Radical induced oxidation of di-oleoyl phosphatidylserine using mass spectrometry revealed preferential oxydation of Sn-2 oleoyl chain

Phosphatidylserine (PS) oxidation products (oxPS) play several roles in cell signaling, in immunity and in cell apoptosis. These different roles seem to be related to different oxPS species that can be generated in vivo. Yet, oxPS formed in biological systems are far from being totally characterized. In this study we evaluated the oxidation pattern of PS bearing two oleic acids (OOPS), one of the most abundant PS molecular species present in mammalian cells, using mass spectrometry (MS) approach. Oxidative modifications of OOPS was induced by hydroxyl radical generated under Fenton reaction. Oxidation products with hydroperoxide, hydroxy and keto groups were identified, similarly to what was previous reported for PS species with one oleic acid (OA). Multiple oxidation products, such as di-hydroperoxides were also observed, and revealed that both hydroperoxy moieties are preferentially linked to the oleoyl fatty acid in sn-2, revealing that radical mediate oxidation is not random. Also, this study shows for the first time that OA can suffer the insertion of multiple oxidative groups, providing further insight on possible oxPS formed in vivo.