Myclobutanil accumulation, transcriptional alteration, and tissue injury in lizards (Eremias argus) treated with myclobutanil enantiomers

Absorption, distribution, metabolism, and elimination of epoxiconazole enantiomers in lizards (Eremias argus)

Epoxiconazole (EPX) is a world widely used chiral triazole fungicide in the agriculture field. The excessive application of this triazole may cause damage to lizards. However, limited information is known about the toxicokinetics of EPX on lizards. Our study aimed to investigate the enantioselective absorption, distribution, metabolism, and elimination (ADME) of EPX in lizards following low and high dose exposure (10 and 100 mg kg-1 bodyweitht (bw)). The results demonstrated that (+)-EPX was easier absorbed than (-)-EPX in lizard plasma. Both (+)-EPX and (-)-EPX were detected in the liver, gonad, kidney, skin, brain, and intestine, with (+)-EPX preferentially distributed in these tissues. The elimination of (-)-EPX was faster than that of (+)-EPX in lizard liver and kidney in the high dose groups. Chiral conversion was found between EPX enantiomers in lizard skin. Simultaneously, five metabolites including M2, M4, M10, M18 and M19 were detected in lizard liver and kidney after EPX enantiomers exposure. The relative concentrations of M2, M4, and M10 were higher in the liver and kidney of (-)-EPX groups than those produced from (+)-EPX groups. The metabolic enzymes CYP3A4 and SULT1A1 primarily mediated enantioselective metabolism of EPX. The conclusions drawn from this study significantly enhance our understanding of the enantioselective behaviors of chiral triazole fungicides in reptiles, offering essential guidance for assessing the risks associated with different enantiomers of triazole fungicides.

Myclobutanil induces neurotoxicity by activating autophagy and apoptosis in zebrafish larvae (Danio rerio)

Myclobutanil (MYC), a typical broad-spectrum triazole fungicide, is often detected in surface water. This study aimed to explore the neurotoxicity of MYC and the underlying mechanisms in zebrafish and in PC12 cells. In this study, zebrafish embryos were exposed to 0, 0.5 and 1 mg/L of MYC from 4 to 96 h post fertilization (hpf) and neurobehavior was evaluated. Our data showed that MYC decreased the survival rate, hatching rate and heart rate, but increased the malformation rate and spontaneous movement. MYC caused abnormal neurobehaviors characterized by decreased swimming distance and movement time. MYC impaired cerebral histopathological morphology and inhibited neurogenesis in HuC:egfp transgenic zebrafish. MYC also reduced the activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), and downregulated neurodevelopment related genes (gfap, syn2a, gap43 and mbp) in zebrafish and PC12 cells. Besides, MYC activated autophagy through enhanced expression of the LC3-II protein and suppressed expression of the p62 protein and autophagosome formation, subsequently triggering apoptosis by upregulating apoptotic genes (p53, bax, bcl-2 and caspase 3) and the cleaved caspase-3 protein in zebrafish and PC12 cells. These processes were restored by the autophagy inhibitor 3-methyladenine (3-MA) both in vivo and in vitro, indicating that MYC induces neurotoxicity by activating autophagy and apoptosis. Overall, this study revealed the potential autophagy and apoptosis mechanisms of MYC-induced neurotoxicity and provided novel strategies to counteract its toxicity.

Myclobutanil induces cardiotoxicity in developing zebrafish larvae by initiating oxidative stress and apoptosis: The protective role of curcumin

Myclobutanil (MYC) is a common triazole fungicide widely applied in agriculture. MYC extensively exists in the natural environment and can be detected in organisms. However, little is known about MYC-induced embryonic developmental damage. This study aimed to unravel the cardiotoxicity of MYC and the underlying mechanisms, as well as the cardioprotective effect of curcumin (CUR, an antioxidant polyphenol) using the zebrafish model. Here, zebrafish embryos were exposed to MYC at concentrations of 0, 0.5, 1 and 2 mg/L from 4 to 96 h post fertilization (hpf) and cardiac development was assessed. As results, MYC reduced the survival and hatching rate, body length and heart rate, but increased the malformation rate and spontaneous movement. MYC caused abnormal cardiac morphology and function in myl7:egfp transgenic zebrafish, and downregulated cardiac developmental genes. MYC promoted oxidative stress through excessive reactive oxygen species (ROS) accumulation and suppressed the activities of antioxidant enzymes, triggering cardiomyocytic apoptosis via upregulated expression of apoptosis-related genes. These adverse toxicities could be significantly ameliorated by the antioxidant properties of CUR, indicating that CUR rescued MYC-induced cardiotoxicity by inhibiting oxidative stress and apoptosis. Overall, our study revealed the potential mechanisms of oxidative stress and apoptosis in MYC-induced cardiotoxicity in zebrafish and identified the cardioprotection of CUR in this pathological process.

Enantiomer-specific burden of metalaxyl and myclobutanil in non-occupationally exposed population with evidence from dietary intake and urinary excretion

Metalaxyl (MET) and myclobutanil (MYC) are two widely used chiral fungicides that may pose health risks to non-occupationally exposed populations. Here, the two fungicides were enantiomer-specific quantified in the dietary food and urine of residents in an Eastern China city, to determine the exposure and excretion of these contaminants in different populations. Results indicate that residues of MET and MYC varied with different food items at 0.42-0.86 ng/g fresh weight (FW) and 0.18-0.33 ng/g FW, respectively. In urine samples, the residual levels after creatinine adjusting (CR) ranged from 10.2 to 1715.4 ng/g CR for MET and were below the detection limit up to 320.7 ng/g CR for MYC. Significant age- and gender-related differences were separately found in urinary MET and MYC of different populations. Monte-Carlo simulations suggested that children had higher daily dietary intake (DDI) but lower urinary excretion (DUE) rates than youths, and thus may suffer higher body burdens. The residues of antifungally ineffective enantiomers (S-MET and R-MYC) were slightly higher than their antipodes in foods. Moreover, the enantiomer-selective urinary excretion resulted in higher retention of S-MET and R-MYC in the human body. Our results suggest that both dietary intake and urinary excretion should be enantiomer-specifically considered when assessing the exposure risk and body burden of chiral fungicides in the non-occupationally exposed population. Furthermore, substitutive application of enantiomer-enriched fungicide formulations can not only benefit the antifungal efficacy but also be safer for human health.

A multiplex lateral flow immunochromatography assay for the quantitative detection of pyraclostrobin, myclobutanil, and kresoxim-methyl residues in wheat

We produced three monoclonal antibodies with high specificity and sensitivity, and developed a lateral flow immunochromatography assay (LFIA) for the qualitative and quantitative detection of pyraclostrobin (PYR), myclobutanil (MYC), and kresoxim-methyl (KRE) in wheat. In the qualitative analysis, the cut-off values of LFIA were 400, 200, and 800 ng/g for PYR, MYC, and KRE in wheat, respectively. Based on the results obtained from the membrane strip reader, we generated calibration curves for the quantitative analysis. PYR, MYC, and KRE monoclonal antibodies (mAbs) had half maximal inhibitory concentrations (IC₅₀) of 25.4, 17.7, and 94.6 ng/g, respectively, and limit of detection (LOD) of 2.5, 2.0, and 8.8 ng/g, respectively. The linear detection scopes were 5.6-116.5, 4.2-74.4, 23.4-383.3 ng/g for PYR, MYC, and KRE, respectively. The intra-assay recoveries ranged from 89.2% to 101.7%, and the coefficients of variation ranged from 4.6% to 6.5%. The inter-assay recoveries ranged from 88.7% to 102.7%, with the coefficients of variation ranged from 7.2% to 9.1%. Thus, our developed LFIA is suitable for the qualitative and quantitative detection of PYR, MYC, and KRE residues in wheat.

[Determination of myclobutanil enantiomers in wheat and its processed products by ultraperformance liquid chromatography-tandem mass spectrometry based on a chiral stationary phase]

A valid method based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) with a chiral stationary phase was established for the determination of myclobutanil enantiomer residue in wheat grain and its processed products (flour, bran, pasta, steamed bun, noodle, and cooking water). The wheat grain and processed product samples were extracted with acetonitrile and purified with primary secondary amine (PSA) and C18. The enantiomers of myclobutanil were separated by Chiral column Lux Cellulose-1 (150 mm×2.0 mm, 3 μm, Phenomenex). The column temperature, sample volume injected, and flow rate were 30 ℃, 5 μL, and 0.25 mL/min, respectively. The mobile phase consisted of phase A (25%), water with 0.1% formic acid and 4 mM ammonium acetate, and phase B (75%), methanol with 0.1% formic acid and 4 mM ammonium acetate. A Waters Xevo TQ-S Micro MS/MS system (Waters, USA) was used for mass spectrometric analysis. An electrospray ionization (ESI) source operating in the positive ionization mode. MS analyses were performed in the multiple reaction monitoring (MRM) mode. The qualitative ions of myclobutanil were m/z 288.9/69.9 and 288.9/124.9, and the quantitative ion of myclobutanil was m/z 288.9/69.9. The source voltage was 3000 V, and the desolvation temperature was 400 ℃. The desolvation gas flow was 800 L/h, and the source temperature was 150 ℃. The matrix effect of wheat grains and their processed products on the determination of myclobutanil enantiomers by UPLC-MS/MS was investigated. S-(+)-myclobutanil and R-(-)-myclobutanil had a mid signal suppression effect on wheat grain, bran, pasta, steamed bun, and noodle, while S-(+)-myclobutanil and R-(-)-myclobutanil had a mid signal enhancement effect on flour and cooking water. Finally, the matrix-matched calibration method was effective in all matrices and was selected for the quantification of the myclobutanil enantiomer residue in the samples. The results showed that the two enantiomers of myclobutanil were well separated by this method. The first and second eluted enantiomers were S-(+)-myclobutanil and R-(-)-myclobutanil, respectively, with the corresponding retention times being 4.34 min and 5.13 min. The limits of detection (LOD) and limits of quantification (LOQ) of S-(+)-myclobutanil and R-(-)-myclobutanil in wheat and its processed products were 0.2 μg/kg and 0.5 μg/kg, respectively. In the linear range of 0.5-25 μg/L, the peak areas of the myclobutanil enantiomers showed a good linear relationship with the concentration, and the R2 values were all greater than 0.99. At fortification levels of 5, 50, and 100 μg/kg (enantiomer concentration), the average recoveries of S-(+)-myclobutanil in wheat grain and its processed products ranged from 82% to 110%, with RSDs between 0.9% and 6.8%. The average recoveries of R-(-)-myclobutanil in wheat grain and its processed products ranged from 80% to 109%, with RSDs between 0.9% and 6.8%. This method fulfils the requirements for pesticide residue analysis. The established method was applied to analyze five flour samples, two noodle samples, and two steamed bread samples. The results showed that S-(+)-myclobutanil and R-(-)-myclobutanil enantiomers were not detected in the samples. In this study, methods for the enantiomeric separation and residue analysis of myclobutanil in wheat were evaluated at the enantiomeric level, which enriched the methods of enantiomeric separation and residue analysis of chiral pesticide myclobutanil enantiomers in raw agricultural product (wheat grain) and its processed foods. This method is effective for the residue analysis of chiral pesticide myclobutanil enantiomers in raw agricultural commodities and its processed products.

Enantioselective accumulation, elimination and metabolism of fenbuconazole in lizards (Eremias argus)

The enantioselective accumulation, elimination and metabolism of fenbuconazole in lizards were determined following a single-dose (25 mg/kg^bw) exposure to racemic or enantiomeric fenbuconazole. Accumulation of fenbuconazole was found in lizard fat with rac-form > enantiopure enantiomers. The enantiomer fractions (EFs) were higher than 0.5 in the blood, while EFs were less than 0.5 in the liver, brain, skin and stomach. There was conversion from (+)-fenbuconazole to (-)-fenbuconazole in lizard liver and conversion from (-)-fenbuconazole to (+)-fenbuconazole in lizard liver and blood. The results showed that enantioselective accumulation appeared in lizards, but the direction varied among blood and different tissues. The elimination half-lives (t_1/2) of (+)-fenbuconazole were higher than those of (-)-fenbuconazole in the blood and liver, suggesting that (-)-fenbuconazole eliminated faster than (+)-fenbuconazole in these tissues. In addition, both (+)-fenbuconazole and (-)-fenbuconazole eliminated faster in the liver and stomach exposed to racemate than those exposed to enantiopure enantiomers. On the contrary, the form of racemate decreased the elimination rate of fenbuconazole in lizard fat. Synergistic elimination may occur when two enantiomers coexisted in lizard liver and stomach, while the racemate produced antagonistic elimination in lizard fat. Simultaneously, three metabolites, RH-6467, RH-9029&RH-9030 and keto-mchlorophenol, were discovered in lizard liver. Only two metabolites, RH-6467 and RH-9029&RH-9030, were found in lizard blood. RH-9029&RH-9030 were the major metabolites. The discovered enantiomers of (+)-fenbuconazole metabolites were different from those of (-)-fenbuconazole. The findings of this study may provide a better understanding of the enantioselective behaviors of chiral triazole fungicides in reptiles.

Chronic exposure to PPCPs mixture at environmentally relevant concentrations (ERCs) altered carbohydrate and lipid metabolism through gut and liver toxicity in zebrafish

Pharmaceuticals and personal care products (PPCPs) have been widely distributed and posed ecotoxicological risks in the aquatic environment. This study aims to evaluate the toxic effects after chronic exposure to PPCPs mixture at the environment relevant concentrations (ERCs). Our results indicated that PPCPs induced serious metabolic effects by disturbing the carbohydrate and lipid metabolism pathways. Chronic exposure caused a significant reduction in the hepatosomatic index (HSI), the gut weight ratios, and histological alterations in liver and gut tissues. Further, exposure to the combined PPCPs disrupted the carbohydrate metabolism via significant upregulation of hk1, gk, pck1, and insr genes. The lipid metabolism was affected with higher ppars expression levels that increased the fatty acid β-oxidation and ultimately decreased the lipidogenesis. Moreover, the altered responses of the insulin growth factor (IGF) pathway more in male gut tissue than that of female revealed sex-dependent disturbance in the gut homeostasis induced by PPCPs mixture. In conclusion, chronic exposure to PPCPs mixtures at ERCs can induce developmental effects and metabolic dysfunction in both male and female fish. The consumption and environmental disposal of these PPCPs should be regulated to ensure ecological health and environmental safety.

A review on the stereospecific fate and effects of chiral conazole fungicides

The production and use of chiral pesticides are triggered by the need for more complex molecules capable of effectively combating a greater spectrum of pests and crop diseases, while sustaining high production yields. Currently, chiral pesticides comprise about 30% of all pesticides in use; however, some pesticide groups such as conazole fungicides (CFs) consist almost exclusively of chiral compounds. CFs are produced and field-applied as racemic (1:1) mixtures of two enantiomers (one chiral center in the molecule) or four diastereoisomers, i.e., two pairs of enantiomers (two chiral centers in the molecule). Research on the stereoselective environmental behavior and effects of chiral pesticides such as CFs has become increasingly important within the fields of environmental chemistry and ecotoxicology. This is motivated by the fact that currently, the fate and effects of chiral pesticides such as CFs that arise due to their stereoselectivity are not fully understood and integrated into risk assessment and regulatory decisions. In order to fill this gap, a summary of the state-of-the-art literature related to the stereospecific fate and effects of CFs is needed. This will also benefit the agrochemistry industry as they enhance their understanding of the environmental implications of CFs which will aid future research and development of chiral products. This review provides a collection of >80 stereoselective studies for CFs related to chiral analytical methods, fungicidal activity, non-target toxicity, and behavior of this broadly used pesticide class in the soil environment. In addition, the review sheds more light on mechanisms behind stereoselectivity, considers possible agricultural and environmental implications, and suggests future directions for the safe use of chiral CFs and the reduction of their environmental footprint.

Effects of difenoconazole on hepatotoxicity, lipid metabolism and gut microbiota in zebrafish (Danio rerio)

In current study, larvae and adult zebrafish were exposed to difenoconazole to assess its effect on hepatotoxicity, lipid metabolism and gut microbiota. Results demonstrated that difenoconazole could induce hepatotoxicity in zebrafish larvae and adult, 0.400, 1.00, 2.00 mg/L difenoconazole caused yolk retention, yolk sac edema or liver degeneration after embryos exposure for 120 h, hepatocyte vacuolization and neoplasm necrosis were observed in adult liver after 0.400 mg/L difenoconazole exposure for 21 d. RNA sequencing showed that the 41 and 567 differentially expressed genes in zebrafish larvae and liver induced by 0.400 mg/L difenoconazole, were concentrated in pathways related to protein digestion and absorption, pancreatic secretion, steroid biosynthesis, and different metabolic pathways including galactose or sugar metabolism. Difenoconazole exposure caused lipid accumulation in larval yolk sac, and the elevated triglyceride (TG), malondialdehyde (MDA) and reactive oxygen species (ROS) levels in larvae and liver, which further confirmed the lipid metabolism disorders induced by difenoconazole. The results further showed that difenoconazole increased the abundance of gut microbiota such as Firmicutes, Aeromonas, Enterobacteriaceae and Bacteroides, further suggested that gut microbiota might participate in lipid metabolism and hepatotoxicity during zebrafish development. These findings advanced the field of the difenoconazole-induced developmental toxicity in larvae and adult zebrafish, and the imbalance of gut microbiota provided the plausible mode of action for the liver damage and disordered lipid metabolism in zebrafish.

Effect of Myclobutanil Pesticide on the Physiological Behavior of Two Newly Isolated Saccharomyces cerevisiae Strains during Very-High-Gravity Alcoholic Fermentation

Yeasts are able to act as biosorbents, as their cell wall includes several components capable of binding organic xenobiotic compounds that can potentially be removed during various fermentation processes. In the present investigation, two novel Saccharomyces cerevisiae strains (LMBF-Y 16 and LMBF-Y-18), previously isolated from grapes, were studied regarding their physiological behavior (dry cell weight-DCW production, substrate uptake, and ethanol and glycerol biosynthesis) during fermentations of grape must, in some cases enriched with commercial glucose and fructose (initial total sugar concentration approximately 150 and 250 g/L, respectively). Myclobutanil (a chiral triazole fungicide broadly used as a protective agent of vine) was also added to the culture media at various concentrations in order to assess the ability of the yeasts to simultaneously perform alcoholic fermentations and detoxify the medium (i.e., to remove the fungicide). In the first set of experiments and for both tested strains, trials were carried out in either 250 mL or 2.0 L agitated shake flasks in either synthetic glucose-based experiments or grape musts. Since the results obtained in the trials where the cultures were placed in 2.0 L flasks with grape musts as substrates were superior in terms of both DCW and ethanol production, these experimental conditions were selected for the subsequent studies. Both strains showed high fermentative efficiency, producing high amounts of DCW (9.5-10.5 g/L) in parallel with high ethanol production, which in some cases achieved values very close to the maximum theoretical ethanol production yield (≈0.49 g of ethanol per g of sugar). When using grape must with initial total sugars at approximately 250 g/L (very high gravity fermentation media, close to winemaking conditions), significantly high ethanol quantities (i.e., ranging between 105 and 123 g/L) were produced. Myclobutanil addition slightly negatively affected sugar conversion into ethanol; however, in all cases, ethanol production was very satisfactory. A non-negligible myclobutanil removal during fermentation, which ranged between 5%-27%, as a result of the adsorptive or degradative capacity of the yeast was also reported. The presence of myclobutanil had no effect on DCW production and resulted in no significant differences in the biosynthesis of glycerol. Therefore, these newly isolated yeast strains could be excellent candidates for simultaneous high ethanol production and parallel pesticide removal in a general biorefinery concept demonstrating many environmental benefits.