Adverse effects of bifenthrin exposure on neurobehavior and neurodevelopment in a zebrafish embryo/larvae model

2-Ethylhexanol induces autism-like neurobehavior and neurodevelopmental disorders in zebrafish

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental disorder characterized by impaired social interaction, communication deficits, and repetitive behaviors. The rising prevalence of ASD necessitates intensified research. 2-Ethylhexanol, is a synthetically produced branched-chain alcohol used in plasticizer synthesis. However, its role in ASD-like symptoms and potential neurotoxic effects remains largely unexplored. This study employed a multimodal neurotoxicity testing approach to evaluate the adverse effects of 2-ethylhexanol on zebrafish neurobehavior and neurodevelopment. Wild-type and transgenic zebrafish lines (tg(elavl3: eGFP) and tg(mbp:mGFP)) were exposed to 2-ethylhexanol for 120 hours post-fertilization (hpf). Significant disruptions were observed in early motor activities, such as tail coiling and touch-evoked responses, which aligned with later locomotor impairments, including reduced distance traveled and increased turn angle. These behavioral changes were accompanied by decreased levels of acetylcholinesterase (AChE) and dopamine (DA). Deficits in social behavior (e.g., reduced body contact) were identified, potentially linked to altered transcription of autism-associated genes (adsl, eif4a1, mbd5, vps13b, and tsc1b). Abnormalities in neurogenesis, including reduced brain and spinal cord size, and demyelination of oligodendrocytes and Schwann cells, were evident. Additionally, transcriptional changes related to neurodevelopment (gap43, manf, sox2) and neurotransmitter signaling (drd1, mao, htr1bd) were observed. Our findings provide compelling evidence that 2-ethylhexanol exposure leads to neurodevelopmental impairments and behavioral alterations reminiscent of ASD. This research highlights the importance of further investigations to assess the potential risks of 2-ethylhexanol exposure and develop prevention and mitigation strategies.

Sublethal exposures to bifenthrin impact stress responses and behavior of juvenile Chinook salmon

Juvenile Chinook salmon (Oncorhynchus tshawytscha) populations have decreased substantially in the Sacramento-San Joaquin (California, USA) Delta (Delta) over the past decades, so considerably that two of the four genetically distinct runs are now listed in the Endangered Species Act. One factor responsible for this decline is the presence of contaminants in the Delta. Insecticides, used globally in agricultural, industrial, and household settings, have the potential to contaminate nearby aquatic systems through spray drift, runoff, and direct wastewater discharge. Chinook salmon are therefore exposed, as they out-migrate through the Delta, to insecticides that have been associated with adverse biological effects in aquatic species, ranging from sublethal impairments to lethality. The goal of this study was to assess whether bifenthrin, a ubiquitous pyrethroid insecticide in the Delta, affects thermal tolerance, hypoxia tolerance, and behavior of juvenile Chinook salmon. Fish were exposed for 10 days to environmentally relevant (125 ng/L, associated with resulting body residues in wild-caught fish) and sublethal bifenthrin concentrations (500 and 1,000 ng/L). Juvenile Chinook salmon exposed to bifenthrin were tolerant to increases in hypoxia but not temperature. Fish exposed to bifenthrin showed dose-dependent behavior changes: hypoactivity at 125 ng/L, hyperactivity at 1,000 ng/L, and reduced anxiety-like behavior, including lower thigmotaxis and decreased social interaction. The results revealed that exposure to sublethal concentrations of bifenthrin, leading to environmentally relevant body burden residues, significantly altered upper thermal tolerance and caused nonlinear behavioral changes. The study suggests the existence of behavioral effect thresholds in wild-caught fish and emphasizes that higher concentrations of contaminants may impair Chinook salmon's ability to avoid predators in natural environments.

Developmental effects of fenpropathrin on zebrafish (Danio rerio) embryo-larvae: Toxic endpoints and potential mechanism

Fenpropathrin (FEN), a highly efficient and broad-spectrum synthetic pyrethroid insecticide. Although sufficient concern has been given to the negative impacts of FEN on non-target organisms, limited knowledge exists regarding the developmental effects of FEN. In this study, effects of FEN (0.45, 1.35, 4.05, and 12.15 μg/L) on various early life-stage endpoints of zebrafish were investigated from 3 to 144 h post-fertilization (hpf) in order to disclose the developmental effects and underlying mechanisms caused by FEN. The results indicate that exposure to FEN induced developmental toxicity in zebrafish, including decreased heart rate, reduced blood flow, shorter body length, smaller eye size, non-inflated swim bladder, and disrupted craniofacial chondrogenesis, which were possibly due to a significant decrease in the levels of thyroxine (T4), triiodothyronine (T3), insulin-like growth factor-1 (IGF-1), and growth hormone (GH), increase in lipid accumulation, and alteration in the contents of total cholesterol (T-CHO) and triglyceride (TG) in larvae exposed to FEN. Besides, FEN exposure also resulted in the inhibition of spontaneous movement of embryo at 24 hpf, a decline in touch evoke response (TER) at 72 hpf, and a reduction in free-swimming activity at 144 hpf, as well as the larval activity at 144 hpf during the dark-light transition stimulus. Mechanistic examinations have shown that FEN treatment inhibits the activities of AChE and elevates the ACh levels. In addition, FEN exposure increased ROS levels and altered the levels of malondialdehyde (MDA), and induced apoptosis as determined by acridine orange staining and elevated caspase-3 levels, suggesting that the involvement of oxidative stress and apoptosis in FEN-induced developmental toxicity of embryos. Transcriptome sequencing of larvae showed that FEN altered the expressions of multiple metabolic and nervous system pathways, including PPAR signaling pathway, lipid metabolism pathway, carbohydrate metabolism pathway, retinol metabolism pathway, and neuroactive ligand-receptor interaction pathway, demonstrating that FEN alters the normal development of zebrafish embryos, and multiple pathways mediating the FEN-induced developmental toxicity. Overall, these findings enhance our understanding of the developmental toxic effects of FEN and provide fundamental data for assessing the risk of FEN on non-target organisms.

Tetrachlorantraniliprole induces neurodevelopmental toxicity through oxidative stress-mediated apoptosis and dysregulation of Wnt signaling pathway

Tetrachlorantraniliprole (TCTP) is a novel bisamide insecticide and widely used to protect against lepidopteran insect species. However, the application of TCTP in rice fields often leads to water pollution, posing threats to aquatic organisms and potentially to human health. Few studies have assessed the toxic effects of TCTP on aquatic animals. In this study, we used zebrafish as a model organism to evaluate the toxicity of TCTP. Our findings indicated that TCTP adversely affected the development of zebrafish larvae, impacting parameters such as heart rate, body length, and pericardial edema. Exposure to TCTP resulted in the increased embryo mortality along with higher concentrations of the compound. The expression of neurodevelopment-related genes was inhibited in embryos exposed to TCTP. Hematoxylin and eosin (HE) staining revealed that TCTP caused damage to the brain cells of the embryos. Behavioral analysis showed a reduction in activity of the larvaes, which aligned with a decrease in acetylcholinesterase (AChE) activity. Additionally, RNA sequencing (RNA-seq) was employed to elucidate the mechanisms of toxicity. GO and KEGG analysis identified that the pathways were related to oxidative stress, apoptosis and Wnt signaling. We observed an increase of reactive oxygen species (ROS) and Ca²/Mg²-ATPase activity, while antioxidant enzyme activities (SOD, MDA, CAT, Na/K-ATPase and T-ATPase) were significantly decreased in TCTP-exposed groups. Furthermore, TCTP induced brain cells apoptosis, as evidenced by the upregulation of pro-apoptotic genes (bax, p53, TNFα, caspase3 and caspase9) and the downregulation of anti-apoptotic gene (bcl2). Moreover, TCTP increased the expression of genes involved in Wnt signaling pathway. Notably, oxidative stress and neuronal damage induced by TCTP could be mitigated by astaxanthin, an antioxidant. Additionally, IWR-1, an inhibitor of Wnt signaling pathway, effectively alleviated the upregulation of genes associated with TCTP treatment and inhibited oxidative stress-induced apoptosis. In conclusion, this study demonstrated TCTP-induced defects of neurodevelopment and the brain cells in zebrafish larvae which were primarily driven by oxidative stress-induced apoptosis and dysregulation of Wnt signaling pathway. Importantly, these toxic phenotypes can be rescued by treatment with astaxanthin or IWR-1.

Transgenerational neurotoxic effects of triphenyltin on marine medaka: Impaired dopaminergic system function

Triphenyltin (TPT), a widely used environmental contaminant in antifouling paints, is known for its neurotoxic effects. To investigate the multigenerational impacts of long-term exposure (6 weeks) to environmental concentrations of TPT (100 ng/L) on either parent, we performed mixed mating between control and exposed groups (males or females). Although there was no direct contact with TPT in the subsequent generations, both the first and second generations displayed behavioral abnormalities, including reduced activity and impaired cognitive function, with pronounced gender differences and anxiety-like behaviors. Females were more susceptible than males, displaying a significantly increased time spent in the mirror-proximal zone in both F1 and F2 generations. Additionally, F0 females exhibited a marked reduction in the time spent in the bright area, further supporting the role of sex differences in behavioral responses. Notably, the maternal contribution of marine medaka (Oryzias melastigma) played a more significant role in the inheritance of TPT-induced cognitive deficits. A reduction in DA levels and AChE activity was observed across generations, regardless of gender, underscoring the critical role of DA-AChE balance in maintaining cognitive function. Additionally, gender differences and the hereditary effects of TPT exposure on anxiety-like behaviors were strongly associated with the transcriptional regulation of pparγ and gst. Impaired transcription of key genes in the dopaminergic system resulted in reduced DA levels, with the intergenerational transmission of mao being closely linked to behavioral impairments. In summary, TPT-induced neurotoxicity presents both hereditary effects and gender-specific differences, emphasizing the maternal influence in the inheritance of cognitive abilities and shedding light on the genetic impact of parental exposure.

Unraveling the degradation mechanism of multiple pyrethroid insecticides by Pseudomonas aeruginosa and its environmental bioremediation potential

Extensive use of pyrethroid insecticides poses significant risks to both ecological ecosystems and human beings. Herein, Pseudomonas aeruginosa PAO1 exhibited exceptional degradation capabilities towards a range of pyrethroid family insecticides including etofenprox, bifenthrin, tetramethrin, D-cypermethrin, allethrin, and permethrin, with a degradation efficiency reaching over 84 % within 36 h (50 mg·L-1). Strain PAO1 demonstrated effective soil bioremediation by removing etofenprox across different concentrations (25-100 mg·kg-1), with a degradation efficiency over 77 % within 15 days. Additionally, 16S rDNA high-throughput sequencing analysis revealed that introduction of strain PAO1 and etofenprox had a notable impact on the soil microbial community. Strain PAO1 displayed a synergistic effect with local degrading bacteria or flora to degrade etofenprox. UPLC-MS/MS analysis identified 2-(4-ethoxyphenyl) propan-2-ol and 3-phenoxybenzoic acid as the major metabolites of etofenprox biodegradation. A new esterase gene (estA) containing conserved motif (GDSL) and catalytic triad (Ser38, Asp310 and His313) was cloned from strain PAO1. Enzyme activity and gene knockout experiments confirmed the pivotal role of estA in pyrethroid biodegradation. The findings from this study shed a new light on elucidating the degradation mechanism of P. aeruginosa PAO1 and present a useful agent for development of effective pyrethroid bioremediation strategies.

Biomarker responses in fish caged in a rice field during a bifenthrin application

The use of pesticides in integrated rice-fish farming could have an impact on fish health. The present study aimed to evaluate, for the first time, the biological effects of the insecticide bifenthrin on fish (Piaractus mesopotamicus and Hoplosternum littorale) using a caging experiment. Fish were divided into two sites: control (C) and bifenthrin exposure (BF). Two cages (n = 8 fish/cage) per species were placed separately at each site. The BF application (Seizer ®) was carried out with a coastal sprayer according to the BF recommended dose for rice cultivation (0.1 L/ha). After 72 h, fish were collected, and gills, liver, brain, and muscle were dissected for the analysis of biomarkers of accumulation, oxidative stress, and neurotoxicity. In P. mesopotamicus, the main changes were observed in the muscle, where BF accumulated and induced neurotoxicity (inhibition of cholinesterase activity) and oxidative stress (activation of antioxidant enzymes, decreased glutathione levels, increased lipid peroxidation). The gills and liver also showed changes in some markers of the antioxidant system. In H. littorale, BF exposure induced changes in oxidative stress biomarkers in liver (activation of antioxidant enzymes and lipid peroxidation) and gill tissues (alteration in antioxidant markers). These results show that the use of bifenthrin in rice fields poses a risk to fish farming under current pesticide management practices. Furthermore, its use could affect other species in these agroecosystems, highlighting the need for further studies to assess the ecological and productive consequences in a context of increasing pyrethroid use worldwide.

Adverse effects of diethyl phthalate and butyl benzyl phthalate on circadian rhythms and sleep patterns in zebrafish larvae

The zebrafish, a diurnal vertebrate, is commonly used in circadian rhythm studies due to its genetic and neurological similarities to humans. Circadian rhythms, which regulate sleep, neurotransmitter, behavior, and physiological responses to environmental changes, can be disrupted by various environmental factors. Phthalic acid esters (PAEs) are pervasive endocrine disruptors that individuals are frequently exposed to in daily life. However, the impact of PAEs on circadian rhythms during early development remains poorly understood. This study aimed to investigate the effects of exposure to diethyl phthalate (DEP) and butyl benzyl phthalate (BBzP) on the behavior and circadian rhythms of developing zebrafish larvae using a series of layered assays. Zebrafish larvae were exposed to the two PAEs from less than 2 hour post-fertilization (hpf) until 96 hpf. The results demonstrated a concentration-dependent reduction in tail coiling (TC), touch-evoked response (TER), and locomotor activity, alongside an increase in sleep time and alterations in sleep bouts and sleep latency during both 24-hour and Light1/Dark/Light2 (7/10/7-hour) periods. Additionally, exposure to BBzP led to increased acetylcholinesterase (AChE) and dopamine (DA) levels, and a decrease in 5-hydroxytryptamine (5-HT) levels. Gene expression analysis revealed that DEP and BBzP exposure increased the expression of circadian rhythm and light-response-related genes. In conclusion, exposure to these PAEs disrupts the circadian rhythm of zebrafish larvae, providing novel insights into the developmental impact of these common environmental contaminants. Further research is needed to understand the broader implications of these findings for human health and environmental safety.

Non-lethal biomarkers as promising tools for fish health assessment: In situ exposure to bifenthrin as a case study

Non-lethal biomonitoring should provide an innovative approach to establish bioethical protocols for the management of both aquaculture and wild fisheries resources. We aimed to assess non-lethal biomarkers in Piaractus mesopotamicus caged in a rice field during a bifenthrin (BF) application. We analyzed parameters related to the immune system, energy metabolism and oxidative stress in fish skin mucus and blood plasma. Fish exposed to BF showed a significant increase in skin mucus glucose levels and the enzymatic activities of protease, alkaline phosphatase and superoxide dismutase. Regarding plasmatic parameters, BF increased the levels of glucose, total protein and albumin, but decreased triglycerides. In addition, increased activities of lysozyme and alkaline phosphatase were found in the blood plasma of exposed fish. Our results indicated an increased energy demand, altered immune function and a mild oxidative stress response in fish exposed in situ to BF. We have shown that skin mucus and blood plasma are very promising matrices for the development of non-lethal biomarkers to assess fish health in a stressed environment.

Bifenthrin Caused Parkinson's-Like Symptoms Via Mitochondrial Autophagy and Ferroptosis Pathway Stereoselectively in Parkin-/- Mice and C57BL/6 Mice

It has been proposed that pyrethroid exposure contributes to the increasing prevalence of neurodegenerative diseases. However, the potential mechanisms remain unclear. The current study aimed to investigate the effects of the widely used pyrethroid bifenthrin on Parkinson's disease (PD) risk. Bifenthrin (1S-cis-bifenthrin, 1R-cis-bifenthrin, raceme) was administered to male Parkin-/- mice and C57BL/6 mice by oral gavage at a dose of 10 mg/kg bw/day for 28 days. Bifenthrin exposure significantly increased the time of pole climbing and decreased the period of rotarod running, indicating that bifenthrin decreased motor coordination in Parkin-/- mice, which was more evident by 1S-cis-bifenthrin. Furthermore, administration of bifenthrin induced obvious decreases in tyrosine hydroxylase (TH)+ cell count and the protein expression of TH. Increased protein of mitochondrial autophagy LC3B and p62 was observed after exposure to bifenthrin. Increased iron deposition and protein expression of iron transport transferrin (Tf) and transferrin receptor 2 (TfR2) was detected. 1S-cis-bifenthrin bound with Tf, TfR2, and GPX4 with lower binding energies than 1R-cis-bifenthrin, resulting in stronger interactions with these proteins. These results show structure-dependent PD-like effects of bifenthrin on motor activity and coordination associated with the disturbed mitochondrial autophagy and ferroptosis-related pathway. These data demonstrate that pyrethroid exposure increases the potential of Parkinson's-like symptoms via the ferroptosis pathway in Parkin-/- mice that is more pronounced than in C57BL/6 mice, providing a prospective enantioselective toxic effect of environmental neurotoxins on PD risk.

Mixture effect of parental exposure to triazophos and fenvalerate on the early development of zebrafish offspring

Triazophos (TRI) and fenvalerate (FEN) have been extensively used in the world and frequently coexist in the water environments, might pose health risk to aquatic species. However, investigations of their mixture toxic effects on offspring after parental exposure have been neglected, especially for aquatic vertebrates such fish. To address this knowledge gap, parental zebrafish (F0 generation) were exposed to TRI, FEN and their mixture for 60 days, as well as the embryos (F1 generation) were hatched without or with continued corresponding exposures at the same concentrations until 7 days post fertilization. The results exhibited that exposure to TRI and FEN altered the expression levels of biomarkers associated with several biological processes, such as apoptosis and inflammatory response. Compared to individual exposure in the F1 generation, the co-exposure to TRI and FEN resulted in increased the expression of T4 and cc-chem mRNA and decreased the expression of ROS, trα, il-8, and gpx mRNA when the F0 generation was similarly exposed. These results revealed that the co-exposure to TRI and FEN has detrimental effects on fish progeny following parental exposure, even if the progeny are not directly exposed to the pesticides, and such negative effects may be intensified if the offspring continue to be exposed. This study enhances the understanding of the harmful impacts of parental exposure to the pesticide mixture on descendants and holds implications for the ecological risk assessment of pesticide mixtures in aquatic vertebrates. Further mechanistic studies are necessary to gain a deeper insight into the mixture effects of pesticides and other kinds of pollutants on subsequent offspring following parental exposure.

Embryonic Zebrafish as a Model for Investigating the Interaction between Environmental Pollutants and Neurodegenerative Disorders

Environmental pollutants have been linked to neurotoxicity and are proposed to contribute to neurodegenerative disorders. The zebrafish model provides a high-throughput platform for large-scale chemical screening and toxicity assessment and is widely accepted as an important animal model for the investigation of neurodegenerative disorders. Although recent studies explore the roles of environmental pollutants in neurodegenerative disorders in zebrafish models, current knowledge of the mechanisms of environmentally induced neurodegenerative disorders is relatively complex and overlapping. This review primarily discusses utilizing embryonic zebrafish as the model to investigate environmental pollutants-related neurodegenerative disease. We also review current applicable approaches and important biomarkers to unravel the underlying mechanism of environmentally related neurodegenerative disorders. We found embryonic zebrafish to be a powerful tool that provides a platform for evaluating neurotoxicity triggered by environmentally relevant concentrations of neurotoxic compounds. Additionally, using variable approaches to assess neurotoxicity in the embryonic zebrafish allows researchers to have insights into the complex interaction between environmental pollutants and neurodegenerative disorders and, ultimately, an understanding of the underlying mechanisms related to environmental toxicants.

Detrimental impacts and QSAR baseline toxicity assessment of Japanese medaka embryos exposed to methylparaben and its halogenated byproducts

Despite the theoretical risk of forming halogenated methylparabens (halo-MePs) during water chlorination in the absence or presence of bromide ions, there remains a lack of in vivo toxicological assessments on vertebrate organisms for halo-MePs. This research addresses these gaps by investigating the lethal (assessed by embryo coagulation) or sub-lethal (assessed by hatching success/heartbeat rate) toxicity and teratogenicity (assessed by deformity rate) of MeP and its mono- and di-halogen derivatives (Cl- or Br-) using Japanese medaka embryos. In assessing selected apical endpoints to discern patterns in physiological or biochemical alterations, heightened toxic impacts were observed for halo-MePs compared to MeP. These include a higher incidence of embryo coagulation (4-36 fold), heartbeat rate decrement (11-36 fold), deformity rate increment (32-223 fold), hatching success decrement (11-59 fold), and an increase in Reactive Oxygen Species (ROS) level (1.2-7.4 fold)/Catalase (CAT) activity (1.7-2.8 fold). Experimentally determined LC50 values are correlated and predicted using a Quantitative Structure Activity Relationship (QSAR) based on the speciation-corrected liposome-water distribution ratio (Dlipw, pH 7.5). The QSAR baseline toxicity aligns well with (sub)lethal toxicity and teratogenicity, as evidenced by toxic ratio (TR) analysis showing TR < 10 for MeP exposure in all cases, while significant specific or reactive toxicity was found for halo-MeP exposure, with TR > 10 observed (excepting three values). Our extensive findings contribute novel insights into the intricate interplay of embryonic toxicity during the early-life-stage of Japanese medaka, with a specific focus on highlighting the potential hazards associated with halo-MePs compared to the parent compound MeP.

Toxic responses of environmental concentrations of bifenthrin in larval freshwater snail Bellamya aeruginosa

Bifenthrin (BF) is ubiquitous in aquatic environments, and studies have indicated that environmental concentrations of BF could cause neurotoxicity and oxidative damage in fish and decrease the abundance of aquatic insects. However, little information is available on the toxicity of BF in freshwater benthic mollusks. Bellamya aeruginosa (B. aeruginosa) is a key benthic fauna species in aquatic ecosystems, and has extremely high economic and ecological values. In this study, larval B. aeruginosa within 24 h of birth were exposed to 0, 30 or 300 ng/L of BF for 30 days, and then the toxic effects from molecular to individual levels were comprehensively evaluated in all the three treatment groups. It was found that BF at 300 ng/L caused the mortality of snails. Furthermore, BF affected snail behaviors, evidenced by reduced crawling distance and crawling speed. The hepatopancreas of snails in the two BF exposure groups showed significant pathological changes, including increase in the number of yellow granules and occurrence of hemocyte infiltration, epithelial cell thinning, and necrosis. The levels of ROS and MDA were significantly increased after exposure to 300 ng/L BF, and the activities of two antioxidant enzymes SOD and CAT were increased significantly. GSH content decreased significantly after BF exposure, indicating the occurrence of oxidative damage in snails. Transcriptomic results showed that differentially expressed genes (DEGs) were significantly enriched in pathways related to metabolism and neurotoxicity (e.g., oxidative phosphorylation and Parkinson disease), and these results were consistent with those in individual and biochemical levels above. The study indicates that environmental concentration of BF results in decreased survival rates, sluggish behavior, histopathological lesions, oxidative damage, and transcriptomic changes in the larvae of B. aeruginosa. Thus, exposure of larval snails to BF in the wild at concentrations similar to those used in this study might have adverse consequences at the population level. These findings provide a theoretical basis for further assessing the ecological risk of BF to aquatic gastropods.

Spatial distribution and risk assessment of pyrethroid insecticides in surface waters of East China Sea estuaries

Pyrethroid insecticides are the most commonly used household insecticides and pose substantial risks to marine aquatic organisms. many studies have detected pyrethroid insecticides in the waters and estuaries of the western United States, but their distributions within western Pacific estuaries have not been reported. Accordingly, we used high-throughput organic analyses combined with high volume solid-phase extraction to comprehensively assess 13 pyrethroid insecticides in East China Sea estuaries and the Huangpu River. The results demonstrated the presence of various ∑13pyrethroid insecticides in East China Sea estuaries (mean and median values of 8.45 ± 5.57 and 7.78 ng L-1, respectively), among which cypermethrin was the primary contaminant. The concentrations of ∑12pyrethroid insecticide detected in the surface waters at the Huangpu River (mean 6.7 ng L-1, outlet 16.4 ng L-1) were higher than those in the Shanghai estuary (4.7 ng L-1), suggesting that runoff from inland areas is a notable source of insecticides. Wetlands reduced the amount of runoff containing pyrethroid insecticides that reached the ocean. Several factors influenced pesticide distributions in East China Sea estuaries, and higher proportions were derived from agricultural sources than from urban sources, with a higher proportion of agricultural sources than urban sources, influenced by anthropogenic use in the region. Permethrin and cypermethrin were the main compounds contributing to the high ecological risk in the estuaries. Consequently, to prevent risks to marine aquatic life, policymakers should aim to reduce insecticide contaminants derived from urban and agricultural sources.

The uses of zebrafish (Danio rerio) as an in vivo model for toxicological studies: A review based on bibliometrics

An in vivo model is necessary for toxicology. This review analyzed the uses of zebrafish (Danio rerio) in toxicology based on bibliometrics. Totally 56,816 publications about zebrafish from 2002 to 2023 were found in Web of Science Core Collection, with Toxicology as the top 6 among all disciplines. Accordingly, the bibliometric map reveals that "toxicity" has become a hot keyword. It further reveals that the most common exposure types include acute, chronic, and combined exposure. The toxicological effects include behavioral, intestinal, cardiovascular, hepatic, endocrine toxicity, neurotoxicity, immunotoxicity, genotoxicity, and reproductive and transgenerational toxicity. The mechanisms include oxidative stress, inflammation, autophagy, and dysbiosis of gut microbiota. The toxicants commonly evaluated by using zebrafish model include nanomaterials, arsenic, metals, bisphenol, and dioxin. Overall, zebrafish provide a unique and well-accepted model to investigate the toxicological effects and mechanisms. We also discussed the possible ways to address some of the limitations of zebrafish model, such as the combination of human organoids to avoid species differences.

The Neurotoxic Effect of Environmental Temperature Variation in Adult Zebrafish (Danio rerio)

Neurotoxicity consists of the altered functionality of the nervous system caused by exposure to chemical agents or altered chemical-physical parameters. The neurotoxic effect can be evaluated from the molecular to the behavioural level. The zebrafish Danio rerio is a model organism used in many research fields, including ecotoxicology and neurotoxicology. Recent studies by our research group have demonstrated that the exposure of adult zebrafish to low (18 °C) or high (34 °C) temperatures alters their brain proteome and fish behaviour compared to control (26 °C). These results showed that thermal variation alters the functionality of the nervous system, suggesting a temperature-induced neurotoxic effect. To demonstrate that temperature variation can be counted among the factors that generate neurotoxicity, eight different protein datasets, previously published by our research group, were subjected to new analyses using an integrated proteomic approach by means of the Ingenuity Pathway Analysis (IPA) software (Release December 2022). The datasets consist of brain proteome analyses of wild type adult zebrafish kept at three different temperatures (18 °C, 26 °C, and 34 °C) for 4 days (acute) or 21 days (chronic treatment), and of BDNF+/- and BDNF-/- zebrafish kept at 26 °C or 34 °C for 21 days. The results (a) demonstrate that thermal alterations generate an effect that can be defined as neurotoxic (p value ≤ 0.05, activation Z score ≤ -2 or ≥2), (b) identify 16 proteins that can be used as hallmarks of the neurotoxic processes common to all the treatments applied and (c) provide three protein panels (p value ≤ 0.05) related to 18 °C, 34 °C, and BDNF depletion that can be linked to anxiety-like or boldness behaviour upon these treatments.