Factor Xa (FXa) has been reported to activate platelet via interaction with glycoprotein (GP) VI but the underlying mechanism has not been fully elucidated. We investigated if Nox2-derived oxidative stress is implicated in FXa-induced platelet aggregation (PA), and the effect of a FXa inhibitor, namely rivaroxaban, with or without aspirin (ASA), on PA. We performed an in vitro study measuring convulxin-induced PA, thromboxane (Tx) B2 and isoprostanes biosynthesis, soluble Nox2-dp (sNox2-dp), a marker of Nox2 activation, soluble GPVI (sGPVI) and PLA2 activation in platelets from healthy subjects (n = 5) added with and without a Nox2 inhibitor. The same variables were also examined in platelets treated with rivaroxaban (15-60 ng/ml), combined or less with ASA (25 µM). Convulxin-stimulated platelets increased sGPVI, sNox2-dp, H2O2, eicosanoid biosynthesis and PLA2 phosphorylation, which were all inhibited by a Nox2 inhibitor. Rivaroxaban alone significantly reduced PA, sGPVI, TxB2 and isoprostanes biosynthesis, concomitantly with Syk, sNox2-dp and PLA2 activation in a dose-dependent fashion; a significant effect was achieved with 30 ng/ml rivaroxaban. Docking simulation analysis showed that rivaroxaban interacts with GPVI. In platelets co-incubated with ASA, rivaroxaban amplified the ASA antiplatelet effect, which was achieved with 30 ng/ml and prevalently attributable to Nox2 inhibition and impaired isoprostane biosynthesis. Here we show that rivaroxaban, at concentrations achievable in human circulation, inhibits PA via GPVI interaction and eventually Nox2-mediated isoprostanes biosynthesis and amplifies the ASA antiplatelet effect.
Keywords: Convulxin; Platelet aggregation; ROS; Rivaroxaban; glycoprotein (GP)VI.
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