Enhancing effect of IL-1, IL-17, and TNF-alpha on macrophage inflammatory protein-3alpha production in rheumatoid arthritis: regulation by soluble receptors and Th2 cytokines

Relationship of IL-17A and IL-17F genetic variations to cervical cancer risk: a meta-analysis

Aim: We performed a meta-analysis to determine a more precise relationship of IL-17A and IL-17F polymorphisms with cervical cancer risk. Materials & methods: PubMed, CNKI and Wan Fang databases were searched for studies on these associations using STATA version 10.0 software. Results: Five studies were included. The AG and AA genotypes and A allele of IL-17A rs2275913 were correlated with an elevated risk of cervical cancer. The TT genotype and T allele of IL-17A rs3748067 and the CC genotype and C allele of IL-17F rs763780 carried a moderate risk of cervical cancer, when compared with the wild-type genotype. Conclusion: IL-17A and IL-17F polymorphisms therefore have the potential to act as predictive biomarkers for cervical cancer risk.

Update on interleukin-17: a role in the pathogenesis of inflammatory arthritis and implication for clinical practice

Interleukin-17 (IL-17A) is a cytokine critical for the acute defence against extracellular bacterial and fungal infections. Excess production during chronic inflammation has been associated with many inflammatory and autoimmune disorders. The present review describes the key molecules of the IL-17 pathway, which are or could be targeted for treatment. Since targeting of IL-17A may affect defence mechanisms, the pathogenesis of such possible adverse events is analysed. Then the contributions of IL-17 to bone changes in various forms of arthritis are discussed. Finally, the results of current inhibitors of the IL-17 pathway in clinical trials are detailed. IL-17A inhibition has been first registered for the treatment of psoriasis, psoriatic arthritis and ankylosing spondylitis. Other therapeutic options are now tested in a long list of diseases.

Neurodegeneration Enhances the Development of Arthritis

The prevalence of neurodegenerative disease and arthritis increases with age. Despite both processes being associated with immune activation and inflammation, little is known about the mechanistic interactions between neurodegenerative disease and arthritis. In this article, we show that tau-transgenic (tau-tg) mice that develop neurodegenerative disease characterized by deposition of tau tangles in the brain are highly susceptible to developing arthritis. Already at steady-state conditions, tau-tg mice exhibit peripheral immune activation that is manifested by higher numbers of granulocytes, plasmablasts, and inflammatory Ly6C^hi CCR2⁺ monocytes, as well as increased levels of proinflammatory cytokines, such as TNF-α and IL-17. Upon induction of collagen-induced arthritis (CIA), tau-tg mice displayed an increased incidence and an earlier onset of CIA that was associated with a more pronounced inflammatory cytokine response. Furthermore, induction of CIA led to significantly elevated numbers of Iba-1-expressing cells in the brain, indicative of microglia activation, and the formation of anti-tau Abs in tau-tg mice. These changes were accompanied by the resolution of tau tangles and significantly decreased neurodegenerative pathology. In summary, these data show that neurodegenerative disease enhances the development of arthritis. In addition, arthritis, once induced, triggers innate immune responses in the brain, leading to resolution of neurodegenerative changes.

Baseline CXCL10 and CXCL13 levels are predictive biomarkers for tumor necrosis factor inhibitor therapy in patients with moderate to severe rheumatoid arthritis: a pilot, prospective study

BACKGROUND

TNF inhibitors have been used as a treatment for moderate to severe RA patients. However, reliable biomarkers that predict therapeutic response to TNF inhibitors are lacking. In this study, we investigated whether chemokines may represent useful biomarkers to predict the response to TNF inhibitor therapy in RA.

METHODS

RA patients (n = 29) who were initiating adalimumab or etanercept were recruited from the rheumatology clinics at Cooper University Hospital. RA patients were evaluated at baseline and 14 weeks after TNF inhibitor therapy, and serum levels of CXCL10, CXCL13, and CCL20 were measured by ELISA. Responders (n = 16) were defined as patients who had good or moderate response at week 14 by EULAR response criteria, and nonresponders (n = 13) were defined as having no response.

RESULTS

Responders had higher levels of baseline CXCL10 and CXCL13 compared to nonresponders (p = 0.03 and 0.002 respectively). There was no difference in CCL20 levels. CXCL10 and CXCL13 were highly correlated with each other, and were higher in seropositive RA patients. CXCL10 and CXCL13 levels were decreased after TNF inhibitor therapy in responders. Baseline additive levels of CXCL10 + 13 were correlated with changes in DAS score at 14 weeks after TNF inhibitor therapy (r = 0.42, p = 0.03), and ROC curve analyses for predictive ability of CXCL10 + 13 showed an AUC of 0.83.

CONCLUSIONS

Elevated baseline levels of CXCL10 and CXCL13 were associated with favorable response to TNF inhibitor therapy in RA. Subjects with high CXCL10 and high CXCL13 may represent a subset of RA patients whose inflammatory reactions are primarily driven by TNF.

IL-17 in Chronic Inflammation: From Discovery to Targeting

Interleukin-17 (IL-17) is a cytokine which elicits protection against extracellular bacterial and fungal infections and which plays important roles in inflammation. However, when produced in excess, it contributes to chronic inflammation associated with many inflammatory and autoimmune disorders. This has made IL-17 an attractive therapeutic target. The present review describes the structure of the IL-17 family, the IL-17 receptor complex, and the cells producing IL-17. The contributions of IL-17 to disease as well as new IL-17-based treatment options are discussed. Finally, the results of IL-17 or IL-17 receptor inhibitors in clinical trials are detailed. With a fruitful outlook, drug registration has now been granted for psoriasis psoriatic arthritis and ankylosing spondylitis, and also bears great potential in a growing number of conditions.

CgIL17-5, an ancient inflammatory cytokine in Crassostrea gigas exhibiting the heterogeneity functions compared with vertebrate interleukin17 molecules

Interleukin 17 (IL17) is a proinflammatory cytokine that plays an important role in immune response. Recently, five novel IL17 homologs have been identified by screening and analyzing the genome of pacific oyster Crassostrea gigas. In the present study, the functions of CgIL17-5 were investigated by examining the distribution of its mRNA and protein, ligands binding and modulation in immune response. The mRNA expression levels of CgIL17-5 in hemocytes of oysters post twice challenges of Vibrio splendidus were all significantly up-regulated (P < 0.01), while the secondary pathogen infection attenuated the expression level of CgIL17-5 mRNA compared with the primary challenge. CgIL17-5 was found to be located on oyster hemocyte membranes through fluorescence confocal assay. The luciferase reporter assays showed that CgIL17-5 could activate the transfactors NF-κB, CREB and ATF-1, and involve in their signal pathways in HEK293T cells. Meanwhile, CgIL17-5 could augment the IL6 synthesis in HuVEC cells, playing the similar roles as human IL17 in inflammatory response. Additionally, the recombinant CgIL17-5 (rCgIL17-5) could directly bind peptidoglycan (PGN), lipopolysaccharide (LPS), poly (I:C) and β-1,3-glucan, with the highest affinity to PGN, and significantly inhibit the growth of Micrococcus luteus and Escherichia coli. All the results collectively suggested that CgIL17-5, as an ancient inflammatory cytokine, could not only activate signal transduction for the release of other cytokines, but also mediate the clearance of extracellular bacteria in oysters.

Lapatinib ameliorates experimental arthritis in rats

Epidermal growth factor receptor (EGFR) and its ligands are commonly expressed by synovial cells. The aim of the present study was to detect the potential effect of lapatinib an inhibitor of EGFR tyrosine kinases on collagen-induced arthritis. Thirty Wistar albino female rats were randomized into three groups. Arthritis was induced by intradermal injection of chicken type II collagen with incomplete Freund's adjuvant. Serum TNF-α, IL-17, and malondialdehyde (MDA) levels were analyzed. Tissue superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) activities, and nuclear factor erythroid 2-related factor-2 (Nrf2) and heme oxgenase-1 (HO-1) expressions were determined. TNF-α, IL-17 and MDA levels, and Nrf2 and HO-1 expressions were lower in lapatinib-treated (30 mg/kg/day) group compared to sham group, while SOD, catalase, and GPx activities were higher (p < 0.05). Moreover, lapatinib ameliorated perisynovial inflammation and cartilage-bone destruction (p < 0.001). In conclusion, EGFR may have prominent pathogenic role and lapatinib may be an effective therapeutic option for arthritis.

Complementary action of granulocyte macrophage colony-stimulating factor and interleukin-17A induces interleukin-23, receptor activator of nuclear factor-κB ligand, and matrix metalloproteinases and drives bone and cartilage pathology in experimental arthritis: rationale for combination therapy in rheumatoid arthritis

Introduction

Type 17 T helper cells and interleukin (IL)-17 play important roles in the pathogenesis of human and murine arthritis. Although there is a clear link between IL-17 and granulocyte macrophage colony-stimulating factor (GM-CSF) in the inflammatory cascade, details about their interaction in arthritic synovial joints are unclear. In view of the introduction of GM-CSF and IL-17 inhibitors to the clinic, we studied how IL-17 and GM-CSF orchestrate the local production of inflammatory mediators during experimental arthritis.

Methods

To allow detection of additive, complementary or synergistic effects of IL-17 and GM-CSF, we used two opposing experimental approaches: treatment of arthritic mice with neutralising antibodies to IL-17 and GM-CSF and local overexpression of these cytokines in naive synovial joints. Mice were treated for 2 weeks with antibodies against IL-17 and/or GM-CSF after onset of collagen-induced arthritis. Naive mice were injected intraarticularly with adenoviral vectors for IL-17 and/or GM-CSF, resulting in local overexpression. Joint inflammation was monitored by macroscopic scoring, X-rays and histology. Joint washouts, synovial cell and lymph node cultures were analysed for cytokines, chemokines and inflammatory mediators by Luminex analysis, flow cytometry and quantitative polymerase chain reaction.

Results

Combined therapeutic anti-IL-17 and anti-GM-CSF ameliorated arthritis progression, and joint damage was dramatically reduced compared with treatment with anti-IL-17 or anti-GM-CSF alone. Anti-IL-17 specifically reduced synovial IL-23 transcription, whereas anti-GM-CSF reduced transcription of matrix metalloproteinases (MMPs) and receptor activator of nuclear factor κB ligand (RANKL). Overexpression of IL-17 or GM-CSF in naive knee joints elicited extensive inflammatory infiltrate, cartilage damage and bone destruction. Combined overexpression revealed additive and synergistic effects on the production of MMPs, RANKL and IL-23 in the synovium and led to complete destruction of the joint structure within 7 days.

Conclusions

IL-17 and GM-CSF differentially mediate the inflammatory process in arthritic joints and show complementary and local additive effects. Combined blockade in arthritic mice reduced joint damage not only by direct inhibition of IL-17 and GM-CSF but also by indirect inhibition of IL-23 and RANKL. Our results provide a rationale for combination therapy in autoinflammatory conditions, especially for patients who do not fully respond to inhibition of the separate cytokines.

Bone Loss Triggered by the Cytokine Network in Inflammatory Autoimmune Diseases

Bone remodeling is a lifelong process in vertebrates that relies on the correct balance between bone resorption by osteoclasts and bone formation by osteoblasts. Bone loss and fracture risk are implicated in inflammatory autoimmune diseases such as rheumatoid arthritis, ankylosing spondylitis, inflammatory bowel disease, and systemic lupus erythematosus. The network of inflammatory cytokines produced during chronic inflammation induces an uncoupling of bone formation and resorption, resulting in significant bone loss in patients with inflammatory autoimmune diseases. Here, we review and discuss the involvement of the inflammatory cytokine network in the pathophysiological aspects and the therapeutic advances in inflammatory autoimmune diseases.

Interleukin-17 and its implication in the regulation of differentiation and function of hematopoietic and mesenchymal stem cells

Adult stem cells have a great potential applicability in regenerative medicine and cell-based therapies. However, there are still many unresolved issues concerning their biology, and the influence of the local microenvironment on properties of stem cells has been increasingly recognized. Interleukin (IL-) 17, as a cytokine implicated in many physiological and pathological processes, should be taken into consideration as a part of a regulatory network governing tissue-associated stem cells' fate. This review is focusing on the published data on the effects of IL-17 on the properties and function of hematopoietic and mesenchymal stem cells and trying to discuss that IL-17 achieves many of its roles by acting on adult stem cells.

Cyr61 participates in the pathogenesis of rheumatoid arthritis by promoting proIL-1β production by fibroblast-like synoviocytes through an AKT-dependent NF-κB signaling pathway

IL-1β plays a major role in the development of rheumatoid arthritis (RA). We previously showed that Cyr61 participates in RA pathogenesis as a proinflammatory factor. Here, we found that the levels of IL-1β and Cyr61 were higher in RA SF than in osteoarthritis (OA) SF. IL-1β mRNA and proIL-1β protein levels were remarkably increased in Cyr61-stimulated FLS; however, IL-1β was hardly detectable in the supernatant. We also found that the level of adenosine triphosphate (ATP) in SF and ST was significantly increased in RA patients and that the level of IL-1β in supernatants from Cyr61-activated FLS increased significantly when we added exogenous ATP to the culture. Mechanistically, Cyr61 induced proIL-1β production in FLS via the AKT-dependent NF-κB signaling pathway, and ATP caused Cyr61-induced proIL-1β to generate IL-1β in a caspase-1-dependent manner. Our results reveal a novel role of Cyr61 in RA that involves the promotion of proIL-1β production in FLS.

CCR2-dependent dendritic cell accumulation in the central nervous system during early effector experimental autoimmune encephalomyelitis is essential for effector T cell restimulation in situ and disease progression

Dendritic cells (DCs)--although absent from the healthy CNS parenchyma--rapidly accumulate within brain and spinal cord tissue during neuroinflammation associated with experimental autoimmune encephalomyelitis (EAE; a mouse model of multiple sclerosis). Yet, although DCs have been appreciated for their role in initiating adaptive immune responses in peripheral lymphoid organ tissues, how DCs infiltrate the CNS and contribute to ongoing neuroinflammation in situ is poorly understood. In this study, we report the following: 1) CD11c(+) bone marrow-derived DCs and CNS-infiltrating DCs express chemokine receptor CCR2; 2) compared with CCR2(+/+) cells, adoptively transferred CCR2(-/-) bone marrow-derived DCs or DC precursors do not accumulate in the CNS during EAE, despite abundance in blood; 3) CCR2(-/-) DCs show less accumulation in the inflamed CNS in mixed bone marrow chimeras, when compared with CCR2(+/+) DCs; and 4) ablation of CCR2(+/+) DCs during EAE clinical onset delays progression and attenuates cytokine production by infiltrating T cells. Whereas the role of CCR2 in monocyte migration into the CNS has been implicated previously, the role of CCR2 in DC infiltration into the CNS has never been directly addressed. Our data suggest that CCR2-dependent DC recruitment to the CNS during ongoing neuroinflammation plays a crucial role in effector T cell cytokine production and disease progression, and signify that CNS-DCs and circulating DC precursors might be key therapeutic targets for suppressing ongoing neuroinflammation in CNS autoimmune diseases.

Effects of Interleukin-17A on Osteogenic Differentiation of Isolated Human Mesenchymal Stem Cells

OBJECTIVES

Rheumatoid arthritis (RA) is characterized by defective bone repair and excessive destruction and ankylosing spondylitis (AS) by increased ectopic bone formation with syndesmophytes. Since TNF-α and IL-17A are involved in both diseases, this study investigated their effects on the osteogenic differentiation of isolated human bone marrow-derived mesenchymal stem cells (hMSCs).

METHODS

Differentiation of hMSCs into osteoblasts was induced in the presence or absence of IL-17A and/or TNF-α. Matrix mineralization (MM) was evaluated by alizarin red staining and alkaline phosphatase (ALP) activity. mRNA expression was measured by qRT-PCR for bone morphogenetic protein (BMP)-2 and Runx2, genes associated with osteogenesis, DKK-1, a negative regulator of osteogenesis, Schnurri-3 and receptor activator of nuclear factor kappa B ligand (RANKL), associated with the cross talk with osteoclasts, and TNF-α receptor type I and TNF-α receptor type II (TNFRII).

RESULTS

TNF-α alone increased both MM and ALP activity. IL-17A alone increased ALP but not MM. Their combination was more potent. TNF-α alone increased BMP2 mRNA expression at 6 and 12 h. These levels decreased in combination with IL-17A at 6 h only. DKK-1 mRNA expression was inhibited by TNF-α and IL-17A either alone or combined. Supporting an imbalance toward osteoblastogenesis, RANKL expression was inhibited by TNF-α and IL-17A. However, TNF-α but not IL-17 alone decreased Runx2 mRNA expression at 6 h. In parallel, TNF-α but not IL-17 alone increased Schnurri-3 expression with a synergistic effect with their combination. This may be related to an increase of TNFRII overexpression.

CONCLUSION

IL-17 increased the effects of TNF-α on bone matrix formation by hMSCs. However, IL-17 decreased the TNF-α-induced BMP2 inhibition. Synergistic interactions between TNF-α and IL-17 were seen for RANKL inhibition and Schnurri-3 induction. Such increase of Schnurri-3 may in turn activate osteoclasts leading to bone destruction as in RA. Conversely, in the absence of osteoclasts, this could promote ectopic bone formation as in AS.

Chimeric anti-IL-17 full-length monoclonal antibody is a novel potential candidate for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease, primarily manifesting as inflammatory arthritis. It is associated with chronic inflammation of the synovial joints, mostly in the hands and feet, as well as with systemic extra-articular inflammation. The chimeric anti-interleukin (IL)-17 full-length monoclonal antibody (CMa17Aab) targets IL-17A, which is an important cytokine in the pathogenesis of RA and other inflammatory disorders. In this study, we investigated whether CMa17Aab exerts therapeutic effects in a mouse model of type II collagen-induced arthritis (CIA). Mice with CIA were subcutaneously injected with the humanized CMa17Aab antibody. The effects of treatment were assessed by estimating the arthritis severity score, the extent of histological damage and bone destruction, the autoreactive humoral and cellular immune responses and the production of cytokines. Treatment with CMa17Aab exerted beneficial effects in the mice with CIA as regards clinical and histological parameters. Compared with the controls, treatment with CMa17Aab resulted in a significant alleviation of the severity of the symptoms of arthritis, by preventing bone damage and cartilage destruction, reducing humoral and cellular immune responses, and downregulating the expression of IL-6, IL-8, matrix metalloproteinase (MMP)-3, IL-17, IL-1β, tumor necrosis factor (TNF)-α, receptor activator for nuclear factor-κB ligand (RANKL) and interferon (IFN)-γ in inflamed tissues. In conclusion, our study demonstrates that treatment with CMa17Aab exerts beneficial effects in mice with CIA, by preventing joint inflammation, cartilage destruction and bone damage. These preliminary results suggest that CMa17Aab is an important regulator in RA, and that it may represent a novel therapeutic agent that may prove useful in the treatment of this disease.

NADPH oxidase mediates synergistic effects of IL-17 and TNF-α on CXCL1 expression by epithelial cells after lung ischemia-reperfusion

Ischemia-reperfusion (I/R) injury leads to increased mortality and morbidity in lung transplant patients. Lung I/R injury involves inflammation contributed by innate immune responses. IL-17 and TNF-α, from iNKT cells and alveolar macrophages, respectively, contribute importantly to lung I/R injury. This study tests the hypothesis that IL-17 and TNF-α synergistically mediate CXCL1 (a potent neutrophil chemokine) production by alveolar type II epithelial (ATII) cells via an NADPH oxidase-dependent mechanism during lung I/R. Using a hilar clamp model, wild-type and p47(phox-/-) (NADPH oxidase-deficient) mice underwent left lung I/R, with or without recombinant IL-17 and/or TNF-α treatment. Wild-type mice undergoing I/R treated with combined IL-17 and TNF-α had significantly enhanced lung dysfunction, edema, CXCL1 production, and neutrophil infiltration compared with treatment with IL-17 or TNF-α alone. However, p47(phox-/-) mice had significantly less pulmonary dysfunction, CXCL1 production, and lung injury after I/R that was not enhanced by combined IL-17-TNF-α treatment. Moreover, in an acute in vitro hypoxia-reoxygenation model, murine ATII cells showed a multifold synergistic increase in CXCL1 expression after combined IL-17-TNF-α treatment compared with treatment with either cytokine alone, which was significantly attenuated by an NADPH oxidase inhibitor. Conditioned media transfer from hypoxia-reoxygenation-exposed iNKT cells and macrophages, major sources of IL-17 and TNF-α, respectively, to ATII cells significantly enhanced CXCL1 production, which was blocked by NADPH oxidase inhibitor. These results demonstrate that IL-17 and TNF-α synergistically mediate CXCL1 production by ATII cells after I/R, via an NADPH oxidase-dependent mechanism, to induce neutrophil infiltration and lung I/R injury.

IL-17A potentiates TNFα-induced secretion from human endothelial cells and alters barrier functions controlling neutrophils rights of passage

Interleukin-17A (IL-17A) is an important pro-inflammatory cytokine that regulates leukocyte mobilization and recruitment. To better understand how IL-17A controls leukocyte trafficking across capillaries in the peripheral blood circulation, we used primary human dermal microvascular endothelial cells (HDMEC) to investigate their secretory potential and barrier function when activated with IL-17A and TNFα. Activation by TNFα and IL-17A causes phosphorylation of p38 as well as IκBα whereby NFκB subsequently becomes phosphorylated, a mechanism that initiates transcription of adhesion molecules such as E-selectin. Members of the neutrophil-specific GRO-family chemokines were significantly up-regulated upon IL-17A stimulation on the mRNA and protein level, whereas all tested non-neutrophil-specific chemokines remained unchanged in comparison. Moreover, a striking synergistic effect in the induction of granulocyte colony-stimulating factors (G-CSF) was elicited when IL-17A was used in combination with TNFα, and IL-17A was able to significantly augment the levels of TNFα-induced E-selectin and ICAM-1. In accordance with this observation, IL-17A was able to markedly increase TNFα-induced neutrophil adherence to HDMEC monolayers in an in vitro adhesion assay. Using a trans-well migration assay with an HDMEC monolayer as a barrier, we here show that pre-stimulating the endothelial cells with TNFα and IL-17A together enhances the rate of neutrophil transmigration compared to TNFα or IL-17A alone. These results show that IL-17A and TNFα act in cooperation to facilitate neutrophil migration across the endothelial cell barrier. In addition, the synergistic actions of IL-17A with TNFα to secrete G-CSF appear to be important for mobilizing neutrophils from the bone marrow to the blood stream.

Connective tissue growth factor promotes interleukin-1β-mediated synovial inflammation in knee osteoarthritis

Connective tissue growth factor (CTGF), also known as CCN2, is a key proinflammatory mediator. In the present study, the involvement of the CTGF signaling pathway in human knee osteoarthritis (OA) fibroblast-like synoviocytes (FLSs) was investigated. FLSs were isolated from human OA synovium and incubated with CTGF in the absence or presence of interleukin‑1β (IL‑1β). The expression of relevant genes and proteins was analyzed by qPCR, western blotting and enzyme-linked immunosorbent assay (ELISA). Matrix metalloproteinase (MMP) activity and nuclear factor (NF)-κB activation were also evaluated. CTGF stimulation resulted in the significant production of IL-6, IL-8, C-C motif ligand 2 (CCL2), CCL20, MMP-1 and MMP-3 in FLSs in the presence, but not in the absence, of IL-1β. CTGF also enhanced the levels of phosphorylated extracellular signal-related kinase 1/2 (ERK1/2) and p38. In addition, CTGF at 25 ng/ml, in the presence of IL‑1β, significantly potentiated NF-κB activation. The results indicated that CTGF interacted with IL‑1β in FLSs to promote the inflammatory response in the synovium, leading to the initiation of the inflammatory cascade. These results support the proinflammatory role of CTGF in synovitis and joint destruction in OA.

Genetic and cellular evidence of decreased inflammation associated with reduced incidence of posttraumatic arthritis in MRL/MpJ mice

OBJECTIVE

To examine the relationship between inflammation and posttraumatic arthritis (PTA) in a murine intraarticular fracture model.

METHODS

Male C57BL/6 and MRL/MpJ "superhealer" mice received tibial plateau fractures using a previously established method. Mice were killed on day 0 (within 4 hours of fracture) and days 1, 3, 5, 7, 28, and 56 after fracture. Synovial tissue samples, obtained prior to fracture and on days 0, 1, 3, 5, and 7 after fracture, were examined by reverse transcription-polymerase chain reaction for gene expression of proinflammatory cytokines and chemokines. Synovial fluid and serum samples were collected to measure cytokine concentrations, using enzyme-linked immunosorbent assay. Whole joints were examined histologically for the extent of synovitis and cartilage degradation, and joint tissue samples from all time points were analyzed immunohistochemically to evaluate the distribution of interleukin-1 (IL-1).

RESULTS

Compared to C57BL/6 mice, MRL/MpJ mice had less severe intraarticular and systemic inflammation following joint injury, as evidenced by lower gene expression of tumor necrosis factor α and IL-1β in the synovial tissue and lower protein levels of IL-1α and IL-1β in the synovial fluid, serum, and joint tissues. Furthermore, after joint injury, MRL/MpJ mice had lower gene expression of macrophage inflammatory proteins and macrophage-derived chemokine (CCL22) in the synovial tissue, and also had reduced acute and late-stage infiltration of synovial macrophages.

CONCLUSION

C57BL/6 mice exhibited higher levels of inflammation than MRL/MpJ mice, indicating that MRL/MpJ mice are protected from PTA in this model. These data thus suggest an association between joint tissue inflammation and the development and progression of PTA in mice.

Investigate pathogenic mechanism of TXNDC5 in rheumatoid arthritis

Hypoxia stimulates synovial hypoperfusion in rheumatoid arthritis (RA). TXNDC5 stimulates cellular proliferation in hypoxic conditions. We previously detected increased TXNDC5 expression in synovial tissues and blood from RA patients and demonstrated that the gene encoding TXNDC5 increased RA risk. The present study investigated the pathogenic roles of TXNDC5 in RA. Transgenic mice that over-expressed TXNDC5 (TXNDC5-Tg) were generated using C57BL/6J mice and treated with bovine collagen II to induce arthritis (CIA). Synovial fibroblasts from RA patients (RASFs) were cultured and incubated with TXNDC5-siRNA or CoCl(2), a chemical that induces hypoxia. CIA was observed in 80% of the TXNDC5-Tg, but only 20% of the wild-type mice (WT) developed CIA. The clinical arthritis scores reached 5 in the TXNDC5-Tg, but this index only reached 2 in the control mice. CIA TXNDC5-Tg exhibited clear pannus proliferation and bone erosion in joint tissues. A significant increase in CD4 T cells was observed in the thymus and spleen of TXNDC5-Tg during CIA. Serum levels of anti-collagen II IgG, IgG1 and IgG2a antibodies were significantly elevated in the mice. Increased cell proliferation, cell migration and TXNDC5 expression were observed in RASFs following incubation with 1 µM CoCl(2). However, this effect was diminished when TXNDC5 expression was inhibited with 100 nM siRNA. TNF-alpha, IL-1α, IL-1β and IL-17 levels were significantly increased in the blood of TXNDC5-Tg mice, but the levels of these cytokines declined in the supernatant of RASFs that were treated with TXNDC5 siRNA. The expression of adiponectin, a cytokine-like mediator, decreased significantly in RASFs following TXNDC5 siRNA treatment. These results suggest that TXNDC5-over-expressing mice were susceptible to CIA. This study also suggests that hypoxia induced TXCNDC5 expression, which contributed to adiponectin expression, cytokine production and the cellular proliferation and migration of fibroblasts in RA.

CC chemokine receptors and chronic inflammation--therapeutic opportunities and pharmacological challenges

Chemokines are a family of low molecular weight proteins with an essential role in leukocyte trafficking during both homeostasis and inflammation. The CC class of chemokines consists of at least 28 members (CCL1-28) that signal through 10 known chemokine receptors (CCR1-10). CC chemokine receptors are expressed predominantly by T cells and monocyte-macrophages, cell types associated predominantly with chronic inflammation occurring over weeks or years. Chronic inflammatory diseases including rheumatoid arthritis, atherosclerosis, and metabolic syndrome are characterized by continued leukocyte infiltration into the inflammatory site, driven in large part by excessive chemokine production. Over years or decades, persistent inflammation may lead to loss of tissue architecture and function, causing severe disability or, in the case of atherosclerosis, fatal outcomes such as myocardial infarction or stroke. Despite the existence of several clinical strategies for targeting chronic inflammation, these diseases remain significant causes of morbidity and mortality globally, with a concomitant economic impact. Thus, the development of novel therapeutic agents for the treatment of chronic inflammatory disease continues to be a priority. In this review we introduce CC chemokine receptors as critical mediators of chronic inflammatory responses and explore their potential role as pharmacological targets. We discuss functions of individual CC chemokine receptors based on in vitro pharmacological data as well as transgenic animal studies. Focusing on three key forms of chronic inflammation--rheumatoid arthritis, atherosclerosis, and metabolic syndrome--we describe the pathologic function of CC chemokine receptors and their possible relevance as therapeutic targets.

Synergistic Induction of Macrophage Inflammatory Protein-3α;/CCL20 Production by Interleukin-17A and Tumor Necrosis Factor-α; in Nasal Polyp Fibroblasts

Background

Accumulation of T cells and immature dendritic cells (DCs) is one of the characteristic features of nasal polyps. However, the question remains why these cells accumulate in nasal polyp tissue. Macrophage inflammatory protein-3α (MIP-3α/CCL20) is a chemokine involved in the migration of T cells and immature DCs into inflammatory tissue sites. Fibroblasts are a rich source of cytokines and chemokines. The objective of this study was to demonstrate the expression of MIP-3α/CCL20 in nasal polyp fibroblasts after stimulation with proinflammatory cytokines such as interleukin-17 (IL-17) and tumor necrosis factor-α (TNF-α).

Methods

Fibroblast lines were established from nasal polyps. MIP-3α/CCL20 mRNA expression was evaluated by real-time reverse transcription-polymerase chain reaction (real-time RT-PCR). The amount of MIP-3α/CCL20 in the supernatants was measured by enzyme-linked immunosorbent assay (ELISA).

Results

IL-17A and TNF-α synergistically induced MIP-3α/CCL20 production by nasal polyp fibroblasts in a dose- and time-dependent manner. This synergy was observed by stimulation with TNF-α plus IL-17A or IL-17F, but not IL-17E.

Conclusions

Nasal polyp fibroblasts, by producing MIP-3α/CCL20, may play an important role in the recruitment of T cells and DCs in upper airway inflammatory lesions such as nasal polyps.

New perspectives on central and peripheral immune responses to acute traumatic brain injury

Traumatic injury to the brain (TBI) results in a complex set of responses involving various symptoms and long-term consequences. TBI of any form can cause cognitive, behavioral and immunologic changes in later life, which underscores the problem of underdiagnosis of mild TBI that can cause long-term neurological deficits. TBI disrupts the blood–brain barrier (BBB) leading to infiltration of immune cells into the brain and subsequent inflammation and neurodegeneration. TBI-induced peripheral immune responses can also result in multiorgan damage. Despite worldwide research efforts, the methods of diagnosis, monitoring and treatment for TBI are still relatively ineffective. In this review, we delve into the mechanism of how TBI-induced central and peripheral immune responses affect the disease outcome and discuss recent developments in the continuing effort to combat the consequences of TBI and new ways to enhance repair of the damaged brain.

TWEAK promotes the production of Interleukin-17 in rheumatoid arthritis

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is an inflammatory cytokine that modulates several biological responses by inducing chemokines and proinflammatory cytokines. We hypothesized that TWEAK could promote secretion of IL-17, an amplifier of inflammatory arthritis. To test this, we investigated the capacity of TWEAK to induce IL-17 production in T cells via the fibroblast growth factor-inducible gene 14 (Fn14, also known as TWEAK receptor) signal pathway in rheumatoid arthritis (RA). Fn14 and IL-17 were highly expressed in arthritic tissues of collagen-induced arthritis (CIA) mice. TWEAK induced production of IL-17 alone and synergistically with lipopolysaccharide. In naïve murine T cells, TWEAK promoted Th17 differentiation. The expression of Fn14 was predominant in Th17 cells. TWEAK and IL-17 concentrations were significantly higher in synovial fluid and serum in RA patients than OA patients. In addition, we identified CD4(+)IL-17(+)Fn14(+) cells in synovium from RA patients. TWEAK promoted IL-17 production synergistically with IL-23 or IL-21 and blockade of Fn14 with Fn14-Fc suppressed Th17 differentiation. Conversely, this treatment enhanced Treg differentiation. These results suggest that TWEAK induces IL-17 production and may be a therapeutic target in the treatment of RA.

Modulation of temporomandibular joint nociception and inflammation in male rats after administering a physiological concentration of 17β-oestradiol

BACKGROUND

Previous studies have shown 17β-estradiol will reduce temporomandibular joint (TMJ) inflammation and hypersensitivity in female rats. Although male rats contain significant amounts of oestradiol, it was unknown whether a physiological concentration of 17β-estradiol would attenuate male TMJ inflammation and nociception.

METHODS

Intact and castrated rats were given a physiological concentration of oestradiol to examine first, if oestradiol will affect male TMJ nociception/inflammation and, second, if administration of oestradiol would act synergistically with endogenous male hormones to attenuate TMJ nociception. The hormonally treated rats were given TMJ injections of complete Freund's adjuvant (CFA) and then nociception was measured using a validated method in which a lengthening in meal duration is directly correlated to the intensity of deep TMJ nociception. Inflammation was assayed by quantitating pro-inflammatory gene expression.

RESULTS

Meal duration was significantly lengthened after TMJ CFA injection and this lengthening was significantly attenuated in the castrated but not intact males after administering a physiological concentration of oestradiol. A physiological concentration of 17β-estradiol also significantly increased IL-6 expression in the inflamed TMJ of castrated males while 17β-estradiol did not alter IL-1β, CXCL2 and CCL20 expression. Castration increased pro-inflammatory mediators IL-6, IL-1β and CXCL2 suggesting male sex hormones were anti-inflammatory. Calcitonin gene-related peptide in the trigeminal ganglia was unchanged.

CONCLUSIONS

Similar to females, male rats with TMJ inflammation showed a reduced nociceptive response after treatment with a physiological concentration of oestradiol suggesting the effects of oestradiol treatment were not constrained by organizational processes in the males.

Adiponectin induces CCL20 expression synergistically with IL-6 and TNF-α in THP-1 macrophages

Adiponectin (Ad) is an adipokine secreted from adipocytes. It is reported that Ad has many biological activities. However, its influence on inflammation is controversial. In the present study, we examined the influence of Ad on production of CCL20 from THP-1 macrophages. THP-1 macrophages were prepared from THP-1 monocytes by PMA treatment. THP-1 macrophages were cultured for 24h with Ad, IL-6, or TNF-α alone or with combinations of Ad and cytokines. CCL20 mRNA expression was then determined by real-time PCR. Full-length Ad (fAd) slightly but significantly induced CCL20 mRNA expression, and interestingly, co-stimulation with fAd and IL-6 or with fAd and TNF-α synergistically increased the expression of CCL20 mRNA. We explored the mechanism behind the synergistic effect of fAd and these cytokines. fAd did not affect the expression of receptors for IL-6 and TNF, and IL-6 and TNF-α did not increase the expression of the receptor for Ad in THP-1 macrophages. The increased expression of CCL20 by fAd is much higher in THP-1 macrophages compared with THP-1 monocytes. Furthermore, MMP-12 production was increased by IL-6 and TNF-α in THP-1 macrophages but it was not detectable in THP-1 monocytes. Treatment of fAd with MMP-12 induced globular Ad (gAd), and the expression of CCL20 in THP-1 macrophages was increased more potently by gAd than by fAd. MMP inhibitor (UK370106) inhibited the expression of CCL20 induced by co-stimulation with fAd and IL-6 or TNF-α. In conclusion, gAd played an important role in CCL20 expression, and MMP-12 induced by IL-6 or TNF-α was involved in the synergistic effect of fAd and cytokines.

Regulation of CCL20 expression in astrocytes by IL-6 and IL-17

Astrocytes have an important role in the regulation of inflammation within the central nervous system (CNS). In neuroinflammatory conditions such as multiple sclerosis, numerous cytokines and chemokines are elevated including IL-6, IL-17, and CCL20. IL-17 enhances IL-6 signaling and subsequent IL-6 expression in astrocytes. CCL20 is a CC motif chemokine that functions as a chemoattractant to facilitate the recruitment of CCR6-expressing cells, including Th17 cells. In this study, we examined the role of IL-6 and IL-17 on CCL20 production in primary murine astrocytes. IL-6 in combination with the IL-6 soluble receptor (sIL-6R) stimulated CCL20 expression in part through STAT3 activation, whereas IL-17 alone had no effect. However, the combination of IL-6, sIL-6R, and IL-17 led to a robust increase in CCL20 production. IL-17 increased the activation-associated phosphorylation of NF-κB, and inhibition of the NF-κB pathway significantly inhibited the enhancement of CCL20 expression by IL-17. In addition, chromatin immunoprecipitation revealed that stimulation of primary astrocytes with IL-6 plus the sIL-6R induced STAT3 binding to the CCL20 promoter. Combined stimulation with IL-6, sIL-6R, and IL-17 increased the recruitment of phosphorylated NF-κB to the CCL20 promoter, increased binding of coactivators such as p300 and CBP, and enhanced H3 and H4 histone acetylation, consistent with a transcriptionally active gene. The astrocyte-produced CCL20 increased T cell migration as determined by transwell migration assay. Collectively, these results suggest that astrocytes, in response to IL-6, sIL-6R, and IL-17, may shift chemokine production to that favoring T cell recruitment to the CNS.

Anti IL-17A therapy inhibits bone loss in TNF-α-mediated murine arthritis by modulation of the T-cell balance

Tumour necrosis factor alpha (TNF-α) is a major inducer for inflammation and bone loss. Here, we investigated whether interleukin (IL)-17 plays a role in TNF-α-mediated inflammation and bone resorption. Human TNF-α transgenic (hTNFtg) mice were treated with a neutralizing anti-IL-17A antibody and assessed for inflammation, cartilage and bone damage. T-cell transcription factors and lymphokine patterns were measured in the LNs. IL-17A inhibition in the absence of IL-1 was also evaluated by treating hTNFtg/IL-1(-/-) mice with an IL-17A neutralizing antibody. IL-17A neutralization had only minor effects on TNF-α-induced inflammation but effectively reduced local and systemic bone loss by blocking osteoclast differentiation in vivo. Effects were based on a shift to bone-protective T-cell responses such as enhanced Th2 differentiation, IL-4 and IL-12 expression and Treg cell numbers. Whereas inflammation in hTNFtg/IL-1(-/-) mice was highly sensitive to IL-17A blockade, no shift in the T-cell lineages and no additional benefit on bone mass were observed in response to IL-17A neutralization. We thus conclude that IL-17A is a key mediator of TNF-α-induced bone loss by closely interacting with IL-1 in blocking bone protective T-cell responses.

Tumor necrosis factor-interleukin-17 interplay induces S100A8, interleukin-1β, and matrix metalloproteinases, and drives irreversible cartilage destruction in murine arthritis: rationale for combination treatment during arthritis

OBJECTIVE

To examine whether synovial interleukin-17 (IL-17) expression promotes tumor necrosis factor (TNF)-induced joint pathologic processes in vivo, and to analyze the surplus ameliorative value of neutralizing IL-17 in addition to TNF during collagen-induced arthritis (CIA).

METHODS

Adenoviral vectors were used to induce overexpression of IL-17 and/or TNF in murine knee joints. In addition, mice with CIA were treated, at different stages of arthritis, with soluble IL-17 receptor (sIL-17R), TNF binding protein (TNFBP), or the combination.

RESULTS

Overexpression of IL-17 and TNF resulted in joint inflammation and bone erosion in murine knees. Interestingly, IL-17 strikingly enhanced both the joint-inflammatory and joint-destructive capacity of TNF. Further analysis revealed a strongly enhanced up-regulation of S100A8, IL-1β, and matrix metalloproteinase (MMP) messenger RNA, only when both TNF and IL-17 were present. Moreover, the increase in irreversible cartilage destruction was not merely the result of enhanced inflammation, but also was associated with a direct synergistic effect of these cytokines in the joint. S100A9 deficiency in mice protected against IL-17/TNF-induced expression of cartilage NITEGE neoepitopes. During established arthritis, the combination of sIL-17R and TNFBP was more effective than the anticytokine treatments alone, and significantly inhibited further joint inflammation and cartilage destruction.

CONCLUSION

Local synovial IL-17 expression enhances the role of TNF in joint destruction. Synergy between TNF and IL-17 in vivo results in striking exaggeration of cartilage erosion, in parallel with a synergistic up-regulation of S100A8, IL-1β, and erosive MMPs. Moreover, neutralizing IL-17 in addition to TNF further improves protection against joint damage and is still effective during late-stage CIA. Therefore, compared with anti-TNF alone, combination blocking of TNF and IL-17 may have additional therapeutic value for the treatment of destructive arthritis.

Lateral fluid percussion injury of the brain induces CCL20 inflammatory chemokine expression in rats

Background

Traumatic brain injury (TBI) evokes a systemic immune response including leukocyte migration into the brain and release of pro-inflammatory cytokines; however, the mechanisms underlying TBI pathogenesis and protection are poorly understood. Due to the high incidence of head trauma in the sports field, battlefield and automobile accidents identification of the molecular signals involved in TBI progression is critical for the development of novel therapeutics.

Methods

In this report, we used a rat lateral fluid percussion impact (LFPI) model of TBI to characterize neurodegeneration, apoptosis and alterations in pro-inflammatory mediators at two time points within the secondary injury phase. Brain histopathology was evaluated by fluoro-jade (FJ) staining and terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay, polymerase chain reaction (qRT PCR), enzyme linked immunosorbent assay (ELISA) and immunohistochemistry were employed to evaluate the CCL20 gene expression in different tissues.

Results

Histological analysis of neurodegeneration by FJ staining showed mild injury in the cerebral cortex, hippocampus and thalamus. TUNEL staining confirmed the presence of apoptotic cells and CD11b⁺ microglia indicated initiation of an inflammatory reaction leading to secondary damage in these areas. Analysis of spleen mRNA by PCR microarray of an inflammation panel led to the identification of CCL20 as an important pro-inflammatory signal upregulated 24 h after TBI. Although, CCL20 expression was observed in spleen and thymus after 24h of TBI, it was not expressed in degenerating cortex or hippocampal neurons until 48 h after insult. Splenectomy partially but significantly decreased the CCL20 expression in brain tissues.

Conclusion

These results demonstrate that the systemic inflammatory reaction to TBI starts earlier than the local brain response and suggest that spleen- and/ or thymus-derived CCL20 might play a role in promoting neuronal injury and central nervous system inflammation in response to mild TBI.

Staphylococcal-associated molecular patterns enhance expression of immune defense genes induced by IL-17 in mammary epithelial cells

Interleukin-17A (IL-17A) and IL-17F have been shown to mediate a crucial crosstalk between the immune system and various epithelial tissues, stimulating various defensive mechanisms to bacterial infections. A number of studies have characterized the response to IL-17A and IL-17F of epithelial cells from airways, intestine, and skin, but not from the mammary gland. To evaluate the potential contribution of IL-17 to the immune defense of the mammary gland, we analyzed the effects of recombinant bovine IL-17A and IL-17F on primary bovine mammary epithelial cells (MEC) by quantitative PCR and ELISA. We found expression (mRNA) of the two components of the IL-17 receptor complex, IL-17RA and IL-17RC, in mammary tissue and MEC in vitro. The expression of a number of genes encoding cytokines, chemokines and proteins endowed with antibacterial activities was increased by IL-17A, and to a lesser extent by IL-17F, but the magnitude of responses was modest. As expected, responses were augmented by the combination of IL-17A or IL-17F with TNF-α. Interestingly, responses of a few of the tested genes, such as IL8, CCL20, iNOS, and CfB, were augmented by the combination of IL-17A with staphylococcal lipoteichoic acid or muramyl dipeptide, bacterial agonists of the innate immune system. This can be interpreted as indicating that IL-17A and IL-17F are tailored to exert their full potential in a septic environment. MEC responses were characterized by the expression of chemokines targeting not only neutrophils (CXCL3 and CXCL8) but also mononuclear leucocytes (CCL2, CCL20). Production of IL-6 was low and the inflammatory cytokines TNF-α and IL-1β were expressed (mRNA) but proteins were not secreted. Altogether, our results suggest that IL-17A and IL-17F have a potential to modulate the mammary gland immune response to mastitis-causing pathogens.

Anti-CXCL5 therapy ameliorates IL-17-induced arthritis by decreasing joint vascularization

IL-17-induced joint inflammation is associated with increased angiogenesis. However, the mechanism by which IL-17 mediates angiogenesis is undefined. Therefore, the pathologic role of CXCL1 and CXCL5 was investigated in arthritis mediated by local expression of IL-17, employing a neutralizing antibody to each chemokine. Next, endothelial chemotaxis was utilized to examine whether endothelial migration was differentially mediated by CXCL1 and CXCL5. Our results demonstrate that IL-17-mediated disease activity was not affected by anti-CXCL1 treatment alone. In contrast, mice receiving anti-CXCL5 demonstrated significantly reduced clinical signs of arthritis, compared to the mice treated with IgG control. Consistently, while inflammation, synovial lining thickness, bone erosion and vascularization were markedly reduced in both the anti-CXCL5 and combination anti-CXCL1 and 5 treatment groups, mice receiving anti-CXCL1 antibody had clinical scores similar to the control group. In contrast to joint FGF2 and VEGF levels, TNF-α was significantly reduced in mice receiving anti-CXCL5 or combination of anti-CXCL1 and 5 therapies compared to the control group. We found that, like IL-17, CXCL1-induced endothelial migration is mediated through activation of PI3K. In contrast, activation of NF-κB pathway was essential for endothelial chemotaxis induced by CXCL5. Although CXCL1 and CXCL5 can differentially mediate endothelial trafficking, blockade of CXCR2 can inhibit endothelial chemotaxis mediated by either of these chemokines. These results suggest that blockade of CXCL5 can modulate IL-17-induced inflammation in part by reducing joint blood vessel formation through a non-overlapping IL-17 mechanism.

CCL20 Stimulates Proinflammatory Mediator Synthesis in Human Fibroblast-like Synoviocytes Through a MAP Kinase-dependent Process with Transcriptional and Posttranscriptional Control

Objective.

To compare levels of the chemokine CCL20 and its receptor CCR6 in donor, osteoarthritic (OA), and rheumatoid arthritis (RA) synovium; and to determine the molecular mechanism of cellular activation induced by chemokine/receptor ligation in human fibroblast-like synoviocytes (FLS).

Methods.

Synovia and isolated FLS from donor, OA, and RA joints were analyzed for CCL20 and CCR6 expression by RT-PCR and immunohistochemistry. The effect of CCL20 on cytokines and mediators of cartilage degradation was examined by PCR for mRNA expression levels and ELISA, and Western blotting for protein. CCL20-dependent transcriptional and posttranscriptional activation of target genes was monitored using reporter constructs and luciferase assays in transfected donor FLS.

Results.

CCL20 and CCR6 proteins were abundantly expressed in RA synovial lining cells compared to donor or OA synovia as judged by immunohistochemistry. RT-PCR of synovial extracts confirmed the predominance of CCL20/CCR6 mRNA expression in RA synovium. CCL20 mRNA expression was low in donor FLS, but increased dramatically after stimulation with recombinant human (rh) interleukin 1ß (IL-1ß). rhCCL20 increased mRNA and protein expression of COX-2, IL-1ß, tumor necrosis factor-α, IL-6, and the matrix-destructive metalloprotease MMP-3 in donor FLS cultures. High constitutive levels of IL-6 were released from RA synovia; CCL20-induced expression of IL-6 occurred through an NSAID/COXIB-sensitive process. CCL20-induced expression of COX-2 was mediated by a PLCP1/PKCα/MEK1/2/ERK1/2-dependent pathway involving both transcriptional and posttranscriptional mechanisms.

Conclusion.

CCL20/CCR6 may play an important role in the pathogenesis of RA by assembling the molecular and cellular components orchestrating synovitis.

IL-17 induces hyperalgesia via TNF-dependent neutrophil infiltration

Interleukin-17 (IL-17) and tumour necrosis factor-α (TNF) are critical in the pathogenesis of arthritis but their relationship during inflammatory pain has received limited attention. We aimed to establish whether IL-17 can induce hyperalgesia in acute conditions, and investigated the role of TNF in mediating the pain response. Hyperalgesia was elicited in C57BL/6 mice by injection of recombinant IL-17, TNF or vehicle into the plantar tissue. Elevated pain was measured by the Hargreaves test for thermal hyperalgesia and Linton incapacitance tester for weight-bearing change. Cellular infiltration during hyperalgesia was determined by histological analysis and myeloperoxidase assay. IL-17 was found to induce hyperalgesia, but this was dependent on neutrophil migration and TNF binding to TNF receptor 1 (TNFR1). Because TNF-induced hyperalgesia was also dependent on neutrophil migration, the relationship between the resident fibroblasts, the cytokines and the migrating neutrophils was further investigated. By means of an air pouch model of cell migration, it was established that IL-17-induced neutrophil infiltration was dependent of TNF/TNFR1 as this interaction was required for the induction of the chemokine keratinocyte chemoattractant. These findings suggest that IL-17 causes acute hyperalgesia indirectly by inducing TNF from resident cells. The subsequent production of keratinocyte chemoattractant then triggers neutrophil chemotaxis to the plantar tissue, releasing algesic mediators locally to sensitise the nerve.

Are Th17 cells an appropriate new target in the treatment of rheumatoid arthritis?

Th17 cells play crucial roles not only in host defense but also in many human autoimmune diseases and corresponding animal models. Although many of the fundamental principles regarding Th17 biology have been rapidly elucidated in mice, there remain numerous controversies regarding the differentiation, plasticity, and pathogenicity of human Th17 cells. In this review, we consider these open questions in comparison to what has already been clarified in mice, and discuss the potential impact of discoveries related to the Th17 pathway on the development of new therapeutic strategies in Th17 driven autoimmune diseases, specifically rheumatoid arthritis.

Dopamine induces IL-6-dependent IL-17 production via D1-like receptor on CD4 naive T cells and D1-like receptor antagonist SCH-23390 inhibits cartilage destruction in a human rheumatoid arthritis/SCID mouse chimera model

A major neurotransmitter dopamine transmits signals via five different seven-transmembrane G protein-coupled receptors termed D1-D5. Several studies have shown that dopamine not only mediates interactions into the nervous system, but can contribute to the modulation of immunity via receptors expressed on immune cells. We have previously shown an autocrine/paracrine release of dopamine by dendritic cells (DCs) during Ag presentation to naive CD4(+) T cells and found efficacious results of a D1-like receptor antagonist SCH-23390 in the experimental autoimmune encephalomyelitis mouse model of multiple sclerosis and in the NOD mouse model of type I diabetes, with inhibition of Th17 response. This study aimed to assess the role of dopaminergic signaling in Th17-mediated immune responses and in the pathogenesis of rheumatoid arthritis (RA). In human naive CD4(+) T cells, dopamine increased IL-6-dependent IL-17 production via D1-like receptors, in response to anti-CD3 plus anti-CD28 mAb. Furthermore, dopamine was localized with DCs in the synovial tissue of RA patients and significantly increased in RA synovial fluid. In the RA synovial/SCID mouse chimera model, although a selective D2-like receptor antagonist haloperidol significantly induced accumulation of IL-6(+) and IL-17(+) T cells with exacerbated cartilage destruction, SCH-23390 strongly suppressed these responses. Taken together, these findings indicate that dopamine released by DCs induces IL-6-Th17 axis and causes aggravation of synovial inflammation of RA, which is the first time, to our knowledge, that actual evidence has shown the pathological relevance of dopaminergic signaling with RA.

Role of TH-17 cells in rheumatic and other autoimmune diseases

In humans multiple pathways can induce TH-17 cell differentiation, whereas in mice this process is mostly modulated by IL-6 and TGF-β. IL-17 produced by TH-17 cells has been associated with a number of inflammatory autoimmune diseases including psoriasis, systemic lupus erythematosus, inflammatory bowel disease, multiple sclerosis, and rheumatoid arthritis. In this review, we have primarily focused on the role of TH-17 cells/IL-17 in the pathogenesis of rheumatoid arthritis and experimental arthritis. The potential role of TH-17 cells in rheumatoid arthritis progression has been demonstrated by correlating the percent TH-17 cells or levels of IL-17 with rheumatoid arthritis disease activity score and C-reactive protein levels. Further, previous studies suggest that IL-17 mediated vascularization may lay the foundation for rheumatoid arthritis joint neutrophil and monocyte recruitment as well as cartilage and bone destruction. The profound role of IL-17 in the pathogenesis of experimental arthritis may be due to its synergistic effect with TNF-α and IL-1β. Although the initial clinical trial employing anti-IL-17 antibody has been promising for rheumatoid arthritis, future studies in humans will shed more light on how anti-IL-17 therapy affects rheumatoid arthritis and other autoimmune disease pathogenesis.

An immune paradox: how can the same chemokine axis regulate both immune tolerance and activation?: CCR6/CCL20: a chemokine axis balancing immunological tolerance and inflammation in autoimmune disease

Chemokines (chemotactic cytokines) drive and direct leukocyte traffic. New evidence suggests that the unusual CCR6/CCL20 chemokine receptor/ligand axis provides key homing signals for recently identified cells of the adaptive immune system, recruiting both pro-inflammatory and suppressive T cell subsets. Thus CCR6 and CCL20 have been recently implicated in various human pathologies, particularly in autoimmune disease. These studies have revealed that targeting CCR6/CCL20 can enhance or inhibit autoimmune disease depending on the cellular basis of pathogenesis and the cell subtype most affected through different CCR6/CCL20 manipulations. Here, we discuss the significance of this chemokine receptor/ligand axis in immune and inflammatory functions, consider the potential for targeting CCR6/CCL20 in human autoimmunity and propose that the shared evolutionary origins of pro-inflammatory and regulatory T cells may contribute to the reason why both immune activation and regulation might be controlled through the same chemokine pathway.

Cell-cell interactions in rheumatoid arthritis synovium

Understanding the pathogenesis of joint inflammation and destruction in rheumatoid arthritis involves dissection of the cellular and molecular interactions that occur in synovial tissue. Development of effective targeted therapies has been based on progress in achieving such insights. Safer and more specific approaches to treatment could flow from discovery of cell-cell interaction pathways that are specific to inflammation of the joint and less important in the defense against systemic infection. This article highlights selected cell-cell interactions in rheumatoid arthritis synovium that may be worthy of evaluation as future therapeutic targets.

Targeting IL-17 and Th17 cells in rheumatoid arthritis

Identification of interleukin-17 (IL-17) as a powerful proinflammatory cytokine and the recent recognition of a T-helper cell subset that secretes it have focused attention on the role of IL-17 and Th17 cells in rheumatoid arthritis (RA) and other immune-mediated diseases. While understanding of its role in RA is still evolving, evidence from both animal models and human systems provides a compelling rationale for therapeutic targeting of IL-17 in RA. Both direct and indirect approaches to accomplish this are feasible. Mechanistic studies in the context of clinical trials will be required to understand why some strategies may be preferable from the perspectives of efficacy and safety.

High mobility group box 1 potentiates the pro-inflammatory effects of interleukin-1β in osteoarthritic synoviocytes

Introduction

High mobility group box 1 (HMGB1) is released by necrotic cells or secreted in response to inflammatory stimuli. Extracellular HMGB1 may act as a pro-inflammatory cytokine in rheumatoid arthritis. We have recently reported that HMGB1 is released by osteoarthritic synoviocytes after activation with interleukin-1beta (IL-1β) The present study investigated the role of HMGB1 in synovial inflammation in osteoarthritis (OA).

Methods

HMGB1 was determined in human synovium using immunohistochemistry, comparing normal to OA. OA synoviocytes were incubated with HMGB1 at 15 or 25 ng/ml in the absence or presence of IL-1β (10 ng/ml). Gene expression was analyzed by quantitative PCR and protein expression by Western Blot and ELISA. Matrix metalloproteinase (MMP) activity was studied by fluorometric procedures and nuclear factor (NF)-κB activation by transient transfection with a NF-κB-luciferase plasmid.

Results

In the normal synovium, HMGB1 was found in the synovial lining cells, sublining cells, and in the vascular wall cells. The distribution of HMGB1 in OA synovium was similar but the number of HMGB1 positive cells was higher and HMGB1 was also present in infiltrated cells. In normal synovial membrane cells, HMGB1 was found mostly in the nuclei, whereas in OA, HMGB1 was generally found mostly in the cytoplasm. In OA synoviocytes, HMGB1 alone at concentrations of 15 or 25 ng/ml did not affect the production of IL-6, IL-8, CCL2, CCL20, MMP-1 or MMP-3, but in the presence of IL-1β, a significant potentiation of protein and mRNA expression, as well as MMP activity was observed. HMGB1 also enhanced the phosphorylated ERK1/2 and p38 levels, with a lower effect on phosphorylated Akt. In contrast, JNK1/2 phosphorylation was not affected. In addition, HMGB1 at 25 ng/ml significantly potentiated NF-κB activation in the presence of IL-1β.

Conclusions

Our results indicate that HMGB1 is overexpressed in OA synovium and mostly present in extracellular form. In OA synoviocytes, HMGB1 cooperates with IL-1β to amplify the inflammatory response leading to the production of a number of cytokines, chemokines and MMPs. Our data support a pro-inflammatory role for this protein contributing to synovitis and articular destruction in OA.

[Role of Th17 cells in rheumatoid arthritis]

Th17 cells are the newly described subset of the CD4(+) T lymphocytes. Activated Th17 cells are characterized by their ability to produce IL-17A and other pro-inflammatory cytokines. IL-17A regulates immune function through its cell-surface receptor expressed on epithelial-and endothelial cells, fibroblasts and leukocytes by promoting neutrophil recruitment and releasing further pro-inflammatory mediators. Failures of the susceptible balance of the immunoregulation may lead to unchecked immune response and autoimmune diseases. The central role of Th17 cells and cytokines produced by Th17 cells were confirmed in a wide variety of human autoimmune diseases, including rheumatoid arthritis. Recently Th17 cells and its cytokines come into the focus of immunological research as potential therapeutic targets.