June 2021
Volume 62, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2021
Detection of reduced mitochondrial ROS production but increased ROS levels and oxidative damage in the young xCT knockout mouse retina
Author Affiliations & Notes
  • Luis James Knight
    Department of Physiology, The University of Auckland, Auckland, Auckland, New Zealand
  • Renita M Martis
    Department of Physiology, The University of Auckland, Auckland, Auckland, New Zealand
  • Monica L Acosta
    School of Optometry and Vision Science, The University of Auckland, Auckland, Auckland, New Zealand
  • Paul J Donaldson
    School of Medical Sciences, The University of Auckland, Auckland, Auckland, New Zealand
  • Julie C Lim
    Department of Physiology, The University of Auckland, Auckland, Auckland, New Zealand
  • Footnotes
    Commercial Relationships   Luis Knight, None; Renita Martis, None; Monica Acosta, None; Paul Donaldson, None; Julie Lim, None
  • Footnotes
    Support  Auckland Medical Research Foundation grant 37177655; New Zealand Optometric Vision Research Foundation grant 3717048; Faculty Research Development Fund - University of Auckland grant 3719594
Investigative Ophthalmology & Visual Science June 2021, Vol.62, 2230. doi:
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      Luis James Knight, Renita M Martis, Monica L Acosta, Paul J Donaldson, Julie C Lim; Detection of reduced mitochondrial ROS production but increased ROS levels and oxidative damage in the young xCT knockout mouse retina. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2230.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The cystine/glutamate antiporter (system xc-) mediates exchange of extracellular cystine for intracellular glutamate. The xCT knockout mouse (KO), in which the light chain subunit (xCT) of system xc- is removed, results in accelerated retinal aging relative to age matched wild-type (WT) mice due to alterations in glutamate and anti-oxidative mechanisms. We have previously shown that lack of xCT alters the glutamate/glutamine cycle and glycolytic metabolism. In this study, we extended our investigation to examine the effect of xCT removal on mitochondrial activity, reactive oxygen species (ROS) production, and oxidative damage.

Methods : Retinas from C57BL/6J and xCT KO mice were collected at 6 weeks (6W) and 9 months (9M). Mitochondrial activity and ROS production were measured via high-resolution respirometry using the Oroboros Oxygraph-2K system (n=6). Succinate, glutathione (GSH) levels and protein carbonyl and lipid peroxidation were measured in whole retinas using biochemical assays (n=6). GSH distribution in the retinal layers was quantified after silver-intensified immunogold labelling (n=6).

Results : High-resolution respirometry revealed 2-fold higher baseline ROS levels in the 6W KO retina compared to WT (ANOVA, p<0.05), but levels were similar in the 9M mice. While whole retina GSH levels did not change between strains or age groups, GSH was significantly decreased in KO photoreceptors nuclear layer compared to WT at 6W. In addition, there were increased levels of protein carbonyls (p<0.05) and 4-HNE (p<0.01) in the 6W KO retina compared to WT. Succinate levels were similar at either age and in both strains of mice. However, high-resolution respirometry revealed increased respiratory complex I activity (p<0.01), a trend for decreased respiratory complex II activity, and decreased mitochondrial ROS production in 6W KO retinas compared to WT (p<0.05).

Conclusions : Loss of xCT function results in reduced photoreceptor GSH levels, increased baseline ROS, increased oxidative stress but decreased mitochondrial ROS production which may alter ROS signalling pathways important for normal retinal function. These early changes are back to normal in the 9M xCT KO which may suggest early metabolic and mitochondrial changes due to xc- pre-conditions the retina to accelerated aging.

This is a 2021 ARVO Annual Meeting abstract.

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