Hepatic xenobiotic metabolism of cylindrospermopsin in vivo in the mouse

Cylindrospermopsin impairs vascular smooth muscle cells by P53-mediated apoptosis due to ROS overproduction

Cylindrospermopsin (CYN) is a toxic secondary metabolite from cyanobacteria that can cause cardiovascular disease. However, the study of CYN-induced cardiovascular toxicity in vitro is very limited and the mechanism is remain to be clarified. Vascular smooth muscle cells (VMSCs) have an important function in maintaining the structural and functional integrity of the aortic wall, and are an important in vitro model for cardiovascular research. Thus, the effects of CYN exposure (2, 20, 200, and 2000 nM) on VMSCs were analyzed. In vitro study, results showed that CYN exposure decreased VMSCs viability, inhibited VMSCs migration, induced DNA damage, destroyed cytoskeleton, changed cell morphology, promoted VMSCs apoptosis, and increased intracellular reactive oxygen species (ROS) levels. In addition, CYN could induce the activities of SOD, CAT and GPX, and promote the expressions of SOD1, CAT, GPx1, p53 and Bax genes and inhibit the expression of Bcl-2 gene, leading to a higher ratio of Bax/Bcl-2. Taken together, CYN may induce ROS overproduction, leading to increased p53 expression and ultimately promoting VSMC apoptosis. Therefore, the present study demonstrates that CYN could impair VMSCs, leading to vascular developmental defects and angiocardiopathy.

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

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

Acute cylindrospermopsin exposure: Pulmonary and liver harm and mitigation by dexamethasone

Cylindrospermopsin (CYN) is a cyanotoxin of increasing worldwide environmental importance as it can harm human beings. Dexamethasone is a steroidal anti-inflammatory agent. Thus, we aimed at evaluating the pulmonary outcomes of acute CYN intoxication and their putative mitigation by dexamethasone. Male BALB/c mice received intratracheally a single dose of saline or CYN (140 μg/kg). Eighteen hours after exposure, mice instilled with either saline solution (Ctrl) or CYN were intramuscularly treated with saline (Tox) or 2 mg/kg dexamethasone (Tox + dexa) every 6 h for 48 h. Pulmonary mechanics was evaluated 66 h after instillation using the forced oscillation technique (flexiVent) to determine airway resistance (R_N), tissue viscance (G) and elastance (H). After euthanasia, the lungs were removed and separated for quantification of CYN, myeloperoxidase activity and IL-6 and IL-17 levels plus histological analysis. CYN was also measured in the liver. CYN increased G and H, alveolar collapse, PMN cells infiltration, elastic and collagen fibers, activated macrophages, peroxidase activity in lung and hepatic tissues, as well as IL-6 and IL-17 levels in the lung. Tox + Dexa mice presented total or partial reversion of the aforementioned alterations. Briefly, CYN impaired pulmonary and hepatic characteristics that were mitigated by dexamethasone.

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

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

A new method for the simultaneous determination of cyanotoxins (Microcystins and Cylindrospermopsin) in mussels using SPE-UPLC-MS/MS

The aim of this study was to optimize the extraction conditions of Microcystin-LR (MC-LR), Microcystin-RR (MC-RR), Microcystin-YR (MC-YR) and Cylindrospermopsin (CYN) simultaneously from mussels by using response surface methodology (RSM) and to validate the method by a dual solid phase extraction (SPE) system combined with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The optimal parameters were: 90% MeOH (% v/v) for the extraction, a solvent/sample ratio of 75 and 15% MeOH in the extract before loading onto SPE. Mussels were spiked at 10; 37.5 and 75 ng g^-1 fresh weight (f.w) of the 4 toxins, showing linear ranges of 0.5-75 ng g^-1 f.w; low values for the limits of detection (0.01-0.39 ng g^-1 f.w.) and quantification (0.23-0.40 ng g^-1 f.w.); acceptable recoveries (70.37-114.03%) and relative standard deviation (%RSD_IP) values (2.61-13.73%). The method was successfully applied to edible mussels exposed to cyanobacterial extracts under laboratory conditions, and it could allow the monitoring of these cyanotoxins in environmental mussel samples.

Plastics in Cyanobacterial Blooms-Genotoxic Effects of Binary Mixtures of Cylindrospermopsin and Bisphenols in HepG2 Cells

Ever-expanding environmental pollution is causing a rise in cyanobacterial blooms and the accumulation of plastics in water bodies. Consequently, exposure to mixtures of cyanotoxins and plastic-related contaminants such as bisphenols (BPs) is of increasing concern. The present study describes genotoxic effects induced by co-exposure to one of the emerging cyanotoxins-cylindrospermopsin (CYN)-(0.5 µg/mL) and BPs (bisphenol A (BPA), S (BPS), and F (BPF); (10 µg/mL)) in HepG2 cells after 24 and 72 h of exposure. The cytotoxicity was evaluated with an MTS assay and genotoxicity was assessed through the measurement of the induction of DNA double strand breaks (DSB) with the γH2AX assay. The deregulation of selected genes (xenobiotic metabolic enzyme genes, DNA damage, and oxidative response genes) was assessed using qPCR. The results showed a moderate reduction of cell viability and induction of DSBs after 72 h of exposure to the CYN/BPs mixtures and CYN alone. None of the BPs alone reduced cell viability or induced DSBs. No significant difference was observed between CYN and CYN/BPs exposed cells, except with CYN/BPA, where the antagonistic activity of BPA against CYN was indicated. The deregulation of some of the tested genes (CYP1A1, CDKN1A, GADD45A, and GCLC) was more pronounced after exposure to the CYN/BPs mixtures compared to single compounds, suggesting additive or synergistic action. The present study confirms the importance of co-exposure studies, as our results show pollutant mixtures to induce effects different from those confirmed for single compounds.

In Vitro Mutagenic and Genotoxic Assessment of a Mixture of the Cyanotoxins Microcystin-LR and Cylindrospermopsin

The co-occurrence of various cyanobacterial toxins can potentially induce toxic effects different than those observed for single cyanotoxins, as interaction phenomena cannot be discarded. Moreover, mixtures are a more probable exposure scenario. However, toxicological information on the topic is still scarce. Taking into account the important role of mutagenicity and genotoxicity in the risk evaluation framework, the objective of this study was to assess the mutagenic and genotoxic potential of mixtures of two of the most relevant cyanotoxins, Microcystin-LR (MC-LR) and Cylindrospermopsin (CYN), using the battery of in vitro tests recommended by the European Food Safety Authority (EFSA) for food contaminants. Mixtures of 1:10 CYN/MC-LR (CYN concentration in the range 0.04-2.5 µg/mL) were used to perform the bacterial reverse-mutation assay (Ames test) in Salmonella typhimurium, the mammalian cell micronucleus (MN) test and the mouse lymphoma thymidine-kinase assay (MLA) on L5178YTk± cells, while Caco-2 cells were used for the standard and enzyme-modified comet assays. The exposure periods ranged between 4 and 72 h depending on the assay. The genotoxicity of the mixture was observed only in the MN test with S9 metabolic fraction, similar to the results previously reported for CYN individually. These results indicate that cyanobacterial mixtures require a specific (geno)toxicity evaluation as their effects cannot be extrapolated from those of the individual cyanotoxins.

Mutagenic and genotoxic potential of pure Cylindrospermopsin by a battery of in vitro tests

Cylindrospermopsin (CYN) is a cyanobacterial toxin with an increasing world-wide occurrence. The main route of human exposure is through the ingestion of contaminated food and water. The European Food Safety Authority has identified the need to further characterize the toxicological profile of cyanotoxins and in this regard the genotoxicity is a key toxicological effect. The data available in the scientific literature show contradictory results. Thus, the aim of this study was to investigate the mutagenic and genotoxic effects of pure CYN using a battery of different in vitro assays including: the bacterial reverse-mutation assay in Salmonella typhimurium (Ames test) (0-10 μg/mL), the mammalian cell micronucleus (MN) test (0-1.35 μg/mL and 0-2 μg/mL in absence or presence of S9 fraction, respectively) and the mouse lymphoma thymidine-kinase assay (MLA)(0-0.675 μg/mL) on L5178YTk ± cells, and the standard and enzyme-modified comet assays (0-2.5 μg/mL) on Caco-2 cells. Positive results were obtained only when the metabolic fraction S9 was employed in the MN test, suggesting pro-genotoxic properties of CYN. Also, DNA damage was not mediated by oxidative stress as CYN did not induced changes in the modified comet assay. These data could contribute to a better risk assessment of this cyanotoxin.

In Vitro Toxicological Assessment of Cylindrospermopsin: A Review

Cylindrospermopsin (CYN) is a cyanobacterial toxin that is gaining importance, owing to its increasing expansion worldwide and the increased frequency of its blooms. CYN mainly targets the liver, but also involves other organs. Various mechanisms have been associated with its toxicity, such as protein synthesis inhibition, oxidative stress, etc. However, its toxic effects are not yet fully elucidated and additional data for hazard characterization purposes are required. In this regard, in vitro methods can play an important role, owing to their advantages in comparison to in vivo trials. The aim of this work was to compile and evaluate the in vitro data dealing with CYN available in the scientific literature, focusing on its toxicokinetics and its main toxicity mechanisms. This analysis would be useful to identify research needs and data gaps in order to complete knowledge about the toxicity profile of CYN. For example, it has been shown that research on various aspects, such as new emerging toxicity effects, the toxicity of analogs, or the potential interaction of CYN with other cyanotoxins, among others, is still very scarce. New in vitro studies are therefore welcome.

Cylindrospermopsin effects on cell viability and redox milieu of Neotropical fish Hoplias malabaricus hepatocytes

Cylindrospermopsin (CYN) is a cyanotoxin that is cytotoxic to a wide variety of cells, particularly to the hepatocytes. In this study, the toxic effects of purified CYN were investigated in primary cultured hepatocytes of Neotropical fish Hoplias malabaricus. After isolation, attachment, and recovery for 72 h, the cells were exposed for 72 h to 0, 0.1, 1.0, 10, and 100 μg l^-1 of CYN. Then, cell viability and a set of oxidative stress biomarker responses were determined. Catalase, superoxide dismutase, glucose-6-phosphate dehydrogenase, and glutathione S-transferase activities were not affected by exposure to CYN. Concentration-dependent decrease of glutathione reductase activity occurred for most CYN-exposed groups, whereas non-protein thiol content increased only for the highest CYN concentration. Lipid peroxidation, protein carbonylation, and DNA damage levels were not altered, but reactive oxygen species levels increased in the cells exposed to the highest concentration of CYN. Cell viability decreased in all the groups exposed to CYN. Thus, CYN may cause a slight change in redox balance, but it is not the main cause of cell death in H. malabaricus hepatocytes.

Cyanobacterial Toxins of the Laurentian Great Lakes, Their Toxicological Effects, and Numerical Limits in Drinking Water

Cyanobacteria are ubiquitous phototrophic bacteria that inhabit diverse environments across the planet. Seasonally, they dominate many eutrophic lakes impacted by excess nitrogen (N) and phosphorus (P) forming dense accumulations of biomass known as cyanobacterial harmful algal blooms or cyanoHABs. Their dominance in eutrophic lakes is attributed to a variety of unique adaptations including N and P concentrating mechanisms, N₂ fixation, colony formation that inhibits predation, vertical movement via gas vesicles, and the production of toxic or otherwise bioactive molecules. While some of these molecules have been explored for their medicinal benefits, others are potent toxins harmful to humans, animals, and other wildlife known as cyanotoxins. In humans these cyanotoxins affect various tissues, including the liver, central and peripheral nervous system, kidneys, and reproductive organs among others. They induce acute effects at low doses in the parts-per-billion range and some are tumor promoters linked to chronic diseases such as liver and colorectal cancer. The occurrence of cyanoHABs and cyanotoxins in lakes presents challenges for maintaining safe recreational aquatic environments and the production of potable drinking water. CyanoHABs are a growing problem in the North American (Laurentian) Great Lakes basin. This review summarizes information on the occurrence of cyanoHABs in the Great Lakes, toxicological effects of cyanotoxins, and appropriate numerical limits on cyanotoxins in finished drinking water.

Responses of the antioxidative and biotransformation enzymes in the aquatic fungus Mucor hiemalis exposed to cyanotoxins

OBJECTIVES

To investigate antioxidative and biotransformation enzyme responses in Mucor hiemalis towards cyanotoxins considering its use in mycoremediation applications.

RESULTS

Catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GPx) in M. hiemalis maintained their activities at all tested microcystin-LR (MC-LR) exposure concentrations. Cytosolic glutathione S-transferase (GST) activity decreased with exposure to 100 µg MC-LR l^-1 while microsomal GST remained constant. Cylindrospermopsin (CYN) at 100 µg l^-1 led to an increase in CAT activity and inhibition of GR, as well as to a concentration-dependent GPx inhibition. Microsomal GST was inhibited at all concentrations tested. β-N-methylamino-L-alanine (BMAA) inhibited GR activity in a concentration-dependent manner, however, CAT, GPx, and GST remained unaffected.

CONCLUSIONS

M. hiemalis showed enhanced oxidative stress tolerance and intact biotransformation enzyme activity towards MC-LR and BMAA in comparison to CYN, confirming its applicability in bioreactor technology in terms of viability and survival in their presence.

Effects of microcystin-LR and cylindrospermopsin on plant-soil systems: A review of their relevance for agricultural plant quality and public health

Toxic cyanobacterial blooms are recognized as an emerging environmental threat worldwide. Although microcystin-LR is the most frequently documented cyanotoxin, studies on cylindrospermopsin have been increasing due to the invasive nature of cylindrospermopsin-producing cyanobacteria. The number of studies regarding the effects of cyanotoxins on agricultural plants has increased in recent years, and it has been suggested that the presence of microcystin-LR and cylindrospermopsin in irrigation water may cause toxic effects in edible plants. The uptake of these cyanotoxins by agricultural plants has been shown to induce morphological and physiological changes that lead to a potential loss of productivity. There is also evidence that edible terrestrial plants can bioaccumulate cyanotoxins in their tissues in a concentration dependent-manner. Moreover, the number of consecutive cycles of watering and planting in addition to the potential persistence of microcystin-LR and cylindrospermopsin in the environment are likely to result in groundwater contamination. The use of cyanotoxin-contaminated water for agricultural purposes may therefore represent a threat to both food security and food safety. However, the deleterious effects of cyanotoxins on agricultural plants and public health seem to be dependent on the concentrations studied, which in most cases are non-environmentally relevant. Interestingly, at ecologically relevant concentrations, the productivity and nutritional quality of some agricultural plants seem not to be impaired and may even be enhanced. However, studies assessing if the potential tolerance of agricultural plants to these concentrations can result in cyanotoxin and allergen accumulation in the edible tissues are lacking. This review combines the most current information available regarding this topic with a realistic assessment of the impact of cyanobacterial toxins on agricultural plants, groundwater quality and public health.

The interactive effects of microcystin-LR and cylindrospermopsin on the growth rate of the freshwater algae Chlorella vulgaris

Microcystin-LR (MC-LR) and cylindrospermopsin (CYN) are the most representative cyanobacterial cyanotoxins. They have been simultaneously detected in aquatic systems, but their combined ecotoxicological effects to aquatic organisms, especially microalgae, is unknown. In this study, we examined the effects of these cyanotoxins individually and as a binary mixture on the growth rate of the freshwater algae Chlorella vulgaris. Using the MIXTOX tool, the reference model concentration addition (CA) was selected to evaluate the combined effects of MC-LR and CYN on the growth of the freshwater green algae due to its conservative prediction of mixture effect for putative similar or dissimilar acting chemicals. Deviations from the CA model such as synergism/antagonism, dose-ratio and dose-level dependency were also assessed. In single exposures, our results demonstrated that MC-LR and CYN had different impacts on the growth rates of C. vulgaris at the highest tested concentrations, being CYN the most toxic. In the mixture exposure trial, MC-LR and CYN showed a synergistic deviation from the conceptual model CA as the best descriptive model. MC-LR individually was not toxic even at high concentrations (37 mg L(-1)); however, the presence of MC-LR at much lower concentrations (0.4-16.7 mg L(-1)) increased the CYN toxicity. From these results, the combined exposure of MC-LR and CYN should be considered for risk assessment of mixtures as the toxicity may be underestimated when looking only at the single cyanotoxins and not their combination. This study also represents an important step to understand the interactions among MC-LR and CYN detected previously in aquatic systems.

Cyanobacterium producing cylindrospermopsin cause histopathological changes at environmentally relevant concentrations in subchronically exposed tilapia (Oreochromis niloticus)

The acute toxicity of cylindrospermopsin (CYN) has been established in rodents, based on diverse intraperitoneal an oral exposure studies and more recently in fish. But no data have been reported in fish after subchronic exposure to cyanobacterial cells containing this cyanotoxin, so far. In this work, tilapia (Oreochromis niloticus) were exposed by immersion to lyophilized Aphanizomenon ovalisporum cells added to the aquaria using two concentration levels of CYN (10 or 100 μg CYN L(-1)) and deoxy-cylindrospermopsin (deoxy-CYN) (0.46 or 4.6 μg deoxy-CYN L(-1)), during two different exposure times: 7 or 14 d. This is the first study showing damage in the liver, kidney, hearth, intestines, and gills of tilapia after subchronic exposure to cyanobacterial cells at environmental relevant concentrations. The major histological changes observed were degenerative processes and steatosis in the liver, membranous glomerulopathy in the kidney, myofibrolysis and edema in the heart, necrotic enteritis in the gastrointestinal tract, and hyperemic processes in gill lamellae and microhemorrhages. Moreover, these histopathological findings confirm that the extent of damage is related to the CYN concentration and length of exposure. Results from the morphometric study indicated that the average of nuclear diameter of hepatocytes and cross-sections of proximal and distal convoluted tubules are useful to evaluate the damage induced by CYN in the main targets of toxicity.

Cylindrospermopsin induces oxidative stress and genotoxic effects in the fish CLC cell line

Cylindrospermopsin (CYN) is a cyanotoxin detected in water reservoirs worldwide. The toxin is a potent protein synthesis inhibitor capable of adversely influencing a wide range of cell functions. While data on the prooxidative potency of CYN are inconsistent, genotoxic effects towards certain mammalian cell types have been described. However, such a potential on fish cells has not yet been investigated. Hence, the aim of the study was to elucidate the prooxidative and genotoxic impact of CYN on a common carp (Cyprinus carpio L.) leucocyte cell line (CLC). The cells were incubated with the cyanotoxin at concentrations of 0.1, 0.5 or 1 µg ml⁻¹. After 24 h, cytotoxic activity of CYN at the highest used concentration was confirmed by decreased cell membrane integrity and inhibited cell proliferation. Additionally, CYN at 0.5 and 1 µg ml⁻¹ increased intracellular ATP levels and decreased the reduced to oxidized glutathione ratio. Furthermore, a significant increase in the reactive oxygen species (ROS) production with concomitant changes in superoxide dismutase activity was observed after a 3.5-h exposure of the cells to the toxin. Genotoxic activity of CYN, manifested as oxidative DNA damage and elevated number of micronuclei, was also detected in exposed cells. The obtained results indicate that CYN is able to exert a wide range of adverse effects, including oxidative stress and genotoxicity in fish leucocytes.

Acute exposure to pure cylindrospermopsin results in oxidative stress and pathological alterations in tilapia (Oreochromis niloticus)

Cylindrospermopsin (CYN) is increasingly recognized as a potential threat to drinking water safety, due to its ubiquity. This cyanotoxin has been found to cause toxic effects in mammals, and although fish could be in contact with this toxin, acute toxicity studies on fish are nonexistent. This is the first study showing that single doses of CYN pure standard (200 or 400 μg CYN/kg fish bw) by oral route (gavage) generate histopathological effects in fish (Tilapia-Oreochromis niloticus) exposed to the toxin under laboratory condition. Among the morphological changes, disorganized parenchymal architecture in the liver, dilated Bowman's space in the kidney, fibrolysis in the heart, necrotic enteritis in the intestines, and hemorrhages in the gills, were observed. Moreover, some oxidative stress biomarkers in the liver and kidney of tilapias were altered. Thus, CYN exposure induced increased protein oxidation products in both organs, NADPH oxidase activity was significantly increased with the kidney being the most affected organ, and decreased GSH contents were also detected in both organs, at the higher dose assayed.

Effects of depuration on oxidative biomarkers in tilapia (Oreochromis niloticus) after subchronic exposure to cyanobacterium producing cylindrospermopsin

Cylindrospermopsin (CYN) is a cytotoxic polyketide-derived alkaloid produced by several freshwater cyanobacterial species. It is now considered the second most studied cyanotoxin worldwide. Among the toxic mechanisms suggested for CYN pathogenicity are inhibition of protein and glutathione synthesis, genotoxicity by DNA fragmentation, and oxidative stress. The study of depuration of cyanobacterial toxins by aquatic organisms, particularly by fish, is important for fish economy and public health, but in the case of CYN is practically nonexistent. In this work, we investigated the efficiency of two distinct depuration periods, 3 or 7d, in a clean environment, as a mean of restoring the levels of several oxidative stress biomarkers in tilapia (Oreochromis niloticus) subchronically exposed to CYN by immersion in an Aphanizomenon ovalisporum culture (by adding 10 μg CYN/L every two days during 14 d). Lipid peroxidation (LPO) and DNA oxidation returned to normal values after 7d of depuration, whereas the time needed for restoring of the oxidatively damaged proteins was longer. Superoxide dismutase (SOD) and gamma-glutamyl-cysteine-synthetase (γ-GCS) activities recovered after just 3d of depuration, while catalase (CAT) activity needed up to 7d to return to control values. Ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) returned to control levels after 7d of depuration in both organs. These results validate the depuration process as a very effective practice for detoxification in fish contaminated with these toxins.

Influence of two depuration periods on the activity and transcription of antioxidant enzymes in tilapia exposed to repeated doses of cylindrospermopsin under laboratory conditions

The cyanobacterial toxin Cylindrospermopsin (CYN), a potent protein synthesis inhibitor, is increasingly being found in freshwater bodies infested by cyanobacterial blooms worldwide. Moreover, it has been reported to be implicated in human intoxications and animal mortality. Recently, the alteration of the activity and gene expression of some glutathione related enzymes in tilapias (Oreochromis niloticus) exposed to a single dose of CYN has been reported. However, little is known about the effects induced by repeated doses of this toxin in tilapias exposed by immersion and the potential reversion of these biochemical alterations after two different depuration periods (3 or 7 days). In the present study, tilapias were exposed by immersion to repeated doses of a CYN-containing culture of Aphanizomenon ovalisporum during 14 days, and then were subjected to depuration periods (3 or 7 days) in clean water in order to examine the potential reversion of the effects observed. The activity and relative mRNA expression by real-time polymerase chain reaction (PCR) of the antioxidant enzymes glutathione peroxidase (GPx) and soluble glutathione-S-transferases (sGST), and also the sGST protein abundance by Western blot analysis were evaluated in liver and kidney of fish. Results showed significant alterations in most of the parameters evaluated and their recovery after 3 days (GPx activity, sGST relative abundance) or 7 days (GPx gene expression, sGST activity). These findings not only confirm the oxidative stress effects produced in fish by cyanobacterial cells containing CYN, but also show the effectiveness of depuration processes in mitigating the CYN-containing culture toxic effects.

Effects of cylindrospermopsin on a common carp leucocyte cell line

Cylindrospermopsin (CYN) is a cytotoxin produced by different cyanobacterial species, increasingly detected in water reservoirs worldwide. There is very little information available concerning the effects of the toxin on fish immune cells. The aim of the study was to elucidate the potential impact of cylindrospermopsin on the selected parameters of a common carp (Cyprinus carpio L.) leucocyte cell line (CLC). The cells were incubated with the cyanotoxin at concentrations of 10, 1 or 0.1 µg ml(-1) for up to 48 h. Cell viability and proliferation, apoptosis/necrosis induction, cell morphology and phagocytic activity were determined. The two higher toxin concentrations occurred to be evidently cytotoxic in a time-dependent manner and influenced all studied parameters. The lowest used concentration had no effects on cell viability and cell number; however, a strong reduction of bacteria uptake after 24-h exposure was detected. The obtained results indicate that cylindrospermopsin may interfere with the basic functions of fish phagocytic cells and as a consequence influence the fish immunity.

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.

Influence of the exposure way and the time of sacrifice on the effects induced by a single dose of pure Cylindrospermopsin on the activity and transcription of glutathione peroxidase and glutathione-S-transferase enzymes in Tilapia (Oreochromis niloticus)

Cylindrospermopsin is a cyanobacterial toxin frequently implicated in cyanobacterial blooms that is approaching an almost cosmopolitan distribution pattern. Moreover, the predominant extracellular availability of this cyanotoxin makes it particularly likely to be taken up by a variety of aquatic organisms including fish. Recently, Cylindrospermopsin has shown to alter the activity and gene expression of some of the glutathione related enzymes in tilapias (Oreochromis niloticus), but little is known about the influence of the route of exposure and the time of sacrifice after a single exposure to Cylindrospermopsin on these biomarkers. With this aim, tilapias were exposed by gavage or by intraperitoneal injection to a single dose of 200 μg kg(-1) bw of pure Cylindrospermopsin and after 24h or 5d they were sacrificed. The activity and relative mRNA expression by real-time PCR of antioxidant enzymes glutathione peroxidase and soluble glutathione-S-transferases (sGST) and the sGST protein abundance by Western blot analysis were evaluated in liver and kidney. Results showed differential responses in dependence on the variables considered with a higher toxicity with the intraperitoneal exposure and with 5d as time of sacrifice.

Cyanobacterium producing cylindrospermopsin cause oxidative stress at environmentally relevant concentrations in sub-chronically exposed tilapia (Oreochromis niloticus)

Cylindrospermopsin (CYN) is a potent cyanobacterial cytotoxin produced by certain freshwater cyanobacteria. Structurally, it is an alkaloid with a tricyclic guanidine moiety combined with hydroxymethyluracil. It has proved to be a potent inhibitor of protein synthesis, and to deplete hepatic glutathione. Recently, some studies have shown that CYN produces changes in some oxidative stress biomarkers in fish acutely exposed to pure CYN by oral and intraperitoneal (i.p.) routes. In the present study tilapia (Oreochromis niloticus) were exposed by immersion to lyophilized Aphanizomenon ovalisporum cells added to the aquaria using two concentration levels, 10 or 100 μg CYN L(-1), during two different exposure times: 7 and 14 d. Fish were sacrificed and liver and kidney were extracted. The oxidative status of fish was evaluated by analyzing in both organs the following biomarkers: lipid peroxidation (LPO), protein oxidation, DNA oxidation, reduced-oxidized glutathione ratio (GSH/GSSG), and changes in the activity of Glutathione-S-transferase (GST), Glutathione Peroxidase (GPx), Superoxide dismutase (SOD), Catalase (CAT), and γ-Glutamyl-cysteine synthetase (GCS). In general, major changes were observed in tilapia treated with 100 μg CYN L(-1) after 14 d of exposure. However, some endpoints were altered at the lowest concentration assayed only after 7d of exposure, such as DNA oxidation and γ-GCS in kidney, and CAT and GSH/GSSG decrease in the liver and kidney. The kidney was the most affected organ. These findings confirm that the oxidative stress play a role in the pathogenicity induced by CYN in this fish species, and the results obtained could be useful for future ecotoxicological risks assessment studies, for the protection of fish and aquatic ecosystems. To our knowledge this is the first study dealing with the oxidative stress changes induced by cyanobacterial cells containing CYN and its derivative deoxy-CYN on fish exposed sub-chronically under laboratory conditions.

Alterations observed in the endothelial HUVEC cell line exposed to pure Cylindrospermopsin

The cyanobacterial toxin Cylindrospermopsin (CYN) is receiving great interest due to its increasing presence in waterbodies, which has lead to recognize it as a potential threat to drinking water safety. CYN is a potent inhibitor of protein and glutathione synthesis. The present work studies for the first time the effects of CYN in endothelial cells. The basal cytotoxicity endpoints studied at 24 and 48 h were total protein content (PC), neutral red (NR) uptake and the tretazolium salt, MTS, reduction. Moreover, the effect of subcytotoxic concentrations of CYN on the generation of intracellular reactive oxygen species (ROS), the activity of γ-glutamylcysteine synthetase (GCS) and glutathione (GSH) content have been investigated. In addition, morphological alterations of HUVEC cells subsequent to CYN exposure were recorded. The cytotoxicity endpoints revealed a decrease in the cellular viability in a time and concentration-dependent way. The most sensitive cytotoxicity endpoint was NR uptake assay, with reductions in cell viability of 95% at 48 h of exposure to 40 μg mL(-1) CYN. Intracellular ROS production was increased only at the lowest concentration assayed, while GCS activity and GSH content underwent concentration-dependent enhancements. The most remarkable morphological alterations observed were: nucleolar segregation with altered nuclei, degenerated Golgi apparatus, increases in the presence of granules and apoptosis.

Cylindrospermopsin: water-linked potential threat to human health in Europe

Cylindrospermopsin (CYN) is a secondary metabolite produced by several cyanobacteria species. Its potential effect on human health includes liver, kidneys, lungs, spleen and intestine injuries. CYN can be cyto- and genotoxic to a variety of cell types. Occurrence and expansion of species able to synthesize CYN in European water bodies has been recently reported and raised awareness of potential harm to human health. Therefore, surface water of different human use should be monitored for the presence of toxic species of blue-green algae. This paper aims to describe the distribution of CYN producers in Europe and the potential effects of the toxin on human health according to the current state of knowledge.

Protective role of dietary N-acetylcysteine on the oxidative stress induced by cylindrospermopsin in tilapia (Oreochromis niloticus)

Cylindrospermopsin (CYN) is a toxin produced by various cyanobacteria species. Fish can be exposed to this cyanotoxin in their natural environments and in aquaculture ponds, and toxic effects can be derived. The present study investigated the effects of dietary N-acetylcysteine (NAC) on the oxidative stress induced by pure CYN and CYN from lyophilized cells of Aphanizomenon ovalisporum in tilapia (Oreochromis niloticus). Fish were pretreated with 0, 22, and 45 mg NAC/fish/d for a week, and on day seven, they received a single dose of 200 µg/kg CYN and were killed after 24 h. Oxidative biomarkers evaluated included lipid peroxidation, protein oxidation, glutathione (GSH)/oxidized glutathione (GSSG) ratio, activity of the enzyme γ-glutamylcysteine synthetase, and activity and gene expression of glutathione-S-transferase and glutathione peroxidase. Results showed that CYN induced oxidative stress as evidenced by the increase of lipid peroxidation and protein oxidation, the decrease in GSH/GSSG, and the alteration of the enzymatic activities assayed. Moreover, exposure to cyanobacterial cells containing CYN induced higher toxic effects in comparison to pure CYN. N-acetylcysteine supplementation was effective at reducing the toxicity induced by CYN, particularly at the highest dose employed, with a recovery of some of the biomarkers assayed to basal levels. Therefore, NAC can be considered a useful chemoprotectant that reduces hepatic and renal oxidative stress in the prophylaxis and treatment of CYN-related intoxication in fish.

Cytotoxic and genotoxic effects of cylindrospermopsin in mice treated by gavage or intraperitoneal injection

Cylindrospermopsin (CYN), a cyanobacterial hepatotoxin mainly produced by Cylindrospermopsis raciborskii, has been involved in human intoxications and livestock deaths. The widespread occurrence of CYN in the water supplies lead us to investigate its genotoxicity to assess potential chronic effects. This study reports evaluation of CYN-induced in vivo DNA damage in mice using alkaline comet assay (ACA) and micronucleus assay (MNA) concomittantly. ACA measures DNA breakage from single and double strand breaks as well as alkali labile sites. Conversely, MNA detects chromosome damage events such as chromosomal breakage and numeric alterations. Male Swiss mice were treated with CYN concentrations of 50, 100, and 200 μg/kg by a single intraperitoneal (ip) injection or with 1, 2, and 4 mg/kg by gavage. Methyl methane sulfonate (MMS) was used as positive control at 80 mg/kg. Twenty-four hours after treatment, samples of liver, blood, bone marrow, kidney, intestine, and colon were taken to perform ACA, the bone marrow and the colon were also used for MNA. Parameters used to quantify DNA damage were % Tail DNA for ACA and both micronucleated immature erythrocytes and epithelial colon cells for MNA. DNA breaks and chromosome damage were significantly increased by MMS in all the organs evaluated. Significant DNA damage was detected within the colon by ACA after ip injection of 100 and 200 μg/kg CYN (P < 0.01). DNA damage was also detected in colon samples after 4 mg/kg oral administration of CYN and in bone marrow after 1 and 2 mg/kg of orally administered CYN. Histological examination showed foci of cell death within the liver and the kidney from mice that received the two highest doses of CYN by either route of administration.

Biochemical and pathological toxic effects induced by the cyanotoxin Cylindrospermopsin on the human cell line Caco-2

Cylindrospermopsin (CYN), a cyanotoxin produced by several freshwater cyanobacteria, causes human intoxications and animal mortalities. The present study focuses on the cytotoxic effects of CYN on Caco-2 cells at 24 and 48 h. The basal cytotoxicity endpoints studied were total protein content (TP), neutral red uptake (NR) and reduction of the tetrazolium salt (MTS). The effect of non-cytotoxic concentrations of CYN on the generation of intracellular reactive oxygen species (ROS), γ-glutamylcysteine synthetase (GCS) activity and glutathione (GSH) content was also studied and the morphological alterations in the Caco-2 cells subsequent to CYN exposure were recorded. The most sensitive endpoint - the reduction of MTS - showed that the viability of Caco-2 cells after exposure to the highest concentration assayed (40 μg/mL CYN) was reduced by about 90%. Intracellular ROS production increased only when exposed to a concentration of 1.25 μg/mL CYN, while GSH content and GCS activity increased when exposed to 2.5 μg/mL CYN. The main insights provided by the present study are the ultrastructural alterations, which reveal lipid degeneration, mitochondrial damage and nucleolar segregation with altered nuclei. Therefore, it has been demonstrated that CYN can induce toxic effects in Caco-2 cells in a time-concentration dependent manner. Moreover, unlike the cytotoxic and biochemical alterations, which were only evident at higher concentrations, morphological damage at the ultrastructural level was noticeable even at the lowest concentration used.

Acute effects of pure cylindrospermopsin on the activity and transcription of antioxidant enzymes in tilapia (Oreochromis niloticus) exposed by gavage

The cyanobacterial toxin cylindrospermopsin (CYN) is a widely distributed contaminant of freshwater systems with the consequent risk for human and wildlife, particularly fish. However, CYN toxicity data on fish are still scarce. It is known that CYN inhibits glutathione synthesis and this could contribute to oxidative damage. In the present work tilapia (Oreochromis niloticus) were exposed by gavage to 200 and 400 μg/kg bw of pure CYN and sacrificed after 24 h. The activity and relative mRNA expression by real-time PCR of antioxidant enzymes glutathione peroxidase (GPx) and soluble glutathione-S-transferases (sGST) and the sGST protein abundance by Western blot analysis were evaluated in liver and kidney. Also the induction of lipid peroxidation (LPO) was assayed. Results show an increase of LPO products in both organs. Moreover, CYN altered the activity, gene expression and protein abundance of the enzymes, indicating the importance of GPx and sGST in CYN pathogenicity. This is the first time that CYN is reported to affect these enzymes in fish and they have shown to be responsive biomarkers of CYN toxicity.

Oxidative stress responses in tilapia (Oreochromis niloticus) exposed to a single dose of pure cylindrospermopsin under laboratory conditions: influence of exposure route and time of sacrifice

Cylindrospermopsin (CYN) is a toxin produced by various cyanobacterial species that are increasingly being found in freshwater systems. Although CYN can have toxic effects in humans, domestic animals and wildlife, it has been subject to very little investigation (particularly in fish). It has been reported to deplete the cellular glutathione content but the role of oxidative stress in the pathogenicity of CYN in fish is unknown. For this reason tilapia fish were exposed to 200 μg/kg pure CYN through two different exposure routes-gavage and intraperitoneal injection-and sacrificed after 24 h and 5 days. The results showed an increase in NADPH oxidase activity (a biomarker of reactive oxygen species formation), lipid peroxidation (LPO) and protein oxidation; no changes in DNA oxidation; and a reduction in glutathione levels (GSH) and γ-glutamylcysteine synthetase (GCS) activity, the limiting enzyme in glutathione synthesis. The time of sacrifice had a bigger influence on the results than the exposure route because after 5 days some of the biomarkers assayed had recovered their pre-intoxication levels, which was not the case after 24 h.

Toxicity and glutathione implication in the effects observed by exposure of the liver fish cell line PLHC-1 to pure cylindrospermopsin

Cylindrospermopsin (CYN), a cyanotoxin produced by several freshwater cyanobacteria species, has been reported to cause human and animal intoxications. CYN is a potent inhibitor of protein and glutathione synthesis. In order to study these effects, various in vitro models have been used, which are representative of the organs targeted by the toxin. However, studies concerning CYN toxicity to fish species, both in vivo and in vitro, are still very scarce. To our knowledge, this is the first work dealing with the effects of CYN in a fish cell line. In the present work, we tried to test the hypothesis that CYN could be hepatotoxic to fish causing cell damage and oxidative stress, which may lead to pathogenicity. To deal this purpose, PLCH-1 cells, derived from fish liver, were exposed to concentrations that ranged from 0.3 to 40 μg/mL CYN during 24 and 48 h for the cytotoxicity study, and 2, 4 and 8 μg/mL CYN for the oxidative stress assays. The basal cytotoxicity endpoints studied were protein content, neutral red uptake and the tetrazolium salt, MTS, reduction. The biomarkers used for the oxidative stress study were reactive oxygen species (ROS) content, reduced glutathione content and γ-glutamylcysteine synthetase activity. The cytotoxicity endpoints revealed a decrease in the cellular viability in a time and concentration-dependent way. Moreover, when cells were exposed to pure CYN, an increase in the ROS content was observed, being more marked at the higher concentrations used. Finally, the present work shows alterations in GSH content and synthesis due to CYN. Moreover, a relationship between cytotoxic effects and ROS production has been evidenced. The results obtained confirm the alteration on fish liver cells, which should be considered relevant to what it may happen in real scenarios since fish are frequently in contact with this cyanotoxin.