Estrogen suppresses retinaldehyde dehydrogenase 1 expression in the anterior pituitary glands of female rats

Retinoic acid (RA) plays a critical role in cell growth and tissue development. RA is also a regulating factor of pituitary function. RA is synthesized from retinoids through oxidation processes. The oxidation of retinal to RA is catalyzed by the retinaldehyde dehydrogenases (RALDHs), including RALDH1, RALDH2 and RALDH3. Recently, we demonstrated that RALDH1 is expressed in the anterior pituitary glands of adult male rats. However, the expression of RALDH1 in the female pituitary gland and the regulation of RALDH1 expression have not been determined. Therefore, we examined the expression of RALDH1 mRNA in the pituitary glands of adult female rats. By in situ hybridization with digoxigenin-labeled cRNA probes and quantitative real-time PCR analysis, we found that the expression level of RALDH1 was significantly lower in estrus as compared to proestrus, metestrus and diestrus. RALDH1 mRNA levels increased after ovariectomy and decreased remarkably after a 1-week treatment with 17beta-estradiol implants. Estradiol (0.01-100 microg per rat) dose-dependently decreased the expression of RALDH1 in the pituitary glands after 24 hours of subcutaneous administration. These results clearly show that RALDH1 mRNA expression is suppressed by estrogen. We speculate that the generation of RA is regulated by estrogen and that RA plays a role in the estrus cycle through paracrine and/or autocrine mechanisms in the anterior pituitary gland of female rats.     

Estrogen receptor alpha signaling pathways differentially regulate gonadotropin subunit gene expression and serum follicle-stimulating hormone in the female mouse

Estrogen, acting via estrogen receptor (ER)alpha, regulates serum gonadotropin levels and pituitary gonadotropin subunit expression. However, the cellular pathways mediating this regulation are unknown. ERalpha signals through classical estrogen response element (ERE)-dependent genomic as well as nonclassical ERE-independent genomic and nongenomic pathways. Using targeted mutagenesis in mice to disrupt ERalpha DNA binding activity, we previously demonstrated that ERE-independent signaling is sufficient to suppress serum LH levels. In this study, we examined the relative roles of ERE-dependent and -independent estrogen signaling in estrogen regulation of LH, FSH, prolactin, and activin/inhibin subunit gene expression, pituitary LH and FSH protein content, and serum FSH levels. ERE-independent signaling was not sufficient for estrogen to induce pituitary prolactin mRNA or suppress pituitary LHbeta mRNA, LH content, or serum FSH in estrogen-treated ovariectomized mice. However, ERE-independent signaling was sufficient to reduce pituitary glycoprotein hormone alpha-subunit, FSHbeta, and activin-betaB mRNA expression. Together with previous serum LH results, these findings suggest ERE-independent ERalpha signaling suppresses serum LH via reduced secretion, not synthesis. Additionally, ERE-dependent and ERE-independent ERalpha pathways may distinctly regulate steps involved in the synthesis and secretion of FSH.     

Estrogen receptor in female lung carcinoma]

80 cases of female lung carcinoma were assayed with avidin-biotin complex method for estrogen receptor (ER) and 73.8% cases revealed positive reaction. The 3 expressive types were cytoplasmic, all cellular and nuclear. There were no correlations between ER content and age, blood type, histologic types, size of tumor and metastasis of regional lymph nodes, but obvious correlations between ER content and prognosis. The 5 year survival rate in ER negative patients (72.7%) was greatly higher than in positive patients (8.8%) (P < 0.01). All had better prognosis in ER negative patients above and below 50-year groups.     

Leptin and leptin receptor expression in rat and mouse pituitary cells

Leptin is a circulating hormone secreted mainly by adipose tissue. Recent studies have shown leptin production by other tissues, including the placenta, stomach, and mammary tissues. Various reports have suggested that the anterior pituitary may have a role in the regulatory effects of leptin. We recently localized leptin in the human anterior pituitary, but analysis of leptin in rodent pituitary has not been previously reported. In this study we examined rat and mouse pituitary tissues and various cell lines for leptin by RT-PCR, immunohistochemistry, and Western blotting. Leptin receptor messenger RNA was also examined in these tissues by RT-PCR. Leptin was present in a small percentage of rat (4.8 +/- 0.7%) and mouse (7 +/- 2%) pituitary cells. Colocalization studies with leptin and pituitary hormones showed leptin expression mainly in TSH cells (24 +/- 2% of TSH cells in the rat pituitary and 31 +/- 1% of TSH cells in the mouse pituitary). A folliculo-stellate (FS) cell line, TtT/GF, also expressed leptin. The long isoform of leptin receptor (OB-Rb) was present in normal pituitary and in various pituitary cell lines, including FS, GH3, and alphaT3-1 cells. Treatment of GH3 and FS cells with leptin (1 x 10(-8) M) inhibited cell proliferation assessed by [3H]thymidine incorporation in GH3, but not in FS, cells. These findings show for the first time that leptin is expressed in rat and mouse anterior pituitaries mainly by TSH cells and by a mouse FS cell line. The finding of leptin and of the long isoform of leptin receptor in normal rat and mouse pituitaries and in various cell lines implicates an autocrine/paracrine loop in the production and regulation of leptin and leptin receptor in the rodent pituitary.     

Transition of leptin receptor expression during pubertal development in female rat pituitary

Leptin is thought to play important roles in pubertal development and reproductive function in the female. Leptin receptor is expressed in various tissues including the pituitary and hypothalamus. We investigated the transition of leptin receptor (Ob-R) expression in female rat pituitary during pubertal development. Real-time RT-PCR was performed for long-form leptin receptor (Ob-Rb) and short-form leptin receptor (Ob-Ra) in the pituitary and cerebrum of the rats aged 4 (juvenile), 6 (pubertal), and 8 weeks (adult). Double immunohistochemical colocalization of Ob-R and luteinizing hormone (LH) was performed in pituitaries from 4-week-old female rats. Serum leptin concentrations of 4-, 6-, and 8-week-old rats were measured by radioimmunoassay. In the pituitary, expression of Ob-Rb mRNA in 4-week-old rats (1.00 +/- 0.16) was significantly higher than in 8-week-old rats (0.61 +/- 0.07, p<0.05), although expression of Ob-Ra mRNA did not differ among 4-, 6-, and 8-week-old rats. In cerebrum, Ob-Ra and Ob-Rb mRNA expressions did not differ significantly among 4-, 6-, and 8-week-old rats. Intense staining of Ob-R and colocalization of Ob-R and LH were seen in 4-week-old rat pituitary. On the other hand, serum concentrations of leptin in 6- and 8-week-old rats were significantly higher than those in 4-week-old rats (p<0.05, p<0.01, respectively). In conclusion, since the pituitary gonadotroph is a potential target of leptin, the juvenile rat pituitary might prepare for a subsequent increase of serum leptin concentration by expressing Ob-Rb.     

Developmental pattern of estrogen receptor expression in female mouse genital tracts

The distribution of the estrogen receptor (ER) was investigated in neonatal female genital tracts (uterus, oviduct, cervix, and vagina) from days 1-22 after birth, using immunohistochemistry employing an anti-ER monoclonal antibody. In uteri, the ER in epithelial cells began to be observed by day 4. The number of positive epithelial cells and the staining intensity gradually increased until day 22 of age. On the other hand, uterine stroma cells gave a strong ER immunostaining even on day 1. The staining intensity reached a maximum by days 4-7 and then slightly decreased with age. In the oviduct, cervix, and vagina, epithelial cells showed positive ER immunostaining on day 1, and the intensity increased gradually until day 22. ER immunostaining in stroma cells was almost constant during the development period. The ER in both epithelial and stroma cells from these younger animals showed similar biochemical properties, i.e. an increased affinity for nuclei and resistance to extraction with PBS. Thus, during neonatal development of the female reproductive tract, ER is present not only in stroma cells but also in epithelial cells. This ER protein exhibits properties and characteristics similar to those of adult mice. The presence of ER suggests that some of the estrogen actions of cell proliferation, differentiation, and tissue abnormalities resulting from prenatal and postnatal estrogen administration may be mediated by receptor interactions.     

Estrogen attenuates expression of calcitonin-like immunoreactivity in the anterior pituitary gland

Estrogens increase prolactin (PRL) synthesis and release in rats and humans, whereas pituitary-derived calcitonin-like immunoreactive peptide (pit-CT) inhibits PRL gene expression and release. To test the hypothesis that estrogens stimulate lactotrophs by diminishing pit-CT expression, the present studies examined effects of ovariectomy (ovx) and estradiol (E2) administration on (1) pit-CT IR cell population; (2) pit-CT IR content and (3) release of pit-CT IR by cultured anterior pituitary (AP) cells. Ability of anti-calcitonin immunoglobulins (anti-CT IgG) to stimulate PRL release from cultured AP cells was also examined. The results suggest that ovariectomy induced a large increase in pit-CT IR cell population in the AP gland and E2-treatment dramatically reversed this increase. Similar changes were observed in pit-CT IR content of AP extracts. Cultured AP cells from ovx rats released significantly higher amounts of pit-CT IR, and anti-CT IgG induced a significant increase in basal PRL release. AP cells from E2-treated rats secreted lower amounts of pit-CT IR and this was associated with significantly higher PRL release. These results suggest that estrogens may stimulate lactotrophs, at least in part, by removing inhibitory influence of endogenous pit-CT.     

Estrogen regulation of kallikrein gene expression in the rat anterior pituitary

Using a rat pancreatic kallikrein cDNA probe (pcXP39), previously shown to hybridize to kallikrein mRNA in a variety of tissues, we have explored the control of kallikrein gene expression in rat anterior pituitary. Intact female rats have substantially higher levels of AP kallikrein mRNA than intact males; male levels are unaffected by castration, whereas female levels fall markedly postovariectomy. Administration of estradiol benzoate to intact male or ovariectomized female rats causes an increase in anterior pituitary levels of kallikrein mRNA. Since the pattern of responsiveness parallels that of PRL, we have studied GH3 cells grown in the presence and absence of estradiol; in neither instance was kallikrein mRNA above detection limits. Parallel changes were seen on Northern blots and by hybridization histochemistry; on emulsion autoradiography of pituitary sections, scattered positive cells were seen, but precise definition was not possible. We conclude that whereas in the submaxillary gland kallikrein gene expression appears androgen dependent and in the kidney is postulated to be mineralocorticoid regulated, in the anterior pituitary expression of the gene is under estrogen control; and that the local role(s) of pituitary kallikrein, whether precursor processing, control of blood flow, or other effects, would, in turn, appear to be modulated by estrogen in vivo.     

Estrogen receptor specificity in the regulation of the skeleton in female mice.

There are two known estrogen receptors, estrogen receptor-alpha (ER alpha) and estrogen receptor-beta (ER beta), which may mediate the actions of estrogen. The aim of the present study was to compare fat content, skeletal growth and adult bone metabolism in female mice lacking ER alpha (ERKO), ER beta (BERKO) or both ERs (DERKO). We demonstrate that endogenous estrogens decrease the fat content in female mice via ER alpha and not ER beta. Interestingly, the longitudinal bone growth was decreased in ERKO, increased in BERKO, but was intermediate in DERKO females, demonstrating that ER alpha and ER beta exert opposing effects in the regulation of longitudinal bone growth. The effects on longitudinal bone growth were correlated with similar effects on serum levels of IGF-I. A complex regulation of the trabecular bone mineral density (BMD), probably caused by a disturbed feedback regulation of estrogen and testosterone, was observed in female ER-inactivated mice. Nevertheless, a partial functional redundancy for ER alpha and ER beta in the maintenance of the trabecular BMD was observed in the female mice at 60 days of age. Thus, ER alpha and ER beta may have separate effects (regulation of fat), opposing effects (longitudinal bone growth) or partial redundant effects (trabecular BMD at 60 days of age), depending on which parameter is studied.     

Estrogen receptor beta modulates estradiol induction of progestin receptor immunoreactivity in male, but not in female, mouse medial preoptic area

The medial preoptic area (mPOA) of the hypothalamus contains many neurons that express estrogen receptor alpha (ER) and/or ERbeta. We examined the distribution of these receptors and assessed responses to estradiol (E2) in the adult mouse mPOA. Gonadectomized adult male and female mice were killed, and brains were processed for immunocytochemistry for ERalpha and ERbeta. More ERalpha immunoreactive (-ir) than ERbeta-ir neurons were present in the mouse mPOA. Numbers of ERalpha-ir cells were equivalent between males and females, but males had significantly more ERbeta-ir neurons than females. Using breeders that were heterozygous for disrupted ERalpha and ERbeta genes, we produced offspring with varying numbers (0, 1, or 2) of functional and disrupted ERalpha and ERbeta genes. After gonadectomy, half the mice received E2 for 5 d before they were killed. Estradiol treatment, sex, and genotype each had independent effects on numbers of PR-ir neurons in the mPOA. In all cases, brains that lacked at least one functional copy of ERalpha had reduced PR-ir cell numbers. In gonadectomized, untreated mice, one functional copy of the ERbeta gene was correlated with the largest amount of PR-ir. After E2 treatment, both sexes had greatly enhanced numbers of PR-ir containing neurons. In females, maximal PR induction required the presence of at least one functional copy of ERalpha, whereas in males, at least a single copy of both functional ERbeta and ERalpha genes was needed for maximal PR-ir induction. We hypothesize that the two ERs have dependent and independent roles in sexual differentiation of neuroendocrine function.     

中国人结直肠腺癌雌激素受体β的表达

目的:确定ER β在中国人结直肠癌中的表达特点.方法:采用免疫组织化学方法对40例结直肠癌进行了ER β检测,10例结肠腺瘤以及10例正常结肠活检标本作为对照组也进行了ER β检测.结果:ER β在正常人结肠黏膜、结肠腺瘤以及结直肠癌组织中均有不同程度的表达,正常结肠黏膜(2/10)和结肠腺瘤组织(3/10)主要表现为上皮及腺体细胞核及核周胞质染色,而结直肠癌呈弥漫性胞质染色,其中约57.5%CRCs患者核染阳性率大于10%.ER β阳性和阴性组与肿瘤浸润深度、淋巴结转移以及生存率无明显相关.结论:结直肠癌组织中存在大量的ER β阳性细胞;部分正常结肠黏膜也存在ER β的表达;ER β在正常人结肠黏膜、结肠腺瘤细胞以核及核周胞质染色为主,而结直肠癌组织以上弥漫性胞质染色为主.     

Estrogen inhibits the vascular injury response in estrogen receptor beta-deficient female mice

The protective effects of estrogen in the cardiovascular system result from both systemic effects and direct actions of the hormone on the vasculature. Two estrogen receptors have been identified, ERalpha and ERbeta. We demonstrated previously that estrogen inhibits the response to vascular injury in both wild-type and ERalpha-deficient mice, and that ERbeta is expressed in the blood vessels of each, suggesting a role for ERbeta in the vascular protective effects of estrogen. In the present study, we examined the effect of estrogen administration on mouse carotid arterial injury in ERbeta-deficient mice. Surprisingly, in ovariectomized female wild-type and ERbeta knockout mice, 17beta-estradiol markedly and equally inhibited the increase in vascular medial area and the proliferation of vascular smooth muscle cells after vascular injury. These data demonstrate that ERbeta is not required for estrogen-mediated inhibition of the response to vascular injury, and suggest that either of the two known estrogen receptors is sufficient to protect against vascular injury, or that another unidentified estrogen receptor mediates the vascular protective effects of estrogen.     

Estrogen receptor beta expression in human prostate tissue

Estrogen receptor subtype beta (ERbeta) is highly expressed in rat prostate epithelium, but its presence in human prostate needs to be confirmed. Here we investigated the expression of ERbeta in five benign (normal and/or hyperplastic) and 10 malignant (Gleasons' score 2-7) prostate tissue specimens using immunohistochemistry. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded tissue sections, using a commercially available ERbeta polyclonal antibody developed against the C-terminal amino acid residue. Nuclear ERbeta expression was found in the nuclei of glandular epithelium of benign prostate tissue specimens; faint nuclear ERbeta positivity was also present in a few stromal cells around normal epithelium. Nuclear ERbeta specific immunostaining was undetectable in all prostate cancer sections.     

Estrogen receptor mRNA expression patterns in the liver and ovary of female rainbow trout over a complete reproductive cycle

Estrogens are critical hormones involved in reproduction and need to bind to estrogen receptors in target organs for biological activity. Fishes have two distinct estrogen receptor subtypes, alpha (α) and beta (β), with variable combinations of additional isoforms of each subtype dependent on the history of genome duplication within a taxon. The comparative expression patterns of estrogen receptor isoforms during the female reproductive cycle will provide important insights into the unique function and importance of each. The purpose of this study was to measure the mRNAs for the four estrogen receptor isoforms (erα1, erα2, erβ1, erβ2) in the liver and ovary of adult, female rainbow trout over the course of an annual reproductive cycle. The expression of estrogen receptor mRNA isoforms was measured by quantitative real-time RT-PCR. Several reproductive indices (gonadosomatic index, maximum oocyte diameter, plasma estradiol-17β, plasma vitellogenin, and ovulation) were also quantified for comparison and used in a correlation analysis to examine any inter-relationships. Of the four isoforms, the expression of erα1 was highest in the liver, and had a significant positive correlation with liver erβ1 expression. Liver expression of erα2 mRNA was the lowest, but showed a significant positive correlation with maximum oocyte diameter in the ovary. The pattern of the erβ isoforms in liver was one of initially elevated mRNA expression followed by a gradual decrease as reproductive development proceeded. In the ovary the erβ1 isoform had the highest mRNA expression of all estrogen receptor isoforms, at the beginning of the reproductive cycle, but then decreased afterward. Both ovarian erβ isoforms had a significant positive correlation with one another. In contrast, erα2 mRNA expression showed a high maximum level in the ovary near the end of the cycle along with a significant positive correlation with plasma estradiol-17β levels; the highest gonadosomatic indices, maximum oocyte diameter, and vitellogenin levels occurred then too.     

Estrogen receptor beta messenger ribonucleic acid expression in the forebrain of proestrous,pregnant, and lactating female rats

Estrogen receptor (ER)beta is present in hypothalamic and limbic neurons of female rat brains, but little is known about its regulation under physiological conditions. To determine whether ER beta expression varies during physiological conditions in which sex steroid hormone profiles are significantly different, we used in situ hybridization to assess ER beta mRNA expression in the periventricular preoptic area, bed nucleus of stria terminalis, paraventricular nucleus, supraoptic nucleus, and the posterodorsal medial amygdala of female rats on proestrus, on d 22 of pregnancy, or on d 10 of lactation (L10). In the periventricular preoptic area, d-22 pregnant females had fewer ER beta-mRNA-expressing cells than did females at proestrus, but the level of ER beta mRNA expression per cell in pregnant females was higher than in the two other groups. In the paraventricular nucleus, no changes in ER beta mRNA expression were observed; whereas in the supraoptic nucleus, proestrous females had fewer ER beta-mRNA-expressing cells than L10 females. In the posterodorsal medial amygdala, proestrous females had a greater number of ER beta-mRNA-expressing cells than did L10 females. These results demonstrate that ER beta mRNA expression is differentially regulated in a brain-region-specific and temporal manner under physiological conditions and suggest that ER beta may participate in the regulation of estrogen-sensitive reproductive functions in female rats.     

Estrogen regulation of neurokinin B gene expression in the mouse arcuate nucleus is mediated by estrogen receptor alpha

Neurokinin B (NKB) gene expression is elevated in the infundibular (arcuate) nucleus of the hypothalamus in postmenopausal women. Estrogen replacement decreases both the number of NKB mRNA-expressing neurons and the level of expression within individual cells. Similarly, NKB gene expression is elevated in ovariectomized rats and reduced after estrogen treatment. The actions of estrogen in the brain can be mediated via either estrogen receptor alpha (ERalpha) or estrogen receptor beta (ERbeta). In the rodent arcuate nucleus (ARC), more ERalpha- than ERbeta-containing cells are present, suggesting that ERalpha might be directly responsible for estrogen regulation of NKB gene expression. However, an indirect effect via ERbeta could not be ruled out. Here we used ERalpha knockout and ERbeta knockout mice to identify the type of ER responsible for mediating estrogen action on NKB gene expression in the ARC. Using in situ hybridization histochemistry, we have found that estrogen treatment significantly reduced NKB gene expression in the ARC of ovariectomized ERbeta knockout mice, but had no effect on NKB mRNA levels in ERalpha knockout mice. These data indicate that ERalpha mediates the increase in NKB gene expression associated with ovariectomy in rodents and might also be responsible for the increase in NKB in postmenopausal women.     

Estrogen modulates expression of putative housekeeping genes in the mouse uterus

Estrogens regulate gene expression and cell proliferation in target tissues. In studies of estrogen-regulated gene expression, identification of appropriate housekeeping genes (HKGs), reference genes whose expression is not altered by treatment, is difficult. The goal of this study was to define HKGs unaltered by estrogen in the mouse uterus. Ovariectomized C57BL6 mice were dosed with 20 micrograms/kg ethinylestradiol and the uterus was collected at 6, 24, and 72 h later to bracket the biphasic time course of estrogen action in the rodent uterus. RNA was isolated, cDNA synthesized and equal amounts of cDNA were added to real-time PCR reactions. The expression of seven out of nine putative HKGs was altered by estrogen in the mouse uterus. Estrogen induced four gene expression profiles, expression of: (1) Actb and Hsp90ab1 were up-regulated early, (2) B2m and Gusb were up-regulated late, (3) Gapdh, Hprt1, and Ppia were up regulated at all time points, and (4) Rpl13a and 18srRNA were unaltered. This highlights the need to empirically determine the appropriate HKG for each experimental condition. Based on these results, we suggest using Rpl13a or 18srRNA as HKGs for xenoestrogen studies in the mouse uterus and as good candidates to test under different experimental conditions.