Enhanced production of IL-17A in patients with severe asthma is inhibited by 1α,25-dihydroxyvitamin D3 in a glucocorticoid-independent fashion

Protease activity of Per a 10 potentiates Th2 polarization by increasing IL-23 and OX40L

Proteases are implicated in exacerbation of allergic diseases. In this study, the role of proteolytic activity of Per a 10 was evaluated on Th2 polarization. Intranasal administration of Per a 10 in mice led to allergic airway inflammation as seen by higher IgE levels, cellular infiltration, IL-17A, and Th2 cytokines, whereas, inactive (Δ)Per a 10 showed attenuated response. There was an increased OX40L expression on lung and lymph node dendritic cells in Per a 10 immunized group and on Per a 10 stimulated BMDCs. Reduction in CD40 expression without any change at transcript level in lungs of Per a 10 immunized mice suggested CD40 cleavage. BMDCs pulsed with Per a 10 showed reduced CD40 expression with lower IL-12p70 secretion as compared to heat inactivated Per a 10. IL-23, TNF-α, and IL-6 levels were significantly higher in Per a 10 stimulated BMDCs supernatant. In DC-T cell coculture studies, Per a 10 pulsed BMDCs showed higher levels of IL-4 and IL-13 that were reduced on blocking of either IL-23 or OX40L. In conclusion, the data suggests a critical role of protease activity of Per a 10 in promoting Th2 polarization by increasing IL-23 secretion and OX40L expression on dendritic cells.

Vitamin D influences asthmatic pathology through its action on diverse immunological pathways

The prevalence of vitamin D insufficiency and deficiency has increased markedly in recent decades to current epidemic levels (Hyppönen E, et al. Am J Clin Nutr 2007;85:860-868). In parallel, there has been an increase in the incidence of a range of immune-mediated conditions ranging from cancer to autoimmune and respiratory diseases, including chronic obstructive pulmonary disease and asthma (Holick MF. N Engl J Med 2007;357:266-281; Finklea et al. Adv Nutr 2011;2:244-253). There is also an association with increased respiratory infections, which are the most common cause of asthma exacerbations (Finklea et al. Adv Nutr 2011;2:244-253). Together, this has resulted in considerable interest in the therapeutic potential of vitamin D to prevent and improve treatment of asthma and other respiratory diseases. To this end, data from clinical trials involving supplementation with active vitamin D, or more commonly a precursor, are starting to emerge. This review considers mechanisms by which vitamin D may act on the immune system to dampen inappropriate inflammatory responses in the airway while also promoting tolerance and antimicrobial defense mechanisms that collectively maintain respiratory health.

Vitamin D, Inflammation, and Colorectal Cancer Progression: A Review of Mechanistic Studies and Future Directions for Epidemiological Studies

Survival from colorectal cancer is positively associated with vitamin D status. However, whether this association is causal remains unclear. Inflammatory processes may link vitamin D to colorectal cancer survival, and therefore investigating inflammatory markers as potential mediators may be a valuable next step. This review starts with an overview of inflammatory processes suggested to be involved in colorectal cancer progression and regulated by vitamin D. Next, we provide recommendations on how to study inflammatory markers in future epidemiologic studies on vitamin D and colorectal cancer survival. Mechanistic studies have shown that calcitriol-active form of vitamin D-influences inflammatory processes involved in cancer progression, including the enzyme cyclooxygenase 2, the NF-κB pathway, and the expression of the cytokines TNFα, IL1β, IL6, IL8, IL17, and TGFβ1. Based on this and taking into account methodologic issues, we recommend to include analysis of specific soluble peptides and proteins, such as cytokines, in future epidemiologic studies on this issue. Vitamin D and the markers should preferably be measured at multiple time points during disease progression or recovery and analyzed using mediation analysis. Including these markers in epidemiologic studies may help answer whether inflammation mediates a causal relationship between vitamin D and colorectal cancer survival.

1α,25-dihydroxyvitamin D3 acts via transforming growth factor-β to up-regulate expression of immunosuppressive CD73 on human CD4+ Foxp3- T cells

Vitamin D deficiency is associated with increased incidence and severity of various immune-mediated diseases. Active vitamin D (1α,25-dihydroxyvitamin D3; 1,25(OH)2 D3) up-regulates CD4(+) T-cell expression of the purine ectonucleotidase CD39, a molecule that is associated with the generation of anti-inflammatory adenosine. Here we aimed to investigate the direct impact of 1,25(OH)2 D3 on expression of the downstream ecto-5'-nucleotidase CD73 by human CD4 T cells, and components of the transforming growth factor-β (TGF-β) pathway, which have been implicated in the modulation of CD73 by murine T cells. At 10(-8) to 10(-7) m, 1,25(OH)2 D3 significantly increased expression of CD73 on peripheral human CD4(+) T cells. Although 1,25(OH)2 D3 did not affect the mRNA expression of latent TGF-β1 , 1,25(OH)2 D3 did up-regulate expression of TGF-β-associated molecules [latency-associated peptide (LAP), glycophorin A repetitions predominant (GARP), GP96, neuropilin-1, thrombospondin-1 and αv integrin] which is likely to have contributed to the observed enhancement in TGF-β bioactivity. CD73 was highly co-expressed with LAP and GARP following 1,25(OH)2 D3 treatment, but unexpectedly, each of these cell surface molecules was expressed primarily on CD4(+) Foxp3(-) T cells, rather than CD4(+) Foxp3(+) T cells. Notably, neutralization of TGF-β significantly impaired 1,25(OH)2 D3-mediated induction of CD73. Collectively, we show that 1,25(OH)2 D3 enhances expression of CD73 on CD4(+) Foxp3(-) T cells in a process that is at least partially TGF-β-dependent. These data reveal an additional contributing mechanism by which vitamin D may be protective in immune-mediated disease.

Dll4 in the DCs isolated from OVA-sensitized mice is involved in Th17 differentiation inhibition by 1,25-dihydroxyvitamin D3 in vitro

INTRODUCTION

T helper 17 cell (Th17) cells play an important role in neutrophilic asthma, and 1,25(OH)2D3 has been reported to modulate the proliferation and differentiation of T cells. In this study, we examined the effects of 1,25(OH)2D3 on the dendritic cell (DC)-mediated regulation of Th17differentiation from OVA-sensitized mice.

METHODS

DCs were isolated from ovalbumin-sensitized mouse spleens. Lipopolysaccharide (LPS) was administered to stimulate the DCs for 24 h, and dexamethasone or 1,25(OH)2D3 was applied simultaneously. The expression of Notch ligand delta-like ligand 4 (Dll4) in the DCs was detected in each group. All the groups of treated DCs were co-cultured with T cells, and Dll4 was inhibited in these groups. After 24 h, Th17 and Treg cell differentiation and the IL-17A levels were measured.

RESULTS

Dll4 expression was increased in LPS-treated DCs compared with the control group (p = 0.05), resulting in increased Th17 cell differentiation (p = 0.002). Treatment with 1,25(OH)2D3 inhibited the Dll4 expression(p = 0.04) and decreased Th17 cell differentiation (p = 0.001) in DCs that was induced by LPS. Directly inhibiting Dll4 reduced Th17 cell differentiation, and Th17 cell differentiation was not further inhibited by 1,25(OH)2D3 once Dll4 was blocked.

CONCLUSIONS

These result suggest that Dll4 in the DCs isolated from OVA-sensitized mice is involved in Th17 differentiation inhibition by 1,25(OH)2D3.

Vitamin D Supplementation for Childhood Asthma: A Systematic Review and Meta-Analysis

Importance

There is growing evidence that vitamin D plays a role in the pathogenesis of asthma but it is unclear whether supplementation during childhood may improve asthma outcomes.

Objectives

The objective of this systematic review and meta-analysis was to evaluate the efficacy and safety of vitamin D supplementation as a treatment or adjunct treatment for asthma.

Data Sources

We searched MEDLINE, Embase, CENTRAL, and CINAHL through July 2014.

Study Selection

We included RCTs that evaluated vitamin D supplementation in children versus active control or placebo for asthma.

Data Extraction and Synthesis

One reviewer extracted data and one reviewer verified data accuracy. We qualitatively summarized the main results of efficacy and safety and meta-analyzed data on comparable outcomes across studies. We used GRADE for strength of evidence.

Main Outcome Measures

Main planned outcomes measures were ED visits and hospitalizations. As secondary outcomes, we examined measures of asthma control, including frequency of asthma exacerbations, asthma symptom scores, measures of lung function, β₂-agonist use and daily steroid use, adverse events and 25-hydroxyvitamin D levels.

Results

Eight RCTs (one parallel, one crossover design) comprising 573 children aged 3 to 18 years were included. One study (moderate-quality, n = 100) reported significantly less ED visits for children treated with vitamin D. No other studies examined the primary outcome (ED visits and hospitalizations). There was a reduced risk of asthma exacerbations in children receiving vitamin D (low-quality; RR 0.41, 95% CI 0.27 to 0.63, 3 studies, n = 378). There was no significant effect for asthma symptom scores and lung function. The serum 25(OH)D level was higher in the vitamin D group at the end of the intervention (low-quality; MD 19.66 nmol/L, 95% CI 5.96 nmol/L to 33.37 nmol/L, 5 studies, n = 167).

Limitations

We identified a high degree of clinical diversity (interventions and outcomes) and methodological heterogeneity (sample size and risk of bias) in included trials.

Conclusions and Relevance

Randomized controlled trials provide some low-quality evidence to support vitamin D supplementation for the reduction of asthma exacerbations. Evidence on the benefits of vitamin D supplementation for other asthma-related outcomes in children is either limited or inconclusive. We recommend that future trials focus on patient-relevant outcomes that are comparable across studies, including standardized definitions of asthma exacerbations.

The effect of vitamin D on airway reactivity and inflammation in asthmatic children: A double-blind placebo-controlled trial

BACKGROUND

Cross-sectional studies have reported an association of vitamin D deficiency with increased asthma prevalence and severity, and with allergies. The effect of vitamin D as sole therapy on airway hyper-reactivity (AHR) and airway inflammation has not been reported.

AIM

To evaluate the effect of vitamin D therapy on AHR as assessed by methacholine concentration, causing a 20% reduction in FEV1 (PC20 -FEV1 ) and fractional exhaled nitric oxide (FeNO), systemic markers of allergy and inflammation, and exhaled breath condensate cytokines.

PATIENTS AND METHODS

Children aged 6-18 years with a clinical diagnosis of mild asthma currently not receiving anti-inflammatory therapy and with low vitamin D levels were included in this randomized, double-blind, placebo-controlled study assessing the effect of 6 weeks of treatment with oral vitamin D 14,000 units once weekly or placebo.

RESULTS

Of the 39 patients included, 20 received vitamin D treatment and 19 received a placebo. Vitamin D replacement resulted in a significant increase in vitamin levels, which remained unchanged in the placebo group (P < 0.0001). There was no change in IgE, eosinophil count, high sensitivity C-reactive protein, FeNO levels or PC20 -FEV1 following treatment. Similar values of exhaled breath condensate cytokines (IL4, IL5, IL10, IL17, and γ interferon) were observed in both groups.

CONCLUSIONS

In our small group of children with mild asthma, no difference could be demonstrated between the effect of vitamin D and placebo, despite significant increases in vitamin D blood levels. Larger interventional studies are needed to fully explore the possible effect of vitamin D in asthma.

Vitamin D Modulates Expression of the Airway Smooth Muscle Transcriptome in Fatal Asthma

Globally, asthma is a chronic inflammatory respiratory disease affecting over 300 million people. Some asthma patients remain poorly controlled by conventional therapies and experience more life-threatening exacerbations. Vitamin D, as an adjunct therapy, may improve disease control in severe asthma patients since vitamin D enhances glucocorticoid responsiveness and mitigates airway smooth muscle (ASM) hyperplasia. We sought to characterize differences in transcriptome responsiveness to vitamin D between fatal asthma- and non-asthma-derived ASM by using RNA-Seq to measure ASM transcript expression in five donors with fatal asthma and ten non-asthma-derived donors at baseline and with vitamin D treatment. Based on a Benjamini-Hochberg corrected p-value <0.05, 838 genes were differentially expressed in fatal asthma vs. non-asthma-derived ASM at baseline, and vitamin D treatment compared to baseline conditions induced differential expression of 711 and 867 genes in fatal asthma- and non-asthma-derived ASM, respectively. Functional gene categories that were highly represented in all groups included extracellular matrix, and responses to steroid hormone stimuli and wounding. Genes differentially expressed by vitamin D also included cytokine and chemokine activity categories. Follow-up qPCR and individual analyte ELISA experiments were conducted for four cytokines (i.e. CCL2, CCL13, CXCL12, IL8) to measure TNFα-induced changes by asthma status and vitamin D treatment. Vitamin D inhibited TNFα-induced IL8 protein secretion levels to a comparable degree in fatal asthma- and non-asthma-derived ASM even though IL8 had significantly higher baseline levels in fatal asthma-derived ASM. Our findings identify vitamin D-specific gene targets and provide transcriptomic data to explore differences in the ASM of fatal asthma- and non-asthma-derived donors.

Developments in the field of allergy in 2013 through the eyes of Clinical and Experimental Allergy

2013 was another exciting year for allergy in general and Clinical and Experimental Allergy in particular. In the field of asthma and rhinitis, there continued to be a focus on heterogeneity and phenotypes with increasing use of biostatistical techniques to determine clusters of similar populations. Obesity- and aspirin-associated disease are intriguing associations with asthma which were explored in a number of papers. We published a number of excellent papers on mechanisms of airway inflammation and how this relates to physiology, pathology, genetics and biomarkers in both human and experimental model systems. In terms of mechanisms, there is less on individual cell types in allergic disease at the moment, but the immunology of allergic disease continued to fascinate our authors. Another area that was popular both in the mechanisms and in the epidemiology sections was early life events and how these lead to allergic disease, with an increasing focus on the role of the microbiome and how this influences immune tolerance. In the clinical allergy section, oral immunotherapy for food allergy is clearly a major topic of interest at the moment as was in vitro testing to distinguish between sensitization and allergic disease. There was less on inhalant allergy this year, but a good representation from the drug allergy community including some interesting work on non-IgE-mediated mechanisms. In the allergen section, important new allergens continue to be discovered, but the major focus as in the last couple of years was on working out how component-resolved approaches can improve diagnosis and management of food and venom allergy.

The impact of diet on asthma and allergic diseases

The incidence of allergic diseases is increasing, both in developed and developing countries, concomitantly with the rise in living standards and the adoption of a 'western lifestyle'. For two decades, the hygiene hypothesis - which proposes that the lack of early childhood exposure to infectious agents increases susceptibility to allergic diseases in later life - provided the conceptual framework for unravelling the mechanisms that could account for the increased incidence of allergic diseases. In this Review, we discuss recent evidence that highlights the role of diet as a key factor influencing immune homeostasis and the development of allergic diseases through a complex interplay between nutrients, their metabolites and immune cell populations. Although further investigations are still required to understand these complex relationships, recent data have established a possible connection between metabolic homeostasis and allergic diseases.

The potential role of vitamin D in the link between obesity and asthma severity/control in children

Childhood obesity and asthma are major public health problems. Obesity is not only associated with increased risk of incident asthma, but it may worsen asthma severity/control. Although the mechanisms linking obesity with asthma expression have not been completely elucidated, evidence suggests that increased frequency of acute respiratory infection (ARI) and decreased corticosteroid responsiveness may help to explain how obesity worsens asthma expression. In addition, obese individuals have low vitamin D status, and emerging evidence suggests vitamin D affects risk of ARI and corticosteroid responsiveness in individuals with asthma. In this review, we summarize the association between obesity and asthma severity/control in children and discuss ARI and corticosteroid responsiveness as potential mediators in the obesity-asthma pathway. We also discuss the potential role of vitamin D, including a brief summary of recent randomized controlled trials of vitamin D supplementation.

Nitric oxide sustains IL-1β expression in human dendritic cells enhancing their capacity to induce IL-17-producing T-cells

The role played by lung dendritic cells (DCs) which are influenced by external antigens and by their redox state in controlling inflammation is unclear. We studied the role played by nitric oxide (NO) in DC maturation and function. Human DCs were stimulated with a long-acting NO donor, DPTA NONOate, prior to exposure to lipopolysaccharide (LPS). Dose-and time-dependent experiments were performed with DCs with the aim of measuring the release and gene expression of inflammatory cytokines capable of modifying T-cell differentiation, towardsTh1, Th2 and Th17 cells. NO changed the pattern of cytokine release by LPS-matured DCs, dependent on the concentration of NO, as well as on the timing of its addition to the cells during maturation. Addition of NO before LPS-induced maturation strongly inhibited the release of IL-12, while increasing the expression and release of IL-23, IL-1β and IL-6, which are all involved in Th17 polarization. Indeed, DCs treated with NO efficiently induced the release of IL-17 by T-cells through IL-1β. Our work highlights the important role that NO may play in sustaining inflammation during an infection through the preferential differentiation of the Th17 lineage.

Glucocorticoid-resistant Th17 cells are selectively attenuated by cyclosporine A

Glucocorticoids remain the cornerstone of treatment for inflammatory conditions, but their utility is limited by a plethora of side effects. One of the key goals of immunotherapy across medical disciplines is to minimize patients' glucocorticoid use. Increasing evidence suggests that variations in the adaptive immune response play a critical role in defining the dose of glucocorticoids required to control an individual's disease, and Th17 cells are strong candidate drivers for nonresponsiveness [also called steroid resistance (SR)]. Here we use gene-expression profiling to further characterize the SR phenotype in T cells and show that Th17 cells generated from both SR and steroid-sensitive individuals exhibit restricted genome-wide responses to glucocorticoids in vitro, and that this is independent of glucocorticoid receptor translocation or isoform expression. In addition, we demonstrate, both in transgenic murine T cells in vitro and in an in vivo murine model of autoimmunity, that Th17 cells are reciprocally sensitive to suppression with the calcineurin inhibitor, cyclosporine A. This result was replicated in human Th17 cells in vitro, which were found to have a conversely large genome-wide shift in response to cyclosporine A. These observations suggest that the clinical efficacy of cyclosporine A in the treatment of SR diseases may be because of its selective attenuation of Th17 cells, and also that novel therapeutics, which target either Th17 cells themselves or the effector memory T-helper cell population from which they are derived, would be strong candidates for drug development in the context of SR inflammation.

Distinct endotypes of steroid-resistant asthma characterized by IL-17A(high) and IFN-γ(high) immunophenotypes: Potential benefits of calcitriol

Background

A small population of patients with severe asthma does not respond to glucocorticoids (steroid resistant [SR]). They have high morbidity, highlighting an urgent need for strategies to enhance glucocorticoid responsiveness.

Objective

We investigated the immunologic differences between steroid-sensitive (SS) and SR asthmatic patients and the effect on immunophenotype of oral calcitriol treatment because it has been previously shown to beneficially modulate the clinical response to glucocorticoids in patients with SR asthma.

Methods

CD8-depleted PBMCs were isolated from 12 patients with SS and 23 patients with SR asthma and cultured for 7 days with anti-CD3 and IL-2 with or without dexamethasone. Cytokine production was assessed in supernatants by using the Cytometric Bead Array. Patients with SR asthma were subsequently randomized to oral calcitriol or placebo therapy, and identical studies were repeated.

Results

Patients with SR asthma produced significantly increased IL-17A and IFN-γ levels compared with those in patients with SS asthma, although it was evident that cells from individual patients might overproduce one or the other of these cytokines. Production of IL-17A was inversely and production of IL-13 was positively associated with the clinical response to prednisolone. Oral calcitriol, compared with placebo, therapy of the patients with SR asthma significantly improved dexamethasone-induced IL-10 production in vitro while suppressing dexamethasone-induced IL-17A production. This effect mirrored the previously demonstrated improvement in clinical response to oral glucocorticoids in calcitriol-treated patients with SR asthma.

Conclusions

IL-17A^high and IFN-γ^high immunophenotypes exist in patients with SR asthma. These data identify immunologic pathways that likely underpin the beneficial clinical effects of calcitriol in patients with SR asthma by directing the SR cytokine profile toward a more SS immune phenotype, suggesting strategies for identifying vitamin D responder immunophenotypes.

IL-17 in severe asthma. Where do we stand?

Asthma is a major chronic disease ranging from mild to severe refractory disease and is classified into various clinical phenotypes. Severe asthma is difficult to treat and frequently requires high doses of systemic steroids. In some cases, severe asthma even responds poorly to steroids. Several studies have suggested a central role of IL-17 (also called IL-17A) in severe asthma. Indeed, high levels of IL-17 are found in induced sputum and bronchial biopsies obtained from patients with severe asthma. The recent identification of a steroid-insensitive pathogenic Th17 pathway is therefore of major interest. In addition, IL-17A has been described in multiple aspects of asthma pathogenesis, including structural alterations of epithelial cells and smooth muscle contraction. In this perspective article, we frame the topic of IL-17A effects in severe asthma by reviewing updated information from human studies. We summarize and discuss the implications of IL-17 in the induction of neutrophilic airway inflammation, steroid insensitivity, the epithelial cell profile, and airway remodeling.

Vitamin D as an adjunctive therapy in asthma. Part 1: A review of potential mechanisms

Vitamin D deficiency (VDD) is highly prevalent worldwide. The classical role for vitamin D is to regulate calcium absorption form the gastrointestinal tract and influence bone health. Recently vitamin D receptors and vitamin D metabolic enzymes have been discovered in numerous sites systemically supporting diverse extra-skeletal roles of vitamin D, for example in asthmatic disease. Further, VDD and asthma share several common risk factors including high latitude, winter season, industrialization, poor diet, obesity, and dark skin pigmentation. Vitamin D has been demonstrated to possess potent immunomodulatory effects, including effects on T cells and B cells as well as increasing production of antimicrobial peptides (e.g. cathelicidin). This immunomodulation may lead to asthma specific clinical benefits in terms of decreased bacterial/viral infections, altered airway smooth muscle-remodeling and -function as well as modulation of response to standard anti-asthma therapy (e.g. glucocorticoids and immunotherapy). Thus, vitamin D and its deficiency have a number of biological effects that are potentially important in altering the course of disease pathogenesis and severity in asthma. The purpose of this first of a two-part review is to review potential mechanisms whereby altering vitamin D status may influence asthmatic disease.

The Role of Vitamin D in Pediatric Asthma

The detrimental effects of vitamin D deficiency in pediatrics have become increasingly apparent and extend beyond skeletal health. Unfortunately, vitamin D deficiency is highly prevalent in atopic pediatric patients, in whom it may disrupt the immune system and induce significant worsening of reactive airways. This review presents evidence that lung development and immune regulatory functions are vitamin D-dependent. We also review clinical studies that explore how vitamin D supplementation may prevent respiratory infections and help improve asthma control, and we elaborate how these effects may vary among populations. We reveal the strong need of screening measures for vitamin D deficiency in high risk pediatric populations, particularly African-Americans, Hispanic-Americans, and children with obesity. Finally, we emphasize that all children, especially those who are asthmatic, should be assessed to ensure adequate intake or supplementation with at least the minimum recommended doses of vitamin D. The simple intervention of vitamin D supplementation may provide significant clinical improvement in atopic disease, especially asthma.

25-Hydroxyvitamin D3-deficiency enhances oxidative stress and corticosteroid resistance in severe asthma exacerbation

Oxidative stress plays a significant role in exacerbation of asthma. The role of vitamin D in oxidative stress and asthma exacerbation remains unclear. We aimed to determine the relationship between vitamin D status and oxidative stress in asthma exacerbation. Severe asthma exacerbation patients with 25-hydroxyvitamin D3-deficiency (V-D deficiency) or 25-hydroxyvitamin D-sufficiency (V-D sufficiency) were enrolled. Severe asthma exacerbation with V-D-deficiency showed lower forced expiratory volume in one second (FEV1) compared to that with V-D-sufficiency. V-D-deficiency intensified ROS release and DNA damage and increased TNF-α, OGG1 and NFκB expression and NFκB phosphorylation in severe asthma exacerbation. Supplemental vitamin D3 significantly increased the rates of FEV1 change and decreased ROS and DNA damage in V-D-deficiency. Vitamin D3 inhibited LPS-induced ROS and DNA damage and were associated with a decline in TNF-α and NFκB in epithelial cells. H₂O₂ reduces nuclear translocation of glucocorticoid receptors in airway epithelial cell lines. V-D pretreatment enhanced the dexamethasone-induced nuclear translocation of glucocorticoid receptors in airway epithelial cell lines and monocytes from 25-hydroxyvitamin D3-deficiency asthma patients. These findings indicate that V-D deficiency aggravates oxidative stress and DNA damage, suggesting a possible mechanism for corticosteroid resistance in severe asthma exacerbation.

Deciphering the complexities of atopic dermatitis: shifting paradigms in treatment approaches

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease. It often precedes the development of food allergy and asthma. Recent insights into AD reveal abnormalities in terminal differentiation of the epidermal epithelium leading to a defective stratum corneum, which allows enhanced allergen penetration and systemic IgE sensitization. Atopic skin is also predisposed to colonization or infection by pathogenic microbes, most notably Staphylococcus aureus and herpes simplex virus. Causes of this abnormal skin barrier are complex and driven by a combination of genetic, environmental, and immunologic factors. These factors likely account for the heterogeneity of AD onset and the severity and natural history of this skin disease. Recent studies suggest prevention of AD can be achieved through early interventions to protect the skin barrier. Onset of lesional AD requires effective control of local and systemic immune activation for optimal management. Early intervention might improve long-term outcomes for AD and reduce the systemic allergen sensitization that leads to associated allergic diseases in the gastrointestinal and respiratory tract.

A mutated vitamin D receptor in hereditary vitamin D-resistant rickets prevents induction of bronchial hyperreactivity and inflammation

CONTEXT

Previous studies have reported an association between vitamin D deficiency and asthma. Hereditary 1,25-dihydroxyvitamin D-resistant rickets (HVDRR) patients provide a natural model to assess the role of the vitamin D receptor (VDR) in regulating human lung immune responses and airway hyperreactivity.

OBJECTIVES

The aim of the study was to determine the role of the VDR on lung functions, airways, and systemic markers of inflammation and allergy in HVDRR patients.

DESIGN AND METHODS

Thirteen HVDRR patients (aged 6-37 y) and 17 normal controls (aged 6-38 y) underwent spirometry, a methacholine challenge test (MCT), blood tests, allergy skin tests, determination of fractional exhaled nitric oxide, and measurement of serum and exhaled breath condensate cytokines, including IL-4, IL-5, IL-10, IL-17, and interferon-γ levels.

RESULTS

All HVDRR patients had negative MCT results, whereas six controls (35.3%) had positive MCT results (P < .014). Serum IgE levels, eosinophil counts, and fractional exhaled nitric oxide and allergy skin test results were similar for the HVDRR patients and controls, as were the serum cytokine concentrations. The HVDRR patients had different cytokine levels in their exhaled breath condensate (increased IL-4 and IL-17 and decreased IL-5, IL-10, and interferon-γ levels) compared to the controls (P < .005).

CONCLUSIONS

HVDRR patients show diverse exhaled cytokine profiles but seem to be protected against provoked bronchial hyperreactivity and clinical asthma. These findings suggest that an intact VDR has an important role in asthma pathophysiology.

Vitamin D reduces the differentiation and expansion of Th17 cells in young asthmatic children

Vitamin D [25(OH)D3] deficiency has been associated with asthma as in many inflammatory and autoimmune pathologies; however, there is still a lack of data about the effects of administration of vitamin D in immune regulation in young asthmatic patients. In this study, we investigated its inhibitory effect on the immune response in young asthmatic patients and the possible mechanisms involved. Peripheral blood CD4(+) T cells from 10 asthmatic patients and 10 healthy controls were cultured under Th17 polarizing conditions in the presence or absence of [25(OH)D3], IL-17 cytokine production was determined by ELISA and flow cytometry. Messenger RNA (mRNA) expression of several factors related to Th17 cell function was determined by real-time PCR. The effect of [25(OH)D3]-treated dendritic cells (DCs) on CD4(+) T cell response was determined by ELISA and flow cytometry. Stimulation of naive CD4(+) T cells under Th17 polarizing conditions showed a higher Th17 cell differentiation in asthmatic patients than healthy controls. The addition of [25(OH)D3] significantly inhibited Th17 cell differentiation both in patients [P<0.001] and in normal controls [P=0.001] in a dose-dependent way. [25(OH)D3] was able to inhibit the gene expression of RORC, IL-17, IL-23R, and CCR6. [25(OH)D3]-treated DCs significantly inhibited IL-17 production [P=0.002] and decreased the percentage of CD4(+)IL-17(+) [P=0.007] in young asthmatics. The findings suggest that the inhibitory effect of [25(OH)D3] on the Th17 response was mediated via both T cells and DCs. DCs pathway is involved in the direct inhibition of 25(OH)D3 on Th17 cell differentiation in young asthmatics.

Development of novel treatment strategies for inflammatory diseases-similarities and divergence between glucocorticoids and GILZ

Glucocorticoids (GC) are the most commonly prescribed medications for patients with inflammatory diseases, despite their well-known adverse metabolic effects. Previously, it was understood that the anti-inflammatory effects of the GC/GC receptor (GR) complex were mediated via transrepression, whilst the adverse metabolic effects were mediated via transactivation. It has recently become clear that this “divergent actions” paradigm of GC actions is likely insufficient. It has been reported that the GC/GR-mediated transactivation also contributes to the anti-inflammatory actions of GC, via up-regulation of key anti-inflammatory proteins. One of these is glucocorticoid-induced leucine zipper (GILZ), which inhibits inflammatory responses in a number of important immune cell lineages in vitro, as well as in animal models of inflammatory diseases in vivo. This review aims to compare the GILZ and GC effects on specific cell lineages and animal models of inflammatory diseases. The fact that the actions of GILZ permit a GILZ-based gene therapy to lack GC-like adverse effects presents the potential for development of new strategies to treat patients with inflammatory diseases.

Directing traffic: IL-17 and IL-22 coordinate pulmonary immune defense

Respiratory infections and diseases are among the leading causes of death worldwide, and effective treatments probably require manipulating the inflammatory response to pathogenic microbes or allergens. Here, we review mechanisms controlling the production and functions of interleukin-17 (IL-17) and IL-22, cytokines that direct several aspects of lung immunity. Innate lymphocytes (γδ T cells, natural killer cells, innate lymphoid cells) are the major source of IL-17 and IL-22 during acute infections, while CD4(+) T-helper 17 (Th17) cells contribute to vaccine-induced immunity. The characterization of dendritic cell (DC) subsets has revealed their central roles in T-cell activation. CD11b(+) DCs stimulated with bacteria or fungi secrete IL-1β and IL-23, potent inducers of IL-17 and IL-22. On the other hand, recognition of viruses by plasmacytoid DCs inhibits IL-1β and IL-23 release, increasing susceptibility to bacterial superinfections. IL-17 and IL-22 primarily act on the lung epithelium, inducing antimicrobial proteins and neutrophil chemoattractants. Recent studies found that stimulation of macrophages and DCs with IL-17 also contributes to antibacterial immunity, while IL-22 promotes epithelial proliferation and repair following injury. Chronic diseases such as asthma and chronic obstructive pulmonary disease have been associated with IL-17 and IL-22 responses directed against innocuous antigens. Future studies will evaluate the therapeutic efficacy of targeting the IL-17/IL-22 pathway in pulmonary inflammation.

A negative feedback loop mediated by STAT3 limits human Th17 responses

The transcription factor STAT3 is critically required for the differentiation of Th17 cells, a T cell subset involved in various chronic inflammatory diseases. In this article, we report that STAT3 also drives a negative-feedback loop that limits the formation of IL-17-producing T cells within a memory population. By activating human memory CD4(+)CD45RO(+) T cells at a high density (HiD) or a low density (LoD) in the presence of the pro-Th17 cytokines IL-1β, IL-23, and TGF-β, we observed that the numbers of Th17 cells were significantly higher under LoD conditions. Assessment of STAT3 phosphorylation revealed a more rapid and stronger STAT3 activation in HiD cells than in LoD cells. Transient inhibition of active STAT3 in HiD cultures significantly enhanced Th17 cell numbers. Expression of the STAT3-regulated ectonucleotidase CD39, which catalyzes ATP hydrolysis, was higher in HiD, than in LoD, cell cultures. Interestingly, inhibition of CD39 ectonucleotidase activity enhanced Th17 responses under HiD conditions. Conversely, blocking the ATP receptor P2X7 reduced Th17 responses in LoD cultures. These data suggest that STAT3 negatively regulates Th17 cells by limiting the availability of ATP. This negative-feedback loop may provide a safety mechanism to limit tissue damage by Th17 cells during chronic inflammation. Furthermore, our results have relevance for the design of novel immunotherapeutics that target the STAT3-signaling pathway, because inhibition of this pathway may enhance, rather than suppress, memory Th17 responses.

Interleukin-17 cytokine signalling in patients with asthma

Asthma remains a global health problem and, therefore, more effective pharmacotherapy is needed. This is particularly true for chronic and severe asthma. In these clinical phenotypes, chronic inflammation involving neutrophils is likely to play a pathogenic role, making it interesting to target cytokine signalling involved in the accumulation of neutrophils. Therefore, it is of interest that the archetype T-helper 17 cell cytokine interleukin (IL)-17A, perhaps also IL-17F, controls neutrophil accumulation, mucus secretion, macrophage mobilisation and smooth muscle reactivity in various experimental airway models. However, much less is known about the involvement of signalling via IL-17 cytokines in humans with asthma. Existing evidence suggests that these cytokines are released from several types of immune cells in asthma and, for IL-17A, there is a local increase associated with disease severity, with the mobilisation of neutrophils and smooth muscle cells locally in the airways. Even though the causative role of IL-17 cytokines remains unclear, there is potential for clinical utility in targeting IL-17A specifically in patients with moderate-to-severe asthma and high reversibility. There is a need for new and well-powered clinical investigations of signalling via IL-17 cytokines in this clinical phenotype.

Association between low vitamin D levels and the diagnosis of asthma in children: a systematic review of cohort studies

BACKGROUND

There is conflicting evidence about the association between low vitamin D levels in children and development of asthma in later life. The objective of this study was to systematically review the evidence for an epidemiological association between low serum levels of vitamin D and the diagnosis of asthma in children.

METHODS

We used the Cochrane methodology for conducting systematic reviews. The search strategy included an electronic search of MEDLINE and EMBASE in February 2013. Two reviewers completed, in duplicate and independently, study selection, data abstraction, and assessment of risk of bias.

RESULTS

Of 1081 identified citations, three cohort studies met eligibility criteria. Two studies found that low serum vitamin D level is associated with an increased risk of developing asthma late in childhood, while the third study found no association with either vitamin D2 or vitamin D3 levels. All three studies suffer from major methodological shortcomings that limit our confidence in their results.

CONCLUSIONS

Available epidemiological evidence suggests a potential association between low serum levels of vitamin D and the diagnosis of asthma in children. High quality studies are needed to reliably answer the question of interest.

Defining severe asthma - an approach to find new therapies

Asthma is a chronic inflammatory disease that has reached epidemic proportions worldwide. It is treatable in the majority of patients, but there is no cure. Moreover, a proportion of patients suffer from severe, difficult-to-control disease with daily symptoms and high morbidity, making it imperative that we continue to improve our understanding of the underlying mechanisms of this disease. Severe asthma is a heterogeneous condition. A systematic approach to identify specific asthma phenotypes, including clinical characteristics and inflammatory processes, is the first step toward individualized, logical therapy. This review focuses on the need to characterize severe asthma phenotypes and on novel, targeted molecular treatment options currently under development.

Anti-inflammatory and corticosteroid-enhancing actions of vitamin D in monocytes of patients with steroid-resistant and those with steroid-sensitive asthma

BACKGROUND

Vitamin D is known for its anti-inflammatory effects.

OBJECTIVE

Vitamin D regulation of responses in patients with steroid-resistant (SR) versus steroid-sensitive (SS) asthma has not been studied.

METHODS

Peripheral blood cells from 11 patients with SR asthma and 8 patients with SS asthma were preincubated with 1,25-dihydroxyvitamin D (1,25[OH]2D [VitD]), followed by dexamethasone (DEX) treatment and LPS stimulation. LPS-induced phosphorylated p38 mitogen-activated protein kinase (p-p38) in monocytes was examined by means of flow cytometry. Mitogen-activated protein kinase phosphatase-1 (MKP-1) mRNA expression, which inhibits p-p38, was analyzed by means of real-time PCR. Glucocorticoid receptor (GR) binding and histone H4 acetylation in the glucocorticoid response element of the MKP-1 promoter in monocytes were analyzed by means of chromatin immunoprecipitation.

RESULTS

DEX significantly inhibited LPS-induced p-p38 in monocytes from patients with SS asthma but not those from patients with SR asthma (P < .01). VitD inhibited LPS-induced p-p38 in monocytes from both patient groups (P < .01) but enhanced DEX suppression of LPS-induced p-p38 only in monocytes from patients with SS asthma (P < .01). VitD induced MKP-1 expression and enhanced DEX induction of MKP-1 in both patients with SS asthma and patients with SR asthma. VitD/DEX-induced MKP-1 mRNA levels remained significantly lower in monocytes from patients with SR asthma (P < .05). DEX-stimulated recruitment of GR and histone H4 acetylation at the glucocorticoid response element 4.6 kbp upstream of the MKP-1 gene were significantly lower in monocytes from patients with SR asthma compared with those from patients with SS asthma. VitD pretreatment enhanced DEX-induced GR binding and histone acetylation in monocytes from both patient groups. However, GR binding and histone H4 acetylation remained significantly lower in monocytes from patients with SR asthma.

CONCLUSION

VitD demonstrated anti-inflammatory and corticosteroid-enhancing effects in monocytes of patients with SR asthma and patients with SS asthma. However, the responses to corticosteroids in patients with SR asthma remained significantly lower than those in patients with SS asthma.

Vitamin D in renal transplantation - from biological mechanisms to clinical benefits

Recent developments in our understanding of vitamin D show that it plays a significant role in immunological health, uniquely occupying both an anti-microbial and immunoregulatory niche. Vitamin D deficiency is widespread amongst renal transplant recipients (RTRs), thus providing one patho-mechanism that may influence the achievement of a successful degree of immunosuppression. It may also influence the development of the infectious, cardiovascular and neoplastic complications seen in RTRs. This review examines the biological roles of vitamin D in the immune system of relevance to renal transplantation (RTx) and evaluates whether vitamin D repletion may be relevant in determining immunologically-related clinical outcomes in RTRs, (including graft survival, cardiovascular disease and cancer). While there are plausible biological and epidemiological reasons to undertake vitamin D repletion in RTRs, there are few randomized-controlled trials in this area. Based on the available literature, we cannot at present categorically make the case for routine measurement and repletion of vitamin D in clinical practice but we do suggest that this is an area in urgent need of further randomized controlled level evidence.

Effect of vitamin D3 on asthma treatment failures in adults with symptomatic asthma and lower vitamin D levels: the VIDA randomized clinical trial

IMPORTANCE

In asthma and other diseases, vitamin D insufficiency is associated with adverse outcomes. It is not known if supplementing inhaled corticosteroids with oral vitamin D3 improves outcomes in patients with asthma and vitamin D insufficiency.

OBJECTIVE

To evaluate if vitamin D supplementation would improve the clinical efficacy of inhaled corticosteroids in patients with symptomatic asthma and lower vitamin D levels.

DESIGN, SETTING, AND PARTICIPANTS

The VIDA (Vitamin D Add-on Therapy Enhances Corticosteroid Responsiveness in Asthma) randomized, double-blind, parallel, placebo-controlled trial studying adult patients with symptomatic asthma and a serum 25-hydroxyvitamin D level of less than 30 ng/mL was conducted across 9 academic US medical centers in the National Heart, Lung, and Blood Institute's AsthmaNet network, with enrollment starting in April 2011 and follow-up complete by January 2014. After a run-in period that included treatment with an inhaled corticosteroid, 408 patients were randomized.

INTERVENTIONS

Oral vitamin D3 (100,000 IU once, then 4000 IU/d for 28 weeks; n = 201) or placebo (n = 207) was added to inhaled ciclesonide (320 µg/d). If asthma control was achieved after 12 weeks, ciclesonide was tapered to 160 µg/d for 8 weeks, then to 80 µg/d for 8 weeks if asthma control was maintained.

MAIN OUTCOMES AND MEASURES

The primary outcome was time to first asthma treatment failure (a composite outcome of decline in lung function and increases in use of β-agonists, systemic corticosteroids, and health care).

RESULTS

Treatment with vitamin D3 did not alter the rate of first treatment failure during 28 weeks (28% [95% CI, 21%-34%] with vitamin D3 vs 29% [95% CI, 23%-35%] with placebo; adjusted hazard ratio, 0.9 [95% CI, 0.6-1.3]). Of 14 prespecified secondary outcomes, 9 were analyzed, including asthma exacerbation; of those 9, the only statistically significant outcome was a small difference in the overall dose of ciclesonide required to maintain asthma control (111.3 µg/d [95% CI, 102.2-120.4 µg/d] in the vitamin D3 group vs 126.2 µg/d [95% CI, 117.2-135.3 µg/d] in the placebo group; difference of 14.9 µg/d [95% CI, 2.1-27.7 µg/d]).

CONCLUSIONS AND RELEVANCE

Vitamin D3 did not reduce the rate of first treatment failure or exacerbation in adults with persistent asthma and vitamin D insufficiency. These findings do not support a strategy of therapeutic vitamin D3 supplementation in patients with symptomatic asthma.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01248065.

Urban particulate matter suppresses priming of T helper type 1 cells by granulocyte/macrophage colony-stimulating factor-activated human dendritic cells

Urban particulate matter (UPM) exacerbates asthmatic lung inflammation and depresses lung immunity. Lung dendritic cells (DCs) react to airway particulates, and have a critical role in linking innate and adaptive immunity, but the direct effects of UPM on DCs, that have been activated by granulocyte/macrophage colony-stimulating factor (GM-CSF), a product of stimulated normal human bronchial epithelial cells, has not been investigated. Human blood CD1c(+) DCs were purified and activated with UPM in the presence or absence of GM-CSF with and without LPS, and DC maturation was assessed by flow cytometry. DC stimulatory capacity and priming of 5-(and -6)-carboxyfluorescein diacetate succinimidyl ester-labeled naive CD4 T cells was investigated using the allogeneic mixed lymphocyte reaction. T cell proliferation and effector function were assessed using flow cytometry and secreted cytokines were measured by combined bead array. UPM enhanced DC maturation in an LPS-independent manner. DCs activated by UPM plus GM-CSF (UPM + GM-CSF DCs) induced higher naive CD4 T cell proliferation in the allogeneic mixed lymphocyte reaction than DCs pretreated by GM-CSF alone (GM-CSF DCs), and elicited both substantially lower levels of IFN-γ, IL-13, and IL-5 secretion, and lower frequencies of alloantigen-specific T helper (Th) type 1 effector cells than naive CD4 T cells primed by GM-CSF DCs. UPM-stimulated DCs produced IL-6 and TNF-α. Neutralization of IL-6 decreased naive CD4 T cell proliferation stimulated by UPM + GM-CSF DCs, and significantly increased the frequency of alloantigen-specific Th1 effector cells, but did not reverse UPM-induced inhibition of IFN-γ secretion. We conclude that UPM enhances GM-CSF-induced DC maturation and stimulatory capacity, but inhibits the generation of Th1 cells. Thus, UPM exposure may impair Th1 responses to pulmonary pathogens.

Immunoregulatory mechanisms of vitamin D relevant to respiratory health and asthma

Vitamin D deficiency is prevalent among people with various immune-mediated conditions, including autoimmune diseases and asthma. Serum 25(OH)D levels inversely correlate with asthma severity, glucocorticoid responsiveness/dosage, and markers of pathogenesis, such as airway remodeling, IgE, and eosinophilia. Trials involving supplementation with active vitamin D or a precursor are beginning to emerge with variable results that, in part, reflect differences in study design. This review looks at the mechanisms by which vitamin D may protect against asthma, including increasing glucocorticoid responsiveness, skewing immune cells towards a regulatory phenotype, reducing the incidence of infections, airway remodeling, eosinophilia, and lowering the levels of IgE. Also discussed is the therapeutic potential for vitamin D, which is likely to be applicable to immune-mediated conditions beyond simply asthma.

Link between vitamin D and airway remodeling

In the last decade, many epidemiologic studies have investigated the link between vitamin D deficiency and asthma. Most studies have shown that vitamin D deficiency increases the risk of asthma and allergies. Low levels of vitamin D have been associated with asthma severity and loss of control, together with recurrent exacerbations. Remodeling is an early event in asthma described as a consequence of production of mediators and growth factors by inflammatory and resident bronchial cells. Consequently, lung function is altered, with a decrease in forced expiratory volume in one second and exacerbated airway hyperresponsiveness. Subepithelial fibrosis and airway smooth muscle cell hypertrophy are typical features of structural changes in the airways. In animal models, vitamin D deficiency enhances inflammation and bronchial anomalies. In severe asthma of childhood, major remodeling is observed in patients with low vitamin D levels. Conversely, the antifibrotic and antiproliferative effects of vitamin D in smooth muscle cells have been described in several experiments. In this review, we briefly summarize the current knowledge regarding the relationship between vitamin D and asthma, and focus on its effect on airway remodeling and its potential therapeutic impact for asthma.

Advances in adult asthma diagnosis and treatment in 2013

In 2013, several themes emerged: (1) a dedicated search for new therapies using new mechanisms; (2) the importance of the plasticity of the immune system (eg, that molecules that mediate inflammation in one setting can promote its resolution and return to homeostasis in other circumstances); (3) the complex role of viruses in asthma exacerbations; (4) the similarities and differences among asthma, asthma in smokers, and chronic obstructive pulmonary disease; and (5) the importance of understanding asthma phenotypes and their stability over time. Once new therapeutics pass the initial clinical trials, patient-oriented and real-world research will be needed.

Dominance of the strongest: inflammatory cytokines versus glucocorticoids

Pro-inflammatory cytokines are involved in the pathogenesis of many inflammatory diseases, and the excessive expression of many of them is normally counteracted by glucocorticoids (GCs), which are steroids that bind to the glucocorticoid receptor (GR). Hence, GCs are potent inhibitors of inflammation, and they are widely used to treat inflammatory diseases, such as asthma, rheumatoid arthritis and inflammatory bowel disease. However, despite the success of GC therapy, many patients show some degree of GC unresponsiveness, called GC resistance (GCR). This is a serious problem because it limits the full therapeutic exploitation of the anti-inflammatory power of GCs. Patients with reduced GC responses often have higher cytokine levels, and there is a complex interplay between GCs and cytokines: GCs downregulate pro-inflammatory cytokines while cytokines limit GC action. Treatment of inflammatory diseases with GCs is successful when GCs dominate. But when cytokines overrule the anti-inflammatory actions of GCs, patients become GC insensitive. New insights into the molecular mechanisms of GR-mediated actions and GCR are needed for the design of more effective GC-based therapies.

Defective IL-10 expression and in vitro steroid-induced IL-17A in paediatric severe therapy-resistant asthma

BACKGROUND

Understanding of immune mechanisms underpinning asthma has emerged from studies in adults. It is increasingly recognised, both immunologically and in the development of novel therapies, that adult responses cannot be used accurately to predict those of children.

METHODS

Using a well-defined paediatric cohort of severe therapy-resistant asthma (STRA) patients, we investigated cytokine profiles in the airway by analysis of bronchoalveolar lavage fluid. The in vitro capacity of peripheral blood mononuclear cells (PBMCs) for cytokine production was also assessed following polyclonal T cell activation in culture, in the absence or presence of dexamethasone and 1α,25-dihydroxyvitamin D3.

RESULTS

Children with both moderate and STRA had significantly diminished levels of anti-inflammatory interleukin (IL)-10 in airway lavage samples when compared with non-asthmatic controls (p<0.001). Their PBMCs also demonstrated significantly impaired capacity to secrete IL-10 in culture (p<0.001). Dexamethasone regulated the balance between PBMC IL-10 and IL-13 production, increasing IL-10 secretion (p<0.001) and decreasing IL-13 (p<0.001) but unexpectedly enhanced IL-17A production in all groups-most strikingly in the STRA cohort (p<0.001). The inclusion of the active form of vitamin D, 1α,25-dihydroxyvitamin D3, in culture enhanced dexamethasone-induced IL-10 (p<0.05) without marked effects on IL-13 or IL-17A production. Furthermore, systemic vitamin D status directly correlated with airway IL-10 (r=0.6, p<0.01).

CONCLUSIONS

These findings demonstrate reduced peripheral and local IL-10 synthesis in paediatric asthma, and support therapeutic augmentation of low circulating vitamin D in severe, difficult-to-treat asthma, in order to correct impaired IL-10 levels. Conversely, steroids enhanced IL-17A levels, and therefore any steroid-sparing properties of vitamin D may have additional benefit in STRA.