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S.J. Fliesler, M.J. Richards, B.J. Kapphahn, D.A. Ferrington; Opsin Resists Oxidative Damage During Retinal Degeneration . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3178.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Lipid and protein oxidation have been implicated in a variety of degenerative disease processes, including those involving the retina and brain. Previously (Richards et al., ARVO 2003), using a rat model of Smith–Lemli–Opitz Syndrome (SLOS) with progressive retinal degeneration, we showed a correlation between lipid hydroperoxide (LPO) accumulation and retinal degeneration, which was exacerbated by exposure to intense constant light ("light damage"). Here, we evaluated oxidative damage of opsin, the predominant rod outer segment (ROS) membrane protein, during retinal degeneration under conditions of light damage and in the rat SLOS model. Methods: Sprague Dawley rats were treated with AY9944, an inhibitor of the affected enzyme in SLOS, as previously described (Fliesler et al., Arch. Ophthalmol. 122:1190, 2004) for up to 11 wk; control litters received no drug. All animals were maintained under dim cyclic light(12L:12D, 20–40 lux) and fed a cholesterol–free diet and water ad lib. Pairs of animals were exposed for 24 h to intense green light (1700 lux, 490–580 nm), while the unexposed cohort was kept in darkness for 24 h. ROS were prepared from pairs of retinas for each condition. In parallel groups, one eye of each animal was taken for morphological analysis. ROS proteins were resolved by 1D SDS–PAGE. One gel from each group was silver–stained (SS) while companion gels were blotted and probed with antibodies to opsin, 4–hydroxynonenal (HNE), and nitrotyrosine (NT). Results: SDS–PAGE (SS gels) of control and SLOS ROS (N=4/group.) showed opsin monomer (Mr ∼39 kDa) as the dominant protein. Corresponding blots showed a few HNE–positive bands in control ROS, with additional, more intense bands in SLOS ROS. However, opsin was not HNE–positive. In contrast, no differences in the number or intensity of NT–positive bands were observed in control vs. SLOS ROS; also, opsin was not NT–positive. Light damage (confirmed morphologically) produced additional immunoreactive bands (particularly for NT), but no immunolabeling of opsin was observed. Conclusions: Opsin is resistant to oxidative damage induced by either intense light or under conditions that mimic SLOS. This finding tends to exclude oxidative damage of opsin as a primary event in the etiology of these retinal degenerations.
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