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: 7.76). 10/2006; 54(10):3135-43. DOI: 10.1002/art.22139
Source: PubMed


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.

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Available from: Paul P Tak, Oct 30, 2014
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    • "Synovial fluid T cell Rap1 inactivation could be mimicked in RA patient peripheral blood T cells incubated with autologous synovial fluid macrophages, or peripheral blood-derived macrophages exposed to synovial fluid, in a cell contact-dependent manner [98]. Previous work had already demonstrated that TCR-dependent activation of Rap1 could be efficiently blocked by CD28 costimulation, and inclusion of CTLA4-Ig (Abatacept) in T cell-synovial fluid macrophage co-cultures prevented Rap1 inactivation (Fig. 2) [91, 98, 99]. Maintenance of Rap1 signaling by CTLA4-Ig was associated with a failure of T cells to produce high levels of ROS, and transduction of T cells with Rap1a-V12 prior to their incubation with synovial macrophages also blocked subsequent T cell ROS production [98]. "
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