Progesterone receptor (hPR) upregulates the fibronectin promoter activity in human decidual fibroblasts

Crosstalk between ferroptosis and steroid hormone signaling in gynecologic cancers

Ferroptosis is a novel types of regulated cell death and is widely studied in cancers and many other diseases in recent years. It is characterized by iron accumulation and intense lipid peroxidation that ultimately inducing oxidative damage. So far, signaling pathways related to ferroptosis are involved in all aspects of determining cell fate, including oxidative phosphorylation, metal-ion transport, energy metabolism and cholesterol synthesis progress, et al. Recently, accumulated studies have demonstrated that ferroptosis is associated with gynecological oncology related to steroid hormone signaling. This review trends to summarize the mechanisms and applications of ferroptosis in cancers related to estrogen and progesterone, which is expected to provide a theoretical basis for the prevention and treatment of gynecologic cancers.

Differential Fibrotic Response of Muscle Fibroblasts, Myoblasts, and Myotubes to Cholic and Deoxycholic Acids

Fibrosis is a condition characterized by an increase in the components of the extracellular matrix (ECM). In skeletal muscle, the cells that participate in the synthesis of ECM are fibroblasts, myoblasts, and myotubes. These cells respond to soluble factors that increase ECM. Fibrosis is a phenomenon that develops in conditions of chronic inflammation, extensive lesions, or chronic diseases. A pathological condition with muscle weakness and increased bile acids (BA) in the blood is cholestatic chronic liver diseases (CCLD). Skeletal muscle expresses the membrane receptor for BA called TGR5. To date, muscle fibrosis in CCLD has not been evaluated. This study aims to assess whether BA can induce a fibrotic condition in muscle fibroblasts, myoblasts, and myotubes. The cells were incubated with deoxycholic (DCA) and cholic (CA) acids, and fibronectin protein levels were evaluated by Western blot. In muscle fibroblasts, both DCA and CA induced an increase in fibronectin protein levels. The same response was found in fibroblasts when activating TGR5 with the specific receptor agonist (INT-777). Interestingly, DCA reduced fibronectin protein levels in both myoblasts and myotubes, while CA did not show changes in fibronectin protein levels in myoblasts and myotubes. These results suggest that DCA and CA can induce a fibrotic phenotype in muscle-derived fibroblasts. On the other hand, DCA decreased the fibronectin in myoblasts and myotubes, whereas CA did not show any effect in these cell populations. Our results show that BA has different effects depending on the cell population to be analyzed.

Immune Tolerance of Embryo Implantation and Pregnancy: The Role of Human Decidual Stromal Cell- and Embryonic-Derived Extracellular Vesicles

Embryo–endometrial communication plays a critical role in embryo implantation and the establishment of a successful pregnancy. Successful pregnancy outcomes involve maternal immune modulation during embryo implantation. The endometrium is usually primed and immunomodulated by steroid hormones and embryo signals for subsequent embryo implantation and the maintenance of pregnancy. The roles of extracellular vesicles (EVs) and microRNAs for the embryo–maternal interactions have been elucidated recently. New evidence shows that endometrial EVs and trophectoderm-originated EV cargo, including microRNAs, proteins, and lipids in the physiological microenvironment, regulate maternal immunomodulation for embryo implantation and subsequent pregnancy. On the other hand, trophoblast-derived EVs also control the cross-communication between the trophoblasts and immune cells. The exploration of EV functions and mechanisms in the processes of embryo implantation and pregnancy will shed light on a practical tool for the diagnostic or therapeutic approaches to reproductive medicine and infertility.

Early Pregnancy Exposure to Ambient Air Pollution among Late-Onset Preeclamptic Cases Is Associated with Placental DNA Hypomethylation of Specific Genes and Slower Placental Maturation

Exposure to ambient air pollution during pregnancy has been associated with an increased risk of preeclampsia (PE). Some suggested mechanisms behind this association are changes in placental DNA methylation and gene expression. The objective of this study was to identify how early pregnancy exposure to ambient nitrogen oxides (NO_x) among PE cases and normotensive controls influence DNA methylation (EPIC array) and gene expression (RNA-seq). The study included placentas from 111 women (29 PE cases/82 controls) in Scania, Sweden. First-trimester NO_x exposure was assessed at the participants’ residence using a dispersion model and categorized via median split into high or low NO_x. Placental gestational epigenetic age was derived from the DNA methylation data. We identified six differentially methylated positions (DMPs, q < 0.05) comparing controls with low NO_x vs. cases with high NO_x and 14 DMPs comparing cases and controls with high NO_x. Placentas with female fetuses showed more DMPs (N = 309) than male-derived placentas (N = 1). Placentas from PE cases with high NO_x demonstrated gestational age deceleration compared to controls with low NO_x (p = 0.034). No differentially expressed genes (DEGs, q < 0.05) were found. In conclusion, early pregnancy exposure to NO_x affected placental DNA methylation in PE, resulting in placental immaturity and showing sexual dimorphism.

Transcriptional control of parturition: insights from gene regulation studies in the myometrium

The onset of labour is a culmination of a series of highly coordinated and preparatory physiological events that take place throughout the gestational period. In order to produce the associated contractions needed for foetal delivery, smooth muscle cells in the muscular layer of the uterus (i.e. myometrium) undergo a transition from quiescent to contractile phenotypes. Here, we present the current understanding of the roles transcription factors play in critical labour-associated gene expression changes as part of the molecular mechanistic basis for this transition. Consideration is given to both transcription factors that have been well-studied in a myometrial context, i.e. activator protein 1, progesterone receptors, oestrogen receptors, and nuclear factor kappa B, as well as additional transcription factors whose gestational event-driving contributions have been demonstrated more recently. These transcription factors may form pregnancy- and labour-associated transcriptional regulatory networks in the myometrium to modulate the timing of labour onset. A more thorough understanding of the transcription factor-mediated, labour-promoting regulatory pathways holds promise for the development of new therapeutic treatments that can be used for the prevention of preterm labour in at-risk women.

Human Endometrial Transcriptome and Progesterone Receptor Cistrome Reveal Important Pathways and Epithelial Regulators

CONTEXT

Poor uterine receptivity is one major factor leading to pregnancy loss and infertility. Understanding the molecular events governing successful implantation is hence critical in combating infertility.

OBJECTIVE

To define Progesterone Receptor (PGR)-regulated molecular mechanisms and epithelial roles in receptivity.

DESIGN

RNA-sequencing and PGR-ChIP-seq were conducted in parallel to identify PGR-regulated pathways during the Window of implantation (WOI) in endometrium of fertile women.

SETTING

Endometrial biopsies from the proliferative and mid-secretory phases were analyzed.

PATIENTS OR OTHER PARTICIPANTS

Participants were fertile, reproductive aged (18-37 years) women with normal cycle length, and without any history of dysmenorrhea, infertility, or irregular cycles. In total, 42 endometrial biopsies obtained from 42 women were analyzed in this study.

INTERVENTIONS

There were no interventions during this study.

MAIN OUTCOME MEASURES

Here we measured the alterations in gene expression and PGR occupancy in the genome during the WOI, based on the hypothesis that PGR binds uterine chromatin cycle dependently to regulate genes involved in uterine cell differentiation and function.

RESULTS

653 genes were identified with regulated PGR binding and differential expression during the WOI. These were involved in regulating inflammatory response, xenobiotic metabolism, epithelial mesenchymal transition, cell death, interleukin/Signal Transducer And Activator Of Transcription (STAT) signaling, estrogen response, and Mammalian target of rapamycin complex 1 (MTORC1) response. Transcriptome of the epithelium identified 3052 differentially expressed genes, of which 658 were uniquely regulated. Transcription factors Interferon Regulatory Factor 8 (IRF8) and Myocyte Enhancer Factor 2C (MEF2C) were found to be regulated in the epithelium during the WOI at the protein level, suggesting potentially important functions that are previously unrecognized.

CONCLUSION

PGR binds the genomic regions of genes regulating critical processes in uterine receptivity and function.

Pregnancy-related hormones, progesterone and human chorionic gonadotrophin, upregulate expression of maternal plasma gelsolin

Plasma gelsolin (pGSN), a protein primarily involved in clearance of circulating actin filaments, is an upcoming novel biomarker. Its level changes in multiple disease and injury conditions, attributable mainly to its consumption during actin clearance; the endogenous regulation of its expression, however, remains elusive as well as unexplored. Here, we are reporting the first isolation of the promoter region of pGSN gene and investigation of its transcriptional regulation during pregnancy (a natural process associated with a well-programmed injury course of parturition). Interestingly, two of the pregnancy-related hormones, human chorionic gonadotrophin (hCG) and progesterone, significantly upregulated pGSN promoter activity in muscle cells. This action of both hormones was found to mediate through their respective cellular receptors and involved a contribution of multiple signaling pathways including those of protein kinase A, protein kinase C, epidermal growth factor receptor and prostaglandin-endoperoxidase synthase 2 in the case of hCG-mediated upregulation. This novel upregulation was further supported by elevated levels of endogenous pGSN transcripts as well as secreted protein upon hormonal treatments of muscle cells compared with untreated controls. A participation of pGSN promoter cis-elements, capable of interacting with endogenous transcription factors, Ap1, Sp1, and p300, was also observed during this hormonal upregulation. Additionally, the augmented pGSN levels observed in pregnant mice compared with the control animals further supported an upregulation of this protein during pregnancy, implicating vital role(s) played by pGSN during this period in mammals.

The transcriptional repressor GATAD2B mediates progesterone receptor suppression of myometrial contractile gene expression

The mechanisms whereby progesterone (P₄), acting via the progesterone receptor (PR), inhibits proinflammatory/contractile gene expression during pregnancy are incompletely defined. Using immortalized human myometrial (hTERT-HM) cells stably expressing wild-type PR-A or PR-B (PR_WT), we found that P₄ significantly inhibited IL-1β induction of the NF-κB target genes, COX-2 and IL-8 P₄-PR_WT transrepression occurred at the level of transcription initiation and was mediated by decreased recruitment of NF-κB p65 and RNA polymerase II to COX-2 and IL-8 promoters. However, in cells stably expressing a PR-A or PR-B DNA-binding domain mutant (PR_mDBD), P₄-mediated transrepression was significantly reduced, suggesting a critical role of the PR DBD. ChIP analysis of hTERT-HM cells stably expressing PR_WT or PR_mDBD revealed that P₄ treatment caused equivalent recruitment of PR_WT and PR_mDBD to COX-2 and IL-8 promoters, suggesting that PR inhibitory effects were not mediated by its direct DNA binding. Using immunoprecipitation, followed by MS, we identified a transcriptional repressor, GATA zinc finger domain-containing 2B (GATAD2B), that interacted strongly with PR_WT but poorly with PR_mDBD P₄ treatment of PR_WT hTERT-HM cells caused enhanced recruitment of endogenous GATAD2B to COX-2 and IL-8 promoters. Further, siRNA knockdown of endogenous GATAD2B significantly reduced P₄-PR_WT transrepression of COX-2 and IL-8 Notably, GATAD2B expression was significantly decreased in pregnant mouse and human myometrium during labor. Our findings suggest that GATAD2B serves as an important mediator of P₄-PR suppression of proinflammatory and contractile genes during pregnancy. Decreased GATAD2B expression near term may contribute to the decline in PR function, leading to labor.

Identifications of novel mechanisms in breast cancer cells involving duct-like multicellular spheroid formation after exposure to the Random Positioning Machine

Many cell types form three-dimensional aggregates (MCS; multicellular spheroids), when they are cultured under microgravity. MCS often resemble the organ, from which the cells have been derived. In this study we investigated human MCF-7 breast cancer cells after a 2 h-, 4 h-, 16 h-, 24 h- and 5d-exposure to a Random Positioning Machine (RPM) simulating microgravity. At 24 h few small compact MCS were detectable, whereas after 5d many MCS were floating in the supernatant above the cells, remaining adherently (AD). The MCS resembled the ducts formed in vivo by human epithelial breast cells. In order to clarify the underlying mechanisms, we harvested MCS and AD cells separately from each RPM-culture and measured the expression of 29 selected genes with a known involvement in MCS formation. qPCR analyses indicated that cytoskeletal genes were unaltered in short-term samples. IL8, VEGFA, and FLT1 were upregulated in 2 h/4 h AD-cultures. The ACTB, TUBB, EZR, RDX, FN1, VEGFA, FLK1 Casp9, Casp3, PRKCA mRNAs were downregulated in 5d-MCS-samples. ESR1 was upregulated in AD, and PGR1 in both phenotypes after 5d. A pathway analysis revealed that the corresponding gene products are involved in organization and regulation of the cell shape, in cell tip formation and membrane to membrane docking.

Human Decidual Stromal Cells as a Component of the Implantation Niche and a Modulator of Maternal Immunity

The human decidua is a specialized tissue characterized by embryo-receptive properties. It is formed during the secretory phase of menstrual cycle from uterine mucosa termed endometrium. The decidua is composed of glands, immune cells, blood and lymph vessels, and decidual stromal cells (DSCs). In the process of decidualization, which is controlled by oestrogen and progesterone, DSCs acquire specific functions related to recognition, selection, and acceptance of the allogeneic embryo, as well as to development of maternal immune tolerance. In this review we discuss the relationship between the decidualization of DSCs and pathological obstetrical and gynaecological conditions. Moreover, the critical influence of DSCs on local immune cells populations as well as their relationship to the onset and maintenance of immune tolerance is described.

Hepatitis B Virus Stimulated Fibronectin Facilitates Viral Maintenance and Replication through Two Distinct Mechanisms

Fibronectin (FN) is a high molecular weight extracellular matrix protein that functions in cell adhesion, growth, migration, and embryonic development. However, little is known about the role of FN during viral infection. In the present study, we found significantly higher levels of FN in sera, and liver tissues from hepatitis B virus (HBV) patients relative to healthy individuals. HBV expression enhanced FN mRNA and protein levels in the hepatic cell lines Huh7 and HepG2. HBV infection of susceptible HepG2-sodium taurocholate co-transporting polypeptide cells also increased FN expression. We also found that transcriptional factor specificity protein 1 was involved in the induction of FN by HBV. Knockdown of FN expression significantly inhibited HBV DNA replication and protein synthesis through activating endogenous IFN-α production. In addition, FN interacted with the transforming growth factor β-activated protein kinase 1 (TAK1) and TAK1-binding protein complex and attenuated interferon signaling by inhibiting TAK1 phosphorylation. Furthermore, the nuclear translocation of NF-κB/p65 was found to be inhibited by FN. We also observed that FN promoted HBV enhancers to support HBV expression. These results suggest novel functions of endogenous FN involved in immune evasion and maintenance of HBV replication.

Progesterone receptor transcriptome and cistrome in decidualized human endometrial stromal cells

Decidualization is a complex process involving cellular proliferation and differentiation of the endometrial stroma that is required to establish and support pregnancy. Progesterone acting via its nuclear receptor, the progesterone receptor (PGR), is a critical regulator of decidualization and is known to interact with certain members of the activator protein-1 (AP-1) family in the regulation of transcription. In this study, we identified the cistrome and transcriptome of PGR and identified the AP-1 factors FOSL2 and JUN to be regulated by PGR and important in the decidualization process. Direct targets of PGR were identified by integrating gene expression data from RNA sequencing with the whole-genome binding profile of PGR determined by chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) in primary human endometrial stromal cells exposed to 17β-estradiol, medroxyprogesterone acetate, and cAMP to promote in vitro decidualization. Ablation of FOSL2 and JUN attenuates the induction of 2 decidual marker genes, IGFBP1 and PRL. ChIP-seq analysis of genomic binding revealed that FOSL2 is bound in proximity to 8586 distinct genes, including nearly 80% of genes bound by PGR. A comprehensive assessment of the PGR-dependent decidual transcriptome integrated with the genomic binding of PGR identified FOSL2 as a potentially important transcriptional coregulator of PGR via direct interaction with regulatory regions of genes actively regulated during decidualization.

Cyclin A2 and its associated kinase activity are required for optimal induction of progesterone receptor target genes in breast cancer cells

A role for the cell cycle protein cyclin A2 in regulating progesterone receptor (PR) activity is emerging. This study investigates the role of cyclin A2 in regulating endogenous PR activity in T47D breast cancer cells by depleting cyclin A2 expression and measuring PR target genes using q-RT-PCR. Targets examined included genes induced by the PR-B isoform more strongly than PR-A (SGK1, FKBP5), a gene induced predominantly by PR-A (HEF1), genes induced via PR tethering to other transcription factors (p21, p27), a gene induced in part via extra-nuclear PR signaling mechanisms (cyclin D1) and PR-repressed genes (DST, IL1R1). Progestin induction of target genes was reduced following cyclin A2 depletion. However, cyclin A2 depletion did not diminish progestin target gene repression. Furthermore, inhibition of the associated Cdk2 kinase activity of cyclin A2 also reduced progestin induction of target genes, while Cdk2 enhanced the interaction between PR and cyclin A2. These results demonstrate that cyclin A2 and its associated kinase activity are important for progestin-induced activation of endogenous PR target genes in breast cancer cells.

Aldosterone stimulates fibronectin synthesis in renal fibroblasts through mineralocorticoid receptor-dependent and independent mechanisms

In addition to its role in regulation of salt transport in the kidney, the mineralocorticoid hormone aldosterone plays an independent role as a mediator of kidney injury and progression of chronic kidney disease. Studies in both animal models and patients have shown that aldosterone enhances the accumulation of extracellular matrix and progression of fibrosis in the kidney. However, the cellular mechanisms that lead to aldosterone-dependent fibrogenesis are poorly understood. In this study we find that aldosterone stimulates fibronectin synthesis through mineralocorticoid receptor (MCR) dependent activation of the c-Jun NH2-terminal protein kinase (JNK) and subsequent phosphorylation of the AP1 transcription factor c-jun, which forms a nuclear complex with the mineralocorticoid receptor in a kidney fibroblast cell line (NRK 49f). Furthermore, MCR-independent phosphorylation of Src family kinase induces IgF1 receptor phosphorylation, which leads to stimulation of the extracellular signal-regulated kinase (ERK1/2) to enhanced fibronectin synthesis. We further find that the IgF1-R-dependent signaling pathway activates fibronectin expression faster than the MCR-dependent pathway. We propose that the mechanisms described in this study are important to aldosterone-dependent progression of interstitial fibrosis in the kidney. Due to the duality of aldosterone-dependent activation of fibronectin synthesis in kidney fibroblasts, MCR-specific inhibitors may not entirely prevent the progression of fibrosis by aldosterone in the kidney.

Research resource: progesterone receptor targetome underlying mammary gland branching morphogenesis

Progesterone (P4)-activated progesterone receptors (PRs) play an essential role in driving pregnancy-associated mammary ductal side-branching morphogenesis and alveologenesis. However, the global cistromic and transcriptome responses that are required to elicit P4-dependent branching morphogenesis have not been elucidated. By combining chromatin immunoprecipitation followed by deep sequencing to identify genome-wide PR-binding sites in PR-positive luminal epithelial cells with global gene expression signatures acutely regulated by PRs in the mammary gland, we have identified a mammary epithelial PR targetome associated with active P4-dependent branching morphogenesis in vivo. We demonstrate that P4-induced side-branching is initiated by epithelial cell rearrangement into a multilayered epithelium that sprouts laterally from quiescent ducts via a mechanism requiring P4-dependent activation of Rac-GTPase signaling. We identify effectors of Rac-GTPases as direct transcriptional targets of PRs, and we demonstrate that disruption of the P4-activated Rac-GTPase signaling axis is sufficient to eliminate P4-dependent side-branching. Our data reveal that the molecular mediators of P4-dependent ductal side-branching overlap with those implicated in breast cancer.

Expression of CCT6A mRNA in chicken granulosa cells is regulated by progesterone

CCT6A, the zeta subunit of the chaperonin containing TCP1 complex, is the only cytosolic chaperonin in eukaryotes and is estimated to assist in the folding of multiple proteins including actin, tubulin, cyclin E, myosin, transducin and the Von Hippel Lindau tumor suppressor. In this study, we examined the expression of CCT6A and progesterone receptor (PGR) mRNA in various tissues of chickens and the regulation of CCT6A and PGR mRNA in ovarian granulosa cells. Northern blot analysis revealed that CCT6A had one transcript and was highly expressed in the ovary tissues from chickens at both the sexually immature and mature stages. CCT6A mRNA expression was increased maximally from pre-hierarchy follicles to F5 follicles and subsequently declined in pre-ovulatory and post-ovulatory follicles. The expression of PGR mRNA exhibited the similar pattern to CCT6A. In granulosa cells isolated from pre-ovulatory follicles, follicle-stimulating hormone (FSH) inhibited the expression of CCT6A mRNA, whereas progesterone activated CCT6A and suppressed PGR expression in a time-dependent manner. We further investigated the regulation of CCT6A transcription by progesterone by constructing various progressive deletions and mutants and identified the core promoter element of CCT6A and the binding region of progesterone, which is located from -2056 to -2051. Taken together, our results indicate that CCT6A likely plays an important role in follicle growth, and in granulosa cells, progesterone activates CCT6A transcription via a progesterone response element (PRE) located in the distal promoter of CCT6A.

Conserved steroid hormone homology converges on nuclear factor κB to modulate inflammation in asthma

Asthma is a complex, multifactorial disease comprising multiple different subtypes, rather than a single disease entity, yet it has a consistent clinical phenotype: recurring episodes of chest tightness, wheezing, and difficulty breathing (Pediatr Pulmonol Suppl. 1997;15:9-12). Despite the complex pathogenesis of asthma, steroid hormones (eg, glucocorticoids) are ubiquitous in the short-term and long-term management of all types of asthma. Overall, steroid hormones are a class of widely relevant, biologically active compounds originating from cholesterol and altered in a stepwise fashion, but maintain a basic 17-carbon, 4-ring structure. Steroids are lipophilic molecules that diffuse readily through cell membranes to directly and/or indirectly affect gene transcription. In addition, they use rapid, nongenomic actions to affect cellular products. Steroid hormones comprise several groups (including glucocorticoids, sex steroid hormones, and secosteroids) with critical divergent biological and physiological functions relevant to health and disease. However, the conserved homology of steroid hormone molecules, receptors, and signaling pathways suggests that each of these is part of a dynamic system of hormone interaction, likely involving an overlap of downstream signaling mechanisms. Therefore, we will review the similarities and differences of these 3 groups of steroid hormones (ie, glucocorticoids, sex steroid hormones, and secosteroids), identifying nuclear factor κB as a common inflammatory mediator. Despite our understanding of the impact of individual steroids (eg, glucocorticoids, sex steroids and secosteroids) on asthma, research has yet to explain the interplay of the dynamic system in which these hormones function. To do so, there needs to be a better understanding of the interplay of classic, nonclassic, and nongenomic steroid hormone functions. However, clues from the conserved homology steroid hormone structure and function and signaling pathways offer insight into a possible model of steroid hormone regulation of inflammation in asthma through common nuclear factor κB-mediated downstream events.

Progesterone receptors, their isoforms and progesterone regulated transcription

This review discusses mechanisms by which progesterone receptors (PR) regulate transcription. We examine available data in different species and tissues regarding: (1) regulation of PR levels; and (2) expression profiling of progestin-regulated genes by total PRs, or their PRA and PRB isoforms. (3) We address current views about the composition of progesterone response elements, and postulate that PR monomers acting through "half-site" elements are common, entailing cooperativity with neighboring DNA-bound transcription factors. (4) We summarize transcription data for multiple progestin-regulated promoters as directed by total PR, or PRA vs. PRB. We conclude that current models and methods used to study PR function are problematical, and recommend that future work employ cells and receptors appropriate to the species, focusing on analyses of the effects of endogenous receptors targeting endogenous genes in native chromatin.

Non-overlapping progesterone receptor cistromes contribute to cell-specific transcriptional outcomes

The transcriptional effects of the ovarian hormone progesterone are pleiotropic, and binding to DNA of the nuclear progesterone receptor (PR), a ligand-activated transcription factor, results in diverse outcomes in a range of target tissues. To determine whether distinct patterns of genomic interaction of PR contribute to the cell specificity of the PR transcriptome, we have compared the genomic binding sites for PR in breast cancer cells and immortalized normal breast cells. PR binding was correlated with transcriptional outcome in both cell lines, with 60% of progestin-regulated genes associated with one or more PR binding regions. There was a remarkably low overlap between the PR cistromes of the two cell lines, and a similarly low overlap in transcriptional targets. A conserved PR binding element was identified in PR binding regions from both cell lines, but there were distinct patterns of enrichment of known cofactor binding motifs, with FOXA1 sites over-represented in breast cancer cell binding regions and NF1 and AP-1 motifs uniquely enriched in the immortalized normal line. Downstream analyses suggested that differential cofactor availability may generate these distinct PR cistromes, indicating that cofactor levels may modulate PR specificity. Taken together these data suggest that cell-specificity of PR binding is determined by the coordinated effects of key binding cofactors.

Progestins activate 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) in breast cancer cells

PFKFB (6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase) catalyses the synthesis and degradation of Fru-2,6-P2 (fructose-2,6-bisphosphate), a key modulator of glycolysis and gluconeogenesis. The PFKFB3 gene is extensively involved in cell proliferation owing to its key role in carbohydrate metabolism. In the present study we analyse its mechanism of regulation by progestins in breast cancer cells. We report that exposure of T47D cells to synthetic progestins (ORG2058 or norgestrel) leads to a rapid increase in Fru-2,6-P2 concentration. Our Western blot results are compatible with a short-term activation due to PFKFB3 isoenzyme phosphorylation and a long-term sustained action due to increased PFKFB3 protein levels. Transient transfection of T47D cells with deleted gene promoter constructs allowed us to identify a PRE (progesterone-response element) to which PR (progesterone receptor) binds and thus transactivates PFKFB3 gene transcription. PR expression in the PR-negative cell line MDA-MB-231 induces endogenous PFKFB3 expression in response to norgestrel. Direct binding of PR to the PRE box (-3490 nt) was confirmed by ChIP (chromatin immunoprecipiation) experiments. A dual mechanism affecting PFKFB3 protein and gene regulation operates in order to assure glycolysis in breast cancer cells. An immediate early response through the ERK (extracellular-signal-regulated kinase)/RSK (ribosomal S6 kinase) pathway leading to phosphorylation of PFKFB3 on Ser461 is followed by activation of mRNA transcription via cis-acting sequences on the PFKFB3 promoter.

Epithelial progesterone receptor exhibits pleiotropic roles in uterine development and function

The ovarian steroid progesterone, acting through the progesterone receptor (PR), coordinates endometrial epithelial-stromal cell communication, which is critical for its development and function. PR expression in these cellular compartments is under tight temporal and endocrine control. Although ex vivo studies demonstrated the importance of stromal PR expression, they failed to show a role for epithelial PR in uterine function. Here, the in vivo role of PR in the uterine epithelium is defined using floxed PR (PR(f/f)) mice crossed to Wnt7a-Cre mice. Progesterone was unable to stimulate the expression of its epithelial target genes, including Ihh, in the Wnt7a-Cre(+)PR(f/-) mice. Analysis was conducted on Ihh to determine whether PR directly regulates epithelial gene transcription. ChIP-on-chip analysis identified PR binding sites in the 5'-flanking region of Ihh. Cotransfection of the proximal Ihh promoter with PR demonstrated that PR directly regulates Ihh transcription. Female Wnt7a-Cre(+)PR(f/-) mice are infertile due to defects in embryo attachment, stromal cell decidualization, and the inability to cease estrogen-induced epithelial cell proliferation. Finally, progesterone was unable to inhibit neonatal endometrial glandular development in Wnt7a-Cre(+)PR(f/-) mice. Thus, epithelial PR is necessary for the regulation of progesterone epithelial target gene expression, as well as uterine function and development.

Progesterone receptor inhibits proliferation of human breast cancer cells via induction of MAPK phosphatase 1 (MKP-1/DUSP1)

The roles of progesterone (P(4)) and of progesterone receptor (PR) in development and pathogenesis of breast cancer remain unclear. In this study, we observed that treatment of T47D breast cancer cells with progestin antagonized effects of fetal bovine serum (FBS) to stimulate cell proliferation, whereas siRNA-mediated knockdown of endogenous PR abrogated progestin-mediated anti-proliferative effects. To begin to define mechanisms for the anti-proliferative action of P(4)/PR, we considered the role of MAPK phosphatase 1 (MKP-1/DUSP1), which catalyzes dephosphorylation and inactivation of MAPKs. Progestin treatment of T47D cells rapidly induced MKP-1 expression in a PR-dependent manner. Importantly, P(4) induction of MKP-1 was associated with reduced levels of phosphorylated ERK1/2, whereas siRNA knockdown of MKP-1 blocked progestin-mediated ERK1/2 dephosphorylation and repression of FBS-induced cell proliferation. The importance of PR in MKP-1 expression was supported by findings that MKP-1 and PR mRNA levels were significantly correlated in 30 human breast cancer cell lines. By contrast, no correlation was observed with the glucocorticoid receptor, a known regulator of MKP-1 in other cell types. ChIP and luciferase reporter assay findings suggest that PR acts in a ligand-dependent manner through binding to two progesterone response elements downstream of the MKP-1 transcription start site to up-regulate MKP-1 promoter activity. PR also interacts with two Sp1 sites just downstream of the transcription start site to increase MKP-1 expression. Collectively, these findings suggest that MKP-1 is a critical mediator of anti-proliferative and anti-inflammatory actions of PR in the breast.

Differential and interactive effects of ligand-bound progesterone receptor A and B isoforms on tyrosine hydroxylase promoter activity

The classical progesterone receptors (PRs) are expressed in some hypothalamic dopaminergic and brainstem noradrenergic neurones. Progesterone influences prolactin and luteinising hormone release from the anterior pituitary gland, in part by regulating the activity of these catecholaminergic neurones. The present study aimed to determine the effects of PRs on tyrosine hydroxylase (TH) promoter activity. When CAD, SK-N-SH and CV-1 cells were transfected with TH promoter constructs and PR-A or PR-B expression vectors, progesterone treatment caused three- to six-fold increases in TH-9.0 kb promoter activity in PR-B expressing cells, although only a modest increase or no change in PR-A expressing cells. Using CAD cells, deletional analysis mapped the site of PR action to the -1403 to -1304 bp region of the TH promoter. Mutational analysis of putative regulatory sequences in this region indicated that multiple DNA elements are required for complete PR-B transactivation. Electrophoretic mobility shift assays were unable to demonstrate direct PR-B binding to TH promoter DNA sequences. However, chromatin immunoprecipitation analysis indicated PR-B was recruited to the TH promoter. Two different PR-B DNA binding domain mutants had opposing effects on PR-B-mediated TH promoter activation. A GS to AA mutation located in the p-box of the first zinc finger of PR-B inhibited progesterone transactivation of the TH promoter, whereas a C to A mutation in the zinc finger increased transactivation. PR-A was able to inhibit PR-B transactivation in a dose-dependent manner, although the degree of PR-A inhibition was dependent on the TH promoter deletion construct. These data indicate that ligand-bound PR-B is recruited to DNA elements in the TH promoter and acts as a transcriptional activator of the TH gene, and also that changes in the ratio of PR-A to PR-B may affect the ability of progesterone to increase TH expression.

Progesterone receptor action: defining a role in breast cancer

The ovarian steroid hormones, estradiol and progesterone, and their nuclear receptors (estrogen receptor [ER] and progesterone receptor [PR]), are involved in breast cancer development. As ER-positive/PR-positive tumors progress, they are likely to become steroid hormone-resistant/independent, yet often retain expression of their steroid receptors. Notably, up to 40% of women with steroid receptor-positive tumors exhibit de novo resistance or eventually fail on estrogen- or ERα-blocking therapies (acquired resistance). Indeed, most of the research on this topic has centered on mechanisms of ER 'escape' from endocrine therapy and the design of better ER-blocking strategies; signaling pathways that mediate endocrine (i.e., anti-estrogen) resistance are also excellent therapeutic targets. However, serious consideration of PR isoforms as important drivers of early breast cancer progression and ER modulators is timely and significant. Indeed, progress has been hindered by ER-centric experimental approaches. This article will focus on defining a role for PR in breast cancer with hopes of providing a refreshing PR-focused perspective.

Signaling inputs to progesterone receptor gene regulation and promoter selectivity

Progesterone receptors (PR) select and control genetic programs in the breast during normal mammary gland development, and progestin-driven processes contribute to the initiation and/or progression of breast cancer [Beral, V., 2003. Breast cancer and hormone-replacement therapy in the Million Women Study. Lancet 362, 419-427; Chlebowski, R.T., Hendrix, S.L., Langer, R.D., Stefanick, M.L., Gass, M., Lane, D., Rodabough, R.J., Gilligan, M.A., Cyr, M.G., Thomson, C.A., et al., 2003. Influence of estrogen plus progestin on breast cancer and mammography in healthy postmenopausal women: the Women's Health Initiative Randomized Trial. JAMA 289, 3243-3253]. Throughout the mammalian life span, progesterone exerts varying biological consequences on the mammary epithelial compartment, from brief proliferative spurts that occur with each luteal phase of the menstrual cycle to the massive expansion of the pregnant gland in preparation for lactation [Brisken, C., Park, S., Vass, T., Lydon, J.P., O'Malley, B.W., Weinberg, R.A., 1998. A paracrine role for the epithelial progesterone receptor in mammary gland development. Proc. Natl. Acad. Sci. U.S.A. 95, 5076-5081; Ismail, P.M., Amato, P., Soyal, S.M., DeMayo, F.J., Conneely, O.M., O'Malley, B.W., Lydon, J.P., 2003. Progesterone involvement in breast development and tumorigenesis-as revealed by progesterone receptor "knockout" and "knockin" mouse models. Steroids 68, 779-787]. These processes, while important developmentally, can become deregulated in breast cancer, thereby contributing to unchecked proliferation, increased survival, and invasive behaviors. Recently, our lab has focused on the molecular mechanisms, including phosphorylation events, by which PRs select specific target genes in response to progestins and other mitogenic hormonal signals (i.e. EGF, heregulin). Herein, we discuss the actions of cytoplasmic signaling molecules such as c-Src and mitogen-activated protein kinases as key mediators of PR promoter selectivity.

Progesterone receptors act as sensors for mitogenic protein kinases in breast cancer models

Progesterone receptors (PR), members of the nuclear receptor superfamily, function as ligand-activated transcription factors and initiators of c-Src kinase and mitogen-activated protein kinase signaling. Bidirectional cross-talk between PR and mitogenic protein kinases results in changes in PR post-translational modification, leading to alterations in PR transcriptional activity and promoter selectivity. PR-induced rapid activation of cytoplasmic protein kinases insures precise regulatory input to downstream cellular processes that are dependent upon nuclear PR, such as cell-cycle progression, and pro-survival signaling. Here, we review interactions between PR and mitogenic protein kinases and discuss the consequences of specific post-translational modifications on PR action in breast cancer cell-line models.

Progesterone and breast cancer

Progesterone is an ovarian steroid hormone that is essential for normal breast development during puberty and in preparation for lactation and breastfeeding. The actions of progesterone are primarily mediated by its high-affinity receptors, which include the classical progesterone receptor (PR)-A and -B isoforms, located in diverse tissues, including the brain, where progesterone controls reproductive behavior, and the breast and reproductive organs. Progestins are frequently prescribed for contraception or during postmenopausal hormone replacement therapy, in which progestins are combined with estrogen as a means to block estrogen-induced endometrial growth. The role of estrogen as a potent breast mitogen is undisputed, and inhibitors of the estrogen receptor and estrogen-producing enzymes (aromatases) are effective first-line cancer therapies. However, PR action in breast cancer is grossly understudied and remains controversial. Herein, we review existing evidence and discuss the challenges to defining a role for progesterone in breast cancer.

Challenges to defining a role for progesterone in breast cancer

Progesterone is an ovarian steroid hormone that is essential for normal breast development during puberty and in preparation for lactation. The actions of progesterone are primarily mediated by its high affinity receptors, including the classical progesterone receptor (PR) -A and -B isoforms, located in diverse tissues such as the brain where progesterone controls reproductive behavior, and the breast and reproductive organs. Progestins are frequently prescribed as contraceptives or to alleviate menopausal symptoms, wherein progestin is combined with estrogen as a means to block estrogen-induced endometrial growth. Estrogen is undisputed as a potent breast mitogen, and inhibitors of the estrogen receptor (ER) and estrogen producing enzymes (aromatases) are effective first-line cancer therapies. However, PR action in breast cancer remains controversial. Herein, we review existing evidence from in vitro and in vivo models, and discuss the challenges to defining a role for progesterone in breast cancer.

Integration of progesterone receptor action with rapid signaling events in breast cancer models

Recent discoveries suggest that several protein kinases are rapidly activated in response to ligand binding to cytoplasmic steroid hormone receptors (SRs), including progesterone receptors (PRs). Thus, PRs act as ligand-activated transcription factor "sensors" for growth factor-initiated signaling pathways in hormonally regulated tissues, such as the breast. Induction of rapid signaling upon progestin binding to PR-B provides a means to ensure that receptors and co-regulators are appropriately phosphorylated as part of optimal transcription complexes. Alternatively, PR-B activated kinase cascades provide additional avenues for progestin-regulated gene expression independent of PR nuclear action. Herein, an overview of progesterone/PR and signaling cross-talk in breast cancer models is provided. Kinases are emerging as key mediators of PR action. Cross-talk between SR and membrane-initiated signaling events suggests a mechanism for coordinate regulation of gene subsets by mitogenic stimuli in hormonally responsive normal tissues, and is suspected to contribute to cancer biology.

Progesterone receptor action: translating studies in breast cancer models to clinical insights

Progesterone receptors (PR) are useful prognostic indicators of breast cancers likely to respond to anti-estrogen receptor (ER) therapies. However, the role of progesterone, therapeutic progestins, or unliganded or liganded PRin breast cancer development or progression remains controversial. PR are ligand-activated transcription factors that act in concert with intracellular signaling pathways as "sensors" of multiple growth factor inputs to hormonally regulated tissues, such as the breast. The recently defined induction of rapid signaling events upon progestin-binding to PR-B provides a means to ensure that receptors and coregulators are appropriately phosphorylated as part of optimal transcription complexes. PR-activated kinase cascades may provide additional avenues for progestin-regulated gene expression independent of PR nuclear action. Herein, we present an overview ofprogesterone/PR and signaling cross-talk in breast cancer models and discuss the potential significance ofprogestin/PR action in breast cancer biology using examples from both in vitro and in vivo models, as well as limited clinical data. Kinases are emerging as key mediators of PR action. Cross-talk between PR and membrane-initiated signaling events suggests a mechanism for coordinated regulation ofgene subsets by mitogenic stimuli in hormonally responsive normal tissues. Dysregulation of this cross-talk mechanism may contribute to breast cancer biology; further studies are needed to address the potential for targeting PR in addition to ER and selected protein kinases as part of more effective breast cancer therapies.

Upregulation of protein S by progestins

BACKGROUND

Users of progestin-only contraceptives have raised protein S (PS) levels compared with baseline. This contrasts with the reduction in PS levels observed in users of combined oral contraceptives, which contain both a progestin and an estrogen.

OBJECTIVES

To determine the effect of progesterone and other progestin isoforms on the expression of PS and to describe the mechanism involved.

METHODS

Promoter activity of the PROS1 gene that encodes PS was assessed in vitro using breast and liver carcinoma cell lines grown in the presence of various progestins, with and without the addition of excess progesterone receptors. An electromobility shift assay (EMSA) was also performed to identify the progesterone receptor binding element.

RESULTS

PROS1 transcriptional levels were directly upregulated by 25% by progesterone via a mechanism that was progesterone receptor isoform B (PR-B)-dependent. The process was blocked by the progesterone receptor modulator RU486. Results for the EMSA demonstrated that a probe comprising nucleotides -397 to -417 of the PROS1 promoter bound to ligand-activated PR-B, suggesting that the domain is a progesterone response element (PRE). The type of progestin isoform greatly influenced the level of PROS1 promoter upregulation, with medroxyprogesterone able to stimulate a > 2-fold stronger response compared with progesterone.

CONCLUSIONS

The PROS1 promoter is responsive to progesterone and other progestins via a mechanism involving PR-B interacting with a PRE. The type of progestin is important as some elicit stronger upregulatory effects than others, which may influence the choice of progestin used for hormonal contraception by PS-deficient individuals.

Activation of the androgen receptor alters the intracellular calcium response to glutamate in primary hippocampal neurons and modulates sarco/endoplasmic reticulum calcium ATPase 2 transcription

Androgens have been shown to have a number of effects on hippocampal function. Although androgen receptors (AR) are found at high levels in hippocampal neurons, the intracellular mechanisms responsible for androgen's actions are unknown. If androgens were capable of altering internal calcium concentration ([Ca(2+)](i)), they could influence a variety of intracellular signaling pathways, maintain neuronal homeostasis and Ca(2+) induced excitotoxicity. In the present study, calcium imaging was used to measure the [Ca(2+)](i) in rat primary hippocampal neurons treated with either the AR agonist dihydrotestosterone (DHT), DHT+flutamide (AR antagonist), flutamide alone, or vehicle for 24 h and subsequently presented with an excitatory glutamate stimulus. In the absence of glutamate stimulation, DHT treatment caused a significant upward shift in baseline [Ca(2+)](i) when compared with neurons from all other groups. Glutamate had a greater effect on [Ca(2+)](i) in DHT-treated neurons and DHT-treated neurons returned to baseline levels significantly faster than all other groups. Cyclopiazonic acid, an inhibitor of sarco/endoplasmic reticulum calcium ATPase (SERCA) had a larger response in DHT-treated neurons compared with controls, suggesting increased Ca(2+) stores in DHT-treated neurons. In all cases the effects of DHT were blocked by treatment with flutamide indicating an AR-mediated mechanism. To determine a possible mechanism by which AR activation could be influencing [Ca(2+)](i), SERCA2 mRNA levels were measured in primary hippocampal neurons. SERCA2 is inserted into the endoplasmic reticulum (ER) membrane and functions to rapidly pump [Ca(2+)](i) into the ER. Following treatment of primary hippocampal neurons with DHT, SERCA2 mRNA was increased, an effect that was blocked in the presence of flutamide. Taken together these results indicate that DHT, working through AR, causes an up-regulation of SERCA2, which increases the sequestering of [Ca(2+)](i) in the endoplasmic reticulum of hippocampal neurons. Such changes may allow the neurons to respond more robustly to a stimulus and recover more quickly following a highly stimulatory challenge.

Uterine TRPV6 expression during the estrous cycle and pregnancy in a mouse model

Maintenance of uterine calcium balance is crucial for physiological functioning, including smooth muscle contraction and embryo implantation. Although calbindins were previously thought to act as important uterine calcium-processing genes for female reproductive function, they were not enough to attest the roles of calcium ions in the reproductive organs. Previously, we reported that rat transient receptor potential cation channel, subfamily V, member 6 (TRPV6) was expressed and regulated by hormones in the uterus. In the present study, we observed uterine TRPV6 expression in a mouse model to clarify the mutual roles of these two calcium-processing genes in female reproductive organs. We investigated uterine TRPV6 mRNA expression during the estrous cycle and pregnancy, as well as its regulation by the steroid hormones estrogen (E2) and progesterone (P4) in mice. Uterine TRPV6 mRNA levels increased at estrus and fluctuated in the uterus, placenta, and fetal membrane during pregnancy. Uterine TRPV6 mRNA increased in mid- and late pregnancy, and its expression was strongly induced in midpregnancy in the labyrinth and spongy zones of the placenta, and in the fetal membrane. E2 (17beta-estradiol) was found to regulate uterine TRPV6 expression in the luminal and glandular epitheliums. In addition, we determined that ERalpha tightly regulated uterine TRPV6 transcription. Together, these results suggest that for uterine function in normal pregnancy, TRPV6 is regulated by E2 via an ERalpha-dependent pathway.

Integration of Rapid Signaling Events with Steroid Hormone Receptor Action in Breast and Prostate Cancer

Steroid hormone receptors (SRs) are ligand-activated transcription factors and sensors for growth factor-initiated signaling pathways in hormonally regulated tissues, such as the breast or prostate. Recent discoveries suggest that several protein kinases are rapidly activated in response to steroid hormone binding to cytoplasmic SRs. Induction of rapid signaling upon SR ligand binding ensures that receptors and coregulators are appropriately phosphorylated as part of optimal transcription complexes. Alternatively, SR-activated kinase cascades provide additional avenues for SR-regulated gene expression independent of SR nuclear action. We provide an overview of SR and signaling cross talk in breast and prostate cancers, using the human progesterone receptor (PR) and androgen receptor (AR) as models. Kinases are emerging as key mediators of SR action. Cross talk between SR and membrane-initiated signaling events suggests a mechanism for coordinate regulation of gene subsets by mitogenic stimuli in hormonally responsive normal tissues; such cross talk is suspected to contribute to cancer biology.

Linkage of progestin and epidermal growth factor signaling: phosphorylation of progesterone receptors mediates transcriptional hypersensitivity and increased ligand-independent breast cancer cell growth

Progesterone receptor (PR) action is linked to epidermal growth factor (EGF) initiated signaling pathways at multiple levels; mitogen-activated protein kinases (MAPKs) are key mediators of this important cross-talk. Herein, we probed the effects of EGF on PR function and regulation of breast cancer cell growth. EGF stimulated rapid and transient phosphorylation of PR-B Ser294 relative to persistent phosphorylation of this site induced by the synthetic progestin, R5020. EGF induced nuclear translocation and DNA binding of unliganded wild-type, but not mutant PRs containing an Ala at position 294 (S294A). However, EGF alone induced little to no PR-B transcriptional activity; S294A PR-B was transcriptionally impaired. In contrast, pretreatment of cells with EGF (30min) significantly increased the potency and efficacy of wild-type, but not S294A PR transcriptional activity in response to progestin, and enhanced ligand-dependent downregulation of wild-type but not S294A PR. Replacement of Ser294 with aspartic acid (S294D) to mimic phosphorylation at this site decreased receptor stability and, as predicted, heightened progestin-induced transcription relative to wild-type PR-B. RT-PCR demonstrated the Ser294 phosphorylation-dependence of selected PR target genes (TGFalpha and HB-EGF). Surprisingly, PR-B expressing cells growing in soft agar were highly responsive to EGF or progestin, and this was further stimulated by the combination of both hormones. Cells expressing S294A PR exhibited reduced soft agar growth, and were also sensitive to R5020 alone, but failed to respond to EGF. These results suggest that PR Ser294 is an important "sensor" for growth factor inputs that affects PR function and breast cancer cell growth in the absence of progestin or in the presence of low or "sub-threshold" progestin concentrations. PR function likely contributes to breast cancer progression when EGFR family members or their ligands are overexpressed, a condition that predicts low abundance, but highly active and nuclear PR.

Cyclin dependent kinase 2 and the regulation of human progesterone receptor activity

The function of the S phase kinase cyclin A/Cdk2 in maintaining and regulating cell cycle kinetics is well established. However an alternative role in the regulation of progesterone receptor (PR) signaling is emerging. PR and its coactivators are phosphoproteins. Cyclin A/Cdk2 phosphorylates several of the PR phosphorylation sites in vitro and there is evidence that it participates in PR phosphorylation in vivo. Cyclin A/Cdk2 also functions as a PR coactivator. Overexpression increases PR transcriptional activity independent of PR phosphorylation. In the presence of hormone, cyclin A/Cdk2 is recruited to PR bound to DNA of target genes. Inhibition of Cdk activity prevents recruitment of the p160 coactivator steroid receptor coactivator-1 (SRC-1), suggesting that Cdk2 phosphorylates SRC-1. Consistent with this finding, phosphatase treatment of SRC-1 reduces its ability to interact with PR in vitro. Moreover, PR transcriptional activity is highest in S phase where cyclin A is expressed. In G1, PR activity is reduced and the capacity to recruit SRC-1 to a progestin responsive promoter is diminished. Future studies will focus on the importance of cyclin A/Cdk2 phosphorylation of other components of the PR transcription complex, such as the p160 coactivator SRC-1, and the specific role of Cdk2 target sites in the regulation of PR activity.

Regulatory role of ovarian sex hormones in calcium uptake activity of cardiac sarcoplasmic reticulum

Alterations in the intracellular Ca2+handling in cardiomyocytes may underlie the cardiac dysfunction observed in the ovarian sex hormone-deprived condition. To test the hypothesis that ovarian sex hormones had a significant role in the cardiac intracellular Ca2+mobilization, the sarcoplasmic reticulum (SR) Ca2+uptake and SR Ca2+-ATPase (SERCA) activity were determined in 10-wk ovariectomized rat hearts. With the use of left ventricular homogenate preparations, a significant suppression of maximum SR Ca2+uptake activity, but with an increase in SR Ca2+responsiveness, was demonstrated in ovariectomized hearts. In parallel measurements of SERCA activity in SR-enriched membrane preparations from ovariectomized hearts, a suppressed maximum SERCA activity with a leftward shift in the relationship between pCa (-log molar free Ca2+concentration) and SERCA activity was also detected. A significant downregulation of SERCA proteins and reduction in the SERCA mRNA level were observed in association with suppressed maximum SERCA activity. While there were no changes in total phospholamban and phosphorylated Ser16phospholamban levels, a decrease in phosphorylated Thr17phospholamban as well as an increase in the suprainhibitory, monomeric form of phospholamban stoichiometry was found. Estrogen and progesterone supplementations were equally effective in preventing changes in ovariectomized hearts. Our data showed for the first time that female sex hormones played an important role in the regulation of the cardiac SR Ca2+uptake. Under hormone-deficient conditions, there was an adaptive response of SERCA that escaped the regulatory effect of phospholamban.

Differential expression of uterine calcium transporter 1 and plasma membrane Ca2+ ATPase 1b during rat estrous cycle

Calcium-related proteins include the calcium transporters 1 and 2 (CaT1 and CaT2), plasma membrane Ca2+-ATPase 1b (PMCA1b), and calbindin-D9k and -D28k. The expression of CaT1 and PMCA1b and their potential roles in the uterine tissue remain to be clarified. Thus, in the present study, the expression patterns of CaT1 and PMCA1b were examined to predict their roles in rat uterus during the estrous cycle. Both CaT1 and PMCA1b mRNAs were detected in rat uterus. Uterine CaT1 mRNA was highly expressed at diestrus compared with proestrus, whereas PMCA1b expression was not altered during the estrus cycle. To evaluate the sex steroids involved in uterine CaT1 mRNA regulation, 17beta-estradiol (E2) and/or progesterone (P4) were injected into immature rats. Treatment with P4 or E2 plus P4 resulted in an increase in CaT1 mRNA, but a synergetic effect of E2 plus P4 was not detected. Uterine CaT1 mRNA was induced by P4 in a time- and dose-dependent manner, with maximal transcript detected 12 h after the final P4 injection. Treatment with RU486, a progesterone receptor (PR) antagonist, completely blocked P4-induced CaT1 mRNA, indicating that P4 regulates CaT1 mRNA expression via a PR-mediated pathway. In addition, CaT1 mRNA was expressed in uterine endometrium and glandular endometrium at diestrus in P4-treated rats. Together, these results suggest that CaT1 is regulated by P4 at diestrus via a PR-dependent pathway.

Transforming growth factor-beta1 differentially mediates fibronectin and inflammatory cytokine expression in kidney tubular cells

Transforming growth factor-beta(1) (TGF-beta(1)) is not only an important fibrogenic but also immunomodulatory cytokine in the human kidney. We have recently demonstrated that TGF-beta(1) induces interleukin-8 (IL-8), macrophage chemoattractant protein-1 (MCP-1), and fibronectin production in renal proximal tubular (HK-2) cells. However, the unique dependence of IL-8, MCP-1, and fibronectin on TGF-beta(1) expression is unknown. The TGF-beta(1) gene was effectively silenced in HK-2 cells using small-interference (si) RNA. Basal secretion of IL-8 and MCP-1 decreased (both P < 0.05) but, paradoxically, fibronectin increased (P < 0.05) in TGF-beta(1)-silenced cells compared with cells transfected with nonspecific siRNA. Significant increases were observed in mRNA for the TGF-beta(2) (P < 0.05), TGF-beta(3) (P < 0.05) isoforms and pSmad2 (P < 0.05), which were reflected in protein expression. Concurrent exposure to pan-specific TGF-beta antibody reversed the observed increase in fibronectin expression, suggesting that TGF-beta(2) and TGF-beta(3) isoforms mediate the increased fibronectin expression in TGF-beta(1)-silenced cells. An increase in the DNA binding activity of activator protein-1 (AP-1; P < 0.05) was also observed in TGF-beta(1)-silenced cells. In contrast, nuclear factor-kappaB (NF-kappaB) DNA binding activity was significantly decreased (P < 0.0005). These studies demonstrate that TGF-beta(1) is a key regulator of IL-8 and MCP-1, whereas fibronectin expression is regulated by a complex interaction between the TGF-beta isoforms in the HK-2 proximal tubular cell line. Decreased expression of TGF-beta(1) reduces chemokine production in association with reduced NF-kappaB DNA binding activity, suggesting that immunomodulatory pathways in the kidney are specifically dependent on TGF-beta(1). Conversely, decreased expression of TGF-beta(1) results in increased TGF-beta(2), TGF-beta(3), AP-1, and pSmad2 that potentially mediates the observed increase in fibronectin.

Difference in progesterone-receptor isoforms ratio between early and late first-trimester human trophoblast is associated with differential cell invasion and matrix metalloproteinase 2 expression

The expression profile of the progesterone-receptor isoforms and progesterone regulation of matrix metalloproteinase 2 (MMP2) were investigated in early and late first-trimester trophoblast cells. Human trophoblast cells were obtained from legal abortions (6-12 wk of gestation). Purity of 95-98% was verified using immunohistochemistry with specific antibodies. Evaluation of cell count was performed with XTT Reagent kit, and invasion was tested using Matrigel invasion assay. Zymography was used to detect proteolytic activity, and Western blot immunoassay was used to study protein concentration. Gene expression of PGRB, PGR, and MMP2 was studied using reverse transcription-polymerase chain reaction with the housekeeping gene GAPDH used for normalization. Promoter activity was determined using luciferase reporter assay. Differential progesterone-receptor profile was documented with the dominance of PGRB in early trophoblast and the dominance of PGRA in late trophoblast. This differential profile is compatible with the inverse effect of progesterone on the two cell populations, decreasing invasion and gelatinase expression in the early first-trimester trophoblast and increasing invasion and gelatinase expression in the late first-trimester trophoblast. A decrease in MMP2 promoter activity in early trophoblast cells exposed to progesterone suggests that MMP2 expression is regulated by progesterone at the transcriptional level as well. Early trophoblast cells transfected with expressing vector for PGR encoding PGRA revealed less MMP2 activity and reversal of its response to progesterone similar to the effect observed in late trophoblast cells.

Peroxisome proliferator-activated receptor-gamma ligands suppress fibronectin gene expression in human lung carcinoma cells: involvement of both CRE and Sp1

Lung carcinoma often occurs in patients with chronic lung disease such as tobacco-related emphysema and asbestos-related pulmonary fibrosis. These diseases are characterized by dramatic alterations in the content and composition of the lung extracellular matrix, and we believe this "altered" matrix has the ability to promote lung carcinoma cell growth. One extracellular matrix molecule shown to be altered in these lung diseases is fibronectin (Fn). We previously reported increased growth and survival of non-small cell lung carcinoma (NSCLC) cells exposed to Fn. Thus Fn may serve as a mitogen/survival factor for NSCLC and therefore represents a novel target for anti-cancer strategies. To this end, we studied the effects of the PPARgamma ligands 15d-PGJ(2), rosiglitazone (BRL49653), and troglitazone on Fn expression in NSCLC cells and found that they were able to inhibit Fn gene transcription. Inhibition of Fn expression by BRL49653 and troglitazone, but not by 15d-PGJ(2), was prevented by the specific PPARgamma antagonist GW-9662 and by PPARgamma small interfering RNA. Working with Fn deletion and mutated promoter constructs, we found that the region between -170 and -50 bp downstream from the transcriptional start site of the promoter was involved in PPARgamma ligand inhibition. PPARgamma ligands also diminished the phosphorylation of CREB, diminished Sp1 nuclear protein expression, and prevented the binding of these transcription factors to CRE and Sp1 sites, respectively, within the Fn promoter. In summary, our results demonstrate that PPARgamma ligands inhibit Fn gene expression in NSCLC cells through PPARgamma-dependent and -independent pathways that affect both CREB and Sp1.

Gonadotropin-releasing hormone and TGF-beta activate MAP kinase and differentially regulate fibronectin expression in endometrial epithelial and stromal cells

Gonadotropin-releasing hormone analog (GnRHa) is used for medical management of endometriosis and premature luteinizing hormone surge during controlled ovarian stimulation. Human endometrium expresses GnRH receptors, and GnRHa alters the expression of transforming growth factor-beta (TGF-beta) and receptors in endometrial cells. Because the diverse biological actions of GnRHa and TGF-beta are mediated in part through the MAPK pathway, we determined whether utilization of MAPK/ERK and transcriptional activation of immediate early genes c-fos and c-jun result in differential regulation of fibronectin, known as key regulator of embryo implantation and endometriosis progression. Using endometrial stromal cells (ESC) and the endometrial epithelial cell line HES, we demonstrated that GnRHa and TGF-beta, in a dose-, time-, and cell-dependent manner, increased the level of phosphorylated ERK1/2 (pERK1/2). GnRH antagonist Antide also increased pERK1/2 induction in ESC and HES, whereas pretreatment reduced GnRHa-induced pERK2 in ESC but not in HES. Cotreatments with GnRHa plus TGF-beta1 did not have an additive or an inhibitory effect on pERK1/2 induction compared with GnRHa or TGF-beta1 action alone. TGF-beta1 and GnRHa increased ERK1/2 nuclear accumulation and inversely regulated the expression of c-fos and c-jun and that of fibronectin in a cell-specific manner. Pretreatment with U-0126, a MEK1/2 inhibitor, blocked basal, as well as GnRHa- and TGF-beta1-induced pERK1/2; however, it differentially affected c-fos, c-jun, and fibronectin expression. In conclusion, the results indicate that GnRHa and TGF-beta signaling through MAPK/ERK results in differential regulation of fibronectin expression in endometrial cells, a molecular mechanism where short- and long-term GnRHa therapy and locally expressed TGF-beta could influence embryo implantation and endometriosis implants, respectively.