Paradoxical effect of increased diastolic Ca(2+) release and decreased sinoatrial node activity in a mouse model of catecholaminergic polymorphic ventricular tachycardia.
Paradoxical effect of increased diastolic Ca(2+) release and decreased sinoatrial node activity in a mouse model of catecholaminergic polymorphic ventricular tachycardia.
复制标题
DOI：
10.1161/circulationaha.111.075382
复制
发表时间：
2012-07-24
期刊：
影响因子：
37.8
通讯作者：
Gómez AM
中科院分区：
文献类型：
--
作者：
Neco P;Torrente AG;Mesirca P;Zorio E;Liu N;Priori SG;Napolitano C;Richard S;Benitah JP;Mangoni ME;Gómez AM
儿茶酚胺能多形性室性心动过速 (CPVT) 的特点是应激引发的晕厥和猝死。 CPVT 患者表现出窦房结 (SAN) 功能障碍，其机制仍待探索。我们研究了携带 CPVT 相关兰尼碱受体突变 (RyR2R4496C) 的小鼠及其野生型 (WT) 同窝小鼠的 SAN [Ca2+]i 处理情况。体内遥测记录显示，注射异丙肾上腺素 (ISO) 后，RyR2R4496C 小鼠的 SAN 自动性受损，类似于 CPVT 患者运动后观察到的情况。通过共聚焦显微镜测量完整 SAN 内 SAN 细胞中的自发 [Ca2+]i 瞬变来探索起搏器活性。在 75% 的病例中，RyR2R4496C SAN 在 β-肾上腺素能刺激下起搏器活动明显减慢，变时性反应受损，并伴有停顿的出现（自发 [Ca2+]i 瞬变和动作电位）。 RyR2R4496C SAN 中的 Ca2+ 火花频率增加了 2 倍。对分离的 RyR2R4496C SAN 细胞进行的全细胞膜片钳实验表明，L 型 Ca2+ 电流 (ICa,L) 密度降低了约 50%，这种效应因内部 Ca2+ 缓冲而减弱。 ISO 将 Ca2+ 火花和波的频率分别显着提高了约 5 倍和约 10 倍。有趣的是，在存在 ISO 的情况下，RyR2R4496C SAN 细胞中的肌浆网 (SR) Ca2+ 含量显着降低，这可能有助于停止“Ca2+-时钟”节律的产生，从而引发 SAN 暂停。 SAN 中 RyR2R4496C 活性的增加导致 SAN 自动性意外下降，这是由于舒张期期间 ICa、L 和 SR Ca2+ 消耗的 Ca2+ 依赖性减少，从而确定了导致 CPVT 患者 SAN 功能障碍的亚细胞病理生理学改变。
Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is characterized by stress-triggered syncope and sudden death. CPVT patients manifest sino-atrial node (SAN) dysfunction, the mechanisms of which remain unexplored. We investigated SAN [Ca2+]i handling in mice carrying the CPVT-linked mutation of ryanodine receptor (RyR2R4496C) and on their wild-type (WT) littermates. In vivo telemetric recordings showed impaired SAN automaticity in RyR2R4496C mice following Isoproterenol (ISO) injection, analogous to what was observed in CPVT patients after exercise. Pacemaker activity was explored by measuring spontaneous [Ca2+]i transients in SAN cells within the intact SAN by confocal microscopy. RyR2R4496C SAN presented significantly slower pacemaker activity and impaired chronotropic response under β-adrenergic stimulation, accompanied by the appearance of pauses (in spontaneous [Ca2+]i transients and action potentials) in 75% of the cases. Ca2+ spark frequency was increased by 2-fold in RyR2R4496C SAN. Whole-cell patch-clamp experiments performed on isolated RyR2R4496C SAN cells showed that L-type Ca2+ current (ICa,L) density was reduced by ~50%, an effect blunted with internal Ca2+ buffering. ISO dramatically increased the frequency of Ca2+ sparks and waves by ~5 and ~10-fold, respectively. Interestingly, the sarcoplasmic reticulum (SR) Ca2+ content was significantly reduced in RyR2R4496C SAN cells in the presence of ISO, which may contribute to stopping the “Ca2+-clock” rhythm generation, originating SAN pauses. The increased activity of RyR2R4496C in SAN leads to an unanticipated decrease on SAN automaticity by Ca2+-dependent decrease of ICa,L and SR Ca2+ depletion during diastole, identifying subcellular pathophysiologic alterations contributing to the SAN dysfunction in CPVT patients.