核受体FXR调控内质网应激途径缓解小鼠溃疡性结肠炎病理损伤

Nuclear receptor relieve pathological injury of ulcerative colitis by FXR regulating the endoplasmic reticulum stress pathway in vivo

目的 探究法尼醇X受体(farnesoid X receptor,FXR)激活对溃疡性结肠炎(ulcerative colitis,UC)模型小鼠结肠组织病理损伤的影响及其作用机制。方法 将40只C57BL/6雄性健康小鼠随机分为对照组、模型组、奥贝胆酸(obeticholic acid,OCA)组、奥贝胆酸+衣霉素(OCA+TM)组,记录各组小鼠体质量、粪便性状与隐血程度、疾病活动指数(disease activity index,DAI)、剥离结肠长度。ELISA法检测各组小鼠血清IL-1β、IL-6、TNF-α含量,HE染色观察各组小鼠结肠组织病理形态变化,免疫组化染色检测各组小鼠结肠组织中GRP78和CCAAT/CHOP阳性表达情况,RT-qPCR和Western blotting检测各组小鼠结肠组织中GRP78和CHOP在mRNA与蛋白水平上的表达变化。结果 与对照组比较,模型组小鼠DAI升高,结肠长度缩短,血清中IL-1β、IL-6、TNF-α含量均增加,结肠组织发生明显损伤,可见广泛炎性细胞浸润,结肠组织中GRP78和CHOP阳性染色增强,GRP78和CHOP的mRNA相对表达量和蛋白相对表达量均上调(P<0.05);与模型组比较,OCA组小鼠DAI降低,结肠长度增加,血清中IL-1β、IL-6、TNF-α含量均减少,结肠组织损伤程度明显改善,未见炎性细胞浸润,结肠组织中GRP78和CHOP阳性染色减弱,且GRP78和CHOP的mRNA相对表达量与蛋白相对表达量均下调(P<0.05);而与OCA组比较,OCA+TM组小鼠DAI升高而结肠长度缩短,血清中IL-1β、IL-6、TNF-α含量也均增加,结肠组织损伤,表现出明显的溃疡现象,同时,结肠组织中GRP78和CHOP阳性染色增强,GRP78和CHOP的mRNA相对表达量与蛋白相对表达量也均上调(P<0.05)。结论 在UC小鼠模型中激活FXR能够有效缓解结肠组织病理损伤,该机制可能与调控内质网应激途径有关。

Objective To explore the effect of farnesoid X receptor(FXR) activation on the pathological damage of colon tissue in ulcerative colitis(UC) model mice and its mechanism.Methods Forty healthy C57BL/6 male mice were randomly divided into control group,model group,obeticholic acid(OCA) group,and obeticholic acid+tunicamycin(OCA+TM) group.The weighed,the fecal characteristics and the degree of occult blood,the disease activity index(DAI),and colon length were recorded.The serum levels of IL-1β,IL-6 and TNF-α in mice in each group were detected by ELISA.HE staining was used to observe the pathological changes of colon tissue of mice in each group.Immunohistochemical staining was used to detect the positive expression of GRP78 and CCAAT/CHOP in colon tissue of mice in each group.RT-qPCR and Western blotting were used to detect the expression changes of GRP78 and CHOP at the mRNA and protein levels in colon tissue of mice in each group.Results Compared with the control group,the DAI of mice in the model group was increased.The length of the colon was shorter,and the contents of IL-1β,IL-6 and TNF-α in the serum were increased.The colon tissue was significantly damaged,and extensive inflammatory cell infiltration was seen in the colon.The positive staining of GRP78 and CHOP in the tissue was enhanced.The relative mRNA and protein expressions of GRP78 and CHOP were up-regulated(P<0.05).Compared with the model group,the DAI of mice in the OCA group was decreased,and the length of the colon was increased.The contents of IL-1β,IL-6 and TNF-α in the serum were decreased.The damage degree of the colon tissue was significantly improved,and infiltrating inflammatory cell was not found in the colon tissue.The positive staining of GRP78 and CHOP was weakened,and the relative mRNA and protein expressions of GRP78 and CHOP were down-regulated(P<0.05).Compared with the OCA group,the DAI of mice in the OCA+TM group was increased while the length of the colon was shortened,and the contents of IL-1β,IL-6 and TNF-α in the serum also increased.The colon tissue was damaged,showing obvious ulceration.At the same time,the positive staining of GRP78 and CHOP in colon tissue was enhanced.The relative mRNA and protein expressions of GRP78 and CHOP were also up-regulated(P<0.05).Conclusion Activating FXR in UC mice model can effectively alleviate the pathological damage of colon tissue,and the mechanism may be related to the regulation of endoplasmic reticulum stress pathway.