Environmental co-exposure to TBT and Cd caused neurotoxicity and thyroid endocrine disruption in zebrafish, a three-generation study in a simulated environment

Decrypting the skeletal toxicity of vertebrates caused by environmental pollutants from an evolutionary perspective: From fish to mammals

The rapid development of modern society has led to an increasing severity in the generation of new pollutants and the significant emission of old pollutants, exerting considerable pressure on the ecological environment and posing a serious threat to both biological survival and human health. The skeletal system, as a vital supportive structure and functional unit in organisms, is pivotal in maintaining body shape, safeguarding internal organs, storing minerals, and facilitating blood cell production. Although previous studies have uncovered the toxic effects of pollutants on vertebrate skeletal systems, there is a lack of comprehensive literature reviews in this field. Hence, this paper systematically summarizes the toxic effects and mechanisms of environmental pollutants on the skeletons of vertebrates based on the evolutionary context from fish to mammals. Our findings reveal that current research mainly focuses on fish and mammals, and the identified impact mechanisms mainly involve the regulation of bone signaling pathways, oxidative stress response, endocrine system disorders, and immune system dysfunction. This study aims to provide a comprehensive and systematic understanding of research on skeletal toxicity, while also promoting further research and development in related fields.

Neurobehavioral toxicity induced by combined exposure of micro/nanoplastics and triphenyltin in marine medaka (Oryzias melastigma)

Microplastics/nanoplastics (MNPs) inevitably coexist with other pollutants in the natural environment, making it crucial to study the interactions between MNPs and other pollutants as well as their combined toxic effects. In this study, we investigated neurotoxicity in marine medaka (Oryzias melastigma) exposed to polystyrene micro/nanoplastics (PS-MNPs), triphenyltin (TPT), and PS-MNPs + TPT from physiological, behavioral, biochemical, and genetic perspectives. The results showed that marine medaka exposed to 200 ng/L TPT or 200 μg/L PS-NPs alone exhibited some degree of neurodevelopmental deficit, albeit with no significant behavioral abnormalities observed. However, in the PS-MP single exposure group, the average acceleration of short-term behavioral indices was significantly increased by 78.81%, indicating a highly stress-responsive locomotor pattern exhibited by marine medaka. After exposure to PS-MNPs + TPT, the swimming ability of marine medaka significantly decreased. In addition, PS-MNPs + TPT exposure disrupted normal neural excitability as well as activated detoxification processes in marine medaka larvae. Notably, changes in neural-related genes suggested that combined exposure to PS-MNPs and TPT significantly increased the neurotoxic effects observed with exposure to PS-MNPs or TPT alone. Furthermore, compared to the PS-MPs + TPT group, PS-NPs + TPT significantly inhibited swimming behavior and thus exacerbated the neurotoxicity. Interestingly, the neurotoxicity of PS-MPs was more pronounced than that of PS-NPs in the exposure group alone. However, the addition of TPT significantly enhanced the neurotoxicity of PS-NPs compared to PS-MPs + TPT. Overall, the study underscores the combined neurotoxic effects of MNPs and TPT, providing in-depth insights into the ecotoxicological implications of MNPs coexisting with pollutants and furnishing comprehensive data.

Maternal exposure to tributyltin alters the breast milk, hormonal profile, and thyroid morphology of dams and induces sex-specific changes in neonate rat offspring

Tributyltin (TBT) is the chemical substance commonly used worldwide to prevent biofouling of vessels. Due to its ability to bioaccumulate and biomagnify, even after being banned, significant concentrations of TBT can be detected in sediment, affecting marine and human life. Although studies have shown that direct exposure to TBT alters physiological parameters in mammals, the relationship between exposure to TBT during pregnancy and lactation, considered critical windows for metabolic programming, has not been fully elucidated. Our hypothesis is that offspring whose mothers were exposed to TBT during critical stages of development may exhibit dysfunctions in endocrine-metabolic parameters. We used pregnant Wistar rats that were divided into groups and received the following treatments from gestational day 7 until the end of lactation by intragastric gavage: vehicle (ethanol 0.01%; Control), low TBT dose (100 ng/kg of body weight (bw)/day; TBT100ng) and high TBT dose (1000 ng/kg bw/day; TBT1000ng). Dams and offspring at birth and weaning (21 days old) were studied. Maternal exposure to TBT promoted dose-dependent changes in dams. The findings for adiposity, milk composition and lipid profile were more pronounced in TBT100 ng dam; however, thyroid morphology was altered in TBT1000 ng dam. Female offspring were differentially affected by the dose of exposure. At birth, females in the TBT100ng group had low body weight, lower naso-anal length (NAL), and higher plasma T4, and at weaning, females in the TBT100ng group had lower insulin and leptin levels. Females in the TBT1000ng group had lower NAL at birth and lower leptinemia and weight of white adipose tissue at weaning. Male offspring from TBT groups showed high T3 at birth, without biometric alterations at birth or weaning. Despite these findings, both sexes exhibited dose-dependent morphological changes in the thyroid gland. Thus, maternal exposure to TBT constitutes an important route of contamination for both dams and offspring.

Neurotoxicity of Combined Exposure to the Heavy Metals (Pb and As) in Zebrafish (Danio rerio)

Lead (Pb) and arsenic (As) are commonly occurring heavy metals in the environment and produce detrimental impacts on the central nervous system. Although they have both been indicated to exhibit neurotoxic properties, it is not known if they have joint effects, and their mechanisms of action are likewise unknown. In this study, zebrafish were exposed to different concentrations of Pb (40 μg/L, 4 mg/L), As (32 μg/L, 3.2 mg/L) and their combinations (40 μg/L + 32 μg/L, 4 mg/L + 3.2 mg/L) for 30 days. The histopathological analyses showed significant brain damage characterized by glial scar formation and ventricular enlargement in all exposed groups. In addition, either Pb or As staining inhibited the swimming speed of zebrafish, which was enhanced by their high concentrations in a mixture. To elucidate the underlying mechanisms, we examined changes in acetylcholinesterase (AChE) activity, neurotransmitter (dopamine, 5-hydroxytryptamine) levels, HPI axis-related hormone (cortisol and epinephrine) contents and neurodevelopment-related gene expression in zebrafish brain. The observations suggest that combined exposure to Pb and As can cause abnormalities in swimming behavior and ultimately exacerbate neurotoxicity in zebrafish by interfering with the cholinergic system, dopamine and 5-hydroxytryptamine signaling, HPI axis function as well as neuronal development. This study provides an important theoretical basis for the mixed exposure of heavy metals and their toxicity to aquatic organisms.

Tributyltin causes generational neurodevelopmental toxicity and the protective effect of folic acid in zebrafish

Tributyltin (TBT), a common organotin environmental pollutant, may pose a threat to human development during critical early-life periods. We aimed to assess the neurodevelopmental intergenerational toxicity of early-life exposure to TBT and the protective effect of DNA methyl donor folic acid (FA). Specifically, after early-life exposure (1-21 days post-fertilization, dpf) to TBT (0, 1, 10 and 100 ng/L), zebrafish (Danio rerio) were cultured in clean medium until sexual maturity. The exposed females were mated with unexposed males to produce embryos (F1). The F1 generation were cultured (4-120 hours post-fertilization, hpf) with and without 1 mmol/L FA. The neurotoxic effects of early-life TBT exposure for zebrafish and their offspring (F1) were significantly enhanced anxiety and reduced aggression, decreased gene expression of DNA methyltransferase in the brain and increased serotonin levels in the body. Moreover, the intergenerational neurodevelopmental toxicity, as manifested in the F1 generation, was attenuated by FA supplementation. In summary, early-life TBT exposure led to intergenerational neurodevelopmental deficits in zebrafish, and DNA methyl donors had a protective effect on F1 neurodevelopment, which can inform the prevention and treatment of intergenerational neurotoxicity due to organotin pollutants.

Long-term tralopyril exposure results in endocrinological and transgenerational toxicity: A two-generation study of marine medaka (Oryzias melastigma)

This study aims to investigate the impact of tralopyril, a newly developed marine antifouling agent, on the reproductive endocrine system and developmental toxicity of offspring in marine medaka. The results revealed that exposure to tralopyril (0, 1, 20 μg/L) for 42 days resulted in decreased reproductive capacity in marine medaka. Moreover, it disrupted the levels of sex hormones E2 and T, as well as the transcription levels of genes related to the HPG axis, such as cyp19b and star. Sex-dependent differences were observed, with females experiencing more pronounced effects. Furthermore, intergenerational toxicity was observed in F1 offspring, including increased heart rate, changes in retinal morphology and cartilage structure, decreased swimming activity, and downregulation of transcription levels of relevant genes (HPT axis, GH/IGF axis, cox, bmp4, bmp2, runx2, etc.). Notably, the disruption of the F1 endocrine system by tralopyril persisted into adulthood, indicating a transgenerational effect. Molecular docking analysis suggested that tralopyril's RA receptor activity might be one of the key factors contributing to the developmental toxicity observed in offspring. Overall, our study highlights the potential threat posed by tralopyril to the sustainability of fish populations, as it can disrupt the endocrine system and negatively impact aquatic organisms for multiple generations.

Whole-Transcriptome Analysis Reveals the RNA Profiles in Mouse Bone Marrow Mesenchymal Stem Cells or Zebrafish Embryos After Exposure to Environmental Level of Tributyltin

To understand the underlying molecular mechanisms, mouse bone marrow mesenchymal stem cells (BMSCs) and zebrafish embryos were exposed to the control group and Tributyltin (TBT) group (10 ng/L, environmental concentration) for 48 h, respectively. The expression profiles of RNAs were investigated using whole-transcriptome analysis in mouse BMSCs or zebrafish embryos after TBT exposure. For mouse BMSCs, the results showed 2,449 differentially expressed (DE) mRNAs, 59 DE miRNAs, 317 DE lncRNAs, and 15 circRNAs. Similarly, for zebrafish embryos, the results showed 1,511 DE mRNAs, 4 DE miRNAs, 272 DE lncRNAs, and 28 circRNAs. According to KEGG pathway analysis showed that DE RNAs were mainly associated with immune responses, signaling, and cellular interactions. Competing endogenous RNA (ceRNA) network analysis revealed that the regulatory network of miRNA-circRNA constructed in zebrafish embryos was more complex compared to that of mouse BMSCs.

Co-exposure to sodium hypochlorite and cadmium induced locomotor behavior disorder by influencing neurotransmitter secretion and cardiac function in larval zebrafish

Sodium hypochlorite (NaClO) and cadmium (Cd) are widely co-occurring in natural aquatic environment; however, no study has been conducted on effects of their combined exposure on aquatic organisms. To assess effects of exposure to NaClO and Cd in zebrafish larvae, we designed six treatment groups, as follows: control group, NaClO group (300 μg/L), 1/100 Cd group (48 μg/L), 1/30 Cd group (160 μg/L), NaClO+1/100 Cd group, and NaClO+1/30 Cd group analyzed behavior, neurological function and cardiac function. Results revealed that exposure to 1/30 Cd and NaClO+1/30 Cd caused abnormal embryonic development in larvae by altering body morphology and physiological indicators. Combined exposure to NaClO and 1/30 Cd affected the free-swimming activity and behavior of larvae in response to light-dark transition stimuli. Moreover, exposure to 1/30 Cd or NaClO+1/30 Cd resulted in a significant increase in tyrosine hydroxylase and acetylcholinesterase activities, as well as significant changes of various neurotransmitters. Lastly, exposure to 1/30 Cd or NaClO+1/30 Cd influenced the transcription of cardiac myosin-related genes and disturbed the myocardial contractile function. Altogether, our results suggested that combined exposure to NaClO and Cd induced oxidative damage in larvae, resulting in detrimental effects on nervous system and cardiac function, thus altering their swimming behavior.

Micro(nano)plastics in marine medaka: Entry pathways and cardiotoxicity with triphenyltin

The simultaneous presence of micro(nano)plastics (MNPs) and pollutants represents a prevalent environmental challenge that necessitates understanding their combined impact on toxicity. This study examined the distribution of 5 μm (PS-MP5) and 50 nm (PS-NP50) polystyrene plastic particles during the early developmental stages of marine medaka (Oryzias melastigma) and assessed their combined toxicity with triphenyltin (TPT). Results showed that 2 mg/L PS-MP5 and PS-NP50 could adhere to the embryo surface. PS-NP50 can passively enter the larvae and accumulate predominantly in the intestine and head, while PS-MP5 cannot. Nonetheless, both types can be actively ingested by the larvae and distributed in the intestine. 2 mg/L PS-MNPs enhance the acute toxicity of TPT. Interestingly, high concentrations of PS-NP50 (20 mg/L) diminish the acute toxicity of TPT due to their sedimentation properties and interactions with TPT. 200 μg/L PS-MNPs and 200 ng/L TPT affect complement and coagulation cascade pathways and cardiac development of medaka larvae. PS-MNPs exacerbate TPT-induced cardiotoxicity, with PS-NP50 exhibiting stronger effects than PS-MP5, which may be related to the higher adsorption capacity of NPs to TPT and their ability to enter the embryos before hatching. This study elucidates the distribution of MNPs during the early developmental stages of marine medaka and their effects on TPT toxicity, offering a theoretical foundation for the ecological risk assessment of MNPs.

Exposure of embryos to fenbuconazole causes persistent neurotoxicity in adult zebrafish

In this study, the persistent effects of embryonic exposure to fenbuconazole (FBZ), a triazole fungicide, on neurobehaviour in zebrafish were investigated. After exposure of fertilized eggs to FBZ for 72 h (h), the larvae were cultured to adulthood in clean water. In adult zebrafish embryonically exposed to 50 and 500 ng L-1 FBZ, the ratio of brain weight/body weight was significantly decreased, and the number of apoptotic cells in the brain was significantly increased, accompanied by upregulated protein levels of P53 and downregulated levels of BCL2. The novel tank test showed a significant reduction in the moved distance and speed, and a longer period of adaptation to new environments in the 500 ng L-1 group. The social preference experiment showed impaired social interaction behaviour and reduced time of aggregation in the 500 ng L-1 group. Increased dopamine and norepinephrine levels in the brain might be responsible for this anxiety-like behaviour. In addition to upregulated protein levels of tyrosine hydroxylase and β2-adrenoceptor, the transcription of genes related to dopamine and norepinephrine synthesis in the brain such as th1, th2, ddc, drd1b, dat, and dbh, was increased. The methylation levels of related genes were reduced, which were matched with their increased transcriptional levels. These results demonstrate that embryonic FBZ exposure might cause persistent neurotoxicity in adulthood, which suggests the rational cautious use of FBZ.

Combined effect of microplastic and triphenyltin: Insights from the gut-brain axis

Microplastics (MPs), an emerging group of pollutants, not only have direct toxic effects on aquatic organisms but also cause combined toxicity by absorbing other pollutants. Triphenyltin (TPT), one of the most widely used organotin compounds, has adverse effects on aquatic organisms. However, little is known about the combined toxicity of MPs and TPT to aquatic organisms. To investigate the individual and combined toxicity of MPs and TPT, we selected the common carp (Cyprinus carpio) for a 42-day exposure experiment. Based on the environmental concentrations in a heavily polluted area, the experimental concentrations of MPs and TPT were set at 0.5 mg L^-1 and 1 μg L^-1, respectively. The effects of MPs combined with TPT on the carp gut-brain axis were evaluated by detecting gut physiology and biochemical parameters, gut microbial 16S rRNA, and brain transcriptome sequencing. Our results suggest that a single TPT caused lipid metabolism disorder and a single MP induced immunosuppression in carp. When MPs were combined with TPT, the involvement of TPT amplified the immunotoxic effect induced by MPs. In this study, we also explored the gut-brain axis relationship of carp immunosuppression, providing new insights for assessing the combined toxicity of MPs and TPT. At the same time, our study provides a theoretical basis for evaluating the coexistence risk of MPs and TPT in the aquatic environment.

Photoaged microplastics induce neurotoxicity via oxidative stress and abnormal neurotransmission in zebrafish larvae (Danio rerio)

Microplastics (MPs) are ubiquitous environmental contaminants and cause neurotoxicity in various organisms. However, previous studies that analyzed the effects of MPs mainly focused on virgin polystyrene (V-PS) as representative models of MPs, and the mechanism underlying the neurotoxicity of photoaged polystyrene (P-PS) remains largely unknown. In this study, zebrafish (Danio rerio) were exposed to environmentally relevant concentrations (0.1-100 μg/L) of V-PS and P-PS(10 μm). The results indicated that UV radiation accelerated the aging process and changed physical and chemical properties of PS. Whereas exposure to both V-PS and P-PS at low concentrations (100 μg/L) significantly reduced the locomotor behavior of zebrafish larvae, P-PS caused more severe neurotoxicity compared to V-PS. The activity of antioxidant enzymes (SOD, CAT, and GST) and MDA content were significantly altered in zebrafish exposed to 10-100 μg/L of P-PS. Similarly, exposure to P-PS significantly increased neurotransmitter (5-HT, GABA, DA, and ACh) levels and activity of AChE, ChAT, and ChE. Star plots based on integrated biomarker response (IBR) values showed more incline toward neurotransmitter biomarkers in response to increasing P-PS concentration, and the behavioral parameters negatively correlated with the neurotransmitter biomarkers. Further investigations revealed that the expression of neurotransmission- (e.g., ache, drd3, 5th2c, and gat1) and oxidative stress- (e.g., cat1, sod1, gpx1a, and gstrl) related genes was significantly affected by PS in larval zebrafish. Thus, this study provides new insights on the potential risks of MPs into the environment.

Ganoderma lucidum polysaccharide alleviates Cd toxicity in common carp (Cyprinus carpio): Neuropeptide, growth performance and lipid accumulation

Cadmium (Cd) is the most common heavy metal and is easily detected in aquatic environments on a global scale. Common carp (Cyprinus carpio) is a common cultural species in aquaculture. This study aimed the polysaccharide from Ganoderma lucidum in ameliorating Cd-induced toxicity in common carp. The study included a blank control group (CK, without Cd and GPL) and LGPL group (2 g/kg LGPL + 0.5 mg/L Cd) and HGPL group (4 g/kg HGPL + 0.5 mg/L Cd). The fish were sampled at 2 and 4 weeks, and bioaccumulation, neurotransmitters, lipid accumulation, and growth performance were measured. Ganoderma lucidum polysaccharide administration can significant protect against Cd toxicity by reducing Cd bioaccumulation in tissues, regulating neurotransmitters, decreasing lipid accumulation, and enhancing growth performance. Our results suggested that administering Ganoderma lucidum polysaccharides can alleviate waterborne Cd toxicity in common carp.

Toxic effects of triphenyltin on the development of zebrafish (Danio rerio) embryos

Triphenyltin (TPT) is known to be an environmental endocrine disruptor and has adverse effects on aquatic animals. In this study, zebrafish embryos were treated with three different concentrations (12.5, 25, 50 nmol/L) based on the LC₅₀ value at 96 h post fertilization (96 hpf), after TPT exposure. The developmental phenotype and hatchability were observed and recorded. Reactive oxygen species (ROS) levels in zebrafish were detected at 72 hpf and 96 hpf using 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) as a probe. The number of neutrophils after exposure was observed using transgenic zebrafish Tg (lyz: DsRed). RNA-seq analysis was used to compare the gene expression changes in zebrafish embryos at 96 hpf in the control group and 50 nmol/L TPT exposure group. The data revealed that TPT caused a delay in hatching of zebrafish embryos in a time- and dose-dependent manner, as well as causing pericardial edema, spinal curvature and melanin reduction. ROS levels in embryos exposed to TPT increased, and the number of neutrophils increased after TPT exposure to Tg (lyz: DsRed) in transgenic zebrafish. RNA-seq results were also analyzed, and KEGG enrichment analysis showed that significant differential genes were enriched in the PPAR signaling pathway (P < 0.05), and the PPAR signaling pathway mainly affected genes related to lipid metabolism. The RNA-seq results were verified using real-time fluorescence quantitative PCR (RT-qPCR). Oil red O and Nile red staining showed increased lipid accumulation after TPT exposure. These findings suggest that TPT affects the development of zebrafish embryos even at relatively low concentrations.

Assessing the ecotoxicity of combined exposure to triphenyltin and norfloxacin at environmental levels: A case study of immunotoxicity and metabolic regulation in carp (Cyprinus carpio)

This paper evaluates the coexistence risks of triphenyltin (TPT) and norfloxacin (NOR) to aquatic organisms in the aquatic environment. Carp (Cyprinus carpio) was used as the test organism, the control and exposure groups (1 μg/L TPT), 1 mg/L (NOR), 1 μg/LTPT+1 mg/LNOR (TPT_NOR)) were set up according to the environmental concentration in the severely polluted area for 42 days. The single/combined toxic effects of TPT and NOR on aquatic organisms were evaluated by analyzing carp brain transcriptome sequencing, gut microbiota structure, and detection of biochemical indicators and RT-qPCR. Our results show that TPT and NOR induce lipid metabolism disorder in carp brain tissue, affecting the metabolism of cytochrome P450 to exogenous substances, and NOR also induces immunosuppression in carp. Long-term exposure to TPT combined with NOR amplifies the monotoxicity of TPT or NOR on lipid metabolism and immunosuppression in carp, induces immune dysfunction in brain tissue and changes in gut microbiota structure. However, TPT_NOR has no obvious neurotoxicity on the brain, but it can inhibit the level of intestinal MDA. This highlights that co-exposure of TPT and NOR amplifies metabolic disorders and immunosuppressive functions in carp.

Prolonged electrolysis injures the neural development of zebrafish (Danio rerio)

Recently, electrolysis technology has been widely applied in nitrogen and phosphorus removal in river water due to its high efficiency, but its effects on aquatic animals, especially on their neurodevelopmental system, are still unclear. In this study, zebrafish (Danio rerio) embryos were used as model organisms and were put into an electrolytic reaction device with a Ti/IrO₂/RuO₂ mesh plate as the anode and a Ti mesh plate as the cathode to explore the effects of prolonged electrolysis on the nervous system. The neural development of zebrafish embryos was injured when the current density was greater than 0.89 A/m². Compared with the control group, the movement speed of zebrafish larvae (120 h postfertilization, hpf) was significantly reduced from 65.48 ± 23.69 to 48.08 ± 22.73 mm/min in a dark environment with an electric current density of 0.89 A/m² in the electrolysis group. In addition, the acetylcholinesterase activity of zebrafish larvae (120 hpf) gradually decreased from 7.60 ± 0.55 to 6.00 ± 0.01 U/mg prot and the dopamine concentration was reduced from 46.96 ± 0.85 to 40.86 ± 1.05 pg/mL with an electric current density from 0 to 0.89 A/m² in the electrolysis groups. Furthermore, the expression of nerve-related genes (syn2a, mbp, nestin, and AChE) was significantly inhibited when the current density was more than 0.89 A/m². However, there were few adverse effects on the neural development of zebrafish embryos when the current density was less than 0.86 A/m². Thus, a current density of 0.86 A/m² is a reference value to reduce the harm to the neural development of fish when electrolysis technology is used in river water pollutant treatment.

Thyroid-like hormone signaling in invertebrates and its potential role in initial screening of thyroid hormone system disrupting chemicals

This review examines the presence and evolution of thyroid-like systems in selected aquatic invertebrates to determine the potential use of these organisms in screens for vertebrate thyroid hormone axis disrupting chemicals (THADCs). Such a screen might support the phasing out of some vertebrate testing. Although arthropods including crustaceans do not contain a functional thyroid signaling system, elements of such a system exist in the aquatic phyla mollusks, echinoderms, tunicates, and cephalochordates. These phyla can synthesize thyroid hormone, which has been demonstrated in some groups to induce the nuclear thyroid hormone receptor (THR). Thyroid hormone may act in these phyla through interaction with a membrane integrin receptor. Thyroid hormone regulates inter alia metamorphosis but, unlike in vertebrates, this does not occur via receptor activation by the ligands triiodothyronine (T3) and thyroxine (T4). Instead, the unliganded nuclear receptor itself controls metamorphosis in mollusks, echinoderms, and tunicates, whereas the T3 derivative tri-iodothyroacetic acid (TRIAC) acts as a THR ligand in cephalochordates. In view of this, it may be possible to develop an invertebrate-based screen that is sensitive to vertebrate THADCs that interfere with thyroid hormone synthesis or metabolism along with interaction with membrane receptors. The review makes some recommendations for the need to develop an appropriate test method. Integr Environ Assess Manag 2023;19:63-82. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Acute Toxicity of a Novel anti-fouling Material Additive DCOIT to Marine Chlorella sp

DCOIT (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one) is the main ingredient in SeaNine-211, a new antifouling agent that replaces organotin compounds to prevent the growth of fouling organisms on board. Biocides from antifoulants can cause problems for marine ecosystems by destroying non-target algal species. This study evaluated the potential adverse effects DCOIT using the Marine Chlorella sp. The concentration of DCOIT were set according to the semi-inhibitory concentrations for acute exposure experiments, and relevant oxidative stress indicators were measured to assess the acute toxic effects. The results showed that the inhibition concentrations (IC50) of DCOIT against Marine Chlorella sp was 2.522 mg/L. The genes related to photosynthesis and antioxidant capacity showed the effect of promoting low concentration and inhibiting high concentration. In addition, based on the ultrastructural observation and the expression analysis of photosynthesis related genes, it was found that DCOIT had a significant effect on plant photosynthesis.

Environmentally relevant dose of the endocrine disruptor tributyltin disturbs redox balance in female thyroid gland

Tributyltin (TBT) is an endocrine disruptor used as a biocide in nautical paints. Even though many TBT effects in marine species are known, data in mammals are scarce, especially regarding the thyroid gland. The present study aimed to evaluate the effect of a subchronic exposure to TBT on thyroid oxidative stress of female Wistar rats. Rats received vehicle (control group), 200 or 1000 ng TBT/kg body weight/day for 40 days. After euthanasia, one part of the thyroids were collected in order to assess iodide uptake; activity and/or mRNA expression of thyroperoxidase (TPO) and dual oxidases (DUOXs); activity and/or mRNA expression of catalase, glutathione peroxidase, superoxide dismutase and NADPH oxidase 4 (CAT, GPx, SOD and NOX4); 4-hydroxynonenal (4-HNE) expression and total thiol groups levels; and mRNA expression of estrogen receptors alpha and beta (ERα and ERβ). The remaining part of the thyroid was processed for morphological analysis of estrogen receptor alpha (ERα) and for collagen deposition. Iodide uptake was not changed with treatments. TPO activity and expression were increased in the TBT1000 group (259.81% and 95.17%). The activity, but not mRNA, of CAT (17.36% TBT200; 27.10% TBT1000) and GPx (29.24% TBT200; 28.97% TBT1000) were decreased by TBT. SOD and NADPH oxidase activity, as well as thiol group and 4-HNE levels remained unchanged. Interstitial collagen deposition increased in the TBT200 group (39.54%). The mRNA expression of ERα increased in TBT-treated rats (44.87% TBT200; 36.43% TBT1000), while protein expression was increased but not reaching significance (TBT1000, p = 0.056) by TBT. Therefore, our results show that TBT increases TPO expression and reduces antioxidant enzyme activities in the thyroid gland leading to oxidative stress. Some of these effects could be mediated by the ERα pathway.

Chronic exposure to tralopyril induced abnormal growth and calcium regulation of turbot (Scophthalmus maximus)

Tralopyril is an emerging marine antifouling agent with limited data on its effects on fish growth and calcium regulation. To determine the changes induced by long-term exposure to tralopyril, multi-levels (such as molecular, biochemical, and individual levels) responses were measured in turbot at different concentrations (1 μg/L, 20 μg/L). The results showed that 1 μg/L mainly affected the immune response, while 20 μg/L affected the synthesis and metabolism of steroids and fat. However, different concentrations of tralopyril affected the synthesis, secretion and action of parathyroid hormone and growth hormone. The expression of GH/IGF axis gene and the level of growth hormone increased significantly, leading to abnormal growth. The energy tradeoff between immunity and growth at 1 μg/L tralopyril pressure may inhibit growth. The change of Ca²⁺ level was accompanied by the disturbance of PTH-related gene expression. The results of molecular docking showed that the disturbance of Ca²⁺ regulation might be attributed to the inhibition of vitamin D receptor by tralopyril, which affected the vitamin D signaling pathway. This study provides scientific data for the in-depth understanding and risk assessment of the toxicological effects of tralopyril and reveals the potential threat of tralopyril to environmental health.

Exposure to enrofloxacin and depuration: Endocrine disrupting effect in juvenile grass carp (Ctenopharyngodon idella)

This study aimed to determine the effects of Enrofloxacin (ENR) exposure and depuration on the disruption of thyroid function and growth of juvenile grass carp (Ctenopharyngodon idella) as well as to assess the risk of ENR exposure to human health. Juvenile grass carp were treated with ENR solutions at different concentration gradients for 21 days and then depurated for 14 days. The results indicated ENR accumulation in the juvenile grass carp muscles, which persisted after depuration. In addition, exposure to ENR could alter growth by regulating the expression of genes associated with growth hormone/insulin-like growth factor (GH)/IGF) axis and the hypothalamic-pituitary-thyroid (HPT) axis. During ENR exposure, no significant changes in growth hormone levels were observed; however, a significant increase in the growth hormone level was noted. GH/IGF axis-related genes were upregulated after ENR exposure, and their expression levels remained high after depuration. Notably, a significant increase in the serum triiodothyronine (T3) and thyroxine (T4) levels coincided with the upregulation of HPT axis-related genes in both exposure and depuration treatments, and their expression levels remained high after depuration. Therefore, juvenile grass carp exposure to ENR induces physiological stress through HPT and GH/IGF axes that cannot be recovered after depuration. ENR accumulates in the muscles of juvenile grass carp and may pose a threat to human health. Therefore, exposure of juvenile grass carp to ENR results in impaired thyroid function and impaired growth. In addition, consumption of ENR-exposed fish poses human health risks.

The ecotoxicology of marine tributyltin (TBT) hotspots: A review

Tributyltin (TBT) was widely used as a highly efficient biocide in antifouling paints for ship and boat hulls. Eventually, TBT containing paints became globally banned when TBT was found to cause widespread contamination and non-target adverse effects in sensitive species, with induced pseudohermaphroditism in female neogastropods (imposex) being the best-known example. In this review, we address the history and the status of knowledge regarding TBT pollution and marine TBT hotspots, with a special emphasis on the Norwegian coastline. The review also presents a brief update on knowledge of TBT toxicity in various marine species and humans, highlighting the current understanding of toxicity mechanisms relevant for causing endocrine disruption in marine species. Despite observations of reduced TBT sediment concentrations in many marine sediments over the recent decades, contaminant hotspots are still prevalent worldwide. Consequently, efforts to monitor TBT levels and assessment of potential effects in sentinel species being potentially susceptible to TBT in these locations are still highly warranted.

Effects of long-term exposure of norfloxacin on the HPG and HPT axes in juvenile common carp

Currently, there is a relatively lack of relevant research on the interference effect of quinolone antibiotics on the endocrine of aquatic animals. In this study, the toxicity of norfloxacin (NOR) on the endocrine system of juvenile common carp (Cyprinus carpio) was evaluated, as well as the hematocyte parameters. Specifically, two important endocrine axes were assessed: the hypothalamus-pituitary-thyroid (HPT) axis and hypothalamus-pituitary-gonadal (HPG) axis. Norfloxacin was used as a representative of quinolone antibiotics. According to the concentration of water pollution areas and considering the bad situation that may be caused by wastewater discharge, a control, 100 ng/L NOR, and 1 mg/L NOR treatment groups were set up. The juvenile carp, as the test animal, was subjected to an exposure experiment for 42 days. Thyroid hormones (T3 and T4) and related genes in HPT axis and sex hormones (11-ketotestosterone [11-KT] and progesterone [PROG]) and related genes in HPG axis and blood count are tested. It was found that the T4 iodine level and conversion process were enhanced after NOR treatment, which in turn led to the increase of T3 content and biological activity in the blood. One hundred nanograms per liter NOR can inhibit the level of sex hormones and inhibit the expression of HPG axis-related genes. In the 1 mg/L NOR treatment group, long-term exposure over a certain concentration range may lead to the development of adaptive mechanisms, making the changes in hormones and related genes insignificant. In conclusion, this study provides reference data for the endocrine interference of quinolone antibiotics on aquatic organisms, and has ecological significance for assessing the health of fish populations of quinolone antibiotics. However, the specific sites and mechanisms of action related to the effects of NOR on the endocrine system remain unclear and require further study.

Chronic Toxic Effects of Waterborne Mercury on Silver Carp (Hypophthalmichthys molitrix) Larvae

Mercury (Hg) is a kind of heavy metal pollutant widely existing in the aquatic environment, and it is also recognized to have a highly toxic effect on fish. In this study, silver carp (Hypophthalmichthys molitrix) larvae were exposed to 0 (control), 1, 5, and 10 μg/L Hg2+ for 2 weeks. Antioxidant ability, neurotoxicity, and thyroid hormones (THs) content were evaluated. In comparison with the control, the superoxide dismutase (SOD) activity and the glutathione (GSH) activity were lower in silver carp exposed to 10 μg/L Hg2+. The lowest catalase (CAT) activity was found in the 10 μg/L Hg2+, while malondialdehyde (MDA) content was not significantly different among all groups. Compared with the control, monoamine oxidase (MAO) activity and nitric oxide (NO) content were significantly higher in the 10 μg/L Hg2+, while acetylcholinesterase (AChE) activity significantly decreased. Compared with the control, triiodothyronine (T3) content was significantly higher in the 1 μg/L Hg2+ and significantly lower in the 10 μg/L Hg2+; the 1 μg/L and 5 μg/L Hg2+ groups had significantly higher thyroxine (T4) content than the other groups. In the 1 μg/L Hg2+, the integrated biomarker response (IBR) index value was the highest. In summary, exposure to Hg could decrease the antioxidant ability, cause changes in neurotoxic parameters, and induce disorders of the thyroid hormone system in silver carp larvae. The results of this study may contribute to the understanding of the adverse effects of chronic mercury poisoning on fish.

Transcriptomic and proteomic analysis of Chinese rare minnow (Gobiocypris rarus) larvae in response to acute waterborne cadmium or mercury stress

In this study, Chinese rare minnow (Gobiocypris rarus) larvae were exposed to the control group, Cd concentrations (0.5 and 2.5 mg/L), and Hg concentrations (0.1 and 0.3 mg/L) for 96 h. Transcriptome analysis showed that 816 and 1599 significantly differentially expressed genes (DEGs) were identified in response to 2.5 mg/L Cd²⁺ and 0.3 mg/L Hg²⁺, respectively. Functional enrichment analysis revealed that DEGs were mostly associated with immune responses after Cd exposure, such as antigen processing and presentation, phagosome, apoptosis, and lysosome. Similarly, functional enrichment analysis showed that many pathways were mostly involved in metabolism after Hg exposure, such as glutathione metabolism and starch and sucrose metabolism. Results of two-dimensional electrophoresis (2-DE) showed that the abundance of 10 protein spots was significantly altered in the Cd²⁺ treatments. The proteomic analysis demonstrated that Cd toxicity might impair cytoskeletal and cell motility-related protein activity in the liver of G. rarus. Similarly, the abundance of 24 protein spots was significantly altered in the Hg²⁺ treatments. Hg toxicity regulates the expression of proteins belonging to several functional categories, including cytoskeleton, oxidative stress, digestive system, and energy metabolism. This study provides valuable relevant insight into the molecular mechanisms in response to Cd or Hg toxicity in aquatic organisms and will help screen for potential biomarkers to respond to Cd and Hg pollutants.

Effects of short-term exposure to tralopyril on physiological indexes and endocrine function in turbot (Scophthalmus maximus)

Tralopyril is an emerging marine antifouling agent with potential toxic effects on non-target aquatic organisms. To evaluate the toxicity of tralopyril, to turbot (Scophthalmus maximus), we assessed biomarkers, including oxidative stress, neurotoxicity, and osmotic homeostasis regulation enzymes, after a 7-day exposure to tralopyril (5 μg/L, 15 μg/L, 30 μg/L). Superoxide dismutase activity was significantly decreased at 30 μg/L, and Ca²⁺-Mg²⁺-ATPase activity in the gills was significantly increased at 15 μg/L and 30 μg/L. No statistically significant differences in the responses of acetylcholinesterase and nitric oxide were detected. In addition, 15 μg/L and 30 μg/L tralopyril induced hyperthyroidism, reflected by significantly increased of T3 levels. The expression levels of hypothalamus-pituitary-thyroid axis-related genes were also upregulated. The molecular docking results showed that the thyroid system disruption was not caused by competitive binding to the receptor. In addition, the integrated biomarker response index showed that 15 μg/L tralopyril had the greatest effect on turbot. In general, tralopyril caused oxidative damage, affected energy metabolism, and interfered with the endocrine system. These findings could provide reference data for assessing the ecological risk of tralopyril in marine environments.

Cadmium exposure promotes activation of cerebrum and cerebellum ferroptosis and necrosis in swine

Cadmium(Cd) is a toxic and carcinogenic heavy metal pollutant leading to serious damage in various organs. Ferroptosis and necrosis as inflammation-related cell death are involved in several diseases of nervous system. In the present study, 10 weaning piglets with similar weight for 6 weeks were randomly divided into two groups. The daily grain containing 0 mg and 20 mg/kg of Cd chloride was fed in 20-26 ℃ environment, animals were sacrificed to collect cerebrum and cerebellum tissues after 40 days. Morphology and ultrastructure results were observed using HE and TEM. Moreover, molecular biological technologies western blot and qRT-PCR were used to detect the expression abundance of genes. Cerebrum and cerebellum injury was observed in Cd-exposed group, antioxidant capacity decreased significantly and oxidative stress increased; immunofluorescence, real-time quantification, and western blot results showed decreased necrosis genes and increased ferroptosis pathway genes abundance in cerebrum, whereas the results were reversed in cerebellum. These results indicated that Cd exposure can activated necrosis and ferroptosis pathways by increased oxidative stress, further resulting in cerebrum and cerebellum damage in pigs. These findings may provide a theoretical basis for early monitoring of Cd exposure in environment.

Toxicity of organotin compounds and the ecological risk of organic tin with co-existing contaminants in aquatic organisms

Although organotin (OT) use is restricted worldwide, with the development of industry and agriculture, a large amount of OT is still discharged into aquatic environments. These OTs may interact with other pollutants that cause adverse biological effects (through bioaccumulation and/or toxicity), resulting in combined toxicity. Most research on OTs have focused on the exposure of a single analyte. Information on the toxicity of OTs and coexisting pollutants is quite limited, but is developing rapidly. This is the first review paper evaluating the current state of knowledge on the combined effects of OTs with co-pollutants. This paper reviews 1) the degradation of organotin; and 2) the combined toxicity of OTs and emerging pollutants (EP), heavy metals, and organic pollutants. Future research needs are discussed to better understand the risks associated with co-exposure to OT pollutants.

Biomimetic and bioinspired surface topographies as a green strategy for combating biofouling: a review

Biofouling refers to the adverse attachment and colonization of fouling organisms, including macromolecules, bacteria, and sessile invertebrates, on the surfaces of materials submerged in aquatic environments. Almost all structures working in watery surroundings, from marine infrastructures to healthcare facilities, are affected by this sticky problem, resulting in massive direct and indirect economic loss and enormous cost every year in protective maintenance and remedial cleaning. Traditional approaches to preventing marine biofouling primarily rely on the application of biocide-contained paints, which certainly impose adverse effects on the ocean environment and marine ecology. Biomimicry offers an efficient shortcut to developing environmentally friendly antifouling techniques and has yielded encouraging and promising results. The antifouling strategies learned from nature can be broadly classified into two categories according to the nature of the cues applied for biofouling control. One is the chemical antifouling techniques, which are dedicated to extracting the effective antifoulant compounds from marine organisms and synthesizing chemicals mimicking natural antifoulants. In contrast, the physical biomimetic (BM) antifouling practices focus on the emulation and optimization of the physical cues such as micro and nanoscale surface topographies learned from naturally occurring surfaces for better antifouling efficacy. In this review, a synopsis of the techniques for manufacturing the BM and bioinspired (BI) antifouling surface topographies is introduced, followed by the bioassay to assess the antifouling performance of the structured surfaces. Then, the BM and BI surface topographies that were reported to possess enhanced antifouling competence are introduced, followed by a summary of theoretical modeling. The whole paper is concluded by summarizing the studies' deficiencies so far and outlooking the research directions in the future.

Cadmium exposure induces inflammation and necroptosis in porcine adrenal gland via activating NF-κB/MAPK pathway

Cadmium (Cd) is a heavy metal harmful to animals and humans. Cd exposure causes inflammation or necroptosis in many tissues, including adrenal tissue. However, the current researches on the effects of Cd²⁺ in adrenal tissues are not enough. Therefore, in our experiment Cd chloride (CdCl₂) was added to the piglet's diet at a concentration of 20 mg/kg to study the effects of Cd²⁺ exposure on the porcine adrenal tissue. Our results showed that Cd²⁺ exposure could cause inflammation by activating the nuclear factor kappa-B (NF-κB) pathway, which in turn induced necroptosis in adrenal tissue with the activated mitogen-activated protein kinase (MAPK) pathway. The expression increase of inflammatory factors and necroptosis downstream genes, and the downregualtion of cysteinyl aspartate specific proteinase 8 (Caspase 8) proved that Cd²⁺ exposure caused inflammation and necroptosis in adrenal tissue. We conclude that this report provides more basic theoretical data for exploring the mechanism of adrenal injury.

Effects of 2-ethylhexyl-4-methoxycinnamate (EHMC) on thyroid hormones and genes associated with thyroid, neurotoxic, and nephrotoxic responses in adult and larval zebrafish (Danio rerio)

One of the most widely used UV filters, 2-ethylhexyl-4-methoxycinnamate (EHMC), has been widely detected in the environment. While its endocrine disruption potential has often been reported, toxicological information on EHMC is limited. This study was conducted to determine the thyroid, neurological and renal toxicity potentials of EHMC in adult male and embryo-larval zebrafish (Danio rerio). Following 21 d of exposure, plasma T3 concentration decreased in a concentration-dependent manner in adult zebrafish. Several genes related to thyroid hormone regulation were also downregulated in the brain, thyroid, and liver of the adult fish. In addition, upregulation of syn2a in the brain and downregulation of podocin and wt1a in the kidney were observed following the exposure in adult fish. In zebrafish larvae, following 120 h exposure to EHMC, whole-body T3 and T4 contents decreased, and thyroid hormone-related genes were downregulated. However, several genes showed different patterns of transcription in the larvae; for example, mbp and etv1 genes were downregulated and podocin was upregulated. Unlike adult fish, the larval fish showed significant genetic changes related to neurotoxicity. The hypothyroidism induced in the larval fish by the exposure might be potentially associated with the neurotoxic potential of EHMC. The implications of the observed hormonal and transcriptional-level changes in zebrafish at different life stages following long-term exposure warrant further investigation.

Effects of the tributyltin on the blood parameters, immune responses and thyroid hormone system in zebrafish

Tributyltin (TBT) is a widely used organotin compound around the world and was frequently detected in surface waters, which would pose risk to aquatic organisms. However, the mechanisms of TBT-induced toxicity is not full clear. The present study investigated the effects of the tributyltin (TBT) on the blood parameters, immune responses and thyroid hormone system in zebrafish. Fish were exposed to sublethal concentrations of TBT (10 ng/L, 100 ng/L and 300 ng/L) for 6 weeks. The effects of long-term exposure to TBT on blood parameters (NH3, ammonia; GLU, glucose; TP, total proteins; CK, creatine kinase; ALT, alanine aminotransferase; AST, aspartate aminotransferase), immune responses (Lys, lysozyme; IgM, immunoglobulin M) and some indexes related thyroid hormone system (T3, 3,5,3'-triiodothyronine; T4, thyroxine) were measured in zebrafish, as well as the expression of genes related to immune responses and thyroid hormone system. Based on the results, the physiological-biochemical responses was significantly enhanced with an increase in TBT concentration, reflected by the abnormal blood indices, dysregulation of endocrine system and immunotoxicity in zebrafish under TBT stress. The present study greatly extends our understanding of adverse effects of TBT on aquatic organisms.

Cadmium exposure alters expression of protective enzymes and protein processing genes in venom glands of the wolf spider Pardosa pseudoannulata

Cadmium (Cd) pollution is currently the most serious type of heavy metal pollution throughout the world. Previous studies have shown that Cd elevates the mortality of paddy field spiders, but the lethal mechanism remains to be explored profoundly. In the present study, we measured the activities of protective enzymes (acetylcholinesterase, glutathione peroxidase, phenol oxidase) and a heavy metal chelating protein (metallothionein) in the pond wolf spider Pardosa pseudoannulata after Cd exposure. The results indicated that Cd initially increased the enzyme activities and protein concentration of the spider after 10- and 20-day exposure before inhibiting them at 30-day exposure. Further analysis showed that the enzyme activities in the cephalothorax were inhibited to some extent. Since the cephalothorax region contains important venom glands, we performed transcriptome sequencing (RNA-seq) analysis of the venom glands collected from the spiders after long-term Cd exposure. RNA-seq yielded a total of 2826 differentially expressed genes (DEGs), and most of the DEGs were annotated into the process of protein synthesis, processing and degradation. Furthermore, a mass of genes involved in protein recognition and endoplasmic reticulum (ER) -associated protein degradation were down-regulated. The reduction of protease activities supports the view that protein synthesis and degradation in organelles and cytoplasm were dramatically inhibited. Collectively, our outcomes illustrate that Cd poses adverse effects on the expression of protective enzymes and protein, which potentially down-regulates the immune function in the venom glands of the spiders via the alteration of protein processing and degradation in the ER.

Environmental neurotoxic pollutants: review

Environmental pollutants are recognized as one of the major concerns for public health and responsible for various forms of neurological disorders. Some of the common sources of environmental pollutants related to neurotoxic manifestations are industrial waste, pesticides, automobile exhaust, laboratory waste, and burning of terrestrial waste. Among various environmental pollutants, particulate matter, ultrafine particulate matter, nanoparticles, and lipophilic vaporized toxicant (acrolein) easily cross the blood-brain barrier, activate innate immune responses in the astrocytes, microglia, and neurons, and exert neurotoxicity. Growing shreds of evidence from human epidemiological studies have correlated the environmental pollutants with neuroinflammation, oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction, myelin sheath disruption, and alterations in the blood-brain barrier anatomy leading to cognitive dysfunction and poor quality of life. These environmental pollutants also considerably cause developmental neurotoxicity, exhibit teratogenic effect and mental growth retardance, and reduce IQ level. Until now, the exact mechanism of pollutant-induced neurotoxicity is not known, but studies have shown interference of pollutants with the endogenous antioxidant defense system, inflammatory pathway (Nrf2/NF-kB, MAPKs/PI3K, and Akt/GSK3β), modulation of neurotransmitters, and reduction in long-term potentiation. In the current review, various sources of pollutants and exposure to the human population, developmental neurotoxicity, and molecular mechanism of different pollutants involved in the pathogenesis of different neurological disorders have been discussed.

Tributyltin enhanced anxiety of adult male zebrafish through elevating cortisol level and disruption in serotonin, dopamine and gamma-aminobutyric acid neurotransmitter pathways

Tributyltin (TBT), a widely and persistently distributed organontin, has been well documented to disrupt reproduction and behaviors in animals due to its anti-aromatase activity. TBT has been also reported to enhance anxiety in several fish species, whereas the mechanism underlying remains largely unknown. To investigate the disruption of TBT on fish anxiety and the mechanisms possibly involved, adult male zebrafish (Danio rerio) were treated with TBT (100 and 500 ng/L) for 28 days and anxiety behavior was further investigated using a novel tank dive test. Result showed that TBT treatment significantly enhanced the total time of the fish spent in the lower half, delayed the onset time to the higher half of the tank and increased the total duration of freezing of the fish, indicating an enhanced anxiety in TBT-treated fish. Accordingly, TBT sharply elevated the cortisol levels in plasma in a concentration-dependent manner, suggesting that the elevated cortisol level might be involved in the enhanced anxiety. Although the expression of crha was significantly increased and crhbp was significantly decreased in the brain of TBT-treated fish which is consistent to the elevated cortisol level, the expressions of actha and acthb were sharply down-regulated. In contrast, the expressions of genes responsible for the synthesis and action of serotonin (5-HT) (pet1, thp2 and htr1aa), dopamine (DA) (th1, slc6a3, drd2a and drd2b) and gamma-aminobutyric acid (GABA) (gad2 and gabrg2) were all significantly inhibited. The down-regulation of these pivotal genes acting in 5-HT, DA and GABA neurotransmitter systems in response to TBT corresponded well with the TBT-enhanced anxiety in fish. It was thus strongly suggested that these neurotransmitters might be also involved in TBT-enhanced anxiety in adult male zebrafish. The present study extended our understanding of the neurotoxicity of TBT on the anxiety control and behavioral modulation in fish.