Blood Pressure-Independent ET A  and AT 1  Receptor Blocker Effects on the Coronaries of Rats Harboring Human Renin and Angiotensinogen Genes

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Abstract

Background:Blood pressure-independent (BP) effects of angiotensin (Ang) II and endothelin (ET) on coronaries (remodeling) in high renin hypertension are incompletely understood. Methods:We studied the effects of subdepressor doses of Ang II receptor (AT1) blockade with losartan (10 mg/kg/day gavage) and endothelin A receptor (ETA) blockade with LU135252 (30 mg/kg/day) on the coronaries of rats harboring human renin and angiotensinogen genes (dTGR). Nontransgenic Sprague-Dawley rats were controls. The rats were treated between the ages of 6 and 10 weeks. Coronary cross-sectional area [CSA; 0.79 × (external diameter2 – internal diameter2)], cell proliferation, and infiltration of monocytes/macrophages were determined. Results:Monotherapy did not lower BP while combination treatment did (p < 0.05). All treatments reduced mortality (p < 0.01). CSA was decreased by all treatments compared to vehicle, independent of blood pressure (p < 0.05). Extensive proliferation by PCNA staining and infiltration of ED-1-positive cells was diminished by both treatment and the combination. Conclusions:The data show that Ang II promotes coronary inflammation and remodeling, in part independent of blood pressure but dependent upon ET signaling. Combination treatment directed at both pathways may improve outcome, independent of blood pressure reduction.

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Angiotensin II stimulated expression of transforming growth factor-beta1 in cardiac fibroblasts and myofibroblasts.

S Campbell, L. C. Katwa (1997)

Angiotensin II (Ang II) stimulates pathologic myocardial fibrosis. Cardiac fibroblasts (CFb) and myofibroblasts mediate this response, perhaps in part by indirect production of specific cytokines. We sought to determine if Ang II could stimulate transforming growth factor-beta1 (TGF-beta1) gene expression and protein production in adult rat CFb and two cardiac myofibroblast cell types, scar myofibroblasts (MyoFb) and valvular interstitial cells (VIC). Confluent CFb, MyoFb, and VIC in serum-deprived (0.4% FCS) media were treated with Ang II (10(-7) m for CFb; 10(-9) m for MyoFb, VIC) for 24 h. Untreated cells served as controls. Culture media was collected and TGF-beta1 levels determined in triplicate using a sandwich ELISA. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was performed to determine TGF-beta1 mRNA expression. Ang II increased CFb (P<0.02) and VIC (P<0.04) TGF-beta1 mRNA expression, while the increase in MyoFb was not statistically significant. MyoFb produced the highest TGF-beta1 levels under control conditions compared to VIC and CFb. Ang II stimulated further TGF-beta1 secretion in VIC and CFb, but not MyoFb. The AT1 receptor antagonist Losartan (10(-7) m) greatly attenuated Ang II-stimulated TGF-B1 secretion and decreased TGF-beta1 immunostaining in VIC. The AT2 receptor antagonist PD123177 (10(-7) m) also decreased secretion and immunostaining of TGF-beta1 in VIC, but to a lesser extent than Losartan. TGF-beta1 secretion by MyoFb was unaffected by Losartan and PD123177, although TGF-B1 immunostaining was absent or greatly decreased, respectively, compared to Ang II-treated MyoFb. Ang II stimulates TGF-beta1 gene expression and/or protein production in cardiac fibroblast-like cells which may act as an autocrine/paracrine stimulus to collagen formation. Furthermore, TGF-beta1 production and secretion in these cells can be modulated by specific Ang II receptor antagonists, suggesting a potential benefit in preventing/attenuating pathologic myocardial fibrosis.

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Evidence for a Role of Mast Cells in the Evolution to Congestive Heart Failure

Masatake Hara, Koh Ono, Myung-Woo Hwang … (2002)

Mast cells are believed to be involved in the pathophysiology of heart failure, but their precise role in the process is unknown. This study examined the role of mast cells in the progression of heart failure, using mast cell-deficient (WBB6F1-W/Wv) mice and their congenic controls (wild-type [WT] mice). Systolic pressure overload was produced by banding of the abdominal aorta, and cardiac function was monitored over 15 wk. At 4 wk after aortic constriction, cardiac hypertrophy with preserved left ventricular performance (compensated hypertrophy) was observed in both W/Wv and WT mice. Thereafter, left ventricular performance gradually decreased in WT mice, and pulmonary congestion became apparent at 15 wk (decompensated hypertrophy). In contrast, decompensation of cardiac function did not occur in W/Wv mice; left ventricular performance was preserved throughout, and pulmonary congestion was not observed. Perivascular fibrosis and upregulation of mast cell chymase were all less apparent in W/Wv mice. Treatment with tranilast, a mast cell–stabilizing agent, also prevented the evolution from compensated hypertrophy to heart failure. These observations suggest that mast cells play a critical role in the progression of heart failure. Stabilization of mast cells may represent a new approach in the management of heart failure.

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Enhanced expression of endothelin-1 gene in resistance arteries in severe human essential hypertension.

E Schiffrin, L Deng, P Sventek … (1997)

Endothelins are potent vasoconstrictors, and may also act as mitogens and hypertrophic agents. Expression of a member of this family of peptides, endothelin-1, is enhanced in the endothelium of blood vessels of rats with severe forms of hypertension, even in the absence of elevated plasma endothelin levels. In some of these hypertensive models enhanced endothelin-1 gene expression may contribute to vascular hypertrophy of small arteries and to elevation of blood pressure.

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Author and article information

Journal

Journal ID (publisher-id): KBR

Journal ID (nlm-ta): Kidney Blood Press Res

Journal ID (doi): 10.1159/issn.1420-4096

Title: Kidney and Blood Pressure Research

Publisher: S. Karger AG

ISSN (Print): 1420-4096

ISSN (Electronic): 1423-0143

Publication date Subscription-year: 2005

Publication date (Print): June 2005

Publication date (Electronic): 10 June 2005

Volume: 28

Issue: 3

Pages: 134-143

Affiliations

Franz Volhard Clinic, HELIOS Klinikum-Berlin and Max Delbrück Center, Medical Faculty of the Charité, Humboldt University of Berlin, Berlin, Germany

Article

Publisher ID: 85956 Other ID: Kidney Blood Press Res 2005;28:134–143

DOI: 10.1159/000085956

PubMed ID: 15915003

SO-VID: 3e065f7b-f361-4e93-a24c-af6f49357db1

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Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

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Blood Pressure-Independent ET _A and AT ₁ Receptor Blocker Effects on the Coronaries of Rats Harboring Human Renin and Angiotensinogen Genes

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Karger: Nephrology

Most cited references 10

Angiotensin II stimulated expression of transforming growth factor-beta1 in cardiac fibroblasts and myofibroblasts.

Evidence for a Role of Mast Cells in the Evolution to Congestive Heart Failure

Enhanced expression of endothelin-1 gene in resistance arteries in severe human essential hypertension.

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