HepaRG cells were acquired from Biopredic International (Rennes, France).The detailed process of HepaRG cell culture was described previously (McGill et al., 2011 (link)). HepG2 cells obtained from ATCC (Manassas, VA, USA) were cultured in DMSO (dimethyl sulfoxide)-free Williams’ E medium containing penicillin/streptomycin, insulin and 10% fetal bovine serum, and were 70%~80% confluent before treatment. Both cell lines were treated with 10 mM APAP (Sigma, St. Louis, MO, USA; Lot #36F-7005-1) dissolved in warm Williams’ E medium. ATP (Sigma) was dissolved in saline and added to the cell culture medium to a final concentration of 10 μM or 100 μM. Twenty-four hours after treatment of either ATP and/or APAP, medium and cell fractions were harvested, and cell viability was determined using the lactate dehydrogenase (LDH) assay (Bajt et al., 2004 (link)).