Modulation of human polymorphonuclear leukocyte adherence by cyanopeptide toxins

In Vivo Biocompatibility of Synechococcus sp. PCC 7002-Integrated Scaffolds for Skin Regeneration

Cyanobacteria, commonly known as blue-green algae, are prevalent in freshwater systems and have gained interest for their potential in medical applications, particularly in skin regeneration. Among these, Synechococcus sp. strain PCC 7002 stands out because of its rapid proliferation and capacity to be genetically modified to produce growth factors. This study investigates the safety of Synechococcus sp. PCC 7002 when used in scaffolds for skin regeneration, focusing on systemic inflammatory responses in a murine model. We evaluated the following three groups: scaffolds colonized with genetically engineered bacteria producing hyaluronic acid, scaffolds with wild-type bacteria, and control scaffolds without bacteria. After seven days, we assessed systemic inflammation by measuring changes in cytokine profiles and lymphatic organ sizes. The results showed no significant differences in spleen, thymus, and lymph node weights, indicating a lack of overt systemic toxicity. Blood cytokine analysis revealed elevated levels of IL-6 and IL-1β in scaffolds with bacteria, suggesting a systemic inflammatory response, while TNF-α levels remained unaffected. Proteome profiling identified distinct cytokine patterns associated with bacterial colonization, including elevated inflammatory proteins and products, indicative of acute inflammation. Conversely, control scaffolds exhibited protein profiles suggestive of a rejection response, characterized by increased levels of cytokines involved in T and B cell activation. Our findings suggest that Synechococcus sp. PCC 7002 does not appear to cause significant systemic toxicity, supporting its potential use in biomedical applications. Further research is necessary to explore the long-term effects and clinical implications of these responses.

Immunotoxic Effects Induced by Microcystins and Cylindrospermopsin: A Review

Cyanotoxin occurrence is gaining importance due to anthropogenic activities, climate change and eutrophication. Among them, Microcystins (MCs) and Cylindrospermopsin (CYN) are the most frequently studied due to their ubiquity and toxicity. Although MCs are primary classified as hepatotoxins and CYN as a cytotoxin, they have been shown to induce deleterious effects in a wide range of organs. However, their effects on the immune system are as yet scarcely investigated. Thus, to know the impact of cyanotoxins on the immune system, due to its importance in organisms’ homeostasis, is considered of interest. A review of the scientific literature dealing with the immunotoxicity of MCs and CYN has been performed, and both in vitro and in vivo studies have been considered. Results have confirmed the scarcity of reports on the topic, particularly for CYN. Decreased cell viability, apoptosis or altered functions of immune cells, and changed levels and mRNA expression of cytokines are among the most common effects reported. Underlying mechanisms, however, are still not yet fully elucidated. Further research is needed in order to have a full picture of cyanotoxin immunotoxicity.

The influence of microcystin-LR on fish phagocytic cells

The in vitro influence of microcystin-LR (MC-LR) on rainbow trout phagocytic cell functions was studied. The cells isolated from the fish blood were exposed on MC-LR at the concentrations of 1, 5, 10, 20 μg/mL. The viability of the cells after 2, 4 and 24 hour incubation with MC-LR was studied as well as phagocytic cell ability measured as zymozan particle phagocytosis and metabolic activity measured as respiratory burst activity. The toxin caused time- and dose-dependent viability decrease, the strongest after cell exposure on 10 and 20 μg/mL and observed only after 24 hours incubation when 1 μg/mL was applied. The phagocytic ability was elevated in the presence of MC-LR at the dose of 5 μg/mL. MC-LR had also modulatory influence on respiratory burst activity. While the two lower doses caused the stimulation of the parameter, the two higher ones diminished superoxide anion production in the triggered cells. The results show the potency of the toxin to influence the fish phagocytic cell functions. Human & Experimental Toxicology (2007) 26: 603—607.

Microcystin-LR Induced Immunotoxicity in Mammals

Microcystins are toxic molecules produced by cyanobacterial blooms due to water eutrophication. Exposure to microcystins is a global health problem because of its association with various other pathological effects and people all over the world are exposed to microcystins on a regular basis. Evidence shows that microcystin-LR (MC-LR) may adversely affect the immune system, but its specific effects on immune functions are lacking. In the present review, immunotoxicological effects associated with MC-LR in animals, humans, and in vitro models have been reported. Overall, the data shows that chronic exposure to MC-LR has the potential to impair vital immune responses which could lead to increased risk of various diseases including cancers. Studies in animal and in vitro models have provided some pivotal understanding into the potential mechanisms of MC-LR related immunotoxicity suggesting that further investigation, particularly in humans, is required to better understand the relationship between development of disease and the MC-LR exposure.

Identification of Microcystis aeruginosa Peptides Responsible for Allergic Sensitization and Characterization of Functional Interactions between Cyanobacterial Toxins and Immunogenic Peptides

BACKGROUND

The cyanobacterium species Microcystis aeruginosa produces microcystin and an array of diverse metabolites believed responsible for their toxicity and/or immunogenicity. Previously, chronic rhinitis patients were demonstrated to elicit a specific IgE response to nontoxic strains of M. aeruginosa by skin-prick testing, indicating that cyanobacteria allergenicity resides in a non-toxin-producing component of the organism.

OBJECTIVES

We sought to identify and characterize M. aeruginosa peptide(s) responsible for allergic sensitization in susceptible individuals, and we investigated the functional interactions between cyanobacterial toxins and their coexpressed immunogenic peptides.

METHODS

Sera from patients and extracts from M. aeruginosa toxic [MC(+)] and nontoxic [MC(-)] strains were used to test IgE-specific reactivity by direct and indirect ELISAs; 2D gel electrophoresis, followed by immunoblots and mass spectrometry (MS), was performed to identify the relevant sensitizing peptides. Cytotoxicity and mediator release assays were performed using the MC(+) and MC(-) lysates.

RESULTS

We found specific IgE to be increased more in response to the MC(-) strain than the MC(+) strain. This response was inhibited by preincubation of MC(-) lysate with increasing concentrations of microcystin. MS revealed that phycocyanin and the core-membrane linker peptide are the responsible allergens, and MC(-) extracts containing these proteins induced β-hexosaminidase release in rat basophil leukemia cells.

CONCLUSIONS

Phycobiliprotein complexes in M. aeruginosa have been identified as the relevant sensitizing proteins. Our finding that allergenicity is inhibited in a dose-dependent manner by microcystin toxin suggests that further investigation is warranted to understand the interplay between immunogenicity and toxicity of cyanobacteria under diverse environmental conditions.

CITATION

Geh EN, Ghosh D, McKell M, de la Cruz AA, Stelma G, Bernstein JA. 2015. Identification of Microcystis aeruginosa peptides responsible for allergic sensitization and characterization of functional interactions between cyanobacterial toxins and immunogenic peptides. Environ Health Perspect 123:1159-1166; http://dx.doi.org/10.1289/ehp.1409065.

Microcystin Contamination in Sea Mussel Farms from the Italian Southern Adriatic Coast following Cyanobacterial Blooms in an Artificial Reservoir

An experimental study was performed in 2009-2010 to investigate the polluting effect of eutrophic inland waters communicating with the sea coast. The study was planned after a heavy and long-lasting Planktothrix rubescens bloom occurred in the Lake Occhito, an artificial reservoir. The waters of the reservoir flow into the southern Adriatic Sea, near several marine breeding of Mytilus galloprovincialis mussels, a typical seafood from the Apulia region (Southern Italy). A monitoring study of water and mussels from the sea coast of northern Apulia region and on the Occhito reservoir was carried out over twelve months, to get more information regarding the contamination by cyanobacteria and related cyanotoxins. Elisa immunoassay analyses estimated total microcystin amounts from 1.73 to 256 ng/g in mussels, up to 0.61 μg/L in sea water and up to 298.7 μg/L in lake water. Analyses of some samples of free-living marine clams as well as of marine and freshwater fish proved microcystin contamination. Selective confirmatory analyses by LC/ESI-Q-ToF-MS/MS on some mussel samples identified the microcystin desMe-MC-RR as the major toxin; this compound has been reported in the literature as a specific marker toxin of Planktothrix rubescens blooms. Our study describes for the first time the direct relationship between environmental pollution and food safety, caused by seafood contamination from freshwater toxic blooms.

Identification and expression profiles of IL-8 in bighead carp (Aristichthys nobilis) in response to microcystin-LR

Microcystin-LR (MCLR) is a widespread cyanotoxin and has immunotoxicity to animals, including fish. Chemokines are considered to play important roles in inflammatory response induced by MCLR. In this study, we cloned the full-length cDNA of interleukin-8 (IL-8) from bighead carp (Aristichthys nobilis) for the first time. The full-length IL-8 cDNA was 552 bp and contained a 297-bp open-reading frame that encoded for a 98-amino acid protein. The deduced IL-8 protein had a typical aspartic acid (D)-leucine (L)-arginine (R) and a CXC motif at the N-terminal, which were conserved in most fish species. Phylogenetic analysis showed that bighead carp IL-8 protein was grouped in the teleost IL-8 lineage 2. Under normal conditions, the expression of IL-8 is constitutive and weak in all tested tissues. However, MCLR treatment could significantly increase the transcription of IL-8 in bighead carp in a temporal- and dose-dependent pattern. The present study will help us to understand more about the evolution of IL-8 and its function in the MCLR induced proinflammatory response in bighead carp.

Comparison of response indices to toxic microcystin-LR in blood of mice

In order to investigate the response indices to toxic microcystin-LR (MC-LR) in blood of mice, concentrations of free and total MC-LR in blood and tissues, accompanied by serous parameters in series including some enzymatic activities, hematology and the function of leukocytes, were determined in mice exposed to the toxin ranging from 3.125 to 25.000 μg kg(-1)day(-1) by intraperitoneal injection for 7 days. On the 7th day, the ratios of mass of free MC-LR in serum to the mass of MC-LR in given dose were 3.843-4.555%, while the ratios of total MC-LR in liver were 34.465-38.567%. Comparing the overall experimental results, the three most sensitive indices are total MC-LR in the liver, the phagocytic index and reactive oxygen species (ROS) which have shown significant differences between the lowest dose group and the control group. Alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase had proportional correlations with the MC-LR exposure doses, and the hematology of the majority of blood cells and the volume of erythrocytes were also influenced by the toxin. The alterations of some cytokines and the ROS of leukocytes were observed. The results of the studies suggest that measurement of MC-LR in blood is powerful and clear evidence to indicate that subjects have been exposed to MC-LR and can be used to discriminate from other causes leading to hepatic lesions although it is not as sensitive as other indices that are usually as useful complements to reflect the liver function.

Apoptotic responses of Carassius auratus lymphocytes to nodularin exposure in vitro

Nodularin, a metabolite of Nodularin spumigena, is widely detected in water blooms worldwide and causes serious negative effects on fish. The apoptosis-related cytotoxic effects and mechanisms of nodularin on Carassius auratus lymphocytes were investigated. Transmission electron microscopy results showed that nodularin-treated lymphocytes display a series of morphological changes, including condensed cytoplasm, nuclear chromatin agglutination and marginalization. DNA fragmentation was verified by the DNA-ladder and formation of sub-G1 DNA peaks. These cell characteristics confirmed the occurrence of apoptosis in lymphocytes. Flow cytometric results showed that the percentages of apoptotic cells incubated with 1, 5, 10, and 100 μg/L nodularin for 12 h reached 15.76%, 17.36%, 20.34% and 44.21%, respectively; controls showed low rates of apoptosis (2.4%). The mechanism of apoptosis induced by nodularin was determined, and results showed that nodularin exposure caused a significant increase in intracellular reactive oxygen species (ROS), loss of mitochondrial transmembrane potential in a dose-dependent manner, upregulation of intracellular Ca²⁺, downregulation of Bcl-2 and upregulation of Bax expression at the mRNA and protein levels, and activation of caspase-3 and caspase-9 without caspase-8. In summary, all the results suggest that nodularin induces lymphocyte apoptosis via the mitochondrial apoptotic pathway and destroys the immune response of fish.

In vivo studies on the immunotoxic effects of microcystins on rabbit

Microcystins (MCs) are the toxic molecules produced by common cyanobacterium in freshwater blooms. Their toxicities raise severe health issues in livestock and human beings. In current study, the immunotoxic effects of MC-LR were investigated in rabbit through evaluating the dynamics of white blood cell (WBC) numbers and cytokine production such as interleukin-3 (IL-3), IL-4, IL-6, interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α). MCs at the high dose (50 μg MC-LReq kg(-1) ) significantly induced increase in the WBC number but decrease in the Th1 (IFN-γ, TNF-α) and Th2 (IL-3, IL-4, IL-6) production. In the low dose group(12.5 μg MC-LReq kg(-1) ), the number of WBC and the production of IFN-γ, IFN-α, IL-4, IL-3, and IL-6 increased gradually in first 12 h, reach the peaks at 12 h, and dropped after 24 h. Significantly positive correlations were found between the cytokines production of IL-4 and IL-6, IFN-γ and IFN-α, or IL-4 and IFN-γ. In conclusion, MC-LR is able to disturb the rabbit immune system and there exists time-dose response relationship in the MC-LR-eliciting perturbation, which probably give a better insight into investigating the immunotoxicity mechanisms of MCs in vivo. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.

Microcystins -LA, -YR, and -LR action on neutrophil migration

Microcystins (MCs) produced by some freshwater cyanobacterial species possess potent liver toxicity as evidenced by acute neutrophil infiltration. Here, we investigate the ability of three structurally distinct toxins (MC-LA, MC-LR, and MC-YR) to evoke neutrophil recruitment per se and their effects on migration pathways. Intravital microscopic studies showed that topical application of only MC-LR enhanced the numbers of rolling and adhered leukocytes in the endothelium of postcapillary mesenteric venules. The latter effects may be dependent upon induction of the synthesis and expression of L-selectin and beta2-integrin in neutrophils, as assessed by flow cytometry and RT-PCR, respectively. Conversely, the three toxins promoted direct locomotion of neutrophils and enhanced their migration in response to fMLP, as measured by Boyden chamber assays, and increased intracellular calcium, a messenger in the chemotaxic process. In conclusion, our results show that MCs act on specific pathways of neutrophil recruitment, indicating their potential effect on neutrophils activation.

Analysis of chemokines and reactive oxygen species formation by rat and human neutrophils induced by microcystin-LA, -YR and -LR

Microcystins (MC), a family of heptapeptide toxins produced by some genera of Cyanobacteria, have potent hepatotoxicity and tumor-promoting activity. Leukocyte infiltration in the liver was observed in MC-induced acute intoxication. Although the mechanisms of hepatotoxicity are still unclear, neutrophil infiltration in the liver may play an important role in triggering toxic injury and tumor development. The present study reports the effects of MC-LA, MC-YR and MC-LR (1 and 1000 nM) on human and rat neutrophils functions in vitro. Cell viability, DNA fragmentation, mitochondrial membrane depolarization and intracellular reactive oxygen species (ROS) levels were measured by flow cytometry. Extracellular ROS content was measured by lucigenin-amplified chemiluminescence, and cytokines were determined by ELISA. We found that these MC increased interleukin-8 (IL-8), cytokine-induced neutrophil chemoattractant-2alphabeta (CINC-2alphabeta) and extracellular ROS levels in human and rat neutrophils. Apart from neutrophil presence during the inflammatory process of MC-induced injury, our results suggest that hepatic neutrophil accumulation is further increased by MC-induced neutrophil-derived chemokine.

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

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

Microcystin diversity in a Planktothrix rubescens population from Lake Albano (Central Italy)

The cyanobacterium Planktothrix rubescens Anagnostidis & Komarek (previously Oscillatoria rubescens DC ex Gomont) is present in several Italian lakes and it is known to produce cyanotoxins. The dynamics and toxin production of P. rubescens population in Lake Albano, a volcanic crater lake in Central Italy, has been studied for 5 years (January 2001-April 2005). Winter-spring superficial blooms with frequent scums were observed every year. Total microcystin (MC) levels were measured from April 2004 to October 2005 by liquid chromatography-tandem mass spectrometry. MC levels up to 14.2mug/l were measured, with high concentrations found in summer at a 20-25m depth. The intracellular toxin content varied between 1.5 (surface, January 2004) and 0.21pg/cell (surface, May 2004). Six different MCs were detected, the most abundant being two desmethyl-MC-RR isomers. Of the 13 water wells monitored in the Lake Albano area, two of them showed MC contamination during winter, confirming the ability of these toxins to migrate through groundwater towards public water sources. These results highlight the need for further studies on the mobility and fate of these pervasive cyanobacterial toxins.

Effect of microcystin on leukocyte viability and function

Microcystin (MC) has been found in several areas of the world. In addition to its hepatotoxicity, microcystin may have an immunomodulatory effect. Considering that patients receiving hemodialysis may be chronically exposed to variable concentrations of MC, and that they present important changes in this immune response, we have assessed the effect of MC on the function of leukocytes. Polymorphonuclear leukocytes isolated from healthy volunteers (HV) and patients receiving hemodialysis (HD) were incubated with microcystin (10 microg/L) for 24h and evaluated for reactive oxygen species production (ROS), phagocytosis and apoptosis. Monocytes incubated with and without LPS (100 ng/mL) and microcystin for 24h were assessed for TNFalpha and IL-10 production. Leukocytes of HV presented an increase in apoptosis rates and leukocytes from HD exhibited a lower production of oxygen-reactive species, both spontaneously and after stimulus with S. aureus, when compared with leukocytes incubated without toxin. Monocytes presented an increase in cytokine production after stimulation by LPS in both groups, but there was no difference between the groups with and without MC that were incubated with or without LPS. Low concentrations of microcystin can induce mild changes in leukocyte function of HV and HDP, particularly in the ability to produce ROS.

Effects of microcystins on human polymorphonuclear leukocytes

Microcystins (MCs) are cyclic heptapeptides produced by cyanobacteria present in water contaminated reservoirs. Reported toxic effects for microcystins are liver injury and tumour promotion. In this study, we evaluated the effects of two MCs, MC-LR and [Asp(3)]-MC-LR, on human neutrophil (PMN). We observed that even at concentrations lower than that recommended by World Health Organization for chronic exposure (0.1 nM), MCs affect human PMN. Both MCs have chemotactic activity, induce the production of reactive oxygen species, and increase phagocytosis of Candida albicans. MC-LR also increased C. albicans killing. The effect of MCs on PMN provides support for a damage process mediated by PMN and oxidative stress, and may explain liver injury and tumour promotion associated to long-term MCs exposures.

Effects of microcystin-LR on patterns of iNOS and cytokine mRNA expression in macrophages in vitro

The presence of cyanobacterial toxins in drinking and recreational waters represent a potential health hazard to the public. Microcystin-LR (MC-LR) is the most commonly encountered toxin and is a potent cyclic heptapeptide hepatotoxin produced by cyanobacteria. In this study, the immunomodulation by MC-LR of BALB/c mice peritoneal macrophages was investigated in vitro on mRNA levels of induced nitric oxide synthase and multiple cytokines by reverse-transcription polymerase chain reaction (RT-PCR). Lavaged peritoneal macrophages were incubated for 6 h with lipopolysaccharide (LPS) at a concentration of 100 microg/L and MC-LR at doses of 1, 10, 100, and 1000 nmol/L. Total RNA was extracted from the incubated macrophages, and then the levels of mRNA for induced nitric oxide synthase (iNOS), IL-1beta, TNF-alpha, GM-CSF, and IFN-gamma were detected. The results showed that expression of mRNA for iNOS, IL-1beta, TNF-alpha, GM-CSF, and IFN-gamma decreased significantly compared to the positive control (LPS only). These results have led us to propose the need for the establishment of a survey of the immunotoxicity of microcystins.

Expression modulation of multiple cytokines in vivo by cyanobacteria blooms extract from taihu lake, China

Cyanobacterial blooms that generate microcystins (MCs) are being increasingly recognized as a potent health hazard in aquatic ecosystems. However, immunomodulation induced by cyanotoxins has not been well documented. This paper reports the in vivo data on the immune disorder caused by crude microcystin (MC) extract of cyanobacteria blooms collected from Taihu Lake, China, with respect to cytokine mRNA levels. Using reverse-transcriptional polymerase chain reaction (RT-PCR), the expression of multiple cytokines, including proinflammatory (IL-1beta, TNF-alpha, and IL-6) and Th1/Th2-related cytokines (IL-2, IL-4 and IL-10), was evaluated following the cyanobacteria blooms extract containing MCs (CBE) exposure at four doses of 23, 38, 77, 115 mg lyophilized algae cells/kg body weight. The results showed that the mRNA levels of TNF-alpha, IL-1beta, IL-2 and IL-4 decreased significantly following injection of all doses as compared to the control (LPS or ConA only), while the IL-6 level was unaffected. Contrast to this decrease, the level of IL-10 mRNA was, however, transiently up regulated following injection of the lowest dose of CBE. The distinct patterns of expression of these cytokines suggested a modulation of cytokine network, the essential component of the host immune system. We further developed a mathematical model to simulate the interaction of T helper cell subsets and related cytokines, which proved to be a good approach to study the kinetics of the interaction of cells and cytokines in microcystin immunosuppression.

The uptake kinetics and immunotoxic effects of microcystin-LR in human and chicken peripheral blood lymphocytes in vitro

Microcystin-LR is a cyanobacterial heptapeptide that presents acute and chronic hazards to animal and human health. We investigated the influence of this toxin on human and chicken immune system modulation in vitro. Peripheral blood lymphocytes were treated with microcystin-LR at environmentally relevant doses of 1, 10 and 25 microg/ml for 12, 24, 48, 72 h (for proliferation assay cells were treated for 72 h). T-cell and B-cell proliferation as well as apoptosis and necrosis were determined in human and chicken samples. IL-2 and IL-6 production by human lymphocytes also was measured. In addition, uptake kinetics of microcystin-LR into human and chicken peripheral blood lymphocytes were calculated by Liquid Chromatography (LS) /Mass Spectrometry (MS) analysis. At the highest dose microcystin-LR decreased T-cell proliferation and all doses of microcystin-LR inhibited B-cell proliferation. The frequency of apoptotic and necrotic cells increased in a dose and time-dependent manner. Human lymphocytes responded to stimulation with microcystin-LR by increased production of IL-6 and decreased production of IL-2. Human lymphocytes were able to uptake from 0.014 to 1.663 microg/ml and chicken lymphocytes from 0.035 to 1.733 microg/ml of the microcystin-LR added to the cultures, depending on the treatment time and dose. In conclusion, microcystin-LR acted as an immunomodulator in cytokine production and down-regulated lymphocyte functions by induction of apoptosis and necrosis. However, further studies dealing with the influence of microcystin-LR on expression cytokine genes and transcription factors are necessary to confirm these hypotheses.

Anatoxin-a toxin in the cyanobacterium Planktothrix rubescens from a fishing pond in northern Italy

A heavy algal bloom occurring in a fishing pond in northern Italy full of Salmo trutta was examined for algae taxonomy and toxic production. The dominant algal species (98%) was identified as the cyanobacterium Planktothrix rubescens (D.C. ex GOMONT) Komarek Anagnostidis, based on morphological examination, and it was revealed to be toxic in mouse and Vibrio fischeri bioassays. The toxin was identified as anatoxin-a using high-performance liquid chromatography and confirmed using liquid chromatography-mass spectrometry (LC-MS). The mouse bioassay gave signs of poisoning, as previously reported for anatoxin-a. The LC-MS confirmed the presence of an anatoxin-a peak at m/z 166 (M+H+). The content of toxin in the field population was estimated at 12.13 microg/g of fresh cells. The bloom was sustained by the very high N/P ratio in the water. This is the first report in Italy of an anatoxin-a-producing Planktothrix rubescens population.

Analysis of immunomodulating nitric oxide, iNOS and cytokines mRNA in mouse macrophages induced by microcystin-LR

Microcystins (MCs) are the toxic molecules produced by common cyanobacterium in freshwater blooms. Their toxicities have brought severe health issues to livestock and human being. Microcystin-LR (MC-LR) is one of the most toxic MCs. This paper presents the profile of the immunomodulation of MC-LR to BALB/c mice peritoneal macrophages. Macrophages were stimulated with 100microg/l lipopolysaccharide (LPS) and MC-LR at dose of 1, 10, 100, 1000nmol/l, respectively, for 24h. Nitric oxide (NO) production in cell culture supernatants was quantified by using Griess reagent method. Total RNA was extracted from incubated macrophages then the mRNA abundance of induced nitric oxide synthase (iNOS), IL-1beta, TNF-alpha, GM-CSF, IFN-gamma was monitored by using reverse-transcriptional polymerase chain reaction (RT-PCR). The results demonstrated that NO production, mRNA levels of iNOS, IL-1beta, TNF-alpha were down regulated by MC-LR dose-dependently and mRNA levels of GM-CSF and IFN-gamma were also decreased but in dose-independent manner. Our results illustrated the involvement of NO production, iNOS and some cytokines in mice immune system in microcystin shock.

Effect of microcystin-LR and cyanobacterial extract from Polish reservoir of drinking water on cell cycle progression, mitotic spindle, and apoptosis in CHO-K1 cells

Microcystin-LR is a cyanobacterial toxin possessing a potent tumor-promoting activity mediated through inhibition of protein phosphatases PP1 and PP2A. Because these enzymes are involved in fundamental cell processes, we decided to examine the influence of microcystin-LR on cell cycle progression, onset of anaphase, segregation of chromosomes by the mitotic spindle, and apoptosis in Chinese hamster ovary (CHO-K1) cells. Cells were incubated with 25, 50, and 100 microM of pure microcystin-LR and a cyanobacterial extract for 14, 18, and 22 h. Giemsa staining of cells treated with these toxins revealed a dose- and time-dependent increase of mitotic indices, accumulation of abnormal G(2)/M figures with hypercondensed chromosomes, abnormal anaphases with defective chromosome separation, and polyploid cells. Because spindle checkpoint is a fundamental regulatory mechanism that assures the onset of anaphase and subsequent exit from mitosis, we examined the spindle organization in microcystin-treated cells. The majority of the mitotic cells showed monopolar and multipolar mitotic spindles (multiple asters). Microtubule bundles were present in interphase cells. Our results indicate that microcystin-LR induces apoptosis and necrosis in a dose- and time-dependent manner and that the frequency of dead cells cells is positively correlated with the frequency of polyploid cells.

Acute effects and bioaccumulation of nodularin in sea trout (Salmo trutta m. trutta L.) exposed orally to Nodularia spumigena under laboratory conditions

Nodularin (NODLN) is a cyclic pentapeptide hepatotoxin that is regularly produced in high amounts by the cyanobacterium Nodularia spumigena in the Baltic Sea, and can bioaccumulate in Baltic biota. Baltic sea trout (Salmo trutta m. trutta L.) were exposed orally to a single dose of food containing NODLN (125 mg/kg ww) from N. spumigena (strain AV1, from the Baltic Sea). The level of exposure was 210-620 (average 440) microg NODLN per kg bw. Based on an 8-day survey under laboratory conditions, NODLN-like compounds accumulated in trout liver, with increasing liver concentrations (from 19 microg/kg on day 1 up to 1200 microg/kg on day 8 as measured with the EnviroLogix ELISA kit) during the experiment. Thus, accumulation of NODLN-like compounds in liver increased from 0.05% of the total NODLN dose administered on day 1 to 0.53% on day 8. However, the ELISA test kit is also sensitive to metabolites of algal hepatotoxins. In the HPLC chromatograms, no NODLN peak was detected after 24 h that also suggested NODLN absorbed in trout was metabolized or bound rapidly. According to ELISA, NODLN-like compounds also accumulated in trout muscle in lower quantities (from 125 to 34 microg/kg dw). Histopathology revealed complete loss of liver architecture after 1-2 days of the single oral dose. From day 4 to 8, there was partial recovery of liver cells. NODLN did not affect thiamine levels or water content of trout liver. The results showed that NODLN rapidly induces severe but reversible liver damage. Apparently NODLN accumulated in trout liver from cyanobacteria in the intestine, but was detoxified rapidly. On the basis of discrepancies between the histopathology and ELISA, and on the other hand, between the HPLC and ELISA methods, analysis of NODLN and its metabolites in biological tissue needs to be improved.