Biologically active metal-independent superoxide dismutase mimics

James B. Mitchell, Amram Samuni, Murali C. Krishna, William G. DeGraff, Min S. Ahn, Uri Samuni, Angelo Russo
1990 Biochemistry  
Superoxide dismutase (SOD) is an enzyme that detoxifies superoxide (02'-), a potentially toxic oxygen-derived species. Attempts to increase intracellular concentrations of SOD by direct application are complicated because SOD, being a relatively large molecule, does not readily cross cell membranes. We have identified a set of stable nitroxides that possess SOD-like activity, have the advantage of being low molecular weight, membrane permeable, and metal independent, and at pH 7.0 have reaction
more » ... rate constants with 02'ranging from 1.1 X IO3 to 1.3 X IO6 M-' s-l. These S O D mimics protect mammalian cells from damage induced by hypoxanthine/xanthine oxidase and H202, although they exhibit no catalase-like activity. In addition, the nitroxide SOD mimics rapidly oxidize DNA-Fe" and thus may interrupt the Fenton reaction and prevent formation of deleterious OH radicals and/or higher oxidation states of metal ions. Whether by SOD-like activity and/or interception of an electron from redox-active metal ions they protect cells from oxidative stress and may have use in basic and applied biological studies. EXPERIMENTAL PROCEDURES Chemicals. Desferrioxamine (DF) was a gift from Ciba Geigy; hypoxanthine (HX) was purchased from Calbiochem-Boehringer Co.; 2,2,6,6-tetramethylpiperidine-1 -oxy1 (TEM-PO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-I-oxy1 (TEM-POL), 4-hydroxypyrazolo[3,4,-d]pyrimidine (allopurinol), p-toluenesulfonic acid, 2-amino-2-methyl-1 -propanol, 2-butanone, and cyclohexanone were purchased from Aldrich Chemical Co.; tris(oxalato)chromate ( III) [K3[Cr(C2O4)J-202'-+ 2H+ -0, + H 2 0 2 I Abbreviations: EPR, electron paramagnetic resonance; CHD, spiro [cyclohexane-1,2'-doxyl] [spiro[cyclohexane-1,2'-(4',4'-dimethyloxazolidine-3'-oxyl)] 1; DTPA, diethylenetriaminepentaacetate; OXANO, 2-ethyl-2,4,4-trimethyloxazolidine-3-oxyl; TEMPOL, 4-hydroxy-2,2,6,6tetramethylpiperidine-1 -0xyl; TEMPO, 2,2,6,6-tetramethylpiperidine-1oxyl; SOD, superoxide dismutase; DF, desferrioxamine; XO, xanthine oxidase; HX, hypoxanthine.
doi:10.1021/bi00463a024 pmid:2161256 fatcat:f3mgsoclhveytp5qknqzacxpli