Changes In Aromatase Research Articles

Leptin induces CREB-dependent aromatase activation through COX-2 expression in breast cancer cells

Leptin plays a key role in the control of adipocyte formation, as well as in the associated regulation of energy intake and expenditure. The goal of this study was to determine if leptin-induced aromatase enhances estrogen production and induces tumor cell growth stimulation. To this end, breast cancer cells were incubated with leptin in the absence or presence of inhibitor pretreatment, and changes in aromatase and cyclooxygenase-2 (COX-2) expression were evaluated at the mRNA and protein levels. Transient transfection assays were performed to examine the aromatase and COX-2 gene promoter activities and immunoblot analysis was used to examine protein expression. Leptin induced aromatase expression, estradiol production, and promoter activity in breast cancer cells. Protein levels of phospho-STAT3, PKA, Akt, ERK, and JNK were increased by leptin. Leptin also significantly increased cAMP levels, cAMP response element (CRE) activation, and CREB phosphorylation. In addition, leptin induced COX-2 expression, promoter activity, and increased the production of prostaglandin E2. Finally, a COX-2 inhibitor and aromatase inhibitor suppressed leptin-induced cell proliferation in MCF-7 breast cancer cells. Together, our data show that leptin increased aromatase expression in breast cancer cells, which was correlated with COX-2 upregulation, mediated through CRE activation and cooperation among multiple signaling pathways.

Aromatase changes in depression: A postmortem and animal experimental study

A hyperactive hypothalamo-pituitary-adrenal (HPA) axis is a prominent feature in depression. It has been shown that androgens inhibit HPA activity and that estrogens stimulate it. We have therefore investigated, in human postmortem hypothalamus, whether depression features an increase in aromatase, which is the rate-limiting enzyme for the conversion of androgens to estrogens. In addition, we have tested the effect of an aromatase inhibitor on depression-like symptoms in a frequently used animal model for depression. At first, aromatase immunoreactivity (ir) was quantified in the central part of the hypothalamic paraventricular nucleus (PVN) of 10 major depressive disorder (MDD) patients and 10 well-matched control subjects. Subsequently an animal experimental study was performed using the chronic unpredictable mild stress (CUMS) rats as depression model. The effect of administration of 1,4,6-androstatriene-3,17-dione (ATD), an aromatase inhibitor, was investigated by silastic capsule implantation. In the postmortem study, the amount of PVN aromatase-ir decreased significantly in the MDD group compared to the controls (P=0.029). In the animal study, ATD was found to cause significantly increased testosterone (T) levels, both in plasma and in the hypothalamus. However, ATD administration did not show significant effects on the depression-like behaviors or plasma corticosterone levels in CUMS rats. Based on our observations in human postmortem material and the animal experiment, we have to conclude that alterations in aromatase in adulthood do not seem to play a major role in the pathogenesis of the symptoms of depression.

Changes in aromatase (CYP19) gene promoter usage in non-small cell lung cancer

In humans, aromatase (CYP19) gene expression is regulated via alternative promoters. Activation of each promoter gives rise to a CYP19 mRNA species with a unique 5′-untranslated region. Inhibition of aromatase has been reported to downregulate lung tumor growth. The genetic basis for CYP19 gene expression and aromatase activity in lung cancer remains poorly understood. We analyzed tissues from 15 patients with non-small cell lung cancer (NSCLC) to evaluate CYP19 promoter usage and promoter-specific aromatase mRNA levels in NSCLC tumor tissues and adjacent non-malignant tissues. CYP19 promoter usage was determined by multiplex RT-PCR and aromatase mRNA levels were measured with real-time RT-PCR. In non-malignant tissues, aromatase mRNA was primarily derived from activation of CYP19 promoter I.4. Although promoter I.4 usage was also dominant in tumor tissues, I.4 activation was significantly lower compared with adjacent non-malignant tissues. Activity of promoters I.3, I.1 and I.7 was significantly higher in tumor tissues compared with non-malignant tissues. In 4 of 15 cases of non-small cell lung cancer, switching from CYP19 promoter I.4 to the alternative promoters II, I.1 or I.7 was observed. In 9 cases, there were significantly higher levels of aromatase mRNA in lung tumor tissues compared with adjacent non-malignant tissues. These findings suggest aberrant activation of alternative CYP19 promoters that may lead to upregulation of local aromatase expression in some cases of NSCLC. Further studies are needed to examine the impact of alternative CYP19 promoter usage on local estrogen levels and lung tumor growth.

Seasonal changes in aromatase and androgen receptor, but not estrogen receptor mRNA expression in the brain of the free‐living male song sparrow, Melospiza melodia morphna

Free-living male song sparrows experience three annually repeating life history stages associated with differential expression of sex steroid-dependent reproductive and aggressive behavior. In the breeding stage, they display reproductive and aggressive behavior and have elevated circulating testosterone levels. During molt, males show little or no aggression and no reproductive behavior, and have basal levels of circulating testosterone. In the non-breeding stage, they display high levels of aggression and no reproductive behavior, and have basal levels of circulating testosterone. In order to understand more fully the neural regulation of seasonal aggressive and reproductive behavior, birds were collected during all three life history stages, and levels of neural aromatase, androgen receptor (AR), and estrogen receptor alpha (ERalpha) and beta (ERbeta) mRNA expression were measured. Breeding males had the highest levels of aromatase expression in both the preoptic area (POA) and medial preoptic area/medial bed nucleus of the stria terminalis (mPOA/BSTm), and the highest AR expression levels in the POA, consistent with the well-established role these regions play in the regulation of male reproductive behavior. Aromatase expression in the ventromedial nucleus of the hypothalamus (VMH) was higher during breeding and non-breeding compared with molt, suggesting that the VMH may play a role in the estrogen-dependent regulation of aggression in this species. AR expression also varied in medial HVC and pvMSt, a newly described periventricular region in the medial striatum. ERalpha and ERbeta mRNA expression did not vary seasonally in any brain region examined, suggesting that estrogen-dependent changes in behavior are mediated by differences in neural estrogen synthesis.

Transactivation of the Epidermal Growth Factor Receptor Is Involved in the Lutropin Receptor-Mediated Down-Regulation of Ovarian Aromatase Expression in Vivo

Ovarian follicular development and differentiation is characterized by dramatic changes in aromatase (Cyp19a1) expression. In preovulatory follicles, activation of the FSH receptor increases aromatase expression until the surge of LH decreases it. Here we provide in vivo evidence that down-regulation of Cyp19a1 by the LH surge requires efficient signaling through the epidermal growth factor receptor (EGFR). The human chorionic gonadotropin (hCG)-induced down-regulation of Cyp19a1 expression in the two different mouse models with inactivating mutations of the EGFR (wa2 and velvet) is impaired but not abolished. The hCG-induced phosphorylation of ovarian ERK1/2, expression of C/EBPbeta, and the phosphorylation of Connexin43 (two downstream targets of ERK1/2 action) are also decreased in these two mouse models. In contrast, disruption of EGFR signaling does not have any affect on the hCG-induced phosphorylation of cAMP response element-binding protein or AKT. This study provides the first in vivo evidence linking the LH receptor, the EGFR, and ERK1/2 as sequential components of a pathway that regulates ovarian Cyp19a1 expression.

Sexual Behavior Activity Tracks Rapid Changes in Brain Estrogen Concentrations

Estrogens are classically viewed as hormones that bind to intracellular receptors, which then act as transcription factors to modulate gene expression; however, they also affect many aspects of neuronal functioning by rapid nongenomic actions. Brain estrogen production can be regulated within minutes by changes in aromatase (estrogen synthase) activity as a result of calcium-dependent phosphorylations of the enzyme. To determine the effects of rapid changes in estrogen availability on male copulatory behavior, we mimicked in male mice the rapid upregulation and downregulation of brain estrogen concentration that should occur after inactivation or activation of aromatase activity. A single injection of different aromatase inhibitors [Vorozole, 1,4,6-androstatrien-3,17-dione (ATD), or its metabolite 17-OH-ATD (1,4,6-androstatrien-17beta-ol-3-one)] almost completely suppressed male sexual behavior (mounts and intromissions) expressed 10-20 min later by C57BL/6J mice but did not affect behavior in aromatase knock-out (ArKO) mice, activated by daily injections of estradiol benzoate, thereby confirming the specificity of the behavioral inhibition observed in wild-type mice. The rapid ATD-induced inhibition was reversed by the simultaneous injection of a large dose of estradiol. A single injection of estradiol to ArKO mice also activated male sexual behavior within 15 min. Thus, rapid increases or decreases in brain estrogen concentrations are followed within minutes by corresponding changes in male sexual behavior. Sexual behavior can thus be used to monitor changes in local estrogen concentrations and analyze the mechanisms mediating the rapid decline in estrogen signaling that takes place after inhibition of estrogen synthesis.

Aromatase and cyclooxygenase-2 expression in endometrial polyps during the menstrual cycle

Objectives. To study the changes in aromatase, Ki-67 and cyclooxygenase-2 (COX-2) expression during the menstrual cycle in both endometrial polyps and normal endometria.Patients and methods. Paraffin-embedded tissue samples from 118 premenopausal patients were submitted to immunohistochemistry for measurement of aromatase, COX-2 and Ki-67 expression. Fifty cases of endometrial polyps and 68 cases of disease-free endometrium were included.Results. The presence of aromatase expression was significantly higher in endometrial polyps than in disease-free endometria. On the other hand, changes in COX-2 and Ki-67 expression followed a similar pattern during the menstrual cycle in both groups, expression peaking during the proliferative phase and falling during the late luteal phase.Conclusion. A significantly higher proportion of endometrial polyps express aromatase compared with disease-free endometrium; however, no correlation was found between aromatase expression and changes in either Ki-67 or COX-2 expression during the menstrual cycle.

Effect of labor induction on the expression of oxytocin receptor, cytochrome P450 aromatase, and estradiol receptor in the reproductive tract of the late-pregnant ewe.

In this study, we investigated the timing of changes in aromatase, estradiol receptor, and oxytocin receptor expression in ovine uterine and placental tissues before parturition. Labor was induced by betamethasone injection into the fetus on Days 130-132 of pregnancy. Tissue samples were collected at injection and then every 14 h until labor (56 h) from four ewes at each time point. Samples were analyzed for aromatase, estradiol receptor, and oxytocin receptor expression by in situ hybridization; for oxytocin binding to its receptor using a specific antagonist; and for estradiol receptor quantitation by immunocytochemistry. Aromatase mRNA expression increased by 14 h postinjection (p < 0.02) in the fetal villi and remained high until labor. Expression of estradiol and oxytocin receptor mRNAs was unchanged in myometrium but increased in the endometrial luminal epithelium by 28 h (p < 0.05) and remained high until labor. Estradiol receptor protein concentration increased modestly at labor while oxytocin receptor binding in the luminal epithelium changed in parallel to the mRNA concentration. 1) induction of aromatase may facilitate the expression of endometrial estradiol and oxytocin receptors in the placentome, 2) changes in endometrial rather than myometrial oxytocin receptor may be important in inducing parturition, and 3) the transcription of estradiol receptor and oxytocin receptor in the uterine epithelium are positively correlated during parturition.

Prenatal stress and glucocorticoid effects on the developing gender-related brainProceedings of Xth International Congress on Hormonal Steroids, Quebec, Canada, 17–21 June 1998.

Hormonal and neurotransmitter environment of nondifferentiated cells in the developing brain determines many of gender-specific behavioural and neuroendocrine functions. Early postnatal and long-term effects of maternal stress or prenatal glucocorticoid on sex-related peculiarities of the brain morphology, biogenic monoamine turnover, testosterone metabolism, hypothalamic noradrenaline (NA) and adrenocortical responses to an acute stress were studied in Wistar rat offsprings. Maternal stress (1 h immobilization daily for gestational days 15–21) prevented development of sexual dimorphism in neuronal cell nuclei volumes in suprachiazmatic nucleus (SCN) in 10 day old pups. That was associated with a disappearance of male–female differences in NA and 5-hydroxytryptamine turnover in the preoptic area (POA) and dopamine (DA) turnover in the mediobasal hypothalamus (MBH) by decreasing them in male pups. Hydrocortisone acetate (5 mg daily during the last week of pregnancy) produced changes in NA turnover in the POA of males and females which were quite similar to those after maternal stress. Changes in aromatase and 5 α-reductase activities in the POA of male pups were quite opposite as affected by maternal stress or prenatal glucocorticoid. Sexual differences in 5 α-reductase activity in the MBH appeared due to its increase in prenatally stressed male pups. In contrast to adult males, in adult females maternal stress did not restrict hypothalamic NA and blood plasma corticosterone response to acute stress (1 h immobilization). Our findings on morphology and functions of gender-related developing brain areas stand in correlation with modifying effects of maternal stress and prenatal glucocorticoid on behavior and neuroendocrine regulations.

In vivo steroid regulation of aromatase and 5α-reductase in goldfish brain and pituitary

The full expression of testosterone (T) actions in neuroendocrine tissues requires aromatization and 5α-reduction to estradiol (E2) and 5α-dihydrotestosterone (DHT), respectively. Recently, we documented striking changes in aromatase and 5α-reductase during the annual reproductive cycle of goldfish ( Carassius auratus). To investigate possible regulatory effects of sex steroids, goldfish were implanted with hormone-filled silastic capsules for 2–5 weeks. Conversion of [ 3H]androstenedione to estrone or 5α-androstanedione by homogenates of anterior hypothalamus/preoptic area, remaining telencephalon, and whole pituitary (PIT) was used to estimate aromatase and 5α-reductase, respectively. Gonadosomatic index and plasma E2, T, and DHT were monitored as an index of reproductive status and capsule effectiveness. In reproductively inactive fish in which plasma steroids and aromatase were basal (October), E2 or T increased aromatase activity in brain of both sexes but stimulated activity in PIT of females only; DHT was not effective. In a subsequent experiment initiated close to the spawning peak and prior to the seasonal decline in plasma steroids and brain aromatase (April), T increased or maintained brain aromatase in a time-dependent manner. 5α-Reductase activity was unaffected by steroid treatment in both reproductively active and inactive fish. These results indicate that variations in circulating steroids are responsible, at least in part, for changes in brain aromatase during the annual reproductive cycle of goldfish and provide the first evidence for steroid control of pituitary aromatase. The steroid specificity of the induction suggests that an estrogen receptor mechanism is involved. Product (E2)-induced increases in aromatization during the spawning period may be part of a positive feedback loop leading to neural E2 accumulation and culminating in ovulation/spermiation and breeding behavior.

Hormonal regulation of estradiol biosynthesis, aromatase activity, and aromatase mRNA in rat ovarian follicles and corpora lutea

To determine the molecular basis for changes in aromatase (P450arom) activity in rat ovarian follicles and corpora lutea, seven clones for rat P450arom cDNA have been identified and isolated from a rat granulosa cell λgtll cDNA expression library using a 62 mer deoxyoligonucleotide probe (derived from an amino acid sequence of purified human placental aromatase) and a human placental P450arom cDNA probe. One of the rat P450arom cDNA clones contained an insert 1.2 kb in size. Both the human 1.8 kb cDNA and the rat 1.2 kb cDNA probes hybridized to a single species of P450arom mRNA that was 2.6 kb in size. Northern blot analysis revealed that corpora lutea isolated on day 15 of pregnancy contained high amounts of P450arom mRNA, whereas granulosa cells of antral follicles of hormonally primed, hypophysectomized rats (i.e., those from which mRNA was isolated to construct the cDNA library) contained only low amounts of P450arom mRNA. The lower amounts of P450arom in granulosa cells of preovulatory follicles in the estradiol-follicle-stimulating hormone primed hypophysectomized rats were unexpected because follicles incubated in medium containing testosterone substrate produce more estradiol than do corpora lutea isolated on day 15 of pregnancy and incubated under similar conditions. Additional studies will determine the hormonal events responsible for the elevated amounts and constitutive maintenance of P450arom mRNA and aromatase activity in luteal cells in vivo and in vitro.