The multiple mechanisms and modes of cell death after acetaminophen overdose.

Acetaminophen (APAP)-induced liver injury and acute liver failure is a significant clinical problem worldwide; in addition, APAP overdoses in animals or in cell culture are used as popular models to study drug-induced liver injury mechanisms and test therapeutic interventions. Early assumptions that APAP toxicity is caused by a single mechanism resulting in a defined mode of cell death in hepatocytes had to be questioned when over the years many different mechanisms and modes of cell death were reported. Although many of the contradictory results and conclusions reported over the years can be attributed to lack of understanding of established mechanisms, methodological problems, and misinterpretation of data, it is increasingly recognized that some of the reported differences in signaling mechanisms and even a switch in the mode of cell death can be caused by variations in the experimental conditions. In this review, examples will be discussed how experimental conditions (dose, solvent, etc.), the experimental system (species, strain, and substrain in vivo, cell type, and in vitro conditions), and also adaptive responses and off-target effects of genetic manipulations and chemical interventions, can impact the mechanisms of cell death. Given that the conditions will determine the results, it is therefore of critical importance to keep in mind the translational aspect of the experiments, i.e., the conditions relevant to the human pathophysiology. Only the full appreciation of these issues will lead to reproducible and clinically relevant results that advance our understanding of all facets of the human pathophysiology and identify clinically relevant therapeutic targets.