Effects of the pharmaceuticals propranolol and fluoxetine evaluated through a battery of biomarkers in the Mediterranean mussel (Mytilus galloprovincialis)

Widespread occurrence of pharmaceuticals is reported in aquatic systems worldwide, posing concerns for the health of aquatic wildlife and a theoretical risk to humans. Pharmaceuticals are designed to have specific (therapeutic) effects at low doses and might have side effects at high doses or after prolonged exposure, which could be induced also in non target organisms. In parallel with studies on specific interactions with molecular targets to understand their mechanism of action (MOA), we investigated the alterations induced by fluoxetine (FX) and propranolol (PROP), alone or in combination (MIX) on Mediterranean mussels, Mytilus galloprovincialis, based on unspecific side effects caused in humans. Mussels were exposed for 7 days to the pharmaceuticals, each at 0.3 ng/L concentration selected as environmentally relevant. A battery of 10 biomarkers was then evaluated. Considering the most relevant results, lysosome membrane stability was strongly decreased, while lysosome/cytosol ratio was increased by all treatments. FX and MIX increased both accumulation of lipofuscins and neutral lipids, while PROP significantly increased only neutral lipid accumulation. PROP, but not FX and MIX, increased glutathione-S-transferase and catalase activities. EROD and DBF activities were significantly reduced by all treatments. Mussels exposure to the pharmaceuticals did not induce DNA damage, evaluated by the Hoechst methodology. In conclusion, FX and PROP caused significant stress at environmentally relevant concentrations. Their action is primarily through oxidation pathways with significant destabilization of the lysosomal membrane, which has been shown to be directly correlated with scope for growth reduction in molluscs. In conclusion biomarker expression is a sensitive endpoint, useful to detect the effects of substances, such as pharmaceuticals, present at low concentrations in the environment