Estrogen receptor beta-deficient female mice develop a bladder phenotype resembling human interstitial cystitis.

Interstitial cystitis/painful bladder syndrome is a disease seen mostly in women, and symptoms tend to be worse premenopausally or during ovulation. The four cardinal symptoms of interstitial cystitis/painful bladder syndrome are bladder pain, urgency, frequency, and nocturia. Estrogen has been implicated in the etiology of this disease, but the role of the two estrogen receptors (ER), ERalpha and ERbeta, has not been investigated. We found that, in the bladders of WT mice, ERbeta is expressed in the basal cell layer of the urothelium. Bladders of male ERbeta(-/-) mice were intact and morphologically indistinguishable from those of their WT littermates. However, in female ERbeta(-/-) mice, there was ulceration and atrophy of bladder urothelium concomitant with infiltration of gammadelta T cells concentrated in the areas of atrophy and shedding of urothelium. The data support the idea that activated gammadelta T cells are causing the damage to the urothelium. The hyperactivity of T cells may be because of an imbalance between ERalpha and ERbeta signaling in female ERbeta(-/-) mice. Our data suggest that reduced ERbeta signaling might have a role in the pathogenesis of interstitial cystitis, and ERbeta could be a candidate for a target of medical therapy.

Role of estrogen receptor beta in uterine stroma and epithelium: Insights from estrogen receptor beta-/- mice.

In this study, we compared the uterine tissue of estrogen receptor (ER)beta(-/-) mice and their WT littermates for differences in morphology, proliferation [the percentage of labeled cells 2 h after BrdUrd injection and EGF receptor (EGFR) expression], and differentiation (expression of progesterone receptor, E-cadherin, and cytokeratins). In ovariectomized mice, progesterone receptor expression in the uterine epithelium was similar in WT and ERbeta(-/-) mice, but E-cadherin and cytokeratin 18 expression was lower in ERbeta(-/-) mice. The percentage of cells in S phase was 1.5% in WT mice and 8% in ERbeta(-/-) mice. Sixteen hours after injection of 17beta-estradiol (E(2)), the number of BrdUrd-labeled cells increased 20-fold in WT mice and 80-fold in ERbeta(-/-) mice. Although ERalpha was abundant in intact mice, after ovariectomy, ERalpha could not be detected in the luminal epithelium of either WT or ERbeta(-/-) mice. In both untreated and E(2)-treated mice, ERalpha and ERbeta were colocalized in the nuclei of many stromal and glandular epithelial cells. However, upon E(2) + progesterone treatment, ERalpha and ERbeta were not coexpressed in any cells. In WT mice, EGFR was located on the membranes and in the cytoplasm of luminal epithelium, but not in the stroma. In ERbeta(-/-) mice, there was a marked expression of EGFR in the nuclei of epithelial and stromal cells. Upon E(2) treatment, EGFR on cell membranes was down-regulated in WT but not in ERbeta(-/-) mice. These findings reveal an important role for ERbeta in response to E(2) and in the organization, growth, and differentiation of the uterine epithelium.

Lung dysfunction causes systemic hypoxia in estrogen receptor beta knockout (ERbeta-/-) mice.

Estrogen receptor beta (ERbeta) is highly expressed in both type I and II pneumocytes as well as bronchiolar epithelial cells. ERalpha is not detectable in the adult lung. Lungs of adult female ERbeta knockout (ERbeta-/-) mice have already been reported to have fewer alveoli and reduced elastic recoil. In this article, we report that, by 5 months of age, there are large areas of unexpanded alveoli in lungs of both male and female ERbeta-/- mice. There is increased staining for collagen and, by EM, abnormal clusters of collagen fibers are seen in the alveolar septa of ERbeta-/- mice. Immunohistochemical analysis and Western blotting with lung membrane fractions of ERbeta-/- mice revealed down-regulation of caveolin-1, increased expression of membrane type-1 metalloproteinase, matrix metalloproteinase 2 (active form), and tissue inhibitors of metalloproteinases 2. Hypoxia, measured by immunohistochemical analysis for hypoxia-inducible factor 1alpha and chemical adducts (with Hypoxyprobe), was evident in the heart, ventral prostate, periovarian sac, kidney, liver, and brain of ERbeta-/- mice under resting conditions. Furthermore, both male and female adult ERbeta-/- mice were reluctant to run on a treadmill and tissue hypoxia became very pronounced after exercise. We conclude that ERbeta is necessary for the maintenance of the extracellular matrix composition in the lung and loss of ERbeta leads to abnormal lung structure and systemic hypoxia. Systemic hypoxia may be responsible for the reported left and right heart ventricular hypertrophy and systemic hypertension in ERbeta-/- mice.

Role of estrogen receptor beta in colonic epithelium.

Several papers report that the colon is one of the tissues regulated by estrogen receptor (ER)beta. To better understand the physiological role of ERbeta in colonic tissue, we have compared morphology, proliferation, and differentiation of colonic epithelium in ERbeta-/- mice and WT littermates. BrdUrd labeling revealed that the number of proliferating cells was higher in ERbeta-/- mice and that the migration of labeled cells toward the luminal surface was faster in ERbeta-/- mice than in WT littermates. Additionally, in the absence of ERbeta, there was a decrease in apoptosis, which was measured by immunohistochemical staining of cleaved caspase-3. The state of differentiation of the colonic epithelial cells was studied by using epithelial markers. In ERbeta-/- mice, there was a significant decrease in the expression of the differentiation marker cytokeratin (CK)20 and in the cellular adhesion molecules alpha-catenin (an adherens junction protein) and plectin (a hemidesmosomal protein). These changes were also evident by electron microscopy as abnormalities in tight junctions and in the number and shape of desmosomes in ERbeta-/- mice. These findings suggest a role for ERbeta in the organization and architectural maintenance of the colon. Furthermore, our results indicate that the rapidly proliferating cells of the colonic epithelium in ERbeta-/- mice are lost by increased shedding and not by increased apoptosis. In this way, hyperproliferative cells that lack ERbeta do not form hyperplastic lesions and do not accumulate in the superficial epithelium.

Estrogen receptor beta in health and disease.

Estrogens, acting through its two receptors, ESR1 (hereafter designated ER alpha) and ESR2 (hereafter designated ER beta), have diverse physiological effects in the reproductive system, bone, cardiovascular system, hematopoiesis, and central and peripheral nervous systems. Mice with inactivated ER alpha, ER beta, or both show a number of interesting phenotypes, including incompletely differentiated epithelium in tissues under steroidal control (prostate, ovary, mammary, and salivary glands) and defective ovulation reminiscent of polycystic ovarian syndrome in humans (in ER beta-/- mice), and obesity, insulin resistance, and complete infertility (both in male and female ER alpha-/- mice). Estrogen agonists and antagonists are frequently prescribed drugs with indications that include postmenopausal syndrome (agonists) and breast cancer (antagonists). Because the two estrogen receptors (ERs) have different physiological functions and have ligand binding pockets that differ enough to be selective in their ligand binding, opportunities now exist for development of novel ER subtype-specific selective-ER modulators.

Estrogen receptor alpha and imprinting of the neonatal mouse ventral prostate by estrogen.

Exposure to estrogen in the neonatal period affects prostatic growth and leads to an increased incidence of prostatic intraepithelial neoplasia in later life. The effects of neonatal estrogen are clearly dependent on estrogen receptor (ER) alpha because they do not occur in ERalpha-knockout mice. Because ERalpha is expressed in the stroma, but not in the epithelium, of the adult ventral prostate, the concept of indirect estrogen effects through stromal signaling has been proposed. Here, we show that during the first 4 weeks of life, there are profound and rapid changes in the ER profile in the mouse ventral prostate. ERalpha is abundant in the stroma during week 1, but by week 2 it is exclusively epithelial, and then by week 4, ERalpha is lost and ERbeta is dominant in the prostatic epithelium. The presence of ERalpha is associated with a high proliferation index, and ERbeta is associated with quiescence. Branching morphogenesis was altered in ERalpha-/-, but not in ERbeta-/-, mice. We conclude that imprinting and branching morphogenesis of the ventral prostate are mediated by estrogen acting directly on epithelial and stromal ERalpha during the first 2 weeks of life.

Aromatase-deficient mice spontaneously develop a lymphoproliferative autoimmune disease resembling Sjogren's syndrome.

Sjögren's syndrome (SS) is an incurable, autoimmune exocrinopathy that predominantly affects females and whose pathogenesis remains unknown. Like rheumatoid arthritis, its severity increases after menopause, and estrogen deficiency has been implicated. We have reported that estrogen receptor-alpha and -beta-knockout mice develop autoimmune nephritis and myeloid leukemia, respectively, but neither develops SS. One model of estrogen deficiency in rodents is the aromatase-knockout (ArKO) mouse. In these animals, there is elevated B lymphopoiesis in bone marrow. We now report that ArKO mice develop severe autoimmune exocrinopathy resembling SS. By 1 year of age, there is B cell hyperplasia in the bone marrow, spleen, and blood of ArKO mice and spontaneous autoimmune manifestations such as proteinuria and severe leukocyte infiltration in the salivary glands and kidney. Also, as is typically found in human SS, there were proteolytic fragments of alpha-fodrin in the salivary glands and anti-alpha-fodrin antibodies in the serum of both female and male ArKO mice. When mice were raised on a phytoestrogen-free diet, there was a mild but significant incidence of infiltration of B lymphocytes in WT mice and severe destructive autoimmune lesions in ArKO mice. In age-matched WT mice fed a diet containing normal levels of phytoestrogen, there were no autoimmune lesions. These results reveal that estrogen deficiency results in a lymphoproliferative autoimmune disease resembling SS and suggest that estrogen might have clinical value in the prevention or treatment of this disease.

Estrogen receptor beta regulates epithelial cellular differentiation in the mouse ventral prostate.

We have previously reported epithelial cellular hyperplasia in ventral prostates (VP) of mice lacking estrogen receptor beta (ER beta). To investigate the causes of this phenomenon, we measured cellular proliferation and apoptosis in VP of ER beta(-/-) and WT mice. With BrdUrd labeling, the number of proliferating cells was 3.6-fold higher in ER beta(-/-) mice. There was also a decrease in apoptosis as measured by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling assay and an increase in expression of the anti-apoptotic bcl-2. The state of differentiation of the epithelial cells of the VP was studied by immunohistochemical staining, Western blotting, and fluorescence-activated cell sorting (FACS). In ER beta(-/-) mouse VP, the number of p63-positive cells (basal phenotype) was 2.6-fold higher, and expression level of cytokeratin (CK) 8, a luminal cell marker, was lower. FACS analysis with p63 showed that in WT mice the ratio of basal to intermediate/luminal cell populations expressing p63 was 1:2.5, whereas in ER beta(-/-) mice it was 1:9. The expression of basal/intermediate marker CK 19 in three FACS areas, g1, g2, and g3, gated according to cellular size and granularity, was 1:0.6:2 in WT and 1:4:6.7 in ER beta(-/-) mice, showing a shift of CK 19-positive cells toward a cell population of intermediate size and granularity. We conclude that, in ER beta(-/-) mouse VP, there is increased epithelial proliferation, decreased apoptosis, and accumulation of incompletely differentiated cells in an intermediate pool. The continued proliferation of intermediate cells leads to the prostatic epithelial hyperplasia observed in the absence of ER beta signaling.

What is the value of measuring MTA-1s in breast cancer?

The presence or absence of estrogen receptor (ER) expression in tumor cells affects prognosis and guides treatment choices. Kumar et al. suggest that a shortened form of the metastatic tumor antigen 1 (MTA1s) acts to sequester the estrogen receptor (ER) in the cytoplasm, inhibiting its ability to transactivate specific genes and, presumably, adding to the ER's ability to transduce non-genomic (cytoplasmic) signaling mechanisms. However, if the cancer is negative for ERalpha in the nucleus, but is positive for ERalpha in the cytoplasm, how does this sequestration affect the treatment of the patient or our understanding of the disease process? Cheng et al. caution that these results must be interpreted carefully with regard to what is known about estrogen-dependent and -independent tumor growth and chemotherapeutic strategies to destroy them.