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 rele ased from ferritin has been shown to stimulate lipid peroxidation. Mic rosomes from rats chronically fed ethanol are more active in generatin g reactive oxygen intermediates than control microsomes. Since superox ide is one of the reductants capable of releasing iron from ferritin, and superoxide generation by microsomes is increased after chronic eth anol treatment, the ability of ferritin to stimulate lipid peroxidatio n of microsomes isolated from control rats and rats treated chronicall y with ethanol was evaluated. Ferritin was much more effective in stim ulating 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 ethan ol-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 ethano l-treated rats, The NADPH- and NADH-dependent increases in lipid perox idation produced by ferritin were prevented by superoxide dismutase, w hich lowered the rates found in the presence of ferritin to values fou nd in the absence of ferritin. Catalase and hydroxyl radical scavenger s 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 I gG. These results show that microsomes from ethanol-fed rats are more reactive than control microsomes in interacting with ferritin to produ ce oxidants capable of catalyzing lipid peroxidation. The inhibition o f the ferritin-catalyzed lipid peroxidation by superoxide dismutase an d anti-CYP2E1 IgG is consistent with a role for CYP2E1-generated super oxide radical in mobilizing iron from ferritin and in the subsequent c atalysis of lipid peroxidation. Since ferritin is the major cellular s torage form of iron, increased mobilization of iron from ferritin by C YP2E1-derived superoxide radical may play a role in the development of oxidative stress after ethanol treatment. (C) 1996 Academic Press, In c.