ADP-dependent platelet activation is required for thrombus formation in mice exposed to simulated flight conditions

The association between venous thromboembolism and air travel is well documented. Prolonged exposure to reduced atmospheric pressure and low oxygen levels during flights triggers coagulation disorders and is considered the primary risk factor for deep vein thrombosis (DVT), surpassing immobility. In this study, we investigated how experimental long-distance flight conditions affect thrombus development in mice exposed to 6 hours of hypobaric hypoxia or normobaric normoxia after inferior vena cava stenosis. Flight-simulated conditions induced a prothrombotic phenotype characterized by larger thrombi with higher neutrophil and fibrin densities, as well as overexpression of platelet P-selectin. Although no differences in circulating platelet activation were observed, the cytokine profile of circulating platelets exposed to hypobaric hypoxia was altered compared with normobaric normoxia. Furthermore, mitochondrial production of reactive oxygen species (ROS) and adenosine triphosphate (ATP) was significantly elevated in platelets of mice exposed to flight-mimicking conditions, leading to increased adenosine levels in the blood. Remarkably, thrombus formation was no longer affected by aircraft conditions in P ₂ RY ₁₂ -deficient or wild-type mice treated with clopidogrel. Thus, we conclude that hypobaric hypoxia promotes the overproduction of ROS and ATP by platelet mitochondria, leading to adenosine diphosphate-induced platelet activation involved in the development of DVT under simulated flight conditions.