(-)-Syringaresinol attenuates ulcerative colitis by improving intestinal epithelial barrier function and inhibiting...

(-)-Syringaresinol (SYR), a natural lignan with significant antioxidant and anti-inflammatory activities, possesses various pharmacological benefits including cardio-protective, antibacterial, anticancer, and anti-aging effects. It was shown that the effectiveness of (+)-syringaresinol diglucoside on the ulcerative colitis (UC) was attributed to the active metabolite (+)-syringaresinol (the enantiomor of SYR). However, the efficacy of SYR against UC remains unclear, and the associated molecular mechanism has not been revealed yet PURPOSE: This study aimed to assess the protective effect of SYR in UC and its underlying mechanism STUDY DESIGN AND METHODS: We examined SYR's protective impact on the intestinal epithelial barrier and its ability to inhibit inflammatory responses in both a lipopolysaccharide (LPS)-induced Caco-2 cell model and a dextran sodium sulfate (DSS)-induced UC mouse model. We also explored the potential signaling pathways regulated by SYR using transcriptome analysis and western blot assay RESULTS: In Caco-2 cells, SYR significantly increased trans-epithelial electrical resistance, reduced tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interferon-γ (IFN-γ), and cyclooxygenase-2 (COX-2) levels, and enhanced cellular tight junction protein expression and distribution. In mice with UC, oral treatment with SYR (10, 20, 40 mg·kg^-1) dose-dependently increased body weight, colon length, and expression of tight junction proteins, decreased disease activity index score, spleen coefficient, cytokine serum levels, bacterial translocation, and intestinal damage, and also preserved the ultrastructure of colonic mucosal cells. Transcriptomics indicated that the anti-UC effect of SYR is mediated via the PI3K-Akt/MAPK/Wnt signaling pathway.

In summary, SYR effectively mitigated the development of UC by enhancing the intestinal epithelial barrier function and attenuating the inflammatory response. The plant-derived product SYR might be a potentially effective therapeutical agent against UC.