Aldose Reductase Mediated Mitophagy Promotes Epithelial-Mesenchymal Transition of Hepatocytes.

Abstract

Background: Recent studies suggest that impaired mitophagy leading to epithelial-mesenchymal transition (EMT) in hepatocytes plays a major role in the progression of hepatic fibrosis (HF). The authors' previous study demonstrated that aldose reductase (AR) promotes radiation-induced EMT in alveolar epithelial cells. This study aims to examine whether AR influences EMT in hepatocytes by regulating defective mitophagy.

Methods: Some histological techniques, including HE staining, Masson's trichrome staining, immunohistochemistry, and transmission electron microscopy, were employed to validate the model and examine mitochondrial injury. Subsequently, EMT was induced in hepatocytes through TGF-β1 treatment. Then experiments such as siRNA-mediated gene silencing, AR inhibition, and AR overexpression were performed. Finally, the activation status of AKT and mTOR, as well as the expression levels of proteins associated with mitophagy and EMT, were evaluated using RT-qPCR, immunofluorescence staining, and Western blotting.

Results: AR knockout significantly reduced AKT and mTOR phosphorylation In vivo but increased the expression of Pink1 and Parkin in CCl₄-exposed liver tissues. This was associated with an increased LC3 II/I expression ratio, decreased p62 expression, reduced mitochondrial damage, enhanced E-cadherin expression, and diminished Snail, α-SMA, and vimentin expression, which collectively alleviated HF. In vitro experiments revealed that AR knockdown significantly attenuated the activation of the TGF-β1-induced AKT/mTOR pathway, restored mitochondrial autophagy function, decreased ROS levels, increased mitochondrial membrane potential (MMP) and ATP production, and reversed EMT in hepatocytes via siRNA or pharmacological inhibition. Conversely, AR overexpression exacerbated the activation of the TGF-β1-induced AKT/mTOR pathway, impaired mitophagy efficiency, increased ROS levels, decreased MMP and ATP levels, and facilitated EMT process.

Conclusion: The study findings demonstrated that AR facilitates EMT in hepatocytes and plays a major role in enhancing HF. This process may be linked to AR-induced activation of the AKT/mTOR. Consequently, this activation suppresses the expression of Pink1 and Parkin, ultimately reducing the risk of mitophagy in hepatocytes.