Abstract 18: Persistent beneficial effects of angiotensinogen small interfering RNA (siRNA) and valsartan in spontaneously hypertensive rats after drug removal

Abstract

Objective: Dual blockade of the renin-angiotensin system (RAS) with siRNA targeting hepatic angiotensinogen (AGT) plus the angiotensin receptor blocker valsartan synergistically lowers blood pressure and diminishes cardiac hypertrophy in spontaneously hypertensive rats (SHR). Since the effects of one siRNA injection may last for up to six months, here we evaluated whether the REVERSIR (reverse siRNA silencing, RVR) technology and/or stopping valsartan might acutely reverse the effects of dual RAS blockade in SHR. Methods: Ten-week old SHR were subjected to a 3-week treatment with vehicle or AGT-siRNA (10 mg/kg) + valsartan (4 mg/kg per day), followed by administration of vehicle or AGT-RVR at doses of 1, 10 and 20 mg/kg, both with and without continuation of valsartan, for 1 week. Mean arterial blood pressure (MAP) was monitored using radiotelemetry, and circulating AGT and renin were measured by enzyme-kinetic assay. Results: Baseline MAP was 143±2 mm Hg. Dual treatment lowered MAP by ≈70 mm Hg, cardiac hypertrophy (heart weight/tibia length) by ≈30%, and circulating AGT by >99%, while renin increased >100-fold versus vehicle. Discontinuing valsartan or applying AGT-RVR (1, 10 or 20 mg/kg) increased MAP similarly (by ≈20 mm Hg), while discontinuing valsartan + AGT-RVR (10 mg/kg) increased MAP by ≈40 mm Hg. Changes in cardiac hypertrophy mimicked those in MAP. Only valsartan discontinuation + AGT-RVR fully restored circulating AGT and renin to normal. When discontinuing valsartan only, AGT remained suppressed by >95%, and renin was up 10-fold, while with AGT-RVR 1, 10 and 20 mg/kg only, AGT suppression was 25, 50 and 50%, while renin was up 25-, 15- and 15-fold, respectively. Conclusions: Discontinuing valsartan or applying AGT-RVR in SHR treated with valsartan + AGT siRNA partially restored MAP, AGT, and renin, likely reflecting the fact that this approach replaces dual RAS blockade by single RAS blockade. However, although discontinuing valsartan plus AGT-RVR fully restored RAS activity, MAP and cardiac hypertrophy remained suppressed under this condition. This agrees with observations that early RAS inhibition resets genetic pathways and networks, allowing persistent blood pressure normalization even when treatment has stopped.