Developmental neurotoxicity of pyrethroid insecticides in zebrafish embryos

Contribution of Immune Responses to the Cardiotoxicity and Hepatotoxicity of Deltamethrin in Early Life Stage Zebrafish (Danio rerio)

Deltamethrin (DM) is a widely used insecticide that has demonstrated developmental toxicity in the early life stages of fish. To better characterize the underlying mechanisms, embryos from Tg(cmlc2:RFP), Tg(apo14:GFP), and Tg(mpx:GFP) transgenic strains of zebrafish were exposed to nominal DM concentrations of 0.1, 1, 10, 25, and 50 μg/L until 120 h post-fertilization (hpf). Heart size increased 56.7%, and liver size was reduced by 17.1% in zebrafish exposed to 22.7 and 24.2 μg/L DM, respectively. RNA sequencing and bioinformatic analyses predicted that key biological processes affected by DM exposure were related to inflammatory responses. Expression of IL-1 protein was increased by 69.0% in the 24.4 μg/L DM treatment, and aggregation of neutrophils in cardiac and hepatic histologic sections was also observed. Coexposure to resatorvid, an anti-inflammatory agent, mitigated inflammatory responses and cardiac toxicity induced by DM and also restored liver biomass. Our data indicated a complex proinflammatory mechanism underlying DM-induced cardiotoxicity and hepatotoxicity which may be important for key events of adverse outcomes and associated risks of DM to early life stages of fish.

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.

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.

Maternal exposure to deltamethrin during pregnancy and lactation impairs neurodevelopment of male offspring

Deltamethrin (DM) is a highly effective and widely used pyrethroid pesticide. It is an environmental factor affecting public and occupational health and exerts direct toxic effects on the central nervous system. As the major target organs for neurotoxicity of DM, the hippocampus and the cerebellum are critical to the learning and motor function. Pregnant Wistar rats were randomly divided into four groups and gavaged at doses of 0, 1, 4or 10 mg/kg/d DM from gestational day (GD) 0 to postnatal day (PN) 21. The PC12 cells were selected to further verify the regulatory mechanisms of DM on the neurodevelopmental injury. We found that maternal exposure to DM caused learning, memory and motor dysfunction in male offspring. Maternal exposure to DM induced the decrease in the density of hippocampal dendritic spines in male offspring through the reduced expression of M1 mAchRs, which in turn reduced the mediated AKT/mTOR signaling pathway, contributing to the inhibition of dynamic changes of GluA1. Meanwhile, DM exposure inhibited the BDNF/TrkB signaling pathway, thereby reducing phosphorylation of stathmin and impairing cerebellar purkinje cell dendrite growth and development. Taken together, maternal exposure to DM during pregnancy and lactation could impair neurodevelopment of male offspring.

Stereoselective toxicity of acetochlor chiral isomers on the nervous system of zebrafish larvae

Acetochlor (ACT) is a widely detected pesticide globally, and the neurotoxic effects of its chiral isomers on humans and environmental organisms remain uncertain. Zebrafish were used to study the neurotoxicity of ACT and its chiral isomers. Our study reveals that the R-ACT, Rac-ACT, and S-ACT induce neurotoxicity in zebrafish larvae by impairing vascular development and disrupting the blood-brain barrier. These detrimental effects lead to apoptosis in brain cells, hindered development of the central nervous system, and manifest as altered swimming behavior and social interactions in the larvae. Importantly, the neurotoxicity caused by the S-ACT exhibits the most pronounced impact and significantly diverges from the effects induced by the R-ACT. The neurotoxicity associated with the Rac-ACT falls intermediate between that of the R-ACT and S-ACT. Fascinatingly, we observed a remarkable recovery in the S-ACT-induced abnormalities in BBB, neurodevelopment, and behavior in zebrafish larvae upon supplementation of the Wnt/β-catenin signaling pathway. This observation strongly suggests that the Wnt/β-catenin signaling pathway serves as a major target of S-ACT-induced neurotoxicity in zebrafish larvae. In conclusion, S-ACT significantly influences zebrafish larval neurodevelopment by inhibiting the Wnt/β-catenin signaling pathway, distinguishing it from R-ACT neurotoxic effects.

The posterity of Zebrafish in paradigm of in vivo molecular toxicological profiling

The aggrandised advancement in utility of advanced day-to-day materials and nanomaterials has raised serious concern on their biocompatibility with human and other biotic members. In last few decades, understanding of toxicity of these materials has been given the centre stage of research using many in vitro and in vivo models. Zebrafish (Danio rerio), a freshwater fish and a member of the minnow family has garnered much attention due to its distinct features, which make it an important and frequently used animal model in various fields of embryology and toxicological studies. Given that fertilization and development of zebrafish eggs take place externally, they serve as an excellent model organism for studying early developmental stages. Moreover, zebrafish possess a comparable genetic composition to humans and share almost 70% of their genes with mammals. This particular model organism has become increasingly popular, especially for developmental research. Moreover, it serves as a link between in vitro studies and in vivo analysis in mammals. It is an appealing choice for vertebrate research, when employing high-throughput methods, due to their small size, swift development, and relatively affordable laboratory setup. This small vertebrate has enhanced comprehension of pathobiology and drug toxicity. This review emphasizes on the recent developments in toxicity screening and assays, and the new insights gained about the toxicity of drugs through these assays. Specifically, the cardio, neural, and, hepatic toxicology studies inferred by applications of nanoparticles have been highlighted.

Towards improved screening of toxins for Parkinson's risk

Parkinson's disease (PD) is a chronic, progressive and disabling neurodegenerative disorder. The prevalence of PD has risen considerably over the past decades. A growing body of evidence suggest that exposure to environmental toxins, including pesticides, solvents and heavy metals (collectively called toxins), is at least in part responsible for this rapid growth. It is worrying that the current screening procedures being applied internationally to test for possible neurotoxicity of specific compounds offer inadequate insights into the risk of developing PD in humans. Improved screening procedures are therefore urgently needed. Our review first substantiates current evidence on the relation between exposure to environmental toxins and the risk of developing PD. We subsequently propose to replace the current standard toxin screening by a well-controlled multi-tier toxin screening involving the following steps: in silico studies (tier 1) followed by in vitro tests (tier 2), aiming to prioritize agents with human relevant routes of exposure. More in depth studies can be undertaken in tier 3, with whole-organism (in)vertebrate models. Tier 4 has a dedicated focus on cell loss in the substantia nigra and on the presumed mechanisms of neurotoxicity in rodent models, which are required to confirm or refute the possible neurotoxicity of any individual compound. This improved screening procedure should not only evaluate new pesticides that seek access to the market, but also critically assess all pesticides that are being used today, acknowledging that none of these has ever been proven to be safe from a perspective of PD. Importantly, the improved screening procedures should not just assess the neurotoxic risk of isolated compounds, but should also specifically look at the cumulative risk conveyed by exposure to commonly used combinations of pesticides (cocktails). The worldwide implementation of such an improved screening procedure, would be an essential step for policy makers and governments to recognize PD-related environmental risk factors.

Tralomethrin causes cardiovascular toxicity in zebrafish (Danio rerio) embryos

Tralomethrin, a synthetic pyrethroid insecticide used to control a wide range of pests in agriculture and public health, is highly toxic to aquatic organisms. However, data regarding the toxicity and underlying mechanisms of tralomethrin in aquatic organisms are limited. Thus, this study aimed to investigate the toxicity of tralomethrin in zebrafish. Zebrafish embryos were exposed to tralomethrin at different concentrations (16.63, 33.25, and 49.88 μg/L). Results showed that tralomethrin exposure caused cardiovascular dysplasia and dysfunction, including developmental abnormalities (pericardial edema, delayed yolk absorption, and uninflated swim bladder), elevated heart rate, and erythrogenesis disorders. Moreover, the expression patterns of crucial genes responsible for cardiovascular development (alas2, gata1a, hbbe2, nkx2.5, myl7, and myh6) also exhibited dysregulation in response to tralomethrin exposure. Oxidative stress occurred in embryos after exposure to tralomethrin. Collectively, our data suggest that exposure to tralomethrin induces cardiovascular and developmental toxicity in zebrafish. These findings are instrumental for evaluations of the environmental risk of tralomethrin in aquatic ecosystems in the future.

Adverse effects of bifenthrin exposure on neurobehavior and neurodevelopment in a zebrafish embryo/larvae model

Bifenthrin, a third-generation synthetic pyrethroid, is widely used as an agricultural insecticide. However, it can flow into surface and groundwater, leading to adverse consequences such as immunotoxicity, hepatotoxicity, hormone dysregulation, or neurotoxicity. Nevertheless, the entire range of its neurotoxic consequences, particularly in aquatic organisms, remains unclear. In this study, we conducted an extensive examination of how exposure to bifenthrin affects the behavior and nervous system function of aquatic vertebrates, using a zebrafish model and multiple-layered assays. We exposed wild-type and transgenic lines [tg(elavl3:eGFP) and tg(mbp:mGFP)] to bifenthrin from <3 h post-fertilization (hpf) to 120 hpf. Our findings indicate that bifenthrin exposure concentrations of 103.9 and 362.1 μg/L significantly affects the tail-coiling response at 24 hpf and the touch-evoked responses at 72 hpf. Moreover, it has a significant effect on various aspects of behavior such as body contact, distance between subjects, distance moved, and turn angle. We attribute these effects to changes in acetylcholinesterase and dopamine levels, which decrease in a concentration-dependent manner. Furthermore, neuroimaging revealed neurogenesis defects, e.g., shortened brain and axon widths, and demyelination of oligodendrocytes and Schwann cells. Additionally, the transcription of genes related to neurodevelopment (e.g., gap43, manf, gfap, nestin, sox2) were significantly upregulated and neurotransmitters (e.g., nlgn1, drd1, slc6a4a, ache) was significantly downregulated. In summary, our data shows that bifenthrin exposure has detrimental effects on neurodevelopmental and neurotransmission systems in the zebrafish embryo/larvae model.

Sulfonamides (SAs) exposure causes neurobehavioral toxicity at environmentally relevant concentrations (ERCs) in early development of zebrafish

Antibiotics, due to their stability and persistence in the environment, can have chronic impacts on various ecosystems and organisms. However, the molecular mechanisms underlying antibiotic toxicity at environmental concentrations, particularly the neurotoxic effects of sulfonamides (SAs), remain poorly understood. In this study, we assessed the neurotoxicity of six SAs including the sulfadiazine (SD), sulfathiazole (ST), sulfamethoxazole (SMX), sulfisoxazole (SIZ), sulfapyridine (SPD), and sulfadimethoxine (SDM) by exposing zebrafish to environmentally relevant concentrations (ERCs). The SAs exhibited concentration-dependent effects on zebrafish behavior, including spontaneous movement, heartbeat, survival rate, and body metrics, ultimately leading to depressive-like symptoms and sublethal toxicity during early life stages. Notably, even the lowest SA concentration (0.05 μg/L) induced neurotoxicity and behavioral impairment in zebrafish. We observed a dose-dependent increase in melancholy behavior as indicated by increased resting time and decreased motor activity in zebrafish larvae. Following exposure to SAs from 4 to 120 h post-fertilization (hpf), key genes involved in folate synthesis [sepiapterin reductase a (spra), phenylalanine hydroxylase (pah), tyrosine hydroxylase (th), and tryptophan hydroxylase 1 (tryptophan 5-monooxygenase) a tryptophan hydroxylase (tph1a)] and carbonic anhydrase (CA) metabolism [carbonic anhydrase II (ca2), carbonic anhydrase IV a (ca4a), carbonic anhydrase VII (ca7), and carbonic anhydrase XIV (ca14)] were significantly downregulated or inhibited at different concentrations. Our findings demonstrate that acute exposure to six SAs at environmentally relevant concentrations induces developmental and neurotoxic effects in zebrafish, impacting folate synthesis pathways and CA metabolism. These results provide valuable insights into the potential role of antibiotics in depressive disorders and neuroregulatory pathways.

Systematic evaluation of the toxicological effects of deltamethrin exposure in zebrafish larvae

Deltamethrin (DM) is a widely used pesticide and has been generally detected in aquatic systems. To systematically investigate the toxic effects, zebrafish embryos were treated with various concentrations of DM for 120h. The LC₅₀ was determined to be 102 μg L^-1. Lethal concentrations of DM induced severe morphological defects in the surviving individuals. Under non-lethal concentrations, DM suppressed the development of neurons in the larvae, which was associated with the reduction in locomotor activity. DM exposure induced cardiovascular toxicity, including suppressed growth of blood vessels and enhanced heart rates. DM also disrupted the development of bones in the larvae. Moreover, liver degeneration, apoptosis and oxidative stress were observed in the larvae treated with DM. Correspondingly, the transcriptional levels of the genes related to the toxic effects were altered by DM. In conclusion, the results obtained in this study provided evidence that DM showed multiple toxic effects on aquatic organisms.

Biopreservative efficacy of Enterococcus faecium-immobilised film and its enterocin against Salmonella enterica

The growing awareness about the adverse health effects of artificial synthetic preservatives has led to a rapid increase in the demand for safe food preservation techniques and bio preservatives. Thus, in this study, the biopreservatives efficacy of enterocin-producing Enterococcus faecium Smr18 and its enterocin, ESmr18 was evaluated against Salmonella enterica contamination in chicken samples. E. faecium Smr18 is susceptible to the antibiotics penicillin-G, ampicillin, vancomycin, and erythromycin, thereby indicating that it is a nonpathogenic strain. Further, the enterocin ESmr18 was purified and characterised as a 3.8 kDa peptide. It possessed broad spectrum antibacterial activity against both Gram-positive and Gram-negative pathogens including S. enterica serotypes Typhi and Typhimurium. Purified ESmr18 disrupted the cell membrane permeability of the target cell thereby causing rapid efflux of potassium ions from L. monocytogenes and S. enterica. Chicken samples inoculated with S. enterica and packaged in alginate films containing immobilised viable E. faecium resulted in 3 log₁₀ colony forming units (CFU) reduction in the counts of S. enterica after 34 days of storage at 7-8 °C. The crude preparation of ESmr18 also significantly (p < 0.05) reduced the CFU counts of salmonella-inoculated chicken meat model. Purified ESmr18 at the concentration upto 4.98 µg/ml had no cytolytic effect against human red blood cells. Crude preparation of ESmr18 when orally administered in fish did not cause any significant (p < 0.05) change in the biochemical parameters of sera samples. Nonsignificant changes in the parameters of comet and micronucleus assays were observed between the treated and untreated groups of fishes that further indicated the safety profile of the enterocin ESmr18.

Environmentally relevant concentrations of Triclosan cause transcriptomic and biomolecular alterations in the hatchlings of Labeo rohita

Suppression (p ≤ 0.05) of antioxidative/detoxification (except GPx and CYP3a) and cytoskeletal (except DHPR) genes but induction of metabolic (except for AST and TRY) and heat shock (except HSP60) genes of Labeo rohita hatchlings after 14 days of exposure to environmentally relevant concentrations of Triclosan (0.0063, 0.0126, 0.0252 and 0.06 mg/L) was followed by an increase (p ≤ 0.05) for most of the genes after 10 days recovery period. After recovery, LDH, ALT, CK, CHY, PA, HSP47 and DHPR declined, while SOD, CAT, GST, GR, GPx, CYP1a, CYP3a, AST, AChE, TRY, HSP60, HSP70, HSc71, HSP90 MLP-3, α-tropomyosin, desmin b and lamin b1 increased over exposure. Peak area of biomolecules (except 3290-3296, 2924-2925 and 2852-2855 cm^-1) declined (p ≤ 0.01) more after recovery [except for an increase (p ≤ 0.01) at 1398-1401 cm^-1]. CYP3a, CK, HSP90, MLP-3 and secondary structure of amide A are the most sensitive markers for the environmentally relevant concentrations of Triclosan.

Synthesis, Crystal Structures, and Biological Activity Evaluation of Novel Xanthine Derivatives Containing a Pyrethroid Moiety

On the basis of the structures of natural xanthines and pyrethroid insecticides, a series of novel xanthine derivatives Ia-Is containing pyrethroid motifs were synthesized and identified by means of melting points, ¹H NMR, ¹³C NMR, and HRMS. The single crystals of compounds In and Iq were obtained, which further confirmed the structures and configurations of this type of compounds. The biological tests showed that some of them exhibited favorable insecticidal activities toward Mythimna separata Walker and Plutella xylostella L. and were superior to the natural methylxanthine compound caffeine and comparable with the insecticide tetramethrin (e.g., compound Im: LC₅₀ = 0.6162 mg/L, against P. xylostella). Among others, Im, Ib, Ij, and Ik could serve as new insecticidal leading structures for further study. Moreover, some of the compounds showed favorable fungicidal activities against a broad spectrum of plant pathogenic fungi (e.g., compound Ie: EC₅₀ = 6.0922 μg/mL, against Physalospora piricola; EC₅₀ = 9.0637 μg/mL, against Rhizoctonia cerealis), which in turn would be an exciting new finding in xanthine chemistry; Ie, Ih, and Ii could be novel fungicidal leading compounds for further investigation. The structure-activity relationships of the compounds were also analyzed and discussed in detail. The research results presented in this paper provide a useful reference and guidance for the development of new natural product-based agrochemicals.

Computational model for fetal skeletal defects potentially linked to disruption of retinoic acid signaling

All-trans retinoic acid (ATRA) gradients determine skeletal patterning morphogenesis and can be disrupted by diverse genetic or environmental factors during pregnancy, leading to fetal skeleton defects. Adverse Outcome Pathway (AOP) frameworks for ATRA metabolism, signaling, and homeostasis allow for the development of new approach methods (NAMs) for predictive toxicology with less reliance on animal testing. Here, a data-driven model was constructed to identify chemicals associated with both ATRA pathway bioactivity and prenatal skeletal defects. The phenotype data was culled from ToxRefDB prenatal developmental toxicity studies and produced a list of 363 ToxRefDB chemicals with altered skeletal observations. Defects were classified regionally as cranial, post-cranial axial, appendicular, and other (unspecified) features based on ToxRefDB descriptors. To build a multivariate statistical model, high-throughput screening bioactivity data from >8,070 chemicals in ToxCast/Tox21 across 10 in vitro assays relevant to the retinoid signaling system were evaluated and compared to literature-based candidate reference chemicals in the dataset. There were 48 chemicals identified for effects on both in vivo skeletal defects and in vitro ATRA pathway targets for computational modeling. The list included 28 chemicals with prior evidence of skeletal defects linked to retinoid toxicity and 20 chemicals without prior evidence. The combination of thoracic cage defects and DR5 (direct repeats of 5 nucleotides for RAR/RXR transactivation) disruption was the most frequently occurring phenotypic and target disturbance, respectively. This data model provides valuable AOP elucidation and validates current mechanistic understanding. These findings also shed light on potential avenues for new mechanistic discoveries related to ATRA pathway disruption and associated skeletal dysmorphogenesis due to environmental exposures.

Environmental Impact of Pharmaceutical Pollutants: Synergistic Toxicity of Ivermectin and Cypermethrin

Veterinary antiparasitic pharmaceuticals as well as pesticides have been detected in surface waters, and they may cause several toxic effects in this environmental compartment. In the present study, we evaluated the toxicity after exposure of different concentration of ivermectin (IVM; 50, 100, and 200 μg L⁻¹) and cypermethrin (CYP; 5, 10, and 25 μg L⁻¹) and the combination of these two compounds at non-toxic concentration (IVM 100 + CYP 5 μg L⁻¹) in zebrafish embryos. Combination of IVM at 100 μg L⁻¹ with CYP at 5 μg L⁻¹ exposure induced hatching delay and malformations at 96 hpf in zebrafish larvae as well as significant induction of cell death in zebrafish larvae. At the same time, the two single concentrations of IVM and CYP did not show a toxic effect on zebrafish development. In conclusion, our study suggests that IVM and CYP show a synergistic effect at common, ineffective concentrations, promoting malformation and cell death in fish development.

Long-term low-dose exposure of permethrin induces liver and kidney damage in rats

BACKGROUND

Permethrin is one of the pyrethroid insecticides, which is widely used in agriculture and public health. Although acute toxicity of the insecticide has been studied, the chronic toxicity upon the long-term exposure has not been clear yet. The purpose of the current study is to investigate the organ toxicities of permethrin following its long-term low-dose exposure.

METHODS

Male Wistar rats were daily administrated orally with permethrin (75 mg/kg body weight/day, gavage) for 90 days, and then the samples of biofluids (blood and urine) and organs including liver and kidney were collected. The serum and urine samples were measured by biochemical assay and the tissues of kidney and liver were examined and analyzed by histopathological method.

RESULTS

The results showed that no change was found in serum and urine biochemical parameters for the toxicity; however, significant changes including hyperchromatic nuclei swollen in the hepatic parenchymal cells and the swelling proximal tubules in the kidneys were observed in the tissue structures of liver and kidneys in the histopathological sections.

CONCLUSION

These results indicate that low-dose long-term exposure of permethrin can cause chronic toxicity with slight liver and kidney damage.

In vivo and in vitro evolution of the effects of cypermethrin on turbot (Scophthalmus maximus, Linnaeus, 1758) spermatozoa

Synthetic pyrethroid pesticide is commonly used in agricultural activities in the Black Sea region during reproduction period of turbot. In this sense, in vivo and in vitro studies have shown that cypermethrin (CYP) could be one of the environmental factors affecting decreasing turbot stocks. In this study, effects of in vivo and in vitro administration of CYP, a synthetic pyrethroid, on sperm kinematics motility (MOT), progressive motility (PM), curvilinear velocity (VCL), straight line velocity (VSL), average path velocity (VAP), linearity (LIN), straight line velocity (STR), amplitude of lateral head (ALH), beat cross frequency (BCF), oxidative stress biomarkers malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and lipid peroxidation (LPO) and also histopathological alterations in gonads were investigated in spermatazoa of turbot (Schopthalmus maximus). Broodstock was supplied from culture origin and used in spawning season, additionally, two (0, 0.187 and 0.218 ppb) and three (0, 1.025, 2.05 and 4.1 ppb) different CYP concentrations were performed for in vivo and in vitro studies, respectively. In vivo and in vitro studies, significant reductions were found in sperm MOT, PM, VCL, VSL, VAP, LIN, and ALH properties depend on the increase in CYP concentrations (p < 0.05). Besides, activities of GSH, GPx, SOD, and CAT increased. In terms of histological alterations, no difference was observed among groups (0, 0.187 and 0.218 ppb) in the maturity stage of the germ cells. According to obtained results, sperm kinematics was affected significantly with increased the dose levels of CYP (p < 0.05).

Side-effects of pesticides on non-target insects in agriculture: a mini-review

Climate change mediated by anthropogenic activity induces significant alterations on pest abundance and behavior and a potential increase in the use of agrochemicals for crop protection. Pesticides have been a tool in the control of pests, diseases, and weeds of agricultural systems. However, little attention has been given to their toxic effects on beneficial insect communities that contribute to the maintenance and sustainability of agroecosystems. In addition to pesticide-induced direct mortality, their sublethal effects on arthropod physiology and behavior must be considered for a complete analysis of their impact. This review describes the sublethal effects of pesticides on agriculturally beneficial insects and provides new information about the impacts on the behavior and physiology of these insects. The different types of sublethal effects of pesticides used in agriculture on pollinators, predators, parasitoids, and coprophagous insects were detailed.

Revisiting pesticide pollution: The case of fluorinated pesticides

Fluorinated pesticides acquired a significant market share in the agrochemical sector due to the surge of new fluoroorganic ingredients approved in the last two decades. This growing trend has not been accompanied by a comprehensive scientific and regulatory framework entailing all their potential negative impacts for the environment, especially when considering the hazardous properties that may result from the incorporation of fluorine into organic molecules. This review aims to address the safe/hazardous dichotomy associated with fluorinated pesticides by providing an updated outlook on their relevancy in the agrochemical sector and how it leads to their role as environmental pollutants. Specifically, the environmental fate and distribution of these pesticides in the ecosystems is discussed, while also analysing their potential to act as toxic substances for non-target organisms.

Estrogen receptor: A potential linker of estrogenic and dopaminergic pathways in zebrafish larvae following deltamethrin exposure

Deltamethrin (DM), a type II pyrethroid insecticide, is widely used to control agricultural pests. However, its excessive use exerts a detrimental effect on the ecological environment and human health, indicating the need to study its potential risks in detail. In the present study, zebrafish embryos were exposed to varying concentrations of DM (0.1, 1, 10, and 25 μg/L) for 96 h to assess the alterations in the transcript levels of proteins of the estrogenic and dopaminergic pathways. In addition, its effect on zebrafish locomotor activity was studied. The mRNA expression of cyp19a1b, erα, erβ2, fshr, gnrh2, gnrhr3, vtg3, dat, and dr1 significantly changed after exposing the embryos to DM. Deltamethrin at 10 and 25 μg/L significantly reduced the average swimming speed of zebrafish larvae. In addition, embryos injected with zebrafish estrogen receptor α (erα) and β (erβ) morpholinos and co-exposed to 25 μg/L DM for 96 h showed reduced expression of vtg3 mRNA compared to embryos exposed to 25 μg/L DM only. The locomotor activity of erα and erβ knockdown zebrafish following DM exposure was increased significantly when compared with that of larvae exposed to 25 μg/L DM only. Our results demonstrated that DM altered the locomotor activity of zebrafish larvae and the transcript levels of the components of estrogenic and dopaminergic pathways; erα and erβ knockdown weakened these effects.

Genomic markers for the biological responses of Triclosan stressed hatchlings of Labeo rohita

Triclosan (TCS) used commonly in pharmaceuticals and personal care products has become the most common pollutant in water. Three-day-old hatchlings of an indigenous fish, Labeo rohita, were given 96h exposure to a nonlethal (60 μg L^-1) and two moderately lethal concentrations (67 and 97 μg L^-1) of TCS and kept for 10 days of recovery for recording transcriptomic alterations in antioxidant/detoxification (SOD, GST, CAT, GPx, GR, CYP1a and CYP3a), metabolic (LDH, ALT and AST) and neurological (AchE) genes and DNA damage. The data were subjected to principal component analysis (PCA) for obtaining biomarkers for the toxicity of TCS. Hatchlings were highly sensitive to TCS (96h LC₅₀ = 126 μg L^-1 and risk quotient = 40.95), 96h exposure caused significant induction of CYP3a, AChE and ALT but suppression of all other genes. However, expression of all the genes increased significantly (except for a significant decline in ALT) after recovery. Concentration-dependent increase was also observed in DNA damage [Tail Length (TL), Tail Moment (TM), Olive Tail Moment (OTM) and Percent Tail DNA (TDNA)] after 96 h. The damage declined significantly over 96h values at 60 and 67 μg L^-1 after recovery, but was still several times more than control. TCS elicited genomic alterations resulted in 5-11% mortality of exposed hatchlings during the recovery period. It is evident that hatchlings of L. rohita are a potential model and PCA shows that OTM, TL, TM, TDNA, SOD and GR (association with PC1 during exposure and recovery) are the biomarkers for the toxicity of TCS. Graphical abstract.

Vitamin C Mitigates Oxidative Stress and Behavioral Impairments Induced by Deltamethrin and Lead Toxicity in Zebrafish

Environmental contamination from toxic metals and pesticides is an issue of great concern due to their harmful effects to human health and the ecosystems. In this framework, we assessed the adverse effects when aquatic organisms are exposed to toxicants such as deltamethrin (DM) and lead (Pb), alone or in combination, using zebrafish as a model. Moreover, we likewise evaluated the possible protective effect of vitamin C (VC) supplementation against the combined acute toxic effects of the two toxicants. Juvenile zebrafish were exposed to DM (2 μg L^-1) and Pb (60 μg L^-1) alone and in combination with VC (100 μg L^-1) and responses were assessed by quantifying acetylcholinesterase (AChE) activity, lipid peroxidation (MDA), some antioxidant enzyme activities (SOD and GPx), three-dimension locomotion responses and changes of elements concentrations in the zebrafish body. Our results show that VC has mitigative effects against behavioral and biochemical alterations induced by a mixture of contaminants, demonstrating that it can be used as an effective antioxidant. Moreover, the observations in the study demonstrate zebrafish as a promising in vivo model for assessing the neuroprotective actions of bioactive compounds.

Impact of environmental chemicals on craniofacial skeletal development: Insights from investigations using zebrafish embryos

Craniofacial skeletal anomalies are among the most common structural birth defects around the world. Various studies using human populations and experimental animals have shown that genetic and environmental factors play significant roles in the causation and progression of these anomalies. Environmental factors, such as teratogens and toxin mixtures, induce craniofacial anomalies are gaining heightened attention. Among experimental investigations, the use of the zebrafish (Danio rerio) has been increasing. A major reason for the increased use is that the zebrafish boast a simple craniofacial structure, and facial morphogenesis is readily observed due to external fertilization and transparent embryo, making it a valuable platform to screen and identify environmental factors involved in the etiology of craniofacial skeletal malformation. This review provides an update on harmful effects from exposure to environmental chemicals, involving metallic elements, nanoparticles, persistent organic pollutants, pesticides and pharmaceutical formulations on craniofacial skeletal development in zebrafish embryos. The collected data provide a better understanding for induction of craniofacial skeletal anomalies and for development of better prevention strategies.

Developmental toxicity of 3-phenoxybenzoic acid (3-PBA) and endosulfan sulfate derived from insecticidal active ingredients: Abnormal heart formation by 3-PBA in zebrafish embryos

Pyrethroid and organochlorine insecticides are enormously used to control agricultural and indoor insect pests. The metabolites of pyrethroid and endosulfan were used to evaluate environmental toxicities using a representative animal model, zebrafish (Danio rerio) embryos in this study. The LC50 values in 3-phenoxy benzoic acid (3-PBA) and endosulfan sulfate (ES) were 1461 μg/L and 1459 μg/L, respectively. At the concentration of 2000 μg/L, spine curvature was observed in the ES-treated embryos. ES showed seizure-like events with an EC50 value of 354 μg/L. At the concentration of 1000 μg/L, the pericardial edema was observed in 3-PBA-treated embryos. The inhibition of heart development and the reduction of beating rates were observed in Tg(cmlc2:EGFP) embryos after the exposure to 3-PBA. Down-regulation of the vmhc gene coding ventricular myosin during heart development was significantly found in 3-PBA-treated embryos at 48 hpf, but recovered afterward. It indicates that ventricular malformation occurred at the initial stage of 3-PBA exposure. Considered together, both 3-PBA and ES need public concerns with periodic monitoring of these metabolites in households and agricultural areas to prevent humans and environmental organisms from their unexpected attacks.

Assessment of deltamethrin toxicity in Macrobrachium nipponense based on histopathology, oxidative stress and immunity damage

Deltamethrin (Del), a commonly used broad-spectrum insecticide, has been reported to have a toxic effect on aquatic animals, but knowledge in freshwater prawns is limited. This study revealed that Del is highly toxic to Macrobrachium nipponens with the 24 h, 48 h, 72 h, and 96 h LC₅₀ values to be 0.268, 0.165, 0.104, and 0.066 μg/L, respectively. To further investigate the toxic effect of Del in M. nipponense and the reversibility of damage, prawns were exposed to 0.05 μg/L Del for four days and then transferred into fresh water for seven days. Histopathological examination, oxidative stress, hepatopancreas function, respiration system, and immune system were analyzed through multiple biomarkers. Results showed that Del exposure caused severe histopathological damage to hepatopancreas and gill in M. nipponense, and the prominent decrease of acid phosphatase (ACP) and alkaline phosphatase (AKP) activity further enhanced the hepatopancreas damage; the accumulation of malonaldehyde (MDA) and hydrogen peroxide (H₂O₂), and the decrease of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity, indicated severe oxidative stress caused by Del. Besides, Del exposure also induced remarkably increased lactic acid (LD) level, decreased lactate dehydrogenase (LDH) activity, and decreased expression of immune-related genes, which demonstrated the respiration disruption and immunosuppression caused by Del. After 7-day decontamination in freshwater, the indicator of hepatopancreas function (ACP and AKP activity) and respiration (LD level and LDH activity) improved to the control group level. However, the histopathological damage and the biomarker in oxidative stress and immune system did not recover to the initial level.

The insecticide permethrin induces transgenerational behavioral changes linked to transcriptomic and epigenetic alterations in zebrafish (Danio rerio)

The pyrethroid insecticide permethrin is widely used for agricultural and domestic purposes. Previous data indicated that it acts as a developmental neurotoxicant and can induce transgenerational effects in non-target organisms. However, associated underlying mechanisms remain unclear. The aim of this study was to investigate permethrin-related transgenerational effects in the zebrafish model, and to identify possible molecular mechanisms underlying inheritance. Zebrafish (F0) were exposed to permethrin during early-life (2 h post-fertilization up to 28 days). The F1 and F2 offspring generations were obtained by pairing exposed F0 males and females, and were bred unexposed. Locomotor and anxiety behavior were investigated, together with transcriptomic and epigenomic (DNA methylation) changes in brains. Permethrin exposed F0 fish were hypoactive at adulthood, while males from the F1 and F2 generations showed a specific decrease in anxiety-like behavior. In F0, transcriptomic data showed enrichment in pathways related to glutamatergic synapse activity, which may partly underlie the behavioral effects. In F1 and F2 males, dysregulation of similar pathways was observed, including a subset of differentially methylated regions that were inherited from the F0 to the F2 generation and indicated stable dysregulation of glutamatergic signaling. Altogether, the present results provide novel evidence on the transgenerational neurotoxic effects of permethrin, as well as mechanistic insight: a transient exposure induces persistent transcriptional and DNA methylation changes that may translate into transgenerational alteration of glutamatergic signaling and, thus, into behavioral alterations.

An Overview on the Potential Hazards of Pyrethroid Insecticides in Fish, with Special Emphasis on Cypermethrin Toxicity

Simple Summary

Pyrethroid insecticides are extensively used in controlling agricultural insects and treatment of ectoparasitic infestation in farm animals. However, the unhygienic disposable and seepage of pyrethroids from the agricultural runoff will lead to contamination of the aquatic ecosystems, which will, in turn, induce harmful toxic effects in the exposed living aquatic organisms, including fish. Cypermethrin (CYP) is a commonly and widely used type II pyrethroid insecticide with known dangerous toxic effects on the exposed organisms. Serious hazardous effects of these toxicants have been reported in several fish species leading to high mortalities and economic losses of the exposed fish.

Abstract

Pesticides are chemicals used to control pests, such as aquatic weeds, insects, aquatic snails, and plant diseases. They are extensively used in forestry, agriculture, veterinary practices, and of great public health importance. Pesticides can be categorized according to their use into three major types (namely insecticides, herbicides, and fungicides). Water contamination by pesticides is known to induce harmful impacts on the production, reproduction, and survivability of living aquatic organisms, such as algae, aquatic plants, and fish (shellfish and finfish species). The literature and information present in this review article facilitate evaluating the toxic effects from exposure to various fish species to different concentrations of pesticides. Moreover, a brief overview of sources, classification, mechanisms of action, and toxicity signs of pyrethroid insecticides in several fish species will be illustrated with special emphasis on Cypermethrin toxicity.

Salinity Changes the Dynamics of Pyrethroid Toxicity in Terms of Behavioral Effects on Newly Hatched Delta Smelt Larvae

Salinity can interact with organic compounds and modulate their toxicity. Studies have shown that the fraction of pyrethroid insecticides in the aqueous phase increases with increasing salinity, potentially increasing the risk of exposure for aquatic organisms at higher salinities. In the San Francisco Bay Delta (SFBD) estuary, pyrethroid concentrations increase during the rainy season, coinciding with the spawning season of Delta Smelt (Hypomesus transpacificus), an endangered, endemic fish. Furthermore, salinity intrusion in the SFBD is exacerbated by global climate change, which may change the dynamics of pyrethroid toxicity on aquatic animals. Therefore, examining the effect of salinity on the sublethal toxicity of pyrethroids is essential for risk assessments, especially during the early life stages of estuarine fishes. To address this, we investigated behavioral effects of permethrin and bifenthrin at three environmentally relevant concentrations across a salinity gradient (0.5, 2 and 6 PSU) on Delta Smelt yolk-sac larvae. Our results suggest that environmentally relevant concentrations of pyrethroids can perturb Delta Smelt larvae behavior even at the lowest concentrations (<1 ng/L) and that salinity can change the dynamic of pyrethroid toxicity in terms of behavioral effects, especially for bifenthrin, where salinity was positively correlated with anti-thigmotaxis at each concentration.

Exposure to permethrin or chlorpyrifos causes differential dose- and time-dependent behavioral effects at early larval stages of an endangered teleost species

Pyrethroid and organophosphate pesticides are two of the most commonly used classes of insecticide worldwide. At sublethal concentrations, permethrin (a pyrethroid) and chlorpyrifos (an organophosphate) impact behavior in model fish species. We investigated behavioral effects of environmentally relevant concentrations of permethrin or chlorpyrifos on early larval delta smelt Hypomesus transpacificus, a Critically Endangered teleost species endemic to the San Francisco Bay Delta, California, USA. Using a photomotor behavioral assay of oscillating light and dark periods, we measured distance moved, turn angle, meander, angular velocity, rotations, thigmotaxis (time spent in the border versus center), and swim speed duration and frequency. The lowest concentrations of permethrin used in the tests (0.05 and 0.5 μg l⁻¹) caused significant increases in distance moved at 72 and 96 h, respectively. At 48, 72, and 96 h of exposure, 5 μg l⁻¹ of permethrin caused a hyperactive state in which the larvae significantly decreased thigmotaxis, quickly turning in short bouts of activity, characterized by significant increases in rotations and freezing events. Larvae exposed to 0.05 μg l⁻¹ chlorpyrifos significantly increased thigmotaxis at 72 and 96 h. In response to 5 μg l⁻¹ chlorpyrifos, larvae significantly increased velocity at 72 h exposure, and significantly increased freezing events at 96 h. Behavioral data on larval delta smelt exposed to contaminants present in their limited habitat have the potential to aid evaluations of the suitability of spawning and rearing habitats for this endangered species, thus improving conservation management strategies focused on this sensitive life stage.

Multi- and transgenerational effects following early-life exposure of zebrafish to permethrin and coumarin 47: Impact on growth, fertility, behavior and lipid metabolism

Transgenerational effects induced by environmental stressors are a threat to ecosystems and human health. However, there is still limited observation and understanding of the potential of chemicals to influence life outcomes over several generations. In the present study, we investigated the effects of two environmental contaminants, coumarin 47 and permethrin, on exposed zebrafish (F0) and their progeny (F1-F3). Coumarin 47 is commonly found in personal care products and dyes, whereas permethrin is used as a domestic and agricultural pyrethroid insecticide/insect repellent. Zebrafish (F0) were exposed during early development until 28 days post-fertilization and their progeny (F1-F3) were bred unexposed. On one hand, the effects induced by coumarin 47 suggest no multigenerational toxicity. On the other hand, we found that behavior of zebrafish larvae was significantly affected by exposure to permethrin in F1 to F3 generations with some differences depending on the concentration. This suggests persistent alteration of the neural or neuromuscular function. In addition, lipidomic analyses showed that permethrin treatment was partially correlated with lysophosphatidylcholine levels in zebrafish, an important lipid for neurodevelopment. Overall, these results stress out one of the most widely used pyrethroids can trigger long-term, multi- and possibly transgenerational changes in the nervous system of zebrafish. These neurobehavioral changes echo the effects observed under direct exposure to high concentrations of permethrin and therefore call for more research on mechanisms underlying effect inheritance.

Changes of embryonic development, locomotor activity, and metabolomics in zebrafish co-exposed to chlorpyrifos and deltamethrin

Organophosphates (OPs) and pyrethroids (PYRs) are extensively used pesticides and often occur in the form of mixture, whereas little was known about their joint toxicities. We aim to investigate the individual and joint effects of OPs and PYRs exposure on zebrafish embryo by employing chlorpyrifos (CPF) and deltamethrin (DM) as representatives. Zebrafish embryos at 2 hours post fertilization (hpf) were exposed to CPF (4.80, 39.06, and 78.13 μg/L), DM exposure (0.06, 1.60, and 3.19 μg/L), and CPF + DM (4.80 + 0.06, 39.06 + 1.60, and 78.13 + 3.19 μg/L) until 144 hpf. Embryonic development, locomotor activity, and metabolomic changes were recorded and examined. Results displayed that individual exposure to CPF and DM significantly increased the mortality and malformation rate of zebrafish embryos, but decreased hatching rate was only found in CPF + DM co-exposure groups (p < .05). Meanwhile, individual CPF exposure had no detrimental effect on locomotor activity, high dose of individual CPF exposure decreased the swimming speed but had adaptability to the conversion from dark to light, whereas high dose of CPF + DM co-exposure exhibited not only significant decline in swimming speed but also no adaptability to the repeated stimulations, suggesting deficit in learning and memory function. In metabolomic analysis, individual CPF exposure mainly influenced the metabolism of glycerophospholipids and amino acids, individual DM exposure mainly influenced glycerophospholipids, and CPF + DM co-exposure mainly influenced glycerophospholipids and amino acids. Taken together, our findings suggested the embryonic toxicities and neurobehavioral changes caused by CPF and/or DM exposure. The disorder metabolomics of glycerophospholipids and amino acids might be involved in the underlying mechanism of those toxicities.

Toxicological assessment and developmental abnormalities induced by butylparaben and ethylparaben exposure in zebrafish early-life stages

Toxicological effects of butylparaben (BuP) and ethylparaben (EtP) on zebrafish (Danio rerio) early-life stages are not well established. The present study evaluated, using zebrafish embryos and larvae, the toxicity of BuP and EtP through benchmark dose (BMD) approach. BuP was more toxic than EtP to zebrafish larvae. In fact, Lethal Concentration 50 (LC50) values at 96 h post-fertilization (hpf) for BuP and EtP were 2.34 mg/L and 20.86 mg/L, respectively. Indeed, BMD confidence interval (lower bound (BMDL) - upper bound (BMDU) was 0.91-1.92 mg/L for BuP and 10.8-17.4 mg/L for EtP. Zebrafish embryos exposed to 1 mg/L, 2.5 mg/L of BuP and 5 mg/L, 10 mg/L, 20 mg/L, 30 mg/L of EtP showed several developmental abnormalities and teratological effects compared to negative control. Exposed zebrafish developed reduced heartbeat, reduction in blood circulation, blood stasis, pericardial edema, deformed notochord and misshaped yolk sac. Embryos exposed to the highest concentrations of the chemicals (2.5 mg/L of BuP, 10 mg/L, 20 mg/L and 30 mg/L of EtP) showed the developmental abnormalities at 48 hpf while those treated with 1 mg/L of BuP and 10 mg/L of EtP reported behavioral changes at 72 hpf, including trembling of head, pectoral fins and spinal cord. This research identified the lethal and sublethal effects of BuP and EtP in zebrafish early-life stages and could be helpful to elucidate the developmental pathways of toxicity of parabens.

Developmental toxicity of chlorpropham induces pathological changes and vascular irregularities in zebrafish embryos

Chlorpropham is used to prevent sprouting in stored agricultural products. It functions through mitosis inhibition or microtubule assembly inhibition in target organisms including plants, protozoa, and fungi. Although the toxicity ranges of chlorpropham in different organisms are known, specific studies on the environmental contamination and the harmful effects of chlorpropham has not been elucidated. In the present study, we demonstrated that toxicity assays of chlorpropham using zebrafish embryos showed pathological morphology alteration with half the embryos undergoing embryonic death. Fluorescent dye was used in live embryos to identify whether oxidative stress and apoptosis mediated developmental malformation. Specific genes related to apoptosis, ccnd1, ccne1, and cdk6, belonging to cell cycle regulation were downregulated on exposure to sublethal concentrations of chlorpropham. Moreover, vascular morphogenesis, which contributes to the cardiovascular circulatory system, was disrupted by chlorpropham along with decreased expression of specific regulators (flt1, kdr, and vegfaa). These data suggest that environmentally preserved chlorpropham is a potential pollutant in non-target species, especially in aquatic organisms, and emphasizes the need for caution regarding the ecotoxicity of chlorpropham.

A Microfluidic Paper-Based Analytical Device for Type-II Pyrethroid Targets in an Environmental Water Sample

A detection method for type-II pyrethroids in an environmental water sample using a microfluidic paper-based analytical device (µPAD) is reported here. The detection approach is based on the formation of cyanide from the hydrolysis of type-II pyrethroids and the colorimetric detection of cyanide on a layer-based µPAD. Parafilm and inexpensive laminating pouches were used to create a hydrophobic barrier for the assay on the µPAD. This detection approach was selective to type-II pyrethroids in water for which an environmental water sample was tested. The calibration curves for cypermethrin, deltamethrin, cyhalothrin, and fenvalerate ranged from 2 to 40 µg/mL without sample preconcentration. The lower concentrations of type-II pyrethroids can be assessed by including a preconcentration step prior to the detection on a µPAD. This detection system provides an alternative platform for fast, semiquantitative testing for pesticide contamination in environmental surface water by allowing for portability, low reagent/sample consumption, and low-cost testing.

Changes in thyroid hormone levels and related gene expressions in embryo-larval zebrafish exposed to binary combinations of bifenthrin and acetochlor

Bifenthrin (BF) and acetochlor (AT) are widely used as an insecticide and herbicide, respectively, which are introduced to the aquatic environment as a natural result. Although the thyroid active substances may coexist in the environment, their joint effects on fish have not been identified. We examined the joint toxicity of BF and AT in zebrafish (Danio rerio) in this study. An acute lethal toxicity test indicated that the median lethal concentration (LC₅₀) values of BF and AT under 96 h treatment were 0.40 and 4.56 µmol L^-1, respectively. The binary mixture of BF + AT displayed an antagonistic effect on the acute lethal toxicity. After 14 days post fertilization (dpf) with exposure to individual pesticides at sub-lethal concentrations of, no effects were observed on the catalase (CAT) and peroxidase (POD) activities, while the binary mixtures (except for the 7.2 × 10^-3 µmol L^-1 BF + 1.2 × 10^-2 µmol L^-1 AT exposure group) significantly induced the CAT activity. The superoxide dismutase (SOD) activity and triiodothyronine (T3) level were significantly increased in all exposure groups. The thyroxine (T4) level remained unchanged after exposure to individual pesticides, but significantly increased in the 7.2 × 10^-3 µmol L^-1 BF + 1.2 × 10^-2 µmol L^-1 AT group. The expressions of the genes Dio2, TRa, TSHβ and CRH in the thyroid hormone (TH) axis were significantly up-regulated in the 7.2 × 10^-3 µmol L^-1 BF + 0.4 × 10^-2 µmol L^-1 AT group. Our data indicated that the binary mixture of BF + AT significantly altered the antioxidant enzyme activities and gene expressions in the hypothalamic-pituitary-thyroid (HPT) axis and changed the TH levels.

Jasmonic acid is not a biosynthetic intermediate to produce the pyrethrolone moiety in pyrethrin II

Pyrethrum (Tanacetumcinerariifolium) produces insecticidal compounds known as pyrethrins. Pyrethrins are esters; the acid moiety is either trans-chrysanthemic acid or pyrethric acid and the alcohol moiety of pyrethrins is either pyrethrolone, cinerolone, or jasmolone. It was generally accepted that cis-jasmone was biosynthetic intermediate to produce the alcohol moieties of pyrethrin, and the biosynthetic origin of the cis-jasmone was postulated to be jasmonic acid. However, there was no direct evidence to prove this hypothesis. In order to uncover the origin of pyrethrolone moiety in pyrethrin II, feeding experiments were performed employing deuterium- and ¹³C-labeled compounds as substrates, and the expected labeled compounds were analyzed using UPLC MS/MS system. It was found that the pyrethrolone moiety in pyrethrin II was derived from 12-oxo-phytodienoic acid (OPDA), iso-OPDA and cis-jasmone but not from methyl jasmonate and 3-oxo-2-(2′-[Z]-pentenyl)-cyclopentane-1-hexanoic acid. The results supported that the biosynthesis of the pyrethrolone moiety in pyrethrin II partially used part of the jasmonic acid biosynthetic pathway, but not whole.

Advancing zebrafish as a model for studying developmental neurotoxicology

The cover photo shows the developing zebrafish nervous system at 5 days post-fertilization. Axon tracts are labeled with an anti-acetylated alpha tubulin antibody. The image, which was acquired on a Zeiss LSM 880 confocal microscope, is a maximum intensity projection of a z-stack that has been color-coded for depth. Major brain regions such as the olfactory bulb, forebrain, habenula, optic tectum, cerebellum, hindbrain, and eye are identifiable. This image is part of a study (Plavicki Lab, Brown University) focused on understanding the impact of toxicant exposures on brain development and activity with the goal of identifyingenvironmental factors that contribute to the etiology of neurodevelopmental disorders.

Developmental toxicity of fipronil in early development of zebrafish (Danio rerio) larvae: Disrupted vascular formation with angiogenic failure and inhibited neurogenesis

Fipronil has been widely used in agriculture to prevent aggressive insects from damaging agricultural products. Fipronil residues circulate in the environment and they have been detected in non-targeted organisms in aquatic environments. To study the effect of fipronil toxicity on environmental health, 6 h post fertilization (hpf) zebrafish embryos were treated with fipronil for 72 h. LC₅₀ value was obtained by applying varying concentrations of fipronil to zebrafish embryos for 72 h. As zebrafish embryos are useful vertebrate models for studying developmental and genetic findings in toxicology research, they were exposed to fipronil to study detailed elucidating mechanisms with hazardous end points of toxicity. Cell cycle arrest-related apoptosis supported pathological alterations, such as increased mortality, shortened body length, and reduced hatchability. Furthermore, observed heart defects, including edema and irregular heartbeat were caused due to abnormal blood circulation. In transgenic zebrafish models (fli1:eGFP and olig2:dsRED), disrupted blood vessel formations were indicated by eGFP⁺ endothelial cells. Moreover, neurogenic defects were observed by studying dsRED⁺ motor neurons and oligodendrocytes. This study demonstrates fipronil accumulation in aquatic environment and its ability to impair essential processes, such as angiogenesis and neurogenesis during early developmental stage of zebrafish, along with general developmental toxicity.

The pyrethroid esfenvalerate induces hypoactivity and decreases dopamine transporter expression in embryonic/larval zebrafish (Danio rerio)

Esfenvalerate is a pyrethroid insecticide used widely for agricultural and residential applications. This insecticide has been detected in aquatic environments at concentrations that can induce sub-lethal effects in organisms. In this study, zebrafish embryos were used to examine the effects of environmentally-relevant concentrations of esfenvalerate on development and behavior. It was hypothesized that esfenvalerate exposure would impair locomotion due to its effects on the central nervous system. We also measured mitochondrial bioenergetics and the expression of genes (dopamine system) as putative mechanisms of locomotor impairment. Concentrations of 0.02, 0.2 and 2 μg/L esfenvalerate did not induce significant mortality nor deformity in zebrafish, but there was an acceleration in hatching time for zebrafish exposed to 2 μg/L esfenvalerate. As an indicator of neurotoxicity, the Visual Motor Response (VMR) test was conducted with 5, 6, and 7 dpf zebrafish after continuous exposure, and higher concentrations were used (4 and 8 μg/L esfenvalerate) to better discern age-and dose dependent responses in behavior. Experiments revealed that, unlike the other stages, 6 dpf larvae showed evidence for hypo-activity with esfenvalerate, suggesting that different stages of larval development may show increased sensitivity to pyrethroid exposure. This may be related to age-dependent maturation of the central nervous system. We hypothesized that reduced larval activity may be associated with impaired production of ATP and the function of mitochondria at earlier life stages, however dramatic alterations in oxidative phosphorylation were not observed. Based on evidence that dopamine regulates behavior and studies showing that other pyrethroids affect dopamine system, we measured transcripts involved in dopaminergic signaling. We found that dopamine active transporter was down-regulated with 0.2 μg/L esfenvalerate. Lastly, we comprehensively summarize the current literature (>20 studies) regarding the toxicity of pyrethroids in zebrafish, which is a valuable resource to those studying these pesticides. This study demonstrates that esfenvalerate at environmentally-relevant levels induces hypoactivity that are dependent upon the age of the zebrafish, and these behavioral changes are hypothesized to be related to impaired dopamine signaling.

Acute embryonic exposure of zebrafish to permethrin induces behavioral changes related to anxiety and aggressiveness in adulthood

Permethrin (PM) is one of the most used synthetic pyrethroid worldwide. Exposure to this compound during pregnancy and early childhood has been indicated as a risk factor for neurodevelopmental disorders. We evaluated the long-term effects of embryonic PM exposure in different stages of zebrafish development. Briefly, embryos (3 hpf) were exposed to sub-lethal concentrations of PM (25 and 50 μg.L^-1) during 24 h and then behavioral parameters were evaluated during embryonic (28 hpf), eleutheroembryonic (3 dpf), larval (7 dpf), and adult stages (90 dpf). PM exposure decreased spontaneous movement at 28 hpf and decreased thigmotaxis in eleutheroembryos. The long-term effects of PM include changes in non-motor behaviors such as fear and anxiety in larva and adults. Adults embryonically exposed to PM also showed a significant increase in aggressiveness parameters. These results demonstrated that embryonic exposure to PM induces persistent neurotoxic effects in adulthood, which can impair the cognitive and behavioral fitness of non-target species contributing to a rise in neurodevelopmental disorders.

Bifenthrin exerts proatherogenic effects via arterial accumulation of native and oxidized LDL in rats: the beneficial role of vitamin E and selenium

The purpose of this study was to investigate, for the first time, the effects of Bifenthrin (Bif) chronic exposure on plasmatic and aortic lipid parameters disturbance and their pro-atherogenic possibility in Wistar rats. The ameliorative role of vitamin E (Vit E) and selenium (Se) were also targeted. Thus, rats were treated by gastric gavage with combination of Vit E (100 mg/kg/bw) and Se (0.25 mg/kg/bw) in alone and co-treated groups for 90 days. Apart from control and Vit E-Se groups, all the groups were subjected to Bif (3 mg/kg, via gavage) toxicity. Results showed that Bif increased markedly plasmatic and aortic total cholesterol, LDL-cholesterol, native LDL-apoB-100, and oxidized-LDL, compared to the control. Moreover, Bif treatment significantly increased the plasmatic levels of the pro-inflammatory cytokines TNF-α, IL-2, and IL-6. In addition, the densitometric quantification of protein bands showed that the amount of hepatic native LDL-receptor protein decreased significantly in the intoxicated rats compared to the control group. The expression of arterial LDL receptors (LDLRs) and scavenger receptors (CD36) was amplified owing to Bif toxicity. This harmful effect was confirmed by histological study using Oil-Red-O staining. Owing to their antioxidant capacities, Vit E and Se have maintained all the changes in plasma and aorta lipids and prevented the pro-atherogenic effect observed in Bif-treated animals.

Toxicity of Deltamethrin to Zebrafish Gonads Revealed by Cellular Biomarkers

Deltamethrin is responsible for health and reproduction problems both in mammals and aquatic organisms. In this study, zebrafish adults were exposed for 15 days to 0.25, 0.5, 1, and 2 μg L−1 non-lethal concentrations of deltamethrin, knowing that is used worldwide on agricultural crops. We investigated the chronic effects of deltamethrin on gonads by histopathological examination, immunohistochemistry, and immunofluorescence using biomarkers for apoptosis (anti-p53, anti-H2A.XS139ph antibodies, and TUNEL assay), oxidative stress (anti-Cox4i1 antibody) and proliferation (anti-PCNA antibody). Among the histopathological changes, the apoptotic response was elevated in ovary and testis of deltamethrin exposed groups as it was seen in the IHC and IF for p53, H2A.XS139ph, and confirmed by TUNEL assay. These were observed in the case of all studied concentrations compared with the control group. Thereby, the gonadal tissue exhibited an up-regulated activity of this cell-death signaling markers, while the proliferation marker (PCNA) increased in the ovary due to its presence not only in primary growth and cortical-alveolar stage follicles but also in atretic follicles, meanwhile decreased notably in the testis. Cox4i1, a mitochondrial marker, decreased both in ovary and testis during deltamethrin treatment, probably inhibited by the overproduction of the free radicals after pesticide exposure.

Coexposure to environmental concentrations of cis-bifenthrin and graphene oxide: Adverse effects on the nervous system during metamorphic development of Xenopus laevis

Despite the great concerns associated with the combined biological effects of nanoparticles and insecticides, the current understanding of the corresponding ecological risks remains limited. Xenopus laevis (X. laevis) tadpoles were exposed to various concentrations of typical pyrethroid (cis-bifenthrin; cis-BF), either alone or in combination with graphene oxide (GO), for 21 days. The presence of GO resulted in increased bioconcentration of cis-BF and a higher 1S-enantiomer fraction. Exposure to cis-BF and GO caused further reduction in pre-metamorphic developmental rates and activated dopaminergic, noradrenergic, and serotonergic neurotransmitter systems. Reduced tadpole activity and levels of genomic DNA methylation at cytosine nucleotides (5hmC) were observed in the coexposure groups. These results indicate that GO enhance the bioconcentration of cis-BF and promote the conversion of its 1R-enantiomer to the 1S form, which lead to disruption of neurotransmitter systems as well as interference in metamorphic development.

Draft genome of Tanacetum cinerariifolium, the natural source of mosquito coil

Pyrethrum (Tanacetum cinerariifolium), which is a perennial Asteraceae plant with white daisy-like flowers, is the original source of mosquito coils and is known for the biosynthesis of the pyrethrin class of natural insecticides. However, the molecular basis of the production of pyrethrins by T. cinerariifolium has yet to be fully elucidated. Here, we present the 7.1-Gb draft genome of T. cinerariifolium, consisting of 2,016,451 scaffolds and 60,080 genes predicted with high confidence. Notably, analyses of transposable elements (TEs) indicated that TEs occupy 33.84% of the genome sequence. Furthermore, TEs of the sire and oryco clades were found to be enriched in the T. cinerariifolium-specific evolutionary lineage, occupying a total of 13% of the genome sequence, a proportion approximately 8-fold higher than that in other plants. InterProScan analysis demonstrated that biodefense-related toxic proteins (e.g., ribosome inactivating proteins), signal transduction-related proteins (e.g., histidine kinases), and metabolic enzymes (e.g., lipoxygenases, acyl-CoA dehydrogenases/oxygenases, and P450s) are also highly enriched in the T. cinerariifolium genome. Molecular phylogenetic analysis detected a variety of enzymes with genus-specific multiplication, including both common enzymes and others that appear to be specific to pyrethrin biosynthesis. Together, these data identify possible novel components of the pyrethrin biosynthesis pathway and provide new insights into the unique genomic features of T. cinerariifolium.

The progressive alteration of urine metabolomic profiles of rats following long-term and low-dose exposure to permethrin

Background: Permethrin is a type of widely used pyrethroid pesticide. Although acute toxicity of permethrin has been well-characterised, the non-acute toxicity of permethrin upon long-term exposure at low dose has been seldom studied yet. The current study investigates the time-course change of the metabolomic profiles of urine following the low level long-term exposure of permethrin and identified biomarkers of the chronic toxicity of permethrin.Methods: Male Wistar rats were administrated orally with permethrin (75 mg/kg body weight/day, 1/20 LD₅₀) daily for consecutive 90 days. The urine samples from day 30, day 60, and day 90 after the first dosing were collected and analysed by ¹H NMR spectrometry. Serum biochemical analysis was also carried out.Results: Permethrin caused significant changes in the urine metabolites such as taurine, creatinine, acetate, lactate, dimethylamine, dimethylglycine, and trimethylamine-N-oxide. These biological markers indicated prominent kidney and liver toxicity induced by permethrin. However, there was no change in serum biochemical parameters for the toxicity, indicating that metabolomic approach was much more sensitive in detecting the chronic toxicity.Conclusion: The time-course alteration of metabolomic profiles of the urine based on ¹H NMR reflects the progressive development of the chronic toxicity with the long-term low-level exposure of permethrin.

Acute Exposure to Permethrin Modulates Behavioral Functions, Redox, and Bioenergetics Parameters and Induces DNA Damage and Cell Death in Larval Zebrafish

Permethrin (PM) is a synthetic pyrethroid insecticide widely used as domestic repellent. Damage effects to nontarget organisms have been reported, particularly in the early stages of development. Studies indicate redox unbalance as secondary PM effect. Therefore, our goal was to investigate the acute PM effects on larval zebrafish. Larvae (6 days postfertilization) were exposed to PM (25–600 μg/L) during 24 hours, and 50% lethal concentration was estimated. For subsequent assays, the sublethal PM concentrations of 25 and 50 μg/L were used. PM increased anxiety-like behaviors according to the Novel Tank and Light-Dark tests. At the molecular level, PM induced increased ROS, which may be related to the increased lipid peroxidation, DNA damage, and apoptosis detected in PM-exposed organisms. In parallel, upregulation of the antioxidant system was detected after PM exposure, with increased superoxide dismutase, glutathione S-transferase and glutathione reductase activities, and thiol levels. The increased of Nrf2 target genes and the activation of an electrophile response element-driven reporter Tg(EPRE:LUC-EGFP) suggest that the Nrf2 pathway can mediate a fast response to PM, leading to antioxidant amplification. By using high-resolution respirometry, we found that exposure to PM decreased the oxygen consumption in all respiratory stages, disrupting the oxidative phosphorylation and inhibiting the electron transfer system, leading to decrease in bioenergetics capacity. In addition, PM led to increases of residual oxygen consumption and changes in substrate control ratio. Glucose metabolism seems to be affected by PM, with increased lactate dehydrogenase and decreased citrate synthase activities. Taken together, our results demonstrated the adverse effects of acute sublethal PM concentrations during larval development in zebrafish, causing apparent mitochondrial dysfunction, indicating a potential mechanism to redox unbalance and oxidative stress, which may be linked to the detected cell death and alterations in normal behavior patterns caused by acute PM exposure.

Pyrethrin Biosynthesis: The Cytochrome P450 Oxidoreductase CYP82Q3 Converts Jasmolone To Pyrethrolone

The plant pyrethrum (Tanacetum cinerariifolium) synthesizes highly effective natural pesticides known as pyrethrins. Pyrethrins are esters consisting of an irregular monoterpenoid acid and an alcohol derived from jasmonic acid (JA). These alcohols, referred to as rethrolones, can be jasmolone, pyrethrolone, or cinerolone. We recently showed that jasmolone is synthesized from jasmone, a degradation product of JA, in a single hydroxylation step catalyzed by jasmone hydroxylase (TcJMH). TcJMH belongs to the CYP71 clade of the cytochrome P450 oxidoreductase family. Here, we used coexpression analysis, heterologous gene expression, and in vitro biochemical assays to identify the enzyme responsible for conversion of jasmolone to pyrethrolone. A further T cinerariifolium cytochrome P450 family member, CYP82Q3 (designated Pyrethrolone Synthase; TcPYS), appeared to catalyze the direct desaturation of the C1-C2 bond in the pentyl side chain of jasmolone to produce pyrethrolone. TcPYS is highly expressed in the trichomes of the ovaries in pyrethrum flowers, similar to TcJMH and other T cinerariifolium genes involved in JA biosynthesis. Thus, as previously shown for biosynthesis of the monoterpenoid acid moiety of pyrethrins, rethrolones are synthesized in the trichomes. However, the final assembly of pyrethrins occurs in the developing achenes. Our data provide further insight into pyrethrin biosynthesis, which could ultimately be harnessed to produce this natural pesticide in a heterologous system.

Environmental chemicals differentially affect epigenetic-related mechanisms in the zebrafish liver (ZF-L) cell line and in zebrafish embryos

A number of chemicals have been shown to affect epigenetic patterning and functions. Since epigenetic mechanisms regulate transcriptional networks, epigenetic changes induced by chemical exposure can represent early molecular events for long-term adverse physiological effects. Epigenetics has thus appeared as a research field of major interest within (eco)toxicological sciences. The present study aimed at measuring effects on epigenetic-related mechanisms of selected environmental chemicals (bisphenols, perfluorinated chemicals, methoxychlor, permethrin, vinclozolin and coumarin 47) in zebrafish embryos and liver cells (ZFL). Transcription of genes related to DNA methylation and histone modifications was measured and global DNA methylation was assessed in ZFL cells using the LUMA assay. The differences in results gathered from both models suggest that chemicals affect different mechanisms related to epigenetics in embryos and cells. In zebrafish embryos, exposure to bisphenol A, coumarin 47, methoxychlor and permethrin lead to significant transcriptional changes in epigenetic factors suggesting that they can impact early epigenome reprogramming related to embryonic development. In ZFL cells, significant transcriptional changes were observed upon exposure to all chemicals but coumarin 47; however, only perfluorooctane sulfonate induced significant effects on global DNA methylation. Notably, in contrast to the other tested chemicals, perfluorooctane sulfonate affected only the expression of the histone demethylase kdm5ba. In addition, kdm5ba appeared as a sensitive gene in zebrafish embryos as well. Taken together, the present results suggest a role for kdm5ba in regulating epigenetic patterns in response to chemical exposure, even though mechanisms remain unclear. To confirm these findings, further evidence is required regarding changes in site-specific histone marks and DNA methylation together with their long-term effects on physiological outcomes.