Histology and multi-omic profiling reveal the mixture toxicity of tebuconazole and difenoconazole in adult zebrafish

Effect of chronic deltamethrin exposure on brain transcriptome and metabolome of juvenile crucian carp

Deltamethrin (Del), a widely administered pyrethroid insecticide, has been established as a common contaminant of the freshwater environment and detected in many freshwater ecosystems. In this study, we investigated the changes in brain transcriptome and metabolome of crucian carp after exposure to 0.6 μg/L Del for 28 days. Elevated MDA levels and inhibition of SOD activity indicate damage to the antioxidant system. Moreover, a total of 70 differential metabolites (DMs) were identified using the liquid chromatography-mass spectrometry, including 32 upregulated and 38 downregulated DMs in the Del-exposed group. The DMs associated with chronic Del exposure were enriched in steroid hormone biosynthesis, fatty acid metabolism, and glycerophospholipid metabolism for prostaglandin G2, 5-oxoeicosatetraenoic acid, progesterone, androsterone, etiocholanolone, and hydrocortisone. Transcriptomics analysis revealed that chronic Del exposure caused lipid metabolism disorder, endocrine disruption, and proinflammatory immune response by upregulating the pla2g4, cox2, log5, ptgis, lcn, and cbr expression. Importantly, the integrative analysis of transcriptomics and metabolomics indicated that the arachidonic acid metabolism pathway and steroid hormone biosynthesis were decisive processes in the brain tissue of crucian carp after Del exposure. Furthermore, Del exposure perturbed the tight junction, HIF-1 signaling pathway, and thyroid hormone signaling pathway. Overall, transcriptome and metabolome data of our study offer a new insight to assess the risk of chronic Del exposure in fish brains.

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

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

Trifloxystrobin induced developmental toxicity by disturbing the ABC transporters, carbohydrate and lipid metabolism in adult zebrafish

The environmental risks of trifloxystrobin (TR) have drawn attention because of its multiplex toxicity on aquatic organisms, but few studies have paid close attention to its chronic toxicity at environmental concentrations. In present study, histopathology, metabolomics and transcriptomics were comprehensively performed to investigate the toxic effects and biological responses on adult zebrafish after exposure to 0.1, 1 and 10 μg/L TR for 21 d. Results demonstrated long-term exposure of TR affected zebrafish liver, ovary and heart development. Metabolomics revealed 0.1, 1 and 10 μg/L TR simultaneously decreased the carbohydrates enriched in glucose metabolism and ABC transporters pathways, such as glycogen, lactose, lactulose, maltose, maltotriose, d-trehalose, while 1 μg/L and 10 μg/L TR significantly increased many metabolites related to glycerophospholipid and sphingolipid metabolism in zebrafish liver. Transcriptomics showed TR activated the transcription of the Abcb4, Abcb5 and Abcb11 involved in ABC transporters, Pck1, Pfk, Hk, Gyg1a and Pygma related to glucose metabolism, as well as the Lpcat1, Lpcat4, Gpat2, Cers and Sgms in glycerophospholipid and sphingolipid metabolism. Results further demonstrated high concentration of TR strongly affected the DNA repair system, while low dose of TR caused pronounced effects on cardiomyocytes and oocyte regulation pathways at transcriptional levels. The results indicated the abnormal liver, gonad and heart development caused by TR might be ascribed to the disturbance of carbohydrates and lipid metabolism mediating by the Abcb4, Abcb5 and Abcb11 ABC transporters, and long-term exposure of environmental concentration of TR was sufficient to affect zebrafish normal metabolism and development.

A comprehensive review on toxicological mechanisms and transformation products of tebuconazole: Insights on pesticide management

Tebuconazole has been widely applied over three decades because of its high efficiency, low toxicity, and broad spectrum, and it is still one of the most popular fungicides worldwide. Tebuconazole residues have been frequently detected in environmental samples and food, posing potential hazards for humans. Understanding the toxicity of pesticides is crucial to ensuring human and ecosystem health, but the toxic mechanisms and toxicity of tebuconazole are still unclear. Moreover, pesticides could transform into transformation products (TPs) that may be more persistent and toxic than their parents. Herein, the toxicities of tebuconazole to humans, mammals, aquatic organisms, soil animals, amphibians, soil microorganisms, birds, honeybees, and plants were summarized, and its TPs were reviewed. In addition, the toxicity of tebuconazole TPs to aquatic organisms and mammals was predicted. Tebuconazole posed potential developmental toxicity, genotoxicity, reproductive toxicity, mutagenicity, hepatotoxicity, neurotoxicity, cardiotoxicity, and nephrotoxicity, which were induced via reactive oxygen species-mediated apoptosis, metabolism and hormone perturbation, DNA damage, and transcriptional abnormalities. In addition, tebuconazole exhibited apparent endocrine-disrupting effects by modulating hormone levels and gene transcription. The toxicity of some TPs was equivalent to and higher than tebuconazole. Therefore, further investigation is necessary into the toxicological mechanisms of tebuconazole and the combined toxicity of a mixture of tebuconazole and its TPs.

Effects of acute exposure to environmentally realistic tebuconazole concentrations on stress responses of kidney and digestive gland of Lymnaea stagnalis

This study aimed to investigate the effects of 24 and 72 h exposure to environmentally relevant concentrations of tebuconazole (TEB) (10, 100 and 500 µg/L) fungicide on the freshwater snail Lymnaea stagnalis. The focus was induction of oxidative stress, alteration of gene expressions and histopathological changes in the kidney and digestive gland. TEB treatment induced a time- and concentration-dependent increase in intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) levels, while the total antioxidant capacity (TAC) was decreased. The activities of glutathione peroxidase (GPx), glutathione reductase (GR), and catalase (CAT) also increased in a time- and concentration-dependent manner in both tissues. TEB exposure significantly increased the mRNA levels of CAT, GPx, GR, heat shock proteins HSP40 and HSP70. Histological analysis revealed nephrocyte degeneration and disrupted digestive cells. The study concludes that acute exposure to TEB induces oxidative stress, alters antioxidant defense mechanisms, and leads to histopathological changes in L. stagnalis.

Waterborne Tebuconazole Exposure Induces Male-Biased Sex Differentiation in Zebrafish (Danio rerio) Larvae via Aromatase Inhibition

Tebuconazole is a widely used fungicide for various crops that targets sterol 14-α-demethylase (CYP51) in fungi. However, attention has shifted to aromatase (CYP19) due to limited research indicating its reproductive impact on aquatic organisms. Herein, zebrafish were exposed to 0.5 mg/L tebuconazole at different developmental stages. The proportion of males increased significantly after long-term exposure during the sex differentiation phase (0-60, 5-60, and 19-60 days postfertilization (dpf)). Testosterone levels increased and 17β-estradiol and cyp19a1a expression levels decreased during the 5-60 dpf exposure, while the sex ratio was equally distributed on coexposure with 50 ng/L 17β-estradiol. Chemically activated luciferase gene expression bioassays determined that the male-biased sex differentiation was not caused by tebuconazole directly binding to sex hormone receptors. Protein expression and phosphorylation levels were specifically altered in the vascular endothelial growth factor signaling pathway despite excluding the possibility of tebuconazole directly interacting with kinases. Aromatase was selected for potential target analysis. Molecular docking and aromatase activity assays demonstrated the interactions between tebuconazole and aromatase, highlighting that tebuconazole poses a threat to fish populations by inducing a gender imbalance.

Sorption behaviour of tebuconazole on microplastics: kinetics, isotherms and influencing factors

Microplastics (MPs) and pesticides are two classes of environmental pollutants and have become global challenges. MPs could adsorb substantial environmental pollutants, which may affect their transportation, distribution and cause combination toxicity. Therefore, the study of sorption properties and mechanisms is the basis of the ecological risk assessment of co-exposure of pesticides and MPs. In this research, typical triazole fungicide tebuconazole (TEB) is selected as a model pollutant, and its sorption behaviour was investigated by kinetic and isotherm models. Meanwhile, a series of environmental influencing factors, like pH, salinity, and metals were conducted. Results showed that the sorption of TEB on MPs could reach equilibrium at 24 h, and the sorption capacity followed the order of PA (polyamide) > PS (polystyrene) > PP (polypropylene). The pseudo-second-order model was the most appropriate model to describe kinetic data, and the Freundlich model was well fit for PA sorption isotherms, in contrast the Langmuir model is better for PP and PS. Additionally, the pH of the solution, salinity, and metals have an important effect on sorption. Combined with Fourier Transform Infrared Spectroscopy and environmental influencing factors, the sorption mechanisms were mainly electrostatic interaction and hydrogen bond for PA and PP, and hydrophobic force, intermolecular force, and electrostatic force for PS, respectively.

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.

Exposure to the fungicide prothioconazole and its metabolite prothioconazole-desthio induced hepatic metabolism disorder and oxidative stress in mice

Prothioconazole (PTC), as a popular triazole fungicide, with its main metabolite prothioconazole desthio (PTC-d), have attracted widespread concern due to their widely use and toxicological effects on non-target organisms. However, toxic effects of study analyzed PTC and PTC-d on the hepatic metabolism of mammalian still remains unclear. In this study, we conducted the study of the C57BL/6 mice which oral exposure to 30 mg/kg PTC and PTC-d via metabolomic analysis. In the liver, the metabolomics profile unveiled that exposure to 30 mg/kg PTC and PTC-d led to significantly altered 13 and 28 metabolites respectively, with 6 metabolites in common including significant decreased d-Fructose, Glutathione, showing the change of carbohydrate, lipid and amino acid metabolism. Via the further exploration of genes related to hepatic glycolipid metabolism and the biomarkers of oxidative stress, we found that liver was potentially damaged after exposure to 5 and 30 mg/kg PTC and PTC-d. Particularly, it was proved that PTC-d caused more adverse effect than its parent compound PTC on hepatotoxicity, and high concentration PTC or PTC-d exposure is more harmful than low concentration exposure.

Multi-omics reveals response mechanism of liver metabolism of hybrid sturgeon under ship noise stress

Underwater noise from ship engines can affect the metabolism and immune system of various fish species. Meanwhile, changes in the metabolic pathways in liver are important for fish to adapt to adverse environments. We used a combined multi-omics analysis to investigate the response mechanism of hybrid sturgeon to continuously played ship noise. A control group and a noise group (simulated ship noise: 12 h) were set up, and liver tissues were extracted for high-throughput transcriptome and metabolome sequencing. The results show that a total of 588 differentially expressed genes (DEGs) and 58 DEGs metabolites were detected. The joint analysis of transcriptome and metabolome showed that under noise stress, apoptosis and cell motility were intensified, DNA replication, RNA transcription and translation, and protein synthesis were inhibited, and lipid metabolism, nucleotide metabolism, and vitamin D3 metabolic pathways were also inhibited. Interestingly, the initiation of a partial immune responses ensured their normal immunity abilities. Moreover, material and energy requirements of the organism under noise stress were guaranteed by upregulation of carbohydrate and amino acid metabolic pathways.

Histology and metabonomics reveal the toxic effects of kresoxim-methyl on adult zebrafish

Studies have shown that kresoxim-methyl (KM) and other strobilurin fungicides have toxic effects on aquatic organisms. However, the potential deleterious effects of kresoxim-methyl (KM) on adult zebrafish regarding the ecological risk of environmental concentration remain unclear. Here, the histology and untargeted metabonomics was used to investigate the adverse effect on female zebrafish after exposure to KM at environmental concentration, aquatic life benchmark and one-half LC₅₀ of adult zebrafish. Results demonstrated KM affected zebrafish liver, ovary and intestine development, blurred the boundary between hepatocytes or caused hepatic vacuoles, increased the percentage of perinucleolar oocyte and cortical alveolus oocyte, decreased intestinal goblet cells and disturbed villus and wall integrity after 21 d exposure. Metabonomics showed different concentrations of KM simultaneously influenced the metabolites annotated to vitamin digestion and absorption, serotonergic synapse, retinol metabolism, ovarian steroidogenesis and arachidonic acid (AA) metabolism in zebrafish liver. Results showed the decreased triglyceride and cholesterol levels, as well as the metabolic alterations in amino acid, lipid, vitamin and retinol metabolism caused by KM, might disturb the energy supply for normal liver development and oocyte maturation. In addition, KM altered the transcription of Tdo2a, Tdo2b, Ido1, Cxcl8b, Cyp7a, Cyp11a, Cyp11b, Cyp17a, Cyp19a, Hsd3β, Hsd17β, Pla2, Ptgs2a and Ptgs2b, the level of TG, TC, MDA, IFN, IL6 and Ca²⁺, and the activity of CAT, SOD Ca²⁺-ATPase in zebrafish liver. Moreover, cytoscape analysis suggested the disturbed AA metabolism caused by KM, might interconnect multiple metabolic pathways to share implicated function in the regulation of oocyte maturation and immune response. Current study brought us closer to an incremental understanding of the toxic mechanism of KM on adult zebrafish, indicated there was crosstalk among different regulatory pathways to regulate the metabolic disorders and biologically hazardous effects induced by KM.

Dose-Dependent Cytotoxicity of Polypropylene Microplastics (PP-MPs) in Two Freshwater Fishes

The massive accumulation of plastics over the decades in the aquatic environment has led to the dispersion of plastic components in aquatic ecosystems, invading the food webs. Plastics fragmented into microplastics can be bioaccumulated by fishes via different exposure routes, causing several adverse effects. In the present study, the dose-dependent cytotoxicity of 8−10 μm polypropylene microplastics (PP-MPs), at concentrations of 1 mg/g (low dose) and 10 mg/g dry food (high dose), was evaluated in the liver and gill tissues of two fish species, the zebrafish (Danio rerio) and the freshwater perch (Perca fluviatilis). According to our results, the inclusion of PP-MPs in the feed of D. rerio and P. fluviatilis hampered the cellular function of the gills and hepatic cells by lipid peroxidation, DNA damage, protein ubiquitination, apoptosis, autophagy, and changes in metabolite concentration, providing evidence that the toxicity of PP-MPs is dose dependent. With regard to the individual assays tested in the present study, the biggest impact was observed in DNA damage, which exhibited a maximum increase of 18.34-fold in the liver of D. rerio. The sensitivity of the two fish species studied differed, while no clear tissue specificity in both fish species was observed. The metabolome of both tissues was altered in both treatments, while tryptophan and nicotinic acid exhibited the greatest decrease among all metabolites in all treatments in comparison to the control. The battery of biomarkers used in the present study as well as metabolomic changes could be suggested as early-warning signals for the assessment of the aquatic environment quality against MPs. In addition, our results contribute to the elucidation of the mechanism induced by nanomaterials on tissues of aquatic organisms, since comprehending the magnitude of their impact on aquatic ecosystems is of great importance.

Pesticides and Their Impairing Effects on Epithelial Barrier Integrity, Dysbiosis, Disruption of the AhR Signaling Pathway and Development of Immune-Mediated Inflammatory Diseases

The environmental and occupational risk we confront from agricultural chemicals increases as their presence in natural habitats rises to hazardous levels, building a major part of the exposome. This is of particular concern in low- and middle-income countries, such as Brazil, known as a leading producer of agricultural commodities and consumer of pesticides. As long as public policies continue to encourage the indiscriminate use of pesticides and governments continue to support this strategy instead of endorsing sustainable agricultural alternatives, the environmental burden that damages epithelial barriers will continue to grow. Chronic exposure to environmental contaminants in early life can affect crucial barrier tissue, such as skin epithelium, airways, and intestine, causing increased permeability, leaking, dysbiosis, and inflammation, with serious implications for metabolism and homeostasis. This vicious cycle of exposure to environmental factors and the consequent damage to the epithelial barrier has been associated with an increase in immune-mediated chronic inflammatory diseases. Understanding how the harmful effects of pesticides on the epithelial barrier impact cellular interactions mediated by endogenous sensors that coordinate a successful immune system represents a crucial challenge. In line with the epithelial barrier hypothesis, this narrative review reports the available evidence on the effects of pesticides on epithelial barrier integrity, dysbiosis, AhR signaling, and the consequent development of immune-mediated inflammatory diseases.

A Retrospective Narrative Mini-Review Regarding the Seminal Microbiota in Infertile Male

Background: Infertility is a global burden that affects both sexes with the male component remaining as an explored yet crucial research field that might offer novel evidence. Material and Methods: The present narrative mini-review aims to summarize all existing literature regarding the composition of the seminal microflora in infertile men. We performed searches in PubMed/Medline, ISI Web of Knowledge, Scopus, and ScienceDirect between 2018 and 2022 using a combination of keywords. Results: A total of n = 33 studies met the eligibility criteria and were further considered. From this, n = 14 were conducted on human patients, n = 3 on zebrafish (Danio rerio), n = 5 on rats, and n = 11 on mice. In twenty-five out of thirty-three papers, the authors sequenced the 16S rRNA; situations occurred where researchers focused on standard laboratory protocols. Lactobacillus and Bifidobacterium are widely recognized as putative beneficial lactic bacteria. These two entities are capable of restoring the host’s eubiosis to some extent, blocking pathogens’ proliferation and endotoxins, and even alleviating specific patterns encountered in disease(s) (e.g., obesity, type 1 diabetes) due to prolonged exposure to toxicants in adults or from a developmental stage. Over the years, distinct approaches have been perfected, such as the transfer of feces between two species or conventional rudimentary products with proven efficiency. Conclusions: The seminal microflora is decisive and able to modulate psychological and physiological responses. Each individual possesses a personalized microbial profile further shaped by exogenous factors, regardless of sex and species.

Insights into the combined effects of environmental concentration of difenoconazole and tebuconazole on zebrafish early life stage

Limited literature had focused on the combined effect of triazole fungicides on aquatic organisms at environmental concentrations. In this research, difenoconazole (DIF) and tebuconazole (TEB) mixture exhibited additive effect on the acute toxicity to zebrafish embryos. The transcriptomics and metabolomics demonstrated DIF and TEB mixtures at aquatic life benchmark and environmental concentration simultaneously influenced the lipid metabolism, arachidonic acid metabolism, steroid hormone biosynthesis and tryptophan metabolism, but showed diverse response patterns mediating the combined effects on zebrafish embryos after 120 h exposure. The DIF and TEB mixture at aquatic life benchmark caused combined effect on yolk sac resorption and metabolites, was less than the additive effect of individual DIF and TEB. It was found environmental concentration of DIF and TEB caused much lower levels of IFN and IL6, induced higher levels of PGE₂, l-kynurenine and formylanthranilate in zebrafish larvae, and their binary mixture caused synergistic effect on the accumulation of metabolites in metabolic pathways, which might cause more negative effect and risk on growth in zebrafish later life stages. Results further demonstrated that adding arachidonic acid (AA) increased the transcripts of Pla₂, Ptgs1, Cyp19a and Cxcl8b, allayed the accumulation of PLA₂ and 17β-E₂, and induced more PGF2α, IFN and IL6 levels in zebrafish larvae, indicated AA metabolism might play important regulatory roles on hormone synthesis and immune response caused by DIF and TEB mixtures. Current results indicated the risk assessment of mixtures based on single concentration may not precisely estimate the environmental risk and health effect, it is crucially important to consider the multi-concentration combinations, and more attention should be paid to the environmental concentration.

Biomarker Responses, Gene Expression Alterations, and Histological Changes in Zebrafish (Danio rerio) After In Vivo Exposure to Polychlorinated Diphenyl Ethers

Polychlorinated diphenyl ethers (PCDEs) have been detected in various aquatic matrices, which pose potential threats to aquatic ecosystem security. In this work, both micro and macro analysis methods were used to assess the toxicity of PCDEs to zebrafish. Results indicated that after in vivo PCDE exposure, the oxidative stress and related gene of Danio rerio were significantly changed. The higher concentration or longer exposure time could cause more severe oxidative stress in zebrafish tissues. Compared with among the five tested compounds, more obvious changes in the level of oxidative biomarkers of lower chlorinated PCDEs’ (4-mono-CDE and 4,4′-di-CDE) exposure groups were observed. The integrated biomarker response analysis and gene expression results also indicate a similar trend. Histopathological observation suggested that 4,4′-di-CDE could render liver nuclei enlargement and necrosis, hepatocyte vacuolation, and the development inhibition of ovarian cells. Transmission electron microscope photos showed that 4,4′-di-CDE caused organelle damage in the liver and ovary, including the rupture of the endoplasmic reticulum, swelling of mitochondria, and condensation of chromatin in the liver and mitochondria disappeared significantly in the ovary. The degree of damage is enhanced with the increasing exposure doses. In addition, PCDEs also significantly altered vitellogenin content and related gene (vtg1) expression, suggesting that PCDEs may be estrogen endocrine disruptors. Overall, these results provided some valuable toxicological data of PCDEs on aquatic species.

Behavioural impairment and oxidative stress by acute exposure of zebrafish to a commercial formulation of tebuconazole

Tebuconazole is a systemic follicular fungicide known to cause diverse problems in non-target organisms namely associated to the pure active ingredient. As such, the objective of this work was to evaluate developmental changes induced by a tebuconazole commercial formulation to a non-target animal model. Zebrafish embryos at ± 2 h post-fertilization were exposed to tebuconazole wettable powder concentrations (0.05, 0.5 and 5 mg L^-1) for 96 h with developmental toxicity assessed throughout the exposure period and biochemical parameters evaluated at the end of the exposure. Behavioural assessment (spatial exploration and response to stimuli) was conducted 24 h after the end of the exposure. While no developmental and physiological alterations were observed, exposure to tebuconazole resulted in an increased generation of reactive oxidative species at the 0.05 and 0.5 mg L^-1 concentrations and a decreased GPx activity at the 0.5 mg L^-1 concentration suggesting a potential protection mechanism. There was also a change in the avoidance-escape behaviour supporting an anxiolytic effect suggesting possible alterations in the central nervous system development demanding further studies.