Raloxifene concurrently stimulates osteoprotegerin and inhibits interleukin-6 production by human trabecular osteoblasts

Protective effect of raloxifene on lipopolysaccharide and acid- induced acute lung injury in rats

AIM

To evaluate the protective effect of oral raloxifene on acute lung injury.

METHODS

Thirty adult, male Sprague-Dawley rats each weighing 180-210 g were used and divided into 3 groups: the raloxifene-lipopolysaccharide (LPS)-HCl group (n=10), the LPS-raloxifene-HCl group (n=10), and the placebo group (n=10). All the rats were injected intraperitoneally (ip) with 5 mg/kg LPS, and raloxifene (30 mg/kg) was orally administered 1 h before and 14 h after LPS injection into the raloxifene-LPS-HCl and the LPS-raloxifene-HCl groups, respectively; the placebo group received nothing. Sixteen hours after LPS injection, all the animals were anesthetized and the femoral artery was cannulated. All the rats received a direct intratracheal (IT) injection of HCl (pH 1.2; 0.5 mL/kg). The mean arterial pressure (MAP) and blood gas concentrations were measured. Fifteen rats (5 in each group, respectively) underwent a micro positron emission tomography (microPET) scan of the thorax 4 h after HCl instillation. The wet/dry (W/D) weight ratio determination and histopathological examination were also performed.

RESULTS

The rats in the LPS-raloxifene-HCl group had a lower [18F]fluorodeoxyglucose uptake compared with the rats in the placebo group (4.67+/-1.33 vs 9.01+/-1.58, respectively, P<0.01). The rats in the LPS-raloxifene-HCl group also had a lower histological lung injury score (8.20+/-1.23 vs 12.6+/-0.97, respectively, P<0.01) and W/D weight ratio (5.335+/-0.198 vs 5.886+/-0.257, respectively, P<0.01) compared to the placebo group. The rats in this group also showed better pulmonary gas exchange and more stable mean arterial pressure (MAP) compared to the placebo group.

CONCLUSION

Raloxifene provides a significant protective effect on acute lung injury in rats induced first by LPS ip injection and then by HCl IT instillation.

Novel perspectives for progesterone in hormone replacement therapy, with special reference to the nervous system

The utility and safety of postmenopausal hormone replacement therapy has recently been put into question by large clinical trials. Their outcome has been extensively commented upon, but discussions have mainly been limited to the effects of estrogens. In fact, progestagens are generally only considered with respect to their usefulness in preventing estrogen stimulation of uterine hyperplasia and malignancy. In addition, various risks have been attributed to progestagens and their omission from hormone replacement therapy has been considered, but this may underestimate their potential benefits and therapeutic promises. A major reason for the controversial reputation of progestagens is that they are generally considered as a single class. Moreover, the term progesterone is often used as a generic one for the different types of both natural and synthetic progestagens. This is not appropriate because natural progesterone has properties very distinct from the synthetic progestins. Within the nervous system, the neuroprotective and promyelinating effects of progesterone are promising, not only for preventing but also for reversing age-dependent changes and dysfunctions. There is indeed strong evidence that the aging nervous system remains at least to some extent sensitive to these beneficial effects of progesterone. The actions of progesterone in peripheral target tissues including breast, blood vessels, and bones are less well understood, but there is evidence for the beneficial effects of progesterone. The variety of signaling mechanisms of progesterone offers exciting possibilities for the development of more selective, efficient, and safe progestagens. The recognition that progesterone is synthesized by neurons and glial cells requires a reevaluation of hormonal aging.

Differential effects of selective oestrogen receptor modulators (SERMs) tamoxifen, ospemifene and raloxifene on human osteoclasts in vitro

BACKGROUND AND PURPOSE

Several selective oestrogen receptor modulators (SERMs) with oestrogen agonist effects in bone cells and without increased risk of breast and endometrial cancer have been developed. Here, we have investigated the effects of different types of SERMs on osteoclast differentiation, bone resorption and apoptosis in vitro.

EXPERIMENTAL APPROACH

Human peripheral blood-derived CD14+ monocytes were cultured on bovine bone slices in the presence of RANKL, M-CSF, TNF-alpha and dexamethasone for seven days. Also, CD14+ monocytes were co-cultured either with human SaOS-2 or MG-63 osteosarcoma cells, in the presence of parathyroid hormone. Osteoclast cultures were treated with different SERMs. TRACP+ multinucleated cells and C-terminal telopeptide of type I collagen were used as markers for osteoclast formation and bone resorption, respectively.

KEY RESULTS

In CD14+ monocyte cultures, tamoxifen directly inhibited human osteoclast formation and bone resorption, while raloxifene and ospemifene had no inhibitory effect. In the co-cultures either with SaOS-2 or MG-63 cells, ospemifene and raloxifene as well as tamoxifen inhibited osteoclast formation in a concentration-dependent manner. The inhibitory effect was associated with an increased production of osteoprotegerin. The anti-oestrogen ICI 182 780 completely reversed the effects of these SERMs.

CONCLUSION AND IMPLICATIONS

Tamoxifen had an oestrogen receptor dependent, direct, inhibitory effect on human osteoclast differentiation and bone resorption, whereas ospemifene and raloxifene required osteoblastic cells to achieve a similar inhibition. The effects of ospemifene and raloxifene were mediated by oestrogen receptors by a mechanism involving paracrine induction of osteoprotegerin in cultures with osteoblast derived osteosarcoma cells.

Raloxifene therapy interacts with serum osteoprotegerin in postmenopausal women

OBJECTIVES

Osteoprotegerin (OPG) is a protein expressed by osteoblasts that, linking the receptor activator of nuclear factor kappaB (RANK) ligand (RANKL), produced by osteoblasts, blocks the process of osteoclastic differentiation and modulates osteoclastic apoptosis. Raloxifene (RAL) stimulates the production of OPG from osteoblasts, as demonstrated in vitro, carring out their antiresorption activity, at least in part, as means of the OPG/RANK/RANKL system. The aim of this study was to evaluate in vivo if the RAL treatment of postmenopausal women was associated to changes in serum OPG; moreover, to evaluate the serum changes of bone turnover modulators interleukin-6 (IL-6) and C-telopeptides of type-1 collagen (CrossLaps).

METHODS

A prospective, randomized, placebo-controlled study was designed. A group of consecutive healthy postmenopausal women (n=40) referred to II Menopause Centre of the Department of Gynaecology of Second University of Naples for climacteric syndrome was enrolled and divided in two groups: (n=20) postmenopausal women received for 6 months oral raloxifene (60 mg/day) versus (n=20) postmenopausal women received placebo tablets.

RESULTS

Serum OPG levels in postmenopausal women after RAL treatment are statistically significant increased (P<0.001) versus baseline (P=0.007) versus placebo.

CONCLUSIONS

These in vivo data demonstrate that RAL could improve osteoporosis, also through an increase of OPG production by osteoblasts.

Antiremodeling agents influence osteoblast activity differently in modeling and remodeling sites of canine rib

Antiremodeling agents reduce bone loss in part through direct actions on osteoclasts. Their effects on osteoblasts and bone formation activity are less clear and may differ at sites undergoing modeling vs. remodeling. Skeletally mature intact beagles, 1-2 years old at the start of the study, were treated daily with clinically relevant doses of alendronate (0.10 or 0.20 mg/kg), risedronate (0.05 or 0.10 mg/kg), raloxifene (0.50 mg/kg), or vehicle (1 mL/kg). Dynamic bone formation parameters were histologically assessed on periosteal, endocortical/trabecular, and intracortical bone envelopes of the rib. Raloxifene significantly increased periosteal surface mineral apposition rate (MAR), a measure of osteoblast activity, compared to all other treatments (+108 to +175%, P < 0.02), while having no significant effect on MAR at either the endocortical/trabecular or intracortical envelope. Alendronate (both 0.10 and 0.20 doses) and risedronate (only the 0.10 dose) significantly (P < or = 0.05) suppressed MAR on the endocortical/trabecular envelope, while none of the bisphosphonate doses significantly altered MAR at either the periosteal or intracortical envelopes compared to vehicle. Based on these results, we conclude that (1) at clinically relevant doses the two classes of antiremodeling agents, bisphosphonates and selective estrogen receptor modulators, exert differential effects on osteoblast activity in the canine rib and (2) this effect depends on whether modeling or remodeling is the predominant mechanism of bone formation.

Osteogenic growth peptide effects on primary human osteoblast cultures: potential relevance for the treatment of glucocorticoid-induced osteoporosis

The osteogenic growth peptide (OGP) is a naturally occurring tetradecapeptide that has attracted considerable clinical interest as a bone anabolic agent and hematopoietic stimulator. In vivo studies on animals have demonstrated that the synthetic peptide OGP (10-14), reproducing the OGP C-terminal active portion [H-Tyr-Gly-Phe-Gly-Gly-OH] increases bone formation, trabecular bone density and fracture healing. In vitro studies performed on cellular systems based on osteoblastic-like cell lines or mouse stromal cells, have demonstrated that OGP (10-14) increases osteoblast proliferation, alkaline phosphatase (ALKP) activity and matrix synthesis and mineralization. In view of a potential application of OGP (10-14) in clinical therapy, we have tested different concentrations of OGP (10-14) on primary human osteoblast (hOB) cultures. We have observed significant increases of hOB proliferation (+35%), ALKP activity (+60%), osteocalcin secretion (+50%), and mineralized nodules formation (+49%). Our experimental model based on mature hOBs was used to investigate if OGP (10-14) could prevent the effects on bone loss induced by sustained glucocorticoid (GC) treatments. A strong decrease in bone formation has been attributed to the effects of GCs on osteoblastogenesis and osteocyte apoptosis, while an increase in bone resorption was due to a transient osteoblastic stimulation, mediated by the OPG/RANKL/RANK system, of osteoclasts recruitment and activation. Moreover, GCs act on hOBs decreasing the release of osteoprotegerin (OPG) a regulator of the RANKL/RANK interaction. Here, we provide evidences that OGP (10-14) inhibits hOB apoptosis induced by an excess of dexamethasone (-48% of apoptotic cells). Furthermore, we show that OGP (10-14) can increase OPG secretion (+20%) and can restore the altered expression of OPG induced by GCs to physiological levels. Our results support the employment of OGP (10-14) in clinical trials addressed to the treatment of different bone remodeling alterations including the GC-induced osteoporosis.

[SERMs for treatment of osteoporosis: state-of-the-art and perspectives]

Every year in France, we observe 60,000 vertebral fractures, 50,000 hip fractures and 35,000 wrist fractures. However, only 20% of these patients receive adequate pharmacologic therapy to prevent new fractures and their complications. At the present time, clinicians have not a perfect knowledge of the therapeutic class of SERMs (Selective Estrogen Receptor Modulators). In this paper, the authors show the strong capacity of these drugs to produce, in osteoporotic postmenopausal women, major therapeutic effects on bone (reduction of fracture risk), on breast (reduction of cancer risk), and without any side effects on arterial diseases except an increased risk of venous thromboembolism.

Inhibition of RANKL as a treatment for osteoporosis: preclinical and early clinical studies

Osteoporosis and several other bone disorders occur when there is an imbalance between the resorption and formation components of bone remodeling activity. Therapies available for some of these conditions modulate the activity of osteoclasts and/or osteoblasts. The recent discoveries of receptor activator of NF-kappaB ligand (RANKL), an endogenous activator of osteoclastogenenesis and osteoclast activity and its inhibitor, osteoprotegerin (OPG) as pivotal regulatory factors in the pathogenesis of bone diseases like osteoporosis provide unique targets for therapeutic agents. In laboratory animals and now in humans, administering forms of OPG markedly inhibits osteoclast activity and improves bone strength, documenting that the strategy of inhibiting RANKL activity has therapeutic promise. A highly specific, fully human antibody against RANKL has been produced (denosumab) that in early studies in humans reduces bone turnover and improves bone density. Attributes of denosumab in these clinical studies include a very rapid onset of action, sustained effects for several months after a single injection, and good tolerability. These results provide the basis for studies evaluating the effectiveness of denosumab in several clinical conditions characterized by increased osteoclastic activity.

Osteoprotegerin as a potential therapy for osteoporosis

The discovery and characterization of the RANKL/RANK/OPG signaling pathway and the identification of its role in the pathogenesis of bone loss have provided the rationale for the development of drugs with the ability to modulate RANK-induced osteoclastogenesis. In vivo studies have identified interfering with the RANKL/RANK interaction as a potential therapeutic target in the management of osteoporosis. Two agents capable of blocking the binding of RANKL to RANK have been so far tested in clinical studies--osteoprotegerin (Fc-OPG fusion molecule) and the RANKL-antibody (AMG 162). Both have been found to have profound inhibitory effects on bone resorption, with AMG 162 appearing to be overall superior to OPG. Data are still very scarce, however, and much remains to be uncovered before novel strategies capable of modulating the RANKL/OPG signaling pathway could be safely and effectively used in the management of osteoporosis.

Raloxifene reduces fractures in postmenopausal women with osteoporosis

Recently, selective estrogen receptor modulators have been developed for the management of osteoporosis based on antiosteoclastic properties similar to that of estrogens but with a safety profile including potential benefits on the breast, heart, and cognitive function. Raloxifene, the first selective estrogen receptor modulator to be marketed for the treatment of osteoporosis has shown reduction in spinal fracture risk in patients with low bone mineral density with (48%) or without (35%) prevalent vertebral fracture. Raloxifene also reduces nonvertebral fractures in high risk patients (47%). The decrease in Type I procollagen N-terminal propeptide at 1 year accounts for 28% of the total reduction in vertebral fracture risk. Raloxifene reduced the risk of estrogen receptor-positive invasive breast cancer by 84%. Among subjects with increased cardiovascular risk at baseline, those assigned to raloxifene had a 40% decrease in the risk of cardiovascular events compared with placebo. The definite anti-fracture efficacy of raloxifene at the spine, its plausible effect on non-spine fracture in high-risk patients and its beneficial effect on breast and heart make this compound an interesting approach for women presenting with osteoporosis.

LEVEL OF EVIDENCE

Therapeutic study, level II (lesser quality randomized controlled trial [eg, < 80% followup, no blinding, or improper randomization]). See the Guidelines for Authors for a complete description of the levels of evidence.

Osteoprotegerin as a potential therapy for osteoporosis

The discovery and characterization of the RANKL/RANK/OPG signaling pathway and the identification of its role in the pathogenesis of bone loss have provided the rationale for the development of drugs with the ability to modulate RANK-induced osteoclastogenesis. In vivo studies have identified interfering with the RANKL/RANK interaction as a potential therapeutic target in the management of osteoporosis. Two agents capable of blocking the binding of RANKL to RANK have been so far tested in clinical studies--osteoprotegerin (Fc-OPG fusion molecule) and the RANKL-antibody (AMG 162). Both have been found to have profound inhibitory effects on bone resorption, with AMG 162 appearing to be overall superior to OPG. Data are still very scarce, however, and much remains to be uncovered before novel strategies capable of modulating the RANKL/OPG signaling pathway could be safely and effectively used in the management of osteoporosis.

Isopropanolic extract of black cohosh stimulates osteoprotegerin production by human osteoblasts

An isopropanolic extract (iCR) from the rhizomes of Cimicifuga racemosa (black cohosh) is used an alternative in the treatment of menopausal symptoms, and animal studies suggest positive skeletal effects. iCR stimulated osteoblastic OPG protein secretion by 3- to 5-fold as early as 12 h without affecting RANKL expression. The iCR effect, abrogated by the pure estrogen receptor antagonist ICI 182,780, also enhanced ALP activity (4-fold) and osteocalcin expression (3-fold), possibly contributing to the skeletal effects of black cohosh.

INTRODUCTION

Despite its positive effects on the skeleton, estrogen replacement therapy is no longer recommended as first-line therapy for the prevention and treatment of postmenopausal osteoporosis because it increases cardiovascular, thromboembolic, and breast cancer risk. Recently, herbal therapeutics such as an isopropanolic extract (iCR) from the rhizomes of Cimicifuga (=Actaea) racemosa (black cohosh) are gaining interest as an alternative in the treatment of menopausal symptoms. Whereas animal studies in rats suggest positive skeletal effects, the mechanism of its actions on bone cells remain unclear. RANKL is essential for osteoclast formation and activation, while osteoprotegerin (OPG) neutralizes RANKL.

MATERIALS AND METHODS

In this study, we assessed the effects of iCR on OPG and RANKL mRNA steady-state levels by semiquantitative RT-PCR and on protein production by an ELISA system in human osteoblasts (hOBs).

RESULTS

Under serum-free conditions, treatment with iCR increased OPG mRNA levels and protein secretion of hOBs by 2- to 3-fold in a dose-dependent manner, with a maximum effect at a 10(6)-fold dilution of iCR (p < 0.001) after 24-48 h. Time-course experiments indicated a stimulatory effect of iCR on osteoblastic OPG protein secretion by 3- to 5-fold (p < 0.001) as early as 12 h, whereas RANKL expression was very low and was not found to be modulated by iCR. Of note, the stimulatory effect of iCR on OPG production was abrogated by the pure estrogen receptor antagonist ICI 182,780. Moreover, iCR enhanced two osteoblastic differentiation markers, bone-specific alkaline phosphatase activity and osteocalcin expression, by up to 4- and 3-fold, respectively (p < 0.001).

CONCLUSIONS

Our data suggest that iCR enhances differentiation and increases the OPG-to-RANKL ratio of normal human osteoblasts. These effects may contribute to the positive skeletal effects of black cohosh.

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

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 17beta-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), 17beta-estradiol (E(2)), 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. E(2) treatment significantly inhibited synthesis of BSP in cells from both groups. In conclusion, E(2) 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.

Oestrogen receptors and selective oestrogen receptor modulators: molecular and cellular pharmacology

The early termination of the two arms of the Women's Health Initiative Trials has led to an increased interest and demand for selective oestrogen receptor modulators because of their potential to retain the benefits of hormone replacement therapy (oestrogen plus a gestagen) and at the same time avoid most of its severe adverse events. Selective oestrogen receptor modulators are a class of oestrogen receptor binding, small organic molecules that take advantage of the plasticity of the oestrogen receptors (alpha and beta, respectively), modulating the surface conformation of the oestrogen receptors upon binding in the respective ligand binding cavity. By doing so they affect the binding of various co-factors to the surface of the oestrogen receptors that, at least in part, explains why selective oestrogen receptor modulators may mimic the activity of oestrogen in some tissues where so desired, while opposing its activity in tissues where oestrogen-like activity is undesirable. Although selective oestrogen receptor modulators have many properties in common they also display unique activities including oestrogen receptor surface modulation and regulation of target gene expression. Selective oestrogen receptor modulators therefore offer the opportunity to develop pharmaceuticals with very distinct pharmacology and mechanism of action. Furthermore, these modulators offer the advantage of decreased risk for the development of breast and endometrial cancer and circumvent the need for combination with a gestagen. Most selective oestrogen receptor modulators in development bind with roughly equal affinity to both oestrogen receptor alpha and beta (balanced) and our view is that it is unlikely that a balanced selective oestrogen receptor modulator will inherit all desired effects of oestrogen (e.g. 17beta-oestradiol) and at the same time be devoid of all undesired effects. We therefore propose that the development of oestrogen receptor-subtype (alpha and beta, respectively) selective pharmaceuticals for specific applications (designer drugs) would better provide the benefits of hormone replacement therapy without its associated risks.

Serum osteoprotegerin and its relationship with bone mineral density and markers of bone turnover

INTRODUCTION

The purpose of this study was to compare age-related differences in osteoprotegerin (OPG) in relationship with BMD and the serum bone markers osteocalcin (OC), collagen crosslinks (CTX), and tartrate-resistant acid phosphatase 5b (TRACP-5b).

METHODS

Data were derived from a cross-sectional study on bone health in a random sample of community-dwelling adults aged 30 to 85 years in the Reykjavik area in Iceland. All subjects had whole body, hip, and lumbar spine BMD measured (by DXA), gave blood samples, and answered a thorough questionnaire on medications and medical history. We assessed relationships using the Spearman correlation coefficient, partial correlation, and multivariable linear regression. Men and women were analyzed separately.

RESULTS

Of 2,310 subjects invited over 2 years, 1,630 participated. After excluding individuals with diseases and medications affecting bone metabolism, 517 women (age 56.1 +/- 16.9 years) and 491 men (age 58.7 +/- 14.9 years) remained for analysis. OPG increased steadily with age in both genders without a gender difference. In women, BMD at all sites declined steadily after age 50. In men, BMD remained relatively stable until age 70, after which it declined significantly. After controlling for age, BMI, and other confounding variables, OPG showed only a borderline positive relationship with whole body BMD in men (P = 0.10), but the relationship was nonsignificant in women. In multivariable models, OPG was inversely related to TRACP-5b (P = 0.002) and positively with OC (P = 0.007), the OC/TRACP-5b (P = 0.001) and OC/CTX (P = 0.02) ratios in women. Among men, multivariable models showed a positive association between OPG and OC (P = 0.05) and OC/TRACP-5b (P < 0.009).

CONCLUSIONS

We conclude that serum OPG levels are associated with a profile of bone turnover markers favoring bone formation, suggesting that OPG may be protective against age-related bone loss. Longitudinal studies are needed to address that issue.

Sodium nitroprusside-induced osteoblast apoptosis is mediated by long chain ceramide and is decreased by raloxifene

Release of high levels of nitric oxide (NO) is associated with osteoblastic cell death. The mechanisms of NO-induced cytotoxicity are not well documented and it is presently not known if estrogenic compounds prevent this effect. We studied the role of ceramides in cell death induced by the NO donor sodium nitroprusside (SNP) and we tested the possibility that 17beta-estradiol, the anti-estrogen ICI 182.780 and two selective estrogen receptor modulators raloxifene and tamoxifen modify osteoblastic cell apoptosis. SNP dose-dependently decreased MC3T3-E1 osteoblast viability, increased NO production in the culture media and enhanced the release of intracellular ceramides C22 and C24. Cell death induced by SNP was partially inhibited when MC3T3-E1 cells were pretreated with raloxifene and tamoxifen but was not modified when the cells were pretreated with 17beta-estradiol or ICI 182.780. Cell death induced by SNP resulted from apoptosis as demonstrated by Annexin-V and propidium iodide labeling and a reduction of SNP-induced MC3T3-E1 apoptosis was confirmed in the presence of raloxifene and tamoxifen. SNP induction of C22 and C24 production was inhibited by a pretreatment with raloxifene but not with 17beta-estradiol. Moreover, the synthetic ceramide C24 (0.75 and 1microM) decreased MC3T3-E1 cell viability and osteoblast cell death induced by C24 was partially decreased by raloxifene and to a lesser extent by 17beta-estradiol. These data demonstrate that SNP-induced cell death is mediated by the long chain ceramides C22 and C24 and that raloxifene protected osteoblast from apoptosis induced by SNP, an effect that might be relevant to its pharmacological properties on bone remodeling.

Atorvastatin stimulates the production of osteoprotegerin by human osteoblasts

Recently, HMG-CoA reductase inhibitors (statins), potent inhibitors of cholesterol biosynthesis, have been linked to protective effects on bone metabolism. Because of their widespread use, prevention of bone loss and fractures would be a desirable side effect. However, the mechanisms how statins may affect bone metabolism are poorly defined. Here, we evaluated the effect of atorvastatin on osteoblastic production of receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG), cytokines that are essential for osteoclast cell biology. While RANKL enhances osteoclast formation and activation, thereby, promoting bone loss, OPG acts as a soluble decoy receptor and antagonizes the effects of RANKL. In primary human osteoblasts (hOB), atorvastatin increased OPG mRNA levels and protein secretion by hOB by up to three fold in a dose-dependent manner with a maximum effect at 10(-6) M (P < 0.001). Time course experiments indicated a time-dependent stimulatory effect of atorvastatin on OPG mRNA levels after 24 h and on OPG protein secretion after 48-72 h (P < 0.001). Treatment of hOB with substrates of cholesterol biosynthesis that are downstream of the HMG-CoA reductase reaction (mevalonate, geranylgeranyl pyrophosphate) reversed atorvastatin-induced enhancement of OPG production. Of note, atorvastatin abrogated the inhibitory effect of glucocorticoids on OPG production. Treatment of hOB with atorvastatin enhanced the expression of osteoblastic differentiation markers, alkaline phosphatase and osteocalcin. In summary, our data suggest that atorvastatin enhances osteoblastic differentiation and production of OPG. This may contribute to the bone-sparing effects of statins.

The molecular triad OPG/RANK/RANKL: involvement in the orchestration of pathophysiological bone remodeling

The past decade has seen an explosion in the field of bone biology. The area of bone biology over this period of time has been marked by a number of key discoveries that have opened up entirely new areas for investigation. The recent identification of the receptor activator of nuclear factor kappaB ligand (RANKL), its cognate receptor RANK, and its decoy receptor osteoprotegerin (OPG) has led to a new molecular perspective on osteoclast biology and bone homeostasis. Specifically, the interaction between RANKL and RANK has been shown to be required for osteoclast differentiation. The third protagonist, OPG, acts as a soluble receptor antagonist for RANKL that prevents it from binding to and activating RANK. Any dysregulation of their respective expression leads to pathological conditions such as bone tumor-associated osteolysis, immune disease, or cardiovascular pathology. In this context, the OPG/RANK/RANKL triad opens novel therapeutic areas in diseases characterized by excessive bone resorption. The present article is an update and extension of an earlier review published by Kwan Tat et al. [Kwan Tat S, Padrines M, Theoleyre S, Heymann D, Fortun Y. IL-6, RANKL, TNF-alpha/IL-1: interrelations in bone resorption pathophysiology. Cytokine Growth Factor Rev 2004;15:49-60].

Relationship between urokinase-type plasminogen activator receptor and vascular endothelial growth factor expression and metastasis of gallbladder cancer

AIM: To investigate the relationship of urokinase type plasminogen activator receptor (uPAR) and vascular endothelial growth factor (VEGF) expression with clinical and pathological characteristics of human gallbladder cancer.

METHODS: uPAR and VEGF expressions in 68 gallbladder cancer tissues were detected with anti-receptor immunohistochemical stain.

RESULTS: Expression rate of uPAR was 57.4% (39/68), and VEGF 51.5% (35/68) in gallbladder cancer tissues. Expression of both uPAR and VEGF was significantly related to metastasis, but not significantly correlated with differentiation stage and size of gallbladder cancer.

CONCLUSION: Expression of uPAR and VEGF may be an invasive phenotype of gallbladder cancer and indicator for predicting prognoses, and uPAR expression is significantly correlated with the expression of VEGF.

Raloxifene relaxes rat cerebral arteries in vitro and inhibits L-type voltage-sensitive Ca2+ channels

BACKGROUND AND PURPOSE

Because of their mixed estrogen-agonist and estrogen-antagonist properties, selective estrogen receptor modulators (SERMs) are considered promising substitutes for hormone replacement therapy. Raloxifene and other SERMs confer estrogen-like cardiovascular protective effects but lack the carcinogenic activity of exogenous estrogen. However, little is known about the cerebrovascular action of raloxifene. Therefore, we studied the effects of raloxifene on the mechanisms regulating rat cerebral artery tone.

METHODS

Ring segments of the isolated rat posterior communicating cerebral arteries were mounted in a microvessel myograph for measurement of isometric tension. Whole-cell L-type voltage-sensitive Ca2+ currents were recorded using the perforated patch-clamp technique. Raloxifene (0.1 to 10 micromol/L) reduced the contractile responses to U46619, phenylephrine, and endothelin-1 in normal Krebs solution or to CaCl2 in Ca2+-free, high K+-containing solution. Raloxifene-induced relaxation was identical in endothelium-intact and endothelium-denuded rings. ICI 182780 had no effect on raloxifene-induced relaxation. Raloxifene reduced L-type Ca2+ currents with a pD2 of 5.98+/-0.06, close to that (6.44+/-0.09) for raloxifene-induced relaxation of 60 mmol/L K+-contracted rings.

CONCLUSIONS

This study demonstrates that raloxifene acutely relaxes rat cerebral arteries largely via an endothelium-independent mechanism, involving inhibition of Ca2+ influx through L-type Ca2+ channels.