LAUSR

We investigated the effect of oxidative stress (OS) on lipidomic perturbations in the subcellular fractions and exosomes of human embryonic kidney (HEK) 293 cells using asymmetrical flow field-flow fractionation (AF4) and nanoflow ultrahigh performance liquid chromatography-electrospray ionization-tandem mass spectrometry (nUHPLC-ESI-MS/MS). We treated HEK 293 cells with hydrogen peroxide (H2O2) and fractionated the cell lysates using AF4 to determine the change in size and population of the subcellular fractions and exosomes, and to obtain narrow size fractions for lipid analysis. A total of 438 lipids from 642 identified species-including oxidized lipids-were quantified. The relative amount of secreted exosomes increased by 28% during OS, whereas the amount of subcellular species decreased by 35%. There was a significant increase in the level of oxidized phospholipids in the mitochondrion-enriched subcellular fractions, but not in the exosomes. Most high-abundance triacylglycerol (TG) species increased in the stressed cells, whereas they decreased in the exosomes. During OS, ceramides involved in the apoptotic mitochondrial pathway were accumulated in the subcellular fractions, whereas their levels were unaffected in the exosomes. The present study demonstrated that AF4 and nUHPLC-ESI-MS/MS can be used to investigate lipid alterations in subcellular and extracellular species during OS, and the pathological relationships in diseases caused by reactive oxygen species.