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Lily Wong, Sudipta Seal, James McGinnis; Kinetics of apoptotic death and oxidative damage in the retina of P23H-1 rats and the protective effects of nanoceria. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4691.
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Chronic rise in reactive oxygen species (ROS) is a hallmark in many forms of retinal degeneration. Excess ROS causes oxidative damage and cell death. Using the P23H-1 rats, we showed that a single intravitreal injection of nanoceria, catalytic scavengers of ROS, delayed rod cell degeneration. However, the cellular mechanisms of this protection are unclear. We seek to understand how nanoceria affect the kinetics of apoptotic death and whether nanoceria reduce oxidative damage in the retinas of these animals.
We injected 2 µl of either saline or nanoceria (CNP) intravitreally to each eye of P23H-1 transgenic rats at postnatal day (P) 15 or 21. Assessments of cell death and oxidative damage were performed at 3, 7, or 14 days post injection. We used the 8-Isoprostane EIA kit to quantify lipid autoxidation in retinal tissues and anti 8-OHdG on retinal sections to measure oxidative DNA damage. We quantified the number of apoptotic (TUNEL+) profiles in the outer nuclear layer of retinas using the ApopTag Plus Fluorescein In Situ Apoptosis Detection kit.
We observed a proportional increase in 8-isoprostane in retinas from wildtype, hetero- and homozygous P23H-1 rats according to the severity of retinal degeneration. When CNP were injected at P15 in heterozygous P23H-1 animals, we observed a reduction of 8-isoprostane in these animals compared to saline injected ones at P29. When we examined the kinetics of cell death in the retinas of heterozygous P23H-1 rats from P18 to P44, we found TUNEL+ profiles peaked at P18 and followed a gradual decline thereafter. Few TUNEL+ profiles were observed in wildtype retinal sections of similar ages. We saw a 60% reduction of TUNEL+ profiles in P18 P23H-1 retinas when CNP were administered at P15.
Our results showed that a single application of CNP in the vitreous reduced oxidative damage in the retinas of these mutant rats. We demonstrated that CNP were effective in preventing rod cell death when administered early in age. We conclude that reduction of photoreceptor cell death after CNP application is likely due to reduction of oxidative damage in the retinas of these animals. Therefore using CNP to lower oxidative damage in retinal degenerative diseases is a promising strategy to extend the functional life span of diseased photoreceptor cells.
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