Cholesterol autoxidation in phospholipid membrane bilayers
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.
- Research Organization:
- Univ. of Southern California, Los Angeles
- OSTI ID:
- 5757493
- Journal Information:
- Lipids; (United States), Vol. 22:9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHOLESTEROL
CHEMICAL RADIATION EFFECTS
METABOLISM
HYDROGEN PEROXIDE
BIOLOGICAL EFFECTS
SUPEROXIDE RADICALS
CELL MEMBRANES
GAMMA RADIATION
LIPOSOMES
PHOSPHOLIPIDS
CELL CONSTITUENTS
CHEMISTRY
ELECTROMAGNETIC RADIATION
ESTERS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
IONIZING RADIATIONS
LIPIDS
MEMBRANES
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANOIDS
OXYGEN COMPOUNDS
PEROXIDES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADICALS
STEROIDS
STEROLS
560120* - Radiation Effects on Biochemicals
Cells
& Tissue Culture