title: In vivo effects of Aphanizomenon flos-aquae DC-1 aphantoxins on gas exchange and ion equilibrium in the zebrafish gill.
abstract: Aphantoxins, neurotoxins or paralytic shellfish poisons (PSPs) generated by Aphanizomenon flos-aquae, are a threat to environmental safety and human health in eutrophic waters worldwide. The molecular mechanisms of neurotoxin function have been studied; however, the effects of these neurotoxins on oxidative stress, ion transport, gas exchange, and branchial ultrastructure in fish gills are not fully understood. Aphantoxins extracted from A. flos-aquae DC-1 were detected by high-performance liquid chromatography. The major ingredients were gonyautoxins 1 and 5 and neosaxitoxin, which comprised 34.04%, 21.28%, and 12.77% of the total, respectively. Zebrafish (Danio rerio) were administered A. flos-aquae DC-1 aphantoxins at 5.3 or 7.61μg saxitoxin equivalents (eq)/kg (low and high doses, respectively) by intraperitoneal injection. The activities of Na(+)-K(+)-ATPase (NKA), carbonic anhydrase (CA), and lactate dehydrogenase (LDH), ultrastructural alterations in chloride and epithelial cells, and reactive oxygen species (ROS) and total antioxidative capacity (T-AOC) were investigated in the gills during the first 24h after exposure. Aphantoxins significantly increased the level of ROS and decreased the T-AOC in zebrafish gills from 3 to 12h post-exposure, suggesting an induction of oxidative stress and inhibition of antioxidant capacity. Reduced activities of NKA and CA demonstrated abnormal ion transport and gas exchange in the gills of aphantoxin-treated fish. Toxin administration also resulted in increased LDH activity and ultrastructural alterations in chloride and epithelial cells, suggesting a disruption of function and structure in zebrafish gills. The observed abnormalities in zebrafish gills occurred in a time- and dose-dependent manner. These findings demonstrate that aphantoxins or PSPs may inhibit ion transport and gas exchange, increase LDH activity, and result in ultrastructural damage to the gills through elevations in oxidative stress and reduced antioxidant capacity. These effects of aphantoxins in the gills of zebrafish suggest an induction of respiratory toxicity. The parameters investigated in this study may be also considered as biomarkers for studying aphantoxin/PSP exposure and cyanobacterial blooms in nature.
authors.affiliation: Department of Lifescience and Biotechnology, College of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, PR China. Electronic address: deluzh@163.com.
authors.forename: Delu
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Department of Lifescience and Biotechnology, College of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, PR China.
authors.forename: Siyi
authors.initials: S
authors.lastname: Liu
authors.affiliation: College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Lifescience and Biotechnology, College of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, PR China.
authors.forename: Jian Kong
authors.initials: JK
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Algal Biology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan 430072, PR China. Electronic address: deluzh@ihb.ac.cn.
authors.forename: Chunxiang
authors.initials: C
authors.lastname: Hu
authors.affiliation: Key Laboratory of Algal Biology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan 430072, PR China.
authors.forename: Yongding
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D046890:Aphanizomenon / Q000378:metabolism*; D001427:Bacterial Toxins / Q000633:toxicity*; D002256:Carbonic Anhydrases / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005880:Gills / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008387:Marine Toxins / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014873:Water Pollutants / Q000633:toxicity*; D015027:Zebrafish / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000378:metabolism
chemical_list: D000975:Antioxidants; D001427:Bacterial Toxins; D008387:Marine Toxins; D017382:Reactive Oxygen Species; D014873:Water Pollutants; D029961:Zebrafish Proteins; C034321:aphantoxin; D007770:L-Lactate Dehydrogenase; D002256:Carbonic Anhydrases; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Carbonic anhydrase; Cyanobacterial neurotoxin; Na(+)-K(+)-ATPase; Respiratory toxicity; Zebrafish gill