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PubMed · 3669925

Cholesterol autoxidation in phospholipid membrane bilayers.

A Sevanian·L L McLeod
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Abstract

Lipid peroxidation in unilamellar liposomes of known cholesterol-phospholipid composition was monitored under conditions of autoxidation or as induced by a superoxide radical generating system, gamma-irradiation or cumene hydroperoxide. Formation of cholesterol oxidation products was indexed to the level of lipid peroxidation. The major cholesterol oxidation products identified were 7-keto-cholesterol, isomeric cholesterol 5,6-epoxides, isomeric 7-hydroperoxides and isomeric 3,7-cholestane diols. Other commonly encountered products included 3,5-cholestadiene-7-one and cholestane-3 beta, 5 alpha, 6 beta-triol. Superoxide-dependent peroxidation required iron and produced a gradual increase in 7-keto-cholesterol and cholesterol epoxides. Cholesterol oxidation was greatest in liposomes containing high proportions of unsaturated phospholipid to cholesterol (4:1 molar ratio), intermediate with low phospholipid to cholesterol ratios (2:1) and least in liposomes prepared with dipalmitoylphosphatidylcholine and cholesterol. This relationship held regardless of the oxidizing conditions used. Cumene hydroperoxide-dependent lipid peroxidation and/or more prolonged oxidations with other oxidizing systems yielded a variety of products where cholesterol-5 beta,6 beta-epoxide, 7-ketocholesterol and the 7-hydroperoxides were most consistently elevated. Oxyradical initiation of lipid peroxidation produced a pattern of cholesterol oxidation products distinguishable from the pattern derived by cumene hydroperoxide-dependent peroxidation. Our findings indicate that cholesterol autoxidation in biological membranes is modeled by the peroxide-induced oxidation of liposomes bearing unsaturated fatty acids and suggest that a number of cholesterol oxidation products are derived from peroxide-dependent propagation reactions occurring in biomembranes.

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CholesterolChromatography, High Pressure LiquidLipid BilayersLipid PeroxidesPhosphatidylcholinesPhosphatidylethanolaminesJournal ArticleResearch Support, U.S. Gov't, P.H.S.

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BibTeXRIS

A Sevanian, L L McLeod. 1987. Cholesterol autoxidation in phospholipid membrane bilayers.. https://doi.org/10.1007/bf02533940

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