title: Tumor necrosis factor alpha acceleration of inflammatory responses by down-regulating heme oxygenase 1 in human peripheral monocytes.
abstract: OBJECTIVE
  To examine the interaction between heme oxygenase 1 (HO-1), a stress-induced antiinflammatory protein, and tumor necrosis factor alpha (TNFalpha) in human peripheral blood monocytes.
  
  
  METHODS
  Peripheral blood mononuclear cells (PBMCs) were obtained from healthy donors or from patients with rheumatoid arthritis (RA) receiving the anti-tumor necrosis factor alpha (anti-TNFalpha) monoclonal antibody infliximab. CD14+ cells were isolated by magnetic cell sorting, cultured with TNFalpha or auranofin, and transfected with a plasmid encoding HO-1 or an HO-1-specific small interfering RNA vector. Protein and messenger RNA (mRNA) levels were examined by immunoblotting and real-time polymerase chain reaction. Cytokine levels in culture supernatants were measured by enzyme-linked immunosorbent assay. HO-1 gene transcription was evaluated using a luciferase reporter gene assay. Actinomycin D and cycloheximide were used to monitor the stability of mRNA and protein.
  
  
  RESULTS
  HO-1 is constitutively expressed by CD14+ PBMCs from healthy donors. TNFalpha suppressed HO-1 expression by accelerating the decay of mRNA without affecting gene transcription or protein stability. Forced expression or selective knock-down of the HO-1 gene expression resulted in down-regulation or up-regulation, respectively, of proinflammatory cytokine synthesis by monocytes. Treatment with infliximab significantly increased HO-1 mRNA levels and reduced TNFalpha synthesis by PBMCs from RA patients.
  
  
  CONCLUSIONS
  TNFalpha accelerated inflammatory responses by down-regulating HO-1 expression in human monocytes. TNF antagonists may block this TNF-dependent suppression of HO-1 expression, resulting in an amelioration of inflammation.
authors.affiliation: Yokohama City University, Graduate School of Medicine, Yokohama, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kirino
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Takeno
authors.forename: Shuji
authors.initials: S
authors.lastname: Murakami
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Hideo
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Kenji
authors.initials: K
authors.lastname: Miura
authors.forename: Haruko
authors.initials: H
authors.lastname: Ideguchi
authors.forename: Shigeru
authors.initials: S
authors.lastname: Ohno
authors.forename: Atsuhisa
authors.initials: A
authors.lastname: Ueda
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Ishigatsubo
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D018501:Antirheumatic Agents / Q000494:pharmacology; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000235:genetics / Q000503:physiopathology*; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics; D015536:Down-Regulation / Q000187:drug effects*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D051547:Heme Oxygenase-1 / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D000069285:Infliximab; D018950:Lipopolysaccharide Receptors / Q000235:genetics / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000201:enzymology* / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000494:pharmacology*
chemical_list: D000911:Antibodies, Monoclonal; D018501:Antirheumatic Agents; D018076:DNA, Complementary; D018950:Lipopolysaccharide Receptors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab; D051547:Heme Oxygenase-1