Showing papers on "Aromatase published in 1998"
TL;DR: The phenotype of these animals differs markedly from that of the previously reported ERKO mice, in which the estrogen receptor alpha is deleted by targeted disruption of the cyp19 gene.
Abstract: The formation of estrogens from C19 steroids is catalyzed by aromatase cytochrome P450 (P450arom), the product of the cyp19 gene. The actions of estrogen include dimorphic anatomical, functional, and behavioral effects on the development of both males and females, considerations that prompted us to examine the consequences of deficiency of aromatase activity in mice. Mice lacking a functional aromatase enzyme (ArKO) were generated by targeted disruption of the cyp19 gene. Male and female ArKO mice were born with the expected Mendelian frequency from F1 parents and grew to adulthood. Female ArKO mice at 9 weeks of age displayed underdeveloped external genitalia and uteri. Ovaries contained numerous follicles with abundant granulosa cells and evidence of antrum formation that appeared arrested before ovulation. No corpora lutea were present. Additionally the stroma were hyperplastic with structures that appeared to be atretic follicles. Development of the mammary glands approximated that of a prepubertal female. Examination of male ArKO mice of the same age revealed essentially normal internal anatomy but with enlargement of the male accessory sex glands because of increased content of secreted material. The testes appeared normal. Male ArKO mice are capable of breeding and produce litters of approximately average size. Whereas serum estradiol levels were at the limit of detection, testosterone levels were elevated, as were the levels of follicle-stimulating hormone and luteinizing hormone. The phenotype of these animals differs markedly from that of the previously reported ERKO mice, in which the estrogen receptor α is deleted by targeted disruption.
874 citations
TL;DR: The binding characteristics and the structure requirement for flavone and isoflavone phytoestrogens to inhibit human aromatase were obtained and these compounds were found to bind to the active site of aromat enzyme in an orientation in which rings A and C mimic rings D and C of the androgen substrate, respectively.
Abstract: Flavone and isoflavone phytoestrogens are plant chemicals and are known to be competitive inhibitors of cytochrome P450 aromatase with respect to the androgen substrate. Aromatase is the enzyme that converts androgen to estrogen; therefore, these plant chemicals are thought to be capable of modifying the estrogen level in women. In this study, the inhibition profiles of four flavones [chrysin (5, 7-dihydroxyflavone), 7,8-dihydroxyflavone, baicalein (5,6,7-trihydroxyflavone), and galangin (3,5,7-trihydroxyflavone)], two isoflavones [genistein (4,5,7-trihydroxyisoflavone) and biochanin A (5,7-dihydroxy-4-methoxyisoflavone)], one flavanone [naringenin (4, 5,7-trihydroxyflavanone)], and one naphthoflavone (alpha-naphthoflavone) on the wild-type and six human aromatase mutants (I133Y, P308F, D309A, T310S, I395F, and I474Y) were determined. In combination with computer modeling, the binding characteristics and the structure requirement for flavone and isoflavone phytoestrogens to inhibit human aromatase were obtained. These compounds were found to bind to the active site of aromatase in an orientation in which rings A and C mimic rings D and C of the androgen substrate, respectively. This study also provides a molecular basis as to why isoflavones are significantly poorer inhibitors of aromatase than flavones.
320 citations
TL;DR: It follows that the product of the aromatase reaction, namely estrone, that is weakly estrogenic can be converted to the potent estrogen, 17β-estradiol, in endometriotic tissues.
Abstract: Aberrant aromatase expression in stromal cells of endometriosis gives rise to conversion of circulating androstenedione to estrone in this tissue, whereas aromatase expression is absent in the eutopic endometrium. In this study, we initially demonstrated by Northern blotting transcripts of the reductive 17beta-hydroxysteroid dehydrogenase (17betaHSD) type 1, which catalyzes the conversion of estrone to 17beta-estradiol, in both eutopic endometrium and endometriosis. Thus, it follows that the product of the aromatase reaction, namely estrone, that is weakly estrogenic can be converted to the potent estrogen, 17beta-estradiol, in endometriotic tissues. It was previously demonstrated that progesterone stimulates the inactivation of 17beta-estradiol through conversion to estrone in eutopic endometrial epithelial cells. Subsequently, 17betaHSD type 2 was shown to catalyze this reaction, and its transcripts were detected in the epithelial cell component of the eutopic endometrium in secretory phase. Because 17beta-estradiol plays a critical role in the development and growth of endometriosis, we studied 17betaHSD-2 expression in endometriotic tissues and eutopic endometrium. We demonstrated, by Northern blotting, 17betaHSD-2 messenger ribonucleic acid (RNA) in all RNA samples of secretory eutopic endometrium (n=12) but not in secretory samples of endometriotic lesions (n=10), including paired samples of endometrium and endometriosis obtained simultaneously from eight patients. This messenger RNA was not detectable in any samples of proliferative eutopic endometrium or endometriosis (n=4) as expected. Next, we confirmed these findings by demonstration of immunoreactive 17betaHSD-2 in epithelial cells of secretory eutopic endometrium in 11 of 13 samples employing a monoclonal antibody against 17betaHSD-2, whereas 17betaHSD-2 was absent in paired secretory endometriotic tissues (n=4). Proliferative eutopic endometrial (n=8) and endometriotic (n=4) tissues were both negative for immunoreactive 17betaHSD-2, except for barely detectable levels in 1 eutopic endometrial sample. Finally, we sought to determine whether deficient 17betaHSD-2 expression in endometriotic tissues is due to impaired progesterone action in endometriosis. We determined by immunohistochemistry the expression of progesterone and estrogen receptors in these paired samples of secretory (n=4) and proliferative (n=4) eutopic endometrium and endometriosis, and no differences could be demonstrated. In conclusion, inactivation of 17beta-estradiol is impaired in endometriotic tissues due to deficient expression of 17betaHSD-2, which is normally expressed in eutopic endometrium in response to progesterone. The lack of 17betaHSD-2 expression in endometriosis is not due to alterations in the levels of immunoreactive progesterone or estrogen receptors in this tissue and may be related to an inhibitory aberration in the signaling pathway that regulates 17betaHSD-2 expression.
312 citations
TL;DR: This chapter describes the different aspects of regulation of androgen action, a member of the steroid-thyroid hormone-retinoid-vitamin D superfamily of nuclear receptors (NRs) that function as ligand-activated transcription factors.
Abstract: Publisher Summary This chapter describes the different aspects of regulation of androgen action. Androgens belong to a class of C-19 steroids secreted primarily by the testis and adrenal cortex. Hormonally active androgens promote reproductive and anabolic functions. Both reproductive and anabolic effects of androgens are mediated by their interaction with the androgen receptor (AR), a member of the steroid-thyroid hormone-retinoid-vitamin D superfamily of nuclear receptors (NRs) that function as ligand-activated transcription factors. Almost all of the androgen functions, except its conversion to estrogen by the enzyme aromatase in certain target cells are known to be mediated by the androgen receptor. The androgen receptor are coded by a single copy gene, which is located on the X chromosome. The functional relevance of the segmented domain structure of the NR superfamily is supported by the results of deletion mutagenesis and domain swapping among various receptor proteins. The interaction between the amino terminal and the steroid-binding carboxy-terminal end in the AR transactivation function was initially indicated by the finding that a segment within the hormone-binding domain exerts an inhibitory influence in the transcription regulatory activity of the AR, and the deletion of this region results in ligand-independent activation of the receptor.
288 citations
TL;DR: An important participation of the aromatase gene in the reproductive behaviors is suggested, as male-typical sexual behavior directed toward females was, however, strongly modified in the ArKO male mice.
287 citations
TL;DR: The localization of aromatase in pre-synaptic boutons suggests possible roles for estrogens at the synapse, and a growing body of evidence indicates that the estrogen regulation of aromAtase is, at least in part, trans- Synaptic.
268 citations
TL;DR: It is argued that many of the effects of oestrogens in the male might stem from its local production and action and, furthermore, that the balance in action between androgens and oestosterone might be of central importance at many oestrogen target sites.
Abstract: Roles for oestrogens in brain masculinization/sexual behaviour, regulation of follicle-stimulating hormone (FSH)secretion and Leydig cell development and function are well established. However, the widespread distribution of oestrogen receptors alpha and beta in reproductive and other tissues of the male, and findings from human males or transgenic animals in which the genes coding for these receptors or for aromatase are non-functional, are changing our perception of the roles of oestrogen in the male. Aspects of pubertal development in boys (growth of the long bones, their mineralization and epiphyseal closure) attributed to the actions of androgens are now recognized as being mediated in part by oestrogens. Oestrogens also play a role (probably vasodilatatory) in the cardiovascular system of the male. Within the reproductive system, oestrogens have been shown to play a role in the regulation of fluid resorption from the efferent ducts and appear to be important in the structural and functional development of the Wolffian/excurrent duct system, as well as that of the prostate; inappropriately low or high oestrogen exposure during development can cause permanent changes to these tissues, which may lead to disorders of spermatogenesis and infertility. Sertoli cells and certain germ cells in the testis are also targets for oestrogen action. Many other tissues (adipose, kidney, thymus/immune system, skin, gut and muscle) are oestrogen targets in the male. Based on these findings and the widespread distribution of aromatase, it is argued that many of the effects of oestrogens in the male might stem from its local production and action and, furthermore, that the balance in action between androgens and oestrogens might be of central importance at many oestrogen target sites.
223 citations
TL;DR: In this paper, a 57-year-old woman who presented with recurrent severe endometriosis after hysterectomy and bilateral salpingo-oophorectomy was administered with anastrozole (1 mg/d) and elemental calcium (1.5 g/d).
223 citations
TL;DR: In human estrogen-dependent neoplasms such as breast, endometrioid endometrial, and surface epithelial-stromal ovarian carcinomas, intratumoral aromatase is considered to play important roles in converting circulating androgens derived from adrenal cortex and/or ovary to estrogens, possibly in association with 17 beta-HSD type 1 and estrogen sulfatase.
Abstract: I. Introduction II. Aromatase Cytochrome P450 and in Situ Estrogen Production III. Aromatase in Breast Cancer A. Introduction B. Localization C. Genetic regulation D. Clinical and pathological correlation E. Male breast cancer IV. Aromatase in Endometrial Cancer A. Introduction B. Localization C. Genetic regulation D. Clinical and pathological correlation V. Aromatase in Ovarian Cancer A. Introduction B. Localization C. Genetic regulation D. Clinical and pathological correlation VI. Summary
222 citations
TL;DR: The expression of the functional P450arom in mature rat germ cells confirms the existence of an additional source of estrogens within the genital tract of the male and indicates that in mature rats, not only Leydig cells and Sertoli cells but also germ cells have the capacity to express functional P 450arom.
Abstract: Aromatase activity has been measured in Leydig cells and Sertoli cells from both immature and mature rats. Cytochrome P450 aromatase (P450arom) has been immunolocalized in germ cells of the rodent, bear, and rooster. Our purpose was to investigate expression of and to immunolocalize P450arom in adult rat testicular cells. After Western blotting with a specific anti-cytochrome P450arom antibody, we demonstrated the presence of a 55-kDa protein in mature rat seminiferous tubules and crude germ cell preparations. Immunoreactive aromatase was detected both in cultured rat Leydig cells and in testis sections (interstitial tissue and elongated spermatids showed positive immunoreactivity for P450arom). We next used reverse transcription-polymerase chain reaction to localize and quantify the P450arom mRNA in the various testicular cells. In rat Leydig cells, the amount of P450arom mRNA was 15 times higher than in Sertoli cells (34.1+/-3.2 to 2.3 +/-0.2 x 10(-3) amol/10(6) cells, respectively). In pachytene spermatocytes, round spermatids, and testicular spermatozoa the P450arom mRNA levels were 38.7+/-8.1, 20.4+/-3.8, and < 1.3 x 10(-3) amol/10(6) cells, respectively. The aromatase activity was 2.5-4 times higher in testicular spermatozoa (8.48+/-1.98 fmol/10(6) cells per hour) than in other germ cells. These results indicate that in mature rats, not only Leydig cells and Sertoli cells but also germ cells have the capacity to express functional P450arom. According to the germ cell maturation state, there was an inverse relationship between P450arom mRNA content and the biological activity of the protein. The expression of the functional P450arom in mature rat germ cells confirms the existence of an additional source of estrogens within the genital tract of the male.
213 citations
Journal Article•
TL;DR: These studies provide the first direct evidence that in situ synthesis of E2 in breast tumors, as opposed to peripheral aromatization and uptake from plasma, can enhance tissue E2 levels and stimulate tumor growth.
Abstract: The high concentrations of estradiol (E2) found in breast tumors of postmenopausal women could be the result of enhanced uptake from plasma or in situ aromatization of androgens to estrogens. To test the relative importance of these two mechanisms, a model system allowing precise distinction between each is required. Such a model was established using aromatase (A+)- and sham (A-)-transfected MCF-7 cells inoculated into ovariectomized (OVX) nude mice. To validate the model, the confounding effect of peripheral aromatization was first excluded experimentally. A- cells were inoculated into OVX mice as homoimplants (A- cells on both flanks) or heteroimplants (A- cells on one flank and A+ cells on the other), and growth of A- cells in response to exogenous aromatase substrate, androstenedione (delta4A), was evaluated. A- cells did not grow in either group during the 8 weeks of observation, indicating the lack of peripheral aromatization in OVX mice. The biological effects of in situ aromatization were then directly examined. We found that A+ cells in the heteroimplant group grew rapidly, and that the average weight of A+ tumor was 7.6-fold larger and tissue E2 concentration was 3-4-fold higher than A- tumors grown in the same animals. These results demonstrate that in situ aromatization rather than uptake can be a determinant of tumor E2 content and growth stimulation. An additional experiment was then designed to evaluate the relative importance of in situ synthesis versus uptake under conditions reflecting postmenopausal physiology. Groups of OVX mice bearing A+ cells received E2 Silastic implants to clamp plasma levels at 5, 7, 10, and 20 pg/ml or delta4A by injection. The highest tumor E2 concentration and growth rate were found in the group receiving delta4A. E2 delivered by Silastic implants always produced lower tissue E2 levels and tumor growth rates than resulted from in situ synthesis. These data provide direct evidence that under physiological conditions reflecting those in postmenopausal women, in situ aromatization in breast tumor makes a major contribution to tissue E2 content. As further validation that our experimental paradigm models the postmenopausal state, we studied OVX animals not given delta4A as substrate. A+ cells also grew under these conditions, and the aromatase inhibitor 4-hydroxyandrostenedione reduced both tumor E2 level and growth rate, providing additional evidence of the importance of in situ synthesis. These studies provide the first direct evidence that in situ synthesis of E2 in breast tumors, as opposed to peripheral aromatization and uptake from plasma, can enhance tissue E2 levels and stimulate tumor growth.
TL;DR: It is shown that cyp450 aromatase is expressed in cardiac myocyte and incubation of cardiac myocytes with oestrogen precursors leads to sexual dimorphic transactivation of an oestrogens-responsive reporter plasmid, and this suggests that local Oestrogen biosynthesis of the heart is effective to activate ostrogen receptor alpha and beta, and downstream target genes in a gender-based fashion.
Abstract: The role of cardiac oestrogen receptor expression and local oestrogen synthesis in the pathogenesis of cardiovascular disease is poorly understood. Therefore we studied the effects of the oestrogen precursors androstendione and testosterone on the expression of cyp450 aromatase, oestrogen receptor alpha and beta, and inducible NO synthase (iNOS) in neonatal rat cardiac myocytes. Here, we show that cyp450 aromatase is expressed in cardiac myocytes and incubation of cardiac myocytes with oestrogen precursors leads to sexual dimorphic transactivation of an oestrogen-responsive reporter plasmid. Furthermore, incubation with oestrogen precursors stimulated expression of oestrogen receptor alpha and beta, and iNOS in a gender-specific fashion. These data suggest that local oestrogen biosynthesis of the heart is effective to activate oestrogen receptor alpha and beta, and downstream target genes in a gender-based fashion and may therefore contribute to the beneficial effects of oestrogen in the pathogenesis of cardiovascular disease.
TL;DR: The clinical picture of endometriosis characterises this disease as a hyperactivation of genuine archimetrial functions such as proliferation, inflammatory defence and peristalsis, and a key event appears to consist in the local production of extraovarian oestrogen by a pathological expression of the P450 aromatase
Abstract: Endometriosis is considered primarily a disease of the endometrial-subendometrial unit or archimetra. The clinical picture of endometriosis characterises this disease as a hyperactivation of genuine archimetrial functions such as proliferation, inflammatory defence and peristalsis. While the aetiology of the disease remains to be elucidated, a key event appears to consist in the local production of extraovarian oestrogen by a pathological expression of the P450 aromatase. The starting event may consist in a hyperactivity of the endometrial inflammatory defence, a hyperactivity of the endometrial oxytocin/oxytocin receptor system or in the pathological expression of the P450 aromatase system itself. Regardless of which of these levels the starting event is localized in, they influence each other on both the level of the archimetra and the endometriotic lesions. Locally elevated oestrogen levels inevitably up-regulate the endometrial oxytocin mRNA and increased levels of oxytocin result in uterine hyperperistalsis, increased transtubal seeding of endometrial tissue fragments and finally subfertility and infertility by impairment of the uterine mechanism of rapid and sustained sperm transport. Locally increased levels of oestrogen lead, on both the level of the endometrial-subendometrial unit and the endometriotic lesion, to processes of hyperproliferation. These processes result, on the level of the uterus, in an infiltrative growth of elements of the archimetra into the neometra and, on the level of the endometriotic lesion, in infiltrative endometriosis. There is circumstantial evidence that trauma might be an important initial event that induces the specific biochemical and cellular responses of the archimetra. This model is able to explain both the pleiomorphic appearance of endometriosis and the, up until now, enigmatic infertility associated with mild and moderate endometriosis.
TL;DR: Anti-Müllerian (AMH), a member of the transforming growth factor beta produced by immature Sertoli cells and, to a lesser degree, by granulosa cells from birth to the end of reproductive life, does not affect gonadal determination but has a negative effect upon gonadal development in both sexes.
TL;DR: The lack of effect of 5alpha-DHT, a potent androgen which cannot be converted to estrogen, suggests that the action of testosterone depends upon its conversion to estrogen by aromatase, and may also explain why estrogen increased the density of 5-HT2AR binding sites in the caudate-putamen, a brain region where aromat enzyme is scarce.
TL;DR: The brain-derived cDNA had 53% and 61-62% sequence identity when compared with human placental and fish ovarian P450arom forms, respectively, and higher homologies in conserved functional domains.
TL;DR: Data provide the first evidence that AMH, like other members of the transforming growth factor-beta family, has an autocrine/paracrine effect on testicular steroidogenic function during the fetal and prepubertal periods.
Abstract: Anti-Mullerian hormone (AMH) is mainly involved in the regression of Mullerian ducts in male fetuses, but it may have other functions linked to gonadal development. The present study examines the effect of AMH on steroidogenesis by Sertoli and Leydig cells in fetal and immature rats during the period where AMH is physiologically produced in the testis. The basal aromatase activity of Sertoli cells in primary culture was strongly stimulated (77-91%) by cAMP. AMH (35 nM) reduced cAMP-stimulated aromatase activity by 49-69% as early as fetal day 16 and until postnatal day 20. This effect was dose dependent and was seen after 48 h in culture. AMH also blocked the Sertoli cell aromatase activity stimulated by FSH, but LH did not stimulate this activity, confirming that the aromatase activity effectively resulted from Sertoli cells and not from contaminating Leydig cells. RT-PCR analysis showed that AMH reduced aromatase activity by decreasing the amount of aromatase messenger RNA. AMH also inhibited the LH-stimulated testosterone production by dispersed fetal Leydig cells in culture in a dose-dependent manner. The inhibitory effect of AMH did not depend on the fetal stage studied (16 or 20 days postconception) and resulted from a drop in the steroidogenic activity of each Leydig cell without affecting the number of 3beta-hydroxysteroid dehydrogenase-positive cells. These data provide the first evidence that AMH, like other members of the transforming growth factor-beta family, has an autocrine/paracrine effect on testicular steroidogenic function during the fetal and prepubertal periods.
TL;DR: A family with the aromatase excess syndrome is described, in which the condition was inherited in an autosomal dominant manner, led to feminizing manifestations in both sexes, and was associated with the aberrant utilization of a novel transcript of the P450arom gene.
Abstract: Increased extraglandular aromatization has been reported as the cause of familial gynecomastia. We studied a kindred with aromatase excess inherited in an autosomal dominant manner, in which affected males had heterosexual precocity and/or gynecomastia, and affected females had isosexual precocity and/or macromastia. The propositus was a 9-yr-old boy with gynecomastia. His 7.5-yr-old sister had precocious puberty, and their father and paternal grandmother had peripubertal gynecomastia and macromastia, respectively. Serum concentrations of gonadal and adrenal steroid hormones were determined before and after the administration of corticotropin and/or hCG. Aromatase activity was determined by[ 3H]Δ4-androstenedione to[ 3H]estrone conversion by cultured skin fibroblasts and/or Epstein-Barr virus-transformed lymphocytes and was detected by immunohistochemistry and/or Western analysis. Linkage was examined with a polymorphism of the aromatase (P450arom) gene. The P450arom messenger ribonucleic acid was analyze...
TL;DR: It is found that 7-hydroxyflavone and apigenin are the most effective aromatase and 17beta-Hydroxysteroid dehydrogenase inhibitors, respectively.
TL;DR: Evidence that a gene for aromatase cytochrome P-450, an enzyme required for the last step in the synthesis of estradiol-17beta, is expressed in medullae of the left and right gonads of a female chicken embryo, but not in those of a male chicken embryo is presented, suggesting that the absence of expression of the estrogen receptor gene in the right gonad is not the result of down-regulation.
Abstract: In birds, differentiation of embryonic gonads is not as strictly determined by the genetic sex as it is in mammals, and can be influenced by early manipulation with a sex steroid hormone. Thus administration of an aromatase inhibitor induces testis development in the genetic female, and administration of estrogen induces a left ovotestis in the genetic male embryo. Another feature of avian gonadogenesis is that only the left ovary develops in most species. Molecular mechanisms underlying these features at the level of gene expression have not been elucidated. In this paper, we present evidence that a gene for aromatase cytochrome P-450, an enzyme required for the last step in the synthesis of estradiol-17beta, is expressed in medullae of the left and right gonads of a female chicken embryo, but not in those of a male chicken embryo, and that an estrogen receptor gene is expressed only in epithelium (and cortex later, in the female) of the left, not the right, gonad of both sexes, but the expression in the male left gonad is temporary and restricted to an early stage of development. Differential expression of these two genes serves well to explain the above features of gonadal development in birds. Furthermore, in ovo administration of estradiol-17beta from the 5th to the 14th day of incubation does not cause expression of the estrogen receptor gene in the right gonad of chicken embryos of either sex, suggesting that the absence of expression of the estrogen receptor gene in the right gonad is not the result of down-regulation, but may be regarded as an important cause of the unilateral ovarian development.
Journal Article•
TL;DR: The results suggest that ERR alpha-1 is one of the nuclear proteins interacting with S1 in breast cancer tissue, and it is thought that the silencer element in the human aromatase gene may function differently in different tissues because of distinct expression patterns of transcription factors.
Abstract: We have previously identified a silencer element (S1) that is situated between promoters I3 and II of the human aromatase gene and that down-regulates the action of these promoters We recently applied the yeast one-hybrid approach to screen a human breast tissue hybrid cDNA expression library for genes encoding the proteins binding to the silencer region Most proteins identified from this approach belong to the nuclear receptor superfamily Fifty % of the positive clones encode for ERRα-1, and other positive clones include EAR-2, EAR-3 (COUP-TF1), RARγ, and p120E4F Because ERRα-1 was found to be the major protein interacting with S1, we decided to examine the regulatory action of ERRα-1 on promoter I3 of the human aromatase gene Using a reporter plasmid that includes the aromatase genomic fragment containing promoter I3 and S1, ERRα-1 was found to have a positive regulatory function in breast cancer SK-BR-3 cells Gel mobility shift assays have confirmed that ERRα-1 binds to S1 in a dose-dependent manner, and DNase I footprinting analysis has revealed that ERRα-1 binds to a region, 5′-AAGGTCAGAAAT-3′, which is within S1 and between 96 and 107 bp relative to the transcriptional start site of promoter I3 In addition, despite the fact that the nuclear receptor SF1 was shown previously to bind to the same site and to mediate a cAMP response in ovary, our yeast one-hybrid screening did not find any SF-1 clones Gel mobility shift assays further revealed that SF-1 can bind to the silencer element with an affinity copmarable with ERRα-1 Because our reverse transcription-PCR analysis was not able to detect SF1 mRNA in breast cancer tissue or in SK-BR-3 cells, it is thought that SF1 protein is not expressed in breast cancer tissue Two ERRα-1 RNA variants with differences at the 5′-end have been reported Our reverse transcription-PCR analysis identified the shorter variant in 28 of 32 breast tumor specimens and the longer variant in only 1 specimen In addition, the shorter variant was detected in breast cancer SK-BR-3 cells as well as in a breast tumor fibroblast line WS3TF The results suggest that ERRα-1 is one of the nuclear proteins interacting with S1 in breast cancer tissue It is thought that the silencer element in the human aromatase gene may function differently in different tissues because of distinct expression patterns of transcription factors
TL;DR: The data suggest that the CYP19 gene may be involved as a low penetrance gene in breast cancer susceptibility.
Abstract: The aromatase P450 (coded by the CYP19 gene) is responsible for the rate limiting step in the metabolism of C19 steroids to estrogens and is expressed in most breast carcinomas. A polymorphic tetranucleotide repeat (TTTA)nin intron 5, about 80 nucleotides downstream of exon 4 has previously been described. The allele frequencies of the polymorphic repeat were studied in series of 182 sporadic and 185 familial breast cancer patients as well as in 252 healthy control individuals. Five different alleles containing 7, 8, 9, 11 and 12 -TTTA-repeats were detected. A relatively rare allele (Al) containing the longest repeat (TTTA)12 was found significantly more frequently in breast cancer patients than in control individuals. This indicates that individuals carrying the A1 allele of CYP19 may have an increased risk of developing breast cancer, OR 2.42 (95% confidence interval [CI] 1.03-5.80). The higher frequency was observed in both sporadic and familial patients, although when each of the groups was compared to the control group only a borderline significance was seen. A higher frequency of A 2 allele carriers was also found in the group of patients with positive estrogen receptor and progesterone receptor positive tumors. These data suggest that the CYP19 gene may be involved as a low penetrance gene in breast cancer Susceptibility.
TL;DR: Oestrogen produced locally by aromatase is thought to participate in numerous biological functions in the adult central nervous system (CNS), however, little is known about aromat enzyme expression in the human CNS.
Abstract: OBJECTIVE Oestrogen produced locally by aromatase is thought to participate in numerous biological functions in the adult central nervous system (CNS). However, little is known about aromatase expression in the human CNS. DESIGN We examined aromatase expression in human brain regions, (4 men, 2 women) obtained from autopsy, by reverse transcriptase (RT)-polymerase chain reaction (PCR) and also studied alternative use of multiple exons 1 of its gene, which is involved in tissue specific expression of aromatase in human. RESULTS The amount of aromatase mRNA determine by RT-PCR assay in 6 cases tended to be highest in pons, thalamus, hypothalamus and hippocampus. Analysis of multiple exons 1 revealed that 1f, considered specific for brain, as well as 1b (fibrolast type) and 1d (gonadal type), were expressed. 1d and 1f tended to be utilized in hypothalamus, thalamus and amygdala. The amount of overall mRNA expression was also higher in hypothalamus, thalamus and amygdala than in other regions of the brain. There were no differences of utilization of exons 1 and mRNA expression of aromatase between female and male brain. CONCLUSIONS These results demonstrate that aromatase is expressed widely in various regions of human brain tissues in both men and women.
TL;DR: The results suggest that bone is an extraglandular source of local estrogen which plays an important role in bone mineral metabolism through autocrine and paracrine actions.
TL;DR: The study provides a molecular basis as to why isoflavones are significantly poorer inhibitors of aromatase than flavones, and will help to determine which fruits and vegetables should be included in the diet of postmenopausal women in order to reduce the incidence for breast cancer by inhibiting estrogen biosynthesis in breast tissue.
Abstract: Estrogens play an important role in breast cancer development. Aromatase (CYP19), a cytochrome P450, is the enzyme that synthesizes estrogens. Aromatase is expressed at a higher level in human breast cancer tissue than in normal breast tissue using enzyme activity measurement, immunocytochemistry, and RT-PCR analysis. Cell culture, animal experiments using aromatase-transfected breast cancer cells, and transgenic mouse studies have demonstrated that in situ produced estrogen plays a more important role than circulating estrogens in breast tumor promotion. In addition, tumor aromatase has been shown to stimulate breast cancer growth in both an autocrine and a paracrine manner. RT-PCR and gene transcriptional studies have revealed that aromatase promoter switches from a glucocorticoid-stimulated promoter, I.4, in normal tissue to cAMP-stimulated promoters, I.3 and II, in cancereous tissue. Suppression of in situ estrogen biosynthesis can be achieved by the prevention of aromatase expression or by the inhibition of aromatase activity in breast tumors. While the control mechanism of aromatase expression in breast cancer tissue is not yet fully understood, aromatase-inhibitor therapy is considered for second-line treatment in patients who fail anti-estrogen therapy. Twenty to thirty percent of the patients who fail anti-estrogen treatment respond to aromatase-inhibitor treatment. Several potent and selective aromatase inhibitors have been developed and used to treat breast cancer. The binding nature of various aromatase inhibitors has been examined by computer modeling, site-directed mutagenesis of aromatase, and inhibition kinetics. The enzyme structure-function studies have led to the development of a computer model of the active site region of human aromatase. The model is used to evaluate the interaction of phytoestrogens such as flavones and isoflavones with aromatase. The study provides a molecular basis as to why isoflavones are significantly poorer inhibitors of aromatase than flavones. The phytoestrogen studies will help to determine which fruits and vegetables (those containing the appropriate phytoestrogens) should be included in the diet of postmenopausal women in order to reduce the incidence for breast cancer by inhibiting estrogen biosynthesis in breast tissue.
TL;DR: It is concluded that rat testicular germ cells from pachytene spermatocytes through elongating sperMatids and epididymal sperm contain active P450arom and that sperm lose aromatase activity as they mature during epididcyal transit.
Abstract: Although testosterone is the principal sex steroid produced by the testis, estrogen is known to be produced by both Leydig and Sertoli cells during different developmental periods. Additionally, evidence is unfolding to suggest that germ cells might also participate in the synthesis of estrogen within the male reproductive tract. We have recently reported that the messenger ribonucleic acid (mRNA) for P450 aromatase (P450arom), the enzyme that converts androgen to estrogen, is synthesized by rat germ cells. Therefore, the present study was conducted to determine which germ cell types synthesize active P450arom and to measure the activity of this enzyme in germ cells throughout spermatogenesis and in maturing sperm during epididymal transit. First, P450arom activity was measured in pachytene spermatocytes, round spermatids, and a mixture of round spermatids, elongating spermatids, and residual bodies using the tritiated water (3H2O) assay. Second, sperm isolated from different regions of the epididymis were assayed for P450arom activity. Sperm isolated from the caput epididymis with attached efferent ductules had the higher P450arom activity, whereas sperm isolated from the corpus and cauda epididymides had lower P450arom activity. The decrease in P450arom activity in cauda sperm was further confirmed by immunocytochemistry. On the basis of these observations, we conclude that rat testicular germ cells from pachytene spermatocytes through elongating spermatids and epididymal sperm contain active P450arom and that sperm lose aromatase activity as they mature during epididymal transit. Therefore, both post-pachytene rat germ cells and epididymal sperm are capable of estrogen synthesis and are an additional, potentially significant, source of estrogen in the male reproductive tract.
TL;DR: Data indicate that P450AROM mRNA expression and oestradiol production begin in developing follicles when they reach approximately 7 mm in diameter, which is similar to size-matched control follicles.
Abstract: Polycystic ovary syndrome (PCOS) is a common reproductive disorder characterized by arrested follicular development prior to selection of a dominant follicle. Dominant follicles produce large amounts of oestradiol but PCOS follicles do not. With several potential aromatase (P450AROM) inhibitors in follicular fluid, the question arises whether P450AROM is expressed in PCOS granulosa cells, but the activity is inhibited, or whether P450AROM is not expressed in PCOS. The purpose of the present study was to determine whether P450AROM mRNA expression is altered in PCOS and to correlate P450AROM mRNA expression in individual follicles with aromatase stimulatory bioactivity and oestradiol in the follicular microenvironments. P450AROM mRNA was measured in individual follicles from 16 PCOS and 48 regularly cycling control women by quantitative polymerase chain reaction (PCR) and correlated with follicular fluid oestradiol concentrations and aromatase stimulating bioactivity measured by the rat granulosa cells aromatase bioassay. Follicular fluid oestradiol was low in all control follicles or = 7 mm contained elevated oestradiol values (P or = 7 mm with an androstenedione:oestradiol ratio of 4 contained little or no bioactivity. All PCOS follicles contained low levels of oestradiol, P450AROM mRNA and aromatase stimulating bioactivity similar to size-matched control follicles. These data indicate that P450AROM mRNA expression and oestradiol production begin in developing follicles when they reach approximately 7 mm in diameter. Oestradiol production is low in PCOS follicles because there is insufficient aromatase stimulating bioactivity to increase P450AROM mRNA expression.
TL;DR: Estrogen deficiency and estrogen resistance lead to absence of the pubertal growth spurt, delayed bone maturation, unfused epiphyses, continued growth into adulthood and very tall adult stature in both sexes.
Abstract: The goals of this presentation are to review the essential roles of aromatase, estrogens and the estrogen receptor in pubertal growth. Estrogen deficiency due to mutations in the aromatase gene (CYP19
TL;DR: The anatomic distribution of P450arom mRNA within hypothalamic and limbic nuclei of the adult male rat and steady state concentrations are regionally regulated by T are confirmed and demonstrate the necessity of using a molecular probe that can distinguish between P 450arom variants in the brain.
Abstract: Recent evidence suggests that two cytochrome P450 aromatase (P450 arom ) mRNA transcripts are present in the rat brain. One of these contains the entire 5'-coding sequence and correlates with the presence of functional enzyme. We designed a new 255-base pair P450 arom probe (AROM255) that recognizes only this full-length P450 arom mRNA. Ribonuclease protection assays verified that the cRNA probe synthesized from this construct recognized a single RNA species in brain tissues that express aromatase activity, but not in the cingulate cortex, an area previously shown to contain only the alternate transcript. Moreover, the P450 arom mRNA content of the preoptic area was significantly lower in castrates than in intact males or testosterone (T)-treated castrates. We employed 33 P-labeled cRNA probes to examine the distribution of P450 arom mRNA by in situ hybridization. High levels of mRNA were detected in the medial preoptic nucleus (MPN), bed nucleus of the stria terminalis (BnST), and medial amygdala (MA). Lower levels were found in the ventromedial hypothalamic nucleus and cortical amygdala. The magnitude of the hybridization signal in the BnST and MPN was greater in males than in females. Treatment with T propionate significantly increased hybridization signal in BnST, MPN, and MA. These results confirm the anatomic distribution of P450 arom mRNA within hypothalamic and limbic nuclei of the adult male rat and demonstrate that steady state concentrations are regionally regulated by T. Moreover, they demonstrate the necessity of using a molecular probe that can distinguish between P450 arom variants in the brain.
TL;DR: Testosterone and/or its estrogenic metabolites act on the developing brain to determine the gender-specific capacity for aromatization and to regulate androgen responsiveness within components of the neural circuitry that mediates male sexual behavior.
Abstract: Androgens regulate aromatase activity in the medial preoptic area and other components of the brain circuit that mediates male sexual behavior. The levels of aromatase activity within these brain regions are greater in males than in females. As the activation of copulation requires aromatization of testosterone to estradiol, this quantitative enzymatic difference between sexes could contribute to the greater behavioral response displayed by males. The present study was designed to test the hypothesis that gender differences in brain aromatase activity of adult rats are dependent on the sexual differentiation of the brain that occurs during perinatal exposure to gonadal hormones. Aromatase activity was measured in vitro in microdissected brain samples using a sensitive radiometric assay. We examined the effect of pre- and postnatal treatment with testosterone propionate or diethylstilbestrol on basal levels and androgen responsiveness of aromatase in adults. In addition, we examined what effect prepubertal gonadectomy exerts on enzyme regulation. Our results demonstrate that perinatal treatments with gonadal hormones that are known to differentiate sexual behavior can completely masculinize the capacity for aromatization in the adult female. The process that differentiates aromatase expression appears to depend on androgen exposure and, in part, local estrogen synthesis, as diethylstilbestrol was able to substitute for testosterone propionate. We also observed that prepubertal gonadectomy reduced the levels of aromatase activity measured in adult brain, suggesting that gonadal hormones that are secreted during puberty may enhance the expression of aromatase activity in adulthood. From this study, we conclude that testosterone and/or its estrogenic metabolites act on the developing brain to determine the gender-specific capacity for aromatization and to regulate androgen responsiveness within components of the neural circuitry that mediates male sexual behavior.