Eleutheroside B Pretreatment Attenuates Hypobaric Hypoxia-Induced High-Altitude Pulmonary Edema by Regulating Autophagic Flux via the AMPK/mTOR Pathway.

High-altitude pulmonary edema (HAPE) is a life-threatening disease, and autophagy deficiency is implicated in the pathogenesis of HAPE. Eleutheroside B (EB), which is the main bioactive component of Acanthopanax senticosus, exhibits various pharmacological activities. Our previous research demonstrated that autophagic structures were widely found in the ultrastructure of lung tissue in HAPE rats. However, whether EB regulates autophagy deficiency in HAPE remains unknown. This study aimed to investigate the protective effects of EB on hypobaric hypoxia-induced HAPE and explore the underlying molecular mechanism of regulating autophagy. The rat model of high-altitude pulmonary edema was replicated using a hypobaric hypoxic chamber. Rats were pretreated with EB or in combination with chloroquine or compound C. The pulmonary edema was assessed by the lung wet/dry ratio, total protein concentration in bronchoalveolar lavage fluid, and histological analysis. Inflammation and oxidative stress were measured using commercial biochemical kits. Autophagy and autophagic flux were evaluated by western blotting, transmission electron microscopy, and adeno-associated virus-mRFP-GFP-labeled tandem fluorescence LC3. The AMPK/mTOR signaling pathway was detected by western blotting. EB alleviated hypobaric hypoxia-induced pulmonary edema, hypoxemia, acid-base imbalance in the blood, inflammation, and oxidative stress in a dose-dependent manner. EB restored impaired autophagic flux by activating the AMPK/mTOR signaling pathway. However, chloroquine or compound C abolished eleutheroside B-mediated autophagy flux restoration. EB has the potential to restore impaired autophagic flux in the lung of hypobaric hypoxia-induced HAPE rats, which could be attributed to the activation of AMPK/mTOR signaling pathway.