemic stroke. This association is stronger for released AP than for intact TAFI, and for released AP, it is present in all ischemic stroke subtypes.
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Affiliation(s)
- Claes Ladenvall
- Institute of Neuroscience and Physiology, Sahlgrenska Academy at Göteborg University, Guldhedsgatan 19, S-413 45 Göteborg, Sweden.
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Boffa MB, Koschinsky ML. Curiouser and curiouser: recent advances in measurement of thrombin-activatable fibrinolysis inhibitor (TAFI) and in understanding its molecular genetics, gene regulation, and biological roles. Clin Biochem 2006; 40:431-42. [PMID: 17331488 DOI: 10.1016/j.clinbiochem.2006.10.020] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Accepted: 10/29/2006] [Indexed: 10/23/2022]
Abstract
The thrombin-activatable fibrinolysis inhibitor (TAFI) pathway defines a novel molecular connection between blood coagulation and both fibrinolysis and inflammation. TAFI is a plasma zymogen that can be activated by thrombin, the thrombin-thrombomodulin complex, or plasmin. The activated form of TAFI (TAFIa) attenuates fibrinolysis by removing the carboxyl-terminal lysine residues from partially degraded fibrin that mediate positive feedback in the fibrinolytic cascade. A role for TAFIa in modulating inflammation is suggested by the ability of this enzyme to down-regulate pericellular plasminogen activation and to inactivate the inflammatory peptides bradykinin and the anaphylatoxins C3a and C5a. The focus of this review is on recent advances in the clinical measurement of the TAFI pathway in human subjects and what this has revealed in terms of the molecular genetics of TAFI, the biological variation in plasma TAFI antigen levels, potential regulators of expression of the gene encoding TAFI, and the TAFI pathway as a risk factor for the development of vascular diseases. Although this field is in its infancy, much recent progress has been made and the available data suggest that the TAFI pathway is an intriguing new player in a variety of physiological and pathophysiological contexts.
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Affiliation(s)
- Michael B Boffa
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6.
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Hillmayer K, Macovei A, Pauwels D, Compernolle G, Declerck PJ, Gils A. Characterization of rat thrombin-activatable fibrinolysis inhibitor (TAFI)--a comparative study assessing the biological equivalence of rat, murine and human TAFI. J Thromb Haemost 2006; 4:2470-7. [PMID: 17002650 DOI: 10.1111/j.1538-7836.2006.02224.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND OBJECTIVES Activated thrombin-activatable fibrinolysis inhibitor (TAFIa) attenuates fibrinolysis. Although rat models to study the role of TAFI are available, the biochemical properties of rat TAFI are not well investigated and immunologic tools are lacking. Therefore, we have characterized recombinant rat TAFI-6His and compared its properties with those of human TAFI as well as of murine TAFI-V5-6His. METHODS AND RESULTS TAFI from all three species is activatable by the thrombin-thrombomodulin complex, generating a highly unstable protein (TAFIa). Half-lives at 37 degrees C are 8.5+/-0.6 min, 3.4+/-0.4 min and 2.2+/-0.2 min for human, rat and murine TAFIa, respectively. The 50% clot lysis times are 6+/-1 min for TAFI-depleted rat plasma and 137+/-34 min, 62+/-9 min and 50+/-8 min when TAFI-depleted rat plasma is supplemented with 0.02 U of human, rat or murine TAFIa, respectively, which correlates with their half-lives. Upon incubation with the thrombin-thrombomodulin complex, the 36-kDa fragment of rat and murine TAFI is not cleaved into 25-kDa and 11-kDa fragments. Upon incubation of rat TAFI and murine TAFI with plasmin, a 32-kDa fragment is formed due to cleavage at Arg147, in contrast to the formation of a 36-kDa fragment for human TAFI. Concomitantly, activity levels upon plasmin incubation are drastically reduced for rat and murine TAFI. CONCLUSIONS Recombinant human, rat and murine TAFI have similar but not identical biochemical characteristics, suggesting a similar role during fibrinolysis in vivo.
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Affiliation(s)
- K Hillmayer
- Laboratory for Pharmaceutical Biology and Phytopharmacology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
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Aso Y. Fibrinolysis and diabetic vascular disease: roles of plasminogen activator inhibitor-1 and thrombin-activatable fibrinolysis inhibitor. ACTA ACUST UNITED AC 2006. [DOI: 10.2217/17460875.1.4.429] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Frère C, Tregouet DA, Morange PE, Saut N, Kouassi D, Juhan-Vague I, Tiret L, Alessi MC. Fine mapping of quantitative trait nucleotides underlying thrombin-activatable fibrinolysis inhibitor antigen levels by a transethnic study. Blood 2006; 108:1562-8. [PMID: 16705091 DOI: 10.1182/blood-2006-01-008094] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Recent studies revisiting the association between plasma thrombin-activatable fibrinolysis inhibitor (TAFI) Ag levels and polymorphisms of the CPB2 gene (coding for TAFI) suggested that TAFI Ag levels were influenced by 2 major quantitative trait nucleotides (QTNs) in European whites. However, the strong linkage disequilibrium (LD) between CPB2 polymorphisms in European whites did not allow one to distinguish which polymorphisms could be the putative QTNs. To get a better insight into the identification of QTNs, a transethnic haplotype analysis contrasting 2 populations of African and European subjects was performed using 13 CPB2 polymorphisms. Results of the haplotype analyses suggested that 3 QTNs had independent effects and explained about 15% of the TAFI variability, consistently in the 2 populations. The lower LD observed in the African population enabled us to identify the 1583T>A SNP located in 3'UTR as one of these QTNs, whereas the -2599C>G and -2345--2344insG SNPs located in the 5' region might be the 2 other QTNs. A phylogenetic study suggested that these 3 polymorphisms occurred before the period of migration "out of Africa." Although this transethnic comparison contributed to better map the putative CPB2 QTNs, further studies are required to clarify the role of the promoter region.
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Affiliation(s)
- Corinne Frère
- Institut National de la Santé et de la Recherche Médicale (INSERM), Unite Mixté de Recherche (UMR) 626, Marseille, F-13385 France
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Ceresa E, Van de Borne K, Peeters M, Lijnen HR, Declerck PJ, Gils A. Generation of a stable activated thrombin activable fibrinolysis inhibitor variant. J Biol Chem 2006; 281:15878-83. [PMID: 16595693 DOI: 10.1074/jbc.m509839200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activated thrombin activable fibrinolysis inhibitor (TAFIa), generated upon activation of TAFI, exerts an antifibrinolytic effect. TAFIa is a thermolabile enzyme, inactivated through a conformational change. The objective of the current study was to generate a stable variant of human TAFIa. Using a site-directed as well as a random mutagenesis approach to generate a library of TAFI mutants, we identified two mutations that increase TAFIa stability, i.e. a Ser305 to Cys and a Thr329 to Ile mutation, respectively. Combining these mutations in TAFI-Ala147-Ile325, the most stable isoform of TAFIa (half-life of 9.4 +/- 0.4 min), revealed a TAFIa half-life of 70 +/- 3.1 min (i.e. an 11-fold increase versus 6.3 +/- 0.3 min for TAFIa-Ala147-Thr325, the most frequently occurring isoform of TAFI in humans) at 37 degrees C. Moreover, clot lysis (induced by tissue plasminogen activator) experiments in which TAFI-Ala147-Cys305-Ile325-Ile329 was added to TAFI-depleted plasma revealed a 50% clot lysis time of 313 +/- 77 min (i.e. a 3.0-fold increase versus 117 +/- 10 min for TAFI-Ala147-Thr325). The availability of a more stable TAFIa variant will facilitate the search for inhibitors and allow further structural analysis to elucidate the mechanisms of the instability of TAFIa.
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Affiliation(s)
- Erik Ceresa
- Laboratory for Pharmaceutical Biology and Phytopharmacology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
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Ceresa E, Brouwers E, Peeters M, Jern C, Declerck PJ, Gils A. Development of ELISAs measuring the extent of TAFI activation. Arterioscler Thromb Vasc Biol 2005; 26:423-8. [PMID: 16339503 DOI: 10.1161/01.atv.0000199246.08616.98] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To date, quantitation of TAFI antigen levels has been mainly focused on "total" antigen levels and has been shown to yield ambiguous results because of the existence of different isoforms and various degrees of activation. Our objective was to develop assays that allow measuring the extent of TAFI activation. METHODS AND RESULTS A variety of enzyme-linked immunosorbent assays (ELISAs) were evaluated for their preferential reactivity toward TAFI before and after activation, and toward the recombinantly expressed activation peptide. Three ELISAs with distinct reactivities were selected: recognizing either exclusively nonactivated TAFI, the released activation peptide, or exclusively TAFIa (activated TAFI). Evaluation of TAFI activation during clot lysis revealed that decreases of TAFI levels are associated with increases of the released activation peptide and TAFIa levels. In addition, antigenic measurement of TAFIa parallels activity measured by chromogenic assay. Analyzing plasma samples revealed that subjects with hyperlipidemia had significantly higher plasma levels of both the activation peptide (109.2 versus 95.5; P<0.001) and TAFIa (112.1 versus 103.3; P=0.03), and not of TAFI antigen (92.5 versus 87.9; P=0.07) (results in % of plasma pooled from normolipidemic subjects). CONCLUSIONS ELISAs that allow to measure the extent of TAFI activation were developed. These ELISAs constitute more sensitive markers in studies on the relationship between TAFI and cardiovascular diseases.
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Affiliation(s)
- Erik Ceresa
- Laboratory for Pharmaceutical Biology and Phytopharmacology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Belgium
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Gils A, Ceresa E, Macovei AM, Marx PF, Peeters M, Compernolle G, Declerck PJ. Modulation of TAFI function through different pathways--implications for the development of TAFI inhibitors. J Thromb Haemost 2005; 3:2745-53. [PMID: 16359512 DOI: 10.1111/j.1538-7836.2005.01629.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To elucidate the mechanism and the binding regions of monoclonal antibodies (MA) that interfere with thrombin-activatable fibrinolysis inhibitor (TAFI)/activated thrombin-activatable fibrinolysis inhibitor (TAFIa) activity. RESULTS Of 42 MA, 19 interfere with the TAFI activation/TAFIa activity resulting in an inhibition of up to 92%. Characterization of the mechanism of inhibition revealed that 14 MA blocked the activation of TAFI by thrombin/thrombomodulin completely whereas five MA interfered directly with the enzymatic activity of TAFIa. Surprisingly, the former, except one, induced a significant reduction of clot lysis time whereas the latter did not. Affinity studies using a human/murine TAFI chimer revealed that the binding region of the 14 activation blocking MA is located between AA1 and AA67. MA that inhibit exclusively the activation of TAFI by thrombin/thrombomodulin bind to Gly66. A MA that inhibits the activation of TAFI by both thrombin/thrombomodulin and plasmin binds to Val41. The MA that interfere with the enzymatic activity bind to the TAFIa moiety. CONCLUSIONS The current study reveals at least three different putative molecular targets in the search for pharmacologically active compounds to modulate TAFIa activity.
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Affiliation(s)
- A Gils
- Laboratory for Pharmaceutical Biology and Phytopharmacology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Leuven, Belgium.
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Willemse JL, Hendriks DF. Measurement of procarboxypeptidase U (TAFI) in human plasma: a laboratory challenge. Clin Chem 2005; 52:30-6. [PMID: 16299049 DOI: 10.1373/clinchem.2005.055814] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND The importance of carboxypeptidase U (CPU) as a novel regulator of the fibrinolytic rate has attracted much interest during recent years. CPU circulates in plasma as a zymogen, proCPU, that can be activated by thrombin, thrombin-thrombomodulin (T-Tm), or plasmin. Given that the proCPU concentration in plasma is far below its K(m) for activation by the T-Tm complex, the formation of CPU will be directly proportional to the proCPU concentration. A low or high proCPU plasma concentration might therefore tip the balance between profibrinolytic and antifibrinolytic pathways and thereby cause a predisposition to bleeding or thrombosis. CONTENT To measure plasma proCPU concentrations, different methods have been developed based on 2 different principles: antigen determination and measurement of CPU activity after quantitative conversion of the proenzyme to its active form by addition of T-Tm. The major drawbacks that should be kept in mind when analyzing clinical samples by both principles are reviewed. CONCLUSIONS proCPU is a potential prothrombotic risk factor. Evaluation of its relationship with thrombosis requires accurate assays. Many assays used in different clinical settings are inadequately validated, forcing reconsideration of conclusions made in these reports.
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Affiliation(s)
- Johan L Willemse
- Laboratory of Medical Biochemistry, University of Antwerp, B-2610 Wilrijk, Belgium
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Smolarczyk K, Boncela J, Szymanski J, Gils A, Cierniewski CS. Fibrinogen contains cryptic PAI-1 binding sites that are exposed on binding to solid surfaces or limited proteolysis. Arterioscler Thromb Vasc Biol 2005; 25:2679-84. [PMID: 16210568 DOI: 10.1161/01.atv.0000189305.84297.8b] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE In this work, we identified the fibrinogen sequence that on exposure serves as the primary binding site for functionally active PAI-1 and to a lesser extent for its latent form. In contrast, this site only weakly interacts with PAI-1 substrate. METHODS AND RESULTS The binding site is located in the N-terminal alpha (20-88) segment of fibrinogen, in the region exposed on (1) adsorption of fibrinogen to solid surfaces; (2) the release of fibrinopeptide A during thrombin conversion of fibrinogen to fibrin; and (3) plasmin degradation of fibrinogen. This region was first identified by the yeast 2-hybrid system, then its binding characteristics were evaluated using the recombinant alpha(16-120) fragment and its shorter version, the alpha(20-88) fragment, in a solid phase binding assay and plasmon surface resonance measurements. Because fibrinogen fragment E does not bind PAI-1, it suggests that sequences of Aalpha chain interacting with PAI-1 are located in the N-terminal part of the alpha(20-88) segment. CONCLUSIONS Therefore, PAI-1 directly bound to the alpha(20-88) and thus concentrated in fibrinogen/fibrin, particularly at sites of injury and inflammation, may account for the recent observations that both its active and latent forms stimulate cell migration and wound healing.
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