Rosmarinic acid alleviates gut injury by modulating Bifidobacterium pseudolongum in the gut microbiota.

Rosmarinic acid (RA), a natural plant-derived compound, plays a key role in modulating beneficial gut bacteria and alleviating intestinal damage. Bifidobacterium pseudolongum (BP), a beneficial gut bacterium, exerts protective effects on the intestine. This study investigates how RA modulates BP to alleviate intestinal injury. Histological examination revealed dextran sulfate sodium (DSS)-induced inflammation, villus shortening, crypt loss, and tight junction disruption. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL) staining revealed that, compared with the dextran sulfate sodium (DSS) group, the fluorescent signal of apoptotic cells was markedly reduced after the administration of RA and BP. Gut microbiota analysis showed that RA enhanced BP abundance. Gene enrichment analysis identified 273 BP-related genes involved in ribosomal function, transcription, aminoacyl-tRNA biosynthesis, and metabolism. Molecular docking revealed a strong binding affinity between RA and BP's core targets, guaA and phet. Functional predictions suggested that RA and BP were linked to pathways involved in ``cell growth and death'' and ``protein folding, sorting, and degradation.'' Further analysis identified 35 core targets and 1,065 potential targets, connecting RA and BP to inflammation, endoplasmic reticulum stress (ERS), tight junctions, smooth muscle contraction, and cell death in intestinal injury. Quantitative Real-time Polymerase Chain Reaction (qRT-PCR) and Western blotting confirmed that RA and BP reduced inflammatory cytokines, ERS markers, tight junction proteins, and apoptosis-related markers. In summary, RA enhances BP abundance, reduces inflammatory responses, mitigates ERS-induced cell death, maintains small intestinal integrity, and supports gut microbiota homeostasis.