Nuclear DNA damage during NAD(P)H oxidation by membrane redox chains

Nuclear DNA damage, as the result of active oxygen formation by NAD(P)H-dependent redox chains, was studied. Isolated rat liver nuclei were incubated in the presence of NAD(P)H and iron chelators. Nuclear DNA damage was analyzed by electrophoresis in alkaline agarose. DNA damage after the addition of electron donors alone or with FeCl3 or DFO-Fe3+ was not visualized. Dramatic decay of high molecular weight DNA was observed with EDTA-Fe3+ or DTPA-Fe3+ in the presence of NAD(P)H. SOD did not prevent DNA damage, whereas catalase was protective. DNA damage was revealed after the addition of cumene hydroperoxide with EDTA-Fe3+, and it was sharply increased in the presence of NADPH. It is suggested that alkoxyl radicals in addition to hydroxyl radicals are involved in DNA damage during NAD(P)H oxidation in the presence of iron chelators, which can be reduced by membrane redox chains.