Abstract
Purpose :
Myopia progression is influenced by ambient light intensity. Previous data suggest that retinal dopamine (DA) and adenosine (Ado) have opposite associations with myopia progression and are also differentially regulated by light intensity. However, ambient brightness is often dynamic, and it is unclear how retinal DA and Ado levels change in such environments. Here, we investigated how retinal DA signaling and Ado levels are influenced by acute exposure to light intensities that are implicated in myopia progression.
Methods :
Wildtype C57/B6J mice, postnatal day 29 (DA) or 30 (Ado), were dark-adapted for 2 hours before being individually placed in a scotopic (1 lux), mesopic (50 lux), or photopic (10,000 lux) ambient lighting for 5 minutes. Immediately after light exposure, retinas were collected and prepared for HPLC analysis to measure DA and DOPAC (n=8 for scotopic and n=15 mice for mesopic and photopic conditions), and Ado (n = 10 for scotopic and n = 9 for mesopic and photopic conditions). HPLC results were normalized by dividing the DA, DOPAC, and Ado concentrations by the retinal protein concentrations obtained with a BCA assay for each individual sample (ng of signaling molecule / mg retinal protein). One-way ANOVA was used to test significance between light conditions.
Results :
Retinal DA levels were highest after acute exposure to scotopic light (21.3±1.7 ng/mg) but decreased in mesopic (19.9±1.4 ng/mg) and photopic light (16.1±1.0 ng/mg, scotopic vs. photopic, p=0.043). In contrast, DOPAC levels were lowest in scotopic light (2.9±0.2 ng/mg) but significantly increased in mesopic (4.3±0.4 ng/mg, p=0.028) and photopic light (4.3±0.3 ng/mg, p=0.031). As a result, the DOPAC/DA ratio, a measure of DA turnover, was lowest in scotopic light, but increased by ~95% in photopic light (0.14±0.01 vs. 0.27±0.07, p=0.01). Furthermore, we found that Ado was highest in scotopic light (6.17±1.39 ng/ml) followed by mesopic (3.82±0.67 ng/mg) and photopic light (2.67±0.59 ng/mg, ~57% decrease from scotopic to photopic light, p=0.041).
Conclusions :
We show that as ambient brightness increases, DA is consumed at greater levels while Ado is significantly reduced. These findings parallel previous work demonstrating opposite effects of chronic light exposure on retinal DA and Ado systems and support further study on connections between DA/Ado balance, ambient light exposure, and myopia progression.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.