Investigating The Potential Agonist Activity of Carvedilol and The Proliferative Effects of Beta Blockers in Smooth Muscle Cells

Abstract

Introduction Beta-adrenergic receptors (βARs) are critical in regulating heart physiological processes. While β-blockers, such as carvedilol, are traditionally used to inhibit βAR activity, recent studies suggest that carvedilol may have biased agonism, selectively activating β-arrestin-mediated signaling pathways while inhibiting G protein-mediated signalling. This study aimed to investigate the potential agonistic effects of carvedilol on βARs and to further uncover the roles of β-arrestin 2 and dynamin in βARs signalling. Methods HEK293 cells were used to perform pharmacological assays to measure real-time cAMP levels and Western blot analysis to assess the activation of downstream signaling pathways, including ERK1/2 phosphorylation. Additionally, CRISPR-Cas9 modified HEK293 cells lacking β-arrestin 2 and 3 were employed to determine the specific contributions of β-arrestin to receptor desensitization and internalization. We also explored the role of the Dynamin-K44A mutant in receptor internalization and its effect on βAR signalling. Results The findings imply that carvedilol shows weak agonist activity by inducing minimal cAMP production compared to other βAR agonists. This aligns with the hypothesis that carvedilol might act as a biased agonist on βARs. The absence of β-arrestin 2 resulted in enhanced cAMP responses to isoproterenol and dobutamine, supporting the role of β-arrestin in receptor desensitization. Western blot analysis revealed that isoproterenol and salbutamol decreased phospho-p38 levels in smooth muscle cells, suggesting enhanced proliferation, while carvedilol increased phospho-p38 levels, indicating increased apoptosis. These findings underscore the complexity of βAR signalling and highlight the need for further research to examine the potential carvedilol biased agonism intended for therapeutic benefit.