Molecular mechanisms mediating the neuroprotective role of the selective estrogen receptor modulator, bazedoxifene, in acute ischemic stroke: A comparative study with 17β-estradiol

As the knowledge on the estrogenic system in the brain grows, the possibilities to modulate it in order to afford further neuroprotection in brain damaging disorders so do it. We have previously demonstrated the ability of the selective estrogen receptor modulator, bazedoxifene (BZA), to reduce experimental ischemic brain damage. The present study has been designed to gain insight into the molecular mechanisms involved in such a neuroprotective action by investigating: 1) stroke-induced apoptotic cell death; 2) expression of estrogen receptors (ER) ERα, ERβ and the G-protein coupled estrogen receptor (GPER); and 3) modulation of MAPK/ERK1/2 and PI3K/Akt signaling pathways. For comparison, a parallel study was done with 17β-estradiol (E2)-treated animals. Male Wistar rats subject to transient right middle cerebral artery occlusion (tMCAO, intraluminal thread technique, 60min), were distributed in vehicle-, BZA- (20.7±2.1ng/mL in plasma) and E2- (45.6±7.8pg/mL in plasma) treated groups. At 24h from the onset of tMCAO, RT-PCR, Western blot and histochemical analysis were performed on brain tissue samples. Ischemia-reperfusion per se increased apoptosis as assessed by both caspase-3 activity and TUNEL-positive cell counts, which were reversed by both BZA and E2. ERα and ERβ expression, but not that of GPER, was reduced by the ischemic insult. BZA and E2 had different effects: while BZA increased both ERα and ERβ expression, E2 increased ERα expression but did not change that of ERβ. Both MAPK/ERK1/2 and PI3K/Akt pathways were stimulated under ischemic conditions. While BZA strongly reduced the increased p-ERK1/2 levels, E2 did not. Neither BZA nor E2 modified ischemia-induced increase in p-Akt levels. These results show that modulation of ERα and ERβ expression, as well as of the ERK1/2 signaling pathway accounts, at least in part, for the inhibitory effect of BZA on the stroke-induced apoptotic cell death. This lends mechanistic support to the consideration of BZA as a potential neuroprotective drug in acute ischemic stroke treatment.

Functional association of oestrogen receptors with HPV infection in cervical carcinogenesis

Repeated parity and usage of oral contraceptives have demonstrated an increased risk of cervical cancer (CC) in HPV-infected women. These lifestyle observations raise the likelihood that oestrogens and HPV infection might act synergistically to affect cancers of the cervix. In vivo studies have indicated the requirement of oestrogens and ERα in the development of atypical squamous metaplasia followed by cervical intraepithelial neoplasia (CIN) I, II and III. CIN II and III are precancerous cervical lesions that can progress over time to CC as an invasive carcinoma. Recently, there has been evidence suggesting that ERα signalling in the tumour epithelium is a preliminary requisite during cancer initiation that is subsequently lost during tumorigenic progression. Conversely, continued expression of stromal ERα gains control over tumour maintenance. This review summarises the current information on the association between oestrogens and HPV infection in contributing to CC and the possibility of SERMs as a therapeutic option.

The effect of selective estrogen receptor modulators on type 2 diabetes onset in women: Basic and clinical insights

Selective estrogen receptor modulators (SERMs) are a class of compounds that interact with estrogen receptors (ERs) and exert agonist or antagonist effects on ERs in a tissue-specific manner. Tamoxifen, a first generation SERM, is used for treatment of ER positive breast cancer. Raloxifene, a second generation SERM, was used to prevent postmenopausal osteoporosis. The third-generation SERM bazedoxifene (BZA) effectively prevents osteoporosis while preventing estrogenic stimulation of breast and uterus. Notably, BZA combined with conjugated estrogens (CE) is a new menopausal treatment. The menopausal state predisposes to metabolic syndrome and type 2 diabetes, and therefore the effects of SERMs on metabolic homeostasis are gaining attention. Here, we summarize knowledge of SERMs' impacts on metabolic, homeostasis, obesity and diabetes in rodent models and postmenopausal women.

The 4Ps of Breast Cancer Chemoprevention: Putting Proven Principles into Practice

The pioneering Royal Marsden Tamoxifen Prevention Trial recruited 2,471 eligible high-risk women to be randomized to either placebo or tamoxifen (20 mg daily) for 8 years. Breast cancer incidence was evaluated at a median of 18.4 years from the start of the study. There was a 32% reduction in estrogen/progesterone receptor (ER/PR)-positive breast cancers after tamoxifen treatment finished. Translational research, to study "the good, the bad, and the ugly of tamoxifen" in the 1980s, subsequently ensured women's safety from possible increases in osteoperosis, coronary heart disease, and endometrial cancer. Other tamoxifen chemoprevention trials followed. The result of laboratory research was the unanticipated discovery of raloxifene to prevent osteoporosis and breast cancer at the same time. A new group of medicines, now known as selective ER modulators, was established. Indeed, the ability to prevent or delay multiple diseases with a single cheap medicine has the potential to alleviate pressure on health care systems that are overwhelmed. It is a priority to educate physicians appropriately to apply recommended proven medicines as preventives. Cancer Prev Res; 10(4); 219-22. ©2017 AACRSee related article by Detre, et al., Cancer Prev Res 2017;10(3):171-6.

[Drug selection and treatment goal in osteoporosis therapy.]

The goal of treatment for osteoporosis is to reduce the risk of fracture. Achieving effective reductions in the risk of fracture requires evidence-based drug selection and careful consideration of patient background, including concomitant diseases and drug adherence. Selective estrogen receptor modulators(SERM)and active vitamin D₃ such as eldecalcitol are well indicated in early menopausal women with no history of fragility fractures. Moreover, elderly individuals with a history of fragility fractures are at high risk of vertebral and hip fractures, so bisphosphonates, denosumab and teriparatide are well indicated in these patients. Although no well-established goal has been devised for the treatment of osteoporosis in Japan, the strategy of goal-directed treatment of osteoporosis has been reported in the United States.

Antiestrogens: structure-activity relationships and use in breast cancer treatment

About 70% of breast tumors express estrogen receptor alpha (ERα), which mediates the proliferative effects of estrogens on breast epithelial cells, and are candidates for treatment with antiestrogens, steroidal or non-steroidal molecules designed to compete with estrogens and antagonize ERs. The variable patterns of activity of antiestrogens (AEs) in estrogen target tissues and the lack of systematic cross-resistance between different types of molecules have provided evidence for different mechanisms of action. AEs are typically classified as selective estrogen receptor modulators (SERMs), which display tissue-specific partial agonist activity (e.g. tamoxifen and raloxifene), or as pure AEs (e.g. fulvestrant), which enhance ERα post-translational modification by ubiquitin-like molecules and accelerate its proteasomal degradation. Characterization of second- and third-generation AEs, however, suggests the induction of diverse ERα structural conformations, resulting in variable degrees of receptor downregulation and different patterns of systemic properties in animal models and in the clinic.

[Calcium and bone metabolism across women's life stages. Bone quality and treatment of osteoporosis by SERM.]

Estrogen deficiency induces bone resorption and bone collagen crosslink abnormalities such as reductions in enzymatic cross-links and accumulation of Advanced glycation end products(AGEs). In this review, we described that the mechanism of poor bone quality in estrogen deficiency and how selective estrogen receptor modulators such as raloxifene and bazedoxifene improve bone structural and material properties.

Bazedoxifene: A Third-Generation Selective Estrogen Receptor Modulator for Treatment of Postmenopausal Osteoporosis

Objective:

To review clinical studies and other available literature regarding the development, pharmacology, toxicology, pharmacokinetics/pharmacodynamics, adverse effects, and place in therapy of bazedoxifene, a selective estrogen receptor modulator (SERM), currently in Phase III clinical trials for the treatment and prevention of postmenopausal osteoporosis.

Data Sources:

A literature search was performed of PubMed (1966–February 2007). International Pharmaceutical Abstracts (1970–February 2007), Web of Science (1975–February 2007), Biological Abstracts (1926–2007), and Google Scholar (2001–February 2007) databases, using the search terms bazedoxifene, TSE-424, Indole-33, WAY-140424, selective estrogen receptor modulator, and SERM. In addition, product information was requested from the manufacturer, and www.clinicaltrials.gov was searched for unpublished Phase III clinical trials in progress.

Study Selection and Data Extraction:

Articles on Phase I and II trials were selected for review, as well as articles discussing preclinical development of bazedoxifene. At the time of writing, no articles on Phase III trials were available for review. Abstracts of unpublished data were reviewed, as was information provided by the manufacturer.

Data Synthesis:

Bazedoxifene is a third-generation SERM currently in Phase III clinical trials. It has been found to act as an agonist on skeletal tissue, with bone turnover reduced by 20–25% with doses of 20 or 40 mg daily. In addition, bazedoxifene has been found to be an antagonist on breast tissue and uterine tissue, demonstrating inhibition of breast tissue proliferation and decreased endometrial stimulation as the dose is increased.

Conclusions:

Current literature suggests that bazedoxifene will likely be safe and effective when used in the treatment of postmenopausal osteoporosis. Completion of Phase III clinical trials will more fully elucidate the safety and efficacy profile of bazedoxifene, as well as more clearly define its place in therapy.

Hormone Therapy and Other Treatments for Symptoms of Menopause

The results of large clinical trials have led physicians and patients to question the safety of hormone therapy for menopause. In the past, physicians prescribed hormone therapy to improve overall health and prevent cardiac disease, as well as for symptoms of menopause. Combined estrogen/progestogen therapy, but not estrogen alone, increases the risk of breast cancer when used for more than three to five years. Therefore, in women with a uterus, it is recommended that physicians prescribe combination therapy only to treat menopausal symptoms such as vasomotor symptoms (hot flashes) and vaginal atrophy, using the smallest effective dosage for the shortest possible duration. Although estrogen is the most effective treatment for hot flashes, nonhormonal alternatives such as low-dose paroxetine, venlafaxine, and gabapentin are effective alternatives. Women with a uterus who are using estrogen should also take a progestogen to reduce the risk of endometrial cancer. Women who cannot tolerate adverse effects of progestogens may benefit from a combined formulation of estrogen and the selective estrogen receptor modulator bazedoxifene. There is no highquality, consistent evidence that yoga, paced respiration, acupuncture, exercise, stress reduction, relaxation therapy, and alternative therapies such as black cohosh, botanical products, omega-3 fatty acid supplements, and dietary Chinese herbs benefit patients more than placebo. One systematic review suggests modest improvement in hot flashes and vaginal dryness with soy products, and small studies suggest that clinical hypnosis significantly reduces hot flashes. Patients with genitourinary syndrome of menopause may benefit from vaginal estrogen, nonhormonal vaginal moisturizers, or ospemifene (the only nonhormonal treatment approved by the U.S. Food and Drug Administration for dyspareunia due to menopausal atrophy). The decision to use hormone therapy depends on clinical presentation, a thorough evaluation of the risks and benefits, and an informed discussion with the patient.

Estrogens and selective estrogen receptor modulators in acromegaly

Despite recent advances in acromegaly treatment by surgery, drugs, and radiotherapy, hormonal control is still not achieved by some patients. The impairment of IGF-1 generation by estrogens in growth hormone deficient patients is well known. Patients on oral estrogens need higher growth hormone doses in order to achieve normal IGF-1 values. In the past, estrogens were one of the first drugs used to treat acromegaly. Nevertheless, due to the high doses used and the obvious side effects in male patients, this strategy was sidelined with the development of more specific drugs, as somatostatin receptor ligands and dopamine agonists. In the last 15 years, the antagonist of growth hormone receptor became available, making possible IGF-1 control of the majority of patients on this particular drug. However, due to its high cost, pegvisomant is still not available in many centers around the world. In this setting, the effect of estrogens and also of selective estrogen receptor modulators on IGF-1 control was reviewed, and proved to be an ancillary tool in the management of acromegaly. This review describes data concerning their efficacy and place in the treatment algorithm of acromegaly.

Selective Estrogen Receptor Modulators Suppress Hif1α Protein Accumulation in Mouse Osteoclasts

Anti-bone resorptive drugs such as bisphosphonates, the anti-RANKL antibody (denosumab), or selective estrogen receptor modulators (SERMs) have been developed to treat osteoporosis. Mechanisms underlying activity of bisphosphonates or denosumab in this context are understood, while it is less clear how SERMs like tamoxifen, raloxifene, or bazedoxifene inhibit bone resorption. Recently, accumulation of hypoxia inducible factor 1 alpha (Hif1α) in osteoclasts was shown to be suppressed by estrogen in normal cells. In addition, osteoclast activation and decreased bone mass seen in estrogen-deficient conditions was found to require Hif1α. Here, we used western blot analysis of cultured osteoclast precursor cells to show that tamoxifen, raloxifene, or bazedoxifene all suppress Hif1α protein accumulation. The effects of each SERM on osteoclast differentiation differed in vitro. Our results suggest that interventions such as the SERMs evaluated here could be useful to inhibit Hif1α and osteoclast activity under estrogen-deficient conditions.

Endometrial Cancer-Associated FGF18 Expression Is Reduced by Bazedoxifene in Human Endometrial Stromal Cells In Vitro and in Murine Endometrium

Endometrial cancer develops during exposure to estrogen unopposed by progesterone. Traditional formulations for menopausal hormone therapy include a progestin in women with a uterus. However, progestin exposure increases breast cancer risk in postmenopausal women. Alternatives to progestin include bazedoxifene (BZA), a selective estrogen receptor modulator, which prevents estrogen induced endometrial hyperplasia in clinical trials. Molecular mechanisms responsible for BZA's antiproliferative effect are not fully elucidated. We profiled endometrial adenocarcinoma, hyperplasia, and normal proliferative endometrium for differential expression in genes known to be regulated by estrogens or progesterone. Fibroblast growth factor (FGF)18, a paracrine growth factor promoting epithelial proliferation, was significantly increased in adenocarcinoma. Progesterone represses FGF18 by inducing heart and neural crest derivatives expressed transcript 2 (HAND2) in stromal cells. Notably, we confirmed lower HAND2 mRNA in adenocarcinoma, along with higher FGF tyrosine kinase receptor 2 and E74-like factor 5, collectively promoting FGF18 activity. We hypothesized BZA reduces epithelial proliferation by inhibiting FGF18 synthesis in stromal cells. To determine whether BZA regulates FGF18, we treated primary stromal cells with BZA or vehicle. In vitro, BZA reduced FGF18, but did not affect, HAND2. CD1 female mice received either BZA, conjugated estrogen (CE), or combined BZA/CE for 8 weeks. CE-treated mice had nearly 3-fold higher FGF18 expression. In contrast, BZA-treated mice, alone or with CE, had similar FGF18 as controls. Unexpectedly, BZA, alone or with CE, reduced HAND2 more than 80%, differing from progesterone regulation. Reduction of FGF18 is a potential mechanism by which BZA reduces endometrial proliferation and hyperplasia induced by estrogens. However, BZA works independently of HAND2, revealing a novel mechanism for progestin-free hormone therapy in postmenopausal women.

[Efficacy and safety of selective estrogen receptor modulators in patients with advanced chronic kidney disease]

Selective estrogen receptor modulators(SERMs)have beneficial effects on the improvement of bone mineral density of the spine and hip, and decrease the vertebral fracture in postmenopausal women. Similar to patients with advanced chronic kidney disease, including dialysis patients, however, SERMs cannot decrease the risk of hip fracture, which is extremely high in Japanese dialysis patients. One of the most important disadvantages of SERMs is an increase in the risk of venous thromboembolic events and fatal stroke in high-risk groups of the Framingham Stroke Risk Score. On the other hand, SERMs may be used in unique osteoporosis drugs for reducing the incidence and progression of breast cancer. Moreover, SERMs attenuate oxidative stress and may lessen the deterioration of kidney function in patients with chronic kidney disease. The evidences for the efficacy and safety of SERMs in patients with advanced chronic kidney disease are insufficient, and knowledge concerning the selection and indication of osteoporosis drugs for those patients need to be developed.

The future of the new selective estrogen receptor modulators

Selective estrogen receptor modulators (SERMs) are compounds that display mixed estrogen agonist/antagonist activity. Currently, four SERMs are licensed for clinical use: tamoxifen, toremifene, clomifene and raloxifene. The STAR and RUTH trials have provided useful data about the potential role of SERMs in the primary prevention of breast cancer and cardiovascular disease in postmenopausal women. New-generation SERMs, such as bazedoxifene, arzoxifene, lasofoxifene and ospemifene, are currently being evaluated. The aim is to find a SERM that conserves the skeleton and prevents breast cancer without increasing the risk of endometrial cancer and venous thromboembolism, and without inducing hot flushes. Technological advances in the study of estrogen receptor activation will provide key information for drug development.

Pharmacologic Therapies in Women's Health: Contraception and Menopause Treatment

Female hormones play a significant role in the etiology and treatment of many women's health conditions. This article focuses on the common uses of hormonal therapy. When prescribing estrogen-containing regimens throughout the span of a woman's life, the risks are similar (ie, cardiovascular risk and venous thromboembolism), but the degree of risk varies significantly depending on a woman's particular set of risk factors and the details of the hormone regimen. In addition to estrogens and progestogens, this article also touches on the use of selective steroid receptor modulators in emergency contraception and in treatment of menopause symptoms.

Evaluation and Treatment of Osteoporosis

As the population ages, the rates of osteoporotic fractures will increase, with postmenopausal women incurring most of these fractures. Diagnosis and treatment of osteoporosis are extremely important. Dual-energy x-ray absorptiometry scan screening is recommended in all women more than 65 years of age or in women aged 50 to 64 years with certain risk factors. Treatment should be considered if osteoporosis is present, there is a history of fragility fracture, or in the setting of osteopenia plus high risk for fracture.

Genomic agonism and phenotypic antagonism between estrogen and progesterone receptors in breast cancer

The functional role of progesterone receptor (PR) and its impact on estrogen signaling in breast cancer remain controversial. In primary ER(+) (estrogen receptor-positive)/PR(+) human tumors, we report that PR reprograms estrogen signaling as a genomic agonist and a phenotypic antagonist. In isolation, estrogen and progestin act as genomic agonists by regulating the expression of common target genes in similar directions, but at different levels. Similarly, in isolation, progestin is also a weak phenotypic agonist of estrogen action. However, in the presence of both hormones, progestin behaves as a phenotypic estrogen antagonist. PR remodels nucleosomes to noncompetitively redirect ER genomic binding to distal enhancers enriched for BRCA1 binding motifs and sites that link PR and ER/PR complexes. When both hormones are present, progestin modulates estrogen action, such that responsive transcriptomes, cellular processes, and ER/PR recruitment to genomic sites correlate with those observed with PR alone, but not ER alone. Despite this overall correlation, the transcriptome patterns modulated by dual treatment are sufficiently different from individual treatments, such that antagonism of oncogenic processes is both predicted and observed. Combination therapies using the selective PR modulator/antagonist (SPRM) CDB4124 in combination with tamoxifen elicited 70% cytotoxic tumor regression of T47D tumor xenografts, whereas individual therapies inhibited tumor growth without net regression. Our findings demonstrate that PR redirects ER chromatin binding to antagonize estrogen signaling and that SPRMs can potentiate responses to antiestrogens, suggesting that cotargeting of ER and PR in ER(+)/PR(+) breast cancers should be explored.

Current medical management of endocrine-related male infertility

Male factor contributes to 50%-60% of overall infertility but is solely responsible in only 20% of couples. Although most male factor infertility is ascertained from an abnormal semen analysis, other male factors can be contributory especially if the sample returns normal. Male infertility can be due to identifiable hormonal or anatomical etiologies that may be reversible or irreversible. This manuscript will highlight existing guidelines and our recommendations for hormone evaluation for male infertility and empiric therapies including multivitamins, estrogen receptor modulators (clomiphene), estrogen conversion blockers (anastrozole), and hormone replacement.

[Female sexual dysfunction: Drug treatment options]

Many women will likely experience a sexual problem in their lifetime. Female sexual dysfunction is a broad term used to describe 3 categories of disorders of a multifactorial nature. Effective, but limited pharmacotherapeutic options exist to address female sexual dysfunction. The FDA recently approved the first agent for treatment of hypoactive sexual desire disorder in pre-menopausal women. Off-label use of hormonal therapies, particularly oestrogen and testosterone, are the most widely employed for female sexual dysfunction, particularly in post-menopausal women. Other drugs currently under investigation include phosphodiesterase inhibitors and agents that modulate dopamine or melanocortin receptors.

Hereditary cancer syndromes as model systems for chemopreventive agent development

Research in chemoprevention has undergone a shift in emphasis for pragmatic reasons from large, phase III randomized studies to earlier phase studies focused on safety, mechanisms, and utilization of surrogate endpoints such as biomarkers instead of cancer incidence. This transition permits trials to be conducted in smaller populations and at substantially reduced costs while still yielding valuable information. This article will summarize some of the current chemoprevention challenges and the justification for the use of animal models to facilitate identification and testing of chemopreventive agents as illustrated though four inherited cancer syndromes. Preclinical models of inherited cancer syndromes serve as prototypical systems in which chemopreventive agents can be developed for ultimate application to both the sporadic and inherited cancer settings.

[Determinants of bone quality and strength independent of bone remodeling]

Bone mineral density(BMD)and bone microstructure are regulated mainly by bone remodeling. In contrast, bone collagen enzymatic immature and mature cross-links and advanced glycation end products such as pentosidine and carboxyl methyl lysine are affected by various factors. Aging bone tissue is repaired in the process of bone remodeling. However, deterioration of bone material properties markedly advances due to increases in oxidative stress, glycation stress, reactive oxygen species, carbonyl stress associated with aging and reduced sex hormone levels, and glucocorticoid use. To improve bone material properties in osteoporosis, we should use different drug (Saito M, Calcif Tissue Int, REVIEW, 97;242-261, 2015). In this review, we summarized determinants of bone quality and strength independent of bone remodeling.

[Pharmacokinetics of selective estrogen receptor modulators(SERMs).]

Selective estrogen receptor modulators(SERMs), or estrogen receptor agonists/antagonists(ERAAs), are a class of compounds that function as estrogen receptor(ER)agonists or antagonists tissue-dependently. Two types of SERMs are currently used in Japan to treat osteoporosis, raloxifene(RLX:Evista)and bazedoxifene(BZA:Viviant). This article describes the pharmacokinetics of these two drugs.