Pathogenesis Of Autoimmune Arthritis Research Articles

Short Peptides of Innate Immunity Protein Tag7 Inhibit the Production of Cytokines in CFA-Induced Arthritis.

The pathogenesis of autoimmune arthritis is a hot topic in current research. The main focus of this work was to study cytokines released in CFA-induced arthritis in ICR mice as well as the regulation of blood levels of cytokines by two peptides of the innate immunity protein Tag7 (PGLYRP1) capable of blocking the activation of the TNFR1 receptor. Arthritis was induced by local periarticular single-dose injections of 40 µL of complete Freund’s adjuvant (CFA) into the left ankle joints of mice. The levels of chemokines and cytokines in plasma were measured using a Bio-Plex Pro Mouse Cytokine Kit at 3, 10, and 21 days after arthritis induction. Tag7 peptides were shown to decrease the blood levels of the pro-inflammatory cytokines IL-6, TNF, and IL-1β. Administration of peptides also decreased the levels of chemokines MGSA/CXCL1, MIP-2α/CXCL2, ENA78/CXCL5, MIG/CXCL9, IP-10/CXCL10, MCP-1/CCL2, and RANTES/CCL5. Furthermore, a decrease in the levels of cytokines IL7, G-CSF, and M-CSF was demonstrated. Addition of the studied peptides strongly affected IFN-γ concentration. We believe that a decrease in the levels of cytokine IFN-γ was associated with a therapeutic effect of Tag7 peptides manifested in alleviation of the destruction of cartilage and bone tissues in the CFA-induced arthritis.

Splenectomy modulates the immune response but does not prevent joint inflammation in a mouse model of RA.

The spleen is the largest secondary lymphoid organ which is involved in the development of B cells and also in systemic (auto)immune responses. Using the recombinant human G1 domain-induced arthritis (GIA) model in splenectomized and control BALB/c mice, we investigated the role of the spleen in the induction and pathogenesis of autoimmune arthritis. Splenectomized mice developed GIA with a similar clinical picture to the control group. However, we observed significant alterations in the humoral and cellular immune responses in splenectomized mice. In the sera of the splenectomized mice, we found lower pro-inflammatory cytokine and anti-rhG1 IgM levels, but higher IL-4, anti-rhG1 IgG1 and anti-CCP and RF antibodies. The arthritis induction in the splenectomized group was associated with a significant expansion of activated helper T cells and an increase in the proportion of the circulating B1 and marginal zone B cell subsets. Importantly, immunization of the splenectomized mice with rhG1 induced the formation of germinal centers in the inguinal- and mesenteric lymph nodes (i/mLNs) which showed an active immune response to rhG1. Finally, both B and T cells from the mLNs of the splenectomized mice showed decreased intracellular Ca2+ signaling than those of the control group. Collectively, these findings indicate that the presence of the spleen is not critical for the induction of GIA, and in its absence the autoimmune arthritis is most likely promoted through the compensatory activity of the i/mLNs. However, our data implies the immunological role of the spleen in arthritis which could be further assessed in human RA.

Dispensable roles of Gsdmd and Ripk3 in sustaining IL-1\u03b2 production and chronic inflammation in Th17-mediated autoimmune arthritis

Programmed necrosis, such as necroptosis and pyroptosis, is a highly pro-inflammatory cellular event that is associated with chronic inflammation. Although there are various triggers of pyroptosis and necroptosis in autoimmune tissue inflammation and subsequent lytic forms of cell death release abundant inflammatory mediators, including damage-associated molecular patterns and IL-1β, capable of amplifying autoimmune Th17 effector functions, it remains largely unclear whether the programs play a crucial role in the pathogenesis of autoimmune arthritis. We herein report that Gasdermin D (Gsdmd) and receptor interacting serine/threonine kinase 3 (Ripk3)—key molecules of pyroptosis and necroptosis, respectively—are upregulated in inflamed synovial tissues, but dispensable for IL-1β production and the development of IL-17-producing T helper (Th17) cell-mediated autoimmune arthritis in SKG mice. Gsdmd−/−, Ripk3−/−, or Gsdmd−/−Ripk3−/− SKG mice showed severe arthritis with expansion of arthritogenic Th17 cells in the draining LNs and inflamed joints, which was comparable to that in wild-type SKG mice. Despite the marked reduction of IL-1β secretion from Gsdmd−/− or Ripk3−/− bone marrow-derived DCs by canonical stimuli, IL-1β levels in the inflamed synovium were not affected in the absence of Gsdmd or Ripk3. Our results revealed that T cell-mediated autoimmune arthritis proceeds independently of the pyroptosis and necroptosis pathways.

T-bet represses collagen-induced arthritis by suppressing Th17 lineage commitment through inhibition of ROR\u03b3t expression and function

T-bet is a key transcription factor for the T helper 1 lineage and its expression level is negatively correlated to inflammation in patients with rheumatoid arthritis (RA). Our previous study using T-bet transgenic mice revealed over-expression of T-bet completely suppressed collagen-induced arthritis (CIA), a murine model of RA, indicating a potential suppressive role of T-bet in the pathogenesis of autoimmune arthritis. Here, we show T-bet-deficiency exacerbated CIA. T-bet in CD4 + T cells, but not in CD11c + dendritic cells, was critical for regulating the production of IL-17A, IL-17F, IL-22, and TNFα from CD4 + T cells. T-bet-deficient CD4 + T cells showed higher RORγt expression and increased IL-17A production in RORγt-positive cells after CII immunization. In addition, T-bet-deficient naïve CD4 + T cells showed accelerated Th17 differentiation in vitro. CIA induced in CD4-Cre T-betfl/fl (cKO) mice was more severe and T-bet-deficient CD4 + T cells in the arthritic joints of cKO mice showed higher RORγt expression and increased IL-17A production. Transcriptome analysis of T-bet-deficient CD4 + T cells revealed that expression levels of Th17-related genes were selectively increased. Our results indicate that T-bet in CD4 + T cells repressed RORγt expression and function resulting in suppression of arthritogenic Th17 cells and CIA.

Contrasting contributions of TNF from distinct cellular sources in arthritis

ObjectivesNeutralisation of tumour necrosis factor (TNF) is widely used as a therapy for rheumatoid arthritis (RA). However, this therapy is only effective in less than a half of patients and...

Immune checkpoint inhibitor-induced inflammatory arthritis as a model of autoimmune arthritis.

The development of inflammatory arthritis in patients receiving immune checkpoint inhibitor therapy is increasingly recognized due to the growing use of these drugs for the treatment of cancer. This represents an important opportunity not only to define the mechanisms responsible for the development of this immune-related adverse event andto ultimately predict or prevent its development, but also to provide a unique window into early events in the development of inflammatory arthritis. Knowledge gained through the study of this patient population, for which the inciting event is known, could shed light into the pathogenesis of autoimmune arthritis. This review will highlight the clinical and immunologic features of these entities to define common elements for future study.

Targeting the CD40-CD154 Signaling Pathway for Treatment of Autoimmune Arthritis.

Full activation of T lymphocytes requires signals from both T cell receptors and costimulatory molecules. In addition to CD28, several T cell molecules could deliver costimulatory signals, including CD154, which primarily interacts with CD40 on B-cells. CD40 is a critical molecule regulating several B-cell functions, such as antibody production, germinal center formation and cellular proliferation. Upregulated expression of CD40 and CD154 occurs in immune effector cells and non-immune cells in different autoimmune diseases. In addition, therapeutic benefits have been observed by blocking the CD40-CD154 interaction in animals with collagen-induced arthritis. Given the therapeutic success of the biologics abatacept, which blocks CD28 costimulation, and rituximab, which deletes B cells in the treatment of autoimmune arthritis, the inhibition of the CD40-CD154 axis has two advantages, namely, attenuating CD154-mediated T cell costimulation and suppressing CD40-mediated B-cell stimulation. Furthermore, blockade of the CD40-CD154 interaction drives the conversion of CD4+ T cells to regulatory T cells that mediate immunosuppression. Currently, several biological products targeting the CD40-CD154 axis have been developed and are undergoing early phase clinical trials with encouraging success in several autoimmune disorders, including autoimmune arthritis. This review addresses the roles of the CD40-CD154 axis in the pathogenesis of autoimmune arthritis and its potential as a therapeutic target.

Amelioration of Autoimmune Arthritis in Mice Treated With the DNA Methyltransferase Inhibitor 5'-Azacytidine.

Disease-associated, differentially hypermethylated regions have been reported in rheumatoid arthritis (RA), but no DNA methyltransferase inhibitors have been evaluated in either RA or any animal models of RA. The present study was conducted to evaluate the therapeutic potential of 5'-azacytidine (5'-azaC), a DNA methyltransferase inhibitor, and explore the cellular and gene regulatory networks involved in the context of autoimmune arthritis. A disease-associated genome-wide DNA methylation profile was explored by methylated CpG island recovery assay-chromatin immunoprecipitation (ChIP) in arthritic B cells. Mice with proteoglycan-induced arthritis (PGIA) were treated with 5'-azaC. The effect of 5'-azaC on the pathogenesis of PGIA was explored by measuring serum IgM and IgG1 antibody levels using enzyme-linked immunosorbent assay, investigating the efficiency of class-switch recombination (CSR) and Aicda gene expression using real-time quantitative polymerase chain reaction, monitoring germinal center (GC) formation by immunohistochemistry, and determining alterations in B cell subpopulations by flow cytometry. The 5'-azaC-induced regulation of the Aicda gene was explored using RNA interference, ChIP, and luciferase assays. We explored arthritis-associated hypermethylated regions in mouse B cells and demonstrated that DNA demethylation had a beneficial effect on autoimmune arthritis. The 5'-azaC-mediated demethylation of the epigenetically inactivated Ahr gene resulted in suppressed expression of the Aicda gene, reduced CSR, and compromised GC formation. Ultimately, this process led to diminished IgG1 antibody production and amelioration of autoimmune arthritis in mice. DNA hypermethylation plays a leading role in the pathogenesis of autoimmune arthritis and its targeted inhibition has therapeutic potential in arthritis management.

Adenosine 2a Receptor Signal Blockade of Murine Autoimmune Arthritis via Inhibition of Pathogenic Germinal Center-Follicular Helper T Cells.

CD4 germinal center (GC)-follicular helper T (Tfh) cells are important in the pathogenesis of autoimmune arthritis. Previous studies have shown that adenosine 2a receptor (A2aR; Adora2a) signaling can divert CD4 T cells away from the GC-Tfh cell lineage during the primary response to foreign antigens. This study was undertaken to examine the effects of A2aR signaling on CD4 T cells during the recognition of self antigen in a murine model of autoimmune arthritis. Wild-type and Adora2a-deficient mouse KRN T cell receptor-transgenic CD4 T cells specific for glucose-6-phosphate isomerase (GPI)/I-Ag7 were transferred into immunodeficient Tcra-/- I-Ag7 -expressing mice to induce arthritis. Recipients were then treated with either the selective A2aR agonist CGS-21680 (CGS) or phosphate buffered saline alone. Severity of disease, autoantibody titers, KRN T cell numbers and phenotype, and GPI-specific isotype class-switched plasmablasts were tracked. CGS treatment inhibited the development of arthritis and differentiation of KRN GC-Tfh cells, blocked the appearance of high-affinity GPI-specific and IgG1 isotype class-switched polyclonal plasmablasts, and led to a reduction in serum titers of anti-GPI IgG1. In addition, therapeutic administration of CGS after the onset of arthritis blocked further disease progression in association with reductions in the number of KRN GC-Tfh cells and anti-GPI IgG1 serum titers. Strong A2aR signaling diverts autoreactive CD4 T cell differentiation away from the GC-Tfh cell lineage, thus reducing help for the differentiation of dangerous autoreactive B cells that promote arthritis. These data in a mouse model of autoimmune arthritis suggest that A2aR and its downstream signaling pathways in CD4 T cells may be promising therapeutic targets for interfering with potentially dangerous autoreactive GC-Tfh cell differentiation.

The involvement of Toll-like receptor 9 in the pathogenesis of erosive autoimmune arthritis.

Endogenous nucleic acids and their receptors may be involved in the initiation of systemic autoimmune diseases including rheumatoid arthritis (RA). As the role of the DNA sensing Toll‐like receptor (TLR) 9 in RA is unclear, we aimed to investigate its involvement in the pathogenesis of autoimmune arthritis using three different experimental models of RA. The data obtained revealed involvement of TLR9 in the T cell‐dependent phase of inflammatory arthritis. In rats with pristane‐induced arthritis (PIA), TLR9 inhibition before disease onset reduced arthritis significantly and almost completely abolished bone erosion. Accordingly, serum levels of IL‐6, α‐1‐acid‐glycoprotein and rheumatoid factor were reduced. Moreover, in TLR9−/− mice, streptococcal cell wall (SCW)‐induced arthritis was reduced in the T cell‐dependent phase, whereas T cell‐independent serum‐transfer arthritis was not affected. Remarkably, while TLR7 expression did not change during in vitro osteoclastogenesis, TLR9 expression was higher in precursor cells than in mature osteoclasts and partial inhibition of osteoclastogenesis was achieved only by the TLR9 antagonist. These results demonstrate a pivotal role for TLR9 in the T cell‐dependent phases of inflammatory arthritis and additionally suggest some role during osteoclastogenesis. Hence, endogenous DNA seems to be crucially involved in the pathophysiology of inflammatory autoimmune arthritis.

Nardilysin is involved in autoimmune arthritis via the regulation of tumour necrosis factor alpha secretion

ObjectiveTumour necrosis factor alpha (TNF-α) plays an important role in rheumatoid arthritis (RA). TNF-α is synthesised as a membrane-anchored precursor and is fully activated by a disintegrin and metalloproteinase 17...

In-vivo quantitative assessment of the therapeutic response in a mouse model of collagen-induced arthritis using 18 F-fluorodeoxyglucose positron emission tomography.

Mouse collagen-induced arthritis (CIA) is the most commonly used animal model to investigate underlying pathogenesis of autoimmune arthritis and to demonstrate the therapeutic efficacy of novel drugs in autoimmune arthritis. The conventional read-outs of CIA are clinical score and histopathology, which have several limitations, including (i) subjected to observer bias; and (ii) longitudinal therapeutic efficacy of a new drug cannot be determined. Thus, a robust, non-invasive, in-vivo drug screening tool is currently an unmet need. Here we have assessed the utility of 18 F-fluorodeoxyglucose positron emission tomography (18 F-FDG) as an in-vivo screening tool for anti-inflammatory drugs using the mouse CIA model. The radiotracer 18 F-FDG and a PET scanner were employed to monitor CIA disease activity before and after murine anti-tumour necrosis factor (TNF)-α antibody (CNTO5048) therapy in the mouse CIA model. Radiotracer concentration was derived from PET images for individual limb joints and on a per-limb basis, and Spearman's correlation coefficient (ρ) was determined with clinical score and histology of the affected limbs. CNTO5048 improved arthritis efficiently, as evidenced by clinical score and histopathology. PET showed an increased uptake of 18 F-FDG with the progression of the disease and a significant decrease in the post-treatment group. 18 F-FDG uptake patterns showed a strong correlation with clinical score (ρ=0·71, P < 0·05) and histopathology (ρ=0·76, P < 0·05). This study demonstrates the potential of 18 F-FDG PET as a tool for in-vivo drug screening for inflammatory arthritis and to monitor the therapeutic effects in a longitudinal setting.

TCR repertoire sequencing identifies synovial Treg cell clonotypes in the bloodstream during active inflammation in human arthritis

ObjectivesThe imbalance between effector and regulatory T (Treg) cells is crucial in the pathogenesis of autoimmune arthritis. Immune responses are often investigated in the blood because of its accessibility, but...

Blockade of Glucocorticoid-Induced Tumor Necrosis Factor–Receptor-Related Protein Signaling Ameliorates Murine Collagen-Induced Arthritis by Modulating Follicular Helper T Cells

Recent studies have shown that glucocorticoid-induced tumor necrosis factor-receptor-related protein (GITR) and its ligand (GITRL) are critically involved in the pathogenesis of autoimmune arthritis, but the role of GITRL/GITR signaling in modulating CD4(+) follicular helper T (Tfh) cell response during autoimmune arthritis remains largely unclear. We showed that splenic Tfh cells from mice with collagen-induced arthritis expressed higher levels of GITR compared with non-Tfh cells. Invitro, GITRL treatment markedly enhanced the percentage and number of Tfh cells. The administration of GITR fused to fragment crystallizable of IgG protein in mice with collagen-induced arthritis suppressed the Tfh cell response, resulting in ameliorated disease severity, and reduced production of autoantibody and the number of autoantibody-secreting cells in both the spleen and bone marrow. Together, these results indicate that blockade of GITR signaling canameliorate arthritis progression mainly by modulating the Tfh cell response.

B1a cells play a pathogenic role in the development of autoimmune arthritis.

Dysregulated functions of B1 cells have been implicated in the disease progression of various autoimmune disorders, but it remains largely unclear whether B1 cells are involved in the pathogenesis of autoimmune arthritis. In this study, we found that peritoneal B1a cells underwent proliferation and migrated to the inflamed joint tissue with upregulated RANKL expression during collagen-induced arthritis (CIA) development in mice. Adoptive transfer of B1a cells exacerbated arthritic severity and joint damage while intraperitoneal depletion of B1 cells ameliorated both arthritic symptoms and joint pathology in CIA mice. In culture, RANKL-expressing B1a cells significantly promoted the expansion of osteoclasts derived from bone marrow cells, which were in accord with the in vivo findings of increased osteoclastogenesis in CIA mice transferred with B1a cells. Together, these results have demonstrated a pathogenic role of B1a cells in the development of autoimmune arthritis through RANKL-mediated osteoclastogenesis.

Inhibition of Inflammation and Bone Erosion by RNA Interference-Mediated Silencing of Heterogeneous Nuclear RNP A2/B1 in Two Experimental Models of Rheumatoid Arthritis.

The nuclear protein heterogeneous nuclear RNP A2/B1 (hnRNP A2/B1) is involved in posttranscriptional regulation of gene expression. It is constitutively expressed in lymphoid organs and highly up-regulated in the synovial tissue of patients with rheumatoid arthritis (RA), who may also generate autoantibodies to this protein. This study was undertaken to investigate the potential involvement of hnRNP A2/B1 in the pathogenesis of autoimmune arthritis, by silencing hnRNP A2/B1 expression in 2 animal models of RA. Collagen-induced arthritis (CIA) and the K/BxN serum-transfer model were used as animal models of RA. Efficient silencing of hnRNP A2/B1 was achieved using a liposome-based carrier system for delivery of small interfering RNAs. Expression of hnRNP A2/B1 was analyzed by flow cytometry, reverse transcription-quantitative polymerase chain reaction, Western blotting, and immunohistochemistry. The number of osteoclasts was determined by tartrate-resistant acid phosphatase staining. Cytokine levels and anticollagen antibody levels were measured by enzyme-linked immunosorbent assay. Efficient silencing of hnRNP A2/B1 was achieved in all lymphoid organs. In both experimental models, the incidence and severity of arthritis were largely reduced and bone erosion was not detectable as compared to the control groups. Down-modulation of hnRNP A2/B1 significantly interfered with the production of proinflammatory cytokines from monocyte/macrophages, but not from T cells. Consistent with these findings, production of T cell cytokines was not impaired when cells were restimulated in vitro with type II collagen. Furthermore, levels of anticollagen antibodies were not affected by hnRNP A2/B1 silencing. Our findings suggest that hnRNP A2/B1 has an important role in regulation of the innate immune system, especially at the level of monocyte/macrophage activation. Therefore, down-modulation of hnRNP A2/B1 seems to affect primarily the effector phase of autoimmune arthritis.

Functional characterization of myeloid-derived suppressor cell subpopulations during the development of experimental arthritis.

Recent evidence indicates the existence of subpopulations of myeloid-derived suppressor cells (MDSCs) with distinct phenotypes and functions. Here, we characterized the role of MDSC subpopulations in the pathogenesis of autoimmune arthritis in a collagen-induced arthritis (CIA) mouse model. The splenic CD11b(+) Gr-1(+) MDSC population expanded in CIA mice, and these cells could be subdivided into polymorphonuclear (PMN) and mononuclear (MO) MDSC subpopulations based on Ly6C and Ly6G expression. During CIA, the proportion of splenic MO-MDSCs was increased in association with the severity of joint inflammation, while PMN-MDSCs were decreased. MO-MDSCs expressed higher levels of surface CD40 and CD86 protein, but lower levels of Il10, Tgfb1, Ccr5, and Cxcr2 mRNA. PMN-MDSCs exhibited a more potent capacity to suppress polyclonal T-cell proliferation in vitro, compared with MO-MDSCs. Moreover, the adoptive transfer of PMN-MDSCs, but not MO-MDSCs, decreased joint inflammation, accompanied by reduced levels of serum cytokine secretion and the frequencies of Th1 and Th17 cells in draining lymph nodes. These results suggest that there could be a shift from potently suppressive PMN-MDSCs to poorly suppressive MO-MDSCs during the development of experimental arthritis, which might reflect the failure of expanded MDSCs to suppress autoimmune arthritis.

Myeloid-derived suppressor cells have a proinflammatory role in the pathogenesis of autoimmune arthritis

ObjectivesAlthough myeloid-derived suppressor cells (MDSCs) have been linked to T cell tolerance, their role in autoimmune rheumatoid arthritis (RA) remains elusive. Here we investigate the potential association of MDSCs with...

OP0179 Apl-1, A Peptide as Immunomodulator for the Treatment of Juvenile Idiopathic Arthritis

BackgroundJuvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases characterized by autoimmune arthritis of unknown cause. Current treatment focuses on reduction of inflammation through anti-inflammatory and immunosuppressive strategies, including...

Pathogenic conversion of forkhead box protein 3-positive T cells into T helper 17 cells: Is this also the case for multiple sclerosis?

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system that affects the brain and spinal cord. T helper 17 (Th17) cells have emerged as a key player in the pathogenesis of MS and other autoimmune disorders previously attributed to Th1 cells. New research published in Nature Medicine has shown that CD25lowFoxP3+CD4+ T cells can differentiate into Th17 cells in vivo, and that these cells play an important role in the pathogenesis of autoimmune arthritis. Considering the role of autoreactive T cells particularly Th17 cells in MS, such exFoxP3 Th17 cells derived from FoxP3+ T cells might also be able to control the initiation and progression of MS.