Study on the common teratogenic pathway elicited by the fungicides triazole-derivatives

Toxicological risk assessment of triadimenol for human exposure, broiler health, and food safety

Triadimenol, a widely used triazole fungicide, leaves residues that pose risks to broiler health, food safety, and human health. Current studies focus on lab animals, leaving limited data regarding its impact on non-target organisms in agricultural ecosystems. Moreover, the doses in current studies often exceed typical agricultural pollution levels of triadimenol. Therefore, this study evaluates the toxic effects of triadimenol by exposing broilers to different concentrations (0.05-20 mg/kg) in their feed for 42 days, assessing growth performance, organ index, hematological parameters, histopathology, jejunum morphology, and tissue residues. The results show that triadimenol contamination at 0.05-20 mg/kg in feed does not significantly affect broiler growth performance. However, the significant changes in hematological parameters suggest the potential hematological toxicity of triadimenol in broilers. Triadimenol at 1 mg/kg or higher induces hepatotoxic and nephrotoxic effects, and significantly alters kidney organ index and histopathology in broilers. Additionally, when the triadimenol contamination level in feed exceeds 1 mg/kg, the residues in edible tissues of broilers exceed the limits set by the EU and China. Overall, our study indicates that even low-dose exposure to triadimenol poses potential risks, highlighting the need for strict regulation of its use in agriculture to protect food safety and human health.

Highly sensitive time-resolved fluorescent microspheres lateral flow immunoassay for the quantitative detection of triadimefon and its metabolite residues in fruits and vegetables

A general one-step lateral flow immunochromatographic assay (LFIA) for the quantitative detection of triadimefon (TDF) and triadimenol (TDN) in fruit and vegetable samples was developed using time-resolved fluorescence microspheres (TRFM) as labels. A specific anti-triadimefon monoclonal antibody (mAb) was conjugated with TRFM to fabricate LFIA test strips. A time-resolved fluorometer as an LFIA reader was applied to obtain quantitative results and assess risk ranges for the LFIA test strips. Under the optimized experimental conditions, the limits of detection (LODs) in buffer/cucumbers/tomatoes/oranges were 0.046 ng/mL, 0.135 µg/kg, 1.047 µg/kg, and 5.811 µg/kg, respectively, which are ca. 1000 times lower than that of colloidal gold-labeled strips. The recovery in cucumber/tomato/orange samples was 109.4-116.7%, 87.7-110.9%, and 88.0-111.9%, respectively, indicating that the test strips had good reliability. Coupled with the easily customizable pretreatment procedures for various samples, the LFIA results were obtained within 18 min without the need for professional personnel or complicated equipment. TRFM-LFIA for TDF and TDN also shows remarkable specificity and precision. The test strips were also low-cost, portable, and convenient to use. These results indicate the test strips could be utilized as a novel strategy for on-site detection of TDF and TDN, which has the potential to expand and detect other pesticide or insecticide residues in food.

Genotoxic damage and apoptosis in rat glioma (F98) cell line following exposure to bromuconazole

Bromuconazole, a fungicide from the triazole family, is widely used to protect the crop from various fungal contaminations to increase product quality and productivity. Although the massive use of bromuconazole poses a serious risk to human health, the exact mechanism of bromuconazole toxicity, especially on brain support cells, called glia cells, remains unclear so far. This study aimed to determine the mechanism of cytotoxicity and genotoxicity of bromuconazole via inspection of apoptotic death in rat glioma (F98) cells. We observed that bromuconazole treatment caused concentration-dependent cell death with an IC50 of 60 µM, and disruption of the cytoskeleton was observed via immunocytochemical analysis. Further, bromuconazole inhibits cell proliferation, it arrests the cell cycle in the G0/G1 phase and so inhibits DNA synthesis. Genotoxic analysis showed that bromuconazole exposition causes DNA fragmentation (comet assay) and nuclear condensation (DAPI staining). Apoptotic cell death was confirmed through: positive Annexin-V/FITC-PI dyes, p53 and Bax overexpression, Bcl2 repression, an increase in Bax/BCL-2 ratios of the mRNA, mitochondrial membrane depolarization, and an increase of caspase-3 activity. All these results demonstrate that bromuconazole exerts its cytotoxic and genotoxic effects through apoptotic cell death, which could implicate mitochondria.

The effect of conazoles on reproductive organs structure and function – a review

Conazoles are azole antifungals used in agricultural and pharmaceutical products. Exposure to conazole fungicides leads to several toxic endpoints, including reproductive and endocrine. The results of animal experiments have shown that various conazole fungicides at high doses affect the structure and functions of reproductive organs. In males, adverse effects of conazole fungicides are manifested in the testes, prostate, sperm viability, fertility and sexual behaviour. Reduced testis weight, testis atrophy and reduced or absent sperm production were frequently observed. In female genitalia, structural changes in the ovaries and uterus have been observed. The extent of the changes depends on the dose and duration of treatment. Triazoles affected the expression of multiple genes involved in steroid hormone metabolism and modulate enzyme activity of multiple cytochrome P450 (CYP) and other metabolic enzymes in mammalian liver and other tissues. Conazole fungicides act as endocrine disruptors. Conazoles have been reported to reduce oestradiol and testosterone production and to increase progesterone concentration, indicating the inhibition of enzymes involved in the conversion of progesterone to testosterone. The reproductive effects are consistent with impairment of testosterone homeostasis. The disruption in steroid homeostasis is a common mode of action, leading to abnormal reproductive development and diminished reproductive function. At high doses, azole fungicides affect reproductive organs and fertility in several species.

Bromuconazole fungicide induces cell cycle arrest and apoptotic cell death in cultured human colon carcinoma cells (HCT116) via oxidative stress process

BACKGROUND

Bromuconazole, a fungicide belonging to the triazole family, is a plant protection product used to control, repel or destroy fungi that may develop on crops. We investigated the pro-apoptotic effect of bromuconazole and the role of oxidative stress in the death mechanism induced by this fungicide in this study.

METHODS

The human colon HCT116 cell line was treated with Bromuconazole (IC50/4, IC50/2, and IC50) for 24 h. Cells were collected and analysed for biomarkers of apoptotic cell death and oxidative stress as well as for the assessment of genotoxic damage.

RESULTS

Our study showed that bromuconazole caused a concentration-dependent increase in cell mortality with an IC50 of 180 µM. Bromuconazole induced cell cycle arrest in the G0/G1 phase and DNA synthesis inhibition. The Comet assay showed that bromuconazole caused DNA damage in a concentration-dependent manner. Bromuconazole-induced apoptosis was observed by, Annexin-V/FITC-PI and BET/AO staining, by mitochondrial membrane depolarisation, and by increased caspase-3 activity. In addition, bromuconazole induced a significant increase in ROS and lipid peroxidation levels and a disruption in SOD and CAT activities. N-acetylcysteine (NAC) strongly prevents cytotoxic and genotoxic damage caused by bromuconazole.

CONCLUSION

Bromuconazole toxicity was through the oxidative stress process, which causes DNA damage and mitochondrial dysfunction, leading to cell cycle arrest and apoptotic death of HCT116 cells.

Brain injury, genotoxic damage and oxidative stress induced by Bromuconazole in male Wistar rats and in SH-SY5Y cell line

BACKGROUND

Bromuconazole is a widely used triazole against various fungi disease. It's employment provokes harmful effects on the environment and human health. In the present study, we explored bromuconazole toxic effects in both rat brain tissue and SH-SY5Y cell line.

METHODS

Male Wistar rats were administrated orally with Bromuconazole (NOEL/4, NOEL o and NOEL ×2) daily for consecutive 28 days. In addition, neuronal SH-SY5Y cell line was used. The rat brains and SH-SY5Y cells were collected and analysed for AChE activity, oxidative stress biomarkers, genotoxicity and histopathological alterations.

RESULTS

Our results showed that rat exposure to bromuconazole at doses corresponding to NOEL/4, NOEL and NOEL ×2 caused brain histopathological alteration and decrease in acetylcholine esterase (AChE) activity. In SH-SY5Y cell line, bromuconazole strongly induced cell mortality with an IC50 about 250 µM. Bromuconazole induced also DNA damage as assessed by comet assay in both rat brain tissue and SH-SY5Y cell. Moreover, bromuconazole increased ROS production, malondialdehyde (MDA) and protein carbonyl (PC) levels and enhanced the enzymatic activities of catalase (CAT), superoxide dismutase (SOD), Glutathione-S-transferase (GST) and peroxidase (GPx) in the two studied systems.

CONCLUSION

Therefore, we can deduce that bromuconazole-caused neurotoxicity may be related to oxidative statue disturbance.HIGHLIGHTSBromuconzole causes oxidative stress in the brain tissue of male Wistar rats.Bromuconazole enhances MDA, PC levels and induces DNA damage in rat brain.Bromuconazole provokes disturbance of the neuronal antioxidant system.Bromuconazole induces histopathological alterations in rat brain.Bromuconazole exposure induced cytotoxic effects and DNA damage in SH-SY5Y cells.Bromuconazole exposure induced oxidative stress in SH-SY5Ycells.

Bromuconazole caused genotoxicity and hepatic and renal damage via oxidative stress process in Wistar rats

Bromuconazole is a triazole pesticide used to protect vegetables and fruits against diverse fungi pathologies. However, its utilization may be accompanied by diverse tissue injuries. In this study, we evaluated the biochemical and histopathological modifications, and we analyzed genotoxic and oxidative stress, in the aim to examine bromuconazole effects in the liver and kidney. We subdivided animals into four groups, each one contains six adult male Wistar rats. Untreated rats received daily a corn oil (vehicle) orally. Three oral bromuconazole doses were tested (1, 5, and 10 % of LD50) daily for 28 days. Bromuconazole increased the plasma activities of alkaline phosphatase, lactate dehydrogenase, and transaminases. It also increased the plasma levels of creatinine and uric acid. Histopathological check showed that bromuconazole caused organ damage. This study makes known that bromuconazole caused conspicuous DNA damage either in hepatic or kidney tissues, with a significant increase in the levels of malondialdehyde and protein carbonyl followed by an enhancement in catalase and superoxide dismutase enzymatic activities, and these increases are in a dose-dependent manner. In other side, we found that Glutathione-S-transferase and peroxidase activities raised. Our outcomes highlight that bromuconazole exposure induced genotoxic damage and organ damage which may be caused by the disturbances of oxidative stress statue in the liver and kidney.

Epoxiconazole profoundly alters rat brain and properties of neural stem cells

Epoxiconazole (EPX), a widely used fungicide for domestic, medical, and industrial applications, could cause neurodegenerative diseases. However, the underling mechanism of neurotoxicity is not well understood. This study aimed to investigate the possible toxic outcomes of Epoxiconzole, a triazole fungicide, on the brain of adult rats in vivo, and in vitro on neural stem cells derived from the subventricular zone of newborn Wistar rats. Our results revealed that oral exposure to EPX at these concentrations (8, 24, 40, 56 mg/kg bw representing respectively NOEL (no observed effect level), NOEL × 3, NOEL × 5, and NOEL × 7) for 28 days caused a considerable generation of oxidative stress in adult rat brain tissue. Furthermore, a significant augmentation in lipid peroxidation and protein oxidation has been found. Moreover, it induced an elevation of DNA fragmentation as assessed by the Comet assay. Indeed, EPX administration impaired activities of antioxidant enzymes and inhibited AChE activity. Concomitantly, this pesticide produced histological alterations in the brain of adult rats. Regarding the embryonic neural stem cells, we demonstrated that the treatment by EPX reduced the viability of cells with an IC50 of 10 μM. It also provoked the reduction of cell proliferation, and EPX triggered arrest in G1/S phase. The neurosphere formation and self-renewal capacity was reduced and associated with decreased differentiation. Moreover, EPX induced cytoskeleton disruption as evidenced by immunocytochemical analysis. Our findings also showed that EPX induced apoptosis as evidenced by a loss of mitochondrial transmembrane potential (ΔΨm) and an activation of caspase-3. In addition, EPX promoted ROS production in neural stem cells. Interestingly, the pretreatment of neural stem cells with the N-acetylcysteine (ROS scavenger) attenuated EPX-induced cell death, disruption of neural stem cells properties, ROS generation and apoptosis. Thus, the use of this hazardous material should be restricted and carefully regulated.

Gene regulation by morpholines and piperidines in the cardiac embryonic stem cell test

The cardiac embryonic stem cell test (ESTc) is an in vitro embryotoxicity screen which uses cardiomyocyte formation as the main differentiation route. Studies are ongoing into whether an improved specification of the biological domain can broaden the applicability of the test, e.g. to discriminate between structurally similar chemicals by measuring expression of dedicated gene transcript biomarkers. We explored this with two chemical classes: morpholines (tridemorph; fenpropimorph) and piperidines (fenpropidin; spiroxamine). These compounds cause embryotoxicity in rat such as cleft palate. This malformation can be linked to interference with retinoic acid balance, neural crest (NC) cell migration, or cholesterol biosynthesis. Also neural differentiation within the ESTc was explored in relation to these compounds. Gene transcript expression of related biomarkers were measured at low and high concentrations on differentiation day 4 (DD4) and DD10. All compounds showed stimulating effects on the cholesterol biosynthesis related marker Msmo1 after 24 h exposure and tridemorph showed inhibition of Cyp26a1 which codes for one of the enzymes that metabolises retinoic acid. A longer exposure duration enhanced expression levels for differentiation markers for cardiomyocytes (Nkx2-5; Myh6) and neural cells (Tubb3) on DD10. This readout gave additional mechanistic insight which enabled previously unavailable in vitro discrimination between the compounds, showing the practical utility of specifying the biological domain of the ESTc.

Flusilazole Induced Cytotoxicity and Inhibition of Neuronal Growth in Differentiated SH-SY5Y Neuroblastoma Cells by All-Trans-Retinoic Acid (Atra)

Objectives

Flusilazole (FLUS) is a broad-spectrum organosilicon triazole fungicide used for protecting economically important cereals and orchard fruits. Considering the exposure route of pesticides, pesticide contamination of food is inevitable. Furthermore, excessive exposure to pesticides causes health problems in both target and non-target organisms. It was aimed to evaluate the effects of the triazole fungicide FLUS on cytotoxicity and neurite extension in differentiated SH-SY5Y neuroblastoma cells.

Materials and Methods

The SH-SY5Y cells were differentiated into mature neurons using 10-µM all-trans-retinoic acid (RA) treatment for 7 days. Then the differentiated SH-SY5Y cells were treated with 50, 100 and 200 μM FLUS for 24 h. Afterwards, cell viability assays were performed including crystal violet, neutral red cell viability, and lactate dehydrogenase leakage assays. The morphological examinations were performed and neurite lenghts of the cells were measured in all experimental groups.

Results

FLUS treatment induced cytotoxicity in SH-SY5Y cells differentiated with RA. Significant decreases in cell viability percentages were observed. Furthermore, neurite lengths were negatively affected by the treatment of FLUS at the highest concentration.

Conclusion

FLUS is a fungicide widely used in agriculture to protect crops from fungal diseases. However, the intensive use of these compounds causes a potential risk to human and environmental health. According to the results of the study, it can be concluded that high concentrations of FLUS cause neurotoxicity by causing neural cell death and adverse effects on neurite outgrowth in differentiated SH-SY5Y cells. FLUS exposure can cause neuronal degeneration in mammals.

Exploring the biological domain of the neural embryonic stem cell test (ESTn): Morphogenetic regulators, Hox genes and cell types, and their usefulness as biomarkers for embryotoxicity screening

Animal-free assessment of compound-induced developmental neurotoxicity will most likely be based on batteries of multiple in vitro tests. The optimal battery is built by combining tests with complementary biological domains that together ideally cover all relevant toxicity pathways. Thus, biological domain definition, i.e. which biological processes and cell types are represented, is an important assay characteristic for determining the place of assays in testing strategies. The murine neural embryonic stem cell test (ESTn) is employed to predict the developmental neurotoxicity of compounds. The aim of this study was to explore the biological domain of ESTn according to three groups of biomarker genes of early (neuro)development: morphogenetic regulators, Hox genes and cell type markers for the ectodermal and neural lineages. These biomarker groups were selected based on their crucial regulatory role in (neuro)development. Analysis of these genes in a series of previously generated whole transcriptome datasets of ESTn showed that at day 7 in culture cell differentiation resembled hindbrain/branchial/thoracic development between E6.5-E12.5 in vivo, with subsequent development into a mixed cell culture containing different neural subtypes, astrocytes and oligodendrocytes by day 13. In addition, the selected biomarkers showed common and distinct responses to compound exposure. Monitoring the biological domain of ESTn through gene expression patterns of morphogenetic regulators, Hox genes and cell type markers proved instrumental in providing mechanistic understanding of compound effects on neural differentiation in ESTn, and can aid in positioning of the test in a battery of complementary in vitro tests in integrated approaches to testing and assessment.

Stereoselective metabolism and potential adverse effects of chiral fungicide triadimenol on Eremias argus

Reptiles are an important part of vertebrates and are the primitive terrestrial vertebrates. However, lots of reptile species are endangered or susceptible to extinction. It is no doubt that contaminants are one of the important reasons for the decline of the lizard population. In this study, the selective metabolism of triadimenol (TN) in the male Eremias argus lizards and the toxic effects of TN on lizards were studied. TN chiral isomers were separated and detected by HPLC-MS/MS system with Lux Cellulose-1 column. Tissue distribution experiments showed the existence of stereoselectivity biotransformation of TN enantiomers among organs in lizards, and RR-TN preferentially emerged over the other enantiomers. The antioxidant enzymes (SOD, CAT, GST) activities and MDA content assays demonstrated that TN induced oxidative stress in most organs, especially in the liver, and the histopathology analysis showed the severe liver and testis damage caused by 14-day continuous TN gavage. The reproductive effects of TN-induced reflected in the increased sex hormone testosterone. This research confirms that TN could induce hepatic and reproductive toxicity of E. argus lizard.

Pesticides and conservation of large ungulates: Health risk to European bison from plant protection products as a result of crop depredation

The coexistence of large mammals and humans in the contemporary landscape is a big challenge for conservationists. Wild ungulates that forage on arable fields are exposed to the negative effects of pesticides, and this problem also applies to protected species for which intoxication by pesticides may pose a health risk and directly affect the effectiveness of conservation efforts. In this paper we assessed the threat posed by pesticides to the European bison Bison bonasus, a species successfully restituted after being extinct in the wild. We studied samples of B. bonasus liver from three free-living populations in Poland (Białowieska, Knyszyńska, and Borecka forests) and captive individuals from breeding centres. LC-QTOF-MS/MS two-step analysis for the detection, identification and confirmation of pesticide residues in liver samples, which included MS and targeted MS/MS scans, was conducted. It was found that European bison are exposed to pesticides as a result of crop depredation: the presence of tetraconazole, fluopyram and diazinon residues in 12 liver samples was confirmed. The concentration levels of the detected substances were quite low, but in the liver samples more than one substance was usually found, and the potential health risk to European bison may result from the synergistic interaction of these substances. The place of occurrence of the population, abundance, and the management regime affect the exposure of European bison to pesticides. Due to the high conservation status of the European bison, the monitoring of intoxication by pesticides should be included in the conservation plans of this species. This issue should also be more widely included in the study of other wild ungulates because knowledge about the impact of pesticides on wildlife is still insufficient.

The role of teratogens in neural crest development

The neural crest (NC), discovered by Wilhelm His 150 years ago, gives rise to a multipotent migratory embryonic cell population that generates a remarkably diverse and important array of cell types during the development of the vertebrate embryo. These cells originate in the neural plate border (NPB), which is the ectoderm between the neural plate and the epidermis. They give rise to the neurons and glia of the peripheral nervous system, melanocytes, chondrocytes, smooth muscle cells, odontoblasts and neuroendocrine cells, among others. Neurocristopathies are a class of congenital diseases resulting from the abnormal induction, specification, migration, differentiation or death of NC cells (NCCs) during embryonic development and have an important medical and societal impact. In general, congenital defects affect an appreciable percentage of newborns worldwide. Some of these defects are caused by teratogens, which are agents that negatively impact the formation of tissues and organs during development. In this review, we will discuss the teratogens linked to the development of many birth defects, with a strong focus on those that specifically affect the development of the NC, thereby producing neurocristopathies. Although increasing attention is being paid to the effect of teratogens on embryonic development in general, there is a strong need to critically evaluate the specific role of these agents in NC development. Therefore, increased understanding of the role of these factors in NC development will contribute to the planning of strategies aimed at the prevention and treatment of human neurocristopathies, whose etiology was previously not considered.

Dose addition in chemical mixtures inducing craniofacial malformations in zebrafish (Danio rerio) embryos

A challenge in cumulative risk assessment is to model hazard of mixtures. EFSA proposed to only combine chemicals linked to a defined endpoint, in so-called cumulative assessment groups, and use the dose-addition model as a default to predict combined effects. We investigated the effect of binary mixtures of compounds known to cause craniofacial malformations, by assessing the effect in the head skeleton (M-PQ angle) in 120hpf zebrafish embryos. We combined chemicals with similar mode of action (MOA), i.e. the triazoles cyproconazole, triadimefon and flusilazole; next, reference compounds cyproconazole or triadimefon were combined with dissimilar acting compounds, TCDD, thiram, VPA, prochloraz, fenpropimorph, PFOS, or endosulfan. These mixtures were designed as (near) equipotent combinations of the contributing compounds, in a range of cumulative concentrations. Dose-addition was assessed by evaluation of the overlap of responses of each of the 14 tested binary mixtures with those of the single compounds. All 10 test compounds induced an increase of the M-PQ angle, with varying potency and specificity. Mixture responses as predicted by dose-addition did not deviate from the observed responses, supporting dose-addition as a valid assumption for mixture risk assessment. Importantly, dose-addition was found irrespective of MOA of contributing chemicals.

The Ascidian Embryo Teratogenicity assay in Ciona intestinalis as a new teratological screening to test the mixture effect of the co-exposure to ethanol and fluconazole

The aim of this work was to evaluate the Ascidian Embryo Teratogenicity assay (AET) as new alternative invertebrate model to test the developmental effects of the co-exposure to ethanol and fluconazole. Ciona intestinalis embryos were exposed to the azolic fungicide fluconazole, (FLUCO, 7.8-250μM), to ethanol (Eth, 0.01-0.5%) and to their mixture (0.01% Eth+FLUCO 7.8-250μM) from neurula to larval stage. At the end of the exposure period, larvae were morphologically evaluated and benchmark analysis performed by using the PROAST modelling software. Both compounds were teratogenic in a concentration-related manner, particularly affecting the pigmented organs. The co-exposure to Eth enhanced the effects of FLUCO, the additive hypothesis was not rejected by the modelling. The results demonstrated that AET could be considered a good vertebrate-free alternative model for toxicological investigation in embryos.

The cardiovascular toxicity of triadimefon in early life stage of zebrafish and potential implications to human health

The health risk of triadimefon (TF) to cardiovascular system of human is still unclear, especially to pesticide suicides population, occupational population (farmers, retailers and pharmaceutical workers), and special population (young children and infants, pregnant women, older people, and those with compromised immune systems) who are at a greater risk. Therefore, firstly we explored the toxic effects and possible mechanism of cardiovascular toxicity induced by TF using zebrafish model. Zebrafish at stage of 48 h post fertilization (hpf) exposed to TF for 24 h exhibited morphological malformations which were further confirmed by histopathologic examination, including pericardial edema, circulation abnormalities, serious venous thrombosis and increased distance between the sinus venosus (SV) and bulbus arteriosus (BA) regions of the heart. In addition to morphological changes, TF induced functional deficits in the heart of zebrafish, including bradycardia and a significant reduced cardiac output that became more serious at higher concentrations. To better understand the possible molecular mechanisms underlying cardiovascular toxicity in zebrafish, we investigated the transcriptional level of genes related to calcium signaling pathway and cardiac muscle contraction. Q-PCR (quantitative real-time polymerase chain reaction) results demonstrated that the expression level of genes related to ATPase (atp2a1l, atp1b2b, atp1a3b), calcium channel (cacna1ab, cacna1da) and cardiac troponin C (tnnc1a) were significantly decreased after TF exposure. For the first time, the present study revealed that TF exposure had observable morphological and functional negative impacts on cardiovascular system of zebrafish. Mechanistically, this toxicity might result from the pressure of down-regulation of genes associated with calcium signaling pathway and cardiac muscle contraction following TF exposure. These findings generated here can provide information for better pesticide poisoning treatments, occupational disease prevention, and providing theoretical foundation for risk management measures.

Zebrafish as an Alternative Vertebrate Model for Investigating Developmental Toxicity-The Triadimefon Example

Triadimefon is a widely used triazole fungicide known to cause severe developmental defects in several model organisms and in humans. The present study evaluated in detail the developmental effects seen in zebrafish embryos exposed to triadimefon, confirmed and expanded upon previous phenotypic findings and compared them to those observed in other traditional animal models. In order to do this, we exposed embryos to 2 and 4 µg/mL triadimefon and evaluated growth until 120 h post-fertilization (hpf) through gross morphology examination. Our analysis revealed significant developmental defects at the highest tested concentration including somite deformities, severe craniofacial defects, a cleft phenotype along the three primary neural divisions, a rigorously hypoplastic or even absent mandible and a hypoplastic morphology of the pharyngeal arches. Interestingly, massive pericardial edemas, abnormal shaped hearts, brachycardia and inhibited or absent blood circulation were also observed. Our results revealed that the presented zebrafish phenotypes are comparable to those seen in other organism models and those derived from human observations as a result of triadimefon exposure. We therefore demonstrated that zebrafish provide an excellent system for study of compounds with toxic significance and can be used as an alternative model for developmental toxicity studies to predict effects in mammals.

An adverse outcome pathway framework for neural tube and axial defects mediated by modulation of retinoic acid homeostasis

Developmental toxicity can be caused through a multitude of mechanisms and can therefore not be captured through a single simple mechanistic paradigm. However, it may be possible to define a selected group of overarching mechanisms that might allow detection of the vast majority of developmental toxicants. Against this background, we have explored the usefulness of retinoic acid mediated regulation of neural tube and axial patterning as a general mechanism that, when perturbed, may result in manifestations of developmental toxicity that may cover a large part of malformations known to occur in experimental animals and in man. Through a literature survey, we have identified key genes in the regulation of retinoic acid homeostasis, as well as marker genes of neural tube and axial patterning, that may be used to detect developmental toxicants in in vitro systems. A retinoic acid-neural tube/axial patterning adverse outcome pathway (RA-NTA AOP) framework was designed. The framework was tested against existing data of flusilazole exposure in the rat whole embryo culture, the zebrafish embryotoxicity test, and the embryonic stem cell test. Flusilazole is known to interact with retinoic acid homeostasis, and induced common and unique NTA marker gene changes in the three test systems. Flusilazole-induced changes were similar in directionality to gene expression responses after retinoic acid exposure. It is suggested that the RA-NTA framework may provide a general tool to define mechanistic pathways and biomarkers of developmental toxicity that may be used in alternative in vitro assays for the detection of embryotoxic compounds.

Stereoselective transformation of triadimefon to metabolite triadimenol in wheat and soil under field conditions

Racemic triadimefon (TF) was applied to wheat and soil at three sites (Beijing, Huaibei, and Zhengzhou in China) under open field conditions. Its enantioselective degradation and stereoselective transformation to the major metabolite, triadimenol (TN), in wheat straw, grain and soil were investigated. At all sites, the degradation of TF enantiomers in straw and soil followed first-order kinetics. In soil from Beijing and Zhengzhou R-(-)-TF was preferentially degraded; however, preferential enantioselective degradations were not recorded in soil from Huaibei or in the straw from all sites. There were noticeable differences in the stereoselective formation of TN stereoisomers in all straw and soil samples. TN diastereomer A with high animal toxicity was preferentially produced via a reductive reaction in straw. In contrast, diastereomer B, was preferential in soil across the experimental period. Different TN concentrations were found in the order of SR-(-)-TN>RR-(+)-TN>RS-(+)-TN>SS-(-)-TN in straw, and RR-(+)-TN>SS-(-)-TN>SR-(-)-TN>RS-(+)-TN in soil. Neither TF nor TN was found in wheat grain at harvest. Because of differences in degradation, formation, and toxicity, the characterization of enantiomers and stereoisomers in this study contributes toward comprehensively assessing the fate and risk of chiral agrochemicals in the environment and food.

Azole fungicides disturb intracellular Ca2+ in an additive manner in dopaminergic PC12 cells

Humans are exposed to complex mixtures of pesticides and other compounds, mainly via food. Azole fungicides are broad spectrum antifungal compounds used in agriculture and in human and veterinary medicine. The mechanism of antifungal action relies on inhibition of CYP51, resulting in inhibition of fungal cell growth. Known adverse health effects of azole fungicides are mainly linked to CYP inhibition. Additionally, azole fungicide-induced neurotoxicity has been reported, though the underlying mechanism(s) are largely unknown. We therefore investigated the effects of a group of six azole fungicides (imazalil, flusilazole, fluconazole, tebuconazole, triadimefon, and cyproconazole) on cell viability using a combined alamar Blue/CFDA-AM assay and on oxidative stress using a H2-DCFDA fluorescent assay. As calcium plays a pivotal role in neuronal survival and functioning, effects of these six azole fungicides and binary and quaternary mixtures of azole fungicides on the intracellular calcium concentration ([Ca(2+)]i) were investigated using single-cell fluorescence microscopy in dopaminergic PC12 cells loaded with the calcium-sensitive fluorescent dye Fura-2. Only modest changes in cell viability and ROS production were observed. However, five out of six azole fungicides induced a nonspecific inhibition of voltage-gated calcium channels (VGCCs), though with varying potency. Experiments using binary IC20 and quaternary IC10 mixtures indicated that the inhibitory effects on VGCCs are additive. The combined findings demonstrate modulation of intracellular Ca(2+) via inhibition of VGCCs as a novel mode of action of azole fungicides. Furthermore, mixtures of azole fungicides display additivity, illustrating the need to take mixture effects into account in human risk assessment.

Removal of ethylenthiourea and 1,2,4-triazole pesticide metabolites from water by adsorption in commercial activated carbons

This study evaluated the adsorption capacity of ethylenthiourea (ETU) and 1H-1,2,4-triazole (1,2,4-T) for two commercial activated carbons: charcoal-powdered activated carbon (CPAC) and bovine bone-powdered activated carbon (BPAC). The tests were conducted at a bench scale, with ETU and 1,2,4-T diluted in water, for isotherm and adsorption kinetic studies. The removal of the compounds was accompanied by a total organic carbon (TOC) analysis and ultraviolet (UV) reduction analysis. The coals were characterized by their surface area using nitrogen adsorption/desorption, by a scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) and by a zero charge point analysis (pHpcz). The results showed that adsorption kinetics followed a pseudo-second-order model for both coals, and the adsorption isotherms for CPAC and BPAC were adjusted to the Langmuir and Freundlich isotherms, respectively. The CPAC removed approximately 77% of the ETU and 76% of the 1,2,4-T. The BPAC was ineffective at removing the contaminants.

Compound-specific effects of diverse neurodevelopmental toxicants on global gene expression in the neural embryonic stem cell test (ESTn)

Alternative assays for developmental toxicity testing are needed to reduce animal use in regulatory toxicology. The in vitro murine neural embryonic stem cell test (ESTn) was designed as an alternative for neurodevelopmental toxicity testing. The integration of toxicogenomic-based approaches may further increase predictivity as well as provide insight into underlying mechanisms of developmental toxicity. In the present study, we investigated concentration-dependent effects of six mechanistically diverse compounds, acetaldehyde (ACE), carbamazepine (CBZ), flusilazole (FLU), monoethylhexyl phthalate (MEHP), penicillin G (PENG) and phenytoin (PHE), on the transcriptome and neural differentiation in the ESTn. All compounds with the exception of PENG altered ESTn morphology (cytotoxicity and neural differentiation) in a concentration-dependent manner. Compound induced gene expression changes and corresponding enriched gene ontology biological processes (GO-BP) were identified after 24h exposure at equipotent differentiation-inhibiting concentrations of the compounds. Both compound-specific and common gene expression changes were observed between subsets of tested compounds, in terms of significance, magnitude of regulation and functionality. For example, ACE, CBZ and FLU induced robust changes in number of significantly altered genes (≥ 687 genes) as well as a variety of GO-BP, as compared to MEHP, PHE and PENG (≤ 55 genes with no significant changes in GO-BP observed). Genes associated with developmentally related processes (embryonic morphogenesis, neuron differentiation, and Wnt signaling) showed diverse regulation after exposure to ACE, CBZ and FLU. In addition, gene expression and GO-BP enrichment showed concentration dependence, allowing discrimination of non-toxic versus toxic concentrations on the basis of transcriptomics. This information may be used to define adaptive versus toxic responses at the transcriptome level.

Comparison of the mouse Embryonic Stem cell Test, the rat Whole Embryo Culture and the Zebrafish Embryotoxicity Test as alternative methods for developmental toxicity testing of six 1,2,4-triazoles

The relatively high experimental animal use in developmental toxicity testing has stimulated the search for alternatives that are less animal intensive. Three widely studied alternative assays are the mouse Embryonic Stem cell Test (EST), the Zebrafish Embryotoxicity Test (ZET) and the rat postimplantation Whole Embryo Culture (WEC). The goal of this study was to determine their efficacy in assessing the relative developmental toxicity of six 1,2,4-triazole compounds,(1) flusilazole, hexaconazole, cyproconazole, triadimefon, myclobutanil and triticonazole. For this purpose, we analyzed effects and relative potencies of the compounds in and among the alternative assays and compared the findings to their known in vivo developmental toxicity. Triazoles are antifungal agents used in agriculture and medicine, some of which are known to induce craniofacial and limb abnormalities in rodents. The WEC showed a general pattern of teratogenic effects, typical of exposure to triazoles, mainly consisting of reduction and fusion of the first and second branchial arches, which are in accordance with the craniofacial malformations reported after in vivo exposure. In the EST all triazole compounds inhibited cardiomyocyte differentiation concentration-dependently. Overall, the ZET gave the best correlation with the relative in vivo developmental toxicities of the tested compounds, closely followed by the EST. The relative potencies observed in the WEC showed the lowest correlation with the in vivo developmental toxicity data. These differences in the efficacy between the test systems might be due to differences in compound kinetics, in developmental stages represented and in the relative complexity of the alternative assays.

Assessing the reproductive toxicity of some (con)azole compounds using a structure-activity relationship approach

The present research investigates the study of a set of 27 (con)azoles and their reproductive toxicity. (Con)azoles are used as fungicides and herbicides in agriculture for treatment of fruits, vegetables, cereals, and seeds, or as human antimycotic therapeutics. According to EEC Directive 91/414, active substances used in plant protection products must undergo reproductive toxicity testing. Reproductive toxicity is a complex biological endpoint, which includes many different biological processes and, therefore, it can only to a limited extent be assessed by a single quantitative structure-activity relationship (QSAR) model. The proposed SAR models are built using unsupervised methods, such as hierarchical clustering, principal component analysis and self-organizing maps, with the aim of studying the similarity relationships between structures. The molecular structures are represented with a set of topological and structural descriptors. The models showing clusters, closest neighbours or outliers may support the categorization and the classification of (con)azoles as potential reproductive toxicants.

Pharmacologic advances in canine and feline reproduction

Substantial improvements in therapeutic options for companion animal reproduction and gynecologic emergencies have been made over the last decade. New, alternative drug treatments, with fewer side effects and improved efficacy, are available. This has widened the spectrum of therapeutic possibilities for diseases that were previously treated only by surgical intervention. New drugs are available for estrus induction and pregnancy termination, as well as for the treatment of pyometra. This review summarizes the pharmacology and toxicology of reproductive agents currently in use for contraception, pyometra, dystocia, eclampsia, premature labor, agalactia, mastitis, metritis, and prostatic disorders, and compares their efficacy and safety with newer agents. Drug use and exposure during pregnancy and lactation, and subsequent risks to the fetuses, are also explored, with emphasis on antimicrobials, antifungals, anthelminthics, anesthetics, and vaccinations.

Disruption of retinoid transport, metabolism and signaling by environmental pollutants

Although the assessment of circulatory levels of retinoids has become a widely used biomarker of exposure to environmental pollutants, the adverse effects caused by imbalance of the retinoid metabolism and signaling in wildlife are not known in detail. Retinoids play an important role in controlling such vital processes as morphogenesis, development, reproduction or apoptosis. Unlike other signaling molecules, retinoids are not strictly endogenous but they are derived from dietary sources of vitamin A or its precursors and thus they are sometimes referred to as 'dietary' hormones. Some environmental pollutants that affect embryogenesis, immunity or epithelial functions were also shown to interfere with retinoid metabolism and signaling in animals. This suggests that at least some of their toxic effects may be related to interaction with the retinoid metabolism, transport or signal transduction. This review summarizes in vivo and in vitro studies on interaction of environmental complex samples, pesticides, polychlorinated dioxins, polychlorinated biphenyls, polycyclic aromatic compounds and other organic pollutants with physiology of retinoids. It sums up contemporary knowledge about levels of interaction and mechanisms of action of the environmental contaminants.

Comparison of four different colorimetric and fluorometric cytotoxicity assays in a zebrafish liver cell line

Background

A broad spectrum of cytotoxicity assays is currently used in the fields of (eco)toxicology and pharmacology. To choose an appropriate assay, different parameters like test compounds, detection mechanism, specificity, and sensitivity have to be considered. Furthermore, tissue or cell line can influence test performance. For zebrafish (Danio rerio), as emerging model organism, cell lines are now increasingly used, but few studies examined cytotoxicity in these cell systems. Therefore, we compared four cytotoxicity assays in the zebrafish liver cell line, ZFL, to test four differently acting model compounds. The tests comprised two colorimetric assays (MTT assay using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide, and the LDH assay detecting lactate dehydrogenase activity) and two fluorometric assays (alamarBlue^® using resazurin, and CFDA-AM based on 5-carboxyfluorescein diacetate acetoxymethyl ester). Model compounds were the pharmaceutical Tamoxifen, its metabolite 4-Hydroxy-Tamoxifen, the fungicide Flusilazole and the polycyclic aromatic hydrocarbon Benzo[a]pyrene.

Results

All four assays performed well in the ZFL cells and led to reproducible dose-response curves for all test compounds. Effective concentrations causing 10% or 50% loss of cell viability (EC₁₀ and EC₅₀ values) varied by a maximum factor of 7.0 for the EC₁₀ values and a maximum factor of 1.8 for the EC₅₀ values. The EC values were not statistically different between the four assays, which is due to the assessed unspecific effects of the compounds. However, most often, the MTT assay and LDH assay showed the highest and lowest EC values, respectively. Nevertheless, the LDH assay showed the highest intra- and inter-assay variabilities and the lowest signal-to-noise ratios. In contrast to MTT, the other three assays have the advantage of being non-destructive, easy to handle, and less time consuming. Furthermore, AB and CFDA-AM can be combined on the same set of cells without damaging the cells, allowing later on their use for the investigation of other endpoints.

Conclusion

We recommend the alamarBlue and CFDA-AM assays for cytotoxicity assessment in ZFL cells, which can be applied either singly or combined.

Maternal use of fluconazole and risk of congenital malformations: a Danish population-based cohort study

OBJECTIVES

Fluconazole is widely used for the treatment of candidiasis. Although the drug is also prescribed to pregnant women, data on the safety of use of fluconazole during pregnancy are limited. We examined the association between the maternal use of fluconazole during pregnancy and the risk of congenital malformations.

PATIENTS AND METHODS

In this population-based cohort study in Northern Denmark, we included 1079 women who had a live birth or a stillbirth after the 20th week of gestation and who redeemed at least one prescription for fluconazole during the first trimester. The reference cohort comprised 170 453 pregnant women who redeemed no fluconazole prescription during pregnancy. The women were identified through the Danish Medical Birth Registry. Data on drug use, birth outcome and covariates were extracted from population-based healthcare databases. We used logistic regression to estimate the prevalence odds ratio (POR) for congenital malformations after fluconazole exposure, while adjusting for maternal smoking, parity, maternal age and concurrent prescriptions for antiepileptics or antidiabetics.

RESULTS

Among 1079 women who filled a fluconazole prescription during the first trimester, 797 (74%) received a total of 150 mg of fluconazole, 235 (22%) received 300 mg of fluconazole, 24 (2%) received 350 mg of fluconazole and 23 (2%) received 600 mg of fluconazole. These women gave birth to 44 (4.1%) children with congenital malformations. The 170 453 women without fluconazole prescriptions gave birth to 6152 (3.6%) children with congenital malformations. For congenital malformations overall, the adjusted POR associated with the first-trimester fluconazole use was 1.0 (95% confidence interval: 0.8-1.4).

CONCLUSIONS

We found no overall increased risk of congenital malformations after exposure to short-course treatment with fluconazole in early pregnancy.

Krox20 is down-regulated following triazole in vitro embryonic exposure: a polycompetitor-based assay

This study was conducted in order to analyse gene-expression alterations in rat embryos following exposure to triazoles, using an easy-handling approach. Triazole derivatives have been shown to alter the morphology of cranio-facial structures and to induce abnormalities in hindbrain patterning and neural crest cell migration. Specification of hindbrain segments is regulated by retinoic acid and the hox code. Krox20 was chosen as molecular marker for its specific distribution in the anterior neural tube. In fact, this zinc-finger protein is expressed in rhombomere 3 and 5. Mis-regulation of Krox20 levels have shown to induce severe alterations in the correct patterning of the rhomboencephalon and the derived structures. In order to analyse Krox20 mRNA levels in rat embryos exposed in vitro to the triazole derivative triadimefon, a semi-quantitative approach utilising the competitive RT-PCR was chosen. A lambda phage-based plasmid construct that could compete with target and internal standard gene at the same time during enzymatic reaction was generated. Results were confirmed by real-time RT-PCR analysis on the same samples. Our data show a down-regulation of Krox20 transcript levels after exposure to the triazole derivative, implying a key role of this molecule in the pathogenic pathway induced by triazole exposure.

Antifungal triazole derivative triadimefon induces ectopic maxillary cartilage by altering the morphogenesis of the first branchial arch

BACKGROUND

The triazole derivative, triadimefon (FON), induces branchial arch abnormalities in post-implantation rat embryos cultured in vitro, and cranio-facial malformations in mouse fetuses. Ectopic maxillary cartilage has been also described as a typical FON-related malformation. This work studies the morphogenesis of the ectopic cartilage in rat embryos and fetuses exposed in vivo to FON during the early postimplantation period.

METHODS

Pregnant rats were treated with 0, 250, and 500 mg/kg FON on Day 9.5 of pregnancy (D9.5) and sacrificed at term (D20), during the early fetal period (D17) or at different embryogenetic periods (D10, D11, D12). The skeleton was examined after stain of bone and cartilage or of cartilage alone respectively at term or at D17. The neural crest cell (NCC) migration and compaction was investigated at D10 and D11 and the cranial nerve organization described at D12.

RESULTS

Triadimefon is teratogenic in rats under the chosen experimental conditions. The malformations were at the level of the cranio-facial and axial skeleton at term and of the hindbrain nerves in embryos. A NCC abnormal migration and compaction was observed at the level of the first branchial arch: in FON-exposed embryos NCC were detected at the level of both maxillary and mandibular processes, whereas control embryos showed the immunostained tissue only at the level of the mandibular bud.

CONCLUSIONS

The pathogenic pathway, proposed to explain the ectopic cartilage, is the displacement of part of the NCC-derived tissues at the maxillary region of the first branchial arch.

Gene expression in Xenopus laevis embryos after Triadimefon exposure

The triazole derivative Triadimefon (FON) is a systemic fungicide used to control powdery mildews, rusts, and other fungal pests. Some data have already been published about the teratogenic activity of this compound: craniofacial malformations were found in mouse, rat, and Xenopus laevis embryos exposed to FON. These alterations were correlated to defective branchial arch development possibly caused by abnormal neural crest cell (NCC) migration into the branchial mesenchyme. As the migration of NCCs is controlled by the HOX code and by an anteroposterior retinoic acid (RA) gradient, we analyzed the expression of CYP26, a key enzyme in RA metabolism, following FON exposure. The increased expression of this gene and the ability of citral (a RA inhibitor) to reduce the teratogenic effects of the fungicide support the notion that endogenous RA is involved in the mechanism of action of FON. Moreover, by in situ hybridization, we studied the effects of FON exposure at gastrula stage on the expression of some genes involved in craniofacial development, hindbrain patterning, and NCC migration. We observed abnormal localization of xCRABP, Hoxa2 and Xbap signal expression at the level of migrating NCC domains, whereas in the hindbrain, we did not find any alteration in Krox20 and Hoxa2 expression.

Developmental toxic effects of antifungal flusilazole administered by gavage to mice

BACKGROUND

The developmental toxicity of flusilazole was studied in CD-1 mice after oral administration.

METHODS

Pregnant mice were given flusilazole at doses of 0 (corn oil), 10, 20, and 40 mg/kg/day, by gavage, on gestational days (GD) 6-15.

RESULTS

Maternal toxicity, as evidenced by reduction in body weight gain and signs of toxicity, was observed at the middle- and high-dose groups. No significant incidence of resorptions or death was observed in any of dose groups. There was a pronounced reduction in fetal weight, which was significantly lower than control from 20 and 40 mg/kg/day. There was no significant increase in the incidence of fetuses with external or visceral malformations in any of dose groups, but there was a significant increase in the incidence of skeletal malformations was observed at 20 and 40 mg/kg/day.

CONCLUSIONS

The results of this study reported marked maternal toxicity, growth retardation, and skeletal abnormalities in the mid- and high-dose groups. It seems likely that marked maternal toxicity contributed to the observed alterations in fetal growth retardation and skeletal development. The no-observed-effect level in the present study for maternal and developmental toxicity was 10 mg/kg/day.