title: Enhanced innate immune responsiveness and intolerance to intestinal endotoxins in human biliary epithelial cells contributes to chronic cholangitis.
abstract: BACKGROUND
  Pattern recognition receptors (PRRs) orchestrate the innate immune defence in human biliary epithelial cells (BECs). Tight control of PRR signalling provides tolerance to physiological amounts of intestinal endotoxins in human bile to avoid constant innate immune activation in BECs.
  
  
  OBJECTIVE
  We wanted to determine whether inappropriate innate immune responses to intestinal endotoxins contribute to the development and perpetuation of chronic biliary inflammation.
  
  
  METHODS
  We examined PRR-mediated innate immune responses and protective endotoxin tolerance in primary BECs isolated from patients with primary sclerosing cholangitis (PSC), alcoholic liver disease and patients without chronic liver disease. Expression studies comprised northern blots, RT-PCR, Western blots and immunocytochemistry. Functional studies comprised immuno-precipitation Western blots, FACS for endotoxin uptake, and NF-κB activation assays and ELISA for secreted IL-8 and tumour necrosis factor (TNF)-α.
  
  
  RESULTS
  Primary BECs from explanted PSC livers showed reversibly increased TLR and NOD protein expression and activation of the MyD88/IRAK signalling complex. Consecutively, PSC BECs exhibited inappropriate innate immune responses to endotoxins and did not develop immune tolerance after repeated endotoxin exposures. This endotoxin hyper-responsiveness was probably because of the stimulatory effect of abundantly expressed IFN-γ and TNF-α in PSC livers, which stimulated TLR4-mediated endotoxin signalling in BECs, leading to increased TLR4-mediated endotoxin incorporation and impaired inactivation of the TLR4 signalling cascade. As TNF-α inhibition partly restored protective innate immune tolerance, endogenous TNF-α secretion probably contributed to inappropriate endotoxin responses in BECs.
  
  
  CONCLUSIONS
  Inappropriate innate immune responses to intestinal endotoxins and subsequent endotoxin intolerance because of enhanced PRR signalling in BECs probably contribute to chronic cholangitis.
authors.affiliation: Medizinische Klinik mit Schwerpunkt Hepatologie und Gastroenterologie, Charité-Universitätsmedizin Berlin, Campus Virchow Klinikum, Berlin, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Mueller
authors.forename: Claudia
authors.initials: C
authors.lastname: Beutler
authors.forename: Almudena Hurtado
authors.initials: AH
authors.lastname: Picó
authors.forename: Oren
authors.initials: O
authors.lastname: Shibolet
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Pratt
authors.forename: Andreas
authors.initials: A
authors.lastname: Pascher
authors.forename: Peter
authors.initials: P
authors.lastname: Neuhaus
authors.forename: Bertram
authors.initials: B
authors.lastname: Wiedenmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Berg
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Podolsky
mesh_terms: D000328:Adult; D001659:Biliary Tract / Q000166:cytology*; D015152:Blotting, Northern; D015153:Blotting, Western; D015209:Cholangitis, Sclerosing / Q000209:etiology*; D004731:Endotoxins / Q000276:immunology* / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000276:immunology*; D005434:Flow Cytometry; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology*; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D016209:Interleukin-8 / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D008875:Middle Aged; D016328:NF-kappa B / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D051192:Receptors, Pattern Recognition / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D004731:Endotoxins; D016209:Interleukin-8; D016328:NF-kappa B; D051192:Receptors, Pattern Recognition; D014409:Tumor Necrosis Factor-alpha