Eleutheroside E alleviates ulcerative colitis by suppressing Th17 immune response via the MAPK signaling pathway and remodeling gut microbiota.

BACKGROUND

Ulcerative colitis (UC) is a long-term, recurrent inflammatory condition marked by bloody feces and mucosal damage. Its rising global incidence and socioeconomic burden necessitate safer long-term interventions. Edible and medicinal herbs (EMHs) are prospective alternatives due to their multi-target profiles and safety. Eleutheroside E (EE), a key component of the well-known EMH Eleutherococcus senticosus, exhibits robust inflammation-suppressing capacities. Nonetheless, its anti-inflammatory protective efficacy and associated mechanisms in acute colitis require further exploration.

PURPOSE: This study endeavored to delineate the anti-inflammatory protective effects and associated molecular cascades of EE in DSS-induced acute colitis.

METHODS

The anti-inflammatory protective properties of EE were evaluated in a dextran sulfate sodium (DSS)-induced colitis model under simultaneous administration conditions. The functional reliance and target engagement of the MAPK pathway were explored in vivo and in vitro using a specific inhibitor (SCH772984), an agonist (Ro 67-7476), small interfering RNA (siRNA) knockdown, and cellular thermal shift assay (CETSA). Protective efficacy, the inflammatory microenvironment, Th17 immune responses, and gut microbiota profiles were assessed via histopathological scoring, ELISA, RT-qPCR, Western blotting, flow cytometry, RNA-seq, and 16S rRNA sequencing.

RESULTS

EE alleviated DSS-mediated body weight reduction, disease progression and colonic shortening, and relieved intestinal mucosal lesions. Secondary to the attenuation of local inflammation, EE maintained the intact intestinal barrier structure. Molecularly, CETSA supported cellular target engagement of EE with MEK1 and ERK2 and their thermal stabilization. In vitro, targeted siRNA silencing of MEK/ERK in LPS-stimulated RAW264.7 macrophages abolished the further inhibitory effects of EE on MAPK activation, while RO stimulation showed that EE reduced the generation of pro-inflammatory cytokines essential for Th17 polarization (IL-6, IL-1β, and IL-23). In vivo, this dampening of the pro-inflammatory microenvironment corresponded with a significant reduction in the proportion of Th17 cells (CD4⁺IL-17A⁺RORγt⁺) in the colonic lamina propria and decreased IL-17A levels. Furthermore, 16S rRNA sequencing indicated that EE treatment was accompanied by gut microbiota remodeling.

CONCLUSION

EE, a bioactive molecule derived from a well-known EMH, exerts anti-inflammatory protective effects against acute UC. This protection is associated with the suppression of Th17 immune responses through modulation of the MAPK (MEK/ERK) signaling pathway and a blunted pro-inflammatory microenvironment. These protective effects are also accompanied by gut microbiota remodeling.