Developmental and cardiovascular toxicities of acetochlor and its chiral isomers in zebrafish embryos through oxidative stress

Enantioselective Metabolism of Mefentrifluconazole by Human Liver Microsomes

A better understanding of the metabolic differences between chiral pesticide enantiomers in organisms is crucial for accurately assessing their risk. The enantioselective metabolism of mefentrifluconazole was investigated by the human liver microsome reaction system. The metabolic rate of S-mefentrifluconazole was found to be 4 times that of R-mefentrifluconazole. The chemical inhibitor method was used to further explore the cause of metabolic difference, and it was found that the inhibitors of CYP2C19 and CYP2C8 significantly reduced the metabolism of S-mefentrifluconazole (70.3-92.0%) and R-mefentrifluconazole (53.0-78.6%), respectively. CYP2C19 is a key metabolic enzyme of S-mefentrifluconazole. Molecular docking indicates that the internal energy of binding of R-mefentrifluconazole to CYP2C19 is too high, resulting in a positive docking fraction (0.1730 kJ/moL). Therefore, R-mefentrifluconazole cannot bind to CYP2C19 under natural conditions. CYP2C8 is the key metabolic enzyme of R-mefentrifluconazole. The lower docking energies (-37.80 kJ/moL for R-mefentrifluconazole and -35.64 kJ/moL for S-mefentrifluconazole) make CYP2C8 more capable of metabolizing R-mefentrifluconazole. This study provides essential data for exploring the toxicological assessment of mefentrifluconazole.

Stereo-selective cardiac toxicity induced by metconazole via oxidative stress and the wnt/β-catenin signaling pathway in zebrafish embryos

Metconazole (MEZ), a chiral triazole fungicide, produces enantioselective adverse effects in non-target organisms. Among MEZ's isomers, cis-MEZ displays robust antimicrobial properties. Evaluating MEZ and cis-MEZ's toxicity may mitigate fungicide usage and safeguard non-target organisms. Our study evaluated the toxicity of MEZ and its cis-isomers at concentrations of 0.02, 0.2, 2, and 4 mg L-1. We report stereoselectivity and severe cardiovascular defects in zebrafish, including pericardial oedema, decreased heart rate, increased sinus venous and bulbous arteries distances, intersegmental vessel defects, and altered cardiovascular development genes (hand2, gata4, nkx2.5, tbx5, vmhc, amhc, dll4, vegfaa, and vegfc). Further, MEZ significantly increased oxidative stress and apoptosis in zebrafish, primarily in the cardiac region. Isoquercetin, an antioxidant found in plants, partially mitigates MEZ-induced cardiac defects. Furthermore, MEZ upregulated the Wnt/β-catenin pathway genes (wnt3, β-catenin, axin2, and gsk-3β) and β-catenin protein expression. Inhibitor of Wnt Response-1 (IWR-1) rescued MEZ-induced cardiotoxicity. Our findings highlight oxidative stress, altered cardiovascular development genes, and upregulated Wnt/β-catenin signaling as contributors to cardiovascular toxicity in response to MEZ and cis-MEZ treatments. Importantly, 1R,5S-MEZ exhibited greater cardiotoxicity than 1S,5R-MEZ. Thus, our study provides a comprehensive understanding of cis-MEZ's cardiovascular toxicity in aquatic life.

Hepatic effects of acetochlor chiral isomers in zebrafish and L02 cells

The pesticide acetochlor (ACT) is a chiral isomer commonly detected in the global environment, yet its specific impacts on liver function remain poorly understood. We utilized zebrafish and L02 cells as research models to comprehensively investigate how ACT and its chiral isomers affect the liver. Our investigations unveiled that the R, Rac, and S isomers of ACT disrupt hepatic lipid transport, catabolism, and synthesis, leading to delayed yolk sac absorption and the accumulation of lipids in zebrafish embryos. These isomers induce oxidative stress in the liver of zebrafish embryos, reducing antioxidant levels and enzyme activity. The accumulated lipids in the liver render it susceptible to oxidative stress, further exacerbating hepatocyte damage. Hepatocyte damage manifests as extensive vacuolization of liver cells and alterations in liver morphology, which are induced by R, Rac, and S. Furthermore, we elucidated the molecular mechanisms underpinning the disturbance of hepatic lipid metabolism by R, Rac, and S in L02 cells. These compounds stimulate lipid synthesis through the upregulation of the AMPK/SREBP-1c/FAS pathway while inhibiting lipolysis via downregulation of the PPAR-α/CPT-1a pathway. Remarkably, our results highlight that S exhibits significantly higher hepatotoxicity in comparison to R. This study provides valuable insights into the hepatic effects of ACT chiral isomers.

Pesticide screening of surface water and soil along the Mekong River in Cambodia

Widespread use of pesticides globally has led to serious concerns about environmental contamination, particularly with regard to aquatic and soil ecosystems. This work involved investigating concentrations of 64 pesticides in surface-water and soil samples collected in four provinces along the Mekong River in Cambodia during the dry and rainy seasons (276 samples in total), and conducting semi-structured interviews with local farmers about pesticide use. Furthermore, an ecological risk assessment of the detected pesticides was performed. In total, 56 pesticides were detected in surface water and 43 in soil, with individual pesticides reaching maximum concentrations of 1300 ng/L in the surface-water samples (tebufenozide) and 1100 ng/g dry weight in the soil samples (bromophos-ethyl). The semi-structured interviews made it quite evident that the instructions that farmers are provided regarding the use of pesticides are rudimentary, and that overuse is common. The perceived effect of pesticides was seen as an end-point, and there was a limited process of optimally matching pesticides to pests and crops. Several pesticides were used regularly on the same crop, and the period between application and harvest varied. Risk analysis showed that bromophos-ethyl, dichlorvos, and iprobenfos presented a very high risk to aquatic organisms in both the dry and rainy seasons, with risk quotient values of 850 for both seasons, and of 67 in the dry season and 78 in the rainy season for bromophos-ethyl, and 49 in the dry season and 16 in the rainy season for dichlorvos. Overall, this work highlights the occurrence of pesticide residues in surface water and soil along the Mekong River in Cambodia, and emphasizes the urgent need for monitoring and improving pesticide practices and regulations in the region.

Stereoselective toxicity of acetochlor chiral isomers on the nervous system of zebrafish larvae

Acetochlor (ACT) is a widely detected pesticide globally, and the neurotoxic effects of its chiral isomers on humans and environmental organisms remain uncertain. Zebrafish were used to study the neurotoxicity of ACT and its chiral isomers. Our study reveals that the R-ACT, Rac-ACT, and S-ACT induce neurotoxicity in zebrafish larvae by impairing vascular development and disrupting the blood-brain barrier. These detrimental effects lead to apoptosis in brain cells, hindered development of the central nervous system, and manifest as altered swimming behavior and social interactions in the larvae. Importantly, the neurotoxicity caused by the S-ACT exhibits the most pronounced impact and significantly diverges from the effects induced by the R-ACT. The neurotoxicity associated with the Rac-ACT falls intermediate between that of the R-ACT and S-ACT. Fascinatingly, we observed a remarkable recovery in the S-ACT-induced abnormalities in BBB, neurodevelopment, and behavior in zebrafish larvae upon supplementation of the Wnt/β-catenin signaling pathway. This observation strongly suggests that the Wnt/β-catenin signaling pathway serves as a major target of S-ACT-induced neurotoxicity in zebrafish larvae. In conclusion, S-ACT significantly influences zebrafish larval neurodevelopment by inhibiting the Wnt/β-catenin signaling pathway, distinguishing it from R-ACT neurotoxic effects.

Molecular mechanisms of cardiotoxicity induced by acetamide and its chiral isomers

Acetamide (ACT) is used in a racemic form, and the considerable residues of this compound in the environment raise potential safety concerns for human health. We investigated the toxicity of ACT and its chiral isomers on human cardiomyocyte (AC16) cell line and zebrafish embryonic heart, and found that (+)-S-ACT was the main component causing cardiac toxicity. Our findings indicate that the IC50 of (±)-Rac-ACT on AC16 cells was 20.19 μg/mL. (-)-R-ACT, (±)-Rac-ACT, and (+)-S-ACT caused DNA damage and apoptosis in AC16 cells at this concentration. The underlying molecular mechanism may involve the induction of reactive oxygen species (ROS). The accumulation of ROS results in a decline in mitochondrial membrane potential (MMP) and prompts the release of cytochrome c (cyt c) from the mitochondria. This cascade of events ultimately activates the caspase-3 and caspase-9 signaling pathways, resulting in apoptosis. Furthermore, in vivo observations in zebrafish hearts demonstrated caspase-3 activation and the presence of the DNA damage marker (γH2AX), indicating that (+)-S-ACT is more toxic to cardiomyocytes than (-)-R-ACT and (±)-Rac-ACT. These findings suggest that (+)-S-ACT may be the primary component responsible for the toxicity of (±)-Rac-ACT in AC16 cells. Overall, these findings raise public awareness regarding the risks associated with chiral isomeric pesticides and provide a scientific foundation for their appropriate use.