Aspirin-intolerant asthma (AIA) is a subtype of bronchial asthma characterized by development of bronchoconstriction evoked by non-steroidal anti-inflammatory drugs (NSAIDs). NSAIDs inhibit the cyclooxygenase pathway, leading to enhancement of the lipoxygenase pathway. We evaluated allelic association of 370 single nucleotide polymorphisms (SNPs) of 63 candidate genes, mostly from the arachidonic acid metabolic cascade, with AIA. After two rounds of screening with 198 AIA patients, multiple SNPs in the prostaglandin E(2) receptor subtype 2 (EP2) gene were associated with AIA (P<0.05). Among the 77 SNPs identified in the EP2 gene, we selected 17 SNPs on the basis of linkage disequilibrium and allelic frequencies (minor allele frequency >0.1) for further association study. SNPs in the promoter region of the EP2 gene, uS5, uS5b, and uS7, were significantly associated with AIA (permutation P=0.039-0.001). Analysis of haplotypes constructed according to the LD pattern showed a significant association with AIA (permutation P=0.001). The most significantly associated SNP, uS5, located in the regulatory region of the EP2 gene, was in a STATs-binding consensus sequence [AIA 31.1% versus control 22.1% (permutation P=0.0016) or versus aspirin-tolerant asthma 22.2% (permutation P=0.0017)]. Although STAT1 binding was not observed in gel mobility shift assay with HeLa nuclear extract, an unidentified protein was specifically bound to the allelic sequence. In in vitro reporter assay in HCT116 cells, the site containing the uS5 allele showed reduced transcription activity. Taken together, these results suggest that uS5 allele serves as a target of a transcription repressor protein. A functional SNP of the EP2 gene associated with risk of AIA should decrease the transcription level, resulting in reduction of the PGE(2) braking mechanism of inflammation and involvement in the molecular mechanism underlying AIA.

There is increasing evidence for the role of basophils in the pathogenesis of bronchial asthma. To examine the presence of basophils in the airways of patients with fatal asthma by immunohistochemistry, we stained lung tissues from four post-mortem cases who had died from severe asthmatic attacks and four controls with a monoclonal antibody raised against tryptase (AA-1) and anti-IgE. Mast cells and basophils were identified in the bronchioles as AA-1- and anti-IgE-positive cells, and anti-IgE-positive cells, respectively. Airway mast cells were found beneath the basement membrane, near blood vessels in the submucosa, and adjacent to the submucosal glands, and scattered throughout the muscle bundles. There was a significant increase of mast cells in the asthma group compared with the control group (203.5+/-84.6/mm2, mean+/-s.d. vs 37.7+/-8.7/mm2, P<0.05, n=4). In contrast, basophils were observed in the airway lumen, in the bronchial epithelium and in the submucosa. The number of basophils in the bronchioles was 81.8+/-55.5/mm2 (n = 4); however, basophils were not found at all in the airways of the control group. Although eosinophils, B lymphocytes and macrophages bear low affinity IgE receptors and could react with anti-IgE, the location of these cells in the close sections did not correspond closely with basophils. The presence of basophils in lung tissues obtained from fatal asthma patients supports the view that basophils play a role in the pathogenesis of bronchial asthma.

We investigated the role of basophils and mast cells in the pathogenesis of bronchial asthma. Eight asthmatics (6 atopic, 2 nonatopic) and 6 control subjects were enrolled in this study. Bronchial responsiveness to acetylcholine (PC20ACh) was measured in asthmatics and endobronchial biopsy from right upper lobe bronchus was performed on the same day. Basophils and mast cells in the airways were identified by immunohistochemistry using a monoclonal antibody against tryptase and anti-IgE. The number of basophils of asthmatics was 52.2 +/- 12.5/mm(2). In contrast, no basophils were found in the airways of control subjects. There was a significant increase of number of mast cells in the asthma group compared to the control group (168.6 +/- 32.6 vs. 22.3 +/- 6.1, p<0.01). There was an inverse correlation between airway basophil and mast cell numbers and PC20ACh (r=-0.82, r=0.72, p<0.05). These findings suggest a possible role for basophils and mast cells in the pathophysiology of asthma.

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