Inhibition of c-Src Tyrosine Kinase Prevents Angiotensin II–Mediated Connexin-43 Remodeling and Sudden Cardiac Death

Abstract

Objectives We sought to test whether c-Src tyrosine kinase mediates connexin 43 (Cx43) reduction and sudden cardiac death in a transgenic mouse model of cardiac-restricted overexpression of angiotensin-converting enzyme (ACE8/8). Background Renin-angiotensin system (RAS) activation is associated with an increased risk of arrhythmia and sudden cardiac death; however, that mechanism is not well understood. The upregulation of c-Src by angiotensin II may result in the reduction of Cx43, which impairs gap junction function and provides a substrate for arrhythmia. Method Wild-type and ACE8/8 mice with and without treatment with the c-Src inhibitor PP1 were studied. Telemetry monitoring, in vivo electrophysiology studies, Western blot analyses for total and phosphorylated c-Src and Cx43, immunohistochemistry staining for Cx43, and functional assessment of Cx43 with fluorescent dye diffusion were performed. Results The majority of the arrhythmic deaths resulted from ventricular tachycardia denegerating to ventricular fibrillation (83%). Levels of total and phosphorylated c-Src were increased and Cx43 reduced in ACE8/8 mice. PP1 reduced total and phospho c-Src levels, increased the Cx43 level by 2.1-fold (P < 0.005), increased Cx43 at the gap junctions (immunostaining), improved gap junctional communication (dye spread), and reduced ventricular tachycardia inducibility and sudden cardiac death. The survival rate increased from 11% to 86% with four weeks of PP1 treatment (P < 0.005). Treatment with an inactive analog did not change survival or Cx43 levels. Conclusion RAS activation is associated with c-Src upregulation, Cx43 loss, reduced myocyte coupling, and arrhythmic sudden death, which can be prevented by c-Src inhibition. This suggests that an increase in c-Src activity may help mediate RAS-induced arrhythmias and that c-Src inhibitors might exert antiarrhythmic activity.

Association between Serum Uric Acid Level and Ventricular Tachyarrhythmia in Heart Failure Patients with Implantable Cardioverter-Defibrillator

“…It has been shown that cardiomyopathy is associated with oxidative stress, which is an imbalance between the production and neutralization of reactive oxygen species [8]. In addition, several experimental studies suggest that oxidant stress can lead to focal activity and reentry, and is a cause of VT [9, 10]. Serum UA is a metabolic product in the terminal stage of purine metabolism produced via the action of xanthine oxidase, an enzyme that is implicated in oxidative processes [11].…”

Newly Identified NO‐Sensor Guanylyl Cyclase/Connexin 43 Association Is Involved in Cardiac Electrical Function

“…A modified protocol from Sovari et al17 was used to evaluate GJ function in WT and GCα1‐KO mice hearts. Hearts were harvested and washed in PBS, as described previously.…”

“…In addition to the GCα1‐KO mouse model, we used an angiotensin II (AngII)–induced cardiac hypertrophy mouse model because AngII‐treated animals have decreased NO‐stimulated GC1 activity in the cardiovascular system 15. In our specific model, we observed cardiac hypertrophy, but the cardiac remodeling associated with arrhythmic sudden death and heart failure has not yet taken place, unlike other renin‐angiotensin mouse models 16, 17…”

Sudden cardiac death in the young: cytokines and pathways

“…Cx43 upregulation occurs primarily at the intercalated disks and correlates with gap junction functional improvement, and associated with a reduced risk of ventricular tachycardia inducibility and SCD. The activation of renin-angiotensin system is associated with c-Src upregulation, Cx43 loss, reduced myocyte coupling and arrhythmic sudden death (43).…”