Effects of 4-epianhydrotetracycline on oxidative stress in zebrafish (Danio rerio) embryos

4-Epianhydrotetracycline (4-EATC) is a major intermediate product of tetracycline during its degradation progress in the natural environment, which is frequently detected in aquatic environments and poses a potential threat to aquatic organisms. In the present study, the ecotoxicity of 4-EATC have been studied from the perspective of oxidative stress by using zebrafish embryos. After 96 h exposure, the reactive oxygen species (ROS) levels, malondialdehyde (MDA) concentrations and protein carbonyl (PC) contents in zebrafish embryos in the lower concentration 4-EATC treatment groups (1.25 mg/L and 2.50 mg/L) showed no significant differences compared with the negative control group. However, the total superoxide dismutase (SOD) activity was increased significantly. After exposed to the higher-concentration of 4-EATC (5.00, 10.0 and 20.0 mg/L) resulted in a significant increase in ROS levels, MDA concentrations and PC contents, in contrast, a significant decrease in SOD activities. The results indicate that exposure to high concentrations of 4-EATC (5.00, 10.0 and 20.0 mg/L) could disrupt the redox equilibrium in zebrafish embryos, leading to the occurrence of oxidative damage. Apoptosis of the embryonic cells could be induced by 4-EATC exposure at different concentration and the rate of apoptosis enhanced with the increase of 4EATC concentration. The pericardium was the most frequent site of apoptosis. The present study points out that more attention should be paid to the potential ecological risks of antibiotic degradation products. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

4-EATC, a major intermediate product during tetracycline degradation, was studied for ecotoxicity in zebrafish embryos. Low concentrations did not significantly affect oxidative stress, while high concentrations led to oxidative damage and increased apoptosis rates in embryonic cells.