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Lipid peroxidation in low density lipoproteins from human plasma and egg yolk promotes accumulation of 1‐acyl analogues of platelet‐activating factor‐like lipids
Author(s) -
Tokumura Akira,
Toujima Masaoki,
Yoshioka Yasuko,
Fukuzawa Kenji
Publication year - 1996
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02587909
Subject(s) - chemistry , yolk , biochemistry , platelet activating factor , lipid peroxidation , lipoprotein , cholesterol , cholesteryl ester , endocrinology , antioxidant , biology , food science
Oxidative modification of low density lipoprotein (LDL) is known to be a key event for induction of atherosclerosis. However, there has been little progress in structural elucidation of oxidized lipids, especially oxidatively fragmented phospholipids retaining a glycerol backbone. In this study, we found that LDL derived from egg yolk has no platelet‐activating factor (PAF) acetylhydrolase activity, and that prolonged incubation of egg yolk LDL with Cu 2+ resulted in the formation of various PAF‐like lipids: 1‐acyl type phosphatidylcholines with an sn ‐2‐short‐chain dicarboxylate or monocarboxylate group. Only a very small amount of the PAF‐like lipid having an sn ‐2‐short‐chain monocarboxylate group was detected by gas chromatography‐mass spectrometry in Cu 2+ ‐oxidized LDL from human plasma with high PAF‐acetylhydrolase activity, which has been reported to hydrolyze PAF‐like lipids to lysophosphatidylcholines. Preincubation of plasma LDL with diisopropyl fluorophosphate dose‐dependently inhibited PAF‐acetylhydrolase activity, resulting in accumulation of the PAF‐like lipids when the LDL was oxidized with Cu 2+ . As well as PAF and lysophosphatidylcholines, several PAF‐like lipids were found to inhibit [ 3 H]thymidine incorporation into cultured vascular smooth muscle cells derived from rat aorta. The possible formation of PAF‐like lipids by lipid peroxidation in LDL is discussed as well as its possible significance for induction of atherosclerosis.