Prostaglandin E2 exacerbates collagen‐induced arthritis in mice through the inflammatory interleukin‐23/interleukin‐17 axis

Objective

Recently, Th17 cells, a new subset of CD4+ T cells, emerged as major players in inflammation/autoimmunity. Maintenance of the Th17 phenotype requires interleukin‐23 (IL‐23), whereas the Th1‐promoting cytokine IL‐12p70 exerts a negative effect on Th17 cell differentiation. The lipid mediator prostaglandin E₂ (PGE₂) acts primarily as a proinflammatory agent in autoimmune conditions, through mechanisms that remain to be elucidated. The aim of this study was to investigate whether PGE₂ released in inflammatory foci activates resident dendritic cells (DCs) to express IL‐23 (at the expense of IL‐12) and IL‐6, resulting in a shift toward Th17 cell responses.

Methods

The effect of PGE₂ on IL‐23 production by DCs and subsequent induction of T cell–derived IL‐17 was assessed in vitro and in vivo. The effect of the stable PGE analog misoprostol was evaluated in a murine model of rheumatoid arthritis, in conjunction with IL‐23 and IL‐17 expression in affected joints and draining lymph nodes.

Results

In vivo administration of PGE₂ induced IL‐23–dependent IL‐17 production. Administration of misoprostol exacerbated collagen‐induced arthritis (CIA). CIA exacerbation was associated with increased levels of IL‐23p19/p40 messenger RNA and reduced expression of IL‐12p35, and with increased levels of the proinflammatory cytokines IL‐17, IL‐1β, IL‐6, and tumor necrosis factor in the affected joint. Following ex vivo restimulation, draining lymph node cells from misoprostol‐treated mice secreted higher levels of IL‐17 and lower levels of interferon‐γ.

Conclusion

Our results indicate that PGE₂ enhances DC‐derived IL‐6 production and induces a shift in the IL‐23/IL‐12 balance in favor of IL‐23, resulting in increased IL‐17 production, presumably through the amplification of self‐reactive Th17 cells.

     

IL-23／IL-17轴与炎症性肠病

传统观点认为,克罗恩病(CD)是与IL-12、IFN-γ、TNF细胞因子轴介导的Th1型反应相关的疾病,溃疡性结肠炎(UC)则与IL-4、IL-5、IL-13轴介导的Th2型反应关系密切.近期研究发现,IL-23/IL-17轴在炎症性肠病的发病机制中可能处于关键地位,并有望成为新的治疗靶标.IL-23诱导幼稚CD4 T细胞分化为高致病性的Th17细胞生成IL-17、IL-6和TNF-α,并引起结肠炎症.     

Prostaglandin E2 synergistically with interleukin-23 favors human Th17 expansion

Microenvironment molecular cues direct T helper (Th) cell differentiation; however, Th17 fate determination is still imprecisely understood in humans. To assess the role of prostaglandin E(2) (PGE(2)) in Th expansion, we activated peripheral blood mononuclear cells by CD3 cross-linking. In the presence of exogenous PGE(2), peripheral blood mononuclear cells produced higher interleukin-17 (IL-17), C-C chemokine ligand 20 (CCL20)/macrophage inflammatory protein 3alpha (MIP-3alpha), CXC chemokine ligand 8 (CXCL8)/IL-8, and lower interferon-gamma and IL-22 levels than in control cultures. Exogenous PGE(2) and IL-23 synergized in inducing IL-17, whereas indomethacin and IL-23 blockade drastically reduced IL-17 but not interferon-gamma production. Furthermore, IL-1 but not tumor necrosis factor was absolutely required for IL-17 production. PGE(2) doubled the frequency of CD4+ T cells producing IL-17 and within the CD4+ subset enhanced C-C chemokine receptor 6 (CCR6) and CCR4 while decreasing CXC chemokine receptor 3 (CXCR3) expression. Furthermore, in CD4+ T-cell lines, the production of IL-17 segregated with the CCR6+ subset. In the presence of CCR6+ compared with CXCR3+ Th cells, monocytes/macrophages produced much higher levels of matrix metalloproteinase-1, -3, and -9 but similar levels of CXCL10 and IL-1beta. These results identify PGE(2) and IL-23 as participating in the expansion of CD4+ T cells endowed with high IL-17 production capacity, which in turn favors monocyte production of mediators important for host defense and tissue destruction.     

Interferon-gamma regulates susceptibility to collagen-induced arthritis through suppression of interleukin-17

OBJECTIVE: The enhanced expression of experimental arthritis in the absence of interferon-gamma (IFNgamma) suggests that IFNgamma suppresses arthritis. Interleukin-17 (IL-17) is a pivotal T cell cytokine in arthritis, and in vitro studies have indicated that IFNgamma suppresses IL-17 production. We undertook this study to test the hypothesis that resistance to collagen-induced arthritis (CIA) in C57BL/6 (B6) mice is regulated by IFNgamma-mediated suppression of IL-17. METHODS: Wild-type (WT) B6 mice, IFNgamma-knockout (KO) B6 mice, and DBA/1 mice were immunized with type II collagen (CII) in Freund's complete adjuvant (CFA). Lymphocytes from immunized mice were analyzed for cytokine production ex vivo by intracellular staining or restimulation with CII and enzyme-linked immunosorbent assays. In vivo blockade of IL-17 was achieved with an anti-IL-17 monoclonal antibody (mAb). RESULTS: CII restimulation of T cells from CII/CFA-immunized mice resulted in an approximately 5-fold increase in IL-17 production in IFNgamma-KO B6 mice compared with WT B6 mice. Neutralization of IFNgamma increased IL-17 production in WT B6 mice, and neutralization of IL-4 had a synergistic effect. Interestingly, the prototypical CIA-susceptible strain DBA/1 also demonstrated a high IL-17 and a low IFNgamma cytokine profile compared with WT B6 mice. Administration of the anti-IL-17 mAb attenuated arthritis in DBA/1 mice and almost completely prevented expression of arthritis in IFNgamma-KO B6 mice. CONCLUSION: These results indicate that sensitivity of IFNgamma-deficient B6 mice to CIA is associated with high IL-17 production and that this cytokine is required for expression of arthritis in this strain.     

Natural killer cell degeneration exacerbates experimental arthritis in mice via enhanced interleukin-17 production

OBJECTIVE: An altered phenotype and dysfunction of natural killer (NK) cells have been observed in patients with rheumatoid arthritis. The aim of this study was to determine whether dysregulated NK cells contribute to the pathogenesis of experimental arthritis. METHODS: For initiation of collagen-induced arthritis (CIA), DBA/1J mice were immunized with type II collagen in Freund's adjuvant. Control mice were immunized with adjuvant alone. NK cells from the blood, spleens, and bone marrow of immunized mice were analyzed by flow cytometry. Levels of interleukin-17 (IL-17) secretion and autoantibody production were measured by enzyme-linked immunosorbent assays. Immunized mice in which NK cells were depleted by anti-asialo G(M1) antibody treatment were assessed for the development of CIA. Moreover, sorting-purified NK cells from both mice with CIA and control mice were analyzed for cytokine gene expression. RESULTS: We observed markedly reduced frequencies of NK cells in the blood and spleens of mice with CIA compared with the frequencies in adjuvant-treated control mice. Upon NK cell depletion, immunized mice displayed an early onset of arthritis with more severe clinical symptoms, which correlated with increased plasma cell generation and autoantibody production. Moreover, a substantially increased number of IL-17-secreting cells in synovial tissue and more pronounced joint damage were observed. Freshly isolated NK cells from mice with CIA showed markedly reduced expression of interferon-gamma (IFNgamma). Furthermore, coculture of normal NK cells and CD4+ T cells revealed that NK cells strongly suppressed production of Th17 cells via their IFNgamma production. CONCLUSION: These results suggest that NK cells play a protective role in the development of experimental arthritis, an effect that is possibly mediated by suppressing Th17 cell generation via IFNgamma production.     

Pivotal roles of the interleukin-23/T helper 17 cell axis in hepatitis B

T helper 17 (Th17) cells are a newly identified subset of T helper cells that play important roles in host defense against extracellular bacteria, as well as in the pathogenesis of autoimmune disease. Research interest in these cells was piqued when hepatitis B virus (HBV)-infected patients were found to have significantly elevated Th17 cell frequency, and it was proposed that these proinflammatory effectors may promote the HBV disease process. Subsequent studies have revealed that Th17 cells drive immune-mediated pathology of HBV infection, and that IL-23 amplifies the Th17 cell responses and liver inflammation. As a result, new pathways of HBV-mediated liver damage have been elucidated, along with promising new targets of molecular therapeutic strategies. Ongoing research is also providing significant insights into the target cells and underlying mechanisms of Th17-secreted cytokines, including IL-17A, IL-21 and IL-22. Future studies are expected to fully uncover the cytokine-related mechanisms mediating HBV-induced liver inflammation, and to determine the yet unknown cell source of IL-23. This review will draw upon the most up-to-date available data to discuss the putative roles and detailed mechanisms of IL-23/Th17 cell axis in HBV infection-mediated liver pathogenesis.     

Mast cell deficiency exacerbates inflammatory bowel symptoms in interleukin-10-deficient mice

AIM: To test the role of mast cells in gut inflammation and colitis using interleukin (IL)-10-deficient mice as an experimental model.METHODS: Mast cell-deficient (Kit^W-sh/W-sh) mice were crossbred with IL-10-deficient mice to obtain double knockout (DKO) mice. The growth, mucosal damage and colitis status of DKO mice were compared with their IL-10-deficient littermates.RESULTS: DKO mice exhibited exacerbated colitis compared with their IL-10-deficient littermates, as shown by increased pathological score, higher myeloperoxidase content, enhanced Th1 type pro-inflammatory cytokines and inflammatory signaling, elevated oxidative stress, as well as pronounced goblet cell loss. In addition, deficiency in mast cells resulted in enhanced mucosal damage, increased gut permeability, and impaired epithelial tight junctions. Mast cell deficiency was also linked to systemic inflammation, as demonstrated by higher serum levels of tumor necrosis factor α and interferon γ in DKO mice than that in IL-10-deficient mice.CONCLUSION: Mast cell deficiency in IL-10-deficient mice resulted in systematic and gut inflammation, impaired gut barrier function, and severer Th1-mediated colitis when compared to mice with only IL-10-deficiency. Inflammation and impaired gut epithelial barrier function likely form a vicious cycle to worsen colitis in the DKO mice.     

Enhanced production of interleukin-6 in mice with type II collagen-induced arthritis

We established an interleukin-6 (IL-6)-dependent cell line from murine plasmacytoma MOPC-104E cells. This cell line (designated PIL-6) was found to respond to murine and to human IL-6, but not to any other cytokines. We used this cell line to investigate the involvement of IL-6 production in type II collagen-induced arthritis in DBA/1 mice. Only marginal IL-6 activity was detected in sera from DBA/1 mice inoculated with Freund's complete adjuvant (FCA) alone, with an unrelated protein (bovine serum albumin) plus FCA, or with type II collagen plus Freund's incomplete adjuvant. However, enhanced IL-6 activity was observed in DBA/1 mice that had been injected with type II collagen plus FCA to induce arthritis. The elevated level of serum IL-6 activity was associated with high levels of IL-6 produced when lymph node cells from arthritic mice were stimulated in vitro with type II collagen. We also found that the L3T4+ T cell subset is responsible for the enhanced production of IL-6 in arthritic mice. The results are discussed in the context of potential roles of IL-6 in the induction and/or expression of chronic, progressive arthritis.     

Contribution of the IL-17/IL-23 axis to the pathogenesis of inflammatory bowel disease

Inflammatory bowel diseases(IBDs) are chronic disorders of modern society, requiring management strategies aimed at prolonging an active life and establishing the exact etiology and pathogenesis.These idiopathic diseases have environmental, genetic,immunologic, inflammatory, and oxidative stress components. On the one hand, recent advances have shown that abnormal immune reactions against the microorganisms of the intestinal flora are responsible for the inflammation in genetically susceptible individuals. On the other hand, in addition to T helper cell-type(Th) 1 and Th2 immune responses,other subsets of T cells, namely regulatory T cells and Th17 maintained by IL-23 are likely to develop IBD. IL-23 acts on innate immune system members and also facilitates the expansion and maintenance of Th17 cells. The IL-17/IL-23 axis is relevant in IBD pathogenesis both in human and experimental studies. Novel biomarkers of IBD could be calprotectin,microRNAs, and serum proinflammatory cytokines.An efficient strategy for IBD therapy is represented by the combination of IL-17 A and IL-17 F in acute IL-17 A knockout TNBS-induced colitis, and also definite decrease of the inflammatory process in IL-17 F knockout, DSS-induced colitis have been observed.Studying the correlation between innate and adaptive immune systems, we hope to obtain a focused reviewin order to facilitate future approaches aimed at elucidating the immunological mechanisms that control gut inflammation.     

Crucial role of the interleukin-6/interleukin-17 cytokine axis in the induction of arthritis by glucose-6-phosphate isomerase

OBJECTIVE: To clarify the glucose-6-phosphate isomerase (GPI)-specific CD4+ T cell lineage involved in GPI-induced arthritis and to investigate their pathologic and regulatory roles in the induction of the disease. METHODS: DBA/1 mice were immunized with GPI to induce arthritis. CD4+ T cells and antigen-presenting cells were cocultured with GPI, and cytokines in the supernatant were analyzed by enzyme-linked immunosorbent assay. Anti-interferon-gamma (anti-IFNgamma) monoclonal antibody (mAb), anti-interleukin-17 (anti-IL-17) mAb, or the murine IL-6 receptor (IL-6R) mAb MR16-1 was injected at different time points, and arthritis development was monitored visually. After MR16-1 was injected, percentages of Th1, Th2, Th17, and Treg cells were analyzed by flow cytometry, and CD4+ T cell proliferation was analyzed using carboxyfluorescein diacetate succinimidyl ester. RESULTS: GPI-specific CD4+ T cells were found to be differentiated to Th1 and Th17 cells, but not Th2 cells. Administration of anti-IL-17 mAb on day 7 significantly ameliorated arthritis (P < 0.01), whereas administration of anti-IFNgamma mAb exacerbated arthritis. Neither anti-IL-17 mAb nor anti-IFNgamma mAb administration on day 14 ameliorated arthritis. Administration of MR16-1 on day 0 or day 3 protected against arthritis induction, and MR16-1 administration on day 8 significantly ameliorated existing arthritis (P < 0.05). After administration of MR16-1, there was marked suppression of Th17 differentiation, without an increase in Th1, Th2, or Treg cells, and CD4+ T cell proliferation was also suppressed. CONCLUSION: IL-6 and Th17 play an essential role in GPI-induced arthritis. Since it has previously been shown that treatment with a humanized anti-IL-6R mAb has excellent effects in patients with rheumatoid arthritis (RA), we propose that the IL-6/IL-17 axis might also be involved in the generation of RA, especially in the early effector phase.     

白细胞介素-23/-17轴在小鼠急性实验性结肠炎中的表达及作用

目的 研究白细胞介素(IL)-23/IL-17轴在小鼠实验性结肠炎结肠组织中的表达和作用.方法 将64只小鼠分为对照组24只、模型组24只、抗体组8只、正常血清组8只.除对照组外,其余各组建立小鼠急性实验性结肠炎模型.对照组和模型组小鼠分别于造模后24 h、48 h、7 d处死.抗体组和正常血清组小鼠分别于造模前2 h腹腔内注射多克隆大鼠抗小鼠IL-17中和抗体和正常大鼠血清,于造模48 h后处死.检测各组小鼠组织学损伤评分、肠组织髓过氧化物酶(MPO)活性;酶联免疫吸附试验检测结肠组织IL-23p19、IL-17含量;免疫组化染色检测核因子(NF)-κB p65在结肠组织中的表达;实时荧光定量(RT)PCR检测IL-23p19、IL-17、IL-12p35的mRNA表达水平.结果 模型组24 h、48 h、7 d时IL-23p19蛋白表达水平和mRNA表达水平[分别为(15.53±3.32)、(31.16±4.98)、(14.03±3.56)ng/mg蛋白和4.09±0.34、3.39±0.46、6.54±1.82]、IL-17的蛋白表达水平和mRNA表达水平[分别为(0.35±0.06)、(0.38±0.08)、(0.26±0.05)ng/mg蛋白和4.21±2.61、2.65±0.91、5.63±1.43]均显著高于正常对照组(P值均＜0.05),48 h时达高峰.IL-23与IL-17蛋白表达水平和mRNA表达水平呈正相关(r值分别为0.745和0.793,P＜0.05).抗体组IL-23p19和IL-12p35高水平表达,但NF-κB p65阳性细胞率、组织学评分及MPO活性[分别为1.86%±0.36%、0.63±0.52、(0.40±0.03)U/g]明显低于48 h模型组[分别为4.35%±0.37%、5.13±0.64、(2.29±0.40)U/g],说明中和IL-17后能明显减轻结肠炎症,抑制NF-κB活性.结论 IL-23/IL-17轴在急性实验性结肠炎早期阶段起关键作用.IL-17有望成为炎症性肠病治疗的新靶标.