title: β-Pro7Ang III is a novel highly selective angiotensin II type 2 receptor (AT2R) agonist, which acts as a vasodepressor agent via the AT2R in conscious spontaneously hypertensive rats.
abstract: We have previously shown that individual β-amino acid substitution in angiotensin (Ang) II reduced Ang II type 1 receptor (AT1R) but not Ang II type 2 receptor (AT2R)-binding and that the heptapeptide Ang III exhibited greater AT2R:AT1R selectivity than Ang II. Therefore, we hypothesized that β-amino-acid-substituted Ang III peptide analogues would yield highly selective AT2R ligands, which we have tested in binding and functional vascular assays. In competition binding experiments using either AT1R- or AT2R-transfected human embryonic kidney (HEK)-293 cells, novel β-substituted Ang III analogues lacked appreciable AT1R affinity, whereas most compounds could fully displace (125)I-Sar(1)Ile(8) Ang II from AT2R. The rank order of affinity at AT2R was CGP42112 > Ang III > β-Pro(7) Ang III=Ang II > β-Tyr(4) Ang III ≥ PD123319 >> β-Phe(8) Ang III >> β Arg(2) Ang III=β-Val(3) Ang III >> β-Ile(5) Ang III. The novel analogue β-Pro(7) Ang III was the most selective AT2R ligand tested, which was >20,000-fold more selective for AT2R than AT1R. IC50 values at AT2R from binding studies correlated with maximum vasorelaxation in mouse aortic rings. Given that β-Pro(7) Ang III was an AT2R agonist, we compared β-Pro(7) Ang III and native Ang III for their ability to reduce blood pressure in separate groups of conscious spontaneously hypertensive rats. Whereas Ang III alone increased mean arterial pressure (MAP), β-Pro(7) Ang III had no effect. During low-level AT1R blockade, both Ang III and β-Pro(7) Ang III, but not Ang II, lowered MAP (by ∼30 mmHg) at equimolar infusions (150 pmol/kg/min for 4 h) and these depressor effects were abolished by the co-administration of the AT2R antagonist PD123319. Thus, β-Pro(7) Ang III has remarkable AT2R selectivity determined in binding and functional studies and will be a valuable research tool for insight into AT2R function and for future drug development.
authors.affiliation: Departments of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Del Borgo
authors.affiliation: Departments of Pharmacology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Departments of Pharmacology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Sanja
authors.initials: S
authors.lastname: Bosnyak
authors.affiliation: Departments of Pharmacology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Morimer
authors.initials: M
authors.lastname: Khan
authors.affiliation: Departments of Pharmacology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Pia
authors.initials: P
authors.lastname: Walters
authors.affiliation: Departments of Pharmacology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Iresha
authors.initials: I
authors.lastname: Spizzo
authors.affiliation: School of Chemistry, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Patrick
authors.initials: P
authors.lastname: Perlmutter
authors.affiliation: Departments of Physiology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Lucinda
authors.initials: L
authors.lastname: Hilliard
authors.affiliation: Departments of Physiology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Kate
authors.initials: K
authors.lastname: Denton
authors.affiliation: Departments of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Marie-Isabel
authors.initials: MI
authors.lastname: Aguilar
authors.affiliation: Departments of Pharmacology, Monash University, Melbourne, VIC 3800, Australia robert.widdop@monash.edu.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Widdop
authors.affiliation: Departments of Pharmacology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Emma S
authors.initials: ES
authors.lastname: Jones
mesh_terms: D000595:Amino Acid Sequence; D000704:Analysis of Variance; D057912:Angiotensin II Type 2 Receptor Blockers / Q000494:pharmacology*; D000805:Angiotensin III / Q000031:analogs & derivatives* / Q000097:blood / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000503:physiopathology; D001562:Benzimidazoles / Q000378:metabolism; D001667:Binding, Competitive; D001713:Biphenyl Compounds; D004355:Drug Stability; D057809:HEK293 Cells; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D007093:Imidazoles / Q000494:pharmacology*; D066298:In Vitro Techniques; D020128:Inhibitory Concentration 50; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000503:physiopathology; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D011945:Receptors, Angiotensin / Q000737:chemistry / Q000378:metabolism; D013777:Tetrazoles / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects
chemical_list: D057912:Angiotensin II Type 2 Receptor Blockers; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D007093:Imidazoles; D011725:Pyridines; D011945:Receptors, Angiotensin; D013777:Tetrazoles; D014662:Vasoconstrictor Agents; C000601738:angiotensin III, beta-Pro(7)-; D000805:Angiotensin III; C073402:PD 123319; C081643:candesartan
keywords: angiotensin II type 2 (AT2) receptor; angiotensin III; blood pressure; vasorelaxation; β-amino acid substitutions