Angiotensin receptor-1 blocker inhibits atherosclerotic changes and endothelial disruption of the aortic valve in hypercholesterolemic rabbits.
OBJECTIVE
We sought to examine the effect of angiotensin receptor blocker (ARB) on the formation of lesions in the aortic valves of hypercholesterolemic rabbits.


BACKGROUND
Recently, atherosclerosis has been recognized as a mechanism that is responsible for calcific aortic stenosis. The effect of ARBs might help to prevent aortic stenosis because they have multiple antiatherosclerotic effects.


METHODS
Male Japanese white rabbits (n = 36) were separated as follows: control with chow diet (C) and vehicle (V) groups, both of which were fed a 1% cholesterol diet for 8 weeks, and an ARB group (A), which was fed a 1% cholesterol diet for 8 weeks with ARB (olmesartan, 1 mg/kg/day) for the last 4 weeks.


RESULTS
This dose of olmesartan did not affect either blood pressure or cholesterol levels. Dietary cholesterol induced fatty deposition with macrophage accumulation and osteopontin coexpression in valve leaflets, whereas ARB decreased macrophage accumulation (% area: V, 9.3 +/- 0.34; A, 1.4 +/- 0.30; p = 0.003) and osteopontin expression (p = 0.017). Angiotensin-converting enzyme was also up-regulated in V and decreased by olmesartan (p = 0.015). Immunohistochemistry with anti-CD31 antibody revealed that dietary cholesterol disrupted and olmesartan preserved endothelial integrity on the lesion-prone aortic side of the valve (% CD31-positive circumference: V, 30 +/- 3.7; A, 62 +/- 4.8; p = 0.003). Numbers of alpha-smooth muscle actin-positive myofibroblasts were increased in V and decreased by olmesartan (p = 0.003). Real-time polymerase chain reaction revealed that increased amounts of messenger ribonucleic acid for osteoblast-specific transcription factor core binding factor alpha-1 in V were diminished by olmesartan.


CONCLUSIONS
Atherosclerotic changes in the aortic valves of rabbits fed with cholesterol were inhibited by ARB, whereas endo-thelial integrity was preserved and transdifferentiation into myofibroblasts and/or osteoblasts in valve leaflets was inhibited.
Arishiro
Kumiko
K
First Department of Internal Medicine, Osaka Medical College, Takatsuki, Osaka, Japan.
Hoshiga
Masaaki
M
Negoro
Nobuyuki
N
Jin
Denan
D
Takai
Shinji
S
Miyazaki
Mizuo
M
Ishihara
Tadashi
T
Hanafusa
Toshiaki
T
D047228:Angiotensin II Type 1 Receptor Blockers / Q000627:therapeutic use*; D000818:Animals; D001021:Aortic Valve / Q000473:pathology*; D050197:Atherosclerosis / Q000150:complications / Q000473:pathology* / Q000517:prevention & control*; D004730:Endothelium, Vascular / Q000473:pathology*; D006937:Hypercholesterolemia / Q000150:complications*; D007093:Imidazoles / Q000627:therapeutic use*; D008297:Male; D011817:Rabbits; D013777:Tetrazoles / Q000627:therapeutic use*
D047228:Angiotensin II Type 1 Receptor Blockers; D007093:Imidazoles; D013777:Tetrazoles; C437965:olmesartan