Differential effects of 17β-estradiol and raloxifene on VSMC phenotype and expression of osteoblast-associated proteins

Abstract

Rzewuska-Lech, Ewa, Muthuvel Jayachandran, Lorraine A. Fitzpatrick, and Virginia M. Miller. Differential effects of 17␤-estradiol and raloxifene on VSMC phenotype and expression of osteoblast-associated proteins. Am J Physiol Endocrinol Metab 289: E105-E112, 2005. First published February 15, 2005 doi:10.1152/ajpendo.00366.2004.-Several studies demonstrate an association between osteoporosis and arterial calcific disease, both of which being common in elderly women. Estradiol and raloxifene, a selective estrogen receptor modulator, prevent bone loss in postmenopausal women. Little is known regarding how these agents affect arterial calcification. The aim of this study was to determine whether or not 17␤-estradiol and raloxifene reduced vascular smooth muscle cell (VSMC) differentiation and expression of bone-associated proteins during phosphate-induced calcification in vitro. Aortic VSMC were cultured from adult, gonadally intact, and ovariectomized (OVX) female pigs. Calcifying medium was added, and cells were treated with solvent (control), 17␤-estradiol (E2), or raloxifene. Extent of calcification and phenotypic expression of bone-associated proteins [matrix gla protein (MGP), osteoprotegerin (OPG), and bone sialoprotein (BSP)] were examined at 3-day intervals over 2 wk. Calcium content increased in all groups but was greater in VSMC derived from intact compared with OVX animals. E 2 reduced calcification and preserved a contractile phenotype. Expression of OPG significantly decreased with time; this decrease was significantly greater in VSMC derived from OVX compared with gonadally intact pigs. E 2 and raloxifene preserved expression of OPG only in VSMC from intact pigs. Expression of MGP increased significantly with time and was not affected by E 2 or raloxifene treatments. E2 treatment significantly inhibited synthesis of BSP in cells from both groups. In conclusion, E2 slows differentiation of VSMC induced by excess phosphate. Effectiveness of raloxifene to preserve expression of bone cell-associated proteins depends on the hormonal status of the tissue donor. vascular smooth muscle cells; estrogen; raloxifene; selective receptor modulator; smooth muscle phenotype

Effects of 17β-estradioland raloxifene on endothelial OPG and RANKL secretion

“…The in vitro studies have shown that estradiol or raloxifene maintain VSMCs' OPG production when cultured under elevated levels of calcium phosphates [22]. We have confirmed that under calcification-promoting conditions, endothelial cells change the sRANKL and OPG release.…”

“…That day, when we administered substances described above was called day 0. Concentrations of raloxifene and estradiol were established on the basis of literature for efficacy at physiological levels [22]. Medium was changed at day 1, 2 and 4.…”

Androgen Receptor-dependent Transactivation of Growth Arrest-specific Gene 6 Mediates Inhibitory Effects of Testosterone on Vascular Calcification

“…In clinical studies, a low serum estradiol level in women was correlated with increased arterial calcification (37), and estrogen replacement could reduce coronary calcification (38,39). However, in experimental studies, estradiol treatment showed variable effects on vascular calcification with either inhibition (40,41) or stimulation of calcification (42). Further studies are needed to elucidate the actions of estrogens in vascular calcification.…”

Vascular Actions of Estrogens: Functional Implications

“…These data support a cardiovascular protective effect of CEE in women for whom estrogenic treatments would not be prescribed under the current practice guidelines. Mechanisms by which estrogen reduces calcification are multifactorial but most likely include modulation of cell differentiation Abedin et al, 2004;Rzewuska-Lech et al, 2005), genetic variation related to bone matrix proteins and osteoblast/clast activation (Doherty et al, 2003), and perhaps susceptibility to infection by calcifying nanoparticles (Miller et al, 2004b). Much remains to be learned about the contribution of specific estrogen receptors in arterial calcific processes.…”