Decarboxylation of Ang-(1–7) to Ala1-Ang-(1–7) leads to significant changes in pharmacodynamics

Abstract

The heptapeptide angiotensin (Ang)–(1–7) is part of the beneficial arm of the renin-angiotensin system. Ang-(1–7) has cardiovascular protective effects, stimulates regeneration, and opposes the often detrimental effects of Ang II. We recently identified the G protein-coupled receptors Mas and MrgD as receptors for the heptapeptide. Ala1-Ang-(1–7) (Alamandine), a decarboxylated form of Ang-(1–7), has similar vasorelaxant effects, but has been described to only stimulate MrgD. Therefore, this study aimed to characterise the consequences of the lack of the carboxyl group in amino acid 1 on intracellular signalling and to identify the receptor fingerprint for Ala1-Ang-(1–7). In primary endothelial and mesangial cells, Ala1-Ang-(1–7) elevated cAMP concentration. Dose response curves generated with Ang-(1–7) and Ala1-Ang-(1–7) significantly differed from each other, with a much lower EC50 and a bell-shape curve for Ala1-Ang-(1–7). We provided pharmacological proof that both, Mas and MrgD, are functional receptors for Ala1-Ang-(1–7). Consequently, in primary mesangial cells with genetic deficiency in both receptors the heptapeptide failed to increase cAMP concentration. As we previously described for Ang-(1–7), the Ala1-Ang-(1–7)-mediated cAMP increase in Mas/MrgD-transfected HEK293 cells and primary cells were blocked by the AT2 receptor blocker, PD123319. The very distinct dose-response curves for both heptapeptides could be explained by in silico modelling, electrostatic potential calculations, and an involvement of Galpha i for higher concentrations of Ala1-Ang-(1–7). Our results identify Ala1-Ang-(1–7) as a peptide with specific pharmacodynamic properties and build the basis for the design of more potent and efficient Ang-(1–7) analogues for therapeutic interventions in a rapidly growing number of diseases.