Effect of ormeloxifene on ovariectomy-induced bone resorption, osteoclast differentiation and apoptosis and TGF beta-3 expression.
Effect of ormeloxifene, a multifunctional selective estrogen receptor modulator, on prevention of ovariectomy-induced bone resorption in retired breeder female rats, osteoclastogenesis using bone marrow cells from adult Balb/c mice cultured in presence of M-CSF and RANKL, osteoclast apoptosis using terminal deoxynucleotidyl transferase fragment end labeling and TGF beta-3 expression were investigated. Raloxifene, a benzothiophene reported to mimic effects of estrogen in bone, and estradiol were used for comparison. Ormeloxifene (10(-6) and 10(-8)M) significantly inhibited osteoclastogenesis (P<0.001 versus vehicle control) as evidenced by lower number of TRAP-positive osteoclasts in bone marrow cultures and caused apoptosis of osteoclasts. The effect was almost equivalent to that observed in presence of estradiol-17 beta, except that significant number of cells undergoing apoptosis was evident even at 10(-9)M concentration of estradiol-17 beta (P<0.001). Raloxifene, though inhibited osteoclastogenesis at much lower concentrations (10(-8) to 10(-12)M; P<0.001), failed to cause apoptosis of osteoclasts at any of the concentrations used. While ormeloxifene, raloxifene and ethynylestradiol significantly prevented ovariectomy-induced bone loss in vivo in retired breeder female rats, prevention of ovariectomy-induced decrease in BMD and trabecular network of proximal tibia, calcium and phosphorus levels in femur and tibia and prevention of ovariectomy-induced down-regulation of TGF beta-3 expression in lumbar vertebrae was of lower order in raloxifene- than ormeloxifene- or ethynylestradiol-supplemented females. Both the SERMs, however, produced considerable estrogenic effects at the uterine level as evidenced by increase in weight, total and endometrial area and luminal epithelial cell height; the effect being generally greater in raloxifene- than ormeloxifene-treated rats. Findings demonstrate that inhibition of estrogen-deficiency osteoporosis by ormeloxifene, as in case of estradiol, was mediated via inhibition of osteoclastogenesis, apoptosis of osteoclasts and up-regulation of TGF beta-3 expression. Raloxifene, though effective in inhibiting osteoclastogenesis in vitro at much lower concentrations, was not only less potent in preventing ovariectomy-induced bone loss in retired breeder female rats in vivo but also appeared to have a different mechanism of action than ormeloxifene and estradiol.
Narayana Murthy
P S
PS
Endocrinology Division, Central Drug Research Institute, Lucknow 226001, India.
Sengupta
S
S
Sharma
S
S
Singh
M M
MM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001578:Benzopyrans / Q000494:pharmacology*; D015519:Bone Density; D001854:Bone Marrow Cells / Q000166:cytology / Q000502:physiology; D001862:Bone Resorption / Q000517:prevention & control*; D002118:Calcium / Q000032:analysis; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D005260:Female; D008159:Lumbar Vertebrae / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D009929:Organ Size; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D010052:Ovariectomy; D010758:Phosphorus / Q000032:analysis; D020849:Raloxifene Hydrochloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology; D013234:Stem Cells / Q000166:cytology / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053782:Transforming Growth Factor beta3; D014599:Uterus / Q000033:anatomy & histology
D001578:Benzopyrans; D020845:Selective Estrogen Receptor Modulators; C509045:Tgfb3 protein, mouse; C509046:Tgfb3 protein, rat; D016212:Transforming Growth Factor beta; D053782:Transforming Growth Factor beta3; D010758:Phosphorus; C508548:ormeloxifene; D020849:Raloxifene Hydrochloride; D002118:Calcium