Impact of aspirin dose on adenosine diphosphate-mediated platelet activities

2013 ◽  
Vol 110 (10) ◽  
pp. 777-784 ◽  
Author(s):  
Antonio Tello-Montoliu ◽  
Estela Thano ◽  
Fabiana Rollini ◽  
Ronakkumar Patel ◽  
Ryan E. Wilson ◽  
...  
Keyword(s):  
Platelet Reactivity ◽  
Stable Coronary Artery Disease ◽  
Adenosine Diphosphate ◽  
P2y12 Receptor ◽  
Reactivity Index ◽  
Receptor Blockade ◽  
Aspirin Dose ◽  
Dosing Regimens ◽  
The Impact

SummaryDifferent aspirin dosing regimens have been suggested to impact outcomes when used in combination with adenosine diphosphate (ADP) P2Y12 receptor antagonists. Prior investigations have shown that not only aspirin, but also potent ADP P2Y12 receptor blockade can inhibit thromboxane A2-mediated platelet activation. The impact of aspirin dosing on ADP mediated platelet activities is unknown and represents the aim of this in vitro pilot pharmacodynamic (PD) investigation. Twenty-six patients with stable coronary artery disease on aspirin 81 mg/day and P2Y12 naïve were enrolled. PD assessments were performed at baseline, while patients were on 81 mg/day aspirin and after switching to 325 mg/day for 7 ± 2 days with and without escalating concentrations (vehicle, 1, 3, and 10 μM) of prasugrel’s active metabolite (P-AM). PD assays included flow cytometric assessment of VASP to define the platelet reactivity index (PRI) and the Multiplate Analyzer (MEA) using multiple agonists [ADP, ADP + prostaglandin (PGE1), arachidonic acid (AA), and collagen]. Escalating P-AM concentrations showed incremental platelet P2Y12 inhibition measured by VASP-PRI (p<0.001). However, there were no differences according to aspirin dosing regimen at any P-AM concentration (vehicle: p=0.899; 1 ïM: p=0.888; 3 ïM: p=0.524; 10 ïM: p=0.548). Similar findings were observed in purinergic markers assessed by MEA (ADP and ADP+PGE1). P-AM addition significantly reduced AA and collagen induced platelet aggregation (p<0.001 for all measures), irrespective of aspirin dose. In conclusion, aspirin dosing does not appear to affect PD measures of ADP-mediated platelet reactivity irrespective of the degree of P2Y12 receptor blockade. P2Y12 receptor blockade modulates platelet reactivity mediated by alternative activators.

Comparison of VASP-phosphorylation assay to light-transmission aggregometry in assessing inhibition of the platelet ADP P2Y12 receptor

2006 ◽  
Vol 96 (12) ◽  
pp. 767-773 ◽  
Author(s):  
Agnieszka Pampuch ◽  
Giovanni de Gaetano ◽  
Chiara Cerletti
Keyword(s):  
Light Transmission ◽  
Platelet Reactivity ◽  
Flow Cytometric Analysis ◽  
Individual Variability ◽  
P2y12 Receptor ◽  
Reactivity Index ◽  
Drug Induced ◽  
Light Transmission Aggregometry ◽  
Adp Receptor

SummaryThere is need to improve platelet function testing to monitor the response to antiplatelet drugs. We compared flow-cytometric analysis of intraplatelet vasodilator-stimulated phosphoprotein phosphorylation (VASP-P) to light-transmission aggregometry for the detection of drug-induced in-vitro inhibition of the platelet P2Y12 ADP receptor on 22 healthy subjects (10 males, 12 females, 28.5 ± 6.6 years). The platelet reactivity index (PRI) of VASP was calculated both from mean fluorescence intensity (MFI) and percent of fluorescence-positive platelets in the presence of PGE1 with or without ADP (10 µM). Platelet aggregation was induced by ADP (1.25, 2.5 and 5 µM). Cangrelor, a competitive inhibitor of the P2Y12 receptor, preincubated 5 minutes, induced a concentration-dependent inhibition of platelet ADP-receptor function in both tests. Indeed PRI (%) based on either MFI or percent platelets gated were highly correlated with each other (r = 0.97, p<0.0001) and with aggregation in- duced by ADP. The IC50 of cangrelor against each of the three ADP concentrations used in aggregometry increased from 5.8 ± 3.4 nM to 23.1 ± 4.0 nM and to 98 ± 25 nM, respectively. The IC50 of cangrelor based on VASP-P was within the same range (25.5 ± 7.7 nM). No correlation was observed between IC50 values of cangrelor and ADP concentrations giving 50% effect (EC50) in the absence of the drug. However, at 10 nM cangrelor seven subjects could be identified by the VASP-P assay as “low responders” to the drug (PRI> 50%), and six of them also had an aggregation response to 5 µM ADP > 50%. These six subjects showed the lowest ADP EC50 values in the absence of the drug, possibly reflecting high sensitivity of their platelet P2Y12 receptors to ADP. In conclusion, both the VASP-P assay and light-transmission aggregometry detect in a comparable way in-vitro pharmacological inhibition of the platelet P2Y12 ADP receptor and its individual variability.

A comparison of the antiplatelet effects of prasugrel and high-dose clopidogrel as assessed by VASP-phosphorylation and light transmission aggregometry

2008 ◽  
Vol 99 (01) ◽  
pp. 215-222 ◽  
Author(s):  
Christopher D Payne ◽  
Ying G Li ◽  
Nagy A Farid ◽  
John T Brandt ◽  
David S Small ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Light Transmission ◽  
Platelet Reactivity ◽  
Platelet Inhibition ◽  
P2y12 Receptor ◽  
Reactivity Index ◽  
High Dose ◽  
Receptor Blockade ◽  
Vasp Phosphorylation ◽  
Light Transmission Aggregometry

SummaryPlatelet inhibition as measured by vasodilator-stimulated phosphoprotein (VASP) and light transmission aggregometry (LTA) have shown concordance following dosing of clopidogrel. No reports have directly compared theVASP assay and LTA at the levels of P2Y12 blockade after loading doses (LDs) of prasugrel or high dose clopidogrel (600 and 900 mg).The aim was to compare theVASP assay and LTA during the loading dose phase of a comparative study of prasugrel and clopidogrel. Prasugrel 60 mg LD/10 mg maintenance dose (MD) and clopidogrel 300 mg/75 mg and 600 mg/75 mg LD/MD regimens were compared in a 3-way crossover study in 41 healthy, aspirin-free subjects. Each LD was followed by seven daily MDs and a 14-day washout period. P2Y12 receptor blockade was estimated using theVASP assay, expressed as platelet reactivity index (VASP-PRI). Platelet aggregation was assessed by light transmission aggregometry (20 and 5 μM ADP).Twenty-four hoursafter prasgurel 60 mg or clopidogrel 300 mg and 600 mg, respectively, VASP-PRI decreased from ∼80% to 8.9%, 54.7%, and 39.0 %, and maximal platelet aggregation (MPA) decreased from ∼79% to 10.8%, 42.7%, and 31.2%, with an overall VASP:MPA correlation of 0.88 (p<0.01). VASP assay responses after the clopidogrel LDs showed a wider range of values (300 mg: 0–93%; 600 mg: 0–80%) than prasugrel (0–13%); MPA responses followed a similar trend. Pearson’s correlation suggested a strong agreement between VASP and LTA (20 μM ADP) for MPA (r=0.86, p<0.0001).VASP and LTA demonstrated concordance across the response range of P2Y12 receptor blockade following thienopyridine LDs.

Comparison of a new ELISA assay with the flow cytometric assay for platelet vasodilator-associated stimulated phosphoprotein (VASP) phosphorylation in whole blood to assess P2Y12 inhibition

2012 ◽  
Vol 107 (02) ◽  
pp. 388-395 ◽  
Author(s):  
Nicolas Bourguet ◽  
Danièle Boulay-Moine ◽  
Atsuhiro Sugidachi ◽  
Shinji Yamaguchi ◽  
Paul Barragan ◽  
...  
Keyword(s):  
Clinical Studies ◽  
Platelet Reactivity ◽  
P2y12 Receptor ◽  
Reactivity Index ◽  
Blood Collection ◽  
Variable Response ◽  
Vasp Phosphorylation ◽  
P2y12 Antagonists ◽  
Wide Range

SummaryThienopyridines and other agents target the platelet P2Y12 receptor and inhibit several platelet activities mediated by adenosine diphosphate (ADP). The measurement of vasodilator-associated stimulated phosphoprotein (VASP) phosphorylation, expressed as platelet reactivity index (PRI), mirrors the degree of P2Y12 receptor inhibition and can detect the well-known variable response to clopidogrel. The commercially available VASP assay uses flow cytometry (FC) and requires that the test be run within 48 hours of blood collection. A new ELISA VASP assay offers the advantages of using more widely available technology and the potential to freeze and store samples before analysis. The objectives of the present study were to compare the performance of the ELISA and FC methods and to describe the relative flexibility of the ELISA-based assay. Human blood samples encompassing a wide range of levels of P2Y12 blockade achieved in vitro by preincubation with P2Y12 antagonists or in vivo from patients treated with clopidogrel were included, reflecting the wide spread of values reported in clinical studies. The correlation between the PRI measured by ELISA and FC was highly significant (r=0.95, p<0.001), (n=80). After the initial activation, samples were stable for at least four weeks when frozen (−20°C) prior to analysis by ELISA. Frozen samples from patients treated with clopidogrel appeared stable for up to nine weeks. Based on these results, the ELISA-based assay appears to provide a reliable and more flexible alternative to the FC method to determine P2Y12 receptor blockade and may enable more extensive utilisation of the VASP assay in clinical studies.Note: All work done at BioCytex, Marseille, France and Daiichi Sankyo, Tokyo, Japan.

Interactions Between Blood Platelets and Vascular Endothelium in vitro Studies

1979 ◽  
Author(s):  
M.A. Gimbrone ◽  
K.D. Curwen ◽  
R. I. Handin
Keyword(s):  
Platelet Aggregation ◽  
Vascular Endothelium ◽  
Potent Inhibitor ◽  
Platelet Reactivity ◽  
Blood Platelets ◽  
Primary Cultures ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Platelet Adherence

Endothelial cells (EC) can actively influence the hemostatic response at sites of vascular injury through multiple mechanisms. For example, EC can degrade adenosine diphosphate, release plasminogen activator, and synthesize prostacyclin (PGI2), a potent inhibitor of platelet aggregation. We have examined whether PGI2 also might account for the normal lack of platelet adherence to the uninjured EC surface. In a monolayer adherence assay, radiolabeled human platelets in citrated plasma showed minimal interaction with primary cultures of human EC (<1 platelet adhering per cell). Platelets from aspirin-treated and untreated donors behaved similarly. However, aspirin pretreatment of EC consistently resulted in ~2-fold increases in platelet adherence which could be completely abolished by exogenous PGI2 (0.5–1.0 μg/ml). SV40-transformed human EC (SVHEC), which are deficient in PGI2 production compared to primary EC, showed 10-30 times more platelet adherence. Exogenous PGI2 produced a dose - related (.001-1.0 μg/ml) decrease in platelet adherence to SVHEC but did not result in the basal levels observed with normal EC monolayers. These data suggest that : 1) In addition to its effects on platelet aggregation, PGI2 can influence platelet endothelial cell interactions; 2) The increased platelet reactivity of transformed EC is associated with, but not completely attributable, to decreased PGI2 production; and 3) Factors other than PGI2 may play a role in the thromboresistance of normal vascular endothelium.

scholarly journals Combination of in vivo phage therapy data with in silico model highlights key parameters for treatment efficacy

2021 ◽  
Author(s):  
Raphaelle Delattre ◽  
Jeremy Seurat ◽  
Feyrouz Haddad ◽  
Thu-Thuy Nguyen ◽  
Baptiste Gaborieau ◽  
...  
Keyword(s):  
Phage Therapy ◽  
Biological Properties ◽  
General Strategy ◽  
In Vivo Experiments ◽  
Bacterial Dynamics ◽  
Optimal Dosing ◽  
Dosing Regimens ◽  
The Impact

The clinical (re)development of phage therapy to treat antibiotic resistant infections requires grasping specific biological properties of bacteriophages (phages) as antibacterial. However, identification of optimal dosing regimens is hampered by the poor understanding of phage-bacteria interactions in vivo. Here we developed a general strategy coupling in vitro and in vivo experiments with a mathematical model to characterize the interplay between phage and bacterial dynamics during pneumonia induced by a pathogenic strain of Escherichia coli. The model estimates some key parameters for phage therapeutic efficacy, in particular the impact of dose and route of administration on phage dynamics and the synergism of phage and the innate immune response on the bacterial clearance rate. Simulations predict a low impact of the intrinsic phage characteristics in agreement with the current semi-empirical choices of phages for compassionate treatments. Model-based approaches will foster the deployment of future phage therapy clinical trials.

Impact of reticulated platelets on antiplatelet response to thienopyridines is independent of platelet turnover

2016 ◽  
Vol 116 (11) ◽  
pp. 941-948 ◽  
Author(s):  
Thomas Nührenberg ◽  
Michael Amann ◽  
Marco Cederqvist ◽  
Pascal Kleiner ◽  
Christian M. Valina ◽  
...  
Keyword(s):  
Platelet Count ◽  
Drug Exposure ◽  
Platelet Reactivity ◽  
Adenosine Diphosphate ◽  
Coronary Intervention ◽  
Underlying Mechanism ◽  
Entire Cohort ◽  
Reticulated Platelets ◽  
Impedance Aggregometry ◽  
The Impact

SummaryReticulated platelets are associated with impaired antiplatelet response to thienopyridines. It is uncertain whether this interaction is caused by a decreased drug exposure due to high platelet turnover reflected by elevated levels of reticulated platelets or by intrinsic properties of reticulated platelets. This study sought to investigate if the impact of reticulated platelets on early antiplatelet response to thienopyridines is mainly caused by platelet turnover as previously suggested. Elective patients undergoing coronary intervention were randomised to loading with clopidogrel 600 mg or prasugrel 60 mg (n=200). Adenosine diphosphate (ADP)-induced platelet reactivity was determined by impedance aggregometry before, at 30, 60, 90, and 120 minutes and at day 1 after loading. Immature platelet count was assessed as marker of reticulated platelets by flow cytometry. Platelet reactivity increased with rising levels of immature platelet count in both groups. This effect was more distinctive in patients on clopidogrel as compared to patients on prasugrel. Overall, immature platelet count correlated well with on-treatment platelet reactivity at all timepoints (p < 0.001). These correlations did not change over time in the entire cohort as well as in patients treated with clopidogrel or prasugrel indicating an effect independent of platelet turnover (comparison of correlations 120 minutes/day 1: p = 0.64). In conclusion, the association of immature platelet count with impaired antiplatelet response to thienopyridines is similar early and late after loading. This finding suggests as main underlying mechanism another effect of reticulated platelets on thienopyridines than platelet turnover.Supplementary Material to this article is available online at www.thrombosis-online.com.

C0495: Experimentally-Induced Cardiac Ischemia in Pigs Increases Platelet Reactivity and Reduces the Effect of P2Y12 Receptor Blockade

2014 ◽  
Vol 133 ◽  
pp. S100
Author(s):  
A. Moscardó ◽  
A. Hernándiz ◽  
B. Cortina ◽  
I. Cerrada ◽  
A. Latorre ◽  
...  
Keyword(s):  
Platelet Reactivity ◽  
Cardiac Ischemia ◽  
P2y12 Receptor ◽  
Receptor Blockade ◽  
Experimentally Induced

scholarly journals Erythrocytes metabolically enhance collagen-induced platelet responsiveness via increased thromboxane production, adenosine diphosphate release, and recruitment

Blood ◽  
1991 ◽  
Vol 78 (1) ◽  
pp. 154-162 ◽  
Author(s):  
J Valles ◽  
MT Santos ◽  
J Aznar ◽  
AJ Marcus ◽  
V Martinez-Sales ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Therapeutic Potential ◽  
Platelet Reactivity ◽  
Adenosine Diphosphate ◽  
Stimulus Response ◽  
Absolute Requirement ◽  
Thromboxane Production ◽  
And Function ◽  
Aspirin Ingestion

Abstract Erythrocytes promoted platelet reactivity in a plasma medium, as demonstrated in an in vitro system that independently evaluated the biochemistry of platelet activation and recruitment. The prothrombotic erythrocyte effects were metabolically regulated, as evidenced by lack of activity of ATP-depleted or glutaraldehyde-fixed erythrocytes. They occurred in the absence of cell lysis as verified by lactate dehydrogenase assays, and had an absolute requirement for platelet activation. The presence of erythrocytes induced a twofold increase in platelet thromboxane B2 (TXB2) synthesis upon collagen stimulation, indicating that erythrocytes modulated platelet eicosanoid formation. Cell-free releasates from stimulated platelet-erythrocyte suspensions, which exhibited increased recruiting capacity, contained 6.9-fold more ADP and 4.9-fold more ATP than releasates from stimulated platelets alone. Following aspirin ingestion, TXB2 formation was blocked, but erythrocyte promotion of platelet reactivity persisted at those doses of collagen that reinduced platelet activation. Moreover, when platelet mixtures consisted of as little as 10% obtained before aspirin plus 90% obtained post-aspirin ingestion, significant erythrocyte enhancement of platelet reactivity occurred, even at low agonist concentrations. These erythrocyte effects would decrease the therapeutic potential of inhibition of platelet cyclooxygenase by aspirin. The erythrocyte- induced modulation of platelet biochemistry and function emphasizes the importance of cell-cell interactions in stimulus-response coupling.

scholarly journals Hypoxia Modulates Platelet Purinergic Signalling Pathways

2019 ◽  
Vol 120 (02) ◽  
pp. 253-261 ◽  
Author(s):  
Gordon G. Paterson ◽  
Jason M. Young ◽  
Joseph A. Willson ◽  
Christopher J. Graham ◽  
Rebecca C. Dru ◽  
...  
Keyword(s):  
High Altitude ◽  
Sea Level ◽  
Platelet Reactivity ◽  
Clinical Importance ◽  
Adenosine Diphosphate ◽  
Purinergic Signalling ◽  
Systematic Assessment ◽  
Vasp Phosphorylation ◽  
The Impact ◽  
Induced Aggregation

Abstract Background Hypoxia resulting from ascent to high-altitude or pathological states at sea level is known to increase platelet reactivity. Previous work from our group has suggested that this may be adenosine diphosphate (ADP)-specific. Given the clinical importance of drugs targeting ADP pathways, research into the impact of hypoxia on platelet ADP pathways is highly important. Methods Optimul aggregometry was performed on plasma from 29 lowland residents ascending to 4,700 m, allowing systematic assessment of platelet reactivity in response to several platelet agonists. Aggregometry was also performed in response to ADP in the presence of inhibitors of the two main ADP receptors, P2Y1 and P2Y12 (MRS2500 and cangrelor, respectively). Phosphorylation of vasodilator-stimulated phosphoprotein (VASP), a key determinant of platelet aggregation, was analysed using the VASPFix assay. Results Hypobaric hypoxia significantly reduced the ability of a fixed concentration of cangrelor to inhibit ADP-induced aggregation and increased basal VASP phosphorylation. However, in the absence of P2Y receptor inhibitors, we did not find evidence of increased platelet sensitivity to any of the agonists tested and found reduced sensitivity to thrombin receptor-activating peptide-6 amide. Conclusion Our results provide evidence of increased P2Y1 receptor activity at high altitude and suggest down-regulation of the P2Y12 pathway through increased VASP phosphorylation. These changes in ADP pathway activity are of potential therapeutic significance to high-altitude sojourners and hypoxic sea level patients prescribed platelet inhibitors and warrant further investigation.

Enhanced active metabolite generation and platelet inhibition with prasugrel compared to clopidogrel regardless of genotype in thienopyridine metabolic pathways

2013 ◽  
Vol 110 (12) ◽  
pp. 1223-1231 ◽  
Author(s):  
Dominick J. Angiolillo ◽  
Jose L. Ferreiro ◽  
Joseph A. Jakubowski ◽  
Kenneth J. Winters ◽  
Mark B. Effron ◽  
...  
Keyword(s):  
Genetic Variants ◽  
Active Metabolite ◽  
Platelet Reactivity ◽  
Coronary Intervention ◽  
Platelet Inhibition ◽  
Reactivity Index ◽  
Coronary Syndrome ◽  
Metabolite Generation ◽  
Artery Disease ◽  
The Impact

SummaryClopidogrel response varies according to the presence of genetic polymorphisms. The CYP2C19*2 allele has been associated with impaired response; conflicting results have been reported for CYP2C19*17, ABCB1, and PON1 genotypes. We assessed the impact of CYP2C19, PON1, and ABCB1 polymorphisms on clopidogrel and prasugrel pharmacodynamic (PD) and pharmacokinetic (PK) parameters. Aspirin-treated patients (N=194) with coronary artery disease from two independent, prospective, randomised, multi-centre studies comparing clopidogrel (75 mg) and prasugrel (10 mg) were genotyped and classified by predicted CYP2C19 metaboliser phenotype (ultra metabolisers [UM] = *17 carriers; extensive metabolisers [EM] = *1/1 homozygotes; reduced metabolisers [RM] = *2 carriers). ABCB1 T/T and C/T polymorphisms and PON1 A/A, A/G and G/G polymorphisms were also genotyped. PD parameters were assessed using VerifyNow® P2Y12 and vasodilator stimulated phosphoprotein (VASP) expressed as platelet reactivity index (PRI) after 14 days of maintenance dosing. Clopidogrel and prasugrel active metabolite (AM) exposure was calculated in a cohort of 96 patients. For clopidogrel, genetic variants in CYP2C19, but not ABCB1 or PON1, affected PK and PD. For prasugrel, none of the measured genetic variants affected PK or PD. Compared with clopidogrel, platelet inhibition with prasugrel was greater even in the CYP2C19 UM phenotype. Prasugrel generated more AM and achieved greater platelet inhibition than clopidogrel irrespective of CYP2C19, ABCB1, and PON1 polymorphisms. The lack of effect from genetic variants on prasugrel AM generation or antiplatelet activity is consistent with previous studies in healthy volunteers and is consistent with improved efficacy in acute coronary syndrome patients managed with percutaneous coronary intervention.

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