title: Cellular differentiation-induced attenuation of LPS response in HT-29 cells is related to the down-regulation of TLR4 expression.
abstract: Intestinal epithelial cells not only present a physical barrier to bacteria but also participate actively in immune and inflammatory responses. The migration of epithelial cells from the crypt base to the surface is accompanied by a cellular differentiation that leads to important morphological and functional changes. It has been reported that the differentiation of colonic epithelial cells is associated with reduced interleukin (IL)-8 responses to IL-1beta. Although toll-like receptor 4 (TLR4) has been previously identified to be an important component of mucosal immunity to lipopolysaccharide (LPS) in the colon, little is known about the regulation of TLR4 in colonic epithelial cells during cellular differentiation. We investigated the effects of differentiation on LPS-induced IL-8 secretion and on the expression of TLR4. Differentiation was induced in colon cancer cell line HT-29 cells by butyrate treatment or by post-confluence culture and assessed by measuring alkaline phosphatase (AP) activity. IL-8 secretion was measured by ELISA, and TLR4 protein and mRNA expressions were followed by Western blot and RT-PCR, respectively. HT-29 cells were found to be dose-dependently responsive to LPS. AP activity increased in HT-29 cells by differentiation induced by treatment with butyrate or post-confluence culture. We found that IL-8 secretion induced by LPS was strongly attenuated in differentiated cells versus undifferentiated cells, and that cellular differentiation also attenuated TLR4 mRNA and protein expressions. Pretreating HT-29 cells with tumor necrosis factor (TNF)-alpha or interferon (INF)-gamma augmented LPS-induced IL-8 secretion and TLR4 expression. These TNF-alpha- or INF-gamma-induced augmentations of LPS response and TLR4 expression were all down-regulated by differentiation. Collectively, we conclude that cellular differentiation attenuates IL-8 secretion induced by LPS in HT-29 cells, and this attenuation is related with the down-regulation of TLR4 expression.
authors.affiliation: Department of Internal Medicine, Brain Korea 21 Project for Medical Sciences, Yonsei University College of Medicine, Seoul.
authors.forename: Sang Kil
authors.initials: SK
authors.lastname: Lee
authors.forename: Tae
authors.initials: T
authors.lastname: Il Kim
authors.forename: Yun Kyung
authors.initials: YK
authors.lastname: Kim
authors.forename: Chang Hwan
authors.initials: CH
authors.lastname: Choi
authors.forename: Kyung Min
authors.initials: KM
authors.lastname: Yang
authors.forename: Boah
authors.initials: B
authors.lastname: Chae
authors.forename: Won Ho
authors.initials: WH
authors.lastname: Kim
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D002087:Butyrates / Q000494:pharmacology; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D003106:Colon / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects*; D019073:HT29 Cells; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D002087:Butyrates; D016209:Interleukin-8; D008070:Lipopolysaccharides; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D000469:Alkaline Phosphatase