Progesterone down-regulation of nuclear estrogen receptor: a fundamental mechanism in birds and mammals

Combined Effects of ESRα DNA Methylation and Progesterone on Glucose Metabolic Disorders: The Henan Rural Cohort Study

To explore the independent and combined effects of ESRα methylation and progesterone on impaired fasting glucose (IFG) and type 2 diabetes mellitus (T2DM), a case-control study including 901 subjects was conducted. Generalized linear models were performed to assess the independent and combined effects of ESRα methylation and progesterone on IFG or T2DM. Methylation level of cytosine-phosphoguanine (CpG) 1 in the estrogen receptor α (ESRα) gene was positively related to IFG in both men (odds ratio (OR) (95% confidence interval (CI)): 1.77 (1.05, 3.00)) and postmenopausal women (OR (95% CI): 1.82 (1.09, 3.04)), whereas the association between CpG 1 and T2DM was not significant. Positive associations of progesterone with IFG and T2DM were observed in both men (OR (95% CI): 2.03 (1.18, 3.49) and 3.00 (1.63, 5.52)) and postmenopausal women (OR (95% CI): 2.13 (1.27, 3.56) and 3.30 (1.85, 5.90)). Participants with high CpG 1 methylation plus high progesterone had an increased risk of IFG and T2DM, both in men and postmenopausal women. ESRα methylation and progesterone were positively associated with IFG, and the positive association between progesterone and T2DM was also found. Importantly, we firstly found the combined effects of ESRα methylation and progesterone on IFG and T2DM.

Hormone ratios suffer from striking lack of robustness to measurement error

Hormone ratios are often used to capture the joint effect (or "balance") of two hormones with opposing or mutually suppressive effects. Despite some statistical and interpretative problems, hormone ratios are being increasingly used to examine associations of testosterone/cortisol, estradiol/progesterone, testosterone/estradiol, and other hormone pairs. Here we discuss a methodological problem that has not been previously recognized, namely, the striking lack of robustness of raw hormone ratios in the face of measurement error. Hormone levels are measured with error, both due to inability of assays to perfectly assess concentrations "in the tube" and due to discrepancies between levels at the time of sample collection and effective levels that produce the physiological and/or behavioral effect of interest. Noise in measured hormone levels can be substantially exaggerated by ratios, especially when the distribution of the hormone at the denominator is positively skewed, as is frequently observed. To evaluate the extent of this problem and explore the conditions that exacerbate it, we present two sets of simulations, one using idealized distributions and one using empirically observed distributions from studies of estrogen and progesterone. Results show that the validity of raw hormone ratios-the correlation between measured levels and underlying effective levels-drops rapidly in the presence of realistic levels of measurement error. Log-ratios are much more robust to measurement error, and their validity is more stable across samples; under some conditions (e.g., moderate amounts of noise with positively correlated hormone levels), they may provide a more valid measurement of the underlying raw ratio than the measured raw ratio itself. These findings have important implications for research that uses hormone ratios as predictors.

Testosterone and estradiol affect adolescent reinforcement learning

During adolescence, gonadal hormones influence brain maturation and behavior. The impact of 17β-estradiol and testosterone on reinforcement learning was previously investigated in adults, but studies with adolescents are rare. We tested 89 German male and female adolescents (mean age ± sd = 14.7 ± 1.9 years) to determine the extent 17β-estradiol and testosterone influenced reinforcement learning capacity in a response time adjustment task. Our data showed, that 17β-estradiol correlated with an enhanced ability to speed up responses for reward in both sexes, while the ability to wait for higher reward correlated with testosterone primary in males. This suggests that individual differences in reinforcement learning may be associated with variations in these hormones during adolescence, which may shift the balance between a more reward- and an avoidance-oriented learning style.

Danazol alters mitochondria metabolism of fibrocystic breast Mcf10A cells

Fibrocystic Breast Disease (FBD) or Fibrocystic change (FC) affects about 60% of women at some time during their life. Although usually benign, it is often associated with pain and tenderness (mastalgia). The synthetic steroid danazol has been shown to be effective in reducing the pain associated with FBD, but the cellular and molecular mechanisms for its action have not been elucidated. We investigated the hypothesis that danazol acts by affecting energy metabolism. Effects of danazol on Mcf10A cells homeostasis, including mechanisms of oxidative phosphorylation, cytosolic calcium signaling and oxidative stress, were assessed by high-resolution respirometry and flow cytometry. In addition to fast physiological responses the associated genomic modulations were evaluated by Affimetrix microarray analysis. The alterations of mitochondria membrane potential and respiratory activity, downregulation of energy metabolism transcripts result in suppression of energy homeostasis and arrest of Mcf10A cells growth. The data obtained in this study impacts the recognition of direct control of mitochondria by cellular mechanisms associated with altered energy metabolism genes governing the breast tissue susceptibility and response to medication by danazol.

Role of G protein-coupled estrogen receptor 1, GPER, in inhibition of oocyte maturation by endogenous estrogens in zebrafish

Estrogen inhibition of oocyte maturation (OM) and the role of GPER (formerly known as GPR30) were investigated in zebrafish. Estradiol-17beta (E2) and G-1, a GPER-selective agonist, bound to zebrafish oocyte membranes suggesting the presence of GPER which was confirmed by immunocytochemistry using a specific GPER antibody. Incubation of follicle-enclosed oocytes with an aromatase inhibitor, ATD, and enzymatic and manual removal of the ovarian follicle cell layers significantly increased spontaneous OM which was partially reversed by co-treatment with either 100 nM E2 or G-1. Incubation of denuded oocytes with the GPER antibody blocked the inhibitory effects of estrogens on OM, whereas microinjection of estrogen receptor alpha (ERalpha) antisense oligonucleotides into the oocytes was ineffective. The results suggest that endogenous estrogens produced by the follicle cells inhibit or delay spontaneous maturation of zebrafish oocytes and that this estrogen action is mediated through GPER. Treatment with E2 and G-1 also attenuated the stimulatory effect of the teleost maturation-inducing steroid, 17,20beta-dihyroxy-4-pregnen-3-one (DHP), on OM. Moreover, E2 and G-1 down-regulated the expression of membrane progestin receptor alpha (mPRalpha), the intermediary in DHP induction of OM. Conversely DHP treatment caused a >50% decline in GPER mRNA levels. The results suggest that estrogens and GPER are critical components of the endocrine system controlling the onset of OM in zebrafish. A model is proposed for the dual control of the onset of oocyte maturation in teleosts by estrogens and progestins acting through GPER and mPRalpha, respectively, at different stages of oocyte development.

Effect of gonadal steroids on progesterone receptor, estrogen receptor, and vitellogenin expression in male turtles (Chrysemys picta)

Hepatic vitellogenin (vtg) is a yolk precursor protein sequestered in follicular oocytes as nutrient supply for developing embryos in nonmammalian vertebrates. In prior research studies we have demonstrated that both progesterone (P) and testosterone (T) inhibit estrogen (E)-induced vitellogenesis in the male fresh water turtle (Chrysemys picta), and have suggested that these hormones may be involved in multihormonal regulation of vitellogenesis in the female turtle. However, the modes of action of progesterone and testosterone on estrogen-induced vitellogenesis are not known. We have proposed that progesterone inhibits vitellogenesis by modulation of progesterone receptor A (PRA) or B (PRB) isoforms and/or estrogen receptor (ER) gene transcription. In this study, we compare the vitellogenic responses of reproductively inactive male turtles to estradiol 17beta in the presence of exogenous testosterone or progesterone. Northern blot analysis was used to monitor the changes in vtg mRNA, ER mRNA, and PR mRNA expression; Western blotting to determine changes in PR isoform expression and a homologous ELISA for measurement of plasma vtg. Progesterone and testosterone reduced estrogen-induced vtg mRNA expression, but plasma vtg was not significantly reduced by these steroids. PRA and PRB were transcribed even though ER mRNA could not be detected, suggesting constitutive PR expression. However, in the presence of estradiol 17beta, both PR isoforms and mRNA transcripts were increased as a correlate of ER mRNA transcription, suggesting both transcriptional and translational effects; these effects were inhibited by testosterone and progesterone treatments. Since ER mRNA was sharply reduced by both testosterone and progesterone, and estradiol 17 beta increased PR mRNA transcription and translation, it is likely that the action of progesterone in reducing vtg mRNA is indirect via down regulation of ER mRNA, thus ER. This study provides further information on the role of progesterone and testosterone in the regulation of hepatic vitellogenesis, suggesting regulation of vitellogenesis mainly via modulation of hepatic ER mRNA.

Seasonal changes in hepatic progesterone receptor mRNA, estrogen receptor mRNA, and vitellogenin mRNA in the painted turtle, Chrysemys picta

Previous studies using the fresh water turtle Chrysemys picta have demonstrated that progesterone (P) inhibits estradiol (E)-induced vitellogenin (vtg) secretion in this species. Further, there is evidence for the differential expression of the two P receptor isoforms (PRA and PRB) in the liver during the turtle seasonal cycle, correlating with hepatic vitellogenesis. In this study we report changes in the hepatic PR mPNA, ER mRNA, and vitellogenin (vtg) mRNA transcripts during the reproductive cycle of the turtle. Fragments of the turtle hepatic PR and ER cDNAs were cloned and sequenced and a previously cloned turtle vtg cDNA were used as probes in Northern blotting. No 3.7-kb PR mRNA, corresponding to the smaller PR transcript, PRA of other species was found, although, a smaller 1.8-kb transcript (putative PRC mRNA) was present. These observations suggest that the turtle as in the chicken and human, the 4.5-kb PR mRNA transcript encodes both PRA and PRB proteins. Only the larger PR mRNA transcript (4.5-kb), was found to vary significantly during the annual cycle, being highest when vitellogenesis was inhibited in winter and summer. Vtg mRNA could not be detected during the summer or winter, was highest during vitellogenesis in the spring, and reappeared during the fall period of vitellogenesis and ovarian recrudescence. ER mRNA followed a similar pattern, being highest during spring and early fall, when vtg synthesis is high. The data suggest that P/PR, as well as E/ER, may be involved in the seasonal regulation of hepatic vitellogenesis in this species.

Distribution of sex steroid hormone receptors in the avian brain: functional implications for neural sex differences and sexual behaviors

Developmental and seasonal changes in the production of androgens, estrogens, and progestins seem to control sex-specific differentiation and seasonal changes in appetitive and consummatory sexual behaviors of birds. This results in profound sex differences in the quality (sex-specific) or quantity (sex-typical) of behaviors such as courtship, territoriality, or copulation. Steroids affect the brain by binding to intracellularly located receptors. The same brain areas express androgen, estrogen, and progesterone receptors in male and female brains. Sex differences in these genetically determined patterns occur in the size of neuron populations that intrinsically express sex steroid receptors. Further permanent sex differences are subsequent to degenerative fates of receptor expressing neuron populations during ontogeny. Transient sex differences in receptor expression appear to be due to area-specific up- and down-regulation of receptor levels, reflecting transient changes in the level of circulating steroids, changes in environmental conditions, or in the physiological status of the individuals. In particular, intrinsic sex differences in the expression pattern of sex steroid receptors and steroid-independent regulation of the expression level of these receptors in the brain are limiting mechanisms for gonad-dependent sexual development and activities.

Progesterone inhibits female courtship behavior in domestic canaries (Serinus canaria)

We studied copulation solicitation display (CSD) responses to playback in photostimulated female canaries given systemic injections of progesterone. Eight females received injections of 0.1 mg of progesterone dissolved in olive oil during their first breeding cycle and were untreated during their second breeding cycle; eight females received only the oil vehicle during their first breeding cycle and received no treatment during their second breeding cycle. The injections were performed every second day during 15 days, after the onset of nest building. Progesterone treatment resulted in a significant increase of plasma progesterone which in turn provoked an inhibition of females' CSDs and decreased the size of the clutch. During the first breeding cycle, progesterone-treated females had lower CSDs and egg-laying scores than did control females. During the second breeding cycle, when females received no treatment, no differences emerged between the two groups. The suppressive effect of progesterone on female sexual responses was observed as soon as 48 h after the beginning of the treatment. We propose that progesterone plays a key role in mediating the transition from active female courtship behavior to sexual refractoriness in this species. Suppressive effects of progesterone on female sexual behavior have been previously described in lizards as well as in rodents. Our data are consistent with the hypothesis of Godwin et al. (J. Godwin, V. Hartman, M. Grammer, and D. Crews, Horm. Behav. 30, 138-144, 1996) which proposed that the decrease in sexual behavior following plasma progesterone increase represents an evolutionarily conserved mechanism in the regulation of female sexual behavior.

Intrahypothalamic implantation of progesterone in castrated male whiptail lizards (Cnemidophorus inornatus) elicits courtship and copulatory behavior and affects androgen receptor- and progesterone receptor-mRNA expression in the brain

A primary tenet of behavioral neuroendocrinology is that gonadal steroid hormones act on limbic nuclei to activate mating behavior in vertebrates. Traditionally, research has focused on the regulation of male-typical sexual behavior by testicular androgens and female-typical sexual behavior by ovarian estrogen and progesterone. Indeed, progesterone generally is regarded as an antiandrogen, acting centrally to inhibit sexual behavior in males. However, experiments with lizards, and more recently with rats, have challenged this paradigm. For example, exogenous progesterone induces mating behavior in some, but not all, castrated male whiptail lizards. The present study determined that implantation of progesterone into the anterior hypothalamus preoptic area of castrated, progesterone-sensitive males completely restored sexual behavior but failed to elicit sexual activity in castrated, progesterone-insensitive males. Further, androgen receptor -and progesterone receptor-mRNA expression in specific brain regions was significantly different in progesterone-sensitive versus progesterone-insensitive animals. Progesterone-sensitive males showed significantly higher relative abundance of androgen receptor-mRNA in the preoptic area, amygdala, and lateral septum, as compared with progesterone-insensitive animals receiving the same treatment. In contrast, progesterone receptor-mRNA abundance was lower in preoptic area of progesterone-sensitive males than in progesterone-insensitive males. No differences were found in the baseline abundance of androgen receptor-or progesterone receptor-mRNA in these nuclei between control groups of progesterone-sensitive and progesterone-insensitive males who were castrated but not implanted. This suggests that progesterone differentially regulates its own receptor as well as androgen receptor in areas of the brain involved in the control of sexual behavior of males and that the nature of this regulation shows individual variability.

Changes in oestrogen, progesterone and epidermal growth factor receptor concentrations and affinities during the oestrous cycle in the normal mammary gland and uterus of dogs

Changes in the concentrations and affinities of receptors for oestrogen (ER), progesterone (PR) and epidermal growth factor (EGF-R) were studied in mammary glands of healthy bitches with regard to age, the location in the mammary chain and the stage of the oestrous cycle. Uterus was used as the reference tissue for the evaluation of steroid receptors. Mammary and uterine samples from 7 healthy bitches were taken at five stages of the oestrous cycle in such a way that all the locations in the mammary chain were represented at each stage of the cycle (10 samples/dog). ER, PR and EGF-R were detected by biochemical assays using increasing concentrations of tritiated (steroids) or iodinated (EGF) ligands. A significant direct correlation was found between the ER and PR concentrations for mammary and uterine samples. No significant correlation was found between the steroid receptors and EGF-R concentrations. Mammary ER concentrations were significantly higher in bitches of 5 years of age or older than in younger ones; in posterior glands (4th and 5th pairs) than in anterior glands; and in the mid-luteal phase. Mammary PR did not vary significantly with age or location but was significantly lower in the early luteal phase than in other phases. A similar decrease in PR concentrations was observed in the uterus during the early luteal phase and uterine ER and PR concentrations were very low in the mid-luteal phase. Mammary EGF-R were not significantly higher in the early or mid-luteal phase than in pro-oestrus or anoestrus. The differences observed between the uterine and mammary steroid receptor concentrations during the oestrous cycle could be due to different mechanisms for regulating steroid receptor expression in the two tissues. Mammary EGF-R concentrations may be linked, as in other species, to cellular proliferation and/or to the serum progesterone concentrations.

Progesterone downregulates progesterone receptor, but not estrogen receptor, in the estrogen-primed oviduct of a turtle (Trachemys scripta)

Progesterone downregulates nuclear progesterone receptor (Rp) and estrogen receptor (Re) in the estrogen-primed mammalian uterus and chick oviduct. We sought to determine if this downregulation mechanism is operative in the turtle oviduct. Female turtles were primed for 4 days with 17-beta-estradiol, after which progesterone (5 mg) was administered by injection every 24 h. Re and Rp levels in progesterone-treated and control turtle oviducts were measured by [3H]steroid-binding assays (pyridoxal 5' phosphate method) at 12, 24, 48 and 72 hr after initial progesterone treatment. Serum progesterone levels of progesterone-treated turtles increased only slightly from 0 hr (0.3 ng/ml) to 12 hr (0.6 ng/ml) after progesterone administration, increased considerably by 24 hr (5.3 ng/ml), and remained elevated (6-8 ng/ml) through 72 hr. Cytosol and nuclear Rp levels of estrogen-primed turtle oviducts showed distinct seasonal variation, with Rp levels higher in spring and summer months than in winter months. There was no seasonal variation in Re levels. Both cytosol and nuclear Rp responded to progesterone treatment. Cytosol Rp levels of progesterone-treated oviducts were significantly reduced below control levels by 12 hr after progesterone administration and remained low through 72 hr. Nuclear Rp levels of progesterone-treated oviducts showed no change at 12 hr, increased at 24 hr and then dropped at 48 and 72 hr. However, progesterone did not downregulate Re in the turtle oviduct.(ABSTRACT TRUNCATED AT 250 WORDS)