title: Interleukin-6 promotes destabilized angiogenesis by modulating angiopoietin expression in rheumatoid arthritis.
abstract: OBJECTIVE
  To examine whether IL-6 promotes angiogenesis by modulating angiopoietin (Ang) expression in RA.
  
  
  METHODS
  Synovial fibroblasts derived from RA patients (RASFs) and human umbilical vein endothelial cells (HUVECs) were co-cultured for 6 days with or without recombinant IL-6, VEGF or Ang-1. HUVECs were stained with anti-CD31 antibody and their growth was determined by quantifying the CD31-positive area. SFs were collected from RA (n = 25) and OA (n = 7) patients.
  
  
  RESULTS
  In the co-culture system, IL-6 and VEGF significantly enhanced HUVEC growth to a similar extent. However, the morphology of proliferating cells was distinct between IL-6- and VEGF-stimulated HUVEC. HUVEC stimulated with IL-6 exhibited small, loose clusters surrounded by dispersed single cells, suggesting destabilized angiogenesis by IL-6. In the supernatants, IL-6 up-regulated VEGF compared with controls and Ang-2, while it down-regulated Ang-1. In contrast, down-regulation of Ang-1 was not observed with VEGF stimulation. Consistent with the destabilized morphology, stimulation with IL-6 decreased cell surface expression of vascular endothelial cadherin (VE-cadherin) on HUVEC, presumably by inducing internalization. Interestingly, adding recombinant Ang-1 partially inhibited IL-6-induced morphological changes in HUVEC including a destabilized morphology with small, loose clusters and internalization of VE-cadherin. In SFs from RA patients, VEGF was negatively correlated with Ang-1 (r = -0.559, P=0.004).
  
  
  CONCLUSIONS
  IL-6 not only enhances VEGF expression but also inhibits Ang-1 signalling by directly down-regulating Ang-1 expression and up-regulating Ang-2, an antagonist of Ang-1. These synergistic effects may play a critical role in destabilized angiogenesis in RA.
authors.affiliation: Division of Rheumatology, Jichi Medical University, Saitama Medical Center, 1-847 Amanuma-cho, Omiya-ku, Saitama, Japan. kuroiwa0911@gmail.com
authors.forename: Ken
authors.initials: K
authors.lastname: Kayakabe
authors.forename: Takashi
authors.initials: T
authors.lastname: Kuroiwa
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Sakurai
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Ikeuchi
authors.forename: Anastasie Tshilela
authors.initials: AT
authors.lastname: Kadiombo
authors.forename: Toru
authors.initials: T
authors.lastname: Sakairi
authors.forename: Takayuki
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Akito
authors.initials: A
authors.lastname: Maeshima
authors.forename: Keiju
authors.initials: K
authors.lastname: Hiromura
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nojima
mesh_terms: D042683:Angiopoietin-1 / Q000378:metabolism* / Q000494:pharmacology; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000473:pathology; D015415:Biomarkers / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D018920:Coculture Techniques; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000502:physiology; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology*; D009389:Neovascularization, Pathologic / Q000188:drug therapy* / Q000473:pathology; D011994:Recombinant Proteins; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology
chemical_list: C467630:ANGPT1 protein, human; D042683:Angiopoietin-1; D015415:Biomarkers; D015850:Interleukin-6; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A