Key result
Cardiac CFTR overexpression triggers stress-induced sudden death and severe AV block in mice.
Overexpression of the CFTR chloride channel in the mouse heart leads to stress-induced AV block, ventricular arrhythmias, and sudden death, highlighting a potential role for anionic channels in arrhythmogenesis.
CFTR overexpression may promote stress-induced arrhythmias in mice; leaves open whether anionic channels contribute to human arrhythmogenesis.
The identification and analysis of several cationic ion channels and their associated genes have greatly improved our understanding of the molecular and cellular mechanisms of cardiac arrhythmia. Our objective in this study was to examine the involvement of anionic ion channels in cardiac arrhythmia. We used a transgenic mouse model to overexpress the human cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes a cAMP-regulated chloride channel. We used RNase protection and in situ hybridization assays to determine the level of CFTR expression, and radiotelemetry and in vivo electrophysiological study in combination with pharmacological intervention to analyse the cardiac function. Cardiac CFTR overexpression leads to stress-related sudden death in this model. In vivo intracardiac electrophysiological studies performed in anaesthetized mice showed no significant differences in baseline conduction parameters including atrial-His bundle (AH) or His bundle-ventricular (HV) conduction intervals, atrioventricular (AV) Wenckebach or 2:1 AV block cycle length and AV nodal functional refractory period. However, following isoproterenol administration, there was marked slowing of conduction parameters, including high-grade AV block in transgenic mice, with non-sustained ventricular tachycardia easily inducible using programmed stimulation or burst pacing. Our sudden death mouse model can be a valuable tool for investigation of the role of chloride channels in arrhythmogenesis and, potentially, for future evaluation of novel anti-arrhythmic therapeutic strategies and pharmacological agents.
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Ye et al. (2010) studied Cardiac arrhythmia and sudden death (n=109). Cardiac CFTR overexpression vs. Wild-type littermates was evaluated on Spontaneous mortality and isoproterenol-induced atrioventricular block. Cardiac overexpression of the human CFTR chloride channel in transgenic mice led to stress-related sudden death and severe isoproterenol-induced atrioventricular conduction block.
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