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

SummaryClinical trials suggest that the risk of thrombosis during coronary angioplasty is lower with ionic contrast agents than with nonionic contrast agents. However, the molecular mechanisms underlying this effect are unknown. This study examined the effects of contrast agents on thrombin formation and its interaction with substrates, inhibitors, and ligands to define potential mechanisms by which contrast agents affect thrombus formation. Two ionic agents, diatrizoate and ioxaglate, and one nonionic agent, ioversol, were studied. Ionic agents inhibited factor X activation by the tissue factor-factor VIIa complex more potently than ioversol (53 ± 3.7, 43.0 ± 1.9, and 26.5 ± 2.4% inhibition by diatrizoate, ioxaglate, and ioversol, respectively, at concentrations of 5%). Ionic contrast agents were potent inhibitors of prothrombinase function, inhibiting thrombin formation by >75% at contrast concentrations of 0.6% (p <0.005). Ioversol inhibited prothrombinase to a significantly lesser extent than ionic agents. Clotting assays suggested that ioxaglate was the most potent inhibitor of thrombin generation in plasma despite having the least effect on fibrin polymerization. Contrast agents inhibited binding of thrombin to fibrin, with ionic agents producing a more potent effect than ioversol (p <0.02). However, contrast agents did not inhibit thrombin-mediated platelet activation, had only a minor effect on inhibition of thrombin by antithrombin III, and did not affect thrombin-hirudin interactions. In summary, these studies identify specific mechanisms by which radiographic contrast agents inhibit thrombin formation and function – i.e. inhibition of tissue factor-dependent factor Xa generation, inhibition of the prothrombinase complex, and inhibition of thrombin binding to fibrin. These findings may help to explain the reduced risk of thrombosis during coronary angioplasty associated with ionic contrast agents.

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Tissue Factor Signaling

Thrombosis and Haemostasis ◽

10.1055/s-0037-1615831 ◽

1999 ◽

Vol 82 (08) ◽

pp. 175-182 ◽

Cited By ~ 40

Author(s):

Barbara Mueller ◽

Wolfram Ruf

Keyword(s):

Tissue Factor

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Elevated Tissue Factor and Tissue Factor Pathway Inhibitor Circulating Levels in Ischaemic Heart Disease Patients

Thrombosis and Haemostasis ◽

10.1055/s-0037-1614932 ◽

1998 ◽

Vol 79 (03) ◽

pp. 495-499 ◽

Cited By ~ 83

Author(s):

Anna Maria Gori ◽

Sandra Fedi ◽

Ludia Chiarugi ◽

Ignazio Simonetti ◽

Roberto Piero Dabizzi ◽

...

Keyword(s):

Heart Disease ◽

Ischaemic Heart Disease ◽

Tissue Factor ◽

Plasma Levels ◽

Tissue Factor Pathway Inhibitor ◽

Common Source ◽

Previous Myocardial Infarction ◽

Control Subjects ◽

Tissue Factor Pathway ◽

Circulating Levels

SummarySeveral studies have shown that thrombosis and inflammation play an important role in the pathogenesis of Ischaemic Heart Disease (IHD). In particular, Tissue Factor (TF) is responsible for the thrombogenicity of the atherosclerotic plaque and plays a key role in triggering thrombin generation. The aim of this study was to evaluate the TF/Tissue Factor Pathway Inhibitor (TFPI) system in patients with IHD.We have studied 55 patients with IHD and not on heparin [18 with unstable angina (UA), 24 with effort angina (EA) and 13 with previous myocardial infarction (MI)] and 48 sex- and age-matched healthy volunteers, by measuring plasma levels of TF, TFPI, Prothrombin Fragment 1-2 (F1+2), and Thrombin Antithrombin Complexes (TAT).TF plasma levels in IHD patients (median 215.4 pg/ml; range 72.6 to 834.3 pg/ml) were significantly (p<0.001) higher than those found in control subjects (median 142.5 pg/ml; range 28.0-255.3 pg/ml).Similarly, TFPI plasma levels in IHD patients were significantly higher (median 129.0 ng/ml; range 30.3-316.8 ng/ml; p <0.001) than those found in control subjects (median 60.4 ng/ml; range 20.8-151.3 ng/ml). UA patients showed higher amounts of TF and TFPI plasma levels (TF median 255.6 pg/ml; range 148.8-834.3 pg/ml; TFPI median 137.7 ng/ml; range 38.3-316.8 ng/ml) than patients with EA (TF median 182.0 pg/ml; range 72.6-380.0 pg/ml; TFPI median 115.2 ng/ml; range 47.0-196.8 ng/ml) and MI (TF median 213.9 pg/ml; range 125.0 to 341.9 pg/ml; TFPI median 130.5 ng/ml; range 94.0-207.8 ng/ml). Similar levels of TF and TFPI were found in patients with mono- or bivasal coronary lesions. A positive correlation was observed between TF and TFPI plasma levels (r = 0.57, p <0.001). Excess thrombin formation in patients with IHD was documented by TAT (median 5.2 μg/l; range 1.7-21.0 μg/l) and F1+2 levels (median 1.4 nmol/l; range 0.6 to 6.2 nmol/l) both significantly higher (p <0.001) than those found in control subjects (TAT median 2.3 μg/l; range 1.4-4.2 μg/l; F1+2 median 0.7 nmol/l; range 0.3-1.3 nmol/l).As in other conditions associated with cell-mediated clotting activation (cancer and DIC), also in IHD high levels of circulating TF are present. Endothelial cells and monocytes are the possible common source of TF and TFPI. The blood clotting activation observed in these patients may be related to elevated TF circulating levels not sufficiently inhibited by the elevated TFPI plasma levels present.

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Characterization of Monoclonal Anti-human Factor VII Antibody (B101/B1) that Recognized Three-dimensional Structures near Arg at Position 79 in the First EGF-like Domain

Thrombosis and Haemostasis ◽

10.1055/s-0037-1614229 ◽

1998 ◽

Vol 79 (01) ◽

pp. 104-109 ◽

Cited By ~ 6

Author(s):

Osamu Takamiya

Keyword(s):

Monoclonal Antibodies ◽

Tissue Factor ◽

Human Factor ◽

Solid Phase ◽

Three Dimensional ◽

Coagulation Factors ◽

Factor Vii ◽

Dimensional Structure ◽

Epidermal Growth

SummaryMurine monoclonal antibodies (designated hVII-B101/B1, hVIIDC2/D4 and hVII-DC6/3D8) directed against human factor VII (FVII) were prepared and characterized, with more extensive characterization of hVII-B101/B1 that did not bind reduced FVIIa. The immunoglobulin of the three monoclonal antibodies consisted of IgG1. These antibodies did not inhibit procoagulant activities of other vitamin K-dependent coagulation factors except FVII and did not cross-react with proteins in the immunoblotting test. hVII-DC2/D4 recognized the light chain after reduction of FVIIa with 2-mercaptoethanol, and hVIIDC6/3D8 the heavy chain. hVII-B101/B1 bound FVII without Ca2+, and possessed stronger affinity for FVII in the presence of Ca2+. The Kd for hVII-B101/B1 to FVII was 1.75 x 10–10 M in the presence of 5 mM CaCl2. The antibody inhibited the binding of FVII to tissue factor in the presence of Ca2+. hVII-B101/B1 also inhibited the activation of FX by the complex of FVIIa and tissue factor in the presence of Ca2+. Furthermore, immunoblotting revealed that hVII-B101/B1 reacted with non-reduced γ-carboxyglutaminic acid (Gla)-domainless-FVII and/or FVIIa. hVII-B101/B1 showed a similar pattern to that of non-reduced proteolytic fragments of FVII by trypsin with hVII-DC2/D4 on immunoblotting test. hVII-B101/B1 reacted differently with the FVII from the dysfunctional FVII variant, FVII Shinjo, which has a substitution of Gln for Arg at residue 79 in the first epidermal growth factor (1st EGF)-like domain (Takamiya O, et al. Haemosta 25, 89-97,1995) compared with normal FVII, when used as a solid phase-antibody for ELISA by the sandwich method. hVII-B101/B1 did not react with a series of short peptide sequences near position 79 in the first EGF-like domain on the solid-phase support for epitope scanning. These results suggested that the specific epitope of the antibody, hVII-B101/B1, was located in the three-dimensional structure near position 79 in the first EGF-like domain of human FVII.

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