Negative effect of chronic cadmium exposure on growth, histology, ultrastructure, antioxidant and innate immune responses in the liver of zebrafish: Preventive role of blue light emitting diodes

The present study explored the possible preventive effects of blue light emitting diodes (LEDs) on cadmium (Cd)induced oxidative stress and immunotoxicity in zebrafish. To this end, zebrafish were exposed in a white fluorescent bulb or blue LEDs (LDB, peak at 450 nm, at an irradiance of 0.9 W/m(2)), and 0 or 30 mu g L-1 waterborne Cd for 5 weeks. Growth performance, survival rate, and hepatic histology, ultrastructure, antioxidant and innate immune responses were determined in zebrafish. Cd exposure alone reduced growth and survival rate, and induced oxidative damage and changes in histology and ultrastructure. However, Cd exposure in combination with LDB apparently relieved these negative effects. The alleviation of adverse effects might 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 kappa B (NF-kappa 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-kappa B-induced immunotoxicity and Nrf2-induced oxidative stress. Finally, for the first time, our data demonstrated that LDB could protect fish against Cd toxicity.