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PubMed1989

Effect of rabbit thrombomodulin on thrombin inhibition by antithrombin in the presence of heparin.

Thrombomodulin acts as a cofactor for protein C activation by thrombin (PC activation cofactor activity) and inhibits thrombin-induced fibrinogen clotting (direct anticoagulant activity). In addition, rabbit thrombomodulin has been shown to promote thrombin inactivation by antithrombin (AT-dependent anticoagulant activity). However, a non-acidic form (i.e. non-retarded on ion-exchange chromatography) of thrombomodulin generated by limited proteolysis retained only the PC activation cofactor activity. The acidic form (retarded on ion-exchange chromatography) of thrombomodulin is now shown to prevent the rapid inactivation of thrombin by antithrombin in the presence of heparin, presumably by preventing the formation of the ternary thrombin-AT-heparin complex. This effect was not observed with non-acidic thrombomodulin. When submitted to chondroitinase digestion, thrombomodulin was converted into an essentially non-acidic form that lacked both the AT-dependent and the direct anticoagulant activities but showed a PC activation cofactor function indistinguishable from that of native thrombomodulin. This chondroitinase-digested form did not prevent the catalytic effect of heparin on the inhibition of thrombin by AT. It is concluded that the acidic domain of rabbit thrombomodulin, a chondroitin (dermatan) sulfate glycosaminoglycan, interacts with a site of the thrombin molecule that is not involved in the protein C activation cofactor function, but is essential to the cleavage of fibrinogen or binding of heparin.

Animals↗

PubMed1989

Coagulation cascade, fibrinolytic system, antithrombin III, protein C and protein S in patients maintained on continuous ambulatory peritoneal dialysis.

We studied the coagulation cascade, fibrinolytic system and naturally occurring anticoagulants in a group of 14 patients with end-stage renal disease maintained on continuous ambulatory peritoneal dialysis (CAPD). The results were compared with those obtained in a group of ten normal volunteers. Plasma procoagulant activities of factors XII, XI, IX, VIII, VII, X and II were significantly greater in the CAPD group as compared to the normal control group. Likewise plasma concentrations of total and free protein S were increased in the CAPD group. Although the mean value for plasma factor V activity in the CAPD group was higher than that found in the control group the difference did not attain statistical significance. In addition plasma fibrinogen concentration and factor VIII-related antigen level were significantly increased in CAPD patients. No significant difference was found between the CAPD patients and the control group with respect to plasma levels of protein C, antithrombin III, plasminogen or alpha 2-antiplasmin. In summary, the results demonstrate a tendency for increased levels of various coagulation factors and protein S in CAPD patients with no significant alterations in the levels of various fibrinolytic and endogenous anticoagulant agents, i.e. antithrombin III and protein C. The clinical significance and the mechanism responsible for the observed changes require further investigation.

Antithrombin III↗

PubMed1991

The influence of sulfate content and molecular weight of a fucan sulfate from the brown seaweed Ecklonia kurome on its antithrombin activity.

The antithrombin effects of the sub-fractionated fucans with different molecular weights and sulfate contents, which were prepared from a fucan sulfate isolated from the brown seaweed Ecklonia kurome, were examined for their abilities to inhibit thrombin-fibrinogen reaction and amidolytic activity of thrombin, and to bind to fibrinogen. The inhibitory effects of the fucans on both fibrinogen clotting by thrombin and amidolysis of the protein in the presence of heparin cofactor II were improved with increase in their molecular weights and reduced with decrease in their sulfate contents. The binding abilities of the fucans with almost the same sulfate content to fibrinogen were unchanged independently of their molecular weights, although the ability diminished with decrease in the sulphate content. These results suggest that heparin cofactor II-mediated antithrombin activity of the fucan sulfate is dependent on both its sulfate content and molecular weight, and also that the inhibitory effect of the polysaccharide on fibrinogen clotting by thrombin may be attributable to the steric hindrance by its binding to fibrinogen.

Amides↗

PubMed1991

Comparison of thrombin-antithrombin complex (TAT) levels and fibrinopeptide A following thrombin incubation of human plasma using hirudin as an inhibitor of TAT formation.

Following incubation of citrated plasma with human thrombin, the interaction of thrombin with antithrombin III was measured as thrombin-antithrombin complex (TAT) concentration. Comparison was made to thrombin activity on fibrinogen, assayed as fibrinopeptide A (FPA). Light scattering studies were included to evaluate polymerization of fibrin. Hirudin, at a final concentration of 100 U/ml, effectively inhibited TAT generation at final thrombin concentrations below 0.4 NIH U/ml. Hirudin by itself did not affect the TAT ELISA analysis. TAT and FPA values correlated closely (r = 0.83, p less than 0.001) and may equally well represent in vitro thrombin activity.

Antithrombin III↗

PubMed1992

Study of low molecular weight heparin effect on the relation between anticoagulant activity and antithrombin III affinity.

Low molecular weight heparin (FR-860), and conventional unfractionated heparin (UF-heparin) were fractionated by rabbit antithrombin III (AT III)-Sepharose, and the effects of each affinity fraction on the coagulation and fibrinolytic activities were investigated. FR-860 was fractionated to no-affinity, low-affinity (LA) and high-affinity (HA) fractions, and UF-heparin to LA and HA fractions. The HA fractions showed higher activities regarding the prolongation of activated partial thromboplastin time, anti-factor Xa activity and antithrombin activity compared with those of LA. The HA and LA fractions exhibited the enhancement of heparin cofactor II (HC II) activity and fibrinolytic activity in a dose-dependent manner. These results suggest that the antithrombotic activity of FR-860 is exerted through AT III and other mechanism such as HC II-mediated system.

Animals↗

PubMed1994

High F1.2 fragment of prothrombin, thrombin-antithrombin III complex (TAT) and soluble fibrin plasma levels demonstrate hypercoagulability induced during loco-regional thrombolytic therapy with rt-PA.

In order to investigate the coagulation and fibrinolysis state in arterial peripheral thrombosis and thrombolysis, we studied 33 consecutive patients (mean age = 65, range: 28-88), 25 males and 8 females diagnosed of acute or subacute lower limb arterial thrombosis, treated with an intrathrombus infusion of rt-PA (0.1 mg/Kg/h) for three hours. Plasma levels of antithrombin III (AT-III), protein C (PC), plasminogen (Pg) and alpha 2-antiplasmin (AP), total and free protein S (PS), thrombin-antithrombin III complex (TAT), F1.2 fragment of prothrombin (F1.2), fibrinogen (Fg), soluble fibrin monomers (FM), tissue-plasminogen activator (t-PA), plasminogen activator inhibitor 1 (PAI-1), total fibrinogen/fibrin degradation products (TDP) and D dimer (DD) were determined prior to the therapeutic regime, at the end of the treatment, and 24 hours later. Levels of AT-III and protein C were somewhat low during the complete study. There was an increase in t-PA, TDP and D Dimer and a decrease of fibrinogen, alpha 2-antiplasmin and plasminogen at 3 hours. An elevation of TAT, fibrin monomers and F1.2 levels was found at three hours. A positive correlation between TAT and F1.2 was observed (r = 0.57, p < 0.05). There was also a positive correlation between soluble fibrin and TAT (r = 0.59, p < 0.05) and with F1.2 (r = 0.56. p < 0.05). These latter facts reflect an hypercoagulable situation induced during loco-regional thrombolytic therapy.

Adult↗

PubMed1995

Antithrombin III deficiency as a risk factor for catheter-related central vein thrombosis in cancer patients.

The fibrin sleeve of venous catheters (VC) and parietal thrombi represent frequent and dangerous side-effects of central venous catheterization (CVC), due to the risk of embolism. Reduced levels of coagulation clotting factors inhibitors (such as Antithrombin III) are known to be associated with increased thrombogenic risk. The aim of this study was to evaluate the role of Antithrombin III (AT III) deficiency as a risk factor for thrombosis in cancer patients undergoing CVC. The study groups included patients with a reduced AT III activity (< 70%, 20 consecutive patients) and with normal AT III values (> 70%, 20 randomly selected patients), requiring a VC for chemotherapy and/or total parenteral nutrition. The study protocol included evaluation of Hb, PLTs, PT (INR), aPTT, Fibrinogen and AT III at days 0, 1, 3 and 8 after CVC and upon VC removal. Peripheral and pullout phlebographies were performed in all patients on catheter withdrawal. A quantitative scale was developed to evaluate both VC and parietal thrombus degree in each catheter-containing venous segment (subclavian, innominate, superior vena cava); the sum of the mean values was defined as overall thrombus. The average VC dwelling time was similar in both groups. There were no significant differences in Hb, PLTs, PT (INR), aPTT, Fibrinogen and in the remaining parameters of the study between the two groups. The group with AT III deficiency presented a higher degree of both parietal (p < 0.05) and overall thrombus (p < 0.02). Data showed a higher severity of CVC-related thrombosis in patients with AT III deficiency than in the control group. Further studies are needed to evaluate whether the therapeutically-induced normalization of AT III levels can reduce the thrombosis degree.

Adult↗

PubMed1991

Production of thrombin and antithrombin III by brain and astroglial cell cultures.

There is increasing evidence that some proteases and protease inhibitors are produced within the central nervous system. It has been proposed that the balance between these two classes of proteins may be an important modulator of brain cell growth and differentiation. Here we report that antithrombin III (ATIII) is produced in brain and primary astroglial cultures. In addition, we show that human astroglial cultures contain prothrombin mRNA, and secrete a thrombin-like protein that makes complexes with antithrombin III.

Animals↗

PubMed1990

Antithrombin III: structural and functional aspects.

Antithrombin III is a plasma glycoprotein responsible for thrombin inhibition in the blood coagulation cascade. The X-ray structure of its cleaved form has been determined and refined to 3.2 A resolution. The overall topology is similar to that of alpha 1-antitrypsin, another member of the serpin (serine protease inhibitor) superfamily. The biological activity of antithrombin III is mediated by a polysaccharide, heparin. The binding site of this effector is described. A possible structural transition from the native to the cleaved structure is discussed.

Amino Acid Sequence↗

PubMed1980

The heparin-accelerated neutralisation of bovine alpha and beta thrombins by antithrombin III.

The heparin-accelerated neutralisation of bovine alpha and beta thrombins has been examined using a peptide substrate H-D-phenylalanyl-pipecolyl-arginine-paranitroanilide-HCl to measure thrombin amidase activity. Alpha and beta thrombins were both neutralised by antithrombin III and this neutralisation was further accelerated by the presence of small amounts of heparin. Low and high molecular weight heparin and heparins fractionated by their affinity for antithrombin III were all able to accelerate the neutralisation of alpha and beta thrombin. This work is therefore unable to confirm reports that alpha and beta thrombins have different heparin sensitivities.

Animals↗

PubMed1991

Effects of thermodynamic nonideality in kinetic studies: evidence of an expanded intermediate complex in the inactivation of thrombin by antithrombin III.

The technique of competitive chromogenic substrate hydrolysis is used to examine the inhibitory effects of sucrose and glycerol on the inactivation of thrombin by antithrombin III. This inhibition is attributed to the existence of a slight increase in volume/asymmetry associated with formation of the thrombin-antithrombin complex that subsequently undergoes covalent modification in an irreversible inactivation step. Partial reversal of the equilibrium step is thus considered to result from the effects of molecular crowding in the highly concentrated environment that is generated by the inclusion of these small insert solutes.

Antithrombin III↗

PubMed1994

Arg-129 plays a specific role in the conformation of antithrombin and in the enhancement of factor Xa inhibition by the pentasaccharide sequence of heparin.

Small amounts of a variant antithrombin (AT) bearing an Arg-129 to Gln mutation were purified from plasma by means of affinity chromatography on insolubilized heparin at very low ionic strength. As a control, two variant antithrombins, one bearing a Pro-41 to Leu mutation and the other an Arg-47 to His mutation, were purified in the same way. The biochemical characterization of the variants and the kinetic study of thrombin and activated factor X (F Xa) inhibition in the presence of heparin and heparin derivatives suggest that Arg-129 plays a specific role in AT conformation and F Xa inhibition enhancement. Indeed, the purified variant adopted the locked conformation described for AT submitted to mild denaturing conditions (Carrell, R.W., Evans, D.Li. and Stein, P.E. (1991) Nature 353, 576-578) and resembling the latent form of plasminogen activator inhibitor (PAI) (Mottonen, J., Strand, A., Symersky, J., Sweet, R.M., Danley, D.E., Geoghegan, K.F., Gerard, R.D. and Goldsmith, E.J. (1992) Nature 355, 270-273). Moreover, the mutant AT was partially reactivated by heparin for thrombin inhibition, but did not respond to the specific pentasaccharide domain of heparin for F Xa inhibition.

Antithrombins↗

PubMed1995

Acute promyelocytic leukemia developed in a patient with congenital antithrombin III deficiency.

A case of acute promyelocytic leukemia (APL) developed in a patient with congenital antithrombin III (AT-III) deficiency is reported. Despite the presence of disseminated intravascular coagulation (DIC), plasma AT-III activity was not decreased at the diagnosis of APL compared to the patient's baseline level (approximately 50% of normal). He was successfully treated with all-trans retinoic acid (ATRA) to achieve complete remission without the use of heparin. Although he developed phlebitis at the site of insertion of the intravenous catheter during remission-induction, no major thrombotic episode was noted. Coagulation parameters including fibrin and fibrinogen degradation products (FDP-E), thrombin-antithrombin complex (TAT), FDP-D dimer (D-D dimer), and plasmin-alpha 2 plasmin inhibitor complex (PIC) improved rapidly after initiation of ATRA. This case is a clear demonstration of the characteristics of DIC developing in APL, i.e. no or minimal decrease in the level of AT-III activity and a predominant increase in the fibrinolytic system, rather than hypercoagulability.

Antithrombin III Deficiency↗

PubMed2005

Effect of genetic background on glycosylation heterogeneity in human antithrombin produced in the mammary gland of transgenic goats.

Glycosylation is involved in the correct folding, targeting, bioactivity and clearance of therapeutic glycoproteins. With the development of transgenic animals as expression systems it is important to understand the impact of different genetic backgrounds and lactations on glycosylation. We have evaluated the glycosylation of recombinant antithrombin produced in several transgenic goat lines, from cloned animals and from different types of lactation including induced lactations. Our results show glycosylation patterns from the protein expressed in animals, derived from the same founder goat, are mostly comparable. Furthermore, the protein expressed in two cloned goats had highly consistent oligosaccharide profiles and similar carbohydrate composition. However, there were significantly different oligosaccharide profiles from the proteins derived from different founder goats. Artificial induction of lactation did not have significant effects on overall carbohydrate structures when compared to natural lactation. The only major difference was that recombinant antithrombin from induced lactations contained a slightly higher ratio of N-acetylneuraminic acid to N-glycolylneuraminic acid and less amount of oligosaccharides containing N-glycolylneuraminic acid. The oligosaccharides from all animals were a mixture of high mannose-, hybrid- and complex-type oligosaccharides. Sialic acid was present as alpha-2,6-linkage and no alpha-1,3-linked galactose was observed. These results indicate that transgenic animals with closely related genetic backgrounds express recombinant protein with comparable glycosylation.

Animals↗

PubMed2005

Clopidogrel has no effect on D-dimer and thrombin-antithrombin III levels in patients with peripheral arterial disease undergoing peripheral percutaneous transluminal angioplasty.

OBJECTIVE: Coagulation activation markers are significantly elevated in patients with peripheral arterial disease compared with healthy controls. The more severe the disease, the higher the markers. Increased coagulation activation may contribute to the disease process and the risk of complications in patients with peripheral arterial disease, particularly after endovascular intervention. Animal studies have shown that clopidogrel significantly inhibits coagulation activation. The aim of this study was to determine whether combination of aspirin and clopidogrel affects thrombin-antithrombin III and D-dimer in patients with intermittent claudication undergoing angioplasty, compared with aspirin alone. METHODS: This was a double blind, randomized placebo-controlled trial conducted in a vascular unit in a tertiary referral center. One hundred thirty-two patients with intermittent claudication were randomized to clopidogrel and aspirin or placebo and aspirin, with a loading dose 12 hours before endovascular intervention. D-dimer and thrombin-antithrombin III (TAT) levels were measured using enzyme-linked immunosorbent assay at baseline, 1 hour before, and 1 hour, 24 hours, and 30 days after intervention in 103 patients who underwent endovascular intervention. RESULTS: There was a significant rise in D-dimer levels at 1 hour and 24 hours after angioplasty in both groups (placebo group: 63.69, 141.45, 122.18 ng/mL; clopidogrel group: 103.79, 159.95, 134.69 ng/mL), but no difference between the two groups (P = .514). Similarly there was a significant rise in TAT levels at 1 hour after angioplasty in both groups (placebo group: 2.93, 6.16 microg/L; clopidogrel group: 3.39, 5.27 microg/L), with no significant difference between the two groups (P = .746). CONCLUSION: Endovascular intervention results in a significant increase in TAT and D-dimer. The addition of clopidogrel to aspirin has no effect on TAT and D-dimer before or after endovascular intervention.

Adolescent↗

PubMed2004

Latent antithrombin does not affect physiological angiogenesis: an in vivo study on vascularization of grafted ovarian follicles.

Latent antithrombin (L-AT), a heat-denatured form of native antithrombin (AT), is a potent inhibitor of pathological tumor angiogenesis. In the present study, we have investigated whether L-AT has comparable antiangiogenic effects on physiological angiogenesis of ovarian tissue. For this purpose, preovulatory follicles of Syrian golden hamsters were mechanically isolated and transplanted into dorsal skinfold chambers chronically implanted in L-AT- or AT-treated hamsters. Non-treated animals served as controls. Over 14 days after transplantation neovascularization of the follicular grafts was assessed in vivo by quantitative analysis of the newly developed microvascular network, its microvessel density, the diameter of the microvessels, their red blood cell velocity and volumetric blood flow as well as leukocyte-endothelial cell interaction using fluorescence microscopic techniques. In each group, all of the grafted follicles were able to induce angiogenesis. At day 3 after transplantation, sinusoidal sacculations and capillary sprouts could be observed, finally developing complete glomerulum-like microvascular networks within 5 to 7 days. Overall revascularization of grafted follicles did not differ between the groups studied. Interestingly, follicular grafts in L-AT- and AT-treated hamsters presented with higher values of microvessel diameters and volumetric blood flow, when compared to non-treated controls, which may be best interpreted as a reactive response to an increased release of vasoactive mediators. In conclusion, the present study demonstrates, that L-AT has no adverse effects on physiological angiogenesis of freely transplanted ovarian follicles. Thus, L-AT may be an effective drug in tumor therapy, which blocks tumor growth by selective suppression of tumor vascularization without affecting new vessel formation in the female reproductive system.

Analysis of Variance↗

PubMed2004

Separation of latent, prelatent, and native forms of human antithrombin by heparin affinity high-performance liquid chromatography.

Latent antithrombin (LAT) is a partially denatured form of human antithrombin (AT). LAT does not inhibit clotting of the blood, but has previously been shown to inhibit angiogenesis and carcinogenesis. Another probably partially denatured form is the so-called prelatent AT (P-LAT), described by Larsson et al. [J. Biol. Chem. 276 (2001) 11996]. In the present work, an analytical heparin affinity chromatography method is described that separates an AT form, which is formed during the pasteurization process and which we believe to be identical to the previously described P-LAT, from native AT and LAT. Non-pasteurized AT was shown to contain no P-LAT, while four, heat-treated commercial AT products all contained P-LAT (1-6%, mean=4%). P-LAT has a slightly lower affinity to heparin than does native AT, but exhibits a much stronger heparin affinity when compared to LAT. P-LAT and native AT were shown to have very similar thrombin inhibiting activity, while LAT lacks such activity.

Antithrombins↗

PubMed2003

The nontoxic mushroom Auricularia auricula contains a polysaccharide with anticoagulant activity mediated by antithrombin.

An acidic polysaccharide with anticoagulant activity was isolated from the edible mushroom Auricularia auricula using water, alkali or acid extracts. The alkali extract showed the highest anticoagulant activity and was thereby further purified using gel filtration chromatography. Specific anticoagulant activity of the purified polysaccharide was 2 IU/mg and its average mass was approximately 160 kDa. The polysaccharide from this species of mushroom contains mainly mannose, glucose, glucuronic acid and xylose but no sulfate esters. Its anticoagulant activity was due to catalysis of thrombin inhibition by antithrombin but not by heparin cofactor II. Inhibition of Factor Xa by antithrombin was not catalyzed by the polysaccharide. The glucuronic acid residues were essential for the anticoagulant action of the mushroom polysaccharide since the activity disappeared after reduction of its carboxyl groups. In ex vivo tests using rats orally fed with the polysaccharide, we observed an inhibitory effect on platelet aggregation as observed with aspirin, a well-known antiplatelet agent. The polysaccharides from these mushrooms may constitute a new source of compounds with action on coagulation, platelet aggregation and, perhaps, on thrombosis.

Animals↗