Evaluation of ecotoxicological effects of drugs on Daphnia magna using different enzymatic biomarkers

Abstract

The increasing occurrence of pharmaceutical drugs in the aquatic environment is cause of concern, due to the possibility of toxic phenomena in non-target species, including oxidative stress and neurotoxicity. The present study aimed to assess the acute effect of four widely used therapeutic agents: acetaminophen (analgesic), chlorpromazine (antipsychotic), diclofenac (anti-inflammatory) and propranolol (antihypertensive), in the cladoceran species Daphnia magna. Considering the involvement of the mentioned compounds in the impairment of cholinesterasic activity and modifications in cellular redox systems, the purpose of this study was to analyze their effects on biomarkers of neuronal regulation, such as total cholinesterases (ChEs), and enzymatic oxidative stress defense, including as catalase (CAT), glutathione-S-transferases (GSTs), and total and selenium-dependent glutathione-peroxidase (total GPx; Se-GPx) activities. Exposure to acetaminophen caused a significant inhibition of AChE and Se-GPx activities in D. magna relative to the control. Among the biomarkers of oxidative stress, only the activity of CAT was significantly altered in concentration of 0.001 mg L−1 of chlorpromazine, which was not always consistent with the literature. Diclofenac caused a significant inhibition of AChE and Se-dependent GPx, and also in total GPx activities. Propranolol was responsible for a significant decrease in the activity of the latter two enzymes, and also a slight increase of GSTs activity. The results indicated that the exposure to all the tested compounds induced alterations on the cellular redox status in the studied species. In addition, acetaminophen and diclofenac were shown to have the capability of interfering with D. magna neurotransmission, through the inhibition of ChEs. Our data enlighten the need for more research on the ecological consequences of pharmaceuticals in non-target organisms.