Benzoresorcinol induces developmental neurotoxicity and injures exploratory, learning and memorizing abilities in zebrafish

2-Hydroxy-4-n-octyloxybenzophenone induces developmental neurotoxicity and multiple sclerosis-like symptoms through cacna1a regulated Ca2 + inward flow and microglial activation

2-Hydroxy-4-n-octyloxybenzophenone (UV-531) is a UV absorber widely used in infrastructure, cosmetics, and rubber products. The previous study found that UV-531 exposure irritate the skin and interfere with androgen secretion. However, the developmental toxicity and neurotoxic effects of UV-531 are still at an exploratory stage, and the effects of UV-531 on the environment and living organisms need to be further explored. Here, we exposed zebrafish to environmental relevant doses of UV-531 (0.1, 0.2, 0.4, 0.8 and 1.6 μg/L) and observed no significant developmental toxicity, but significant neurotoxicity. We assessed locomotor ability and responsiveness of zebrafish by general locomotion and light/dark challenge. Changes in dopaminergic (DA) neurons were observed using transgenic zebrafish slc18a2:GFP. Changes in cerebral vessels and blood-brain barrier (BBB) were observed using transgenic zebrafish fli1:GFP. Gene expression was detected by transcriptome and real-time qPCR. The effect of UV-531 on calcium homeostasis was determined by measuring Ca2+ levels. Microglia status was assessed by in situ hybridization. It was observed that UV-531 treatment resulted in a reduced locomotor activity, DA neurons injury, cerebral vessels damage, BBB leakage, calcium homeostasis imbalance, and abnormal expression of genes related to neurodevelopment and function. RNA-seq results indicated that Ca2+ import across plasma membrane was highly associated with UV-531-induced developmental neurotoxicity and cacna1aa and cacna1ab were key regulators. These findings suggest that UV-531 induced calcium homeostasis imbalance caused by upregulating cacna1aa and cacna1ab may contribute to multiple sclerosis (MS). Accordingly, UV-531 exposure triggered neuroinflammation, injured myelin, ultimately leading to the development of MS-like symptoms, including decreased responsiveness to external stimuli, microglia activation, dysregulation of mbp and MS-related genes ahsg1, btg1, and grna. In summary, exposure to environmental relevant doses of UV-531 caused neurological damage and led to MS-like symptoms. Given the effects of UV-531 on the organisms, a safe dose range should be established.

Reserpine Causes Neuroendocrine Toxicity, Inducing Impairments in Cognition via Disturbing Hypothalamic-Pituitary-Thyroid Axis in Zebrafish

Reserpine is used as a cheap and effective first-line antihypertensive, and presently, it is applied as treatment for difficult-to-control cases of hypertension. Despite its significance, reserpine's neuroendocrine toxicity remains largely underexplored. Here, we investigated the effects of reserpine on development, locomotion, central nervous system (CNS) neurons, thyroid development, and the expression of genes related to neurodevelopment, endocrine, learning and memory, and depression in zebrafish exposed to different doses of reserpine ranging from 0.5 mg/L to 16 mg/L. The results of our study demonstrated that reserpine exerts dose-dependent toxicity on the neuroendocrine system (NES). An investigation into its underlying mechanism suggests that reserpine disrupted the hypothalamic-pituitary-thyroid (HPT) axis via down-regulating hhex, tg, and tshβ genes, impairing thyroid hormone synthesis and endocrine balance. Meanwhile, it affected neurodevelopment, as evidenced by the reduced expression of gfap, gap43, mbp, syn2a, and tuba1b genes, which compromised neuronal structure and function, while impaired neurotransmitter release and uptake could occur due to the suppression of crhb and mao genes. To conclude, these findings illustrate the interconnected impact of pathways involved in endocrine and neurodevelopment in reserpine-induced toxicity.

Understanding of Benzophenone UV Absorber-Induced Damage and Apoptosis in Human Hepatoma Cells

Benzophenone UV absorbers (BPs), a widely used family of organic UV absorbers (UVAs), have attracted considerable attention for their effects on organisms in recent years. Previous research has been unable to illuminate the intricate situation of BP pollution. To address this knowledge gap, we devised a BAPG-chain model that surpasses existing approaches based on biochemical detection, antioxidant defense systems, proteins, and genes to investigate the biological mechanisms of benzophenone-1 (BP-1) and benzophenone-3 (BP-3) within human hepatoma SMMC-7721 cells as model organisms. The BAPG-chain model links the cellular model, molecular level, macroscopic scale, and microscopic phenomena by adopting a global assessment mindset. Our findings indicate that BPs induce apoptosis via the excessive production of reactive oxygen species (ROS), mitochondrial and nuclear damage, and disruption of the antioxidant stress system. Notably, BPs induce apoptosis via alterations in the expression of genes and proteins associated with apoptosis in the mitochondria. Our experimental evidence sheds light on the biological effects of BPs and highlights the need for further research in this area.

Phenyl salicylate induces neurotoxicity and early Alzheimer's disease-like symptoms through ndrg1-regulated myelin damage, increasing bace1 in zebrafish

Phenyl salicylate, an important industrial raw material, is widely used in plastics, cosmetics, and pharmaceuticals. However, little is known about its neurotoxicity on wildlife. Here, we exposed zebrafish embryos at 4 hours post-fertilization (hpf) to 0.025, 0.05, 0.1, 0.25, 0.5, and 1.0 mg/L of phenyl salicylate up to 144 hpf and found its developmental- and neuro-toxicity. Specifically, a dose-dependent increase in mortality and malformation in zebrafish were revealed. Phenyl salicylate also adversely affected the development of monoaminergic neurons, cerebral blood vessels, and the blood-brain barrier (BBB), as well as induced cerebral hemorrhages and locomotion change. RNA-sequencing results combined with verification data showed that phenyl salicylate downregulated the expression of the N-myc downstream regulated gene-1 (ndrg1), caused myelin damage in zebrafish, and then increased expression of beta-secretase 1 (bace1), which ultimately led to early Alzheimer's disease (AD)-like symptoms, including BBB leakage, bleeding in the brain, and upregulation of the glial fibrillary acidic protein gene (gfap) and cholinergic system-related gene (chrna7a). In conclusion, phenyl salicylate exposure triggered developmental toxicity and neurotoxicity in zebrafish, which has a potential risk for the development of AD. Given the effects of phenyl salicylate exposure to ecosystem, the safety usage limit should be treated with caution.

Fosab, but not fosaa, plays important role in learning and memory in fish-insights from zebrafish gene knockout study

Introduction: Learning and memory allow individuals to adapt to their environmental needs and survive. Fish have the ability to solve complex learning tasks, associative learning, and flexible spatial memory. The proto-oncogene fos (c-fos) has been reported to be involved in brain development, learning and memory in mammals. However, whether the c-fos plays a vital role in learning and memory in fish is unclear. Methods: Almost all fish have two paralogues of c-fos named fosaa and fosab. We used CRISPR/Cas9 technology to generate fosaa and fosab knockout zebrafish models. Results: In this study, we discovered the brain weight marked reduction in fosaa -/- and fosab -/- zebrafish compared with the wild-type (WT) (AB strain) zebrafish. In the T-maze behavioral assay, the fosab -/- zebrafish took significantly more than the average time to complete the assigned trial as the increase in the days compared to WT zebrafish, while the fosaa -/- zebrafish did not show a notable variance. The average time to complete the trial in fosab -/- zebrafish was significantly higher than in WT zebrafish. The relative mRNA expression level of c-jun in fosab -/- zebrafish was significantly higher than that in WT zebrafish, while the fosaa -/- zebrafish has no discernible trend. Additionally, the phylogenetic and multiple amino acid alignment results indicated that fish fosab has a higher identity with mammals Fos. Discussion: By integrating the above results, we found that fosab, but not fosaa, may possess a learning and memory function in fish. For the first time, we illustrated the role of fosaa and fosab in learning and memory via c-fos knockout in fish, which can provide new insights into environmental adaptation.

Effect of functional groups of polystyrene nanoplastics on the neurodevelopmental toxicity of acrylamide in the early life stage of zebrafish

Polystyrene nanoplastics (PS NPs) and acrylamide (ACR), both emerging contaminants, have been found to be related to neurotoxicity. However, the effects of PS NPs on ACR-induced neurodevelopmental toxicity remain unclear. In this study, anionic carboxyl polystyrene nanoplastics (PS NPs-COOH), cationic amino polystyrene nanoplastics (PS NPs-NH2) and unmodified PS NPs were selected to investigate their interaction with ACR. A serious of the neurotoxicity biomarkers from individual to molecular level were evaluated to explore the specific mechanisms. The results indicated that the unmodified PS NPs had the most significant impact on embryonic development at low concentrations in combination with ACR. The toxicity of the other two functionalized PS NPs increased with concentration, exhibiting a clear dose-response relationship. Meanwhile, all three kinds of PS NPs significantly enhanced the impacts of ACR on the locomotion behavior of zebrafish larvae. Analysis of zebrafish nervous system development showed that PS NPs-COOH exhibit greater toxicity to the central nervous system. In contrast, PS NPs-NH2 had a more significant impact on the motor nervous system. Gene expression analysis revealed that ACR and PS NPs significantly affected the expression levels of neurodevelopmental related genes, including Neurog1, Elavl3, Gfap, Gap43, Mbpa, Shha. PS NPs modified with functional groups could induce corresponding neurotoxicity by affecting genes expression related to neuronal differentiation, motor neuron, and axonal development. Based on the comprehensive biomarker response index, the order of the impacts of NPs on the neurotoxicity of ACR was PS NPs-COOH > PS NPs-NH2 > PS NPs. In conclusion, this study provides new insights into the interactive biological effects of NPs and ACR on zebrafish embryo, contributing to a better understanding of their environmental risk to aquatic ecosystem.

Tri-iso-butyl phosphate (TiBP) exposure induces neurotoxicity by triggering oxidative stress accompanied by neurotransmitter system disruptions and apoptosis in zebrafish larvae

The current research sheds light on the biological toxicity of organophosphate flame retardants (OPFRs), yet it overlooks the neurotoxicity and potential molecular mechanisms of tris(1,3-dichloro-2-propyl) phosphate (TiBP), a prominent constituent of the OPFRs. To address this, we utilized zebrafish larvae as a model to investigate TiBP's acute toxicity and neurotoxic effects, along with the associated molecular pathways. Our findings revealed that the 96 h and 120 h LC50 values for TiBP were 56.51 mg/L and 48.85 mg/L, respectively. Gradient exposure based on the 120 h LC50 demonstrated that TiBP induced developmental toxicity, characterized by elevated heart rate, reduced body length, and diminished eye distance. Additionally, a decrease in swimming activity was observed in the light test, along with the inhibition of the neuro crest cell development in Tg (HuC:eGFP) and Tg (sox10: eGFP) zebrafish larvae following TiBP exposure, as well as the alterations of neurogenesis and ACh-related genes. Expression of key neurodevelopment genes, including mbpa, gap43, nestin, ngfra, was significantly downregulated. Furthermore, heightened anxiety-like behaviors in open field and phototaxis tests were observed, concomitant with neurotransmitter imbalances. Specifically, there was an increase in DA levels, a decrease in GABA, and an upregulation of AChE activity. These disruptions were primarily mediated through transcriptional dysregulation of neurotransmitter synthesis, transport, and reception. Upon exposure to TiBP, zebrafish larvae exhibited a concentration-dependent increase in both ROS level and apoptosis. An upregulation of antioxidant enzymes and their transcription levels indicated the presence of oxidative stress in the larvae. The induction of ddit3 was congruent with the observed apoptosis, suggesting that it may be triggered by oxidative stress via the ERs-CHOP pathway. In summary, our study indicates that oxidative stress is a pivotal molecular event in the neurotoxicity induced by TiBP, implicating the disruption of the GABAergic, dopaminergic, and cholinergic systems, as well as triggering apoptosis.

Genetic Evidence for Estrogenic Effects of Benzophenone-2 on Zebrafish Neurodevelopment and Its Signaling Mechanism

Estrogens play a crucial role in regulating various biological responses during the early stages of neurodevelopment. Benzophenone-2 (BP2), a widely used organic ultraviolet (UV) filter, has been proven as an estrogenic compound, whereas the estrogenic effects of BP2 on neurodevelopment remain largely unknown. Here, we investigated the neurodevelopmental toxicity of BP2 by exposing zebrafish embryos from 2 to 120 h postfertilization (hpf) at environmentally relevant concentrations. We demonstrated that early life exposure to BP2 induced multiple concentration-dependent impairments in the nervous system, including hypoactivity, abnormal brain morphology, impaired neurocyte proliferation, shortened axon, and increased neurocyte apoptosis. Moreover, metabolomic profiling revealed a decrease in dopamine (DA) and its metabolites in BP2-treated larvae. Using E2 treatment and morpholino knockdown assays, we provided strong genetic evidence that the BP2-induced behavioral disorders were associated with estrogen-dependent signaling, especially estrogen receptors 2a and 2b (esr2). Subsequently, transcriptomic profiling indicated that the activation of esr2 further inhibited the expression of LIM homeobox transcription factor 1 β a (lmx1ba), which is vital for normal neurodevelopment. Consistently, the overexpression of lmx1ba and inhibition of esr2 obviously alleviated BP2-caused neurotoxicity, uncovering a seminal role of esr2 and lmx1ba in BP2-induced neurodevelopmental toxicity. Our findings provide the first evidence in fish that BP2 can induce neurodevelopmental deficits and brain dysfunction and offer novel insights into the mechanisms of toxicity of BP2 as well as other emerging benzophenones.

Behavioral neuroscience in zebrafish: unravelling the complexity of brain-behavior relationships

This paper reviews the utility of zebrafish (Danio rerio) as a model system for exploring neurobehavioral phenomena in preclinical research, focusing on physiological processes, disorders, and neurotoxicity biomarkers. A comprehensive review of the current literature was conducted to summarize the various behavioral characteristics of zebrafish. The study examined the etiological agents used to induce neurotoxicity and the biomarkers involved, including Aβ42, tau, MMP-13, MAO, NF-Кβ, and GFAP. Additionally, the different zebrafish study models and their responses to neurobehavioral analysis were discussed. The review identified several key biomarkers of neurotoxicity in zebrafish, each impacting different aspects of neurogenesis, inflammation, and neurodegeneration. Aβ42 was found to alter neuronal growth and stem cell function. Tau's interaction with tubulin affected microtubule stability and led to tauopathies under pathological conditions. MMP-13 was linked to oxidative assault and sensory neuron degeneration. MAO plays a role in neurotransmitter metabolism and neurotoxicity conversion. NF-Кβ was involved in pro-inflammatory pathways, and GFAP was indicative of neuroinflammation and astroglial activation. Zebrafish provide a valuable model for neurobehavioral research, adhering to the "3Rs" philosophy. Their neurotoxicity biomarkers offer insights into the mechanisms of neurogenesis, inflammation, and neurodegeneration. This model system aids in evaluating physiological and pathological conditions, enhancing our understanding of neurobehavioral phenomena and potential therapeutic interventions.

Prenatal exposure to low doses of benzophenone-3 elicits disruption of cortical vasculature in fetuses through perturbations in Wnt/β-catenin signaling correlating with depression-like behavior in offspring mice

Benzophenone-3 (BP-3), commonly used in personal care products, is routinely detected in environmental and human matrices. Evidence delineates a correlation between gestational BP-3 exposure and emotional and social disorders in children and adolescents. However, sensitive target cells and the mode of action underlying the early responses to environmentally relevant level of BP-3 exposure remain unclear. In this study, 0.3 and 3 mg/kg of BP-3 were administered to pregnant mice. Compared with the control group, the cortical blood vessel development process manifested the highest susceptibility to BP-3 exposure using transcriptomic sequencing at embryonic day 14 (E14). Notably, the diminution in vascular density and tight junction proteins presence was observed in the fetal cortex at E14, concomitant with the suppressed transcriptional activity of genes essential to angiogenesis and barrier formation. Strikingly, the investigation revealed that BP-3 exposure impeded vascular sprouting in aortic ring explants and neuroendothelial migration, implicating the Wnt/β-catenin signaling pathway. Moreover, BP-3 exposure compromised perivascular neural stem cell differentiation. Cortical vascular injury correlated with the exhibition of depression-like behavior in four-week postnatal progeny. These insights underscore the cerebrovasculature as an early sensitive target for low doses of BP-3 exposure, fostering the development of biomarkers and the establishment of the adverse outcome pathway framework for BP-3 hazard evaluation.

Thyroid, neurodevelopmental, and kidney toxicities of common organic UV filters in embryo-larval zebrafish (Danio rerio), and their potential links

Organic UV filters (OUVFs) have been commonly used in sunscreen and many consumer products. Following dermal application, these compounds can enter circulation and may cause systemic effects in humans. In the present study, we chose four OUVFs frequently detected in the environment, i.e., avobenzone (AVB), benzophenone-3 (BP-3), octocrylene (OC), and octyl methoxycinnamate (OMC), and evaluated their thyroid, neurodevelopmental, and kidney toxicities. For this purpose, zebrafish embryos (<4 h post fertilization, hpf) were exposed to sublethal concentrations of AVB, BP-3, OC, or OMC until 120 hpf. Exposure to all OUVFs decreased thyroid hormone (TH) levels, probably by enhanced metabolism and excretion of THs (ugt1ab and/or sult1 st5) in the larval fish. Exposure to the OUVFs also induced hypoactivities and/or anxiety-like behaviors: Regulatory changes of mbp, gfap, c-fos, syn2a, sty1a, and stxbp1b genes, support the changes in normal neurobehavior of the larval fish. Moreover, the OUVFs exposure caused increased proteinuria in the fish, along with transcriptional changes of wt1, nephrin, podocin, and cdh17 genes, which could explain the observed reduction in kidney functions. Principal component analysis (PCA) implied the potential interplay of THs with neurogenesis, or podocyte differentiation of the larval fish. Toxicological consequences of altered TH homeostasis, neurobehavior, and kidney function at the early life stage warrant further investigations not only in humans but also in aquatic ecosystems.

Exploring Cr(VI)-induced blood-brain barrier injury and neurotoxicity in zebrafish and snakehead fish, and inhibiting toxic effects of astaxanthin

Cr(VI) is a common hazardous heavy metal contaminant that seriously endangers human and aquatic animal health. GPX4 was the key enzyme that reduces heavy metal toxicity through inhibiting ferroptosis pathway. Astaxanthin was GPX4 activator that can weaken biological toxicity induced by Cr(VI) exposure. The present study was conducted to evaluate the major role of GPX4 in astaxanthin protects Cr(VI)-induced oxidative damage, blood-brain barrier injury and neurotoxicity in brain-liver axis through inhibiting ferroptosis pathway. In the current study, astaxanthin intervention can effectively alleviate Cr(VI)-induced oxidative stress, blood-brain barrier damage, and neurotoxicity. GPX4 plays a major role in mediating astaxanthin nutritional intervention to reduce ROS and liver non-heme iron accumulation, which would contribute to the reduction of ferroptosis. Meanwhile, astaxanthin maintains the stability of transport receptors and protein macromolecules such as TMEM163, SLC7A11, SLC3A2, FPN1 and GLUT1 in the brain liver axis, promoting substance exchange and energy supply. Moreover, astaxanthin alleviates Cr(VI)-induced neurotoxicity by promoting tight protein expression and reducing blood-brain barrier permeability.

Hydroxylase-like Biomimetic Nanozyme Synthesized via a Urea-Mediated MOF Pyrolytic Reconstruction Strategy for Non-"o-Phenol hydroxyl"-Dependent Dopamine Electrochemical Sensing

Dopamine (DA), an essential neurotransmitter, is closely associated with various neurological disorders, whose real-time dynamic monitoring is significant for evaluating the physiological activities of neurons. Electrochemical sensing methods are commonly used to determine DA, but they mostly rely on the redox reaction of its o-phenolic hydroxyl group, which makes it difficult to distinguish it from substances with this group. Here, we design a biomimetic nanozyme inspired by the coordination structure of the copper-based active site of dopamine β-hydroxylase, which was successfully synthesized via a urea-mediated MOF pyrolysis reconstruction strategy. Experimental studies and theoretical calculations revealed that the nanozyme with Cu-N3 coordination could hydroxylate the carbon atom of the DA β-site at a suitable potential and that the active sites of this Cu-N3 structure have the lowest binding energy for the DA β-site. With this property, the new oxidation peak achieves the specific detection of DA rather than the traditional electrochemical signal of o-phenol hydroxyl redox, which would effectively differentiate it from neurotransmitters, such as norepinephrine and epinephrine. The sensor exhibited good monitoring capability in DA concentrations from 0.05 to 16.7 μM, and its limit of detection was 0.03 μM. Finally, the sensor enables the monitoring of DA released from living cells and can be used to quantitatively analyze the effect of polystyrene microplastics on the amount of DA released. The research provides a method for highly specific monitoring of DA and technical support for initial screening for neurocytotoxicity of pollutants.

Neurotoxicity of Benzotriazole Ultraviolet Stabilizers in Teleost Fishes: A Review

Plastic additives that maintain integrity have been extensively studied for potential toxicity to fish; however, chemicals that protect polymers from (artificial) UV degradation are less studied. Benzotriazole UV stabilizers (BUVSs) are the most widely used UV stabilizers in plastics and are often used in sunscreens, cosmetics, paint, and food packaging. BUVSs can negatively affect aquatic wildlife when released into the environment via plastic degradation. In this review, we summarize the distribution of BUVSs globally and discuss neurotoxicological endpoints measured in fish to understand how these plastic additives can affect the neurological health of teleost fishes. BUVSs have been detected in aquatic environments at concentrations ranging from 0.05 up to 99,200 ng/L. Studies show that BUVSs affect behavioral responses and acetylcholinesterase activity, indicators of neurotoxicity. Our computational analysis using transcriptome data suggests certain pathways associated with neurodegeneration are responsive to exposure to BUVSs, like "Complement Activation in Alzheimer's Disease". Based on our review, we identify some research needs for future investigations: (1) molecular studies in the central nervous system to define precise mechanisms of neurotoxicity; (2) a wider range of tests for assessing aberrant behaviors given that BUVSs can affect the activity of larval zebrafish; and (3) histopathology of the nervous system to accompany biochemical analyses. These data are expected to enhance understanding of the neurotoxicity potential of benzotriazoles and other plastic additives.

Health risks posed by environmental benzophenone-type ultraviolet filters (BP-UVFs): An investigation into the binding of BP-UVFs to trypsin and their adverse effects

Benzophenone-type ultraviolet filters (BP-UVFs) are ubiquitous in the environment, and people frequently ingest them via food chain and drinking water. However, there is no clear information about whether BP-UVFs are detrimental to human health. Herein, experiments using multi-spectroscopy revealed typical BP-UVFs, i.e., benzophenone (BP), 2-hydroxybenzophenone (2-OHBP), 4-hydroxybenzophenone (4-OHBP), 2,2'-dihydroxybenzophenone (2,2'-OHBP), 2,4-dihydroxybenzophenone (2,4-OHBP), 4,4'-dihydroxybenzophenone (4,4'-OHBP), 2,4,4'-trihydroxybenzophenone (2,4,4'-OHBP), 2,2',4,4'-tetraphydroxybenzophenone (2,2',4,4'-OHBP), 2-hydroxy-4-methoxybenzophenone (2-OH-4-MeOBP) and 2,2'-dihydroxy-4-methoxybenzophenone (2,2'-OH-4-MeOBP), could bind to the active site of trypsin with different binding constants (2.69 × 104-1.07 × 106 L/mol), cause structural abnormalities and inhibit the enzymatic activity in varying degrees, indicating that the BP-UVFs ingestion poses a risk to human health. In contrast to previous research, this study systematically analysed the binding mechanism using an innovative combination of molecular docking and advanced quantum chemistry calculations, including molecular dynamics simulations, energy calculations, etc. The results revealed that most amino acids that make up trypsin have a greater positive electrostatic surface potential (ESP). Therefore, the greater the area and distribution of negative ESP in a particular BP-UVFs, the more easily it will bind to trypsin. This provides new insight into the binding of pollutants to proteins. This study suggests a need for better monitoring and control of environmental BP-UVFs.

Temperature- and chemical-induced neurotoxicity in zebrafish

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

Safety of benzophenone-type UV filters: A mini review focusing on carcinogenicity, reproductive and developmental toxicity

Consumer products containing benzophenone-type ultraviolet (UV) filters (BPs) have been widely accepted by the public, resulting in the widely existence of various BPs in the human body and environment. In recent years, more and more evidences show that BPs are endocrine disruptors. In view of the continuous exposure risk of BPs and their endocrine disrupting characteristics, the carcinogenicity of BPs and their effects on reproduction and development are of particular concern. However, due to the wide varieties of BPs and the scattered toxicity studies on BPs, people have a limited understanding on the safety of BPs. Therefore, this paper systematically reviews the carcinogenicity, reproductive and developmental toxicity of BPs in order to expand people's knowledge on the health risks of BPs and screen for more safe BPs. Although existing toxicological studies are insufficient, it can be determined that BPs have different potentials for carcinogenicity, and reproductive and developmental toxicity. Among those BPs, 2-hydroxyl-4-methoxyl benzophenone needs to be used with caution due to its adverse effects on cancer cell proliferation and migration, reproductive ability, sex differentiation, neurodevelopment, and so on. It is worth noting that functional group substitutions significantly affect the interaction between BPs and biomolecules such as DNA, cancer cells, and seminal fluid, resulting in different levels of toxicity. In short, it is very necessary to evaluate the carcinogenicity, reproductive and developmental toxicity of BPs, which is of great significance for establishing reasonable BPs content standards in cosmetics, water quality treatment standards for BPs, and so on.

Short-term effects of an environmentally relevant concentration of organic UV filters on signal crayfish Pacifastacus leniusculus

Personal care products, including organic UV filters, are considered emerging contaminants, with their toxic effects being a concern in recent decades. UV filters continually enter surface waters via wastewater and human activity. Despite the presence of organic UV filters in the freshwater environment, little is known of their impact on aquatic biota. In this study, we evaluated the cardiac and locomotor responses of signal crayfish Pacifastacus leniusculus exposed to environmentally relevant concentrations of either 2-Phenylbenzimidazole-5-sulfonic acid (PBSA, 3 µg/L) or 5-Benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid (BP4, 2.5 µg/L). Specimens exposed to the tested compounds for 30 min exhibited significantly greater changes in distance moved and time active than did unexposed controls. Significant differences of mean heart rate change compared to control were detected in both PBSA and BP4 experimental groups. Such behavior and physiological alterations demonstrate ecological effects of personal care products with the tested sunscreen compounds even with a short exposure. Evidence of the consequences of organic UV filters on aquatic organisms is scarce and is an important topic for future research.

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.

Lifetime exposure to benzophenone-3 at an environmentally relevant concentration leads to female-biased social behavior and cognition deficits in zebrafish

Benzophenone-3 (BP3) is an organic UV filter widely used in the commercial formulations of various personal care products. It has been detected ubiquitously in the environment and human tissues. Recently, BP3-induced neurotoxicity has been identified as the main health risk to humans and aquatic organisms. However, most research has been focused on embryonic development, and few studies explore chronic lifetime exposure. In the present study, we evaluated the neurotoxicity of lifetime exposure to an environmentally relevant concentration of BP3 in zebrafish. Our findings revealed that continuous BP3 exposure at 10 μg/L (0.04 μM) from 6 h post fertilization (hpf) to adulthood at 5 months led to female-biased social behavioral deficits and learning and memory impairment. These neurobehavioral effects were characterized by decreased prosocial activities in the social preference test and mirror biting assay, and reduced learning and memory in a T-maze test. Furthermore, these effects were accompanied by female-specific decreases in brain weight and brain dopamine concentration, female-biased decrease of neurogenesis in the telencephalon as well as female-specific increases in apoptotic cells and expression levels of genes and proteins related to the apoptosis pathway in the brain. Our results suggest that BP3-induced social behavior and learning/memory deficits are correlated to the cell loss in the telencephalon region of the zebrafish brain.

Revealing the relationship between molecular weight of lignin and its color, UV-protecting property

Lignin has great potential as a natural, green, and sustainable broad-spectrum sunscreen active ingredient. However, the coexistence of dark color and sunscreen properties hinders its application in cosmetics. In this study, we focus on the effects of the molecular weight of lignin on tis UV-protecting property and color in order to prepare lignin-based sunscreen with high performance. A prepared sunscreen containing low molecular weight lignin (F5, <1000 g/mol) exhibits good UV-protecting property (sun protection factor (SPF) = 7.14) and light color advantages (ΔE = 46.2). Moreover, a strong synergistic effect on UV-protecting property exists between low molecular weight lignin and ethylhexyl methoxycinnamate (EHMC), resulting in high SPF of F5@EHMC-based sunscreen (55.56). Additionally, added TiO2 can efficiently mitigate the dark color of lignin-based sunscreens due to prominent covering power of TiO2. Moreover, lignin-based sunscreens have good biocompatibility with HaCaT cells. This work is useful for understanding the mechanism of the UV-protecting property and dark color of lignin, and for designing an efficient and safe lignin-based sunscreen.

Zebrafish: A Pharmacological Model for Learning and Memory Research

Learning and memory are essential to organism survival and are conserved across various species, especially vertebrates. Cognitive studies involving learning and memory require using appropriate model organisms to translate relevant findings to humans. Zebrafish are becoming increasingly popular as one of the animal models for neurodegenerative diseases due to their low maintenance cost, prolific nature and amenability to genetic manipulation. More importantly, zebrafish exhibit a repertoire of neurobehaviors comparable to humans. In this review, we discuss the forms of learning and memory abilities in zebrafish and the tests used to evaluate the neurobehaviors in this species. In addition, the pharmacological studies that used zebrafish as models to screen for the effects of neuroprotective and neurotoxic compounds on cognitive performance will be summarized here. Lastly, we discuss the challenges and perspectives in establishing zebrafish as a robust model for cognitive research involving learning and memory. Zebrafish are becoming an indispensable model in learning and memory research for screening neuroprotective agents against cognitive impairment.