Targeting liver angiotensinogen using a GalNAc-siRNA improves cardiac remodeling in spontaneously hypertensive rats

Abstract Background Dysregulation of the Renin-Angiotensin-Aldosterone System (RAAS) leads to hypertension and cardiac hypertrophy. Angiotensinogen (AGT) is the only precursor of all angiotensin peptide products. Liver-specific AGT silencing has been proven to be a promising treatment option in lowering blood pressure (BP) in patients, characterized by full RAAS inhibition and little RAAS escape phenomena. However, the long-term effects of AGT knockdown on cardiac remodeling is still unclear. Purpose To explore the long-term effects of a GalNAc-conjugated siRNA drug R0797070 on AGT inhibition, BP and cardiac functions in Spontaneously Hypertensive Rats (SHRs). Methods In vitro inhibitory activities of siRNAs were assessed in primary rat hepatocytes. The selected siRNA was conjugated with GalNAc based on RIBO-GALSTAR liver targeting system and named R0797070. In vivo effects of repeated doses of R0797070 were evaluated in SHR model. The animals were treated with R0797070 (3 mg/kg, every 8 weeks; subcutaneous injection) or PBS (5 ml/kg, every 8 weeks; subcutaneous injection) for 7 months with the first dose (day1) at the 3 months of age. Captopril (100 mg/kg per day; oral administration) was taken as a positive drug control and Wistar rats were used as normotensive control group. Blood pressure was monitored by tail-cuff method after an initial acclimatization training period. Serum AGT protein was measured by ELISA and liver mRNA expression was detected by qPCR. Echocardiography was used to determine the changes of cardiac morphology and functions，and wheat germ agglutinin (WGA) staining was used to measure myocyte cross-sectional size. Results R0797070 showed 90-99% inhibitory activities on hepatic AGT mRNA at different doses. In SHRs, a single dose of R0797070 at 3 mg/kg resulted in a maximum inhibition of 97% for serum AGT protein with 27 mmHg mean blood pressure (MBP) reduction on Day 15. Daily administration of Captopril could reduce MBP by 33 mmHg on average, while the duration of drug efficacy of R0797070 could reach 2 months with the average 25 mmHg MBP reduction. At the end of study, the echocardiographic results showed that R0797070 significantly reduced left ventricular hypertrophy in the 10-month-old SHRs. Consistently, R0797070 treatment reduced the heart weight by 10%，and LV myocyte size by 17%. Conclusion We showed the long-term effects of a GalNAc-siRNA R0797070 on silencing angiotensinogen expression, reducing blood pressure and left ventricular hypertrophy. Compared to daily oral administration of Captopril and its effect on blood pressure R0797070 demonstrated significant effect on cardiac hypertrophy.Figure 1Figure 2