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Antiphosphatidylserine antibody removes annexin-V and facilitates the binding of prothrombin at the surface of a choriocarcinoma model of trophoblast differentiation.

OBJECTIVE: Trophoblast differentiation is associated with externalization of phosphatidylserine from the inner to the outer surface of the plasma membrane. In this study we tested the hypothesis that concurrent externalization and binding of annexin-V blocks the phosphatidylserine-rich surface from acting as a site for activation of coagulation and that antiphospholipid antibodies lead to a procoagulant state by preventing annexin-V binding. STUDY DESIGN: A choriocarcinoma model of trophoblast differentiation, forskolin-activated BeWo cells and immunoperoxidase techniques were used to determine surface and cytoplasmic localization of annexin-V related to differentiation. Monoclonal immunoglobulin M antibodies against phosphatidylserine- and cardiolipin-dependent antigens were used to determine the effects of antiphospholipid antibodies on annexin-V localization and on the binding of prothrombin to the BeWo surface. RESULTS: During differentiation BeWo cells externalized phosphatidylserine and increased the expression of surface annexin-V. Monoclonal antibody against phosphatidylserine removed annexin-V from the BeWo surface and increased binding of prothrombin. CONCLUSION: Antiphosphatidylserine antibody induces sites for prothrombin binding on the surface of a BeWo model of trophoblast, most likely by removing annexin-V. This mechanism could explain the frequent observation of increased thrombosis at the maternal-fetal interface in miscarriages associated with antiphospholipid antibodies.

Annexin A5↗

Idiopathic central retinal vein occlusion in a thrombophilic patient with the heterozygous 20210 G/A prothrombin genotype.

PURPOSE: To report the occurrence of monolateral central retinal vein occlusion in a patient with heterozygous 20210 G/A prothrombin genotype, known to be associated with high thrombophilic risk. METHODS: A monolateral central retinal vein occlusion was diagnosed in a 71-year-old woman, who had suffered from a deep vein thrombosis in her left leg at the age of 36 years. Mutations of the genes involved in the coagulation process were investigated by DNA polymerase chain reaction. RESULT: DNA analysis showed the patient to be heterozygous for the prothrombin 20210 G/A genetic variation. CONCLUSION: The 20210 G/A prothrombin gene mutation may be associated with central retinal vein occlusion.

Aged↗

A novel prothrombin activator from the venom of Micropechis ikaheka: isolation and characterization.

A novel prothrombin activator, Mikarin, has been isolated from Micropechis ikaheka venom. It is a single polypeptide chain metalloproteinase with the apparent molecular weight of 47kDa. Mikarin exhibits Ca(2+)-independent prothrombin activation, but no effects on other blood coagulation factors, such as factor X and fibrinogen. Mikarin is the first member of group I prothrombin activators from elapid venom. Like other high-molecular-weight snake venom proteinases, it has three structural domains, metalloproteinase and disintegrin-like and Cys-rich domains, and belongs to the P-III class of snake venom metalloproteinases. The N-terminal of Mikarin exhibits 76% sequence identity with Cobrin, a metalloproteinase identified from Naja naja venom, but very lower identities were found when compared with those from viperid and crotalid venom. In addition, the presence of disintegrin-like and Cys-rich domains in snake venom metalloproteinases with diverse biological activities suggests that these domains may be important for their function.

Amino Acid Sequence↗

Characterization of 'basparin A,' a prothrombin-activating metalloproteinase, from the venom of the snake Bothrops asper that inhibits platelet aggregation and induces defibrination and thrombosis.

A prothrombin activator, named 'basparin A,' was isolated from the venom of the crotaline snake Bothrops asper, the species responsible for the majority of snakebite cases in Central America. It is an acidic (pI 5.4), 70kDa, single chain P-III metalloproteinase comprising, in addition to the metalloproteinase domain, disintegrin-like, and high-cysteine domains. Basparin A is a glycoprotein displaying immunological cross-reactivity with BaH1, a P-III hemorrhagic metalloproteinase isolated from the same venom. It activates prothrombin through the formation of meizothrombin, without requiring additional cofactors; it is, therefore, a class A snake venom prothrombin activator. In contrast with most venom metalloproteinases, it does not degrade components of the extracellular matrix. Apart from its clotting activity, basparin A inhibits collagen-dependent platelet aggregation in vitro, an effect that does not depend on proteolytic activity. Clotting activity on human plasma is not abrogated by the plasma proteinase inhibitors alpha(2) macroglobulin and murinoglobulin, whereas activity is completely inhibited by Costa Rican polyvalent (Crotalinae) anti-venom. Basparin A does not induce local tissue alterations, such as hemorrhage, myonecrosis, and edema, in mice. Moreover, it does not induce systemic hemorrhage, thrombocytopenia nor prolongation of the bleeding time following intravenous administration. At low doses, the only observed effect induced by basparin A, when injected intravenously or intramuscularly into mice, is defibrin(ogen)ation. At higher doses, intravenous administration resulted in sudden death due to numerous occluding thrombi in pulmonary vessels. Basparin A is likely to play an important role in the coagulopathy associated with B. asper envenoming.

Animals↗

Binding of prothrombin and its fragment 1 to phospholipid membranes studied by the solvent relaxation technique.

The phospholipid headgroup mobility of small unilamellar vesicles composed of different mixtures of phosphatidyl-L-serine (PS) and phosphatidylcholine is characterized by the solvent relaxation behavior of the polarity sensitive dyes 6-propionyl-2-(dimethylamino)naphthalene (Prodan) and 6-palmitoyl-2-[trimethylammoniumethyl]-methylamino]naphthalene chloride (Patman). If the PS content exceeds 10%, the addition of calcium leads to a substantial deceleration of the solvent relaxation of both dyes, indicating the formation of Ca(PS)2 complexes. Addition of prothrombin and its fragment 1 leads to a further decrease of the headgroup mobility, as explained by the binding of more than two PS-molecules by a single protein molecule. Prodan monitors the outermost region of the bilayer and it clearly distinguishes between the binding of prothrombin and its fragment 1. The deeper incalated Patman does not distinguish between both proteins. The validity of the solvent relaxation technique for the investigation of the membrane binding of peripheral proteins is demonstrated by the studies of prothrombin induced changes in the steady-state fluorescence anisotropies of 1,6-diphenyl-1,3, 5-hexatriene.

2-Naphthylamine↗

Characterization of membrane-associated prothrombin activator in normal and injured murine tissues.

Thrombin is a multifunctional enzyme involved in coagulation, cell modulation and inflammation. We recently reported a novel membrane-associated prothrombin activator, abbreviated as MAPA, found in cultured fibroblasts and glial cell lines. In this study, we examined the physiological role of this enzyme. MAPA-like activity was detected in the liver, kidney, lung and heart but not in the spleen or brain in normal mice. To examine whether MAPA participates in biological reactions, hepatic and renal injury were induced by administration of CCl4 and HgCl2, respectively. MAPA-like activity was specifically increased in the injured tissues: the activity was elevated by about 100-fold in 48 h in the liver and increased by about 5-fold in 12 h in the kidney. Their enzymatic properties were the same as those of MAPA in 8C feline kidney fibroblast cells. Phospholipids are required for activation of prothrombin by MAPA obtained from both 8C cells and tissues. These results suggest that MAPA activates prothrombin on the cell surface in injured tissue and participates in inflammation and regeneration associated with tissue injury.

Animals↗

Arterial wall thickness and the risk of recurrent ischemic events in carriers of the prothrombin G20210A mutation with clinical manifestations of atherosclerosis.

The G20210A mutation in the prothrombin gene is an established risk factor for venous thrombosis. There is controversy about the role of this mutation in arterial thrombotic disease and atherosclerosis. We determined the presence of the prothrombin mutation and examined its influence on carotid and femoral artery intima-media thickness (IMT) and the occurrence of new ischemic events during follow-up in 277 patients with clinically manifest atherosclerotic disease: ischemic stroke, myocardial infarction or peripheral arterial disease. The mean age at entry was 63 years. Mean IMT was significantly higher in carriers of the prothrombin mutation (1.17 (SD 0.29) mm versus 0.97 (SD 0.25) mm: (delta)IMT=0.20, P=0.02). The increase in IMT was not attributable to differences in age, type of arterial disease or cardiovascular risk factors between carriers and non-carriers. During a mean follow-up of 3.5 years, a strong trend for more ischemic events was observed: 4 of the 11 carriers suffered from a recurrent ischemic event, compared with 30 of the 164 male non-carriers (36 versus 18%; P=0.06). These results suggest that the G20210A mutation contributes to the process of arterial wall thickening and is associated with the occurrence of ischemic events in a cohort of elderly persons with established atherosclerosis.

Aged↗

Purification and characterization of a prothrombin-activating protease from Nephila clavata.

We report upon the purification and characterization of a novel prothrombin-activating enzyme from the body fluid (total homogenates of isolated digestive tract without eggs, spinnerets and silk glands) of the spider, Nephila clavata by a combination of acetone fractionation, ion exchange, and Soybean trypsin inhibitor-Sepharose chromatography. Analysis of the purified enzyme with SDS-PAGE and gel filtration revealed a single polypeptide chain with an apparent molecular weight of 24kDa. The proteolytic activity of the enzyme was stable up to 50 degrees C, however, it became unstable over 55 degrees C. The enzyme had an optimum pH of 8, and Ca(2+) was not required for the enzyme activity. According to inhibition profiles obtained with several serine protease inhibitors such as PMSF and benzamidine, the purified protease is a member of the serine proteases. Bz-Ile-Glu(gamma-OR)- Gly-Arg-pNA and Z-Arg-Gly-Arg-pNA which are known as substrates for factor Xa, were hydrolyzed favorably by the enzyme. And the Nephila protease could produce thrombin from prothrombin at nM range, and form the turbid ring using fibrinogen-agarose plate. The results obtained confirmed that the purified protease is a potent prothrombin-activating activity belonging to the family of serine protease.

Animals↗

Prothrombin and factor X activator activities in the venoms of Viperidae snakes.

A Ca(2+)-dependent prothrombin activator, carinactivase-1 (CA-1), was previously found in the venom of Echis carinatus leucogaster. In the present study, the activities of CA-1-like enzymes were screened in the venoms of various Viperidae snakes. The addition of 1 mM Ca2+ ions to the venoms of only Echis snakes in Viperidae produced considerably high prothrombin activator activity, indicating that only the Echis snake venoms contain not only the Ca(2+)-independent prothrombin activator, ecarin, but also Ca(2+)-dependent activator(s). CA-1-like activators and ecarin in the venom of each Echis snake were efficiently separated by Blue Sepharose column chromatography. The venoms of the various Viperidae snakes were also examined for factor X activator activity. The venoms of genera Daboia, Vipera, Cerastes, Echis, Calloselasma and Bothrops contained factor X activator activity in the presence of Ca2+ ions. Cerastes cerastes and Calloselasma rhodostoma venoms also had Ca(2+)-independent factor X activator activity.

Animals↗

Alpha 2-macroglobulin enhances prothrombin activation and thrombin potential by inhibiting the anticoagulant protein C/protein S system in cord and adult plasma.

Protein S (PS) is a vitamin K-dependent plasma protein and serves as a cofactor for the anticoagulant activities of activated protein C (APC). We investigated the effects of different PS concentrations on prothrombin activation and thrombin generation in cord and adult plasma containing APC and different amounts of alpha 2-macroglobulin (a2-M). Prothrombin activation was assessed by monitoring the time-course of prothrombin fragment 1+2 (F1+2) generation. Thrombin generation curves were determined by means of a subsampling technique using the chromogenic substrate S-2238. We demonstrate a dose-dependent inhibition of the anticoagulant action of PS by a2-M: suppression of F1+2 and thrombin generation due to addition of PS was stronger in plasma containing low amounts of a2-M than in plasma with elevated a2-M levels. Since no complex formation between a2-M and PS was observed by means of SDS-PAGE, we attribute decreased anticoagulant action of PS at high a2-M levels to enhanced complex formation between APC and a2-M. Thereby, APC is subtracted from its cofactor PS, resulting in suppressed formation of the anticoagulant APC/PS complex. Thus, our data suggest that a2-M, besides its well-known anticoagulant effects, also acts as a procoagulant by suppressing the formation of the anticoagulant APC/PS complex. Our findings have implications particularly on thrombin generation and inhibition in cord plasma, since a2-M levels in newborns are elevated over adult values and the antithrombotic APC/PS pathway is up-regulated at birth. Therefore, elevated levels of a2-M might restrict the up-regulation of the APC/PS pathway.

Adult↗

Factor V gene G1691A mutation, prothrombin gene G20210A mutation, and MTHFR gene C677T mutation are not risk factors for pulmonary thromboembolism in Chinese population.

A mutation in coagulant factor V gene, a substitution in the 3' untranslated region of prothrombin gene, and a variant in 5,10-methylenetetrahydrofolate reductase (MTHFR) gene have been reported to be related to venous thromboembolism in Caucasians, but this relationship remains in debate in other populations. In this case-control study, we aimed to determine the prevalence of these three mutations in the Chinese population and investigate whether they are associated with pulmonary thromboembolism. The subjects consisted of 90 patients with pulmonary thromboembolism and 143 age- and sex-matched healthy controls. Traditional risk factors for venous thrombosis and pulmonary thromboembolism were investigated as well. We found that the frequencies of varicose vein, phlebitis, trauma, and surgery were significantly higher in cases than in controls. Of all subjects, none was a carrier of coagulant factor V gene G1691A mutation or prothrombin gene G 20210A mutation, which are common point mutations in Caucasians, while the frequency of MTHFR gene 677T allele exceeded 55% in cases (56.7%), controls (55.2%), and all subjects (55.8%) studied. The homozygous mutation rate of MTHFR gene was over 30% in both cases (33.3%) and controls (32.2%), but no significant difference was found in genotype distribution (chi(2)=0.100, P=0.951). Model fitting using logistic regression did not find that MTHFR gene C677T mutation was associated with pulmonary thromboembolism, consistent with the results of stratification analysis. In conclusion, coagulant factor V gene G1691A mutation and prothrombin G20210A mutation are very rare, while MTHFR C677T mutation is very common, and all of them are not associated with pulmonary thromboembolism in the Chinese population.

Case-Control Studies↗

Large-scale preparation of human thrombin: polyethylene glycol potentiates the factor Xa-mediated activation of prothrombin.

We investigated the ability of polyethylene glycol 4000 to accelerate thrombin generation in a mixture of prothrombin and factor X at concentrations of 1-30%. In the presence of 5 mM of CaCl2, polyethylene glycol 4000 promoted prothrombin activation at concentrations above 1%. The peak of activation was seen at levels of 14 and 20% of polyethylene glycol 4000. The effect of the polyethylene glycol was remarkably dependent on its molecular weight; molecular weights greater than 2000 were required for accelerating thrombin generation. Under optimal conditions, polyethylene glycol 4000, in the presence of CaCl2, promoted conversion of all of the prothrombin into thrombin and its derivatives. We conclude that polyethylene glycol 4000, at concentrations ranging from 14 to 20%, effectively accelerates thrombin generation in the presence of 5 mM of CaCl2. This new method for preparing thrombin is based on the use of polyethylene glycol 4000 and CaCl2 and is applicable to the manufacture of thrombin.

Calcium Chloride↗

Expression of prothrombin fragment 1+2 in cancer tissue as an indicator of local activation of blood coagulation.

Immunohistochemistry was applied to AMeX-fixed tissue sections of 12 adenocarcinomas of the stomach (seven intestinal adenocarcinomas and five diffuse carcinomas), 12 adenocarcinomas of the pancreas (nine ductal adenocarcinomas and three signet ring carcinomas), and 12 squamous cell carcinomas of the larynx obtained at surgical resection to examine the possibility of extravascular activation of blood coagulation in cancer tissues by exploring the in loco patterns of distribution of fibrinogen, a final product of blood coagulation, fibrin, and a by-product of coagulation reactions (prothrombin fragment 1+2). Gastric, pancreatic, and laryngeal cancers exhibited fibrinogen antigen in abundance throughout the tumor stroma. Fibrin was detected along the edges of nests of carcinoma cells and at the host-tumor interface. Prothrombin fragment 1+2 was present in the blood vessels in areas of neoangiogenesis at the host-tumor interface (gastric and pancreatic cancer tissues) and on the tumor cell bodies (pancreatic and laryngeal cancer tissues). The presence of prothrombin fragment 1+2 in cancer tissues appears to be a good indicator of coagulation activation and thrombin generation at the tumor burden.

Adenocarcinoma↗

Correction of abnormal coagulation in chronic liver disease by combined use of fresh-frozen plasma and prothrombin complex concentrates.

The effect on abnormal coagulation tests of infusions of fresh-frozen plasma (F.F.P), prothrombin complex concentrates, and a combination of these treatments was compared in 30 patients with chronic liver disease undergoing needle biopsy. A single dose of F.F.P. (12 ml/kg body-weight) was found to be the least effective therapeutic regimen. The concentrate containing factors II, IX, and X was also not adequate, but the additional administration of factor-VII concentrate corrected the prothrombin-time (P.T.) and "Normotest" (N.T.) in most patients. However, this regimen did not correct the prolonged kaolin activated partial thromboplastin-time (K.P.T.T.). The results of tests for exploring both the extrinsic (P.T. and N.T.) and intrinsic (K.P.T.T.) coagulation systems only became normal after the combined administration of a lower dose of F.F.P. (8 ml/kg body-weight) and of both concentrates (12 units/ml). There was no clinical or laboratory evidence of thrombotic complications. No patient developed acute hepatitis or hepatitis-B surface antigen in the twelve months after biopsy. These results indicate that prothrombin-complex concentrates in combination with F.F.P. may therefore be used to allow liver biopsy to be performed safely in patients presenting with severe coagulation defects.

Biopsy↗

Kringles of the plasminogen--prothrombin gene family share conformational epitopes with recombinant apolipoprotein (a): specificity of the fibrin-binding site.

Monoclonal antibodies directed against recombinant apolipoprotein (a) (r-apo(a)) lacking plasminogen-like KIV-2 repeats were used to identify structurally related conformational epitopes in various members of the plasminogen-prothrombin gene family. A number of procedures including a fibrin-binding inhibition immunoassay and surface plasmon resonance studies were used. Two antibodies (A10.1 and A10.4) recognised common conformational structures in r-apo(a), prothrombin, factor XII, plasminogen and its tissue-type and urokinase-type activators. In contrast, two other antibodies recognised specifically an epitope comprising residues of the lysine-binding site (A10.2) or close to it (A10.5) and inhibited the fibrin-binding function of r-apo(a) (IC(50)=36 pmol/l and 9.76 nmol/l, respectively). Interestingly, these antibodies distinctly recognised the elastase-derived fragments of plasminogen K4 (A10.2) and K1+2+3 (A10.5) without affecting plasminogen binding to fibrin. These results suggest that highly conserved conformational regions are common to various proteins of the plasminogen-prothrombin gene family and are in agreement with the concept that these proteins constitute a monophyletic group derived from an ancestral gene.

Antibodies, Monoclonal↗

Prothrombin fragments F1+2, thrombin-antithrombin III complexes, fibrin monomers and fibrinogen in patients with coronary atherosclerosis.

We determined the plasma levels of prothrombin fragment F1+2, thrombin-antithrombin III complexes (TAT), fibrin monomers (FM), D-dimers (DD) and fibrinogen in 57 patients with angiographically verified graded coronary artery disease (CAD) free of concomitant peripheral atherosclerosis, cerebrovascular disease or diabetes mellitus and a group of 21 apparently healthy controls. Blood was collected from the antecubital vein through atraumatic venipuncture prior to the angiographic procedure. Plasma levels of hemostatic markers were related to the presence and graded severity of CAD. The levels of prothrombin fragment F1+2 (1.74+/-0.11 vs. 1.0+/-0.07 nmol/l, P<0.001), FM (41.6+/-5.5 vs. 7.42+/-3.05 nmol/l, P<0.001), TAT (15.6+/-2.7 vs. 2.96+/-0.32 microg/l, P<0.001) and fibrinogen (3.64+/-1.3 vs. 3.08+/-0.33 g/l, P<0.01) were significantly higher in patients with CAD compared to controls, while there was no difference regarding the fibrinolytic system represented by DD (441.6+/-58.9 vs. 337.4+/-42.05 microg/l, n.s.). Within the CAD group, patients with extensive coronary atherosclerosis (> or =2 vessel disease) had significantly higher values for prothrombin fragment F1+2 (1.89 vs. 1.57 nmol/l, P = 0.04), FM (50.7 vs. 29.8 nmol/l, P = 0.03), and a trend to significance was noted for fibrinogen (3.9 vs. 3.3 g/l, P = 0.07) suggesting that blood coagulability was related to the severity of the disease and that hemostatic markers of thrombin activity represent a useful tool to identify patients with a latent hypercoagulable state with a higher susceptibility to sustain coronary thrombosis.

Antithrombin III↗

Detailed characterization of an anti-factor IX monoclonal antibody that neutralizes the prolonged ox brain prothrombin time of hemophilia B(M) by synthetic peptides.

In a previous study, we prepared a monoclonal antibody (MoAb) to coagulation factor IX (FIX), designated 65-10, which interfered with the activation of FIX by the activated factor XI/Ca(2+) and neutralized the prolonged ox brain prothrombin time of hemophilia B(M) [11,12]. The location of the epitope on the FIX for 65-10 MoAb is (168) Ile-Thr-Gln-Ser-Thr-Gln-Ser-Phe-Asn-Asp-Phe-Thr-Arg-Val-Val(182) [21]. In this paper, we studied in more detail an epitope on FIX using the systematic substitution of different amino acids at each residue of the epitope peptides and the influence of the epitope peptide on the prolonged ox brain prothrombin time of the hemophilia B(M) plasma of 65-10 MoAb. In the replacement set of amino acids, peptides showing low or no reactivity to 65-10 were (175)Phe --> Asp, Glu, Gly, Lys, Arg, Thr, Val, (176)Asn --> Asp, Glu, Phe, Ile, Lys, Leu, Pro, Val, Tyr, (177)Asp --> Cys, Glu, Phe, Ile, Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, Tyr, and (178) Phe --> Pro. These results imply that a hydrophobic molecule of (175) Phe, a hydrophilic molecule of (176)Asn, and a negative charge molecule of (177)Asp were important to the epitope. The 65-10 MoAb antibody neutralized the prolonged ox brain prothrombin time of hemophilia B(M) Nagoya 2 ((180)Arg -->Trp) and Kashihara ((181)Val --> Phe) as well as B(M) Kiryu ((313)Val --> Asp) and Niigata ((390)Ala --> Val). This reaction was inhibited by preincubation with a (168) Ile-Thr-Gln-Ser-Thr-Gln-Ser-Phe-Asn-Asp-Phe-Thr-Arg-Val-Val(182) peptide conjugated with bovine serum albumin (BSA). 65-10 MoAb that has been useful in detailing epitopes will be useful for qualitative analysis of hemophilia B(M).

Amino Acid Sequence↗

[Heterozygous prothrombin gene mutation G20210A and associated diseases].

PURPOSE: Prothrombin gene mutation G20210A (factor II) is, in frequency, the second genetic polymorphism involved in venous thrombosis. We report a retrospective studies on 38 patients issued from our medical department, all heterozygous for the factor II mutation and a literature review. METHODS: We have studied 38 patients, all heterozygous for the factor II mutation, selected through a population of 516 tested patients issued from our medical department from 1997 to 2002. The research was performed face with history of thrombotic or obstetrical events, angiopathy or familial screening. RESULTS: Twenty out of thirty-eight patients have at least one episode of venous thrombosis: superficial thromboses, deep thromboses and/or pulmonary embolism. One case of cerebral thrombophlebitis is observed. Venous thrombotic risk factors are associated in 12 cases (60%). Four out of thirty-eight patients have one episode of arterial thrombosis: cardiovascular, peripheral or cerebral. Arterial thrombotic risk factors are associated in all cases. Median age of the first venous thrombosis is earlier than the one of arterial thrombosis (39.11 versus 49.25 years). CONCLUSION: Our studies confirms the interest to search the prothrombin gene mutation when faced with a venous thrombotic event (deep vein thrombosis and/or pulmonary embolism) with or without acquired risk factors. Its involvement in thrombotic arterial disease is still a matter of debate. Data concerning its involvement in systemic diseases and angiopathies (thromboangeitis obliterans, Raynaud's phenomenon and migraine) are still needed. Mechanisms of thromboses could be an increase of prothrombin plasma level with high thrombin synthesis.

Adult↗