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1.
Ecotoxicol Environ Saf ; 188: 109945, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31753309

RESUMO

Cyanobacterial harmful algal blooms dominated by Microcystis frequently produce microcystins, a family of toxins capable of inflicting harm to pelagic and benthic freshwater invertebrates. Research on the effect of microcystins on invertebrates is inconclusive; from one perspective, studies suggest invertebrates can coexist in toxic blooms; however, studies have also measured negative food-associated effects from microcystins. To test the latter perspective, we examined the reproduction, growth, and survival of laboratory-cultured Ceriodaphnia dubia, Daphnia magna, and Hexagenia spp. exposed to cell-bound microcystins through a series of life-cycle bioassays. Test organisms were exposed to a concentration gradient ranging from 0.5 µg L-1 to 300 µg L-1 microcystins, which corresponds to values typically found in freshwaters during bloom season. Lethal concentrations in C. dubia (LC50 = 5.53 µg L-1) and D. magna (LC50 = 85.72 µg L-1) exposed to microcystins were among the lowest recorded to date, and reproductive effects were observed at concentrations as low as 2.5 µg L-1. Length of D. magna was significantly impacted in microcystin treatments great than 2.5 µg L-1. No lethality or growth impairments were observed in Hexagenia. This information will improve our understanding of the risks posed by microcystins to food webs in freshwaters.


Assuntos
Daphnia/efeitos dos fármacos , Ephemeroptera/efeitos dos fármacos , Água Doce/química , Microcistinas/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Daphnia/crescimento & desenvolvimento , Ephemeroptera/crescimento & desenvolvimento , Cadeia Alimentar , Proliferação Nociva de Algas , Dose Letal Mediana , Estágios do Ciclo de Vida , Reprodução/efeitos dos fármacos
2.
Ecotoxicol Environ Saf ; 187: 109824, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31654863

RESUMO

Microcystin-LR (MC-LR), a widespread environmental contaminant, has been shown to have potent acute testicular toxicity. However, magnitudes of toxic effects, induced by MCs, depend on route and magnitude of exposure to the toxin. In the present study, male mice were orally exposed 1, 10 or 100 µg/L MC-LR for 90 or 180 days, and pathological approach and the isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomics were employed with testes. Proteomics revealed that a number of differentially altered proteins may be involved in MC-LR-induced chronic testicular toxicity. The biological process analysis indicated the altered proteins played an important role in biological adhesion, cellular process, response to stimulus or rhythmic process. The cellular component analysis revealed that most of the proteins with altered expression associated with cell part, extracellular region, extracellular region part, membrane, membrane part, organelle or organelle part. The molecular function showed that these proteins were critical in molecular transducer activity. Integrity analyses provide first compelling evidence that MC-LR significantly cause dysfunction of blood-testis barrier (BTB) through affecting tight junctions and gap junctions. Moreover, phosphatidylinositol 3-kinase (PI3K)/AKT eventually contributed to injury result from chronic low-level MC-LR treatment. Identification of proteins in testis responsive to MC-LR provides insights into molecular mechanisms of chronic toxicity of MCs.


Assuntos
Poluentes Ambientais/toxicidade , Microcistinas/toxicidade , Proteoma/efeitos dos fármacos , Testículo/efeitos dos fármacos , Animais , Barreira Hematotesticular/efeitos dos fármacos , Barreira Hematotesticular/fisiopatologia , Masculino , Camundongos , Fosfatidilinositol 3-Quinases/metabolismo , Proteômica , Transdução de Sinais/efeitos dos fármacos , Testículo/metabolismo
3.
Chemosphere ; 240: 124966, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31726608

RESUMO

The hepatotoxic cyanotoxins microcystins (MCs) are emerging contaminants naturally produced by cyanobacteria. Yet their ecological role remains unsolved, previous research suggests that MCs have allelopathic effects on competing photosynthetic microorganisms, even eliciting toxic effects on other freshwater cyanobacteria. In this context, the bioluminescent recombinant cyanobacterium Anabaena sp. PCC7120 CPB4337 (hereinafter Anabaena) was exposed to extracts of MCs. These were obtained from eight natural samples from freshwater reservoirs that contained MCs with a concentration range of 0.04-11.9 µg MCs L-1. MCs extracts included the three most common MCs variants (MC-LR, MC-RR, MC-YR) in different proportions (MC-LR: 100-0%; MC-RR: 100-0%; MC-YR: 14.2-0%). The Anabaena bioassay based on bioluminescence inhibition has been successfully used to test the toxicity of many emerging contaminants (e.g., pharmaceuticals) but never for cyanotoxins prior to this study. Exposure of Anabaena to MCs extracts induced a decrease in its bioluminescence with effective concentration decreasing bioluminescence by 50% ranging from 0.4 to 50.5 µg MC L-1 in the different samples. Bioluminescence responses suggested an interaction between MCs variants which was analyzed via the Additive Index method (AI), indicating an antagonistic effect (AI < 0) of MC-LR and MC-RR present in the samples. Additionally, MC extracts exposure triggered an increase of intracellular free Ca2+ in Anabaena. In short, this study supports the use of the Anabaena bioassay as a sensitive tool to assess the presence of MCs at environmentally relevant concentrations and opens interesting avenues regarding the interactions between MCs variants and the possible implication of Ca2+ in the mode of action of MCs towards cyanobacteria.


Assuntos
Bioensaio/métodos , Ecotoxicologia/métodos , Microcistinas/toxicidade , Anabaena/efeitos dos fármacos , Anabaena/metabolismo , Cálcio/metabolismo , Cianobactérias/isolamento & purificação , Cianobactérias/metabolismo , Água Doce/microbiologia
4.
Chemosphere ; 240: 124905, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31563103

RESUMO

Microcystin-LR (MCLR) was commonly regarded as a potent hepatotoxin and has been reported to cause neurotoxicity. This study was aimed to investigate how maternal MCLR exposure during pregnancy alters behavioral responses in offspring mice and the possible molecular mechanism involved in this procedure. Three doses of MCLR solutions (0, 3 or 15 µg/kg body weight) were administered subcutaneously to pregnant C57bl/6 from gestation day (GD) 6-19. Our results showed that MCLR prenatal exposure led to the impairment of learning and memory function in offspring on postnatal days (PND) 35, accompanied by endoplasmic reticulum (ER) stress and neuronal apoptosis in hippocampal CA1 regions of mice. Sixteen miRNAs in hippocampus of pups on PND 35 were significantly affected by MCLR exposure with the markedly decreased transcription of miR-181a-5p. We then found that miR-181a-5p was down-regulated, accompanied by activation of ER stress after prenatal exposure to MCLR using qPCR analysis. Furthermore, glucose-regulated protein, 78kDa/binding immunoglobulin protein (Grp78/BIP), a major ER chaperone and signaling regulator, was identified as a target of miR-181a-5p. Our study showed that miR-181a could lead to a decrease in the mRNA expression and protein levels of Grp78 by directly binding to its 3'-untranslated region (3'-UTR) in primary hippocampal neurons. Our findings indicate that the up-regulation of Grp78 mediated by inhibition of miR-181a-5p is a possible mechanism resulting in ER stress and cognitive impairment in pups following prenatal MCLR exposure.


Assuntos
Estresse do Retículo Endoplasmático/fisiologia , MicroRNAs/metabolismo , Microcistinas/toxicidade , Animais , Apoptose , Regulação para Baixo , Feminino , Hipocampo/metabolismo , Masculino , Memória , Camundongos , MicroRNAs/genética , Gravidez , Regulação para Cima
5.
Sci Total Environ ; 699: 134325, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31678882

RESUMO

Decaying cyanobacterial blooms carry a potential risk for submerged macrophyte and periphyton biofilms in aquatic environments. This study comprehensively studied the responses in growth, oxidative response, detoxification pathway, and ultrastructure characteristics of aquatic plants to Microcystis aeruginosa (M. aeruginosa) exudates and extracts released during the decline phase. Particular emphasis was placed on the variation of extracellular polymeric substances (EPS) and quorum-sensing signaling molecules. The results showed that superoxide dismutase, peroxidase, and glutathione S-transferase were significantly induced as antioxidant response, and the malondialdehyde content increased. Increased content of MC-LR (1.129 µg L-1) and NH4+-N (1.35 mg L-1) were found in the decline phase of M. aeruginosa, which played a vital role in the damage to submerged plants. In addition, a change in the amount of osmiophilic granules and a variation of organelles and membranes was observed. A broad distribution of α-d-glucopyranose polysaccharides was dominant and aggregated into clusters in biofilm EPS in response to exposure to decaying M. aeruginosa. Furthermore, exposure to exudates and extracts changed the abundance and structure of the microbial biofilm community. Increased contents of N-acylated-L-homoserine lactone signal molecule might result in a variation of biofilm EPS production in response to decaying M. aeruginosa. These results expand the understanding of how submerged macrophyte and periphyton biofilms respond to environmental stress caused by exudates and extracts of decaying M. aeruginosa.


Assuntos
Microcistinas/toxicidade , Folhas de Planta/microbiologia , Plantas/metabolismo , Antioxidantes/metabolismo , Microcystis , Plantas/ultraestrutura
6.
Sci Total Environ ; 702: 134969, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31710851

RESUMO

Waterborne microcystin-LR (MC-LR) released by cyanobacterial blooms in eutrophic water bodies have caused serious risk to aquatic animal and human health. In the present study, we for the first time conducted a comprehensive in vivo investigation on chronic inflammatory responses and its molecular pathways of different environmental relevant levels of MC-LR (0, 0.4, 2 and 10 µg/L) in male zebrafish (Danio rerio). The results showed that chronic MC-LR exposure caused splenic inflammatory changes including the formation of melano-macrophage centers, remarkable elevation of serum tumor necrosis factor alpha (TNFα) and interleukin 1 beta (IL1ß) levels as well as significant upregulated expression of MyD88-dependent toll-like receptor (TLR/MyD88) signaling pathway genes (tlr4a, myd88, erk2, p38a, il1ß and tnfα). The immunohistochemical and western blot results further validated that higher MC-LR concentrations tended to enhance the MyD88 signal. Moreover, significant decreases of serum C3 levels along with splenic c3b expression in the 10 µg/L exposure group proved that chronic MC-LR exposure could ultimately decrease the innate immunity of fish. Our findings revealed that chronic exposure of MC-LR could cause chronic inflammation through TLR/MyD88 signaling pathway and subsequently induce immune disorders in male zebrafish, which also urge us to pay more attention on the potential immunotoxicity of long-term exposure to low concentration of MC-LR.


Assuntos
Microcistinas/toxicidade , Fator 88 de Diferenciação Mieloide/metabolismo , Poluentes Químicos da Água/toxicidade , Proteínas de Peixe-Zebra/metabolismo , Animais , Masculino , Peixe-Zebra
7.
Sci Total Environ ; 688: 1348-1358, 2019 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-31726564

RESUMO

Proliferating cyanobacterial blooms due eutrophication in reservoirs is a major global problem. The production of cyanotoxins often increases with grazing pressure and temperature while the sensitivity of zooplankton to cyanotoxins is directly related to temperature. Here we evaluate the effect of different concentrations of the crude extract of cyanobacteria from Valle de Bravo reservoir during dry (January) and rainy (September) seasons at 20 and 25 °C on the rotifer Brachionus calyciflorus based on acute and chronic toxicity tests. We filtered 20 or 150 l of lake water, depending on the intensity of the bloom, and estimated the density and diversity of the cyanobacteria. The crude extracts, after 5 cycles of freezing, thawing and sonication at 14 MHz, were filtered and the microcystin concentration quantified based on ELISA. The extracts were used to conduct the acute and chronic toxicity tests, all in quadruplicate. Acute toxicity tests were based on 24 h mortality. Chronic toxicity tests (population growth and life table experiments) were conducted at 5 and 10% of the median lethal concentration. The field samples were dominated by Microcystis sp. (January) or Woronichinia naegeliana (September). The microcystin concentration in lake water was 9.57 µg/l and 0.097 µg/l and the median lethal concentration was 5.34 µg microcystin/L and 0.35 µg microcystin/L in January and September, respectively. Survival and reproduction of B. calyciflorus were lower in the presence of the cyanobacteria crude extract, more so at 20° than at 25 °C. Our results highlight the urgency of regular monitoring based on zooplankton assays for reservoirs in tropical and temperate regions, subject to frequent and dominant cyanobacterial blooms, often as a result of climate change.


Assuntos
Cianobactérias/crescimento & desenvolvimento , Monitoramento Ambiental , Proliferação Nociva de Algas , Microcistinas/toxicidade , Rotíferos/fisiologia , Animais , Eutrofização , México , Testes de Toxicidade Crônica
8.
Ecotoxicol Environ Saf ; 185: 109668, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31574372

RESUMO

Microcystins and polycyclic aromatic hydrocarbons commonly co-exist in eutrophic freshwater environments. However, their combined toxicity remains unknown. The aim of this study was to evaluate the combined toxic effects of microcystin-LR (MC-LR) and phenanthrene (Phe) on duckweed (Lemna gibba L.) during a short-term exposure (7 d). L. gibba was exposed to a range of environmentally relevant concentrations of MC-LR (5, 50, 250, 500 µg/L) and Phe (0.1, 1, 5, 10 µg/L), both individually and in MC-LR + Phe mixtures (5 + 0.1, 50 + 1, 250 + 5, 500 + 10 µg/L). Subsequently, biomarkers of toxicity such as growth, chlorophyll-a, and antioxidant enzyme activity (catalase, superoxide dismutase, and peroxidase) were analyzed in L. gibba. Growth and the antioxidant system of L. gibba were not significantly inhibited by Phe alone, whereas higher concentrations of individual MC-LR (≥50 µg/L) significantly inhibited growth and induced oxidative stress. Based on Abott's formula, their interaction effects were concentration dependent. Antagonistic effects were observed when exposed to combinations of lower concentrations of MC-LR and Phe (≤50 + 1 µg/L), while additive or synergistic effects were induced at higher concentrations of both compounds (≥250 + 5 µg/L). Moreover, higher concentrations of Phe (≥5 µg/L) increased the accumulation of MC-LR in L. gibba. Our results suggested that the toxic effects of MC-LR and phenanthrene were exacerbated only when they co-exist in water bodies at relatively high concentrations. Consequently, co-existence of MC-LR and Phe at low levels are unlikely to exacerbate ecological hazards to L. gibba in most aquatic environments, at least based on responses of this plant.


Assuntos
Antioxidantes/metabolismo , Araceae/efeitos dos fármacos , Microcistinas/toxicidade , Fenantrenos/toxicidade , Araceae/enzimologia , Catalase/metabolismo , Clorofila/análogos & derivados , Clorofila/metabolismo , Sinergismo Farmacológico , Estresse Oxidativo/efeitos dos fármacos , Peroxidase/metabolismo , Superóxido Dismutase/metabolismo
9.
Ecotoxicol Environ Saf ; 183: 109527, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31400723

RESUMO

Eutrophication is an ecological process that results in cyanobacterial blooms. Microcystin-LR is the most toxic variant of microcystins and may cause toxic effects in the organisms, mainly in hepatic tissues. The aims of this study were to use multiple biomarkers in order to evaluate the sublethal effects of a low concentration of MC-LR (1 µg/L) in fish Geophagus brasiliensis by waterborne exposure; and evaluate the depuration of this toxin during 15 days. A group of 30 fish was exposed to 1 µg/L of MC-LR solution for 96 h in a static bioassay. After this time, blood, brain, muscle, liver, gonad and gills were collected from half of the exposed fish group in order to evaluate chemical, biochemical, histological and genotoxic biomarkers. The rest of the fish group was submitted to the depuration experiment with free MC-LR water for 15 days. After this time the same tissues were collected and evaluated using biomarkers analysis. Toxic effects were found mostly in the fish liver from depuration time as alterations on the antioxidant system and histopathologies. The results showed that even low concentrations can cause sublethal effects to aquatic organisms, and cyanotoxins monitoring and regulation tools are required.


Assuntos
Ciclídeos/metabolismo , Microcistinas/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Antioxidantes/metabolismo , Biomarcadores/sangue , Biomarcadores/metabolismo , Ciclídeos/sangue , Ciclídeos/genética , Relação Dose-Resposta a Droga , Eutrofização , Brânquias/efeitos dos fármacos , Brânquias/metabolismo , Gônadas/efeitos dos fármacos , Gônadas/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Taxa de Depuração Metabólica , Microcistinas/metabolismo , Especificidade de Órgãos , Alimentos Marinhos , Poluentes Químicos da Água/metabolismo
10.
Ecotoxicol Environ Saf ; 183: 109509, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31398579

RESUMO

Microcystin-LR (MC-LR) is the most widely distributed and harmful variant toxins released by cyanobacteria, which poses potential threaten to people and aquatic animals when entering natural water. In our research, solar/chlorine process was comprehensively investigated to degrade and detoxify MC-LR. Under the chlorine concentration of 1.0 mg L-1, MC-LR (1.0 µM) was decreased by 96.7%, 26%, and 9% by solar/chlorine process, chlorination, and solar irradiation respectively. Quenching experiments confirmed that reactive chlorine species (RCS) and hydroxyl radical (HO) were the predominant reactive species in solar/chlorine process at neutral condition, and ozone was generated because of the participation of triplet-state oxygen (O(3P)). The respective contributions of each reactive species were calculated with the order as: RCS, HO, ozone, and solar irradiation. The presence of HCO3- and natural organic matter in water inhibited the degradation efficiency of MC-LR. Moreover, the transformation products of MC-LR generated during the solar/chlorine process were identified and a possible pathway was proposed. The hepatotoxicity of MC-LR and its transformation products was compared using protein phosphatase 2A. Our experimental results revealed that the concentration and hepatotoxicity of MC-LR both significantly decreased, and most products were not hepatoxic. Overall, the solar/chlorine process is a promising alternative technology to degrade MC-LR during eutrophication.


Assuntos
Cloro/química , Microcistinas/química , Luz Solar , Poluentes Químicos da Água/química , Purificação da Água/métodos , Animais , Recuperação e Remediação Ambiental , Halogenação , Microcistinas/isolamento & purificação , Microcistinas/toxicidade , Oxirredução , Água/química , Poluentes Químicos da Água/isolamento & purificação , Poluentes Químicos da Água/toxicidade
11.
Chemosphere ; 237: 124508, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31408798

RESUMO

Microcystis is a notorious cyanobacterial genus due to its rapid growth rate, huge biomass, and producing toxins in some eutrophic freshwater environments. To reveal the regulatory factors of interspecific competition between toxic and non-toxic Microcystis, three dominant Microcystis strains were selected, and their photosynthesis, population dynamics and microcystins (MCYST) production were measured. The results suggested that nitrogen-limitation (N-limitation) had a greater restriction for the growth of toxic Microcystis than that of non-toxic Microcystis, especially when cultured at high light or high temperature based on the weight analysis of key factors. Comparison of photosynthesis showed that low light or N-rich would favor the competitive advantage of toxic Microcystis while high light combined with N-limitation would promote the competitive advantage of non-toxic Microcystis, and these two competitive advantages could be further amplified by temperature increase. Mixed competitive experiments of toxic and non-toxic Microcystis were conducted, and the results of absorption spectrum (A485/A665) and qPCR (real-time quantitative PCR) suggested that the proportion of toxic Microcystis and the half-time of succession process were significantly reduced by 69.4% and 28.4% (p < 0.01) respectively by combining N-limitation with high light intensity than that measured under N-limitation condition. N-limitation led to a significant decrease of MCYST cellular quota in Microcystis biomass, which would be further decreased to a lower level by the high light. Based on above mentioned analysis, to decrease the MCYST production of Microcystis blooms, we should control nutrient, especial nitrogen through pollutant intercepting and increase the light intensity through improving water transparency.


Assuntos
Microcistinas/toxicidade , Microcystis/fisiologia , Nitrogênio/análise , Biomassa , Luz , Microcystis/crescimento & desenvolvimento , Fotossíntese
12.
Environ Toxicol Pharmacol ; 71: 103222, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31426013

RESUMO

The Roodeplaat Dam and its three inflowing rivers are highly impacted by surrounding anthropogenic activities. The system is hyper-eutrophic and characterized by seasonal algal blooms and previous studies have reported levels of the hepatotoxin microcystin in the water of the impoundment. Limited information is available on the microcystin concentrations in the inflowing rivers and no information is available on the bioaccumulated levels and potential health effects in fish inhabiting these rivers. The aim of this study was to do a histopathological assessment and to determine the concentrations of bioaccumulated microcystins in the livers of two indicator fish species Clarias gariepinus and Oreochromis mossambicus. The results showed that the two species bioaccumulate microcystins at different concentrations and that their hepatic health response varied. The liver index was significantly higher for C. gariepinus compared to O. mossambicus. No significant positive correlation was found between the bioaccumulated microcystin levels and the liver histology index. It is recommended that this pilot study be followed by a controlled exposure study to confirm a possible cause and effect relationship between microcystin exposure and the specific liver alterations identified.


Assuntos
Peixes-Gato/metabolismo , Fígado/efeitos dos fármacos , Fígado/patologia , Microcistinas/toxicidade , Rios/química , Tilápia/metabolismo , Poluentes Químicos da Água/toxicidade , Animais , Bioacumulação , Monitoramento Ambiental , Eutrofização , Fígado/metabolismo , Microcistinas/metabolismo , Projetos Piloto , África do Sul , Especificidade da Espécie , Poluentes Químicos da Água/metabolismo
13.
Ecotoxicol Environ Saf ; 183: 109568, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31437729

RESUMO

We employed nematode Caenorhabditis elegans to determine the combinational effect between nanopolystyrene at predicted environmental concentration and microcystin-LR (MC-LR). Prolonged exposure to nanopolystyrene (1 µg/L) increased MC-LR (0.1 µg/L) toxicity in reducing brood size and locomotion behavior and in inducing oxidative stress. Moreover, the adsorption of MC-LR by nanopolystyrene particles played an important role in inducing the enhancement in MC-LR toxicity by nanopolystyrene particles. Additionally, only exposure to resuspension of nanopolystyrene (1 µg/L) caused the increased intestinal permeability in MC-LR (0.1 µg/L) exposed nematodes. Our data indicates the potential of nanopolystyrene at predicted environmental concentration in enhancing MC-LR toxicity on environmental organisms.


Assuntos
Caenorhabditis elegans/efeitos dos fármacos , Poluentes Ambientais/toxicidade , Intestinos/efeitos dos fármacos , Microcistinas/toxicidade , Nanoestruturas/toxicidade , Poliestirenos/toxicidade , Animais , Comportamento Animal/efeitos dos fármacos , Caenorhabditis elegans/metabolismo , Relação Dose-Resposta a Droga , Mucosa Intestinal/efeitos dos fármacos , Mucosa Intestinal/metabolismo , Locomoção/efeitos dos fármacos , Microcistinas/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Permeabilidade
14.
Environ Pollut ; 254(Pt A): 113019, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31419664

RESUMO

Microcystis aeruginosa is one of the main species of cyanobacteria that causes water blooms. M. aeruginosa can release into the water several types of microcystins (MCs), which are harmful to aquatic organisms and even humans. However, few studies have investigated the hepatotoxicity of M. aeruginosa itself in zebrafish in environments that simulate natural aquatic systems. The objective of this study was to evaluate the hepatotoxicity of M. aeruginosa in adult zebrafish (Danio rerio) after short-term (96 h) exposure and to elucidate the potential underlying mechanisms. Distinct histological changes in the liver, such as enlargement of the peripheral nuclei and sinusoids and the appearance of fibroblasts, were observed in zebrafish grown in M. aeruginosa culture. In addition, antioxidant enzyme activity was activated and protein phosphatase (PP) activity was significantly decreased with increasing microalgal density. A proteomic analysis revealed alterations in a number of protein pathways, including ribosome translation, immune response, energy metabolism and oxidative phosphorylation pathways. Western blot and real-time PCR analyses confirmed the results of the proteomic analysis. All results indicated that M. aeruginosa could disrupt hepatic functions in adult zebrafish, thus highlighting the necessity of ecotoxicity assessments for M. aeruginosa at environmentally relevant densities.


Assuntos
Microcistinas/toxicidade , Poluentes da Água/toxicidade , Peixe-Zebra/fisiologia , Animais , Antioxidantes/metabolismo , Doença Hepática Induzida por Substâncias e Drogas , Cianobactérias , Humanos , Microcystis/metabolismo , Proteoma/metabolismo , Proteômica , Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/metabolismo
15.
Aquat Toxicol ; 215: 105261, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31419757

RESUMO

Harmful cyanobacteria and their production of microcystins (MCs) exert significant toxicity on reproduction of fish, especially the process of oogenesis. Our previous studies demonstrated that MCs have negative impacts on the quantity and quality of mature oocytes in female zebrafish. However, the underlying mechanisms of MCs disrupting oocyte maturation (OM) have been rarely reported. In the present study, in vitro oocytes (immature) were separated from zebrafish and treated with 1, 10, 100 µg/L MC-LR. The serine/threonine protein phosphatase 2A (PP2A) activity was downregulated significantly in oocytes exposed to 10 and 100 µg/L MC-LR for both 2 and 4 h. The phosphorylation levels of mitogen-activated protein kinase (MAPK) were detected without noticeable change in all oocytes treated with MC-LR for 2 h, whereas the activated levels of MAPK subtypes (ERK, p38 and JNK) increased remarkably in the 100 µg/L MC-LR treatment of 4 h. In the oocytes exposed to 100 µg/L MC-LR for 4 h, germinal vesicle breakdown (GVBD) rates changed abnormally and maturation-promoting factor (MPF) activity increased significantly, in accordance with the upregulation of Cyclin B protein levels. Moreover, the MAPK inhibitors (10 µM) were applied to explore the role of MAPK subtypes during MC-LR influencing OM and results showed that ERK inhibitor U0126 and p38 inhibitor SB203580 mitigated the effects of 100 µg/L MC-LR-induced MAPK hyper-phosphorylation and elevated GVBD in the oocytes. In conclusion, the present study indicates that microcystins disrupt the meiotic maturation by the pathway of MC-PP2A-MAPK-OM due to the phosphorylation disorder in oocytes.


Assuntos
Técnicas de Maturação in Vitro de Oócitos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Microcistinas/toxicidade , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Peixe-Zebra/fisiologia , Animais , Ciclina B/metabolismo , Ativação Enzimática/efeitos dos fármacos , Feminino , Fator Promotor de Maturação/metabolismo , Oócitos/efeitos dos fármacos , Oócitos/enzimologia , Fosforilação/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia , Proteína Fosfatase 2/metabolismo , Vitelogeninas/metabolismo , Poluentes Químicos da Água/toxicidade
16.
Sci Total Environ ; 693: 133540, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31374495

RESUMO

Owing to the eutrophication in freshwater and industrial emissions, the detected concentrations of MCLR and nano-TiO2 in nature water increase year by year. The purpose of this study was to evaluate the joint effect of microcystin-LR (MCLR) and titanium dioxide nanoparticles (nano-TiO2) on the zebrafish brain and to investigate the underlying mechanisms. In this study, four-month old zebrafish were exposed to 0, 0.5, 4, and 32 µg/L MCLR and MCLR-co-nano-TiO2 (100 µg/L) for 45 days. Obvious brain injury characterized by formation of glial scars and ventriculomegaly was observed in both MCLR groups and MCLR-co-nano-TiO2 groups. In addition, our results showed the existence of nano-TiO2 aggravated MCLR-induced abnormity of swimming behavior and social behavior of zebrafish. To clarify the mechanisms of nano-TiO2 aggravated MCLR-induced brain injury, we firstly examined the reactive oxygen species (ROS) generation in the zebrafish brain. The results showed that co-exposure with nano-TiO2 could further increase ROS content compared with MCLR only groups. We also detected a significant change of lipid peroxidation products (MDA, malondialdehyde) content, antioxidant enzyme (SOD, superoxide dismutase) activity, and non-enzymatic antioxidant (GSH, glutathione) content in MCLR-co-nano-TiO2 groups. Transcriptional analysis indicated the expression of genes related to the antioxidant system was significantly altered in the zebrafish brain. Collectively, the observations in this study showed that the existence of nano-TiO2 could exacerbate the damage of the zebrafish brain through the aggravation of MCLR-induced oxidative stress, ultimately leading to the abnormity of swimming behavior and social behavior.


Assuntos
Nanopartículas Metálicas/toxicidade , Microcistinas/toxicidade , Titânio/toxicidade , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/fisiologia , Animais , Antioxidantes , Lesões Encefálicas , Água Doce , Glutationa , Peroxidação de Lipídeos , Estresse Oxidativo , Superóxido Dismutase
17.
Sci Total Environ ; 689: 662-678, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31279213

RESUMO

Microcystin-leucine-arginine (MC-LR), which produced by toxic cyanobacteria and widely present in eutrophic waters, has been shown to have potent acute hepatotoxicity. MC-LR has been revealed to inflict damage to brain, while the neurotoxicity of chronic exposure to MC-LR and mechanisms underlying it are still confusing. Here, the mice were exposed to MC-LR dissolved in drinking water at dose of 1, 7.5, 15, and 30 µg/L for consecutive 180 days. MC-LR accumulated in mouse brains and impaired the blood-brain barrier by inducing the expression of matrix metalloproteinase-8 (MMP-8), which was regulated by NF-κB, c-Fos and c-Jun. Furthermore, MC-LR exposure induced microglial and astrocyte activation and resultant neuroinflammatory response. This study highlights the risks to human health of the current microcystin exposure.


Assuntos
Barreira Hematoencefálica/efeitos dos fármacos , Inflamação/fisiopatologia , Microcistinas/toxicidade , Junções Íntimas/efeitos dos fármacos , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/fisiologia , Expressão Gênica/efeitos dos fármacos , Inflamação/induzido quimicamente , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Microglia/efeitos dos fármacos , Microglia/fisiologia , Junções Íntimas/metabolismo
18.
Aquat Toxicol ; 214: 105240, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31319295

RESUMO

Fish has a strong resistance to microcystins (MCs), cyclic heptapeptide cyanotoxins, known as endocrine disrupting chemicals (EDCs) which are released during cyanobacterial blooms and many laboratory and field studies have found the hepatic recovery of fish from the MCs exposure. The aim of the present study was to investigate the recovery mechanisms of reproductive function of adult zebrafish (Danio rerio) from microcystin-LR (MC-LR) exposure. Therefore, adult female zebrafish were exposed to 0, 1 or 50 µg/L of MC-LR for 21days and transferred to MC free water for another 21 days to investigate the recovery. After MC-LR exposure, marked histological lesions in the gonads, decreased the percentage of mature oocytes, decreased number of spawned eggs, decreased fertilization and hatching rates were observed. MC-LR exposure increased the concentration of 17ß-estradiol (E2), testosterone (T) and vitellogenin (VTG) in female zebrafish. Some gene transcriptions of the hypothalamic-pituitary-gonad (HPG) axis significantly changed. The protein levels of 17ßhsd and cyp19a remarkably increased in the MC-LR exposure groups. However, our laboratory observation also indicates that zebrafish transferred from microcystin exposure to toxin-free water and reared for 21 days exhibited a nearly complete recovery of reproductive functions, including histological structure, increased the percentage of matured oocytes and spawned eggs, stable hormone levels, well-balanced transcriptional and translational levels. These results indicate that after MC-LR exposure, the reproductive impairments in zebrafish are also reversible likewise hepatic recovery seen by different studies in fish. Future studies should be conducted to explore a better understanding of the recovery mechanisms of fish from microcystins exposure.


Assuntos
Exposição Ambiental , Microcistinas/toxicidade , Reprodução/efeitos dos fármacos , Peixe-Zebra/fisiologia , Animais , Disruptores Endócrinos/toxicidade , Feminino , Hormônios/sangue , Hipotálamo/efeitos dos fármacos , Hipotálamo/metabolismo , Ovário/citologia , Ovário/efeitos dos fármacos , Ovário/fisiologia , Hipófise/efeitos dos fármacos , Hipófise/metabolismo , Transcrição Genética/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/sangue , Peixe-Zebra/genética , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismo
19.
Environ Pollut ; 253: 61-67, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31302403

RESUMO

Uptake of the commonly occurring cyanobacterial toxin microcystin-LR (MC-LR) into crop plants via spray irrigation has been demonstrated. As other hazardous compounds such as pesticides were shown to be transported within plants, it was essential to understand the transport and fate of MC-LR in plants and the risks posed to grazers and other consumers. Of specific interest was to investigate if MC-LR could be detected in guttation drops and the toxicity thereof. Triticum aestivum (wheat) seedlings were exposed to 100 µg L-1 MC-LR in two separate experiments during which guttation drops were collected at various time points. The plants of one experiment were sectioned to investigate MC-LR distribution to the various plant appendages via liquid chromatography-tandem mass spectrometry analysis. After exposure, MC-LR could be detected in the roots, stems, leaves, and the guttation drops. However, the guttation drops were not toxic to Daphnia. As the environmentally relevant toxin concentration used was not sufficient to promote mortality in Daphnia, the physiological effect in insects, which rely on guttation drops as a water source, remains unknown. Combined with other contaminants that insects may be exposed to, the additional MC-LR exposure could contribute to the overall toxicity through the "tears of death".


Assuntos
Microcistinas/metabolismo , Triticum/metabolismo , Toxinas Bacterianas , Cromatografia Líquida , Toxinas Marinhas , Microcistinas/toxicidade , Folhas de Planta , Raízes de Plantas , Plântula
20.
Environ Toxicol ; 34(10): 1074-1084, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31157505

RESUMO

Microcystin-LR (MC-LR), a potent endotoxin, can induce reproductive toxicity. In order to investigate the role and mechanisms of apoptosis (p53-dependent and mitochondrial pathways) of germ cells induced by MC-LR, the co-cultured primary Sertoli-germ cells from Sprague-Dawley rats were used for the experiments. Expression levels of proteins, genes, and mitochondrial membrane potential (MMP) were obtained after exposing co-cultured Sertoli-germ cells to MC-LR with or without the addition of the p53 inhibitor, pifithrin-α (PFT-α), and MMP inhibitor, cyclosporin A (CsA). Results indicated that MC-LR could activate p53-dependent pathway-associated proteins in Sertoli-germ cells, leading to a decrease in MMP (indicating the opening of mitochondrial permeability transition pore [mPTP] and the release of Cytochrome-c [Cyt-c]) from the mitochondria into the cytoplasm and eventually the induction of apoptosis. PFT-α inhibited the expression ofp53, ameliorated the MMP of the co-cultured Sertoli-germ cells, and prevented the release of Cyt-c from the mitochondria into the cytoplasm, which reduces the occurrence of apoptosis. Similarly, the decreased release of Cyt-c from the mitochondria into the cytoplasm and the declined level of apoptosis in Sertoli-germ cells induced by MC-LR were observed after the addition of CsA. These results indicated that the apoptosis of the co-cultured Sertoli-germ cells induced by MC-LR was mediated by the p53-dependent pathway, with the involvement of the opening of mPTP.


Assuntos
Células Germinativas/efeitos dos fármacos , Microcistinas/toxicidade , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Células de Sertoli/efeitos dos fármacos , Proteína Supressora de Tumor p53/metabolismo , Animais , Apoptose/efeitos dos fármacos , Técnicas de Cocultura , Células Germinativas/citologia , Células Germinativas/metabolismo , Masculino , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Ratos , Ratos Sprague-Dawley , Células de Sertoli/citologia , Células de Sertoli/metabolismo
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