Renal functional effects of the highly selective AT2R agonist, β-Pro7 Ang III, in normotensive rats

Abstract

Recently, we designed a group of peptides by sequential substitution of the naturally occurring α-amino acid throughout the Ang III peptide sequence with the corresponding β-amino acid. β-Amino acid substitution at the proline residue of Ang III (β-Pro7-Ang III) resulted in a highly selective AT2R ligand, demonstrating remarkable selectivity for the AT2R in both binding and functional studies. To provide additional functional evidence for the suitability of β-Pro7 Ang III as a novel AT2R agonist, we tested effects of acute systemic administration of β-Pro7-Ang III on renal hemodynamic and excretory function in anesthetized normotensive male and female rats. We also compared the natriuretic effects of acute intrarenal administration of native Ang III and β-Pro7-Ang III in the presence of systemic AT1R blockade in anesthetized female rats to allow for the differentiation of systemic versus direct intrarenal natriuretic actions of β-Pro7-Ang III. In both male and female rats, acute systemic administration of β-Pro7-Ang III elicited renal vasodilatation and natriuresis. Notably, greater renal vasodilatory effects were observed in female versus male rats at the highest dose of β-Pro7-Ang III administered. Moreover, intra-renal administration of β-Pro7-Ang III produced significant natriuretic effects in female rats and, like Ang III, evoked AT2R translocation to the apical plasma membrane in renal proximal tubular cells. Taken together, our findings support the use of β-Pro7-Ang III as a novel AT2R agonist and experimental tool for exploring AT2R function and its potential as a therapeutic target. Furthermore, our findings provide further evidence of a sex-specific influence of AT2R stimulation on renal function.

Kidney Angiotensin in Cardiovascular Disease: Formation and Drug Targeting

“…Studies in normotensive rat kidneys have demonstrated that Ang III, but not Ang II, induced AT 2 receptor–mediated natriuresis ( Padia et al, 2007 ) and that this effect was mediated via activation of proximal tubule AT 2 receptors via a cGMP-dependent pathway ( Kemp et al, 2012 ). Similar findings have been reported recently in response to a novel β -amino acid substituted Ang III, β -Pro 7 -Ang III, which has high specificity for the AT 2 receptor ( Krause et al, 2020 ). Further, the Ang III–induced AT 2 receptor–mediated natriuretic effect was augmented by the blockade of aminopeptidase N, an enzyme metabolizing Ang III to Ang IV, thereby increasing Ang III levels ( Padia et al, 2007 ; Kemp et al, 2012 ).…”

“…Since AT 2 receptor activation increases renal blood flow but not GFR (Hilliard et al, 2012(Hilliard et al, , 2014Kemp et al, 2014Kemp et al, , 2016, AT 2 receptormediated natriuresis must be due to changes in tubular function rather than renal hemodynamics. Within the proximal tubule, AT 2 receptor-mediated natriuresis is achieved by translocation of AT 2 receptors to the apical plasma membrane of proximal tubular cells (Kemp et al, 2014(Kemp et al, , 2016Krause et al, 2020), inhibition of HCO 3…”

“…Since AT 2 receptor activation increases renal blood flow but not GFR ( Hilliard et al, 2012 , 2014 ; Kemp et al, 2014 , 2016 ), AT 2 receptor–mediated natriuresis must be due to changes in tubular function rather than renal hemodynamics. Within the proximal tubule, AT 2 receptor–mediated natriuresis is achieved by translocation of AT 2 receptors to the apical plasma membrane of proximal tubular cells ( Kemp et al, 2014 , 2016 ; Krause et al, 2020 ), inhibition of HCO 3 − reabsorption ( Haithcock et al, 1999 ), and the translocation, internalization, and inactivation of NHE3 in the apical membrane and Na + /K + -ATPase in the basolateral membrane ( Kemp et al, 2014 ). The latter occurs via the NO/cGMP pathway.…”

Update on Angiotensin II Subtype 2 Receptor: Focus on Peptide and Nonpeptide Agonists

“…β-Pro 7 -Ang III also induced encouraging renal vasodilatory and natriuretic effects, a classic AT2R agonist activity, in both male and female normotensive rats. This study highlighted specific roles for the AT2R in the regulation of renal function according to gender since renal vasodilator response was much greater in female rats than males (Krause et al, 2020).…”

Backbone Modifications of HLA-A2-Restricted Antigens Induce Diverse Binding and T Cell Activation Outcomes

“…Unexpectedly, we found that α-to-β replacement could, in some cases, alter the nature of the message, relative to the original α-peptide. Examples included discovery of partner-selective α/β-peptides derived from a promiscuous α-peptide − and pathway-selective analogues of peptide hormones (“biased agonists”). , Studies involving backbone modification via α-to-β replacement in derivatives of neuropeptide Y family members, − angiotensins, , and phosphopeptides that bind to 14–3–3 proteins provide further evidence that replacing one or a few α residues in a polypeptide with β homologues can generate novel derivatives with interesting properties. , These precedents led us to wonder whether antigen analogues containing an α-to-β replacement might form MHC I complexes that retain the signaling properties of the native pMHC I, as manifested via engagement of TCRs, or perhaps display altered signaling properties.…”