Oxidative stress and DNA damage in earthworms induced by methyl tertiary-butyl ether in natural soils.

Abstract

Adverse effects of methyl tertiary-butyl ether (MTBE) have been noticed at different trophic levels by international researchers. However, there was unclear evidence about its effects on oxidative stress and DNA damage in earthworms. In this study, earthworms were cultivated in various doses of MTBE (0.0mg/kg, 10.0mg/kg, 30.0mg/kg, and 60.0mg/kg) contaminated agricultural soil for 7days, 14days, 21days, and 28days, respectively. The result showed that the reactive oxygen species (ROS) content of earthworms significantly increased in MTBE treatment groups compared to the control group. In MTBE treatment groups, the activities of superoxide dismutase, catalase, peroxidase, and glutathione S-transferase were significantly activated at the exposure of 7days, which increased by 36.3-78.9%, 51.8-97.3%, 36.5-61.9%, and 12.0-54.8%, respectively. Then, the activities of these defense enzymes showed various changes following the changes in exposure times and MTBE concentrations. Especially in the 60.0mgkg-1 group, both antioxidant enzymes and GST were still significantly activated at the exposure of 14days and then significantly inhibited at the exposure of 28days. The analysis of olive tail moment showed significant DNA damage in the 10.0mgkg-1 group at the exposure of 28days, and this damage in 30.0mg/kg and 60.0mg/kg groups was found at the exposure of 7days. This result was consistent with the malondialdehyde accumulation in earthworms. Additionally, the analysis of IBRv2 showed the effects of MTBE treatments on earthworms in dose- and time-dependent manners. This study helps better to understand the effects of MTBE on soil invertebrate animals and provide theoretical support for soil protection in governing MTBE application.