Zebrafish Embryos and Larvae as Alternative Animal Models for Toxicity Testing

Toxicological screening of jambolan hydroalcoholic extract (Syzygium cumini (L.) Skeels) in zebrafish (Danio rerio)

Jambolan (Syzygium cumini (L.) Skeels) is an important source of phenolic compounds, especially anthocyanins, known for their biological properties. This study investigated the acute toxicity of jambolan hydroalcoholic extract (JE) in zebrafish (Danio rerio) at different life stages. JE, obtained from freeze-dried fruits, was analyzed by high-performance liquid chromatography (HPLC) and found to be rich in total phenolic compounds (TPC). A total of 15 phenolic compounds were identified in the HPLC extracts, mainly anthocyanins (≈ 82 % of TPC), and JE presented relevant antioxidant properties in in vitro tests. Exposure to concentrations between 50 and 200 µg/ml resulted in increased malformations and mortality in both embryos and adult zebrafish, and doses of 300 and 400 µg/ml were lethal to the animals. Lethal concentrations (LC50) were estimated at 118.4 µg/ml for embryos and 68.86 µg/ml for adults. Despite no significant cardiovascular or neurological toxicities, behavioral impacts were observed at lower concentrations (10 µg/ml), indicating a nonmonotonic concentration-response curve. Our findings suggest that moderate JE doses (around 25 µg/ml) are safe for zebrafish; however, further studies are needed to ensure its safety and efficacy under different health conditions and exposure regimes.

An integrated approach to understanding the effects of exposome on neuroplasticity

Anthropogenic factors are those that occur due to human activities. The exposome is proposed to complement the genome, wherein an individual's exposure begins before birth. The range of exposures includes physical, chemical, dietary, lifestyle, biological, and occupational sources. Exposome has a positive or negative influence on neuroplasticity during different stages of life. A comprehensive study of the exposome is thus necessary to incorporate these factors and their influence on the individual, community, and the population as a whole. Exposomic research and global health present significant opportunities for interdisciplinary research. This review gives an overview of the exposome and its influence on neuroplasticity. It proposes methods to study the exposome on neuroplasticity across the lifespan of the individual. This is possible with the use of self-reported data, large-scale cohort formation, physiological sensors, neuroimaging, omics, molecular biology, and systems approaches. These approaches aim to provide a holistic understanding of an individual's neurological well-being and its implications for the population at large. This will also enable the designing of novel preventive and treatment strategies for managing neurological disorders.

Environmental concentrations of glyphosate through direct or parental exposure alter nervous system development and reduce the fertility rate in zebrafish

N-(phosphonomethyl)glycine (glyphosate) is the most widely used herbicide worldwide. Although it has been extensively studied, few studies use realistic environmental concentrations to assess its potential effects on fish embryos and larvae. This work aims to evaluate potential neurotoxic and reproductive effects of realistic concentrations of glyphosate in non-target aquatic species using zebrafish larvae. Biological and reproductive biomarkers (condition factor, hepatic and gonadic indices, and fertility rate) were evaluated for adults exposed to 0, 10, 100, and 1000 µg/L, while a transcriptomic comparison was carried out for larvae from both exposure scenarios at 1000 µg/L. The fertility rate of exposed parents decreased with increasing glyphosate concentration, while gonadosomatic (GSI) and hepatosomatic (HIS) indices of females treated with 100 µg/L glyphosate were significantly higher in glyphosate-exposed fish compared to the control group; however, glyphosate treatment did not significantly change GSI or HSI in males. Transcriptomic analysis in larvae showed that glyphosate could alter developmental and metabolic processes, targeting the nervous system in both exposure schemes. The ability of glyphosate to alter the development of the nervous system in larvae of exposed parents suggests that exposure to gametes could produce intergenerational alterations, with potential ecotoxicological implications that remain to be determined.

Unravelling the developmental toxicity of heavy metals using zebrafish as a model: a narrative review

Developmental toxicity is the disruption of an organism's normal development which may occur in either the parent before conception or in the growing creature itself. Zebrafish (Danio rerio) are being employed as effective vertebrate models to evaluate the safety and toxicity of chemicals because they can breed multiple times in a year so we can observe the toxic effects in the next generation and their development mental stages can be observed and define clearly because their 1 cell stage to prime stage is transparent so we can observe the development of every organ also they have nearly about 80% genetic similarity with humans and shares the similar neuromodulatory structure along with multiple neurotransmitter. The recent research endeavours to examine the harmful outcome of various heavy metals such as cadmium, chromium, nickel, arsenic, lead, mercury, bismuth, iron, manganese, and thallium along with microplastics on zebrafish embryos when subjected to environmentally acceptable levels of every single metal in addition to co-exposure at various points in time. These heavy metals can alter the mRNA expression levels, increase the reactive oxygen species (ROS) generation, decrease antioxidant expression, damage neuronal function, alter neurotransmitter release, alter the expression of several apoptotic proteins, interfere with the different signalling pathways, decrease heat rates, increase malformations like - pericardial oedema, heart oedema, reduce in length tail bending abnormal formation in fins. Thereafter we concluded that due to its involvement in the food chain, it also causes severe effects on human beings.

Synthesis of immunomodulatory biomimetic lipid polymer hybrid nanoparticles and application of zebrafish larvae in immunomodulation screening

Since the antibiotic golden era of the mid-20th century, there have been limited antibiotics approved, while antibiotic resistance continues to escalate disproportionately, outpacing the rate of novel antibiotic discovery. This imbalance poses a serious global health concern, with an estimated annual death toll of 10 million due to antibiotic resistance by 2050. There is a growing interest in immunotherapy as an alternative approach to conventional antibiotics due to its ability to target and stimulate immune system, leveraging its innate ability to self-eradicate pathogens. This study synthesized lipid polymer hybrid nanoparticles (LPHNPs) conjugated with two immunomodulatory agents, namely, curdlan and mycolic acid (MA), as a potential immunotherapy for bacterial infections. LPHNPs were synthesized using lecithin and polycaprolactone (PCL) at a 15 % lipid-to-polymer (w/w) ratio. Additionally, PCL-curdlan copolymer, comprising 15 % w/w curdlan, was successfully synthesized and used to conjugate the LPHNPs with various curdlan concentrations. Furthermore, The LPHNPs were conjugated with varying MA concentrations, with or without curdlan. In-vivo assessment of the immunomodulatory effect of the LPHNPs was conducted using a larval zebrafish model assessing behaviour and immunofluorescence, as indicators of immune stimulation. The data suggests that curdlan exhibits a more complex immunoregulatory role as demonstrated by the countered stimulated behavioural effect while inflammation remained heightened. This work also provides new insights that zebrafish larvae are a valuable screening tool in the development of nanoparticle immunotherapies.

Methodological and Ethical Considerations in the Use of Chordate Embryos in Biomedical Research

Animal embryos are vital tools in scientific research, providing insights into biological processes and disease mechanisms. This paper explores their historical and contemporary significance, highlighting the shift towards the refinement of in vitro systems as alternatives to animal experimentation. We have conducted a data review of the relevant literature on the use of embryos in research and synthesized the data to highlight the importance of this model for scientific progress and the ethical considerations and regulations surrounding embryo research, emphasizing the importance of minimizing animal suffering while promoting scientific progress through the principles of replacement, reduction, and refinement. Embryos from a wide range of species, including mammals, fish, birds, amphibians, and reptiles, play a crucial experimental role in enabling us to understand factors such as substance toxicity, embryonic development, metabolic pathways, physiological processes, etc., that contribute to the advancement of the biological sciences. To apply this model effectively, it is essential to match the research objectives with the most appropriate methodology, ensuring that the chosen approach is appropriate for the scope of the study.

Liquid mosquito repellent induces toxic effects in zebrafish

Mosquitoes serve as vectors for life-threatening parasitic diseases, presenting a continuous threat throughout human history. This has resulted in the extensive utilization of various mosquito repellents, including liquid mosquito repellents (LMRs), roll-ons, and topical creams. While these products demonstrate significant efficacy, the toxicological implications associated with their use are not yet fully understood and continue to be a subject of debate. The analysis conducted using gas chromatography-mass spectrometry (GC-MS) on LMR revealed the presence of 158 distinct compounds, among which were Piperazine 2,5-dimethyl propyl and a range of hydrocarbons. The analysis of network toxicology indicated that 78 of the examined compounds contravened Lipinski's rule of five and exhibited considerable overlap with target genes associated with lung cancer pathways, thereby highlighting potential concerns regarding their carcinogenic properties. The exposure of zebrafish embryos to LMR concentrations between 0.1 and 14 µg/mL resulted in developmental toxicity assays that demonstrated a dose-dependent escalation in mortality rates and the occurrence of morphological abnormalities, such as pericardial edema and skeletal deformities. Behavioral assays demonstrated a marked decrease in locomotor activity at elevated LMR concentrations, indicating potential neurotoxic effects. Biochemical analyses revealed elevated levels of reactive oxygen species (ROS), enhanced lipid peroxidation, and diminished glutathione, which are indicative of oxidative stress. Enzyme activity assays indicated a reduction in superoxide dismutase (SOD) and catalase (CAT) activities, alongside an increase in lactate dehydrogenase (LDH) activity, which suggests the occurrence of cellular damage. Analysis of gene expression demonstrated significant dysregulation in genes associated with oxidative stress (SOD1, CAT), inflammatory markers (TNF-α, IL-1β), apoptotic regulators (p53, bcl2), and neurobiological genes (brain-derived neurotrophic factor, bdnf). The results highlight the possible health hazards linked to LMR exposure, which manifest as developmental, biochemical, and genetic alterations in zebrafish embryos.

Designing lysyl hydroxylase inhibitors for oral submucous fibrosis - Insights from molecular dynamics

Alpha-ketoglutarate (αKG) dependent Lysyl hydroxylase (LH) is a critical enzyme in the post-translational conversion of lysine into hydroxylysine in collagen triple helix and telopeptide regions. Overexpression of LH increases collagen hydroxylation and covalent cross-linkage, causing fibrosis. Currently, no drugs are available to inhibit LH potentially. Virtual screening of the Zinc database was employed to identify new leads. They were docked using Glide. Lead1 complex exhibits a notably superior docking score compared to other leads. This complex hinders iron stabilization by engaging with the HXD..Xn..H motif and competitively inhibiting 2OG binding at the catalytic site via interactions with Cys691 and Arg729 by forming a salt bridge. Molecular dynamics simulations over a 500 ns time scale and molecular mechanics Poisson-Boltzmann surface area calculations illustrate the stable binding of Leads. DCCA analysis finds the coordinated residue motions and the influence of the second coordinating sphere in long-range interactions. In-silico results were validated by quantifying the amount of collagen in zebrafish through histology and hydroxyproline assay. These findings demonstrated a reduction in collagen deposition in the treated samples compared to the positive control. This computational study unveiled insights into how leads may impede collagen lysine hydroxylation and potentially impact collagen-related processes.

Zebrafish as a model organism in One Health Toxicology: Impact of solvents and exposure routes on the toxicity of platinum anticancer drugs

Zebrafish are widely used not only as a model in ecotoxicology but also to study the potential impact of chemicals on human health. Typically, zebrafish are exposed to chemicals dissolved in egg water or other defined media, which is the standard routine for ecotoxicology testing. This straightforward exposure method is usually also employed to monitor adverse effects in zebrafish to predict potential hazards and modes of action in humans. Here, we compared different exposure media and studied the impact of salinity and solvents relevant to ecotoxicity testing. For comparison, toxicants also were directly injected into the bloodstream of zebrafish embryos, as this method better simulates the exposure scenario for assessing the adverse effects of drugs administered intravenously to patients. As model compounds we studied platinum-based anticancer drugs, which are known micropollutants, but also lead to severe side effects in humans. Striking differences in sensitivity and phenotypes, i.e. adverse outcomes, were observed dependent on the exposure route and media. The bioavailability of the platinum compounds was significantly altered in the different media and by the commonly used solvent DMSO. These findings highlight the relevance of the exposure route and media as well as of solvents to be considered when interpreting zebrafish studies in the field of ecotoxicology or in cross-species comparisons to predict effects on human health.

Advancements in the Developmental Zebrafish Model for Predictive Human Toxicology

The rapid assessment of chemical hazards to human health, with reduced reliance on mammalian testing, is essential in the 21st century. Early life stage zebrafish have emerged as a leading model in the field due to their amenability to high throughput developmental toxicity testing while retaining the benefits of using a whole vertebrate organism with high homology with humans. Zebrafish are particularly well suited for a variety of study areas that are more challenging in other vertebrate model systems including microbiome work, transgenerational studies, gene-environment interactions, molecular responses, and mechanisms of action. The high volume of data generated from zebrafish screening studies is highly valuable for QSAR modeling and dose modeling for use in predictive hazard assessment. Recent advancements and challenges in using early life stage zebrafish for predictive human toxicology are reviewed.

Advances in bioinformatic methods for the acceleration of the drug discovery from nature

BACKGROUND

Drug discovery from nature has a long, ethnopharmacologically-based background. Today, natural resources are undeniably vital reservoirs of active molecules or drug leads. Advances in (bio)informatics and computational biology emphasized the role of herbal medicines in the drug discovery pipeline.

PURPOSE

This review summarizes bioinformatic approaches applied in recent drug discovery from nature.

STUDY DESIGN

It examines advancements in molecular networking, pathway analysis, network pharmacology within a systems biology framework and AI for assessing the therapeutic potential of herbal preparations.

METHODS

A comprehensive literature search was conducted using Pubmed, SciFinder, and Google Database. Obtained data was analyzed and organized in subsections: AI, systems biology integrative approach, network pharmacology, pathway analysis, molecular networking, structure-based virtual screening.

RESULTS

Bioinformatic approaches is now essential for high-throughput data analysis in drug target identification, mechanism-based drug discovery, drug repurposing and side-effects prediction. Large datasets obtained from "omics" approaches require bioinformatic calculations to unveil interactions, and patterns in disease-relevant conditions. These tools enable databases annotations, pattern-matching, connections discovery, molecular relationship exploration, and data visualisation.

CONCLUSION

Despite the complexity of plant metabolites, bioinformatic approaches assist in characterization of herbal preparations and selection of bioactive molecule. It is perceived as powerful tool for uncovering multi-target effects and potential molecular mechanisms of compounds. By integrating multiple networks that connect gene-disease, drug-target and gene-drug-target, drug discovery from natural sources is experiencing a remarkable comeback.

Zebrafish as a Suitable Model for Utilizing the Bioactivity of Coumarins and Coumarin-Based Compounds

The aim of this review is to summarize the current knowledge on the use of coumarin-derived compounds in the zebrafish (Danio rerio) model. Coumarins, a class of naturally occurring compounds with diverse biological activities, including compounds such as coumarin, angelicin, and warfarin, have attracted considerable attention in the study of potential therapeutic agents for cancer, central nervous system disorders, and infectious diseases. The capabilities of coumarins as active compounds have led to synthesizing various derivatives with their own properties. While such variety is certainly promising, it is also cumbersome due to the large amount of research needed to find the most optimal compounds. The zebrafish model offers unique advantages for such studies, including high genetic and physiological homology to mammals, optical transparency of the embryos, and rapid developmental processes, facilitating the assessment of compound toxicity and underlying mechanisms of action. This review provides an in-depth analysis of the chemical properties of coumarins, their mechanisms of biological activity, and the results of previous studies evaluating the toxicity and efficacy of these compounds in zebrafish assays. The zebrafish model allows for a holistic assessment of the therapeutic potential of coumarin derivatives, offering valuable insights for advancing drug discovery and development.

Behavioral Profiling in Zebrafish Identifies Insecticide-Related Compounds

Pesticides, including insecticides, are indispensable for large-scale agriculture. Modulating chloride ion channels has proven highly successful as a mode of action (MoA) for insect management. Identifying new ligands for these channels affords opportunities for the potential development of new insecticide products. We discovered an unexpected behavioral response in larval zebrafish exposed to endosulfan, a γ-aminobutyric acid (GABA)-gated chloride channel modulator. At low concentrations, endosulfan increased zebrafish motor activity under strobing blue or green light stimuli. Using this distinct behavioral phenotype as a proxy for similar modes of action, we screened over 9,000 compounds and identified several structurally diverse hits that phenocopied endosulfan's effects in vivo. Nine selected hits were tested in an in vitro GABA receptor (GABAR) oocyte assay, confirming that certain compounds block Drosophila GABAR activation. Subsequent in vivo insect assays revealed that one of these GABAR antagonists showed insecticidal activity against the Western corn rootworm (Diabrotica virgifera virgifera), which is a commercially important pest of corn. Our findings demonstrate a new approach for identifying GABAR-targeting insecticides through behavior-based screening in zebrafish.

Methylene blue at recommended concentrations alters metabolism in early zebrafish development

Methylene blue (MB) is an antifungal agent widely used during critical stages of zebrafish development. Most guidelines recommend 0.00005% or 0.0001% of MB for embryo/larval rearing. The Organisation for Economic Co-operation and Development zebrafish embryo toxicity test guideline omits MB recommendations, leading to inconsistent MB use in zebrafish research. Because MB affects oxidative energy metabolism in vitro and in vivo, we investigate possible metabolic effects of recommended MB concentrations in developing zebrafish (1-5 days post-fertilization (dpf)). MB increases O2 consumption rate at 1 dpf, followed by an overall reduction in oxidative energy metabolism in post-hatch eleutheroembryos (4-5 dpf). Concomitantly, mitochondrial transcripts decrease in 1 and 4 dpf zebrafish. Our findings show that MB, at recommended husbandry concentrations, affects oxidative metabolism and can thus confound experiments. Since the zebrafish embryo/larval model is gaining traction as a high-throughput New Approach Methodology (NAM) for toxicity assessment, researchers should reconsider MB use.

Thermal Characterisation and Toxicity Profile of Potential Drugs from a Class of Disubstituted Heterofused Triazinones

The thermal characterisation and toxicity profile of a class of disubstituted heterofused triazinones were revealed in this article for the first time. The thermal behaviour of molecules 1-12 was investigated by means of TG and DSC analyses performed in an air atmosphere and by the coupled TG/FTIR technique in a nitrogen atmosphere. The heating atmosphere affects both the stability of compounds and the degradation mechanism. A two-step degradation occurs in air, while a one-step degradation takes place in nitrogen, both preceded by a melting process. Compound 3 shows the highest thermal stability, while molecule 10-the lowest. The thermal decomposition of the studied heterocyclic molecules begins with the degradation of the bicyclic system, resulting in the formation of volatile gaseous products such as ammonia/hydrazine, hydrogen cyanide, carbon dioxide, and isocyanates. In the further stage, mainly aromatic compounds are released, and their chemical composition depends on the presence and type of substituents at the phenyl and benzyl moieties. In addition, the toxicity profiles of molecules were assessed in the animal (zebrafish) and cellular (erythrocytes) models, and the antihaemolytic activity was evaluated in the AAPH- and H2O2-induced haemolysis inhibition assays. It was found that all the tested compounds are safe for the developing zebrafish and red blood cells, and they are able to effectively protect erythrocytes from oxidative damage. These favourable properties make them promising drug candidates suitable for further in vivo studies.

In Vitro, In Vivo, Ex Vivo Characterisation of Dihydroimidazotriazinones and Their Thermal Decomposition Course Studied by Coupled and Simultaneous Thermal Analysis Methods

The biological and thermal properties of a class of synthetic dihydroimidazotriazinones were disclosed in this article for the first time. Molecules 1-6-as potential innovative antimetabolites mimicking bicyclic aza-analogues of isocytosine-were evaluated for their in vitro anticancer activity. Moreover, in vivo, in vitro, and ex vivo toxicity profiles of all the compounds were established in zebrafish, non-tumour cell, and erythrocyte models, respectively. Their antihaemolytic activity was also evaluated. Additionally, the thermal decomposition mechanism, path, and key thermal properties of heterocycles 1-6 were analysed. It was found that all the studied compounds revealed significant antiproliferative activities against tumour cells of the lung, cervix, ovary, and breast, as well as acute promyelocytic leukaemia cells, superior or comparable to that of an anticancer agent gemcitabine. Most of them were less toxic to non-tumour cells than this standard drug, and none had a haemolytic effect on red blood cells. All the tested heterocycles proved to be safer for zebrafish than a standard drug pemetrexed. Some exhibited the ability to inhibit oxidative haemolysis, suggesting their protective action on erythrocytes. The differential scanning calorimetry (DSC) analyses confirmed that all molecules melted within one narrow temperature range, proving their purity. The melting points depended solely on the type of substituent and increased as follows: 4 (R = 3-ClPh) < 2 (R = 4-CH3Ph) = 3 (R = 4-OCH3Ph) < 5 (R = 4-ClPh) = 1 (R = Ph) < 6 (R = 3,4-Cl2Ph). The thermogravimetry/differential thermogravimetry (TG/DTG) studies confirmed high thermal stability of all the investigated heterocycles in inert (>230 °C) and oxidising (>260 °C) atmospheres, which depended directly on the R. The pyrolysis process included one main decomposition stage and was connected with the emission of NH3, HCN, CH3CN, HNCO, alkane, alkene, aromatic fragments, CO2 (for all the compounds), and HCl (for the molecule with 3,4-Cl2Ph), which was confirmed by FTIR and QMS analyses. In turn, the oxidative decomposition process of the tested polyazaheterocycles took place in two main stages connected with the formation of the same volatiles as those observed in an inert atmosphere and additionally with the release of N2, NO, CO, and H2O. These results proved that the pyrolysis and oxidative decomposition run through the radical mechanism connected with the additional reactions between radicals and oxygen in synthetic air. The favourable biological and thermal properties of this class of dihydroimidazotriazinones imply their usefulness as potential pharmaceutics.

Amino modifications exacerbate the developmental abnormalities of polystyrene microplastics via mitochondria-mediated apoptosis pathway in zebrafish larvae

Microplastics (MPs) are ubiquitous in the environment and have been identified as a potential threat to ecosystems. However, the mechanisms of toxicity of modified MPs remain unknown. This study investigated the developmental toxicity of amino-modified polystyrene microplastics (PS-NH2) with environmentally relevant concentrations ranging from 0.1 to 100 μg/L in the early developmental stages of zebrafish. Adding amino functional groups resulted in significant alterations in the surface morphology and zeta potential of traditional polystyrene microplastics (PS-MPs). Zebrafish larvae exposed to PS-NH2 exhibited increased developmental toxicity compared to PS-MPs, as indicated by reduced body length, heart rate, and spontaneous movement. The expression of cat1, sod1, gstr1, nrf2a, nrf2b, and HO-1, as well as alterations in ROS, SOD, CAT, and MDA levels, all demonstrated oxidative damage caused by PS-NH2 exposure. Mitochondrial dysfunction was also induced, as evidenced by changes in the expression of cox4i1, ndufs1, and uqcrc1, as well as changes in the levels of ATP, cytochrome c, NAD, and NADH. Furthermore, PS-NH2 exposure disrupted apoptosis regulation, increasing apoptotic cells and caspase activity, along with changes in caspase-3 and bcl-2 expression. Molecular docking showed that PS-NH2 interacts with bcl-2 with high binding energy. This study contributes to understanding the toxic effects and mechanisms of charge-modified MPs in zebrafish.

Identification and characterization of etomidate and metomidate metabolites in zebrafish, HLMs and S9 fraction by quadrupole-orbitrap LC-MS/MS for drug control

Etomidate is a common non-barbiturate anesthetic with psychoactivity, and metomidate, a structural modifier of etomidate, also has the same psychoactive effect, and the abuse of both has gradually intensified. In this study, etomidate, metomidate and their metabolic profiles with 4 days postfertilization (4dpf) zebrafish, 4 months postfertilization (4mpf) zebrafish, human liver microsomes (HLMs) and human liver S9 fraction were investigated using Liquid chromatography with high resolution mass spectrometry (LC-HRMS) for the first time. 14 etomidate metabolites and 11 metomidate metabolites were found, and the related metabolic pathways included monohydroxylation, dihydroxylation, dehydrogenation, N-dealkylation, O-dealkylation, oxidation, N-glucuronidation, O-glucuronidation and combination. Etomidate acid (E6 and M6) was considered a common biomarker for monitoring the abuse of etomidate and its analogues. Two characteristic metabolites (E4 and M4) could be used as biomarkers to monitor etomidate or metomidate abuse, respectively. Dealkylation, hydroxylation and glucuronidation were the main metabolic pathways of etomidate and metomidate. The differences in metabolic profiles of the three metabolic models were also compared for the first time. The results of this study can provide important reference for the detection of target compounds against the abuse of etomidate and metomidate, and the metabolic analysis of similar substances.

Nano-bio interactions of Gum Arabic-stabilized lanthanide-based upconverting nanoparticles: in vitro and in vivo study

Lanthanide-based nanoparticles (Ln-NPs) are highly valued for their unique optical and magnetic properties, making them useful in various scientific fields, including materials science and biomedicine. This study investigated the use of Gum Arabic (GA), a natural, non-toxic biopolymer, as capping agent for Ln-NPs to enhance their biocompatibility and chemical and colloidal stability. Specifically, Er3+/Yb3+ co-doped NaGdF4 Ln-NPs were modified with GA, followed by their characterization with respect to upconversion properties and in vitro as well as in vivo toxicity. Herein, widely used ligand-free and polyacrylic acid (PAA)-capped Ln-NPs were used as reference materials. Importantly, the GA-modified Ln-NPs exhibited superior stability in aqueous and biologically relevant media, as well as relatively lower cytotoxicity across multiple cell lines, including U-87 MG, HEPG2, and J774A.1. In vivo studies using zebrafish embryos confirmed the minimal toxicity of GA-capped Ln-NPs. Despite overall low non-specific cellular uptake, hyperspectral imaging and inductively coupled plasma mass spectrometry confirmed the colocalization of the Ln-NPs as a function of their surface chemistry in both cell models and zebrafish. The results suggest GA as an effective surface-stabilizing agent for Ln-NPs, paving the way for future functionalization with targeting agents.

Embryoid Body Test: A Simple and Reliable Alternative Developmental Toxicity Test

The increasing emphasis on animal welfare and ethics, as well as the considerable time and cost involved with animal testing, have prompted the replacement of many aspects of animal testing with alternative methods. In the area of developmental toxicity, the embryonic stem cell test (EST) has played a significant role. The EST evaluates toxicity using mouse embryonic stem cells and somatic cells and observes the changes in heartbeat after cardiac differentiation. Nevertheless, the EST is a relatively complex testing process, and an in vitro test requires a long duration. Several attempts have been made to develop a more straightforward testing method than the EST, with improved reproducibility and accuracy, leading to the development of the embryoid body test (EBT). Unlike the EST, which involves cardiac differentiation stages, the EBT verifies toxicity by measuring the changes in the area of the embryoid body. Despite its short testing period and simple procedure, the EBT offers high accuracy and reproducibility and is fully validated through two rounds of validation, making it ready for practical application. The EBT is expected to play a crucial role in the rapidly increasing demand for alternative methods to animal testing, particularly for screening early developmental toxicity.

A green approach coupled with molecular dynamics simulations and toxicity assays to infer the mode of action for organophosphate esters

Organophosphate esters (OPEs) have attracted extensive attention due to their toxic effects on human health and biological systems as plasticizers and flame retardants. This study focused on exploring a green approach to get toxicity mechanisms that used less solvents or organisms. The toxicity values of selected organophosphate esters including tri (2-chloroethyl) phosphate (TCEP), tri (1, 3-dichloro-2-propyl) phosphate (TDCP), tripropyl phosphate (TPrP), tri-n-butyl phosphate (TnBP), and tritolyl Phosphate (TCrP) to Photobacterium phosphoreum were determined. Their EC50 range was between 7.27 × 10-8-5.12 × 10-6 mol/L. Based on molecular dynamics simulation the data of binding affinity between OPEs and n-octanol / phospholipid bilayer were calculated respectively. Coupling with binding affinity energies and toxicity values, the mode of action (MOA) of OPEs including types of reactive or anesthetic mechanism could be fast deduced. The proposed hypothesis of n-octanol (C8H18O) as a virtual biofilm to replace phospholipid bilayer was verified. The alternative green approach could simplify toxicity assay and realize fast predicting MOA for different chemicals and model organisms.

Zebrafish: A Cost-Effective Model for Enhanced Forensic Toxicology Capabilities in Low- and Middle-Income Countries

Low- and middle-income countries (LMICs) are increasingly challenged by the rising burden of medicolegal cases. Traditional forensic infrastructure and in vivo rodent models often have significant limitations due to high costs and ethical concerns. As a result, zebrafish (Danio rerio) are gaining popularity as an attractive alternative model for LMICs because of their cost-effectiveness and practical advantages. Zebrafish have a lower acquisition cost, require less demanding husbandry, and have rapid development cycles, all of which facilitate faster and more economical toxicological studies, even in limited laboratory space. Additionally, the optical transparency of zebrafish embryos and larvae allows for non-invasive in vivo observations, reducing the need for extra resources. Research has shown that zebrafish can effectively investigate the behavioral, developmental, and cardiotoxic effects of various novel psychoactive substances (NPSs), including synthetic opioids, cathinones, and hallucinogens. They also excel in metabolic profiling, producing a broader range of metabolites than other models, with significant overlap in human metabolism. The presence of mammalian-like metabolic enzymes further positions zebrafish as a valuable tool for understanding human NPS metabolism and predicting potential effects. Notably, they can identify metabolites that traditional models may not detect, underscoring their potential for novel metabolite discovery. Despite these advantages, standardizing data collection protocols and addressing interlaboratory variability are crucial challenges that must be overcome for the widespread adoption of the zebrafish model. However, ongoing global efforts are paving the way to address these limitations and ensure the successful integration of zebrafish models into the field of forensic toxicology. This review highlights the potential of zebrafish as a cost-effective and versatile model for LMICs, emphasizing their growing application in NPS research and forecasting broader adoption in forensic toxicology.

Evaluation of organ developmental toxicity of environmental toxicants using zebrafish embryos

There is increasing global concern about environmental pollutants, such as heavy metals, plastics, pharmaceuticals, personal care products, and pesticides, which have been detected in a variety of environments and are likely to be exposed to nontarget organisms, including humans. Various animal models have been utilized for toxicity assessment, and zebrafish are particularly valuable for studying the toxicity of various compounds owing to their similarity to other aquatic organisms and 70% genetic similarity to humans. Their development is easy to observe, and transgenic models for organs such as the heart, liver, blood vessels, and nervous system enable efficient studies of organ-specific toxicity. This suggests that zebrafish are a valuable tool for evaluating toxicity in specific organs and forecasting the potential impacts on other nontarget species. This review describes organ toxicity caused by various toxic substances and their mechanisms in zebrafish.

Systematic investigation on the pharmaceutical components and mechanism of the treatment against zebrafish enteritis by Sporisorium reilianum f. sp. reilianum based on histomorphology and pathology

ETHNOPHARMACOLOGICAL RELEVANCE

Sporisorium reilianum f. sp. reilianum (SSR) is a fungus isolated from a medicinal plant. Recorded in the "Compilation of National Chinese Herbal Medicine" and "Compendium of Materia Medica," it was used for preventing and treating intestinal diseases, enhancing immune function, etc. In this study, we investigated the chemical composition and bioactivity of SSR. Network pharmacology is utilized for predictive analysis and targeting pathway studies of anti-inflammatory bowel disease (IBD) mechanisms. Pharmacological activity against enteritis is evaluated using zebrafish (Danio rerio) as model animals.

AIM OF THE STUDY

To reveal the treatment of IBD by SSR used as traditional medicine and food, based on molecular biology identification of SSR firstly, and the pharmaceutical components & its toxicities, biological activity & mechanism of SSR were explored.

MATERIALS AND METHODS

Using chromatography and zebrafish IBD model induced by dextran sulfate sodium (DSS), nine compounds were first identified by nuclear magnetic resonance (NMR). The toxicity of ethanol crude extract and monomers from SSR were evaluated by evaluating the phenotypic characteristics of zebrafish embryos and larvae, histomorphology and pathology of the zebrafish model guided by network pharmacology were conducted.

RESULTS

The zebrafish embryo development did not show toxicity. The molecular docking and enrichment pathway results predicted that metabolites 3 & 4 (N-trans- feruloyl-3-methoxytyramine & N-cis-feruloyl-3-methoxytyramine) and 7 & 8 (4-N- trans-p-coumaroyltyramine & 4-N-cis--p-coumaroyltyramine) have anti-enteritis activities. This paper lays an experimental foundation for developing new drugs and functional foods.

Nano-alumina induced developmental and neurobehavioral toxicity in the early life stage of zebrafish, associated with mTOR

The study aims to investigate the effects of nano-alumina (AlNPs) on the early development and neurobehavior of zebrafish and the role of mTOR in this process. After embryos and grown-up larvae exposed to AlNPs from 0 to 200 μg/mL, we examined the development, neurobehavior, AlNPs content, and mTOR pathway genes. Moreover, embryos were randomly administered with control, negative control, mTOR knockdown, AlNPs, and mTOR knockdown + AlNPs, then examined for development, neurobehavior, oxidative stress, neurotransmitters, and development genes. As AlNPs increased, swimming speed and distance initially increased and then decreased; thigmotaxis and panic-avoidance reflex substantially decreased in the high-dose AlNPs group; aluminum and nanoparticles considerably accumulated in the 100 μg/mL AlNPs group; AlNPs at high dose decreased mTOR gene and protein levels, stimulating autophagy via increasing ULK1 and ULK2. mTOR knockdown exacerbated the harm to normal development rate, eye and body length, and neurobehavior induced by AlNPs through raising ROS, SOD, and ACH levels but decreasing AchE activity and development genes. Therefore, AlNPs suppress neurobehavior through downregulating mTOR, and mTOR knockdown further aggravates their early development and neurobehavior loss, suggesting mTOR could be a potential target for the toxicity of AlNPs.

The downregulation of TREM2 exacerbates toxicity of development and neurobehavior induced by aluminum chloride and nano-alumina in adult zebrafish

To investigate the difference in the development and neurobehavior between aluminum chloride (AlCl3) and nano-alumina (AlNPs) in adult zebrafish and the role of triggering receptor expressed on myeloid cells (TREM2) in this process. Zebrafish embryos were randomly administered with control, negative control, TREM2 knockdown, AlCl3, TREM2 knockdown + AlCl3, AlNPs, and TREM2 knockdown + AlNPs, wherein AlCl3 and AlNPs were 50 mg/L and TREM2 knockdown was achieved by microinjecting lentiviral-containing TREM2 inhibitors into the yolk sac. We assessed development, neurobehavior, histopathology, ultrastructural structure, neurotransmitters (AChE, DA), SOD, genes of TREM2 and neurodevelopment (α1-tubulin, syn2a, mbp), and AD-related proteins and genes. AlCl3 significantly lowered the malformation rate than AlNPs, and further increased rates of malformation and mortality following TREM2 knockdown. The locomotor ability, learning and memory were similar between AlCl3 and AlNPs. TREM2 deficiency further exacerbated their impairment in panic reflex, microglia decrease, and nerve fibers thickening and tangling. AlCl3, rather than AlNPs, significantly elevated AChE activity and p-tau content while decreasing TREM2 and syn2a levels than the control. TREM2 loss further aggravated impairment in the AChE and SOD activity, and psen1 and p-tau levels. Therefore, AlCl3 induces greater developmental toxicity but equivalent neurobehavior toxicity than AlNPs, while their toxicity was intensified by TREM2 deficiency.

Preclinical toxicological assessment of polydatin in zebrafish model

Polydatin (3,4',5-trihydroxystilbene-3-β-D-glucoside, piceid), a natural stilbenoid found in different plant sources, has gained increasing attention for its potential health benefits. However, prior to its widespread adoption in human therapeutics and consumer products, a comprehensive investigation of its toxicological effects is crucial. In this study, the toxicity of polydatin was investigated in a developmental toxicity test using zebrafish (Danio rerio) as a valuable model for preclinical assessments. We employed the Fish Embryo Test (FET test - OECD n°236) to investigate the effects of polydatin on survival, hatchability, development, and behavior of zebrafish embryo-larval stage. Remarkably, the results demonstrated that polydatin up to 435 μM showed no toxicity. Throughout the exposure period, zebrafish embryos exposed to polydatin exhibited normal development, with no significant mortality observed. Furthermore, hatching success and heartbeat rate were unaffected, and no morphological abnormalities were identified, signifying a lack of teratogenic effects and cardiotoxicity. Locomotion activity assessment revealed normal swimming patterns and response to stimuli, indicating no neurotoxic effects. Our study provides valuable insights into the toxicological profile of polydatin, suggesting that it may offer potential therapeutic benefits under a considerable concentration range. In addition, zebrafish model proves to be an efficient system for early-stage toxicological screening, guiding further investigations into the secure utilization of polydatin for human health and wellness.

A Zebrafish Embryo Model to Screen Potential Therapeutic Compounds in Sapindaceae Poisoning

Hypoglycin A (HGA) and methylenecyclopropylglycine (MCPrG) are protoxins produced by Sapindaceae plants, particularly Acer pseudoplatanus, and are responsible for causing atypical myopathy (AM) in equids. These protoxins metabolise into toxic compounds, such as methylenecyclopropylacetyl-CoA (MCPA-CoA), which alters energy metabolism and induces severe rhabdomyolysis. Currently, no specific treatment exists for this poisoning, in vitro models fail to reproduce HGA's toxic effects on equine primary myoblasts, and mammalian models are impractical for large-scale drug screening. This study aimed to develop a zebrafish embryo model for screening therapeutic compounds against AM. Zebrafish embryos were exposed to various concentrations of HGA, MCPrG, and methylenecyclopropylacetate (MCPA) for 72 h. MCPrG did not induce toxicity, while HGA and MCPA showed median lethal concentration (LC50) values of 1.7 µM and 1 µM after 72 h, respectively. The highest levels of the conjugated metabolite MCPA-carnitine were detected 24 h after HGA exposure, and the acylcarnitines profile was highly increased 48 h post-exposure. Isovaleryl-/2- methylbutyrylcarnitine levels notably rose after 24 h, suggesting potential exposition biomarkers. Glycine and carnitine effectively reduced mortality, whereas riboflavin showed no protective effect. These findings suggest that the zebrafish embryo represents a valuable model for identifying therapeutic compounds for Sapindaceae poisoning.

Combined effects of glyphosate and chemical hypoxia in zebrafish: A new toxicological point of view

Glyphosate (Gly), a systemic and non-selective post-emergence herbicide used worldwide, has emerged as a pollutant. However, its toxic effects are debated by regulatory authorities. In addition, in the aquatic environment, often the presence of pollutants is associated with a hypoxia condition that could change their toxicological effects. We used zebrafish embryos to evaluate the toxic effects of Gly and its mechanisms in a hypoxic condition chemically induced by cobalt chloride (CoCl2). We found that Gly induced toxicity in a time and concentration-dependent manner. The toxicity of Gly was determined at 96 h post fertilization as a lethal concentration (LC), and LC10, LC20, and LC50 values were 85.7, 97, and 122.9 mg/L, respectively. When Gly was combined with CoCl2 the toxicological endpoints were lower than values referred to the Gly alone indicating the worse effects of chemical hypoxia on Gly toxicity. Histological observations were performed at 25, 50, 75, and 100 mg/L for Gly both alone and in combination with 10 mM CoCl2. Fisher's exact test showed significant differences in the presence of hepatic and gut inflammation at 75 and 100 mg/L of Gly both alone and in combination with CoCl2. To deeply investigate the effects of hypoxia on Gly toxicity we decided to test the lowest dose of Gly, 50 mg/L, alone or in combination with CoCl2 10 mM on liver glycogen storage and oxidative stress. Again the results obtained indicate the worse effects of chemical hypoxia on Gly toxicity. Thus Gly toxicity could be reconsidered in light of the damage it causes to the liver and intestines and its effect in combination with factors that induce chemical hypoxia.

FXR contributes to obstructive jaundice-induced vascular hyporeactivity in mesenteric arteries by reconstituting BKCa channels

OBJECTIVE

Vascular hyporeactivity increases with the incidence of obstructive jaundice (OJ). Evidence suggests that OJ activates the farnesoid X receptor (FXR) as well as the large-conductance Ca2+-activated K+ (BKCa or MaxiK) channel. This study was designed to explore the role of the FXR in vascular hyporesponsiveness induced by cholestasis.

METHODS

The OJ model rats were constructed by bile duct ligation (BDL) and treated with an FXR agonist or antagonist. Vasoconstriction of the mesenteric arteries (MAs) was assessed in vitro. Whole-cell patch clamp recordings were used to investigate BKCa channel function. Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot were used to detect mRNA and protein levels.

RESULTS

A significant increase in vascular tone and responsiveness to norepinephrine (NE) was observed after the MaxiK channel blocker (IbTX) was administered. This effect was pronounced in BDL animals and can be mimicked by the FXR agonist GW4064 and inhibited by the FXR antagonist Z-guggulsterone (Z-Gu). GW4064 has a similar effect as cholestasis in promoting MaxiK currents in isolated arterial smooth muscle cells (ASMCs), while Z-Gu blunted this effect. The mRNA and protein expression of FXR and MaxiK-β1, but not MaxiK-α, were significantly increased in the BDL group in comparison to the sham. Furthermore, activation or inhibition of FXR promoted or inhibited the mRNA and protein expression of the MaxiK-β1 subunit, respectively.

CONCLUSION

Activation of FXR enhances the capability of the MaxiK channel to regulate vascular tone and leads to vascular hyporesponsiveness in the MAs of BDL rats, which may be mediated by the nonparallel upregulation of MaxiK-α and MaxiK-β1 subunit expression.

The natural compound sinometumine E derived from Corydalis decumbens promotes angiogenesis by regulating HIF-1/ VEGF pathway in vivo and in vitro

The rhizome of Corydalis decumbens is a traditional Chinese medicine commonly utilized in the clinical treatment of acute ischemic stroke. Numerous phytochemical and biological investigations have demonstrated that protoberberine alkaloids from C. decumbens exhibit diverse pharmaceutical activities against various diseases. Sinometumine E (SE), a protoberberine alkaloid isolated from C. decumbens for the first time, is characterized by a complex 6/6/6/6/6/6 hexacyclic skeleton. In the current study, we investigated the protective effects of SE on endothelial cell injury and its angiogenesis effects in zebrafish. The results suggested that SE showed significant anti-ischemic effects on OGD/R-induced HBEC-5i and HUVECs cell ischemia/reperfusion injury model. Furthermore, it promoted angiogenesis in PTK787-induced, MPTP-induced, and atorvastatin-induced vessel injury models of zebrafish, while also suppressing hypoxia-induced locomotor impairment in zebrafish. Transcriptome sequencing analysis provided a sign that SE likely to promotes angiogenesis through the HIF-1/VEGF signaling pathway to exert anti-ischemic effects. Consistently, SE modulated several genes related to HIF-1/VEGF signal pathway, such as hif-1, vegf, vegfr-2, pi3k, erk, akt and plcγ. Molecular docking analysis revealed that VEGFR-2 exhibited high binding affinity with SE, and western blot analysis confirmed that SE treatment enhanced the expression of VEGFR-2. In conclusion, our study profiled the angiogenic activities of SE in vitro and in vivo. The key targets and related pathways involved in anti-ischemic effects of SE, shedding light on the pharmacodynamic components and mechanisms of Corydalis decumbens, and provides valuable insights for identifying effective substances for the treatment of ischemic stroke.

Differing temperature dependencies of functional homologs zebrafish Abcb4 and human ABCB1

The ATP binding cassette (ABC) transporters human ABCB1 and zebrafish (Danio rerio) Abcb4 are functionally homologous multixenobiotic/multidrug (MXR/MDR) efflux transporters that confer the efflux of a broad range of diverse chemical compounds from the cell. As ATPases, the transporters utilize the energy released by ATP cleavage for protein conformation changes and concomitant active transport of substrate compounds. The temperatures, at which human ABCB1 and zebrafish Abcb4 need to function, can substantially differ: Whereas the ambient temperature of human ABCB1, which is that of the human body, is constant, zebrafish Abcb4 has to be active in a wider temperature range as the body temperature of zebrafish can considerably vary, depending on the ambient water temperature (18°C-40°C). Here, we examined the effect of temperature on the ATPase activities of recombinant human ABCB1 and zebrafish Abcb4 generated with the baculovirus expression system. Incubation temperatures for enzyme reactions were set to 37°C and 27°C, corresponding to the human body temperature and the cultivation temperature of zebrafish in our lab, respectively. For stimulation and inhibition of zebrafish Abcb4 and human ABCB1 ATPase activities verapamil and cyclosporin A were added at different concentrations and 50% effect concentrations (EC50) were determined. The different temperatures had a stronger effect on the human ABCB1 than on the zebrafish Abcb4 ATPase: Differences between EC50 values for verapamil at 37°C and 27°C, respectively, were 1.8-fold for human ABCB1 but only 1.2-fold for zebrafish Abcb4. Activation energies (Ea) of basal and verapamil-stimulated ATPases, calculated based on the Arrhenius equation, were 2-fold (basal) and 1.5-fold (verapamil-stimulated) higher for human ABCB1 than for zebrafish Abcb4. The differences between zebrafish Abcb4 and human ABCB1 ATPases in temperature sensitivity and activation energy could be important for the comparison of the functional properties of the two transporter proteins in the context of pharmaco-/toxicokinetics. Related to this, our finding that at equal reaction conditions the zebrafish Abcb4 ATPase activity tended to be generally higher than that of human ABCB1 may also be important, as this may point to a higher substrate compound transport rate of Abcb4.

Effect of Acetylsalicylic Acid on Biological Properties of Novel Cement Based on Calcium Phosphate Doped with Ions of Strontium, Copper, and Zinc

This study aimed to compare the biological properties of newly synthesized cements based on calcium phosphate with a commercially used cement, mineral trioxide aggregate (MTA). Strontium (Sr)-, Copper (Cu)-, and Zinc (Zn)-doped hydroxyapatite (miHAp) powder was obtained through hydrothermal synthesis and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDX). Calcium phosphate cement (CPC) was produced by mixing miHAp powder with a 20 wt.% citric acid solution, followed by the assessment of its compressive strength, setting time, and in vitro bioactivity. Acetylsalicylic acid (ASA) was added to the CPC, resulting in CPCA. Biological tests were conducted on CPC, CPCA, and MTA. The biocompatibility of the cement extracts was evaluated in vitro using human dental pulp stem cells (hDPSCs) and in vivo using a zebrafish model. Antibiofilm and antimicrobial effect (quantified by CFUs/mL) were assessed against Streptococcus mutans and Lactobacillus rhamnosus. None of the tested materials showed toxicity, while CPCA even increased hDPSCs proliferation. CPCA showed a better safety profile than MTA and CPC, and no toxic or immunomodulatory effects on the zebrafish model. CPCA exhibited similar antibiofilm effects against S. mutans and L. rhamnosus to MTA.

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

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

Behavioral impairments and disrupted mitochondrial energy metabolism induced by polypropylene microplastics in zebrafish larvae

Polypropylene microplastics (PP-MPs) are emerging pollutant commonly detected in various environmental matrices and organisms, while their adverse effects and mechanisms are not well known. Here, zebrafish embryos were exposed to environmentally relevant concentrations of PP-MPs (0.08-50 mg/L) from 2 h post-fertilization (hpf) until 120 hpf. The results showed that the body weight was increased at 2 mg/L, heart rate was reduced at 0.08 and 10 mg/L, and behaviors were impaired at 0.4, 10 or 50 mg/L. Subsequently, transcriptomic analysis in the 0.4 and 50 mg/L PP-MPs treatment groups indicated potential inhibition on the glycolysis/gluconeogenesis and oxidative phosphorylation pathways. These findings were validated through alterations in multiple biomarkers related to glucose metabolism. Moreover, abnormal mitochondrial ultrastructures were observed in the intestine and liver in 0.4 and 50 mg/L PP-MPs treatment groups, accompanied by significant decreases in the activities of four mitochondrial electron transport chain complexes and ATP contents. Oxidative stress was also induced, as indicated by significantly increased ROS levels and significant reduced activities of CAT and SOD and GSH contents. All the results suggested that environmentally relevant concentrations of PP-MPs could induce disrupted mitochondrial energy metabolism in zebrafish, which may be associated with the observed behavioral impairments. This study will provide novel insights into PP-MPs-induced adverse effects and highlight need for further research.

Screening tools to evaluate the neurotoxic potential of botanicals: building a strategy to assess safety

AREAS COVERED

This paper outlines the selection of NAMs, including in vitro assays using primary rat cortical neurons, zebrafish embryos, and Caenorhabditis elegans. These assays aim to assess neurotoxic endpoints such as neuronal activity and behavioral responses. Microelectrode array recordings of rat cortical neurons provide insights into the impact of botanical extracts on neuronal function, while the zebrafish embryos and C. elegans assays evaluate neurobehavioral responses. The paper also provides an account of the selection of botanical case studies based on expert judgment and existing neuroactivity/toxicity information. The proposed battery of assays will be tested with these case studies to evaluate their utility for neurotoxicity screening.

EXPERT OPINION

The complexity of botanicals necessitates the use of multiple NAMs for effective neurotoxicity screening. This paper discusses the evaluation of methodologies to develop a robust framework for evaluating botanical safety, including complex neuronal models and key neurodevelopmental process assays. It aims to establish a comprehensive screening framework.

Exposure to the pesticide tefluthrin causes developmental neurotoxicity in zebrafish

BACKGROUND

The insecticide tefluthrin is widely used in agriculture, resulting in widespread pollution. Tefluthrin is a type I pyrethroid characterized by its high persistence in the environment. Understanding the mechanisms of toxicity of tefluthrin will improve its risk assessment.

OBJECTIVES

We aimed to decipher the molecular modes of action of tefluthrin.

METHODS

Phenotypic developmental toxicity was assessed by exposing zebrafish embryos and larvae to increasing concentrations of tefluthrin. Tg(mnx:mGFP) line was used to assess neurotoxicity. Multi-omics approaches including transcriptomics and lipidomics were applied to analyze RNA and lipid contents, respectively. Finally, an in-silico ligand-protein docking computational method was used to study a possible interaction between tefluthrin and a protein target.

RESULTS

Tefluthrin exposure caused severe morphological malformations in zebrafish larvae, including motor neuron abnormalities. The differentially expressed genes were associated with neurotoxicity and metabolic disruption. Lipidomics analysis revealed a disruption in fatty acid, phospholipid, and lysophospholipid recycling. Protein docking modeling suggested that the LPCAT3 enzyme, which recycles lysophospholipids in the Land's cycle, directly interacts with tefluthrin.

CONCLUSIONS

Tefluthrin exposure causes morphological and neuronal malformations in zebrafish larvae at nanomolar concentrations. Multi-omics results revealed a potential molecular initiating event i.e., inhibition of LPCAT3, and key events i.e., an altered lysophospholipid to phospholipid ratio, leading to the adverse outcomes of neurotoxicity and metabolic disruption.

Zebrafish as Versatile Model for Assessing Animal Venoms and Toxins: Current Applications and Future Prospects

Animal venoms and toxins hold promise as sources of novel drug candidates, therapeutic agents, and biomolecules. To fully harness their potential, it is crucial to develop reliable testing methods that provide a comprehensive understanding of their effects and mechanisms of action. However, traditional rodent assays encounter difficulties in mimicking venom-induced effects in human due to the impractical venom dosage levels. The search for reliable testing methods has led to the emergence of zebrafish (Danio rerio) as a versatile model organism for evaluating animal venoms and toxins. Zebrafish possess genetic similarities to humans, rapid development, transparency, and amenability to high-throughput assays, making it ideal for assessing the effects of animal venoms and toxins. This review highlights unique attributes of zebrafish and explores their applications in studying venom- and toxin-induced effects from various species, including snakes, jellyfish, cuttlefish, anemones, spiders, and cone snails. Through zebrafish-based research, intricate physiological responses, developmental alterations, and potential therapeutic interventions induced by venoms are revealed. Novel techniques such as CRISPR/Cas9 gene editing, optogenetics, and high-throughput screening hold great promise for advancing venom research. As zebrafish-based insights converge with findings from other models, the comprehensive understanding of venom-induced effects continues to expand, guiding the development of targeted interventions and promoting both scientific knowledge and practical applications.

Gelsenicine disrupted the intestinal barrier of Caenorhabditis elegans

Gelsemium elegans Benth. (G. elegans) is a traditional medicinal herb that has anti-inflammatory, analgesic, sedative, and detumescence effects. However, it can also cause intestinal side effects such as abdominal pain and diarrhea. The toxicological mechanisms of gelsenicine are still unclear. The objective of this study was to assess enterotoxicity induced by gelsenicine in the nematodes Caenorhabditis elegans (C. elegans). The nematodes were treated with gelsenicine, and subsequently their growth, development, and locomotion behavior were evaluated. The targets of gelsenicine were predicted using PharmMapper. mRNA-seq was performed to verify the predicted targets. Intestinal permeability, ROS generation, and lipofuscin accumulation were measured. Additionally, the fluorescence intensities of GFP-labeled proteins involved in oxidative stress and unfolded protein response in endoplasmic reticulum (UPRER) were quantified. As a result, the treatment of gelsenicine resulted in the inhibition of nematode lifespan, as well as reductions in body length, width, and locomotion behavior. A total of 221 targets were predicted by PharmMapper, and 731 differentially expressed genes were screened out by mRNA-seq. GO and KEGG enrichment analysis revealed involvement in redox process and transmembrane transport. The permeability assay showed leakage of blue dye from the intestinal lumen into the body cavity. Abnormal mRNAs expression of gem-4, hmp-1, fil-2, and pho-1, which regulated intestinal development, absorption and catabolism, transmembrane transport, and apical junctions, was observed. Intestinal lipofuscin and ROS were increased, while sod-2 and isp-1 expressions were decreased. Multiple proteins in SKN-1/DAF-16 pathway were found to bind stably with gelsenicine in a predictive model. There was an up-regulation in the expression of SKN-1:GFP, while the nuclear translocation of DAF-16:GFP exhibited abnormality. The UPRER biomarker HSP-4:GFP was down-regulated. In conclusion, the treatment of gelsenicine resulted in the increase of nematode intestinal permeability. The toxicological mechanisms underlying this effect involved the disruption of intestinal barrier integrity, an imbalance between oxidative and antioxidant processes mediated by the SKN-1/DAF-16 pathway, and abnormal unfolded protein reaction.

Neurotoxicity of Some Environmental Pollutants to Zebrafish

The aquatic environment encompasses a wide variety of pollutants, from plastics to drug residues, pesticides, food compounds, and other food by-products, and improper disposal of waste is the main cause of the accumulation of toxic substances in water. Monitoring, assessing, and attempting to control the effects of contaminants in the aquatic environment are necessary and essential to protect the environment and thus human and animal health, and the study of aquatic ecotoxicology has become topical. In this respect, zebrafish are used as model organisms to study the bioaccumulation, toxicity, and influence of environmental pollutants due to their structural, functional, and material advantages. There are many similarities between the metabolism and physiological structures of zebrafish and humans, and the nervous system structure, blood-brain barrier function, and social behavior of zebrafish are characteristics that make them an ideal animal model for studying neurotoxicity. The aim of the study was to highlight the neurotoxicity of nanoplastics, microplastics, fipronil, deltamethrin, and rotenone and to highlight the main behavioral, histological, and oxidative status changes produced in zebrafish exposed to them.

Butylparaben induced zebrafish (Danio rerio) kidney injury by down-regulating the PI3K-AKT pathway

Butylparaben, a common endocrine disruptor in the environment, is known to be toxic to the reproductive system, heart, and intestines, but its nephrotoxicity has rarely been reported. In order to study the nephrotoxicity and mechanism of butylparaben, we examined the acute and chronic effects on human embryonic kidney cells (HEK293T) and zebrafish. Additionally, we assessed the potential remedial effects of salidroside against butylparaben-induced nephrotoxicity. Our in vitro findings demonstrated oxidative stress and cytotoxicity to HEK293T cells caused by butylparaben. In the zebrafish model, the concentration of butylparaben exposure ranged from 0.5 to 15 μM. An assortment of experimental techniques was employed, including the assessment of kidney tissue morphology using Hematoxylin-Eosin staining, kidney function analysis via fluorescent dextran injection, and gene expression studies related to kidney injury, development, and function. Additionally, butylparaben caused lipid peroxidation in the kidney, thereby damaging glomeruli and renal tubules, which resulted from the downregulation of the PI3K-AKT signaling pathway. Furthermore, salidroside ameliorated butylparaben-induced nephrotoxicity through the PI3K-AKT signaling pathway. This study reveals the seldom-reported kidney toxicity of butylparaben and the protective effect of salidroside against toxicological reactions related to nephrotoxicity. It offers valuable insights into the risks to kidney health posed by environmental toxins.

Ototoxicity: a high risk to auditory function that needs to be monitored in drug development

Hearing loss constitutes a major global health concern impacting approximately 1.5 billion people worldwide. Its incidence is undergoing a substantial surge with some projecting that by 2050, a quarter of the global population will experience varying degrees of hearing deficiency. Environmental factors such as aging, exposure to loud noise, and the intake of ototoxic medications are implicated in the onset of acquired hearing loss. Ototoxicity resulting in inner ear damage is a leading cause of acquired hearing loss worldwide. This could be minimized or avoided by early testing of hearing functions in the preclinical phase of drug development. While the assessment of ototoxicity is well defined for drug candidates in the hearing field - required for drugs that are administered by the otic route and expected to reach the middle or inner ear during clinical use - ototoxicity testing is not required for all other therapeutic areas. Unfortunately, this has resulted in more than 200 ototoxic marketed medications. The aim of this publication is to raise awareness of drug-induced ototoxicity and to formulate some recommendations based on available guidelines and own experience. Ototoxicity testing programs should be adapted to the type of therapy, its indication (targeting the ear or part of other medications classes being potentially ototoxic), and the number of assets to test. For multiple molecules and/or multiple doses, screening options are available: in vitro (otic cell assays), ex vivo (cochlear explant), and in vivo (in zebrafish). In assessing the ototoxicity of a candidate drug, it is good practice to compare its ototoxicity to that of a well-known control drug of a similar class. Screening assays provide a streamlined and rapid method to know whether a drug is generally safe for inner ear structures. Mammalian animal models provide a more detailed characterization of drug ototoxicity, with a possibility to localize and quantify the damage using functional, behavioral, and morphological read-outs. Complementary histological measures are routinely conducted notably to quantify hair cells loss with cochleogram. Ototoxicity studies can be performed in rodents (mice, rats), guinea pigs and large species. However, in undertaking, or at the very least attempting, all preclinical investigations within the same species, is crucial. This encompasses starting with pharmacokinetics and pharmacology efficacy studies and extending through to toxicity studies. In life read-outs include Auditory Brainstem Response (ABR) and Distortion Product OtoAcoustic Emissions (DPOAE) measurements that assess the activity and integrity of sensory cells and the auditory nerve, reflecting sensorineural hearing loss. Accurate, reproducible, and high throughput ABR measures are fundamental to the quality and success of these preclinical trials. As in humans, in vivo otoscopic evaluations are routinely carried out to observe the tympanic membrane and auditory canal. This is often done to detect signs of inflammation. The cochlea is a tonotopic structure. Hair cell responsiveness is position and frequency dependent, with hair cells located close to the cochlea apex transducing low frequencies and those at the base transducing high frequencies. The cochleogram aims to quantify hair cells all along the cochlea and consequently determine hair cell loss related to specific frequencies. This measure is then correlated with the ABR & DPOAE results. Ototoxicity assessments evaluate the impact of drug candidates on the auditory and vestibular systems, de-risk hearing loss and balance disorders, define a safe dose, and optimize therapeutic benefits. These types of studies can be initiated during early development of a therapeutic solution, with ABR and otoscopic evaluations. Depending on the mechanism of action of the compound, studies can include DPOAE and cochleogram. Later in the development, a GLP (Good Laboratory Practice) ototoxicity study may be required based on otic related route of administration, target, or known potential otic toxicity.

Biological Response Following the Systemic Injection of PEG-PAMAM-Rhodamine Conjugates in Zebrafish

Numerous therapeutic and diagnostic approaches used within a clinical setting depend on the administration of compounds via systemic delivery. Biomaterials at the nanometer scale, as dendrimers, act as delivery systems by improving cargo bioavailability, circulation time, and the targeting of specific tissues. Although evaluating the efficacy of pharmacological agents based on nanobiomaterials is crucial, conducting toxicological assessments of biomaterials is essential for advancing clinical translation. Here, a zebrafish larvae model was explored to assess the biocompatibility of poly(amido amine) (PAMAM), one of the most exploited dendrimers for drug delivery. We report the impact of a systemic injection of polyethylene glycol (PEG)-modified G4 PAMAM conjugated with rhodamine (Rho) as a mimetic drug (PEG-PAMAM-Rho) on survival, animal development, inflammation, and neurotoxicity. A concentration- and time-dependent effect was observed on mortality, developmental morphology, and innate immune system activation (macrophages). Significant effects in toxicological indicators were reported in the highest tested concentration (50 mg/mL PEG-PAMAM-Rho) as early as 48 h post-injection. Additionally, a lower concentration of PEG-PAMAM-Rho (5 mg/mL) was found to be safe and subsequently tested for neurotoxicity through behavioral assays. In accordance, no significative signs of toxicity were detected. In conclusion, the dose response of the animal was assessed, and the safe dosage for future use in theragnostics was defined. Additionally, new methodologies were established that can be adapted to further studies in toxicology using other nanosystems for systemic delivery.

Empirical Characterization of False Discovery Rates of Differentially Expressed Genes and Transcriptomic Benchmark Concentrations in Zebrafish Embryos

High-throughput transcriptomics (HTTr) is increasingly applied to zebrafish embryos to survey the toxicological effects of environmental chemicals. Before the adoption of this approach in regulatory testing, it is essential to characterize background noise in order to guide experimental designs. We thus empirically quantified the HTTr false discovery rate (FDR) across different embryo pool sizes, sample sizes, and concentration groups for toxicology studies. We exposed zebrafish embryos to 0.1% dimethyl sulfoxide (DMSO) for 5 days. Pools of 1, 5, 10, and 20 embryos were created (n = 24 samples for each pool size). Samples were sequenced on the TempO-Seq platform and then randomly assigned to mock treatment groups before differentially expressed gene (DEG), pathway, and benchmark concentration (BMC) analyses. Given that all samples were treated with DMSO, any significant DEGs, pathways, or BMCs are false positives. As expected, we found decreasing FDRs for DEG and pathway analyses with increasing pool and sample sizes. Similarly, FDRs for BMC analyses decreased with increasing pool size and concentration groups, with more stringent BMC premodel filtering reducing BMC FDRs. Our study provides foundational data for determining appropriate experiment designs for regulatory toxicity testing with HTTr in zebrafish embryos.

Narcissin induces developmental toxicity and cardiotoxicity in zebrafish embryos via Nrf2/HO-1 and calcium signaling pathways

Narcissin is a natural flavonoid from some edible and traditional medicinal plants. It has been proven to have multiple biological functions and exhibits potential therapeutic effects on hypertension, cancer, and Alzheimer's disease. However, the toxicity of narcissin is largely unknown. Here, we revealed that narcissin treatment led to reduced hatchability, increased malformation rate, shorter body length, and slowed blood flow in zebrafish. Furthermore, bradycardia, pericardial edema, increased SV-BA distance, diminished stroke volume, ejection fraction, and ventricular short-axis shortening rate were also found. A large accumulation of ROS, increased apoptotic cells, and histopathological changes were detected in the heart region. Moreover, the gene expression profiles and molecular docking analysis indicated that Nrf2/HO-1 and calcium signaling pathways were involved in narcissin-induced toxicity. In conclusion, here we provide the first evidence that demonstrates narcissin-induced developmental toxicity and cardiotoxicity in zebrafish via Nrf2/HO-1 and calcium signaling pathways for the first time.

Enantioselectivity in ecotoxicity of pharmaceuticals, illicit drugs, and industrial persistent pollutants in aquatic and terrestrial environments: A review

At present, there is a serious concern about the alarming number of recalcitrant contaminants that can negatively affect biodiversity threatening the ecological status of marine, estuarine, freshwater, and terrestrial ecosystems (e.g., agricultural soils and forests). Contaminants of emerging concern (CEC) such as pharmaceuticals (PHAR), illicit drugs (ID), industrial persistent pollutants, such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) and chiral ionic solvents are globally spread and potentially toxic to non-target organisms. More than half of these contaminants are chiral and have been measured at different enantiomeric proportions in diverse ecosystems. Enantiomers can exhibit different toxicodynamics and toxicokinetics, and thus, can cause different toxic effects. Therefore, the enantiomeric distribution in occurrence cannot be neglected as the toxicity and other adverse biological effects are expected to be enantioselective. Hence, this review aims to reinforce the recognition of the stereochemistry in environmental risk assessment (ERA) of chiral CEC and gather up-to-date information about the current knowledge regarding the enantioselectivity in ecotoxicity of PHAR, ID, persistent pollutants (PCBs and PBDEs) and chiral ionic solvents present in freshwater and agricultural soil ecosystems. We performed an online literature search to obtain state-of-the-art research about enantioselective studies available for assessing the impact of these classes of CEC. Ecotoxicity assays have been carried out using organisms belonging to different trophic levels such as microorganisms, plants, invertebrates, and vertebrates, and considering ecologically relevant aquatic and terrestrial species or models organisms recommended by regulatory entities. A battery of ecotoxicity assays was also reported encompassing standard acute toxicity to sub-chronic and chronic assays and different endpoints as biomarkers of toxicity (e.g., biochemical, morphological alterations, reproduction, behavior, etc.). Nevertheless, we call attention to the lack of knowledge about the potential enantioselective toxicity of many PHAR, ID, and several classes of industrial compounds. Additionally, several questions regarding key species, selection of most appropriate toxicological assays and ERA of chiral CEC are addressed and critically discussed.

Recent advances and perspectives on natural latex serum and its fractions for biomedical applications

Advances and the discovery of new biomaterials have opened new frontiers in regenerative medicine. These biomaterials play a key role in current medicine by improving the life quality or even saving the lives of millions of people. Since the 2000s, Natural Rubber Latex (NRL) has been employed as wound dressings, mechanical barrier for Guided Bone Regeneration (GBR), matrix for drug delivery, and grafting. NRL is a natural polymer that can stimulate cell proliferation, neoangiogenesis, and extracellular matrix (ECM) formation. Furthermore, it is well established that proteins and other biologically active molecules present in the Natural Latex Serum (NLS) are responsible for the biological properties of NRL. NLS can be obtained from NRL by three main methods, namely (i) Centrifugation (fractionation of NRL in distinct fractions), (ii) Coagulation and sedimentation (coagulating NRL to separate the NLS from rubber particles), and (iii) Alternative extraction process (elution from NRL membrane). In this review, the chemical composition, physicochemical properties, toxicity, and other biological information such as osteogenesis, vasculogenesis, adhesion, proliferation, antimicrobial behavior, and antitumoral activity of NLS, as well as some of its medical instruments and devices are discussed. The progress in NLS applications in the biomedical field, more specifically in cell cultures, alternative animals, regular animals, and clinical trials are also discussed. An overview of the challenges and future directions of the applications of NLS and its derivatives in tissue engineering for hard and soft tissue regeneration is also given.

Standardization of zebrafish drug testing parameters for muscle diseases

Skeletal muscular diseases predominantly affect skeletal and cardiac muscle, resulting in muscle weakness, impaired respiratory function and decreased lifespan. These harmful outcomes lead to poor health-related quality of life and carry a high healthcare economic burden. The absence of promising treatments and new therapies for muscular disorders requires new methods for candidate drug identification and advancement in animal models. Consequently, the rapid screening of drug compounds in an animal model that mimics features of human muscle disease is warranted. Zebrafish are a versatile model in preclinical studies that support developmental biology and drug discovery programs for novel chemical entities and repurposing of established drugs. Due to several advantages, there is an increasing number of applications of the zebrafish model for high-throughput drug screening for human disorders and developmental studies. Consequently, standardization of key drug screening parameters, such as animal husbandry protocols, drug compound administration and outcome measures, is paramount for the continued advancement of the model and field. Here, we seek to summarize and explore critical drug treatment and drug screening parameters in the zebrafish-based modeling of human muscle diseases. Through improved standardization and harmonization of drug screening parameters and protocols, we aim to promote more effective drug discovery programs.

Combined toxicity of aflatoxin B1 and tebuconazole to the embryo development of zebrafish (Danio rerio)

Mycotoxins and pesticides are pervasive elements within the natural ecosystem. Furthermore, many environmental samples frequently exhibit simultaneous contamination by multiple mycotoxins and pesticides. Nevertheless, a significant portion of previous investigations has solely reported the occurrence and toxicological effects of individual chemicals. Global regulations have yet to consider the collective impacts of mycotoxins and pesticides. In our present study, we undertook a comprehensive analysis of multi-level endpoints to elucidate the combined toxicity of aflatoxin B1 (AFB1) and tebuconazole (TCZ) on zebrafish (Danio rerio). Our findings indicated that AFB1 (with a 10-day LC50 value of 0.018 mg L-1) exhibits higher toxicity compared to TCZ (with a 10-day LC50 value of 2.1 mg L-1) toward D. rerio. The co-exposure of AFB1 and TCZ elicited synergistic acute responses in zebrafish. The levels of GST, CYP450, SOD, and Casp-9 exhibited significant variations upon exposure to AFB1, TCZ, and their combined mixture, in contrast to the control group. Additionally, eight genes, namely cat, cxcl-cic, il-1β, bax, apaf-1, trβ, ugtlab, and vtg1, displayed marked alterations when exposed to the chemical mixture as opposed to individual substances. Therefore, further exploration of the underlying mechanisms governing joint toxicity is imperative to establish a scientific basis for evaluating the risk associated with the combined effects of AFB1 and TCZ. Moreover, it is essential to thoroughly elucidate the organ system toxicity triggered by the co-occurrence of mycotoxins and pesticides.