These authors contributed equally to this work.
Therapeutic concentrations of raloxifene augment nitric oxide-dependent coronary artery dilatation in vitro
Article first published online: 29 JAN 2009
2007 British Pharmacological Society
British Journal of Pharmacology
Volume 152, Issue 2, pages 223–229, September 2007
How to Cite
Leung, F. P., Yung, L. M., Leung, H. S., Au, C. L., Yao, X., Vanhoutte, P. M., Laher, I. and Huang, Y. (2007), Therapeutic concentrations of raloxifene augment nitric oxide-dependent coronary artery dilatation in vitro. British Journal of Pharmacology, 152: 223–229. doi: 10.1038/sj.bjp.0707387
- Issue published online: 29 JAN 2009
- Article first published online: 29 JAN 2009
- (Received March 23, 2007, Revised May 14, 2007, Accepted June 4, 2007)
- coronary artery;
- nitric oxide synthase;
Background and purpose:
Raloxifene improves cardiovascular function. This study examines the hypothesis that therapeutic concentrations of raloxifene augment endothelium-dependent relaxation via up-regulation of eNOS expression and activity in porcine coronary arteries.
Isometric tension was measured in rings from isolated arteries. Intracellular Ca2+ concentrations ([Ca2+]i) in arterial endothelial cells were detected by Ca2+ fluorescence imaging. Phosphorylation of eNOS at Ser-1177 was assayed by Western blot analysis.
In arterial rings pre-contracted with 9,11-dideoxy-11α,9α-epoxy-methano-prostaglandin F2α (U46619), treatment with raloxifene (1-3 nM) augmented bradykinin- or substance P-induced relaxation and this effect was antagonized by ICI 182,780, an estrogen receptor antagonist. The enhanced relaxation was abolished in rings treated with inhibitors of nitric oxide/cyclic GMP-dependent dilation, NG-nitro-L-arginine methyl ester (L-NAME) plus 1H-[1,2,4]oxadizolo[4,3-a]quinoxalin-1-one (ODQ). In contrast, effects of raloxifene were unaffected after inhibition of endothelium-derived hyperpolarizing factors by charybdotoxin plus apamin. Raloxifene (3 nM) did not influence endothelium-independent relaxation to sodium nitroprusside. 17ß-Estradiol (3-10 nM) also enhanced bradykinin-induced relaxation, which was inhibited by ICI 182,780. Treatment with raloxifene (3 nM) did not affect bradykinin-stimulated rise in endothelial cell [Ca2+]i. Raloxifene, 17ß-estradiol, and bradykinin increased eNOS phosphorylation at Ser-1177 and ICI 182,780 prevented effects of raloxifene or 17ß-estradiol but not that of bradykinin. Raloxifene had neither additive nor antagonistic effects on 17ß-estradiol-induced eNOS phosphorylation.
Conclusions and implications:
Raloxifene in therapeutically relevant concentrations augmented endothelial function in porcine coronary arteries in vitro through ICI 182,780-sensitive mechanisms that were associated with increased phosphorylation of eNOS but independent of changes in endothelial cell [Ca2+]i.
British Journal of Pharmacology (2007) 152, 223–229; doi:10.1038/sj.bjp.0707387