Objectives: To observe the effect of electroacupuncture (EA) at "Zusanli"(ST36) on intestinal mucosal damage, intestinal mucosal oxidative stress injury and apoptosis induced by 5-fluorouraeil (5-FU) chemotherapy in colorectal cancer-bearing mice.
Methods: Thirty male BALB/c mice were randomly divided into normal control, colorectal cancer (CT26), 5-FU, non-acupoint and ST36 groups, with 6 mice in each group. Except for those of the normal control group, mice of the remaining 4 groups received subcutaneous implantation of colorectal CT26 cell suspension (0.1 mL) in the right armpit for establishing colorectal cancer model. Rats of the 5-FU group, non-acupoint group and ST36 group were given with 5 mg/mL 5-FU solution once every 3 days for a total of 21 days. For mice of the non-acupoint group and ST36 group, EA (2 Hz, 1-2 mA) was applied to bilateral ST36 or non-acupoints (the bilateral sunken spots about 3 mm to the midpoint between the tail root and the anus) for 5 min after each intraperitoneal infusion of 5-FU, once every 3 days, for a total of 21 days. After the intervention, the diarrhea index was assessed. The length of colon (from the endpoint of cecum to the anal orifice) was measured. Histopathological changes of colonic mucosa were observed by H.E. staining, and the length of colonic villi was measured. The content of malondialdehyde (MDA), and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) of colonic tissue were detected by thibabituric acid, xanthine oxidase and colorimetric method, respectively. The rate of cell apoptosis in the colonic tissue was measured by TUNEL assay. The positive expressions of Bax and Bcl-2 in colonic tissue were determined by immunohistochemistry.
Results: The CT26 model group didn't show any significant changes in the diarrhea index, colon length, colon villus length, MDA content, SOD and GSH-Px activities, colonic cell apoptosis rate, and Bax and Bcl-2 expression levels when compared with the normal group. Compared with the CT26 group, the 5-FU group had a remarkable increase in the diarrhea index, MDA content, colonic cell apoptosis rate and Bax expression level (P<0.01, P<0.05), and a marked decrease in the colon length, colon villus length, SOD and GSH-Px activities and Bcl-2 expression level (P<0.01), suggesting the side effects of administration of 5-FU. Compared with the 5-FU group, the diarrhea index, MDA content, colonic cell apoptosis rate and Bax expression level were markedly decreased (P<0.05, P<0.01) and those of the colon length, colon villus length, SOD and GSH-Px activities and Bcl-2 expression level were obviously increased (P<0.01) in the ST36 group. Compared with the 5-FU group, the non-acupoint group also had an increase in the colon villus length, SOD and GSH-Px activities (P<0.01, P<0.05) and a decrease in the cell apoptosis rate (P<0.01).
Conclusions: EA at ST36 has a positive effect in reducing intestinal mucosal damage induced by 5-FU chemotherapy in cancer-bearing mice, which may be related to its function in relieving oxidative stress injury and inhibiting apoptosis of colonic tissue.
目的: 观察电针“足三里”对大肠癌荷瘤小鼠5-氟尿嘧啶（5-FU）化疗后肠黏膜损伤的减轻作用及对结肠组织氧化应激及细胞凋亡的影响，探讨电针缓解化疗后肠黏膜损伤的部分机制。方法: BALB/c小鼠随机分为正常组、CT26组、5-FU组、非穴组和足三里组，每组6只。除正常组外，其余4组采用大肠癌CT26细胞皮下注射种植移植瘤；5-FU组、非穴组和足三里组腹腔注射 5-FU（5 mg/mL）溶液，每3 d注射 1次，共7次。足三里组和非穴组小鼠在每次给予5-FU腹腔注射后进行电针，足三里组电针双侧“足三里”，非穴组电针双侧非穴，每次5 min，3 d治疗1次，共治疗21 d。治疗结束后评估小鼠腹泻指数，测量小鼠结肠长度；HE染色法观察小鼠结肠黏膜病理形态，测量结肠绒毛长度；生化分析法检测小鼠结肠组织丙二醛（MDA）含量、超氧化物歧化酶（SOD）和谷胱甘肽过氧化物酶（GSH-Px）活性；TUNEL法检测小鼠结肠组织细胞凋亡水平；免疫组织化学法检测小鼠结肠组织B淋巴细胞瘤-2蛋白（Bcl-2）、B淋巴细胞瘤-2基因相关X蛋白（Bax）阳性表达水平。结果: 与正常组比较，CT26组小鼠腹泻指数、结肠长度、结肠绒毛长度、MDA含量、SOD活性、GSH-Px活性、细胞凋亡率、Bax、Bcl-2阳性表达率差异均无统计学意义。与CT26组比较，5-FU组小鼠腹泻指数升高（P<0.01），结肠长度及结肠绒毛均缩短（P<0.01），结肠组织MDA含量升高（P<0.05），SOD和GSH-Px活性降低（P<0.01），细胞凋亡率升高（P<0.01），Bax阳性表达升高（P<0.05），Bcl-2阳性表达率降低（P<0.01）。与5-FU组比较，足三里组小鼠腹泻指数降低（P<0.01），结肠长度及结肠绒毛均增长（P<0.01），结肠组织MDA含量降低（P<0.05），SOD和GSH-Px活性升高（P<0.01），细胞凋亡率降低（P<0.01），Bax表达降低（P<0.05），Bcl-2表达升高（P<0.01）；非穴组小鼠结肠绒毛长度增长（P<0.01），结肠组织SOD、GSH-Px活性升高（P<0.05，P<0.01），结肠组织细胞凋亡率降低（P<0.01）。结论: 电针“足三里”可减轻大肠癌荷瘤小鼠5-FU化疗后肠黏膜损伤，其作用机制可能与调节结肠组织氧化应激、抑制细胞凋亡有关。.
Keywords: 5-FU chemotherapy; Apoptosis; Damage of intestinal mucosa; Electroacupuncture; Oxidative stress; Zusanli (ST36).