title: Tumor Necrosis Factor Receptor-associated Factor 6 Plays a Role in the Inflammatory Responses of Human Periodontal Ligament Fibroblasts to Enterococcus faecalis.
abstract: BACKGROUND
  Enterococcus faecalis is a frequently isolated microorganism in persistent periapical lesion or secondary infection. However, no evidence has demonstrated that E. faecalis induced inflammation directly in the apical area. This study aimed to explore the mechanism of the inflammatory responses of human periodontal ligament fibroblasts (PDLs) to E. faecalis.
  
  
  METHODS
  PDLs were stimulated with heat-killed E. faecalis (HKEF) or lipoteichoic acid from E. faecalis (LTA) with or without silencing of tumor necrosis factor receptor-associated factor 6 (TRAF6). The expressions of toll-like receptor 2/4, nucleotide-binding oligomerization domain 1/2, and TRAF6 were detected by using quantitative real-time polymerase chain reaction and Western blot. The secretions of proinflammatory cytokines, including interleukin-1β, interleukin-6, interleukin-8, and tumor necrosis factor-α, were determined in the cell supernatants with enzyme-linked immunosorbent assay.
  
  
  RESULTS
  Both HKEF and LTA stimulated the expression of toll-like receptor 2 and TRAF6 in a time-dependent manner. The secretions of proinflammatory cytokines were also increased. After silencing TRAF6, the upregulations of proinflammatory cytokines induced by HKEF or LTA were attenuated.
  
  
  CONCLUSIONS
  TRAF6 plays a pivotal role in inflammation induced by E. faecalis or its LTA in PDLs.
authors.affiliation: Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, Chengdu, China; Department of Conservative Dentistry, West China College of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Lan
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Wang
authors.affiliation: Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, Chengdu, China; Department of Conservative Dentistry, West China College of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, Chengdu, China; Department of Conservative Dentistry, West China College of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Xuedong
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, Chengdu, China; Department of Conservative Dentistry, West China College of Stomatology, Sichuan University, Chengdu, China. Electronic address: dingminghuang@163.com.
authors.forename: Dingming
authors.initials: D
authors.lastname: Huang
mesh_terms: D002478:Cells, Cultured; D013293:Enterococcus faecalis / Q000502:physiology*; D005347:Fibroblasts / Q000276:immunology; D006801:Humans; D007113:Immunity, Innate; D008070:Lipopolysaccharides / Q000276:immunology; D010485:Periapical Periodontitis / Q000276:immunology* / Q000382:microbiology; D010513:Periodontal Ligament / Q000276:immunology* / Q000382:microbiology*; D048029:TNF Receptor-Associated Factor 6 / Q000276:immunology*; D013682:Teichoic Acids / Q000276:immunology
chemical_list: D008070:Lipopolysaccharides; D048029:TNF Receptor-Associated Factor 6; D013682:Teichoic Acids; C009900:lipoteichoic acid
keywords: Enterococcus faecalis; inflammation; lipoteichoic acid; toll-like receptor; tumor necrosis factor receptor-associated factor 6