Assays provide information on the ability of a compound to traverse through cell based epithelial layers or complex, anatomically (bronchial, alveolar) more primary tissue-like models.
The study involves sampling of the test compounds on both sides at given time points, followed by analysis of the test item concentration by liquid chromatography with tandem mass spectrometry or fluorescency method. Based on the measured concentrations, apparent permeation coefficient is calculated (P(app)). A set of reference compounds with low and high permeation profiles in cell based permeation studies are included in the study.
The models express active drug transporter systems including P-glycoprotein efflux transporter (also known as P-gp, MDR1 or ABCB1). The involvement of the transporters can be estimated by analysis of apical-to-basolateral vs basolateral-to-apical permeabilities as well as by using specific transporter inhibitors, like vanadate and indomethacin and specific substrates e.g. calcein-acetoxylamin.
Measurement of P450 activity
P450 enzyme activity can be investigated in our model tissues using Invitrogen substrates. CYP450 selection of our models reflect CYP450 enzymes of the bronchial and alveolar epithelial layers.
Modulatory effect of immune cells
Permeability of the alveoli are strongly modulated by the presence or absence of immune cells. Resident macrophages are characteristic for a normal alveolar tissue that can phagocytose chemicals, produce cytokines and chemokines that affect epithelial and endothelial cell layers. Adding macrophages and neutrophils to our model tissue system therefore is able to mimic specific disease characteristics e.g. neutrophil penetration in ALI.