S-12-2: ENHANCING MAS1:ETBR INTERACTION AS A POTENTIAL VASOPROTECTIVE STRATEGY IN STROKE-PRONE SHR

Abstract

We previously demonstrated that Ang-(1–7) has anti-inflammatory effects in endothelial cells by inducing interaction between Mas1 and ETBR. Using HTS of > 20,000 druggable compounds, we identified several compounds that enhance Mas1:ETBR interaction as a novel strategy to promote vasoprotection. The objective of this study was to evaluate effects of 2 candidate compounds, termed enhancers 3 and 4 (Enh3 and Enh4), on functional responses in vascular smooth muscle cells (VSMCs) and their therapeutic potential in hypertensive (SHRSP) rats. VSMCs from normotensive (WKY) and SHRSP rats were exposed to Enh3 and Enh4(10–5 M; 5–30 mins). Expression of pro-contractile and mitogenic molecules was assessed by immunoblotting. Ca2+ influx was evaluated using fluorescence microscopy. ROCK2 activity was assessed using a colorimetric immunoassay which detected MYPT1 phosphorylation at Thr696. Male SHRSP rats (18–21weeks) were treated subcutaneously with Enh4 (10 mg/kg/day) for 7 days. Changes in blood pressure and vascular function were assessed via radiotelemetry and wire myography respectively. In WKY VSMCs, Enh3 reduced basal ERK1/2 phosphorylation (26.8 ± 5.9% vs veh,), an effect absent in SHRSP VSMCs, while Enh4 had no effect. Only in SHRSP VSMCs, Enh3, but not Enh4, reduced basal AKT phosphorylation (63.5 ± 8.9% vs veh). Enh4, but not Enh3, reduced basal MLC20 phosphorylation (54.9 ± 7.5% vs veh) in WKY but not in SHRSP VSMCs. ET-1-induced Ca2+ influx in WKY and SHRSP VSMCs was unaffected by Enh3 and Enh4. Assessment of Ca2+ -independent contractile mechanisms in VSMCs showed that ROCK2 activity is increased in SHRSP compared to WKY VSMCs (WKY: 0.27 ± 0.05; SHRSP:4.78 ± 0.34) and Enh4, but not Enh3, reduced ROCK2 activity in SHRSP VSMCs (61.5 ± 0.43% vs veh). Enh4 treatment in SHRSP rats reduced daytime systolic (SBP), diastolic (DBP) and mean arterial pressure (MAP) (SBP:4.26 ± 1.98; DBP:1.48 ± 0.92; MAP:2.07 ± 0.99 vs veh) compared to baseline. Furthermore, Enh4 treatment reduced U46619 induced contraction in SHRSP rat vessels (Emax(Mn): Veh- 13.16 ± 1.81; Enh4- 9.48 ± 1.31). Taken together, enhancing Mas1:ETBR interaction attenuates mitogenic and contractile signaling pathways in WKY and SHRSP VSMCs, and does not increase Ca2+ signaling, important in VSMC contraction. Enhancing Mas1:ETBR interaction reduces blood pressure and improves vascular function in SHRSP rats. Hence, Mas1:ETBR enhancers may be of potential therapeutic use as a new vasoprotective strategy to improve vascular function and to reduce blood pressure in hypertension.