Plasma and tissue angiotensin‐converting enzyme 2 activity and plasma equilibrium concentrations of angiotensin peptides in dogs with heart disease

Abstract

Background Angiotensin‐converting enzyme 2 (ACE2) is a homologue of angiotensin‐converting enzyme (ACE) and produces angiotensin peptides (APs), such as angiotensin 1‐9 and 1‐7 that are vasodilatory and natriuretic, and act to counterbalance angiotensin II. Hypothesis Evidence of ACE2 can be found in tissues and plasma of dogs. Equilibrium concentrations of renin angiotensin aldosterone system (RAAS) APs differ in dogs with heart disease compared to healthy dogs and recombinant human ACE2 (rhACE2) alters relative concentrations of APs. Animals Forty‐nine dogs with and 34 dogs without heart disease. Methods Immunohistochemistry and assays for tissue and plasma ACE2 activity and equilibrium concentrations of plasma RAAS APs were performed. Results Immunolabeling for ACE2 was present in kidney and myocardial tissue. Median plasma ACE2 activity was significantly increased in dogs with congestive heart failure (CHF; 6.9 mU/mg; interquartile range [IQR], 5.1‐12.1) as compared to control (2.2 mU/mg; IQR, 1.8‐3.0; P = .0003). Plasma equilibrium analysis of RAAS APs identified significant increases in the median concentrations of beneficial APs, such as angiotensin 1‐7, in dogs with CHF (486.7 pg/mL; IQR, 214.2‐1168) as compared to those with preclinical disease (41.0 pg/mL; IQR, 27.4‐45.1; P < .0001) or control (11.4 pg/mL; IQR, 7.1‐25.3; P = .01). Incubation of plasma samples from dogs with CHF with rhACE2 increased beneficial APs, such as angiotensin 1‐9 (preincubation, 10.3 pg/mL; IQR, 4.4‐37.2; postincubation, 2431 pg/mL; IQR, 1355‐3037; P = .02), while simultaneously decreasing maladaptive APs, such as angiotensin II (preincubation, 53.4 pg/mL; IQR, 28.6‐226.4; postincubation, 2.4 pg/mL; IQR, 0.50‐5.8; P = .02). Conclusions and Clinical Importance Recognition of the ACE2 system expands the conventional view of the RAAS in the dog and represents an important potential therapeutic target.

Renin‐angiotensin aldosterone profile before and after angiotensin‐converting enzyme‐inhibitor administration in dogs with angiotensin‐converting enzyme gene polymorphism

“…The major end‐metabolites of the classical RAAS are angiotensin II and aldosterone, both of which directly or indirectly mediate sodium and water retention, vasoconstriction, and pathological remodeling of cardiac, vascular, and renal tissues . Recent reports describe an alternative RAAS pathway mediated by ACE2, prolyl‐carboxy‐peptidase 16, prolyl‐endo‐peptidase, and neprilysin, with production of the metabolites angiotensin 1‐9, angiotensin 1‐7 and angiotensin 1‐5 in people and dogs . Additional metabolites within this cascade have also been discovered including angiotensin 2‐10, angiotensin 2‐7, and angiotensin 3‐7 .…”

“…Although the RAAS has historically been challenging to investigate, renin‐angiotensin system equilibrium analysis has emerged as a novel technique that allows for comprehensive evaluation of this complex neurohormonal system. Catalyzing enzymes other than ACE (such as ACE2, neprilysin, chymase, and aminopeptidases) mediate production of RAAS metabolites in this pathway, and recent publications have begun to shed light on blood and tissue activities in dogs . This methodology has shown that ACE‐inhibitors not only suppress angiotensin II formation, but also increase levels of the beneficial peptide hormone angiotensin 1‐7, which is known to be metabolized to angiotensin 1‐5 by the N‐domain of ACE .…”

“…1,4,6,7 Recent reports describe an alternative RAAS pathway mediated by ACE2, prolyl-carboxy-peptidase 16, prolyl-endopeptidase, and neprilysin, with production of the metabolites angiotensin 1-9, angiotensin 1-7 and angiotensin 1-5 in people and dogs. [8][9][10][11] Additional metabolites within this cascade have also been discovered including angiotensin 2-10, angiotensin 2-7, and angiotensin 3-7. 8,10,11 Whereas the functional importance of some metabolites…”

“…[8][9][10][11] Additional metabolites within this cascade have also been discovered including angiotensin 2-10, angiotensin 2-7, and angiotensin 3-7. 8,10,11 Whereas the functional importance of some metabolites…”

“…Catalyzing enzymes other than ACE (such as ACE2, neprilysin, chymase, and aminopeptidases) mediate production of RAAS metabolites in this pathway, and recent publications have begun to shed light on blood and tissue activities in dogs. [8][9][10][11] This methodology has shown that ACE-inhibitors not only suppress angiotensin II formation, but also increase levels of the beneficial peptide hormone angiotensin 1-7, which is known to be metabolized to angiotensin 1-5 by the N-domain of ACE. 15 We sought to use equilibrium analysis to further investigate the functional effects of the ACE gene polymorphism at 9:11507816:G>A in dogs.…”