Restoration of estrogen-dependent progesterone receptor expression in a uterine myocyte cell line

New Insights of Uterine Leiomyoma Pathogenesis: Endocannabinoid System

Background

The aim of this study was to determine if components of the endocannabinoid system are modulated in uterine leiomyomas (fibroids). Components studied included cannabinoid receptors 1 (CB1) and 2 (CB2); the G protein-coupled receptor GPR55; transient potential vanilloid receptor 1 (TRPV1) and the endocannabinoid modulating enzymes N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD) and fatty acid amide hydrolase (FAAH), and their N-acylethanolamine (NAE) ligands: N-arachidonylethanolamine (AEA), N-oleoylethanolamine (OEA), and N-palmityolethanaolamine (PEA).

Material/Methods

Transcript levels of CB1, CB2, TRPV1, GPR55, NAPE-PLD, and FAAH were measured using RT-PCR and correlated with the tissue levels of the 3 NAEs in myometrial tissues. The tissues studied were: 1) fibroids, 2) myometrium adjacent/juxtaposed to the fibroid lesions, and 3) normal myometrium. Thirty-seven samples were processed for NAE measurements and 28 samples were used for RT-PCR analyses.

Results

FAAH expression was significantly lower in fibroids, resulting in a NAPE-PLD: FAAH ratio that favors higher AEA levels in pre-menopausal tissues, whilst PEA levels were significantly lower, particularly in post-menopausal women, suggesting PEA protects against fibroid pathogenesis. The CB1: CB2 ratio was lower in fibroids, suggesting that loss of CB1 expression affects the fibroid cell phenotype. Significant correlations between reduced FAAH, CB1, and GPR55 expression and PEA in fibroids indicate that the loss of these endocannabinoid system components are biomarkers of leiomyomata.

Conclusions

Loss of expression of CB1, FAAH, GPR55, and PEA production are linked to the pathogenesis of uterine fibroids and further understanding of this might eventually lead to better disease indicators or the development of therapeutic potentials that might eventually be used in the management of uterine fibroids.

The expression and localization of N-myc downstream-regulated gene 1 in human trophoblasts

The protein N-Myc downstream-regulated gene 1 (NDRG1) is implicated in the regulation of cell proliferation, differentiation, and cellular stress response. NDRG1 is expressed in primary human trophoblasts, where it promotes cell viability and resistance to hypoxic injury. The mechanism of action of NDRG1 remains unknown. To gain further insight into the intracellular action of NDRG1, we analyzed the expression pattern and cellular localization of endogenous NDRG1 and transfected Myc-tagged NDRG1 in human trophoblasts exposed to diverse injuries. In standard conditions, NDRG1 was diffusely expressed in the cytoplasm at a low level. Hypoxia or the hypoxia mimetic cobalt chloride, but not serum deprivation, ultraviolet (UV) light, or ionizing radiation, induced the expression of NDRG1 in human trophoblasts and the redistribution of NDRG1 into the nucleus and cytoplasmic membranes associated with the endoplasmic reticulum (ER) and microtubules. Mutation of the phosphopantetheine attachment site (PPAS) within NDRG1 abrogated this pattern of redistribution. Our results shed new light on the impact of cell injury on NDRG1 expression patterns, and suggest that the PPAS domain plays a key role in NDRG1’s subcellular distribution.

Effects of progesterone treatment on expression of genes involved in uterine quiescence

An important action of progesterone during pregnancy is to maintain the uterus in a quiescent state and thereby prevent preterm labor. The causes of preterm labor are not well understood, so progesterone action on the myometrium can provide clues about the processes that keep the uterus from contracting prematurely. Accordingly, we have carried out Affymetrix GeneChip analysis of progesterone effects on gene expression in immortalized human myometrial cells cultured from a patient near the end of pregnancy. Progesterone appears to inhibit uterine excitability by a number of mechanisms, including increased expression of calcium and voltage-operated K(+) channels, which dampens the electrical activity of the myometrial cell, downregulation of agents, and receptors involved in myometrial contraction, reduction in cell signal components that lead to increased intracellular Ca(2+) concentrations in response to contractile stimuli, and downregulation of proteins involved in the cross-linking of actin and myosin filaments to produce uterine contractions.

Renin and angiotensin II receptor expression in the brains of DES-treated Syrian hamsters

BACKGROUND

The renin angiotensin system (RAS) promotes vasoconstriction. Expression of RAS is induced by different factors.

METHODS

In this study, forebrain sections of hamster brains were studied by immunohistochemical methods to determine the location of renin-positive and angiotensin II receptor-positive cells. The brain sections were obtained from diethylstilbesterol- (DES-) treated hamsters, adult non-DES-treated hamsters, elderly non-DES-treated hamsters, neonatal hamsters, and 15-day fetal hamsters. Circulating renin activity was determined for all but the neonatal and 15-day fetal hamsters.

RESULTS

Renin-positive and angiotensin II receptor-positive vascular smooth muscle cells were observed in DES-treated hamsters. No positive cells were observed in neonatal, 15-day fetal, and adult non-DES-treated hamsters. Some expression was observed in elderly hamsters.

CONCLUSIONS

Therefore, focal expression of the renin angiotensin system in brain vasculature was induced by the synthetic estrogen DES.

Characterization of the estrogen receptor transfected MCF10A breast cell line 139B6

There has been increasing evidence which suggests that abnormal expression of the estrogen receptor (ER) protein in nonmalignant breast tissue may be important in the carcinogenic process. To examine the effects of ER expression in immortalized nonmalignant mammary epithelial cells, an expression vector containing human ER cDNA was transfected into the ER negative human breast cells, MCF10A. Characterization of a clone stably expressing ER, 139B6, provided evidence for the regulated synthesis of a functional ER capable of binding estradiol-17 beta (E2) and undergoing processing. Expression of the ER gene did not enable E2 to stimulate endogenous genes [progesterone receptor (PgR), pS2, cathepsin D and TGF alpha] which normally respond to estrogens in breast cancer cells. The ER in 139B6 cells was, however, capable of inducing expression of an ERE-regulated reporter gene, indicating its ability to interact with transcriptional machinery. Furthermore, cultures in log growth displayed a slight increase in doubling time in the presence of E2. These results indicate that ER expression alone is not sufficient to induce a transformed phenotype. Thus, the 139B6 cell line should provide a new model for determining what additional changes lead to increased growth potential in response to E2 and for exploring how E2 itself may help bring about changes leading to progression of preneoplastic breast epithelial cells.

Rat uterine myometrium contains the gap junction protein connexin45, which has a differing temporal expression pattern from connexin43

OBJECTIVE

Our purpose was to determine whether myometrial cell lines and rat myometrial tissue contained additional gap junction proteins besides connexin43.

STUDY DESIGNS

Syrian hamster myocytes (SHM-ER) and human SK-UT-1 myometrial cell lines were analyzed for intercellular coupling by microinjection of Lucifer yellow. These cell lines and myometrial tissue isolated from pregnant rats were analyzed for connexin expression by ribonucleic acid blotting and immunofluorescence.

RESULTS

SHM-ER and SK-UT-1 cells showed functional gap junctional coupling by intercellular passage of microinjected dye. Both cell lines contained connexin43 and connexin45 messenger ribonucleic acids but did not contain any other detectable connexin messenger ribonucleic acids. Immunofluorescence confirmed the presence of connexin43 and connexin45 proteins in these cells. Connexin 43 and connexin45 messenger ribonucleic acids and immunoreactive proteins were detected in pregnant rat myometrium. Connexin 43 messenger ribonucleic acid levels increased dramatically at term. In contrast, connexin45 messenger ribonucleic acid was present in nonpregnant myometrium, remained relatively constant early in gestation, fell just before term, and more than doubled post partum.

CONCLUSIONS

Rat uterine myometrium contains connexin45 and connexin43. Coexpression of connexin45 with connexin43 in uterine myometrium may regulate gap junctional coupling between these cells. The different temporal expression patterns suggest that connexin45 and connexin43 may have different roles or that the ratio of these connexins may be important in the increased cellular coupling coincident with the onset of labor.

Estrogenic activity of RU 486 (mifepristone) in rat uterus and cultured uterine myocytes

OBJECTIVE

Our purpose was to determine whether RU 486 (mifepristone) has direct estrogenic activity in uterine myocytes.

STUDY DESIGN

Ovariectomized adult rats were treated with RU 486, and its effect on uterine oxytocin receptor concentration, as a marker of estrogenic activity, was measured. Results were compared with the induction by RU 486 of an estrogen-responsive reporter gene in a cultured Syrian hamster uterine myocyte cell line.

RESULTS

Baseline oxytocin receptor concentration was 58.8 +/- 7.2 fmol/mg protein (mean +/- SEM) and increased to 227 +/- 49 fmol/mg with 17 beta-estradiol (2.5 micrograms/kg) and to 145 +/- 18 fmol/mg after RU 486 (5 mg/kg) treatment, an effect that was inhibited by the antiestrogen ICI 182,780 (1.5 mg/kg). In the cultured Syrian hamster uterine myocyte cell line cells RU 486 (10(-6) mol/L) caused a 2.17 +/- 0.17-fold increase in the expression of the reporter gene versus 113.0 +/- 7.4-fold with 17 beta-estradiol (10(-8) mol/L). The estrogenic activity of RU 486 was dependent on the presence of both estrogen receptor and the promoter's estrogen response element.

CONCLUSION

RU 486 has a weak estrogen-like activity in uterine myocytes. This activity may partly explain the therapeutic effects of RU 486 on this target organ.

Progesterone: a critical role in the pathogenesis of uterine myomas

Uterine leiomyomas are monoclonal tumors. However, the factors involved in their initiation and growth remain poorly understood. The neoplastic transformation of myometrium to leiomyoma likely involves somatic mutations of normal myometrium and the complex interactions of sex steroids and local growth factors. Traditionally, estrogen has been considered the major promoter of myoma growth. The purpose of this review is to highlight the biochemical, histologic, and clinical evidence that supports an equally important role for progesterone in the growth of uterine myomas. Biochemical studies suggest that progesterone, progestins, and the progesterone receptor modulate myoma mitotic activity. Several clinical trials demonstrate that progestins inhibit and/or reverse the ability of hypoestrogenism induced by a gonadotropin-releasing hormone agonist to shrink uterine myomas, suggesting a critical role for progesterone in growth of myomas. A new hypothesis to explain the pathogenesis of myomas is presented.

Screening and characterization of estrogenic activity from a hydroxystilbene library

BACKGROUND

Compounds that either inhibit or induce an estrogen response in vivo are important as potential drugs and biochemical tools. Non-steroidal stilbene analogs such as tamoxifen are known to function as both estrogen agonists and antagonists depending upon the analog structure. This family of compounds is amenable to parallel-manifold synthesis because stilbene analogs are easily synthesized using a single-step olefination reaction.

RESULTS

We have prepared a small 23-component hydroxystilbene library using a solid phase synthesis approach. The library was screened for estrogenic and antiestrogenic activity using a cell-based bioassay that measures estrogen receptor-mediated transcription of a reporter gene. Three of the analogs proved to have dose-dependent estrogenic activity with EC50 values between 5 microM and 15 microM. Further characterization of the hydroxystilbene-mediated estrogenic activity suggests that the agonist activity results from direct binding to the steroid site on the estrogen receptor with IC50 values of 1-10 microM.

CONCLUSIONS

The results of this study show that classic olefination chemistry can be adapted to a solid-phase format for parallel synthesis of analog libraries. Although yields varied for the individual analogs, sufficient quantity of pure material was obtained directly from the resin for structural characterization and biological evaluation. This study further validates solid-phase organic synthesis as a useful approach for rapid parallel-manifold library synthesis to augment both lead compound discovery and optimization.