title: Mn(III)-desferrioxamine superoxide dismutase-mimic: alternative modes of action.
abstract: Various low-molecular-weight copper chelates have been synthesized to mimic superoxide dismutase (SOD) by catalyzing O2-. dismutation. However, in the presence of cellular proteins, such chelates dissociate and thereby lose their SOD-mimetic activity. In contrast, desferrioxamine-Mn(III) 1:1 chelate (DF-Mn), an SOD-mimic that affords protection from oxidative damage, reportedly is stable in the presence of serum albumin. DF-Mn, unlike SOD, is reported to permeate the membrane of at least one cell type and can protect cells by detoxifying intracellular O2-.. Recently DF-Mn was shown to protect hypoxic cells from H2O2-induced damage. Such results suggest that DF-Mn can protect cells from O2-.-independent damage by alternative mechanisms. This study examines such possibilities. To avoid O2-. participation in the damaging process, killing of monolayered V79 Chinese hamster cells was induced in a hypoxic environment by t-butyl hydroperoxide (t-BHP). Damage induced by t-BHP was inhibitable by DF-Mn. DF-Mn was also found to rapidly oxidize iron(II)-bound DNA. Additionally, once DF-Mn oxidizes Fe(II) or Cu(I), the DF moiety of DF-Mn dissociates and rapidly binds to Fe(III) or Cu(II). Without excluding the possibility that DF-Mn protects cells by facilitating the removal of O2-., the present results show that this SOD-mimic can confer protection from cytotoxic processes independent of O2-. or of O2-.-derived active species.
authors.affiliation: Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: S M
authors.initials: SM
authors.lastname: Hahn
authors.forename: C M
authors.initials: CM
authors.lastname: Krishna
authors.forename: A
authors.initials: A
authors.lastname: Samuni
authors.forename: J B
authors.initials: JB
authors.lastname: Mitchell
authors.forename: A
authors.initials: A
authors.lastname: Russo
mesh_terms: D000818:Animals; D002374:Catalase / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003300:Copper / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D003676:Deferoxamine / Q000494:pharmacology* / Q000031:analogs & derivatives; D008670:Metals / Q000378:metabolism; D009942:Organometallic Compounds / Q000494:pharmacology; D010084:Oxidation-Reduction; D013482:Superoxide Dismutase / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism
chemical_list: D008670:Metals; D009942:Organometallic Compounds; D013481:Superoxides; C068338:manganese desferioxamine; D003300:Copper; D004247:DNA; D002374:Catalase; D013482:Superoxide Dismutase; D003676:Deferoxamine