Ca2+ dependent arrhythmias, a leading cause of sudden cardiac death, often arises unexpectedly in heart muscle. The proposed work seeks to examine the hypothesis that spatial remodeling of key intracellular Ca2+ signaling proteins may underlie this dysfunction. The has recently discovered in preliminary work that even a small (~10%) change in the spatial distribution of these proteins can dramatically alter the stability of the Ca2+ control system;as clusters of the proteins get closer together, dramatic instability arises and changes normal cellular stability into an arrhythmogenic substrate. The proposed work will combine mathematical modeling of cardiac Ca2+ signaling with critical experimental investigations in single cells, trabeculae, and whole heart to determine how abnormal Ca2+ signals arise at the cellular level and affect electrical activity in the heart. Ryanodine receptors (RyRs) form clusters in the junctional sarcoplasmic reticulum and constitute the Ca2+ release unit (CRU) of the heart. The CRUs are apposed to nearby sarcolemmal or transverse tubular membranes containing L-type Ca2+ channels (LTCC). On depolarization, the LTCC trigger the CRU to produce Ca2+ sparks which, when synchronized, produce a [Ca2+]i transient. When they are not synchronized, rare spontaneous Ca2+ sparks do not normally trigger nearby CRUs because local [Ca2+]i is insufficiently elevated to activate the RyRs in the CRU. Remodeling of the spatial distribution of the CRUs in specific disease state, however, may change that safety factor and contribute to the aberrant triggering of CRUs. Should this occur with great frequency, an otherwise normal Ca2+ spark will trigger an arrhythmogenic propagating wave of elevated Ca2+ at the cellular level. This propagating wave of elevated Ca2+ wave can activate inward current to produce extrasystoles and arrhythmias. Using two animal models prone to unexpected Ca2+ dependent arrhythmogenesis, the PI will investigate the core hypothesis that CRU spatial remodeling underlies or contributes to arrhythmic dysfunction. Mice expressing genetically defined familiar hypertrophic cardiomyopathy (FHC) and spontaneous hypertensive rats will be examined. Three questions will be addressed: (1) Does sarcomere shortening destabilize Ca2+ control system according to new, state- of-the-art mathematical models? (2) If so, can pharmacological means of shortening CRU spacing also produce Ca2+ instability? (3) Finally, do the animal models that have unexplained Ca2+ dependent arrhythmogenesis reveal the same dependence of their arrhythmias on CRU spacing? Taken together, the planned work will provide new information of cardiac Ca2+ signaling and arrhythmogenesis and lay the foundation for new approaches to treating perplexing and heretofore unexplained Ca2+ dependent arrhythmia

Public Health Relevance

Calcium dependent arrhythmias, a leading cause of sudden cardiac death, often arises unexpectedly in heart muscle. The proposed work seeks to test the hypothesis that spatial remodeling of key intracellular calcium signaling proteins during the development of some heart diseases may underlie this dysfunction. These studies bring together mathematical modeling, supercomputer simulations, state-of-the-art imaging, and heart disease models to examine how even subtle changes in the spatial distribution of these key molecules can trigger arrhythmias and sudden cardiac death. These studies will lay the foundation for new approaches to treating perplexing and heretofore unexplained calcium dependent cardiac arrhythmias.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL090880-02
Application #
7882352
Study Section
Cardiac Contractility, Hypertrophy, and Failure Study Section (CCHF)
Program Officer
Przywara, Dennis
Project Start
2009-07-01
Project End
2013-06-30
Budget Start
2010-07-01
Budget End
2011-06-30
Support Year
2
Fiscal Year
2010
Total Cost
$379,850
Indirect Cost
Name
University of California Davis
Department
Pharmacology
Type
Schools of Medicine
DUNS #
047120084
City
Davis
State
CA
Country
United States
Zip Code
95618
Hegyi, Bence; Bossuyt, Julie; Griffiths, Leigh G et al. (2018) Complex electrophysiological remodeling in postinfarction ischemic heart failure. Proc Natl Acad Sci U S A 115:E3036-E3044
Hegyi, Bence; Bossuyt, Julie; Ginsburg, Kenneth S et al. (2018) Altered Repolarization Reserve in Failing Rabbit Ventricular Myocytes: Calcium and ?-Adrenergic Effects on Delayed- and Inward-Rectifier Potassium Currents. Circ Arrhythm Electrophysiol 11:e005852
Hegyi, Bence; Horváth, Balázs; Váczi, Krisztina et al. (2017) Ca2+-activated Cl- current is antiarrhythmic by reducing both spatial and temporal heterogeneity of cardiac repolarization. J Mol Cell Cardiol 109:27-37
Awasthi, Samir; Izu, Leighton T; Mao, Ziliang et al. (2016) Multimodal SHG-2PF Imaging of Microdomain Ca2+-Contraction Coupling in Live Cardiac Myocytes. Circ Res 118:e19-28
Hegyi, Bence; Bányász, Tamás; Shannon, Thomas R et al. (2016) Electrophysiological Determination of Submembrane Na(+) Concentration in Cardiac Myocytes. Biophys J 111:1304-1315
Chen-Izu, Ye; Izu, Leighton T (2015) Measuring the metrics: Correlating t-tubule structure and muscle contraction in the intact heart. J Mol Cell Cardiol 85:153-4
Banyasz, T; Szentandrássy, N; Magyar, J et al. (2015) An emerging antiarrhythmic target: late sodium current. Curr Pharm Des 21:1073-90
Izu, Leighton T; Bányász, Tamás; Chen-Izu, Ye (2015) Optimizing Population Variability to Maximize Benefit. PLoS One 10:e0143475
Hegyi, Bence; Chen-Izu, Ye; Jian, Zhong et al. (2015) KN-93 inhibits IKr in mammalian cardiomyocytes. J Mol Cell Cardiol 89:173-6
Jian, Zhong; Han, Huilan; Zhang, Tieqiao et al. (2014) Mechanochemotransduction during cardiomyocyte contraction is mediated by localized nitric oxide signaling. Sci Signal 7:ra27

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