TNF and ADRB2 polymorphisms did not seem to directly influence the effect of air pollution from traffic on the development of asthmatic symptoms and sensitization, but in combination with GSTP1, TNF substantially modified the effect of traffic-related exposure.
Polymorphisms in the ADRB2 gene (especially Glyl6Arg) have been reported to affect not only the long-term response to ADRB2 agonists but also the risk of asthma in relation to active and passive smoking, and we specifically selected ADRB2 in this study based on previous interaction effects (Israel et al.
The increasing clinical relevance of ADRB2 SNP phenotypes makes automated screening methods important as tools for routine assessment of ADRB2 polymorphisms.
To generate ADRB2 PCR products for subsequent sequencing, we amplified a 219-bp ADRB2 fragment from 300 ng of DNA with 10 pmol of forward (5'-AGCCAGTGCGCTTACCTGCCAGACT-3'; nucleotides 188-212) and reverse (5'-GCTCGAACTTGGCAATGGCTGTGA-3'; nucleotides 406-383) primers (10) by initial denaturation at 95[degrees]C for 2 min, followed by 35 cycles of amplification at 95[degrees]C, denaturation for 30 s, annealing at 60[degrees]C for 30 s, and extension at 72[degrees]C for 1 min, with a final extension at 72[degrees]C for 7 min.
Compared with the directly sequenced ADRB2 locus, which was routinely determined in 20% of the DNA samples, this assay correctly identified all base combinations at these positions and distinguished G16E27, G16Q27, and R16Q27 homozygotes from the simple G16Q27/R16Q27 and compound G16Q27/G16E27 heterozygotes.
ADRB2 polymorphism frequencies are known to differ among Caucasian, African-American, and Chinese populations (15, 22).