1,25D3 prevents CD8(+)Tc2 skewing and asthma development through VDR binding changes to the Cyp11a1 promoter

Serum 25-hydroxyvitamin D levels and peripheral blood eosinophil percentages as predictive indicators for eosinophilic chronic sinusitis with nasal polyps

PURPOSE

Chronic rhinosinusitis (CRS) has a high incidence rate and different endotypes. Serum 25-hydroxyvitamin D (25(OH)D) deficiency is common in patients with eosinophilic and non-eosinophilic chronic rhinosinusitis with nasal polyps (ECRSwNP and nECRSwNP, respectively). This study explored the relationship between serum 25(OH)D levels and CRS risk and determined the value of combining serum 25(OH)D with peripheral blood markers in distinguishing between ECRSwNP and nECRSwNP.

METHODS

This study enrolled 275 CRS patients and 298 healthy controls. The relationship between serum 25(OH)D levels and CRS risk was determined using logistic regression after propensity score matching (PSM). The efficiency of various peripheral blood markers in distinguishing between ECRSwNP and nECRSwNP was assessed using a decision-tree model.

RESULTS

The final analysis included 189 CRS patients and 189 controls after 1:1 PSM. Serum 25(OH)D levels were significantly lower in CRS patients than in controls. Patients with mild CRS showed higher serum 25(OH)D levels than those with moderate or severe CRS, and ECRSwNP patients had lower serum 25(OH)D levels than nECRSwNP patients (all Ps < 0.05). Eosinophil percentages and IgE levels were independent risk factors for ECRSwNP, whereas serum 25(OH)D was an independent protective factor. 25(OH)D deficiency increased the ECRSwNP risk (OR = 3.074, P = 0.04). An eosinophil percentage ≥ 5% and a 25(OH)D level < 61.8 nmol/L could be used to predict ECRSwNP, with training and test set accuracies of 89.7% and 85.7%, respectively.

CONCLUSION

Our findings suggest that serum 25(OH)D deficiency is an independent risk factor for CRS, especially ECRSwNP. Combining serum 25(OH)D levels with peripheral eosinophil percentages could be a promising biomarker for ECRSwNP.

Gene editing in allergic diseases: Identification of novel pathways and impact of deleting allergen genes

Gene editing technology has emerged as a powerful tool in all aspects of health research and continues to advance our understanding of critical and essential elements in disease pathophysiology. The clustered regularly interspaced short palindromic repeats (CRISPR) gene editing technology has been used with precision to generate gene knockouts, alter genes, and identify genes that cause disease. The full spectrum of allergic/atopic diseases, in part because of shared pathophysiology, is ripe for studies with this technology. In this way, novel culprit genes are being identified and allow for manipulation of triggering allergens to reduce allergenicity and disease. Notwithstanding current limitations on precision and potential off-target effects, newer approaches are rapidly being introduced to more fully understand specific gene functions as well as the consequences of genetic manipulation. In this review, we examine the impact of editing technologies of novel genes relevant to peanut allergy and asthma as well as how gene modification of common allergens may lead to the deletion of allergenic proteins.

Research progress of glucocorticoid resistance in chronic rhinosinusitis with nasal polyps: A review

Chronic rhinosinusitis with nasal polyps (CRSwNP) is one of the common chronic inflammatory diseases in otolaryngology. Glucocorticoid (GC) acts as the first-line drug for the treatment of CRSwNP in clinical practice, and they play an irreplaceable role in reducing nasal mucosal inflammation and restoring the normal physiological function of the nasal mucosa. However, many patients are still insensitive to GC treatment, known as GC resistance, which leads to poor control of the disease, and the underlying mechanisms are still not fully elucidated. This article provides a comprehensive overview of the research progress of GC resistance of patients with CRSwNP in recent years.

CD8 T-cell subsets: heterogeneity, functions, and therapeutic potential

CD8 T cells play crucial roles in immune surveillance and defense against infections and cancer. After encountering antigenic stimulation, naïve CD8 T cells differentiate and acquire effector functions, enabling them to eliminate infected or malignant cells. Traditionally, cytotoxic T cells, characterized by their ability to produce effector cytokines and release cytotoxic granules to directly kill target cells, have been recognized as the constituents of the predominant effector T-cell subset. However, emerging evidence suggests distinct subsets of effector CD8 T cells that each exhibit unique effector functions and therapeutic potential. This review highlights recent advancements in our understanding of CD8 T-cell subsets and the contributions of these cells to various disease pathologies. Understanding the diverse roles and functions of effector CD8 T-cell subsets is crucial to discern the complex dynamics of immune responses in different disease settings. Furthermore, the development of immunotherapeutic approaches that specifically target and regulate the function of distinct CD8 T-cell subsets holds great promise for precision medicine.

The Role of Vitamins in the Pathogenesis of Asthma

Vitamins play a crucial role in the proper functioning of organisms. Disturbances of their levels, seen as deficiency or excess, enhance the development of various diseases, including those of the cardiovascular, immune, or respiratory systems. The present paper aims to summarize the role of vitamins in one of the most common diseases of the respiratory system, asthma. This narrative review describes the influence of vitamins on asthma and its main symptoms such as bronchial hyperreactivity, airway inflammation, oxidative stress, and airway remodeling, as well as the correlation between vitamin intake and levels and the risk of asthma in both pre- and postnatal life.

Nuclear receptor Nr1d1 alleviates asthma by abating GATA3 gene expression and Th2 cell differentiation

Nuclear receptors are a unique family of transcription factors that play cardinal roles in physiology and plethora of human diseases. The adopted orphan nuclear receptor Nr1d1 is a constitutive transcriptional repressor known to modulate several biological processes. In this study, we found that Nr1d1 plays a decisive role in T helper (Th)-cell polarization and transcriptionally impedes the formation of Th2 cells by directly binding to the promoter region of GATA binding protein 3 (GATA3) gene. Nr1d1 interacts with its cellular companion, the nuclear receptor corepressor and histone deacetylase 3 to form a stable repression complex on the GATA3 promoter. The presence of Nr1d1 also imparts protection against associated inflammatory responses in murine model of asthma and its ligand SR9011 eased disease severity by suppressing Th2 responses. Moreover, Chip-seq profiling uncovered Nr1d1 interactions with other gene subsets that impedes Th2-linked pathways and regulates metabolism, immunity and brain functions, therefore, providing empirical evidence regarding the genetic link between asthma and other comorbid conditions. Thus, Nr1d1 emerges as a molecular switch that could be targeted to subdue asthma.

Vitamin D as therapeutic modulator in cerebrovascular diseases: a mechanistic perspectives

Vitamin D deficiency has been linked to several major chronic diseases, such as cardiovascular and neurodegenerative diseases, diabetes, and cancer, linked to oxidative stress, inflammation, and aging. Vitamin D deficiency appears to be particularly harmful to the cardiovascular system, as it can cause endothelial dysfunctioning and vascular abnormalities through the modulation of various downstream mechanisms. As a result, new research indicates that therapeutic approaches targeting vitamin D inadequacies or its significant downstream effects, such as impaired autophagy, abnormal pro-inflammatory and pro-oxidant reactions, may delay the onset and severity of major cerebrovascular disorders such as stroke and neurologic malformations. Vitamin D modulates the various molecular pathways, i.e., Nitric Oxide, PI3K-Akt Pathway, cAMP pathway, NF-kB Pathway, Sirtuin 1, Nrf2, FOXO, in cerebrovascular disorder. The current review shows evidence for vitamin D's mitigating or slowing the progression of these cerebrovascular disorders, which are significant causes of disability and death worldwide.

Autocrine vitamin D signaling switches off pro-inflammatory programs of TH1 cells

The molecular mechanisms governing orderly shutdown and retraction of CD4+ type 1 helper T (TH1) cell responses remain poorly understood. Here we show that complement triggers contraction of TH1 responses by inducing intrinsic expression of the vitamin D (VitD) receptor and the VitD-activating enzyme CYP27B1, permitting T cells to both activate and respond to VitD. VitD then initiated the transition from pro-inflammatory interferon-γ+ TH1 cells to suppressive interleukin-10+ cells. This process was primed by dynamic changes in the epigenetic landscape of CD4+ T cells, generating super-enhancers and recruiting several transcription factors, notably c-JUN, STAT3 and BACH2, which together with VitD receptor shaped the transcriptional response to VitD. Accordingly, VitD did not induce interleukin-10 expression in cells with dysfunctional BACH2 or STAT3. Bronchoalveolar lavage fluid CD4+ T cells of patients with COVID-19 were TH1-skewed and showed de-repression of genes downregulated by VitD, from either lack of substrate (VitD deficiency) and/or abnormal regulation of this system.

Identification of potential biomarkers and immune infiltration characteristics in severe asthma

OBJECTIVES

We hope to identify key molecules that can be used as markers of asthma severity and investigate their correlation with immune cell infiltration in severe asthma.

METHODS

An asthma dataset was downloaded from the Gene Expression Omnibus database and then processed by R software to obtain differentially expressed genes (DEGs). First, multiple enrichment platforms were applied to analyze crucial biological processes and pathways and protein-protein interaction networks related to the DEGs. We next combined least absolute shrinkage and selection operator logistic regression and the support vector machine-recursive feature elimination algorithms to screen diagnostic markers of severe asthma. Then, a local cohort consisting of 40 asthmatic subjects (24 with moderate asthma and 16 with severe asthma) was used for biomarker validation. Finally, infiltration of immune cells in asthma bronchoalveolar lavage fluid and their correlation with the screened markers was evaluated by CIBERSORT.

RESULTS

A total of 97 DEGs were identified in this study. Most of these genes are enriched in T cell activation and immune response in the asthma biological process. CC-chemokine receptor 7 (CCR7) and natural killer cell protein 7(NKG7) were identified as markers of severe asthma. The highest area under the ROC curve (AUC) was from a new indicator combining CCR7 and NKG7 (AUC = 0.851, adj. p < 0.05). Resting and activated memory CD4 T cells, activated NK cells, and CD8 T cells were found to be significantly higher in the severe asthma group (adj. p < 0.01). CCR7 and NKG7 were significantly correlated with these infiltrated cells that showed differences between the two groups. In addition, CCR7 was found to be significantly positively correlated with eosinophils (r = 0.38, adj. p < 0.05) infiltrated in bronchoalveolar lavage fluid.

CONCLUSION

CCR7 and NKG7 might be used as potential markers for asthma severity, and their expression may be associated with differences in immune cell infiltration in the moderate and severe asthma groups.

Effect of Perinatal Vitamin D Deficiency on Lung Mesenchymal Stem Cell Differentiation and Injury Repair Potential

Stem cells, including the resident lung mesenchymal stem cells (LMSCs), are critically important for injury repair. Compelling evidence links perinatal vitamin D (VD) deficiency to reactive airway disease; however, the effects of perinatal VD deficiency on LMSC function is unknown. We tested the hypothesis that perinatal VD deficiency alters LMSC proliferation, differentiation, and function, leading to an enhanced myogenic phenotype. We also determined whether LMSCs' effects on alveolar type II (ATII) cell function are paracrine. Using an established rat model of perinatal VD deficiency, we studied the effects of four dietary regimens (0, 250, 500, or 1,000 IU/kg cholecalciferol-supplemented groups). At Postnatal Day 21, LMSCs were isolated, and cell proliferation and differentiation (under basal and adipogenic induction conditions) were determined. LMSC paracrine effects on ATII cell proliferation and differentiation were determined by culturing ATII cells in LMSC-conditioned media from different experimental groups. Using flow cytometry, >95% of cells were CD45-ve, >90% were CD90 + ve, >58% were CD105 + ve, and >64% were Stro-1 + ve, indicating their stem cell phenotype. Compared with the VD-supplemented groups, LMSCs from the VD-deficient group demonstrated suppressed PPARγ, but enhanced Wnt signaling, under basal and adipogenic induction conditions. LMSCs from 250 VD- and 500 VD-supplemented groups effectively blocked the effects of perinatal VD deficiency. LMSC-conditioned media from the VD-deficient group inhibited ATII cell proliferation and differentiation compared with those from the 250 VD- and 500 VD-supplemented groups. These data support the concept that perinatal VD deficiency alters LMSC proliferation and differentiation, potentially contributing to increased respiratory morbidity seen in children born to mothers with VD deficiency.

Vitamin D receptor gene polymorphisms in atopy

Background

The occurrence of allergic conditions, for example allergic asthma, rhinitis, and atopic dermatitis, is rising worldwide. These allergic conditions are associated with poor life quality. Vitamin D is proposed to be linked with increased risk and severe forms of allergic diseases.

Aims

This review article aimed to evaluate the vitamin D level role and polymorphisms of vitamin D receptor gene (VDR) in atopy.

Methods & Materials

We analyzed publications that were focusing on levels of vitamin D and/or polymorphism analysis of vitamin D receptor gene in allergic asthma, rhinitis, and atopic dermatitis patients.

Results

We noticed that levels of vitamin D are extensively studied in atopy by many research groups, however, polymorphisms of vitamin D receptor gene and their link with levels of vitamin D lack comprehensive data. There is evidence that vitamin D may be associated with anti‐inflammatory effects in allergic diseases. Some of VDR polymorphisms also may play a role in pathogenesis of these diseases. However, the data from different studies are controversial.

Discussion

The results of different studies are usually inconsistent, most probably due to populational bias or differences in methodology. Even though, more evidence shows a positive impact of vitamin D on the risk and outcomes of allergic diseases, especially atopic dermatitis, and asthma.

Conclusions

There is controversial data about the level of vitamin D and its role in atopy; however, more evidence shows a positive impact on the risk and outcomes of allergic diseases.

The significance of CYP11A1 expression in skin physiology and pathology

CYP11A1, a member of the cytochrome P450 family, plays several key roles in the human body. It catalyzes the first and rate-limiting step in steroidogenesis, converting cholesterol to pregnenolone. Aside from the classical steroidogenic tissues such as the adrenals, gonads and placenta, CYP11A1 has also been found in the brain, gastrointestinal tract, immune systems, and finally the skin. CYP11A1 activity in the skin is regulated predominately by StAR protein and hence cholesterol levels in the mitochondria. However, UVB, UVC, CRH, ACTH, cAMP, and cytokines IL-1, IL-6 and TNFα can also regulate its expression and activity. Indeed, CYP11A1 plays several critical roles in the skin through its initiation of local steroidogenesis and specific metabolism of vitamin D, lumisterol, and 7-dehydrocholesterol. Products of these pathways regulate the protective barrier and skin immune functions in a context-dependent fashion through interactions with a number of receptors. Disturbances in CYP11A1 activity can lead to skin pathology.

Vitamin D and Primary Ciliary Dyskinesia: A Topic to Be Further Explored

Primary ciliary dyskinesia (PCD) is a genetic disease characterized by abnormalities in ciliary structure/function. The diagnosis of PCD relies on a combination of clinical evaluation and ultrastructural (electron microscopic) analysis of the ciliary architecture. This diagnosis may be challenging due to clinical and genetic heterogeneity and artifacts during the ciliary ultrastructure preparation and assessment. Recently, vitamin D supplementation has been proposed for several groups probably suffering from D-hypovitaminosis. Some patients with inflammatory bowel disease may have significant malabsorption, and vitamin D supplementation in these patients is recommended. Two recent reports suggest that a low plasmatic level of this vitamin is present in the PCD population. The utility of vitamin D supplementation may be essential in this group of individuals, and further investigations are warranted. Still, in examining the literature papers, it seems relevant that the authors concentrate solely on lung function in both studies. Future studies should probably target the intestinal function in patients with PCD independently from the vitamin D supplementation to fully evaluate its role.

Nuclear Receptors in Asthma: Empowering Classical Molecules Against a Contemporary Ailment

The escalation in living standards and adoption of 'Western lifestyle' has an allied effect on the increased allergy and asthma burden in both developed and developing countries. Current scientific reports bespeak an association between allergic diseases and metabolic dysfunction; hinting toward the critical requirement of organized lifestyle and dietary habits. The ubiquitous nuclear receptors (NRs) translate metabolic stimuli into gene regulatory signals, integrating diet inflences to overall developmental and physiological processes. As a consequence of such promising attributes, nuclear receptors have historically been at the cutting edge of pharmacy world. This review discusses the recent findings that feature the cardinal importance of nuclear receptors and how they can be instrumental in modulating current asthma pharmacology. Further, it highlights a possible future employment of therapy involving dietary supplements and synthetic ligands that would engage NRs and aid in eliminating both asthma and linked comorbidities. Therefore, uncovering new and evolving roles through analysis of genomic changes would represent a feasible approach in both prevention and alleviation of asthma.

Flow Cytometry: From Experimental Design to Its Application in the Diagnosis and Monitoring of Respiratory Diseases

Recent advances in the field of flow cytometry (FCM) have highlighted the importance of incorporating it as a basic analysis tool in laboratories. FCM not only allows the identification of cell subpopulations by detecting the expression of molecules in the cell membrane or cytoplasm, but it can also quantify and identify soluble molecules. The proper functioning of the FCM requires six fundamental systems, from those related to the transport of events to the systems dedicated to the analysis of information. In this review, we have identified the main considerations that every FCM user must know for an optimal antibody panel design, the quality systems that must govern the FCM protocols to guarantee reproducible results in research or clinical laboratories. Finally, we have introduced the current evidence that highlights the relevance of FCM in the investigation and clinical diagnosis of respiratory diseases, establishing important advances in the basic and clinical study of diseases as old as Tuberculosis along with the recent proposals for the monitoring and classification of patients infected with the new SARS-CoV2 virus.

Back to basics: review on vitamin D and respiratory viral infections including COVID-19

IMPORTANCE

As the scientific community is in a marathon in finding out the cure for COVID-19, in this crisis, it is essential for the physicians not to forget about the basics. Due to the pandemic crisis, in many nursing homes and hospitals, there established new policies on decreasing unnecessary medications to minimize cross-contamination. Sometimes these policies are making providers avoid essential drugs such as Vitamins, including Vitamin D. In this paper, we try to emphasize the importance of Vitamin D in COVID-19 and respiratory viral patients.

RELEVANCE

Vitamin D helps in decreasing the 'pro-inflammatory cytokines' in the lungs and acts in immunomodulatory function, and 'also it will increase the anti-inflammatory, antiviral responses of the respiratory epithelial cells during infection.'

CONCLUSION

Due to the highly contagious nature of COVID-19 and the increased morbidity and mortality with no appropriate therapy and vaccine, one must be cautious and do everything to help COVID-19 patients. In hospitals and other health care settings to decrease cross-contamination, holding other non-essential medications is taking place. Discontinuing Vitamins could increase the mortality and morbidity of those affected, especially in deficient/insufficient individuals. Obtaining serum 25 (OH) D levels in all patients with viral respiratory infections, especially COVID-19, could help in the detection and treatment of Vitamin D deficiency and potentially decrease recovery time and improve outcome. Even though evidence suggests that vitamin D has the anti-inflammatory, antiviral properties, randomized double-blinded controlled trials are needed to verify this further, and to understand Vitamin D and COVID-19 better.

ABBREVIATIONS

Vitamin D receptor-VDR; 25(OH)D- 25 hydroxyvitamin D; 1,25 (OH)D-1,25 dihydroxy Vitamin D; 1α,25-dihydroxy Vitamin D-1,25[OH]2 D or calcitriol; IU- International Units; Interferons stimulated genes- ISG; ARI- acute respiratory infection; RSV- respiratory syncytial virus; RTI- Respiratory tract infections; COPD-Chronic obstructive pulmonary disease; BMI-Basal metabolic index; USA-USA.

Intestinal vitamin D receptor knockout protects from oxazolone-induced colitis

Crohn’s disease (CD) and ulcerative colitis (UC) actually had different pathological mechanisms, as the former was mainly induced by Th1 and Th17 response and the latter by Th2 response. Our previous study found that oxazolone-induced Th2-mediated colitis could not be attenuated by vitamin D supplementation. This study investigated the influence of intestinal vitamin D receptor (VDR) knockout on oxazolone-induced colitis and explored the possible immunological mechanism. Intestinal VDR knockout mice had milder oxazolone-induced colitis than wildtype controls, as demonstrated by less body weight decrease and faster recovery, more intact local structure, reduced cell apoptosis, and better preserved barrier function. Th2-mediated inflammation was significantly inhibited by VDR deficiency. Meanwhile, the percentage of invariant natural killer T (iNKT) cells did not increase as much in intestinal VDR knockout mice as in wild-type controls, nor did the iNKT cells develop normally as in the controls. Intestinal VDR knockout protected against oxazolone-induced colitis in mice by blocking Th2 cell response and reducing the function of intestinal iNKT cells. Vitamin D status had no influence on the severity of colitis. This study may explain the diverse outcomes after vitamin D supplementation in literature and add some clue to the targeted therapy of IBD.

Expression and activation of the steroidogenic enzyme CYP11A1 is associated with IL-13 production in T cells from peanut allergic children

Activation of the steroidogenic enzyme CYP11A1 was shown to be necessary for the development of peanut-induced intestinal anaphylaxis and IL-13 production in allergic mice. We determined if levels of CYP11A1 in peripheral blood T cells from peanut-allergic (PA) children compared to non-allergic controls were increased and if levels correlated to IL-13 production and oral challenge outcomes to peanut. CYP11A1 mRNA and protein levels were significantly increased in activated CD4⁺ T cells from PA patients. In parallel, IL-13 production was significantly increased; IFNγ levels were not different between groups. There were significant correlations between expression levels of CYP11A1 mRNA and levels of IL13 mRNA and protein, levels of serum IgE anti-Ara h 2 and to outcomes of peanut challenge. The importance of CYP11A1 on cytokine production was tested using a CYP11A1 CRISPR/Cas9 KO plasmid or an inhibitor of enzymatic CYP11A1 activity. Inhibition of CYP11A1 activation in patient cells treated with the inhibitor, aminoglutethimide, or CD4⁺ T cell line transfected with the CYP11A1 KO plasmid resulted in reduced IL-13 production. These data suggest that the CYP11A1-CD4⁺Tcell-IL-13 axis in activated CD4⁺ T cells from PA children is associated with development of PA reactions. CYP11A1 may represent a novel target for therapeutic intervention in PA children.

Current Molecular Markers of Melanoma and Treatment Targets

Melanoma is a deadly skin cancer that becomes especially difficult to treat after it metastasizes. Timely identification of melanoma is critical for effective therapy, but histopathologic diagnosis can frequently pose a significant challenge to this goal. Therefore, auxiliary diagnostic tools are imperative to facilitating prompt recognition of malignant lesions. Melanoma develops as result of a number of genetic mutations, with UV radiation often acting as a mutagenic risk factor. Novel methods of genetic testing have improved detection of these molecular alterations, which subsequently revealed important information for diagnosis and prognosis. Rapid detection of genetic alterations is also significant for choosing appropriate treatment and developing targeted therapies for melanoma. This review will delve into the understanding of various mutations and the implications they may pose for clinical decision making.

Vitamin D Deficiency and the Risk of Cerebrovascular Disease

Vitamin D deficiency has been clearly linked to major chronic diseases associated with oxidative stress, inflammation, and aging, including cardiovascular and neurodegenerative diseases, diabetes, and cancer. In particular, the cardiovascular system appears to be highly sensitive to vitamin D deficiency, as this may result in endothelial dysfunction and vascular defects via multiple mechanisms. Accordingly, recent research developments have led to the proposal that pharmacological interventions targeting either vitamin D deficiency or its key downstream effects, including defective autophagy and abnormal pro-oxidant and pro-inflammatory responses, may be able to limit the onset and severity of major cerebrovascular diseases, such as stroke and cerebrovascular malformations. Here we review the available evidence supporting the role of vitamin D in preventing or limiting the development of these cerebrovascular diseases, which are leading causes of disability and death all over the world.

Extra-adrenal glucocorticoid biosynthesis: implications for autoimmune and inflammatory disorders

Glucocorticoid synthesis is a complex, multistep process that starts with cholesterol being delivered to the inner membrane of mitochondria by StAR and StAR-related proteins. Here its side chain is cleaved by CYP11A1 producing pregnenolone. Pregnenolone is converted to cortisol by the enzymes 3-βHSD, CYP17A1, CYP21A2 and CYP11B1. Glucocorticoids play a critical role in the regulation of the immune system and exert their action through the glucocorticoid receptor (GR). Although corticosteroids are primarily produced in the adrenal gland, they can also be produced in a number of extra-adrenal tissue including the immune system, skin, brain, and intestine. Glucocorticoid production is regulated by ACTH, CRH, and cytokines such as IL-1, IL-6 and TNFα. The bioavailability of cortisol is also dependent on its interconversion to cortisone which is inactive, by 11βHSD1/2. Local and systemic glucocorticoid biosynthesis can be stimulated by ultraviolet B, explaining its immunosuppressive activity. In this review, we want to emphasize that dysregulation of extra-adrenal glucocorticoid production can play a key role in a variety of autoimmune diseases including multiple sclerosis (MS), lupus erythematosus (LE), rheumatoid arthritis (RA), and skin inflammatory disorders such as psoriasis and atopic dermatitis (AD). Further research on local glucocorticoid production and its bioavailability may open doors into new therapies for autoimmune diseases.

Dichotomous role of TGF-β controls inducible regulatory T-cell fate in allergic airway disease through Smad3 and TGF-β-activated kinase 1

BACKGROUND

Inducible CD4+CD25+ regulatory T (iTreg) cells can become pathogenic effector cells, enhancing lung allergic responses.

OBJECTIVE

We aimed to define the underlying cellular and molecular pathways activated by TGF-β, which determine the suppressor or enhancing activities of iTreg cells.

METHODS

Sensitized wild-type and CD8-deficient (CD8-/-) mice were challenged with allergen. Isolated CD4+CD25- T cells were activated by using anti-CD3/anti-CD28. To generate suppressor iTreg cells, cells were then differentiated in the presence of TGF-β, whereas IL-17-producing effector T cells were additionally exposed to IL-6. After TGF-β, Smad3 and TGF-β-activated kinase 1 (TAK1) kinase levels were monitored. The consequences of inhibiting either kinase were determined in vitro and after transfer into CD8-/- recipients. Quantitative PCR and chromatin immunoprecipitation were used to monitor gene expression and histone modifications at the retinoic acid-related orphan receptor γt (Rorγt) locus.

RESULTS

In wild-type mice, iTreg cells suppressed lung allergic responses linked to Smad3-dependent forkhead box P3 (Foxp3) expression and IL-10 production. In the presence of IL-6, iTreg cells converted to TH17 cells, mediating a neutrophil-dependent enhancement of lung allergic responses in CD8-/- mice. Conversion was regulated by TAK1. Inhibition or silencing of TAK1 prevented expression of Rorγt and TH17 differentiation through histone modifications of Rorγt; Foxp3 expression and iTreg cell-mediated suppression remained intact. In the same cell, TGF-β induced coexpression of Smad3 and TAK1 proteins; in the presence of IL-6, expression of Smad3 and Foxp3 but not TAK1 decreased.

CONCLUSION

TGF-β regulates iTreg cell outcomes through 2 distinct signal transduction pathways: one Smad3 dependent and the other TAK1 dependent. The balance of these pathways has important implications in TH17-mediated autoimmune diseases and neutrophil-dependent asthma.

Influence of vitamin D receptor gene FokI and ApaI polymorphisms on glucocorticoid response in patients with asthma

BACKGROUND

Glucocorticoid (GC)-resistant asthma, a complex disease phenotype, has a high morbidity and mortality and takes up a disproportionate share of healthcare costs. The aim of this work was to assess serum 25-hydroxyvitamin D (25(OH)VD) levels in steroid-resistant, steroid-sensitive patients with asthma and in healthy controls, and to investigate the association between the vitamin D receptor gene (VDR) FokI and ApaI polymorphisms and GC resistance in patients with asthma.

METHODS

This case-control study included 70 patients with severe bronchial asthma and 30 apparently healthy controls. Atopic status was determined by skin-prick test reaction to the most common locally-encountered allergens. A GC reversibility test was performed to differentiate between GC-sensitive and GC-resistant asthma. For all subjects, analysis of the VDR FokI and ApaI polymorphisms by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and measurement of serum 25(OH)VD levels by enzyme-linked immunosorbent assay (ELISA) were performed.

RESULTS

The frequencies of FokI polymorphism genotypes and alleles differed significantly between patients with asthma and controls. The frequencies of the TT genotype and T allele carriers were significantly higher among patients with asthma than among controls, and also among GC-resistant patients with asthma than among GC-sensitive patients with asthma. Additionally, serum 25(OH)VD levels differed significantly among the 3 VDR FokI polymorphic genotypes in GC-resistant patients with asthma; the highest level was detected in the TT genotype. No significant differences in ApaI were found.

CONCLUSION

We found a possible association between the FokI T allele and GC resistance in patients with asthma. Variations in VDR FokI might also play a role in 25(OH)VD levels.

Immunomodulatory Effects of Vitamin D in Pregnancy and Beyond

In addition to its role in calcium homeostasis and bone formation, a modulatory role of the active form of vitamin D on cells of the immune system, particularly T lymphocytes, has been described. The effects of vitamin D on the production and action of several cytokines has been intensively investigated in recent years. In this connection, deficiency of vitamin D has been associated with several autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), antiphospholipid syndrome (APS), Hashimoto Thyroiditis (HT), and multiple sclerosis (MS). In a successful pregnancy, the maternal immune response needs to adapt to accommodate the semiallogeneic fetus. Disturbances in maternal tolerance are implicated in infertility and pregnancy complications such as miscarriages (RM) and preeclampsia (PE). It is well-known that a subset of T lymphocytes, regulatory T cells (Tregs) exhibit potent suppressive activity, and have a crucial role in curtailing the destructive response of the immune system during pregnancy, and preventing autoimmune diseases. Interestingly, vitamin D deficiency is common in pregnant women, despite the widespread use of prenatal vitamins, and adverse pregnancy outcomes such as RM, PE, intrauterine growth restriction have been linked to hypovitaminosis D during pregnancy. Research has shown that autoimmune diseases have a significant prevalence within the female population, and women with autoimmune disorders are at higher risk for adverse pregnancy outcomes. Provocatively, dysregulation of T cells plays a crucial role in the pathogenesis of autoimmunity, and adverse pregnancy outcomes where these pathologies are also associated with vitamin D deficiency. This article reviews the immunomodulatory role of vitamin D in autoimmune diseases and pregnancy. In particular, we will describe the role of vitamin D from conception until delivery, including the health of the offspring. This review highlights an observational study where hypovitaminosis D was correlated with decreased fertility, increased disease activity, placental insufficiency, and preeclampsia in women with APS.

CD8+ Tc2 cells: underappreciated contributors to severe asthma

The complexity of asthma is underscored by the number of cell types and mediators implicated in the pathogenesis of this heterogeneous syndrome. Type 2 CD4⁺ T-cells (Th2) and more recently, type 2 innate lymphoid cells dominate current descriptions of asthma pathogenesis. However, another important source of these type 2 cytokines, especially interleukin (IL)-5 and IL-13, are CD8⁺ T-cells, which are increasingly proposed to play an important role in asthma pathogenesis, because they are abundant and are comparatively insensitive to corticosteroids. Many common triggers of asthma exacerbations are mediated via corticosteroid-resistant pathways involving neutrophils and CD8⁺ T-cells. Extensive murine data reveal the plasticity of CD8⁺ T-cells and their capacity to enhance airway inflammation and airway dysfunction. In humans, Tc2 cells are predominant in fatal asthma, while in stable state, severe eosinophilic asthma is associated with greater numbers of Tc2 than Th2 cells in blood, bronchoalveolar lavage fluid and bronchial biopsies. Tc2 cells strongly express CRTH2, the receptor for prostaglandin D2, the cysteinyl leukotriene receptor 1 and the leukotriene B4 receptor. When activated, these elicit Tc2 cell chemotaxis and production of chemokines and type 2 and other cytokines, resulting directly or indirectly in eosinophil recruitment and survival. These factors position CD8⁺ Tc2 cells as important and underappreciated effector cells contributing to asthma pathogenesis. Here, we review recent advances and new insights in understanding the pro-asthmatic functions of CD8⁺ T-cells in eosinophilic asthma, especially corticosteroid-resistant asthma, and the molecular mechanisms underlying their pathologic effector function.

Alongside Th2 and ILC2 cells, CD8⁺ T-cells are a cellular source of type 2 cytokines. We review recent findings and insights into the pathologic effector functions of type 2 CD8⁺ T-cells in eosinophilic asthma, especially steroid-resistant disease.http://bit.ly/2KbVGL2

Identification of multiple dysregulated metabolic pathways by GC-MS-based profiling of lung tissue in mice with PM2.5-induced asthma

The risk of development of asthma, a multi-faceted chronic disease, increases as a result of exposure to PM_2.5. However, the mechanism underlying asthma-related metabolic changes caused by PM_2.5 exposure is unclear. Here, we investigated the major metabolic changes, metabolic pathways involved, and underlying molecular mechanisms in mice with PM_2.5 exposure-induced asthma. Forty-eight adult female mice were randomly assigned to control (C), low concentration-PM_2.5 exposure: 0.50 mg kg^-1 (L), medium concentration-PM_2.5 exposure: 1.58 mg kg^-1 (M), and high concentration-PM_2.5 exposure: 4.98 mg kg^-1 (H) groups. M and H groups presented significantly higher IL-4, IL-8, IL-1β, IL-5, IL-13, and OVA-specific IgE levels, and significantly lower IFN-γ levels, than the C group, as well as significantly increased eosinophil count and MUC5AC expression in the lung tissue. These findings indicate that exposure to medium and high concentrations of PM_2.5 induced asthma in mice. Statistical analyses identified 13 asthma-related major metabolites, which were analyzed by gas chromatography-mass spectrometry (GC-MS). Meta Mapp Software revealed 4 major metabolic pathways. PM_2.5-induced ATP requirement and oxidative stress may perturb metabolic processes in asthma. The present findings increase our understanding of the toxic effect of PM_2.5 in the development of asthma and identify potentially useful biomarkers.

Vitamin D receptor interacts with NLRP3 to restrict the allergic response

Vitamin D receptor (VDR) mediates various biochemical activities between the cytoplasm and the nucleus in the cell. The nucleotide-binding, oligomerization domain (NOD)-like receptor family, pyrin domain containing 3 (NLRP3) protein is involved in the T helper type 2 (Th2) response. This study tests a hypothesis that VDR interacts with NLRP3 to restrict the Th2-biased response. In this study, VDR^-/- mice and WT (WT) mice were used. Th2 cell differentiation between VDR^-/- mice and WT mice was observed. We observed that CD4⁺ T cell activation was higher in VDR^-/- mice. The VDR^-/-CD4⁺ T cells were prone to Th2 polarization. VDR^-/- mice produced more immunoglobulin (Ig)E. VDR bound NLRP3 to prevent Th2 differentiation by restricting IL4 gene transcription. Th2 biased inflammation spontaneously developed in the intestine of VDR^-/- mice. In conclusion, VDR binds NLRP3 to restrict IL4 gene transcription and prevent biased Th2 polarization.

Synergistic activation of pro-inflammatory type-2 CD8+ T lymphocytes by lipid mediators in severe eosinophilic asthma

Human type-2 CD8⁺ T cells are a cell population with potentially important roles in allergic disease. We investigated this in the context of severe asthma with persistent airway eosinophilia-a phenotype associated with high exacerbation risk and responsiveness to type-2 cytokine-targeted therapies. In two independent cohorts we show that, in contrast to Th2 cells, type-2 cytokine-secreting CD8⁺CRTH2⁺ (Tc2) cells are enriched in blood and airways in severe eosinophilic asthma. Concentrations of prostaglandin D₂ (PGD₂) and cysteinyl leukotriene E₄ (LTE₄) are also increased in the airways of the same group of patients. In vitro PGD₂ and LTE₄ function synergistically to trigger Tc2 cell recruitment and activation in a TCR-independent manner. These lipids regulate diverse genes in Tc2 cells inducing type-2 cytokines and many other pro-inflammatory cytokines and chemokines, which could contribute to eosinophilia. These findings are consistent with an important innate-like role for human Tc2 cells in severe eosinophilic asthma and suggest a potential target for therapeutic intervention in this and other diseases.

Reduction of respiratory infections in asthma patients supplemented with vitamin D is related to increased serum IL-10 and IFNγ levels and cathelicidin expression

BACKGROUND

Vitamin D is a molecule that modulates the immune response and shows anti-inflammatory effects that are beneficial for the control of chronic diseases such as asthma. The trial aim was to explore the effect of vitamin D supplementation on the colonization of pathogenic bacteria in the upper respiratory tract of allergic asthmatic patients.

METHODS

This study was conducted in 86 patients between 18 and 50 years of age who were randomly divided into two groups. Both groups received the treatment recommended by the Global Initiative for Asthma (GINA). One group also received calcitriol (1,25-(OH)₂D₃), and the other group received a placebo. At baseline and 6 months, skin prick tests were conducted, pharyngeal bacterial cultures were performed, and cathelicidin LL-37 was measured in sputum. Serum levels of IgE, eosinophils, IL-5, IL-9, IL-10, IL-13, and IFNγ were quantified at the beginning and the end of the study.

RESULTS

Serum levels of IL-10 and IFNγ increased significantly in the group of patients with vitamin D supplementation, while IL-5, IL-9, and IL-13 decreased significantly. At the end of the trial, IgE and eosinophil levels significantly decreased but allergen sensitivity did not show any changes from baseline. Respiratory infections were drastically reduced, and this decrease was related to the number of patients who had high serum levels of IL-10 and IFNγ and expressed LL-37 in their sputum.

CONCLUSION

Treatment of asthma patients with vitamin D reduced respiratory infections, and this effect was related to the increase of cathelicidin LL-37.

The burgeoning role of cytochrome P450-mediated vitamin D metabolites against colorectal cancer

The metabolites of vitamin D₃ (VD3) mediated by different cytochrome P450 (CYP) enzymes, play fundamental roles in many physiological processes in relation to human health. These metabolites regulate a variety of cellular signal pathways through the direct binding of activated vitamin D receptor/retinoic X receptor (VDR/RXR) heterodimeric complex to specific DNA sequences. Thus, the polymorphisms of VDR and VD3 metabolizing enzymes lead to differentiated efficiency of VD3 and further affect serum VD3 levels. Moreover, VDR activation is demonstrated to inhibit the growth of various cancers, including colorectal cancer. However, excessive intake of vitamin D may lead to hypercalcemia, which limits the application of vitamin D tremendously. In this review, we have summarized the advances in VD3 research, especially the metabolism map of VD3 and the molecular mechanisms of inhibiting growth and inducing differentiation in colorectal cancer mediated by VDR-associated cellular signal pathways. The relationship between VDR polymorphism and the risk of colorectal cancer is also illustrated. In particular, novel pathways of the activation of VD3 started by CYP11A1 and CYP3A4 are highlighted, which produce several noncalcemic and antiproliferative metabolites. At last, the hypothesis is put forward that further research of CYP-mediated VD3 metabolites may develop therapeutic agents for colorectal cancer without resulting in hypercalcemia.

Asthma and Allergy "Epidemic" and the Role of Vitamin D Deficiency

The increase in asthma and allergies prevalence that has been recorded in many countries during the last decades, and the reemergence of vitamin D (VD) deficiency in many populations worldwide, renders fairly plausible the assumption of an underlying association between these two conditions and justifies the research effort invented in this issue. Indeed, there is growing body of evidence from epidemiological, laboratory, and clinical studies, suggesting that such an association does exist. The hypothesis of low levels of VD leading to compromised fetal programming and impairment of various immune functions involved in asthma and allergic disorders, stands as the most credible explanation of this presumed association. However, the evidence is not yet definite and there are some conflicting results among studies. As a consequence, no safe conclusions can be drawn yet, and more research is required in order to fully clarify the involvement of VD deficiency in the pathogenesis of asthma and allergies, and decide if VD has a role to play in the prevention and therapy of these disorders.

Vitamin D3 Supplementation Reduces Subsequent Brain Injury and Inflammation Associated with Ischemic Stroke

Acute inflammation can exacerbate brain injury after ischemic stroke. Beyond its well-characterized role in calcium metabolism, it is becoming increasingly appreciated that the active form of vitamin D, 1,25-dihydroxyvitamin D₃ (1,25-VitD₃), has potent immunomodulatory properties. Here, we aimed to determine whether 1,25-VitD₃ supplementation could reduce subsequent brain injury and associated inflammation after ischemic stroke. Male C57Bl6 mice were randomly assigned to be administered either 1,25-VitD₃ (100 ng/kg/day) or vehicle i.p. for 5 day prior to stroke. Stroke was induced via middle cerebral artery occlusion for 1 h followed by 23 h reperfusion. At 24 h post-stroke, we assessed infarct volume, functional deficit, expression of inflammatory mediators and numbers of infiltrating immune cells. Supplementation with 1,25-VitD₃ reduced infarct volume by 50% compared to vehicle. Expression of pro-inflammatory mediators IL-6, IL-1β, IL-23a, TGF-β and NADPH oxidase-2 was reduced in brains of mice that received 1,25-VitD₃ versus vehicle. Brain expression of the T regulatory cell marker, Foxp3, was higher in mice supplemented with 1,25-VitD₃ versus vehicle, while expression of the transcription factor, ROR-γ, was decreased, suggestive of a reduced Th17/γδ T cell response. Immunohistochemistry indicated that similar numbers of neutrophils and T cells were present in the ischemic hemispheres of 1,25-VitD₃- and vehicle-supplemented mice. At this early time point, there were also no differences in the impairment of motor function. These data indicate that prior administration of exogenous vitamin D, even to vitamin D-replete mice, can attenuate infarct development and exert acute anti-inflammatory actions in the ischemic and reperfused brain.

Vitamin A and D in allergy: from experimental animal models and cellular studies to human disease

Introduction

Vitamins A and D are able to modulate innate and adaptive immune responses and may therefore influence the development and the course of allergic diseases.

Materials and methods

This article reviews the current evidence for the experimental effects of vitamins A and D in vivo in animal models and on immune cells in vitro, and discusses their translational implication. A systematic literature search over the last 10 years was performed using MEDLINE and PubMed databases.

Results

Deficiencies of vitamin A or vitamin D in mouse models of allergic asthma seem to exacerbate allergic symptoms along with enhanced lung inflammation and Th2 cytokine production. In contrast, supplementation regimes especially with vitamin D were able to attenuate symptoms in therapeutic mouse models. The active metabolites retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (VD3) induced tolerogenic dendritic cells (DCs) and up-regulated T‑regulatory cells in the allergic sensitization phase, which likely contributes to tolerance induction. Additionally, RA and VD3 maintained the stability of eosinophils and mast cells in the effector phase, thereby reducing allergic mediator release. Thus, both active vitamin metabolites RA and VD3 are able to influence allergic immune responses at several immunological sites.

Conclusion

Animal studies predict that vitamin A and D may also be attractive players in the control of allergy in humans. Whether these experimental observations can be translated to the human situation remains open, as results from clinical trials are controversial.

Vitamin D3 levels and NLRP3 expression in murine models of obese asthma: association with asthma outcomes

Vitamin D (25(OH)D3) is an essential nutrient that plays a role in the immune system. Serum 25(OH)D3 is found to be associated with asthma. However, the role of vitamin D in obese asthma remains unclear. Therefore, we investigated the association between vitamin D levels and asthma outcomes in a murine model of obese asthma. We also evaluated NLRP3 inflammasome activity in the pathogenesis of obese asthma. We divided 20 male Balb/c mice (3–4 weeks old) into 4 groups: normal control, asthma, obese, and obese asthma and developed an obese asthma mouse model. Airway hyperreactivity, cytokine concentrations, 25(OH)D3 levels, NLRP3 mRNA and IL-1β mRNA expressions were measured. Lung histology and bronchoalveolar lavage fluid (BALF) cell count were also determined. Obese asthma mice showed a significant increase in airway hyper-responsiveness, airway inflammation, pro-inflammatory cytokine levels and NLRP3 mRNA, IL-1β mRNA expression. Both asthma and obese groups had lower 25(OH)D3 levels. Vitamin D levels in obese asthma were the lowest among all groups. Vitamin D levels correlated negatively with body weight, lung resistance levels at 25 mg/mL of methacholine, total inflammatory cells, and IL-1β and IL-17 concentrations in BALF. These data demonstrated an association between serum vitamin D levels and outcomes of obese asthma, and indicated that NLRP3 inflammasome may play a role in this disorder.

Beneficial effects of bile acid receptor agonists in pulmonary disease models

INTRODUCTION

Bile acids act as steroid hormones, controlling lipid, glucose and energy metabolism, as well as inflammation and fibrosis. Their actions are implemented through activation of nuclear (FXR, VDR, PXR) and membrane G protein-coupled (TGR5, S1PR2) receptors. Areas covered: This review discusses the potential of FXR and TGR5 as therapeutic targets in the treatment of pulmonary disorders linked to metabolism and/or inflammation. Obeticholic acid (OCA) is the most clinically advanced bile acid-derived agonist for FXR-mediated anti-inflammatory and anti-fibrotic effects. It therefore represents an attractive pharmacological approach for the treatment of lung conditions characterized by vascular and endothelial dysfunctions. Expert opinion: Inflammation, vascular remodeling and fibrotic processes characterize the progression of pulmonary arterial hypertension (PAH) and idiopathic pulmonary fibrosis (IPF). These processes are only partially targeted by the available therapeutic options and still represent a relevant medical need. The results hereby summarized demonstrate OCA efficacy in preventing experimental lung disorders, i.e. monocrotaline-induced PAH and bleomycin-induced fibrosis, by abating proinflammatory and vascular remodeling progression. TGR5 is also expressed in the lung, and targeting the TGR5 pathway, using the TGR5 agonist INT-777 or the dual FXR/TGR5 agonist INT-767, could also contribute to the treatment of pulmonary disorders mediated by inflammation and fibrosis.

Dysregulation of metabolic pathways in a mouse model of allergic asthma

BACKGROUND

Asthma is a complex lung disease resulting from the interplay of genetic and environmental factors. To understand the molecular changes that occur during the development of allergic asthma without genetic and environmental confounders, an experimental model of allergic asthma in mice was used. Our goals were to (1) identify changes at the small molecule level due to allergen exposure, (2) determine perturbed pathways due to disease, and (3) determine whether small molecule changes correlate with lung function.

METHODS

In this experimental model of allergic asthma, matched bronchoalveolar lavage (BAL) fluid and plasma were collected from three groups of C57BL6 mice (control vs sensitized and/or challenged with ovalbumin, n=3-5/group) 6 hour, 24 hour, and 48 hour after the last challenge. Samples were analyzed using liquid chromatography-mass spectrometry-based metabolomics. Airway hyper-responsiveness (AHR) measurements and differential cell counts were performed.

RESULTS

In total, 398 and 368 dysregulated metabolites in the BAL fluid and plasma of sensitized and challenged mice were identified, respectively. These belonged to four, interconnected pathways relevant to asthma pathogenesis: sphingolipid metabolism (P=6.6×10^-5 ), arginine and proline metabolism (P=1.12×10^-7 ), glycerophospholipid metabolism (P=1.3×10^-10 ), and the neurotrophin signaling pathway (P=7.0×10^-6 ). Furthermore, within the arginine and proline metabolism pathway, a positive correlation between urea-1-carboxylate and AHR was observed in plasma metabolites, while ornithine revealed a reciprocal effect. In addition, agmatine positively correlated with lung eosinophilia.

CONCLUSION

These findings point to potential targets and pathways that may be central to asthma pathogenesis and can serve as novel therapeutic targets.

Spectrum of T-lymphocyte activities regulating allergic lung inflammation

Despite advances in the treatment of asthma, optimization of symptom control remains an unmet need in many patients. These patients, labeled severe asthma, are responsible for a substantial fraction of the disease burden. In these patients, research is needed to define the cellular and molecular pathways contributing to disease which in large part are refractory to corticosteroid treatment. The causes of steroid-resistant asthma are multifactorial and result from complex interactions of genetics, environmental factors, and innate and adaptive immunity. Adaptive immunity, addressed here, integrates the activities of distinct T-cell subsets and by definition is dynamic and responsive to an ever-changing environment and the influences of epigenetic modifications. These T-cell subsets exhibit different susceptibilities to the actions of corticosteroids and, in some, corticosteroids enhance their functional activation. Moreover, these subsets are not fixed in lineage differentiation but can undergo transcriptional reprogramming in a bidirectional manner between protective and pathogenic effector states. Together, these factors contribute to asthma heterogeneity between patients but also in the same patient at different stages of their disease. Only by carefully defining mechanistic pathways, delineating their sensitivity to corticosteroids, and determining the balance between regulatory and effector pathways will precision medicine become a reality with selective and effective application of targeted therapies.

Increased IL-4- and IL-17-producing CD8+ cells are related to decreased CD39+CD4+Foxp3+ cells in allergic asthma

OBJECTIVE

In allergic asthma, regulatory T cell (Treg) number and function are decreased. Antigen-primed CD8⁺ T cells play an indispensable role in the full development of airway inflammation and airway hyper-responsiveness (AHR) occurring in asthma. In this study, we investigated the relationship between subpopulations of CD8⁺ T cells and CD39⁺ Tregs.

METHODS

Female C57BL/6 mice were used to develop the model of allergic asthma. Experimental mice were immunized with ovalbumin (OVA) by intra-peritoneal (i.p) injection and then challenged with OVA by intra-tracheal administration. Control mice were immunized with vehicle by i.p injection and challenged with OVA. Airway inflammation was determined by histology and AHR was measured by an invasive method. Levels of interferon (IFN)-γ, IL-4, and IL-17 in bronchoalveolar lavage fluid (BALF) were determined by enzyme-linked immunosorbent assay. The frequencies of CD8⁺IFN-γ⁺ cells (Tc1), CD8⁺IL-4⁺ cells (Tc2), CD8⁺IL-17⁺cells (Tc17), and CD39⁺Tregs were measured by flow cytometry. The correlation between CD39⁺Tregs and Tc subsets was analyzed by Pearson's test.

RESULTS

Experimental mice displayed phenotypes of allergic asthma, including inflammatory cell infiltration into the lungs, goblet cell hyperplasia, increased airway resistance, and increased IL-4 and IL-17 in BALF. Compared to control mice, experimental mice displayed lower CD39⁺Tregs and Tc1 but higher Tc2 and Tc17. There was a negative correlation between CD39⁺Tregs and Tc2 or Tc17.

CONCLUSION

In allergic asthma, increased Tc2 and Tc17 are possibly related to insufficient CD39⁺Tregs.

Role of Vitamin D in the Hygiene Hypothesis: The Interplay between Vitamin D, Vitamin D Receptors, Gut Microbiota, and Immune Response

The hygiene hypothesis postulates that higher levels of cleanliness and improper exposure to microorganisms early in childhood could disturb the intestinal microbiome resulting in abnormal immune responses. Recently, more attention has been put on how a lack of sun exposure and consequently vitamin D deficiency could lead to less immune tolerance and aberrant immune responses. Moreover, vitamin D receptor (VDR) function has been positioned to be a critical aspect of immune response and gut homeostasis. Therefore, this review focuses on the role that the interaction between vitamin D, VDR function, and gut microbiome might have on autoimmune diseases in the context of the hygiene hypothesis. Literature shows that there is a high correlation between vitamin D deficiency, VDR dysfunction, gut microbiota composition, and autoimmune diseases. The biologically active form of vitamin D, 1,25(OH)₂D₃, serves as the primary ligand for VDRs, which have been shown to play a fundamental role in reducing autoimmune disease symptoms. Although the biological functions of VDR, the effects of its genetic variants, and the effects of epigenetic profiles in its promoter region are largely unknown in humans, studies in murine models are increasingly demonstrating that VDRs play a crucial role in attenuating autoimmune disease symptoms by regulating autophagy and the production of antimicrobial peptides, such cathelicidin and β-defensin, which are responsible for modifying the intestinal microbiota to a healthier composition. Remarkably, evidence shows that hormonal compounds and byproducts of the microbiota such as secondary bile acids might also activate VDR. Therefore, understanding the interaction between VDR and gut microbiota is of the utmost importance toward understanding the rise in autoimmune diseases in Western countries. We have gained insights on how the VDR functions affects inflammation, autophagy, and microbiota composition that could lead to the development of pathogenesis of autoimmune diseases, while confirming the role vitamin D and VDRs have in the context of hygiene hypothesis.

Vitamin D improves immune function in immunosuppressant mice induced by glucocorticoid

Vitamin D is an essential fat-soluble vitamin with multiple functions. Vitamin D receptor has been shown to be expressed in several types of immune cells suggesting vitamin D may have immune regulatory roles. Vitamin D insufficiency has been suggested to increase the risk of autoimmune diseases. However, little is known regarding its immunomodulatory effects in the condition of immune suppression. The aim of the present study was to investigate the regulatory effects of vitamin D on immune function in immunosuppressant mice. An immunosuppressant mouse model was induced by intraperitoneal injection with glucocorticiod for 3 days. Immunosuppressant mice were intragastrically administered with 1,25-dihydroxy-vitamin D3 [1,25(OH)₂D₃; 0,4, 6 or 10 IU/g body weight] for 7 days. On day 8, the mice were decapitated. The body weight and the weights of thymus and spleen were measured. Thymus and spleen indexes were calculated. The ratio of CD4⁺/CD8⁺ T lymphocytes in the peripheral blood, proliferation and interleukin-2 (IL-2) production of spleen T lymphocytes was detected. Compared with the mice in the control group, the body weight, thymus and spleen indexes, the ratios of CD4⁺/CD8⁺ in peripheral blood and IL-2 production and proliferation of spleen T lymphocytes were decreased in immunosuppressant mice induced by glucocorticiod. However, in vitamin D-treated mice, the thymus indexes, the ratios of CD4⁺/CD8⁺, secretion of IL-2 and the proliferation index of spleen T lymphocytes were significantly increased (P<0.05). Among the three doses of 1,25(OH)₂D₃, 6 IU/g was most effective in improving the immune function. These results indicate that vitamin D supplementation can improve immune recovery in immunosuppressant mice by stimulating T-cell proliferation and elevating IL-2 production.

Vitamin D modulation of innate immune responses to respiratory viral infections

Vitamin D, in addition to its classical functions in bone homeostasis, has a modulatory and regulatory role in multiple processes, including host defense, inflammation, immunity, and epithelial repair. Patients with respiratory disease are frequently deficient in vitamin D, implying that supplementation might provide significant benefit to these patients. Respiratory viral infections are common and are the main trigger of acute exacerbations and hospitalization in children and adults with asthma and other airways diseases. Respiratory monocytes/macrophages and epithelial cells constitutively express the vitamin D receptor. Vitamin D, acting through this receptor, may be important in protection against respiratory infections. Whether the in vitro findings can be translated into a substantial in vivo benefit still remains uncertain. Here we review the in vitro data on the role of vitamin D in antiviral innate immunity, the data concerning the deficient levels of vitamin D in lung diseases, and the in vivo role of supplementation as protection against respiratory viral infections in healthy individuals and in patients with chronic respiratory diseases. Finally, we suggest ways of improving the effectiveness of vitamin D as an adjuvant in the prevention and treatment of acute respiratory infections.

Vitamin D3 intake modulates diaphragm but not peripheral muscle force in young mice

Recent data support an important role for vitamin D in respiratory health. We tested the hypothesis that dietary vitamin D3 (VD3) intake modulates diaphragm (DIA) strength. Four-week-old female A/J mice (n = 10/group) were randomized to receive diets containing 100 IU VD3/kg (low), 1,000 IU VD3/kg (reference), or 10,000 IU VD3/kg (pharmacologic). After 6 wk of dietary intervention, plasma 25-hydroxyvitamin D3 (25D3) levels, DIA and extensor digitorum longus (EDL) in vitro contractile properties, and fiber cross-sectional area (CSA) were measured. Myosin heavy chain (MHC) composition and Akt/Foxo3A growth signaling were studied in the DIA and tibialis anterior. Mice fed the low, reference, and pharmacologic diets had average 25D3 levels of 7, 21, and 59 ng/ml, respectively. Maximal DIA force, twitch force, and fiber CSA were reduced 26%, 28%, and 10% (P < 0.01), respectively, in mice receiving the low-VD3 diet compared with the reference and pharmacologic diets. EDL force parameters were unaltered by diet. Effects of VD3 intake on DIA force were not observed in mice that began dietary intervention at 12 wk of age. VD3 intake did not alter the MHC composition of the DIA, indicating that decreases in force and CSA in young mice were not due to a switch in fiber type. Paradoxically, low VD3 intake was associated with activation of anabolic signaling in muscle (hyperphosphorylation of Akt and Foxo3A and decreased expression of autophagy marker LC3). These studies identify a potential role of dietary VD3 in regulating DIA development and insulin sensitivity.