Repetitive Exposure to Nicotine-Free Vaping Impairs Airway Defences and Delays Recovery

PURPOSE: E-cigarette use, or vaping, is increasing in prevalence, especially among adolescents. There is a paucity of information on the impact of e-cigarette aerosols on lung health, particularly to the airway protective components. In this study, disruptions to airway protective functions in response to increasing repetitive exposure to nicotine-free e-cigarette aerosols were examined. The recovery capability of the airway defence was also investigated. METHODS: Cultured primary nasal airway cells from five healthy individuals were exposed to repetitive exposures to e-cigarette aerosols. Cilia function was analysed via high-speed video microscopy, while epithelial barrier integrity was assessed through trans-epithelial electrical resistance measurements and immunofluorescence. Cytokine secretion was assessed using multiplex screening. RESULTS: Significant impairment in cilia function and epithelial barrier integrity was observed after 24 or more vaping exposures. Cilia beating frequency declined by 18.6% (6.78 ± 0.23 Hz) after 24 sessions and by 53.0% (3.91 ± 0.27 Hz) after 60 sessions (p < 0.01). Trans-epithelial electrical resistance values dropped by 45.6% (315.37 ± 13.38 Ωcm²) after 24 sessions and by 77.4% (131.29 ± 6.84 Ωcm²) after 60 sessions (p < 0.01). Nicotine-free aerosols disrupted Occludin-1 and ZO-1 expression but not E-cadherin. Cytokine analysis showed increased secretion of IL-1ra, IL-6, FGF-basic, IFN-γ, and VEGF following 36 vaping sessions. Recovery experiments indicated cilia function normalised within 48 h, while epithelial barrier required up to 72 h. CONCLUSION: Repetitive vaping progressively impairs airway protective functions in vitro. While cilia function and epithelial integrity recover in the short term, the delay may increase susceptibility to infections.