Cardiac fibrosis occurs early and involves endothelin and AT-1 receptors in hypertension due to endogenous angiotensin II.

Abstract

OBJECTIVES:

We investigated if endothelin (ET)-1 and the renin-angiotensin-aldosterone system play a role in cardiac fibrosis.

BACKGROUND:

Angiotensin II (Ang II) can induce cardiac fibrosis, but the underlying mechanisms are incompletely understood.

METHODS:

Four-week-old transgenic (mRen2)27 rat (TGRen2) received for four weeks a placebo, the mixed ET(A)/ET(B) endothelin receptor antagonist bosentan, the angiotensin II type I receptor (AT-1) antagonist irbesartan, the ET(A) endothelin receptor antagonist BMS-182874, and a combined treatment with irbesartan plus BMS-182874. We measured collagen density on Sirius red-stained serial sections of the left ventricle (LV) with a photomicroscope equipped with specific software and assessed the gene expression of procollagen alpha1(I), atrial natriuretic peptide (ANP), transforming growth factor-beta 1 (TGFbeta1), endothelin converting enzyme, and ET(B) receptor.

RESULTS:

In the placebo group, hypertension was associated with LV hypertrophy and cardiac fibrosis (LV weight: 4.0 +/- 0.3 mg/g body weight; collagen density: 2.21 +/- 0.16%), which were all prevented with irbesartan (2.3 +/- 0.1, 1.30 +/- 0.13, p < 0.001), but not with BMS-182874 (4.0 +/- 0.2, 2.41 +/- 0.22). Bosentan also prevented fibrosis (1.39 +/- 0.18) but not hypertension and LV hypertrophy (3.38 +/- 0.27). Combined irbesartan and BMS-182874 treatment prevented LV hypertrophy (2.9 +/- 0.1) but not fibrosis (2.52 +/- 0.16). Collagen density correlated (r = 0.414, p < 0.05) with plasma aldosterone levels. In TGRen2 with LV hypertrophy, the gene expression of ANP and ET(B) but not that of TGFbeta1 and procollagen alpha1(I) was increased.

CONCLUSIONS:

In Ang II-dependent hypertension, cardiac fibrosis was associated with LV hypertrophy and was hindered by both mixed ET(A)/ET(B) blockade and AT-1 blockade. Only the latter treatment prevented both hypertension and LV hypertrophy. Thus, there is a dissociation between the mechanisms of cardiac fibrosis and hypertension, which do and do not entail ET-1, respectively.

• Authors: Teresa M Seccia, Anna S Belloni, Reinhold Kreutz, Martin Paul, Gastone G Nussdorfer, Achille C Pessina, Gian Paolo Rossi
• Journal: Journal of the American College of Cardiology (J Am Coll Cardiol) Vol. 41 Issue 4 Pg. 666-73 (Feb 19 2003) ISSN: 0735-1097 [Print] United States
• PMID: 12598081 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antihypertensive Agents
• Biphenyl Compounds
• Dansyl Compounds
• Endothelin-1
• Receptor, Angiotensin, Type 1
• Receptors, Angiotensin
• Receptors, Cell Surface
• Sulfonamides
• Tetrazoles
• Vasoconstrictor Agents
• Angiotensin II
• 5-(dimethylamino)-N-(3,4-dimethyl-5-isoxazolyl)-1-naphthalenesulfonamide
• Irbesartan
• Bosentan

Topics

• Angiotensin II (adverse effects)
• Animals
• Animals, Genetically Modified
• Antihypertensive Agents (pharmacology)
• Biphenyl Compounds (pharmacology)
• Bosentan
• Cardiomyopathies (etiology, pathology, physiopathology)
• Dansyl Compounds (pharmacology)
• Disease Models, Animal
• Endothelin-1 (drug effects, physiology)
• Fibrosis (etiology, pathology, physiopathology)
• Hypertension (chemically induced, complications, physiopathology)
• Irbesartan
• Male
• Rats
• Receptor, Angiotensin, Type 1
• Receptors, Angiotensin (drug effects, physiology)
• Receptors, Cell Surface (drug effects, physiology)
• Sulfonamides (pharmacology)
• Tetrazoles (pharmacology)
• Time Factors
• Vasoconstrictor Agents (adverse effects)