Detected cyanotoxins by UHPLC MS/MS technique in tropical reservoirs of northeastern Colombia

Cyanopeptides occurrence and diversity in a Brazilian tropical reservoir: Exploring relationships with water quality

Microcystins (MCs) are a class of toxic secondary metabolites produced by some cyanobacteria strains that endanger aquatic and terrestrial organisms in various freshwater systems. Although patterns in MC occurrence are being recognized, divergences in the global data still hamper our ability to predict the toxicity of cyanobacterial blooms. This study aimed (i) to determine the dynamics of MCs and other cyanopeptides in a tropical reservoir, (ii) to investigate the correlation between peptides and potential cyanotoxin producers (iii) identifying the possible abiotic factors that influence the peptides. We analyzed, monthly, eight MC variants (MC-RR, -LA, -LF, -LR, -LW, -YR, [D-Asp3]-RR and [D-Asp3]-LR) and other peptides in 47 water samples collected monthly, all season long, from two sampling sites in a tropical eutrophic freshwater reservoir, in southeastern Brazil. The cyanopeptides were assessed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The biomass of potential cyanobacterial producers and water quality variables were measured. MCs were detected in both sampling sites year-round; the total MC concentration varied from 0.21 to 4.04 μg L-1, and three MC variants were identified and quantified (MC-RR, [D-Asp3]-RR, -LR). Additionally, we identified 28 compounds belonging to three other cyanopeptide classes: aeruginosin, microginin, and cyanopeptolin. As potential MC producers, Microcystis spp. and Dolichospermum circinalis were dominant during the study, representing up to 75% of the total phytoplankton. Correlational and redundancy analysis suggested positive effects of dissolved oxygen, nitrate, and total phosphorus on MC and microginins concentration, while water temperature appeared to favor aeruginosins. A comparison between our results and historical data showed a reduction in total phosphorus and cyanobacteria, suggesting increased water quality in the reservoir. However, the current MC concentrations indicate a rise in cyanobacterial toxicity over the last eight years. Moreover, our study underscores the pressing need to explore cyanopeptides other than MCs in tropical aquatic systems.

Capillary electrophoresis tandem mass spectrometry to determine multiclass cyanotoxins in reservoir water and spinach samples

Cyanotoxins constitute a group of toxic secondary metabolites, the presence of which in any water body poses a major health risk. Moreover, advanced organisms such as edible plants exposed to these toxins, are a possible pathway for human exposure. Green analytical chemistry is demanding environmentally friendly analytical techniques. In this sense, we propose the use of capillary electrophoresis coupled to tandem mass spectrometry (CE-MS/MS) to determine a mixture of eight cyanotoxins belonging to three different classes: cyclic peptides (microcystin-LR, microcystin-RR and nodularin), alkaloids (cylindrospermopsin and anatoxin-a) and three isomeric non-protein amino acids (β-methylamino-l-alanine, 2,4-diaminobutyric acid and N-(2-aminoethyl)glycine). Separation was achieved by using an acidic background electrolyte consisting of 2 M formic acid and 20% acetonitrile in water. Parameters affecting MS/MS detection and the sheath-liquid interface were also studied. Finally, a combination of pH-junction, field-amplified sample stacking (FASS) and acid barrage as online preconcentration strategies, was employed to improve sensitivity and efficiency. The online preconcentration applied, in combination with a dual cartridge solid-phase extraction (SPE) system, allows to obtain limits of detection in the very low range of µg·L-1 for these multiclass cyanotoxins in reservoir water samples (from 0.005 to 0.10 µg·L-1). Furthermore, for the first time cyanotoxins are analysed in spinach samples through CE-MS/MS using the same SPE procedure, following lyophilisation and solid-liquid extraction with 6 mL 80 % aqueous MeOH.

Freshwater Cyanobacterial Toxins, Cyanopeptides and Neurodegenerative Diseases

Cyanobacteria produce a wide range of structurally diverse cyanotoxins and bioactive cyanopeptides in freshwater, marine, and terrestrial ecosystems. The health significance of these metabolites, which include genotoxic- and neurotoxic agents, is confirmed by continued associations between the occurrence of animal and human acute toxic events and, in the long term, by associations between cyanobacteria and neurodegenerative diseases. Major mechanisms related to the neurotoxicity of cyanobacteria compounds include (1) blocking of key proteins and channels; (2) inhibition of essential enzymes in mammalian cells such as protein phosphatases and phosphoprotein phosphatases as well as new molecular targets such as toll-like receptors 4 and 8. One of the widely discussed implicated mechanisms includes a misincorporation of cyanobacterial non-proteogenic amino acids. Recent research provides evidence that non-proteinogenic amino acid BMAA produced by cyanobacteria have multiple effects on translation process and bypasses the proof-reading ability of the aminoacyl-tRNA-synthetase. Aberrant proteins generated by non-canonical translation may be a factor in neuronal death and neurodegeneration. We hypothesize that the production of cyanopeptides and non-canonical amino acids is a more general mechanism, leading to mistranslation, affecting protein homeostasis, and targeting mitochondria in eukaryotic cells. It can be evolutionarily ancient and initially developed to control phytoplankton communities during algal blooms. Outcompeting gut symbiotic microorganisms may lead to dysbiosis, increased gut permeability, a shift in blood-brain-barrier functionality, and eventually, mitochondrial dysfunction in high-energy demanding neurons. A better understanding of the interaction between cyanopeptides metabolism and the nervous system will be crucial to target or to prevent neurodegenerative diseases.

Cyanophage technology in removal of cyanobacteria mediated harmful algal blooms: A novel and eco-friendly method

Cyanophages are highly abundant specific viruses that infect cyanobacterial cells. In recent years, the cyanophages and cyanobacteria interactions drew attention to environmental restoration due to their discovery in marine and freshwater systems. Cyanobacterial harmful algal blooms (cyanoHABs) are increasing throughout the world and contaminating aquatic ecosystems. The blooms cause severe environmental problems including unpleasant odors and cyanotoxin production. Cyanotoxins have been reported to be lethal agents for living beings and can harm animals, people, aquatic species, recreational activities, and drinking water reservoirs. Biological remediation of cyanoHABs in aquatic systems is a sustainable and eco-friendly approach to increasing surface water quality. Therefore, this study compiles the fragmented information with the solution of removal of cyanoHABs using cyanophage therapy techniques. To date, scant information exists in terms of bloom formation, cyanophage occurrence, and mode of action to remediate cyanoHABs. Overall, this study illustrates cyanobacterial toxin production and its impacts on the environment, the mechanisms involved in the cyanophage-cyanobacteria interaction, and the application of cyanophages for the removal of toxic cyanobacterial blooms.

Effect of cold food storage techniques on the contents of Microcystins and Cylindrospermopsin in leaves of spinach (Spinacia oleracea) and lettuce (Lactuca sativa)

The presence of Cylindrospermopsin (CYN) and Microcystins (MCs) in vegetables is considered as a significant worldwide toxicological risk. Thus, this work aims to assess for the first time the impact of refrigeration (4 °C) and freezing (-20 °C) on the levels of CYN, MCs and their mixtures (CYN + MCs) in lettuce and spinach. Samples were spiked with 750 μg cyanotoxins/g dry weight (d.w.). Several storage conditions were studied: refrigeration after 24, 48 h and 7 days, and freezing for 7 days, 1 and 3 months. Cyanotoxin concentrations were determined by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS). For CYN, refrigeration at 48 h and 7 days was effective to decrease its concentrations up to 26% and 32%, respectively, in spinach. For MCs, refrigeration was only effective in lettuce compared to spinach, showing an important decrease of 80.3% MC-LR and 85.1% MC-YR. In spinach, CYN was stable after 3 months freezing, whereas MC contents were still reduced up to 44%. Overall, cyanotoxins were less stable in the mixture compared to individual toxins for both processes, and the effect of these storage techniques were toxin and food-specific. Further studies of cyanotoxins in foods are required for evaluating the risk for humans.

Monitoring of cyanobacteria and cyanotoxins in a Colombian tropical reservoir

Anthropogenic pollution and global climate change have resulted in favorable environmental conditions for increased frequency and duration of cyanobacterial blooms in aquatic systems. Cyanobacteria can produce toxic metabolites called cyanotoxins, which have become a worldwide concern as they threaten human and animal health. The presence of cyanobacteria and four cyanotoxins were evaluated in a Colombian reservoir. The reservoir was monitored for a year, with sampling campaigns every 3 months in seven stations. To identify and quantify cyanotoxins, the ultra-high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-QqQ-MS/MS) technique was used, and the quantification of cyanobacteria was done by quantitative real-time PCR (qPCR) assay using a cyanobacterial-specific 16S rRNA gene fragment as a target. Cyanobacteria concentration was between 4.02 (± 0.11) × 10⁴ and 2.72 (± 0.28) × 10⁷ copies of Cyan 16S/μL, the minimum value corresponds to the station located in the central zone and the maximum to the station at the entrance of one of the tributary rivers. The presence of MC-RR, MC-LR, MC-YR, and NOD was detected in at least six of the seven sampling stations at different times of the year. In all cases, the concentration of the toxins detected was below 0.05 μg/L, so the guideline value established by the WHO for MC-LR was not exceeded.

Statistical model applied in the qualitative and quantitative analysis of the relationships between environmental variables and cyanotoxin concentrations in tropical reservoirs

This article presents the use of generalized additive model for location scale and shape (GAMLSS) in the qualitative and quantitative analysis of the relationships between environmental parameters and cyanotoxins in the tropical reservoirs of Colombia. The physicochemical parameters were evaluated on each of the cyanotoxins detected with levels high by ultra-high-performance liquid chromatography coupled to triple quadrupole mass spectrometry. The models showed a relation between cyanotoxins and the nutrients as soluble total Kjeldahl nitrogen (NTK), soluble phosphorus (soluble P), total phosphorus (total P), and nitrates (NO₃^-), among other nutrients that are necessary for the growth of organisms that produce toxins. This model confirms that the NTK and soluble P variables favor an increase in the concentration of MC-LR and MC-YR cyanotoxins in the Abreo Malpaso reservoir. The variables NO₃^- and dissolved O₂ contribute to a higher concentration of MC-LR, MC-YR, and MC-ADRR cyanotoxins in the Peñol reservoir. Finally, the variable total P favors the increase in the concentration of MC-LR cyanotoxin and the variable dissolved O₂ favors the increase in the concentration of cyanotoxin [D-Asp³, (E)-Dhb⁷] -MC-RR in the Playas reservoir.

Cyanobacterial anabaenopeptin-B, microcystins and their mixture cause toxic effects on the behavior of the freshwater crustacean Daphnia magna (Cladocera)

Comparison of the toxic effects caused by the pure cyanobacterial cyclic hexapeptide anabaenopeptin-B (AN-B), the heptapeptides: microcystin-LR (MC-LR) and MC-LF as well as a binary mixture of AN-B with MC-LR on the swimming speed and hopping frequency - essential activities of Daphnia, was experimentally determined. Till now, no information on behavioral effects of AN-B and its mixture with microcystins, commonly produced by cyanobacteria, was available. Also MC-LF effect on aquatic crustaceans was determined for the first time. The results showed that AN-B exerted considerable inhibition of D. magna swimming speed and hopping frequency similar to MC-LR and MC-LF. The mixture of AN-B and MC-LR caused stronger toxic effects, than the individual oligopeptides used at the same concentration. The much lower 48 h- EC₅₀ value of the AN-B and MC-LR mixture (0.95 ± 0.12 μg/mL) than those of individual oligopeptides AN-B (6.3 ± 0.63 μg/mL), MC-LR (4.0 ± 0.27 μg/mL), MC-LF (3.9 ± 0.20 μg/mL) that caused swimming speed inhibition explains the commonly observed stronger toxicity of complex crude cyanobacterial extracts to daphnids than individual microcystins. The obtained results indicated that AN-B, microcystins and their mixture exerted time- and concentration-dependent motility disturbances of crustaceans and they can be good candidates for evaluation of toxicity in early warning systems. Other cyanobacterial oligopeptides beyond microcystins should be considered as a real threat for aquatic organisms.

Overview of toxic cyanobacteria and cyanotoxins in Ibero-American freshwaters: Challenges for risk management and opportunities for removal by advanced technologies

The increasing occurrence of cyanobacterial blooms worldwide represents an important threat for both the environment and public health. In this context, the development of risk analysis and management tools as well as sustainable and cost-effective treatment processes is essential. The research project TALGENTOX, funded by the Ibero-American Science and Technology Program for Development (CYTED-2019), aims to address this ambitious challenge in countries with different environmental and social conditions within the Ibero-American context. It is based on a multidisciplinary approach that combines ecology, water management and technology fields, and includes research groups from Chile, Colombia, Mexico, Peru and Spain. In this review, the occurrence of toxic cyanobacteria and cyanotoxins in freshwaters from these countries are summarized. The presence of cyanotoxins has been confirmed in all countries but the information is still scarce and further monitoring is required. In this regard, remote sensing or metagenomics are good alternatives at reasonable cost. The risk management of freshwaters from those countries considering the most frequent uses (consumption and recreation) has been also evaluated. Only Spain and Peru include cyanotoxins in its drinking water legislation (only MC-LR) and thus, there is a need for regulatory improvements. The development of preventive strategies like diminishing nutrient loads to aquatic systems is also required. In the same line, corrective measures are urgently needed especially in drinking waters. Advanced Oxidation Processes (AOPs) have the potential to play a major role in this scenario as they are effective for the elimination of most cyanotoxins classes. The research on the field of AOPs is herein summarized considering the cost-effectiveness, environmental character and technical applicability of such technologies. Fenton-based processes and photocatalysis using solar irradiation or LED light represent very promising alternatives given their high cost-efficiency. Further research should focus on developing stable long-term operation systems, addressing their scale-up.

Four decades of progress in cylindrospermopsin research: The ins and outs of a potent cyanotoxin

The cyanotoxin cylindrospermopsin (CYN), a toxic metabolite from cyanobacteria, is of particular concern due to its cosmopolitan occurrence, aquatic bioaccumulation, and multi-organ toxicity. CYN is the second most often recorded cyanotoxin worldwide, and cases of human morbidity and animal mortality are associated with ingestion of CYN contaminated water. The toxin poses a great challenge for drinking water treatment plants and public health authorities. CYN, with the major toxicity manifested in the liver, is cytotoxic, genotoxic, immunotoxic, neurotoxic and may be carcinogenic. Adverse effects are also reported for endocrine and developmental processes. We present a comprehensive review of CYN over the past four decades since its first reported poisoning event, highlighting its global occurrence, biosynthesis, toxicology, removal, and monitoring. In addition, current data gaps are identified, and future directions for CYN research are outlined. This review is beneficial for understanding the ins and outs of this environmental pollutant, and for robustly assessing health hazards posed by CYN exposure to humans and other organisms.

Potential applications of CRISPR/Cas for next-generation biomonitoring of harmful algae blooms: A review

Research on harmful algal and cyanobacterial blooms (HABs and CHABs) has risen dramatically due to their increasing global distribution, frequency, and intensity. These blooms jeopardize public health, ecosystem function, sustainability and can have negative economic impacts. Numerous monitoring programs have been established using light microscopy, liquid chromatography coupled to mass spectrometry (LC-MS), ELISA, and spectrophotometry to monitor HABs/CHABs outbreaks. Recently, DNA/RNA-based molecular methods have been integrated into these programs to replace or complement traditional methods through analyzing environmental DNA and RNA (eDNA/eRNA) with techniques such as quantitative polymerase chain reaction (qPCR), fluorescent in situ hybridization (FISH), sandwich hybridization assay (SHA), isothermal amplification methods, and microarrays. These have enabled the detection of rare or cryptic species, enhanced sample throughput, and reduced costs and the need for visual taxonomic expertise. However, these methods have limitations, such as the need for high capital investment in equipment or detection uncertainties, including determining whether organisms are viable. In this review, we discuss the potential of newly developed molecular diagnosis technology based on Clustered Regularly Interspaced Short Palindromic Repeats/Cas proteins (CRISPR/Cas), which utilizes the prokaryotic adaptative immune systems of bacteria and archaea. Cas12 and Cas13-based platforms can detect both DNA and RNA with attomolar sensitivity within an hour. CRISPR/Cas diagnostic is a rapid, inexpensive, specific, and ultrasensitive technology that, with some further development, will provide many new platforms that can be used for HABs/CHABs biomonitoring and research.

Genotoxic Effects of Cylindrospermopsin, Microcystin-LR and Their Binary Mixture in Human Hepatocellular Carcinoma (HepG2) Cell Line

Simultaneous occurrence of cylindrospermopsin (CYN) and microcystin-LR (MCLR) has been reported in the aquatic environment and thus human exposure to such mixtures is possible. As data on the combined effects of CYN/MCLR are scarce, we aimed to investigate the adverse effects related to genotoxic activities induced by CYN (0.125, 0.25 and 0.5 µg/mL) and MCLR (1 µg/mL) as single compounds and their combinations in HepG2 cells after 24 and 72 h exposure. CYN and CYN/MCLR induced DNA double-strand breaks after 72 h exposure, while cell cycle analysis revealed that CYN and CYN/MCLR arrested HepG2 cells in G0/G1 phase. Moreover, CYN and the combination with MCLR upregulated CYP1A1 and target genes involved in DNA-damage response (CDKN1A, GADD45A). Altogether, the results showed that after 72 h exposure genotoxic activity of CYN/MCLR mixture was comparable to the one of pure CYN. On the contrary, MCLR (1 µg/mL) had no effect on the viability of cells and had no influence on cell division. It did not induce DNA damage and did not deregulate studied genes after prolonged exposure. The outcomes of the study confirm the importance of investigating the combined effects of several toxins as the effects can differ from those induced by single compounds.

Cylindrospermopsin-Microcystin-LR Combinations May Induce Genotoxic and Histopathological Damage in Rats

Cylindrospermopsin (CYN) and microcystins (MC) are cyanotoxins that can occur simultaneously in contaminated water and food. CYN/MC-LR mixtures previously investigated in vitro showed an induction of micronucleus (MN) formation only in the presence of the metabolic fraction S9. When this is the case, the European Food Safety Authority recommends a follow up to in vivo testing. Thus, rats were orally exposed to 7.5 + 75, 23.7 + 237, and 75 + 750 μg CYN/MC-LR/kg body weight (b.w.). The MN test in bone marrow was performed, and the standard and modified comet assays were carried out to measure DNA strand breaks or oxidative DNA damage in stomach, liver, and blood cells. The results revealed an increase in MN formation in bone marrow, at all the assayed doses. However, no DNA strand breaks nor oxidative DNA damage were induced, as shown in the comet assays. The histopathological study indicated alterations only in the highest dose group. Liver was the target organ showing fatty degeneration and necrotic hepatocytes in centrilobular areas, as well as a light mononuclear inflammatory periportal infiltrate. Additionally, the stomach had flaking epithelium and mild necrosis of epithelial cells. Therefore, the combined exposure to cyanotoxins may induce genotoxic and histopathological damage in vivo.

Endocytosis in microcystis aeruginosa accelerates the synthesis of microcystins in the presence of lanthanum(III)

Microcystis aeruginosa bloom releases microcystins (MCs) into global aquatic environment, which other living organisms can ingest the released MCs. The toxic effects of MCs on organisms are amplified through the food chain, threatening human and animal health. Lanthanum(III) [La(III)], a pollutant in aquatic environments worldwide, has been confirmed to stimulate MC synthesis in M. aeruginosa. However, the involved cellular mechanism remains unclear. Here, using interdisciplinary approaches, it was first observed that La(III) activated the clathrin-mediated endocytosis in M. aeruginosa. This allowed the algal cells to rapidly absorb macro-elements (C, N and P) and micro-elements (K, Ca and Mg) through the clathrin-mediated endocytosis. These in turn stimulated chlorophyll production, photosynthesis, the growth of the algal cells, and the increases in the productions of MC-LW, MC-LR and MC-YR in M. aeruginosa. These results provide valuable insights for understanding the involved cellular mechanism on MC synthesis and managing MC pollution, which is important to protect global food chain and the ecosystem.

Metabolome Variation between Strains of Microcystis aeruginosa by Untargeted Mass Spectrometry

Cyanobacteria are notorious for their potential to produce hepatotoxic microcystins (MCs), but other bioactive compounds synthesized in the cells could be as toxic, and thus present interest for characterization. Ultra performance liquid chromatography and high-resolution accurate mass spectrometry (UPLC-QTOF-MS/MS) combined with untargeted analysis was used to compare the metabolomes of five different strains of the common bloom-forming cyanobacterium, Microcystis aeruginosa. Even in microcystin-producing strains, other classes of oligopeptides including cyanopeptolins, aeruginosins, and aerucyclamides, were often the more dominant compounds. The distinct and large variation between strains of the same widespread species highlights the need to characterize the metabolome of a larger number of cyanobacteria, especially as several metabolites other than microcystins can affect ecological and human health.

Dhb Microcystins Discovered in USA Using an Online Concentration LC-MS/MS Platform

Based on current structural and statistical calculations, thousands of microcystins (MCs) can exist; yet, to date, only 246 MCs were identified and only 12 commercial MC standards are available. Standard mass spectrometry workflows for known and unknown MCs need to be developed and validated for basic and applied harmful algal bloom research to advance. Our investigation focuses on samples taken in the spring of 2018 from an impoundment fed by Oser and Bischoff Reservoirs, Indiana, United States of America (USA). The dominant cyanobacterium found during sampling was Planktothrix agardhii. The goal of our study was to identify and quantify the MCs in the impoundment sample using chemical derivatization and mass spectrometry. Modifying these techniques to use online concentration liquid chromatography tandem mass spectrometry (LC-MS/MS), two untargeted MCs have been identified, [d-Asp3, Dhb7]-MC-LR and [Dhb7]-MC-YR. [Dhb7]-MC-YR is not yet reported in the literature to date, and this was the first reported incidence of Dhb MCs in the United States. Furthermore, it was discovered that the commercially available [d-Asp3]-MC-RR standard was [d-Asp3, Dhb7]-MC-RR. This study highlights a workflow utilizing online concentration LC-MS/MS, high-resolution MS (HRMS), and chemical derivatization to identify isobaric MCs.