Jin-Sil Park

Interleukin‐22 promotes osteoclastogenesis in rheumatoid arthritis through induction of RANKL in human synovial fibroblasts

OBJECTIVE To examine the regulatory role of interleukin-22 (IL-22) in the expression of RANKL and induction of osteoclastogenesis in rheumatoid arthritis (RA). METHODS Concentrations of IL-22 and RANKL in the serum and synovial fluid of RA patients were measured using enzyme-linked immunosorbent assay. RA synovial fibroblasts were treated with recombinant human IL-22 (rhIL-22), and the expression of RANKL messenger RNA (mRNA) and protein was measured using real-time polymerase chain reaction, Western blotting, and intracellular immunostaining. Human monocytes were cocultured with IL-22-prestimulated RA synovial fibroblasts and macrophage colony-stimulating factor, and osteoclastogenesis was assessed by counting the multinucleated cells (those staining positive for tartrate-resistant acid phosphatase). RESULTS The IL-22 concentration in the synovial fluid was higher in RA patients than in patients with osteoarthritis (OA). The serum IL-22 concentration was also higher in RA patients than in OA patients and healthy volunteers, and this correlated with serum titers of rheumatoid factor and anti-cyclic citrullinated peptide antibodies. In RA synovial fibroblasts treated with rhIL-22, the expression of RANKL mRNA and protein was increased in a dose-dependent manner. IL-22-induced RANKL expression was down-regulated significantly by the inhibition of p38 MAPK/NF-κB or JAK-2/STAT-3 signaling. In human monocytes cocultured with IL-22-prestimulated RA synovial fibroblasts in the absence of exogenous RANKL, the monocytes differentiated into osteoclasts, but this osteoclastogenesis decreased after p38 MAPK/NF-κB or JAK-2/STAT-3 signaling was inhibited. CONCLUSION These results show that IL-22 up-regulates RANKL expression in RA synovial fibroblasts and induces osteoclastogenesis. These effects are mediated by the p38 MAPK/NF-κB and JAK-2/STAT-3 signaling pathways.

IL-23 Induces Receptor Activator of NF-κB Ligand Expression on CD4+ T Cells and Promotes Osteoclastogenesis in an Autoimmune Arthritis Model

IL-23, a clinically novel cytokine, targets CD4+ T cells. Recent IL-1Ra−/− mouse studies have demonstrated that IL-23 indirectly stimulates the differentiation of osteoclast precursors by enhancing IL-17 release from CD4+ T cells. IL-17, in turn, stimulates osteoclastogenesis in osteoclast precursor cells. In this study, we found that IL-23 up-regulates receptor activator of NF-κB ligand expression by CD4+ T cells, and thus contributes to osteoclastogenesis. This indirect pathway is mediated by NF-κB and STAT3. We have also demonstrated that IL-23 can influence osteoclastogenesis positively under the special conditions in the IL-1-dominant milieu of IL-1Ra−/− mice. We propose that IL-23-enhanced osteoclastogenesis is mediated mainly by CD4+ T cells. The results of this study show that IL-23 is a promising therapeutic target for the treatment of arthritis-associated bone destruction.

Interleukin-21 promotes osteoclastogenesis in humans with rheumatoid arthritis and in mice with collagen-induced arthritis

OBJECTIVE Bone destruction is a critical pathology involved in the functional disability caused by rheumatoid arthritis (RA). Osteoclasts, which are specialized bone-resorbing cells regulated by cytokines such as RANKL, are implicated in bone destruction in RA. The aim of this study was to determine whether interleukin-21 (IL-21), a potent immunomodulatory 4-α-helical bundle type 1 cytokine, has osteoclastogenic activity in patients with RA and in mice with collagen-induced arthritis (CIA). METHODS The expression of IL-21 in synovial tissue was examined using immunohistochemistry. The concentrations of IL-21 in serum and synovial fluid were determined by enzyme-linked immunosorbent assay. The levels of RANKL and osteoclastogenic markers were measured using real-time polymerase chain reaction. CD14+ monocytes from patients with RA or mouse bone marrow cells were cocultured with fibroblast-like synoviocytes (FLS) from patients with RA or CD4+ T cells from mice with CIA in the presence of IL-21 and subsequently stained for tartrate-resistant acid phosphatase activity to determine osteoclast formation. RESULTS IL-21 was up-regulated in the synovium, synovial fluid, and serum of patients with RA and in the synovium and serum of mice with CIA. IL-21 induced RANKL expression in mixed joint cells and CD4+ T cells from mice with CIA and in CD4+ T cells and FLS from patients with RA. Moreover, IL-21 enhanced in vitro osteoclastogenesis without the presence of RANKL-providing cells and by inducing RANKL expression in CD4+ T cells and FLS. CONCLUSION Our data suggest that IL-21 promotes osteoclastogenesis in RA. We believe that therapeutic strategies targeting IL-21 might be effective for the treatment of patients with RA, especially in preventing bone destruction.

STA‐21, a Promising STAT‐3 Inhibitor That Reciprocally Regulates Th17 and Treg Cells, Inhibits Osteoclastogenesis in Mice and Humans and Alleviates Autoimmune Inflammation in an Experimental Model of Rheumatoid Arthritis

To investigate the impact of STA‐21, a promising STAT‐3 inhibitor, on the development and progression of inflammatory arthritis and to determine the possible mechanisms by which STA‐21 has antiarthritic effects in interleukin‐1 receptor antagonist–knockout (IL‐1Ra–KO) mice, an animal model of rheumatoid arthritis (RA).

Grape seed proanthocyanidin extract (GSPE) attenuates collagen-induced arthritis

To examine whether grape seed proanthocyanidin extract (GSPE) which is known to act as an antioxidant has therapeutic effect on collagen-induced arthritis (CIA) in mice, an animal model of rheumatoid arthritis. Mice were treated with an intraperitoneal injection of GSPE (10, 50, or 100 mg/kg) or saline. Clinical, histological, and biochemical parameters were assessed. The effects of GSPE on osteoclastogenesis were determined by tartrate-resistant acid phosphatase (TRAP) staining of the inflamed joints and bone-marrow cells cultured with the receptor activator of nuclear factor B ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). Intracellular levels of hydrogen peroxide were determined using carboxy-dichlorodihydrofluorescein diacetate. GSPE treatment significantly attenuated the severity of CIA in a dose-dependent manner and reduced the histology scores for synovial inflammation, cartilage erosion, bone erosion, and the number of TRAP+ osteoclasts. GSPE treatment significantly reduced the numbers of tumor necrosis factor alpha (TNF-alpha)- or interleukin 17 (IL-17)-producing cells in the synovial tissue and the spontaneous production of TNF-alpha and IL-17 by splenocytes compared with those in the control mice. The serum levels of type-II-collagen-specific IgG2a and plasma levels of 8-isoprostane in the GSPE-treated mice were significantly lower than those in the control mice. GSPE dose-dependently suppressed osteoclastogenesis in vitro. GSPE significantly reduced hydrogen peroxide production by anti-CD3-monoclonal-antibody-stimulated CD4+ splenocytes. These results indicate that intraperitoneal injection of GSPE attenuated CIA in mice. GSPE may be useful in the treatment of rheumatoid arthritis.

Modulation of STAT-3 in rheumatoid synovial T cells suppresses Th17 differentiation and increases the proportion of Treg cells

OBJECTIVE To investigate the impact of STAT-3-mediated regulation on Th17 differentiation in patients with rheumatoid arthritis (RA). METHODS CD4+ T cells isolated from peripheral blood (PB) and synovial fluid (SF) were stimulated to differentiate into Th17 cells or Treg cells. The activity of STAT-3 was knocked down by transfecting CD4+ T cells with small interfering RNA (siRNA). After 3 days in culture, the proportions of Th17 cells and Treg cells were measured by flow cytometry, and the production of interleukin-17 (IL-17) was measured by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay. RESULTS The levels of IL-17, IL-6, IL-23, IL-1, and tumor necrosis factor α were significantly higher in RA SF and synovial tissue than in SF and synovial tissue from osteoarthritis patients. In RA synovial tissue, the expression of STAT-3 increased in proportion to the severity of synovitis, as shown by stromal cellularity, intimal hyperplasia, and inflammatory infiltration. The degree of Th17 differentiation was highest in RA SF, followed by RA PB, and lowest in normal subjects. In CD4+ T cells, transfection with STAT-3 siRNA prevented Th17 differentiation of mononuclear cells from RA PB and SF but increased the proportion of Treg cells. In contrast, inhibition of STAT-5, the transcription factor for Treg cells, increased the proportion of Th17 cells and reduced that of Treg cells. CONCLUSION Our findings indicate that modulation of STAT-3 in CD4+ T cells affects the differentiation of Th17 cells and Treg cells in patients with RA. This role of STAT-3 in RA synovial T cells may provide a new therapeutic target for the management of RA.

Grape seed proanthocyanidin extract (GSPE) differentially regulates Foxp3 + regulatory and IL-17 + pathogenic T cell in autoimmune arthritis

Grape seed proanthocyanidin extract (GSPE), which is the antioxidant derived from grape seeds, has been reported to possess a variety of potent properties. We have previously shown that GSPE attenuates collagen-induced arthritis. However the mechanism by which GSPE regulates the immune response remains unclear, although it may involve effects on the regulation of pathogenic T cells in autoimmune arthritis. To clarify this issue, we have assessed the effects of GSPE on differential regulation of Th17 and regulatory T (Treg) cells subsets in vitro in mouse and human CD4(+) T cells. We observed that GSPE decreased the frequency of IL-17(+)CD4(+)Th17 cells and increased induction of CD4(+)CD25(+)forkhead box protein 3 (Foxp3)(+) Treg cells. In vivo, GSPE effectively attenuated clinical symptoms of established collagen-induced arthritis in mice with concomitant suppression of IL-17 production and enhancement of Foxp3 expression (type II collagen-reactive Treg cells) in CD4(+) T cells of joints and splenocytes. The presence of GSPE decreased the levels of IL-21, IL-22, IL-26 and IL-17 production by human CD4(+) T cells in a STAT3-dependent manner. In contrast, GSPE induces Foxp3(+) Treg cells in humans. Our results suggest that GSPE possesses a reciprocal control over IL-17 and Foxp3. By potently regulating inflammatory T cell differentiation, GSPE may serve as a possible novel therapeutic agent for inflammatory and autoimmune diseases, including rheumatoid arthritis.

p53 Controls Autoimmune Arthritis via STAT‐Mediated Regulation of the Th17 Cell/Treg Cell Balance in Mice

OBJECTIVE To investigate the connection between p53 and interleukin-17-producing Th17 cell/Treg cell balance in rheumatoid arthritis (RA). METHODS Th17 cell and Treg cell frequencies were analyzed by flow cytometry, and cytokine levels in the supernatant were determined using enzyme-linked immunosorbent assays. The expression of transcription factors was analyzed by immunostaining and Western blotting, and the interactions between p53 and STAT-3 or STAT-5 were determined by immunoprecipitation-Western blot analysis. A p53 agonist was administered in the collagen-induced arthritis (CIA) model, and the effects in vivo were determined. RESULTS CD4+ T cells from p53-/- mice decreased the activity of STAT-5, lowered the level of phosphorylated STAT-5, and compromised Treg cell differentiation. The protein p53 bound STAT-5 directly, and this interaction was enhanced with increasing p53 activity. Under inflammatory conditions, p53 suppressed Th17 cell differentiation and skewed T cells toward Treg cell differentiation through the activation of STAT-5 signaling cascades. In mice with CIA, injection of a p53 overexpression vector or an antagonist of Mdm2 had the effect of controlling arthritis development in vivo. The regulatory effect of p53 was recapitulated in the cells of RA patients, with more pronounced suppression due to the repressed status of p53 in RA. CONCLUSION We demonstrated a link between p53-mediated and STAT-mediated regulation of Th17 cells/Treg cells in RA. Our results suggest that factors involved in this pathway might constitute novel therapeutic targets for the treatment of RA.

In vivo action of IL-27: reciprocal regulation of Th17 and Treg cells in collagen-induced arthritis

Interleukin (IL)-27 is a novel cytokine of the IL-6/IL-12 family that has been reported to be involved in the pathogenesis of autoimmune diseases and has a pivotal role as both a pro- and anti-inflammatory cytokine. We investigated the in vivo effects of IL-27 on arthritis severity in a murine collagen-induced arthritis (CIA) model and its mechanism of action regarding control of regulatory T (Tregs) and IL-17-producing T helper 17 (Th17) cells. IL-27-Fc-treated CIA mice showed a lower severity of arthritis. IL-17 expression in the spleens was significantly decreased in IL-27-Fc-treated CIA mice compared with that in the CIA model. The Th17 population was decreased in the spleens of IL-27-Fc-treated CIA mice, whereas the CD4+CD25+Foxp3+ Treg population increased. In vitro studies revealed that IL-27 inhibited IL-17 production in murine CD4+ T cells, and the effect was associated with retinoic acid-related orphan receptor γT and signal transducer and activator of transcription 3 inhibition. In contrast, fluorescein isothiocyanate-labeled forkhead box P3 (Foxp3) and IL-10 were profoundly augmented by IL-27 treatment. Regarding the suppressive capacity of Treg cells, the proportions of CTLA-4+ (cytotoxic T-lymphocyte antigen 4), PD-1+ (programmed cell death protein 1) and GITR+ (glucocorticoid-induced tumor necrosis factor receptor) Tregs increased in the spleens of IL-27-Fc-treated CIA mice. Furthermore, in vitro differentiated Treg cells with IL-27 exerted a more suppressive capacity on T-cell proliferation. We found that IL-27 acts as a reciprocal regulator of the Th17 and Treg populations in CD4+ cells isolated from healthy human peripheral blood mononuclear cells (PBMCs), as well as from humans with rheumatoid arthritis (RA) PBMCs. Our study suggests that IL-27 has the potential to ameliorate overwhelming inflammation in patients with RA through a reciprocal regulation of Th17 and Treg cells.

Induction of Macrophage Migration Inhibitory Factor in ConA-Stimulated Rheumatoid Arthritis Synovial Fibroblasts through the P38 MAP Kinase-Dependent Signaling Pathway

Background/Aims This study was undertaken to identify the intracellular signaling pathway involved in induction of macrophage migration inhibitory factor (MIF) in human rheumatoid arthritis (RA) synovial fibroblasts. Methods Human RA synovial fibroblasts were treated with concanavalin A (ConA), various cytokines, and inhibitors of signal transduction molecules. The production of MIF by synovial fibroblasts was measured in culture supernatants by ELISA. The expression of MIF mRNA was determined using reverse transcriptase polymerase chain reaction (RT-PCR) and real-time PCR. Phosphorylation of p38 mitogen-activated protein (MAP) kinase in synovial fibroblasts was confirmed using Western blotting. The expression of MIF and p38 MAP kinase in RA synovium was determined using dual immunohistochemistry. Results The production of MIF by RA synovial fibroblasts increased in a dose-dependent manner after ConA stimulation. MIF was also induced by interferon-γ, CD40 ligand, interleukin-15, interleukin-1β, tumor necrosis factor-α, and transforming growth factor-β. The production of MIF by RA synovial fibroblasts was significantly reduced after inhibition of p38 MAP kinase. The expression of MIF and p38 MAP kinase was upregulated in the RA synovium compared with the osteoarthritis synovium. Conclusions These results suggest that MIF production was induced through a p38 MAP-kinase-dependent pathway in RA synovial fibroblasts.