Angiotensin II-mediated oxidative stress promotes myocardial tissue remodeling in the transgenic (mRen2) 27 Ren2 rat.
Angiotensin II (ANG II) contributes to cardiac remodeling, hypertrophy, and left ventricular dysfunction. ANG II stimulation of the ANG type 1 receptor (AT(1)R) generates reactive oxygen species via NADPH oxidase, which facilitates this hypertrophy and remodeling. This investigation sought to determine whether cardiac oxidative stress and cellular remodeling could be attenuated by in vivo AT(1)R blockade (AT(1)B) (valsartan) or superoxide dismutase/catalase mimetic (tempol) treatment in a rodent model of chronically elevated tissue levels of ANG II, the transgenic (mRen2) 27 rat (Ren2). Ren2 rats overexpress the mouse renin transgene with resultant hypertension, insulin resistance, proteinuria, and cardiovascular damage. Young (6-7 wk old) male Ren2 and age-matched Sprague-Dawley rats were treated with valsartan (30 mg/kg), tempol (1 mmol/l), or placebo for 3 wk. Heart tissue NADPH oxidase (NOX) activity and immunohistochemical analysis of subunits NOX2, Rac1, and p22(phox), heart tissue malondialdehyde, and insulin-stimulated protein kinase B (Akt) activation were measured. Structural changes were assessed with cine MRI, transmission electron microscopy, and light microscopy. Increases in septal wall thickness and altered systolic function (cine MRI) were associated with perivascular fibrosis and increased mitochondria in Ren2 on light and transmission electron microscopy (P < 0.05). AT(1)B, but not tempol, reduced blood pressure (P < 0.05); significant improvements were seen with both AT(1)B and tempol on NOX activity, subunit expression, malondialdehyde, and insulin-mediated activation/phosphorylation of Akt (each P < 0.05). Collectively, these data suggest cardiac oxidative stress-induced structural and functional changes are driven, in part, by AT(1)R-mediated increases in NADPH oxidase activity.
Whaley-Connell
Adam
A
University of Missouri--Columbia School of Medicine, Division of Nephrology, MA436, DC043.0, One Hospital Dr., Columbia, MO 65212, USA. whaleyconnella@health.missouri.edu
Govindarajan
Gurushankar
G
Habibi
Javad
J
Hayden
Melvin R
MR
Cooper
Shawna A
SA
Wei
Yongzhong
Y
Ma
Lixin
L
Qazi
Mahnaz
M
Link
Daniel
D
Karuparthi
Poorna R
PR
Stump
Craig
C
Ferrario
Carlos
C
Sowers
James R
JR
D000804:Angiotensin II / Q000494:pharmacology*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D030801:Animals, Genetically Modified; D000975:Antioxidants / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D003497:Cyclic N-Oxides / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D008929:Mitochondria, Heart / Q000648:ultrastructure; D019255:NADPH Oxidases / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D021122:Protein Subunits / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012083:Renin / Q000235:genetics; D013113:Spin Labels; D013777:Tetrazoles / Q000494:pharmacology; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology; D000068756:Valsartan; D020257:Ventricular Remodeling / Q000187:drug effects / Q000235:genetics
D047228:Angiotensin II Type 1 Receptor Blockers; D000975:Antioxidants; D003497:Cyclic N-Oxides; D021122:Protein Subunits; D013113:Spin Labels; D013777:Tetrazoles; D000804:Angiotensin II; D000068756:Valsartan; D019255:NADPH Oxidases; D051057:Proto-Oncogene Proteins c-akt; D012083:Renin; D014633:Valine; C001803:tempol