Objectives: Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD) mainly characterized by inflammation, ulceration and erosion of colonic mucosa and submucosa. Transient receptor potential vanilloid 1 (TRPV1) is an important mediator of visceral pain and inflammatory bowel disease. This study aims to investigate the protective effect of water soluble propolis (WSP) on UC colon inflammatory tissue and the role of TRPV1.
Methods: Male SD rats were randomly divided into 6 groups (n=8): a normal control (NC) group, an ulcerative colitis model (UC) group, a low-WSP (L-WSP) group, a medium-WSP (M-WSP) group, a high-WSP (H-WSP) group, and a salazosulfapyridine (SASP) group. The rats in the NC group drank water freely, and the other groups drank 4% dextran sulfate sodium (DSS) solution freely for 7 d to replicate the ulcerative colitis model. Based on the successful replication of the UC, the L-WSP, M-WSP, and H-WSP groups were given 50, 100, and 200 mg/kg of water-soluble propolis by gavage for 7 d, and the SASP group was given 100 mg/kg of sulfasalazine by gavage for 7 d. The body weight of rats in each group was measured at the same time every day, the fecal traits and occult blood were observed to record the disease activity index (DAI). After intragastric administration, the animals were sacrificed after fasted 24 h. Serum and colonic tissue were collected, and the changes of MDA, IL-6 and TNF-α were detected. The pathological changes of colon tissues were observed by HE staining, and the expression of TRPV1 in colon tissues was observed by Western blotting, immunohistochemistry, and immunofluorescence.
Results: The animals in each group that drank DSS freely showed symptoms such as weight loss, decreased appetite, depressed state, and hematochezia, indicating that the model was successfully established. Compared with the NC group, DAI scores of other groups were increased (all P<0.05). MDA, IL-6, TNF-α in serum and colon tissues of the UC group were increased compared with the NC group (all P<0.01), and they were decreased after WSP and SASP treatment (all P<0.01). The results of showed that the colon tissue structure was obviously broken and inflammatory infiltration in the UC group, while the H-WSP group and the SASP group significantly improved the colon tissue and alleviated inflammatory infiltration. The expression of TRPV1 in colon tissues in the UC group was increased compared with the NC group (all P<0.01), and it was decreased after WSP and SASP treatment.
Conclusions: WSP can alleviate the inflammatory state of ulcerative colitis induced by DSS, which might be related to the inhibition of inflammatory factors release, and down-regulation or desensitization of TRPV1.
目的: 溃疡性结肠炎(ulcerative colitis，UC)是一类以结肠黏膜及黏膜下层炎症、溃疡、糜烂为主的炎症性肠病(inflammatory bowel disease，IBD)。瞬时受体电位香草酸1(transient receptor potential vanilloid 1，TRPV1)是内脏痛及炎症性肠病的重要介质。本研究旨在探讨水溶性蜂胶(water soluble propolis，WSP)对UC结肠炎症组织的保护作用，以及TRPV1在其中的作用。方法: 将雄性SD大鼠随机分成6组(n=8)：正常对照(normal control，NC)组、UC组、低剂量蜂胶(low-WSP，L-WSP)组、中剂量蜂胶(middle-WSP，M-WSP)组、高剂量蜂胶(high-WSP，H-WSP)组和柳氮磺胺吡啶(salazosulfapyridine，SASP)组。NC组大鼠自由饮水，其余组大鼠自由饮用4%右旋糖酐硫酸钠(dextran sulfate sodium，DSS)溶液7 d后复制UC模型。在UC模型复制成功基础上，L-WSP、M-WSP、H-WSP组每天分别给予50、100、200 mg/kg的WSP灌胃处理7 d，SASP组每天给予100 mg/kg的SASP灌胃7 d。每天同一时间测量各组大鼠体重，观察其粪便性状和便血情况，行大鼠的疾病活动指数(disease activity index，DAI)评分。采用比色法检测丙二醛(malondialdehyde，MDA)的水平，ELISA法检测白细胞介素-6(interleukin-6，IL-6)、肿瘤坏死因子α(tumor necrosis factor-α，TNF-α)的变化，HE染色观察结肠病理学变化，蛋白质印迹法、免疫组织化学和免疫荧光实验观察结肠组织中TRPV1的表达情况。结果: 自由饮用DSS的各组动物出现体重下降、食欲下降、状态低迷、拖尾便血等症状，表明造模成功。与NC组相比，其余各组大鼠服用DSS后DAI评分均增加(均P<0.05)。与NC组相比，UC组大鼠血清和结肠组织中MDA、IL-6、TNF-α表达水平均升高(均P<0.01)，WSP和SASP用药后MDA、IL-6、TNF-α表达水平均降低(均P<0.01)。UC组大鼠结肠组织结构明显被破环，炎性浸润，H-WSP和SASP组结肠组织明显改善，炎性浸润缓解。与NC组相比，UC组大鼠结肠组织TRPV1的表达水平升高(均P<0.01)，WSP和SASP组结肠组织TRPV1的表达水平降低。结论: WSP可以缓解DSS诱导的UC大鼠结肠组织的炎症状态，其机制可能与抑制炎症因子释放，下调TRPV1或TRPV1脱敏等机制有关。.
Keywords: inflammatory medium; propolis; transient receptor potential vanilloid 1; ulcerative colitis.