Ambient NO₂ induces premature pulmonary senescence in rats: The role of the ROS-DRG1/CDK5 axis

Cellular senescence plays a crucial role in respiratory diseases. Nitrogen dioxide (NO₂), a major air pollutant, causes multi-system toxicity, primarily affecting the respiratory system. However, the association between NO₂ and pulmonary senescence remains unclear. This study systematically explored the association between NO₂ exposure and premature pulmonary senescence using animal and cellular models. Rats were exposed for 45 days (4 h/day) to filtered air, 0.5 ppmV, or 5.0 ppmV NO₂. Human bronchial epithelial (HBE) cells were treated with 0 or 120 μmol/L NaNO₃, a stable metabolite of NO₂, for 96 h. HBE cells exhibited hallmark senescence phenotypes, including elevated reactive oxygen species (ROS), increased expression of senescence-associated proteins (Fibronectin 1 (Fn1), Clusterin (CLU), senescence Marker Protein 30 (SMP30)), elevated β-galactosidase (β-gal) activity, increased developmentally regulated GTP-binding protein 1 (DRG1) and cyclin-dependent protein kinase 5 (CDK5) expression, and G1-phase cell cycle arrest. Treatment with the ROS inhibitor N-acetylcysteine (NAC), si-DRG1, or a CDK5 inhibitor alleviated these effects. Co-immunoprecipitation assays revealed that NaNO₃ promoted the interaction between DRG1 and CDK5 during senescence. The study demonstrated that NO₂/NaNO₃ induces bronchial epithelial cellular senescence, contributing to pulmonary senescence via ROS-dependent upregulation of DRG1 and CDK5 expression and interaction. Targeting the ROS-DRG1/CDK5 axis may represent a therapeutic strategy for environmental pollutant-induced premature respiratory senescence and provide new insights for the management of related disorders.