title: Enhanced susceptibility to biomechanical stress in ACE2 null mice is prevented by loss of the p47(phox) NADPH oxidase subunit.
abstract: OBJECTIVE
  Angiotensin-converting enzyme 2 (ACE2) is an important negative regulator of the renin-angiotensin system. Loss of ACE2 enhances the susceptibility to heart disease but the mechanism remains elusive. We hypothesized that ACE2 deficiency activates the NADPH oxidase system in pressure overload-induced heart failure.
  
  
  RESULTS
  Using the aortic constriction model, we subjected wild-type (Ace2(+/y)), ACE2 knockout (ACE2KO, Ace2(-/y)), p47(phox) knockout (p47(phox)KO, p47(phox-)(/-)), and ACE2/p47(phox) double KO mice to pressure overload. We examined changes in peptide levels, NADPH oxidase activity, gene expression, matrix metalloproteinases (MMP) activity, pathological signalling, and heart function. Loss of ACE2 resulted in enhanced susceptibility to biomechanical stress leading to eccentric remodelling, increased pathological hypertrophy, and worsening of systolic performance. Myocardial angiotensin II (Ang II) levels were increased, whereas Ang 1-7 levels were lowered. Activation of Ang II-stimulated signalling pathways in the ACE2-deficient myocardium was associated with increased expression and phosphorylation of p47(phox), NADPH oxidase activity, and superoxide generation, leading to enhanced MMP-mediated degradation of the extracellular matrix. Additional loss of p47(phox) in the ACE2KO mice normalized the increased NADPH oxidase activity, superoxide production, and systolic dysfunction following pressure overload. Ang 1-7 supplementation suppressed the increased NADPH oxidase and rescued the early dilated cardiomyopathy in pressure-overloaded ACE2KO mice.
  
  
  CONCLUSIONS
  In the absence of ACE2, biomechanical stress triggers activation of the myocardial NAPDH oxidase system with a critical role of the p47(phox) subunit. Increased production of superoxide, activation of MMP, and pathological signalling leads to severe adverse myocardial remodelling and dysfunction in ACE2KO mice.
authors.affiliation: Division of Cardiology, Department of Medicine, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada T6G 2S2.
authors.forename: Sreedhar
authors.initials: S
authors.lastname: Bodiga
authors.forename: Jiu Chang
authors.initials: JC
authors.lastname: Zhong
authors.forename: Wang
authors.initials: W
authors.lastname: Wang
authors.forename: Ratnadeep
authors.initials: R
authors.lastname: Basu
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lo
authors.forename: George C
authors.initials: GC
authors.lastname: Liu
authors.forename: Danny
authors.initials: D
authors.lastname: Guo
authors.forename: Steven M
authors.initials: SM
authors.lastname: Holland
authors.forename: James W
authors.initials: JW
authors.lastname: Scholey
authors.forename: Josef M
authors.initials: JM
authors.lastname: Penninger
authors.forename: Zamaneh
authors.initials: Z
authors.lastname: Kassiri
authors.forename: Gavin Y
authors.initials: GY
authors.lastname: Oudit
mesh_terms: D000704:Analysis of Variance; D000803:Angiotensin I; D000804:Angiotensin II / Q000008:administration & dosage / Q000378:metabolism; D000085962:Angiotensin-Converting Enzyme 2; D000818:Animals; D001794:Blood Pressure; D002311:Cardiomyopathy, Dilated / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D004195:Disease Models, Animal; D004789:Enzyme Activation; D005109:Extracellular Matrix / Q000378:metabolism; D006333:Heart Failure / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D008297:Male; D020782:Matrix Metalloproteinases / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D019255:NADPH Oxidases / Q000172:deficiency* / Q000235:genetics; D018384:Oxidative Stress; D010446:Peptide Fragments / Q000008:administration & dosage / Q000378:metabolism; D007703:Peptidyl-Dipeptidase A / Q000172:deficiency* / Q000235:genetics; D010766:Phosphorylation; D013314:Stress, Mechanical; D013481:Superoxides / Q000378:metabolism; D013997:Time Factors; D016277:Ventricular Function, Left; D020257:Ventricular Remodeling
chemical_list: D010446:Peptide Fragments; D013481:Superoxides; D000804:Angiotensin II; D000803:Angiotensin I; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; D007703:Peptidyl-Dipeptidase A; C000705328:Ace2 protein, mouse; D000085962:Angiotensin-Converting Enzyme 2; D020782:Matrix Metalloproteinases; C118790:angiotensin I (1-7)