ω‑Alkynyl Lipid Surrogates for Polyunsaturated Fatty Acids: Free Radical and Enzymatic Oxidations

• Published in: Journal of the American Chemical Society 2014-08, Vol.136 (32), p.11529-11539
• Main Authors: Beavers, William N, Serwa, Remigiusz, Shimozu, Yuki, Tallman, Keri A, Vaught, Melissa, Dalvie, Esha D, Marnett, Lawrence J, Porter, Ned A
• Format: Article
• Language: English
• Subjects: Animals; Arachidonate 15-Lipoxygenase - chemistry; Arachidonic acid; Arachidonic Acid - chemistry; Carbon - chemistry; Cell Line; Chromatography, High Pressure Liquid; Cyclooxygenase 1 - chemistry; Cyclooxygenase 2 - chemistry; Enzymes; Fatty acids; Fatty Acids - chemistry; Fatty Acids, Unsaturated - chemistry; Free Radicals; Glycine max - enzymology; Hydroxyeicosatetraenoic Acids - chemistry; Linoleic Acid - chemistry; Lipids; Lipids - chemistry; Lipoxygenase; Lipoxygenases - chemistry; Macromolecular Substances; Macrophages - metabolism; Metabolites; Mice; Oxidation; Oxygen - chemistry; Spectrophotometry, Ultraviolet; Tandem Mass Spectrometry; Tracking
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja506038v

Lipid and lipid metabolite profiling are important parameters in understanding the pathogenesis of many diseases. Alkynylated polyunsaturated fatty acids are potentially useful probes for tracking the fate of fatty acid metabolites. The nonenzymatic and enzymatic oxidations of ω-alkynyl linoleic acid and ω-alkynyl arachidonic acid were compared to that of linoleic and arachidonic acid. There was no detectable difference in the primary products of nonenzymatic oxidation, which comprised cis,trans-hydroxy fatty acids. Similar hydroxy fatty acid products were formed when ω-alkynyl linoleic acid and ω-alkynyl arachidonic acid were reacted with lipoxygenase enzymes that introduce oxygen at different positions in the carbon chains. The rates of oxidation of ω-alkynylated fatty acids were reduced compared to those of the natural fatty acids. Cyclooxygenase-1 and -2 did not oxidize alkynyl linoleic but efficiently oxidized alkynyl arachidonic acid. The products were identified as alkynyl 11-hydroxy-eicosatetraenoic acid, alkynyl 11-hydroxy-8,9-epoxy-eicosatrienoic acid, and alkynyl prostaglandins. This deviation from the metabolic profile of arachidonic acid may limit the utility of alkynyl arachidonic acid in the tracking of cyclooxygenase-based lipid oxidation. The formation of alkynyl 11-hydroxy-8,9-epoxy-eicosatrienoic acid compared to alkynyl prostaglandins suggests that the ω-alkyne group causes a conformational change in the fatty acid bound to the enzyme, which reduces the efficiency of cyclization of dioxalanyl intermediates to endoperoxide intermediates. Overall, ω-alkynyl linoleic acid and ω-alkynyl arachidonic acid appear to be metabolically competent surrogates for tracking the fate of polyunsaturated fatty acids when looking at models involving autoxidation and oxidation by lipoxygenases.