Diflubenzuron Induces Cardiotoxicity in Zebrafish Embryos.

Diflubenzuron is an insecticide that serves as a chitin inhibitor to restrict the growth of many harmful larvae, including mosquito larvae, cotton bollworm and flies. The residue of diflubenzuron is often detected in aquaculture, but its potential toxicity to aquatic organisms is still obscure. In this study, zebrafish embryos (from 6 h to 96 h post-fertilization, hpf) were exposed to different concentrations of diflubenzuron (0, 0.5, 1.5, 2.5, 3.5 and 4.5 mg/L), and the morphologic changes, mortality rate, hatchability rate and average heart rate were calculated. Diflubenzuron exposure increased the distance between the venous sinus and bulbar artery (SV-BA), inhibited proliferation of myocardial cells and damaged vascular development. In addition, diflubenzuron exposure also induced contents of reactive oxygen species (ROS) and malondialdehyde (MDA) and inhibited the activity of antioxidants, including SOD (superoxide dismutase) and CAT (catalase). Moreover, acridine orange (AO) staining showed that diflubenzuron exposure increased the apoptotic cells in the heart. Q-PCR also indicated that diflubenzuron exposure promoted the expression of apoptosis-related genes (bax, bcl2, p53, caspase3 and caspase9). However, the expression of some heart-related genes were inhibited. The oxidative stress-induced apoptosis damaged the cardiac development of zebrafish embryos. Therefore, diflubenzuron exposure induced severe cardiotoxicity in zebrafish embryos. The results contribute to a more comprehensive understanding of the safety use of diflubenzuron.

Fenpropathrin exposure induces neurotoxicity in zebrafish embryos.

Fenpropathrin has been a commonly used insecticide to control agricultural and household insects over a few decades. Up to now, fenpropathrin residue in soil and water has been often determined due to its widespread use, which poses serious threat to environment and aquatic organisms. The potential of fenpropathrin to affect aquatic lives is still poorly understood. In this study, we used zebrafish (Danio rerio) embryo as an experimental model system to evaluate the toxicity of fenpropathrin to the development of zebrafish nervous system. Zebrafish embryos were separately exposed to fenpropathrin at the dose of 0.016 mg/L, 0.032 mg/L, 0.064 mg/L, starting at 6 h post-fertilizationhpf (hpf) up to 96 hpf. The results showed that fenpropathrin exposure gives rise to physiological, behavioral, and neurodevelopmental impairments in zebrafish embryos, including enhanced acetylcholinesterase (AChE) activity, abnormal swimming behavior, karyopyknosis in brain cells, increased intercellular space, and uneven migration of neuron in brain area. In addition, the expressions of genes concerning neurodevelopment and neurotransmitter system were inhibited following fenpropathrin exposure. We also found that fenpropathrin exposure distinctly induced oxidative stress by increasing reactive oxygen species (ROS) generation and inhibiting the production of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). Expectedly, some apoptosis-associated genes were induced and the apoptosis appeared in the brain and heart cells of zebrafish embryos. Moreover, fenpropathrin exposure also inhibited the expressions of genes in Nrf2 signaling pathway, such as heme oxygenase-1 (HO-1) and SOD. In summary, the results of this study indicate that oxidative stress-triggered apoptosis may be an underlying fundamental of fenpropathrin-induced neurotoxicity in zebrafish embryos.

Ethoprophos induces cardiac toxicity in zebrafish embryos.

Ethoprophos is an effective and widely pesticide that used in controlling nemathelminth and soil insect. However, ethoprophos has been frequently detected in environment and freshwater. The potential toxicity to aquatic organisms is still not be explored. In this study, zebrafish embryo model was used to evaluated the toxicity of ethoprophos during cardiovascular developmental process of zebrafish. Zebrafish embryos were separately exposed to 10 mg/L, 20 mg/L, 30 mg/L, 40 mg/L and 50 mg/L of ethoprophos exposure at 96 h post-fertilization (hpf), which induced cardiac defects, such as low heart rate, pericardium edema and long SV-BA distance, but had no influence to vascular development. Mechanistically, the expression of cardiac-related genes were abnormal. Moreover, ethoprophos exposure significantly increased oxidative stress in zebrafish embryos by inhibiting the production of antioxidant enzyme (SOD) and activating reactive oxygen species. Expectedly, some apoptosis genes were induced and the apoptotic cardiomyocytes were detected by acridine orange staining. In addition, ethoprophos exposure also inhibited the expression of genes in wnt signaling pathway, such as ß-catenin, Axin2, GSK3ß and Sox9b. BML284, an activator of wnt signaling pathway, can rescue the cardiotoxic effect of embryos. These results indicated that oxidative stress and blocking wnt signaling pathway were molecular basis of ethoprophos-induced injure in zebrafish. Generally, our study showed that ethoprophos exposure led to severe cardiotoxicity to zebrafish embryo.