Aquatic Toxicology 105 (2011) 497–507 Contents lists available at ScienceDirect Aquatic Toxicology jou rn al h om epa ge: www.elsevier.com/locate/aquatox In vitro modulation of intracellular receptor signaling and cytotoxicity induced by extracts of cyanobacteria, complex water blooms and their fractions T. ˇ Stˇ epánková a , L. Ambroˇ zová a , L. Bláha a , J.P. Giesy b,c,d,e,f , K. Hilscherová a,∗ a Research Centre for Toxic Compounds in the Environment (RECETOX), Faculty of Science, Masaryk University, Kamenice 126/3, 625 00 Brno, Czech Republic b Department of Biomedical Veterinary Sciences and Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada c Zoology Department and Center for Integrative Toxicology, Michigan State University, East Lansing, MI 48824, USA d Department of Biology and Chemistry, City University of Hong Kong, Hong Kong, China e Zoology Department, College of Science, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia f Environmental Science Program, Nanjing University, Nanjing, China a r t i c l e i n f o Article history: Received 16 April 2011 Received in revised form 21 July 2011 Accepted 2 August 2011 Keywords: Cyanobacteria Cell extract Endocrine disruption Estrogenicity Microcystin Planktothrix agardhii a b s t r a c t The biological activity of cyanobacteria and their chemical components have been widely studied due to their blooms in eutrophic waters worldwide. The primary goal of this study was to determine if indi- vidual cyanobacterial species and mixtures of cyanobacteria collected from the environment contain compounds with the potential for interaction with signaling pathways of the aryl hydrocarbon receptor (AhR), androgen receptor (AR), estrogen receptor (ER), glucocorticoid receptor (GR) and retinoid acid receptor (RAR). Cytotoxicity and specific toxic potencies of products of freshwater cyanobacteria were determined by use of in vitro reporter gene trans-activation assays. The testing included samples prepared from five selected single cyanobacterial species cultivated in laboratory and five complex cyanobacte- rial biomasses collected from blooms in surface waters in the Czech Republic. The results demonstrate estrogenic potencies of extracts of cyanobacterial biomasses. Among the laboratory single species, the extract of Planktothrix agardhii (intracellular metabolites) had a potency of estrogenic equivalents (EEQ) of 3.8 ng 17-estradiol/g dw. The estimates of EEQs of samples prepared from complex cyanobacterial biomasses collected from freshwaters in the Czech Republic ranged from 19 to 2200 ng 17-estradiol/g dw. Several samples prepared from the environmental cyanobacterial biomasses potentiated the andro- genic potency of dihydrotestosterone. There was no dioxin-like, glucocorticoid or anti/retinoic activity observed for any of the extracts studied. Extracts of natural complex cyanobacterial biomasses exhib- ited greater and more frequent presence of compounds with specific modes of action, mainly estrogenic, and also greater cytotoxicity than extracts of single cyanobacterial species. The demonstrated estrogenic potency of the compounds present in complex cyanobacterial biomasses is of environmental relevance, and could potentially contribute to endocrine disruptive effects in aquatic ecosystems in case of great bloom densities. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Cyanobacteria are photosynthesizing, gram-negative bacte- ria, whose growth is dependent on a number of factors. These include primarily flux of sunlight, temperature and concentrations of nutrients such as phosphorus and nitrogen. Large masses of cyanobacteria can occur under conditions of eutrophication. The cyanobacterial blooms can cause a number of problems such as shading of macrophytes and phytoplankton in the water column, and through their degradation deplete oxygen in water. In addi- ∗ Corresponding author. Tel.: +420 54949 3256; fax: +420 54949 2840. E-mail address: hilscherova@recetox.muni.cz (K. Hilscherová). tion, cyanobacteria are a source of secondary metabolites that can be released to the water where these extracellular products can be toxic to aquatic organisms including both invertebrates and vertebrates. These cyanobacterial toxins can cause a range of effects including skin irritation, gastrointestinal tract and res- piratory distress, neurotoxicity, immunotoxicity or hepatotoxic, cancerogenic, genotoxic and mutagenic effects (Rastogi and Sinha, 2009). Cyanobacterial toxins can cause lethality to aquatic organ- isms and in some cases terrestrial vertebrates exposed to surface water (Codd et al., 2005; Wiegand and Pflugmacher, 2005). The best known cyanotoxin, microcystin (MC), produced by several species of cyanobacteria, is one of the more important contributors to toxicity of cyanobacterial blooms (Masango et al., 2008). However, due to their molecular volume, structure and 0166-445X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2011.08.002