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

Exploring the dynamic behaviors of five pesticides in lettuce: Implications for consumer health through field and modeling experiments

Lettuce, a globally consumed nutritious vegetable, is often linked to concerns regarding pesticide residues. To address this issue, we conducted field trials and utilized dynamiCROP modeling to examine the uptake, distribution, translocation, and dissipation of five pesticides (λ-cyhalothrin, difenoconazole, acetamiprid, dimethomorph, and β-cypermethrin) commonly detected in lettuce. At harvest, pesticides residues were below the maximum residue limits (MRLs) at 0.05, 0.39, 0.047, 0.72, and 0.072 mg kg-1, respectively. Simulation results elucidated distinct behaviors of the pesticides following application to lettuce foliage across various compartments. However, all pesticides exhibited a common dissipation trend, initially stabilizing or increasing before gradually declining. For all five pesticides, the largest contribution of residues on lettuce leaves came from the leaf surface during the early period after application, and from the soil in the long term. Health risk assessments indicated negligible risks associated with consuming lettuce containing these pesticides, both in the short and long term.

Thresholds of adversity for endocrine disrupting substances: a conceptual case study

For endocrine disrupting chemicals (EDC) the existence of "safe exposure levels", that is exposure levels that do not present an appreciable risk to human health is most controversially discussed, as is the existence of health-based reference values. Concerns have been especially raised that EDCs might not possess a threshold level such that no exposure level to EDCs can be considered safe. To explore whether or not threshold levels can be identified, we performed a screening exercise on 14 pesticidal and biocidal active substances previously identified as EDCs in the European Union. The respective substances are ideal subjects for case studies to review for endocrine activity and disruptive potential following well-defined regulatory assessment based on solid data to effectually establish adversity as consequence of endocrine disruption. Dimethomorph, metiram and propiconazole for which the weight of evidence demonstrating endocrine disruption was the strongest were used as subjects for further study. Epoxiconazole was additionally selected as its effects on the endocrine system are extensive. For all four substances, analysis of the toxicological data clearly indicated thresholds of adversity below which no adverse effects mediated through an endocrine mechanism were observed. Particular emphasis was placed on mechanistic considerations including homeostasis and the concept of adversity. As a proof of concept this study provides evidence that like other substances of toxicological concern EDCs have threshold levels for adversity. While for some EDCs the respective thresholds might indeed be very low this shows that, data allowing, for other EDCs sufficiently protective reference values can be derived.

Multi-omic responses of fish exposed to complex chemical mixtures in the Shenandoah River watershed

To evaluate relationships between different anthropogenic impacts, contaminant occurrence, and fish health, we conducted in situ fish exposures across the Shenandoah River watershed at five sites with different land use. Exposure water was analyzed for over 500 chemical constituents, and organismal, metabolomic, and transcriptomic endpoints were measured in fathead minnows. Adverse reproductive outcomes were observed in fish exposed in the upper watershed at both wastewater treatment plant (WWTP) effluent- and agriculture-impacted sites, including decreased gonadosomatic index and altered secondary sex characteristics. This was accompanied with increased mortality at the site most impacted by agricultural activities. Molecular biomarkers of estrogen exposure were unchanged and consistent with low or non-detectable concentrations of common estrogens, indicating that alternative mechanisms were involved in organismal adverse outcomes. Hepatic metabolomic and transcriptomic profiles were altered in a site-specific manner, consistent with variation in land use and contaminant profiles. Integrated biomarker response data were useful for evaluating mechanistic linkages between contaminants and adverse outcomes, suggesting that reproductive endocrine disruption, altered lipid processes, and immunosuppression may have been involved in these organismal impacts. This study demonstrated linkages between human-impact, contaminant occurrence, and exposure effects in the Shenandoah River watershed and showed increased risk of adverse outcomes in fathead minnows exposed to complex mixtures at sites impacted by municipal wastewater discharges and agricultural practices.

Azole fungicides inhibit human and rat gonadal 3β-hydroxysteroid dehydrogenases: Structure-activity relationship and in silico docking analysis

Azole fungicides are widely used in the agricultural industry to control fungal infections in crops. However, recent studies have shown that some azole fungicides inhibit the activity of 3β-hydroxysteroid dehydrogenases (3β-HSDs) in the gonads. Out of the 16 azole fungicides tested, 8 were found to inhibit human KGN cell 3β-HSD2 with IC50 values of less than 100 μM. The strongest inhibitor was difenoconazole, with an IC50 value of 1.88 μM. In contrast, only 3 of the azole fungicides inhibited rat testicular 3β-HSD1, which was less sensitive to inhibition. Azole fungicides potently inhibited progesterone secretion by KGN cells under basal and forskolin stimulated conditions at ≥ 5 μM. The inhibitory strength of azole fungicides was determined by their lipophilicity (LogP), molecular weight, pKa, and binding energy. A pharmacophore analysis revealed that the hydrogen bond acceptor-lipid group was a critical feature required for inhibition. Overall, these findings suggest that the use of azole fungicides have unintended consequences on reproductive health due to their inhibition of gonadal 3β-HSDs. Key words: Azole fungicides; steroid hormones; 3β-hydroxysteroid dehydrogenase; docking analysis; lipophilicity.

Potency of Hexaconazole to Disrupt Endocrine Function with Sex Hormone-Binding Globulin

Hexaconazole is widely used as a fungicide for agricultural purposes. However, the endocrine-disrupting potential of hexaconazole is still under investigation. In addition, an experimental study found that hexaconazole may disrupt the normal synthesis of steroidal hormones. The potency of hexaconazole to bind with sex hormone-binding globulin (SHBG), a plasma carrier protein that binds androgens and oestrogens, is unknown. In this study, we evaluated the efficacy of hexaconazole to bind with SHBG by molecular interaction, a molecular dynamics method. In addition, principal component analysis was performed to understand the dynamical behaviour of hexaconazole with SHBG in comparison with dihydrotestosterone and aminoglutethimide. The binding scores of hexaconazole, dihydrotestosterone, and aminoglutethimide with SHBG were found to be -7.12 kcal/mol, -11.41 kcal/mol, and -6.84 kcal/mol, respectively. With respect to stable molecular interaction, hexaconazole showed similar molecular dynamics patterns of root mean square deviation (RMSD), root mean square fluctuation (RMSF), radius of gyration (Rg), and hydrogen bonding. The solvent surface area (SASA) and principal component analysis (PCA) of hexaconazole exhibit similar patterns in comparison with dihydrotestosterone and aminoglutethimide. These results show that hexaconazole has a stable molecular interaction with SHBG, which may acquire the active site of the native ligand, resulting in significant endocrine disruption during agricultural work.

Inhibition of human and rat placental 3β-hydroxysteroid dehydrogenase/Δ5,4-isomerase activities by insecticides and fungicides: Mode action by docking analysis

Many insecticides and fungicides are endocrine-disrupting compounds, which possibly interfere with the placental endocrine system. In the placenta, 3β-hydroxysteroid dehydrogenase/Δ^5,4-isomerase type 1 (HSD3B1) is the major steroidogenic enzyme, which makes progesterone from pregnenolone to support the placental stability. In this study, we screened 12 classes of insecticides and fungicides to inhibit placental HSD3B1 activity and compared them to the rat homolog type 4 (HSD3B4) isoform. Human HSD3B1 activity and rat HSD3B4 activity were measured in the presence of 200 nM pregnenolone and 0.2 mM NAD⁺ and 100 μM of test chemical. Triclosan, triflumizole, dichlone, and oxine at 100 μM significantly inhibited human HSD3B1 activity with the residual activity being less than 50% of the control. Further study showed that the half-maximal inhibitory concentration (IC₅₀) values of triclosan, triflumizole, dichlone, and oxine were 85.53 ± 9.14, 73.75 ± 3.42, 2.54 ± 0.40, and 102.93 ± 6.10 μM, respectively. In the presence of pregnenolone, triclosan, triflumizole, and dichlone were mixed inhibitors of HSD3B1, while oxine was a noncompetitive inhibitor. In the presence of NAD⁺, triclosan exhibited competitive inhibition while triflumizole possessed uncompetitive inhibition. Docking analysis showed that triclosan bound NAD⁺-binding site, while triflumizole, dichlone, and oxine mostly bound steroid-binding site. When the effect of these insecticides on rat placental HSD3B4 activity was screened in the presence of 200 nM pregnenolone, atrazine, triclosan, triflumizole, oxine, cyprodinil, and diphenyltin at 100 μM significantly inhibited rat HSD3B4 activity, with IC₅₀ values of triclosan, triflumizole, oxine, and cyprodinil were 82.99 ± 6.48, 35.45 ± 2.73, 105.59 ± 12.04, and 43.37 ± 3.00 μM, respectively. The mode action analysis showed that triflumizole and cyprodinil were almost competitive inhibitors, while triclosan and oxine were almost noncompetitive inhibitors of rat HSD3B4. Docking analysis showed that triclosan and oxine bound cofactor NAD⁺ binding residues more than steroid-binding residues of rat HSD3B4 while triflumizole and cyprodinil bound most pregnenolone-interactive residues. In conclusion, some insecticides such as triclosan, triflumizole, and oxine can effectively inhibit both human and rat placental HSD3B activity and they have unique mode action due to the structure difference.

Study of Different Chiral Columns for the Enantiomeric Separation of Azoles Using Supercritical Fluid Chromatography

The enantiomeric separation of antifungal compounds is an arduous task in pharmaceutical and biomedical fields due to the different properties that each diastereoisomer presents. The enantioseparation of a group of fungicides (sulconazole, bifonazole, triadimefon and triadimenol) using supercritical fluid chromatography was achieved in this work. For this goal, four different chiral columns based on polysaccharide derivatives, as well as the effect of different chromatographic parameters such as temperature, type and percentage of organic modifier (methanol, ethanol and isopropanol), were thoroughly investigated. The inversion of the elution order of enantiomers as a result of a change in the stationary phase or organic modifier was also evaluated by employing a circular dichroism detector. The best separation conditions, in terms of the enantioresolution and analysis time, were obtained with the Lux® Cellulose-2 column using isopropanol as the organic modifier.

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

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

Commonly used triazole fungicides accelerate the metamorphosis of digger wasps (Hymenoptera: Spheciformes)

Azole fungicides have been essential pillars of global food security since the commercialization of triadimefon. However, the potential for fungicides to induce sublethal effects on larval development and emergence from overwintering is underresearched. We hypothesized that contact exposure to field-realistic concentrations of a broad spectrum of triazole fungicides alters the pupation and metamorphosis of crabronid wasps. Therefore, triazole fungicides shape the hymenopteran communities in agrocenoses. We applied field-realistic concentrations of three triazole fungicides, difenoconazole, penconazole, and tebuconazole, to the defecated prepupae of Pemphredon fabricii (Hymenoptera: Crabronidae). We monitored their survival, pupation, and metamorphosis into adults, including the timing of these events. All three tested triazole fungicides altered the time to the metamorphosis into adults of P. fabricii prepupae compared to the vehicle-treated controls. This effect was concentration-independent within the recommended concentration ranges for foliar applications. However, the three triazole fungicides were not associated with any significant declines in overall survival. Thus, the commonly used triazole fungicides affect the synchronization of the metamorphosis into adults with the availability of food and nesting resources of the study species. The study compounds did not affect the survival, which agrees with previous studies of other azole fungicides, which revealed effects on survival only when used in combination with other compounds. Further research should address the multiplicative effects of the triazole fungicides with other agrochemicals on the timing of the metamorphosis of bees and wasps.