Novel role of aminopeptidase-A in angiotensin-(1-7) metabolism post myocardial infarction

Am J Physiol Heart Circ Physiol. 2014 Apr 1;306(7):H1032-40. doi: 10.1152/ajpheart.00911.2013. Epub 2014 Jan 24.

Abstract

Aminopeptidase-A (APA) is a less well-studied enzyme of the renin-angiotensin system. We propose that it is involved in cardiac angiotensin (ANG) metabolism and its pathologies. ANG-(1-7) can ameliorate remodeling after myocardial injury. The aims of this study are to (1) develop mass spectrometric (MS) approaches for the assessment of ANG processing by APA within the myocardium; and (2) investigate the role of APA in cardiac ANG-(1-7) metabolism after myocardial infarction (MI) using sensitive MS techniques. MI was induced in C57Bl/6 male mice by ligating the left anterior descending (LAD) artery. Frozen mouse heart sections (in situ assay) or myocardial homogenates (in vitro assay) were incubated with the endogenous APA substrate, ANG II. Results showed concentration- and time-dependent cardiac formation of ANG III from ANG II, which was inhibited by the specific APA inhibitor, 4-amino-4-phosphonobutyric acid. Myocardial APA activity was significantly increased 24 h after LAD ligation (0.82 ± 0.02 vs. 0.32 ± 0.02 ρmol·min(-1)·μg(-1), MI vs. sham, P < 0.01). Both MS enzyme assays identified the presence of a new peptide, ANG-(2-7), m/z 784, which accumulated in the MI (146.45 ± 6.4 vs. 72.96 ± 7.0%, MI vs. sham, P < 0.05). Use of recombinant APA enzyme revealed that APA is responsible for ANG-(2-7) formation from ANG-(1-7). APA exhibited similar substrate affinity for ANG-(1-7) compared with ANG II {Km (ANG II) = 14.67 ± 1.6 vs. Km [ANG-(1-7)] = 6.07 ± 1.12 μmol/l, P < 0.05}. Results demonstrate a novel role of APA in ANG-(1-7) metabolism and suggest that the upregulation of APA, which occurs after MI, may deprive the heart of cardioprotective ANG-(1-7). Thus APA may serve as a potentially novel therapeutic target for management of tissue remodeling after MI.

Keywords: MALDI-imaging; aminopeptidase-A; angiotensin peptides; myocardial infarction; renin-angiotensin system.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Angiotensin I / metabolism*
  • Angiotensin II / metabolism
  • Angiotensin III / metabolism
  • Angiotensin-Converting Enzyme 2
  • Animals
  • Disease Models, Animal
  • Enzyme Inhibitors / pharmacology
  • Glutamyl Aminopeptidase / antagonists & inhibitors
  • Glutamyl Aminopeptidase / metabolism*
  • Kinetics
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Myocardial Infarction / enzymology*
  • Myocardial Infarction / pathology
  • Myocardium / enzymology*
  • Myocardium / pathology
  • Peptide Fragments / metabolism*
  • Peptidyl-Dipeptidase A / metabolism
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Substrate Specificity
  • Tandem Mass Spectrometry
  • Ventricular Remodeling

Substances

  • Enzyme Inhibitors
  • Peptide Fragments
  • angiotensin II (2-7)
  • Angiotensin II
  • Angiotensin III
  • Angiotensin I
  • Glutamyl Aminopeptidase
  • Peptidyl-Dipeptidase A
  • Ace2 protein, mouse
  • Angiotensin-Converting Enzyme 2
  • angiotensin I (1-7)