Compound essential oils relieve oxidative stress caused by PM_{2 .5} exposure by inhibiting autophagy through the...

Fine particulate matter (PM_2.5 ) potentially damages the respiratory system and causes respiratory diseases. Compound essential oils (CEOs) have been shown to alleviate the damage to the lung and macrophages caused by PM_2.5 . However, the effect of PM_2.5 exposure on the brain has rarely been investigated. When oxidative stress occurs in the brain, it readily causes neurological diseases. Autophagy is intimately involved in many physiological processes, especially processes important for the brain. Blocked or excessive autophagy causes a series of brain diseases, such as cerebral ischemia and stroke. This study investigated whether CEOs regulate excessive autophagy and reduce the oxidative stress caused by PM_2.5 in the brain and BV2 microglial cells. PM_2.5 increased the levels of ROS, Nox2, NF-κB and MDA while decreasing superoxide dismutase and HO-1 levels, which led to oxidative stress in the brain. The increased LC3 level and decreased P62 level suggested that PM_2.5 exposure increased the level of autophagy. After exposure to PM_2.5 , the levels of 5'-adenosine monophosphate-activated protein kinase (AMPK) increased, while the levels of mammalian target of rapamycin (mTOR) decreased, suggesting that PM_2.5 might induce autophagy by activating the AMPK/mTOR pathway. In addition, CEOs alleviated oxidative stress and autophagy induced by PM_2.5 . Therefore, we concluded that CEOs reduce oxidative stress induced by PM_2.5 exposure by inhibiting autophagy via the AMPK/mTOR signaling pathway, and these findings provide new opportunities for the prevention of PM_2.5 -induced brain diseases.