PROTECTIVE EFFECT OF A NEW SYNTHETIC COMPOUND: PCA-4230, ON SEVERAL In vivo THROMBOSIS MODELS.

1987 ◽  
Author(s):  
M P Ortega ◽  
C Sunkel ◽  
J G Priego
Keyword(s):  
Protective Effect ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Platelet Activating Factor ◽  
Phase I Trials ◽  
Synthetic Compound ◽  
Prolonged Bleeding Time ◽  
Series Of Experiments ◽  
Pre Treatment

PCA-4230 is a new anti-thrombotic compound which inhibits pla. telet aggregation In vltn.0 and ex. vivo in several species, including man, prolongs the bleeding time and has potent protective ac tivity in several thrombosis models. Phase I trials with different dosage schedules have recently been initiated.In the present study, the effects of PCA-4230 on bleeding time and on several In vivo thrombosis models were studied in mice. Mice were treated with one single oral dose of PCA-4230 (1-10 mg/ kg). One hour after treatment, mice were injected intravenously with four thrombotic challengers {arachidonic acid (AA), thromboxane agonist (U46619), Platelet Activating Factor (PAF) or collagen/epinephrine combination (C/E)} at a dose which induced 80-90% of mortality. The thrombotic agents were prepared in saline. The appropiate doses were dissolved in a volume of 100 μl/mouse. Bleeding time was measured in non-anesthetized mice by the tail transection technique.Effects of compound were recorded from1 to 4 hours after dosage. Acute pre-treatment with PCA-4230 showed a significant dose-depen dent protective effect.Results of each series of experiments are given in the next table.The compound inhibited thrombotic sudden death induced by U46619, PAF or C/E combination, reduced the duration of respiratory distress induced by AA and prolonged bleeding time. Thus, PCA-4230 is protective against a variety of thrombotic stimuli.These results suggest that PCA-4230 may be a promising anti-throm botic drug.

Antithrombotic Effects and Bleeding Time Prolongation with Synthetic Platelet GPIIb/llla Inhibitors in Animal Models of Platelet-Mediated Thrombosis

1994 ◽  
Vol 71 (01) ◽  
pp. 095-102 ◽  
Author(s):  
Désiré Collen ◽  
Hua Rong Lu ◽  
Jean-Marie Stassen ◽  
Ingrid Vreys ◽  
Tsunehiro Yasuda ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Bolus Injection ◽  
Cell Injury ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Femoral Vein ◽  
Thrombotic Occlusion ◽  
Antithrombotic Effects

SummaryCyclic Arg-Gly-Asp (RGD) containing synthetic peptides such as L-cysteine, N-(mercaptoacetyl)-D-tyrosyl-L-arginylglycyl-L-a-aspartyl-cyclic (1→5)-sulfide, 5-oxide (G4120) and acetyl-L-cysteinyl-L-asparaginyl-L-prolyl-L-arginyl-glycyl-L-α-aspartyl-[0-methyltyrosyl]-L-arginyl-L-cysteinamide, cyclic 1→9-sulfide (TP9201) bind with high affinity to the platelet GPIIb/IIIa receptor.The relationship between antithrombotic effect, ex vivo platelet aggregation and bleeding time prolongation with both agents was studied in hamsters with a standardized femoral vein endothelial cell injury predisposing to platelet-rich mural thrombosis, and in dogs with a carotid arterial eversion graft inserted in the femoral artery. Intravenous administration of G4120 in hamsters inhibited in vivo thrombus formation with a 50% inhibitory bolus dose (ID50) of approximately 20 μg/kg, ex vivo ADP-induccd platelet aggregation with ID50 of 10 μg/kg, and bolus injection of 1 mg/kg prolonged the bleeding time from 38 ± 9 to 1,100 ± 330 s. Administration of TP9201 in hamsters inhibited in vivo thrombus formation with ID50 of 30 μg/kg, ex vivo platelet aggregation with an ID50 of 50 μg/kg and bolus injection of 1 mg/kg did not prolong the template bleeding time. In the dog eversion graft model, infusion of 100 μg/kg of G4120 over 60 min did not fully inhibit platelet-mediated thrombotic occlusion but was associated with inhibition of ADP-induccd ex vivo platelet aggregation and with prolongation of the template bleeding time from 1.3 ± 0.4 to 12 ± 2 min. Infusion of 300 μg/kg of TP9201 over 60 min completely prevented thrombotic occlusion, inhibited ex vivo platelet aggregation, but was not associated with prolongation of the template bleeding time.TP9201, unlike G4120, inhibits in vivo platelet-mediated thrombus formation without associated prolongation of the template bleeding time.

PAF increases vascular permeability without increasing pulmonary arterial pressure in the rat

2001 ◽  
Vol 90 (1) ◽  
pp. 261-268 ◽  
Author(s):  
Leonardo C. Clavijo ◽  
Mary B. Carter ◽  
Paul J. Matheson ◽  
Mark A. Wilson ◽  
William B. Wead ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Pulmonary Edema ◽  
Pulmonary Arterial Pressure ◽  
Ex Vivo ◽  
Platelet Activating Factor ◽  
Microvascular Permeability ◽  
Blue Dye ◽  
E Coli ◽  
Pulmonary Arterial

In vivo pulmonary arterial catheterization was used to determine the mechanism by which platelet-activating factor (PAF) produces pulmonary edema in rats. PAF induces pulmonary edema by increasing pulmonary microvascular permeability (PMP) without changing the pulmonary pressure gradient. Rats were cannulated for measurement of pulmonary arterial pressure (Ppa) and mean arterial pressure. PMP was determined by using either in vivo fluorescent videomicroscopy or the ex vivo Evans blue dye technique. WEB 2086 was administered intravenously (IV) to antagonize specific PAF effects. Three experiments were performed: 1) IV PAF, 2) topical PAF, and 3) Escherichia coli bacteremia. IV PAF induced systemic hypotension with a decrease in Ppa. PMP increased after IV PAF in a dose-related manner. Topical PAF increased PMP but decreased Ppa only at high doses. Both PMP (88 ± 5%) and Ppa (50 ± 3%) increased during E. coli bacteremia. PAF-receptor blockade prevents changes in Ppa and PMP after both topical PAF and E. coli bacteremia. PAF, which has been shown to mediate pulmonary edema in prior studies, appears to act in the lung by primarily increasing microvascular permeability. The presence of PAF might be prerequisite for pulmonary vascular constriction during gram-negative bacteremia.

scholarly journals Preclinical Evaluation of [18F]FACH in Healthy Mice and Piglets: An 18F-Labeled Ligand for Imaging of Monocarboxylate Transporters with PET

2021 ◽  
Vol 22 (4) ◽  
pp. 1645
Author(s):  
Daniel Gündel ◽  
Masoud Sadeghzadeh ◽  
Winnie Deuther-Conrad ◽  
Barbara Wenzel ◽  
Paul Cumming ◽  
...  
Keyword(s):  
Molecular Imaging ◽  
Ex Vivo ◽  
Specific Binding ◽  
Monocarboxylate Transporters ◽  
Binding Potential ◽  
Kidney Cortex ◽  
Binding Studies ◽  
Imaging Tool ◽  
Pre Treatment

The expression of monocarboxylate transporters (MCTs) is linked to pathophysiological changes in diseases, including cancer, such that MCTs could potentially serve as diagnostic markers or therapeutic targets. We recently developed [18F]FACH as a radiotracer for non-invasive molecular imaging of MCTs by positron emission tomography (PET). The aim of this study was to evaluate further the specificity, metabolic stability, and pharmacokinetics of [18F]FACH in healthy mice and piglets. We measured the [18F]FACH plasma protein binding fractions in mice and piglets and the specific binding in cryosections of murine kidney and lung. The biodistribution of [18F]FACH was evaluated by tissue sampling ex vivo and by dynamic PET/MRI in vivo, with and without pre-treatment by the MCT inhibitor α-CCA-Na or the reference compound, FACH-Na. Additionally, we performed compartmental modelling of the PET signal in kidney cortex and liver. Saturation binding studies in kidney cortex cryosections indicated a KD of 118 ± 12 nM and Bmax of 6.0 pmol/mg wet weight. The specificity of [18F]FACH uptake in the kidney cortex was confirmed in vivo by reductions in AUC0–60min after pre-treatment with α-CCA-Na in mice (−47%) and in piglets (−66%). [18F]FACH was metabolically stable in mouse, but polar radio-metabolites were present in plasma and tissues of piglets. The [18F]FACH binding potential (BPND) in the kidney cortex was approximately 1.3 in mice. The MCT1 specificity of [18F]FACH uptake was confirmed by displacement studies in 4T1 cells. [18F]FACH has suitable properties for the detection of the MCTs in kidney, and thus has potential as a molecular imaging tool for MCT-related pathologies, which should next be assessed in relevant disease models.

INITIAL STUDIES IN MAN WITH A NOVEL THROMBOXANE RECEPTOR BLOCKING DRUG GR32191

1987 ◽  
Author(s):  
M Thomas ◽  
P Lumley ◽  
P Ballard ◽  
J R O'Brien
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Plasma Concentrations ◽  
Blocking Drug ◽  
Double Blind ◽  
Receptor Blocking ◽  
Thromboxane Receptor ◽  
Pre Treatment ◽  
Induced Aggregation

In-vitro GR32191 is a potent and specific thromboxane receptor blocking drug on platelets, and vascular and airways smooth muscle (Lumley et al this meeting). We have undertaken studies in healthy male subjects (n) to examine the effects of oral GR32191 upon platelet aggregation ex-vivo and template bleeding time. Platelet aggregation was monitored in whole blood by counting platelets electronically. Concentration-effect curves to U-46619 and ADP were constructed prior to and following drug or placebo. The degree of rightward displacement of a curve due to treatment was expressed as a concentration-ratio (CR) which was calculated at the 50% aggregation level (ECso post-treatment ECso pre-treatment). Plasma concentrations of GR32191 were determined by h.p.l.c. After single doses of GR32191 mean peak CR's of 8 and 80 were achieved with 0.125 and 0.25mg/kg (n=4) and values of 74 and 234 with 0.5 and lmg/kg (n=4). Peak effects were seen within 2 hours of dosing while activity was still present between 8 and 24 hours. ADP-induced aggregation was unaffected by drug (CR<2) and placebo was without significant effect upon the sensitivity to either aggregating agent (CR<2). GR32191 was rapidly absorbed and the plasma elimination half-life was about 2 hours. GR32191 17.5mg 12-hourly for 10 days (n=6) produced a progressive antagonism of U-46619 induced aggregation which resulted in a large continuous blockade in all subjects (range of 12htrough CR's 85 to 287). However, plasma concentrations of GR32191 did not accumulate on repeated administration. In a double-blind, placebo-controlled, cross-over study (n=16), a statistically significant (p= 0.002) increase in bleeding time was seen following treatment with GR32191 40mg twice daily for 7 days (pre-treatment mean 3.79 min, post-placebo mean 3.47 min, post-GR32191 mean 5.42 min). Rectal bleeding (n=l) has occurred with GR32191 but otherwise tolerability has been good. No drug related changes have been seen in routine laboratory safety screens. Clinical studies are in progress.

scholarly journals Nuclear localization of platelet-activating factor receptor controls retinal neovascularization

2016 ◽  
Vol 2 (1) ◽  
Author(s):  
Vikrant K Bhosle ◽  
José Carlos Rivera ◽  
Tianwei (Ellen) Zhou ◽  
Samy Omri ◽  
Melanie Sanchez ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Cellular Localization ◽  
Nuclear Translocation ◽  
Ex Vivo ◽  
Platelet Activating Factor ◽  
Plasma Membrane Permeability ◽  
Independent Manner ◽  
Endothelial Growth Factor

Abstract Platelet-activating factor (PAF) is a pleiotropic phospholipid with proinflammatory, procoagulant and angiogenic actions on the vasculature. We and others have reported the presence of PAF receptor (Ptafr) at intracellular sites such as the nucleus. However, mechanisms of localization and physiologic functions of intracellular Ptafr remain poorly understood. We hereby identify the importance of C-terminal motif of the receptor and uncover novel roles of Rab11a GTPase and importin-5 in nuclear translocation of Ptafr in primary human retinal microvascular endothelial cells. Nuclear localization of Ptafr is independent of exogenous PAF stimulation as well as intracellular PAF biosynthesis. Moreover, nuclear Ptafr is responsible for the upregulation of unique set of growth factors, including vascular endothelial growth factor, in vitro and ex vivo. We further corroborate the intracrine PAF signaling, resulting in angiogenesis in vivo, using Ptafr antagonists with distinct plasma membrane permeability. Collectively, our findings show that nuclear Ptafr translocates in an agonist-independent manner, and distinctive functions of Ptafr based on its cellular localization point to another dimension needed for pharmacologic selectivity of drugs.

scholarly journals Protective Effect of Eckol against Acute Hepatic Injury Induced by Carbon Tetrachloride in Mice

Marine Drugs ◽  
2018 ◽  
Vol 16 (9) ◽  
pp. 300 ◽  
Author(s):  
Shulan Li ◽  
Juan Liu ◽  
Mengya Zhang ◽  
Yuan Chen ◽  
Tianxing Zhu ◽  
...  
Keyword(s):  
Carbon Tetrachloride ◽  
Liver Injury ◽  
Protective Effect ◽  
Acute Liver Injury ◽  
Treated Group ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Enhanced Expression ◽  
Pre Treatment

Several in vitro studies have shown the potential hepatoprotective properties of eckol, a natural phlorotannin derived from the brown alga. However, the in vivo hepatoprotective potential of eckol has not been determined. In this study, we performed an in vivo study to investigate the protective effect of eckol and its possible mechanisms on the carbon tetrachloride (CCl4)-induced acute liver injury model in mice. Results revealed that eckol pre-treatment at the dose of 0.5 and 1.0 mg/kg/day for 7 days significantly suppressed the CCl4-induced increases of alanine transaminase (ALT) and aspartate aminotransferase (AST) levels in serum and meliorated morphological liver injury. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) analysis showed that the number of positive apoptotic hepatocytes in the eckol-treated group was lower than that in the CCl4 model group. Western blotting analysis also demonstrated the enhanced expression of bcl-2 and suppressed expression of cleaved caspase-3 by eckol. The CCl4-induced oxidative stress in liver was significantly ameliorated by eckol, which was characterized by reduced malondialdehyde (MDA) formations, and enhanced superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities and glutathione (GSH) content. Moreover, the CCl4-induced elevations of pro-inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were markedly suppressed in the eckol-treated group. However, eckol enhanced the level of IL-10, a potent anti-inflammatory cytokine, and recruited CD11c+ dendritic cells into the liver tissues of CCl4-treated mice. These results indicated that eckol has the protective effect on CCl4-induced acute liver injury via multiple mechanisms including anti-apoptosis, anti-oxidation, anti-inflammation and immune regulation.

CD34+CD90+ Cord Blood Cells Which Have Undergone Multiple Cell Divisions Retain Marrow Repopulating Potential.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3228-3228
Author(s):  
Hiroto Araki ◽  
Nadim Mahmud ◽  
Mohammed Milhem ◽  
Hetal S. Patel ◽  
Rafael Nunez ◽  
...  
Keyword(s):  
Cord Blood ◽  
Ex Vivo ◽  
Trichostatin A ◽  
Cell Divisions ◽  
Cd34 Cells ◽  
Sequential Addition ◽  
Multiple Cell ◽  
Cord Blood Cells ◽  
Pre Treatment

Abstract We have previously shown that the sequential addition of a hypomethylating agent, 5-aza-2′-deoxyctidine (5azaD) and a histone deacetylase inhibitor, trichostatin A (TSA) is capable of changing the fate of adult bone marrow CD34+ cells (Milhem M et al Blood 2004). We have now studied whether these drugs could alter the behavior of dividing CD34+CD90+ cord blood (CB) cells. The 5azaD/TSA treated cultures yielded 10 times greater numbers of CD34+CD90+ cells as compared to the cultures containing cytokines alone after 9 days of culture. The 5azaD/TSA treated cultures contained 2 fold greater numbers of colony forming cells (CFC) and 14 fold greater numbers of long-term (5wk) cobblestone area forming cells (CAFC) in comparison to culture containing cytokines alone. Although the CFC/CAFC plating efficiency of cells in cultures exposed to cytokines alone declined during the time of incubation, the cloning efficiency of cells exposed to 5azaD/TSA was equivalent to that of primary CD34+ cells. In order to determine the effects of cell division on the behavior of CD34+CD90+ cells in the 5azaD/TSA treated cultures, we utilized the cytoplasmic dye, CFSE. All of the CD34+CD90+ cells within the 5azaD/TSA pre-treated cultures divided at least once after 9 days of culture. 60% of the 5azaD/TSA treated CD34+CD90+ cells divided 5 times or more while 40% divided 1–4 times. The CD34+CD90+ cells lacking 5azaD/TSA pre-treatment underwent more cell divisions (90%, 5 or more divisions). The CD34+CD90+ cells pre-treated with 5azaD/TSA which had undergone 1-2 cell divisions had 11 fold greater numbers of CFU-Mix and 9 fold greater number of CAFC as compared to CD34+CD90+ cell population cultured in presence of cytokines alone. Furthermore CD34+CD90+ cells having 5 and more divisions had 4 fold more CFU-mix and 6.5 fold more CAFC in comparison to cells lacking 5azaD/TSA exposure. The CD34+CD90+ cells experiencing 1–4 divisions had 60 fold greater number of CFU-mix and 54 fold more CAFC in contrast to culture treated with cytokines alone. The in vivo SCID repopulating potential of CD34+CD90+ cells generated in presence or absence of 5azaD/TSA was then evaluated. When 5x104 CD34+CD90+ cells having undergone 1-2 cell divisions were re-isolated from 5azaD/TSA pre-treated cultures, all mice contained human hematopoietic cells. In addition, 1 of 3 mice transplanted with CD34+CD90+ cells (5x104) having undergone 3 and more cell divisions isolated from cultures pre-treated with 5azaD/TSA also displayed human hematopoietic engraftment. Furthermore 1 of 3 mice transplanted with equal numbers of the 5azaD/TSA pre-treated CD34+CD90+ cells having undergone 5 and more cell divisions also had evidence of human multilineage hematopoietic engraftment. By contrast, an equivalent number of CD34+CD90+ cells which had undergone more than 3 or more than 5 cell divisions from the cultures containing cytokines alone were incapable of engrafting NOD/SCID mice. These data suggest that the sequential addition of 5azaD and TSA ex vivo is not only capable of expanding the numbers of CD34+CD90+ cells and assayable progenitor cells but also capable of preserving their SCID repopulating potential. We conclude that 5azaD/TSA treatment of CD34+CD90+ cells results in their retention of the cellular program required to maintain their marrow repopulating potential despite their undergoing multiple cell divisions.

A Novel Mutation In Bruton Tyrosine Kinase Confers Acquired Resistance To Ibrutinib (PCI-32765) In CLL

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4914-4914 ◽  
Author(s):  
Richard R. Furman ◽  
Shuhua Cheng ◽  
Pin Lu ◽  
Menu Setty ◽  
Alexandar Perez ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Ex Vivo ◽  
Novel Mutation ◽  
Expression Profiles ◽  
Covalent Binding ◽  
Lymphocytic Leukemia ◽  
Brdu Incorporation ◽  
Bruton Tyrosine Kinase ◽  
Pre Treatment

Abstract The Bruton tyrosine kinase (BTK) inhibitor, ibrutinib has produced durable remissions in chronic lymphocytic leukemia (CLL). We describe a CLL patient who progressed while receiving ibrutinib following 20 months of once daily dosing. A cysteine-to-serine amino acid replacement was identified in BTK at position 481 that disrupts the covalent, but not non-covalent, binding of ibrutinib to BTK in silico structural modeling1. The mutation was present in relapsed samples while absent in the pre-treatment and responding samples. Following the mutation, the B cell receptor (BCR) pathway was reactivated as evidenced by increased cell signaling activities and gene expression profiles. Comparing the relapsed samples with the pre-treatment and responding samples, at the cellular level, mutated CLL cells displayed higher levels of the cell proliferation marker Ki67 in vivo and higher levels of ex-vivo BrdU incorporation. Transfection of the C481S mutant construct into a sensitive lymphoma cell line rendered it much more resistant to ibrutinib treatment demonstrating the cellular impact of the mutation (see attached graph). Interestingly, the ibrutinib-resistant CLL cells remained sensitive to other BCR inhibitors such as dasatinib and SYK inhibitors. These results confirm BTK as an important pharmacologic target of ibrutinib. Further, a mechanism of resistance was revealed, and alternative therapeutic options for ibrutinib resistance were explored. (First three authors with equal contribution) Disclosures: Furman: Genentech: Consultancy, Speakers Bureau; GlaxoSmithKline: Consultancy, Speakers Bureau; Pharmacyclics: Consultancy; Gilead: Consultancy. Chang:Pharmacyclics: Employment, Equity Ownership.

scholarly journals Synthesis and Thrombin, Factor Xa and U46619 Inhibitory Effects of Non-amidino and Amidino N2-Thiophenecarbonyl- and N2-Tosylanthranilamides

2017 ◽  
Author(s):  
Soo Hyun Lee ◽  
Wonhwa Lee ◽  
Nguyen Thi Ha ◽  
Il Soo Um ◽  
Jong-Sup Bae ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Factor Xa ◽  
Inhibitory Effects ◽  
Human Endothelial Cells ◽  
Antithrombotic Activity ◽  
Pharmacological Targets

Thrombin (factor IIa) and factor Xa (FXa) are key enzymes at the junction of the intrinsic and extrinsic coagulation pathways and are the most attractive pharmacological targets for the development of novel anticoagulants. Twenty non-amidino N2-thiophencarbonyl- and N2-tosyl anthranilamides 1-20 and six amidino N2-thiophencarbonyl- and N2-tosylanthranilamides 21-26 were synthesized and evaluated prothrombin time (PT) and activated partial thromboplastin time (aPTT) using human plasma at concentration 30 &mu;g/mL in vitro. From these results, compounds 5, 9, and 21-23 were selected to study the further antithrombotic activity. The anticoagulant properties of 5, 9, and 21-23 significantly exhibited a concentration-dependent prolongation of in vitro PT and aPTT, in vivo bleeding time, and ex vivo clotting time. These compounds concentration-dependently inhibited the activities of thrombin and FXa and inhibited the generation of thrombin and FXa in human endothelial cells. In addition, data showed that 5, 9, and 21-23 significantly inhibited thrombin catalyzed fibrin polymerization and mouse platelet aggregation and inhibited platelet aggregation induced U46619 in vitro and ex vivo. N-(3'-Amidinophenyl)-2-((thiophen-2''-yl)carbonyl amino)benzamide (21) was most active.

Antithrombotic Effect of a Recombinant von Willebrand Factor, VCL, on Nitrogen Laser-Induced Thrombus Formation in Guinea Pig Mesenteric Arteries

1995 ◽  
Vol 73 (02) ◽  
pp. 318-323 ◽  
Author(s):  
K Azzam ◽  
L I Garfinkel ◽  
C Bal dit Sollier ◽  
M Cisse Thiam ◽  
L Drouet
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Mesenteric Arteries ◽  
Antithrombotic Effects ◽  
Von Willebrand ◽  
Willebrand Factor

SummaryTo assess the antithrombotic effectiveness of blocking the platelet glycoprotein (GP) Ib/IX receptor for von Willebrand factor (vWF), the antiaggregating and antithrombotic effects were studied in guinea pigs using a recombinant fragment of vWF, Leu 504-Lys 728 with a single intrachain disulfide bond linking residues Cys 509-Cys 695. The inhibitory effect of this peptide, named VCL, was tested in vitro on ristocetin- and botrocetin-induced platelet aggregation and compared to the ADP-induced platelet aggregation. In vivo, the antithrombotic effect of VCL was tested in a model of laser-injured mesentery small arteries and correlated to the ex vivo ristocetin-induced platelet aggregation. In this model of laser-induced thrombus formation, five mesenteric arteries were studied in each animal, and the number of recurrent thrombi during 15 min, the time to visualization and time to formation of first thrombus were recorded.In vitro, VCL totally abolished ristocetin- and botrocetin-induced platelet aggregation, but had no effect on ADP-induced platelet aggregation. Ex vivo, VCL (0.5 to 2 mg/kg) administered as a bolus i. v. injection inhibits ristocetin-induced platelet aggregation with a duration of action exceeding 1 h. The maximum inhibition was observed 5 min after injection of VCL and was dose related. The same doses of VCL had no significant effect on platelet count and bleeding time. In vivo, VCL (0.5 to 2 mg/kg) had no effect on the appearance of the thrombi formed but produced dose-dependent inhibition of the mean number of recurrent thrombi (the maximal effect was obtained at 5 min following i. v. injection of the highest dose: 0.8 ± 0.2 thrombi versus 4 ± 0.4 thrombi in controls). The three doses of VCL increased the time in which the first thrombus in a concentration-dependent manner was formed. However, the time to visualize the first thrombus was only prolonged in the higher dose-treated group.These in-vivo studies confirm that VCL induces immediate, potent, and transient antithrombotic effects. Most importantly, this inhibition was achieved without inducing thrombocytopenia nor prolongation of the bleeding time.

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