Is angiotensin-(3-4) (Val-Tyr), the shortest angiotensin II-derived peptide, opening new vistas on the renin-angiotensin system?

Abstract

Angiotensin-(3-4) (Ang-(3-4) or Val-Tyr) is the shorter angiotensin (Ang) II-derived peptide, formed through successive hydrolysis that culminates with the release of Val-Tyr as a dipeptide. It is formed both in plasma and in kidney from Ang II and Ang III, and can be considered a component of the systemic and organ-based renin-angiotensin system. It is potently antihypertensive in humans and rats, and its concerted actions on proximal tubule cells culminate in the inhibition of fluid reabsorption, hyperosmotic urinary excretion of Na⁺. At the renal cell signaling level, Ang-(3-4) counteracts Ang II-type 1 receptor-mediated responses by acting as an allosteric enhancer in Ang II-type 2 receptor populations that target adenosine triphosphate-dependent Ca²⁺ and Na⁺ transporters through a cyclic adenosine monophosphate-activated protein kinase pathway.

Keywords: AT1R/AT2R heterodimer dissociation; Ang-(3–4); Na+-ATPase; antihypertensive action; cyclic adenosine monophosphate-dependent protein kinase; hyperosmotic urinary Na+ excretion; local renal RAS.

Figure 1.

Proliferation of angiotensin II (Ang II)-stimulated vascular smooth muscle cells is inhibited by angiotensin-(3−4) (Ang-(3–4)) (represented by VY) in a dose-dependent manner. This figure shows WST-8 reduction by nicotinamide adenine dinucleotide (NADH) in the presence of 1 μmol/L Ang II and increasing concentrations of Ang-(3–4). The inset shows that antiproliferative action of Ang-(3–4) has a 50% inhibitory concentration (IC₅₀) in the micromolar range. Reproduced from Matsui et al., with permission.

Figure 2.

Oral treatment of mild hypertensive individuals with 3 mg angiotensin-(3−4) (Ang-(3–4)) (represented by VY), twice daily. (a) Plasma concentration of Ang-(3–4), angiotensin II (Ang II) and aldosterone before and after a 4-week experimental period. Increased levels of circulating Ang-(3–4) are seen in parallel with reduced plasma Ang II and aldosterone, supporting the idea that the dipeptide acts as a systemic angiotensin-converting enzyme inhibitor. (b) Systolic and diastolic blood pressure of hypertensive individuals were reduced during treatment with Ang-(3–4), which persisted for up to 7 weeks after the treatment was interrupted. Modified from Kawasaki et al., with permission.

Figure 3.

Plasma and kidney levels of angiotensin-(3−4) (Ang-(3–4)) after a single oral dose (10 mg/kg) in 18-week old spontaneously hypertensive rats. Although circulating concentrations of the dipeptide return to base levels 6 hours after administration, its level remains higher in the kidney, indicating the existence of a mechanism of tissue concentration or local production of Ang-(3–4). Modified from Matsui et al., with permission.

Figure 4.

Enzymes and pathways responsible for angiotensin-(3−4) (Ang-(3–4)) formation in basolateral membranes from sheep kidney proximal tubule cells. Aminopeptidases and neprilysin are key enzymes required for at least one step of each pathway. AP: aminopeptidase; NEP: neprilysin; EP: endopeptidase; APA: aminopeptidase A; PsCP: Plummer’s sensitive carboxypeptidase; PCP: prolylcarboxypeptidase; ACE: angiotensin-converting enzyme; APN: aminopeptidase N; DPP: dipeptidylpeptidase. Reproduced from Axelband et al., with permission.

Figure 5.

(a) Angiotensin-(3−4) (Ang-(3–4)) reactivates, with a very high affinity (pA_1/2 ~15.5), the angiotensin II (Ang II)-inhibited basolateral plasma membrane Ca²⁺-ATPase. Ca²⁺ pump activity was assayed with 10^-10 mol/L Ang II and increasing concentrations of Ang-(3–4). Modified from Axelband et al., with permission. (b) Ang-(3−4) creates a probable high affinity site for Ang II at Ang II-type 2 receptors at ~10^-12 mol/L, i.e. with an affinity ~5 orders of magnitude higher than in the absence of Ang-(3−4) (10^-7 mol/L). The competition binding assay was carried out in HEK 293T cells overexpressing AT₂R in 10^-10 mol/L Ang-(3–4). Modified from Axelband et al., with permission.

Figure 6.

(a) Angiotensin-(3−4) (Ang-(3–4)) induces dissociation of Ang II-type 1 receptor (AT₁R)/Ang II-type 2 receptor(AT₂R) heterodimers in normotensive rats, but not in spontaneously hypertensive rats (SHRs). SHRs have a constitutively lower content of heterodimers. Immunoprecipitation assays were carried out using specific AT₁R antibody, followed by western blotting using specific AT₂R antibody. The specificity of the antibodies was confirmed by preadsorption of the antibodies onto the recombinant immunogenic peptide. (b) Inhibition of SHR hyperactive Na⁺ pump by Ang-(3–4) is mediated by protein kinase A (PKA), downstream AT₂R activation. Na⁺-ATPase activity was assayed without any peptide, or in 10^-8 mol/L Ang-(3–4) and 10^-6 mol/L PKA inhibitor peptide PKA_(5-24) in the combinations shown on the abscissae. Reproduced from Dias et al., with permission.