Evaluation system for cell-permeable CYP3A4 inhibitory activity using 1α,25-dihydroxy-vitamin D₃-induced intestinal...

We developed an assay system to evaluate the cytochrome P450 (CYP) 3A4-inhibitory activity of compounds, taking account of their cellular permeability, using intestine-derived cell lines pre-treated with the CYP3A4 inducer 1α,25-dihydroxy-vitamin D₃ (250 nM).Ketoconazole (KTZ), saquinavir (SQV), naringin, naringenin (NGE), bergamottin (BG), 6',7'-dihydroxybergamottin (DHBG), epigallocatechin gallate (EGCG), and resveratrol (RES) were evaluated as known CYP3A4 inhibitors. The apparent IC₅₀ (IC_50,app) values of known inhibitors were determined in Caco-2 cells with 10 µM midazolam as a CYP3A4 substrate, and compared with the IC₅₀ values in a human liver microsome assay.SQV and BG with high lipophilicity and good membrane permeability show similar concentrations inside and outside the cells, and consequently IC_50,app and IC₅₀ are similar.KTZ, EGCG, DHBG, NGE, and RES showed a difference between IC₅₀ and IC_50,app. This is considered to result from a difference between the intracellular and extracellular concentrations of the compound, which is likely due to the involvement of efflux and/or influx transporters.This method to evaluate CYP inhibition taking account of membrane permeation should be helpful to assess the potential clinical relevance of drug-drug or drug-food interactions in the gastrointestinal tract.