Toxicity of cyanobacterial bloom in the eutrophic dam reservoir (Southeast Poland)

Combined methods elucidate the multi-organ toxicity of cylindrospermopsin (CYN) on Daphnia magna

Global water bodies are now at risk from inevitable cyanobacterial blooms and their production of multiple cyanotoxins, in particular cylindrospermopsin (CYN). However, research on the CYN toxicity and its molecular mechanisms is still limited, whilst the responses of aquatic species against CYN are uncovered. By integrating behavioral observations, chemical detections and transcriptome analysis, this study demonstrated that CYN exerted multi-organ toxicity to model species, Daphnia magna. The present study confirmed that CYN could cause protein inhibition by undermining total protein contents, and altered the gene expression related to proteolysis. Meantime, CYN induced oxidative stress by increasing reactive oxygen species (ROS) level, decreasing the glutathione (GSH) concentration, and interfered with protoheme formation process molecularly. Neurotoxicity led by CYN was solidly determined by abnormal swimming patterns, reduced acetylcholinesterase (AChE), and downward expression of muscarinic acetylcholine receptor (CHRM). Importantly, for the first time, this research determined CYN directly interfered with energy metabolism in cladocerans. CYN distinctively reduced filtration and ingestion rate by targeting on heart and thoracic limbs, which declined the energy intake, and could be further displayed by the reduction of motional strength and the trypsin concentration. These phenotypic alterations were supported by transcriptomic profile, including the down-regulation of oxidative phosphorylation and ATP synthesis. Moreover, CYN was speculated to trigger the self-defense responses of D. magna, known as "abandon-ship" by moderating lipid metabolism and distribution. This study, overall, comprehensively demonstrated the CYN toxicity and the responses of D. magna against it, which is of great significance to the advancements of CYN toxicity knowledge.

Determination of Multiclass Cyanotoxins in Blue-Green Algae (BGA) Dietary Supplements Using Hydrophilic Interaction Liquid Chromatography-Tandem Mass Spectrometry

In recent years, the consumption of blue-green algae (BGA) dietary supplements is increasing because of their health benefits. However, cyanobacteria can produce cyanotoxins, which present serious health risks. In this work we propose hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry (HILIC-MS/MS) to determine cyanotoxins in BGA dietary supplements. Target toxins, including microcystin-leucine-arginine (MC-LR) and microcystin-arginine-arginine (MC-RR), nodularin, anatoxin-a and three non-protein amino acids, β-N-methylamino-L-alanine (BMAA), 2,4-diaminobutyric acid (DAB) and N-(2-aminoethyl)glycine (AEG), were separated using a SeQuant ZIC-HILIC column. Cyanotoxin extraction was based on solid-liquid extraction (SLE) followed by a tandem-solid phase extraction (SPE) procedure using Strata-X and mixed-mode cation-exchange (MCX) cartridges. The method was validated for BGA dietary supplements obtaining quantification limits from 60 to 300 µg·kg^-1. Nine different commercial supplements were analyzed, and DAB, AEG, and MCs were found in some samples, highlighting the relevance of monitoring these substances as precaution measures for the safe consumption of these products.

Cyanobacteria-From the Oceans to the Potential Biotechnological and Biomedical Applications

Cyanobacteria are photosynthetic prokaryotic organisms which represent a significant source of novel, bioactive, secondary metabolites, and they are also considered an abundant source of bioactive compounds/drugs, such as dolastatin, cryptophycin 1, curacin toyocamycin, phytoalexin, cyanovirin-N and phycocyanin. Some of these compounds have displayed promising results in successful Phase I, II, III and IV clinical trials. Additionally, the cyanobacterial compounds applied to medical research have demonstrated an exciting future with great potential to be developed into new medicines. Most of these compounds have exhibited strong pharmacological activities, including neurotoxicity, cytotoxicity and antiviral activity against HCMV, HSV-1, HHV-6 and HIV-1, so these metabolites could be promising candidates for COVID-19 treatment. Therefore, the effective large-scale production of natural marine products through synthesis is important for resolving the existing issues associated with chemical isolation, including small yields, and may be necessary to better investigate their biological activities. Herein, we highlight the total synthesized and stereochemical determinations of the cyanobacterial bioactive compounds. Furthermore, this review primarily focuses on the biotechnological applications of cyanobacteria, including applications as cosmetics, food supplements, and the nanobiotechnological applications of cyanobacterial bioactive compounds in potential medicinal applications for various human diseases are discussed.

Simultaneous preparation of N2 and CO2 from water nitrates for δ15N and δ18O analysis on the example of the Zemborzycki Reservoir studies

Nitrates are bioavailable compounds, which are necessary for every living organisms. However, their excess could be harmful, because it could lead to, i.e., methemoglobinemia, formation of carcinogenic nitrosamines and reservoir eutrophication. Isotopic analysis of δ¹⁵N and δ¹⁸O in nitrates allows to distinguish their different sources. To simplify the way of nitrate source monitoring, we developed a less complex and cheap "off-line" method for nitrate isotopic analysis, in which we obtain both gases required for isotopic analysis of NO₃^-, N₂ for δ¹⁵N and CO₂ for δ¹⁸O measurements, in one procedure. The developed method is based on simultaneous conversion of AgNO₃ (mixed with C and placed into PtIr boat) to N₂ and CO₂ in a glass vacuum apparatus. A small amount of sample (8 mg of AgNO₃) required for this procedure and a good reproducibility of the isotopic analysis (better than 0.3‰ for δ¹⁸O and 1‰ for δ¹⁵N) make this method a useful tool for environmental research. Using the developed method, we analyzed the isotopic composition of N and O in nitrates in the Zemborzycki Reservoir near Lublin (Poland), in 2015. The results indicate a large variation of δ¹⁵N (from -1.4 to +37.7‰) and δ¹⁸O (from +5.5 to +25.9‰) values in NO₃^- ions, while the concentration of NO₃^- varied from 0.2 to 15.3 mg/dm³. These preliminary results suggest that nitrate fertilizers probably are the main source of NO₃^- pollution. Our study points out the input of manure and/or sewage to the analyzed reservoir in the subsequent periods of sample collection.

The Diversity of Cyanobacterial Toxins on Structural Characterization, Distribution and Identification: A Systematic Review

The widespread distribution of cyanobacteria in the aquatic environment is increasing the risk of water pollution caused by cyanotoxins, which poses a serious threat to human health. However, the structural characterization, distribution and identification techniques of cyanotoxins have not been comprehensively reviewed in previous studies. This paper aims to elaborate the existing information systematically on the diversity of cyanotoxins to identify valuable research avenues. According to the chemical structure, cyanotoxins are mainly classified into cyclic peptides, alkaloids, lipopeptides, nonprotein amino acids and lipoglycans. In terms of global distribution, the amount of cyanotoxins are unbalanced in different areas. The diversity of cyanotoxins is more obviously found in many developed countries than that in undeveloped countries. Moreover, the threat of cyanotoxins has promoted the development of identification and detection technology. Many emerging methods have been developed to detect cyanotoxins in the environment. This communication provides a comprehensive review of the diversity of cyanotoxins, and the detection and identification technology was discussed. This detailed information will be a valuable resource for identifying the various types of cyanotoxins which threaten the environment of different areas. The ability to accurately identify specific cyanotoxins is an obvious and essential aspect of cyanobacterial research.

Evaluation of usefulness of Microbial Assay for Risk Assessment (MARA) in the cyanobacterial toxicity estimation

The aim of the study was to elucidate the usefulness of the Microbial Assay for Risk Assessment (MARA) to evaluate toxicity in samples containing cyanobacterial products. Cyanobacterial extracts with different cyanotoxin contents and pure cyanotoxins-microcystin-LR, cylindrospermopsin and anatoxin-a-were tested. On the basis of the microbial reaction, MARA indicated only slight or no toxicity in the studied extracts. Similarly, no or low toxicity of pure toxins was detected at the concentrations used (up to 10 μg/ml). Weak relationships between the reactions of individual organisms exposed to cyanotoxin-containing extracts and to the same pure toxins were observed. On the other hand, inhibition of some organisms, such as Pichia anomalia, whose growth was not impacted by pure cyanotoxins, indicated the presence of other biologically active compounds in the studied extracts. In conclusion, MARA assay is not enough sensitive to be used as a good tool for cyanotoxin screening. It may, however, be applied in searching for antimicrobial/antifungal cyanobacteria-derived compounds.

Toxin content and cytotoxicity of algal dietary supplements

Blue-green algae (Spirulina sp., Aphanizomenon flos-aquae) and Chlorella sp. are commercially distributed as organic algae dietary supplements. Cyanobacterial dietary products in particular have raised serious concerns, as they appeared to be contaminated with toxins e.g. microcystins (MCs) and consumers repeatedly reported adverse health effects following consumption of these products. The aim of this study was to determine the toxin contamination and the in vitro cytotoxicity of algae dietary supplement products marketed in Germany. In thirteen products consisting of Aph. flos-aquae, Spirulina and Chlorella or mixtures thereof, MCs, nodularins, saxitoxins, anatoxin-a and cylindrospermopsin were analyzed. Five products tested in an earlier market study were re-analyzed for comparison. Product samples were extracted and analyzed for cytotoxicity in A549 cells as well as for toxin levels by (1) phosphatase inhibition assay (PPIA), (2) Adda-ELISA and (3) LC-MS/MS. In addition, all samples were analyzed by PCR for the presence of the mcyE gene, a part of the microcystin and nodularin synthetase gene cluster. Only Aph. flos-aquae products were tested positive for MCs as well as the presence of mcyE. The contamination levels of the MC-positive samples were ≤ 1 μg MC-LR equivalents g(-1) dw. None of the other toxins were found in any of the products. However, extracts from all products were cytotoxic. In light of the findings, the distribution and commercial sale of Aph. flos-aquae products, whether pure or mixed formulations, for human consumption appear highly questionable.

Pro- and anti-inflammatory cytokine expression in carp blood and head kidney leukocytes exposed to cyanotoxin stress--an in vitro study

Cyanotoxins are toxic, secondary metabolites produced by different species of cyanobacteria that are present all over the world in aquatic environments. No data are available about the molecular mechanisms underlying the stress associated with exposure of fish immune cells to low concentrations of cyanotoxins. The purpose of this study was to determine whether the expression of cytokines that underlie immune regulation are changed after incubation of fish leukocytes with pure cyanotoxins: microcystin- LR (MC-LR), anatoxin-a (Antx-a), or an extract containing Antx-a. The study investigated the relative gene expression of four important cytokines, IL-1β, TNF-α, IL-10, and TGF-β, in carp head kidney and blood leukocytes exposed to toxins at concentrations of 0.01 or 0.1 μg/ml for 4 h. The data showed that pure toxins could induce dysregulation of pro-/anti-inflammatory cytokine expression. Expression of cytokine IL-1 β was highly upregulated following Antx-a exposure, whereas MC-LR induced merely moderate reactions. The expression of TNF-α mRNA was significantly suppressed in blood and head kidney cells incubated with toxins at the higher concentration. These results showed that pure toxins dysregulated the expression of pro-inflammatory cytokines IL-1β and TNF-α more promptly than the anti-inflammatory cytokines TGF-β and IL-10. In contrast, the studies demonstrated a clearly downward trend of pro-inflammatory cytokines and an upward trend of anti-inflammatory cytokines in leukocytes exposed to an extract containing defined concentrations of Antx-a. This study suggests that cyanotoxins present in aquatic environments may exert immunotoxic effects by altering the transcription of important mediators of the fish immune system.