title: Regulation of NF-kappaB responses by epigenetic suppression of IkappaBalpha expression in HCT116 intestinal epithelial cells.
abstract: Intestinal epithelial cells play critical roles in regulating mucosal immunity. Since epigenetic factors such as DNA methylation and histone modifications are implicated in aging, carcinogenesis, and immunity, we set out to assess any role for epigenetic factors in the regulation of intestinal epithelial cell immune responses. Experiments were conducted using the HCT116 cell line, and a subclone was genetically engineered to lack DNA methyltransferases (DNMT). The induction of the chemokine interleukin-8 and the antiapoptotic protein cFLIP by tumor necrosis factor-alpha were markedly less in HCT116 cells lacking DNMT than in parental cells. These effects were accompanied by lower monocyte chemotaxis and higher caspase signaling in HCT116 cells lacking DNMT than parental cells. Tumor necrosis factor-alpha-induced NF-kappaB activation was blocked and IkappaBalpha expression was higher in HCT116 cells lacking DNMT than in parental cells. A CpG island in the IkappaBalpha gene promoter region was found to contain variable levels of methylation in parental HCT116 cells. Chromatin immunoprecipitation analysis of histone proteins bound to the IkappaBalpha gene promoter revealed that higher levels of IkappaBalpha expression in HCT116 cells lacking DNMT compared with parental cells were accompanied by more chromatin marks permissive to gene transcription. These findings show that epigenetic factors influence the NF-kappaB system in intestinal epithelial cells, resulting in a previously unrecognized mechanism of innate immune regulation.
authors.affiliation: Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway, Ireland.
authors.forename: Angela
authors.initials: A
authors.lastname: O'Gorman
authors.forename: Amy
authors.initials: A
authors.lastname: Colleran
authors.forename: Aideen
authors.initials: A
authors.lastname: Ryan
authors.forename: Jelena
authors.initials: J
authors.lastname: Mann
authors.forename: Laurence John
authors.initials: LJ
authors.lastname: Egan
mesh_terms: D001665:Binding Sites; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002634:Chemotaxis, Leukocyte; D042002:Chromatin Assembly and Disassembly; D018899:CpG Islands; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D004847:Epithelial Cells / Q000276:immunology*; D045325:HCT116 Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism*; D018928:Immunity, Mucosal / Q000235:genetics*; D016209:Interleukin-8 / Q000378:metabolism; D007413:Intestinal Mucosa / Q000276:immunology*; D009000:Monocytes / Q000276:immunology; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D013997:Time Factors; D015533:Transcriptional Activation; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; C508606:CXCL8 protein, human; D006657:Histones; D016209:Interleukin-8; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C505407:CASP3 protein, human; D053148:Caspase 3