Background Cyclooxygenase (COX)-2 is an inducible enzyme responsible for catalysing the formation of prostaglandins (PGs) in settings of inflammation. Single nucleotide polymorphisms (SNPs) of the COX-2 gene may influence gene transcription and PG production in the asthmatic airway.
Objective To evaluate the frequencies of COX-2 SNPs in an Australian Caucasian population, and determine potential associations between common COX-2 promoter SNPs and asthma, asthma severity and aspirin-intolerant asthma (AIA).
Methods The frequencies of 25 COX-2 SNPs were determined in a random population (n=176). The SNPs with a minor allele frequency of >10% were then studied in asthmatic (n=663), non-asthmatic controls (n=513) and AIA subjects (n=58). Genotype, allele and haplotype associations were assessed. Functional assessment of SNPs was performed by transfection into HeLa cells measured using the luciferase dual-reporter assay system.
Results Eighteen COX-2 SNPs were not detected, five were rare and two promoter SNPs, −1195G>A (rs689465), and −1290A>G (rs689466), were further studied. The A allele of the −1195 SNP was present at a significantly higher frequency among all asthmatic subjects (P=0.012). Over 60% of the asthmatic individuals were −1195A homozygotes compared with 54.6% of the control subjects (odds ratio, 1.35; 95% CI, 1.06–1.72, P=0.03). After classifying for severity, the mild asthmatics represented 64.6% of −1195AA individuals, the highest of all the asthma groups compared with 54.6% of the control subjects (odds ratio, 1.5; 95% CI, 1.12–2.02, P=0.02). The −1290A/−1195G/−765G haplotype was associated with a reduced incidence of asthma (odds ratio, 0.76; 95% CI, 0.61–0.95, P=0.017).
Conclusion The −1195G>A polymorphism appears to be associated with asthma, and in particular with mild asthma.