Outer Membrane Protein A from Escherichia coli Nissle 1917 Vesicles Alleviates Colon Inflammation by Modulating Specific Inflammatory Signaling Pathway.

Inflammatory bowel disease (IBD) is a chronic, relapsing intestinal condition. Probiotic-derived outer membrane vesicles (OMVs) have emerged as a promising postbiotic strategy for IBD. Here, we evaluated the protective effects of Escherichia coli Nissle 1917 (EcN)-derived OMVs in a DSS-induced colitis mouse model using a pretreatment regimen. EcN OMVs attenuated colitis by improving the intestinal barrier and suppressing inflammatory responses, and this anti-inflammatory effect is largely attributed to outer membrane protein A (OmpA). OmpA-carrying EcN OMVs were associated with inhibition of excessive inflammation through a mechanism associated with suppression of TLR4/NF-κB signaling activation. Our work identifies potential mechanisms and key active components by which EcN OMVs may prevent intestinal inflammation. These results underscore the promise of EcN OMVs as functional food ingredients or dietary supplements for gut health maintenance.