Silencing of sodium/hydrogen exchanger in the heart by direct injection of naked siRNA

PATRICIO E. MORGAN; MARÍA V. CORREA; IRENE L. ENNIS; ARIEL A. DIEZ; NÉSTOR G. PÉREZ; HORACIO E. CINGOLANI

JOURNAL OF APPLIED PHYSIOLOGY

AMER PHYSIOLOGICAL SOC

Año: 2011 vol. 111 p. 566 - 572

8750-7587

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 (si) RNA produced in vitro to specifically silence NHE1 (siRNANHE1) 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 siRNANHE1-injected mice compared to siRNASCRAMBLE (siRNASCR) 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, siRNANHE1 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 pHi recovery (dpHi/dt) after an ammonium prepulse-induced acidic load. Maximal dpHi/dt was reduced to 14% in siRNANHE1-isolated left ventricular papillary muscles compared to siRNASCR. In conclusion, only one injection of naked siRNANHE1 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.