Multi-generational impacts of organic contaminated stream water on Daphnia magna: A combined proteomics, epigenetics and ecotoxicity approach

Carryover effects of tire wear particle leachate threaten the reproduction of a model zooplankton across multiple generations

The toxic additives that leach from tire wear particles (TWPs) cause mass die-offs in fish and impact zooplankton as secondary consumers in the aquatic food web. In addition to the direct impacts of TWP leachate on a single generation, there may be potential delayed carryover effects across multiple generations from parental exposure, which may amplify the adverse effects of the leachate on individual reproduction and, consequently, on the entire population. In this study, the single, multiple, and transgenerational effects of TWP leachate at various concentrations on the reproduction and lifespan of the rotifer Brachionus calyciflorus were investigated. The results indicated that the lifespan and reproductive output of rotifers exposed to TWP leachate (0-1500 mg/L) decreased as the concentration increased above 250 mg/L. There was a clear multigenerational effect of TWP leachate on rotifer reproduction. The inhibition rates were consistently greater at 500 mg/L than at 250 mg/L leachate. Although the reproduction of rotifers exposed to 250 mg/L TWP leachate increased in the first two generations (P and F1), it was inhibited in subsequent generations. The inhibitory effect of 500 mg/L TWP leachate persisted across all generations, leading to population extinction by the F4 generation. A significant transgenerational effect of TWP leachate was found on reproduction. The adverse impact of exposure to 250 mg/L leachate for fewer than three generations could be reversed when offspring were transferred to clean media. However, this recovery was not observed after continuous exposure for more than four generations. Exposure to high-dose TWP leachate also caused irreversible damage to reproduction. Therefore, TWP leachate can result in cascading toxicity on zooplankton populations through carryover and cumulative effects on reproduction.

Developmental, behavioral, and biochemical effects of chronic exposure to sublethal concentrations of organic UV-filter compounds on a freshwater model species

The prevalence of organic/chemical UV-filter compounds in aquatic ecosystems represents a growing environmental issue. The long-term toxicity risks of many UV-filters at environmentally relevant concentrations to aquatic biota are still less studied, especially in the case of invertebrates. This study was designed to evaluate the chronic toxicity of avobenzone (AVO), octocrylene (OCTO), and octinoxate (OCTI), three UV-filters which frequently occur in the aquatic environment, to the water flea (Daphnia magna) at an environmentally relevant concentration of 200 ng l-1 in a 21-day exposure. Potential alterations in the growth, reproduction, and heart rate were continuously monitored during the treatments. Filtration rate, swimming, and the state of the antioxidant- and metabolic functions were evaluated at the end of exposures. Avobenzone significantly increased the reproductive output, heart rate, and filtration rate, while evoked a significant decrease of swimming behavior, and inhibited the activity of catalase (CAT) and glutathione S-transferase (GST) enzymes. The body size, reproduction, heart rate, and superoxide dismutase (SOD) activity were significantly increased whereas the activity of GST and CAT was significantly reduced by OCTO. OCTI significantly increased reproduction, heart rate, CAT and SOD activity but significantly decreased the swimming behavior. Our results confirmed that chronic exposure to organic UV-filters even at environmentally relevant concentrations affect basic physiological traits and cellular defense pathways in D. magna. Highlighting, our observations revealed previously unknown physiological changes (e.g., altered heart rate, filtration rate, SOD activity) caused by the investigated UV-filter compounds. Future research is to be aimed at investigating the mixture effects of these compounds and at the understanding of the potential cellular and molecular mechanisms underlying the changes induced.

A review of environmental epigenetics in aquatic invertebrates

Aquatic ecosystems face significant challenges due to increasing human-induced environmental stressors. Recent studies emphasize the role of epigenetic mechanisms in the stress responses and adaptations of organisms to those stressors. Epigenetics influences gene expression, enabling phenotypic plasticity and transgenerational effects. Therefore, understanding the epigenetic responses of aquatic invertebrates to environmental stressors is imperative for aquatic ecosystem research. In this study, we organize the mechanisms of epigenetics in aquatic invertebrates and explore their roles in the responses of aquatic invertebrates to environmental stressors. Furthermore, we discuss the inheritance of epigenetic changes and their influence across generations in aquatic invertebrates. A comprehensive understanding of epigenetic responses is crucial for long-term ecosystem management and conservation strategies in the face of irreversible climate change in aquatic environments. In this review, we synthesize existing knowledge about environmental epigenetics in aquatic invertebrates to provide insights and suggest directions for future research.

Multigenerational tests on Daphnia spp.: a vision and new perspectives

Multigenerational toxicity testing is a valuable tool for understanding the long-term effects of contaminants on aquatic organisms. This review focuses on the use of multigenerational tests with Daphnia, a widely used model organism in aquatic toxicological studies. The review highlights the importance of studying multiple generations to assess Daphnia spp. reproductive, growth, and physiological responses to various contaminants. We discuss the outcomes of multigenerational tests involving different contaminants, including nanoparticles, pesticides, and pharmaceuticals. The results reveal that multigenerational exposure can lead to transgenerational effects, where the impacts of contaminants are observed in subsequent generations even after the initial exposure has ceased. These transgenerational effects often manifest as reproduction, growth, and development alterations. Furthermore, we emphasize the need for standardized protocols in multigenerational testing to ensure comparability and reproducibility of results across studies. We also discuss the implications of multigenerational testing for ecological risk assessment, as it provides a more realistic representation of the long-term effects of contaminants on populations and ecosystems. Overall, this review highlights the significance of multigenerational tests with Daphnia in advancing our understanding of the ecological impacts of contaminants. Such tests provide valuable insights into the potential risks associated with long-term exposure to pollutants and contribute to the development of effective mitigation strategies for aquatic ecosystems.

Environmental metabolomics uncovers oxidative stress, amino acid dysregulation, and energy impairment in Daphnia magna with exposure to industrial effluents

Anthropogenic activities are regarded as point sources of pollution entering freshwater bodies worldwide. With over 350,000 chemicals used in manufacturing, wastewater treatment and industrial effluents are comprised of complex mixtures of organic and inorganic pollutants of known and unknown origins. Consequently, their combined toxicity and mode of action are not well understood in aquatic organisms such as Daphnia magna. In this study, effluent samples from wastewater treatment and industrial sectors were used to examine molecular-level perturbations to the polar metabolic profile of D. magna. To determine if the industrial sector and/or the effluent chemistries played a role in the observed biochemical responses, Daphnia were acutely (48 h) exposed to undiluted (100%) and diluted (10, 25, and 50%) effluent samples. Endogenous metabolites were extracted from single daphnids and analyzed using targeted mass spectrometry-based metabolomics. The metabolic profile of Daphnia exposed to effluent samples resulted in significant separation compared to the unexposed controls. Linear regression analysis determined that no single pollutant detected in the effluents was significantly correlated with the responses of metabolites. Significant perturbations were uncovered across many classes of metabolites (amino acids, nucleosides, nucleotides, polyamines, and their derivatives) which serve as intermediates in keystone biochemical processes. The combined metabolic responses are consistent with oxidative stress, disruptions to energy metabolism, and protein dysregulation which were identified through biochemical pathway analysis. These results provide insight into the molecular processes driving stress responses in D. magna. Overall, we determined that the metabolic profile of Daphnia could not be predicted by the chemical composition of environmentally relevant mixtures. The findings of this study demonstrate the advantage of metabolomics in conjunction with chemical analyses to assess the interactions of industrial effluents. This work further demonstrates the ability of environmental metabolomics to characterize molecular-level perturbations in aquatic organisms exposed to complex chemical mixtures directly.

Trans- and Multigenerational Effects of Isothiazolinone Biocide CMIT/MIT on Genotoxicity and Epigenotoxicity in Daphnia magna

The mixture of 5-chloro-2-methylisothiazol-3(2H)-one and 2-methylisothiazol-3(2H)-one, CMIT/MIT, is an isothiazolinone biocide that is consistently detected in aquatic environments because of its broad-spectrum usage in industrial fields. Despite concerns about ecotoxicological risks and possible multigenerational exposure, toxicological information on CMIT/MIT is very limited to human health and within-generational toxicity. Furthermore, epigenetic markers altered by chemical exposure can be transmitted over generations, but the role of these changes in phenotypic responses and toxicity with respect to trans- and multigenerational effects is poorly understood. In this study, the toxicity of CMIT/MIT on Daphnia magna was evaluated by measuring various endpoints (mortality, reproduction, body size, swimming behavior, and proteomic expression), and its trans- and multigenerational effects were investigated over four consecutive generations. The genotoxicity and epigenotoxicity of CMIT/MIT were examined using a comet assay and global DNA methylation measurements. The results show deleterious effects on various endpoints and differences in response patterns according to different exposure histories. Parental effects were transgenerational or recovered after exposure termination, while multigenerational exposure led to acclimatory/defensive responses. Changes in DNA damage were closely associated with altered reproduction in daphnids, but their possible relationship with global DNA methylation was not found. Overall, this study provides ecotoxicological information on CMIT/MIT relative to multifaceted endpoints and aids in understanding multigenerational phenomena under CMIT/MIT exposure. It also emphasizes the consideration of exposure duration and multigenerational observations in evaluating ecotoxicity and the risk management of isothiazolinone biocides.

Can short-term data accurately model long-term environmental exposures? Investigating the multigenerational adaptation potential of Daphnia magna to environmental concentrations of organic ultraviolet filters

Organic ultraviolet filters (UVFs) are contaminants of concern, ubiquitously found in many aquatic environments due to their use in personal care products to protect against ultraviolet radiation. Research regarding the toxicity of UVFs such as avobenzone, octocrylene and oxybenzone indicate that these chemicals may pose a threat to invertebrate species; however, minimal long-term studies have been conducted to determine how these UVFs may affect continuously exposed populations. The present study modeled the effects of a 5-generation exposure of Daphnia magna to these UVFs at environmental concentrations. Avobenzone and octocrylene resulted in minor, transient decreases in reproduction and wet mass. Oxybenzone exposure resulted in > 40% mortality, 46% decreased reproduction, and 4-fold greater reproductive failure over the F0 and F1 generations; however, normal function was largely regained by the F2 generation. These results indicate that Daphnia are able to acclimate over long-term exposures to concentrations of 6.59 μg/L avobenzone, ∼0.6 μg/L octocrylene or 16.5 μg/L oxybenzone. This suggests that short-term studies indicating high toxicity may not accurately represent long-term outcomes in wild populations, adding additional complexity to risk assessment practices at a time when many regions are considering or implementing UVF bans in order to protect these most sensitive invertebrate species.

Acute toxicity characterization of organic UV-filters and chronic exposure revealing multigenerational effects in DAPHNIA MAGNA

Organic ultraviolet (UV) filters have often been detected in aquatic ecosystems in concentrations ranging from ng/L to μg/L. However, both their acute and chronic effects on aquatic organisms have been insufficiently explored. This study aimed to evaluate acute toxicity of some of the main UV filters used worldwide (2-ethylhexyl,4-methoxycinnamate/EHMC, avobenzone/AVO, benzophenone-3/BP-3, and octocrylene/OC), in three aquatic organisms (Artemia salina, Desmodesmus subspicatus, and Daphnia magna), and to further investigate multigenerational effects in D. magna. After acute toxicity was confirmed, daphnids were chronically exposed to environmentally relevant concentrations of UV filters for two consecutive generations (F0 and F1), and reproductive endpoints, as well as catalase (CAT) and glutathione-S-transferase (GST) activities, were assessed. EHMC showed the most toxic potential, with the lowest EC₅₀ values for the three organisms. On the other hand, reproductive delays and a decrease in the reproduction rate were observed in the F1 generation exposed to AVO (4.4 µg/L), BP-3 (0.17 µg/L), EHMC (0.2 µg/L), and MIX. An increase of the CAT activity in organisms exposed to BP-3 and EHMC suggested induction of the antioxidant system. Although no reproductive effect was observed in the first generation, toxic effects obtained in the F1 revealed the importance of multigenerational studies and the potential harm of UV filters to the life cycle of D. magna, even at environmentally relevant concentrations. This emphasizes the need for further studies considering these levels of exposure and more realistic experimental designs to better understand their potential risks. Environmentally relevant concentrations of Organic UV filters are not lethal to aquatic organisms, however may affect reproductive parameters in Daphnia magna though multigenerational exposures.

Proteome changes in an aquatic invertebrate consumer in response to different nutritional stressors

Nutrient imbalances in zooplankton are caused by the differences in elemental content of producers and the demand for elements in consumers, which alter the life-history traits in consumers. Changes in life-history traits are mediated through metabolic pathways that affect gene expression and the metabolome. However, less is known about proteomic changes to elemental-limitation in zooplankton. Here, we grew Daphnia pulex under high food quantity and quality (HF), low food quantity (LF), and phosphorus (P)-limited (PL) diets for six days and measured growth, elemental composition, and the proteome. Daphnids in both LF and PL diets grew less. Animals in LF diets had less carbon (C), while daphnids in PL diets had less P compared to HF fed animals. In total, we identified 1719 proteins that were used in a partial least squares regression discriminant analysis (PLS-DA). Focusing on a subset of the proteome, the PLS-DA resulted in a clear separation between animals fed HF diets and PL and LF diets. Many proteome changes in nutrient-limited diets are associated with growth, reproduction, lipid metabolism, and nutrient assimilation. Regardless of the limiting nutrient, there were less hemoglobin and small subunit processome component proteins compared to HF fed animals. Daphnids fed LF diets had less vitellogenin fused superoxide dismutase and more lipid-droplet hydrolase, whereas Daphnia fed PL diets had higher abundances of cytochrome P450 and serine protease. Our proteome results compliment other "omic" studies that could be used to study Daphnia physiology in lakes.

Protecting our environment, a motivating outdoor game for proteomics!

The global Earth ecosystem faces many intertwined threats, primarily anthropogenic pollution, drastic reduction of wild spaces, faster spread of pathogens, and global climate warming. Ecotoxicology, the integration of toxicology and ecology, aims to describe the effects of toxicants on organisms, whether at the level of the population, the community, the ecosystem, or the biosphere. Sentinel species are employed to assess threats to life, giving advance warning of danger. In this issue of Proteomics, Wilde and collaborators (Proteomics 2022, 22, https://doi.org/10.1002/pmic.202100289) present a comprehensive coverage of the proteome of the crustacean Daphnia magna, a species used to evaluate aquatic pollution. This study illustrates how current shotgun proteomics technology allows straightforward quantitation of any protein for whole animals or dissected organs, making global molecular phenotyping a reality for animals. Tandem mass spectrometry operated in data-independent acquisition can be used to compare the response of sentinels to various environmental conditions. The current low number of well-annotated animal or plant genomes, the high diversity of genetic backgrounds of each species, and the paucity of knowledge about protein functions for most of the relevant sentinels pose huge challenges for data interpretation. As a result, ecology and ecotoxicology today constitute an exceptional field for proteomics.

Integrative description of changes occurring on zebrafish embryos exposed to water-soluble crude oil components and its mixture with a chemical surfactant

The effects of crude oil spills are an ongoing problem for wildlife and human health in both marine and freshwater aquatic environments. Bioassays of model organisms are a convenient way to assess the potential risks of the substances involved in oil spills. Zebrafish embryos (ZFE) are a useful to reach a fast and detailed description of the toxicity of the pollutants, including both the components of the crude oil itself and substances that are commonly used for crude oil spill mitigation (e.g. surfactants). Here, we evaluated the survival rate, as well as histological, morphological, and proteomic changes in ZFE exposed to Water Accumulated Fraction (WAF) of light crude oil and in mixture with dioctyl sulfosuccinate sodium (DOSS, e.g. CEWAF: Chemically Enhanced WAF), a surfactant that is frequently used in chemical dispersant formulations. Furthermore, we compared de hydrocarbon concentration of WAF and CEWAF of the sublethal dilution. In histological, morphological, and gene expression variables, the ZFE exposed to WAF showed less changes than those exposed to CEWAF. Proteomic changes were more dramatic in ZFE exposed to WAF, with important alterations in spliceosomal and ribosomal proteins, as well as proteins related to eye and retinal photoreceptor development and heart function. We also found that the concentration of high molecular weight hydrocarbons in water was slighly higher in presence of DOSS, but the low molecular weight hydrocarbons concentration was higher in WAF. These results provide an important starting point for identifying useful crude-oil exposure biomarkers in fish species.

Improving the proteome coverage of Daphnia magna - implications for future ecotoxicoproteomics studies

Aquatic pollution is an increasing problem and requires extensive research efforts to understand associated consequences and to find suitable solutions. The crustacean Daphnia is a keystone species in lacustrine ecosystems by connecting primary producers with higher trophic levels. Therefore, Daphnia is perfectly suitable to investigate biological effects of freshwater pollution and is frequently used as an important model organism in ecotoxicology. The field of ecotoxicoproteomics has become increasingly prevalent, as proteins are important for an organism's physiology and respond rapidly to changing environmental conditions. However, one obstacle in proteome analysis of Daphnia is highly abundant proteins like vitellogenin, decreasing the analytical depth of proteome analysis. To improve proteome coverage in Daphnia, we established an easy-to-use procedure based on the LC-MS/MS of whole daphnids and the dissected Daphnia gut, which is the main tissue getting in contact with soluble and particulate pollutants, separately. Using a comprehensive spectral library, generated by gas-phase fractionation and a data-independent acquisition method, we identified 4621 and 5233 protein groups at high confidence (false discovery rate < 0.01) in Daphnia and Daphnia gut samples, respectively. By combining both datasets, a proteome coverage of 6027 proteins was achieved, demonstrating the effectiveness of our approach. This article is protected by copyright. All rights reserved.

Ecotoxicological epigenetics in invertebrates: Emerging tool for the evaluation of present and past pollution burden

The effect of environmental pollution on epigenetic changes and their heredity in affected organisms is of major concern as such changes can play a significant role in adaptation to changing environmental conditions. Changes of epigenetic marks including DNA methylation, histone modifications, and non-coding RNA's can induce changes in gene transcription leading to physiological long-term changes or even transgenerational inheritance. Such mechanisms have until recently been scarcely studied in invertebrate organisms, mainly focusing on model species including Caenorhabditis elegans and Daphnia magna. However, more data are becoming available, particularly focused on DNA methylation changes caused by anthropogenic pollutants in a wide range of invertebrates. This review examines the literature from field and laboratory studies utilising invertebrate species exposed to environmental pollutants and their effect on DNA methylation. Possible mechanisms of epigenetic modifications and their role on physiology and adaptation as well as the incidence of intergenerational and transgenerational inheritance are discussed. Furthermore, critical research challenges are defined and the way forward is proposed. Future studies should focus on the use of next generation sequencing tools to define invertebrate methylomes under environmental stress in higher resolution, those data should further be linked to gene expression patterns and phenotypes and detailed studies focusing on transgenerational effects are encouraged. Moreover, studies of other epigenetic mechanisms in various invertebrate species, apart from DNA methylation would provide better understanding of interconnected cross-talk between epigenetic marks. Taken together incorporating epigenetic studies in ecotoxicology context presents a promising tool for development of sensitive biomarkers for environmental stress assessment.

Acquiring an evolutionary perspective in marine ecotoxicology to tackle emerging concerns in a rapidly changing ocean

Tens of thousands of anthropogenic chemicals and wastes enter the marine environment each year as a consequence of the ever-increasing anthropogenic activities and demographic growth of the human population, which is majorly concentrated along coastal areas. Marine ecotoxicology has had a crucial role in helping shed light on the fate of chemicals in the environment, and improving our understanding of how they can affect natural ecosystems. However, chemical contamination is not occurring in isolation, but rather against a rapidly changing environmental horizon. Most environmental studies have been focusing on short-term within-generation responses of single life stages of single species to single stressors. As a consequence, one-dimensional ecotoxicology cannot enable us to appreciate the degree and magnitude of future impacts of chemicals on marine ecosystems. Current approaches that lack an evolutionary perspective within the context of ongoing and future local and global stressors will likely lead us to under or over estimations of the impacts that chemicals will exert on marine organisms. It is therefore urgent to define whether marine organisms can acclimate, i.e. adjust their phenotypes through transgenerational plasticity, or rapidly adapt, i.e. realign the population phenotypic performances to maximize fitness, to the new chemical environment within a selective horizon defined by global changes. To foster a significant advancement in this research area, we review briefly the history of ecotoxicology, synthesis our current understanding of the fate and impact of contaminants under global changes, and critically discuss the benefits and challenges of integrative approaches toward developing an evolutionary perspective in marine ecotoxicology: particularly through a multigenerational approach. The inclusion of multigenerational studies in Ecological Risk Assessment framework (ERA) would provide significant and more accurately information to help predict the risks of pollution in a rapidly changing ocean.

Metal contamination, bioaccumulation, ROS generation, and epigenotoxicity influences on zebrafish exposed to river water polluted by mining activities

Epigenetic mechanisms are important for gene expression regulation, which is closely related to human health, and epigenetic effects of polluted water bodies have gained increasing research attention. Le'an River suffers from severe trace metal pollution owing to mining activities. In this study, zebrafish was used as a biological model to study pollution of Le'an River after seven consecutive days of exposure. The results showed that midstream and downstream sections of the river were seriously polluted by trace metals. The liver and gill of zebrafish were enriched with trace metals, and cadmium had the highest bioaccumulation factor. Trace metals caused oxidative stress in zebrafish cells, with increases in reactive oxygen species levels. Significant increase of global DNA methylation in liver of middle and downstream section were observed, with values from 125.67% to 165.45% compared with control. Changes in DNA methylation in the promoter region cause significant increase or decrease of the expression of repair genes and apoptosis genes in liver and gill. In summary, Le'an River water exhibited significant epigenetic effects, and it is necessary to consider epigenetic effects in the evaluation of pollution and health risks of river water.

A burning issue: The effect of organic ultraviolet filter exposure on the behaviour and physiology of Daphnia magna

Ultraviolet (UV) filters are compounds utilized in many manufacturing processes and personal care products such as sunscreen to protect against UV-radiation. These highly lipophilic compounds are emerging contaminants of concern in aquatic environments due to their previously observed potential to bioaccumulate and exert toxic effects in marine ecosystems. Currently, research into the toxic effects of UV filter contamination of freshwater ecosystems is lacking, thus the present study sought to model the effects of acute and chronic developmental exposures to UV filters avobenzone, oxybenzone and octocrylene as well as a mixture of these substances in the freshwater invertebrate, Daphnia magna, at environmentally realistic concentrations. Median 48-hour effect and lethal concentrations were determined to be in the low mg/L range, with the exception of octocrylene causing 50% immobilization near environmental concentrations. 48-hour acute developmental exposures proved to behaviourally impair daphnid phototactic response; however, recovery was observed following a 19-day post-exposure period. Although no physiological disruptions were detected in acutely exposed daphnids, delayed mortality was observed up to seven days post-exposure at 200 μg/L of avobenzone and octocrylene. 21-day chronic exposure to 7.5 μg/L octocrylene yielded complete mortality within 7 days, while sublethal chronic exposure to avobenzone increased Daphnia reproductive output and decreased metabolic rate. 2 μg/L oxybenzone induced a 25% increase in metabolic rate of adult daphnids, and otherwise caused no toxic effects at this dose. These data indicate that UV filters can exert toxic effects in freshwater invertebrates, therefore further study is required. It is clear that the most well-studied UV filter, oxybenzone, may not be the most toxic to Daphnia, as both avobenzone and octocrylene induced behavioural and physiological disruption at environmentally realistic concentrations.

Critical window of exposure of CMIT/MIT with respect to developmental effects on zebrafish embryos: Multi-level endpoint and proteomics analysis

Systemic toxicity, particularly, developmental defects of humidifier disinfectant chemicals that have caused lung injuries in Korean children, remains to be elucidated. This study evaluated the mechanisms of the adverse effects of 5-chloro-2-methyl-4-isothiazoline-3-one/2methyl-4-isothiazolin-3-one (CMIT/MIT), one of the main biocides of the Korean tragedy, and identify the most susceptible developmental stage when exposed in early life. To this end, the study was designed to analyze several endpoints (morphology, heart rate, behavior, global DNA methylation, gene expressions of DNA methyl-transferases (dnmts) and protein profiling) in exposed zebrafish (Danio rerio) embryos at various developmental stages. The results showed that CMIT/MIT exposure causes bent tail, pericardial edema, altered heart rates, global DNA hypermethylation and significant alterations in the locomotion behavior. Consistent with the morphological and physiological endpoints, proteomics profiling with bioinformatics analysis suggested that the suppression of cardiac muscle contractions and energy metabolism (oxidative phosphorylation) were possible pivotal underlying mechanisms of the CMIT/MIT mediated adverse effects. Briefly, multi-level endpoint analysis indicated the most susceptible window of exposure to be ≤ 6 hpf followed by ≤ 48 hpf for CMIT/MIT. These results could potentially be translated to a risk assessment of the developmental exposure effects to the humidifier disinfectants.

Can proteomics contribute to biomonitoring of aquatic pollution? A critical review

Aquatic pollution is one of the greatest environmental problems, and therefore its control represents one of the major challenges in this century. In recent years, proteomics has emerged as a powerful tool for searching protein biomarkers in the field of pollution biomonitoring. For biomonitoring marine contamination, there is a consensus that bivalves are preferred organisms to assess organic and inorganic pollutants. Thus, the bivalve proteome was intensively studied, particularly the mussel. It is well documented that heavy metal pollution and organic chemicals altered the structural proteins causing degradation of tissues of molluscs. Also, it is well known that proteins involved in stress oxidative such as glutathione and enzymes as catalase, superoxide dismutase or peroxisomes are overexpressed in response to contaminants. Additionally, using bivalves, other groups of proteins proposed as pollution biomarkers are the metabolic proteins. Even though other marine species are used to monitor the pollution, the presence of proteomic tools in these studies is scarce. Concerning freshwater pollution field, a great variety of animal species (fish and crustaceans) are used as biomonitors in proteomics studies compared to plants that are scarcely analysed. In fish species, proteins involved in stress oxidative such as heat shock family or proteins from lipid and carbohydrate metabolism were proposed as candidate biomarkers. On the contrary, for crustaceans there is a lack of proteomic studies individually assessing the contaminants. Novel scenarios, including emerging contaminants and new threats, will require proteomic technology for a systematic search of protein biomarkers and a greater knowledge at molecular level of those cellular pathways induced by contamination.

Proteomics reveals surface electrical property-dependent toxic mechanisms of silver nanoparticles in Chlorella vulgaris

Silver nanoparticles (AgNPs) are known to exert adverse effects on both humans and aquatic organisms; however, the toxic mechanisms underlying these effects remain unclear. In this study, we investigated the toxic mechanisms of various AgNPs with different surface electrical properties in the freshwater algae Chlorella vulgaris using an advanced proteomics approach with Data-Independent Acquisition. Citrate-coated AgNPs (Cit-AgNPs) and polyethyleneimine-coated AgNPs (PEI-AgNPs) were selected as representatives of negatively and positively charged nanoparticles, respectively. Our results demonstrated that the AgNPs exhibited surface electrical property-dependent effects on the proteomic profile of C. vulgaris. In particular, the negatively charged Cit-AgNPs specifically regulated mitochondrial function-related proteins, resulting in the disruption of several associated metabolic pathways, such as those related to energy metabolism, oxidative phosphorylation, and amino acid synthesis. In contrast, the positively charged PEI-AgNPs primarily targeted ribosome function-related proteins and interrupted pathways of protein synthesis and DNA genetic information transmission. In addition, Ag⁺ ions released from the AgNPs had a significant influence on protein regulation and the induction of cellular stress. Collectively, our findings provide new insight into the surface electrical property-dependent proteomic effects of AgNPs on C. vulgaris and should improve our understanding of the toxic mechanisms of AgNPs in freshwater algae.

Phloroglucinol Treatment Induces Transgenerational Epigenetic Inherited Resistance Against Vibrio Infections and Thermal Stress in a Brine Shrimp (Artemia franciscana) Model

Emerging, infectious diseases in shrimp like acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio parahaemolyticus and mortality caused by other Vibrio species such as Vibrio harveyi are worldwide related to huge economic losses in industrial shrimp production. As a strategy to prevent disease outbreaks, a plant-based phenolic compound could be used as a biocontrol agent. Here, using the brine shrimp (Artemia franciscana) as a model system, we showed that phloroglucinol treatment of the parental animals at early life stages resulted in transgenerational inherited increased resistance in their progeny against biotic stress, i.e., bacteria (V. parahaemolyticus AHPND strain and V. harveyi) and abiotic stress, i.e., lethal heat shock. Increased resistance was recorded in three subsequent generations. Innate immune-related gene expression profiles and potential epigenetic mechanisms were studied to discover the underlying protective mechanisms. Our results showed that phloroglucinol treatment of the brine shrimp parents significantly (P < 0.05) enhanced the expression of a core set of innate immune genes (DSCAM, proPO, PXN, HSP90, HSP70, and LGBP) in subsequent generations. We also demonstrated that epigenetic mechanisms such as DNA methylation, m6A RNA methylation, and histone acetylation and methylation (active chromatin marker i.e., H3K4Me3, H3K4me1, H3K27me1, H3 hyperacetylation, H3K14ac and repression marker, i.e., H3K27me3, H4 hypoacetylation) might play a role in regulation of gene expression leading toward the observed transgenerational inheritance of the resistant brine shrimp progenies. To our knowledge, this is the first report on transgenerational inheritance of a compound-induced robust protected phenotype in brine shrimp, particularly protected against AHPND caused by V. parahaemolyticus and vibriosis caused by V. harveyi. Results showed that epigenetic reprogramming is likely to play a role in the underlying mechanism.

Genetic, epigenetic, and developmental toxicity of Chironomus riparius raised in metal-contaminated field sediments: A multi-generational study with arsenic as a second challenge

Ecotoxicity tests conducted under well-controlled lab conditions often do not reflect the real environmental conditions. To this end, we designed an ecotoxicity test using an aquatic midge, Chironomus riparius, raised in metal-contaminated field sediments (MCFS), which reflect the real environmental conditions, for five consecutive generations (F0-F4) followed by a toxic response to arsenic exposure (as a second challenge). The toxic responses (i.e. DNA damage, DNA methylation, stress response gene expression, and mortality) were compared to those organisms reared in lab sediments (LS). Under the MCFS condition, increased adult emergence was observed for the second and third generations (F1 and F2), while a decreased tendency was evident thereafter (F3 and F4) compared to that of F0. When comparing C. riparius raised in MCFS or LS exposed to arsenic, increased sensitivity (declined survival) was observed in the larvae from F2. However, that tendency was not present in F4 of the MCFS midges, indicating a possible physiological adaptation. Increased DNA damage was observed in the MCFS-exposed organisms (F0, F2, and F4) compared to the those exposed to LS, particularly at F0. Arsenic exposure induced hypermethylation at F0 and, in contrast, hypomethylation at the later generations (F2, F4) in the MCFS-exposed organisms. Global DNA methylation results were supported by the expression of genes involved in enzymatic methylation. Moreover, alterations in oxidative stress related to gene expression showed that significant oxidative stress and perturbation of glutathione reserves occurred under the MCFS and the subsequent arsenic exposure conditions. Overall, our results suggest that multigenerational rearing under MCFS conditions resulted in physiological adaptation of C. riparius to metal exposure, specifically at later generations, which in turn modulated its response to arsenic stress through possible genetic and epigenetic mechanisms.