Effects Of Blue LEDs Pre-exposure On Oxidative Stress And Immunity In Zebrafish Exposed To Cadmium

Cadmium(Cd²⁺)is an environmental contaminant that poses serious risks to antioxidant and immune systems of aquatic organisms.Contrarily,blue light emitting diodes?LDB?possess the potential to relieve oxidative stress and promote immunity in fish.Thus,the present hypothesis is that LDB pre-exposure will lead to amelioration of Cd-induced oxidative stress and immunotoxicity in zebrafish.To the end,zebrafish were pre-exposed to a white fluorescent bulb or LDB?peak at 450 nm,at an irradiance of 0.9W/m²?for 4 weeks,and then exposed to 0.97 mg/L Cd²⁺for 4 days.In the ovary,Cd exposure alone increased the levels of malondialdehyde?MDA?and nitric oxide?NO?,up-regulated related genes at mRNA or activity levels,including copper and zinc superoxide dismutase?Cu/Zn-SOD?,catalase?CAT?,inducible nitric oxide synthase?iNOS?,and ciclooxigenase-2?COX-2?,tumor necrosis factor alpha?TNF-??.However,Cd exposure in accompanition with LDB acclimation did not significantly affect these indicators in the ovary.In the liver,although Cd exposure alone or with LDB acclimation increased MDA and NO levels and the activity levels of iNOS and COX-2,LDB acclimation mitigated Cd-induced disturbance of Cu/Zn-SOD,CAT,iNOS,COX-2 and TNF-?at mRNA levels.In the ovary and liver,Cd exposure alone dramatically enhanced mRNA levels of nuclear transcription factor?B?NF-?B?and E2-related factor?Nrf2?.However,Cd exposure in combination with LDB acclimation did not affected expression of both transcription factors.The corresponding changes in the mRNA levels of Kelch-like-ECH-associated protein 1?Keap1a and Keap1b?and the inhibitor of?B??I?B?a and I?B?b?may contribute to regulate the transcriptional activity of Nrf2 and NF-?B,respectively.In conclusion,we demonstrated for the first time blue spectra acclimation could protects against Cd-induced oxidative stress and immunotoxicity via suppressing Nrf2 and NF-?B signaling pathways in fish.