title: A single beta-amino acid substitution to angiotensin II confers AT2 receptor selectivity and vascular function.
abstract: Novel AT(2)R ligands were designed by substituting individual β-amino acid in the sequence of the native ligand angiotensin II (Ang II). Relative ATR selectivity and functional vascular assays (in vitro AT(2)R-mediated vasorelaxation and in vivo vasodepressor action) were determined. In competition binding experiments using either AT(1)R- or AT(2)R- transfected HEK-293 cells, only β-Asp(1)-Ang II and Ang II fully displaced [(125)I]-Ang II from AT(1)R. In contrast, β-substitutions at each position of Ang II exhibited AT(2)R affinity, with β-Tyr(4)-Ang II and β-Ile(5)-Ang II exhibiting ≈ 1000-fold AT(2)R selectivity. In mouse aortic rings, β-Tyr(4)-Ang II and β-Ile(5)-Ang II evoked vasorelaxation that was sensitive to blockade by the AT(2)R antagonist PD123319 and the nitric oxide synthase inhibitor L-NAME. When tested with a low level of AT(1)R blockade, β-Ile(5)-Ang II (15 pmol/kg per minute IV for 4 hours) reduced blood pressure (BP) in conscious spontaneously hypertensive rats (β-Ile(5)-Ang II plus candesartan, -24 ± 4 mm Hg) to a greater extent than candesartan alone (-11 ± 3 mm Hg, n=7, P<0.05), an effect that was abolished by concomitant PD123319 infusion. However, in an identical experimental protocol, β-Tyr(4)-Ang II had no influence on BP (n=10), and it was less stable than β-Ile(5)-Ang II in plasma stability assays. Thus, this study demonstrated that a single β-amino acid substitution resulted in a compound that demonstrated both in vitro vasorelaxation and in vivo depressor activity via AT(2)R. This approach to the design and synthesis of novel AT(2)R-selective peptidomimetics shows great potential to provide insight into AT(2)R function.
authors.affiliation: Department of Pharmacology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Emma S
authors.initials: ES
authors.lastname: Jones
authors.forename: Mark P
authors.initials: MP
authors.lastname: Del Borgo
authors.forename: Julian F
authors.initials: JF
authors.lastname: Kirsch
authors.forename: Daniel
authors.initials: D
authors.lastname: Clayton
authors.forename: Sanja
authors.initials: S
authors.lastname: Bosnyak
authors.forename: Iresha
authors.initials: I
authors.lastname: Welungoda
authors.forename: Nicholas
authors.initials: N
authors.lastname: Hausler
authors.forename: Sharon
authors.initials: S
authors.lastname: Unabia
authors.forename: Patrick
authors.initials: P
authors.lastname: Perlmutter
authors.forename: Walter G
authors.initials: WG
authors.lastname: Thomas
authors.forename: Marie-Isabel
authors.initials: MI
authors.lastname: Aguilar
authors.forename: Robert E
authors.initials: RE
authors.lastname: Widdop
mesh_terms: D019943:Amino Acid Substitution; D000704:Analysis of Variance; D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology*; D057912:Angiotensin II Type 2 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D051379:Mice; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D011485:Protein Binding; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism; D011945:Receptors, Angiotensin / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
chemical_list: D057912:Angiotensin II Type 2 Receptor Blockers; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin; D000804:Angiotensin II; C073402:PD 123319; D019331:NG-Nitroarginine Methyl Ester