Peroxidase-catalyzed oxidation of 3,5-dimethyl acetaminophen causes cell death by selective protein thiol modification in isolated rat hepatocytes

In this study we used a peroxidase model system (glucose/glucose oxidase and horseradish peroxidase) to investigate the effect of extracellularly generated reactive metabolites of 3,5-Me2-acetaminophen on cell viability and on cellular thiol levels. Incubation of hepatocytes with 3,5-Me2-acetaminophen in the presence of glucose/glucose oxidase and horseradish peroxidase caused a concentration-dependent loss of cell viability. Loss of viability was associated with decreased protein thiol levels. Addition of the reducing agent DTT, but not catalase, during the incubation restored cellular protein thiol levels and arrested the cell killing. Protein thiol depletion occurred selectively to the mitochondrial and microsomal fractions and was specific for a very limited number of protein bands. The data suggest that the oxidative modification of individual protein cysteine residues within the latter two organelle fractions is critically involved in the mechanism of toxicity.