title: Manganese superoxide dismutase modulates hypoxia-inducible factor-1 alpha induction via superoxide.
abstract: Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that plays an important role in O(2) homeostasis. Numerous observations suggest that changes in reactive oxygen species affect HIF-1 alpha stabilization and HIF-1 alpha transcriptional activation in many cell types. The antioxidant enzyme manganese superoxide dismutase (MnSOD) modulates the cellular redox environment by converting superoxide (O(2)(*-)) to hydrogen peroxide and dioxygen. Previous results from our group have shown that overexpression of MnSOD in MCF-7 cells alters stabilization of HIF-1 alpha under hypoxic conditions; however, the underlying mechanism(s) is not known. Here, we tested the hypothesis that MnSOD regulates the expression of HIF-1 alpha by modulating the steady-state level of O(2)(*-). We found that decreasing MnSOD with small interfering RNA in MCF-7 cells resulted in (a) an associated increase in the hypoxic accumulation of HIF-1 alpha immunoreactive protein, (b) a significant increase in the levels of O(2)(*-) (P < 0.01), but (c) no significant change in the steady-state level of H(2)O(2). Removal of O(2)(*-) using spin traps (alpha-4-pyridyl-1-oxide-N-tert-butylnitrone and 5,5-dimethyl-1-pyrroline N-oxide) or the O(2)(*-) scavenger Tempol or an SOD mimic (AEOL10113) resulted in a decrease in HIF-1 alpha protein, consistent with the hypothesis that O(2)(*-) is an important molecular effector responsible for hypoxic stabilization of HIF-1 alpha. The evidence from both genetic and pharmaceutical manipulation is consistent with our hypothesis that O(2)(*-) can contribute to the stabilization of HIF-1 alpha.
authors.affiliation: Free Radical and Radiation Biology Program, Department of Radiation Oncology, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, IA 52242-1181, USA.
authors.forename: Suwimol
authors.initials: S
authors.lastname: Kaewpila
authors.forename: Sujatha
authors.initials: S
authors.lastname: Venkataraman
authors.forename: Garry R
authors.initials: GR
authors.lastname: Buettner
authors.forename: Larry W
authors.initials: LW
authors.lastname: Oberley
mesh_terms: D001940:Breast / Q000166:cytology / Q000502:physiology; D015687:Cell Hypoxia / Q000502:physiology; D002460:Cell Line; D004847:Epithelial Cells / Q000502:physiology; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D007700:Kinetics; D034622:RNA Interference; D013482:Superoxide Dismutase / Q000235:genetics* / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D013481:Superoxides; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase