Paricalcitol (19-nor-1,25-dihydroxyvitamin D2) and calcitriol (1,25-dihydroxyvitamin D3) exert potent immunomodulatory effects on dendritic cells and inhibit induction of antigen-specific T cells

Evaluation of the effect and predictive role of vitamin D and vitamin D receptor expression in CD4 + , CD8 + , CD14 + , CD56 + cells on the development of chronic rejection and graft functions in kidney transplant patients

PURPOSE

It is known that vitamin D has positive effects on graft functions (reduce fibrosis, suppress excessive inflammatory response, improve graft functions). In our study, it was aimed to evaluate the effects and predictive roles of vitamin D, the expression of vitamin D receptor (VDR) in lymphocytes, monocytes, natural killer cells on chronic rejection and graft functions in kidney transplant patients.

METHODS

Seventy one people were included in the study and analyses were made by dividing them into 3 groups. Group 1: Healthy control (n = 29), Group 2: Kidney transplant patients with stable kidney function (n = 17), and Group 3: Kidney transplant patients with chronic rejection diagnosis (n = 25). Serum 25-hydroxycholecalciferol, 1.25 dihydroxycholecalciferol levels and VDR percentages in CD4 + , CD8 + , CD14 + , CD56 + cells were measured in 3 groups. ROC analyses and logistic regression models were performed to predict rejection and long-term graft functions.

RESULTS

The percentage of VDR expression in CD4 + lymphocytes (p < 0.001) and CD14( +) monocytes (p < 0.001), 25-hydroxycholecalciferol and 1.25 dihydroxycholecalciferol levels were lower in group 3 was detected. In ROC analyses and logistic regression models, VDR expression in CD4( +)T lymphocytes was shown to have a statistically significant value in the development of chronic rejection (Odds ratio 0.86: 0.76-0.92; p = 0.001/AUC = 0.941, p < 0.001) and prediction of 5th-year graft functions (Odds ratio 0.93: 0.88-0.98; p = 0.017/AUC = 0.745, p = 0.007).

CONCLUSION

In our study, it was shown that low vitamin D and VDR expression is associated with poor outcome and VDR expression in CD4( +)T lymphocytes is predictive in terms of graft function and rejection.

Is Vitamin D3 a Worthy Supplement Protecting against Secondary Infections in Dogs with Atopic Dermatitis?

Canine atopic dermatitis (CAD) is a common, chronic, inflammatory skin disease in dogs worldwide. This disease often predisposes for secondary organisms overgrowth and skin infections with pathogens, such as Staphylococcus pseudintermedius and Malassezia pachydermatis. Unfortunately, the causes of this disease in both humans and animals are not fully understood; therefore, the only possible option is a lifelong, symptomatic treatment. The management of CAD is mainly based on limiting contact with allergens and antipruritic therapy, most often with glucocorticoids and antihistamines. A serious problem in this situation is the fact, that long-term administration of glucocorticoids leads to side effects like polyuria, alopecia, increased susceptibility to infection, muscle atrophy, and many others. For this reason, great emphasis is placed on the development of replacement and supportive therapies. It is a well-documented fact that reduced concentrations of serum vitamin D3 contribute to the severity of atopic dermatitis symptoms in humans. Moreover, unlike the most commonly used therapeutic methods, of which the main goal is to ameliorate inflammation and pruritus, namely the symptoms of AD, vitamin D3 supplementation affects some underlying factors of this disease. Therefore, in this review, we summarize the current state of knowledge regarding the role of vitamin D3 in CAD, its protective effect against secondary bacterial and fungal infections, and the potential of its supplementation in dogs.

Tolerogenic Dendritic Cells Induce Apoptosis-Independent T Cell Hyporesponsiveness of SARS-CoV-2-Specific T Cells in an Antigen-Specific Manner

Although the global pandemic caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still ongoing, there are currently no specific and highly efficient drugs for COVID-19 available, particularly in severe cases. Recent findings demonstrate that severe COVID-19 disease that requires hospitalization is associated with the hyperactivation of CD4⁺ and CD8⁺ T cell subsets. In this study, we aimed to counteract this high inflammatory state by inducing T-cell hyporesponsiveness in a SARS-CoV-2-specific manner using tolerogenic dendritic cells (tolDC). In vitro-activated SARS-CoV-2-specific T cells were isolated and stimulated with SARS-CoV-2 peptide-loaded monocyte-derived tolDC or with SARS-CoV-2 peptide-loaded conventional (conv) DC. We demonstrate a significant decrease in the number of interferon (IFN)-γ spot-forming cells when SARS-CoV-2-specific T cells were stimulated with tolDC as compared to stimulation with convDC. Importantly, this IFN-γ downmodulation in SARS-CoV-2-specific T cells was antigen-specific, since T cells retain their capacity to respond to an unrelated antigen and are not mediated by T cell deletion. Altogether, we have demonstrated that SARS-CoV-2 peptide-pulsed tolDC induces SARS-CoV-2-specific T cell hyporesponsiveness in an antigen-specific manner as compared to stimulation with SARS-CoV-2-specific convDC. These observations underline the clinical potential of tolDC to correct the immunological imbalance in the critically ill.

Inhibition of PI3K/C/EBPβ axis in tolerogenic bone marrow-derived dendritic cells of NOD mice promotes Th17 differentiation and diabetes development

Dendritic cells (DCs) are key regulators of the adaptive immune response. Tolerogenic dendritic cells play a crucial role in inducing and maintaining immune tolerance in autoimmune diseases such as type 1 diabetes in humans as well as in the NOD mouse model. We previously reported that bone marrow-derived DCs (BM.DCs) from NOD mice, generated with a low dose of GM-CSF (GM/DCs), induce Treg differentiation and are able to protect NOD mice from diabetes. We had also found that the p38 MAPK/C/EBPβ axis is involved in regulating the phenotype, as well as the production of IL-10 and IL-12p70, by tolerogenic GM/DCs. Here, we report that the inhibition of the PI3K signaling switched the cytokine profile of GM/DCs toward Th17-promoting cytokines without affecting their phenotype. PI3K inhibition abrogated the production of IL-10 by GM/DCs, whereas it enhanced their production of IL-23 and TGFβ. Inhibition of PI3K signaling in tolerogenic GM/DCs also induced naive CD4⁺ T cells differentiation toward Th17 cells. Mechanistically, PI3K inhibition increased the DNA-binding activity of C/EBPβ through a GSK3-dependent pathway, which is important to maintain the semimature phenotype of tolerogenic GM/DCs. Furthermore, analysis of C/EBPβ^-/- GM/DCs demonstrated that C/EBPβ is required for IL-23 production. Of physiological relevance, the level of protection from diabetes following transfusion of GM/DCs into young NOD mice was significantly reduced when NOD mice were transfused with GM/DCs pretreated with a PI3K inhibitor. Our data suggest that PI3K/C/EBPβ signaling is important in controlling tolerogenic function of GM/DCs by limiting their Th17-promoting cytokines.

Treatment of alopecia totalis/universalis/focalis with vitamin D and analogs: Three case reports and a literature review

BACKGROUND

Alopecia areata (AA) is an inflammatory disease with autoimmune, environmental, and inherited components directed at the hair follicle, either limited to patchy hair loss over the scalp (Focalis, AF), total loss of scalp hair (Totalis, AT), or total loss of both scalp and body hair (Universalis, AU). Despite multiple treatment modalities, no therapy exists. Vitamin D deficiency in patients with AA/AT/AF influences disease severity and duration, inversely correlating with inflammation histologically.

CASE SUMMARY

Three girls presented with AT (P1), AU (P2), and AF (P3) at the ages of 1, 5, and 5 years, respectively. For P1-P2, all available treatments implemented for 2 years had failed. We started an initial 6-mo repletion with oral cholecalciferol 2000/4000 IU/d, with no apparent effect. Then we attempted immunomodulation using oral calcitriol and its analog paricalcitol. On calcitriol, 0.5 mcg/d P1 regrew hair within 6 mo. After 4 years, a relapse with loss of eyebrow hair was resolved after doubling the calcitriol dose to 0.5 mcg × 2/d; the results have been maintained for 6 years to date. On calcitriol, 0.25 mcg × 3/d P2 led to the development of asymptomatic hypercalcemia-hypercalciuria, which was immediately resolved by switching to paricalcitol 2 mcg × 3/d; mild tolerable hypercalciuria was maintained. Hair regrowth was observed at 6 mo, stabilizing only as fur at 12 mo. AF in P3 was resolved completely within 3 mo on a daily high dose (8000 IU) of cholecalciferol.

CONCLUSION

Vitamin D may have immunomodulating therapeutic impact on AT/AU/AF, which needs to be explored with further pilot clinical trials.

Preclinical Therapy with Vitamin D3 in Experimental Encephalomyelitis: Efficacy and Comparison with Paricalcitol

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system (CNS). MS and its animal model called experimental autoimmune encephalomyelitis (EAE) immunopathogenesis involve a plethora of immune cells whose activation releases a variety of proinflammatory mediators and free radicals. Vitamin D3 (VitD) is endowed with immunomodulatory and antioxidant properties that we demonstrated to control EAE development. However, this protective effect triggered hypercalcemia. As such, we compared the therapeutic potential of VitD and paricalcitol (Pari), which is a non-hypercalcemic vitamin D analog, to control EAE. From the seventh day on after EAE induction, mice were injected with VitD or Pari every other day. VitD, but not Pari, displayed downmodulatory ability being able to reduce the recruitment of inflammatory cells, the mRNA expression of inflammatory parameters, and demyelination at the CNS. Lower production of proinflammatory cytokines by lymph node-derived cells and IL-17 by gut explants, and reduced intestinal inflammation were detected in the EAE/VitD group compared to the EAE untreated or Pari groups. Dendritic cells (DCs) differentiated in the presence of VitD developed a more tolerogenic phenotype than in the presence of Pari. These findings suggest that VitD, but not Pari, has the potential to be used as a preventive therapy to control MS severity.

Vitamin D3-Induced Tolerogenic Dendritic Cells Modulate the Transcriptomic Profile of T CD4+ Cells Towards a Functional Hyporesponsiveness

The use of autologous tolerogenic dendritic cells (tolDC) has become a promising alternative for the treatment of autoimmune diseases. Among the different strategies available, the use of vitamin D3 for the generation of tolDC (vitD3-tolDC) constitutes one of the most robust approaches due to their immune regulatory properties, which are currently being tested in clinical trials. However, the mechanisms that vitD3-tolDC trigger for the induction of tolerance remain elusive. For this reason, we performed a full phenotypical, functional, and transcriptomic characterization of T cells upon their interaction with autologous, antigen-specific vitD3-tolDC. We observed a strong antigen-specific reduction of T cell proliferation, combined with a decrease in the relative prevalence of TH1 subpopulations and IFN-γ production. The analysis of the transcriptomic profile of T CD4+ cells evidenced a significant down-modulation of genes involved in cell cycle and cell response to mainly pro-inflammatory immune-related stimuli, highlighting the role of JUNB gene as a potential biomarker of these processes. Consequently, our results show the induction of a strong antigen-specific hyporesponsiveness combined with a reduction on the TH1 immune profile of T cells upon their interaction with vitD3-tolDC, which manifests the regulatory properties of these cells and, therefore, their therapeutic potential in the clinic.

A deep dive into UV-based phototherapy: Mechanisms of action and emerging molecular targets in inflammation and cancer

UV-based phototherapy (including psoralen plus UVA (PUVA), UVB and UVA1) has a long, successful history in the management of numerous cutaneous disorders. Photoresponsive diseases are etiologically diverse, but most involve disturbances in local (and occasionally systemic) inflammatory cells and/or abnormalities in keratinocytes that trigger inflammation. UV-based phototherapy works by regulating the inflammatory component and inducing apoptosis of pathogenic cells. This results in a fascinating and complex network of simultaneous events-immediate transcriptional changes in keratinocytes, immune cells, and pigment cells; the emergence of apoptotic bodies; and the trafficking of antigen-presenting cells in skin-that quickly transform the microenvironment of UV-exposed skin. Molecular elements in this system of UV recognition and response include chromophores, metabolic byproducts, innate immune receptors, neurotransmitters and mediators such as chemokines and cytokines, antimicrobial peptides, and platelet activating factor (PAF) and PAF-like molecules that simultaneously shape the immunomodulatory effects of UV and their interplay with the microbiota of the skin and beyond. Phototherapy's key effects-proapoptotic, immunomodulatory, antipruritic, antifibrotic, propigmentary, and pro-prebiotic-promote clinical improvement in various skin diseases such as psoriasis, atopic dermatitis (AD), graft-versus-host disease (GvHD), vitiligo, scleroderma, and cutaneous T-cell lymphoma (CTCL) as well as prevention of polymorphic light eruption (PLE). As understanding of phototherapy improves, new therapies (UV- and non-UV-based) are being developed that will modify regulatory T-cells (Treg), interact with (resident) memory T-cells and /or utilize agonists and antagonists as well as antibodies targeting soluble molecules such as cytokines and chemokines, transcription factors, and a variety of membrane-associated receptors.

Natural and Induced Tolerogenic Dendritic Cells

Dendritic cells (DCs) are highly susceptible to extrinsic signals that modify the functions of these crucial APCs. Maturation of DCs induced by diverse proinflammatory conditions promotes immune responses, but certain signals also induce tolerogenic functions in DCs. These "induced tolerogenic DCs" help to moderate immune responses such as those to commensals present at specific anatomical locations. However, also under steady-state conditions, some DCs are characterized by inherent tolerogenic properties. The immunomodulatory mechanisms constitutively present in such "natural tolerogenic DCs" help to promote tolerance to peripheral Ags. By extending tolerance initially established in the thymus, these functions of DCs help to regulate autoimmune and other immune responses. In this review we will discuss the mechanisms and functions of natural and induced tolerogenic DCs and offer further insight into how their possible manipulations may ultimately lead to more precise treatments for various immune-mediated conditions and diseases.

MiR-125a-5p Regulates Vitamin D Receptor Expression in a Mouse Model of Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) is a chronic and incurable autoimmune neurodegenerative disease of the central nervous system. Although the symptoms of MS can be managed by vitamin D3 treatment alone, this condition cannot be completely eradicated. Thus, there might be unknown factors capable of regulating the vitamin D receptor (VDR). Genome-wide analysis showed that miRNAs were associated with VDRs. We sought to determine the role and mechanism of action of miRNA-125a-5p and VDRs in a model of MS, mice with experimental autoimmune encephalomyelitis (EAE), which was induced by myelin oligodendrocyte glycoprotein 35-55 peptides. EAE mice showed decreased mean body weight but increased mean clinical scores compared with vehicle or control mice. And inflammatory infiltration was found in the lumbosacral spinal cord of EAE mice. In addition, VDR expression was significantly lower while the expression of miR-125a-5p was markedly higher in the spinal ventral horn of EAE mice than in vehicle or control mice. Importantly, activation of VDRs by paricalcitol or inhibition of miR-125a-5p by its antagomir markedly decreased the mean clinical scores in EAE mice. Interestingly, VDR and miR-125a-5p were co-localized in the same neurons of the ventral horn. More importantly, inhibition of miR-125a-5p remarkably blocked the decrease of VDRs in EAE mice. These results support a critical role for miR-125a-5p in modulating VDR activity in EAE and suggest potential novel therapeutic interventions.

Optimal Tolerogenic Dendritic Cells in Type 1 Diabetes (T1D) Therapy: What Can We Learn From Non-obese Diabetic (NOD) Mouse Models?

Tolerogenic dendritic cells (tolDCs) are explored as a promising standalone or combination therapy in type 1 diabetes (T1D). The therapeutic application of tolDCs, including in human trials, has been tested also in other autoimmune diseases, however, T1D displays some unique features. In addition, unlike in several disease-induced animal models of autoimmune diseases, the prevalent animal model for T1D, the NOD mouse, develops diabetes spontaneously. This review compares evidence of various tolDCs approaches obtained from animal (mainly NOD) models of T1D with a focus on parameters of this cell-based therapy such as protocols of tolDC preparation, antigen-specific vs. unspecific approaches, doses of tolDCs and/or autoantigens, application schemes, application routes, the migration of tolDCs as well as their preventive, early pre-onset intervention or curative effects. This review also discusses perspectives of tolDC therapy and areas of preclinical research that are in need of better clarification in animal models in a quest for effective and optimal tolDC therapies of T1D in humans.

To Supplement or not to Supplement? The Rationale of Vitamin D Supplementation in Systemic Lupus Erythematosus

Background:

Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease characterised by abnormal activation of the immune system, chronic inflammation and organ damage. Lupus patients are more prone to be vitamin D deficient. However, current evidence is not conclusive with regards to the role played by vitamin D in SLE development, progression, and clinical manifestations.

Objective:

Here, we will summarise the current knowledge about vitamin D deficiency prevalence, risk factors, molecular effects, and potential pathogenic role in SLE. We will focus on the link between vitamin D deficiency and lupus clinical manifestations, and on the clinical trials assessing the effects of vitamin D supplementation in SLE.

Method:

A detailed literature search was performed exploiting the available databases, using “vitamin D and lupus/SLE” as keywords. The relevant interventional trials published over the last decade have been considered and the results are reported here.

Conclusion:

Several immune cells express vitamin D receptors. Thus, an immunomodulatory role for vitamin D in lupus is plausible. Numerous observational studies have investigated the relationship between vitamin D levels and clinical/serological manifestations of SLE with contrasting results. Negative correlations between vitamin D levels and disease activity, fatigue, renal and cardiovascular disease, and anti-dsDNA titres have been described but not conclusively accepted. In experimental models of lupus, vitamin D supplementation can improve the disease. Interventional trials have assessed the potential therapeutic value of vitamin D in SLE, but further larger studies are needed.

Successful Treatment of Severe Atopic Dermatitis with Calcitriol and Paricalcitol in an 8-Year-Old Girl

Atopic dermatitis (AD) is a chronic inflammatory disease affecting children and adolescence. The traditional therapeutic options for AD, including emollients topically and immune modulatory agents systemically focusing on reducing skin inflammation and restoring the function of the epidermal barrier, are proven ineffective in many cases. Several studies have linked vitamin D supplementation with either a decreased risk to develop AD or a clinical improvement of the symptoms of AD patients. In this report, we present a girl with severe AD who under adequate supplementation with cholecalciferol was treated with calcitriol and subsequently with paricalcitol. She had significant improvement—almost healing of her skin lesions within 2 months, a result sustained for more than 3 years now. Because of hypercalciuria as a side effect from calcitriol therapy, treatment was continued with paricalcitol, a vitamin D analogue used in secondary hyperparathyroidism in chronic kidney disease. Calcitriol therapy may be considered as a safe and efficacious treatment option for patients with severe AD, particularly for those with refractory AD, under monitoring for possible side effects. Treatment with paricalcitol resolves hypercalciuria, is safe, and should be further investigated as an alternative treatment of atopic dermatitis and possibly other diseases of autoimmune origin.

Vitamin D status and its influence on outcomes following major burn injury and critical illness

Vitamin D deficiency is common among the general population. It is also observed in up to 76% of critically ill patients. Despite the high prevalence of hypovitaminosis D in critical illness, vitamin D is often overlooked by medical staff as the clinical implications and consequences of vitamin D deficiency in acute contexts remain to be fully understood. Vitamin D has a broad range of pleotropic effects on various processes and systems including the immune-inflammatory response. 1α,25-dihydroxyvitamin D (1,25(OH)₂D), has been shown to promote a tolerogenic immune response limiting deleterious inflammatory effects, modulation of the innate immune system, and enhancement of anti-microbial peptides. Vitamin D deficiency is frequently observed in critically ill patients and has been related to extrinsic causes (i.e., limited sunlight exposure), magnitude of injury/illness, or the treatment started by medical doctors including fluid resuscitation. Low levels of vitamin D in critically ill patients have been associated with sepsis, organ failure, and mortality. Despite this, there are subpopulations of critical illness, such as burn patients, where the literature regarding vitamin D status and its influence on outcomes remain insufficient. Thermal injury results in damage to both burned and non-burned tissues, as well as induces an exaggerated and persistent immune-inflammatory and hypermetabolic response. In this review, we propose potential mechanisms in which burn injury affects the vitamin D status and summarizes current literature investigating the influence of vitamin D status on outcomes. In addition, we reviewed the literature and trials investigating vitamin D supplementation in critically ill patients and discuss the therapeutic potential of vitamin D supplementation in burn and critically ill patients. We also highlight current limitations of studies that have investigated vitamin D status and supplementation in critical illness. Thermal injury influences vitamin D status. More studies investigating vitamin D depletion in burn patients and its influence on prognosis, via standardized methodology, are required to reach definitive conclusions and influence clinical practice.

Antigen Loading (e.g., Glutamic Acid Decarboxylase 65) of Tolerogenic DCs (tolDCs) Reduces Their Capacity to Prevent Diabetes in the Non-Obese Diabetes (NOD)-Severe Combined Immunodeficiency Model of Adoptive Cotransfer of Diabetes As Well As in NOD Mice

Tolerogenic DCs (tolDCs) are being researched as a promising intervention strategy also in autoimmune diseases including type 1 diabetes (T1D). T1D is a T-cell-mediated, organ-specific disease with several well-defined and rather specific autoantigens, i.e., proinsulin, insulin, glutamic acid decarboxylase 65 (GAD65), that have been used in animal as well as human intervention trials in attempts to achieve a more efficient, specific immunotherapy. In this study, we have tested tolerogenic DCs for their effectiveness to prevent adoptive transfer of diabetes by diabetogenic splenocytes into non-obese diabetes (NOD)-severe combined immunodeficiency (NOD-SCID) recipients. While i.p. application of tolDCs prepared from bone marrow of prediabetic NOD mice by vitamin D2 and dexamethasone significantly reduced diabetes transfer into the NOD-SCID females, this effect was completely abolished when tolDCs were loaded with the mouse recombinant GAD65, but also with a control protein—ovalbumin (OVA). The effect was not dependent on the presence of serum in the tolDC culture. Similar results were observed in NOD mice. Removal of possible bystander antigen-presenting cells within the diabetogenic splenocytes by negative magnetic sorting of T cells did not alter this surprising effect. Tolerogenic DCs loaded with an immunodominant mouse GAD65 peptide also displayed diminished diabetes-preventive effect. Tolerogenic DCs were characterized by surface maturation markers (CD40, CD80, CD86, MHC II) and the lipopolysaccharide stability test. Data from alloreactive T cell proliferation and cytokine induction assays (IFN-γ) did not reveal the differences observed in the diabetes incidence. Migration of tolDCs, tolDCs-GAD65 and tolDCs-OVA to spleen, mesenteric- and pancreatic lymph nodes displayed similar, mucosal pattern with highest accumulation in pancreatic lymph nodes present up to 9 days after the i.p. application. These data document that mechanisms by which tolDCs operate in vivo require much better understanding for improving efficacy of this promising cell therapy, especially in the presence of an antigen, e.g., GAD65.

Vitamin D shows in vivo efficacy in a placebo-controlled, double-blinded, randomised clinical trial on canine atopic dermatitis

Atopic dermatitis (AD) in dogs is among the most common skin diseases in small animal practice. It is an inflammatory disease based on a genetic predisposition to develop hypersensitivity against environmental and food allergens and typical clinical signs up exposure. Treatment sometimes can be difficult and associated with adverse effects. Previous studies evaluating cholecalciferol as treatment for human AD have shown promising results. With canine AD being a good animal model for its human counterpart, it was hypothesised that cholecalciferol might have beneficial clinical effects in dogs, too. In this randomised, placebo-controlled, double-blinded eight-week cross-over study, 23 client-owned dogs received either systemic cholecalciferol (n=16), a vitamin D receptor analogue (n=8) or placebo (n=13). Blood samples for ionised calcium were obtained regularly during the study, and Canine Atopic Dermatitis Extent and Severity Index and pruritus scores, blood levels of vitamin D metabolites, measurements of skin pH and transepidermal water loss were determined before and after. Pruritus and lesion scores decreased significantly in the cholecalciferol group versus placebo. No differences in water loss or skin pH were observed. An increase in serum 25-hydroxycholecalciferol strongly correlated with a reduction in pruritus. Systemic cholecalciferol may be a viable treatment option for canine AD.

Association between vitamin D receptor polymorphisms and hepatitis B virus infection susceptibility: A meta-analysis study

BACKGROUND

Hepatitis B virus (HBV) infection is still a serious public health problem. Understanding risk factors associated with development of HBV is greatly important. Numerous studies focus on relationship between vitamin D receptor (VDR) polymorphisms (TaqI, FokI, ApaI, BsmI) and the risk of HBV infection in different ethnic groups. However the results published so far are inconsistent. The aim of this study is to quantify the association between VDR polymorphisms with HBV infection by meta-analysis approach.

METHODS

A systematic search was performed in Pubmed, Embase, China National Knowledge Infrastructure (CNKI), Database of Chinese Scientific and Technical Periodicals (VIP), and WANFANG. All the relevant studies were published up to October 2016.

RESULTS

Finally, 15 published studies included 4218 cases and 2298 controls were included in this meta-analysis. It is interesting to note that FokI FF tends to be a risk factor for HBV infection [FF vs. ff: P<0.01, OR (95%CI)=1.54 (1.19-2.00), I²=0.0%], with no heterogeneity. In addition, genotype Ff and allele F could increase HBV infection risk [Ff vs. ff: P<0.01, OR (95%CI)=1.39 (1.13-1.72); F vs. f: P=0.02, OR (95%CI)=1.23(1.04-1.45)]. However, no associations were found about VDR TaqI, ApaI and BsmI polymorphisms with HBV infection based on each comparison model.

CONCLUSION

This meta-analysis indicates that FokI genotype FF, Ff and allele F increase the risk of HBV infection. All these results support the notion that VDR FokI genotype might has potential role in HBV susceptibility.

Decreased sensitivity to 1,25-dihydroxyvitamin D3 in T cells from the rheumatoid joint

1,25-dihydroxyvitaminD₃ (1,25(OH)₂D₃), has potent anti-inflammatory effects, including suppression of IL-17 + and IFNγ+ T cells implicated in rheumatoid arthritis (RA), but efficacy at the site of active disease is unclear. To investigate this, T cells from synovial fluid (SF) and paired blood of patients with active RA were studied. 1,25(OH)₂D₃ had significantly less suppressive effect on Th17 cells (IL-17+IFNγ-) and Th17.1 cells (IL-17+IFNγ+) from SF compared to those from blood, and had no effect on SF CD4⁺ or CD8⁺ IFNγ+ T cell frequencies. Memory T cells (CD45RO+) predominate in SF, and 1,25(OH)₂D₃ had less effect on memory T cells relative to naïve (CD45RA+) T cells. RT-PCR and flow cytometry showed that this was not due to decreased expression of the vitamin D receptor or its transcription partners in memory T cells. Further studies using stimulated CD4⁺ T cells sorted according to IL-17 and IFNγ expression confirmed the ability of 1,25(OH)₂D₃ to suppress pre-existing cytokines. However, 1,25(OH)₂D₃ was most effective at suppressing de novo IL-17 and IFNγ induction. Correspondingly, T cell responses to 1,25(OH)₂D₃ correlated directly with capacity for phenotype change, which was lower in cells from SF compared to blood. These findings indicate that anti-inflammatory effects of 1,25(OH)₂D₃ in active RA are impaired because of reduced effects on phenotype-committed, inflammatory memory T cells that are enriched in SF. Restoration of 1,25(OH)₂D₃ responses in memory T cells may provide a new strategy for treatment of inflammatory diseases such as RA.

Experimental Autoimmune Encephalomyelitis Is Successfully Controlled by Epicutaneous Administration of MOG Plus Vitamin D Analog

Multiple sclerosis (MS) is an inflammatory and demyelinating disorder of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE) has been widely employed to evaluate new strategies to control MS, including procedures to induce immunological tolerance. Considering that skin exposure to protein antigens can induce tolerance and that vitamin D analogs conserve immunomodulatory potential and are less toxic, we investigated the efficacy of epicutaneous application of a myelin oligodendrocyte glycoprotein peptide (MOG_35–55) associated with paricalcitol (PARI) on EAE development. Three and 11 days after EAE induction, C57BL/6 mice were treated with an occlusive patch containing MOG plus PARI. Clinical parameters were daily assessed, whereas immunological and histological evaluations were performed during the acute EAE phase. MOG and MOG + PARI significantly controlled disease development reducing weight loss and clinical score. Moreover, MOG and MOG + PARI reduced the inflammatory process and preserved the myelin sheath in the CNS. High percentages of Foxp3⁺ regulatory T cells (Tregs) and lower MHCII fluorescence intensity in dendritic cells in draining lymph nodes were concomitantly observed. MOG + PARI association was, however, more efficient being able to reduce disease incidence and clinical scores more significantly than MOG or PARI alone. This experimental group also displayed a higher ratio between mRNA expression for Foxp3 and RORc and a higher percentage of Foxp3⁺ cells in the CNS. Modulation of activation markers observed in microglial cells eluted from EAE treated mice were confirmed by in vitro studies with the BV-2 microglial cell line. The results show that MOG + PARI association applied by an epicutaneous route controlled EAE development. Protective involved mechanisms include mainly a higher proportion of Tregs and also a direct immunomodulatory effect of PARI on microglial cells.

High-dose vitamin D3 supplementation decreases the number of colonic CD103+ dendritic cells in healthy subjects

PURPOSE

Vitamin D may induce tolerance in the intestinal immune system and has been shown to regulate the phenotype of tolerogenic intestinal dendritic cells (DCs) in vitro. It is unknown whether vitamin D supplementation affects human intestinal DCs in vivo, and we aimed to investigate the tolerability and effect on intestinal CD103⁺DCs of high-dose vitamin D₃ treatment in healthy subjects.

METHODS

Ten healthy subjects received a total of 480,000 IU oral vitamin D₃ over 15 days and colonic biopsies were obtained before and after intervention by endoscopy. Lamina propria mononuclear cells (LPMCs) were isolated from the biopsies, stained with DC surface markers and analysed with flow cytometry. Snap-frozen biopsies were analysed with qPCR for DC and regulatory T cell-related genes.

RESULTS

No hypercalcemia or other adverse events occurred in the test subjects. Vitamin D decreased the number of CD103⁺ DCs among LPMCs (p = 0.006). Furthermore, vitamin D induced mRNA expression of TGF-β (p = 0.048), TNF-α (p = 0.006) and PD-L1 (p = 0.02) and tended to induce IL-10 expression (p = 0.06). Multivariate factor analysis discriminated between pre- and post-vitamin D supplementation with a combined increased qPCR expression of PD1, PD-L1, TGF-β, IL-10, CD80, CD86, FOXP3, NFATc2 and cathelicidin.

CONCLUSION

High-dose vitamin D supplementation is well tolerated by healthy subjects and has a direct effect on the CD103⁺ DCs, local cytokine and surface marker mRNA expression in the colonic mucosa, suggestive of a shift towards a more tolerogenic milieu.

Vitamin D receptor activation reduces VCaP xenograft tumor growth and counteracts ERG activity despite induction of TMPRSS2:ERG

Whether vitamin D is chemopreventive and/or has potential therapeutically in prostate cancer is unresolved. One confounding factor is that many prostate cancers express a TMPRSS2:ERG fusion gene whose expression is increased both by androgens and by vitamin D receptor (VDR) activation. Two challenges that limit VDR agonist use clinically are hypercalcemia and the cooperation of VDR with ERG to hyper-induce the 1α,25-dihydroxyvitamin D3 metabolizing enzyme, CYP24A1, thus reducing VDR activity. Using the VCaP TMPRSS2:ERG positive cell line as a model, we found that a nonsecosteroidal CYP24A1 resistant VDR agonist, VDRM2, substantially reduces growth of xenograft tumors without inducing hypercalcemia. Utilizing next generation RNA sequencing, we found a very high overlap of 1,25D(OH)2D3 and VDRM2 regulated genes and by drawing upon previously published datasets to create an ERG signature, we found activation of VDR does not induce ERG activity above the already high basal levels present in VCaP cells. Moreover, we found VDR activation opposes 8 of the 10 most significant ERG regulated Hallmark gene set collection pathways from Gene Set Enrichment Analysis (GSEA). Thus, a CYP24A1 resistant VDR agonist may be beneficial for treatment of TMPRSS2:ERG positive prostate cancer; one negative consequence of TMPRSS2:ERG expression is inactivation of VDR signaling.

Vitamin D in Autoimmunity: Molecular Mechanisms and Therapeutic Potential

Over the last three decades, it has become clear that the role of vitamin D goes beyond the regulation of calcium homeostasis and bone health. An important extraskeletal effect of vitamin D is the modulation of the immune system. In the context of autoimmune diseases, this is illustrated by correlations of vitamin D status and genetic polymorphisms in the vitamin D receptor with the incidence and severity of the disease. These correlations warrant investigation into the potential use of vitamin D in the treatment of patients with autoimmune diseases. In recent years, several clinical trials have been performed to investigate the therapeutic value of vitamin D in multiple sclerosis, rheumatoid arthritis, Crohn’s disease, type I diabetes, and systemic lupus erythematosus. Additionally, a second angle of investigation has focused on unraveling the molecular pathways used by vitamin D in order to find new potential therapeutic targets. This review will not only provide an overview of the clinical trials that have been performed but also discuss the current knowledge about the molecular mechanisms underlying the immunomodulatory effects of vitamin D and how these advances can be used in the treatment of autoimmune diseases.

Dexamethasone and Monophosphoryl Lipid A-Modulated Dendritic Cells Promote Antigen-Specific Tolerogenic Properties on Naive and Memory CD4+ T Cells

Tolerogenic dendritic cells (DCs) are a promising tool to control T cell-mediated autoimmunity. Here, we evaluate the ability of dexamethasone-modulated and monophosphoryl lipid A (MPLA)-activated DCs [MPLA-tolerogenic DCs (tDCs)] to exert immunomodulatory effects on naive and memory CD4⁺ T cells in an antigen-specific manner. For this purpose, MPLA-tDCs were loaded with purified protein derivative (PPD) as antigen and co-cultured with autologous naive or memory CD4⁺ T cells. Lymphocytes were re-challenged with autologous PPD-pulsed mature DCs (mDCs), evaluating proliferation and cytokine production by flow cytometry. On primed-naive CD4⁺ T cells, the expression of regulatory T cell markers was evaluated and their suppressive ability was assessed in autologous co-cultures with CD4⁺ effector T cells and PPD-pulsed mDCs. We detected that memory CD4⁺ T cells primed by MPLA-tDCs presented reduced proliferation and proinflammatory cytokine expression in response to PPD and were refractory to subsequent stimulation. Naive CD4⁺ T cells were instructed by MPLA-tDCs to be hyporesponsive to antigen-specific restimulation and to suppress the induction of T helper cell type 1 and 17 responses. In conclusion, MPLA-tDCs are able to modulate antigen-specific responses of both naive and memory CD4⁺ T cells and might be a promising strategy to “turn off” self-reactive CD4⁺ effector T cells in autoimmunity.

Immunomodulatory Effects of 1,25-Dihydroxyvitamin D3 on Dendritic Cells Promote Induction of T Cell Hyporesponsiveness to Myelin-Derived Antigens

While emerging evidence indicates that dendritic cells (DC) play a central role in the pathogenesis of multiple sclerosis (MS), their modulation with immunoregulatory agents provides prospect as disease-modifying therapy. Our observations reveal that 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) treatment of monocyte-derived DC results in a semimature phenotype and anti-inflammatory cytokine profile as compared to conventional DC, in both healthy controls and MS patients. Importantly, 1,25(OH)₂D₃-treated DC induce T cell hyporesponsiveness, as demonstrated in an allogeneic mixed leukocyte reaction. Next, following a freeze-thaw cycle, 1,25(OH)₂D₃-treated immature DC could be recovered with a 78% yield and 75% viability. Cryopreservation did not affect the expression of membrane markers by 1,25(OH)₂D₃-treated DC nor their capacity to induce T cell hyporesponsiveness. In addition, the T cell hyporesponsiveness induced by 1,25(OH)₂D₃-treated DC is antigen-specific and robust since T cells retain their capacity to respond to an unrelated antigen and do not reactivate upon rechallenge with fully mature conventional DC, respectively. These observations underline the clinical potential of tolerogenic DC (tolDC) to correct the immunological imbalance in MS. Furthermore, the feasibility to cryopreserve highly potent tolDC will, ultimately, contribute to the large-scale production and the widely applicable use of tolDC.

Inflammation, vitamin D and dendritic cell precursors in chronic kidney disease

Decreased blood dendritic cell precursors (DCP) count is linked with atherosclerotic disease, while reduction of circulating DCP is also seen in patients with chronic kidney disease (CKD). As poor vitamin D status could be linked to a compromised innate immune response, we hypothesized that vitamin D status might be involved in the decrease in circulating DCP in CKD. Moreover, the potential role of inflammation was considered. Circulating myeloid (mDCP), plasmacytoid (pDCP) and total DCP (tDCP) were analysed using flow cytometry in 287 patients with CKD stage 3. Serum 25(OH)D and 1,25(OH)2D levels were measured using enzyme-linked immunosorbent assays (ELISA), interleukin (IL)-6, IL-10 and tumour necrosis factor (TNF)-α using cytometric bead array, C-reactive protein (CRP) using a high-sensitivity (hs) ELISA. Contrary to our hypothesis, there was no association between vitamin D levels and DCP, although their number was decreased significantly in CKD (P < 0·001). Instead, mDCP (r = -0·211) and tDCP (r = -0·188,) were associated slightly negatively with hsCRP but positively with the estimated glomerular filtration rate (eGFR, r = 0·314 for tDCP). According to multivariate linear regression, only higher hsCRP concentration and the presence of diabetes mellitus had a significant negative influence on DCP count (P < 0·03, respectively) but not vitamin D, age and eGFR. A significant impact of vitamin D on the reduction of circulating DCP in CKD 3 patients can be neglected. Instead, inflammation as a common phenomenon in CKD and diabetes mellitus had the main influence on the decrease in DCP. Thus, a potential role for DCP as a sensitive marker of inflammation and cardiovascular risk should be elucidated in future studies.

The immunomodulatory effect of vitamin D in chickens is dose-dependent and influenced by calcium and phosphorus levels

Vitamin D requirement is estimated to be higher than recommended values for the first two weeks of a broiler chicken's life, and is heavily dependent on the concentrations of Ca and P in the diet. There are data indicating the beneficial effect of higher vitamin D levels on performance and overall health of the chickens. However, data on the role of higher vitamin D levels on the innate immune response of chickens are limited. Therefore, in the current study, we examined the effect of higher doses of vitamin D supplementation on the innate immune response in broiler chickens receiving optimal or calcium (Ca) and phosphorus (P) deficient diets. Three hundred Ross-308 male broiler chicks were randomly allocated into 60 cages with 5 birds per cage in a 3 × 2 factorial design with three levels of vitamin D and two levels of Ca/P with each experimental diet fed to 10 cages (10 replicates). Quantitative reverse transcription PCR (n = 5) was used to assess Toll-like receptor (TLR2b and 4), cytokine/chemokine (IL-12, IFN-γ, IL-10, IL-4, IL-13, IL-18, CxCLi2) and cathelicidin (CATH1, CATHB1, CATH3) transcription levels in peripheral blood mononuclear cells (PBMCs), spleen, and bursa of Fabricius. Vitamin D supplementation of the Ca and P deficient diet considerably augmented transcription of TLR2b, TLR4, CATH1, and CATHB1 and predominantly Th2 cytokines in spleen. Supplementation of the control diet with vitamin D downregulated TLR4 transcription, and dose-dependently increased CATH1, CATHB1, Th1, and Th2 cytokine transcription (Th2>Th1). All diets downregulated CATH3 transcription. In conclusion, vitamin D or its derivative 25-OH-D₃ both have a robust immunomodulatory property with a more favorable Th2 response, while at the same time enhancing observed Th2 cytokine responses under both optimal and lower Ca and P inclusion levels in the diets of broiler chickens.

Vitamin D treatment for connective tissue diseases: hope beyond the hype?

The prevalence of vitamin D deficiency is increased among patients with CTDs. The active form of vitamin D (calcitriol) is a potent regulator of the immune system and may suppress inflammatory responses. This has led to claims that vitamin D may be a safe treatment, or a treatment adjunct, to reduce systemic inflammation in this patient population. It is important to note, however, that there is insufficient evidence from robust clinical trials to support these novel uses for vitamin D. In this review we examine the potential role of vitamin D as a treatment adjunct for CTDs. We will discuss how vitamin D may modulate the immune response and review the current evidence for using vitamin D to treat CTDs and their associated co-morbidities. We conclude that while there is much excitement about vitamin D in this context, further well-designed trials are needed to demonstrate its efficacy in the treatment of patients with CTDs.

NF-κB, p38 MAPK, ERK1/2, mTOR, STAT3 and increased glycolysis regulate stability of paricalcitol/dexamethasone-generated tolerogenic dendritic cells in the inflammatory environment

Tolerogenic dendritic cells (tDCs) may offer an intervention therapy in autoimmune diseases or transplantation. Stable immaturity and tolerogenic function of tDCs after encountering inflammatory environment are prerequisite for positive outcome of immunotherapy. However, the signaling pathways regulating their stable tolerogenic properties are largely unknown. In this study, we demonstrated that human monocyte-derived tDCs established by using paricalcitol (analogue of vitamin D2), dexamethasone and monophosphoryl lipid A exposed for 24h to LPS, cytokine cocktail, polyI:C or CD40L preserved reduced expression of co-stimulatory molecules, increased levels of inhibitory molecules ILT-3, PDL-1 and TIM-3, increased TLR-2, increased secretion of IL-10 and TGF-β, reduced IL-12 and TNF-α secretion and reduced T cell stimulatory capacity. tDCs further induced IL-10-producing T regulatory cells that suppressed the proliferation of responder T cells. In the inflammatory environment, tDCs maintained up-regulated indoleamine 2, 3 dioxygenase but abrogated IκB-α phosphorylation and reduced transcriptional activity of p65/RelA, RelB and c-Rel NF-κB subunits except p50. Mechanistically, p38 MAPK, ERK1/2, mTOR, STAT3 and mTOR-dependent glycolysis regulated expression of ILT-3, PDL-1 and CD86, secretion of IL-10 and T cell stimulatory capacity of tDCs in the inflammatory environment. Stability of tDCs in the inflammatory environment is thus regulated by multiple signaling pathways.

Vitamin D in rheumatoid arthritis-towards clinical application

In addition to its well-documented involvement in mineral homeostasis, vitamin D seems to have broad effects on human health that go beyond the skeletal system. Prominent among these so-called nonclassical effects of vitamin D are its immunomodulatory properties. In vitro studies have shown anti-inflammatory effects of 1,25-dihydroxyvitamin D (1,25(OH)2D), the active form of vitamin D. In addition, epidemiological analysis of patients with established inflammatory disease identified associations between vitamin D deficiency (low serum concentrations of inactive 25-hydroxyvitamin D, abbreviated to 25(OH)D) and inflammatory conditions, including rheumatoid arthritis (RA). The association of vitamin D deficiency with RA severity supports the hypothesis of a role for vitamin D in the initiation or progression of the disease, or possibly both. However, whether 25(OH)D status is a cause or consequence of RA is still incompletely understood and requires further analysis in prospective vitamin D supplementation trials. The characterization of factors that promote the transition from preclinical to clinical phases of RA has become a major focus of research, with the aim to facilitate earlier diagnosis and treatment, and improve therapeutic outcomes. In this Review, we aim to describe the current knowledge of vitamin D and the immune system specifically in RA, and discuss the potential benefits that vitamin D might have on slowing RA progression.

Regulation of Dendritic Cell Function by Vitamin D

Studies over the last two decades have revealed profound immunomodulatory aspects of vitamin D on various aspects of the immune system. This review will provide an overview of Vitamin D metabolism, a description of dendritic cell subsets, and highlight recent advances on the effects of vitamin D on dendritic cell function, maturation, cytokine production and antigen presentation. The active form of vitamin D, 1,25(OH)₂D₃, has important immunoregulatory and anti-inflammatory effects. Specifically, the 1,25(OH)₂D₃-Vitamin D₃ complex can affect the maturation and migration of many dendritic cell subsets, conferring a special immunoregulatory role as well as tolerogenic properties affecting cytokine and chemokine production. Furthermore, there have been many recent studies demonstrating the effects of Vitamin D on allergic disease and autoimmunity. A clear understanding of the effects of the various forms of Vitamin D will provide new opportunities to improve human health.

CD38-Expressing Myeloid-Derived Suppressor Cells Promote Tumor Growth in a Murine Model of Esophageal Cancer

Myeloid-derived suppressor cells (MDSC) are an immunosuppressive population of immature myeloid cells found in advanced-stage cancer patients and mouse tumor models. Production of inducible nitric oxide synthase (iNOS) and arginase, as well as other suppressive mechanisms, allows MDSCs to suppress T-cell-mediated tumor clearance and foster tumor progression. Using an unbiased global gene expression approach in conditional p120-catenin knockout mice (L2-cre;p120ctn(f/f)), a model of oral-esophageal cancer, we have identified CD38 as playing a vital role in MDSC biology, previously unknown. CD38 belongs to the ADP-ribosyl cyclase family and possesses both ectoenzyme and receptor functions. It has been described to function in lymphoid and early myeloid cell differentiation, cell activation, and neutrophil chemotaxis. We find that CD38 expression in MDSCs is evident in other mouse tumor models of esophageal carcinogenesis, and CD38(high) MDSCs are more immature than MDSCs lacking CD38 expression, suggesting a potential role for CD38 in the maturation halt found in MDSC populations. CD38(high) MDSCs also possess a greater capacity to suppress activated T cells, and promote tumor growth to a greater degree than CD38(low) MDSCs, likely as a result of increased iNOS production. In addition, we have identified novel tumor-derived factors, specifically IL6, IGFBP3, and CXCL16, which induce CD38 expression by MDSCs ex vivo. Finally, we have detected an expansion of CD38(+) MDSCs in peripheral blood of advanced-stage cancer patients and validated targeting CD38 in vivo as a novel approach to cancer therapy.

Synovial fluid myeloid dendritic cells display important differences compared to monocyte-derived dendritic cells prepared in vitro

The object of this study was to characterise synovial fluid dendritic cells (SFDCs) with regard to morphology, phenotype and responses to 1,25hydroxy-cholecalciferol (1,25D) and lipopolysaccharide (LPS), and to compare these characteristics with those of peripheral blood (PB) monocyte-derived DCs (MDDCs). SF was aspirated from knees with inflammatory effusions. PB samples were obtained contemporaneously. SFDCs were separated by flow cytometry. Morphology was determined on cytosmears. Expression of accessory molecules, cytokines and prostaglandin synthases mRNA was quantified by reverse transcription PCR. Analyses were performed on freshly prepared DCs and after incubation with 1,25D and LPS, separately and in combination. SFDCs and MDDCs displayed broadly similar morphology. Expression of accessory molecules, cytokines, cyclooxygenase-2 (COX-2) and prostaglandin E-synthase (PGES) was similar. SFDCs, but not MDDCs, expressed prostaglandin D-synthase (PGDS). PGDS was lost on incubation with SFDCs, but was induced by 1,25D in MDDCs. LPS in the presence or absence of 1,25D, induced interleukin 23 (IL23), IL1β and tumour necrosis factor-α in SFDCs and MDDCs, with SFDC showing stronger expression of these cytokines. 1,25D in combination with LPS induced PGES and enhanced LPS induction of IL6 in SFDCs and MDDCs. LPS reduced 1,25D-induced expression of PGDS in MDDCs. SFDCs and MDDCs display similar basal characteristics but differ in PGDS expression and responsiveness to LPS and 1,25D. MDDCs have limitations as a model of SFDCs which have differentiated in vivo.

Vitamin D in inflammatory diseases

Changes in vitamin D serum levels have been associated with inflammatory diseases, such as inflammatory bowel disease (IBD), rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis (MS), atherosclerosis, or asthma. Genome- and transcriptome-wide studies indicate that vitamin D signaling modulates many inflammatory responses on several levels. This includes (i) the regulation of the expression of genes which generate pro-inflammatory mediators, such as cyclooxygenases or 5-lipoxygenase, (ii) the interference with transcription factors, such as NF-κB, which regulate the expression of inflammatory genes and (iii) the activation of signaling cascades, such as MAP kinases which mediate inflammatory responses. Vitamin D targets various tissues and cell types, a number of which belong to the immune system, such as monocytes/macrophages, dendritic cells (DCs) as well as B- and T cells, leading to individual responses of each cell type. One hallmark of these specific vitamin D effects is the cell-type specific regulation of genes involved in the regulation of inflammatory processes and the interplay between vitamin D signaling and other signaling cascades involved in inflammation. An important task in the near future will be the elucidation of the regulatory mechanisms that are involved in the regulation of inflammatory responses by vitamin D on the molecular level by the use of techniques such as chromatin immunoprecipitation (ChIP), ChIP-seq, and FAIRE-seq.

Immunoregulatory mechanisms of vitamin D relevant to respiratory health and asthma

Vitamin D deficiency is prevalent among people with various immune-mediated conditions, including autoimmune diseases and asthma. Serum 25(OH)D levels inversely correlate with asthma severity, glucocorticoid responsiveness/dosage, and markers of pathogenesis, such as airway remodeling, IgE, and eosinophilia. Trials involving supplementation with active vitamin D or a precursor are beginning to emerge with variable results that, in part, reflect differences in study design. This review looks at the mechanisms by which vitamin D may protect against asthma, including increasing glucocorticoid responsiveness, skewing immune cells towards a regulatory phenotype, reducing the incidence of infections, airway remodeling, eosinophilia, and lowering the levels of IgE. Also discussed is the therapeutic potential for vitamin D, which is likely to be applicable to immune-mediated conditions beyond simply asthma.

Regulatory dendritic cells for immunotherapy in immunologic diseases

We recognize well the abilities of dendritic cells to activate effector T cell (Teff cell) responses to an array of antigens and think of these cells in this context as pre-eminent antigen-presenting cells, but dendritic cells are also critical to the induction of immunologic tolerance. Herein, we review our knowledge on the different kinds of tolerogenic or regulatory dendritic cells that are present or can be induced in experimental settings and humans, how they operate, and the diseases in which they are effective, from allergic to autoimmune diseases and transplant tolerance. The primary conclusions that arise from these cumulative studies clearly indicate that the agent(s) used to induce the tolerogenic phenotype and the status of the dendritic cell at the time of induction influence not only the phenotype of the dendritic cell, but also that of the regulatory T cell responses that they in turn mobilize. For example, while many, if not most, types of induced regulatory dendritic cells lead CD4⁺ naïve or Teff cells to adopt a CD25⁺Foxp3⁺ Treg phenotype, exposure of Langerhans cells or dermal dendritic cells to vitamin D leads in one case to the downstream induction of CD25⁺Foxp3⁺ regulatory T cell responses, while in the other to Foxp3⁻ type 1 regulatory T cells (Tr1) responses. Similarly, exposure of human immature versus semi-mature dendritic cells to IL-10 leads to distinct regulatory T cell outcomes. Thus, it should be possible to shape our dendritic cell immunotherapy approaches for selective induction of different types of T cell tolerance or to simultaneously induce multiple types of regulatory T cell responses. This may prove to be an important option as we target diseases in different anatomic compartments or with divergent pathologies in the clinic. Finally, we provide an overview of the use and potential use of these cells clinically, highlighting their potential as tools in an array of settings.

Regulation of monocyte differentiation by specific signaling modules and associated transcription factor networks

Monocyte/macrophages are important players in orchestrating the immune response as well as connecting innate and adaptive immunity. Myelopoiesis and monopoiesis are characterized by the interplay between expansion of stem/progenitor cells and progression towards further developed (myelo)monocytic phenotypes. In response to a variety of differentiation-inducing stimuli, various prominent signaling pathways are activated. Subsequently, specific transcription factors are induced, regulating cell proliferation and maturation. This review article focuses on the integration of signaling modules and transcriptional networks involved in the determination of monocytic differentiation.

The role of the intraplaque vitamin d system in atherogenesis

Vitamin D has been shown to play critical activities in several physiological pathways not involving the calcium/phosphorus homeostasis. The ubiquitous distribution of the vitamin D receptor that is expressed in a variety of human and mouse tissues has strongly supported research on these "nonclassical" activities of vitamin D. On the other hand, the recent discovery of the expression also for vitamin D-related enzymes (such as 25-hydroxyvitamin D-1 α -hydroxylase and the catabolic enzyme 1,25-dihydroxyvitamin D-24-hydroxylase) in several tissues suggested that the vitamin D system is more complex than previously shown and it may act within tissues through autocrine and paracrine pathways. This updated model of vitamin D axis within peripheral tissues has been particularly investigated in atherosclerotic pathophysiology. This review aims at updating the role of the local vitamin D within atherosclerotic plaques, providing an overview of both intracellular mechanisms and cell-to-cell interactions. In addition, clinical findings about the potential causal relationship between vitamin D deficiency and atherogenesis will be analysed and discussed.

Vitamin D and systemic lupus erythematosus: an update

Vitamin D is a steroid hormone that, in addition to its actions on calcium and bone metabolism, exhibits a plethora of regulatory effects on growth, proliferation, apoptosis and function of the cells of the immune system that are relevant to the pathophysiology of systemic lupus erythematosus (SLE). Hypovitaminosis D is highly prevalent in SLE as a result of avoidance of sunshine, photoprotection, renal insufficiency and the use of medications such as glucocorticoids, anticonvulsants, antimalarials and the calcineurin inhibitors, which alter the metabolism of vitamin D or downregulate the functions of the vitamin D receptor. Low levels of vitamin D correlate with disease activity, and is associated with osteoporosis, fatigue and certain cardiovascular risk factors in SLE patients. This review updates the recent evidence on the relationship between vitamin D status and the onset, activity and complications of SLE, and summarizes the recommendations for vitamin D supplementation.

Toll-like receptors: sensing and reacting to diabetic injury in the kidney

Accumulating evidence indicates that immunologic and inflammatory elements play an important role in initiating and orchestrating the development of diabetic nephropathy (DN), but until recently, the identity of specific innate immune pattern recognition receptors or sensors that recognize diverse diabetic 'danger signals' to trigger the proinflammatory cascade during DN remains unknown. Toll-like receptors (TLRs) are an emerging family of receptors that recognize pathogen-associated molecular patterns as well as damage-associated molecular patterns to promote the activation of leukocytes and intrinsic renal cells in non-immune kidney disease. Recent data from in vitro and in vivo studies have highlighted the critical role of TLRs, mainly TLR2 and TLR4, in the pathogenesis of DN. This review focuses on emerging findings elucidating how TLR signaling could sense and react to the metabolic stress and endogenous ligands activated by the diabetic state, thereby initiating and perpetuating renal inflammation and fibrogenesis in diabetic kidney disease. Novel strategies potentially targeting TLR signaling that could have therapeutic implications in DN are also discussed.

A short protocol using dexamethasone and monophosphoryl lipid A generates tolerogenic dendritic cells that display a potent migratory capacity to lymphoid chemokines

Background

Generation of tolerogenic dendritic cells (TolDCs) for therapy is challenging due to its implications for the design of protocols suitable for clinical applications, which means not only using safe products, but also working at defining specific biomarkers for TolDCs identification, developing shorter DCs differentiation methods and obtaining TolDCs with a stable phenotype. We describe here, a short-term protocol for TolDCs generation, which are characterized in terms of phenotypic markers, cytokines secretion profile, CD4+ T cell-stimulatory ability and migratory capacity.

Methods

TolDCs from healthy donors were generated by modulation with dexamethasone plus monophosphoryl lipid A (MPLA-tDCs). We performed an analysis of MPLA-tDCs in terms of yield, viability, morphology, phenotypic markers, cytokines secretion profile, stability, allogeneic and antigen-specific CD4+ T-cell stimulatory ability and migration capacity.

Results

After a 5-day culture, MPLA-tDCs displayed reduced expression of costimulatory and maturation molecules together to an anti-inflammatory cytokines secretion profile, being able to maintain these tolerogenic features even after the engagement of CD40 by its cognate ligand. In addition, MPLA-tDCs exhibited reduced capabilities to stimulate allogeneic and antigen-specific CD4+ T cell proliferation, and induced an anti-inflammatory cytokine secretion pattern. Among potential tolerogenic markers studied, only TLR-2 was highly expressed in MPLA-tDCs when compared to mature and immature DCs. Remarkable, like mature DCs, MPLA-tDCs displayed a high CCR7 and CXCR4 expression, both chemokine receptors involved in migration to secondary lymphoid organs, and even more, in an in vitro assay they exhibited a high migration response towards CCL19 and CXCL12.

Conclusion

We describe a short-term protocol for TolDC generation, which confers them a stable phenotype and migratory capacity to lymphoid chemokines, essential features for TolDCs to be used as therapeutics for autoimmunity and prevention of graft rejection.

Nuclear receptor expression patterns in murine plasmacytoid and conventional dendritic cells

Dendritic cells (DC) play a central role in the immune system. They can either induce immunity or promote tolerance. The DC family is generally comprised of two functionally distinct DC subsets. Conventional dendritic cells (cDC) are the classical antigen presenting cells; plasmacytoid dendritic cells (pDC) are the main producers of type I interferons thereby serving innate immunity. Upon activation DCs are able to present antigen and stimulate T cells. The immune modulatory functions of DCs largely depend on the recognition of soluble cues. Besides pathogen derived cues, recent data indicate that the tissue micro-environment, i.e. of the gut and skin affects cDC function. Many of these micro-environmental factors are ligands for the nuclear receptor (NR) family of transcription regulators known to affect immunity and tolerance. Whether pDC function is also influenced by tissue derived cues, like hormones, vitamins and metabolic products, is largely unknown. Here, we investigated the NR expression profile of murine pDCs and cDCs. We assessed the mRNA levels of 19 NRs of in vitro derived as well as ex vivo isolated DCs from four different lymphoid tissues. We observed that cDCs and pDCs expressed the same repertoire of NRs. Expression levels, however, differed between the two subsets, especially upon maturation of DCs. These data imply that NR ligands do impact pDC function and that their activity might be regulated in a DC-specific manner.

Synergy between vitamin D(3) and Toll-like receptor agonists regulates human dendritic cell response during maturation

Human dendritic cells (DC) can be differentiated from blood monocytes in the presence of GM-CSF and IL-4 and matured by lipopolysaccharide (LPS). Vitamin D₃ inhibits the maturation of human DC measured by changes in surface expression of HLA-DR, CD14, CD40, CD80, CD83, and CD86. We here examine the function of vitamin D₃ during DC maturation. One of the earliest changes to LPS-induced maturation was an increase in CD83 expression. Vitamin D₃ inhibited the increase in expression of HLA-DR, CD40, CD80, CD83, and CD86 and the decrease in expression of CD14, which was paralleled morphologically by vitamin D₃-induced inhibition of dendritic cell differentiation. Vitamin D₃ acted in synergy with the TLR agonists LPS and peptidoglycan (PGN) in inducing IL-6, IL-8, and IL-10, whereas vitamin D₃ completely inhibited LPS-induced secretion of IL-12. The synergy occurred at concentrations where neither vitamin D₃ nor the TLR agonists alone induced measurable cytokine secretion. Both LPS and PGN enhanced the level of the vitamin D₃ receptor (VDR). Taken together, these data demonstrated that vitamin D₃ and TLR agonists acted in synergy to alter secretion of cytokines from human DC in a direction that may provide an anti-inflammatory environment.

The influence of selective vitamin D receptor activator paricalcitol on cardiovascular system and cardiorenal protection

The ubiquitous distribution of vitamin D receptors in the human body is responsible for the pleiotropic effects of vitamin D-receptor activation. We discuss the possible beneficial effects of a selective activator of vitamin D receptor, paricalcitol, on the cardiovascular system in chronic heart failure patients and chronic kidney patients, in light of new trials. Paricalcitol should provide additional clinical benefits over the standard treatment for chronic kidney and heart failure, especially in cases of cardiorenal syndrome.

Immuno-modulatory effects of vitamin D3 in human monocyte and macrophages

Vitamin D3 [1α,25-(OH)(2)D(3)], involved in the regulation of body calcium homeostasis, promotes immature myeloid precursor cells differentiation into monocytes/macrophages. In this study we compared the regulatory interaction between 1α,25-(OH)(2)D(3) and tumor necrosis factor (TNF)-α or lipopolysaccharide (LPS) in the mRNA expression of interleukin (IL)-1β, (IL)-6, TNF-α, toll like receptors (TLR)-2 and (TLR)-4 in freshly isolated human monocyte (MonoT0) and in macrophages cultured for seven days (MØT7). Additionally, we detected the effect of 1α,25-(OH)(2)D(3) on macrophages chemotaxis. The expression of IL-1β, IL-6 and TNF-α, as well as TLR-2 and TLR-4 in MonoT0 and in MØT7 was examined by real time RT-PCR. Macrophages chemotaxis was analyzed by using horizontal chemotaxis agarose spot assay. We found that 1α,25-(OH)(2)D(3) influences macrophages chemotaxis and differently modulates the expression of IL-1β, IL-6, TNF-α and TLRs in the two different stages of monocytes/macrophage maturation. In conclusion our data add new information about the role of 1α,25-(OH)(2)D(3) on the expression of inflammatory mediators in human monocyte/macrophages, underlying the complex function of these cells. Investigating the differences in the pattern of expression of immune-mediators produced by MonoT0 and MØT7 may provide a new way to examine their biochemical and molecular function and may constitute a model system with well-defined behavior with respect to early or tardive events in the innate immune response.