Purpose: To characterise in detail the patterns of expression and functional activities of CYP and efflux pump genes in Caco-2 cells stably transfected with human Pregnane X Receptor or murine Constitutive Androstane Receptor.
Materials and methods: Cell lines transfected with nuclear receptors were treated with established ligands, and gene expression of CYP and efflux pump genes were quantified by qRT-PCR and Western blot. P-glycoprotein activity was assessed by measuring calcein-AM accumulation and bidirectional permeability coefficients of digoxin and quinidine. CYP activities were measured with both fluorescent and non-fluorescent substrates.
Results: hPXR and mCAR upregulated some CYP and efflux pump genes ligand dependently. P-glycoprotein level was increased, but CYP3A4 protein remained below the limit of detection. P-glycoprotein activity was markedly elevated in Caco/mCAR cells and more modestly in Caco/hPXR cells. CYP3A4 activity remained lower than that in vitamin D-treated Caco-2 cells.
Conclusions: Nuclear receptors can modulate the expression of metabolic genes in Caco-2 cells, but the overall level of metabolism could not be efficiently controlled. P-glycoprotein activity increased, but CYP activities remained very low.