Cigarette smoke-induced ClC-3 deficiency drives chronic bronchitis via the AKT/CREB1 axis and lysosomal-autophagic impairment.

Cigarette smoke (CS) exposure disrupts bronchial epithelial redox homeostasis, serving as a primary etiology of chronic bronchitis; however, the specific mechanisms linking ion transport dysregulation to CS-induced cytotoxicity remain poorly understood. This study identifies a critical protective role for the voltage-gated chloride channel ClC-3, a Cl-/H+ exchanger, in maintaining airway epithelial integrity against oxidative insult. We report significant downregulation of ClC-3 in the bronchial epithelium of chronic bronchitis patients and CS-exposed mice. Using transgenic overexpression and conditional knockout mouse models, we demonstrate that ClC-3 deficiency exacerbates, while its overexpression mitigates, CS-induced airway inflammation, systemic oxidative stress (SOD/MDA), and lung injury. Mechanistically, we show that CS exposure suppresses AKT phosphorylation, leading to the inactivation of the transcription factor CREB1. We validate that CREB1 acts as a direct transcriptional activator of CLCN3 by binding to its promoter; thus, the CS-mediated inhibition of the AKT/CREB1 axis results in transcriptional silencing of ClC-3. At the cellular level, loss of ClC-3 disrupts lysosomal acidification, resulting in a blockade of autophagic flux. This impairment prevents the effective clearance of oxidative damage, thereby promoting epithelial cell death and amplifying inflammatory responses. Collectively, these findings delineate a novel "CS-AKT/CREB1-ClC-3-Lysosome" axis, suggesting that restoring ClC-3-mediated lysosomal function represents a promising therapeutic strategy to restore redox balance in chronic bronchitis.