title: Human peritoneal mesothelial cells respond to bacterial ligands through a specific subset of Toll-like receptors.
abstract: BACKGROUND
  Bacterial infection remains a major cause of morbidity and mortality in peritoneal dialysis (PD) patients worldwide. Previous studies have identified a key role for mesothelial cells, lining the peritoneal cavity, in coordinating inflammation and host defense. Toll-like receptor (TLR) involvement in early activation events within the mesothelium, however, remains poorly defined. To investigate the initiation of bacterial peritonitis, we characterized TLR activation by bacterial ligands in human peritoneal mesothelial cells (HPMC).
  
  
  METHODS
  Primary HPMC were isolated from omental biopsies and TLR expression detected by real-time polymerase chain reaction (PCR), reverse transcription (RT)-PCR and flow cytometry. The responsiveness of HPMC to specific bacterial TLR agonists was determined using chemokine production as a biological readout. The requirement for CD14 in HPMC responses to a clinically relevant Staphylococcus epidermidis cell-free supernatant (SES) was investigated using soluble CD14 or anti-CD14-blocking antibodies.
  
  
  RESULTS
  Real-time PCR detected TLR1-6 messenger RNA expression in HPMC and responses to TLR2/1 and TLR2/6 ligands and SES. No cell surface TLR4 expression or responses to lipopolysaccharide were detectable in HPMC, but they did respond to flagellin, a TLR5 ligand. SES-mediated responses were dependent on TLR2 but did not require CD14 in HPMC for optimal efficiency, unlike peripheral blood mononuclear cells. HPMC expression of TLR2 was also modulated by TLR2 ligands and inflammatory cytokines.
  
  
  CONCLUSIONS
  These data suggest that mesothelial cell activation by TLR2/1, TLR2/6 and TLR5 contributes to bacterial recognition influencing the course of the infective process and has implications for improving treatment of infection in PD patients.
authors.affiliation: Department of Infection, Immunity and Biochemistry, School of Medicine, Cardiff University, Cardiff, UK.
authors.forename: Chantal S
authors.initials: CS
authors.lastname: Colmont
authors.forename: Anne-Catherine
authors.initials: AC
authors.lastname: Raby
authors.forename: Vincent
authors.initials: V
authors.lastname: Dioszeghy
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Lebouder
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Foster
authors.forename: Simon A
authors.initials: SA
authors.lastname: Jones
authors.forename: Mario O
authors.initials: MO
authors.lastname: Labéta
authors.forename: Ceri A
authors.initials: CA
authors.lastname: Fielding
authors.forename: Nicholas
authors.initials: N
authors.lastname: Topley
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000502:physiology*; D006801:Humans; D008024:Ligands; D010537:Peritoneum / Q000166:cytology*; D051193:Toll-Like Receptors / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D008024:Ligands; D051193:Toll-Like Receptors