Exposure to human pharmaceuticals Carbamazepine, Ibuprofen and Bezafibrate causes molecular effects in Dreissena polymorpha

Abstract

Carbamazepine (CBZ), Ibuprofen (IBU) and Bezafibrate (BEZ) were tested for their potential to bioaccumulate and provoke molecular changes in the non-target organism Dreissena polymorpha. mRNA changes of enzymes and other proteins involved in the prevention from protein damage (heat shock protein 70, hsp70) and oxidative stress (superoxide dismutase, SOD; catalase, CAT; metallothionein, MT), biotransformation (pi-class glutathione S-transferase, piGST; aryl hydrocarbon receptor, AH-R), elimination (P-glycoprotein, P-gp) and reversible protein posttranslational modification (protein phosphatase 2A, PP2A) served as molecular biomarkers. Mussels were exposed in a flow-through system to increasing concentrations of the three substances (1, 10, 100 and 1000 nM). The two lower concentrations correspond to environmentally relevant concentrations detected in surface and effluent waters, respectively. Measuring tissue concentration after one, four and seven days the uptake of CBZ and IBU by the mussels could be evidenced, whereas no accumulation data could be achieved for BEZ. The bioconcentration factor was highest for mussels exposed to the lowest CBZ and IBU concentrations, with 90 and 460-fold higher tissue concentration, respectively, after seven days. CBZ was the only substance tested which caused a significant increase in gill mRNA level of hsp70 after only one day exposure, evidencing the potential of CBZ to immediately provoke a stress condition and assumingly protein damage in gills. After longer exposure, mussels displayed down-regulated mRNA levels of hsp70 and SOD in gills, as well as of MT and P-gp in the digestive gland, hinting on an inhibitory character of CBZ. In IBU exposed mussels increased oxidant stress conditions were evidenced by induced mRNA levels in the digestive gland of CAT and MT, as well as SOD after one and four days, respectively. A concentration as found at sewage treatment plant effluents provoked an increase in transcript levels of piGST, suggesting enhanced need for biotransformation of IBU or by-products derived from oxidative stress. Also exposure to an environmentally relevant BEZ concentration provoked an immediate increase in piGST transcript level in the digestive gland followed by up-regulated hsp70 after four and seven days evidencing a chronic stress condition for the mussels.