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 manipulations that enhance cellular antioxidant systems are protective. Using a recently 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 oxygen were seen using all three agents, in association with hyperpolarization of the mitochondrial inner membrane. Increased reactive oxygen occurred when mitochondria were energized using substrates for either complex I or complex II, indicating that the likely source is complex III (cytochrome c reductase). These findings are consistent with impaired adenine nucleotide exchange across the mitochondrial membrane, recently proposed to be an important event during the early stages of apoptosis induction (M. G. Vander Heiden et al., 1999, Mol. Cell 3, 159-167). Elevations of the antioxidants glutathione and thioredoxin occurred in association with this oxidative stress, likely the result of feedback mechanisms based on redox-sensitive transcription factors. Since glutathione and thioredoxin can protect from drug-induced apoptosis, their upregulation in response to respiratory chain-generated reactive oxygen might represent a cellular adaptation to DNA damage that promotes cell survival.
Pham
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Division of Experimental Therapeutics, Department of Medical Oncology and Hematology, Ontario Cancer Institute/ Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario, M5G 2M9, Canada.
Hedley
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D017209:Apoptosis; D002518:Ceramides / Q000494:pharmacology; D003561:Cytarabine / Q000494:pharmacology; D004249:DNA Damage; D004072:Digitonin / Q000378:metabolism; D004579:Electron Transport / Q000502:physiology; D014450:Electron Transport Complex III / Q000378:metabolism* / Q000502:physiology; D005047:Etoposide / Q000494:pharmacology; D005720:Gamma Rays; D007938:Leukemia; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D018384:Oxidative Stress; D010539:Permeability; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013879:Thioredoxins / Q000096:biosynthesis; D014407:Tumor Cells, Cultured
D002518:Ceramides; D019384:Nucleic Acid Synthesis Inhibitors; D017382:Reactive Oxygen Species; D003561:Cytarabine; D013879:Thioredoxins; D005047:Etoposide; D014450:Electron Transport Complex III; D004072:Digitonin