Structural identification of phosphatidylcholines having an oxidatively shortened linoleate residue generated through its oxygenation with soybean or rabbit reticulocyte lipoxygenase.
Phosphatidylcholines (PCs) with platelet-activating factor (PAF)-like biological activities are known to be generated by fragmentation of the sn-2-esterified polyunsaturated fatty acyl group. The reaction is free radical-mediated and triggered by oxidants such as metal ions, oxyhemoglobin, and organic hydroperoxides. In this study, we characterized the PAF-like phospholipids produced on reaction of PC having a linoleate group with lipoxygenase enzymes at low oxygen concentrations. When the oxidized PCs were analyzed by gas chromatography-mass spectrometry, two types of oxidatively fragmented PC were detected. One PC had an sn-2-short chain saturated or unsaturated acyl group (C(8)-C(13)) with an aldehydic terminal; the abundant species were PCs with C(9) and C(13). The other PC had a short chain saturated acyl group (C(6)-C(9)) with a methyl terminal, and the most predominant species was PC with C(8). When the extracts of oxidation products were subjected to catalytic hydrogenation, PCs having saturated acyl groups (C(6)-C(14)) were detected; the most abundant was C(12) species. The less regiospecific formation of PAF-like lipids suggests that they were generated by oxidative fragmentation of PC hydroperoxides formed by non-stereoselective oxygenation of the alkyl radical of esterified linoleate that escaped from the active centers of lipoxygenases. One of the PAF-like PC with an aldehydic terminal was found to be bioactive; it inhibited the production of nitric oxide induced by lipopolysaccharide and interferon-gamma in vascular smooth muscle cells from rat aorta.
Tokumura
A
A
Laboratory of Health Chemistry, School of Medicine, The University of Tokushima, 1-78 Shomachi, Tokushima 770-8505, Japan.
Sumida
T
T
Toujima
M
M
Kogure
K
K
Fukuzawa
K
K
Takahashi
Y
Y
Yamamoto
S
S
D000818:Animals; D002478:Cells, Cultured; D002855:Chromatography, Thin Layer; D008401:Gas Chromatography-Mass Spectrometry; D019787:Linoleic Acid / Q000737:chemistry*; D008084:Lipoxygenase / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry* / Q000302:isolation & purification; D010972:Platelet Activating Factor / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D012156:Reticulocytes / Q000201:enzymology; D013025:Glycine max / Q000201:enzymology
D010713:Phosphatidylcholines; D010972:Platelet Activating Factor; D009569:Nitric Oxide; D019787:Linoleic Acid; D008084:Lipoxygenase; D010100:Oxygen