MALDI-TOF MS Detection of Oxidized Major Phospholipids in Biological Samples Using Conventional Matrices and 1-Pyrenebutyric Hydrazide

Oxidized lipids are involved in many widespread diseases associated with dysregulated lipid metabolism and/or low-level chronic inflammation. An increase in reactive oxygen species due to redox imbalance leads to the generation of various lipid peroxidation products, including lysolipids and truncated carbonyl compounds, particularly carboxylic acids and aldehydes. The latter can readily react with other biomolecules, such as DNA or proteins, and thereby impair their biological functions. Despite the growing interest in the role and function of oxidized lipids, their analysis remains challenging. This is due to several factors affecting their straightforward analysis, including their low abundance, their structural diversity, and their transient nature as well as method-specific factors such as the impact of matrix-assisted laser desorption/ionization (MALDI) matrices on the detectability of such oxidized lipids. Here, we evaluate the detectability of different oxidized major phospholipids, using different MALDI matrices including 2,5-dihydroxybenzoic acid, 4-(dimethylamino)cinnamic acid, and 9-aminoacridine with rat liver extracts serving as a proxy for complex biological specimen. We also show that 1-pyrenebutyric hydrazide is a suitable matrix compound for the MALDI mass spectrometric analysis of native and oxidized phosphatidylcholine and phosphatidylethanolamine lipids, as it can function both as a derivatization agent for truncated oxidized aldehyde lipids and as a regular (UV)-MALDI matrix.