Vitamin D and hematopoiesis

NAD Modulates DNA Methylation and Cell Differentiation

Nutritional intake impacts the human epigenome by directing epigenetic pathways in normal cell development via as yet unknown molecular mechanisms. Consequently, imbalance in the nutritional intake is able to dysregulate the epigenetic profile and drive cells towards malignant transformation. Here we present a novel epigenetic effect of the essential nutrient, NAD. We demonstrate that impairment of DNMT1 enzymatic activity by NAD-promoted ADP-ribosylation leads to demethylation and transcriptional activation of the CEBPA gene, suggesting the existence of an unknown NAD-controlled region within the locus. In addition to the molecular events, NAD- treated cells exhibit significant morphological and phenotypical changes that correspond to myeloid differentiation. Collectively, these results delineate a novel role for NAD in cell differentiation, and indicate novel nutri-epigenetic strategies to regulate and control gene expression in human cells.

Reduced survival after autologous stem cell transplantation in myeloma and lymphoma patients with low vitamin D serum levels

High-dose chemotherapy (HDCT) with autologous stem cell transplantation (ASCT) is applied for consolidation in myeloma and relapsing lymphoma patients. Vitamin D (VitD) exerts effects during hematopoietic stem cell proliferation, differentiation and interactions with the immune system. VitD deficiency is frequent in patients with hematological malignancies, but its prognostic relevance after ASCT remains unclear. We investigated the effect of VitD serum levels in patients with lymphomas and myeloma at ASCT on progression-free (PFS) and overall survival (OS). The cohort (n = 183) was divided into two groups: 81 (44%) had VitD levels >52 nmol/L and 102 (56%) ≤52 nmol/L at ASCT. VitD levels >52 nmol/L were associated with better PFS (P = 0.0194) and OS (P = 0.011). Similarly, when evaluating myeloma patients alone, patients with lower VitD levels (≤52 nmol/L) had inferior PFS (P = 0.0412) and OS (P = 0.049). Finally, the multivariate analysis was consistent that varying VitD levels were significantly associated with OS (P = 0.0167), also when stratifying patients in groups with VitD levels > versus ≤52 nmol/L (P = 0.0421). Our data suggest that reduced serum VitD levels in myeloma and lymphoma patients undergoing HDCT/ASCT are associated with inferior outcome. Optimizing VitD levels before ASCT may be warranted.

Association of VDBP rs4701 Variant, but not VDR/RXR-α Over-Expression with Bone Mineral Density in Pediatric Well-Chelated β-Thalassemia Patients

Background

The reduced rate of bone formation despite the availability of vitamin D has been reported in β-thalassemia. Genetic factors, together with environmental ones, could be implicated in this condition. Since vitamin D binding protein (VDBP) maintains bioavailability of vitamin D which binds to vitamin D receptor (VDR)-retinoid X receptor alpha (RXRA) heterodimer to exert its molecular actions, we speculated that vitamin D metabolic-axis expression signature and variants could be potential molecular candidates for bone turnover/disease in thalassemia. To this end, this study aims to analyze VDR/RXRA expression signature, and two VDBP variants in a pilot sample of Egyptian β-thalassemia children in correlation with bone mineral density (BMD).

Patients and methods

Forty-four well-chelated β-thalassemia children and 40 unrelated controls were enrolled. The serum bone chemistry profile was measured. Peripheral blood mononuclear cells (PBMN) VDR/RXRA expression levels were quantified by Real-Time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). VDBP rs7041 and rs4588 variants were identified by Real-Time allelic discrimination assay. All patients were subjected to lumbar-spine Dual-energy X-ray absorptiometry (DEXA).

Results

VDR/RXRA expressions were significantly higher in β-thalassemia children compared to controls (P = 0.001 and <0.001, respectively) and showed higher values in β-thalassemia major relative to β-thalassemia intermedia. Expression levels of both genes were not associated with sex or BMD. However, VDBP rs4701 genotyping revealed lower BMD-L4 and a higher frequency of osteoporosis.

Conclusions

β-Thalassemia children had higher expression levels of PBMN VDR/RXRA. VDBP rs4701 variant was associated with osteoporosis in our β-thalassemia patients on vitamin D supplementation. Further large-scale studies in other ethnic populations are warranted.

Role of Vitamins A and D in BCR-ABL Arf-/- Acute Lymphoblastic Leukemia

The effects of vitamin A and/or vitamin D deficiency were studied in an Arf^−/− BCR-ABL acute lymphoblastic leukemia murine model. Vitamin D sufficient mice died earlier (p = 0.003) compared to vitamin D deficient (VDD) mice. Vitamin A deficient (VAD) mice fared worst with more rapid disease progression and decreased survival. Mice deficient for vitamins A and D (VADD) had disease progression similar to VAD mice. Regulatory T cells, previously shown to associate with poor BCR-ABL leukemia control, were present at higher frequencies among CD4⁺ splenocytes of vitamin A deficient vs. sufficient mice. In vitro studies demonstrated 1,25-dihydroxyvitamin D (1,25(OH)₂VD₃) increased the number of BCR-ABL ALL cells only when co-cultured with bone marrow stroma. 1,25(OH)₂VD₃ induced CXCL12 expression in vivo and in vitro in stromal cells and CXCL12 increased stromal migration and the number of BCR-ABL blasts. Vitamin D plus leukemia reprogrammed the marrow increasing production of collagens, potentially trapping ALL blasts. Vitamin A (all trans retinoic acid, ATRA) treated leukemic cells had increased apoptosis, decreased cells in S-phase, and increased cells in G₀/G₁. ATRA signaled through the retinoid X receptor to decrease BCR-ABL leukemic cell viability. In conclusion, vitamin A and D deficiencies have opposing effects on mouse survival from BCR-ABL ALL.

Brazilian Nutritional Consensus in Hematopoietic Stem Cell Transplantation: Adults

The nutritional status of patients submitted to hematopoietic stem cell transplant is considered an independent risk factor, which may influence on quality of life and tolerance to the proposed treatment. The impairment of nutritional status during hematopoietic stem cell transplant occurs mainly due to the adverse effects resulting from conditioning to which the patient is subjected. Therefore, adequate nutritional evaluation and follow-up during hematopoietic stem cell transplant are essential. To emphasize the importance of nutritional status and body composition during treatment, as well as the main characteristics related to the nutritional assessment of the patient, the Brazilian Consensus on Nutrition in Hematopoietic Stem Cell Transplant: Adults was prepared, aiming to standardize and update Nutritional Therapy in this area. Dietitians, nutrition physicians and hematologists from 15 Brazilian centers thar are references in hematopoietic stem cell transplant took part.

Oral calcitriol in hematopoietic recovery and survival after autologous stem cell transplantation: a randomized clinical trial

BACKGROUND

Calcitriol, the active metabolite of vitamin D, is an essential regulator in the hematopoiesis and immunity. However, knowledge revealing its influence on the immune and hematologic reconstitution after hematopoietic stem cell transplantation (HSCT) in clinical trials is very limited.

OBJECTIVES

The effects of calcitriol on short-term and long-term hematopoietic recovery, relapse-free survival (RFS) and overall survival (OS) in multiple myeloma, Hodgkin's and non-Hodgkin's lymphoma following autologous peripheral blood HSCT were assessed.

METHODS

Eighty patients (age: 18-68 years) in complete remission were allocated 1:1 to two groups by balanced block randomization. Calcitriol 0.25 μg or placebo capsule was administered three times daily from transplantation to day 30. Absolute neutrophil count (ANC), absolute lymphocyte count (ALC), and platelet count (PC) were determined daily from transplantation to day 30. White blood cell count (WBC), PC, and hemoglobin concentration (HC) of days 180 and 365 were extracted from clinic files. A thorough examination for oral mucositis (OM) was completed daily during hospital stay. Adverse drug reactions (ADRs) as well as two-year RFS and OS were evaluated.

RESULTS

Median time to ANC engraftment (≥0.5 × 103/μl: 10.0 vs. 11.0 days; P = 0.98) and PC engraftment (≥20.0 × 103/μl: both 14.0 days; P = 0.58) was similar between groups. However, the median time to ALC recovery was significantly shorter in the calcitriol group (≥0.5 × 103/μl: 13.0 vs. 20.0 days; P < 0.001). Moreover, ALC recovery rates on day 15 (≥0.5 × 103/μl: 82.1% vs. 42.5%; P < 0.001) and on day 30 (≥1.0 × 103/μl: 91.7% vs. 57.5%; P = 0.001) was significantly higher with calcitriol. WBC, PC, and HC on days 180 and 365 were not significantly different between groups. None of the OM indices were modulated by calcitriol. All the ADRs were non-serious and mild, possibly or unlikely related to the intervention. In a median of 29 months follow-up, RFS was significantly better in the calcitriol group (77.0%, SE = 7.0% vs. 59.0%, SE = 8.0%; P = 0.03), albeit the OS was not affected (87.0%, SE = 5.0% vs. 92.0%, SE = 4.0%; P = 0.72).

CONCLUSION

Calcitriol could improve ALC recovery and RFS as a safe option post-HSCT. Graphical abstract Oral calcitriol 0.25 µg three times daily from transplantation to day 30 improved lymphocytes recovery and two-year relapse-free survival as a safe option in 80 patients of autologous hematopoietic stem cell transplantation in comparison with placebo.

Steroid Hormone Vitamin D: Implications for Cardiovascular Disease

Understanding of vitamin D physiology is important because about half of the population is being diagnosed with deficiency and treated with supplements. Clinical guidelines were developed based on observational studies showing an association between low serum levels and increased cardiovascular risk. However, new randomized controlled trials have failed to confirm any cardiovascular benefit from supplementation in the general population. A major concern is that excess vitamin D is known to cause calcific vasculopathy and valvulopathy in animal models. For decades, administration of vitamin D has been used in rodents as a reliable experimental model of vascular calcification. Technically, vitamin D is a misnomer. It is not a true vitamin because it can be synthesized endogenously through ultraviolet exposure of the skin. It is a steroid hormone that comes in 3 forms that are sequential metabolites produced by hydroxylases. As a fat-soluble hormone, the vitamin D-hormone metabolites must have special mechanisms for delivery in the aqueous bloodstream. Importantly, endogenously synthesized forms are carried by a binding protein, whereas dietary forms are carried within lipoprotein particles. This may result in distinct biodistributions for sunlight-derived versus supplement-derived vitamin D hormones. Because the cardiovascular effects of vitamin D hormones are not straightforward, both toxic and beneficial effects may result from current recommendations.

A comprehensive overview on osteoporosis and its risk factors

Osteoporosis is a bone disorder with remarkable changes in bone biologic material and consequent bone structural distraction, affecting millions of people around the world from different ethnic groups. Bone fragility is the worse outcome of the disease, which needs long term therapy and medical management, especially in the elderly. Many involved genes including environmental factors have been introduced as the disease risk factors so far, of which genes should be considered as effective early diagnosis biomarkers, especially for the individuals from high-risk families. In this review, a number of important criteria involved in osteoporosis are addressed and discussed.

Investigation of the Relationship Between Fok1 and Col1A1 Gene Polymorphisms and Development of Treatment-Related Bone Complications in Children with Acute Lymphoblastic Leukemia

Objective:

In acute lymphoblastic leukemia (ALL), various clinical risk factors and genetic predispositions contribute to the development of bone complications during and after chemotherapy. In this study, we aimed to investigate whether vitamin D receptor (VDR) Fok1 and collagen protein Col1A1 Sp1-binding site gene polymorphisms, which are important in bone mineral and matrix formation, have effects on the development of bone abnormalities in childhood ALL survivors.

Materials and Methods:

Fifty children with ALL who were treated with the ALL Berlin-Frankfurt-Muenster-95 protocol between 1998 and 2008 and were followed for at least 7 years were enrolled. The control group consisted of 96 healthy children. VDR Fok1 and Col1A1 Sp1-binding site gene polymorphisms were analyzed by polymerase chain reaction and restriction fragment length polymorphism. Bone mineral density (BMD) and markers of bone metabolism were all noted. All patients who presented with pain in the joints were examined for bone pathologies while on chemotherapy or during long-term follow-up.

Results:

Low BMD (16%), osteoporosis (12%), and osteonecrosis (8%) were present in a total of 18 patients (36%). The frequency of osteonecrosis and total bone abnormalities was significantly higher in children aged ≥10 years (p=0.001). The risk of low BMD and osteonecrosis was higher in those with vitamin D deficiency. Only the Col1A1 Sp1-binding site gene polymorphism showed a significant association in ALL patients with osteonecrosis.

Conclusion:

The development of therapy-induced bone mineral loss and osteonecrosis in children with ALL is frequent and the risk is especially higher in children aged ≥10 years and with vitamin D deficiency. The association between Col1A1 Sp1-binding site gene polymorphisms and osteonecrosis has to be assessed in a larger group of ALL survivors.

Vitamin D: Effect on Haematopoiesis and Immune System and Clinical Applications

Vitamin D is a steroid-like hormone which acts by binding to vitamin D receptor (VDR). It plays a main role in the calcium homeostasis and metabolism. In addition, vitamin D display other important effects called “non-classical actions.” Among them, vitamin D regulates immune cells function and hematopoietic cells differentiation and proliferation. Based on these effects, it is currently being evaluated for the treatment of hematologic malignancies. In addition, vitamin D levels have been correlated with patients’ outcome after allogeneic stem cell transplantation, where it might regulate immune response and, accordingly, might influence the risk of graft-versus-host disease. Here, we present recent advances regarding its clinical applications both in the treatment of hematologic malignancies and in the transplant setting.

Relationship between vitamin D receptor gene polymorphisms and anemia in postmenopausal Vietnamese women

Background: Both in vitro and in vivo studies have shown that calcitriol, the active form of vitamin D, is involved in hematopoiesis. Vitamin D receptor (VDR) gene has been suggested as one of the candidate genes for anemia. Objective: Investigate relationship between anemia and the commonly studied polymorphisms of VDR gene (FokI, BsmI, ApaI and TaqI) in terms of genotype and haplotype in Vietnamese. Methods: A case-control study including 132 postmenopausal women without chronic kidney diseases was designed to investigate the relationship between VDR polymorphism and anemia. Four single nucleotide polymorphisms (SNPs) FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232), and TaqI (rs731236) were typed by polymerase chain reaction and restriction fragment length polymorphism method. Results: Genotype distributions of four SNPs were in Hardy-Weinberg equilibrium in both anemia and control groups. The SNPs at the 3’end of the VDR gene (BsmI, ApaI and TaqI) exhibited a strong linkage disequilibrium. There was no significant association between anemia and VDR polymorphism in terms of allele, genotype, and haplotype in the analyses unadjusted or adjusted for the covariates (age, body mass index, educational level, serum ferritin, iron and albumin). Conclusion: VDR gene did not influence anemia in postmenopausal women without chronic kidney disease. For further study on the association between VDR gene and anemia, the use of larger sample size, a prospective study design, and additional markers would enhance the reliability and validity of findings.

Role of Vitamin A/Retinoic Acid in Regulation of Embryonic and Adult Hematopoiesis

Vitamin A is an essential micronutrient throughout life. Its physiologically active metabolite retinoic acid (RA), acting through nuclear retinoic acid receptors (RARs), is a potent regulator of patterning during embryonic development, as well as being necessary for adult tissue homeostasis. Vitamin A deficiency during pregnancy increases risk of maternal night blindness and anemia and may be a cause of congenital malformations. Childhood Vitamin A deficiency can cause xerophthalmia, lower resistance to infection and increased risk of mortality. RA signaling appears to be essential for expression of genes involved in developmental hematopoiesis, regulating the endothelial/blood cells balance in the yolk sac, promoting the hemogenic program in the aorta-gonad-mesonephros area and stimulating eryrthropoiesis in fetal liver by activating the expression of erythropoietin. In adults, RA signaling regulates differentiation of granulocytes and enhances erythropoiesis. Vitamin A may facilitate iron absorption and metabolism to prevent anemia and plays a key role in mucosal immune responses, modulating the function of regulatory T cells. Furthermore, defective RA/RARα signaling is involved in the pathogenesis of acute promyelocytic leukemia due to a failure in differentiation of promyelocytes. This review focuses on the different roles played by vitamin A/RA signaling in physiological and pathological mouse hematopoiesis duddurring both, embryonic and adult life, and the consequences of vitamin A deficiency for the blood system.

Differential Effects of Vitamins A and D on the Transcriptional Landscape of Human Monocytes during Infection

Vitamin A and vitamin D are essential nutrients with a wide range of pleiotropic effects in humans. Beyond their well-documented roles in cellular differentiation, embryogenesis, tissue maintenance and bone/calcium homeostasis, both vitamins have attracted considerable attention due to their association with-immunological traits. Nevertheless, our knowledge of their immunomodulatory potential during infection is restricted to single gene-centric studies, which do not reflect the complexity of immune processes. In the present study, we performed a comprehensive RNA-seq-based approach to define the whole immunomodulatory role of vitamins A and D during infection. Using human monocytes as host cells, we characterized the differential role of both vitamins upon infection with three different pathogens: Aspergillus fumigatus, Candida albicans and Escherichia coli. Both vitamins showed an unexpected ability to counteract the pathogen-induced transcriptional responses. Upon infection, we identified 346 and 176 immune-relevant genes that were regulated by atRA and vitD, respectively. This immunomodulatory activity was dependent on the inflammatory stimulus, allowing us to distinguish regulatory patterns which were specific for each stimulatory setting. Moreover, we explored possible direct and indirect mechanisms of vitamin-mediated regulation of the immune response. Our findings highlight the importance of vitamin-monitoring in critically ill patients. Moreover, our results underpin the potential of atRA and vitD as therapeutic options for anti-inflammatory treatment.

The human cytomegalovirus lytic cycle is induced by 1,25-dihydroxyvitamin D3 in peripheral blood monocytes and in the THP-1 monocytic cell line

Human cytomegalovirus (HCMV) resides in a latent form in hematopoietic progenitors and undifferentiated cells within the myeloid lineage. Maturation and differentiation along the myeloid lineage triggers lytic replication. Here, we used peripheral blood monocytes and the monocytic cell line THP-1 to investigate the effects of 1,25-dihydroxyvitamin D3 on HCMV replication. Interestingly, 1,25-dihydroxyvitamin D3 induces lytic replication marked by upregulation of HCMV gene expression and production of infectious virus. Moreover, we demonstrate that the effects of 1,25-dihydroxyvitamin D3 correlate with maturation/differentiation of the monocytes and not by directly stimulating the MIEP. These results are somewhat surprising as 1,25-dihydroxyvitamin D3 typically boosts immunity to bacteria and viruses rather than driving the infectious life cycle as it does for HCMV. Defining the signaling pathways kindled by 1,25-dihydroxyvitamin D3 will lead to a better understanding of the underlying molecular mechanisms that determine the fate of HCMV once it infects cells in the myeloid lineage.

The role of vitamin D in hematologic disease and stem cell transplantation

Vitamin D is a steroid hormone with a broad range of biological effects ranging from the classical role as a mediator of calcium and phosphate balance to cellular differentiation and immune modulation. These effects impact normal and dysfunctional hematopoietic and immune function, which may allow an avenue for improved treatment and support of patients suffering from hematologic disorders. In this review, we will summarize the role of vitamin D in normal hematopoiesis, discuss ways in which vitamin D may improve outcomes, and discuss a potential role of vitamin D for treating hematologic disorders and modulating the immune system to improve the outcome of allogeneic stem cell transplant.

Frequency of fokI and taqI polymorphism of vitamin D receptor gene in Indian population and its association with 25-hydroxyvitamin D levels

BACKGROUND:

The VDR protein is at the centre of the vitamin D endocrine system, a complex physiological system with substantial feedback regulatory mechanisms involved in maintaining serum calcium and 1, 25 dihydroxy vitamin D3. Variations in VDR gene are shown to have implications in several diseases and have also been implicated as an important genetic factor affecting bone mass.

AIM:

To determine the frequency of Fok I and Taq I variants in healthy Indian individuals and its association with 25-OH-Vitamin D levels.

SETTINGS AND DESIGN:

Blood samples were collected from 143 unrelated normal individuals (Male-84 and Female-59) and their genotypes determined.

MATERIALS AND METHODS:

After amplification by polymerase chain reaction, each polymorphism was genotyped by restriction fragment length polymorphism. For 100 normal healthy individuals 25-hydroxyvitamin D estimation was done using DiaSorin kit method.

STATISTICAL ANALYSIS:

Graph pad software was used to calculate the P values from the Chi-square.

RESULTS:

Out of 143 samples analyzed for FokI and TaqI polymorphisms the following genotypic frequency was obtained FF 59%, Ff 36%, ff 5% and TT 49%, Tt 43%, tt 8% respectively.

CONCLUSIONS:

Results indicate that the distribution of the polymorphic loci Fok I and Taq I vary considerably not only in different populations, but also within India. Furthermore, when the genotypes were analyzed with respect to 25-OH-Vitamin D levels, a significant association was seen for the Taq 1 SNP but not with the Fok I.

Antibacterial effects of vitamin D

Interaction between vitamin D and the immune system has been recognized for many years, but its relevance to normal human physiology has only become evident in the past 5 years. Studies of innate immune responses to pathogens such as Mycobacterium tuberculosis have shown that pathogen-recognition receptor-mediated activation of localized vitamin D metabolism and signaling is a key event associated with infection. Vitamin D, acting in an intracrine fashion, is able to induce expression of antibacterial proteins and enhance the environment in which they function. The net effect of these actions is to support increased bacterial killing in a variety of cell types. The efficacy of such a response is highly dependent on vitamin D status; in other words, the availability of circulating 25-hydroxyvitamin D for intracrine conversion to active 1,25-dihydroxyvitamin D by the enzyme 25-hydroxyvitamin D-1α-hydroxylase. The potential importance of this mechanism as a determinant of human disease is underlined by increasing awareness of vitamin D insufficiency across the globe. This Review will explore the molecular and cellular systems associated with antibacterial responses to vitamin D in different tissues and possible consequences of such a response for the prevention and treatment of human immune disorders.

Enhanced radiosensitivity in 1,25-dihydroxyvitamin D3 deficient mice

To investigate whether impaired osteogenesis resulting from vitamin D deficiency can influence hematopoiesis recovery after radiation, the 25-hydroxyvitamin D-1α-hydroxylase (1α-hydroxylase) gene knockout (KO) mice and wild type (WT) mice were subjected to different doses of gamma ray. The survival rates, peripheral blood cell counts and bone marrow cellularity were studied after irradiation (IR). The survival rates of the KO mice were significantly lower than that of WT mice after 6 or 8 Gy dose of radiation. The recovery of white blood cells in KO mice was significantly delayed compared with that in WT mice after radiation. The red blood cell number in WT mice was observed to increase more than that in KO mice at days 14 and 28 after radiation. The nadir platelet count in KO mice was nearly half of that in WT mice. Dramatically higher bone marrow cell numbers were found in WT mice compared with KO mice. Our findings demonstrate the enhanced radiosensitivity in 1,25-dihydroxyvitamin D3 (1,25-(OH)(2)D(3)) deficient mice.

Association of vitamin D receptor gene polymorphisms with BMD and their effect on 1, 25-dihydroxy vitamin D3 levels in pre- and postmenopausal South Indian women from Andhra Pradesh

BACKGROUND

Osteoporosis is a multifactorial disorder with a strong genetic component and vitamin D receptor gene has been suggested as a candidate gene for osteoporosis. Therefore the present study was aimed to investigate the role of the VDR Fok 1 gene polymorphism and its influence on vitamin D3 levels and BMD in pre- and postmenopausal osteoporotic women of Indian ethnicity.

METHODS

427 osteoporotic women and 460 age matched controls were included in the study. VDR FOK1 gene polymorphism was assessed by the PCR-RFLP method. Serum vitamin D3 was measured by the HPLC method.

RESULTS

The frequency of ff genotype and f allele was significantly high in pre- and postmenopausal osteoporotic women in comparison with controls (p<0.001).In each case individuals with ff genotype had significantly low BMD in comparison with Ff and FF genotypes. No significant association was found between the genotypes and vitamin D3 levels.

CONCLUSION

The VDR Fok 1 gene is associated with low bone mass in all our study subjects. The genotype ff of the VDR Fok 1 gene is associated with osteoporosis. Further ff genotype associated significantly with low bone mass. Therefore the f allele of VDR Fok1 gene is an important risk factor for osteoporosis.

Vitamin D and the intracrinology of innate immunity

An immunomodulatory role for vitamin D was first proposed more than 25 years ago, based on two salient observations. Firstly it was shown that monocytes/macrophages from patients with the granulomatous disease sarcoidosis constitutively synthesize the active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)(2)D) from precursor 25-hydroxyvitamin D (25OHD). Secondly, the receptor for 1,25(OH)(2)D (vitamin D receptor, VDR) is detectable in activated, proliferating lymphocytes. These observations suggested a mechanism whereby 1,25(OH)(2)D produced by monocytes could act upon adjacent T-cells or B-cells, but the impact of such a system on normal immune regulation was uncertain. Indeed, it is only in recent years that a much clearer picture of the role of vitamin D as a determinant of immune responsiveness has emerged. Two new concepts have prompted this change. Firstly studies of innate immunity have shown that intracrine induction of antimicrobial activity by vitamin D is a pivotal component of monocyte/macrophage response to infection. Secondly, it is now clear that sub-optimal vitamin D status is a common feature of many populations throughout the world, with the potential to compromise monocyte/macrophage metabolism of 25OHD and subsequent actions of 1,25(OH)(2)D. The current review details these new developments with specific reference to the metabolic and signaling mechanisms associated with innate immune regulation by vitamin D and implications for human disease.

Side-chain modified vitamin D analogs induce rapid accumulation of VDR in the cell nuclei proportionately to their differentiation-inducing potential

1,25-Dihydroxyvitamin D(3) (1,25D) regulates gene transcription through a nuclear vitamin D receptor (VDR) which acts as a ligand-regulated transcription factor. Some structural vitamin D analogs (VDAs) are selective in their biological actions, because they retain cell-differentiating potential, while their calcemic activity is reduced. In this article we have shown that in untreated HL60 cells the expression level of VDR is low, in spite of constant presence of VDR mRNA. Furthermore we have shown that one of the most rapid effects of either 1,25D or VDAs is nuclear accumulation of VDR, which is proportional to the differentiation-inducing potential of given analog. We observed this effect not only in HL60 cells, but also in blast cells isolated from patients with acute myeloid leukemias. After longer incubation time of the cells with various VDAs, the expression levels of VDR have become unrelated to the final differentiation effect.

Vitamin D receptor gene polymorphisms and bone mineral density in postmenopausal Indian women

OBJECTIVES

Osteoporosis is a common condition in postmenopausal women. Bone mineral density (BMD), the major determinant of osteoporotic fracture risk, has a particular genetic background. However, consensus on the association of BMD with specific gene locus has not been reached. The race and ethnicity specific divergence in association studies must be assessed to predict the susceptibility and therapeutic response of associated genes. We investigated the potential association of Vitamin D receptor (VDR) gene polymorphisms ApaI, BsmI, FokI and TaqI with BMD in 246 postmenopausal Indian women (average age 54.2+/-3.4 years).

METHODS

The subjects were genotyped by PCR-RFLP and underwent BMD measurements at spine and hip by dual energy X-ray absorptiometery.

RESULTS

The average BMD at spine and hip of women with genotypes aa, bb (presence of restriction sites for ApaI and BsmI), FF and TT (absence of restriction sites for FokI and TaqI) was more than 10% higher than those with genotypes AA, BB, ff and tt, respectively. The interaction between BsmI, ApaI and TaqI genotypes showed significant effect of BsmI-ApaI genotypes (p=0.052) in this combination on BMD. However, presence of T allele in combination showed positive influence on BMD. Within the group, genotypes BB, ff and tt were significantly prevalent in women with osteoporotic bone mass, tt and BB had significantly higher adjusted odd ratio (OR) for age more than 55years.

CONCLUSION

Study reveals that VDR gene polymorphisms are associated with BMD in Indian women and perhaps, influence some determinant of bone metabolism. Ethnicity may attribute to frequency variation, however, allele impact remains same.

Normal myelopoiesis but abnormal T lymphocyte responses in vitamin D receptor knockout mice

The vitamin D receptor (VDR) is a transcription factor that mediates the actions of its ligand, 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], which can promote monocyte/macrophage differentiation and inhibit proliferation and cytokine production by activated T lymphocytes. In this study, VDR knockout (KO) mice were used to investigate the possible role of VDR in hematopoiesis. The relative number of red and white peripheral blood cells and the percentage of bone marrow macrophages did not differ between VDR KO and wild-type mice. 12-O-tetradecanoylphorbol-13-acetate, but not 1,25(OH)(2)D(3), induced differentiation of bone marrow-committed myeloid stem cells from VDR KO mice to monocytes/macrophages. Production of IL-18, a Th1-promoting cytokine, was reduced in macrophages from these mice. Antigen-stimulated spleen cells from VDR KO mice showed an impaired Th1 cell response and had decreased expression of STAT4, a Th1 cell transcription factor. These results demonstrate the absolute requirement of VDR for 1,25(OH)(2)D(3)-induced monocyte/macrophage differentiation but show that monocyte/macrophage differentiation can occur in the absence of this receptor. The observed reduction in Th1 population in these mutant mice may be explained by a loss of macrophage IL-18 production or a suppression of STAT4 expression by activated splenocytes.

Estrone potentiates myeloid cell differentiation: a role for 17 beta-hydroxysteroid dehydrogenase in modulating hemopoiesis

Hormones such as 1 alpha, 25-dihydroxy vitamin D3 (D3), all-trans retinoic acid, and 9-cis retinoic acid stimulate differentiation of myeloid progenitor cells via their interaction with specific hormone receptors. However, the sensitivity of cells to these agents is not merely governed by the expression of their receptors and the availability of ligand to bind them. Recent studies from our group suggested that the actions of D3 and retinoids on myelopoiesis also are influenced by endogenous mechanisms involving other steroid hormones. In this study we examined the influence of local estrogen metabolism on the differentiation of HL60 cells and normal primitive myeloid progenitor cells. Quantitative thin-layer chromatography (TLC) analyses showed that HL60 and normal cells are able to generate estrone (E1) from estradiol (E2). Neither cell population generated significant amounts of E2 from E1. Reverse transcriptase polymerase chain reaction and Northern analyses confirmed that normal and leukemic myeloid progenitor cells expressed mRNA for the type I and IV isoforms of 17 beta-hydroxysteroid dehydrogenase. Conversion of E2 to E1 was upregulated within 24 hours when HL60 cells were treated with either all-trans retinoic acid or D3 at doses that induce their differentiation toward neutrophils or monocytes, respectively. Similarly, D3-induced monocyte differentiation of normal myeloid progenitor cells was associated with increased capacity to generate E1 from E2. When HL60 cells or normal myeloid progenitor cells were exposed to exogenous E1 they became more sensitive to the differentiation-inducing effects of D3. Data presented provide further evidence for the local modulation of myelopoiesis by intracrine mechanisms. In particular, our findings suggest that local metabolism of steroids by normal as well as leukemic myeloid cells influences their responsiveness to D3 and retinoids.

The selenoprotein thioredoxin reductase is expressed in peripheral blood monocytes and THP1 human myeloid leukemia cells--regulation by 1,25-dihydroxyvitamin D3 and selenite

1,25(OH)2 Vitamin D3 (1,25(OH)2D3) and adhesion propagate monocyte differentiation. We identified the selenoprotein thioredoxin reductase (TrxR) as a new molecular target for 1,25(OH)2D3 in monocytes during this process. In THP1 monocytic leukemia cells 1,25(OH)2D3 stimulated TrxR mRNA levels 2-4-fold by 4-8 h and enhanced TrxR activity (60%) (as measured by the dithionitrobenzole-assay) after 24 h, which declined below baseline after 96 h. The addition of 100 nM selenite enhanced (approx. 50%) basal and stimulated enzyme activity in THP1 cells. The relative stimulation by 1,25(OH)2D3 was very similar but peak levels were sustained in THP1 cells up to 48 h. Human peripheral blood monocytes (PBM) of different donors showed very low basal TrxR steady state mRNA levels which were markedly enhanced (as analyzed by Northern blotting) after 4 h of adherence to culture dishes. 1,25(OH)2D3 (100 nM) further stimulated TrxR mRNA expression (4 h, 3-fold). TrxR enzyme activity mirrored the mRNA changes. Basal activity was stimulated approx. 25% by adhesion in culture alone and was further stimulated (approximately 15%) by 1,25(OH)2D3 after 4 h. By 24 h similar results were achieved but the effect of 1,25(OH)2D3 could be seen in the presence of 100 nM selenium only. The expression of TrxR and its regulation by 1,25(OH)2D3 and selenite in monocytes might be important for their induction of differentiation and maintenance of function.