Immunotoxicity evaluation by subchronic oral administration of clothianidin in Sprague-Dawley rats

Abstract

Neonicotinoid pesticides (NNs) act as agonists on nicotinic acetylcholine receptors (nAChRs) of insects, and there has been concern about the effects of NNs on the health of mammals. Since nAChRs are expressed in immune cells, it is possible that NNs disturb the immune system. However, few reports have examined the immunotoxicity of clothianidin (CLO), a widely-used NN. Here, we report the effects of CLO on immune organs and type IV allergic reactions in ear auricles. We orally administered CLO at 0, 30 and 300 mg/kg/day (CLO-0, 30 and 300) to Sprague-Dawley rats for 28 days. The effects were evaluated by organ and body weights, histopathology, and immunohistochemistry (TCRαβ, CD4, CD8, CD11b, CD68, CD103). In addition, some cecal contents were subjected to preliminary gut microbiota analysis, because microbiota contribute to host homeostasis, including the immunity. Our results showed loose stool, suppression of body weight gain, significant changes in organ weights (thymus: decreased; liver: increased) and changes of the gut microbiota in the CLO-300 group. There were no obvious histopathological changes in immune organs. Granulomas of the ear auricles were found in one rat of each of the CLO-30 and 300 groups, but CLO had no apparent effect on the thickness or immunohistochemistry in the ear auricles. We present new evidence that CLO affects the thymus and intestine, and might enhance the local inflammatory response. These findings should contribute to the appropriate evaluation of the safety of NNs in the future.

Toxicology and Microbiota: How Do Pesticides Influence Gut Microbiota? A Review

“…Onaru et al described the effects of clothianidin on rats. The animals showed a loss of body weight and significant alterations in the gut microbiota, principally Firmicutes was strongly decreased, inversely Bacteroidetes was augmented and the dominance of Proteobacteria and Actinobacteria was inverted [ 90 ].…”

Effects of <i>in utero</i> and lactational exposure to the no-observed-adverse-effect level (NOAEL) dose of the neonicotinoid clothianidin on the reproductive organs of female mice

“…The immunoreactivities of the primary antibodies were examined with 3,3-diaminobenzidine tetrahydrochloride solution (EnVision ® + kit/HRP [DAB], Dako, Glostrup, Denmark). Immunostaining of all sections was performed as previously described [ 28 ].…”

Next-generation effects of fetal and lactational exposure to the neonicotinoid pesticide clothianidin on the immune system and gut microbiota

“…immunomodulatory disorders [39], and neuropsychiatric disorders [25]. Our previous study revealed that subchronic ingestion of clothianidin (CLO), a type of NN, caused a decrease in thymus weight and induced dysbiosis in rats [36], showing for the first time an association between NNs and dysbiosis in mammals. In addition, CLO and its metabolites are rapidly transferred from pregnant dam to fetus [34] and are highly concentrated in breast milk [43].…”

“…Since the gut microbiota influences host immune responses and metabolic mechanisms through complex interactions [ 47 ], it has been shown that dysbiosis, an imbalance of the gut microbiota, causes allergies [ 41 ], immunomodulatory disorders [ 39 ], and neuropsychiatric disorders [ 25 ]. Our previous study revealed that subchronic ingestion of clothianidin (CLO), a type of NN, caused a decrease in thymus weight and induced dysbiosis in rats [ 36 ], showing for the first time an association between NNs and dysbiosis in mammals. In addition, CLO and its metabolites are rapidly transferred from pregnant dam to fetus [ 34 ] and are highly concentrated in breast milk [ 43 ].…”

“…Cecal contents are not contaminated by external bacteria until the time of collection, compared to feces that have been discharged from the body. We also used the cecal contents to compare our present results with those of the previous study, which used rat cecal contents for microbiota analysis [ 36 ].…”