The Activation of AMPK/NRF2 Pathway in Lung Epithelial Cells Is Involved in the Protective Effects of Kinsenoside on Lipopolysaccharide-Induced Acute Lung Injury

The disorder of mitochondrial dynamic equilibrium of lung epithelial cell is one of the critical causes of acute lung injury (ALI). Kinsenoside (Kin) serves as an active small-molecule component derived from traditional medicinal herb displaying multiple pharmacological actions in cancers, hyperglycemia, and liver disease. The objective of this study was to investigate the effects of Kin on lipopolysaccharide- (LPS-) induced ALI and further explore possible molecular mechanisms. Kin was administered orally (100 mg/kg/day) for 7 consecutive days before LPS instillation (5 mg/kg). After 12 hours, pathological injury, inflammatory response, and oxidative stress were detected. The results demonstrated that Kin significantly alleviated lung pathological injury and decreased the infiltration of inflammatory cells and the release of inflammatory mediators in bronchoalveolar lavage fluid (BALF), apart from inhibiting the production of reactive oxygen species (ROS) and lipid peroxidation. Meanwhile, Kin also promoted mitochondrial fusion and restrained mitochondrial fission in mice with ALI. In terms of mechanism, Kin pretreatment increased the phosphorylation of AMP-activated protein kinase (AMPK) and the protein level of nuclear factor erythroid 2-related factor 2 (NRF2). In Ampk-α knockout mice challenged with LPS, Kin lost its pulmonary protective effects, accompanied by lower NRF2 level. In vitro experiments further unveiled that either AMPK inhibition by Compound C or NRF2 knockdown by siRNA abolished the protective roles of Kin in LPS-treated A549 lung epithelial cells. And NRF2 activator TAT-14 could reverse the effects of Ampk-α deficiency. In conclusion, Kin possesses the ability to prevent LPS-induced ALI by modulating mitochondrial dynamic equilibrium in lung epithelial cell in an AMPK/NRF2-dependent manner.