title: Differentiation of monocytes into macrophages induces the upregulation of histamine H1 receptor.
abstract: BACKGROUND
  Histamine modulates several functions in human monocytes, macrophages, and dendritic cells. However, responses elicited by histamine differ depending on cell type, suggesting variable expression of histamine receptors in the monocyte/macrophage lineage.
  
  
  OBJECTIVE
  We sought to examine whether the expression of H(1) receptors was regulated by cell differentiation of human monocytes into macrophages or dendritic cells.
  
  
  METHODS
  Expression of H(1) receptor was evaluated by RT-PCR and western blot in monocytes, monocyte-derived macrophages (MDMs), monocyte-derived dendritic cells (DCs) and human lung macrophages (HLMs).
  
  
  RESULTS
  Expression of H(1) receptor mRNA and protein was higher in HLMs and DCs than in monocytes. H(1) expression was approximately 15-fold and 4-fold higher in MDMs and HLMs, respectively, as compared with that seen in monocytes. H(1) receptor protein was undetectable in monocytes, whereas it was conspicuous in MDMs. Simultaneous analysis of H(2) and H(1) mRNA expression indicated that the H(2)/H(1) ratio decreased from 202.7 +/- 14.8 in monocytes to 2.2 +/- 0.4 in MDM and 39.5 +/- 5.0 in DCs. Incubation of monocytes with histamine neither affected intracellular Ca(2+) concentrations nor influenced IL-8 production. In contrast, histamine rapidly induced a Ca(2+) signal and stimulated IL-8 production in MDMs. Both effects were inhibited by H(1) blockade with levocetirizine, but not by H(2) blockade with ranitidine.
  
  
  CONCLUSIONS
  Differentiation of monocytes into macrophages or dendritic cells is associated with profound changes of histamine receptor expression. Upregulation of H(1) receptors confers on macrophages the capacity of being activated by histamine.
  
  
  CONCLUSIONS
  Regulation of H(1) and H(2) receptor expression in the monocyte/macrophage lineage can be relevant to the pathogenesis of allergic inflammation.
authors.affiliation: Division of Clinical Immunology and Allergy, University of Naples Federico II, Naples, Italy. triggian@unina.it <triggian@unina.it>
authors.forename: Massimo
authors.initials: M
authors.lastname: Triggiani
authors.forename: Angelica
authors.initials: A
authors.lastname: Petraroli
authors.forename: Stefania
authors.initials: S
authors.lastname: Loffredo
authors.forename: Annunziata
authors.initials: A
authors.lastname: Frattini
authors.forename: Francescopaolo
authors.initials: F
authors.lastname: Granata
authors.forename: Paolo
authors.initials: P
authors.lastname: Morabito
authors.forename: Rosaria Ilaria
authors.initials: RI
authors.lastname: Staiano
authors.forename: Agnese
authors.initials: A
authors.lastname: Secondo
authors.forename: Lucio
authors.initials: L
authors.lastname: Annunziato
authors.forename: Gianni
authors.initials: G
authors.lastname: Marone
mesh_terms: D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation; D005786:Gene Expression Regulation; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis; D008264:Macrophages / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D011969:Receptors, Histamine H1 / Q000032:analysis / Q000235:genetics*; D011970:Receptors, Histamine H2 / Q000235:genetics; D015854:Up-Regulation
chemical_list: D015850:Interleukin-6; D012333:RNA, Messenger; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D006632:Histamine; D002118:Calcium