Enhanced cardiac PI3Kα signalling mitigates arrhythmogenic electrical remodelling in pathological hypertrophy and heart failure.
OBJECTIVE
Cardiac hypertrophy and heart failure are associated with QT prolongation and lethal ventricular arrhythmias resulting from decreased K(+) current densities and impaired repolarization. Recent studies in mouse models of physiological cardiac hypertrophy revealed that increased phosphoinositide-3-kinase-α (PI3Kα) signalling results in the up-regulation of K(+) channels and the normalization of ventricular repolarization. The experiments here were undertaken to test the hypothesis that increased PI3Kα signalling will counteract the adverse electrophysiological remodelling associated with pathological hypertrophy and heart failure.


RESULTS
In contrast to wild-type mice, left ventricular (LV) hypertrophy, induced by transverse aortic constriction (TAC), did not result in prolongation of ventricular action potentials or QT intervals in mice with cardiac-specific expression of constitutively active PI3Kα (caPI3Kα). Indeed, repolarizing K(+) currents and K(+) channel subunit transcripts were increased in caPI3Kα + TAC LV myocytes in proportion to the TAC-induced cellular hypertrophy. Congestive heart failure in a transgenic model of dilated cardiomyopathy model is accompanied by prolonged QT intervals and ventricular action potentials, reduced K(+) currents and K(+) channel transcripts. Increased PI3Kα signalling, but not renin-angiotensin system blockade, in this model also results in increased K(+) currents and improved ventricular repolarization.


CONCLUSIONS
In the setting of pathological hypertrophy or heart failure, enhanced PI3Kα signalling results in the up-regulation of K(+) channel subunits, normalization of K(+) current densities and preserved ventricular function. Augmentation of PI3Kα signalling, therefore, may be a useful and unique strategy to protect against the increased risk of ventricular arrhythmias and sudden death associated with cardiomyopathy.
Department of Developmental Biology,  Washington University Medical School, 660 South Euclid Avenue Box 8103, St Louis, MO 63110-1093,  USA.
Kai-Chien
KC
Yang
Patrick Y
PY
Jay
Julie R
JR
McMullen
Jeanne M
JM
Nerbonne
D000200:Action Potentials; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000209:etiology / Q000503:physiopathology*; D002311:Cardiomyopathy, Dilated / Q000503:physiopathology; D058534:Class I Phosphatidylinositol 3-Kinases; D004562:Electrocardiography; D006333:Heart Failure / Q000503:physiopathology*; D017379:Hypertrophy, Left Ventricular / Q000503:physiopathology*; D008297:Male; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*
D058534:Class I Phosphatidylinositol 3-Kinases; D019869:Phosphatidylinositol 3-Kinases; D015221:Potassium Channels; C546639:Pik3ca protein, mouse