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Emily Brown, Alfred S Lewin, John D Ash; Superoxide Dismutase 2 Deletion in Retinal Pigment Epithelium (RPE) Results in Age and Light-Dependent Mitochondrial Oxidative Stress and RPE-damage. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2453.
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© ARVO (1962-2015); The Authors (2016-present)
Mitochondrial dysfunction and oxidative stress have been implicated in the pathogenesis of AMD. To better understand the mitochondrial mechanism of RPE dysfunction, deletion of the gene encoding the mitochondrial antioxidant enzyme, superoxide dismutase 2 (Sod2) was induced in the retinal pigment epithelium (RPE).
VMD2Cre;Sod2flox/flox BALB/cJ mice were housed in cyclic 12-hour light, 12 hour-dark conditions, with either 200 lux lighting (normal mouse room light) or <10 lux lighting (dim light). Electroretinography (ERG) was performed to assess retinal function, fundoscopy was used to assess retinal morphology, and SD-OCT was utilized to examine retinal morphology and outer nuclear layer (ONL) thickness in vivo with aging from 1 to 5 months of age. IHC was used to examine protein expression; qRT-PCR was used to measure gene expression. All procedures were conducted in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Visual Research.
At 1 month of age, the Sod2 knockout (KO) mice housed in normal lighting had decreased RPE function, as measured by ERG c-wave, compared to wild type (WT) littermates. RPE function continued to decrease with aging, with a statistically significant reduction in the c-wave by 5 months of age (n≥ 5, 2-way ANOVA, p<0.01). At 3 months of age, KO mice housed in normal lighting had hyper-reflective spots visible by fundus photography, which were not present in WT mice. Interestingly, these differences were not observed in mice housed in dim lighting.
Deletion of Sod2 in the RPE results in increased oxidative stress, dysfunction of the RPE, and visible differences in retinal morphology under normal lighting conditions, but not dim lighting. This suggests that deletion of Sod2 does not cause oxidative stress and RPE degeneration without the additional stress of light stimulation. These findings suggest that genetics, aging, and environmental stressors interact to damage RPE in vivo. This has significant implications for RPE injury in age-related macular degeneration.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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