10.1517/14622416.6.4.399 © 2005 Future Medicine Ltd ISSN 1462-2416 Pharmacogenomics (2005) 6(4), 399–410 399 R ESEARCH R EPORT For reprint orders, please contact: reprints@futuremedicine.com β 2 -adrenergic receptor polymorphisms and response to salbutamol among Indian asthmatics* Ritushree Kukreti 1† , Pallav Bhatnagar 1 , Chandrika B-Rao 2,5 , Simone Gupta 2 , Babita Madan 1 , Chinmoyee Das 3 , Randeep Guleria 3 , Amita Umesh Athavale 4 , Samir Kumar Brahmachari 2 & Balaram Ghosh 2 † Author for correspondence 1 GenoMed Lab, (Gene Quest Laboratory, Nicholas Piramal India Ltd) at Institute of Genomics and Integrative Biology (CSIR), Delhi 110007, India Tel.: +91 11 27662202; E-mail: ritushree @hotmail.com 2 Institute of Genomics and Integrative Biology, CSIR, Delhi University Campus, Delhi 110007, India 3 All India Institute of Medical Sciences (AIIMS), Department of Medicine, Delhi 110029, India 4 KEM hospital, Chest and EPRC Department, Parel, Mumbai 400012 5 Current address: ChemInformatics, Quest Institute of life Sciences, Nicholas Piramal India Ltd, Goregaon East, Bombay 400063, India *US and PCT patent pending Keywords: β2-adrenergic receptor gene, asthma, pharmacogenetic locus, responsiveness, salbutamol, single nucleotide polymorphism Introduction: The β 2 -adrenergic receptor (β 2 AR or ADRβ 2 ) is the target for β 2 -agonist drugs used for bronchodilation in asthma and other respiratory diseases. The aim of this study was to identify common single nucleotide polymorphisms (SNPs) and haplotypes in asthmatics and healthy individuals from an Indian population, and determine the influence of β 2 AR SNPs in responsiveness to β 2 -agonist therapy in asthma patients. Methods: Ten variable SNP sites within a span of 2.193 kb were identified in the β 2 AR gene by sequencing and genotyping 374 bronchial asthma patients and healthy individuals from an Indian population. Spirometry tests were performed on 80 unrelated patients before and after administration of 200 μg of salbutamol. A postbronchodilator forced expiratory volume in one second (FEV 1 ) change of ≥ 15.3% was considered a good response, and a change of < 15.3% was defined as a poor response, to salbutamol. Results: The pattern of linkage disequilibrium between the ten SNPs showed a single, linked SNP block consisting of sites -468, -367, -47, -20, and 79 having strong linkage disequilibrium, while the SNPs at sites - 1023, -654, 46, 252, and 523 showed very low linkage with one another and with the linked region. The SNPs were found to be organized into 16 haplotypes in the studied population. We found that patients with a homozygous Arg-16 form at nucleotide position 46 are poor responders with probability of 0.81, and patients with a homozygous Gly-16 form are good responders with a probability of 0.73. The responder status to salbutamol treatment and the genotype at nucleotide position 46 in β 2 AR gene of an asthmatic patient are significantly associated in the studied Indian population (χ 2 = 9.98, df = 2, p = 0.0068). Most importantly, this association for responsiveness to salbutamol at nucleotide position 46 is independent of other SNPs in the β 2 AR gene. Conclusion: This study suggests that the SNP at nucleotide position 46 has particular relevance to pharmacogenetics in the Indian population studied. Asthma is one of the most common respiratory diseases worldwide. It is a chronic inflammatory disease of the airways, characterized by recurrent episodes of wheezing, chest tightness and cough- ing, which varies in severity and frequency from person to person [1]. β 2 adrenergic receptor (β 2 AR)-agonists are recommended for first-line use as bronchodilator therapy in asthma [2]. The β 2 AR is the key target for the β 2 -agonist drugs. β 2 AR is widely distributed throughout the body, especially in the smooth muscle cells of the bron- chi, and mediates the action of catecholamines in various tissues and organs [3]. It is G protein- coupled and has an extracellular amino termi- nus, seven transmembrane spanning domains, three intra- and three extracellular loops, and an intracellular carboxyl terminus. The β 2 AR is encoded by an intronless gene on chromosome 5q31-32 [3] and was first cloned in 1987 [4]. The β 2 AR gene contains numerous SNPs, and it has been suggested that some of the polymorphisms may act as disease modifiers in asthma or may be the basis for the known interindividual variation in the bronchodilating response to β 2 -agonists [3]. In the human population, Reihsaus and col- leagues identified nonsynonymous SNPs at nucleotides 46, 79 and 491 that result in changes in amino acid residues 16 and 27 of the amino terminus and 164 of the fourth intracellular loop, respectively [5]. Investigations in cell-based systems have shown that the amino-terminal polymorphisms at amino acid positions 16 and 27 alter cellular trafficking of the receptor, such that the magnitude of agonist-promoted down- regulation varies with certain alleles [6,7]. In transfected cells, it has been shown that poly- morphic receptors are markedly dysfunctional, with altered high-affinity binding and decreased coupling to the stimulatory G protein, G s [3]. Recent studies have demonstrated the presence of a number of SNPs within the 5′-untranslated region (UTR) of the human β 2 AR gene. It con- tains the majority of promoter activity for the human β 2 AR gene and also includes a short open