Ticagrelor promotes atherosclerotic plaque stability in a mouse model of advanced atherosclerosis

Objective: There is increasing evidence supporting the role of platelets in atherosclerotic vascular disease. The G-protein-coupled receptor P2Y12 is a central mediator of platelet activation and aggregation but has also been linked to platelet-independent vascular disease. Ticagrelor is an oral P2Y12 antagonist that is used as a standard treatment in patients after acute myocardial infarction. However, the effects of ticagrelor on advanced atherosclerosis have not been investigated. Materials and methods: Twenty-week-old apolipoprotein-E-deficient mice received standard chow or standard chow supplemented with 0.15% ticagrelor (approximately 270 mg/kg/day) for 25 weeks. The lesion area was evaluated in the aortic sinus by Movat's pentachrome staining and lesion composition, thickness of the fibrous cap, and size of the necrotic core evaluated by morphometry. RAW 264.7 macrophages were serum starved and treated with ticagrelor in vitro for the detection and quantification of apoptosis. In addition, oxLDL uptake in RAW 264.7 macrophages was evaluated. Results: A trend toward the reduction of total lesion size was detected. However, data did not reach the levels of significance (control, n=11, 565,881 mu m(2) [interquartile range {IQR} 454,778-603,925 mu m(2)] versus ticagrelor, n= 13, 462,595 mu m(2) [IQR 379,740-546,037 mu m(2)]; P=0.1). A significant reduction in the relative area of the necrotic core (control, n= 11, 0.46 [IQR 0.4-0.51] versus ticagrelor, n= 13, 0.34 [IQR 0.31-0.39]; P=0.008), and a significant increase in fibrous caps thickness (control, n= 11, 3.7 mu m [IQR 3.4-4.2 mu m] versus ticagrelor, n= 13, 4.7 [IQR 4.3-5.5 mu m], P=0.04) were seen in ticagrelor-treated mice. In vitro studies demonstrated a reduction in apoptotic RAW 264.7 macrophages (control 0.07 +/- 0.03 versus ticagrelor 0.03 +/- 0.03; P=0.0002) when incubated with ticagrelor. Uptake of oxLDL in RAW 264.7 was significantly reduced when treated with ticagrelor (control 9.2 [IQR 5.3-12.9] versus ticagrelor 6.4 [IQR 2.5-9.5], P=0.02). Conclusion: The present study demonstrates for the first time a plaque-stabilizing effect of ticagrelor in a model of advanced vascular disease, potentially induced by a reduction of oxLDL uptake or an inhibition of apoptosis as seen in vitro.