Abstract 17524: c-Src Tyrosine Kinase Is a Potential Therapeutic Target to Prevent Angiotensin-II Mediated Connexin43 Remodeling and Ventricular Arrhythmia
Introduction: We created a transgenic mouse model of cardiac restricted overexpression of angiotensin converting enzyme (ACE8/8). These mice show spontaneous ventricular tachycardia and fibrillation (VT/VF), sudden cardiac death (SCD), and a reduced Cx43 level, which is known to result in impaired conduction and predisposes to arrhythmia. Studies suggest c-Src tyrosine kinase reduces Cx43 by competing for binding to Zonula Occludence-1 at the gap junctions. We sought to determine whether c-Src upregulation by angiotensin II resulted in Cx43 remodeling and VT/VF.
Method: Wild type and ACE8/8 mice with and without treatment with the c-Src inhibitor PP1 (1.5mg/kg IP twice/week x 4 weeks) were studied. Gene expression microarray analysis, Western blotting (with derivatization to dinitrophenylhydrozone to detect oxidized protein levels), and immunohistochemistry staining for Cx43 were performed. Functional assessment of Cx43 was performed using fluorescent dye diffusion.
Results: Expression microarray analysis did not show a change in any gene related to Cx43, suggesting post transcriptional modifications caused Cx43 remodeling. Proteins were more oxidized (increased protein-carbonyl detection), total and phospho (active) c-Src were upregulated, and Cx43 was reduced in ACE8/8 to 33% of control. PP1 effectively reduced total and phospho c-Src, increased Cx43 protein level by 2.1 fold (P=0.002), increased Cx43 at the gap junctions (immunostaining), improved gap junctional communication (dye spread in WT 0.21 ± 0.02 mm, ACE8/8 0.14 ± 0.007 mm, and PP1 0.207 ± 0.02mm), and reduced SCD (increased survival rate from 11% to 86% with PP1 treatment, P < 0.0001). Treatment with the inactive analog, PP3, did not change survival, or Cx43 levels.
Conclusions: In a model of angiotensin II activation, inhibition of c-Src by PP1 improved the Cx43 level and function resulting in prevention of spontaneous VT/VF, which suggests that c-Src is a potential novel therapeutic target to prevent Cx43 remodeling and the risk of ventricular arrhythmia.
- Angiotensin II
- Arrhythmias, treatment of
- Free radicals/Free-radical scavengers
- Ventricular arrhythmia
- © 2010 by American Heart Association, Inc.