title: Superoxide is the major reactive oxygen species regulating autophagy.
abstract: Autophagy is involved in human diseases and is regulated by reactive oxygen species (ROS) including superoxide (O(2)(*-)) and hydrogen peroxide (H(2)O(2)). However, the relative functions of O(2)(*-) and H(2)O(2) in regulating autophagy are unknown. In this study, autophagy was induced by starvation, mitochondrial electron transport inhibitors, and exogenous H(2)O(2). We found that O(2)(*-) was selectively induced by starvation of glucose, L-glutamine, pyruvate, and serum (GP) whereas starvation of amino acids and serum (AA) induced O(2)(*-) and H(2)O(2). Both types of starvation induced autophagy and autophagy was inhibited by overexpression of SOD2 (manganese superoxide dismutase, Mn-SOD), which reduced O(2)(*-) levels but increased H(2)O(2) levels. Starvation-induced autophagy was also inhibited by the addition of catalase, which reduced both O(2)(*-) and H(2)O(2) levels. Starvation of GP or AA also induced cell death that was increased following treatment with autophagy inhibitors 3-methyladenine, and wortamannin. Mitochondrial electron transport chain (mETC) inhibitors in combination with the SOD inhibitor 2-methoxyestradiol (2-ME) increased O(2)(*-) levels, lowered H(2)O(2) levels, and increased autophagy. In contrast to starvation, cell death induced by mETC inhibitors was increased by 2-ME. Finally, adding exogenous H(2)O(2) induced autophagy and increased intracellular O(2)(*-) but failed to increase intracellular H(2)O(2). Taken together, these findings indicate that O(2)(*-) is the major ROS-regulating autophagy.
authors.affiliation: Manitoba Institute of Cell Biology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: M B
authors.initials: MB
authors.lastname: Azad
authors.forename: S B
authors.initials: SB
authors.lastname: Gibson
mesh_terms: D000077584:2-Methoxyestradiol; D000975:Antioxidants / Q000494:pharmacology; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D000071193:Autophagy-Related Protein 7; D000071186:Beclin-1; D002374:Catalase / Q000494:pharmacology; D002460:Cell Line; D045744:Cell Line, Tumor; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D016877:Oxidants / Q000378:metabolism / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism*; D044764:Ubiquitin-Activating Enzymes / Q000235:genetics / Q000378:metabolism
chemical_list: D000975:Antioxidants; D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; C477012:MAP1LC3A protein, human; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D016877:Oxidants; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D013481:Superoxides; D004958:Estradiol; D000077584:2-Methoxyestradiol; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes