EL20, a potent antiarrhythmic compound, selectively inhibits calmodulin-deficient ryanodine receptor type 2

Area of Science:

• Cardiovascular Research
• Molecular Cardiology
• Pharmacology

Background:

• Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an arrhythmogenic disorder linked to mutations in the cardiac ryanodine receptor RyR2.
• Increased diastolic calcium (Ca2+) leak from the sarcoplasmic reticulum (SR) is a hallmark of CPVT, often associated with Calmodulin (CaM) dissociation from RyR2.

Purpose of the Study:

• To evaluate the efficacy of the tetracaine-derivative compound EL20 in inhibiting aberrant Ca2+ release from RyR2 in a CPVT mouse model.
• To elucidate the underlying mechanism by which EL20 exerts its inhibitory effects on RyR2 function.

Main Methods:

• Assessment of spontaneous Ca2+ sparks in cardiomyocytes and inducible ventricular tachycardia in CPVT mice (R176Q/+ RyR2 mutation).
• Single-channel studies of sheep cardiac SR and purified RyR2 reconstituted into proteoliposomes, with and without exogenous CaM, to determine EL20's mechanism of action.

Main Results:

• EL20 demonstrated potent inhibition of abnormal Ca2+ release in R176Q/+ myocytes (IC50 = 35.4 nM) and reduced arrhythmias in vivo.
• EL20 inhibited purified RyR2 single-channel activity with an IC50 of 8.2 nM.
• The presence of CaM significantly reduced EL20's inhibitory potency (200- to 1000-fold), indicating CaM-dependent inhibition.

Conclusions:

• EL20 presents a potential therapeutic strategy for antiarrhythmic drug development targeting leaky RyR2 channels, particularly those associated with CaM dissociation in heart failure.
• CaM dissociation may play a significant role in the pathogenesis of CPVT arrhythmias linked to the R176Q mutation.