Role of luteal glucocorticoid metabolism during maternal recognition of pregnancy in women

Seminal Plasma Triggers the Differential Expression of the Glucocorticoid Receptor (NR3C1/GR) in the Rabbit Reproductive Tract

Rabbits are interesting as research animal models for reproduction, due to their condition of species of induced ovulation, with the release of endogenous gonadotropin-releasing hormone (GnRH) due to coitus. Glucocorticoid (GC) signaling, crucial for physiological homeostasis, is mediated through a yet unclear mechanism, by the GC receptor (NR3C1/GR). After mating, the female reproductive tract undergoes dynamic modifications, triggered by gene transcription, a pre-amble for fertilization and pregnancy. This study tested the hypothesis that when ovulation is induced, the expression of NR3C1 is influenced by sperm-free seminal plasma (SP), similarly to after mating (whole semen), along the different segments of the internal reproductive tract of female rabbits. Semen (mating) was compared to vaginal infusion of sperm-free SP (Experiment 1), and changes over time were also evaluated, i.e., 10, 24, 36, 68, and 72 h post-mating, corresponding to specific stages, i.e., ovulation, fertilization, and the interval of early embryo development up to the morula stage (Experiment 2). All does were treated with GnRH to induce ovulation. Samples were retrieved from seven segments of the reproductive tract (from the cervix to infundibulum), at 20 h post-mating or sperm-free SP infusion (Experiment 1) or at 10, 24, 36, 68, and 72 h post-mating (Experiment 2). Gene expression of NR3C1 was analyzed by qPCR. Results showed an increase in NR3C1 expression in the infundibulum compared to the other anatomical regions in the absence of spermatozoa when sperm-free SP infusion was performed (Experiment 1). Moreover, during the embryo transport through the oviduct, the distal isthmus was time-course upregulated, especially at 72 h, when morulae are retained in this anatomical region, while it was downregulated in the distal uterus at 68 h (Experiment 2). The overall results suggest that NR3C1, the GC receptor gene, assessed in the reproductive tract of does for the first time, shows differential expression changes during the interval of oviductal and uterine embryo transport that may imply a relevant role of the GC action, not only close to the site of ovulation and fertilization, but also in the endometrium.

Pregnancy stage determines the effect of chronic stress on ovarian progesterone synthesis

Although stress-induced glucocorticoid release is thought to be a primary driver by which maternal stress negatively impacts pregnancy outcomes, the downstream neuroendocrine targets mediating these adverse outcomes are less well understood. We hypothesized that stress-induced glucocorticoid secretion inhibits pituitary hormone secretion, resulting in decreased ovarian progesterone synthesis. Using a chronic restraint model of stress in mice, we quantified steroid hormone production, pituitary hormones, and expression of ovarian genes that support progesterone production at both early ( day 5) and midpregnancy ( day 10). Females subjected to daily restraint had elevated baseline glucocorticoids during both early and midpregnancy; however, lower circulating progesterone was observed only during early pregnancy. Lower progesterone production was associated with lower expression of steroidogenic enzymes in the ovary of restrained females during early pregnancy. There were no stress-related changes to luteinizing hormone (LH) or prolactin (PRL). By midpregnancy, circulating LH decreased regardless of treatment, and this was associated with downregulation of ovarian steroidogenic gene expression. Our results are consistent with a role for LH in maintaining steroidogenic enzyme expression in the ovary, but neither circulating PRL nor LH were associated with the stress-induced inhibition of ovarian progesterone production during early pregnancy. We conclude that chronic stress impacts endocrine networks differently in pregnant and nonpregnant mammals. These findings underscore the need for further studies exploring dynamic changes in endocrine networks participating in pregnancy initiation and progression to elucidate the physiological mechanisms that connect stress exposure to adverse pregnancy outcomes.

Detection and activity of 11 beta hydroxylase (CYP11B1) in the bovine ovary

Glucocorticoids (GCs) such as cortisol and corticosterone are important steroid hormones with different functions in intermediate metabolism, development, cell differentiation, immune response and reproduction. In response to physiological and immunological stress, adrenocorticotropic hormone (ACTH) acts on the adrenal gland by stimulating the synthesis and secretion of GCs. However, there is increasing evidence that GCs may also be synthesized by extra-adrenal tissues. Here, we examined the gene and protein expression of the enzyme 11β-hydroxylase P450c11 (CYP11B1), involved in the conversion of 11-deoxycortisol to cortisol, in the different components of the bovine ovary and determined the functionality of CYP11B1in vitro.CYP11B1mRNA was expressed in granulosa and theca cells in small, medium and large antral ovarian follicles, and CYP11B1 protein was expressed in medium and large antral follicles. After stimulation by ACTH, we observed an increased secretion of cortisol by the wall of large antral follicles. We also observed a concentration-dependent decrease in the concentration of cortisol in response to metyrapone, an inhibitor of CYP11B1. This decrease was significant at 10−5 µM metyrapone. In conclusion, this study demonstrated for the first time the presence of CYP11B1 in the bovine ovary. This confirms that there could be a local synthesis of GCs in the bovine ovary and therefore a potential endocrine responder to stress through these hormones.

Local Regeneration of Cortisol by 11β-HSD1 Contributes to Insulin Resistance of the Granulosa Cells in PCOS

CONTEXT

Insulin resistance (IR) of the granulosa cells may account for the ovarian dysfunctions observed in polycystic ovarian syndrome (PCOS). The underlying mechanism remains largely unresolved.

OBJECTIVE

The objective of the study was to investigate the relationship of IR of the granulosa cells with cortisol in the follicular fluid and 11β-hydroxysteroid dehydrogenase 1 and 2 (11β-HSD1 and -2) in the granulosa cells in PCOS.

DESIGN

Follicular fluid and granulosa cells were collected from non-PCOS and PCOS patients with and without IR to measure cortisol concentration and the amounts of 11β-HSD1 and -2, which were then correlated with IR status. The effects of cortisol on the expression of genes pertinent to IR were studied in cultured human granulosa cells.

RESULTS

Cortisol concentration in the follicular fluid, 11β-HSD1 but not 11β-HSD2 mRNA in the granulosa cells were significantly elevated in PCOS with IR. Increased reductase and decreased oxidase activities of 11β-HSD were observed in granulosa cells in PCOS with IR. In cultured granulosa cells, insulin-induced Akt phosphorylation was significantly attenuated by cortisol. Cortisol not only increased phosphatase and tensin homolog deleted on chromosome 10, an inhibitor of Akt phosphorylation, but also 11β-HSD1 in the cells.

CONCLUSIONS

Increased 11β-HSD1 expression and its reductase activity in granulosa cells are the major causes of increased cortisol concentration in the follicular fluid of PCOS with IR. The consequent excessive cortisol might contribute to IR of the granulosa cells in PCOS patients by attenuating Akt phosphorylation via induction of phosphatase and tensin homolog deleted on chromosome 10 expression, which might be further exacerbated by the induction of 11β-HSD1.

Role of Glucocorticoids in Cystic Ovarian Disease: Expression of Glucocorticoid Receptor in the Bovine Ovary

The aim of this study was to characterize the expression of glucocorticoid receptor (GR) in the components of normal bovine ovary and in animals with cystic ovarian disease (COD). Changes in the protein and mRNA expression levels were determined in control cows and cows with COD by immunohistochemistry and real-time PCR. GR protein expression in granulosa cells was higher in cysts from animals with spontaneous COD and adrenocorticotropic hormone-induced COD than in tertiary follicles from control animals. In theca interna cells, GR expression was higher in cysts from animals with spontaneous COD than in tertiary follicles from control animals. The increase in GR expression observed in cystic follicles suggests a mechanism of action for cortisol and its receptor through the activation/inactivation of specific transcription factors. These factors could be related to the pathogenesis of COD in cattle.

Management of adrenal tumors in pregnancy

Adrenal diseases, including Cushing syndrome (CS), primary aldosteronism (PA), pheochromocytoma, and adrenocortical carcinoma, are uncommon in pregnancy; a high degree of clinical suspicion must exist. Physiologic changes to the hypothalamus-pituitary-adrenal axis in a normal pregnancy result in increased cortisol, renin, and aldosterone levels, making the diagnosis of CS and PA in pregnancy challenging. However, catecholamines are not altered in pregnancy and allow a laboratory diagnosis of pheochromocytoma that is similar to that of the nonpregnant state. Although adrenal tumors in pregnancy result in significant maternal and fetal morbidity, and sometimes mortality, early diagnosis and appropriate treatment often improve outcomes.

Potential role of hCG in apoptosis of human luteinized granulosa cells

The corpus luteum (CL) forms after ovulation and acts as a temporary endocrine gland that produces progesterone (P4), a hormone that is essential for implantation and maintenance of pregnancy in mammals. In pregnant women, human chorionic gonadotropin (hCG) secreted by the conceptus prevents luteolysis. hCG also increases the survival of cultured human luteinized granulosa cells (hLGCs). To clarify the maintenance mechanism of the human CL, we investigated the effects of hCG and P4 receptor antagonists, onapristone (OP) and RU486, on the viability of hLGCs. With the patients’ consent, hLGCs were isolated from follicular aspirates for in vitro fertilization. The cells were cultured with hCG (0.1, 1, 10, 100 IU/ml), OP (10, 25, 50, 100 μM), RU486 (100 μM), P4 (1, 10, 25, 50 μM) or some combination of the four for 24 h. Cell viability was significantly increased by hCG (100 IU/ml) and significantly decreased by OP (100 μM) compared with the control. Cells treated with hCG and OP together were significantly less viable than the control and OP-treated cells. The combined treatment also significantly increased CASP3 activity and cleaved CASP3 protein expression. Furthermore, P4 addition reversed the reduction in cell viability caused by the combination of hCG and OP treatment. The overall findings suggest that hCG cooperates with P4 to increase survival of hLGCs and to induce apoptosis when P4 action supported by hCG is attenuated in the human CL.

Physiology and Endocrinology Symposium: role of immune cells in the corpus luteum

The immune system is essential for optimal function of the reproductive system. The corpus luteum (CL) is an endocrine organ that secretes progesterone, which is responsible for regulating the length of the estrous cycle, and for the establishment and maintenance of pregnancy in mammals. This paper reviews literature that addresses 2 areas; i) how immune cells are recruited to the CL, and ii) how immune cells communicate with luteal cells to affect the formation, development, and regression of the CL. Immune cells, primarily recruited to the ovulatory follicle from lymphoid organs after the LH surge, facilitate ovulation and populate the developing CL. During the luteal phase, changes in the population of macrophages, eosinophils, neutrophils, and T lymphocytes occur at critical functional stages of the CL. In addition to their role in facilitating ovulation, immune cells may have an important role in luteal function. Evidence shows that cytokines secreted by immune cells modulate both luteotropic and luteolytic processes. However, the decision to pursue either function may depend on the environment provided by luteal cells. It is suggested that understanding the role immune cells play could lead to identification of new strategies to improve fertility in dairy cattle and other species.

Glucocorticoid regulation of SLIT/ROBO tumour suppressor genes in the ovarian surface epithelium and ovarian cancer cells

The three SLIT ligands and their four ROBO receptors have fundamental roles in mammalian development by promoting apoptosis and repulsing aberrant cell migration. SLITs and ROBOs have emerged as candidate tumour suppressor genes whose expression is inhibited in a variety of epithelial tumours. We demonstrated that their expression could be negatively regulated by cortisol in normal ovarian luteal cells. We hypothesised that after ovulation the locally produced cortisol would inhibit SLIT/ROBO expression in the ovarian surface epithelium (OSE) to facilitate its repair and that this regulatory pathway was still present, and could be manipulated, in ovarian epithelial cancer cells. Here we examined the expression and regulation of the SLIT/ROBO pathway in OSE, ovarian cancer epithelial cells and ovarian tumour cell lines. Basal SLIT2, SLIT3, ROBO1, ROBO2 and ROBO4 expression was lower in primary cultures of ovarian cancer epithelial cells when compared to normal OSE (P<0.05) and in poorly differentiated SKOV-3 cells compared to the more differentiated PEO-14 cells (P<0.05). Cortisol reduced the expression of certain SLITs and ROBOs in normal OSE and PEO-14 cells (P<0.05). Furthermore blocking SLIT/ROBO activity reduced apoptosis in both PEO-14 and SKOV-3 tumour cells (P<0.05). Interestingly SLIT/ROBO expression could be increased by reducing the expression of the glucocorticoid receptor using siRNA (P<0.05). Overall our findings indicate that in the post-ovulatory phase one role of cortisol may be to temporarily inhibit SLIT/ROBO expression to facilitate regeneration of the OSE. Therefore this pathway may be a target to develop strategies to manipulate the SLIT/ROBO system in ovarian cancer.

Expression of the repulsive SLIT/ROBO pathway in the human endometrium and Fallopian tube

We investigated whether the repulsive SLIT/ROBO pathway is expressed in the endometrium and is negatively regulated during implantation. We also examined whether deficient expression in the Fallopian tube (FT) may predispose to ectopic pregnancy (EP). Endometrium (n = 21) and FT (n = 17) were collected across the menstrual cycle from fertile women with regular cycles. Decidualized endometrium (n = 6) was obtained from women undergoing termination, and FT (n = 6) was obtained from women with EP. SLIT/ROBO expression was quantified by reverse transcription-PCR and protein localized by immunohistochemistry. The regulation of SLIT/ROBO expression in vitro, by sex steroids and hCG, was assessed in endometrial (hTERT-EEpC) epithelial cells, and the effects of Chlamydia trachomatis infection and smoking were studied in oviductal (OE-E6/E7) epithelial cells. Endometrial SLIT3 was highest in the mid-secretory phase (P = 0.0003) and SLIT1,2 and ROBO1 showed a similar trend. ROBO2 was highest in proliferative phase (P = 0.027) and ROBO3,4 showed a similar trend. SLIT2,3 and ROBO1, 4 were lower in decidua compared with mid-secretory endometrium (P < 0.05). SLITs and ROBOs, excepting ROBO2, were expressed in FT but there were no differences across the cycle or in EP. SLIT/ROBO proteins were localized to endometrial and FT epithelium. Treatment of hTERT-EEpC with a combination of estradiol and medroxyprogesterone acetate inhibited ROBO1 expression (P < 0.01) but hCG had no effect. Acute treatment of OE-E6/E7 with smoking metabolite, cotinine, and C. trachomatis had no effect. These findings imply a regulated role for the endometrial SLIT/ROBO interaction during normal development and pregnancy but that it may not be important in the aetiology of EP.

The SLIT-ROBO pathway: a regulator of cell function with implications for the reproductive system

The secreted SLIT glycoproteins and their Roundabout (ROBO) receptors were originally identified as important axon guidance molecules. They function as a repulsive cue with an evolutionarily conserved role in preventing axons from migrating to inappropriate locations during the assembly of the nervous system. In addition the SLIT-ROBO interaction is involved in the regulation of cell migration, cell death and angiogenesis and, as such, has a pivotal role during the development of other tissues such as the lung, kidney, liver and breast. The cellular functions that the SLIT/ROBO pathway controls during tissue morphogenesis are processes that are dysregulated during cancer development. Therefore inactivation of certain SLITs and ROBOs is associated with advanced tumour formation and progression in disparate tissues. Recent research has indicated that the SLIT/ROBO pathway could also have important functions in the reproductive system. The fetal ovary expresses most members of the SLIT and ROBO families. The SLITs and ROBOs also appear to be regulated by steroid hormones and regulate physiological cell functions in adult reproductive tissues such as the ovary and endometrium. Furthermore several SLITs and ROBOs are aberrantly expressed during the development of ovarian, endometrial, cervical and prostate cancer. This review will examine the roles this pathway could have in the development, physiology and pathology of the reproductive system and highlight areas for future research that could further dissect the influence of the SLIT/ROBO pathway in reproduction.

Differential expression and functional characterization of luteinizing hormone receptor splice variants in human luteal cells: implications for luteolysis

The human LH receptor (LHR) plays a key role in luteal function and the establishment of pregnancy through its interaction with the gonadotropins LH and human chorionic gonadotropin. We previously identified four splice variants of the LHR in human luteinized granulosa cells (LGCs) and corpora lutea (CL). Real-time quantitative PCR revealed that expression of the full-length LHR (LHRa) and the most truncated form (LHRd) changed significantly in CL harvested at different stages of the ovarian cycle (P < 0.01, ANOVA). LHRa expression was reduced in the late luteal CL (P < 0.05). Conversely, an increase in LHRd expression was observed in the late luteal CL (P < 0.01). Chronic manipulation of human chorionic gonadotropin in LGC primary cultures supported the in vivo findings. LHRd encodes a protein lacking the transmembrane and carboxyl terminal domains. COS-7 cells expressing LHRd were unable to produce cAMP in response to LH stimulation. COS-7 cells coexpressing LHRd and LHRa also failed to generate cAMP in response to LH, suggesting that this truncated form has a negative effect on the signaling of LHRa. Immunofluorescence staining of LGC and COS-7 cells implied that there is a reduction in cell surface expression of LHRa when LHRd is present. Overall, these results imply expression of LHR splice variants is regulated in the human CL. Furthermore, during functional luteolysis a truncated variant could modulate the cell surface expression and activity of full-length LHR.

Novel regulated expression of the SLIT/ROBO pathway in the ovary: possible role during luteolysis in women

The human corpus luteum (CL) undergoes luteolysis, associated with marked tissue and vascular remodeling, unless conception occurs and the gland is rescued by human chorionic gonadotropin (hCG). In Drosophila the Slit gene product, a secreted glycoprotein, acts as a ligand for the roundabout (robo) transmembrane receptor. Together they influence the guidance and migration of neuronal and nonneuronal cells. In vertebrates three Slit (Slit1, Slit2, Slit3) and four Robo (Robo1, Robo2, Robo3/Rig-1, Robo4/Magic Robo) genes have been identified. ROBO1, SLIT2, and SLIT3 are also inactivated in human cancers and may regulate apoptosis and metastasis. Because processes such as apoptosis and tissue remodeling occur during the regression of the CL, the aim of this study was to investigate the expression, regulation, and effects of the SLIT and ROBO genes in human luteal cells. Immunohistochemistry and RT-PCR revealed that SLIT2, SLIT3, ROBO1, and ROBO2 are expressed in luteal steroidogenic cells and fibroblast-like cells of the human CL. Furthermore, using real-time quantitative PCR, expression of SLIT2, SLIT3, and ROBO2 was maximal in the late-luteal phase and significantly reduced after luteal rescue in vivo with exogenous hCG (P<0.05). Additionally, hCG significantly inhibited SLIT2, SLIT3, and ROBO2 expression in cultured luteinized granulosa cells (P<0.05). Blocking SLIT-ROBO activity increased migration and significantly decreased levels of apoptosis in primary cultures of luteal cells (P<0.05). Overall, these results suggest the SLIT/ROBO pathway could play an important role in luteolysis in women.

Cortisol is a suppressor of apoptosis in bovine corpus luteum

Glucocorticoid (GC) acts as a modulator of physiological functions in several organs. In the present study, we examined whether GC suppresses luteolysis in bovine corpus luteum (CL). Cortisol (an active GC) reduced the mRNA expression of caspase 8 (CASP8) and caspase 3 (CASP3) and reduced the enzymatic activity of CASP3 and cell death induced by tumor necrosis factor (TNF) and interferon gamma (IFNG) in cultured bovine luteal cells. mRNAs and proteins of GC receptor (NR3C1), 11beta-hydroxysteroid dehydrogenase type 1 (HSD11B1), and HSD11B2 were expressed in CL throughout the estrous cycle. Moreover, the protein expression and the enzymatic activity of HSD11B1 were high at the early and the midluteal stages compared to the regressed luteal stage. These results suggest that cortisol suppresses TNF-IFNG-induced apoptosis in vitro by reducing apoptosis signals via CASP8 and CASP3 in bovine CL and that the local increase in cortisol production resulting from increased HSD11B1 at the early and midluteal stages helps to maintain CL function by suppressing apoptosis of luteal cells.