The transcriptional regulator BCL6 participates in the secondary gene regulatory response to vitamin D

Genomic signaling of vitamin D

It took several hundred million years of evolution, in order to develop the endocrine vitamin D signaling system, which is formed by a nuclear receptor, the transcription factor VDR (vitamin D receptor), its ligand, the vitamin D3 metabolite 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) and several metabolizing enzymes and transport proteins. Even within the nuclear receptor superfamily the affinity of VDR for 1,25(OH)2D3 is outstandingly high (KD = 0.1 nM). The activation of VDR by 1,25(OH)2D3 is the core mechanism of genomic signaling of vitamin D3, which results in the modulation of the epigenome at thousands of promoter and enhancer regions as well as finally in the activation or repression of hundreds of target gene transcription. In addition, rapid non-genomic actions of vitamin D are described, which are mechanistically far less understood. The main function of vitamin D is to keep the human body in homeostasis. This implies the control of calcium levels, which is essential for bone mineralization, as well as for pushing of innate immunity to react sufficiently strong to microbe infection and preventing overreactions of adaptive immunity, i.e., not to cause autoimmune diseases. This review will discuss whether genomic signaling is sufficient for explaining all physiological functions of vitamin D3.

Circulating vitamin D levels and colorectal cancer risk: A meta-analysis and systematic review of case-control and prospective cohort studies

The associations between circulating vitamin D concentrations and total and site-specific colorectal cancer (CRC) incidence have been examined in several epidemiological studies with overall inconclusive findings. The aim of this systematic review and meta-analysis of both case-control and prospective cohort studies was to evaluate the association between CRC and circulating levels of vitamin D. The main exposure and outcome were circulating total 25(OH)D and CRC, respectively, in the overall population (i.e., all subjects). Two reviewers, working independently, screened all the literature available to identify studies that met the inclusion criteria (e.g., case-control or prospective cohort studies, published in English, and excluding non-original papers). Data were pooled by the generic inverse variance method using a random or fixed effect model, as approriate. Heterogeneity was identified using the Cochran's Q-test and quantified by the I² statistic. Results were stratified by study design, sex, and metabolite of vitamin D. Sensitivity and subgroup analyses were also performed. A total of 28 original studies were included for the quantitative meta-analysis. Meta-analyses comparing the highest vs lowest categories, showed a 39% lower risk between levels of total 25(OH)D and CRC risk (OR (95% CI): 0.61 (0.52; 0.71); 11 studies) in case-control studies; whereas a 20% reduced CRC risk in prospective cohort studies (HR (95% CI): 0.80 (0.66; 0.97); 6 studies). Results in women mirrored main results, whereas results in men were non-significant in both analyses. Our findings support an inverse association between circulating vitamin D levels and CRC risk.

Vitamin D and Its Target Genes

The vitamin D metabolite 1α,25-dihydroxyvitamin D₃ is the natural, high-affinity ligand of the transcription factor vitamin D receptor (VDR). In many tissues and cell types, VDR binds in a ligand-dependent fashion to thousands of genomic loci and modulates, via local chromatin changes, the expression of hundreds of primary target genes. Thus, the epigenome and transcriptome of VDR-expressing cells is directly affected by vitamin D. Vitamin D target genes encode for proteins with a large variety of physiological functions, ranging from the control of calcium homeostasis, innate and adaptive immunity, to cellular differentiation. This review will discuss VDR’s binding to genomic DNA, as well as its genome-wide locations and interaction with partner proteins, in the context of chromatin. This information will be integrated into a model of vitamin D signaling, explaining the regulation of vitamin D target genes.

MED12 is overexpressed in glioblastoma patients and serves as an oncogene by targeting the VDR/BCL6/p53 axis

Glioblastoma is the most life-threatening tumor of the central nervous system. Despite recent therapeutic advancements, maximum survival of glioblastoma patients remains dismal. The mediator complex is a set of proteins, essential for eukaryotic gene expression. Abnormal expression/mutations of specific mediator genes have been associated with progression of various cancers, however, its role and status in glioblastoma remains largely unknown. Our work shows overexpression of a subunit of kinase assembly of mediator complex, MED12, in various glioblastoma patient cohorts including Indian glioblastoma patients and cell lines. Functional characterization of MED12 using both overexpression and knockdown approach revealed that it promotes glioblastoma cell proliferation, migration and inhibits apoptosis. Transcriptome analysis post MED12 knockdown revealed Vitamin D receptor (VDR) pathway to be one of the key pathways affected by MED12 in glioblastoma. We studied direct interaction of MED12 with VDR protein using docking studies and co-immunoprecipitation assay. We identify BCL6, a secondary regulator of VDR signaling, to be directly regulated by MED12 through a combination of chromatin immunoprecipitation, qRT-PCR and western analyses. We further show that MED12 brings about the inhibition of p53 levels and apoptosis partly through induction of BCL6 in glioblastoma. Overall, this stands as the first report of MED12 over-expression and involvement in glioblastoma pathogenesis and identifies MED12 as an important mediator of VDR signaling and an attractive molecule for development of new therapeutic interventions.

Vitamin d and leishmaniasis: Neither seasonal nor risk factor in canine host but potential adjuvant treatment through cbd103 expression

Vitamin D (VitD) deficiency has been shown to be a risk factor for a plethora of disorders. We have shown that dogs with clinical leishmaniasis presented lower VitD serum levels than non-infected dogs, and even lower than those with asymptomatic infection. However, if VitD deficiency is a risk factor to develop clinical leishmaniasis remains to be answered. It is also unknown if VitD participates in Leishmania control. First, we retrospectively analysed VitD concentration in serum samples from 36 healthy dogs collected in different periods of the year concluding that there isn't a seasonal variation of this vitamin in dogs. We also included 9 dogs with clinical leishmaniasis and 10 non-infected healthy dogs, in which we measured VitD levels at the beginning of the study, when all dogs were negative for serology and qPCR, and 1 year later. Whereas non-infected dogs showed no change in VitD levels along the study, those developing clinical leishmaniasis showed a significant VitD reduction at the end of the study (35%). When we compared VitD concentration between the two groups at the beginning of the study, no differences were detected (43.6 (38-59) ng/mL, P = 0.962). Furthermore, an in vitro model using a canine macrophage cell line proved that adding active VitD leads to a significant reduction in L. infantum load (31.4%). Analyzing expression of genes related to VitD pathway on primary canine monocytes, we showed that CBD103 expression was significantly enhanced after 1,25(OH)2D addition. Our results show that VitD concentration is neither seasonal nor a risk factor for developing canine leishmaniasis, but it diminishes with the onset of clinical disease suggesting a role in parasitic control. Our in vitro results corroborate this hypothesis and point out that VitD regulates infection through CBD103 expression. These results open the possibility for studies testing VitD as an adjuvant in leishmaniasis therapy.

An Epigenetic Signature is Associated with Serum 25-Hydroxyvitamin D in Colorectal Cancer Tumors

INTRODUCTION

Vitamin D has been widely associated with colorectal cancer (CRC) through different insights. This study aims to explore the association between serum 25-hydroxyvitamin D (25(OH)D) and the global DNA methylation in tumor from CRC patients.

METHODS AND RESULTS

A genome-wide DNA methylation analysis is conducted in 20 CRC patients under categorical (10 patients have 25(OH)D <30 ng mL^-1 ; 10 patients with 25(OH)D ≥30 ng mL^-1 ) and continuous models of 25(OH)D. A total of 95 differentially methylated CpGs (DMCpGs) are detected under the categorical model (false discovery rate (FDR) < 0.05), while 16 DMCpGs are found under the continuous model. Regional analysis showed eight vitamin D-associated differentially methylated regions (DMR). Between them, a DMR is the most significant at cAMP-Dependent Protein Kinase Inhibitor Alpha (PKIA) locus. Furthermore, seven genes, including PKIA gene, have more or equal than two significant DMCpGs. The protein networking analysis found pathways implicated in cell adhesion and extracellular matrix, as well as signaling transduction.

CONCLUSIONS

This study identifies novel epigenetic loci associated with serum 25(OH)D status. Interestingly, also, a positive association between vitamin D and DNA methylation in the CRC context is found, suggesting a role in CRC. Further studies are warranted to clarify and replicate these results.

Gene expression during THP-1 differentiation is influenced by vitamin D3 and not vibrational mechanostimulation

Background

In injury or infection, monocytes migrate into the affected tissues from circulation and differentiate into macrophages which are subsequently involved in the inflammatory responses. Macrophage differentiation and activation have been studied in response to multiple chemokines and cytokines. However, mechanical, and physical stimuli can also influence macrophage differentiation, activation, cytokine production, and phagocytic activity.

Methods

In this study the macrophage differentiation from THP-1 monocytes was assessed upon the stimulation with 1,25-dihydroxyvitamin D3 and 1,000 Hz vibrations, using qPCR for quantification of transcript expression. Vitamin D binds the vitamin D receptor (VDR) and subsequently modulates the expression of a variety of genes in monocytes. The effects of the 1,000 Hz vibrational stimulation, and the combined treatment of vitamin D3 and 1000 Hz vibrations were unknown. The differentiation of macrophages was assessed by looking at transcription of macrophage markers (e.g., CD14, CD36), antigen presenting molecules (e.g., HLA-DRA), transcription factors (e.g., LEF-1, TCF7L2), and mechanosensors (e.g., PIEZO1 and PKD2).

Results

The results showed that vitamin D3 induced THP-1 macrophage differentiation, which was characterized by upregulation of CD14 and CD36, downregulation of HLA-DRA, upregulation of the PKD2 (TRPP2), and an inverse relationship between TCF7L2 and LEF-1, which were upregulated and downregulated respectively. The 1,000 Hz vibrations were sensed from the cells which upregulated PIEZO1 and TCF3, but they did not induce expression of genes that would indicate macrophage differentiation. The mRNA transcription profile in the cells stimulated with the combined treatment was comparable to that of the cells stimulated by the vitamin only. The 1,000 Hz vibrations slightly weakened the effect of the vitamin for the regulation of CD36 and HLA-DMB in the suspension cells, but without causing changes in the regulation patterns. The only exception was the upregulation of TCF3 in the suspension cells, which was influenced by the vibrations. In the adherent cells, the vitamin D3 cancelled the upregulating effect of the 1,000 Hz vibrations and downregulated TCF3. The vitamin also cancelled the upregulation of PIEZO1 gene by the 1,000 Hz vibrations in the combined treatment.

Conclusion

The mechanical stimulation with 1,000 Hz vibrations resulted in upregulation of PIEZO1 in THP-1 cells, but it did not affect the differentiation process which was investigated in this study. Vitamin D3 induced THP-1 macrophage differentiation and could potentially influence M2 polarization as observed by upregulation of CD36 and downregulation of HLA-DRA. In addition, in THP-1 cells undergoing the combined stimulation, the gene expression patterns were influenced by vitamin D3, which also ablated the effect of the mechanical stimulus on PIEZO1 upregulation.

A hierarchical regulatory network analysis of the vitamin D induced transcriptome reveals novel regulators and complete VDR dependency in monocytes

The transcription factor vitamin D receptor (VDR) is the high affinity nuclear target of the biologically active form of vitamin D₃ (1,25(OH)₂D₃). In order to identify pure genomic transcriptional effects of 1,25(OH)₂D₃, we used VDR cistrome, transcriptome and open chromatin data, obtained from the human monocytic cell line THP-1, for a novel hierarchical analysis applying three bioinformatics approaches. We predicted 75.6% of all early 1,25(OH)₂D₃-responding (2.5 or 4 h) and 57.4% of the late differentially expressed genes (24 h) to be primary VDR target genes. VDR knockout led to a complete loss of 1,25(OH)₂D₃–induced genome-wide gene regulation. Thus, there was no indication of any VDR-independent non-genomic actions of 1,25(OH)₂D₃ modulating its transcriptional response. Among the predicted primary VDR target genes, 47 were coding for transcription factors and thus may mediate secondary 1,25(OH)₂D₃ responses. CEBPA and ETS1 ChIP-seq data and RNA-seq following CEBPA knockdown were used to validate the predicted regulation of secondary vitamin D target genes by both transcription factors. In conclusion, a directional network containing 47 partly novel primary VDR target transcription factors describes secondary responses in a highly complex vitamin D signaling cascade. The central transcription factor VDR is indispensable for all transcriptome-wide effects of the nuclear hormone.

Common and personal target genes of the micronutrient vitamin D in primary immune cells from human peripheral blood

Vitamin D is essential for the function of the immune system. In this study, we treated peripheral blood mononuclear cells (PBMCs) of healthy adults with the biologically active form of vitamin D₃, 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) using two different approaches: single repeats with PBMCs obtained from a cohort of 12 individuals and personalized analysis based on triplicates of five study participants. This identified 877 (cohort approach) and 3951 (personalized approach) genes that significantly (p < 0.05) changed their expression 24 h after 1,25(OH)₂D₃ stimulation. From these, 333 and 1232 were classified as supertargets, a third of which were identified as novel. Individuals differed largely in their vitamin D response not only by the magnitude of expression change but also by their personal selection of (super)target genes. Functional analysis of the target genes suggested the overarching role of vitamin D in the regulation of metabolism, proliferation and differentiation, but in particular in the control of functions mediated by the innate and adaptive immune system, such as responses to infectious diseases and chronic inflammatory disorders. In conclusion, immune cells are an important target of vitamin D and common genes may serve as biomarkers for personal responses to the micronutrient.

Immunoregulatory effects and therapeutic potential of vitamin D in multiple sclerosis

Initially recognised as an important factor for bone health, vitamin D is now known to have a range of effects on the immune system. Vitamin D deficiency is associated with an increased risk of multiple sclerosis (MS), a chronic immune-mediated demyelinating disease of the CNS. In this review, we explore the links between vitamin D deficiency, MS risk, and disease activity. We also discuss the known immune effects of vitamin D supplementation and the relevance of these observations to the immunopathology of MS. Finally, we review the existing evidence for vitamin D supplementation as an MS therapy, highlighting several recent clinical studies and trials.

Vitamin D-modulated dendritic cells delay lethal graft-versus-host disease through induction of regulatory T cells

Graft-versus-host disease (GVHD) is the most lethal complication after allogeneic bone marrow transplantation (allo-BMT). Current approaches to prevent GVHD rely on donor lymphocyte/T cell depletion or general immunosuppression, leading to opportunistic infections and cancer relapse. Tolerogenic dendritic cells can induce regulatory T cells (Tregs) with the ability to suppress inflammation and prevent transplant rejection, making them an attractive cellular therapy to control GVHD. Active vitamin D (1α,25-dihydroxyvitamin D₃; 1α,25(OH)₂D₃) promotes the generation of tolerogenic dendritic cells (1,25D₃-DCs). This study aimed to determine the ability of ex vivo generated 1,25D₃-DCs to trigger the expansion of Tregs that are able to control lethal xenogeneic GVHD in humanized NOD/LtSz-Prkdc^scidIL2rγ^tm1Wjl (NSG) mice. We demonstrate that 1,25D₃-DCs express lower levels of HLA-DR and costimulatory molecules, such as CD80 and CD86, and produce higher levels of IL-10 and TNF-α and lower amounts of IL-12, compared to vehicle-treated DCs. Moreover, these cells express increased levels of various co-inhibitory molecules such as PD-L1 and ILT-3 and the glycoprotein CD52 that is known to suppress T cell activation. Consequently, 1,25D₃-DCs are poor stimulators of alloantigen-primed T cells, but foster the generation of antigen-specific suppressive Tregs. When adoptively transferred in humanized NSG mice, these 1,25D₃-DC-induced Tregs delayed GVHD caused by the co-transferred autologous human peripheral blood mononuclear cells (PBMCs). These results indicate that 1,25D₃-DC-induced Tregs can inhibit xenogeneic GVHD and maintain their immunomodulatory function under conditions of inflammation.

Primary Vitamin D Target Genes of Human Monocytes

The molecular basis of vitamin D signaling implies that the metabolite 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) of the secosteroid vitamin D₃ activates the transcription factor vitamin D receptor (VDR), which in turn modulates the expression of hundreds of primary vitamin D target genes. Since the evolutionary role of nuclear receptors, such as VDR, was the regulation of cellular metabolism, the control of calcium metabolism became the primary function of vitamin D and its receptor. Moreover, the nearly ubiquitous expression of VDR enabled vitamin D to acquire additional physiological functions, such as the support of the innate immune system in its defense against microbes. Monocytes and their differentiated phenotypes, macrophages and dendritic cells, are key cell types of the innate immune system. Vitamin D signaling was most comprehensively investigated in THP-1 cells, which are an established model of human monocytes. This includes the 1,25(OH)₂D₃-modulated cistromes of VDR, the pioneer transcription factors PU.1 and CEBPA and the chromatin modifier CTCF as well as of the histone markers of promoter and enhancer regions, H3K4me3 and H3K27ac, respectively. These epigenome-wide datasets led to the development of our chromatin model of vitamin D signaling. This review discusses the mechanistic basis of 189 primary vitamin D target genes identified by transcriptome-wide analysis of 1,25(OH)₂D₃-stimulated THP-1 cells and relates the epigenomic basis of four different regulatory scenarios to the physiological functions of the respective genes.

Pathway analysis of transcriptomic data shows immunometabolic effects of vitamin D

Unbiased genomic screening analyses have highlighted novel immunomodulatory properties of the active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)₂D). However, clearer interpretation of the resulting gene expression data is limited by cell model specificity. The aim of the current study was to provide a broader perspective on common gene regulatory pathways associated with innate immune responses to 1,25(OH)₂D, through systematic re-interrogation of existing gene expression databases from multiple related monocyte models (the THP-1 monocytic cell line (THP-1), monocyte-derived dendritic cells (DCs) and monocytes). Vitamin D receptor (VDR) expression is common to multiple immune cell types, and thus, pathway analysis of gene expression using data from multiple related models provides an inclusive perspective on the immunomodulatory impact of vitamin D. A bioinformatic workflow incorporating pathway analysis using PathVisio and WikiPathways was utilized to compare each set of gene expression data based on pathway-level context. Using this strategy, pathways related to the TCA cycle, oxidative phosphorylation and ATP synthesis and metabolism were shown to be significantly regulated by 1,25(OH)₂D in each of the repository models (Z-scores 3.52-8.22). Common regulation by 1,25(OH)₂D was also observed for pathways associated with apoptosis and the regulation of apoptosis (Z-scores 2.49-3.81). In contrast to the primary culture DC and monocyte models, the THP-1 myelomonocytic cell line showed strong regulation of pathways associated with cell proliferation and DNA replication (Z-scores 6.1-12.6). In short, data presented here support a fundamental role for active 1,25(OH)₂D as a pivotal regulator of immunometabolism.

Molecular endocrinology of vitamin D on the epigenome level

The molecular endocrinology of vitamin D is based on the facts that i) its metabolite 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) is the high affinity ligand of the nuclear receptor vitamin D receptor (VDR) and ii) the transcription factor VDR is the unique target of 1,25(OH)₂D₃ in the nucleus. Short-term alterations of the epigenome are primarily changes in the post-translational modification status of nucleosome-forming histone proteins, the consequences of which are i) a local increase or decrease in chromatin accessibility and ii) the activation or repression of gene transcription. Vitamin D has via VDR a direct effect on the expression of several hundred primary target genes implying numerous effects on the epigenome. Next-generation sequencing methods, such as ChIP-seq and FAIRE-seq, were applied to cellular model systems of vitamin D signaling, such as THP-1 human monocytes, and provided data for a chromatin model of vitamin D signaling. Key points of this model are that i) in the absence of ligand VDR binds to a limited number of loci within accessible chromatin, ii) a stimulation with ligand increases the number of DNA-bound VDR molecules, iii) VDR's access to genomic DNA is supported by pioneer factors, such as PU.1 in monocytes, iv) VDR binding leads to local opening of chromatin and v) the binding strength of topologically associating domain anchor forming CCCTC-binding factor sites upstream and downstream of prominent VDR binding sites is changing in response to ligand stimulation. This model provides the present basis of the molecular endocrinology of vitamin D and will be in future refined by the integration of vitamin D-sensitive chromatin markers and other genome-wide data, such as the 1,25(OH)₂D₃-sensitive binding of co-factors, chromatin modifying enzymes and chromatin remodeling proteins.

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.

The vitamin D-dependent transcriptome of human monocytes

Monocytes are important cells of the innate immune system that can differentiate into macrophages and dendritic cells. The biologically active form of vitamin D, 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), serves as a ligand of the nuclear receptor vitamin D receptor (VDR). A key physiological function of 1,25(OH)₂D₃ is the defense against pathogens, such as those causing tuberculosis, that involves the modulation of the monocyte transcriptome. THP-1 cells are an established model of human monocytes, for which the at present largest set of 1,25(OH)₂D₃-affected genome-wide data are available. Here we summarize the insight obtained from the recent transcriptome of 1,25(OH)₂D₃-stimulated THP-1 cells, that was determined by triplicate RNA sequencing (RNA-seq). Primary and secondary vitamin D target genes being up- and down-regulated were related to changes in the epigenome of THP-1 cells, such as 1,25(OH)₂D₃-dependent chromatin opening and modulation of the genome-wide association of the transcription factors VDR and CCCTC-binding factor (CTCF) with their respective genomic binding sites. The anti-microbial response is the top-ranking early physiological function represented by 1,25(OH)₂D₃-stimulated genomic regions and genes, but also other immunity-related pathways, such as IL10 signaling, are activated. Taken together, the epigenomic and transcriptomic responses of THP-1 cells to 1,25(OH)₂D₃ represent a master example of the impact of vitamin D on human physiology.

1,25-Dihydroxyvitamin-D3 Induces Avian β-Defensin Gene Expression in Chickens

Host defense peptides (HDPs) play a critical role in innate immunity. Specific modulation of endogenous HDP synthesis by dietary compounds has been regarded as a novel approach to boost immunity and disease resistance in animal production. 1,25-dihydroxy vitamin D3 (1,25D3) is well known as a powerful HDP inducer in humans, but limited information about the effect of 1,25D3 on HDPs in poultry is available. Here, we sought to examine whether 1,25D3 could stimulate avian β-defensin (AvBD) expression in chickens. We used chicken embryo intestinal epithelial cells (CEIEPCs) and peripheral blood mononuclear cells (PBMCs) to study the effect of 1,25D3 on the expression of AvBDs. We observed that 1,25D3 is able to up-regulate the expression of several AvBDs in CEIEPCs and PBMCs, whereas it increased the amounts of AvBD4 mRNA in CEIEPCs only in the presence of lipopolysaccharide (LPS). On the other hand, LPS treatment not only inhibited the expression of CYP24A1 but also altered the expression pattern of VDR in CEIEPCs. Furthermore, AvBDs were not directly regulated by 1,25D3, as cycloheximide completely blocked 1,25D3-induced expression of AvBDs. Our observations suggest that 1,25D3 is capable of inducing AvBD gene expression and is a potential antibiotic alternative through augmentation of host innate immunity as well as disease control in chickens.

Vitamin D Control of Hematopoietic Cell Differentiation and Leukemia

It is now well known that in the mammalian body vitamin D is converted by successive hydroxylations to 1,25-dihydroxyvitamin D (1,25D), a steroid-like hormone with pleiotropic properties. These include important contributions to the control of cell proliferation, survival and differentiation, as well as the regulation of immune responses in disease. Here, we present recent advances in current understanding of the role of 1,25D in myelopoiesis and lymphopoiesis, and the potential of 1,25D and analogs (vitamin D derivatives; VDDs) for the control of hematopoietic malignancies. The reasons for the unimpressive results of most clinical studies of the therapeutic effects of VDDs in leukemia and related diseases may include the lack of a precise rationale for the conduct of these studies. Further, clinical trials to date have generally used extremely heterogeneous patient populations and, in many cases, small numbers of patients, generally without controls. Although low calcemic VDDs have been used and combined with agents that can increase the leukemia cell killing or differentiation effects in acute leukemias, the sequencing of agents used for combination therapy should to be more clearly delineated. Most importantly, it is recommended that in future clinical trials the rationale for the basis of the enhancing action of drug combinations should be clearly articulated and the effects on anticancer immunity should also be evaluated.

Multiple β-defensin genes are upregulated by the vitamin D pathway in cattle

Experimental models of bacterial and viral infections in cattle have suggested vitamin D has a role in innate immunity of cattle. The intracrine vitamin D pathway of bovine macrophages, however, has only been shown to activate a nitric oxide-mediated defense mechanism, as opposed to cathelicidin and β-defensin antimicrobial peptides in human macrophages. In this study we have investigated the actions of 1,25-dihydroxyvitamin D3 (1,25D) on a cluster of eleven bovine β-defensin genes on the basis of RNAseq data indicating they were targets of 1,25D in cattle. Treatment of bovine monocyte cultures with 1,25D (10 nM, 18 h) in the absence and presence of LPS stimulation increased the expression of bovine β-defensin 3 (BNBD3), BNBD4, BNBD6, BNBD7, and BNBD10 genes 5 to 10-fold compared to control (P<0.05). Treatment of lipopolysaccharide (LPS)-stimulated monocytes with 0-100 ng/mL 25-hydroxyvitamin D3 also increased BNBD3, BNBD4, BNBD7, and BNBD10 in a dose-dependent manner. Treatment of monocytes with the protein translation inhibitor, cycloheximide, however, blocked upregulation of the β-defensins in response to 1,25D suggesting the β-defensins in cattle are not direct targets of the vitamin D receptor. Furthermore, preliminary investigation of vitamin D's contribution to β-defensin expression in vivo revealed that intramammary 1,25D treatment of lactating cows increased BNBD7 expression in mammary macrophages. In conclusion, our data demonstrate that multiple β-defensin genes are upregulated by 1,25D in cattle, providing further indication that vitamin D contributes to bovine innate immunity.

Relevance of vitamin D receptor target genes for monitoring the vitamin D responsiveness of primary human cells

Vitamin D₃ has transcriptome- and genome-wide effects and activates, via the binding of its metabolite 1α,25-dihydroxyvitamin D₃ to the transcription factor vitamin D receptor (VDR), several hundred target genes. Using samples from a 5-month vitamin D₃ intervention study (VitDmet), we recently reported that the expression of 12 VDR target genes in peripheral blood mononuclear cells (PBMCs) as well as 12 biochemical and clinical parameters of the study participants are significantly triggered by vitamin D₃. In this study, we performed a more focused selection of further 12 VDR target genes and demonstrated that changes of their mRNA expression in PBMCs of VitDmet subjects significantly correlate with alterations of 25-hydroxyvitamin D3 serum levels. Network and self-organizing map analysis of these datasets together with that of the other 24 parameters was followed by relevance calculations and identified changes in parathyroid hormone serum levels and the expression of the newly selected genes STS, BCL6, ITGAM, LRRC25, LPGAT1 and TREM1 as well as of the previously reported genes DUSP10 and CD14 as the most relevant parameters for describing vitamin D responsiveness in vivo. Moreover, parameter relevance ranking allowed the segregation of study subjects into high and low responders. Due to the long intervention period the vitamin D response was not too prominent on the level of transcriptional activation. Therefore, we performed in the separate VitDbol trial a short-term but high dose stimulation with a vitamin D3 bolus. In PBMCs of VitDbol subjects we observed direct transcriptional effects on the selected VDR target genes, such as an up to 2.1-fold increase already one day after supplementation onset. In conclusion, both long-term and short-term vitamin D₃ supplementation studies allow monitoring the vitamin D responsiveness of human individuals and represent new types of human in vivo vitamin D₃ investigations.