Dendritic Cells Modified by Vitamin D: Future Immunotherapy for Autoimmune Diseases

Vitamin D regulates immunoglobulin mucin domain molecule-4 expression in dendritic cells

BACKGROUND

Dendritic cell (DC)-derived immunoglobulin domain molecule (TIM)4 plays a critical role in the initiation of T helper (Th)2 polarization. Vitamin D (VitD) involves the regulation of a number of immune responses.

OBJECTIVES

This study tests a hypothesis that VitD regulates TIM4 expression in DCs.

METHODS

Peripheral blood samples were collected from patients with allergic rhinitis (AR) and healthy subjects. DCs were isolated from the samples and analyzed for the expression of TIM4.

RESULTS

We observed that the levels of calcitriol, the active form of VitD3, in the sera of AR patients were lower than that in healthy subjects. The peripheral DC expressed higher levels of TIM4 and lower levels of VDR. A negative correlation was identified between the data of serum calcitriol and TIM4 in DCs. Exposure DCs to calcitriol in the culture increased the expression of VDR. We also found that VDR bound to the TIM4 promoter locus in DCs to repress the TIM4 gene transcription and expression.

CONCLUSIONS AND CLINICAL RELEVANCE

VitD deficiency may contribute to the pathogenesis of AR by increasing the TIM4 expression. The results suggest that to regulate the serum calcitriol levels and the expression of VDR in DCs may be necessary to be taken into account in the treatment of AR.

SLE-associated risk factors affect DC function

Numerous risk alleles for systemic lupus erythematosus (SLE) have now been identified. Analysis of the expression of genes with risk alleles in cells of hematopoietic origin demonstrates them to be most abundantly expressed in B cells and dendritic cells (DCs), suggesting that these cell types may be the drivers of the inflammatory changes seen in SLE. DCs are of particular interest as they act to connect the innate and the adaptive immune response. Thus, DCs can transform inflammation into autoimmunity, and autoantibodies are the hallmark of SLE. In this review, we focus on mechanisms of tolerance that maintain DCs in a non‐activated, non‐immunogenic state. We demonstrate, using examples from our own studies, how alterations in DC function stemming from either DC‐intrinsic abnormalities or DC‐extrinsic regulators of function can predispose to autoimmunity.

Tolerogenic Vaccination with MOG/VitD Overcomes Aggravating Effect of C. albicans in Experimental Encephalomyelitis

AIMS

Multiple sclerosis (MS) is an immune-mediated demyelinating disorder of the central nervous system (CNS). We described that Candida albicans (Ca) aggravates experimental autoimmune encephalomyelitis (EAE) that is a model to study MS. We also observed that vaccination with a myelin peptide (MOG) in the presence of vitamin D (VitD) protected mice against EAE. In this work, we investigated whether Ca infection interferes with the efficacy of this vaccine.

METHODS

EAE was induced in C57BL/6 female mice previously vaccinated with MOG+VitD and then infected 3 days before encephalomyelitis induction.

RESULTS

Vaccination was able to control EAE development in infected mice. These animals gained weight, and only a few progressed to very low clinical scores. Protection was confirmed by a lower inflammatory infiltration in the CNS and was also associated with a reduced production of encephalitogenic cytokines by spleen and CNS cell cultures. The elevated percentage of CD25(+) FoxP3(+) cells suggests that regulatory T cells are involved in the protection. Adoptive transfer of splenocytes from mice vaccinated with MOG+VitD supports the view that protection is mediated by immunoregulatory cells.

CONCLUSION

Together, these experiments provide evidence demonstrating that EAE can be prevented by the inverse vaccination with MOG+VitD even in the presence of a disease-aggravating infectious agent.

Treatment with Vitamin D/MOG Association Suppresses Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an animal model to study multiple sclerosis (MS). Considering the tolerogenic effects of active vitamin D, we evaluated the therapeutic effect of myelin oligodendrocyte glycoprotein (MOG) associated with active vitamin D in EAE development. EAE was induced in female C57BL/6 mice by immunization with MOG emulsified with Complete Freund's Adjuvant plus Mycobacterium tuberculosis. Animals also received two intraperitoneal doses of Bordetella pertussis toxin. One day after immunization, mice were treated with 0,1 μg of 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) every other day during 15 days (on days 1, 3, 5, 7, 9, 11, 13 and 15). MOG (150 μg) was co-administered on days 3 and 11. The administration of 1,25(OH)2D3 or MOG determined significant reduction in EAE incidence and in clinical scores. When MOG was associated with 1,25(OH)2D3 the animals did not develop EAE. Spleen and central nervous system (CNS) cell cultures from this group produced less IL-6 and IL-17 upon stimulation with MOG in comparison to the EAE control group. In addition, this treatment inhibited dendritic cells maturation in the spleen and reduced inflammatory infiltration in the CNS. The association of MOG with 1,25(OH)2D3 was able to control EAE development.

Regulatory myeloid cells in transplantation

Regulatory myeloid cells (RMC) are emerging as novel targets for immunosuppressive (IS) agents and hold considerable promise as cellular therapeutic agents. Herein, we discuss the ability of regulatory macrophages, regulatory dendritic cells, and myeloid-derived suppressor cells to regulate alloimmunity, their potential as cellular therapeutic agents, and the IS agents that target their function. We consider protocols for the generation of RMC and the selection of donor- or recipient-derived cells for adoptive cell therapy. Additionally, the issues of cell trafficking and antigen (Ag) specificity after RMC transfer are discussed. Improved understanding of the immunobiology of these cells has increased the possibility of moving RMC into the clinic to reduce the burden of current IS agents and to promote Ag-specific tolerance. In the second half of this review, we discuss the influence of established and experimental IS agents on myeloid cell populations. IS agents believed historically to act primarily on T cell activation and proliferation are emerging as important regulators of RMC function. Better insights into the influence of IS agents on RMC will enhance our ability to develop cell therapy protocols to promote the function of these cells. Moreover, novel IS agents may be designed to target RMC in situ to promote Ag-specific immune regulation in transplantation and to usher in a new era of immune modulation exploiting cells of myeloid origin.

What is the role of vitamin D in autism?

A growing body of literature suggests that higher serum 25-hydroxyvitamin D [25(OH)D] concentrations, either in utero or in early life, may reduce the risk of autism. For example, an ecological study in the companion paper inversely correlated solar UV-B doses in the United States with prevalence of autism among those aged 6–17 y. That study proposed that vitamin D deficiency during pregnancy could account for this finding, although the findings are also consistent with childhood vitamin D deficiency contributing to the condition. Also, in a recent study, children with autism had lower serum 25(OH)D concentrations than did control subjects (19 vs. 33 ng/ml), despite parents of each group reporting the same amount of sun exposure. The same study found highly significant inverse correlations between 25(OH)D and autism rating scales and between 25(OH)D and levels of an antineuronal antibody. This finding indicates that higher serum 25(OH)D concentrations may reduce the symptoms of established autism. Because activated vitamin D, a secosteroid, upregulates DNA-repair genes, vitamin D deficiency during development may inhibit the repair of de novo DNA mutations in fetuses and infants and thus contribute to risk of autism. Vitamin D might also reduce the risk or severity of autism through its anti-inflammatory actions, antiautoimmune effects, increasing seizure threshold, increasing T-regulatory cells, protecting the mitochondria, and upregulating glutathione, which scavenges oxidative by-products and chelates (captures and excretes) heavy metals. Vitamin D deficiency during pregnancy and childhood is a widespread and growing epidemic.

Should vitamin D supplementation be a regular part of asthma care?

Vitamin D (vitD3) deficiency occurs frequently and has profound effects on health, especially asthma. This article examines how current knowledge of vitD3 actions and the worldwide distribution of vitD3 deficiency influences everyday clinical allergy practice. Within the limits of current knowledge, the article concisely explains the molecular nature of vitD3 actions, reviews key vitD3 research as it applies to clinical care, answers questions about the potential clinical impact of low vitD3 levels, and discusses use and safety of vitD3 supplements.

Chaetoglobosin F, a small molecule compound, possesses immunomodulatory properties on bone marrow-derived dendritic cells via TLR9 signaling pathway

Chaetoglobosin F (Cha F), a cytochalasan-based alkaloid, was obtained from the EtOAc extract of a solid culture of Chaetomium globosum IFB-E019. Dendritic cells (DCs), the most potent antigen presenting cells, are considered as the major target in the modulation of excessive immune responses. Recognition of CpG-DNA by Toll-like receptor 9 (TLR9) on DCs is an important step in the pathogenesis of autoimmune diseases. However, the effect of Cha F on the maturation and immunostimulatory function of CpG-stimulated DCs remains unclear. This study investigated the effects of Cha F on bone marrow (BM)-derived DCs. We found that Cha F inhibits the CpG-induced DCs maturation and function by suppressing the expression of surface molecules (CD40, CD80, CD86 and MHC-II), reducing the production of cytokines and chemokines (IL-12 and CXCL-10), inhibiting the CpG-induced DCs-elicited allogeneic T-cell proliferation, and impairing the migration ability to chemokines. The Cha F-treated DCs were highly efficient at Ag capture, via mannose receptor-mediated endocytosis. Additionally, Cha F was also demonstrated to inhibit CpG-induced activation of MAPKs (p38 and JNK, but not ERK) and the nuclear translocation of NF-κB and STAT1. Furthermore, we confirmed that Cha F was able to suppress TLR9 expression of CpG-induced DCs. Collectively, these findings provide novel insight into the immunopharmacological functions of Cha F, especially with regard to their impact on CpG-induced DCs. These immunosuppressive properties of Cha F may prove useful in controlling DCs-associated autoimmune and/or inflammatory diseases.