Pharmacological and Transcriptomic Exploration of β2-Adrenergic Receptor-Gα15 Signaling in THP-1-Derived Macrophages.

UNLABELLED: Myocardial infarction and heart failure are leading global causes of mortality. Chronic β-adrenergic receptor (βAR) activation in cardiomyocytes promotes heart failure via Gαs signaling after myocardial infarction, whereas β2AR activation may also provide cardiac protection and repair through alternative pathways. Macrophages play a pivotal role in cardiac repair, and β2AR has been reported to signal via the hematopoietic-specific Gα15 in these cells. We aimed to characterize signaling bias between Gαs and Gα15 downstream of β2AR and to elucidate their roles in macrophage polarization. Using TRUPATH triple assays, we observed that several β2AR agonists activate Gα15 with at least an order of magnitude greater potency than Gαs in this system. In addition, clinically used β-blockers may exhibit differential inhibition on these two pathways. Macrophages are briefly classified into M1 and M2 polarization according to their activating stimuli and functional properties. Transcriptomic profiling of THP-1-derived macrophage-like cells treated with the β2AR agonist clenbuterol revealed enrichment of M1 transcriptional profile and repair-related hallmarks. Knockdown of Gαs showed M1 enrichment, whereas Gα15 knockdown was associated with negative M2 enrichment as well as M1 enrichment. Loss of either Gαs or Gα15 negatively affected repair-associated hallmarks. In contrast, pharmacological intervention of the Gαs-cAMP signaling produced opposing M1/M2 transcriptional responses, while suppressing repair-associated hallmarks. These in vitro findings explore the distinct pharmacological profiles of β2AR ligands toward Gαs and Gα15 and reveal how β2AR agonism may modulate macrophage function through dual-transducer signaling.

SIGNIFICANCE STATEMENT: β2AR agonism engaged Gα15 signaling in the TRUPATH triple assay, with several agonists showing higher apparent potency for Gα15 than Gαs and β-blockers showing distinct inhibitory profiles across Gαs and Gα15. In macrophage-like cells, β2AR was associated with an M1 transcriptional profile. Notably, Gα15 may contribute to M2-associated transcriptional profile under β2AR activation, whereas the Gαs-cAMP showed an opposing M1 transcriptional pattern. These findings suggest that Gα15 signaling may represent a noncanonical pathway contributing to β2AR-induced transcriptional responses in macrophages.