Increased Autophagy-Related 5 Gene Expression Is Associated with Collagen Expression in the Airways of Refractory Asthmatics.

BACKGROUND: Fibrosis, particularly excessive collagen deposition, presents a challenge for treating asthmatic individuals. At present, no drugs can remove or reduce excessive collagen in asthmatic airways. Hence, the identification of pathways involved in collagen deposition would help to generate therapeutic targets to interfere with the airway remodeling process. Autophagy, a cellular degradation process, has been shown to be dysregulated in various fibrotic diseases, and genetic association studies in independent human populations have identified autophagy-related 5 (ATG5) to be associated with asthma pathogenesis. Hence, the dysregulation of autophagy may contribute to fibrosis in asthmatic airways. OBJECTIVE: This study aimed to determine if (1) collagen deposition in asthmatic airways is associated with ATG5 expression and (2) ATG5 protein expression is associated with asthma per se and severity. METHODS: Gene expression of transforming growth factor beta 1, various asthma-related collagen types [collagen, type I, alpha 1; collagen, type II, alpha 1; collagen, type III, alpha 1; collagen, type V, alpha 1 (COL5A1) and collagen, type V, alpha 2], and ATG5 were measured using mRNA isolated from bronchial biopsies of refractory asthmatic subjects and assessed for pairwise associations. Protein expression of ATG5 in the airways was measured and associations were assessed for asthma per se, severity, and lung function. MAIN RESULTS: In refractory asthmatic individuals, gene expression of ATG5 was positively associated with COL5A1 in the airways. No association was detected between ATG5 protein expression and asthma per se, severity, and lung function. CONCLUSION AND CLINICAL RELEVANCE: Positive correlation between the gene expression patterns of ATG5 and COL5A1 suggests that dysregulated autophagy may contribute to subepithelial fibrosis in the airways of refractory asthmatic individuals. This finding highlights the therapeutic potential of ATG5 in ameliorating airway remodeling in the difficult-to-treat refractory asthmatic individuals.

Severe Asthma: Have We Made Progress?

Tremendous efforts have been invested in research to (1) discover risk factors, biomarkers, and clinical characteristics; (2) understand the pathophysiology and treatment response variability in severe asthma; and (3) design new therapies. However, to combat severe asthma, many questions concerning the pathogenesis of severe asthma, including its natural history, genetic and environmental risk factors, and disease mechanisms, must be answered. In this article we highlight some of the major discoveries concerning the pathogenesis of severe asthma and its therapeutic development. We conclude that discoveries on numerous fronts of severe asthma, from disease heterogeneity, features of airway remodeling, cytokine mediators and signaling pathways underlying disease pathogenesis, disease mechanisms, potential biomarkers, to new therapeutic targets, demonstrate that progress has been made in understanding and developing more effective treatments for this difficult-to-treat disease.

Variants of asthma and chronic obstructive pulmonary disease genes and lung function decline in aging.

BACKGROUND: A substantial proportion of the general population has low lung function, and lung function is known to decrease as we age. Low lung function is a feature of several pulmonary disorders, such as uncontrolled asthma and chronic obstructive pulmonary disease. The objective of this study is to investigate the association of polymorphisms in asthma and chronic obstructive pulmonary disease candidate genes with rates of lung function decline in a general population sample of aging men. METHODS: We analyzed data from a cohort of 1,047 Caucasian men without known lung disease, who had a mean of 25 years of lung function data, and on whom DNA was available. The cohort was randomly divided into two groups, and we tested a total of 940 single-nucleotide polymorphisms in 44 asthma and chronic obstructive pulmonary disease candidate genes in the first group (testing cohort, n = 545) for association with change in forced expiratory volume in 1 second over time. RESULTS: One hundred nineteen single-nucleotide polymorphisms that showed nominal associations in the testing cohort were then genotyped and tested in the second group (replication cohort, n = 502). Evidence for association from the testing and replication cohorts were combined, and after adjustment for multiple testing, seven variants of three genes (DPP10, NPSR1, and ADAM33) remained significantly associated with change in forced expiratory volume in 1 second over time. CONCLUSIONS: Our findings that genetic variants of genes involved in asthma and chronic obstructive pulmonary disease are associated with lung function decline in normal aging participants suggest that similar genetic mechanisms may underlie lung function decline in both disease and normal aging processes.

Vitamin D deficiency and severe asthma.

Vitamin D has received tremendous amount of attention recently due to the ever-increasing reports of association between vitamin D deficiency and a wide range of conditions, from cancer to fertility to longevity. The fascination of disease association with vitamin D deficiency comes from the relatively easy solution to overcome such a risk factor, that is, either by increase in sun exposure and/or diet supplementation. Many reviews have been written on a protective role of vitamin D in asthma and related morbidities; here, we will summarize the epidemiological evidence supporting a role of vitamin D against hallmark features of severe asthma, such as airway remodeling and asthma exacerbations. Furthermore, we discuss data from in vitro and in vivo studies which provide insights on the potential mechanisms of how vitamin D may protect against severe asthma pathogenesis and how vitamin D deficiency may lead to the development of severe asthma. Approximately 5-15% of asthmatic individuals suffer from the more severe forms of disease in spite of aggressive therapies and they are more likely to have irreversible airflow obstruction associated with airway remodeling. At present drugs commonly used to control asthma symptoms, such as corticosteroids, do not significantly reverse or reduce remodeling in the airways. Hence, if vitamin D plays a protective role against the development of severe asthma, then the most effective therapy may simply be a healthy dose of sunshine.

Asthma phenotypes and endotypes.

PURPOSE OF REVIEW: It is increasingly clear that asthma is not a single disease, but a disorder with vast heterogeneity in pathogenesis, severity, and treatment response. In this review, we discuss the present understanding of different asthma phenotypes and endotypes, and the prospects of personalized medicine for asthma. RECENT FINDINGS: The recognition of diverse biological backgrounds in which asthma, and particularly severe asthma, can manifest has prompted the search for refined phenotypes and endotypes in asthma. Such appreciation of the heterogeneity in asthma is also prompting clinical trials to focus on specific subgroups of asthma, as demonstrated by the clinical trial of lebrikizumab. SUMMARY: Patients with severe asthma have asthma symptoms that are difficult to control, require high dosages of medication, and continue to experience persistent symptoms, asthma exacerbations or airflow obstruction even with aggressive therapy. Although asthma is traditionally viewed as an eosinophilic inflammatory disorder associated with a T-helper cell type 2 (Th2) immune response, recent studies have identified involvement of other effector cells, nonclassical Th2 cytokines and non-Th2 cytokines in severe asthma pathogenesis. Results of several clinical trials of anticytokine antibodies demonstrated the effectiveness of tailoring asthma treatment on the basis of an individual's biology.

ATG5, autophagy and lung function in asthma.

Reactive oxidative species (ROS) are essential in cellular survival; however, excessive production and chronic exposure to ROS pose serious health threats. Excessive production of ROS is thought to play a pivotal role in the pathogenesis of asthma, where exhaled levels of ROS have been found to positively correlate with disease severity. Autophagy is induced by ROS to remove oxidized proteins or organelles to minimize tissue damage, and presents itself as a good candidate pathway for investigation in asthma pathogenesis. Given the role of oxidative stress in the pathogenesis of asthma and disease severity, we hypothesized that autophagy is associated with asthma pathogenesis, and sought to detect its presence using both genetic and histological approaches. We found variant rs12212740, an intronic SNP of ATG5, to be associated with asthma and forced expiratory volume in 1 second (FEV(1)) percent predicted in the French Canadian population and with FEV(1) in an American Caucasian cohort. Furthermore, double-membrane autophagosomes were more easily detected in fibroblast and epithelial cells from a bronchial biopsy tissue of a moderately severe asthma patient compared with corresponding cells of a healthy subject. Asthma is associated with a cytokine milieu [e.g., interleukin (IL)-13] that promotes transforming growth factor-ß1 (TGFß1) affiliated airway remodeling, and agonistic relationships existed among these cytokines and ROS. Hence, autophagy may be a cellular mechanism that promotes TGFß1 airway remodeling and loss of lung function in asthma.

Association of variants in innate immune genes with asthma and eczema.

BACKGROUND: The innate immune pathway is important in the pathogenesis of asthma and eczema. However, only a few variants in these genes have been associated with either disease. We investigate the association between polymorphisms of genes in the innate immune pathway with childhood asthma and eczema. In addition, we compare individual associations with those discovered using a multivariate approach. METHODS: Using a novel method, case control based association testing (C2BAT), 569 single nucleotide polymorphisms (SNPs) in 44 innate immune genes were tested for association with asthma and eczema in children from the Boston Home Allergens and Asthma Study and the Connecticut Childhood Asthma Study. The screening algorithm was used to identify the top SNPs associated with asthma and eczema. We next investigated the interaction of innate immune variants with asthma and eczema risk using Bayesian networks. RESULTS: After correction for multiple comparisons, 7 SNPs in 6 genes (CARD25, TGFB1, LY96, ACAA1, DEFB1, and IFNG) were associated with asthma (adjusted p-value<0.02), while 5 SNPs in 3 different genes (CD80, STAT4, and IRAKI) were significantly associated with eczema (adjusted p-value < 0.02). None of these SNPs were associated with both asthma and eczema. Bayesian network analysis identified 4 SNPs that were predictive of asthma and 10 SNPs that predicted eczema. Of the genes identified using Bayesian networks, only CD80 was associated with eczema in the single-SNP study. Using novel methodology that allows for screening and replication in the same population, we have identified associations of innate immune genes with asthma and eczema. Bayesian network analysis suggests that additional SNPs influence disease susceptibility via SNP interactions. CONCLUSION: Our findings suggest that innate immune genes contribute to the pathogenesis of asthma and eczema, and that these diseases likely have different genetic determinants.

Effects of endotoxin exposure on childhood asthma risk are modified by a genetic polymorphism in ACAA1.

BACKGROUND: Polymorphisms in the endotoxin-mediated TLR4 pathway genes have been associated with asthma and atopy. We aimed to examine how genetic polymorphisms in innate immunity pathways interact with endotoxin to influence asthma risk in children. METHODS: In a previous analysis of 372 children from the Boston Home Allergens and the Connecticut Childhood Asthma studies, 7 SNPs in 6 genes (CARD15, TGFB1, LY96, ACAA1, DEFB1 and IFNG) involved in innate immune pathways were associated with asthma, and 5 SNPs in 3 genes (CD80, STAT4, IRAK2) were associated with eczema. We tested these SNPs for interaction with early life endotoxin exposure (n = 291), in models for asthma and eczema by age 6. RESULTS: We found a significant interaction between endotoxin and a SNP (rs156265) in ACAA1 (p = 0.0013 for interaction). Increased endotoxin exposure (by quartile) showed protective effects for asthma in individuals with at least one copy of the minor allele (OR = 0.39 per quartile increase in endotoxin, 95% CI 0.15 to 1.01). Endotoxin exposure did not reduce the risk of asthma in children homozygous for the major allele. CONCLUSION: Our findings suggest that protective effects of endotoxin exposure on asthma may vary depending upon the presence or absence of a polymorphism in ACAA1.

Relevance and implication of genetic determinants to asthma pathophysiology.

PURPOSE OF REVIEW: The number of single nucleotide polymorphisms (SNPs) found to be associated with asthma and related phenotypes outnumbers those with functional impacts. In this review we briefly described some of the approaches used to investigate functionality of SNPs, and summarized recent findings related to the characterization of functional SNPs in asthma. RECENT FINDINGS: For disease-associated SNPs residing in the promoter or 3' untranslated regions, differential protein binding affinity between the major and minor alleles is often the first logical area of investigation. In this review, we described SNPs associated with asthma or related phenotypes in five genes which in the past 12 months have new data implicating potential mechanisms in asthma development. SUMMARY: Variability in treatment responses poses a great challenge in asthma management. It is established that the genetic makeup of individuals plays a role in asthma development, yet the mechanisms remain unclear. Investigations on the functional impacts of disease-associated SNPs will help us gain insights into potential disease mechanisms, and ultimately lead to effective therapies for those who suffer from asthma.

Asthma and genes encoding components of the vitamin D pathway.

BACKGROUND: Genetic variants at the vitamin D receptor (VDR) locus are associated with asthma and atopy. We hypothesized that polymorphisms in other genes of the vitamin D pathway are associated with asthma or atopy. METHODS: Eleven candidate genes were chosen for this study, five of which code for proteins in the vitamin D metabolism pathway (CYP27A1, CYP27B1, CYP2R1, CYP24A1, GC) and six that are known to be transcriptionally regulated by vitamin D (IL10, IL1RL1, CD28, CD86, IL8, SKIIP). For each gene, we selected a maximally informative set of common SNPs (tagSNPs) using the European-derived (CEU) HapMap dataset. A total of 87 SNPs were genotyped in a French-Canadian family sample ascertained through asthmatic probands (388 nuclear families, 1064 individuals) and evaluated using the Family Based Association Test (FBAT) program. We then sought to replicate the positive findings in four independent samples: two from Western Canada, one from Australia and one from the USA (CAMP). RESULTS: A number of SNPs in the IL10, CYP24A1, CYP2R1, IL1RL1 and CD86 genes were modestly associated with asthma and atopy (p < 0.05). Two-gene models testing for both main effects and the interaction were then performed using conditional logistic regression. Two-gene models implicating functional variants in the IL10 and VDR genes as well as in the IL10 and IL1RL1 genes were associated with asthma (p < 0.0002). In the replicate samples, SNPs in the IL10 and CYP24A1 genes were again modestly associated with asthma and atopy (p < 0.05). However, the SNPs or the orientation of the risk alleles were different between populations. A two-gene model involving IL10 and VDR was replicated in CAMP, but not in the other populations. CONCLUSION: A number of genes involved in the vitamin D pathway demonstrate modest levels of association with asthma and atopy. Multilocus models testing genes in the same pathway are potentially more effective to evaluate the risk of asthma, but the effects are not uniform across populations.

Postural changes in blood pressure associated with interactions between candidate genes for chronic respiratory diseases and exposure to particulate matter.

BACKGROUND: Fine particulate matter [aerodynamic diameter

Candidate genes for respiratory disease associated with markers of inflammation and endothelial dysfunction in elderly men.

BACKGROUND: Inflammation and endothelial dysfunction are important risk factors for cardiovascular disease (CVD). We hypothesized that candidate genes selected for a study of asthma and chronic obstructive pulmonary disorder (COPD) are associated with markers of systemic inflammation and endothelial dysfunction in an aging population. METHODS: Plasma levels of circulating C-reactive protein (CRP), fibrinogen, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were obtained from 679 elderly male participants in the Normative Aging Study. Blood samples were analyzed for 202 single nucleotide polymorphisms (SNPs) in 25 candidate genes and included both haplotype tagSNPs and functional SNPs based on literature review. Data were stratified into discovery and replication cohorts for 2-stage analysis. In the discovery cohort, the relationship between biomarker level and genotype was analyzed using linear mixed effects with random intercepts for each subject and models were adjusted for age and BMI. A positive outcome in the discovery cohort was defined as a p-value <0.1 for the SNP. SNPs that met this criterion were analyzed in the replication cohort and confirmed for those which met a criterion of significance (p<0.025). RESULTS: In our analyses, SNPs in the CRHR1, ITPR2, and VDR genes met significance criteria. CONCLUSIONS: Our results suggest that genes thought to play a role in the pathogenesis of asthma and COPD may influence levels of serum markers of inflammation and endothelial dysfunction via novel SNP associations which have not previously been associated with cardiovascular disease.

Association of corticotropin-releasing hormone receptor-2 genetic variants with acute bronchodilator response in asthma.

OBJECTIVE: Corticotropin-releasing hormone receptor (CRHR)-2 participates in smooth muscle relaxation response and may influence acute airway bronchodilator response to short-acting beta2-agonist treatment of asthma. We aim to assess associations between genetic variants of CRHR2 and acute bronchodilator response in asthma. METHODS: We investigated 28 single nucleotide polymorphisms in CRHR2 for associations with acute bronchodilator response to albuterol in 607 Caucasian asthmatic patients recruited as part of the Childhood Asthma Management Program. Replication was conducted in two Caucasian adult asthma cohorts--a cohort of 427 participants enrolled in a completed clinical trial conducted by Sepracor Inc. (Massachusetts, USA) and a cohort of 152 participants enrolled in the Clinical Trial of Low-Dose Theophylline and Montelukast conducted by the American Lung Association Asthma Clinical Research Centers. RESULTS: Five variants were significantly associated with acute bronchodilator response in at least one cohort (P

Alleles of the NRAMP1 gene are risk factors for pediatric tuberculosis disease.

Relatively little is known about the human genetics of susceptibility to common diseases caused by bacterial pathogens. Tuberculosis, caused by Mycobacterium tuberculosis, is a major cause of morbidity and mortality worldwide. So far, genetic studies of tuberculosis susceptibility have largely been focused on adult patients despite the fact that tuberculosis is highly prevalent among children. To study the host genetic component of pediatric tuberculosis susceptibility, we enrolled 184 ethnically diverse families from the Greater Houston area with at least one child affected by pediatric tuberculosis disease. Using a family-based control design, we found allelic variants of the natural resistance-associated macrophage protein gene 1 (NRAMP1) (alias SLC11A1) significantly associated with tuberculosis disease in this pediatric patient population [P = 0.01; odds ratio = 1.75 (95% confidence interval, 1.10-2.77)]. The association of NRAMP1 with pediatric tuberculosis disease was significantly heterogeneous (P = 0.01) between simplex [P <0.0008; odds ratio = 3.13 (1.54-6.25)] and multiplex families (P = 1), suggesting an interplay between mechanisms of genetic control and exposure intensities. In striking contrast to previous studies in the adult population, we observed that the common alleles of NRAMP1 polymorphisms were risk factors for pediatric tuberculosis disease. To explain the different direction of allelic association between adult and pediatric disease, we hypothesize that NRAMP1 influences the speed of progression from infection to tuberculosis disease.

Association of vitamin D receptor genetic variants with susceptibility to asthma and atopy.

Genome scans for asthma have identified suggestive or significant linkages on 17 different chromosomes, including chromosome 12, region q13-23, housing the vitamin D receptor (VDR) gene. Through interaction with VDR, 1,25-dihydroxyvitamin D3 mediates numerous biological activities, such as regulation of helper T-cell development and subsequent cytokine secretion profiles. Variants of the VDR have been found to be associated with immune-mediated diseases that are characterized by an imbalance in helper T-cell development, such as Crohn's disease and tuberculosis. The VDR, hence, is a good candidate to be investigated for association with asthma, which is characterized by enhanced helper T-cell type 2 activity. Here, we examined VDR genetic variants in an asthma family-based cohort from Quebec. We report six variants to be strongly associated with asthma and four with atopy (0.0005 < or = p < or = 0.05). Analysis of the linkage disequilibrium pattern and haplotypes also revealed significant association with both phenotypes (0.0004 < or = p < or = 0.01). The findings have been replicated by another research team in a second but not in a third cohort. These results identify VDR variants as genetic risk factors for asthma/atopy and implicate a non-human leukocyte antigen immunoregulatory molecule in the pathogenesis of asthma and atopy.