Isoliquiritigenin inhibits TGF-β1-induced epithelial–mesenchymal transition in pulmonary fibrosis by promoting Nix-mediated mitophagy

Nix-mediated mitophagy has been implicated in the regulation of pathological processes in cardiac and cerebral diseases; however, its role in pulmonary fibrosis (PF) remains insufficiently understood. Epithelial–mesenchymal transition (EMT), a key contributor to PF pathogenesis, is closely associated with autophagy and mitophagy. Isoliquiritigenin (ISL), the major active component of licorice, has been reported to exert anti-inflammatory, antioxidant, and anti-EMT effects. However, whether the effects of ISL on EMT involve mitophagy regulation remains unclear. This study aimed to investigate the relationship between Nix-related mitophagy and EMT and to elucidate the mechanism by which ISL regulates EMT through Nix signaling. Our results showed that ISL inhibited cell migration and modulated the levels of E-cadherin, N-cadherin, and fibronectin. ISL also significantly promoted Nix-induced mitophagy by upregulating Nix, Beclin1, and LC3 expression, downregulating p62 expression, and increasing mitophagy-positive fluorescent puncta. In addition, ISL alleviated mitochondrial dysfunction in A549 cells by improving mitochondrial membrane potential (MMP), reducing reactive oxygen species (ROS) production, and maintaining adenosine triphosphate (ATP) levels. The anti-EMT effects of ISL were further enhanced by Nix overexpression, which further upregulated Nix, Beclin1, and E-cadherin expression and downregulated N-cadherin and fibronectin expression. These findings suggest that ISL inhibits TGF-β1-induced EMT in PF by upregulating Nix-mediated mitophagy and support its potential as a candidate therapeutic agent for PF.