In situ confocal imaging in intact heart reveals stress-induced Ca(2+) release variability in a murine catecholaminergic polymorphic ventricular tachycardia model of type 2 ryanodine receptor(R4496C+/-) mutation.
In situ confocal imaging in intact heart reveals stress-induced Ca(2+) release variability in a murine catecholaminergic polymorphic ventricular tachycardia model of type 2 ryanodine receptor(R4496C+/-) mutation.
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DOI：
10.1161/circep.111.969733
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发表时间：
2012-08-01
期刊：
影响因子：
--
通讯作者：
Song LS
中科院分区：
文献类型：
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作者：
Chen B;Guo A;Gao Z;Wei S;Xie YP;Chen SR;Anderson ME;Song LS
儿茶酚胺能多态性室性心动过速（CPVT）与蛋白质突变直接相关（例如，RyR 2 R4496 C）负责心脏中的细胞内Ca 2+稳态。然而，CPVT的Ca 2+释放功能障碍的机制仅在分离的细胞中进行了研究，而不是在原位未破坏的心肌中。我们使用激光扫描共聚焦显微镜研究了野生型（WT）和RyR 2 R4496 C +/−小鼠完整Langendorff灌注心脏（离体）中的原位肌细胞Ca 2+动力学。我们发现WT和RyR 2 R4496 C +/−心脏的心肌细胞均显示出均匀、同步的Ca 2+瞬变。在WT和RyR 2 R4496 C +/−心脏中，搏动之间的Ca 2+瞬变幅度相当，具有相同的激活和衰减动力学，表明肌膜Ca 2+通道和突变的RyR 2 R4496 C +/−通道之间的兴奋-收缩（EC）偶联在基线静息条件下保持完整。肾上腺素能刺激后，RyR 2 R4496 C +/−心脏表现出高度的Ca 2+释放变异性（CRV）。单个分离的心肌细胞中不存在不同的Ca 2+释放模式，其与细胞周期长度无关，在相邻的心肌细胞中是同步的，并且与CPVT相关。一个类似的模式动作电位的变异，这是同步相邻的心肌细胞，也揭示了肾上腺素能应激在完整的心脏，但不是在孤立的心肌细胞。我们使用原位共聚焦成像方法的研究表明，突变的RyR 2在休息时功能正常，但在强烈的肾上腺素能刺激后显示出高度的CRV。CRV是由电缺陷引起的Ca 2+释放异常，而不是突变心室肌细胞中Ca 2+释放对动作电位的响应失败。我们的数据提供了重要的见解钙释放和电功能障碍的CPVT模型。
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is directly linked to mutations in proteins (e.g., RyR2R4496C) responsible for intracellular Ca2+ homeostasis in the heart. However, the mechanism of Ca2+ release dysfunction underlying CPVT has only been investigated in isolated cells but not in the in situ undisrupted myocardium. We investigated in situ myocyte Ca2+ dynamics in intact Langendorff perfused hearts (ex vivo) from wildtype (WT) and RyR2R4496C+/− mice using laser scanning confocal microscopy. We found that myocytes from both WT and RyR2R4496C+/− hearts displayed uniform, synchronized Ca2+ transients. Ca2+ transients from beat to beat were comparable in amplitude with identical activation and decay kinetics in WT and RyR2R4496C+/− hearts, suggesting that excitation-contraction (EC) coupling between the sarcolemmal Ca2+ channels and mutated RyR2R4496C+/− channels remains intact under baseline resting conditions. Upon adrenergic stimulation, RyR2R4496C+/− hearts exhibited a high degree of Ca2+ release variability (CRV). The varied pattern of Ca2+ release was absent in single isolated myocytes, independent of cell cycle length, synchronized among neighboring myocytes, and correlated with CPVT. A similar pattern of action potential variability, which was synchronized among neighboring myocytes, was also revealed under adrenergic stress in intact hearts but not in isolated myocytes. Our studies using in situ confocal imaging approach suggest that mutated RyR2s are functionally normal at rest but display a high degree of CRV upon intense adrenergic stimulation. CRV is a Ca2+ release abnormality resulting from electrical defects rather than the failure of the Ca2+ release response to action potentials in mutated ventricular myocytes. Our data provide important insights into Ca2+ release and electrical dysfunction in an established model of CPVT.