Antioxidant mechanism of Mn(II) in phospholipid peroxidation

Abstract

Antioxidant action of Mn 2+ on radical-mediated lipid peroxidation without added iron in microsomal lipid liposomes and on iron-supported lipid peroxidation in phospholipid liposomers or in microsomes was investigated. High concentrations of Mn 2+ above 50 μM inhiibited 2,2′-azobis (2-amidinopropane) (ABAP)-supported lipid peroxidation without added iron at the early stage, while upon prolonged incubation, malondialdehyde production was rather enhanced as compared with the control in the absence of Mn 2+. However, in a lipid-soluble radical initiator, 2,2′-azobis, (2,4-dimethyl-valeronitrile) (AMVN)- supported lipid peroxidation of methyl linoleate in methanol Mn 2+ apparently did not scavenge lipid radicals and lipid peroxyl radicals, contrary to a previous report. At concentrations lower than 5 μM, Mn 2+ competitively inhibited Fe 2+-pyrophosphate-supported lipid peroxidation in liposomes consisting of phosphatidylcholine with arachidonic acid at the β-position and phosphatidylserine dipalmitoyl, and reduced nicotinamide adenine dinucleotide phosphate (NADPH)-supported lipid peroxidation in the presence of iron complex in microsomes. Iron reduction responsible for lipid peroxidation in microsomes was not influenced by Mn 2+.