Blue light decreases VEGF in an in vitro model of AMD

Abstract

Purpose : Blue light is an identified risk factor for age-related macular degeneration (AMD). Using a custom-made illumination system delivering 10 nm-wide illumination bands within the blue-green range, we recently showed that the narrow range 415-455 nm was the most toxic for A2E-loaded RPE cells (Arnault et al., 2013). To further understand the mechanisms involved in AMD, we investigated the impact of light on the expression of VEGF and its receptors in A2E-loaded RPE cells under illumination in the blue-green range.

Methods : Primary culture of porcine retinal pigment epithelium cells (RPE) were incubated for 6 hours with A2E and then exposed for 15 hours to 10 nm-wide illumination bands centered from 390 to 520 nm in 10 nm increments; one additional band centered at 630 nm was used as a light control. Light irradiances were normalized with respect to the natural sunlight reaching the retina after being filtered by the ocular structures. These conditions were selected because they induce oxidative stress in RPE cells but remain below the maximal cell death induction threshold. VEGF, VEGFR1 and VEGFR2 mRNA contents were quantified by qPCR after light exposure, results were normalized to the ribosomal gene 18S. VEGF protein content was quantified by ELISA in cell lysates and in cell culture medium.

Results : In A2E-loaded RPE cells exposed to blue-violet light, VEGF mRNA expression decreased significantly while VEGFR1 mRNA expression increased. VEGFR2 was less expressed than VEGFR1 and was not affected by light exposure, except in RPE cells exposed to 400nm without A2E in which an increase was observed. Secreted and intracellular VEGF protein expression increased in the presence of A2E. VEGF protein expression levels decreased in A2E loaded-RPE cells and the culture medium when exposed to blue-violet light.

Conclusions : Using our in vitro model of AMD and our custom-made illumination system, we showed that the expression of the VEGF and its receptors could be modified by light exposure at the mRNA level but also at the protein level. We have also confirmed that A2E is able to induce VEGF production and secretion in RPE cells. Surprisingly, blue-violet light, which we previously found to induce oxidative stress and apoptosis, tend to decreases VEGF production. These results suggest that blue light toxicity might contribute preferentially to the development of dry AMD rather than to the complications of wet AMD.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.