The Secreted Metabolite Isopentenyladenine from <i>Faecalibacterium prausnitzii</i> Is Anti-inflammatory with Barrier-Protective Properties

Colonic microbiome dysbiosis is correlated with inflammatory bowel disease (IBD), and depletion of the commensal bacterium <i>Faecalibacterium prausnitzii</i> (<i>F. prausnitzii</i>) is routinely observed in the metagenomic analyses of IBD patient microbiome samples. <i>F. prausnitzii</i> is likely beneficial to hosts, as oral administration of <i>F. prausnitzii</i> strain A2-165 has anti-inflammatory properties in murine models of colitis. Previous studies attribute the anti-inflammatory effects of <i>F. prausnitzii</i> A2-165 to production of the short-chain fatty acid butyrate, as well as a secreted protein known as microbial anti-inflammatory molecule (MAM). Here, we verified that oral dosing of strain A2-165 protects against DSS-induced murine colitis and further showed that the aqueous-soluble secreted fraction of overnight cultures from a collection of <i>F. prausnitzii</i> strains inhibits inflammatory signatures, including the activation of the host's NF-κB pathway, production of IL-8, and differentiation of naïve T cells into the T_H17 lineage. Our findings against a panel of <i>in vitro</i> assays suggested that the anti-inflammatory responses were attributable to secreted small-molecule or peptide metabolites, as both heat-inactivated and proteinase K-treated <i>F. prausnitzii</i> culture supernatants retained activity. Untargeted and targeted mass spectrometry metabolomics analyses on the soluble anti-inflammatory secretome yielded several unique <i>F. prausnitzii</i> metabolites, including isopentenyladenine. We demonstrated that isopentenyladenine independently modulates host cellular signaling and immune responses and suggest that this newly identified metabolite with human immunomodulatory properties may be useful toward the discovery of IBD-focused therapeutics.