Assessment of the in vivo genotoxicity of pendimethalin via mitochondrial bioenergetics and transcriptional profiles during embryogenesis in zebrafish: Implication of electron transport chain activity and developmental defects

Flusilazole induced developmental toxicity, neurotoxicity, and cardiovascular toxicity via apoptosis and oxidative stress in zebrafish

Flusilazole is a well-known triazole fungicide applied to various crops and fruits worldwide. Flusilazole residues are frequently detected in the environment, and many researchers have reported the hazardous effects of flusilazole on non-target organisms; however, the developmental toxicity of flusilazole has not been fully elucidated. In this study, we investigated flusilazole-induced developmental defects in zebrafish, which are used in toxicology studies to assess the toxic effects of chemicals on aquatic species or vertebrates. We confirmed that flusilazole exposure affected the viability and hatching rate of zebrafish larvae, and resulted in morphological defects, reduced body length, diminished eye and head sizes, and inflated pericardial edema. Apoptosis, oxidative stress, and inflammation were also observed. These factors interrupted the normal organ formation during early developmental stages, and transgenic models were used to identify organ defects. We confirmed the effects of flusilazole on the nervous system using olig2:dsRed transgenic zebrafish, and on the cardiovascular system using cmlc2:dsRed and fli1:eGFP transgenic zebrafish. Our results demonstrate the developmental toxicity of flusilazole and its mechanisms in zebrafish as well as the detrimental effects of flusilazole.

Environmental presence and toxicological outcomes of the herbicide pendimethalin in teleost fish

Herbicides are often detected in aquatic ecosystems due to residential and agricultural applications and can harm aquatic organisms once deposited into water systems. Pendimethalin is part of the dinitroaniline chemical family and is applied to crops like corn, legumes, potatoes, and soybeans. The potential toxicity of pendimethalin to aquatic species is understudied compared to other widely studied herbicides, like atrazine and glyphosate. The objectives of this review were to (1) collate information on sub-lethal responses to pendimethalin exposure in fish, (2) evaluate how exposure studies relate to environmental concentrations, and (3) identify putative bioindicators for exposure studies. Overall, studies reporting pendimethalin in water systems worldwide indicate a range of 100-300 ng/L, but levels have been reported as high as ~15 µg/g in sediment. In teleost fish, studies demonstrate developmental toxicity, immunotoxicity, and behavioral disruptions. The strongest evidence for pendimethalin-induced toxicity involves oxidative stress, although studies often test toxicity at higher concentrations than environmentally relevant levels. Using the Comparative Toxicogenomics Database, pathway analysis reveals linkages to neurotoxicity and mechanisms of neurodegeneration like "Ubiquitin Dependent Protein Degradation", "Microtubule Cytoskeleton", "Protein Oxidation and Aggregation in Aging", and "Parkinson's Disease". Other prominent pathways included those related to mTOR signaling and reproduction. Thus, two potential mechanisms underlying pendimethalin-induced toxicity in fish include the neural and reproductive systems. This review synthesizes current data regarding environmental fate and ecotoxicology of pendimethalin in teleost fish and points to some putative physiological and molecular responses that may be beneficial for assessing toxicity of the herbicide in future investigations.

Bifenox induces hepatotoxicity and vascular toxicity in zebrafish embryos via ROS production and alterations in signaling pathways

Existing evidence shows that currently used pesticides pose toxicological risks to exposed wildlife. Chemically, bifenox belongs to diphenyl ethers, a well-known group of herbicides. Its mechanism of action primarily involves inducing lipid peroxidation and blocking protoporphyrinogen oxidases. Toxicity of diphenyl ether herbicides has been elucidated in animal cells; however, in vivo toxicological evaluations of bifenox are required to determine its unexpected effects. This study aimed to determine the negative effects of bifenox, and its effects on higher eukaryotes. We found that early stages of zebrafish embryo exposed to bifenox demonstrated increased mortality and physiological defects, based on the LC50 value. Bifenox severely inhibited blood vessel growth by reducing key elements of complex connectivity; fluorescently tagged transgenic lines (fli1a:EGFP) showed morphological changes. Additionally, transgenic lines that selectively identified hepatocytes (fabp10a:DsRed) showed reduced fluorescence, indicating that bifenox may inhibit liver development. To evaluate the level of oxidative stress, we used 2',7'-dichlorofluorescein diacetate (DCFH-DA) probes in zebrafish embryos to identify the underlying mechanisms causing developmental damage. Our findings demonstrate that exposure to bifenox causes abnormalities in the hepatic and cardiovascular systems during zebrafish embryogenesis. Therefore, this study provides new information for the evaluation of toxicological risks of bifenox in vertebrates.

Non-clinical safety assessment of Annona atemoya leaf extract: evaluation of genotoxicity

The leaves, stems, and fruits of Annona atemoya (A. atemoya; AA), a fruit-bearing plant of the family Annonaceae, exhibit anti-angiogenic, anti-oxidative, anti-inflammatory, and neuroprotective activities. However, the safety of AA has not been comprehensively elucidated. In this study, we evaluated the potential genotoxicity of an AA leaf (AAL) ethanol extract using a standard three-test battery constituting in vitro mammalian chromosomal aberration, in vivo micronucleus, and bacterial reverse mutation (also known as the Ames test) tests, as recommended by the Ministry of Food and Drug Safety of Korea. In vitro chromosomal aberration assay revealed that AAL extract did not induce structural or numerical aberrations, with or without metabolic activation (S9). In vivo micronucleus assay revealed that the number of micronucleated polychromatic erythrocytes (PCEs) and the PCE/normochromatic erythrocyte ratio after AAL extract treatment were not substantially different from those in the negative control. Changes in body weight and mortality were not observed. However, AAL extract partially induced mutagenic activity in all three bacterial strains in the bacterial reverse mutation assay, indicating that it could potentially aid in determining the genotoxic safety of AAL. QuantSeq 3' mRNA sequencing analysis to elucidate the genotoxicity mechanisms of AAL extract using TK6 cells revealed that the genotoxic effects of AAL may be associated with cellular morphology-associated (cell development and keratinization), nucleotide metabolism, and electron transport chain functions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-024-00241-4.

Developmental toxicity and potential mechanisms exposed to polystyrene microplastics and polybrominated diphenyl ethers during early life stages of fat greenling (Hexagrammos otakii)

The occurrence of microplastics (MPs) in aquatic ecosystems and their ability to absorb hydrophobic pollutants, such as persistent organic pollutants (POPs), is currently a significant concern. MPs, which are the main breakdown product of plastics, have been frequently detected in the environment, posing serious threats to organisms' health. One particular pollutant, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), is a dominant congener of PBDEs and is highly toxic to organisms. However, there is limited knowledge regarding the exposure of marine fishes to PBDEs through MPs and their combined toxic effects. In this study, the embryo toxicity of Hexagrammos otakii was conducted to investigate the combined effects of MPs and BDE-47. The results showed that MPs and BDE-47 co-exposure had detrimental effects on embryonic development, such as reduced hatchability, increased mortality, decreased heart rate, and body malformation. Moreover, the combined toxicity of these substances appeared more pronounced harmful effects compared to exposure to BDE-47 alone. Histopathological examination revealed that co-exposure can cause greater damage to hatching glands and yolk. The enrichment of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways included phagosome, metabolism of xenobiotics by cytochrome P450, TCA cycle, and Wnt signaling pathway, which are closely related to embryonic growth. BDE-47 and MPs may activate the Wnt signaling pathway to affect the normal development of embryos. Our results suggest that MPs and BDE-47 exposure may cause growth disorders in the early life stages of H.otakii, leading to abnormal embryonic development. All these results will contribute to the further study of the ecological risk assessment and toxicity of MPs and organic pollutant mixtures in marine fish.

Hexaconazole induces developmental toxicities via apoptosis, inflammation, and alterations of Akt and MAPK signaling cascades

Hexaconazole is a highly effective triazole fungicide that is frequently applied in various countries to elevate crop productivity. Given its long half-life and high water solubility, this fungicide is frequently detected in the environment, including water sources. Moreover, hexaconazole exerts hazardous effects on nontarget organisms. However, little is known about the toxic effects of hexaconazole on animal development. Thus, this study aimed to investigate the developmental toxicity of hexaconazole to zebrafish, a valuable animal model for toxicological studies, and elucidate the underlying mechanisms. Results showed that hexaconazole affected the viability and hatching rate of zebrafish at 96 h postfertilization. Hexaconazole-treated zebrafish showed phenotypic defects, such as reduced size of head and eyes and enlarged pericardiac edema. Moreover, hexaconazole induced apoptosis, DNA fragmentation, and inflammation in developing zebrafish. Various organ defects, including neurotoxicity, cardiovascular toxicity, and hepatotoxicity, were observed in transgenic zebrafish models olig2:dsRed, fli1:eGFP, and l-fabp:dsRed. Furthermore, hexaconazole treatment altered the Akt and MAPK signaling pathways, which possibly triggered the organ defects and other toxic mechanisms. This study demonstrated the developmental toxicity of hexaconazole to zebrafish and elucidated the underlying mechanisms.

High-Resolution Respirometry for the Assessment of Teratogenic Chemicals

Pesticides are often used in agriculture and residential areas to mitigate pests and weeds. These chemicals can enter aquatic ecosystems via runoff and rain events, exerting negative effects on aquatic species. In rapidly developing fish embryos, metabolic disruption can alter the developmental trajectory and alter ATP levels. Therefore, it is important to quantify mitochondrial integrity in organisms following exposure to pesticides. To achieve this, a high throughput method to assess pesticide effects on oxidative phosphorylation and mitochondria has been optimized for fish embryos. Fish embryos are first exposed to pesticides for 24 or 48 h, and oxygen consumption rates are measured using the Seahorse XFe24/96 Flux Analyzer (formerly Seahorse Biosciences, now Agilent). The assay utilizes a single embryo and precisely measures oxygen consumption and extracellular acidification. Based upon these measurements, characteristics related to mitochondrial bioenergetics are calculated to provide information on mitochondrial integrity. Using this approach, one can identify pesticides affecting the electron transport chain and ultimately ATP production. In this chapter, we describe the mitochondrial stress test to understand mitochondrial dysfunction and metabolic shifts within the fish embryo.

Mevinphos induces developmental defects via inflammation, apoptosis, and altered MAPK and Akt signaling pathways in zebrafish

Mevinphos, an organophosphate insecticide, is widely used to control pests and enhance crop yield. Because of its high solubility, it can easily flow into water and threaten the aquatic environment, and it is known to be hazardous to non-target organisms. However, little is known about its developmental toxicity and the underlying toxic mechanisms. In this study, we utilized zebrafish, which is frequently used for toxicological research to estimate the toxicity in other aquatic organisms or vertebrates including humans, to elucidate the developmental defects induced by mevinphos. Here, we observed that mevinphos induced various phenotypical abnormalities, such as diminished eyes and head sizes, shortened body length, loss of swim bladder, and increased pericardiac edema. Also, exposure to mevinphos triggered inflammation, apoptosis, and DNA fragmentation in zebrafish larvae. In addition, MAPK and Akt signaling pathways, which control apoptosis, inflammation, and proper development of various organs, were also altered by the treatment of mevinphos. Furthermore, these factors induced various organ defects which were confirmed by various transgenic models. We identified neuronal toxicity through transgenic olig2:dsRed zebrafish, cardiovascular toxicity through transgenic fli1:eGFP zebrafish, and hepatotoxicity and pancreatic toxicity through transgenic lfabp:dsRed;elastase:GFP zebrafish. Overall, our results elucidated the developmental toxicities of mevinphos in zebrafish and provided the parameters for the assessment of toxicities in aquatic environments.

Toxicity effects of pesticides based on zebrafish (Danio rerio) models: Advances and perspectives

Pesticides inevitably enter aquatic environments, posing potential risks to organisms. The common aquatic model organism, zebrafish (Danio rerio), are widely used to evaluate the toxicity of pesticides. In this review, we searched the Web of Science database for articles published between 2012 and 2022, using the keywords "pesticide", "zebrafish", and "toxicity", retrieving 618 publications. Furthermore, we described the main pathways by which pesticides enter aquatic environments and the fate of their residues in these environments. We systematically reviewed the toxicity effects of pesticides on zebrafish, including developmental toxicity, endocrine-disrupting effects, reproductive toxicity, neurotoxicity, immunotoxicity, and genotoxicity. Importantly, we summarized the latest research progress on the toxicity mechanism of pesticides to zebrafish based on omics technologies, including transcriptomics, metabolomics, and microbiomics. Finally, we discussed future research prospects, focusing on the combined exposure of multiple pollutants including pesticides, the risk of multigenerational exposure to pesticides, and the chronic toxicity of aquatic nanopesticides. This review provides essential data support for ecological risk assessments of pesticides in aquatic environments, and has implications for water management in the context of pesticide pollution.

Fluchloralin induces developmental toxicity in heart, liver, and nervous system during early zebrafish embryogenesis

The zebrafish is a prominent vertebrate model popularly used for toxicity testing because of its rapid development and transparent embryos. Fluchloralin, a dinitroaniline herbicide used to control weeds, inhibits microtubule formation and cell division. The structurally homologous substances ethalfluralin and pendimethalin, which belong to the dinitroaniline family, were found to be genotoxic and to exert developmental toxicity via mitochondrial dysfunction in a zebrafish model. To date, developmental toxicity of fluchloralin in zebrafish has not been reported. In the present study, we identified morphological changes in developing zebrafish, including decreased survival rate and body length, and increased yolk sac edema. In dose-dependent response to fluchloralin exposure, inhibition of neurogenesis in the spinal cord and motor neuron defects were observed in transgenic zebrafish models (olig2:dsRed). Zebrafish exposed to fluchloralin also displayed organ dysfunction in the heart, liver, and pancreas in cmlc2:dsRed and lfabp:dsRed;elastase:GFP transgenic models. Fluchloralin increased cell death in the brain by promoting apoptosis, visualized via acridine orange staining, and by activating apoptosis signaling proteins, including cytochrome c1, zBax, and Bcl-XL. This study provides novel evidence supporting the necessity of controlling pollutants in aquatic environments.

Mitochondrial dysfunction in metabolic disorders induced by per- and polyfluoroalkyl substance mixtures in zebrafish larvae

Several per- and polyfluoroalkyl substances (PFAS) have been linked to metabolic disorders in organisms. However, few studies have considered their combined effects, which would be more representative of PFAS occurring in the environment. In this study, zebrafish embryos were exposed to a mixture of 18 PFAS at three environmentally relevant concentrations for 5 days to assess their bioconcentration and metabolic consequences. The burdens of ∑PFAS in zebrafish larvae were 0.12, 1.58, and 9.63 mg/kg in the 0.5, 5, and 50 μg/L treatment groups, respectively. Exposure to the PFAS mixture accelerated hatching and larval heart rates, increased energy expenditure, and reduced ATP levels and glucose contents due to decreased feed intake and glucose uptake. Metabolomic analysis revealed that exposure to the PFAS mixture enhanced glycolysis but inhibited phospholipid synthesis, and significantly increased the expression of lipid metabolism related genes (srebf1, acox, and pparα), which indicated enhanced β-oxidation. The significant changes in mitochondrial membrane potential, mitochondrial content, and the transcription of genes involved in the mitochondrial respiratory chain (mfn2, ndufs1, atp5fa1, and mt-nd1) and mitochondrial DNA replication and transcription (18rs-rrn, and polg1) suggested that exposure to the PFAS mixture could cause mitochondrial dysfunction and further disrupt glucose and lipid metabolic pathways, ultimately causing metabolic disorders in zebrafish larvae. These findings demonstrate the importance of assessing the metabolic effects of PFAS mixtures on early development in wildlife and humans.

Reduction in the Use of Some Herbicides Favors Nitrogen Fixation Efficiency in Phaseolus vulgaris and Medicago sativa

In recent decades, the quality of agricultural soils has been seriously affected by the excessive application of pesticides, with herbicides being one of the most abundant. Continuous use of herbicides alters the soil microbial community and beneficial interactions between plants and bacteria such as legume-rhizobia spp. symbiosis, causing a decrease in the biological nitrogen fixation, which is essential for soil fertility. Therefore, the aim of this work was to study the effect of two commonly used herbicides (pendimethalin and clethodim) on the legume-rhizobia spp. symbiosis to improve the effectiveness of this process. Phaseolus vulgaris plants grown in pots with a mixture of soil:perlite (3:1 v/v), showed a 44% inhibition of nitrogen fixation rate with pendimethalin. However, clethodim, specifically used against monocots, did not induce significant differences. Additionally, we analyzed the effect of herbicides on root exudate composition, detecting alterations that might be interfering with the symbiosis establishment. In order to assess the effect of the herbicides at the early nodulation steps, nodulation kinetics in Medicago sativa plants inoculated with Sinorhizobium meliloti were performed. Clethodim caused a 30% reduction in nodulation while pendimethalin totally inhibited nodulation, producing a reduction in bacterial growth and motility as well. In conclusion, pendimethalin and clethodim application reduced the capacity of Phaseolus vulgaris and Medicago sativa to fix nitrogen by inhibiting root growth and modifying root exudate composition as well as bacterial fitness. Thus, a reduction in the use of these herbicides in these crops should be addressed to favor a state of natural fertilization of the soil through greater efficiency of leguminous crops.

Mepanipyrim induces cardiotoxicity of zebrafish (Danio rerio) larvae via promoting AhR-regulated COX expression pathway

The wide use of pesticides has seriously threatened human health and the survival of beneficial organisms. The fungicide mepanipyrim is widely used in viticulture practices. Studies of mepanipyrim-induced toxicity in organisms are still scarce, especially studies on cardiotoxicity. In this study, we aimed to investigate mepanipyrim-induced cardiotoxicity in zebrafish (Danio rerio) larvae. We found that mepanipyrim could induce cardiotoxicity by altering the heart rate and cardiomyocyte diameter of larvae. Meanwhile, RNA sequencing and RT-qPCR data indicated that mepanipyrim exposure could dramatically alter the mRNA expression of calcium signaling pathway-, cardiac muscle contraction-, and oxidative respiratory chain-related genes. Interestingly, by the CALUX cell bioassay, we found that most cytochrome c oxidase (COX) family genes exhibited potential AhR-regulated activity, suggesting that mepanipyrim induced cardiotoxicity via a novel AhR-regulated manner in larvae. Additionally, the AhR antagonist CH223191 could effectively prevent mepanipyrim-induced cardiotoxicity in zebrafish larvae. In conclusion, the AhR agonist mepanipyrim could induce cardiotoxicity in a novel unreported AhR-regulated manner, which could specifically affect the expression of COX family genes involved in the mitochondrial oxidative respiratory chain. Our data will help explain the toxic effects of mepanipyrim on organisms and provide new insight into the AhR agonistic activity pesticide-induced cardiotoxicity.

Triadimenol promotes the production of reactive oxygen species and apoptosis with cardiotoxicity and developmental abnormalities in zebrafish

Various types of fungicides, especially triazole fungicides, are used to prevent fungal diseases on farmlands. However, the developmental toxicity of one of the triazole fungicides, triadimenol, remains unclear. Therefore, we used the zebrafish animal model, a representative toxicological model, to investigate it. Triadimenol induced morphological alterations in the eyes and body length along with yolk sac and heart edema. It also stimulated the production of reactive oxygen species and expression of inflammation-related genes and caused apoptosis in the anterior regions of zebrafish, especially in the heart. The phosphorylation levels of Akt, ERK, JNK, and p38 proteins involved in the PI3K and MAPK pathways, which are important for the development process, were also reduced by triadimenol. These changes led to malformation of the heart and vascular structures, as observed in the flk1:eGFP transgenic zebrafish models and a reduction in the heart rate. In addition, the expression of genes associated with cardiac and vascular development was also reduced. Therefore, we elucidated the mechanisms associated with triadimenol toxicity that leads to various abnormalities and developmental toxicity in zebrafish.

Developmental toxicity of prometryn induces mitochondrial dysfunction, oxidative stress, and failure of organogenesis in zebrafish (Danio rerio)

Prometryn, 2-methylthio-4,6-bis(isopropylamino)-1,3,5-triazine, is a selective thiomethyl triazine herbicide widely used to control unwanted weeds and harmful insects by inhibiting electron transport in target organisms. Despite having various advantages, herbicides pose as a major threat to the environment and human health due to persistent contamination, bioaccumulation, and damage to non-target organisms. In this study, the developmental toxicity of 5, 10, and 20 mg/L prometryn in zebrafish (Danio rerio) embryos was evaluated and compared to that of the solvent control for 96 h. Several transgenic zebrafish models (fli1a:eGFP, flk1:eGFP, olig2:dsRed and L-fabp:dsRed) were visually assessed to detect fluorescently tagged genes. Results showed that prometryn shortened body length, and induced yolk sac, heart edema, abnormal heart rate, and loss of viability. Fluorescence microscopy revealed that prometryn exposure caused defects in organ development, reactive oxygen species accumulation, and apoptotic cell death. Mitochondrial bioenergetics were also evaluated to determine the effect of prometryn on the electron transport chain activity and metabolic alterations. Prometryn was found to interfere with mitochondrial function, ultimately inhibiting energy metabolism and embryonic development. Collectively, our findings suggest that prometryn is a potential contaminate for non-target sites and organisms, especially aquatic, and emphasize the need to consider the toxic effects of prometryn.

Ethalfluralin induces developmental toxicity in zebrafish via oxidative stress and inflammation

Ethalfluralin, of dinitroaniline herbicide family, is an effective weed controller. Following residue detection in herbicide-treated fields, ethalfluralin was reported to interfere with early stages of implantation in some vertebrate species. However, the role of ethalfluralin in the development of zebrafish embryos has not been elucidated yet. Therefore, in the present study, we investigated the morphological and physiological changes that occur in the embryonic development of zebrafish due to ethalfluralin exposure. Results indicated that ethalfluralin decreased survival rate along with reduction in the hatching ratio and heartbeat. It was observed to cause edema in the heart and yolk sac, and apoptosis in the anterior region of the developing zebrafish larvae; as visualized through acridine orange and TUNEL staining. In addition, ethalfluralin increased the expression of the apoptosis-associated genes including tp53, cyc1, casp8, casp9, and casp3. The Seahorse Mito Stress analysis revealed that ethalfluralin slightly reduced mitochondrial respiration in live zebrafish embryos. Reactive oxygen species (ROS) production was also observed to be elevated in zebrafish larvae in response to ethalfluralin. Treatment with ethalfluralin decreased blood vessel formation in brain and intestine in flk1 transgenic zebrafish embryos. The decrease in angiogenesis related gene expression was specifically observed in vegfc, flt1, and kdrl, and in the intestinal vasculature related genes apoa4a, aqp3, fabp2, and vil1. Moreover, an increase in inflammatory genes such as cox2a, cox2b, cxcl-c1c, il8, mcl1a, mcl1b, and nf-κb was observed using real-time PCR analysis. Collectively, these results indicate that oxidative stress generated by exposure to ethalfluralin induced ROS generation, apoptosis, inflammation and anti-angiogenic effects, and therefore, ethalfluralin may be toxic to the development of zebrafish embryos.

Pendimethalin exposure induces bovine mammary epithelial cell death through excessive ROS production and alterations in the PI3K and MAPK signaling pathways

Herbicides are chemicals that have been established to have adverse impacts. However, they are still widely used in agriculture. Pendimethalin (PDM) is an herbicide that is widely used in many countries to control annual grasses. The possibility of livestock being exposed to PDM is relatively high, considering the half-life of PDM and its residues in water, soil and crops. However, the toxicity of PDM in cattle, especially in the mammary glands, has not been reported. Therefore, we investigated whether PDM has toxic effects in the mammary epithelial cells (MAC-T) of cattle. MAC-T cells were treated with various doses (0, 2.5, 5 and 10 μM) of PDM. We found that PDM affected cell viability and cell proliferation and causes cell cycle arrest. Furthermore, PDM triggered cell apoptosis, induced excessive ROS production and mitochondrial membrane potential (MMP) loss, and disrupted calcium homeostasis. In addition, PDM altered the activation of proteins associated with the endoplasmic reticulum (ER) stress response and modified PI3K and MAPK signaling cascades. In conclusion, our current study unveiled the mechanism of PDM in MAC-T cells and we suggest that PDM might be harmful to the mammary gland system of cattle, possibly affecting milk production.

Tox21-Based Comparative Analyses for the Identification of Potential Toxic Effects of Environmental Pollutants

Chemical pollution has become a prominent environmental problem. In recent years, quantitative high-throughput screening (qHTS) assays have been developed for the fast assessment of chemicals' toxic effects. Toxicology in the 21st Century (Tox21) is a well-known and continuously developing qHTS project. Recent reports utilizing Tox21 data have mainly focused on setting up mathematical models for in vivo toxicity predictions, with less attention to intuitive qHTS data visualization. In this study, we attempted to reveal and summarize the toxic effects of environmental pollutants by analyzing and visualizing Tox21 qHTS data. Via PubMed text mining, toxicity/structure clustering, and manual classification, we detected a total of 158 chemicals of environmental concern (COECs) from the Tox21 library that we classified into 13 COEC groups based on structure and activity similarities. By visualizing these COEC groups' bioactivities, we demonstrated that COECs frequently displayed androgen and progesterone antagonistic effects, xenobiotic receptor agonistic roles, and mitochondrial toxicity. We also revealed many other potential targets of the 13 COEC groups, which were not well illustrated yet, and that current Tox21 assays may not correctly classify known teratogens. In conclusion, we provide a feasible method to intuitively understand qHTS data.

Pendimethalin induces apoptotic cell death through activating ER stress-mediated mitochondrial dysfunction in human umbilical vein endothelial cells

Pendimethalin is globally registered for control of a wide range of weeds in agriculture and home landscaping. Human exposure to pendimethalin can occur by the oral route through food and other sources. Endothelial function is vital to numerous biological processes, and endothelial dysfunction and poor vascular health is associated with increased atherosclerotic events; however, no study has yet investigated the potential effect of pendimethalin on endothelial function and vasculature formation. The objective of the current study is to investigate if pendimethalin may affect the viability and function of vascular endothelial cells. We observed that pendimethalin significantly repressed viability of human endothelial cells, inducing G1 cell cycle arrest and apoptotic/necrotic cell death. Pendimethalin treatment also activated ER stress and autophagy, leading to loss of mitochondrial membrane potential. In addition, pendimethalin impaired the tube forming and migratory abilities of endothelial cells. This study provides previously unrecognized adverse effects of pendimethalin in vascular endothelial cells, mediated by ER stress-induced mitochondrial dysfunction.

ROS antagonizes the protection of Parkin-mediated mitophagy against aluminum-induced liver inflammatory injury in mice

Aluminum (Al) is a food pollutant that has extensive deleterious effects on the liver. Our previous research proposed that E3 ubiquitin ligase PARK2 knockout (Parkin^-/-) could aggravate Al-induced liver damage by inhibiting mitophagy, during which the reactive oxygen species (ROS) content increases. Inhibition of mitophagy can activate inflammasome. But the link between Parkin-mediated mitophagy and liver inflammatory injury caused by Al, and the role of ROS in it remain unclear. In this study, we applied Al, Parkin^-/- and N-acetyl-L-cysteine (NAC) to act on C57BL/6N mice to investigate them. We found that Al could induce liver inflammatory injury and Parkin^-/- could aggravate it. Meanwhile, inhibition of ROS alleviated oxidative stress, mitochondrial damage, mitophagy and inflammatory injury caused by Al in Parkin^-/- mice liver. These results indicated that ROS antagonized the protection of Parkin-mediated mitophagy against Al-induced liver inflammatory damage in mice.

Elimination of Pendimethalin in Integrated Rice and Procambarus clarkii Breeding Models and Dietary Risk Assessments

This study investigated elimination of the herbicide pendimethalin using an integrated rice and Procambarus clarkii breeding model of indoor and outdoor (pond culture) exposure tests. The pendimethalin levels in 484 samples from the primary rice and P. clarkii integrated breeding areas in Hubei province were monitored, and dietary risk assessments of pendimethalin were calculated. Pendimethalin was quantified using high-performance liquid chromatography tandem mass spectrometry, and detection levels were linear in the range of 1.0 to 10.0 μg/L, and peak areas were positively correlated with concentration, with a correlation coefficient of 0.9996. Recoveries ranged from 86.9 to 103.5%, and the limit of quantitation was 2.5 × 10⁻⁴ μg/L in water, and 1 × 10⁻² μg/kg in tissues, sediments, and waterweeds. The dissipation rate of pendimethalin in tissues and water followed first-order kinetics, with half-lives of 0.51–5.64 d. In 484 samples taken from aquaculture farms, pendimethalin was detected in 8.67% of the samples at levels in the range of 1.95 to 8.26 μg/kg in Hubei province from 2018 to 2020. The maximum residue limit of pendimethalin in P. clarkii has not been established in China, but our dietary risk assessments indicated that consumption of P. clarkii from integrated rice farms was acceptable.

Clinicohematological, Mutagenic, and Oxidative Stress Induced by Pendimethalin in Freshwater Fish Bighead Carp (Hypophthalmichthys nobilis)

Currently, aquatic and terrestrial ecosystems are continuously and chronically polluted by cocktails of countless chemical compounds. The susceptibility to infections is tremendously increasing in a variety of organisms due to exposure to environmental pollutants. Pendimethalin, an herbicide, is continuously used in agriculture to remove unwanted broadleaf weeds across the globe. Therefore, this study investigates the mechanisms of toxicity of pendimethalin in freshwater fish bighead carp upon exposure to low and environmentally relevant concentrations. For this purpose, 48 fish without any clinical abnormalities were kept in a glass aquarium in different experimental groups (T0, T1, T2, and T3). These groups were treated with pendimethalin at 0.00, 0.25, 0.50, and 0.75 mg/L, respectively. Four fish were randomly picked from each experimental group and killed at 72, 96, and 120 hours of the trial to study hematobiochemical parameters and visceral tissues including the brain, liver, heart, gills, and kidneys for histopathology. Herbicide-treated fish indicated various physical and behavioral abnormalities including hypersecretion of mucus, erratic swimming, operculum movement, air gulping, tremors of fins, loss of equilibrium, and increased surface breathing. Histopathologically, gills tissues of treated fish indicated atrophied lamellae, uplifting of secondary lamellae, necrosis of primary and secondary lamellar epithelial cells, telogenesis, congestion, and lamellar fusion. Histopathological examination of liver tissues of treated fish showed mild to moderate congestion, necrosis of hepatocytes, and atrophy of hepatocytes while kidneys revealed degeneration of renal tubules, glomerular atrophy, ceroid, and necrosis of renal tubules. The erythrocyte counts, monocyte and lymphocyte counts, and hemoglobin values were significantly (P < 0.05) reduced in pendimethalin-treated fish. Results on serum biochemistry showed that the biomarkers of kidneys, heart, and liver were significantly higher in fish of treated groups. In addition, values of different biochemical reactions like reactive oxygen species (ROS), thiobarbituric acid reactive species (TBARS), total proteins, and quantity of different antioxidant enzymes including reduced glutathione (GSH), catalase, and superoxide dismutase (SOD) were significantly different when compared to untreated fish. Moreover, the percentile of different nuclear abnormalities in red blood cells and frequency of DNA damage increased significantly in treated fish. It can be concluded from the findings that pendimethalin causes its toxic effects via disruption of physiological and hematobiochemical reactions of fish.

The effects of beta-cypermethrin, chlorbenzuron, chlorothalonil, and pendimethalin on Apis mellifera ligustica and Apis cerana cerana larvae reared in vitro

BACKGROUND

Declines in bee populations and diversity have drawn international attention. The long-term use of chemical pesticides has affected bee behavior and physiology. This study aimed to investigate the effects of chronic exposure to four commonly used chemical pesticides (beta-cypermethrin, chlorbenzuron, chlorothalonil and pendimethalin) on the growth of Apis mellifera ligustica and Apis cerana cerana larvae reared in vitro.

RESULTS

Pesticide type and concentration were the main factors affecting honeybee fitness. Beta-cypermethrin and chlorbenzuron had chronic toxic effects on bee larvae. They reduced the fitness of A. m. ligustica and A. c. cerana even at low doses of 323.5 ng g^-1 for beta-cypermethrin and 62.6 ng g^-1 for chlorbenzuron in bee bread. The effects were positively associated with the dietary amounts of pesticides. By contrast, chlorothalonil and pendimethalin exposure did not affect bee larvae despite changes in enzyme activities. Caution is still needed with chlorothalonil, which led to a decrease in harvest adult bee numbers at a high dose (6937.2 ng g^-1 ). Furthermore, a difference in pesticide resistance was observed, suggesting that A. m. ligustica may tolerate toxic effects better than A. c. cerana.

CONCLUSION

This study sheds new light on chronic toxicity in bee larvae exposed to residues in bee bread. The results could guide the scientific and rational use of chemical pesticides to reduce the potential risks to A. m. ligustica and A. c. cerana. © 2021 Society of Chemical Industry.

Developmental toxicity of fenbuconazole in zebrafish: effects on mitochondrial respiration and locomotor behavior

Triazole fungicides are used to control the disease of cereal crops but may also cause adverse effects on non-target organisms. There is a lack of toxicity data for some triazoles such as fenbuconazole in aquatic organisms. This research was conducted to evaluate the toxicity of fenbuconazole at environmentally relevant concentrations with attention on the mitochondria, antioxidant system, and locomotor activity in zebrafish. Zebrafish were exposed to one concentration of 5, 50, 200 or 500ng/L fenbuconazole for 96h. There was no effect on survival nor percentage of fish hatched, but exposure to 200 and 500ng/L fenbuconazole resulted in malformation and hypoactivity in zebrafish. Oxygen consumption rates (OCR) of embryos were measured to determine if the fungicide impaired mitochondrial respiration. Exposure to 500ng/L fenbuconazole reduced basal OCR and oligomycin-induced ATP linked respiration in exposed fish. Fenbuconazole reduced mitochondrial membrane potential and reduced the activities of mitochondrial Complex II and III. Transcript levels of both sdhc and cyc1, each related to Complex II and III, were also altered in expression by fenbuconazole exposure, consistent with mitochondrial dysfunction in embryos. Fenbuconazole activated the antioxidant system, based upon both transcriptional and enzymatic data in zebrafish. Consistent with mitochondrial impairment, molecular docking confirmed a strong binding capacity of the fungicide at the Q_i site of Complex III, revealing this complex is susceptible to fenbuconazole. This study reveals potential toxicity pathways related to fenbuconazole exposure in aquatic organisms; such data can improve risk assessments for triazole fungicides.

Study of the inhibitory effects of chrysin and its nanoparticles on mitochondrial complex II subunit activities in normal mouse liver and human fibroblasts

BACKGROUND

Mitochondrial complex ΙΙ has a unique biological role owing to its participation in both the citric acid cycle and the electron transport chain. Our goal was to evaluate the succinate dehydrogenase and ubiquinone oxidoreductase activity of mitochondrial complex II in the presence of chrysin and chrysin-chitosan nanoparticles. Chrysin chitosan nanoparticles were synthesized and characterized using ultraviolet spectroscopy, Fourier transform-infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, drug release, and zeta potential. The binding affinity of chrysin to complex II subunits was assessed by molecular docking. The IC50 values were measured in a suspension of mouse mitochondria, and the inhibitory effect of chrysin and chrysin chitosan nanoparticles on mitochondrial complex ΙΙ was determined.

RESULTS

The free energy of binding between chrysin and complex ΙΙ subunits A, B, C, and D was -4.9, -5, -8.2, and -8.4 kcal/mol, respectively. The characteristic peak of chrysin was confirmed at 348 nm. The chrysin chitosan nanoparticles contained characteristic bands of both chrysin and chitosan. The crystalline nature of chrysin chitosan nanoparticles was confirmed by X-ray powder diffraction measurements showing the characteristic Bragg peaks of (11.2°), (32.2°), (19.6°), (27.6°), and (31.96°). Transmission and scanning electron microscopy revealed their spherical shape and an average particle size of 49.7 ± 3.02 nm. Chrysin chitosan nanoparticles showed a burst release within the initial 2 h followed by a steady release at 8 h. Their zeta potential was positive, between +35.5 and +80 mV. The IC50 of chrysin, chitosan nanoparticles, chrysin chitosan nanoparticles, and 5-fluorouracil was 34.66, 184.1, 12.2, and 0.05 μg/mL, respectively, in adult mice liver and 129, 311, 156, and 8.07 μg/mL, respectively, in normal human fibroblasts. When comparing the inhibitory effects on complex ΙΙ activity, application of the IC50 of chrysin, chitosan nanoparticles, chrysin chitosan nanoparticles, and 5-fluorouracil resulted in 40.14%, 90.9%, 86.7%, and 89% decreases in SDH activity and 70.09%, 86.74%, 60.8%, and 80.23% decreases in ubiquinone oxidoreductase activity in normal adult mice, but 80.9%, 89.06%, and 90% significant decreases in SDH activity, and 90%, 85%, and 95% decreases in ubiquinone reductase after treatment with chrysin, chrysin chitosan nanoparticles, and 5-fluorouracil, in normal human fibroblasts, respectively.

CONCLUSIONS

Chrysin and CCNPs exhibit potent inhibitory effects on SDH activity ubiquinone oxidoreductase activity.

Combined Developmental Toxicity of the Pesticides Difenoconazole and Dimethomorph on Embryonic Zebrafish

Difenoconazole (DIF) and dimethomorph (DIM) are widely used pesticides frequently detected together in environmental samples, so the deleterious effects of combined exposure warrant detailed examination. In this study, the individual and combined effects of DIM and DIF on conventional developmental parameters (hatching rate, deformity rate, lethality) and gene expression were measured in embryonic zebrafish. Both DIF and DIM interfered with normal zebrafish embryo development, and the most sensitive toxicity index for both was 96 h post-fertilization (hpf) deformity rate (BMDL₁₀ values of 0.30 and 1.10 mg/L, respectively). The combination of DIF and DIM had mainly synergistic deleterious effects on 96 hpf deformity and mortality rates. Transcriptome analysis showed that these compounds markedly downregulated expression of mcm family genes, cdk1, and cdc20, thereby potentially disrupting DNA replication and cell cycle progression. Enhanced surveillance for this pesticide combination is recommended as simultaneous environmental exposure may be substantially more harmful than exposure to either compound alone.

Assessing sub-lethal effects of the dinitroaniline herbicide pendimethalin in zebrafish embryos/larvae (Danio rerio)

Pendimethalin is a dinitroaniline herbicide used to control broadleaf weeds by inhibiting the formation of microtubules during cell division. Its use on a variety of crops leads to its potential entry into aquatic environments, but little is known about its sub-lethal toxicity to early developmental stages of aquatic vertebrates. To address this knowledge gap, we assessed the toxicity of pendimethalin to zebrafish embryos and larvae by measuring mortality, developmental abnormalities, oxidative respiration, reactive oxygen species, gene expression, and locomotor activity following exposure to the herbicide throughout early development. Embryos at ~6 h post-fertilization (hpf) were exposed to either a solvent control (0.1% DMSO, v/v), embryo rearing medium (ERM), or one dose of either 1, 2.5, 5, or 25 μM pendimethalin for up to 7-days post fertilization depending on the bioassay. Exposure to 25 μM pendimethalin resulted in high prevalence of spinal curvature, tail malformations, pericardial edema, and yolk sac edema at 4 dpf, while exposure to 5 μM pendimethalin induced pericardial edema and lordosis in the fish exposed over 7 dpf. Exposure to pendimethalin up to 5 μM did not negatively impact oxidative respiration (e.g., basal respiration, oligomycin-induced ATP production) in embryos following a 24-h exposure. Pendimethalin did not induce reactive oxygen species at concentrations of 1-5 μM. Levels of transcripts associated with oxidative respiration and damage response were altered in 7d-larvae; cox1 mRNA was increased in larvae fish exposed to 1 μM while cox5a1 and sod2 mRNA were decreased with 2.5 μM exposure. The Visual Motor Response (VMR) test for light-dark response revealed that larval activity in the dark period was reduced for zebrafish exposed to >1 μM pendimethalin compared to ERM and DMSO solvent control groups. These data inform on the sub-lethal toxicity of pendimethalin to early stages of fish embryos and larvae.

Dinitramine induces cardiotoxicity and morphological alterations on zebrafish embryo development

Dinitramine (DN), an herbicide in the dinitroaniline family, is used in agricultural areas to prevent unwanted plant growth. Dinitroaniline herbicides inhibit cell division by preventing microtubulin synthesis. They are strongly absorbed by the soil and can contaminate groundwater; however, the mode of action of these herbicides in non-target organisms remains unclear. In this study, we examined the developmental toxicity of DN in zebrafish embryos exposed to 1.6, 3.2, and 6.4 mg/L DN, compared to embryos exposed to DMSO (control) for 96 h. Visual assessments using transgenic zebrafish (fli1:eGFP) indicated abnormal cardiac development with enlarged ventricles and atria, decreased heartbeats, and impaired cardiac function. Along with cardiac development, vessel formation and angiogenesis were suppressed through activation of the inflammatory response. In addition, exposure to 6.4 mg/L DN for 96 h induced cell death, with upregulation of genes related to apoptosis. Our results showed that DN induced morphological changes and triggered an inflammatory response and apoptotic cell death that can impair embryonic growth and survival, providing an important mechanism of DN in aquatic organisms.

Improving pollutants environmental risk assessment using a multi model toxicity determination with in vitro, bacterial, animal and plant model systems: The case of the herbicide alachlor

Several environmental pollutants, including pesticides, herbicides and persistent organic pollutants play an important role in the development of chronic diseases. However, most studies have examined environmental pollutants toxicity in target organisms or using a specific toxicological test, losing the real effect throughout the ecosystem. In this sense an integrative environmental risk of pollutants assessment, using different model organisms is necessary to predict the real impact in the ecosystem and implications for target and non-target organisms. The objective of this study was to use alachlor, a chloroacetanilide herbicide responsible for chronic toxicity, to understand its impact in target and non-target organisms and at different levels of biological organization by using several model organisms, including membranes of dipalmitoylphosphatidylcholine (DPPC), rat liver mitochondria, bacterial (Bacillus stearothermophilus), plant (Lemna gibba) and mammalian cell lines (HeLa and neuro2a). Our results demonstrated that alachlor strongly interacted with membranes of DPPC and interfered with mitochondrial bioenergetics by reducing the respiratory control ratio and the transmembrane potential. Moreover, alachlor also decreased the growth of B. stearothermophilus and its respiratory activity, as well as decreased the viability of both mammalian cell lines. The values of TC₅₀ increased in the following order: Lemna gibba < neuro2a < HeLa cells < Bacillus stearothermophilus. Together, the results suggest that biological membranes constitute a putative target for the toxic action of this lipophilic herbicide and point out the risks of its dissemination on environment, compromising ecosystem equilibrium and human health.