Multi-biomarker approach for the evaluation of the cyto-genotoxicity of paracetamol on the zebra mussel (Dreissena polymorpha)

Paracetamol (PCM: N-(4-hydroxyphenyl)acetamide) is a widely used analgesic and antipyretic agent that is utilized in human medicine. Its use is so widespread that it is constantly being introduced into global water bodies where it reaches concentrations up to several mu g L-1. A battery of eight biomarkers was applied in the freshwater bivalve Dreissena polymorpha in order to evaluate its potential sub-lethal effect. Mussels were exposed for 96 h to increasing environmental concentrations (1, 5, 10 nM) of PCM. Cytogenotoxicity was determined in mussel hemocytes by the lysosomal membrane stability (Neutral Red Retention Assay), the single cell gel electrophoresis (SCGE) assay, the micronucleus test (MN test) and assessments of the apoptotic frequency (DNA diffusion assay). Moreover, in order to evaluate the probable alterations to the mussels' oxidative status, measurements of the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and the detoxifying enzyme glutathione S-transferase (GST) were performed using the cytosolic fraction extracted from a pool of entire mussels. The biomarker battery demonstrated moderate cyto-genotoxicity in zebra mussel hemocytes since no primary DNA fragmentation was measured by the SCGE assay and only a slight increase in fixed DNA damage was registered by apoptotic and MN frequencies. Significant destabilization of the lysosomal membrane from baseline levels was evident at 5 and 10 nM at the end of the exposures, as was a high induction capacity of the activities of CAT and GST.