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Ellen R Weiss, Shoji Osawa, Suraj Dhungana, Susan McRitchie, Susan Sumner; Metabolic Differences Between Light- and Dark-Adapted Mouse Retinas. Invest. Ophthalmol. Vis. Sci. 2014;55(13):426.
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In normal retinas, production of large amounts of ATP, as well as exposure to UV light and high levels of oxygen all give rise to reactive oxygen species (ROS). Excess production of ROS can damage proteins, lipids and DNA in photoreceptors. Additionally, these cells have high levels of photosensitive retinoid derivatives that are easily oxidized, becoming toxic to the cell. The goal of the present work is to define metabolic changes that occur in retinas from light- and dark-adapted mice. These results will be compared with animal models of retinal degeneration where light is often an exacerbating factor.
C57BL/6J mice raised under a normal light/dark cycle were exposed to 250 lux for 3 h or adapted overnight in complete darkness. Eyes from these animals were enucleated and the retinas dissected in PBS, followed by rapid freezing in liquid nitrogen. Four retinas (~15-20 mg) were treated as a single sa¬mple. Each sample was homogenized in buffer containing 50:50 acetonitrile:water. The homogenate was centrifuged, the supernatant was dried and re-suspended in 95:5 H2O:methanol for UPLC-TOF-MS analysis. Samples were chromatographed on a BEH HSST3 column followed by analysis on a G-2 SYNAPT-QTOF mass spectrometer equipped with the Acquity UPLC system. Data were analyzed using TransOmics software to determine the group differentiating markers of dark- and light-adapted retinas.
Approximately 2,000 compound ions were detected. Differences in the metabolic profiles of retinas from dark- and light-adapted animals were observed using Orthogonal Projections to Latent Structure-Discriminant Analysis (OPLS-DA). Analysis of the group differentiating markers using the Human Metabolome Data Base revealed members of the retinol metabolism pathway as well as several classes of lipids, amino acid derivatives and nucleotides that were distinguished between the dark- and light-adapted retinas.
We evaluated the metabolic profile of wild type mice to determine the normal metabolic changes that occur in the retina under dark- and light-adapted conditions. Since light is an exacerbating factor in a number of retinal degenerative diseases, our results serve as a foundation for evaluating changes in metabolism that occur in animal models for retinal degeneration. We anticipate that these studies will reveal novel pathways leading to improved therapeutic strategies.
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