Alice M. Wood

The vitamin D axis in the lung: a key role for vitamin D-binding protein.

There has been much recent interest in the role of the vitamin D axis in lung disease, which includes vitamin D, vitamin D receptor (VDR) and vitamin D-binding protein (VDBP; also known as Gc-globulin). VDBP is a serum protein which has immunomodulatory functions relevant in the lung, predominantly relating to macrophage activation and neutrophil chemotaxis. Variations within its gene are also associated with airways disease, implying a role for the protein product in pathogenesis. Thus far the majority of evidence relates to chronic obstructive pulmonary disease (COPD), but is scant in other airways diseases, such as asthma and bronchiectasis. VDBP also acts as a scavenger protein to clear extracellular G-actin released from necrotic cells, which may be of relevance in severe lung infections and acute lung injury. Vitamin D protects against the development of cancer and tuberculosis, although optimal levels are unknown. The majority of circulating vitamin D is bound to VDBP, and its uptake into cells occurs in both bound and unbound forms, which suggests the role of VDBP warrants further study in these conditions as well. This article reviews the evidence of the role VDBP and its gene (GC) in a range of lung diseases, including asthma, COPD and tuberculosis.

Availability of 25-Hydroxyvitamin D3 to APCs Controls the Balance between Regulatory and Inflammatory T Cell Responses

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the active form of vitamin D, exerts potent effects on several tissues including cells of the immune system, where it affects T cell activation, differentiation and migration. The circulating, inactive form of vitamin D, 25(OH)D3, is generally used as an indication of vitamin D status. However, use of this precursor depends on its uptake by cells and subsequent conversion by the enzyme 25(OH)D3-1α-hydroxylase (CYP27B1) into active 1,25(OH)2D3. Using human T cells, we show in this study that addition of inactive 25(OH)D3 is sufficient to alter T cell responses only when dendritic cells (DCs) are present. Mechanistically, CYP27B1 is induced in DCs upon maturation with LPS or upon T cell contact, resulting in the generation and release of 1,25(OH)2D3, which subsequently affects T cell responses. In most tissues, vitamin D binding protein acts as a carrier to enhance the use of vitamin D. However, we show that vitamin D binding protein modulates T cell responses by restricting the availability of inactive 25(OH)D3 to DC. These data indicate that the level of free 25(OH)D3 available to DCs determines the inflammatory/regulatory balance of ensuing T cell responses.

Vitamin D-binding protein contributes to COPD by activation of alveolar macrophages

Background Vitamin D-binding protein (DBP) genetic polymorphisms have been associated with chronic obstructive pulmonary disease (COPD). DBP has an indirect role in macrophage activation; thus it was hypothesised that DBP is present in the airway and contributes to lung disease by this mechanism. Methods 471 PiZZ subjects with α1-antitrypsin deficiency (AATD) were genotyped for tag single nucleotide polymorphisms (SNPs) covering the DBP gene (GC), together with known functional variants, prior to seeking association with COPD phenotypes. 140 subjects with usual COPD and 480 controls were available for replication. Vitamin D and DBP levels were measured by tandem mass spectrometry and ELISA, respectively, in serum and DBP in the sol phase of sputum in a subset of 60 patients. Concentrations were related to phenotype and to alveolar macrophage activation. Results rs2070741 was associated with airway bacterial colonisation (p=0.04) and bronchiectasis (p=0.01), as was rs7041 (p=0.03) which also influenced vitamin D concentrations (p=0.01). The GC2 variant predisposed to bronchiectasis in AATD (p=0.04) and protected against COPD (p=0.05); the latter association was replicated in usual COPD versus controls (p=0.04). Circulating DBP related inversely to forced expiratory volume in 1 s (FEV1) (p=0.02), in direct contrast to vitamin D, where deficiency related to low FEV1 (p=0.04). Sol DBP related directly to alveolar macrophage activation (p=0.004). Conclusions The genetic association of DBP with COPD may be mediated by effects on macrophage activation, since DBP relates to FEV1, and affects macrophage activation. Vitamin D effects may be independent of this, relating more strongly to innate immunity.

Alpha One Antitrypsin Deficiency: From Gene to Treatment

α1-antitrypsin deficiency is a genetic disorder which contributes to the development of chronic obstructive pulmonary disease, bronchiectasis, liver cirrhosis and panniculitis. The discovery of α1-antitrypsin and its function as an antiprotease led to the protease-antiprotease hypothesis, which goes some way to explaining the pathogenesis of emphysema. This article will review the clinical features of α1-antitrypsin deficiency, the genetic mutations known to cause it, and how they do so at a molecular level. Specific treatments for the disorder based on this knowledge will be reviewed, including α1-antitrypsin replacement, gene therapy and possible future therapies, such as those based on stem cells.

Availability of 25-Hydroxyvitamin D 3 to APCs Controls the Balance between Regulatory and Inflammatory T Cell Responses

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the active form of vitamin D, exerts potent effects on several tissues including cells of the immune system, where it affects T cell activation, differentiation and migration. The circulating, inactive form of vitamin D, 25(OH)D3, is generally used as an indication of vitamin D status. However, use of this precursor depends on its uptake by cells and subsequent conversion by the enzyme 25(OH)D3-1α-hydroxylase (CYP27B1) into active 1,25(OH)2D3. Using human T cells, we show in this study that addition of inactive 25(OH)D3 is sufficient to alter T cell responses only when dendritic cells (DCs) are present. Mechanistically, CYP27B1 is induced in DCs upon maturation with LPS or upon T cell contact, resulting in the generation and release of 1,25(OH)2D3, which subsequently affects T cell responses. In most tissues, vitamin D binding protein acts as a carrier to enhance the use of vitamin D. However, we show that vitamin D binding protein modulates T cell responses by restricting the availability of inactive 25(OH)D3 to DC. These data indicate that the level of free 25(OH)D3 available to DCs determines the inflammatory/regulatory balance of ensuing T cell responses.

Rate of progression of lung function impairment in α1-antitrypsin deficiency

The aim of the present study was to identify α1-antitrypsin (α1-AT)-deficient patients who had rapidly progressive disease. PiZ patients (n = 101) underwent annual lung function measurements over a 3-yr period, and the results were related to factors that may influence decline. The mean annual decline in forced expiratory volume in 1 s (FEV1) was 49.9 mL. The greatest FEV1 decline occurred in the moderate severity group (FEV1 50–80% of the predicted value), with a mean annual decline of 90.1 mL, compared with 8.1 mL in the very severe group (FEV1 <30% pred). However, annual decline in transfer coefficient of the lung for carbon monoxide (KCO) was greatest in the severe and very severe groups. When the whole group was divided into tertiles of FEV1 decline, the fast tertile compared with the slow tertile had more patients with bronchodilator reversibility (BDR) (73 versus 41%; p = 0.010), more males (79 versus 56%; p = 0.048) and lower body mass index (BMI) (24.0 versus 26.1; p = 0.042). Logistic regression analyses confirmed that FEV1 decline was independently associated with BMI, BDR, exacerbation rate and high physical component 36-item short-form health survey scores. In PiZ α1-AT-deficient patients, FEV1 decline was greatest in moderate disease, unlike KCO decline, which was greatest in severe disease. The FEV1 decline showed associations with BDR, BMI, sex and exacerbation rate.

The genetics of chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease caused by the interaction of genetic susceptibility and environmental influences. There is increasing evidence that genes link to disease pathogenesis and heterogeneity by causing variation in protease anti-protease systems, defence against oxidative stress and inflammation. The main methods of genomic research for complex disease traits are described, together with the genes implicated in COPD thus far, their roles in disease causation and the future for this area of investigation.

Tumor Necrosis Factor–α rs361525 Polymorphism Is Associated with Increased Local Production and Downstream Inflammation in Chronic Obstructive Pulmonary Disease

RATIONALE Chronic obstructive pulmonary disease (COPD) has a genetic component, explaining susceptibility. Tumor necrosis factor (TNF)-alpha polymorphisms have been associated with COPD, but it is unclear if genotype influences clinical phenotype, protein expression, and bioactivity. OBJECTIVES To determine if a functional polymorphism was important by assessing TNF-alpha expression and activity and its association with clinical severity over time. METHODS Patients with COPD with rs361525 polymorphism were matched to patients with COPD without rs361525 polymorphism. TNF-alpha, its antagonists, and downstream mediators were measured in plasma and sputum. To determine TNF-alpha bioactivity, IL-8 secretion from primary bronchial epithelial cells (PBECs) was measured, and neutrophil migration was assessed using sputum from both subject groups in the presence and absence of TNF-alpha antibody. Subjects were followed annually and compared. MEASUREMENTS AND MAIN RESULTS Patients with polymorphism had more chronic bronchitis, a lower body mass index, and a greater annual decline in FEV(1) than patients with COPD without rs361525 polymorphism. TNF-alpha concentrations were 100-fold higher in airway secretions from the patients with the rs361525 polymorphism, with no difference in TNF-alpha antagonists. Their lung secretions contained more IL-8 and myeloperoxidase, consistent with downstream inflammation. Sputum from patients with rs361525 polymorphism induced greater secretion of IL-8 from PBECs and increased neutrophil migration. These effects could be abrogated by TNF-alpha antibody, demonstrating the bioactivity of TNF-alpha in lung secretions from this group. CONCLUSIONS This TNF-alpha polymorphism is associated with clinical features of disease including progression. There is clear evidence of TNF-alpha overexpression and bioactivity with neutrophilic inflammation. The polymorphism is likely to be a factor that influences a COPD disease phenotype and its progression.

The TNFalpha gene relates to clinical phenotype in alpha-1-antitrypsin deficiency.

BackgroundGenetic variation may underlie phenotypic variation in chronic obstructive pulmonary disease (COPD) in subjects with and without alpha 1 antitrypsin deficiency (AATD). Genotype specific sub-phenotypes are likely and may underlie the poor replication of previous genetic studies. This study investigated subjects with AATD to determine the relationship between specific phenotypes and TNFα polymorphisms.Methods424 unrelated subjects of the PiZZ genotype were assessed for history of chronic bronchitis, impairment of lung function and radiological presence of emphysema and bronchiectasis. A subset of subjects with 3 years consecutive lung function data was assessed for decline of lung function. Four single nucleotide polymorphisms (SNPs) tagging TNFα were genotyped using TaqMan® genotyping technologies and compared between subjects affected by each phenotype and those unaffected. Plasma TNFα levels were measured in all PiZZ subjects.ResultsAll SNPs were in Hardy-Weinberg equilibrium. A significant difference in rs361525 genotype (p = 0.01) and allele (p = 0.01) frequency was seen between subjects with and without chronic bronchitis, independent of the presence of other phenotypes. TNFα plasma level showed no phenotypic or genotypic associations.ConclusionVariation in TNFα is associated with chronic bronchitis in AATD.

Association of IREB2 and CHRNA3 polymorphisms with airflow obstruction in severe alpha-1 antitrypsin deficiency

BackgroundThe development of COPD in subjects with alpha-1 antitrypsin (AAT) deficiency is likely to be influenced by modifier genes. Genome-wide association studies and integrative genomics approaches in COPD have demonstrated significant associations with SNPs in the chromosome 15q region that includes CHRNA3 (cholinergic nicotine receptor alpha3) and IREB2 (iron regulatory binding protein 2).We investigated whether SNPs in the chromosome 15q region would be modifiers for lung function and COPD in AAT deficiency.MethodsThe current analysis included 378 PIZZ subjects in the AAT Genetic Modifiers Study and a replication cohort of 458 subjects from the UK AAT Deficiency National Registry. Nine SNPs in LOC123688, CHRNA3 and IREB2 were selected for genotyping. FEV1 percent of predicted and FEV1/FVC ratio were analyzed as quantitative phenotypes. Family-based association analysis was performed in the AAT Genetic Modifiers Study. In the replication set, general linear models were used for quantitative phenotypes and logistic regression models were used for the presence/absence of emphysema or COPD.ResultsThree SNPs (rs2568494 in IREB2, rs8034191 in LOC123688, and rs1051730 in CHRNA3) were associated with pre-bronchodilator FEV1 percent of predicted in the AAT Genetic Modifiers Study. Two SNPs (rs2568494 and rs1051730) were associated with the post-bronchodilator FEV1 percent of predicted and pre-bronchodilator FEV1/FVC ratio; SNP-by-gender interactions were observed. In the UK National Registry dataset, rs2568494 was significantly associated with emphysema in the male subgroup; significant SNP-by-smoking interactions were observed.ConclusionsIREB2 and CHRNA3 are potential genetic modifiers of COPD phenotypes in individuals with severe AAT deficiency and may be sex-specific in their impact.