Cytotoxicity of TBBPA and effects on proliferation, cell cycle and MAPK pathways in mammalian cells Siegfried Strack a, * , Tanja Detzel a , Markus Wahl a , Bertram Kuch b , Harald F. Krug a a Forschungszentrum Karlsruhe, Institut fu ¨ r Toxikologie und Genetik, 76021 Karlsruhe, Postfach 3640, Germany b Universita ¨ t Stuttgart, Institut fu ¨ r Siedlungswasserbau und Wassergu ¨ tewirtschaft, 70569 Stuttgart, Bandta ¨ le 2, Germany Accepted 26 May 2006 Available online 24 January 2007 Abstract Poly-brominated flame retardants are ecotoxicologically relevant chemicals that can show high persistency in environmental samples and bioaccumulation in marine and fresh water animals. One of the most widely used compound is tetrabromobisphenol A (TBBPA). Until today, the toxicological data are rather fragmentary. Our studies on acute and sub-acute toxic effects with established cell lines demonstrate that TBBPA interferes with cellular signaling pathways. Cell viability is significantly reduced in a time- and concentra- tion-dependent manner. The observed EC 50 for rat kidney cells (NRK) was 52 lM (27 mg/l), 168 lM (90 mg/l) for A549 human lung cells, and 200 lM (108 mg/l) for Cal-62 human thyroid cells, respectively. The comparison of TBBPA with the non-brominated sub- stance bisphenol A (BPA) clearly demonstrates that only the brominated compound exerts these effects on proliferation and cell viability. Cell cycle regulation was influenced considerably in Cal-62 cells, showing an explicit G2/M arrest in the cell cycle at TBBPA concentra- tions higher than 75 lM. Cellular signaling pathways directly connected to these affected parameters, e.g. the mitogen activated protein kinase (MAPK) cascades, are partly influenced in a cell specific and dose dependent manner. The extracellular-signal regulated kinase (ERK) is deactivated in NRK and A549 cells and activated in Cal-62 cells with increasing TBBPA concentrations. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Brominated flame retardants; Tetrabromobisphenol A; in vitro cytotoxic effects; MAPK; ERK pathway 1. Introduction Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame-retardants in the world (de Wit, 2000, 2002). It is contained together with other bromi- nated organic compounds in many technical flame retar- dant products. These are used as additive or reactive constituents in polymers for the production of electrical and electronic equipment, such as computers and television sets. They are also used for a variety of plastic materials and textiles in vehicles and aircraft to prevent fire. TBBPA is applied particularly as a reactive retardant in polymers, however, it may be released to the environment in cases of incomplete polymerisation. TBBPA as well as most of the other brominated aro- matic flame retardants are lipophilic substances and show a high persistency in the environment, comparable to poly- chlorinated biphenyls and dioxins (de Boer et al., 1998). Because of that persistency brominated aromatic com- pounds can bioaccumulate and are globally traceable in environmental samples. They could be detected in sedi- ments and soils, marine and fresh water animals, but also in blood serum of computer technicians (Jakobsson et al., 2002). Recently, human exposure to brominated flame retardants has been extensively reviewed by Sjo ¨din et al. (2003). The observed elevated concentrations of poly-bro- minated biphenyls, e.g. in whales and dolphins, indicate the bio-availability of those chemicals (Law et al., 2003). Adverse effects of TBBPA published so far have been recently reviewed by Birnbaum and Staskal (2004). The LD 50 indicating the acute toxicity in vivo due to a single 0045-6535/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2006.05.136 * Corresponding author. Tel.: +49 7247 82 2708; fax: +49 7247 82 3557. E-mail address: strack@itg.fzk.de (S. Strack). www.elsevier.com/locate/chemosphere Chemosphere 67 (2007) S405–S411