title: Differential induction of nitric oxide synthase in hepatocytes during endotoxemia and the acute-phase response.
abstract: OBJECTIVE
  Nitric oxide (NO) is a potent biologic mediator produced by hepatocytes following exposure to cytokines and lipopolysaccharide (LPS). These cytokines are also known to regulate induction of the hepatic acute-phase response. The objective of this study was to determine whether inducible nitric oxide synthase (iNOS), the enzyme that produces NO, is expressed as part of the hepatic acute-phase response.
  
  
  METHODS
  The gene expression for inducible NOS (iNOS) as well as alpha 1-acid glycoprotein (AGP), an established acute-phase reactant, was measured by Northern blot analysis in rat hepatocytes in vivo during endotoxemia (LPS injection) and during the acute-phase response produced by hindlimb turpentine injection. Hepatocyte iNOS messenger RNA (mRNA) levels were correlated with iNOS activity and circulating plasma nitrite and nitrate levels. In vitro, iNOS and AGP mRNA levels were determined in cultured hepatocytes stimulated with interleukin 6 (IL-6), interleukin 1 beta (IL-1 beta), tumor necrosis factor alpha (TNF-alpha), or dexamethasone.
  
  
  RESULTS
  The AGP mRNA levels were increased in vivo following both LPS and turpentine injection, while iNOS expression was induced only by LPS injection. Hepatocyte iNOS activity and plasma nitrite and nitrate levels also increased after LPS treatment. In vitro, the cytokine combination IL-6, IL-1 beta, and TNF-alpha induced hepatocyte iNOS expression but had minimal effects on AGP in the absence of dexamethasone. Addition of dexamethasone alone markedly increased AGP mRNA levels, with further increases seen with TNF-alpha or IL-1 beta addition. In contrast, dexamethasone decreased iNOS expression.
  
  
  CONCLUSIONS
  The results show that hepatocyte iNOS expression is not part of the acute-phase response induced by remote inflammation and indicates that iNOS is differentially regulated from the acute-phase reactant, AGP.
authors.affiliation: Department of Surgery, University of Pittsburg, Pa.
authors.forename: D A
authors.initials: DA
authors.lastname: Geller
authors.forename: P D
authors.initials: PD
authors.lastname: Freeswick
authors.forename: D
authors.initials: D
authors.lastname: Nguyen
authors.forename: A K
authors.initials: AK
authors.lastname: Nussler
authors.forename: M
authors.initials: M
authors.lastname: Di Silvio
authors.forename: R A
authors.initials: RA
authors.lastname: Shapiro
authors.forename: S C
authors.initials: SC
authors.lastname: Wang
authors.forename: R L
authors.initials: RL
authors.lastname: Simmons
authors.forename: T R
authors.initials: TR
authors.lastname: Billiar
mesh_terms: D000210:Acute-Phase Reaction / Q000097:blood / Q000201:enzymology*; D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D000818:Animals; D002478:Cells, Cultured; D004731:Endotoxins / Q000009:adverse effects* / Q000097:blood; D004790:Enzyme Induction; D004926:Escherichia coli; D005786:Gene Expression Regulation; D015971:Gene Expression Regulation, Enzymologic; D007375:Interleukin-1 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000009:adverse effects / Q000097:blood; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D008297:Male; D009566:Nitrates / Q000097:blood; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase; D009573:Nitrites / Q000097:blood; D009961:Orosomucoid / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014425:Turpentine / Q000009:adverse effects
chemical_list: D004731:Endotoxins; D007375:Interleukin-1; D015850:Interleukin-6; D008070:Lipopolysaccharides; D009566:Nitrates; D009573:Nitrites; D009961:Orosomucoid; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D014425:Turpentine