Mechanistic study on the role of NCSTN in regulating the differentiation of airway epithelial basal cells into ciliated cells following CSE exposure.

Background: Chronic obstructive pulmonary disease (COPD) ranks as the third leading cause of death worldwide and is primarily caused by cigarette smoke (CS) exposure. A reduction in the number of ciliated cells significantly contributes to the development and progression of COPD. Nicastrin (NCSTN), a core subunit of γ-secretase, plays an important role in the pathogenesis of various tumors. However, to date, no studies have demonstrated its role in COPD. The aim of this study was to investigate the effect and underlying mechanism of NCSTN on the differentiation of airway epithelial basal cells into ciliated cells under cigarette smoke extract (CSE) exposure. Methods: Mouse tracheal epithelial basal cells were differentiated at the air-liquid interface (ALI) in vitro and exposed to CSE for 7 days. Lentiviral overexpression and knockdown of NCSTN in basal cells were performed. The effects on cell differentiation, NCSTN expression and the Notch signaling pathway in response to CSE were assessed using reverse transcription‑quantitative PCR (RT-qPCR) and western blotting (WB). Results: We found that CSE exposure in vitro inhibited ciliated cell differentiation, while simultaneously increasing the expression of NCSTN, Notch3, and Hes1. Overexpression of NCSTN suppressed ciliated cell differentiation and induced Notch3 activation. Conversely, knockdown of NCSTN attenuated the CSE-mediated reduction in ciliated cell differentiation and inhibited Notch3 activation. Our findings indicate that CSE exposure inhibits basal cell differentiation into ciliated cells by upregulating the NCSTN-Notch3-Hes1 pathway. Conclusions: Inhibition of the NCSTN-Notch3-Hes1 pathway promoted ciliated cell differentiation and ameliorated the CSE-induced reduction in ciliated cells.