沉默信号调节蛋白6在溃疡性结肠炎小鼠结肠组织中的表达及意义

Expression and role of silent information regulator 6 in colon tissues of mice with ulcerative colitis

探讨沉默信号调节蛋白(SIRT)6在溃疡性结肠炎(UC)小鼠结肠组织中的表达及意义。方法将22只14日龄清洁级无病原体C57BL6/J野生型(WT)小鼠分为WT对照组(n=6)和WT-葡聚糖硫酸钠(WT-DSS)组(n=16),将13只肠道上皮细胞敲除SIRT6基因(SIRT6^(IKO))小鼠分为SIRT6^(IKO)对照组(n=3)和SIRT6^(IKO)-DSS组(n=10)。WT对照组和SIRT6^(IKO)对照组小鼠给予正常蒸馏水喂养,WT-DSS组和SIRT6^(IKO)-DSS组小鼠给予25 g·L^(-1) DSS间断性喂养(每日5 mL,连续7 d,然后更换正常饮用水喂养14 d为1个循环,共3个循环)建立UC模型。每天称小鼠体质量,观察小鼠大便性状、肉眼血便,计算小鼠疾病活动度指数(DAI)评分。于造模第3个循环末,将各组小鼠采用颈椎脱臼法处死,取新鲜结肠组织,应用苏木精-伊红(HE)染色观察WT-DSS组和SIRT6^(IKO)-DSS组小鼠结肠黏膜损伤的病理学变化并进行评分,Western blot法检测WT对照组,SIRT6^(IKO)对照组和WT-DSS组小鼠结肠组织中SIRT6蛋白表达来判断基因敲除效率,免疫组织化学法检测WT-DSS组和SIRT6^(IKO)-DSS组小鼠结肠组织中巨噬细胞特异性标志物F4/80的表达,实时荧光定量聚合酶链反应法检测WT-DSS组和SIRT6^(IKO)-DSS组小鼠结肠组织中白细胞介素-6(IL-6)和肿瘤坏死因子-α(TNF-α)mRNA表达水平。结果SIRT6^(IKO)对照组小鼠结肠组织中SIRT6蛋白相对表达量显著高于WT对照组(P<0.05)。WT对照组小鼠结肠组织中SIRT6蛋白相对表达量显著高于WT-DSS组(P<0.05)。造模第3个循环末,WT-DSS组和SIRT6^(IKO)-DSS组小鼠体质量均显著低于第1、2个循环末(P<0.05);2组小鼠造模第1循环末与第2个循环末体质量比较差异无统计学意义(P>0.05);造模第1、2个循环末,SIRT6^(IKO)-DSS组与WT-DSS组小鼠体质量比较差异无统计学意义(P>0.05);造模第3个循环末,SIRT6^(IKO)-DSS组小鼠体质量显著低于WT-DSS组(P<0.05)。造模第3个循环末,WT-DSS组和SIRT6^(IKO)-DSS组小鼠DAI评分均显著高于第1、2个循环末(P<0.05);WT-DSS组小鼠造模第2个循环末与第1个循环末DAI评分比较差异无统计学意义(P>0.05);造模第2个循环末,SIRT6^(IKO)-DSS组小鼠DAI评分显著高于第1个循环末(P<0.05);造模第2、3个循环末,SIRT6IKO-DSS组小鼠DAI评分显著高于WT-DSS组(P<0.05)。SIRT6^(IKO)-DSS组小鼠结肠组织组织学损伤指数显著低于WT-DSS组(P<0.05)。SIRT6^(IKO)-DSS组小鼠结肠组织F4/80表达评分显著高于WT-DSS组(P<0.05)。SIRT6^(IKO)-DSS组小鼠结肠组织中IL-6、TNF-αmRNA相对表达量显著高于WT-DSS组(P<0.05)。结论UC小鼠结肠组织中SIRT6呈低表达,结肠组织中SIRT6缺失会加重结肠组织的炎症反应和损伤,增加UC易感性。

Objective To investigate the expression and role of silent information regulator 6(SIRT6)in colon tissues of mice with ulcerative colitis(UC)and its significance.Methods Twenty-two 14-day-old pathogen free C57BL6/J wild-type(WT)mice were divided into WT control group and WT-dextran sulfate sodium salt(DSS)group,and 13 intestinal epithelial SIRT6 gene knockout(SIRT6^(IKO))mice were divided into SIRT6^(IKO) control group and SIRT6^(IKO)-DSS group.The mice in the WT-control group and SIRT6^(IKO) control group were fed with normal distilled water,and the mice in the WT-DSS group and SIRT6^(IKO)-DSS group were fed with 25 g·L^(-1) DSS(5 mL every day for 7 days,then normal drinking distilled water for 14 d,a total of three cycles)to establish the UC model.The body weight of mice was measured,the stool characteristics and gross bloody stool were observed on every day;and the disease activity index(DAI)was calculated.The mice in each group were killed by cervical dislocation and fresh colon tissue was collected at the end of the third cycle of modeling,hematoxylin-eosin(HE)staining was used to examine the pathological changes of colonic mucosal injury of mice in the WT-DSS group and SIRT6^(IKO)-DSS group,and the pathological score was conducted;the expression of SIRT6 protein in colon tissue of mice in the WT control group,SIRT6^(IKO) control group and WT-DSS group was detected by Western blot to determine gene knockout efficiency;immunohis-tochemistry(IHC)was used to detect the expression of the macrophage specific marker F4/80 in the colon tissues of mice in the WT-DSS group and SIRT6^(IKO)-DSS group;the expression levels of interleukin-6(IL-6)and tumor necrosis factor-α(TNF-α)mRNA in colon tissue of mice in the WT-DSS group and SIRT6^(IKO)-DSS group were detected by real-time fluorescence quantitative polymerase chain reaction.Results The relative expression level of SIRT6 protein in colon tissue of mice in the SIRT6^(IKO) control group was significantly higher than that in the WT control group(P<0.05).The relative expression of SIRT6 protein in colon tissue of mice in the WT control group was significantly higher than that in the WT-DSS group(P<0.05).At the end of the third cycle of modeling,the body weight of mice was significantly lower than that at the end of the first and the second cycle of modeling in the WT-DSS group and SIRT6^(IKO)-DSS group(P<0.05);there was no significant difference in the body weight of mice at the end of the first cycle and the second cycle of modeling in the two groups(P>0.05).At the end of the first and the second cycles of modeling,there was no significant difference in body weight between WT-DSS group and SIRT6^(IKO)-DSS group(P>0.05);at the end of the third cycle of modeling,the body weight of mice in the SIRT6^(IKO)-DSS group was significantly lower than that in the WT-DSS group(P<0.05).At the end of the third cycle of modeling,the DAI score of mice were significantly higher than that at the end of the first and the second cycle of modeling in the WT-DSS group and SIRT6^(IKO)-DSS group(P<0.05);there was no significant difference in DAI score of mice between the end of the second cycle of modeling and the end of the first cycle of modeling in the WT-DSS group(P>0.05);at the end of the second cycle of modeling,the DAI score of mice was significantly higher than that at the end of the first cycle in the SIRT6^(IKO)-DSS group(P<0.05);at the end of the second and the third cycles of modeling,the DAI score of mice in the SIRT6^(IKO)-DSS group was significantly higher than that in the WT-DSS group(P<0.05).The colonic histological injury index of mice in the SIRT6^(IKO)-DSS group was significantly lower than that in the WT-DSS group(P<0.05).The F4/80 expression score in colon tissue of mice in the SIRT6^(IKO)-DSS was significantly higher than that in the WT-DSS group(P<0.05).The expression levels of IL-6 and TNF-αmRNA in colon tissue of mice in the SIRT6^(IKO)-DSS were significantly higher than those in the WT-DSS group(P<0.05).Conclusion The expression of SIRT6 in colon tissues of mice with UC is lower,the absence of SIRT6 in colonic tissue can aggravate the inflammatory response and colonic tissue injury,and increase the susceptibility of UC.