Computational simulations uncover enantioselective metabolism of chiral triazole fungicides by human CYP450 enzymes: A case study of tebuconazole

Tebuconazole (TEB), a prominent chiral triazole fungicide, has been extensively utilized for plant pathogen control globally. Despite experimental evidence of TEB metabolism in mammals, the enantioselectivity in the biotransformation of R- and S-TEB enantiomers by specific CYP450s remains elusive. In this work, integrated in silico simulations were employed to unveil the binding interactions and enantioselective metabolic fate of TEB enantiomers within human CYP1A2, 2B6, 2E1, and 3A4. Molecular dynamics (MD) simulations clearly delineated the binding specificity of R- and S-TEB to the four CYP450s, crucially determining their differences in metabolic activity and enantioselectivity. The primary driving force for robust ligand binding was identified as van der Waals interactions with CYP450s, particularly involving the hydrophobic residues. Mechanistic insights derived from quantum mechanics/molecular mechanics (QM/MM) calculations established C2-methyl hydroxylation as the predominant route of R-/S-TEB metabolism, while C6-hydroxylation and triazol epoxidation were deemed kinetically infeasible pathways. Specifically, the resulting hydroxy-R-TEB metabolite primarily originates from R-TEB biotransformation by 1A2, 2E1 and 3A4, whereas hydroxy-S-TEB is preferentially produced by 2B6. These findings significantly contribute to our comprehension of the binding specificity and enantioselective metabolic fate of chiral TEB by CYP450s, potentially informing further research on human health risk assessment associated with TEB exposure.

Ferulic acid attenuates difenoconazole exposure induced liver injury in carp by modulating oxidative damage, inflammation and apoptosis

Difenoconazole (DFZ) is a widely used triazole fungicide in agricultural production. However, the presence of DFZ residue in the environment poses a significant risk to non-target organisms. Ferulic acid (FA) is a phenolic compound known for its antioxidant and anti-inflammatory properties. This study aims to investigate the hepatic damage caused by DFZ in carp and explore the mechanism through which FA alleviates this damage. The findings revealed that FA enhanced the antioxidant capability of the carp's liver and reduced the accumulation of reactive oxygen species (ROS) in the liver tissue. Moreover, FA regulated the transcriptional levels of inflammation-related factors, effectively preventing the inflammatory response triggered by the NF-κB signaling pathway. Additionally, TUNEL results demonstrated that DFZ initiated apoptosis, while dietary supplementation with FA decreased the protein expression levels of Bax and Cytochrome C (Cyt c) and the transcriptional levels of bax, caspase3, caspase9, p53 genes. Furthermore, FA increased the protein expression and transcriptional levels of Bcl-2. In conclusion, FA protects against liver injury induced by DFZ exposure in carp by modulating oxidative damage, inflammation, and apoptosis.

Transcriptomic and proteomic fingerprints induced by the fungicides difenoconazole and metalaxyl in zebrafish embryos

In this study, we applied OMICs analysis to identify substance-specific biomarker candidates, which may act as early indicators for specific ecotoxic modes of actions (MoA). Zebrafish embryos were exposed to two sublethal concentrations of difenoconazole and metalaxyl according to a modified protocol of the OECD test guideline No. 236. At the end of exposure, total RNA and protein were extracted, followed by transcriptomics and proteomics analysis. The analysis of significantly differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) revealed a positive exposure-response correlation in all test concentrations for both fungicides. Similarly, also a positive correlation between the obtained transcriptome and proteome data was observed, highlighting the robustness of our approach. From the detected DEGs, candidate biomarkers specific for difenoconazole (apoa1b, gatm, mylpfb and acta1b) and metalaxyl (lgals2b, abat, fabp1b.1 and myh9a) were selected, and their biological functions were discussed to assess the predictive potential.

Dipicolinic acid enhances kiwifruit resistance to Botrytis cinerea by promoting phenolics accumulation

BACKGROUND

Kiwifruit is highly susceptible to fungal pathogens, such as Botrytis cinerea, which reduce crop production and quality. In this study, dipicolinic acid (DPA), which is one of the main components of Bacillus spores, was evaluated as a new elicitor to enhance kiwifruit resistance to B. cinerea.

RESULTS

DPA enhances antioxidant capacity and induces the accumulation of phenolics in B. cinerea-infected 'Xuxiang' kiwifruit. The contents of the main antifungal phenolics in kiwifruit, including caffeic acid, chlorogenic acid and isoferulic acid, increased after DPA treatment. DPA enhanced H2 O2 levels after 0 and 1 days, which promoted catalase (CAT) and superoxide dismutase (SOD) activities, reducing long-term H2 O2 levels. DPA promoted the up-regulation of several kiwifruit defense genes, including CERK1, MPK3, PR1-1, PR1-2, PR5-1 and PR5-2. Furthermore, DPA at 5 mM inhibited B. cinerea symptoms in kiwifruit (95.1% lesion length inhibition) more effectively than the commercial fungicides carbendazim, difenoconazole, prochloraz and thiram.

CONCLUSIONS

The antioxidant properties of DPA and the main antifungal phenolics of kiwifruit were examined for the first time. This study uncovers new insights regarding the potential mechanisms used by Bacillus species to induce disease resistance. © 2023 Society of Chemical Industry.

Dissipation dynamics and comparative dietary exposure assessment of mefentrifluconazole in rice

A fast and sensitive analytical method based on UHPLC coupled with tandem mass spectrometry was established to investigate the dissipation and final residual amounts of mefentrifluconazole in rice, and dietary risk to consumers was evaluated. The method provided good linearity (R² ≥ 0.9979), accuracy (recovery range, 79.0-101.5%), precision (relative standard deviation range, 1.3-13.9%), and sensitivity (limit of quantification, 0.005 mg/kg). The dissipation dynamics of mefentrifluconazole in rice followed first-order kinetics, with half-lives of 2.8-16.6 days. The final residues of mefentrifluconazole in various samples of harvested brown rice ranged from less than the limit of quantification to 0.092 mg/kg, the latter value being higher than the maximum residue limit recommended by the European Union. Comparative dietary exposure of mefentrifluconazole was assessed using field data and Chinese dietary patterns for different genders, regions, and age data. Although the results showed acceptable levels of risk for both acute exposure (the percentage of the acute reference dose ≤ 0.7483%) and chronic dietary intake (the percentage of acceptable daily intake ≤ 31.8516%), more studies of children are needed because they are at higher risk than other groups. This work provides the necessary data for registering and establishing the maximum residue limit for mefentrifluconazole in rice in China and reveals the potential risks to different groups of long-term application of mefentrifluconazole to rice and other crops.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Triazole fungicide tebuconazole induces apoptosis through ROS-mediated endoplasmic reticulum stress pathway

Tebuconazole (TEB) is a common triazole fungicide that has been widely applied in the treatment of fungal diseases. It is reported that TEB could exert harmful effects on mammals' health. However, the molecular mechanism involved in TEB toxicity remain undefined. Our study aimed to investigate the mechanisms of TEB-induced toxicity in intestinal cells. We found that TEB stimulates apoptosis through the mitochondrial pathway. Additionally, TEB triggers endoplasmic reticulum (ER) stress as demonstrated by the activation of the three arms of unfolded protein response (UPR). The incubation with the chemical chaperone 4-phenylbutyrate (4-PBA) alleviated ER stress and reduced TEB-induced apoptosis, suggesting that ER stress plays an important role in mediating TEB-induced toxicity. Furthermore, inhibition of ROS by N-acetylcysteine (NAC) inhibited TEB-induced ER stress and apoptosis. Taken together, these findings suggest that TEB exerts its toxic effects in HCT116 cells by inducing apoptosis through ROS-mediated ER stress and mitochondrial apoptotic pathway.

A Cheminformatics Study Regarding the Human Health Risks Assessment of the Stereoisomers of Difenoconazole

Difenoconazole is a chemical entity containing two chiral centers and having four stereoisomers: (2R,4R)-, (2R,4S)-, (2S,4R)- and (2S,4S)-difenoconazole, the marketed product containing a mixture of these isomers. Residues of difenoconazole have been identified in many agricultural products and drinking water. A computational approach has been used to evaluate the toxicological effects of the difenoconazole stereoisomers on humans. It integrates predictions of absorption, distribution, metabolism, excretion and toxicity (ADMET) profiles, prediction of metabolism sites, and assessment of the interactions of the difenoconazole stereoisomers with human cytochromes, nuclear receptors and plasma proteins by molecular docking. Several toxicological effects have been identified for all the difenoconazole stereoisomers: high plasma protein binding, inhibition of cytochromes, possible hepatotoxicity, neurotoxicity, mutagenicity, skin sensitization potential, moderate potential to produce endocrine disrupting effects. There were small differences in the predicted probabilities of producing various biological effects between the distinct stereoisomers of difenoconazole. Furthermore, there were significant differences between the interacting energies of the difenoconazole stereoisomers with plasma proteins and human cytochromes, the spectra of the hydrogen bonds and aromatic donor-acceptor interactions being quite distinct. Some distinguishing results have been obtained for the (2S,4S)-difenoconazole: it registered the highest value for clearance, exposed reasonable probabilities to produce cardiotoxicity and carcinogenicity and negatively affected numerous nuclear receptors.

DNA damage and cell apoptosis induced by fungicide difenoconazole in mouse mononuclear macrophage RAW264.7

Difenoconazole (DFC) is a typical triazole fungicide. Because of its effective bactericidal activity, it has been widely used in agricultural products such as fruits and vegetables. This study revealed the cytotoxic effect of fungicide DFC on mouse monocyte macrophage RAW264.7. The results showed that the IC₅₀ value of DFC on RAW264.7 cells was 37.08 μM (24 h). DFC can significantly inhibit the viability of RAW264.7 cells, induce DNA damage and enhance apoptosis. The established cytotoxicity test showed that DFC-induced DNA double strand breaks in RAW264.7 cells. DFC-treated cells showed typical morphological changes of apoptosis, including chromatin condensation and nuclear lysis. In addition, DFC can induce the release of Cyt c, promote the collapse of mitochondrial membrane potential and increase the Bax/Bcl-2 ratio in RAW264.7 cells. Through this research, people further understand the toxicity of DFC and provide a more scientific basis for its safety application and risk management.

A comprehensive review of 1,2,4-triazole fungicide toxicity in zebrafish (Danio rerio): A mitochondrial and metabolic perspective

In this critical review, we synthesize data from peer-reviewed literature reporting on triazole fungicide exposures in the zebrafish model. Based on their mode of action in plants (potent inhibitors of ergosterol synthesis), we focused attention on mechanisms related to cellular, lipid, and steroid metabolism. Evidence from several studies reveals that zebrafish exposed to triazoles present with impaired mitochondrial oxidative phosphorylation and oxidative stress, as well as dysregulation of lipid metabolism. Such metabolic disruptions are expected to underscore developmental delays, deformity, and aberrant locomotor activity and behaviors often observed following exposure. We begin by summarizing physiological and behavioral effects observed with triazole fungicide exposure in zebrafish. We then discuss mechanisms that may underlie adverse apical effects, focusing on mitochondrial bioenergetics and metabolism. Using computational approaches, we also identify novel biomarkers of triazole fungicide exposure. Extracting and analyzing data contained in the Comparative Toxicogenomics Database (CTD) revealed that transcriptional signatures responsive to different triazoles are related to metabolism of lipids and lipoproteins, biological oxidations, and fatty acid, triacylglycerol, and ketone body metabolism among other processes. Pathway and sub-network analysis identified several transcripts that are responsive in organisms exposed to triazole fungicides, several of which include lipid-related genes. Knowledge gaps and recommendations for future investigations include; (1) targeted metabolomics for metabolites in glycolysis, Krebs cycle, and the electron transport chain; (2) additional studies conducted at environmentally relevant concentrations to characterize the potential for endocrine disruption, given that studies point to altered cholesterol (precursor for steroid hormones), as well as altered estrogen receptor alpha and thyroid hormone expression; (3) studies into the potential role for lipid peroxidation and oxidation of lipid biomolecules as a mechanism of triazole-induced toxicity, given the strong evidence for oxidative damage in zebrafish following exposure to triazole fungicides.

Ginger reserves testicular spermatogenesis and steroidogenesis in difenoconazole-intoxicated rats by conducting oxidative stress, apoptosis and proliferation

Difenoconazole, a triazole fungicide, can induce reproductive toxicity in aquatic species, but the probable mechanisms of this hazard in mammals are not formally reported. Here, we have examined the possible ameliorative efficiency of the ginger aqueous extract against the reproductive toxicity of difenoconazole in male rats. Thirty-six animals were equally divided into six groups: control, ginger aqueous extract (50 mg/kg), difenoconazole (15 mg/kg), difenoconazole (30 mg/kg) and ginger co-treated with two doses of difenoconazole. Difenoconazole markedly decreased sperm count, motility and normality percentage, together with the Johnson score. Difenoconazole also significantly reduced serum testosterone, luteinizing hormone and follicle-stimulating hormone levels, as well as the activities of testicular steroidogenic acute regulatory protein and 17 β-hydroxysteroid dehydrogenases. Furthermore, difenoconazole brought a significant decrease in the testicular activity of catalase, but it increased the activity of glutathione peroxidase. Moreover, difenoconazole upregulated the testicular transcripts of Bax and caspase-3, increased Ki-67 immunoreactivity and induced histoarchitecture alterations plus DNA damage. Remarkably, ginger co-treatment preserved sperm toxicity, restored hormone profiles, increased steroidogenic activity and prevented oxidative injury-promoted testicular apoptosis. In conclusion, phenolic acids and flavonoids of ginger can reserve spermatogenesis and steroidogenesis in difenoconazole-intoxicated rats by improving testicular redox status, inhibiting apoptosis and refining proliferation capacity.

Cumulative risk assessment of dietary exposure to triazole fungicides from 13 daily-consumed foods in China

The agroeconomic benefits of the routine use of triazole fungicides on crops have been evident for more than 40 years. However, increasing evidence shows that residues of triazoles are ubiquitous in various foods and thus could pose a potential health risk to humans. We analyzed 3406 samples of 13 food commodities that were collected from markets in 9 regions across China, and assessed the health risk of both chronic and acute exposure to the triazoles for Chinese children (1-6 years old) and the general population. Among all samples, 55.52% had triazoles in concentrations of 0.10-803.30 μg/kg, and 29.77% of samples contained a combination of 2-7 triazoles. Tebuconazole and difenoconazole were the most commonly found triazoles in the foods, being detected in 33.44% and 30.45% of samples, respectively. Chronic and acute cumulative risk assessment for total triazoles based on a relative potency factor method revealed that exposure to triazoles from these particular commodities was below the levels that might pose a health risk (chronic hazard index range, 5.90×10^-7 to 1.83×10^-3; acute hazard index range, 7.77×10^-5 to 0.39, below 1). Notably, dietary exposure risk for children was greater than that for the general population-particularly for the acute intake of mandarin, grape, and cucumber (acute hazard index values of 0.35-0.39). Despite the low health risk, the potential hazards of exposure to triazoles should raise public concern owing to their ubiquitous presence in common foods and potential cumulative effects.

Effects of Flutriafol Fungicide on the Lipid Accumulation in Human Liver Cells and Rat Liver

Flutriafol (FTF) is a triazole fungicide that can cause liver toxicity through the ingestion of its residues in food and water. However, little is known about the liver toxicity of FTF, particularly nonalcoholic fatty liver disease (NAFLD) in humans. Therefore, the purpose of this study was to investigate whether FTF induces NAFLD in human liver cells and animal liver. HepG2 cells and Sprague Dawley (SD) rats were treated with FTF at doses of 0–640 µM for 24 h and 0–150 mg/kg bw/day for 28 days, respectively. FTF (80, 160, and 320 µM) treatment to cells induced lipid accumulation. FTF (80 and 160 µM)-treated cells had higher levels of cytochrome P450 enzymes and reactive oxygen species and increased mitochondrial membrane potential loss than the control. FTF also increased the mRNA levels of antioxidant enzymes through oxidative stress and nuclear factor erythroid 2-related factor 2 pathways in HepG2 cells. However, a higher level of FTF (320 µM) induced apoptosis. The treatment of SD rats with FTF (2.5–150 mg/kg bw/day) induced fatty infiltration in the liver by impairing liver metabolism and inducing apoptosis. Therefore, our data suggest that human exposure to FTF residues may be a risk factor for liver diseases, such as NAFLD.

A highly sensitive "ON-OFF-ON" dual optical sensor for the detection of Cu(II) ion and triazole pesticides based on novel BODIPY-substituted cavitand

The synthesis with full structural characterization including elemental analysis and 1H, 13C, 11B and 19F NMR, FT-IR and MALDI-TOF spectral data, along with the florescence sensing behavior of a new resorcin[4]arene cavitand 3 bearing multiple BODIPY sites achieved by the Cu-catalyzed azide-alkyne cycloaddition (CuAAC) is being reported. The spatial orientation of multiple BODIPY-1,2,3-triazole arms based on the macrocyclic rigid core is of great interest since the resulting structure has been utilized as a fluorescent chemosensor for numerous metal cations. In particular, a remarkable decrease in the fluorescence emission towards Cu(ii) ions, i.e., "turn-off" response, has been obtained giving rise to an optical sensor for the detection of triazole fungicides, namely tebuconazole, triadimenol, triadimefon, i.e. "turn-on" response. Such a molecular system, hence, can be feasibly applied as a dual optical sensor, i.e. "a turn-on-off-on" system, for dangerous contaminants such as heavy metals and pesticides.

Three widely used pesticides and their mixtures induced cytotoxicity and apoptosis through the ROS-related caspase pathway in HepG2 cells

Difenoconazole, cypermethrin and triazophos are widely used pesticides in agricultural production and frequently detected in foods. The aim of this study was to determine the effect of these pesticides and their mixtures on cell viability, reactive oxygen species (ROS), lactate dehydrogenase (LDH) content, apoptosis rate and DNA fragmentation and synthesis in human hepatocellular carcinoma cells (HepG2). The order of inhibitory effects for the individual pesticides was ranked as difenoconazole > cypermethrin > triazophos. The enhanced expression of caspase-3, caspase-7 and PARP activity was observed in HepG2 cells, which was 1.7, 1.3 and 1.6-fold higher than the control, respectively, along with significant protein cleavage; and induced apoptosis in a concentration-dependent manner. Further, the pesticide mixtures significantly increased ROS level (up to 1.3-fold), induced DNA fragmentation (up to 1.8-fold), inhibited DNA synthesis (up to 53%), and damaged the cells by destroying the cell membrane and producing a large amount of LDH at concentration range of 10-30 μM. Specifically, mixtures containing difenoconazole showed stronger toxicities than individual pesticides, implying higher health risks associated with mixtures. Our results show that three widely used pesticides exhibited cytotoxicity and apoptosis through the ROS-related caspase pathway, providing a basis for evaluation of health risks from pesticide mixtures via food consumption.

Tebuconazole induced oxidative stress related hepatotoxicity in adult and larval zebrafish (Danio rerio)

Tebuconazole is widely used as fungicide and has frequently been detected at elevated concentrations in environmental media. To characterize the potential toxicity of tebuconazole on vertebrate and humans. Using zebrafish as a vertebrate model, the toxic effects in liver that produced by low-toxic concentrations of tebuconazole were assessed in adult zebrafish. We further focused on tebuconazole-induced toxicity and its possible mechanism in larval zebrafish using a hepatotoxicity assay. The induction of oxidative stress in adult fish was evaluated by superoxide dismutase (T-SOD), catalase (CAT), peroxidase (POD), glutathione S-transferase (GST) activity, and the increased aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ratio. Significantly increased enzyme activity was observed in the liver of male and female fish at both exposure and depuration stage. Exposure to maximum non-lethal (MNLC) concentration of tebuconazole from 72 to 120 h post-fertilization (hpf) affected the liver size and yolk retention in larval zebrafish. Decreased fluorescence intensity was observed in larval Tg(Apo14:GFP) zebrafish, indicating liver degeneration after tebuconazole treated. Histopathological examination confirmed the alterations in liver histoarchitecture in exposed zebrafish. Significant 1.28-fold and 1.65-fold increases in reactive oxygen species levels were observed in juveniles exposed to MNLC and lethal concentration 10 (LC₁₀) group, respectively. The acridine orange staining assay showed that apoptotic cells occurred in the liver regions. These results indicated that tebuconazole exposure resulted in impacts on the ecological risk in fish and vertebrate. Overall, the present study suggested further research in needed to better understand the tebuconazole-induced toxicity mechanism that associated with oxidative stress.

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.

Beneficial role of vanillin, a polyphenolic flavoring agent, on maneb-induced oxidative stress, DNA damage, and liver histological changes in Swiss albino mice

Vanillin, a widely used flavoring agent, has antimutagenic and antioxidant properties. The current study was performed to evaluate its beneficial role against hepatotoxicity induced by maneb, a dithiocarbamate fungicide. Mice were divided into four groups of six each: group 1, serving as negative controls which received by intraperitoneal way only distilled water, a solvent of maneb; group 2, received daily, by intraperitoneal way, maneb (30 mg kg^-1 body weight (BW)); group 3, received maneb at the same dose of group 2 and 50 mg kg^-1 BW of vanillin by intraperitoneal way; and group 4, serving as positive controls, received daily only vanillin. After 10 days of treatment, mice of all groups were killed. Our results showed that vanillin significantly reduced the elevated hepatic levels of malondialdehyde, hydrogen peroxide, and advanced oxidation protein product and attenuated DNA fragmentation induced by maneb. In addition, vanillin modulated the alterations of antioxidant status: enzymatic (superoxide dismutase, catalase, and glutathione peroxidase) and nonenzymatic (reduced glutathione, nonprotein thiol, and vitamin C) antioxidants in the liver of maneb-treated mice. This natural compound was also able to ameliorate plasma biochemical parameters (aspartate aminotransferase, alanine aminotransferase, gamma glutamyl transpeptidase, alkaline phosphatase, total bilirubin, and total protein). The protective effect of vanillin was further evident through the histopathological changes produced by maneb in the liver tissue. Thus, we concluded that vanillin might be beneficial against maneb-induced hepatic damage in mice.

Metabolic Susceptibility of 2-Chlorothioxanthone and Its Toxic Effects on mRNA and Protein Expression and Activities of Human CYP1A2 and CYP3A4 Enzymes

Thioxanthones (TXs) are photoinitiators widely used in UV curable resins and food packaging, and their residues have been frequently detected in human bodies. Our current understanding of the susceptibility of residual TXs to metabolism and their effects on human health is very limited. The in vitro metabolism of TXs and its toxic effects on cytochrome P450 (CYP) (the key xenobiotic metabolizing enzymes) were examined in this study. 2-Chlorothioxanthone (2-Cl-TX) significantly inhibited the enzymatic activities of CYP1A2 and CYP3A4 with IC₅₀ of 8.36 and 0.86 μM, respectively. The exposure to 2-Cl-TX at 2.5 μM up-regulated the mRNA expression of CYP1A2 and CYP3A4 in human hepatocellular carcinoma cells to 3.03-fold and 2.02-fold, respectively. 2-Cl-TX at 2.5 μM caused 2.19-fold and 1.98-fold overexpression of CYP1A2 and CYP3A4, respectively. In vitro studies revealed that 2-Cl-TX was biotransformed into two metabolites through the sulfoxidation of the sulfur atom, or via the hydroxylation of aromatic carbon. Results from this study, including the metabolic susceptibility of residual 2-Cl-TX, the proposed metabolites and the significant toxic effect on the activities, mRNA, and protein expression of CYP1A2 and CYP3A4, are vital to the human health and safety risk assessment from this ubiquitous xenobiotic.

Potential chromosome damage, cell-cycle kinetics/and apoptosis induced by epoxiconazole in bovine peripheral lymphocytes in vitro

The epoxiconazole was tested in vitro for its potential on induction of chromosome damage and/or cell cycle kinetics in cultured bovine peripheral lymphocytes. Cytogenetic endpoints such as: Chromosome Aberrations (CA); Sister Chromatid Exchanges (SCE); Micronuclei (MN); Mitotic Index (MI); Proliferation Index (PI); and Cytokinesis Block Proliferation Index (CBPI) were investigated for 24 h and 48 h of incubation. The cultured lymphocytes were exposed to the epoxiconazole at concentrations of 2.5, 5, 10, 25, 50 and 100 μg mL^-1. From our results is evident that treatment of bovine peripheral lymphocytes with the epoxiconazole was not related to DNA damage; no genotoxic effect and/or clastogenic/aneugenic effects were recorded. However, epoxiconazole has ability to significantly affect cell cycle kinetics/and induce apoptosis. A decrease of proliferation in the MI, CBPI and identically in the PI were observed; hence, cytostatic/cytotoxic effects of epoxiconazole have been recorded. The prolonged time of exposure at the highest concentration caused an inhibition of the replication. Electrophoretic analysis confirmed the epoxiconazole potential to induce ladder-like patterns of DNA fragments that are a hallmark of apoptosis.

Effects of triazole fungicides on androgenic disruption and CYP3A4 enzyme activity

Triazole fungicides are widely used as broad-spectrum fungicides, non-steroidal antiestrogens and for various industrial applications. Their residues have been frequently detected in multiple environmental and human matrices. The increasingly reported toxicity incidents have led triazole fungicides as emerging contaminants of environmental and public health concern. However, whether triazole fungicides behave as endocrine disruptors by directly mimicking environmental androgens/antiandrogens or exerting potential androgenic disruption indirectly through the inhibition of cytochrome P450 (CYP450) enzyme activity is yet an unresolved question. We herein evaluated five commonly used triazole fungicides including bitertanol, hexaconazole, penconazole, tebuconazole and uniconazole for the androgenic and anti-androgenic activity using two-hybrid recombinant human androgen receptor (AR) yeast bioassay and comparatively evaluated their effects on enzymatic activity of CYP3A4 by P450-Glo™ CYP3A4 bioassay. All five fungicides showed moderate anti-androgenic activity toward human AR with the IC₅₀ ranging from 9.34 μM to 79.85 μM. The anti-androgenic activity remained no significant change after the metabolism mediated by human liver microsomes. These fungicides significantly inhibited the activity of CYP3A4 at the environmental relevant concentrations and the potency ranks as tebuconazole > uniconazole > hexaconazole > penconazole > bitertanol with the corresponding IC₅₀ of 0.81 μM, 0.93 μM, 1.27 μM, 2.22 μM, and 2.74 μM, respectively. We found that their anti-androgenic activity and the inhibition potency toward CYP3A4 inhibition was significantly correlated (R² between 0.83 and 0.97, p < 0.001). Our results indicated that the risk assessment of triazole pesticides and structurally similar chemicals should fully consider potential androgenic disrupting effects and the influences on the activity of CYP450s.

Evaluation of cytotoxic and genotoxic activity of fungicide formulation Tango® Super in bovine lymphocytes

Tango^® Super is a two-compound fungicide formulation widely employed in grain protection. However, details of Tango^® Super effects on cell cultures have not been fully investigated. In this study, bovine lymphocytes were exposed to a concentration range 0.5; 1.5; 3; 6; and 15 μg mL^-1 for 4 h to assess the cytotoxicity and genotoxicity of the fungicide. Our experiments revealed that this fungicide treatment reduced cell viability, decreased cell proliferation and provoked apoptotic cell death. Cell cycle analysis showed predominant accumulation of cells in the G₀/G₁ phase of the cell cycle. The fungicide was able to induce mitochondrial superoxide production accompanied by elevated levels of carbonylated proteins and changes in the lipid membrane composition. The fungicide did not induce micronuclei production, but stimulated both DNA double-strand breaks and the formation of p53 binding protein, which is accumulated during the DNA repair process at the site of double-strand breaks. Based on the obtained data we suppose that the fungicide-induced DNA damage is the result of oxidative stress, which may contribute to higher occurrence of apoptotic cell death. Because ergosterol biosynthesis-inhibiting fungicides are widely used in agriculture to ensure higher crop yields and may cause health impairment of animals and humans, there is a need for further testing to elucidate their potential genotoxic effects using in vivo and/or in vitro systems.

Genotoxic risk of quinocetone and its possible mechanism in in vitro studies

Quinoxalines possessing the quinoxaline-1,4-dioxide (QdNOs) basic structure are used for their antibacterial action, although their mechanism of genotoxicity is not clear. After comparing the sensitivity of V79 cells and HepG2 cells to quinocetone (QCT) and other QdNOs, it was found that HepG2 cells are more sensitive. The results show that QCT induces the generation of O2˙- and OH˙ during metabolism. Free radicals could then attack guanine and induce 8-hydroxy-deoxyguanine (8-OHdG) generation, causing DNA strand breakage, the inhibition of topoisomerase II (topo II) activity, and alter PCNA, Gadd45 and topo II gene expression. QCT also caused mutations in the mtDNA genes COX1, COX3 and ATP6, which might affect the function of the mitochondrial respiratory chain and increase the production of reactive oxygen species (ROS). Nuclear extracts from HepG2 cells treated with QCT had markedly reduced topo II activity, as judged by the inability to convert pBR322 DNA from the catenated to the decatenated form by producing stable DNA-topo II complexes. This study suggests that QCT electrostatically bound to DNA in a groove, affecting the dissociation of topo II from DNA and impacting DNA replication. Taken together, these data reveal that DNA damage induced by QCT resulted from O2˙- and OH˙ generated in the metabolism process. This data throws new light onto the genotoxicity of quinoxalines.