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Jie Fan, E Ellen Jones, Richard R Drake, Craig E Crosson; Spatial Distribution of Sphingolipids in The Mouse Retina by MALDI Imaging Mass Spectrometry. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):156.
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Studies have been shown that sphingolipids play and important role in regulating photoreceptors and retinal pigment epithelial function, and modulating of conventional outflow resistance. These bioactive lipids are also critical stress mediating apoptotic cell death and have been implicate in the pathogenesis of several diseases. The purpose of this study was to investigate how acute ischemia alters retinal sphingolipid levels and their spatial distribution in the mouse retina.
Unilateral retinal ischemia was induced in mice by elevating IOP to 120 mmHg for 45 minutes. Ischemic retinas were analyzed 24 hour post-injury and compared to contralateral controls. The sphingolipid levels were determined by liquid chromatography-mass spectrometry (LC-MS). Matrix assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) analysis of sphingolipids was performed on the mouse retina cross-sections using a dual source Bruker Solarix 70 FTICR mass spectrometer operating in positive ion mode. Light microscopy from adjacent sections was used to verify retinal morphology of MALDI imaged sections.
The LC-MS studies showed that the C16-, C18- and C20-ceramides were the dominant retinal sphingolipids in the normal mouse retina comprising over 81% of the total. The MALDI imaging result demonstrated that phosphatidylcholine, C16-, C18-,and C20-ceramides were identified in all retinal layers. While sphingomyelin was predominately localized in RPE. Following ischemic injury C16-, C18-, C20-, C22-, C24-ceramides and sphingosine were significantly elevated.
This initial study provides evidence that retinal sphingolipids are significantly elevated following acute ischemic injury. MALDI imaging studies provide initial evidence that specific sphingolipids and their metabolites exhibit unique special distribution in the retina. Together there support the idea that sphingolipid signaling is important for the progression of ischemia related retinal degeneration.
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