title: TLR4 expression in mouse embryonic stem cells and in stem cell-derived vascular cells is regulated by epigenetic modifications.
abstract: Embryonic stem (ES) cells and ES cell-derived differentiated cells can be used in tissue regeneration approaches. However, inflammation may pose a major hurdle. To define the inflammatory response of ES and ES cell-derived vascular cells, we exposed these cells to LPS. With the exception of MIF no significant cytokine mRNA levels were observed either at baseline or after stimulation. Further experiments revealed that these cells do not express TLR4. Analysis of the DNA methylation status of the TLR4 upstream region showed increased methylation. Moreover, in vitro methylation suppressed TLR4 promoter activity in reporter gene assays. ChIP assays showed that in this region histones H3 and H4 are hypoacetylated in ES cells. Interestingly, 5-aza-dC or TSA partially relieves this gene repression. Finally, the increased levels of TLR4 observed in ES cells after treatment with 5-aza-dC or TSA confer responsiveness to LPS, as induction of IL-6 and TNFalpha mRNA was detected in endotoxin stimulated ES cells.
authors.affiliation: Department of Cardiac and Vascular Sciences, St. George's, University of London, UK. azampeta@sgul.ac.uk
authors.forename: Anna
authors.initials: A
authors.lastname: Zampetaki
authors.forename: Qingzhong
authors.initials: Q
authors.lastname: Xiao
authors.forename: Lingfang
authors.initials: L
authors.lastname: Zeng
authors.forename: Yanhua
authors.initials: Y
authors.lastname: Hu
authors.forename: Qingbo
authors.initials: Q
authors.lastname: Xu
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D044127:Epigenesis, Genetic / Q000187:drug effects / Q000276:immunology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D006877:Hydroxamic Acids / Q000008:administration & dosage; D018836:Inflammation Mediators / Q000276:immunology*; D008070:Lipopolysaccharides / Q000008:administration & dosage; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000276:immunology*
chemical_list: D006877:Hydroxamic Acids; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; C012589:trichostatin A