Cytotoxic action induced by single and combined exposure of realistic doses of caffeine and salicylic acid in mussel Mytilus galloprovincialis

The consumption of active pharmaceutical products (PhACs) has increased globally.1 Most of the PhACs are not fully metabolized, and so are excreted in an active form. Due to the inadequacy of wastewater treatment plants (WWTPs) towards all types of PhACs,2 these compounds easily reach the aquatic environment, becoming potential micropollutants for biota. Among PhACs, caffeine (CAF), a nervous stimulant, and salicylic acid (SA), a nonsteroidal anti-inflammatory drug (NSAID), are the most abundant.3 Therefore, their single and combined (SA+CAF) effects were evaluated at different time-points on the filter-feeder mussel Mytilus galloprovincialis following a short-term exposure at their environmentally relevant concentrations (ng/L-μg/L) for 12 days, selecting the digestive gland as target organ. Absence of histomorphological damage parallelly with haemocyte infiltration highlighted an inflammatory response and activation of systemic defensive mechanisms in response to the tested PhACs. This was also supported by induction of the oxidative stress pathway, as revealed by the modulated activity and gene expression of a battery of oxidative stress end-points (SOD, CAT, GST). It is interesting to note that, under realistic conditions, the two compounds alone provoked the most pronounced effects whereas, when combined, the stimulating action of CAF was compensated by the inhibitory action of SA. Overall, these results enlarge knowledge on pharmaceuticals effects on non-target organisms and emphasize the need for proper environmental risk assessment finalized to enhance the efficacy of WWTPs towards PhACs