MTOR and pulmonary arterial hypertension: In aging, COPD is manifested by an increased level of oxidative stress and accelerated lung cellular senescence activation through activation of the PI3K/Akt/mTOR pathway [49,50,51], as corroborated by studies in a murine model, where overactivation of mTOR stimulates lung cell senescence, with the rapid development of lung emphysema, pulmonary hypertension, and inflammation [52].