Cytotoxic and genotoxic effects of in vitro exposure to Triclosan and Trimethoprim on zebra mussel (Dreissena polymorpha) hemocytes

Pharmaceuticals and personal care products (PPCPs) have been detected in several aquatic ecosystems for a number of years, but the potential for biological effects in exposed non-target organisms is only now being reported. In this study the potential cellular damage due to two of the main PPCPs found in aquatic environments was investigated by in vitro exposures. Hemolymph samples of the freshwater bivalve Dreissena polymorpha were collected and treated with increasing concentrations of the antibacterial agent Triclosan (TCS) and the antibiotic Trimethoprim (TMP). Doses selected for TCS were 0.1, 0.15, 0.2, and 0.3 µM, while 0.2, 1, and 5 µM for TMP exposures, respectively. We evaluated the potential genotoxicity on hemocytes by the SCGE (single cell gel electrophoresis) assay and apoptosis frequency evaluation, while the cytotoxicity was measured by the lysosomal membranes stability test (NRRA, neutral red retention assay). TCS genotoxicity increased in a dose-dependent manner and this pharmaceutical significantly affects hemocyte functionality due to severe DNA injuries at very low doses. In contrast, TMP seems to be less dangerous than TCS for D. polymorpha because the cytotoxic and the moderate genotoxic effects noticed were obtained only at very high concentration levels.