血管紧张素Ⅱ#23545;心室延迟整流钾电流的调节及其信号传导机制

项目名称： 血管紧张素Ⅱ#23545;心室延迟整流钾电流的调节及其信号传导机制

项目编号： No.30871010

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 建筑科学

项目作者： 许彦芳

作者单位： 河北医科大学

项目金额： 29万元

中文摘要： 肾素-血管紧张素系统（RAS）的激活大大提高心律失常和心源性猝死的危险性，但其机制未明。本课题在急性分离的豚鼠心肌细胞和异源表达系统研究了血管紧张素II（Ang II）对心肌离子通道的调控作用。主要发现为：（1）Ang II对心室外、中及内膜下心肌细胞IKr呈不同程度下调，以外膜下细胞作用最显著，同时明显延长外膜下心肌细胞APD，这种非同步延长APD作用使得心室跨壁复极梯度减小，造成复极异常；（2）在异源表达系统，AngⅡ#38271;时间孵育减少HERG膜通道蛋白的含量，此作用由PKC中介；AngⅡ#36824;减少KCNQ1蛋白含量，此作用与KCNE1上S102位点无关；（3）Ang II通过选择性激动PKC?，进而使通道磷酸化而下调HERG电流，而PKC激动剂主要通过cPKC（可能不同的通道磷酸化位点）下调HERG；（4）Ang II 对急性分离的豚鼠心室肌细胞和表达系统均呈浓度依赖性抑制IKs，PKC?亚型中介此作用；（5）Ang II通过增强窦房结细胞Iks和抑制ICa-L减慢窦房结自律性。以上对理解Ang II对心肌离子通道的调节、特别是心脏病理状态下的电生理重构机制提供了重要实验依据。

中文关键词： 血管紧张素II；延迟整流K+电流快激活成份；延迟整流K+电流慢激活成份；心室细胞；PKC

英文摘要： Renin-angiotensin system (RAS) activation is associated with an increased risk for arrhythmia and sudden cardiac death, but the mechanism is not well understood. Angiotensin (Ang II) is the key terminal effector of RAS. Our previous study has shown that Ang II produces an inhibitory effect on IKr /hERG currents via AT1 receptor. The present study was designed to further examine the regulations of Ang II on IKr and IKs and try to elucidate the intracellular molecular mechanism in isolated guinea pig cardiomyocytes and heterologous expression system by using patch clamp combined with molecular biological techniques. The major findings were as follows: (1) The inhibition of Ang II on IKr was more prominent in subepicardial myocytes than both mid- and subendomyocytes and thus produced a preferential prolongation of the action potential duration (APD) in subepicardial myocytes, which resulted in a reduction of the transmural repolarization gradient and abnormal ventricular repolarization. (2) In a heterologous expression system sustained AT1 receptor stimulation by Ang II decreased the mature HERG protein abundance in PKC-dependent fashion. Meanwhile, Ang II down-regulated KCNQ1 protein (pore-forming subunit of IKs channel) abundance in a time- and concentration-dependent manner. Comparison of wild-type KCNQ1/KCNE1 and mutant KCNQ1/KCNE1-S102A showed that the mutant didn't influence the effect of Ang II, suggesting that serine 102 in KCNE1 was not involved in the regulation. (3) Activation of PKCεsoform contributed to Ang II-mediated inhibition on Ikr/HERG through a mechanism involving the 17 of 18 putative phosphorylation sites; Whereas, PKC general activators down-regulated the HERG current by cPKC through a different manner or phosphorylation site. (4) Ang II produced an inhibitory effect on Iks currents in a concentration-dependent manner. The results with selective PKC inhibitor or peptide suggested that PKCεsoform contributed to Ang II-mediated inhibition on Iks. (5) In guinea-pig sinoatrial node (SAN) cells Ang II reduced the spontaneous firing rate with a concomitant reduction in the velocity of phase 4 depolarization. The enhancement of Iks through the slowing of deactivation kinetics of the channel and down-regulation of the L-type Ca2+ current may contribute to the inhibition on the auto rhythm of SAN. Our study has provided a potential mechanistic explanation for the electrophysiological remodeling in cardaic pathophysiology.

英文关键词： angiotensin Ⅱ#65307;ventricular myocytes；IKr；IKs；PKC