Mechanism of Shaoyao Decoction alleviating dampness-heat ulcerative colitis via regulating macrophage polarization and eosinophil infiltration

This study aims to investigate the regulatory effects and underlying mechanisms of Shaoyao Decoction (SYD) on macrophage polarization and eosinophil infiltration in the colon tissues of mice with ulcerative colitis (UC). Sixty male BALB/c mice were randomly divided into six groups: normal control, model, sulfasalazine treatment, and SYD low-dose, medium-dose, and high-dose groups. Except for the normal control group, all mice were fed a high-sugar and high-fat diet and maintained in a high-temperature and high-humidity environment, combined with intragastric administration of dextran sulfate sodium to establish a damp-heat accumulation type UC model. Following the modeling, drug intervention was administered for 7 days. Colonic injury was evaluated by assessing body weight, disease activity index (DAI), colon length, and histopathology. The levels of inflammatory factors, including interleukin-5 (IL-5), IL-8, IL-10, transforming growth factor-β (TGF-β), and granulocyte-macrophage colony-stimulating factor (GM-CSF) in serum or colon tissues were detected by ELISA. Western blot and RT-qPCR were utilized to detect the expression of zonula occludens-1 (ZO-1), Occludin, inducible nitric oxide synthase (iNOS), arginase-1 (ARG-1), and key molecules of the C-C motif chemokine receptor 3/Eotaxin (CCR3/CCL11) signaling pathway in colon tissues. The results showed that compared with the normal control group, the model group exhibited significant body weight loss, obvious hematochezia, significantly increased DAI, shortened colon length, and severe histopathological damage (including epithelial destruction, goblet cell depletion, and crypt structure impairment), indicating the successful establishment of the UC mouse model. SYD treatment, particularly in the medium-dose and high-dose groups, significantly ameliorated the aforementioned pathological indices. Mechanistic studies demonstrated that SYD effectively reduced the expression of cytokines IL-5, IL-8, TGF-β, and GM-CSF, increased the anti-inflammatory factor IL-10, and upregulated the expression of tight junction proteins ZO-1 and Occludin (P < 0.05). Furthermore, SYD decreased the content of the M1 macrophage polarization protein iNOS, increased the content of the M2 macrophage polarization protein ARG-1 (P < 0.05), and inhibited the expression of key proteins in the CCR3/CCL11 signaling pathway (P < 0.05), thereby reducing the recruitment of eosinophils to the inflammatory site. In conclusion, SYD alleviates intestinal inflammation and tissue injury in mice with damp-heat type UC through multiple mechanisms, including inhibiting the release of pro-inflammatory factors, promoting the production of anti-inflammatory factors, repairing the intestinal barrier, regulating macrophage polarization toward the M2 phenotype, and inhibiting CCR3/CCL11-mediated eosinophil infiltration.