Suppression of the asthmatic phenotype by ultraviolet B-induced, antigen-specific regulatory cells

Solar ultraviolet B radiation promotes α-MSH secretion to attenuate the function of ILC2s via the pituitary-lung axis

The immunomodulatory effects of ultraviolet B (UVB) radiation in human diseases have been described. Whether type 2 lung inflammation is directly affected by solar ultraviolet (UV) radiation is not fully understood. Here, we show a possible negative correlation between solar UVB radiation and asthmatic inflammation in humans and mice. UVB exposure to the eyes induces hypothalamus-pituitary activation and α-melanocyte-stimulating hormone (α-MSH) accumulation in the serum to suppress allergic airway inflammation by targeting group 2 innate lymphoid cells (ILC2) through the MC5R receptor in mice. The α-MSH/MC5R interaction limits ILC2 function through attenuation of JAK/STAT and NF-κB signaling. Consistently, we observe that the plasma α-MSH concentration is negatively correlated with the number and function of ILC2s in the peripheral blood mononuclear cells (PBMC) of patients with asthma. We provide insights into how solar UVB radiation-driven neuroendocrine α-MSH restricts ILC2-mediated lung inflammation and offer a possible strategy for controlling allergic diseases.

Current Overview on Therapeutic Potential of Vitamin D in Inflammatory Lung Diseases

Inflammatory lung disorders (ILDs) are one of the world’s major reasons for fatalities and sickness, impacting millions of individuals of all ages and constituting a severe and pervasive health hazard. Asthma, lung cancer, bronchiectasis, pulmonary fibrosis acute respiratory distress syndrome, and COPD all include inflammation as a significant component. Microbe invasions, as well as the damage and even death of host cells, can cause and sustain inflammation. To counteract the negative consequences of irritants, the airways are equipped with cellular and host defense immunological systems that block the cellular entrance of these irritants or eliminate them from airway regions by triggering the immune system. Failure to activate the host defense system will trigger chronic inflammatory cataracts, leading to permanent lung damage. This damage makes the lungs more susceptible to various respiratory diseases. There are certain restrictions of the available therapy for lung illnesses. Vitamins are nutritional molecules that are required for optimal health but are not produced by the human body. Cholecalciferol (Vitamin D) is classified as a vitamin, although it is a hormone. Vitamin D is thought to perform a function in bone and calcium homeostasis. Recent research has found that vitamin D can perform a variety of cellular processes, including cellular proliferation; differentiation; wound repair; healing; and regulatory systems, such as the immune response, immunological, and inflammation. The actions of vitamin D on inflammatory cells are dissected in this review, as well as their clinical significance in respiratory illnesses.

Metabolic dysfunction induced by a high-fat diet modulates hematopoietic stem and myeloid progenitor cells in brown adipose tissue of mice

Brown adipose tissue (BAT) may be an important metabolic regulator of whole-body glucose. While important roles have been ascribed to macrophages in regulating metabolic functions in BAT, little is known of the roles of other immune cells subsets, particularly dendritic cells (DCs). Eating a high-fat diet may compromise the development of hematopoietic stem and progenitor cells (HSPCs)-which give rise to DCs-in bone marrow, with less known of its effects in BAT. We have previously demonstrated that ongoing exposure to low-dose ultraviolet radiation (UVR) significantly reduced the 'whitening' effect of eating a high-fat diet upon interscapular (i) BAT of mice. Here, we examined whether this observation may be linked to changes in the phenotype of HSPCs and myeloid-derived immune cells in iBAT and bone marrow of mice using 12-colour flow cytometry. Many HSPC subsets declined in both iBAT and bone marrow with increasing metabolic dysfunction. Conversely, with rising adiposity and metabolic dysfunction, conventional DCs (cDCs) increased in both of these tissues. When compared with a low-fat diet, consumption of a high-fat diet significantly reduced proportions of myeloid, common myeloid and megakaryocyte-erythrocyte progenitors in iBAT, and short-term hematopoietic stem cells in bone marrow. In mice fed the high-fat diet, exposure to low-dose UVR significantly reduced proportions of cDCs in iBAT, independently of nitric oxide release from irradiated skin [blocked using the scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO)], but did not significantly modify HSPC subsets in either tissue. Further studies are needed to determine whether changes in these cell populations contribute towards metabolic dysfunction .

Vitamin D and its therapeutic relevance in pulmonary diseases

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

Vitamin D supplementation of initially vitamin D-deficient mice diminishes lung inflammation with limited effects on pulmonary epithelial integrity

In disease settings, vitamin D may be important for maintaining optimal lung epithelial integrity and suppressing inflammation, but less is known of its effects prior to disease onset. Female BALB/c dams were fed a vitamin D₃‐supplemented (2280 IU/kg, VitD⁺) or nonsupplemented (0 IU/kg, VitD⁻) diet from 3 weeks of age, and mated at 8 weeks of age. Male offspring were fed the same diet as their mother. Some offspring initially fed the VitD⁻ diet were switched to a VitD⁺ diet from 8 weeks of age (VitD^−/+). At 12 weeks of age, signs of low‐level inflammation were observed in the bronchoalveolar lavage fluid (BALF) of VitD⁻ mice (more macrophages and neutrophils), which were suppressed by subsequent supplementation with vitamin D₃. There was no difference in the level of expression of the tight junction proteins occludin or claudin‐1 in lung epithelial cells of VitD⁺ mice compared to VitD⁻ mice; however, claudin‐1 levels were reduced when initially vitamin D‐deficient mice were fed the vitamin D₃‐containing diet (VitD^−/+). Reduced total IgM levels were detected in BALF and serum of VitD^−/+ mice compared to VitD⁺ mice. Lung mRNA levels of the vitamin D receptor (VDR) were greatest in VitD^−/+ mice. Total IgG levels in BALF were greater in mice fed the vitamin D₃‐containing diet, which may be explained by increased activation of B cells in airway‐draining lymph nodes. These findings suggest that supplementation of initially vitamin D‐deficient mice with vitamin D₃ suppresses signs of lung inflammation but has limited effects on the epithelial integrity of the lungs.

Investigating the roles of regulatory T cells, mast cells and interleukin-9 in the control of skin inflammation by vitamin D

Topical application of biologically active vitamin D [1,25-dihydroxyvitamin D (1,25(OH)₂D)], or low-calcemic analogues, curb skin inflammation through mechanisms that involve migratory dendritic cells (DCs) and regulatory T (T_Reg) cells. 1,25(OH)₂D also promotes immunoregulation by mast cells, and inhibits the development of T helper type-9 (Th9) cells that secrete interleukin-9 (IL-9). Here, we investigated the ability of topical 1,25(OH)₂D to suppress contact dermatitis through an IL-9-dependent process, examining mast cells and IL-9-secreting T cells. Contact dermatitis was modelled in adult BALB/c female mice by initiating a "biphasic ear swelling response" following a single application of 2,4-dinitrofluorobenzene (DNFB). Topical 1,25(OH)₂D (125 ng) applied to ear pinnae prior to (but not after) DNFB sensitisation suppressed the efferent phase of the ear swelling response. This dose of 1,25(OH)₂D did not cause hypercalcemia. At the peak of the efferent ear swelling response, proportions of T_Reg (CD3 + Foxp3+) cells and numbers of mast cells were increased in ear skin of 1,25(OH)₂D-treated mice. Topical 1,25(OH)₂D increased the proportion of Foxp3 + IL-9 + T_Reg cells and the capacity of T_Reg cells to secrete IL-9 ex vivo. However, the proportion of the IL-9 + cells of the total T_Reg cell population was small (< 1%), and the amount of IL-9 secreted by T_Reg cells from mice treated with IL-9 was low (< 50 pg/ml). Furthermore, injection of anti-IL-9 neutralising antibody (100 µg, intraperitoneally) prior to sensitisation did not significantly reverse the suppressive effects of 1,25(OH)₂D. In conclusion, topically applied 1,25(OH)₂D suppressed the efferent phase of a biphasic cutaneous ear swelling response through mechanism(s) that may be dependent on mast cells and T_Reg cells; however, the role of IL-9 in mediating these responses is uncertain. More studies are needed to further characterise the mechanisms by which topical 1,25(OH)₂D modulates cell-mediated immune responses central to its suppressive effects upon contact dermatitis.

Sub-erythemal ultraviolet radiation reduces metabolic dysfunction in already overweight mice

Exposure to sunlight may limit cardiometabolic risk. In our previous studies, regular exposure to sub-erythemal (non-burning) ultraviolet radiation (UVR) reduced signs of adiposity and cardiometabolic dysfunction in mice fed a high-fat diet. Some of the observed effects were dependent on skin release of nitric oxide after UVR exposure. Here, we examine the effects of sub-erythemal UVR on signs of adiposity and metabolic dysfunction in already overweight mice, comparing the effects of two sunlamps with distinct emitted light spectra. Mice were fed a high-fat diet from 8 weeks of age, with UVR administered twice a week from 14 weeks of age until they were killed at 20 weeks of age. Mice were irradiated with the same dose of UVB radiation (1 kJ/m²) from either FS40 (65% UVB, 35% UVA) or CLEO (4% UVB, 96% UVA) sunlamps, but substantially more UVA from the latter. FS40 UVR (but not CLEO UVR) significantly reduced mouse weights and weight gain, compared to mice fed a high-fat diet (only). These effects were dependent on nitric oxide. Conversely, CLEO UVR (but not FS40 UVR) significantly reduced circulating LDL cholesterol. Both light sources reduced fasting insulin levels, and the extent of hepatic steatosis; the latter was reversed by topical application of cPTIO, suggesting an important role for skin release of nitric oxide in preventing hepatic lipid accumulation. These results suggest that there may be a number of benefits achieved by regular exposure to safe (non-burning) levels of sunlight or UV-containing phototherapy, with effects potentially dependent on the predominance of the wavelengths of UVR administered.

Short-range ultraviolet irradiation with LED device effectively increases serum levels of 25(OH)D

Impairment of the activities of daily living (ADL) by osteoporosis is an important concern in developed countries with a super-aging population. Vitamin D, which is a crucial molecule in bone metabolism and mainly produced endogenously with ultraviolet (UV) light exposure, is known to be insufficient in the elderly population. We used an UV Light-Emitting Diode (UV-LED) instrument generating a narrow-range wavelength to analyze the efficacy of endogenous vitamin D production. The primary purpose of this study was to examine the effects of UV irradiation at various narrow-range wavelengths using UV-LED on vitamin D supplementation. The second one was to clarify the short-term effects of UV irradiation on bone morphology in mice. Vitamin D-starved C57BL/6 female mice (n=7 per group) were UV-irradiated (268nm, 282nm, 290nm, 305nm, and 316nm) with 1kJ/m² twice a week for 4weeks. UV irradiation using UV-LED had significant effects on increasing serum 25(OH)D levels in all wavelength groups (P<0.001, all groups) as compared to a control group. Among irradiated groups, wavelength of 316nm had a less marked effect on 25(OH)D production compared with other wavelengths at 1week of UV irradiation (P<0.05). Levels of 1,25(OH)₂D were significantly increased after 4weeks irradiation with UV-B or UV-C irradiation (P<0.05). mRNA levels of vitamin D 25-hydroxylase were increased with UV-B or UV-C irradiation (268nm-305nm), significantly. Micro-CT examination revealed that short-term (4weeks) UV-irradiation did not induce morphological change of mice in any group. This study provides essential information that narrow-range UV irradiation with LED can increase the endogenous production of vitamin D, and mRNA levels of the responsible enzyme. Although bone morphology was not altered by short-term UV irradiation in this study, an increase of serum vitamin D might improve bone morphology with long-term irradiation.

Vitamin D and allergic airway disease shape the murine lung microbiome in a sex-specific manner

Background

Vitamin D is under scrutiny as a potential regulator of the development of respiratory diseases characterised by chronic lung inflammation, including asthma and chronic obstructive pulmonary disease. It has anti-inflammatory effects; however, knowledge around the relationship between dietary vitamin D, inflammation and the microbiome in the lungs is limited. In our previous studies, we observed more inflammatory cells in the bronchoalveolar lavage fluid and increased bacterial load in the lungs of vitamin D-deficient male mice with allergic airway disease, suggesting that vitamin D might modulate the lung microbiome. In the current study, we examined in more depth the effects of vitamin D deficiency initiated early in life, and subsequent supplementation with dietary vitamin D on the composition of the lung microbiome and the extent of respiratory inflammation.

Methods

BALB/c dams were fed a vitamin D-supplemented or -deficient diet throughout gestation and lactation, with offspring continued on this diet post-natally. Some initially deficient offspring were fed a supplemented diet from 8 weeks of age. The lungs of naïve adult male and female offspring were compared prior to the induction of allergic airway disease. In further experiments, offspring were sensitised and boosted with the experimental allergen, ovalbumin (OVA), and T helper type 2-skewing adjuvant, aluminium hydroxide, followed by a single respiratory challenge with OVA.

Results

In mice fed a vitamin D-containing diet throughout life, a sex difference in the lung microbial community was observed, with increased levels of an Acinetobacter operational taxonomic unit (OTU) in female lungs compared to male lungs. This effect was not observed in vitamin D-deficient mice or initially deficient mice supplemented with vitamin D from early adulthood. In addition, serum 25-hydroxyvitamin D levels inversely correlated with total bacterial OTUs, and Pseudomonas OTUs in the lungs. Increased levels of the antimicrobial murine ß-defensin-2 were detected in the bronchoalveolar lavage fluid of male and female mice fed a vitamin D-containing diet. The induction of OVA-induced allergic airway disease itself had a profound affect on the OTUs identified in the lung microbiome, which was accompanied by substantially more respiratory inflammation than that induced by vitamin D deficiency alone.

Conclusion

These data support the notion that maintaining sufficient vitamin D is necessary for optimal lung health, and that vitamin D may modulate the lung microbiome in a sex-specific fashion. Furthermore, our data suggest that the magnitude of the pro-inflammatory and microbiome-modifying effects of vitamin D deficiency were substantially less than that of allergic airway disease, and that there is an important interplay between respiratory inflammation and the lung microbiome.

Vitamin D supplementation during pregnancy and infancy reduces aeroallergen sensitization: a randomized controlled trial

BACKGROUND

Vitamin D has immune-modulating effects. We determined whether vitamin D supplementation during pregnancy and infancy prevents aeroallergen sensitization and primary care respiratory illness presentations.

METHODS

A randomized, double-blind, placebo-controlled parallel-group trial. We assigned pregnant women, from 27-week gestation to birth, and then their infants, from birth to 6 months, to placebo or one of two dosages of daily oral vitamin D. Woman/infant pairs were randomized to: placebo/placebo, 1000 IU/400 IU or 2000 IU/800 IU. When the children were 18 months old, we measured serum-specific IgE antibodies and identified acute primary care visits described by the doctor to be due to a cold, otitis media, an upper respiratory infection, croup, asthma, bronchitis, bronchiolitis, a wheezy lower respiratory infection or fever and cough.

RESULTS

Specific IgE was measured on 185 of 260 (71%) enrolled children. The proportion of children sensitized differed by study group for four mite antigens: Dermatophagoides farinae (Der-f1, Der-f2) and Dermatophagoides pteronyssinus (Der-p1, Der-p2). With results presented for placebo, lower dose, and higher dose vitamin D, respectively (all P < 0.05): Der-f1 (18%, 10%, 2%), Der-f2 (14%, 3%, 2%), Der-p1 (19%, 14%, 3%) and Der-p2 (12%, 2%, 3%). There were study group differences in the proportion of children with primary care visits described by the doctor as being for asthma (11%, 0%, 4%, P = 0.002), but not for the other respiratory diagnoses.

CONCLUSIONS

Vitamin D supplementation during pregnancy and infancy reduces the proportion of children sensitized to mites at age 18 months. Preliminary data indicate a possible effect on primary care visits where asthma is diagnosed.

B cells are required for sunlight protection of mice from a CNS-targeted autoimmune attack

The ultraviolet (UV) radiation contained in sunlight is a powerful immune suppressant. While exposure to UV is associated with protection from the development of autoimmune diseases, particularly multiple sclerosis, the precise mechanism by which UV achieves this protection is not currently well understood. Regulatory B cells play an important role in preventing autoimmunity and activation of B cells is a major way in which UV suppresses adaptive immune responses. Whether UV-protection from autoimmunity is mediated by the activation of regulatory B cells has never been considered before. When C57BL/6 mice were exposed to low, physiologically relevant doses of UV, a unique population of B cells was activated in the skin draining lymph nodes. As determined by flow cytometry, CD1d(low)CD5(-)MHC-II(hi)B220(hi) UV-activated B cells expressed significantly higher levels of CD19, CD21/35, CD25, CD210 and CD268 as well as the co-stimulatory molecules CD80, CD86, CD274 and CD275. Experimental autoimmune encephalomyelitis (EAE) in mice immunized with MOG/CFA was reduced by exposure to UV. UV significantly inhibited demyelination and infiltration of inflammatory cells into the spinal cord. Consequently, UV-exposed groups showed elevated IL-10 levels in secondary lymphoid organs, delayed EAE onset, reduced peak EAE score and significantly suppressed overall disease incidence and burden. Importantly, protection from EAE could be adoptively transferred using B cells isolated from UV-exposed, but not unirradiated hosts. Indeed, UV-protection from EAE was dependent on UV activation of lymph node B cells because UV could not protect mice from EAE who were pharmacologically depleted of B cells using antibodies. Thus, UV maintenance of a pool of unique regulatory B cells in peripheral lymph nodes appears to be essential to prevent an autoimmune attack on the central nervous system.

Reduced immune responses in chimeric mice engrafted with bone marrow cells from mice with airways inflammation

OBJECTIVE

During respiratory inflammation, it is generally assumed that dendritic cells differentiating from the bone marrow are immunogenic rather than immunoregulatory. Using chimeric mice, the outcomes of airways inflammation on bone marrow progenitor cells were studied.

METHODS

Immune responses were analyzed in chimeric mice engrafted for >16 weeks with bone marrow cells from mice with experimental allergic airways disease (EAAD).

RESULTS

Responses to sensitization and challenge with the allergen causing inflammation in the bone marrow-donor mice were significantly reduced in the chimeric mice engrafted with bone marrow cells from mice with EAAD (EAAD-chimeric). Responses to intranasal LPS and topical fluorescein isothiocyanate (non-specific challenges) were significantly attenuated. Fewer activated dendritic cells from the airways and skin of the EAAD-chimeric mice could be tracked to the draining lymph nodes, and may contribute to the significantly reduced antigen/chemical-induced hypertrophy in the draining nodes, and the reduced immune responses to sensitizing allergens. Dendritic cells differentiating in vitro from the bone marrow of >16 weeks reconstituted EAAD-chimeric mice retained an ability to poorly prime immune responses when transferred into naïve mice.

CONCLUSIONS

Dendritic cells developing from bone marrow progenitors during airways inflammation are altered such that daughter cells have reduced antigen priming capabilities.

Vitamin D as an adjunctive therapy in asthma. Part 2: A review of human studies

Vitamin D deficiency (VDD) is highly prevalent worldwide, with adverse effects on bone health but also potentially other unfavorable consequences. VDD and asthma-incidence/severity share many common risk factors, including winter season, industrialization, poor diet, obesity, dark skin pigmentation, and high latitude. Multiple anatomical areas relevant to asthma contain both the enzyme responsible for producing activated vitamin D and the vitamin D receptor suggesting that activated vitamin D (1,25-dihydroxyvitamin D) may have important local effects at these sites. Emerging evidence suggests that VDD is associated with increased airway hyperresponsiveness, decreased pulmonary function, worse asthma control, and possibly decreased response to standard anti-asthma therapy. However the effect is inconsistent with preliminary evidence from different studies suggesting vitamin D is both beneficial and detrimental to asthma genesis and severity. Current evidence suggests that supplementation with moderate doses of vitamin D may be appropriate for maintenance of bone health in asthmatics, particularly steroid users. However emerging data from an increasing number of randomized, controlled, intervention studies of vitamin D supplementation in pediatric and adult asthma are becoming available and should help determine the importance, if any of vitamin D for asthma pathogenesis. The purpose of this second of a two-part review is to review the current human literature on vitamin D and asthma, discussing the possible consequences of VDD for asthma and the potential for vitamin D repletion as adjunct therapy.

Photoimmunology and Multiple Sclerosis

The ultraviolet (UV) radiation contained in sunlight is a powerful immune suppressant. While exposure to UV is best known for its ability to cause skin cancer, it is also associated with protection against a range of autoimmune diseases, particularly multiple sclerosis (MS). Although the precise mechanism by which sunlight affords protection from MS remains to be determined, some have hypothesised that UV immunosuppression explains the "latitude-gradient effect" associated with MS. By stimulating the release of soluble factors in exposed skin, UV activates immune suppressive pathways that culminate in the induction of regulatory cells in distant tissues. Each and every one of the immune suppressive cells and molecules activated by UV exposure are potential targets for treating and preventing MS. A thorough understanding of the mechanisms involved is therefore required if we are to realise the therapeutic potential of photoimmunology.

Ultraviolet radiation suppresses obesity and symptoms of metabolic syndrome independently of vitamin D in mice fed a high-fat diet

The role of vitamin D in curtailing the development of obesity and comorbidities such as the metabolic syndrome (MetS) and type 2 diabetes has received much attention recently. However, clinical trials have failed to conclusively demonstrate the benefits of vitamin D supplementation. In most studies, serum 25-hydroxyvitamin D [25(OH)D] decreases with increasing BMI above normal weight. These low 25(OH)D levels may also be a proxy for reduced exposure to sunlight-derived ultraviolet radiation (UVR). Here we investigate whether UVR and/or vitamin D supplementation modifies the development of obesity and type 2 diabetes in a murine model of obesity. Long-term suberythemal and erythemal UVR significantly suppressed weight gain, glucose intolerance, insulin resistance, nonalcoholic fatty liver disease measures; and serum levels of fasting insulin, glucose, and cholesterol in C57BL/6 male mice fed a high-fat diet. However, many of the benefits of UVR were not reproduced by vitamin D supplementation. In further mechanistic studies, skin induction of the UVR-induced mediator nitric oxide (NO) reproduced many of the effects of UVR. These studies suggest that UVR (sunlight exposure) may be an effective means of suppressing the development of obesity and MetS, through mechanisms that are independent of vitamin D but dependent on other UVR-induced mediators such as NO.

Mast cell function: a new vision of an old cell

Since first described by Paul Ehrlich in 1878, mast cells have been mostly viewed as effectors of allergy. It has been only in the past two decades that mast cells have gained recognition for their involvement in other physiological and pathological processes. Mast cells have a widespread distribution and are found predominantly at the interface between the host and the external environment. Mast cell maturation, phenotype and function are a direct consequence of the local microenvironment and have a marked influence on their ability to specifically recognize and respond to various stimuli through the release of an array of biologically active mediators. These features enable mast cells to act as both first responders in harmful situations as well as to respond to changes in their environment by communicating with a variety of other cells implicated in physiological and immunological responses. Therefore, the critical role of mast cells in both innate and adaptive immunity, including immune tolerance, has gained increased prominence. Conversely, mast cell dysfunction has pointed to these cells as the main offenders in several chronic allergic/inflammatory disorders, cancer and autoimmune diseases. This review summarizes the current knowledge of mast cell function in both normal and pathological conditions with regards to their regulation, phenotype and role.

The effects of vitamin D supplementation on airway functions in mild to moderate persistent asthma

BACKGROUND

Vitamin D is hypothesized to have some roles in innate and adaptive immunity, inflammation reduction, and remodeling; therefore, it is supposed to affect the asthma phenotype, severity, and response to inhaled corticosteroid (ICS).

OBJECTIVE

To explore the synergistic effects of vitamin D supplementation in addition to asthma controllers (ICS or ICS plus long-acting β-agonist) on airway functions.

METHODS

A randomized clinical trial was conducted in 130 individuals aged 10 to 50 years who lived in Tehran during a 24-week period. Data on age, sex, body mass index, stage of asthma, serum total IgE, history of allergic rhinitis, atopic dermatitis, food allergy, and urticaria were collected. Spirometric parameters (forced expiratory volume in 1 second [FEV1] and ratio of FEV1 to forced vital capacity) and serum vitamin D measurement were obtained before and 8 and 24 weeks after the intervention. Patients were divided in 2 groups randomly. Both groups received asthma controllers (budesonide or budesonide plus formoterol) according to their stage, but the intervention group received vitamin D supplementation (100,000-U bolus intramuscularly plus 50,000 U orally weekly) in addition to asthma controllers.

RESULTS

FEV1 improved significantly in both groups after 8 weeks, but no significant difference was found between the 2 groups at baseline (P = .20) or after 8 weeks (P = .99); however, a significant improvement was seen in the intervention group in the last 16 weeks, and FEV1 was significantly better in the intervention group than the other group after 24 weeks (P < .001).

CONCLUSION

Vitamin D supplementation associated with asthma controllers could significantly improve FEV1 in mild to moderate persistent asthma after 24 weeks.

TRIAL REGISTRATION

irct.ir Identifier: IRCT201302079608N1.

Characterization of regulatory dendritic cells differentiated from the bone marrow of UV-irradiated mice

When antigen-loaded dendritic cells (DCs) differentiated from the bone marrow (BM) of UV-irradiated mice (UV-BMDCs) were adoptively transferred into naive mice or mice pre-sensitized with that antigen, the recipients exhibited a reduced immune response following antigen challenge. Hence, UV-BMDCs are poorly immunogenic and can suppress pre-existing immunity. The UV-induced effect on BM-derived DCs was rapid (observed 1 day after UV radiation), long-lasting (observed 10 days after UV radiation) and UV dose-dependent. The mechanism by which UV-BMDCs could regulate immunity was investigated. The CD11c(+) cells, differentiated using granulocyte-macrophage colony-stimulating factor + interleukin-4, were confirmed to be DCs because they did not express the myeloid-derived suppressor cell marker, Gr1. UV-BMDCs did not display altered antigen uptake, processing or ability to activate T cells in vitro. When gene expression in UV-BMDCs and DCs differentiated from the BM of non-irradiated mice (control-BMDCs) was examined, Ccl7, Ccl8 and CSF1R (CD115) mRNA transcripts were up-regulated in UV-BMDCs compared with control-BMDCs. However, neutralizing antibodies for Ccl7 and Ccl8 did not abrogate the reduced immunogenicity of UV-BMDCs in vivo. Moreover, the up-regulation of CSF1R transcript did not correspond with increased receptor expression on UV-BMDCs. The phenotypes of UV-BMDCs and control-BMDCs were similar, with no difference in the expression of CD4, CD8α, CD103, B220 or F4/80, or the regulatory molecules CCR7 (CD197), FasL (CD95L), B7H3 (CD276) and B7H4. However, PDL1 (CD274) expression was reduced in UV-BMDCs compared with control-BMDCs following lipopolysaccharide stimulation. In summary, UV-BMDCs do not express the classical phenotypic or gene expression properties of DCs reported by others as 'regulatory' or 'tolerogenic'.

Vitamin D, the immune system and asthma

The effects of vitamin D on bone metabolism and calcium homeostasis have long been recognized. Emerging evidence has implicated vitamin D as a critical regulator of immunity, playing a role in both the innate and cell-mediated immune systems. Vitamin D deficiency has been found to be associated with several immune-mediated diseases, susceptibility to infection and cancer. Recently, there has been increasing interest in the possible link between vitamin D and asthma. Further elucidation of the role of vitamin D in lung development and immune system function may hold profound implications for the prevention and treatment of asthma.

Reversible control by vitamin D of granulocytes and bacteria in the lungs of mice: an ovalbumin-induced model of allergic airway disease

Vitamin D may be essential for restricting the development and severity of allergic diseases and asthma, but a direct causal link between vitamin D deficiency and asthma has yet to be established. We have developed a 'low dose' model of allergic airway disease induced by intraperitoneal injection with ovalbumin (1 µg) and aluminium hydroxide (0.2 mg) in which characteristics of atopic asthma are recapitulated, including airway hyperresponsiveness, antigen-specific immunoglobulin type-E and lung inflammation. We assessed the effects of vitamin D deficiency throughout life (from conception until adulthood) on the severity of ovalbumin-induced allergic airway disease in vitamin D-replete and -deficient BALB/c mice using this model. Vitamin D had protective effects such that deficiency significantly enhanced eosinophil and neutrophil numbers in the bronchoalveolar lavage fluid of male but not female mice. Vitamin D also suppressed the proliferation and T helper cell type-2 cytokine-secreting capacity of airway-draining lymph node cells from both male and female mice. Supplementation of initially vitamin D-deficient mice with vitamin D for four weeks returned serum 25-hydroxyvitamin D to levels observed in initially vitamin D-replete mice, and also suppressed eosinophil and neutrophil numbers in the bronchoalveolar lavage fluid of male mice. Using generic 16 S rRNA primers, increased bacterial levels were detected in the lungs of initially vitamin D-deficient male mice, which were also reduced by vitamin D supplementation. These results indicate that vitamin D controls granulocyte levels in the bronchoalveolar lavage fluid in an allergen-sensitive manner, and may contribute towards the severity of asthma in a gender-specific fashion through regulation of respiratory bacteria.

The current state of play of rodent models to study the role of vitamin D in UV-induced immunomodulation

Ultraviolet radiation (UVR) from sunlight is immunomodulatory and the main source of vitamin D for humans. Vitamin D can also regulate adaptive immunity, through mechanisms that involve the induction or activation of regulatory T cells. Similar mechanisms have also been proposed for the induction of regulatory T cells after skin exposure to UVR. Here we discuss the converging and diverging immunoregulatory pathways of UVR and vitamin D, including the molecular pathways for regulatory T cell induction, non-genomic pathways regulated by vitamin D, antimicrobial peptides, skin integrity and potential interactions between vitamin D and other UVR-induced mediators. We then discuss possible in vivo approaches that could be used to demonstrate a direct (or otherwise) role for vitamin D in mediating the immunosuppressive effects of UVR such as the use of dietary vitamin D restriction to induce vitamin D deficiency, gene knockout mice or drugs to block enzymes of vitamin D metabolism. We end with discussion of the epigenetic effects of vitamin D and UVR for immunosuppression.

Acute erythemal ultraviolet radiation causes systemic immunosuppression in the absence of increased 25-hydroxyvitamin D3 levels in male mice

Vitamin D is synthesised by ultraviolet (UV) irradiation of skin and is hypothesized to be a direct mediator of the immunosuppression that occurs following UV radiation (UVR) exposure. Both UVR and vitamin D drive immune responses towards tolerance by ultimately increasing the suppressive activities of regulatory T cells. To examine a role for UVR-induced vitamin D, vitamin D₃-deficient mice were established by dietary vitamin D₃ restriction. In comparison to vitamin D₃-replete mice, vitamin D₃-deficient mice had significantly reduced serum levels of 25-hydroxyvitamin D₃ (25(OH)D₃, <20 nmol.L⁻¹) and 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃, <20 pmol.L⁻¹). Following either acute erythemal UVR, or chronic sub-erythemal UVR (8 exposures over 4 weeks) treatment, serum 25(OH)D₃ levels significantly increased in vitamin D₃-deficient female but not male mice. To determine if UVR-induced vitamin D was a mediator of UVR-induced systemic immunosuppression, responses were measured in mice that were able (female) or unable (male) to increase systemic levels of 25(OH)D₃ after UVR. Erythemal UVR (≥4 kJ/m²) suppressed contact hypersensitivity responses (T helper type-1 or -17), aspects of allergic airway disease (T helper type-2) and also the in vivo priming capacity of bone marrow-derived dendritic cells to a similar degree in female and male vitamin D₃-deficient mice. Thus, in male mice, UVR-induced 25(OH)D₃ is not essential for mediating the immunosuppressive effects of erythemal UVR.

Effect of oral feeding with Clostridium leptum on regulatory T-cell responses and allergic airway inflammation in mice

BACKGROUND

Allergic lung inflammation is mediated by allergen-specific T responses, which are negatively regulated by regulatory T cells (Tregs). Previous studies have reported that inoculation of indigenous Clostridium species in the early lives of mice can induce Tregs that colonize the colon. However, whether inoculation of C leptum alone in adult mice could induce systemic Treg responses and inhibit allergic airway inflammation remains unclear.

OBJECTIVE

To investigate the effect of oral administration of C leptum on systemic Treg responses and allergic airway inflammation in a mouse model of asthma.

METHODS

Adult BABL/c mice were injected with ovalbumin to induce asthma and treated orally with C leptum or vehicle daily for 2 weeks. The numbers of Foxp3(+)CD4(+)CD25(+) Tregs in both the spleen and mediastinal lymph nodes were examined by flow cytometry. After allergen challenge, the airway hyperresponsiveness of individual mice was measured, and the numbers of inflammatory infiltrates and the levels of cytokines in bronchoalveolar lavage fluids ere determined.

RESULTS

Oral feeding with C leptum increased the percentage and total number of Tregs in the spleens and mediastinal lymph nodes at 14 days after inoculation and attenuated allergen-induced airway hyperresponsiveness and inflammation by inhibiting inflammatory cytokine production but enhancing interleukin 10 and transforming growth factor β1 production in the lungs.

CONCLUSION

Oral treatment with C leptum can attenuate induced allergic airway inflammation in adult mice.

The effects of low-dose ionizing radiation in the activated rat basophilic leukemia (RBL-2H3) mast cells

Mast cells play important roles in many biological responses, such as those during allergic diseases and inflammatory disorders. Although laser and UV irradiation have immunosuppressive effects on inflammatory diseases by suppressing mast cells, little is known about the effects of γ-ionizing radiation on mast cells. In this study, we investigated the effects of γ-ionizing radiation on RBL-2H3 cells, a convenient model system for studying regulated secretion by mast cells. Low-dose radiation (<0.1 gray (Gy)) did not induce cell death, but high-dose radiation (>0.5 Gy) induced apoptosis. Low-dose ionizing radiation significantly suppressed the release of mediators (histamine, β-hexosaminidase, IL-4, and tumor necrosis factor-α) from immunoglobulin E (IgE)-sensitized RBL-2H3 cells. To determine the mechanism of mediator release inhibition by ionizing radiation, we examined the activation of intracellular signaling molecules such as Lyn, Syk, phospholipase Cγ, PKCs, and MAPK, and intracellular free calcium concentrations ([Ca(2+)](i)). The phosphorylation of signaling molecules following stimulation of high-affinity IgE receptor I (FcεRI) was specifically inhibited by low-dose ionizing radiation (0.01 Gy). These results were due to the suppression of FcεRI expression by the low-dose ionizing radiation. Therefore, low-dose ionizing radiation (0.01 Gy) may function as a novel inhibitor of mast cell activation.

Effect of probiotics on allergic rhinitis in Df, Dp or dust-sensitive children: a randomized double blind controlled trial

OBJECTIVE

To study, we examined the effect of Lactobacillus salivarius on the clinical symptoms and medication use among children with established allergic rhinitis (AR).

DESIGN

Double blind, randomized, controlled trial.

SETTING

Hualien Tzu-Chi General Hospital.

METHODS

Atopic children with current allergic rhinitis received 4x10(9) colony forming units/g of Lactobacillus salivarius (n=99) or placebo (n=100) daily as a powder mixed with food or water for 12 weeks. The SCORing Allergic rhinitis index (specific symptoms scores [SSS] and symptom medication scores [SMS]), which measures the extent and severity of AR, was assessed in each subject at each of the visits--2 weeks prior to treatment initiation (visit 0), at the beginning of the treatment (visit 1), then at 4 (visit 2), 8 (visit 3) and 12 weeks (visit 4) after starting treatment. The WBC, RBC, platelet and, eosinophil counts as well as the IgE antibody levels of the individuals were evaluated before and after 3 months of treatment.

RESULTS

The major outcome, indicating the efficacy of Lactobacillus salivarius treatment, was the reduction in rhinitis symptoms and drug scores. No significant statistical differences were found between baseline or 12 weeks in the probiotic and placebo groups for any immunological or blood cell variables.

CONCLUSIONS

Our study demonstrates that Lactobacillus salivarius treatment reduces rhinitis symptoms and drug usage in children with allergic rhinitis.

FICZ, a tryptophan photoproduct, suppresses pulmonary eosinophilia and Th2-type cytokine production in a mouse model of ovalbumin-induced allergic asthma

Most studies about functions of aryl hydrocarbon receptor (AhR) in the pathogenesis of asthma have been carried out with non-physiological industrial by-products such as 2,3,7,8-tetrachlorodibenzo-p-dioxin and benzo(a)pyrene. In the present study, effects of 6-formylindolo[3,2-b]carbazole (FICZ), a tryptophan photoproduct postulated as a candidate physiological ligand of AhR, on the pathogenesis of asthma were examined and then underlying mechanisms of its immumodulatory effects were investigated. FICZ significantly reduced pulmonary eosinophilia and Th2 cytokine expression in the lungs. Flow cytometric analysis of mediastinal lymph nodes showed that IL-4 producing cells decreased in FICZ-treated mice compared with PBS control. Next, effects of FICZ on in vitro Th2 differentiation and expression of the Th2 transcription factor GATA-3 were examined. CD4+ T cells were isolated from the spleen and incubated under the Th2 differentiation conditions. FICZ inhibited both Th2 differentiation and the expression of GATA-3. Finally, activation of STAT6, which is necessary for Th2 differentiation, was inhibited by FICZ.

Vitamin D(3) deficiency enhances allergen-induced lymphocyte responses in a mouse model of allergic airway disease

There is debate as to whether vitamin D deficiency contributes towards the extent of the asthma epidemic. In this study, using a mouse model, we determined whether vitamin D deficiency in utero and during early life modulated the severity of asthma. Using dietary restriction, vitamin D(3) -replete and vitamin D(3) -deficient colonies of BALB/c mice were established. Utilizing the allergic airway disease model of asthma with the experimental allergen ovalbumin (OVA), we examined asthma-like responses 24 h after airway challenge with OVA in adult offspring born to vitamin D(3) -replete and vitamin D(3) -deficient mothers. The ability of airway-draining lymph node cells to proliferate and secrete cytokines in response to OVA ex vivo was significantly enhanced by vitamin D(3) deficiency. However, other aspects of allergic disease, including the numbers and proportions of inflammatory cells and cytokines in the lungs and the quantity of OVA-specific IgE in serum, were not modified. These results suggest that vitamin D(3) deficiency modulates the capacity of lymphocytes to respond to allergens.

Vitamin D and asthma

Vitamin D deficiency and asthma are common conditions that share risk factors such as African American ethnicity, inner-city residence, and obesity. This review provides a critical examination of current experimental and epidemiologic evidence of a causal association between vitamin D status and asthma or asthma morbidity, including potential protective mechanisms such as antiviral effects and enhanced steroid responsiveness. Because most published epidemiologic studies of vitamin D and asthma or asthma morbidity are observational, a recommendation for or against vitamin D supplementation as preventive or secondary treatment for asthma is not advisable and must await results of ongoing clinical trials. Should these trials confirm a beneficial effect of vitamin D, others will be needed to assess the role of vitamin D supplementation to prevent or treat asthma in different groups such as infants, children of school age, and ethnic minorities.

Differences in control by UV radiation of inflammatory airways disease in naïve and allergen pre-sensitised mice

Exposure of skin to UV radiation (UVR) prior to allergen exposure can inhibit inflammatory airways disease in mice by reducing effector CD4+ T cells in both the trachea and the airway draining lymph nodes. This study analysed the immunomodulatory properties of UVR delivered to naïve versus allergen pre-sensitised mice. In a model of inflammatory airways disease, BALB/c mice were sensitised by peritoneal injection of the allergen, ovalbumin (OVA) (20 μg/mouse), in the adjuvant, alum (4 mg/mouse), on days 0 and 14. On day 21, the mice were exposed to aerosolised OVA and 24 h later, proliferative responses by the cells in the airway draining lymph nodes were examined. UVR (8 kJ m(-2)) was administered 3 days prior to first OVA sensitisation (day -3), or OVA aerosol challenge (day 18). UVR before sensitisation reduced immune responses associated with expression of allergic airways disease; seven days after first OVA sensitisation, regulation of OVA-induced proliferation in vitro but not in vivo by CD4+CD25+ cells from UV-irradiated mice was detected. UVR administered to pre-sensitised mice regulated allergen responsiveness by cells from the airway draining lymph nodes only with a sensitisation protocol involving allergen and adjuvant at 5% strength of the original dose (1 μg OVA in 0.2 mg alum/mouse). These results suggest that UVR may modulate allergic airways disease by two mechanisms. The first, and more potent, is by reducing effector cells in respiratory tissues and requires UV delivery prior to sensitisation. The second, associated with administration to pre-sensitised mice, is weaker and is detected when the mice are sensitised with lower levels of allergen and adjuvant.

The challenges of UV-induced immunomodulation for children’s health. Prog Biophys Mol Biol. 2011;107:323-332. [PMID: 21875613 DOI: 10.1016/j.pbiomolbio.2011.07.014]

Exposure to solar ultraviolet radiation (UVR) is recognised to have both beneficial and harmful effects on human health. With regard to immune responses, it can lead to suppression of immunity and to the synthesis of vitamin D, a hormone that can alter both innate and adaptive immunity. The consequences in children of such UV-induced changes are considerable: first there are positive outcomes including protection against some photoallergic (for example polymorphic light eruption) and T cell-mediated autoimmune diseases (for example multiple sclerosis) and asthma, and secondly there are negative outcomes including an increased risk of skin cancer (squamous cell carcinoma, basal cell carcinoma and cutaneous malignant melanoma) and less effective control of several infectious diseases. Many uncertainties remain regarding the amount of sun exposure that would provide children with the most effective responses against the variety of immunological challenges that they are likely to experience.

The consequences of UV-induced immunosuppression for human health

Exposure to UV radiation can cause suppression of specific immune responses. The pathways leading to the down-regulation are complex, starting from the absorption of UV photons by chromophores in the skin and ending with local and systemic changes in immune mediators, the generation of T and B regulatory cells and inhibition of effector and memory T cell activation. The consequences for human health are thought to be both beneficial and adverse. The former are illustrated by protection against polymorphic light eruption, and possible protection against T cell-mediated autoimmune diseases and asthma. The latter are illustrated by skin cancer, cutaneous lupus erythematosus and infectious diseases including vaccination. Many outstanding questions remain in this rapidly developing and controversial area, not least what advice to give the general public regarding their sun exposure. While considerable advances have been made in the development of strategies that preserve the health benefits of sunlight exposure and decrease its detrimental effects, further research is required before optimal levels of protection are achieved.

The immune-modulating cytokine and endogenous Alarmin interleukin-33 is upregulated in skin exposed to inflammatory UVB radiation

The cellular and molecular mechanisms by which UV radiation modulates inflammation and immunity while simultaneously maintaining skin homeostasis is complex and not completely understood. Similar to the effects of UV, IL-33 has potent immune-modulating properties that are mediated by the downstream induction of cytokines and chemokines. We have discovered that exposure of mice in vivo or human skin samples ex vivo to inflammatory doses of UVB induced IL-33 expression within the epidermal and dermal skin layers. Using a combination of murine cell lines and primary human cells, we demonstrate that both UV and the oxidized lipid platelet activating factor induce IL-33 expression in keratinocytes and dermal fibroblasts. Highlighting the significance of these results, we found that administering IL-33 to mice in vivo suppressed the induction of Th1-mediated contact hypersensitivity responses. This may have consequences for skin cancer growth because UV-induced squamous cell carcinomas that evade immunological destruction were found to express significantly higher levels of IL-33. Finally, we demonstrate that dermal mast cells and skin-infiltrating neutrophils closely associate with UV-induced IL-33-expressing fibroblasts. Our results therefore identify and support a role for IL-33 as an important early danger signal produced in response to inflammation-inducing UV radiation.

Sunny hours and variations in the prevalence of asthma in schoolchildren according to the International Study of Asthma and Allergies (ISAAC) Phase III in Spain

The objective of this study was to estimate the relationship between the prevalence of asthma in schoolchildren aged 6-7 years and 13-14 years and the mean annual sunny hours (MASH) in Spain, and to explore predictive models for asthma prevalence. The prevalence of asthma was obtained from the International Study of Asthma and Allergies (ISAAC) Phase III 2002-2003, and climate and socio-economic variables from official sources. Nine centres were studied and a further four centres, two of which are in ISAAC, to test the predictive models. Logistic regression was used to estimate adjusted prevalence rates of asthma for each centre, and multiple regression models to study the effects of MASH and other meteorological and socio-economic variables. The adjusted prevalence rate of asthma decreased 0.6% [95% confidence interval (CI) 0.4-0.8%] for the 6-7 years group and 1.1% (95% CI 0.8-1.3%) for the 13-14 years group with an increase in the MASH of 100 h. Relative humidity was negatively associated with asthma in the older age group, and gross province product per capita (GPP) was positively associated with asthma in the younger age group. The predictive models, which included MASH, gender, relative humidity, and GPP, anticipated prevalence rates of asthma without significant differences between the levels observed and those expected in 9 of the 11 measurements carried out. The results indicate that sunny hours have a protective effect on the prevalence of asthma in schoolchildren.

Vitamin D and asthma

PURPOSE OF REVIEW

asthma is a disease that continues to carry a significant health burden on humanity. Vitamin D is thought to play a role in many chronic diseases as it may possess immunomodulatory properties. This article will review the role of vitamin D regulation on the immune system and its potential implication in the pathophysiology of asthma.

RECENT FINDINGS

vitamin D receptors are present on many cells in the body, specifically peripheral blood mononuclear cells. Vitamin D has been shown to regulate the balance of several pro-inflammatory and anti-inflammatory responses in the immune system. Studies have suggested that prenatal vitamin D intake has an effect on childhood wheezing and asthma. Additionally, vitamin D may play a role in asthma exacerbations, and recent evidence also suggests its importance in steroid resistant asthma.

SUMMARY

vitamin D has a complex role on the immune system and its regulation of various aspects of immunity has allowed speculation on its potential role in asthma. However, the net effect of vitamin D on the immune system and its role in asthma still remains unanswered. More research needs to address the diagnostic and therapeutic implications vitamin D may have in the future of asthma management.

UV exposure and protection against allergic airways disease

Asthma is a chronic inflammatory disease of the small and large conducting airway mucosa characterised by Th2 cell immunity. Allergen-specific IgE levels control the immediate response whilst the interplay between airway mucosal antigen presenting cells, Th2 effector cells and CD4+CD25+ regulatory T cells control the late phase, cell-mediated response. Using two experimental systems in mice with ovalbumin and papain, respectively, as the allergens, UV irradiation of skin prior to allergen sensitisation reduced the expression of allergic airways disease, particularly the late phase response. In this review, the reduced Th2-driven, asthma-like responses in respiratory tissues of UV-irradiated mice are detailed. Possible mechanisms of UV regulation are debated. The potential beneficial effects of UV irradiation of skin in controlling allergic airways disease are discussed. This review gives some scientific understanding to century-old anecdotal reports that beach and mountain resort holidays associated with increased UV exposure are beneficial in asthma treatment.

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.

UV inhibits allergic airways disease in mice by reducing effector CD4 T cells

BACKGROUND

In human asthma, and experimental allergic airways disease in mice, antigen-presenting cells and CD4(+) effector cells at the airway mucosa orchestrate, and CD4(+)CD25(+) regulatory T cells attenuate, allergen immunity. UV irradiation of skin before sensitization with ovalbumin (OVA) causes significantly reduced asthma-like responses in respiratory tissues.

OBJECTIVE

To determine whether UV-induced changes in CD11c(+) cells, CD4(+)CD25(+) effector cells or CD4(+)CD25(+) regulatory cells in the trachea and airway draining lymph nodes (ADLNs) were responsible for reduced allergic airways disease.

METHODS

The phenotype and function of CD11c(+) cells and CD4(+)CD25(+) cells in the trachea and ADLNs of UV- and non-irradiated, OVA-sensitized mice was examined 24 h after a single exposure to aerosolized OVA.

RESULTS

No changes in the function of CD11c(+) cells from UV-irradiated mice were observed. CD4(+)CD25(+) cells from UV-irradiated, OVA-sensitized mice harvested 24 h after OVA aerosol proliferated less in response to OVA in vitro and were unable to suppress the proliferation of OVA-sensitized responder cells. This result suggested reduced activation of effector T cells in the airway mucosa of UV-irradiated, OVA-sensitized mice. To exclude regulatory cells of any type, there was similar proliferation in vivo to aerosolized OVA by CFSE-loaded, OVA-TCR-specific CD4(+) cells adoptively transferred into UV- and non-irradiated, OVA-sensitized mice. In addition, there was no difference in the expression of regulatory T cell markers (Foxp3, IL-10, TGF-beta mRNA). To examine effector T cells, ADLN cells from UV-irradiated, OVA-sensitized and -challenged mice were cultured with OVA. There was reduced expression of the early activation marker CD69 by CD4(+)CD25(+) cells, and reduced proliferation in the absence of the regulatory cytokine, IL-10.

CONCLUSION

Reduced allergic airways disease in UV-irradiated mice is due to fewer effector CD4(+)CD25(+) cells in the trachea and ADLNs, and not due to UV-induced regulatory cells.

The role of vitamin D in asthma

OBJECTIVE

To review the current literature on vitamin D and asthma, discussing the possible roles of vitamin D on asthma pathogenesis and the potential consequences of vitamin D deficiency.

DATA SOURCES

PubMed database was searched from 1950 to 2009. Keywords used included asthma, vitamin D, inflammation, airway smooth muscle and cytokines.

STUDY SELECTION

Articles were selected based on relevance to the subject.

RESULTS

Vitamin D deficiency has been associated with epidemiologic patterns observed in the asthma epidemic. Vitamin D deficiency is more common with obesity, African American ethnicity, and westernization of countries with higher-risk populations for asthma. Evidence suggests that vitamin D deficiency is associated with increased airway hyperresponsiveness, lower pulmonary functions, worse asthma control, and possibly steroid resistance. Lung epithelial cells express high baseline levels of 1alpha-hydroxylase. This allows the conversion of inactive calcidiol to active calcitriol locally within the lung. Calcitriol has been shown to inhibit the synthesis and release of certain cytokines, such as RANTES, platelet-derived growth factor, and matrix metalloproteinases, from bronchial smooth muscle cells, thereby leading to decreased lung inflammation and smooth muscle cell proliferation. Vitamin D also increases synthesis of interleukin 10 by CD4+CD25+Foxp3+ T-regulatory cells and dendritic cells, while concurrently inhibiting dendritic cell activation by downregulating expression of costimulatory molecules CD40 and CD80/86. Vitamin D is also capable of inducing the expression of several anti-infective molecules, such as cathelicidin. Thus, vitamin D has a number of biologic effects that are likely important in regulating key mechanisms in asthma.

CONCLUSIONS

We hypothesize that vitamin D supplementation may lead to improved asthma control by inhibiting the influx of inflammatory cytokines in the lung and increasing the secretion of interleukin 10 by T-regulatory cells and dendritic cells.

Bacterial strain-specific induction of Foxp3+ T regulatory cells is protective in murine allergy models

BACKGROUND

The incidence of atopic disease has increased dramatically during recent decades and the potential immunoregulatory influence of the microbiota in these individuals is under investigation.

OBJECTIVE

The aim of our study was to identify a bacterial strain that is protective in murine allergy models and to determine if microbial induction of T regulatory cells was associated with protection from allergic inflammation.

METHODS

Three microbes (Bifidobacterium breve AH1205, B. longum AH1206 and Lactobacillus salivarius AH102) of human origin were fed to newborn, adult and germ-free animals. Induction of Foxp3(+) T regulatory cells was assessed by flow cytometry. Gene array analysis was performed on Peyer's patches. Strains were also examined for their protective effects in the ovalbumin (OVA) respiratory allergy model and the OVA-cholera toxin dietary allergy model.

RESULTS

Bifidobacterium longum AH1206 consumption resulted in increased numbers of Foxp3(+) T regulatory cells in infant, adult and germ-free animals. B. breve AH1205 induced Foxp3(+) T regulatory cell expansion only in infant mice while L. salivarius AH102 did not alter T regulatory cell numbers in any animal model tested. B. longum AH1206 reduced the Peyer's patch gene expression associated with antigen presentation, TLR signalling and cytokine production while increasing the expression of genes associated with retinoic acid metabolism. B. longum AH1206 protected against airway inflammation in OVA-sensitized animals and B. longum AH1206 blocked the induction of IgE to orally administered OVA. Neither B. breve AH1205 nor L. salivarius AH102 had a protective effect in either model.

CONCLUSION

Bacterial strain-specific induction of Foxp3(+) T regulatory cells in vivo is associated with protection from respiratory and oral allergy.

1,25-dihydroxyvitamin D3 enhances the ability of transferred CD4+ CD25+ cells to modulate T helper type 2-driven asthmatic responses

The severity of allergic diseases may be modified by vitamin D. However, the immune pathways modulated by the active form of vitamin D, 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], are yet to be fully elucidated. In this study, naturally occurring CD4(+) CD25(+) cells from the skin-draining lymph nodes (SDLN) of mice treated with topical 1,25(OH)(2)D(3) had an increased ability to suppress T helper type 2 (Th2) -skewed immune responses. CD4(+) CD25(+) cells transferred from mice treated with topical 1,25(OH)(2)D(3) into ovalbumin (OVA) -sensitized mice challenged intranasally with OVA 18 hr later, significantly suppressed the capacity of airway-draining lymph node (ADLN) cells to proliferate and secrete cytokines in response to further OVA stimulation ex vivo. The CD4(+) CD25(+) cells from 1,25(OH)(2)D(3)-treated mice also reduced airway hyperresponsiveness and the proportions of neutrophils and eosinophils in bronchoalveolar lavage fluid (BALF). To test the effect of 1,25(OH)(2)D(3) on cells able to respond to a specific antigen, CD4(+) CD25(+) cells were purified from the SDLN of OVA-T-cell receptor (TCR) transgenic mice treated 4 days earlier with topical 1,25(OH)(2)D(3). CD4(+) CD25(+) cells from OVA-TCR mice treated with 1,25(OH)(2)D(3) were able to alter BALF cell content and suppress ADLN responses to a similar degree to those cells from non-transgenic mice, suggesting that the effect of 1,25(OH)(2)D(3) was not related to TCR signalling. In summary, topical 1,25(OH)(2)D(3) increased the regulatory capacity of CD4(+) CD25(+) cells from the SDLN to suppress Th2-mediated allergic airway disease. This work highlights how local 1,25(OH)(2)D(3) production by lung epithelial cells may modulate the suppressive activity of local regulatory T cells.

Childhood asthma may be a consequence of vitamin D deficiency

PURPOSE OF REVIEW

Vitamin D deficiency has been rediscovered as a public-health problem worldwide. It has been postulated that vitamin D deficiency may explain a portion of the asthma epidemic. The purpose of this review is to present the evidence for a role of vitamin D in asthma.

RECENT FINDINGS

Both animal models and studies in human fetal tissues show that vitamin D plays a role in fetal lung growth and maturation. Epidemiologic studies have also suggested that higher prenatal vitamin D intakes have a protective role against wheezing illnesses in young children. Vitamin D may protect against wheezing illnesses through its role in upregulating antimicrobial proteins or through its multiple immune effects. In addition, vitamin D may play a therapeutic role in steroid resistant asthmatics, and lower vitamin D levels have recently been associated with higher risks for asthma exacerbations.

SUMMARY

Improving vitamin D status holds promise in primary prevention of asthma, in decreasing exacerbations of disease, and in treating steroid resistance. However, the appropriate level of circulating vitamin D for optimal immune functioning remains unclear. Because vitamin D deficiency is prevalent even in sun-replete areas, clinical trials are needed to definitively answer questions about the role of vitamin D in asthma.

Update on allergies in pregnancy, lactation, and early childhood

The factors responsible for the induction of allergic disease at an early age have not been completely identified. Therefore a major research focus is their identification to elaborate recommendations for prevention of sensitization in high-risk or atopic children. This review analyzes known or suspected reasons for sensitization in pregnant women and infants from both clinical and experimental animal studies. Recent studies and meta-analyses could not confirm the protective effect of an allergen-poor diet on the part of the mother during pregnancy and lactation. Likewise, the type of bottle feeding or the introduction of solid food into the child's diet might not significantly influence the development of atopy, allergy, or asthma in the child's life. Disappointingly, the few preventive measures remaining to reduce the risk of allergic sensitization and atopic diseases in mother and child are the avoidance of smoking and alcohol consumption during pregnancy and lactation and the avoidance of the impairment of gastric function. Further studies are urgently needed to address the influence of certain foods and nutrients, as well as environmental factors, for prevention of allergic diseases in the low- or high-risk infant.

Lactobacillus reuteri-induced regulatory T cells protect against an allergic airway response in mice

RATIONALE

We have previously demonstrated that oral treatment with live Lactobacillus reuteri can attenuate major characteristics of the asthmatic response in a mouse model of allergic airway inflammation. However, the mechanisms underlying these effects remain to be determined.

OBJECTIVES

We tested the hypothesis that regulatory T cells play a major role in mediating L. reuteri-induced attenuation of the allergic airway response.

METHODS

BALB/c mice were treated daily with L. reuteri by gavage. Flourescent-activated cell sorter analysis was used to determine CD4(+)CD25(+)Foxp3(+)T cell populations in spleens following treatment with L. reuteri or vehicle control. Cell proliferation assays were performed on immunomagnetic bead separated CD4(+)CD25(+) and CD4(+)CD25(-) T cells. CD4(+)CD25(+) T cells isolated from, ovalbumin naive, L. reuteri treated mice were transferred into ovalbumin-sensitized mice. Following antigen challenge the airway responsiveness, inflammatory cell influx and cytokine levels in bronchoalveolar lavage fluid of recipient mice were assessed.

MEASUREMENTS AND MAIN RESULTS

Following 9 days of oral L. reuteri treatment, the percentage and total number of CD4(+)CD25(+)Foxp3(+)T cells in spleens significantly increased. CD4(+)CD25(+) cells isolated from L. reuteri-fed animals also had greater capacity to suppress T-effector cell proliferation. Adoptive transfer of CD4(+)CD25(+) T cells from L. reuteri-treated mice to ovalbumin-sensitized animals attenuated airway hyper-responsiveness and inflammation in response to subsequent antigen challenge.

CONCLUSIONS

These results strongly support a role for nonantigen-specific CD4(+)CD25(+)Foxp3(+) regulatory T cells in attenuating the allergic airway response following oral treatment with L. reuteri. This potent immuno-regulatory action may have therapeutic potential in controlling the Th2 bias observed in atopic individuals.