Toxicity of cylindrospermopsin to the brine shrimp Artemia salina: comparisons with protein synthesis inhibitors and microcystins

Biotests in Cyanobacterial Toxicity Assessment-Efficient Enough or Not?

Cyanobacteria are a diverse group of organisms known for producing highly potent cyanotoxins that pose a threat to human, animal, and environmental health. These toxins have varying chemical structures and toxicity mechanisms and several toxin classes can be present simultaneously, making it difficult to assess their toxic effects using physico-chemical methods, even when the producing organism and its abundance are identified. To address these challenges, alternative organisms among aquatic vertebrates and invertebrates are being explored as more assays evolve and diverge from the initially established and routinely used mouse bioassay. However, detecting cyanotoxins in complex environmental samples and characterizing their toxic modes of action remain major challenges. This review provides a systematic overview of the use of some of these alternative models and their responses to harmful cyanobacterial metabolites. It also assesses the general usefulness, sensitivity, and efficiency of these models in investigating the mechanisms of cyanotoxicity expressed at different levels of biological organization. From the reported findings, it is clear that cyanotoxin testing requires a multi-level approach. While studying changes at the whole-organism level is essential, as the complexities of whole organisms are still beyond the reach of in vitro methodologies, understanding cyanotoxicity at the molecular and biochemical levels is necessary for meaningful toxicity evaluations. Further research is needed to refine and optimize bioassays for cyanotoxicity testing, which includes developing standardized protocols and identifying novel model organisms for improved understanding of the mechanisms with fewer ethical concerns. In vitro models and computational modeling can complement vertebrate bioassays and reduce animal use, leading to better risk assessment and characterization of cyanotoxins.

Analysis of Total-Forms of Cyanotoxins Microcystins in Biological Matrices: A Methodological Review

Microcystins (MCs) are cyclic heptapeptidic toxins produced by many cyanobacteria. Microcystins can be accumulated in various matrices in two forms: a free cellular fraction and a covalently protein-bound form. To detect and quantify the concentration of microcystins, a panel of techniques on various matrices (water, sediments, and animal tissues) is available. The analysis of MCs can concern the free or the total (free plus covalently bound) fractions. Free-form analyses of MCs are the most common and easiest to detect, whereas total-form analyses are much less frequent and more complex to achieve. The objective of this review is to summarize the different methods of extraction and analysis that have been developed for total forms. Four extraction methods were identified: MMPB (2-methyl-3-methoxy-4-phenylbutyric acid) method, deconjugation at basic pH, ozonolysis, and laser irradiation desorption. The study of the bibliography on the methods of extraction and analysis of the total forms of MCs showed that the reference method for the subject remains the MMPB method even if alternative methods and, in particular, deconjugation at basic pH, showed results encouraging the continuation of the methodological development on different matrices and on naturally-contaminated samples.

Mixture toxicity of TiO2 NPs and tetracycline at two trophic levels in the marine ecosystem: Chlorella sp. and Artemia salina

Increasing usage of both nanomaterials and pharmaceuticals and their unabated release to the marine ecosystem pose a serious concern nowadays. The toxicity of the mixture of TiO₂ NPs and tetracycline (TC) in the marine species are not very well covered in prior literature. The current study explores the joint toxic effects of TiO₂ NPs and TC in a simulated marine food chain: Chlorella sp. and Artemia salina. Chlorella sp. was interacted with pristine TiO₂ NPs (0.05, 05, and 5 mg/L), TC (0.5 mg/L), and their combinations for 48 h. The toxicity induced in Chlorella sp. by pristine TiO₂ NPs through oxidative stress and chloroplast damage was not significantly changed in the presence of TC. Principal component analysis for the toxicity parameters revealed a strong association between growth inhibition and adsorption/internalization. In the second trophic level (A. salina), the waterborne exposure of TC additively increased the toxicity of TiO₂ NPs. Both adsorption and degradation played a major role in the removal of TC from the suspension, resulting in additive toxic effects in both Chlorella sp. and A. salina. Compared to the waterborne exposure, the foodborne exposure of TiO₂ NPs and TC induced lesser toxic effects owing to reduced uptake and accumulation in A. salina. Biomagnification results indicate that the dietary transfer of TiO₂ NPs and TC does not pose a serious environmental threat in this two-level marine food chain.

Antibiotics in mariculture systems: A review of occurrence, environmental behavior, and ecological effects

Antibiotics are widely applied to prevent and treat diseases occurred in mariculture. The often-open nature of mariculture production systems has led to antibiotic residue accumulation in the culturing and adjacent environments, which can adversely affect aquatic ecosystems, and even human. This review summarizes the occurrence, environmental behavior, and ecological effects of antibiotics in mariculture systems based on peer-reviewed papers. Forty-five different antibiotics (categorized into ten groups) have been detected in mariculture systems around the world, which is far greater than the number officially allowed. Indiscriminate use of antibiotics is relatively high among major producing countries in Asia, which highlights the need for stricter enforcement of regulations and policies and effective antibiotic removal methods. Compared with other environmental systems, some environmental characteristics of mariculture systems, such as high salinity and dissolved organic matter (DOM) content, can affect the migration and transformation processes of antibiotics. Residues of antibiotics favor the proliferation of antibiotic resistance genes (ARGs). Antibiotics and ARGs alter microbial communities and biogeochemical cycles, as well as posing threats to marine organisms and human health. This review may provide a valuable summary of the effects of antibiotics on mariculture systems.

Evaluation of toxic effects induced by repeated exposure to Cylindrospermopsin in rats using a 28-day feeding study

Cylindrospermopsin (CYN) is a toxin with a world-wide increasing occurrence. It can induce toxic effects both in humans and the environment, and toxicity studies are needed to complete its toxicological profile. In this sense, in vivo oral toxicity studies with pure CYN are scarce. The aim of this work was to perform a repeated dose 28-day oral study in rats following the OECD guideline 407 to provide information on health hazard likely to arise from this kind of exposure. Male and female Sprague-Dawley rats were dosed with 18.75, 37.5 and 75 μg CYN/kg b.w./day. After the study period, no clinical signs or mortality and no significant differences in final body weight, body weight gain and total feed intake in both sexes were observed. Only in females some biochemical parameters (triglycerides (TRIG) levels and aspartate aminotransferase (AST) activity) as well as changes in the weight of organs (absolute liver weight values, relative kidney/body weight ratios or relative liver weight/brain weight ratios) were altered, but without toxicological relevance. Histopathological analysis revealed a very mild affectation of liver and kidney in rats. These results suggest the need to perform longer oral toxicity studies to define the potential consequences of long term CYN exposure.

In Vivo and In Vitro Toxicity Testing of Cyanobacterial Toxins: A Mini-Review

Harmful cyanobacterial blooms are increasing and becoming a worldwide concern as many bloom-forming cyanobacterial species can produce toxic metabolites named cyanotoxins. These include microcystins, saxitoxins, anatoxins, nodularins, and cylindrospermopsins, which can adversely affect humans, animals, and the environment. Different methods to assess these classes of compounds in vitro and in vivo include biological, biochemical, molecular, and physicochemical techniques. Furthermore, toxic effects not attributable to known cyanotoxins can be observed when assessing bloom material. In order to determine exposures to cyanotoxins and to monitor compliance with drinking and bathing water guidelines, it is necessary to have reliable and effective methods for the analysis of these compounds. Many relatively simple low-cost methods can be employed to rapidly evaluate the potential hazard. The main objective of this mini-review is to describe the assessment of toxic cyanobacterial samples using in vitro and in vivo bioassays. Newly emerging cyanotoxins, the toxicity of analogs, or the interaction of cyanobacteria and cyanotoxins with other toxicants, among others, still requires bioassay assessment. This review focuses on some biological and biochemical assays (MTT assay, Immunohistochemistry, Micronucleus Assay, Artemia salina assay, Daphnia magna test, Radionuclide recovery, Neutral red cytotoxicity and Comet assay, Enzyme-Linked Immunosorbent Assay (ELISA), Annexin V-FITC assay and Protein Phosphatase Inhibition Assay (PPIA)) for the detection and measurement of cyanotoxins including microcystins, cylindrospermopsins, anatoxin-a, saxitoxins, and nodularins. Although most bioassay analyses often confirm the presence of cyanotoxins at low concentrations, such bioassays can be used to determine whether some strains or blooms of cyanobacteria may produce other, as yet unknown toxic metabolites. This review also aims to identify research needs and data gaps concerning the toxicity assessment of cyanobacteria.

Global scanning of cylindrospermopsin: Critical review and analysis of aquatic occurrence, bioaccumulation, toxicity and health hazards

Cylindrospermopsin (CYN), a cyanotoxin produced by harmful algal blooms, has been reported worldwide; however, there remains limited understanding of its potential risks to surface water quality. In the present study, we critically reviewed available literature regarding the global occurrence, bioaccumulation, and toxicity of CYN in aquatic systems with a particular focus on freshwater. We subsequently developed environmental exposure distributions (EEDs) for CYN in surface waters and performed probabilistic environmental hazard assessments (PEHAs) using guideline values (GVs). PEHAs were performed by geographic region, type of aquatic system, and matrix. CYN occurrence was prevalent in North America, Europe, and Asia/Pacific, with lakes being the most common system. Many global whole water EEDs exceeded guideline values (GV) previously developed for drinking water (e.g., 0.5 μg L-1) and recreational water (e.g., 1 μg L-1). GV exceedances were higher in the Asia/Pacific region, and in rivers and reservoirs. Rivers in the Asia/Pacific region exceeded the lowest drinking water GV 73.2% of the time. However, lack of standardized protocols used for analyses was alarming, which warrants improvement in future studies. In addition, bioaccumulation of CYN has been reported in mollusks, crustaceans, and fish, but such exposure information remains limited. Though several publications have reported aquatic toxicity of CYN, there is limited chronic aquatic toxicity data, especially for higher trophic level organisms. Most aquatic toxicity studies have not employed standardized experimental designs, failed to analytically verify treatment levels, and did not report purity of CYN used for experiments; therefore, existing data are insufficient to derive water quality guidelines. Considering such elevated exceedances of CYN in global surface waters and limited aquatic bioaccumulation and toxicity data, further aquatic monitoring, environmental fate and mechanistic toxicology studies are warranted to robustly assess and manage water quality risks to public health and the environment.

Degradation of widespread cyanotoxins with high impact in drinking water (microcystins, cylindrospermopsin, anatoxin-a and saxitoxin) by CWPO

The occurrence of harmful cyanobacterial blooms has unabated increased over the last few decades, posing a significant risk for public health. In this work, we investigate the feasibility of catalytic wet peroxide oxidation (CWPO) promoted by modified natural magnetite (Fe₃O₄-R400/H₂O₂), as an inexpensive, simple-operation and environmentally-friendly process for the removal of the cyanotoxins that show the major impact on drinking water: microcystins (MC-LR and MC-RR), cylindrospermopsin (CYN), anatoxin-a (ATX) and saxitoxin (STX). The performance of the system was evaluated under ambient conditions and circumneutral pH (pH₀ = 5) using relevant cyanotoxin concentrations (100-500 μg L^-1). The nature of the cyanotoxins determined their reactivity towards CWPO, which decreased in the following order: MC-RR > CYN > MC-LR ≫ ATX > STX. In this sense, microcystins and CYN were completely removed in short reaction times (1-1.5 h) with a low catalyst concentration (0.2 g L^-1) and the stoichiometric amount of H₂O₂ (2-2.6 mg L^-1), while only 60-80% conversion was achieved with ATX and STX in 5 h. In these cases, an intensification of the operating conditions (1 g L^-1 catalyst and up to 30 mg H₂O₂ L^-1) was required to remove both toxins in 1 h. The impact of the main components of freshwaters i.e. natural organic matter (NOM) and several inorganic ions (HCO₃^-, HPO₄^2-, SO₄^2-) on the performance of the process was also investigated. Although the former led to a partial inhibition of the reaction due to HO· scavenging and catalyst coating, the latter did not show any remarkably effect, and the versatility of the process was finally confirmed in a real surface water. To further demonstrate the effectiveness of the catalytic system, the toxicity of both the initial cyanotoxins and the resulting CWPO effluents was measured with the brine shrimp Artemia salina. Remarkably, all CWPO effluents were non-toxic at the end of the treatment.

Screening of cyanobacterial cultures originating from different environments for cyanotoxicity and cyanotoxins

Eighty cultures from the Novi Sad Cyanobacterial Culture Collection (NSCCC) were screened for toxicity with Artemia salina bioassay and for common cyanobacterial toxins, microcystins/nodularin (MCs/NOD) and saxitoxin (STX), with ELISA assays. The results show that 22.5% (11) of the investigated cyanobacterial cultures in exponential phase exhibited toxicity in the A. salina bioassay and 38.7% (31) produced MCs/NOD and/or STX. However, the findings in the two methods applied were contradictory. Therefore, A. salina bioassay was repeated on 28 cultures in stationary growth phase, which were positive in ELISA assays but not in the initial A. salina bioassay. Seven more cultures exhibited cell-bound toxicity, and only one extracellular toxicity. The observed difference in the toxicity indicates that cyanobacterial growth phase could affect the screening results. The findings also varied depending on the environment from which the cultures originated. In the initial screening via bioassay, 11.8% (6 cultures out of 51) from terrestrial and 17.2% (5 out of 29) from aquatic environment showed cell-bound toxicity. Furthermore, based on the ELISA assay, 31.4% (16) of the cultures from terrestrial ecosystems were positive for the presence of the investigated cyanotoxins, and 51.7% (15) from aquatic ecosystems. Based on all results, more frequent toxin production was observed in cultures originating from aquatic environments. Furthermore, the group of terrestrial cultures that originated from biological loess crusts were basically non-toxic. The discrepancies in the results by two different methods indicates that the use of several complementary methods would help to improve the assessment of cyanobacterial toxicity and cyanotoxin analyses.

Ecological risk assessment of microcystin-LR in the upstream section of the Haihe River based on a species sensitivity distribution model

The eutrophication of surface water has been the main problem of water quality management in recent decades, and the ecological risk of microcystin-LR (MC-LR), which is the by-product of eutrophication, has drawn more attention worldwide. The aims of our study were to determine the predicted no effect concentration (PNEC) of MC-LR and to assess the ecological risk of MC-LR in the upstream section of the Haihe River. HC₅ (hazardous concentration for 5% of biological species) and PNEC were obtained from a species sensitivity distribution (SSD) model, which was constructed with the acute toxicity data of MC-LR on aquatic organisms. The concentrations of MC-LR in the upstream section of the Haihe River from April to August of 2015 were analysed, and the ecological risk characteristics of MC-LR were evaluated based on the SSD model. The results showed that the HC₅ of MC-LR in freshwater was 17.18 μg/L and PNEC was 5.73 μg/L. The concentrations of MC-LR ranged from 0.68 μg/L to 32.21 μg/L and were obviously higher in summer than in spring. The values of the risk quotient (RQ) ranged from 0.12 to 5.62, suggesting that the risk of MC-LR for aquatic organisms in the river was at a medium or high level during the study period. Compared with other waterbodies in the world, the pollution level of MC-LR in the Haihe River was at a moderate level. This research could promote the study of the ecological risk of MC-LR at the ecosystem level.

Impact of the toxicity of Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju on laboratory rats in vivo

In vivo laboratory studies of toxicity were performed on Wistar rats using a methanol extract produced by the natural population of Cylindrospermopsis raciborskii (abundance of 2.13 × 10⁵ trichomes mL^-1) collected at Aleksandrovac Lake (Serbia). HPLC analysis showed that the extract contains 6.65 μg cylindrospermopsin (CYN) mg^-1. The rats were killed 24 or 72 h after a single intraperitoneal injection of C. raciborskii extract in concentrations of 1500, 3000, 6000 and 12,000 μg kg^-1 body weight (bw) and an equivalent amount of CYN as present in the highest dose of the extract (79.80 μg CYN kg^-1 bw). The genotoxic effect on the livers treated with C. raciborskii was evaluated using comet assay and potential induction of oxidative stress as the toxicity mechanism associated with the presence of CYN in extract. The results from the analyses of DNA damage in the comet tail length, tail moment and percentage of DNA in the tail in the liver indicated that administration of extract and CYN present statistically significant difference when compared with the negative control group. Although an increase in the frequency of selected parameters induced by the CYN was observed in the liver, this damage was less than the damage resulting from the administration of the highest dose of extract. The changes in the biochemical parameters of the hepatic damage showed that the application of single doses of the extract and CYN did not cause serious liver damage in rats. The extract and CYN significantly increased oxidative stress in rats' liver after a single exposure.

Pharmacological studies confirm neurotoxic metabolite(s) produced by the bloom-forming Cylindrospermopsis raciborskii in Hungary

A rapid cyanobacterial bloom of Cylindrospermopsis raciborskii (3.2 × 10(4) filaments/mL) was detected early November, 2012, in the Fancsika pond (East Hungary). The strong discoloration of water was accompanied by a substantial fish mortality (even dead cats were seen on the site), raising the possibility of some toxic metabolites in the water produced by the bloom-forming cyanobacteria (C. raciborskii). The potential neuronal targets of the toxic substances in the bloom sample were studied on identified neurons (RPas) in the central nervous system of Helix pomatia. The effects of the crude aqueous extracts of the Fancsika bloom sample (FBS) and the laboratory isolate of C. raciborskii from the pond (FLI) were compared with reference samples: C. raciborskii ACT 9505 (isolated in 1995 from Lake Balaton, Hungary), the cylindrospermopsin producer AQS, and the neurotoxin (anatoxin-a, homoanatoxin-a) producer Oscillatoria sp. (PCC 6506) strains. Electrophysiological tests showed that both FBS and FLI samples as well the ACT 9505 extracts modulate the acetylcholine receptors (AChRs) of the neurons, evoking ACh agonist effects, then inhibiting the ACh-evoked neuronal responses. Dose-response data suggested about the same range of toxicity of FBS and FLI samples (EC50  = 0.397 mg/mL and 0.917 mg/mL, respectively) and ACT 9505 extracts (EC50  = 0.734 mg/mL). The extract of the neurotoxin-producing PCC 6506 strain, however, proved to be the strongest inhibitor of the ACh responses on the same neurons (EC50  = 0.073 mg/mL). The presented results demonstrated an anatoxin-a-like cholinergic inhibitory effects of cyanobacterial extracts (both the environmental FBS sample, and the laboratory isolate, FLI) by some (yet unidentified) toxic components in the matrix of secondary metabolites. Previous pharmacological studies of cyanobacterial samples collected in other locations (Balaton, West Hungary) resulted in similar conclusions; therefore, we cannot exclude that this chemotype of C. raciborskii which produce anatoxin-a like neuroactive substances is more widely distributed in this region.

Toxic potencies of metabolite(s) of non-cylindrospermopsin producing Cylindrospermopsis raciborskii isolated from temperate zone in human white cells

Cylindrospermopsis raciborskii (Nostocales, Cyanobacteria) has worldwide distribution and is well known for producing the toxic alkaloid, cylindrospermopsin (CYN). Strains unable to synthesize this compound but potentially toxic were recently identified in Europe. Here, for the first time the effect of cell-free extracts of a non-CYN-producing strain of C. raciborskii was studied in human cells (neutrophils and lymphocytes) isolated from healthy donors. The observed effects were compared to those induced by CYN (1.0-0.01 μg mL(-1)). Short-term (1h) extract treatments resulted in altered viability of cells demonstrated by increased necrosis and apoptosis in neutrophils and elevated apoptosis in lymphocytes. CYN did not induce similar effects, regardless of the toxin concentration. Exposure of T-lymphocytes to 100% C. raciborskii extract in isolated and whole-blood 72 h cultures resulted in decrease of proliferation by 20.6% and 32.5%, respectively. In comparison, exposure to 1.0 μg mL(-1) of CYN caused lymphocytes proliferation to be inhibited by 91.0% in isolated cultures and 56.5% in whole-blood assay. Significant antiproliferative properties were also found for 0.1 μg mL(-1) of CYN in whole-blood culture. From the results we conclude that strains occurring in temperate zones may pose a threat to human health through the production of hitherto unknown metabolites that reveal a toxic pattern different to that of CYN. At the same time our study demonstrates that CYN is a powerful but slowly-acting toxin in human immune cells.

In search of environmental role of cylindrospermopsin: a review on global distribution and ecology of its producers

Despite a significant interest in cyanotoxins over recent decades, their biological role is still poorly elucidated. Cylindrospermopsin (CYN) is a cyanobacterial metabolite that is globally identified in surface fresh- and brackish waters and whose producers are observed to spread throughout different climate zones. This paper provides a comprehensive review of the characteristics and global distribution of CYN-producing species, the variety of their chemotypes and the occurrence of strains which, while incapable of toxin synthesis, are able to produce other bioactive compounds including those that are hitherto unknown and yet to be identified. Environmental conditions that can trigger CYN production and promote growth of CYN-producers in aquatic ecosystems are also discussed. Finally, on the basis of existing experimental evidence, potential ecological role(s) of CYN are indicated. It is eventually concluded that CYN can be at least partially responsible for the ecological success of certain cyanobacteria species.

Nitrogen limitation promotes accumulation and suppresses release of cylindrospermopsins in cells of Aphanizomenon sp

As the biosynthesis of cylindrospermopsin (CYN) is assumed to depend on nitrogen availability, this study investigated the impact of nitrogen availability on intra- and extracellular CYN and deoxy-CYN (D-CYN) contents in three Aphanizomenon strains from temperate waters. Nitrogen deficient (−N) cultures showed a prolonged growth phase and intracellular toxin accumulation by a factor of 2–6. In contrast, cultures with additional nitrate supply (+N) did not accumulate CYN within the cells. Instead, the maximum conceivable CYN release estimated for dead cells (identified by SYTOX^® Green staining) was much lower than the concentrations of dissolved CYN actually observed, suggesting these cultures actively release CYN from intact cells. Furthermore, we found remarkably altered proportions of CYN to D-CYN: as batch cultures grew, the proportion of D-CYN increased by up to 40% in +N medium, whereas D-CYN remained constant or decreased slightly in −N medium. Since +N cultures showed similar toxin patterns as −P cultures with increased extracellular CYNs and higher proportion of D-CYN we conclude that nitrogen limitation may affect the way the cells economize resources, especially the yield from phosphorus pools, and that this has an impact on CYN production and release. For water management, these result imply that nutrient availability not only determines the abundance of potentially CYN-producing cyanobacteria, but also the amount of extracellular CYNs (challenging drinking-water treatment) as well as the ratio of D-CYN to CYN (affecting toxicity).

The course of toxicity in the pregnant mouse after exposure to the cyanobacterial toxin cylindrospermopsin: clinical effects, serum chemistries, hematology, and histopathology

Cylindrospermopsin (CYN) is a toxin produced by a variety of fresh-water cyanobacterial species worldwide and induces significant adverse effects in both livestock and humans. This study investigated the course of CYN-induced toxicity in pregnant mice exposed daily during either the period of major organogenesis (gestation days [GD] 8-12) or fetal growth (GD13-17). Endpoints include clinical signs of toxicity, serum analyses to evaluate hepatic and renal function, histopathology of liver and kidney, and hematology. Study animals were administered 50 μg/kg CYN once daily by ip route and euthanized 24 h after 1, 2, 3, 4, or 5 consecutive doses, or 6 or 13 d after the dosing period. The course of the CYN-induced effects was determined at all euthanasia times for the endpoints just outlined. Results indicated that CYN is a toxin, producing lethality in dams during the early part of gestation, significant weight loss, and bleeding in the gastrointestinal tract, tail tip, and peri-orbital tissues. Effects also included alterations in serum markers for liver function, histopathological changes in liver and kidney tissues, electrolyte abnormalities, leukocytosis, and posttreatment thrombocytopenia and reticulocytosis. The onset of symptoms was rapid, producing reductions in weight gain in GD8-12 animals, bleeding in the vaginal area in GD13-17 animals, and significant increases in sorbitol dehydrogenase (SDH) in both groups after a single dose. Although the GD8-12 dams displayed a 50% lethality, in GD13-17 animals only a single death occurred. Alterations seen in hepatic and renal function or histopathology do not appear to be of sufficient severity to produce death. Evidence indicates that bleeding may play a critical role in the onset of symptoms and eventually, in the observed lethality.

A review on cylindrospermopsin: the global occurrence, detection, toxicity and degradation of a potent cyanotoxin

Cylindrospermopsin is an important cyanobacterial toxin found in water bodies worldwide. The ever-increasing and global occurrence of massive and prolonged blooms of cylindrospermopsin-producing cyanobacteria poses a potential threat to both human and ecosystem health. Its toxicity is associated with metabolic activation and may involve mechanisms that adversely affect a wide variety of targets in an organism. Cylindrospermopsin has been shown to be cytotoxic, dermatotoxic, genotoxic, hepatotoxic in vivo, developmentally toxic, and may be carcinogenic. Human exposure may occur through drinking water, during recreational activities and by consuming foods in which the toxin may have bioaccumulated. Drinking water shortages of sufficient quality coupled with growing human pressures and climate variability and change necessitate an integrated and sustainable water management program. This review presents an overview of the importance of cylindrospermopsin, its detection, toxicity, worldwide distribution, and lastly, its chemical and biological degradation and removal by natural processes and drinking water treatment processes.

Histological, cytological and biochemical alterations induced by microcystin-LR and cylindrospermopsin in white mustard (Sinapis alba L.) seedlings

This study compares the histological, cytological and biochemical effects of the cyanobacterial toxins microcystin-LR (MCY-LR) and cylindrospermopsin (CYN) in white mustard (Sinapis alba L.) seedlings, with special regard to the developing root system. Cyanotoxins induced different alterations, indicating their different specific biochemical activities. MCY-LR stimulated mitosis of root tip meristematic cells at lower concentrations (1 μg ml-1) and inhibited it at higher concentrations, while CYN had only inhibitory effects. Low CYN concentrations (0.01 μg ml-1) stimulated lateral root formation, whereas low MCY-LR concentrations increased only the number of lateral root primordia. Both inhibited lateral root development at higher concentrations. They induced lignifications, abnormal cell swelling and inhibited xylem differentiation in roots and shoots. MCY-LR and CYN induced the disruption of metaphase and anaphase spindles, causing altered cell divisions. Similar alterations could be related to decreased protein phosphatase (PP1 and PP2A) activities in shoots and roots. However, in vitro phosphatase assay with purified PP1 catalytic subunit proved that CYN in contrast to MCY-LR, decreased phosphatase activities of mustard in a non-specific way. This study intends to contribute to the understanding of the mechanisms of toxic effects of a protein phosphatase (MCY-LR) and a protein synthesis (CYN) inhibitory cyanotoxin in vascular plants.

Toxic risk associated with sporadic occurrences of Microcystis aeruginosa blooms from tidal rivers in marine and estuarine ecosystems and its impact on Artemia franciscana nauplii populations

Microcystis aeruginosa is a species of freshwater cyanobacteria which can form harmful algal blooms in freshwater water bodies worldwide. However, in spite its sporadic occurrences for short periods of time in estuarine waters, their influence on zooplankton populations present in these ecosystems has not been extensively studied. In this work, Artemia franciscana was used as test organism model, studying mortality against several strains of M. aeruginosa with different degrees of toxigenicity, measuring whole-live cells and homogenate extracts. Results were compared with microcystin-LR equivalent content, measured by immunoassay. The results show that there were no significant differences between both exposure models (whole cells and extracts), and there are significant differences respect to the toxigenicity of cyanobacterial blooms depending of the M. aerugionosa strain involved in the process. Analysis of microcystin-LR equivalent concentration test immediately below the lowest significant concentration in all M. aerugionosa strains was used to determine the potential risk associated with the cell densities during a bloom. Comparison among the selected M. aerugionsa strains show that these factors have influence in the results obtained, and thus, several differences have been evidenced depending of the microcystin-LR equivalent production and the strain type involved.

Decolorization of reactive textile dyes using water falling film dielectric barrier discharge

Decolorization of reactive textile dyes Reactive Black 5, Reactive Blue 52, Reactive Yellow 125 and Reactive Green 15 was studied using advanced oxidation processes (AOPs) in a non-thermal plasma reactor, based on coaxial water falling film dielectric barrier discharge (DBD). Used initial dye concentrations in the solution were 40.0 and 80.0mg/L. The effects of different initial pH of dye solutions, and addition of homogeneous catalysts (H(2)O(2), Fe(2+) and Cu(2+)) on the decolorization during subsequent recirculation of dye solution through the DBD reactor, i.e. applied energy density (45-315kJ/L) were studied. Influence of residence time was investigated over a period of 24h. Change of pH values and effect of pH adjustments of dye solution after each recirculation on the decolorization was also tested. It was found that the initial pH of dye solutions and pH adjustments of dye solution after each recirculation did not influence the decolorization. The most effective decolorization of 97% was obtained with addition of 10mM H(2)O(2) in a system of 80.0mg/L Reactive Black 5 with applied energy density of 45kJ/L, after residence time of 24h from plasma treatment. Toxicity was evaluated using the brine shrimp Artemia salina as a test organism.

Cylindrospermopsin and microcystin-LR alter the growth, development and peroxidase enzyme activity of white mustard (Sinapis alba L.) seedlings, a comparative analysis

This work focuses on the comparative analysis of the effects of two cyanobacterial toxins of different chemical structure cylindrospermopsin (CYN) and microcystin-LR (MC-LR) on the white mustard (Sinapis alba L.) seedlings. Both cyanotoxins reduced significantly the fresh mass and the length of cotyledons, hypocotyls and main roots of seedlings in a concentration dependent manner. For various mustard organs the 50% inhibitory concentration values (IC50) of growth were between 3-5 μg ml(-1) for MC-LR and between 5-10 μg ml-1 for CYN, respectively. Cyanotoxins altered the development of cotyledons, the accumulation of photosynthetically active pigments and anthocyanins. Low MC-LR concentrations (0.01 and 0.1 μg ml(-1)) stimulated anthocyanin formation in the cotyledons but higher than 1 μg ml(-1) MC-LR concentrations strongly inhibited it. The CYN treated chlorotic cotyledons were violet coloured in consequence of high level of anthocyanins, while MC-LR induced chlorosis was accompanied by the appearance of necrotic patches. Necrosis and increases of peroxidase enzyme activity (POD) are general stress responses but these alterations were characteristic only for MC-LR treated mustard plants. These findings provide experimental evidences of developmental alterations induced by protein synthesis and protein phosphatase inhibitory cyanotoxins (CYN and MC-LR) in a model dicotyledonous plant.

Toxicity and recovery in the pregnant mouse after gestational exposure to the cyanobacterial toxin, cylindrospermopsin

Cylindrospermopsin (CYN) is a tricyclic alkaloid toxin produced by fresh water cyanobacterial species worldwide. CYN has been responsible for both livestock and human poisoning after oral exposure. This study investigated the toxicity of CYN to pregnant mice exposed during different segments of gestation. The course of recovery and individual responses to the toxin were evaluated. Adverse effects of CYN were monitored up to 7 weeks post-dosing by clinical examination, histopathology, biochemistry and gene expression. Exposure on gestational days (GD) 8-12 induced significantly more lethality than GD13-17 exposure. Periorbital, gastrointestinal and distal tail hemorrhages were seen in both groups. Serum markers indicative of hepatic injury (alanine amino transferase, aspartate amino transferase and sorbitol dehydrogenase) were increased in both groups; markers of renal dysfunction (blood urea nitrogen and creatinine) were elevated in the GD8-12 animals. Histopathology was observed in the liver (centrilobular necrosis) and kidney (interstitial inflammation) in groups exhibiting abnormal serum markers. The expression profiles of genes involved in ribosomal biogenesis, xenobiotic and lipid metabolism, inflammatory response and oxidative stress were altered 24 h after the final dose. One week after dosing, gross, histological and serum parameters had returned to normal, although increased liver/body weight ratio and one instance of gastrointestinal bleeding was found in the GD13-17 group. Gene expression changes persisted up to 2 weeks post-dosing and returned to normal by 4 weeks. Responses of individual animals to CYN exposure indicated highly significant inter-animal variability within the treated groups.

Cylindrospermopsin: a decade of progress on bioaccumulation research

Cylindrospermopsin (CYN) is rapidly being recognised as one of the most globally important of the freshwater algal toxins. The ever-expanding distribution of CYN producers into temperate zones is heightening concern that this toxin will represent serious human, as well as environmental, health risks across many countries. Since 1999, a number of studies have demonstrated the ability for CYN to bioaccumulate in freshwater organisms. This paper synthesizes the most current information on CYN accumulation, including notes on the global distribution of CYN producers, and a précis of CYN's ecological and human effects. Studies on the bioaccumulation of CYN are systematically reviewed, together with an analysis of patterns of accumulation. A discussion on the factors influencing bioaccumulation rates and potential is also provided, along with notes on detection, monitoring and risk assessments. Finally, key gaps in the existing research are identified for future study.

Identification and quantification of cyanobacterial toxins (microcystins) in two Moroccan drinking-water reservoirs (Mansour Eddahbi, Almassira)

Mansour Eddahbi (MED) (30 degrees 55'N, 6 degrees 53'W) and Almassira (ALM) (31 degrees 95'N, 6 degrees 72'W) are two Moroccan lake reservoirs located at an arid and semi-arid hydrographic basin, respectively. Both are used for irrigation, recreational activities and drinking-water production. This paper deals with the characterization and quantification of microcystins (MC) from two Microcystis aeruginosa blooms occurring in those reservoirs. The toxicity of the blooms was confirmed and evaluated by both mouse and Artemia bioassays. The calculated LD50 values revealed that the MED bloom had a medium toxicity (LD50=358 mg kg(-1) body weight), whereas the ALM bloom had low toxicity (LD50=829 mg kg(-1) body weight). The 24-h LC50 values were 1.88 and 4.15 mg ml(-1) for the MED and ALM blooms, respectively, using Artemia assay. The identification and quantification of MC variants were carried out by high performance liquid chromatography (HPLC) equipped with a photodiode array detector, and HPLC coupled to mass spectrometry. The MC content, as Microcystin-LR (MC-LR) equivalents, was higher in the MED bloom (64.4 microg g(-1) dry weight) than in the ALM bloom (9.9 microg g(-1) dry weight). Five MC variants were identified in the MED cyanobacteria bloom (MC-RR, MC-YR, MC-LR, MC-FR, and MC-WR) and only one (MC-LR) in the ALM bloom. The results show that the occurrence of toxic cyanobacteria blooms in the studied reservoirs may be regarded as a health hazard; therefore, cyanotoxin monitoring in them is highly recommended.

Protective efficacy of the antioxidants vitamin E and Trolox against Microcystis aeruginosa and microcystin-LR in Artemia franciscana nauplii

This study was undertaken to evaluate the protective efficacy of the antioxidants vitamin E and Trolox (a water-soluble vitamin E derivative) against the toxicity of microcystin-LR (MC-LR), Microcystis aeruginosa aqueous extract (CE), and a reference toxin, menadione sodium bisulfite (MSB), in Artemia franciscana nauplii. This was achieved by using the well-established brine shrimp bioassay. The experiment was conducted in 2 stages, with (1) 12-h mortality time course and (2) LC50 determination for 12- and 24-h exposures. Treatments consisted of MC-LR, CE, and MSB alone and with 4-h pretreatments of either vitamin E or Trolox. Sensitivity of A. franciscana nauplii with 24-h LC50 values of 11 (10.1-12.1) microg/ml for MSB and 9.5 (8.8-10.4) microg/ml for MC-LR were in general agreement with values reported for Artemia sp. Both antioxidant pretreatments resulted in significant reductions in mortality of approximately 50% at 9 h postexposure when challenged by either 40 microg/ml MC-LR or 20 microg/ml MSB. In contrast, the antioxidant pretreatments offered little to no protection from CE, suggesting that other uncharacterized bioactive compounds contributed to overall toxicity. The described bioassay is easily accessible, inexpensive, rapid, and complies with animal ethics guidelines of many countries, and thus provides a potential alternative to the mouse bioassay for the initial screening for chemoprotectants against MC-LR toxicity.

Investigation of antimicrobial and protease-inhibitory activity from cultured cyanobacteria

A culture collection of cyanobacteria has been established at the University of Illinois at Chicago. This collection includes marine, terrestrial, and freshwater strains and contains representatives of the five orders of cyanobacteria: Chroococcales, Pleurocapsales, Oscillatoriales, Nostocales, and Stigonematales. In this study, extracts from a subset of 61 strains, 16 marine and 45 freshwater/terrestrial, were evaluated against three current protease targets, i.e. 20S proteasome and two SARS viral proteases, two important bacterial targets, i.e. Mycobacterium tuberculosis and Bacillus anthracis, and in the Artemia salina toxicity assay. In total, extracts of 12 strains possessed significant levels of activity in one or more targets. The overwhelming majority of active extracts (11 of 12) were from either freshwater or terrestrial forms of cyanobacteria, with the greater part of these (9 of 12) being heterocyst-forming strains. These results further support the use of cultured cyanobacteria as a source of biologically active natural products.

Brine shrimp bioassay: importance of correct taxonomic identification of Artemia (Anostraca) species

Despite the common use of the brine shrimp bioassay in toxicology, there is confusion in the literature regarding citation of the correct taxonomic identity of the Artemia species used. The genus Artemia, once thought to be represented by a single species Artemia salina, is now known to be composed of several bisexual species as well as parthenogenetic populations. Artemia franciscana is the best studied of the Artemia species and is considered to represent the vast majority of studies in which Artemia is used as an experimental test organism. We found that in studies referring to the use of A. salina, the zoogeography of the cyst harvest site indicated that the species used was actually A. franciscana. Those performing bioassays with Artemia need to exercise diligence in assigning correct species identification, as the identity of the test organism is an important parameter in assuring the validity of the results of the assay.

Toxicity of microcystin-LR, a cyanobacterial toxin, to multiple life stages of the burrowing mayfly, Hexagenia, and possible implications for recruitment

Burrowing mayflies, genus Hexagenia, were extirpated from the major water bodies of North America in the early 1950s, paralleling an increase in eutrophication and organic pollution, and a decrease in dissolved oxygen concentrations. Burrowing mayflies recolonized the western basin of Lake Erie, but remain absent in other former habitats such as Oneida Lake, New York. Eutrophication is commonly associated with a shift in the phytoplankton community toward dominance by cyanobacteria, and therefore, one class of cyanobacterial toxins, microcystins, were investigated as a contributing factor to Hexagenia's eradication or as an impediment to recolonization. Laboratory experiments were conducted to determine if microcystin-LR (MC-LR) produced negative effects on Hexagenia at three points within its life cycle: egg, hatchling nymph (<24-h old, <1 mm total length), and pre-emergence nymph (>17 mm). Treatment concentrations ranged from the guideline set by the World Health Organization for drinking water (0.001 microg mL(-1)) to 0.1 microg mL(-1) for the egg experiment and 10 microg mL(-1) for the nymph trials. Eggs showed a delay in hatching and an altered distribution of hatching over the study period when submerged in 0.1 microg mL(-1) MC-LR (an elevated concentration representative of bloom scum). The 72-h (1.1 microg mL(-1)) and 96-h (0.049 microg mL(-1)) LC(50) values for hatchling nymphs exceeded typical bloom concentrations of North American lakes, (0.01 microg mL(-1)). Large nymphs were more tolerant of the toxin, as indicated by 100% survival over seven days exposure to 10 microg mL(-1), suggesting older larvae can withstand brief encounters with high microcystin levels for at least short periods of time. The sensitivity of young nymphs and eggs to MC-LR may have implications for the recruitment of the genus in water bodies with persistent summer cyanobacterial blooms.

In vivo influence of cyanobacterial toxins on enzyme activity and gene expression of protein phosphatases in Alfalfa (Medicago sativa)

Irrigation of crop plants with surface water can be a threat if cyanobacterial toxins are present in the water. Cyanotoxins are known to cause adverse effects in plants. Microcystin (MC), a cyclic heptapeptide, with more than 70 structural variants, is a frequently occurring toxin. MC is a specific inhibitor of serine/threonine protein phosphatases 1 and 2A (PP1 and 2A), important regulatory enzymes in eukaryotic cells. Protein phosphatases consist of a catalytic subunit and one or more regulatory subunits. In Alfalfa several isoforms of the catalytic subunit of PP1 (MsPP1alpha, MsPP1beta, MsPP1gamma, MsPP1delta, MsPP1varepsilon) and PP2A (MsPP2A Calpha/beta/gamma) are known along with isoforms of the regulatory subunits of PP2A (MsPP2A Aalpha/beta, MsPP2A Balpha/beta). The in vivo effect of environmentally relevant concentrations of cyanobacterial components on the mRNA transcript level of the subunits of protein phosphatases 1 and 2A in Alfalfa (Medicago sativa) was examined using semi-quantitative RT-PCR. Plants were exposed for one week to 5 microg L(-1) microcystin-LR, microcystin-LW, okadaic acid and to cell-free cyanobacterial crude extracts from Microcystis aeruginosa containing 5 microg L(-1) microcystin-LR and a toxin-free crude extract from Synechocystis spp. The protein phosphatase activity in vivo was inhibited when exposed to toxins and crude extract containing microcystin-LR, no change was induced by Synechocystis crude extract. The gene expression of the MsPP1gamma subunit and the MsPP1varepsilon subunit was induced in plants exposed to MC-LW.

An examination of the antibiotic effects of cylindrospermopsin on common gram-positive and gram-negative bacteria and the protozoan Naegleria lovaniensis

The importance of the toxin cylindrospermopsin to the function and fitness of the cyanobacteria that produce it remains a matter of conjecture. Given that the structure of cylindrospermopsin has commonalities with other antibacterial protein synthesis inhibitors, such as streptomycin, authors tested the possibility that the toxin might act as an antibacterial compound that can kill competing microbes. Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa were tested by the minimal inhibitory concentration method and significant antibacterial activity was only observed at a cylindrospermopsin concentration of 300 microg mL(-1) after exposure for 5 days. No effect on log phase growth of E. coli was observed for this same toxin concentration. Protein synthesis was inhibited by cylindrospermopsin in E. coli 70S extracts, reduced by 25% compared with controls when treated with 41.5 microg mL(-1) of the toxin; however, a much greater reduction of 97% was observed for chloramphenicol in the same experiment. Naegleria lovaniensis, a phagotrophic protozoan, was more susceptible to cylindrospermopsin, with a decrease in the number of N. lovaniensis plaques after 24-h treatment with 5-50 microg mL(-1) of toxin and an LC(50) of approximately 60 microg mL(-1). Given these results, cylindrospermopsin is clearly not antibacterial at concentrations found in environmental waters, nor will it adversely affect N. lovaniensis at these concentrations. For organisms that are able to ingest cylindrospermopsin-producing cells, the response of N. lovaniensis to the toxin suggests that only a few ingested cells would be enough to kill predatory organisms with similar susceptibility.

Cyanobacterial toxins: a qualitative meta-analysis of concentrations, dosage and effects in freshwater, estuarine and marine biota

This paper reviews the rapidly expanding literature on the ecological effects of cyanobacterial toxins. The study employs a qualitative meta-analysis from the literature examining results from a large number of independent studies and extracts general patterns from the literature or signals contradictions. The meta-analysis is set up by putting together two large tables--embodying a large and representative part of the literature (see Appendix A). The first table (Table A.1) reviews the presence (concentrations) of different cyanobacterial toxins in the tissues of various groups of aquatic biota after exposure via different routes, experimentally in the lab or via natural routes in the environment. The second table (Table A.2) reviews the dose dependent effect of toxins on biota. The great majority of studies deal with the presence and effects of microcystin, especially of the MC-LR congener. Although this may partly be justified--MC-LR is an abundant and highly toxic protein--our review also emphasizes what is known about (i) other MC congeners (a number of studies showed a preferred accumulation of the less toxic variant MC-RR in animal tissues), (ii) nodularin (data on a range of biota from studies on the Baltic Sea), (iii) neurotoxins like anatoxin-a(s), which are conspicuously often present at times when mass mortalities of birds occur, (iv) a few studies on the presence and effects of cylindrospermposin, as well as (v) the first examples of ecological effects of newly identified bioactive compounds, like microviridin-J. Data were reorganized to assess to what extent bioconcentration (uptake and concentration of toxins from the water) or biomagnification (uptake and concentration via the food) of cyanobacterial toxins occurs in ecosystems. There is little support for the occurrence of biomagnification, and this reduces the risk for biota at higher trophic levels. Rather than biomagnification biodilution seems to occur in the foodweb with toxins being subject to degradation and excretion at every level. Nevertheless toxins were present at all tropic levels, indicating that some vectorial transport must take place, and in sufficient quantities for effects to possibly occur. Feeding seemed to be the most important route for exposure of aquatic biota to cyanobacterial toxins. A fair number of studies focus on dissolved toxins, but in those studies purified toxin typically is used, and biota do not appear very sensitive to this form of exposure. More effects are found when crude cyanobacterial cell lysates are used, indicating that there may be synergistic effects between different bioactive compounds. Aquatic biota are by no means defenseless against toxic cyanobacteria. Several studies indicate that those species that are most frequently exposed to toxins in their natural environment are also the most tolerant. Protection includes behavioral mechanisms, detoxication of MC and NODLN by conjugation with glutathione, and fairly rapid depuration and excretion. A common theme in much of the ecological studies is that of modulating factors. Effects are seldom straightforward, but are dependent on factors like the (feeding) condition of the animals, environmental conditions and the history of exposure (acclimation and adaptation to toxic cyanobacteria). This makes it harder to generalize on what is known about ecological effects of cyanobacterial toxins. The paper concludes by summarizing the risks for birds, fish, macroinvertebrates and zooplankton. Although acute (lethal) effects are mentioned in the literature, mass mortalities of--especially--fish are more likely to be the result of multiple stress factors that co-occur during cyanobacterial blooms. Bivalves appear remarkably resistant, whilst the harmful effects of cyanobacteria on zooplankton vary widely and the specific contribution of toxins is hard to evaluate.

Multiple-organ toxicity resulting from cylindrospermopsin exposure in tadpoles of the cane toad (Bufo marinus)

Histological examinations were made of cane toad (Bufo marinus) tadpoles after exposure to freeze-thawed Cylindrospermopsis raciborskii whole cell extracts and live C. raciborskii cultures containing sublethal concentrations of the blue-green algal toxin, cylindrospermopsin (CYN). Toxin exposure resulted in tissue injuries to multiple organs, with particular severity noted in the liver, intestine, nephric ducts and gill epithelia. The extent of cellular damage was similar across trials exposing tadpoles to aqueous and cell-bound toxins, despite unequal toxin concentrations being present in each. It was concluded that the presence of cell-bound toxin, which may be directly ingested via grazing, plays a crucial role in the exertion of histological effects in B. marinus. This work provides baseline information regarding the ecotoxicity of CYN toward amphibians. The range of cellular effects noted in CYN-exposed tadpoles suggests that toxic C. raciborskii blooms could represent considerable health risks to amphibian populations and indicate potentially far-reaching ecological impacts of toxic C. raciborskii blooms.

Induction of p53-regulated gene expression in human cell lines exposed to the cyanobacterial toxin cylindrospermopsin

Cylindrospermopsin (CYN) is a cyanobacterial toxin that induces a range of genotoxic indicators in a variety of models. The possible involvement of the tumor suppressor protein p53 in cylindrospermopsin-induced gene expression was examined in cultured human dermal fibroblasts and the human hepatocellular carcinoma cell line HepG2. After 6 h of exposure to CYN, concentration-dependent increases in mRNA levels were observed for the p53 target genes CDKN1A, GADD45alpha, BAX, and MDM2, indicating an early activation of p53. After 24 h, relative mRNA levels for these genes remained elevated. Accumulation of p53 protein occurred after longer exposures in the HepG2-derived cell line C3A. Data suggest that cylindrospermopsin induces stress responses that result in the activation of the p53 transcription factor.

Toxins of cyanobacteria

Blue-green algae are found in lakes, ponds, rivers and brackish waters throughout the world. In case of excessive growth such as bloom formation, these bacteria can produce inherent toxins in quantities causing toxicity in mammals, including humans. These cyanotoxins include cyclic peptides and alkaloids. Among the cyclic peptides are the microcystins and the nodularins. The alkaloids include anatoxin-a, anatoxin-a(S), cylindrospermopsin, saxitoxins (STXs), aplysiatoxins and lyngbyatoxin. Both biological and chemical methods are used to determine cyanotoxins. Bioassays and biochemical assays are nonspecific, so they can only be used as screening methods. HPLC has some good prospects. For the subsequent detection of these toxins different detectors may be used, ranging from simple UV-spectrometry via fluorescence detection to various types of MS. The main problem in the determination of cyanobacterial toxins is the lack of reference materials of all relevant toxins. In general, toxicity data on cyanotoxins are rather scarce. A majority of toxicity data are known to be of microcystin-LR. For nodularins, data from a few animal studies are available. For the alkaloids, limited toxicity data exist for anatoxin-a, cylindrospermopsin and STX. Risk assessment for acute exposure could be relevant for some types of exposure. Nevertheless, no acute reference doses have formally been derived thus far. For STX(s), many countries have established tolerance levels in bivalves, but these limits were set in view of STX(s) as biotoxins, accumulating in marine shellfish. Official regulations for other cyanotoxins have not been established, although some (provisional) guideline values have been derived for microcystins in drinking water by WHO and several countries.

A rapid microbiotest for the detection of cyanobacterial toxins

Cyanobacteria occur widely in lakes, reservoirs, ponds, and slow flowing rivers. Many species are known to produce toxins (cyanotoxins), a number of which are of concern for health. Cyanotoxins vary in chemical structure and may be found intracellular or released into water. There is not only a wide variation in the toxicity of known cyanotoxins but a substantial number of toxins have to date not been identified chemically. Chemical analysis of cyanotoxins is nowadays not used for routine monitoring because it is time consuming, it requires specialized equipment and expertise, and is hence expensive. There is hence an urgent need for rapid tests in surface waters to detect cyanobacterial toxins because of the need for safe drinking water and safe natural bathing waters, which may be burdened by cyanobacterial blooms or scums. Previous investigations have already shown that larvae of the anostracan crustacean Thamnocephalus platyurus are quite sensitive to neurotoxic and hepatotoxic cyanotoxins. The present paper reports on the sensitivity comparison of the (1 h) Rapidtoxkit (based on a sublethal endpoint) and the (24 h) Thamnotoxkit microbiotest (based on mortality). Both assays make use of larvae of T. platyurus. The Rapidtoxkit is a new microbiotest that determines the decrease of ingestion of colored particles by the crustacean larvae, which are stressed by a short exposure to toxicants. Fifteen cyanobacterial samples composed of laboratory strains and natural bloom samples were tested by both microbiotests. All samples were also analyzed concurrently by HPLC for microcystins and cylindrospermopsin. The correlation coefficient between the two microbiotests (r = 0.82) showed the very good correspondence between the sublethal and the lethal effects. No known toxins could be detected in some samples, although the latter were found highly toxic to the test organisms in both bioassays. These results point to the presence of unknown toxin(s) produced by some cyanobacteria such as e.g., the Cylindrospermopsis raciborskii strain isolated from Lake Balaton in Hungary. This comparative study clearly showed that the 1 h Rapidtoxkit is an attractive rapid alternative to the Thamnotoxkit microbiotest.

The cyanobacterial toxin, cylindrospermopsin, induces fetal toxicity in the mouse after exposure late in gestation

Cylindrospermopsin (cyn) is a cyanobacterial toxin implicated in human and wildlife poisonings. We have completed studies investigating the potential of purified cyn to induce developmental toxicity in mammals. The teratology study involved intraperitoneal injections (8.0-128 microg kg(-1)) on gestational days (GD) 8-12 with subsequent examination of term fetuses for viability, weight and morphological anomalies. Cyn was lethal to a significant portion of the dams receiving > or = 32 microg kg(-1). Surviving pregnant females were killed and fetuses removed for examination. Analysis indicates no adverse effects on litter size, fetal weight, or incidence of anomalies. Subsequently, 50 microg kg(-1) cyn was administered on GD 8-12 or 13-17. Animals were allowed to give birth and litters monitored for growth and viability. A reduction in litter size occurred in treated groups. Avg. pup wt. was only affected in the GD 13-17 group. GD 13-17 dams did not exhibit the toxicity noted in the GD 8-12 group but gave birth significantly earlier than controls. There was a significant number of dead GD 13-17 pups and incidences of blood in the gastrointestinal tract and hematomas in the tips of the tails in survivors. Pups were cross-fostered to control mothers in litters of 10. On postnatal days (PND) 5-6 there were no significant differences in weight gain or viability in GD 8-12 litters, while GD 13-17 litters had significantly reduced weight gain and viability. GD 13-17 exposed male pups still weighed significantly less than the controls after 15 months.

Protection against the toxicity of microcystin-LR and cylindrospermopsin in Artemia salina and Daphnia spp. by pre-treatment with cyanobacterial lipopolysaccharide (LPS)

Purified cyanobacterial lipopolysaccharide (LPS) was not acutely toxic to three aquatic invertebrates (Artemia salina, Daphnia magna and Daphnia galeata) in immersion trials. However, pre-exposure (24 h) to 2 ngmL(-1) LPS increased the LC(50) of microcystin-LR significantly in all 3 species. Similar results were observed with A. salina pre-treated with the same concentration of cyanobacterial LPS and subsequently exposed to cylindrospermopsin, increasing the LC(50) by 8. The findings indicate the need to include exposures to defined combinations of cyanotoxins, and in defined sequences, to understand the contributions of individual cyanotoxins in accounting for cyanobacterial toxicity to invertebrates in natural aquatic environments.

ELISA and LC-MS/MS methods for determining cyanobacterial toxins in blue-green algae food supplements

The use of natural products as a diet supplement is increasing worldwide but sometimes is not followed by adequate sanitary controls and analyses. Twenty samples of pills and capsules of lyophilised cyanobacteria (blue-green algae), commercialised in Italy as dietary supplements, were found positive at the Vibrio fischeri bioassay. Further analyses with ELISA and LC-MS/MS methods revealed the presence of four microcystin (MC) analogues, MC-LR, -YR, -LA, -RR and two demethylated forms of MC-RR. The highest total microcystin content was 4.5 and 1.4 microg g-1 in pills and capsules, respectively. The ELISA measurements, compared to the LC-MS/MS analyses, showed significantly lower concentrations of microcystins in pills, this confirming a possible ELISA underestimate of mixed microcystins, due to different sensitivities for some toxic analogues.

Cyanobacterial (blue-green algal) toxins in water supplies: Cylindrospermopsins

The toxic alkaloid cylindrospermopsin is produced by a range of cyanobacterial species worldwide. It was first identified in the species Cylindrospermopsis raciborskii from tropical waters, and has since been isolated from four other genera in locations ranging from Israel to Japan. High concentrations of the organisms and toxin have been identified in reservoirs, natural lakes, and rivers in summer in the USA and in Australia. The toxin is a particular problem in drinking water sources as concentrations in the free water are appreciable, so that removal of the filaments during water treatment does not remove the toxin. The toxicity resulting from oral ingestion is seen in the liver, kidneys, stomach, intestine, and white blood cells, with some vascular damage in mice. Gastrointestinal as well as liver injury has been observed in human poisoning. Studies of toxicity in vitro have shown inhibition of protein synthesis. Genotoxicity has also been demonstrated, and there is preliminary evidence for carcinogenicity. A Guideline Value for safe water supply of 1 microg/L has been proposed. Research into toxin measurement techniques and water treatment methods has indicated that effective control measures may be practicable for this toxin in drinking water. Considerably more research is needed to fully define the health risks from this toxin.

Ecotoxicological effects of selected cyanobacterial secondary metabolites: a short review

Cyanobacteria are one of the most diverse groups of gram-negative photosynthetic prokaryotes. Many of them are able to produce a wide range of toxic secondary metabolites. These cyanobacterial toxins can be classified in five different groups: hepatotoxins, neurotoxins, cytotoxins, dermatotoxins, and irritant toxins (lipopolysaccharides). Cyanobacterial blooms are hazardous due to this production of secondary metabolites and endotoxins, which could be toxic to animals and plants. Many of the freshwater cyanobacterial blooms include species of the toxigenic genera Microcystis, Anabaena, or Plankthotrix. These compounds differ in mechanisms of uptake, affected organs, and molecular mode of action. In this review, the main focus is the aquatic environment and the effects of these toxins to the organisms living there. Some basic toxic mechanisms will be discussed in comparison to the mammalian system.