Comparative study of cyanotoxins affecting cytoskeletal and chromatin structures in CHO-K1 cells

The cytotoxicity of microcystin-LR: ultrastructural and functional damage of cells

Microcystin-LR (MC-LR) is a toxin produced by cyanobacteria, which is widely distributed in eutrophic water bodies and has multi-organ toxicity. Previous cytotoxicity studies have mostly elucidated the effects of MC-LR on intracellular-related factors, proteins, and DNA at the molecular level. However, there have been few studies on the adverse effects of MC-LR on cell ultrastructure and function. Therefore, research on the cytotoxicity of MC-LR in recent years was collected and summarized. It was found that MC-LR can induce a series of cytotoxic effects, including decreased cell viability, induced autophagy, apoptosis and necrosis, altered cell cycle, altered cell morphology, abnormal cell migration and invasion as well as leading to genetic damage. The above cytotoxic effects were related to the damage of various ultrastructure and functions such as cell membranes and mitochondria. Furthermore, MC-LR can disrupt cell ultrastructure and function by inducing oxidative stress and inhibiting protein phosphatase activity. In addition, the combined toxic effects of MC-LR and other environmental pollutants were investigated. This review explored the toxic targets of MC-LR at the subcellular level, which will provide new ideas for the prevention and treatment of multi-organ toxicity caused by MC-LR.

Insight to biotechnological utility of phycochemicals from cyanobacterium Anabaena sp.: An overview

Cyanobacteria (blue-green algae) are well-known for the ability to excrete extra-cellular products, as a variety of cyanochemicals (phycocompounds) of curio with several extensive therapeutic applications. Among these phycocompound, the cyanotoxins from certain water-bloom forming taxa are toxic to biota, including crocodiles. Failure of current non-renewable source compounds in producing sustainable and non-toxic therapeutics led the urgency of discovering products from natural sources. Particularly, compounds of the filamentous N2-fixing Anabaena sp. have effective antibacterial, antifungal, antioxidant, and anticancer properties. Today, such newer compounds are the potential targets for the possible novel chemical scaffolds, suitable for mainstream-drug development cascades. Bioactive compounds of Anabaena sp. such as, anatoxins, hassallidins and phycobiliproteins have proven their inherent antibacterial, antifungal, and antineoplastic activities, respectively. Herein, the available details of the biomass production and the inherent phyco-constituents namely, alkaloids, lipids, phenols, peptides, proteins, polysaccharides, terpenoids and cyanotoxins are considered, along with geographical distributions and morphological characteristics of the cyanobacterium. The acquisitions of cyanochemicals in recent years have newly addressed several pharmaceutical aliments, and the understanding of the associated molecular interactions of phycochemicals have been considered, for plausible use in drug developments in future.

Cylindrospermopsin induces oocyte maturation and disrupts gene expression in zebrafish ovarian follicles

There is evidence that cylindrospermopsin (CYN) exerts reproductive toxicity in mice. However, little information is available concerning the toxicity of CYN in nonmammalian vertebrates. Here, we investigated the direct action of CYN on female reproduction by studying germinal vesicle breakdown, transcript abundance, caspase-3 activity, and testosterone production using cultured follicle-enclosed zebrafish oocytes as a model system. Treatment of follicles with 1,000 μg/L CYN significantly increased GVBD, Caspase-3 activity, and hCG-induced testosterone secretion. Exposure to CYN also reduced the abundance of 3βhsd as well as hCG-induced fshr and era transcripts and increased cyp19a1 mRNA levels. In summary, this study provides a framework for a better understanding of the adverse action of CYN on female reproduction in zebrafish and other vertebrate species. The findings are also relevant to developing valid biomarkers for CYN by measuring zebrafish oocyte maturation and gene expression.

Cylindrospermopsin directly disrupts spermatogenesis in isolated male zebrafish testis

Cylindrospermopsin (CYN) is a cytotoxin, and its documented effects in mammals include damage to several organs. CYN also has hormone-disrupting properties, including estrogenic activity, progesterone production inhibition, and apoptosis induction. While CYN has been reported to exert reproductive toxicity in mice, little is known about its effect on fish reproductive function. Using ex vivo organ culture, we investigated the direct action of CYN on the male reproductive system. Isolated zebrafish testis was exposed to 250, 500, and 1000 µg/L CYN for 24 h and 7 d, followed by histo-morphological analysis. The results demonstrate that exposure to CYN led to a decrease in cell types from all three phases of spermatogenesis in zebrafish testis. There were also significant changes in fshr, lhr, and igf3 transcript levels, as well as testosterone secretion following exposure to CYN. In summary, this study provides novel information on the adverse effects of CYN on testicular spermatogenesis and male reproduction in zebrafish. These results provide a framework for a better understanding of CYN toxicity and the mechanism underlying the adverse action of CYN on male reproduction in fish.

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.

The mechanisms of mitochondrial dysfunction and glucose intake decrease induced by Microcystin-LR in ovarian granulosa cells

Microcystin-LR (MC-LR) is a cyclic heptapeptide; it is an intracellular toxin released by cyanobacteria that exhibits strong reproductive toxicity. Previous studies have demonstrated that MC-LR induces oxidative stress in granulosa cells by damaging the mitochondria, which eventually leads to follicle atresia and female subfertility. In the present study, granulosa cells were exposed to 0, 0.01, 0.1 and 1 μM MC-LR. After 24 h, we observed changes in mitochondrial cristae morphology and dynamics by analyzing the results of mitochondrial transmission electron microscopy and detecting the expression of DRP1. We also evaluated glucose intake using biochemical assays and expression of glucose transport related proteins. MC-LR exposure resulted in mitochondrial fragmentation and glucose intake decrease in granulosa cells, as shown by increasing mitochondrial fission via dynamin-related protein 1 (DRP1) upregulation and decreasing glucose transporter 1 and 4 (GLUT1 and GLUT4). Furthermore, the expression levels of forkhead box protein M1 (FOXM1) significantly increased due to the overproduction of reactive oxygen species (ROS) after MC-LR exposure. Our results proved that MC-LR exposure causes mitochondrial fragmentation and glucose intake decrease in granulosa cells, which provides new insights to study the molecular mechanism of female reproductive toxicity induced by MC-LR.

Cylindrospermopsin impairs tubular transport function in kidney cells LLC-PK1

Cylindrospermopsin (CYN) has been involved in cases of poisoning in humans following ingestion. Studies have demonstrated that the kidney is the most affected organ. CYN exposure leads to low-molecular-weight proteinuria and increased excretions of the tubular enzymes in mice, suggesting the damage caused by CYN is mainly tubular. However, the mechanism involved in CYN nephrotoxicity remains unknown. Thus, in order to evaluate the effects of CYN exposure (0.1, 0.5 and 1.0 μg/mL) on tubular renal cells LLC-PK1 distinct mechanisms were analyzed by assessing cell death using flow cytometry, albumin uptake by fluorescence analysis, Na⁺/K⁺-ATPase activity by a colorimetric method, RT-qPCR of genes related to tubular transport and function as well as internalization of CYN by ELISA. In this study, CYN was found to induce necrosis in all concentrations. CYN also decreased albumin uptake as well as downregulated megalin and dab2 expression, both proteins involved in albumin endocytosis process. Moreover, CYN appears to be internalized by renal tubular cells through a receptor-mediated endocytosis. Finally, the present study demonstrates that CYN is responsible for disrupting tubular cell transport and function in LLC-PK1 cells.

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

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

Application of advanced HepG2 3D cell model for studying genotoxic activity of cyanobacterial toxin cylindrospermopsin

Cylindrospermopsin (CYN) is an emerging cyanotoxin increasingly being found in freshwater cyanobacterial blooms worldwide. Humans and animals are exposed to CYN through the consumption of contaminated water and food as well as occupational and recreational water activities; therefore, it represents a potential health threat. It exhibits genotoxic effects in metabolically active test systems, thus it is considered as pro-genotoxic. In the present study, the advanced 3D cell model developed from human hepatocellular carcinoma (HepG2) cells was used for the evaluation of CYN cyto-/genotoxic activity. Spheroids were formed by forced floating method and were cultured for three days under static conditions prior to exposure to CYN (0.125, 0.25 and 0.5 μg/mL) for 72 h. CYN influence on spheroid growth was measured daily and cell survival was determined by MTS assay and live/dead staining. The influence on cell proliferation, cell cycle alterations and induction of DNA damage (γH2AX) was determined using flow cytometry. Further, the expression of selected genes (qPCR) involved in the metabolism of xenobiotics, proliferation, DNA damage response, apoptosis and oxidative stress was studied. Results revealed that CYN dose-dependently reduced the size of spheroids and affected cell division by arresting HepG2 cells in G1 phase of the cell cycle. No induction of DNA double strand breaks compared to control was determined at applied conditions. The analysis of gene expression revealed that CYN significantly deregulated genes encoding phase I (CYP1A1, CYP1A2, CYP3A4, ALDH3A) and II (NAT1, NAT2, SULT1B1, SULT1C2, UGT1A1, UGT2B7) enzymes as well as genes involved in cell proliferation (PCNA, TOP2α), apoptosis (BBC3) and DNA damage response (GADD45a, CDKN1A, ERCC4). The advanced 3D HepG2 cell model due to its more complex structure and improved cellular interactions provides more physiologically relevant information and more predictive data for human exposure, and can thus contribute to more reliable genotoxicity assessment of chemicals including cyanotoxins.

Microcystin-LR exposure results in aberrant spindles and induces apoptosis in porcine oocytes

Microcystin-LR (MC-LR), as a well-known hepatotoxin, was recently found to accumulate in gonads and induce a variety of reproductive damages in zebrafish, mice and other model organisms, however, little information is available on whether MC-LR has toxic effects on the mammalian oocytes, especially in livestock species. In this study, the effects of MC-LR on meiotic maturation of porcine oocytes were investigated, and the potential mechanism of MC-LR toxicity was explored. Germinal vesicle (GV)-stage oocytes were exposed to 0, 20, 40 and 60 μM MC-LR, respectively, during the in vitro maturation for 44 h, and the results showed that the first polar body (PbI) extrusion rate of the oocytes decreased significantly when the MC-LR concentration reached 40 (P < 0.01) or 60 μM (P < 0.001). After treated with 60 μM MC-LR for 44 h, a significant higher percentage of the oocytes arrested at anaphase-telophase I (ATI) stage (P < 0.01). Laser scanning confocal results further confirmed that a significantly larger proportion of the 60 μM MC-LR-treated oocytes exhibited aberrant spindles and misaligned chromosomes, suggesting a failure of spindle assembly and homologous chromosome segregation during the ATI stage. Furthermore, the ROS levels in the 60 μM MC-LR-exposed oocytes were significantly higher than the control group (P < 0.01), while the expression of antioxidant related genes (SOD1, CAT and GPX) were much lower compared with control group, indicating that oxidative stress was induced and the antioxidant capacity of oocytes was depleted by 60 μM MC-LR treatment. Additionally, markedly decreased mitochondrial membrane potential (MMP) (P < 0.01) and significantly higher incidence of early apoptosis (P < 0.01) were observed in the 60 μM MC-LR-treated oocytes, suggesting that MC-LR exposure induced apoptosis in porcine oocytes. Moreover, the protein expression of PP2A was remarkably inhibited, whereas the expression of p53, BAX, Caspase3 and Cleaved-caspase3 were prominently increased in the 60 μM MC-LR-exposed oocytes. Together, these results suggested that 60 μM of MC-LR exposure can induce oxidative stress, and lead to aberrant spindles, impaired MMP, and trigger apoptosis, which eventually result in failure of porcine oocyte maturation.

The effects of microcystin-LR in Oryza sativa root cells: F-actin as a new target of cyanobacterial toxicity

Microcystins are toxins produced by cyanobacteria, notorious for negatively affecting a wide range of living organisms, among which several plant species. Although microtubules are a well-established target of microcystin toxicity, its effect on filamentous actin (F-actin) in plant cells has not yet been studied. Τhe effects of microcystin-LR (MC-LR) and an extract of a microcystin-producing freshwater cyanobacterial strain (Microcystis flos-aquae TAU-MAC 1510) on the cytoskeleton (F-actin and microtubules) of Oryza sativa (rice) root cells were studied with light, confocal, and transmission electron microscopy. Considering the role of F-actin in endomembrane system distribution, the endoplasmic reticulum and the Golgi apparatus in extract-treated cells were also examined. F-actin in both MC-LR- and extract-treated meristematic and differentiating root cells exhibited time-dependent alterations, ranging from disorientation and bundling to the formation of ring-like structures, eventually resulting in a collapse of the F-actin network after longer treatments. Disorganization and eventual depolymerization of microtubules, as well as abnormal chromatin condensation were observed following treatment with the extract, effects which could be attributed to microcystins and other bioactive compounds. Moreover, cell cycle progression was inhibited in extract-treated roots, specifically affecting the mitotic events. As a consequence of F-actin network disorganization, endoplasmic reticulum elements appeared stacked and diminished, while Golgi dictyosomes appeared aggregated. These results support that F-actin is a prominent target of MC-LR, both in pure form and as an extract ingredient. Endomembrane system alterations can also be attributed to the effects of cyanobacterial bioactive compounds (including microcystins) on the F-actin cytoskeleton.

Harmful Cyanobacterial Blooms (HCBs): innovative green bioremediation process based on anti-cyanobacteria bioactive natural products

Over the last decades, Harmful Cyanobacterial Blooms (HCBs) represent one of the most conspicuous hazards to human health in freshwater ecosystems, due to the uses of the water for drinking, recreation and aquaculture. Cyanobacteria are one of the main biological components in freshwater ecosystems and they may proliferate in nutrients rich ecosystems causing severe impacts at different levels. Therefore, several methods have been applied to control cyanobacterial proliferation, including physical, chemical and biological strategies. However, the application of those methods is generally not very efficient. Research on an eco-friendly alternative leading to the isolation of new bioactive compounds with strong impacts against harmful cyanobacteria is a need in the field of water environment protection. Thus, this paper aims to give an overview of harmful cyanobacterial blooms and reviews the state of the art of studying the activities of biological compounds obtained from plants, seaweeds and microorganisms in the cyanobacterial bloom control.

Cylindrospermopsin induces abnormal vascular development through impairing cytoskeleton and promoting vascular endothelial cell apoptosis by the Rho/ROCK signaling pathway

Cylindrospermopsin (CYN) is a widely distributed cyanobacterial toxin in water bodies and is considered to pose growing threats to human and environmental health. Although its potential toxicity has been reported, its effects on the vascular system are poorly understood. In this study, we examined the toxic effects of CYN on vascular development and the possible mechanism of vascular toxicity induced by CYN using zebrafish embryos and human umbilical vein endothelial cells (HUVECs). CYN exposure induced abnormal vascular development and led to an increase in the growth of common cardinal vein (CCV), in which CCV remodeling was delayed as reflected by the larger CCV area and wider ventral diameter. CYN decreased HUVECs viability, inhibited HUVECs migration, promoted HUVECs apoptosis, destroyed cytoskeleton, and increased intracellular ROS levels. Additionally, CYN could promote the expression of Bax, Bcl-2, and MLC-1 and inhibit the expression of ITGB1, Rho, ROCK, and VIM-1. Taken together, CYN may induce cytoskeleton damage and promote vascular endothelial cell apoptosis by the Rho/ROCK signaling pathway, leading to abnormal vascular development. The current results provide potential insight into the mechanism of CYN toxicity in angiocardiopathy and are beneficial for understanding the environmental risks of CYN for aquatic organisms and human health.

Oxidative Stress Mediates Microcystin-LR-Induced Endoplasmic Reticulum Stress and Autophagy in KK-1 Cells and C57BL/6 Mice Ovaries

Microcystin-leucine arginine (MC-LR) is a cyclic heptapeptide intracellular toxin released by cyanobacteria that exhibits strong reproductive toxicity. However, little is known about its biotoxicity to the female reproductive system. The present study investigates unexplored molecular pathways by which oxidative stress acts on MC-LR-induced endoplasmic reticulum stress (ERs) and autophagy. In the present study, immortalized murine ovarian granular cells (KK-1 cells) were exposed to 8.5, 17, and 34 μg/mL (IC₅₀) of MC-LR with or without N-acetyl-l-cysteine (NAC, 10 mM) for 24 h, and C57BL/6 mice were treated with 12.5, 25.0, and 40.0 μg/kg⋅bw of MC-LR with or without NAC (200 mg/kg⋅bw) for 14 days. The results revealed that MC-LR could induce cells apoptosis and morphologic changes in ovarian tissues, induce oxidative stress by stimulating the generation of reactive oxygen species (ROS), destroying antioxidant capacity, and subsequently trigger ERs and autophagy by inducing the hyper-expression of ATG12, ATG5, ATG16, EIF2α (phosphorylated at S51), CHOP, XBP1, GRP78, Beclin1, and PERK (Thr980). Furthermore, NAC pretreatment partly inhibited MC-LR-induced ERs and autophagy via the PERK/ATG12 and XBP1/Beclin1 pathways. These results suggest that oxidative stress mediated MC-LR-induced ERs and autophagy in KK-1 cells and C57BL/6 mice ovaries. Therefore, oxidative stress plays an important role in female toxicity induced by MC-LR.

Multi-Toxin Occurrences in Ten French Water Resource Reservoirs

Cyanobacteria are known to produce a wide array of metabolites, including various classes of toxins. Among these, hepatotoxins (Microcystins), neurotoxins (Anatoxin-A and PSP toxins) or cytotoxins (Cylindrospermopsins) have been subjected to numerous, individual studies during the past twenty years. Reports of toxins co-occurrences, however, remain scarce in the literature. The present work is an inventory of cyanobacteria with a particular focus on Nostocales and their associated toxin classes from 2007 to 2010 in ten lakes used for drinking water production in France. The results show that potential multiple toxin producing species are commonly encountered in cyanobacteria populations. Individual toxin classes were detected in 75% of all samples. Toxin co-occurrences appeared in 40% of samples as two- or three-toxin combinations (with 35% for the microcystins–anatoxin combination), whereas four-toxin class combinations only appeared in 1% of samples. Toxin co-occurrences could be partially correlated to species composition and water temperature. Peak concentrations however could never be observed simultaneously and followed distinct, asymmetrical distribution patterns. As observations are the key for preventive management and risk assessment, these results indicate that water monitoring should search for all four toxin classes simultaneously instead of focusing on the most frequent toxins, i.e., microcystins.

Cylindrospermopsin induces biochemical changes leading to programmed cell death in plants

In the present study we provide cytological and biochemical evidence that the cyanotoxin cylindrospermopsin (CYN) induces programmed cell death (PCD) symptoms in two model vascular plants: the dicot white mustard (Sinapis alba) and the monocot common reed (Phragmites australis). Cytological data include chromatin fragmentation and the increase of the ratio of TUNEL-positive cells in roots, the latter being detected in both model systems studied. The strongest biochemical evidence is the elevation of the activity of several single-stranded DNA preferring nucleases-among them enzymes active at both acidic and alkaline conditions and are probably directly related to DNA breaks occurring at the initial stages of plant PCD: 80 kDa nucleases and a 26 kDa nuclease, both having dual (single- and double-stranded nucleic acid) specificity. Moreover, the total protease activity and in particular, a 53-56 kDa alkaline protease activity increases. This protease could be inhibited by PMSF, thus regarded as serine protease. Serine proteases are detected in all organs of Brassicaceae (Arabidopsis) having importance in differentiation of specialized plant tissue through PCD, in protein degradation/processing during early germination and defense mechanisms induced by a variety of biotic and abiotic stresses. However, knowledge of the physiological roles of these proteases and nucleases in PCD still needs further research. It is concluded that CYN treatment induces chromatin fragmentation and PCD in plant cells by activating specific nucleases and proteases. CYN is proposed to be a suitable molecule to study the mechanism of plant apoptosis.

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.

Paralytic Shellfish Toxins and Cyanotoxins in the Mediterranean: New Data from Sardinia and Sicily (Italy)

Harmful algal blooms represent a severe issue worldwide. They affect ecosystem functions and related services and goods, with consequences on human health and socio-economic activities. This study reports new data on paralytic shellfish toxins (PSTs) from Sardinia and Sicily (Italy), the largest Mediterranean islands where toxic events, mainly caused by Alexandrium species (Dinophyceae), have been ascertained in mussel farms since the 2000s. The toxicity of the A. minutum, A. tamarense and A. pacificum strains, established from the isolation of vegetative cells and resting cysts, was determined by high performance liquid chromatography (HPLC). The analyses indicated the highest toxicity for A. pacificum strains (total PSTs up to 17.811 fmol cell-1). The PSTs were also assessed in a strain of A. tamarense. The results encourage further investigation to increase the knowledge of toxic species still debated in the Mediterranean. This study also reports new data on microcystins (MCs) and β-N-methylamino-L-alanine (BMAA) from a Sardinian artificial lake (Lake Bidighinzu). The presence of MCs and BMAA was assessed in natural samples and in cell cultures by enzyme-linked immunosorbent assay (ELISA). BMAA positives were found in all the analysed samples with a maximum of 17.84 µg L-1. The obtained results added further information on cyanotoxins in Mediterranean reservoirs, particularly BMAA, which have not yet been thoroughly investigated.

Uncovering Potential Applications of Cyanobacteria and Algal Metabolites in Biology, Agriculture and Medicine: Current Status and Future Prospects

Cyanobacteria and algae having complex photosynthetic systems can channelize absorbed solar energy into other forms of energy for production of food and metabolites. In addition, they are promising biocatalysts and can be used in the field of "white biotechnology" for enhancing the sustainable production of food, metabolites, and green energy sources such as biodiesel. In this review, an endeavor has been made to uncover the significance of various metabolites like phenolics, phytoene/terpenoids, phytols, sterols, free fatty acids, photoprotective compounds (MAAs, scytonemin, carotenoids, polysaccharides, halogenated compounds, etc.), phytohormones, cyanotoxins, biocides (algaecides, herbicides, and insecticides) etc. Apart from this, the importance of these metabolites as antibiotics, immunosuppressant, anticancer, antiviral, anti-inflammatory agent has also been discussed. Metabolites obtained from cyanobacteria and algae have several biotechnological, industrial, pharmaceutical, and cosmetic uses which have also been discussed in this review along with the emerging technology of their harvesting for enhancing the production of compounds like bioethanol, biofuel etc. at commercial level. In later sections, we have discussed genetically modified organisms and metabolite production from them. We have also briefly discussed the concept of bioprocessing highlighting the functioning of companies engaged in metabolites production as well as their cost effectiveness and challenges that are being addressed by these companies.

Cylindrospermopsin effects on protein profile of HepG2 cells

Human hepatoma cells (HepG2) were exposed to purified cylindrospermopsin (CYN), a potent toxicant for eukaryotic cells produced by several cyanobacteria. Exposure to 10 μg l^-1 of CYN for 24 h resulted in alteration of expression of 48 proteins, from which 26 were identified through mass spectrometry. Exposure to 100 μg l^-1 of CYN for 24 h affected nuclear area and actin filaments intensity, which can be associated with cell proliferation and toxicity. The proteins are implicated in different biological processes: protein folding, xenobiotic efflux, antioxidant defense, energy metabolism and cell anabolism, cell signaling, tumorigenic potential, and cytoskeleton structure. Protein profile indicates that CYN exposure may lead to alteration of glucose metabolism that can be associated with the supply of useful energy to cells respond to chemical stress and proliferate. Increase of G protein-coupled receptors (GPCRs), heterogeneous nuclear ribonucleoproteins (hnRNP), and reactive oxygen species (ROS) levels observed in HepG2 cells can associate with cell proliferation and resistance. Increase of MRP3 and glutathione peroxidase can protect cells against some chemicals and ROS. CYN exposure also led to alteration of the expression of cytoskeleton proteins, which may be associated with cell proliferation and toxicity.

A review of reproductive toxicity of microcystins

Animal studies provide strong evidence of positive associations between microcystins (MCs) exposure and reproductive toxicity, representing a threat to human reproductive health and the biodiversity of wild life. This paper reviews current knowledge of the reproductive toxicity of MCs, with regard to mammals, fishes, amphibians, and birds, mostly in males. Toxicity of MCs is primarily governed by the inhibition of protein phosphatases 1 and 2A (PP1 and PP2A) and disturbance of cellular phosphorylation balance. MCs exposure is related to excessive production of reactive oxygen species (ROS) and oxidative stress, leading to cytoskeleton disruption, mitochondria dysfunction, endoplasmic reticulum (ER) stress, and DNA damage. MCs induce cell apoptosis mediated by the mitochondrial and ROS and ER pathways. Through PP1/2A inhibition and oxidative stress, MCs lead to differential expression/activity of transcriptional factors and proteins involved in the pathways of cellular differentiation, proliferation, and tumor promotion. MC-induced DNA damage is also involved in carcinogenicity. Apart from a direct effect on testes and ovaries, MCs indirectly affect sex hormones by damaging the hypothalamic-pituitary-gonad (HPG) axis and liver. Parental exposure to MCs may result in hepatotoxicity and neurotoxicity of offspring. We also summarize the current research gaps which should be addressed by further studies.

Involvement of oxidative stress and cytoskeletal disruption in microcystin-induced apoptosis in CIK cells

The outbreak of cyanobacterial blooms induces the production and release of microcystins (MCs) into water, representing a health hazard to aquatic organisms and even humans. Some recent studies have suggested that kidney is another important target organ of MCs except liver, however, the potential toxicity mechanisms are still unclear. In this study, we first investigated the collaborative effect of oxidative stress and cytoskeletal disruption in microcystin-induced apoptosis in CIK (Ctenopharyngodon idellus kidney) cells in vitro. CIK cells were treated with 0, 1, 10, and 100μg/L microcystin-LR (MC-LR) for 24 and 48h. Cell viability was increased by MC-LR in 1μg/L group, while decreased in 100μg/L group at 48h. Cell cycle assay showed that 1 and 10μg/L MC-LR induced cell cycle through G1 into S and G2/M phases, while 100μg/L MC-LR reduced G2/M phase population. MC-LR markedly induced apoptosis in 10 and 100μg/L groups. Elevated reactive oxygen species (ROS) production, increased malondialdehyde (MDA) contents, decreased glutathione (GSH) levels, and modulated antioxidant enzymes including catalase (CAT) and superoxide dismutase (SOD) were observed in CIK cells exposed to MC-LR. These alterations were more pronounced at higher doses (10 and 100μg/L), indicating that oxidative stress was induced by MC-LR. Laser scanning confocal microscope observation showed aggregation and collapse of microfilaments (MFs) and microtubules (MTs) in CIK cells, and even loss of some cytoskeleton structure. Moreover, transcriptional changes of cytoskeletal genes (β-actin, lc3a, and keratin) were also determined, which have a high probability with cytoskeleton structure damage. Our data suggest that oxidative stress and cytoskeletal disruption may interact with each other and jointly lead to apoptosis and renal toxicity induced by MCs.

Effects of cylindrospermopsin on the phagocytic cells of the common carp (Cyprinus carpio L.)

Cylindrospermopsin is a cyanotoxin with cytotoxic activity. It is released into water during and after cyanobacterial water blooms and thus poses a threat to the health of fish. There is very little information available concerning the effects of the toxin on fish immune cells. In this study, we assessed the potential impact of cylindrospermopsin on the basic functions of phagocytic cells from common carp (Cyprinus carpio L.), including phagocytosis, reactive oxygen and nitrogen species production, and the structure of microfilaments and selected cytokine expression. Phagocytic cells, isolated from fish head kidneys, were exposed to the toxin at concentrations of 0.05, 0.1, 0.5 or 1 µg ml(-1), for up to 24 h. Cytotoxicity, detected by lactate dehydrogenase release, was observed at the highest studied concentration. A decrease in phagocytic activity and changes in actin cytoskeletal structures were observed after the cell exposure to the toxin at 0.5 and 1 µg ml(-1). Moreover, at all tested concentrations, cylindrospermopsin increased the production of reactive oxygen and nitrogen species. It also evidently influenced the expression of genes of proinflammatory cytokines interleukin-1β and tumour necrosis factor-α and, to a minor extent, anti-inflammatory transforming growth factor-β, but had no effects on interleukin-10. The results indicated that the cyanotoxin cylindrospermopsin is able to modify basic features of carp phagocytic cells, which might result in adverse consequences for fish health.

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.

Toxicity of cylindrospermopsin in human lymphocytes: proliferation, viability and cell cycle studies

The global expansion of cylindrospermopsin (CYN) producing cyanobacteria in surface freshwater increases the risk of human exposure and poisoning. Following ingestion, CYN is transported with blood in general circulation to the liver and kidneys, and can potentially interact with immune system cells. In the present study, we investigated whether CYN (0.01-1.0 μg ml(-1)) can alter the function of human peripheral blood lymphocytes isolated from healthy donors. It was found that CYN demonstrates significant antiproliferative activity in lymphocytes during different phases of their activation. The most remarkable effects (decrease by>90%) were observed in lymphocytes exposed to 1 μg ml(-1) CYN at the beginning of activation. Further analyses revealed a cell-cycle arrest at G0/G1 and prolonged S phase in lymphocytes undergoing activation and significant apoptosis inducement in activated cells. Reduced abilities to fight pathogenic microorganisms or malignant cells should be taken into consideration in CYN exposure and risk assessments.

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.

Epidemiology of cancers in Serbia and possible connection with cyanobacterial blooms

Cyanobacteria produce toxic metabolites known as cyanotoxins. These bioactive compounds can cause acute poisoning, and some of them may promote cancer through chronic exposure. Direct ingestion of and contact with contaminated water is one of the many exposure routes to cyanotoxins. The aim of this article was to review the incidence of 13 cancers during a 10-year period in Serbia and to assess whether there is a correlation between the cancer incidences and cyanobacterial bloom occurrence in reservoirs for drinking water supply. The types of cancers were chosen and subjected to epidemiological analyses utilizing previously published data. Based on the epidemiological and statistical analysis, the group of districts in which the incidences of cancers are significant, and may be considered as critical, include Nišavski, Toplički, and Šumadijski district. A significantly higher incidence of ten cancers was observed in the three critical districts as compared to the remaining 14 districts in Central Serbia. These elevated incidences of cancer include: brain cancer, heart, mediastinum and pleura cancer, ovary cancer, testicular cancer, gastric cancer, colorectal cancer, retroperitoneum and peritoneum cancer, leukemia, malignant melanoma of skin, and primary liver cancer. In addition, the mean incidence of five chosen cancers was the highest in the three critical regions, then in the rest of Central Serbia, while the lowest values were recorded in Vojvodina. Persistent and recurrent cyanobacterial blooms occur during summer months in reservoirs supplying water to waterworks in the three critical districts. People in Central Serbia mainly use surface water as water supply (but not all the water bodies are blooming) while in Vojvodina region (control region in this study) only groundwater is used. Among the 14 "noncritical" districts, reservoirs used for drinking water supply have been affected by recurrent cyanobacterial blooms in two districts (Rasinski and Zaječarski), but the waterworks in these districts have been performing ozonation for more than 30 years. We propose that the established statistical differences of cancer incidences in Serbia could be related to drinking water quality, which is affected by cyanobacterial blooms in drinking water reservoirs in certain districts. However, more detailed research is needed regarding cyanobacterial secondary metabolites as risk factors in tumor promotion and cancerogenesis in general.

Microcystin-LR and cylindrospermopsin induced alterations in chromatin organization of plant cells

Cyanobacteria produce metabolites with diverse bioactivities, structures and pharmacological properties. The effects of microcystins (MCYs), a family of peptide type protein-phosphatase inhibitors and cylindrospermopsin (CYN), an alkaloid type of protein synthesis blocker will be discussed in this review. We are focusing mainly on cyanotoxin-induced changes of chromatin organization and their possible cellular mechanisms. The particularities of plant cells explain the importance of such studies. Preprophase bands (PPBs) are premitotic cytoskeletal structures important in the determination of plant cell division plane. Phragmoplasts are cytoskeletal structures involved in plant cytokinesis. Both cyanotoxins induce the formation of multipolar spindles and disrupted phragmoplasts, leading to abnormal sister chromatid segregation during mitosis. Thus, MCY and CYN are probably inducing alterations of chromosome number. MCY induces programmed cell death: chromatin condensation, nucleus fragmentation, necrosis, alterations of nuclease and protease enzyme activities and patterns. The above effects may be related to elevated reactive oxygen species (ROS) and/or disfunctioning of microtubule associated proteins. Specific effects: MCY-LR induces histone H3 hyperphosphorylation leading to incomplete chromatid segregation and the formation of micronuclei. CYN induces the formation of split or double PPB directly related to protein synthesis inhibition. Cyanotoxins are powerful tools in the study of plant cell organization.

The influence of cylindrospermopsin on oxidative DNA damage and apoptosis induction in HepG2 cells

Cylindrospermopsin (CYN) a potent cyanobacterial cytotoxin and protein synthesis inhibitor is increasingly being found in surface freshwaters worldwide. Due to its genotoxic activity and potential carcinogenicity it was recognized as a potential threat to humans. However, the mechanisms of CYN genotoxicity are not well understood. We explored whether CYN at non-cytotoxic exposure conditions causes DNA damage through induction of oxidative stress and whether it induces apoptosis in HepG2 cells. With the DCFH-DA probe a significant increase in the intracellular formation of reactive oxygen species (ROS) was observed, which steadily increased with incubation. Induction of oxidative DNA damage was determined with the modified comet assay with formamidopyrimidine glycosylase (Fpg) digestion. No DNA damage was observed after 4h exposure to CYN. After 12 and 24 h exposure, CYN (at 0.25 and 0.5 μg mL(-1)) induced significant increase of DNA strand breaks, but not oxidative DNA damage, suggesting minor role of oxidative stress in CYN mediated genotoxicity. CYN also significantly increased the mitochondrial membrane potential (MMP), determined with the JC-1 probe, while no induction of caspase 3 and 7 activity and no increase in the number of apoptotic cells, measured with Annexin V/PI staining, could be determined. These results show that at non-cytotoxic concentrations CYN induced DNA damage was not the consequence of oxidative stress and that CYN did not induce apoptosis, which may add to the hazard of this toxin, as cells with damaged DNA are not removed from the population, enhancing the risk of mutations and consequently carcinogenesis.

Zebrafish neurotoxicity from aphantoxins--cyanobacterial paralytic shellfish poisons (PSPs) from Aphanizomenon flos-aquae DC-1

Aphanizomenon flos-aquae (A. flos-aquae), a cyanobacterium frequently encountered in water blooms worldwide, is source of neurotoxins known as PSPs or aphantoxins that present a major threat to the environment and to human health. Although the molecular mechanism of PSP action is well known, many unresolved questions remain concerning its mechanisms of toxicity. Aphantoxins purified from a natural isolate of A. flos-aquae DC-1 were analyzed by high-performance liquid chromatography (HPLC), the major component toxins were the gonyautoxins1 and 5 (GTX1 and GTX5, 34.04% and 21.28%, respectively) and the neosaxitoxin (neoSTX, 12.77%). The LD50 of the aphantoxin preparation was determined to be 11.33 μg/kg (7.75 μg saxitoxin equivalents (STXeq) per kg) following intraperitoneal injection of zebrafish (Danio rerio). To address the neurotoxicology of the aphantoxin preparation, zebrafish were injected with low and high sublethal doses of A. flos-aquae DC-1 toxins 7.73 and 9.28 μg /kg (5.3 and 6.4 μg STXeq/kg, respectively) and brain tissues were analyzed by electron microscopy and RT-PCR at different timepoints postinjection. Low-dose aphantoxin exposure was associated with chromatin condensation, cell-membrane blebbing, and the appearance of apoptotic bodies. High-dose exposure was associated with cytoplasmic vacuolization, mitochondrial swelling, and expansion of the endoplasmic reticulum. At early timepoints (3 h) many cells exhibited characteristic features of both apoptosis and necrosis. At later timepoints apoptosis appeared to predominate in the low-dose group, whereas necrosis predominated in the high-dose group. RT-PCR revealed that mRNA levels of the apoptosis-related genes encoding p53, Bax, caspase-3, and c-Jun were upregulated after aphantoxin exposure, but there was no evidence of DNA laddering; apoptosis could take place by pathways independent of DNA fragmentation. These results demonstrate that aphantoxin exposure can cause cell death in zebrafish brain tissue, with low doses inducing apoptosis and higher doses inducing necrosis.

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

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

The interactive effects of cytoskeleton disruption and mitochondria dysfunction lead to reproductive toxicity induced by microcystin-LR

The worldwide occurrence of cyanobacterial blooms evokes profound concerns. The presence of microcystins (MCs) in waters and aquatic food increases the risk to human health. Some recent studies have suggested that the gonad is the second most important target organ of MCs, however, the potential toxicity mechanisms are still unclear. For a better understanding of reproductive toxicity of MCs on animals, we conducted the present experimental investigation. Male rats were intraperitoneally injected with MC-LR for 50 d with the doses of 1 and 10 µg/kg body weight per day. After prolonged exposure to MC-LR, the testes index significantly decreased in 10 µg/kg group. Light microscope observation indicated that the space between the seminiferous tubules was increased. Ultrastructural observation showed some histopathological characteristics, including cytoplasmic shrinkage, cell membrane blebbing, swollen mitochondria and deformed nucleus. Using Q-PCR methods, the transcriptional levels of some cytoskeletal and mitochondrial genes were determined. MC-LR exposure affected the homeostasis of the expression of cytoskeletal genes, causing possible dysfunction of cytoskeleton assembly. In MC-LR treatments, all the 8 mitochondrial genes related with oxidative phosphorylation (OXPHOS) significantly increased. The reactive oxygen species (ROS) level significantly increased in 10 µg/kg group. The mitochondria swelling and DNA damage were also determined in 10 µg/kg group. Hormone levels of testis significantly changed. The present study verified that both cytoskeleton disruption possibly due to cytoskeletal reorganization or depolymerization and mitochondria dysfunction interact with each other through inducing of reactive oxygen species and oxidative phosphorylation, and jointly result in testis impairment after exposure to MC-LR.

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.

Microcystin-LR induces cytotoxicity and affects carp immune cells by impairment of their phagocytosis and the organization of the cytoskeleton

Microcystin-LR (MC-LR) is the main isoform of hepatotoxin produced by cyanobacteria, which occur worldwide in the aquatic environment. The present study investigated the in vitro toxic MC-LR effects on immune cells isolated from the blood of carp. Cells were exposed to different MC-LR concentrations ranging from 0.01 to 1 µg ml(-1) for 2, 6 and 24 h. In addition, the effect of the toxin on the phagocytic activity of leukocytes and on actin and tubulin re-organization in phagocytic cells was studied. We observed that MC-LR induces apoptosis in lymphocytes 2 h after incubation, whereas high toxin concentrations induced necrosis in lymphocytes in a time- and concentration-dependent manner. Incubation of the cells for 2 h with 0.1 and 1 µg ml(-1) MC-LR inhibited phagocytosis without affecting apoptosis or glutathione (GSH) levels. Moreover, at this time point and with these concentrations, the toxin also induced a significant re-organization of the actin cytoskeleton in phagocytes, which subsequently collapsed around the nucleus leading to cell shrinkage and the disappearance of filopodia. These results suggest that both phagocytes and lymphocytes are targets for MC-LR and the disturbances of phagocytosis may impair the balance of the immune system.

Microcystin-LR, a protein phosphatase inhibitor, induces alterations in mitotic chromatin and microtubule organization leading to the formation of micronuclei in Vicia faba

BACKGROUND AND AIMS

Microcystin-LR (MCY-LR) is a cyanobacterial toxin, a specific inhibitor of type 1 and 2A protein phosphatases (PP1 and PP2A) with significant impact on aquatic ecosystems. It has the potential to alter regulation of the plant cell cycle. The aim of this study was improved understanding of the mitotic alterations induced by cyanotoxin in Vicia faba, a model organism for plant cell biology studies.

METHODS

Vicia faba seedlings were treated over the long and short term with MCY-LR purified in our laboratory. Short-term treatments were performed on root meristems synchronized with hydroxylurea. Sections of lateral root tips were labelled for chromatin, phosphorylated histone H3 and β-tubulin via histochemical and immunohistochemical methods. Mitotic activity and the occurrence of mitotic alterations were detected and analysed by fluorescence microscopy. The phosphorylation state of histone H3 was studied by Western blotting.

KEY RESULTS

Long-term MCY-LR exposure of lateral root tip meristems increased the percentage of either early or late mitosis in a concentration-dependent manner. We observed hypercondensed chromosomes and altered sister chromatid segregation (lagging chromosomes) leading to the formation of micronuclei, accompanied by the formation of disrupted, multipolar and monopolar spindles, disrupted phragmoplasts and the hyperphosphorylation of histone H3 at Ser10. Short-term MCY-LR treatment of synchronized cells showed that PP1 and PP2A inhibition delayed the onset of anaphase at 1 µg mL(-1) MCY-LR, accelerated cell cycle at 10 µg mL(-1) MCY-LR and induced the formation of lagging chromosomes. In this case mitotic microtubule alterations were not detected, but histone H3 was hyperphosphorylated.

CONCLUSIONS

MCY-LR delayed metaphase-anaphase transition. Consequently, it induced aberrant chromatid segregation and micronucleus formation that could be associated with both H3 hyperphosphorylation and altered microtubule organization. However, these two phenomena seemed to be independent. The toxin may be a useful tool in the study of plant cell cycle regulation.

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.

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.

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

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

Differential protein expression in two bivalve species; Mytilus galloprovincialis and Corbicula fluminea; exposed to Cylindrospermopsis raciborskii cells

The cyanobacteria Cylindrospermopsis raciborskii is considered a threat to aquatic organisms due to the production of the toxin cylindrospermopsin (CYN). Despite the numerous reports evidencing the toxic effects of C. raciborskii cells and CYN in different species, not much is known regarding the toxicity mechanisms associated with this toxin and the cyanobacteria. In this work, a proteomics approach based in the two-dimensional gel electrophoresis and mass spectrometry was used to study the effects of the exposure of two bivalve species, Mytilus galloprovincialis and Corbicula fluminea, to CYN producing (CYN+) and non-producing (CYN-) C. raciborskii cells. Additionally the activities of glutathione S-transferase (GST) and glutathione peroxidase (GPx) were determined. Alterations in actin and tubulin isoforms were detected in gills of both bivalve species and digestive gland of M. galloprovincialis when exposed to CYN- and CYN+ cells. Moreover, GST and GPx activities changed in gills and digestive tract of bivalves exposed to both C. raciborskii freeze dried cells, in comparison to control animals exposed to the green alga Chlorella vulgaris. These results suggest the induction of physiological stress and tissue injury in bivalves by C. raciborskii. This condition is supported by the changes observed in GPx and GST activities which indicate alterations in the oxidative stress defense mechanisms. The results also evidence the capacity of CYN non-producing C. raciborskii to induce biochemical responses and therefore its toxicity potential to bivalves. The heat shock protein 60 (HSP60), extrapallial (EP) fluid protein and triosephosphate isomerase homologous proteins from gills of M. galloprovincialis were down-regulated specifically with the presence of CYN+ C. raciborskii cells. The presence of CYN may lead to additional toxic effects in M. galloprovincialis. This work demonstrates that proteomics is a powerful approach to characterize the biochemical effects of C. raciborskii and to investigate the physiological condition of the exposed organisms.