Extracellularly signal-regulated kinase activity in the human endometrium: possible roles in the pathogenesis of endometriosis

The effect of antioxidant supplementation on dysmenorrhea and endometriosis-associated painful symptoms: a systematic review and meta-analysis of randomized clinical trials

This study aimed to review randomized controlled trials (RCTs) investigating the effects of dietary antioxidant supplements on the severity of endometriosis-related pain symptoms. The PubMed/Medline, Scopus, and Web of Science databases were searched until April 2022. Additionally, we manually searched the reference lists. Endpoints were summarized as standardized mean difference (SMD) with 95% confidence intervals (CIs) in a random-effects model. The I2 statistic was used to assess heterogeneity. Ten RCTs were included in this meta-analysis. Overall, 10 studies were related to dysmenorrhea, four to dyspareunia, and four to pelvic pain. Antioxidants significantly reduced dysmenorrhea (SMD, -0.48; 95% CI, -0.82 to -0.13; I2=75.14%). In a subgroup analysis, a significant reduction of dysmenorrhea was observed only in a subset of trials that administered vitamin D (SMD, -0.59; 95% CI, -1.13 to -0.06; I2=69.59%) and melatonin (SMD, -1.40; 95% CI, -2.47 to -0.32; I2=79.15%). Meta-analysis results also suggested that antioxidant supplementation significantly improved pelvic pain (SMD, -1.51; 95% CI, -2.74 to -0.29; I2=93.96%), although they seem not to have a significant beneficial impact on the severity of dyspareunia. Dietary antioxidant supplementation seems to beneficially impact the severity of endometriosis-related dysmenorrhea (with an emphasis on vitamin D and melatonin) and pelvic pain. However, due to the relatively small sample size and high heterogeneity, the findings should be interpreted cautiously, and the importance of further well-designed clinical studies cannot be overstated.

Research advances in endometriosis-related signaling pathways: A review

Endometriosis (EM) is characterized by the existence of endometrial mucosa outside the uterine cavity, which causesinfertility, persistent aches, and a decline in women's quality of life. Both hormone therapies and nonhormone therapies, such as NSAIDs, are ineffective, generic categories of EM drugs. Endometriosis is a benign gynecological condition, yet it shares a number of features with cancer cells, including immune evasion, survival, adhesion, invasion, and angiogenesis. Several endometriosis-related signaling pathways are comprehensively reviewed in this article, including E2, NF-κB, MAPK, ERK, PI3K/Akt/mTOR, YAP, Wnt/β-catenin, Rho/ROCK, TGF-β, VEGF, NO, iron, cytokines and chemokines. To find and develop novel medications for the treatment of EM, it is essential to implicitly determine the molecular pathways that are disordered during EM development. Additionally, research on the shared pathways between EM and tumors can provide hypotheses or suggestions for endometriosis therapeutic targets.

Gene expression analysis in endometriosis: Immunopathology insights, transcription factors and therapeutic targets

Background

Endometriosis is recognized as an estrogen-dependent inflammation disorder, estimated to affect 8%-15% of women of childbearing age. Currently, the etiology and pathogenesis of endometriosis are not completely clear. Underlying mechanism for endometriosis is still under debate and needs further exploration. The involvement of transcription factors and immune mediations may be involved in the pathophysiological process of endometriosis, but the specific mechanism remains to be explored. This study aims to investigate the underlying molecular mechanisms in endometriosis.

Methods

The gene expression profile of endometriosis was obtained from the gene expression omnibus (GEO) database. Gene set variation analysis (GSVA) and gene set enrichment analysis (GSEA) were applied to the endometriosis GSE7305 datasets. Cibersort and MCP-counter were used to explore the immune response gene sets, immune response pathway, and immune environment. Differentially expressed genes (DEGs) were identified and screened. Common biological pathways were being investigated using the kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis. Transcription factors were from The Human Transcription Factors. The least absolute shrinkage and selection operator (Lasso) model identified four differential expressions of transcription factors (AEBP1, HOXB6, KLF2, and RORB). Their diagnostic value was calculated by receiver operating characteristic (ROC) curve analysis and validated in the validation cohort (GSE11691, GSE23339). By constructing the interaction network of crucial transcription factors, weighted gene coexpression network analysis (WGCNA) was used to search for key module genes. Metascape was used for enrichment analysis of essential module genes and obtained HOXB6, KLF2. The HOXB6 and KLF2 were further verified as the only two intersection genes according to Support Vector Machine Recursive Feature Elimination (SVM-RFE) and random forest models. We constructed ceRNA (lncRNA-miRNA-mRNA) networks with four potential transcription factors. Finally, we performed molecular docking for goserelin and dienogest with four transcription factors (AEBP1, HOXB6, KLF2, and RORB) to screen potential drug targets.

Results

Immune and metabolic pathways were enriched in GSVA and GSEA. In single sample gene set enrichment analysis (ssGSEA), most immune infiltrating cells, immune response gene sets, and immune response pathways are differentially expressed between endometriosis and non-endometriosis. Twenty-seven transcription factors were screened from differentially expressed genes. Most of the twenty-seven transcription factors were correlated with immune infiltrating cells, immune response gene sets and immune response pathways. Furthermore, Adipocyte enhancer binding protein 1 (AEBP1), Homeobox B6 (HOXB6), Kruppel Like Factor 2 (KLF2) and RAR Related Orphan Receptor B (RORB) were selected out from twenty-seven transcription factors. ROC analysis showed that the four genes had a high diagnostic value for endometriosis. In addition, KLF2 and HOXB6 were found to play particularly important roles in multiple modules (String, WGCNA, SVM-RFE, random forest) on the gene interaction network. Using the ceRNA network, we found that NEAT1 may regulate the expressions of AEBP1, HOXB6 and RORB, while X Inactive Specific Transcript (XIST) may control the expressions of HOXB6, RORB and KLF2. Finally, we found that goserelin and dienogest may be potential drugs to regulate AEBP1, HOXB6, KLF2 and RORB through molecular docking.

Conclusions

AEBP1, HOXB6, KLF2, and RORB may be potential biomarkers for endometriosis. Two of them, KLF2 and HOXB6, are critical molecules in the gene interaction network of endometriosis. Discovered by molecular docking, AEBP1, HOXB6, KLF2, and RORB are targets for goserelin and dienogest.

Elevated phosphorylation of estrogen receptor α at serine-118 in ovarian endometrioma

OBJECTIVE

To evaluate the phosphorylation of estrogen receptor α at serine-118 (phospho-ERα S118) in the endometrium, ovarian endometrioma, and deep infiltrating endometriosis (DIE).

DESIGN

Experimental study.

SETTING

University-affiliated hospital and academic research laboratory.

PATIENT(S)

Twenty-five patients underwent a hysterectomy, 18 patients underwent surgical removal of ovarian endometrioma, and 6 patients underwent DIE.

INTERVENTION(S)

Tissue samples were obtained from patients who underwent surgical procedures.

MAIN OUTCOME MEASURE(S)

Immunostaining for phospho-ERα S118, ERα, or phosphorylated p44/42 mitogen-activated protein kinase (phospho-p44/42 MAPK) was performed to evaluate the endometrium with or without endometriosis, ovarian endometrioma, and DIE. For in vitro analysis, endometrial epithelial cells (Ishikawa cells) were stimulated with estradiol (E2) or tumor necrosis factor alpha (TNFα), and the expression levels of phospho-ERα S118 and phospho-p44/42 MAPK were evaluated via Western blotting.

RESULT(S)

First, phospho-ERα S118 level was significantly higher in the glands and stroma of ovarian endometriosis samples than in those of endometrial and DIE samples. Second, colocalization of phospho-p44/42 MAPK and phospho-ERα S118 was observed in the glands of ovarian endometrioma. The proportions of cells strongly expressing phospho-p44/42 and phospho-ERα were 87% in phosphor-p44/42 MAPK-positive cells and 79% in phosphor-ERα-positive cells. Third, E2 stimulation significantly enhanced phospho-ERα S118 after 15 and 30 minutes in in vitro analysis using endometrial epithelial cells. Fourth, TNFα stimulation modestly but significantly enhanced phospho-ERα S118 after 15 and 30 minutes. Fifth, in Ishikawa cells, treatment with a p44/42 inhibitor (PD98059) significantly reduced phospho-ERα S118 by TNFα but not by E2.

CONCLUSION(S)

ERα-S118 phosphorylation was increased in ovarian endometriosis. Our findings may provide a new perspective for understanding the mechanism of increased ERα action in the pathophysiology of endometriosis.

Menstruation Dysregulation and Endometriosis Development

Endometriosis is a common gynecological condition characterized by the growth of endometrial-like tissue outside of the uterus which may cause symptoms such as chronic pelvic pain or subfertility. Several surgical and medical therapies are available to manage symptoms, but a cure has yet to be determined which can be attributed to the incomplete understanding of disease pathogenesis. Sampson's theory of retrograde menstruation is a widely accepted theory describing how shed endometrial tissue can enter the peritoneal cavity, but other factors are likely at play to facilitate the establishment of endometriosis lesions. This review summarizes literature that has explored how dysregulation of menstruation can contribute to the pathogenesis of endometriosis such as dysregulation of inflammatory mediators, aberrant endometrial matrix metalloproteinase expression, hypoxic stress, and reduced apoptosis. Overall, many of these factors have overlapping pathways which can prolong the survival of shed endometrial debris, increase tissue migration, and facilitate implantation of endometrial tissue at ectopic sites. Moreover, some of these changes are also implicated in abnormal uterine bleeding and endometrial diseases. More research is needed to better understand the underlying mechanisms driving dysregulation of menstruation in endometriosis specifically and identifying specific pathways could introduce new treatment targets. Analyzing menstrual fluid from women with endometriosis for inflammatory markers and other biomarkers may also be beneficial for earlier diagnosis and disease staging.

Pharmaceuticals targeting signaling pathways of endometriosis as potential new medical treatment: A review

Endometriosis (EM) is defined as endometrial tissues found outside the uterus. Growth and development of endometriotic cells in ectopic sites can be promoted via multiple pathways, including MAPK/MEK/ERK, PI3K/Akt/mTOR, NF-κB, Rho/ROCK, reactive oxidative stress, tumor necrosis factor, transforming growth factor-β, Wnt/β-catenin, vascular endothelial growth factor, estrogen, and cytokines. The underlying pathophysiological mechanisms include proliferation, apoptosis, autophagy, migration, invasion, fibrosis, angiogenesis, oxidative stress, inflammation, and immune escape. Current medical treatments for EM are mainly hormonal and symptomatic, and thus the development of new, effective, and safe pharmaceuticals targeting specific molecular and signaling pathways is needed. Here, we systematically reviewed the literature focused on pharmaceuticals that specifically target the molecular and signaling pathways involved in the pathophysiology of EM. Potential drug targets, their upstream and downstream molecules with key aberrant signaling, and the regulatory mechanisms promoting the growth and development of endometriotic cells and tissues were discussed. Hormonal pharmaceuticals, including melatonin, exerts proapoptotic via regulating matrix metallopeptidase activity while nonhormonal pharmaceutical sorafenib exerts antiproliferative effect via MAPK/ERK pathway and antiangiogenesis activity via VEGF/VEGFR pathway. N-acetyl cysteine, curcumin, and ginsenoside exert antioxidant and anti-inflammatory effects via radical scavenging activity. Natural products have high efficacy with minimal side effects; for example, resveratrol and epigallocatechin gallate have multiple targets and provide synergistic efficacy to resolve the complexity of the pathophysiology of EM, showing promising efficacy in treating EM. Although new medical treatments are currently being developed, more detailed pharmacological studies and large sample size clinical trials are needed to confirm the efficacy and safety of these treatments in the near future.

Can Endometriosis-Related Oxidative Stress Pave the Way for New Treatment Targets?

Endometriosis is a disease of reproductive age characterized by chronic pelvic pain and infertility. Its pathogenesis is complex and still partially unexplained. However, there is increasing evidence of the role of chronic inflammation, immune system dysregulation, and oxidative stress in its development and progression. The latter appears to be involved in multiple aspects of the disease. Indeed, disease progression sustained by a hyperproliferative phenotype can be related to reactive oxygen species (ROS) imbalance, as numerous experiments using drugs to counteract hyperproliferation have shown in recent years. Chronic pelvic pain is also associated with cell function dysregulation favoring chronic inflammation and oxidative stress, specifically involving macrophages and mast cell activation. Moreover, there is increasing evidence of a role for ROS and impaired mitochondrial function not only as deleterious effectors of the ovarian reserve in patients with endometriomas but also in terms of oocyte quality and, hence, embryo development impairment. Targeting oxidative stress looks to be a promising strategy to both curb endometriotic lesion progression and alleviate endometriosis-associated symptoms of chronic pain and infertility. More investigations are nevertheless needed to develop effective therapeutic strategies for clinical application.

Characterization and Proteomic Analysis of Endometrial Stromal Cell-Derived Small Extracellular Vesicles

CONTEXT

Small extracellular vesicles (sEVs) have emerged as modulators of the disease microenvironment, thereby supporting disease progression. However, the potential role of EVs and their content to the pathophysiology of endometriosis remain unclear.

OBJECTIVE

This work aimed to investigate whether the EVs from eutopic (Eu) and ectopic (Ec) endometrial stromal cells (ESCs) differ with respect to protein composition and role in endometriosis.

METHODS

Human Eu and Ec endometrium-derived ESCs were isolated from samples of the same patients (n = 3). sEVs were isolated from ESCs via ultracentrifugation; these sEVs were characterized by Western blotting, transmission electron microscopy, and nanoparticle tracking analysis and analyzed using mass spectrometry. The potential role of EcESCs-derived sEVs (EcESCs-sEVs) in endometriosis was explored by assaying their effects on cell viability/proliferation, migration, and angiogenesis.

RESULTS

In total, 105 ESCs-sEV-associated proteins were identified from EcESCs-sEVs and EuESCs-sEVs by mass spectrometry analysis. The protein content differed between EcESCs-sEVs and EuESCs-sEVs, with annexin A2 (ANXA2) being the most prominent difference-present in EcESCs-sEVs but not EuESCs-sEVs. We also found that sEVs-ANXA2 regulates the motility, proliferation, and angiogenesis of ESCs via the extracellularly regulated kinase (ERK)/STAT3 pathway. Notably, treatment of ESCs with sEVs-ANXA2 resulted in increased proliferation and motility, suggesting that sEVs-ANXA2 may be involved in regulating endometriosis. Our data suggest that EcESCs-sEVs-ANXA2 regulates the motility and the angiogenic potential of ESCs, implying a role for sEVs-ANXA2 in the pathogenesis of endometriosis.

CONCLUSION

The study of sEVs-ANXA2 from Ec endometriotic cells uncovers a new mechanism of endometriosis progression and will inform the development of novel therapeutic strategies.

Exposure to Phthalate Esters and the Risk of Endometriosis

Endometriosis is a common gynecologic disease, worldwide, whose true prevalence is uncertain because it is a difficult disease to diagnose. Endometriosis is a common cause of chronic pelvic pain, dysmenorrhea, and infertility, and is also associated with ovarian cancer. Although the risk factors for endometriosis are unclear, there is increasing evidence that exposure to environmental contaminants, especially phthalates, could affect the pathogenesis of endometriosis. Phthalates are industrial chemicals, used to make flexible plastics, and are present in numerous common plastic products, including medical devices and materials. Several in vitro studies have suggested a positive association between exposure to phthalate, or phthalate metabolites, and the risk of endometriosis. Since the 2000s, studies based on human plasma and urinary concentrations of various phthalate metabolites have been published, but there are still limitations to our understanding of the pathophysiology of phthalates and endometriosis. This report aims to review the current state of knowledge about a possible role of phthalates in the pathogenesis of endometriosis based on cell culture, animal models, and human data.

Interleukin-1β inhibits estrogen receptor-α, progesterone receptors A and B and biomarkers of human endometrial stromal cell differentiation: implications for endometriosis

Human blastocyst nidation in the uterus and successful pregnancy require coordinated endometrial expression of estrogen receptor (ER)-α, progesterone receptors (PR)-A and -B and the gap junction protein, connexin (Cx)43. Our prior work established that inflammation associated with conditions of reduced fecundity, particularly endometriosis, can perturb eutopic decidual function. In the current studies, we have modeled endometrial decidualization in primary human endometrial stromal cell cultures derived from normal controls (NESC) and from the eutopic endometria of women with endometriosis (EESC) to test the hypothesis that a proinflammatory cytokine, interleukin (IL)-1β, can disrupt stromal cell differentiation. The cells were grown under a standard protocol with hormones (10 nM 17β-estradiol, 100 nM progesterone and 0.5 mM dibutyryl cAMP) for up to 7 days in the absence or presence of IL-1β. Time-course experiments showed that IL-1β compromised decidual function in both NESC and EESC, which was accompanied by rapid phosphorylation of ER-α, PR and Cx43 and their cellular depletion. Inhibition of the extracellular signal-regulated kinase (ERK)1/2 pathway by a selective pharmacological blocker (PD98059) or siRNA interference, or the addition of hormones themselves, blocked the phosphorylation of ERK mediators; increased the production of steroid receptors, Cx43, prolactin, insulin-like growth factor binding protein-1 (IGFBP)-1 and vascular endothelial growth factor (VEGF) and accelerated the differentiation. The results indicate that inhibition of IL-1β can enhance decidualization in NESC and EESC in vitro. Strategies to interfere with this pathway might be implemented as an in vivo approach to enhance fertility in women with endometriosis and, potentially, other inflammatory pathologies.

Potential roles of aquaporin 9 in the pathogenesis of endometriosis

Aquaporins (AQPs) are involved in cell migration, proliferation and carcinogenesis in tumor development and physiologic inflammatory processes, but their associations with endometriosis have not been fully evaluated. In this study, tissue samples were obtained from women undergoing laparoscopic surgery for endometriosis and other benign conditions. Analysis of expressions of AQP subtypes in eutopic and ectopic endometrium of patients with endometriosis (Eu-EMS and Ect-EMS, respectively) and eutopic endometrium of control patients without endometriosis (Eu-CTL) were performed using the NanoString nCounter System and western blotting. Human endometrial stromal cells (HESCs) were cultured and transfected with the siRNA of the AQP of interest. Among the AQP1–9 subtypes, endometrial expression of AQP2 and AQP8 was significantly increased, whereas AQP9 expression was significantly decreased in the Eu-EMS group compared to the Eu-CTL group. Comparison of expression of AQP2, AQP8 and AQP9 among Eu-EMS, Ect-EMS and Eu-CTL groups revealed significant differences for only AQP9. Expression of AQP9 in the Eu-EMS group was decreased compared with that in Eu-CTL. After transfection of AQP9 siRNA in HESCs, expressions of MMP2 and MMP9 were significantly elevated. Increased expression of phosphorylated ERK 1/2 and phosphorylated p38 MAPK proteins after transfection was also confirmed using western blot analysis. Increased migration and invasion potentials of HESCs after transfection were determined by migration and wound healing assays. These findings suggest that AQP9 may be involved in the pathogenesis of endometriosis and warrant further investigation as a potential therapeutic target for treating endometriosis.

Dual inhibition of ERK1/2 and AKT pathways is required to suppress the growth and survival of endometriotic cells and lesions

Endometriosis is an estrogen-dependent and progesterone-resistant gynecological inflammatory disease of reproductive-age women. Current hormonal therapies targeting estrogen can be prescribed only for a short time. It indicates a need for non-hormonal therapy. ERK1/2 and AKT pathways control several intracellular signaling molecules that control growth and survival of cells. Objectives of the present study are to determine the dual inhibitory effects of ERK1/2 and AKT pathways: (i) on proliferation, survival, and apoptosis of human endometrioitc epithelial cells and stromal cells in vitro; (ii) on growth and survival of endometrioitc lesions in vivo in xenograft mouse model of endometriosis of human origin; and (iii) establish the associated ERK1/2 and AKT downstream intracellular signaling modules in the pathogenesis of endometriosis. Our results indicated that combined inhibition of ERK1/2 and AKT pathways highly decreased the growth and survival of human endometriotic epithelial cells and stromal cells in vitro and suppressed the growth of endometriotic lesions in vivo compared to inhibition of either ERK1/2 or AKT pathway individually. This cause-effect is associated with dysregulated intracellular signaling modules associated with cell cycle, cell survival, and cell apoptosis pathways. Collectively, our results indicate that dual inhibition of ERK1/2 and AKT pathways could emerge as potential non-hormonal therapy for the treatment of endometriosis.

Silymarin amplifies apoptosis in ectopic endometrial tissue in rats with endometriosis; implication on growth factor GDNF, ERK1/2 and Bcl-6b expression

The present prospective study was done to evaluate the effect of silymarin (SMN) on endometriotic-like legions establishment and growth in experimentally-induced endometriosis. For this purpose, the experimental endometriosis was induced in 12 rats and then the animals subdivided into endometriosis-sole and SMN (50 mg kg^-1, orally)+endometriosis groups. Following 28 days, the legions establishment, size, Glial cell line-derived neurotrophic factor (GDNF), gfrα1, B Cell Lymphoma 6 (Bcl-6b), Bcl-2, extracellular regulator kinase (ERK1/2) expression ratios, angiogenesis, the apoptosis and fibrosis indices were investigated. The SMN significantly (P < 0.05) decreased the enometriotic-like legions establishment and size, decreased mRNA levels of GDNF, gfrα1, Bcl-6b and Bcl-2 and remarkably diminished GDNF, gfrα1, Bcl-6b and Bcl-2-positive cells distribution/mm² of tissue versus endometriosis-sole group. The SMN + endometriosis group exhibited a significant (P < 0.05) enhancement in ERK1/2 expression and represented diminished vascularized area and increased apoptosis and fibrosis indices, as well. In conclusion, the SMN by down-regulating GDNF and its receptor gfrα1 expression inhibits GDNF-gfrα1 complex generation and consequently suppresses Bcl-6b expression. Moreover, the SMN by enhancing the ERK1/2 expression and by suppressing the Bcl-2 expression promotes the apoptosis pathway. Finally, the SMN by down-regulating the angiogenesis ratio accelerates apoptosis and consequently induces severe fibrosis in endometriotic-like legions.

Disrupting Y-Box-Binding Protein 1 Function Using OSU-03012 Prevents Endometriosis Progression in In Vitro and In Vivo Models

The objective of the present study was to test the ability of OSU-03012 (2-amino-N-[4-[5-phenanthren-2-yl-3-(trifluoromethyl)pyrazol-1-yl]phenyl]acetamide), a novel and potent celecoxib-derivative, to impair endometriosis progression in in vitro and in vivo models based on its ability to indirectly block Y-box-binding protein 1 (YB-1) function. 12Z human endometriotic epithelial cells and sexually mature female C57BL/6J mice were treated with OSU-03012. Cellular proliferation was quantified by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromid assay. Expression of YB-1 and phosphorylated YB-1 in 12Z cells and endometriotic lesions was evaluated by Western blotting and immunohistochemistry (IHC). The IHC for proliferating cell nuclear antigen was performed. OSU-03012 treatment resulted in decreased YB-1 and its phosphorylated form in both in vitro and in vivo models. Endometriotic lesion size was significantly reduced in OSU-03012-treated mice (27.6 ± 4.0 mm³) compared to those from the control group (50.5 ± 6.9 mm³, P < .0001). A significant reduction in endometriotic epithelial cell proliferation was observed in endometriotic lesions exposed to OSU-03012 treatment ( P = .0346). In conclusion, targeting YB-1 via OSU-03012 showed a potent antiproliferative effect on endometriotic epithelial cells in vitro and in a mouse model of disease.

Possible Role of Phthalate in the Pathogenesis of Endometriosis: In Vitro, Animal, and Human Data

CONTEXT

Although phthalates were shown to have several negative effects on reproductive function in animals, its role in the pathogenesis of endometriosis remains to be elucidated.

OBJECTIVE

We aimed to investigate the in vitro and in vivo effects of di-(2-ethylhexyl)-phthalate (DEHP) and to compare the urinary levels of several phthalate metabolites between women with and without endometriosis.

DESIGN

For experimental studies, we used endometrial cell culture and nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mouse models. We also performed a prospective case-control study for human sample analyses.

SETTING

The study was conducted at an academic center.

MAIN OUTCOME MEASURES

The activities of matrix metalloproteinase (MMP)-2 and 9, cellular invasiveness, phosphorylation of extracellular signal-regulated kinase (Erk), and expression of p21-activated kinase 4 were analyzed in endometrial cells treated with DEHP. The implant size was compared between NOD/SCID mice fed with and without DEHP. Urinary concentrations of several phthalate metabolites were compared between women with and without endometriosis.

RESULTS

In vitro treatment of endometrial cells with DEHP led to significant increases of MMP-2 and 9 activities, cellular invasiveness, Erk phosphorylation, and p21-activated kinase 4 expression. The size of the endometrial implant was significantly larger in the NOD/SCID mice fed with DEHP compared with those fed with vehicle. The urinary concentration of mono (2-ethyl-5-hydroxyhexyl) phthalate, mono (2-ethyl-5-oxohexyl) phthalate, and mono (2-ethyl-5-carboxyphentyl) phthalate were significantly higher in women with endometriosis compared with controls.

CONCLUSION

These findings strongly suggest that exposure to phthalate may lead to establishment of endometriosis by enhancing invasive and proliferative activities of endometrial cells.

Enhanced Human Decidual Cell-Expressed FKBP51 May Promote Labor-Related Functional Progesterone Withdrawal

Sustained plasma progesterone (P4) levels suggest initiation of human term labor by functional P4 withdrawal, reflecting reduced progesterone receptor (PR) and/or glucocorticoid receptor (GR) expression or activity. The steroid-induced immunophilin cochaperone FKBP51 inhibits PR- and GR-mediated transcription, suggesting a labor-initiating role. Gestational age-matched decidual sections were immunostained for FKBP51 and decidual cell (DC) and interstitial trophoblast (IT) markers, vimentin and cytokeratin, respectively. Term DC cultures were incubated with vehicle (control), estradiol (E2) with or without medroxyprogesterone acetate, dexamethasone (Dex), or Organon 2058. FKBP51 histologic scoring was significantly higher in DC nuclei during labor versus prelabor decidua, whereas FKBP51 immunostaining was undetected in interstitial trophoblasts (P < 0.05). In term DC cultures, E2 + medroxyprogesterone acetate or E2 + Dex enhanced FKBP51 expression (P < 0.01), whereas E2 + Organon 2058 inhibited PR expression (P < 0.05), and E2 + Dex inhibited GR expression (P < 0.05). Unlike term DCs, FKBP51 was undetected in control or Dex-treated cultured third-trimester trophoblasts. Electrophoretic mobility shift assays revealed that FKPB51 overexpression or silencing in cultured DCs altered PR-DNA binding. Increased FKBP51 levels in term DCs during labor complement our prior in situ observations of significantly lower PR in labor versus prelabor DCs. In a milieu of sustained plasma P4 levels, these reciprocal changes will amplify functional P4 withdrawal in DCs via FKBP51-mediated PR resistance coupled with declining PR levels, whereas the lack of FKBP51 expression in interstitial trophoblasts suggests unopposed constitutive GR action.

17β-Estradiol and steady-state concentrations of H2O2: antiapoptotic effect in endometrial cells from patients with endometriosis

Increased levels of hydrogen peroxide (H2O2) can initiate protective responses to limit or repair oxidative damage. However, H2O2 signals also fine-tune responses to growth factors and cytokines controlling cell division, differentiation, and proliferation. Because 17β-estradiol (E2) also plays important roles in these processes, and is considered a major risk factor in the development and progression of endometriosis, this study evaluated whether E2 has an antiapoptotic effect on oxidative stress in endometrial cells in combination with steady-state H2O2 levels ([H2O2]ss). Endometrial stromal cells were prepared from the eutopic endometrium of 18 women with and without endometriosis to produce primary cells. These cells were stimulated with E2 for 20h, exposed to [H2O2]ss, and examined for cell viability, proliferation, and apoptosis. The endometrial cells from women with endometriosis maintained the steady state for 120min at high H2O2 concentrations. When they were pretreated with E2 and exposed to [H2O2]ss, a decrease in apoptosis level was observed compared to the control cells (p<0.01). The endometrial cells from patients with endometriosis subjected to both E2 and [H2O2]ss showed increased ERK phosphorylation. These findings suggested that H2O2 is a signaling molecule that downregulates apoptosis in endometrial cells, supporting the fact that endometriosis, albeit a benign disease, shares some features with cancer such as decreased catalase levels. These results link the E2 effects on [H2O2]ss to resistance to apoptosis and progression of endometriosis.

Endometriosis: hormone regulation and clinical consequences of chemotaxis and apoptosis

BACKGROUND

The recruitment of immune cells by chemokines and the regulation of endometrial cell apoptosis are critical aspects of endometriosis biology. Here, we review the local (paracrine) and systemic hormone (endocrine) modulation of these two specific, but highly related phenomena.

METHODS

We searched Pubmed for items published in English between September 1991 and September 2011 and selected the studies evaluating the effects of hormones on chemokines or apoptosis in normal human endometrium and endometriosis.

RESULTS

Estradiol has proinflammatory and antiapoptotic effects in endometrial cells, and these effects appear to be exacerbated in women with endometriosis. In these women, physiological estradiol concentrations are able to induce an enhanced inflammatory response mediated by local chemokine production and to reinforce mechanisms of cell survival mediated by extracellular signal-regulated kinases and Bcl-2. The main effect of progestogens is to inhibit interleukin-8 and other chemokines in stromal cells from both eutopic and ectopic endometrium. Progesterone is also effective in inducing apoptosis in endometrial and endometriotic cells through the inhibition of Bcl-2 and nuclear factor-κB.

CONCLUSIONS

Estrogens and progestogens modulate chemotaxis and apoptosis in human endometrium and endometriotic cells and tissues. These endocrine and paracrine pathways are perturbed in women with endometriosis, contributing to inflammatory responses, abnormal tissue remodeling, therapeutic refractoriness and disease persistence. Ultimately, they promote adhesion formation and the clinical symptoms of pelvic pain and infertility. A more detailed understanding of the molecular mechanisms involved will offer new opportunities for novel pharmacological strategies to diagnose and treat endometriosis.

PRKAR1A gene analysis and protein kinase A activity in endometrial tumors

PRKAR1A codes for the type 1a regulatory subunit (RIα) of the cAMP-dependent protein kinase A (PKA), an enzyme with an important role in cell cycle regulation and proliferation. PKA dysregulation has been found in various tumors, and PRKAR1A-inactivating mutations have been reported in mostly endocrine neoplasias. In this study, we investigated PKA activity and the PRKAR1A gene in normal and tumor endometrium. Specimens were collected from 31 patients with endometrial cancer. We used as controls 41 samples of endometrium that were collected from surrounding normal tissues or from women undergoing gynecological operations for other reasons. In all samples, we sequenced the PRKAR1A-coding sequence and studied PKA subunit expression; we also determined PKA activity and cAMP binding. PRKAR1A mutations were not found. However, PKA regulatory subunit protein levels, both RIα and those of regulatory subunit type 2b (RIIβ), were lower in tumor samples; cAMP binding was also lower in tumors compared with normal endometrium (P<0.01). Free PKA activity was higher in tumor samples compared with that of control tissue (P<0.01). There are significant PKA enzymatic abnormalities in tumors of the endometrium compared with surrounding normal tissue; as these were not due to PRKAR1A mutations, other mechanisms affecting PKA function ought to be explored.

Hypoxia-induced microRNA-20a expression increases ERK phosphorylation and angiogenic gene expression in endometriotic stromal cells

CONTEXT

Aberrant activation of MAPK has been implicated to play important roles in pathological processes of endometriosis. However, how MAPK are constitutively activated in endometriotic tissues remains largely unknown. microRNA are small noncoding RNA that regulate the stability or translational efficiency of target mRNA by interacting with the 3' untranslated region. Thus, miRNA are thought to be modulators of the transcriptional response, fine-tuning gene expression.

OBJECTIVE

The aim of this study was to evaluate the functional roles of microRNA-20a (miR20a) in MAPK activation and the pathogenesis of endometriosis.

DESIGN

miR20a expression was analyzed in nonpaired (endometrium = 17; endometriosis = 37) and paired (n = 12) endometriotic tissues by quantitative RT-PCR. Overexpression of miR20a in eutopic endometrial stromal cells or inhibition of miR20a in ectopic endometriotic stromal cells was used to evaluate its impact on ERK phosphorylation and subsequently angiogenesis- and proliferation-related gene expression.

RESULTS

Levels of miR20a were up-regulated in endometriotic stromal cells. Elevation of miR20a was up-regulated by hypoxia inducible factor-1α. The up-regulation of miR20a causes the down-regulation of dual-specificity phosphatase-2, which leads to prolonged ERK phosphorylation and an increase in the expression of several angiogenic genes. Furthermore, the up-regulation of miR20a enhances the prostaglandin E(2)-induced expression of fibroblast growth factor-9, a potent mitogen that stimulates both endothelial and endometrial cell proliferation.

CONCLUSION

Our findings provide the novel mechanism that not only functionally links together hypoxic stress, miR20a expression, aberrant ERK phosphorylation, and angiogenesis but also demonstrates that miR20a is an important modulator in the development of endometriosis.

Macrophage migration inhibitory factor antagonist blocks the development of endometriosis in vivo

Endometriosis, a disease of reproductive age women, is a major cause of infertility, menstrual disorders and pelvic pain. Little is known about its etiopathology, but chronic pelvic inflammation is a common feature in affected women. Beside symptomatic treatment of endometriosis-associated pain, only two main suboptimal therapeutic approaches (hormonal and invasive surgery) are generally recommended to patients and no specific targeted treatment is available. Our studies led to the detection of a marked increase in the expression of macrophage migration inhibitory factor (MIF) in the eutopic endometrium, the peripheral blood and the peritoneal fluid of women with endometriosis, and in early, vascularized and active endometriotic lesions. Herein, we developed a treatment model of endometriosis, where human endometrial tissue was first allowed to implant into the peritoneal cavity of nude mice, to assess in vivo the effect of a specific antagonist of MIF (ISO-1) on the progression of endometriosis and evaluate its efficacy as a potential therapeutic tool. Administration of ISO-1 led to a significant decline of the number, size and in situ dissemination of endometriotic lesions. We further showed that ISO-1 may act by significantly inhibiting cell adhesion, tissue remodeling, angiogenesis and inflammation as well as by altering the balance of pro- and anti-apoptotic factors. Actually, mice treatment with ISO-1 significantly reduced the expression of cell adhesion receptors αv and ß3 integrins (P<0.05), matrix metalloproteinases (MMP) 2 and 9 (P<0.05), vascular endothelial cell growth factor (VEGF) (P<0.01), interleukin 8 (IL8) (P<0.05), cyclooxygenease (COX)2 (P<0.001) and the anti-apoptotic protein Bcl2 (P<0.01), but significantly induced the expression of Bax (P<0.05), a potent pro-apoptotic protein. These data provide evidence that specific inhibition of MIF alters endometriotic tissue growth and progression in vivo and may represent a promising potential therapeutic avenue.

Somatostatin and somatostatin analogues reduce PDGF-induced endometrial cell proliferation and motility

BACKGROUND

Endometriosis is characterized by ectopic implantation of endometrial cells, which show increased proliferation and migration. Somatostatin (SST) and its analogues inhibit normal and cancer cell growth and motility through the SST receptors, sst1-5. Cortistatin (CST), which displays high structural and functional homology with SST, binds all ssts, as well as MrgX2. Our objective was to investigate the gene expression of the SST/CST system and to determine the effect of SST and its analogues on platelet-derived growth factor (PDGF)-induced proliferation and motility in telomerase-immortalized human endometrial stromal cell (T HESC) line and in primary endometrial stromal cell (ESCs) isolated from human endometriotic tissues.

METHODS

Ectopic endometrial tissues were collected from women (n= 23) undergoing laparoscopic surgery for endometriosis (Stage III/IV). Gene expression was evaluated by real-time PCR, cell motility by wound healing assay, protein expression and β-actin rearrangement by immunofluorescence, cell proliferation by the Alamar blue assay and ERK1/2 and Akt phosphorylation by western blot.

RESULTS

Human endometriotic tissues, primary ESCs and T HESCs expressed SST, CST and ssts. SST, its analogues SOM230 and octreotide, as well as CST, counteracted PDGF-induced proliferation and migration in both ESCs and T HESCs. SST also inhibited vascular endothelial growth factor and metalloprotease-2 mRNA expression, and reduced basal and PDGF-induced ERK1/2 phosphorylation.

CONCLUSION

These results indicate that the SST/CST system is expressed in endometriotic tissues and cells. The inhibitory effects of SST and its analogues on PDGF-induced proliferation and motility suggest that these peptides may represent promising tools in the treatment of endometriosis.

Statins inhibit monocyte chemotactic protein 1 expression in endometriosis

Statins are potent inhibitors of the endogenous mevalonate pathway. Besides inhibiting cholesterol biosynthesis, statins may also demonstrate anti-inflammatory properties. Inflammation is implicated in the attachment and invasion of endometrial cells to the peritoneal surface and growth of ectopic endometrium by inducing proliferation and angiogenesis. In this study, the effect of statins on monocyte chemotactic protein 1 (MCP-1) expression in endometriotic implants in nude mouse model and in cultured endometriotic cells was evaluated. In mouse model, simvastatin decreased MCP-1 expression in a dose-dependent manner in endometriotic implants (P < .05). Similarly, both simvastatin and mevastatin revealed a dose-dependent inhibition of MCP-1 production in cultured endometriotic cells (P < .01). This inhibitory effect of the statins on MCP-1 production was reversed by the downstream substrates of the mevalonate pathway. Moreover, statins decreased MCP-1 messenger RNA expression in cultured endometriotic cells (P < .05). In conclusion, statins exert anti-inflammatory effect in endometriotic cells and could provide a potential treatment of endometriosis in the future.

Tumor necrosis factor-α activates estrogen signaling pathways in endometrial epithelial cells via estrogen receptor α

The pro-inflammatory cytokine TNF-α and the female hormone estrogen have been implicated in the pathophysiology of two common gynecological diseases, endometriosis and endometrial adenocarcinoma. Here we describe a novel capacity of TNF-α to activate ER signaling in endometrial epithelial cells. TNF-α induced luciferase expression in the absence and presence of estradiol and also augmented expression of the estrogen-regulated genes c-fos, GREB1, and progesterone receptor. Furthermore, TNF-α mediated ER transcriptional activity is dependent on the Extracellular Regulated Kinase (ERK) 1/2 pathway. Co-treatment with a pure ER antagonist resulted in an inhibition of this TNF-α-induced ERE luciferase activity and gene expression, demonstrating that this cytokine signals through ERs. Additional investigations confirmed that TNF-α acts specifically via ERα. Taken together, these data provide a rationale for the potential use of inhibitors of TNF-α and estrogen production/activity in combination for the treatment of endometrial pathologies.

The mTOR/AKT inhibitor temsirolimus prevents deep infiltrating endometriosis in mice

Deep infiltrating endometriosis (DIE) is a particular clinical and histological entity of endometriosis responsible for chronic pelvic pain and infertility. Here we characterize the proliferative phenotype of DIE cells, to explore the cellular and molecular mechanisms that could explain their aggressive potential. In addition, the inhibition of mTOR/AKT pathway was tested, as a potential treatment of DIE. Included were 22 patients with DIE and 12 control patients without endometriosis. Epithelial and stromal cells were extracted from biopsies of eutopic endometrium and deep infiltrating endometriotic nodules from patients with DIE. Cell proliferation was determined by thymidine incorporation. Oxidative stress was assayed by spectrofluorometry. The ERK and mTOR/AKT pathways were analyzed in vitro by Western blot and for AKT in vivo in a mouse model of DIE. The proliferation rate of eutopic endometrial cells and of deep infiltrating endometriotic cells from DIE patients was higher than that of endometrial cells from controls. The hyperproliferative phenotype of endometriotic cells was associated with an increase in endogenous oxidative stress, and with activation of the ERK and mTOR/AKT pathways. mTOR/AKT inhibition by temsirolimus decreased endometriotic cell proliferation both in vitro and in vivo in a mouse model of DIE. Blocking the mTOR/AKT pathway offers new prospects for the treatment of DIE.

Aberrant expression of apoptosis-related molecules in endometriosis: a possible mechanism underlying the pathogenesis of endometriosis

Endometriosis, a disease affecting 3% to 10% of women of reproductive age, is characterized by the ectopic growth of endometrial tissue under the influence of estrogen. It is also becoming recognized as a condition in which ectopic endometrial cells exhibit abnormal proliferative and apoptotic regulation in response to appropriate stimuli. Apoptosis plays a critical role in maintaining tissue homeostasis and represents a normal function to eliminate excess or dysfunctional cells. Accumulated evidence suggests that, in healthy women, endometrial cells expelled during menstruation do not survive in ectopic locations because of programmed cell death, while decreased apoptosis may lead to the ectopic survival and implantation of these cells, resulting in the development of endometriosis. Both the inability of endometrial cells to transmit a "death" signal and the ability of endometrial cells to avoid cell death have been associated with increased expression of antiapoptotic factors and decreased expression of preapoptotic factors. Further investigations may elucidate the role of apoptosis-associated molecules in the pathogenesis of endometriosis. Medical treatment with apoptosis-inducing agents may be novel and promising therapeutic strategy for endometriosis.

Macrophage migration inhibitory factor elicits an angiogenic phenotype in human ectopic endometrial cells and triggers the production of major angiogenic factors via CD44, CD74, and MAPK signaling pathways

CONTEXT

An active angiogenesis is required for ectopic endometrial tissue growth. Our previous studies led to the identification of macrophage migration inhibitory factor (MIF), which is markedly elevated in active, vascularized, and early-stage endometriotic lesions, as a potent mitogenic factor for endothelial cells.

OBJECTIVE

Our objective was to study the mechanisms by which MIF may stimulate angiogenesis in ectopic endometrial implantation sites.

DESIGN

Primary cultures of ectopic endometrial cells were exposed to MIF, and the release of major angiogenic factors with targeted disruption of MIF signaling pathways was assessed.

PATIENTS

Patients were women found to have endometriosis during laparoscopy.

SETTING

The study was conducted at a hospital and reproduction research laboratory.

INTERVENTIONS

Biopsies were removed from endometriotic lesions.

MAIN OUTCOME MEASURES

Vascular endothelial cell growth factor (VEGF), IL-8, and monocyte chemotactic protein-1 (MCP-1) mRNA and protein levels and expression and small interfering RNA silencing of MIF CD74/CD44 receptor complex and phosphorylation of ERK and p38 MAPKs were evaluated.

RESULTS

MIF markedly up-regulated VEGF, IL-8, and MCP-1 expression in endometriotic cells. Such an effect was abolished by (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1), a specific inhibitor of MIF, and significantly down-regulated after specific small interfering RNA silencing of CD44 or CD74. MIF treatment strongly activated ERK and p38 MAPKs, and specific inhibitors of both pathways completely blocked basal and MIF-induced VEGF, IL-8, and MCP-1 synthesis.

CONCLUSIONS

These results show for the first time that MIF exerts a potent indirect angiogenic effect by interacting with ectopic endometrial cells and inducing the secretion of major angiogenic factors via CD44, CD74, and MAPK signaling pathways and provide evidence for a possible new mechanism underlying endometriosis development and pathophysiology.

Protein kinase inhibitors can control the progression of endometriosis in vitro and in vivo

Endometriosis affects 6-10% of women in their reproductive years, causing chronic pelvic pain and infertility. Its pathogenesis remains poorly understood and current treatments, based on hormonal therapy or surgery, are often insufficient. The purpose of our study was to investigate the role of the ERK pathway in the development of endometriosis and to test the effects of protein kinase inhibitors on the proliferation of endometriotic cells in vitro and in vivo. We studied ex vivo human endometrial and endometriotic cells in culture. Stromal and epithelial cells were extracted from endometrial and endometriotic biopsies from patients with endometriosis and from patients without endometriosis. The ERK pathway was explored by western blot on cell lysates and by ELISA on total crushed specimens of endometrium. Cells in culture were treated with A771726, PD98059, and U0126. Human endometriotic lesions were implanted in nude mice. Mice were treated with A771726, leflunomide, PD98059, U0126 or PBS during 2 weeks before sacrifice and extraction of the endometriotic implants for histological examination. We found that the ERK pathway was significantly activated in endometriotic cells and in endometrial cells from patients with endometriosis compared to endometrial cells of control patients, both by ELISA and by western blot. This phenomenon was associated with an increased proliferation of endometriotic cells compared to endometrial cells. Treating endometriotic cells with A771726, PD98059 or U0126 abrogated the phosphorylation of ERK and significantly decreased the cellular proliferation in vitro. In vivo, A771726, leflunomide, PD98059, and U0126 controlled the growth of endometriotic implants in the mouse model of endometriosis. Our study shows that protein kinase inhibitors could be new candidates to treat endometriosis. However, further studies are needed to evaluate their effects and tolerability in humans.

The protein kinase A pathway-regulated transcriptome of endometrial stromal fibroblasts reveals compromised differentiation and persistent proliferative potential in endometriosis

Intrinsic abnormalities in transplanted eutopic endometrium are believed to contribute to the pathogenesis of pelvic endometriosis. Herein we investigated transcriptomic differences in human endometrial stromal fibroblasts (hESFs) from women with (hESF(endo)) vs. without (hESF(nonendo)) endometriosis, in response to activation of the protein kinase A (PKA) pathway with 8-bromoadenosine-cAMP (8-Br-cAMP). hESF(nonendo) (n = 4) and hESF(endo) (n = 4) were isolated from eutopic endometrium and treated +/- 0.5 mm 8-Br-cAMP for 96 h. Purified total RNA was subjected to microarray analysis using the whole-genome Gene 1.0 ST Affymetrix platform. A total of 691 genes were regulated in cAMP-treated hESF(nonendo) vs. 158 genes in hESF(endo), suggesting a blunted response to cAMP/PKA pathway activation in women with disease. Real-time PCR and ELISA validated the decreased expression of decidualization markers in hESF(endo) compared with hESF(nonendo). In the absence of disease, 8-Br-cAMP down-regulated progression through the cell cycle via a decrease in cyclin D1, cyclin-dependent kinase 6, and cell division cycle 2 and an increase in cyclin-dependent kinase inhibitor 1A. However, cell cycle components in hESF(endo) were not responsive to 8-Br-cAMP, resulting in persistence of a proliferative phenotype. hESF(endo) treated with 8-Br-cAMP exhibited altered expression of immune response, extracellular matrix, cytoskeleton, and apoptosis genes. Changes in phosphodiesterase expression and activity were not different among experimental groups. These data support that eutopic hESF(endo) with increased proliferative potential can seed the pelvic cavity via retrograde menstruation and promote establishment, survival, and proliferation of endometriosis lesions, independent of hydrolysis of cAMP and likely due to an inherent abnormality in the PKA pathway.

Increased mitogen-activated protein kinase kinase/extracellularly regulated kinase activity in human endometrial stromal fibroblasts of women with endometriosis reduces 3',5'-cyclic adenosine 5'-monophosphate inhibition of cyclin D1

Endometriosis is characterized by endometrial tissue growth outside the uterus, due primarily to survival, proliferation, and neoangiogenesis of eutopic endometrial cells and fragments refluxed into the peritoneal cavity during menses. Although various signaling molecules, including cAMP, regulate endometrial proliferation, survival, and embryonic receptivity in endometrium of women without endometriosis, the exact molecular signaling pathways in endometrium of women with disease remain unclear. Given the persistence of a proliferative profile and differential expression of genes associated with the MAPK signaling cascade in early secretory endometrium of women with endometriosis, we hypothesized that ERK1/2 activity influences cAMP regulation of the cell cycle. Here, we demonstrate that 8-Br-cAMP inhibits bromodeoxyuridine incorporation and cyclin D1 (CCND1) expression in cultured human endometrial stromal fibroblasts (hESF) from women without but not with endometriosis. Incubation with serum-containing or serum-free medium resulted in higher phospho-ERK1/2 levels in hESF of women with vs. without disease, independent of 8-Br-cAMP treatment. The MAPK kinase-1/2 inhibitor, U0126, fully restored cAMP down-regulation of CCND1, but not cAMP up-regulation of IGFBP1, in hESF of women with vs. without endometriosis. Immunohistochemistry demonstrated the highest phospho-ERK1/2 in the late-secretory epithelial and stromal cells in women without disease, in contrast to intense immunostaining in early-secretory epithelial and stromal cells in those with disease. These findings suggest that increased activation of ERK1/2 in endometrial cells from women with endometriosis may be responsible for persistent proliferative changes in secretory-phase endometrium.

Up-regulation of cyclooxygenase-2 expression and prostaglandin E2 production in human endometriotic cells by macrophage migration inhibitory factor: involvement of novel kinase signaling pathways

Cyclooxygenase (COX) is the rate-limiting enzyme in the metabolic conversion of arachidonic acid to prostaglandins (PGs), including prostaglandin E(2) (PGE(2)), a major mediator of inflammation and angiogenesis. Herein, we report that macrophage migration inhibitory factor (MIF), a potent proinflammatory and growth-promoting factor found at elevated concentrations in the peritoneal fluid of women with endometriosis and active endometriosis lesions, acts directly on ectopic endometrial cells to stimulate the synthesis of COX-2, the inducible form of COX, and the release of PGE(2). MIF treatment strongly activated p38 and ERK MAPK, and specific inhibitors of both pathways completely blocked basal and MIF-induced PGE(2) synthesis. Whereas p38 inhibitors negatively affected the stimulated synthesis of COX-2 and that of PGE(2), ERK inhibitors only decreased the production of PGE(2). These findings show for the first time a direct role for MIF in the up-regulation of COX-2 synthesis and PGE(2) secretion in ectopic endometrial cells. They further indicate that whereas p38 and ERK MAPK signaling pathways both play a significant role in the regulation of basal and MIF-induced synthesis of PGE(2) by ectopic endometrial cells, only p38 kinase is involved in the regulation of COX-2 expression in these cells. This suggests that MIF acts at more than one level to stimulate the synthesis of PGE(2) and triggers the coordinate activation of multiple enzymes in the biosynthesis pathway. Our data provide evidence for a novel mechanism by which MIF can induce a proinflammatory phenotype in ectopic endometrial cells, and favor the establishment of endometriosis and its related clinical symptoms.

Reactive oxygen species controls endometriosis progression

Endometriosis is associated with chronic inflammation, and reactive oxygen species (ROS) are proinflammatory mediators that modulate cell proliferation. We have investigated whether the dysregulation of ROS production in endometriotic cells correlates with a pro-proliferative phenotype and can explain the spreading of this disease. Stromal and epithelial cells were purified from ovarian endometrioma and eutopic endometrium from 14 patients with endometriosis to produce four primary cell lines from each patient. ROS production, detoxification pathways, cell proliferation, and mitogen-activated protein kinase pathway activation were studied and compared with epithelial and stromal cell lines from 14 patients without endometriosis. Modulation of the proliferation of endometriosis by N-acetyl-cysteine, danazol, and mifepristone was tested in vitro and in 28 nude mice implanted with endometriotic tissue of human origin. Endometriotic cells displayed higher endogenous oxidative stress with an increase in ROS production, alterations in ROS detoxification pathways, and a drop in catalase levels, as observed for tumor cells. This increase in endogenous ROS correlated with increased cellular proliferation and activation of ERK1/2. These phenomena were abrogated by the antioxidant molecule N-acetyl-cysteine both in vitro and in a mouse model of endometriosis. Human endometriotic cells display activated pERK, enhanced ROS production, and proliferative capability. Our murine model shows that antioxidant molecules could be used as safe and efficient treatments for endometriosis.