Modulation of D-3-hydroxybutyrate dehydrogenase activity by estrogens

Liver D-3-hydroxybutyrate dehydrogenase (OHBD) is subjected to estrogen modulation. Estrogen action was demonstrated by (a) the lesser activity of liver OHBD in female rats, as compared with their male counterparts; (b) the increase of OHBD activity after ovariectomy of sexually mature rats; (c) the decrease of OHBD activity after treatment of gonadectomized or normal rats with 17 beta-estradiol or with artificial estrogens; (d) the decrease of OHBD activity in female rats during sexual development; (e) the effects of tamoxifen on the enzyme activity. The kinetics of OHBD reaction using liver mitochondria from estrogen-treated rats showed a 50% decrease of Vmax, as compared with the control value, in contrast to the other parameters which did not vary. These results, taken together with the effect of estrogens on liver mitochondrial phospholipids, point to a decreased content of OHBD in liver mitochondria from estrogen-treated rats. In contrast to OHBD, succinate dehydrogenase and cytochrome oxidase activities, mitochondrial protein synthesis and L-malate + L-glutamate oxidation by coupled liver mitochondria either increased or were not affected by estrogens. Kidney and heart OHBD were affected by ovariectomy and estrogens like the liver enzyme, though to a lesser degree.     

The effect of estrogens on serum ferritin levels in duck

Serum and tissue ferritin content is measured in duck by a RIA method before and after treatment with estrogens, as well as serum ferritin in laying and non-laying hen. Both serum ferritin and tissue ferritin decrease after treatment with estrogens, while serum iron increases. A relationship between serum ferritin and iron stores in duck is shown.     

Production of free estrogens and estrogen conjugates by the preimplantation equine embryo

In vitro production of free estrogens and estrogen conjugates by intact Day 12.5, 13.5 and 14.5 equine embryos was measured at 2-h intervals over a 24-h culture period. Production of free estrogens was higher for Day 14.5 than Day 12.5 embryos. Differences in production of conjugated estrogens were not significant, but a trend toward increased production with increased age of embryo was apparent. No trend toward increased free and conjugated estrogen production per cell was observed with age. Embryo diameter and number of cells increased with age but varied considerably within groups. The amount of free and conjugated estrogens measured in blastocoelic fluid did not decrease over the 24-h culture period, suggesting that estrogens detected in culture medium were produced by the embryo and not the result of leakage of maternal estrogen from the blastocoele. The results of this study support previous results that estrogen production increases with development of equine embryos. This increase in estrogen production appears to be more closely associated with the diameter of the embryo, and hence its number of cells, than with increased intracellular steroidogenic activity.     

Differential interactions of estrogens and antiestrogens at the 17 beta-hydroxy or counterpart function with the estrogen receptor

The action of diethylpyrocarbonate on lamb uterine estrogen receptor produced an homogeneous population of the receptor (approximately 55%) which still bound triarylethylene antiestrogens such as 4-hydroxytamoxifen with a high affinity but bound classical potent estrogens such as estradiol or diethylstilbestrol with a very low affinity. To specify the structural features of the ligands involved in the decrease of ligand affinity upon modification of the estrogen receptor, we determined the relative affinity constants of 17 steroidal estrogens or antiestrogens (deriving from estradiol by a 7 alpha- or 11 beta-substitution) and 14 nonsteroidal estrogens or antiestrogens (all including the 1,2-trans-diphenylethylene structure of diethylstilbestrol) for native and diethylpyrocarbonate-modified estrogen receptors. Then the ratio of the relative affinity constant for the native receptor to that for the modified receptor (rho) was calculated for each ligand, to compare the variation in the affinity of the ligand upon modification of the receptor to that of 4-hydroxytamoxifen (rho = 1). The results showed that the strong decrease of ligand affinity upon modification of the receptor displayed by classical estrogens (rho greater than or equal to 200) is strictly dependent on the presence of the 17 beta-hydroxyl group in steroidal compounds or its alpha-4- and beta-4-counterparts in diethylstilbestrol-related compounds. However, for the 7 alpha- or 11 beta-derivatives of estradiol displaying potent antiestrogenic properties, the relative decrease in affinity was much more limited (rho less than or equal to 19). For 11 beta-derivatives displaying a relative estrogenic activity weaker than that of estradiol itself, an average decrease in affinity was observed (23 less than or equal to rho less than or equal to 62). With the diethylstilbestrol-related compounds, bearing or not the alpha-4-hydroxyl and/or the beta-4-hydroxy functions and showing either weak relative estrogenic or antiestrogenic properties, the relative variation in affinity was weak (0.6 less than or equal to rho less than or equal to 24). These results indicate that the interaction of 7 alpha- or 11 beta-substituted steroidal antiestrogens and of 1,2-trans-diphenylethylene or triphenylethylene derivatives, displaying either weak relative estrogenic or antiestrogenic properties with the receptor, differs at the 17 beta-hydroxy or at the alpha-4-/beta-4-hydroxy functions from that of potent estrogens. They suggest that the strong decrease in the relative affinity of ligands upon receptor modification may reflect the high efficiency of the ligands to activate the receptor properly.(ABSTRACT TRUNCATED AT 400 WORDS)     

Estrogen decreases biglycan mRNA expression in resistance blood vessels

This study was designed to identify new gene targets of estrogen in the mesenteric arteries and to determine whether the soy phytoestrogens could mimic estrogen effects. Ovariectomized rats were treated with estradiol, genistein, or daidzein for 4 days. The mesenteric arteries were harvested, total RNA was extracted, mRNA was reverse transcribed in the presence of [33P]dCTP, and the labeled probes were hybridized with DNA microarrays. Analysis of the microarray data identified biglycan as a target of estrogenic regulation. Semiquantitative RT-PCR was used to confirm and quantitate the decrease in biglycan gene expression in response to estrogen (-37%), genistein (-15%), and daidzein (-10%). Treatment with the pure estrogen receptor antagonist ICI-182,780 reversed the inhibition of biglycan gene expression. The decrease in biglycan gene expression in response to estrogens was paralleled with a decrease in biglycan protein expression. Biglycan protein was localized to the media of the mesenteric arteries by immunohistochemistry. Collectively, these data suggest that biglycan is a vascular protein regulated at the genomic level by estrogens.     

Effect of the administration of estrogen-antiestrogen combinations on the experimental infection of the hamster with Schistosoma mansoni

In the purpose of establishing if the antiestrogens may inhib the protective effects of the estrogens during an experimental infection with Schistosoma mansoni in golden female hamster, we have studied the following estrogen-anti-estrogen associations: 17 beta-estradiol + trans-tamoxifène, 17 beta-estradiol + trans-clomifène, hexestrol + trans-tamoxifène. The decrease of the number of worms in the animals under experiment shows that these associations still give a protective effect. This protection is however weaker than the one which is induced by estrogens administration only. The interpretation of these results agree with the intervention of an estrogen receptor.     

The influence of steroidal and nonsteroidal estrogens on the 5 alpha-reduction of testosterone by the ventral prostate of the rat

The 5 alpha-reduction of testosterone to dihydrotestosterone (DHT) correlates with the androgen-mediated growth of the prostate under different experimental and clinical conditions. The aim was to study the regulation of the prostatic growth and enzyme activity by steroidal and nonsteroidal estrogens. Estrogens did not activate the androgen-dependent 5 alpha-reductase activity in cultured prostate of the rat. The direct inhibition of the enzyme activity by estrogens at the concentrations achievable in the male is not probable either. However, early estrogenization of the male rats in utero (on Day 17 of pregnancy) with diethylstilbestrol (DES) resulted in a persistent decrease of the enzyme activity and growth of the prostate indicating a critical estrogen-sensitive period in the regulation of the ultimate enzyme activity. The similar DES-like inhibitory effect on the growth of the prostate was achieved by keeping animals from fertilization throughout the pregnancy until weaning on diet containing soy, rich in environmental estrogens. Zearalenone (Zeranol) and coumestrol, two nonsteroidal estrogens found in human and animal food mimicked estradiol action in culture, but they were not estrogenic or antiestrogenic when administered to normal adults.     

2-hydroxyestrone induced rise in serum luteinizing hormone in the immature male rat.

Subcutaneous injection of 50 or 100 μg of 2-hydroxyestrone in 35 day old male rats resulted in a dramatic (4–7 fold) rise in serum luteinizing hormone at 6 hours post treatment. Estrone in similar doses (1–200 μg) caused a small decrease in serum luteinizing hormone which was not statistically significant. The discrepancy between the actions of naturally occurring estrogens may be useful in explaining the time and dose related biphasic effects of estrogens on gonadotropin levels.     

Estrogens and menopause: pharmacology of conjugated equine estrogens and their potential role in the prevention of neurodegenerative diseases such as Alzheimer's

Menopause marks the start of a new phase in a woman's life that is associated with a decrease in circulating estrogen levels. Although the average age of women has increased from 50 to nearly 85 years, the average age at menopause has remained essentially constant at 50 years. Thus, women now spend nearly a third of their lives in an estrogen deficient state. This normal aging process in women is associated with increasing health problems such as osteoporosis, cardiovascular disease, neurodegenerative diseases, and cancer. Estrogen replacement therapy (ERT) has been shown to play an important beneficial role in the health and well being of postmenopausal women. Several estrogen preparations are available and among these conjugated equine estrogens (CEE) are most frequently used. The drug CEE, is a complex natural urinary extract of pregnant mare's urine and contains at least 10 estrogens in their sulfate ester form and these are the ring B saturated estrogens: estrone (E(1)), 17beta-estradiol (17beta-E(2)), 17alpha-estradiol (17alpha-E(2)), and the ring B unsaturated estrogens equilin (Eq), 17beta-dihydroequilin (17beta-Eq), 17alpha-dihydroequilin (17alpha-Eq), equilenin (Eqn), 17beta-dihydroequilenin (17beta-Eqn), 17alpha-dihydroequilenin (17alpha-Eqn), and Delta(8)-estrone (Delta(8)-E(1)). All of these estrogens in their unconjugated form are biologically active and can interact with recombinant human estrogen receptor alpha (ERalpha) and beta (ERbeta) with 17beta-estradiol and 17beta-dihydroequilin having the highest affinity for both receptors. A number of the ring B unsaturated estrogens had nearly twofold higher affinity for the ERbeta. The pharmacokinetics of these estrogens in postmenopausal women indicate that the unconjugated estrogens compared to their sulfated forms are cleared more rapidly. The 17-keto estrogens are metabolized to the more potent 17beta-reduced products which are cleared at a slower rate. In postmenopausal women, the extent of 17beta-activation is much higher with the ring B unsaturated estrogens than with ring B saturated estrogens. Oxidized LDL and oxidative stress are thought to contribute to both atherosclerosis and neurodegenerative disorders. Neurons in particular are at a high risk from damage resulting from oxidative stress. In vivo and in vitro studies indicate that the oxidation of LDL isolated from postmenopausal women was inhibited differently by various estrogens and other antioxidants. The unique ring B unsaturated estrogens were the most potent while the red wine component t-resveratrol was the least potent.Studies were designed to explore the cellular and molecular mechanisms that may be involved in the neuroprotective effects of CEE components. The data indicate that the neurotoxic effects of oxidized LDL and glutamate can be inhibited by various estrogens, with the ring B unsaturated estrogens being the most active. These effects are involved in the inhibition of DNA fragmentation and up-regulation of anti-apoptotic protein Bcl-2 and down-regulation of pro-apoptotic protein Bax. These combined data suggest that some of the neuroprotective benefits associated with long-term estrogen therapy may occur by the above mechanism(s). Because estrogens such as the Delta(8)-estrogens are relatively less feminizing than the classical estrogen 17beta-estradiol, they may be important in the development of more neuro-specific estrogens that will be useful in the prevention of neurodegenerative diseases, such as Alzheimer's and Parkinson disease, in both men and women.     

17β-HSD2 inhibitors for the treatment of osteoporosis: Identification of a promising scaffold

17β-Hydroxysteroid dehydrogenase type 2 (17β-HSD2) catalyses the conversion of active 17β-hydroxysteroids into the less active 17-ketosteroids thereby controlling the availability of biologically active estrogens (E2) and androgens (T) in the tissues. The skeletal disease osteoporosis occurs mainly in post-menopausal women and in elderly men when the levels of estrogens and androgens, respectively, decrease. Since 17β-HSD2 is present in osteoblasts, inhibition of this enzyme may provide a new and promising approach to prevent the onset of osteoporosis, keeping a certain level in estrogens and androgens in bone cells of ageing people. Hydroxynaphthyl, hydroxyphenyl and hydroxymethylphenyl-substituted moieties were synthesised as mimetics of the steroidal substrate. Compound 8 has been identified as promising scaffold for 17β-HSD2 inhibitors displaying high activity and good selectivity toward 17β-HSD1, ERα and ERβ.     

Somatomedins and steroids

Somatomedin levels measured by radioreceptor assay, competitive protein-binding assay or radioimmunoassay are normal in hypercortisolism; the decrease of somatomedin activity consistently found in this condition is due to an increase in circulating somatomedin inhibitors resulting in an inhibition of somatomedin action. Progestagens could possibly have a direct stimulatory effect on somatomedin-C (Sm-C) production. During puberty, the increase of Sm-C is correlated with the increase in plasma estradiol and testosterone. In young subjects, relatively low doses of estrogens and of testosterone enhance Sm-C secretion, and in adult menstruating women, a positive relationship is found between testosterone and Sm-C values. An inhibitory effect of estrogens on Sm-C is observed with higher doses and/or in older subjects. Thus, somatomedin levels might be modulated by variations of sex steroids.     

An estrogen replacement therapy containing nine synthetic plant-based conjugated estrogens promotes neuronal survival

Epidemiological data from retrospective and case-control studies have indicated that estrogen replacement therapy can decrease the risk of developing Alzheimer's disease. In addition, estrogen replacement therapy has been found to promote neuronal survival both in vivo and in vitro. We have shown that conjugated equine estrogens (CEE), containing 238 different molecules composed of estrogens, progestins, and androgens, exerted neurotrophic and neuroprotective effects in cultured neurons. In the current study, we sought to determine whether a steroidal formulation of nine synthetic conjugated estrogens (SCE) chemically derived from soybean and yam extracts is as effective as the complex multisteroidal formulation of CEE. Analyses of the neuroprotective efficacy indicate that SCE exhibited significant neuroprotection against beta amyloid, hydrogen peroxide, and glutamate-induced toxicity in cultured hippocampal neurons. Indices of neuroprotection included an increase in neuronal survival, a decrease in neurotoxin-induced lactate dehydrogenase release, and a reduction in neurotoxin-induced apoptotic cell death. Furthermore, SCE was found to attenuate excitotoxic glutamate-induced [Ca2+]i rise. Quantitative analyses indicate that the neuroprotective efficacy of SCE was comparable to that of the multisteroidal CEE formulation. Data derived from these investigations predict that SCE could exert neuroprotective effects comparable to CEE in vivo and therefore could reduce the risk of Alzheimer's disease in postmenopausal women.     

Influence of indole-3-acetic acid,kinetin and abscisic acid on the estrogens content of beans

No influence of IAA on the endogenous estrogen content in bean plants was stated. At the same time kinetin was found to increase and abscisic acid to decrease the amounts of estrogens.     

Bone medullary arterioles from ovariectomized rats have smaller baseline diameters but normal eNOS expression and NO-mediated dilation

This study was designed to test the hypothesis that endogenous estrogens decrease the expression of endothelial nitric oxide synthase (eNOS) in resistance-size bone arterioles, thereby reducing endothelium-dependent vasodilator function. Sexually mature female rats were ovariectomized to reduce endogenous estrogens. Age-matched female rats served as controls. Seven to ten days after ovariectomy, bone marrow tissue was collected from the femoral canal. Immuno-histochemistry was performed to detect expression of estrogen receptors, alpha and beta and eNOS. eNOS protein content in medullary bone arterioles was compared using Western blot analysis. Endothelial cell function was assessed by quantitating the dilation of isolated, pressurized bone arterioles in response to acetylcholine. The results indicate that the endothelium of bone arterioles from ovariectomized and control rats express ER-alpha, ER-beta and eNOS. eNOS protein content in the two groups of arterioles did not differ. However, the baseline diameter of arterioles from ovariectomized rats (63+/-4 microm) was significantly smaller than the diameter of arterioles from control rats (75+/-3 microm, p<0.05). The two groups of arterioles dilated equally in response to acetylcholine. L-NAME, an inhibitor of eNOS, almost completely abolished the dilator responses to acetylcholine, but not to sodium nitroprusside. L-Arginine restored acetylcholine-induced dilation after L-NAME treatment. Thus, arteriole dilation to acetylcholine appears to be mediated almost exclusively by NO. The smaller diameter of arterioles from ovariectomized rats suggests that endogenous estrogens exert a significant dilator influence on bone arterioles. However, the dilator influence does not appear to be mediated by an increase in eNOS expression or enhanced NO-dependent vasodilation. These results indicate that estrogens do not decrease eNOS expression or diminish NO-mediated dilation of bone medullary arterioles.     

Androgen and estrogen treatments alter steady state messengers RNA (mRNA) levels of testicular steroidogenic enzymes in the rainbow trout, Oncorhynchus mykiss

Recent investigations have shown that estrogens have profound inhibitory effects on steroidogenic enzyme gene expressions before and after testicular differentiation in the rainbow trout, Oncorhynchus mykiss. This present study bring new data on juvenile rainbow trout treated with estrogens and androgens. Following a 8 days oral treatment of juvenile male with 17alpha-ethynyl-estradiol (EE2, 20 mg/kg diet) or 11beta-hydroxyandrostenedione (11betaOHDelta4, 10 mg/kg diet), we observed a fast and marked decrease of steady-state mRNA levels for 3betaHSD, P450scc, P450c17, and P450c11 enzymes in the testis. After completion of these treatments, mRNA levels of these enzymes remained low in EE2 treated males whereas in 11betaOHDelta4 treated males they recovered their initial levels in 8 days. This demonstrate that both androgen and estrogen treatments have profound effects on testicular steroidogenesis by decreasing steroid enzymes steady-state mRNA. After in vitro incubation of testicular explants with 17beta-estradiol (E2, 600 ng/ml of medium), we also observed a decrease of mRNA levels for 3betaHSD and P450c11. This suggest that estrogens effects could be triggered, at least to some extend, directly on the testis. We also investigated the hypothesis of a negative feedback of steroids on follicle stimulating hormone (FSH) secretion, but FSH plasmatic levels in treated fish did not showed any significant decrease. This demonstrate that FSH is not implied in this steroids inhibition of steroidogenic enzymes gene expression.     

Structure/function analyses of human sex hormone-binding globulin: effects of zinc on steroid-binding specificity

In humans, sex hormone-binding globulin (SHBG) binds and transports the biologically most important androgens and estrogens in the blood, and regulates the access of these steroids to their targets tissues. In addition to binding sex steroids, SHBG has specific binding sites for divalent cations including calcium and zinc. Zinc binding to a site at the entrance of the steroid-binding pocket in human SHBG has been shown to reduce its affinity for estrogens, while having no impact on the binding of C19 steroids. Crystallographic studies indicate that C18 and C19 steroids are bound in opposite orientations within the SHBG steroid-binding site, and we have obtained new information that supports a molecular model explaining the mechanism by which zinc alters the affinity of human SHBG for estrogens, by studying directly the estradiol-binding properties SHBG variants created by site-directed mutagenesis. In this model, the coordination of a zinc ion by the side chains of residues Asp65 and His136 eliminates a critical hydrogen bond between Asp65 and the hydroxyl at C3 of estrogens, such as estradiol and 2-methoxyestradiol, and causes disorder in a polypeptide loop segment that covers the steroid-binding site. The combination of these structural changes explains the specific decrease in the affinity of human SHBG for C18 steroids in the presence of a zinc ion.     

Comparable amounts of sex steroids are made outside the gonads in men and women: Strong lesson for hormone therapy of prostate and breast cancer

The objective of this study was comparison of circulating androgens and their metabolites as well as estrogens measured for the first time by a validated mass spectrometry technology in 60–80-year-old men and women of comparable age.Castration in men (n = 34) reduces the total androgen pool by only about 60% as indicated by the decrease in the serum levels of the glucuronide metabolites of androgens compared to intact men (n = 1302). Such data are in agreement with the 50 to 75% decrease in intraprostatic dihydrotestosterone (DHT) concentration after castration. Most interestingly, the same amounts of androgens and estrogens are found in postmenopausal women (n = 369) and castrated men of comparable age.The most significant therapeutic implication of these findings is the absolute need to add a pure (nonsteroidal) antiandrogen to castration in men with prostate cancer in order to block the action of the 25 to 50% DHT left in the prostate after castration. Not adding an antiandrogen to castration in men treated for prostate cancer is equivalent to not prescribing a blocker of estrogens in women suffering from breast cancer because they are postmenopausal and have low circulating estradiol.     

Is fetal testis in danger?

Estrogens are classically known to play a major role in female reproduction, but there is now compelling evidence that they may also be involved in the regulation of male reproductive function. In humans, a decrease in sperm count and an increase in the incidences of testicular cancer, cryptorchidism and hypospadia have been observed in many countries over the last 50 years. Male reproductive alterations were also observed in wildlife. Such male reproductive disorders have been attributed to the increase in concentration of xenobiotics, and of xenoestrogens in particular, in the environment and in food. Epidemiological, clinical and experimental studies have suggested that excessive exposure to estrogens during fetal/neonatal life can lead to reproductive disorders in adulthood. Using an in vitro model, we showed that estrogens directly affected the development of the fetal testis. Lastly, we clearly demonstrated that the fetal and neonatal testis is very sensitive to estrogens since the invalidation of estrogen receptor alpha leads to an increase of steroidogenesis and the invalidation of estrogen receptor beta enhances the development of the germ cell lineage in the male.     

Nongenomic effects of estradiol on aggression under short day photoperiods

In several vertebrate species, the effects of estrogens on male aggressive behavior can be modulated by environmental cues. In song sparrows and rodents, estrogens modulate aggression in the nonbreeding season or winter-like short days, respectively. The behavioral effects of estrogens are rapid, which generally is considered indicative of nongenomic processes. The current study further examined the hypothesis that estradiol acts nongenomically under short days by utilizing a protein synthesis inhibitor, cycloheximide (CX). Mice were housed in either short or long day photoperiods, and treated with an aromatase inhibitor. One hour before resident–intruder testing mice were injected with either CX or saline vehicle, and 30 min later were treated orally with either cyclodextrin conjugated estradiol or vehicle. Under short days, mice treated with estradiol showed a rapid decrease in aggressive behavior, independent of CX administration. CX alone had no effect on aggression. These results show that protein synthesis is not required for the rapid effects of estradiol on aggression, strongly suggesting that these effects are mediated by nongenomic processes. We also showed that estradiol suppressed c-fos immunoreactivity in the caudal bed nucleus of the stria terminalis under short days. No effects of estradiol on behavior or c-fos expression were observed in mice housed under long days. Previously we had also demonstrated that cage bedding influenced the directional effects of estrogens on aggression. Here, we show that the phenomenon of rapid action of estradiol on aggression under short days is a robust result that generalizes to different bedding conditions.