| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Original Studies |
Departments of Obstetrics and Gynecology (G.K., S.G., C.J.L.) and Biochemistry (S.G.), New York University Medical Center, New York, New York 10016; and Departments of Immunology and Vascular Biology, The Scripps Research Institute (N.M.), La Jolla, California 92037
Address all correspondence and requests for reprints to: Dr. Graciela Krikun, New York University Medical Center, Tisch Hospital, Room 533, 550 First Avenue, New York, New York 10016.
| Abstract |
|---|
|
|
|---|
Our results also demonstrated that induction of steady state TF mRNA by MPA was abolished by treating cells with E2 plus MPA in conjunction with the protein synthesis inhibitor cycloheximide. In light of the absence of a complete progesterone or estrogen response element in the published 5'-sequence of the TF promoter, our results suggest that progestin-enhanced transcription of TF mRNA in stromal cells may be mediated by an uncharacterized protein intermediate(s).
| Introduction |
|---|
|
|
|---|
, or phorbol myristate
13-acetate (PMA) has been shown to be mediated by cis-acting
regulatory elements on the promoter region of the TF gene, such as
activating protein-1 (AP-1), Sp-1, and a nuclear factor-
B
(NF
B)-like site (2, 3, 4, 10). In the endothelial cells, an NF
B-like
nuclear protein was induced by cytokines or endotoxin, whereas AP-1
nuclear binding proteins were constitutively expressed (4, 3). Similar
results were found with monocytes (11). In contrast, serum-enhanced
TF mRNA in cultured fibroblasts was mediated by increased AP-1 binding,
whereas NF
B binding was shown to be constitutive (5). In cultured
human epithelial cells, serum- or PMA-enhanced TF transcription was
shown to be mediated by constitutively expressed Sp-1 and by inducibly
expressed Egr-1-binding protein (12). In contrast to the immediate, but transient, expression of TF in the cell types described above, prior work from our laboratory established that TF expression was gradually, but chronically, enhanced by progestins in human endometrial stromal cells undergoing decidualization in vivo and in vitro (13, 14). Immunohistochemistry of human endometrium demonstrated increased staining for TF in decidualized stromal cells of late secretory phase and gestational endometrium (14). Medroxyprogesterone acetate (MPA), but not estradiol (E2), enhanced TF protein and mRNA levels in cultured human endometrial stromal cells (HESCs) (13). Consistent with E2 enhancement of progesterone receptor levels, addition of E2 further augmented the MPA-modulated increase in TF protein and mRNA levels. Elevated TF mRNA and protein levels were observed after 4872 h of MPA treatment and persisted beyond 21 days, consistent with its putative role as a mediator of hemostasis during implantation and placentation (13, 14).
In the current study we used message stability, transient transfections, and cycloheximide (CHX) studies to elucidate a mechanism through which progestins chronically induce TF expression in HESCs.
| Materials and Methods |
|---|
|
|
|---|
Freshly isolated stromal cells were isolated and grown to confluence in a basal medium, as previously described (13). The experimental period was initiated by the addition of 10-8 mol/L E2, 5 x 10-7 mol/L MPA, E2 plus MPA, or 0.1% ethanol as vehicle control. The medium was changed every 24 days. The cells were kept in culture for approximately 10 days.
For message stability studies, cells were pretreated with E2 or E2 plus MPA as described above, then dichlororibofuranosylbenzimidazole (DRB) was added at a final concentration of 300 µmol/L for a time course ranging from 07 h (where 0 reflects the addition of DRB). Total RNA was extracted at the appropriate time points, and Northern blots were conducted, probed with TF complementary DNA (14), and corrected for loading efficiencies using a glyceraldehyde-3-phosphate complementary DNA, as previously described (15).
Experiments conducted in the presence of CHX were carried out as follows. Cultures were treated with E2 or E2 plus MPA, as described above, in the presence of 0, 10, 100, or 500 ng/mL CHX. The medium was changed every 48 h, and cells were treated for 8 days. Total RNA was extracted within 16 h of the last medium change, and Northern blots were conducted as described above.
Promoter constructs
TF promoter-plasmid constructs contain the 5' flanking sequence
of the TF promoter spanning -2106 to +121, -278 to +121, and -111 to
+14 bp cloned upstream of VP16/TET transcription factors inserted
between the PstI and BamHI site in pBSKSII
(Stratagene, La Jolla, CA) (16). The TF promoter-containing plasmids
were cotransfected into target cells with the plasmid pUHG10.3CAT
containing the chloramphenicol acetyltransferase (CAT) reporter (17).
Enhanced expression of the TF promoter drives VP16/TET expression,
which, in turn, drives expression of the reporter-containing plasmid
(see Fig. 1
).
|
Transient transfections
Primary or once passaged HESCs were seeded at a density of 2 x 105 cells/3-cm polystyrene well and allowed to attach and proliferate to approximately 60% subconfluence for 24 h. HESCs were then treated with E2 (10-8 mol/L) or E2 plus MPA (10-6 mol/L) for 6 days. Subsequent to this treatment, the cultures were transiently transfected in OPTI-MEM medium (Life Technologies, Grand Island, NY) with 1 µg of the various TF promoters and 1 µg of the CAT reporter construct, using 10 µL Lipofectamine (Life Technologies) for 6 h. The medium was then changed back to basal medium containing either E2 or E2 plus MPA as described above for an additional 48 h. Transfection efficiency was determined in parallel wells using 3 µg ß-galactosidase control vector. Cells were lysed after 48 h according to the manufacturers instructions (Promega). The lysates to be used for CAT analysis were heated to 60 C. All samples were centrifuged, and the supernatant was stored at -80 C.
Transfection reporter assays
CAT assay. One hundred microliters of cell extract was mixed with [14C]chloramphenicol (0.05 mCi/mL; New England Nuclear, Boston, MA) and n-butyryl coenyzme A (Promega) and incubated for 3 h at 37 C, and the reaction was terminated by the addition of 300 µL xylene. The xylene phase was extracted twice with Tris-HCl (0.25 mol/L; pH 8.0), and the final xylene phase containing only the butyrylated [14C]chloramphenicol was added to a scintillant and counted in a Beckman LS 5000TD scintillation counter (Palo Alto, CA). All experiments were conducted in triplicate.
ß-Galactosidase assay. Fifty microliters of cell extract were added to 50 µL 2 x assay buffer (Promega) containing o-nitrophenyl-ß-D-galactopyranoside, placed in a Microlite 96-well plate, and allowed to incubate at 37 C until a faint yellow color was visible. The reaction was stopped by the addition of 150 µL sodium carbonate (1 mol/L) and was immediately read at 405 nm with an automatic microplate reader (Molecular Devices, Menlo Park, CA).
Statistical analysis
All data were analyzed with a Mann-Whitney rank sum test, Sigma Stat computer program (Jandell Scientific, San Rafael, CA). P < 0.05 was considered significant.
| Results |
|---|
|
|
|---|
The effects of steroids on levels of steady state TF mRNA in
cultured primary endometrial stromal cells were determined by Northern
analysis (Fig. 2
). E2
treatment alone did not affect levels of TF mRNA compared with those in
the vehicle control group. The addition of E2 plus MPA,
however, dramatically increased TF mRNA levels. The content of TF
protein and its functional activity were similarly regulated by
steroids in HESCs (14). As E2 is present at significant
levels throughout the proliferative and secretory phases of the
menstrual cycle, these studies employed E2-treated cells as
controls.
|
|
As MPA enhancement of steady state TF mRNA levels cannot be
accounted for by changes in message stability, we examined the
possibility that increased TF mRNA occurs through transcriptional
activation. Thus, HESCs were transiently transfected with constructs
containing -2106 to +121 bp of the TF promoter (TFp-2106)
and a CAT reporter gene. Figure 4
(left panel) shows that CAT activity is augmented by MPA
treatment. When these results are corrected for transfection
efficiencies by parallel transfections with a ß-galactosidase
reporter plasmid (Fig. 4
, right panel), E2 plus
MPA was found to enhance TF transcription rates 20-fold compared to
treatment with E2 alone (P < 0.05).
Parallel transfections, rather than cotransfections, with
ß-galactosidase were carried out to avoid compromising cell viability
by introducing excess DNA. Figure 4
depicts results obtained with a MPA
concentration of 10-6 mol/L. Identical results were
observed at 10-7 mol/L.
|
|
As no complete progesterone or estrogen response elements have
been reported in the TF promoter, we determined whether a protein
intermediate(s) is required for the observed induction of TF mRNA by
MPA. Cultured HESCs were treated with either E2 or
E2 plus MPA with or without the protein synthesis inhibitor
CHX and analyzed by Northern analysis. Figure 6
shows that CHX treatment strongly
inhibited the induction of TF mRNA in E2- plus MPA-treated
HESCs. This inhibitory response was evident at 10 ng/mL CHX and was
maximal at 500 ng/mL CHX. The results indicate that a protein
intermediate(s) is involved in the progestational induction of TF mRNA.
Moreover, the increased expression of TF mRNA by cells concomitantly
treated with E2 and CHX may reveal the existence of an
inhibitor of E2 action. It is interesting to note that CHX
treatment also inhibited morphological decidualization of HESCs induced
by MPA (not shown).
|
| Discussion |
|---|
|
|
|---|
To determine whether progestins modulate the rate of transcription of the TF gene in HESCs, transfection studies were carried out using a construct spanning -2106 to +121 bp of the TF promoter. These studies demonstrated that MPA enhances TF promoter activity in HESCs approximately 4-fold. Although it was evident that treating HESCs with E2 plus MPA increased the expression of CAT compared to that in cells treated with E2 alone, the differences did not seem large enough to account for the magnitude of the MPA-associated increases in steady state levels of TF mRNA. We, therefore, considered the possibility that MPA-mediated decidualization of HESCs reduced cellular uptake of exogenous DNA. Indeed, parallel transfections indicated that decidualization greatly reduced ß-galactosidase expression. This experimental problem was also noted by Gao et al. (20) in transfecting decidualized HESCs with the insulin-like growth factor-binding protein-1 promoter. We believe that this phenomenon reflects permeability changes caused by decidualization in the surrounding basal laminar component and/or the tendency of these cells to form multicellular layers in vitro (21).
In HeLa cells, basal TF promoter activity requires Sp-1 binding,
whereas induction of TF gene transcription by serum and PMA required
Egr-1 binding, and maximal induction required both Sp1 and Egr-1
binding (12). To investigate the role of cis-acting elements
responsible for the progestational induction of TF in HESCs, we
employed truncated TF-CAT promoter constructs. Deletion of -2106 to
-278 bp showed increased CAT activity in response to both
E2 and E2 plus MPA. In contrast, deletion of
-2106 to -111 bp maintained the differential effects of E2vs. E2 plus MPA, but the relative CAT
activities were reduced by 60% compared to those in cultures
transfected with TFp-2106 and by 80% compared to those in
cultures transfected with TFp-278. This suggests that
although the presence of Egr-1, Sp-1, or yet to be identified
cis-acting regulatory elements present within the -111
promoter is necessary for MPA regulation of the TF gene in HESCs, it is
not sufficient to account for all of the effects on TF gene
transcription. In addition, we cannot rule out changes in transport
effected by MPA treatment of HESCs. To address this issue, future
studies will be conducted employing site-directed mutagenesis of the
promoters Sp-1 region, Egr-1 region, or both. As AP-1 and
B sites
regulate expression of TF promoter in other cell types (9), it is
possible that deletion of AP-1 and/or the NF
B-like elements between
-278 and -111 bp was responsible for decreased levels of TF
transcription for both E2-treated and E2- plus
MPA-treated HESCs.
In contrast with the rapid induction of TF mRNA observed in endothelial, monocytic, or fibroblast cells, TF is chronically induced in HESCs. It is interesting to note that, to date, the TF promoter has not been shown to contain complete estrogen or progesterone response elements (22). We posit that MPA acting on the estrogen-primed HESCs is activating one or more intermediary agents responsible for the chronic induction of TF at the level of the gene. Results in this study using CHX are consistent with this hypothesis. Furthermore, it would appear that the same intermediate protein(s) is crucial to the process of decidualization itself, as reflected by the absence of decidualization-associated morphological changes in CHX-treated cultures. The HESC system employed in these studies is a valuable model for dissecting the regulation of hemostatic factors requisite for menstruation and implantation. These two events require that the system allow for the paradoxical maintenance of hemostasis during endovascular trophoblast invasion and the facilitation of the diffuse endometrial hemorrhage accompanying menstruation. Failure to properly regulate this system could result in infertility, spontaneous abortion, and placental abruption as well as dysfunctional uterine bleeding and breakthrough bleeding associated with hormonal contraception. Understanding the regulation of TF expression may provide insight into the development of new therapies in the attempt to target these prevalent disorders.
| Footnotes |
|---|
Received August 11, 1997.
Revised October 20, 1997.
Accepted November 18, 1997.
| References |
|---|
|
|
|---|
B-like site. Mol Cell Biol. 14:37723781.
B binding sites. J Exp Med. 174:15171526.This article has been cited by other articles:
![]() |
G. Krikun and C. J. Lockwood Steroid Hormones, Endometrial Gene Regulation and the Sp1 Family of Proteins Reproductive Sciences, November 1, 2002; 9(6): 329 - 334. [Abstract] [PDF] |
||||
![]() |
J. K. Richer, B. M. Jacobsen, N. G. Manning, M. G. Abel, D. M. Wolf, and K. B. Horwitz Differential Gene Regulation by the Two Progesterone Receptor Isoforms in Human Breast Cancer Cells J. Biol. Chem., February 8, 2002; 277(7): 5209 - 5218. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. J. LOCKWOOD, G. KRIKUN, and F. SCHATZ Decidual Cell-Expressed Tissue Factor Maintains Hemostasis in Human Endometrium Ann. N.Y. Acad. Sci., September 1, 2001; 943(1): 77 - 88. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Okada, T. Nakajima, T. Yoshimura, K. Yasuda, and H. Kanzaki The inhibitory effect of dienogest, a synthetic steroid, on the growth of human endometrial stromal cells in vitro Mol. Hum. Reprod., April 1, 2001; 7(4): 341 - 347. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Okada, T. Nakajima, M. Sanezumi, A. Ikuta, K. Yasuda, and H. Kanzaki Progesterone Enhances Interleukin-15 Production in Human Endometrial Stromal Cells in Vitro J. Clin. Endocrinol. Metab., December 1, 2000; 85(12): 4765 - 4770. [Abstract] [Full Text] |
||||
![]() |
R. Runic, F. Schatz, L. Wan, R. Demopoulos, G. Krikun, and C. J. Lockwood Effects of Norplant on Endometrial Tissue Factor Expression and Blood Vessel Structure J. Clin. Endocrinol. Metab., October 1, 2000; 85(10): 3853 - 3859. [Abstract] [Full Text] |
||||
![]() |
G. Krikun, F. Schatz, N. Mackman, S. Guller, R. Demopoulos, and C. J. Lockwood Regulation of Tissue Factor Gene Expression In Human Endometrium by Transcription Factors Sp1 and Sp3 Mol. Endocrinol., March 1, 2000; 14(3): 393 - 400. [Abstract] [Full Text] |
||||
![]() |
C. J. Lockwood, G. Krikun, R. Runic, L. B. Schwartz, A. F. Mesia, and F. Schatz Progestin-Epidermal Growth Factor Regulation of Tissue Factor Expression during Decidualization of Human Endometrial Stromal Cells J. Clin. Endocrinol. Metab., January 1, 2000; 85(1): 297 - 301. [Abstract] [Full Text] |
||||
![]() |
S. Okada, H. Okada, M. Sanezumi, T. Nakajima, K. Yasuda, and H. Kanzaki Expression of interleukin-15 in human endometrium and decidua Mol. Hum. Reprod., January 1, 2000; 6(1): 75 - 80. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. E. Mendelsohn and R. H. Karas The Protective Effects of Estrogen on the Cardiovascular System N. Engl. J. Med., June 10, 1999; 340(23): 1801 - 1811. [Full Text] [PDF] |
||||
![]() |
H. Okada, M. Sanezumi, T. Nakajima, S. Okada, K. Yasuda, and H. Kanzaki Rapid down-regulation of CD63 transcription by progesterone in human endometrial stromal cells Mol. Hum. Reprod., June 1, 1999; 5(6): 554 - 558. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |