Department of Physics, Portland State University, Portland, Oregon.
Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas; Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas.
Heart Rhythm. 2018 Apr;15(4):578-586. doi: 10.1016/j.hrthm.2017.12.017. Epub 2017 Dec 14.
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an arrhythmogenic disorder caused by mutations in the cardiac ryanodine receptor RyR2 that increase diastolic calcium cation (Ca) leak from the sarcoplasmic reticulum (SR). Calmodulin (CaM) dissociation from RyR2 has been associated with diastolic Ca leak in heart failure.
Determine whether the tetracaine-derivative compound EL20 inhibits abnormal Ca release from RyR2 in a CPVT model and investigate the underlying mechanism of inhibition.
Spontaneous Ca sparks in cardiomyocytes and inducible ventricular tachycardia were assessed in a CPVT mouse model, which is heterozygous for the R176Q mutation in RyR2 (R176Q/+ mice) in the presence of EL20 or vehicle. Single-channel studies using sheep cardiac SR or purified RyR2 reconstituted into proteoliposomes with and without exogenous CaM were used to assess mechanisms of inhibition.
EL20 potently inhibits abnormal Ca release in R176Q/+ myocytes (half-maximal inhibitory concentration = 35.4 nM) and diminishes arrhythmia in R176Q/+ mice. EL20 inhibition of single-channel activity of purified RyR2 occurs in a similar range as seen in R176Q/+ myocytes (half-maximal inhibitory concentration = 8.2 nM). Inhibition of single-channel activity for cardiac SR or purified RyR2 supplemented with 100-nM or 1-μM CaM shows a 200- to 1000-fold reduction in potency.
This work provides a potential therapeutic mechanism for the development of antiarrhythmic compounds that inhibit leaky RyR2 resulting from CaM dissociation, which is often associated with failing hearts. Our data also suggest that CaM dissociation may contribute to the pathogenesis of arrhythmias with the CPVT-linked R176Q mutation.
儿茶酚胺多形性室性心动过速（CPVT）是一种由心脏兰尼碱受体 RyR2 中的突变引起的心律失常疾病，该突变会增加肌浆网（SR）中的舒张钙离子（Ca）渗漏。钙调蛋白（CaM）与 RyR2 的解离与心力衰竭中的舒张 Ca 渗漏有关。
确定四卡因衍生物化合物 EL20 是否抑制 CPVT 模型中 RyR2 的异常 Ca 释放，并研究抑制的潜在机制。
在 RyR2 的 R176Q 突变杂合（R176Q/+ 小鼠）的 CPVT 小鼠模型中评估自发 Ca 火花和可诱导的室性心动过速，同时存在 EL20 或载体。使用绵羊心脏 SR 或纯化的 RyR2 重构到含有和不含有外源性 CaM 的蛋白脂质体中的单通道研究用于评估抑制机制。
EL20 强烈抑制 R176Q/+ 心肌细胞中的异常 Ca 释放（半抑制浓度=35.4 nM），并减少 R176Q/+ 小鼠的心律失常。EL20 对纯化 RyR2 的单通道活性的抑制作用与在 R176Q/+ 心肌细胞中观察到的抑制作用相似（半抑制浓度=8.2 nM）。当心脏 SR 或纯化 RyR2 补充 100 nM 或 1 μM CaM 时，对单通道活性的抑制作用的效力降低 200 至 1000 倍。
这项工作为开发抑制 CaM 解离导致的漏 RyR2 的抗心律失常化合物提供了一种潜在的治疗机制，而 CaM 解离通常与衰竭的心脏有关。我们的数据还表明，CaM 解离可能导致与 CPVT 相关的 R176Q 突变的心律失常的发病机制。
