Effects of thiacloprid exposure on microbiota–gut–liver axis: Multiomics mechanistic analysis in Japanese quails

Highlights

• Multiomics was used to analyze the toxic mechanism of THI in quails.

• Chronic THI exposure induces liver injury via disrupting intestinal flora in quails.

• THI promotes endotoxin translocation by increasing intestinal mucosal permeability.

• Microbiota–gut–liver axis provides a novel mechanism of THI toxicity.

Abstract

Neonicotinoid insecticides (NNIs) are the most widely used class of pesticides globally. However, NNIs may cause adverse health effects, including chronic liver disease, and perturbation of the gut microbiota. Thiacloprid (THI) is one of the NNIs widely used in agriculture. Therefore, it is essential to elucidate effects of THI on the microbiota–gut–liver axis to assess the risk of chronic liver disease following exposure to NNIs. This study aimed at investigating whether THI exposure promoted liver injury by altering the gut microbiota and related metabolites. In this study, healthy male quails were exposed to 2 or 4 mg/kg THI or 0.75 % (w/v) saline once daily for 6 weeks, respectively. Metabolomics, 16S rRNA sequencing, and transcriptomic methods were performed to analyze the toxic mechanisms of THI in Japanese quails. We found that THI evoked damage and disruption to intestinal barrier function, leading to increased harmful substances such as lipopolysaccharide (LPS) and phenylacetic acid entering the liver. Besides, our results showed significantly altered hepatic bile acid and cholesterol metabolism in THI-exposed quails, with abnormal liver lipid metabolism, showing severe liver injury, fibrosis, and steatosis compared with the control quails. In conclusion, THI exposure aggravates liver injury via microbiota–gut–liver axis.

Introduction

In the past few decades, liver disease has rapidly increased and become a leading cause of death and illness worldwide. The incidence of death for human caused by liver diseases is 4.6 % in the Asia–Pacific Region, 2.1 % in Europe, and 2.7 % in the USA (Sarin et al., 2020). Fatty liver syndrome results in the death of laying hens, with serious economic losses to the poultry industry (Shini et al., 2019). Dysregulation of lipid and bile acid (BA) metabolism occurs at the different stages of liver disease (Trauner and Fuchs, 2022). Lots of evidence supports the association of environmental toxicants such as pesticides and heavy metals with chronic liver disease (Stratakis et al., 2021, Wang et al., 2021, Sen et al., 2022).

Increasing evidence suggests a close connection between the gut microbiome and the development of liver diseases (Trebicka et al., 2021). Lipopolysaccharide (LPS) from the cell walls of Gram-negative bacteria has harmful effects on several organs, including liver. When there is an increase in the number of LPS-carrying bacteria in the gut flora, or when the integrity of the gut barrier is broken, it leads to more LPS entering the body. Therefore, all factors that disrupt the microbiome balance or increase intestinal permeability have the potential to induce liver disease through the microbiota–gut–liver axis. Neonicotinoid insecticides (NNIs) are the most widely consumed insecticides globally, and long-term exposure can negatively impact on gut flora (Liu et al., 2020, Yan et al., 2022). However, whether the alteration of gut microbiota reflects a link between NNIs exposure and chronic liver disease remains to be confirmed.

NNIs are the most widely used class of pesticides globally, and their pollution of the environment and food has raised increasing concern (He et al., 2021, Malhotra et al., 2021, Zheng et al., 2022). NNIs inevitably remain in food and are ingested by humans and animals. Serum concentrations of NNIs are significantly associated with lipid metabolism disorders in humans, and increase the risk of chronic liver injury in animal models (Alarcan et al., 2020, Chen et al., 2021). Nevertheless, the adverse effects of NNIs exposure on liver health in humans and other vertebrates have not been thoroughly studied.

Thiacloprid (THI) is one of the NNIs that the European Union has begun to ban, but it is still widely used in many countries and has a high frequency of detection (, 2019, Bonmatin et al., 2019). For instance, the maximum residue levels of THI in the soil profiles from citrus orchards located in the Pingjiang River Basin in the upper reaches of the Ganjiang River reached 0.81 ng/g dry weight in China (Zheng et al., 2022). Studies have shown that the relevant THI no‐observed adverse effect level is 7 mg/kg body weight (bw) per day from the 90–day study in rats (European Food Safety Authority et al., 2019). In an evaluation of the risk to consumers eating boar meat, neonicotinoid insecticides were found in more than 83 % of pork samples, with the highest mean concentration of THI (6.2 ng/g) (Kaczyński et al., 2021). Some studies reported that 99 % of feather samples from wild house sparrows (Passer domesticus) in Swiss lowland agricultural areas contained THI (Humann-Guilleminot et al., 2019). The unregulated use of THI poses a risk to animal and even human health as migration and transformation allow them to enter the food chain (Lu et al., 2020, Zhao et al., 2022). Hence, it is essential to elucidate the effects of THI on the microbiota–gut–liver axis to assess the risk of chronic liver disease following NNIs exposure.

In recent years, multiomics approaches have been powerful techniques to study the toxic mechanisms of pesticide residues in the environment (Lee et al., 2021, Mesnage et al., 2021, Li et al., 2022a). Japanese quails (Coturnix japonica) are widely used as a higher vertebrate model for toxicological tests of pesticides. This study aimed to comprehensively and systematically investigate the mechanisms involved in liver injury and intestinal microbiota changes induced by THI in Japanese quails. To the best of our knowledge, this is the first study to use a combination of potent and promising 16S rRNA sequencing, metabolomics, and transcriptomic methods to analyze the toxic mechanisms of THI in Japanese quails.