Environmentally relevant lead (Pb) water concentration induce toxicity in zebrafish (Danio rerio) larvae

Early developmental stages of aquatic organisms including fish are inherently vulnerable to lead (Pb) and other water metal contaminants. However, reports on the deleterious effects of environmentally relevant Pb levels are limited. To this end, we exposed 2.5 h post fertilization (hpf) old zebrafish (Danio rerio) embryos to a range of Pb concentrations encompassing environmentally relevant levels (1, 10, 25, 50 and 100 μg/L Pb) until 96 hpf. Exposure negatively impacted the development and survival of zebrafish embryos by inducing embryo coagulation related mortalities in a concentration-dependent manner. At 24 hpf, the highest level of exposure (100 μg/L Pb) had impaired embryo activity characterized by reduced burst activity and the number of movements per minute made by embryos. At 72 hpf, newly hatched larvae exhibited adverse cardiovascular effects (100 μg/L Pb group) and neuromuscular effects (50 and 100 μg/L Pb groups). The antioxidant system dysregulation evidenced by downregulation of catalase, and upregulation of mRNA expression of glutathione S-transferase and cytochrome oxidase subunit I were observed. The pro-apoptotic tumour protein P53 (TP53) and the anti-apoptotic B cell lymphoma −2 (Bcl-2) mRNA expression levels were also affected. The former was downregulated across exposed groups and the latter was upregulated and downregulated in the groups with Pb concentrations less than 50 μg/L Pb and downregulated in 50 μg/L Pb, respectively. These findings suggest that Pb within environmentally relevant levels may be deleterious to developing zebrafish.