Extracellular signal regulated kinase and SMAD signaling both mediate the angiotensin II driven progression towards overt heart failure in homozygous TGR(mRen2)27

• Published in: Journal of molecular medicine (Berlin, Germany) Germany), 2004-10, Vol.82 (10), p.678-687
• Main Authors: DE BOER, Rudolf A, POKHAREL, Saraswati, FLESCH, Markus, VAN KAMPEN, Derk A, SUURMEIJER, Albert J. H, BOOMSMA, Frans, VAN GILST, Wiek H, VAN VELDHUISEN, Dirk J, PINTO, Yigal M
• Format: Article
• Language: English
• Subjects: Angiotensin II - pharmacology; Angiotensin II Type 1 Receptor Blockers - pharmacology; Animals; Animals, Genetically Modified; Atrial Natriuretic Factor - physiology; Benzimidazoles - pharmacology; Biological and medical sciences; Blood Pressure - drug effects; Cardiology. Vascular system; Collagen Type I - analysis; Disease Models, Animal; DNA-Binding Proteins - metabolism; Enzyme Activation - drug effects; Enzyme Inhibitors - pharmacology; Fibrosis; General aspects; Heart; Heart Failure - genetics; Heart Failure - metabolism; Heart failure, cardiogenic pulmonary edema, cardiac enlargement; Homozygote; Hypertrophy, Left Ventricular - physiopathology; Imidazoles - pharmacology; Immunohistochemistry; Male; Medical sciences; Mitogen-Activated Protein Kinases - metabolism; Myocardium - chemistry; Protein-Tyrosine Kinases - antagonists & inhibitors; Pyrimidines - pharmacology; Rats; Rats, Sprague-Dawley; Receptors, Angiotensin - drug effects; Renin - genetics; Smad Proteins; Tetrazoles - pharmacology; Time Factors; Trans-Activators - metabolism; Tyrphostins - pharmacology
• ISSN: 0946-2716; 1432-1440
• DOI: 10.1007/s00109-004-0579-3

Angiotensin (Ang) II is a key player in left ventricular (LV) remodeling and cardiac fibrosis. Its effects are thought to be transferred at least in part by mitogen-activated protein kinases (MAPK), transforming growth factor (TGF) beta1, and the Smad pathway. In this study we sought to elucidate whether Ang II related effects on LV dysfunction and fibrosis in vivo are mediated via MAPK or rather via Smad stimulation. We treated homozygous REN2 rats (7-11 weeks) with placebo, Ang II type 1 (AT1) receptor blocker or tyrphostin A46 (TYR), an inhibitor of epidermal growth factor receptor tyrosine kinase that blocks extracellular signal-regulated kinase (ERK) activity. REN2 rats had LV hypertrophy (LVH) and LV dysfunction that progressed to heart failure between 10 and 13 weeks. Blood pressure normalized over time. Renin, N-terminal atrial natriuretic peptide (N-ANP), and ERK were activated while p38 MAPK was not. Treatment with AT1 receptor blockade prevented LVH and right ventricular hypertrophy, normalized systolic and diastolic d P/d t, N-ANP levels, and reduced collagen apposition. Similarly, TYR reduced LVH, N-ANP levels, and collagen apposition. Myocardial ERK activation did not depend on AT1 receptor signaling as it was not affected by AT1 receptor blockade. TYR abolished myocardial ERK activity. Smad2 activation was inhibited by AT1 receptor blockade but was unaltered by TYR. Ang II induced LV remodeling and fibrosis are dependent on both ERK and Smad2 activation. This process is prevented by both AT1 receptor blockade and TYR, and therefore inhibition of either pathway is equally efficacious in restoring LV function and architecture.