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Identification of an estrogen response element activated by metabolites of 17beta-estradiol and raloxifene.

Yang NN, Venugopalan M, Hardikar S, Glasebrook A.

Endocrine Research, Lilly Research Labs, Eli Lilly and Co., Indianapolis, IN 46285, USA.

17beta-Estradiol modulates gene transcription through the estrogen receptor and the estrogen response element in DNA. The human transforming growth factor-beta3 gene was shown to be activated by the estrogen receptor in the presence of estrogen metabolites or estrogen antagonists. Activation was mediated by a polypurine sequence, termed the raloxifene response element, and did not require the DNA binding domain of the estrogen receptor. Interaction of the estrogen receptor with the raloxifene response element appears to require a cellular adapter protein. The observation that individual estrogens modulate multiple DNA response elements may explain the tissue-selective estrogen agonist or antagonist activity of compounds such as raloxifene.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8703055&dopt=Abstract raloxifene Evista



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Time-dependent changes in biochemical bone markers and serum cholesterol in ovariectomized rats: effects of raloxifene HCl, tamoxifen, estrogen, and alendronate.

Frolik CA, Bryant HU, Black EC, Magee DE, Chandrasekhar S.

Lilly Research Laboratories, Indianapolis, IN 46285, USA.

Bone loss associated with postmenopausal osteoporosis can be reduced by treatment with antiresorptive agents such as estrogen or bisphosphonates. Whereas bisphosphonates primarily affect bone loss, estrogens have an advantage of also lowering serum cholesterol levels, although they have a detrimental effect in the uterus. Recently, raloxifene HCl, a selective estrogen receptor modulator (SERM), has been shown to decrease both bone loss and cholesterol levels without the negative uterine effects. These antiresorptive agents reduce bone turnover, which can be evaluated by measuring bone turnover markers. To compare the effects of estrogen, two SERMs (raloxifene HCl and tamoxifen), and alendronate, a bisphosphonate that inhibits bone loss by an estrogen-independent pathway, on metabolic bone markers and cholesterol levels, rats were ovariectomized 2 weeks prior to 3 weeks of daily oral treatment with raloxifene HCl (3 mg/kg), ethynyl estradiol (0.1 mg/kg), tamoxifen (3 mg/kg), or alendronate (3 mg/kg). Raloxifene HCl, tamoxifen, and ethynyl estradiol reduced serum cholesterol to levels below control values within 4 days after initiation of treatment, whereas alendronate had no effect. After 3 weeks of treatment, serum cholesterol values in ethynyl estradiol treated animals, although still below the control value, had risen 6.4-fold; raloxifene HCl and tamoxifen values rose by only 1.4-1.5-fold. Therefore, compared with estrogen, SERMs may have a longer-term suppressive effect on serum cholesterol. At 4 days of treatment, ovariectomized rats had a 1.4-fold increase in serum osteocalcin level compared with controls. Ethynyl estradiol lowered this level within 1 week of treatment by 18%, with a more pronounced reduction of 34% at 3 weeks. In contrast, raloxifene HCl, tamoxifen, or alendronate had very little effect after the first week (6% to 13% reduction), although there was an 18% to 25% reduction by 3 weeks. Urinary pyridinoline levels, elevated 1.4-fold in the ovariectomized rat compared with controls 2 weeks after surgery, were reduced to control values after 2 weeks of treatment with raloxifene HCl, ethynyl estradiol, tamoxifen, or alendronate. These data support the concept that estrogen, raloxifene HCl, tamoxifen, and alendronate inhibit bone loss in the ovariectomized animal by reducing bone resorption. The results also indicate that for treatment of postmenopausal osteoporosis, raloxifene HCl may have an advantage over the other antiresorptives studied in having both non-uterotrophic and hypocholesterolemic effects in addition to its ability to inhibit bone resorption.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8806005&dopt=Abstract raloxifene Evista



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Raloxifene inhibits bone turnover and prevents further cancellous bone loss in adult ovariectomized rats with established osteopenia.

Evans GL, Bryant HU, Magee DE, Turner RT.

Department of Orthopedics, Mayo Clinic, Rochester, Minnesota 55905, USA.

Estrogen (E) treatment has proven to be effective in preventing bone loss after menopause with, however, some undesirable side effects. Many of these side effects are related to the hormone's actions on reproductive tissues. Raloxifene is an organ-selective estrogen agonist that prevents acute cancellous osteopenia in ovariectomized (OVX'd) growing rats. The effects of raloxifene on adult rats with established bone loss are not known. We now compare the dose response effects of 4 months of treatment with raloxifene and estrogen in 8-month-old rats that had been OVX'd 2 months before treatment. OVX resulted in increased body weight, uterine atrophy and severe cancellous bone loss. Estrogen resulted in a dose-dependent increase in uterine weight in OVX'd rats whereas raloxifene did not promote uterine growth. Both treatments reduced body weight and serum cholesterol. Raloxifene and estrogen were each effective in stabilizing cancellous bone by preventing additional cancellous bone loss, but neither treatment replaced lost bone. These findings provide further evidence that raloxifene is a much more potent estrogen agonist on the skeleton and liver than on the uterus.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8828469&dopt=Abstract raloxifene Evista



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Advantages of raloxifene over alendronate or estrogen on nonreproductive and reproductive tissues in the long-term dosing of ovariectomized rats.

Sato M, Bryant HU, Iversen P, Helterbrand J, Smietana F, Bemis K, Higgs R, Turner CH, Owan I, Takano Y, Burr DB.

Department of Endocrine Research or Statistics, Lilly Research Laboratories, Indianapolis, Indiana, USA.

For the first time, raloxifene or alendronate was administered to rats immediately after ovariectomy for 10 months and compared with estrogen to elucidate mechanisms behind the raloxifene effects observed in nonreproductive and reproductive tissues. Specifically, 75-day-old rats were randomly selected as sham controls (Sham), ovariectomized controls (Ovx) or ovariectomized rats treated with fully efficacious doses of raloxifene (RA), 17 alpha-ethynyl estradiol (EE2) or alendronate (ABP). Lumbar vertebrae and proximal tibiae were examined by computed tomography (QCT) and by histomorphometry. Histomorphometry showed differences in bone architecture between groups when QCT densities were similar, but tibial trabecular bone analysis by QCT correlated with histomorphometry with r = .86 to .93, depending on the parameter. Both techniques confirmed that Ovx had substantially less bone than Sham, with greater loss of trabecular bone in the proximal tibia than vertebrae. Both techniques showed that RA had effects similar to but not identical with EE2 in preventing bone loss in vertebrae and tibiae. ABP partially prevented loss of bone in L-5, but was not significantly different from Ovx in the proximal tibia. This may be caused by ABP suppression of bone apposition, beyond effects observed for EE2 or RA. RA appeared to be more similar to EE2 because ABP significantly depressed bone formation (bone formation rate, mineral apposition rate) to below RA or EE2 levels, especially in L-5. Mechanical loading to failure of L-6 vertebrae showed a rank order of vertebral strength of Sham > RA > EE2 > Ovx > ABP, although significant differences were not observed between treatment groups. These data show that ABP suppression of bone formation can affect bone quality with long-term treatment. In other tissues, RA had minimal uterine effects, while significantly lowering serum cholesterol to below EE2-treated levels. Both EE2 and RA rats had significantly lower body weights than the other groups. ABP had no effect on serum lipids, uterine weight or body weight. Therefore, RA appears to have a broader range of desirable effects on bone, body weight, uteri and cholesterol than ABP or EE2 in ovariectomized rats.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8859007&dopt=Abstract raloxifene Evista



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Inhibition of LDL oxidation and myeloperoxidase dependent tyrosyl radical formation by the selective estrogen receptor modulator raloxifene (LY139481 HCL).

Zuckerman SH, Bryan N.

Department of Cardiovascular Research, Lilly Research Laboratories, Indianapolis, IN, USA.

Cellular oxidation of protein and lipoproteins is believed to contribute to the pathology associated with both acute and chronic inflammatory processes. Enzymatic, myeloperoxidase and lipoxygenase, and non- enzymatic oxidation of low density lipoprotein, LDL, has been implicated in foam cell formation and the progression of atherosclerotic changes within the arterial wall. In the present study, the in vitro protective role of the selective estrogen receptor modulator, raloxifene, in these oxidant triggered processes has been investigated. Raloxifene, as with estrogen was observed to inhibit both copper mediated LDL oxidation as well as the cellular modification of LDL by murine peritoneal macrophages. Raloxifene was, however, a more potent inhibitor of LDL oxidation than 17 beta-estradiol. The inhibition of macrophage LDL modification by raloxifene was not due to a non-specific effect on all effector functions as phagocytosis of opsonized yeast was comparable with control macrophage cultures. In addition to the protective effects on LDL oxidation, raloxifene also inhibited tyrosyl radical formation catalyzed by myeloperoxidase. The inhibition of myeloperoxidase activity was observed for both the isolated enzyme and in phorbol ester stimulated murine peritoneal neutrophils. In contrast, raloxifene was a weaker inhibitor of horseradish peroxidase. These results demonstrate a potential protective role for raloxifene as an anti-oxidant in in vitro assays designed to evaluate oxidant mediated radical formation and tissue damage.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8879435&dopt=Abstract raloxifene Evista



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Hypocholesterolemic activity of raloxifene (LY139481): pharmacological characterization as a selective estrogen receptor modulator.

Kauffman RF, Bensch WR, Roudebush RE, Cole HW, Bean JS, Phillips DL, Monroe A, Cullinan GJ, Glasebrook AL, Bryant HU.

Division of Cardiovascular Research, Lilly Research Laboratories, Eli Lilly and Co., Indianapolis, Indiana, USA.

After once-daily oral dosing in ovariectomized rats, raloxifene (LY139481) hydrochloride produced dose- and time-dependent reductions in serum cholesterol and high-density lipoprotein-cholesterol. Paired-feeding studies demonstrated that effects of raloxifene on serum lipids were not secondary to effects on food consumption. Maximal reductions in serum cholesterol occurred within 4 days of raloxifene administration or sooner, depending on the administered dose. The ED50 for 50% reduction in serum cholesterol by raloxifene was 0.13 +/- 0.04 mg/kg/day (mean +/- S.E.M., n = 17); maximal cholesterol reduction by raloxifene (68%) was significantly less than that produced by estrogen (17 alpha-ethinylestradiol; 89%) after 4 to 7 days of daily dosing. Dose-response curves for cholesterol lowering by raloxifene were generated in the presence of varying doses of 17 alpha-ethinylestradiol; two-way analysis of variance revealed significant interactions between estrogen and raloxifene with respect to cholesterol lowering (P < .001). Furthermore, a high dose of raloxifene (10 mg/kg/day) prevented further reduction of serum cholesterol by estrogen (1-100 micrograms/kg/ day) beyond that produced by raloxifene alone. For a series of closely related structural analogs of raloxifene, log(ED50) values for cholesterol lowering were highly correlated with log(relative binding affinity) for the estrogen receptor (r = 0.93; P < .0001). Thus, cholesterol lowering by raloxifene in ovariectomized rats is mediated primarily via partial agonist effects at estrogen receptors. Taken together with previous observations in uterine tissue of estrogen antagonism by raloxifene in the absence of significant agonism, the present findings support the classification of raloxifene as a selective estrogen receptor modulator.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8996192&dopt=Abstract raloxifene Evista