Gene-by-environment effect of house dust mite on purinergic receptor P2Y12 (P2RY12) and lung function in children with asthma

Abstract

Background: Distinct receptors likely exist for leukotriene (LT)E(4), a potent mediator of airway inflammation. Purinergic receptor P2Y12 is needed for LTE(4)-induced airways inflammation, and P2Y12 antagonism attenuates house dust mite-induced pulmonary eosinophilia in mice. Although experimental data support a role for P2Y12 in airway inflammation, its role in human asthma has never been studied.

Objective: To test for association between variants in the P2Y12 gene (P2RY12) and lung function in human subjects with asthma, and to examine for gene-by-environment interaction with house dust mite exposure.

Methods: Nineteen single nucleotide polymorphisms (SNPs) in P2RY12 were genotyped in 422 children with asthma and their parents (n = 1266). Using family based methods, we tested for associations between these SNPs and five lung function measures. We performed haplotype association analyses and tested for gene-by-environment interactions using house dust mite exposure. We used the false discovery rate to account for multiple comparisons.

Results: Five SNPs in P2RY12 were associated with multiple lung function measures (P-values 0.006–0.025). Haplotypes in P2RY12 were also associated with lung function (P-values 0.0055–0.046). House dust mite exposure modulated associations between P2RY12 and lung function, with minor allele homozygotes exposed to house dust mite demonstrating worse lung function than those unexposed (significant interaction P-values 0.0028–0.040).

Conclusions and clinical relevance: The P2RY12 variants were associated with lung function in a large family-based asthma cohort. House dust mite exposure caused significant gene-by-environment effects. Our findings add the first human evidence to experimental data supporting a role for P2Y12 in lung function. P2Y12 could represent a novel target for asthma treatment.

Fig. 1

(A) Linkage disequilibrium plot for single nucleotide polymorphisms (SNPs) in P2RY12 and its 20kb flanks. r² values for pairwise correlation are shown. (B) Haplotype blocks for P2RY12. Two blocks were defined using the confidence interval method. Haplotypes for each block are shown in order of frequency.

Fig. 2

Relationship between P2RY12 SNPs and airways responsiveness stratified by house dust mite exposure. (A) House dust mite exposure dichotomized at 4^th quartile of measured Der p level, and (B) House dust mite exposure dichotomized at 10µg/g of measured Der p level. With both definitions of house dust mite exposure, subjects with two copies of the minor allele and dust exposure had greater airway responsiveness (lower PC₂₀) than minor allele homozygotes without dust exposure. Tests for gene-by-environment interaction were significant.