Microbial Anti-Inflammatory Molecule (MAM) secreted by Faecalibacterium prausnitzii ameliorates colitis through autophagy and gut microbiota modulation

Faecalibacterium prausnitzii is a major commensal bacterium that plays a crucial role in intestinal homeostasis. Its secretes an microbial anti-inflammatory molecule (MAM) that functions as a potential therapeutic agent in inflammatory bowel disease (IBD). However, the molecular mechanisms through which MAM exerts its beneficial effects remain incompletely understood. Here, we investigate whether MAM modulates autophagy and to evaluate its therapeutic potential in a murine model of colitis. A genetically engineered Lactococcus lactis strain expressing MAM was administered to mice with dextran sulfate sodium (DSS)-induced or 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. The therapeutic effects of MAM were evaluated using clinical scoring, histopathological analysis, and inflammatory cytokines measurement. Intestinal barrier function was assessed based on tight junction protein expression. Autophagy-related signaling pathways were analyzed using western blotting and immunohistochemistry. To determine how autophagy affects MAM, DSS-treated mice were treated with the autophagy inhibitor hydroxychloroquine (HCQ) and bafilomycin A1 (BafA1). Gut microbiota composition was profiled 16 S rRNA gene amplicon sequencing. Fecal short-chain fatty acid (SCFA) levels were quantified by gas chromatography–mass spectrometry (GC-MS). MAM treatment significantly alleviated colitis in both DSS- and TNBS-induced models, as evidenced by reduced disease activity, improved colon length, attenuated histopathological damage, and decreased pro-inflammatory cytokine production. MAM enhanced intestinal barrier integrity by upregulating ZO-1 and occludin. Notably, MAM counteracted the inhibitory effect of HCQ/BafA1 on autophagy, enhancing autophagic flux despite autophagy suppression. Furthermore, MAM treatment significantly increased the fecal concentrations of acetate, propionate, and butyrate. 16 S sequencing revealed the enrichment of beneficial taxa, including Lactobacillus and Lachnospiraceae_NK4A136_group, The abundance of these taxa was positively correlated with SCFA levels and improvement of colitis symptoms. We identified MAM as a multifunctional microbial effector with potent anti-inflammatory properties. MAM improves intestinal barrier function and attenuates experimental colitis through dual mechanisms involving the modulation of autophagy and gut microbiota composition. These findings highlight the translational potential of MAM and support further investigation into its use as a novel therapeutic strategy for IBD.