A marked stimulation of Fe(3+)-dependent lipid peroxidation in phospholipid liposomes under acidic conditions.
Lipid peroxidation in phosphatidylcholine liposomes induced by Fe(3+) alone, assessed by thiobarbituric acid-reactive substances (TBARS) production, was markedly enhanced as the solution pH was lowered from 7.4 to 5.5. On the other hand, at physiological pH, TBARS production by Fe(3+) was almost negligible. Results of the radical scavenger experiments with superoxide dismutase, catalase and hydroxyl radical ((&z.rad;)OH) scavengers (sodium benzoate, mannitol and dimethylthiourea), deoxyribose degradation and ESR spectrometry suggest that the stimulation of Fe(3+)-dependent lipid peroxidation under acidic conditions is involved in generation of superoxide anion (O(2)(&z.rad;-)), hydrogen peroxide (H(2)O(2)) and (&z.rad;)OH during the reaction. The stimulation of Fe(3+)-dependent TBARS production by increasing the [H(+)] completely disappeared by triphenylphosphine (TPP) treatment of the liposomes, but the reaction was reversible with either incorporation of cumen hydroperoxide (CumOOH) into the TPP-treated liposomes or the addition of CumOOH to the treated liposomes. Incubation of the CumOOH-incorporated TPP-treated liposomes with Fe(3+) at pH 5.5 also resulted in (&z.rad;)OH generation. Based on these results, a possible mechanism of stimulatory effect of Fe(3+) on lipid peroxidation under acidic conditions is discussed.
Ohyashiki
T
T
Department of Clinical Chemistry, Faculty of Pharmaceutical Sciences, Hokuriku University, Kanagawa-machi, Kanazawa, Ishikawa, Japan. t-ohyashiki@hokuriku-u.ac.jp
Nunomura
M
M
D000975:Antioxidants / Q000494:pharmacology; D002712:Chlorides; D003855:Deoxyribose / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000494:pharmacology*; D016166:Free Radical Scavengers / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D015227:Lipid Peroxidation / Q000187:drug effects*; D008081:Liposomes / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis
D000975:Antioxidants; D002712:Chlorides; D005290:Ferric Compounds; D016166:Free Radical Scavengers; D008081:Liposomes; D010743:Phospholipids; D017392:Thiobarbituric Acid Reactive Substances; D003855:Deoxyribose; C024555:ferric chloride