The role of novel genes in modifying airway responses in asthma

Copy number variation burden on asthma subgenome in normal cohorts identifies susceptibility markers

PURPOSE

Asthma is a complex disease caused by interplay of genes and environment on the genome of an individual. Copy number variations (CNVs) are more common compared to the other variations that disrupt genome organization. The effect of CNVs on asthma subgenome has been less studied compared to studies on the other variations. We report the assessments of CNV burden in asthma genes of normal cohorts carried out in different geographical areas of the world and discuss the relevance of the observation with respect to asthma pathogenesis.

METHODS

CNV analysis was performed using Affymerix high-resolution arrays, and various bioinformatics tools were used to understand the influence of genes on asthma pathogenesis.

RESULTS

This study identified 61 genes associated with asthma and provided various mechanisms and pathways underlying asthma pathogenesis. CCL3L1, ADAM8, and MUC5B were the most prevalent asthma genes. Among them, CCL3L1 was found across all 12 populations in varying copy number states. This study also identified the inheritance of asthma-CNVs from parents to offspring creating the latent period for manifestation of asthma.

CONCLUSIONS

This study revealed CNV burden with varying copy number states and identified susceptibility towards the disease manifestation. It can be hypothesized that primary CNVs may not be the initiating event in the pathogenesis of asthma and additional preceding mutations or CNVs may be required. The initiator or primary CNVs sensitize normal cohorts leading to an increased probability of accumulating mutations or exposure to allergic stimulating agents that can augment the development of asthma.

Genome-wide methylation profiling of the bronchial mucosa of asthmatics: relationship to atopy

Background

Asthma is a common respiratory disease that is characterized by bronchial hyperresponsiveness and airway obstruction due to chronic airway inflammation. Atopic asthma is a typical IgE-mediated disease in which the enhanced production of IgE is driven by the activation of Th2 cells, which release a distinct pattern of cytokines, including interleukin 4 (IL4) and IL3, in response to specific antigen presentation. To evaluate the methylation status of the whole genomes of bronchial mucosa tissues from subjects who lacked or had sensitization to Dermatophagoides farina (Df) and Dermatophagoides pteronyssinus (Dp).

Methods

The genome-wide DNA methylation levels in the bronchial mucosa tissues of atopic asthmatics (N = 10), non-atopic asthmatics (N = 7), and normal controls (N = 7) were examined using microarrays.

Results

In the bronchial mucosa of atopic asthmatics, hypermethylation was detected at 6 loci in 6 genes, while hypomethylation was detected at 49 loci in 48 genes compared to those of non-atopic asthmatics. Genes that were assigned the ontologies of multicellular organismal process, response to organic substance, hormone metabolic process, and growth factor receptor binding were hypomethylated. The methylation levels in the mucosa of asthmatics and normal controls were similar.

Conclusions

The bronchial mucosa of asthmatics who are atopic to Df or Dp have characteristic methylation patterns for 52 genes. The genes and pathways identified in the present study may be associated with the presence of atopy in asthmatics and therefore represent attractive targets for future research.

Lack of association between eotaxin-1 gene polymorphisms and nasal polyposis

OBJECTIVE

To examine whether there is an association of eotaxin-1 gene polymorphisms with nasal polyposis (NP).

STUDY DESIGN

Cross-sectional study.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

The study group included 85 patients with NP and 93 controls without sinonasal disease. Genotypes of eotaxin-1 (-384 A>G and +67 G>A) were identified by restriction fragment length polymorphism analyses after polymerase chain reaction.

RESULTS

The -384 A>G and +67 G>A single nucleotide polymorphisms were higher in patients with NP than in controls (P = .044 and P = .019, respectively). However, their relation was statistically poor (association coefficient = 0.18). Consistent with this result, comparisons of allele frequencies for both single nucleotide polymorphisms were not significantly different (-384 A>G, P = .164; +67 G>A, P = .144).

CONCLUSION

In this study, eotaxin-1 -384 A>G or 67 G>A genotypes were not associated with susceptibility to NP.

Association of IKBA gene polymorphisms with the development of asthma

Nuclear factor-κB (NF-κB) orchestrates the expression of genes responsible for airway inflammation and remodeling in asthma. The activity of NF-κB is tightly regulated by IKBA, which may be modulated by genetic polymorphisms of the IKBA gene. We investigated the association between asthma susceptibility and IKBA gene polymorphisms in a Korean population. Genotyping was performed in BA (bronchial asthma) and NC (normal control). We measured reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay, and luciferase reporter assays, respectively. A -673A>T (rs2233407) was associated with asthma development in subjects with atopic asthma (odds ratio = 0.56, p = 0.004). The IKBA mRNA level was higher in B-cell lines with the rs2233407 TT genotype compared with those with the AA genotype (p = 0.024). The luciferase activity of the rs2233407 T genotype was higher than that of the A (p = 0.002). The cytoplasmic levels of total IKBA and IKBA [p-S32] were higher in B cell lines of the rs2233407 TT genotype than those of the AA (p = 0.016 and p = 0.036, respectively), whereas nuclear NF-κB activity in cells with the IKBA rs2233407 AA genotype was higher than in cells with the AA (p = 0.038). The IKBA rs2233407 A>T polymorphism may predispose individuals to the development of atopic asthma via regulation of IKBA gene expression at the transcriptional level.

Past, present, and future of allergy in Korea

Korean allergology has made great progress in keeping pace with global scientific advances in spite of a short history. Outstanding academic and scientific researches have been performed in a variety of allergy fields in Korea. Epidemiologic studies revealed increasing prevalence of asthma and allergic diseases and considerable morbidity and mortality in Korea. Novel inhalant allergens such as citrus red mite and two-spotted spider mite as causes of asthma and allergic rhinitis have been discovered and reported in Korea. Bidirectional translational researches have been performed and are underway to elucidate the pathogenesis of asthma and allergy, mechanisms of airway inflammation and remodeling, and new therapeutic modalities for asthma and allergic diseases. Experimental asthma models of different phenotypes according to exposed levels of lipopolysaccharide or double-stranded RNA suggested the crucial role of the innate immunity in the development of allergic airway inflammation and a new insight for asthma pathogenesis, in which both Th1 and Th2 inflammation are involved. In the field of genetic researches, numerous genetic associations with asthma and asthma-related phenotypes, such as atopy, IgE production, and airway hyperresponsiveness, have been demonstrated in Korean population. The Easy Asthma Management (EAM) program, a computer-assisted asthma management program, is anticipated to facilitate the achievement of more successful clinical outcomes by filling the gaps between guidelines and actual practices. The Integration of these multi-disciplinary allergy research resources and translation of scientific achievements to the bedside and society will lead to better allergy and asthma control in Korea.

A new approach for analyzing cellular infiltration during allergic airway inflammation

A mouse model for allergic airway inflammation involving ovalbumin (OVA) sensitization and challenge has been developed that reproduces hallmark features of human asthma and has provided valuable insight into the mechanisms by which this disease occurs. Cellular infiltrate in lungs of mice used in this model have conventionally been evaluated using histological examination of tissue sections and light microscopic analysis of lung lavage samples. As an alternative or complementary approach for characterizing cellular infiltrate, we developed a multicolor fluorescence-activated cell sorter (FACS) method involving the simultaneous detection of seven different markers on lung cell suspensions: CD4, CD8, B220, CD11b, Gr-1, CD49b, and FcepsilonRI. Only some of these cell types increased in OVA-challenged mice compared to PBS controls, including the CD4(+), B220(+), CD11b(+), and FcepsilonRI(+) groups. We also examined subpopulations of cells for coexpression of these markers and dissected heterogeneous populations as further evaluation procedures to characterize the cellular infiltrate resulting from OVA challenge. Finally, we combined FACS with real-time PCR to analyze certain cell types in terms of mRNA levels for factors involved in asthma, including GATA-3 and IL-1beta. Overall, these FACS-based techniques provide a powerful approach for analyzing cellular profiles in lung tissue from mice used in the mouse model of asthma and may also prove valuable in evaluating cellular infiltrates for other models of inflammation and immune responses.

Eosinophil trafficking in allergy and asthma

Blood eosinophilia and tissue eosinophilia are characteristic features of allergic inflammation and asthma, conditions associated with prominent production of T(H)2 cytokines IL-4, IL-5, and IL-13. In this review, we will consider recent advances in our understanding of the molecular mechanisms that promote expansion and differentiation of eosinophil progenitors in bone marrow, eosinophil recruitment in response to chemokine receptor 3 agonists eosinophil transit mediated by specific ligand-receptor interactions, and prolonged survival of eosinophils in peripheral tissues. Novel rational therapies including antiselectin and antichemokine receptor modalities designed to block eosinophil development and trafficking are discussed, together with the implications of recent clinical studies that have evaluated the efficacy of humanized anti-IL-5 mAb therapy.