Overexpression of HCN-encoded pacemaker current silences bioartificial pacemakers
Overexpression of HCN-encoded pacemaker current silences bioartificial pacemakers
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DOI：
10.1016/j.hrthm.2008.05.010
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发表时间：
2008-09-01
期刊：
影响因子：
5.5
通讯作者：
Li, Ronad A.
中科院分区：
文献类型：
--
作者：
Lieu, Deborah K.;Chan, Yau Chi;Li, Ronad A.
目前从其他沉默但易兴奋的成年心房和心室心肌细胞工程化生物人工起搏器的策略主要依赖于最大化超极化激活的If或最小化其假定的对手，内向整流钾电流I-K1。目的定量测定I-f和I-的相对电流密度方法成年豚鼠心房心肌细胞的自律性通过腺病毒（Ad）介导的门控工程化HCN 1构建体HCN 1-Delta Delta Delta（具有S3-S4接头残基EVY 235 - 1）的过表达来诱导。结果对照组心房肌细胞保持电静止，无I-f，18%的Ad-CMV-GFP-IRES-HCN 1-Delta Delta（Ad-CGI-HCN 1-Delta Delta Delta）转导的细胞表现出自律性（240 +/- 14 bpm），逐渐4期去极化（143 +/- 28 mV/s）、去极化最大舒张电位（-45.3 +/- 2.2 mV）和-140 mV时的大量I-f（If-140（mV）= -9.32 +/- 1.84 pA/pF）。在剩余的静息状态的Ad-CGI-HCN 1-Delta Delta Delta转导的心房心肌细胞中，观察到两种不同的即刻表型：（1）13%的细胞具有高电位的静息膜电位（-56.7 +/- 1.3 mV），I-f，（-140）（mV）为-4.85 +/- 0.97 pA/pF;（2）其余69%显示去极化静息膜电位（-27.6 +/- 1.3 mV），I-f，（-140）（mV）为-23.0 +/- 3.71 pA/pF。电刺激后，两个静止组均诱发了在对照组中从未观察到的具有不完全的4相去极化的单个动作电位。进一步的电生理分析表明，I-f和I-K1的复杂平衡是诱导心房自律性的必要条件。结论通过设计I-f/I-K1比而不是单个电流，可以更好地实现优化的起搏诱导和调制。
BACKGROUND Current strategies of engineering bioartificial pacemakers from otherwise silent yet excitable adult atrial and ventricular cardiomyocytes primarily rely on either maximizing the hyperpotarization-activated If or on minimizing its presumptive opponent, the inwardly rectifying potassium current I-K1.OBJECTIVE The purpose of this study was to determine quantitativelly the relative current densities of I-f and I-K1 necessary to induce automaticity in adult atrial cardiomyocytes.METHODS Automaticity of adult guinea pig atrial cardiomyocytes was induced by adenovirus (Ad)-mediated overexpression of the gating-engineered HCN1 construct HCN1-Delta Delta Delta with the S3-S4 linker residues EVY235-7 deleted to favor channel opening.RESULTS Whereas control atrial cardiomyocytes remained electrically quiescent and had no I-f, 18% of Ad-CMV-GFP-IRES-HCN1-Delta Delta Delta (Ad-CGI-HCN1-Delta Delta Delta)-transduced cells demonstrated automaticity (240 +/- 14 bpm) with gradual phase 4 depotarization (143 +/- 28 mV/s), a depolarized maximal diastolic potential (-45.3 +/- 2.2 mV), and substantial I-f at -140 mV (If-140 (mV) = -9.32 +/- 1.84 pA/pF). In the remaining quiescent Ad-CGI-HCN1-Delta Delta Delta-transduced atrial cardiomyocytes, two distinct immediate phenotypes were observed: (1) 13% had a hyperpotarized resting membrane potential (-56.7 +/- 1.3 mV) with I-f,(-140) (mV) of -4.85 +/- 0.97 pA/pF; and (2) the remaining 69% displayed a depolarized resting membrane potential (-27.6 +/- 1.3 mV) with I-f,(-140) (mV) of -23.0 +/- 3.71 pA/pF. Upon electrical stimulation, both quiescent groups elicited a single action potential with incomplete phase 4 depotarization that was never seen in controls. Further electrophysiologic analysis indicates that an intricate balance of I-f and I-K1 is necessary for induction of atrial automaticity.CONCLUSION optimized pacing induction and modulation can be better achieved by engineering the I-f/I-K1 ratio rather than the individual currents.