Enantioselective metabolism of triadimefon and its chiral metabolite triadimenol in lizards

Subzero-temperature homogeneous liquid-liquid extraction for the stereoselective determination of chiral triadimefon and its metabolite in water, fruit juice, vinegar, and fermented liquor by HPLC

A novel method based on homogeneous liquid-liquid extraction with deep eutectic solvents (DES) under subzero-temperature conditions in combination with high performance liquid chromatography (HPLC) for the determination of chiral fungicide triadimefon (TF) and its metabolite triadimenol (TN) in water, fruit juice, vinegar, and fermented liquor was developed in this study. The method involved using deep eutectic solvents (DES) under subzero-temperature conditions in combination with high performance liquid chromatography (HPLC). This novel technique, known as subzero-temperature homogeneous liquid-liquid extraction (STHLLE), offers several advantages, including high efficiency, time-saving, low-cost, and eco-friendliness. The enantiomers of chiral TF and TN were simultaneously separated and quantified using HPLC coupled with a Daicel Chiralpak OD-RH column. Various experimental parameters such as DES composition and volume, freezing condition, salt concentration, and pH were optimized to enhance the recoveries of the target analytes. Under the optimized conditions, spiked recoveries of six enantiomers (i.e., S-TF, R-TF, SR-TN, RS-TN, SS-TN, and RR-TN) in the water, fruit juice, vinegar, and fermented liquor samples were 82.2-100.1% with relative standard deviations of 0.4-10.1%. The current method demonstrated a detection range of 0.03-0.06 mg L-1 in the target analytes. This established technique exhibits potential for efficient and precise extraction and quantification of the enantiomers of TF and TN in water phase samples.

Difenoconazole disrupts the blood-brain barrier and results in neurotoxicity in carp by inhibiting the Nrf2 pathway mediated ROS accumulation

Excessive use of hard-to-degrade pesticides threatens the ecological health of aquatic systems. This study aimed to investigate difenoconazole (DFZ) residues in the environment induced neurotoxicity in carp and the underlying mechanisms. A total of thirty-six carps were divided into three groups and exposed to 0, 0.5, and 2.0 mg/L DFZ for 96 h, respectively. The alterations in behavior and blood-brain barrier (BBB) were examined, and potential mechanisms were explored using immunological assays and biochemical methods. The results showed that DFZ exposure caused behavioral freezing, reduced feeding, and neuronal necrosis in carp. Mechanistically, DFZ triggered ROS accumulation and destroyed the balance between oxidation and antioxidation with increased lipid peroxidation product MDA contents and reduced antioxidant enzymes SOD and CAT activities in the carp brain by inhibiting the NF-E2-related factor 2 (Nrf2) pathway. The activation of oxidative stress further reduced tight junction proteins and MMP levels, thereby destroying BBB and leading to DFZ leakage into the brain. Increased BBB permeability additionally led to DFZ activation of nuclear factor kappa-B signaling-mediated inflammatory cytokine storm, exacerbating neuroinflammation. Meanwhile, DFZ exposure activated mitochondria-associated apoptosis in the carp's brain by up-regulating Bcl-2 associated X protein, cleaved-caspase3, and cytochrome C and decreasing B-cell lymphoma-2 levels. Interestingly, the carp's brain initiated a protective autophagic response via the PI3K/AKT/TOR pathway intending to counteract the neurotoxicity of DFZ. Overall, we concluded that accumulation of DFZ at high concentrations in the aquatic systems disrupted the BBB and resulted in neurotoxicity in carp through inhibition of Nrf2 pathway-mediated ROS accumulation. This study provides a reference for monitoring DFZ residues in the environment and a new target for the treatment of DFZ-induced neurotoxicity in carp.

Thermoregulation of Eremias argus alters temperature-dependent toxicity of beta-cyfluthrin: Ecotoxicological effects considering ectotherm behavior traits

Risk assessments of the ecotoxicological effects insecticides impose on ectotherms have increasingly considered temperature. However, the changes toxicants induce in thermoregulatory behavioral traits may lead to a divergence of thermal selection and temperature-dependent changes of contaminant toxicity. This study demonstrated the interaction of behavioral thermoregulation and temperature-dependent toxicity of beta-cyfluthrin (BC) in the lizard Eremias argus. Based on the negative relationship between temperature and BC toxicity, seeking a warming environment was assumed to represent a self-rescue behavior (and vice versa). The results showed that BC-treated lizards (0-20 μg/g body weight (bw)) showed such self-rescue behavior, while lizards exposed to an extremely high BC dose (200 μg/g bw) sought a cooler environment. Biochemical assays showed that BC affected neurotransmitter systems, caused oxidative stress, and interfered with ion-transport in the central nervous system. Biomarkers of the cholinergic and glutamatergic system, ion-transport function, and oxidative stress were identified as potential biochemical variables related to thermoregulatory behavior. Apparently, seeking a warmer environment is a survival strategy with the aim to neutralize BC toxicity, while seeking a cooler environment aims to attenuate the harmful effects of metabolic and oxidative stress, and to decelerate internal BC diffusion. This phenomenon could be also explained by the concept of the "cooling trap", i.e., a behavior where cooler temperatures are sought. This impairs survival after exposure to BC at it has a negative temperature coefficient, derived from a dysfunction of the central nervous system regarding thermoregulation caused by the high dosage of neurotoxicant and resulting temperature maladaptation. Implications of the interaction between thermoregulatory behavior and temperature-dependent toxicity are presented, which may aid further temperature-dependent risk assessments.

Form and Function of the Vertebrate and Invertebrate Blood-Brain Barriers

The need to protect neural tissue from toxins or other substances is as old as neural tissue itself. Early recognition of this need has led to more than a century of investigation of the blood-brain barrier (BBB). Many aspects of this important neuroprotective barrier have now been well established, including its cellular architecture and barrier and transport functions. Unsurprisingly, most research has had a human orientation, using mammalian and other animal models to develop translational research findings. However, cell layers forming a barrier between vascular spaces and neural tissues are found broadly throughout the invertebrates as well as in all vertebrates. Unfortunately, previous scenarios for the evolution of the BBB typically adopt a classic, now discredited 'scala naturae' approach, which inaccurately describes a putative evolutionary progression of the mammalian BBB from simple invertebrates to mammals. In fact, BBB-like structures have evolved independently numerous times, complicating simplistic views of the evolution of the BBB as a linear process. Here, we review BBBs in their various forms in both invertebrates and vertebrates, with an emphasis on the function, evolution, and conditional relevance of popular animal models such as the fruit fly and the zebrafish to mammalian BBB research.

Absolute Configuration, Enantioselective Bioactivity, and Degradation of the Novel Chiral Triazole Fungicide Mefentrifluconazole

Mefentrifluconazole is a new chiral triazole fungicide with a pair of enantiomers. However, the enantioselective differences in the biological effects and environmental behaviors of mefentrifluconazole are unclear. In the present work, a new simultaneous determination method of mefentrifluconazole enantiomers was established using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The absolute configuration of the two mefentrifluconazole enantiomers was confirmed by comparing the experimental and calculated ECD spectra. The enantioselective bioactivity to target fungi and degradation in cucumber samples were also assessed. The absolute configurations of the two enantiomers eluted on the Superchiral IG-3 column were confirmed as R-(-)-mefentrifluconazole and S-(+)-mefentrifluconazole. The R-(-)-mefentrifluconazole possessed 5-473 times higher bioactivity than S-(+)-mefentrifluconazole toward six kinds of target pathogenic fungi. In addition, R-(-)-mefentrifluconazole exhibited stronger efficacy of suppression of ergosterol biosynthesis. The molecular docking results indicated that R-(-)-mefentrifluconazole had shorter binding distances and lower energies with the target protein than S-(+)-mefentrifluconazole, which may result in the enantioselective bioactivity. The high-efficiency enantiomer of R-(-)-mefentrifluconazole has longer duration in cucumber samples due to the relatively long half-life of 4.0 days. This research has clarified the bioactivity differences and mechanism between mefentrifluconazole enantiomers against target fungi and laid the foundation for an in-depth study of mefentrifluconazole at the chiral level.

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.

Enantioselective endocrine-disrupting effects of the phenylpyrazole chiral insecticides in vitro and in silico

The phenylpyrazole chiral insecticides, including the widely used fipronil, ethiprole, and flufiprole, have generated a worldwide interest due to their environmental toxicity. However, up to now,only few studies focused on their their potential endocrine-disrupting effects (EDEs). In this study, we investigated the endocrine hormonal disorder caused by the fipronil, ethiprole, and flufiprole enantiomers in vitro and in silico approach. Results of the luciferase reporter assay indicated that the enantiomers of fipronil, ethiprole, or flufiprole have shown stereoselective endocrine-disrupting effects. S-(-)-ethiprole and S-(-)-flufiprole have anti-thyroidal disorder effects whereas R-(-)-fipronil, R-(+)-ethiprole, and R-(+)-flufiprole showed anti-estrogenic disorder effects. The results of the molecular dynamics simulations revealed that the happened EDEs could be partially attributed to the enantioselective specific receptor binding affinities. It also suggested that Vander Waals interactions plays an important role in the binding procedure. This study could provide helpful information for the explanation of enantioselectivity in the EDEs of chiral phenylpyrazole pesticides at the molecular level.

Thermal effects on tissue distribution, liver biotransformation, metabolism and toxic responses in Mongolia racerunner (Eremias argus) after oral administration of beta-cyfluthrin

Effects of temperature on metabolism/biotransformation and toxicokinetics to lizards are significant, but frequently ignored in toxicology studies. Beta-cyfluthrin (BC) is a pyrethroid insecticide and has been widely used globally. The study aimed to understand the diverse adverse effects of BC to the lizard (Eremias argus) at different temperature regimes. We carried out a single oral BC treatment (20 mg/kg bw) for toxicokinetic study and a 7-day BC (10 mg/kg bw) gavage to look at toxicology by monitoring changes in the biomarkers HSP70, SOD, MDA, CarE, UDPGT, GST, cyp genes, and other metabolic responses. Results showed that BC was lethal to lizards, showing oxidative damages in the liver at ambient temperature (25 °C). Heat stress (35 °C) could exacerbate the oxidative damage (MDA increased) caused by BC, due to the disorder of the antioxidant defense system. The result of tissue distribution and toxicokinetic study also showed that temperature affected the BC biotransformation in lizards. The biotransformation of BC maybe relates to the activation of CarE and UDGPT by heat stress. However, the cyp system and GST didn't increase under BC or/and heat treatments. ¹H-NMR metabolomics analysis showed that BC or/and heat stress interfered with energy and amino acid metabolism of the liver. Unlike acute lethal toxicity, the occurrence of the BC and heat stresses has detrimental effects on lizard individuals and populations on sub-lethal levels. Our results indicate that pollution and global warming (or some other extremely weather) may generate significant and harmful effects on lizards.

Enrichment of imidacloprid and its metabolites in lizards and its toxic effects on gonads

Soil contaminants can cause direct harm to lizards due to their regular swallowing of soil particles. As the world's fastest growing insecticide with long half-life in soil, the endocrine disrupting effect of neonicotinoids on lizards deserves more attention. In this report, we assessed the endocrine disrupting effect of imidacloprid on Eremias argus during 28 days of continuous exposure. Among the imidacloprid and its metabolites, only the metabolite 6-chloropyridic acid had a significant accumulation in the gonads and was positively correlated with its blood concentration. Imidacloprid might cause endocrine disrupting effects on lizards in two ways. First, the desnitro metabolites of imidacloprid could accumulate in the brain, inhibited the secretion of gonadotropin-releasing hormone, and ultimately affected the feedback regulation of hypothalamic-pituitary-gonadal related hormones. Secondly, imidacloprid severely inhibited the gene expression of the corresponding enzymes in the gonadal anti-oxidative stress system, causing histological damage to the gonads and ultimately affecting gonadal function. Specifically, exposure to imidacloprid resulted in abnormal arrangement of spermatogenic epithelial epithelium, hyperplasia of epididymal wall, and oligospermia of male lizard. Meanwhile, gene expressions of cyp17, cyp19, and hsd17β were severely inhibited in the imidacloprid exposure group, consistent with decreased levels of testosterone and estradiol in plasma. Imidacloprid exposure could cause insufficient androgen secretion and less spermatogenesis in male lizards. The risk of imidacloprid exposure to female lizards was not as severe as that of male lizards, but it still inhibited the expression of cyp19 in the ovaries and led to a decrease in the synthesis of estradiol. This study firstly reported the endocrine disruption of imidacloprid to lizards, providing new data for limiting the use of neonicotinoids.

Stereoselective metabolism and potential adverse effects of chiral fungicide triadimenol on Eremias argus

Reptiles are an important part of vertebrates and are the primitive terrestrial vertebrates. However, lots of reptile species are endangered or susceptible to extinction. It is no doubt that contaminants are one of the important reasons for the decline of the lizard population. In this study, the selective metabolism of triadimenol (TN) in the male Eremias argus lizards and the toxic effects of TN on lizards were studied. TN chiral isomers were separated and detected by HPLC-MS/MS system with Lux Cellulose-1 column. Tissue distribution experiments showed the existence of stereoselectivity biotransformation of TN enantiomers among organs in lizards, and RR-TN preferentially emerged over the other enantiomers. The antioxidant enzymes (SOD, CAT, GST) activities and MDA content assays demonstrated that TN induced oxidative stress in most organs, especially in the liver, and the histopathology analysis showed the severe liver and testis damage caused by 14-day continuous TN gavage. The reproductive effects of TN-induced reflected in the increased sex hormone testosterone. This research confirms that TN could induce hepatic and reproductive toxicity of E. argus lizard.

Accumulation and toxicity of thiamethoxam and its metabolite clothianidin to the gonads of Eremias argus

The endocrine disrupting effect of pesticides is considered to be an important factor in the decline of reptile populations. The large-scale application of neonicotinoids in the environment poses a potential threat to small farmland lizards Eremias argus. In this study, we evaluated the disruption effects of thiamethoxam and its metabolite clothianidin on the endocrine disruption of Eremias argus during 28 d exposure. Thiamethoxam and clothianidin could accumulate in the testis and ovary. Adequate blood exchange was the main cause of thiamethoxam and clothianidin accumulation in the gonads. The production of clothianidin aggravated the effect of endocrine disruption to lizards. Thiamethoxam/clothianidin exhibited two distinct ways of interfering with the endocrine disruption of the male and female lizards. Thiamethoxam/clothianidin significantly up-regulated the expression of cyp17 and cyp19 genes in the testis, which ultimately led to a significant decrease in testosterone levels and a significant increase in the 17-estradiol concentrations in plasma. The expression of the estrogen receptor gene in the liver was also significantly increased in male lizards. The significant declines in testosterone and prostaglandin D2 levels in the plasma indicated that thiamethoxam and clothianidin could cause androgen deficiency in male lizards. Meanwhile, in female lizards, thiamethoxam/clothianidin increased the expression of hsd17β gene in the ovary, causing an increase in testosterone levels in the plasma and an up-regulation of androgen receptor expression in the liver. The effects of thiamethoxam and clothianidin on male lizards were more pronounced. This study verified the possible endocrine disrupting effects of neonicotinoids and provided a new perspective for the study of global recession of reptiles.

Study on neurotoxicity of dinotefuran, thiamethoxam and imidacloprid against Chinese lizards (Eremias argus)

The neurotoxicity of dinotefuran, thiamethoxam and imidacloprid against Chinese lizards (Eremias argus) were evaluated in acute oral exposure and 28d subchronic exposure. Dinotefuran was not easily metabolized and showed strong persistence in the lizard brain. Thiamethoxam and imidacloprid were rapidly absorbed and excreted in lizards, and were not easily enriched in the lizard brain. Dinotefuran and thiamethoxam could directly increase the concentrations of acetylcholine in the brain and blood by up-regulating the expression of the ach gene, which in turn enhanced the binding of acetylcholine and acetylcholinesterase receptors, eventually causing the release of dopamine. The effect of dinotefuran was more pronounced than thiamethoxam. Clothianidin was a major metabolite of thiamethoxam in the brain and aggravated the neurotoxic effects of thiamethoxam. Imidacloprid desnitro olefin was the only metabolite of imidacloprid that enriched in the brain. The protonation effect of imidacloprid desnitro olefin was stronger than that of the parent imidacloprid, which increased its binding ability to lizard acetylcholinesterase receptors. Competitive inhibition of imidacloprid desnitro olefin and acetylcholine led to the down-regulation of ach gene expression. Although neonicotinoids caused the opening of ligand-gated ion channel through the activation of acetylcholinesterase receptors, the body would alleviate these effects by the inhibition of voltage-dependent channel activity for compensatory mechanisms. This study provided a new perspective on the neotoxic effects of neonicotinoids.

The metabolism distribution and effect of dinotefuran in Chinese lizards (Eremias argus)

The Chinese lizards (Eremias argus) were used to evaluate the metabolism, distribution and effect of dinotefuran following oral exposed. The HPLC equipped with Q Exactive focus was used for metabolite identification and concentration analysis. After single oral administration, the time-concentration curves of dinotefuran and its metabolites were tissue-dependent. The liver and kidney were the major metabolic organs. Percutaneous and urinary excretions were the main ways for lizards to eliminate dinotefuran, and the urine output was the limiting factor. Nitro-reduction was an important process of the metabolism of dinotefuran that was dominated by aldehyde oxidase, and P450 enzymes were involved. The CYP3A4 and CYP2C19 played a crucial role in the other metabolic pathways of dinotefuran. The mRNA expressions of GST family were severely inhibited in liver, which showed dinotefuran might pose a risk of damaging the oxidative stress system in liver. Prolonged residuals of dinotefuran and its demethylation metabolite might enhance the risk of dinotefuran to brain. The results enrich and supplement the knowledge of the environmental fate of dinotefuran in reptiles.

Metabolism Distribution and Effect of Thiamethoxam after Oral Exposure in Mongolian Racerunner ( Eremias argus)

Systematic evaluation of the metabolism, distribution, and effect of thiamethoxam in Mongolian racerunner ( Eremias argus) was carried out after oral exposure. HPLC equipped with Q Exactive focus was used for identification and concentration analysis of thiamethoxam and its metabolites. Percutaneous and urine excretions were the primary ways for the elimination of thiamethoxam and its metabolites, and the limiting factor was urine output. Demethylated thiamethoxam and clothianidin were the main metabolites of thiamethoxam in lizards. CYP3A4, CYP3A7, and CYP2C9 played a crucial role in the metabolism process. Aldehyde oxidase only dominated the nitro-reduction process of demethylated thiamethoxam and clothianidin. Glutathione S-transferase might be related to the clearance process of thiamethoxam and its metabolites. The findings indicated that thiamethoxam might pose potential carcinogenic and hepatic injury risk to lizards. The results enrich and supplement the knowledge of the environmental fate of thiamethoxam in reptiles.

Tissue distribution and toxicity effects of myclobutanil enantiomers in lizards (Eremias argus)

In recent years, serious environmental pollution has caused a decrease in the abundance of many species worldwide. Reptiles are the most diverse group of terrestrial vertebrates. There are large amounts of toxicological data available regarding myclobutanil, but the adverse effects of myclobutanil on lizards has not been widely reported. In this study, treatment groups were orally administered a single-dose of myclobutanil (20mg/kg body weight (bw)). Subsequently, it was found that there were differences in myclobutanil levels between the different tissues and concentrations also changed with degradation time. The tissue concentrations of myclobutanil decreased in the order of: stomach > liver > lung > blood > testis > kidney > heart > brain. Based on our results, the liver and testis were considered to be the main target organs in lizards, indicating that the myclobutanil could induce potential hepatic and reproductive toxicity on lizards. Meanwhile, it was also demonstrated that the toxic effects of myclobutanil was different in different species, and the distribution of different pesticides in lizards were different.