Thioredoxin-1 regulates the autophagy induced by oxidative stress through LC3-II in human lens epithelial cells

Oxidative stress plays a major role in age-related cataract development. The cellular antioxidant protein thioredoxin-1 (Trx-1) and its negative regulator, thioredoxin binding protein-2 (TBP-2), are pivotal in the cellular redox balance during oxidative stress. The aim of this study is to investigate the effect of Trx-1 and TBP-2 on LC3 I/LC3 II in oxidative stress-induced autophagy in human lens epithelial cells (LECs). In our study, LECs were treated with 50 μM H₂ O₂ for different durations, and the expression of Trx-1 and TBP-2 were measured by RT-PCR and Western blot. Trx-1 activity was evaluated by the thioredoxin activity fluorescent assay. The subcellular localization of Trx-1 and TBP-2 was evaluated by cellular immunofluorescence. The interaction between Trx-1 and TBP-2 was examined by co-immunoprecipitation. The cell viability was detected using CCK-8, and the expression of LC3-II/LC3-I was detected to evaluate the autophagy. The results showed that the mRNA levels of the Trx-1 and TBP-2 were kinetically changed after treatment with H₂ O₂ for different durations. Exposure to H₂ O₂ increased the expression of TBP-2 but not Trx-1, while the exposure inhibited Trx-1 activity. TBP-2 was co-localized with Trx-1, and exposure to H₂ O₂ increased the interaction between TBP-2 and Trx-1. Trx-1 overexpression enhanced the autophagic response under normal circumstances and it might regulate autophagy in the initial phase. This study demonstrates the differential role of Trx-1 in cellular oxidative stress response, oxidative stress increased Trx-1 interaction with TBP-2, and Trx-1/TBP-2 regulated the autophagic response in the initial phase through LC3-II.