Toxicity of single and combined 4-epianhydrotetracycline and cadmium at environmentally relevant concentrations on the zebrafish embryos

The combined pollution of antibiotics and heavy metals has attracted a worldwide attention in the recent years. 4-epianhydrotetracycline (EATC) is the major degradation product of tetracycline (TC), which has been detected frequently in environment and its concentration is even higher than TC under some circumstances. Cadmium (Cd) is a common heavy metal contaminant and has highly toxic to organisms, plants and humans even at low doses. In the present study, zebrafish (Danio rerio) embryo toxicity test was performed to investigate the single and combined effects of EATC and Cd on aquatic organisms. Exposure to EATC and Cd at environmentally relevant concentrations had a series of hazardous impacts on the embryonic development, including lethality, hatching rate, heart rate and teratogenic effects. Compared to the contaminant existed alone, combined pollution produced stronger toxicity, which appeared as the decreasing of heart rate and hatching rate, and the increasing of malformation of zebrafish embryos. After 96 h exposure, the reactive oxygen species (ROS) levels in zebrafish embryos were increased significantly, revealing that EATC-Cd co-exposure resulted in potential oxidative stress -induced damage. Acridine orange (AO) staining showed that combined exposure resulted in stronger cell apoptosis. The potential health risks of the combined pollution of EATC and Cd should be paid more attention to higher level vertebrates and humans.

Automated summary

The combined pollution of antibiotics and heavy metals has harmful effects on the embryonic development of aquatic organisms, particularly zebrafish. The toxicity of the combined pollution is stronger than that of individual contaminants and leads to decreased heart rate, hatching rate, and increased malformation of zebrafish embryos. The co-exposure to antibiotics and heavy metals also results in oxidative stress-induced damage and increased cell apoptosis. This study highlights the importance of paying attention to the potential health risks of combined pollution for higher vertebrates and humans.