1,25(OH)2D3 and dexamethasone additively suppress synovial fibroblast activation by CCR6+ T helper memory cells and enhance the effect of tumor necrosis factor alpha blockade

BACKGROUND

Despite recent improvements in the treatment of rheumatoid arthritis (RA), an insufficient treatment response and the development of treatment resistance in many patients illustrates the need for new therapeutic strategies. Chronic synovial inflammation could be suppressed by targeting RA synovial fibroblast (RASF) activation by, for example, interleukin (IL)-17A-producing CCR6+ T helper memory (memTh) cells. Here, we modulated this interaction by combining the active vitamin D metabolite 1,25(OH)2D3 with dexamethasone (DEX) and explored the potential therapeutic applications.

METHODS

CCR6+ memTh cells from peripheral blood mononuclear cells (PBMCs) of healthy donors or treatment-naive early RA patients were cultured alone or with RASF from established RA patients for 3 days and treated with or without 1,25(OH)2D3, DEX, or etanercept. Treatment effects were assessed using enzyme-linked immunosorbent assay (ELISA) and flow cytometry.

RESULTS

1,25(OH)2D3, and to lesser extent DEX, reduced production of the pro-inflammatory cytokines IL-17A, IL-22, and interferon (IFN)γ in CCR6+ memTh cells. Tumor necrosis factor (TNF)α was only inhibited by the combination of 1,25(OH)2D3 and DEX. In contrast, DEX was the strongest inhibitor of IL-6, IL-8, and tissue-destructive enzymes in RASF. As a result, 1,25(OH)2D3 and DEX additively inhibited inflammatory mediators in CCR6+ memTh-RASF cocultures. Interestingly, low doses of mainly DEX, but also 1,25(OH)2D3, combined with etanercept better suppressed synovial inflammation in this coculture model compared with etanercept alone.

CONCLUSION

This study suggests that 1,25(OH)2D3 and DEX additively inhibit synovial inflammation through targeting predominantly CCR6+ memTh cells and RASF, respectively. Furthermore, low doses of DEX and 1,25(OH)2D3 enhance the effect of TNFα blockade in inhibiting RASF activation, thus providing a basis to improve RA treatment.

Th22 cells are expanded in multiple sclerosis and are resistant to IFN-β

Th1 and Th17 cells have been considered as effectors in mouse EAE and in the human counterpart, MS. Recently, IL-22, a Th17-related, proinflammatory cytokine, has been associated with a new Th cell subset, defined as Th22, involved in chronic inflammatory conditions, such as psoriasis; the role of IL-22 in MS has not yet been elucidated. Here, we report that similar to Th17 cells, the number of Th22 cells increased in the PB and the CSF of RR MS patients, especially during the active phases of the disease. However, as opposed to Th17 cells, the expansion of Th22 cells occurred before the active phases of the disease. Th22 cells were found to be specific for the autoantigen MBP and also expressed high levels of CCR6 and T-bet, as for Th17 cells, indicating that Th22 self-reactive cells could have CNS-homing properties and be pathogenic in active RRMS patients. Conversely to Th17 cells, Th22 cells displayed lower levels of IFNAR1 and were insensitive to IFN-β inhibition. These data suggest that expansion of Th22 cells in MS could be one of the factors that critically influence resistance to IFN-β therapy.

Unlike αβ T cells, γδ T cells, LTi cells and NKT cells do not require IRF4 for the production of IL-17A and IL-22

Apart from conventional CD4(+) Th17 cells, the cytokines IL-17A and IL-22 can also be produced by γδ T cells, NK cells and lymphoid tissue inducer (LTi) cells. Th17 cells develop from precursor cells after T-cell receptor stimulation in the presence of TGF-β, IL-6 and IL-23. In contrast, a subset of γδ T cells ("γδT17") is committed for fast IL-17 production already in the thymus; however, γδ T cells can also produce IL-17 after prolonged in vitro stimulation via their γδ T-cell receptor plus IL-23. Here, we show that γδ T-, LTi- and NKT cells differ extensively from Th17 cells in their signalling requirements for the generation of IL-17A and IL-22. While production of these cytokines by Th17 cells totally depends on the transcription factor interferon regulatory factor 4 (IRF4), IRF4 is irrelevant in the other cell types. As for γδ T cells, this finding pertains to both thymic commitment and prolonged in vitro culture. Furthermore, IL-17A-producing γδ T cells accumulate in the central nervous system of IRF4 deficient (Irf4(-/-)) mice during experimental autoimmune encephalomyelitis. IL-17A-producing WT and Irf4(-/-) γδ T cells equally express CCR6 and lack CD27. The underlying IRF4-independent pathway partially involves STAT3 during in vitro stimulation.

Epidermal CCR6+ γδ T cells are major producers of IL-22 and IL-17 in a murine model of psoriasiform dermatitis

Cytokine components of Th17 pathway play vital roles in human psoriasis. Although much is known about TCR αβ T cells in psoriasis, the role of unconventional T cells, including γδ T cells, is unclear. In this study, using an IL-23 skin injection model of psoriasiform dermatitis in mice, we demonstrate that IL-22, IL-17A, and the IL-23R were highly enriched in a population of CCR6(+), TCR γδ-low expressing (GDL) T cells that accumulated in the epidermis after IL-23 injections. GDL cells were distinct from resident TCR γδ-high, Vγ3(+),CCR6(-) T cells in the epidermis that did not change appreciably in numbers following IL-23 injection. Large numbers of CCR6(+) cells were detected at or above the level of the epidermal basement membrane by confocal microscopy 5 d after repeated IL-23 injections at the same time GDL cells increased in numbers in the epidermis. TCR δ-deficient mice (lacking γδ T cells) exhibited decreased ear swelling and downregulated expression of IL-22 and IL-17A in the epidermis following IL-23 injection. Our data suggest that a subset of γδ T cells play a critical role in IL-23-mediated psoriasiform dermatitis.

Tumor-associated macrophages recruit CCR6+ regulatory T cells and promote the development of colorectal cancer via enhancing CCL20 production in mice

Background

Tumor-associated macrophages (TAMs) remodel the colorectal cancer (CRC) microenvironment. Yet, findings on the role of TAMs in CRC seem to be contradictory compared with other cancers. FoxP3⁺ regulatory T (Treg)-cells dominantly infiltrate CRC. However, the underlying molecular mechanism in which TAMs may contribute to the trafficking of Treg-cells to the tumor mass remains unknown.

Methodology/Principal Findings

CRC was either induced by N-methyl-N-nitrosourea (MNU) and H. pylori or established by subcutaneous injection of mouse colorectal tumor cell line (CMT93) in mice. CMT93 cells were co-cultured with primary macrophages in a transwell apparatus. Recruitment of FoxP3 green fluorescence protein positive (FoxP3^GFP+) Treg-cells was assessed using the IVIS Imaging System or immunofluorescence staining. A role for macrophages in trafficking of Treg-cells and in the development of CRC was investigated in CD11b diphtheria toxin receptor (CD11b-DTR) transgenic C57BL/6J mice in which macrophages can be selectively depleted. Treg-cells remarkably infiltrated solid tumor, and predominantly expressed the homing chemokine receptor (CCR) 6 in the induced CRC model. Both CMT93 cancer cells and macrophages produced a large amount of CCL20, the sole ligand of CCR6 in vitro and in vivo. Injection of recombinant mouse CCL20 into tumor sites promoted its development with a marked recruitment of Treg-cells in the graft CRC model. Conditional macrophage ablation decreased CCL20 levels, blocked Treg-cell recruitment and inhibited tumor growth in CD11b-DTR mice grafted with CMT93.

Conclusions/Significance

TAMs recruit CCR6⁺ Treg-cells to tumor mass and promote its development via enhancing the production of CCL20 in a CRC mouse model.

CCL20 and β-defensin-2 induce arrest of human Th17 cells on inflamed endothelium in vitro under flow conditions

CCR6 is a chemokine receptor that is expressed at the cell surface of Th17 cells, an IL-17- and IL-22-secreting population of CD4(+) T cells with antipathogenic, as well as inflammatory, properties. In the current study, we have determined the involvement of CCR6 in human Th17 lymphocyte migration toward inflamed tissue by analyzing the capacity of its ligands to induce arrest of these cells onto inflamed endothelium in vitro under flow conditions. We show that polarized, in situ-differentiated, skin-derived Th17 clones activated via the TCR-CD3 complex produce CCL20 in addition to IL-17 and IL-22. The latter cytokines induce, in a synergic fashion, the production of human β-defensin (hBD)-2, but neither hBD-1 nor hBD-3, by epidermal keratinocytes. Both CCL20 and hBD-2 are capable of inducing the arrest of Th17 cells, but not Th1 or Th2 cells, on HUVEC in an CD54-dependent manner that is CCR6 specific and independent from the expression of CXCR4, reported to be an alternative receptor for hBD-2. In addition, Ag-specific activation induces a transient loss of CCR6 expression, both at the transcriptional and protein level, which occurs with slow kinetics and is not due to endogenous CCL20-mediated internalization of CCR6. Together, these results indicate that Ag-specific activation will initially contribute to CCR6-mediated Th17 cell trafficking toward and sequestration in inflamed tissue, but that it eventually results in a transitory state of nonresponsiveness to further stimulation of these cells with CCR6 ligands, thus permitting their subsequent migration out of the inflamed site.

[Expression and function analysis of chemokine receptor CCR6 in HEK293 cells]

AIM

To construct a cell line which stably expresses human chemokine receptor 6 (CCR6).

METHODS

The human CCR6 cDNA and plasmid G were co-transfected into HEK 293 cells and the clones stably expressing CCR6 were picked out. The expression of CCR6 in HEK293 cells was detected by RT-PCR, Western blotting, immunofluorescence test, calcium mobilization and in vitro chemotaxis assay.

RESULTS

The transfected HEK293 cells could stably express functional human CCR6.

CONCLUSION

Successfully establish a cell line which stably express human CCR6 and lays the foundation for its biological function's study and specific antagonist screening.

Thymic self-reactivity selects natural interleukin 17-producing T cells that can regulate peripheral inflammation

Interleukin 17 (IL-17)-producing CD4(+) helper T cells (T(H)-17 cells) share a developmental relationship with Foxp3(+) regulatory T cells (T(reg) cells). Here we show that a T(H)-17 population differentiates in the thymus in a manner influenced by recognition of self antigen and by the cytokines IL-6 and transforming growth factor-beta (TGF-beta). Like previously described T(H)-17 cells, the T(H)-17 cells that developed in the thymus expressed the transcription factor RORgamma t and the IL-23 receptor. These cells also expressed alpha(4)beta(1) integrins and the chemokine receptor CCR6 and were recruited to the lung, gut and liver. In the liver, these cells secreted IL-22 in response to self antigen and mediated host protection during inflammation. Thus, T(H)-17 cells, like T(reg) cells, can be selected by self antigens in the thymus.

Recombinant human granulocyte colony-stimulating factor significantly decreases the expression of CXCR3 and CCR6 on T cells and preferentially induces T helper cells to a T helper 17 phenotype in peripheral blood harvests

The aim of this study was to investigate the expression of chemokine receptors on T cells and functional changes of T helper (Th) cells in peripheral blood stem cell (PBSC) harvests after treating healthy donors with recombinant human granulocyte colony-stimulating factor (rhG-CSF). Using multiparameter flow cytometry, we analyzed the expression of CXCR3 and CCR6 on T cells and the production of interferon-gamma (IFN-gamma), interleukin-4 (IL-4), and IL-17 by CD4(+) Th cells in PBSC grafts of healthy donors after in vivo rhG-CSF application. Alterations in the relative expression levels of T cell receptor beta variable (TCRBV) family members were determined using real-time polymerase chain reaction (PCR). rhG-CSF mobilization significantly decreased the expression of CXCR3 and CCR6 on T cells. Treating donors with rhG-CSF resulted in decreased IFN-gamma production and dramatically increased IL-4 and IL-17 secretion by CD4(+) Th cells, leading to T cell polarization from the Th1 to the Th2 phenotype and a preferential increase in IL-17-producing CD4(+) Th cells. We did not observe any differences in the relative expression levels of TCRBV family members before and after in vivo rhG-CSF application. Our results suggest that the expression of CXCR3 and CCR6 on donor T cells was dramatically downregulated and an IL-17 phenotype of CD4(+) Th cells was preferentially induced in PBSC grafts after treating healthy donors with rhG-CSF. The observed effects of rhG-CSF on T cells may be independent of the relative expression levels of TCRBV family members.

Identification of a human helper T cell population that has abundant production of interleukin 22 and is distinct from T(H)-17, T(H)1 and T(H)2 cells

Interleukin 22 (IL-22) is a member of the IL-10 cytokine family that is involved in inflammatory and wound healing processes. Originally considered a T helper type 1 (T(H)1)-associated cytokine, IL-22 has since been shown to be produced mainly by IL-17-producing helper T cells (T(H)-17 cells). Here we describe a previously uncharacterized IL-22-producing human helper T cell population that coexpressed the chemokine receptor CCR6 and the skin-homing receptors CCR4 and CCR10. These cells were distinct from both T(H)-17 cells and T(H)1 cells. Downregulation of either the aryl hydrocarbon receptor (AHR) or the transcription factor RORC by RNA-mediated interference affected IL-22 production, whereas IL-17 production was affected only by downregulation of RORC by RNA-mediated interference. AHR agonists substantially altered the balance of IL-22- versus IL-17-producing cells. This subset of IL-22-producing cells may be important in skin homeostasis and pathology.

Tracing functional antigen-specific CCR6 Th17 cells after vaccination

Background

The function of T helper cell subsets in vivo depends on their location, and one hallmark of T cell differentiation is the sequential regulation of migration-inducing chemokine receptor expression. CC-chemokine receptor 6 (CCR6) is a trait of tissue-homing effector T cells and has recently been described as a receptor on T helper type 17 (Th17) cells. Th17 cells are associated with autoimmunity and the defence against certain infections. Although, the polarization of Th cells into Th17 cells has been studied extensively in vitro, the development of those cells during the physiological immune response is still elusive.

Methodology/Principal Findings

We analysed the development and functionality of Th17 cells in immune-competent mice during an ongoing immune response. In naïve and vaccinated animals CCR6⁺ Th cells produce IL-17. The robust homeostatic proliferation and the presence of activation markers on CCR6⁺ Th cells indicate their activated status. Vaccination induces antigen-specific CCR6⁺ Th17 cells that respond to in vitro re-stimulation with cytokine production and proliferation. Furthermore, depletion of CCR6⁺ Th cells from donor leukocytes prevents recipients from severe disease in experimental autoimmune encephalomyelitis, a model for multiple sclerosis in mice.

Conclusions/Significance

In conclusion, we defined CCR6 as a specific marker for functional antigen-specific Th17 cells during the immune response. Since IL-17 production reaches the highest levels during the immediate early phase of the immune response and the activation of Th17 cells precedes the Th1 cell differentiation we tent to speculate that this particular Th cell subset may represent a first line effector Th cell subpopulation. Interference with the activation of this Th cell subtype provides an interesting strategy to prevent autoimmunity as well as to establish protective immunity against infections.

Regulation of IL-17 in human CCR6+ effector memory T cells

IL-17-secreting T cells represent a distinct CD4(+) effector T cell lineage (Th17) that appears to be essential in the pathogenesis of numerous inflammatory and autoimmune diseases. Although extensively studied in the murine system, human Th17 cells have not been well characterized. In this study, we identify CD4(+)CD45RO(+)CCR7(-)CCR6(+) effector memory T cells as the principal IL-17-secreting T cells. Human Th17 cells have a unique cytokine profile because the majority coexpress TNF-alpha but not IL-6 and a minor subset express IL-17 with IL-22 or IL-17 and IFN-gamma. We demonstrate that the cytokines that promote the differentiation of human naive T cells into IL-17-secreting cells regulate IL-17 production by memory T cells. IL-1beta alone or in association with IL-23 and IL-6 markedly increase IL-17(+) CCR6(+) memory T cells and induce IL-17 production in CCR6(-) memory T cells. We also show that T cell activation induces Foxp3 expression in T cells and that the balance between the percentage of Foxp3(+) and IL-17(+) T cells is inversely influenced by the cytokine environment. These studies suggest that the cytokine environment may play a critical role in the expansion of memory T cells in chronic autoimmune diseases.

Expression and role of CCR6/CCL20 chemokine axis in pulmonary sarcoidosis

We have shown previously that the chemokine receptors CXCR3 and CXCR6 are coexpressed by Th1 cells infiltrating the lung and the granuloma of patients with sarcoidosis. In this study, we evaluated the role of CCL20/CCR6 interaction in the pathogenesis of acute and chronic pulmonary sarcoidosis. By flow cytometry and molecular analyses, we have demonstrated that Th1 cells isolated from the bronchoalveolar lavage (BAL) of patients with sarcoidosis and T cell alveolitis are equipped with CCR6. Furthermore, CCR6(+) T cells coexpressed the chemokine receptors CXCR3 and CXCR6. Immunohistochemical analysis of lung specimens has shown that CCR6(+) T cells infiltrate lung interstitium and surround the central core of the granuloma. It is interesting that CCR6 was never detected on the alveolar macrophage (AM) surface, and it is observed in the cytoplasm of AMs from patients with sarcoidosis and alveolitis. The CCR6 ligand CCL20 was expressed by macrophages, multinucleated giant cells, and epithelioid cells infiltrating the granuloma. Furthermore, detectable levels of CCL20 protein are seen in the BAL fluid components of patients with active sarcoidosis, and sarcoid AMs release the CCR6 ligand in vitro. From a functional point of view, sarcoid Th1 cells were able to respond to CXCL10, CXCL16, and CCL20 in migratory assays. In vitro kinetic studies demonstrated that CCR6 is induced rapidly by IL-2, IL-18, and IFN-gamma. In conclusion, T cells expressing CCR6, CXCR3, and CXCR6 act coordinately with respective ligands and Th1 inflammatory cytokines in the alveolitic/granuloma phases of the disease.