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

ADB-FUBINACA-induced developmental toxicity, neurotoxicity, and cardiotoxicity in embryonic zebrafish (Danio rerio)

As an emerging pollutant, the synthetic cannabinoid N-(1-amino-3,3-dimethyl-1-oxobutan-2-yl)-1-(4-fluorobenzyl)-1H-indazole-3-carboxamide (ADB-FUBINACA) is widely abused and frequently detected in metropolitan wastewater. However, its effect on aquatic organisms remains unexplored. In this study, embryonic and larval zebrafish were exposed to sublethal concentrations of ADB-FUBINACA to assess its toxic effects via behavioral, biochemical, and metabolomic analyses. The observed morphological defects included reduced heartbeat, shorter body length, spinal deformation, and pericardial edema. Transgenic zebrafish exhibited cardiac developmental defects and apoptosis, indicating that cardiotoxicity is associated with dysregulated gene expression. Impaired motor activity and disrupted neuronal development suggested neurotoxicity. Elevated reactive oxygen species (ROS) and malondialdehyde (MDA) levels indicate oxidative stress, whereas transcriptional changes in immune-related genes reflect a dysregulated inflammatory response. Metabolomic analyses revealed disruptions in pathways related to alanine, purine, and pyrimidine metabolism, and arginine biosynthesis, which correlated with oxidative damage, cardiotoxicity, and neurodevelopmental effects. In conclusion, ADB-FUBINACA induces developmental toxicity in zebrafish embryos via oxidative stress and metabolic disruption, highlighting the potential environmental risks posed by this emerging pollutant.

Propanil impairs organ development in zebrafish by inducing apoptosis and inhibiting mitochondrial respiration

Propanil, an anilide herbicide, has frequently been detected in surface waters in Europe and the United States, largely due to its use in paddy cultivation areas. Particularly in specific regions like Sri Lanka, propanil is considered a potential cause of certain diseases and toxicities due to its high environmental runoff; however, there has been little research on its developmental toxicity. In the present study, we confirmed the developmental toxicity of propanil in zebrafish embryos exposed to 0, 2, 5, and 6 mg/L based on the LC50 value. Propanil exposure in embryos induced morphological changes, including decreased body length and eye size, and increased the heart and yolk sac edema. It increased the number of apoptotic cells in the brains and eyes of zebrafish larvae by 214 % and 184 %, respectively. Propanil-treated embryos exhibited altered mitochondrial metabolism, reducing basal respiration by 28 %, maximal respiration by 24 %, and ATP production by 38 %. These alterations induced organ defects in transgenic zebrafish models (cmlc2:DsRed, flk1:EGFP, olig2:DsRed, lfabp:DsRed;elastase:EGFP, and insulin:EGFP). It induced cardiovascular toxicity, as confirmed by the reduced atrial area, cerebrovascular intensity, and intersegmental vessels. Additionally, propanil decreased the fluorescence intensity of neurons, liver, and pancreas. Collectively, this study indicates that propanil causes early developmental toxicity through apoptosis and mitochondrial dysfunction. It presents a new perspective on how mitochondrial dysfunction, previously unreported in toxicity studies of other anilide herbicides, may affect developmental toxicity.

Evaluation of organ developmental toxicity of environmental toxicants using zebrafish embryos

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

Pyraclostrobin induces developmental toxicity and cardiotoxicity through oxidative stress and inflammation in zebrafish embryos

Pyraclostrobin, a typical representative of strobilurin fungicides, is extensively used in agriculture to control fungi and is often detected in water bodies and food. However, the comprehensive toxicological molecular mechanism of pyraclostrobin requires further study. To assess the toxic effects and underlying mechanisms of pyraclostrobin on aquatic organisms, zebrafish embryos were exposed to pyraclostrobin (20, 40, and 60 μg/L) until 96 h post fertilization (hpf). These results indicated that exposure to pyraclostrobin induces morphological alterations, including spinal curvature, shortened body length, and smaller eyes. Furthermore, heart developmental malformations, such as pericardial edema and bradycardia, were observed. This indicated severe cardiotoxicity induced by pyraclostrobin in zebrafish embryos, which was confirmed by the dysregulation of genes related to heart development. Besides, our findings also demonstrated that pyraclostrobin enhanced the contents of reactive oxygen species (ROS) and malondialdehyde (MDA), up-regulated catalase (CAT) activity, but inhibited superoxide dismutase (SOD) activity. Subsequently, the NF-κb signaling pathway was further studied, and the results indicated that the up-regulation of tnf-α, tlr-4, and myd88 activated the NF-κb signaling pathway and up-regulated the relative expression level of pro-inflammatory cytokines, such as cc-chemokine, ifn-γ, and cxcl-clc. Collectively, this study revealed that pyraclostrobin exposure induces developmental toxicity and cardiotoxicity, which may result from a combination of oxidative stress and inflammatory responses. These findings provide a basis for continued evaluation of the effects and ecological risks of pyraclostrobin on the early development of aquatic organisms.

Occurrence, sources and transport of triazine herbicides in the Antarctic marginal seas

The extensively applied triazine herbicides are easily transported by ocean currents over long distances. This study analyzed ten triazine herbicides in the Antarctic marginal seas and the Southern Indian Ocean during the austral summer for the first time, addressing their largely unexplored behavior in remote marine environments. The total triazine herbicides showed great spatial heterogeneity, with a range of 20-790 pg/L and an average of 31 ± 66 pg/L. The waterborne transport of triazine herbicides in the Antarctic was affected by hydrological processes, especially the blocking and accumulation effect of the polar front. Variations in sea ice extent and temperature were also important influencing factors, resulting in elevated triazine herbicides in surface seawater of East Antarctica, but reduced levels in West Antarctica. Furthermore, the source apportionment results indicated that approximately 55 % of the herbicides originated from sugarcane cultivation, 28 % from algaecide use, and 16 % from corn and sorghum farming.

Long-term exposure to prometryn damages the visual system and changes color preference of female zebrafish (Danio rerio)

Color vision, initiated from the cone photoreceptors, is essential for fish to obtain environmental information. Although the visual impairment of triazine herbicide prometryn has been reported, data on the effect of herbicide such as prometryn on natural color sensitivity of fish is scarce. Here, zebrafish were exposed to prometryn (0, 1, 10, and 100 μg/L) from 2 h post-fertilization to 160 days post-fertilization, to explore the effect and underlying mechanism of prometryn on color perception. The results indicated that 10 and 100 μg/L prometryn shortened the height of red-green cone cells, and down-regulated expression of genes involved in light transduction pathways (arr3a, pde6h) and visual cycle (lrata, rpe65a); meanwhile, 1 μg/L prometryn increased all-trans-retinoic acid levels in zebrafish eyes, and up-regulated the expression of genes involved in retinoid metabolism (rdh10b, aldh1a2, cyp26a1), finally leading to weakened red and green color perception of female zebrafish. This study first clarified how herbicide such as prometryn affected color vision of a freshwater fish after a long-term exposure from both morphological and functional disruption, and its hazard on color vision mediated-ecologically relevant tasks should not be ignored.

Triazine herbicide prometryn alters epoxide hydrolase activity and increases cytochrome P450 metabolites in murine livers via lipidomic profiling

Oxylipins are a group of bioactive fatty acid metabolites generated via enzymatic oxygenation. They are notably involved in inflammation, pain, vascular tone, hemostasis, thrombosis, immunity, and coagulation. Oxylipins have become the focus of therapeutic intervention since they are implicated in many conditions, such as nonalcoholic fatty liver disease, cardiovascular disease, and aging. The liver plays a crucial role in lipid metabolism and distribution throughout the organism. Long-term exposure to pesticides is suspected to contribute to hepatic carcinogenesis via notable disruption of lipid metabolism. Prometryn is a methylthio-s-triazine herbicide used to control the growth of annual broadleaf and grass weeds in many cultivated plants. The amounts of prometryn documented in the environment, mainly waters, soil and plants used for human and domestic consumption are significantly high. Previous research revealed that prometryn decreased liver development during zebrafish embryogenesis. To understand the mechanisms by which prometryn could induce hepatotoxicity, the effect of prometryn (185 mg/kg every 48 h for seven days) was investigated on hepatic and plasma oxylipin levels in mice. Using an unbiased LC-MS/MS-based lipidomics approach, prometryn was found to alter oxylipins metabolites that are mainly derived from cytochrome P450 (CYP) and lipoxygenase (LOX) in both mice liver and plasma. Lipidomic analysis revealed that the hepatotoxic effects of prometryn are associated with increased epoxide hydrolase (EH) products, increased sEH and mEH enzymatic activities, and induction of oxidative stress. Furthermore, 9-HODE and 13-HODE levels were significantly increased in prometryn treated mice liver, suggesting increased levels of oxidation products. Together, these results support that sEH may be an important component of pesticide-induced liver toxicity.

High expression of 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) associated with Diquat-induced damage

Diquat (DQ) is a commonly used bipyridine herbicide known for its toxic properties and adverse effects on individuals. However, the mechanism underlying DQ-induced damage remain elusive. Our research aimed to uncover the regulatory network involved in DQ-induced damage. We analyzed publicly accessible gene expression patterns and performed research using a DQ-induced damage animal model. The GSE153959 dataset from the Gene Expression Omnibus collection and the animal model of DQ-induced kidney injury were used to identify differentially expressed genes (DEGs). Pathways including the regulation of DNA-templated transcription in response to stress, RNA polymerase II transcription regulator complex and transcription coregulatory activity were shown to be enriched in 21 DEGs. We used least absolute shrinkage and selection operator (LASSO) regression analysis to find possible diagnostic biomarkers for DQ-induced damage. Then, we used an HK-2 cell model to confirm these results. Additionally, we confirmed that 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) was the major gene associated with DQ-induced damage using multi-omics screening. The sample validation strongly suggested that HMGCS2 has promise as a diagnostic marker and may provide new targets for therapy in the context of DQ-induced damage.

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.

Exposure to acifluorfen induces developmental toxicity in the early life stage of zebrafish

Acifluorfen, a selective herbicide from the diphenyl ether family, targets broad leaf weeds. Diphenyl ether inhibits chlorophyll production in green plants by inhibiting protoporphyrinogen oxidase (PPO), causing cellular damage. Despite its known impacts on plants, the influence of acifluorfen on zebrafish embryo development remains unclear. In this study, we explored the LC50 of acifluorfen in early-stage wild-type zebrafish, determining it to be 54.99 mg/L. Subsequent examinations revealed morphological changes in zebrafish, including reduced body length. Using the cmlc2:dsRED transgenic model, we observed heart dysfunction in acifluorfen-exposed zebrafish, marked by an enlarged heart area, edema, and decreased heart rate. In response to dose-dependent acifluorfen exposure, the inhibition of angiogenesis in the brain was observed in transgenic zebrafish models (fli1a:eGFP). Organ malformations, specifically in the liver and pancreas, were noted, in lfabp:dsRED;elastase:eGFP transgenic models, indicating reduced organ size in acifluorfen-exposed zebrafish. Furthermore, acifluorfen heightened the expression of apoptosis-related genes (casp8, casp9, and tp53) in zebrafish embryos. We then determined whether acifluorfen affected the viability of zebrafish liver (ZFL) cells based on its effects on liver development in vivo. The results indicated that the proliferation of ZFL cells decreased significantly in a dose-dependent manner. Additionally, acifluorfen-treated ZFL cells exhibited a slight increase in apoptotic cells stained with annexin V and propidium iodide. In summary, these findings establish a baseline concentration for acifluorfen's effects on aquatic ecosystems and non-target organisms.

Meptyldinocap induces implantation failure by forcing cell cycle arrest, mitochondrial dysfunction, and endoplasmic reticulum stress in porcine trophectoderm and endometrial luminal epithelial cells

Meptyldinocap is a dinitrophenol fungicide used to control powdery mildew. Although other dinitrophenol pesticides have been found to exhibit reproductive toxicity, studies of meptyldinocaps are scarce. This study investigated the adverse effects of meptyldinocap on porcine trophectoderm (pTr) and porcine endometrial luminal epithelial (pLE) cells, which play crucial roles in implantation. We confirmed that meptyldinocap decreased cell viability, induced apoptosis, and inhibited proliferation by decreasing proliferation-related gene expression and inducing changes in the cell cycle. Furthermore, meptyldinocap treatment caused mitochondrial dysfunction, endoplasmic reticulum stress, and disruption of calcium homeostasis. Moreover, it induces alterations in mitogen-activated protein kinase signaling cascades and reduces the migration ability, leading to implantation failure. Our findings suggest that meptyldinocap reduces the cellular functions of pTr and pLE cells, which are important for the implantation process, and interferes with interactions between the two cell lines, potentially leading to implantation failure. We also propose a mechanism by which the understudied fungicide meptyldinocap exerts its cytotoxicity.

Mechanisms of female reproductive toxicity in pigs induced by exposure to environmental pollutants

Environmental pollutants, including endocrine disruptors, heavy metals, nanomaterials, and pesticides, have been detected in various ecosystems and are of growing global concern. The potential for toxicity to non-target organisms has consistently been raised and is being studied using various animal models. In this review, we focus on pesticides frequently detected in the environment and investigate their potential exposure to livestock. Owing to the reproductive similarities between humans and pigs, various in vitro porcine models, such as porcine oocytes, trophectoderm cells, and luminal epithelial cells, are used to verify reproductive toxicity. These cell lines are being used to study the toxic mechanisms induced by various environmental toxicants, including organophosphate insecticides, pyrethroid insecticides, dinitroaniline herbicides, and diphenyl ether herbicides, which persist in the environment and threaten livestock health. Collectively, these results indicate that these pesticides can induce female reproductive toxicity in pigs and suggest the possibility of adverse effects on other livestock species. These results also indicate possible reproductive toxicity in humans, which requires further investigation.

Prometryn exposure disrupts the intestinal health of Eriocheir sinensis: Physiological responses and underlying mechanism

Most toxicity studies of prometryn in non-target aquatic animals have focused on hepatotoxicity, cardiotoxicity, embryonic developmental and growth toxicity, while studies on the molecular mechanisms of intestinal toxicity of prometryn are still unknown. In the current study, the intestinal tissues of the Chinese mitten crab (Eriocheir sinensis) were used to uncover the underlying molecular mechanisms of stress by 96-h acute in vivo exposure to prometryn. The results showed that prometryn activated the Nrf2-Keap1 pathway and up-regulated the expression of downstream antioxidant genes. Prometryn induced the expression of genes associated with non-specific immunity and autophagy, and induced apoptosis through the MAPK pathway. Interestingly, the significant up-or down-regulation of the above genes mainly occurred at 12 h- 24 h after exposure. Intestinal flora sequencing revealed that prometryn disrupted the intestinal normal barrier function mainly by reducing beneficial bacteria abundance, which further weakened the intestinal resistance to exogenous toxicants and caused an inflammatory response. Correlation analyses found that differential flora at the genus level had potential associations with gut stress-related genes. In conclusion, our study contributes to understanding the molecular mechanisms behind the intestinal stress caused by herbicides on aquatic crustaceans.

Zebrafish neuromast sensory system: Is it an emerging target to assess environmental pollution impacts?

Environmental pollution poses risks to ecosystems. Among these risks, one finds neurotoxicity and damage to the lateral line structures of fish, such as the neuromast and its hair cells. Zebrafish (Danio rerio) is recommended as model species to be used in ecotoxicological studies and environmental biomonitoring programs aimed at assessing several biomarkers, such as ototoxicity. However, little is known about the history of and knowledge gaps on zebrafish ototoxicity. Thus, the aim of the current study is to review data available in the scientific literature about using zebrafish as animal model to assess neuromast toxicity. It must be done by analyzing the history and publication category, world production, experimental design, developmental stages, chemical classes, neuromasts and hair cell visualization methods, and zebrafish strains. Based on the results, number, survival and fluorescence intensity of neuromasts, and their hair cells, were the parameters oftentimes used to assess ototoxicity in zebrafish. The wild AB strain was the most used one, and it was followed by Tübingen and transgenic strains with GFP markers. DASPEI was the fluorescent dye most often applied as method to visualize neuromasts, and it was followed by Yo-Pro-1 and GFP transgenic lines. Antibiotics, antitumorals, metals, nanoparticles and plant extracts were the most frequent classes of chemicals used in the analyzed studies. Overall, pollutants can harm zebrafish's mechanosensory system, as well as affect their behavior and survival. Results have shown that zebrafish is a suitable model system to assess ototoxicity induced by environmental pollution.

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.

Effects of butyl benzyl phthalate on zebrafish (Danio rerio) brain and the underlying molecular mechanisms revealed by transcriptome analysis

Butyl benzyl phthalate (BBP), a widely used class of plasticizers, has caused considerable concerns due to its widespread detection in various environmental media. However, the potential impact of BBP on the brain and its underlying molecular mechanisms remain poorly understood. In this study, adult zebrafish (Danio rerio) were exposed to 0, 5, 50, and 500 μg/L BBP for 28 days. Elevated levels of both reactive oxygen species and 8-hydroxydeoxyguanosine were observed, indicating the occurrence of oxidative stress and DNA damage. Furthermore, exposure to BBP resulted in neurotoxicity, apoptosis, and histopathological damage within the zebrafish brain. Transcriptome analysis further revealed that Gene Ontology terms associated with muscle contraction were specifically expressed in the brain after BBP exposure. In addition, BBP altered the transcriptome profile of the brain, with 293 genes induced and 511 genes repressed. Kyoto Encyclopedia of Genes and Genomes analysis highlighted the adverse effects of BBP on the complement and coagulation cascades and two cardiomyopathy-related pathways. Taken together, our results revealed that BBP resulted in brain oxidative stress, histological damage, and transcriptome alterations. These findings have the potential to offer novel insights into the adverse outcome pathways of key events in the brain.

Mitochondrial and Proteasome Dysfunction Occurs in the Hearts of Mice Treated with Triazine Herbicide Prometryn

Prometryn is a methylthio-s-triazine herbicide used to control the growth of annual broadleaf and grass weeds in many cultivated plants. Significant traces of prometryn are documented in the environment, mainly in waters, soil, and plants used for human and domestic consumption. Previous studies have shown that triazine herbicides have carcinogenic potential in humans. However, there is limited information about the effects of prometryn on the cardiac system in the literature, or the mechanisms and signaling pathways underlying any potential cytotoxic effects are not known. It is important to understand the possible effects of exogenous compounds such as prometryn on the heart. To determine the mechanisms and signaling pathways affected by prometryn (185 mg/kg every 48 h for seven days), we performed proteomic profiling of male mice heart with quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) using ten-plex tandem mass tag (TMT) labeling. The data suggest that several major pathways, including energy metabolism, protein degradation, fatty acid metabolism, calcium signaling, and antioxidant defense system were altered in the hearts of prometryn-treated mice. Proteasome and immunoproteasome activity assays and expression levels showed proteasome dysfunction in the hearts of prometryn-treated mice. The results suggest that prometryn induced changes in mitochondrial function and various signaling pathways within the heart, particularly affecting stress-related responses.

Effects of Prometryn Exposure on Hepatopancreas Oxidative Stress and Intestinal Flora in Eriocheir sinensis (Crustacea: Decapoda)

There is growing evidence that long-term exposure to prometryn (a widely used herbicide) can induce toxicity in bony fish and shrimp. Our previous study demonstrated its 96 h acute toxicity on the crab Eriocheir sinensis. However, studies on whether longer exposure to prometryn with a lower dose induces toxicity in E. sinensis are scarce. Therefore, we conducted a 20 d exposure experiment to investigate its effects on the hepatopancreas and intestine of E. sinensi. Prometryn reduce the activities of antioxidant enzymes, increase the level of lipid peroxidation and cause oxidative stress. Moreover, long-term exposure resulted in immune and detoxification fatigue, while short-term exposure to prometryn could upregulate the expression of genes related to immunity, inflammation and detoxification. Prometryn altered the morphological structure of the hepatopancreas (swollen lumen) and intestine (shorter intestinal villi, thinner muscle layer and thicker peritrophic membrane). In addition, prometryn changed the species composition of the intestinal flora. In particular, Bacteroidota and Proteobacteria showed a dose-dependent decrease accompanied by a dose-dependent increase in Firmicutes at the phylum level. At the genus level, all exposure groups significantly increased the abundance of Zoogloea and a Firmicutes bacterium ZOR0006, but decreased Shewanella abundance. Interestingly, Pearson correlation analysis indicated a potential association between differential flora and hepatopancreatic disorder. Phenotypic abundance analysis indicated that changes in the gut flora decreased the intestinal organ's resistance to stress and increased the potential for opportunistic infection. In summary, our research provides new insights into the prevention and defense strategies in response to external adverse environments and contributes to the sustainable development of E. sinensis culture.

A novel electrochemical aptasensor for ultrasensitive detection of herbicide prometryn based on its highly specific aptamer and Ag@Au nanoflowers

Herbicide prometryn has become a common pollutant in aquatic environments and caused adverse impacts on ecosystems. This study developed an ultrasensitive electrochemical aptasensor for prometryn based on its highly affinitive and specific aptamer and Ag@Au nanoflowers (Ag@AuNFs) for signal amplification. Firstly, this study improved the Capture-SELEX strategy to screen aptamers and obtained aptamer P60-1, which had a high affinity (Kd: 23 nM) and could distinguish prometryn from its structural analogues. Moreover, the typical stem-loop structure in aptamer P60-1 was found to be the binding pocket for prometryn. Subsequently, an electrochemical aptasensor for prometryn was established using multiwalled carbon nanotubes and reduced graphene oxide as electrode substrate, Ag@Au NFs as signal amplification element, and aptamer P60-1 as recognition element. The aptasensor had a detection range of 0.16-500 ng/mL and a detection limit of 60 pg/mL, which was much lower than those of existing detection methods. The aptasensor had high stability and good repeatability, and could specifically detecting prometryn. Furthermore, the utility of the aptasensor was validated by measuring prometryn in environmental and biological components. Therefore, this study provides a robust and ultrasensitive aptasensor for accurate detection for prometryn pollution.

Effects of prometryn on oxidative stress, immune response and apoptosis in the hepatopancreas of Eriocheir sinensis (Crustacea: Decapoda)

Prometryn, a triazine pesticide product used to control weed growth, poses a high risk to aquatic organisms in the environment. Several toxicological evaluations have been performed on bony fish and shrimp exposed to prometryn. However, there have been no reports conducted on the toxic mechanism of prometryn with regard to Eriocheir sinensis. In this study, our research evaluated the toxic effects of prometryn via in vitro and in vivo toxicity tests on E. sinensis. Firstly, we estimated the exposure toxicity of prometryn to E. sinensis, and then we constructed a 6 h transcriptional profile and conducted an enrichment analysis. To further reveal the toxicity of prometryn, the hepatopancreas (hepatopancreatic cells) was analyzed for antioxidant, immune and lipid-metabolism-related enzymes, antioxidant- and apoptosis-related gene expression, histopathology and TUNEL. From the results, we determined that the 96 h-LD50 was 70.059 mg/kg, and using RNA-seq, we identified 933 differentially expressed genes (DEGs), which were mainly enriched in the amino and fatty acid metabolism and the cell-fate-determination-related signaling pathway. The results of the biochemical assays showed that prometryn could significantly decrease the activities/levels of CAT, SOD, GSH, AKP and ACP, reduce the levels of T-AOC, TG, TCH, C3 and C4, and increase the MDA content. In addition, the expression levels of Nrf2, GSTs and HO-1 were first upregulated and then downregulated with increasing time. Histopathology showed that prometryn damaged the structure of the hepatopancreas cells and induced apoptosis, suggesting that the PI3K-Akt signaling pathway may be involved in the damage process of hepatopancreas cells (PI3K, PDK and Akt were downregulated whereas Bax was upregulated), leading to their apoptosis. The above results indicated that prometryn could cause injury of the hepatopancreas through oxidative stress, induce cell apoptosis, disrupt the lipid metabolism and cause immune damage. This study provided useful data for understanding and evaluating the toxicity of prometryn to aquatic crustacea.

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.

Oxyfluorfen induces cell cycle arrest by regulating MAPK, PI3K and autophagy in ruminant immortalized mammary epithelial cells

Oxyfluorfen, a phenoxy phenyl-type herbicide, causes significant damage to ecosystems through chronically effecting invertebrates, fish, and mammals. Considering its adverse effect on ecosystem conservation, it is necessary to investigate its toxic effects on animals. However, the mechanisms of oxyfluorfen toxicity on bovines are not well established. This study investigated the cytotoxic effect of oxyfluorfen on bovine mammary epithelial cells (MAC-T). We conducted several functional experiments to examine the response of MAC-T to oxyfluorfen under various concentrations (0, 1, 2, 5, and 10 ppm). Oxyfluorfen decreased cell viability and increased apoptotic cells by regulating the expression of apoptotic genes and proteins in MAC-T. In addition, oxyfluorfen-treated cells exhibited reduced PCNA expression with a low 3D spheroid formation as compared to that of control cells. Furthermore, oxyfluorfen treatment suppressed cell cycle progression with a decrease in cyclin D1 and cyclin A2 in MAC-T. Next, we performed western blot analysis to verify intercellular signaling changes in oxyfluorfen-treated MAC-T. The phosphor-AKT protein was increased, whereas MAPK signal pathways were decreased. Particularly, the combination of oxyfluorfen with U0126 or SP600125 completely blocked the ERK1/2 and JNK pathways leading to cell viability in MAC-T. Moreover, oxyfluorfen induced inflammatory gene expression and autophagy by increasing phosphorylation of P62 and LC3B in MAC-T. These results demonstrated that oxyfluorfen has cytotoxic effect on MAC-T, implying that the milk production capacity in cows may eventually harm humans.

Occurrence, fate, seasonal variability, and risk assessment of twelve triazine herbicides and eight related derivatives in source, treated, and tap water of Wuhan, Central China

Triazine herbicides have been widely used, are frequently detected in aqueous environments and soils, and can cause acute or chronic toxicity to living organisms. We collected source water samples (n = 20) originating from the Hanshui River and the Yangtze River of Wuhan section, treated water samples (n = 20), and tap water samples (n = 169) in Wuhan, Central China during 2019 for determination of twelve triazine herbicides and their eight derivatives (collectively defined as TZs) and characterizing their fate during water treatment. Eighteen of the twenty TZs were detected in the source water. Atrazine (ATZ) had the highest concentrations (median: 22.4 ng/L) in the source water samples while DACT had the highest concentrations (median: 31.4 ng/L) in the treated water. "Tryns" (ametryn, prometryn, simetryn, terbutryn) were efficiently removed by conventional water treatment, while other target analytes were not; interestingly, hydroxypropazine and prometon increased significantly accompanied by prometryn disappearance, which implicated potential transformation pathways. In addition, "tryns" might be transformed into "tons" (atraton, prometon, secbumeton, terbumeton) by ozonation. In the tap water samples, diaminochlorotriazine had the highest concentrations (median: 34.9 ng/L) among the target analytes, followed by ATZ (18.3 ng/L), hydroxyatrazine (5.17 ng/L), deethylatrazine (5.00 ng/L), hydroxypropazine (3.20 ng/L), deisopropylatrazine (2.05 ng/L), hydroxydesethylatrazine (1.68 ng/L), and others. The TZs had the highest cumulative concentration in July in the tap water samples (median: 89.7 ng/L). This study found that ozonation in combination with activated carbon was more efficient in removing triazine herbicides, although "tryns" could also be transformed during conventional treatment. Ecological risk assessment showed moderate risks posed by hydroxyterbuthylazine, prometryn, and simetryn; the Hanshui River had higher risks than the Yangtze River, and July had higher risks than February. Human exposure to the TZs via water ingestion was low compared to the reference doses. This study characterized the occurrence of some new emerging TZs in the source water, their fate during drinking water treatment, and their seasonal variability in the tap water.

Characterization and catalytic mechanism of a direct demethylsulfide hydrolase for catabolism of the methylthiol-s-triazine prometryn

Demethylthio is one of the most important ways for microorganisms to metabolize triazine herbicides. Previous studies have found that the initial reaction of prometryn catabolism in Leucobacter triazinivorans JW-1 was the hydroxylation of its methylthio group, however, the corresponding functional enzyme was not yet clear. In this study, the gene proA was responsible for the initial step of prometryn catabolism from the strain JW-1 was cloned and expressed, and the purified amidohydrolases ProA have the ability to transform prometryn to 2-hydroxypropazine and methanethiol. The optimized reaction temperature and pH of ProA were 45 °C and 7.0, respectively, and the kinetic constants K_m and V_max of ProA for the catalysis of prometryn were 32.6 μM and 0.09 μmol/min/mg, respectively. Molecular docking analyses revealed that different catalysis efficiency of ProA and TrzN (Nocardioides sp. C190) for prometryn and atrazine was due to non-covalent changes in amino acid residues. Our findings provide new insights into the understanding of s-triazine catabolism at the molecular level.