title: Acute-phase hepatocytes regulate liver sinusoidal cell mediator production.
abstract: BACKGROUND
  Overproduction of liver sinusoidal cell (LCS) mediators in response to endotoxemia or gram-negative infection that follows tissue injury may contribute to hepatic dysfunction.
  
  
  OBJECTIVE
  To better define the role of hepatocyte-derived acute-phase reactants in the regulation of sinusoidal cell mediator production following sequential insults, we tested the hypothesis that interleukin-6 (IL-6) prestimulation alters hepatocyte regulation of lipopolysaccharide (LPS)-stimulated sinusoidal cell tumor necrosis factor (TNF), IL-6, and nitric oxide production.
  
  
  METHODS
  Hepatocytes and LSCs were isolated from Wistar rats, and in vitro responses were compared between LSCs alone and hepatocyte-LSC cocultures. Cocultures and LSCs alone were sequentially stimulated with IL-6 (5000 U/mL) then LPS (dose-response), and culture supernatants were analyzed for TNF (L929 cytolysis), IL-6 (7TD1 proliferation), and nitric oxide (Griess reaction). Induction of acute-phase protein synthesis by the stimulation of hepatocytes with IL-6 and dexamethasone (0.1 mumol/L) was assayed by methionine radiolabeling and SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). Coculture levels of messenger RNA for TNF-alpha and IL-6 were examined by RNA extraction and reverse transcriptase polymerase chain reaction with specific primers.
  
  
  RESULTS
  Interleukin-6 and dexamethasone signal hepatocyte acute-phase protein synthesis. Prestimulation of cocultures, but not of LSCs alone, with IL-6 inhibits LPS-stimulated IL-6 and nitric oxide production significantly. Bioactivity of TNF is reduced to a lesser extent. Polymerase chain reaction analysis demonstrated similar levels of TNF and IL-6 message following sequential stimulation.
  
  
  CONCLUSIONS
  Interleukin-6-stimulated acute-phase hepatocytes limit LPS-stimulated coculture cytokine bioactivity and nitric oxide production. This hepatocyte response may provide a local counterregulatory mechanism to limit LSC-mediated injury.
authors.affiliation: Department of Surgery, University of Texas, Southwestern Medical Center, Dallas.
authors.forename: P
authors.initials: P
authors.lastname: Bankey
authors.forename: M
authors.initials: M
authors.lastname: Prager
authors.forename: D
authors.initials: D
authors.lastname: Geldon
authors.forename: S
authors.initials: S
authors.lastname: Taylor
authors.forename: K
authors.initials: K
authors.lastname: McIntyre
mesh_terms: D000209:Acute-Phase Proteins / Q000096:biosynthesis; D000210:Acute-Phase Reaction / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D066298:In Vitro Techniques; D018836:Inflammation Mediators / Q000378:metabolism*; D015850:Interleukin-6 / Q000096:biosynthesis / Q000502:physiology; D008099:Liver / Q000098:blood supply / Q000166:cytology / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis; D016133:Polymerase Chain Reaction; D051381:Rats; D017208:Rats, Wistar; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D000209:Acute-Phase Proteins; D018836:Inflammation Mediators; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide