Raloxifene protects endothelial cell function against oxidative stress.
OBJECTIVE
Maintaining a delicate balance between the generation of nitric oxide (NO) and removal of reactive oxygen species (ROS) within the vascular wall is crucial to the physiological regulation of vascular tone. Increased production of ROS reduces the effect and/or bioavailability of NO, leading to an impaired endothelial function. This study tested the hypothesis that raloxifene, a selective oestrogen receptor modulator, can prevent endothelial dysfunction under oxidative stress.


METHODS
Changes in isometric tension were measured in rat aortic rings. The content of cyclic GMP in aortic tissue was determined by radioimmunoassay. Phosphorylation of endothelial NOS (eNOS) and Akt was assayed by Western blot analysis.


RESULTS
In rings with endothelium, ACh-induced relaxations were attenuated by a ROS-generating reaction (hypoxanthine plus xanthine oxidase, HXXO). The impaired relaxations were ameliorated by acute treatment with raloxifene. HXXO suppressed the ACh-stimulated increase in cyclic GMP levels; this effect was antagonized by raloxifene. The improved endothelial function by raloxifene was abolished by ICI 182,780, and by wortmannin or LY294002. Raloxifene also protected endothelial cell function against H2O2. Raloxifene increased the phosphorylation of eNOS at Ser-1177 and Akt at Ser-473; this effect was blocked by ICI 182,780. Finally, raloxifene was not directly involved in scavenging ROS, and neither inhibited the activity of xanthine oxidase nor stimulated that of superoxide dismutase.


CONCLUSIONS
Raloxifene is effective against oxidative stress-induced endothelial dysfunction in vitro through an ICI 182,780-sensitive mechanism that involves the increased phosphorylation and activity of Akt and eNOS in rat aortae.
Institute of Vascular Medicine and Department of Physiology, Chinese University of Hong Kong, Hong Kong, China.
C M
CM
Wong
L M
LM
Yung
F P
FP
Leung
S-Y
SY
Tsang
C L
CL
Au
Z-Y
ZY
Chen
X
X
Yao
C H K
CH
Cheng
C-W
CW
Lau
M
M
Gollasch
Y
Y
Huang
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D004965:Estrogen Antagonists / Q000494:pharmacology*; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000187:drug effects / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism; D020849:Raloxifene Hydrochloride / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D004965:Estrogen Antagonists; D009569:Nitric Oxide; D020849:Raloxifene Hydrochloride; D052250:Nitric Oxide Synthase Type III; D051057:Proto-Oncogene Proteins c-akt; D006152:Cyclic GMP