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Prevention of bone loss by EM-800 and raloxifene in the ovariectomized rat.

Martel C, Picard S, Richard V, Belanger A, Labrie C, Labrie F.

MRC Group in Molecular Endocrinology, Laboratory of Molecular Endocrinology, CHUL Research Center and Laval University, 2705 Laurier Boulevard, G1V 4G2, Quebec, Canada.

Some undesirable effects are associated with chronic estrogen and progestin administration used to prevent bone loss in postmenopausal women, thus leading to poor compliance and the need for improved therapeutic and preventive agents. We have thus studied the ability of the new antiestrogen EM-800 (SCH 57050) to prevent bone loss and lower serum cholesterol levels and compared its effects with those of raloxifene. Ovariectomized (OVX) female rats were treated by oral gavage for 37 weeks with increasing daily doses (0.01, 0.03, 0.1, 0. 3 or 1 mg/kg) of EM-800 or raloxifene. At 35 weeks after OVX, lumbar spine bone mineral density (BMD) was 19% lower than in intact animals (P<0.01), while the OVX animals given EM-800 or raloxifene had 90-93 and 85-90%, respectively, of the BMD values observed in intact rats. Similar effects were observed on femoral BMD. Bone histomorphometry measurements were performed on proximal tibia. At the 0.01 mg/kg dose, EM-800 prevented the effect of OVX on TBV by 34% (P<0.01), while raloxifene had no detectable effect. Treatment with 1 mg/kg EM-800 and raloxifene resulted in, respectively, 68% (P<0.01) and 64% (P<0.01) prevention of the OVX-induced decrease in TBV. In addition, the administration of 0.01 and 0.03 mg/kg EM-800 caused, respectively, 54% (P<0.01) and 56% (P<0.01) inhibitions of serum cholesterol levels, while raloxifene administered at the same doses caused, respectively, 24% (P<0.01) and 41% (P<0.01) decreases of the value of the same parameter. At the highest doses used (0.1-1 mg/kg), both compounds lowered serum cholesterol levels by approximately 65% (P<0.01). No stimulatory effect of EM-800 was observed on the endometrial epithelial cells at doses up to 1 mg/kg, while hypertrophy of uterine epithelium was observed with raloxifene. EM-800 and raloxifene achieve the same degree of effectiveness on bone and serum cholesterol at higher doses, but EM-800 is at least three to ten times more potent than raloxifene at lower concentrations and has no stimulatory effect on uterine epithelium. The present data show the potent effect of EM-800 preventing bone loss and lower serum cholesterol levels without the negative effect on the endometrium, thus suggesting the particular interest of this new fully tissue-specific selective estrogen receptor modulator.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11074355&dopt=Abstract raloxifene Evista



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Raloxifene acts as an estrogen agonist on the rabbit growth plate.

Nilsson O, Falk J, Ritzen EM, Baron J, Savendahl L.

Pediatric Endocrinology Unit, Department of Women and Child Health, Karolinska Institutet, SE-17176 Stockholm, Sweden. ola.nilsson kbh.ki.se

Estrogen treatment has been used to induce growth plate fusion, thereby reducing the final height in girls expected to achieve extreme tall stature. The treatment is effective, in terms of limiting final height, but concerns have been raised that it might also increase the risk for malignancies later in life. Raloxifene, a selective estrogen receptor modulator, has been shown to act as an estrogen agonist on bone density but as an estrogen antagonist on breast and uterine tissue. The effect of raloxifene treatment on growth plate fusion and final height is unknown. The aim of this study was to determine whether raloxifene would act as an estrogen agonist or antagonist on growth plate cartilage. Ovariectomized immature rabbits were treated for 4 wk with vehicle (controls), estradiol cypionate (E2), or raloxifene. Tibial growth velocity was decreased in both E2- (P < 0.001) and raloxifene-treated animals (P < 0.001), compared with controls. E2 and raloxifene treatment also decreased chondrocyte proliferation and the height of the proximal tibial growth plate. In addition, E2 and raloxifene hastened fusion of the distal tibial growth plate (P < 0.05) and decreased the number of proliferative and hypertrophic chondrocytes per column in the proximal tibial growth plate. As expected, the uterus was enlarged by estrogen, but not raloxifene, treatment. We conclude that raloxifene acts as an estrogen agonist on the growth plate, accelerating growth plate senescence and thus hastening epiphyseal fusion.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12639932&dopt=Abstract raloxifene Evista



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Effects of raloxifene, a selective estrogen receptor modulator, on thymus, T cell reactivity, and inflammation in mice.

Erlandsson MC, Gomori E, Taube M, Carlsten H.

Department of Rheumatology, University of Goteborg, Goteborg, Sweden.

Raloxifene is a selective estrogen receptor modulator approved for prevention of osteoporosis in postmenopausal women. It is selective by virtue of having estrogen agonistic effects in bone, vessels, and blood lipids, while it is antagonistic with mammary and uterine tissue. The aim of the study was to examine whether the raloxifene analogue LY117018 (LY) has estrogenic effects on the thymus, T cell responsiveness, and inflammation. Oophorectomized normal mice were treated with subcutaneous injections of equipotent antiosteoporotic doses of LY (3 mg/kg) and 17beta-estradiol (E2) (0.1 mg/kg) or vehicle as controls. Effects on thymus were studied by analyses of thymus weight, cellularity, and CD4 and CD8 phenotype expression and histology, while inflammation was determined as T-cell-mediated delayed-type hypersensitivity (DTH) and granulocyte-mediated footpad swelling. LY lacked the suppressive properties of E2 on DTH and granulocyte-mediated inflammation. Furthermore, LY induced only minor thymus atrophy compared with E2 and did not, in contrast to E2, alter the thymic CD4/CD8 phenotypes. These results clearly demonstrate that raloxifene principally lacks the modulatory effects of estrogen on T cell responsiveness and inflammation. Our data are discussed in the context of recent findings in estrogen receptor biology and also with respect to estrogen-mediated alteration of autoimmune rheumatic diseases. Copyright 2000 Academic Press.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11104582&dopt=Abstract raloxifene Evista



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The effect of raloxifene on coronary arteries in aged ovariectomized ewes.

Gaynor JS, Monnet E, Selzman C, Parker D, Kaufman L, Bryant HU, Mallinckrodt C, Wrigley R, Whitehill T, Turner AS.

Department of Clinical Sciences, Colorado State University, Fort Collins 80523, USA. jgaynor vth.colostate.edu

BACKGROUND: Ovariectomized sheep are a useful model of postmenopausal osteoporosis and other postmenopausal conditions. Estrogen may have a protective effect on the coronary arteries in postmenopausal women. The effects of raloxifene, a selective estrogen receptor modulator, on coronary arteries in aged ovariectomized ewes was investigated. METHODS AND RESULTS: Forty eight aged ewes were randomly assigned to undergo sham surgery (Sham, n = 7), ovariectomy (OVX, n = 10), ovariectomy with estradiol supplementation (OVXE, n = 8), ovariectomy with raloxifene supplementation, 0.02 mg/kg per day (RAL1, n = 10), or ovariectomy with raloxifene supplementation, 0.10 mg/kg per day (RAL2, n = 13). Contrast coronary angiography was performed 6 months after intervention. Diameters of the right main and left anterior descending coronary arteries in the RAL1, RAL2 and Sham groups were not different from each other, but were significantly greater than the OVX and OVXE groups. Intracoronary nitroglycerin did not affect the relationships of the diameters in any group. There were no differences in vascular remodeling between the groups. CONCLUSIONS: The results indicate that raloxifene in this sheep model allows greater dilation of coronary arteries than estrogen. Raloxifene may provide a significant protective functional effect on coronary arteries in postmenopausal heart disease.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11110106&dopt=Abstract raloxifene Evista



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Raloxifene and estrogen reduces progression of advanced atherosclerosis--a study in ovariectomized, cholesterol-fed rabbits.

Bjarnason NH, Haarbo J, Byrjalsen I, Alexandersen P, Kauffman RF, Christiansen C.

Center for Clinical and Basic Research, Ballerup Byvej 222, 2750, Ballerup, Denmark. nb ccbr.dk

The present study investigated the effect of raloxifene, a selective estrogen receptor modulator (SERM), on aortic atherosclerosis in 80 ovariectomized, cholesterol-fed rabbits with pre-induced atherosclerosis. The animals were fed an atherogenic diet containing 240 mg cholesterol/day for 15 weeks, after this period a baseline control group was sacrificed. Thereafter, oral treatment was initiated with either estradiol 4 mg/day (n=20), raloxifene (210 mg/day) or placebo (n=20). In the treatment period of 39 weeks, the dietary cholesterol content was reduced to 80 mg cholesterol/day. Postmortem evaluation showed a significantly increased uterine weight induced by estradiol treatment (10.3+/-1.2 g), whereas raloxifene intervention caused a decreased uterus weight (1.21+/-0.1 g) when compared to placebo (2.48+/-0.47 g). Throughout the study, serum lipids increased in all groups to levels seen in very high risk humans. After 58 weeks the cholesterol content in the aorta was 3.18+/-0.54 micromol/cm(2) (38% reduction) in the estradiol group, 3.66+/-0.52 micromol/cm(2) (29% reduction) in the raloxifene group and 5.12+/-0.60 micromol/cm(2) in the placebo group. Analyses of the aortic cholesterol content corrected for time-averaged serum cholesterol revealed that both estradiol and raloxifene therapy significantly reduced the progression of atherosclerosis (P<0.01 for both) as compared to placebo.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11137087&dopt=Abstract raloxifene Evista



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Molecular mechanism of action at estrogen receptor alpha of a new clinically relevant antiestrogen (GW7604) related to tamoxifen.

Bentrem D, Dardes R, Liu H, MacGregor-Schafer J, Zapf J, Jordan V.

Department of Surgery, The Robert H. Lurie Comprehensive Cancer Center, Northwestern University Medical School, Chicago, Illinois 60611, USA.

Tamoxifen is the endocrine treatment of choice for all stages of estrogen receptor (ER)-positive breast cancer, and it is the first drug approved to reduce the incidence of breast cancer in high-risk women. Unfortunately, tamoxifen also possesses some estrogen-like effects in the uterus that cause a modest increase in the risk of endometrial cancer. GW5638 is a tamoxifen derivative with a novel carboxylic acid side chain with no uterotropic activity in the rat (Willson et al., J Med Chem, 1994, 37:1550-1552). We have compared and contrasted the actions of 4-hydroxytamoxifen (4-OHT, the active metabolite of tamoxifen) with GW7604 [the presumed metabolite of GW5638 in breast (MCF-7) and endometrial (ECC-1) cell lines in vitro]. GW7604 did not cause the growth of ECC-1 cells at any concentration (10(-11)-10(-6) M), but 4-OHT was weakly estrogen-like at low concentrations (10(-11)-10(-10) M). Compounds (10(-7) M) blocked the growth promoting action of estradiol (10(-10) M) in both ECC-1 and MCF-7 cells. Western blotting was used to show that GW7604 and raloxifene did not affect ER levels significantly, compared with controls, in MCF-7 cells; whereas the pure antiestrogen ICI182,780 decreased ER levels (P < 0.05). An assay system was used that can classify compounds into tamoxifen-like, raloxifene-like, or pure antiestrogens. The assay depends on the activation of the transforming growth factor alpha (TGFalpha) gene in situ by wild-type or D351Y mutant ER stably transfected into MDA-MB-231 cells (MacGregor-Schafer et al., Cancer Res, 1999, 59:4308-4313). GW7604 inhibited both estradiol (10(-9) M) and 4-OHT (10(-8), 10(-7) M) induction of TGFalpha in a concentration related manner (10(-9)-10(-6) M). GW7604 and raloxifene stimulated TGFalpha with the D351Y ER. In contrast, ICI 182,780 (10(-6) M) did not initiate TGFalpha and blocked the induction of TGFalpha with GW7604, raloxifene, and 4-OHT in D351Y-transfected cells. Using computer-assisted molecular models of ER complexes, we found that the antiestrogenic side chain of 4-OHT weakly interacted with the surface amino acid 351 (aspartate), but the carboxylic acid of GW7604 caused a strong repulsion of aspartate 351. We propose that GW7604 is less estrogen-like than 4-OHT, because it disrupts the surface charge around aa351 required for coactivator docking in the 4-OHT:ER complex. This charge is restored in the D351Y ER, thus converting GW7604 from an antiestrogen to an estrogen-like molecule.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11159857&dopt=Abstract raloxifene Evista