Toxicity of cylindrospermopsin, and other apparent metabolites from Cylindrospermopsis raciborskii and Aphanizomenon ovalisporum, to the zebrafish (Danio rerio) embryo

Abstract

Cyanobacteria produce a diverse array of toxic or otherwise bioactive compounds that pose growing threats to human and environmental health. We utilized the zebrafish (Danio rerio) embryo, as a model of vertebrate development, to investigate the inhibition of development pathways (i.e. developmental toxicity) by the cyanobacterial toxin, cylindrospermopsin (CYN), as well as extracts from various isolates of Cylindrospermopsis raciborskii and Aphanizomenon ovalisporum. CYN was toxic only when injected directly into embryos, but not by direct immersion at doses up to 50 μg/ml. Despite the dose dependency of toxicity observed following injection of CYN, no consistent patterns of developmental defects were observed, suggesting that toxic effects of CYN may not target specific developmental pathways. In contrast, direct immersion of embryos in all of the extracts resulted in both increased mortality and reproducible, consistent, developmental dysfunctions. Interestingly, there was no correlation of developmental toxicity observed for these extracts with the presence of CYN or with previously reported toxicity for these strains. These results suggest that CYN is lethal to zebrafish embryos, but apparently inhibits no specific developmental pathways, whereas other apparent metabolites from C. raciborskii and A. ovalisporum seem to reproducibly inhibit development in the zebrafish model. Continued investigation of these apparent, unknown metabolites is needed.

High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance of Intact Zebrafish Embryos Detects Metabolic Changes Following Exposure to Teratogenic Polymethoxyalkenes from Algae

“…10,11,[13][14][15][16] Briefly, 100 embryos (12 h postfertilization [hpf]) per replicate (n = 4) were exposed in 35-mm-diameter polystyrene dishes to 20 lg/mL of PMA (in E3 medium 21 ) for 24 h. Exposure concentration was based on previously determined teratogenicity of PMA and specifically represent concentrations that are not acutely toxic (i.e., teratogenic or lethal) to minimize metabolic changes associated with mortality or severe development deformities.…”

“…[7][8][9] In particular, embryonic and subsequent larval stages have proven particularly useful for characterizing teratogenicity (i.e., developmental toxicity). 8,9 With respect to the current study, the zebrafish embryo teratogenicity assay (ZETA) has been specifically used in the investigation of toxic, and specifically, teratogenic metabolites from marine and freshwater algae, including cyanobacteria, 10 and has enabled both characterization of known algal toxins [11][12][13] and identification (through screening, bioassay-guided isolation, and chemical/toxicological characterization) of otherwise unknown toxic metabolites. [14][15][16] In one such study, ZETA was used to identify a family of teratogenic secondary metabolites, namely, the polymethoxy-1-alkenes (PMAs), and subsequently demonstrate a taxonomically widespread distribution of these metabolites among both prokaryotic cyanobacteria and eukaryotic algae (i.e., Chlorophyta or green algae).…”

The ecotoxicological evaluation of Cylindrospermopsis raciborskii from Lake Balaton (Hungary) employing a battery of bioassays and chemical screening

“…In general, the presence of C. raciborskii in freshwaters is of particular concern due to the ability of certain strains to produce various toxins, from potent hepatotoxins (CYNs: cylindrospermopsins), to neurotoxins (PSPs: paralytic shellfish poisons), (Saker et al 2003;Fastner et al, 2007;Berry et al 2009). Although for the European C. raciborskii isolates investigated so far the ability of synthesizing CYNs and PSPs has never been documented, many of them proved to be toxic in the mouse bioassay (Bernard et al, 2003;Fastner et al, 2003;Saker et al, 2003;Hamilton et al, 2005).…”

Acute Effects of a Cylindrospermopsis Raciborskii (Cyanobacteria) Strain on Mouse, Daphnia and Fish

“…While Daphnia main exposure route seems to be the digestive tract, by ingestion of the cells [29], fish might by exposed mainly through gills, absorbing toxins directly from the water. However, the absorption of toxins by gills and epidermis in aquatic vertebrates is considered low [38][39][40][41]. In natural systems, the concentration of dissolved toxins is relatively low, up to 0.02 mg L -1 [42].…”