Low LED light exposure as a model of retinal degeneration in Albino rats

BENEDETTO, MARIA MERCEDES; GUIDO, MARIO EDUARDO; CONTIN, MARIA ANA

Hawai

Congreso; ARVO ANNUAL MEETING; 2018

Purpose: Constant LED light exposure to 200 lx for 8 days, produces rods and cones reduce functionality that finally died but does not alter rhodopsin (Rho) expression before cell death in male albino Wistar rats. However, Rho was found to be more phosphorylated in ser334 than in controls, (Contín et al, 2013; Quinteros ?Quintana et al, 2016). Later, we found that melanopsin and neuropsin expressed in the inner retina were seen to modify their localization and expression during constant LED light exposure (Benedetto et al, 2017). These findings suggest that constant light during several days produces retinal remodeling and outer nuclear layer (ONL) cell death as well as changes in opsin expression in the inner nuclear layer in our model of retinal degeneration. In the present study we investigated the molecular mechanisms involved in ONL cell death, studying the oxidative stress mechanism, fatty acids status and wether Rho ?phosphorylation is a reversible mechanism.Methods: Male Albino Wistar rats (12-15 weeks old) were exposed to constant light stimulation (LL); light: dark cycle (0 lx: 200 lx, LD) or constant dark (DD) according experimental design. Cellular redox state was evaluated by reactive oxygen species (ROS) levels quantification by flow cytometer using DCFH/DA and Catalase (CAT) activity assay by spectrophotometry. Fatty acids status was studied by gas chromatography?mass spectrometry (GC-MS) and Rho phosphorylation was evaluated by western blot. Data are expressed as mean ± SD. Statistical comparisons were made using one-way ANOVA; p-value < 0.05 was considered statistically significant. In all cases with significance, a Tukey post hoc test with a p value < 0.05 was considered statistically significant. Results: We found a significant increase in retinal ROS production after 5 days of constant light exposure (LL5-LL8) vs control animals. The enzymatic activity of CAT was not different between groups. GC-MS results demonstrated diferent fatty acid composition between groups. Also, we found that Rho phosphorylation was reversible if the animals were exposed to 48 hours of darkness after light treatment.Conclusion: All this results suggest that photoreceptors cell death in low LED light exposure model of RD could be triggered by an oxidative stress mechanism.