Silver nanoparticles induced heat shock protein 70, oxidative stress and apoptosis in Drosophila melanogaster Maqusood Ahamed a , Ryan Posgai a , Timothy J. Gorey a , Mark Nielsen a , Saber M. Hussain b , John J. Rowe a, ⁎ a Department of Biology, Center for Tissue Regeneration and Engineering, University of Dayton, Dayton, OH 45469, USA b Applied Biotechnology Branch, Human Effectiveness Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, OH 45433, USA abstract article info Article history: Received 6 August 2009 Revised 12 October 2009 Accepted 21 October 2009 Available online 27 October 2009 Keywords: Silver nanoparticles Hsp 70 Oxidative stress DNA damage Apoptosis Due to the intensive commercial application of silver nanoparticles (Ag NPs), risk assessment of this nanoparticle is of great importance. Our previous in vitro study demonstrated that Ag NPs caused DNA damage and apoptosis in mouse embryonic stem cells and fibroblasts. However, toxicity of Ag NPs in vivo is largely lacking. This study was undertaken to examine the toxic effects of well-characterized polysaccharide coated 10 nm Ag NPs on heat shock stress, oxidative stress, DNA damage and apoptosis in Drosophila melanogaster. Third instar larvae of D. melanogaster were fed a diet of standard cornmeal media mixed with Ag NPs at the concentrations of 50 and 100 μg/ml for 24 and 48 h. Ag NPs up-regulated the expression of heat shock protein 70 and induced oxidative stress in D. melanogaster. Malondialdehyde level, an end product of lipid peroxidation was significantly higher while antioxidant glutathione content was significantly lower in Ag NPs exposed organisms. Activities of antioxidant enzyme superoxide dismutase and catalase were also significantly higher in the organisms exposed to Ag NPs. Furthermore, Ag NPs up-regulated the cell cycle checkpoint p53 and cell signaling protein p38 that are involved in the DNA damage repair pathway. Moreover, activities of caspase-3 and caspase-9, markers of apoptosis were significantly higher in Ag NPs exposed organisms. The results indicate that Ag NPs in D. melanogaster induce heat shock stress, oxidative stress, DNA damage and apoptosis. This study suggests that the organism is stressed and thus warrants more careful assessment of Ag NPs using in vivo models to determine if chronic exposure presents developmental and reproductive toxicity. © 2009 Elsevier Inc. All rights reserved. Introduction Silver nanoparticles (Ag NPs) are emerging as one of the fastest growing product categories in the nanotechnology industry. Ag NPs are used in clothing, food industry, paints, cosmetics, electronics, coating application and medical products (Cheng et al., 2004; Cohen et al., 2007; Lee et al., 2007; Vigneshwaran et al., 2007). Among the 580 consumer nanotechnology-based products, the most common material in product descriptions is silver-based nanoparticles (Woodrow Wilson International Center, 2007). Nanoparticle exposure can occur through inhalation, dermal contact and ingestion. The toxicology of inhaled nanoparticles has been the route most extensively studied compared to other exposure routes, such as dermal contact or ingestion (Kreyling et al., 2006). Nanomaterials may be delivered into the gastrointestinal tract via accidental ingestion by individuals who work in the nanomaterials manufacturing industry or nanomaterials research laboratories or by drinking or eating water or food that is contaminated by nano-silver from food packaging or from waste. Recent studies suggest that nanoparticles may be absorbed as they pass through the gastrointes- tinal tract and distributed throughout the body via the circulatory system. Ingested single-walled carbon nanotubes in mice were distributed to most of the organs and tissues (Wang et al., 2004). Hillyer and Albrecht (2001) reported blood and tissue distribution of ingested colloidal gold nanoparticles in mice. Jani et al. (1990) showed that polystyrene nanoparticles administered by ingestion in rats were subsequently detected in the blood and in several organs. Medaka fish exposed to fluorescent solid latex nanoparticles demon- strated a homogeneous distribution of the nanoparticles throughout the body (Kashiwada, 2006). More recently, Kim et al. (2008) examined the oral toxicity of Ag NPs in rats and found significant dose-dependent changes in alkaline phosphatase activity, cholesterol level and liver function. Living organisms exposed to different environmental stressors respond by synthesizing a small number of highly conserved proteins called heat shock or stress proteins (Lindquist, 1986). Among the different stress proteins, the stress inducible heat shock protein 70 kDa (Hsp70) is well characterized (Bierkens, 2000). The Hsp70 has been proposed as a potential biomarker for monitoring environmental stressors (Ait-Aissa et al., 2000; Siddique et al., 2008). Numerous in Toxicology and Applied Pharmacology 242 (2010) 263–269 ⁎ Corresponding author. Fax: +1 937 229 2021. E-mail address: John.Rowe@notes.udayton.edu (J.J. Rowe). 0041-008X/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.taap.2009.10.016 Contents lists available at ScienceDirect Toxicology and Applied Pharmacology journal homepage: www.elsevier.com/locate/ytaap