Angiotensin II-mediated oxidative stress promotes myocardial tissue remodeling in the transgenic (mRen2) 27 Ren2 rat

Adam Whaley-Connell, Gurushankar Govindarajan, Javad Habibi, Melvin R. Hayden, Shawna A. Cooper, Yongzhong Wei, Lixin Ma, Mahnaz Qazi, Daniel Link, Poorna R. Karuparthi, Craig Stump, Carlos Ferrario, James R. Sowers

Research output: Contribution to journalArticlepeer-review

79 Scopus citations

Abstract

Angiotensin II (ANG II) contributes to cardiac remodeling, hypertrophy, and left ventricular dysfunction. ANG II stimulation of the ANG type 1 receptor (AT1R) 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 AT1R blockade (AT1B) (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). AT1B, but not tempol, reduced blood pressure (P < 0.05); significant improvements were seen with both AT1B 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 AT1R- mediated increases in NADPH oxidase activity.

Original languageEnglish (US)
Pages (from-to)E355-E363
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume293
Issue number1
DOIs
StatePublished - Jul 2007

Keywords

  • Akt
  • Malondialdehyde
  • Reduced nicotinamide adenine dinucleotide phosphate oxidase

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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