A New Method for Quantifying Platelet Deposition in Flowing Native Blood in an Ex Vivo Model of Human Thrombogenesis

1998 ◽  
Vol 79 (01) ◽  
pp. 162-168 ◽  
Author(s):  
J. P. Bossavy ◽  
K. S. Sakariassen ◽  
A. Barret ◽  
B. Boneu ◽  
Y. Cadroy
Keyword(s):  
Unfractionated Heparin ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Plasma Concentrations ◽  
New Method ◽  
Dependent Manner ◽  
Fibrin Deposition ◽  
Simple Method ◽  
Arterial Thrombus ◽  
Platelet Deposition

SummaryNo quantitative, simple and non-radioactive method has been described for measuring the platelet content of experimental thrombi. The aim of the present study was to develop a simple method for quantifying platelets in thrombi formed on thrombogenic surfaces in flowing native human blood. To test the relevance of this new method, the effect of unfractionated heparin on arterial thrombus formation was investigated. Tissue factor (TF)- and collagen-coated coverslips were exposed to non-anticoagulated blood at an arterial wall shear rate (2,600 s–1) for 1 to 4 min. Platelet deposition was quantified by measuring the P-selectin (PS) and β-thromboglobulin (βTG) content of dissolved plasmin-digested thrombi using immunoenzymoassays; fibrin deposition was determined by measuring the D-dimer levels. These results were compared to those established by morphometrical analysis.Morphometric evaluation showed that fibrin deposition was maximum on TF by 1 min perfusion time. Platelets deposited subsequently and reached a maximum at 3 min. On collagen, platelets deposited directly on the collagen fibrils without detectable fibrin deposit. Platelet deposition increased from 1 to 4 min. Platelet deposition quantified by PS was correlated to the values obtained by morphometry (r = 0.72, r = 0.67, p <0.001, on TF and collagen, respectively). As compared to PS, βTG measurements gave an underestimation of the size of the thrombus platelet number. Unfractionated heparin infused through a mixing device proximal to the perfusion chamber to obtain plasma concentrations of 0.5, 1 and 3 IU/ml, reduced fibrin deposition on TF-coated coverslips in a dose-dependent manner (77% reduction at 3 IU/ml, p <0.01), but had no significant effect on platelet deposition (33% at 3 IU/ml, p >0.05). In contrast, heparin had no effect on fibrin or platelet deposition on collagen-coated coverslips.Thus, a new quantitative and simple method for measuring platelet deposition in flowing blood has been developed and characterized. Utilizing this system, we have demonstrated that unfractionated heparin did not inhibit arterial thrombus formation either on procoagulant or on proaggregant surface.

scholarly journals Hirudin interruption of heparin-resistant arterial thrombus formation in baboons

Blood ◽  
1991 ◽  
Vol 77 (5) ◽  
pp. 1006-1012 ◽  
Author(s):  
AB Kelly ◽  
UM Marzec ◽  
W Krupski ◽  
A Bass ◽  
Y Cadroy ◽  
...  
Keyword(s):  
Bleeding Time ◽  
Thrombus Formation ◽  
Dependent Manner ◽  
Fibrin Deposition ◽  
Recombinant Hirudin ◽  
Arterial Thrombus ◽  
Dependent Inhibition ◽  
Antithrombotic Effects ◽  
Dose Dependent

Abstract To determine the role of thrombin in high blood flow, platelet- dependent thrombotic and hemostatic processes we measured the relative antithrombotic and antihemostatic effects in baboons of hirudin, a highly potent and specific antithrombin, and compared the effects of heparin, an antithrombin III-dependent inhibitor of thrombin. Thrombus formation was determined in vivo using three relevant models (homologous endarterectomized aorta, collagen-coated tubing, and Dacron vascular graft) by measuring: (1) platelet deposition, using gamma camera imaging of 111In-platelets; (2) fibrin deposition, as assessed by the incorporation of circulating 125I-fibrinogen; and (3) occlusion. The continuous intravenous infusion of 1, 5, and 20 nmol/kg per minute of recombinant hirudin (desulfatohirudin) maintained constant plasma levels of 0.16 +/- 0.03, 0.79 +/- 0.44, and 3.3 +/- 0.77 mumol/mL, respectively. Hirudin interrupted platelet and fibrin deposition in a dose-dependent manner that was profound at the highest dose for all three thrombogenic surfaces and significant at the lowest dose for thrombus formation on endarterectomized aorta. Thrombotic occlusion was prevented by all doses studied. In contrast, heparin did not inhibit either platelet or fibrin deposition when administered at a dose that maximally prolonged clotting times (100 U/kg) (P greater than .1), and only intermediate effects were produced at 10-fold that dose (1,000 U/kg). Moreover, heparin did not prevent occlusion of the test segments. Hirudin inhibited platelet hemostatic function in concert with its antithrombotic effects (bleeding times were prolonged by the intermediate and higher doses). By comparison, intravenous heparin failed to affect the bleeding time at the 100 U/kg dose (P greater than .5), and only minimally prolonged the bleeding time at the 1,000 U/kg dose (P less than .05). We conclude that platelet-dependent thrombotic and hemostatic processes are thrombin-mediated and that the biologic antithrombin hirudin produces a potent, dose-dependent inhibition of arterial thrombus formation that greatly exceeds the minimal antithrombotic effects produced by heparin.

The Direct Factor Xa Inhibitor Apixaban Produces Broad Antithrombotic Activity with Limited Effects on Bleeding Time in Rats.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 4005-4005
Author(s):  
William A. Schumacher ◽  
Jeffrey S. Bostwick ◽  
Anne B. Stewart ◽  
Thomas E. Steinbacher ◽  
Donald J. Pinto ◽  
...  
Keyword(s):  
Bleeding Time ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Plasma Concentrations ◽  
Vena Cava ◽  
Factor Xa ◽  
Experimental Models ◽  
Factor Xa Inhibitor ◽  
Dependent Manner ◽  
Venous Shunt

Abstract Apixaban is an oral, direct and highly selective factor Xa inhibitor which is in late stage clinical development for the prevention and treatment of thromboembolic diseases. Apixaban is potent against human and rat factor Xa (Ki = 0.08 and 1.3 nM, respectively). The efficacy/safety profile of apixaban was determined in experimental models of thrombosis and hemostasis performed in anesthetized rats. Thrombosis was induced either by topical application of FeCl2 to the vena cava (VT) or carotid artery (AT), tissue factor infusion into the vena cava (TF-VT), or within an extracorporeal arterial-venous shunt (ST). Bleeding time was measured in response to template incision of the renal cortex. Apixaban was administered as a continuous i.v. infusion of 0.1, 0.3, 1 or 3 mg/kg/h starting 60 min before each experimental procedure (n=5 or 6 per dose). These respective doses increased the ex vivo prothrombin time by 1.3, 1.9, 3.0 and 3.9 times control baseline, and achieved plasma concentrations of 0.3, 1.4, 5.0 and 12.2 μM. In comparison to vehicle treatment, the 3 mg/kg/h dose of apixaban decreased thrombus weight by 90 ± 2% in VT, 62 ± 7% in TF-VT, 62 ± 4% in AT, and 79 ± 3% in ST (all p<0.05). A 50% thrombus weight reduction sufficient to prevent vascular occlusion in each model would require projected doses (mg/kg/h) of 0.4 (VT), 1.9 (TF-VT), 0.8 (AT) and 1.1 (ST). The lowest dose level which preserved carotid blood flow at the pre-injury level during thrombus formation was 0.3 mg/kg/h. Apixaban prolonged bleeding time in a dose-dependent manner with no effect detected at 0.1 and 0.3 mg/kg/h, while significant (p<0.05) increases of 1.34 ± 0.12 and 2.13 ± 0.17 times control were observed at 1 and 3 mg/kg/h, respectively. In comparison, aspirin increased bleeding time by 1.42 ± 0.1 times control (n=7, p<0.05) when tested at a 10 mg/kg dose, a dose which produced maximum cyclooxygenase inhibition. These studies predict a wide therapeutic index for apixaban based on the prevention of occlusive thrombosis in a variety of experimental models without excessive bleeding time prolongation. These results are consistent with the safety and efficacy observed with apixaban in phase II clinical trials.

Anti-thrombotic effect of bivalirudin compared with eptifibatide and unfractionated heparin in diabetic patients

2006 ◽  
Vol 95 (03) ◽  
pp. 441-446 ◽  
Author(s):  
Eli Lev ◽  
Rajnikant Patel ◽  
Azim Karim ◽  
Amanda Kleiman ◽  
Juan Badimon ◽  
...  
Keyword(s):  
Unfractionated Heparin ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Coronary Intervention ◽  
Diabetic Patients ◽  
Fibrin Deposition ◽  
Perfusion Studies ◽  
Patients With Diabetes ◽  
Dosing Regimens ◽  
Platelet Thrombus

SummaryPatients with diabetes who undergo percutaneous coronary intervention (PCI) are at high risk for thrombotic complications following the procedure. We sought to compare the anti-thrombotic effect of bivalirudin to that of eptifibatide plus unfractionated heparin in diabetic patients undergoing elective PCI. Thirty diabetic patients were randomized to receive during PCI either bivalirudin (bivalirudin group, n=15) or eptifibatide plus heparin (eptifibatide group, n=15) at standard dosing regimens. The drugs were continued for 20 minutes (bivalirudin) or 18 hours (eptifibatide) after PCI. Blood thrombogenicity was assessed using the Badimon ex vivo perfusion chamber. Each patient underwent two perfusion studies – at baseline (on aspirin and clopidogrel) and 15–20 minutes following PCI. Perfusion studies were performed at rheologic conditions of low and high shear rates (LSR, HSR). Porcine aortic tunica media served as the thrombogenic substrate. Aortic specimens were stained for total platelet-thrombus and fibrin deposition. Thrombus area was measured using computerized planimetry. There were no differences in clinical characteristics or baseline thrombus area between the two groups. Total platelet-thrombus area was reduced significantly in both groups, but the degree of reduction was lower in the bivalirudin group compared with the eptifibatide group (HSR: 69.5% vs. 89.3% reduction, respectively, P=0.04; LSR: 50.6% vs. 73.2%, P=0.03). Fibrin deposition was reduced in both groups by 47–49%. In conclusion, both bivalirudin and the combination of eptifibatide plus heparin, given to diabetic patients during PCI, achieved marked reductions in total thrombus formation and fibrin deposition. However, glycoprotein IIb/IIIa inhibition by eptifibatide causeda more pronounced reduction in thrombus formation.

scholarly journals Hirudin interruption of heparin-resistant arterial thrombus formation in baboons

Blood ◽  
1991 ◽  
Vol 77 (5) ◽  
pp. 1006-1012 ◽  
Author(s):  
AB Kelly ◽  
UM Marzec ◽  
W Krupski ◽  
A Bass ◽  
Y Cadroy ◽  
...  
Keyword(s):  
Bleeding Time ◽  
Thrombus Formation ◽  
Dependent Manner ◽  
Fibrin Deposition ◽  
Recombinant Hirudin ◽  
Arterial Thrombus ◽  
Dependent Inhibition ◽  
Antithrombotic Effects ◽  
Dose Dependent

To determine the role of thrombin in high blood flow, platelet- dependent thrombotic and hemostatic processes we measured the relative antithrombotic and antihemostatic effects in baboons of hirudin, a highly potent and specific antithrombin, and compared the effects of heparin, an antithrombin III-dependent inhibitor of thrombin. Thrombus formation was determined in vivo using three relevant models (homologous endarterectomized aorta, collagen-coated tubing, and Dacron vascular graft) by measuring: (1) platelet deposition, using gamma camera imaging of 111In-platelets; (2) fibrin deposition, as assessed by the incorporation of circulating 125I-fibrinogen; and (3) occlusion. The continuous intravenous infusion of 1, 5, and 20 nmol/kg per minute of recombinant hirudin (desulfatohirudin) maintained constant plasma levels of 0.16 +/- 0.03, 0.79 +/- 0.44, and 3.3 +/- 0.77 mumol/mL, respectively. Hirudin interrupted platelet and fibrin deposition in a dose-dependent manner that was profound at the highest dose for all three thrombogenic surfaces and significant at the lowest dose for thrombus formation on endarterectomized aorta. Thrombotic occlusion was prevented by all doses studied. In contrast, heparin did not inhibit either platelet or fibrin deposition when administered at a dose that maximally prolonged clotting times (100 U/kg) (P greater than .1), and only intermediate effects were produced at 10-fold that dose (1,000 U/kg). Moreover, heparin did not prevent occlusion of the test segments. Hirudin inhibited platelet hemostatic function in concert with its antithrombotic effects (bleeding times were prolonged by the intermediate and higher doses). By comparison, intravenous heparin failed to affect the bleeding time at the 100 U/kg dose (P greater than .5), and only minimally prolonged the bleeding time at the 1,000 U/kg dose (P less than .05). We conclude that platelet-dependent thrombotic and hemostatic processes are thrombin-mediated and that the biologic antithrombin hirudin produces a potent, dose-dependent inhibition of arterial thrombus formation that greatly exceeds the minimal antithrombotic effects produced by heparin.

A sensitive new method of “ex vivo” platelet deposition

1982 ◽  
Vol 28 (2) ◽  
pp. 237-250 ◽  
Author(s):  
L. Badimon ◽  
V. Fuster ◽  
M.K. Dewanjee ◽  
J.C. Romero
Keyword(s):  
Ex Vivo ◽  
New Method ◽  
Platelet Deposition

Abstract 56: Coagulation Factor XI Promotes Distal Platelet Activation and Single Platelet Consumption in the Bloodstream Under Shear Flow

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Jenya Zilberman-Rudenko ◽  
Chantal Wiesenekker ◽  
Asako Itakura ◽  
Owen J McCarty
Keyword(s):  
Shear Flow ◽  
Platelet Activation ◽  
Platelet Adhesion ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Coagulation Factor ◽  
Thrombin Inhibitor ◽  
Dependent Manner ◽  
Factor Xi ◽  
Primate Model

Objective: Coagulation factor XI (FXI) has been shown to contribute to thrombus formation on collagen or tissue factor (TF)-coated surfaces in vitro and in vivo by enhancing thrombin generation. Whether the role of the intrinsic pathway of coagulation is restricted to the local site of thrombus formation is unknown. This study was designed to determine whether FXI could promote both proximal and distal platelet activation and aggregate formation in the bloodstream. Approach and Results: Pharmacological blockade of FXI activation or thrombin activity in blood did not affect local platelet adhesion, yet reduced local platelet aggregation, thrombin localization and fibrin formation on immobilized collagen and TF under shear flow, ex vivo . Downstream of the thrombus formed on immobilized collagen or collagen and 10 pM TF, platelet CD62P expression and microaggregate formation and progressive platelet consumption were significantly reduced in the presence of FXI-function blocking antibodies or a thrombin inhibitor in a shear rate- and time-dependent manner. In a non-human primate model of thrombus formation, we found that inhibition of FXI reduced single platelet consumption in the bloodstream distal to a site of thrombus formation. Conclusions: This study demonstrates that the FXI-thrombin axis contributes to distal platelet activation and procoagulant microaggregate formation in the blood flow downstream of the site of thrombus formation. Our data highlights FXI as a novel therapeutic target for inhibiting distal platelet activation without affecting proximal platelet adhesion.

Prevention of Laser Arterial Thrombus Formation with Unfractionated Heparin

1993 ◽  
Vol 23 (5) ◽  
pp. 244-248 ◽  
Author(s):  
F. Doutremepuich ◽  
O. Aguejouf ◽  
F.A. Azougagh Oualane ◽  
Ch. Doutremepuich
Keyword(s):  
Unfractionated Heparin ◽  
Thrombus Formation ◽  
Arterial Thrombus

scholarly journals Strenuous but not moderate exercise increases the thrombotic tendency in healthy sedentary male volunteers

2002 ◽  
Vol 93 (3) ◽  
pp. 829-833 ◽  
Author(s):  
Yves Cadroy ◽  
Fabien Pillard ◽  
Kjell S. Sakariassen ◽  
Claire Thalamas ◽  
Bernard Boneu ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Maximal Oxygen Uptake ◽  
Thrombus Formation ◽  
Strenuous Exercise ◽  
Moderate Exercise ◽  
Fibrin Deposition ◽  
Healthy Male ◽  
Healthy Male Volunteers ◽  
Male Volunteers ◽  
Arterial Thrombus

We have investigated the effect of moderate and strenuous exercise on experimental arterial thrombus formation in men. Thrombogenesis was measured in 15 sedentary healthy male volunteers at rest or immediately after two standardized exercise tests performed for 30 min on a bicycle ergometer. The exercises were performed at a constant load corresponding to either 50 or 70% maximal oxygen uptake. Thrombus formation was induced ex vivo by exposing a collagen-coated coverslip in a parallel plate perfusion chamber to native nonanticoagulated blood for 3 min. The shear rate at the collagen surface was 2,600 s−1. Platelet and fibrin deposition was quantified by immunoenzymatic methods. The results show that moderate exercise did not affect arterial thrombus formation. In contrast, platelet thrombus formation on collagen was increased on the average by 20% after 30 min at 70% maximal oxygen uptake ( P = 0.03). Fibrin deposition on collagen remained unchanged with exercise, regardless of its intensity. Thus, with the use of a clinically relevant human experimental model of thrombosis, the present study suggests that exercise of heavy intensity may increase the risk for arterial thrombogenesis in sedentary young healthy male volunteers.

A New Mechanism of Platelet Activation and Oxidative Death Induced by ADAMTS-18 and Regulating Bleeding Time.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 133-133
Author(s):  
Zongdong Li ◽  
Michael Nardi ◽  
Ruimin Pan ◽  
Herman Yee ◽  
Simon Karpatkin
Keyword(s):  
Amino Acid ◽  
Platelet Activation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Activation Mechanism ◽  
Dependent Manner ◽  
Cell Secretion ◽  
Concentration Dependent Manner ◽  
Buffer Control

Abstract Anti-platelet integrin GPIIIa49-66 Ab obtained from HIV-ITP patients (or raised in rabbits) induces complement-independent platelet oxidative fragmentation and death by activating platelet 12-lipoxygenase (generation of 12(S)-HETE) and NADPH oxidase (JCI, 113:973, 2004). Platelet oxidative fragmentation is measured by flow cytometry of generated microparticles as well as intracellular DCFH oxidation. We now report that oxidative fragmentation in human platelets is preceded by Ca++ flux and P-selectin activation, n=6. However, the activation mechanism is different from classic platelet activation in that it is not inhibited by PGE1 or dibutryl cyclic AMP and is operative with Gαq−/− mouse platelets, whereas under these conditions, thrombin-induced platelet activation is completely inhibited, n=5–6. We chose to identify putative physiologic ligands that behave similarly to the GPIIIa49-66 Ab, and are therefore capable of regulating platelet reactive oxygen species (ROS) as well as arterial thrombus formation. The GPIIIa49-66 platelet peptide was used as bait to screen a 7-mer peptide phage display library. A peptide was found with 70% homology at the C-terminal position of ADAMTS-18, an ‘orphan’ disintegrin and metalloproteinase with thrombospondin (TSR)-like motifs, with unknown substrate. We have found it present in HUVEC as well as human pulmonary artery endothelial cells, on fixed sections of pathology specimens employing immunohistochemistry with a specific rabbit Ab raised against a C-terminal 18 mer peptide ADAMTS-18 (no staining with preimmune Ab). Recombinant ADAMTS-18 was produced in HEK 293 T cells and shown to induce ROS and oxidative platelet fragmentation in an identical kinetic fashion as anti-GPIIIa49-66 Ab. HUVEC ADAMTS-18 activity could be inhibited by a human scFv Ab raised against its C-terminal 18 mer peptide, as well as the ADAMTS-18 peptide itself, but not by a rabbit Ab against the N-terminal domain or an irrelevant peptide. Endothelial cell secretion and activation of ADAMTS-18 was optimally induced with 0.5 u/ml thrombin at 2 – 4 hrs, n=3–4. The truncated 385 amino acid C-terminal rADAMTS-18 fragment containing the 4 TSR motifs (produced in E.coli) had full activity at (<0.3 uM) whereas the C-terminal 66 amino acid fragment not containing the 18-mer binding site was inactive at 65 fold higher concentration, n=4. The physiologic significance of ADAMTS-18 was supported by demonstrating its secretion into plasma following iv injection of 4–16 u/ml thrombin into mice. Wild type mice have no detectable ADAMTS-18 in their plasma, with a sensitive ELISA assay (1 ng detectability). Thrombin stimulated mice secrete ADAMTS-18 in a concentration dependent manner. Platelet aggregates produced ex vivo with ADP and fibrinogen were destroyed with ADAMTS-18 as documented by LDH release at 1, 2 and 4 hrs of 83, 241 and 260 fold respectively, of PBS buffer control. In vivo tail vein bleeding time was shortened 4.5 fold with 1 hr prior infusion of 25 ug of a polyclonal rabbit IgG against ADAMTS-18, but not with preimmune IgG, n=10. Thus, a new mechanism is proposed for platelet activation, ROS release, death and platelet thrombus regulation, via platelet membrane oxidative fragmentation induced by thrombin-induced secretion and activation of ADAMTS-18.

scholarly journals Bruton tyrosine kinase is essential for botrocetin/VWF-induced signaling and GPIb-dependent thrombus formation in vivo

Blood ◽  
2006 ◽  
Vol 108 (8) ◽  
pp. 2596-2603 ◽  
Author(s):  
Junling Liu ◽  
Malinda E. Fitzgerald ◽  
Michael C. Berndt ◽  
Carl W. Jackson ◽  
T. Kent Gartner
Keyword(s):  
Tyrosine Kinase ◽  
Thrombus Formation ◽  
Dependent Manner ◽  
Akt Phosphorylation ◽  
Atp Secretion ◽  
Arterial Thrombus ◽  
Bruton Tyrosine Kinase ◽  
Von Willebrand ◽  
Willebrand Factor

AbstractBotrocetin (bt)-facilitated binding of von Willebrand factor (VWF) to the platelet membrane glycoprotein (GP) Ib-IX-V complex on platelets in suspension initiates a signaling cascade that causes αIIbβ3 activation and platelet aggregation. Previous work has demonstrated that bt/VWF-mediated agglutination activates αIIbβ3 and elicits ATP secretion in a thromboxane A2 (TxA2)-dependent manner. The signaling that results in TxA2 production was shown to be initiated by Lyn, enhanced by Src, and propagated through Syk, SLP-76, PI3K, PLCγ2, and PKC. Here, we demonstrate that the signaling elicited by GPIb-mediated agglutination that results in TxA2 production is dependent on Bruton tyrosine kinase (Btk). The results demonstrate that Btk is downstream of Lyn, Syk, SLP-76, and PI3K; upstream of ERK1/2, PLCγ2, and PKC; and greatly enhances Akt phosphorylation. The relationship(s), if any, between ERK1/2, PLCγ2, and PKC were not elucidated. The requirement for Btk and TxA2 receptor function in GPIb-dependent arterial thrombosis was confirmed in vivo by characterizing blood flow in ferric chloride-treated mouse carotid arteries. These results demonstrate that the Btk family kinase, Tec, cannot provide the function(s) missing because of the absence of Btk and that Btk is essential for both bt/VWF-mediated agglutination-induced TxA2 production and GPIb-dependent stable arterial thrombus formation in vivo.

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