Identification and purification of vitamin K-dependent proteins and peptides with monoclonal antibodies specific for gamma -carboxyglutamyl (Gla) residues.
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Novel monoclonal antibodies that specifically recognize gamma-carboxyglutamyl (Gla) residues in proteins and peptides have been produced. As demonstrated by Western blot and time-resolved immunofluorescence assays the antibodies are pan-specific for most or all of the Gla-containing proteins tested (factors VII, IX, and X, prothrombin, protein C, protein S, growth arrest-specific protein 6, bone Gla protein, conantokin G from a cone snail, and factor Xa-like proteins from snake venom). Only the Gla-containing light chain of the two-chain proteins was bound. Decarboxylation destroyed the epitope(s) on prothrombin fragment 1, and Ca(2+) strongly inhibited binding to prothrombin. In Western blot, immunofluorescence, and surface plasmon resonance assays the antibodies bound peptides conjugated to bovine serum albumin that contained either a single Gla or a tandem pair of Gla residues. Binding was maintained when the sequence surrounding the Gla residue(s) was altered. Replacement of Gla with glutamic acid resulted in a complete loss of the epitope. The utility of the antibodies was demonstrated in immunochemical methods for detecting Gla-containing proteins and in the immunopurification of a factor Xa-like protein from tiger snake venom. The amino acid sequences of the Gla domain and portions of the heavy chain of the snake protein were determined. (+info)
The role of coagulation abnormalities in the development of Perthes' disease.
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Recent reports have suggested an association between Perthes' disease and an underlying thrombophilic or hypofibrinolytic tendency. In Northern Ireland there is a high incidence of Perthes' disease (11.7 per 100,000 or 1 in 607 children) in a stable paediatric population. We reviewed 139 children with Perthes' disease and compared them with a control group of 220 aged- and gender-matched healthy primary schoolchildren with similar racial and ethnic backgrounds. There were no significant deficiencies of antithrombotic factors protein C, protein S, antithrombin III or resistance to activated protein C. A total of 53 (38.1%) of the children with Perthes' disease had a prolonged activated partial thromboplastin time (>38) compared with 13 (5.9%) of the control group (p < 0.001). Our findings have shown that using standard assays, thrombophilia secondary to antithrombotic factor deficiency or resistance to activated protein does not appear to be an aetiological factor for Perthes' disease. The cause of the prolonged activated partial thromboplastin time, usually associated with a clotting factor deficiency, is under further investigation. (+info)
Factor V Leiden mutation, prothrombin gene mutation, and deficiencies in coagulation inhibitors associated with Budd-Chiari syndrome and portal vein thrombosis: results of a case-control study.
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In a collaborative multicenter case-control study, we investigated the effect of factor V Leiden mutation, prothrombin gene mutation, and inherited deficiencies of protein C, protein S, and antithrombin on the risk of Budd-Chiari syndrome (BCS) and portal vein thrombosis (PVT). We compared 43 BCS patients and 92 PVT patients with 474 population-based controls. The relative risk of BCS was 11.3 (95% CI 4.8-26.5) for individuals with factor V Leiden mutation, 2.1(95% CI 0.4-9.6) for those with prothrombin gene mutation, and 6.8 (95% CI 1.9-24.4) for those with protein C deficiency. The relative risk of PVT was 2.7 (95% CI 1.1-6.9) for individuals with factor V Leiden mutation, 1.4 (95% CI 0.4-5.2) for those with prothrombin gene mutation, and 4.6 (95% CI 1.5-14.1) for those with protein C deficiency. The relative risk of BCS or PVT was not increased in the presence of inherited protein S or antithrombin deficiency. Concurrence of either acquired or inherited thrombotic risk factors was observed in 26% of the BCS patients and 37% of the PVT patients. We conclude that factor V Leiden mutation and hereditary protein C deficiency appear to be important risk factors for BCS and PVT. Although the prevalence of the prothrombin gene mutation was increased, it was not found to be a significant risk factor for BCS and PVT. The coexistence of thrombogenic risk factors in many patients indicates that BCS and PVT can be the result of a combined effect of different pathogenetic mechanisms. (+info)
Structural basis for inhibition promiscuity of dual specific thrombin and factor Xa blood coagulation inhibitors.
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BACKGROUND: A major current focus of pharmaceutical research is the development of selective inhibitors of the blood coagulation enzymes thrombin or factor Xa to be used as orally bioavailable anticoagulant drugs in thromboembolic disorders and in the prevention of venous and arterial thrombosis. Simultaneous direct inhibition of thrombin and factor Xa by synthetic proteinase inhibitors as a novel approach to antithrombotic therapy could result in potent anticoagulants with improved pharmacological properties. RESULTS: The binding mode of such dual specific inhibitors of thrombin and factor Xa was determined for the first time by comparative crystallography using human alpha-thrombin, human des-Gla (1--44) factor Xa and bovine trypsin as the ligand receptors. The benzamidine-based inhibitors utilize two different conformations for the interaction with thrombin and factor Xa/trypsin, which are evoked by the steric requirements of the topologically different S2 subsites of the enzymes. Compared to the unliganded forms of the proteinases, ligand binding induces conformational adjustments of thrombin and factor Xa active site residues indicative of a pronounced induced fit mechanism. CONCLUSION: The structural data reveal the molecular basis for a desired unselective inhibition of the two key components of the blood coagulation cascade. The 4-(1-methyl-benzimidazole-2-yl)-methylamino-benzamidine moieties of the inhibitors are able to fill both the small solvent accessible as well as the larger hydrophobic S2 pockets of factor Xa and thrombin, respectively. Distal fragments of the inhibitors are identified which fit into both the cation hole/aromatic box of factor Xa and the hydrophobic aryl binding site of thrombin. Thus, binding constants in the medium-to-low nanomolar range are obtained against both enzymes. (+info)
The dynamics of thrombin formation.
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The central event of the hemostatic process is the generation of thrombin through the tissue factor pathway. This is a highly regulated, dynamic process in which thrombin itself plays many roles, positively and negatively its production and destruction. The hemostatic process is essential to normal physiology and is also the Achilles heel of our aging population. The inappropriate generation of thrombin may lead to vascular occlusion with the consequence of myocardial infarction, stroke, pulmonary embolism, or venous thrombosis. In this review, we summarize our present views regarding the tissue factor pathway by which thrombin is generated and the roles played by extrinsic and intrinsic factor Xa generating complexes in hemostasis and the roles of the stoichiometric and dynamic inhibitors that regulate thrombin generation. (+info)
Thrombotic risk factors and extent of liver fibrosis in chronic viral hepatitis.
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BACKGROUND AND AIMS: Thrombosis of the small intrahepatic veins has been suggested to trigger liver tissue remodelling. We evaluated the prevalence of multiple thrombotic risk factors and their association with the extent of fibrosis in chronic viral hepatitis. METHODS: Ninety consecutive patients with chronic hepatitis B or C without malignancy, a history of venous thrombosis, or antiviral/immunosuppressive therapy within the last six months were included. Thrombophilic and coagulation factors were evaluated on the liver biopsy day. RESULTS: One or more thrombotic risk factors were found in 68% and > or =2 factors in 37% of patients. Higher necroinflammatory activity was independently associated with higher prothrombin time (p=0.003), alanine aminotransferase level (p=0.011), and histological staging (p=0.018). Patients with staging scores of 4-6 compared with those with scores of 0-3 more frequently had deficiency of protein C (24% v 3%; p=0.007), antithrombin III (28% v 5%; p=0.005), and plasminogen (19% v 2%; p=0.03), and a trend for more frequent activated protein C resistance (8% v 0%; p=0.075). The presence of > or =1 significant thrombotic risk factor was observed in 11/25 (44%) patients with staging scores of 4-6 and in 6/65 (9%) patients with scores of 0-3 (p<0.001), being the only variable independently associated with advanced staging (odds ratio 2.4, p=0.02). CONCLUSIONS: Thrombotic risk factors are frequently detected in patients with chronic viral hepatitis and the presence of > or =1 significant factor is associated with more advanced fibrosis. Whether the association of such thrombophilic conditions with advanced fibrosis is a primary or secondary phenomenon and whether their development in combination with local inflammation accelerate the progression of liver fibrosis need further evaluation. (+info)
Mikamo Lecture: a radical view on the 'superfamily' of cardiovascular risk factors.
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Many risk factors for cardiovascular disease generate superoxide in the blood vessels and thereby impair endothelial function. To emphasize the critical role of oxygen radicals, this is a 'radical view' of those risk factors. It will be useful to organize risk factors into a 'superfamily', with consideration of mediators, mechanisms, and target organs. Studies are summarized which suggest that, in parallel with the impairment of endothelial vasomotor function, the thrombin/thrombomodulin/activated protein C anticoagulant mechanism, which requires endothelial thrombomodulin, is also impaired by atherosclerosis and improves during regression of atherosclerosis. Impairment of the anticoagulant mechanism may contribute to thrombosis in atherosclerotic arteries, and improvement of the anticoagulant mechanism during regression of atherosclerosis may reduce the risk of cardiovascular events. (+info)
Time course of coagulation parameters, cytokines and adhesion molecules in Plasmodium falciparum malaria.
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We studied 38 patients with malaria tropica over a period of 5 days during antiparasitic therapy. Serum or plasma levels of interleukin (IL) 1beta, IL-6, IL-10, tumour necrosis factor-alpha (TNF-alpha), the soluble vascular adhesion molecule (sVCAM) and the soluble intracellular adhesion molecule (sICAM) were determined by enzyme-linked immunosorbent assay. Protein C and antithrombin III activity were analysed by chromogenic tests and protein S activity by a clotting test. Antithrombin III, protein C and protein S activity was significantly lower in patients with severe malaria and displayed a highly significant increase in activity over the time of evaluation. Levels of sVCAM and sICAM were increased for the whole study period, but no significant differences were found between severe and mild malaria cases. Serum IL-1beta, IL-6 and IL-10 levels were significantly higher in patients with severe malaria, whereas no significant differences were found for TNF-alpha. IL-6 and IL-10 decreased significantly over 5 days during schizontocidal therapy. Our data show an impairment of the coagulation system which correlates with pro-inflammatory cytokines and therefore with the severity of the disease. (+info)