Antioxidant defenses and metabolic responses of blue mussels (Mytilus edulis) exposed to various concentrations of erythromycin.

Erythromycin, one of the most widely used macrolide antibiotics, has been detected in various aquatic environments, so erythromycin ecotoxicity should deserve more attention. In this study, blue mussels (Mytilus edulis) were exposed to erythromycin to explore its potential physiological toxicity. After 2d acute and 7d sub-acute exposure to erythromycin, blue mussel glutathione S-transferase (GST) and catalase (CAT) activities were determined with microplate methods and metabolic responses were analyzed using H-1 nuclear magnetic resonance (H-1 NMR). The results revealed that GST was approximately 1.6 times higher in exposed mussels at 200 mg/L and higher concentrations. CAT was about 1.9 times higher in exposed mussels at 200 mg/L, indicating that erythromycin exposure led that blue mussels enhanced antioxidant responses. Low doses of erythromycin exposure had a relatively small impact on the metabolism, while high doses of erythromycin exposure (200 and 400 mg/L) disturbed metabolic balance. With the increase of erythromycin concentrations, the individual metabolic differences within the same treatment groups also increased. The significant increase in alanine, glutamate, taurine, glycine and betaine were observed after acute and subacute exposure. Betaine played an important role in protecting antioxidant enzyme activities through adjusting osmotic pressure. The metabolomic results also showed the modes of erythromycin acted on the energy metabolism, osmoregulation, nerve activities and amino acid metabolism. This study highlighted how metabolomics can provide a comprehensive picture of metabolic responses, although significant antioxidant and metabolic responses were observed at high exposure concentrations. (C) 2019 Elsevier B.V. All rights reserved.