Effects Of LED Spectra And Cadmium Exposure On Oxidative Stress Reaction In Zebrafish

As an effective light source,Light Emitting Diodes?LEDs?could influence the growth and development of fish by changing the spectral composition.Cadmium?Cd?,which was a source of pollution in the environment of water,had toxic effects on the growth and survival of aquatic organisms.Moreover,it even had a harmful effects on humans,such as carcinogenic and teratogenic.Although the emission of pollution sources had been controlled,it could not be completely avoided.A large number of scholars had studied the effects of cadmium pollution on fish growth,development,oxidative stress,immunity and histopathology.The study shown that cadmium could cause toxic effects of oxidative damage and immune interference by inducing oxidative stress and inhibiting immunity in fish.In order to avoid or ameliorate the negative effects of cadmium pollution,studies had begun to focus on improving the interference of metal toxicity by enhancing antioxidant defenses and immunity in fish.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.Moreover,the zebrafish was exposed to Cd and LDB for 5 weeks and analyzes for oxidative stress and immune responses.The study assessed the interaction between cadmium and LDB.The results of the study are as follows:1.The different effects of blue and red light emitting diodes on antioxidant responses in the liver and ovary of zebrafish Danio rerioThe 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 was evaluated by measuring body weight,body length,condition factor?CF?and specific growth rate?SGR?.Morphological parameters were measured including liver weight,ovarian weight,hepatosomatic index?HSI?,and gonadosomatic index?GSI?.Oxidative stress was determined by measuring lipid peroxidation?LPO?and protein carbonylation?PC?levels and investigating the protein,activity,and mRNA levels of Cu/Zn-SOD and CAT.In order to realize the management mechanism of antioxidant gene,the mRNA level of Nrf2 was also analyzed.Under LDB condition,growth maintained relatively constant,but was reduced under the LDR condition.In the liver,hepatosomatic index?HSI?and protein carbonylation?PC?increased under the LDR condition,whereas,lipid peroxidation?LPO?declined and HSI remained unchanged under the 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?GSI?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.2.The effect of LDB on cadmium-induced oxidative stress and immunotoxicityThis study investigated the effects of blue light-emitting diodes?LDB?and cadmium?Cd?on oxidative stress and immune responses in zebrafish.For this purpose,zebrafish were exposed to a white fluorescent bulb or LDB?peak at 450 nm,at an irradiance of 0.9 W/m²?,and 0 or 30?g L^-1 waterborne Cd for 5 weeks.Growth performance,survival rate,histology,ultrastructure,antioxidant and innate immune responses in liver of zebrafish were determined.Cd exposure alone reduced growth and survival rate,and induced oxidative damage.However,Cd exposure in combination with LDB apparently relieved these negative effects.The alleviation of adverse effects may result from the up-regulation of antioxidant and innate immune genes at transcriptional,translational,or post-translational levels.Cd exposure alone dramatically enhanced mRNA levels of nuclear transcription factor?B?NF-?B?and E2-related factor?Nrf2?.However,compared to Cd exposure alone,Cd exposure in combination with LDB apparently down-regulated both genes.Taken together,our results suggest that chronic Cd exposure induced a negative effect on zebrafish,possibly involved in NF-?B-induced immunotoxicity and Nrf2-induced oxidative stress.