Enhanced lipid peroxidation of erythrocyte membranes and phosphatidylcholine liposomes induced by a xanthine oxidase system in the presence of catalase.

Abstract

When rat erythrocyte membranes or phosphatidylcholine (PC) liposomes were incubated in a xanthine oxidase system, lipid peroxidation was stimulated by the addition of catalase. Addition of a large amount of xanthine oxidase caused no significant increase in the lipid peroxidation of PC liposomes unless catalase was present in the reaction system. Enhanced peroxidations of both membranes and liposomes observed in the presence of catalase were strongly inhibited by superoxide dismutase (SOD), suggesting that O-2 is an essential species in these reactions. Several iron-chelators strongly inhibited the lipid peroxidations, suggesting an involvement of iron in the peroxidation reaction. Unless catalase was present, the rate of liposome peroxidation was stimulated only slightly by addition of Fe3+, but in the presence of catalase, the addition of Fe3+ markedly accelerated the peroxidation reaction, which was inhibited by SOD or desferrioxamine. Furthermore, the addition of Fe3+ to the xanthine oxidase system in the presence of catalase caused a significant decrease in the rate of cytochrome c reduction, suggesting that Fe3+ may be reduced to Fe2+ by O-2. The peroxidations enhanced by catalase may be induced by supply of sufficient O-2 and Fe2+ for lipid peroxidation. Histidine and 1, 4-diazabicyclo-(2, 2, 2)-octane, quenchers of 1O2, inhibited the peroxidation of membranes and liposomes. Mannitol and benzoate, scavengers of OH·, showed no significant effect on the peroxidation of membranes or liposomes. These results indicate possible participation of 1O2 species in the O-2-dependent lipid peroxidation induced by the xanthine oxidase system in the presence of catalase.