Oxidative Stress and Epithelial-Mesenchymal Transition: The Impact of Ubiquitin C-terminal Hydrolase L1 in Cigarette Smoke-Induced COPD.

Purpose: Cigarette smoke (CS) has been demonstrated to mediate oxidative stress (OS) and epithelial-mesenchymal transition (EMT) in bronchial epithelial cells, thereby contributing to airway remodeling in chronic obstructive pulmonary disease (COPD). Studies have shown upregulation of Ubiquitin C-terminal hydrolase L1 (UCHL1), a deubiquitinating enzyme, in the airway epithelium of smokers. Many studies indicate that UCHL1's regulation of EMT and OS has a complex role in various cell types, including respiratory epithelium. Thus, we aimed to investigate UCHL1's regulation of EMT, OS, and related mechanisms in cigarette smoke-exposed airway epithelium.

Methods: Exposure to cigarette smoke (CS) or cigarette smoke extract (CSE) was employed to establish both animal and cellular models. Protein expression was analyzed using immunohistochemistry, immunofluorescence, and Western blotting. Lentiviral UCHL1 or GPX1-siRNA was used to modulate UCHL1 or GPX1 expression, respectively. Transwell assays were employed to evaluate cell migration and EMT-related alterations. Oxidative stress levels were assessed using specific assay kits.

Results: This study validated that exposure to CS induces UCHL1 expression in bronchial epithelial cells both in vitro and in vivo, a phenomenon positively correlated with increased OS and EMT in the airway. Notably, UCHL1 overexpression counteracted CSE's impact on EMT markers, cell migration, and oxidative stress in BEAS-2B cells, while UCHL1 knockdown exacerbated these effects. Furthermore, in BEAS-2B cells treated with CSE, upregulation of UCHL1 was found to enhance the expression of glutathione peroxidase 1 (GPX1), an antioxidant enzyme. The effect of UCHL1 overexpression on EMT-related protein markers and cell migration was reversed upon GPX1 silencing via siRNA.

Conclusions: These findings suggest that UCHL1-mediated regulation of GPX1 expression alleviates cigarette smoke-induced EMT-related protein markers change and cell migration in BEAS-2B cell.