Influence of β2-adrenergic receptor polymorphism on methacholine hyperresponsiveness in asthmatic patients

Abstract

BackgroundWe previously reported that the β2-adrenergic receptor (ADRB2) polymorphism had no effect on bronchial hyperresponsiveness (BHR) to methacholine in asthmatic patients. We have now replicated this analysis in a different and larger cohort of patients. ObjectiveTo assess the effect of the ADRB2 polymorphism in methacholine-responsive patients with asthma. MethodsWe conducted a retrospective analysis of the effects of ADRB2 haplotypes at position 16 (Gly/Arg) and 27(Gln/Glu) in 449 patients with a physician diagnosis of asthma who were responsive to methacholine (ie, provocation concentration that caused a decrease in forced expiratory volume in 1 second [FEV1] of 20% [PC20], <8 mg/mL). ResultsNo differences were found in age, FEV1, or inhaled corticosteroid dose among the genotypes or haplotypes. No significant differences were found in methacholine PC20 (ie, <8 mg/mL) between the separate genotypes at position 16 or 27 or between the haplotypes at positions 16/27 combined. In addition, no significant differences were found among individual genotypes when stratified according to severity of BHR using different doubling dilution cutoff points for methacholine PC20 (ie, <4 mg/mL, <2 mg/mL, and <1 mg/mL). ConclusionWe have confirmed in this replication study that common ADRB2 genotypes or haplotypes at positions 16/27 do not influence BHR in methacholine-responsive patients with asthma.