Objectives: To investigate the effect of ecliptasaponin A (ESA) for alleviating dextran sulfate sodium (DSS)-induced inflammatory bowel disease (IBD) in mice and the underlying mechanism.
Methods: Twenty-four male C57BL/6 mice (8-10 weeks old) were equally randomized into control group, DSS-induced IBD model group, and DSS+ESA (50 mg/kg) treatment group. Disease activity index (DAI), colon length and spleen index of the mice were measured, and intestinal pathology was examined with HE staining. The expressions of inflammatory mediators (TNF-α, IL-6, and iNOS) in the colon mucosa were detected using ELISA and RT-qPCR, and intestinal barrier integrity was assessed using AB-PAS staining and by detecting ZO-1 and claudin-1 expressions using immunofluorescence staining and Western blotting. In cultured RAW264.7 macrophages, the effects of treatment with 50 μmol/L ESA, alone or in combination with 20 μmol/L RO8191 (a JAK2/STAT3 pathway activator), on M1 polarization of the cells induced by LPS and IFN-γ stimulation and expressions of JAK2/STAT3 pathway proteins were analyzed using flow cytometry and Western blotting.
Results: In the mouse models of DSS-induced IBD, ESA treatment significantly alleviated body weight loss and colon shortening, reduced DAI, spleen index and histological scores, and ameliorated inflammatory cell infiltration in the colon tissue. ESA treatment also suppressed TNF‑α, IL-6 and iNOS expressions, protected the goblet cells and the integrity of the mucus and mechanical barriers, and upregulated the expressions of ZO-1 and claudin-1. ESA treatment obviously decreased CD86+ M1 polarization in the mesenteric lymph nodes of IBD mice and in LPS and IFN-γ-induced RAW264.7 cells, and significantly reduced p-JAK2 and p-STAT3 expressions in both the mouse models and RAW264.7 cells. Treatment with RO8191 caused reactivation of JAK2/STAT3 and strongly attenuated the inhibitory effect of ESA on CD86+ polarization in RAW264.7 cells.
Conclusions: ESA alleviates DSS-induced colitis in mice by suppressing JAK2/STAT3-mediated M1 macrophage polarization and mitigating inflammation-driven intestinal barrier damage.
目的: 探讨旱莲苷A（ESA）对葡聚糖硫酸钠（DSS）诱导的小鼠炎症性肠病（IBD）模型的影响及其对巨噬细胞极化的作用机制。方法: 体内实验采用24只8~10周龄雄性C57BL/6小鼠，随机分成对照组（WT组）、2.5% DSS诱导模型组（DSS组）、ESA治疗组（DSS+ESA组，50 mg/kg），8只/组。每日记录小鼠体质量，观察粪便性状，通过DAI评分、结肠长度、脾指数、结肠组织HE染色及组织炎症评分、ELISA和RT-qPCR检测的肠黏膜炎症介质（TNF-α、IL-6和iNOS）水平评估ESA对小鼠肠炎症状的影响；采用AB-PAS染色标记杯状细胞，免疫荧光和Western blotting检测紧密连接蛋白水平（ZO-1和Claudin-1），评估ESA对小鼠肠道屏障的作用。体外培养小鼠单核巨噬细胞白血病细胞RAW264.7，分为Control组（M0组）、LPS（1 μg/mL）+IFN-γ（20 ng/mL）诱导组（M1组）和ESA治疗组（ESA组，50 μmol/L），采用流式细胞术评估ESA对小鼠肠系膜淋巴结及体外模型M1型极化标志物（CD86）比例的影响。Western blotting检测JAK2/STAT3通路关键蛋白表达，并使用信号通路激活剂RO8191（20 μmol/L）干预，分析ESA调控巨噬细胞极化的分子机制。结果: 体内实验显示，ESA可明显缓解DSS诱导的小鼠体质量下降、结肠长度缩短及DAI评分、脾指数、组织炎症评分的升高（P<0.05）；HE结果显示，ESA可保护肠道固有层，减轻肠道炎症细胞浸润；ELISA和RT-qPCR显示，ESA可抑制DSS诱导的小鼠肠黏膜组织相关炎症介质（TNF-α、IL-6和iNOS）的高表达（P<0.05）；AB-PAS和免疫荧光结果显示，ESA可保护结肠组织杯状细胞、黏液屏障和机械屏障的损伤。流式细胞术结果发现，ESA可降低DSS诱导的小鼠肠系膜淋巴结和体外诱导的M1型巨噬细胞极化标志物（CD86）的阳性比例（P<0.05）。Western blotting结果显示，体内外ESA治疗组p-JAK2和p-STAT3水平低于诱导组（P<0.05）；体外经JAK2/STAT3激活剂RO8191干预后显示，ESA药物治疗未能抑制JAK2/STAT3信号通路活化，同时M1型极化标志物CD86阳性比例增加（P<0.05）。结论: ESA可靶向拮抗JAK2/STAT3通路活化介导的M1型巨噬细胞极化，抑制炎症因子导致的肠道屏障的损伤，从而缓解DSS诱导的小鼠结肠炎。.
Keywords: JAK2/STAT3; ecliptasaponin A; inflammatory bowel disease; intestinal barrier; macrophage polarization.