Screening the Tox21 Compound Library for Chemicals That Stimulate the Adrenergic β1 Receptor.

Beta-1 adrenergic receptors (ADRβ1) are critical regulators of cardiac function; however, the potential modulation of ADRβ1 by environmental chemicals remains largely underexplored, raising concerns about unintended impacts on cardiovascular health. We applied a quantitative high-throughput screening (qHTS) approach to identify ADRβ1 agonists within the Tox21 10K compound library, which includes environmental chemicals, pharmaceuticals, industrial agents, and consumer products, using an HTRF-based cAMP assay in ADRβ1-overexpressing HEK293 cells. Primary screening of 8,947 unique compounds identified 118 potential ADRβ1 agonists. Among these, 94 were confirmed and further evaluated for β-adrenergic receptor subtype selectivity (ADRβ2 and ADRβ3) and hERG channel inhibition to assess potential cardiotoxicity liability. Known ADRβ1 agonists, isoproterenol (EC50, 0.91 nM) and dobutamine (EC50, 10 nM), were identified, supporting the validity of the assay. In addition, several compounds with limited prior ADRβ1-specific characterization, such as GR 103691 and N,N'-dibenzylethane-1,2-diamine, demonstrated subtype-selective or mixed agonist profiles, with some exhibiting minimal hERG inhibition. These findings expand the catalog of ADRβ1 modulators and demonstrate the utility of qHTS for identifying chemicals that may affect cardiovascular signaling pathways.