ABSTRACT
ß-Arrestins are a small family of proteins important for signal transduction at G protein-coupled receptors (GPCRs). ß-Arrestins are involved in the desensitization of GPCRs. Recently, biased ligands possessing different efficacies in activating the G protein- versus the ß-arrestin-dependent signals downstream of a single GPCR have emerged, which can be used to selectively modulate GPCR signal transduction in such a way that desirable signals are enhanced to produce therapeutic effects while undesirable signals of the same GPCR are suppressed to avoid side effects. In the present study, we evaluated agonist bias for compounds developed along a drug discovery project of ß2-adrenoceptor agonists. About 150 compounds, including derivatives of fenoterol, 2-amino-1-phenylethanol and 2-amino-2-phenylethanol, were obtained or synthesized, and initially screened for their ß-adrenoceptor-mediated activities in the guinea pig tracheal smooth muscle relaxation assay or the cardiomyocyte contractility assay. Nineteen bioactive compounds were further assessed using both the HTRF cAMP assay and the PathHunter ß-arrestin assay. Their concentration-response data in stimulating cAMP synthesis and ß-arrestin recruitment were applied to the Black-Leff operational model for ligand bias quantitation. As a result, three compounds (L-2, L-4, and L-12) with the core structure of 5-(1-amino-2-hydroxyethyl)-8-hydroxyquinolin-2(1H)-one were identified as a new series of ß-arrestin-biased ß2-adrenoceptor agonists, whereas salmeterol was found to be Gs-biased. These findings would facilitate the development of novel drugs for the treatment of both heart failure and asthma.
Subject(s)
Adrenergic beta-Agonists/therapeutic use , Ethanolamines/therapeutic use , beta-Arrestins/metabolism , Adrenergic beta-Agonists/chemical synthesis , Animals , Bronchodilator Agents/chemical synthesis , Bronchodilator Agents/therapeutic use , CHO Cells , Cricetulus , Drug Discovery , Ethanolamines/chemical synthesis , Guinea Pigs , HEK293 Cells , Humans , Ligands , Male , Trachea/drug effectsABSTRACT
ß2-Adrenoceptor agonists are highly effective bronchodilators and are widely used in the treatment of both chronic obstructive pulmonary disease (COPD) and asthma. In the last 15 years, there has been great interest within the pharmaceutical industry in the discovery of a long ß2-adrenoceptor agonist for a mono-therapy or combination therapy. The search for new long-acting ß2-adrenoreceptor agonists (LABA's), for the treatment of asthma and COPD, has become a very active area of drug discovery. This article reviews the mechanisms, potential candidates and research advances of long ß2-adrenoceptor agonists.
