Synergism between Angiotensin receptors ligands: Role of Angiotensin‐(1‐7) in modulating AT 2 R agonist response on nitric oxide in kidney cells

Angiotensin‐(1‐7), an endogenous agonist for the MasR, has been shown to interact with ang‐II AT 1 R and AT 2 R. Earlier we showed a physical and functional interaction between MasR and AT 2 R in response to their respective agonists ang‐(1‐7) and C21. Moreover, ang‐(1‐7) is cardio‐protective via AT 1 R and alters ang‐II function. Such complex nature of ang‐(1‐7) function is not clearly understood, particularly in relation to its functional interaction with these receptors. We tested how ang‐(1‐7) affects AT 2 R function by utilizing HK‐2 cells. The HK‐2 cells were treated with a wide range of concentrations of angiotensin receptor agonists. The generation of NO • in response to agonists was determined as a readout and subjected to Bliss definition (δ score) to assess the nature of functional interaction between these receptors. Preincubation with ang‐(1‐7) followed by incubation with endogenous AT 1 R/AT 2 R agonist ang‐II (δ = 162) or selective AT 2 R agonist C21 (δ = 304) synergized NO • formation. The synergism was also observed when the order of incubation with ang‐(1‐7)/C21 was reversed (δ = 484), but not when the cells were simultaneously incubated with a mixture of ang‐(1‐7) and C21 (δ = 76). The synergism with nonpeptidic MasR agonist AVE0991 followed by C21 (δ = 45) was minimal. Ligand binding experiment suggested the binding of ang‐(1‐7) with these three receptors. However, the synergism observed with ang‐(1‐7) and ang‐II/C21 was sensitive to the antagonists of AT 2 R (PD123319) and AT 1 R (candesartan), but not MasR (A779). Ang‐(1‐7) at lower concentrations synergies the AT 2 R function in an AT 1 R‐dependent but MasR‐independent manner. This phenomenon may have a physiological significance.