Ferritin stimulation of lipid peroxidation by microsomes after chronic ethanol treatment: role of cytochrome P4502E1.

Ferritin is the major storage form of iron within cells, and iron released from ferritin has been shown to stimulate lipid peroxidation. Microsomes from rats chronically fed ethanol are more active in generating reactive oxygen intermediates than control microsomes. Since superoxide is one of the reductants capable of releasing iron from ferritin, and superoxide generation by microsomes is increased after chronic ethanol treatment, the ability of ferritin to stimulate lipid peroxidation of microsomes isolated from control rats and rats treated chronically with ethanol was evaluated. Ferritin was much more effective in stimulating lipid peroxidation of microsomes after ethanol treatment; net increases in thiobarbituric acid-reactive components by ferritin were 4-fold greater in the presence of NADPH with microsomes from the ethanol-treated rats compared to pair-fed controls and 10-fold greater with NADH as the microsomal reductant. Net increases in chemiluminescence by ferritin were about 10-fold greater with microsomes from the ethanol-treated rats. The NADPH- and NADH-dependent increases in lipid peroxidation produced by ferritin were prevented by superoxide dismutase, which lowered the rates found in the presence of ferritin to values found in the absence of ferritin. Catalase and hydroxyl radical scavengers had no effect on the stimulation by ferritin. Nonheme iron chelators prevented the ferritin stimulation as did glutathione, propylgallate, and trolox. Basal rates of lipid peroxidation were inhibited by anti-CYP2E1 IgG; the stimulation by ferritin was decreased by anti-CYP2E1 IgG. These results show that microsomes from ethanol-fed rats are more reactive than control microsomes in interacting with ferritin to produce oxidants capable of catalyzing lipid peroxidation. The inhibition of the ferritin-catalyzed lipid peroxidation by superoxide dismutase and anti-CYP2E1 IgG is consistent with a role for CYP2E1-generated superoxide radical in mobilizing iron from ferritin and in the subsequent catalysis of lipid peroxidation. Since ferritin is the major cellular storage form of iron, increased mobilization of iron from ferritin by CYP2E1-derived superoxide radical may play a role in the development of oxidative stress after ethanol treatment.