Protective Effect of the Abelmoschus manihot Flower Extract on DSS-Induced Ulcerative Colitis in Mice

The flower of Abelmoschus manihot (AM) has been widely used in the treatment of chronic inflammatory diseases, including ulcerative colitis. This paper aimed to confirm the therapeutic effect of AM on ulcerative colitis (UC) and explore its mechanism.

Mouse models were induced by 2.5% dextran sulfate sodium (DSS) and treated with AM. UC signs, symptoms, colon macroscopic lesion scores, and disease activity index (DAI) scores were observed. Colon levels of interleukin- (IL-) 6, IL-1β, IL-18, IL-17, tumor necrosis factor- (TNF-) α, and IL-10 were quantified by ELISA. The colon protein expression levels of NLRP3, ASC, caspase 1 p10, β-arrestin1, ZO-1, occludin-1, and claudin-1 were examined by immunohistochemistry and western blotting. The mRNA levels of IL-1β, IL-18, NLRP3, ASC, and caspase 1 p10 in the colon were determined by real-time quantitative polymerase chain reaction (qPCR).

After treatment with AM, the mortality of mice, pathological damage to the colon, splenomegaly, and the spleen coefficient were decreased. AM reduced the levels of proinflammatory cytokines (IL-6, IL-1β, IL-18, IL-17, and TNF-α) and increased the level of IL-10. The mRNA expression levels of NLRP3, ASC, and caspase 1 in colon tissue were decreased by AM in a dose-dependent manner. In addition, AM also reduced the protein expression of NLRP3, ASC, caspase 1 p10, IL-1β, IL-18, and β-arrestin1 in the colon tissue of model mice. Western blot analysis confirmed that AM increased the expression of occludin-1, claudin-1, and ZO-1 in a dose-dependent manner.

This study shows that AM has a significant therapeutic effect on mice with UC, and the mechanism may be related to the inhibition of the β-arrestin1/NLRP3 inflammasome signaling pathway and the protection of intestinal barrier function.