Abstract
Nitric oxide (*NO) and *NO-derived reactive species (e.g., peroxynitrite anion, nitrogen dioxide radical) react with lipids containing unsaturated fatty acids to generate nitrated species. In the present work, we synthesized, characterized, and detected a nitrated derivative of cholesteryl linoleate (Ch18:2) in human blood plasma and lipoproteins using a high-pressure liquid chromatography coupled to electrospray ionization tandem mass spectrometry method. It was synthesized by a reaction of Ch18:2 with nitronium tetrafluoroborate, yielding a species with m/z 711, which is characteristic of the cholesteryl nitrolinoleate (Ch18:2NO2) ammonium adduct. The presence of the nitro group was confirmed by using [15N]nitrite, which gave a product with m/z 712, with the same chromatographic and spectrometric characteristics of those of m/z 711. Furthermore, a C-NO2 structure was also demonstrated in Ch18:2NO2 by infrared analysis (Vmax 1549, 1374 cm-1). A stable product with m/z of 711, showing the same chromatographic characteristics and fragmentation pattern as those of synthesized standard, was found in human blood plasma and lipoproteins of normolipidemic subjects. The presence of this novel nitrogen-containing lipid product in human plasma and lipoproteins could represent a potential indicator of the oxidative/nitrative roles that *NO or its metabolites play during in vivo lipid oxidation, generating a compensatory mechanism of protection in vascular disease.
Highlights
IntroductionNitric oxide (NO) and NO-derived reactive species (e.g., peroxynitrite anion, nitrogen dioxide radical) react with lipids containing unsaturated fatty acids to generate nitrated species
Nitric oxide (NO) and NO-derived reactive species react with lipids containing unsaturated fatty acids to generate nitrated species
The reaction of Ch18:2 with NO2BF4 yielded a main product that exhibited a molecular ion with m/z 711, when analyzed by LC-ESI/MS/MS, characteristic of a nitrated Ch18:2 ammonium adduct
Summary
Nitric oxide (NO) and NO-derived reactive species (e.g., peroxynitrite anion, nitrogen dioxide radical) react with lipids containing unsaturated fatty acids to generate nitrated species. Nitric oxide (NO) is an endogenously produced free radical that can modulate several relevant biological actions. NO is the primary source of several substances with oxidant and nitrating activities [e.g., nitrogen dioxide radical (NO2), peroxynitrite anion] (Reaction 1) that can yield nitrated and/or nitrosylated endogenous substances [1, 2]. 1660 Journal of Lipid Research Volume 44, 2003 sures of pulmonary lipids to NO2 in severely polluted urban atmospheres, providing evidence that at low ppm levels, NO2 reacts with unsaturated fatty acids, leading to nitrolipids formation [3,4,5]. Nitrolipids can be formed by a direct reaction of NO2 with nonoxidized lipids at physiological pH [16], or by a reaction of nitrous acid (HONO)
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