Makiko Shimizu

Variations in the C3, C3a receptor, and C5 genes affect susceptibility to bronchial asthma

Bronchial asthma (BA) is a common chronic inflammatory disease characterized by hyperresponsive airways, excess mucus production, eosinophil activation, and the production of IgE. The complement system plays an immunoregulatory role at the interface of innate and acquired immunities. Recent studies have provided evidence that C3, C3a receptor, and C5 are linked to airway hyperresponsiveness. To determine whether genetic variations in the genes of the complement system affect susceptibility to BA, we screened single nucleotide polymorphisms (SNPs) in C3, C5, the C3a receptor gene (C3AR1), and the C5a receptor gene (C5R1) and performed association studies in the Japanese population. The results of this SNP case-control study suggested an association between 4896C/T in the C3 gene and atopic childhood BA (P=0.0078) as well as adult BA (P=0.010). When patient data were stratified according to elevated total IgE levels, 4896C/T was more closely associated with adult BA (P=0.0016). A patient-only association study suggested that severity of childhood BA was associated with 1526G/A of the C3AR1 gene (P=0.0057). We identified a high-risk haplotype of the C3 gene for childhood (P=0.0021) and adult BA (P=0.0058) and a low-risk haplotype for adult BA (P=0.00011). We also identified a haplotype of the C5 gene that was protective against childhood BA (P=1.4×10−6) and adult BA (P=0.00063). These results suggest that the C3 and C5 pathways of the complement system play important roles in the pathogenesis of BA and that polymorphisms of these genes affect susceptibility to BA.

Functional promoter polymorphism in the TBX21 gene associated with aspirin-induced asthma

Asthma is a phenotypically heterogeneous disorder with many etiologic factors and clinical characteristics. T-bet, a Th1-specific transcription factor of T-box family, has been found to control interferon-γ (IFN-γ) expression in T cells. Mice lacking the T-bet gene (tbx21) demonstrate multiple physiological and inflammatory features reminiscent of human asthma. In order to examine whether polymorphisms in the candidate gene, TBX21, located on chromosome 17q21.32, are related to the risk of human asthma phenotypes, we have searched for genetic variations in the human TBX21 gene and identified 24 single nucleotide polymorphisms (SNPs), including five novel SNPs, by direct sequencing in Japanese subjects. Among asthma phenotypes, a promoter −1993T→C SNP, which is in linkage disequilibrium with a synonymous coding 390A→G SNP in exon 1, is significantly associated with a risk of aspirin-induced asthma (AIA; P=0.004, Pc=0.016). This association has also been confirmed in additional independent samples of asthma with nasal polyposis (P=0.008), regardless of aspirin hypersensitivity. Furthermore, our data indicate that the −1993T→C substitution increases the affinity of a particular nuclear protein to the binding site of TBX21 covering the −1993 position, resulting in increased transcriptional activity of the TBX21 gene. Thus, in addition to the antigen-driven excess Th2 response, increased T-bet (and subsequent IFN-γ) production in human airways of individuals with the −1993T→C polymorphism could contribute to the development of certain asthma-related phenotypes, such as AIA.

Polymorphisms in ADAM33 are associated with allergic rhinitis due to Japanese cedar pollen

Background A recent report provided evidence that a disintegrin and metalloprotease domain 33 (ADAM33), a member of the ADAM family, is a novel susceptibility gene in asthma linked to bronchial hyper‐responsiveness. However, there has been no investigation of the genetic role of ADAM33 variants in nasal allergy.

An association study of asthma and related phenotypes with polymorphisms in negative regulator molecules of the TLR signaling pathway

AbstractAlthough associations between endotoxin exposure or respiratory infection and asthma have been recognized, the genetic effects in these conditions are unclear. Toll-like receptors (TLRs) play an essential role in innate host defense and in the control of adaptive immune responses. IL-1R-associated kinase-M (IRAK-M) and single immunoglobulin IL-1R-related molecule (SIGIRR) negatively regulate TLR-signaling pathways. To investigate whether polymorphisms in these genes were associated with asthma or asthma-related phenotypes, we screened these genes for polymorphisms by direct sequencing of 24 asthmatics and identified 19 variants in IRAK-M and 12 variants in SIGIRR. We next conducted linkage disequilibrium mapping of the genes, and examined the association of polymorphisms and haplotypes using 391 child patients with asthma, 462 adult patients with asthma, and 639 controls. None of the alleles or haplotypes of IRAK-M and SIGIRR were associated with asthma susceptibility or asthma-related phenotype. Our results indicate that polymorphisms in IRAK-M and SIGIRR are not likely to be associated with the development of asthma in the Japanese population.

Association between genetic variation in the gene for death-associated protein-3 (DAP3) and adult asthma.

AbstractLung epithelium plays a central role in modulation of the lung inflammatory response, and lung repair and airway epithelial cells are targets in asthma and viral infection. Activated T lymphocytes release cytokines such as interferon-gamma (IFN-γ) that induce apoptosis, or programmed cell death, of damaged epithelial cells. Death-associated protein-3 (DAP3) is involved in mediating IFN-γ-induced cell death. To assess the possible involvement of genetic variants of DAP3 with asthma, we searched for single-nucleotide polymorphisms (SNPs) in the gene and conducted a case-control study with 1,341 subjects. We found a strong association between bronchial asthma (BA) in adults (P=0.0051, odds ratio=1.87, 95% CI=1.20-2.92), whereas no association was found with childhood asthma. The tendency was more prominent in patients with higher serum total immunoglobulin E (IgE) (>250 IU/ml) (P=0.00061, odds ratio=2.40, 95% CI=1.44-4.00). DAP3 was expressed in normal bronchial epithelial cells, and the expression was induced by IFN-γ. These results indicated that specific variants of the DAP3 gene might be associated with the mechanisms responsible for adult BA and contribute to airway inflammation and remodeling.

Lack of Association between the IL13 Variant Arg110Gln and Susceptibility to Cedar Pollinosis in a Japanese Population

Background:Interleukin (IL)-13 has come to be appreciated as a molecule critically involved in allergic inflammatory responses. Recent studies revealed that a common variant in the coding region of the IL13 gene, Arg110Gln, has been implicated in the development of asthma and atopy. Methods:To assess whether the IL13 variant Arg110Gln is associated with cedar pollinosis, one of the most common atopic diseases in the Japanese population, we examined the Arg110Gln variant using PCR-RFLP to compare the genotype and allele frequencies between 95 patients with cedar pollinosis and 95 healthy control subjects. Relationships between the Arg110Gln variant and the pollinosis-related traits, e.g. rhinitis severity, eosinophil counts in nasal secretion and serum total and allergen-specific IgE levels, were also investigated. Results: The frequencies of the minor allele Gln110 were 25.8% in patients with cedar pollinosis and 30.9% in healthy control subjects (p > 0.05). There was also no significant difference in the genotype frequencies between cases and controls (p > 0.05). In addition, we found no significant association of the Arg110Gln variant with any of the pollinosis-related phenotypes (p > 0.05). Conclusions: Our data suggest lack of evidence for identifying the variant Arg110Glnat the IL13 locus as a genetic risk factor involved in the development of Japanese cedar pollinosis.