Abstract
Purpose :
Patients suffering from Dry Eye Disease (DED), one of the most common ocular pathologies, frequently complain of exacerbated photosensitivity and increased DED symptoms when exposed to light. However, the mechanisms involved in the relationship between DED and light exposure are still not clear. In this study, we investigated the cytotoxicity of visible light on epithelial cells of the ocular surface.
Methods :
Human epithelial cell lines of cornea (HCE) and conjunctiva (IOBA) were illuminated by 10nm wavebands centered at 390, 420, 430, 480 and 630 nm of average intensity of 1.1mW/cm2 for 17 hours. Control cells were kept in the dark. Hyperosmolar (HO) stress, commonly used for in vitro DED models, was induced 7 hours before the beginning of exposure. Light cytotoxicity was assessed by measuring cellular viability, reactive oxygen species (ROS) production (H2O2 and O2-), mitochondrial membrane potential and level of glutathione.
Results :
At the end of light exposure,for both cell lines, the viability significantly decreased under 390 and 420 nm; this decline was more pronounced after HO stress. After 4 or 24 hours in the dark after exposure, HCE viability mostly recovered whereas IOBA cells' viability did not. Accordingly, H2O2 production drastically increased at 390nm but weakened in 24 hours for both cell lines. Mitochondrial O2- significantly rose at 390nm. Under HO stress, ROS generation was enhanced for IOBA cells but not for HCE. Mitochondrial membrane potential of both cell types decreased at 390nm. For IOBA cells, significant changes at 420, 430 and 480 nm also appeared. In parallel, the level of total and oxidized glutathione increased after light exposure and was modulated by HO stress.
Conclusions :
Light induced a cytotoxic effect on ocular surface cells, mainly at 390nm wavelength, leading to a significant cell viability decline and to an increase in ROS production reported to play an important role in ocular surface inflammation. Thus, both cell types suffered from higher phototoxicity when exposed to a more energetic violet light. Conjunctival cells appeared to be more sensitive to light than the corneal ones. Hyperosmolar stress influenced the induced phototoxic impact, suggesting that patients already suffering from DED might be more prone to light toxicity.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.