Survey of microcystins in environmental water by a highly sensitive immunoassay based on monoclonal antibody

Microcystin Incidence in the Drinking Water of Mozambique: Challenges for Public Health Protection

Microcystins (MCs) are cyanotoxins produced mainly by freshwater cyanobacteria, which constitute a threat to public health due to their negative effects on humans, such as gastroenteritis and related diseases, including death. In Mozambique, where only 50% of the people have access to safe drinking water, this hepatotoxin is not monitored, and consequently, the population may be exposed to MCs. The few studies done in Maputo and Gaza provinces indicated the occurrence of MC-LR, -YR, and -RR at a concentration ranging from 6.83 to 7.78 µg·L-1, which are very high, around 7 times above than the maximum limit (1 µg·L-1) recommended by WHO. The potential MCs-producing in the studied sites are mainly Microcystis species. These data from Mozambique and from surrounding countries (South Africa, Lesotho, Botswana, Malawi, Zambia, and Tanzania) evidence the need to implement an operational monitoring program of MCs in order to reduce or avoid the possible cases of intoxications since the drinking water quality control tests recommended by the Ministry of Health do not include an MC test. To date, no data of water poisoning episodes recorded were associated with MCs presence in the water. However, this might be underestimated due to a lack of monitoring facilities and/or a lack of public health staff trained for recognizing symptoms of MCs intoxication since the presence of high MCs concentration was reported in Maputo and Gaza provinces.

Analysis of Microcystins in Cyanobacterial Blooms from Freshwater Bodies in England

Cyanobacterial blooms in freshwater bodies in England are currently monitored reactively, with samples containing more than 20,000 cells/mL of potentially toxin-producing species by light microscopy resulting in action by the water body owner. Whilst significantly reducing the risk of microcystin exposure, there is little data describing the levels of these toxins present in cyanobacterial blooms. This study focused on the quantitative LC-MS/MS analysis of microcystins in freshwater samples, collected across England during 2016 and found to contain potentially toxin-producing cyanobacteria. More than 50% of samples contained quantifiable concentrations of microcystins, with approximately 13% exceeding the WHO medium health threshold of 20 μg/L. Toxic samples were confirmed over a nine-month period, with a clear increase in toxins during late summer, but with no apparent geographical patterns. No statistical relationships were found between total toxin concentrations and environmental parameters. Complex toxin profiles were determined and profile clusters were unrelated to cyanobacterial species, although a dominance of MC-RR was determined in water samples from sites associated with lower rainfall. 100% of samples with toxins above the 20 μg/L limit contained cell densities above 20,000 cells/mL or cyanobacterial scum, showing the current regime is suitable for public health. Conversely, with only 18% of cell density threshold samples having total microcystins above 20 μg/L, there is the potential for reactive water closures to unnecessarily impact upon the socio-economics of the local population. In the future, routine analysis of bloom samples by LC-MS/MS would provide a beneficial confirmatory approach to the current microscopic assessment, aiding both public health and the needs of water users and industry.

Rapid and Highly Sensitive Non-Competitive Immunoassay for Specific Detection of Nodularin

Nodularin (NOD) is a cyclic penta-peptide hepatotoxin mainly produced by Nodularia spumigena, reported from the brackish water bodies of various parts of the world. It can accumulate in the food chain and, for safety reasons, levels of NOD not only in water bodies but also in food matrices are of interest. Here, we report on a non-competitive immunoassay for the specific detection of NOD. A phage display technique was utilized to interrogate a synthetic antibody phage library for binders recognizing NOD bound to an anti-ADDA (3-Amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4(E),6(E)-dienoic acid) monoclonal antibody (Mab). One of the obtained immunocomplex binders, designated SA32C11, showed very high specificity towards nodularin-R (NOD-R) over to the tested 10 different microcystins (microcystin-LR, -dmLR, -RR, -dmRR, -YR, -LY, -LF, -LW, -LA, -WR). It was expressed in Escherichia coli as a single chain antibody fragment (scFv) fusion protein and used to establish a time-resolved fluorometry-based assay in combination with the anti-ADDA Mab. The detection limit (blank + 3SD) of the immunoassay, with a total assay time of 1 h 10 min, is 0.03 µg/L of NOD-R. This represents the most sensitive immunoassay method for the specific detection of NOD reported so far. The assay was tested for its performance to detect NOD using spiked (0.1 to 3 µg/L of NOD-R) water samples including brackish sea and coastal water and the recovery ranged from 79 to 127%. Furthermore, a panel of environmental samples, including water from different sources, fish and other marine tissue specimens, were analyzed for NOD using the assay. The assay has potential as a rapid screening tool for the analysis of a large number of water samples for the presence of NOD. It can also find applications in the analysis of the bioaccumulation of NOD in marine organisms and in the food chain.

Microcystin-LR Detected in a Low Molecular Weight Fraction from a Crude Extract of Zoanthus sociatus

Cnidarian constitutes a great source of bioactive compounds. However, research involving peptides from organisms belonging to the order Zoanthidea has received very little attention, contrasting to the numerous studies of the order Actiniaria, from which hundreds of toxic peptides and proteins have been reported. In this work, we performed a mass spectrometry analysis of a low molecular weight (LMW) fraction previously reported as lethal to mice. The low molecular weight (LMW) fraction was obtained by gel filtration of a Zoanthus sociatus (order Zoanthidea) crude extract with a Sephadex G-50, and then analyzed by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight (MALDI-TOF/TOF) mass spectrometry (MS) in positive ion reflector mode from m/z 700 to m/z 4000. Afterwards, some of the most intense and representative MS ions were fragmented by MS/MS with no significant results obtained by Protein Pilot protein identification software and the Mascot algorithm search. However, microcystin masses were detected by mass-matching against libraries of non-ribosomal peptide database (NORINE). Subsequent reversed-phase C18 HPLC (in isocratic elution mode) and mass spectrometry analyses corroborated the presence of the cyanotoxin Microcystin-LR (MC-LR). To the best of our knowledge, this finding constitutes the first report of MC-LR in Z. sociatus, and one of the few evidences of such cyanotoxin in cnidarians.

Presence of the Cyanotoxin Microcystin in Arctic Lakes of Southwestern Greenland

Cyanobacteria and their toxins have received significant attention in eutrophic temperate and tropical systems where conspicuous blooms of certain planktonic taxa release toxins into fresh water, threatening its potability and safe use for recreation. Although toxigenic cyanobacteria are not confined to high nutrient environments, bloom-forming species, or planktonic taxa, these other situations are studied les often studied. For example, toxin production in picoplankton and benthic cyanobacteria—the predominant photoautotrophs found in polar lakes—is poorly understood. We quantified the occurrence of microcystin (MC, a hepatotoxic cyanotoxin) across 18 Arctic lakes in southwestern Greenland. All of the focal lakes contained detectable levels of MC, with concentrations ranging from 5 ng·L⁻¹ to >400 ng·L⁻¹ during summer, 2013–2015. These concentrations are orders of magnitude lower than many eutrophic systems, yet the median lake MC concentration in Greenland (57 ng·L⁻¹) was still 6.5 times higher than the median summer MC toxicity observed across 50 New Hampshire lakes between 1998 and 2008 (8.7 ng·L⁻¹). The presence of cyanotoxins in these Greenlandic lakes demonstrates that high latitude lakes can support toxigenic cyanobacteria, and suggests that we may be underestimating the potential for these systems to develop high levels of cyanotoxins in the future.

Inhibition equivalency factors for microcystin variants in recombinant and wild-type protein phosphatase 1 and 2A assays

In this work, protein phosphatase inhibition assays (PPIAs) have been used to evaluate the performance of recombinant PP1 and recombinant and wild-type PP2As. The enzymes have been compared using microcystins-LR (MC-LR) as a model cyanotoxin. Whereas PP2ARec provides a limit of detection (LOD) of 3.1 μg/L, PP1Rec and PP2AWild provide LODs of 0.6 and 0.5 μg/L, respectively, lower than the guideline value proposed by the World Health Organization (1 μg/L). The inhibitory potencies of seven MC variants (-LR, -RR, -dmLR, -YR, -LY, -LW and -LF) have been evaluated, resulting on 50 % inhibition coefficient (IC50) values ranging from 1.4 to 359.3 μg/L depending on the MC variant and the PP. The PPIAs have been applied to the determination of MC equivalent contents in a natural cyanobacterial bloom and an artificially contaminated sample, with multi-MC profiles. The inhibition equivalency factors (IEFs) have been applied to the individual MC quantifications determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis, and the estimated MC-LR equivalent content has been compared to PPIA results. PPIAs have demonstrated to be applicable as MC screening tools for environmental applications and to protect human and animal health.

Methods to detect cyanobacteria and their toxins in the environment

Cyanobacteria blooms are since early times a cause for environmental concern because of their negative impact through the release of odors, water discoloration, and more dangerously through the release of toxic compounds (i.e. the cyanotoxins) that can affect both human and animal welfare. Surveillance of the aquatic ecosystems is therefore obligatory, and methods to achieve such require a prompt answer not only regarding the species that are producing the blooms but also the cyanotoxins that are being produced and/or released. Moreover, besides this well-known source of possible intoxication, it has been demonstrated the existence of several other potential routes of exposure, either for humans or other biota such as through food additives and in terrestrial environments (in plants, lichens, biological soil crusts) and the recognition of their harmful impact on less studied ecosystems (e.g. coral reefs). Nowadays, the most frequent approaches to detect toxic cyanobacteria and/or their toxins are the chemical-, biochemical-, and molecular-based methods. Above their particular characteristics and possible applications, they all bring to the environmental monitoring several aspects that are needed to be discussed and scrutinized. The end outcome of this review will be to provide newer insights and recommendations regarding the methods needed to apply in an environmental risk assessment program. Therefore, a current state of the knowledge concerning the three methodological approaches will be presented, while highlighting positive and negative aspects of each of those methods within the purpose of monitoring or studying cyanobacteria and their toxins in the environment.

Assessment of microcystins in lake water and fish (Mugilidae, Liza sp.) in the largest Spanish coastal lake

Cyanobacteria dominance and cyanotoxin production can become major threats to humans and aquatic life, especially in warm shallow lakes, which are often dominated by cyanobacteria. This study investigates the occurrence and distribution of microcystins (MCYST) in water, cell-bound and in the tissues of the commercial mugilid Liza sp. in the largest, coastal, Spanish Mediterranean lake (Albufera of Valencia). This is the first report concerning microcystin accumulation in tissues of mugilid fish species. Considerable amounts of microcystins were found in the water and seston, which correlated with development of Microcystis aeruginosa populations in the lake. The MCYST concentrations found in Lake Albufera (mean 1.7 and 17 μg/L and maximum 16 and 120 μg/L in water and seston, respectively) exceeded by one to two orders of magnitude the guideline levels proposed by the World Health Organization and were higher than that reported in other lakes of the Mediterranean zone. The presence of MCYST was found in all the fishes studied and accumulated differently among tissues of the commercial species Liza sp. Toxin accumulation in fish tissues showed that although the target organ for MCYST was the liver, high concentrations of microcystins were also found in other analysed tissues (liver>intestine>gills>muscle). Human tolerable daily intake for microcystins is assessed relative to the WHO guidelines, and potential toxicological risks for humans, wildlife and related ecosystems of the lake are discussed.

Bioaccumulation of microcystins by fish associated with a persistent cyanobacterial bloom in Lago de Patzcuaro (Michoacan, Mexico)

Lago de Patzcuaro is a historically important freshwater fishery in Mexico. The lake is presently characterized by a persistent bloom of cyanobacteria, specifically dominated by recognized producers of toxic microcystins (MCYSTs). We evaluated MCYSTs in sestonic and dissolved fractions of the water column, as well as representative fish species (silversides, Chirostoma spp.; Goodea sp.; and carp, Cyprinus carpio) obtained from local markets and small commercial catches during the bloom. Samples were evaluated primarily by enzyme-linked immunosorbent assay (ELISA), and secondarily by protein phosphatase (PPase) inhibition assay and liquid chromatography-mass spectrometry (LC-MS). Sestonic MCYST concentration (0.02-0.36 µg/L) generally correlated inversely with distance from the bloom, supporting the bloom as the source of the toxin. Several MCYST variants, including MC-LR, -LA and -LY, as well as didemethyl variants, were identified by LC-MS/MS analysis. All three species of fish bioaccumulated MCYSTs in relevant tissues, and toxin content correlated with trophic level, with highest and lowest levels measured in phytoplanktivorous and zooplanktivorous representatives, respectively. Detection of MCYST in silversides and Goodea sp. is particularly relevant because both are consumed in their entirety, including viscera (e.g., liver) known to primarily accumulate MCYST. These results indicate that Lago de Patzcuaro is indeed characterized by a toxigenic bloom, and that commercially important fish species from the lake accumulate toxic MCYST in tissues relevant to human consumption. As such, this system may represent an ideal model of the trophic transfer of MCYSTs and its relevance to human and environmental health.

Differentiation between microcystin contaminated and uncontaminated fish by determination of unconjugated MCs using an ELISA anti-Adda test based on receiver-operating characteristic curves threshold values: application to Tinca tinca from natural ponds

The aim of this study was to evaluate whether the enzyme-linked immunosorbent assay (ELISA) anti-Adda technique could be used to monitor free microcystins (MCs) in biological samples from fish naturally exposed to toxic cyanobacteria by using receiver operating characteristic (ROC) curve software to establish an optimal cut-off value for MCs. The cut-off value determined by ROC curve analysis in tench (Tinca tinca) exposed to MCs under laboratory conditions by ROC curve analysis was 5.90-μg MCs/kg tissue dry weight (d.w.) with a sensitivity of 93.3%. This value was applied in fish samples from natural ponds (Extremadura, Spain) in order to asses its potential MCs bioaccumulation by classifying samples as either true positive (TP), false positive (FP), true negative (TN), or false negative (FN). In this work, it has been demonstrated that toxic cyanobacteria, mainly Microcystis aeruginosa, Aphanizomenon issatchenkoi, and Anabaena spiroides, were present in two of these ponds, Barruecos de Abajo (BDown) and Barruecos de Arriba (BUp). The MCs levels were detected in waters from both ponds with an anti-MC-LR ELISA immunoassay and were of similar values (between 3.8-6.5-μg MC-LR equivalent/L in BDown pond and 4.8-6.0-μg MC-LR equivalent/L in BUp). The MCs cut-off values were applied in livers from fish collected from these two ponds using the ELISA anti-Adda technique. A total of 83% of samples from BDown pond and only 42% from BUp were TP with values of free MCs higher than 8.8-μg MCs/kg tissue (d.w.).

Accumulation of microcystins in water and fish tissues: an estimation of risks associated with microcystins in most of the Greek Lakes

Toxin-producing cyanobacteria in lakes and reservoirs form a threat to humans as well as various forms of aquatic life. This study is an investigation into the occurrence and distribution of Microcystins (MCYST) in 13 Greek Lakes. The distribution of MCYST in water and surface scum and toxin bioaccumulations in the omnivorous fish species Carassius gibelio were surveyed in all lakes. Considerable amounts of MCYST were found in water and scum of all lakes, irrespective of the trophic state, the type of the lake, and the reported dominant cyanobacterial species. Toxin accumulation in six tissues (liver, brain, intestine, kidney, ovary, and muscle) of C. gibelio was also analyzed. Even though the target organ for MCYST is the liver, in our study, MCYST were found also in the rest of C. gibelio tissues in the following order: liver > intestine > kidney > brain > ovaries > muscle. Risk assessments were carried out, taking into account the WHO guidelines and the tolerable daily intake (TDI) for MCYST. Our findings suggest that the amounts of MCYST found in water of Lakes Kastoria, Koronia, Pamvotis, Doirani, Mikri Prespa, Petron, and Zazari, pose adverse health risks. Also, it is likely to be unsafe to consume C. gibelio in Lakes Koronia, Kastoria, Pamvotis, and Mikri Prespa due to the high concentrations of accumulated MCYST.

Comparison of sensitivity of grasses (Lolium perenne L. and Festuca rubra L.) and lettuce (Lactuca sativa L.) exposed to water contaminated with microcystins

The effects of aqueous extracts from Microcysts aeruginosa strains (both microcystin-producers and non-microcystin producers) on germination and root growth were investigated for three economically important plant species: Festuca rubra L., Lolium perenne L., and Lactuca sativa L. There was a clear inhibition of root growth for L. sativa exposed to strains containing microcystins (5.9-56.4 microg L(-1)). The strain that produced the most pronounced effects contained the lowest concentration of microcystin suggesting that other cellular compounds may also affect growth.

The influence of a toxic cyanobacterial bloom and water hydrology on algal populations and macroinvertebrate abundance in the upper littoral zone of Lake Krugersdrift, South Africa

The biological interactions and the physical and chemical properties of the littoral zone of Lake Krugersdrift were studied for a 4-month period when a dense, toxic cyanobacterial bloom dominated by Microcystis aeruginosa was present in the main lake basin. The presence of a toxic strain of M. aeruginosa was confirmed through the use of ELISA and molecular markers that detect the presence of the mcyB and mcyD genes of the mcy gene cluster that synthesizes microcystin. An increase in Microcystis toxicity at sites dominated by the cyanobacterial scum was accompanied by an increase in total abundance of the macroinvertebrate families Hirudinae, Chironomidae, and Tubificidae. Sites located away from the cyanobacterial scum had a lower abundance but a higher diversity of macroinvertebrates. The water quality under the Microcystis scum was characterized by low pH values, low concentrations of dissolved oxygen, and lower total alkalinity values. The periphytic alga Ulothrix zonata was absent in areas dominated by the cyanobacterial scum, possibly as a result of overshadowing by the scum or direct toxic allelopathic effects on growth and photosynthesis. The diatom Diatoma vulgare dominated the benthic algal flora beneath the cyanobacterial scum.

Non-microcystin producing Microcystis wesenbergii (Komárek) Komárek (Cyanobacteria) representing a main waterbloom-forming species in Chinese waters

It is well known that several morphospecies of Microcystis, such as Microcystis aeruginosa (Kützing) Lemmermann and Microcystis viridis (A. Brown) Lemmermann can produce hepatotoxic microcystins. However, previous studies gave contradictory conclusions about microcystin production of Microcystis wesenbergii (Komárek) Komárek. In the present study, ten Microcystis morphospecies were identified in waterblooms of seven Chinese waterbodies, and Microcystis wesenbergii was shown as the dominant species in these waters. More than 250 single colonies of M. wesenbergii were chosen, under morphological identification, to examine whether M. wesenbergii produce hepatotoxic microcystin by using multiplex PCR for molecular detection of a region (mcyA) of microcystin synthesis genes, and chemical analyses of microcystin content by ELISA and HPLC for 21 isolated strains of M. wesenbergii from these waters were also performed. Both molecular and chemical methods demonstrated that M. wesenbergii from Chinese waters did not produce microcystin.

Microcystin removal by a naturally-occurring substance: pumice

Microcystins (MCs) are among the most prevalent and potent of the cyanobacterial toxins (cyanotoxins) and their potential occurrence in waters required for drinking has prompted investigations into remedial water treatments for their removal. We have investigated the suitability of local pumice, as a possible low-cost material for environmental application for the removal of cyanotoxins. Adsorption and desorption rates of pure MC-LR, one of the most common and toxic forms of MC and with crude extracts of the cyanobacterium. Microcystis aeruginosa containing MCs, were studied using bench-scale, pumice-packed glass columns, with good retention of the toxins being achieved. Research is in progress to optimize MC removal and to determine the applicability of pumice as a treatment material for cyanotoxin removal.

New measurements of cyanobacterial toxins in natural waters using high performance liquid chromatography coupled to tandem mass spectrometry

The presence and levels of the cyanobacterial toxins microcystin-LR, anatoxin-a, and cylindrospermopsin were measured in various Wisconsin waters where algal nuisance or bloom conditions were noted. Out of 74 samples analyzed, 36 had detectable levels of microcystin-LR (49%), and four had detectable levels of anatoxin-a (5%). Cylindrospermopsin, the toxin produced by Cylindrospermopsis (a warm water species that has been moving its range northward, including to Wisconsin), was not detected in the field samples tested. Concentrations of microcystin-LR ranged from 1.2 to 7600 microg L(-1). Anatoxin-a ranged from 0.68 to 1750 microg L(-1), which is the highest concentration reported from around the world. Cyanobacterial toxins, because of their high potency, deserve continued scrutiny by resource managers and public health officials responsible for recreational waters.

Toxic cyanobacteria and microcystin concentrations in a public water supply reservoir in the Brazilian Amazonia region

Toxic cyanobacteria in public water supply reservoirs represent a serious health risk as they can release potent cyanotoxins into the water. In the present study we analyzed surface water collected from the Utinga Reservoir, the main source of drinking water for the city of Belem-PA, in order to characterize the reservoir's cyanobacterial biota and to determine the toxicity of these organisms and the concentration of microcystins in raw and treated water. The cyanobacterial biota included potentially toxic genera such as Aphanizomenon, Microcystis, Nostoc, Oscillatoria, Planktothrix and Radiocystis. Mouse bioassays revealed a 43.6% frequency of hepatotoxic strains, including 30.8% Microcystis viridis strains and 12.8% Radiocystis fernandoi strains, with the lowest LD(100) (ip) of 45 and 75 mg kg(-1) body weight, respectively. Subacute hepatotoxicity was observed for Aphanizomenon cf. gracile and Coelomoron pusillum strains. HPLC analysis confirmed the production of microcystins at maximum concentrations of 4.22 microg mg(-1) dry weight for M. viridis and 2.47 microg mg(-1) for R. fernandoi. Microcystins at concentrations of up to 1.25 microg L(-1) detected in raw water by ELISA, together with a cyanobacterial density of 20,000 cells mL(-1), represents the first report of a bloom of cyanobacteria for an Amazonian water body.

Chronic toxicity and responses of several important enzymes in Daphnia magna on exposure to sublethal microcystin-LR

In the current study, the toxicological mechanisms of microcystin-LR and its disadvantageous effects on Daphnia magna were examined. Survival rate, number of newborn, activity of several important enzymes [glutathione S-transferase (GST), lactate dehydrogenase (LDH), phosphatases, and glutathione], accumulated microcystins, and ultrastructural changes in different organs of Daphnia were monitored over the course of 21-day chronic tests. The results indicated that low concentrations of dissolved microcystin had no harmful effect on Daphnia. On the contrary, stimulatory effects were detected. In the presence of toxin at high dosage and for long-term exposure, GST and glutathione levels decreased significantly. The decreased enzyme activity in the antioxidant system probably was caused by detoxification reactions with toxins. And these processes of detoxification at the beginning of chronic tests may enable phosphatases in Daphnia magna to withstand inhibition by the toxins. At the same time, we also found that the LDH activity in test animals increased with exposure to microcystin-LR, indicating that adverse effects occurred in Daphnia. With microcystin given at a higher dosage or for a longer exposure, the effect on Daphnia magna was fatal. In the meantime, microcystin began to accumulate in Daphnia magna, and phosphatase activity started to be inhibited. From the ultrastructure results of cells in D. magna, we obtained new information: the alimentary canal may be the target organ affected by exposure of microcystins to D. magna. The results of the current study also suggested that the oxidative damage and PPI (protein phosphatase inhibition) mechanisms of vertebrates also are adapted to Daphnia.

Guidance values for microcystins in water and cyanobacterial supplement products (blue-green algal supplements): a reasonable or misguided approach?

This article reviews current scientific knowledge on the toxicity and carcinogenicity of microcystins and compares this to the guidance values proposed for microcystins in water by the World Health Organization, and for blue-green algal food supplements by the Oregon State Department of Health. The basis of the risk assessment underlying these guidance values is viewed as being critical due to overt deficiencies in the data used for its generation: (i) use of one microcystin congener only (microcystin-LR), while the other presently known nearly 80 congeners are largely disregarded, (ii) new knowledge regarding potential neuro and renal toxicity of microcystins in humans and (iii) the inadequacies of assessing realistic microcystin exposures in humans and especially in children via blue-green algal food supplements. In reiterating the state-of-the-art toxicology database on microcystins and in the light of new data on the high degree of toxin contamination of algal food supplements, this review clearly demonstrates the need for improved kinetic data of microcystins in humans and for discussion concerning uncertainty factors, which may result in a lowering of the present guidance values and an increased routine control of water bodies and food supplements for toxin contamination. Similar to the approach taken previously by authorities for dioxin or PCB risk assessment, the use of a toxin equivalent approach to the risk assessment of microcystins is proposed.

Reversed-phase liquid chromatographic–mass spectrometric determination of microcystin-LR in cyanobacteria blooms under alkaline conditions

Reversed-phase HPLC coupled to the atmospheric pressure ionization-electrospray ionization (API-ESI) MS was used for microcystin-LR detection and quantitation in samples of dried Microcystis aeruginosa cells. An alkaline linear gradient (20 mmol/l ammonium hydroxide-acetonitrile, pH 9.7) was used for elution of the toxic peptides. Limit of detection was 1 microg/ml (20 ng per injection) in the scan mode of MS and 0.1 microg/ml (2 ng per injection) in the case of selective ion monitoring.

Hepatic accumulation and effects of microcystin-LR on juvenile goldfish Carassius auratus L

After intraperitoneal injection of microcystin-LR (MC-LR) (125 microg kg(-1) body wt.), the concentration of MC-LR in the liver of juvenile goldfish Carassius auratus (30 g body wt.) was assayed by a modified protein phosphatase inhibition method. A temporary accumulation occurred from 3 to 48 h post-injection, followed by a significant decrease between 48 and 96 h. Under our experimental conditions, contamination by MC-LR did not change ionic homeostasis, as attested by blood osmolality values and gill Na(+)/K(+) ATPase activity. Light microscopy observations revealed lesions and cellular necrosis progression, which was concomitant with an increase in enzyme activity of plasma aspartate aminotransferase (AspAT), alanine aminotransferase (AlaAT) and L-lactate dehydrogenase (LDH) and with a decrease of hepatic glutathione-S-transferase (GST) activity. Structural alterations and enzymatic activity modifications became significant within 24 h post-injection. Recovery of hepatocytes on day 21 after MC-LR injection was evident, together with a decrease in the MC-LR equivalent content of the liver.

Effects of light on the microcystin content of Microcystis strain PCC 7806

Many cyanobacteria produce microcystins, hepatotoxic cyclic heptapeptides that can affect animals and humans. The effects of photosynthetically active radiation (PAR) on microcystin production by Microcystis strain PCC 7806 were studied in continuous cultures. Microcystis strain PCC 7806 was grown under PAR intensities between 10 and 403 micro mol of photons m(-2) s(-1) on a light-dark rhythm of 12 h -12 h. The microcystin concentration per cell, per unit biovolume and protein, was estimated under steady-state and transient-state conditions and on a diurnal timescale. The cellular microcystin content varied between 34.5 and 81.4 fg cell(-1) and was significantly positively correlated with growth rate under PAR-limited growth but not under PAR-saturated growth. Microcystin production and PAR showed a significant positive correlation under PAR-limited growth and a significant negative correlation under PAR-saturated growth. The microcystin concentration, as a ratio with respect to biovolume and protein, correlated neither with growth rate nor with PAR. Adaptation of microcystin production to a higher irradiance during transient states lasted for 5 days. During the period of illumination at a PAR of 10 and 40 micro mol of photons m(-2) s(-1), the intracellular microcystin content increased to values 10 to 20% higher than those at the end of the dark period. Extracellular (dissolved) microcystin concentrations were 20 times higher at 40 micro mol of photons m(-2) s(-1) than at 10 micro mol of photons m(-2) s(-1) and did not change significantly during the light-dark cycles at both irradiances. In summary, our results showed a positive effect of PAR on microcystin production and content of Microcystis strain PCC 7806 up to the point where the maximum growth rate is reached, while at higher irradiances the microcystin production is inhibited.

Using an enzyme linked immunosorbent assay (ELISA) and a protein phosphatase inhibition assay (PPIA) for the detection of microcystins and nodularins

Cyanotoxins produced by cyanobacteria (blue-green algae) include potent neurotoxins and hepatotoxins. The hepatotoxins include cyclic peptide microcystins and nodularins plus the alkaloid cylindrospermopsins. Among the cyanotoxins the microcystins have proven to be the most widespread, and are most often implicated in animal and human poisonings. This paper presents a practical guide to two widely used methods for detecting and quantifying microcystins and nodularins in environmental samples-the enzyme linked immunosorbant assay (ELISA) and the protein phosphatase inhibition assay (PPIA).

Characterization of sublethal microcystin-LR exposure in mice

Microcystin-LR (MCLR) is a potent hepatotoxin produced by the cyanobacterium Microcystis aeruginosa. The histology of acute lethal toxicity has been well characterized, but histology is limited regarding sublethal exposure. Balb/C mice were given a single sublethal dose of MCLR (45 microg/kg) and euthanized at 2, 4, 12, and 24 hours after exposure. Centrilobular to midzonal hepatocellular hypertrophy with loss of cytosolic vacuolation consistent with glycogen depletion occurred at 2 hours. At 4 hours, central lobular hepatocytes exhibited eccentric areas of eosinophilic cytoplasmic condensation that were partially aggregated around the outer nuclear membrane. The areas were weakly positive for cytokeratin and somewhat resembled the Mallory bodies of alcoholic human hepatitis. Small numbers of apoptotic hepatocytes were seen at 24 hours. The toxin was detectable by immunohistochemistry (IHC) as early as 2 hours and was colocalized with the areas of hepatocellular hypertrophy. Intense nuclear staining occurred at 4 hours; this was no longer evident after 12 hours. Strong staining of apoptotic bodies occurred at 24 hours. Mice that received two daily doses had a marked increase in apoptotic hepatocytes in the centrilobular areas. Lesions at four and seven doses consisted of marked hepatocytomegaly and karyomegaly with parenchymal disarray and cytosolic vacuolation. IHC revealed diffuse staining throughout the liver parenchyma consistent with toxin accumulation. An anti-MCLR monoclonal antibody detected bands at the 40-kDa mark in nuclear extracts that were identified as protein phosphatases 1 and 2A by western blotting, consistent with a covalent interaction between MCLR and nuclear protein phosphatases.

Production and specificity of monoclonal antibodies against nodularin conjugated through N-methyldehydrobutyrine

Nodularin (Nod) is a cyclic pentapeptide hepatotoxin produced by the cyanobacterial genus Nodularia living in brackish waters and coastal lagoons. The toxicity of Nod is due to specific inhibition of the type-1 and type-2A intracellular protein phosphatases (PP1 and PP2A, respectively). We have developed a monoclonal antibody against Nod using chemical modification (aminoethylation) of one of its core amino acids, N-methyldehydrobutyrine. The developed antibody is highly specific for Nod, with negligible reactivity to the closely related cyanobacterial toxin microcystin (MC). The monoclonal antibody was employed for quantitative competitive ELISA assay. The analytical sensitivity of the assay was up to 0.2 ng/ml. Comparison of the developed ELISA test with HPLC-based measurements of Nod, with both laboratory and field samples, showed a good correspondence between the results yielded by these two methods. The antibodies developed by this technique provide means for developing extremely sensitive and specific analytical assays for direct measurement of nodularin and related toxins in cyanobacterial or water samples.

Determination of microcystins in blue-green algae, fish and water using liquid chromatography with ultraviolet detection after sample clean-up employing immunoaffinity chromatography

Anti-microcystin LR immunnoaffinity cartridges were evaluated for their ability to selectively remove microcystins from extracts of blue-green algae, fish and water samples for subsequent analysis by liquid chromatography with UV absorbance detection at 238 nm. Blue-green algae and fish samples were extracted with 75% methanol in water. A portion of the extract was diluted and passed through an immunoaffinity cartridge. Water samples were applied directly to the cartridge. The cartridge was rinsed with water and 25% methanol in water. The microcystins were eluted with 80% methanol in water containing 4% acetic acid. It was found that the cartridges were effective in isolating the microcystins from blue-green algae, fish and water samples, resulting in extracts that were clean enough to enable direct LC-UV detection down to approximately 0.03 microg/g in the blue-green algae and fish samples, and as low as 0.02 ng/ml for water samples. The cartridges were found to have a capacity of approximately 200 ng each for a mixture of microcystins RR, YR, LR and LA, or as much as 525-800 ng for individual compounds. Recoveries trough the complete analytical procedure ranged from 64 to 115% (all values) with an overall average of approximately 80% at spiking levels of 0.5-4.0 microg/g for the microcystins in blue-green algae. The average recoveries (n=8) from spiked (0.1-0.5 microg/g) fish samples were 73% for RR, 79% for YR, 81% for LR and 77% for LA, while from the spiked (2.0-0.04 ng/g) tap and river water samples (n=6), recoveries were 78% for RR, 86% for YR, 94% for LR and 89% for LA.

Production and specificity of mono and polyclonal antibodies against microcystins conjugated through N-methyldehydroalanine

Microcystins (MCs) are a group of closely related toxic cyclic heptapeptides produced by common cyanobacteria (blue-green algae). Their toxicity is associated with specific inhibition of intracellular protein phosphatases type-1 and type-2A (PP1 and PP2A, respectively). We have developed a battery of antibodies to microcystins using chemical modification (aminoethylation) of one of its core amino acids, N-methyl-dehydroalanine. The developed antibodies displayed different reactivities to closely related MCs. Selected monoclonal antibodies were used for quantitative competitive ELISA assays. The analytical sensitivity of these assays was up to 1 ng/ml. Comparison of the developed ELISA tests with HPLC-based measurements of MCs in laboratory and field samples showed a good correspondence between the results yielded by these two methods. The antibodies developed by this technique provide the means for developing extremely sensitive and specific analytical assays for direct measurement of toxins in cyanobacterial or water samples.

Toxin production in cyanobacterial mats from ponds on the McMurdo ice shelf, Antarctica

Cyanobacteria are known to produce hepatotoxic substances, the functional and ecological role of these toxins, however, remains largely unclear. Toxic properties of cyanobacteria collected in Antarctica were investigated to determine whether toxin-producing species can also be found under these environmental conditions. Samples were collected from meltwater ponds on the McMurdo Ice Shelf, Antarctica in the summers of 1997 to 1999. These ponds are colonized by benthic algae and cyanobacterial mats. Oscillatoriales, Nodularia sp., and Nostoc sp. constituted the major taxa in freshwater ponds, while Nostoc sp. was missing from brackish and saline ponds. Samples were taken from either floating, submerged or benthic mats, and extracted for in vitro toxicity testing. The presence of toxins was determined by the phosphatase-inhibition assay and by high performance liquid chromatography. The cytotoxic properties of the extracts were investigated in hepatocytes determining 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide metabolism and trypan blue dye exclusion. The results show that all cyanobacterial extracts display phosphatase-inhibiting activity, of which approximately half had significantly greater than 50% inhibiting activity. The presence of nodularin and microcystin-LR was established by high performance liquid chromatography. Cytotoxic properties, independent of the phosphatase inhibiting activity, were also detected. Toxic strains of cyanobacteria can therefore also be found in Antarctica and this finding may lead to further insight into potential ecological roles of cyanobacterial phosphatase inhibiting toxins.

Immunoaffinity column as clean-up tool for determination of trace amounts of microcystins in tap water

Trace amounts of microcystins (MCs) in drinking water should be monitored because of their potential hazard for human health as an environmental tumor promoter. We describe here a new clean-up tool with immunoaffinity column (IAC) for determination of trace amounts of MCs (from pg to microg/litre) in tap water. The water samples were concentrated with IAC clean-up and MCs levels were determined by HPLC with UV detection or enzyme-linked immunosorbent assay (ELISA). In the combination with HPLC analysis, mean recovery of microcystin-LR (MCLR),-RR and-YR spiked to tap water were 91.8%, 77.3% and 86.4%, respectively, in the range 2.5-100 microg/litre. The chromatogram of MCs-spiked tap water sample cleaned up with IAC showed effective elimination of the impurities compared to that with octadecyl silanized cartridge, which had been cleaned up with a conventional method. Also, in the combination with highly sensitive ELISA, mean recovery of MCLR spiked to tap water was 80% in the range 0.1-1000 ng/litre. The combined methods developed here can detect pg to microg/litre of MCs in tap water. The overall results indicated that IAC will be suitable as a clean-up tool for trace amounts of MCs in tap water.

Generation of antibodies directed against the low-immunogenic peptide-toxins microcystin-LR/RR and nodularin

The preparation of antibodies against the liver toxin microcystin, as described here, is of major importance for its detection and purification in food and water, and for a therapeutic approach to neutralize the toxin by passive immunization. Microcystin-LR (MLR) and microcystin-RR (MRR) were purified from cyanobacterial cell materials by extraction, Sephadex LH-20-, ODS silica gel-, ionic exchange and RP-HPLC-chromatography. In order to reduce the toxicity for parenteral administration, microcystins were coupled by the carbodiimide method to poly-L-lysine (PLL(50.000)). Mice and rabbits were immunized with the conjugates in the presence of two lipopeptide immunoadjuvants (P(3)CSK(4) and P(3)CS-T(h)). High MLR-specific antibody levels were observed after parenteral coadministration of antigen and lipopeptides, whereas no anti-MLR antibodies were obtained with free microcystin or the microcystin-PLL(50.000)-conjugate in the absence of lipopeptide. In oral immunization, coadministration of antigen and adjuvants resulted in an accelerated development of anti MLR-specific antibodies and high antibody levels. Using the antisera, we could detect different microcystins and nodularin down to a concentration range of 10-50 ng/ml by a competitive inhibition ELISA; detection of microcystins in crude cell preparations was also possible. Furthermore, microcystins from different sources could be detected and discriminated from cyclic cyanopeptolines.

Survey of microcystins in water between 1995 and 1996 in Paraná, Brazil using ELISA

An enzyme-linked immunosorbent assay (ELISA) based on a monoclonal antibody was used to determine microcystin (MC) concentrations in water supplies and water plant samples collected between November 1995 and October 1996, from five regions of Paraná, Brazil. In addition, the presence of Microcystis sp. was monitored. Of the 50 samples obtained, 12 were from an urban lake, 8 from human water supplies, 10 from recreational lakes, 13 from farm waters used for animal pasture and 7 from aquaculture facilities. M. aeruginosa was positive in all locations. MCs were positive (>50 pg ml(-1)) in 9 samples (2 samples from human water supplies, 5 from recreational lakes and 2 from animal pasture). Heavy contamination with MCs was observed in water samples collected in May 1996 from 2 recreation (swimming-fishing sites at Itaipu dam, 6380 and 10,000 pg ml(-1)) and human supplies (6627 pg ml(-1)) samples. At these sites, a large bloom of Microcystis sp. was detected. Treatment with 1 ppm Cl- reduced MCs levels, although 267 pg ml(-1) remained in the water plant samples. Our data showed frequent occurrence of Microcystis sp., which may be a hazard to humans and animals in the state of Paraná. More detailed investigations are required to evaluate the risk of natural MC contamination in the water supplied in this region.

Cyanobacterial toxins in Portugal: effects on aquatic animals and risk for human health

Toxic cyanobacteria are common in Portuguese freshwaters and the most common toxins are microcystins. The occurrence of microcystin-LR (MCYST-LR) has been reported since 1990 and a significant number of water reservoirs that are used for drinking water attain high levels of this toxin. Aquatic animals that live in eutrophic freshwater ecosystems may be killed by microcystins but in many cases the toxicity is sublethal and so the animals can survive long enough to accumulate the toxins and transfer them along the food chain. Among these, edible mollusks, fish and crayfish are especially important because they are harvested and sold for human consumption. Mussels that live in estuarine waters and rivers where toxic blooms occur may accumulate toxins without many significant acute toxic effects. In this study data are presented in order to understand the dynamics of the accumulation and depuration of MCYST-LR in mussels. The toxin is readily accumulated and persists in the shellfish for several days after contact. In the crayfish the toxin is accumulated mainly in the gut but is also cleared very slowly. In carps, although the levels of the toxins found in naturally caught specimens were not very high, some toxin was found in the muscle and not only in the viscera. This raises the problem of the toxin accumulation by fish and possible transfer through the food chain. The data gathered from these experiments and from naturally caught specimens are analyzed in terms of risk for human consumption. The occurrence of microcystins in tap water and the incidence of toxic cyanobacteria in fresh water beaches in Portugal are reported. The Portuguese National Monitoring Program of cyanobacteria is mentioned and its implications are discussed.

Enhancement of glutathione S-transferase placental-form positive liver cell foci development by microcystin-LR in aflatoxin B1-initiated rats

The objective of this study was to elucidate whether microcystin-LR (MC-LR), a hepatotoxic blue-green algal toxin in drinking water, is carcinogenic or possesses the ability to modulate aflatoxin B1 (AFB1)-induced hepatocarcinogenicity. In a medium-term liver bioassay, male Fischer 344 rats were given a single i.p. injection of diethylnitrosamine (DEN, 200 mg/kg) followed by an i.p. injection of MC-LR for 6 weeks after 2 weeks of DEN treatment. To study the synergism between AFB1 and MC-LR, DEN-treated rats were given an i.p. injection of AFB1 (0.5 mg/kg) dissolved in dimethyl sulfoxide (DMSO) followed by MC-LR at 2 weeks after the treatment. In a separate experiment, the rats were first given AFB1 (0.5 mg/kg) and 2 weeks later an i.p. injection of 1 or 10 microg/kg of MC-LR twice a week for 6 weeks. Most rats were subjected to a two-thirds partial hepatectomy (PH) at week 3 and were killed under anesthesia at week 8. Liver sections were analyzed for glutathione S-transferase placental form (GST-P) expression, and subjected to histopathological examination for phenotypic alteration of hepatocellular foci. In rats that did not receive DEN, MC-LR did not cause a significant increase in the numbers of GST-P-positive foci, whereas AFB1 induced a slight increase in GST-P-positive foci development. In rats given DEN, MC-LR enhanced the expression of GST-P-positive foci, as did AFB1 but no synergism was observed. Histopathological analysis revealed that the area of eosinophilic foci, a biomarker for preneoplastic liver lesion, markedly increased because of MC-LR. In rats given AFB1 as an initiator, treatment with MC-LR resulted in a synergistic increase in the development of GST-P-positive foci. These results suggest that the hepatocarcinogenicities of MC-LR and AFB1 can be predicted in experimental animals with a medium-term bioassay. Furthermore, tumor promoting activity of MC-LR was demonstrated in rats treated with AFB1.

Immunohistochemical localization of microcystin-LR in the liver of mice: a study on the pathogenesis of microcystin-LR-induced hepatotoxicity

The relationship between the intralobular sites of hepatotoxic injury and the distribution of microcystin-LR (MCLR), an inhibitor of protein phosphatases 1 (PP1) and 2A (PP2A), was examined using an immunohistochemical method with a monoclonal antibody specific to MCLR on the livers of mice receiving a single i.p. injection of the MCLR. Immunoblotting and high-performance liquid chromatography analyses of liver extracts were also performed to determine the binding form of MCLR to PP1 and PP2A (MCLR-PP1/PP2A adducts) and free MCLR. Immunohistochemistry revealed a discernible intensity of staining in the centrilobular regions where hemorrhage and apoptosis occurred. In these regions, immunopositivity was evident in the cytoplasm and nuclei of the hepatocytes; some apoptotic cells were also immunopositive. In contrast, coagulative necrosis, which was mainly evident in the midlobular regions, was completely negative. Analysis of liver extracts demonstrated MCLR-PP1/PP2A adducts, but free MCLR was below detection limit. These results suggest that the immunohistochemical localization of MCLR in centrilobular hepatocytes is closely associated with the onset of hemorrhage and apoptosis and is related to adduct formation. The occurrence of coagulative necrosis however might also be related to other factors such as ischemia/hypoxia.

Anti-idiotype monoclonal antibodies against anti-microcystin antibody and their use in enzyme immunoassay

Microcystins (MCs), a group of heptapeptide hepatotoxins produced by cyanobacteria, are suspected as tumor-promoter contaminants of environmental water. We have previously developed an enzyme-linked immunosorbent assay (ELISA) for MCs based on an anti-MC MAb (MAb-mc). We describe here the production of anti-idiotype MAbs (MAb-ids) which react with MAb-mc and their use in a new ELISA for MCs. For the production of MAb-id, hybridoma cells were generated from mice immunized with MAb-mc. Two MAbs were selected for their ability to inhibit the binding of MAb-mc to microcystin-LR (MCLR)-bovine serum albumin conjugate in ELISA. The one with the higher inhibitory activity, designated Id7 (IgG1, kappa), was further characterized. ELISA and immunoprecipitation analysis revealed that Id7 specifically bound to MAb-mc but not to control IgG1, and the binding was inhibited by free MCLR. Therefore, Id7 is a MAb-id to MAb-mc and potentially possesses the structural image of MCLR. To establish MAb-id based ELISA, Id7 was tested for use in three types of competitive ELISA for MCs. The best format enabled reliable measurements of MCLR in the range of 100-1000 pg/ml with a coefficient of variation of less than 3%. In addition, microcystin-RR and microcystin-YR, principal MCs found in environmental water, were cross-reacted well (67-111% of MCLR) in the ELISA although 6(Z)-MCLR, a minor component, was less reactive (7% of MCLR). A comparative study of the MAb-id based ELISA with previously established MAb-mc based ELISA revealed good correlation (n = 14, r = 0.97) between the two methods for measurements of MCs content in freshwater samples. Thus, developed MAb-id based ELISA is an useful alternative for environmental monitoring of MCs.