Antioxidant metabolism of zebrafish after sub-lethal exposure to graphene oxide and recovery

Graphene oxide (GO) is a carbon nanomaterial with specific properties, which allow its use in several areas. Some studies have characterized the effects of GO on aquatic organisms, but the ability of recovery after exposure remains largely unknown. In this study, we evaluated the effects of GO on the antioxidant metabolism of zebrafish after 48 h of sub-lethal exposure, and the fish recovery after 168 h in nanoparticle-free water. After the sub-lethal exposure, superoxide dismutase (SOD) activity was significantly increased in 20 mg L-1, as well as catalase (CAT) activity in 2, 10, and 20 mg L-1, and the lipid peroxidation (LPO) had an increase in 2 mg L-1. On other hand, the glutathione peroxidase (GPx) activity was inhibited at 20 mg L-1. After 168 h of recovery in clean water, the SOD activity remained significantly increased in 20 mg L-1; the CAT activity was unchanged in all tested concentrations; the GPx activity was inhibited in 2, 10, and 20 mg L-1; and the LPO significantly decreased in 2 mg L-1. Our study suggests that GO exposure disrupts the antioxidant metabolism of adult zebrafish. Even after 168 h of recovery in clean water, homeostasis was not completely restored, although organisms developed mechanisms of recovery, and toxic effects were more subtle. Our results are pivotal to better understanding the physiological mechanisms involved in the detoxification process after GO exposure, and for strategies of protection on fish species. (AU)