1α,25-Dihydroxyvitamin D3 and all-trans retinoic acid synergistically inhibit the differentiation and expansion of Th17 cells
Introduction
It has been well accepted that CD4+ T helper (Th) cells play a pivotal role for the regulation of the immune responses. More than 20 years ago, Mosmann and Coffman [1] defined two distinct CD4+ T cell subsets (Th1 and Th2 cells) in terms of their differential cytokine-producing patterns. Th1 cells, producing IL-2, IFN-γ and TNF-α (type-1 cytokines), have been thought to mediate protective immunity to infectious diseases and tumors [2], [3], [4], [5] by promoting effector functions of macrophages, dendritic cells (DCs), natural killer (NK) cells and cytotoxic T lymphocytes (CTLs). However, it is also well known that abnormal activation of Th1 cells promotes pathogenic inflammatory responses [6] and mediates autoimmune diseases, such as multiple sclerosis and rheumatoid arthritis [7], [8]. On the other hand, Th2 cells, producing IL-4, IL-5, IL-6, IL-10 and IL-13 (type-2 cytokines), have been thought to support the maturation of B cells to plasma cells which produce antibodies, and mediate protective immunity to extracellular pathogens although their excessive activation causes allergic diseases [9], [10]. Therefore, the proper regulation of the Th1/Th2 balance is required for the maintenance of good health.
A seco-steroid hormone, 1α,25-dihydroxyvitamin D3 (1,25D3) is the active form of vitamin D3 and plays a critical role in the maintenance of mineral homeostasis and normal skeletal architecture. Moreover, it acts as a potent biological response modifier including immunomodulatory activities [11]. In relation to the Th1/Th2 balance, 1,25D3 and its derivatives show their immunomodulating activities through their direct effect on naïve CD4+ T cells [12], [13] and their indirect effect on DCs [12], [13], [14]. It has also been demonstrated that the administration of 1,25D3 prevented Th1-mediated autoimmune diseases in animal models [15], [16], [17], [18]. 1,25D3 and its analog also enhance CD4+ CD25+ regulatory T cells in the model of type 1 diabetes [19] and contact hypersensitivity response [20]. In addition, IL-10-producing regulatory T cells can be induced in vitro by 1,25D3 in the presence of dexamethasone [21]. 1,25D3 also represses IL-2 transcriptional activation by direct inhibition of NFAPp/AP-1 complex formation by VDR-retinoid X receptor heterodimer [22]. Despite these immunomodulating effects, VDR ligands have not been widely applied to the therapy for immune diseases, because of the side effect, hypercalcemia. Therefore, less calcemic analogs have been synthesized to overcome the side effect [11]. Another strategy to resolve this is to develop a more efficient protocol to downmodulate the function of pathogenic effector cells using a lower dose of 1,25D3.
Interleukin 17 (IL-17)-producing helper T (Th17) cells have been described as a functionally new CD4+ helper T cell subset [23]. It has been reported that Th17 cells produce IL-21, IL-22, and TNF-α in addition to IL-17A and IL-17F, and have a critical role in host defense against infection by recruiting neutrophils and macrophages to infected tissues. Th17 cells have also been considered as a key player in autoimmune and inflammatory diseases [24], [25], [26], and the high expression of IL-17 has been reported in human diseases including multiple sclerosis [27], [28], rheumatoid arthritis [29], psoriasis [30] and inflammatory bowel disease [31], though some of these diseases had been thought to be mediated by Th1 cells. There are a few studies that demonstrated 1,25D3 suppressed IL-17 production in animal models, such as TNBS colitis [32] and experimental autoimmune uveitis [33], and in human CD4+ T cells [34], [35]. Tang et al. [33] shows that 1,25D3 directly suppresses IL-17 production by CD4+ T cells and also inhibits the production of IL-1, IL-6, TNF-α, and IL-12/IL-23p40 by DCs in mice.
We demonstrated here that 1,25D3 directly inhibits the development and expansion of Th17 cells from both naïve and memory CD4+ T cells. Moreover, we revealed that the combination of 1,25D3 with all-trans retinoic acid (ATRA), a vitamin A metabolite, which was also reported to inhibit Th17 generation and promoted Foxp3+ Treg differentiation [36], [37], exhibited synergistically inhibitory effects on the development of Th17 cells. In the present study, we described the mechanisms of the inhibitory effects by 1,25D3 and ATRA on human Th17 cells, indicating that a combination therapy using 1,25D3 and ATRA would be a novel and beneficial strategy to overcome the hypercalcemic effect of 1,25D3.
Section snippets
Mice
Wild-type BALB/c mice and C57BL/6 mice were purchased from Charles River Breeding Laboratories (Kanagawa, Japan). OVA323–339-specific I-Ad-restricted T cell receptor (TCR) transgenic mice (DO11.10) were kindly donated by Dr. K. Murphy (Washington University School of Medicine, St. Louis, MO, USA). OVA323–339-specific I-Ab-restricted TCR transgenic mice (OT-II) maintained on the C57BL/6-background were kindly provided by F.R. Carbone (University of Melbourne, Victoria, Australia).
1,25D3 inhibits IL-17-producing CD4+ T cells
To address the immunomodulating effects of 1,25D3 on the cytokine profiles of CD4+ helper T cell subsets, CD4+CD62L+ naïve T cells from DO11.10 TCR transgenic mice were cultured under Th0 (IL-2), Th1 (IL-2, IL-12, IFN-γ anti-IL-4), Th2 (IL-2, IL-4, anti-IFN-γ and anti-IL-12) or Th17 (TGF-β, IL-6, anti-IFN-γ, anti-IL-4) conditions in the presence of OVA peptide with or without 1,25D3 for 6 days. As previously reported [12], 1,25D3 slightly suppressed IFN-γ, type-1 cytokine, production and
Discussion
CD4+ helper T cells including Th1, Th2, and Th17 cells are critical for regulation of immune responses, and the disordered activation promotes inflammatory responses and occasionally mediates the pathogenesis in certain autoimmune diseases [7], [8], [24]. Although it has been reported that Vitamin D and its analogs including 1,25D3 have immunomodulating effects on naïve CD4+ T cells to inhibit the development of Th1 cells and promote the development of Th2 cells [12], [13], we demonstrated here
Acknowledgements
We would like to thank Dr. T. Sawada (Shionogi Pharmaceutical Institute Co., Osaka, Japan) and Dr. H. Tashiro (Fujiya Co. Ltd., Hadano, Japan) for their kind donations of rhIL-2 and OVA323–339 peptide, respectively. We also thank Chugai Pharmaceutical Co. Ltd. for its generous donation of Rocaltrol® and rhIL-6. This work was partially supported by a Grant-in-Aid and a National Project “Knowledge Cluster Initiative” (2nd stage, “Sapporo Biocluster Bio-S”), Ministry of Education, Culture, Sports,
References (67)
- et al.
An overview of the immune system
Lancet
(2001) - et al.
1 Alpha-hydroxyvitamin D3 inhibits type II collagen-induced arthritis in rats
FEBS Lett
(1994) - et al.
Interleukin-17 and interferon-gamma synergize in the enhancement of proinflammatory cytokine production by human keratinocytes
J Invest Dermatol
(1998) - et al.
Retinoic acid inhibits Th17 polarization and enhances FoxP3 expression through a Stat-3/Stat-5 independent signaling pathway
Blood
(2008) - et al.
Ox40-ligand has a critical costimulatory role in dendritic cell:T cell interactions
Immunity
(1999) - et al.
Antigen-specific T cell sensitization is impaired in IL-17-deficient mice, causing suppression of allergic cellular and humoral responses
Immunity
(2002) - et al.
Retinoic acid enhances Foxp3 induction indirectly by relieving inhibition from CD4+CD44hi cells
Immunity
(2008) - et al.
The IL-23/Th17 axis in the immunopathogenesis of psoriasis
J Invest Dermatol
(2009) - et al.
TH1 and TH2 cells: different patterns of lymphokine secretion lead to different functional properties
Annu Rev Immunol
(1989) - et al.
Distinct role of antigen-specific T helper type 1 (Th1) and Th2 cells in tumor eradication in vivo
J Exp Med
(1999)