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Arthritis protection conferred by a subset of antibodies to citrullinated proteins in rheumatoid arthritis - macrophage samples

ABSTRACT: Anti-citrullinated protein antibodies (ACPAs) are one of the hallmarks in rheumatoid arthritis (RA), but the in vivo function remained unclear. To investigate the effects of ACPAs, we expressed monoclonal ACPAs derived from RA patients, and analyzed the functions in mouse models, as well as the reactivity to tissue and peptides/proteins. All ACPAs showed no arthritogenicity and could not induce pain-like behavior in mice whereas one of them (E4) profoundly protected against antibody-induced arthritis. E4 showed a tissue binding pattern restricted to skin epithelial cells, to macrophages and dendritic cells in lymphoid tissue and to cartilage from mouse and human arthritic joints. Proteomic analysis showed that E4 had a distinct binding pattern to macrophage and RA synovial fluid proteins (e.g. alpha-enolase). The protective effect was epitope specific but also dependent on Fc-FCGR2B interaction on macrophages following the immune complex formation, resulting an increased IL-10 production and osteoclastogenesis reduction. The findings suggest that certain ACPAs could be protective in arthritis with therapeutic potentials.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Primary Cell, Macrophage

DISEASE(S): Rheumatoid Arthritis

SUBMITTER: Christian Beusch

LAB HEAD: Rikard Holmdahl

PROVIDER: PXD035177 | Pride | 2023-01-09

REPOSITORIES: Pride

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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:The variant rs26232, in the first intron of the C5orf30 locus, has recently been associated with both risk of developing rheumatoid arthritis (RA) and severity of tissue damage. The biological activities of human C5orf30 are unknown, and neither the gene nor protein show significant homology to any other characterized human sequences. The C5orf30 gene is present only in vertebrate genomes with a high degree of conservation implying a central function in these organisms. Here we report that C5orf30 is highly expressed in the synovium of RA patients compared with control synovial tissue, and that it is predominately expressed by synovial fibroblast (RASF) and macrophages in the lining and sublining layer of the tissue. These cells play a central role in the initiation and perpetuation of RA and are implicated in cartilage destruction. RASFs lacking C5orf30 exhibit increased cell migration and invasion in vitro and gene-profiling following C5orf30 inhibition confirmed upregulation of genes involved in cell migration, adhesion, angiogenesis, and immune and inflammatory pathways. Importantly, loss of C5orf30 contributes to the pathology of inflammatory arthritis in vivo, since inhibition of C5orf30 in the collagen-induced arthritis model markedly accentuated joint inflammation and tissue damage. Our study reveal C5orf30 to be a novel negative regulator of tissue damage in RA and this may act by modulating the autoaggressive phenotype that is characteristic of RASFs. Rheumatoid arthritis (RA) is a chronic, autoimmune, inflammatory disease that affects synovial joints. A key characteristic of RA is hyperplasia of fibroblast-like synoviocytes (FLS) which develop a stable, auto-aggressive phenotype that augments tissue destruction. It is unknown how this phenotype is stably maintained; however, epigenetic changes have been implicated. Histone deacetylation is one proposed method; a process controlled by histone deacetylases (HDACs). However, there have recently been reports publishing conflicting data regarding the expression of HDACs in RA synovium and FLS. The objective of this thesis is to determine the role of HDACs in regulating the auto-aggressive phenotype of RA through studies in FLS and in mice. Real time-quantitative PCR was used to assess the levels of HDAC1-11 in RA compared to osteoarthritis (OA) FLS. Immunohistochemistry and western blotting were used to assess protein expression of HDAC1 in RA and OA synovial tissue and FLS. HDAC1 was found to be overexpressed in RA compared to OA. HDAC1 was knocked down in RA FLS, then cell proliferation, migration and invasion were assessed by using tritiated thymidine, a scratch assay and a Matrigel invasion assay respectively. All three functions were significantly reduced following HDAC1 knockdown. An Illumina BeadChip (47,000 transcripts) was used to analyse global gene expression changes after knockdown. This revealed significant gene changes in important functional clusters, such as proliferation and migration. HDAC1 knockout is embryonic lethal in mice, so the in vivo role of HDAC1 was investigated in a mouse model of collagen-induced arthritis (CIA) using in vivo siRNAs. Clinical scores of CIA were measured daily and HDAC1 knockdown mice showed a significantly reduced clinical score compared to controls, comparable to dexamethasone-treated mice. The bones were analysed using a microCT scanner and histology. Knocking down HDAC1 showed reduced bone erosion, joint inflammation and cartilage degradation compared to controls. Overall, this study shows that HDAC1 is dysregulated in RA and it has a significant role in the autoaggressive phenotype shown in RA FLS and collagen-induced arthritis. The novel data shown in this thesis demonstrates that inhibiting HDAC1 may provide a powerful new target for treating RA. Three independent patient RASF samples were analysed in this study for each siRNA gene knockdown. Also a non targerting control siRNA was also used for each of the patient RASFs

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Arthritis protection conferred by a subset of antibodies to citrullinated proteins in rheumatoid arthritis - macrophage samples

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