Estrogen regulation of protein synthesis in the immature rat uterus: the effects of progesterone on proteins released into the medium during in vitro incubations

Progesterone agonists and antagonists induce down– and up–regulation of estrogen receptors and estrogen inducible genes in human breast cancer cell lines

The effects of the synthetic progestin R5020 and the antiprogestin RU486 on the cellular content of estrogen receptors (ER) and on cell responsiveness to estrogens, have been investigated in the sex hormone-sensitive human breast cancer cell lines MCF-7 and T47D. When T47D cells were treated with R5020 (Promegestone) (10–8 M), ER was down-regulated to about 50% of the control level in a time-dependent manner. Maximum down-regulation was observed after 24 hours and remained at this level for the next 24 hours. Dihydrotestosterone (DHT) or dexamethasone (DEX) had no effect on ER sites. R5020 also down-regulated, although to a lesser extent, ER in the MCF-7 cells which contain fewer progesterone receptor (PR) sites.

When MCF-7 cells were transfected with a progesterone receptor expression vector (tMCF-7) to increase the number of PR sites, R5020 down-regulated the ER to a level similar to that reached in T47D cells. In both cell lines ER down-regulation was completely inhibited by a 10-fold molar excess of the antiprogestin RU486 (Mifepristone) (10–7 M). Surprisingly, when incubated with RU486 alone, T47D cells responded by up-regulating ER 2-4 fold.

The functional relevance of inhibition and up-regulation of ER for the estrogen responsiveness of hormone-sensitive human breast cancer cells was tested by assaying the synthesis of an estrogen-regulated product, the PS2 protein. Estrogen induction of this protein was inhibited by at least 70% in T47D cells exposed to R5020 for 24 hours before estrogen administration and by about 25% in MCF-7 cells under the same conditions. A 55% inhibition was observed in tMCF-7 cells. Up-regulation of ER by RU486 in T47D cells led to an increase in the estrogen induction of PS2 by about 18-20% compared to RU486 untreated cells.

These results indicate that the progestin and antiprogestin regulation of ER is functionally important for the estrogen responsiveness of breast cancer cells.

Regulation of a uterine 250 kDa protein by estradiol and antiestrogens

A 250 kDa secretory protein was isolated from the uterine luminal fluid (ULF) obtained from estradiol-treated ovariectomized rats. Antiestrogens blocked the production of this protein. The protein components were separated and purified by SDS-PAGE. Polyclonal antibodies were raised against the 250 kDa protein and used to identify the protein by Western blot. 17 beta-estradiol (E2) at a dose of 0.005 mg/kg/d administered s.c. for 3 days to ovariectomized rats stimulated a marked increase in the production of the 250 kDa protein. Anordiol at a low dose of 5 mg/kg/d x 3 p.o. or 0.25 mg/kg/d x 3 s.c. stimulated the production of the 250 kDa protein. Treatment with higher doses (10 mg/kg/d x 3 p.o., or 1.25 mg/kg/d x 3 s.c.) was less effective in inducing production of this protein. Also anordiol partially inhibited the stimulatory action of E2; whereas ICI 182,780, a pure antiestrogen, at a dose of 0.3 mg/kg/d x 3 s.c. completely blocked the stimulatory action of E2. The 250 kDa protein was not detected in the blood obtained from E2-treated ovariectomized rats. The anti-complement C3 and anti-alpha 2-macroglobulin antibodies did not react with the ULF 250 kDa protein. The present results show that the production of the ULF 250 kDa protein is regulated by estradiol and is not a component of blood plasma. It is proposed that the estrogen-responsive 250 kDa protein may be involved in maintaining the viability of the fertilized ova and in the implantation of the blastocyst.

Antiandrogenic property of RU 486: enhancement of estrogen-induced uterine peroxidase activity in the rat

The contragestational steroid RU 486 enhanced the increase in peroxidase activity produced by estradiol in estrogen-primed immature rat uteri and, like the antiandrogen flutamide, RU 486 reversed the inhibitory effect of testosterone on this estrogen-induced response. It antagonized the inhibition produced by progesterone but had no effect on peroxidase induction by itself or in unprimed immature animals. RU 486 also enhanced the effect of estradiol on the synthesis of complement component C3 in the rat uterus. The results confirm that RU 486 possesses antiandrogenic as well as antiprogestational properties. They also suggest that, in normal adult animals, the increase in peroxidase activity in the uterus in response to estrogen is not expressed fully but held in check by other endogenous steroids acting through their individual receptors.

Progesterone and dexamethasone inhibition of estrogen-induced synthesis of DNA and complement in rat uterine epithelium: effects of antiprogesterone compounds

Progesterone (P) blocks estrogen induction of cell proliferation and synthesis of complement C3 in the epithelium of the immature rat uterus. Here it is shown that dexamethasone (Dex) exerts a similar inhibitory effect on these two parameters. Furthermore, analysis of the newly synthesized, secreted proteins produced during a 20 h explant culture period showed that not only does the uterus synthesize complement C3 but it is capable of proteolytically cleaving complement into its biologically active peptides. Since large doses of P are required for its inhibitory effects and since P can interact with the glucocorticoid receptor (GR), the role of the GR in mediating the P effect was questioned. Two antiprogesterone compounds with reportedly differing antiglucocorticoid activity, ZK98.734 and RU486, were tested for their ability to antagonize the inhibitory actions of P and Dex. Attenuation of estrogen-induced epithelial DNA synthesis by either P or Dex was fully overcome by concurrent administration of either ZK98.734 or RU486. On the other hand, while either antagonist was effective against the inhibitory action of P on estrogen-induced complement C3 synthesis, only ZK98.734 was fully effective in blocking inhibition by Dex. Thus, unlike its activity in rat hepatic cells, ZK98.734 is a potent antiglucocorticoid in the immature rat uterus. Because of this antiglucocorticoid activity, differential antagonism of the P response was not possible using these two steroid analogs. Although these observations support the notion of GR mediated inhibition of estrogen action in the uterus, they do not answer the question of whether P might act through a GR mediated pathway.

The effect of 6-nitro-1,3,8-trichlorodibenzofuran as a partial estrogen in the female rat uterus

Administration of 6-nitro-1,3,8-trichlorodibenzofuran (6-NCDF) caused a dose- and time-dependent increase in uterine wet weight and cytosolic and nuclear estrogen receptor (ER) and progesterone receptor (PR) levels in immature female Sprague-Dawley rats. These estrogenic effects persisted for up to 96 or 144 hr after initial administration of 6-NCDF and could be observed at a dose as low as 2 mumol/kg. In contrast, 6-NCDF (25 mumol/kg) did not increase rat uterine peroxidase activity or epidermal growth factor (EGF) receptor binding activity. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), which exhibits a broad spectrum of antiestrogenic effects in the female rat uterus, inhibited the 17 beta-estradiol-induced increase in uterine wet weights, cytosolic and nuclear ER and PR levels, peroxidase activity, and EGF receptor binding activity. In contrast, 2,3,7,8-TCDD inhibited the uterotropic effects caused by 6-NCDF but did not affect the 6-NCDF-induced uterine ER and PR levels. 6-NCDF is a weak inducer of hepatic microsomal ethoxyresorufin O-deethylase activity and competitively binds to the aryl hydrocarbon (Ah) receptor but not the PR or ER. Thus both 6-NCDF and 2,3,7,8-TCDD, two ligands which bind to the Ah receptor, exhibit both partial estrogenic and antiestrogenic properties and serve as useful models for delineating the complex biochemical interactions between the ER and Ah receptor signal transduction pathways.

Complement C3 synthesis, peroxidase activity and eosinophil chemotaxis in the rat uterus: effect of estradiol and testosterone

Treatment of immature rats with estradiol (E2) produced a large increase in uterine peroxidase activity which was accompanied by an increase in eosinophil chemotactic factor (ECF-U). The synthesis of complement C3 was also induced in the uterus and the amount of this 180 kDa protein was determined both by immunoprecipitation and after separation by polyacrylamide gel electrophoresis. Testosterone (T) did not produce an increase in any of these parameters although it antagonized the estrogen-induced increase in uterine peroxidase activity and these effects were more pronounced in estrogen-primed animals. This antagonism was prevented by the antiandrogen, flutamide. Testosterone showed little effect on eosinophil chemotactic activity and did not inhibit the E2-stimulated synthesis of C3. The results with T were supported by the lack of any significant effect by flutamide which antagonizes receptor-mediated androgenic events. These findings are discussed in relation to the action of other types of hormonal steroids (progesterone, dexamethasone) in inhibiting these estrogen-induced molecular changes in the rat uterus and contribute to our understanding of steroid-steroid interaction and the regulation of uterine function.

Reactivity to alloantigens and polyclonal mitogens and CD4+/CD8+ cell ratio shifts of cervical lymph node and spleen cells during pregnancy in rats

Cervical lymph node (CLN) cells and spleen cells were harvested from virgin and pregnant rats bearing syngeneic or allogeneic fetuses at all stages of pregnancy including the pre-implantation period. The specific and non-specific alloreactivity of these cells were analyzed in MLR against mitomycin-C treated paternal strain or unrelated cells. Mitogen stimulation of the cell cultures utilized PHA, Con-A and PWM. Cells bearing T cell markers were labeled in an indirect assay using the monoclonal antibodies W3/25 and MRC OX 8. Specific alloreactivity is enhanced at mid-pregnancy in both cell populations. Non-specific alloreactivity was suppressed in the cervical lymph node cells. Spleen cells demonstrated an increased non-specific alloreactivity and T polyclonal mitogen reactivity (PHA and Con-A) at mid-pregnancy. Reactivity to Con-A was depressed in the early phase and at the end of allogeneic pregnancy in the CLN. The CD4+/CD8+ ratio was very low during all phases of pregnancy.

The estrogen-responsive 110K and 74K rat uterine secretory proteins are structurally related to complement component C3

Estrogens stimulate the synthesis of specific secretory proteins in the rat uterus. Here we show that two of these, polypeptides of relative molecular weight 110,000 (110K) and 74,000 (74K), are structurally related to C3, the third component of complement, a glycoprotein that plays a central role in regulating complement-mediated inflammatory and immune responses. The similarities were based on the observations that (1) NH2-terminal amino acid sequence of the 74K polypeptide showed sequence homology with the beta chain of mouse C3, (2) comparison of the electrophoretic mobilities of the 110K and 74K polypeptides in the presence and absence of reducing agents revealed that they were disulfide-linked subunits of a protein of Mr approximately 180,000, (3) the native protein was immunoreactive with antibodies specific for rat C3, and (4) both polypeptides were immunoprecipitated with antibodies to rat C3.

Development of morphological and functional polarity in primary cultures of immature rat uterine epithelial cells

The present study describes a culture environment in which luminal epithelial cells isolated from immature rat uteri and cultured on a matrix-coated permeable surface, with separate apical and basal secretory compartments, proliferate to confluence. Subsequently the cells undergo a process of differentiation accompanied by progressive development of functional polarity. Ultrastructural and immunocytochemical evidence verifies the ability of these primary cultures to regain polar organization, separate membrane domains, and form functional tight junctions as demonstrated by the development of transepithelial resistance. The appearance of uvomorulin is restricted to the lateral cell surface. Coordinated indices of functional polarity that develop progressively in post-confluent cultures include the preferential uptake of [35S]methionine from the basal surface and a rise in uterine epithelial cell secretory activity characterized by a progressive preference for apical secretion. The time dependent development of polarity was characterized by differences in the protein profiles of the apical and basolateral secretory compartments. The maintenance of hormone responsiveness by the cultured cells was validated by the secretion of two proteins identified as secretory markers of estrogen response in the intact uterus. The technique of culturing the cells on a matrix-coated permeable surface with separate secretory compartments produces a uterine epithelial cell that morphologically and functionally resembles its in situ equivalent. The culture method and analytical approach used in this present study may be applied to primary cultures of a variety of natural epithelia, which have hitherto proven resistant to more conventional culture methodologies.

Detection and quantification of CUPED, an estrogen-dependent uterine protein, in uterine fluid and endometrial tissue of estrous and pregnant cats

Uterine flushings, media from cultured endometrial explants, and endometrial tissue obtained from estrous and pregnant cats were analyzed for the presence of a previously characterized, high-molecular-weight, estrogen-dependent glycoprotein (CUPED) by polyacrylamide-gel electrophoresis, Western blots, radioimmunoassay, and immunocytochemistry. Elevated levels of CUPED were present within the flushings, media, and tissue of estrous and 3-day postcoital animals. High levels of CUPED were also present in the flushings of 5-day postcoital animals; but the ability of endometrial explants to synthesize CUPED during short-term culture was greatly reduced, and only some of the endometrial glands contained CUPED secretory granules. CUPED was essentially nondetectable in the flushings, media, and tissues of animals pregnant for 7 or more days. Thus CUPED is present within the uterine lumen of the cycling cat at the time of sperm migration through the uterus and also for the first day or two that the developing blastocyst is present within the uterine lumen. The disappearance of CUPED from the tissue and flushings was correlated with the luteal production of progesterone.