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

Exosomes Derived from Yak Follicular Fluid Increase 2-Hydroxyestradiol Secretion by Activating Autophagy in Cumulus Cells

Exosomes in the follicular fluid can carry and transfer regulatory molecules to recipient cells, thus influencing their biological functions. However, the specific effects of yak follicular fluid exosomes on 2-hydroxyestrodiol (2-OHE₂) secretion remain unknown. Here, we investigated whether yak follicular fluid exosomes can increase 2-OHE₂ secretion through the activation of autophagy in cumulus cells (YCCs). In vitro cultured YCCs were treated with yak follicular fluid exosomes for 6, 12, and 24 h. The effects of yak follicular fluid exosomes on autophagy and 2-OHE₂ secretion were evaluated through real-time quantitative fluorescence PCR (RT-qPCR), Western blotting (WB), transfected with RFP-GFP-LC3, immunohistochemistry, and ELISA. To further investigate whether 2-OHE₂ secretion was related to autophagy, YCCs were administered with yak follicular fluid exosomes, 3-methyladenine (3-MA), and rapamycin (RAPA). The results revealed that treatment with yak follicular fluid exosomes activated autophagy in YCCs and increased 2-OHE₂ secretion. Conversely, the inhibition of autophagy with 3-MA blocked these effects, suggesting that autophagy has an important role in 2-OHE₂ secretion in YCCs. Treatment of YCCs with rapamycin showed similar results with yak follicular fluid exosomes as there was an increase in 2-OHE2 secretion due to the activation of autophagy in the treated cumulus cells. Our results demonstrate that autophagy is enhanced by yak follicular fluid exosomes, and this is associated with an increase in 2-OHE₂ secretion in YCCs.

DPP4 Inhibition, NPY1-36, PYY1-36, SDF-1α, and a Hypertensive Genetic Background Conspire to Augment Cell Proliferation and Collagen Production: Effects That Are Abolished by Low Concentrations of 2-Methoxyestradiol

By reducing their metabolism, dipeptidyl peptidase 4 inhibition (DPP4I) enhances the effects of numerous peptides including neuropeptide Y_1–36 (NPY_1–36), peptide YY_1–36 (PYY_1–36), and SDF-1α. Studies show that separately NPY_1–36, PYY_1–36 and SDF-1α stimulate proliferation of, and collagen production by, cardiac fibroblasts (CFs), preglomerular vascular smooth muscle cells (PGVSMCs), and glomerular mesangial cells (GMCs), particularly in cells isolated from genetically hypertensive rats. Whether certain combinations of these factors, in the absence or presence of DPP4I, are more profibrotic than others is unknown. Here we contrasted 24 different combinations of conditions (DPP4I, hypertensive genotype and physiologic levels [3 nM] of NPY_1–36, PYY_1–36, or SDF-1α) on proliferation of, and [³H]-proline incorporation by, CFs, PGVSMCs, and GMCs. In all three cell types, the various treatment conditions differentially increased proliferation and [³H]-proline incorporation, with a hypertensive genotype + DPP4I + NPY_1–36 + SDF-1α being the most efficacious combination. Although the effects of this four-way combination were similar in male versus female CFs, physiologic (1 nM) concentrations of 2-methoxyestradiol (2ME; nonestrogenic metabolite of 17β-estradiol), abolished the effects of this combination in both male and female CFs. In conclusion, this study demonstrates that CFs, PGVSMCs, and GMCs are differentially activated by various combinations of NPY_1–36, PYY_1–36, SDF-1α, a hypertensive genetic background and DPP4I. We hypothesize that as these progrowth conditions accumulate, a tipping point would be reached that manifests in the long term as organ fibrosis and that 2ME would obviate any profibrotic effects of DPP4I, even under the most profibrotic conditions (i.e., hypertensive genotype with high NPY_1–36 + SDF-1α levels and low 2ME levels).

Catechol-O-methyltransferase is dispensable for vascular protection by estradiol in mouse models of atherosclerosis and neointima formation

Estradiol is converted to the biologically active metabolite 2-methoxyestradiol via the activity of the enzyme catechol-O-methyltransferase (COMT). Exogenous administration of both estradiol and 2-methoxyestradiol reduces experimental atherosclerosis and neointima formation, and COMT-dependent formation of 2-methoxyestradiol likely mediates the antimitogenic effect of estradiol on smooth muscle cells in vitro. This study evaluated whether 2-methoxyestradiol mediates the vasculoprotective actions of estradiol in vivo. Wild-type (WT) and COMT knockout (COMTKO) mice on an apolipoprotein E-deficient background were gonadectomized and treated with estradiol or placebo. Exogenous estradiol reduced atherosclerotic lesion formation in both females (WT, -78%; COMTKO, -82%) and males (WT, -48%; COMTKO, -53%) and was equally effective in both genotypes. We further evaluated how exogenous estradiol affected neointima formation after ligation of the carotid artery in ovariectomized female mice; estradiol reduced intimal hyperplasia to a similar extent in both WT (-80%) and COMTKO (-77%) mice. In ovarian-intact female COMTKO mice, atherosclerosis was decreased (-25%) compared with WT controls. In conclusion, the COMT enzyme is dispensable for vascular protection by exogenous estradiol in experimental atherosclerosis and neointima formation in vivo. Instead, COMT deficiency in virgin female mice with intact endogenous production of estradiol results in relative protection against atherosclerosis.

Pregnancy ameliorates the inhibitory effects of 2-methoxyestradiol on angiogenesis in primary sheep uterine endothelial cells

The estrogen metabolite 2-methoxyestradiol (2-ME2) is one of the most potent antiangiogenic and proapoptotic endogenous steroids. Herein, we investigate the effects of 2-ME2 on angiogenesis of cultured primary ovine uterine artery endothelial cells (UAECs) from nonpregnant follicular (F-UAECs), nonpregnant luteal (L-UAECs), and pregnant ewes (P-UAECs). Uterine artery endothelial cells were treated with vehicle control, 10(-8) mol/L 17β-estradiol (17βE2), or 10(-9) to 10(-6) mol/L 2-ME2. Angiogenesis, apotosis, and cell morphology were assessed by capillary tube formation, flowcytometry, and immunohistochemistry. 17βE2 stimulated while 10(-6) mol/L 2-ME2 inhibited capillary tube formation in F-UAECs (P < .05). The inhibitory effects of 2-ME2 on angiogenesis were minimal in L-UAECs and were absent in P-UAECs when compared to controls. 10(-6) mol/L 2-ME2 increased apoptosis and inhibited microtubular structure equally in pregnant and nonpregnant UAECs when compared to control or 17βE2 treatments. Thus, 2-ME2 inhibit capillary tube formation in F-UAECs while L-UAECs and P-UAECs are relatively unresponsive to the inhibitory effects of 2ME2 indicating that the pregnancy phenotypic state of the UAECs may modulate the action of 2-ME2 on capillary angiogenesis.

Potential vascular actions of 2-methoxyestradiol

2-Methoxyestradiol (2-ME) is a biologically active metabolite of 17beta-estradiol that appears to inhibit key processes associated with cell replication in vitro. The molecule has been suggested to have potent growth-inhibitory effects on proliferating cells, including smooth muscle cells and endothelial cells, and may be antiangiogenic. Because of these potential roles for 2-ME, its lack of cytotoxicity and low estrogenic activity, we hypothesize that 2-ME could be a valuable therapeutic molecule for prevention and treatment of cardiovascular diseases. Whether 2-ME is as effective in vivo as it is in vitro at modulating vascular processes remains controversial. Here we discuss recent developments regarding mechanisms by which 2-ME might regulate vascular activity and angiogenesis and speculate on the therapeutic implications of these developments.

Sex/gender medicine. The biological basis for personalized care in cardiovascular medicine

Sex differences in morbidity and mortality associated with cardiovascular disease have been recognized by the medical community for decades. Investigation into the underlying biological basis of these differences was largely neglected by the scientific community until a report released by the Institute of Medicine in the United States in 2001 "Exploring the Biological Contributions to Human Health: Does Sex Matter?" Recommendations from this report included the need for more accurate use of the terms "sex" and "gender", better tools and resources to study the biological basis of sex differences, integration of findings from different levels of biological organization and continued synergy between basic and clinical researchers. Ten years after the Institute's report, this review evaluates some of the sex differences in cardiovascular disease, reviews new approaches to study sex differences and emphasizes areas where further research is required. In the era of personalized medicine, the study of the biological basis of sex differences promises to optimize preventive, diagnostic and therapeutic strategies for cardiovascular disease in men and women, but will require diligence by the scientific and medical communities to remember that sex does matter.

Vascular actions of estrogens: functional implications

The impact of estrogen exposure in preventing or treating cardiovascular disease is controversial. But it is clear that estrogen has important effects on vascular physiology and pathophysiology, with potential therapeutic implications. Therefore, the goal of this review is to summarize, using an integrated approach, current knowledge of the vascular effects of estrogen, both in humans and in experimental animals. Aspects of estrogen synthesis and receptors, as well as general mechanisms of estrogenic action are reviewed with an emphasis on issues particularly relevant to the vascular system. Recent understanding of the impact of estrogen on mitochondrial function suggests that the longer lifespan of women compared with men may depend in part on the ability of estrogen to decrease production of reactive oxygen species in mitochondria. Mechanisms by which estrogen increases endothelial vasodilator function, promotes angiogenesis, and modulates autonomic function are summarized. Key aspects of the relevant pathophysiology of inflammation, atherosclerosis, stroke, migraine, and thrombosis are reviewed concerning current knowledge of estrogenic effects. A number of emerging concepts are addressed throughout. These include the importance of estrogenic formulation and route of administration and the impact of genetic polymorphisms, either in estrogen receptors or in enzymes responsible for estrogen metabolism, on responsiveness to hormone treatment. The importance of local metabolism of estrogenic precursors and the impact of timing for initiation of treatment and its duration are also considered. Although consensus opinions are emphasized, controversial views are presented to stimulate future research.

The complex role of estrogens in inflammation

There is still an unresolved paradox with respect to the immunomodulating role of estrogens. On one side, we recognize inhibition of bone resorption and suppression of inflammation in several animal models of chronic inflammatory diseases. On the other hand, we realize the immunosupportive role of estrogens in trauma/sepsis and the proinflammatory effects in some chronic autoimmune diseases in humans. This review examines possible causes for this paradox. This review delineates how the effects of estrogens are dependent on criteria such as: 1) the immune stimulus (foreign antigens or autoantigens) and subsequent antigen-specific immune responses (e.g., T cell inhibited by estrogens vs. activation of B cell); 2) the cell types involved during different phases of the disease; 3) the target organ with its specific microenvironment; 4) timing of 17beta-estradiol administration in relation to the disease course (and the reproductive status of a woman); 5) the concentration of estrogens; 6) the variability in expression of estrogen receptor alpha and beta depending on the microenvironment and the cell type; and 7) intracellular metabolism of estrogens leading to important biologically active metabolites with quite different anti- and proinflammatory function. Also mentioned are systemic supersystems such as the hypothalamic-pituitary-adrenal axis, the sensory nervous system, and the sympathetic nervous system and how they are influenced by estrogens. This review reinforces the concept that estrogens have antiinflammatory but also proinflammatory roles depending on above-mentioned criteria. It also explains that a uniform concept as to the action of estrogens cannot be found for all inflammatory diseases due to the enormous variable responses of immune and repair systems.

Effects of 2-methoxyestradiol on endometrial carcinoma xenografts

PURPOSE

We have previously demonstrated that 2-methoxyestradiol (2-ME) inhibits the growth of human endometrial cancer HEC-1-A and RL-95-2 cells in vitro. In this study, we examined the effects of 2-ME on human endometrial carcinoma in severe combined immune deficient (SCID) mice. The potential side effects of 2-ME on SCID mice were also investigated.

METHODS

Severe combined immune deficient mice were injected with HEC-1-A cells (1 x 10(6)/mouse) and a 18 day administration of 2-ME was followed after 1 week cell implantation. Tumor volume, weight, body weight and blood chemistry were determined. Tumor tissues were examined with an antibody against the proliferative cell nuclear antigen (PCNA) and Ki-67. Liver, spleen, kidney, heart, lung and uterus were screened by pathological examinations.

RESULTS

2-ME (100 mg/kg p.o.) did not inhibit the growth of human endometrial carcinoma as compared to control. Necrotic areas were similar in both 2-ME-treated and -untreated tumor tissues. The expressions of PCNA and Ki-67 were similar in 2-ME-treated and untreated tumor sections. The wet weight of uterus was increased to more than threefold. The epithelial cells and glands in endometrium were increased. No significant difference was detected in blood AST, ALT and BUN.

CONCLUSIONS

2-ME has no antitumor effects on human endometrial carcinoma in our animal model. Its proliferative effects on endometrium and uterus might limit its use in gynecological cancers.

Effect of catecholestrogen administration during adriamycin-induced cardiomyopathy in ovariectomized rat

The therapeutical beneficial effect of estrogen-derived metabolites or catecholestrogens is controversial. These molecules are produced during estrogen therapy based on 17-beta-estradiol treatment. The metabolization of 17-beta-estradiol is carried out in brain, kidney or liver, and triggers different products such as 2- and 4- hydroxyestradiol (2OH and 4OH). These products have shown antioxidant properties against oxidative stress (OS) in several experimental models. Different noxious side effects related to those metabolites have also been observed upon estrogen therapy. In this sense, catecholestrogens seem to be implicated in tumoral and mutagenic process after long treatment with estrogens substitutive therapy. In our study, we have verified that 2OH and 4OH have antioxidant and cardioprotective effects against adriamycin (AD)-induced cardiomyopathy in ovariectomized (OVX) rats. Catecholestrogens diminished the lipid peroxides and carbonyl protein (CO) content, and different enzymes related to cell injury (creatinine kinase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase) in cardiac tissue from OVX-, AD-, and OVX+AD-treated rats. All these changes were correlated to a recovery on reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) in heart tissue. The present study showed that 2OH and 4OH reduced all the parameters related to OS, antioxidant depletion and cardiac injury in OVX rats treated or not with AD.

Sex dimorphism in cardiac pathophysiology: experimental findings, hormonal mechanisms, and molecular mechanisms

The higher cardiovascular risk in men and post-menopausal women implies a protective action of estrogen. A large number of experimental studies have provided strong support to this concept. However, the recent clinical trials with negative outcomes regarding hormone replacement therapy call for "post hoc" reassessment of existing information, models, and research strategies as well as a summary of recent findings. Sex steroid hormones, in particular estrogen, regulate numerous processes that are related to the development and progression of cardiovascular disease through a variety of signaling pathways. Use of genetically modified models has resulted in interesting information on diverse actions mediated by steroid receptors. By focusing on experimental findings, we have reviewed hormonal, cellular, and signaling mechanisms responsible for sex dimorphism and actions of hormone replacement therapy and addressed current limitations and future directions of experimental research.

Catecholamines block the antimitogenic effect of estradiol on human coronary artery smooth muscle cells

Sequential conversion of estradiol to catecholestradiols and methoxyestradiols by cytochrome-P(450) (CYP450) and catechol-O-methyltransferase (COMT), respectively, contributes to the antimitogenic effects of estradiol on vascular smooth muscle cell (SMC) growth via estrogen receptor-independent mechanisms. Because catecholamines are also substrates for COMT, we hypothesize that catecholamines may abrogate the vasoprotective effects of estradiol by competing for COMT and inhibiting methoxyestradiol formation. To test this hypothesis, we investigated the antimitogenic/inhibitory effects of estradiol on human coronary artery SMC growth (cell number, DNA synthesis, collagen synthesis, and SMC migration) and ERK1/2 phosphorylation in the presence and absence of catecholamines. Norepinephrine, epinephrine, isoproterenol, and OR486 (COMT inhibitor) abrogated the inhibitory effects of estradiol on SMC growth and ERK1/2 phosphorylation. The interaction of catecholamines with estradiol was not affected by phentolamine or propanolol, alpha- and beta-adrenoceptor antagonists, respectively. The antimitogenic effects of 2-hydroxy-estradiol, but not 2-methoxyestradiol, were abrogated by epinephrine, isoproterenol, and OR486. Catecholamines inhibited the conversion of both estradiol and 2-hydroxy-estradiol to 2-methoxyestradiol, and SMCs expressed CYP1A1 and CYP1B1. Our findings suggest that catecholamines within the coronary arteries may abrogate the antivasoocclusive effects of estradiol by blocking the conversion of catecholestradiols to methoxyestradiols. The interaction between catecholamines and estradiol metabolism may importantly define the cardiovascular effects of estradiol therapy in postmenopausal women.

2-Hydroxyestradiol Is a Prodrug of 2-Methoxyestradiol

Previous in vivo studies indicate that 2-hydroxyestradiol (2OHE) attenuates cardiovascular and renal diseases. In vitro studies suggest that the biological effects of 2OHE are mediated by 2-methoxyestradiol (2MEOE) after methylation of 2OHE by catechol-O-methyltransferase (COMT). This study tested the hypothesis that in vivo 2OHE is a prodrug of 2MEOE. We administered to male rats i.v. boluses of either 2OHE or 2MEOE and measured plasma levels of 2OHE and 2MEOE by gas chromatography-mass spectrometry at various time points after drug administration. After administration of 2OHE, plasma levels of 2OHE declined extremely rapidly [t(1/2(1)) = 0.94 min and t(1/2(2)) = 10.2 min] becoming undetectable after 45 min. Concomitant with the disappearance of 2OHE, 2MEOE occurred and then declined [t(1/2(1)) = 7.9 min and t(1/2(2)) = 24.9 min]. The peak concentration and total exposure (area under the curve) for 2OHE were much lower than for 2MEOE. 2OHE had a much higher plasma clearance (CL) and volume of distribution (V(d)) compared with 2MEOE (2OHE: CL = 1215 ml min(-1) kg(-1) and V(d) = 17,875 ml/kg; 2MEOE: CL = 50 ml min(-1) kg(-1) and V(d) = 1760 ml/kg). After administration of 2MEOE, plasma levels of 2MEOE declined [t(1/2(1)) = 2.5 min and t(1/2(2)) = 20.2 min] with a plasma CL of 50 ml min(-1) kg(-1) and a V(d) of 1500 ml/kg. We could not detect 2OHE in plasma from rats receiving 2MEOE. We conclude that the conversion of 2OHE to 2MEOE is so efficient that in terms of 2MEOE exposure, administration of 2OHE is bioequivalent to administration of 2MEOE itself.

Neuroprotective and neurotoxic effects of estrogens

The ovarian hormone 17beta-estradiol (E2) is neuroprotective in animal models of neurodegenerative diseases. Some studies suggest that the neuroprotective effects of 17beta-estradiol are a consequence of its antioxidant activity that depend on the hydroxyl group in the C3 position of the A ring. As in other tissues, 17beta-estradiol is metabolized in the brain to 2-hydroxyestradiol (2OHE2) and 2-methoxyestradiol (2MEOHE2). These two molecules present the hydroxyl group in the A ring and have a higher antioxidant activity than 17beta-estradiol. To test the hypothesis that conversion to 2-hydroxyestradiol and 2-methoxyestradiol may mediate neuroprotective actions of 17beta-estradiol in vivo, we have assessed whether these molecules protect hilar hippocampal neurons from kainic acid toxicity. Ovariectomized Wistar rats received an i.p. injection of 1, 10 or 100 microg 17beta-estradiol, 2-hydroxyestradiol or 2-methoxyestradiol followed by an i.p. injection of kainic acid (7 mg/kg) or vehicle. Treatment with kainic acid resulted in a significant loss of hilar neurons. Only the highest dose tested of 17beta-estradiol (100 microg/rat) prevented kainic acid-induced neuronal loss. 2-Hydroxyestradiol and 2-methoxyestradiol did not protect hilar neurons from kainic acid, suggesting that the mechanism of neuroprotection by 17beta-estradiol in vivo is not mediated by its metabolism to catecholestrogens or methoxycatecholestrogens. Furthermore, 2-methoxyestradiol (100 microg/rat), by itself, resulted in a significant neuronal loss in the hilus that was detected 96 h after the treatment with the steroid. This finding suggests that endogenous metabolism of 17beta-estradiol to 2-methoxyestradiol may counterbalance the neuroprotective effects of the hormone.

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.