NITROXIDE SOD-MIMICS - MODES OF ACTION

Low molecular weight superoxide dismutase mimics have been shown to afford protection from oxidative damage. Such SOD-mimics can readily permeate cell membrane achieving sufficiently high levels both inside and outside the cell to effectively detoxify intracellular O-2. Preliminary findings also indicated that metal-based and metal-free SOD-mimics can protect hypoxic cells from H2O2-induced damage. The present study explored the possibility that SOD-mimics such as desferrioxamine-Mn(III) chelate [DF-Mn] or cyclic nitroxide stable free radicals could protect from O-2-independent damage. Killing of monolayered V79 Chinese hamster cells was induced by H2O2 or by t-butyl hydroperoxide (t-BHP) and assayed clonogenically. Neither catalase nor native SOD protected the cells from t-BHP. In contrast. both DF-Mn and cyclic nitroxides protected suggesting cytotoxic processes independent of O-2 or of O-2 -derived active species. The inhibition of the damage by both metal-free and metal-based SOD mimics is attributable to either SOD-mimic reacting with reduced transition metal to block the Fenton reaction and/or intercepting and detoxifying intracellular organic free radicals. © 1991 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.