Efectos de las cianotoxinas sobre la reproducción y el desarrollo

Las cianobacterias son microorganismos procariotas fotosintéticos que se desarrollan en aguas eutrofizadas. Algunas de las especies de estos organismos acuáticos son capaces de producir metabolitos secundarios con carácter tóxico, llamados cianotoxinas, que generan una gran preocupación en términos de salud pública. La exposición humana a estas toxinas puede producirse a través de la vía dérmica o inhalatoria; por ejemplo, en aguas de recreo, o mediante la vía oral, en la que cobra especial importancia la transmisión a través de la cadena alimentaria. Entre las cianotoxinas más estudiadas por su toxicidad se encuentran las microcistinas (MCs) y la cilindrospermopsina (CYN). El objetivo del presente trabajo ha sido realizar una revisión bibliográfica de la literatura científica existente sobre la toxicidad de MCs y CYN en los procesos de reproducción y desarrollo. En general, las MCs han demostrado afectar, en mamíferos y peces, a la viabilidad de las células reproductoras al producir estrés oxidativo, lesiones celulares y aumento de la apoptosis; así como, también afectan a órganos sexuales tanto masculinos como femeninos. A su vez, ya sea por transmisión parental o por exposición directa, los efectos sobre el desarrollo en la descendencia pueden ser desde retraso del crecimiento y desarrollo, malformaciones, y alteraciones endocrinas, hasta una menor supervivencia. Por otro lado, aunque los efectos de las CYN no han sido estudiados con tanta profundidad, esta toxina también ha demostrado producir efectos citotóxicos en células reproductivas. Asimismo, la CYN produce sobre el desarrollo, al igual que las MCs, alteraciones del crecimiento, deformaciones en la descendencia, e incluso aumento de la mortalidad.Universidad de Sevilla. Grado en Físic

Developmental neurotoxicity of an anatoxin-a-producing cyanobacteria (Aphanizomenon gracile) lysate to zebrafish (Danio rerio)

Harmful cyanobacterial blooms occur frequently worldwide with serious environmental impacts. Many detrimental cyanobacteria are well known for their potential to synthesize various cyanotoxins, posing significant threats to aquatic ecosystems and public health worldwide. While most studies focus on the toxicological impacts of microcystins and its main producer Microcystis aeruginosa, the ecotoxic effects of anatoxin-a and anatoxin-a-producing cyanobacteria are not fully understood. This study investigated the response of zebrafish (Danio rerio) to a ruptured cell solution (RCS) of a planktonic anatoxin-a-producing Aphanizomenon gracile. The RCS exposure negatively affected the hatching of zebrafish embryos, and promoted malformation. Furthermore, RCS treatment also disrupted neurobehaviors, and induced severe oxidative stress. In addition, the RCS inhibited the activity of acetylcholinesterase, and dysregulated the expression of several genes related to neuron-development and activated apoptosis in zebrafish. These results suggest that blooms of anatoxin-a-producing Aphanizomenon gracile will have neurotoxic effects on aquatic animals, and could impact human health. They help to further understand the potential neurotoxicity of harmful cyanobacteria, and highlight the need for further studies and risk assessments of the ecological impacts of harmful cyanobacterial blooms in freshwater ecosystems

Temperature- and chemical-induced neurotoxicity in zebrafish

Throughout their lives, humans encounter a plethora of substances capable of inducing neurotoxic effects, including drugs, heavy metals and pesticides. Neurotoxicity manifests when exposure to these chemicals disrupts the normal functioning of the nervous system, and some neurotoxic agents have been linked to neurodegenerative pathologies such as Parkinson's and Alzheimer's disease. The growing concern surrounding the neurotoxic impacts of both naturally occurring and man-made toxic substances necessitates the identification of animal models for rapid testing across a wide spectrum of substances and concentrations, and the utilization of tools capable of detecting nervous system alterations spanning from the molecular level up to the behavioural one. Zebrafish (Danio rerio) is gaining prominence in the field of neuroscience due to its versatility. The possibility of analysing all developmental stages (embryo, larva and adult), applying the most common "omics" approaches (transcriptomics, proteomics, lipidomics, etc.) and conducting a wide range of behavioural tests makes zebrafish an excellent model for neurotoxicity studies. This review delves into the main experimental approaches adopted and the main markers analysed in neurotoxicity studies in zebrafish, showing that neurotoxic phenomena can be triggered not only by exposure to chemical substances but also by fluctuations in temperature. The findings presented here serve as a valuable resource for the study of neurotoxicity in zebrafish and define new scenarios in ecotoxicology suggesting that alterations in temperature can synergistically compound the neurotoxic effects of chemical substances, intensifying their detrimental impact on fish populations

Ten years of research on synergisms and antagonisms in chemical mixtures: A systematic review and quantitative reappraisal of mixture studies

Background: Several reviews of synergisms and antagonisms in chemical mixtures have concluded that synergisms are relatively rare. However, these reviews focused on mixtures composed of specific groups of chemicals, such as pesticides or metals and on toxicity endpoints mostly relevant to ecotoxicology. Doubts remain whether these findings can be generalised. A systematic review not restricted to specific chemical mixtures and including mammalian and human toxicity endpoints is missing. Objectives: We conducted a systematic review and quantitative reappraisal of 10 years’ of experimental mixture studies to investigate the frequency and reliability of evaluations of mixture effects as synergistic or antagonistic. Unlike previous reviews, we did not limit our efforts to certain groups of chemicals or specific toxicity outcomes and covered mixture studies relevant to ecotoxicology and human/mammalian toxicology published between 2007 and 2017. Data sources, eligibility criteria: We undertook searches for peer-reviewed articles in PubMed, Web of Science, Scopus, GreenFile, ScienceDirect and Toxline and included studies of controlled exposures of environmental chemical pollutants, defined as unintentional exposures leading to unintended effects. Studies with viruses, prions or therapeutic agents were excluded, as were records with missing details on chemicals’ identities, toxicities, doses, or concentrations. Study appraisal and synthesis methods: To examine the internal validity of studies we developed a risk-of-bias tool tailored to mixture toxicology. For a subset of 388 entries that claimed synergisms or antagonisms, we conducted a quantitative reappraisal of authors’ evaluations by deriving ratios of predicted and observed effective mixture doses (concentrations). Results: Our searches produced an inventory of 1220 mixture experiments which we subjected to subgroup analyses. Approximately two thirds of studies did not incorporate more than 2 components. Most experiments relied on low-cost assays with readily quantifiable endpoints. Important toxicity outcomes of relevance for human risk assessment (e.g. carcinogenicity, genotoxicity, reproductive toxicity, immunotoxicity, neurotoxicity) were rarely addressed. The proportion of studies that declared additivity, synergism or antagonisms was approximately equal (one quarter each); the remaining quarter arrived at different evaluations. About half of the 1220 entries were rated as “definitely” or “probably” low risk of bias. Strikingly, relatively few claims of synergistic or antagonistic effects stood up to scrutiny in terms of deviations from expected additivity that exceed the boundaries of acceptable between-study variability. In most cases, the observed mixture doses were not more than two-fold higher or lower than the predicted additive doses. Twenty percent of the entries (N = 78) reported synergisms in excess of that degree of deviation. Our efforts of pinpointing specific factors that predispose to synergistic interactions confirmed previous concerns about the synergistic potential of combinations of triazine, azole and pyrethroid pesticides at environmentally relevant doses. New evidence of synergisms with endocrine disrupting chemicals and metal compounds such as chromium (VI) and nickel in combination with cadmium has emerged. Conclusions, limitations and implications: These specific cases of synergisms apart, our results confirm the utility of default application of the dose (concentration) addition concept for predictive assessments of simultaneous exposures to multiple chemicals. However, this strategy must be complemented by an awareness of the synergistic potential of specific classes of chemicals. Our conclusions only apply to the chemical space captured in published mixture studies which is biased towards relatively well-researched chemicals. Systematic review registration number: The final protocol was published on the open-access repository Zenodo and attributed the following digital object identifier, doi: https://doi.org//10.5281/zenodo.1319759 (https://zenodo.org/record/1319759#.XXIzdy7dsqM)

Ten years of research on synergisms and antagonisms in chemical mixtures: A systematic review and quantitative reappraisal of mixture studies

Background Several reviews of synergisms and antagonisms in chemical mixtures have concluded that synergisms are relatively rare. However, these reviews focused on mixtures composed of specific groups of chemicals, such as pesticides or metals and on toxicity endpoints mostly relevant to ecotoxicology. Doubts remain whether these findings can be generalised. A systematic review not restricted to specific chemical mixtures and including mammalian and human toxicity endpoints is missing. Objectives We conducted a systematic review and quantitative reappraisal of 10 years’ of experimental mixture studies to investigate the frequency and reliability of evaluations of mixture effects as synergistic or antagonistic. Unlike previous reviews, we did not limit our efforts to certain groups of chemicals or specific toxicity outcomes and covered mixture studies relevant to ecotoxicology and human/mammalian toxicology published between 2007 and 2017. Data sources, eligibility criteria We undertook searches for peer-reviewed articles in PubMed, Web of Science, Scopus, GreenFile, ScienceDirect and Toxline and included studies of controlled exposures of environmental chemical pollutants, defined as unintentional exposures leading to unintended effects. Studies with viruses, prions or therapeutic agents were excluded, as were records with missing details on chemicals’ identities, toxicities, doses, or concentrations. Study appraisal and synthesis methods To examine the internal validity of studies we developed a risk-of-bias tool tailored to mixture toxicology. For a subset of 388 entries that claimed synergisms or antagonisms, we conducted a quantitative reappraisal of authors’ evaluations by deriving ratios of predicted and observed effective mixture doses (concentrations). Results Our searches produced an inventory of 1220 mixture experiments which we subjected to subgroup analyses. Approximately two thirds of studies did not incorporate more than 2 components. Most experiments relied on low-cost assays with readily quantifiable endpoints. Important toxicity outcomes of relevance for human risk assessment (e.g. carcinogenicity, genotoxicity, reproductive toxicity, immunotoxicity, neurotoxicity) were rarely addressed. The proportion of studies that declared additivity, synergism or antagonisms was approximately equal (one quarter each); the remaining quarter arrived at different evaluations. About half of the 1220 entries were rated as “definitely” or “probably” low risk of bias. Strikingly, relatively few claims of synergistic or antagonistic effects stood up to scrutiny in terms of deviations from expected additivity that exceed the boundaries of acceptable between-study variability. In most cases, the observed mixture doses were not more than two-fold higher or lower than the predicted additive doses. Twenty percent of the entries (N = 78) reported synergisms in excess of that degree of deviation. Our efforts of pinpointing specific factors that predispose to synergistic interactions confirmed previous concerns about the synergistic potential of combinations of triazine, azole and pyrethroid pesticides at environmentally relevant doses. New evidence of synergisms with endocrine disrupting chemicals and metal compounds such as chromium (VI) and nickel in combination with cadmium has emerged. Conclusions, limitations and implications These specific cases of synergisms apart, our results confirm the utility of default application of the dose (concentration) addition concept for predictive assessments of simultaneous exposures to multiple chemicals. However, this strategy must be complemented by an awareness of the synergistic potential of specific classes of chemicals. Our conclusions only apply to the chemical space captured in published mixture studies which is biased towards relatively well-researched chemicals.European Commission, Directorate-General Joint Research Centre, Service Contract CCR.F.933992.X

Co-Occurrence of Cyanobacteria and Cyanotoxins with Other Environmental Health Hazards: Impacts and Implications

Toxin-producing cyanobacteria in aquatic, terrestrial, and aerial environments can occur alongside a wide range of additional health hazards including biological agents and synthetic materials. Cases of intoxications involving cyanobacteria and cyanotoxins, with exposure to additional hazards, are discussed. Examples of the co-occurrence of cyanobacteria in such combinations are reviewed, including cyanobacteria and cyanotoxins plus algal toxins, microbial pathogens and fecal indicator bacteria, metals, pesticides, and microplastics. Toxicity assessments of cyanobacteria, cyanotoxins, and these additional agents, where investigated in bioassays and in defined combinations, are discussed and further research needs are identified

Toxicidade de misturas de cianotoxinas e compostos químicos

Mestrado em Biologia Aplicada - Toxicologia e EcotoxicologiaOs organismos aquáticos podem estar constantemente expostos a cianotoxinas e contaminantes antropogénicos provenientes das florescências de cianobactérias e das atividades humanas, respetivamente. A microcistina-LR (MC-LR) e a cilindrospermopsina (CYN) são as cianotoxinas mais frequentemente detetadas nas florescências de cianobactérias e têm sido encontradas simultaneamente na água. Os metais e pesticidas são contaminantes antropogénicos normalmente encontrados no ambiente aquático como resultado da intensificação das atividades agrícolas e industriais. O cádmio (Cd) e a terbutilazina (TBA) foram selecionados como exemplos de metais e pesticidas que podem co-ocorrer com cianotoxinas no ambiente. No entanto, o risco ecotoxicológico combinado de cianotoxinas e/ou contaminantes antropogénicos existentes no ambiente aquático é ainda pouco conhecido. O presente trabalho teve como objetivo identificar alguns padrões e comportamentos biológicos relativamente a este tipo de combinações. Os efeitos de misturas binárias de MC-LR, CYN, Cd e TBA foram avaliados nas taxas de crescimento da alga Chlorella vulgaris após 4 e 7 dias de exposição, usando o modelo de referência de ação independente (AI). A ferramenta MIXTOX foi usada para avaliar possíveis desvios ao modelo de referência (devido a interações entre compostos), tais como sinergismo/antagonismo, dependência da dose ou do rácio da mistura. Os resultados demonstraram vários padrões de resposta, dependendo da mistura binária testada. Foi detetado sinergismo na mistura de MC-LR e CYN em ambos os períodos de exposição. Na mistura de MC-LR e TBA, houve um desvio dependente do nível da dose entre os componentes para ambos os períodos de exposição, onde se observou antagonismo e sinergismo para concentrações baixas e elevadas de ambos os compostos, respetivamente. Na mistura de MC-LR e Cd, registou-se antagonismo após 4 dias de exposição e um desvio dependente do nível da dose entre os componentes após 7 dias de exposição, observando-se sinergismo e antagonismo para concentrações baixas e elevadas de ambos os compostos, respetivamente. Embora na mistura de CYN e TBA se tenha observado um desvio dependente do rácio entre os componentes, com um padrão de antagonismo perante a dominância da CYN, na mistura de CYN e Cd observou-se antagonismo após 4 dias de exposição. Após 7 dias de exposição foi observado um padrão semelhante de resposta em ambas as misturas contendo CYN, ou seja, um desvio dependente do nível da dose entre os componentes na qual se observou sinergismo para as concentrações baixas e antagonismo para as concentrações elevadas testadas de ambos os compostos. Para a mistura de TBA e Cd, registou-se antagonismo após 4 dias de exposição e um desvio dependente do nível das doses entre os componentes (antagonismo para concentrações baixas e sinergismo para concentrações elevadas de ambos os componentes) após 7 dias de exposição. Devido à diversidade de efeitos e comportamentos que podem resultar da combinação de tóxicos bastante comuns, este estudo mostra a importância de avaliar os efeitos combinados de cianotoxinas e/ou contaminantes antropogénicos.Aquatic organisms may be exposed to cyanotoxins and anthropogenic contaminants originated from harmful cyanobacterial blooms and human activities, respectively. Microcystin-LR (MC-LR) and cylindrospermopsin (CYN) are the most frequently detected cyanotoxins in harmful cyanobacterial blooms and have been simultaneously reported in the water. Metals and pesticides are anthropogenic contaminants commonly found in the aquatic environment as a result of the intensification of agricultural and industrial activities. Cadmium (Cd) and terbuthylazine (TBA) were chosen as an example of the possible metals and pesticides that can co-occurr with cyanotoxins in the environment. However, the ecotoxicological risk of combinations of cyanotoxins and/or anthropogenic contaminants in the aquatic environment needs more studies. The present work aimed to elucidate some biological behaviours and patterns regarding these combinations. The effects of binary mixtures of MC-LR, CYN, Cd and TBA on the growth rate of the freshwater algae Chlorella vulgaris were assessed after 4 and 7 days of exposure using the reference model of independent action (IA). The MIXTOX tool was used to detect possible deviations (due to the interaction between compounds) from the reference model such as synergism/antagonism, dose ratio and dose level dependency. The results demonstrated that several patterns of response were obtained depending on the binary mixture. Synergism was detected in the mixture of MC-LR and CYN for the two exposure periods. In the MC-LR and TBA mixture, a dose-level deviation was observed for the two exposure periods indicating antagonism at low dose levels and synergism at high dose levels. In the MC-LR and Cd mixture, deviations for antagonism were found for a 4-day exposure period while a dose-level deviation was observed for a 7-day exposure period showing synergism at low dose levels and antagonism at high dose levels. A dose-ratio deviation was observed in the CYN and TBA mixture, with a pattern for antagonism when CYN was the compound dominant, while deviations for antagonism were observed in the CYN and Cd mixture for a 4-day exposure period. Similar patterns of response were obtained for both mixtures involving CYN after 7 days of exposure, namely dose-level deviation indicating synergism at low dose levels and antagonism at high dose levels. For TBA and Cd mixture, antagonism was found for a 4-day exposure period and a dose-level deviation (antagonism at low dose levels and synergism at high dose levels) was observed for a 7-day exposure period. Due to the diversity of effects and behaviours that can result from the combination of very common toxicants, this study shows the importance of evaluating the combined effects of cyanotoxins and/or anthropogenic contaminants

Effects of polystyrene nanoplastics and copper on gill tissue structure, metabolism, and immune function of the Chinese mitten crab (Eriocheir sinensis)

Nanoplastics (NPs) and copper (Cu) are increasingly released into aquatic environments, posing significant risks to aquatic organisms, including crabs. As the primary interface between the organism and the surrounding environment, gills are particularly susceptible to the impacts of NPs and Cu exposure. Investigating the toxicity of these pollutants, especially their combined effects, is crucial for assessing their environmental risks. This study evaluated the toxicity of NPs (0.4 mg/L), Cu²+ (0.1 mg/L), and the combination (NPs + Cu²+) on the gill tissues of Eriocheir sinensis, focusing on tissue morphology, metabolism, and immune functions. The results demonstrated that exposure to NPs, Cu²+ and NPs + Cu²+ caused structural damage to gill tissues and significantly elevated antioxidant parameters such as GSH-Px activity and GSH content, as well as immune parameters including ACP and AKP activity. Compared with the single exposure group, energy metabolism-related genes (TAT, TPI, HK) were down-regulated in the combined exposure group. Pathways associated with glutathione metabolism and cytochrome P450 were notably affected, and the combined exposure suppressed the expression of immune-related genes such as CYP450, GST, and UGT. In summary, we found an enhanced toxicological impact of NPs when combined with Cu2+. Thus, this study provides insights into the toxicological mechanisms of NPs and Cu²+ in aquatic organisms, highlighting their ecological risks to aquatic ecosystems

Cd2+ Toxicity to a Green Alga Chlamydomonas reinhardtii as Influenced by Its Adsorption on TiO2 Engineered Nanoparticles

In the present study, Cd2+ adsorption on polyacrylate-coated TiO2 engineered nanoparticles (TiO2-ENs) and its effect on the bioavailability as well as toxicity of Cd2+ to a green alga Chlamydomonas reinhardtii were investigated. TiO2-ENs could be well dispersed in the experimental medium and their pHpzc is approximately 2. There was a quick adsorption of Cd2+ on TiO2-ENs and a steady state was reached within 30 min. A pseudo-first order kinetics was found for the time-related changes in the amount of Cd2+ complexed with TiO2-ENs. At equilibrium, Cd2+ adsorption followed the Langmuir isotherm with the maximum binding capacity 31.9, 177.1, and 242.2 mg/g when the TiO2-EN concentration was 1, 10, and 100 mg/l, respectively. On the other hand, Cd2+ toxicity was alleviated in the presence of TiO2-ENs. Algal growth was less suppressed in treatments with comparable total Cd2+ concentration but more TiO2-ENs. However, such toxicity difference disappeared and all the data points could be fitted to a single Logistic dose-response curve when cell growth inhibition was plotted against the free Cd2+ concentration. No detectable amount of TiO2-ENs was found to be associated with the algal cells. Therefore, TiO2-ENs could reduce the free Cd2+ concentration in the toxicity media, which further lowered its bioavailability and toxicity to C. reinhardtii