Abstract 14385: c-Src Tyrosine Kinase Mediates the Effect of Mitochondrial Oxidative Stress on Gap Junctional Remodeling and Ventricular Tachycardia
Introduction: Reactive oxygen species (ROS) are thought to play a central role in the genesis of arrhythmia. Mitochondria are the major source of cardiac ROS. Studies suggest ROS activates c-Src tyrosine kinase, which reduces Cx43 at the gap junctions by competing with Cx43 for binding to Zonula Occludence-1. We sought to determine the role of mitochondria oxidative stress in the genesis of ventricular arrhythmia in a manganese superoxide dismutase (MnSOD) knock out mouse model. We hypothesized that excess ROS in this model would activate c-Src and reduce Cx43 levels and that inhibition of c-Src would prevent Cx43 remodeling and the risk of arrhythmia.
Method: Wild type and MnSOD+/- mice with and without treatment with the c-Src inhibitor PP1 (1.5 mg/kg IP three times/week x 2 weeks) were studied. Western blotting and immunohistochemistry staining for Cx43 were performed. Mitochondrial ROS was measured by confocal microscopy and flow cytometry from isolated cardiomyocytes using mitoSOX red. In-vivo epicardial mapping was performed using a 30-channel bipolar electrode array with 1 mm resolution.
Results: MnSOD+/- myocytes showed a 66% increase in the level of mitochondrial ROS compared to the control (by mitoSOX, P < 0.05). Total protein level of Cx43 was reduced to the 27% of the control (by Western blot and immunochemistry, P < 0.05). Sustained ventricular tachycardia (VT) was induced by programmed stimulation in 85% of MnSOD+/- mice (6 of 7 mice) compared to none in the control group (P < 0.05). Five of six inducible VTs were monomorphic. Treatment of MnSOD+/- mice with PP1 effectively increased Cx43 at the gap junctions to the 73% of the control level (Western blot and immunostaining, P < 0.05) and reduced the VT inducibility from 85% in untreated MnSOD+/- to 25% in the treatment group (P < 0.05). Treatment with the inactive analog, PP3, did not change the Cx43 levels.
Conclusion: Mitochondrial oxidative stress is associated with increased risk of ventricular arrhythmia and a significant reduction in Cx43 at the gap junctions, providing the impaired conduction substrate for reentry arrhythmia. c-Src tyrosine kinase seems to mediate the effect of mitochondrial ROS on Cx43 and may be an effective antiarrhythmic target in oxidative stress states.
- © 2011 by American Heart Association, Inc.