Developmental toxicity of embryonic 1-naphthol exposure in zebrafish

Abstract

Objective To investigate the toxic effects of embryonic exposure to 1-naphthol (1-NAP) on zebrafish development and explore the possible mechanism. Methods Fertilized zebrafish eggs were exposed to 1-NAP at the concentrations of 40, 80, 160 and 200 μmol/L on 24 h post fertilization (hpf). The numbers of zebrafish malformations and deaths were recorded at 120 hpf, and the deformity rate, hatching rate and the median lethal concentration (IC50) of 1-NAP were calculated. The hatched zebrafish with or without embryonic exposure to 50 μmol/L 1-NAP and pretreatment with N-acetylcysteine (NAC) were examined for levels of reactive oxygen species (ROS), malondialdehyde (MDA), reduced glutathione (GSH), total sulfhydryl, and activities of superoxide dismutase (SOD) and catalase (CAT); Western blotting was performed to detect the expression of Caspase-3 and Bax. Results The IC50 of 1-NAP in zebrafish embryos was 111.31 μmol/L, and the zebrafish embryos exposed to high-concentration (>80 μmol/L) 1-NAP exhibited obviously increased mortality and deformity rates with a significantly reduced hatching rate, demonstrating significant developmental toxicity of 1-NAP. Embryonic exposure to 50 μmol/L 1-NAP significantly increased the levels of ROS and MDA, lowered the levels of GSH and total sulfhydryl, suppressed the activities of antioxidant enzymes CAT and SOD (P < 0.001), and decreased the expression levels of Caspase-3 and Bax in the hatched zebrafish. The zebrafish embryos pretreated with 0.5 mmol/L NAC prior to 1-NAP exposure showed a significantly decreased abnormality rate with obviously lowered ROS and MDA levels, restoration of GSH and total sulfhydryl content and SOD and CAT activities, and obviously reduced expression levels of Caspase-3 and Bax. Conclusion The developmental toxicity of 1-NAP in zebrafish embryos is probably associated with enhanced oxidative stress induced by 1-NAP.

Keywords

• zebrafish
• embryonic stage
• 1-naphthol
• developmental toxicity
• oxidative stress