Respiratory chain-generated oxidative stress following treatment of leukemic blasts with DNA-damaging agents

Oxidative stress occurs in diverse life forms during programmed cell death and appears to be a significant mediator since a wide range of manipulation s that enhance cellular antioxidant systems are protective. Using a recentl y developed flow cytometry technique to assess respiratory chain function, we have investigated the mechanism of reactive oxygen generation in OCI/AML -2 leukemic blasts following treatment with cytosine arabinoside, etoposide , and gamma -irradiation. Increases in mitochondrially generated reactive o xygen were seen using all three agents, in association with hyperpolarizati on of the mitochondrial inner membrane. Increased reactive oxygen occurred when mitochondria were energized using substrates for either complex I or c omplex II, indicating that the likely source is complex III (cytochrome c r eductase). These findings are consistent with impaired adenine nucleotide e xchange across the mitochondrial membrane, recently proposed to be an impor tant event during the early stages of apoptosis induction (M. G, Vender Hei den et at, 1999, Mol Cell 3, 159-167), Elevations of the antioxidants gluta thione and thioredoxin occurred in association with this oxidative stress, likely the result of feedback mechanisms based on redox-sensitive transcrip tion factors. Since glutathione and thioredoxin can protect from drug-induc ed apoptosis, their upregulation in response to respiratory chain-generated reactive oxygen might represent a cellular adaptation to DNA damage that p romotes cell survival. (C) 2001 Academic Press.