Transgenerational effects of developmental neurotoxicity induced by exposure to a no-observed-adverse-effect level (NOAEL) of neonicotinoid pesticide clothianidin

Effect of the neonicotinoid pesticide clothianidin at a no-observed-adverse-effect-level (NOAEL) dose on maternal behavior in pregnant mice and their female offspring

Our previous reports showed that exposure to the neonicotinoid pesticide clothianidin (CLO) at a no-observed-adverse-effect-level (NOAEL) dose during fetal development and lactation in mice led to higher rates of maternal neglect and infanticide. Although the demonstrated association between decreased oxytocin secretion and decreased maternal parenting behavior implies a link to declining oxytocin levels, no evidence has yet emerged in CLO to clearly establish such an association. This study investigated the effects of CLO on maternal behavior and oxytocin in C57BL/6N mice exposed during pregnancy and lactation (F0 mothers) as well as in their adult female offspring (F1 mothers). The effects were assessed using nest building assays during pregnancy and pup retrieval assessment after delivery. The results showed a decrease in oxytocin secretion and a marked decrease in pup retrieval behavior among the F0 mothers in the CLO exposure group compared to those in the control group. Their offspring, the F1 mothers, showed significantly lower nest-building scores during pregnancy. In conclusion, this study is the first to examine the potential mechanisms by which CLO exposure in mothers at the NOAEL dose during pregnancy and lactation results in reduced plasma oxytocin levels, subsequently leading to a decline in maternal behaviors such as pup retrieval. Furthermore, these effects may impair maternal behaviors in the next generation, when the offspring mice become mothers.

Evaluating the toxicity effects of thiamethoxam and its main metabolite clothianidin to earthworms (Eisenia fetida) from the perspective of endogenous metabolites

The widespread application of neonicotinoid insecticides (NNIs) has attracted widespread attention to their potential ecotoxicological effects. In this study, we systematically evaluated the toxic effects of thiamethoxam (TMX) and its metabolite clothianidin (CLO) on earthworms (Eisenia fetida). Specifically, the antioxidant system responses and endogenous metabolite metabolism responses in earthworms were analyzed in the temporal dimension after 7, 14, 21 and 28 days of exposure to TMX and CLO. The results found that TMX and CLO could inhibit the growth phenotype of earthworms and cause significant changes in antioxidant system related indicators. More importantly, we found that TMX and CLO could cause significant changes in the metabolic profiles of earthworms through NMR-based metabolomics. From the changes in endogenous metabolites, the toxicity effects of TMX on earthworms gradually increases with prolonged exposure time. Differently, the toxicity effects of CLO on earthworms is significantly higher than that of TMX in the early stages of exposure. Meanwhile, these impacts will not weaken with prolonged exposure time. Furthermore, the results of KEGG enrichment pathway analysis indicated that TMX and CLO could significantly interfere with energy homeostasis, redox homeostasis, osmotic regulation, amino acid metabolism and protein synthesis in earthworms. These findings further deepen our understanding of the ecotoxicological effects of NNIs on soil organism.

No-observed-adverse-effect-level (NOAEL) clothianidin, a neonicotinoid pesticide, impairs hippocampal memory and motor learning associated with alteration of gene expression in cerebellum

Neonicotinoid pesticides (NNs) have been associated with numerous neurobehavioral effects in rodents, raising concerns about their impact on cognitive function. Clothianidin (CLO), a type of NN, was orally administered to male mice (10 weeks old, C57BL/6N) at the no-observed-adverse-effect level (NOAEL) of 50 mg/kg/day as indicated in the pesticide risk assessment report. Behavioral tests (novel location recognition and rotarod tests) evaluated hippocampal memory and cerebellar motor learning. After each test, plasma monoamines (3-methoxytyramine, histamine, serotonin, tryptamine) were measured by LC-ESI/MS/MS (Liquid chromatography-electrospray ionization/tandem mass spectrometry), and cerebellar mRNA expression was quantified by microarray and qRT-PCR analyses. The NOAEL of CLO was found to impair hippocampal memory, leading to decreased spontaneous locomotor activity and motor function. We reported, for the first time, multiple alterations of gene expression in the cerebellum associated with motor dysfunction.

Effects of exposure to the neonicotinoid pesticide clothianidin on α-defensin secretion and gut microbiota in mice

The mechanism by which the neonicotinoid pesticide clothianidin (CLO) disrupts the intestinal microbiota of experimental animals is unknown. We focused on α-defensins, which are regulators of the intestinal microbiota. Subchronic exposure to CLO induced dysbiosis and reduced short-chain fatty acid-producing bacteria in the intestinal microbiota of mice. Levels of cryptdin-1 (Crp1, a major α-defensin in mice) in feces and cecal contents were lower in the CLO-exposed groups than in control. In Crp1 immunostaining, Paneth cells in the jejunum and ileum of the no-observed-adverse-effect-level CLO-exposed group showed a stronger positive signal than control, likely due to the suppression of Crp1 release. Our results showed that CLO exposure suppresses α-defensin secretion from Paneth cells as part of the mechanism underlying CLO-induced dysbiosis.