Angiotensin-(1-9) attenuates cardiac fibrosis in the stroke-prone spontaneously hypertensive rat via the angiotensin type 2 receptor

Flores, M., Work, L.M. , Douglas, K., Denby, L., Dominiczak, A.F. , Graham, D. and Nicklin, S.A. (2012) Angiotensin-(1-9) attenuates cardiac fibrosis in the stroke-prone spontaneously hypertensive rat via the angiotensin type 2 receptor. Hypertension, 59(2), pp. 300-307. (doi: 10.1161/HYPERTENSIONAHA.111.177485)

Abstract

The renin-angiotensin system regulates cardiovascular physiology via angiotensin II engaging the angiotensin type 1 or type 2 receptors. Classic actions are type 1 receptor mediated, whereas the type 2 receptor may counteract type 1 receptor activity. Angiotensin-converting enzyme 2 metabolizes angiotensin II to angiotensin-(1-7) and angiotensin I to angiotensin-(1-9). Angiotensin-(1-7) antagonizes angiotensin II actions via the receptor Mas. Angiotensin-(1-9) was shown recently to block cardiomyocyte hypertrophy via the angiotensin type 2 receptor. Here, we investigated in vivo effects of angiotensin-(1-9) via the angiotensin type 2 receptor. Angiotensin-(1-9) (100 ng/kg per minute) with or without the angiotensin type 2 receptor antagonist PD123 319 (100 ng/kg per minute) or PD123 319 alone was infused via osmotic minipump for 4 weeks into stroke-prone spontaneously hypertensive rats. We measured blood pressure by radiotelemetry and cardiac structure and function by echocardiography. Angiotensin-(1-9) did not affect blood pressure or left ventricular mass index but reduced cardiac fibrosis by 50% (P<0.01) through modulating collagen I expression, reversed by PD123 319 coinfusion. In addition, angiotensin-(1-9) inhibited fibroblast proliferation in vitro in a PD123 319-sensitive manner. Aortic myography revealed that angiotensin-(1-9) significantly increased contraction to phenylephrine compared with controls after N-nitro-l-arginine methyl ester treatment, an effect abolished by PD123 319 coinfusion (area under the curve: angiotensin-(1-9) N-nitro-l-arginine methyl ester=98.9±11.8%; control+N-nitro-l-arginine methyl ester=74.0±10.4%; P<0.01), suggesting that angiotensin-(1-9) improved basal NO bioavailability in an angiotensin type 2 receptor–sensitive manner. In summary, angiotensin-(1-9) reduced cardiac fibrosis and altered aortic contraction via the angiotensin type 2 receptor supporting a direct role for angiotensin-(1-9) in the renin-angiotensin system.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Graham, Dr Delyth and Flores, Dr Monica and Nicklin, Professor Stuart and Denby, Dr Laura and Douglas, Dr Kirsten and Dominiczak, Professor Anna and Work, Dr Lorraine
• Authors: Flores, M., Work, L.M., Douglas, K., Denby, L., Dominiczak, A.F., Graham, D., and Nicklin, S.A.
• College/School: College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
• Journal Name: Hypertension
• ISSN: 0194-911X
• ISSN (Online): 1524-4563
• Published Online: 19 December 2011
• Copyright Holders: Copyright © 2011 American Heart Association
• First Published: First published in Hypertension 59(2):300-307
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher