Division of Cardiology, Laboratory of Molecular and Cellular Cardiology, Department of Medical and Surgical Sciences, University Magna Graecia, Catanzaro, Italy.
PLoS One. 2013 Jul 26;8(7):e70158. doi: 10.1371/journal.pone.0070158. Print 2013.
Downregulation of the muscle-specific microRNA-1 (miR-1) mediates the induction of pathologic cardiac hypertrophy. Dysfunction of the gap junction protein connexin 43 (Cx43), an established miR-1 target, during cardiac hypertrophy leads to ventricular tachyarrhythmias (VT). However, it is still unknown whether miR-1 and Cx43 are interconnected in the pro-arrhythmic context of hypertrophy. Thus, in this study we investigated whether a reduction in the extent of cardiac hypertrophy could limit the pathological electrical remodeling of Cx43 and the onset of VT by modulating miR-1 levels. Wistar male rats underwent mechanical constriction of the ascending aorta to induce pathologic left ventricular hypertrophy (LVH) and afterwards were randomly assigned to receive 10mg/kg valsartan, VAL (LVH+VAL) delivered in the drinking water or placebo (LVH) for 12 weeks. Sham surgery was performed for control groups. Programmed ventricular stimulation reproducibly induced VT in LVH compared to LVH+VAL group. When compared to sham controls, rats from LVH group showed a significant decrease of miR-1 and an increase of Cx43 expression and its ERK1/2-dependent phosphorylation, which displaces Cx43 from the gap junction. Interestingly, VAL administration to rats with aortic banding significantly reduced cardiac hypertrophy and prevented miR-1 down-regulation and Cx43 up-regulation and phosphorylation. Gain- and loss-of-function experiments in neonatal cardiomyocytes (NCMs) in vitro confirmed that Cx43 is a direct target of miR-1. Accordingly, in vitro angiotensin II stimulation reduced miR-1 levels and increased Cx43 expression and phosphorylation compared to un-stimulated NCMs. Finally, in vivo miR-1 cardiac overexpression by an adenoviral vector intra-myocardial injection reduced Cx43 expression and phosphorylation in mice with isoproterenol-induced LVH. In conclusion, miR-1 regulates Cx43 expression and activity in hypertrophic cardiomyocytes in vitro and in vivo. Treatment of pressure overload-induced myocyte hypertrophy reduces the risk of life-threatening VT by normalizing miR-1 expression levels with the consequent stabilization of Cx43 expression and activity within the gap junction.
肌肉特异性 microRNA-1 (miR-1) 的下调介导病理性心肌肥厚的诱导。在心肌肥厚过程中，间隙连接蛋白 connexin 43 (Cx43) 的功能障碍，作为 miR-1 的一个既定靶点，导致室性心动过速（VT）。然而，miR-1 和 Cx43 是否在肥厚的致心律失常环境中相互关联仍然未知。因此，在这项研究中，我们研究了通过调节 miR-1 水平，减少心肌肥厚的程度是否可以限制 Cx43 的病理性电重构和 VT 的发生。雄性 Wistar 大鼠接受升主动脉机械缩窄以诱导病理性左心室肥厚（LVH），随后随机接受缬沙坦 10mg/kg（VAL），VAL 通过饮用水给药（LVH+VAL）或安慰剂（LVH）12 周。假手术作为对照组。与 LVH+VAL 组相比，LVH 组的程序性心室刺激可重复性地诱导 VT。与 sham 对照组相比，LVH 组的大鼠 miR-1 表达显著降低，Cx43 表达及其 ERK1/2 依赖性磷酸化增加，从而使 Cx43 从间隙连接中移位。有趣的是，VAL 给药于主动脉缩窄大鼠可显著减少心肌肥厚，并防止 miR-1 下调和 Cx43 上调及磷酸化。在体外新生心肌细胞（NCMs）的 Gain-和 Loss-of-function 实验中证实 Cx43 是 miR-1 的直接靶标。因此，与未刺激的 NCMs 相比，体外血管紧张素 II 刺激降低了 miR-1 水平并增加了 Cx43 的表达和磷酸化。最后，体内通过腺病毒载体心肌内注射过表达 miR-1 可降低异丙肾上腺素诱导的 LVH 小鼠的 Cx43 表达和磷酸化。总之，miR-1 在体外和体内调节肥厚心肌细胞中的 Cx43 表达和活性。治疗压力超负荷诱导的心肌肥厚通过使 miR-1 表达水平正常化，从而稳定 Cx43 在间隙连接中的表达和活性，降低危及生命的 VT 的风险。
