Pharmacogenomics of β2-agonist: key focus on signaling pathways.

Asthma is one of the most common respiratory diseases, where inhalation and exhalation are obstructed due to narrowing of the airways by broncho-constriction or by inflammation. Among all the available anti-asthma therapies, β₂-agonists are the most effective bronchodilators available, and give rapid relief of asthma symptoms. Evidence suggests that the degree of β₂-agonist response varies greatly between patients and genetic factors have a major role in it. Despite several studies on the β₂-agonist pharmacogenetics, significant gaps in knowledge still remain and need to be resolved before the pharmacotyping of β₂-agonist responsiveness comes to clinical practice. As we know, β₂-agonists show their influence by targeting β₂-adrenergic receptors, leading to the activation of β₂-adrenergic receptors and its downstream cascade. Signaling through β₂-adrenergic receptors mediates numerous airway functions by regulating broncho-constriction and dilation pathways. Therefore, it is an important prerequisite to understand these pathways, which will assist in defining the variability in therapeutic responses for β₂-agonists. Owing to the complexity of the action of a β₂-agonist and its therapeutic response, a broader genomics approach will help in optimizing therapy for the individual patient. This might be achieved by considering and focusing on receptor/s at which the drug binds directly, signal transduction cascades or downstream proteins and proteins involved in the relaxation and constriction of the airway smooth muscle. Considering that a drug response may involve a large number of proteins, it seems unlikely that a single polymorphism or haplotype in a single gene would explain a high degree of drug response variability in a consistent fashion. Thus, it shows that a polygenic approach will be more appropriate. In order to follow this, the mode of action of the β₂-agonist and its downstream signaling cascade should essentially be assessed to resolve the β₂-agonist enigma. [ABSTRACT FROM AUTHOR]