ACE2 and Ang1–7 have been shown to protect against pulmonary hypertension (PH). Mechanisms remain unclear. Considering the important role of ET-1 in PH pathophysiology and endothelial dysfunction, we asked whether Ang1–7 influences ET-1 signalling in PH. Human endothelial cells (HMEC) were stimulated with ET-1 in absence/presence of Ang1–7 and showed that Ang1–7 increased ET-1 release (125%) and ETBR protein (50%), p < 0.05. Ang1–7 increased NO production (257%) in a Mas and ETBR-dependent manner. Mas and ETBR interaction was observed by immunoprecipitation. To characterise physical interaction between Mas/ETBR, we utilised novel technology, employing peptides scanning the MasR sequence, to define sites of ETBR binding. Mutagenesis identified regions on MasR that confer specificity for ETBR. Peptide disruptors were used for in vitro validation. We previously demonstrated in HMEC that Ang1–7 stimulates Akt phosphorylation (180%), an effect inhibited by peptide disruptors, p < 0.05. To investigate pathophysiological significance, we investigated whether Ang1–7 treatment ameliorates PH. Hypoxia was used to induce PH in mice: normoxic controls (NC), hypoxic PH (HP), normoxic (NA) and hypoxic PH (HA) treated with Ang1–7 30 µg/kg/day. In HP mice, RVSP (18.7 NC vs. 47.6 mmHg HP, p < 0.05) RVH (0.19 NC vs. 0.28 HP, p < 0.01) and ET-1 levels (0.8 NC vs 2.4 pg/ml HP, p < 0.05) were increased and blocked by Ang1–7. Hypercontractility and endothelial dysfunction in HP mice was attenuated by Ang1–7. These findings indicate that vasoprotective effects of Ang1–7 may be mediated through MAS: ETBR dimerization. In conclusion we have identified a novel link between Ang1–7 and ET-1 through physical interactions between MAS and ETBR.
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