Project description:The pathogenesis of rheumatoid arthritis (RA) is complicated and involves both innate and adaptive immunity [5]. The innate immunity such as macrophages or fibroblast-like synoviocytes (FLS) in the synovium can generate inflammatory mediators, including TNF-α, IL-1, IL-6, IL-17, IFN-γ, and chemo kines that lead to synovial inflammation, bone erosion, and cartilage damage [6-8]. The IL-17 signaling mediates the autoantibody production in collagen-induced arthritis (CIA) model [9]. However, the treatment response with an anti-IL17 monoclonal antibody in RA patients shows a high degree of heterogeneity [10]. The inhibitors of the Janus kinase (JAK) pathway are approved for RA patients [11]. These data suggest that the targeted multiple cytokines through the JAK pathway are useful for RA treatment. Disturbance of type I IFNs (IFNs-I) signaling and production drive autoimmune development [12]. The presymptomatic RA patients display an increase of IFNs-I before the onset of symptoms [13]. The RA patients also show the elevation of IFN- α in the synovial fluid and high expression of IFNs-I regulated gene in peripheral blood mononuclear cells (PBMC) [14]. However, the role of IFNs-I in arthritis and bone homeostasis has suggested the accelerating effect of arthritis and bone damage. The interferon-alpha receptor knockout mice develop arthritis severity higher than wild-type mice in the model of antigen-induced arthritis [15]. IFNs-I also affects the bone homeostasis by inhibiting osteoclastogenesis via receptor activator of nuclear factor-kappa B (RANK) pathway, and reduction of c-FOS expression [16-18]. Therefore, the goal of RA treatment with antagonizing the IFNs-I pathway has to be optimized between efficacy and potentially adverse effect. STING is a cytosolic DNA sensor that initiates the production of IFNs-I. STING functions have been reported as both pro-inflammatory signaling and negative regulator against inflammation [19-21]. The mutation in exon 5 of the STING gene results in gain function leading to initiate inflammation and cause the Sting associated vasculopathy with onset in infancy (SAVI) [22]. Loss of STING function rescues DNaseII-deficient mice from lethality and polyarthritis [23]. However, Sting-deficient lupus mice (MRL/Lpr mice) show higher and earlier mortality than Sting-sufficient MRL/Lpr mice [24]. The pathology also shows lymphoid hypertrophy with a higher amount of macrophages and granulocytes infiltration, autoantibodies, and cytokine [24]. The objective of this study was to identify the role of STING in the pathogenesis of rheumatoid arthritis using collagen-induced arthritis (CIA) model as a representative model of the human RA.

Project description:Rheumatoid arthritis is a prototypical autoimmune arthritis affecting nearly 1% of the world population and is a significant cause of worldwide disability. Though prior studies have demonstrated the appearance of RA-related autoantibodies years before the onset of clinical RA, the pattern of immunologic events preceding the development of RA remains unclear. To characterize the evolution of the autoantibody response in the preclinical phase of RA, we used a novel multiplex autoantigen array to evaluate development of the anti-citrullinated protein antibodies (ACPA) and to determine if epitope spread correlates with rise in serum cytokines and imminent onset of clinical RA. To do so, we utilized a cohort of 81 patients with clinical RA for whom stored serum was available from 1-12 years prior to disease onset. We evaluated the accumulation of ACPA subtypes over time and correlated this accumulation with elevations in serum cytokines. We then used logistic regression to identify a profile of biomarkers which predicts the imminent onset of clinical RA (defined as within 2 years of testing). We observed a time-dependent expansion of ACPA specificity with the number of ACPA subtypes. At the earliest timepoints, we found autoantibodies targeting several innate immune ligands including citrullinated histones, fibrinogen, and biglycan, thus providing insights into the earliest autoantigen targets and potential mechanisms underlying the onset and development of autoimmunity in RA. Additionally, expansion of the ACPA response strongly predicted elevations in many inflammatory cytokines including TNF-α, IL-6, IL-12p70, and IFN-γ. Thus, we observe that the preclinical phase of RA is characterized by an accumulation of multiple autoantibody specificities reflecting the process of epitope spread. Epitope expansion is closely correlated with the appearance of preclinical inflammation, and we identify a biomarker profile including autoantibodies and cytokines which predicts the imminent onset of clinical arthritis. A total of 559 human sera were profiled using a custom made panel of putative rheumatoid arthritis associated autoantigens. The cohort was comprised of 79 patients with clinical RA for whom stored serum was available from 1-10 years prior to disease onset and 80 control subjects without RA that were matched to cases based on age, gender, race, region of assignment, and time of serum sampling.

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