前列腺素E_(2)介导的EP4受体通路通过抑制内质网应激减轻溃疡性结肠炎黏膜损伤的研究

PGE_(2)/EP4 signaling pathway attenuates mucosal damage in ulcerative colitis by inhibiting endoplasmic reticulum stress

背景前列腺素E_(2)介导的EP4受体通路(PGE_(2)/EP4信号通路)可以减轻溃疡性结肠炎(ulcerative colitis,UC)黏膜损伤,但其调节内质网应激的机制尚未完全明确。目的探索PGE_(2)/EP4信号通路调控内质网应激在溃疡性结肠炎黏膜损伤中的作用及其机制。方法首先将小鼠分为模型组和对照组,通过免疫组化和PCR技术检测EP4的表达水平,再将40只小鼠随机分为模型组(DSS)、前列腺素处理组(DSS+PGE_(2))、吲哚美辛处理组(DSS+吲哚美辛)和正常对照组(正常饮用水),前三组通过自由饮用5%DSS构建小鼠UC模型。观察和记录4组小鼠的疾病活动指数变化,通过免疫组化和Western blot评估经过PGE_(2)处理后小鼠结肠标本中EP4和GRP78(葡萄糖调节蛋白78)水平及其是否影响上皮细胞凋亡和增殖。通过siRNA转染HCT116细胞下调β-arrestin1的表达,再用PGE_(2)处理经过肿瘤坏死因子α诱导的细胞,通过Western blot检测GRP78表达水平。结果模型组小鼠模型上皮细胞的EP4水平下降(P<0.05)。四组实验中,PGE_(2)处理组小鼠上皮细胞凋亡指数和UC疾病活动指数下降(P<0.05),EP4表达水平、肠上皮细胞增殖水平升高(P<0.05)。GRP78蛋白表达水平在模型组结肠黏膜中表达升高,给予PGE_(2)后水平下降(P<0.05)。细胞实验中Western blot结果显示进一步沉默β-arrestin1表达后,GRP78表达水平升高(P<0.05)。结论PGE_(2)/EP4信号通路可能通过抑制肠上皮细胞内质网应激减轻UC肠道炎症反应,起到抑制上皮细胞凋亡、促进其增殖的作用。

Background PGE_(2)/EP4 signaling pathway can alleviate mucosal damage in ulcerative colitis,but the mechanism of its regulation of endoplasmic reticulum stress is not fully understood.Objective To clarify the mechanism of PGE_(2)/EP4 signaling pathway in regulating ER stress in mucosal injury in ulcerative colitis(UC).Methods Firstly,divide the mice into a model group and a control group,and detect the expression level of EP4 through immunohistochemistry and PCR,by constructing mice UC model,the experimental mice were divided into acute UC group(DSS),PGE_(2)-treated group(DSS+PGE_(2)),indomethacin treatment group(DSS+indomethacin),and control group.The disease activity index of mice was observed and recorded.The colonic mucosal tissues were collected to detect the levels of EP4 and GRP78,epithelial cell apoptosis and proliferation after PGE_(2)treatment.The expression ofβ-arrestin1 was downregulated by siRNA in HCT116 cells,then the expression of GRP78 was detected by PGE_(2)treatment.Results EP4 levels decreased and GRP78 levels increased in the colon mucosa of acute UC mice(P<0.05).After PGE_(2)treatment,the colon mucosal epithelial cells showed apoptosis,and the UC disease activity index decreased significantly(P<0.05),while EP4 levels and the level of intestinal epithelial cell proliferation increased significantly(P<0.05).The protein level of GRP78 in UC colon mucosa of mice were increased,and it decreased significantly after PGE_(2)administration.After knocking down the expression ofβ-arrestin1by siRNA in HCT116 cells,the expression level of GRP78 was significantly up-regulated(P<0.05).Conclusion PGE_(2)/EP4 signaling pathway attenuates mucosal injury by inhibiting endoplasmic reticulum stress signaling in colitis,which inhibits epithelial cell apoptosis and promotes its proliferation.