Mitochondria are often referred to as ‘powerhouses of the cell’, with their dominant roles being to produce cellular energy (ATP) and to regulate cellular metabolism. The number of mitochondria within a cell differs depending on the cell type and function, with some organs being highly dependent on mitochondria due to their increased energy demands (for example, the heart, skeletal muscle and the liver).
Mitochondria contain a distinct, highly folded inner membrane, populated with five complexes which are involved in oxidative phosphorylation and associated production of ATP. Interaction of drugs with these complexes can disrupt the electron transport chain in the mitochondria leading to mitochondrial dysfunction and drug-induced toxicity. Identifying which complex is affected can be beneficial in understanding the mechanism of mitochondrial toxicity and, in turn, can be used to reduce liability through drug design during lead optimisation.
Mitochondria are frequently a target for drug-induced toxicity. Cyprotex has developed an assay designed to understand the mechanisms of mitochondrial toxicity using permeabilised cells. Permeabilisation of the cellular membrane leaves the mitochondria intact, allowing the study of mitochondrial function without the need to isolate the mitochondria outside of the cell. Using complex-specific substrates and inhibitors it is possible to identify individual complexes which are often off-targets in mitochondrial toxicity.
Determination of which complex is affected in the electron transport chain is achieved by using a series of substrates and inhibitors of the individual complexes sequentially in combination with the Seahorse XFe96 Flux Analyzer to decipher the mechanism. A reduction in oxygen consumption rate following the addition of an inhibitory test compound indicates the electron transport chain complex which is inhibited.
To find out more about the mitochondrial respiratory complex assay, follow this link: https://www.cyprotex.com/toxicology/mechanistic-toxicity/mitochondrial-respiratory-complex-assay
And to download our Mechanisms of Drug-Induced Toxicity guide, follow this link: https://www.cyprotex.com/guides