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Marie-Christine Lambert, Mathieu Ouellette, Quentin Maestracci, Elodie Boisselier, Stephanie Proulx, Patrick J Rochette; Effect of High Energy Visible Light on A2E-loaded Retinal Pigmented Epithelium in Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5255.
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Age-Related Macular Degeneration (AMD) is the leading cause of vision loss in the occidental elderly. This disease is characterized by the loss of central vision following the death of photoreceptors and of the retinal pigmented epithelium (RPE) in the macula. Epidemiological studies brought to light an association between lifetime sun exposure and the probability to develop AMD. Sunlight contains 30% of high energy visible (HEV) light which reach the retina, unlike ultraviolet light. HEV light, also known as blue light (400-500 nm) is the most energetic light reaching the RPE. It has been observed that RPE accumulates lipofuscin with age. Its predominant component is N-retinylidene-N-retinylethanolamin or A2E. This molecule absorbs light at 430 nm, which leads to photooxidation. Our hypothesis is that the reactive oxygen species (ROS) produced by chronic HEV exposure of cells containing A2E would attack cellular structures such as mitochondria and telomeres.
We used immortalized RPE cells (ARPE-19) in which various concentrations of A2E were added for incorporation. We measured A2E fluorescence to quantify the A2E uptake of the cells. Then, we irradiated the cells with or without A2E with HEV to determine the lethal dose of HEV+A2E in ARPE-19 cells with the objective to find a sub-lethal dose for chronic irradiations. We chronically irradiated the cells with HEV in the presence of A2E and we measured by qPCR telomere length and mitochondrial DNA deletions and quantity.
Incorporation of A2E in ARPE-19 cells is proportional to the concentration in the culture medium. The lethal dose of HEV light in A2E-containing cells is 3000 kJ/m2. The chronic irradiation regime is done under these conditions: 300 kJ/m2 of HEV light, 100 µM of A2E, 4 days/week and during 11 weeks. We did not observe any variations in telomere length, mitochondrial DNA deletions or quantity after 11 weeks of irradiation.
We observed that A2E sensibilize the cells to HEV-induced cell death. The chronic irradiation regime does not seem to produce enough ROS to affect cellular structures. We also bring the hypothesis that HEV irradiation of A2E degrades it or modifies the molecular structure, which would inhibit its oxidative properties.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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