Increased 2-methoxyestradiol production in human coronary versus aortic vascular cells

Sex Differences, Estrogen Metabolism and Signaling in the Development of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex and devastating disease with a poor long-term prognosis. While women are at increased risk for developing PAH, they exhibit superior right heart function and higher survival rates than men. Susceptibility to disease risk in PAH has been attributed, in part, to estrogen signaling. In contrast to potential pathological influences of estrogen in patients, studies of animal models reveal estrogen demonstrates protective effects in PAH. Consistent with this latter observation, an ovariectomy in female rats appears to aggravate the condition. This discrepancy between observations from patients and animal models is often called the "estrogen paradox." Further, the tissue-specific interactions between estrogen, its metabolites and receptors in PAH and right heart function remain complex; nonetheless, these relationships are essential to characterize to better understand PAH pathophysiology and to potentially develop novel therapeutic and curative targets. In this review, we explore estrogen-mediated mechanisms that may further explain this paradox by summarizing published literature related to: (1) the synthesis and catabolism of estrogen; (2) activity and functions of the various estrogen receptors; (3) the multiple modalities of estrogen signaling in cells; and (4) the role of estrogen and its diverse metabolites on the susceptibility to, and progression of, PAH as well as their impact on right heart function.

Sex, Gender, and Sex Hormones in Pulmonary Hypertension and Right Ventricular Failure

Pulmonary hypertension (PH) encompasses a syndrome of diseases that are characterized by elevated pulmonary artery pressure and pulmonary vascular remodeling and that frequently lead to right ventricular (RV) failure and death. Several types of PH exhibit sexually dimorphic features in disease penetrance, presentation, and progression. Most sexually dimorphic features in PH have been described in pulmonary arterial hypertension (PAH), a devastating and progressive pulmonary vasculopathy with a 3-year survival rate <60%. While patient registries show that women are more susceptible to development of PAH, female PAH patients display better RV function and increased survival compared to their male counterparts, a phenomenon referred to as the "estrogen paradox" or "estrogen puzzle" of PAH. Recent advances in the field have demonstrated that multiple sex hormones, receptors, and metabolites play a role in the estrogen puzzle and that the effects of hormone signaling may be time and compartment specific. While the underlying physiological mechanisms are complex, unraveling the estrogen puzzle may reveal novel therapeutic strategies to treat and reverse the effects of PAH/PH. In this article, we (i) review PH classification and pathophysiology; (ii) discuss sex/gender differences observed in patients and animal models; (iii) review sex hormone synthesis and metabolism; (iv) review in detail the scientific literature of sex hormone signaling in PAH/PH, particularly estrogen-, testosterone-, progesterone-, and dehydroepiandrosterone (DHEA)-mediated effects in the pulmonary vasculature and RV; (v) discuss hormone-independent variables contributing to sexually dimorphic disease presentation; and (vi) identify knowledge gaps and pathways forward. © 2020 American Physiological Society. Compr Physiol 10:125-170, 2020.

Palmitate decreases migration and proliferation and increases oxidative stress and inflammation in smooth muscle cells: role of the Nrf2 signaling pathway

Fatty acids are essential to cell functionality and may exert diverging vascular effects including migration, proliferation, oxidative stress, and inflammation. This study examined the effect of palmitate on human coronary artery smooth muscle cell (HCASMC) function. An in vitro wound-healing assay indicated that palmitate decreased HCASMC migration in dose- and time-dependent manners. Furthermore, bromodeoxyuridine incorporation assays indicated that palmitate decreased HCASMC proliferation in a dose-response manner. Palmitate also increased reactive oxygen species formation, malondialdehyde content, and intracellular lipid droplets accompanied with increased fatty acid binding protein 4 expression. Moreover, palmitate induced gene expression (monocyte chemoattractant protein 1, matrix metalloproteinase-2, IL-1β, IL-6, IL-8, and TNF-α) and intracellular protein content (plasminogen activator inhibitor-1 and urokinase plasminogen activator) of inflammatory mediators. Finally, we showed that palmitate activates the transcription factor Nrf2 and the upstream kinases ERK1/2 and Akt in HCASMCs. The inhibitor of Nrf2, trigonelline, significantly attenuated palmitate-induced HCASMC expression of the Nrf2 target gene NQO1. These findings indicate that palmitate might be critically related to HCASMC function by slowing cell migration and proliferation and inducing lipid-laden cells, oxidative stress, and inflammation in part by activation of the Nrf2 transcription factor. Palmitate's activation of proinflammatory Nrf2 signaling may represent a novel mechanism mediating the proatherogenic actions of saturated fatty acids.

Recent Advances in chemistry and pharmacology of 2-methoxyestradiol: An anticancer investigational drug

2-Methoxyestradiol (2ME2), an estrogen hormone metabolite is a potential cancer chemotherapeutic agent. Presently, it is an investigational drug under various phases of clinical trials alone or in combination therapy. Its anticancer activity has been attributed to its antitubulin, antiangiogenic, pro-apoptotic and ROS induction properties. This anticancer drug candidate has been explored extensively in last twenty years for its detailed chemistry and pharmacology. Present review is an update of its chemistry and biological activity. It also extends an assessment of potential of 2ME2 and its analogues as possible anticancer drug in future.

2-Methoxyestradiol ameliorates glucose tolerance with the increase in β-cell mass in db/db mice

Aims/Introduction:  2‐Methoxyestradiol (2ME) is an estradiol metabolite with little estrogenic activity. Previous data identified its anti‐carcinogenic properties and possible cardiovascular benefits. However, its effect on diabetes mellitus has not been fully elucidated. The aim of the present study was to determine the effects of 2ME on glucose metabolism in the diabetic state.

Materials and Methods:  To evaluate the effects of 2ME, pellets of two different doses of the drug were implanted into female db/db mice at the age of 5 weeks. Intraperitoneal glucose tolerance test and insulin tolerance test were carried out at the age of 8 weeks. The pancreas was harvested for morphological analysis and β‐cell function at the age of 9 weeks.

Results:  2ME improved random blood glucose levels and glucose tolerance with increases in insulin levels during an intraperitoneal glucose tolerance test. Insulin sensitivity judged by an insulin tolerance test was comparable in the low‐ and high‐dose 2ME groups and the control group. Although glucose‐stimulated insulin secretion in isolated islets was comparable among the three groups, β‐cell mass in 2ME‐treated groups was higher than the control group. In the 2ME‐treated groups, the number of Ki67‐positive cells in islets was higher, whereas the number of cleaved caspase‐3‐positive cells was comparable with the control.

Conclusions:  2ME ameliorates glucose tolerance by promoting the proliferation of β‐cell mass in db/db mice. Our data suggests its potential clinical usefulness as a disease‐modifying drug for type 2 diabetes mellitus. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00087.x, 2011)

Progress in solving the sex hormone paradox in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a devastating and progressive disease with marked morbidity and mortality. Even though being female represents one of the most powerful risk factors for PAH, multiple questions about the underlying mechanisms remain, and two "estrogen paradoxes" in PAH exist. First, it is puzzling why estrogens have been found to be protective in various animal models of PAH, whereas PAH registries uniformly demonstrate a female susceptibility to the disease. Second, despite the pronounced tendency for the disease to develop in women, female PAH patients exhibit better survival than men. Recent mechanistic studies in classical and in novel animal models of PAH, as well as recent studies in PAH patients, have significantly advanced the field. In particular, it is now accepted that estrogen metabolism and receptor signaling, as well as estrogen interactions with key pathways in PAH development, appear to be potent disease modifiers. A better understanding of these interactions may lead to novel PAH therapies. It is the purpose of this review to 1) review sex hormone synthesis, metabolism, and receptor physiology; 2) assess the context in which sex hormones affect PAH pathogenesis; 3) provide a potential explanation for the observed estrogen paradoxes and gender differences in PAH; and 4) identify knowledge gaps and future research opportunities. Because the majority of published studies investigated 17β-estradiol and/or its metabolites, this review will primarily focus on pulmonary vascular and right ventricular effects of estrogens. Data for other sex hormones will be discussed very briefly.

Metabolic pathways involved in 2-methoxyestradiol synthesis and their role in preeclampsia

Preeclampsia (PE) remains a major cause of maternal/fetal morbidity-mortality worldwide. The first stage of PE is characterized by placental hypoxia due to a relative reduction in uteroplacental blood flow, resulting from restricted trophoblast invasion. However, hypoxia is also an essential element for the success of invasion. Under hypoxic conditions, 2-methoxyestradiol (2-ME) could induce the differentiation of cytotrophoblast cells into an invasive phenotype in culture. 2-Methoxyestradiol is generated by catechol-O-methyltransferase, an enzyme involved in the metabolic pathway of estrogens. During pregnancy, circulating 2-ME levels increase significantly when compared to the menstrual cycle. Interestingly, plasma levels of 2-ME are lower in women with PE than in controls, and these differences are apparent weeks or even months before the clinical manifestations of the disease. This article reviews the metabolic pathways involved in 2-ME synthesis and discusses the roles of these pathways in normal and abnormal pregnancies, with particular emphasis on PE.

Estrogens and development of pulmonary hypertension: interaction of estradiol metabolism and pulmonary vascular disease

Severe pulmonary arterial hypertension (PAH) is characterized by clustered proliferation of endothelial cells (ECs) in the lumina of small size pulmonary arteries resulting in concentric obliteration of the lumina and formation of complex vascular structures known as plexiform lesions. This debilitating disease occurs more frequently in women, yet both animal studies in classical models of PAH and limited clinical data suggest protective effects of estrogens: the estrogen paradox in pulmonary hypertension. Little is known about the role of estrogens in PAH, but one line of evidence strongly suggests that the vascular protective effects of 17β-estradiol (estradiol; E2) are mediated largely by its downstream metabolites. Estradiol is metabolized to 2-hydroxyestradiol (2HE) by CYP1A1/CYP1B1, and 2HE is converted to 2-methoxyestradiol (2ME) by catechol-O-methyl transferase. 2ME is extensively metabolized to 2-methoxyestrone, a metabolite that lacks biologic activity, but which may be converted back to 2ME. 2ME has no estrogenic activity, and its effects are mediated by estrogen receptors–independent mechanism(s). Notably, in systemic and pulmonary vascular ECs, smooth muscle cells, and fibroblasts, 2ME exerts stronger antimitotic effects than E2 itself. E2 and 2ME, despite having similar effects on other cardiovascular cells, have opposing effects on ECs; that is, in ECs, E2 is promitogenic, proangiogenic, and antiapoptotic, whereas 2ME is antimitogenic, antiangiogenic, and proapoptotic. This may have significant ramifications in severe PAH that involves uncontrolled proliferation of monoclonal apoptosis-resistant ECs. Based on its cellular effects, 2ME should be expected to attenuate the progression of disease and provide protection in severe PAH. In contrast, E2, due to its mitogenic, angiogenic, and antiapoptotic effects (otherwise desirable in normal quiescent ECs), may even adversely affect endothelial remodeling in PAH, and this may be even more significant if the E2's effects on injured endothelium are not opposed by 2ME (eg, in the event of reduced E2 conversion to 2ME due to hypoxia, inflammation, drugs, environmental factors, or genetic polymorphism of metabolizing enzymes). This review focuses on the effects of estrogens and their metabolites on pulmonary vascular pathobiology and the development of experimental PAH and offers potential explanation for the estrogen paradox in PAH. Furthermore, we propose that unbalanced estradiol metabolism may lead to the development of PAH. Recent animal data and studies in patients with PAH support this concept.

Resveratrol, a red wine constituent, blocks the antimitogenic effects of estradiol on human female coronary artery smooth muscle cells

CONTEXT

Antimitogenic effects of estradiol on vascular smooth muscle cells (VSMCs) may be cardioprotective, and these effects are mediated by estrogen receptor-alpha-dependent and -independent mechanisms, with the latter involving the conversion of estradiol to 2-hydroxyestradiol/2-methoxyestradiol by CYP450. Because resveratrol inhibits CYP450 and is an estrogen-receptor-alpha antagonist, resveratrol may abrogate the antimitogenic effects of estradiol.

OBJECTIVE

The objective of the study was to examine the interaction of pharmacologically relevant concentrations of resveratrol with estradiol, 2-hydroxyestradiol, and 2-methoxyestradiol in human female coronary artery VSMCs.

METHODS AND RESULTS

In human female coronary VSMCs, resveratrol (0.1-10 microm) alone did not influence serum-induced DNA or collagen synthesis or cell proliferation or migration; however, resveratrol abrogated the inhibitory effects of estradiol, but not 2-hydroxyestradiol or 2-methoxyestradiol, on these responses. Resveratrol also abrogated the inhibitory effects of estradiol on positive growth regulators (cyclin A, cyclin D, MAPK phosphorylation) and the stimulatory effects of estradiol on negative growth regulators (p21, p27). In microsomes and cells, dietarily relevant levels of resveratrol (0.001-1 microm) inhibited the metabolism of estradiol to 2-hydroxestradiol/2-methoxyestradiol. Propylpyrazoletriol (estrogen receptor-alpha agonist, 100 nmol/liter), but not diarylpropionitrile (estrogen receptor-beta agonist, 10 nmol/liter), inhibited VSMC mitogenesis, and this effect was blocked by resveratrol (5 micromol/liter). Higher concentrations (>25-50 microm) of resveratrol, never attainable in vivo, inhibited VSMC growth, an effect blocked by GW9662 (peroxisomal proliferator-activated receptor-gamma antagonist).

CONCLUSION

In conclusion, dietarily relevant levels of resveratrol abrogate the antimitogenic effects of estradiol by inhibiting CYP450-mediated estradiol metabolism and blocking estrogen receptor-alpha.

Metabolism and actions of conjugated linoleic acids on atherosclerosis-related events in vascular endothelial cells and smooth muscle cells

Conjugated linoleic acids (CLAs) are biologically highly active lipid compounds that have attracted great scientific interest due to their ability to cause either inhibition of atherosclerotic plaque development or even regression of pre-established atherosclerotic plaques in mice, hamsters and rabbits. The underlying mechanisms of action, however, are only poorly understood. Since cell culture experiments are appropriate to gain insight into the mechanisms of action of a compound, the present review summarizes data from cell culture studies about the metabolism and the actions of CLAs on atherosclerosis-related events in endothelial cells (ECs) and smooth muscle cells (SMCs), which are important cells contributing to atherosclerotic lesion development. Based on these studies, it can be concluded that CLAs exert several beneficial actions including inhibition of inflammatory and vasoactive mediator release from ECs and SMCs, which may help explain the anti-atherogenic effect of CLAs observed in vivo. The observation that significant levels of CLA metabolites, which have been reported to have significant biological activities, are well detectable in ECs and SMCs indicates that the anti-atherogenic effects observed with CLAs are presumably mediated not only by CLAs themselves but also by their metabolites.

Acute effects of 2-methoxyestradiol on endothelial aortic No release in male and ovariectomized female rats

The endogenous metabolites of 17beta-estradiol are thought to have protective vascular effects, especially in males and estrogen-deprived females. The present study evaluated the acute in vitro effects of the active metabolite 2-methoxyestradiol on endothelial NO release from ovariectomized female and intact male and female rat aortas. NO was measured electrochemically by differential normal pulse amperometry using carbon fiber microsensors, and also by fluorescence microscopy using 4,5-diaminofluorescein diacetate. 2-Methoxyestradiol alone induced a maintained increase in endothelial NO release in male and ovariectomized rats that was reduced by pretreatment with L-NAME. NO release induced by calcium ionophore alone (A23187) was lower in aortas from ovariectomized rats than from intact females, indicating that estrogen deprivation induces endothelial dysfunction. Pretreatment of aortas with 2-methoxyestradiol potentiated significantly the A23187-induced-NO release in ovariectomized as well as in males, but not in intact females. This potentiation was reduced or abolished by L-NAME. 2-Methoxyestradiol potentiated the vasodilatory effect of A23187 on intestinal arterioles, and also increased intestinal tissular laser-Doppler blood flow signal. These results demonstrate that 17beta-estradiol and its active metabolite 2-methoxyestradiol increase basal aortic endothelial NO production and also cause a potentiation of the calcium ionophore-stimulated NO release in male and ovariectomized, while it has no effects on intact females. 2-Methoxyestradiol appears to be a promising pharmacological agent capable of improving endothelial function in men and postmenopausal women.

Estradiol-17beta and its cytochrome P450- and catechol-O-methyltransferase-derived metabolites stimulate proliferation in uterine artery endothelial cells: role of estrogen receptor-alpha versus estrogen receptor-beta

Estradiol-17beta (E(2)beta) and its metabolites, which are sequentially synthesized by cytochrome P450s and catechol-O-methyltransferase to form 2 and 4-hydroxyestradiol (OHE(2)) and 2- and 4-methoxestradiol (ME(2)), are elevated during pregnancy. We investigated whether cytochrome P450s and catechol-O-methyltransferase are expressed in uterine artery endothelial cells (UAECs) and whether E(2)beta and its metabolites modulate cell proliferation via ER-alpha and/or ER-beta and play roles in physiological uterine angiogenesis during pregnancy. Cultured ovine UAECs from pregnant and nonpregnant ewes were treated with 0.1 to 100.0 nmol/L of E(2)beta, 2-OHE(2), 4-OHE(2), 2-ME(2), and 4-ME(2). ER-alpha or ER-beta specificity was tested using ICI 182 780, ER-alpha-specific 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinyleth oxy)phenol]-1H-pyrazole dihydrochloride, ER-beta-specific 4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo [1,5-a]pyrim idin-3-yl]phenol antagonists and their respective agonists ER-alpha-specific 4,4',4"-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol and ER-beta-specific 2,3-bis(4-Hydroxyphenyl)-propionitrile. Angiogenesis was evaluated using 5-bromodeoxyuridine proliferation assay. Using confocal microscopy and Western analyses to determine enzyme location and levels, we observed CYP1A1, CYP1A2, CYP1B1, CYP3A4, and catechol-O-methyltransferase expression in UAECs; however, expressions were similar between nonpregnant UAECs and pregnant UAECs. E(2)beta, 2-OHE(2), 4-OHE(2), and 4-ME(2) treatments concentration-dependently stimulated proliferation in pregnant UAECs but not in nonpregnant UAECs; 2-ME(2) did not stimulate proliferation in either cell type. Proliferative responses of pregnant UAECs to E(2)beta were solely mediated by ER-beta, whereas responses to E(2)beta metabolites were neither ER-alpha nor ER-beta mediated. We demonstrate an important vascular role for E(2)beta, its cytochrome P450- and catechol-O-methyltransferase-derived metabolites, and ER-beta in uterine angiogenesis regulation during pregnancy that may be dysfunctional in preeclampsia and other cardiovascular disorders.

Effects of sex and estrogen on chicken ductus arteriosus reactivity

Sex hormones have an important influence on cardiovascular physiology and pathophysiology and sex differences in vascular reactivity have been widely demonstrated. In the present study we hypothesized 1) the presence of sexual dimorphism in chicken ductus arteriosus (DA) responsiveness to contractile and relaxant stimuli and 2) that estrogens are vasoactive in the chicken DA. In vitro contractions (assessed with a wire myograph) induced by normoxia, KCl, 4-aminopyridine, norepinephrine, phenylephrine, U46619, or endothelin-1, as well as relaxations induced by ACh, sodium nitroprusside, BAY 41-2272, PGE(2), isoproterenol, forskolin,Y-27632, and hydroxyfasudil were not significantly different between males and females. The estrogen 17beta-estradiol elicited concentration-dependent relaxation of KCl-, phenylephrine-, and oxygen-induced active tone in male and female chicken DA. The stereoisomer 17alpha-estradiol showed lesser relaxant effects, and the selective estrogen receptor (ER) agonists 4,4',4''-(4-propyl-[(1)H]pyrazole-1,3,5-triyl)tris-phenol (ERalpha) and 2,3-bis(4-hydroxyphenyl)-propionitrile (ERbeta) did not show any effect. There were no sex differences in the responses to estrogen. Endothelium removal or the presence of the soluble guanylate cyclase inhibitor ODQ, the K(+) channel blockers tetraethylammonium, glibenclamide, and charybdotoxin, or the ER antagonist fulvestrant did not modify 17beta-estradiol-induced relaxation. CaCl(2) (30 muM-10 mM) induced concentration-dependent contraction in DA rings depolarized by 62.5 mM KCl or stimulated with 21% O(2) in Ca(2+)-free medium. Preincubation with 17beta-estradiol or the L-type Ca(2+) channel blocker nifedipine produced an inhibition of CaCl(2)-induced contractions. In conclusion, there are no sex-related differences in chicken DA reactivity. The estrogen 17beta-estradiol induces an endothelium-independent relaxation of chicken DA that is not mediated by ER activation. This relaxant effect is, at least partially, due to inhibition of Ca(2+) entry from extracellular space.

Chemical target and pathway toxicity mechanisms defined in primary human cell systems

INTRODUCTION

The ability to predict the health effects resulting from drug or chemical exposure has been challenging due to the complexity of human biology. Approaches that detect and discriminate a broad range of mechanisms in testing formats that are predictive and yet cost-effective are needed.

METHODS

Here, we evaluated the performance of BioMAP systems, primary human cell-based disease models, as a platform for characterization of chemical toxicity mechanisms. For this we tested a set of compounds with known or well-studied mechanisms in a panel of 8 BioMAP assays relevant to human respiratory, skin, immune and vascular exposure sites.

RESULTS

We evaluated the ability to detect and distinguish compounds based on mechanisms of action, comparing the BioMAP activity profiles generated in a reduced sample number format to reference database profiles derived from multiple experiments. We also studied the role of BioMAP assay panel size and concentration effects, both of which were found to contribute to the ability to discriminate chemicals and mechanisms.

DISCUSSION

Compounds with diverse mechanisms, including modulators of the NFkappaB pathway, microtubule function and mitochondrial activity, could be discriminated and classified into target and pathway mechanisms in both assay formats. Certain inhibitors of mitochondrial function, such as rotenone and sodium azide, but not others, were classified with inducers of endoplasmic reticulum stress, providing insight into the toxicity mechanisms of these agents. This method may have utility in classifying novel agents with unknown modes of action according to their effects on toxicity pathways.

Influence of conjugated linoleic acids on functional properties of vascular cells

Conjugated linoleic acids (CLA) are biologically highly active lipid compounds that inhibit the development of atherosclerotic plaques in experimental animals. The underlying mechanisms of action, however, are only poorly understood. Since cell-culture experiments are appropriate to provide a detailed view into the mechanisms of action of a compound, the present review summarises results fromin vitrostudies dealing with the effects of CLA isomers and CLA mixtures on functional properties of cells of the vascular wall, such as endothelial cells, smooth muscle cells and monocyte-derived macrophages, which are amongst the major cells contributing to atherosclerotic lesion development. Based on these studies, it can be concluded that CLA exert several beneficial actions in cells of the vascular wall through the activation of nuclear PPAR. These actions of CLA, which may, at least partially, explain the inhibition of atherogenesis by dietary CLA, include modulation of vasoactive mediator release from endothelial cells, inhibition of inflammatory and fibrotic processes in activated smooth muscle cells, abrogation of inflammatory responses in activated macrophages, and reduction of cholesterol accumulation in macrophage-derived foam cells.

Conjugated linoleic acid isomers inhibit platelet-derived growth factor-induced NF-kappaB transactivation and collagen formation in human vascular smooth muscle cells

BACKGROUND

Atherosclerosis is characterized by extensive thickening of the arterial intima partially resulting from deposition of collagen by vascular smooth muscle cells (SMCs). Polyunsaturated fatty acids stimulate collagen formation through NF-kappaB activation.

AIM OF THE STUDY

The present study aimed to explore the effect of conjugated linoleic acids (CLAs) which are known to inhibit NF-kappaB activation on collagen formation by SMCs.

METHODS

Vascular SMCs were cultured with 50 micromol/l of CLA isomers (c9t11-CLA, t10c12-CLA) or linoleic acid (LA) and analysed for collagen formation and NF-kappaB p50 transactivation.

RESULTS

Treatment with CLA isomers but not LA significantly reduced PDGF-stimulated [(3)H] proline incorporation into cell layer protein of SMCs without altering cell proliferation. Simultaneous treatment with the PPARgamma inhibitor T0070907 abrogated this effect. Treatment of SMCs with c9t11-CLA and t10c12-CLA significantly reduced PDGF-induced NF-kappaB p50 activation.

CONCLUSIONS

CLA isomers inhibit PDGF-stimulated collagen production by vascular SMCs, which is considered to be a hallmark of atherosclerosis, in a PPARgamma-dependent manner. Whether inhibition of the NF-kappaB-pathway is of significance for the reduction of collagen formation by CLA isomers needs further investigation.

Characterization of in vitro and in vivo metabolic pathways of the investigational anticancer agent, 2-methoxyestradiol

The aim of this study was to characterize the metabolic pathways of 2-methoxyestradiol (2ME2), an investigational anticancer drug. In vitro metabolism studies were performed by incubation of 2ME2 with human liver microsomes under various conditions and metabolite identification was performed using liquid chromatography-tandem mass spectrometry. In microsomal mixtures, four major oxidative metabolites and two glucuronic acid conjugates were observed originating from 2ME2. Human liver S9 protein fraction was used to screen for in vitro sulfation but no prominent conjugates were observed. The total hepatic clearance as estimated using the well-stirred model was approximately 712 mL/min. In vivo metabolism, assessed using 24-h collections of urine from cancer patients treated with 2ME2 revealed that <0.01% of the total administered dose of 2ME2 is excreted unchanged in urine and about 1% excreted as glucuronides. Collectively, this suggests that glucuronidation and subsequent urinary excretion are elimination pathways for 2ME2.

The COMT val158met polymorphism is associated with peak BMD in men

The associations between the functional val158met polymorphism of the estrogen-degrading COMT enzyme and skeletal properties in young men were investigated. BMD was associated with COMT genotype.

INTRODUCTION

Peak BMD is an important predictor of future risk of osteoporosis, and it is to a large extent determined by genetic factors. Estrogens are involved in the accretion of bone mass during puberty. Catechol-O-methyltransferase (COMT) is involved in the degradation of estrogens. There is a functional polymorphism in the COMT gene (val158met), resulting in a 60-75% difference in enzyme activity between the val (high activity [H]) and met (low activity [L]) variants. The aim of this cross-sectional study was to investigate the associations between this polymorphism and peak BMD in young men.

MATERIALS AND METHODS

A total of 458 healthy men (mean age, 19 +/- 0.6 years) were genotyped and classified as COMT(LL), COMT(HL), or COMT(HH). Areal BMD (aBMD) was measured by DXA. Cortical and trabecular volumetric BMD (vBMD) were measured by pQCT. The associations between COMT genotype and skeletal phenotypes were determined.

RESULTS AND CONCLUSIONS

Regression models using physical activity, height, weight, age, and COMT genotype as covariates showed that COMT genotype was an independent predictor of aBMD in the total body and in all femur locations investigated, but not in the spine. The values for COMT(HL) and COMT(HH) were very similar, and therefore, they were pooled into one group. aBMD at Ward's triangle, trochanter, and total femur were 4.9%, 4.5%, and 3.7% lower, respectively, in the COMT(LL) than in the COMT(HL/HH) group (p < 0.01). pQCT analyses showed that COMT genotype was an independent predictor of trabecular vBMD of the tibia, radius, and fibula. Trabecular vBMD of the radius and fibula in COMT(LL) was 5.3% and 7.4% lower, respectively, than that of the combined COMT(HL/HH) group. COMT genotype was associated with cortical vBMD but not with cortical cross-sectional area in the tibia. These findings show that the COMT polymorphism is associated with BMD in young adult men.

Cardiovascular Pharmacology of Estradiol Metabolites

A discussion of the role of endogenous estradiol metabolites in mediating important biological actions of estradiol is essentially nonexistent in standard textbooks of pharmacology and endocrinology. Indeed, the prevailing view is that all biological effects of estradiol are initiated by binding of estradiol per se to estrogen receptors and that estradiol metabolites are more or less irrelevant. This orthodox view, which is most likely incorrect, is the fundamental premise (an estrogen is an estrogen is an estrogen) underlying the design of important clinical trials such as the Heart and Estrogen/Progestin Replacement Study and the Women's Health Initiative Study. Accumulating data provide convincing evidence that some metabolites of estradiol, the major estrogen secreted by human ovaries, are biologically active and mediate multiple effects on the cardiovascular and renal systems that are largely independent of estrogen receptors. More specifically, metabolites of estradiol, particularly catecholestradiols and methoxyestradiols, induce multiple estrogen receptor-independent actions that protect the heart, blood vessels, and kidneys from disease. These protective effects are mediated in part by the inhibition of the ability of vascular smooth muscle cells, cardiac fibroblasts, and glomerular mesangial cells to migrate, proliferate, and secrete extracellular matrix proteins, as well as by an improvement in vascular endothelial cell function. The purpose of this review is to highlight the cardiovascular and renal pharmacology of catecholestradiols and methoxyestradiols. The take home message is simple: that when it comes to cardiovascular and renal protection, the concept that all estrogenic compounds are created equal may not be true.

2-Methoxyestradiol, a promising anticancer agent

Estrogens occurring naturally in the body are metabolized to catecholestrogens (2- and 4-hydroxyestradiol) by the cytochrome P450 enzymes. 2-Hydroxy catecholestrogens are further metabolized by catechol-O-methyltransferase to 2-methoxyestradiol, which is known to be protective against tumor formation. 2-Methoxyestradiol exhibits potent apoptotic activity against rapidly growing tumor cells. It also possesses antiangiogenic activity through a direct apoptotic effect on endothelial cells. Other molecular mechanisms, including microtubule stabilization by inhibition of the colchicine-binding site, have been reported. The exact mechanism of action of 2-methoxyestradiol is still unclear, but it has been shown to be effective in preventing tumor growth in a variety of cell lines. 2-Methoxyestradiol also possesses cardioprotective activity by inhibiting vascular smooth muscle cell growth in arteries. It has a lower binding affinity for estrogen receptor alpha compared with that of estradiol, and its affinity for estrogen receptor beta is even lower than that of estrogen receptor alpha, thus it has minimal estrogenic activity. 2-Methoxyestradiol is distinct because of its inability to engage estrogen receptors as an agonist, and its unique antiproliferative and apoptotic activities are mediated independently of estrogen receptors alpha and beta. A phase I clinical trial of 2-methoxyestradiol 200, 400, 600, 800, and 1,000 mg/day in 15 patients with breast cancer showed significant reduction in bone pain and analgesic intake in some patients, with no significant adverse effects. Another phase I study of 2-methoxyestradiol 200-1,000 mg/day in combination with docetaxel 35 mg/m2/week for 4-6 weeks performed in 15 patients with advanced refractory metastatic breast cancer showed no serious drug-related adverse effects. A phase II randomized, double-blind trial of 2-methoxyestradiol 400 and 1,200 mg/day in 33 patients with hormone-refractory prostate cancer showed that it was well tolerated and showed prostate specific antigen stabilizations and declines. We have started a phase I clinical trial to explore dosages greater than 1,000 mg/day.

2-Hydroxyestradiol attenuates renal disease in chronic puromycin aminonucleoside nephropathy

It has been previously shown that 2-hydroxyestradiol (2-OHE) attenuates the development of renal disease in genetic nephropathy associated with obesity and the metabolic syndrome. The purpose of this study was to test the hypothesis that 2-OHE, irrespective of its effects on metabolic status and/or obesity, exerts direct renoprotective effects in vivo. First, the effects of increasing doses of 2-OHE on mesangial cell growth, proliferation, and collagen synthesis in isolated rat glomerular mesangial cells were evaluated in vitro. Second, the effects of 12-wk administration of 2-OHE (10 micro g/h per kg) on renal function and structure in chronic puromycin aminonucleoside (PAN)-induced nephropathy in rats were evaluated in vivo. 2-OHE concentration-dependently (0.001 to 1 micro mol/L; P < 0.001) inhibited serum (2.5%)-induced cell growth ((3)H-thymidine incorporation), collagen synthesis ((3)H-proline incorporation), and cell proliferation (cell number). Importantly, the inhibitory effects of 2-OHE (0.1 micro mol/L) were not blocked by ICI182780 (50 micro mol/L), an estrogen receptor antagonist. In vivo, chronic administration of PAN (75 mg/kg + 5 x 20 mg/kg) over 12 wk induced severe chronic renal disease. Chronic treatment with 2-OHE significantly (P < 0.05) attenuated PAN-induced decrease in glomerular filtration, reduced proteinuria, and the elevated BP, and it had no effect on PAN-induced increase in plasma cholesterol and triglycerides levels. 2-OHE had no effects on plasma testosterone levels in male nephropathic animals. Immunohistochemical staining for collagen IV and proliferating cell nuclear antigen (PCNA) in glomeruli and transforming growth factor-beta (TGF-beta) in renal tubular cells were significantly higher in PAN nephropatic rats versus control animals with intact kidneys. PAN also markedly increased glomerular and interstitial macrophage infiltration (ED1(+) cells). 2-OHE had no effects on renal tubular cell TGF-beta, but it significantly reduced glomerular PCNA and collagen IV and glomerular and interstitial macrophage infiltration. In summary, this study provides the first evidence that 2-OHE exerts direct renoprotective effects in vivo. These effects are mediated by estrogen receptor-independent mechanisms and are due, at least in part, to the inhibition of some of the key proliferative mechanisms involved in glomerular remodeling and sclerosis.

Arterial intima-media thickness: site-specific associations with HRT and habitual exercise

We determined the site-specific relations of hormone replacement therapy (HRT) and habitual exercise status with intima-media thickness (IMT) in both elastic (carotid) and muscular (femoral) arteries in 77 healthy postmenopausal women: 43 women were sedentary (20 no-HRT and 23 HRT users) and 34 women were endurance trained (14 no-HRT and 20 HRT users). Femoral IMT was not different among the sedentary HRT and endurance-trained no-HRT and HRT groups, but was lower (P < 0.005) in these three groups than in the sedentary no-HRT women. There were no significant group differences in carotid IMT. However, in older women (> or =65 yrs) carotid IMT was smaller (P < 0.05) in HRT compared with no-HRT women. We conclude that both endurance training and HRT status are independently associated with a smaller IMT and these effects are evident primarily in muscular arteries. These results suggest that HRT and habitual exercise may protect postmenopausal women against cardiovascular disease through influences on IMT. The site-specific relations may be due to a greater number of smooth muscle cells and plasticity of muscular arteries compared with elastic arteries and/or differences in heterogeneous influences such as metabolic requirements and hydrostatic pressures.

Catecholamines abrogate antimitogenic effects of 2-hydroxyestradiol on human aortic vascular smooth muscle cells

Catechol-O-methyltransferase (COMT)-mediated methylation of 2-hydroxyestradiol (endogenous estradiol metabolite) to 2-methoxyestradiol (angiogenesis inhibitor) may be responsible for the antimitogenic effects of 2-hydroxyestradiol on vascular smooth muscle cells (VSMCs). Catecholamines are also substrates for COMT, and increased levels of catecholamines are associated with vasoocclusive disorders. We hypothesize that catecholamines may abrogate the vasoprotective effects of 2-hydroxyestradiol by competing for COMT and inhibiting 2-methoxyestradiol formation. To test this hypothesis, we investigated the antimitogenic effects of 0.001 to 0.1 micromol/L of 2-hydroxyestradiol on human aortic VSMC proliferation (cell number and DNA synthesis), collagen synthesis, and migration in the presence and absence of catecholamines. Norepinephrine, epinephrine, and isoproterenol concentration-dependently abrogated the inhibitory effects of 2-hydroxyestradiol on cell number, DNA synthesis, collagen synthesis, and cell migration. These modulatory/attenuating effects of catecholamines were not abrogated in the presence of the alpha- and beta-adrenergic receptor antagonists, phentolamine mesylate and propranolol, respectively. In contrast to 2-hydroxyestradiol, the antimitogenic effects of 2-methoxyestradiol (0.1 micromol/L) were not attenuated by isoproterenol (1 micromol/L) or quercetin (competitive inhibitor of COMT, 10 micromol/L). Norepinephrine, epinephrine, and isoproterenol concentration-dependently (10 to 500 micromol/L) inhibited the metabolism of 2-hydroxyestradiol (0.25 to 2 micromol/L) to 2-methoxyestradiol, and the potency of the catecholamines to reverse 2-hydroxyestradiol-induced inhibition of VSMC proliferation, collagen synthesis, and migration was correlated with their ability to inhibit 2-methoxyestradiol formation. Our findings suggest that catecholamines within the vasculature may abrogate the anti-vaso-occlusive effects of estradiol and 2-hydroxyestradiol by blocking 2-methoxyestradiol formation.

Cardiovascular protective effects of 17beta-estradiol metabolites

17beta-estradiol (estradiol), the most abundant endogenous estrogen, affords cardiovascular protection. However, in a given cohort of postmenopausal women, estradiol replacement therapy provides cardiovascular protection in only a subset. The reasons for this variable action can only be understood once the mechanisms by which estradiol induces its cardiovascular protective effects are known. Because most biological effects of estradiol are mediated via estrogen receptors (ERs) and the heart and blood vessels contain both ER-alpha and ER-beta, the prevailing view is that ERs mediate estradiol-induced cardiovascular protection. However, recent findings that estradiol protects against vascular injury in arteries of mice lacking either ER-alpha or ER-beta seriously challenges this concept. Thus other non-ER mechanisms may be operative. Endogenous estradiol is enzymatically converted to several nonestrogenic metabolites, and some of these metabolites induce potent biological effects via ER-independent mechanisms. Therefore, it is conceivable that the cardiovascular protective effects of estradiol are mediated via its endogenous metabolites. On the basis of the evidence cited in this review, the cardiovascular protective effects of estradiol are both ER dependent and independent. The purpose of this article is to review the evidence regarding the cardiovascular protective effects of estradiol metabolites and to discuss the cellular, biochemical, and molecular mechanisms involved.