Characterization of Mitochondrial and Metabolic Changes Following Retinal Detachment

Abstract

Purpose : Despite the compelling lines of evidence that photoreceptor (PR) cell death, secondary to retinal detachment (RD), is caused by oxidative damage, the effect of RD-dependent failure on PR function and survival has not been investigated. This study aims to characterize the effect of RD on PRs oxidative and mitochondrial metabolism and identify novel therapeutic targets.

Methods : RD was induced in mice by sub-retinal injection of sodium hyaluronate and harvested over 48 hrs. Expression of transcriptional co-activators, Pgc-1a and Pgc-1b, and downstream effectors were measured by quantitative PCR. Changes in mitochondrial content were assessed by cytochrome oxidase subunit IV (COX IV) immunolabeling and quantification using ImageJ software. Mouse cone-like 661w cells were exposed to low glucose (1mM) conditions over 24 hrs and mitochondrial respiratory function was measured with a Seahorse XF24 Bioanalyzer. Long-Range PCR was used to assess the accumulation mitochondrial DNA lesions.

Results : Significant up regulation in expression of Pgc-1a and Pgc-1b was observed as early as 3 hrs post-RD (n=4, p<.01). Downstream genes, including superoxide dismutase 2 and estrogen-related receptor a were also induced (p<.05). COXIV staining demonstrated an increase in mitochondrial content that was most prominent within the PR inner segments 24 hrs post-RD (p<.05). We observed that exposure of 661w cells to low glucose increased oxidative phosphorylation (p<.05) as shown by higher oxygen consumption at baseline and after systematic inhibition of the electron transport chain. Simultaneously we observed decreased glycolytic flux and accumulation of mitochondrial DNA lesions (p<.05).

Conclusions : In this study, we demonstrate that RD leads to dramatic changes in photoreceptor metabolism and mitochondrial content consistent with the induction of master redox and metabolic regulators, PGC-1a and PGC-1b. Modeling of RD in vitro indicates that LG alone is able to shift PR metabolism towards oxidative phosphorylation while reducing mitochondrial DNA damage, suggesting that the hypoxic insult or its combination with low glucose is required for PR stress and degeneration. Further characterization of the effects of these stressors are needed to fully evaluate the protective role of PGC-1a isoforms and may lead to novel therapeutic options for patients with RD.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.