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

Area of Science:

• Toxicology
• Pharmacokinetics
• In vitro modeling

Background:

• Inhalation exposure is a primary route for chemical uptake, but understanding chemical behavior at the pulmonary barrier is challenging.
• Existing in vitro lung models have limitations, including reliance on nominal concentrations and lack of standardization, leading to inaccurate permeability assessments.

Purpose of the Study:

• To evaluate two human lung epithelial cell models (Calu-3 and h-AELVi) cultured at Air-Liquid Interface (ALI) for their ability to form tight barriers.
• To compare the permeability of five xenobiotics across these models.
• To propose a framework for standardizing in vitro lung epithelial permeability assays.

Main Methods:

• Calu-3 and h-AELVi cells were cultured at ALI for two weeks.
• Barrier integrity was assessed using lucifer yellow permeability and Trans-Epithelial Electrical Resistance (TEER).
• Occludin expression was analyzed, and cell growth kinetics were monitored.

Main Results:

• Both Calu-3 and h-AELVi models formed stable, tight epithelial barriers with low lucifer yellow permeability and high TEER.
• Occludin expression confirmed barrier integrity in both models.
• Nearly identical xenobiotic permeability values were observed across both models, highlighting their comparability.
• Chemical losses (adsorption, volatilization, degradation) can lead to underestimation of apparent permeability.

Conclusions:

• Both Calu-3 and h-AELVi ALI models reliably assess xenobiotic permeability when effective compound concentrations are determined.
• Accurate determination of effective concentrations is essential for reliable in vitro lung epithelial permeability assays.
• A standardized framework is proposed to improve the accuracy and reproducibility of these assays.