Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan;
Division of Applied Bioscience, Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan;
Am J Physiol Cell Physiol. 2014 Jul 15;307(2):C162-8. doi: 10.1152/ajpcell.00271.2013. Epub 2014 May 21.
N-acyl-homoserine lactones (AHL) are quorum-sensing molecules in bacteria that play important roles in regulating virulence gene expression in pathogens such as Pseudomonas aeruginosa. The present study compared responses between undifferentiated and differentiated Caco-2 cells to N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12-HSL). A low concentration of 3-oxo-C12-HSL (30 μM) is sufficient to reduce viability accompanied by apoptosis via the suppression of phosphorylation by Akt in undifferentiated Caco-2 cells. The suppression of Akt phosphorylation appears specific in 3-oxo-C12-HSL, because other AHLs did not influence the phosphorylation status of Akt. The reduced viability induced by 3-oxo-C12-HSL was partially recovered by constitutively active Akt overexpression in undifferentiated Caco-2 cells. Since mucin is considered a vital component of the gut barrier, we investigated whether mucin protects cellular functions induced by 3-oxo-C12-HSL in undifferentiated Caco-2 cells. The results showed that mucin protected undifferentiated Caco-2 cells from apoptosis induced by 3-oxo-C12-HSL. 3-Oxo-C12-HSL did not induce cell death in differentiated Caco-2 cells that expressed higher levels of mucin 3 (MUC3) than undifferentiated Caco-2 cells. In addition, 3-oxo-C12-HSL promoted cell death in undifferentiated Caco-2 cells transfected with MUC3 siRNA and reduced MUC3 expression in undifferentiated Caco-2 cells. Therefore, MUC3 might be responsible for the survival of undifferentiated intestinal epithelial cells in the presence of 3-oxo-C12-HSL through regulating Akt phosphorylation. In conclusion, 3-oxo-C12-HSL might influence the survival of undifferentiated intestinal epithelial cells as well as interactions between these cells and pathogens.
N-酰基高丝氨酸内酯（AHL）是细菌中的群体感应分子，在调节铜绿假单胞菌等病原体的毒力基因表达方面发挥着重要作用。本研究比较了未分化和分化的 Caco-2 细胞对 N-（3-氧代十二烷酰基）-L-高丝氨酸内酯（3-oxo-C12-HSL）的反应。低浓度的 3-oxo-C12-HSL（30 μM）足以通过抑制未分化的 Caco-2 细胞中 Akt 的磷酸化来降低细胞活力并伴随细胞凋亡。Akt 磷酸化的抑制作用在 3-oxo-C12-HSL 中似乎是特异性的，因为其他 AHL 不会影响 Akt 的磷酸化状态。在未分化的 Caco-2 细胞中，过表达组成型活性 Akt 可部分恢复 3-oxo-C12-HSL 诱导的细胞活力降低。由于粘蛋白被认为是肠道屏障的重要组成部分，我们研究了粘蛋白是否可以保护未分化的 Caco-2 细胞免受 3-oxo-C12-HSL 诱导的细胞功能。结果表明，粘蛋白可防止 3-oxo-C12-HSL 诱导的未分化 Caco-2 细胞凋亡。3-oxo-C12-HSL 不会诱导表达粘蛋白 3（MUC3）水平高于未分化的 Caco-2 细胞的分化的 Caco-2 细胞死亡。此外，3-oxo-C12-HSL 促进转染 MUC3 siRNA 的未分化 Caco-2 细胞死亡，并降低未分化 Caco-2 细胞中的 MUC3 表达。因此，MUC3 可能通过调节 Akt 磷酸化来负责在存在 3-oxo-C12-HSL 的情况下未分化肠上皮细胞的存活。总之，3-oxo-C12-HSL 可能会影响未分化肠上皮细胞的存活以及这些细胞与病原体之间的相互作用。
