Angiotensin-(1-7)

Overview

Angiotensin-(1-7) [Ang-(1-7)] is a heptapeptide formed primarily by cleavage of the C-terminal phenylalanine from angiotensin II by the enzyme angiotensin-converting enzyme 2 (ACE2). It can also be generated directly from angiotensin I by neprilysin, thimet oligopeptidase, and prolyl endopeptidase. Ang-(1-7) is the signature effector of the protective, counterregulatory arm of the renin-angiotensin system (RAS), opposing many of the classical hypertensive, pro-fibrotic, and pro-inflammatory actions of angiotensin II.

The identification of Ang-(1-7) as a biologically active peptide emerged in the 1980s through studies by Ferrario, Santos, and colleagues showing that the heptapeptide produced distinct cardiovascular effects — vasodilation, natriuresis, anti-proliferative effects in vascular smooth muscle — that could not be attributed to AT1 or AT2 receptors. In 2003, Santos and colleagues identified the orphan GPCR Mas as the specific Ang-(1-7) receptor, establishing the ACE2/Ang-(1-7)/Mas axis as a pharmacologically distinct pillar of RAS biology.

Research interest in Ang-(1-7) expanded dramatically with the discovery that ACE2 also serves as the cellular receptor for SARS-CoV and SARS-CoV-2 coronaviruses, bringing renewed attention to the full ACE2/Ang-(1-7)/Mas pathway and its dysregulation in viral and cardiovascular pathology. The peptide has become central to the conceptual framework of "balanced RAS" in which the pro-hypertensive ACE/AngII/AT1R arm is counterweighed by the ACE2/Ang-(1-7)/Mas arm.

Structure/Sequence

Angiotensin-(1-7): Asp-Arg-Val-Tyr-Ile-His-Pro (DRVYIHP)

• Length: 7 amino acids
• Molecular weight: ~899 g/mol
• Source: N-terminal 7 residues of angiotensin I; equivalent to angiotensin II minus C-terminal Phe
• Generation: Primarily from angiotensin II by ACE2; also from angiotensin I directly by neprilysin, POP
• Free C-terminus: Unamidated

Comparison to Angiotensin II

Angiotensin II (DRVYIHPF, 8 residues) and Ang-(1-7) differ only by C-terminal phenylalanine, yet have qualitatively different receptor profiles and physiological actions. The C-terminal Phe of Ang II is essential for AT1R binding; its removal creates a peptide that no longer binds AT1R with high affinity but now engages Mas receptor preferentially.

Other RAS Peptides

• Ang III (Ang 2-8): AT1R/AT2R ligand with distinct profile
• Ang IV (Ang 3-8): AT4 receptor (IRAP) ligand
• Ang A: Ala-substituted Ang II derivative
• Alamandine: Asp→Ala-substituted Ang-(1-7) analog with related but distinct profile

Mechanism of Action

Mas Receptor

Ang-(1-7) signals primarily through the Mas receptor (MAS1):

• G-protein coupling: Gq and Gi in different systems
• Downstream pathways:
  • PI3K/Akt activation
  • eNOS activation → NO production → vasodilation
  • MAPK modulation (often inhibition of ERK1/2)
  • Arachidonic acid release
• Widely expressed: Vasculature, heart, kidney, brain, reproductive tissues

AT2 Receptor Interactions

Ang-(1-7) has weak AT2R binding and may contribute to some AT2-mediated effects. The overlap between Mas and AT2R signaling — both generally opposing AT1R — makes parsing exclusive vs shared effects challenging.

Vasodilation and Hemodynamics

• NO-dependent vasodilation, particularly in resistance arteries
• Bradykinin potentiation — Ang-(1-7) enhances bradykinin B2 receptor signaling, amplifying endothelial relaxation
• Blood pressure reduction in hypertensive models
• Improved endothelial function

Cardiac Effects

• Anti-hypertrophic: opposes cardiac hypertrophy driven by pressure overload or AngII
• Anti-fibrotic: reduces cardiac collagen deposition
• Anti-arrhythmic in ischemia-reperfusion models
• Cardioprotective in myocardial infarction models

Anti-Proliferative and Anti-Fibrotic Effects

• Inhibits vascular smooth muscle proliferation
• Reduces tissue fibrosis (cardiac, renal, pulmonary, hepatic)
• Downregulates TGF-β signaling in some contexts

Metabolic Effects

• Improves insulin sensitivity
• Anti-inflammatory effects on adipose tissue
• May contribute to the metabolic benefits of ACE inhibition (which raises Ang I availability for Ang-(1-7) generation)

ACE2 Regulation

ACE2 is the key enzyme generating Ang-(1-7). ACE2 expression is regulated in cardiovascular disease, diabetes, and infection (coronavirus binding). Downregulation of ACE2 reduces Ang-(1-7) availability and tilts the RAS balance toward the pro-hypertensive arm.

Research Summary

Common Discussion Topics

1. Counterregulatory arm — The ACE2/Ang-(1-7)/Mas axis is conceptually critical as the endogenous counterweight to the ACE/AngII/AT1R axis. This balance framework explains many physiological and pathological states: diseases characterized by low Ang-(1-7) activity (heart failure, diabetic nephropathy) and therapeutic approaches that tilt the balance (ACE inhibitors, ARBs both increase Ang-(1-7) levels).

2. ACE inhibitor mechanism — The clinical benefits of ACE inhibitors derive from both reduced Ang II formation and increased Ang I availability, which can then be converted to Ang-(1-7). This is part of why ACE inhibitors have efficacy beyond simple angiotensin II blockade.

3. ACE2 and coronaviruses — SARS-CoV-2 binding to ACE2 links viral infection to RAS biology: viral occupancy of ACE2 may reduce its catalytic activity, decreasing Ang-(1-7) generation and contributing to inflammatory and cardiovascular complications of severe infection.

4. Bradykinin potentiation — Ang-(1-7) enhances bradykinin B2 receptor signaling, creating cross-talk between the RAS and kallikrein-kinin systems. This potentiation contributes to endothelial vasodilation and anti-thrombotic effects.

5. Oral formulation challenges — Native Ang-(1-7) is rapidly degraded by peptidases. Research on oral formulations, cyclodextrin inclusion complexes, hydroxypropyl-β-cyclodextrin-Ang-(1-7), and stable analogs (e.g., AVE 0991) reflects efforts to make this pathway therapeutically accessible.

Related Compounds

• Angiotensin II — octapeptide parent and counterregulatory target
• Bradykinin — cross-talking vasoactive peptide potentiated by Ang-(1-7)
• Bradykinin-2 — related kinin peptide