Paracrine regulation of endometrial function: interaction between progesterone and corticotropin-releasing factor (CRF) and activin A

The Link Between Stress and Endometriosis: from Animal Models to the Clinical Scenario

There is strong evidence from humans and animal models showing that abnormal functioning of the hypothalamic-pituitary-adrenal (HPA) axis and/or the inflammatory response system disrupts feedback regulation of both neuroendocrine and immune systems, contributing to disease. Stress is known to affect the physiology of pelvic organs and to disturb the HPA axis leading to chronic, painful, inflammatory disorders. A link between stress and disease has already been documented for many chronic conditions. Endometriosis is a complex chronic gynecological disease associated with severe pelvic pain and infertility that affects 10% of reproductive-aged women. Patients report the negative impact of endometriosis symptoms on quality of life, work/study productivity, and personal relationships, which in turn cause high levels of psychological and emotional distress. The relationship between stress and endometriosis is not clear. Still, we have recently demonstrated that stress increases the size and severity of the lesions as well as inflammatory parameters in an animal model. Furthermore, the "controllability" of stress influences the pathophysiology in this model, offering the possibility of using stress management techniques in patients. The crosstalk between stress-inflammation-pain through HPA axis activity indicates that stress relief should alleviate inflammation and, in turn, decrease painful responses. This opens up the opportunity of altering brain-body-brain pathways as potential new therapeutic option for endometriosis. The goal of this review is to gather the research evidence regarding the interaction between stress (psychological and physiological) and the development and progression of endometriosis on the exacerbation of its symptoms with the purpose of proposing new lines of emerging research and possible treatment modalities for this still incurable disease.

Antagonizing the corticotropin releasing hormone receptor 1 with antalarmin reduces the progression of endometriosis

Endometriosis is a disorder in which endometrial tissue is found outside the uterus causing pain, infertility and stress. Finding effective, non-hormonal and long-term treatments for endometriosis still remains one of the most significant challenges in the field. Corticotropin releasing hormone (CRH) is one of the main signaling peptides within the hypothalamic pituitary adrenal (HPA) axis released in response to stress. CRH can affect nervous and visceral tissues such as the uterus and gut via activation of two types of CRH receptors: CRHR1 and CRHR2. Our aim was to determine if blocking CRHR1 with antalarmin will reduce endometriosis progression. In experiment 1 we induced endometriosis in female rats by suturing uterine horn tissue next to the intestinal mesentery and allowed to progress for 7 days. We determined that after 7 days, there was a significant increase in CRHR1 within endometriotic vesicles as compared to normal uterus. In Experiment 2, we induced endometriosis and administered either antalarmin (20 mg/kg, i.p.) or vehicle during the first 7 days after surgery. A separate group of sham surgery rats served as non-endometriosis controls. Endometriosis was allowed to progress until 60 days after surgery, at which time rats were tested for anxiety behaviors. At the time of sacrifice, endometriotic vesicles, uterus and blood were collected. Treatment with antalarmin significantly reduced the size (67% decrease) and number (30% decrease) of endometriotic vesicles. Antalarmin also prevented the increase in CRH and CRHR1 mRNA within endometriotic vesicles but not of glucocorticoid receptor. Endometriosis did not change anxiety behaviors in the open field and zero-maze tests and prior antalarmin administration did not modify this. Our data provides the first in-vivo demonstration for use of CRHR1 antagonist for the treatment of endometriosis opening the possibility for further exploring CRH signaling as a treatment target for this debilitating disease.

Chronic endometritis modifies decidualization in human endometrial stromal cells

BACKGROUND

Chronic endometritis (CE) is a continuous inflammation of uterine endometrium, and it is usually symptomless. As CE has been thought not to affect the reproductive status and general health of affected women, its significance has not been explored. However, recent studies have shown that CE is related with repeated implantation failures after in vitro fertilization-embryo transfer, unexplained infertility, and recurrent miscarriages. As decidua differentiates to support the implantation process and maintains the pregnancy, we hypothesized that CE may influence the process of decidualization.

METHODS

Seventeen patients were employed in the experiment involving culture of endometrial stromal cells (ESCs). After obtaining endometrial samples, ESCs were harvested and cultured for 13 days. The concentrations in culture media and the protein expressions in ESCs of prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1), two well known decidualization markers used in a large number of in vitro models, were analyzed by ELISA and Western blotting, respectively, and the cell numbers were also counted. The mRNA levels of PRL and IGFBP-1 were tested by quantitative real time polymerase chain reaction (RT-PCR). Since sex hormone induce proliferation and differentiation to decidua via binding to the sex hormone receptors (ERα, ERβ, PRA, and PRB), their expression was assessed in another 17 patients' paraffin-embedded endometrial tissue specimens by immunohistochemistry and semi-quantified by H-score.

RESULTS

Increased cell numbers and reduced secretion of PRL and IGFBP-1 were detected by ELISA in the ESCs of CE patients after culture for 13 days compared with non-CE patients. The decreased protein expression of IGFBP-1 in ESCs of CE patients was detected by Western blotting. The decreased expression of PRL mRNA and IGFBP-1 mRNA were detected by RT-PCR. Increased expressions of ERα, ERβ, PRA, and PRB were observed in the stromal cells of CE patients in comparison to non-CE patients, whereas increased expressions of ERα and ERβ were detected in the glandular cells of CE.

CONCLUSION

Our data suggests that CE modifies decidualization of human ESC through untuning the function of sex steroid hormone receptor.

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.

Urocortin protects chondrocytes from NO-induced apoptosis: a future therapy for osteoarthritis?

Osteoarthritis (OA) is characterized by a loss of joint mobility and pain resulting from progressive destruction and loss of articular cartilage secondary to chondrocyte death and/ or senescence. Certain stimuli including nitric oxide (NO) and the pro-inflammatory cytokine tumor necrosis factor α (TNF-α have been implicated in this chondrocyte death and the subsequent accelerated damage to cartilage. In this study, we demonstrate that a corticotrophin releasing factor (CRF) family peptide, urocortin (Ucn), is produced by a human chondrocyte cell line, C-20/A4, and acts both as an endogenous survival signal and as a cytoprotective agent reducing the induction of apoptosis by NO but not TNF-α when added exogenously. Furthermore, treatment with the NO donor S-nitroso-N-acetyl-D-L-penicillamine upregulates chondrocyte Ucn expression, whereas treatment with TNF-α does not. The chondroprotective effects of Ucn are abolished by both specific ligand depletion (with an anti-Ucn antibody) and by CRF receptor blockade with the pan-CRFR antagonist α-helical CRH(9-41). CRFR expression was confirmed by reverse transcription-PCR with subsequent amplicon sequence analysis and demonstrates that C-20/A4 cells express both CRFR1 and CRFR2, specifically CRFR1α and CRFR2β. Protein expression of these receptors was confirmed by western blotting. The presence of both Ucn and its receptors in these cells, coupled with the induction of Ucn by NO, suggests the existence of an endogenous autocrine/paracrine chondroprotective mechanism against stimuli inducing chondrocyte apoptosis via the intrinsic/mitochondrial pathway.

Expression of inhibin/activin subunits in the equine uteri during the early pregnancy

The establishment of equine pregnancy is a unique and long process during which a series of physical and possibly biochemical interactions are required between the conceptus and uterus. In this study, we investigated the expression pattern of inhibin/activin subunits in the uterus during early pregnancy. The uteri from four adult mares on cyclic day 13 or pregnancy day 25 were obtained. Immunohistochemical experiments suggested that inhibin/activin subunits were immunolocalized in the luminal and glandular epithelium on pregnancy day 25. In addition, the inhibin α and inhibin/activin βB subunits were not detected, and inhibin/activin βA subunit was detected, in the luminal and glandular epithelium on cyclic day 13. Real-time polymerase chain reaction and Western blotting results for the inhibin/activin subunits suggested a significant increase in the expression of inhibin/activin subunit βB and a significant decrease in the expression of inhibin/activin subunit βA on pregnancy day 25 compared with those on cyclic day 13. Enzyme-linked immunosorbent assays suggested a significant decrease in the concentration of activin A in endometrium extracts from cyclic day 13 to pregnancy day 25. These results suggest that inhibins or activins synthesized in the uterus, as endocrine factors and necessary nutriments, have different expression patterns and may play different, important roles during early embryonic development of the equine.

Inflammation: a link between endometriosis and preterm birth

Endometriosis is a chronic inflammatory disease affecting women's health. Pain and infertility are the major symptoms caused by a hormonal/immunological dysfunction, which causes an endometrial impairment. The same pathogenetic mechanisms are also associated with preterm birth: hormones, cytokines, neurohormones, and growth factors interact in modulating extracellular matrix and prostaglandin secretion, thus activating the inflammatory process in placental membranes and myometrium. An overlap of molecules and mechanisms may explain the evidence that preterm birth is a common outcome in pregnant patients with endometriosis.

Serum activin A levels are lower in tubal than intrauterine spontaneously conceived pregnancies

OBJECTIVE

To measure serum activin A levels together with progesterone and hCG, in women with overt clinical signs and symptoms of ectopic pregnancy (EP) and, in gestational age-matched intrauterine pregnancy (IUP).

DESIGN

Retrospective case-control study.

SETTING

Department of Pediatrics, Obstetrics and Reproductive Medicine, Section of Obstetrics and Gynecology, University of Siena, Siena, Italy.

POPULATION

The study group was composed by 30 women with an EP; the control group was composed by 30 women with a sonographic evidence of a single spontaneous IUP.

METHODS

Clinical examination; transvaginal ultrasound scan; hCG, progesterone and activin-A measurements; laparoscopy; uterine curettage; histological examination.

MAIN OUTCOME MEASURE

Pregnancy outcome; sensitivity and specificity of hCG, progesterone, and activin A for EP.

RESULTS

Serum hCG levels did not differ significantly between tubal EP and IUP, while P concentrations were significantly (P < 0.001) lower in tubal EP than IUP. Serum levels of activin A were significantly (P < 0.0001) lower in tubal EP than in IUP and, at the cutoff 0.43 ng/mL achieved a sensitivity of 96.7% and a specificity of 100% for EP.

CONCLUSION

Activin A secretion in EP is reduced and measurement of its serum levels may have the potential clinical advantage to signal the presence of EP.

Activins and related proteins in the establishment of pregnancy

Activin A and related proteins (inhibins, follistatin [FS], follistatin-related gene [FLRG], endometrial bleeding associated factors [ebaf]) are involved in the complex mechanisms allowing the establishment and the maintenance of pregnancy. As a consequence of ovarian progesterone stimuli, activin A is expressed and secreted by the stromal endometrial cells, which locally induces the decidualization process, a prerequisite for implantation. Moreover, activin A does influence the implantation phase, also enhancing cytotrophoblast differentiation, indirectly, by increasing the expression of other molecules involved in embryo implantation, such as matrix metalloproteinases (MMPs) and leukemia inhibitory factor (LIF). The local derangement of activin A pathway in some pregnancy disorders (incomplete and complete miscarriages, recurrent abortion, and ectopic pregnancy [EP]) further sustains the hypothesis that activin A and its related proteins play a relevant role in the establishment of pregnancy.

Expression and subcellular localization of CRH and its receptors in human endometrial cancer

CRH and its receptors are expressed in human normal endometrial cells, where they are associated to anti-proliferative progesterone-like activity. We aimed to investigate CRH, CRH-R1 and CRH-R2 expression and intracellular localization in human endometrial cancers and their relationships with tumor biological parameters. Surgical specimens were obtained from 51 untreated endometrial cancer patients and immunohistochemistry for CRH, CRH receptors, ER, PR and Ki-67 was performed. We found a diffuse cytoplasmic staining in 100%, 92 % and 60.7 % of tumor specimens for CRH, CRH-R1 and CRH-R2, respectively. At variance with tumor tissues, the surrounding normal endometrial glands exhibit a typical paranuclear/apical pattern for CRH and stained for CRH-R2 at the nuclear level, whereas CRH-R1 staining was similar to that observed in tumor area. Positive correlations were found between CRH-R1 and PR expression, as well as between CRH-R2 cytoplasmic pattern and more advanced FIGO stage disease, respectively.

Immune function in pregnancy: the role of corticotropin-releasing hormone

Pregnancy represents a major challenge to the maternal immune system since it has to tolerate the semi-allograft fetus. Indeed, the success of pregnancy requires an appropriate immunological interaction between the mother and the fetus. Furthermore, evidence suggests that some pregnancy complications, such as spontaneous abortions, preeclampsia and intrauterine growth restriction, are associated with abnormal maternal-fetal immune responses. Corticotropin-releasing hormone (CRH), a 41-amino acid peptide originally found in the hypothalamus, appears to have a fundamental role in the mechanisms responsible for the implantation and maintenance of human pregnancy. Reproductive CRH is a form of tissue CRH (CRH found in peripheral tissues), analogous to the immune CRH detected in peripheral inflammatory sites. Reproductive CRH has been identified in the endometrial glands, the decidualized endometrial stroma and the placental trophoblast, synctiotrophoblast and decidua. Reproductive CRH participates in various reproductive functions with an inflammatory component, where it serves as an autocrine/paracrine modulator. The immunological mechanisms contributing to the establishment and maintenance of pregnancy are not fully understood. The present article focuses on the potential roles of CRH on the physiology and pathophysiology of pregnancy and highlights its participation in implantation, early fetal immunotolerance and parturition.

Interleukin 1beta and progesterone stimulate activin a expression and secretion from cultured human endometrial stromal cells

Steroid hormones, cytokines, and growth factors have a major role in evoking local endometrial changes needed for trophoblast implantation. In the present study, the effect of interleukin-1beta (IL-1beta), 17-beta estradiol (E2), and progesterone (Pr) on activin A and follistatin (FS) secretion from cultured human endometrial stromal cells (HESCs) is evaluated. HESCs were obtained from healthy human endometrial samples (n = 8) collected from healthy women. The cells were cultured and stimulated with E2 (10(-7) M, 10(-6)M), Pr (10(-7)M, 10(-6)M), IL-1beta (500 pg/mL), IL-1beta (500 pg/mL) + E2 (10(-6)M), and IL-1beta (500 pg/mL) + Pr (10(-6)M). Activin A and FS secretion and mRNA expression were assayed by enzyme-linked immunosorbent assay and semiquantitative reverse transcriptase-polymerase chain reaction, respectively. Pr (10(-7) M, 10(-6) M) significantly increased activin A secretion and mRNA expression from HESCs, but E2 did not show remarkable effects. The addition of IL-1beta (P< .001), IL- 1beta + E2 (P < .01), and IL-1beta + Pr (P< .001). significantly stimulated activin A secretion and mRNA expression, compared to untreated cells. Activin A expression and secretion after the coincubation of IL-1beta+ Pr were significantly higher than after IL-1betaand IL-1beta+ E2 stimuli ( P< .01 and P< .001, respectively). Neither Pr nor E2 and IL-1beta had a significant effect on FS secretion and expression. IL-1betaand Pr stimulated activin A but not FS secretion from cultured HESCs, and the effect of IL-1betawas augmented by Pr. These findings, together with the evidence that activin A is involved in trophoblast implantation, suggest the existence of a complex cross-talk by which the ovary, through Pr secretion, and the embryo, through IL-1beta production, may trigger the endometrial induction of activin A and consequently timing implantation.

Deranged expression of follistatin and follistatin-like protein in women with ovarian endometriosis

OBJECTIVE

To evaluate the messenger RNA (mRNA) expression and peptide localization of follistatin and follistatin-like protein (FLRG) in ovarian endometriosis, compared to healthy human endometrium.

DESIGN

Samples of ovarian endometriotic and healthy endometrial tissues were processed by semiquantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry.

SETTING

Academic health centers in Siena, Italy, and Belo Horizonte, Brazil.

PATIENT(S)

Women with endometrioma who underwent laparoscopic excision of ovarian endometriotic cysts (n = 16), and healthy, nonpregnant women (n = 18, control group).

MAIN OUTCOME MEASURE(S)

Immunostaining and relative quantification of follistatin and FLRG mRNA in ovarian endometriosis and eutopic endometrium.

RESULT(S)

Both ovarian endometriosis and healthy endometrium expressed and localized follistatin and FLRG. In endometriotic glands, follistatin immunostaining was homogeneously distributed throughout the cytoplasm of the epithelial cells, contrasting with normal eutopic endometrium, where follistatin expression was focal, irregular, and confined to the basal side of the glands. Follistatin-like protein was immunolocalized in the nuclei of both glandular epithelial cells and stromal cells, with less intense staining in endometriotic samples. The relative intensity of follistatin and FLRG immunostaining was significantly higher and lower, respectively, in endometriosis than in controls. The expression of follistatin mRNA was higher, while that of FLRG mRNA was lower, in ovarian endometriosis than in healthy eutopic endometrium.

CONCLUSION(S)

Ovarian endometriotic lesions show a deranged expression of FLRG and follistatin, which are activin A-binding proteins. This may result in an altered effect of activin A on angiogenesis and/or endometrial differentiation.

Single serum activin a testing to predict ectopic pregnancy

CONTEXT

Ectopic pregnancy (EP) is an important cause of maternal deaths in early pregnancy because most fatal cases result from delayed diagnosis and inappropriate investigation.

OBJECTIVE

We evaluated whether the measurement of activin A may be useful in the diagnosis of EP in women with unknown pregnancy location.

DESIGN

The study was designed as an open observational study.

SETTING

The study was set in a tertiary referral center for obstetric care.

PATIENTS

Patients were women with unknown pregnancy location (n = 536) who had complaints of bleeding, pain, or cramping.

INTERVENTIONS

Interventions included clinical examination; transvaginal ultrasound scan; human chorionic gonadotropin (hCG), progesterone, and activin A measurements; laparoscopy; uterine curettage; and histological examination.

MAIN OUTCOME MEASURES

Main outcome measures were pregnancy outcomes and evaluation of sensitivity, specificity, and predictive values of hCG, progesterone, and activin A as diagnostic tests for the detection of EP.

RESULTS

Pregnancy outcomes included 155 (28.9%) viable intrauterine pregnancies (IUP), 305 (56.9%) first-trimester spontaneous abortion (SAB), and 76 (14.2%) EP. SAB had the lowest (P < 0.0001) hCG and progesterone concentrations, significantly lower than EP (P < 0.001) and IUP (P < 0.001). In EP, levels were significantly (P < 0.001) lower than in IUP. On the contrary, activin A levels were lowest (P < 0.0001) in EP, significantly lower than in SAB (P < 0.001) and IUP (P < 0.001). IUP had significantly (P < 0.001) lower activin A levels than SAB. When evaluated by the receiver operating curve analysis, activin A at the cutoff of 0.37 ng/ml combined a sensitivity and a specificity of 100 and 99.6%, respectively, for prediction of EP. When activin A concentrations were below the cutoff, the positive predictive value for EP was 97.43%, and 0% for concentrations higher than 0.37 ng/ml.

CONCLUSIONS

Activin A measurement may identify patients at risk of EP with a high sensibility and specificity.

Evidence that corticotropin-releasing hormone inhibits cell growth of human breast cancer cells via the activation of CRH-R1 receptor subtype

It has been previously shown that corticotropin-releasing hormone (CRH) exerts antiproliferative activity on an estrogen-dependent tumor cell line, i.e. human endometrial adenocarcinoma Ishikawa (IK) cells. Here we have investigated the effects of CRH on another estrogen-dependent tumor cell line, human breast cancer MCF7 cells. In this paradigm, CRH given at a fixed concentration of 100 nM significantly inhibited cell growth induced by 100 nM estradiol (E2) after 48 and 72 h of incubation. This effect was not associated with the induction of apoptosis. CRH inhibition of cell proliferation was counteracted in a concentration-dependent manner by the non-selective CRH receptor antagonist, astressin, as well as by a CRH-R1 selective receptor antagonist, antalarmin. RNase protection assays carried out on MCF7 under basal conditions showed that these cells express in a constitutive manner the CRH-R1 receptor subtype. We have also investigated the putative source of CRH acting on breast cancer cells; we found that MCF7 cells express CRH mRNA under basal conditions and secrete sizable amounts of immunoreactive CRH, which leads to postulate the existence of paracrine-autocrine inhibitory mechanism operated by CRH in breast cancer cells.

Effect of activin A on tumor necrosis factor-α/intercellular adhesion molecule-1 pathway in endometrial stromal cells

OBJECTIVE[S]: Activin A and inhibin A are growth factors expressed by human endometrium involved in the control of endometrial functions. In the present study we investigated the effects of activin A and inhibin A in modulating the tumor necrosis factor (TNF)-alpha/intercellular adhesion molecule (ICAM)-1 system in cultured human endometrial stromal cells.

STUDY DESIGN

Endometrial samples were obtained from 34 reproductive age women undergoing laparoscopy for benign ovarian cysts or infertility. Endometrial stromal cells were cultured and soluble ICAM-1 and TNF-alpha were measured in cell-free supernatants following treatment with or without activin A or inhibin A. Cell surface ICAM-1 was assayed by flow cytometry by staining endometrial cells with specific monoclonal antibodies.

RESULTS

Activin A and inhibin A did not influence either the expression of cell surface ICAM-1 or soluble ICAM-1 shedding by cultured endometrial cells. On the other hand, TNF-alpha secretion significantly increased in presence of activin A but not of inhibin A.

CONCLUSIONS

Since TNF-alpha modulates several endometrial processes such as menstruation, proliferation, apoptosis, implantation and decidualization, an effect of activin A in the physiological control of endometrium is further supported by the present data.

Inhibin alpha-subunit and the inhibin coreceptor betaglycan are downregulated in endometrial carcinoma

OBJECTIVE

In the present study we evaluated the protein distribution and mRNA levels of inhibin alpha-subunit and its coreceptor betaglycan in endometrial adenocarcinoma.

DESIGN

Two groups of postmenopausal women were studied: the first group had recently diagnosed endometrial adenocarcinoma (n = 16; age range 61-79 years), and the second group (n = 12; age range 64-78 years) had undergone hysterectomy for uterine prolapse and served as control.

METHODS

Inhibin alpha-subunit and betaglycan gene expression and tissue distribution were evaluated by semiquantitative RT-PCR and immunohistochemistry respectively.

RESULTS

Inhibin alpha-subunit and betaglycan mRNAs were expressed by both healthy and tumoral endometria, but their expression was significantly lower in endometrial carcinoma (P < 0.001, based on Student's t test). Inhibin alpha-subunit expression was much weaker in the glands of tumours than in non-neoplastic specimens. Betaglycan protein was identified in the epithelial cells lining non-tumoral endometrium, and in endothelial cells of both normal and tumoral endometria. Well-differentiated neoplastic cells had a faint and scarce betaglycan staining, and poorly differentiated cells did not express betaglycan at all.

CONCLUSIONS

The lower inhibin alpha and betaglycan expression in endometrial adenocarcinoma suggests that the inhibin action may be disrupted. However, the expression of betaglycan in the endothelia of the tumour vasculature suggests that a selective vascular response to inhibin may be possible in these tumours.

Urocortins in human reproduction

Data on biological effects and localization of corticotropin-releasing factor (CRF), a neuropeptide structurally and biologically related to urocortins, have triggered the study on expression of urocortins and their function in human reproductive tissues. Ovary, endometrium, placenta and fetal membranes (amnion and chorion), myometrium, and prostate are sources of urocortin 1 and, they also express urocortin binding sites (receptors and CRF-binding protein), thus suggesting that these tissues are also targets of urocortin 1. The current concept thus is that urocortin 1 may affect the physiology of human reproduction through paracrine/autocrine actions. In particular, in vitro data have shown that urocortin 1 plays a major role in human placenta: it stimulates the secretion of ACTH, prostaglandins and activin A from cultured human placental cells, and regulates placental vessel resistance to blood flow. Furthermore, when incubated in myometrial strips, urocortins stimulate uterine contractility, by activating specific intracellular pathways. Taken together, these findings do suggest an important role of urocortins in the physiology of pregnancy and parturition.