Abstract P219: Site-1 Protease-Derived Soluble (Pro)Renin Receptor Contributes to Salt-Sensitive Hypertension via Activation of the Intrarenal RAS

Abstract

Dahl salt-sensitive (SS) hypertensive rats exhibit increased expression of renal (pro)renin receptor (PRR) and aberrant activation of the intrarenal renin-angiotensin system (RAS) with unclear functional implication. Recent evidence demonstrates that soluble PRR (sPRR) serves as a potential regulator of tubular transport via activating Wnt/ β-catenin pathway in the distal nephron and is derived from the cleavage by site-1 protease (S1P). The present study attempted to define the role of sPRR during salt-sensitive hypertension in SS rats. The effect of S1P inhibitor PF-429242 (PF at 20 mg/kg/d via mini-pump) on blood pressure, proteinuria, and urinary renin were tested in SS rats during high salt loading. In a separate group, a recombinant sPRR (sPRR-His at 20 μg/kg/d) was infused via catheterization of jugular vein to SS rats during PF treatment. In High sodium (HS)-loaded SS rats, administration of PF attenuated the hypertension development (MAP on day 10, HS+PF group: 124.5 ± 4.6 mmHg vs. HS group: 144.1 ± 8.2 mmHg) as assessed by radiotelemetry and proteinuria (HS+PF group: 50.9 ± 5.5 μg/24h vs. HS group: 105.3 ± 7.4 μg/24h). PF treatment reduced HS-stimulated urinary sPRR excretion by 65% in SS rats. Supplement of sPRR restored HS-induced hypertension during PF treatment (MAP on day 10, HS+PF+sPRR-His group: 138.7 ± 6.1 vs. HS+PF group: 124.5 ± 4.6 mmHg) and proteinuria (HS+PF+sPRR-His group: 79.0 ± 5.8 μg/24h vs. HS+PF group: 50.9 ± 5.5 μg/24h) in SS rats. Concurrently, PF treatment reduced HS-stimulated urinary renin activity (by 80%), aldosterone excretion (by 36%) and renal medullary prorenin and renin (by 60%), which were all restored by sPRR-His infusion (1.5- to 3-fold). Indices of Wnt/β-catenin pathway including protein levels of renal cytosolic Axin-2 and nuclear β-catenin as assessed by immunoblotting were elevated by HS (3.4-fold, 2.2-fold respectively) in SS but not SR rats, which were all suppressed by S1P inhibition (by 80% and 50% respectively) and restored by sPRR-His infusion. Given β-catenin signaling as a known regulator of intrarenal RAS, our results suggest that S1P-derived sPRR plays a pathogenic role in salt-sensitive hypertension in SS rats via β-catenin/intrarenal RAS pathway.