Lipidomic analysis for lipid peroxidation-derived aldehydes using gas chromatography-mass spectrometry

A lipidomic method is described for the measurement of lipid peroxidation-derived aldehydes using gas chromatography/electron ionization/mass spectrometry with selected ion monitoring (GC/EI/MS-SIM). Aldehydes in the samples were converted into their pentafluorobenzyl (PFB)-oximes using PFB-hydroxylamine, and other functional groups such as the hydroxyl groups were further derivatized into the trimethylsilyl ethers. The PFB-oxime derivatives could be comprehensively detected by the SIM of m/z 181, which is a characteristic fragment ion of the PFB-oxime derivatives. At the same time, each aldehyde was classified into five groups (alkanals, 2-alkenals, 2,4-alkadienals, 2-hydroxyalkanals, and 4-hydroxy-2-alkenals) by SIM of the structure-specific fragment ions. Determination of the 4-hydroxy-2-alkenals was also performed by confirmation of their higher reactivity with the sulfhydryl group. On the basis of the mass spectrometric characterization, we have identified at least 33 aldehydes formed upon the FeII-mediated decomposition of the arachidonic acid-, linoleic acid-, and docosahexaenoic acid-hydroperoxides in vitro. We then applied this system to the in vivo samples and successfully observed the increase in aldehydes in the liver of mice intraperitoneally injected with bromobenzene, an experimental animal model for lipid peroxidation. Using this comprehensive analysis, unique differences in the formation between each aldehyde could be observed. This method is useful for simultaneously monitoring the lipid peroxidation-derived aldehydes formed under oxidative stress in vivo.