Available online at www.sciencedirect.com Toxicology 245 (2008) 90–100 Oxidative stress induced by cerium oxide nanoparticles in cultured BEAS-2B cells Eun-Jung Park a , Jinhee Choi b , Young-Kwon Park b , Kwangsik Park a,∗ a College of Pharmacy, Dongduk Women’s University, 23-1, Wolgok-dong, Seongbuk-gu, Seoul 136-714, Republic of Korea b Faculty of Environmental Engineering, College of Urban Science, University of Seoul, 90 Jeonnong-dong, Dongdaemun-gu, Seoul 130-743, Republic of Korea Received 18 August 2007; received in revised form 17 December 2007; accepted 17 December 2007 Available online 3 January 2008 Abstract Cerium oxide nanoparticles of different sizes (15, 25, 30, 45 nm) were prepared by the supercritical synthesis method, and cytotoxicity was evaluated using cultured human lung epithelial cells (BEAS-2B). Exposure of the cultured cells to nanoparticles (5, 10, 20, 40 g/ml) led to cell death, ROS increase, GSH decrease, and the inductions of oxidative stress-related genes such as heme oxygenase-1, catalase, glutathione S-transferase, and thioredoxin reductase. The increased ROS by cerium oxide nanoparticles triggered the activation of cytosolic caspase-3 and chromatin condensation, which means that cerium oxide nanoparticles exert cytotoxicity by an apoptotic process. Uptake of the nanoparticles to the cultured cells was also tested. It was observed that cerium oxide nanoparticles penetrated into the cytoplasm and located in the peri-region of the nucleus as aggregated particles, which may induce the direct interaction between nanoparticles and cellular molecules to cause adverse cellular responses. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Ceria oxide nanoparticles; Cytotoxicity; Oxidative stress; BEAS-2B cells 1. Introduction Due to their unique physical and chemical characteristic, nanoparticles have been the focus of much research such as in industrial applications, environmental toxicity studies and human health impacts (Oberdorster et al., 2005; Priestly et al., 2007; Warheit et al., 2007). Various industrial nanomaterials made from titanium oxide, silver, gold, cadmium selenide and other carbon nanoparticles have been widely used for indus- trial purposes, and, cerium oxide nanoparticles may be the most important materials with wide ranges of applications for solar cells, fuel cells, gas sensors, oxygen pumps, and glass/ceramic applications (Gao et al., 2006). With the increased applications of cerium oxide nanoparticles, the concerns about their poten- tial human toxicity effects and their environmental impact were also increased. However, toxicity data for cerium oxide nanopar- ticles relating to human health are limited and only a few results ∗ Corresponding author. Tel.: +82 29404522; fax: +82 29404159. E-mail address: kspark@dongduk.ac.kr (K. Park). from basic studies have been published. Furthermore, the toxic- ity of cerium oxide nanoparticles is still controversial, especially regarding the oxidant/antioxidant effect (Thill et al., 2006; Lin et al., 2006; Schubert et al., 2006). When bacteria were treated with cerium oxide nanoparti- cles (7 nm CeO 2 ), Gram-negative bacteria (Escherichia coli) adsorbed the positively charged particles in the pH 7 growth media. The adsorption of cerium oxide nanoparticles to bacteria may induce oxidative stress and cause cell death (Thill et al., 2006). In A549 cells treated with 20 nm CeO 2 nanoparticles, reactive oxygen species (ROS) were induced, and cell viabil- ity was decreased. The elevated oxidative stress was found to increase the production of MDA and LDH, indicators of lipid peroxidation and membrane damage, respectively (Lin et al., 2006). However, there are a few papers that show antioxidative and cell protective effects of ceria nanoparticles using nervous cell systems. Ceria nanoparticles decreased the endogenous ROS induced by glutamate and showed cell protective effect in cultured HT22 cells which are derived from the rodent nervous (Schubert et al., 2006). In the publication, authors wrote that cerium oxide act 0300-483X/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.tox.2007.12.022