1,25-Dihydroxyvitamin D3 induces biphasic NF-κB responses during HL-60 leukemia cells differentiation through protein induction and PI3K/Akt-dependent phosphorylation/degradation of IκB

Vitamin D and its therapeutic relevance in pulmonary diseases

Vitamin D is customarily involved in maintaining bone and calcium homeostasis. However, contemporary studies have identified the implication of vitamin D in several cellular processes including cellular proliferation, differentiation, wound healing, repair and regulatory systems inclusive of host defence, immunity, and inflammation. Multiple studies have indicated corelations between low serum levels of vitamin D, perturbed pulmonary functions and enhanced incidences of inflammatory diseases. Almost all of the pulmonary diseases including acute lung injury, cystic fibrosis, asthma, COPD, Pneumonia and Tuberculosis, all are inflammatory in nature. Studies have displayed strong inter-relations with vitamin D deficiency and progression of lung disorders; however, the underlying mechanism is still unknown. Vitamin D has emerged to possess inhibiting effects on pulmonary inflammation while exaggerating innate immune defenses by strongly influencing functions of inflammatory cells including dendritic cells, monocyte/macrophages, T cells, and B cells along with structural epithelial cells. This review dissects the effects of vitamin D on the inflammatory cells and their therapeutic relevance in pulmonary diseases. Although, the data obtained is very limited and needs further corroboration but presents an exciting area of further research. This is because of its ease of supplementation and development of personalized medicine which could lead us to an effective adjunct and cost-effective method of therapeutic modality for highly fatal pulmonary diseases.

Oroxylin A, a natural compound, mitigates the negative effects of TNFα-treated acute myelogenous leukemia cells

Tumor necrosis factor alpha (TNFα) is a complicated cytokine which is involved in proliferation and differentiation of acute myelogenous leukemia (AML) cells through a poorly understood mechanism. Mechanistic studies indicate that TNFα induced binding of PI3K subunit p85α to N-terminal truncated nuclear receptor RXRα (tRXRα) proteins, and activated AKT. The activated PI3K/AKT pathway negatively regulated differentiation of AML cells through the upregulation of c-Myc. In addition, TNFα also induced activation of nuclear factor κB (NF-κB), a nuclear transcription factor which was shown to promote cell proliferation. The present study demonstrates that oroxylin A, a natural compound isolated from Scutellariae radix, sensitizes leukemia cells to TNFα and markedly enhances TNFα-induced growth inhibition and differentiation of AML cell including human leukemia cell lines and primary AML cells. Activation of PI3K/AKT pathway could be inhibited by oroxylin A through inhibiting expression of tRXRα in NB4 and HL-60-resistant cells. Furthermore, we found that oroxylin A inhibited the activation of NF-κB and the DNA binding activity by TNFα proved by EMSA in these two AML cell lines. Moreover, in vivo studies showed that treatment with oroxylin A in combination with TNFα decreased AML cell population and prolonged survival in NOD/SCID mice with xenografts of primary AML cells. Overall, our results indicate that oroxylin A is able to inhibit the negative effects of TNFα for AML therapy, suggesting that combination of oroxylin A and TNFα have the potential to delay growth or eliminate the abnormal leukemic cells, thus representing a promising strategy for AML treatment.

Vitamin D and Influenza-Prevention or Therapy?

Vitamin D generates many extraskeletal effects due to the vitamin D receptor (VDR) which is present in most tissues throughout the body. The possible role of vitamin D in infections is implied from its impact on the innate and adaptive immune responses. A significant effect is also the suppression of inflammatory processes. Because vitamin D could be acknowledged as a “seasonal stimulus”, as defined by R. Edgar Hope-Simpson, it would be crucial to prove it from a potential easy and cheap prophylaxis or therapy support perspective as far as influenza infections are concerned. The survey of the literature data generates some controversies and doubts about the possible role of vitamin D in the prevention of influenza virus. The most important point is to realise that the broad spectrum of this vitamin’s activity does not exclude such a possibility. According to most of the authors, more randomized controlled trials with effective, large populations are needed to explore the preventive effect of vitamin D supplementation on viral influenza infections.

Serum 25-hydroxyvitamin D concentrations are associated with nuclear factor kappa-B activity but not with inflammatory markers in healthy normoglycemic adults

Vitamin D has been reported to have anti-inflammatory properties in in vitro and animal studies, which are thought to occur via inhibition of the nuclear factor kappa-B (NFκB) pathway. However, the association between vitamin D and in vivo NFκB activity in humans has not previously been reported. The aim of the present study was to examine the associations between circulating 25-hydroxyvitamin D (25(OH)D) concentrations and NFκB activity in peripheral blood mononuclear cells (PBMCs) as well as plasma inflammatory markers in healthy individuals. We hypothesized that 25(OH)D concentrations would be negatively associated with NFκB activity and pro-inflammatory markers downstream of NFκB, and positively associated with anti-inflammatory markers. We measured circulating 25(OH)D (chemiluminescent immunoassay); anthropometry: body mass index (BMI), waist-to-hip ratio (WHR), and % body fat (dual X-ray absorptiometry); plasma pro- and anti-inflammatory markers: high sensitivity C-reactive protein (hsCRP), tumor necrosis factor (TNF), monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), and IL-10 (ELISA); and NFκB activity in PBMCs (DNA-binding assay). Forty-nine participants were included in the study (21M/28F; age=31.6±10.2years (mean±SD); BMI=28.4±4.6kg/m²; % body fat=30.2±9.3%). Mean 25(OH)D concentration was 48.2±24.5 nmol/l. There were no differences in 25(OH)D concentrations between genders and no association between 25(OH)D concentrations and age, BMI, or % body fat (all p>0.1). Serum 25(OH)D concentrations were positively associated with NFκB activity in PBMCs (r=0.48, p=0.0008) but not with any of the pro- or anti-inflammatory markers measured (all p>0.1). After adjusting for age, sex, and % body fat, 25(OH)D concentrations remained positively associated with NFκB activity in PBMCs (β=0.55, p<0.0001). Although in-vitro studies suggest that vitamin D inhibits NFκB activity, our novel cross-sectional data from a cohort of healthy individuals suggest that vitamin D may regulate rather than inhibit the NFκB pathway. Large-scale intervention and mechanistic studies are needed to further investigate the effects of vitamin D on NFκB activity in vivo in humans.

Effect of vitamin D supplementation on inflammation and nuclear factor kappa-B activity in overweight/obese adults: a randomized placebo-controlled trial

In-vitro studies suggest that vitamin D reduces inflammation by inhibiting nuclear factor kappa-B (NFκB) activity. Yet, no trials have examined the effects of vitamin D supplementation on NFκB activity in-vivo in humans. We conducted a double-blind randomized trial (RCT) examining effects of vitamin D supplementation on inflammatory markers and NFκB activity in peripheral blood mononuclear cells (PBMCs). Sixty-five overweight/obese, vitamin D-deficient (25-hydroxyvitamin D [25(OH)D] ≤ 50 nmol/L) adults were randomized to a single 100,000 IU bolus followed by 4,000 IU daily cholecalciferol or matching placebo for 16 weeks. We measured BMI, % body fat, serum 25(OH)D, high-sensitivity C-reactive protein (hsCRP), tumour necrosis factor (TNF), monocyte chemoattractant protein-1 (MCP-1), interferon-gamma (IFN-γ), several interleukins, and NFκB activity in PBMCs. Fifty-four participants completed the study. Serum 25(OH)D concentrations increased with vitamin D supplementation compared to placebo (p < 0.001). Vitamin D and placebo groups did not differ in any inflammatory markers or NFκB activity (all p > 0.05). Results remained non-significant after adjustment for age, sex, and % body fat, and after further adjustment for sun exposure, physical activity, and dietary vitamin D intake. Although in-vitro studies report anti-inflammatory effects of vitamin D, our RCT data show no effect of vitamin D supplementation on inflammatory markers or NFκB activity in-vivo in humans.

Vitamin D signaling and melanoma: role of vitamin D and its receptors in melanoma progression and management

Ultraviolet B (UVB), in addition to having carcinogenic activity, is required for the production of vitamin D3 (D3) in the skin which supplies >90% of the body's requirement. Vitamin D is activated through hydroxylation by 25-hydroxylases (CYP2R1 or CYP27A1) and 1α-hydroxylase (CYP27B1) to produce 1,25(OH)₂D3, or through the action of CYP11A1 to produce mono-di- and trihydroxy-D3 products that can be further modified by CYP27B1, CYP27A1, and CYP24A1. The active forms of D3, in addition to regulating calcium metabolism, exert pleiotropic activities, which include anticarcinogenic and anti-melanoma effects in experimental models, with photoprotection against UVB-induced damage. These diverse effects are mediated through an interaction with the vitamin D receptor (VDR) and/or as most recently demonstrated through action on retinoic acid orphan receptors (ROR)α and RORγ. With respect to melanoma, low levels of 25(OH)D are associated with thicker tumors and reduced patient survival. Furthermore, single-nucleotide polymorphisms of VDR and the vitamin D-binding protein (VDP) genes affect melanomagenesis or disease outcome. Clinicopathological analyses have shown positive correlation between low or undetectable expression of VDR and/or CYP27B1 in melanoma with tumor progression and shorter overall (OS) and disease-free survival (DFS) times. Paradoxically, this correlation was reversed for CYP24A1 (inactivating 24-hydroxylase), indicating that this enzyme, while inactivating 1,25(OH)₂D3, can activate other forms of D3 that are products of the non-canonical pathway initiated by CYP11A1. An inverse correlation has been found between the levels of RORα and RORγ expression and melanoma progression and disease outcome. Therefore, we propose that defects in vitamin D signaling including D3 activation/inactivation, and the expression and activity of the corresponding receptors, affect melanoma progression and the outcome of the disease. The existence of multiple bioactive forms of D3 and alternative receptors affecting the behavior of melanoma should be taken into consideration when applying vitamin D management for melanoma therapy.

MiR-146a affects the alteration in myeloid differentiation induced by hydroquinone in human CD34+ hematopoietic progenitor cells and HL-60 cells

The MiR-146a/TRAF6/NF-κB axis is important for the regulation of hematopoiesis and the immune system. To identify the key axis that regulates benzene-induced hematotoxicity or even leukemia, we investigated miR-146a expression in human CD34+ hematopoietic progenitor cells (HPCs) and human acute promyelocytic leukemia cells (HL-60) during the differentiation process. By performing a colony formation assay and flow cytometry on cells in the differentiation process after hydroquinone treatment, we found that hydroquinone induced a marked reduction of differentiation toward myeloid cells and immune cells in CD34+ cells (5 days exposure) as well as in HL-60 cells (3 h exposure). Further study using real-time PCR and western blot showed that the impaired myeloid differentiation was accompanied by the up-regulation of miR-146a and the down-regulation of TRAF6 and NF-κB. Using the miR-146a-5p inhibitor to suppress miR-146a expression could relieve the inhibitory effect on myeloid differentiation induced by hydroquinone to a certain extent. At the same time, the level of TRAF6 protein, as well as the phosphorylated IκBα protein which indicates NF-κB transcriptional activity was restored to the same levels as the control group. These results suggested that hydroquinone induced a dysregulation of miR-146a and its downstream NF-κB transcriptional factor pathway, which might be an early event in the generation of benzene-induced differentiation disturbance and subsequent leukemogenesis.

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.

Fatigue and Vitamin D Status in Iranian Female Nurses

Introduction:

Given that nurses are among professions with frequent problems of fatigue, and given the nature of their profession that provides little exposure to sunlight and the subsequent deficiency of vitamin D, the present study examined the relation between fatigue and circulating vitamin D levels in female nurses working in Shahid Beheshti Hospital, Kashan, Iran in 2013.

Material and Methods:

This cross-sectional study was conducted in 200 female nurses working in Shahid Beheshti Hospital. To measure fatigue, fatigue questionnaire containing 9 questions eliciting the subject’s feeling in scales of 1 to 7, getting a possible score of 9 to 63, and Visual Analogue Scale in which nurses specified their fatigue in a band of zero to 10 were used. The 25-hydroxyvitamin D, which is the most important vitamin D metabolite, also was determined. The data was analyzed by SPSS-16. The Pearson’s correlation of coefficients, t-test, and multiple regression analysis were used in this study.

Results:

The mean fatigue score of nurses was 38.76±12.66 in questionnaire and 5.73±2.12 in Visual Analog Scale. The 89 per cent of nurses suffered from vitamin D deficiency, 9.5 percent of them had normal level and 1.5 per cent had toxicity level of vitamin D. There was a significant relationship between vitamin D level and fatigue scores (P<0.0001), and visual fatigue scores (P<0.0001). According to multivariate regression analysis, vitamin D level accounted for 13 per cent of the fatigue based on data on questionnaire and 18.6 per cent of fatigue according to Visual Analog Scale.

Conclusion:

High prevalence of fatigue among nurses could be attributed to vitamin D deficiency.

Role of vitamin D in cytotoxic T lymphocyte immunity to pathogens and cancer

The discovery of vitamin D receptor (VDR) expression in immune cells has opened up a new area of research into immunoregulation by vitamin D, a niche that is distinct from its classical role in skeletal health. Today, about three decades since this discovery, numerous cellular and molecular targets of vitamin D in the immune system have been delineated. Moreover, strong clinical associations between vitamin D status and the incidence/severity of many immune-regulated disorders (e.g. infectious diseases, cancers and autoimmunity) have prompted the idea of using vitamin D supplementation to manipulate disease outcome. While much is known about the effects of vitamin D on innate immune responses and helper T (T(H)) cell immunity, there has been relatively limited progress on the frontier of cytotoxic T lymphocyte (CTL) immunity--an arm of host cellular adaptive immunity that is crucial for the control of such intracellular pathogens as human immunodeficiency virus (HIV), tuberculosis (TB), malaria, and hepatitis C virus (HCV). In this review, we discuss the strong historical and clinical link between vitamin D and infectious diseases that involves cytotoxic T lymphocyte (CTL) immunity, present our current understanding as well as critical knowledge gaps in the realm of vitamin D regulation of host CTL responses, and highlight potential regulatory connections between vitamin D and effector and memory CD8 T cell differentiation events during infections.

Vitamin D attenuates pro-inflammatory TNF-α cytokine expression by inhibiting NF-кB/p65 signaling in hypertrophied rat hearts

A growing body of evidence suggests that immune activation and inflammatory mediators may play a key role in the development and progression of left ventricle (LV) hypertrophy. The present study was designed to test the hypothesis that the cardioprotective effect of cholecalciferol (Vit-D3) is mediated via the regulation of messenger RNA (mRNA) expression of pro-inflammatory cytokines. Rats were randomly divided into four groups: control group received normal saline (0.9 % NaCl) i.p. for 14 days; Vit-D3 group received Vit-D3 at a dose of 12 μg/kg/day by gavage for 14 days; ISO group received saline for 7 days, and at day 7, ISO (5 mg/kg/day) was injected i.p. for 7 consecutive days to induce cardiac hypertrophy; and Vit-D3 + ISO group was treated with Vit-D3 for 14 days, and at day 7, ISO was administered for 7 consecutive days. Heart/body weight ratio, troponin-T, creatine kinase-MB, and tumor necrosis factor-α (TNF-α) levels of LV tissue were estimated. Levels of mRNA expression of NF-кB (NF-кB)/p65 and inhibitory kappa B (IкB)-α were determined by real-time PCR. Vit-D3 administration before and during induction of cardiac hypertrophy significantly reduced (P < 0.001) cardiac biomarkers. The histopathological examination further confirmed these results. In addition, Vit-D3 significantly decreased (P < 0.001) NF-кB-p65 mRNA expression and increased (P < 0.01) IкB-α mRNA expression in LV tissues compared to ISO group. Based on these findings, it was concluded that the administration of cholecalciferol markedly attenuated the development of ISO-induced cardiac hypertrophy likely through downregulation of TNF-α /NF-кb/p65 signaling pathways. However, it should be pointed out that other signaling pathways may contribute to the cardioprotective effect of Vit-D3 which requires further investigation.

Non-classical mechanisms of transcriptional regulation by the vitamin D receptor: insights into calcium homeostasis, immune system regulation and cancer chemoprevention

Hormonal 1,25-dihydroxyvitamin D [1,25(OH)2D] signals through the nuclear vitamin D receptor (VDR), a ligand-regulated transcription factor. Gene expression profiling studies have revealed that 1,25(OH)2D signaling through the VDR can lead to activation or repression of target gene transcription in roughly equal proportions. Classically, transcriptional regulation by the VDR, similar to other nuclear receptors, has been characterized by its capacity to recognize high affinity cognate vitamin D response elements (VDREs), located in the regulatory regions of target genes. Several biochemical studies revealed that the VDRE-bound receptor recruits a series of coregulatory proteins, leading to transactivation of adjacent target genes. However, genome-wide and other analyses of VDR binding have revealed that a subset of VDR binding sites does not contain VDREs, and that VDREs are not associated with transcriptionally repressed VDR target genes. Work over the last ∼20 years and in particular recent findings have revealed a diverse array of mechanisms by which VDR can form complexes with several other classes of transcriptional activators, leading to repression of gene transcription. Moreover, these efforts have led to several insights into the molecular basis for the physiological regulation of calcium homeostasis, immune system function and cancer chemoprevention by 1,25(OH)2D/VDR signaling. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.

Curcuma Contra Cancer? Curcumin and Hodgkin's Lymphoma

Curcumin, a phytochemical isolated from curcuma plants which are used as coloring ingredient for the preparation of curry powder, has several activities which suggest that it might be an interesting drug for the treatment or prevention of cancer. Curcumin targets different pathways which are involved in the malignant phenotype of tumor cells, including the nuclear factor kappa B (NFKB) pathway. This pathway is deregulated in multiple tumor entities, including Hodgkin’s lymphoma (HL). Indeed, curcumin can inhibit growth of HL cell lines and increases the sensitivity of these cells for cisplatin. In this review we summarize curcumin activities with special focus on possible activities against HL cells.

NFκB pathway is down-regulated by 1α,25(OH)(2)-vitamin D(3) in endothelial cells transformed by Kaposi sarcoma-associated herpes virus G protein coupled receptor

We have previously demonstrated that 1α,25 dihydroxy-vitamin D(3) (1α,25(OH)(2)D(3)) has antiproliferative effects on the growth of endothelial cells transformed by the viral G protein-coupled receptor associated to Kaposi sarcoma (vGPCR). In this work, we have investigated whether 1α,25(OH)(2)D(3) exerts its growth inhibitory effects by inhibiting the Nuclear Factor κ B (NFκB) pathway which is highly activated by vGPCR. Cell proliferation studies demonstrated that 1α,25(OH)(2)D(3), similarly to bortezomib, a proteosome inhibitor that suppresses the activation of NFκB, reduced the proliferation of endothelial cells transformed by vGPCR (SVEC-vGPCR). The activity of NFκB in these cells decreased by 70% upon 1α,25(OH)(2)D(3) treatment. Furthermore, time and dose response studies showed that the hormone significantly decreased NFκB and increased IκBα mRNA and protein levels in SVEC-vGPCR cells, whereas in SVEC only IκBα increased significantly. Moreover, NFκB translocation to the nucleus was inhibited and occurred by a mechanism independent of NFκB association with vitamin D(3) receptor (VDR). 1α,25(OH)(2)D(3)-induced increase in IκBα required de novo protein synthesis, and was independent of MAPK and PI3K/Akt pathways. Altogether, these results suggest that down-regulation of the NFκB pathway is part of the mechanism involved in the antiproliferative effects of 1α,25(OH)(2)D(3) on endothelial cells transformed by vGPCR.

Vitamin D and influenza

Vitamin D has become increasingly recognized in the literature for its extra-skeletal roles, including an effect on inflammation and the immune response to infection. Our goal was to describe the role of vitamin D in the immune response and implications for the risk of influenza infection in humans. In this review, we first consider literature that provides molecular and genetic support to the idea that vitamin D is related to the adaptive and innate immune responses to influenza infection in vitro and in animal models. We then discuss observational studies and randomized controlled trials of vitamin D supplementation in humans. Finally, we consider some of the knowledge gaps surrounding vitamin D and immune response that must be filled.

1,25-dihydroxyvitamin D3 impairs NF-κB activation in human naïve B cells

1α,25-dihydroxyvitamin D(3) (calcitriol), the bioactive metabolite of vitamin D, modulates the activation and inhibits IgE production of anti-CD40 and IL-4 stimulated human peripheral B cells. Engagement of CD40 results in NF-κB p50 activation, which is essential for the class switch to IgE. Herein, we investigated by which mechanism calcitriol modulates NF-κB mediated activation of human naïve B cells. Naïve B cells were predominantly targeted by calcitriol in comparison with memory B cells as shown by pronounced induction of the VDR target gene cyp24a1. Vitamin D receptor activation resulted in a strongly reduced p105/p50 protein and mRNA expression in human naïve B cells. This effect is mediated by impaired nuclear translocation of p65 and consequently reduced binding of p65 to its binding site in the p105 promoter. Our data indicate that the vitamin D receptor reduces NF-κB activation by interference with NF-κB p65 and p105. Thus, the vitamin D receptor inhibits costimulatory signal transduction in naïve B cells, namely by reducing CD40 signaling.

Blocking of PI3K/AKT induces apoptosis by its effect on NF-κB activity in gastric carcinoma cell line SGC7901

NF-κB plays an important role in many aspects of tumorigenesis and tumor progression by its antiapoptosis effect. Hence, NF-κB has been regarded as a therapeutic target in cancer, because inhibition of NF-κB not only induces enhancing apoptosis but also causes increasing sensitivity to radiation or chemotherapy in several tumor cells. The activation of NF-κB is presumed to be associated with PI3K/Akt signal pathway in gastric carcinoma, but the underlying molecular mechanism remains unclear. Our work demonstrates that blocking PI3K/Akt by LY294002 inhibits the NF-κB activity with significantly increased apoptosis in gastric cancer cell. Furthermore, when the cells were pretreated with IKK siRNA and/or IκB siRNA then exposed to LY294002, the results suggest that the regulatory significantly increased apoptosis in gastric cancer cell. Furthermore, when the cells were pretreated, effect of PI3K/AKT on NF-κB activity is associated with the influence of PI3K/AKT on IKK/IκB. The apoptosis induced by blocking PI3K/AKT might be ascribed to inhibition of NF-κB activity through IKK/IκB at least in part.

Isoforms of p38MAPK gamma and delta contribute to differentiation of human AML cells induced by 1,25-dihydroxyvitamin D₃

Inhibition of p38MAPK alpha/beta is known to enhance 1,25-dihydroxyvitamin (1,25D)-induced monocytic differentiation, but the detailed mechanism of this effect was not clear. We now show that the enhancement of differentiation becomes apparent with slow kinetics (12-24 h). Interestingly, the inhibition of p38MAPK alpha/beta by their selective inhibitor SB202190 (SB) leads to an upregulated expression of p38MAPK isoforms gamma and delta in 1,25D-treated AML cells, in cell lines and in primary culture. Although the expression and activating phosphorylations of p38MAPK alpha are also increased by an exposure of the cells to SB, its kinase activity is blocked by SB, as shown by reduced levels of phosphorylated Hsp27, a downstream target of p38MAPK alpha. A positive role of p38MAPKs in 1,25D-induced differentiation is shown by the inhibition of differentiation by antisense oligonucleotides to all p38MAPK isoforms. Other principal branches of MAPK pathways showed early (6 h) activation of MEK/ERK by SB, followed by activation of JNK1/2 pathway and enhanced expression and/or activation of PU.1, ATF-2 differentiation-related transcription factors. Taken together with previous reports, the results indicate that 1,25D-induced differentiation is enhanced by the activation of at least three branches of MAPK pathways (ERK1/2; p38MAPK gamma/delta; JNK1/2). This activation may result from the removal of feedback inhibition of an upstream regulator of those pathways, when p38MAPK alpha and beta are inhibited by SB.

Vitamin D and respiratory health

Vitamin D is now known to be of physiological importance outside of bone health and calcium homeostasis, and there is mounting evidence that it plays a beneficial role in the prevention and/or treatment of a wide range of diseases. In this brief review the known effects of vitamin D on immune function are described in relation to respiratory health. Vitamin D appears capable of inhibiting pulmonary inflammatory responses while enhancing innate defence mechanisms against respiratory pathogens. Population-based studies showing an association between circulating vitamin D levels and lung function provide strong justification for randomized controlled clinical trials of vitamin D supplementation in patients with respiratory diseases to assess both efficacy and optimal dosage.

Vitamin-regulated cytokines and growth factors in the CNS and elsewhere

There is a growing awareness that natural vitamins (with the only exception of pantothenic acid) positively or negatively modulate the synthesis of some cytokines and growth factors in the CNS, and various mammalian cells and organs. As natural vitamins are micronutrients in the human diet, studying their effects can be considered a part of nutritional genomics or nutrigenomics. A given vitamin selectively modifies the synthesis of only a few cytokines and/or growth factors, although the same cytokine and/or growth factor may be regulated by more than one vitamin. These effects seem to be independent of the effects of vitamins as coenzymes and/or reducing agents, and seem to occur mainly at genomic and/or epigenetic level, and/or by modulating NF-kappaB activity. Although most of the studies reviewed here have been based on cultured cell lines, but their findings have been confirmed by some key in vivo studies. The CNS seems to be particularly involved and is severely affected by most avitaminoses, especially in the case of vitamin B(12). However, the vitamin-induced changes in cytokine and growth factor synthesis may initiate a cascade of events that can affect the function, differentiation, and morphology of the cells and/or structures not only in the CNS, but also elsewhere because most natural vitamins, cytokines, and growth factors cross the blood-brain barrier. As cytokines are essential to CNS-immune and CNS-hormone system communications, natural vitamins also interact with these circuits. Further studies of such vitamin-mediated effects could lead to vitamins being used for the treatment of diseases which, although not true avitaminoses, involve an imbalance in cytokine and/or growth factor synthesis.

5-Lipoxygenase inhibitors potentiate 1alpha,25-dihydroxyvitamin D3-induced monocytic differentiation by activating p38 MAPK pathway

The treatment of human promyelocytic leukemia cell lines HL-60, and to some extent NB-4, with 1alpha,25-dihydroxyvitamin D(3) (VD3) induces differentiation toward the monocytic/macrophage lineage, demonstrated by the increased expression of CD11b and CD14, and the production of opsonized zymosan particles (OZP)-stimulated reactive oxygen species (ROS). Moreover, in more sensitive HL-60 cells, increased expression of 5-lipoxygenase (5-LPO), Mcl-1, IkappaB, and c-Jun, accompanied by the activation of p38 MAPK, was detected. These VD3 effects on HL-60 cell differentiation were significantly potentiated by 5-LPO inhibitors MK-886 and AA-861 and were inverted by SB202190 (SB), a p38 MAPK inhibitor. The inhibition of differentiation by SB was demonstrated by a reduction of CD14 expression and by a decrease in OZP-activated ROS production. These results indicated that p38 MAPK pathway is involved in 5-LPO inhibitors-dependent potentiation of VD3-induced monocytic differentiation.

Monocytic differentiation of leukemic HL-60 cells induced by co-treatment with TNF-alpha and MK886 requires activation of pro-apoptotic machinery

The block of hematopoietic differentiation program in acute myeloid leukemia cells can be overcome by differentiating agent like retinoic acid, but it has several side effects. A study of other differentiation signaling pathways is therefore useful to predict potential targets of anti-leukemic therapy. We demonstrated previously that the co-treatment of HL-60 cells with Tumor necrosis factor-alpha (TNF-alpha) (1 ng/mL) and inhibitor of 5-lipoxygenase MK886 (5 microm) potentiated both monocytic differentiation and apoptosis. In this study, we detected enhanced activation of three main types of mitogen-activated protein kinases (MAPKs) (p38, c-Jun amino-terminal kinase [JNK], extracellular signal-regulated kinase [ERK]), so we assessed their role in differentiation using appropriate pharmacologic inhibitors. The inhibition of pro-apoptotic MAPKs (p38 and JNK) suppressed the effect of MK886 + TNF-alpha co-treatment. On the other hand, down-regulation of pro-survival ERK pathway led to increased differentiation. Those effects were accompanied by increased activation of caspases in cells treated by MK886 + TNF-alpha. Pan-caspase inhibitor ZVAD-fmk significantly decreased both number of apoptotic and differentiated cells. The same effect was observed after inhibition of caspase 9, but not caspase 3 and 8. To conclude, we evidenced that the activation of apoptotic processes and pathways supporting apoptosis (p38 and JNK MAPKs) is required for the monocytic differentiation of HL-60 cells.

The vitamin D receptor-mediated activation of phosphatidylinositol 3-kinase (PI3Kα) plays a role in the 1α,25-dihydroxyvitamin D3-stimulated increase in steroid sulphatase activity in myeloid leukaemic cell lines

In this article we show that 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) stimulates the activity of the class IA phosphatidylinositol 3-kinase PI3Kalpha and its downstream target Akt in HL60, U937 and THP-1 myeloid leukaemic cell lines. Furthermore, we show that the classical nuclear vitamin D receptor (VDR(nuc)) is involved in this activation of the PI3K/Akt signalling in these cell lines. We have previously shown that the activity of steroid sulphatase is stimulated in HL60, U937 and THP-1 myeloid leukaemic cell lines by 1alpha,25(OH)(2)D(3) (Hughes et al., [2001] Biochem J 355:361-371; Hughes et al., [2005] J Cell Biochem 94:1175-1189; Hughes and Brown [2006] J Cell Biochem 98:590-617). In this article we show that the 1alpha,25(OH)(2)D(3)-stimulated increase in signalling via the PI3K/Akt pathway plays a role in the increase in steroid sulphatase activity in the HL60 U937 and THP-1 cell lines. We used a variety of pharmacological and biochemical approaches to show that activation of PI3Kalpha mediates the 1alpha,25(OH)(2)D(3)-stimulated increase in steroid sulphatase activity in myeloid leukaemic cells. We also show that the PI3K/Akt dependent activation of NF-kappaB plays a role in the 1alpha,25(OH)(2)D(3)-stimulated increase in steroid sulphatase activity in myeloid leukaemic cells.