An ecotoxicological view on neurotoxicity assessment

Chronic dimethomorph exposure induced behaviors abnormalities and cognitive performance alterations in adult zebrafish (Danio rerio)

Dimethomorph is a systematic fungicide that inhibits sterol synthesis in fungi and unfortunately, there was only scarce data regarding its toxicity. Therefore, considering its extensive application in agriculture and its presence in food residues and the environment, its toxicities in non-target organisms, including aquatic animals, are required to be evaluated since they are sensitive indicators of ecological change. In this study, we evaluated the toxicities of dimethomorph after chronic exposure to adult zebrafish (Danio rerio) by conducting various behavioral assays, a passive avoidance test, and biochemical assays by ELISA. From the results, ∼ 2 weeks exposure to dimethomorph caused lower locomotion, aggressiveness, and conspecific social interaction, and more robust predator avoidance behaviors. Furthermore, alterations in color preferences and short-term memory loss were also observed in the treated fish. In helping to elucidate the mechanism, the expression level of several important neurotransmitters in the brain tissue was measured. Interestingly, increment in several biomarkers, including serotonin, kisspeptin, epinephrine, norepinephrine, and dopamine was observed in the treated group along with a slight increase in other tested neurotransmitters, which were catalase, acetylcholine, and melatonin, which might play a role in the observed behavior alterations. Nevertheless, the results from the current study suggested possible alterations in the central nervous system by dimethomorph, and thus, consideration is required prior to the usage of this fungicide in the agricultural fields surrounding natural freshwater reservoirs.

Pharmaceuticals and Microplastics in Aquatic Environments: A Comprehensive Review of Pathways and Distribution, Toxicological and Ecological Effects

Pharmaceuticals and microplastics are persistent emerging contaminants that pose significant risks to aquatic ecosystems and ecological health. Although extensively reviewed individually, a comprehensive, integrated assessment of their environmental pathways, bioaccumulation dynamics, and toxicological impacts remains limited. This review synthesizes current research on the environmental fate and impact of pharmaceuticals and microplastics, emphasizing their combined influence on aquatic organisms and ecosystems. This review provides a thorough and comprehensive examination of their predominant pathways, sources, and distribution, highlighting wastewater disposal, agricultural runoff, and atmospheric deposition. Studies indicate that pharmaceuticals, such as antibiotics and painkillers, are detected in concentrations ranging from ng/L to μg/L in surface waters, while MPs are found in densities up to 106 particles/m3 in some marine and freshwater systems. The toxicological effects of these pollutants on aquatic organisms, particularly fish, are discussed, with emphasis on bioaccumulation and biomagnification in the food chain, physiological effects including effects on growth, reproduction, immune system performance, and behavioral changes. The ecological consequences, including disruptions to trophic dynamics and ecosystem stability, are also addressed. Although valuable efforts, mitigation and remediation strategies remain inadequate, and further research is needed because they do not capture the scale and complexity of these hazards. This review highlights the urgent need to advance treatment technologies, establish comprehensive regulatory frameworks, and organize intensive research on long-term ecological impacts to address the environmental threats posed by pharmaceuticals and microplastics.

Critical insights into the potential risks of antipsychotic drugs to fish, including through effects on behaviour

Antipsychotic drugs (APDs) are a diverse class of neuroactive pharmaceuticals increasingly detected in surface and ground waters globally. Some APDs are classified as posing a high environmental risk, due, in part, to their tendency to bioaccumulate in wildlife, including fish. Additional risk drivers for APDs relate to their behavioural effects, potentially impacting fitness outcomes. However, standard ecotoxicological tests used in environmental risk assessment (ERA) do not currently account for these mechanisms. In this review, we critically appraise the environmental risks of APDs to fish. We begin by reading-across from human and mammalian effects data to standard ecotoxicological effects endpoints in fish. We then explore the wide range of behaviours suitable for ecotoxicological assessment of APDs (and other neuroactive) pharmaceuticals, principally through laboratory studies with zebrafish, and assess the potential for using these behavioural phenotypes to predict adverse individual- and population-level outcomes in wild fish, taking into account phenotypic plasticity. Next, we illustrate the advantages and challenges of measuring and applying behavioural endpoints for fish, including within current regulatory risk assessments. In our final analysis, the implications of relying on apical endpoints for ERA of neuroactive drugs (including APDs) are assessed and recommendations provided for the development of a more refined and tailored mechanistic approach, which would enable more robust assessment of their environmental risk(s).

Neurological Outcomes of Joint Exposure to Polystyrene Micro/Nanospheres and Silver Nanoparticles in Zebrafish

BACKGROUND

Micro/nanoplastics and silver nanoparticles (AgNPs) are emerging environmental contaminants widely detected in aquatic environments. However, previous research has primarily focused on the interactions between micro/nanoplastics and organic substances or heavy metals, whereas the interactions and combined toxic effects of micro/nanoplastics with AgNPs remain unclear.

OBJECTIVE

Our study aimed to investigate the effects and mechanisms of coexposure to AgNPs and polystyrene micro/nanospheres (PS M/NPs) on the nervous system, comparing the toxicity of AgNPs alone and in combination with PS M/NPs in larval zebrafish.

METHODS

We investigated the dynamics of AgNPs' (5  nm ) adsorption onto PS M/NPs (5 μ m / 100  nm ) using inductively coupled plasma-mass spectrometry. Zebrafish larvae were coexposed to PS M/NPs (200 μ g / L ) and AgNPs (10 μ g / L ) from 6 h post fertilization (hpf) to 72  hpf to ∼ 120  hpf to evaluate neuroinflammatory effects from multiple perspectives, including developmental abnormalities, oxidative stress, neurobehavioral differences, vascular development, immune responses, differences in gene expression, and differences upon neuroinflammation inhibitor addition.

RESULTS

Adsorption experiments showed PS M/NPs could stably adsorb AgNPs, with higher adsorption in smaller particles. Zebrafish larvae exposed to combined PS M/NPs and AgNPs demonstrated neurodevelopmental abnormalities, including developmental malformations, lower levels of locomotor activity, delayed response, and abnormal neuronal development. In addition, exposed zebrafish also exhibited disrupted neurodevelopmental markers, including vascular and apoptotic indicators, and oxidative stress and neuroimmune responses. Quantitative real-time polymerase chain reaction analysis showed differences in gene expression within neurotoxic pathways in PS M/NPs and AgNPs-exposed zebrafish, focusing on key genes in immunity, apoptosis, vascular, and neural development. Furthermore, these neurotoxic effects induced by combined exposure were alleviated following the introduction of the neuroinflammation inhibitor curcumin.

DISCUSSION

Our findings demonstrate that polystyrene nanospheres (PSNPs) intensified AgNPs-induced neurotoxicity in larval zebrafish, whereas polystyrene microspheres (PSMPs) had a lesser effect, indicating distinct gene regulation roles when combined with AgNPs. These findings enhance the assessment of environmental risks in settings with coexisting nanomaterials and microplastics, offering important insights for evaluating combined exposure risks. https://doi.org/10.1289/EHP14873.

Locomotion (behavioural) test in the terrestrial oligochaetes Eisenia exposed to carbamate model substance

This study examines earthworm behaviour by combining locomotion-based motility assessments with evaluations of acetylcholinesterase (AChE) inhibition. Motility analysis revealed significant differences in the two-dimensional movement patterns of earthworms exposed to carbamate pesticides compared to those in the control group, indicating altered trajectories. AChE assays demonstrated a pronounced inhibitory effect on enzyme activity in exposed earthworms relative to unexposed individuals. Both univariate and multivariate analyses confirmed that the pesticide contaminant significantly affects AChE activity as well as the quantitative and directional characteristics of earthworm movement. These results suggest that behavioural testing in earthworms is a valuable tool for understanding the impact of pesticides on non-target organisms and the environment.

Caging Gammarus roeseli to track pesticide contamination: How agricultural practices shape water quality in small waterbodies?

Contaminant monitoring in agroecosystems is increasingly revealing overlooked molecules, particularly within complex pesticide mixtures. This study assessed the effectiveness of chemical and ecotoxicological methods for evaluating contamination and biological responses in Gammarus roeseli exposed to pesticides and transformation products (TPs) in lentic small water bodies (LSWBs) near agricultural zones. We examined 7 LSWBs, finding variable contamination levels shaped by watershed composition differences. Analysis of 136 compounds identified key TPs, including chlorothalonil R471811, metazachlor ESA, and OXA, which collectively represented 86.2 % of the total quantified contaminants. These results underscore the persistence of both current and banned pesticides in the ponds studied. While G. roeseli showed favorable survival rates, significant reductions in locomotion and ventilation were observed at heavily contaminated sites, with biochemical analyses suggesting neurotoxic effects and activation of detoxification mechanisms in response to contaminants. Multivariate analyses revealed site-specific variations, highlighting the complex interactions between contamination levels and environmental conditions. Biomarker responses in gammarids served as sensitive indicators of residual toxicity in LSWBs, with frequent associations with historical contamination or current pesticide applications. This in situ caging approach across a contamination gradient demonstrates strong potential for biomonitoring and ecotoxicological assessments in agroecosystems. Extending exposure durations and including more heavily contaminated ponds could further enhance risk evaluation, thereby improving biomonitoring accuracy in headwater aquatic ecosystems. By integrating site-specific environmental conditions, contamination profiles, and biological responses, this study provides valuable insights into the influence of agricultural practices on LSWBs contamination and underscores the critical need to incorporate TPs into future risk assessment frameworks.

Evidence of the impacts of pharmaceuticals on aquatic animal behaviour (EIPAAB): a systematic map and open access database

BACKGROUND

Over the last decade, pharmaceutical pollution in aquatic ecosystems has emerged as a pressing environmental issue. Recent years have also seen a surge in scientific interest in the use of behavioural endpoints in chemical risk assessment and regulatory activities, underscoring their importance for fitness and survival. In this respect, data on how pharmaceuticals alter the behaviour of aquatic animals appears to have grown rapidly. Despite this, there has been a notable absence of systematic efforts to consolidate and summarise this field of study. To address this, our objectives were twofold: (1) to systematically identify, catalogue, and synthesise primary research articles on the effects of pharmaceuticals on aquatic animal behaviour; and (2) to organise this information into a comprehensive open-access database for scientists, policymakers, and environmental managers.

METHODS

We systematically searched two electronic databases (Web of Science and Scopus) and supplemented these with additional article sources. The search string followed a Population-Exposure-Comparison-Outcome framework to capture articles that used an aquatic organism (population) to test the effects of a pharmaceutical (exposure) on behaviour (outcome). Articles were screened in two stages: title and abstract, followed by full-text screening alongside data extraction. Decision trees were designed a priori to appraise eligibility at both stages. Information on study validity was collected but not used as a basis for inclusion. Data synthesis focused on species, compounds, behaviour, and quality themes and was enhanced with additional sources of metadata from online databases (e.g. National Center for Biotechnology Information (NCBI) Taxonomy, PubChem, and IUCN Red List of Threatened Species).

REVIEW FINDINGS

We screened 5,988 articles, of which 901 were included in the final database, representing 1,739 unique species-by-compound combinations. The database includes data collected over 48 years (1974-2022), with most articles having an environmental focus (510) and fewer relating to medical and basic research topics (233 and 158, respectively). The database includes 173 species (8 phyla and 21 classes). Ray-finned fishes were by far the most common clade (75% of the evidence base), and most studies focused on freshwater compared to marine species (80.4% versus 19.6%). The database includes 426 pharmaceutical compounds; the most common groups were antidepressants (28%), antiepileptics (11%), and anxiolytics (10%). Evidence for the impacts on locomotion and boldness/anxiety behaviours were most commonly assessed. Almost all behaviours were scored in a laboratory setting, with only 0.5% measured under field conditions. Generally, we detected poor reporting and/or compliance with several of our study validity criteria.

CONCLUSIONS

Our systematic map revealed a rapid increase in this research area over the past 15 years. We highlight multiple areas now suitable for quantitative synthesis and areas where evidence is lacking. We also highlight some pitfalls in method reporting and practice. More detailed reporting would facilitate the use of behavioural endpoints in aquatic toxicology studies, chemical risk assessment, regulatory management activities, and improve replicability. The EIPAAB database can be used as a tool for closing these knowledge and methodological gaps in the future.

Sublethal effects of acidified water on sensorimotor responses and the transcriptome of zebrafish embryos

Acidification of freshwater due to human activities is a widespread environmental problem. Its effects on the sensorimotor responses of fish, particularly during embryonic stages, may affect population fitness. To address this, zebrafish embryos were exposed to water at pH 7, 5 and 4.5 (adjusted with HCl) for 120 h. Acidic water did not increase mortality or cause obvious morphological abnormalities but reduced the size of the inner ear organs (otic vesicle and otolith) and the eye lens. It also suppressed ion uptake (Na+, Ca2+, K+) and induced embryonic acidosis. Behavioral tests at 4 or 5 days post fertilization revealed significant sensorimotor impairments: reduced touch-evoked escape responses (TEER), decreased acoustic startle responses (ASR) and decreased cadaverine avoidance responses (CAR). There were no effects on speed, acceleration and optomotor responses (OMR). Transcriptomic analyses identified 114 differentially expressed genes (DEGs) associated with ion transport, sensorimotor functions and other physiological processes. Overall, the jeopardizing effect of freshwater acidification threatens survival, highlighting the ecological risks and its potential impacts on fish populations.

Shark-on-a-dish: Elasmobranch cell cultures as a promising tool for the conservation of threatened species

Anthropogenic activities have increasingly contaminated aquatic ecosystems worldwide, requiring the development of adequate methods to assess the effects of environmental pollution on aquatic biota. Currently, ecotoxicological research on fish is largely based on in vivo studies, many times using post-mortem fish samples bought in fish markets or obtained through capture-and-release programs. However, such samples provide a narrow window to the cellular and molecular processes that occur to fish upon exposure to pollutants and other toxicants or pathogens. In thi sense, in vitro cell culture systems have been increasingly proven a valuable tool in several research fields, from molecular biology studies to conservation efforts. To date, however, cell cultures obtained from bony fish have been the most studied and with the best-described protocols and models. Elasmobranchs, comprising shark and rays, play important trophic and environmental roles, employed as chemical contamination environmental sentinels, suffering the effects of such contamination due to bioaccumulation and biomagnification processes. For these reasons, the development of new experimental tools to study elasmobranch cellular and molecular responses to environmental stimuli in controlled conditions is highly desirable. However, only some research groups have attempted to develop elasmobranch cell culture protocols to be used in an ecotoxicological context. In this sense, this review discusses the current elasmobranch cell culture scenario, its importance and potential applications in ecotoxicology assessments and conservation actions.

NeuTox 2.0: A hybrid deep learning architecture for screening potential neurotoxicity of chemicals based on multimodal feature fusion

Chemically induced neurotoxicity is a critical aspect of chemical safety assessment. Traditional and costly experimental methods call for the development of high-throughput virtual screening. However, the small datasets of neurotoxicity have limited the application of advanced deep learning techniques. The current study developed a hybrid deep learning architecture, NeuTox 2.0, through multimodal feature fusion for enhanced prediction accuracy and generalization ability. We incorporated transfer learning based on self-supervised learning, graph neural networks, and molecular fingerprints/descriptors. Four datasets were used to profile neurotoxicity; these were related to blood-brain barrier permeability, neuronal cytotoxicity, microelectrode array-based neural activity, and mammalian neurotoxicity. Comprehensive performance evaluations demonstrated that NeuTox 2.0 has relatively higher predictive capability across all statistical metrics. Specifically, NeuTox 2.0 exhibits remarkable performance in three of the four datasets. In the BBB dataset, although it does not outperform the PaDEL descriptor model, its performance closely approximates that of the top single-modal model. The ablation experiments indicated that NeuTox 2.0 can learn the deeper structural differences of molecules from various feature extractions and capture complex interactions and mapping relationships between various modalities, thereby improving performance for neurotoxicity prediction. Evaluations of anti-noise ability indicated that NeuTox 2.0 has excellent noise resistance relative to traditional machine learning. We applied the NeuTox 2.0 model to predict the neurotoxicity of 315,790 compounds in the REACH database. The results showed that 701 compounds exhibited potential neurotoxicity in the four neurotoxicity-related predictions. In conclusion, NeuTox 2.0 can be used as an efficient tool for early neurotoxicity screening of environmental chemicals.

Long-term impact of embryonic exposure to ethinylestradiol and clotrimazole on behavior and neuroplasticity in zebrafish (Danio rerio)

Estrogen receptors (ER) are widely expressed in the brain of many species and experimental results highlighted the role of estradiol in neuronal plasticity and behavior. Consequently, the brain is therefore a prime target for endocrine disrupting chemicals (EDCs) interacting with estrogen signaling. Very little is known about the late effects of early disruption of estrogen signaling by EDCs. We focused on: ethinylestradiol (EE2; ER agonist) and clotrimazole (inhibitor of key steroidogenesis enzymes, including aromatases). Zebrafish eleutheroembryos were exposed (0-5 days) and then raised normally until adulthood. Several behavioral tests were performed in adults, then cell proliferation and dopaminergic neurons were quantified in several brain regions using immunostaining. Overall, a developmental exposure to EDCs stimulates cell proliferation in the dorsal telencephalon. At environmentally-relevant concentrations, male fish exposed to EE2 exhibited increased activity levels and decreased social behavior, posing a potential risk to population balance and health.

ChemNTP: Advanced Prediction of Neurotoxicity Targets for Environmental Chemicals Using a Siamese Neural Network

Environmental chemicals can enter the human body through various exposure pathways, potentially leading to neurotoxic effects that pose significant health risks. Many such chemicals have been identified as neurotoxic, but the molecular mechanisms underlying their toxicity, including specific binding targets, remain unclear. To address this, we developed ChemNTP, a predictive model for identifying neurotoxicity targets of environmental chemicals. ChemNTP integrates a comprehensive representation of chemical structures and biological targets, improving upon traditional methods that are limited to single targets and mechanisms. By leveraging these structural representations, ChemNTP enables rapid screening across 199 potential neurotoxic targets or key molecular initiating events (MIEs). The model demonstrates robust predictive performance, achieving an area under the receiver operating characteristic curve (AUCROC) of 0.923 on the test set. Additionally, ChemNTP's attention mechanism highlights critical residues in binding targets and key functional groups or atoms in molecules, offering insights into the structural basis of interactions. Experimental validation through in vitro enzyme activity assays and molecular docking confirmed the binding of eight polybrominated diphenyl ethers (PBDEs) to acetylcholinesterase (AChE). We also provide a user-friendly software interface to facilitate the rapid identification of neurotoxicity targets for emerging environmental pollutants, with potential applications in studying MIEs for more types of toxicity.

Identifying Organic Chemicals with Acetylcholinesterase Inhibition in Nationwide Estuarine Waters by Machine Learning-Assisted Mass Spectrometric Screening

Neurotoxicity is frequently observed in the global aquatic environment, threatening aquatic ecosystems and human health. However, a very limited proportion of neurotoxic effects (∼1%) has been explained by known chemicals of concern. Here, we integrated machine learning, nontargeted analysis, and in vitro biotesting to identify neurotoxic drivers of acetylcholinesterase (AChE) inhibition in estuarine waters along the coast of China. Machine learning was used to predict AChE inhibitors in a large chemical space. The prediction output was profiled into a suspect screening list to guide high-resolution mass spectrometry (HRMS) screening of AChE inhibitors in estuarine water samples. Ultimately, 60 chemicals with diverse known and presently unknown structures were identified, explaining 82.1% of the observed AChE inhibition. Polyunsaturated fatty acids were unexpectedly found to be neurotoxic drivers, accounting for 80.5% of the overall effect. This proof-of-concept study demonstrates that machine learning-based toxicological prediction can achieve a virtual fractionation role to pinpoint HRMS features with the bioactivity potential. Our approach is expected to enable rapid and comprehensive screening of organic pollutants associated with various in vitro end points for large-scale monitoring of water quality.

Nano-phytosome loaded Retama raetam extract/colistin: antibacterial, antioxidant activities and in vivo lipopolysaccharide-induced-neurotoxicity inhibition

Antibiotics are misused nowadays, leading to the prevalence of antibiotic resistant bacterial strains; causing the world to move towards natural medicine. Retama raetam had wide medicinal use. In the present study, R. raetam ethanolic extract proved to be active against Pseudomonas aeruginosa with MIC values ranged from 15.62 to 250 µg/ml. Antioxidant analysis showed that the extract had high scavenging activity reached 92.40%. GC/MS analysis revealed that Sparteine and Tributyl acetylcitrate represent the extract major components. Furthermore, the combination between Retama raetam extract and colistin showed a synergistic effect. Moreover, nano-phytosome was designated and optimized to encapsulate Retama raetam extract/Colistin. Nano-phytosome characterized by particle size, Zeta potential, polydispersity index and Entrapment efficiency percentage of 16.92-32.85 nm, -30.40 mV, 0.26 and 89% respectively. The antibacterial activity of the prepared nano-phytosome formula against P. aeruginosa showed promising MIC, MBC, MIC index, and IZ diameter reaching 7.81, 15.62 µg/ml, 2, and 39 mm, respectively. While TEM examination of P. aeruginosa cells treated with nano-phytosome formula revealed cell wall breakage which led to cell death. Finally, P. aeruginosa LPS was used to induce neurodegenerative disease in rat model. Rats treated with nano-phytosome formula showed normal histoarchitecture organization and the cerebral cortex was partially restored compared to control groups.

Central nervous system disturbances by thiamethoxam in Japanese quail (Coturnix japonica): In vivo, ex vivo, and in silico study

The neurotoxic effects of neonicotinoids (NEOs) have been widely reported in relation to the poisoning of wild birds, yet the underlying molecular mechanism has remained elusive. This study employed Japanese quails (Coturnix japonica) and primary quail embryonic neurons as in vivo and ex vivo models, respectively, to investigate the neurotoxic effects and mechanism of thiamethoxam (TMX), a representative neonicotinoid insecticide, at environmentally relevant concentrations. Following a 28-day exposure to TMX, metabolomic analysis of quail brain revealed TMX-induced changes in glutamatergic, GABA-ergic, and dopaminergic function. Subsequent ex vivo and in silico experimentation revealed that the activation of nicotinic acetylcholine receptors and calcium signaling, induced by clothianidin (CLO), the primary metabolite of TMX, served as upstream events for the alterations in neurotransmitter synthesis, metabolism, release, and uptake. Our findings propose that the disruption of the central nervous system, caused by environmentally significant concentrations of NEOs, may account for the avian poisoning events induced by NEOs.

Non-conventional endpoints show higher sulfoxaflor toxicity to Chironomus riparius than conventional endpoints in a multistress environment

Evidence grows that standard toxicity testing might underestimate the environmental risk of neurotoxic insecticides. Behavioural endpoints such as locomotion and mobility have been suggested as sensitive and ecologically relevant additions to the standard tested endpoints. Possible interactive effects of chemicals and additional stressors are typically overlooked in standardised testing. Therefore, we aimed to investigate how concurrent exposure to environmental stressors (increased temperature and predation cues) and a nicotinic acetylcholine receptor (nAChR)-modulating insecticide ('sulfoxaflor') impact Chironomus riparius across a range of conventional and non-conventional endpoints. We used a multifactorial experimental design encompassing three stressors, sulfoxaflor (2.0-110 µg/L), predation risk (presence/absence of predatory cues), and elevated temperature (20 °C and 23 °C), yielding a total of 24 distinct treatment conditions. Additional stressors did not change the sensitivity of C. riparius to sulfoxaflor. To assess potential additive effects, we applied an Independent Action (IA) model to predict the impact on eight endpoints, including conventional endpoints (growth, survival, total emergence, and emergence time) and less conventional endpoints (the size of the adults, swimming abilities and exploration behaviour). For the conventional endpoints, observed effects were either lower than expected or well-predicted by the IA model. In contrast, we found greater than predicted effects of predation cues and temperature in combination with sulfoxaflor on adult size, larval exploration, and swimming behaviour. However, in contrast to the non-conventional endpoints, no conventional endpoints detected interactive effects of the neurotoxic insecticide and the environmental stressors. Acknowledging these interactions, increasing ecological context of ecotoxicological test systems may, therefore, advance environmental risk analysis and interpretation as the safe environmental concentrations of neurotoxic insecticides depend on the context of both the test organism and its environment.

Analysis of total RNA as a potential biomarker of developmental neurotoxicity in silico

A vast number of neurodegenerative disorders arise from neurotoxicity. In neurotoxicity, more than 250 RNA molecules are up and downregulated. The manuscript investigates the exposure of chlorpyrifos organophosphate pesticide (COP) effect on total RNA in murine brain tissue in 4 genotypes for in silico neurodegeneration development. The GSE58103 dataset from the Gene Expression Omnibus (GEO) database applies for data preprocessing, normalization, and quality control. Differential expression analysis (DEG) uses the limma package in R. Study compared expression profiles from murine fetal brain tissues across four genotypes: PON-1 knockout (KO), tgHuPON1Q192 (Q-tg), tgHuPON1R192 (R-tg), and wild-type (WT). We analyze 60 samples, 15 samples per genotype, to identify DEGs. The significance criteria are adjusted p-value <.05 and a |log2 fold change| > 1. The study identifies microRNA485 as the potential biomarker of COP toxicity using the GSE58103 dataset. Significant differences exist for microRNA485 between KO and WT groups by differential expression analysis. Moreover, graphical analysis shows sample relationships among genotype groups. MicroRNA485 represents a promising biomarker for developmental COP neurotoxicity by utilizing in silico analysis in scientific practice.

Phylogeny predicts sensitivity in aquatic animals for only a minority of chemicals

There are substantial gaps in our empirical knowledge of the effects of chemical exposure on aquatic life that are unlikely to be filled by traditional laboratory toxicity testing alone. One possible alternative of generating new toxicity data is cross-species extrapolation (CSE), a statistical approach in which existing data are used to predict the effect of a chemical on untested species. Some CSE models use relatedness as a predictor of chemical sensitivity, but relatively little is known about how strongly shared evolutionary history influences sensitivity across all chemicals. To address this question, we conducted a survey of phylogenetic signal in the toxicity data from aquatic animal species for a large set of chemicals using a phylogeny inferred from taxonomy. Strong phylogenetic signal was present in just nine of thirty-six toxicity datasets, and there were no clear shared properties among those datasets with strong signal. Strong signal was rare even among chemicals specifically developed to target insects, meaning that these chemicals may be equally lethal to non-target taxa, including chordates. When signal was strong, distinct patterns of sensitivity were evident in the data, which may be informative when assembling toxicity datasets for regulatory use. Although strong signal does not appear to manifest in aquatic toxicity data for most chemicals, we encourage additional phylogenetic evaluations of toxicity data in order to guide the selection of CSE tools and as a means to explore the patterns of chemical sensitivity across the broad diversity of life.

17α-Ethinylestradiol exposure disrupts anxiety-like behaviours but not social preference in sea bass larvae (Dicentrarchus labrax)

Endocrine-disrupting chemicals (EDCs) are widespread pollutants known to interfere with hormonal pathways and to disrupt behaviours. Standardised behavioural procedures have been developed in common fish model species to assess the impact of various pollutants on behaviours such as locomotor activity and anxiety-like as well as social behaviours. These procedures need now to be adapted to improve our knowledge on the behavioural effects of EDCs on less studied marine species. In this context, the European sea bass (Dicentrarchus labrax) is emerging as a valuable species representative of the European marine environment. Here, we designed and validated a two-step procedure allowing to sequentially assess anxiety-like behaviours (novel tank test) and social preference (visual social preference test) in sea bass. Thereafter, using this procedure, we evaluated whether social behavioural disruption occurs in 2-month-old larvae after an 8-day exposure to a xenoestrogen, the 17α-ethinylestradiol (EE2 at 0.5 and 50 nM). Our results confirmed previous studies showing that exposure to 50 nM of EE2 induces a significant increase in anxiety-like behaviours in sea bass larvae. On the contrary, social preference seemed unaffected whatever the EE2 concentration, suggesting that social behaviour has more complex mechanical regulations than anxiety.

Screening 800 putative endocrine disrupting chemicals in a representative mammal, bird, and fish using a neurochemical cell-free testing platform

There is global demand for novel ecotoxicity testing tools that are based on alternative to animal models, have high throughput potential, and may be applicable to a wide diversity of taxa. Here we scaled up a microplate-based cell-free neurochemical testing platform to screen 800 putative endocrine disrupting chemicals from the U.S. Environmental Protection Agency's ToxCast e1k library against the glutamate (NMDA), muscarinic acetylcholine (mACh), and dopamine (D2) receptors. Each assay was tested in cellular membranes isolated from brain tissues from a representative bird (zebra finch = Taeniopygia castanotis), mammal (mink = Neogale vison), and fish (rainbow trout = Oncorhynchus mykiss). The primary objective of this short communication was to make the results database accessible, while also summarising key attributes of assay performance and presenting some initial observations. In total, 7200 species-chemical-assay combinations were tested, of which 453 combinations were classified as a hit (radioligand binding changed by at least 3 standard deviations). There were some differences across species, and most hits were found for the D2 and NMDA receptors. The most active chemical was C.I. Solvent Yellow 14 followed by Diphenhydramine hydrochloride, Gentian Violet, SR271425, and Zamifenacin. Nine chemicals were tested across multiple plates with a mean relative standard deviation of the specific radioligand binding data being 24.6%. The results demonstrate that cell-free assays may serve as screening tools for large chemical libraries especially for ecological species not easily studied using traditional methods.

Neurodevelopmental toxicity of a ubiquitous disinfection by-product, bromoacetic acid, in Zebrafish (Danio rerio)

Disinfection of public drinking water and swimming pools is crucial for preventing waterborne diseases, but it can produce harmful disinfection by-products (DBPs), increasing the risk of various diseases for those frequently exposed to such environments. Bromoacetic acid (BAA) is a ubiquitous DBP, with toxicity studies primarily focused on its in vitro cytotoxicity, and insufficient research on its neurodevelopmental toxicity. Utilizing zebrafish as a model organism, this study comprehensively explored BAA's toxic effects and uncovered the molecular mechanisms through neurobehavioral analysis, in vivo two-photon imaging, transcriptomic sequencing, pharmacological intervention and molecular biological detection. Results demonstrated BAA induced significant changes on various indicators in the early development of zebrafish. Furthermore, BAA disrupted behavioral patterns in zebrafish larvae across locomotion activity, light-dark stimulation, and vibration stimulation paradigms. Subsequent investigation focused on larvae revealed BAA inhibited neuronal development, activated neuroinflammatory responses, and altered vascular morphology. Transcriptomic analysis revealed BAA-stressed zebrafish exhibited downregulation of visual transduction-related genes and activation of ferroptosis and cellular apoptosis. Neurobehavioral disorders were recovered by inhibiting ferroptosis and apoptosis. This study elucidates the neurodevelopmental toxicity associated with BAA, which is crucial for understanding health risks of DBPs and for the development of more effective detection methods and regulatory strategies.

Enhanced electrophysiological activity and neurotoxicity screening of environmental chemicals using 3D neurons from human neural precursor cells purified with PSA-NCAM

The assessment of neurotoxicity for environmental chemicals is of utmost importance in ensuring public health and environmental safety. Multielectrode array (MEA) technology has emerged as a powerful tool for assessing disturbances in the electrophysiological activity. Although human embryonic stem cell (hESC)-derived neurons have been used in MEA for neurotoxicity screening, obtaining a substantial and sufficiently active population of neurons from hESCs remains challenging. In this study, we successfully differentiated neurons from a large population of human neuronal precursor cells (hNPC) purified using a polysialylated neural cell adhesion molecule (PSA-NCAM), referred to as hNPCPSA-NCAM+. The functional characterization demonstrated that hNPCPSA-NCAM+-derived neurons improve functionality by enhancing electrophysiological activity compared to total hNPC-derived neurons. Furthermore, three-dimensional (3D) neurons derived from hNPCPSA-NCAM+ exhibited reduced maturation time and enhanced electrophysiological activity on MEA. We employed subdivided population analysis of active mean firing rate (MFR) based on electrophysiological intensity to characterize the electrophysiological properties of hNPCPSA-NCAM+-3D neurons. Based on electrophysiological activity including MFR and burst parameters, we evaluated the sensitivity of hNPCPSA-NCAM+-3D neurons on MEA to screen both inhibitory and excitatory neuroactive environmental chemicals. Intriguingly, electrophysiologically active hNPCPSA-NCAM+-3D neurons demonstrated good sensitivity to evaluate neuroactive chemicals, particularly in discriminating excitatory chemicals. Our findings highlight the effectiveness of MEA approaches using hNPCPSA-NCAM+-3D neurons in the assessment of neurotoxicity associated with environmental chemicals. Furthermore, we emphasize the importance of selecting appropriate signal intensity thresholds to enhance neurotoxicity prediction and screening of environmental chemicals.

Defending and Defining Environmental Responsibilities for the Health Research Sector

Six planetary boundaries have already been exceeded, including climate change, loss of biodiversity, chemical pollution, and land-system change. The health research sector contributes to the environmental crisis we are facing, though to a lesser extent than healthcare or agriculture sectors. It could take steps to reduce its environmental impact but generally has not done so, even as the planetary emergency worsens. So far, the normative case for why the health research sector should rectify that failure has not been made. This paper argues strong philosophical grounds, derived from theories of health and social justice, exist to support the claim that the sector has a duty to avoid or minimise causing or contributing to ecological harms that threaten human health or worsen health inequity. The paper next develops ideas about the duty's content, explaining why it should entail more than reducing carbon emissions, and considers what limits might be placed on the duty.

Behavioral Effects of the Mixture and the Single Compounds Carbendazim, Fipronil, and Sulfentrazone on Zebrafish (Danio rerio) Larvae

Pesticides are often detected in freshwater, but their impact on the aquatic environment is commonly studied based on single compounds, underestimating the potential additive effects of these mixtures. Even at low concentrations, pesticides can negatively affect organisms, altering important behaviors that can have repercussions at the population level. This study used a multi-behavioral approach to evaluate the effects of zebrafish larvae exposure to carbendazim (C), fipronil (F), and sulfentrazone (S), individually and mixed. Five behavioral tests, thigmotaxis, touch sensitivity, optomotor response, bouncing ball test, and larval exploratory behavior, were performed to assess potential effects on anxiety, fear, and spatial and social interaction. Significant changes were observed in the performance of larvae exposed to all compounds and their mixtures. Among the single pesticides, exposure to S produced the most behavioral alterations, followed by F and C, respectively. A synergistic effect between the compounds was observed in the C + F group, which showed more behavioral effects than the groups exposed to pesticides individually. The use of behavioral tests to evaluate pesticide mixtures is important to standardize methods and associate behavioral changes with ecologically relevant events, thus creating a more realistic scenario for investigating the potential environmental impacts of these compounds.

Comprehensive analysis of a widely pharmaceutical, furosemide, and its degradation products in aquatic systems: Occurrence, fate, and ecotoxicity

Many pharmaceutical compounds end up in the environment due to incomplete removal by wastewater treatment plants (WWTPs). Some compounds are sometimes present in significant concentrations and therefore represent a risk to the aquatic environment. Furosemide is one of the most widely used drugs in the world. Considered as an essential drug by the World Health Organization, this powerful loop diuretic is used extensively to treat hypertension, heart and kidney failure and many other purposes. However, this important consumption also results in a significant release of furosemide in wastewater and in the receiving environment where concentrations of a few hundred ng/L to several thousand have been found in the literature, making furosemide a compound of great concern. Also, during its transport in wastewater systems and WWTPs, furosemide can be degraded by various processes resulting in the production of more than 74 by-products. Furosemide may therefore present a significant risk to ecosystem health due not only to its direct cytotoxic, genotoxic and hepatotoxic effects in animals, but also indirectly through its transformation products, which are poorly characterized. Many articles classify furosemide as a priority pollutant according to its occurrence in the environment, its persistence, its elimination by WWTPs, its toxicity and ecotoxicity. Here, we present a state-of-the-art review of this emerging pollutant of interest, tracking it, from its consumption to its fate in the aquatic environment. Discussion points include the occurrence of furosemide in various matrices, the efficiency of many processes for the degradation of furosemide, the subsequent production of degradation products following these treatments, as well as their toxicity.

Nanoplastic Exposure Mediates Neurodevelopmental Toxicity by Activating the Oxidative Stress Response in Zebrafish (Danio rerio)

The global accumulation and adverse effects of nanoplastics (NPs) are a growing concern for the environment and human health. In recent years, more and more studies have begun to focus on the toxicity of plastic particles for early animal development. Different particle sizes of plastic particles have different toxicities to biological development. Nevertheless, the potential toxicological effects of 20 nm NPs, especially on neurodevelopment, have not been well investigated. In this paper, we used fluorescence microscopy to determine neurotoxicity in zebrafish at different concentrations of NPs. Moreover, the behavioral analysis demonstrated that NPs induced abnormal behavior of zebrafish. The results revealed developmental defects in zebrafish embryos after exposure to different concentrations (0, 0.3, 3, and 9 mg/L) of NPs. The morphological deformities, including abnormal body length and the rates of heart, survival, and hatching, were induced after NP exposure in zebrafish embryos. In addition, the development of primary motor neurons was observed the inhibitory effects of NPs on the length, occurrence, and development of primary motor neurons in Tg(hb9:GFP). Quantitative polymerase chain reaction analysis suggested that exposure to NPs significantly affects the expression of the genes involved in the occurrence and differentiation of primary motor neurons in zebrafish. Furthermore, the indicators associated with oxidative stress and apoptosis were found to be modified in zebrafish embryos at 24 and 48 h following exposure to NPs. Our findings demonstrated that NPs could cause toxicity in primary motor neurons by activating the oxidative stress response and inducing apoptosis, consequently impairing motor performance.

Methods: A bioinformatic protocol for rapid analysis of zebrafish embryo photo-motory responses (PMR) in neurotoxicity testing

Chemobehavioural phenotyping presents unique opportunities for analyzing neurotoxicants and discovering behavior-modifying neuroceuticals in small aquatic model organisms such as zebrafish (Danio rerio). A recently popularized approach in this field involves the utilization of zebrafish embryos for a photo-motor response (PMR) bioassay. The PMR bioassay entails stimulating zebrafish embryos between 24 and 36 h post fertilization (hpf) with a high-intensity light stimulus, inducing a transient increase in the frequency of photo-induced embryo body flexions. These flexions can be computationally analyzed to derive behavioral signatures, enabling the categorization of neuromodulating chemicals. Despite the significant advantages of the PMR bioassay, its widespread implementation is hindered by lack of well described and straightforward high-throughput bioinformatic analysis of behavioral data. In this methods article, we present an easily implementable bioinformatics protocol specifically designed for rapid behavioral analysis of large cohorts of zebrafish specimens in PMR bioassays. We also address common pitfalls encountered during PMR analysis, discuss its limitations, and propose future directions for developing next-generation biometric analysis techniques in chemobehavioural assays utilizing zebrafish embryos.

Novel protective aspects of dietary polyphenols against pesticidal toxicity and its prospective application in rice-fish mode: A Review

The rice fish system represents an innovative and sustainable approach to integrated farming, combining rice cultivation with fish rearing in the same ecosystem. However, one of the major challenges in this system is the pesticidal pollution resulting from various sources, which poses risks to fish health and overall ecosystem balance. In recent years, dietary polyphenols have emerged as promising bioactive compounds with potential chemo-preventive and therapeutic properties. These polyphenols, derived from various plant sources, have shown great potential in reducing the toxicity of pesticides and improving the health of fish within the rice fish system. This review aims to explore the novel aspects of using dietary polyphenols to mitigate pesticidal toxicity and enhance fish health in the rice fish system. It provides comprehensive insights into the mechanisms of action of dietary polyphenols and their beneficial effects on fish health, including antioxidant, anti-inflammatory, and detoxification properties. Furthermore, the review discusses the potential application methods of dietary polyphenols, such as direct supplementation in fish diets or through incorporation into the rice fields. By understanding the interplay between dietary polyphenols and pesticides in the rice fish system, researchers can develop innovative and sustainable strategies to promote fish health, minimize pesticide impacts, and ensure the long-term viability of this integrated farming approach. The information presented in this review will be valuable for scientists, aqua-culturists, and policymakers aiming to implement eco-friendly and health-enhancing practices in the rice fish system.

Participatory hackathon to determine ecological relevant endpoints for a neurotoxin to aquatic and benthic invertebrates

The aim of this study is twofold: i) to determine innovative yet sensitive endpoints for sulfoxaflor and ii) to develop best practices for innovative teaching in ecotoxicology. To this end, a group of 52 MSc students participated in an environmental hackathon, during which they did creative toxicity testing on 5 freshwater invertebrate species: Daphnia magna, Chironomus riparius, Asellus aquaticus, Lymnaea stagnalis, and Anisus vortex. Involving the students in an active learning environment stimulated increased creativity and productivity. In total, 28 endpoints were investigated, including standard endpoints (e.g., mortality) as well as biomechanistic and energy-related endpoints. Despite high variances in the results, likely linked to the limited lab experience of the students and interpersonal differences, a promising set of endpoints was selected for further investigation. A more targeted follow-up experiment focused on the most promising organism and set of endpoints: biomechanistic endpoints of C. riparius larvae. Larvae were exposed to a range of sulfoxaflor concentrations (0.90-67.2 μg/L) for 21 days. Video tracking showed that undulation and swimming were significantly reduced at 11.1 μg sulfoxaflor/L after 9 days of exposure, and an EC50 = 10.6 μg/L for mean velocities of the larvae in the water phase was found. Biomechanistic endpoints proved much more sensitive than mortality, for which an LC50 value of 116 μg/L was found on Day 9. Our results show that performing a hackathon with students has excellent potential to find sensitive endpoints that can subsequently be verified using more targeted and professional follow-up experiments. Furthermore, utilising hackathon events in teaching can increase students' enthusiasm about ecotoxicology, driving better learning experiences.

Zebrafish neuromast sensory system: Is it an emerging target to assess environmental pollution impacts?

Environmental pollution poses risks to ecosystems. Among these risks, one finds neurotoxicity and damage to the lateral line structures of fish, such as the neuromast and its hair cells. Zebrafish (Danio rerio) is recommended as model species to be used in ecotoxicological studies and environmental biomonitoring programs aimed at assessing several biomarkers, such as ototoxicity. However, little is known about the history of and knowledge gaps on zebrafish ototoxicity. Thus, the aim of the current study is to review data available in the scientific literature about using zebrafish as animal model to assess neuromast toxicity. It must be done by analyzing the history and publication category, world production, experimental design, developmental stages, chemical classes, neuromasts and hair cell visualization methods, and zebrafish strains. Based on the results, number, survival and fluorescence intensity of neuromasts, and their hair cells, were the parameters oftentimes used to assess ototoxicity in zebrafish. The wild AB strain was the most used one, and it was followed by Tübingen and transgenic strains with GFP markers. DASPEI was the fluorescent dye most often applied as method to visualize neuromasts, and it was followed by Yo-Pro-1 and GFP transgenic lines. Antibiotics, antitumorals, metals, nanoparticles and plant extracts were the most frequent classes of chemicals used in the analyzed studies. Overall, pollutants can harm zebrafish's mechanosensory system, as well as affect their behavior and survival. Results have shown that zebrafish is a suitable model system to assess ototoxicity induced by environmental pollution.

Exploitation of environmental DNA (eDNA) for ecotoxicological research: A critical review on eDNA metabarcoding in assessing marine pollution

The rise in worldwide population has led to a noticeable spike in the production, consumption, and transportation of energy and food, contributing to elevated environmental pollution. Marine pollution is a significant global environmental issue with ongoing challenges, including plastic waste, oil spills, chemical pollutants, and nutrient runoff, threatening marine ecosystems, biodiversity, and human health. Pollution detection and assessment are crucial to understanding the state of marine ecosystems. Conventional approaches to pollution evaluation usually represent laborious and prolonged physical and chemical assessments, constraining their efficacy and expansion. The latest advances in environmental DNA (eDNA) are valuable methods for the detection and surveillance of pollution in the environment, offering enhanced sensibility, efficacy, and involvement. Molecular approaches allow genetic information extraction from natural resources like water, soil, or air. The application of eDNA enables an expanded evaluation of the environmental condition by detecting both identified and unidentified organisms and contaminants. eDNA methods are valuable for assessing community compositions, providing indirect insights into the intensity and quality of marine pollution through their effects on ecological communities. While eDNA itself is not direct evidence of pollution, its analysis offers a sensitive tool for monitoring changes in biodiversity, serving as an indicator of environmental health and allowing for the indirect estimation of the impact and extent of marine pollution on ecosystems. This review explores the potential of eDNA metabarcoding techniques for detecting and identifying marine pollutants. This review also provides evidence for the efficacy of eDNA assessment in identifying a diverse array of marine pollution caused by oil spills, harmful algal blooms, heavy metals, ballast water, and microplastics. In this report, scientists can expand their knowledge and incorporate eDNA methodologies into ecotoxicological research.

Nanoparticles and neurodegeneration: Insights on multiple pathways of programmed cell death regulated by nanoparticles

Currently, nanoparticles (NPs) are extensively applied in the diagnosis and treatment of neurodegenerative diseases (NDs). With the rapid development and increasing exposure to the public, the potential neurotoxicity associated with NDs caused by NPs has attracted the researchers' attentions but their biosafety assessments are still far behind relevant application studies. Based on recent research, this review aims to conduct a comprehensive and systematic analysis of neurotoxicity induced by NPs. The 191 studies selected according to inclusion and exclusion criteria were imported into the software, and the co-citations and keywords of the included literatures were analyzed to find the breakthrough point of previous studies. According to the available studies, the routes of NPs entering into the normal and injured brain were various, and then to be distributed and accumulated in living bodies. When analyzing the adverse effects induced by NPs, we focused on multiple programmed cell deaths (PCDs), especially ferroptosis triggered by NPs and their tight connection and crosstalk that have been found playing critical roles in the pathogenesis of NDs and their underlying toxic mechanisms. The activation of multiple PCD pathways by NPs provides a scientific basis for the occurrence and development of NDs. Furthermore, the adoption of new methodologies for evaluating the biosafety of NPs would benefit the next generation risk assessment (NGRA) of NPs and their toxic interventions. This would help ensure their safe application and sustainable development in the field of medical neurobiology.

Long-term exposure to cadmium disrupts neurodevelopment in mature cerebral organoids

Cadmium (Cd) is a pervasive environmental pollutant. Increasing evidence suggests that Cd exposure during pregnancy can induce adverse neurodevelopmental outcomes. However, due to the limitations of neural cell and animal models, it is challenging to study the developmental neurotoxicity and underlying toxicity mechanism of long-term exposure to environmental pollutants during human brain development. In this study, chronic Cd exposure was performed in human mature cerebral organoids for 49 or 77 days. Our study found that prolonged exposure to Cd resulted in the inhibition of cerebral organoid growth and the disruption of neural differentiation and cortical layer organization. These potential consequences of chronic Cd exposure may include impaired GFAP expression, a reduction in SOX2+ neuronal progenitor cells, an increase in TUJ1+ immature neurons, as well as an initial increase and a subsequent decrease in both TBR2+ intermediate progenitors and CTIP2+ deep layer cortical neurons. Transcriptomic analyses revealed that long-term exposure to Cd disrupted zinc and copper ion homeostasis through excessive synthesis of metallothionein and disturbed synaptogenesis, as evidenced by inhibited postsynaptic protein. Our study employed mature cerebral organoids to evaluate the developmental neurotoxicity induced by long-term Cd exposure.

Effects of petrogenic pollutants on North Atlantic and Arctic Calanus copepods: From molecular mechanisms to population impacts

Oil and gas industries in the Northern Atlantic Ocean have gradually moved closer to the Arctic areas, a process expected to be further facilitated by sea ice withdrawal caused by global warming. Copepods of the genus Calanus hold a key position in these cold-water food webs, providing an important energetic link between primary production and higher trophic levels. Due to their ecological importance, there is a concern about how accidental oil spills and produced water discharges may impact cold-water copepods. In this review, we summarize the current knowledge of the toxicity of petroleum on North Atlantic and Arctic Calanus copepods. We also review how recent development of high-quality transcriptomes from RNA-sequencing of copepods have identified genes regulating key biological processes, like molting, diapause and reproduction in Calanus copepods, to suggest linkages between exposure, molecular mechanisms and effects on higher levels of biological organization. We found that the available ecotoxicity threshold data for these copepods provide valuable information about their sensitivity to acute petrogenic exposures; however, there is still insufficient knowledge regarding underlying mechanisms of toxicity and the potential for long-term implications of relevance for copepod ecology and phenology. Copepod transcriptomics has expanded our understanding of how key biological processes are regulated in cold-water copepods. These advances can improve our understanding of how pollutants affect biological processes, and thus provide the basis for new knowledge frameworks spanning the effect continuum from molecular initiating events to adverse effects of regulatory relevance. Such efforts, guided by concepts such as adverse outcome pathways (AOPs), enable standardized and transparent characterization and evaluation of knowledge and identifies research gaps and priorities. This review suggests enhancing mechanistic understanding of exposure-effect relationships to better understand and link biomarker responses to adverse effects to improve risk assessments assessing ecological effects of pollutant mixtures, like crude oil, in Arctic areas.

The posterity of Zebrafish in paradigm of in vivo molecular toxicological profiling

The aggrandised advancement in utility of advanced day-to-day materials and nanomaterials has raised serious concern on their biocompatibility with human and other biotic members. In last few decades, understanding of toxicity of these materials has been given the centre stage of research using many in vitro and in vivo models. Zebrafish (Danio rerio), a freshwater fish and a member of the minnow family has garnered much attention due to its distinct features, which make it an important and frequently used animal model in various fields of embryology and toxicological studies. Given that fertilization and development of zebrafish eggs take place externally, they serve as an excellent model organism for studying early developmental stages. Moreover, zebrafish possess a comparable genetic composition to humans and share almost 70% of their genes with mammals. This particular model organism has become increasingly popular, especially for developmental research. Moreover, it serves as a link between in vitro studies and in vivo analysis in mammals. It is an appealing choice for vertebrate research, when employing high-throughput methods, due to their small size, swift development, and relatively affordable laboratory setup. This small vertebrate has enhanced comprehension of pathobiology and drug toxicity. This review emphasizes on the recent developments in toxicity screening and assays, and the new insights gained about the toxicity of drugs through these assays. Specifically, the cardio, neural, and, hepatic toxicology studies inferred by applications of nanoparticles have been highlighted.

Neurotoxic pesticides change respiratory parameters in early gill-breathing, but not in skin-breathing life-stages of zebrafish (Danio rerio)

Neurotoxic compounds can interfere with active gill ventilation in fish, which might lead to premature death in adult fish, but not in skin-breathing embryos of zebrafish, since these exclusively rely on passive diffusion across the skin. Regarding lethality, this respiratory failure syndrome (RFS) has been discussed as one of the main reasons for the higher sensitivity of adult fish in the acute fish toxicity test (AFT), if compared to embryos in the fish embryo toxicity test (FET). To further elucidate the relationship between the onset of gill respiration and death by a neurotoxic mode of action, a comparative study into oxygen consumption (MO2), breathing frequency (fv) and amplitude (fampl) was performed with 4 d old skin-breathing and 12 d old early gill-breathing zebrafish. Neurotoxic model substances with an LC50 FET/AFT ratio of > 10 were used: chlorpyrifos, permethrin, aldicarb, ziram, and fluoxetine. Exposure to hypoxia served as a positive control, whereas aniline was tested as an example of a narcotic substance interfering non-specifically with gill membranes. In 12 d old larvae, all substances caused an increase in MO2, fv and partly fampl, whereas effects were minor in 4 d old embryos. An increase of fv in 4 d old embryos following exposure to chlorpyrifos, aldicarb and hypoxia could not be correlated with an increased MO2 and might be attributed either to (1) to the successfully postponed decrease of arterial partial pressure of oxygen (PO2) through support of skin respiration by increased fv, (2) to an unspecific stimulation of the sphincter muscles at the base of the gill filaments, or (3) to the establishment of oxygen sensing for later stages. In gill-breathing 12 d old zebrafish, a concentration-dependent increase of fv was detected for aniline and chlorpyrifos, whereas for aldicarb, fluoxetine and permethrin, a decline of fv at higher substance concentrations was measured, most likely due to the onset of paralysis and/or fatigue of the gill filament sphincter muscles. Since alterations of fv serve to postpone the decrease in arterial PO2 and MO2 increased with decreasing fv, the respiratory failure syndrome could clearly be demonstrated in 12 d old zebrafish larvae. Passive respiration across the skin in zebrafish embryos could thus be confirmed as a probable reason for the lower sensitivity of early life-stages to neurotoxicants. Integration of respiratory markers into existing testing protocols with non-protected developmental stages such as embryos might help to not underestimate the toxicity of early life-stages of fish.

Neurotoxic effects of chloroquine and its main transformation product formed after chlorination

Pharmaceutical transformation products (TPs) generated during wastewater treatment have become an environmental concern. However, there is limited understanding regarding the TPs produced from pharmaceuticals during wastewater treatment. In this study, chloroquine (CQ), which was extensively used for treating coronavirus disease-19 (COVID-19) infections during the pandemic, was selected for research. We identified and fractionated the main TP produced from CQ during chlorine disinfection and investigated the neurotoxic effects of CQ and its main TP on zebrafish (Danio rerio) embryos. Halogenated TP353 was observed as one of the main TPs produced from CQ during chlorine disinfection. Zebrafish embryos test revealed that TP353 caused higher neurotoxicity in zebrafish larvae, as compared to the CQ, and that was accompanied by significantly decreased expression levels of the genes related to central nervous system development (e.g., gfap, syn2a, and elavl3), inhibited activity of acetylcholinesterase (AChE), reduced GFP fluorescence intensity of motor neuron axons in transgenic larvae (hb9-GFP), and reduced total swimming distance and swimming velocity of larvae during light-dark transition stimulation. The results of this study can potentially be utilized as a theoretical reference for future evaluations of environmental risks associated with CQ and its related TPs. This work presents a methodology for assessing the environmental hazards linked to the discharge of pharmaceutical TPs after wastewater treatment.

Physiological response of thiamethoxam and ulexite in rainbow trout: A neural network-mediated approach

Fish, which are in constant contact with water, serve as an important ecological indicator of aquatic environment health. Therefore, in this study, in the name of neural degeneration, thiamethoxam (TMX) insecticide in the cerebral tissue of Oncorhynchus mykiss; neurotoxic endpoints such as biomarkers of oxidative stress, DNA damage and the status of antioxidant enzymes have been identified. Antioxidant enzyme (CAT, SOD, GPx, GSH) activities were significantly inhibited by TMX administration, and MDA and MPO values increased as a result of the stimulation of ROS (p < 0.05). It was interpreted that ulexite (UX) added to the medium was effective in favor of antioxidants and tried to prevent MDA and MPO levels. It was determined that Nrf-2, one of the inflammation parameters, was inhibited as a result of TMX application, and the supplementation of UX to the medium created merits similar to the no treatment group. In the 48th and 96th hour analyses of cerebral tissue, it was determined that IL-6 and TNF-α values were induced in TMX applied groups and UX tried to inhibit this situation. It was commented that TMX induced DNA damage and apoptosis at 48th-96th h, whereas UX suppressed this situation. The results provide possible in vivo evidence that UX supplements can reduce TMX-mediated oxidative stress and brain damage in O. mykiss brain tissue.

Embryonic Exposure to Benzotriazole Ultraviolet Stabilizer 327 Alters Behavior of Rainbow Trout Alevin

Benzotriazole ultraviolet (UV) stabilizers (BUVSs) are used in great quantities during industrial production of a variety of consumer and industrial goods. As a result of leaching and spill, BUVSs are detectable ubiquitously in the environment. As of May 2023, citing concerns related to bioaccumulation, biomagnification, and environmental persistence, (B)UV(S)-328 was recommended to be listed under Annex A of the Stockholm Convention on Persistent Organic Pollutants. However, a phaseout of UV-328 could result in a regrettable substitution because the replacement chemical(s) could cause similar or unpredicted toxicity in vivo, relative to UV-328. Therefore, the influence of UV-327, a potential replacement of UV-328, was investigated with respect to early life development of newly fertilized rainbow trout embryos (Oncorhynchus mykiss), microinjected with environmentally relevant concentrations of UV-327. Developmental parameters (standard length), energy consumption (yolk area), heart function, blue sac disease, mortality, and behavior were investigated. Alevins at 14 days posthatching, exposed to 107 ng UV-327 g-1 egg, presented significant signs of hyperactivity; they moved on average 1.8-fold the distance and at 1.5-fold the velocity of controls. Although a substantial reduction in body burden of UV-327 was observed at hatching, it is postulated that UV-327, due to its lipophilic properties, interfered with neurological development and signaling from the onset of neurogenesis. If these results hold true across multiple taxa and species, a potential contributor to neurodevelopmental disorders might have been identified. These findings suggest that UV-327 poses an unknown hazard to rainbow trout embryos and alevins, rendering UV-327 a potential regrettable substitution to UV-328. However, a qualified statement on a regrettable substitution requires a comparative investigation on the teratogenic effects between the two BUVSs. Environ Toxicol Chem 2024;00:1-10. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Toward Real-Time Animal Tracking with Integrated Stimulus Control for Automated Conditioning in Aquatic Eco-Neurotoxicology

Aquatic eco-neurotoxicology is an emerging field that requires new analytical systems to study the effects of pollutants on animal behaviors. This is especially true if we are to gain insights into one of the least studied aspects: the potential perturbations that neurotoxicants can have on cognitive behaviors. The paucity of experimental data is partly caused by a lack of low-cost technologies for the analysis of higher-level neurological functions (e.g., associative learning) in small aquatic organisms. Here, we present a proof-of-concept prototype that utilizes a new real-time animal tracking software for on-the-fly video analysis and closed-loop, external hardware communications to deliver stimuli based on specific behaviors in aquatic organisms, spanning three animal phyla: chordates (fish, frog), platyhelminthes (flatworm), and arthropods (crustacean). The system's open-source software features an intuitive graphical user interface and advanced adaptive threshold-based image segmentation for precise animal detection. We demonstrate the precision of animal tracking across multiple aquatic species with varying modes of locomotion. The presented technology interfaces easily with low-cost and open-source hardware such as the Arduino microcontroller family for closed-loop stimuli control. The new system has potential future applications in eco-neurotoxicology, where it could enable new opportunities for cognitive research in diverse small aquatic model organisms.

Fenpropathrin causes alterations in locomotion and social behaviors in zebrafish (Danio rerio)

Fenpropathrin is one of the widely used pyrethroid pesticides in agriculture and is frequently detected in the environment, groundwater, and food. While fenpropathrin was found to have neurotoxic effects in mammals, it remains unclear whether it has similar effects on fish. Here, we used adult zebrafish to investigate the impacts of fenpropathrin on fish social behaviors and neural activity. Exposure of adult zebrafish to 500 ppb of fenpropathrin for 72 h increased anxiety levels but decreased physical fitness, as measured by a novel tank diving test and swimming tunnel test. Fish exposed to fenpropathrin appeared to spend more time in the conspecific zone of the tank, possibly seeking greater comfort from their companions. Although learning, memory, and aggressive behavior did not change, fish exposed to fenpropathrin appeared to have shorter fighting durations. The immunocytochemical results showed the tyrosine hydroxylase antibody-labeled dopaminergic neurons in the teleost posterior tuberculum decreased in the zebrafish brain. According to a quantitative polymerase chain reaction (qPCR) analysis of the brain, exposure to fenpropathrin resulted in a decrease in the messenger (m)RNA expression of monoamine oxidase (mao), an enzyme that facilitates the deamination of dopamine. In contrast, the mRNA expression of the sncga gene, which may trigger Parkinson's disease, was found to have increased. There were no changes observed in expressions of genes related to antioxidants and apoptosis between the control and fenpropathrin-exposed groups. We provide evidence to demonstrate the defect of the neurotoxicity of fenpropathrin toward dopaminergic neurons in adult zebrafish.

A novel approach for the assessment of invertebrate behavior and its use in behavioral ecotoxicology

Sublethal effects are becoming more relevant in ecotoxicological test methods due to their higher sensitivity compared to lethal endpoints and their preventive nature. Such a promising sublethal endpoint is the movement behavior of invertebrates which is associated with the direct maintenance of various ecosystem processes, hence being of special interest for ecotoxicology. Disturbed movement behavior is often related to neurotoxicity and can affect drift, mate-finding, predator avoidance, and therefore population dynamics. We show the practical implementation of the ToxmateLab, a new device that allows monitoring the movement behavior of up to 48 organisms simultaneously, for behavioral ecotoxicology. We quantified behavioral reactions of Gammarus pulex (Amphipoda, Crustacea) after exposure to two pesticides (dichlorvos and methiocarb) and two pharmaceuticals (diazepam and ibuprofen) at sublethal, environmentally relevant concentrations. We simulated a short-term pulse contamination event that lasted 90 min. Within this short test period, we successfully identified behavioral patterns that were most pronounced upon exposure to the two pesticides: Methiocarb initially triggered hyperactivity, after which baseline behavior was restored. On the other hand, dichlorvos induced hypoactivity starting at a moderate concentration of 5 μg/L - a pattern we also found at the highest concentration of ibuprofen (10 μg/L). An additional acetylcholine esterase inhibition assay revealed no significant impact of the enzyme activity that would explain the altered movement behavior. This suggests that in environmentally realistic scenarios chemicals can induce stress - apart from mode-of-action - that affects non-target organisms' behavior. Overall, our study proves the practical applicability of empirical behavioral ecotoxicological approaches and thus represents a next step towards routine practical use.

Neurotoxicity in complex environmental mixtures-a case-study at River Danube in Novi Sad (Serbia) using zebrafish embryos

Acetylcholinesterase (AChE) inhibitors are an important class of neuroactive chemicals that are often detected in aquatic and terrestrial environments. The correct functionality of the AChE enzyme is linked to many important physiological processes such as locomotion and respiration. Consequently, it is necessary to develop new analytical strategies to identify harmful AChE inhibitors in the environment. It has been shown that mixture effects and oxidative stress may jeopardize the application of in vivo assays for the identification of AChE inhibitors in the environment. To confirm that in vivo AChE assays can be successfully applied when dealing with complex mixtures, an extract from river water impacted by non-treated wastewater was bio-tested using the acute toxicity fish embryo test (FET) and AChE inhibition assay with zebrafish. The zebrafish FET showed high sensitivity for the extract (LC10 = relative extraction factor 2.8) and we observed a significant inhibition of the AChE (40%, p < 0.01) after 4-day exposure. Furthermore, the extract was chromatographically fractionated into a total of 26 fractions to dilute the mixture effect and separate compounds according to their physico-chemical properties. As expected, non-specific acute effects (i.e., mortality) disappeared or evenly spread among the fractions, while AChE inhibition was still detected in five fractions. Chemical analysis did not detect any known AChE inhibitors in these active fractions. These results confirm that the AChE assay with Danio rerio can be applied for the detection of neuroactive effects induced in complex environmental samples, but also, they highlight the need to increase analytical and identification techniques for the detection of neurotoxic substances.

Avoidance behaviour of aquatic macroinvertebrates for real-time detection of micropollutant surge in wastewater effluents

Micropollutants are regularly detected at the outlets of wastewater treatment plants (WWTPs). Across urban and industrial WWTPs, monitoring directives only require assessment for a handful of chemicals via sampling methods that fail to capture the temporal variability in micropollutant discharge. In this study, we develop a biotest for real-time on-line monitoring of micropollutant discharge dynamics in WWTPs effluents. The selected biomonitoring device ToxMate uses videotracking of invertebrate movement, which was used to deduce avoidance behaviour of the amphipod Gammarus fossarum. Organism conditioning was set up to induce a state of minimal locomotor activity in basal conditions to maximise avoidance signal sensitivity to micropollutant spikes. We showed that with a standardised protocol, it was possible to minimise both overall movement and sensitivity to physio-chemical variations typical to WWTP effluents, as well as capture the spikes of two micropollutants upon exposure (copper and methomyl). Spikes in avoidance behaviour were consistently seen for the two chemicals, as well as a strong correlation between avoidance intensity and spiked concentration. A two-year effluent monitoring case study also illustrates how this biomonitoring method is suitable for real-time on-site monitoring, and shows a promising non-targeted approach for characterising complex micropollutant discharge variability at WWTP effluents, which today remains poorly understood.

Early environmental exposure to oxytetracycline in Danio rerio may contribute to neurobehavioral abnormalities in adult zebrafish

The common antibiotic oxytetracycline (OTC) is nowadays commonly found in natural aquatic environments. However, the underlying mechanisms of low-dose OTC exposure and its neurotoxic effects on aquatic animals remain unknown. In this study, we exposed zebrafish larvae to environmental concentrations of OTC in early life and performed neurobehavioral, 16S rRNA gene sequencing, and transcriptomic analyses. OTC exposure resulted in hyperactivity of larvae and a significant reduction in the number of neurons in the midbrain. The expression levels of 15 genes related to neural function changed. Additionally, the composition of 65 genera of the gut microbiota of larvae was altered, which may be one of the reasons for the abnormal neural development. We further studied the long-term outcomes among adult fish long after cessation of OTC exposure. OTC treatment caused adult fish to be depressive and impulsive, symbolizing bipolar disorder. Adult fish exposed to OTC had significantly fewer neurons and their gut bacteria composition did not recover 104 days after terminating OTC exposure. Finally, we analyzed the correlation between the gut microbiota of larvae, genes related to neural function, and metabolites of adult fish brain tissue. The results showed that the abundance of several members of the biome in larvae was related to the transcription levels of genes related to neural function, which were related to the metabolic levels in the adult brain. In conclusion, our study showed that early-life exposure to environmental concentrations of OTC can lead to persistent neurobehavioral abnormalities until adulthood through dysbiosis in the gut microbiota.

Impaired Physiological Responses and Neurotoxicity Induced by a Chlorpyrifos-Based Formulation in Caenorhabditis elegans are not Solely Dependent on the Active Ingredient

The current massive and indiscriminate agrochemicals usage, which is inexorably linked to the toxic consequences to the environment and people, represents a great concern. Our work aimed to compare the toxicity induced by chlorpyrifos in its pure form (CPF) with that of a commercial formulation containing allegedly inert ingredients (CBCF) using Caenorhabditis elegans as in vivo model. After a 48h exposure period, CBCF was 14 times more lethal than CPF; Hatching, brood size, body length and motor-related behavioral parameters were decreased, but these effects were significantly higher in CBCF-exposed worms. Additionally, CBCF induced significant morphological changes in cholinergic neurons, which are associated with the motor-related behavioral parameters. Finally, by analyzing the CBCF, were detected the presence of potentially-toxic metals that were not specified in the label. The presented results highlight the toxicological relevance of components present in the commercial formulations of pesticides, which have been claimed as inert compounds.

Mechanistic insights into phenanthrene-triggered oxidative stress-associated neurotoxicity, genotoxicity, and behavioral disturbances toward the brandling worm (Eisenia fetida) brain: The need for an ecotoxicological evaluation

In this study, earthworm (Eisenia fetida) brain was chosen as targeted receptors to probe the mechanisms of oxidative stress-related neurotoxicity, genotoxicity, and behavioral disturbances triggered by PHE. Results showed that PHE stress can initiate significant amounts of ROS, thus triggering oxidative stress in E. fetida brain. These effects were accompanied by a significant increase of damage to macromolecules DNA and lipids, resulting in severe oxidative effects. PHE exposure can induce AChE inhibition by ROS-induced injury and the accumulation of excess ACh at the nicotinic post-synaptic membrane, thus inducing aggravated neurological dysfunction and neurotoxicity of E. fetida through an oxidative stress pathway. Moreover, the burrowing behavior of earthworms was disturbed by oxidative stress-induced neurotoxicity after exposure to PHE. Furthermore, the abnormal mRNA expression profiles of oxidative stress- and neurotoxicity-related genes in worm brain were induced by PHE stress. The IBR results suggested that E. fetida brain was suffered more serious damage caused by PHE under higher doses and long-term exposure. Taken together, PHE exposure can trigger oxidative stress-mediated neurotoxicity and genotoxicity in worm brain and behavioral disorder through ROS-induced damage. This study is of great significance to evaluate the harmful effects of PHE and its mechanisms on soil ecological health.

Neurotoxicity of polystyrene nanoplastics with different particle sizes at environment-related concentrations on early zebrafish embryos

Nanoplastics (NPs) have received global attention due to their wide application and detection in various environmental or biological media. NPs can penetrate physical barriers and accumulate in organisms after being ingested, producing a variety of toxic effects and possessing particle size-dependent effects, distinguishing them from traditional contaminants. This paper explored the neurotoxicity of polystyrene (PS)-NPs of different particle sizes on zebrafish (Danio rerio) embryos at environmental concentrations at the tissue and molecular levels using visualized transgenic zebrafish. Results showed that all particle sizes of PS-NPs produced developmental toxicity in zebrafish embryos and induced neuronal loss, axonal deletion/shortening/hybridization, and developmental and apoptotic-related genetic alterations, ultimately leading to behavioral abnormalities. PS-NPs with smaller sizes may have more severe neurotoxicity due to their entry into the embryo and brain through the chorionic pore before hatching. In addition, PS-NPs at 100 nm and 1000 nm can specifically interfere with GABAergic, cholinergic or serotonergic system and affect neuronal signaling. Our results reveal the neurotoxic risk of NPs, and smaller particle-size NPs may have a greater ecological risk. We anticipate that our study can provide a basis for exploring the toxicity mechanisms of NPs and the environmental risk assessment of NPs.

Cadmium effects on the freshwater teleost Prochilodus lineatus: Accumulation and biochemical, genotoxic, and behavioural biomarkers

In order to evaluate the effects of Cd, juveniles of the Neotropical fish Prochilodus lineatus were exposed to 1 and 10 μg L^-1 Cd, for 24 and 96 h. Fish exposed to Cd showed metal accumulation in the gills, kidney, and liver, an increase in DNA damage in erythrocytes, and an increase in lipid peroxidation (LPO) in the kidney. Cd exposure also caused a reduction in catalase activity, metallothionein induction, and LPO in the liver. Cd stimulated the swimming activity of exposed fish, resulting in longer swimming times and distances travelled, especially for the shortest exposure time. Changes in acetylcholinesterase activity (AChE) in the muscle and brain are probably related to these behavioural responses. These results show that Cd affects the functioning of several organs in P. lineatus, which is indicated by the genotoxic damage and changes in the AChE and swimming pattern of the exposed fish.

Heart rate and behavioral responses in three phylogenetically distant aquatic model organisms exposed to environmental concentrations of carbaryl and fenitrothion

Carbaryl and fenitrothion are two insecticides sharing a common mode of action, the inhibition of the acetylcholinesterase (AChE) activity. Their use is now regulated or banned in different countries, and the environmental levels of both compounds in aquatic ecosystems have decreased to the range of pg/L to ng/L. As these concentrations are below the non-observed-adverse-effect-concentrations (NOAEC) for AChE inhibition reported for both compounds in aquatic organisms, there is a general agreement that the current levels of these two chemicals are safe for aquatic organisms. In this study we have exposed zebrafish, Japanese medaka and Daphnia magna to concentrations of carbaryl and fenitrothion under their NOAECs for 24-h, and the effects on heart rate (HR), basal locomotor activity (BLA), visual motor response (VMR), startle response (SR) and its habituation have been evaluated. Both pesticides increased the HR in the three selected model organisms, although the intensity of this effect was chemical-, concentration- and organism-dependent. The exposure to both pesticides also led to a decrease in BLA and an increase in VMR in all three species, although this effect was only significant in zebrafish larvae. For SR and its habituation, the response profile was more species- and concentration-specific. The results presented in this manuscript demonstrate that concentrations of carbaryl and fenitrothion well below their respective NOAECs induce tachycardia and the impairment of ecologically relevant behaviors in phylogenetically distinct aquatic model organisms, both vertebrates and invertebrates, emphasizing the need to include this range of concentrations in the environmental risk assessment.