Early life stage and genetic toxicity of stannous chloride on zebrafish embryos and adults: toxic effects of tin on zebrafish

Elementomics of 32 elements in cord serum depicts the risk of orofacial clefts: A case-control study in Shanxi, China

Maternal exposure to various metallic and non-metallic elements has been linked to the occurrence of orofacial clefts (OFCs), yet there remains a dearth of comprehensive research on the potential ramifications of simultaneous exposure to multiple elements. In this study, we investigated the individual and combined effects of element exposure on OFCs in a cohort of 168 pregnant women (49 cases and 119 controls) in the Shanxi province of northern China from 2010 to 2015. Cord serum samples were obtained from all participants to analyze the levels of 32 elements using inductively coupled plasma-mass spectrometry. The study examined the independent correlation between element concentrations and OFCs using two machine screening models, Boruta and Least Absolute Shrinkage and Selection Operator. Bayesian kernel machine regression (BKMR) was utilized to determine the combined effects of key exposure elements on OFCs and to clarify the interaction between exposed elements through the generalized additive model (GAM). The screening models identified lead (Pb), tin (Sn), iron (Fe), and cesium (Cs) as the most significant risk factors for OFC development in offspring. In the BKMR model, the probability of OFCs increased with higher overall levels of these risk elements, with Pb emerging as the primary contributor to the combined effect of the mixture. The findings of the GAM indicated that the combined exposure to Pb and Sn had a synergistic effect on the risk of developing OFCs. Analysis of elemental exposure in umbilical cord serum suggested that Pb exposure may have detrimental effects on OFC development in offspring, which may be further intensified by a synergistic interaction between Sn and Pb in the occurrence of OFCs.

Comparative Toxicity of TiO2 and Sn-Doped TiO2 Nanoparticles in Zebrafish After Acute and Chronic Exposure

This study was conducted to assess the toxicological potential of synthesized pure and Sn-doped TiO2 NPs (Sn-TiO2 NPs) in zebrafish after acute and chronic exposure. The pure TiO2 NPs, 4%, and 8% Sn-TiO2 NPs were synthesized and characterized using X-ray diffraction, Scanning Electron Microscope, diffuse reflectance spectra, dynamic light scattering, and zeta potential analyses. The pure TiO2 NPs, 4%, and 8% Sn-TiO2 NPs were spherical with average sizes of about 40, 28, and 21 nm, respectively, indicating significant size reduction of TiO2 NPs following Sn doping. According to our results, the LC50-96h increased in the order of 8% Sn-TiO2 NPs (45 mg L-1) < 4% Sn-TiO2 NPs (80.14 mg L-1) < pure TiO2 NPs (105.47 mg L-1), respectively. Exposure of fish to Sn-TiO2 NPs after 30 days resulted in more severe histopathological alterations in gills, liver, intestine, and kidneys than pure TiO2 NPs. Furthermore, Sn-doping significantly elevated malondialdehyde levels and micronuclei frequency, indicating increased oxidative stress and genotoxicity. Expression analysis revealed altered expression of various genes, including upregulation of pro-apoptotic Bax gene and downregulation of anti-apoptotic Bcl-2 gene, suggesting potential induction of apoptosis in response to Sn-doped NPs. Additionally, antioxidant genes (Gpx, Sod, Cat, and Ucp-2) and stress response gene (Hsp70) showed altered expression, suggesting complex cellular responses to mitigate the toxic effects. Overall, this study highlights the concerning impact of Sn-doping on the toxicity of TiO2 NPs in zebrafish and emphasizes the need for further research to elucidate the exact mechanisms underlying this enhanced toxicity.

Integrated histopathology and transcriptome metabolome profiling reveal the toxicity mechanism of phenazine-1-carboxylic acid in zebrafish

Phenazine-1-carboxylic acid (PCA) is a new type of agrochemical used to prevent plant diseases, but its effects on aquatic organisms are unclear. To comprehensively assess the impacts of PCA for aquatic organisms and its associated environmental risks, this study investigated, taking zebrafish as the research object, the toxicological mechanism of PCA by means of optical microscopy, hematoxylin and eosin (HE) staining, ultrastructural observation, physiological and biochemical testing, transcriptome sequencing, metabolome analysis, fluorescence quantitative PCR and molecular simulation. The results indicated that PCA was detrimental to zebrafish embryos, larvae and adults, with LC50 values at 96 h of 3.9093 mg/L, 8.5075 mg/L, and 13.6388 mg/L, respectively. PCA caused abnormal spontaneous movement, slowed the heart rate, delayed hatching, shortened the body length, slowed growth, and caused malformations. PCA mainly affected the brain, liver, heart, and ovaries. PCA distorted cell morphology, damaged mitochondrial membranes, disintegrated mitochondrial ridges, and dissociated nuclear membranes. PCA inhibited the enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX), decreased the malondialdehyde (MDA) content and disrupted antioxidant effects. The results of omics studies confirmed that PCA interfered with the transcriptional and metabolic network of zebrafish, downregulating most genes and metabolites. PCA mainly affected functions related to mitochondrial steroids, lipids, sterols, oxidoreductase activity and pathways involving cofactors, steroids, porphyrin, cytochromes, which specifically bound to targets such as panx3, agmat, and ace2. PCA was moderately toxic to zebrafish, and its usage should be strictly controlled to reduce toxic effects on aquatic organisms. The results of this study provide a new insights for ecotoxicology research.

Impact of exposure to glyphosate-based herbicide on morphological and physiological parameters in embryonic and larval development of zebrafish

Glyphosate-based herbicides (GBH) have been commonly used in agriculture to inhibit weed growth and increase yields. However, due to the high solubility of these herbicides in water, they can reach aquatic environments, by infiltration, erosion, and/or lixiviation, affecting non target organisms. Thus, this study aimed to characterize the toxicity of GBH Roundup WG® (RWG®) during the embryonic and larval development of Danio rerio. Embryos (3 hours post fertilization, hpf-until hatching) and larvae (3 days post fertilization, dpf to 6 dpf) were exposed to concentrations of 0.065 and 6.5 mg L-1 . They were evaluated for survival, hatching, spontaneous movements, heartbeat, morphology, and morphometry by in vivo photographs in microscope, cell proliferation and apoptosis by immunohistochemistry, and exploratory behavior and phototropism by video recording. Our results showed an increase in embryo and larvae mortality in those exposed to 0.065 mg L-1 , as well as a reduction in spontaneous embryo movements. The larval heartbeats showed a decrease at 4 dpf in the group exposed to 0.065 mg L-1 and an increase at 5 and 6 dpf in both exposed groups. Cell proliferation was reduced in both groups exposed in embryos and only in the 0.065 mg L-1 group in larvae, while cell death increased in embryos exposed to 6.5 mg L-1 . These results demonstrated the toxic effect of low concentrations of the herbicide RWG® during embryonic and larval development of non target organisms, as well as the importance of constantly reviewing acceptable limits for exposure in natural environments.

Associations of maternal exposure to multiple plasma trace elements with the prevalence of fetal congenital heart defects: A nested case-control study

BACKGROUND

Scanty knowledge prevails regarding the combined impact of multiple plasma trace elements and main contributors on the prevalence of congenital heart defects (CHDs) in offspring. Thus, we performed a nested case-control analysis in a neonates cohort to investigate this important public health issue.

METHODS

We selected 164 pairs of cases and non-malformed controls from live births registered in the parent cohort (n = 11,578) at the same hospital. Plasma levels of 14 trace elements were determined by inductively coupled plasma-mass spectrometry. The odds ratios (ORs) of exposure were compared between cases and controls. Bayesian Kernel Machine Regression (BKMR) and Quantile g-Computation (QgC) models were employed to assess the cumulative effect of exposure to trace elements.

RESULTS

We found positive associations and linear dose-response relationships between plasma Pb and Sn and CHD. BKMR models indicated that the overall effect of the trace element mixture was associated with CHDs below the 45th percentile or above the 50th percentile, and the combined effect was primarily attributed to Sn and Pb. The QgC model indicated significantly increased odds of CHD with simultaneous exposure to all studied trace elements (OR: 2.19, 95%CI: 1.44-3.33).

CONCLUSIONS

This study is the first to report an association between elevated levels of mixed trace elements in maternal plasma with an increased prevalence of fetal CHDs, particularly in the case of Pb and Sn. Findings from this study provide further evidence of the important of heavy metal pollution to human health, and can help stakeholders prioritize policies and develop interventions to target the leading contributors to human exposure.

Intergenerational toxic effects of parental exposure to [Cn mim]NO3 (n = 2,4,6) on nervous and skeletal development in zebrafish offspring

Ionic liquids (ILs) are thought to have negative effects on human health. Researchers have explored the effects of ILs on zebrafish development during the early stages, but the intergenerational toxicity of ILs on zebrafish development has rarely been reported. Herein, parental zebrafish were exposed to different concentrations (0, 12.5, 25, and 50 mg/L) of [Cn mim]NO3 (n = 2, 4, 6) for 1 week. Subsequently, the F1 offspring were cultured in clean water for 96 h. [Cn mim]NO3 (n = 2, 4, 6) exposure inhibited spermatogenesis and oogenesis in F0 adults, even causing obvious lacunae in the testis and atretic follicle oocytes in ovary. After parental exposure to [Cn mim]NO3 (n = 2, 4, 6), the body length and locomotor behavior were measured in F1 larvae at 96 hours post-fertilization (hpf). The results showed that the higher the concentration of [Cn mim]NO3 (n = 2, 4, 6), the shorter the body length and swimming distance, and the longer the immobility time. Besides, a longer alkyl chain length of [Cn mim]NO3 had a more negative effect on body length and locomotor behavior. RNA-seq analysis revealed several downregulated differentially expressed genes (DEGs)-grin1b, prss1, gria3a, and gria4a-enriched in neurodevelopment-related pathways, particularly the pathway for neuroactive ligand-receptor interaction. Moreover, several upregulated DEGs, namely col1a1a, col1a1b, and acta2, were mainly associated with skeletal development. Expression of DEGs was tested by RT-qPCR, and the outcomes were consistent with those obtained from RNA-Seq. We provide evidence showing the effects of parental exposure to ILs on the regulation of nervous and skeletal development in F1 offspring, demonstrating intergenerational effects.

A coumarin-based fluorescent chemosensor as a Sn indicator and a fluorescent cellular imaging agent†

In the present study, fluorogenic coumarin-based probes (1–3) through condensation of 4-hydroxy coumarin with malondialdehyde bis(diethyl acetal)/triethyl orthoformate were prepared. The absorption and fluorescence emission properties of 2b and 3 in different solvents were studied, and a considerable solvatochromic effect was observed. The sensitivity of chemosensors 2b and 3 toward various cations and anions was investigated. It was revealed that compound 3 had a distinct selectivity toward Sn²⁺, possibly via a chelation enhanced quenching mechanism. The fluorescence signal was quenched over the concentration range of 6.6–120 μM, with an LOD value of 3.89 μM. The cytotoxicity evaluation of 3 against breast cancer cell lines demonstrated that the chemosensor was nontoxic and could be used successfully in cellular imaging. The probe responded to tin ions not only via fluorescence quenching, but also through colorimetric signal change. The change in optical properties was observed in ambient conditions and inside living cells.

A fluorogenic and colorimetric coumarin-based probe was synthesized and used for sensing Sn²⁺ inside and ouside of living cells.

In silico modelling of acute toxicity of 1, 2, 4-triazole antifungal agents towards zebrafish (Danio rerio) embryos: Application of the Small Dataset Modeller tool

Nowadays, there is a widespread use of triazole antifungal agents to kill broad classes of fungi in farming lands and to protect herbs, fruits and grains. These agents further deposit into the aquatic systems causing toxicity to the living aquatic creatures, which can then affect human beings. Considering this issue, risk assessment of these toxic chemicals is a very essential task. Due to the inadequate experimental data on acute toxicity of antifungal agents containing the 1, 2, 4-triazole ring, higher testing costs along with the regulatory restrictions and the international regulations to lessen animal testing emphasize on in silico techniques such as quantitative structure-activity relationship (QSAR) studies. The application of QSAR modelling has created an easier avenue to predict activity/property/toxicity of newly synthesized compounds. In the present study, we have used 23 antifungal agents containing the 1, 2, 4-triazole ring to develop 2D-QSAR models and explored their structural attributes crucial for acute toxicity towards embryonic phase of zebrafish (Danio rerio). Here, we have employed simple 2D descriptors to develop the QSAR models. The models were evolved by executing the Small Dataset Modeller tool (https://dtclab.webs.com/software-tools), and the validation of the models was achieved by employing different precise validation principles. The statistical validation metrics confirm that built models are robust, useful and well predictive to forecast the acute toxicity of new compounds.

Exposure to metal mixtures in relation to blood pressure among children 5-7 years old: An observational study in Bangladesh

Hypertension in later life, a significant risk factor for cardiovascular disease, has been linked to elevated blood pressure in early life. Exposure to metals may influence childhood blood pressure; however, previous research is limited and has mainly focused on evaluating the toxicity of single metal exposures. This study evaluates the associations between exposure to metal mixtures and blood pressure among Bangladeshi children age 5-7 years.

METHODS

We investigated the associations of 17 toenail metal concentrations with blood pressure using linear regression models. Principal component analysis (PCA), weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) were conducted as secondary analyses.

RESULTS

Associations were observed for selenium with diastolic blood pressure (per doubling of exposure β = 2.91, 95% confidence interval [CI] = 1.08, 4.75), molybdenum with systolic (β = 0.33, 95% CI = 0.05, 0.61) and diastolic blood pressure (β = 0.39, 95% CI = 0.12, 0.66), tin with systolic blood pressure (β = -0.33, 95% CI = -0.60, -0.06), and mercury with systolic (β = -0.83, 95% CI = -1.49, -0.17) and diastolic blood pressure (β = -0.89, 95% CI = -1.53, -0.26). Chromium was associated with diastolic blood pressure among boys only (β = 1.10, 95% CI = 0.28, 1.92, P for interaction = 0.02), and copper was associated with diastolic blood pressure among girls only (β = -1.97, 95% CI = -3.63, -0.32, P for interaction = 0.01). These findings were largely robust to the secondary analyses that utilized mixture modeling approaches (PCA, WQS, and BKMR).

CONCLUSIONS

Future prospective studies are needed to investigate further the impact of early life exposure to metal mixtures on children's blood pressure trajectories and cardiovascular disease risk later in life.

Teratogenic, Oxidative Stress and Behavioural Outcomes of Three Fungicides of Natural Origin (Equisetum arvense, Mimosa tenuiflora, Thymol) on Zebrafish (Danio rerio)

The improper use of synthetic fungicides has raised public concerns related to environmental pollution and animal health. Over the years, plant-derived antifungals have been investigated as safer alternatives, although little scientific evidence of its neurodevelopmental effects exist. The main objective of this study was to explore the effects of three alternative natural extracts (Equisetum arvense, Mimosa tenuiflora, Thymol) with antifungal properties during the early development of zebrafish by evaluating different teratogenic, oxidative stress and behavioural outcomes. Following the determination of the 96 h-LC₅₀, exposure to sublethal concentrations showed the safety profile of both E. arvense and M. tenuiflora. However, following 96-h exposure to Thymol, increased lethality, pericardial oedema, yolk and eye deformations, and decreased body length were observed. The reduced and oxidized glutathione (GSH:GSSG) ratio was increased, and the glutathione-s-transferase activity in the group exposed to the highest Thymol concentration. Overall, these results support a more reducing environment associated with possible effects at the cellular proliferation level. In addition, the disruption of behavioural states (fear- and anxiety-like disorders) were noted, pointing to alterations in the c-Jun N-terminal kinase developmental signalling pathway, although further studies are required to explore this rationale. Notwithstanding, the results provide direct evidence of the teratogenic effects of Thymol, which might have consequences for non-target species.

Don't Let the Lead Out: New Material Chemistry Approaches for Sustainable Lead Halide Perovskite Solar Cells

Lead halide perovskites are seriously considered for next generation photovoltaic technology. They have a unique combination of easy synthesis, high efficiency, and cost-effective techniques. Still, the major concern is the toxicity of lead used in perovskite devices. The research community is still debating whether the amount of lead used in a solar cell really poses a danger or not. However, it is pretty clear that mitigating the lead leakage from the lead halide perovskite device is of utmost importance. In this review, we discuss new material chemistry approaches that can be applied to reduce the lead leakage/wastage from damaged lead halide perovskite solar cells. ECR (encapsulate, capture, and recycle) approaches have the potential to significantly reduce the environmental and health hazard risks of lead halide perovskite devices. Encapsulation by a self-healing material and rigid glass can help the perovskite survive the extreme conditions and avoid exposure of the perovskite layer to the external environment. Capturing of lead can also be done by an encapsulant layer that can very quickly and efficiently bind to lead, in the case that it leaks from the damaged perovskite device. Moreover, the recycling of damaged or decommissioned devices helps to avoid the lead wastage and contamination in the environment. Finally, we also discuss the potential of lead-free perovskite for optoelectronic applications.

A Smart Route for Encapsulating Pd Nanoparticles into a ZIF-8 Hollow Microsphere and Their Superior Catalytic Properties

The encapsulation of catalytically active noble metal nanoparticles (NM NPs) into metal-organic frameworks (MOFs) represents an effective strategy for enhancing their catalytic performance. Despite a myriad of reports on the nanocomposites consisting of NM NPs and MOFs, it remains challenging to develop a sustainable and convenient method for realizing confined integration of NM NPs within a porous and hollow zinc-based MOF. Herein, a simple and well-designed approach is reported to the fabrication of Pd@ZIF-8 hollow microspheres with a number of Pd nanoparticles immobilized on the inner surface. This method capitalized on the use of polyvinylpyrrolidone (PVP)-stabilized polystyrene (PS) microspheres as templates, to harness the dual functions of PVP for reducing PdCl₂ to generate Pd NPs and coordinating with zinc ions to grow ZIF-8 shells. Consequently, it avoids the complicated protocols involving surface treatment of template microspheres that conventionally adopts hazardous or costly agents. The obtained Pd@ZIF-8 hollow microspheres exhibit outstanding catalytic activity, size selectivity, and stability in the hydrogenation of alkenes. This study presents both the advances in the green synthesis and great potential of Pd@ZIF-8 hollow microspheres for catalytic applications.

Thymol exposure mediates pro-oxidant shift by regulating Nrf2 and apoptotic events in zebrafish (Danio rerio) embryos

The biochemical process of oxidative stress is an integral mechanism of chemical toxicity, contributing to complex pathological disorders. Thymol (THY) has a wide range of therapeutic applications for several ailments, although a better understanding of signaling cues regulated by this compound is needed to address the mechanism of its action. To better perceive the mode of action, we investigated the potential impact of THY on zebrafish embryos, with special emphasis on ROS biogenesis. In this study, we exposed the zebrafish embryos to 25, 50 and 100μM of THY for 96 hours post fertilization (hpf). Noticeable teratogenic effects were observed upon assessing the survival rate (LC₅₀ = 42.35μM), hatching process, morphological exam and cardiac functions, thereby verifying the toxicity of THY on zebrafish embryos. Furthermore, we analyzed the effect of THY on the levels of ROS, mitochondrial membrane potential (ΔΨm) and immunofluorescence by DCFH-DA, JC-1, Casp-3-FITIC staining, respectively. Furthermore, we preformed the expressional analysis of Nrf2, superoxide dismutase-1 (SOD-1), catalase (CAT), Cytochrome P450 (CYP450) and apoptotic marker proteins (AIF, p53, Bax, Bcl-2, Casp-3 and Casp-9) in zebrafish embryos. As expected, we noticed a significant modulatory effect on the above-mentioned activities by THY. Collectively, our findings suggest that ROS might be the prime mediator responsible for THY-induced oxidative damage, thereby affecting the cellular defense mechanism and apoptotic events in zebrafish embryos.

Re-evaluation of stannous chloride (E 512) as food additive

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re‐evaluating the safety of stannous chloride and stannous chloride dihydrate (E 512) as food additives. The Panel considered that adequate exposure and toxicity data were available. Stannous chloride is only permitted as food additives in one food category and no reply on the actual use level of stannous chloride (E 512) as a food additive and on its concentration in food was provided by any interested party. According to the Mintel's Global New Products Database (GNPD), stannous chloride was not labelled on any products in the EU nor in Norway. The regulatory maximum level exposure assessment scenario is based on the maximum permitted levels (MPLs) for stannous chloride (E 512), which is 25 mg Sn/kg. The mean exposure to stannous chloride (E 512) from its use as a food additive was below 1.3 μg Sn/kg body weight (bw) per day for all age groups. The 95th percentile of exposure to stannous chloride (E 512) ranged from 0.0 μg Sn/kg bw per day in all groups to 11.2 μg Sn/kg bw per day in adults. Absorption of stannous chloride from the gastrointestinal tract is low there is no concern with respect to carcinogenicity and genotoxicity. Gastrointestinal irritation was reported in humans after ingestion of a bolus dose of 40 mg Sn. The Panel concluded that stannous chloride (E 512) is of no safety concern in this current authorised use and use levels.

Effects of starch-coating of magnetite nanoparticles on cellular uptake, toxicity and gene expression profiles in adult zebrafish

Engineered magnetite nanoparticles (Fe₃O₄ NPs) have been used in many fields. To prevent particle agglomeration, stabilizers or coatings are often required. While such coatings have been shown to enhance performances, the environmental impact or toxicity of stabilized or coated Fe₃O₄ NPs remain poorly understood. In an effort to understand the impacts of such coatings on the toxicity of Fe₃O₄ NPs, we used the transcriptome sequencing (RNA-seq) technique to characterize the gill and liver transcriptomes from adult zebrafish when exposed to bare and starch-stabilized Fe₃O₄ NPs for 7days, demonstrating remarkable differences in gene expression profiles, also known as differentially expressed genes (DEGs) profiles, in both tissues. Bare Fe₃O₄ NPs exerted greater toxicity than starch-coated Fe₃O₄ NPs in gill; in contrast, starch-Fe₃O₄ NPs triggered more severe damage on liver, though both bare and stabilized NPs appeared to share similar regulatory mechanisms. Quantitative real-time polymerase chain reactions using six genes each for the two tissues verified the RNA-seq results. The surface coatings play an important role in determining the nanoparticle toxicity, which in turn modulate cell uptake and biological responses, consequently impacting the potential safety and efficacy of nanomaterials.

Developmental toxicity and molecular responses of marine medaka (Oryzias melastigma) embryos to ciguatoxin P-CTX-1 exposure

Ciguatoxins are produced by toxic benthic dinoflagellates and cause ciguatera fish poisoning worldwide, but the toxic effects on developing marine fish have not been well investigated. The Pacific ciguatoxin (P-CTX-1), is a potent sodium channel agonist, which is one of the most toxic members among all CTXs. This study evaluated the toxic effects of microinjecting purified Pacific ciguatoxin-1 (P-CTX-1) on embryonic development of marine medaka Oryzias melastigma. A lower 96h-LD₅₀ value was estimated for eleuthero-embryos (1.32ngg^-1) than that for embryos (1.71ngg^-1), indicating that P-CTX-1 is more lethal to newly hatched medaka larvae. P-CTX-1 induced detrimental effects during embryonic development, including hatching failure, abnormalities in physical development (caudal fin malformation and spinal deformities), internal damage (green coloration of the gall bladder and hemorrhaging), immune dysfunction, and altered muscle physiology (bradycardia and hyperkinetic twitching). The results of a transcriptional expression analysis of genes related to the stress/immune responses, cardiac and bone development, and apoptosis supported the observed developmental abnormalities. This study advanced the understanding of P-CTX-1 mediated toxic mechanisms in the development of early life stages of a fish, and thus contributed to the toxicity assessment of CTXs in marine ecosystems.

Biological response of zebrafish embryos after short-term exposure to thifluzamide

Thifluzamide is a new amide fungicide, and its extensive application may have toxic effects on zebrafish. To better understand the underlying mechanism, we investigated in detail the potential toxic effects of thifluzamide on zebrafish embryos. In the present study, embryos were exposed to 0, 0.19, 1.90, and 2.85 mg/L thifluzamide for 4 days. Obvious pathological changes were found upon a histological exam, and negative changes in mitochondrial structure were observed under Transmission Electron Microscopy (TEM), which qualitatively noted the toxic effects of thifluzamide on embryos. Moreover, we quantitatively evaluated the enzyme activities [succinate dehydrogenase (SDH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), caspases], the contents of malonaldehyde (MDA) and interleukin-8 (IL-8) and the expression levels of the related genes. This study suggests that the negative changes in mitochondrial structure and SDH activity might be responsible for oxidative damage, cell apoptosis and inflammation, which would facilitate the action of these factors in cell death and might play a crucial role during toxic events. In addition to providing the first description of the mechanism of the toxic effects of thifluzamide on embryos, this study also represents a step towards using embryos to assess mitochondrial metabolism and disease.

Toxic Effects of Bromothalonil and Flutolanil on Multiple Developmental Stages in Zebrafish

In this study, we applied various developmental stages of zebrafish to address the potential environmental risk and aquatic toxicity of bromothalonil and flutolanil. This results demonstrated that the acute toxicity of bromothalonil to the three phases of zebrafish were 4.34 (embryo) < 3.27 (12 h old larvae) < 2.52 mg/L (adult fish) and that of flutolanil were 5.47 (embryo) < 4.09 (72 h old larvae) < 3.91 (12 h old larvae) < 2.70 mg/L (adult). Sublethal effects induced by both bromothalonil and flutolanil on zebrafish embryos were noted, including growth inhibition, abnormal spontaneous movement, slower heart rate, complete hatching failure, and morphological deformities. In addition, both bromothalonil and flutolanil could cause notochord deformation and short body length of larvae. This study provides a foundation for future investigation into the mechanism of bromothalonil and flutolanil toxicity in zebrafish.

Ecotoxicological assessment of solar cell leachates: Copper indium gallium selenide (CIGS) cells show higher activity than organic photovoltaic (OPV) cells

Despite the increasing use of photovoltaics their potential environmental risks are poorly understood. Here, we compared ecotoxicological effects of two thin-film photovoltaics: established copper indium gallium selenide (CIGS) and organic photovoltaic (OPV) cells. Leachates were produced by exposing photovoltaics to UV light, physical damage, and exposure to environmentally relevant model waters, representing mesotrophic lake water, acidic rain, and seawater. CIGS cell leachates contained 583 μg L(-1) molybdenum at lake water, whereas at acidic rain and seawater conditions, iron, copper, zinc, molybdenum, cadmium, silver, and tin were present up to 7219 μg L(-1). From OPV, copper (14 μg L(-1)), zinc (87 μg L(-1)) and silver (78 μg L(-1)) leached. Zebrafish embryos were exposed until 120 h post-fertilization to these extracts. CIGS leachates produced under acidic rain, as well as CIGS and OPV leachates produced under seawater conditions resulted in a marked hatching delay and increase in heart edema. Depending on model water and solar cell, transcriptional alterations occurred in genes involved in oxidative stress (cat), hormonal activity (vtg1, ar), metallothionein (mt2), ER stress (bip, chop), and apoptosis (casp9). The effects were dependent on the concentrations of cationic metals in leachates. Addition of ethylenediaminetetraacetic acid protected zebrafish embryos from morphological and molecular effects. Our study suggests that metals leaching from damaged CIGS cells, may pose a potential environmental risk.

Assessing the toxicity of Pb- and Sn-based perovskite solar cells in model organism Danio rerio

Intensive development of organometal halide perovskite solar cells has lead to a dramatic surge in power conversion efficiency up to 20%. Unfortunately, the most efficient perovskite solar cells all contain lead (Pb), which is an unsettling flaw that leads to severe environmental concerns and is therefore a stumbling block envisioning their large-scale application. Aiming for the retention of favorable electro-optical properties, tin (Sn) has been considered the most likely substitute. Preliminary studies have however shown that Sn-based perovskites are highly unstable and, moreover, Sn is also enlisted as a harmful chemical, with similar concerns regarding environment and health. To bring more clarity into the appropriateness of both metals in perovskite solar cells, we provide a case study with systematic comparison regarding the environmental impact of Pb- and Sn-based perovskites, using zebrafish (Danio Rerio) as model organism. Uncovering an unexpected route of intoxication in the form of acidification, it is shown that Sn based perovskite may not be the ideal Pb surrogate.

Occurrence and origin of sensitivity toward difenoconazole in zebrafish (Danio reio) during different life stages

We report here an investigation of the mechanisms contributing to the divergent sensitivity toward the triazole fungicide difenoconazole of zebrafish (Danio reio) during different life stages. Adult and embryonic zebrafish were exposed to three different concentrations of difenoconazole (0.01, 0.5 and 1.0mg/L). The death rate, bioaccumulation of difenoconazole, oxidative stress parameters and transcription of related genes were tested at 4 and 8 days post-exposure (dpe). The death rate for adult zebrafish was much higher than that of the embryos at an exposure concentration of 1.0mg/L at both 4 and 8 dpe. The concentrations of difenoconazole in both the embryos and adult fish were similar, except for the group exposed to 0.01mg/L difenoconazole. A decrease in antioxidant enzyme activities was observed in both the embryos and the livers of adult fish after exposure to difenoconazole. Significant lipid peroxidation was found in the livers of adult fish in all exposure groups at 8 dpe, but was not observed in the treated embryos. The gene transcription response of the embryos toward difenoconazole was different from that in the livers of adult fish at 4 dpe. At 8 dpe, the modification in the transcription of the tested genes in the embryos and adult fish was similar, except for the genes related to the synthesis of sterols.

Embryotoxicity of nitrophenols to the early life stages of zebrafish (Danio rerio)

The nitrophenols (NPs) are water-soluble compounds. These compounds pose a significant health threat since they are priority environmental pollutants. In this study, 2-Nitrophenol (2NP) and 2,4-dinitrophenol (DNP) were examined for embryo and early life stage toxicity in zebrafish ( Danio rerio). Acute toxicity and teratogenicity of 2NP and DNP were tested for 4 days using zebrafish embryos. The typical lesions observed were no somite formation, incomplete eye and head development, tail curvature, weak pigmentation (≤48 hours postfertilization (hpf)), kyphosis, scoliosis, yolk sac deformity, and nonpigmentation (72 hpf). Also, embryo and larval mortality increased and hatching success decreased. The severity of abnormalities and mortalities were concentration- and compound-dependent. Of the compounds tested, 2,4-DNP was found to be highly toxic to the fish embryos following exposure. The median lethal concentrations and median effective concentrations for 2NP are 18.7 mg/L and 7.9 mg/L, respectively; the corresponding values for DNP are 9.65 mg/L and 3.05 mg/L for 48 h. The chorda deformity was the most sensitive endpoint measured. It is suggested that the embryotoxicity may be mediated by an oxidative phosphorylation uncoupling mechanism. This article is the first to describe the teratogenicity and embryotoxicity of two NPs to the early life stages of zebrafish.

Effects of dietary tin on growth performance, hematology, serum biochemistry, antioxidant status, and tin retention in broilers

Tin (Sn) is widely used in daily life and distributed in many tissues and nutrients. Although over-ingestion of Sn can cause health problems, relatively little attention has been given to the toxic effects of Sn in livestock health and productivity. This study was performed to investigate the toxic effects of prolonged high intake of dietary Sn on broilers. 150 one-day-old Avian broilers were randomly divided into five treatment groups, with five replicates of six birds. For 6 weeks, each group was fed a corn-soybean basal diet (BD) or BD + Sn (as SnCl2) at 120, 240, 480, or 720 mg/kg, respectively. Compared with the control, hepatic glutathione peroxidase (GPX) and superoxide dismutase (SOD) activities were significantly decreased when supplemented with Sn up to 480 mg/kg, while malondialdehyde (MDA) was increased until Sn supplementation at 720 mg/kg. Moreover, dietary Sn supplementation at 720 mg/kg decreased BW gain, feed intake, and impaired feed conversion ratio. The 720 mg Sn/kg group also increased activities of alkaline phosphatase (AKP), while decreased hemoglobin (HGB), red blood cell (RBC), and hematocrit (HCT) in the blood. Furthermore, the accumulation of Sn in various tissues was dose dependent on Sn ingestion. It was found that the tibia and feather are the two main tissues for Sn accumulation, followed by the liver, kidney, and other tissues in broilers. In conclusion, the adverse effects on broilers were induced when diets supplemented with Sn up to 480 mg/kg. Sn levels also managed to accumulate in the tibia and feather of broilers.

Unexpected phenotypes of malformations induced in Xenopus tropicalis embryos by combined exposure to triphenyltin and 9-cis-retinoic acid

Xenopus tropicalis embryos were exposed for 48 hr to the mixtures of 5 μg Sn/L triphenyltin (TPT), which is a well-known endocrine disruptor, and 0.25-5 μg/L 9-cis retinoic acid (9c-RA), which is the natural ligand of retinoid X receptor. The phenotypes induced by combined exposure were more variable than those resulting from single exposure to either TPT or 9c-RA. The prominent phenotypes included underdeveloped head structures, abnormal eyes, narrow fins, enlarged proctodaeum, etc. Especially, combined exposure induced unexpected notochord malformations, which ranged from small swellings of the surface of the tails to the extension and extrusion of notochord out of the posterior tails. Compared with the 5 μg Sn/L TPT-treated group, the index of fin deficiency was not affected, and the index of axis deficiency was significantly increased with increasing RA concentrations in the mixtures. Our results suggest that combined exposure to TPT and 9c-RA induced not only more variable phenotypes of malformations than exposure to single compound but also some new and unexpected phenotypes.

A molecular method for assessing the effects of potential contaminants on the rate of zebrafish (Danio rerio) development

Monitoring expression of the developmentally regulated genes shh, sox2, and tnnt1 by reverse transcriptase polymerase chain reaction (RT-PCR) allows determination of the rate of embryogenesis in zebrafish (Danio rerio) embryos without direct visual observation. The utility of combining this approach and morphological methods during toxicity studies was demonstrated with embryos developing at either 28.5 °C or 24.5 °C and with embryos exposed to sublethal doses of silver nanoparticles.

Evaluation of acute and developmental effects of difenoconazole via multiple stage zebrafish assays

Zebrafish, during embryo, larvae and adult stages were selected to investigate the potential environmental risk and aquatic toxicity of a widely used fungicide, difenoconazole. In addition to mortality, embryo development endpoints, teratogenic effects and behavior abnormity were measured. Finally, the developmental parameters of the adult fish were assessed after 14 days' exposure. This study concluded that the acute toxicity of difenoconazole to the three phases of zebrafish were larvae (1.17 mg/L) > adult fish (1.45 mg/L) > embryo (2.34 mg/L). A large suite of symptoms was induced in embryonic development by different dosages of difenoconazole, including hatching inhibition, abnormal spontaneous movement, slow heart rate, growth regression and morphological deformities. 0.50 mg/L of difenoconazole could cause significant body color blackening and decrease in the heart rate of zebrafish larvae over 24 h. In addition, 0.25 mg/L of difenoconazole apparently inhibited the growth weight of adult zebrafish measured after 14 days' exposure.

Comparison of neurobehavioral effects of methylmercury exposure in older and younger adult zebrafish (Danio rerio)

It is widely recognized that the nature and severity of responses to toxic exposure are age-dependent. Using active avoidance conditioning as the behavioral paradigm, the present study examined the effect of short-term methylmercury (MeHg) exposure on two adult age classes, 1- and 2-year-olds to coincide with zebrafish in relatively peak vs. declining health conditions. In Experiment 1, 2-year-old zebrafish were randomly divided into groups and were exposed to no MeHg, 0.15% ethanol (EtOH), 0.01, 0.03, 0.1, or 0.3 μM of MeHg (in 0.15% ethanol) for 2 weeks. The groups were then trained and tested for avoidance responses. The results showed that older zebrafish exposed to no MeHg or EtOH learned and retained avoidance responses. However, 0.01 μM or higher concentrations of MeHg exposure impaired avoidance learning in a dose-dependent manner with 0.3 μM of MeHg exposure producing death during the exposure period or shortly after the exposure but before the avoidance training. In Experiment 2, 1-year-old zebrafish were randomly divided into groups and were exposed to the same concentrations of MeHg used in Experiment 1 for 2 weeks. The groups were then trained and tested for avoidance responses. The results showed that younger zebrafish exposed to no MeHg, EtOH, or 0.01 μM of MeHg learned and retained avoidance responses, while 0.1 or 0.3 μM of MeHg exposure impaired avoidance learning in a dose-dependent manner. The study suggested that MeHg exposure produced learning impairments at a much lower concentration of MeHg exposure and more severely in older adult compared against younger adult zebrafish even after short exposure times.

In vivo quantitative study of sized-dependent transport and toxicity of single silver nanoparticles using zebrafish embryos

Nanomaterials possess distinctive physicochemical properties (e.g., small sizes and high surface area-to-volume ratios) and promise a wide variety of applications, ranging from the design of high quality consumer products to effective disease diagnosis and therapy. These properties can lead to toxic effects, potentially hindering advances in nanotechnology. In this study, we have synthesized and characterized purified and stable (nonaggregation) silver nanoparticles (Ag NPs, 41.6 ± 9.1 nm in average diameter) and utilized early developing (cleavage-stage) zebrafish embryos (critical aquatic and eco- species) as in vivo model organisms to probe the diffusion and toxicity of Ag NPs. We found that single Ag NPs (30-72 nm diameters) passively diffused into the embryos through chorionic pores via random Brownian motion and stayed inside the embryos throughout their entire development (120 hours-post-fertilization, hpf). Dose- and size-dependent toxic effects of the NPs on embryonic development were observed, showing the possibility of tuning biocompatibility and toxicity of the NPs. At lower concentrations of the NPs (≤0.02 nM), 75-91% of embryos developed into normal zebrafish. At the higher concentrations of NPs (≥0.20 nM), 100% of embryos became dead. At the concentrations in between (0.02-0.2 nM), embryos developed into various deformed zebrafish. Number and sizes of individual Ag NPs embedded in tissues of normal and deformed zebrafish at 120 hpf were quantitatively analyzed, showing deformed zebrafish with higher number of larger NPs than normal zebrafish and size-dependent nanotoxicity. By comparing with our previous studies of smaller Ag NPs (11.6 ± 3.5 nm), we found striking size-dependent nanotoxicity that, at the same molar concentration, the larger Ag NPs (41.6 ± 9.1 nm) are more toxic than the smaller Ag NPs (11.6 ± 3.5 nm).

Single-cell protein as an alternative food for zebrafish, Danio rerio: a toxicological assessment

Single-cell protein (SCP) refers to the dried cells of microorganisms. The aim of this research was to evaluate the nutrional characteristics and possible toxic effects of the SCP of Trichoderma harzianum. First, T. harzianum was grown on whey filtrate agar medium and the obtained SCP was analysed. It was rich in both total protein (34.21%) and ash (4.78%). Furthermore, the biomass contained all the essential amino acids, and the amino acid concentrations were very close to the FAO reference protein levels. Second, we exposed zebrafish (Danio rerio) embryos to diluted SCP at various concentrations for 96 hours postfertilization (hpf). Compared with the control group, we did not observe any developmental abnormalities, delayed hatching, and lethal effects on zebrafish embryos (96 hpf) found in the SCP group. To test diet effects on spawning success and growth of embryos, adult zebrafish were fed on SCP and flake feed diets for 10 weeks. The number of laid eggs, wet weight and diameter of eggs, and the percentages of hatched eggs from fish fed the flake diet and SCP diet were not significantly different from each other. Also, larval length and weight were not significantly affected by diets. Finally, SCP did not cause any toxic effect on zebrafish adults and their offsprings and could be useful as fish food or food additive.