Y. Ohara et al., DIETARY CORRECTION OF HYPERCHOLESTEROLEMIA IN THE RABBIT NORMALIZES ENDOTHELIAL SUPEROXIDE ANION PRODUCTION, Circulation, 92(4), 1995, pp. 898-903
Background We have shown that hypercholesterolemia increases vascular
superoxide anion (O-2(-)) production, which could be responsible for a
ugmented inactivation of endothelium-derived vascular relaxing factor.
We sought to determine whether this increased vascular O-2(-) product
ion is due to infiltration of macrophages into the intima and whether
dietary treatment of hypercholesterolemia normalizes O-2(-) production
. Methods and Results A specific and sensitive assay for O-2(-) based
on chemiluminescence of lucigenin was used; the amount of O-2(-) produ
ced by vascular ring segments was quantified based on known quantities
of O-2(-) produced by xanthine-xanthine oxidase standards. O-2(-) pro
duction of aortic segments from normal rabbits (n=9), cholesterol-fed
rabbits (1% cholesterol diet for 1 month, n=7), and rabbits fed a 1% c
holesterol diet for 1 month followed by a normal diet for 1 month (reg
ression rabbits, n=5) was measured. At the end of these diets, serum c
holesterol levels were 1.5+/-0.2, 26.0+/-3.9, and 1.8+/-0.5 mmol/L (58
+/-6, 1000+/-150, and 71+/-19 mg/dL) in the normal, cholesterol-fed, a
nd regression animals, respectively. Vessels from normal rabbits with
endothelium produced 0.32+/-0.06 nmol O-2(-)/mg dry wt per minute, whe
reas those without endothelium produced approximately twice as much O-
2(-) (0.66+/-0.12 nmol O-2(-) mg dry wt per minute. Vessels with endot
helium from cholesterol-fed rabbits produced 4.5-fold more O-2(-) than
vessels from normal animals. This increased production of O-2(-) was
normalized by endothelial removal. This increased production of O-2(-)
was not due to infiltration of macrophages in the intima, because the
re was no correlation between vascular O-2(-) production and macrophag
e infiltration assessed by immunohistochemistry with use of a specific
antibody against rabbit macrophage. O-2(-) production by vessels from
regression rabbits was similar to that observed in normal animals, an
d as in the normal rabbits, endothelial removal increased O-2(-) produ
ction. Aortic rings from these animals also were studied in organ cham
bers. Dietary lowering of cholesterol dramatically improved vasodilato
r responses to acetylcholine and A23187 (P<.05 versus cholesterol-fed
rabbits). Conclusions Dietary lowering of cholesterol not only improve
s endothelium-dependent vascular relaxation but also normalizes endoth
elial O-2(-) production. Decreases of O-2(-) production by dietary low
ering of cholesterol not only may improve vasomotor control but also m
ay improve other aspects of vascular integrity in atherosclerosis.