Comparative effect of heparin and heparan sulphate on two abnormal antithrombin III type 3 variants

Hypercoagulable States

The hypercoagulable states consist of a group of prothrombotic clinical disorders associated with an increased risk for thromboembolic events. The abnormalities lead to inappropriate thrombus formation. After a review of the coagulation process, inherited disorders (including antithrombin-III deficiency, protein CS system deficiencies, disorders of plasmin generation, dysfibrinogenemias, and homocysteinuria) and acquired disorders (including responses to surgery, cancer, drugs, and the antiphospholipid syndrome) are described. Screening and management methods are discussed. Copyright © 1997 by W. B. Saunders Company.

Inhibition of factor VIII with a partially inhibitory human recombinant monoclonal antibody prevents thrombotic events in a transgenic model of type II HBS antithrombin deficiency in mice

Venous thromboembolic disease is a major cause of morbidity and mortality, necessitating antithrombotic therapy. A human monoclonal anti-factor (F)VIII antibody, LCL-mAb-LE2E9, produced by a lymphoblastoid cell line derived from a hemophilia A patient with inhibitor to wild-type but not mutant self FVIII, was previously reported to achieve efficient inhibition of thrombosis in an experimental vena cava thrombosis model in mice. Here, the antithrombotic efficacy of a recombinant DNA-derived version of this anti-FVIII antibody (rec-mAb-LE2E9) was tested in mice which carry a type II heparin binding site antithrombin deficiency mutation and display spontaneous chronic thrombosis in several sites including the penile vein of sexually active males. The recombinant anti-FVIII antibody (100 microg, repeated after 3 days) prevented thrombotic priapism in all treated males, whereas all control animals treated with saline (group of four animals) developed priapism within 6 days after mating (P < 0.05 for treated vs. saline). The rec-mAb-LE2E9 and the original LCL-mAb-LE2E9 were equally effective (five and seven males/group, respectively). These results confirm that FVIII inhibition represents a potent antithrombotic strategy, and show that both LCL-mAb-LE2E9 and rec-mAb-LE2E9 efficiently prevent thrombosis in a physiological model representative of thrombosis in patients with a severe prothrombotic risk.

Heparin-like functionalized polymer surfaces: discrimination between catalytic and adsorption processes during the course of thrombin inhibition

Thrombus formation on blood-contacting artificial surfaces is a major problem. Antithrombogenic polymer surfaces have been obtained either by heparin binding, or by grafting sulphonate and/or amino acid sulphonamide groups on insoluble polystyrene. In addition to their capacity to adsorb thrombin, such surfaces were shown to be able to catalyse its inhibition by antithrombin III (AT), i.e. they are endowed with heparin-like activity. The results were mainly obtained by using clotting assays. In many cases, delineating adsorption and catalytic processes by such assays is not possible when evaluating anticoagulant polymer surfaces. To overcome this problem, the kinetics of thrombin adsorption and inhibitions by AT and heparin cofactor II (HC) in the presence of such surfaces have been measured by using an assay performed with a thrombin-specific chromogenic substrate. A simple kinetic model of thrombin consumption is proposed. The relevant calculations, carried out with the help of a computer program, lead to determination of relative second order rate constants of thrombin adsorption and inhibitions by AT and HC in the presence of the polymers. In addition to thrombin adsorption, polystyrene surfaces bearing only sulphonate groups catalyse inhibition by AT, whereas polystyrene surfaces bearing either aspartate, glycinate or isophthalate sulphonamide groups catalyse both inhibitions by AT and HC.

Anticoagulant effects of sulphonated polyurethanes

Sulphonated polyurethanes have been shown to have excellent blood contacting properties. In this paper, similar polyurethanes which are water soluble have been investigated to determine their influence on thrombus formation. These polymers were shown to delay clotting times in the following ways: by direct complex formation between the polymer and thrombin; by interference with fibrin polymerization; and by complex interactions between polymer, thrombin, plasma antiproteases and fibrinogen in plasma.

Anticoagulant properties of a fucoïdan fraction

Fucoïdans are a family of high molecular weight sulphated polysaccharides in the Mr range 8 x 10(5) -10(6), widely dispersed in brown seaweed cell wall. When extracted from several brown algae, they exhibit anticoagulant properties. The chemical degradation of a crude extract, from Pelvetia canaliculata, was undertaken to obtain a low molecular weight polysaccharide (Mr 20,000 +/- 5,000) with the purpose of a possible clinical use. Its anticoagulant potency was investigated through the inhibition of factor IIa and factor Xa in the presence of antithrombin III or heparin cofactor II. The degraded fucoïdan revealed a potent antithrombin activity: studied in an antithrombin III depleted plasma or in the presence of purified heparin cofactor II, the fucoïdan was as efficient as heparin and dermatan sulphate on heparin cofactor II potentiation, at the same concentration by weight. In whole plasma or in the presence of the purified inhibitor, an anti-factor IIa activity mediated by antithrombin III was detected (30 times less potent than for heparin, on a weight to weight basis). In contrast, no anti-factor Xa activity was detected in the presence of the degraded fucoïdan, under the same experimental conditions. These fucoïdans, by-products of alginates preparation in the food and cosmetologic industries, are obtained easily. Thus, they may represent a cheap and easy source of a new type of anticoagulants.

Antithrombin III-Amiens: a new family with an Arg47----Cys inherited variant of antithrombin III with impaired heparin cofactor activity

A family with an antithrombin III variant (AT-III-Amiens) demonstrating abnormal heparin cofactor activity is described. Amplification and direct sequencing of genomic DNA by the polymerase chain reaction procedure permitted the identification of an Arg47----Cys mutation in exon 2 of the variant antithrombin III gene.

Plasmatic antiproteinase activity enhancement by insoluble functionalized polystyrene surfaces

Antithrombogenic functional polymer surfaces have been obtained by grafting heparin or by substituting insoluble polystyrene with sulphonate and/or amino acid sulphamide groups. Their heparin-like properties have been related to their catalytic effects on the antithrombin III - thrombin complex formation. Amongst these antithrombogenic surfaces, this study demonstrates that some insoluble amino acid sulphamide derivatives of polystyrene strongly potentiate heparin cofactor II, in addition to antithrombin III. In contrast, an insoluble polystyrene sulphonate and, to a lesser extent, an insoluble heparin copolymer, are better catalysts of antithrombin III. It is hypothesized that such different behaviours result from different conformations of the species adsorbed onto the surfaces. The conclusions support the possible use of such amino acid sulphamide groups to prepare antithrombogenic surfaces in contact with blood.

Molecular characterization of antithrombin III (ATIII) variants using polymerase chain reaction. Identification of the ATIII Charleville as an Ala 384 Pro mutation

The genes of seven structural mutants of antithrombin III (ATIII), presenting either defective serine protease reactivity or abnormal heparin binding, were analyzed. The polymerase chain reaction (PCR) was used to amplify the corresponding gene exon and the mutation was identified by either dot blot analysis using a battery of allele-specific oligonucleotide probes or sequencing. Variants Paris and Paris 2 were identified as Arg 47 Cys mutations, and Clichy, Clichy 2, and Franconville were found to be Pro 41 Leu mutations. All five are heparin binding-site variants. ATIII Avranches is an Arg 393 His mutation and ATIII Charleville is an Ala 384 Pro mutation. These two mutations impair the reactive site of the molecule. ATIII Charleville is a new mutation of the reactive center, as predicted by previous biochemical data. The position of this new mutation, together with the other previously described mutations of the reactive center, sheds light on the molecular function of this site in inhibiting thrombin. Finally, genomic amplification by PCR is a powerful technique for the fast identification of antithrombin III mutations and their homozygous/heterozygous status, and should be useful for predicting thrombotic risk.

Proposed heparin binding site in antithrombin based on arginine 47. A new variant Rouen-II, 47 Arg to Ser

Antithrombin Rouen-II, a new inherited variant of antithrombin-III, was found in two members of a family with no definite history of thrombosis. The subjects had normal antigenic concentrations of antithrombin and normal progressive inhibitory activity. However, the variant had defective heparin and heparan sulfate cofactor activities, and was not activated by a synthetic pentasaccharide representing the minimum heparin sequence. The abnormal antithrombin was isolated using heparin-Sepharose chromatography, and on electrophoresis at pH 8.6 migrated more anodally than normal. Two-dimensional peptide mapping of tryptic and Staphylococcus aureus V8 protease digests was performed and the abnormal peptide was located by tryptophan staining. Amino acid sequence studies demonstrated a substitution of arginine at residue 47 by a serine. Evidence strongly suggests that arginine 47 is a prime heparin binding site in antithrombin and that it forms part of a proposed positively charged linear site (to which heparin binds) that stretches across the surface of the molecule from the A to the D helix.