Common mechanism for the estrogen agonist and antagonist activities of droloxifene

Grasser, William A.; Pan, Lydia C.; Thompson, David D.; Paralkar, Vishwas

doi:10.1002/(sici)1097-4644(199705)65:2<159::aid-jcb3>3.0.co;2-t

Cited by 13 publications

(9 citation statements)

References 31 publications

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“…Cells were stimulated with 10 nM 1,25-dihydroxyvitamin D 3 and TRAP stained as described (26). Bone resorption was assessed by culturing bone marrow cells on bone slices for 21 days and counting the resorption pits as has been described by Grasser et al (27).…”

Section: Methodsmentioning

confidence: 99%

Targeted Disruption of the Osteoblast/Osteocyte Factor 45 Gene (OF45) Results in Increased Bone Formation and Bone Mass

Gowen¹,

Petersen²,

Mansolf³

et al. 2003

Journal of Biological Chemistry

264

209

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We have previously described osteoblast/osteocyte factor 45 (OF45), a novel bone-specific extracellular matrix protein, and demonstrated that its expression is tightly linked to mineralization and bone formation. In this report, we have cloned and characterized the mouse OF45 cDNA and genomic region. Mouse OF45 (also called MEPE) was similar to its rat orthologue in that its expression was increased during mineralization in osteoblast cultures and the protein was highly expressed within the osteocytes that are imbedded within bone. To further determine the role of OF45 in bone metabolism, we generated a targeted mouse line deficient in this protein. Ablation of OF45 resulted in increased bone mass. In fact, disruption of only a single allele of OF45 caused significantly increased bone mass. In addition, knockout mice were resistant to aging-associated trabecular bone loss. Cancellous bone histomorphometry revealed that the increased bone mass was the result of increased osteoblast number and osteoblast activity with unaltered osteoclast number and osteoclast surface in knockout animals. Consistent with the bone histomorphometric results, we also determined that OF45 knockout osteoblasts produced significantly more mineralized nodules in ex vivo cell cultures than did wild type osteoblasts. Osteoclastogenesis and bone resorption in ex vivo cultures was unaffected by OF45 mutation. We conclude that OF45 plays an inhibitory role in bone formation in mouse.The constant modulation of the balance between skeletal strength and mineral availability in bone is effected by competing cell types in response to physiological needs. Osteoblasts produce, organize, and mineralize bone matrix in forming bone. Osteoclasts break down matrix by forming a lytic pocket in which bone is degraded and calcium is released. The generation and activity of these cell types is tightly regulated to provide equilibrium between formation and resorption and, thereby, an appropriate balance of strength and mineral release. Under certain conditions, such as aging, postmenopausal estrogen deficiency, or some pathophysiological states, there can exist an imbalance between bone resorption and bone formation. As a result, skeletal mass and strength are compromised and osteoporotic fractures can occur in the afflicted individuals.Bone is produced by the organization and mineralization of the extracellular matrix produced by osteoblasts. The major component of the extracellular matrix of these cells is Type I collagen, which functions as a scaffold for new bone. In addition, non-collagenous matrix proteins have been identified that influence the operations of bone turnover, formation, and repair. These proteins are generally acidic and highly posttranslationally modified by phosphorylation, glycosylation, or sulfation (1).Targeted deletion of extracellular matrix genes in mice has been a useful method to determine the in vivo functions of several matrix proteins. For example, osteocalcin is an abundant gamma carboxyl glutamic acid-containing bone matrix...

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Section: Methodsmentioning

confidence: 99%

Targeted Disruption of the Osteoblast/Osteocyte Factor 45 Gene (OF45) Results in Increased Bone Formation and Bone Mass

Gowen¹,

Petersen²,

Mansolf³

et al. 2003

Journal of Biological Chemistry

264

209

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“…Isolation and culture of mouse bone marrow have been described (24). For osteoclastic differentiation, bone marrow cells from 4-month-old mice (n ϭ 10, each genotype) were plated into dishes or onto calcium phosphate-coated discs (BD Biosciences, Bedford, MA) at 1 ϫ 10 5 cells per square centimeter in 24-well plates in complete media (phenol red-free MEM␣ with 15% FBS and 50 g/ml gentamicin) containing 25 ng/ml each of osteoprotegerin ligand and macrophage colony-stimulating factor (R & D Systems, Minneapolis, MN) and cultured in 5% CO 2 at 37°C.…”

Section: Peripheral Quantitative Computerized Tomography (Rat)mentioning

confidence: 99%

Proline-rich tyrosine kinase 2 regulates osteoprogenitor cells and bone formation, and offers an anabolic treatment approach for osteoporosis

Buckbinder

Crawford²,

Hua³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

141

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Bone is accrued and maintained primarily through the coupled actions of bone-forming osteoblasts and bone-resorbing osteoclasts. Cumulative in vitro studies indicated that proline-rich tyrosine kinase 2 (PYK2) is a positive mediator of osteoclast function and activity. However, our investigation of PYK2؊/؊ mice did not reveal evidence supporting an essential function for PYK2 in osteoclasts either in vivo or in culture. We find that PYK2؊/؊ mice have high bone mass resulting from an unexpected increase in bone formation. Consistent with the in vivo findings, mouse bone marrow cultures show that PYK2 deficiency enhances differentiation and activity of osteoprogenitor cells, as does expressing a PYK2-specific short hairpin RNA or dominantly interfering proteins in human mesenchymal stem cells. Furthermore, the daily administration of a small-molecule PYK2 inhibitor increases bone formation and protects against bone loss in ovariectomized rats, an established preclinical model of postmenopausal osteoporosis. In summary, we find that PYK2 regulates the differentiation of early osteoprogenitor cells across species and that inhibitors of the PYK2 have potential as a bone anabolic approach for the treatment of osteoporosis.human mesenchymal stem cell ͉ osteoclast ͉ osteoblast P roline-rich tyrosine kinase 2 (PYK2) and focal adhesion kinase (FAK) are nonreceptor tyrosine kinases, and together they constitute the focal adhesion kinase subfamily (1). Unlike FAK, PYK2 expression is relatively restricted, with highest levels in the brain and the hematopoietic system. PYK2Ϫ/Ϫ mice have been described previously and appear normally developed (2, 3). Characterization of the immune system of PYK2Ϫ/Ϫ animals revealed the absence of marginal zone B cells along and abnormal T cell-independent type II responses (2), as well as altered macrophage morphology, adhesion, and migration (3).Although PYK2 is expressed in both bone-forming osteoblasts and bone-resorbing osteoclasts, the skeletal phenotype of PYK2Ϫ/Ϫ mice has not been described. In vitro studies pointed to a positive role for PYK2 in osteoclast maturation and bone resorption. PYK2 localizes to the podosomes of osteoclasts (4), and, upon integrin binding, cell attachment, and actin ring formation, PYK2 associates with a variety of proteins including p130 CAS (5), Src (4), Cbl (6), integrins (4), gelsolin (7), and paxillin (8). Antisense depletion of PYK2 (9), but not the expression of a kinase inactive dominant negative mutant (10), blocked osteoclast spreading and bone resorption, indicating that PYK2 catalytic activity may be dispensable. The in vitro effects of bone anabolic stimuli suggested that PYK2 might have a positive role in osteoblasts as well. Treatment of osteoblast cells with fluoroaluminate led to increased PYK2 autophosphorylation, Src association, and kinase activity (11) and was associated with increased cell attachment and spreading (12). Likewise, in an anabolic model of mechanical loading, PYK2 autophosphorylation and kinase activity were stimulated in o...

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“…The rat bone marrow osteoclast differentiation culture system was established as previously described (25). In brief, bone marrow was collected from 5-month-old OVX or sham rats 2 weeks post surgery.…”

Section: In Vitro Rat Bone Marrow Culture Studymentioning

confidence: 99%

“…The purposes of this report were to describe: 1) binding affinity of CP-336,156 to human estrogen receptor-␣ (ER-␣), compared with estradiol; 2) the estrogenic effects of CP-336,156 on uterine growth in an immature female rat model, that is widely accepted as the model for studying estrogenic effects (9); 3) the effects of CP-336,156 on uterine weight, uterine histology, total serum cholesterol, and body composition in an aged female rat model, a model that most closely mimics the endocrine status of postmenopausal women (see Ref. 23); 4) the estrogenic effects of CP-336,156 on bone and total serum cholesterol in an OVX rat model of postmenopausal bone loss (22)(23)(24); and 5) a potential mechanism of CP-336,156's estrogen agonistic effects in bone using the rat bone marrow culture system, as described previously (25).…”

mentioning

confidence: 99%

Effects of CP-336,156, a New, Nonsteroidal Estrogen Agonist/Antagonist, on Bone, Serum Cholesterol, Uterus, and Body Composition in Rat Models

et al. 1998

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We have discovered a new, nonsteroidal, potent estrogen agonist/antagonist, CP-336,156. CP-336,156 binds selectively and with high affinity to the human estrogen receptor-alpha with a half-inhibition concentration of 1.5 nM, which is similar to that seen with estradiol (4.8 nM). When given orally to immature (3-week-old) female Sprague-Dawley rats for 3 days at doses of 0.1, 1.0, 10, or 100 microg/kg x day, unlike 17alpha-ethynyl estradiol, CP-336,156 had no effect on uterine wet or dry weight. Similarly, no uterine hypertrophy was observed in aged (17-month-old) female rats treated (p.o.) with CP-336,156 at 10 or 100 microg/kg x day for 28 days. We also found that CP-336,156 decreased total serum cholesterol and fat body mass and had no effect on lean body mass in these aged female rats. In 5-month-old ovariectomized (OVX) Sprague-Dawley female rats, CP-336,156 completely prevented OVX-induced increases in body weight gain, total serum cholesterol, and serum osteocalcin at doses between 10 and 1000 microg/kg x day after 4 weeks. At these doses, CP-336,156 completely prevented OVX-induced bone loss and inhibited the increased bone turnover associated with estrogen deficiency in lumbar vertebrae, proximal tibiae, and distal femora. Similar to estrogen, CP-336,156 induced apoptosis and p53 expression with a concomitant decrease in the number of tartrate-resistant acid phosphatase-positive multinuclear cells in rat bone marrow cell cultures in vitro, suggesting that the induction of apoptosis may be a mechanism for the estrogenic activities of CP-336,156 in bone. In summary, CP-336,156 is a new, orally active, nonsteroidal, potent estrogen agonist/antagonist that has similar effects in bone as estradiol but without the uterine-stimulating effects associated with estradiol in rats.

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Common mechanism for the estrogen agonist and antagonist activities of droloxifene

Cited by 13 publications

References 31 publications

Targeted Disruption of the Osteoblast/Osteocyte Factor 45 Gene (OF45) Results in Increased Bone Formation and Bone Mass

Targeted Disruption of the Osteoblast/Osteocyte Factor 45 Gene (OF45) Results in Increased Bone Formation and Bone Mass

Proline-rich tyrosine kinase 2 regulates osteoprogenitor cells and bone formation, and offers an anabolic treatment approach for osteoporosis

Effects of CP-336,156, a New, Nonsteroidal Estrogen Agonist/Antagonist, on Bone, Serum Cholesterol, Uterus, and Body Composition in Rat Models

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