AT1R Dependence of Proangiogenic Ang‐(1–7)/Mas Signaling in Endothelial Cells and Endothelial Progenitors

Abstract

The renin‐angiotensin system (RAS) is a critical regulator of microvascular function and cardiovascular risk. Success of clinical interventions that interfere with the signaling of angiotensin II (AngII) at the angiotensin II receptor type 1 (AT1R) suggested signaling via AT1R is predominantly associated with pathology; however, recent studies have reaffirmed that AngII/AT1R signaling has a key role in maintaining vascular homeostasis. Angiotensin‐(1–7) (Ang‐(1–7)) is a RAS effector peptide that counteracts many effects of pathologically high AngII. In a previous study, we observed that at low doses, both AngII/AT1R and Ang‐(1–7) signaling through the receptor Mas restore angiogenesis in a low renin model of microvascular dysfunction. We have also observed beneficial effects of low dose AngII on endothelial progenitor cell (EPC) function. While competitive inhibition of ligand binding at the converse receptor did not abolish the effects of each peptide, AT1R was identified as a component of the Ang‐(1–7)/Mas signaling complex. It has been suggested that AT1R and Mas form heterodimers based on data showing rescued function of mutant AT1R upon coexpression of Mas. Here, we test the hypothesis that Ang‐(1–7) has proangiogenic effects in both endothelial cells (ECs) and EPCs that is dependent upon the presence of AT1R. In the Dahl salt‐sensitive (SS) rat, a low‐renin model of microvascular dysfunction, we confirm the beneficial effects of low‐dose Ang‐(1–7) on angiogenesis and observe Ang‐(1–7) mediated restoration of EPC function. In an AT1R knockout on the SS background, the ability of Ang‐(1–7) to restore angiogenesis and EPC function is lost. In addition, in vitro analogues of angiogenic capability recapitulate this phenotype in both ECs and EPCs. Using qPCR arrays and mass‐spectrometry based proteomics, we find both the transcriptional response and the Ang‐(1–7)/Mas signaling complex to be altered in the absence of AT1R. These results support the hypothesis that AT1R is a key component of the Ang‐(1–7)/Mas signaling pathway and further support the previous hypothesis by others and ourselves that AT1R and Mas heterodimerize. Computational models of AT1R and Mas have been constructed to examine the potential mechanism of AT1R and Mas heterodimerization, with biological confirmation to follow.Support or Funding InformationThis work was supported by NHLBI grant F30HL131153.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.