Simultaneous identification of GSTP1 Ile105 -> Val105 and Ala114 -> Val114substitutions using an amplification refractory mutation system polymerasechain reaction assay: studies in patients with asthma

Background: The glutathione S-transferase (GST) enzyme GSTP1 utilizes bypro ducts of oxidative stress. We previously showed that alleles of GSTP1 that encode the Ile105 --> Val105 substitution are associated with the asthma ph enotypes of atopy and bronchial hyperresponsiveness (BHR). However, a furth er polymorphic site (Ala114 --> Val114) has been identified that results in the following alleles: GSTP1*A (wild-type Ile105 --> Ala114), GSTP1*B (Val 105 --> Ala114), GSTP1*C (Val105 --> Val114) and GSTP1*D (Ile105 --> Val114 ). Methods: Because full identification of GSTP1 alleles may identify stronger links with asthma phenotypes, we describe an amplification refractory muta tion system (ARMS) assay that allows identification of all genotypes. We ex plored whether the GSTP1 substitutions influence susceptibility to asthma, atopy and BHR. Results: Among 191 atopic nonasthmatic, atopic asthmatic and nonatopic nona sthmatic individuals, none had the BD, CD, or DD genotypes. GSTP1 BC was si gnificantly associated with reduced risk for atopy (P = 0.031). Compared wi th AA, trend test analysis identified a significant decrease in the frequen cy of GSTP1 BC with increasing severity of BHR (P = 0.031). Similarly, the frequency of GSTP1 AA increased with increasing BHR. Conclusion: These data suggest that GSTP1*B and possibly GSTP1*C are protec tive against asthma and related phenotypes.