Immortalized liver cells have been used for evaluating the toxicity of compounds; however, excessive
glutathione is considered to lessen cytotoxicity. In this study, we compared the effects of
glutathione depletion on cytotoxicities of drugs using HepaRG and HepG2 cells, which express and lack
drug-metabolizing
enzymes, respectively, for predicting
drug-induced liver injury (DILI) risks. These cells were pre-incubated with L-
buthionine-S,R-sulfoximine (BSO) and then exposed to 34 test compounds with various DILI risks for 24 h.
ATP level exhibited the highest predictability of DILI among tested parameters. BSO treatment rendered cells susceptible to
drug-induced cytotoxicity when evaluated by cell viability and
caspase 3/7 activity with the sensitivity of cell viability from 50% in non-treated HepaRG cells to 71% in BSO-treated HepaRG cells. These results indicate that cytotoxicity assays using GSH-depleted HepaRG cells improve the predictability of DILI risks. However, HepaRG cells were not always superior to HepG2 cells when assessed by
ATP level. The combination of HepG2 and HepaRG cells index produced the best prediction in the cases of
caspase 3/7 acitivity and
ATP level. In conclusions, the developed highly sensitive cell-based assay using GSH-reduced cells would be useful for predicting potential DILI risks at an early stage of
drug development.