Assessment of mitochondrial toxicity in HepG2 cells cultured in high-glucose- or galactose-containing media.

Drug-induced mitochondrial toxicity has been recognized as contributing to a variety of organ toxicities, such as liver, heart, kidney, and CNS, and has been found to contribute to drug attrition and black box warnings. Here, we describe a cell-based assay that can detect direct drug-induced mitochondrial toxicity, providing protocols for screening in 96- and 384-well format. Cultured cells grown in glucose media produce their ATP by glycolysis, largely bypassing the mitochondria, and hence are fairly resistant to drugs that affect mitochondrial function. However, when growing the same cells in media supplemented with galactose as opposed to glucose, they are forced to produce ATP through oxidative phosphorylation, which then makes them vulnerable to mitochondrial insult. By measuring viability of cells grown in either glucose- or galactose-supplemented media, direct mitochondrial impairment can be detected.