Pulmonary permeability assessment using two human lung epithelial cell models in air-liquid interface cultures

Inhalation is a major route of human exposure to chemicals, while the fate of inhaled chemicals across the pulmonary barrier remains unclear due to accessibility challenges and animal model limitations. In vitro lung epithelial models offer valuable insights into absorption. However, reliance on nominal concentrations and lack of a standardized model led to inaccurate permeability assessment. This study investigates the transport of five xenobiotics across two human epithelial models: bronchial (Calu-3), and alveolar (h-AELVi), cultured at Air-Liquid Interface. Their ability to form a tight epithelial barrier over a two-week culture period was compared, and along with an assessment of their growth kinetics on inserts. Both Calu-3 and h-AELVi cells cultured at ALI formed stable, tight epithelial barriers, evidenced by low Lucifer yellow permeability, stable high TEER and occludin expression. Despite differences in cell origin and growth kinetics, both models provided nearly identical permeability values for tested xenobiotics. Neglecting chemical losses such as binding to plastic, volatilization and metabolic degradation leads to an underestimation of apparent permeability values. In conclusion, Both barrier models provide reliable apparent permeability values only when effective compound concentrations are accurately determined. A framework based on experimental results was proposed to standardize in vitro lung epithelial permeability assays.