Flusilazole induces spatio-temporal expression patterns of retinoic acid-, differentiation- and sterol biosynthesis-related genes in the rat Whole Embryo Culture

Flusilazole induced developmental toxicity, neurotoxicity, and cardiovascular toxicity via apoptosis and oxidative stress in zebrafish

Flusilazole is a well-known triazole fungicide applied to various crops and fruits worldwide. Flusilazole residues are frequently detected in the environment, and many researchers have reported the hazardous effects of flusilazole on non-target organisms; however, the developmental toxicity of flusilazole has not been fully elucidated. In this study, we investigated flusilazole-induced developmental defects in zebrafish, which are used in toxicology studies to assess the toxic effects of chemicals on aquatic species or vertebrates. We confirmed that flusilazole exposure affected the viability and hatching rate of zebrafish larvae, and resulted in morphological defects, reduced body length, diminished eye and head sizes, and inflated pericardial edema. Apoptosis, oxidative stress, and inflammation were also observed. These factors interrupted the normal organ formation during early developmental stages, and transgenic models were used to identify organ defects. We confirmed the effects of flusilazole on the nervous system using olig2:dsRed transgenic zebrafish, and on the cardiovascular system using cmlc2:dsRed and fli1:eGFP transgenic zebrafish. Our results demonstrate the developmental toxicity of flusilazole and its mechanisms in zebrafish as well as the detrimental effects of flusilazole.

Triazole fungicides disrupt embryonic stem cell differentiation: Potential modulatory role of the retinoic acid signaling pathway

The developmental toxicity and human health risks of triazole fungicides (TFs) have attracted worldwide attention due to the ability to enter the human body in a variety of ways. Nevertheless, the specific mechanism by which TFs exert remains incompletely understood. Given that retinoic acid (RA) signaling pathway are closely related to development, this study aimed to screen and identify developmentally disabled chemicals in commonly used TFs and to reveal the potential effects of TFs on developmental retardation through the RA signaling pathway in mouse embryonic stem cells (mESCs). Specifically, six typical TFs (myclobutanil, tebuconazole, hexaconazole, propiconazole, difenoconazole, and flusilazole) were exposed through the construction of an embryoid bodies (EBs)-based in vitro global differentiation models. Our results clarified that various TFs disturbed lineage commitment during early embryonic development. Crucially, the activation of RA signaling pathway, which alters the expression of key genes and interferes the transport and metabolism of retinol, may be responsible for this effect. Furthermore, molecular docking, molecular dynamics simulations, and experiments using a retinoic acid receptor α inhibitor provide evidence supporting the potential modulatory role of the retinoic acid signaling pathway in developmental injury. The current study offers new insights into the TFs involved in the RA signaling pathway that interfere with the differentiation process of mESCs, which is crucial for understanding the impact of TFs on pregnancy and early development.

Adsorption behavior of azole fungicides on polystyrene and polyethylene microplastics

Agricultural plastic films and triazole fungicides are widely used in agricultural production process. Exposure to natural environment, agricultural plastic films will degrade into micron plastic particles, which will adsorb pesticide molecules and may affect their toxicity, biological activity and persistence. The long-term coexistence of microplastics (MPs) and triazole fungicides will bring potential harms to the agricultural ecological environment. Therefore, two kinds of triazole fungicides flusilazole (FLU) and epoxiconazole (EPO) were selected as cases and the adsorption behaviors of them on polystyrene and polyethylene were investigated. A series of factors which could affect the adsorption behavior were evaluated. Specifically, the particle size of MPs could affect its adsorption capacity, and the smaller the particle size, the stronger the adsorption capacity. Moreover, with the increase of pH value from 6.0 to 9.0, the adsorption capacity of MPs to target compounds gradually increased. The effect of ionic strength was evaluated by NaCl, and 0.05% of NaCl was beneficial to the adsorption process, while the continuous increase of NaCl concentration inhibited the adsorption. Oxalic acid and humic acid decreased the adsorption capacity of flusilazole on PE by 15.99-32.00% and PS by 35.02-48.67%, respectively. In addition, compared with the single pesticide system, the adsorption capacity of MPs for flusilazole and epoxiconazole in the binary pesticides system decreased by 36.13-37.93% and 44.36-51.35%, respectively, indicating that competitive adsorption occurred between the two pesticides. Meanwhile, the adsorption process was evaluated by adsorption kinetics and adsorption isotherms and were consistent with pseudo-second-order kinetic model and Freundlich isotherm model, respectively. Finally, several characterization analyses were conducted to investigated the adsorption mechanism, and hydrogen, halogen bonding and hydrophobic interaction proved to play an important role. The study on the adsorption behavior and mechanism of pesticide on MPs was the basis of assessing the risk of joint exposure.

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.

Assessment of the in vitro developmental toxicity of diethylstilbestrol and estradiol in the zebrafish embryotoxicity test

The present study investigated the developmental toxicity of diethylstilbestrol (DES) in the zebrafish embryotoxicity test (ZET). This was done to investigate whether the ZET would better capture the developmental toxicity of DES than the embryonic stem cells test (EST) that was previously shown to underpredict the DES-induced developmental toxicity as compared to in vivo data, potentially because the EST does not capture late events in the developmental process. The ZET results showed DES-induced growth retardation, cumulative mortality and dysmorphisms (i.e. induction of pericardial edema) in zebrafish embryos while the endogenous ERα agonist 17β-estradiol (E2) showed only growth retardation and cumulative mortality with lower potency compared to DES. Furthermore, the DES-induced pericardial edema formation in zebrafish embryos could be counteracted by co-exposure with ERα antagonist fulvestrant, indicating that the ZET captures the role of ERα in the mode of action underlying the developmental toxicity of DES. Altogether, it is concluded that the ZET differentiates DES from E2 with respect to their developmental toxicity effects, while confirming the role of ERα in mediating the developmental toxicity of DES. Furthermore, comparison to in vivo data revealed that, like the EST, in a quantitative way also the ZET did not capture the relatively high in vivo potency of DES as a developmental toxicant.

Retinoids and developmental neurotoxicity: Utilizing toxicogenomics to enhance adverse outcome pathways and testing strategies

The use of genomic approaches in toxicological studies has greatly increased our ability to define the molecular profiles of environmental chemicals associated with developmental neurotoxicity (DNT). Integration of these approaches with adverse outcome pathways (AOPs), a framework that translates environmental exposures to adverse developmental phenotypes, can potentially inform DNT testing strategies. Here, using retinoic acid (RA) as a case example, we demonstrate that the integration of toxicogenomic profiles into the AOP framework can be used to establish a paradigm for chemical testing. RA is a critical regulatory signaling molecule involved in multiple aspects of mammalian central nervous system (CNS) development, including hindbrain formation/patterning and neuronal differentiation, and imbalances in RA signaling pathways are linked with DNT. While the mechanisms remain unresolved, environmental chemicals can cause DNT by disrupting the RA signaling pathway. First, we reviewed literature evidence of RA and other retinoid exposures and DNT to define a provisional AOP related to imbalances in RA embryonic bioavailability and hindbrain development. Next, by integrating toxicogenomic datasets, we defined a relevant transcriptomic signature associated with RA-induced developmental neurotoxicity (RA-DNT) in human and rodent models that was tested against zebrafish model data, demonstrating potential for integration into an AOP framework. Finally, we demonstrated how these approaches may be systematically utilized to identify chemical hazards by testing the RA-DNT signature against azoles, a proposed class of compounds that alters RA-signaling. The provisional AOP from this study can be expanded in the future to better define DNT biomarkers relevant to RA signaling and toxicity.

Estrogen receptor alpha (ERα)-mediated coregulator binding and gene expression discriminates the toxic ERα agonist diethylstilbestrol (DES) from the endogenous ERα agonist 17β-estradiol (E2)

Diethylstilbestrol (DES) is a synthetic estrogen and proven human teratogen and carcinogen reported to act via the estrogen receptor α (ERα). Since the endogenous ERα ligand 17β-estradiol (E2) does not show these adverse effects to a similar extent, we hypothesized that DES' interaction with the ERα differs from that of E2. The current study aimed to investigate possible differences between DES and E2 using in vitro assays that detect ERα-mediated effects, including ERα-mediated reporter gene expression, ERα-mediated breast cancer cell (T47D) proliferation and ERα-coregulator interactions and gene expression in T47D cells. Results obtained indicate that DES and E2 activate ERα-mediated reporter gene transcription and T47D cell proliferation in a similar way. However, significant differences between DES- and E2-induced binding of the ERα to 15 coregulator motifs and in transcriptomic signatures obtained in the T47D cells were observed. It is concluded that differences observed in binding of the ERα with several co-repressor motifs, in downregulation of genes involved in histone deacetylation and DNA methylation and in upregulation of CYP26A1 and CYP26B1 contribute to the differential effects reported for DES and E2.

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.

Reaction kinetics and mechanisms of organosilicon fungicide flusilazole with sulfate and hydroxyl radicals

Flusilazole is an organosilane fungicide used for treatments in agriculture and horticulture for control of diseases. The reaction kinetics and mechanism of flusilazole with sulfate and hydroxyl radicals were studied. The rate constant of the radicals with the fungicide were determined by laser flash photolysis of peroxodisulfate and hydrogen peroxide. The results were 2.0 × 10⁹ s^-1M^-1 for the reaction of the fungicide with HO and 4.6 × 10⁸ s^-1 M^-1 for the same reaction with SO₄^- radicals. The absorption spectra of organic intermediates detected by laser flash photolysis of S₂O₈^2- with flusilazole, were identified as α-aminoalkyl and siloxyl radicals and agree very well with those estimated employing the time-dependent density functional theory with explicit account for bulk solvent effects. In the continuous photolysis experiments, performed by photo-Fenton reaction of the fungicide, the main degradation products were: (bis(4-fluorophenyl)-hydroxy-methylsilane) and the non-toxic silicic acid, diethyl bis(trimethylsilyl) ester, in ten and twenty minutes of reaction, respectively.

Retinoic acid in developmental toxicology: Teratogen, morphogen and biomarker

This review explores the usefulness retinoic acid (RA) related physiological factors as possible biomarkers of embryotoxicity. RA is involved in the morphogenesis of the early embryo as well as in the development and maturation of a wide variety of organ anlagen. The region-specific homeostasis of RA in the embryo is in many ways the driving force determining developmental cell proliferation versus differentiation. As a consequence, RA concentrations are carefully controlled in time and space in the developing embryo. RA deficiency and overdosing both result in characteristic patterns of malformations that may involve many different organ systems. The central role of RA in embryo development provides us with a set of sensitive biomarkers that may be employed in developmental toxicity testing. This includes the synthesizing and metabolizing enzymes of RA, but also a myriad of related morphogenetic factors and their genes, of which the expression may be affected by changes in RA balance. Several examples of embryotoxicants interfering with the homeostasis of RA and related parameters have been described. A preliminary adverse outcome pathway framework for RA mediated malformations has been published. Expansion of this framework and its application in developmental toxicity testing may allow the detection of a large variety of embryotoxicants with diverse modes of action. RA homeostasis therefore provides a promising set of molecular tools that may be employed in the advancement of mode of action driven animal-free developmental toxicity testing.