Disruption of testosterone homeostasis as a mode of action for the reproductive toxicity of triazole fungicides in the male rat

Fungicide-albumin interactions: unraveling the complex relationship-a comprehensive review

This review will give an insight into the interactions of serum albumins, which are proteins found in the blood, with fungicides. There are molecular interactions between several fungicides and two serum albumin proteins: human serum albumin (HSA) and bovine serum albumin (BSA). The main objective of this review is to through some light on the interactions of the fungicides with serum albumins and to highlight their toxicity level. The interactions of serum albumins with fungicides are complex and can be affected by the properties of the proteins themselves. This review provides valuable insight into the interactions between serum albumins and fungicides, which can help to know the efficacy and mechanism of fungicides and may help in designing new fungicides with low or no toxicity.

Epoxiconazole altered hepatic metabolism in adult zebrafish based on transcriptomic analysis

Epoxiconazole (EPX) is a triazole fungicide, which has been widely used in pest control of cereal crops. However, its extensive use has led to concerning levels of residue in water bodies, posing substantial risks to aquatic life. In this study, we characterized the toxicological effects of EPX on 6-month-old male and female zebrafish at 70 and 700 μg/L, respectively. The results revealed that EPX exposure markedly increased both body length and weight in zebrafish of both sexes, consequently elevating their condition factor. Besides, EPX exposure resulted in notable alterations in hepatic histopathology. These changes included loosened hepatocyte structure, ballooning degeneration, nucleolysis, and disappearance of cell line, with male zebrafish exhibiting more severe damage. High concentration of EPX also significantly increased hepatic lipid accumulation in male zebrafish, as well as increased hepatic triglyceride (TG) levels. Correspondingly, there was a notable alteration in the transcription of genes including cyp51, hmgcr, and PPAR-γ, which associated with cholesterol and lipid metabolism. Interestingly, with the hepatic transcriptomic analysis, high concentration of EPX produced 195 upregulated and 107 downregulated differential expression genes. Both KEGG and GO analyses identified significant enrichment of these genes in lipid and amino acid metabolism pathways. Notably, some key genes involved in the steroid synthesis pathway were marked upregulated. In addition, molecular docking study confirmed that EPX could bind CYP51 protein well (△G = -7.7 kcal/mol). Taken together, these findings demonstrated the multiple toxic effects of EPX on adult zebrafish.

Transgenerational effects of triazole fungicides on gene expression and egg compounds in non-exposed offspring: A case study using Red-Legged Partridges (Alectoris rufa)

Triazole fungicides are widely used to treat cereal seeds before sowing. Granivorous birds like the Red-legged Partridge (Alectoris rufa) have high exposure risk because they ingest treated seeds that remain on the field surface. As triazole fungicides can act as endocrine disruptors, affecting sterol synthesis and reproduction in birds several months after exposure, we hypothesized that these effects could also impact subsequent generations of exposed birds. To test this hypothesis, we exposed adult partridges (F0) to seeds treated at commercial doses with four different formulations containing triazoles as active ingredients (flutriafol, prothioconazole, tebuconazole, and a mixture of the latter two), simulating field exposure during late autumn sowing. During the subsequent reproductive season, two to four months after exposure, we examined compound allocation of steroid hormones, cholesterol, vitamins, and carotenoids in eggs laid by exposed birds (F1), as well as the expression of genes encoding enzymes involved in sterol biosynthesis in one-day-old chicks of this F1. One year later, F1 animals were paired again to investigate the expression of the same genes in the F2 chicks. We found changes in the expression of some genes for all treatments and both generations. Additionally, we observed an increase in estrone levels in eggs from partridges treated with flutriafol compared to controls, a decrease in tocopherol levels in partridges exposed to the mixture of tebuconazole and prothioconazole, and an increase in retinol levels in partridges exposed to prothioconazole. Despite sample size limitations, this study provides novel insights into the mechanisms of action of the previously observed effects of triazole fungicide-treated seeds on avian reproduction with evidence that the effects can persist beyond the exposure windows, affecting unexposed offspring of partridges fed with treated seeds. The results highlight the importance of considering long-term chronic effects when assessing pesticide risks to wild birds.

Hormonal and haematological biomarkers as indicators of stress induced by Diuron herbicide toxicity on Clarias gariepinus (Burchell, 1822) sub-adults

Diuron is a globally used herbicide for weed control but has anti-androgenic effects on androgens (testosterone and androstenedione), antagonist effects on thyroid hormone signaling, and haematological effects due to their biotransformation in fish. Endocrine-disrupting biomarkers such as thyroid hormones, sex hormones, and haematological indices of Clarias gariepinus sub-adults exposed to sub-lethal diuron concentrations were studied over a 28-day period. C. gariepinus (n = 200) sub-adults were exposed to sub-lethal concentrations (0.00, 0.09, 0.18, 0.26, and 0.35 mg/L) of diuron. Changes in the hormonal and haematological profiles of the exposed fish were concentration and exposure duration-dependent. The thyroxine (T4), tri-iodothyronine (T3), and 17β-estradiol (E2) profiles decreased with an increase in concentration and exposure duration. The haemoglobin, pack cell volume, red blood cell, white blood cell, mean cell volume, and mean corpuscular haemoglobin cell decreased, while the mean corpuscular haemoglobin increased with an increase in concentration and exposure duration. Diuron induced stress and altered the physiological mechanisms of fish, and its application in farmlands should be regulated so as to enable a sustainable aquatic eco-system and fishery resources.

Application and Progress of Machine Learning in Pesticide Hazard and Risk Assessment

Long-term exposure to pesticides is associated with the incidence of cancer. With the exponential increase in the number of new pesticides being synthesized, it becomes more and more important to evaluate the toxicity of pesticides by means of simulated calculations. Based on existing data, machine learning methods can train and model the predictions of the effects of novel pesticides, which have limited available data. Combined with other technologies, this can aid the synthesis of new pesticides with specific active structures, detect pesticide residues, and identify their tolerable exposure levels. This article mainly discusses support vector machines, linear discriminant analysis, decision trees, partial least squares, and algorithms based on feedforward neural networks in machine learning. It is envisaged that this article will provide scientists and users with a better understanding of machine learning and its application prospects in pesticide toxicity assessment.

Comprehensive Stereoselectivity Assessment of Toxicokinetics, Tissue Distribution, Cytotoxicity, and Environmental Fate of Chiral Pesticide Propiconazole

Propiconazole (PRO) has been widely used in the treatment of fungal infection in fruits, vegetables, cereals, and seeds. In this study, a newly established chiral liquid chromatography tandem mass spectrometry method was applied to the systemic stereoselectivity evaluation of PRO enantiomers, including toxicokinetics, tissue distributions, cytotoxicity, accumulation, and degradation. Our results showed that both trans (+)-2S,4S-PRO and cis (-)-2S,4R-PRO had lower Cmax and AUC0-∞ and higher CLz/F values in plasma and lower accumulation concentrations in the liver, heart, and brain. In cytotoxic assays, cis (-)-2S,4R-PRO exhibited the lowest cytotoxicity in PC12 neuronal, N9 microglia, SH-SY5Y neuroblastoma, and MRC5 lung fibroblast cell lines. Moreover, the Eisenia fetida incubation experiment revealed that the accumulations of both trans (+)-2S,4S-PRO and cis (-)-2S,4R-PRO were higher than those of their antipodes in E. fetida. In summary, our findings first suggested that the application of cis (-)-2S,4R-PRO for agriculture would hugely reduce the environmental risk.

Evaluation of a high-throughput H295R homogenous time resolved fluorescence assay for androgen and estrogen steroidogenesis screening

The H295R test guideline assay evaluates the effect of test substances on synthesis of 17β-estradiol (E2) and testosterone (T). The objective of this study was to leverage commercial immunoassay technology to develop a more efficient H295R assay to measure E2 and T levels in 384-well format. The resulting Homogenous Time Resolved Fluorescence assay platform (H295R-HTRF) was evaluated against a training set of 36 chemicals derived from the OECD inter-laboratory validation study, EPA guideline 890.1200 aromatase assay, and azole fungicides active in the HT-H295R assay. Quality control performance criteria were met for all conditions except E2 synthesis inhibition where low basal hormone synthesis was observed. Five proficiency chemicals were active for both the E2 and T endpoints, consistent with guideline classifications. Of the nine OECD core reference chemicals, 9/9 were concordant with outcomes for E2 and 7/9 for T. Likewise, 9/13 and 11/13 OECD supplemental chemicals were concordant with anticipated effects for E2 and T, respectively. Of the 10 azole fungicides screened, 7/10 for E2 and 8/10 for T exhibited concordant outcomes for inhibition. Generally, all active chemicals in the training set demonstrated equivalent or greater potency in the H295R-HTRF assay, supporting the sensitivity of the platform. The adaptation of HTRF technology to the H295R model provides an efficient way to evaluate E2 and T modulators in accordance with guideline specifications.

Chronic exposure to tebuconazole alters thyroid hormones and plumage quality in house sparrows (Passer domesticus)

Triazoles belong to a family of fungicides that are ubiquitous in agroecosystems due to their widespread use in crops. Despite their efficiency in controlling fungal diseases, triazoles are also suspected to affect non-target vertebrate species through the disruption of key physiological mechanisms. Most studies so far have focused on aquatic animal models, and the potential impact of triazoles on terrestrial vertebrates has been overlooked despite their relevance as sentinel species of contaminated agroecosystems. Here, we examined the impact of tebuconazole on the thyroid endocrine axis, associated phenotypic traits (plumage quality and body condition) and sperm quality in wild-caught house sparrows (Passer domesticus). We experimentally exposed house sparrows to realistic concentrations of tebuconazole under controlled conditions and tested the impact of this exposure on the levels of thyroid hormones (T3 and T4), feather quality (size and density), body condition and sperm morphology. We found that exposure to tebuconazole caused a significant decrease in T4 levels, suggesting that this azole affects the thyroid endocrine axis, although T3 levels did not differ between control and exposed sparrows. Importantly, we also found that exposed females had an altered plumage structure (larger but less dense feathers) relative to control females. The impact of tebuconazole on body condition was dependent on the duration of exposure and the sex of individuals. Finally, we did not show any effect of exposure to tebuconazole on sperm morphology. Our study demonstrates for the first time that exposure to tebuconazole can alter the thyroid axis of wild birds, impact their plumage quality and potentially affect their body condition. Further endocrine and transcriptomic studies are now needed not only to understand the underlying mechanistic effects of tebuconazole on these variables, but also to further investigate their ultimate consequences on performance (i.e. reproduction and survival).

Mammary Gland Development in Male Rats Perinatally Exposed to Propiconazole, Glyphosate, or their Mixture

This study aimed to assess whether perinatal exposure to propiconazole (PRO), glyphosate (GLY) or their mixture (PROGLY) alters key endocrine pathways and the development of the male rat mammary gland. To this end, pregnant rats were orally exposed to vehicle, PRO, GLY, or a mixture of PRO and GLY from gestation day 9 until weaning. Male offspring were euthanized on postnatal day (PND) 21 and PND60. On PND21, GLY-exposed rats showed reduced mammary epithelial cell proliferation, whereas PRO-exposed ones showed increased ductal p-Erk1/2 expression without histomorphological alterations. On PND60, GLY-exposed rats showed reduced mammary gland area and estrogen receptor alpha expression and increased aromatase expression, whereas PRO-exposed ones showed enhanced lobuloalveolar development and increased lobular hyperplasia. However, PROGLY did not modify any of the endpoints evaluated. In summary, PRO and GLY modified the expression of key molecules and the development of the male mammary gland individually but not together.

Tebuconazole Induces ER-Stress-Mediated Cell Death in Bovine Mammary Epithelial Cell Lines

Tebuconazole (TEB) is a triazole fungicide used to increase crop production by controlling fungi, insects, and weeds. Despite their extensive use, people are concerned about the health risks associated with pesticides and fungicides. Numerous studies have defined the cellular toxicity of triazole groups in pesticides, but the mechanisms of TEB toxicity in bovine mammary gland epithelial cells (MAC-T cells) have not yet been studied. Damage to the mammary glands of dairy cows directly affects milk production. This study investigated the toxicological effects of TEB on MAC-T cells. We found that TEB decreases both cell viability and proliferation and activates apoptotic cell death via the upregulation of pro-apoptotic proteins, such as cleaved caspases 3 and 8 and BAX. TEB also induced endoplasmic reticulum (ER) stress via the upregulation of Bip/GRP78; PDI; ATF4; CHOP; and ERO1-Lα. We found that TEB induced mitochondria-mediated apoptotic MAC-T cell death by activating ER stress. This cell damage eventually led to a dramatic reduction in the expression levels of the milk-protein-synthesis-related genes LGB; LALA; CSN1S1; CSN1S2; and CSNK in MAC-T cells. Our data suggest that the exposure of dairy cows to TEB may negatively affect milk production by damaging the mammary glands.

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.

Evaluating structure-based activity in a high-throughput assay for steroid biosynthesis

Data from a high-throughput human adrenocortical carcinoma assay (HT-H295R) for steroid hormone biosynthesis are available for >2000 chemicals in single concentration and 654 chemicals in multi-concentration (mc). Previously, a metric describing the effect size of a chemical on the biosynthesis of 11 hormones was derived using mc data referred to as the maximum mean Mahalanobis distance (maxmMd). However, mc HT-H295R assay data remain unavailable for many chemicals. This work leverages existing HT-H295R assay data by constructing structure-activity relationships to make predictions for data-poor chemicals, including: (1) identification of individual structural descriptors, known as ToxPrint chemotypes, associated with increased odds of affecting estrogen or androgen synthesis; (2) a random forest (RF) classifier using physicochemical property descriptors to predict HT-H295R maxmMd binary (positive or negative) outcomes; and, (3) a local approach to predict maxmMd binary outcomes using nearest neighbors (NNs) based on two types of chemical fingerprints (chemotype or Morgan). Individual chemotypes demonstrated high specificity (85-98%) for modulators of estrogen and androgen synthesis but with low sensitivity. The best RF model for maxmMd classification included 13 predicted physicochemical descriptors, yielding a balanced accuracy (BA) of 71% with only modest improvement when hundreds of structural features were added. The best two NN models for binary maxmMd prediction demonstrated BAs of 85 and 81% using chemotype and Morgan fingerprints, respectively. Using an external test set of 6302 chemicals (lacking HT-H295R data), 1241 were identified as putative estrogen and androgen modulators. Combined results across the three classification models (global RF model and two local NN models) predict that 1033 of the 6302 chemicals would be more likely to affect HT-H295R bioactivity. Together, these in silico approaches can efficiently prioritize thousands of untested chemicals for screening to further evaluate their effects on steroid biosynthesis.

Azole Fungicides and Their Endocrine Disrupting Properties: Perspectives on Sex Hormone-Dependent Reproductive Development

Azoles are antifungal agents used in both agriculture and medicine. They typically target the CYP51 enzyme in fungi and, by so doing, disrupt cell membrane integrity. However, azoles can also target various CYP enzymes in mammals, including humans, which can disrupt hormone synthesis and signaling. For instance, several azoles can inhibit enzymes of the steroidogenic pathway and disrupt steroid hormone biosynthesis. This is of particular concern during pregnancy, since sex hormones are integral to reproductive development. In other words, exposure to azole fungicides during fetal life can potentially lead to reproductive disease in the offspring. In addition, some azoles can act as androgen receptor antagonists, which can further add to the disrupting potential following exposure. When used as pharmaceuticals, systemic concentrations of the azole compounds can become significant as combatting fungal infections can be very challenging and require prolonged exposure to high doses. Although most medicinal azoles are tightly regulated and used as prescription drugs after consultations with medical professionals, some are sold as over-the-counter drugs. In this review, we discuss various azole fungicides known to disrupt steroid sex hormone biosynthesis or action with a focus on what potential consequences exposure during pregnancy can have on the life-long reproductive health of the offspring.

Triadimefon increases fetal Leydig cell proliferation but inhibits its differentiation of male fetuses after gestational exposure

Triadimefon is a broad-spectrum fungicide widely applied in the agriculture. It is believed to be an endocrine disruptor. Whether triadimefon can inhibit the development of fetal Leydig cells and the underlying mechanisms are unknown. Thirty-two female pregnant Sprague-Dawley rats were randomly assigned into four groups and were dosed via gavage of triadimefon (0, 25, 50, and 100 mg/kg/day) for 9 days from gestational day (GD) 12-20. Triadimefon significantly reduced serum testosterone level in male fetuses at 100 mg/kg. The double immunofluorescence staining of proliferating cell nuclear antigen (PCNA) and cytochrome P450 cholesterol side-chain cleavage (a biomarker for fetal Leydig cells) was used to measure PCNA-labeling in fetal Leydig cells. It markedly increased fetal Leydig cell number primarily via increasing single cell population and elevated the PCNA-labeling of fetal Leydig cells in male fetuses at 100 mg/kg while it induced abnormal aggregation of fetal Leydig cells. The expression levels of fetal Leydig cell genes, Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, Hsd17b3, Insl3 and Nr5a1, were determined to explore its effects on fetal Leydig cell development. We found that triadimefon markedly down-regulated the expression of Leydig cell genes, Hsd17b3, Insl3, and Nr5a1 as low as 25 mg/kg and Scarb1 and Cyp11a1 at 100 mg/kg. It did not affect Sertoli cell number but markedly down-regulated the expression of Sertoli cell gene Amh at 50 and 100 mg/kg. Triadimefon significantly down-regulated the expression of antioxidant genes Sod1, Gpx1, and Cat at 25-100 mg/kg, suggesting that it can induce oxidative stress in fetal testis, and it reduced the phosphorylation of ERK1/2 and AKT2 at 100 mg/kg, indicating that it can inhibit the development of fetal Leydig cells. In conclusion, gestational exposure to triadimefon inhibits the development of fetal Leydig cells in male fetuses by inhibiting its differentiation.

Application, release, ecotoxicological assessment of biocide in building materials and its soil microbial response

Biocides are used in building materials to protect the building against microbial colonization and biodeterioration. However, these biocides are introduced by gradual leaching into soils in proximity of the buildings. This review discusses the aspects and characteristics of biocides from building materials in terms of (i) in-situ leaching and simulation thereof in-vitro and in-field tests, (ii) persistence, as well as photolytic and biodegradation, and its influence on toxicological evaluation, and (iii) evaluation of terrestrial toxicity by conventional ecotoxicological tests and novel holistic testing approaches. These aspects are influenced by multiple parameters, out of which water availability, physicochemical properties of microhabitats, combination of biocidal building materials, soil parameters, and composition of the soil microbiome are of utmost relevance. Deeper understanding of this multiparametric system and development of comprehensive characterization methodologies remains crucial, as to facilitate realistic assessment of the environmental impact of biocides used in construction materials and the corresponding degradation byproducts.

Fungicide bromuconazole has the potential to induce hepatotoxicity at the physiological, metabolomic and transcriptomic levels in rats

Bromuconazole (BROMU), a representative triazole fungicide, has been widely used in agriculture for its low cost and highly efficiency against various fungi. BROMU residue was often detected in the environment and food chain, even though there is indication of health risk to animals, and in humans. However, the data related to the toxicity of BROMU in animals remains unclear, and the mechanism is still not fully elucidated. Here, male adult rats were exposed to 0, 13.8, 32.8 and 65.6 mg/kg/d of BROMU for 10 days by oral gavage. It was observed that short time BROMU exposure not only caused liver histological damage, including vacuolar degeneration of hepatocytes with pyknotic nuclei, but also changed the levels of some hepatic physiological parameters, including aspartate transaminase (AST), triglyceride (TG), pyruvate and total cholesterol (TC), indicating that BROMU causes hepatotoxicity in rats. In addition, according to the transcriptomics and metabolomics analysis, a total of 58 metabolites and 259 genes significantly changed in the high-dose BROMU treated group. Although several different pathways are involved, lipid metabolism- and bile acids metabolism-related pathways were highlighted in both metabolomics and transcriptomics analysis. More importantly, further validation had proven that BROMU could not only interact with peroxisome proliferator-activated receptor γ (PPAR-γ), but also significantly decrease its protein and gene expression in the liver, supporting that BROMU decreased the TG synthesis via inhibiting the PPAR-γ pathway. These results clearly showed that BROMU exposure could result in hepatotoxicity at metabolomic and transcriptomic level in rats. These observations could provide some important steps toward understanding the mechanism underlying BROMU-induced mammalian toxicity.

Assessment of tebuconazole exposure on bovine testicular cells and epididymal spermatozoa

This study is the first to investigate the effects of tebuconazole (TEB) on the physiological functions of bovine testicular cells and epididymal spermatozoa. Motility and plasma membrane integrity of spermatozoa exposed to TEB (0.001-100 µM) were evaluated at different incubation times (0-6 h), while TEB-induced spermiotoxicity was assessed after 24 h in cell cultures. Testicular cells, obtained from the parenchyma of bovine testes, were seeded at 1.0 × 104 and 1.5 × 106 cells/well in 96- and 12-well culture plates and incubated for 48 h in culture media containing TEB (0.001-100 µM) to evaluate cytotoxicity and hormone release, respectively. TEB did not affect the motility and plasma membrane integrity. However, significant spermiotoxicity occurred at higher TEB (1-100 µM) concentrations (P < 0.05) compared to control and lower doses. Although no dose caused cytotoxicity in testicular cells (P > 0.05), 1 and 100 µM TEB caused a significant increase in testosterone secretion (P < 0.05). As a result, high doses of TEB (1-100 µM) had slightly suppressive effects on spermatozoa; however, these doses had stimulatory effects on testosterone secretion by testicular cells. It appears that the disruption of hormonal homeostasis of testicular cells after TEB exposure may result in metabolic and especially reproductive adverse effects in bulls.

Human-relevant concentrations of the antifungal drug clotrimazole disrupt maternal and fetal steroid hormone profiles in rats

Clotrimazole is a non-prescription and broad-spectrum antifungal drug sold under brand names such as Canesten® and Lotrimin®. It is used to treat different types of fungal infections, from oral thrush to athlete's foot and vaginal mycosis. The level of exposure to clotrimazole is uncertain, as the exact usage amongst self-medicating patients is unclear. Recent studies have raised potential concern about the unsupervised use of clotrimazole during pregnancy, especially since it is a potent inhibitor of CYP enzymes of the steroidogenesis pathway. To address some of these concerns, we have assessed the effects of intrauterine exposure to clotrimazole on developing rat fetuses. By exposing pregnant rats to clotrimazole 25 or 75 mg/kg bw/day during gestation days 7-21, we obtained internal fetal concentrations close to those observed in humans. These in vivo data are in strong agreement with our physiologically-based pharmacokinetic (PBK)-modelled levels. At these doses, we observed no obvious morphological changes to the reproductive system, nor shorter male anogenital distance; a well-established morphometric marker for anti-androgenic effects in male offspring. However, steroid hormone profiles were significantly affected in both maternal and fetal plasma, in particular pronounced suppression of estrogens was seen. In fetal testes, marked up-concentration of hydroxyprogesterone was observed, which indicates a specific action on steroidogenesis. Since systemic clotrimazole is rapidly metabolized in humans, relevant exposure levels may not in itself cause adverse changes to the reproductive systems. Its capacity to significantly alter steroid hormone concentrations, however, suggests that clotrimazole should be used with caution during pregnancy.

Classical toxicity endpoints in female rats are insensitive to the human endocrine disruptors diethylstilbestrol and ketoconazole

Developmental exposure to endocrine disrupting chemicals can have negative consequences for reproductive health in both men and women. Our knowledge about how chemicals can cause adverse health outcomes in females is, however, poorer than our knowledge in males. This is possibly due to lack of sensitive endpoints to evaluate endocrine disruption potential in toxicity studies. To address this shortcoming we carried out rat studies with two well-known human endocrine disruptors, diethylstilbestrol (DES) and ketoconazole (KTZ), and evaluated the sensitivity of a series of endocrine related endpoints. Sprague-Dawley rats were exposed orally from gestational day 7 until postnatal day 22. In a range-finding study, disruption of pregnancy-related endpoints was seen from 0.014 mg/kg bw/day for DES and 14 mg/kg bw/day for KTZ, so doses were adjusted to 0.003; 0.006; and 0.0012 mg/kg bw/day DES and 3; 6; or 12 mg/kg bw/day KTZ in the main study. We observed endocrine disrupting effects on sensitive endpoints in male offspring: both DES and KTZ shortened anogenital distance and increased nipple retention. In female offspring, 0.0012 mg/kg bw/day DES caused slightly longer anogenital distance. We did not see effects on puberty onset when comparing average day of vaginal opening; however, we saw a subtle delay after exposure to both chemicals using a time-curve analysis. No effects on estrous cycle were registered. Our study shows a need for more sensitive test methods to protect the reproductive health of girls and women from harmful chemicals.

Interaction of Conazole Pesticides Epoxiconazole and Prothioconazole with Human and Bovine Serum Albumin Studied Using Spectroscopic Methods and Molecular Modeling

The interactions of epoxiconazole and prothioconazole with human serum albumin and bovine serum albumin were investigated using spectroscopic methods complemented with molecular modeling. Spectroscopic techniques showed the formation of pesticide/serum albumin complexes with the static type as the dominant mechanism. The association constants ranged from 3.80 × 104-6.45 × 105 L/mol depending on the pesticide molecule (epoxiconazole, prothioconazole) and albumin type (human or bovine serum albumin). The calculated thermodynamic parameters revealed that the binding of pesticides into serum albumin macromolecules mainly depended on hydrogen bonds and van der Waals interactions. Synchronous fluorescence spectroscopy and the competitive experiments method showed that pesticides bind to subdomain IIA, near tryptophan; in the case of bovine serum albumin also on the macromolecule surface. Concerning prothioconazole, we observed the existence of an additional binding site at the junction of domains I and III of serum albumin macromolecules. These observations were corroborated well by molecular modeling predictions. The conformation changes in secondary structure were characterized by circular dichroism, three-dimensional fluorescence, and UV/VIS absorption methods.

Transcriptome analysis of fetal rat testis following intrauterine exposure to the azole fungicides triticonazole and flusilazole reveals subtle changes despite adverse endocrine effects

Azoles are used in agriculture and medicine to combat fungal infections. We have previously examined the endocrine disrupting properties of the agricultural azole fungicides triticonazole and flusilazole. Triticonazole displayed strong androgen receptor (AR) antagonism in vitro, whereas in utero exposure resulted in anti-androgenic effects in vivo evidenced by shorter anogenital distance (AGD) in fetal male rats. Flusilazole displayed strong AR antagonism, but less potent than triticonazole, and disrupted steroidogenesis in vitro, whereas in utero exposure disrupted fetal male plasma hormone levels. To elaborate on how these azole fungicides can disrupt male reproductive development by different mechanisms, and to investigate whether feminization effects such as short AGD in males can also be detected at the transcript level in fetal testes, we profiled fetal testis transcriptomes after in utero exposure to triticonazole and flusilazole by 3'Digital Gene Expression (3'DGE). The analysis revealed few transcriptional changes after exposure to either compound at gestation day 17 and 21. This suggests that the observed influence of flusilazole on hormone production may be by directly targeting steroidogenic enzyme activity in the testis at the protein level, whereas observations of shorter AGD by triticonazole may primarily be due to disturbed androgen signaling in androgen-sensitive tissues. Expression of Calb2 and Gsta2 was altered by flusilazole but not triticonazole and may pinpoint novel pathways of disrupted testicular steroid synthesis. Our findings have wider implication for how we integrate omics data in chemical testing frameworks, including selection of non-animal test methods and building of Adverse Outcome Pathways for regulatory purposes.

Comparing the effect of triadimefon and its metabolite on male and female Xenopus laevis: Obstructed growth and gonad morphology

Amphibians are the most endangered class of vertebrates. In this study, Xenopus laevis frogs were exposed to 0, 1 and 10 mg/L of triadimefon or triadimenol. After 14 or 28 days of exposure, high levels of triadimefon or triadimenol obstructed the growth of frogs. However, low levels of triadimefon induced the growth of females after the longer period of exposure. We also found that the antioxidant enzyme activity and LDH levels in males were higher than those in females after 28-days exposure. In histopathology tests, triadimenol exerted more effect on the ovary while triadimefon exerted more effect on the testes. Additionally, the levels of Estradiol in all 14-day treatments, except 1 mg/L triadimenol, were significantly decreased, however, there was no difference in testosterone levels. Furthermore, triadimefon and triadimenol disrupted the expression of genes controlling hormone homeostasis and reproduction, and this effect depended on the exposure time and the gender of the organism. Our experiments explored the effect of triadimefon and its metabolite on the gonads of frogs and highlighted the role that pesticides are likely to play in the global decline of amphibians.

Multi-level analysis of exposure to triazole fungicides through treated seed ingestion in the red-legged partridge

Triazole fungicides are the most widely used products to treat cereal seeds. Granivorous birds, such as red-legged partridges (Alectoris rufa), which consume seeds left on the surface of fields after sowing, have a high risk of exposure. As triazole fungicides can affect sterol synthesis, we tested the hypothesis that treated seed consumption could alter the synthesis of sex hormones and reduce the reproductive capacity of partridges. We exposed adult partridges to seeds treated with four different formulations containing triazoles as active ingredients (flutriafol, prothioconazole, tebuconazole, and a mixture of the latter two) simulating a field exposure during the late autumn sowing season. All treatments produced biochemical changes and an overexpression of genes encoding for enzymes involved in the biosynthesis of sterols and steroid hormones, such as PMVK, ABCA1, MVD, PSCK9, DHCR7 and HSD17B7. Plasma levels of oestradiol were reduced in partridges exposed to tebuconazole. We also monitored reproduction 3 months after exposure (laying date, egg fertilization and hatching rates). We observed a 14-day delay in the laying onset of partridges that had been exposed to flutriafol as compared to controls. These results show that the consumption of seeds treated with triazole fungicides has the potential to affect granivorous bird reproduction. We recommend the evaluation of lagged reproductive effects as part of the protocols of environmental risk assessment of pesticides in wild birds in light of the effects resulting from the exposure to triazole-treated seeds.

Oxidative stress, DNA damage and apoptosis induced by tebuconazole in the kidney of male Wistar rat

Tebuconazole (TEB) is a broad-spectrum conazole fungicide that has been used in agriculture in the control of foliar and soil-borne diseases of many crops. The present study has investigated the adverse effects of subchronic exposure to TEB on the kidney of male rats. Animals were divided into four equal groups and treated with TEB at increasing doses 0.9, 9 and 27 mg/kg body weight for 28 consecutive days. The results showed that TEB induced oxidative stress in the kidney demonstrated by an increase in malondialdehyde (MDA), protein carbonyl (PC), advanced oxidation protein product (AOPP) levels and DNA damage, as compared to the controls. Furthermore, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities were increased in the renal tissue of treated rats. Moreover, significant decrease in reduced glutathione (GSH) content in TEB-treated rats was observed, while oxidized glutathione (GSSG) levels were increased, thus a marked fall in GSH/GSSG ratio was registered in the kidney. Glutathione reductase (GR) activity showed a significant increase after TEB exposure. Moreover, TEB down-regulated the expression of Bcl2 and up-regulated the expression of Bax and caspase 3, which triggered apoptosis via the Bax/Bcl2 and caspase pathway. Also, TEB administration resulted in altered biochemical indicators of renal function and varying lesions in the overall histo-architecture of renal tissues. Taken together, our findings brought into light the renal toxicity induced by TEB, which was found to be significant at low doses.

Modulation of steroid metabolism and xenobiotic biotransformation responses in zebrafish (Danio rerio) exposed to triadimefon

The widely used fungicide triadimefon (TDF) has been detected in aquatic environments, and appears to disrupt steroid homeostasis; however, the toxic effects on fish reproduction triggered by TDF via the key receptor signaling pathways remain largely unknown. The present study showed that TDF (0.069, 0.138, 0.690 mg/L) exposure not only caused disordered germ cell maturation, but also decreased spawned egg production. In order to better understand this reproductive inhibition, we investigated the effects of TDF based on quantitative PCR, Western blot and mass spectrometry methodology in zebrafish. Due to the preferential accumulation of TDF in the liver, a general pattern of up-regulation of genes involved in biotransformation pathway was observed. A significant increase in abcb4 expression appeared to be responsible for TDF excretion. TDF-induced receptors (AhR2 and PXR) changed many genes involved in steroid metabolism, and subsequent disruptions in steroid homeostasis, which might be the key biological pathway in TDF reproductive toxicity. However, due to the different metabolic demands, the transcript profiles involved in steroid metabolism in zebrafish exhibited a sex-specific expression pattern. For example, the increase in gene expression of ahr2 was accompanied by a reduction in the rate of E2 biosynthesis resulting from the diminished cyp19a1a expression, and in turn led to down-regulation of esr1 and vtg1 in the liver, supporting the anti-estrogenic effect of TDF in male fish. In contrast, the increase in E2 production was accompanied by an increase in Esr1 protein expression caused by TDF and paralleled the increase in ahrr1 expression, suggesting that TDF may induce estrogenic activity through AhR-ER interactions in females. In addition, over-induction of cyp3a65 activity mediated through pxr, which helped to accelerate the transformation from TDF to triadimenol in the liver, appeared to elevate T metabolite rate in females. The down-regulation of fshβ transcript in males further suggested that TDF might adversely affect normal gametogenesis and induce reproductive toxicity.

Short-term toxicogenomics as an alternative approach to chronic in vivo studies for derivation of points of departure: A case study in the rat with a triazole fungicide

The derivation of an apical endpoint point of departure (POD) from animal-intensive testing programs has been the traditional cornerstone of human health risk assessment. Replacement of in vivo chronic studies with novel approaches, such as toxicogenomics, holds promise for future alternative testing paradigms that significantly reduce animal testing. We hypothesized that a toxicogenomic POD following a 14 day exposure in the rat would approximate the most sensitive apical endpoint POD derived from a battery of chronic, carcinogenicity, reproduction and endocrine guideline toxicity studies. To test this hypothesis, we utilized myclobutanil, a triazole fungicide, as a model compound. In the 14 day study, male rats were administered 0 (vehicle), 30, 150, or 400 mg/kg/day myclobutanil via oral gavage. Endpoints evaluated included traditional apical, hormone, and liver and testis transcriptomic (whole genome RNA sequencing) data. From the transcriptomic data, liver and testis biological effect POD (BEPOD) values were derived. Myclobutanil exposure for 14 days resulted in increased liver weight, altered serum hormones, liver histopathology, and differential gene expression in liver and testis. The liver and testis BEPODs from the short-term study were 22.2 and 25.4 mg/kg/day, respectively. These BEPODs were approximately an order of magnitude higher than the most sensitive apical POD identified from the two year cancer bioassay based on testis atrophy (1.4 mg/kg/day). This study demonstrates the promise of using a short-term study BEPOD to derive a POD for human health risk assessment while substantially reducing animal testing.

Comparative cytotoxic effects of five commonly used triazole alcohol fungicides on human cells of different tissue types

The widespread application of triazole fungicides makes people attach great concern over its adverse effects in mammalian. In this paper, cytotoxic effects of triazole alcohol fungicides (TAFs) were assessed on human HeLa, A549, HCT116 and K562 cells, and the potential mechanism of TAFs cytotoxicity was studied preliminarily. Results showed that TAFs had cytotoxicity on human cells with different level and cytotoxic selectivity. TAFs cytotoxicity was resonated with a typical hormetic biphasic dose action that produced a complex pattern of stimulatory or inhibitory effects on cell viability. Among the five TAFs, diniconazole revealed a widest range of cytotoxicity to inhibit the viability of the adherent and the suspension cells, causing HeLa cells shrinkage, A549 cells shrunken, and K562 cells collapse, and showed stronger cytotoxicity than hexaconazole. Moreover, the involvement of ROS generation in the cytotoxicity of TAFs on human cells was observed, and the apoptosis of HeLa cells and the formation of apoptotic body in K562 cells induced by diniconazole were characterized. The results indicated the cytotoxicity of TAFs with different structures on human cells was depended on their own property and cell specificity, K562 cells were the most susceptible to TAFs and diniconazole was the strongest toxic.

A Case Study with Triazole Fungicides to Explore Practical Application of Next-Generation Hazard Assessment Methods for Human Health

The ongoing developments in chemical risk assessment have led to new concepts building on integration of sophisticated nonanimal models for hazard characterization. Here we explore a pragmatic approach for implementing such concepts, using a case study of three triazole fungicides, namely, flusilazole, propiconazole, and cyproconazole. The strategy applied starts with evaluating the overall level of concern by comparing exposure estimates to toxicological potential, followed by a combination of in silico tools and literature-derived high-throughput screening assays and computational elaborations to obtain insight into potential toxicological mechanisms and targets in the organism. Additionally, some targeted in vitro tests were evaluated for their utility to confirm suspected mechanisms of toxicity and to generate points of departure. Toxicological mechanisms instead of the current "end point-by-end point" approach should guide the selection of methods and assays that constitute a toolbox for next-generation risk assessment. Comparison of the obtained in silico and in vitro results with data from traditional in vivo testing revealed that, overall, nonanimal methods for hazard identification can produce adequate qualitative hazard information for risk assessment. Follow-up studies are needed to further refine the proposed approach, including the composition of the toolbox, toxicokinetics models, and models for exposure assessment.

Gonadal disruption after single dose exposure of prothioconazole and prothioconazole-desthio in male lizards (Eremias argus)

Prothioconazole (PTC) is a widely used triazole fungicide with low toxicity, and its desulfurization metabolite, prothioconazole-desthio (PTC-d), is reported to have higher reproductive toxicity to mammals. However, little is known about the reproductive toxicity, much less endocrine disrupting effect, of these two chemicals on reptiles. In this study, we investigated the effects of single dose of PTC/PTC-d (100 mg kg^-1 body weight) exposure on the pathomorphism of testes and epididymides, serum sex steroid hormones (testosterone and 17β-estradiol) and transcription of steroidogenic-related genes (STARD, cyp11A, cyp17, cyp19A, 17β-HSD, 3β-HSD, AR and ER-α) in gonads of male lizards (Eremias argus). Although structural disorder existed in PTC-d exposure group, severe gonadal disruption, especially suppression of spermatogenesis was only observed in testis after PTC treatment, which consequently led to the lack of spermatozoa in epididymal ducts. Consistent with this result, T/E₂ value in PTC exposure was elevated to a significant higher level compared with control and continually increased over time, while T/E₂ value in the PTC-d exposure group slightly increased only at 12 h. These results demonstrated a more serious disruption of PTC on male lizard gonads than PTC-d. In addition, the expression of cyp17 gene was inhibited at 6 h, however, was induced at 12 h, and exhibited negative correlations with STARD, cyp11A and 3β-HSD after PTC exposure at each timepoint. In PTC-d group, the expression of STARD and 3β-HSD were significantly down-regulated, in contrast, cyp11A and cyp17 were up-regulated, and each gene showed consistent changes over time. For 17β-HSD, no significance was observed in both treated groups. This study was the first to compare the gonadal disruption of PTC and PTC-d in male lizards and elucidated that these two chemicals influenced the physiological function of male gonads through differential transcriptional modulation.

In vitro and in vivo endocrine disrupting effects of the azole fungicides triticonazole and flusilazole

Azoles are effective antifungal agents used in both medicine and agriculture. They typically work by inhibiting cytochrome P450 enzymes, primarily CYP51 of the ergosterol biosynthesis pathway, thus damaging the fungal cell membrane. However, apart from their desired antifungal properties, several azoles also exhibit endocrine disrupting properties in mammals, both in vitro and in vivo. Here, we have tested two currently used agricultural azole fungicides, triticonazole and flusilazole, for their in vitro anti-androgenic activity and potential effects on reproductive parameters. Both fungicides showed strong androgen receptor (AR) antagonism and disruption of steroid biosynthesis in vitro. Following gestational exposure to flusilazole (15 or 45 mg/kg bw/day) or triticonazole (150 or 450 mg/kg bw/day) in time-mated Sprague Dawley rats, triticonazole induced shorter male anogenital distance (AGD). Flusilazole exposure did not affect the AGD, but altered fetal male blood hormone profile, with increased androstenedione and decreased estrone levels. Flusilazole and triticonazole have dissimilar effects on reproductive parameters in vivo, but both show endocrine disrupting activities.

Sperm quality of rats exposed to difenoconazole using classical parameters and surface-enhanced Raman scattering: classification performance by machine learning methods

Difenoconazole is a fungicide extensively used in agriculture. The aim of this study was to evaluate the effects of difenoconazole fungicide on the sperm quality of rats. Wistar rats were divided into four groups: control and exposed to 5 (D5), 10 (D10), or 50 mg^-1 kg bw^-1day (D50) of difenoconazole for 30 days, by gavage. Classical sperm parameters and surface-enhanced Raman scattering (SERS) were performed. Progressive motility, acrosomal integrity, and percentage of morphologically normal spermatozoa were reduced in the D10 and D50 groups in comparison with the control group. Sperm viability was reduced only in the D50 group. Sperm number in the testis and caput/corpus epididymis and daily sperm production were reduced in the three exposed groups. SERS measurements showed changes in the spectra of spermatozoa from D50 group, suggesting DNA damage. In addition, machine learning (ML) methods were used to evaluate the performance of three classification algorithms (artificial neural network-ANN, K-nearest neighbors-K-NN, and support vector machine-SVM) in the identification task of the groups exposed to difenoconazole. The results obtained by ML algorithms were very promising with accuracy ≥ 90% and validated the hypothesis of the exposure to difenoconazole reduces sperm quality. In conclusion, exposure of rats to different doses of the fungicide difenoconazole may impair sperm quality, with a recognizable classification pattern of exposure groups.

Genotoxic, cytotoxic, and cytopathological effects in rats exposed for 18 months to a mixture of 13 chemicals in doses below NOAEL levels

The present study investigates the genotoxic and cytotoxic effects of long term exposure to low doses of a mixture consisting of methomyl, triadimefon, dimethoate, glyphosate, carbaryl, methyl parathion, aspartame, sodium benzoate, EDTA, ethylparaben, buthylparaben, bisphenol A and acacia gum in rats. Four groups of ten Sprangue Dawley rats (5 males and 5 females per group) were exposed for 18 months to the mixture in doses of 0xNOAEL, 0.0025xNOAEL, 0.01xNOAEL and 0.05xNOAEL (mg/kg bw/day). After 18 months of exposure, the rats were sacrificed and their organs were harvested. Micronuclei frequency was evaluated in bone marrow erythrocytes whereas the organs were cytopathologically examined by the touch preparation technique. The exposure to the mixture caused a genotoxic effect identified only in females. Cytopathological examination showed specific alterations of tissue organization in a tissue-type dependent manner. The observed effects were dose-dependent and correlated to various tissue parameters. Specifically, testes samples revealed degenerative and cellularity disorders, liver hepatocytes exhibited decreased glycogen deposition whereas degenerative changes were present in gastric cells. Lung tissue presented increased inflammatory cells infiltration and alveolar macrophages with enhanced phagocytic activity, whereas brain tissue exhibited changes in glial and astrocyte cells' numbers. In conclusion, exposure to very low doses of the tested mixture for 18 months induces genotoxic effects as well as monotonic cytotoxic effects in a tissue-dependent manner.

Enantioselective metabolism of four chiral triazole fungicides in rat liver microsomes

Triazole fungicides with one or two chiral centers are widely used worldwide. The liver microsomes plays a major role in the metabolism and systemic elimination of chiral pesticides after exposure. In this present work, enantioselective metabolism of four representative chiral triazole fungicides (prothioconazole, flutriafol, triticonazole, and epoxiconazole) in rat liver microsomes (RLM) was investigated using LC-MS/MS. Baseline separation of the four chiral fungicides and prothioconazole-desthio was achieved on Lux-cellulose-1. The results demonstrated that the R-enantiomers of flutriafol and triticonazole were preferentially metabolized with half-life ranged from 17.33 min to 99.00 min. The R,S-epoxiconazole accumulated with a half-life of 173.25 min. There was no stereoselectivity for prothioconazole. However, remarkable stereoselective metabolism was observed for prothioconazole-desthio. The results of enzyme kinetic revealed different affinities between the enantiomers and metabolic enzymes. In addition, homologous modeling and molecular docking results indicated that enantioselectivity were partially to enantiospecific binding affinities with CYP enzymes. This study highlights a new quantitative approach for stereoselective metabolism of chiral agrochemicals and provides more accurate data on risk assessment of triazole fungicides.

Oxidative stress, genotoxicity, biochemical and histopathological modifications induced by epoxiconazole in liver and kidney of Wistar rats

Epoxiconazole (EPX) is a triazole fungicide commonly used in agriculture and for domestic purposes around the world. The excessive application of this pesticide may result in a variety of adverse effects on non-target organisms, including humans. Since, the liver and kidneys are the target organs of this fungicide, potential hepatotoxic and nephrotoxic effects are of high relevance. Thus, our study aimed to investigate the toxic effects of EPX on the liver and kidney of Wistar rats. The exposure of rats 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 significantly enhances hepatic and renal lipid peroxidation which is accompanied by an increase in the level of protein oxidation. Furthermore, the results of the present study clearly indicated that EPX administration induces an increase in the levels of DNA damage in a dose-dependent manner. In addition, the activities of liver and kidney antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione S-transferase (GST) are increased significantly in EPX-treated rats at concentrations of 8, 24, and 40 mg/kg bw. However, with the dose NOEL × 7 (56 mg/kg bw of EPX), the activities of CAT, GPx, and GST are decreased. Indeed, EPX-intoxicated rats revealed a significant reduction in acetylcholinesterase (AChE) activity in both liver and kidney compared with the control group. Also, our results demonstrated that the EPX administration leads to a disruption of the hepatic (aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH)) and renal (uric acid and creatinine) functions. The biochemical perturbations obtained in the present study are corroborated with the histopathological modifications. Since EPX treatment caused severe damage in the overall histo-architecture of liver and kidney tissues, these results suggest that administration of EPX induced a marked deregulation of liver and kidney functions. Graphical abstract.

Brood size is reduced by half in birds feeding on flutriafol-treated seeds below the recommended application rate

Despite the efforts of the European Commission to implement measures that offset the detrimental effects of agricultural intensification, farmland bird populations continue to decline. Pesticide use has been pointed out as a major cause of decline, with growing concern about those agro-chemicals that act as endocrine disruptors. We report here on the effects of flutriafol, a ubiquitous systemic fungicide used for cereal seed treatment, on the physiology and reproduction of a declining gamebird. Captive red-legged partridges (Alectoris rufa; n = 11-13 pairs per treatment) were fed wheat treated with 0%, 20% or 100% of the flutriafol application rate during 25 days in late winter. We studied treatment effects on the reproductive performance, carotenoid-based coloration and cellular immune responsiveness of adult partridges, and their relationship with changes in oxidative stress biomarkers and plasma biochemistry. We also studied the effect of parental exposure on egg antioxidant content and on the survival, growth and cellular immune response of offspring. Exposed partridges experienced physiological effects (reduced levels of cholesterol and triglycerides), phenotypical effects (a reduction in the carotenoid-based pigmentation of their eye rings), and most importantly, severe adverse effects on reproduction: a reduced clutch size and fertile egg ratio, and an overall offspring production reduced by more than 50%. No effects on body condition or cellular immune response of either exposed adult or their surviving offspring were observed. These results, together with previous data on field exposure in wild partridges, demonstrate that seed treatment with flutriafol represents a risk for granivorous birds; they also highlight a need to improve the current regulation system used for foreseeing and preventing negative impacts of Plant Protection Products on wildlife.

Anogenital distance as a toxicological or clinical marker for fetal androgen action and risk for reproductive disorders

Male reproductive development is intricately dependent on fetal androgen action. Consequently, disrupted androgen action during fetal life can interfere with the development of the reproductive system resulting in adverse effects on reproductive function later in life. One biomarker used to evaluate fetal androgen action is the anogenital distance (AGD), the distance between the anus and the external genitalia. A short male AGD is strongly associated with genital malformations at birth and reproductive disorders in adulthood. AGD is therefore used as an effect readout in rodent toxicity studies aimed at testing compounds for endocrine activity and anti-androgenic properties, and in human epidemiological studies to correlate fetal exposure to endocrine disrupting chemicals to feminization of new-born boys. In this review, we have synthesized current data related to intrauterine exposure to xenobiotics and AGD measurements. We discuss the utility of AGD as a retrospective marker of in utero anti-androgenicity and as a predictive marker for male reproductive disorders, both with respect to human health and rodent toxicity studies. Finally, we highlight four areas that need addressing to fully evaluate AGD as a biomarker in both a regulatory and clinical setting.

Fenbuconazole exposure impacts the development of zebrafish embryos

Fenbuconazole (FBZ), a triazole-containing fungicide, is widely used in agriculture and horticulture. In the present study, the development and cardiac functioning were observed and determined in zebrafish embryos exposed to FBZ at 5, 50 and 500 ng/L nominal concentrations for 72 h. The results showed that 500 ng/L FBZ significantly increased pericardial edema rate, spine curvature rate, disturbed cardiac function, and led a shortened lower jaw. The transcription of genes such as tbx5, nkx2.5, tnnt2, gata4, bmp2b, myl7 was altered, which might be responsible for the cardiac developmental and functioning defects in the larvae. The deformation in bone development might be related with the impaired transcription levels of shh and bmp2b. The transcription of cyp26a1 (encoding retinoic acid metabolism enzyme) was significantly up-regulated in the 500 ng/L group, which might be a reason causing the teratogenic effect of FBZ. These results suggest that FBZ could have toxic effects on embryonic development, which should be considered in the risk evaluation of FBZ application.

Enantioselective Distribution, Degradation, and Metabolite Formation of Myclobutanil and Transcriptional Responses of Metabolic-Related Genes in Rats

Myclobutanil (MT), a chiral fungicide, can be metabolized enantioselectively in organisms. In this work, the associated absorption, distribution, metabolism and transcriptional responses of MT in rats were determined following a single-dose (10 mg·kg^-1 body weight) exposure to rac-, (+)- or (-)-MT. The enantiomer fractions (EFs) were less than 0.5 with time in the liver, kidney, heart, lung, and testis, suggesting preferential enrichment of (-)-MT in these tissues. Furthermore, there was conversion of (+)-form to (-)-form in the liver and kidney after 6 h exposure to enantiopure (+)-MT. Enrichment and degradation of the two enantiomers differed between rac-MT and MT-enantiomers groups, suggesting that MT bioaccumulation is enantiomer-specific. Interestingly, the degradation half-life of MT in the liver with rac-MT treatment was shorter than that with both MT-enantiomer treatments. One reason may be that the gene expression levels of cytochrome P450 1a2 ( cyp1a2) and cyp3a2 genes in livers treated with rac-MT were the highest among the three exposure groups. In addition, a positive correlation between the expression of cyp2e1 and cyp3a2 genes and rac-MT concentration was found in livers exposed to rac-MT. Simultaneously, five chiral metabolites were detected, and the enantiomers of three metabolites, RH-9090, RH-9089, and M2, were separated. The detected enantiomers of (+)-MT metabolites were in complete contrast with those of (-)-MT metabolites. According to the results, a metabolic pathway of MT in male rats was proposed, which included the following five metabolites: RH-9089, RH-9090, RH-9090 Sulfate, M1, and M2. The possible metabolic enzymes were marked in the pathway. The findings of this study provide more specific insights into the enantioselective metabolic mechanism of chiral triazole fungicides.

Exposure to difenoconazole inhibits reproductive ability in male marine medaka (Oryzias melastigma)

Difenoconazole (DFZ) is a triazole fungicide which has been detected in the aquatic environment, including estuaries and embayments. However, few studies addressing the reproductive toxicity and transgenerational effects of DFZ on marine fishes are available. The present study was conducted to investigate the effects of DFZ on male marine medaka (Oryzias melastigma). After exposure of the embryo to 1, 10, 100 and 1000ng/L DFZ for 180days, the gonadosomatic index was significantly decreased in the 1000ng/L treatment. The number of sperm was reduced while the abundances of spermatocytes and spermatogonia in the testes were increased in all the treatments. The mRNA levels of salmon-type gnrh (sgnrh), the luteinizing hormone (lhβ) and the follicle-stimulating hormone (fshβ) genes in the brain all exhibited a significant down-regulation, the expression of androgen receptors (arα and arβ) was decreased and that of estrogen receptor β and cytochrome P450 aromatase (cyp19B) was increased in the testes. The expression levels of cyp19A and cyp19B were increased in the liver. The decrease of ars mRNA levels might be one of the reasons causing the reduction of sperm. The down-regulation of sgnrh, lhβ and fshβ mRNA levels suggested that DFZ might impact the spermatogenesis via the brain-pituitary-gonad pathway. The decrease of the fertilization success, the hatch ability and the swim-up success in the F1 generation indicated that DFZ pollution at environmental levels might cause a decrease of wild fish populations.

Nitraria retusa fruit prevents penconazole-induced kidney injury in adult rats through modulation of oxidative stress and histopathological changes

CONTEXT

Nitraria retusa (Forssk.) Asch. (Nitrariaceae) is a medicinal plant which produces edible fruits whose antioxidant activity has been demonstrated.

OBJECTIVE

The current study elucidates the potential protective effect of N. retusa fruit aqueous extract against nephrotoxicity induced by penconazole, a triazole fungicide, in the kidney of adult rats.

MATERIALS AND METHODS

Adult Wistar rats were exposed either to penconazole (67 mg/kg body weight), or to N. retusa extract (300 mg/kg body weight) or to their combination. Penconazole was administered by intra-peritoneal injection every 2 days from day 7 until day 15, the sacrifice day, while N. retusa extract was administered daily by gavage during 15 days. Oxidative stress parameters, kidney biomarkers and histopathological examination were determined.

RESULTS

Nitraria retusa extract administration to penconazole treated rats decreased kidney levels of malondialdehyde (-10%), hydrogen peroxide (-12%), protein carbonyls (PCOs, -11%) and advanced oxidation protein products (AOPP, -16%); antioxidant enzyme activities: catalase (-13%), superoxide dismutase (-8%) and glutathione peroxidase (GPx, -14%), and the levels of non-enzymatic antioxidants: non-protein thiols (-9%), glutathione (-7%) and metallothionein (-12%). Furthermore, this plant extract prevented kidney biomarker changes by reducing plasma levels of creatinine, urea, uric acid and LDH and increasing those of ALP and GGT. Histopathological alterations induced by penconazole (glomeruli fragmentation, Bowman's space enlargement, tubular epithelial cells necrosis and infiltration of inflammatory leucocytes) were attenuated following N. retusa administration.

DISCUSSION AND CONCLUSION

Our results indicated that N. retusa fruit extract had protective effects against penconazole-induced kidney injury, which could be attributed to its phenolic compounds.

Reproductive effects of life-cycle exposure to difenoconazole on female marine medaka (Oryzias melastigma)

Difenoconazole (DFZ) is a widely used triazole fungicide which has been detected in some estuaries and embayments. This study was conducted to investigate the effects of DFZ on ovarian development in female marine medaka (Oryzias melastigma). After 180 days exposure of the embryo to DFZ (0, 1, 10, 100 and 1000 ng/L), the gonadosomatic index and percentage of mature oocytes produced were significantly reduced in the 1, 10 and 100 ng/L treatments but not the 1000 ng/L treatment compared to the control, thus exhibiting a U-shaped dose response curve. The relative mRNA levels of brain follicle-stimulating hormone, ovarian cytochrome P450 aromatase (CYP19s), hepatic estrogen receptors and vitellogenin, and the ratio of 17β-estradiol to testosterone in the muscle, also showed a U-shaped dose response, which was consistent with the development of oocytes. In addition, glutathione S-transferase activity in the ovary showed a U-shaped dose-response. These results gave an explanation for this U-shaped dose-response. The egg number produced, the hatch ability and the swim-up success in the F1 generation all showed a U-shaped dose response, indicating that exposure to DFZ at low concentrations can cause a decrease of fecundity and viability of the next generation. Thus, a more extensive evaluation of the impact of DFZ on marine fish reproduction at realistic environmental concentrations is needed.