An exploratory investigation of various modes of action and potential adverse outcomes of fluoxetine in marine mussels

• Published in: Aquatic toxicology Vol. 151; pp. 14 - 26
• Main Authors: Franzellitti, Silvia, Buratti, Sara, Capolupo, Marco, Du, Bowen, Haddad, Samuel P., Chambliss, C. Kevin, Brooks, Bryan W., Fabbri, Elena
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2014
• Subjects: Adverse outcome pathway; Animals; Aquatic Organisms - drug effects; Biomarkers; cAMP signaling; Digestive System - drug effects; Enzyme Activation - drug effects; Fluoxetine; Fluoxetine - toxicity; Gene Expression Regulation - drug effects; Gills - drug effects; Hemocytes - drug effects; Liver - drug effects; Marine mussel; Mode of action; Mytilus - drug effects; Mytilus galloprovincialis; Protein Binding - drug effects; Water Pollutants, Chemical - toxicity; Biomarkers; Marine mussel; cAMP signaling; Fluoxetine; Mode of action; Adverse outcome pathway
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2013.11.016

•Mode of action (MOA) related endpoints and biomarkers of toxicity were assessed in mussels exposed to fluoxetine (FX).•Significant FX bioaccumulation was observed in tissues of mussels exposed to 30 and 300ng/L FX.•Alterations of cAMP-related cell signaling were observed in exposed mussels as part of the MOA of FX.•FX reduced the health status of mussels inducing lysosomal effects in digestive gland and antioxidant responses in gills.•The importance of considering additional MOAs and adverse outcome pathways for FX impacts on mussels is highlighted. The present study investigated possible adverse outcome pathways (AOPs) of the antidepressant fluoxetine (FX) in the marine mussel Mytilus galloprovincialis. An evaluation of molecular endpoints involved in modes of action (MOAs) of FX and biomarkers for sub-lethal toxicity were explored in mussels after a 7-day administration of nominal FX concentrations encompassing a range of environmentally relevant values (0.03–300ng/L). FX bioaccumulated in mussel tissues after treatment with 30 and 300ng/L FX, resulting in bioconcentration factor (BCF) values ranging from 200 to 800, which were higher than expected based solely on hydrophobic partitioning models. Because FX acts as a selective serotonin (5-HT) re-uptake inhibitor increasing serotonergic neurotransmission at mammalian synapses, cell signaling alterations triggered by 5-HT receptor occupations were assessed. cAMP levels and PKA activities were decreased in digestive gland and mantle/gonads of FX-treated mussels, consistent with an increased occupation of 5-HT1 receptors negatively coupled to the cAMP/PKA pathway. mRNA levels of a ABCB gene encoding the P-glycoprotein were also significantly down-regulated. This membrane transporter acts in detoxification towards xenobiotics and in altering pharmacokinetics of antidepressants; moreover, it is under a cAMP/PKA transcriptional regulation in mussels. Potential stress effects of FX were investigated using a battery of biomarkers for mussel health status that included lysosomal parameters, antioxidant enzyme activities, lipid peroxidation, and acetylcholinesterase activity. FX reduced the health status of mussels and induced lysosomal alterations, as suggested by reduction of lysosomal membrane stability in haemocytes and by lysosomal accumulation of neutral lipids in digestive gland. No clear antioxidant responses to FX were detected in digestive gland, while gills displayed significant increases of catalase and glutathione-s-transferase activities and a significant decrease of acetylcholinesterase activity. Though AOPs associated with mammalian therapeutic MOAs remain important during assessments of pharmaceutical hazards in the environment, this study highlights the importance of considering additional MOAs and AOPs for FX, particularly in marine mussels.