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Pesticides and heavy metals commonly coexist in soil. In this study, the influence of Cd and Cu on the toxicity of rac-dinotefuran and the enantioselective behavior of dinotefuran enantiomers in soil-earthworm microcosms were investigated. The acute toxic tests showed that S-dinotefuran has higher toxic than that of R-dinotefuran. The rac-dinotefuran and Cd has an antagonistic effect on earthworms, and the Cu and rac-dinotefuran has a synergistic effect. Earthworms maybe promoted the enantioselective behavior of dinotefuran in soil. Co-exposure to Cd or Cu inhibited the dissipation of dinotefuran enantiomers (S-dinotefuran and R-enantiomers), and slightly reduced the enantioselectivity in soil. The earthworms were found to be preferentially enriched with S-dinotefuran. However, Cd or Cu attenuated the accumulation of dinotefuran enantiomers in earthworms and decreased the enantioselectivity. The effect of Cd and Cu on the environmental behaviors of dinotefuran enantiomers were correlated positively with the dose of Cd/Cu. These results showed that Cd and Cu alter the environmental behaviors and the toxicity of dinotefuran enantiomers in soil-earthworm microcosms. Thus, the influence of coexistent heavy metals on the ecological risk assessment of chiral pesticides should be considered.

Pesticides and heavy metals commonly coexist in soil. In this study, the influence of Cd and Cu on the toxicity of rac -dinotefuran and the enantioselective behavior of dinotefuran enantiomers in soil-earthworm microcosms were investigated. The acute toxic tests showed that S -dinotefuran has higher toxic than that of R -dinotefuran. The rac -dinotefuran and Cd has an antagonistic effect on earthworms, and the Cu and rac -dinotefuran has a synergistic effect. Earthworms maybe promoted the enantioselective behavior of dinotefuran in soil. Co-exposure to Cd or Cu inhibited the dissipation of dinotefuran enantiomers (S -dinotefuran and R -enantiomers), and slightly reduced the enantioselectivity in soil. The earthworms were found to be preferentially enriched with S -dinotefuran. However, Cd or Cu attenuated the accumulation of dinotefuran enantiomers in earthworms and decreased the enantioselectivity. The effect of Cd and Cu on the environmental behaviors of dinotefuran enantiomers were correlated positively with the dose of Cd/Cu. These results showed that Cd and Cu alter the environmental behaviors and the toxicity of dinotefuran enantiomers in soil-earthworm microcosms. Thus, the influence of coexistent heavy metals on the ecological risk assessment of chiral pesticides should be considered. [Display omitted] • Toxicity of rac -dinotefuran with Cd is antagonistic, while that with Cu is synergistic. • Cu/Cd decelerates dinotefuran degradation in soil. • Earthworms in soil lead to EF increase of dinotefuran enantiomers. • Cd/Cu reduces the accumulation of dinotefuran enantiomers in earthworm. • Cd/Cu decreases the enantioselectivity of dinotefuran enantiomers in earthworm. [ABSTRACT FROM AUTHOR]

With the increasing demand for pollinating services, the wellness of honeybees has received widespread attention. Recent evidence indicated honeybee health might be posed a potential threat by widely used neonicotinoids worldwide. However, little is known about the molecular mechanism of these insecticides in honeybees especially at an enantiomeric level. In this study, we selected two species of bees, Apis mellifera ( A. mellifera ) and Apis cerana ( A. cerana ), to assess the toxicity and molecular mechanism of neonicotinoid dinotefuran and its enantiomers. The results showed that S -dinotefuran was more toxic than rac -dinotefuran and R -dinotefuran to honeybees by oral and contact exposures as much as 114 times. A. cerana was more susceptible to highly toxic enantiomer S -dinotefuran. S -dinotefuran induced the immune system response in A. cerana after 48 h exposure and significant changes were observed in the neuronal signaling of A. mellifera under three forms of dinotefuran exposure. Moreover, molecular docking also revealed that S -dinotefuran formed more hydrogen bonds than R -dinotefuran with nicotinic acetylcholine receptor, indicating the higher toxicity of S -dinotefuran. Data provided here show that R -dinotefuran may be a safer alternative to control pests and protect pollinators than rac -dinotefuran.

Co-occurrence of pesticides and heavy metals has attracted extensive attention. The enantioselective behaviors of dinotefuran to aquatic organisms have not been reported, and the effects of cadmium (Cd) was absent, which were investigated in this study at environmentally relevant concentrations. The enantioselective accumulation and elimination of dinotefuran enantiomers were observed in zebrafish, and it had tissue specificity. The S -dinotefuran concentrations were higher than R -dinotefuran in heads and viscera, but it was opposite in muscles. There existed competition between S -dinotefuran and R -dinotefuran, and the existence of S -dinotefuran might decrease the accumulation and elimination of the R -dinotefuran in zebrafish. When co-exposure to Cd and dinotefuran, the accumulation concentrations of dinotefuran enantiomers increased in zebrafish at the initial stage, which were opposite latterly. The accumulation concentrations of R -dinotefuran in R + Cd treatment in fish were 3.4 times higher than those in R -dinotefuran treatment, and the enantiomer fraction (EF) values changed from 0.484 to 0.195. The oxidative stress of S -dinotefuran on zebrafish was highest, followed by rac- and R -dinotefuran. Co-exposure to Cd led to toxicity increase for R -dinotefuran, the malonaldehyde (MDA) content decreased significantly in R + Cd treatment during 7–28 days, while obvious declination of MDA contents was found on the 28th day in R -dinotefuran treatment. Furthermore, compared to R -dinotefuran treatment, Cd increased the relative expression of cz-sod (3.4 times), cas3 (1.6 times) and p53 (5.7 times) in R + Cd treatment. The co-exposure of Cd might alter the environmental behaviors and toxicity effects of dinotefuran enantiomers in zebrafish, including the enantioselectivity. The effects of Cd on accumulation and toxicity of R -dinotefuran were greater than those on S -dinotefuran. Thus, it is necessary to consider the effects of coexistent metals to chiral pesticides in ecological risk. The enantioselective accumulation and elimination of dinotefuran enantiomers had tissue specificity. Cd increased the accumulation and toxicity of R -dinotefuran in zebrafish. Image 1 • 1、 S -dinotefuran was enriched in head and viscera, but it was opposite in muscles. • 2、The toxic effects of S -dinotefuran were higher than that of R -dinotefuran. • 3、Cd increased the enrichment of R -isomer (1.4–3.4 times), changing enantioselectivity. • 4、Cd increased the oxidative stress of R -dinotefuran on zebrafish. • 5、The effects of Cd on R -dinotefuran were greater than those on S -dinotefuran. [ABSTRACT FROM AUTHOR]

In last decade, there has been a concerted effort to reduce the potential threats of honeybees' population due to exposure to neonicotinoid pesticides. A new perspective was put forward to reduce the potential ecological toxicity of neonicotinoid dinotefuran to honeybee in terms of an enantiomeric level in the study. Toxicity of dinotefuran was enantioselective, and S -dinotefuran was 41.1- to 128.4-fold more toxic than R -dinotefuran to honeybee Apis mellifera (Apis mellifera Linnaeus), whereas R -dinotefuran exhibited comparative insecticidal activities (1.7–2.4 times) to typical sucking pests Aphis gossypii and Apolygus lucorum compared to racemic mixtures. Our data suggested that use of R -dinotefuran could have a good efficacy in controlling target pests while minimizing hazard to honeybees. The mechanism for chiral specific toxicity to honeybee was further characterized by electrophysiological studies and molecular docking. S -dinotefuran appears to be more toxic by binding to α8 subunit of nAChR of Apis mellifera. The α8 also have a more stable, functional binding cavity to S -dinotefuran with a higher binding score of 7.15, primarily due to an extensive hydrogen bond network. Therefore, new chiral products with a high proportion of or an enantiomeric pure R -dinotefuran are recommended to achieve effective pests control reducing hazard to honeybee populations. • Enantioselective lethality of dinotefuran was evaluated to honeybee and two target pests • Toxicological properties of dinotefuran enantiomers were elucidated with each nAChR subunits of Apis mellifera Linnaeus • Binding interactions between dinotefuran enantiomers and AmeIα8/ratβ2 were further investigated • New chiral pesticide product with R -dinotefuran was finally recommended in agroenvironment [ABSTRACT FROM AUTHOR]