Abstract 16279: Measurements of ROS in Subcellular Compartments in Adult Cardiomyocytes in a Model of Heart Failure and Sudden Cardiac Death
Intro: Reactive oxygen species (ROS) are central to the pathophysiology of heart failure (HF) and sudden cardiac death (SCD), but the effects of ROS depend on where and how ROS are generated. Investigation of compartmentalized ROS in HF and arrhythmogenesis has been limited by the lack of: (1) quantitative, compartment-specific ROS measurements, and (2) an experimental model that mimics human HF with spontaneous arrhythmic SCD.
Objective: To determine which sources of ROS (e.g, NADPH oxidase, mitochondria) contribute to oxidative stress in the submembrane compartment, cytoplasm, and mitochondria of adult cardiac myocytes isolated from failing hearts and to explore the effects of angiotensin II (AngII) activation and inhibition by AngII receptor blockers (ARB) on ROS.
Methods: In a unique guinea pig model that mimics human non-ischemic HF with a high incidence of spontaneous arrhythmic SCD, we performed in vivo gene transfer with novel, genetically-encoded ratiometric redox sensors targeted to cytosol (cROS), mitochondria, or caveolae (CavROS) of cardiomyocytes. In isolated left ventricular (LV) myocytes, we quantified ROS during field stimulation (1 Hz, 37°C) in the presence or absence of mitoTEMPO, apocynin, AngII and ARB.
Results: Baseline ROS (mROS>cROS) in HF myocytes was higher than in controls and were strongly suppressed by MitoTEMPO. Exogenous H2O2 increased ROS in all intracellular compartments, but scavenging of mROS was impaired more than cROS in HF, consistent with downregulation of mitochondrial antioxidant enzymes. Interestingly, apocynin, an NADPH oxidase (NOX) inhibitor, decreased baseline ROS, but ARB did not, suggesting constitutive activation of NOX in HF. AngII increased cROS, CavROS and mROS in an ARB-inhibitable manner, while MitoTEMPO prevented the AngII-induced mROS, but not the cROS response.
Conclusions: Mitochondria are a source of cellular oxidative stress in failing arrhythmogenic hearts, but also are the major sink of ROS. Impairment of the mROS scavenging system may cause failing hearts to become more vulnerable to demand-induced oxidative stress or susceptible to NOX derived ROS. Maintaining global redox balance by preventing mitochondrial dysfunction may an effective therapeutic strategy for HF and SCD.
- Mitochondrial energetics, heart failure, arrhythmias
- Oxidative stress
- Sudden cardiac death
- Heart failure
Author Disclosures: S. Dey: Research Grant; Significant; AHA-14POST20380749. D. DeMazumder: None. B. O’Rourke: None.
- © 2016 by American Heart Association, Inc.