title: Modulation of interleukin-1 receptors followed by endotoxin lipopolysaccharide treatment in the mouse AtT-20 pituitary tumor cell line.
abstract: OBJECTIVE
  We have previously reported the characterization and regulation of interleukin-1 (IL-1) receptors utilizing [125I]IL-1 binding assay in male C57BL/6 mice and the mouse AtT-20 pituitary tumor cells. In the present study, we examine IL-1 receptors using an immunoblotting method to further characterize the mechanisms regulating the interactions of IL-1 receptors with endotoxin, lipopolysaccharide (LPS).
  
  
  METHODS
  We established Western blotting for IL-1 receptors using AtT-20 mouse pituitary tumor cells.
  
  
  RESULTS
  Several bands were seen; however, only the 105-kD band was neutralized with a 5-fold excess of IL-1 receptor- blocking peptides, suggesting that this band is specific for IL-1 receptors. Next, we investigated the effect of LPS and IL-1beta on IL-1 receptors. Treatment of AtT-20 cells with 0.01 microg/ml of LPS did not affect IL-1 receptors. In contrast, 1 microg/ml of LPS significantly increased IL-1 receptors in AtT-20 cells compared with the control group. In addition, [125I]IL-1beta binding was markedly increased followed by 1 microg/ml of LPS. In contrast, 1 nM recombinant human IL-1beta significantly decreased IL-1 receptors in AtT-20 cells compared with the control group although treatment of AtT-20 cells with 0.01 nM IL-1beta did not affect IL-1 receptors. LPS (0.1 and 1 microg/ml) did not affect IL-1beta concentrations in the medium of AtT-20 cell culture. IL-1beta concentrations in the homogenates from AtT-20 cells were significantly decreased after 1 microg/ml of LPS treatment but not after 0.01 microg/ml LPS.
  
  
  CONCLUSIONS
  These data demonstrate that LPS and IL-1beta differentially modulate IL-1 receptors in AtT-20 cells and LPS-induced modulation of IL-1 receptors may provide a novel mechanism for the actions of LPS to alter pituitary function during endotoxemia. Additional in vivo studies are necessary to determine the physiological relevance of this in vitro phenomenon.
authors.affiliation: Second Department of Internal Medicine, Kochi Medical School, Nankoku, Kochi, Japan. kumagaic@kochi-ms.ac.jp
authors.forename: Chizuru
authors.initials: C
authors.lastname: Kumagai
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Takao
authors.forename: Reiko
authors.initials: R
authors.lastname: Matsumoto
authors.forename: Koichi
authors.initials: K
authors.lastname: Asaba
authors.forename: Kozo
authors.initials: K
authors.lastname: Hashimoto
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects / Q000276:immunology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000276:immunology; D019446:Endotoxemia / Q000276:immunology / Q000503:physiopathology; D007155:Immunologic Factors / Q000276:immunology / Q000494:pharmacology*; D007375:Interleukin-1 / Q000276:immunology / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology*; D008297:Male; D051379:Mice; D010911:Pituitary Neoplasms / Q000188:drug therapy / Q000276:immunology* / Q000378:metabolism; D017472:Receptors, Interleukin-1 / Q000187:drug effects / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000276:immunology / Q000494:pharmacology
chemical_list: D007155:Immunologic Factors; D007375:Interleukin-1; D008070:Lipopolysaccharides; D017472:Receptors, Interleukin-1; D011993:Recombinant Fusion Proteins