Hediste diversicolor as bioindicator of pharmaceutical pollution: Results from single and combined exposure to carbamazepine and caffeine

• Caffeine and carbamazepine induced oxidative stress on Hediste diversicolor.
• Polychaetes increased LPO levels and the activity of biotransformation enzymes (GSTs, CYP3A4).
• At higher concentrations ETS activity decreased, increasing glycogen content.
• Impacts induced by individual or combined exposures were similar.

Several environmental stressors have been identified as key and/or emerging drivers of habitat change that could significantly influence marine near-shore ecosystems. These include increasing discharges of pharmaceutical contaminants into the aquatic coastal systems. Pharmaceutical drugs are often detected in aquatic environments but still information on their toxicity impacts on inhabiting species is scarce, especially when acting in combination. Furthermore, almost no information is available on the impacts of pharmaceuticals in polychaetes, often the most abundant taxon in benthic communities and commonly used as indicator species of environmental conditions. Therefore, the present study aimed to evaluate the biochemical alterations induced in the polychaete Hediste diversicolor, from a low contaminated area at the Ria de Aveiro lagoon (Portugal), by the antiepileptic drug carbamazepine (0.0 - control, 0.3, 3.0, 6.0 and 9.0 μg/L) and the stimulant caffeine (0.0 - control, 0.5, 3.0, and 18.0 μg/L), acting alone and in combination (0.3 CBZ + 0.5 CAF and 6.0 CBZ + 3.0 CAF). Glutathione S-transferases (GSTs), superoxide dismutase (SOD) and catalase (CAT) activities was determined in Hediste diversicolor from each condition. Lipid peroxidation (LPO), glutathione reduced and oxidized (GSH and GSSG), glycogen and electron transport system (ETS) were also measured. The results obtained clearly revealed that both drugs induced oxidative stress in H. diversicolor, shown by the increase on LPO levels and decrease on total glutathione and GSH/GSSG ratio with the increase of exposure concentrations. Furthermore, the present findings demonstrated that polychaetes biotransformation capacity as well as antioxidant defense mechanisms were not sufficiently efficient to fight against the excess of reactive oxygen species (ROS) leading to LPO when organisms were exposed to both drugs. Our results also demonstrated that polychaetes tended to decrease the activity of ETS when exposed to drugs, avoiding energy expenditure which may prevent them from greater damages. The present study further revealed that the impacts induced by the combination of both drugs were similar to those obtained at the highest drugs concentrations acting alone.