Stable lentiviral-mediated expression of Cytochrome P450 2D6 in HepaRG cells: New means for in vitro assessment of xenobiotic biotransformation and cytotoxicity.

The human hepatic HepaRG cell line is often considered as the closest surrogate to primary culture of normal human hepatocytes (PHH) for toxicity studies. However, differentiated HepaRGcells express very low levels of the cytochrome P450 2D6 (CYP2D6) protein, which is essential for the biotransformation of nearly 25% of drugs on the market. To overcome this limitation, infection of progenitor HepaRG cells were performed using lentiviral particles containing a transgene encoding a single mRNA translated into a polypeptide undergoing proteolytic cleavage via the T2A peptide to produce both human CYP2D6 and GFP proteins. Differentiated HepaRG cells transduced with this lentivirus stably expressed GFP and catalytically active CYP2D6 enzyme at levels close to those found in PHH with high CYP2D6 activities. Using the CYP2D6 transgenic HepaRG cells, we showed that tramadol was metabolized into both, N- and O-desmethyl tramadol as observed in human serum in contrast with the production of N-desmethyl tramadol only in parental HepaRG cells via the CYP3A4 activity. Similarly, after perhexiline (PHX) treatments, higher IC50 were found in CYP2D6 expressing HepaRG cells associated to lower mitochondrial damages compared to those found in parental cells for the same PHX concentrations. Gene profiling between parental and transgenic cells demonstrated that the CYP2D6 expressing HepaRG cells had kept their ability to proliferate and differentiate with low impact on the expression of the hepatocyte specific functions, however, we identified a limited set of genes including NXF3 and TRIM63 that were up-regulated in CYP2D6 expressing HepaRG cells. By knocking-down GFP and CYP2D6 expression using CRISP/Cas9 technology in the transgenic cell line, we demonstrated that NXF3 and TRIM63 induction was triggered by the mRNA encoding GFP and CYP2D6 but not by the lentiviral transgene inserted into the HepaRG cell genome. Together, these data confirmed that the CYP2D6 transgenic HepaRG cells represent a suitable optimized transgenic model of HepaRG cells to evaluate biotransformation and toxicity of specific compounds metabolized by CYP2D6.