title: CTLA-4IG suppresses reactive oxygen species by preventing synovial adherent cell-induced inactivation of Rap1, a Ras family GTPASE mediator of oxidative stress in rheumatoid arthritis T cells.
abstract: OBJECTIVE
  Oxidative stress contributes to the inflammatory properties of rheumatoid arthritis (RA) synovial T lymphocytes. This study was undertaken to investigate the mechanisms leading to production of reactive oxygen species (ROS) and oxidative stress in RA synovial T lymphocytes.
  
  
  METHODS
  ROS production in T lymphocytes from the peripheral blood (PB) of healthy donors and from the PB and synovial fluid (SF) of RA patients was measured by ROS-dependent fluorescence of 6-carboxy-2',7'-dichlorofluorescein. Rap1 GTPase activation was assessed by activation-specific probe precipitation. Proliferation of RA PB and SF T lymphocytes was assayed by 3H-thymidine incorporation. In some experiments, RA PB T cells were preincubated with autologous SF or with PB or SF adherent cells. Experiments were performed in the absence or presence of transwell membranes or CTLA-4Ig fusion proteins. Short- and long-term stimulations of healthy donor PB T lymphocytes were performed with inflammatory cytokines, in the absence or presence of activating anti-CD28 antibodies.
  
  
  RESULTS
  T lymphocyte ROS production and Rap1 inactivation were mediated by cell-cell contact with RA synovial adherent cells, and this correlated with T cell mitogenic hyporesponsiveness. CTLA4-Ig blockade of synovial adherent cell signaling to CD28 T cells reversed the inhibition of Rap1 activity and prevented induction of ROS. Introduction of active RapV12 into T cells also prevented induction of ROS production. Coincubation of T cells with stimulating anti-CD28 antibodies and inflammatory cytokines synergistically increased T cell ROS production.
  
  
  CONCLUSIONS
  Cell-cell contact between T cells and RA synovial adherent cells mediates Rap1 inactivation and subsequent ROS production in T lymphocytes following exposure to inflammatory cytokines. This process can be blocked by CTLA4-Ig fusion protein.
authors.affiliation: Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. p.h.remans@amc.uva.nl
authors.forename: P H J
authors.initials: PH
authors.lastname: Remans
authors.forename: C A
authors.initials: CA
authors.lastname: Wijbrandts
authors.forename: M E
authors.initials: ME
authors.lastname: Sanders
authors.forename: R E
authors.initials: RE
authors.lastname: Toes
authors.forename: F C
authors.initials: FC
authors.lastname: Breedveld
authors.forename: P P
authors.initials: PP
authors.lastname: Tak
authors.forename: J M
authors.initials: JM
authors.lastname: van Laar
authors.forename: K A
authors.initials: KA
authors.lastname: Reedquist
mesh_terms: D000069594:Abatacept; D018501:Antirheumatic Agents / Q000494:pharmacology; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D018106:CD28 Antigens / Q000235:genetics / Q000378:metabolism; D002450:Cell Communication / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D018796:Immunoconjugates / Q000494:pharmacology*; D008297:Male; D018384:Oxidative Stress / Q000235:genetics / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013583:Synovial Membrane / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D020827:rap1 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D018501:Antirheumatic Agents; D018106:CD28 Antigens; D018796:Immunoconjugates; D017382:Reactive Oxygen Species; D000069594:Abatacept; D020827:rap1 GTP-Binding Proteins; D018631:ras Proteins