Emerging Selective Estrogen Receptor Modulators

Breast Cancer: Lifestyle, the Human Gut Microbiota/Microbiome, and Survivorship

Patients with a current diagnosis of breast cancer are enjoying dramatic cure rates and survivorship secondary to an increase in awareness, earlier detection, and more effective therapies. Although strategies such as Breast Cancer Awareness Month in October focus on early detection, lifestyle changes are seldom discussed other than dietary concerns and physical activity. Lifestyle modifications centered on diet and exercise have been demonstrated to affect overall disease-free survival in breast cancer. Since the early 2000s, the role of the human gut microbiota and its relation to breast cancer has become a major area of interest in the scientific and medical community. We live and survive owing to the symbiotic relationship with the microorganisms within us: the human microbiota. Scientific advances have identified a subset of the gut microbiota: the estrobolome, those bacteria that have the genetic capability to metabolize estrogen, which plays a key role in most breast cancers. Recent research provides evidence that the gut microbiome plays a substantial role in estrogen regulation. Gut microbiota diversity appears to be an essential component of overall health, including breast health. Future research attention should include a more extensive focus on the role of the human gut microbiota in breast cancer.

Design, synthesis and biological evaluation of novel 2-methoxyestradiol analogs as dual selective estrogen receptor modulators (SERMs) and antiangiogenic agents

2-methoxyestradiol is a novel agent showing both anti-angiogenic and vascular disrupting properties. In this study, a series of 11α-substituted 2-methoxyestradiol analogs have been designed and synthesized targeting dual ERα and microtubulin. Biological evaluation was performed on their anti-proliferative activities against 5 different cell lines. The results indicated that most compounds exhibited good activities, in which compound 24c and 30c showed the best activity with low micromolar IC₅₀ (2.73 μM -7.75 μM) in all cell lines. The investigation of ER affinity showed that the majority of the compounds displayed good activity at the concentration of 50 μM. In further mechanism study, it was observed that 24c and 30c could induce G2/M cell cycle arrest as well as significant anti-estrogenic activity. In CAM assay, compound 24c and 30c presented significantly anti-angiogenesis activity comparable with 2-methoxyestradiol. Overall, based on biological activities data, 24c and 30c can be identified as a potential lead molecule which might be of therapeutic importance for cancer treatment.

Synthesis of targeted dibenzo[b,f]thiepines and dibenzo[b,f]oxepines as potential lead molecules with promising anti-breast cancer activity

A targeted library of substituted dibenzo[b,f]thiepines and dibenzo[b,f]oxepines (prototypes I, II and III), and structurally analogous to tamoxifen have been synthesized as a new class of anti-breast cancer agents. All the prototype molecules exhibited potential antiproliferative activity against ER + ve and ER-ve breast cancer cell lines. Dibenzo[b,f]thiepine prototypes were found to be more active. Of all the compound tested, 14b exhibited potent in-vitro antiproliferative activity at 1.33 μM and 5 μM concentration in MCF-7 and MDA-MB-231 cell lines and was devoid of any cytotoxicity in normal HEK cells even at 50 μM. Cell cycle analysis showed that the compound 14b inhibited cell proliferation due to G0/G1 arrest in MCF-7 cells. Annexin-V FITC and PI staining experiments confirmed that the cell inhibition was primarily due to apoptosis and not by necrosis, which was also supported by LDH release assay experiment. Molecular docking studies showed better binding interaction of the new dibenzo[b,f]thiepine analogue 14b with the estrogen receptor (ER) as compared to 4-hydroxy-tamoxifen and this enhanced binding might be responsible for its estrogen antagonistic activity that induces cell cycle arrest, apoptosis and inhibition of breast cancer cells.

An overview of current and emerging SERMs

Selective estrogen receptor modulators (SERMs) are compounds that exhibit tissue-specific estrogen receptor (ER) agonist or antagonist activity, and are used for various indications, including treatment of breast cancer, osteoporosis, and menopausal symptoms. Endometrial safety has been a key differentiator between SERMs in clinical practice. For example, tamoxifen exhibits ER agonist activity in the uterus, resulting in an increased risk of endometrial hyperplasia and malignancy, whereas raloxifene and bazedoxifene have neutral effects on the uterus. Based on their efficacy and long-term safety, SERMs are increasingly being prescribed for women who cannot tolerate other treatment options and for younger women at an increased risk of fracture who may remain on therapy for long periods of time. Continuing advances in the understanding of SERM mechanisms of action and structural interactions with the ER may lead to the development of new agents and combinations of agents to provide optimal treatments to meet the varying needs of postmenopausal women. One such example is the tissue selective estrogen complex, which partners a SERM with 1 or more estrogens, with the aim of blending the desired estrogen-receptor agonist activities of estrogens on vasomotor symptoms, vulvar-vaginal atrophy, and loss of bone mass with the tissue selectivity of a SERM.

Use of SERMs for treatment in postmenopausal women

Selective estrogen receptor modulators (SERMs) are synthetic non-steroidal agents which have varying estrogen agonist and antagonist activities in different tissues, most likely due to the receptor conformation changes associated with that SERM's binding and the subsequent effect on transcription. Clinical trials aim to differentiate amongst SERMs on selected target tissues for use in postmenopausal women including effects on breast, bone, cardiovascular venous thrombosis risk, endometrium, vagina, vasomotor symptoms, and brain. This paper describes differences in clinical effects on selected target tissues of SERMs that are approved, discontinued or in development. FDA approved SERMs include tamoxifen and toremifene used for prevention and treatment of breast cancer, raloxifene approved for prevention and treatment of osteoporosis and prevention of invasive breast cancer, and ospemifene approved for treatment of dyspareunia from menopausal vaginal atrophy. The FDA approved first tissue selective estrogen complex (TSEC) a pairing of conjugated equine estrogens with the SERM, bazedoxifene. This pairing reduces the risk of endometrial hyperplasia that can occur with the estrogenic component of the TSEC without the need for a progestogen in women with a uterus. It also allows for the estrogenic benefits on relief of hot flashes and prevention of bone loss without stimulating the breast or the endometrium. In clinical practice, the tissue-selective actions of SERMs, alone or paired with estrogens, allow for individualization in meeting the treatment needs of postmenopausal women by providing targeted tissue effects. This article is part of a Special Issue entitled 'Menopause'.

Anatomical location and redistribution of G protein-coupled estrogen receptor-1 during the estrus cycle in mouse kidney and specific binding to estrogens but not aldosterone

Prior studies have linked renoprotective effects of estrogens to G-protein-coupled estrogen receptor-1 (GPER-1) and suggest that aldosterone may also activate GPER-1. Here, the role of GPER-1 in murine renal tissue was further evaluated by examining its anatomical distribution, subcellular distribution and steroid binding specificity. Dual immunofluorescent staining using position-specific markers showed that GPER-1 immunoreactivity primarily resides in distal convoluted tubules and the Loop of Henle (stained with Tamm-Horsfall Protein-1). Lower GPER-1 expression was observed in proximal convoluted tubules marked with megalin, and GPER-1 was not detected in collecting ducts. Plasma membrane fractions prepared from whole kidney tissue or HEK293 cells expressing recombinant human GPER-1 (HEK-GPER-1) displayed high-affinity, specific [(3)H]-17β-estradiol ([(3)H]-E2) binding, but no specific [(3)H]-aldosterone binding. In contrast, cytosolic preparations exhibited specific binding to [(3)H]-aldosterone but not to [(3)H]-E2, consistent with the subcellular distribution of GPER-1 and mineralocorticoid receptor (MR) in these preparations. Aldosterone and MR antagonists, spironolactone and eplerenone, failed to compete for specific [(3)H]-E2 binding to membranes of HEK-GPER-1 cells. Furthermore, aldosterone did not increase [(35)S]-GTP-γS binding to membranes of HEK-GPER-1 cells, indicating that it is not involved in G protein signaling mediated through GPER-1. During the secretory phases of the estrus cycle, GPER-1 is upregulated on cortical epithelia and localized to the basolateral surface during proestrus and redistributed intracellularly during estrus. GPER-1 is down-modulated during luteal phases of the estrus cycle with significantly less receptor on the surface of renal epithelia. Our results demonstrate that GPER-1 is associated with specific estrogen binding and not aldosterone binding and that GPER-1 expression is modulated during the estrus cycle which may suggest a physiological role for GPER-1 in the kidney during reproduction.

Assessment of raloxifene, estradiol-17β, dl-ormeloxifene and levormeloxifene on thrombin activity

Abstract Background: Cancer is one of the leading causes of morbidity and mortality globally. Cancer-associated thrombosis is well established in clinical settings, and thrombin has been found to induce angiogenesis at cancer sites. This establishes a link between cardiovascular diseases and cancer, where cancer and thrombin have been intricately associated. Various selective estrogen receptor modulators (SERMs) have been reported to exhibit anticancer activity. Therefore, we investigated estradiol-17β and SERMs dl-ormeloxifene (centchroman), raloxifene and levormeloxifene (l-centchroman) for their anticancer effects and their effect on thrombin activity. Methods: Anticancer activity was assessed against PC-3 cell line by flow cytometry following treatment with estradiol-17β and SERMs at 10 nM-1 mM concentrations. The cells were stained with propidium iodide and the percentage of cells in the sub-G0/G1 region was considered apoptotic. Thrombin inhibitory effect was evaluated by thrombin inhibition assay in vitro following incubation with 100 nM-3 mM concentrations of estradiol-17β or various SERMs. Further, the effect of estradiol-17β and SERMs on endogenous thrombin generation potential (ETP) was assessed by thrombin generation assay on rat plasma in vitro. Results: These compounds exhibited >90% cell death in PC-3 cell lines at 1 mM concentration except estradiol-17β. Neither estradiol-17β, dl-ormeloxifene and levormeloxifene showed any thrombin inhibitory or enhancing activity in thrombin inhibition assay, nor did they show any effect on ETP on rat plasma in vitro. However, raloxifene inhibited thrombin activity in a concentration-dependent manner. Raloxifene decreased ETP of the plasma at 3 and 1 mM,which is equivalent to that of 30-100 U/mL of heparin. Interestingly, raloxifene increased thrombin generation at lower concentrations and it inhibited thrombin generation at higher concentrations. Conclusions: These observations suggest that dl-ormeloxifene, estradiol-17β and levormeloxifene do not possess thrombin inhibitory activity. Raloxifene possesses thrombin modulatory effect in addition to its anticancer activity, and this observation may help us in understanding the thromboembolic complications associated with raloxifene.

Effect of raloxifene and atorvastatin in atherosclerotic process in ovariectomized rats

AIM

The goal of this study was to investigate the combined effects of raloxifene and atorvastatin in aged ovariectomized rats during endothelial dysfunction and atherosclerotic process.

MATERIAL AND METHODS

This study was conducted on 28 Wistar albino female rats randomly divided into four groups. All groups were ovariectomized and one group was kept as the control group (OVX). For four weeks, the remaining three groups were treated with the statin atorvastatin (OVX+AV), the selective estrogen receptor modulator raloxifene (OVX+RL), and both atorvastatin and raloxifene (OVX+RL+AV), respectively. At the end of the treatment period, all rats were sacrificed and thoracic aortas excised, and endothelial cells were immunohistochemically stained for markers in the atherosclerotic process, such as inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), endothelin-1 (ET-1), monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor alpha (TNF-α).

RESULTS

  Compared to the ovariectomized group, the iNOS level was significantly increased in the OVX+RL group (P=0.002), but contrarily decreased in the groups OVX+AV (P=0.002) and OVX+RL+AV (P=0.002). eNOS levels in the groups OVX+AV (P=0.002) and OVX+RL+AV (P=0.002) were significantly lower than that in the OVX group. When compared to the OVX group, significant reductions in ET-1 and TNF-α levels were found in all treatment groups. A significant decrement in MCP-1 level was found in the OVX+AV group (P=0.002).

CONCLUSION

  In aged ovariectomized rats, the administration of both raloxifene and atorvastatin significantly decreased the levels of ET-1 and TNF-α on endothelial cells. Combined treatment with these drugs shortly after menopause might play a potential preventive role in the early stages of atherosclerosis development.

Antidepressive and anxiolytic activity of selective estrogen receptor modulators in ovariectomized mice submitted to chronic unpredictable stress

Estradiol has antidepressive and anxiolytic actions. However, its therapeutic use is limited by its peripheral effects. Selective estrogen receptor modulators may represent an alternative to estradiol for the treatment of depressive symptoms. Here we report that tamoxifen and raloxifene decrease immobility time in the forced swim test and increases the time spent in open arms in the elevated plus maze in ovariectomized mice submitted to chronic unpredictable stress.

Lasofoxifene: selective estrogen receptor modulator for the prevention and treatment of postmenopausal osteoporosis

OBJECTIVE

To review literature evaluating the pharmacology, pharmacokinetics, clinical efficacy, and adverse effects of lasofoxifene (CP-336156), a selective estrogen receptor modulator (SERM) that is not approved for use in the US.

DATA SOURCES

Literature was accessed through the MEDLINE and EMBASE databases (1985-June 2010) using the terms lasofoxifene and selective estrogen receptor modulators. Reference lists from retrieved articles were also manually reviewed. The Food and Drug Administration and Pfizer provided additional information.

STUDY SELECTION AND DATA EXTRACTION

All clinical trials evaluating lasofoxifene were included in this review. In addition, all articles evaluating the pharmacology, pharmacokinetics, and safety of lasofoxifene in humans were reviewed.

DATA SYNTHESIS

Lasofoxifene is a third-generation SERM with markedly higher in vitro and in vivo potency and oral bioavailability than other SERMs. The drug has produced significant improvements in bone density and biochemical markers of bone turnover in preclinical studies and in Phase 2 and 3 clinical trials. In these trials, lasofoxifene has shown a favorable safety profile, with adverse events including hot flushes, leg cramps, and increased vaginal moisture. One 2-year major comparative study in postmenopausal women determined that lasofoxifene and raloxifene were equally effective at increasing total hip bone mineral density (BMD), while lasofoxifene had a significantly greater effect on lumbar spine BMD.

CONCLUSIONS

Osteoporosis is a significant health problem. While the results of further clinical trials are needed to define the risks and benefits of treatment, particularly relating to fractures, lasofoxifene may prove to be an effective and well-tolerated therapeutic option for the prevention of bone loss in postmenopausal women.

Cardiovascular effects of systemic cancer treatment

Many methods of systemic anticancer treatment have detrimental effects on the cardiovascular system, thus limiting the possibility of further therapy, worsening patients' quality of life and increasing mortality. The best recognized and most clinically relevant is the cardiotoxicity of anthracyclines. Other cytotoxic drugs associated with significant risk of cardiovascular complications include alkylating agents, 5-fluorouracil and paclitaxel. Cardiovascular adverse effects are also associated with the use of targeted therapies, such as trastuzumab, bevacizumab and tyrosine kinase inhibitors, and some of the drugs used in the treatment of hematological malignancies, such as all-trans-retinoic acid and arsenic trioxide. The most serious cardiac complication of anticancer therapy is congestive heart failure, associated predominantly with the use of anthracyclines, trastuzumab and high-dose cyclophosphamide. Myocardial ischemia is mainly caused by antimetabolite and interferon alpha treatment. Other adverse effects may include hypotension, hypertension, arrhythmias and conduction disorders, edema, pericarditis and thrombo-embolic complications. The aim of this review is to summarize and critically analyze the available evidence on the cardiovascular toxicity of systemic anticancer therapies, with particular attention to the recently recognized adverse effects of targeted therapies.

SERMs and SERMs with estrogen for postmenopausal osteoporosis

Bone loss with aging places postmenopausal women at a higher risk for osteoporosis and its consequences such as fractures, pain, disability, and increased morbidity and mortality. Approximately 200 million patients worldwide are affected. The Third National Health and Nutrition Examination Survey (NHANES III) estimated that up to 18% of US women aged 50 and older have osteoporosis and up to 50% have osteopenia. Greater than 2 million osteoporotic related fractures occurred in the United States with direct healthcare costs exceeding $17 billion. Hormone Replacement Therapy (HRT) was a popular option for postmenopausal women before the Women's Health Initiative (WHI). Several agents are available in the U.S., including bisphosphonates, hormone therapy, calcitonin, parathyroid hormone and the selective estrogen receptor modulator (SERM) raloxifene. There are concerns about long term safety and compliance. Therefore, other agents are under investigation. SERMs are a diverse group of agents that bind to the estrogen receptor and each SERM appears to have a unique set of clinical responses, which are not always consistent with the typical responses seen with other SERMs. This article will discuss the SERMs approved in the United States, tamoxifene and raloxifene, and investigational SERMs. The ideal SERM would include the beneficial effects of estrogen in bone, heart and the central nervous system, with neutral or antagonistic effects in tissues where estrogen effects are undesirable(breast and endometrium). A new target in treating postmenopausal osteoporosis is the tissue estrogen complex or the pairing of a SERM with a conjugated estrogen known as a tissue selective estrogen complex (TSEC). This novel approach is currently being evaluated with bazodoxifene which could yield the beneficial effects of estrogens and SERMS, while potentially being more tolerable and safer than either therapy alone.

Current and emerging therapies for the treatment of osteoporosis

Osteoporosis represents a weakening of bone tissue due to an imbalance in the dynamic processes of bone formation and bone resorption that are continually ongoing within bone tissue. Most currently available osteoporosis therapies are antiresorptive agents. Over the past decade, bisphosphonates, notably alendronate and risedronate, have become the dominant agents with newer bisphosphonates such as ibandronate and zoledronic acid following a trend of less frequent dosing regimens. Synthetic estrogen receptor modulators (SERMs) continue to be developed as drugs that maintain the bone-protective effects of estrogen while avoiding its associated adverse side effects. Currently available agents of this class include raloxifene, the only SERM available in the United States (US), and lasofoxifene and bazedoxifene, available in Europe. Calcitonin, usually administered as a nasal spray, completes the list of currently approved antiresorptive agents, while parathyroid hormone analogs represent the only anabolic agents currently approved in both the US and Europe. Strontium ranelate is an additional agent available in Europe but not the US that has both anabolic and antiresorptive activity. New agents expected to further expand therapeutic options include denosumab, a monoclonal antibody inhibitor of the resorptive enzyme cathepsin K, which is in the final stages of Food and Drug Administration approval. Other agents in preclinical development include those targeting specific molecules of the Wnt/β-catenin pathway involved in stimulating bone formation by osteoblast cells. This review discusses the use of currently available agents as well as highlighting emerging agents expected to bring significant changes to the approach to osteoporosis therapy in the near future.

Long-term safety and efficacy of raloxifene in the prevention and treatment of postmenopausal osteoporosis: an update

The integrity of bone tissue and its remodeling that occurs throughout life requires a coordinated activity of osteoblasts and osteoclasts. The decreased estrogen circulating level during postmenopausal transition, with a prevalence of osteoclastic activity over osteoblastic activity, represents the main cause of bone loss and osteoporosis. Osteoporosis is a chronic disease requiring long-term therapy and it is important to evaluate the efficacy and safety of treatments over several years, as the fear of health risks is a common reason for discontinuing therapy. Raloxifene is a selective estrogen receptor modulator (SERM) leading to estrogen-agonist effects in some tissues and estrogen-antagonist effects in others. Raloxifene is effective to prevent and treat postmenopausal vertebral osteoporosis, with reduction of spine fractures and, in post-hoc analyses, non-spine fractures in high-risk subjects. Moreover, raloxifene reduces the risk of invasive breast cancer and improves the levels of serum lipoprotein but with an increased risk of venous thromboembolism and fatal stroke, without significant change in the incidence of coronary events. For these reasons the overall risk-benefit profile is favorable. Therefore, when considering the use of raloxifene in a postmenopausal woman, we should take into account the osteoporosis-related individual risk and weigh the potential benefits, skeletal and extra-skeletal, against the health risks.

Identification and structure-activity relationships of chromene-derived selective estrogen receptor modulators for treatment of postmenopausal symptoms

As part of a program aimed at the development of selective estrogen receptor modulators (SERMs), novel chromene scaffolds, benzopyranobenzoxapanes, were discovered. Many compounds showed binding affinity as low as 1.6-200 nM, displayed antagonist behaviors in the MCF-7 human breast adenocarcinoma cell line as well in Ishikawa cell line with IC(50) values in the range 0.2-360 nM. On the basis of the side chain substitution, various compounds demonstrated strong inhibitory activity in anti-uterotropic assay. Compound 7-(R) and its major metabolites 5-(R) and 6-(R) were evaluated in several in vivo models of estrogen action. Relative to a full estrogen agonist (ethynyl estradiol) and the SERM raloxifene, 7-(R) was found to be a potent SERM that behaved as antagonist in the uterus and exhibited estrogen agonistic activity on bone, plasma lipids, hot flush, and vagina. The overall pharmacokinetic profile and stability were significantly improved compared to those of the phase 2 development compound 9-(R).

An estrogen receptor alpha activity indicator model in mice

Estrogen receptor alpha (ERalpha), plays essential roles in the female reproduction. To investigate the dynamic changes in ERalpha activity in vivo, we have developed an ER Alpha Activity Indicator (ERAAI) mouse. This ERAAI mouse harbors both a modified ERalpha Bacterial Artificial Chromosome (BAC) clone and a reporter gene which is regulated specifically by the modified receptor. The ERalpha modification (Gal4-ERalpha) consists replacing the DNA binding domain (DBD) of ERalpha with the DBD of yeast Gal4 transcription factor. This reporter transgene consisting of a humanized renilla Green Fluorescent Protein (hrGFP) sequence controlled by the Upstream Activating Sequences for the Gal4 gene (UAS(G)) was inserted into the modified ERalpha BAC clone. Expression of Gal4-ERalpha and hrGFP reliably recapitulates endogenous ERalpha expression and activity in the estrogen target tissues in response to estrogen stimulation. Therefore, the ERAAI mouse represents a novel animal model to investigate dynamic ERalpha activity in vivo.

Estrogen and SERM neuroprotection in animal models of Parkinson's disease

A higher prevalence and incidence of Parkinson disease (PD) is observed in men and beneficial motor effects of estrogens are observed in parkinsonian women. Lesion of the dopamine (DA) nigrostriatal pathway in animals with 1-methyl 4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) provides a model of PD and this is based on its use in humans as side-product of a drug abuse. Presently treatment of PD is mainly symptomatic. The MPTP mouse is used to study the neuroprotective roles of estrogenic drugs on the DA system. Estrogens, but not androgens, are active neuroprotectants as well as progesterone and dehydroepiandrosterone. An estrogen receptor agonist PPT and the selective estrogen receptor modulator raloxifene are also neuroprotective. Striatal DA neurons of estrogen receptor alpha knockout mice are more susceptible to MPTP toxicity than wild-type mice and neuroprotection by estradiol is associated with the activation of the PI3-K pathway involving Akt, GSK3beta, Bcl2 and BAD.

Rationale for using raloxifene to prevent both osteoporosis and breast cancer in postmenopausal women

Both osteoporosis with fracture and breast cancer are important health issues for postmenopausal women. It is well known that estrogen and estrogen receptors (ERs) play an important role in the pathogenesis of both diseases. In past decades, hormone therapy (HT), mainly estrogen plus progestin (EPT), has been frequently used for the purpose of preventing and treating postmenopausal osteoporosis because of its efficacy, but it also contributes to a significant increase in breast cancer. Currently, there is a dilemma regarding the use of estrogen for postmenopausal women. Fortunately, an increasing understanding of the action of estrogen has led ultimately to the design of new drugs that work by virtue of their interaction with the ER; these drugs have come to be known as selective estrogen receptor modulators (SERMs), and are not only effective in preventing osteoporosis and managing those with osteoporosis, but also in decreasing the incidence of breast cancer. Among these SERMs, raloxifene may be the most attractive agent based on the evidence from five recent large trials (Multiple Outcomes of Raloxifene Evaluation [MORE], Continuing Outcomes Relevant to Evista [CORE], Raloxifene Use for the Heart [RUTH], Study of Tamoxifen and Raloxifene [STAR], and Evista Versus Alendronate [EVA]). The former three trials showed that raloxifene not only decreases the incidence of osteoporosis-associated fractures, but also has efficacy in breast cancer prevention. The head-to-head comparison with the anti-fracture agent alendronate (EVA trial) and the chemoprevention agent tamoxifen (STAR trial) further confirmed that raloxifene is a better choice. We concluded that since there is an absence of a therapeutic effect on relieving climacteric symptoms and there is the presence of a potential risk of thromboembolism in the use of raloxifene, this drug can be prescribed for clear indications, such as the management of osteoporosis, the prevention of fracture, and decreasing the incidence of invasive breast cancer, with careful monitoring for thromboembolism. It is reasonable to use raloxifene as an appropriate medicine that targets climacteric symptom-free postmenopausal women because of its overall favorable risk-benefit safety profile using the global index proposed by the Women's Health Initiation (WHI).

Selective estrogen receptor modulators: an update on recent clinical findings

Recent clinical data on selective estrogen receptor modulators (SERMs) have provided the basis for reassessment of the SERM concept. The molecular basis of SERM activity involves binding of the ligand SERM to the estrogen receptor (ER), causing conformational changes which facilitate interactions with coactivator or corepressor proteins, and subsequently initiate or suppress transcription of target genes. SERM activity is intrinsic to each ER ligand, which accomplishes its unique profile by specific interactions in the target cell, leading to tissue selective actions. We discuss the estrogenic and anti-estrogenic effects of early SERMs, such as clomiphene citrate, used for treatment of ovulation induction, and the triphenylethylene, tamoxifen, which has ER antagonist activity in the breast, and is used for prevention and treatment of ER-positive breast cancer. Since the development of tamoxifen, other triphenylethylene SERMs have been studied for breast cancer prevention, including droloxifene, idoxifene, toremifene, and ospemifene. Other SERMs have entered clinical development more recently, including benzothiophenes (raloxifene and arzoxifene), benzopyrans (ormeloxifene, levormeloxifene, and EM-800), lasofoxifene, pipendoxifene, bazedoxifene, HMR-3339, and fulvestrant, an anti-estrogen which is approved for breast cancer treatment. SERMs have effects on tissues containing ER, such as the breast, bone, uterine and genitourinary tissues, and brain, and on markers of cardiovascular risk. Current evidence indicates that each SERM has a unique array of clinical activities. Differences in the patterns of action of SERMs suggest that each clinical end point must be evaluated individually, and conclusions about any particular SERM can only be established through appropriate clinical trials.

Mitochondrial effects of estrogen are mediated by estrogen receptor alpha in brain endothelial cells

Mitochondrial reactive oxygen species (ROS) and endothelial dysfunction are key contributors to cerebrovascular pathophysiology. We previously found that 17beta-estradiol profoundly affects mitochondrial function in cerebral blood vessels, enhancing efficiency of energy production and suppressing mitochondrial oxidative stress. To determine whether estrogen specifically affects endothelial mitochondria through receptor mechanisms, we used cultured human brain microvascular endothelial cells (HBMECs). 17beta-Estradiol treatment for 24 h increased mitochondrial cytochrome c protein and mRNA; use of silencing RNA for estrogen receptors (ERs) showed that this effect involved ERalpha, but not ERbeta. Mitochondrial ROS were determined by measuring the activity of aconitase, an enzyme with an iron-sulfur center inactivated by mitochondrial superoxide. 17beta-Estradiol increased mitochondrial aconitase activity in HBMECs, indicating a reduction in ROS. Direct measurement of mitochondrial superoxide with MitoSOX Red showed that 17beta-estradiol, but not 17alpha-estradiol, significantly decreased mitochondrial superoxide production, an effect blocked by the ER antagonist, ICI-182,780 (fulvestrant). Selective ER agonists demonstrated that the decrease in mitochondrial superoxide was mediated by ERalpha, not ERbeta. The selective estrogen receptor modulators, raloxifene and 4-hydroxy-tamoxifen, differentially affected mitochondrial superoxide production, with raloxifene acting as an agonist but 4-hydroxy-tamoxifen acting as an estrogen antagonist. Changes in superoxide by 17beta-estradiol could not be explained by changes in manganese superoxide dismutase. Instead, ERalpha-mediated decreases in mitochondrial ROS may depend on the concomitant increase in mitochondrial cytochrome c, previously shown to act as an antioxidant. Mitochondrial protective effects of estrogen in cerebral endothelium may contribute to sex differences in the occurrence of stroke and other age-related neurodegenerative diseases.

Contribution of estrogen receptors alpha and beta to the effects of estradiol in the brain

Clinical and experimental studies show a modulatory role of estrogens in the brain and suggest their beneficial action in mental and neurodegenerative diseases. The estrogen receptors ERalpha and ERbeta are present in the brain and their targeting could bring selectivity and reduced risk of cancer. Implication of ERs in the effect of estradiol on dopamine, opiate and glutamate neurotransmission is reviewed. The ERalpha agonist, PPT, is shown as estradiol to modulate hippocampal NMDA receptors and AMPA receptors in cortex and striatum of ovariectomized rats whereas the ERbeta agonist DPN is inactive. Striatal DPN activity suggests implication of ERbeta in estradiol modulation of D2 receptors and transporters in ovariectomized rats and is supported by the lack of effect of estradiol in ERbeta knockout (ERKObeta) mice. Both ERalpha and ERbeta agonists modulate striatal preproenkephalin (PPE) gene expression in ovariectomized rats. In male mice PPT protects against MPTP toxicity to striatal dopamine; this implicates Akt/GSK3beta signaling and the apoptotic regulators Bcl2 and Bad. This suggests a role for ERalpha in striatal dopamine neuroprotection. ERKOalpha mice are more susceptible to MPTP toxicity and not protected by estradiol; differences in ERKObeta mice are subtler. These results suggest therapeutic potential for the brain of ER specific agonists.

Raloxifene for older women: a review of the literature

Raloxifene is a non-steroidal selective estrogen-receptor modulator (SERM) which is used for prevention and treatment of postmenopausal osteoporosis. Raloxifene decreases the incidence of vertebral fractures by 30%-50% in postmenopausal women with osteoporosis but has not been shown to decrease the incidence of hip fractures or other non-vertebral fractures. At the present time, estrogen-replacement therapy and bisphosphonate treatment are the only medical treatments that are proven to prevent hip fractures with the exception of vitamin D and calcium replacement, which has been shown to prevent hip fractures in elderly individuals and nursing home residents. Raloxifene has been shown to have additive effects on bone turnover and bone mineral density (BMD) when used along with alendronate and teriparatide. Raloxifene could have a role in renal failure as it has been shown to increase BMD of the vertebra over 1 year of therapy. Raloxifene is as effective as tamoxifen in reducing the risk of invasive breast cancer. The increased incidence of venous thromboembolism is the main concern of raloxifene therapy and previous history of venous thromboembolism is a contraindication for use of raloxifene. Raloxifene has a role in treatment of vertebral osteoporosis in older women. The decision to use raloxifene should be based on evaluation of fracture risk and on potential other benefits than fracture reduction along with consideration of side effects.

Benzothiophene Selective Estrogen Receptor Modulators with Modulated Oxidative Activity and Receptor Affinity

The regulation of estrogenic and antiestrogenic effects of selective estrogen receptor modulators (SERMs) is thought to underlie their clinical use. Most SERMs are polyaromatic phenols susceptible to oxidative metabolism to quinoids, which are proposed to be genotoxic. Conversely, the redox reactivity of SERMs may contribute to antioxidant and chemopreventive mechanisms, providing a new approach to improve the therapeutic properties of SERMs. An improved synthetic strategy was developed to generate a family of benzothiophene SERMs. Using computational modeling methods and measurements of antioxidant activity and estrogen receptor (ER) ligand binding, this SERM family was shown to provide both a range of ERalpha/ERbeta selectivity from 1.2- to 67-fold and a range of redox activity. Antioxidant activity was successfully modulated by varying a substituent remote from the OH group; the source of the antioxidant capacity. An efficient synthetic procedure is reported yielding benzothiophene SERMs wherein redox activity and ER affinity are modulated.

Effects on asymmetric dimethylarginine of HMR 3339, a novel selective estrogen receptor modulator

OBJECTIVE

To investigate the short-term effects of three different doses of the selective estrogen receptor modulator HMR 3339 in comparison with placebo and raloxifene on asymmetric dimethylarginine (ADMA), a nitric oxide synthase inhibitor.

DESIGN

This study was a multicenter, randomized, placebo-controlled, double-blind, dose-ranging study. Ninety-four healthy postmenopausal women received daily doses of either placebo (n=16), HMR 3339 2.5 mg (n=20), HMR 3339 10 mg (n=19), HMR 3339 50 mg (n=20), or raloxifene 60 mg (n=19) for 12 weeks. Fasting plasma concentrations of ADMA, arginine, and symmetric dimethylarginine (SDMA) were measured at baseline and after 4 and 12 weeks by high-performance liquid chromatography.

RESULTS

HMR 3339 induced a dose-dependent reduction of ADMA and SDMA concentrations, with the largest effects (P<0.01 for both) in the HMR 3339 50 mg group compared with baseline and placebo (at 12 weeks: -7.0% [95% CI, -14.2% to 0.2%] for ADMA and -16.2% [95% CI, -22.4% to -10.0%] for SDMA). Twelve weeks of raloxifene 60 mg significantly reduced SDMA (P=0.03) but not ADMA concentrations. Arginine concentrations were not altered by any treatment.

CONCLUSIONS

The reduction of the nitric oxide synthase inhibitor ADMA by HMR 3339 may potentially have a beneficial effect on the cardiovascular system in postmenopausal women.

Characterization of the relaxant response to N,N'-dipropyl-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine in porcine coronary arteries

N,N'-Dialkyl-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamines show structural analogy with estrogens and selective estrogen receptor modulators. Because the vasodilator properties of these compounds are unknown, we investigated their potential to relax porcine coronary arteries and determined the mechanism(s) of relaxation. Isolated porcine coronary arterial rings were suspended in organ chambers, precontracted with KCl (30 mM), and the relaxant response was determined by measurement of changes in isometric force. Dependent on the chemical structure, the drugs induced concentration-dependent relaxation in rings with and without endothelium. N,N'-Dipropyl-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine (8) was most potent and showed a 12- to 15-fold higher vasodilatory effect than 17beta-estradiol (E2). The vasorelaxation was independent of endothelium. Calcium concentration-dependent contractions in high-potassium depolarizing medium were insurmountably inhibited by 8. The effect of the L-type Ca2+ channel activator (S)-(-)-Bay K 8644 [(S)-(-)-1,4-dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)phenyl]-3-pyridine-carboxylic acid methyl ester], which induced a leftward shift of Ca2+ contraction, was blocked by 8. The relaxant response to 8 was unaffected by the estrogen receptor antagonist ICI 182,780 (7alpha-[9-[(4,4,5,5,5-pentafluoropentyl]-sulfinyl]nonyl]-estra-1,3,5(10)-triene-3,17beta-diol) and K+ channel blockers, i.e., TEA, glibenclamide, and 4-aminopyridine. Furthermore, the vasodilatory effect of 8 was unaffected by the adenylyl cyclase inhibitor SQ 22536 [9-(tetrahydro-2-furanyl)-9H-purin-6-amine], the guanylyl cyclase inhibitor ODQ [1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one], the protein kinase A inhibitor KT 5720 [(9S,10S,12R)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg: 3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid hexyl ester], the protein kinase G inhibitor KT 5823 [(9S,10R,12R)-2,3,9,10,11,12-hexahydro-10-methoxy-2,9-dimethyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid methyl ester], and the p38 mitogen-activated protein kinase (MAPK) inhibitor SB 203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole]. Western blot analysis demonstrated that 8, unlike E2, raloxifene, and tamoxifen, failed to stimulate p38 MAPK. It is concluded that N,N'-dipropyl-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine induces endothelium-independent relaxation of coronary arteries; the mechanism apparently involves inhibition of L-type Ca2+ channels. The drug may be protective against cardiovascular diseases.

Genistein inhibits glutamate-induced apoptotic processes in primary neuronal cell cultures: an involvement of aryl hydrocarbon receptor and estrogen receptor/glycogen synthase kinase-3beta intracellular signaling pathway

Phytoestrogens prevent neuronal damage, however, mechanism of their neuroprotective action has not been fully elucidated. This study aimed to evaluate the effects of genistein on glutamate-induced apoptosis in mouse primary neuronal cell cultures. Glutamate (1 mM) enhanced caspase-3 activity and lactate dehydrogenase (LDH) release in the hippocampal, neocortical and cerebellar neurons in time-dependent manner, and these data were confirmed at the cellular level with Hoechst 33342 and calcein AM staining. Genistein (10-10,000 nM) significantly inhibited glutamate-induced apoptosis, and the effect of this isoflavone was most prominent in the hippocampal cells. Next, we studied an involvement of estrogen and aryl hydrocarbon receptors in anti-apoptotic effects of genistein. A high-affinity estrogen receptor antagonist, ICI 182, 780 (1 microM), reversed, whereas less specific antagonist/partial agonist, tamoxifen (1 microM), either intensified or partially inhibited genistein effects. Aryl hydrocarbon receptor antagonist, alpha-naphthoflavone (1 microM), exhibited a biphasic action: it enhanced genistein action toward a short-term exposure (3 h) to glutamate, but antagonized genistein action toward prolonged exposure (24 h) to that insult. SB 216763 (1 microM), which preferentially inhibits glycogen synthase kinase-3beta (GSK-3beta), potentiated genistein effects. These data point to strong effects of genistein at low micromolar concentrations in various brain tissues against glutamate-evoked apoptosis. Moreover, this study provided evidence for involvement of aryl hydrocarbon receptor and estrogen receptor/GSK-3beta intracellular signaling pathway in anti-apoptotic action of genistein.

Endometriosis: the way forward

Endometriosis, a common cause of morbidity, affects 10% of women of reproductive age. In this review we focus on the new developments in pathogenesis, diagnosis and treatment options, reviewing the literature published about this enigmatic disorder over the past three years. More specifically, new theories of the pathogenesis of the syndrome of Sampson and Cullen are discussed. The new era of genomics may characterize endometriosis and transform clinical management of the disease. Literature suggesting that endometriosis may have an environmental origin is reviewed. New approaches to medical therapy of endometriosis have been developed, including the levonorgestrel-releasing intrauterine device, aromatase inhibitors, immunomodulatory drugs, angiogenesis inhibitors, selective estrogen and progesterone receptor modulators, and statins. Subfertility is another well-known result of endometriosis and often complex decisions must be made regarding management of the endometriosis patient who wishes to conceive. Laparoscopic surgery and assisted reproduction--with or without gonadotropin-releasing hormone-agonist treatment--are reviewed. Finally we speculate about new developments in the field of endometriosis in the coming three years.

Characterisation of the relaxant response to raloxifene in porcine coronary arteries

The present study characterises the vasorelaxant response to raloxifene in isolated rings of porcine coronary artery. Tissues precontracted either with KCl (30 mM) or prostaglandin F(2alpha) (PGF(2alpha); 3 microM) were concentration-dependently relaxed by raloxifene (0.1-10 microM). Relaxation was not inhibited by the estrogen receptor antagonist 7alpha-[9-[(4,4,5,5,5-pentafluoropentyl)sulfinyl]nonyl]-estra-1,3,5(10)-triene-3,17beta-diol (ICI 182,780; 1 microM). Preincubation with raloxifene (1-3 microM) caused an inhibition of the KCl or PGF(2alpha)-induced contraction. The effects of raloxifene were independent of the endothelium. The relaxant response to raloxifene was slow in the onset and could not be reversed after repeated washings. Raloxifene did not affect Ca(2+) release from intracellular stores since it failed to inhibit a transient contraction induced by caffeine (10 mM). Raloxifene-induced relaxation was not influenced by the intracellular calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) (BAPTA-AM; 10-20 microM). Calcium-induced contractions in Ca(2+)-free high K(+) (60 mM) depolarising medium were concentration-dependently inhibited by raloxifene (0.3-3 microM). If arterial rings were incubated with the L-type Ca(2+) channel activator (S)-(-)-1,4-dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)phenyl]-3-pyridine carboxylic acid methyl ester ((S)-(-)-Bay K 8644; 0.1 microM), cumulative concentration-response curves to Ca(2+) were shifted to the left. Raloxifene (0.3-3 microM) inhibited the effect of (S)-(-)-Bay K 8644 in a concentration-dependent manner. 4-(4-Fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole (SB 203580; 10 microM), an inhibitor of p38 mitogen-activated protein kinase (MAPK), diminished raloxifene-induced relaxation in endothelium-denuded arterial rings. Western blot analysis demonstrated that raloxifene stimulated p38 MAPK. It is concluded that raloxifene has an inhibitory effect on voltage-gated and receptor-operated L-type Ca(2+) channels in porcine coronary arteries, thus inducing vascular relaxation independent of the endothelium. p38 MAPK is, at least in part, involved in the relaxant response to raloxifene.