Tamoxifen inhibits arterial accumulation of LDL degradation products and progression of coronary artery atherosclerosis in monkeys

TRAP1 drives smooth muscle cell senescence and promotes atherosclerosis via HDAC3-primed histone H4 lysine 12 lactylation

BACKGROUND AND AIMS

Vascular smooth muscle cell (VSMC) senescence is crucial for the development of atherosclerosis, characterized by metabolic abnormalities. Tumour necrosis factor receptor-associated protein 1 (TRAP1), a metabolic regulator associated with ageing, might be implicated in atherosclerosis. As the role of TRAP1 in atherosclerosis remains elusive, this study aimed to examine the function of TRAP1 in VSMC senescence and atherosclerosis.

METHODS

TRAP1 expression was measured in the aortic tissues of patients and mice with atherosclerosis using western blot and RT-qPCR. Senescent VSMC models were established by oncogenic Ras, and cellular senescence was evaluated by measuring senescence-associated β-galactosidase expression and other senescence markers. Chromatin immunoprecipitation (ChIP) analysis was performed to explore the potential role of TRAP1 in atherosclerosis.

RESULTS

VSMC-specific TRAP1 deficiency mitigated VSMC senescence and atherosclerosis via metabolic reprogramming. Mechanistically, TRAP1 significantly increased aerobic glycolysis, leading to elevated lactate production. Accumulated lactate promoted histone H4 lysine 12 lactylation (H4K12la) by down-regulating the unique histone lysine delactylase HDAC3. H4K12la was enriched in the senescence-associated secretory phenotype (SASP) promoter, activating SASP transcription and exacerbating VSMC senescence. In VSMC-specific Trap1 knockout ApoeKO mice (ApoeKOTrap1SMCKO), the plaque area, senescence markers, H4K12la, and SASP were reduced. Additionally, pharmacological inhibition and proteolysis-targeting chimera (PROTAC)-mediated TRAP1 degradation effectively attenuated atherosclerosis in vivo.

CONCLUSIONS

This study reveals a novel mechanism by which mitonuclear communication orchestrates gene expression in VSMC senescence and atherosclerosis. TRAP1-mediated metabolic reprogramming increases lactate-dependent H4K12la via HDAC3, promoting SASP expression and offering a new therapeutic direction for VSMC senescence and atherosclerosis.

The beneficial effects of tamoxifen on arteries: a key player for cardiovascular health of breast cancer patient

Breast cancer is the most common cancer in women. Over the past few decades, advances in cancer detection and treatment have significantly improved survival rate of breast cancer patients. However, due to the cardiovascular toxicity of cancer treatments (chemotherapy, anti-HER2 antibodies and radiotherapy), cardiovascular diseases (CVD) have become an increasingly important cause of long-term morbidity and mortality in breast cancer survivors. Endocrine therapies are prescribed to reduce the risk of recurrence and specific death in estrogen receptor-positive (ER+) early breast cancer patients, but their impact on CVD is a matter of debate. Whereas aromatase inhibitors and luteinizing hormone-releasing hormone (LHRH) analogs inhibit estrogen synthesis, tamoxifen acts as a selective estrogen receptor modulator (SERM), opposing estrogen action in the breast but mimicking their actions in other tissues, including arteries. This review aims to summarize the main clinical and experimental studies reporting the effects of tamoxifen on CVD. In addition, we will discuss how recent findings on the mechanisms of action of these therapies may contribute to a better understanding and anticipation of CVD risk in breast cancer patients.

Estrogen Receptor and Vascular Aging

Cardiovascular diseases remain an age-related pathology in both men and women. These pathologies are 3-fold more frequent in men than in women before menopause, although this difference progressively decreases after menopause. The vasculoprotective role of estrogens are well established before menopause, but the consequences of their abrupt decline on the cardiovascular risk at menopause remain debated. In this review, we will attempt to summarize the main clinical and experimental studies reporting the protective effects of estrogens against cardiovascular diseases, with a particular focus on atherosclerosis, and the impact of aging and estrogen deprivation on their endothelial actions. The arterial actions of estrogens, but also part of that of androgens through their aromatization into estrogens, are mediated by the estrogen receptor (ER)α and ERβ. ERs belong to the nuclear receptor family and act by transcriptional regulation in the nucleus, but also exert non-genomic/extranuclear actions. Beside the decline of estrogens at menopause, abnormalities in the expression and/or function of ERs in the tissues, and particularly in arteries, could contribute to the failure of classic estrogens to protect arteries during aging. Finally, we will discuss how recent insights in the mechanisms of action of ERα could contribute to optimize the hormonal treatment of the menopause.

Natural and Synthetic Estrogens in Chronic Inflammation and Breast Cancer

The oncogenic role of estrogen receptor (ER) signaling in breast cancer has long been established. Interaction of estrogen with estrogen receptor (ER) in the nucleus activates genomic pathways of estrogen signaling. In contrast, estrogen interaction with the cell membrane-bound G-protein-coupled estrogen receptor (GPER) activates the rapid receptor-mediated signaling transduction cascades. Aberrant estrogen signaling enhances mammary epithelial cell proliferation, survival, and angiogenesis, hence is an important step towards breast cancer initiation and progression. Meanwhile, a growing number of studies also provide evidence for estrogen's pro- or anti-inflammatory roles. As other articles in this issue cover classic ER and GPER signaling mediated by estrogen, this review will discuss the crucial mechanisms by which estrogen signaling influences chronic inflammation and how that is involved in breast cancer. Xenoestrogens acquired from plant diet or exposure to industrial products constantly interact with and alter innate estrogen signaling at various levels. As such, they can modulate chronic inflammation and breast cancer development. Natural xenoestrogens generally have anti-inflammatory properties, which is consistent with their chemoprotective role in breast cancer. In contrast, synthetic xenoestrogens are proinflammatory and carcinogenic compounds that can increase the risk of breast cancer. This article also highlights important xenoestrogens with a particular focus on their role in inflammation and breast cancer. Improved understanding of the complex relationship between estrogens, inflammation, and breast cancer will guide clinical research on agents that could advance breast cancer prevention and therapy.

c-Kit expression in smooth muscle cells reduces atherosclerosis burden in hyperlipidemic mice

BACKGROUND AND AIMS

Increased receptor tyrosine kinase (RTK) activity has been historically linked to atherosclerosis. Paradoxically, we recently found that global deficiency in c-Kit function increased atherosclerosis in hyperlipidemic mice. This study aimed to investigate if such unusual atheroprotective phenotype depends upon c-Kit's function in smooth muscle cells (SMC).

METHODS

We studied atherosclerosis in a SMC-specific conditional knockout mice (Kit^SMC) and control littermate. Tamoxifen (TAM) and vehicle treated mice were fed high fat diet for 16 weeks before atherosclerosis assessment in the whole aorta using oil red staining. Smooth muscle cells were traced within the aortic sinus of conditional c-Kit tracing mice (Kit^SMC eYFP) and their control littermates (Kit^WT eYFP) by immunofluorescent confocal microscopy. We then performed RNA sequencing on primary SMC from c-Kit deficient and control mice, and identified significantly altered genes and pathways as a result of c-Kit deficiency in SMC.

RESULTS

Atherosclerosis significantly increased in Kit^SMC mice with respect to control groups. In addition, the loss of c-Kit in SMC increased plaque size and necrotic core area in the aortic sinus of hyperlipidemic mice. Smooth muscle cells from Kit^SMC eYFP mice were more prone to migrate and express foam cell markers (e.g., Mac2 and MCAM) than those from control littermate animals. RNAseq analysis showed a significant upregulation in genes associated with cell proliferation, migration, lipid metabolism, and inflammation secondary to the loss of Kit function in primary SMCs.

CONCLUSIONS

Loss of c-Kit increases SMC migration, proliferation, and expression of foam cell markers in atherosclerotic plaques from hyperlipidemic mice.

The Impact of Estrogen Receptor in Arterial and Lymphatic Vascular Diseases

The lower incidence of cardiovascular diseases in pre-menopausal women compared to men is well-known documented. This protection has been largely attributed to the protective effect of estrogens, which exert many beneficial effects against arterial diseases, including vasodilatation, acceleration of healing in response to arterial injury, arterial collateral growth and atheroprotection. More recently, with the visualization of the lymphatic vessels, the impact of estrogens on lymphedema and lymphatic diseases started to be elucidated. These estrogenic effects are mediated not only by the classic nuclear/genomic actions via the specific estrogen receptor (ER) α and β, but also by rapid extra-nuclear membrane-initiated steroid signaling (MISS). The ERs are expressed by endothelial, lymphatic and smooth muscle cells in the different vessels. In this review, we will summarize the complex vascular effects of estrogens and selective estrogen receptor modulators (SERMs) that have been described using different transgenic mouse models with selective loss of ERα function and numerous animal models of vascular and lymphatic diseases.

Acquired resistance to aromatase inhibitors: where we stand!

Aromatase inhibitors (AIs) are one of the principal therapeutic approaches for estrogen receptor-positive (ER⁺) breast cancer in postmenopausal women. They block estrogen biosynthesis through aromatase inhibition, thus preventing tumour progression. Besides the therapeutic success of the third-generation AIs, acquired resistance may develop, leading to tumour relapse. This resistance is thought to be the result of a change in the behaviour of ER in these breast cancer cells, presumably by PI3K/AKT pathway enhancement along with alterations in other signalling pathways. Nevertheless, biological mechanisms, such as apoptosis, autophagy, cell cycle modulation and activation of androgen receptor (AR), are also implicated in acquired resistance. Moreover, clinical evidence demonstrated that there is a lack of cross-resistance among AIs, although the reason is not fully understood. Thus, there is a demand to understand the mechanisms involved in endocrine resistance to each AI, since the search for new strategies to surpass breast cancer acquired resistance is of major concern.

Extended adjuvant endocrine therapy - A standard to all or some?

Patients with estrogen receptor-positive (ER +) early breast cancer (EBC) are at a continuous risk for distant relapse despite 5 years of standard endocrine therapy, even after 10-15 years after primary diagnosis. Hence, large randomized clinical trials were conducted to evaluate the role of extended endocrine treatment (ET) with the primary goal to prevent or at least delay distant relapse. Two very large trials of extended tamoxifen (TAM), the ATLAS and the aTTom trial, proved the efficacy of prolonged TAM particularly important after 10 years due to the carry-over effect of the five initial years. Additionally, the extended use of AIs after 5 years of tamoxifen, also proved to be efficacious in preventing late distant relapses. For letrozole (LET) it was shown in the MA.17 trial that it also improves overall survival (OS) in node-positive BC patients. There are many options and still unanswered questions related to extended ET, which are discussed in this review. The most important issue in deciding prolonged duration of ET is undoubtfully how to identify ER+ patients who benefit most from this approach. With this purpose, not only classical pathological factors have been studied, but also molecular profiles of individual tumors, which might help us in the near future to better tailor ET. Not only efficacy, but also toxicity of such prolonged treatment is essential for optimal use, particularly maintained compliance in a routine clinical practice. These issues are discussed in this review.

Inhibition of Macrophage CD36 Expression and Cellular Oxidized Low Density Lipoprotein (oxLDL) Accumulation by Tamoxifen: A PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR (PPAR)γ-DEPENDENT MECHANISM

Macrophage CD36 binds and internalizes oxidized low density lipoprotein (oxLDL) to facilitate foam cell formation. CD36 expression is activated by peroxisome proliferator-activated receptor γ (PPARγ). Tamoxifen, an anti-breast cancer medicine, has demonstrated pleiotropic functions including cardioprotection with unfully elucidated mechanisms. In this study, we determined that treatment of ApoE-deficient mice with tamoxifen reduced atherosclerosis, which was associated with decreased CD36 and PPARγ expression in lesion areas. At the cellular level, we observed that tamoxifen inhibited CD36 protein expression in human THP-1 monocytes, THP-1/PMA macrophages, and human blood monocyte-derived macrophages. Associated with decreased CD36 protein expression, tamoxifen reduced cellular oxLDL accumulation in a CD36-dependent manner. At the transcriptional level, tamoxifen decreased CD36 mRNA expression, promoter activity, and the binding of the PPARγ response element in CD36 promoter to PPARγ protein. Tamoxifen blocked ligand-induced PPARγ nuclear translocation and CD36 expression, but it increased PPARγ phosphorylation, which was due to that tamoxifen-activated ERK1/2. Furthermore, deficiency of PPARγ expression in macrophages abolished the inhibitory effect of tamoxifen on CD36 expression or cellular oxLDL accumulation both in vitro and in vivo Taken together, our study demonstrates that tamoxifen inhibits CD36 expression and cellular oxLDL accumulation by inactivating the PPARγ signaling pathway, and the inhibition of macrophage CD36 expression can be attributed to the anti-atherogenic properties of tamoxifen.

Tamoxifen induces the development of hernia in mice by activating MMP-2 and MMP-13 expression

Hernia is a disease with defects in collagen synthesis/metabolism. However, the underlying mechanisms for hernia formation have not been fully defined. Tamoxifen is a selective estrogen receptor modulator and used for patients with breast cancer. Tamoxifen also has pleiotropic and side effects. Herein, we report that tamoxifen treatment resulted in an appearance of a large bulge in the low abdomen between the hind legs in male but not in female mice. The autopsy demonstrated that the low abdominal wall was broken and a large amount of intestine herniated out of the abdominal cavity. Histological analysis indicated that tamoxifen caused structural abnormalities in the low abdominal wall which were associated with decreased type II collagen content. Furthermore, we determined increased matrix metalloproteinase-2 (MMP-2) and MMP-13 expression in the tissue. In vitro, tamoxifen induced MMP-2 and MMP-13 expression in fibroblasts. The promoter activity analysis and ChIP assay demonstrate that induction of MMP-13 expression was associated with activation of JNK-AP-1 and ERK1/2 signaling pathways while induction of MMP-2 expression was related to activation of the ERK1/2 signaling pathway. Taken together, our study establishes a novel murine hernia model, defines a severe side effect of tamoxifen, and suggests a caution to male patients receiving tamoxifen treatment.

Tamoxifen inhibits macrophage FABP4 expression through the combined effects of the GR and PPARγ pathways

Macrophage adipocyte fatty acid-binding protein (FABP4) plays an important role in foam cell formation and development of atherosclerosis. Tamoxifen inhibits this disease process. In the present study, we determined whether the anti-atherogenic property of tamoxifen was related to its inhibition of macrophage FABP4 expression. We initially observed that tamoxifen inhibited macrophage/foam cell formation, but the inhibition was attenuated when FABP4 expression was selectively inhibited by siRNA. We then observed that tamoxifen and 4-hydroxytamoxifen inhibited FABP4 protein expression in primary macrophages isolated from both the male and female wild-type mice, suggesting that the inhibition is sex-independent. Tamoxifen and 4-hydroxytamoxifen inhibited macrophage FABP4 protein expression induced either by activation of GR (glucocorticoid receptor) or PPARγ (peroxisome-proliferator-activated receptor γ). Associated with the decreased protein expression, Fabp4 mRNA expression and promoter activity were also inhibited by tamoxifen and 4-hydroxytamoxifen, indicating transcriptional regulation. Analysis of promoter activity and EMSA/ChIP assays indicated that tamoxifen and 4-hydroxytamoxifen activated the nGRE (negative glucocorticoid regulatory element), but inhibited the PPRE (PPARγ regulatory element) in the Fabp4 gene. In vivo, administration of tamoxifen to ApoE (apolipoprotein E)-deficient (apoE−/−) mice on a high-fat diet decreased FABP4 expression in macrophages and adipose tissues as well as circulating FABP4 levels. Tamoxifen also inhibited FABP4 protein expression by human blood monocyte-derived macrophages. Taken together, the results of the present study show that tamoxifen inhibited FABP4 expression through the combined effects of GR and PPARγ signalling pathways. Our findings suggest that the inhibition of macrophage FABP4 expression can be attributed to the anti-atherogenic properties of tamoxifen.

Liver-specific cholesteryl ester hydrolase deficiency attenuates sterol elimination in the feces and increases atherosclerosis in ldlr-/- mice

OBJECTIVE

Liver is the major organ responsible for the final elimination of cholesterol from the body either as biliary cholesterol or as bile acids. Intracellular hydrolysis of lipoprotein-derived cholesteryl esters (CEs) is essential to generate the free cholesterol required for this process. Earlier, we demonstrated that overexpression of human CE hydrolase (Gene symbol CES1) increased bile acid synthesis in human hepatocytes and enhanced reverse cholesterol transport in mice. The objective of the present study was to demonstrate that liver-specific deletion of its murine ortholog, Ces3, would decrease cholesterol elimination from the body and increase atherosclerosis.

APPROACH AND RESULTS

Liver-specific Ces3 knockout mice (Ces3-LKO) were generated, and Ces3 deficiency did not affect the expression of genes involved in cholesterol homeostasis and free cholesterol or bile acid transport. The effects of Ces3 deficiency on the development of Western diet-induced atherosclerosis were examined in low density lipoprotein receptor knock out(-/-) mice. Despite similar plasma lipoprotein profiles, there was increased lesion development in low density lipoprotein receptor knock out(-/-)Ces3-LKO mice along with a significant decrease in the bile acid content of bile. Ces3 deficiency significantly reduced the flux of cholesterol from [(3)H]-CE-labeled high-density lipoproteins to feces (as free cholesterol and bile acids) and decreased total fecal sterol elimination.

CONCLUSIONS

Our results demonstrate that hepatic Ces3 modulates the hydrolysis of lipoprotein-delivered CEs and thereby regulates free cholesterol and bile acid secretion into the feces. Therefore, its deficiency results in reduced cholesterol elimination from the body, leading to significant increase in atherosclerosis. Collectively, these data establish the antiatherogenic role of hepatic CE hydrolysis.

Primary Prevention of Cardiovascular Disease with HRT

Prevention of cardiovascular disease has increasingly important health implications as our population ages. Menopause is associated with the development of cardiovascular risk factors and there are many plausible biological mechanisms through which estrogen may confer cardiovascular protection. Despite a wealth of observational data to support the use of estrogen, large randomized controlled trials failed to demonstrate a benefit. It is now becoming clearer that the beneficial cardiovascular effects of estrogen are greatest in younger women and those closest to menopause. This has led to the development of the timing hypothesis. Use of age-appropriate estrogen doses is crucial to maximize cardiovascular benefits while minimizing risk of adverse effects such as venous thromboembolism and stroke.

Estrogen-dependent activation of neutral cholesterol ester hydrolase underlying gender difference of atherogenesis in apoE-/- mice

OBJECTIVE

Mechanisms underlying gender difference of atherogenesis were investigated focusing on direct effects of estrogen on the artery.

METHODS

First, male and female apoE(-/-) mice were fed an atherogenic diet for 16 weeks from 10 weeks of age. Second, female apoE(-/-) mice were ovariectomized (ovx) or sham operated at 8 weeks of age, and 2-weeks afterwards, one-third of each ovx-group received conjugated equine estrogens (CEE) (0, 2.5 or 5.0 μg/day) for 16 weeks. Atherosclerotic lesions were examined after experimental periods. To clarify anti-atherogenic effect of 17β-estradiol (E2) on artery, neutral cholesteryl ester hydrolase (N-CEase) activity in aorta and peritoneal macrophages, and E2-treated J774A.1 cells were measured.

RESULTS

First, atherosclerotic lesion in female mice was significantly less than male mice without any changes in serum lipids and lipoprotein profile. N-CEase activity in aorta and peritoneal macrophages in female mice was significantly higher than male mice. Second, atherosclerotic lesion in ovx-group was significantly greater than sham-group. CEE-replacement to ovx-group decreased atherosclerotic lesion in a dose-dependent manner. N-CEase activity in aorta and peritoneal macrophages was decreased in ovx-group compared to sham-group, and restored by CEE-replacement in macrophages. To study detailed mechanisms, J774A.1 cells were treated with E2. E2 significantly increased N-CEase activity, and cAMP-dependent protein kinase (A-kinase) type II activity and the protein in cytosol fraction without any changes of total protein of A-kinase type II.

CONCLUSION

These results suggest that gender difference of atherogenesis is partly accounted for activation of N-CEase through estrogen-dependent translocation of A-kinase type II in macrophages.

Effects of hormonally active agents on steroid hormone receptor expression and cell proliferation in the myometrium of ovariectomized macaques

Hormone replacement therapy and selective estrogen receptor modulators have been controversial treatment options for postmenopausal women because of their potential health benefits and/or risks. In this study, we determine the effects of the hormonally active compounds, conjugated equine estrogens (CEE), medroxyprogesterone acetate (MPA), CEE + MPA, and tamoxifen (TAM) on the myometrium of ovariectomized macaques. Immunoexpression of estrogen receptor-α (ERα), progesterone receptor (PR), and Ki-67 in the myometrium is assessed. We found no significant difference in ERα myometrial expression in the CEE, MPA, and CEE + MPA treatment groups, but there was a significant decrease in expression in animals administered TAM versus controls. Conjugated equine estrogen-, TAM-, and CEE + MPA-treated animals had significantly increased expression of PR in myometrial cells and there was no difference in PR expression in cells from MPA-treated animals versus control animals. Myometrial cell proliferation did not significantly differ between the controls and any of the treatment groups, although normalized Ki-67 values were somewhat higher in the CEE and TAM groups. These data suggest that ERα and PR expression in the myometrium is influenced by treatment with hormonally active agents.

Endometrial profile of tamoxifen and low-dose estradiol combination therapy

PURPOSE

Combination estrogen + progestin therapy has been associated with increased breast cancer risk in postmenopausal women. Selective estrogen receptor modulators (SERM) are potential alternatives to progestins, although the endometrial safety of estrogen + SERM co-therapies is not known. The goal of this study was to evaluate the endometrial profile of low-dose estradiol and the SERM tamoxifen alone and in combination.

EXPERIMENTAL DESIGN

Twenty-four postmenopausal female cynomolgus macaques were randomized by social group to receive placebo, low-dose micronized estradiol (E(2); 0.25 mg/1,800 kcal), the SERM tamoxifen (Tam; 20 mg/1,800 kcal), or E(2) + Tam for 4 months in a parallel-arm design.

RESULTS

Tamoxifen alone resulted in overlapping but distinct effects compared with E(2). Both E(2) and Tam increased uterine weight and endometrial thickness, whereas only E(2) increased endometrial proliferation. Morphologic effects were similar for Tam and E(2) + Tam, which both induced stromal fibrosis and cystic change. Tamoxifen inhibited E(2)-induced proliferation and expression of genes related to cell cycle progression while exhibiting mixed agonist and antagonist effects on gene markers of estrogen receptor activity. The gene expression profile for E(2) + Tam was distinct from either E(2) or Tam alone but dominated by the Tam effect for estrogen-regulated genes. Tam also attenuated E(2) effects on both vaginal maturation and cervical epithelial height.

CONCLUSIONS

These findings characterize a novel phenotype resulting from estrogen + SERM co-therapy. The predominance of Tam effects on endometrial proliferation, morphology, and transcriptional profiles suggests that endometrial risks for E(2) + Tam may be similar to Tam alone.

Pharmacology and clinical applications of selective estrogen receptor modulators

Compounds that can be described as selective estrogen receptor modulators (SERMs) have expanded dramatically over the past two decades. The ability of SERMs to act as estrogens in certain tissues while remaining inert or acting as an anti-estrogen in other tissues has opened up opportunities for treating specific estrogen-modulated diseases without accepting the risk of systemic estrogen activity. SERM development has resulted in significant therapeutic advances for breast cancer, osteoporosis and potentially other diseases associated with the menopause. After the publication of the Women's Health Initiative, interest in compound selectivity that reduces menopausal symptoms while protecting bone, breast, uterus and the heart has increased. Future SERMs may also have a therapeutic profile that can be tailored to specific patient populations, including men. This review paper summarizes the characteristics of different SERMs from various pharmacological categories and the feasibility and scope of their use for a large range of disease/health conditions.

Estrogen-mediated protection in myocardial ischemia-reperfusion injury

Before menopause, a woman has a relatively low risk for developing cardiovascular disease. After menopause, however, the risk increases nearly twofold and cardiovascular disease remains the number one cause of death among women. Observational trials and studies in animal models of cardiovascular disease suggested that females have reduced injury after myocardial ischemia and reperfusion injury. However, two large clinical trials, the women's health initiative (WHI) and the heart estrogen and progestin replacement study (HERS), found an increase in cardiovascular incidences in women taking hormone replacement therapy. The discrepancy between these data highlights the need for further research on the mechanism of estrogen in the cardiovascular system. Animal studies have demonstrated protective effects by endogenous estrogen (gender differences) and also by the administration of exogenous estrogen. In vivo studies suggest a possible anti-inflammatory mechanism of estrogen. Exogenous estrogen has been shown to have anti-oxidant activities. Pre-treatment with estrogen prior to myocardial ischemia and reperfusion causes a decrease in neutrophil infiltration into the irreversibly injured myocardium, decrease in C-reactive protein expression, and deposition of the membrane attack complex. This review will summarize the protection afforded by estrogen as well as discuss several possible mechanisms of protection for exogenous estrogen administration.

Non-nuclear actions of estrogen: new targets for prevention and treatment of cardiovascular disease

Gender-based differences in the incidence of hypertensive and coronary artery disease, the development of atherosclerosis, and myocardial remodeling after infarction are attributable to the indirect effect of estrogen on risk factor profiles, such as cholesterol levels, glucose metabolism, and insulin levels. More recent evidence, however, suggests that activated estrogen receptor (ER) mediates signaling cascades that culminate in direct protective effects such as vasodilation, inhibition of response to vessel injury, limiting myocardial injury after infarction, and attenuating cardiac hypertrophy. Although the ER is usually thought of as a ligand-dependent transcription factor, it can also rapidly mobilize signals at the plasma membrane and in the cytoplasm. Thus, a greater understanding of ER function and regulation may lead to the development of highly specific therapeutics that mediate the prevention and treatment of cardiovascular diseases.

Cardiovascular Actions of Selective Estrogen Receptor Modulators and Phytoestrogens

Cardiovascular disease is the leading cause of death among men and women in Western societies. Over the past decade, interest in a better understanding of gender differences in cardiovascular disease has heightened. Concomitantly, the use of hormone therapy for cardiovascular risk reduction in postmenopausal women has come into question in light of recent landmark clinical studies casting doubt on the benefits of this therapy. As a consequence, alternatives to conventional hormone replacement, including selective estrogen receptor modulators and phytoestrogens, have attracted considerable attention. The authors provide an up-to-date review of the clinical actions of selective estrogen receptor modulators on cardiovascular disease. The actions of tamoxifen, raloxifene, droloxifene, and soy phytoestrogens are discussed in the context of cardiovascular disease epidemiology, coronary events, clinical markers of cardiovascular risk, and vascular function. In addition, the authors' current understanding of the mechanism of action of these agents is discussed and recommendations for clinical practice are reviewed.

Lipid transfer proteins (LTP) and atherosclerosis

This review deals with four lipid transfer proteins (LTP): three are involved in cholesteryl ester (CE) synthesis or transport, the fourth deals with plasma phospholipid (PL) transfer. Experimental models of atherosclerosis, clinical and epidemiological studies provided information as to the relationship of these LTP(s) to atherosclerosis, which is the main focus of this review. Thus, inhibition of acyl-CoA:cholesterol acyltransferase (ACAT) 1 and 2 decreases cholesterol absorption, plasma cholesterol and aortic cholesterol esterification in the aorta. The discovery that tamoxifen is a potent ACAT inhibitor explained the plasma cholesterol lowering of the drug. The use of ACAT inhibition in humans is under current investigation. As low cholesteryl ester transfer protein (CETP) activity is connected with high HDL-C, several CETP inhibitors were tried in rabbits, with variable results. A new CETP inhibitor, Torcetrapib, was tested in humans and there was a 50-100% increase in HDL-C. Lecithin cholesterol acyl-transferase (LCAT) influences oxidative stress, which can be lowered by transient LCAT gene transfer in LCAT-/- mice. Phospholipid transfer protein (PLTP) deficiency reduced apo B production in apo E-/- mice, as well as oxidative stress in four models of mouse atherosclerosis. In conclusion, the ability to increase HDL-C so markedly by inhibitors of CETP introduces us into a new era in prevention and treatment of coronary heart disease (CHD).

Selective estrogen receptor modulators prevent neointima formation after vascular injury

Exploitation of estrogen's vasculoprotective properties in drug design is difficult due to its adverse effects on endometrium and breast. Selective estrogen receptor modulators (SERM) act as estrogen agonists in some tissues but are anti-estrogenic in others. We investigate here whether tamoxifen, raloxifene, and two novel SERMs, ospemifene and fispemifene, preserve estrogen's beneficial effects on the ovariectomized rat vascular wall, and correlate their effects with natural estrogen (17beta-E2) and a pure anti-estrogen ICI 182,780. All compounds dose-dependently (0.0025-25 mg/kg/day) inhibited neointimal thickening at 7 days after aorta denudation injury. At 28 days, tamoxifen and ospemifene (2.5 mg/kg/day) reduced intimal nuclei number and intimal area equal to 17beta-E2, while raloxifene and fispemifene had no effect. Replacing the drug at 14 days with vehicle did not induce any rebound effect at 28 days, and furthermore, resulted in a smaller neointima with raloxifene and fispemifene. 17beta-E2 and the SERMs also significantly enhanced reendothelialization. All compounds inhibited replication and all but fispemifene inhibited migration of vascular SMC and cells from cultured aortic explants in vitro. Finally, only 17beta-E2 increased the weight of the uterus above that of normal rats. Interestingly, ICI 182,780 also weakly inhibited neointima formation and SMC proliferation at 7 days, suggesting that non-estrogen receptor mediated effects may have also played a role. In conclusion, SERMs have beneficial estrogen agonist effects in the injured vascular wall through their regulation of vascular SMC function and reendothelialization. Early intervention is of particular importance in preventing the injury-response.

Tamoxifen improves endothelial function and reduces carotid intima-media thickness in postmenopausal women

BACKGROUND

Tamoxifen is a selective estrogen-receptor modulator shown to improve several cardiovascular risk factors in postmenopausal women with breast cancer. In animal studies tamoxifen inhibits the progression of atherosclerosis. Although the presence of a history with tamoxifen treatment is related to a lower intima-media thickness (IMT) of the common carotid artery, data from controlled follow-up studies are lacking to support this observation.

METHODS

We examined 14 postmenopausal women with early stage breast cancer with indication for tamoxifen treatment (20 mg/d) and 13 healthy postmenopausal women. Flow-mediated dilatation (FMD) of the brachial artery, combined carotid IMT, and aortic pulse wave were measured before and 6 months after treatment in the tamoxifen group and at the same times in the control group.

RESULTS

FMD and IMT were significantly increased and decreased, respectively, in the treatment group compared to the control group (FMD: +2.2% +/- 0.9% vs +0.085% +/- 1%, P =.012; IMT: -0.088 +/- 0.03 mm vs +0.04 +/- 0.03 mm, P =.018, mean +/- standard error of the mean, treatment vs control group). These differences remained significant even when adjusted for age, duration of menopause, and cardiovascular risk factors. Low-density lipoprotein cholesterol was also significantly reduced after tamoxifen treatment.

CONCLUSIONS

Tamoxifen treatment slows the progression of atherosclerosis in postmenopausal women with breast cancer as assessed by changes in carotid IMT. An improvement in endothelial function and blood lipid profile may be the reason for this beneficial effect.

Tamoxifen Is a Potent Inhibitor of Cholesterol Esterification and Prevents the Formation of Foam Cells

Tamoxifen is a selective estrogen receptor modulator (SERM) used for the treatment and prevention of breast cancer. Tamoxifen has been reported to protect against the progression of coronary artery diseases in human and different atherosclerosis animal models by blocking the appearance of the atheromatous plaque. However, the molecular mechanism of this effect remains unknown. Acyl-CoA:cholesterol acyl transferase (ACAT) catalyzes the biosynthesis of cholesteryl esters, which are the major lipids found in the atheromatous plaque. In this paper we have tested whether ACAT might be inhibited by tamoxifen. We show, using molecular modeling, that tamoxifen displays three-dimensional structural homology with Sah 58-035 (3-[decyldimethylsilyl]-N-[2-(4-methylphenyl)-1-phenylethyl]-propanamide), a prototypical inhibitor of ACAT. We report that tamoxifen inhibits ACAT in a concentration-dependent manner on rat liver microsomal extract. We show that the presence on estrogen receptor ligands of a backbone isosteric to the diphenyl ethane backbone of Sah 58-035 constitutes a pharmacophore for ACAT inhibition. More importantly, tamoxifen was able to inhibit ACAT on intact macrophages stimulated with acetylated low-density lipoproteins and blocked the formation of foam cells, a step that precedes the formation of the atheromatous plaque. This work constitutes the first evidence that tamoxifen is an inhibitor of ACAT and foam cell formation at therapeutic doses and that this may account for its atheroprotective action.

Meta-analysis of vascular and neoplastic events associated with tamoxifen

OBJECTIVE

Tamoxifen reduces the risk of developing breast cancer but also affects the risks of certain vascular and neoplastic events. Our purpose was to estimate the effects of tamoxifen on potentially life-threatening vascular and neoplastic outcomes.

DESIGN

Random effects meta-analysis of published randomized controlled trials.

PATIENTS

Participants in all trials in which a treatment arm that included tamoxifen was compared to a similar control arm. Breast cancer risk reduction and treatment trials were included.

INTERVENTIONS

Tamoxifen at variable dose and duration.

MEASUREMENTS AND MAIN RESULTS

Thirty-two trials (52,929 patients) reported one or more outcomes of interest. Tamoxifen was associated with significantly increased risks of endometrial cancer (relative risk [RR] 2.70; 95% CI, 1.94 to 3.75), gastrointestinal cancers (RR 1.31; 95% CI, 1.01 to 1.69), strokes (RR 1.49; 95% CI, 1.16 to 1.90), and pulmonary emboli (RR 1.88; 95% CI, 1.77 to 3.01). Tamoxifen had no effect on secondary malignancies other than endometrial and gastrointestinal cancers (RR 0.96; 95% CI, 0.81 to 1.13). In contrast, tamoxifen significantly decreased myocardial infarction deaths (RR 0.62; 95% CI, 0.41 to 0.93) and was associated with a statistically insignificant decrease in myocardial infarction incidence (RR 0.90; 95% CI, 0.66 to 1.23). Postmenopausal women had greater risk increases for neoplastic outcomes.

CONCLUSIONS

This meta-analysis of randomized trials found tamoxifen use to be significantly associated with several neoplastic and vascular outcomes. Consideration of tamoxifen use requires balance of potential benefits and risks.

What is the cardioprotective role of hormone replacement therapy?

A very large body of literature has yielded strong biologic and mechanistic plausibility for the consistent observational findings that estrogen is cardioprotective. Recently completed randomized, controlled trials have been interpreted as challenging the doctrine that hormone replacement is cardioprotective for postmenopausal women. However, other than the Estrogen in the Prevention of Atherosclerosis Trial, none of the currently completed (and no ongoing) randomized, controlled trials have appropriately tested the hypothesis generated from observational data that estrogen replacement is cardioprotective. This mainly results from the fact that randomized, controlled trials have not tested the same pattern and type of hormone use in the same population of women observed in the epidemiologic studies. On the other hand, recently completed randomized, controlled trials provide important but limited information concerning the clinical use of a specific regimen of hormone replacement for the prevention of cardiovascular disease in a particular population of postmenopausal women. Observations made from epidemiologic studies will have to be appropriately tested in randomized, controlled trials before any real conclusions can be drawn as to whether hormone replacement is cardioprotective.

Long-term dosing of arzoxifene lowers cholesterol, reduces bone turnover, and preserves bone quality in ovariectomized rats

Long-term effects of a new selective estrogen receptor modulator (SERM) arzoxifene were examined in ovariectomized (OVX) rats. Arzoxifene was administered postoperatively (po) at 0.1 mg/kg per day or 0.5 mg/kg per day to 4-month-old rats, starting 1 week after OVX for 12 months. At study termination, body weights for arzoxifene groups were 16-17% lower than OVX control, which was caused by mainly reduced gain of fat mass. Longitudinal analysis of the proximal tibial metaphysis (PTM) by computed tomography (CT) at 0, 2, 4, 6,9, and 12 months showed that OVX induced a 22% reduction in bone mineral density (BMD) at 2 months, which narrowed to a 12% difference between sham-operated (sham) and OVX rats by 12 months. Both doses of arzoxifene prevented the OVX-induced decline in BMD. Histomorphometry of the PTM showed that arzoxifene prevented bone loss by reducing osteoclast number in OVX rats. Arzoxifene maintained bone formation indices at sham levels and preserved trabecular number above OVX controls. Micro-CT analysis of lumbar vertebrae showed similar preservation of BMD compared with OVX, which were not different from sham. Compression testing of the vertebra and three-point bending testing of femoral shaft showed that strength and toughness were higher for arzoxifene-treated animals compared with OVX animals. Arzoxifene reduced serum cholesterol by 44-59% compared with OVX. Uteri wet weight from arzoxifene animals was 38-40% of sham compared with OVX rats, which were 29% of sham. Histology of the uterine endometrium showed that cell heights from both doses of arzoxifene were not significantly different from OVX controls. In summary, treatment of OVX rats with arzoxifene for nearly one-half of a lifetime maintained beneficial effects on cholesterol and the skeleton. These data suggest that arzoxifene may be a useful therapeutic agent for osteoporosis in postmenopausal women.

Reproductive hormones and cardiovascular disease mechanism of action and clinical implications

The bulk of the experimental data suggest beneficial effects of estrogen (both premenopausal use of OCs and postmenopausal use of ERT-HRT). An intriguing finding from the monkey studies is that social subordination, which induces estrogen deficiency in female monkeys, accelerates atherosclerosis premenopausally and predicts extent of postmenopausal atherosclerosis. This effect can be inhibited by exogenous estrogen, premenopausally. The results suggest that more effort on detecting and regulating premenopausal ovarian dysfunction may be justified. A complication in understanding estrogen action may be the result of varying extents of arterial damage. For example, primary prevention studies in both postmenopausal animals and women have provided strong evidence of atheroprotection with a variety of estrogens. In contrast, the results of secondary prevention studies [10,12] have in general suggested little cardioprotection with either ERT or HRT. Studies in rabbits suggest the antiatherogenic effect of estrogen may not be present when the endothelium is damaged [64]. The state of the endothelium may be critical for some estrogen actions. For those effects of estrogen that require the ER, be it ERalpha or ERbeta, the presence of the receptor may vary with age, disease state, or type of hormone therapy. If continuous combined HRT therapy decreases ER in the artery as it does in the uterus, this may eliminate those estrogen actions requiring the ER, but not others. Older women who have not been exposed to estrogens for many years may be more sensitive to some estrogen effects, and may need lower doses of ERT-HRT. Recent reports suggest that lower doses of estrogens maintain beneficial effects on lipoproteins and coagulation factors [95], while also requiring lower doses of progestogens to protect the uterus [96]. These beneficial findings are very promising in light of the improvements in CHD risk and decreased stroke risk reported with low-dose estrogens [5]. It ill be interesting to see if CRP is increased with lower doses of estrogens and whether these changes are associated with increased early risk of CHD. Perhaps older women with CHD are also more obese, may have diabetes, and may be more susceptible to inflammatory and thrombotic effects of higher doses of estrogens. There are many questions left unanswered. It is hoped that some of the answers may come from the WHI, which is a large prospective trial assessing ERT and HRT. The age range is also relatively large and may be able to determine if older women respond differently than younger women. Some initial data from the WHI have been made available suggesting a small increased risk in the first 2 years and a trend for decreasing risk in the last months of the first 2 years [34]. Just recently, the CEE + MPA arm of the study was stopped early by the data and-safety monitoring board as the overall health risks exceeded benefits with increases in both breast cancer and CVD [97]. The remainder of the study groups including an estrogen-only arm, are expected to continue until 2005.

Postmenopausal hormone replacement therapy as antiatherosclerotic therapy

Cardiovascular disease remains the number one killer of women. Although important for the reduction of cardiovascular events, lipid alteration does not appear to be sufficient to obtain optimum reduction in cardiovascular risk. Women have a potential opportunity for further reduction in cardiovascular risk through postmenopausal hormone replacement therapy. More than 50 observational studies indicate that postmenopausal use of hormone replacement therapy reduces atherosclerosis and cardiovascular events. However, recently reported, randomized, controlled clinical trials have yielded mixed results as to whether hormone replacement therapy reduces cardiovascular events relative to placebo. These, as well as other randomized controlled trials of hormone replacement therapy and cardiovascular disease in postmenopausal women, are reviewed. Although conclusions concerning the specific hormones used in the specific populations studied can be offered from the completed trials, more broad conclusions concerning the use of hormone replacement therapy in the prevention of cardiovascular disease will have to await conduction and completion of other trials.

Tamoxifen is not detrimental to endothelial function in postmenopausal women with breast cancer

BACKGROUND

Tamoxifen has mixed estrogen agonist and antagonist properties in estrogen-regulated tissues. Its effect on the cardiovascular system is not well defined. We carried out a study to investigate the effect of tamoxifen on peripheral vascular endothelial function.

METHODS

Three groups of postmenopausal women (median age, 56 years; range, 39 to 69 years) with breast cancer were studied. Patients in group 1 (n = 10) were newly diagnosed with breast cancer and studied before and after 4 weeks treatment with tamoxifen. Group 2 women (n = 6) had been receiving long-term tamoxifen (3 to 5 years) and were studied while taking tamoxifen and 4 weeks after stopping it. The final group of 6 subjects were in remission from primary breast cancer and were not receiving or had previously received tamoxifen. Ultrasound assessments of endothelial function were done before and 4 weeks after the initiation or discontinuation of tamoxifen with the nontreatment group acting as control. All ultrasound imaging was made by a single investigator blinded to the therapeutic status of the subject. Brachial artery diameter was measured by ultrasound at baseline and 1 minute after reactive hyperemia. Flow-mediated reactivity (FMR) was defined as percent change in artery diameter from baseline 1 minute after reactive hyperemia.

RESULTS

There was no change in FMR in patients before compared with 4 weeks after starting tamoxifen (4.06% +/- 1.44% vs 3.97% +/- 1.20%, respectively, mean +/- standard error of the mean [SEM], P =.97). There was no significant change in FMR on withdrawal from tamoxifen (1.84% +/- 1.98% vs -0.42% +/- 1.44% on tamoxifen vs off tamoxifen, mean +/- SEM, P =.36). FMR in subjects taking tamoxifen was no different from the control group (3.17% +/- 1.05% vs 3.16% +/- 0.91%, respectively, mean +/- SEM, P =.995).

CONCLUSIONS

Tamoxifen does not appear to affect endothelial function in the short term in postmenopausal women with breast cancer.

Postmenopausal oestrogen replacement therapy and atherosclerosis: can current compounds provide cardiovascular protection?

The natural oestrogen, 17 beta-oestradiol, has been implicated in protection from atherosclerosis, a chronic systemic vascular disease with an inflammatory component accounting for the majority of morbidity and mortality in Western countries. Despite the protective effects of 17 beta-oestradiol in premenopausal women and experimental evidence demonstrating inhibitory effects of oestrogen on atherosclerosis progression, it is currently unclear whether hormone replacement therapy can affect cardiovascular morbidity and mortality in postmenopausal women. The recent advances in understanding the mechanisms of oestrogen action demonstrated roles for different oestrogen receptors and oestrogen metabolites in the pathogenesis of vascular injury and endothelial cell dysfunction. However, their respective role in the process of atherogenesis remains yet to be elucidated. Moreover, the availability of novel drugs with tissue- and/or receptor-specific actions will help to understand the role of oestrogen in cardiovascular diseases. Several ongoing large-scale clinical trials using opposed or unopposed replacement therapy with natural or synthetic oestrogens, or selective oestrogen receptor modulators (SERMs) will resolve the question whether the drugs currently available have therapeutic potential to interfere with the progression of atherosclerosis and its complications.

Direct effects of estrogen on the vessel wall

The understanding of the biological effects of estrogen on the vessel wall has improved dramatically since the discovery of estrogen receptors (ERs). Most, but not all estrogen-mediated effects in blood vessels are thought to be mediated by ERs. Two major ER subclasses have been characterized so far: the ERalpha and the more recently described ERbeta. This review will primarily focus on a new perspective that highlights ERs as essential mediators of the vascular effects of estrogen. In view of the rising research interest in this area, it can be also expected that tissue- and ER subclass-selective agonists and antagonists will be developed over the next few years, thus providing invaluable tools for pharmacological and clinical applications.

Cardiovascular effects of tamoxifen in women with and without heart disease: breast cancer prevention trial. National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial Investigators

BACKGROUND

The overall effect of prophylactic tamoxifen in women depends on the balance between the effects of the drug, which include preventing breast cancer and altering cardiovascular risk. In a recent clinical trial, postmenopausal estrogen-progestin therapy was shown to increase the risk of early cardiovascular events among women with a history of coronary heart disease (CHD). The cardiovascular effects of tamoxifen in women with and without CHD are not known. The National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial (BCPT) is the only clinical trial that provides data to assess the cardiovascular effects of tamoxifen in women with and without CHD.

METHODS

A total of 13 388 women at increased risk for breast cancer were randomly assigned in the BCPT to receive either tamoxifen (20 mg/day) or placebo. Cardiovascular follow-up was available for 13 194 women, 1048 of whom had prior clinical CHD. Fatal and nonfatal myocardial infarction, unstable angina, and severe angina were tabulated (mean follow-up: 49 months). All statistical tests were two-sided.

RESULTS

Cardiovascular event rates were not statistically significantly different between women assigned to receive tamoxifen and those assigned to receive placebo, independent of pre-existing CHD. Among women without CHD (6074 on tamoxifen versus 6072 on placebo), risk ratios (95% confidence intervals [CIs]) for tamoxifen users were 1.75 (0.44 to 8.13) for fatal myocardial infarction, 1.11 (0.55 to 2.28) for nonfatal myocardial infarction, 0.69 (0.29 to 1.57) for unstable angina, and 0.83 (0.32 to 2.10) for severe angina. In women with CHD (516 on tamoxifen versus 532 on placebo), risk ratios (95% CIs) for tamoxifen users were 0.00 (0 to 1.58) for fatal myocardial infarction, 1.25 (0.32 to 5.18) for nonfatal myocardial infarction, 2.26 (0.87 to 6.55) for unstable angina, and 1.39 (0.23 to 9.47) for severe angina. There was no evidence that the lack of association between tamoxifen and cardiovascular events was related to an early increase in risk that may have been offset by a late decrease in risk.

CONCLUSION

When used for breast cancer prevention in women with or without heart disease, tamoxifen is not associated with beneficial or adverse cardiovascular effects.

Vascular endothelial growth factor is modulated in vascular muscle cells by estradiol, tamoxifen, and hypoxia

Vascular endothelial growth factor (VEGF) promotes neovascularization, microvascular permeability, and endothelial proliferation. We described previously VEGF mRNA and protein induction by estradiol (E2) in human endometrial fibroblasts. We report here E2 induction of VEGF expression in human venous muscle cells [smooth muscle cells (SMC) from human saphenous veins; HSVSMC] expressing both ER-alpha and ER-beta estrogen receptors. E2 at 10(-9) to 10(-8) M increases VEGF mRNA in HSVSMC in a time-dependent manner (3-fold at 24 h), as analyzed by semiquantitative RT-PCR. This level of induction is comparable with E2 endometrial induction of VEGF mRNA. Tamoxifen and hypoxia also increase HSVSMC VEGF mRNA expression over control values. Immunocytochemistry of saphenous veins and isolated SMC confirms translation of VEGF mRNA into protein. Immunoblot analysis of HSVSMC-conditioned medium detects three bands of 18, 23, and 28 kDa, corresponding to VEGF isoforms of 121, 165, and 189 amino acids. Radioreceptor assay of the conditioned medium produced by E2-stimulated HSVSMC reveals an increased VEGF secretion. Our data indicate that VEGF is E2, tamoxifen, and hypoxia inducible in cultured HSVSMC and E2 inducible in aortic SMC, suggesting E2 modulation of VEGF effects in angiogenesis, vascular permeability, and integrity.

Raloxifene and estrogen inhibit neointimal thickening after balloon injury in the carotid artery of male and ovariectomized female rats

The effects of raloxifene and 17alpha-ethinyl estradiol (EE2) on intimal thickening in response to balloon injury were tested in male and ovariectomized female rats. In male rats, oral raloxifene and EE2, administered either by gavage or in the diet, inhibited arterial intimal thickening in response to balloon injury to a maximum of approximately 60 and 50%, respectively. The effect of oral raloxifene to decrease cholesterol was observed at doses (> or = 3 mg/kg/day) higher than those required to inhibit intimal thickening (> or = 0.03 mg/kg/day). Coadministration of the estrogen receptor antagonist, ICI 182,780 (5 mg/kg/day, s.c.), blocked the inhibition of balloon injury by raloxifene and EE2. Direct adventitial delivery of raloxifene (0.03 mg/kg/day) and EE2 (0.001 mg/kg/day) to the vascular wall inhibited intimal thickening by 63 and 53%, respectively. In ovariectomized female rats, oral raloxifene (0.01-3.0 mg/kg/day) and EE2 (0.08 mg/kg/day) inhibited intimal thickening to a maximum of 32 and 60%, respectively. Together, these data suggest that raloxifene and EE2, inhibit balloon arterial injury in the rat through direct effects on the vascular wall that involve the estrogen receptor and are at least partially independent of serum cholesterol.

Selective estrogen receptor modulators: structure, function, and clinical use

The sex hormone estrogen is important for many physiologic processes. Prolonged stimulation of breast ductal epithelium by estrogen, however, can contribute to the development and progression of breast cancer, and treatments designed to block estrogen's effects are important options in the clinic. Tamoxifen and other similar drugs are effective in breast cancer prevention and treatment by inhibiting the proliferative effects of estrogen that are mediated through the estrogen receptor (ER). However, these drugs also have many estrogenic effects depending on the tissue and gene, and they are more appropriately called selective estrogen receptor modulators (SERMs). SERMs bind ER, alter receptor conformation, and facilitate binding of coregulatory proteins that activate or repress transcriptional activation of estrogen target genes. Theoretically, SERMs could be synthesized that would exhibit nearly complete agonist activity on the one hand or pure antiestrogenic activity on the other. Depending on their functional activities, SERMs could then be developed for a variety of clinical uses, including prevention and treatment of osteoporosis, treatment and prevention of estrogen-regulated malignancies, and even for hormone replacement therapy. Tamoxifen is effective in patients with ER-positive metastatic breast cancer and in the adjuvant setting. The promising role for tamoxifen in ductal carcinoma-in-situ or for breast cancer prevention is evolving, and its use can be considered in certain patient groups. Other SERMs are in development, with the goal of reducing toxicity and/or improving efficacy, and future agents have the potential of providing a new paradigm for maintaining the health of women.

Dietary fat and reduced levels of TGFbeta1 act synergistically to promote activation of the vascular endothelium and formation of lipid lesions

Transforming growth factor-(beta) (TGF(beta)) has a wide range of activities on vascular cells and inflammatory cells, suggesting it may have different functions during various stages of atherogenesis. We report that mice heterozygous for the deletion of the tgfb1 gene (tgfb1(+/-) mice) have reduced levels of TGF(beta)1 in the artery wall until at least 8 weeks of age. On a normal mouse chow diet, the vascular endothelium of tgfb1(+/-) mice is indistinguishable from wild-type littermates, assessed by morphology and intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression. In contrast, levels of the smooth muscle isoforms of actin and myosin in medial smooth muscle cells of tgfb1(+/-) mice are significantly reduced. Following feeding a cholesterol-enriched diet for 12 weeks, high levels of ICAM-1 and VCAM-1 were detected in the vascular endothelial cells of tgfb1(+/-) mice, but not wild-type mice. Furthermore, marked deposition of lipid into the artery wall was only observed in the tgfb1(+/-) mice on the cholesterol-enriched diet. These vascular lipid lesions were accompanied by local invasion of macrophages. We conclude that deletion of a single allele of the tgfb1 gene results in a reduced level of TGFbeta1 antigen in the aorta together with reduced smooth muscle cell differentiation, whereas the addition of a high fat dietary challenge is required to activate the vascular endothelium and to promote the formation of fatty streaks resembling early atherosclerosis in humans.

Clinical management of BRCA1- and BRCA2-associated breast cancer

The recent discovery of the breast cancer-associated genes BRCA1 and BRCA2 has changed the clinical care provided to women at high risk of breast cancer. We will review what is currently known about the clinical management of patients who bear (or are suspected of bearing) mutations in either of these two genes. The issues related to establishing a diagnosis of inherited breast cancer, deciding which women are candidates for testing, the limitations of testing, and the predictive power of these tests are addressed. The prognostic features of cancers associated with a BRCA1 and BRCA2 mutation are reviewed. Further, guidelines for prophylaxis of women with a BRCA1 or BRCA2 mutation are given and recommendations are made for the care of mutation carriers with cancer.

Steroid regulation of tryptophan hydroxylase protein in the dorsal raphe of macaques

BACKGROUND

Tryptophan hydroxylase (TPH) is the rate-limiting enzyme for the synthesis of serotonin, and serotonin is a pivotal neurotransmitter in the regulation of mood, affective behavior, pituitary hormone secretion, and numerous autonomic functions. We previously demonstrated that estradiol (E) and progesterone (P) increase TPH mRNA levels in the dorsal raphe of macaques.

METHODS

This study employed western blotting and densitometric quantitation to determine whether the changes observed at the level of gene expression were manifested by changes in TPH protein expression and whether modified estrogens or progestins had actions similar to the native ligands. In addition, the effect of the antiestrogen tamoxifen was examined. Ovariectomized (ovx) rhesus and cynomolgus macaques were untreated or treated with E, P, E+P, equine estrogens (EE), medroxyprogesterone (MPA), EE+MPA, or tamoxifen. The dorsal raphe region was subjected to Western analysis.

RESULTS

E treatment for 28 days increased TPH protein mass four to six fold over ovariectomized controls. Addition of P to the E regimen or treatment with P for 28 days after E priming did not alter TPH from E treatment alone. Treatment of ovx macaques with a low dose of P caused a two-fold increase in TPH protein. Treatment of ovariectomized macaques for 30 months with EE alone or MPA alone significantly increased TPH protein; however, unlike P, the addition of MPA to the EE regimen blocked the stimulatory effect of EE. Tamoxifen treatment significantly reduced TPH protein compared to EE and ovariectomized control animals.

CONCLUSION

The stimulatory effect of E and P on TPH protein in the dorsal raphe of macaques correlates with the previously observed effect at the level of mRNA expression. P had no effect on the stimulatory action of E, whereas MPA blocked the stimulatory effect of EE. Tamoxifen acted as a potent antiestrogen on TPH protein expression. If TPH protein mass influences serotonin synthesis, then these steroids will impact many autonomic systems that are regulated by serotonin.

Raloxifene reduces atherosclerosis: studies of optimized raloxifene doses in ovariectomized, cholesterol-fed rabbits

OBJECTIVE

We have previously shown that raloxifene, a selective oestrogen receptor modulator, 35 mg/day inhibits atherosclerosis in ovariectomized, cholesterol-fed rabbits. This effect was only partial as compared to 17beta-oestradiol 4 mg/day; however, plasma raloxifene concentrations were low relative to those obtained in raloxifene-treated women. We therefore investigate the effects of raloxifene at higher doses.

DESIGN

The study on atherosclerosis in ovariectomized, cholesterol-fed rabbits (n = 80) compared raloxifene 70 mg/day and 210 mg/day to 17beta-oestradiol 4 mg/day and placebo.

RESULTS

After 48 weeks of therapy, the aortic cholesterol content in the 70 mg/day and 210 mg/day raloxifene treatment groups were 471 +/- 56 nmol/mg protein and 456 +/- 56 nmol/mg protein, respectively. This was significantly less than in the placebo group (654 +/- 69 nmol/mg protein; P < 0.05). In the oestrogen-treated group, the aortic cholesterol content was 357 +/- 62 nmol/mg protein (P < 0.01 as compared to placebo). Differences in serum lipids between the treatment groups could only partly explain the effect on aortic cholesterol content, indicating that additional anti-atherogenic mechanisms may contribute to the decrease in aortic atherosclerosis. This anti-atherosclerotic activity of raloxifene was observed at plasma concentrations comparable to those in postmenopausal women during raloxifene treatment.

CONCLUSIONS

We conclude that clinically relevant raloxifene treatment inhibits aortic atherosclerosis in ovariectomized, cholesterol-fed rabbits.

The Potential of SERMs for Reducing the Risk of Coronary Heart Disease

Selective estrogen receptor modulators (SERMs) represent a growing class of compounds that act as either estrogen receptor agonists or antagonists in a tissue-selective manner. Preclinical and clinical studies have shown that estrogen has favorable effects on serum lipids and might affect processes at the blood vessel wall to inhibit atherosclerosis. SERMs with the appropriate selectivity profile offer the opportunity to dissociate these favorable cardiovascular effects of estrogen from its unfavorable stimulatory effects on the breast and uterus. This article reviews the data from both animal and human studies that document the cardiovascular effects of SERMs and discusses the clinical implications of these results.

Selective estrogen receptor modulators: Women's panacea for the next millennium?

The purpose of this review is to assimilate relevant experimental and clinical information available on selective estrogen receptor modulators with respect to their potential use as agents to improve women's health in the postmenopausal years. In addition, the mechanisms of action of these drugs are outlined. Selective estrogen receptor modulators represent an exciting group of antiestrogens that possess agonist action on bone, lipids, and lipoproteins and antagonistic action in the endometrium and breast. Thus in theory these drugs may preserve bone density and reduce the risk of osteoporotic fracture and coronary heart disease at the same time that they lower the incidences of breast and endometrial neoplasms. Short-term data with the use of raloxifene suggest that bone is preserved and lipid profiles are less atherogenic. Long-term studies are needed to determine whether raloxifene or other selective estrogen receptor modulators are associated with any decrease in the risk of breast or endometrial cancer.

Estrogens and atherosclerosis: phytoestrogens and selective estrogen receptor modulators

The development of atherosclerosis in animal models and the incidence of coronary heart disease in postmenopausal women are markedly reduced by estrogen treatment. Estrogen have acute beneficial effects on vascular reactivity and longer-term effects on critical steps in the pathogenesis of atherosclerosis. Phytoestrogens present in soybeans and other plant products are weak estrogens but appear to have potent beneficial effects on the arterial wall. The phytoestrogens have certain similarities to 'designer hormones' which are being developed to retain their beneficial effects on the cardiovascular system and the skeleton without having cancer promoting effects on the breast and endometrium.

Women, dyslipoproteinemia, and estrogens

The most common cause of death in both men and women is coronary atherosclerosis, although atherosclerotic death in women occurs 5 to 10 years later than it does in men. Major risk factors predict coronary risk in both. Available evidence suggests that women benefit from cholesterol lowering just as men do. The role of exogenous estrogenic compounds in favorably affecting lipoprotein levels and promoting antiatherogenesis in both men and women is a promising area for future research.

Effects of conjugated estrogens, medroxyprogesterone acetate, and tamoxifen on the mammary glands of macaques

The purpose of this work was to examine the mammary glands of adult, ovariectomized female cynomolgus macaques (Macaca fascicularis) in a long-term study of the effects of hormone treatments on chronic disease. Treatments included conjugated equine estrogens (CEE), medroxyprogesterone acetate (MPA), CEE+MPA, and tamoxifen. Doses were scaled from those given women. Treatments were given in the diet for three years, followed by necropsy and tissue collection. Endpoints evaluated included glandular histology, histomorphometry, and immunohistochemical detection of the proliferation marker Ki-67, estrogen receptor (ER), and progesterone receptor (PR) in mammary epithelial cells. Major findings were as follows: CEE induced PR expression and focal to diffuse lobuloalveolar proliferation. Proliferation was increased by the addition of MPA, but was not induced by MPA alone. Tamoxifen induced ER and PR but not Ki-67 expression or glandular hyperplasia. Neoplasms were not seen. These findings indicate that progestogens may exacerbate, not antagonize mammary gland proliferation induced by estrogen replacement therapy, and that tamoxifen has both estrogen agonist and antagonist effects on sex steroid receptor expression in the normal primate breast.