Effects of RNA interference targeting angiotensin 1a receptor on blood pressure and cardiac hypertrophy of rats with renovascular hypertension

Abstract

The aim of this study is to investigate the effects of RNA interference (RNAi) targeting angiotensin 1a receptor (AT1a) on blood pressure and cardiac hypertrophy of rats with renovascular hypertension. Two RNAi plasmids, pAT1a-shRNA1 and pAT1a-shRNA2 each carrying a U6 promoter and an AT1a-specific shRNA-coding template sequence corresponding to the sites 928–946, 978–996 of the mRNA transcript, and a control plasmid pCon carrying a nonspecific shRNA-coding sequence were constructed. Thirty Sprague – Dawley rats with renovascular hypertension (2-kidney 1-clip) were randomly divided into 5 equal groups: Control group (without any intervention), pAT1a-shRNA1, pAT1a-shRNA2, pCon groups (with injection of the corresponding plasmid 4 mg/kg respectively into the tail vein), and valsartan group (30 mg/kg·d^-1 by gavage). Three weeks after drug administration, pAT1a-shRNA1, pAT1a-shRNA2 and valsartan respectively resulted in decrease of the tail blood pressure by (15.1 ± 5.4), (16.4 ± 8.4) and (30.6 ± 18.2) mmHg. However, the tail blood pressure increased further by about 25 mmHg in both of pCon and control groups. The carotid artery pressures of pAT1a-shRNA1, pAT1a-shRNA2 and valsartan groups were all significantly lower than those of the control and pCon groups. The ratio of left ventricle weight to body weight (LV/BW) of the rats in pAT1a-shRNA1, pAT1a-shRNA2, and valsartan groups decreased significantly than in the control group (P < 0.01), similar to those of the normal SD rats(P > 0.05). Histopathological examination showed that the myocardiocytes were significantly hypertrophic and the basal membrane of the aorta was significantly thickened in the control group and such changes were alleviated in the pAT1a-shRNA1, pAT1a-shRNA2 and valsartan groups. Compared with the control group, pAT1a-shRNA1 and pAT1a-shRNA2 groups had lowered expression of AT1 receptor (in the myocardium and the thoracic aorta (all P < 0.01); however, there were no significant differences in expression levels of AT1 receptor in valsartan and the control groups (P > 0.05). We conclude that RNAi targeting AT1a receptor inhibits the development of renovascular hypertension and the accompanying cardiac hypertrophy. RNAi technology may become a new strategy of gene therapy for hypertension.

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