Blue light toxic action spectrum on A2E-loaded RPE cells in sunlight normalized conditions

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Abstract

Purpose

Sunlight exposure is supposed to induce cumulative damage to the retina in retinal pathologies, such as AMD. The high energy visible spectrum between 380 nm and 500 nm (blue light) is incriminated. The goal of this study was to identify the spectrum of retinal toxicity induced by sunlight in physiological irradiance conditions.

Methods

RPE cells incubated for 6 hours with 0, 12.5, 20 and 40 μM of A2E were exposed for 18 hours to 10 nm illumination bands with the first band centered at 390 nm and going up to 520 nm. Light irradiances were normalized with respect to the natural sunlight reaching the retina after filtering by the eye ocular media. Six hours after light exposure, cell viability, necrosis and caspase-3/7 activity were assessed using the Apotox-Glo Triplex Assay.

Results

A2E-loaded RPE cells presented fluorescent bodies within the cytoplasm with a similar spectrum to that of A2E. Exposure to the 10 nm illumination bands induced morphological changes associated to a loss in cell viability. Light toxicity was dependant of A2E concentration and was higher in the blue spectral range with maxima in a specific 30 to 40 nm bandwidth. In addition, caspase-3/7 activity, indicative of cell apoptosis, was highly induced by the same narrow range whereas necrosis was not significantly different to that of cells maintained in darkness.

Conclusion

We described for the first time the precise spectrum of light toxicity in physiological irradiance conditions on an in vitro model of AMD. The 415-455 nm narrow spectral range generated the greatest phototoxic risk to RPE cells. This provides new information for designing selective protective filters, without disrupting visual and non-visual functions.

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