生物活性肽对产肠毒素大肠杆菌诱导的小鼠肠道损伤的缓解作用

Mitigative Effects of Bioactive Peptide on Intestinal Injury of Mice Induced by Enterotoxigenic Escherichia coli

本试验旨在研究生物活性肽(BTP)对产肠毒素大肠杆菌(ETEC)诱导的小鼠肠道损伤的缓解作用。选用6周龄体重为(18±2)g的C57BL/6小鼠40只,随机分为4组,分别为对照组、ETEC组、试验Ⅰ组和试验Ⅱ组,每组10只。试验期共15 d,在第8~14天,空白对照组和阴性对照组小鼠每天灌胃0.1 mL的磷酸盐缓冲液(PBS),试验Ⅰ组和试验Ⅱ组小鼠每天分别灌胃150和300 mg/kg的BTP(溶于0.1 mL PBS中);在第15天,空白对照组小鼠灌胃0.2 mL的PBS,阴性对照组、试验Ⅰ组和试验Ⅱ组小鼠灌胃5×109 CFU/mL的ETEC菌悬液(重悬于0.2 mL PBS中),连续观察8 h后进行屠宰。结果表明:1)与空白对照组相比,阴性对照组小鼠的存活率显著降低(P<0.05),腹泻指数显著升高(P<0.05);空肠肿瘤坏死因子-α(TNF⁃α)的mRNA相对表达量显著升高(P<0.05),白细胞介素-1β(IL⁃1β)、白细胞介素-6(IL⁃6)含量显著升高(P<0.05);空肠闭合蛋白(Occludin)、闭锁小带蛋白-1(ZO⁃1)、闭锁小带蛋白-2(ZO⁃2)、转录因子核受体77(Nur77)的mRNA相对表达量显著降低(P<0.05);血清谷胱甘肽过氧化物酶(GSH⁃Px)活性显著降低(P<0.05),丙二醛(MDA)含量显著升高(P<0.05)。2)与阴性对照组相比,试验Ⅰ组和试验Ⅱ组小鼠的存活率显著升高(P<0.05),腹泻指数显著降低(P<0.05);试验Ⅰ组和试验Ⅱ组的空肠TNF⁃α的mRNA相对表达量显著降低(P<0.05),IL⁃1β、IL⁃6含量显著降低(P<0.05);试验Ⅱ组的空肠Occludin和Nur77的mRNA相对表达量显著升高(P<0.05);试验Ⅰ组和试验Ⅱ组的血清MDA含量显著降低(P<0.05),试验Ⅱ组的血清GSH⁃Px活性显著升高(P<0.05)。综上所述,BTP能够缓解ETEC感染导致的小鼠肠道炎症及屏障功能损伤,该作用可能与BTP上调了Nur77表达,抑制小肠上皮细胞凋亡、坏死性凋亡及焦亡有关。

This experiment was conducted to investigate the mitigative effects of bioactive peptide(BTP)on intestinal injury of mice induced by enterotoxigenic Escherichia coli(ETEC).Forty 6⁃week⁃old C57BL/6 mice with body weight of(18±2)g were randomly divided into 4 groups,which were blank control group,negative control group,experiment groupⅠand experiment groupⅡ,each group contained 10 mice.The ex⁃periment lasted for 15 days,during days 8 to 14,mice in blank control group and negative control group were received 0.1 mL phosphate buffer solution(PBS)by gavage every day,and mice in experiment groupⅠand experiment groupⅡwere received 150 and 300 mg/kg BTP(dissolved in 0.1 mL PBS)by gavage every day,respectively;on day 15,mice in the blank control group were received 0.2 mL PBS by gavage,and mice in negative control group,experiment groupⅠand experiment groupⅡwere received 5×109 CFU/mL ETEC bacterial suspension(resuspended in 0.2 mL PBS)by gavage,slaughter after continuous observation for 8 h.The results showed as follows:1)compared with the blank control group,the survival rate of mice of negative control group was significantly decreased(P<0.05),and the diarrhea index was significantly increased(P<0.05);the jejunum tumor necrosis factor⁃α(TNF⁃α)mRNA relative expression level was significantly in⁃creased(P<0.05),and the interleukin⁃1β(IL⁃1β)and interleukin⁃6(IL⁃6)contents were significantly in⁃creased(P<0.05);the mRNA relative expression levels of Occludin,zonula occludens⁃1(ZO⁃1),zonula oc⁃cludens⁃2(ZO⁃2)and nuclear receptor 77(Nur77)in jejunum were significantly decreased(P<0.05);the serum glutathione peroxidase(GSH⁃Px)activity was significantly decreased(P<0.05),and the malondialde⁃hyde(MDA)content was significantly increased(P<0.05).2)Compared with the negative control group,the survival rate of mice of experiment groupⅠand experiment groupⅡwas significantly increased(P<0.05),and the diarrhea index was significantly decreased(P<0.05);the jejunum TNF⁃αmRNA relative ex⁃pression level of experiment groupⅠand experiment groupⅡwas significantly decreased(P<0.05),and the IL⁃1βand IL⁃6 contents were significantly decreased(P<0.05);the mRNA relative expression levels of Oc⁃cludin and Nur77 in jejunum of experiment groupⅡwere significantly increased(P<0.05);the serum MDA content of experiment groupⅠand experiment groupⅡwas significantly decreased(P<0.05),and the serum GSH⁃Px activity of experiment groupⅡwas significantly increased(P<0.05).In conclusion,BTP can allevi⁃ate intestinal inflammation and barrier function damage caused by ETEC infection in mice,and this effect may be related to the up⁃regulation of Nur77 expression and inhibition of intestinal epithelial cell apoptosis,necrop⁃tosis and pyroptosis by BTP.