Combined Effects of Fluoride and Dietary Seleno-L-Methionine at Environmentally Relevant Concentrations on Female Zebrafish (Danio rerio) Liver: Histopathological Damages, Oxidative Stress and Inflammation

Fluoride, a global environmental pollutant, is ubiquitous in aquatic environments and coexists with selenium, which can cause complex effects on exposed organisms. However, data on the interaction of fluoride and selenium remain scarce. In this study, female zebrafish (Danio rerio) were exposed to fluoride (80 mg/L sodium fluoride) and/or dietary selenomethionine (Se-Met) for 30, 60 and 90 days, the effects on the liver of zebrafish were investigated. The results indicated that an increase in fluoride burden, inhibited growth and impaired liver morphology were recorded after fluoride exposure. Furthermore, fluoride alone caused oxidative stress and inflammation in the liver, as reflected by the increase in ROS and MDA contents, the reduction of anti-oxidative enzymes, the altered immune related enzymes (ACP, AKP, LZM and MPO) and the expression of IL-6, IL-1 ss, TNF-alpha, IL-10 and TGF-ss. In contrast, co- exposure to fluoride and Se-Met decreased fluoride burden and restored growth. Furthermore, dietary Se-Met alleviated oxidative stress, inflammation and impaired morphology in liver trigger by fluoride. However, dietary Se-Met alone increased the activities of SOD and CAT. These results demonstrate that the protective effect of dietary Se-Met against chronic fluoride toxicity at a certain level.