Mitochondrial Toxicity Assays

The mitochondrial toxicity assays provide a means to measure mitochondrial dysfunction due to the toxic effect of a test compound. We provide mitochondrial toxicity assays for all small molecule formulations such as pharmaceuticals, industrial chemicals and consumer products.

Our mitochondrial toxicity assays use a genetically modified version of the immortalized human liver cell line HepaRG™, created with our proprietary CompoZr® zinc finger nuclease (ZFN) technology. Apart from fresh human hepatocytes, HepaRG cells are the most metabolically active liver cell line described to date and have the potential for use as a viable surrogate in many functional liver assays, including toxicity testing, with none of the drawbacks of limited availability and donor-to-donor variation.

Evaluating mitochondrial toxicity is an important component in the overall assessment of drug safety. This is due in part to the recognition that mitochondrial dysfunction is a contributor to compound attrition and post-market drug withdrawals (e.g., nefazodone and troglitazone). In the past, these types of effects were often missed in part because they are subtle and only manifest themselves over time; thus, they do not lead to overt histopathology within the time frame of most pre-clinical studies. A second reason is that most early discovery toxicity screens use highly proliferative immortalized cell lines, which are adapted for rapid growth under hypoxic and acidic conditions. These cell lines derive almost all of their energy from glycolysis rather than mitochondrial oxidative phosphorylation, and thus the common use of high glucose media with these cell lines masks the effects of potential mitochondrial toxicants. This is referred to as the Crabtree effect and can be addressed by comparing the cytotoxic effect of drug candidates in glucose versus galactose supplemented media. Another common mechanism of mitochondrial toxicity is the loss of mitochondrial membrane potential.

We offers two format for assessing mitochondrial toxicity:

 Mitochondrial Cytotoxicity Assay Protocol

Test System HepaRG liver cell, clone 5F (human)
Media Williams’ Medium E containing 25 mM glucose
Williams’ Medium E containing 10 mM galactose
Test Compound Concentration 0.1 -100 µM in half log increments, or custom
Replicates 3 per concentration
Controls Vehicle (0.5% DMSO)
Antimycin A (positive control)
Analysis Method ATP depletion
Data Delivery IC50 determined in each medium
Minimum effective concentration (MEC) determined in each medium
Fold change in Glu/Gal IC50


 Mitochondrial Membrane Potential (MMP) Assay Protocol

The mitochondrial membrane potential assay uses JC-10 to screen for mitochondrial depolarization in cell lines.  JC-10 (a more water-soluble analog of JC-1) is a cationic dye that accumulates in energized mitochondria. At high membrane potentials, the dye aggregates yielding a red/orange-colored emission, while at low membrane potentials the dye exists as a monomer and emits a green fluorescence. Mitochondrial membrane potential can therefore be monitored by following the loss of red/orange fluorescence. FCCP (carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone), an uncoupler of oxidative phosphorylation, is used as a positive control.

Test System HepaRG liver cell, clone 5F (human)
Test Compound Concentration 0.1 -100 µM in half log increments, or custom
Replicates 3 per concentration
Controls Vehicle (0.5% DMSO)
FCCP (positive control)
Analysis Method JC-10, fluorescence
Data Delivery IC50

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  • Dykens JA and Will Y (2007) The significance of mitochondrial toxicity testing in drug development, Drug Discovery Today 12, 777-785
  • Marroquin LD et al. (2007) Circumventing the Crabtree effect: Replacing media glucose with galactose increases susceptibility of HepG2 cells to mitochondrial toxicants, Toxicol Sci 97, 539-547
  • Pernelle K et al. (2011) Automated detection of hepatotoxic compounds in human hepatocytes using HepaRG cells and image-based analysis of mitochondrial dysfunction with JC-1 dye, Toxicol Appl Pharmacol 254, 256-266