Sudden cardiac death (SCD) claims the lives of approximately 350,000 Americans each year. Emerging evidence indicates an important role for genetic predisposition to SCD;however, the molecular determinants have remained elusive. The overall goal of this proposal is to investigate new mechanisms that underlie SCD through the application of innovative technology and the novel use of new genetic models of long QT syndrome 2 (LQT2). This multi-pronged approach includes the investigation of hormone-treated prepubertal, ovariectomized LQT2 rabbits to explore new mechanistic paradigms that underlie the effects of sex hormones on cardiac arrhythmias using in vitro and in silico experimental approaches that will integrate novel molecular, cellular, tissue, and theoretical models. Because gender and the sympathetic nervous system plays a key role in triggering SCD in LQT2, the influence of sex hormones and the autonomic factors on SCD risk will be studied in detail. The proposal is composed of Four Specific Aims:
Aim 1 : To characterize of the sex hormone induced changes in cardiac repolarization (QT duration and cardiac refractory periods), incidence of spontaneous TdP and sudden cardiac death with the use of telemetric ECG monitoring and in vivo invasive electrophysiological studies;
Aim 2 : To analyze the action potential duration, dispersion of repolarization, conduction, triggered activity and the heterogeneities in electrical/mechanical restitution, and conduction block using optical mapping of action potential and calcium transients.
Aim 3 : To define (based on the optical studies) the molecular determinants of the gender differences in cardiac repolarization and excitation by analyzing the gender or sex hormone related differences in the expression of genes coding for the or subunits of the repolarizing potassium currents, calcium currents, and proteins that control Ca++ cycling, and the adrenergic receptors with the use of protein expression studies and quantitative real-time PCR, and cellular electrophysiological studies;
and Aim 4 : To perform a comparative analysis of action potential and calcium-handling properties in myocytes isolated from hormone-treated LQT2 rabbits under control conditions and during autonomic receptor stimulation, using patch-clamp and fluorescent-indicator techniques. b) To use computer modeling to examine how experimentally defined cellular/molecular alterations in these LQT2 models influence afterdepolarizations and arrhythmogenic substrate formation in simulated cardiac tissue. These studies will contribute to the understanding of the mechanisms that trigger and maintain arrhythmias in hormone-treated rabbits, and therefore lead to a better understanding of gender-related arrhythmias in long QT syndrome.

Public Health Relevance

The characterization of transgenic rabbit models for cardiac arrhythmias, the effects of sex hormones, and the identification of the relationship between mutant LQTS genes that encode for dysfunctional ion channels and life-threatening ventricular tachyarrhythmias should provide more complete knowledge into the genetic and electrophysiologic factors involved in repolarization disorders. These studies into altered ventricular repolarization should contribute important new insights into sudden cardiac death mechanisms associated with acquired cardiac disorders that accompany ischemic and nonischemic cardiomyopathy and QT-prolonging drugs. This enhanced knowledge should lead to more effective strategies for prevention of sudden death in a broad spectrum of genetic and acquired cardiac disorders with meaningful public health benefits.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL093205-04
Application #
8242689
Study Section
Special Emphasis Panel (ZRG1-CVS-P (02))
Program Officer
Lathrop, David A
Project Start
2009-04-01
Project End
2014-03-31
Budget Start
2012-04-10
Budget End
2014-03-31
Support Year
4
Fiscal Year
2012
Total Cost
$580,624
Indirect Cost
$161,893
Name
Rhode Island Hospital
Department
Type
DUNS #
075710996
City
Providence
State
RI
Country
United States
Zip Code
02903
Moshal, Karni S; Zhang, Zhe; Roder, Karim et al. (2014) Progesterone modulates SERCA2a expression and function in rabbit cardiomyocytes. Am J Physiol Cell Physiol 307:C1050-7
Terentyev, Dmitry; Rochira, Jennifer A; Terentyeva, Radmila et al. (2014) Sarcoplasmic reticulum Ca²⁺ release is both necessary and sufficient for SK channel activation in ventricular myocytes. Am J Physiol Heart Circ Physiol 306:H738-46
Odening, Katja E; Koren, Gideon (2014) How do sex hormones modify arrhythmogenesis in long QT syndrome? Sex hormone effects on arrhythmogenic substrate and triggered activity. Heart Rhythm 11:2107-15
Qu, Zhilin; Xie, Lai-Hua; Olcese, Riccardo et al. (2013) Early afterdepolarizations in cardiac myocytes: beyond reduced repolarization reserve. Cardiovasc Res 99:6-15
Odening, Katja E; Choi, Bum-Rak; Liu, Gong Xin et al. (2012) Estradiol promotes sudden cardiac death in transgenic long QT type 2 rabbits while progesterone is protective. Heart Rhythm 9:823-32
Liu, Gong-Xin; Choi, Bum-Rak; Ziv, Ohad et al. (2012) Differential conditions for early after-depolarizations and triggered activity in cardiomyocytes derived from transgenic LQT1 and LQT2 rabbits. J Physiol 590:1171-80
Jindal, Hitesh K; Merchant, Elisabeth; Balschi, James A et al. (2012) Proteomic analyses of transgenic LQT1 and LQT2 rabbit hearts elucidate an increase in expression and activity of energy producing enzymes. J Proteomics 75:5254-65
Nivala, Michael; Qu, Zhilin (2012) Calcium alternans in a couplon network model of ventricular myocytes: role of sarcoplasmic reticulum load. Am J Physiol Heart Circ Physiol 303:H341-52
Odening, Katja E; Choi, Bum-Rak; Koren, Gideon (2012) Sex hormones and cardiac arrest in long QT syndrome: does progesterone represent a potential new antiarrhythmic therapy? Heart Rhythm 9:1150-2
Qu, Zhilin; Chung, Douglas (2012) Mechanisms and determinants of ultralong action potential duration and slow rate-dependence in cardiac myocytes. PLoS One 7:e43587

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