Tridegin, a Novel Peptidic Inhibitor of Factor XIIIa from the Leech, Haementeria ghilianii, Enhances Fibrinolysis In Vitro

1997 ◽  
Vol 77 (05) ◽  
pp. 0959-0963 ◽  
Author(s):  
Lisa Seale ◽  
Sarah Finney ◽  
Roy T Sawyer ◽  
Robert B Wallis
Keyword(s):  
Potent Inhibitor ◽  
Platelet Rich Plasma ◽  
Factor Xiiia ◽  
Cross Linking ◽  
Fibrinolytic Enzymes ◽  
Small Polypeptide ◽  
Tissue Plasminogen ◽  
Protein Cross Linking

SummaryTridegin is a potent inhibitor of factor Xllla from the leech, Haementeria ghilianii, which inhibits protein cross-linking. It modifies plasmin-mediated fibrin degradation as shown by the absence of D-dimer and approximately halves the time for fibrinolysis. Plasma clots formed in the presence of Tridegin lyse more rapidly when either streptokinase, tissue plasminogen activator or hementin is added 2 h after clot formation. The effect of Tridegin is markedly increased if clots are formed from platelet-rich plasma. Platelet-rich plasma clots are lysed much more slowly by the fibrinolytic enzymes used and if Tridegin is present, the rate of lysis returns almost to that of platelet- free clots. These studies indicate the important role of platelets in conferring resistance to commonly used fibrinolytic enzymes and suggest that protein cross-linking is an important step in this effect. Moreover they indicate that Tridegin, a small polypeptide, may have potential as an adjunct to thrombolytic therapy.

Haemostatic Platelet Plug Formation in the Isolated Rabbit Mesenteric Preparation - An Analysis of Red Blood Cell Participation

1980 ◽  
Vol 44 (01) ◽  
pp. 006-008 ◽  
Author(s):  
D Bergqvist ◽  
K-E Arfors
Keyword(s):  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Adenosine Diphosphate ◽  
In Vitro Test ◽  
Pharmacological Agents ◽  
Vitro Test ◽  
Releasing Effect ◽  
Plug Formation

SummaryIn a model using an isolated rabbit mesenteric preparation microvessels were transected and the time until haemostatic plugs formed was registered. Perfusion of platelet rich plasma gave no haemostasis whereas whole blood did. Addition of chlorpromazine or adenosine to the whole blood significantly prolonged the time for haemostasis, and addition of ADP to the platelet rich plasma significantly shortened it. It is concluded that red cells are necessary for a normal haemostasis in this model, probably by a combination of a haemodynamic and ADP releasing effect.The fundamental role of platelets in haemostatic plug formation is unquestionable but there are still problems concerning the stimulus for this process to start. Three platelet aggregating substances have been discussed – thrombin, adenosine diphosphate (ADP) and collagen. Evidence speaking in favour of thrombin is, however, very minimal, and the discussion has to be focused on collagen and ADP. In an in vitro system using polyethylene tubings we have shown that "haemostasis" can be obtained without the presence of collagen but against these results can be argued that it is only another in vitro test for platelet aggregation (1).To be able to induce haemostasis in this model, however, the presence of red blood cells is necessary. To further study this problem we have developed a model where haemostatic plug formation can be studied in the isolated rabbit mesentery and we have briefly reported on this (2).Thus, it is possible to perfuse the vessels with whole blood as well as with platelet rich plasma (PRP) and different pharmacological agents of importance.

A Thiazole Compound with Potential Antithrombotic Activity

1982 ◽  
Vol 47 (02) ◽  
pp. 173-176 ◽  
Author(s):  
E E Nishizawa ◽  
A R Mendoza ◽  
T Honohan ◽  
K A Annis
Keyword(s):  
Platelet Aggregation ◽  
Potent Inhibitor ◽  
Platelet Rich Plasma ◽  
Development Program ◽  
Antithrombotic Agent ◽  
Antithrombotic Activity ◽  
Thiazole Derivative ◽  
Cyclooxygenase Activity ◽  
Drug Development Program

SummaryA thiazole derivative, 4,5-bis(p-methoxyphenyl)-2-(trifluoromethyl)-thiazole was found to be a potent inhibitor of collagen-induced platelet aggregation, in vitro, using platelets from at least six species, including man. It was active in human platelet-rich plasma at a concentration of 1 ng/ml. While its antiplatelet activity was greater than that of flurbiprofen, its cyclooxygenase activity was equivalent to that of flurbiprofen. Also, compared to flurbiprofen, the thiazole had less anti-inflammatory activity in the hind-paw edema test. The thiazole derivative inhibited platelet aggregation following oral administration in five laboratory species. In the guinea pig it was active at 0.5 mg/kg. The LD50 in mice was greater than 1000 mg/kg (i.p.). This compound, which was designed through a systematic drug development program, may have high potential as an antithrombotic agent.

scholarly journals Haemodynamic flow conditions at the initiation of high-shear platelet aggregation: a combined in vitro and cellular in silico study

2020 ◽  
Vol 11 (1) ◽  
pp. 20190126 ◽  
Author(s):  
B. J. M. van Rooij ◽  
G. Závodszky ◽  
A. G. Hoekstra ◽  
D. N. Ku
Keyword(s):  
Platelet Aggregation ◽  
In Silico ◽  
Platelet Rich Plasma ◽  
High Shear ◽  
Shear Rates ◽  
Flow Simulations ◽  
In Silico Study ◽  
Platelet Aggregates

The influence of the flow environment on platelet aggregation is not fully understood in high-shear thrombosis. The objective of this study is to investigate the role of a high shear rate in initial platelet aggregation. The haemodynamic conditions in a microfluidic device are studied using cell-based blood flow simulations. The results are compared with in vitro platelet aggregation experiments performed with porcine whole blood (WB) and platelet-rich-plasma (PRP). We studied whether the cell-depleted layer in combination with high shear and high platelet flux can account for the distribution of platelet aggregates. High platelet fluxes at the wall were found in silico . In WB, the platelet flux was about twice as high as in PRP. Additionally, initial platelet aggregation and occlusion were observed in vitro in the stenotic region. In PRP, the position of the occlusive thrombus was located more downstream than in WB. Furthermore, the shear rates and stresses in cell-based and continuum simulations were studied. We found that a continuum simulation is a good approximation for PRP. For WB, it cannot predict the correct values near the wall.

Aberrant fibrin formation and cross-linking of fibrinogen Nieuwegein, a variant with a shortened Aα-chain, alters endothelial capillary tube formation

Blood ◽  
2001 ◽  
Vol 97 (4) ◽  
pp. 973-980 ◽  
Author(s):  
Annemie Collen ◽  
Annemarie Maas ◽  
Teake Kooistra ◽  
Florea Lupu ◽  
Jos Grimbergen ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Capillary Tube ◽  
Stop Codon ◽  
Tissue Transglutaminase ◽  
Tube Formation ◽  
Factor Xiiia ◽  
Cross Linking ◽  
Molecular Abnormalities ◽  
Fibrin Network

Abstract A congenital dysfibrinogenemia, fibrinogenNieuwegein, was discovered in a young man without any thromboembolic complications or bleeding. A homozygous insertion of a single nucleotide (C) in codon Aα 453 (Pro) introduced a stop codon at position 454, which resulted in the deletion of the carboxyl-terminal segment Aα 454-610. The ensuing unpaired cysteine at Aα 442 generated fibrinogen-albumin complexes of different molecular weights. The molecular abnormalities of fibrinogenNieuwegein led to a delayed clotting and a fibrin network with a low turbidity. Electron microscopy confirmed that thin fibrin bundles were organized in a fine network. The use of fibrinogenNieuwegein-derived fibrin (fibrinNieuwegein) in an in vitro angiogenesis model resulted in a strong reduction of tube formation. The ingrowth of human microvascular endothelial cells (hMVEC) was independent of αvβ3, indicating that the reduced ingrowth is not due to the absence of the RGD-adhesion site at position Aα 572-574. Rather, the altered structure of fibrinNieuwegeinis the cause, since partial normalization of the fibrin network by lowering the pH during polymerization resulted in an increased tube formation. Whereas factor XIIIa further decreased the ingrowth of hMVEC in fibrinNieuwegein, tissue transglutaminase (TG), which is released in areas of vessel injury, did not. This is in line with the absence of the cross-linking site for TG in the α-chains of fibrinogenNieuwegein. In conclusion, this newly discovered congenital dysfibrinogenemia has a delayed clotting time and leads to the formation of an altered fibrin structure, which could not be cross-linked by TG and which is less supportive for ingrowth of endothelial cells.

Pharmacology of MK-0591 (3-[1-(4-chlorobenzyl)-3-(t-butylthio)-5-(quinolin-2-yl-methoxy)-indol-2-yl]-2,2-dimethyl propanoic acid), a potent, orally active leukotriene biosynthesis inhibitor

1992 ◽  
Vol 70 (6) ◽  
pp. 799-807 ◽  
Author(s):  
C. Brideau ◽  
C. Chan ◽  
S. Charleson ◽  
D. Denis ◽  
J. F. Evans ◽  
...  
Keyword(s):  
Polymorphonuclear Leukocytes ◽  
Potent Inhibitor ◽  
Ex Vivo ◽  
Late Phase ◽  
Squirrel Monkeys ◽  
Propanoic Acid ◽  
Orally Active

MK-0591 (3-[1-(4-chlorobenzyl)-3-(t-butylthio)-5-(quinolin-2-yl-methoxy)-indol-2-yl]-2,2-dimethyl propanoic acid, previously L-686,708) is a potent inhibitor of leukotriene (LT) biosynthesis in intact human and elicited rat polymorphonuclear leukocytes (PMNLs) (IC50 values 3.1 and 6.1 nM, respectively) and in human, squirrel monkey, and rat whole blood (IC50 values 510, 69, and 9 nM, respectively). MK-0591 had no effect on rat 5-lipoxygenase. MK-0591 has a high affinity for 5-lipoxygenase activating protein (FLAP) as evidenced by an IC50 value of 1.6 nM in a FLAP binding assay and inhibition of the photoaffinity labelling of FLAP by two different photoaffinity ligands. Inhibition of activation of 5-lipoxygenase was shown through inhibition of the translocation of the enzyme from the cytosol to the membrane in human PMNLs. MK-0591 was a potent inhibitor of LT biosynthesis in vivo, first, following ex vivo challenge of blood obtained from treated rats and squirrel monkeys, second, in a rat pleurisy model, and, third, as monitored by inhibition of the urinary excretion of LTE4 in antigen-challenged allergic sheep. Inhibition of antigen-induced bronchoconstriction by MK-0591 was observed in inbred rats pretreated with methysergide, Ascaris-challenged squirrel monkeys, and Ascaris-challenged sheep (early and late phase response). These results indicate that MK-0591 is a potent inhibitor of LT biosynthesis both in vitro and in vivo indicating that the compound will be suitable for assessing the role of leukotrienes in pathological situations.Key words: leukotriene, 5-lipoxygenase, leukotriene inhibitor, bronchoconstriction, inflammation, 5-lipoxygenase activating protein.

Improvement of Thrombolysis by Rivaroxaban, An Anti Xa Inhibitor. Potential Therapeutic Importance in Patients with Thrombosis

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3031-3031 ◽  
Author(s):  
Remi Varin ◽  
Shasultan Mirshahi ◽  
Pehzman Mirshahi ◽  
Li Lu-Hong ◽  
Gerald Kierzek ◽  
...  
Keyword(s):  
Potent Inhibitor ◽  
Thrombus Formation ◽  
Factor Xa ◽  
Structure Modification ◽  
Antithrombotic Effect ◽  
Thrombin Activatable Fibrinolysis Inhibitor ◽  
Fibrinolytic Enzymes ◽  
Tissue Plasminogen ◽  
Fibrinolysis Inhibitor ◽  
Clot Structure

Abstract Background and objective Rivaroxaban – an oral, direct Factor Xa inhibitor – inhibits thrombus formation and growth in animal models. We have investigated the effects of rivaroxaban on thrombolysis because impaired fibrinolysis is a risk factor for venous thrombosis and it occurs more often in patients who had a myocardial infarction. As the propensity of a clot to be degraded depends on its structure, we tested the effects of rivaroxaban on clot structure and degradability by tissue plasminogen activator (t-PA). This was done in the absence and presence of thrombomodulin because the thrombin - thrombomodulin complex is the activator of TAFI (thrombin-activatable fibrinolysis inhibitor), a potent inhibitor of fibrinolysis. Methods Clots were formed in a microchamber in the presence or absence of rivaroxaban at pharmacological concentrations (0.15 and 0.25 μg/ml). Clot structure was analyzed by confocal microscopy, and permeability calculated by measuring flow rates. Degradation was evaluated by the amount of D-dimers in the eluate of clot perfused with t-PA, in the presence or absence of thrombomodulin. Results Microscopy showed that clots formed in the presence of rivaroxaban had thicker fibers and a looser fibrin structure with larger pores than controls, leading to increased permeation rate (Darcy constant 2.16-fold and 2.45-fold higher than controls with rivaroxaban at 0.15 μg/ml and 0.25 μg/ml, respectively). This clot structure modification renders the clots more susceptible to fibrinolytic enzymes. The degradation of clots containing 0.15 μg/ml of rivaroxaban was 3.6-fold higher than that of control clots, after 90 minutes perfusion with t-PA. In addition, when clots are formed in the presence of thrombomodulin, the degradability is decreased in control, while In the presence of rivaroxaban, fibrin degradation remains enhanced. Conclusion Rivaroxaban increased thrombolysis by t-PA. This was due to a decrease in thrombin generation. Two mechanisms are involved: modification of clot structure, which makes it more accessible to thrombolytic enzymes; and decrease in TAFI activation by the thrombomodulin–thrombin complex. This property of rivaroxaban may contribute to its antithrombotic effect.

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