Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Ras GTPase Homologues Make Redundant Contributions to RA FLS Activation and Broad Silencing of Ras Proteins Decreases Inflammation and Joint Destruction in Experimental Arthritis.

de Launay1,  Daphne, Vreijling1,  Jeroen, Abreu1,  Joana, Grabiec1,  Aleksander, van Maanen2,  Marjolein, Sanders2,  Marjolein, Vervoordeldonk2,  Margriet

Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
Academic Medical Center, University of Amsterdam, The Netherlands
Santaris Pharma A/S, Horsholm, Denmark

Changes in expression and activation of Ras proteins are thought to contribute to the pathologic phenotype of stromal fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA). Here we examined the expression of each Ras protein in the synovial tissue of RA patients and disease controls, and the contributions of H-, K-, and N-Ras homologues to FLS activation in vitro and experimental arthritis in vivo.

Methods:

Synovial Ras homolog expression was determined by immunohistochemistry and digital image analysis in patients with RA (n = 10), inflammatory osteoarthritis (n = 4) and reactive arthritis (n = 7). In a second cohort consisting of patients with RA (n = 20) and psoriatic arthritis (PsA) (n = 19), Ras homolog expression was monitored by immunohistochemistry and mRNA expression. Ras protein and mRNA expression was examined in RA and PsA FLS. The activation status of Ras homolgues in RA FLS following stimulation with TNF and IL-1 was determined by affinity precipitation and immunoblotting. RA FLS were transfected with active mutants of H-, K-, and N-Ras, and Ras protein expression was specifically or broadly silenced using locked nucleic acids (LNA), and effects on basal and IL-1-dependent cytokine and MMP-3 production assessed. The potential therapeutic effects of broad, pan-Ras silencing in murine collagen-induced arthritis (CIA) were examined using pan-Ras and control LNA (1 mg/kg, 3 times weekly ip, 8 mice per group).

Results:

Similar levels of each Ras homolog were expressed in RA and disease control synovial tissue, although H-Ras protein and mRNA expression was significantly elevated in RA synovial tissue and FLS compared to PsA. Each Ras protein was also expressed in RA FLS and activated by TNF and IL-1. H-Ras, but not other Ras homolgues, was sufficient and required for spontaneous FLS MMP-3 production (P < 0.05), while multiple Ras proteins induced IL-6 and IL-8 induction, and each silencing of each Ras homolog suppressed IL-1-induced IL-6 production (P < 0.05). The three Ras homologues also redundantly activated overlapping sets of MAP kinase, NF-kappaB and PI3-kinase intracellular signalling pathway in FLS. In vivo, pan-Ras LNA, which significantly suppressed synovial expression of H- and N-Ras, decreased clinical severity of CIA in mice compared to control LNA (p< 0.005), as well as cartilage destruction (P < 0.05), bone erosion (P < 0.05), and the ratio of anti-collagen IgG2a/IgG1 auto-antibodies (P < 0.01).

Conclusions:

Overlapping contributions of Ras homologues to global inflammatory parameters of RA FLS activation and pathology in CIA, suggesting a therapeutic potential in broadly, rather than specifically, targeting closely related Ras proteins may be effective in treating RA.

Disclosures:

The authors have no disclosures or competing interests to declare.

To cite this abstract, please use the following information:
de Launay, Daphne, Vreijling, Jeroen, Abreu, Joana, Grabiec, Aleksander, van Maanen, Marjolein, Sanders, Marjolein, et al; Ras GTPase Homologues Make Redundant Contributions to RA FLS Activation and Broad Silencing of Ras Proteins Decreases Inflammation and Joint Destruction in Experimental Arthritis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :1529
DOI: 10.1002/art.29295

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