Control of autoimmune diseases by the vitamin D endocrine system

Vitamin D and the intracrinology of innate immunity

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

Regulatory T cells, inflammation and the allergic response-The role of glucocorticoids and Vitamin D

Regulatory T cells (TRegs) play a central role in the maintenance of peripheral tolerance. They prevent inappropriate immune responses to ubiquitous allergens in healthy individuals, and contribute to the maintenance of immune homeostasis in the airways. Both Foxp3+ and IL-10+ TReg have been implicated in these functions. Glucocorticoids represent the mainstay of treatment for asthma and other allergic conditions, and evidence that steroids influence TReg function will be reviewed. Growing bodies of epidemiological and immunological data suggest a role for endogenous Vitamin D in immune regulation. This review will discuss the role of glucocorticoids and Vitamin D, and their potential interactions in promoting tolerance in the context of allergic disease and asthma.

A pilot study assessing the role of 25 hydroxy vitamin D levels in patients with vitiligo vulgaris

BACKGROUND

Very low vitamin D levels have been noted in patients with a variety of autoimmune diseases.

OBJECTIVE

To determine whether low vitamin D levels are associated with autoimmunity in the setting of vitiligo vulgaris.

METHODS

A prospective cohort study was conducted on 45 consecutive patients with vitiligo vulgaris. 25-Hydroxyvitamin D levels were determined from sera collected at the time of study enrollment. Logistic regression analysis of the relationship of 25-hydroxyvitamin D levels to disease state was performed, including surface area, recent-onset vitiligo, Fitzpatrick skin type and ethnicity, dairy intake, and both personal and family history of autoimmunity. Multiple univariate and multivariate logistic regression models were developed to assess the interrelationship of these parameters.

RESULTS

25-Hydroxyvitamin D levels were divided into 3 groups: 31.1% were normal (>30 ng/mL), 55.6% were insufficient (<30 ng/mL), and 13.3% were very low (<15 ng/mL). Insufficient 25-hydroxyvitamin D levels were associated with increasing Fitzpatrick phototypes (odds ratio [OR] = 1.76, 95% confidence interval [CI] = 1.12-2.77). Very low 25-hydroxyvitamin D levels were associated with comorbid autoimmune illness (OR = 10.00, 95% CI = 1.06-94.7), but not with age, gender, race/ethnicity, family history of vitiligo or autoimmune disease, new-onset disease, or body surface area affected. None of the surveyed patients reported daily vitamin D intake of greater than 200 IU.

LIMITATIONS

This study consists of a small cohort that assesses point prevalence without assessing seasonal variation in vitamin D levels.

CONCLUSIONS

Very low 25-hydroxyvitamin D levels (<15 ng/mL) appear to be a reasonable screening tool for the presence of comorbid autoimmunity. Furthermore, we demonstrate that Fitzpatrick phototype, rather than ethnicity, is specifically associated with 25-hydroxyvitamin D levels that are insufficient (<30 ng/mL).

Effects of sleep and circadian rhythm on the human immune system

Many immune parameters show systematic fluctuations over the 24-h day in human blood. Circulating naive T-cells and production of proinflammatory cytokines, like interleukin-12 (IL-12), peak during nighttime, whereas cytotoxic effector leukocytes and production of the anti-inflammatory cytokine IL-10 peak during daytime. These temporal changes originate from a combined influence of the circadian system and sleep. Both brain functions act synergistically and share neuroendocrine effector mechanisms to convey control over immune functions. Sympathetic tone and cortisol levels show a circadian nadir during nighttime and are further suppressed by sleep, whereas growth hormone and prolactin show a circadian peak during nighttime and are further enhanced by sleep. Thus, the circadian system and sleep jointly evoke a unique endocrine constellation that is extremely effective in inducing changes in leukocyte traffic and a shift toward proinflammatory type 1-cytokines during the nocturnal period of sleep, that is, an action with strong clinical implications.

Vitamin D receptor agonists target static, dynamic, and inflammatory components of benign prostatic hyperplasia

The bioactive form of vitamin D, 1,25-dihydroxyvitamin D(3), is a secosteroid hormone that binds to the vitamin D receptor (VDR), a member of the nuclear receptor superfamily, and modulates a variety of biological functions. The VDR is expressed by most cell types, including cells of the urogenital system, such as prostate and bladder cells. In particular, the prostate is a target organ of VDR agonists and represents an extrarenal synthesis site of 1,25-dihydroxyvitamin D(3). We have analyzed the capacity of VDR agonists to treat benign prostatic hyperplasia (BPH), a complex syndrome characterized by a static component related to prostate overgrowth, a dynamic component responsible for urinary irritative symptoms, and an inflammatory component. Data reviewed here demonstrate that VDR agonists, and notably elocalcitol, reduce the static component of BPH by inhibiting the activity of intraprostatic growth factors downstream of the androgen receptor, the dynamic component by targeting the RhoA/ROCK pathway in prostate and bladder cells, and the inflammatory component by targeting the NF-kappaB pathway.

Update on the genetic risk factors for rheumatoid arthritis

Rheumatoid arthritis (RA) is a complex disease, meaning that multiple genetic variants, environmental factors and random events interact to trigger pathological pathways. Although many of these etiological factors have not yet been identified, recent groundbreaking advances have expanded our knowledge about the genetic factors that contribute to RA. Here, we review the most recent findings on the genetic risk factors for RA. First, we give an overview of the genetics of RA and briefly describe the susceptibility loci discovered prior to the availability of genome-wide association studies (GWAS). Second, we focus on the newly discovered RA loci that have arisen from GWAS in populations of European ancestry. Through these studies, the number of established RA susceptibility loci has now grown to 13. Third, we discuss several important issues emerging from GWAS, such as ethnic heterogeneity and shared autoimmunity risk loci. Finally, we discuss what still needs to be accomplished before a more complete picture of the genetic risk to RA can be attained.

Epidemiology of vitamin D in health and disease

Results from ecological, case-control and cohort studies have shown that vitamin D reduces the risk of bone fracture, falls, autoimmune diseases, type 2 diabetes, CVD and cancer. However, there is still epidemic vitamin D insufficiency especially among individuals living at high latitudes or with dark skin. Serum levels of 25-hydroxyvitamin D (25(OH)D) are considered the best biomarker of vitamin D nutritional status. Appropriate sunshine exposure or oral supplementation is necessary to maintain sufficient vitamin D status, which is generally accepted as serum 25(OH)D>75 nmol/l. Immunoassays, especially RIA, have been primarily used to measure serum 25(OH)D while liquid chromatography-MS (LC-MS) is considered the 'gold standard'. There is significant disparity among the immunoassays, and all immunoassays have considerable bias compared with LC-MS methods. Because of the variations among the results from these different assays, it is necessary that assay-specific reference ranges be established or standardisation of the assays take place. The present review focuses on ecological, case-control, and cohort studies that investigated the role of vitamin D in health and disease. In addition, analytical techniques used in laboratory evaluation of vitamin D nutritional status are also critically reviewed. The majority of the literature included in the present review is selected from that searchable in PubMed up to the end of September 2008.

Comparison between VDR analogs and current immunosuppressive drugs in relation to CXCL10 secretion by human renal tubular cells

During kidney allograft rejection, CXC chemokine ligand 10 (CXCL10)-CXC chemokine receptor 3 (CXCR3) trafficking between peripheral blood and tissues initiates alloresponse and perpetuates a self-inflammatory loop; thus, CXCL10-CXCR3 axis could represent a pharmacologic target. In this perspective, immunosuppressors targeting graft-resident cells, beside immune cells, could be very advantageous. Vitamin D receptor (VDR) agonists exhibit considerable immunomodulatory properties. This study aimed to investigate whether elocalcitol and BXL-01-0029 could decrease the expression of CXCL10 in activated renal tubular cells in vitro and thus be useful in kidney allograft rejection treatment. Experiments were performed in human tubular renal cells stimulated with interferon-gamma + tumor necrosis factor-alpha with and without VDR agonists, tacrolimus, sirolimus, hydrocortisone, methylprednisolone, cyclosporin A and mycophenolate mofetil. CXCL10 protein secretion and gene expression were measured by ELISA and by quantitative PCR. Specific inhibitors were used to investigate intracellular pathways involved in tubular cells activation. For IC(50) determination and comparison, dose-response curves with VDR agonists, tacrolimus and mycophenolic acid were performed. Elocalcitol and BXL-01-0029 inhibited CXCL10 secretion by renal cells, without affecting cell viability, while almost all the immunosuppressors were found to be ineffective, except for tacrolimus and mycophenolate mofetil. BXL-01-0029 was the most potent drug and, notably, it was found to be capable of allowing reduction in tacrolimus-inhibitory doses. Our data suggest that BXL-01-0029 could potentially be a dose-reducing agent for conventional immunosuppressors in kidney rejection management.

The vitamin D-antimicrobial peptide pathway and its role in protection against infection

Vitamin D deficiency has been correlated with increased rates of infection. Since the early 19th century, both environmental (i.e., sunlight) and dietary sources (cod liver) of vitamin D have been identified as treatments for TB. The recent discovery that vitamin D induces antimicrobial peptide gene expression explains, in part, the 'antibiotic' effect of vitamin D and has greatly renewed interest in the ability of vitamin D to improve immune function. Subsequent work indicates that this regulation is biologically important for the response of the innate immune system to wounds and infection and that deficiency may lead to suboptimal responses toward bacterial and viral infections. The regulation of the cathelicidin antimicrobial peptide gene is a human/primate-specific adaptation and is not conserved in other mammals. The capacity of the vitamin D receptor to act as a high-affinity receptor for vitamin D and a low-affinity receptor for secondary bile acids and potentially other novel nutritional compounds suggests that the evolutionary selection to place the cathelicidin gene under control of the vitamin D receptor allows for its regulation under both endocrine and xenobiotic response systems. Future studies in both humans and humanized mouse models will elucidate the importance of this regulation and lead to the development of potential therapeutic applications.

Defining and analyzing geoepidemiology and human autoimmunity

Autoimmune diseases cumulatively affect 5-10% of the industrial world population and are a significant cause of morbidity and mortality. In recent decades rates are rising worldwide, and autoimmunity can no longer be associated solely with the more developed "Western" countries. Geoepidemiology of autoimmune diseases portrays the burden of these illnesses across various regions and ethnic populations. Furthermore, Geoepidemiology may yield important clues to the genetic and triggering environmental mechanisms of autoimmunity. In this review we compiled and discuss in depth abundant geoepidemiological data pertaining to four major autoimmune conditions, namely type-1 diabetes mellitus, multiple sclerosis, autoimmune thyroid disease, and inflammatory bowel disease. The following key results manifested in this review: 1) Ethno-geographic gradients in autoimmune disease risk are attributable to a complex interplay of genetic and environmental pressures. 2) Industrial regions, particularly Northern Europe and North America, still exhibit the highest rates for most autoimmune diseases. 3) Methods particularly useful in demonstrating the significant influence of genetic and environmental factors include comparative ethnic differences studies, migration studies, and recognition of 'hotspots'. 4) Key environmental determinants of geographical differences include diminished ultraviolet radiation exposure, Western or affluence-related lifestyle, infection exposure, environmental pollutants, nutritional factors and disease-specific precipitants (e.g., iodine exposure).

Traumatic brain injury and aging: is a combination of progesterone and vitamin D hormone a simple solution to a complex problem?

Although progress is being made in the development of new clinical treatments for traumatic brain injury (TBI), little is known about whether such treatments are effective in older patients, in whom frailty, prior medical conditions, altered metabolism, and changing sensitivity to medications all can affect outcomes following a brain injury. In this review we consider TBI to be a complex, highly variable, and systemic disorder that may require a new pharmacotherapeutic approach, one using combinations or cocktails of drugs to treat the many components of the injury cascade. We review some recent research on the role of vitamin D hormone and vitamin D deficiency in older subjects, and on the interactions of these factors with progesterone, the only treatment for TBI that has shown clinical effectiveness. Progesterone is now in phase III multicenter trial testing in the United States. We also discuss some of the potential mechanisms and pathways through which the combination of hormones may work, singly and in synergy, to enhance survival and recovery after TBI.

Nuclear receptors, inflammation, and neurodegenerative diseases

Chronic inflammation is associated with many neurodegenerative diseases, including multiple sclerosis, Parkinson's disease, and Alzheimer's disease. Increasing evidence that neuroinflammation contributes to disease severity has generated considerable interest in determining whether inhibition of inflammation pathways might be of therapeutic benefit. One potential avenue of intervention is provided by members of the nuclear receptor superfamily of ligand-dependent transcription factors that exert anti-inflammatory effects in many cell types. Here, we review recent studies providing insights into the distinct mechanisms that enable nuclear receptors to modulate immune responses, describe inflammatory components of neurodegenerative diseases, and discuss recent literature relevant to roles of nuclear receptors in influencing these processes.

1,25-Dihydroxyvitamin D3 and IL-2 combine to inhibit T cell production of inflammatory cytokines and promote development of regulatory T cells expressing CTLA-4 and FoxP3

The active form of vitamin D, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), has potent immunomodulatory properties that have promoted its potential use in the prevention and treatment of infectious disease and autoimmune conditions. A variety of immune cells, including macrophages, dendritic cells, and activated T cells express the intracellular vitamin D receptor and are responsive to 1,25(OH)(2)D(3.) Despite this, how 1,25(OH)(2)D(3) regulates adaptive immunity remains unclear and may involve both direct and indirect effects on the proliferation and function of T cells. To further clarify this issue, we have assessed the effects of 1,25(OH)(2)D(3) on human CD4(+)CD25(-) T cells. We observed that stimulation of CD4(+)CD25(-) T cells in the presence of 1,25(OH)(2)D(3) inhibited production of proinflammatory cytokines including IFN- gamma, IL-17, and IL-21 but did not substantially affect T cell division. In contrast to its inhibitory effects on inflammatory cytokines, 1,25(OH)(2)D(3) stimulated expression of high levels of CTLA-4 as well as FoxP3, the latter requiring the presence of IL-2. T cells treated with 1,25(OH)(2)D(3) could suppress proliferation of normally responsive T cells, indicating that they possessed characteristics of adaptive regulatory T cells. Our results suggest that 1,25(OH)(2)D(3) and IL-2 have direct synergistic effects on activated T cells, acting as potent anti-inflammatory agents and physiologic inducers of adaptive regulatory T cells.

Nutrition, geoepidemiology, and autoimmunity

As well represented by the impaired immune function of malnourished individuals encountered in developing countries and the incidence of specific diseases following local nutrient deficiencies, nutrition and immunity have been linked to each other for centuries while the specific connection between dietary factors and autoimmunity onset or modulation is a more recent acquisition. Autoimmune diseases manifest limited prevalence rates in developing countries while numerous immunity-related claims have been proposed in the field of functional foods. Nevertheless, over the past years multiple lines of evidence have supported a major role for specific dietary factors (including vitamin D, vitamin A, selenium, zinc, omega-3 fatty acids, probiotics, and flavanols) in determining the immune responses involved in infections, allergies, and autoimmune diseases. Interestingly, the link between nutrition and autoimmunity may well contribute to the geoepidemiology observed for numerous conditions. In general terms, most data that will be discussed herein were obtained in experimental or animal models while human data from real-life clinical settings or randomized clinical trials remain largely unsatisfactory. Our current knowledge on the beneficial impact of nutrition on autoimmunity prompts us to encourage the search for evidence-based nutrition to support the everyday diet choices of patients.

Vitamin D receptor deletion leads to reduced level of IkappaBalpha protein through protein translation, protein-protein interaction, and post-translational modification

Vitamin D receptor plays an essential role in the regulation of inflammation. Previous studies demonstrate that vitamin D receptor negatively modulates the proinflammatory NF-kappaB pathway. However, it is unknown how vitamin D receptor regulates IkappaBalpha, the endogenous inhibitor of NF-kappaB. Here we investigated the molecular mechanism of vitamin D receptor deletion and IkappaBalpha expression. We found that cells lacking vitamin D receptor had significantly increased levels of IkappaBalpha mRNA and simultaneously decreased levels of IkappaBalpha protein. Lacking vitamin D receptor abolished its binding to the IkappaBalpha promoter. Moreover, the levels of protein translation regulators and the rate of protein synthesis were both decreased in cells lacking vitamin D receptor. At the post-translational level, IkappaBalpha ubiquitination was enhanced, indicating increased degradation of IkappaBalpha in the absence of vitamin D receptor. We further transfected cells with a plasmid carrying either wild-type or mutant IkappaBalpha. The expression of wild-type IkappaBalpha was much higher in the cells with vitamin D receptor than in the cells without vitamin D receptor, whereas the expression of exogenous IkappaBalpha was equally high in both cell lines. In summary, vitamin D receptor deletion affects IkappaBalpha through mRNA transcription, protein translation, protein-protein interaction, post-translational modification, and protein degradation, thus reducing the level of IkappaBalpha protein. Cells lacking vitamin D receptor are known in a proinflammatory state with activation of NF-kappaB. Our study provides new insight into vitamin D receptor regulation of an inhibitor of NF-kappaB in inflammation. Deletion of vitamin D receptor contributes to the activation of NF-kappaB on multiple levels.

Modulation of osteoclast function in bone by the immune system

Osteoclast differentiation and function is regulated by cellular signals and cytokines that also play significant roles in the immune system. There is much scope, therefore, for immune cell influence on osteoclasts and bone metabolism. Many examples of this have been identified and T cells in particular are a source of factors affecting osteoclast formation and activity, a number which have either pro-osteolytic or anti-osteolytic actions depending on the cellular and microenvironmental context. For example, IL-12 and IL-18 participate in inflammatory processes that can lead to highly destructive osteolysis, yet these cytokines potently block osteoclast formation through mediation of T cells. IL-23 participates in chronic inflammatory processes, but lack of this cytokine results in reduced bone mass in mice, pointing to an influence on physiological regulation of bone mass. Such insights suggest that therapies that target immune responses may significantly influence osteolysis. Investigations into links between the immune system and bone metabolism are thus uncovering important information about the functioning of both systems.

Multiple sclerosis, osteoporosis, and vitamin D

Multiple sclerosis (MS) is associated with reduced bone mass and higher frequency of osteoporosis. Although high-dose short-term intravenous glucocorticoid regimens cause a decrease in bone formation, this effect is usually reversible and osteoporosis in MS patients may be independent of the short-term corticosteroid treatment. Clinical evidence suggests an important role of vitamin D as a modifiable risk factor in MS. Low circulating levels of vitamin D have been found in MS patients, especially during relapses, suggesting that vitamin D could be involved in the regulation of the clinical disease activity. Vitamin D mediates its function through a single vitamin D receptor (VDR). Polymorphisms of the VDR have major effects on vitamin D function and metabolism, and some VDR genotypes have been linked to osteoporosis and MS. Because the safety of high doses of vitamin D has not been established yet, vitamin D hasn't been used in enough doses to increase the serum level to a desired therapeutic target. Future clinical trials should determine the upper limit of vitamin D intake in order to achieve therapeutic benefit in MS patients.

Regulatory T cells in asthma

Asthma is characterized by T helper cell 2 (Th2) type inflammation, leading to airway hyperresponsiveness and tissue remodeling. Th2 cell-driven inflammation is likely to represent an abnormal response to harmless airborne particles. These reactions are normally suppressed by regulatory T cells, which maintain airway tolerance. The anti-inflammatory cytokine IL-10 is likely to play a central role. The role of the cytokine transforming growth factor beta (TGF-beta) is more complex, with evidence for immune suppression and remodeling in the airways. In asthmatic individuals there is a breakdown in these regulatory mechanisms. There is emerging evidence that early life events, including exposure to allergen and infections, are critical in programming effective regulatory pathways to maintain pulmonary homeostasis. In this review we examine the clinical and experimental evidence for T regulatory cell function in the lung and discuss the events that might influence the functioning of these cells. Ultimately, the ability to enhance regulatory function in affected individuals may represent an effective treatment for asthma.

Vitamin D deficiency in the intensive care unit: an invisible accomplice to morbidity and mortality?

The association between vitamin D deficiency and chronic illness is well-known. Vitamin D deficiency has been associated with increased mortality in the general population. Despite this knowledge, vitamin D insufficiency is seldom considered and rarely replaced adequately, if at all, in critically ill patients in intensive care. We present a hypothetic model demonstrating how vitamin D deficiency may be an unrecognized contributor to adverse outcome in intensive care patients.

The vitamin D3 transcriptomic response in skin cells derived from the Atlantic bottlenose dolphin

The Atlantic bottlenose dolphin has attracted attention due to the evident impact that environmental stressors have taken on its health. In order to better understand the mechanisms linking environmental health with dolphin health, we have established cell cultures from dolphin skin as in vitro tools for molecular evaluations. The vitamin D3 pathway is one mechanism of interest because of its well established chemopreventative and immunomodulatory properties in terrestrial mammals. On the other hand, little is known of the physiological role of this molecule in aquatic animals. 1,25-dihydroxyvitamin D3 (1,25D3), the bioactive and hormonal form of vitamin D3, exerts its biological function by binding to the vitamin D receptor (VDR), a ligand-activated regulator of gene transcription. Therefore, we investigated the transcriptomic changes induced by 1,25D3 administration in dolphin skin cells. Identification of specific genes activated by 1,25D3 has provided clues to the physiological function of the vitamin D3 pathway in the dolphin. We found that exposure of the cells to 1,25D3 upregulated transactivation of a vitamin D-sensitive promoter. cDNA microarray analysis, using a novel dolphin array, identified specific gene targets within this pathway, and real-time PCR (qPCR) confirmed the enhanced expression of select genes of interest. These transcriptional changes correlated with an increase in VDR levels. This is the first report of the presence and activation of the vitamin D3 pathway in a marine mammal, and our experimental results demonstrate a number of similarities to terrestrial animals. Conservation of this pathway in the Atlantic bottlenose dolphin is consistent with the importance of nonclassic functions of vitamin D3, such as its role in innate immunity, similar to what has been demonstrated in other mammals.

Plasmacytoid dendritic cells in autoimmune diabetes - potential tools for immunotherapy

Type 1 diabetes (T1D) is an autoimmune disease in which a T-cell-mediated attack destroys the insulin-producing cells of the pancreatic islets. Despite insulin supplementation severe complications ask for novel treatments that aim at cure or delay of the onset of the disease. In spontaneous animal models for diabetes like the nonobese diabetic (NOD) mouse, distinct steps in the pathogenesis of the disease can be distinguished. In the past 10 years it became evident that DC and macrophages play an important role in all three phases of the pathogenesis of T1D. In phase 1, dendritic cells (DC) and macrophages accumulate at the islet edges. In phase 2, DC and macrophages are involved in the activation of autoreactive T cells that accumulate in the pancreas. In the third phase the islets are invaded by macrophages, DC and NK cells followed by the destruction of the beta-cells. Recent data suggest a role for a new member of the DC family: the plasmacytoid DC (pDC). pDC have been found to induce tolerance in experimental models of asthma. Several studies in humans and the NOD mouse support a similar role for pDC in diabetes. Mechanisms found to be involved in tolerance induction by pDC are inhibition of effector T cells, induction of regulatory T cells, production of cytokines and indoleamine 2,3-dioxygenase (IDO). The exact mechanism of tolerance induction by pDC in diabetes remains to be established but the intrinsic tolerogenic properties of pDC provide a promising, yet underestimated target for therapeutic intervention.

Combination treatment with progesterone and vitamin D hormone may be more effective than monotherapy for nervous system injury and disease

More than two decades of pre-clinical research and two recent clinical trials have shown that progesterone (PROG) and its metabolites exert beneficial effects after traumatic brain injury (TBI) through a number of metabolic and physiological pathways that can reduce damage in many different tissues and organ systems. Emerging data on 1,25-dihydroxyvitamin D(3) (VDH), itself a steroid hormone, have begun to provide evidence that, like PROG, it too is neuroprotective, although some of its actions may involve different pathways. Both agents have high safety profiles, act on many different injury and pathological mechanisms, and are clinically relevant, easy to administer, and inexpensive. Furthermore, vitamin D deficiency is prevalent in a large segment of the population, especially the elderly and institutionalized, and can significantly affect recovery after CNS injury. The combination of PROG and VDH in pre-clinical and clinical studies is a novel and compelling approach to TBI treatment.

Vitamin D and immune function: understanding common pathways

Vitamin D, acting through its active metabolite 1,25(OH)(2)D(3), exerts its influence on many physiologic processes in addition to the regulation of calcium and phosphate homeostasis. These processes include the immune system. Both the adaptive and innate immune systems are affected by 1,25(OH)(2)D(3) and its receptor, and the cells involved express not only the vitamin D receptor but also, in most cases, the enzyme CYP27B1, which produces 1,25(OH)(2)D(3). Both the vitamin D receptor and CYP27B1 can be constitutive or induced by the ligands that activate the immune processes in these cells, providing feedback loops that help regulate the immune response. In general, 1,25(OH)(2)D(3) suppresses most elements of the adaptive immune system while inducing most elements of the innate immune system. Thus 1,25(OH)(2)D(3) may be protective against various autoimmune diseases and may limit graft rejection by suppressing adaptive immunity while enhancing the first line of defense against invading microorganisms via upregulation of innate immunity.

Function and dysfunction of dendritic cells in autoimmune rheumatic diseases

Dendritic cells (DC) have been implicated both in initiation of immunity and in immune tolerance. The mechanisms whereby tolerogenic DC may induce and maintain peripheral tolerance include the generation or expansion of regulatory T cells (Treg) and the promotion of T-cell anergy or deletion. A wide spectrum of hematopoietic growth factors and cytokines are endowed with the ability to differentiate tolerogenic DC both in vitro and in vivo. Based on this knowledge, therapeutic vaccination with cytokine-modulated tolerogenic DC has been applied to animal models of autoimmune disorders. This article will review the current experimental evidence underpinning DC dysfunction in rheumatic autoimmune diseases and will discuss how the manipulation of DC and Treg number and function may control undesired T-cell responses.

Dendritic cell tolerogenicity: a key mechanism in immunomodulation by vitamin D receptor agonists

Dendritic cells (DC) induce or tolerize T cells, and tolerogenic DCs can promote the development of regulatory T cells (Treg) with suppressive activity. Thus, the possibility of manipulating DCs and enhancing their tolerogenic properties using different pharmacologic or biologic agents could be exploited to control a variety of chronic immuno-mediated inflammatory conditions. Among agents able to promote induction of tolerogenic DCs, vitamin D receptor (VDR) agonists have attracted considerable attention, also because of their potential in clinical translation. DCs are key targets for the immunomodulatory effects of VDR agonists, which shape DC phenotype and function, enhancing their tolerogenicity in adaptive immune responses. Tolerogenic DCs induced by a short treatment with VDR agonists promote CD4+CD25+Foxp3+ Treg cells that are able to mediate transplantation tolerance and to arrest the development of autoimmune diseases. VDR agonists not only favor induction of CD4+CD25+ Treg cells, but can also enhance their recruitment at inflammatory sites. The tolerogenic properties induced by VDR agonists in DCs, leading to enhanced Treg cell development, likely contribute to the beneficial activity of these hormone-like molecules in autoimmune disease and graft rejection models, highlighting their applicability to the treatment of chronic inflammatory conditions sustained by autoreactive or alloreactive immune responses.

Genome-wide association study identifies new multiple sclerosis susceptibility loci on chromosomes 12 and 20

To identify multiple sclerosis (MS) susceptibility loci, we conducted a genome-wide association study (GWAS) in 1,618 cases and used shared data for 3,413 controls. We performed replication in an independent set of 2,256 cases and 2,310 controls, for a total of 3,874 cases and 5,723 controls. We identified risk-associated SNPs on chromosome 12q13-14 (rs703842, P = 5.4 x 10(-11); rs10876994, P = 2.7 x 10(-10); rs12368653, P = 1.0 x 10(-7)) and upstream of CD40 on chromosome 20q13 (rs6074022, P = 1.3 x 10(-7); rs1569723, P = 2.9 x 10(-7)). Both loci are also associated with other autoimmune diseases. We also replicated several known MS associations (HLA-DR15, P = 7.0 x 10(-184); CD58, P = 9.6 x 10(-8); EVI5-RPL5, P = 2.5 x 10(-6); IL2RA, P = 7.4 x 10(-6); CLEC16A, P = 1.1 x 10(-4); IL7R, P = 1.3 x 10(-3); TYK2, P = 3.5 x 10(-3)) and observed a statistical interaction between SNPs in EVI5-RPL5 and HLA-DR15 (P = 0.001).

Chronic inflammation in the pathogenesis of benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a common disorder affecting 50-80% of the aged male population. Androgens and age have been traditionally considered the main determinants of prostate enlargement, but in the last years a potentially important role of chronic inflammation in BPH pathogenesis has emerged. Bacterial and non-infectious chronic prostatitis could represent inciting factors leading to tissue hyperproliferation, possibly via the recently demonstrated antigen-presenting capacity of prostatic stromal cells, enabling them to induce and sustain intraglandular immune responses. The prostate growth-promoting chemokine IL-8 could represent a direct link between chronic prostate inflammation and autocrine/paracrine stromal cell proliferation, in agreement with its marked secretion induced in BPH stromal cells by a combination of Th1 and Th17 cell-derived inflammatory cytokines. BPH stromal cells express the vitamin D receptor (VDR), which is up-regulated by exposure to inflammatory stimuli. The non-hypercalcaemic VDR agonist elocalcitol, shown to arrest BPH development by decreasing the intra-prostatic androgen signalling without directly interfering with systemic androgen action, exerts immunoregulatory and anti-inflammatory properties in different prostatic pathology characterized by growth and inflammation. The mechanism of action of VDR agonists supports an important role of chronic inflammation in BPH pathogenesis and strengthens the concept of these agents as a therapeutic option for pharmacological treatment of BPH.

Vitamin D receptor polymorphisms are associated with increased susceptibility to primary biliary cirrhosis in Japanese and Italian populations

BACKGROUND/AIMS

Vitamin D receptor (VDR) agonists have recently been identified as potent immunomodulators capable of inhibiting Th1-mediated immune response, leading us to consider the hypothesis that functional VDR polymorphisms might contribute to enhanced risk for developing primary biliary cirrhosis (PBC), a Th1-mediated autoimmune disease. In the current study, we aimed at elucidating the genetic association of VDR polymorphisms with susceptibility to PBC in Japanese and Italian populations.

METHODS

We enrolled 334 PBC patients (195 Japanese and 139 Italians), as well as 334 age- and sex-matched controls (179 Japanese and 156 Italians). VDR genotyping was performed by PCR-RFLP, using BsmI, ApaI and TaqI endonucleases.

RESULTS

The genotype BB of BsmI polymorphism was significantly associated with PBC (OR = 1.80 [95% CI; 1.19-2.73], p = 0.005). The association of the genotype BB was observed in Japanese (OR = 13.77, p = 0.001), and Italians (OR = 1.83, p = 0.019), respectively, although not significant in Italians after Bonferroni correction. The frequency of the B allele at the BsmI polymorphism was significantly higher in PBC patients (OR = 1.27 [95% CI; 1.02-1.59], p = 0.040).

CONCLUSIONS

The genotype 'BB' as well as 'B' allele at BsmI polymorphism of the VDR gene contribute to the risk of PBC development.

Calcitriol suppresses antiretinal autoimmunity through inhibitory effects on the Th17 effector response

Experimental autoimmune uveitis (EAU) serves as a model for human autoimmune uveitis and for cell-mediated autoimmunity in general. EAU induced in mice by immunization with the retinal Ag interphotoreceptor retinoid-binding protein in CFA is driven by the Th17 response. Oral calcitriol (1,25-dihydroxyvitamin D(3)) prevented as well as partly reversed disease and suppressed immunological responses. In vitro, calcitriol directly suppressed IL-17 induction in purified naive CD4(+) T cells without inhibiting Th17 lineage commitment, as reflected by unaltered RORgammat, STAT3, and FoxP3 expression. In contrast, in vivo treatment with calcitriol of mice challenged for EAU impaired commitment to the Th17 lineage, as judged by reduction of both RORgammat and IL-17 in CD4(+) T cells. Innate immune response parameters in draining lymph nodes of treated mice were suppressed, as was production of IL-1, IL-6, TNF-alpha, and IL-12/IL-23p40, but not IL-10, by explanted splenic dendritic cells (DC). Finally, supernatants of calcitriol-conditioned bone marrow-derived DC had reduced ability to support Th17 polarization of naive CD4(+) T cells in vitro and in vivo. Thus, calcitriol appears to suppress autoimmunity by inhibiting the Th17 response at several levels, including the ability of DC to support priming of Th17 cells, the ability of CD4(+) T cells to commit to the Th17 lineage, and the ability of committed Th17 T cells to produce IL-17.

Insights into endocrine-immunological disturbances in autoimmunity and their impact on treatment

The neuroendocrine immune (NEI) system is regarded as a fundamental network for the maintenance of health status (homeostasis), and it plays an important role in several systemic diseases, including autoimmune disorders. Among the major players of NEI pathways are steroid hormones of the adrenal (cortisol) and gonadal glands (sex hormones), neurohormones such as melatonin, and more recently the vitamin D endocrine system. Estrogens, melatonin and chronic stress (inducing decreased adrenal glucocorticoid release over a long time) strongly modulate the NEI system and stimulate the immune response. The vitamin D endocrine system is regarded as a potential immunosuppressive factor. Consequently, estrogens (especially in patients affected by B-cell-driven immunity) and melatonin should be avoided, and glucocorticoids (as replacement therapy) and vitamin D are allowed in the treatment of autoimmunity.

The vitamin D receptor agonist elocalcitol inhibits IL-8-dependent benign prostatic hyperplasia stromal cell proliferation and inflammatory response by targeting the RhoA/Rho kinase and NF-kappaB pathways

BACKGROUND

Benign prostatic hyperplasia (BPH) is characterized by an important inflammatory component. Stimulation of human prostate stromal cells from BPH tissues with proinflammatory cytokines leads to secretion of IL-8, a chemokine involved in BPH pathogenesis. The vitamin D receptor (VDR) agonist elocalcitol can arrest prostate growth in BPH patients, but its mechanism of action in this pathology is still incompletely understood.

METHODS

IL-8 levels were measured by real-time RT-PCR and ELISA. NF-kappaB translocation and COX-2 expression were evaluated by confocal microscopy. RhoA and Rho-kinase (ROCK) gene expression and functional activity were studied by real-time RT-PCR, immuno-kinase assays, Western blot analysis, confocal microscopy, and cell invasion.

RESULTS

Stimulation of BPH cells with IL-8 activates the calcium-sensitizing RhoA/ROCK pathway, as demonstrated by the increased membrane translocation of RhoA and by phosphorylation of the ROCK substrate myosin phosphatase target subunit 1 (MYPT-1). In agreement with these data, C3 exoenzyme, a selective RhoA inhibitor, inhibits IL-8-induced invasion of BPH cells. The VDR agonist elocalcitol significantly inhibits IL-8 production by BPH cells stimulated with inflammatory cytokines, and IL-8-induced proliferation of BPH cells. In addition, elocalcitol inhibits IL-8-induced membrane translocation of RhoA and MYPT-1 phosphorylation in BPH cells, and inhibits dose-dependently their IL-8-dependent invasion. The inhibition induced by elocalcitol of IL-8 production by BPH cells is accompanied by decreased COX-2 expression and PGE(2) production and by arrest of NF-kappaB p65 nuclear translocation, associated with inhibition of the RhoA/ROCK pathway.

CONCLUSIONS

These data provide a mechanistic explanation for the anti-proliferative and anti-inflammatory properties of elocalcitol in BPH cells.

Immunomodulatory effects of Vitamin D in multiple sclerosis

Although Vitamin D is best known as a modulator of calcium homeostasis, it also has immune modulating potential. A protective effect of Vitamin D on multiple sclerosis is supported by the reduced risk associated with sun exposure and use of Vitamin D supplements. Moreover, high circulating levels of Vitamin D have been associated with lower risk of multiple sclerosis. In this study, we measured 1,25 (OH)(2) Vitamin D and 25 (OH) Vitamin D levels in multiple sclerosis patients separated into different clinical subgroups according to disease status. In addition, direct effects of 1,25 (OH)(2) Vitamin D on ex vivo CD4+ T cells and myelin-peptide specific T cell lines were investigated to gain more insight into putative regulatory mechanisms in the disease pathogenesis. One hundred and thirty-two Hispanic patients with clinically definite multiple sclerosis were studied, 58 with relapsing remitting multiple sclerosis during remission, 34 during relapse and 40 primary progressive multiple sclerosis cases. Sixty healthy individuals matched with respect to place of residence, race/ethnicity, age and gender served as controls. Levels of 25(OH)D(3) and 1,25(OH)(2)D(3), measured by ELISA were significantly lower in relapsing-remitting patients than in controls. In addition, levels in patients suffering relapse were lower than during remissions. In contrast, primary progressive patients showed similar values to controls. Proliferation of both freshly isolated CD4+ T cells and MBP-specific T cells was significantly inhibited by 1,25(OH)(2)D(3). Moreover, activated Vitamin D enhanced the development of IL-10 producing cells, and reduced the number of IL-6 and IL-17 secreting cells. Notably, Vitamin D receptor expression was induced by 1,25(OH)(2)D(3) in both activated and resting cells. Interestingly, T cells were able to metabolize 25(OH)D(3) into biologically active 1,25(OH)(2)D(3), since T cells express alpha1-hydroxylase constitutively. Finally, 1,25(OH)(2)D(3) also increased the expression and biological activity of indoleamine 2,3-dioxygenase, mediating significant increase in the number of CD4+CD25+ T regulatory cells. Collectively, these data suggest that 1,25(OH)(2)D(3) plays an important role in T cell homeostasis during the course of multiple sclerosis, thus making correction of its deficiency may be useful during treatment of the disease.

1,25-dihydroxyvitamin D3 is an autonomous regulator of the transcriptional changes leading to a tolerogenic dendritic cell phenotype

Activation of vitamin D receptor (VDR) by 1,25-dihydroxyvitamin D(3) (1,25-vitD) reprograms dendritic cells (DC) to become tolerogenic. Previous studies suggested that 1,25-vitD could inhibit the changes brought about by differentiation and maturation of DCs. Underpinning the described phenotypic and functional alterations, there must be 1,25-vitD-coordinated transcriptional events. However, this transcriptional program has not been systematically investigated, particularly not in a developmental context. Hence, it has not been explored how 1,25-vitD-regulated genes, particularly the ones bringing about the tolerogenic phenotype, are connected to differentiation. We conducted global gene expression analysis followed by comprehensive quantitative PCR validation to clarify the interrelationship between 1,25-vitD and differentiation-driven gene expression patterns in developing human monocyte-derived and blood myeloid DCs. In this study we show that 1,25-vitD regulates a large set of genes that are not affected by differentiation. Interestingly, several genes, impacted both by the ligand and by differentiation, appear to be regulated by 1,25-vitD independently of the developmental context. We have also characterized the kinetics of generation of 1,25-vitD by using three early and robustly regulated genes, the chemokine CCL22, the inhibitory receptors CD300LF and CYP24A1. We found that monocyte-derived DCs are able to turn on 1,25-vitD sensitive genes in early phases of differentiation if the precursor is present. Our data collectively suggest that exogenous or endogenously generated 1,25-vitD regulates a large set of its targets autonomously and not via inhibition of differentiation and maturation, leading to the previously characterized tolerogenic state.

Type 1 diabetes, the A1 milk hypothesis and vitamin D deficiency

The 'A1' genetic variant of beta-casein in milk has been linked to type 1 diabetes (T1D). The keystone piece of supporting evidence is an ecological study positively correlating the incidence of T1D with amount of A1 beta-casein consumption per capita. Of relevance, A1 beta-casein consumption is also positively correlated with latitude, itself implicated in T1D through vitamin D deficiency. Ecological and biological evidence convincingly implicate vitamin D deficiency in T1D. Latitude is a confounder of the ecological data that underpin the hypothesis that A1 beta-casein in cow's milk is a causative factor in T1D.

Immunomodulatory effects of BXL-01-0029, a less hypercalcemic vitamin D analogue, in human cardiomyocytes and T cells

Current immunosuppressive protocols have reduced rejection occurrence in heart transplantation; nevertheless, management of heart transplant recipients is accompanied by major adverse effects, due to drug doses close to toxic range. In allograft rejection, characterized by T-helper 1 (Th1) cell-mediated response, the CXCL10-CXCR3 axis plays a pivotal role in triggering a self-promoting inflammatory loop. Indeed, CXCL10 intragraft production, required for initiation and development of graft failure, supports organ infiltration by Th1 cells. Thus, targeting the CXCL10-CXCR3 axis while avoiding generalized immunosuppression, may be of therapeutic significance. Based on preclinical evidence for immunoregulatory properties of vitamin D receptor agonists, we propose that a less hypercalcemic vitamin D analogue, BXL-01-0029, might have the potential to contribute to rejection management. We investigated the effect of BXL-01-0029 on CXCL10 secretion induced by proinflammatory stimuli, both in human isolated cardiomyocytes (Hfcm) and purified CD4+ T cells. Mycophenolic acid (MPA), the active agent of mycophenolate mofetil, was used for comparison. BXL-01-0029 inhibited IFNgamma and TNFalpha-induced CXCL10 secretion by Hfcm more potently than MPA, impairing cytokine synergy and pathways. BXL-01-0029 reduced also CXCL10 protein secretion and gene expression by CD4+ T cells. Furthermore, BXL-01-0029 did not exert any toxic effect onto both cell types, suggesting its possible use as a dose-reducing agent for conventional immunosuppressive drugs in clinical transplantation.