Abstract P237: The At2 Receptor Agonist, C21, Can Also Stimulate Mas and Mrgd Receptors

Abstract

Background: It is well accepted that Compound 21 (C21) is a highly selective non-peptide angiotensin AT2 receptor agonist. C21 as well as angiotensin (Ang)-(1-7) have cardiovascular protective effects and are opponents of the often detrimental Ang II within the renin-angiotensin system. Since the chemical structure of C21 is similar to the Mas receptor specific non-peptidic agonist AVE0991, and we could recently show that the AT2 receptor blocker, PD123319, can also block the effects of Ang-(1-7) at its natural receptors, Mas and MrgD, we tested whether C21 is also not AT2-specific but can stimulate the two Ang-(1-7) receptors, too. Methods and Results: Using cAMP as readout in receptor-transfected HEK293 cells, we generated pharmacological proof that Mas (EC 50 = 1.995 x 10 -12 M) and MrgD (EC 50 = 2.958 x 10 -9 M) are functional receptors for C21, whereby the three receptor blockers, A779, D-Pro7-Ang-(1-7), and PD123319 showed receptor-specific effects towards C21 signalling. Furthermore, C21 elevated the cAMP concentration in primary cells such as mesangial cells (EC 50 = 1.12 x 10 -6 M). However, significant increase in cAMP levels, but not in PKA activity, was still detectable in mesangial cells isolated from AT2-deficient mice, but completely blunted in Mas/MrgD-double knockouts. Finally, in silico modelling was performed to illustrate the structural similarities and differences between C21, AVE0991, and Ang-(1-7). Conclusions: Our results identify C21 as not being a specific AT2 receptor agonist but also interacting with the two Ang-(1-7) receptors, Mas and MrgD. Therefore, the partial overlap in beneficial effects of Ang-(1-7) and C21 might be based on the stimulation of the same receptors under specific pathophysiological circumstances. This also enforces the revisit of such publications which concluded on AT2 function by only using C21.