Different effects of blue and red light-emitting diodes on antioxidant responses in the liver and ovary of zebrafish Danio rerio

The present study assessed the effects of a white fluorescent bulb (the control) and two different light-emitting diodes (blue LEDs, LDB; red, LDR) on growth, morphology, and oxidative stress in the liver and ovary of zebrafish for 5 weeks. Growth maintained relatively constant under LDB condition, but was reduced under LDR condition. In the liver, hepatosomatic index (HSI) and protein carbonylation (PC) increased under LDR condition, whereas lipid peroxidation (LPO) declined and HSI remained unchanged under LDB condition. The decrease in oxidative damage by LDB could be attributed to the up-regulated levels of mRNA, protein, and activity of Cu/Zn-SOD and CAT. A failure to activate the activity of both enzymes may result in the enhanced PC levels under LDR condition, though both genes were up-regulated at transcriptional and translational levels. In the ovary, although gonadosomatic index sharply increased under LDR condition, LPO and PC dramatically accumulated. The increase in oxidative damage by LDR might result from the down-regulated levels of protein and activity of Cu/Zn-SOD and CAT, though both genes were up-regulated at a transcriptional level. Furthermore, a sharp increase in expression of transcription factor Nrf2 that targets antioxidant genes was observed in the liver but not in the ovary under LDB and LDR conditions. In conclusion, our data demonstrated a positive effect of LDB and negative effect of LDR on fish antioxidant defenses, emphasizing the potentials of LDB as an effective light source in fish farming.