Pathophysiological remodeling of mouse cardiac myocytes expressing dominant negative mutant of neuron restrictive silencing factor.
Pathophysiological remodeling of mouse cardiac myocytes expressing dominant negative mutant of neuron restrictive silencing factor.
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DOI：
10.1253/circj.cj-10-0652
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发表时间：
2010-10
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影响因子：
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通讯作者：
M. Takano;Hideyuki Kinoshita;T. Shioya;M. Itoh;K. Nakao;K. Kuwahara
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作者：
M. Takano;Hideyuki Kinoshita;T. Shioya;M. Itoh;K. Nakao;K. Kuwahara
背景以往报道心脏表达神经元限制性沉默因子（neuronrestrictingsilencingfactor，dnNRSF）显性失活突变体的转基因小鼠死于致死性心律失常，本研究旨在阐明dnNRSF小鼠心室肌细胞的电生理改变。方法和结果采用全细胞膜片钳技术记录动作电位（AP）和膜电流。用Indo-1AM测定细胞内Ca（2+）。dnNRSF心肌细胞的AP表现为静息膜电位降低，AP持续时间延长和频繁的早期后除极（EAD）。Na（+）-Ca（2+）交换体（NCX）阻断剂SEA 0400可完全抑制EAD。膜电流最显著的变化是内向整流钾电流（I（K1））密度的减少。除了胎儿型心脏离子通道的重新表达外，在小群体的dnNRSF肌细胞中观察到Na（+）-可渗透的晚期内向电流。dnNRSF心肌细胞舒张期内Ca（2+）浓度也升高，β-肾上腺素能刺激可引起自发性Ca（2+）振荡。结论：在dnNRSF心肌细胞中，AP的“复极储备”显著降低，膜电流的特定改变。在这些条件下，由内向NCX电流产生的EAD的幅度可能会增大，从而增加细胞对室性心律失常的脆弱性。
BACKGROUND It has been previously reported that the transgenic mouse expressing the dominant negative mutant of the neuron restrictive silencing factor (dnNRSF) in the heart died from lethal arrhythmia, so the present study aimed to clarify the electrophysiological alteration of the ventricular myocyte isolated from the dnNRSF mouse. METHODS AND RESULTS The action potential (AP) and membrane currents were recorded using the whole-cell patch-clamp method. Intracellular Ca(2+) was measured with Indo-1AM. The AP of dnNRSF myocytes exhibited reduction of resting membrane potential, prolongation of AP duration, and frequent early afterdepolarization (EAD). The EAD was completely inhibited by SEA0400, a specific blocker of the Na(+)-Ca(2+) exchanger (NCX). The most notable alteration of membrane current was a reduction in the inward rectifier K(+) current (I(K1)) density. In addition to re-expression of fetal type cardiac ion channels, a Na(+)-permeable, late inward current was observed in a small population of dnNRSF myocytes. The diastolic intracellular Ca(2+) concentration was also raised in dnNRSF myocytes, and spontaneous Ca(2+) oscillation was induced by β-adrenergic stimulation. CONCLUSIONS In dnNRSF myocytes, the "repolarization reserve" of the AP was significantly reduced by specific alterations in membrane currents. Under these conditions, the amplitude of EAD generated by the inward NCX current might be enlarged, thereby increasing the cells' vulnerability to ventricular arrhythmia.