Direct transcriptional regulation of RelB by 1alpha,25-dihydroxyvitamin D3 and its analogs: physiologic and therapeutic implications for dendritic cell function

Vitamin D in Central Nervous System: Implications for Neurological Disorders

Vitamin D, obtained from diet or synthesized internally as cholecalciferol and ergocalciferol, influences bodily functions through its most active metabolite and the vitamin D receptor. Recent research has uncovered multiple roles for vitamin D in the central nervous system, impacting neural development and maturation, regulating the dopaminergic system, and controlling the synthesis of neural growth factors. This review thoroughly examines these connections and investigates the consequences of vitamin D deficiency in neurological disorders, particularly neurodegenerative diseases. The potential benefits of vitamin D supplementation in alleviating symptoms of these diseases are evaluated alongside a discussion of the controversial findings from previous intervention studies. The importance of interpreting these results cautiously is emphasised. Furthermore, the article proposes that additional randomised and well-designed trials are essential for gaining a deeper understanding of the potential therapeutic advantages of vitamin D supplementation for neurological disorders. Ultimately, this review highlights the critical role of vitamin D in neurological well-being and highlights the need for further research to enhance our understanding of its function in the brain.

NRF2 Plays a Crucial Role in the Tolerogenic Effect of Ethyl Pyruvate on Dendritic Cells

Ethyl pyruvate (EP) is a redox-active compound that has been previously shown to be effective in restraining immune hyperactivity in animal models of various autoimmune and chronic inflammatory diseases. Importantly, EP has also been proven to have a potent tolerogenic effect on dendritic cells (DCs). Here, the influence of EP on the signaling pathways in DCs relevant for their tolerogenicity, including anti-inflammatory NRF2 and pro-inflammatory NF-κB, was explored. Specifically, the effects of EP on DCs obtained by GM-CSF-directed differentiation of murine bone marrow precursor cells and matured under the influence of lipopolysaccharide (LPS) were examined via immunocytochemistry and RT-PCR. EP counteracted LPS-imposed morphological changes and down-regulated the LPS-induced expression of pro-inflammatory mediators in DCs. While it reduced the activation of NF-κB, EP potentiated NRF2 and downstream antioxidative molecules, thus implying the regulation of NRF2 signaling pathways as the major reason for the tolerizing effects of EP on DCs.

BRD4/nuclear PD-L1/RelB circuit is involved in the stemness of breast cancer cells

BACKGROUND

Breast cancer (BC) is the most common cancer diagnosed in women worldwide. BC stem cells (BCSCs) have been known to be involved in the carcinogenesis of the breast and contribute to therapeutic resistance. The programmed death-ligand 1 (PD-L1) expression of BC correlated with a poor prognosis. Immunotherapies that target PD-L1 have great potential and have been successful when applied to cancer treatment. However, whether PD-L1 regulates BCSC formation is unknown.

METHODS

BCSCs were enriched by serum-free suspension culture. The properties of BCSCs were examined by mammosphere formation assay, CD44+/Cd24-, aldehyde dehydrogenase (ALDH) assay, CSC marker analysis, and mammosphere growth assay. To elucidate the functions of bromodomain-containing protein 4 (BRD4), nuclear PD-L1, and RelB proteins in the stemness of BCSCs, mammosphere formation was examined using BRD4 inhibitor and degrader, PD-L1 degrader, and RelB inhibitor. The antitumor function of 3',4',7,8-tetrahydroxyflavone (THF), a specific BRD4 inhibitor, was studied through in vivo tumor model and mouse studies, and the protein levels of c-Myc, PD-L1, and RelB were examined in tumor model under THF treatment.

RESULTS

BRD4 was upregulated in breast CSCs and regulates the stemness of BCs. The downregulation of BRD4 using BRD4 PROTAC, ARV-825, and BRD4 inhibitor, (+)-JQ1, inhibits mammosphere formation and reduces the levels of breast CSC markers (CD44+/CD24- and ALDH1), stem cell marker genes, and mammosphere growth. BRD4 inhibitor (JQ1) and degrader (ARV825) downregulate membrane and nuclear fractions of PD-L1 through the inhibition of PD-L1 transcript levels. The knockdown of PD-L1 inhibits mammosphere formation. Verteporfin, a PD-L1 degrader, inhibits the transcripts and protein levels of PD-L1 and downregulates the transcript and protein levels of RelB. Calcitriol, a RelB inhibitor, and the knockdown of RelB using si-RelB regulate mammosphere formation through interleukin-6 (IL-6) expression. THF is a natural product and a potent selective BRD4 inhibitor, inhibits mammosphere formation, and reduces the levels of CD44+/CD24- and mammosphere growth by downregulating c-Myc, PD-L1, and RelB. 3',4',7,8-THF shows tumoricidal activity and increased levels of CD3+CD4+ and CD3+CD8+ T-cells in the tumor and tumor-draining lymph nodes (TDLNs) in the murine tumor model using 4T1 and MC38 cells.

CONCLUSIONS

The results show the first evidence of the essential role of the BRD4/nuclear PD-L1/RelB axis in breast CSC formation. The nuclear PD-L1 regulates RelB, and the RelB/p65 complex induces IL6 and breast CSC formation. Targeting nuclear PD-L1 represents a potential and novel tool for immunotherapies of intractable BC. Video Abstract.

Vitamin D and COVID-19: where are we now?

The pandemic caused by the SARS-CoV-2 virus has triggered great interest in the search for the pathophysiological mechanisms of COVID-19 and its associated hyperinflammatory state. The presence of prognostic factors such as diabetes, cardiovascular disease, hypertension, obesity, and age influence the expression of the disease's clinical severity. Other elements, such as 25-hydroxyvitamin D (25(OH)D3) concentrations, are currently being studied. Various studies, mostly observational, have sought to demonstrate whether there is truly a relationship between 25(OH)D3 levels and the acquisition and/or severity of the disease. The objective of this study was to carry out a review of the current data that associate vitamin D status with the acquisition, evolution, and/or severity of infection by the SARS-CoV-2 virus and to assess whether prevention through vitamin D supplementation can prevent infection and/or improve the evolution once acquired. Vitamin D system has an immunomodulatory function and plays a significant role in various bacterial and viral infections. The immune function of vitamin D is explained in part by the presence of its receptor (VDR) and its activating enzyme 25-hydroxyvitamin D-1alpha-hydroxylase (CYP27B1) in immune cells. The vitamin D, VDR, and Retinoid X Receptor complex allows the transcription of genes with antimicrobial activities, such as cathelicidins and defensins. COVID-19 characteristically presents a marked hyperimmune state, with the release of proinflammatory cytokines such as IL-6, TNF-α, and IL-1β. Thus, there are biological factors linking vitamin D to the cytokine storm, which can herald some of the most severe consequences of COVID-19, such as acute respiratory distress syndrome. Hypovitaminosis D is widespread worldwide, so the prevention of COVID-19 through vitamin D supplementation is being considered as a possible therapeutic strategy easy to implement. However, more-quality studies and well-designed randomized clinical trials are needed to address this relevant question.

A Vitamin D-RelB/NF-κB Pathway Limits Chandipura Virus Multiplication by Rewiring the Homeostatic State of Autoregulatory Type 1 IFN-IRF7 Signaling

Besides its functions in the skeletomuscular system, vitamin D is known to alleviate viral-inflicted pathologies. However, the mechanism underlying protective vitamin D function remains unclear. We examined the role of vitamin D in controlling cellular infections by Chandipura virus, an RNA virus implicated in human epidemics. How immune signaling pathways, including those regulating NF-κB and IFN regulatory factors (IRFs), are activated in virus-infected cells has been well studied. Our investigation involving human- and mouse-derived cells revealed that vitamin D instructs the homeostatic state of these antiviral pathways, leading to cellular resilience to subsequent viral infections. In particular, vitamin D provoked autoregulatory type 1 IFN-IRF7 signaling even in the absence of virus infection by downmodulating the expression of the IFN-inhibitory NF-κB subunit RelB. Indeed, RelB deficiency rendered vitamin D treatment redundant, whereas IRF7 depletion abrogated antiviral vitamin D action. In sum, immune signaling homeostasis appears to connect micronutrients to antiviral immunity at the cellular level. The proposed link may have a bearing on shaping public health policy during an outbreak.

Vitamin D3 Priming of Dendritic Cells Shifts Human Neutrophil-Dependent Th17 Cell Development to Regulatory T Cells

Vitamin D3 (VD3) is a potential adjuvant for use in tolerogenic vaccine formulations that target dendritic cells (DCs) for the treatment of chronic inflammatory disorders, e.g., autoimmune diseases. These disorders are often associated with enhanced activity of IL-17-producing T helper 17 (Th17) cells which develop in a DC-driven and neutrophil-dependent fashion. Here, we investigated the effect of VD3 on Candida albicans-specific human T-cell differentiation, since C. albicans is a model pathogen for Th17 cell development. VD3 priming of DCs restricted neutrophil-dependent Th17 cell development and neutrophil-independent Th1 cell formation from naive CD4⁺ T cells. In line with this, the production of Th1/Th17-polarizing cytokines IL-12 and IL-23 by DCs was reduced by VD3 priming. Development of both FoxP3⁺CD127_lowCD25⁺ Tregs and IL-10-producing T cells was significantly enhanced in VD3-primed conditions, even in the presence of neutrophils. ICOS⁺ Tregs, major IL-10 producers, CD69⁺FoxP3⁺, and TIGIT⁺FoxP3⁺ Tregs were significantly induced by VD3 priming as well. Our data support the potential use of VD3 as an adjuvant to induce tolerance in the treatment of autoimmune disorders, including those in which neutrophils are involved in pathogenesis, since we show that Treg development is enhanced by VD3 even in the presence of neutrophils, while Th17 cell development is restricted.

The Role of Vitamin D in Sleep Disorders of Children and Adolescents: A Systematic Review

This review investigates the association between vitamin D and sleep disorders. Vitamin D is an essential nutrient known to play an important role in the growth and bone health of the human body, but it also appears to play a role in sleep. The goal of our review is to examine the association between vitamin D and sleep disorders in children and adolescents. We summarize the evidence about the role and the mechanism of action of vitamin D in children and adolescents with sleep disorders such as insomnia, obstructive sleep apnea (OSA), restless legs syndrome (RLS), and other sleep disorders. Systematic electronic database searches were conducted using Pubmed and Cochrane Library. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline was followed. The studies that met the established inclusion criteria were analyzed and compared. Results suggest a strict relationship between vitamin D deficiency in children and sleep disorders. There is evidence that vitamin D is implicated in the different neurochemical mechanisms involved in sleep regulation and mainly in the serotonergic and dopaminergic pathways. This might be responsible for the association of vitamin D deficiency and restless sleep, sleep hyperhidrosis, OSA, and RLS.

A novel treatment for skin repair using a combination of spironolactone and vitamin D3

Injury of the skin from exposure to toxic chemicals leads to the release of inflammatory mediators and the recruitment of immune cells. Nitrogen mustard (NM) and other alkylating agents cause severe cutaneous damage for which there are limited treatment options. Here, we show that combined treatment of vitamin D3 (VD3) and spironolactone (SP), a mineralocorticoid receptor antagonist, significantly improves the resolution of inflammation and accelerates wound healing after NM exposure. SP enhanced the inhibitory effect of VD3 on nuclear factor-kB activity. Combined treatment of NM-exposed mice with VD3 and SP synergistically inhibited the expression of iNOS in the skin and decreased the expression of matrix metallopeptidase-9, C-C motif chemokine ligand 2, interleukin (IL)-1α, and IL-1β. The combined treatment decreased the number of local proinflammatory M1 macrophages resulting in an increase in the M2/M1 ratio in the wound microenvironment. Apoptosis was also decreased in the skin after combined treatment. Together, this creates a proresolution state, resulting in more rapid wound closure. Combined VD3 and SP treatment is effective in modulating the immune response and activating anti-inflammatory pathways in macrophages to facilitate tissue repair. Altogether, these data demonstrate that VD3 and SP may constitute an effective treatment regimen to improve wound healing after NM or other skin chemical injury.

Dendritic Cells as Arbiters of Peritoneal Immune Responses

During the past few years, there has been a substantial increase in the understanding of innate immunity. Dendritic cells are emerging as key players in the orchestration of this early phase of immune responses, with a role that will translate into the subsequent type of adaptive immune response against infection. Here we provide an overview of dendritic cell differentiation and function, with particular emphasis on those features unique to the immune defense of the peritoneal cavity and in the context of peritoneal dialysis-associated immune responses. The reader is referred to the primary references included in the accompanying list for specific details in this fascinating field.

Biological characteristics of transcription factor RelB in different immune cell types: implications for the treatment of multiple sclerosis

Transcription factor RelB is a member of the nuclear factror-kappa B (NF-κB) family, which plays a crucial role in mediating immune responses. Plenty of studies have demonstrated that RelB actively contributes to lymphoid organ development, dendritic cells maturation and function and T cells differentiation, as well as B cell development and survival. RelB deficiency may cause a variety of immunological disorders in both mice and humans. Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system which involves a board of immune cell populations. Thereby, RelB may exert an impact on MS by modulating the functions of dendritic cells and the differentiation of T cells and B cells. Despite intensive research, the role of RelB in MS and its animal model, experimental autoimmune encephalomyelitis, is still unclear. Herein, we give an overview of the biological characters of RelB, summarize the updated knowledge regarding the role of RelB in different cell types that contribute to MS pathogenesis and discuss the potential RelB-targeted therapeutic implications for MS.

PD-L1- and calcitriol-dependent liposomal antigen-specific regulation of systemic inflammatory autoimmune disease

Autoimmune diseases resulting from MHC class II-restricted autoantigen-specific T cell immunity include the systemic inflammatory autoimmune conditions rheumatoid arthritis and vasculitis. While currently treated with broad-acting immunosuppressive drugs, a preferable strategy is to regulate antigen-specific effector T cells (Teffs) to restore tolerance by exploiting DC antigen presentation. We targeted draining lymph node (dLN) phagocytic DCs using liposomes encapsulating 1α,25-dihydroxyvitamin D3 (calcitriol) and antigenic peptide to elucidate mechanisms of tolerance used by DCs and responding T cells under resting and immunized conditions. PD-L1 expression was upregulated in dLNs of immunized relative to naive mice. Subcutaneous administration of liposomes encapsulating OVA323-339 and calcitriol targeted dLN PD-L1hi DCs of immunized mice and reduced their MHC class II expression. OVA323-339/calcitriol liposomes suppressed expansion, differentiation, and function of Teffs and induced Foxp3+ and IL-10+ peripheral Tregs in an antigen-specific manner, which was dependent on PD-L1. Peptide/calcitriol liposomes modulated CD40 expression by human DCs and promoted Treg induction in vitro. Liposomes encapsulating calcitriol and disease-associated peptides suppressed the severity of rheumatoid arthritis and Goodpasture's vasculitis models with suppression of antigen-specific memory T cell differentiation and function. Accordingly, peptide/calcitriol liposomes leverage DC PD-L1 for antigen-specific T cell regulation and induce antigen-specific tolerance in inflammatory autoimmune diseases.

Immunomodulatory liposomes targeting liver macrophages arrest progression of nonalcoholic steatohepatitis

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) is characterized by hepatic macrophage inflammation, steatosis and fibrosis. Liposomes injected intravenously passively target hepatic myeloid cells and have potential to deliver immunomodulatory compounds and treat disease. We investigated targeting, delivery, immunomodulation and efficacy of liposomes in mice with diet-induced NASH.

METHODS

Liposome-encapsulated lipophilic curcumin or 1,25-dihydroxy-vitamin D3 (calcitriol) were injected intravenously into mice with diet-induced NASH. Liver and cell liposome uptake was assessed by in vivo imaging and flow cytometry. Immunomodulation of targeted cells were assessed by RNA transcriptome sequencing. NASH was assessed by histological scoring, serum liver enzymes and fasting glucose/insulin and liver RNA transcriptome sequencing.

RESULTS

Liposomes targeted lipid containing MHC class-II⁺ hepatic dendritic cells in mice and humans. Delivery of liposomal curcumin to hepatic dendritic cells shifted their inflammatory profile towards a regulatory phenotype. Delivery of liposomal curcumin or calcitriol to mice with diet-induced NASH led to reduced liver inflammation, fibrosis and fat accumulation, and reduced insulin resistance. RNA transcriptome sequencing of liver from treated mice identified suppression of pathways of immune activation, cell cycle and collagen deposition.

CONCLUSIONS

Liposomes are a new strategy to target lipid rich inflammatory dendritic cells and have potential to deliver immunomodulatory compounds to treat NASH.

Vitamin D endocrinology on the cross-road between immunity and metabolism

The effects of vitamin D on the immune function have been recognized for more than a quarter of a century. However, our understanding of the multifactorial nature of the effects of vitamin D at the cellular, molecular and metabolic level in different immune cells of the innate and adaptive immune system has dramatically progressed during the last decades. In this review, we summarize the main metabolic pathways preferentially used in different subsets of macrophages, dendritic cells, T and B cells as well as the immunomodulatory effects of vitamin D on these cells. We will highlight the metabolic reprogramming happening in vitamin D-conditioned tolerogenic dendritic cells. A better knowledge of the dynamics of metabolic states in immune subsets and their possible roles in inflammation and autoimmunity may advance the development of novel immunotherapies. Likewise, the implications of effects of vitamin D on immunometabolism may progress our insights in the nature of immune responses in health and disease.

Integration of VDR genome wide binding and GWAS genetic variation data reveals co-occurrence of VDR and NF-κB binding that is linked to immune phenotypes

Background

The nuclear hormone receptor superfamily acts as a genomic sensor of diverse signals. Their actions are often intertwined with other transcription factors. Nuclear hormone receptors are targets for many therapeutic drugs, and include the vitamin D receptor (VDR). VDR signaling is pleotropic, being implicated in calcaemic function, antibacterial actions, growth control, immunomodulation and anti-cancer actions. Specifically, we hypothesized that the biologically significant relationships between the VDR transcriptome and phenotype-associated biology could be discovered by integrating the known VDR transcription factor binding sites and all published trait- and disease-associated SNPs. By integrating VDR genome-wide binding data (ChIP-seq) with the National Human Genome Research Institute (NHGRI) GWAS catalog of SNPs we would see where and which target gene interactions and pathways are impacted by inherited genetic variation in VDR binding sites, indicating which of VDR’s multiple functions are most biologically significant.

Results

To examine how genetic variation impacts VDR function we overlapped 23,409 VDR genomic binding peaks from six VDR ChIP-seq datasets with 191,482 SNPs, derived from GWAS-significant SNPs (Lead SNPs) and their correlated variants (r² > 0.8) from HapMap3 and the 1000 genomes project. In total, 574 SNPs (71 Lead and 503 SNPs in linkage disequilibrium with Lead SNPs) were present at VDR binding loci and associated with 211 phenotypes. For each phenotype a hypergeometric test was used to determine if SNPs were enriched at VDR binding sites. Bonferroni correction for multiple testing across the 211 phenotypes yielded 42 SNPs that were either disease- or phenotype-associated with seven predominately immune related including self-reported allergy; esophageal cancer was the only cancer phenotype. Motif analyses revealed that only two of these 42 SNPs reside within a canonical VDR binding site (DR3 motif), and that 1/3 of the 42 SNPs significantly impacted binding and gene regulation by other transcription factors, including NF-κB. This suggests a plausible link for the potential cross-talk between VDR and NF-κB.

Conclusions

These analyses showed that VDR peaks are enriched for SNPs associated with immune phenotypes suggesting that VDR immunomodulatory functions are amongst its most important actions. The enrichment of genetic variation in non-DR3 motifs suggests a significant role for the VDR to bind in multimeric complexes containing other transcription factors that are the primary DNA binding component. Our work provides a framework for the combination of ChIP-seq and GWAS findings to provide insight into the underlying phenotype-associated biology of a given transcription factor.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3481-4) contains supplementary material, which is available to authorized users.

Vitamin D3 inhibits TNFα-induced latent HIV reactivation in J-LAT cells

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) is known to suppress NF-kB activity by interfering with its pathways. The aim of this study was to investigate the ability of 1,25(OH)2D3 in reducing the reactivation of the HIV virus J-LAT cells, an established model of latently infected cells, which were treated with TNFalpha (100 ng/ml) for 2 h with or without 24 h 1,25(OH)2D3 (100 nM) pretreatment. Reactivation of HIV RNA in J-LAT was evaluated in terms of green fluorescent protein (GFP) expression. The same experimental setting was repeated on T cells from HIV-infected patients. Treatment with TNFalpha was associated with a 16 % increase in GFP+ cells and a five-fold increase in unspliced HIV RNA expression (p < 0.04). Pretreatment of J-LAT cells with 1,25(OH)2D3 for 24 h followed by TNFalpha (100 ng/ml) for 2 h reduced the percentage of GFP+ cells by 8 %; moreover, a 2.4-fold decrease in unspliced HIV RNA expression was observed (p < 0.002). In T cells from patients, treatment with TNFalpha significantly increased unspliced HIV RNA expression (sixfold increase, p < 0.02), whereas prestimulation with 1,25(OH)2D3 reduced its expression (2.5-fold decrease, p < 0.02) compared to controls.1,25(OH)2D3 is able to reduce the ability of TNFalpha to upregulate the transcription of HIV RNA from latently infected cells. These data provide further understanding of the pathogenic mechanisms regulating viral reactivation from latent reservoirs, along with new insight in viral internalization.

Vitamin D improves corticosteroid efficacy and attenuates its side-effects in an animal model of asthma

The subacute use of corticosteroids has side-effects such as glucose intolerance, dyslipidemia, anxiety, and depression, which could be halted with vitamin D, which is an immunomodulatory vitamin. Thus, we aimed to study the anti-asthmatic efficacy and side-effects profile of vitamin D, the corticosteroid dexamethasone, and their combination on ovalbumin-induced airway inflammation in rats. For this, 2 different doses of vitamin D (50 IU/kg, daily for 2 weeks, or and 60000 IU/kg, bolus dose, by intraperitoneal injection (i.p.)) were administered in combination with dexamethasone (2.5 mg/kg, i.p., for 2 weeks) prior to challenge with ovalbumin. At the end of the therapy, the asthmatic parameters such as differential white blood cell counts, serum levels of immunoglobulin E, bronchoalveolar lavaged fluid, and interleukin-5, as well as serum levels of nitric oxide were significantly increased after allergen challenges in asthmatic rats as compared with the controls. Such increases were significantly attenuated by monotherapy with vitamin D and with combination therapy of vitamin D and dexamethasone, where the combination therapy was superior to the monotherapy. Dexamethasone-induced hyperglycemia, hyperlipidemia, and behavioral abnormalities in the allergic rats were attenuated with vitamin D. The daily dose was better for controlling serum levels of immunoglobulin E than the bolus dose, whereas the bolus was superior for reducing dexamethasone-induced psychotropic abnormalities. There were no significant changes in other parameters between the daily and the bolus dose. In conclusion, a daily dose of vitamin D in combination with dexamethasone is more efficacious for treating asthma in allergic rats than monotherapy.

Vitamin D inhibits lipopolysaccharide-induced inflammatory response potentially through the Toll-like receptor 4 signalling pathway in the intestine and enterocytes of juvenile Jian carp (Cyprinus carpio var. Jian)

The present study was conducted to investigate the anti-inflammatory effect of vitamin D both in juvenile Jian carp (Cyprinus carpio var. Jian) in vivo and in enterocytes in vitro. In primary enterocytes, exposure to 10 mg lipopolysaccharide (LPS)/l increased lactate dehydrogenase activity in the culture medium (P<0·05) and resulted in a significant loss of cell viability (P<0·05). LPS exposure increased (P<0·05) the mRNA expression of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6 and IL-8), which was decreased by pre-treatment with 1,25-dihydroxyvitamin D (1,25D3) in a dose-dependent manner (P<0·05). Further results showed that pre-treatment with 1,25D3 down-regulated Toll-like receptor 4 (TLR4), myeloid differentiation primary response gene 88 (Myd88) and NF-κB p65 mRNA expression (P<0·05), suggesting potential mechanisms against LPS-induced inflammatory response. In vivo, intraperitoneal injection of LPS significantly increased TNF-α, IL-1β, IL-6 and IL-8 mRNA expression in the intestine of carp (P<0·05). Pre-treatment of fish with vitamin D3 protected the fish intestine from the LPS-induced increase of TNF-α, IL-1β, IL-6 and IL-8 mainly by downregulating TLR4, Myd88 and NF-κB p65 mRNA expression (P<0·05). These observations suggest that vitamin D could inhibit LPS-induced inflammatory response in juvenile Jian carp in vivo and in enterocytes in vitro. The anti-inflammatory effect of vitamin D is mediated at least in part by TLR4-Myd88 signalling pathways in the intestine and enterocytes of juvenile Jian carp.

1,25-Dihydroxy-vitamin D3 regulates NK-cell cytotoxicity, cytokine secretion, and degranulation in women with recurrent pregnancy losses

Vitamin D has a pivotal role in regulating immune responses by promoting Th2 immune responses and suppressing Th1 responses. Propensities to a Th1 immune response and increased NK-cell levels and cytotoxicity have been reported in women with recurrent pregnancy losses (RPL). In women with RPL, vitamin D deficiency is prevalent; however, the effect of vitamin D on NK cells is largely unknown. In this study, we demonstrated that CD69(+) activating receptor expression on NK cells was significantly decreased by incubation with 1,25(OH)2 D3 in a dose-dependent manner, while CD158a and CD158b inhibitory receptor expression was upregulated. The degranulation marker CD107a was significantly downregulated on NK cells following incubation with 1,25(OH)2 D3 . NK-cell conjugation with K562 target cells was not affected by 1,25(OH)2 D3 ; however, depolarization of perforin granules in conjugated NK cells was significantly increased. TLR4 expression on NK cells was significantly decreased and TNF-α and IFN-γ production was significantly reduced by 1,25(OH)2 D3 through interference with NF-κB. Our results suggest 1,25(OH)2 D3 has immune regulatory effects on NK cell cytotoxicity, cytokine secretion and degranulation process as well as TLR4 expression. Potential therapeutic application of 1,25(OH)2 D3 for dysregulated NK-cell immunity should be explored in the future.

Impaired Vitamin D Signaling in Endothelial Cell Leads to an Enhanced Leukocyte-Endothelium Interplay: Implications for Atherosclerosis Development

Endothelial cell activation leading to leukocyte recruitment and adhesion plays an essential role in the initiation and progression of atherosclerosis. Vitamin D has cardioprotective actions, while its deficiency is a risk factor for the progression of cardiovascular damage. Our aim was to assess the role of basal levels of vitamin D receptor (VDR) on the early leukocyte recruitment and related endothelial cell-adhesion-molecule expression, as essential prerequisites for the onset of atherosclerosis. Knockdown of VDR in endothelial cells (shVDR) led to endothelial cell activation, characterized by upregulation of VCAM-1, ICAM-1 and IL-6, decreased peripheral blood mononuclear cell (PBMC) rolling velocity and increased PBMC rolling flux and adhesion to the endothelium. shVDR cells showed decreased IκBα levels and accumulation of p65 in the nucleus compared to shRNA controls. Inhibition of NF-κB activation with super-repressor IκBα blunted all signs of endothelial cell activation caused by downregulation of VDR in endothelial cells. In vivo, deletion of VDR led to significantly larger aortic arch and aortic root lesions in apoE^-/- mice, with higher macrophage content. apoE^-/-VDR^-/-mice showed higher aortic expression of VCAM-1, ICAM-1 and IL-6 when compared to apoE^-/-VDR^+/+ mice. Our data demonstrate that lack of VDR signaling in endothelial cells leads to a state of endothelial activation with increased leukocyte-endothelial cell interactions that may contribute to the more severe plaque accumulation observed in apoE^-/-VDR^-/- mice. The results reveal an important role for basal levels of endothelial VDR in limiting endothelial cell inflammation and atherosclerosis.

Vitamin D and immune function in chronic kidney disease

The common causes of death in chronic kidney disease (CKD) patients are cardiovascular events and infectious disease. These patients are also predisposed to the development of vitamin D deficiency, which leads to an increased risk of immune dysfunction. Many extra-renal cells possess the capability to produce local active 1,25(OH)2D in an intracrine or paracrine fashion, even without kidney function. Vitamin D affects both the innate and adaptive immune systems. In innate immunity, vitamin D promotes production of cathelicidin and β-defensin 2 and enhances the capacity for autophagy via toll-like receptor activation as well as affects complement concentrations. In adaptive immunity, vitamin D suppresses the maturation of dendritic cells and weakens antigen presentation. Vitamin D also increases T helper (Th) 2 cytokine production and the efficiency of Treg lymphocytes but suppresses the secretion of Th1 and Th17 cytokines. In addition, vitamin D can decrease autoimmune disease activity. Vitamin D has been shown to play an important role in maintaining normal immune function and crosstalk between the innate and adaptive immune systems. Vitamin D deficiency may also contribute to deterioration of immune function and infectious disorders in CKD patients. However, it needs more evidence to support the requirements for vitamin D supplementation.

The hormone-bound vitamin D receptor enhances the FBW7-dependent turnover of NF-κB subunits

Signaling by hormonal vitamin D, 1,25-dihydroxyvitamin D (1,25D) has attracted increasing interest because of its non-classical actions, particularly its putative anticancer properties and its role in controlling immune system function. Notably, the hormone-bound vitamin D receptor (VDR) suppresses signaling by pro-inflammatory NF-κB transcription factors, although the underlying mechanisms have remained elusive. Recently, the VDR was shown to enhance the turnover of the oncogenic transcription factor cMYC mediated by the E3 ligase and tumor suppressor FBW7. As FBW7 also controls the turnover of the p100 (NF-κB2) subunit of the family, we determined whether the 1,25D enhanced FBW7-dependent turnover of NF-κB subunits p100, p105 (NF-κB1) and p65 (RELA). Protein levels of all three subunits declined markedly in the presence of 1,25D in multiple cell lines in the absence of substantial changes in mRNA expression. The VDR coimmunoprecipitated with all three subunits, and 1,25D treatment accelerated subunit turnover in cycloheximide-treated cells. Importantly, we observed an association of FBW7 with p105 and p65, as well as p100, and knockdown of FBW7 eliminated 1,25D-dependent subunit turnover. Moreover, expression of NF-κB target genes was elevated in FBW7-depleted cells. These results reveal that 1,25D signaling suppresses NF-κB function by enhancing FBW7-dependent subunit turnover.

Vitamin D, inflammation, and relations to insulin resistance in premenopausal women with morbid obesity

OBJECTIVE

In this study, the associations between vitamin D, insulin sensitivity, and inflammation and their relationships with adipose tissue expression of vitamin D receptor (VDR) and inflammatory markers in women with morbid obesity were determined.

METHODS

An oral glucose tolerance test prior to surgery was completed by healthy premenopausal women (n = 76) seeking bariatric surgery. Abdominal subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) were collected during surgery.

RESULTS

Approximately, 70% of our subjects were vitamin D sufficient or optimal, and 80% had normal glucose tolerance. No significant association between serum 25-hydroxyvitamin D [25(OH)D] with circulating inflammatory markers or insulin sensitivity was identified. In subjects with waist circumference of <139 cm (n = 42), log25(OH)D positively predicted VAT logIL-6 mRNA expression (P = 0.003). LogVDR expression was positively correlated with the expression of inflammatory markers in both SAT (logIL-1β mRNA: r = 0.95, P < 0.0001; logTNF mRNA: r = 0.82, P < 0.0001) and VAT (logIL-1β mRNA: r = 0.89, P < 0.0001; logTNF mRNA: r = 0.75, P < 0.0001). VAT logVDR expression positively predicted logHOMA-IR in non-African American subjects (P = 0.05).

CONCLUSIONS

The beneficial effects of vitamin D on inflammation and insulin sensitivity were not supported by our findings. VDR does not appear to possess a protective effect in adipose tissue.

Vitamin D: Immuno-modulation and tuberculosis treatment

Tuberculosis (TB) is a major global health problem and often coincides with vitamin D deficiency. High doses of vitamin D were widely used to treat TB during the pre-antibiotic era. Vitamin D exerts its action through vitamin D receptor (VDR), and VDR gene polymorphisms are associated with susceptibility or resistance to tuberculosis as well as sputum smear and culture conversion during anti-TB treatment. In-vitro studies have revealed that 1,25-dihydroxyvitamin D3 enhances innate immunity by increased expression of various antimicrobial peptides, including cathelicidin, and induction of autophagy of the infected cells thus restricts the intracellular growth of Mycobacterium tuberculosis in macrophages. On the other hand, vitamin D has been shown to suppress the pro-inflammatory cytokine response and enhance the anti-inflammatory response. Supplementation with vitamin D in concert with treatment for TB may be beneficial with respect to minimizing the excessive tissue damage that occurs during the active stage of tuberculosis disease. Several clinical trials have evaluated vitamin D supplementation as an adjunct therapy in the treatment for tuberculosis. However, results are conflicting, owing to variations in dose regimens and outcomes. Further investigations are needed to find the optimal concentration of vitamin D for supplementation with standard anti-TB drugs to optimize treatment, which could help to effectively manage both drug-sensitive and drug-resistant tuberculosis.

The emerging biomolecular role of vitamin D in skeletal muscle

In this review, we summarize current evidence for a direct effect of vitamin D on skeletal muscle. A number of studies identify the receptor for 1,25-dihydroxyvitamin-D3 (vitamin D receptor (VDR)) and the enzyme CYP27B1 (1-α-hydroxylase) in muscle. We hypothesize that vitamin D acts on myocytes via the VDR, and we examine proposed effects on myocyte proliferation, differentiation, growth, and inflammation.

1α,25-dihydroxyvitamin D3 ameliorates seawater aspiration-induced acute lung injury via NF-κB and RhoA/Rho kinase pathways

INTRODUCTION

Inflammation and pulmonary edema are involved in the pathogenesis of seawater aspiration-induced acute lung injury (ALI). Although several studies have reported that 1α,25-Dihydroxyvitamin D3 (calcitriol) suppresses inflammation, it has not been confirmed to be effective in seawater aspiration-induced ALI. Thus, we investigated the effect of calcitriol on seawater aspiration-induced ALI and explored the probable mechanism.

METHODS

Male SD rats receiving different doses of calcitriol or not, underwent seawater instillation. Then lung samples were collected at 4 h for analysis. In addition, A549 cells and rat pulmonary microvascular endothelial cells (RPMVECs) were cultured with calcitriol or not and then stimulated with 25% seawater for 40 min. After these treatments, cells samples were collected for analysis.

RESULTS

Results from real-time PCR showed that seawater stimulation up-regulated the expression of vitamin D receptor in lung tissues, A549 cells and RPMVECs. Seawater stimulation also activates NF-κB and RhoA/Rho kinase pathways. However, we found that pretreatment with calcitriol significantly inhibited the activation of NF-κB and RhoA/Rho kinase pathways. Meanwhile, treatment of calcitriol also improved lung histopathologic changes, reduced inflammation, lung edema and vascular leakage.

CONCLUSIONS

These results demonstrated that NF-κB and RhoA/Rho kinase pathways are critical in the development of lung inflammation and pulmonary edema and that treatment with calcitriol could ameliorate seawater aspiration-induced ALI, which was probably through the inhibition of NF-κB and RhoA/Rho kinase pathways.

Inhibition of Methicillin-resistant Staphylococcus aureus-induced cytokines mRNA production in human bone marrow derived mesenchymal stem cells by 1,25-dihydroxyvitamin D3

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is the predominant cause of bone infection. Toll like receptors (TLRs) are an important segments of host response to infection and are expressed by a variety of cells including human mesenchymal stem cells (hMSCs). The active form of Vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)₂D₃) has potent immunoregulatory properties, but the mechanism remains poorly understood. The genomic action of 1,25(OH)₂D₃ is mediated by vitamin D receptor (VDR), hormone-regulated transcription factor. VDR interacts with co-activators and co-repressors are associated with chromatin histone modifications and transcriptional regulation. The aim of our study is to explore MRSA-induced TLRs-mediated pro-inflammatory cytokines expression in hMSCs. Further, we hypothesized that 1,25(OH)₂D₃ inhibits MRSA-induced cytokines synthesis in hMSCs via inhibition of NF-кB transcription factor. Finally, we explored the regulatory role of 1,25(OH)₂D₃ in MRSA-mediated global epigenetic histone H3 mark, such as, trimethylated histone H3 lysine 9 (H3K9me3), which is linked to gene silencing.

Results

Quantitative PCR data revealed that MRSA-infection predominantly induced expression of TLRs 1, 2, 6, NR4A2, and inflammatory cytokines IL-8, IL-6, TNFα in hMSCs. MRSA-mediated TLR ligands reduced osteoblast differentiation and increased hMSCs proliferation, indicating the disrupted multipotency function of hMSCs. Pretreatment of 1,25(OH)₂D₃ followed by MRSA co-culture inhibited nuclear translocation of NF-кB-p65, reduced expression of NR4A2 and pro-inflammatory cytokines IL-8, IL-6, and TNFα in hMSCs. Further, NF-κB-p65, VDR, and NR4A2 were present in the same nuclear protein complex, indicating that VDR is an active part of the nuclear protein complexes for transcriptional regulation. Finally, 1,25(OH)₂D₃ activated VDR, restores the global level of H3K9me3, to repress MRSA-stimulated inflammatory cytokine IL-8 expression. Pretreatment of 5-dAZA, DNA methylatransferases (Dnmts) inhibitor, dramatically re-expresses 1,25(OH)₂D₃-MRSA-mediated silenced IL-8 gene.

Conclusions

This data indicates that TLR 1, 2, and 6 can be used as markers for localized S. aureus bone infection. 1,25(OH)₂D₃-VDR may exhibits its anti-inflammatory properties in MRSA-stimulated infection by inhibiting nuclear translocation of NF-kB-p65 and transcripts of IL-8, IL-6, TNFα, and NR4A2 in hMSCs. Finally, 1,25(OH)₂D₃-activated VDR, acting as an epigenetic regulator, inhibits synthesis of cytokines in MRSA-stimulated infection by restoring the global level of H3K9me3, a histone H3 mark for gene silencing.

RelB: an outlier in leukocyte biology

RelB is one of the more unusual members of the NF-κB family. This family, arguably the best known group of transcription regulators, regulates an astonishing array of cell types and biological processes. This includes regulation of cell growth, differentiation and death by apoptosis, and the development and function of the innate and adaptive-immune system. RelB is best known for its roles in lymphoid development, DC biology, and noncanonical signaling. Within the last few years, however, surprising functions of RelB have emerged. The N-terminal leucine zipper motif of RelB, a motif unique among the NF-κB family, may associate with more diverse DNA sequences than other NF-κB members. RelB is capable of direct binding to the AhR that supports the xenobiotic-detoxifying pathway. RelB can regulate the circadian rhythm by directly binding to the BMAL partner of CLOCK. Finally, RelB also couples with bioenergy NAD(+) sensor SIRT1 to integrate acute inflammation with changes in metabolism and mitochondrial bioenergetics. In this review, we will explore these unique aspects of RelB, specifically with regard to its role in immunity.

A purine scaffold HSP90 inhibitor BIIB021 has selective activity against KSHV-associated primary effusion lymphoma and blocks vFLIP K13-induced NF-κB

PURPOSE

Kaposi sarcoma-associated herpes virus (KSHV)-associated primary effusion lymphomas (PEL) have extremely poor prognosis when treated with conventional chemotherapy. KSHV-encoded viral FLICE-inhibitory protein (vFLIP) K13 binds to the IkappaB kinase (IKK) complex to constitutively activate the NF-κB pathway, which has been shown to be essential for the survival and proliferation of PEL cells. The molecular chaperone HSP90 is a component of the IKK complex and is required for its activity.

EXPERIMENTAL DESIGN

We have analyzed the effect of HSP90 inhibitors on the survival and proliferation of PEL cells and on the activity of the NF-κB pathway.

RESULTS

We show that BIIB021, a purine scaffold-based orally administrable HSP90 inhibitor, shows preferential cytotoxicity toward PEL cells as compared with non-PEL cells. The cytotoxic effect of BIIB021 against PEL was associated with induction of cell-cycle arrest and apoptosis. BIIB021 blocked the expression of a number of cellular proteins involved in the regulation of cell cycle and apoptosis. BIIB021 also blocked constitutive NF-κB activity present in PEL cells, in part, by blocking the interaction of vFLIP K13 with the IKK complex subunits. In a xenograft model of PEL, BIIB021 significantly reduced tumor growth.

CONCLUSION

BIIB021 blocks constitutive NF-κB activity in PEL and shows preferential antitumor activity against PEL in vitro and in vivo. BIIB021 may be a promising agent for treatment of PEL.

Vitamin D receptor inhibits nuclear factor κB activation by interacting with IκB kinase β protein

1,25-Dihydroxyvitamin D (1,25(OH)2D3) is known to suppress NF-κB activity, but the underlying mechanism remains poorly understood. Here we show that the vitamin D receptor (VDR) physically interacts with IκB kinase β (IKKβ) to block NF-κB activation. 1,25(OH)2D3 rapidly attenuates TNFα-induced p65 nuclear translocation and NF-κB activity in a VDR-dependent manner. VDR overexpression inhibits IKKβ-induced NF-κB activity. GST pull-down assays and coimmunoprecipitation experiments demonstrated that VDR physically interacts with IKKβ and that this interaction is enhanced by 1,25(OH)2D3. Protein mapping reveals that VDR-IKKβ interaction occurs between the C-terminal portions of the VDR and IKKβ proteins. Reconstitution of VDR(-/-) cells with the VDR C terminus restores the ability to block TNFα-induced NF-κB activation and IL-6 up-regulation. VDR-IKKβ interaction disrupts the formation of the IKK complex and, thus, abrogates IKKβ phosphorylation at Ser-177 and abolishes IKK activity to phosphorylate IκBα. Consequently, stabilization of IκBα arrests p65/p50 nuclear translocation. Together, these data define a novel mechanism whereby 1,25(OH)2D3-VDR inhibits NF-κB activation.

Nuclear receptors and their selective pharmacologic modulators

Nuclear receptors are ligand-activated transcription factors and include the receptors for steroid hormones, lipophilic vitamins, sterols, and bile acids. These receptors serve as targets for development of myriad drugs that target a range of disorders. Classically defined ligands that bind to the ligand-binding domain of nuclear receptors, whether they are endogenous or synthetic, either activate receptor activity (agonists) or block activation (antagonists) and due to the ability to alter activity of the receptors are often termed receptor "modulators." The complex pharmacology of nuclear receptors has provided a class of ligands distinct from these simple modulators where ligands display agonist/partial agonist/antagonist function in a tissue or gene selective manner. This class of ligands is defined as selective modulators. Here, we review the development and pharmacology of a range of selective nuclear receptor modulators.

Tolerogenic Donor-Derived Dendritic Cells Risk Sensitization In Vivo owing to Processing and Presentation by Recipient APCs

Modification of allogeneic dendritic cells (DCs) through drug treatment results in DCs with in vitro hallmarks of tolerogenicity. Despite these observations, using murine MHC-mismatched skin and heart transplant models, donor-derived drug-modified DCs not only failed to induce tolerance but also accelerated graft rejection. The latter was inhibited by injecting the recipient with anti-CD8 Ab, which removed both CD8(+) T cells and CD8(+) DCs. The discrepancy between in vitro and in vivo data could be explained, partly, by the presentation of drug-modified donor DC MHC alloantigens by recipient APCs and activation of recipient T cells with indirect allospecificity, leading to the induction of alloantibodies. Furthermore, allogeneic MHC molecules expressed by drug-treated DCs were rapidly processed and presented in peptide form by recipient APCs in vivo within hours of DC injection. Using TCR-transgenic T cells, Ag presentation of injected OVA-pulsed DCs was detectable for ≤ 3 d, whereas indirect presentation of MHC alloantigen by recipient APCs led to activation of T cells within 14 h and was partially inhibited by reducing the numbers of CD8(+) DCs in vivo. In support of this observation when mice lacking CD8(+) DCs were pretreated with drug-modified DCs prior to transplantation, skin graft rejection kinetics were similar to those in non-DC-treated controls. Of interest, when the same mice were treated with anti-CD40L blockade plus drug-modified DCs, skin graft survival was prolonged, suggesting endogenous DCs were responsible for T cell priming. Altogether, these findings highlight the risks and limitations of negative vaccination using alloantigen-bearing "tolerogenic" DCs.

Vitamin D-dependent cathelicidin inhibits Mycobacterium marinum infection in human monocytic cells

BACKGROUND

1α,25-Dihydroxyvitamin D3 (1,25(OH)2D3) up-regulates the production of human cathelicidin antimicrobial peptide (CAMP) from monocytes/macrophages infected with Mycobacterium tuberculosis (M. tbc). CAMP facilitates the co-localization of autophagolysosomes with M. tbc, promoting the antimicrobial activity of monocytes. Mycobacterium marinum (M. marinum) is an acid-fast bacillus that causes less severe granulomatous skin lesions compared with M. tbc.

OBJECTIVE

We investigated whether autophagic antimicrobial activity is promoted by 1,25(OH)2D3 or C-terminal of cathelicidin LL-37 in human monocytes upon infection with M. marinum.

METHODS

Human monocytes (THP-1) were infected with M. marinum. Effects of simultaneous treatments of 1,25(OH)2D3, exogenous LL-37 peptide, autophagolysosome inhibitors, 3-methyladenine or chloroquine, were examined.

RESULTS

CAMP was strongly induced by adding 1,25(OH)2D3 to the culture of THP-1 cells. In the absence of 1,25(OH)2D3 M. marinum infection alone did not induce CAMP, however, simultaneous addition of 1,25(OH)2D3 to M. marinum infection accelerated CAMP production more than 1,25(OH)2D3 alone. Proliferation of M. marinum was markedly decreased in the presence of 1,25(OH)2D3 or exogenous LL-37 in THP-1 cells. Co-localization of CAMP with autophagolysosome was evident in 1,25(OH)2D3 and LL-37 treated THP-1 cells after M. marinum infection. Autophagolysosome inhibitors abrogated the antimicrobial effects of 1,25(OH)2D3 and exogenous LL-37 against M. marinum infection in THP-1 cells.

CONCLUSIONS

Human monocytic cells, whose CAMP production is up-regulated by 1,25(OH)2D3-vitamin D receptor pathway, accelerate antimicrobial function of autophagolysosome in M. marinum infection.

Association of vitamin D with cardiometabolic risk factors in rheumatoid arthritis

OBJECTIVE

Individuals with rheumatoid arthritis (RA) are at a greater risk for cardiovascular disease (CVD). Vitamin D deficiency is a potential risk factor for CVD and metabolic syndrome. Since patients with RA have a high prevalence of vitamin D deficiency, we investigated the association of vitamin D levels with cardiometabolic risk factors in a cohort of RA patients with no prior history of CVD.

METHODS

Serum 25-hydroxyvitamin D (25[OH]D) levels were measured among RA patients enrolled in a cohort study of subclinical CVD. The cross-sectional associations of 25(OH)D levels with traditional CVD risk factors such as insulin resistance (IR; estimated using the homeostatic model assessment [HOMA]), adipokines, markers of systemic inflammation, and endothelial activation were explored, adjusting for pertinent sociodemographic, lifestyle, and RA characteristics.

RESULTS

Among 179 RA patients, 73 (41%) had a 25(OH)D level <30 ng/ml. Only 23 patients (13%) had a 25(OH)D level ≥45 ng/ml. After adjusting for demographics and body mass index (BMI), 25(OH)D remained significantly associated with high-density lipoprotein (HDL) cholesterol and inversely associated with HOMA-IR, fibrinogen, E-selectin, and soluble intercellular adhesion molecule 1 (sICAM-1). Significant associations with HDL cholesterol, E-selectin, and sICAM-1 were maintained after adjusting for the Disease Activity Score in 28 joints (DAS28) and autoantibody status. These associations were similar between the groups subdivided by sex, ethnicity, BMI, DAS28 level, and autoantibody status.

CONCLUSION

These data suggest that vitamin D deficiency is common in RA and may be independently associated with several cardiometabolic intermediates in this population.

Kaposi's sarcoma-associated herpesvirus oncoprotein K13 protects against B cell receptor-induced growth arrest and apoptosis through NF-κB activation

Kaposi's sarcoma-associated herpesvirus (KSHV) has been linked to the development of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease (MCD). We have characterized the role of KSHV-encoded viral FLICE inhibitory protein (vFLIP) K13 in the modulation of anti-IgM-induced growth arrest and apoptosis in B cells. We demonstrate that K13 protects WEHI 231, an immature B-cell line, against anti-IgM-induced growth arrest and apoptosis. The protective effect of K13 was associated with the activation of the NF-κB pathway and was deficient in a mutant K13 with three alanine substitutions at positions 58 to 60 (K13-58AAA) and a structural homolog, vFLIP E8, both of which lack NF-κB activity. K13 upregulated the expression of NF-κB subunit RelB and blocked the anti-IgM-induced decline in c-Myc and rise in p27(Kip1) that have been associated with growth arrest and apoptosis. K13 also upregulated the expression of Mcl-1, an antiapoptotic member of the Bcl2 family. Finally, K13 protected the mature B-cell line Ramos against anti-IgM-induced apoptosis through NF-κB activation. Inhibition of anti-IgM-induced apoptosis by K13 may contribute to the development of KSHV-associated lymphoproliferative disorders.

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.

Effect of vitamin D3 on chemokine expression in pulmonary tuberculosis

1,25 Dihydroxy vitamin D(3) (vitamin D(3)) is an immunomodulator and its deficiency has been associated with susceptibility to tuberculosis. We have studied the immunoregulatory role of vitamin D(3) on various chemokine expression in pulmonary tuberculosis. Peripheral blood mononuclear cells obtained from 21 pulmonary tuberculosis (PTB) patients and 24 healthy controls (HCs) were cultured for 48 h with culture filtrate antigen (CFA) of Mycobacterium tuberculosis with or without vitamin D(3) at a concentration 1 × 10(-7)M. The relative mRNA expression of monocyte chemoattractant protein-1 (MCP-1, CCL2), macrophage inflammatory protein-1α (MIP-1α, CCL3), macrophage inflammatory protein-1β (MIP-1β, CCL4), and regulated upon-activation, normal T cell-expressed and secreted (RANTES, CCL5) and IFN-γ inducible protein-10 (IP-10, CXCL10) chemokines were estimated from 48 h old macrophages using real-time polymerase chain reaction (RT-PCR). The culture supernatants were used to estimate the various chemokines including monokine induced by IFN-γ (MIG, CXCL9) levels using cytometric bead array. In HCs, vitamin D(3) significantly suppressed the MCP-1 mRNA expression of CFA stimulated cells (p=0.0027), while no such effect was observed in PTB patients. Vitamin D(3) showed no significant effect on MIP-1α, MIP-1β and RANTES in both the study groups. The CFA induced IP-10 mRNA and protein expression was significantly suppressed by vitamin D(3) in both the study groups (p<0.05). A similar suppressive effect of vitamin D(3) was observed with MIG protein in healthy controls (p=0.0029) and a trend towards a suppression was observed in PTB patients. The suppressive effect of vitamin D(3) is more prominent in CXC chemokines rather than CC chemokines. This suggests that vitamin D(3) may down regulate the recruitment and activation of T-cells through CXC chemokines at the site of infection and may act as a potential anti-inflammatory agent.

Nuclear hormone receptors enable macrophages and dendritic cells to sense their lipid environment and shape their immune response

A key issue in the immune system is to generate specific cell types, often with opposing activities. The mechanisms of differentiation and subtype specification of immune cells such as macrophages and dendritic cells are critical to understand the regulatory principles and logic of the immune system. In addition to cytokines and pathogens, it is increasingly appreciated that lipid signaling also has a key role in differentiation and subtype specification. In this review we explore how intracellular lipid signaling via a set of transcription factors regulates cellular differentiation, subtype specification, and immune as well as metabolic homeostasis. We introduce macrophages and dendritic cells and then we focus on a group of transcription factors, nuclear receptors, which regulate gene expression upon receiving lipid signals. The receptors we cover are the ones with a recognized physiological function in these cell types and ones which heterodimerize with the retinoid X receptor. These are as follows: the receptor for a metabolite of vitamin A, retinoic acid: retinoic acid receptor (RAR), the vitamin D receptor (VDR), the fatty acid receptor: peroxisome proliferator-activated receptor γ (PPARγ), the oxysterol receptor liver X receptor (LXR), and their obligate heterodimeric partner, the retinoid X receptor (RXR). We discuss how they can get activated and how ligand is generated and eliminated in these cell types. We also explore how activation of a particular target gene contributes to biological functions and how the regulation of individual target genes adds up to the coordination of gene networks. It appears that RXR heterodimeric nuclear receptors provide these cells with a coordinated and interrelated network of transcriptional regulators for interpreting the lipid milieu and the metabolic changes to bring about gene expression changes leading to subtype and functional specification. We also show that these networks are implicated in various immune diseases and are amenable to therapeutic exploitation.

Vitamin D modulates airway smooth muscle function in COPD

COPD is a disease manifested as persistent airflow obstruction with an enhanced inflammatory response in the airways and lungs to noxious particles and gases which evokes symptoms of dyspnea on exertion, cough and mucus production. Airway smooth muscle plays a central role in the COPD diathesis and is implicated in many aspects of COPD pathogenesis. Vitamin D deficiency has been associated with COPD severity and studies suggest a role for Vitamin D as a treatment for COPD. In this review, we describe the effects of 1,25-dihydroxyvitamin D on airway smooth muscle function, including agonist-induced shortening, secretion of inflammatory mediators, and myocyte hypertrophy and hyperplasia.

Defective renal maintenance of the vitamin D endocrine system impairs vitamin D renoprotection: a downward spiral in kidney disease

In kidney disease, the progressive loss of renal capacity to produce calcitriol, the vitamin D hormone, is a key contributor to elevations in parathyroid hormone (PTH) and mineral and skeletal disorders predisposing to renal and cardiovascular damage, ectopic calcifications, and high mortality rates. Thus, the safe correction of calcitriol deficiency to suppress PTH has been the treatment of choice for decades. However, recent epidemiological and experimental data suggest that calcitriol replacement may improve outcomes through renal and cardioprotective actions unrelated to PTH suppression. Furthermore, a striking incidence of vitamin D deficiency occurs in kidney disease and associates more strongly than calcitriol deficiency with a higher risk for kidney disease progression and death. Despite the translational relevance of these findings, no prospective trials are currently available in support of the efficacy of vitamin D supplementation and/or calcitriol replacement to safely halt/moderate renal disease progression. This review updates the pathophysiology behind the vicious cycle by which kidney injury impairs the maintenance of normal vitamin D and calcitriol levels, which in turn impedes vitamin D/calcitriol renoprotective actions, a requirement for the design of prospective trials to improve current recommendations for vitamin D interventions at all stages of kidney disease.

Vitamin D, vitamin D receptor, and cathelicidin in the treatment of tuberculosis

Vitamin D plays a major role in bone mineral density and calcium homeostasis. Apart from its classical action, the active form of vitamin D [1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3))] influences the innate and adaptive immune functions through vitamin D receptor (VDR) that are present in various cells of the immune system. Vitamin D deficiencies have been associated with development of tuberculosis (TB) disease, caused by Mycobacterium tuberculosis. Vitamin D(3) is shown to enhance macrophage phagocytosis of M. tuberculosis and increases the production of antimicrobial peptide cathelicidin and killing of M. tuberculosis. During the preantibiotic era, exposure to sunlight and supplementation of vitamin D were the methods of choice for treatment of TB. Vitamin D supplementation showed sputum clearance and radiological improvement and reduction in mortality among human immunodeficiency virus (HIV)-infected patients with TB. VDR gene polymorphisms regulate the immunomodulatory effect of vitamin D(3) and are associated with faster sputum conversion during anti-TB treatment. The emerging evidences regarding immunomodulatory properties of vitamin D(3) have rekindled interest in vitamin D as an adjunct to anti-TB therapy. The current review explains the important potential application of vitamin D in enhancing the innate immunity to TB and the role of VDR gene variants on anti-TB treatment.

1,25-Dihydroxyvitamin D₃ suppresses inflammation-induced expression of plasminogen activator inhibitor-1 by blocking nuclear factor-κB activation

Plasminogen activator inhibitor (PAI)-1 is a major fibrinolytic inhibitor. High PAI-1 is associated with increased renal and cardiovascular disease risk. Previous studies demonstrated PAI-1 down-regulation by 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), but the molecular mechanism remains unknown. Here we show that exposure of mouse embryonic fibroblasts to TNFα or LPS led to a marked induction of PAI-1, which was blunted by 1,25(OH)₂D₃, NF-κB inhibitor or p65 siRNA, suggesting the involvement of NF-κB in 1,25(OH)₂D₃-induced repression. In mouse Pai-1 promoter a putative cis-κB element was identified at -299. EMSA and ChIP assays showed that TNF-α increased p50/p65 binding to this κB site, which was disrupted by 1,25(OH)₂D₃. Luciferase reporter assays showed that PAI-1 promoter activity was induced by TNFα or LPS, and the induction was blocked by 1,25(OH)₂D₃. Mutation of the κB site blunted TNFα, LPS or 1,25(OH)₂D₃ effects. 1,25(OH)₂D₃ blocked IκBα degradation and arrested p50/p65 nuclear translocation. In mice LPS stimulated PAI-1 expression in the heart and macrophages, and the stimulation was blunted by pre-treatment with a vitamin D analog. Together these data demonstrate that 1,25(OH)₂D₃ down-regulates PAI-1 by blocking NF-κB activation. Inhibition of PAI-1 production may contribute to the reno- and cardio-protective effects of vitamin D.

Induction of pathogenic cytotoxic T lymphocyte tolerance by dendritic cells: a novel therapeutic target

IMPORTANCE OF THE FIELD

Dendritic cells (DCs) have an important role, both direct and indirect, in controlling the expansion and function of T cells. Of the different subsets of T cells, cytotoxic T lymphocytes (CTLs/CD8(+) T cells) have been implicated in the pathogenesis and development of many diseases, including various forms of autoimmunity and transplant rejection. It may therefore be of therapeutic benefit to control the function of CTL in order to modulate disease processes and to ameliorate disease symptoms. Currently, pharmacological approaches have been employed to either directly or indirectly modulate the function of T cells. However, these treatment strategies have many limitations. Many experimental data have suggested that it is possible to alter CTL activity through manipulation of DC.

AREAS COVERED IN THIS REVIEW

Novel strategies that condition DCs to influence disease outcome through manipulation of CTL activity, both directly and indirectly. This includes the modulation of co-stimulation, negative co-stimulation, as well as manipulation of the cytokine milieu during CTL generation. Furthermore, DCs may also impact CTL activity through effects on effector and regulatory cells, along with manipulation of bioenergetic regulation, apoptotic-cell mediated tolerance and through the generation of exosomes. The implications of related interventions in the clinical arena are in turn considered.

WHAT THE READER WILL GAIN

Insight into such indirect methods of controlling CTL activity allows for an understanding of how disease-specific T cells may be regulated, while also sparing other aspects of adaptive immunity for normal physiological function. Such an approach towards the treatment of disease represents an innovative therapeutic target in the clinical arena.

TAKE HOME MESSAGE

There are numerous innovative methods for using DCs to control CTL responses. Manipulation of this interaction is thus an attractive avenue for the treatment of disease, particularly those of immune dysregulation, such as seen in autoimmunity and transplantation. With the number of studies moving into clinical stages constantly increasing, further advances and successes in this area are inevitable.

Human prostatic urethra expresses vitamin D receptor and responds to vitamin D receptor ligation

BACKGROUND

Chronic inflammation is now considered a determinant of benign prostatic hyperplasia (BPH), promoting, together with the hormonal milieu, prostate overgrowth and lower urinary tract symptoms (LUTS). Prostatic urethra actively participates in determining progression of LUTS associated with BPH.

AIM

To investigate the expression of the vitamin D receptor (VDR) and the ability of the VDR agonist elocalcitol to reduce inflammatory responses in human prostatic urethra (hPU) cells.

MATERIALS AND METHODS

Human prostatic urethra, prostate and bladder neck were obtained from patients affected by BPH. Immunohistochemical studies for VDR expression were performed in tissue samples, from which primary cell cultures were also derived. In hPU cells, proliferation and chemiotaxis were studied, along with Rho kinase (ROCK) activity (MYPT-1 phosphorylation) by western blot. Quantitative RT-PCR was performed for VDR, cyclooxygenase (COX-2), and interleukin (IL)-8 expression.

RESULTS

Urethra displays higher VDR expression compared to prostate and bladder neck tissues. The VDR agonist elocalcitol partially reverts COX-2 and IL-8 mRNA upregulation induced by a pro-inflammatory cytokine mixture (IL-17, interferon-γ, tumor necrosis factor-α) and inhibits cell migration in urethral cells. Elocalcitol prevents activation of ROCK, as previously demonstrated in bladder and prostate cell cultures.

CONCLUSIONS

Our results suggest that prostatic urethra is, within the lower urinary tract, a novel target for VDR agonists, as shown by the capacity of elocalcitol to inhibit ROCK activity and to limit inflammatory responses in human primary urethra cells.