Investigating the effect of e-cigarettes on alveolar epithelial cells using a novel in vitro aerosol exposure device

E-cigarettes (ECs) create aerosols by heating an e-liquid that contains propylene glycol (PG), vegetable glycerol (VG), nicotine, and flavourings. In vitro Air Liquid Interface (ALI) studies, which replicate histological and functional features of lung cells, allow us to examine the impact of EC aerosols during acute and repeat dose treatments of ECs. Here, the human alveolar epithelial cell line NCI-H441 has been used to investigate the effect of aerosols, aerosol condensate, and e-liquid containing 50/50 PG/VG, tobacco flavour, and 15 mg/ml nicotine. H441 cells were cultured on transwells under ALI conditions. On day 9, the aerosol condensate or e-liquid in Dulbecco's Phosphate-Buffered Saline (DPBS) was added to the apical side of the transwell and incubated for 24 h at 37 °C and 5% CO2 Aerosol exposure was conducted using a custom-built aerosol cell exposure device. Cells were exposed to the EC aerosols or air with a flow rate of 20 mL/min for 30 min (equivalent to 60 puffs) and returned to the incubator. After 24 h, transepithelial electrical resistance (TEER) values and lactate dehydrogenase (LDH) were measured to evaluate the physiological change and cell viability. TEER and LDH results for cells exposed to airflow only were not significantly different from no flow. TEER values showed a significant reduction from around 607±54 Ω cm2 to 386±23, 365±17, 313±38 and 352±68 Ω cm2 (p≤0.05) and LDH results showed cytotoxicity of 16%, 21%, 31%, and 23% for DPBS only, e-liquid, condensate, and aerosol exposures, respectively. Results demonstrate the capability of the exposure device for ALI studies and show that EC condensate has the greatest impact on TEER and LDH.