title: Differential expression of Toll-like receptor 4 in healthy and diseased human gingiva.
abstract: OBJECTIVE
  Lipopolysaccharide (LPS)-mediated signaling in host cells involves Toll-like receptor 4 (TLR4) accessory molecules, including LPS-binding protein (LBP), cluster of differentiation 14 (CD14) and lymphocyte antigen 96 (MD-2). However, expression of these innate defense molecules in various compartments of the human periodontium is unclear. The aim of this study was to investigate the expression profile of TLR4 in human gingiva.
  
  
  METHODS
  Human gingival biopsies were collected from healthy gingival or chronic periodontitis tissue. Primary gingival keratinocytes and fibroblasts were cultured. Immunohistochemical analysis for TLR4 was performed. Transcripts of TLR4, MD-2, CD14 and LBP, and their protein products, were examined using RT-PCR, immunoprecipitation and immunoblotting. The interactions between these molecules in keratinocytes and fibroblasts were investigated by co-immunoprecipitation.
  
  
  RESULTS
  TLR4 immunoreactivity was found in healthy gingival epithelium and periodontitis tissue, and appeared to be lower in junctional epithelium ( p ≤ 0.01). Fibroblasts and inflammatory cells stained more strongly for TLR4 in diseased periodontal tissues (p < 0.001). Three TLR4 splicing variants, two MD-2 splicing variants and one CD14 mRNA were expressed by gingival keratinocytes and fibroblasts. Expression of TLR4, CD14 and MD-2 proteins was detected in keratinocytes and fibroblasts in vitro. TLR4 protein from gingival keratinocytes and fibroblasts could be co-immunoprecipitated with CD14 or MD-2, suggesting an association between the related molecules in vivo. LBP transcript was detected in gingival biopsies, but not in primary cultures of gingival keratinocytes or fibroblasts.
  
  
  CONCLUSIONS
  TLR4, CD14 and MD-2, but not LBP, are expressed in human gingival keratinocytes and fibroblasts. The TLR4 expression level in the junctional epithelium appeared to be lowest within the periodontal epithelial barrier.
authors.affiliation: Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China; Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou, China.
authors.forename: J-P
authors.initials: JP
authors.lastname: Li
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: C H C
authors.initials: CH
authors.lastname: Ng
authors.forename: M-L
authors.initials: ML
authors.lastname: Fung
authors.forename: A
authors.initials: A
authors.lastname: Xu
authors.forename: B
authors.initials: B
authors.lastname: Cheng
authors.forename: S W
authors.initials: SW
authors.lastname: Tsao
authors.forename: W K
authors.initials: WK
authors.lastname: Leung
mesh_terms: D000209:Acute-Phase Proteins / Q000032:analysis; D000328:Adult; D017398:Alternative Splicing / Q000235:genetics; D016301:Alveolar Bone Loss / Q000145:classification; D002352:Carrier Proteins / Q000032:analysis; D002478:Cells, Cultured; D055113:Chronic Periodontitis / Q000145:classification / Q000276:immunology*; D004846:Epithelial Attachment / Q000276:immunology; D004848:Epithelium / Q000276:immunology; D005091:Exons / Q000235:genetics; D005260:Female; D005347:Fibroblasts / Q000276:immunology; D005881:Gingiva / Q000276:immunology* / Q000473:pathology; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology; D015603:Keratinocytes / Q000276:immunology; D007962:Leukocytes / Q000276:immunology; D018950:Lipopolysaccharide Receptors / Q000032:analysis / Q000235:genetics; D008070:Lipopolysaccharides / Q000276:immunology; D051218:Lymphocyte Antigen 96 / Q000032:analysis / Q000235:genetics; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis; D008875:Middle Aged; D017622:Periodontal Attachment Loss / Q000145:classification; D010514:Periodontal Pocket / Q000145:classification / Q000473:pathology; D051197:Toll-Like Receptor 4 / Q000032:analysis* / Q000235:genetics; D000099231:Lipopolysaccharide-Binding Protein
chemical_list: D000209:Acute-Phase Proteins; D002352:Carrier Proteins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins; D051197:Toll-Like Receptor 4; D000099231:Lipopolysaccharide-Binding Protein; C495377:LY96 protein, human; C495345:TLR4 protein, human
keywords: Toll-like receptor 4; chronic periodontitis; cluster of differentiation; fibroblasts; keratinocytes; lymphocyte antigen 96