Wavelength-dependency of the impact of light on proliferation and DNA damage of corneal cells in vitro

The wavelength-dependent impact of light has been mainly studied focusing on retina. In particular, an opposite effect of the two ends of the visible spectrum was observed, with blue wavelengths being harmful and red wavelengths being protective. However, few studies on the cornea indicate that the increasing exposition to artificial light due to digital devices is linked to an increase in computer vision syndrome affecting the cornea. In this study, we aim at deciphering the impact of blue and red LED light on a primary culture of corneal endothelial cells, by looking at cell death and proliferation, and at DNA replication and DNA breaks. Our results show that exposure to blue light at 5.35 J/cm² (455 nm) induces the inhibition of DNA replication and cell proliferation, and the formation of DNA breaks, highlighted by the formation of γH2AX foci and DNA fragmentation. Addition of red light at 0.3 J/cm² (630 nm) to blue light mitigates the formation of DNA damage and delays the kinetics of formation and repair of the damage. Interestingly, exposure of the corneal cells to red light alone induces the formation of γH2AX foci that do not correspond to DNA breaks, but to DNA replication forks in proliferative cells. Our results highlight the wavelength-dependent effect of light on the cornea, and point out that the formation of γH2AX foci is not always representative of DNA breaks. This emphasizes the importance of light spectrum in eye health, an important issue in today's changing light environment.