The effects of light emission diode (LED) light exposure on retinal pigment epithelial (RPE) cells were examined to clarify the mechanisms of cellular damage or change caused by LED. The RPE cells were isolated from bovine eyes and exposed to the LED light. After exposure, cell proliferation, the lactate dehydrogenase (LDH) activity in medium, 4-hydroxy-2-nonenal (HNE) and apoptosis were determined as indicators of oxidative stress and cell injury. Also, we determined reactive oxygen species (ROS) which mediated the tissue injury in RPE cells after LED light exposure. Wavelengths of 460 nm, 620 nm or 880 nm were chosen for the examinations. Cell proliferation decreased by 24% and 15% of control by 50 J/cm2 of 460 nm LED and 620 nm LED exposure, respectively, although no change was observed at 100 J/cm2 of 880 nm LED exposure. LDH activity in the medium was increased to 50% above control by 10 J/cm2 460 nm LED light but did not increase after 620 nm LED light exposure. ROS generation was increased to 73% and 35% above control by 10 J/cm2 of 460 nm and 620 run LED exposure, respectively. After 24 hr at 10 J/cm2 of 460 nm exposure, RPE cells showed a positive staining for HNE. After 72 hr, apoptosis was not observed by 10 J/cm2 of 460 nm (1/300) and 620 nm (1/501). These results indicate that photochemical damage to RPE cells occurred at 10 J/cm2 of 460 nm and 620 nm LED light exposure, suggesting in part, mediation by mitochondrial free radical signaling and oxidative stress after LED light exposure.

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