Propafenone treatment at 50 µM increased connexin-43 protein content significantly and reduced gap junctional coupling in cardiac-relevant cell lines after 24 hours.
In cell models, propafenone induces the intracellular accumulation of non-functional Connexin-43 and decreases gap-junctional coupling, revealing a potential mechanism for unintended proarrhythmic side effects.
Effect estimate: Significant increase in Cx43 protein content at 50 µM propafenone compared to control (p=0.0222 in Ex-HEK cells, p=0.0155 in EPI-7 cells, p=0.0108 in END-2 cells); significant decrease in gap junctional coupling after 24h treatment (p=0.0002 in EPI-7 and p=0.0004 in END-2)
p-value: p=<0.05 for Cx43 increase, 0.0002 and 0.0004 for coupling decrease
Connexin-43 (Cx43) is the principal gap junction protein in the heart, mediating electrical coupling and ion exchange between cardiomyocytes to maintain synchronous contraction. Any disruption or malfunction of Cx43 can lead to arrhythmias and other cardiac issues. Understanding the functions and regulation of Cx43 is vital in both basic research and clinical contexts. Propafenone, a class Ic antiarrhythmic drug, has shown promise in rhythm control; however, its precise impact on cardiac cellular physiology, particularly regarding Cx43, remains incompletely understood. The present study investigated propafenone’s effects on Cx43 protein content, physiology, and underlying mechanisms in cell systems. Cell lines include human embryonic kidney HEK293 cells transfected with Cx43 (Ex-HEK); differentiated murine embryonic carcinoma EPI7 cells with an epithelioid morphology and visceral endoderm-like END2 cells, both endogenously expressing functional Cx43. Cx43 protein contents were determined by Western blot analysis, whereas immunofluorescence (IF) imaging was used to assess the subcellular localization of Cx43 proteins. Dye injections were used to gain insight into the effects of propafenone on Cx43 function. Full-length Cx43 protein levels were dose-dependently increased after propafenone treatment and IF microscopy showed an intracellular accumulation of Cx43 protein, both on heterologously and endogenously expressed Cx43. Propafenone did not alter the Cx43 half-life, in contrast to the lysosomal inhibitor chloroquine. Finally, gap-junctional coupling was decreased by chronic propafenone treatment. We conclude that propafenone increases non-functional Cx43 protein content, resulting in its intracellular accumulation, as a side effect.
Li et al. (Mon,) conducted a other in Cardiac cell models including human embryonic kidney cells transfected with connexin-43 and murine embryonic carcinoma cells expressing endogenous connexin-43. Propafenone vs. Control (DMSO) and chloroquine (10 µM) was evaluated on Connexin-43 protein content and gap junctional coupling in cardiac-related cell lines (Significant increase in Cx43 protein content at 50 µM propafenone compared to control (p=0.0222 in Ex-HEK cells, p=0.0155 in EPI-7 cells, p=0.0108 in END-2 cells); significant decrease in gap junctional coupling after 24h treatment (p=0.0002 in EPI-7 and p=0.0004 in END-2), p=<0.05 for Cx43 increase, 0.0002 and 0.0004 for coupling decrease). Propafenone treatment at 50 µM increased connexin-43 protein content significantly and reduced gap junctional coupling in cardiac-relevant cell lines after 24 hours.