Article

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

Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
Arthritis & Rheumatology (Impact Factor: 7.87). 10/2006; 54(10):3135-43. DOI: 10.1002/art.22139
Source: PubMed

ABSTRACT 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.
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.
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.
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.

Download full-text

Full-text

Available from: Paul P Tak, Oct 30, 2014
0 Followers
 · 
61 Views
  • Source
  • Source
  • [Show abstract] [Hide abstract]
    ABSTRACT: Leukocyte-function-associated antigen-1 (LFA-1) is an integrin that is critical for T-cell adhesion and immunologic responses. As a transmembrane receptor and adhesion molecule, LFA-1 signals bidirectionally, whereby information about extracellular ligands is passed outside-in while cellular activation is transmitted inside-out to the adhesive ectodomain. Here, we review the role of small guanosine triphosphatases (GTPases) in LFA-1 signaling. Rap1, a Ras-related GTPase, appears to be central to LFA-1 function. Rap1 is regulated by receptor signaling [e.g. T-cell receptor (TCR), CD28, and cytotoxic T-lymphocyte antigen-4 (CTLA-4)] and by adapter proteins [e.g. adhesion and degranulation-promoting adapter protein (ADAP) and Src kinase-associated phosphoprotein of 55 kDa (SKAP-55)]. Inside-out signaling flows through Rap1 to regulator of adhesion and cell polarization enriched in lymphoid tissues (RAPL) and Rap1-GTP interacting adapter molecule (RIAM) that act in conjunction with the cytoskeleton on the cytosolic domain of LFA-1 to increase adhesion of the ectodomain. Outside-in signaling also relies on small GTPases such as Rho proteins. Vav-1, a guanine nucleotide exchange factor for Rho proteins, is activated as a consequence of LFA-1 engagement. Jun-activating binding protein-1 (JAB-1) and cytohesin-1 have been implicated as possible outside-in signaling intermediates. We have recently shown that Ras is also downstream of LFA-1 engagement: LFA-1 signaling through phospholipase D (PLD) to RasGRP1 was required for Ras activation on the plasma membrane following stimulation of TCR.
    Immunological Reviews 09/2007; 218(1):114-25. DOI:10.1111/j.1600-065X.2007.00538.x · 12.91 Impact Factor
Show more