Optimization of green LED light intensity for accelerating wound healing in olive flounder Paralichthys olivaceus (Temminck et Schlegel)

Recent studies showed that green wavelength light-emitting diodes (LEDs) were effective for wound healing in various animal models, including olive flounder. However, determining the optimal light intensity for phototherapy is very important for accelerating wound healing and safety. Therefore, the purpose of this study was to investigate the optimal intensity of green LEDs (520 nm) for accelerating wound healing using olive flounder Paralichthys olivaceus. In vitro studies, a Paralichthys olivaceus-derived embryo cell line (Hirame natural embryo cells; HINAE) was used to verify the proliferative effects of various intensities (20, 40, 80, and 120 mu mol center dot m(-2)center dot s(-1)) of green LED (520 nm) light in 24-h light for seven days. In vivo studies, artificial wounds (4 mm in diameter) were made in flounders using a biopsy punch, and the wounds were exposed to green LED (520 nm) light at 20, 40, and 60 mu mol center dot m(-2)center dot s(-1), as well as ambient light as a control, in 12-h light/ dark cycles for 28 days. The results showed that 520 nm LED treatment at 40 mu mol center dot m(-2)center dot s(-1) significantly stimulated HINAE cell proliferation relative to ambient light (3 +/- 1 mu mol center dot m(-2)center dot s(-1)) and the 20, 80 and 120 mu mol center dot m(-2)center dot s(-1) LED intensity groups. The relative wound healing rate of fish exposed to 40 mu mol center dot m(-2)center dot s(-1) of green LED light was significantly higher than that of the other groups and showed a high expression of wound healing-related genes such as matrix metalloproteinase (mmp)-9, mmp-13, epidermal growth factor (egf), and vascular endothelial growth factor (vegf)-a. After the in-juries, the survival rate of fish exposed to 520 nm LED light at an intensity of 60 mu mol center dot m(-2)center dot s(-1) was markedly lower (82%) than those of the control and 20 and 40 mu mol center dot m(-2)center dot s(-1)-treated groups (over 95%). Stress-related factors such as catalase and superoxide dismutase (SOD) in the fish wound areas and serum glucose levels were significantly increased in the 60 mu mol center dot m(-2)center dot s(-1) exposure group, showing that prolonged exposure to strong light intensity could negatively affect physiology and wound healing. Therefore, the results showed that 40 mu mol center dot m(-2)center dot s(-1) intensity green LED (520 nm) light was the most effective light condition for accelerating wound healing in olive flounder.