Pre-mating nitenpyram exposure in male mice leads to depression-like behavior in offspring by affecting tryptophan metabolism in gut microbiota

Several studies have confirmed that the health status of the paternal affects the health of the offspring, however, it remains unknown whether paternal exposure to pesticides affect the offspring health. Here, we used untargeted metabolomics and 16S rRNA sequencing technology, combined with tail suspension test and RT-qPCR to explore the effects of paternal exposure to nitenpyram on the neurotoxicity of offspring. Our results found that the paternal exposure to nitenpyram led to the offspring's depressive-like behaviors, accompanied by the reduction of tryptophan content and the disorder of microbial abundance in the gut of the offspring. Further, we determined the expression of tryptophan metabolism-related genes tryptophanase (tnaA) and tryptophan hydroxylase 1 (TpH1) in gut bacteria and colonic tissues. We found that tryptophan is metabolized to indoles rather than being absorbed into colonocytes, which coursed the reduce of tryptophan availability after nitenpyram exposure. In conclusion, our study deepens our understanding of the intergenerational toxic effects of pesticides.

A dual-emitting fluoroprobe fabricated by aloe leaf-based N-doped carbon quantum dots and copper nanoclusters for nitenpyram detection in waters by virtue of inner filter effect and static quenching principles

Fluorescence sensing technique has been used in environmental analysis due to its simplicity, low cost, and visualization. Although the fruit pulp-based biomass carbon quantum dots (CQDs) have excellent luminescent properties, aloe leaves possess the superiority of being easily accessible in all seasons compared to fruit pulp. Thus, we fabricated Aloe carazo leaf-based nitrogen doping-CQDs (N-CQDs) using a facile hydrothermal approach, which emitted bright blue fluorescence with a quantum yield of 21.4 %. By comparison, the glutathione-encapsulated copper nanoclusters (GSH-CuNCs) displayed strong red fluorescence. A blue/red dual emission based on the N-CQDs/CuNCs mixture was established for nitenpyram detection. At the 350-nm excitation, the N-CQD/CuNCs system produced dual-wavelength emitting peaks at 440 and 660 nm, respectively. Moreover, when nitenpyram was introduced into the system, the fluorescence intensities (FIs) of N-CQDs significantly decreased, whereas the FIs of GSH-CuNCs varied slightly; simultaneously, the solution color changed from bright blue to dark red. Both the spectral overlapping between nitenpyram's UV-Vis absorption and N-CQDs' excitation and almost unchanged fluorescence lifetimes indicated the occurrence of inner-filtering effect (IFE) in the dual-emitting fluoroprobe. In addition, the Stern-Volmer constant (Ksv = 6.92 × 103 M-1), temperature effect, as well as UV-Vis absorption of N-CQD/CuNCs before and after the addition of nitenpyram corroborated the static-quenching behavior. Consequently, the fluorescence-quenching of N-CQDs by nitenpyram was attributable to the joint IFE and static-quenching principles. A good linearity existed between the F660/F440 values and nitenpyram concentrations (0.5-200 μM) with a method detection limit of 0.15 μM. The dual-emitting fluoroprobe provided the satisfactory recoveries (95.0%-107.0 %) for nitenpyram detection in real-world waters, which were comparable with the results of traditional liquid chromatography coupled to tandem mass spectrometry method. Owing to its simple operations, low-cost, and adaptability for on-site outdoor monitoring, the newly developed dual-emitting fluoroprobe possesses great potential applications in routine monitoring of nitenpyram under field conditions.

Selective detection of nitenpyram by silica-supported carbon quantum dots

In this study, a fluorescent sensor of nitrogen-doped carbon quantum dots (N-CQDs) and silica gel hybrid was developed for the quantitative detection of nitenpyram, a toxic neonicotinoid existing in groundwater and/or surface water.The prepared N-CQDs@SiO₂ sensor exhibited remarkable sensing selectivity and sensitivity towards nitenpyram among the four pesticides and six metal ions. A prominent fluorescence quenching of N-CQDs@SiO₂ at 445 nm was observed in the presence of nitenpyram with a linear response range of 0-300.0 mg L^-1 and an estimated limit of detection of 1.53 mg L^-1. The main cause for selective sensing is that nitenpyram absorbs the excitation light of N-CQDs@SiO₂, leading to fluorescence quenching of the sensor through the inner filter effect.

Novel hydrophilic straw biochar for the adsorption of neonicotinoids: kinetics, thermodynamics, influencing factors, and reuse performance

Nitenpyram (NIT) is the most water-soluble neonicotinoid (NEO). It has been shown to pose a serious threat to human health and the environment but was always ignored due to its limited market share. There were few experts who studied NIT's transport behavior on biochar. In this study, two types of biochar were co-activated separately using zinc chloride combined with phosphoric acid and potassium hydroxide combined with acetic acid, marked as ZBC and KBC. Characterizations suggested that hydrophilic ZBC and KBC had more surface functional groups than unmodified biochar (BC), and specific surface areas of ZBC (456.406 m²·g^-1) and KBC (750.588 m²·g^-1) were significantly higher than of BC (67.181 m²·g^-1). The pore structures of KBC and ZBC were hierarchical porous structures with different pore sizes and typical microporous structure, respectively. The adsorption performance of either NIT or IMI on KBC was better than that on ZBC. Only 0.4 g·L^-1 of KBC can absorb 89.62% of NIT in just 5 min. The equilibrium adsorption amounts of NIT on ZBC and KBC were 17.995 mg·g^-1 and 82.910 mg·g^-1. Elovich and Langmuir models were used to evaluate the whole adsorption process, which was attributed to the chemisorption mechanism. In addition, removal rates of NIT were negatively correlated to NIT's initial concentration and positively correlated to the dose of biochar. pH had almost no effect on adsorption, but the presence of salt ions can inhibit the removal of NIT. Long-term stabilities of biochars were also acceptable. These findings will promote the development in the preparation of biochar fields and provide a positive reference value for NEO removal.

Toxicity of nitenpyram to silkworm (Bombyx mori L.) and its potential mechanisms

Silkworm (Bombyx mori L.), as an economic insect, occupies a certain position in the development of China's economy. The neonicotinoid insecticide nitenpyram is commonly used in farmland to control planthoppers and aphids. In China, mulberry orchards are often planted adjacent to fields or commercial crops, and mist drifts occur during application, which may affect the production safety of Bombyx mori. In this study, a risk assessment of nitenpyram was carried out, and the results showed that there were risks in spraying nitenpyram around the periphery and subperipheries of mulberry fields. However, few studies have reported the mechanism underlying nitenpyram's toxic effect on silkworms. Here, we validated 25 differentially expressed (DE) miRNAs in the nitenpyram treatment group of silkworms, and the significantly enriched mTOR signaling pathway, oxidative phosphorylation and FoxO signaling pathway were verified. Among them, bmo-miR-2766-5P was up-regulated by 2.122-fold, and the expression of its regulated target gene 101,741,287 was up-regulated. After the injection of bmo-miR-2766-5P inhibitor, the Log₂FC value of 101,741,287 was changed from 1.26 to -2.19. Bmo-miR-3326, bmo-miR-3378-5P and bmo-miR-2761-3P were down-regulated by 2.386-fold, 1.158-fold and 2.359-fold, respectively. After injecting miRNA mimics into silkworms, the Log₂FC values of the target genes 100,302,609, 101,740,730 and 101,746,319 were changed from 1.24 to -11.94, -1.12 changed to 2.84 and 1.93 changed to -0.37, respectively. In addition, nitenpyram induced oxidative damage in silkworms, and the degree of DNA damage increased with the increase of concentration and time. Meanwhile Imd was significantly up-regulated in IMD-related pathways (38.7-fold, p < 0.01). The results indicated that nitenpyram could affect the growth and development process of silkworms, and these DE-miRNAs may have an important impact on the stress response of silkworms to nitenpyram.

Covalent-anion-driven self-assembled cadmium/ molybdenum sulfide hybrids for efficient nitenpyram degradation

Photocatalytic technology is an attractive and promising approach for nitenpyram degradation; however, how to ensure the carrier separation efficiency and catalytic sites exposure is still great challenges. In this study, we construct CdS@MoS₂ (CM) nanohybrids with a 3D hierarchical configuration to enhance the separation and transfer efficiency of the photo-induced electron by a covalent-anion-driven self-assembly method. The vertical orientation of MoS₂ ultrathin nanosheets not only provides a large specific surface area for the oxidation and reduction reactions but also enables the active edge sites of MoS₂ to be maximally exposed. As a result, this structure drastically facilitates the exposure of the catalytic active region and the performance of the carrier transfer and injection into photocatalytic degradation for nitenpyram (NTP). The optimal CdS-MoS₂ has an impressive and stable NTP removal efficiency with a high reaction rate constant up to 0.078 min^-1, which is 3.25 times higher than that of pure cadmium sulfide. The photocatalytic degradation mechanism and degradation pathway of NTP were presented by synthesizing the results of experimental analysis and density flooding theory (DFT) calculations. In further, for the first time, the cytotoxicity and genotoxicity of NTP on moving bed biofilm reactors (MBBRs) was disclosed and a continuous photocatalytic wastewater pretreatment device based on the CM is proposed for the stable biological nitrogen removal activity of MBBRs, which can degrade more than 80% NTP per hour.

Genotoxicity, oxidative stress and transcriptomic effects of Nitenpyram on human bone marrow mesenchymal stem cells

Despite of the global contamination and ubiquitous exposure to nitenpyram (NIT), little knowledge is available on the adverse effects to human health, with some evidence referring to its genotoxic potency to non-target organisms and esophageal squamous papilloma in rats. Human bone marrow mesenchymal stem cells (hBMSCs) was employed as an in vitro model more relevant to humans to assess the potential genotoxicity of NIT and to understand the underlying mechanisms at cellular and molecular levels. Noncytotoxic concentrations of NIT, 50-2500 μg/mL, dose-dependently elevated MNs and nuclear buds frequencies to 8.7-29‰ and 15-35‰, respectively. Additional metabolism by rat liver S9 fraction decreased chromosome impairment by 27-52% on MN frequencies and 63-76% on NB frequencies. A commercial NIT product, containing 20% of NIT and 60% of pymetrozine, caused higher cytotoxicity and chromosome impairment in comparison with NIT alone. Expressions of genes responses to DNA damage, ATM, ATR, p53, p21, Bax, H2AX, and GADD45A were disturbed by NIT treatment. Reactive oxygen species (ROS) amount and superoxide dismutase (SOD) activity were enhanced by NIT. Comet assay showed that lower concentrations of NIT, 12.5-100 μg/mL, induced the DNA damage. Transcriptomic analysis identified 468 differentially expressed genes (p < 0.05, |log2(Foldchange)| ≥ 1), from which 22 pathways were enriched. Multiple affected pathways were related to cancer including viral carcinogenesis and bladder cancer. NIT may produce genotoxicity via inducing oxidative stress and deregulating PI3K/Akt, AMPK and mTOR signaling pathways, associated with carcinogenetic potency. While environmental levels of NIT alone may pose little risk to human health, attention should be paid to the health risk arose from the synergistic or additive effects that may exist among NEOs and other types of pesticides.

Odorant binding protein 3 is associated with nitenpyram and sulfoxaflor resistance in Nilaparvata lugens

Odorant binding protein (OBP) can interact with small-molecule compounds insecticides and thereby modulate variation in insecticide susceptibility in insects. However, the regulatory mechanism of OBP-mediated insecticide resistance in Nilaparvata lugens, a destructive rice pest in Asia, remains unclear. Here, we explored the role of NlOBP3 in the resistance of N. lugens to nitenpyram and sulfoxaflor. The results showed that NlOBP3 was overexpressed in association with nitenpyram and sulfoxaflor resistance, and NlOBP3 silencing significantly increased the mortality of N. lugens to nitenpyram and sulfoxaflor, suggesting that NlOBP3 may be associated with nitenpyram and sulfoxaflor resistance in N. lugens. OBP localization revealed that NlOBP3 was highly expressed in all nymph stages and was enriched in the antennae, legs, body wall, and fat body. RT-qPCR analyses showed that the mRNA levels of NlOBP3 were significantly affected by nitenpyram and sulfoxaflor. Additionally, molecular docking predicted that there were multiple binding sites that may played key roles in the binding of NlOBP3 with nitenpyram and sulfoxaflor. The current study identifies a previously undescribed mechanism of insecticide resistance in N. lugens, showing that NlOBP3 is likely to be involved in the evolution of nitenpyram and sulfoxaflor resistance in N. lugens.

Ultrafast photodegradation of nitenpyram by Ag/Ag3PO4/Zn-Al LDH composites activated by persulfate system: Removal efficiency, degradation pathway and reaction mechanism

In this study, an investigation is conducted into the degradation of nitenpyram (NTP) using highly efficient APMMO/PDS/Vis system. As photocatalysts, silver phosphate (AP) and calcined Zn-Al layered double hydroxides (MMO) exhibit high efficiency in achieving charge separation. Besides, the injection of electrons into peroxydisulfate (PDS) from the APMMO can contribute to obtaining the species in the active state with higher efficiency. Based on the APMMO/PDS/Vis system, 50 mg/L of nitenpyram (NTP, 50 mL) can be completely removed in 60 min using 0.8 g/L photocatalyst and 0.2 g/L PDS under the optimum condition and visible light (780 nm > λ > 420 nm). Meanwhile, as demonstrated under visible light within 30 min, an ultrahigh degradation efficiency can be achieved by NTP based on APMMO1/PDS/Vis system. Besides, the electron paramagnetic resonance (EPR) technique and radical quenching experiments suggested ¹O₂, h⁺, SO₄^-•, •O₂^-, and •OH are all contributory to the removal of pollutants. Given the outcomes achieved by LC/MS system and mass spectrometry, the primary degradation intermediates of NTP end up being converted into photodegradation products (such as 2-Chloropyridine, 6-Chloropurine Riboside and dl-Leucine). Additionally, there are three potential photodegradation pathways to NTP degradation have been deployed. Moreover, the NTP light degradation occurring in APMMO1/PDS/Vis system is competent under the three types of real water sample. Accordingly, the high-efficiency APMMO1/PDS/Vis system is fit for use in water pollution control for agricultural productions.

Short exposure to nitenpyram pesticide induces effects on reproduction, development and metabolic gene expression profiles in Drosophila melanogaster (Diptera: Drosophilidae)

Although the toxicity of neonicotinoid insecticides has been demonstrated in several studies, the information on metabolism, behavior, and health risk remains limited and has raised concerns about its potential toxicity. Thus, in this study we assessed the effects of nitenpyram using different sublethal concentrations (one-third and one-tenth of the acute LC₅₀ values) on various developmental and metabolic parameters from gene expression regulation in Drosophila melanogaster (model system used worldwide in ecotoxicological studies). As a result, nitenpyram sublethal concentrations prolonged the developmental time for both pupation and eclosion. Additionally, nitenpyram sublethal concentrations significantly decreased the lifespan, pupation rate, eclosion rate, and production of eggs of D. melanogaster. Moreover, the mRNA expression of genes relevant for development and metabolism was significantly elevated after exposure. Mixed function oxidase enzymes (Cyp12d1), (Cyp9f2), and (Cyp4ae1), hemocyte proliferation (RyR), and immune response (IM4) genes were upregulated, whereas lifespan (Atg7), male mating behavior (Ple), female fertility (Ddc), and lipid metabolism (Sxe2) genes were downregulated. These findings support a solid basis for further research to determine the hazardous effects of nitenpyram on health and the environment.

Actinomycetes Rhodococcus ruber CGMCC 17550 degrades neonicotinoid insecticide nitenpyram via a novel hydroxylation pathway and remediates nitenpyram in surface water

Neonicotinoid insecticides are neurotoxicants that cause serious environmental pollution and ecosystem risks. In the present study, a nitenpyram-degrading bacterium, Rhodococcus ruber CGMCC 17550, was isolated from a nitenpyram production sewage treatment tank. Liquid chromatography-mass spectrometry analysis revealed R. ruber degraded nitenpyram via a novel hydroxylation pathway to form three different metabolites, one of which was confirmed to hydroxylate nitenpyram at the C3 site of the 6-chlorpyridine cycle by nuclear magnetic resonance analysis. The nitenpyram degradation rate increased as the biomass of resting R. ruber CGMCC 17550 cells increased, reaching 98.37% at an OD₆₀₀ of 9 in transformation broth containing 100 mg L^-1 nitenpyram after 72 h of incubation. Nitenpyram degradation by R. ruber CGMCC 17550 was insensitive to dissolved oxygen levels. Use of glucose, fructose and pyruvate as co-substrates slightly increased nitenpyram degradation. The cytochrome P450 inhibitor 1-aminobenzotriazole strongly inhibited nitenpyram degradation, indicating that P450 enzymes may mediate nitenpyram hydroxylation. Inoculation of R. ruber CGMCC 17550 enhanced nitenpyram degradation in surface water. Additionally, R. ruber cells immobilized by calcium-alginate remediated 87.11% of 100 mg L^-1 NIT in 8 d. Genome sequencing analysis confirmed that R. ruber CGMCC 17550 has metabolic diversity and abundant KEGG genes involved in xenobiotics biodegradation and metabolism. These findings demonstrate that R. ruber CGMCC 17550 is capable of unique biodegradation of nitenpyram via the hydroxylation pathway and is a promising bacterium for bioremediation of contaminants.

Role of nicotinic acetylcholine receptor subunits in the mode of action of neonicotinoid, sulfoximine and spinosyn insecticides in Drosophila melanogaster

Insecticides remain valuable tools for the control of insect pests that significantly impact human health and agriculture. A deeper understanding of insecticide targets is important in maintaining this control over pests. Our study systematically investigates the nicotinic acetylcholine receptor (nAChR) gene family, in order to identify the receptor subunits critical to the insect response to insecticides from three distinct chemical classes (neonicotinoids, spinosyns and sulfoximines). Applying the CRISPR/Cas9 gene editing technology in D. melanogaster, we were able to generate and maintain homozygous mutants for eight nAChR subunit genes. A ninth gene (Dβ1) was investigated using somatic CRISPR in neural cells to overcome the low viability of the homozygous germline knockout mutant. These findings highlight the specificity of the spinosyn class insecticide, spinosad, to receptors containing the Dα6 subunit. By way of contrast, neonicotinoids are likely to target multiple receptor subtypes, beyond those receptor subunit combinations previously identified. Significant differences in the impacts of specific nAChR subunit deletions on the resistance level of flies to neonicotinoids imidacloprid and nitenpyram indicate that the receptor subtypes they target do not completely overlap. While an R81T mutation in β1 subunits has revealed residues co-ordinating binding of sulfoximines and neonicotinoids differ, the resistance profiles of a deletion of Dβ1 examined here provide new insights into the mode of action of sulfoxaflor (sulfoximine) and identify Dβ1 as a key component of nAChRs targeted by both these insecticide classes. A comparison of resistance phenotypes found in this study to resistance reported in insect pests reveals a strong conservation of subunit targets across many different insect species and that mutations have been identified in most of the receptor subunits that our findings would predict to have the potential to confer resistance.

Exposure to nitenpyram during pregnancy causes colonic mucosal damage and non-alcoholic steatohepatitis in mouse offspring: The role of gut microbiota

Environmental pollutants contribute to metabolic diseases. Recent studies have shown that exposure to environmental chemicals during pregnancy can cause obesity and other metabolic diseases in mouse offspring, and these effects have been linked to the changes in the gut microbiota. However, the mechanism of such effects has yet to be fully elucidated. In the present study, we aimed at assessing the metabolic effects of exposure to an environmental pollutant, like nitenpyram, during pregnancy on mouse offspring, and we further explored its potential mechanisms. Our results have demonstrated that exposure to nitenpyram (4 mg/kg/day body weight) in mice during pregnancy (from gestational day 6 to gestational day 19) can increase the count of Desulfovibrio strains (increased from 0.55% to 5.56%) and the concentration of H₂S (increased from 28.98 to 41.31 nmol/g) in the gut of the offspring. These alterations can destroy colonic mucosa and increase intestinal inflammation and bacterial translocation, thus leading to non-alcoholic steatohepatitis (NASH). Overall, these results highlight the role of the gut microbiota in developing intestinal barrier dysfunction and liver inflammation and provide new insights into the pathophysiology of NASH.

Oxidative stress and genotoxicity of nitenpyram to earthworms (Eisenia foetida)

In this study, the artificial soil poisoning method was used to explore the antioxidative stress mechanism and gene changes of earthworms (Eisenia foetida) after application of nitenpyram. The toxic effects of nitenpyram on earthworms were combined with the method called the second-generation integrated biomarker response index method (IBRv2) to be comprehensively analyzed by studying the reactive oxygen species (ROS) content, superoxide dismutase (SOD) activity, catalase (CAT) activity, glutathione S-transferase (GST) activity, malondialdehyde (MDA) content and DNA damage degree in earthworms. The results showed that the ROS content in the high-concentration (2.5 mg/kg) nitenpyram treatment group changed significantly. The changes of antioxidant enzymes in earthworms were also obvious. In terms of SOD enzyme activity, under the induction of nitenpyram, SOD activity in the 1 mg/kg and 2.5 mg/kg treatment groups was significantly enhanced. The concentration-treated group could all affect the activity of earthworm detoxifying enzyme GST. Earthworm DNA olive tail in the nitenpyram treatment group with different concentrations was mainly concentrated at low and medium levels at 21d, and the proportion was the largest during the whole exposure period, showing a significant dose-effect relationship. This study confirms that nitenpyram not only has a toxic effect on the physiological and biochemical indicators of earthworms, but also cannot be underestimated on its genetic level.

Imbalance of gut microbiota and fecal metabolites in offspring female mice induced by nitenpyram exposure during pregnancy

Ubiquitous exposure to the neonicotinoid insecticide nitenpyram has raised concerns about its potential toxicity. In this study, we explored its health effects on the female offspring of mice that had been exposed during pregnancy. We found that exposure of pregnant mice to nitenpyram resulted in decreased levels of serum triglycerides, total cholesterol, and glucose in female offspring, and additional research uncovered gut microbiota disturbances, accompanied by abnormal fecal metabolic profiles. Based on Pearson correlation analysis, we found that decreased abundance of Lactobacillus may play the most critical role, and changes in gut bacterial purine metabolism, BCAAs metabolism, and the TCA cycle are all closely related to the abundance of Lactobacillus. In summary, these results help explain the observed serum biochemical abnormalities and provide new insights into the intergenerational toxicity of nitenpyram.

All-solid-state Z-scheme WO3 nanorod/ZnIn2S4 composite photocatalysts for the effective degradation of nitenpyram under visible light irradiation

A Z-scheme WO₃/ZnIn₂S₄ photocatalyst was synthesized via a simple solvothermal method. Compared with pure WO₃ and ZnIn₂S₄, photocatalytic experiments showed that these Z-scheme photocatalysts exhibited enhanced activity for the degradation of nitenpyram (NTP). The apparent rate constant (k) of NTP degradation on 50WZ (WO₃/ 50 wt% Znln₂S₄) was 0.042 min^-1 (∼3.8 times higher than WO₃ and ∼2.5 times higher than ZnIn₂S₄). Photoluminescence (PL), photocurrent (PC), and electrochemical impedance spectroscopy (EIS) showed that the separation and transfer efficiency of photogenerated carriers in 50WZ was markedly enhanced, which was favorable for improving its photocatalytic activity. Active species capture experiments and electron spin resonance (ESR) measurements showed that superoxide radicals and holes were the main active species for NTP degradation, and they confirmed the formation of the Z-scheme structure. Furthermore, a possible NTP degradation pathway was deduced based on the results of high-performance liquid chromatography mass spectrometry (HPLC-MS).

Nitenpyram disturbs gut microbiota and influences metabolic homeostasis and immunity in honey bee (Apis mellifera L.)

Recently, environmental risk and toxicity of neonicotinoid insecticides to honey bees have attracted extensive attention. However, toxicological understanding of neonicotinoid insecticides on gut microbiota is limited. In the present study, honey bees (Apis mellifera L.) were exposed to a series of nitenpyram for 14 days. Results indicated that nitenpyram exposure decreased the survival and food consumption of honey bees. Furthermore, 16S rRNA gene sequencing revealed that nitenpyram caused significant alterations in the relative abundance of several key gut microbiotas, which contribute to metabolic homeostasis and immunity. Using high-throughput RNA-Seq transcriptomic analysis, we identified a total of 526 differentially expressed genes (DEGs) that were significantly altered between nitenpyram-treated and control honey bee gut, including several genes related to metabolic, detoxification and immunity. In addition, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed nitenpyram affected several biological processes, of which most were related to metabolism. Collectively, our study demonstrates that the dysbiosis of gut microbiota in honey bee caused by nitenpyram may influence metabolic homeostasis and immunity of bees, and further decrease food consumption and survival of bees.

Biotransformation and detoxification of the neonicotinoid insecticides nitenpyram and dinotefuran by Phanerochaete sordida YK-624

Neonicotinoid insecticides have been widely used throughout the world over the last two decades. In the present study, we investigated the degradation of neonicotinoid insecticides nitenpyram (NIT) and dinotefuran (DIN) by the white-rot fungus Phanerochaete sordida YK-624. While NIT was completely degraded by P. sordida YK-624 under ligninolytic conditions, only a 20% decrease was observed under nonligninolytic conditions. On the other hand, P. sordida YK-624 degraded 31% of DIN under ligninolytic conditions after a 20-day incubation, while it did not degrade DIN under nonligninolytic conditions. We found that cytochromes P450 played a key role in the biotransformation of NIT and DIN by P. sordida YK-624. A novel NIT metabolite (E)-N-((6-chloropyridin-3-yl)methyl)-N-ethyl-N'-hydroxy acetimidamide (CPMHA) and a novel DIN metabolite N-((4aS,7aS,E)-1-methylhexahydrofuro[2,3-d]pyrimidin-2(1H)-ylidene)nitramide (PHPF) were identified in this study. In addition, to evaluate neurotoxicity, the effects of NIT, DIN and their metabolites on the viability of human neuroblastoma cells SH-SY5Y were determined. PHPF showed higher neurological toxicity than DIN, whereas the metabolite of NIT, CPMHA, showed no toxic effect. Our results indicated that the neurological toxicity of NIT could be effectively removed by P. sordida YK-624.

Characterization of nitenpyram resistance in Nilaparvata lugens (Stål)

Nitenpyram is very effective in controlling Nilaparvata lugens (brown planthopper, BPH), and its resistance has been reported in field populations; however, the resistance mechanism remains unclear. In the present study, cross-resistance and resistance mechanisms in nitenpyram-resistant BPH were investigated. A resistant strain (NR) with a high resistance level (164.18-fold) to nitenpyram was evolved through successive selection for 42 generations from a laboratory susceptible strain (NS). The bioassay results showed that the NR exhibited cross-resistance to imidacloprid (37.46-fold), thiamethoxam (71.66-fold), clothianidin (149.17-fold), dinotefuran (98.13-fold), sulfoxaflor (47.24-fold), cycloxaprid (9.33-fold), etofenprox (10.51-fold) and isoprocarb (9.97-fold) but not to triflumezopyrim, chlorpyrifos and buprofezin. The NR showed a 3.21-fold increase in cytochrome P450 monooxygenase (P450) activity compared to that in the NS, while resistance was also synergized (4.03-fold) with the inhibitor piperonyl butoxide (PBO), suggesting a role of P450. Furthermore, the mRNA expression levels of cytochrome P450 (CYP) genes by quantitative real-time PCR results indicated that twelve P450 genes were significantly overexpressed in the NR strain, especially CYP6ER1 (203.22-fold). RNA interference (RNAi) suppression of CYP6ER1 through injection of dsCYP6ER1 led to significant susceptibility in the NR strain. The current study expands our understanding of the nitenpyram resistance mechanism in N. lugens, provides an important reference for integrated pest management (IPM), and enriches the theoretical system of insect toxicology.

The minimally effective dosages of nitenpyram and thiamethoxam seed treatments against aphids (Aphis gossypii Glover) and their potential exposure risks to honeybees (Apis mellifera)

Neonicotinoid seed coatings have been used as a major method to control seedling pests, especially the cotton aphid (Aphis gossypii Glover), around the world. However, their negative influence on natural enemies and pollinators has been criticized for decades. The present study was designed to compare the efficacy of nitenpyram and thiamethoxam for A. gossypii control, impacts on natural enemies and their potential risks to honeybees. Investigations in two locations in China revealed that the seed treatment with nitenpyram at a dosage of 3 g a.i. kg^-1 seed could effectively control A. gossypii throughout the seedling stage. In addition, Nitenpyram at the dosage of 2 g a.i. kg^-1 seed did not significantly change present number of the 7-spot ladybeetles in fields, compared with thiamethoxam treatments and blank control. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS) was utilized to identify and quantify the residue dynamics and transformation of parental and metabolite products in pollen and leaves. On the basis of residue data, the first-tier risk assessment disclosed that nitenpyram applied at doses of 2, 3 and 4 g a.i. kg^-1 seed might result in relative lower potential exposure risks to honeybees when compared with thiamethoxam. These results enable us to better understand the performance of nitenpyram seed treatments against A. gossypii during the seedling stage, indicating that nitenpyram may be safer than thiamethoxam for natural enemies and honeybees.

Photodegradation of nitenpyram under UV and solar radiation: Kinetics, transformation products identification and toxicity prediction

The photodegradation of the neonicotinoid insecticide nitenpyram (NPY) under UV and solar irradiation has been investigated in water solutions in order to assess its persistence in the environment and its transformation into other potentially more toxic species. Time-courses were followed by ultra-high performance liquid chromatography-tandem mass spectrometry. Transformation products (TPs) were identified by their accurate product ion spectra, obtained with a quadrupole time-of-flight mass spectrometer after their liquid chromatographic separation. NPY was rapidly photodegraded under all the investigated conditions, following a first-order model and with half-lives varying from seconds to <10 min. Quantum yields were between 0.0385 and 0.0534 mol einstein^-1. The identified TPs, some of them reported for the first time in this study, were formed through different reactions involving the nitro-ethylene moiety of the parent insecticide. Conversely to the lability of NPY, its TPs were more photo-stable in both ultrapure and river water. Moreover, in-silico toxicity assessment showed that most of them display a higher acute toxicity than NPY.

Superhydrophobic SERS substrates based on silver dendrite-decorated filter paper for trace detection of nitenpyram

In the present work, highly sensitive Raman detection of nitenpyram using superhydrophobic filter paper as substrates is introduced. The process is simple, and efficient. By sequentially coating silver dendrites and Octyltrimethoxysilane (OTMOS) on filter paper, we produced highly active surface-enhanced Raman scattering (SERS) substrates which show advancing and receding water contact angles of θ_A/θ_R = 159°/156°. Nitenpyram, a type of pesticides popularly used in agriculture, can be easily detected with the detection limit as low as 1 nM using the superhydrophobic filter paper as SERS substrates, which validates their use in Raman applications.

(Coleoptera: Coccinellidae)

The increasing demand for lessening the chemical input in agricultural ecosystems requires an efficient combination of pesticides and biological controls. Thus, fully understanding the compatibility of pesticides and beneficial arthropod predators is helpful and essential. In this study, we evaluated the influence of nitenpyram on both larvae and adults of Coccinella septempunctata using exposure doses of 10, 25, 50, 100, and 150% of the maximum recommended field rate (MRFR) (3, 7.5, 15, 30, and 45 g a.i. ha^-1, respectively) and a blank control based on a preliminary acute 72-h toxicity experiment. In the long-term test, the LR₅₀ (application rate causing the mortality of 50% of the individuals) of nitenpyram for C. septempunctata decreased from 73.43 to 63.0 g a.i. ha^-1, while the HQ (hazard quotient) values remained below the threshold value of 2. Nitenpyram did not significantly influence the survival rate, fecundity, pupation, or adult emergence at 150% of the label rate (lowest LR₅₀ = 63.0 g a.i. ha^-1), and its demonstrated NOER (No Observed Effect application Rates) values are all above 45 g a.i. ha^-1. Likewise, the total developmental time and egg hatchability were not significantly affected at 100% of the label rate (NOER = 30 g a.i. ha^-1). The assessment of the total effect (E) suggested that nitenpyram could be classified as harmless to C. septempunctata below/at a dose of 30 g a.i. ha^-1. The lowest LR₅₀ and NOER values were both above the maximum recommended field application rate for nitenpyram (30 g a.i. ha^-1) for controlling aphids in China. All results indicated that the on-label use of nitenpyram is compatible with the natural enemy C. septempunctata in agricultural ecosystems.

Development of a simple measurement method for GluR2 protein expression as an index of neuronal vulnerability

In vitro estimating strategies for potential neurotoxicity are required to screen multiple substances. In a previous study, we showed that exposure to low-concentrations of some chemicals, such as organotin, decreased the expression of GluR2 protein, which is a subunit of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type glutamate receptors, and led to neuronal vulnerability. This result suggested that GluR2 decreases as an index of neuronal cell sensitivity and vulnerability to various toxic insults. Accordingly, we developed a versatile method that is a large scale determination of GluR2 protein expression in the presence of environmental chemicals by means of AlphaLISA technology. Various analytical conditions were optimized, and then GluR2 protein amount was measured by the method using AlphaLISA. The GluR2 amounts were strongly correlated with that of measured by western blotting, which is currently used to determine GluR2 expression. An ideal standard curve could be written with the authentic GluR2 protein from 0 ng to 100 ng. Subsequently, twenty environmental chemicals were screened and nitenpyram was identified as a chemical which lead to decrease in GluR2 protein expression. This assay may provide a tool for detecting neurotoxic chemicals according to decreases in GluR2 protein expression.