Couto Daniela, Santinha Deolinda, Melo Tânia, Ferreira-Fernandes Emanuel, Videira Romeu A, Campos Ana, Fardilha Margarida, Domingues Pedro, Domingues M Rosário M
Mass Spectrometry Centre, UI-QOPNA, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
Mass Spectrometry Centre, UI-QOPNA, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal; Laboratory of Signal Transduction, IBIMED, Health Sciences Department, University of Aveiro, Aveiro 3810-193, Portugal.
Chem Phys Lipids. 2015 Oct;191:106-14. doi: 10.1016/j.chemphyslip.2015.08.014. Epub 2015 Aug 24.
Galactosylceramide (GalCer) and lactosylceramide (LacCer) are structural and signaling lipids, playing important roles in signal transduction and cell adhesion. They are especially abundant in the nervous system and in important components of the myelin sheath. Although neurodegenerative disorders are associated with increased oxidative stress and lipid oxidation, the connection between oxidative stress and glycosphingolipid modification has been scarcely addressed. In this study, we aimed to characterize the structural changes caused by the hydroxyl radical to GalCer and LacCer molecular species using electrospray ionization mass spectrometry (ESI-MS and MS/MS) and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS(n)). ESI-MS and LC-MS spectra of 24:1GalCer and 24:1LacCer after free radical oxidation showed the formation of new species, which were identified as keto, hydroxyl and hydroperoxy derivatives, arising from modification in the mono unsaturated fatty acyl chain. Formation of ceramide and oxidized ceramides was also observed as a result of 24:1GalCer and 24:1LacCer radical oxidation. 24:1GlcCer (glucosylceramide) was detected after LacCer oxidation, probably due to oxidative cleavage of lactosyl moiety. This study shows that glycosphingolipids are prone to radical induced oxidation, which can be one of the causes of the increased ceramides content and pro apoptotic events during oxidative conditions and neurodegeneration. This MS study will support the future identification of oxidized galactosyl- and lactosylceramide species in sphingolipidomic studies applied to biological samples related with oxidative conditions.
半乳糖神经酰胺（GalCer）和乳糖神经酰胺（LacCer）是结构脂质和信号脂质，在信号转导和细胞黏附中发挥重要作用。它们在神经系统和髓鞘的重要组成部分中尤其丰富。尽管神经退行性疾病与氧化应激增加和脂质氧化有关，但氧化应激与糖鞘脂修饰之间的联系却很少被探讨。在本研究中，我们旨在利用电喷雾电离质谱（ESI-MS和MS/MS）以及高效液相色谱-串联质谱（HPLC-MS(n)）来表征羟基自由基对GalCer和LacCer分子种类所引起的结构变化。自由基氧化后24:1GalCer和24:1LacCer的ESI-MS和LC-MS谱显示形成了新的种类，这些新种类被鉴定为酮、羟基和氢过氧衍生物，它们是由单不饱和脂肪酰链的修饰产生的。由于24:1GalCer和24:1LacCer的自由基氧化，还观察到了神经酰胺和氧化神经酰胺的形成。LacCer氧化后检测到了24:1GlcCer（葡萄糖神经酰胺），这可能是由于乳糖基部分的氧化裂解。本研究表明糖鞘脂易于发生自由基诱导的氧化，这可能是氧化条件和神经退行性变期间神经酰胺含量增加和促凋亡事件的原因之一。这项质谱研究将支持未来在应用于与氧化条件相关的生物样品的鞘脂组学研究中鉴定氧化的半乳糖基和乳糖基神经酰胺种类。
