To investigate the mechanism responsible for the increased cardiac stiffness associated with hypertensive heart failure in Dahl salt-sensitive (DS) rats and the effects of treatment with the combination of a calcium channel blocker [azelnidipine (AZE)] and angiotensin II type 1 receptor blocker [olmesartan (OLM)].
DS rats fed a high-salt diet from 7 weeks of age were treated (or not) from 12 to 19 weeks of age with the vasodilator hydralazine, OLM plus AZE, or the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor apocynin. Rats fed a low-salt diet served as controls.
Treatment with OLM plus AZE attenuated changes in the expression of collagen isoforms and a decrease in the ratio of elastin to collagen in the left ventricle and prevented the increase in myocardial stiffness and diastolic dysfunction in DS rats in a manner independent of the hypotensive effect of these drugs. Such treatment also inhibited the expression and activation of elastolytic proteases (including cathepsins S and K and metalloproteinases-2, -9, and -12), NADPH oxidase-dependent superoxide production, and inflammatory changes in the failing myocardium. All these effects were mimicked by treatment with apocynin.
The changes in collagen isoform expression and the decrease in the elastin to collagen ratio in the failing myocardium likely account for the increase in diastolic stiffness in this model of hypertensive heart failure. Administration of angiotensin receptor and calcium channel blockers prevented these changes in a manner independent of the hypotensive effect of these drugs by inhibiting the increase in elastolytic activity induced by activation of NADPH oxidase.
From the *Department of Cardiology, Nagoya University Graduate School of Medicine, Nagoya, Japan; †Department of Cardiology, Yanbian University Hospital, Yanji, China; ‡Department of Geriatrics, Nagoya University Graduate School of Medicine, Nagoya, Japan; §Department of Medical Technology, Nagoya University School of Health Sciences, Nagoya, Japan; ¶Department of Pharmacology, Aichi Gakuin University School of Dentistry, Nagoya, Japan; ‖Department of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA; and **Department of Genome Science, Aichi Gakuin University School of Dentistry, Nagoya, Japan.
Received for publication February 6, 2009; accepted April 22, 2009.
Supported in part by grants from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (nos. 17590719 and 19590812 to X.W.C.) and from the Japan Heart Foundation (no. 26-7508 to X.W.C.); by a Japan Heart Foundation/Novartis Research Award on Molecular and Cellular Cardiology (no. 26-7523 to X.W.C); and by a grant from the Takeda Science Foundation (no. 26-7527 to X.W.C).
The authors report no conflicts of interest.
Reprints: Xian Wu Cheng, MD, PhD, Department of Cardiology, Nagoya University School of Medicine, 65 Tsuruma-cho, Showa-ku, Nagoya 466-8550, Japan (e-mail: email@example.com).