Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.
J Appl Physiol (1985). 2011 Aug;111(2):566-72. doi: 10.1152/japplphysiol.00200.2011. Epub 2011 May 19.
Cardiac Na(+)/H(+) exchanger (NHE1) hyperactivity is a central factor in cardiac remodeling following hypertension, myocardial infarction, ischemia-reperfusion injury, and heart failure. Treatment of these pathologies by inhibiting NHE1 is challenging because specific drugs that have been beneficial in experimental models were associated with undesired side effects in clinical practice. In the present work, small interference RNA (siRNA) produced in vitro to specifically silence NHE1 (siRNA(NHE1)) was injected once in vivo into the apex of the left ventricular wall of mouse myocardium. After 48 h, left ventricular NHE1 protein expression was reduced in siRNA(NHE1)-injected mice compared with scrambled siRNA by 33.2 ± 3.4% (n = 5; P < 0.05). Similarly, NHE1 mRNA levels were reduced by 20 ± 2.0% (n = 4). At 72 h, siRNA(NHE1) spreading was evident from the decrease in NHE1 expression in three portions of the myocardium (apex, medium, base). NHE1 function was assessed based on maximal velocity of intracellular pH (pH(i)) recovery (dpH(i)/dt) after an ammonium prepulse-induced acidic load. Maximal dpH(i)/dt was reduced to 14% in siRNA(NHE1)-isolated left ventricular papillary muscles compared with scrambled siRNA. In conclusion, only one injection of naked siRNA(NHE1) successfully reduced NHE1 expression and activity in the left ventricle. As has been previously suggested, extensive NHE1 expression reduction may indicate myocardial spread of siRNA molecules from the injection site through gap junctions, providing a valid technique not only for further research into NHE1 function, but also for consideration as a potential therapeutic strategy.
心脏 Na(+)/H(+) 交换器 (NHE1) 活性亢进是高血压、心肌梗死、缺血再灌注损伤和心力衰竭后心脏重构的核心因素。通过抑制 NHE1 来治疗这些病理情况具有挑战性，因为在实验模型中有益的特定药物在临床实践中与不良副作用相关。在本工作中，体外产生的针对 NHE1 的小干扰 RNA (siRNA) (siRNA(NHE1)) 一次被注射到小鼠左心室壁的顶部。在 48 h 后，与对照 siRNA 相比，siRNA(NHE1) 注射的小鼠左心室 NHE1 蛋白表达减少了 33.2 ± 3.4%（n = 5；P < 0.05）。类似地，NHE1 mRNA 水平降低了 20 ± 2.0%（n = 4）。在 72 h 时，从左心室心肌三个部位（顶部、中部、底部）的 NHE1 表达减少可以看出 siRNA(NHE1) 的扩散。根据铵脉冲诱导酸性负荷后细胞内 pH（pH(i)）恢复的最大速度（dpH(i)/dt）评估 NHE1 功能。与对照 siRNA 相比，siRNA(NHE1) 分离的左心室乳头肌的最大 dpH(i)/dt 降低至 14%。总之，只有一次注射裸 siRNA(NHE1) 就能成功降低左心室中的 NHE1 表达和活性。如前所述，广泛的 NHE1 表达减少可能表明 siRNA 分子从注射部位通过缝隙连接扩散到心肌，这不仅为进一步研究 NHE1 功能提供了有效技术，而且也为作为一种潜在的治疗策略提供了考虑。
