The discovery and role of ADAM33, a new candidate gene for asthma

Single nucleotide polymorphisms in asthma candidate genes TBXA2R, ADAM33 FCER1B and ORMDL3 in Pakistani asthmatics a case control study

BACKGROUND

Genetic variations in different loci and genes are important in asthma pathogenesis. There is much importance of various immunological pathways in the IgE secretion regulation. Alterations in any main part of these pathways can increase the risk of asthma development. Polymorphisms in these genetic markers can effect certain pathways which predict the asthma susceptibility. In the present study, SNPs directly or indirectly affecting the immunological process pathways are selected.

METHODS

This study was conducted to determine association of 16 SNPs in 10 candidate genes with asthma in Pakistani population in 333 asthmatic cases and 220 healthy controls. Genotyping was performed using the Sequenom Mass ARRAY iPLEX platform (14 SNPs) and TaqMan assay (2 SNPs).

RESULTS

The minor allele at two of the SNPs showed association with protection from asthma, rs1131882 in TBXA2R gene (OR 0.73, 95% CI 0.52-1.01, P = 0.05) and rs2280091 in the ADAM33 gene (OR 0.69, 95% CI 0.50-0.97, P = 0.03). For FCER1B gene, rs2583476 the asthmatic male gender had higher TT genotype counts as compared to controls (OR = 1.86, 95% CI = 1.09-3.17, p = 0.01). In rs11650680 of ORMDL3 gene the CT genotype is more prevalent in female asthma cases in comparison with female controls (OR = 1.99, 95% CI = 1.02-3.89, p = 0.03).

CONCLUSIONS

This data suggests that variations at TBXA2R and ADAM33 genes are found to be associated with asthma susceptibility in Pakistan. FCER1B gene is associated with male and ORMDL3 in female asthmatics. These genetic markers can be important source of asthma risk in Pakistani population.

Environment Changes Genetic Effects on Respiratory Conditions and Allergic Phenotypes

The prevalence of asthma and allergic diseases is disproportionately distributed among different populations, with an increasing trend observed in Western countries. Here we investigated how the environment affected genotype-phenotype association in a genetically homogeneous, but geographically separated population. We evaluated 18 single nucleotide polymorphisms (SNPs) corresponding to 8 genes (ADAM33, ALOX5, LT-α, LTC4S, NOS1, ORMDL3, TBXA2R and TNF-α), the lung function and five respiratory/allergic conditions (ever asthma, bronchitis, rhinitis, dermatitis and atopy) in two populations of Inuit residing either in the westernized environment of Denmark or in the rural area of Greenland. Our results showed that lung function was associated with genetic variants in ORMDL3, with polymorphisms having a significant interaction with place of residence. LT-α SNP rs909253 and rs1041981 were significantly associated with bronchitis risk. LT-α SNP rs2844484 was related to dermatitis susceptibility and was significantly influenced by the place of residence. The observed gene-phenotype relationships were exclusively present in one population and absent in the other population. We conclude that the genotype-phenotype associations relating to bronchitis and allergy susceptibility are dependent on the environment and that environmental factors/lifestyles modify genetic predisposition and change the genetic effects on diseases.

An ADAM33 polymorphism associates with progression of preschool wheeze into childhood asthma: a prospective case-control study with replication in a birth cohort study

BACKGROUND

The influence of asthma candidate genes on the development from wheeze to asthma in young children still needs to be defined.

OBJECTIVE

To link genetic variants in asthma candidate genes to progression of wheeze to persistent wheeze into childhood asthma.

MATERIALS AND METHODS

In a prospective study, children with recurrent wheeze from the ADEM (Asthma DEtection and Monitoring) study were followed until the age of six. At that age a classification (transient wheeze or asthma) was based on symptoms, lung function and medication use. In 198 children the relationship between this classification and 30 polymorphisms in 16 asthma candidate genes was assessed by logistic regression. In case of an association based on a p<0.10, replication analysis was performed in an independent birth cohort study (KOALA study, n = 248 included for the present analysis).

RESULTS

In the ADEM study, the minor alleles of ADAM33 rs511898 and rs528557 and the ORMDL3/GSDMB rs7216389 polymorphisms were negatively associated, whereas the minor alleles of IL4 rs2243250 and rs2070874 polymorphisms were positively associated with childhood asthma. When replicated in the KOALA study, ADAM33 rs528557 showed a negative association of the CG/GG-genotype with progression of recurrent wheeze into childhood asthma (0.50 (0.26-0.97) p = 0.04) and no association with preschool wheeze.

CONCLUSION

Polymorphisms in ADAM33, ORMDL3/GSDMB and IL4 were associated with childhood asthma in a group of children with recurrent wheeze. The replication of the negative association of the CG/GG-genotype of rs528557 ADAM33 with childhood asthma in an independent birth cohort study confirms that a compromised ADAM33 gene may be implicated in the progression of wheeze into childhood asthma.

Association study on ADAM33 polymorphisms in mite-sensitized persistent allergic rhinitis in a Chinese population

Background

The ADAM33 gene has been identified as a potentially important asthma candidate gene and polymorphisms in this gene have been shown to be associated with asthma and seasonal allergic rhinitis.

Objective

To assess whether the ADAM33 polymorphisms are associated with persistent allergic rhinitis (PER) due to house dust mites in a Chinese population.

Methods

In a hospital-based case-control study of 515 patients with mite-sensitized PER and 495 healthy controls, we genotyped seven single nucleotide polymorphisms (SNPs) in ADAM33. Serum levels of eosinophil cationic protein, total IgE and allergen-specific IgE against Dermatophagoides pteronyssinus and Dermatophagoides farinae were measured by the ImmunoCAP assays.

Results

In the single-locus analysis, three polymorphisms, rs3918392 (F1), rs528557 (S2) and rs2787093, were significantly associated with mite-sensitized PER. SNP S2 was associated with significantly increased risk both of asthmatic and nonasthmatic mite-sensitized PER. In the combined genotypes analysis, individuals with 2–4 risk alleles had a significantly higher risk of mite-sensitized PER (adjusted OR = 1.99, 95% CI = 1.50–2.62) than those with 0–1 risk alleles. Haplotype-based association analysis revealed that the ACAGCCT haplotype might have potential to protect against mite-sensitized PER (adjusted OR = 0.67; 95% CI = 0.49–0.90).

Conclusions

Polymorphisms in the ADAM33 gene may contribute to susceptibility of mite-sensitized PER in this Chinese population.

Association of ADAM33 gene polymorphisms with COPD in the Mongolian population of China

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a respiratory disorder with increasing prevalence and mortality, influenced by both environmental and genetic factors. ADAM33 gene has been found to be associated with asthma, declined lung function and COPD.

AIM

The aim of this study was to find out if SNPs in ADAM33 (V4, T+1, T1, T2, S1, S2, Q-1 and F+1) play any role in genetic susceptibility to COPD in the Mongolian population of China.

SUBJECTS AND METHODS

Two hundred and fifteen Mongolian COPD patients and 223 Mongolian healthy individuals were recruited for the study. Eight polymorphic loci (V4, T+1, T2, T1, S2, S1, Q-1, and F+1) of ADAM33 were selected for genotyping. Genotyping was carried out using the Polymerase Chain Reaction and Restriction Fragment Length polymorphism (PCR-RFLP) method.

RESULTS

Seven SNPs in ADAM33 were associated with COPD (T+1, p = 0.014; T2, p = 0.018; T1, p = 0.048; S2, p = 0.003; S1, p = 0.000; Q-1, p = 0.000 and F+1, p = 0.000), even after Bonferroni correction, SNPs S2, S1, Q-1 and F+1 remained significant. Haplotype analysis showed that the frequencies of haplotype H1 (GGAGGGT), H5 (GGAGGGC) and H10 (GGGGAGT) were significantly higher in the COPD group than in the control group (p = 0.002, 0.031 and 0.009, respectively). In contrast, the haplotype H11 (GGACAGC) was more common in the control group than in the case group (p = 0.015).

CONCLUSIONS

Seven SNPs in ADAM33 were associated with COPD in the Mongolian population of China.

Role of ADAM33 gene and associated single nucleotide polymorphisms in asthma

Asthma is a multifactorial disorder, primarily resulting from interactions between genetic and environmental factors. ADAM33 gene (located on chromosome 20p13) has been reported to play an important role in asthma. This review article is intended to include all of the publications, to date, which have assessed the association of ADAM33 gene polymorphisms as well as have shown the role of ADAM33 gene in airway remodeling and their expression with asthma. A PubMed search was performed for studies published between 1990 and 2010. The terms “ADAM33,” “ADAM33 gene and asthma,” and “ADAM33 gene polymorphisms” were used as search criteria. Based on available literature we can only speculate its role in the morphogenesis and functions of the lung. Fourteen studies conducted in different populations were found showing an association of ADAM33 gene polymorphisms with asthma. However, none of the single nucleotide polymorphisms (SNPs) of ADAM33 gene had found association with asthma across all ethnic groups. Because higher expression of ADAM33 is found in the fibroblast and smooth muscle cells of the lung, over- or underexpression of ADAM33 gene may result in alterations in airway remodeling and repair processes. However, no SNP of ADAM33 gene showed significant associations with asthma across all ethnic groups; the causative polymorphism, if any, still has to be identified.

The role of vitamin D in asthma

Vitamin D metabolites are important immune-modulatory hormones and are able to suppress Th2-mediated allergic airway disease. Some genetic factors that may contribute to asthma are regulated by vitamin D, such as vitamin D receptor (VDR), human leukocyte antigen genes (HLA), human Toll-like receptors (TLR), matrix metalloproteinases (MMPs), a disintegrin and metalloprotein-33 (ADAM-33), and poly(ADP-ribosyl) polymerase- 1 (PARP-1). Vitamin D has also been implicated in asthma through its effects on the obesity, bacillus Calmettee Guérin (BCG) vaccination and high vitamin D level, vitamin D supplement, checkpoint protein kinase 1 (Chk1), plasminogen activator inhibitor-1 (PAI-1) and gamma delta T cells (gdT). Vitamin D plays a role in asthma and exerts its action through either genomic and/or non-genomic ways.

Pathogens and immunologic memory in asthma: what have we learned?

Animal models and clinical studies of asthma have generated important insights into the first effector phase leading to the development of allergic airway disease and bronchial hyper-reactivity. In contrast, mechanisms related to asthma chronicity or persistence are less well understood. The CD4(+) T-helper 2 lymphocytes are known initiators of the inflammatory response associated with asthma. There is now increasing evidence that memory T-cells, sensitized against allergenic, occupational or viral antigens, are also involved in the persistence of asthma. Additionally, the role of pathogens in asthma has been linked to both the initial susceptibility to and flares of this disease. This review will discuss the potential links between infection and asthma, the role of the memory T-cells in asthma, and the potential mechanisms by which these factors interact to lead to the development and/or persistence of asthma.

Adam33 polymorphisms are associated with COPD and lung function in long-term tobacco smokers

Background

Variation in ADAM33 has been shown to be important in the development of asthma and altered lung function. This relationship however, has not been investigated in the population susceptible to COPD; long term tobacco smokers. We evaluated the association between polymorphisms in ADAM33 gene with COPD and lung function in long term tobacco smokers.

Methods

Caucasian subjects, at least 50 year old, who smoked ≥ 20 pack-years (n = 880) were genotyped for 25 single nucleotide polymorphisms (SNPs) in ADAM33. COPD was defined as an FEV1/FVC ratio < 70% and percent-predicted (pp)FEV1 < 75% (n = 287). The control group had an FEV1/FVC ratio ≥ 70% and ppFEV₁ ≥ 80% (n = 311) despite ≥ 20 pack years of smoking. Logistic and linear regressions were used for the analysis. Age, sex, and smoking status were considered as potential confounders.

Results

Five SNPs in ADAM33 were associated with COPD (Q-1, intronic: p < 0.003; S1, Ile → Val: p < 0.003; S2, Gly → Gly: p < 0.04; V-1 intronic: p < 0.002; V4, in 3' untranslated region: p < 0.007). Q-1, S1 and V-1 were also associated with ppFEV1, FEV1/FVC ratio and ppFEF25–75 (p values 0.001 – 0.02). S2 was associated with FEV1/FVC ratio (p < 0.05). The association between S1 and residual volume revealed a trend toward significance (p value < 0.07). Linkage disequilibrium and haplotype analyses suggested that S1 had the strongest degree of association with COPD and pulmonary function abnormalities.

Conclusion

Five SNPs in ADAM33 were associated with COPD and lung function in long-term smokers. Functional studies will be needed to evaluate the biologic significance of these polymorphisms in the pathogenesis of COPD.