The mechanism of iron (III) stimulation of lipid peroxidation.
A study conducted on Fe2+ autoxidation showed that its rate was extremely slow at acidic pH values and increased by increasing the pH; it was stimulated by Fe3+ addition but the stimulation did not present a maximum at a Fe2+/Fe3+ ratio approaching 1:1. The species generated during Fe(3+)-catalyzed Fe2+ autoxidation was able to oxidize deoxyribose; the increased Fe2+ oxidation observed at higher pHs was paralleled by increased deoxyribose degradation. The species generated during Fe(3+)-catalyzed Fe2+ autoxidation could not initiate lipid peroxidation in phosphatidylcholine liposomes from which lipid hydroperoxides (LOOH) had been removed by treatment with triphenylphosphine. Neither Fe2+ oxidation nor changes in the oxidation index of the liposomes due to lipid peroxidation were observed at pHs where the Fe3+ effect on Fe2+ autoxidation and on deoxyribose degradation was evident. In our experimental system, a Fe2+/Fe3+ ratio ranging from 1:3 to 2:1 was unable to initiate lipid peroxidation in LOOH-free phosphatidylcholine liposomes. By contrast Fe3+ stimulated the peroxidation of liposomes where increasing amounts of cumene hydroperoxide were incorporated. These results argue against the participation of Fe3+ in the initiation of LOOH-independent lipid peroxidation and suggest its possible involvement in LOOH-dependent lipid peroxidation.
Istituto di Chimica Biologica, Università di Sassari, Italy.
B
B
Tadolini
G
G
Hakim
D002712:Chlorides; D003855:Deoxyribose / Q000737:chemistry; D005290:Ferric Compounds / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry / Q000494:pharmacology*; D015227:Lipid Peroxidation / Q000187:drug effects*; D008081:Liposomes; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000378:metabolism; D013268:Stimulation, Chemical; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis
D002712:Chlorides; D005290:Ferric Compounds; D008081:Liposomes; D010713:Phosphatidylcholines; D017392:Thiobarbituric Acid Reactive Substances; D003855:Deoxyribose; D007501:Iron; C024555:ferric chloride