257Ticagrelor decreases concentrations of prothrombotic extracellular vesicles compared to clopidogrel
Authors: Gasecka A , Nieuwland R , Budnik M , Dignat-George F , Eyileten C , Harrison P , Kaplon-Cieslicka A , Lacroix R , Opolski G , Van Der Pol E , Postula M , Leroyer A , Siljander P , Sturk A , Filipiak K 
Published: October 2019

Abstract

Introduction
The platelet P2Y12 antagonist ticagrelor reduces all-cause and cardiovascular mortality in patients after acute myocardial infarction (AMI) compared to clopidogrel, but the underlying mechanism is unknown. Because activated platelets release prothrombotic extracellular vesicles (EVs) exposing P-selectin, fibrinogen and phosphatidylserine (PS), we hypothesized that ticagrelor inhibits the release of EVs compared to clopidogrel.

Purpose
To compare the effects of ticagrelor and clopidogrel on the concentrations of platelet EVs in relation to platelet reactivity, and on the concentrations of EVs from other P2Y12-exposing cells (leukocytes, endothelial cells).

Methods
After the percutaneous coronary intervention, patients with first AMI (n=60, age 64.5±10.8 years, 68% male) were randomized in 1:1 ratio to antiplatelet therapy with ticagrelor or clopidogrel. Venous blood was collected from fasting patients at randomisation, 48 hours after randomisation, and 6 months following the index hospitalization with informed consent. Flow cytometry (Apogee A60 Micro) was used to determine plasma concentrations of EVs labelled with antibodies for activated platelets (CD61, CD62p; PEVs), fibrinogen, phosphatidylserine (PS), leukocytes (CD45; LEVs) and endothelial cells (CD146; EEVs). To maximize the reliability, the analysis of the 1,224 flow cytometry data files was performed with software enabling automatic flow rate stabilization, diameter and refractive index determination, size distribution fitting, fluorescent gate determination, and statistics reporting (MATLAB R2018a). To differentiate between EVs and small platelets, only particles <700 nm were included. Platelet reactivity was assessed by impedance aggregometry (Multiplate Analyzer) using the ASPI test (arachidonic acid, 0.5 mM) and the ADP test (adenosine diphosphate, 6.5 μM).

Results
Concentrations of PEVs exposing P-selectin, fibrinogen and PS were lower after 6 months of therapy with ticagrelor compared to clopidogrel, and decreased over time (p=0.034; p=0.021; p=0.018, respectively). Concentrations of LEVs were lower both after 72 hours and after 6 months of therapy with ticagrelor compared to clopidogrel (p=0.018; p<0.001, respectively). There was a trend towards higher concentrations of EEVs both after 72 hours and after 6 months of therapy with ticagrelor, compared to clopidogrel. There were no correlations between the concentrations of PEVs and platelet reactivity.

Conclusions
Ticagrelor decreases concentrations of prothrombotic EVs, compared to clopidogrel, suggesting that the clinical benefits of ticagrelor may be at least partly explained by inhibition of EV release from activated platelets. Further research is warranted to link this effect with clinical outcomes.

Acknowledgement/Funding
Medical University of Warsaw (1WR/PM2/18)