# Effects of chronic allergic lung inflammation on gut microbiota and depression-like behavior in mice

## TL;DR

Chronic allergic lung inflammation in mice leads to changes in gut bacteria and depression-like behavior, suggesting a gut-brain connection.

## Contribution

This study shows that chronic allergic lung inflammation in mice alters gut microbiota and is linked to depression-like behavior.

## Key findings

- Gut microbiota β-diversity significantly differed between HDM and PBS groups.
- Certain bacteria like Clostridia and Faecalibaculum were more abundant in the HDM group.
- Changes in gut microbiota correlated with depression-like behavior in mice.

## Abstract

Emerging epidemiological studies have reported a link between allergic diseases, including asthma, and depression. Evidently, the gut microbiota is involved in the pathogenesis of asthma and depression. Therefore, we investigated whether allergic lung inflammation in mice causes gut microbial dysbiosis, via the gut-brain axis, which is potentially associated with depression.

Wild-type C57BL/6J female mice were sensitized with intranasal house dust mite (HDM) antigen or phosphate-buffered saline (PBS) for 6 weeks to induce chronic allergic lung inflammation. Sucrose preference tests were performed for assessing depression. Fecal samples were collected, and 16S ribosomal RNA gene sequencing was performed to detect differences in gut microbiota composition between the HDM and PBS groups. The distance calculation, clustering of operational taxonomic units, rarefaction analysis, and estimator calculation (α- and β-diversity) were performed.

There was a significant difference in β-diversity (Bray-Curtis dissimilarity, F-statistics = 6.16, p = 0.001) of the gut microbiota between HDM and PBS groups. However, there was no difference in the α-diversity. We observed multiple differentially abundant bacteria in the HDM and PBS groups. The order class Clostridia (p = 0.0036) and genus Faecalibaculum (p = 0.028) were more abundant in the HDM group, whereas the phylum Firmicutes (p = 0.037) and genera Dubosiella (p = 0.00024) and Turicibacter (p = 0.037) were more abundant in the PBS group. Notably, the relative abundance of some bacteria was correlated with the sucrose preference test results.

Six weeks of intranasal HDM administration to mimic the chronic status of lung inflammation in asthma changed the gut microbiome in mice and was associated with depression-like behavioral changes.