Blue light-induced oxidative stress in human corneal epithelial cells: protective effects of ethanol extracts of various medicinal plant mixtures.

To investigate the effects of visible light on human corneal epithelial cells and the impact of natural antioxidants on oxidative stress produced by overexposure to light. Light-emitting diodes with various wavelengths (410-830 nm) were used to irradiate human corneal epithelial cells, and cell viability was assessed. The production of reactive oxygen species (ROS) was analyzed using 2',7'-dichlorodihydrofluorescein diacetate (DCF-DA). Ethyl alcohol (EtOH) extracts were prepared from mixtures of medicinal plants. After application of the EtOH extracts, the free radical scavenging activity was measured using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. The induction of antioxidant enzymes including heme oxygenase-1 (HO-1), peroxiredoxin-1 (Prx-1), catalase (CAT), and superoxide dismutase-2 (SOD-2) by the extracts was evaluated by reverse transcription-polymerase chain reaction and Western blotting. The ability of the extracts to inhibit ROS was also analyzed using DCF-DA. The viability of corneal epithelial cells was diminished after irradiation of blue light (above 10 J at 410 nm and 50 J at 480 nm). Reactive oxygen species production was induced by irradiation at 410 and 480 nm at doses of 5 J/cm(2) and higher. Ethyl alcohol extracts had potent radical scavenging activity. Application of the extracts not only increased the expression of HO-1, Prx-1, CAT, and SOD-2, but it also attenuated the ROS production induced by blue light in a dose-dependent manner. Overexposure to blue light (410-480 nm) may have a harmful effect on human corneal epithelial cells compared with other visible light wavelengths. Medicinal plant extracts can have potent protective effects on blue light-induced oxidative stress.