Exposure and coexposure to cocaine and benzoylecgonine at environmentally relevant levels cause long-term oxidative effects in zebrafish.

Cocaine (COC) and its main metabolite, benzoylecgonine (BE), have been detected in water bodies worldwide and may have unknown biota effects. This is especially true considering chronic effects at environmentally relevant concentrations (μg and ng L-1 range) on the Danio rerio (zebrafish) model. In this sense, this study exposed adult zebrafish for 21 days to COC (10-1000 ng L-1), BE (10-1000 ng L-1) and mixtures (COC 10 + BE 1000 ng L-1 and COC 1000 + BE 10 ng L-1) and evaluated antioxidant and oxidative effect biomarkers. Superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), total thiols (TOT), lipid peroxidation (LPO) and protein carbonylation (PC) were determined in the brains and livers of exposed fish at 7, 14 and 21 days. Antioxidant biomarker modulations were observed in exposed fish, noted by increased SOD activity and TOT levels at 7 days in both organs. Increased SOD and GST activities and TOT levels were observed in the brain at 21 days, while the same induction was observed in the liver for CAT, GST and TOT. Greater oxidative effects were observed in the brain, with increased MDA and PC levels observed at 21 days. Oxidative effects in the liver were observed up to 14 days. The findings reveal that COC and BE can cause oxidative damage in aquatic organisms during 21 days of exposures, potentially affecting natural environments and leading to ecological risks, even at environmental concentrations commonly found in surface waters.