MicroRNA-21a-5p inhibition alleviates systemic sclerosis by targeting STAT3 signaling.

BACKGROUND: MicroRNA (miRNA)-21-5p participates in various biological processes, including cancer and autoimmune diseases. However, its role in the development of fibrosis in the in vivo model of systemic sclerosis (SSc) has not been reported. This study investigated the effects of miRNA-21a-5p overexpression and inhibition on SSc fibrosis using a bleomycin-induced SSc mouse model. METHODS: A murine SSc model was induced by subcutaneously injecting 100 µg bleomycin dissolved in 0.9% NaCl into C57BL/6 mice daily for 5 weeks. On days 14, 21, and 28 from the start of bleomycin injection, 100 µg pre-miRNA-21a-5p or anti-miRNA-21a-5p in 1 mL saline was hydrodynamically injected into the mice. Fibrosis analysis was conducted in lung and skin tissues of SSc mice using hematoxylin and eosin as well as Masson's trichrome staining. Immunohistochemistry was used to examine the expression of inflammatory cytokines, phosphorylated signal transducer and activator of transcription-3 (STAT3) at Y705 or S727, and phosphatase and tensin homologue deleted on chromosome-10 (PTEN) in skin tissues of SSc mice. RESULTS: MiRNA-21a-5p overexpression promoted lung fibrosis in bleomycin-induced SSc mice, inducing infiltration of cells expressing TNF-α, IL-1ß, IL-6, or IL-17, along with STAT3 phosphorylated cells in the lesional skin. Conversely, anti-miRNA-21a-5p injection improved fibrosis in the lung and skin tissues of SSc mice, reducing the infiltration of cells secreting inflammatory cytokines in the skin tissue. In particular, it decreased STAT3-phosphorylated cell infiltration at Y705 and increased the infiltration of PTEN-expressing cells in the skin tissue of SSc mice. CONCLUSION: MiRNA-21a-5p promotes fibrosis in an in vivo murine SSc model, suggesting that its inhibition may be a therapeutic strategy for improving fibrosis in SSc.

Lactobacillus acidophilus and propionate attenuate Sjögren's syndrome by modulating the STIM1-STING signaling pathway.

BACKGROUND: Sjögren's syndrome (SS) is an autoimmune disease characterized by inflammation of the exocrine gland. An imbalance of gut microbiota has been linked to SS. However, the molecular mechanism is unclear. We investigated the effects of Lactobacillus acidophilus (L. acidophilus) and propionate on the development and progression of SS in mouse model. METHODS: We compared the gut microbiomes of young and old mice. We administered L. acidophilus and propionate up to 24 weeks. The saliva flow rate and the histopathology of the salivary glands were investigated, and the effects of propionate on the STIM1-STING signaling pathway were evaluated in vitro. RESULTS: Lactobacillaceae and Lactobacillus were decreased in aged mice. SS symptoms were ameliorated by L. acidophilus. The abundance of propionate-producing bacterial was increased by L. acidophilus. Propionate ameliorated the development and progression of SS by inhibiting the STIM1-STING signaling pathway. CONCLUSIONS: The findings suggest that Lactobacillus acidophilus and propionate have therapeutic potential for SS. Video Abstract.

Methotrexate-loaded nanoparticles ameliorate experimental model of autoimmune arthritis by regulating the balance of interleukin-17-producing T cells and regulatory T cells.

BACKGROUND: Rheumatoid arthritis (RA) is a progressive systemic autoimmune disease that is characterized by infiltration of inflammatory cells into the hyperplastic synovial tissue, resulting in subsequent destruction of adjacent articular cartilage and bone. Methotrexate (MTX), the first conventional disease-modifying antirheumatic drug (DMARD), could alleviate articular damage in RA and is implicated in humoral and cellular immune responses. However, MTX has several side effects, so efficient delivery of low-dose MTX is important. METHODS: To investigate the efficacy of MTX-loaded nanoparticles (MTX-NPs) against experimental model of RA, free MTX or MTX-NPs were administered as subcutaneous route to mice with collagen-induced arthritis (CIA) at 3 weeks after CII immunization. The levels of inflammatory factors in tissues were determined by immunohistochemistry, confocal microscopy, real-time PCR, and flow cytometry. RESULTS: MTX-NPs ameliorated arthritic severity and joint destruction in collagen-induced arthritis (CIA) mice compared to free MTX-treated CIA mice. The levels of inflammatory cytokines, including interleukin (IL)-1ß, tumor necrosis factor-α, and vascular endothelial growth factor, were reduced in MTX-NPs-treated mice. Number of CD4 + IL-17 + cells decreased whereas the number of CD4 + CD25 + Foxp3 + cells increased in spleens from MTX- NPs-treated CIA mice compared to MTX-treated CIA mice. The frequency of CD19 + CD25 + Foxp3 + regulatory B cells increased in ex vivo splenocytes from MTX-loaded NPs-treated CIA mice compared to MTX-treated CIA mice. CONCLUSION: The results suggest that MTX-loaded NPs have therapeutic potential for RA.

A bispecific soluble receptor fusion protein that targets TNF-α and IL-21 for synergistic therapy in inflammatory arthritis.

This study was aimed at investigating the therapeutic effects of BITRAP, a bispecific fusion protein targeting TNF-α and IL-21, on the development of autoimmune arthritis in humans and mice. To verify the effects of BITRAP in human, peripheral blood mononuclear cells were cultured with BITRAP under IL-17-producing T (Th17) cell-polarizing conditions or osteoclast differentiation conditions. BITRAP treatment inhibited the production of IL-17 and vascular endothelial growth factor but increased the production of IL-10 in CD4+ T cells, as well as directly suppressed osteoclastogenesis. Collagen-induced arthritis (CIA) and IL-1R antagonist (IL-1Ra) knockout mice were treated with BITRAP. Following injection in CIA mice, BITRAP rapidly migrated into the inflamed joints and remained there for 72 hours. Application of BITRAP attenuated the severity of autoimmune arthritis in CIA and IL-1Ra knockout mice by reducing the numbers of inflammatory cytokine-expressing cells and Th17 cells and antibody secretion. Finally, BITRAP suppressed STAT3 phosphorylation, as well as production of IL-17 and TNF-α, in murine splenic CD4+ T cells. These findings suggest that BITRAP, a bispecific fusion protein targeting TNF-α and IL-21, may be an effective treatment to overcome the limitations of anti-TNF therapy for patients with rheumatoid arthritis.

Metabolic abnormalities exacerbate Sjögren's syndrome by and is associated with increased the population of interleukin-17-producing cells in NOD/ShiLtJ mice.

BACKGROUND: Sjögren's syndrome (SS) is an autoimmune disease mediated by lymphocytic infiltration into exocrine glands, resulting in progressive lacrimal and salivary destruction and dysfunctional glandular secretion. Metabolic syndrome influences the immune system. To investigate its relationship with metabolic abnormalities, we evaluated the pathogenesis of SS and the immune cell populations in non-obese diabetic NOD/ShiLtJ mice with type 1 diabetes (T1D). METHODS: To induce metabolic abnormalities, streptozotocin (STZ)-a glucosamine-nitrosourea compound that destroys pancreatic ß cells, resulting in T1D-was injected into NOD/ShiLtJ mice. The blood glucose level was measured to evaluate induction of T1D. The severity of SS was assessed by determining the body weight, salivary flow rate, and histologic parameters. The expression levels of proinflammatory factors in the salivary glands, lacrimal gland, and spleen were quantified by real-time PCR. The populations of various T- and B-cell subtypes in the peripheral blood, spleen, and salivary glands were assessed by flow cytometry. RESULTS: Induction of T1D in NOD/ShiLtJ mice increased both the severity of SS and the levels of proinflammatory cytokines in the salivary glands compared to the controls. Furthermore, the number of interleukin-17-producing immune cells in the peripheral blood, spleen, and salivary glands was increased in STZ- compared to vehicle-treated NOD/ShiLtJ mice. CONCLUSIONS: Metabolic abnormalities play an important role in the development of SS.

Interleukin-21-mediated suppression of the Pax3-Id3 pathway exacerbates the development of Sjögren's syndrome via follicular helper T cells.

Sjögren's syndrome (SS) is a systemic autoimmune disease with severe dysfunction of glandular secretory function mediated by T and B lymphocyte infiltration into the exocrine glands, including the salivary and lacrimal glands. Follicular helper T (Tfh) cells exacerbate the disease by causing B cell hyperactivity. Inhibitor of DNA binding 3 (Id3) deficiency causes activation of Tfh cells and is known to be a clinical manifestation of human SS disease. In this study, we investigated the mechanism of action of Pax3, which is reduced in SS and can interact with Id3, in NOD/ShiLtJ mice as an animal model of SS. Treatment with interleukin (IL)-21, a major cytokine secreted from Tfh cells, suppressed Pax3 and Id3 expression via STAT3 in splenic T cells in vitro. Administration of pCMV14-3xFlag PAX3 vector improved the severity of SS by reducing the number of Tfh cells in NOD/ShiLtJ mice. Application of IL-21R-Fc increased the number of Pax3- and Id3-positive cells in the salivary glands, while reducing the proportion of Tfh cells and IL-17-producing T cells in NOD/ShiLtJ mice. The salivary glands from SS patients showed decreased levels of Pax3 or Id3 expression compared with healthy controls. Our findings regarding reinforcement of the Pax3-Id3 signal pathway may facilitate the development of novel therapeutic strategies for SS.

CR6-interacting factor 1 controls autoimmune arthritis by regulation of signal transducer and activator of transcription 3 pathway and T helper type 17 cells.

CR6-interacting factor 1 (CRIF1) is a nuclear protein that interacts with other nuclear factors and androgen receptors, and is implicated in the regulation of cell cycle progression and cell growth. In this study, we examined whether CRIF1 exerts an immunoregulatory effect by modulating the differentiation and function of pathogenic T cells. To this end, the role of CRIF1 in rheumatoid arthritis, a systemic autoimmune disease characterized by hyperplasia of synovial tissue and progressive destruction of articular cartilage structure by pathogenic immune cells [such as T helper type 17 (Th17) cells], was investigated. p3XFLAG-CMV-10-CRIF1 was administered to mice with collagen-induced arthritis 8 days after collagen type II immunization and the disease severity and histologic evaluation, and osteoclastogenesis were assessed. CRIF1 over-expression in mice with collagen-induced arthritis attenuated the clinical and histological signs of inflammatory arthritis. Furthermore, over-expression of CRIF1 in mice with arthritis significantly reduced the number of signal transducer and activator of transcription 3-mediated Th17 cells in the spleen as well as osteoclast differentiation from bone marrow cells. To investigate the impact of loss of CRIF1 in T cells, we generated a conditional CRIF1 gene ablation model using CD4-cre transgenic mice and examined the frequency of Th17 cells and regulatory T cells. Deficiency of CRIF1 in CD4+ cells promoted the production of interleukin-17 and reduced the frequency of regulatory T cells. These results suggest a role for CRIF1 in modulating the activities of Th17 cells and osteoclasts in rheumatoid arthritis.

Enrichment of vascular endothelial growth factor secreting mesenchymal stromal cells enhances therapeutic angiogenesis in a mouse model of hind limb ischemia.

Critical limb ischemia, a severe manifestation of peripheral artery disease, is emerging as a major concern in aging societies worldwide. Notably, cell-based gene therapy to induce angiogenesis in ischemic tissue has been investigated as treatment. Despite many studies demonstrating the efficacy of this approach, better therapies are required to prevent serious sequelae such as claudication, amputation and other cardiovascular events. We have now established a simplified method to enhance the effects of therapeutic transgenes by selecting for and transplanting only transduced cells. Herein, mesenchymal stromal cells were transfected to co-express vascular endothelial growth factor as angiogenic factor and enhanced green fluorescent protein as marker. Transfected cells were then collected using flow cytometry based on green fluorescence and transplanted into ischemic hind limbs in mice. Compared with unsorted or untransfected cells, purified cells significantly improved blood perfusion within 21days, suggesting that transplanting only cells that overexpress vascular endothelial growth factor enhances therapeutic angiogenesis. Importantly, this approach may prove to be useful in cell-based gene therapy against a wide spectrum of diseases, simply by replacing the gene to be delivered or the cell to be transplanted.

A probiotic complex, rosavin, zinc, and prebiotics ameliorate intestinal inflammation in an acute colitis mouse model.

BACKGROUND: An altered gut microbiota balance is involved in the pathogenesis of inflammatory bowel disease (IBD), and several probiotic strains are used as dietary supplements to improve intestinal health. We evaluated the therapeutic effect of 12 probiotics in combination with prebiotics, rosavin, and zinc in the dextran sodium sulfate (DSS)-induced colitis mouse model. METHODS: The probiotic complex or the combination drug was administered orally to mice with DSS-induced colitis, and the body weight, disease activity index, colon length, and histopathological parameters were evaluated. Also, the combination drug was applied to HT-29 epithelial cells, and the expression of monocyte chemoattractant protein 1 (MCP-1) was evaluated by real-time polymerase chain reaction. RESULTS: Administration of the combination drug attenuated the severity of DSS-induced colitis. Moreover, the combination drug significantly reduced the levels of the proinflammatory cytokines tumor necrosis factor-α, interleukin (IL)-6, IL-1ß, and IL-17, and significantly increased the levels of Foxp3 and IL-10 in colon sections. Additionally, treatment with the combination drug reduced MCP-1 expression in HT-29 cells. Treatment with the combination drug decreased the levels of α-smooth muscle actin and type I collagen compared with vehicle treatment in mice with DSS-induced colitis. CONCLUSION: These results suggest that the combination of a probiotic complex with rosavin, zinc, and prebiotics exerts a therapeutic effect on IBD by modulating production of pro- and anti-inflammatory cytokines and the development of fibrosis.

Regulator of Calcineurin 3 Ameliorates Autoimmune Arthritis by Suppressing Th17 Cell Differentiation.

Regulator of calcineurin 3 (RCAN3), an endogenous regulator of the calcineurin-nuclear factor of activated T cells (NFAT) signaling pathway, inhibits the phosphatase activity of calcineurin, the nuclear translocation of NFAT, and the NFAT downstream pathway. To investigate the effects of RCAN3 on T-cell regulatory function and the development and progression of inflammatory arthritis, we studied the effects of RCAN3 transfection on regulation of Th17 cell differentiation in a murine T-lymphoma cell line and primary splenic CD4+ T cells. Overexpression of RCAN3 suppressed Th17 cell differentiation through the down-regulation of RAR receptor orphan receptor γT mRNA and up-regulation of forkhead box P3 mRNA. In mice with collagen-induced arthritis, injection of an RCAN3-overexpression vector controlled arthritis development in vivo. Injection of RCAN3 reduced the formation of osteoclasts and expression of inflammatory cytokines in vivo. Antioxidants stimulated the expression of RCAN3 in vitro, and combination therapy with pcDNA-RCAN3 had a synergistic suppressive effect on the development of arthritis. These data suggest that RCAN3 may be an effective treatment for rheumatoid arthritis.

Fraxinellone Attenuates Rheumatoid Inflammation in Mice.

This study aimed to evaluate the therapeutic effect of fraxinellone on inflammatory arthritis and identify the underlying mechanisms. Fraxinellone (7.5 mg/kg) or a vehicle control was injected into mice with collagen-induced arthritis (CIA). The severity of arthritis was evaluated clinically and histologically. The differentiation of CD4⁺ T cells and CD19⁺ B cells was investigated in the presence of fraxinellone. Osteoclastogenesis after fraxinellone treatment was evaluated by staining with tartrate-resistant acid phosphatase (TRAP) and by measuring the mRNA levels of osteoclastogenesis-related genes. Fraxinellone attenuated the clinical and histologic features of inflammatory arthritis in CIA mice. Fraxinellone suppressed the production of interleukin-17 and the expression of RAR-related orphan receptor γ t and phospho-signal transducer and activator of transcription 3 in CD4⁺ T cells. CD19⁺ B cells showed lower expression of activation-induced cytidine deaminase and B lymphocyte-induced maturation protein-1 after treatment with fraxinellone. The formation of TRAP-positive cells and the expression of osteoclastogenesis-related markers were reduced in the presence of fraxinellone. Inhibition of interleukin-17 and osteoclastogenesis was also observed in experiments using human peripheral mononuclear cells. Fraxinellone alleviated synovial inflammation and osteoclastogenesis in mice. The therapeutic effect of fraxinellone was associated with the inhibition of cellular differentiation and activation. The data suggests that fraxinellone could be a novel treatment for inflammatory arthritis, including rheumatoid arthritis.

Fn14-Fc suppresses germinal center formation and pathogenic B cells in a lupus mouse model via inhibition of the TWEAK/Fn14 Pathway.

BACKGROUND: Systemic lupus erythematosus (SLE) is an autoimmune-mediated chronic inflammatory disease. Half of patients with SLE suffer from lupus nephritis, which is major cause of death in SLE. TNF-like weak inducer of apoptosis (TWEAK)/fibroblast growth factor-inducible 14 (Fn14) interactions mediate inflammatory responses that are linked to the pathogenesis of lupus nephritis. Blocking of the TWEAK/Fn14 pathway by Fn14-Fc was performed in a SLE mouse model and the likely therapeutic mechanisms were investigated. METHODS: To investigate the impact of TWEAK on B cell differentiation in SLE, the levels of AID, Blimp-1, and IRF4 messenger RNA were measured in CD19(+) B cells extracted from the spleens of sanroque mice and cultured with TWEAK. To identify the therapeutic effects of Fn14-Fc in SLE, sanroque mice were treated with Fn14-Fc or a control-Fc for 3 weeks. Immunoglobulin (Ig) G, IgG1, IgG2a, and anti-dsDNA antibody (Ab) levels were measured in the sera of each group. Spleens from each group were stained with antibodies against CD4, B220, GL-7, CD138, and PD-1. Kidneys were stained with hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS). RESULTS: Administration of TWEAK increased the mRNA levels of AID, Blimp-1, and IRF4. Treatment with Fn14-Fc suppressed levels of IgG, IgG1, IgG2a, and anti-dsDNA Ab in sera and reduced numbers of B, plasma, and follicular helper T (Tfh) cells in spleens of sanroque mice. In addition, renal protective effects of Fn14-Fc were shown. CONCLUSION: Fn14-Fc had beneficial effects in a SLE mouse model by repressing B cells, plasma cells, Tfh, and renal damage. This suggested that Fn14-Fc represents a potential therapeutic agent for SLE.

JAK2-STAT3 blockade by AG490 suppresses autoimmune arthritis in mice via reciprocal regulation of regulatory T Cells and Th17 cells.

IL-6-mediated STAT3 signaling is essential for Th17 differentiation and plays a central role in the pathogenesis of rheumatoid arthritis. To investigate the molecular mechanism underlying the antirheumatic effects and T cell regulatory effects of STAT3 inhibition, we studied the effects of the JAK 2 inhibitor AG490 on Th17 cell/regulatory T cell (Treg) balance and osteoclastogenesis. AG490 was administered to mice with collagen-induced arthritis (CIA) via i.p. injection, and its in vivo effects were determined. Differential expression of proinflammatory cytokines, including IL-17A, IL-1ß, and IL-6, was analyzed by immunohistochemistry. Levels of phosphorylated STAT3 and STAT5 and differentiation of Th17 cells and Tregs after AG490 treatment in our CIA model were analyzed by immunostaining. In vitro development of Th17 cells and Tregs was analyzed by flow cytometry and real-time PCR. AG490 ameliorated the arthritic phenotype in CIA and increased the proportion of Foxp3(+) Tregs. In contrast, the proportion of IL-17A-producing T cells and levels of inflammatory markers were reduced in AG490-treated mice. Numbers of p-STAT3(+) CD4(+) T cells and p-STAT5(+) CD4(+) T cells were reduced and elevated, respectively, after treatment with AG490. Furthermore, AG490 markedly increased the expression of molecules associated with Treg development (ICOS, programmed cell death protein 1, ICAM-1, and CD103). The development and function of osteoclasts were suppressed by AG490 treatment. Our results suggest that AG490, specifically regulating the JAK2/STAT3 pathway, may be a promising treatment for rheumatoid arthritis.

TWEAK promotes osteoclastogenesis in rheumatoid arthritis.

Bone destruction is critical in the functional disability of patients with rheumatoid arthritis (RA). Osteoclasts, specialized bone-resorbing cells regulated by cytokines, such as receptor activator of NF-κB ligand (RANKL), are primarily implicated in bone destruction in RA. The aim of the study was to examine whether tumor necrosis factor-like weak inducer of apoptosis (TWEAK), a member of the tumor necrosis factor superfamily, has osteoclastogenic activity in patients with RA and in animal models, including mice with collagen-induced arthritis (CIA) and IL-1 receptor antagonist knockout (IL-1RaKO) mice. TWEAK was increased in the synovium, synovial fluid, and serum of patients with RA and in the synovium of CIA mice and IL-1RaKO mice. TWEAK induced RANKL expression in mixed joint cells and splenocytes from CIA mice, IL-1RaKO mice, and fibroblast-like synoviocytes from patients with RA. Both osteoclast precursor cells and osteoclasts express TWEAK receptor fibroblast growth factor-inducible 14. In addition, TWEAK enhanced in vitro osteoclastogenesis without the presence of RANKL-providing cells and by inducing RANKL expression in fibroblast-like synoviocytes. Moreover, treatment with fibroblast growth factor-inducible 14-Fc inhibited RANKL-induced osteoclastogenesis, indicating that endogenous TWEAK also has osteoclastogenic activity. Our data demonstrated that TWEAK promotes osteoclastogenesis in RA, suggesting that therapeutic strategies targeting TWEAK could be effective for treatment of patients with RA, especially in preventing bone destruction.

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.

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.

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.

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.

A green-lipped mussel prevents rheumatoid arthritis via regulation of inflammatory response and osteoclastogenesis.

Rheumatoid arthritis (RA) is a chronic inflammatory disorder characterized by progressive joint destruction. Green-lipped mussel (GLM) has chondro-modulatory and anti-inflammatory properties, but the mechanism underlying the effect of GLM on RA is unclear. To investigate the roles of GLM on the pathogenesis of RA, we examined the effects of GLM in collagen-induced arthritis (CIA) mice and osteoclast differentiation. GLM was orally administrated CIA mice at 3 weeks after chicken type II collagen (CII) immunizations. GLM reduced arthritis severity and the histologic score of CIA mice compared to vehicle. The expression of proinflammatory cytokines (TNF-α, IL-1ß, and IL-17) was decreased in the ankle joints of GLM-treated CIA mice. The expression of CD4+ IL-17+ cells decreased in ex vivo splenocytes and the spleens of GLM-treated CIA mice. Moreover, GLM inhibited TRAP+ multinucleated cells among mouse bone marrow-derived monocytes/macrophages (BMM), and the expression of osteoclast-related genes in mouse BMMs and human monocytes in vitro. These results suggest that GLM has potential as a therapeutic agent that can improve disease by controlling pathologic immune cells and osteoclastogenesis.

A newly developed PLD1 inhibitor ameliorates rheumatoid arthritis by regulating pathogenic T and B cells and inhibiting osteoclast differentiation.

Phospholipase D1 (PLD1), which catalyzes the hydrolysis of phosphatidylcholine to phosphatidic acid and choline, plays multiple roles in inflammation. We investigated the therapeutic effects of the newly developed PLD1 inhibitors A2998, A3000, and A3773 in vitro and in vivo rheumatoid arthritis (RA) model. A3373 reduced the levels of LPS-induced TNF-α, IL-6, and IgG in murine splenocytes in vitro. A3373 also decreased the levels of IFN-γ and IL-17 and the frequencies of Th1, Th17 cells and germinal-center B cells, in splenocytes in vitro. A3373 ameliorated the severity of collagen-induced arthritis (CIA) and suppressed infiltration of inflammatory cells into the joint tissues of mice with CIA compared with vehicle-treated mice. Moreover, A3373 prevented systemic bone demineralization in mice with CIA and suppressed osteoclast differentiation and the mRNA levels of osteoclastogenesis markers in vitro. These results suggest that A3373 has therapeutic potential for RA.