We have recently showed that 11-cis retinal, the light-detecting chromophore of the visual pigment, is a major source of the toxic deposits that originate in the photoreceptors and accumulate in the Retinal Pigment Epithelium in the form of lipofuscin. This work was carried out with mice, and we now propose to extend these studies to the human. Our finding indicates that 11-cis retinal may play a major role in events resulting in retinal degenerations. Defects of retinoid processing in the eye have long been linked to diseases of the retina, but most pathogenic mechanisms have been hitherto associated with either lack of 11-cis retinal or accumulation of its photoproduct all-trans retinal. Here we propos to examine the damage to the human retina initiated by 11-cis retinal. This is particularly important for the human retina, where rhodopsin regeneration is rapid, requiring high fluxes of 11-cis retinal. We will investigate the damage mediated by 11-cis retinal in single living rod photoreceptors from human donor eyes. Mouse rods will be used for comparison, in order to aid in the extrapolation of results from whole animal studies with mice to the human situation. We will use fluorescence imaging of single photoreceptors to measure oxidative damage and the formation of lipofuscin precursors. To determine the relation between the flux of 11-cis retinal and the rate of rhodopsin regeneration, we will measure rhodopsin levels with microspectrophotometry.
The aims of the research are:
Specific Aim #1 : Test if sequestration of 11-cis retinal prevents damage to the rod outer segment.
Specific Aim #2 : Test if increases in the 11-cis retinal flux increase damage to the rod outer segment. Results from these studies will provide new insights into the basic pathogenic mechanisms underlying vision loss in diseases like Age-Related Macular Degeneration and Stargardt, and suggest possible pathogenic mechanisms for a host of other diseases that might involve the generation and delivery of 11-cis retinal. They will elucidate the process of rhodopsin regeneration, which is essential for the recovery of visual sensitivity after light exposure. By using living human rod photoreceptors, the experimental approach is uniquely able to obtain mechanistic information about the origins of lipofuscin and the process of rhodopsin regeneration in the human eye. These studies will allow the evaluation of the potential toxicity of therapies for 11-cis retinal deficiencies that depend on boosting the chromophore supply. They will also provide a measure for the effectiveness of the opposite type of therapies, which aim to limit lipofuscin formation by slowing down the generation of 11-cis retinal.

Public Health Relevance

11-cis retinal, the light-detecting chromophore of the visual pigment, is required for vision. It is also a major source of the toxic deposits that accumulate with age in the retina, and have been implicated in diseases such as Age-Related Macular Degeneration and Stargardt. This project will use living photoreceptors isolated from human donor eyes to determine the factors that prevent damage from 11-cis retinal in the human retina.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Special Emphasis Panel (BVS)
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Neuhold, Lisa
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Medical University of South Carolina
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Chen, Chunhe; Adler 4th, Leopold; Goletz, Patrice et al. (2017) Interphotoreceptor retinoid-binding protein removes all-trans-retinol and retinal from rod outer segments, preventing lipofuscin precursor formation. J Biol Chem 292:19356-19365
Sheridan, Colleen; Boyer, Nicholas P; Crouch, Rosalie K et al. (2017) RPE65 and the Accumulation of Retinyl Esters in Mouse Retinal Pigment Epithelium. Photochem Photobiol 93:844-848
Adler 4th, Leopold; Chen, Chunhe; Koutalos, Yiannis (2017) All-trans retinal levels and formation of lipofuscin precursors after bleaching in rod photoreceptors from wild type and Abca4-/- mice. Exp Eye Res 155:121-127
Frederiksen, Rikard; Nymark, Soile; Kolesnikov, Alexander V et al. (2016) Rhodopsin kinase and arrestin binding control the decay of photoactivated rhodopsin and dark adaptation of mouse rods. J Gen Physiol 148:1-11
Adler 4th, Leopold; Boyer, Nicholas P; Chen, Chunhe et al. (2015) The 11-cis Retinal Origins of Lipofuscin in the Retina. Prog Mol Biol Transl Sci 134:e1-12
Adler 4th, Leopold; Boyer, Nicholas P; Anderson, David M et al. (2015) Determination of N-retinylidene-N-retinylethanolamine (A2E) levels in central and peripheral areas of human retinal pigment epithelium. Photochem Photobiol Sci 14:1983-90
Pallitto, Patrick; Ablonczy, Zsolt; Jones, E Ellen et al. (2015) A2E and lipofuscin distributions in macaque retinal pigment epithelium are similar to human. Photochem Photobiol Sci 14:1888-95
Crouch, Rosalie K; Koutalos, Yiannis; Kono, Masahiro et al. (2015) A2E and Lipofuscin. Prog Mol Biol Transl Sci 134:449-63
Adler 4th, Leopold; Chen, Chunhe; Koutalos, Yiannis (2014) Mitochondria contribute to NADPH generation in mouse rod photoreceptors. J Biol Chem 289:1519-28
Ablonczy, Zsolt; Smith, Noah; Anderson, David M et al. (2014) The utilization of fluorescence to identify the components of lipofuscin by imaging mass spectrometry. Proteomics 14:936-44

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