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Jingyu Yao, Jianhui Xiao, Lin Jia, Thomas A Ferguson, David N. Zacks; Role of autophagy activation on photoreceptor survival in retinal detachment. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4222. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal detachment (RD), or separation of the neurosensory retina from the underlying retinal pigment epithelium, results in photoreceptor (PR) hypoxia, reduced metabolic support and PR cell death. Paradoxically, a surprising number of PRs can survive the acute phase of RD and survive for extended periods of time. Our previous works have shown that activation of autophagy occurs in the PRs during RD, inhibits Fas-mediated apoptosis and is protective. The purpose of this study is to further assess the effect of inhibition of autophagy on photoreceptor survival during RD and to define the intracellular contents degraded through autophagy.
The ATG5Δrod mouse, which contains a rod-specific deletion of the Atg5 gene, was used to study the effect of suppressing autophagy on detached retina. RD was created by subretinal injections of 1% hyaluronic acid in both ATG5Δrod and control mice at 2 month of age. Apoptotic cell death was assessed by histology, real time-PCR, caspase 8 activity assay and TUNEL staining. To further identify the intracellular material that was degraded through autophagy during RD, autophagosomes were isolated from detached and attached retinas of GFP-LC3 mice by immunoprecipitation with an antibody against GFP. Protein contents of isolated autophagosomes were then compared by Mass Spectrometry (MS).
Inhibition of autophagy by genetic knock out of Atg5 in rod PRs resulted in increased apoptotic PR death during RD, demonstrated by elevated caspase 8 activity, Fas receptor transcript and TUNEL-positive cells compared with controls. More than 600 proteins were identified by MS from autophagosomes isolated from detached retinas compared with less than 250 proteins identified from attached retinas. Among various cellular compartments, proteins from cytoskeleton, cytoplasm and intracellular organelles constituted a large portion of increased autophagosome contents.
Absence of autophagy in rods resulted in increased PR cell death during RD, suggesting that activated autophagic degradation contributes to PR survival. MS confirmed elevated protein types and contents in the autophagosomes of detached retinas. Altogether, our findings suggested that increased degradation of intracellular material through the autophagic pathway is important for PR survival during periods of nutritional deprivation.
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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