In contrast, other genes ITF2357 that had increased transcript levels in the presence of L. plantarum MB452 are known to be involved in tight junction disassembly. The gene encoding ITCH, an ubiquitin-ligase molecule, had increased expression levels in the presence of L. plantarum MB452; however, the ITCH protein is known to contribute to the degradation of occludin [27]. The increased expression of the ITCH gene may lead to an increase in the turnover of occludin protein and, therefore, may have contributed to the increased occludin

mRNA noted in this data. The gene encoding the SNAI1 protein also had increased expression in the presence of L. plantarum MB452; however, the SNAI1 protein is known to bind to occludin and claudin genes promoters suppressing their expression [28]. Although these two genes, ITCH and SNAI1, have been linked to tight junction disassembly, 17 out of the 19 tight junction-related genes with increased expression levels in response to L. plantarum MB452 exposure contribute to tight junction stability; therefore, the cumulative effect would most likely be enhanced intestinal barrier function. The ‘tightness’ of tight junctions is commonly thought to be, at least partly, due to claudins, which Antiinfection Compound Library cost are a set of bridging proteins; however, none of the claudin genes were

differentially expressed in response to L. plantarum MB452. Decreases in the abundance of claudin-2, -3 and -4 proteins (measured using western blotting) have been associated with a decrease in TEER [29]. Another study showed

that a decrease in TEER was associated with altered cellular localisation of claudin-1 and -5, but not altered abundance [30], so it is possible that L. plantarum MB452 may have altered the distribution of claudin proteins without changing gene expression and/or protein abundance. The results of this study showed that L. plantarum MB452 enhanced the expression of Carnitine palmitoyltransferase II 19 genes involved in the tight junction signalling pathway in healthy cells. A previous study showed that L. plantarum CGMCC 1258 is able to protect against the disruption of four tight junction proteins caused by Enteroinvasive E. coli ATCC 43893 (serotype O124:NM) [17]. However, another study looking at the effect of L. plantarum ATCC202195 on the expression of genes in Caco-2 cells challenged with Enteroinvasive E. coli ATCC43893 (serotype O124:NM) did not report any changes in tight junction gene expression [31]. This suggests that the L. plantarum protection against tight junction disruption was not due to it altering host gene expression, and was likely due to it inhibiting the action of the pathogen in that study. The ability to enhance the expression of tight junction-related genes is not common to all L. plantarum strains. In addition to the study that showed that L. plantarum ATCC202195 nullifies changes in Caco-2 cell gene expression induced by Enteroinvasive E.