# Metagenomics-Metabolomics Reveals the Alleviation of Indole-3-Ethanol on Radiation-Induced Enteritis in Mice

## TL;DR

This study shows that indole-3-ethanol reduces radiation-induced gut inflammation in mice by improving gut health and reducing inflammation.

## Contribution

The novel finding is that IEt alleviates radiation enteritis through Roseburia and anti-inflammatory metabolites like indole-3-carbinol.

## Key findings

- IEt reduced pro-inflammatory factors like IL-17A and improved colonic structure in irradiated mice.
- IEt enriched Roseburia, an anti-inflammatory gut bacteria, and increased beneficial metabolites like indole-3-carbinol.
- Roseburia was positively correlated with indole-3-carbinol and negatively with IL-17A, suggesting a protective mechanism.

## Abstract

Indole-3-ethanol (IEt), a small molecule metabolite from intestinal microbial tryptophan metabolism, has been established to have anti-inflammatory properties. However, its effect on radiation-induced enteritis has not been reported. Here, we aim to explore the effects and potential mechanisms of IEt on radiation enteritis. C57BL/6J mice were orally administered an IEt solution before radiation exposure. Inflammatory factors, including IL-17A, IFN-γ, IL-6 and IL-1β, were detected using enzyme-linked immunosorbent assay. Colonic histopathology was assessed through H&E staining. Subsequently, gut microbiota and its metabolites were analyzed using metagenomics and metabolomics. The results suggested that IEt alleviated radiation-induced enteritis, as evidenced by improved colonic structural integrity, decreased levels of pro-inflammatory factors like IL-17A, and the restoration of intestinal microecological and metabolic balance. IEt enriched the abundance of Lachnospiraceae family members, particularly the genus Roseburia – a known anti-inflammatory commensal. In addition, IEt upregulated the levels of metabolites with anti-inflammatory effects such as indole-3-carbinol, pteridine, and pyropheophorbide-a. Furthermore, Roseburia was significantly positively correlated with indole-3-carbinol and negatively correlated with the pro-inflammatory factor IL-17A. Therefore, IEt may alleviate radiation enteritis through Roseburia-indole-3-carbinol and Roseburia-IL-17A axes. This study revealed the potential mechanisms by which IEt alleviated radiation enteritis, providing a potential protective candidate for radiation enteritis.