Aquatic Toxicology 157 (2014) 215–224 Contents lists available at ScienceDirect Aquatic Toxicology j ourna l ho me pa ge: www.elsevier.com/locate/aquatox Morphological alterations and acetylcholinesterase and monoamine oxidase inhibition in liver of zebraﬁsh exposed to Aphanizomenon ﬂos-aquae DC-1 aphantoxins De Lu Zhang a , Jing Zhang b , Chun Xiang Hu c,∗ , Gao Hong Wang c , Dun Hai Li c , Yong Ding Liu c a Department of Lifescience and Biotechnology, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan 430070, PR China b College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China c Key Laboratory of Algal Biology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan 430072, PR China a r t i c l e i n f o Article history: Received 12 September 2014 Received in revised form 18 October 2014 Accepted 21 October 2014 Available online 28 October 2014 Keywords: Cyanobacterial neurotoxin Zebraﬁsh liver Morphological alteration Acetylcholinesterase Monoamine oxidase Neurotoxicity a b s t r a c t Aphanizomenon ﬂos-aquae is a cyanobacterium that produces neurotoxins or paralytic shellﬁsh poisons (PSPs) called aphantoxins, which present threats to environmental safety and human health via eutro- phication of water bodies worldwide. Although the molecular mechanisms of this neurotoxin have been studied, many questions remain unsolved, including those relating to in vivo hepatic neurotransmitter inactivation, physiological detoxiﬁcation and histological and ultrastructural alterations. Aphantoxins extracted from the natural strain of A. ﬂos-aquae DC-1 were analyzed by high-performance liquid chro- matography. The main components were gonyautoxins 1 and 5 (GTX1, GTX5) and neosaxitoxin (neoSTX), which comprised 34.04%, 21.28%, and 12.77% respectively. Zebraﬁsh (Danio rerio) were exposed intraperi- toneally to 5.3 or 7.61 g STX equivalents (eq)/kg (low and high doses, respectively) of A. ﬂos-aquae DC-1 aphantoxins. Morphological alterations and changes in neurotransmitter conduction functions of acetyl- cholinesterase (AChE) and monoamine oxidase (MAO) in zebraﬁsh liver were detected at different time points 1–24 h post-exposure. Aphantoxin signiﬁcantly enhanced hepatic alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and histological and ultrastructural damage in zebraﬁsh liver at 3–12 h post-exposure. Toxin exposure increased the reactive oxygen species content and reduced total antioxidative capacity in zebraﬁsh liver, suggesting oxidative stress. AChE and MAO activities were signiﬁcantly inhibited, suggesting neurotransmitter inactivation/conduction function abnormalities in zebraﬁsh liver. All alterations were dose- and time-dependent. Overall, the results indicate that aphantox- ins/PSPs induce oxidative stress through inhibition of AChE and MAO activities, leading to neurotoxicity in zebraﬁsh liver. The above parameters may be useful as bioindicators for investigating aphantoxins/PSPs and cyanobacterial blooms in nature. © 2014 Published by Elsevier B.V. 1. Introduction Toxicogenic cyanobacterial blooms dominated by Aphani- zomenon ﬂos-aquae secrete cyanobacterial neurotoxins or paralytic shellﬁsh poisons (PSPs). They occur worldwide and represent a global problem (Ballot et al., 2010; Gkelis and Zaoutsos, 2014). These blooms and the harmful secondary metabolites produced (cyanotoxins) have a deleterious effect on water ecosystems (Gkelis and Zaoutsos, 2014). Blooms dominated by A. ﬂos-aquae DC-1 ∗ Corresponding author at: Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan 430072, PR China. Tel.: +86 27 68780866; fax: +86 27 68780866. E-mail addresses: deluzh@163.com (D.L. Zhang), cxhu@ihb.ac.cn (C.X. Hu). strains have occurred in Dianchi Lake, which has provided fresh water for agriculture, drinking, entertainment, and tourism for sev- eral million people in the vicinity of Kunming city, Yunnan Province, China in recent decades (Liu et al., 2006). Water blooms and their associated toxins have been responsible for severe environmental safety and human health problems for people living around the lake (Liu et al., 2006; Zhang et al., 2011, 2013a,b). PSPs are potent alkaloid neurotoxins that mainly occur in the ocean where they are produced by dinoﬂagellates, but also in freshwater, where they are secreted by freshwater cyanobacte- ria and bacteria (Prol et al., 2009; Ballot et al., 2010; Hackett et al., 2013). PSPs may accumulate at high levels in aquatic ani- mals with no immediate affect; however, consumption of these contaminated foodstuffs by humans or other animals leads to http://dx.doi.org/10.1016/j.aquatox.2014.10.016 0166-445X/© 2014 Published by Elsevier B.V.