Seung-Ki Kwok

IL-10 suppresses Th17 cells and promotes regulatory T cells in the CD4+ T cell population of rheumatoid arthritis patients.

Interleukin-17-producing CD4(+) T cells (Th17 cells) are the dominant pathogenic cellular component in autoimmune inflammatory diseases, including autoimmune arthritis. IL-10 promotes the generation of Foxp3(+) regulatory T cells via the IL-10 receptor signal. The objective of this study was to examine whether IL-10, which acts as an anti-inflammatory cytokine, has a suppressive effect on the activation of human Th17 cells. Expression of IL-17 and IL-10 was examined immunohistochemically in tissue obtained from rheumatoid arthritis patients. Human peripheral blood CD4(+) T cells were isolated and cultured under various stimulatory conditions. Th17 cells and regulatory T (Treg) cells were detected by flow cytometry. The gene expression of related cytokines and transcription factors were assessed by ELISA and RT-PCR. IL-17 was overexpressed in rheumatoid arthritis patients. IL-10 treatment significantly decreased the numbers of IL-17-producing and RORc-expressing cells among human CD4(+) T cells that had been activated in vitro by Th17-differentiating conditions in autoimmune arthritis patients. IL-10 induced Foxp3(+) regulatory T cells in the human CD4(+) T cell population. Our results demonstrate that IL-17 is overexpressed in autoimmune disease patients and that IL-10 suppresses IL-17 expression. IL-10 may be useful in the treatment of autoimmune diseases.

Lupus mesenteric vasculitis can cause acute abdominal pain in patients with SLE

Lupus mesenteric vasculitis (LMV) is a unique clinical entity found in patients who present with gastrointestinal manifestations of systemic lupus erythematosus, and is the main cause of acute abdominal pain in these patients. LMV usually presents as acute abdominal pain with sudden onset, severe intensity and diffuse localization. Other causes of abdominal pain, such as acute gastroenteritis, peptic ulcers, acute pancreatitis, peritonitis, and other reasons for abdominal surgery should be ruled out. Prompt and accurate diagnosis of LMV is critical to ensure implementation of appropriate immunosuppressive therapy and avoidance of unnecessary surgical intervention. The pathology of LMV comprises immune-complex deposition and complement activation, with subsequent submucosal edema, leukocytoclastic vasculitis and thrombus formation; most of these changes are confined to small mesenteric vessels. Abdominal CT is the most useful tool for diagnosing LMV, which is characterized by the presence of target signs, comb signs, and other associated findings. The presence of autoantibodies against phospholipids and endothelial cells might provide information about the likelihood of recurrence of LMV. Immediate, high-dose, intravenous steroid therapy can lead to a favorable outcome and prevent serious complications such as bowel ischemia, necrosis and perforation.

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.

Proinflammatory Role of Vascular Endothelial Growth Factor in the Pathogenesis of Rheumatoid Arthritis: Prospects for Therapeutic Intervention

Recent experimental and clinical studies have placed new emphasis on the role of angiogenesis in chronic inflammatory disease. Vascular endothelial growth factor (VEGF) and its receptors are the best characterized system in the regulation of rheumatoid arthritis (RA) by angiogenesis. Furthermore, in addition to its angiogenic role, VEGF can act as a direct proinflammatory mediator during the pathogenesis of RA, and protect rheumatoid synoviocytes from apoptosis, which contributes to synovial hyperplasia. Therefore, the developments of synovial inflammation, hyperplasia, and angiogenesis in the joints of RA patients seem to be regulated by a common cue, namely, VEGF. Agents that target VEGF, such as anti-VEGF antibody and aptamer, have yielded promising clinical data in patients with cancer or macular degeneration, and in RA patients, pharmacologic modulations targeting VEGF or its receptor may offer new therapeutic approaches. In this review, the authors integrate current knowledge of VEGF signaling and information on VEGF antagonists gleaned experimentally and place emphasis on the use of synthetic anti-VEGF hexapeptide to prevent VEGF interacting with its receptor.

CTLA4-Ig modifies dendritic cells from mice with collagen-induced arthritis to increase the CD4+CD25+Foxp3+ regulatory T cell population

Cytotoxic T lymphocyte antigen-4 (CTLA4) and IgG fusion protein, CTLA4-Ig, is a therapeutic agent used for rheumatoid arthritis. It binds B7 molecules on dendritic cells (DCs) and thereby blocks B7/CD28 costimulatory interaction and inhibits effective T cell proliferation. However, the effect of CTLA4-Ig on the regulatory T cell (Treg) is still not known. In this study, we investigated the influence of CTLA4-Ig on the CD4+CD25+Foxp3+ Treg population in collagen-induced arthritis (CIA) mouse model. CTLA4-Ig suppressed CIA and increased the CD4+CD25+Foxp3+ Treg population in joint and spleen. When CD11c + DCs and CD4+T cells from CIA mice were cultured with anti-CD3, CTLA4-Ig increased the CD4+CD25 + Foxp3+ Treg population in a TGF-beta-dependent manner. When CD11c + DCs from CIA mice were treated with CTLA4-Ig and adoptively transferred into CIA-induced mice, arthritis did not develop in association with the increase in CD4+CD25+Foxp3+ Treg population. However, in CTLA4-Ig-untreated DC-transferred CIA mice, arthritis developed and then rapidly progressed. Our study demonstrated that CTLA4-Ig suppressed CIA by modifying DCs from CIA mice into tolerogenic DCs to increase the CD4+CD25+Foxp3+ Treg population and this seems to be the new immune regulatory mechanism of CTLA4-Ig.

Impact of interleukin-21 in the pathogenesis of primary Sjogren's syndrome: increased serum levels of interleukin-21 and its expression in the labial salivary glands.

IntroductionInterleukin (IL)-21 is a cytokine that controls the functional activity of effector T helper cells and the differentiation of Th17 cells, and promotes B-cell differentiation. To test whether IL-21 participates in the pathogenesis of primary Sjögrens syndrome (SS), serum IL-21 level was measured and IL-21 expression in the labial salivary glands (LSG) was examined.MethodsSerum IL-21 levels in 40 primary SS, 40 rheumatoid arthritis (RA), and 38 systemic lupus erythematosus (SLE) patients and 20 healthy controls were measured. Serum IL-21 levels of SS patients were assessed for correlations with laboratory data, including anti-nuclear antibody, anti-Ro/La antibodies, globulin, immunoglobulin (Ig) class, and IgG subclass. LSGs from 16 primary SS and 4 controls with sicca symptoms were evaluated for IL-21 and IL-21 receptor (IL-21R) expression by immunohistochemistry. Confocal microscopy was performed to further characterize the IL-21 positive cells.ResultsPrimary SS patients had significantly higher serum IL-21 levels than controls, and these increments correlated positively with levels of IgG, IgG1. Serum IgG1 levels correlated with anti-Ro antibody titers. Immunohistochemical analyses showed that lymphocytic foci and the periductal area of the LSGs from SS patients expressed high levels of IL-21 and lower levels of IL-21R, whereas the control LSGs showed minimal expression of both antigens. The more the lymphocyte infiltrated, IL-21expression in LSGs showed a tendency to increase. Confocal microscopic analyses revealed that IL-21 expressing infiltrating lymphocytes in the LSGs of SS patients also expressed CXCR5.ConclusionsPrimary SS is associated with high serum IL-21 levels that correlate positively with serum IgG, especially IgG1, levels. The expression of IL-21 is increased as more lymphocytes infiltrated in LSGs. These observations suggest that IL-21 may play an important role in primary SS pathogenesis.

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).

Retinoic Acid Attenuates Rheumatoid Inflammation in Mice

Retinoic acid is the active vitamin A derivative and is well-known to have diverse immunomodulatory actions. In this study, we investigated the impact of all-trans retinoic acid (ATRA), a biologic key metabolite of vitamin A, on the development of arthritis and the pathophysiologic mechanisms by which ATRA might have antiarthritic effects in animal model of rheumatoid arthritis (RA; collagen-induced arthritis [CIA] in DBA/1J mice). We showed that treatment with ATRA markedly suppressed the clinical and histologic signs of arthritis in the CIA mice. It reduced the expression of IL-17 in the arthritic joints. Interestingly, Foxp3+ regulatory T cells were markedly increased and IL-17–producing CD4+ T cells (Th17 cells) were decreased in the spleens of ATRA-treated mice. In vitro treatment with ATRA induced the expression of Foxp3 and repressed the IL-17 expression in the CD4+ T cells in mice. ATRA suppressed the production of total IgG and IgG2a in splenocytes that were stimulated by LPS. It also reduced serum levels of total IgG and IgG2 anti-collagen Abs and germinal center formation in CIA mice. In addition, the ATRA-treated mice showed decreased osteoclast formation in arthritic joints. Moreover, ATRA downregulated the expression of receptor activator of NF-κB ligand, the leading player of osteoclastogenesis, in the CD4+ T cells and fibroblast-like synoviocytes from patients with RA. Furthermore, ATRA prevented both human monocytes and mice bone marrow-derived monocytes/macrophage cells from differentiating into osteoclasts. These data suggest ATRA might be an effective treatment modality for RA patients.

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.

IL-17-mediated Bcl-2 expression regulates survival of fibroblast-like synoviocytes in rheumatoid arthritis through STAT3 activation

IntroductionFibroblast-like synoviocytes (FLSs) are a major cell population of the pannus that invades adjacent cartilage and bone in rheumatoid arthritis (RA). The study was undertaken to determine the effect of interleukin-17 (IL-17) on the survival and/or proliferation of FLSs from RA patients and to investigate whether signal tranducer and activator of transcription 3 (STAT3) is implicated in this process.MethodsBcl-2 and Bax expression in FLSs was determined using the real-time PCR and western blot analysis. The expression of Bcl-2 and phosphoSTAT3 in synovial tissues was investigated by confocal microscope. Apoptosis of FLSs was detected by Annexin V/propidium iodide staining and/or phase contrast microscopy. The proliferation of FLSs was determined by CCK-8 ELISA assay.ResultsThe pro-apoptotic Bax is decreased and anti-apoptotic Bcl-2 is increased in FLSs from RA patients compared with those from patients with osteoarthritis (OA). IL-17 upregulated the expression of Bcl-2 in FLSs from RA patients, but not in FLSs from OA patients. STAT3 was found to mediate IL-17-induced Bcl-2 upregulation in FLSs from RA patients. Additionally, IL-17 promoted the survival and proliferation of FLSs from RA patients. Most importantly, treatment with STAT3 inhibitor reversed the protective effect of IL-17 on FLSs apoptosis induced by sodium nitroprusside (SNP).ConclusionsOur data demonstrate that STAT3 is critical in IL-17-induced survival of FLS from RA patients. Therefore, therapeutic strategies that target the IL-17/STAT3 pathway might be strong candidates for RA treatment modalities.