Diminuição da expressão renal da enzima conversora de angiotensina por meio de um pequeno RNA interferente reduz pressão arterial sistêmica em ratos espontaneamente hipertensos.

Abstract

In the present study we evaluated the effects of a small interfering RNA (siRNA) targeting angiotensin converting enzyme (ACE) gene in spontaneously hypertensive rats (SHR). Nineteen male sixteen weeks-old SHR were submitted under anesthesia to femoral vessels catheterization for chronic recordings of arterial pressure (AP) and drug administration, respectively. After baseline AP and heart rate (HR) recordings in a computerized system, nine animals received by intravenous infusion 150ug/Kg of ACE-siRNA and other ten animals (control group) received also intravenously siRNA targeting enhanced green fluorescent protein (eGFP) gene, not expressed in mammalians. Following, each twelve hours for the next four days, continuous recordings of AP and HR for 30 minutes each one were performed in quiet and controlled room. At the end of forth day, after last AP recording and evaluation of angiotensin I (100 ng/Kg, i.v.) pressor response, all animals were sacrificed and lungs and kidneys were extracted to perform western-blot and RTPCR analysis of tissue ACE expression. Baseline values of mean AP (MAP) and HR did not differ between groups before treatment (182±3 mmHg e 366±10 bpm in ACEsiRNA group and 172±4 mmHg e 356±16 bpm in control group, respectively, p=ns). MAP values remained similar in both groups until second day, after which they began to decrease in ACE-siRNA group reaching the lowest values in the forth day (136±8 mmHg versus 167±4 mmHg in control, p<0,02). HR values as well as angiotensin I pressure responses did not differ between groups. Western-blot analysis of tissue ACE expression revealed 52,9% of reduction of kidneys ACE expression in ACEsiRNA group as compared to control group, without changes in lung ACE expression. Despite of reduction of protein expression in the kidneys of the treated animals, RTPCR was not able to demonstrate any change in messenger RNA expression for ACE in treated animals. These data suggest that a naked small RNA targeting ACE gene, intravenously injected, may act in vivo attenuating ACE expression in a tissueselective way, with marked repercussion on systemic arterial pressure in SHR. Since the expression of messenger RNA for ACE was not modified, a possible microRNA effect could be suggested. These findings point out small interferent RNAs or microRNAs as a promising strategy to treat systemic arterial hypertension.