Short Communication Hemocyte responses of Dreissena polymorpha following a short-term in vivo exposure to titanium dioxide nanoparticles: Preliminary investigations Nicolas Couleau a , Didier Techer a , Christophe Pagnout b, c , Stéphane Jomini b , Laurent Foucaud a , Philippe Laval-Gilly a , Jairo Falla a , Amar Bennasroune a, ⁎ a Université de Lorraine, Laboratoire des Interactions Ecotoxicologie, Biodiversité, Ecosystèmes (LIEBE), CNRS UMR 7146, IUT Thionville-Yutz, Espace Cormontaigne, Yutz, F-57970, France b Université de Lorraine, Laboratoire des Interactions Ecotoxicologie, Biodiversité, Ecosystèmes (LIEBE), UMR 7146, Campus Bridoux, rue du Général Delestraint, Metz, F-57070, France c International Consortium for the Environmental Implications of Nanotechnology, iCEINT, http://www.i-ceint.org, France HIGHLIGHTS ► Phagocytosis inhibition at TiO 2 NP exposure concentrations of 0.1 and 1 mg/L. ► Internalization of TiO 2 NP in freshwater mussel hemocytes. ► Increased phosphorylation level of p38 and ERK 1/2 after in vivo exposure to TiO 2 NP. abstract article info Article history: Received 6 July 2012 Received in revised form 24 August 2012 Accepted 26 August 2012 Available online 30 September 2012 Keywords: Titanium dioxide nanoparticles Dreissena polymorpha Immune system parameters Hemocytes The widespread use of titanium-based nanoparticles and their environmental release may pose a significant risk to aquatic organisms within freshwater ecosystems. Suspension-feeder invertebrates like bivalve mol- luscs represent a unique target group for nanoparticle toxicology. The aim of this work was to investigate the short-term responses of Dreissena polymorpha hemocytes after in vivo exposure to titanium dioxide nanoparticles (TiO 2 NP). For this purpose, freshwater mussels were exposed to P25 TiO 2 NP at the concentra- tions of 0.1, 1, 5 and 25 mg/L during 24 h. Viability, phagocytosis activity and mitogen activated protein ki- nase (MAPK) phosphorylation level of ERK 1/2 and p38 in hemocytes extracted from exposed mussels were compared to those from control specimens. Results demonstrated an inhibition of the phagocytosis ac- tivity after exposure to TiO 2 NP at 0.1 and 1 mg/L. Similar trends, albeit less pronounced, were reported for higher concentrations of NP. Transmission electron microscopy showed for the first time the internalization of TiO 2 NP into Dreissena polymorpha hemocytes. Besides, exposure to NP increased the ERK 1/2 phosphory- lation levels in all treatments. Concerning the phosphorylation level of p38, only exposures to 5 and 25 mg/L of NP induced significant p38 activation in comparison to that of the control. Finally, these short-term effects observed at environmentally relevant concentrations highlighted the need for further studies concerning ecotoxicological evaluation of nanoparticle release into an aquatic environment. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Nanotechnology represents one of the most rapidly expanding field of applied science and technology since funds allocated for research and development substantially increase each year, e.g. from $ 270 million invested by the US Government in 2000 to $ 849 million in 2004 (Roco, 2003; Nowack and Bucheli, 2007). The industrial production may encompass more than 58,000 t of engineered nanomaterials in the next decade, presumably leading to the enhancement of environ- mental exposure to nanoparticles (NP) (Daughton, 2004; Nowack and Bucheli, 2007). As an illustration, the aquatic environment may be contaminated not only by atmospheric deposition or industrial runoff but also by urban applications (Harley, 2008). Several studies have highlighted the influence of the nature, size, surface area and concentration of NP on their adverse effects on ter- restrial organisms with particular emphasis on human health. For in- stance, Goulaouic et al. (2008) showed that carbon black NP induced a proinflammatory response in human immune system cells through a modification of cytokine secretion. On the contrary, little is known about the behavior, fate and accumulation of NP in aquatic ecosys- tems and the issue of their potential ecotoxicological effects must Science of the Total Environment 438 (2012) 490–497 Abbreviations: CB, carbon black; ERK 1/2, extracellular signal regulating kinase 1 et 2; MAPK, mitogen activated protein kinase; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyl tetrazolium bromide; NP, nanoparticle; PAH, polycyclic aromatic hydrocar- bon; PEC, predict effect concentration; P-ERK 1/2, phosphorylated ERK 1/2; P-p38, phosphorylated p38; ROS, reactive oxygen species; TEM, transmission electron micros- copy; TiO 2 NP, titanium dioxide nanoparticle; XRD, X-ray powder diffraction. ⁎ Corresponding author at: IUT Thionville-Yutz Impasse Alfred Kastler Espace Cormontaigne F-57970 Yutz France. Tel.: +33 3 82 82 06 23. E-mail address: amar.bennasroune@univ-metz.fr (A. Bennasroune). 0048-9697/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2012.08.095 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv