中文摘要：

目的观察益生菌诱导的乳鼠结肠MUC2基因的表达及其对益生菌抑制E．coliK1株E44黏附侵袭肠屏障作用的影响。方法SD乳鼠分别用益生菌、E44株和益生菌＋E44株三组灌胃7d后，RT-PCR法观察益生菌和E44株诱导结肠MUC2基因的表达；靶向MUC2基因的shRNA真核质粒表达载体（shRNAMUC2）和阴性对照shRNANC转染人结肠癌Lovo细胞，荧光定量PCR法检测其表达水平，并通过竞争陛排斥方法检测MUC2基因对益生菌拈抗致病菌E44粘附侵袭的影响。结果灌胃益生菌组SD乳鼠肠道MUC2基因明显上调，而E44组则显著降低。用shRNAMUC2转染Lovo细胞后，与阴性对照组和空白对照组相比，其表达水平明显降低，干扰率为66．7％；益生菌对E44株粘附侵袭抑制作用明显低于未处理组，与对照组相比，E44相对粘附率为56．64％，相对侵袭率为66．64％。结论益生菌诱导的MUC2基因表达上调可能成为拮抗致病菌易位的保护机制之一；MUC2基因沉默后，益生菌对E44粘附侵袭肠上皮细胞的抑制作用明显降低。

英文摘要：

Objective To investigate MUC2 expression in rat colons induced by probiotics and its effects on the inhibition of E.coli K1 （E44） penetration of the intestinal barrier by probiotics. Methods SD rats were subjected to intragastric administration of probiotics, E44, or probiotics ＋ E44 on a daily basis for 7 days, and MUC2 expression in the colons was determined by RT-PCR. MUC2-targeted shRNA （shRNA MUC2） and scrambled shRNA plasmids （shRNA NC） were respectively transfected into Lovo cells, and the efficiency of MUC2 knockdown was determined using qRT-PCR. Competitive exclusion assay was used to evaluate the effects of the probiotics against E44 adhesion and invasion. Results Intestinal MUC2 mRNA expression was up-regulated in the rats after intragastric administration of probiotics, while E44 administration caused significantly lowered MUC2 expression. MUC2 expression was down-regulated （by 66.7%） by transfection with shRNA MUC2 in Lovo cells as compared with the negative control and mock control cells. The inhibition of E44 adherence and invasion by probiotics was significantly attenuated in transfected Lovo cell culture （in which the relative adhesion and invasion rates of E44 were 56.64% and 66.64%, respectively） as compared with those in the control group. Conclusion The up-regulation of MUC2 in rat colons can be one of the mechanisms of the probiotics in antagonizing the translocation of the pathogenic bacteria. Silencing MUC2 expression causes attenuated inhibitory effect of the probiotics on E. coli K1 penetration across human intestinal epithelial cells.