Environmental relevant concentrations of benzophenone-3 induced developmental neurotoxicity in zebrafish

The exposure to UV filters: Prevalence, effects, possible molecular mechanisms of action and interactions within mixtures

Substances that can absorb sunlight and harmful UV radiation such as organic UV filters are widely used in cosmetics and other personal care products. Since humans use a wide variety of chemicals for multiple purposes it is common for UV filters to co-occur with other substances either in human originating specimens or in the environment. There is increasing interest in understanding such co-occurrence in form of potential synergy, antagonist, or additive effects of biological systems. This review focuses on the collection of data about the simultaneous occurrence of UV filters oxybenzone (OXYB), ethylexyl-methoxycinnamate (EMC) and 4-methylbenzylidene camphor (4-MBC) as well as other classes of chemicals (such as pesticides, bisphenols, and parabens) to understand better any such interactions considering synergy, additive effect and antagonism. Our analysis identified >20 different confirmed synergies in 11 papers involving 16 compounds. We also highlight pathways (such as transcriptional activation of estrogen receptor, promotion of estradiol synthesis, hypothalamic-pituitary-gonadal (HPG) axis, and upregulation of thyroid-hormone synthesis) and proteins (such as Membrane Associated Progesterone Receptor (MAPR), cytochrome P450, and heat shock protein 70 (Hsp70)) that can act as important key nodes for such potential interactions. This article aims to provide insight into the molecular mechanisms on how commonly used UV filters act and may interact with other chemicals.

Sunscreen use during recreational activities on a French Atlantic beach: release of UV filters at sea and influence of air temperature

Organic UV filters are emerging contaminants in personal care products such as sunscreens. The toxicity of numerous of these UV filter compounds has been demonstrated in several marine taxa. However, whilst the biological impact has already been largely demonstrated, the anthropogenic drivers leading to UV filter contamination still need to be identified. In this work, a survey was conducted on a site of the French Atlantic Coast (i) to describe beachgoers' behaviours (sunscreen use and beach frequentation), (ii) provide an estimation of the UV filters released at sea and (iii) highlight the effect of air temperature on these behaviours and on the release of UV filters. In parallel with these estimations of the UV filters released at sea, in situ chemical measurements were performed. By comparing the results of both approaches, this interdisciplinary work provides an insight of how the observations of beachgoers' behaviour modulations and attendance level fluctuations could be used to prevent UV filter contaminations and ultimately manage the ecotoxicological risk.

Toxicity of UV Filter Benzophenone-3 in Brine Shrimp Nauplii (Artemia salina) and Zebrafish (Danio rerio) Embryos

The benzophenone (BP) family, including oxybenzone (BP-3), a prevalent sunscreen ingredient and environmental contaminant, has raised concerns since the year 2005. This study investigated oxybenzone toxicity in zebrafish (Danio rerio) eleutheroembryos and brine shrimp (Artemia salina) nauplii, focusing on the LC50 and developmental impacts. Zebrafish embryos (0.100-1.50 mg/L BP-3, 96 h) and A. salina (0.100-5.00 mg/L BP-3, 48 h) were tested with ultrasound-assisted emulsified liquid-phase microextraction (UA-ELPME) used for zebrafish tissue analysis. HPLC-DAD determined BP-3 concentrations (highest: 0.74 ± 0.13 mg/L). Although no significant zebrafish embryo mortality or hatching changes occurred, developmental effects were evident. Lethal concentrations were determined (A. salina LC50 at 24 h = 3.19 ± 2.02 mg/L; D. rerio embryos LC50 at 24 h = 4.19 ± 3.60 mg/L), with malformations indicating potential teratogenic effects. A. salina displayed intestinal tract alterations and D. rerio embryos exhibited pericardial edema and spinal deformities. These findings highlight oxybenzone's environmental risks, posing threats to species and ecosystem health.

Hybrid radical coupling during MnO2-mediated transformation of a mixture of organic UV filters: Chemistry and toxicity assessment

Manganese oxide (MnO2) is one of the most abundant metal oxides, and it is renowned for its ability to degrade various phenolic micropollutants. However, under MnO2-mediated transformation, BP-3 transforms into 12 different radical-coupled transformation products (TPs) out of 15 identified TPs. These radical-coupled TPs are reported with adverse environmental impacts. This study explored the effects of MnO2 on organic UV filter mixtures and different water constituents (i.e., bicarbonate ion (HCO3-), humic acid (HA) and halide ions) in terms of degradation efficiency and transformation chemistry. When a mixture of benzophenone-3 (BP-3) and avobenzone (AVO) underwent transformation by MnO2, hybrid radical-coupled TPs derived from both organic UV filters were generated. These hybrid radical-coupled TPs were evaluated by an in silico prediction tool and Vibrio fischeri bioluminescence inhibition assay (VFBIA). Results showed that these TPs were potentially toxic to aquatic organisms, even more so than their parent compounds. The higher the concentration of HCO3-, HA, chloride ion (Cl-) and bromide ion (Br-), the greater the reduction in the efficiencies of degrading BP-3 and AVO. Contrastingly, in the presence of iodide ion (I-), degradation efficiencies of BP-3 and AVO were enhanced; however, iodinated TPs and iodinated radical-coupled TPs were formed, with questionable toxicity. This study has revealed the environmental risks of hybrid radical-coupled TPs, iodinated TPs and iodinated radical-coupled TPs when the organic UV filters BP-3 and AVO are transformed by MnO2.

Post-fertilization 2-ethylhexyl-4-methoxycinnamate (EHMC) exposure affects axonal growth, muscle fiber length, and motor behavior in zebrafish embryos

Organic UV filters, which are often found in the environment, have been the focus of much public health concern. 2-ethylhexyl-4-methoxycinnamate (EHMC) is one of the most common organic UV filters present in the environment. However, few studies have investigated its developmental neurotoxic (DNT) effects and the underlying molecular mechanisms. In the present study, zebrafish embryos were exposed to low concentration of EHMC (0, 0.01, 0.1, 1 mg/L) in static water starting from 6 h post-fertilization (hpf). Results showed that EHMC exposure caused a reduction in somite count at 13 hpf, a diminishment in head-trunk angle at 30 hpf, a delay in hatching at 48 hpf, and a decrease in head depth and head length at both 30 and 48 hpf. Additionally, EHMC led to abnormal motor behaviors at various developmental stages including altered spontaneous movement at both 23 and 24 hpf, and decreased touch response at 30 hpf. Consistent with these morphological changes and motor behavior deficits, EHMC inhibited axonal growth of primary motor neurons at 30 and 48 hpf, and yielded subtle changes in muscle fiber length at 48 hpf, suggesting the functional relevance of structural changes. Moreover, EHMC exposure induced excessive cell apoptosis in the head and spinal cord regions, increased the production of reactive oxygen species (ROS) and malondialdehyde (MDA), and reduced the level of glutathione (GSH). Defects of lateral line system neuromasts were also observed, but no structural deformity of blood vessels was seen in developing zebrafish. Abnormal expression of axonal growth-related genes (gap43, mbp, shha, and α1-tubulin) and apoptosis-related genes (bax/bcl-2 and caspase-3) revealed potential molecular mechanisms regarding the defective motor behaviors and aberrant phenotype. In summary, our findings indicate that EHMC induced developmental neurotoxicity in zebrafish, making it essential to assess its risks and provide warnings regarding EHMC exposure.

A review of sources, pathways, and toxic effects of human exposure to benzophenone ultraviolet light filters

Benzophenone ultraviolet light filters (BPs) are high-production-volume chemicals extensively used in personal care products, leading to widespread human exposure. Given their estrogenic properties, the potential health risks associated with exposure to BPs have become a public health concern. This review aims to summarize sources and pathways of exposure to BPs and associated health risks. Dermal exposure, primarily through the use of sunscreens, constitutes a major pathway for BP exposure. At a recommended application rate, dermal exposure of BP-3 via the application of sunscreens may reach or exceed the suggested reference dose. Other exposure pathways to BPs, such as drinking water, seafood, and packaged foods, contribute minimal to the overall dose. Inhalation is a minor pathway of exposure; however, its contribution cannot be ignored. Human exposure to BPs is an order of magnitude higher in North America than in Asia and Europe. Studies conducted on laboratory animals and cells have consistently demonstrated the toxic effects of BP exposure. BPs are estrogenic and elicit reproductive and developmental toxicities. Furthermore, neurotoxicity, hepatotoxicity, nephrotoxicity, and carcinogenicity have been reported from chronic BP exposure. In addition to animal and cell studies, epidemiological investigations have identified associations between BPs and couples' fecundity and other reproductive disorders, as well as adverse birth outcomes. Further studies are urgently needed to understand the risks posed by BPs on human health.

Ethylene thiourea exposure induces neurobehavioral toxicity in zebrafish by disrupting axon growth and neuromuscular junctions

Ethylene thiourea (ETU) converted from ethylene bisdithiocarbamate (EBDC) fungicides has aroused great concern because of its prevalence and harmful effects. Although ETU-induced neurotoxicity has been reported, the potential mechanisms remain unclear. This study provided insights into its neurotoxic effects at environmentally relevant concentrations in zebrafish. Our findings showed that embryonic exposure to ETU decreased the hatch rate and delayed somite development. Furthermore, ETU treatment significantly reduced the dark velocity in the locomotion assay. The upregulated tendency of the mitogen-activated protein kinases (MAPK) pathway (mknk1, atf4, mapkapk3) screened by transcriptome analysis implied motor neuron degeneration, which was validated by subsequent morphological observation, as axon length and branches were truncated in the 62.5 µg/L ETU group. However, although the rescue experiment with a p38 MAPK inhibitor (SB203580) successfully ameliorated axon degeneration, it failed to reverse the locomotion behaviors. Further exploration of transcriptome data revealed the varied expression of presynaptic scaffold protein-related genes (pcloa, pclob, bsna), whose downregulation might impair the neuromuscular junction (NMJ). Therefore, we reasonably suspected that ETU-induced neurobehavioral deficits might result from the combined effects of the MAPK pathway and presynaptic proteins. Considering this, we highlighted the necessity to take precautions and early interventions for susceptible ETU-exposed populations.

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.

4-Methylbenzylidene camphor induced neurobehavioral toxicity in zebrafish (Danio rerio) embryos

4-Methylbenzylidene camphor (4-MBC) is a widely used organic UV filter in personal care products. Extensive use of 4-MBC and its frequent detection in aquatic ecosystems defile the biota with muscular and neuronal impairments. This study investigates the neurobehavioral toxicity of 4-MBC using Danio rerio as a model organism. Embryos were exposed semi-statically to 4-MBC at 5, 50, and 500 μg/L concentrations for 10-day post fertilization (dpf). Embryos exhibited a significant thigmotaxis and decreased startle touch response with altered expression of nervous system mRNA transcripts on 5 & 10 dpf. Compared to the sham-exposed group, 4-MBC treated larvae exhibited changes in the expression of shha, ngn1, mbp, elavl3, α1-tubulin, syn2a, and gap43 genes. Since ngn1 induction is mediated by shh signaling during sensory neuron specification, the elevated protein expression of NGN1 indicates 4-MBC interference in the sonic hedgehog signaling pathway. This leads to sensory neuron impairment and function such as 'sense' as evident from reduced touch response. In addition, larval brain histology with a reduced number of cells in the Purkinje layer emblazing the defunct motor coordination. Predictive toxicity study also showed a higher affinity of 4-MBC to modeled Shh protein. Thus, the findings of the present work highlighted that 4-MBC is potential to induce developmental neurotoxicity at both behavioral and molecular functional perspectives, and developing D. rerio larvae could be considered as a suitable alternate animal model to assess the neurological dysfunction of organic UV filters.

Fish gut and skin microbiota dysbiosis induced by exposure to commercial sunscreen formulations

UV filters (organic or mineral) present in sunscreen products are emerging contaminants of coastal aquatic environments. There is an urgent need to understand marine organisms responses to these compounds. In this study, we investigated the effect of exposure to dilutions of commercial sunscreen formulations on bacterial communities of mullet (Chelon sp.). The gut and skin mucus microbial communities were characterized using a metabarcoding approach targeting the 16S rRNA gene. Our results revealed that mullets had its own bacterial communities that differ from their surrounding habitats and specific to tissue. The dilutions of commercial sunscreens modified the relative abundance of Actinobacteroita, Bacteriodota and Proteobacteria for both gut and skin microbiota. They also allowed to bacteria affiliated to Mycobacterium, Nocardia and Tenacibaculum genera, known to house pathogenic species, to colonize the epithelium which may have implications for fish host health.

4-Methylbenzylidene camphor triggers estrogenic effects via the brain-liver-gonad axis in zebrafish larvae

4-Methylbenzylidene camphor (4-MBC), an emerging contaminant, is a widely-used ultraviolet (UV) filter incorporated into cosmetics because it protects the skin from UV rays and counters photo-oxidation. Despite the well-established estrogenic activity of 4-MBC, the link between this activity and its effects on neurobehavior and the liver remains unknown. Thus, we exposed zebrafish larvae to environmentally relevant concentrations of 4-MBC with 1.39, 4.17, 12.5 and 15.4 μg/mL from 3 to 5 days postfertilization. We found that 4-MBC produced an estrogenic effect by intensifying fluorescence in the transgenic zebrafish, which was counteracted by co-exposure with estrogen receptor antagonist. 4-MBC-upregulated estrogen receptor alpha (erα) mRNA, and an interaction between 4-MBC and ERα suggested ERα's involvement in the 4-MBC-induced estrogenic activity. RNA sequencing unearthed 4-MBC-triggered responses in estrogen stimulus and lipid metabolism. Additionally, 4-MBC-induced hypoactivity and behavioral phenotypes were dependent on the estrogen receptor (ER) pathway. This may have been associated with the disruption of acetylcholinesterase and acetylcholine activities. As a result, 4-MBC increased vitellogenin expression and caused lipid accumulation in the liver of zebrafish larvae. Collectively, this is the first study to report 4-MBC-caused estrogenic effects through the brain-liver-gonad axis. It provides novel insight into how 4-MBC perturbs the brain and liver development.

Benzophenone-3 causes oxidative stress in the brain and impairs aversive memory in adult zebrafish

Oxybenzone (BP-3) is an ultraviolet (UV) filter widely used in industries that is directly or indirectly released into the aquatic environment. However, little is known about its effects on brain performance. Here, we investigated whether BP-3 exposure affects the redox imbalance in zebrafish and how they respond to a task that requires memory of an aversive situation. Fish were exposed to BP-3 10 and 50 μg L-1 for 15 days and then tested using an associative learning protocol with electric shock as a stimulus. Brains were extracted for reactive oxygen species (ROS) measurement and qPCR analysis of antioxidant enzyme genes. ROS production increased for exposed animals, and catalase (cat) and superoxide dismutase 2 (sod 2) were upregulated. Furthermore, learning and memory were reduced in zebrafish exposed to BP-3. These results suggested that BP-3 may lead to a redox status imbalance, causing impaired cognition and reinforcing the need to replace the toxic UV filters with filters that minimize environmental effects.

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.

Biomarkers activity in Oreochromis niloticus under sub-chronic exposure to a UV filters ternary mixture

The behavior of organic UV filters in aquatic ecosystems and living organisms raises concern. For the first time, biochemical biomarkers were evaluated in the liver and brain of juvenile Oreochromis niloticus exposed to 0.001 and 0.5 mg L^-1 of a benzophenone-3 (BP-3), octyl methoxycinnamate (EHMC), and octocrylene (OC) mixture for 29 days. Before the exposure, the stability of these UV filters was investigated using liquid chromatography. The experiment with aeration in the aquarium showed a high percentage of concentration reduction (%) after 24 h: 62 ± 2 for BP-3, 96 ± 6 for EHMC, and 88 ± 2 for OC versus 5 ± 4 for BP-3, 8 ± 7 for EHMC, and 2 ± 3 for OC when without aeration. These results defined the bioassay protocol. The stability of the filters concentrations after being stored in PET flasks and subjected to freezing and thawing cycles was also verified. In PET bottles, the BP-3, EHMC, and OC presented concentration reductions of 8 ± 1, 28 ± 7 and 25 ± 5 respectively, after 96 h storage and four freezing cycles. In falcon tubes the concentration reductions observed were 47 ± 2 for BP-3, >95 ± 1 for EHMC and 86 ± 2 for OC after 48 h and two cycles. The 29 days of sub-chronic exposure indicated the occurrence of oxidative stress through the enhanced lipid peroxidation (LPO) levels for the groups exposed to both bioassay concentrations. The catalase (CAT), glutathione-S-transferase (GST), and acetylcholinesterase (AChE) activities did not show significant alterations. The genetic adverse effects were analyzed in erythrocytes of fish exposed to 0.001 mg L^-1 of the mixture by comet and micronucleus biomarkers and no significant damage was observed.

Comparison of developmental toxicity of benzophenone-3 and its metabolite benzophenone-8 in zebrafish

Benzophenone-3 (BP-3) as one of frequently used organic UV filters has been considered an emerging pollutant due to its toxicities. Benzophenone-8 (BP-8) is one of the main metabolites of BP-3 in organisms. Current reports show that BP-8 may be more toxic than BP-3. However, difference of their toxicities on embryonic development has rarely been reported. In this study, zebrafish embryos were chosen as the target organism to explore the developmental toxicities of BP-3 and BP-8. Non-targeted metabolomic analysis was performed to compare their modes of action. Results showed that BP-8 exposures led to higher bioaccumulation and lower hatching rate of zebrafish larvae than BP-3. Both BP-8 and BP-3 exposures caused behavioral abnormalities of zebrafish larvae, but no significant difference was found between them. At the metabolome level, 1 μg/L BP-3 and 1 μg/L BP-8 exposures altered neuroactive ligand-receptor interaction pathway and FoxO signaling pathway, respectively, which might be involved in the abnormal behaviors in zebrafish larvae. For higher exposure groups (30 and 300 μg/L), both BP-3 and BP-8 exposures changed metabolism of cofactors and vitamins of zebrafish larvae. Exposure of BP-3 altered the metabolism by pantothenate and CoA biosynthesis pathway, while BP-8 exposure changed riboflavin metabolism and folate biosynthesis. The above results indicated different modes of action of BP-3 and BP-8 in zebrafish embryonic development. This study sheds new light to biological hazards of BP-3 due to its metabolism in aquatic organisms.

11.4 T ultra-high static magnetic field has no effect on morphology but induces upregulation of TNF signaling pathway based on transcriptome analysis in zebrafish embryos

As magnetic resonance imaging (MRI) scanners with ultra-high field (UHF) have optimal performance, scientists have been working to develop high-performance devices with strong magnetic fields to improve their diagnostic potential. However, whether an MRI scanner with UHF poses a risk to the safety of the organism require further evaluation. This study evaluated the effects of 11.4 Tesla (T) UHF on embryonic development using a zebrafish model. Multiple approaches, including morphological parameters, physiological behaviors, and analyses of the transcriptome at the molecular level, were determined during 5 days after laboratory-controlled exposure from 6 hour post fertilization (hpf) to 24 hpf. No significant effects were observed in embryo mortality, hatching rate, body length, Left-Right patterning, locomotor behavior, etc. RNA-sequencing analysis revealed up-regulated tumor necrosis factor (TNF) inflammatory factors and activated TNF signaling pathways in the 11.4 T exposure group. The results were further validated using qPCR. Our findings indicate that although UHF exposure under 11.4 T has no effect on the development of zebrafish embryos, it has specific effects on the immune response that require further investigation.

Molecular, morphological and behavioral alterations of zebrafish (Danio rerio) embryos/larvae after clorprenaline hydrochloride exposure

Chlorprenaline hydrochloride (CLOR) is a typical representative of β-adrenergic agonists that may be used illegally as a livestock feed additive and may have adverse impacts on the environment. In the present study, zebrafish embryos were exposed to CLOR to investigate its developmental toxicity and neurotoxicity. The results demonstrated that CLOR exposure led to adverse effects on developing zebrafish, such as morphological changes, a high heart rate, and increased body length, resulting in developmental toxicity. Moreover, the up-regulation of activities of superoxide dismutase (SOD) and catalase (CAT) and the enhancement of malondialdehyde (MDA) content illustrated that CLOR exposure activated oxidative stress in exposed zebrafish embryos. Meanwhile, CLOR exposure also caused alterations in locomotive behavior in zebrafish embryos, including an increase in acetylcholinesterase (AChE) activity. Quantitative polymerase chain reaction (QPCR) results showed that the transcription of genes related to the central nervous system (CNS) development, namely, mbp, syn2a, α1-tubulin, gap43, shha, and elavl3, indicated that CLOR exposure could lead to neurotoxicity in zebrafish embryos. These results showed that CLOR exposure could cause developmental neurotoxicity in the early stages of zebrafish development and that CLOR might induce neurotoxicity by altering the expression of neuro-developmental genes, elevating AChE activity, and activating oxidative stress.

Toxic effects of isofenphos-methyl on zebrafish embryonic development

Isofenphos-methyl (IFP) is widely used as an organophosphorus for controlling underground insects and nematodes. However, excessive use of IFP may pose potential risks to the environment and humans, but little information is available on its sublethal toxicity to aquatic organisms. To address this knowledge gap, the current study exposed zebrafish embryos to 2, 4, and 8 mg/L IFP within 6-96 h past fertilization (hpf) and measured mortality, hatching, developmental abnormalities, oxidative stress, gene expressions, and locomotor activity. The results showed that IFP exposure reduced the rates of heart and survival rate, hatchability, and body length of embryos and induced uninflated swim bladder and developmental malformations. Reduction in locomotive behavior and inhibition of AChE activity indicated that IFP exposure may induce behavioral defects and neurotoxicity in zebrafish larvae. IFP exposure also led to pericardial edema, longer venous sinus-arterial bulb (SV-BA) distance, and apoptosis of the heart cells. Moreover, IFP exposure increased the accumulation of reactive oxygen species (ROS) and the content of malonaldehyde (MDA), also elevated the levels of antioxidant enzymes of superoxide dismutase (SOD) and catalase (CAT), but decreased glutathione (GSH) levels in zebrafish embryos. The relative expressions of heart development-related genes (nkx2.5, nppa, gata4, and tbx2b), apoptosis-related genes (bcl2, p53, bax, and puma), and swim bladder development-related genes (foxA3, anxa5b, mnx1, and has2) were significantly altered by IFP exposure. Collectively, our results indicated that IFP induced developmental toxicity and neurotoxicity to zebrafish embryos and the mechanisms may be relevant to the activation of oxidative stress and reduction of acetylcholinesterase (AChE) content.

Maternal Effect of Polyethylene Microplastic Fragments Containing Benzophenone-3 in Different Ages and Broods of Daphnia Magna

The maternal effect of microplastics (MPs) toxicity is likely influenced by age and brood of test species. This study investigated the maternal effect of polyethylene MP fragments (18.23 ± 8.02 μm) with benzophenone-3 (BP-3; 2.89 ± 0.20% w/w) on chronic toxicity to Daphnia magna over two generations. Neonate (< 24 h old) and adult (5 d old) daphnids in the F0 generation were exposed until 21 d old, then first and third brood neonates in the F1 generation were recovered in clean M4 medium for 21 d. Higher chronic toxicity and maternal effect of MP/BP-3 fragments were observed in the adult group compared with the neonate group, reducing growth and reproduction in both F0 and F1 generations. First brood neonates in the F1 generation showed a higher maternal effect of MP/BP-3 fragments than third brood ones, resulting in enhanced growth and reproduction relative to the control. This study provided insights into the ecological risk of MPs containing plastic additives in the natural environment.

Structure-based developmental toxicity and ASD-phenotypes of bisphenol A analogues in embryonic zebrafish

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that has become more prevalent in recent years. Environmental endocrine disruptor bisphenol A (BPA) has been linked to ASD. BPA analogues (BPs) are structure-modified substitutes widely used as safer alternatives in consumer products, yet few studies have explored the developmental neurotoxicity (DNT) of BPA analogues. In the present study, we used the larval zebrafish model to assess the DNT effects of BPA and its analogues. Our results showed that many BPA analogues are more toxic than BPA in the embryonic zebrafish assay regarding teratogenic effect and mortality, which may partially due to differences in lipophilicity and/or different substitutes of structural function groups such as CF3, benzene, or cyclohexane. At sublethal concentrations, zebrafish embryos exposed to BPA or BPs also displayed reduced prosocial behavior in later larval development, evidenced by increased nearest neighbor distance (NND) and the interindividual distance (IID) in shoaling, which appears to be structurally independent. An in-depth analysis of BPA, bisphenol F (BPF), and bisphenol S (BPS) revealed macrocephaly and ASD-like behavioral deficits resulting from exposures to sublethal concentrations of these chemicals. The ASD-like behavioral deficits were characterized by hyperactivity, increased anxiety-like behavior, and decreased social contact. Mechanistically, accelerated neurogenesis that manifested by increased cell proliferation, the proportion of newborn mature neurons, and the number of neural stem cells in proliferation, as well as upregulated genes related to the K⁺ channels, may have contributed to the observed ASD-like morphological and behavioral alterations. Our findings indicate that BPF and BPS may also pose significant risks to ASD development in humans and highlight the importance of a comprehensive assessment of DNT effects for all BPA analogues in the future.

Association between environmental phenols and all-cause and cancer mortality

To study the association between environmental phenols exposure, including benzophenone-3 (BP3) and triclosan, and all-cause mortality and cancer mortality in adults. A total of 8035 participants were included from the National Health and Nutrition Examination Survey (2003-2012). Urinary BP3 and triclosan were measured with liquid chromatography-tandem mass spectrometry. The associations between urinary BP3 and triclosan with cancer and all-cause mortality were explored by multivariable logistic regressions and restricted cubic splines. During an average of 7.25-year follow-up, 696 cases (8.7%) of all-cause mortality and 137 cases (1.71%) of cancer mortality occurred. The average levels of BP3 and triclosan were 12.2 and 10.3 ng/mL, respectively. Compared with the lowest quartile, the multivariable-adjusted hazard ratio of the highest quartile was 0.64 (95% confidence interval: 0.50 to 0.81; P < 0.001) for BP3 and 0.76 (0.61 to 0.94; P = 0.011) for triclosan. However, no significant associations between urinary BP3 and triclosan and cancer mortality were observed. BP3 and triclosan exposure decreased the risk of all-cause mortality while they were not associated with cancer mortality.

Embryonic benzophenone-3 exposure inhibited fertility in later-life female zebrafish and altered developmental morphology in offspring embryos

Benzophenone-3 (BP3), an organic UV filter widely used in personal care products, is ubiquitous in aquatic environments. Previous studies have shown that BP3 can interfere with oocytes development in the ovary. The current study was conducted to evaluate the effects of embryonic BP3 exposure on reproductive outcomes in later life. Zebrafish embryos were exposed to different concentrations of BP3 (0, 1, 10, 100 μg/L) for 5 days in the developmental stage and subsequently fed for 4 months without any toxins. The body length, body weight, and ovary weight in F0 female adult zebrafish and morphology indices in F1 offspring embryos were measured. The reproductive behaviors of adult zebrafish were recorded by a digital camera. HE staining was used to estimate the development of oocytes and the proportion of different phases was calculated. qPCR was used to detect the expression levels of reproduction-related genes of the hypothalamic-pituitary-gonadal (HPG) axis. Our findings revealed that the body length and body weight were not changed with embryonic BP3 exposure, but BP3 exposure inhibited the development and maturation of ovaries in later-life female zebrafish, accompanied by an increased proportion of follicles in the primary growth and early vitellogenic stages, and a decline in the full-growth stage in ovaries. Meanwhile, reduced egg production, delayed hatching rate, altered somite count and increased mortality rate were observed at 100 μg/L in offspring embryos. Behavioral results showed that BP3 exposure reduced the frequency of chasing, touching, entering the spawning area, and the duration of fish entering the spawning area later in life, qPCR analysis showed that the expression levels of reproduction-related genes of the HPG axis were downregulated in females, following a decreasing trend in plasma E2 and 11-KT levels. These results suggested that embryonic BP3 exposure negatively affected the fertility of fish and the development of their offspring embryos, which may cause potential risks to aquatic ecosystems and human health.

Benzophenones in the Environment: Occurrence, Fate and Sample Preparation in the Analysis

The ubiquitous presence of emerging contaminants in the environment is an issue of great concern. Notably, for some of them, no established regulation exists. Benzophenones are listed as emerging contaminants, which have been identified in the environment as well as in human fluids, such as urine, placenta, and breast milk. Their accumulation and stability in the environment, combined with the revealed adverse effects on ecosystems including endocrine, reproductive, and other disorders, have triggered significant interest for research. Benzophenones should be extracted from environmental samples and determined for environmental-monitoring purposes to assess their presence and possible dangers. Numerous sample preparation methods for benzophenones in environmental matrices and industrial effluents have been proposed and their detection in more complex matrices, such as fish and sludges, has also been reported. These methods range from classical to more state-of-the-art methods, such as solid-phase extraction, dispersive SPE, LLE, SBSE, etc., and the analysis is mostly completed with liquid chromatography, using several detection modes. This review critically outlines sample preparation methods that have been proposed to date, for the extraction of benzophenones from simple and complex environmental matrices and for cleaning up sample extracts to eliminate potential interfering components that coexist therein. Moreover, it provides a brief overview of their occurrence, fate, and toxicity.

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.

High levels of synthetic antioxidants and ultraviolet filters in children's car seats

Forty-seven compounds among synthetic phenolic and amino antioxidants and ultraviolet filters, three suites of widely used chemical additives, were measured in eighteen popular children's car seats (fabric, foam, and laminated composites of both layers) marketed in the United States in 2018. Significantly higher levels of target compounds were found in foam and composite samples than in fabric samples. Median total concentrations of phenolic antioxidants and their transformation products ranged from 8.11 μg/g in fabric to 213 μg/g in foam In general, isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (AO-1135) and 2,4-di-tert-butylphenol (24-DBP) were the most abundant among all target compounds with maximum levels of526 μg/g in composite and 13.7 μg/g, respectively. The total concentrations of amino antioxidants and their transformation products and of ultraviolet filters were at least one order of magnitude lower than those of phenolic antioxidants, with medians of 0.15-37.1 μg/g and 0.29-1.81 μg/g, respectively, in which the predominant congeners were 4-tert-butyl diphenylamine (BDPA), 4,4'-di-tert-butyl diphenylamine (DBDPA), 4-tert-octyl diphenylamine (ODPA), 2,4-dihydroxybenzophenone (BP-1), 2-hydroxy-4-methoxybenzophenone (BP-3), and 2-(2-benzotriazol-2-yl)-4-methylphenol (UV-P). Large variabilities in usage of these chemicals resulted in different compositional patterns among the car seats. These results suggest that these compounds are major polymeric additives in children's car seats as they are present at greater levels than previously measured groups of chemicals like brominated flame retardants and per- and polyfluoroalkyl substances. Given the documented toxic potentials of synthetic antioxidants and ultraviolet filters, their abundances in children products are a cause for concern.

Environmentally relevant concentrations of organic (benzophenone-3) and inorganic (titanium dioxide nanoparticles) UV filters co-exposure induced neurodevelopmental toxicity in zebrafish

UV filters, widely used in personal care products, are ubiquitous environmental pollutants detected and pose a significant public health concern. Benzophenone-3 (BP3) and titanium dioxide nanoparticles (nano-TiO₂) are the predominant organic and inorganic UV filters in environmental media. However, few studies have explored the combined developmental neurotoxic (DNT) effects and the underlying mechanisms when co-exposed to BP3 and nano-TiO₂. In the present study, zebrafish (Danio rerio) embryos were exposed to environmentally relevant concentrations of BP3 (10 μg/L), nano-TiO₂ (100 μg/L), and mixtures starting from 6 h post fertilization (hpf), respectively. Developmental indicators and motor behaviors were investigated at various developmental stages. Our results showed that BP3 alone or co-exposed with nano-TiO₂ increased spontaneous movement at 24 hpf, co-exposure decreased touch response at 30 hpf and hatching rate at 60 hpf. Consistent with these motor deficits, co-exposure to BP3 and nano-TiO₂ inhibited relative axon length of primary motor neuron during the early developmental stages, disturbed the expression of axonal growth-related genes at 30 and 48 hpf, increased cell apoptosis on the head region and mRNA levels of apoptosis-related genes, and also increased reactive oxygen species (ROS) levels in zebrafish, suggesting the functional relevance of structural changes. Taken together, our findings demonstrated that BP3 alone or in combination with nano-TiO₂ at environmentally relevant concentrations induced evident neurotoxic effects on the developing embryos in zebrafish.

Embryonic exposure to fentanyl induces behavioral changes and neurotoxicity in zebrafish larvae

The use of fentanyl during pregnancy, whether by prescription or illicit use, may result in high blood levels that pose an early risk to fetal development. However, little is known regarding the neurotoxicity that might arise from excessive fentanyl exposure in growing organisms, particularly drug-related withdrawal symptoms. In this study, zebrafish embryos were exposed to fentanyl solutions (0.1, 1, and 5 mg/L) for 5 days post fertilization (dpf), followed by a 5-day recovery period, and then the larvae were evaluated for photomotor response, anxiety behavior, shoaling behavior, aggression, social preference, and sensitization behavior. Fentanyl solutions at 1 and 5 mg/L induced elevated anxiety, decreased social preference and aggressiveness, and behavioral sensitization in zebrafish larvae. The expression of genes revealed that embryonic exposure to fentanyl caused substantial alterations in neural activity (bdnf, c-fos) and neuronal development and plasticity (npas4a, egr1, btg2, ier2a, vgf). These results suggest that fentanyl exposure during embryonic development is neurotoxic, highlighting the importance of zebrafish as an aquatic species in research on the neurobehavioral effects of opioids in vertebrates.

Comparative transcriptome analysis reveals immunotoxicology induced by three organic UV filters in Manila clam (Ruditapes philippinarum)

Benzophenone-3 (BP-3), 4-methyl-benzylidene camphor (4-MBC) and 2-ethyl-hexyl-4-trimethoxycinnamate (EHMC) are commonly used organic ultraviolet (UV) filters and are frequently detected in water environments. In the present study, we studied the potential adverse impacts of UV filter exposures in Ruditapes philippinarum by investigating transcriptomic profiles and non-specific immune enzyme activities. Transcriptome analysis showed that more genes were differentially regulated in EHMC-treated group, and down-regulated genes (2009) were significantly more than up-regulated ones (410) at day 7. Function annotation revealed that pathways "immune system", "cell growth and death" and "infectious diseases" were significantly enriched. Generally, combined qPCR and biochemical analyses demonstrated that short-term exposure to low dose of UV filters could activate immune responses, whereas the immune system would be restrained after prolonged exposure. Taken together, the present study firstly demonstrated the immunotoxicology induced by BP-3, 4-MBC and EHMC on R. philippinarum, indicating their potential threats to the survival of marine bivalves.

Synthesis of cross-linked magnetic chitosan beads immobilised with bacteria for aerobic biodegrading benzophenone-type UV filter

Bacterial immobilisation is a technique by which bacteria are embedded into or adsorbed onto a carrier material thereby increasing bacterial tolerance to harsh environments. This technique can be used to enhance bacterial activity and to degrade pollutants. Immobilised bacterial beads that contain nanomagnetic particles allow bead recycling and reuse. In this study, our objective was to produce cross-linked nanomagnetic chitosan beads (MCBs) for the biodegradation of benzophenone-type UV filter chemicals such as 2,4-dihydroxybenzophenone (BP-1) and oxybenzone (BP-3). We found that the optimal concentration for creating these MCBs to be 1.2% by weight chitosan and 10% by weight nano-magnetite. We selected and isolated six benzophenone-n (BPs)-biodegrading bacteria identified to be various Pseudomonas spp., a Gordonia sp., and Rhodococcus zopfii; these were used to create MCBs that were able to effectively biodegrade BP-1 or BP-3 as a sole carbon source. Both BPs were effectively biodegraded and mineralised over 8 days in the presence of the selected MCB-immobilised bacterial strains. The highest pseudo-first-order constant rates for BP biodegradation were 8.7 × 10^-3 h^-1 for BP-1 (strain BP1-D) and 1.02 × 10^-3 h^-1 for BP-3 (strain BP3-1). The mechanical strength of the MCBs was measured to be above 90% based on recovered weight. The MCBs released their bacteria at rates in the range of 10⁴-10⁵ CFU/day. We also determined the pathway through which the BPs were being aerobically biodegraded based on the GC/MS profiles of the intermediates. Our findings provide a novel strategy for treating BPs via the use of reusable and recyclable MCBs that are cheap, easy and fast to synthesise.

Soil degradation kinetics of oxybenzone (Benzophenone-3) and toxicopathological assessment in the earthworm, Eisenia fetida

A preponderance of recent evidence indicates that oxybenzone and other personal-care product chemicals threaten the biota inhabiting various ecological niches. What is understudied is the ecotoxicological impact of oxybenzone, a UV filter in sunscreens and anti-aging products, to terrestrial/soil organisms that are keystone species in these habitats. In the present study, acute exposure (14-day) to oxybenzone resulted in earthworm mortality (LC₅₀ of 364 mg/kg) and growth rate inhibition. Environmentally relevant concentration of oxybenzone (3.64, 7.28 and 36.4 mg/kg) at exposures of 7-day, 14-day, 28-day induced oxidative stress and neurotoxicity followed by perturbations in reproduction processes and changes in vital organs. Decreased levels of superoxide dismutase (SOD) and catalase (CAT) activity were statistically lower than controls (p < 0.05) on day 14 for all three concentrations, while glutathione-s-transferase (GST) activity was significantly elevated from controls on days 7 and 14. On day 28, SOD and CAT activities were either not significantly different from the control or were higher, demonstrating a temporal multiphasic response of anti-oxidant enzymes. GST activity on day 28 was significantly reduced compared to controls. Acetylcholinesterase levels across the three-time points exhibited a complicated behaviour, with every exposure concentration being significantly different from the control. Chronic exposure negatively influences earthworm health status with elevated biomarker values analysed using IBRv2 index. This, in turn, impacted higher levels of hierarchical organization, significantly impairing reproduction and organismal homeostasis at the histological level and manifesting as decreasing cocoon formation and successful hatching events. Thus, the overall findings demonstrate that oxybenzone is toxic to Eisenia fetida at low-level, long-term exposure. Based on the concentration verification analysis and application of the EPA PestDF tool, oxybenzone undergoes single first-order kinetics degradation in OECD soil with DT50 and DT90 as 8.7-28.9 days, respectively.

Natural colloids at environmentally relevant concentrations affect the absorption and removal of benzophenone-3 in zebrafish

Aquatic natural colloids are closely related to the environmental behavior of pollutants, which may affect their bioavailability in aquatic organisms. This study explored the potential mechanisms of the natural colloids at environmentally relevant concentrations affecting the bioaccumulation process of benzophenone-3 (BP3) in zebrafish (Danio rerio). The results of kinetic model fitting showed that the natural colloids decreased the uptake and loss rate of BP3 by zebrafish but prolonged the time to reach the cumulative equilibrium, eventually resulting in a higher cumulative concentration in zebrafish. According to the tissue concentration at equilibrium and the results of toxicokinetic analysis, the presence of high molecular colloids could enhance the bioaccumulation of freely dissolved BP3 due to its high desorption rate with BP3 in the intestines of fish, increasing the freely dissolved BP3 concentrations to which zebrafish were exposed. Both natural colloids and BP3 could enhance the cell permeability of zebrafish, which allowed colloid-bound BP3 to directly enter the fish and accumulate in its muscle. Besides, although both natural colloids and BP3 could cause the metabolic disorders in adult zebrafish, they affected the physiological and biochemical activities of zebrafish through different pathways. The disturbance of glutathione metabolism in zebrafish induced by natural colloids may be the reason for the diminished ability of zebrafish to clear and transform BP3 in the mixture system. The carrier effect of natural colloids and reduced clearance ability of zebrafish eventually increased the bioaccumulation of BP3 in zebrafish. This study highlights the significance of natural colloids at environmentally relevant concentrations on the biological effects of emerging contaminants in actual waters, however, natural colloids are always ignored in most field investigation of pollutants, which would ultimately lead to an underestimation of the true ecological risk of pollutants.

Beach showers as sources of contamination for sunscreen pollution in marine protected areas and areas of intensive beach tourism in Hawaii, USA

In 2019, sands in nearby runoff streams from public beach showers were sampled on three islands in the State of Hawaii and tested for over 18 different petrochemical UV filters. Beach sands that are directly in the plume discharge of beach showers on three of the islands of Hawaii (Maui, Oahu, Hawai'i) were found to be contaminated with a wide array of petrochemical-based UV-filters that are found in sunscreens. Sands from beach showers across all three islands had a mean concentration of 5619 ng/g of oxybenzone with the highest concentration of 34,518 ng/g of oxybenzone at a beach shower in the Waikiki area of Honolulu. Octocrylene was detected at a majority of the beach shower locations, with a mean concentration of 296.3 ng/g across 13 sampling sites with the highest concentration of 1075 ng/g at the beach shower in Waikiki. Avobenzone, octinoxate, 4-methylbenzylidene camphor and benzophenone-2 were detected, as well as breakdown products of oxybenzone, including benzophenone-1, 2,2'-dihydroxy-4-methoxybenzophenone, and 4-hydroxybenzophenone. Dioxybenzone (DHMB) presented the highest concentration in water (75.4 ng/mL), whereas octocrylene was detected in all water samples. Some of these same target analytes were detected in water samples on coral reefs that are adjacent to the beach showers. Risk assessments for both sand and water samples at a majority of the sampling sites had a Risk Quotient > 1, indicating that these chemicals could pose a serious threat to beach zones and coral reef habitats. There are almost a dozen mitigation options that could be employed to quickly reduce contaminant loads associated with discharges from these beach showers, like those currently being employed (post-study sampling and analysis) in the State of Hawaii, including banning the use of sunscreens using petrochemical-based UV filters or educating tourists before they arrive on the beach.

2, 5-dichloro-1, 4-benuinone exposure to zebrafish embryos/larvae causes neurodevelopmental toxicity

2, 5-dichloro-1, 4-benuinone (2, 5-DCBQ) is an emerging disinfection by-product belonging to the class of halobenzoquinones (HBQs). However, there is limited evidence regarding the neurotoxic effects of 2, 5-DCBQ. To better understand the toxicological mechanisms of aquatic organisms, zebrafish embryos were exposed to 0.2 mg/L, 0.4 mg/L, and 0.6 mg/L of 2, 5-DCBQ from 4 h post-fertilization (hpf) to 120 hpf. Developmental defects, such as reduced body length, decreased heart rate, decreased pigmentation, and abnormal motor axon structure was observed. In particular, the locomotor activity of zebrafish larvae reduced with exposure to increasing 2, 5-DCBQ concentrations, and this effect was more pronounced under dark stimulation. The results indicated that the genes associated with neuronal development (gfap, mbp, syn2a, elavl3, ache, and a1-tubulin) were significantly downregulated after treatment with 2, 5-DCBQ. Furthermore, the KEGG result showed the neuroactive ligand-receptor interaction and apoptosis pathways were visibly disrupted, and we found acetylcholinesterase activity was also affected. In summary, the disinfection by-product, 2, 5-DCBQ, exhibits neurodevelopmental toxicity in zebrafish embryos, providing novel evidence for comprehensive analyses of its toxicity.

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

Benzophenones (BPs) are a class of UV absorber commonly used in skin care products like sunscreens. With its wide range of application, its environmental and human hazards have received much attention in recent days. Previous studies on the toxicity of BPs mainly focused on its endocrine-disrupting effects, but there are limited studies on its neurodevelopment and neurotoxicity. Herein, using the zebrafish model we studied the neurodevelopmental- and neuro-toxicity of benzophenone 1 (BP1) (0.8, 1.0, 1.2, 1.6, and 2.4 μg/mL). As a result, BP1 led to an increase of embryo mortality, a decrease in hatching rate, and an increase in the rate of developmental abnormalities in a concentration-dependent manner. BP1 also caused developmental defects in the central nervous system (CNS) and dopaminergic (DA) neurons. Accordingly, BP1 injured larval zebrafish general locomotion and response to stimuli in light/dark challenge. In adult zebrafish, BP1 exposure (1, 10, 100, 1000 μg/L) caused inhibition of learning and memory abilities in the T-maze tests, and inhibited exploratory behavior and activity in the novel tank diving tests. Further, transcription levels of genes related to neurotoxicity, neurodevelopment, and anxiety revealed that BP1 may affect the development and function of the myelin sheath, inducing structural and functional defects of CNS, manifested as abnormal behaviors such as anxiety. Hence, the current study revealed the neurodevelopmental toxicity and neurotoxicity of BP1, expanded our knowledge about the toxic effects of BP1 on organisms, posing a possible threat to the environment and human health.

Evaluation of toxicity of Personal Care Products (PCPs) in freshwaters: Zebrafish as a model

Personal care products (PCPs) are part of the large and growing family of emerging contaminants (ECs). Many daily products such as sunscreens, toothpaste, make-up products, perfume, and others, fall under this definition, and their use is increasing exponentially. Furthermore, the degradation of some components of these products is limited. Indeed, they are able to easily reach and accumulate in aquatic systems, representing a new class of contaminants. Moreover, due to their chemical properties, they can interfere at different biological levels, and for this reason, they need to be thoroughly investigated. We have reviewed the literature on PCPs, with a special focus on the adverse effects on the freshwater zebrafish (Danio rerio). The aim of this work is to provide a careful assessment of the toxicity of these compounds, in order to raise awareness for more conscious and responsible use.

Characterization of Developmental Neurobehavioral Toxicity in a Zebrafish MPTP-Induced Model: A Novel Mechanism Involving Anemia

Zebrafish represent an economical alternative to rodents for developmental neurotoxicity (DNT) testing. Mechanistic understanding is the key to successfully translating zebrafish findings to humans. In the present study, we used a well-known dopaminergic (DA) neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as a model chemical to uncover the molecular pathways for observed DNT effects. To enhance the specificity of potential molecular targets, we restricted our exposure to a concentration that is nonteratogenic yet exhibits high DNT effects and an exposure window sensitive to MPTP. Our DNT assessment based on a battery of motor and social behavioral tests revealed an effective concentration of 1 μM and a sensitive window of 48-96 h postfertilization (hpf) for MPTP-induced hypoactivity. It is worth noting that this hypoactivity persisted into later larval development until 28 dpf. We observed increased cell apoptosis, oxidative stress, and decreased ATP levels in larvae immediately after exposure at 96 hpf. Significant reductions of DA neurons were found in the retina at 72, 96, and 120 hpf. No visible deformity was found in motoneurons at 72, 96, and 120 hpf. Transcriptome analysis uncovered a novel pathway manifested by significant upregulation of genes enriched with erythropoiesis. Sensitive window exposure of MPTP and other DA neurotoxins rotenone and paraquat exhibited a concentration-dependent effect on transcriptional changes of embryonic hemoglobins and anemia. Given that anemia is a significant risk factor for Parkinson's disease and MPTP is known to cause parkinsonism in humans, we concluded that anemia resulting from dysregulation of primitive erythropoiesis during embryonic development might serve as a common mechanism underlying DA neurotoxin-induced DNT effects between zebrafish and humans.

Transient MPTP exposure at a sensitive developmental window altered gut microbiome and led to male-biased motor and social behavioral deficits in adult zebrafish

Zebrafish is an economical alternative model for developmental neurotoxicity (DNT) testing. DNT studies in zebrafish have been focused on acute effects; few studies explore enduring neurotoxicity in adults. More recently, gut microbiome has emerged as an important modulator between chemical exposure and neurotoxicity, rendering its necessity to be included in DNT testing. The present study used a well-known dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as a model chemical to explore long-lasting neurotoxicity in adults after transient exposure during early development. We demonstrated that transient MPTP exposure at 1μM during a sensitive developmental window of 48-96hours post-fertilization (hpf) altered gut microbiome and led to male-biased locomotion and behavioral deficits in adult fish. The locomotion deficit was manifested as hypoactivity observed in adult males under light conditions or specifically the reduction of fast swim bouts. The social behavioral deficits were characterized by the reduced number of times fish crossed the mirror zone in the mirror response assay and the reduced percent time fish spent at the area proximal to conspecific fish shoal in the social preference test. Gut microbiome analysis revealed that transient MPTP exposure during early development might render fish more susceptible to the colonization of the pathogenic Vibrio. In conclusion, our study revealed that transient MPTP exposure during early development could lead to long-lasting neurotoxicity in adult fish and cause altered gut microbiome composition in both larval and adult fish.

Fish consumption is an indicator of exposure to benzophenone derivatives: A probabilistic risk assessment in Taiwanese population

Benzophenone (BP) derivatives (BPs) ultraviolet filters are used in industrial and commercial products and have been reported to be toxic. Studies have investigated the ecological risks but not the human exposure risks of BPs. Residues of 10 BPs (BP, BP-1, BP-2, BP-3, BP-8, 2-OHBP, 4-OHBP, 4-MBP, M2BB, and PBZ) were measured in 110 commercial samples of saltwater fish (SF) and freshwater fish (FF) from Taiwan. The estimated daily intakes (EDIs) and noncarcinogenic risks (as hazard quotients [HQs] and hazard indices [HIs]) were predicted for eight age groups by using Monte Carlo simulation, and sensitivity analysis was conducted to determine the factors influencing risks. The carcinogenic risk of exposure to BP was estimated using lifetime cancer risk (LTCR). The results revealed that seven BPs (BP, BP-3, 2-OHBP, 4-OHBP, 4-MBP, PBZ, and M2BB) were ubiquitous in the fish samples. The mean sums of the content of these seven BPs in FF and SF were 46.4 ng/g and 25.0 ng/g, respectively. Infants (age 0-3 years) exhibited the highest HI of BPs (1.6E-2) and LTCR of BP (2.8E-7) among all age groups. The HQs and HIs of all BPs were less than 1 and the LTCR for BP was lower than the acceptable range (10^-4 to10^-6) in all age groups, suggesting that BPs intake through fish consumption is not a health concern for Taiwanese people. The results of the sensitivity analysis demonstrated that the amount of SF consumed and 2-OHBP levels exerted the greatest effect on risk. Considering the relatively higher risk of fish consumption and concerns that ultraviolet filters are endocrine disruptors, the potential health risks of BPs intake for infants deserves further attention.

Oxybenzone contamination from sunscreen pollution and its ecological threat to Hanauma Bay, Oahu, Hawaii, U.S.A

Hanauma Bay is a 101-acre bay created by the partial collapse of a volcanic cone and once supported a vibrant coral reef system. It is the most popular swimming area in the Hawaiian Islands and has been reported to have averaged between 2.8 and 3.5 million visitors a year between the 1980s and the 2010s, with visitors averaging between 3000-4000 a day and peaking around 10,000-13,000 per day. Concentrations of oxybenzone and other common UV filters were measured in subsurface water samples and in sands from the beach-shower areas in Hanauma Bay. Results demonstrate that beach showers also can be a source of sunscreen environmental contamination. Hydrodynamic modeling indicates that oxybenzone contamination within Hanauma Bay's waters could be retained between 14 and 50 h from a single release event period. Focusing on only oxybenzone, two different Hazard and Risk Assessment analyses were conducted to determine the danger of oxybenzone to Hanauma Bay's coral reef system. Results indicate that oxybenzone contamination poses a significant threat to the wildlife of Hanauma Bay. To recover Hanauma Bay's natural resources to a healthy condition and to satisfactorily conserve its coral reef and sea grass habitats, effective tourism management policies need to be implemented that mitigate the threat of sunscreen pollution.

Effects of oxybenzone on zebrafish behavior and cognition

The increased ultraviolet (UV) radiation on the Earth's surface increased the need for UV filters products. One of the most used is oxybenzone, which is indiscriminately released in the environment. Oxybenzone's ecotoxicological effects on physiology have been investigated because of the bioaccumulation and action as an endocrine disruptor. However, little is known about its effects on behavior or cognition. In this study, we approach the effects of short-term oxybenzone exposure on locomotion, anxiety-like, social behavior, and short-term memory in zebrafish (Danio rerio). Adult zebrafish were exposed to oxybenzone 10, 100 and 1000 μg L^-1 for 15 days and then tested (novel tank, shoal preference, mirror test, and T-maze with novelty). Fish exposed to oxybenzone showed reduced locomotion, decreased anxiety-like behavior, less time near/interacting with the shoal, fewer interactions with the mirror image, and decreased exploration of the novel arm in the T-maze test. These results suggest that oxybenzone affects perception, increases risk-taking, impairs proper aggressive response, and jeopardizes the animals' ability to retain information. These results reinforce the risk posed by products discarded into the aquatic ecosystems, especially those with underestimated toxic potential.

Effect of benzophenone-3 on the blood cells of zebrafish (Danio rerio)

Benzophenone-3 (BP-3) is a common component of organic sunscreen widely used that can affect especially aquatic ecosystems health, including fish. To verify the biological effects of low concentrations of BP-3 on blood cells, one hundred and forty zebrafish (D. rerio) were used and then randomly divided into five groups: control group (water), solvent group (alcoholic water), and BP-3 group (BP-3 at 7 µg L^-1, BP-3 at 70 µg L^-1, and BP-3 at 700 µg L^-1). The blood slices were stained with Panoptic stain and with Giemsa solution for the hematological analysis. During the exposure to BP-3, no behavioral changes were observed. Although no significant difference in total leukocytes occurred, an increase in neutrophils and a reduction of lymphocytes at the highest concentration on both 7th and 14th days were detected. The total and cytoplasmic area of erythrocytes on the 7th day at the highest concentration were reduced. In addition, alterations on the erythrocyte nuclear morphology in fish exposed to BP-3 were usually visualized, mainly when considered the occurrence of blebbed nucleus and micronucleus, indicating that BP-3 exhibits cytotoxic and mutagenic effects. The results indicate that BP-3 can interfere with the morphophysiology of aquatic organisms.

Benzophenone-3 induced abnormal development of enteric nervous system in zebrafish through MAPK/ERK signaling pathway

Hirschsprung disease (HSCR) is a congenital disease characterized by the absence of enteric neurons, which is derived from the failure of the proliferation, differentiation or migration of the enteric neural crest cells (ENCCs). HSCR is associated with multiple risk factors, including polygenic inheritance factors and environmental factors. Genetic studies have been extensively performed, whereas studies related to environmental factors remain insufficient. Benzophenone-3 (BP-3), one important component of the ultraviolet (UV) filters, has been proved to have cytotoxicity and neurotoxicity which might be associated with HSCR. In this study, we used zebrafish as a model to investigate the relationship between BP-3 exposure and the development of the enteric nervous system (ENS) in vivo. Embryos exposed to BP-3 showed an average of 46% reduction of the number of the enteric neurons number. Besides, the ENCCs specific markers (ret and hand2) were downregulated upon BP-3 exposure. Moreover, we identified potential targets of BP-3 through Network Pharmacology Analysis and Autodock and demonstrated that the attenuation of the MAPK/ERK signaling might be the potential mechanism underlying the inhibition of the ENS development by BP-3. Importantly, MAPK/ERK signaling agonist could be used to rescue the ENS defects of zebrafish induced by BP-3. Overall, we characterized the influence of BP-3 on ENS development in vivo and explored possible molecular mechanisms.

Environmentally relevant concentrations of benzophenone-3 induce differential histopathological responses in gills and liver of freshwater fish

BP-3 is one of the most used organic UV filters. However, its widespread use and release into aquatic environment can induce ecotoxicological impact on aquatic organisms. Thus, the aim of the current study is to evaluate the gills and liver of freshwater fish Poecilia reticulata subjected to acute exposure (96 h) to BP-3 at environmentally relevant concentrations (10-1000 ng L^-1). The study was based on adopting qualitative and semi-quantitative approach to assess histopathological changes and integrated the biomarker response in order to investigate organ-specific responses to BP-3 exposure. BP-3 has induced high histopathological index associated with circulatory disturbances, as well as with regressive and immunological changes in gills, whereas the hepatic histopathological index was associated with circulatory disturbances. Moreover, lower BP-3 concentrations were mostly associated with changes in gills, whereas higher BP-3 concentration was mostly linked to hepatic changes. In conclusion, acute exposure to BP-3 at environmentally relevant concentrations had stronger impact on gills than on the liver of P. reticulata, which confirmed organ-specific responses to UV filters.

Moxidectin toxicity to zebrafish embryos: Bioaccumulation and biomarker responses

Moxidectin is an antiparasitic drug belonging to the class of the macrocyclic lactones, subgroup mylbemicins. It is used worldwide in veterinary practice, but little is known about its potential environmental risks. Thus, we used the zebrafish embryo as a model system to study the potential effects of moxidectin on aquatic non-target organisms. The analyses were performed in two experimental sets: (1) acute toxicity and apical endpoints were characterized, with biomarker assays providing information on the activity levels of catalase (CAT), glutathione S-transferase (GST), lactate dehydrogenase (LDH), and acetylcholinesterase (AChE); and (2) internal concentration and spatial distribution of moxidectin were determined using ultraperformance liquid chromatography quadrupole-time-of-flight mass spectrometry (UPLC-QToF-MS) and matrix-assisted laser desorption/ionization-MS imaging (MALDI-MSi). The acute toxicity to zebrafish embryos (96 hpf) appeared mainly as a decrease in hatching rates (EC₅₀ = 20.75 μg/L). It also altered the enzymatic activity of biomarker enzymes related to xenobiotic processing, anaerobic metabolism, and oxidative stress (GST, LDH, and CAT, respectively) and strongly accumulated in the embryos, as internal concentrations were 4 orders of magnitude higher than those detected in exposure solutions. MALDI-MSi revealed accumulations of the drug mainly in the head and eyes of the embryos (72 and 96 hpf). Thus, our results show that exposure to moxidectin decreases hatching success by 96 h and alters biochemical parameters in the early life stages of zebrafish while accumulating in the head and eye regions of the animals, demonstrating the need to prioritize this compound for environmental studies.

Influence of suspended sediment on the bioavailability of benzophenone-3: Focus on accumulation and multi-biological effects in Daphnia magna

The UV-filter benzophenone-3 (BP3) tends to associate with suspended sediment (SPS) due to hydrophobicity, which could alter its toxicological effects on non-target aquatic organisms. In this study, the freshwater cladoceran Daphnia magna (D. magna) was selected as a model organism to investigate the impacts of the source and composition of SPS on the accumulation and multiple toxicological effects (from the molecular level to individual level) of BP3. Among the three components of SPS, amorphous organic carbon (AOC) and minerals promoted the body burden of BP3, while black carbon (BC) inhibited the bioaccumulation. The inhibition effects of BP3 on swimming and feeding behaviors of D. magna were also enhanced due to the presence of AOC and BC. Compared with BP3 exposure alone, higher oxidative stress and neurotoxicity were observed in the presence of SPS containing AOC, BC and minerals, corresponding to that superoxide dismutase, catalase and glutathione-S-transferase activities were further induced, and acetylcholinesterase activity was inhibited. Furthermore, BP3 induced mRNA expression levels of the endocrine system (ecdysone receptor, cytochrome P450 CYP314) and metabolic system (toxicant nuclear receptor HR96, P-glycoprotein), and the presence of SPS containing AOC, BC and minerals exhibited an enhanced effect. Combined with all endpoints, evident relationship was observed between the bioaccumulation level and the response of individual behavior and molecular biomarkers. The results demonstrated that the effects of SPS compositions on bioaccumulation and toxicological effects of organic UV-filters should be considered in aquatic environments.

Trends in environmental and toxicity research on organic ultraviolet filters: A scientometric review

In recent decades, the potential toxicological and environmental effects of organic ultraviolet filters (OUVF) have received growing attention. The number of studies in this area has increased; however, presently there is no scientometric perspective addressing this topic. The purpose of this study is to identify the intellectual base and research front using the visualization and analysis software, CiteSpace. We retrieved 453 articles, published in print or online as an early-access article between 2002 and 2020, from the Web of Science with a topic search related to OUVFs, environment, and toxicology. We then analysed synthesized networks of co-authorship (author, institution, country), co-citation (author, document, journal) and co-occurring keywords. The annual publication output has trended upwards since 2002. Authors based in China accounted for 29.4% of the total publications, followed by USA (17.4%); but overall publications from Switzerland and Spain were more influential. Major research themes identified included OUVF concentrations in aquatic environments, and hormonal effects. Emerging themes included improving the sensitivity of analytical detection methods for both OUVFs and their metabolites, consequences of OUVF transport to the marine environment, and concerns over prenatal exposure. Based on keyword analysis, benzophenone-3, 4-methylbenzylidene-camphor, 3-benzylidene camphor, and ethylhexyl-methoxycinnamate are the most studied OUVFs, and effects on estrogenic activity, gene expression, reproduction, and more recently, oxidative stress, have received most attention from a toxicological perspective. Other prominent topics were sources of environmental contamination and ecological risk assessments. This study maps the major research domains of OUVF environmental toxicology research; explanations and implications of the findings are discussed; and emerging trends highlighted.

Effects of Low Concentration Benzophenone-3 Exposure on the Sex Ratio and Offspring Development of Zebrafish (Danio rerio)

Benzophenone-3 (BP-3) is an important ultraviolet (UV)-screening agent using in cosmetics, however, the associated environmental pollution and the toxicity to organisms, particularly aquatic organisms, cannot be neglected. In this study, the potential risks posed to zebrafish when exposed to environmental residual concentrations of BP-3 were evaluated. Zebrafish embryos (F0) were exposed to 0, 0.056, 2.3, and 38 μg/L BP-3 until 42 days' post-fertilization (dpf). The effects of BP-3 on the sex ratio and gene expression of F0 zebrafish were investigated. In the F1 embryos, cumulative hatching rate, body length, and heartbeats were observed. The result showed that F0 and F1 exposure to concentrations of 0.056 and 38 μg/L BP-3 elicited stronger toxicity at 96 hpf than single generation exposures. Overall, our results provide a new understanding on the effects of low BP-3 concentration chronic exposure on sex ratio and offspring developmental toxicity of the F0 zebrafish.

Risks of organic UV filters: a review of environmental and human health concern studies

Organic UV filters are compounds that absorb UV irradiation by their highly conjugated structure. With the developing consciousness over the last century of the skin damage UV radiation can cause, the demand for organic UV filters has risen, for use not only in sunscreens, but also in other personal care products. The massive production and usage of these organic UV filters has resulted in extensive release into the aquatic environment, and thereby making an important group of emerging contaminants. Considering the widespread occurrence of organic UV filters in not only ambient water, but also sediment, soil and even indoor dust, their threats towards the health of living organisms have been a subject of active investigation. In this review article, we present an overall review of existing knowledge on the risks of organic UV filters from the aspects of both environmental and human health impacts. As for the environment, some organic UV filters are proven to bioaccumulate in various kinds of aquatic organisms, and further to have adverse effects on different kinds of animal models. Toxicological studies including in vivo and in vitro studies are important and effective means to ascertain the effects and mechanisms of organic UV filters on both the ecosystem and humans. Subsequent concerns arise that these compounds will affect human health in the long term. This review concludes by suggesting future lines of research based on the remaining knowledge gaps.

Mild Effects of Sunscreen Agents on a Marine Flatfish: Oxidative Stress, Energetic Profiles, Neurotoxicity and Behaviour in Response to Titanium Dioxide Nanoparticles and Oxybenzone

UV filters are potentially harmful to marine organisms. Given their worldwide dissemination and the scarcity of studies on marine fish, we evaluated the toxicity of an organic (oxybenzone) and an inorganic (titanium dioxide nanoparticles) UV filter, individually and in a binary mixture, in the turbot (Scophthalmus maximus). Fish were intraperitoneally injected and a multi-level assessment was carried out 3 and 7 days later. Oxybenzone and titanium dioxide nanoparticles induced mild effects on turbot, both isolated and in mixture. Neither oxidative stress (intestine, liver and kidney) nor neurotoxicity (brain) was found. However, liver metabolic function was altered after 7 days, suggesting the impairment of the aerobic metabolism. An increased motility rate in oxybenzone treatment was the only behavioural alteration (day 7). The intestine and liver were preferentially targeted, while kidney and brain were unaffected. Both infra- and supra-additive interactions were perceived, with a toxicodynamic nature, resulting either in favourable or unfavourable toxicological outcomes, which were markedly dependent on the organ, parameter and post-injection time. The combined exposure to the UV filters did not show a consistent increment in toxicity in comparison with the isolated exposures, which is an ecologically relevant finding providing key information towards the formulation of environmentally safe sunscreen products.

A systematic review and ecological risk assessment for organic ultraviolet filters in aquatic environments

Organic ultraviolet filters (OUVFs) are used in a wide range of manufactured products including personal care (e.g. sunscreens) and plastic items. This review summarizes the available data regarding the toxic effects of OUVFs on marine and freshwater organisms and generates the predicted no-effect concentration (PNEC) values necessary for assessing ecological risk. Through a systematic search of the literature, 89 studies were identified and ecotoxicological data extracted. Collectively, these studies described toxicity testing with 39 OUVF from 10 structural classes, with derivatives of benzophenones (49%) and camphors (16%) most studied. There was a bias towards selecting freshwater species (61%), and evaluating single OUVF effects (87%) rather than OUVF mixtures. Short-term (acute) experimentation (58%) was marginally more common than long-term (chronic) testing (42%). Reproductive, developmental, genetic, and neurological toxicity were the most commonly identified effects in aquatic organism, and were associated with molecular interactions with steroid receptors, DNA, or the production of reactive oxygen species. Species sensitivity distribution and/or assessment factors were used to calculate PNECs for 22 OUVFs and the risk quotients for 12 OUVFs. When using maximum concentrations, high risk was observed for six OUVFs in marine environments (4-methylbenzylidene-camphor, octocrylene, padimate-O, benzophenone-1, and oxybenzone, ethylhexyl-4-methoxycinnamate), and for four OUVFs in freshwater environments (ethylhexyl-4-methoxycinnamate, octocrylene, avobenzone and oxybenzone). When using median concentrations, a risk to marine environments was observed for oxybenzone. The results of this review underline that there is limited knowledge of the pathological effects of OUVFs and their metabolites in aquatic environments, and this inhibits the development of informed water-quality guidelines.