Ethanolic Extract of Selaginella tamariscina Alleviates DSS-induced Ulcerative Colitis by Restoring Epithelial Barrier Function.

ETHNOPHARMACOLOGICAL RELEVANCE Selaginella tamariscina (P. Beauv.) Spring is a traditional Chinese herbal medicine used to treat hematemesis, metrorrhagia, hematochezia, rectal prolapse, and other diseases. Based on its efficacy in treating bloody stools, S. tamariscina is also used in formulations for ulcerative colitis (UC).

Aim

OF THE STUDY This study aimed to investigate the efficacy and the potential mechanism of S. tamariscina ethanol extract (STE) against UC.

Methods

STE samples were prepared by reflux extraction. The UC mouse model was induced by freely drinking 3% DSS solution. The therapeutic efficacy of STE in UC was assessed by measuring the disease activity index (DAI), histopathological score, colon length, and cytokine expression levels. Intestinal permeability was evaluated using a FITC-dextran permeability assay. Differentially expressed genes in colon tissues were analyzed using transcriptomics. Calcium imaging was performed to detect the effect of STE on intracellular Ca2+ levels in HT-29 cells. Cell proliferation was detected using BrdU staining. Epithelial barrier destruction of HT-29 cells was induced by exposure to a combination of LPS and IFNγ. Expression levels of junction proteins in colon tissue and HT-29 cells were detected by Western blot and immunofluorescence. Epithelial barrier integrity was assessed using the transepithelial electrical resistance (TEER) assay.

Results

STE dose-dependently alleviated body weight loss, colon shortening, DAI scores, pathological changes, epithelial barrier function, and inflammatory status (including TNF-α, IL-6, and IL-1β) in colon tissues of UC mice. Mechanistically, STE induced a concentration-dependent increase in intracellular Ca2+ levels in HT-29 cells (EC50 = 33 μg/mL). This response was completely abolished in Ca2+-free medium, indicating that STE primarily promotes extracellular Ca2+ influx rather than Ca2+ release from intracellular stores. STE alone (3 μg/mL) promoted HT-29 cell proliferation, upregulated Cyclin D1 expression, and increased ERK1/2 and p38 MAPK phosphorylation, while ERK1/2 and p38 inhibitors (U0126, SB203580) suppressed STE-induced proliferation. Ca2+ deprivation diminished STE-induced ERK1/2 and p38 phosphorylation. In parallel, under inflammatory conditions, STE inhibited the aberrantly activated JAK2-STAT3 pathway, upregulated tight junction proteins (ZO-1, Occludin, Claudin-1), and restored TEER in LPS/IFN-γ-treated HT-29 cells. The JAK2 agonist Coumermycin A1 reversed these protective effects. Collectively, STE activates the Ca2+/ERK/p38 MAPK pathway to promote regeneration while suppressing the JAK2-STAT3 pathway to counteract junctional disruption, operating as parallel and complementary mechanisms to restore intestinal epithelial barrier function.

Conclusion

STE significantly ameliorated UC symptoms and restored intestinal barrier integrity in UC mice. These protective effects are mediated through Ca2+-dependent activation of the ERK/p38 MAPK pathway and inhibition of the JAK-STAT signaling cascade.