Contents lists available at ScienceDirect Aquatic Toxicology journal homepage: www.elsevier.com/locate/aqtox Dechlorane Plus induces oxidative stress and decreases cyclooxygenase activity in the blue mussel Pierre-Luc Gagné a,b , Marlène Fortier c , Marc Fraser b,c , Lise Parent b,d , Cathy Vaillancourt b,c , Jonathan Verreault a,b, ⁎ a Centre de recherche en toxicologie de l’environnement (TOXEN), Département des sciences biologiques, Université du Québec à Montréal, C.P. 8888, succursale Centre- ville, Montreal, QC, H3C 3P8, Canada b Center for Interdisciplinary Research on Well-Being, Health, Society and Environment (CINBIOSE), Université du Québec à Montréal, C.P. 8888, Succursale Centre-ville, Montreal, QC, H3C 3P8, Canada c INRS-Institut Armand-Frappier, Université du Québec, 531 boulevard des Prairies, Laval, QC, H7V 1B7, Canada d Département Science et Technologie, Télé-université (TÉLUQ), 5800 rue Saint-Denis, bureau 1105, Montreal, QC, H2S 3L5, Canada ARTICLE INFO Keywords: Dechlorane plus Flame retardant Blue mussel Cyclooxygenase Lipid peroxidation DNA damage ABSTRACT Dechlorane Plus (DP) is a chlorinated flame retardant used mainly in electrical wire and cable coating, computer connectors, and plastic roofing materials. Concentrations of DP (syn and anti isomers) are increasingly being reported in aquatic ecosystems worldwide. However, there is exceedingly little information on the exposure- related toxicity of DP in aquatic organisms, especially in bivalves. The objective of this study was to investigate the in vivo and in vitro effects of DP exposure on histopathology, lipid peroxidation (LPO) levels, cyclooxygenase (COX) activity, phagocytosis capacity and efficiency, and DNA strand breakage in the blue mussel (Mytilus edulis) following a 29 days exposure (0.001, 0.01, 0.1 and 1.0 μg DP/L). Blue mussels accumulated DP in muscle and digestive gland in a dose-dependent manner. LPO levels in gills were found to increase by 82% and 67% at the 0.01 and 1.0 μg DP/L doses, respectively, while COX activity in gills decreased by 44% at the 1 μg/L dose. No histopathological lesion was found in gonads following DP exposure. Moreover, no change in hemocyte DNA strand breakage, phagocytosis rate, and viability was observed following DP exposure. Present study showed that toxicity of DP may occur primarily via oxidative stress in the blue mussel and potentially other bivalves, and that gills represent the most responsive tissue to this exposure. 1. Introduction Dechlorane Plus (DP) is a highly chlorinated compound that has been manufactured over the last 40 years as a replacement to Dechlorane (Mirex) (Fang et al., 2014) and is mainly used today as flame retardant (Wang et al., 2016). DP is synthesized by a Diels-Alder reaction of hexachlorocyclopentadiene and cyclooctadiene (Shen et al., 2011). The DP technical mixture contains two stereoisomers (syn- and anti-DP) in a ratio of approximately 1:3 (Wu et al., 2010). Usages of DP include electrical wire and cable coating, computer connectors, plastic roofing materials, and other polymeric materials (Feo et al., 2012). DP is currently unregulated and listed as a high production-volume chemical in the USA with an annual production or importation volume estimated to 500 t (EPA, 2015). Studies have also reported the presence of DP as an impurity in other chlorinated compound mixtures including the pesticide Chlordane (Shen et al., 2011; Sverko et al., 2010). The environmental persistence, bioaccumulation propensity and potential for toxicity suggest that DP may represent a persistent organic pollutant (POP) candidate (Feo et al., 2012; Sverko et al., 2011). The global bans of Octa- and Penta-bromodiphenyl ether (BDE) technical mixtures (UN, 2009) have resulted in an increased market demand for alternative flame retardants (Bergman et al., 2012; Chen et al., 2013). DP has been identified as a possible replacement product to the recently phased-out Deca-BDE in North America and Europe (EPA, 2014), and was recently proposed for listing under the Stockholm Convention on POPs (UN, 2015). Due to its high hydrophobicity (log K ow = 9.3; Hoh et al., 2006), DP has a high tendency to adsorb onto organic materials, and exhibits long half-life in the aquatic environment. DP has been reported in wastewater from Shanghai and water samples from the coastal shore of northern China at concentra- tions up to 1.4 and 1.8 ng/L, respectively (Xiang et al., 2014; Jia et al., 2011). It has also been determined in sediments of tributaries of the http://dx.doi.org/10.1016/j.aquatox.2017.04.009 Received 5 December 2016; Received in revised form 12 April 2017; Accepted 14 April 2017 ⁎ Corresponding author at: Centre de recherche en toxicologie de l’environnement (TOXEN), Département des sciences biologiques, Université du Québec à Montréal, C.P. 8888, succursale Centre-ville, Montreal, QC, H3C 3P8, Canada. E-mail address: verreault.jonathan@uqam.ca (J. Verreault). Aquatic Toxicology 188 (2017) 26–32 Available online 17 April 2017 0166-445X/ © 2017 Elsevier B.V. All rights reserved. MARK