17β-Estradiol Protects Against Quinolinic Acid-Induced Lipid Peroxidation in the Rat Brain

The neurotoxin quinolinic acid has been identified as a causative agent in Huntington's disease and is a metabolite of the tryptophan pathway in the brain. In the present study, the in vivo and in vitro effect of 17-estradiol on lipid peroxidation induced by quinolinic acid was investigated. For the in vivo experiments ovariectomized female rats were administered with 100 g 17-estradiol daily for seven days prior to and seven days following the intrahippocampal injection of 1 mol quinolinic acid. The level of lipid peroxidation in brain homogenate was investigated using the thiobarbituric acid test. The in vitro experiments were performed in brain homogenates of ovariectomized female rats. The homogenate was treated with quinolinic acid alone or in combination with 17-estradiol. Quinolinic acid increased lipid peroxidation in a dose dependent manner in vitro, while homogenate co-treated with 17-estradiol showed a significant reduction in lipid peroxidation. 17-estradiol was also shown to be protective against quinolinic acid in vivo. These results could explain the neuroprotective effect of 17-estradiol.     

11β-Hydroxysteroid Dehydrogenase in the Dahl Rat

Dahl salt sensitive (Dahl-S) rats develop hypertension soon after birth. The cause of the increased salt-sensitivity in the Dahl-S rat is unknown. The mineralocorticoid specificity of the kidney receptor is conferred by the activity of 11β-hydroxysteroid dehydrogenase (11β-HSD). There are two isoforms of 11β-HSD (11β-HSD1 and 11β-HSD2). Deficiency or inhibition of 11β-HSD2 causes sodium retention and hypertension. In the present study we measured the activity of hepatic and kidney 11β-HSD1 in Dahl-S and R rats before and after the development of hypertension. The activity of 11β-HSD1 in the liver was lower in the Dahl-S rats at 6 weeks of age (S = 8.01 ± 0.89 v R = 11.91 ± 0.84 nmol/mg protein/10 min (P < .02) but there was no difference at 10 weeks. In contrast, 11β-HSD1 in the kidney was not different at 6 weeks but it was significantly lower in the Dahl-S rats at 10 weeks (S = 0.91 ± 0.04 v R = 1.12 ± 0.01 nmol/mg protein/10 min (P < .001). Plasma renin concentration was lower at 6 (6w) and 10 weeks (10w) in the Dahl-S rats: S-6w = 4.2 ± 0.4 versus R-6W = 6.3 ± 0.8 ng angiotensin I (AI)/mL/h (P < .04) and S-10w = 6.4 ± 0.7 versus R-10w = 10 ± 0.9 ng Al/mL/h (P < .009). Plasma aldosterone and corticosterone were not different between the two strains. Systolic blood pressure (SBP) in the Dahl-S rats was 124 ± 3 mm Hg at 6 weeks and 241 ± 6 mm Hg at 10 weeks (P < .001). SBP in the Dahl-R rats was 113 ± 5 mm Hg at 6 weeks and 143 ± 4 mm Hg at 10 weeks. In conclusion, Dahl-S rats have lower hepatic 11β-HSD1 activity at 6 weeks of age and lower kidney 11β-HSD1 at 10 weeks of age compared with Dahl-R rats of the same age. These findings suggest that diminished activity of both liver and kidney 11β-HSD1 may play a role in the salt sensitivity and development of hypertension in the Dahl-S rat.     

17β-Estradiol Prevents Early-Stage Atherosclerosis in Estrogen Receptor-Alpha Deficient Female Mice

Estrogen is atheroprotective and a high-affinity ligand for both known estrogen receptors, ERα and ERβ. However, the role of the ERα in early-stage atherosclerosis has not been directly investigated and is incompletely understood. ERα-deficient (ERα−/−) and wild-type (ERα+/+) female mice consuming an atherogenic diet were studied concurrent with estrogen replacement to distinguish the actions of 17β-estradiol (E₂) from those of ERα on the development of early atherosclerotic lesions. Mice were ovariectomized and implanted with subcutaneous slow-release pellets designed to deliver 6 or 8 μg/day of exogenous 17β-estradiol (E₂) for a period of up to 4 months. Ovariectomized mice (OVX) with placebo pellets (E₂-deficient controls) were compared to mice with endogenous E₂ (intact ovaries) and exogenous E₂. Aortas were analyzed for lesion area, number, and distribution. Lipid and hormone levels were also determined. Compared to OVX, early lesion development was significantly (p < 0.001) attenuated by E₂ with 55–64% reduction in lesion area by endogenous E₂ and >90% reduction by exogenous E₂. Compared to OVX, a decline in lesion number (2- to 4-fold) and lesser predilection (~4-fold) of lesion formation in the proximal aorta also occurred with E₂. Lesion size, development, number, and distribution inversely correlated with circulating plasma E₂ levels. However, atheroprotection was independent of ERα status, and E₂ athero-protection in both genotypes was not explained by changes in plasma lipid levels (total cholesterol, triglyceride, and high-density lipoprotein cholesterol). The ERα is not essential for endogenous/exogenous E₂-mediated protection against early-stage atherosclerosis. These observations have potentially significant implications for understanding the molecular and cellular mechanisms and timing of estrogen action in different estrogen receptor (ER) deletion murine models of atherosclerosis, as well as implications to human studies of ER polymorphisms and lipid metabolism. Our findings may contribute to future improved clinical decision-making concerning the use of hormone therapy.     

17β-Estradiol administration attenuates seawater aspiration-induced acute lung injury in rats

There is very little evidence on the value of administering estrogen in cases of seawater drowning which can induce acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Therefore, this study aimed to investigate whether 17β-estradiol (E2) treatment can attenuate seawater aspiration-induced ALI in rats. In the experiment, ALI was induced by endotracheal instillation of seawater (4 mL/kg) and the rats were then given intraperitoneal injection of E2 (5 mg/kg) 20 min after seawater instillation. Finally, the changes of arterial blood gases which contained hydrogen ion concentration (pH), arterial oxygen tension (PaO₂) and arterial carbon dioxide tension (PaCO₂) were measured and the measurement of extravascular lung water (EVLW) was observed. The pulmonary histological changes were evaluated by hematoxylin–eosin stain. The expression of aquaporins (AQPs) 1, AQP5, and estrogen receptor-β (ERβ) was measured by western blotting and immunohistochemical methods. The results showed that compared with normal saline water, seawater aspiration induced more serious ALI in rats which was markedly alleviated by E2 treatment. Meanwhile, the ERβ in lung tissues was activated after E2 administration. The seawater aspiration group also presented with severe pulmonary edema which was paralleled with over expressed AQP1 and AQP5. However, the up-regulation of AQP1 and AQP5 was suppressed by the administration of E2, resulting in an attenuation of lung edema. In conclusion, E2 treatment could effectively attenuate seawater aspiration-induced acute lung injury in rats by the down-regulation of AQP1 and AQP5.     

α-Melanocyte-Stimulating Hormone Gene Transfer Attenuates Inflammation after Bile Duct Ligation in the Rat

Cholestasis occurs in a wide variety of human liver diseases, and hepatocellular injury is an invariant feature of cholestasis causing liver dysfunction and inflammation, promoting fibrogenesis, and ultimately leading to liver failure. α-Melanocyte-stimulating hormone (α-MSH) is a potent anti-inflammatory agent in many models of inflammation, suggesting that it inhibits a critical step common to different forms of inflammation. The aim of this study was to investigate whether the gene transfer of α-MSH could attenuate hepatic inflammation after bile duct ligation in the rat. Studies were performed in bile duct-ligated (BDL) rats. Hydrodynamic-based gene transfection with α-MSH plasmid via rapid tail vein injection was performed 30 min after ligation of bile duct. The endpoints were studied as markers of inflammation 7 days after bile duct ligation. α-MSH expression in liver via a single administration of naked plasmid was demonstrated. Liver inflammation index, including neutrophil infiltration and serum alanine aminotransferase, were significantly reduced in α-MSH gene transfer rats. Markers for liver inflammation, including expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and inducible NO synthase (iNOS) mRNA, as assessed by real-time PCR, were also attenuated by α-MSH gene therapy. Expression of iNOS protein in liver diminished after α-MSH gene transfer. Consistent with these data, hepatic stellate cells (HSC) and Kupffer cells were markedly inhibited in α-MSH gene-treated rats. Our findings show that gene transfer of α-MSH could attenuate hepatic inflammation after bile duct ligation in the rat.     

17β-Estradiol is critical for the preovulatory induction of prostaglandin E(2) synthesis in mice

Aromatase-deficient (ArKO) mice are totally anovulatory due to insufficient estrogen production. However, sequential administrations of high doses of 17β-estradiol (E2) and gonadotropins were found to induce ovulation in these mice. Here, we examined how the ovulatory stimulation for ArKO mice alters the expressions of genes related to prostaglandin (PG) E(2) metabolism and ovarian contents of PGE(2), as PGE(2) is one of the critical mediators of ovulatory induction. The ovulatory stimulation significantly increased mRNA expressions of prostaglandin-endoperoxide synthase 2, PGE(2) receptor type 4 and sulfotransferase family 1E, member 1, in preovulatory ArKO ovaries. In contrast, it suppressed the mRNA expression of 15-hydroxyprostaglandin dehydrogenase. Furthermore, significant elevation in the PGE(2) contents was detected in the preovulatory ovaries of ArKO mice after stimulation with E2 plus ovulatory doses of gonadotropins. Thus, these analyses demonstrate a requirement of E2 for the preovulatory enhancement of PGE(2) synthesis, leading to future success in ovulation.     

Rapamycin Attenuates Pulmonary Allergic Vasculitis in Murine Model by Reducing TGF-βProduction in the Lung

Background: Rapamycin has been reported to inhibit mesenchymal cell proliferation in a murine model of pulmonary fibrosis. In the present study, we examined the effects of rapamycin on vascular remodeling including intraluminal myofibroblast proliferation in a murine model of allergic vasculitis with eosinophil infiltration.Methods: C57BL/6 mice were sensitized with ovalbumin (OVA) and alum. The positive controls were exposed to aerosolized OVA daily for 7 days. The other group of mice was administered with rapamycin (1 mg/ kg) intraperitoneally, in parallel with daily exposure to aerosolized OVA for 7 days. On the 3rd and 7th day, bron- choalveolar lavage (BAL) was performed and the lungs were excised for pathological analysis. Cell differentials were determined and concentrations of IL-4, IL-5, IL-13 and TGF-β in the BAL fluid (BALF) were measured. Semi-quantitative analysis of pathological changes in the pulmonary arteries was evaluated according to the severity of vasculitis.Results: The number of eosinophils in BALF was reduced significantly in the mice treated with rapamycin compared to the positive control. There was a significant decrease in the TGF-β concentration of the BALF in the rapamycin-treated group compared to that of the positive control. The pathological scores were reduced significantly in the rapamycin-treated group compared to the positive control group. Intraluminal myofibroblasts in pulmonary arteries were reduced dramatically in the rapamycin-treated group compared to the positive control group.Conclusions: Rapamycin suppressed pulmonary vascular remodeling in a murine model of allergic vasculitis with eosinophil infiltration through reducing eosinophil infiltration and TGF-β production in the lung and inhibition against biological action of TGF-β.     

Hepatoprotective Effect of 17β-Estradiol as Antioxidant Modulators Against Stress Damage

Background:

Liver is one of the most important organs affected by exercise. According to the literature a few study to date has investigated the effects of estrogen supplementation on exercise-induced oxidative stress in liver tissue of rats.

Objectives:

We aimed to investigate the effects of estrogen supplementation on oxidative stress markers in liver tissue of exercised rats.

Materials and Methods:

Male rats (n = 35) were divided as estrogen supplemented (n = 18) and non-supplemented groups (n = 17); these groups were further divided as rest and eccentric exercised groups. Eccentric exercise groups were further divided as rats killed after 1 hour and 48 hours of eccentric exercise. Estrogen (10 mg/kg) was administered subcutaneously for 30 days. Eccentric exercise was applied as treadmill run (15° downhill, 20 m/min) consisting of periods of "5 min" run and 2 min rest repeated 18 times. The rat liver was examined biochemically and histologically. Activities of GST, GSH-Px, CAT, SOD and MDA concentration were also measured spectrophotometrically.

Results:

Some disruptions were detected in experimental groups compared with the control group. Additionally, exercise training caused an increase in SOD and decrease in GSH-Px activities in some experimental groups. SOD activities increased significantly in group 3 (Estrogen (-), eccentric exercise (+) killed (after 1 h), compared with group 5 (Estrogen (-), eccentric exercise (+) killed (after 48 h). On the other hand, GSH-Px activities were also significantly decreased in groups 3, 4 and 5 compared with the control group. Leukocyte infiltration in liver increased after 48 hours compared with after 1 hour and estrogen supplementation was not able to prevent this infiltration.

Conclusions:

Estrogen seemed to be not very effective to prevent eccentric exercise-induced liver damage.     

17-β-Estradiol increases neuronal excitability through MAP kinase-induced calpain activation

17-β-Estradiol (E2) is a steroid hormone involved in numerous brain functions. E2 regulates synaptic plasticity in part by enhancing NMDA receptor function and spine density in the hippocampus, resulting in increased long-term potentiation and facilitation of learning and memory. As the calcium-dependent neutral protease, calpain, is also involved in these processes, we tested whether E2 could activate calpain and examined the functional consequences of E2-mediated calpain activation in hippocampus. Calpain activity was analyzed by a fluorescence resonance energy transfer (FRET)-based assay that allows both quantitative determination and spatial resolution. E2 rapidly activated calpain in cultured cortical and hippocampal neurons, prominently in dendrites and dendritic spines. E2-induced calpain activation was mediated through mitogen-activated protein kinase (MAPK), as it was completely blocked by MEK inhibitors. It was also calcium-independent, as it was still evident in presence of the calcium chelator, BAPTA-AM. Activation of ERα and ERβ receptors by specific agonists stimulated calpain activity. Finally, the rapid E2-mediated increase in excitability in acute hippocampal slices was prevented by a membrane-permeable calpain inhibitor. Furthermore, E2 treatment of acute hippocampal slices resulted in increased actin polymerization and membrane levels of GluR1 but not GluR2/3 subunits of AMPA receptors; both effects were also blocked by a calpain inhibitor. Our results indicate that E2 rapidly stimulates calpain activity through MAP kinase-mediated phosphorylation, resulting in increased membrane levels of AMPA receptors. These effects could be responsible for E2-mediated increase in neuronal excitability and facilitation of cognitive processes.     

Hormonal Modulation of Hepatic cAMP Prevents Estradiol 17β-d-Glucuronide-Induced Cholestasis in Perfused Rat Liver

Background

Estradiol-17β-d-glucuronide (E17G) induces cholestasis in vivo, endocytic internalization of the canalicular transporters multidrug resistance-associated protein 2 (Abcc2) and bile salt export pump (Abcb11) being a key pathomechanism. Cyclic AMP (cAMP) prevents cholestasis by targeting these transporters back to the canalicular membrane. In hepatocyte couplets, glucagon and salbutamol, both of which increase cAMP, prevented E17G action by stimulating the trafficking of these transporters by different mechanisms, namely: glucagon activates a protein kinase A-dependent pathway, whereas salbutamol activates an exchange-protein activated by cAMP (Epac)-mediated, microtubule-dependent pathway.

Methods

The present study evaluated whether glucagon and salbutamol prevent E17G-induced cholestasis in a more physiological model, i.e., the perfused rat liver (PRL). Additionally, the preventive effect of in vivo alanine administration, which induces pancreatic glucagon secretion, was evaluated.

Results

In PRLs, glucagon and salbutamol prevented E17G-induced decrease in both bile flow and the secretory activity of Abcc2 and Abcb11. Salbutamol prevention fully depended on microtubule integrity. On the other hand, glucagon prevention was microtubule-independent only at early time periods after E17G administration, but it was ultimately affected by the microtubule disrupter colchicine. Cholestasis was associated with endocytic internalization of Abcb11 and Abcc2, the intracellular carriers being partially colocalized with the endosomal marker Rab11a. This effect was completely prevented by salbutamol, whereas some transporter-containing vesicles remained colocalized with Rab11a after glucagon treatment. In vivo, alanine administration increased hepatic cAMP and accelerated the recovery of bile flow and Abcb11/Abcc2 transport function after E17G administration. The initial recovery afforded by alanine was microtubule-independent, but microtubule integrity was required to sustain this protective effect.

Conclusion

We conclude that modulation of cAMP levels either by direct administration of cAMP modulators or by physiological manipulations leadings to hormone-mediated increase of cAMP levels (alanine administration), prevents estrogen-induced cholestasis in models with preserved liver architecture, through mechanisms similar to those arisen from in vitro studies.     

17β-Estradiol stimulates the translocation of endogenous estrogen receptor α at the plasma membrane of normal anterior pituitary cells

In the present work we aimed at identifying ERα in the plasma membrane of normal anterior pituitary cells and investigated if 17β-estradiol was able to induce their subcellular redistribution. Our results show that about 8% of anterior pituitary cells expressed ERα in the plasma membrane, with the geometrical mean fluorescence intensity being increased after steroid hormone treatment. 17β-Estradiol and the selective ERα agonist PPT induced an increase of ERα expression in the plasma membrane and activated the PKCα/ERK 1/2 pathway in a time-course not compatible with genomic actions, thus supporting the notion of membrane-initiated effects. These findings suggest that 17β-estradiol stimulates the translocation of endogenous ERα to the plasma membrane, consequently modulating this ER pool and leading to cellular biological effects in normal anterior pituitary gland.     

Long-Term Cardiovascular Effects of High “Osteoprotective” Dose Levels of 17β-Estradiol in Spontaneously Hypertensive Rats

The effects of estrogen replacement therapy in menopausal women are more obvious on bones than on the cardiovascular system. The optimal estrogen dosage may differ in these different parts of the body. In hypertensive rats, low doses have been shown to reduce arterial collagen and stiffness, whereas higher dosages are required for osteoprotection. From 4 to 20 weeks of age, female spontaneously hypertensive rats (SHRs) were divided into four groups: without ovariectomy, under placebo or 17-estradiol (10 g/kg/day), and with ovariectomy under either placebo or 17-estradiol (same dosage). Serial tail systolic blood pressure measurements were performed, and histomorphometry of the thoracic aorta was determined at the end of the study. Under estrogen, blood pressure was unchanged, whereas the aortic wall–to–lumen ratio was increased, particularly in the presence of ovariectomy. The elastin to collagen ratio was significantly decreased, due both to a decrease in elastin and an increase in collagen density, with no change in media thickness. The latter findings were not observed when ovariectomy was performed. Independent of changes in wall stress, high-dose estrogen increases the aortic extracellular matrix in female SHRs. This increase may be reversed in the presence of ovariectomy, suggesting that estrogen was not the only gonadal factor responsible for altered vascular structure and function.     

17β-Estradiol regulates cyclin A1 and cyclin B1 gene expression in adult rat seminiferous tubules

Spermatogenesis, which is the fundamental mechanism allowing male gamete production, is controlled by several factors, and among them, estrogens are likely concerned. In order to enlighten the potential role of estrogen in rat spermatogenesis, seminiferous tubules (ST) from two groups of seminiferous epithelium stages (II-VIII and IX-I) were treated with either 17β-estradiol (E(2)) agonists or antagonists for estrogen receptors (ESRs). In this study, we show that cyclin A1 and cyclin B1 gene expression is controlled by E(2) at a concentration of 10(-9)?M only in stages IX-I. This effect is mimicked by a treatment with the G-protein coupled estrogen receptor (GPER) agonist G1 and is abolished by treatment with the ESR antagonist ICI 182?780. Moreover, using letrozole, a drug that blocks estrogen synthesis, we demonstrate that these genes are under the control of E(2) within rat ST. Thus, germ cell differentiation may be regulated by E(2) which acts through ESRs and GPER, expressed in adult rat ST.