Biomedical subjects

Jan-Ake Gustafsson

Publications and source records attributed to Jan-Ake Gustafsson.

At least 19 recordsLinked to original sources

PubMed2006

Ovarian wedge resection restores fertility in estrogen receptor beta knockout (ERbeta-/-) mice.

Ovulation rarely occurs in mice in which the estrogen receptor beta (ERbeta) gene has been inactivated (ERbeta-/- mice). Here, we investigated whether this subfertility is due to a defect in the ovary itself or to more general endocrine changes in ERbeta-/- mice. We transplanted ERbeta-/- ovaries into WT mice and WT ovaries into ERbeta-/- mice. Upon mating with ERbeta-/- males, fertility increased from 20% in control intact ERbeta-/- group to 40% in the WT recipients with ERbeta-/- ovaries. The transplantation procedure was not efficient, and when WT ovaries were transplanted into WT mice, fertility was only 36%. Surgical ovarian wedge resection, a procedure which induces ovulation in anovulatory women with polycystic ovarian syndrome, resulted in 100% fertility of ERbeta-/- mice. In ERbeta-/- mice, as the follicles enlarged, the thecal layer remained very compact (revealed by H&E and collagen staining), and there was no increase in vascularization (measured as smooth muscle actin). In addition, there was an increase in PDGF receptor alpha (PDGFRalpha) and a decrease in PDGFbeta expression in the granulosa cells, similar to what has been found in follitropin receptor knockout mice. After wedge resection, expression of both smooth muscle actin and PDGFRs was normalized. During normal follicular development, increased vascularization of the thecal layer is a prerequisite for further follicular growth. We suggest that the defect in ERbeta-/- mouse ovaries is a failure of communication between the granulosa and thecal layers. The follicles do not mature because of insufficient blood supply. This problem is overcome by stimulating neovascularization by simple wedge resection of the ovaries.

Animals↗

PubMed2006

Subtle side-chain modifications of the hop phytoestrogen 8-prenylnaringenin result in distinct agonist/antagonist activity profiles for estrogen receptors alpha and beta.

In search of therapeutic agents for estrogen-related pathologies, phytoestrogens are being extensively explored. In contrast to naringenin, 8-prenylnaringenin is a potent hop-derived estrogenic compound, highlighting the importance of the prenyl group for hormonal activity. We investigated the effects of substituting the prenyl group at C(8) with alkyl chains of varying lengths and branching patterns on estrogen receptor (ER) subtype ERalpha- and ERbeta-binding affinities and transcriptional activities. In addition, features of the ligand-induced receptor conformations were explored using a set of specific ER-binding peptides. The new 8-alkylnaringenins were found to span an activity spectrum ranging from full agonism to partial agonism to antagonism. Most strikingly, 8-(2,2-dimethylpropyl)naringenin exhibited full agonist character on ERalpha, but pronounced antagonist character on ERbeta. Knowledge on how ER-subtype-selective activities can be designed provides valuable information for future drug or tool compound discovery.

Binding, Competitive↗

PubMed2006

Estrogen receptor beta expression in the embryonic brain regulates development of calretinin-immunoreactive GABAergic interneurons.

Our previous studies with estrogen receptor beta knockout (ERbeta(-/-)) mice demonstrated that ERbeta is necessary for embryonic development of the brain as early as embryonic day 14.5 (E14.5) and is involved in neuronal migration. Such early effects of ER were unexpected because estradiol synthesis and action in the brain occur at E18.5. In the present study, we examined the distribution of ERbeta in the developing brain and identified a population of ERbeta-regulated interneurons. ERbeta appears in the brain at E12.5, mainly localized in the wall of the midbrain, neuromere, hypothalamus, thalamus, and basal plate of pons. At E15.5 and E16.5, ERbeta expression increased in the hypothalamus, thalamus, and midbrain and appeared in the limbic forebrain. At E18.5, ERbeta expression was strongly expressed throughout the brain, including the cerebellum and striatum, whereas there were very few positive cells in the ventricular region. In the paraventricular thalamic nucleus and parafascicular nucleus, most of the calretinin-immunopositive interneurons expressed ERbeta. In ERbeta(-/-) mice, calretinin expression was markedly lower than in WT mice in the hippocampus, thalamus, and amygdala both at E16.5 and at E18.5. Epidermal growth factor receptor expression was lower in the cortex of ERbeta(-/-) than in WT mice at E15.5 and, unlike WT mice, was absent from the superficial marginal zone. These findings suggest that ERbeta in the embryonic brain is necessary for the development of calretinin-immunoreactive GABAergic interneurons and for neuronal migration in the cortex through modulating epidermal growth factor receptor expression at middle and later embryonic stages.

Animals↗

PubMed2006

Estrogen receptor beta inhibits angiogenesis and growth of T47D breast cancer xenografts.

Estrogens, which are stimulators of growth of both the normal breast and malignant breast, mediate their effects through two estrogen receptors (ER), namely ERalpha and ERbeta. ERalpha mediates the proliferative effect of estrogen in breast cancer cells, whereas ERbeta seems to be antiproliferative. We engineered ERalpha-positive T47D breast cancer cells to express ERbeta in a Tet-Off-regulated manner. These cells were then injected orthotopically into severe combined immunodeficient mice, and the growth of the resulting tumors was compared with tumors resulting from injecting the parental T47D cells that do not express ERbeta. The presence of ERbeta resulted in a reduction in tumor growth. Comparison of the ERbeta-expressing and non-ERbeta-expressing tumors revealed that the expression of ERbeta caused a reduction in the number of intratumoral blood vessels and a decrease in expression of the proangiogenic factors vascular endothelial growth factor (VEGF) and platelet-derived growth factor beta (PDGFbeta). In cell culture, with the Tet-Off-regulated ERbeta-expressing cells, expression of ERbeta decreased expression of VEGF and PDGFbeta mRNA under normoxic as well as hypoxic conditions and reduced secreted VEGF and PDGFbeta proteins in cell culture medium. Transient transfection assays with 1,026 bp VEGF and 1,006 bp PDGFbeta promoter constructs revealed a repressive effect of ERbeta at the promoter level of these genes. Taken together, these data show that introduction of ERbeta into malignant cells inhibits their growth and prevents tumor expansion by inhibiting angiogenesis.

Animals↗

PubMed2006

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.

Animals↗

PubMed2006

The oestrogen receptor beta contributes to sex related differences in endothelial function of murine small arteries via EDHF.

Sex related differences in cardiovascular function have been reported in oestrogen receptor beta knockout (ERbetaKO) mice. In this study we examined the role of endothelium-derived hyperpolarizing factor (EDHF) in differences in small artery endothelial function between ERbetaKO and wild-type (WT) mice. Small femoral arteries were isolated from ERbetaKO and WT mice and mounted on a wire myograph. Concentration-response curves to ACh were compared before and after incubation with inhibitors of nitric oxide (NO) and prostacyclin (PGI2) synthesis. Comparison of the expression of the principal vascular connexins (Cx37, 40 and 43), implicated in EDHF-mediated dilatation were undertaken by immunohistochemistry. Vascular ultrastructure was studied by transmission and scanning electron microscopy. ACh-induced relaxation of arteries (< 200 microm internal diameter) was greater in WT females versus males and was attributable to a greater EDHF component of relaxation. This sex difference was absent in ERbetaKO mice. Arteries from ERbetaKO males (but not females) were more sensitive to ACh compared to WT. The pharmacological evidence and morphological prerequisite for involvement of gap junctions in EDHF-mediated responses was confirmed in male arteries. The absence of ERbeta had no influence on expression of main Cx subtypes within vascular wall or on ultrastructure and morphology of the endothelium. The data suggest that in WT male mice, ERbeta reduces EDHF-mediated relaxation through gap junction communication.

Acetylcholine↗

PubMed2006

Reduced fertility and inability of oocytes to resume meiosis in mice deficient of the Lxr genes.

Cholesterol precursors act as activators of the nuclear hormone receptor, liver X receptor (LXR). One of these LXR-activating ligands is meiosis activating sterol (MAS), which also induces resumption of meiosis in oocytes from mice in vitro. Whether LXR participates in the regulation of oocyte maturation and whether the expression of either one of the two paralogues of LXR (alpha and beta) affect fertility of mice has, however, not yet been clarified. Female mice lacking Lxra, Lxrb or both genes (Lxra(-/-), Lxrb(-/-) and Lxrab(-/-), respectively) conceive less frequently and have significantly fewer pups per litter as compared to wild type mice. Both Lxra and Lxrb mRNA were found to be expressed in mouse oocytes. The relative expression of, in particular, Lxrb was almost two orders of magnitude higher than in liver, brain and testis. A water-soluble LXR agonist caused naked oocytes, but not cumulus enclosed oocytes (CEO), from wild type mice to resume meiosis significantly more often than control oocytes. Follicle stimulating hormone (FSH) is a potent stimulator of meiosis in CEO from wild type mice, but was without effect in mice lacking both Lxr genes. Zymosterol, a MAS active substance, induced resumption of meiosis in oocytes from Lxrab(-/-) mice, but significantly less effectively than in oocytes from wild type mice. Taken together, LXRs seem to affect ovarian function, suggesting specific roles of cholesterol precursors in regulation of female reproduction.

Animals↗

PubMed2006

Estrogen receptors: new players in diabetes mellitus.

Diabetes mellitus type 2 is a systemic disease characterized by imbalance of energy metabolism, which is mainly caused by inadequate insulin action. Recent data have revealed a surprising role for estradiol in regulating energy metabolism and opened new insights into the role of the two estrogen receptors, ERalpha and ERbeta, in this context. New findings on gene modulation by ERalpha and ERbeta of insulin-sensitive tissues indicate that estradiol participates in glucose homeostasis by modulating the expression of genes that are involved in insulin sensitivity and glucose uptake. Drugs that can selectively modulate the activity of either ERalpha or ERbeta in their interactions with target genes represent a promising frontier in diabetes mellitus coadjuvant therapy.

Animals↗

PubMed2006

The hair follicle as an estrogen target and source.

For many decades, androgens have dominated endocrine research in hair growth control. Androgen metabolism and the androgen receptor currently are the key targets for systemic, pharmacological hair growth control in clinical medicine. However, it has long been known that estrogens also profoundly alter hair follicle growth and cycling by binding to locally expressed high-affinity estrogen receptors (ERs). Besides altering the transcription of genes with estrogen-responsive elements, 17beta-estradiol (E2) also modifies androgen metabolism within distinct subunits of the pilosebaceous unit (i.e., hair follicle and sebaceous gland). The latter displays prominent aromatase activity, the key enzyme for androgen conversion to E2, and is both an estrogen source and target. Here, we chart the recent renaissance of estrogen research in hair research; explain why the hair follicle offers an ideal, clinically relevant test system for studying the role of sex steroids, their receptors, and interactions in neuroectodermal-mesodermal interaction systems in general; and illustrate how it can be exploited to identify novel functions and signaling cross talks of ER-mediated signaling. Emphasizing the long-underestimated complexity and species-, gender-, and site-dependence of E2-induced biological effects on the hair follicle, we explore targets for pharmacological intervention in clinically relevant hair cycle manipulation, ranging from androgenetic alopecia and hirsutism via telogen effluvium to chemotherapy-induced alopecia. While defining major open questions, unsolved clinical challenges, and particularly promising research avenues in this area, we argue that the time has come to pay estrogen-mediated signaling the full attention it deserves in future endocrinological therapy of common hair growth disorders.

Animals↗

PubMed2006

Improved metabolic control by depletion of Liver X Receptors in mice.

Liver X Receptors (LXRs) coordinate the regulation of lipid and carbohydrate metabolism and insulin signaling. LXR-ligands lower plasma glucose in hyperglycemic rodents and have consequently been proposed as anti-diabetic agents. We investigated the metabolic effects induced by high carbohydrate diet in LXRalpha(-/-)beta(-/-) mice. Irrespective of diets, LXRalpha(-/-)beta(-/-) mice had reduced fatty acid, insulin, and C-peptide plasma levels than wild-type controls, suggesting a lower insulin production. High carbohydrate diet decreased the plasma glucose levels and the homeostasis model assessment (HOMA)-index in LXRalpha(-/-)beta(-/-) mice and increased hepatic triglyceride content and mRNA levels of lipogenic genes in wild-type and LXRalpha(-/-)beta(-/-) mice, proportionally. In wild-type mice high carbohydrate diet was associated with induced expression of LXR (1.5-fold), despite unchanged SREBP-1c expression. LXRalpha(-/-)beta(-/-) mice responded to this diet by induction of SREBP-1c. Our study suggests that in LXRalpha(-/-)beta(-/-) mice, glucose utilization seems to be privileged possibly due to reduced circulating free fatty acid levels.

Animals↗

PubMed2006

Estrogen receptor and aryl hydrocarbon receptor signaling pathways.

Estrogen receptors (ERs) and the aryl hydrocarbon receptor (AhR) are ligand activated transcription factors and members of the nuclear receptor and bHLH-PAS superfamilies, respectively. AhR is involved in xenobiotic metabolism and in mediating the toxic effects of dioxin-like compounds. Crosstalk has been observed among AhR and nuclear receptors, but has been most well studied with respect to ER signaling. Activated AhR inhibits ER activity through a number of different mechanisms, whereas ERalpha has been reported to have a positive role in AhR signaling. Here we will discuss recent data revealing that dioxin bound AhR recruits ERalpha to AhR regulated genes. We will also consider the implications of ER recruitment to AhR target genes on ER and AhR signaling.

Journal Article↗

PubMed2006

Liver X receptor (LXR)-beta regulation in LXRalpha-deficient mice: implications for therapeutic targeting.

The nuclear receptors liver X receptor (LXR) LXRalpha and LXRbeta are differentially expressed ligand-activated transcription factors that induce genes controlling cholesterol homeostasis and lipogenesis. Synthetic ligands for both receptor subtypes activate ATP binding cassette transporter A1 (ABCA1)-mediated cholesterol metabolism, increase reverse cholesterol transport, and provide atheroprotection in mice. However, these ligands may also increase hepatic triglyceride (TG) synthesis via a sterol response element binding protein 1c (SREBP-1c)-dependent mechanism through a process reportedly regulated by LXRalpha. We studied pan-LXRalpha/beta agonists in LXRalpha knockout mice to assess the contribution of LXRbeta to the regulation of selected target genes. In vitro dose-response studies with macrophages from LXRalpha-/- and beta-/- mice confirm an equivalent role for LXRalpha and LXRbeta in the regulation of ABCA1 and SREBP-1c gene expression. Cholesterol-efflux studies verify that LXRbeta can drive apoA1-dependent cholesterol mobilization from macrophages. The in vivo role of LXRbeta in liver was further evaluated by treating LXRalpha-/- mice with a pan-LXRalpha/beta agonist. High-density lipoprotein (HDL) cholesterol increased without significant changes in plasma TG or very low density lipoprotein. Analysis of hepatic gene expression consistently revealed less activation of ABCA1 and SREBP-1c genes in the liver of LXRalpha null animals than in treated wild-type controls. In addition, hepatic CYP7A1 and several genes involved in fatty acid/TG biosynthesis were not induced. In peripheral tissues from these LXRalpha-null mice, LXRbeta activation increases ABCA1 and SREBP-1c gene expression in a parallel manner. However, putative elevation of SREBP-1c activity in these tissues did not cause hypertriglyceridemia. In summary, selective LXRbeta activation is expected to stimulate ABCA1 gene expression in macrophages, contribute to favorable HDL increases, but circumvent hepatic LXRalpha-dominated lipogenesis.

ATP Binding Cassette Transporter 1↗

PubMed2006

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.

Animals↗

PubMed2006

DAX-1 expression is regulated during mammary epithelial cell differentiation.

In recent studies, we have found that DAX-1 (dosage-sensitive sex reversal/adrenal hypoplasia congenita critical region on the X chromosome) is expressed in the mouse mammary epithelial cell line HC11. In this study, we focused on the regulation of DAX-1 expression and subcellular localization throughout mouse mammary epithelial cell differentiation and its hormonal regulation in the mouse mammary gland. Proliferating HC11 cells grown in epidermal growth factor (EGF)-containing medium, expressed very low levels of DAX-1 as detected by Western blotting and quantitative real-time PCR, whereas, upon EGF withdrawal and induction of differentiation, DAX-1 expression increased. Inhibition of MAPK pathway with PD 098059 resulted in increased DAX-1 levels even in the presence of EGF. Using confocal microscopy, we showed that DAX-1 cytoplasmic levels increased as cells differentiated. DAX-1 staining was nuclear in luminal cells of mouse mammary glands from 3-month-old virgin mice. A nucleo-cytoplasmic pattern was observed in pseudopregnant mice and a cytoplasmic pattern was found in mammary glands from 6-d lactating mice. The influence of DAX-1 on transcriptional activity of endogenously expressed estrogen receptors alpha (ERalpha) and beta (ERbeta) in HC11 mammary epithelial cells was evaluated with an estrogen response element-luciferase reporter assay and by quantitative real-time PCR of the ER-regulated gene receptor-interacting protein 140 kDa. Cotransfection of HC11 cells with human DAX-1 inhibited estrogen response element-reporter and receptor-interacting protein 140 kDa expression induced by 17beta-estradiol, the ERalpha-selective agonist 4,4',4'-(4-propyl-(1H)-pyrazole-1,3,5-triyl)trisphenol, or the ERbeta-selective agonist 2,3-bis(4-hydroxyphenyl)-propionitrile. In summary, DAX-1 expression increased upon differentiation induced by EGF withdrawal, and DAX-1 decreased response to estrogens in HC11 cells. Further studies are needed to determine whether DAX-1 is also important in regulation of differentiation of HC11 cells.

Animals↗

PubMed2006

Long-term administration of estradiol decreases expression of hepatic lipogenic genes and improves insulin sensitivity in ob/ob mice: a possible mechanism is through direct regulation of signal transducer and activator of transcription 3.

In this study, we used ob/ob mice as a model to investigate the effects of long-term estradiol administration on insulin sensitivity and to explore the mechanisms that underlie the antidiabetic effects of estrogen on mouse liver. Female ob/ob mice were randomly divided into two groups and given estradiol (100 microg/kg.d) or vehicle alone for 4 wk. Estrogen administration improved glucose tolerance and insulin response to glucose in ob/ob mice. Moreover, insulin resistance and liver triglyceride levels were decreased in response to estrogen administration. Microarray analysis revealed that expression of genes involved in hepatic lipid biosynthesis was decreased in ob/ob mouse livers after estradiol treatment. Further searches for direct estrogen target genes revealed increased hepatic mRNA expression of signal transducer and activator of transcription 3 (Stat3) and several known Stat3 target genes in ob/ob livers after long-term estradiol treatment. Furthermore, Stat3 and phosphorylated Stat3 protein is induced in ob/ob mouse liver after long-term estrogen treatment. We also present data showing that Stat3 is rapidly induced by estradiol in mouse livers. This, together with data showing recruitment of ERalpha to the promoter of Stat3 in vivo, suggests that Stat3 is a direct target gene for estradiol. In conclusion, estradiol treatment improves glucose tolerance and insulin sensitivity in ob/ob mice. We propose that this may be mediated, at least partially, via estrogen stimulation of the hepatic expression of Stat3, leading to decreased expression of hepatic lipogenic genes, and thereby to antidiabetic effects.

Animals↗

PubMed2006

Estrogen receptor beta polymorphism is associated with prostate cancer risk.

PURPOSE: After cloning of the second estrogen receptor, estrogen receptor beta (ERbeta) in 1996, increasing evidence of its importance in prostate cancer development has been obtained. ERbeta is thought to exert an antiproliferative and proapoptotic effect. We examined whether sequence variants in the ERbeta gene are associated with prostate cancer risk. EXPERIMENTAL DESIGN: We conducted a large population-based case-control study (CAncer Prostate in Sweden, CAPS) consisting of 1,415 incident cases of prostate cancer and 801 controls. We evaluated 28 single nucleotide polymorphisms (SNP) spanning the entire ERbeta gene from the promoter to the 3'-untranslated region in 94 subjects of the control group. From this, we constructed gene-specific haplotypes and selected four haplotype-tagging SNPs (htSNP: rs2987983, rs1887994, rs1256040, and rs1256062). These four htSNPs were then genotyped in the total study population of 2,216 subjects. RESULTS: There was a statistically significant difference in allele frequency between cases and controls for one of the typed htSNPs (rs2987983), 27% in cases and 24% in controls (P = 0.03). Unconditional logistics regression showed an odds ratio of 1.22 (95% confidence interval, 1.02-1.46) for men carrying the variant allele TC or CC versus the wild-type TT, and an odds ratio of 1.33 (95% confidence interval, 1.08-1.64) for localized cancer. No association of prostate cancer risk with any of the other SNPs or with any haplotypes were seen. CONCLUSION: We found an association with a SNP located in the promoter region of the ERbeta gene and risk of developing prostate cancer. The biological significance of this finding is unclear, but it supports the hypothesis that sequence variation in the promoter region of ERbeta is of importance for risk of prostate cancer.

Case-Control Studies↗

PubMed2006

False positives in MALDI-TOF detection of ERbeta in mitochondria.

Recently, Yang et al. reported that estrogen receptor beta (ERbeta) is a mitochondrial protein rather than a nuclear receptor. Because this claim would lead to a significant change in our understanding of estrogen signaling, we have attempted to reproduce the MALDI-TOF data of Yang et al. We separated proteins extracted from mouse liver mitochondria by SDS-PAGE and analysed a gel band covering the molecular weight range of 50-65 kDa by MALDI-TOF/TOF. Analysis of the data with the MASCOT database algorithm provided no evidence for the presence of ERbeta in the mitochondria. If we search (as the authors did) with only the peptide masses which match to tryptic fragments of ERbeta, ERbeta is identified with a significant score of 69. However, fragmentation of these peptides shows that they are not from ERbeta. Our conclusion is that ERbeta cannot be identified by MALDI-TOF from a mixture of mitochondrial proteins resolved on SDS-PAGE.

Animals↗

PubMed2006

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.

Animals↗