Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease characterized by life-threatening arrhythmias elicited by
adrenergic activation. CPVT is caused by mutations in the cardiac
ryanodine receptor gene (
RyR2). In vitro studies demonstrated that
RyR2 mutations respond to sympathetic activation with an abnormal diastolic Ca(2+) leak from the sarcoplasmic reticulum; however the pathways that mediate the response to
adrenergic stimulation have not been defined. In our
RyR2(R4496C+/-) knock-in mouse model of CPVT we tested the hypothesis that inhibition of
Ca(2+)/calmodulin-dependent protein kinase II (
CaMKII) counteracts the effects of
adrenergic stimulation resulting in an antiarrhythmic activity.
CaMKII inhibition with
KN-93 completely prevented
catecholamine-induced sustained
ventricular tachyarrhythmia in
RyR2(R4496C+/-) mice, while the inactive congener
KN-92 had no effect. In ventricular myocytes isolated from the hearts of
RyR2(R4496C+/-) mice,
CaMKII inhibition with an
autocamtide-2 related inhibitory
peptide or with
KN-93 blunted triggered activity and transient inward currents induced by
isoproterenol.
Isoproterenol also enhanced the activity of the
sarcoplasmic reticulum Ca(2+)-ATPase (SERCA), increased spontaneous Ca(2+) release and spark frequency.
CaMKII inhibition blunted each of these parameters without having an effect on the SR Ca(2+) content. Our data therefore indicate that
CaMKII inhibition is an effective intervention to prevent arrhythmogenesis (both in vivo and in vitro) in the
RyR2(R4496C+/-) knock-in mouse model of CPVT. Mechanistically,
CAMKII inhibition acts on several elements of the EC coupling cascade, including an attenuation of SR Ca(2+) leak and blunting
catecholamine-mediated SERCA activation.
CaMKII inhibition may therefore represent a novel therapeutic target for patients with CPVT.