Reinaldo González-Ramos

Potential involvement of iron in the pathogenesis of peritoneal endometriosis

The aim of this study is to review the current literature associating endometriosis with iron and to discuss the potential causes and consequences of iron overload in the pelvic cavity. Indeed, iron is essential for all living organisms. However, excess iron can result in toxicity and is associated with pathological disorders. In endometriosis patients, iron overload has been demonstrated in the different components of the peritoneal cavity (peritoneal fluid, endometriotic lesions, peritoneum and macrophages). Animal models allow us to gather essential information on the origin, metabolism and effect of iron overload in endometriosis, which may originate from erythrocytes carried into the pelvic cavity mainly by retrograde menstruation. Peritoneal macrophages play an important role in the degradation of these erythrocytes and in subsequent peritoneal iron metabolism. Iron overload could affect a wide range of mechanisms involved in endometriosis development, such as oxidative stress or lesion proliferation. In conclusion, excess iron accumulation can result in toxicity and may be one of the factors contributing to the development of endometriosis. Treatment with an iron chelator could thus be beneficial in endometriosis patients to prevent iron overload in the pelvic cavity, thereby diminishing its deleterious effect.

Agents Blocking the Nuclear Factor-κB Pathway Are Effective Inhibitors of Endometriosis in an in vivo Experimental Model

Background: In vitro studies suggest that the transcription factor nuclear factor-kappa B (NF-ĸB) is implicated in the transduction of proinflammatory signals in endometriosis. The aim of this study was to investigate the involvement of NF-ĸB and the processes regulated by NF-ĸB in the initial development of endometriotic lesionsin vivo.Methods: Endometriosis was induced in nude mice by intraperitoneal injection of fluorescent-labeled menstrual endometrium. Two NF-ĸB inhibitors (BAY 11-7085 and SN-50) were injected intraperitoneally on days 0, 2 and 4 after endometriosis induction, and endometriotic lesions were recovered on day 5. Number, mass, fluorimetry and surface (morphometry) of endometriotic lesions were quantified. NF-ĸB activation, intercellular adhesion molecule (ICAM)-1 expression, cell proliferation and apoptosis were evaluated by immunohistochemical analyses and the TUNEL method. Results: Both NF-ĸB inhibitors induced a significant reduction in lesion development compared to control mice. NF-ĸB activation and ICAM-1 expression of endometriotic lesions were significantly reduced in treated mice, and cell proliferation was significantly reduced in BAY 11-7085-treated mice. Both inhibitors produced a significant increase in apoptosis of endometriotic lesions, as assessed by active caspase-3 immunostaining and the TUNEL method. Conclusion: This study demonstrates, for the first time, that the NF-ĸB pathway is implicated in the development of endometriotic lesions in vivo and that NF-ĸB inhibition reduces ICAM-1 expression and cell proliferation, but increases apoptosis of endometriotic lesions, diminishing the initial development of endometriosis in an animal model.

Iron storage is significantly increased in peritoneal macrophages of endometriosis patients and correlates with iron overload in peritoneal fluid

OBJECTIVE To further investigate peritoneal iron disruption in endometriosis by studying iron storage in peritoneal macrophages of patients with endometriosis compared with controls. DESIGN Cross-sectional study. SETTING Academic gynecology research unit in a university hospital. PATIENT(S) Fifty patients undergoing laparoscopy. INTERVENTION(S) Collection of peritoneal fluid samples (N = 50) from patients with (n = 27) and without (n = 23) endometriosis undergoing laparoscopy. MAIN OUTCOME MEASURE(S) Quantification of peritoneal macrophage ferritin by immunocytochemical staining and immunodensitometry and measurement of peritoneal iron, transferrin, ferritin, and prohepcidin concentrations. RESULT(S) The optical density of peritoneal macrophage ferritin staining was statistically significantly higher in endometriosis patients than in controls. Higher iron concentrations, transferrin saturations, and ferritin concentrations were also detected in case of endometriosis. A statistically significant positive correlation was found between the optical density of macrophage ferritin staining and peritoneal iron concentrations in endometriosis and control patients. CONCLUSION(S) Iron storage is statistically significantly increased in peritoneal macrophages of patients with endometriosis and correlates with iron overload in peritoneal fluid. The potential implications of iron accumulation in peritoneal macrophages in case of endometriosis are discussed.

Physiologic activation of nuclear factor kappa-B in the endometrium during the menstrual cycle is altered in endometriosis patients.

OBJECTIVE To evaluate nuclear factor kappaB (NF-κB) activation and NF-κB-p65 subunit activation, immunolocalization, and expression in the endometrium of healthy women and endometriosis patients throughout the menstrual cycle. DESIGN Prospective observational study. SETTING Affiliated hospital and university research laboratory. PATIENT(S) Twenty-four healthy women and 24 endometriosis patients. INTERVENTION(S) Menstrual, proliferative, and secretory endometrial biopsies. MAIN OUTCOME MEASURE(S) Assessment of NF-κB and p65 activation by protein-DNA binding assays and p65 localization and expression by immunohistochemistry. RESULT(S) Total NF-κB-DNA binding was constitutive and variable in human endometrium accross the menstrual cycle. Healthy women (physiologic conditions) showed higher p65-DNA binding in proliferative than in menstrual and secretory endometrium. Conversely, in endometriosis patients, p65-DNA binding was higher in proliferative and secretory endometrium than in menstrual endometrium. Endometrial epithelial cells showed higher p65 expression level score than endometrial stromal cells. CONCLUSION(S) NF-κB activity is constitutive, physiologic, and variable in human endometrium. The physiologic cyclic p65 activation pattern was altered in endometriosis patients, showing no cyclic variation between the proliferative and secretory phase of the menstrual cycle. The absence of decreased p65 activity in secretory endometrium from endometriosis patients is concurrent with progesterone resistance and could participate in endometrial biologic alterations during the implantation window in endometriosis patients.

hCG activates Epac-Erk1/2 signaling regulating Progesterone Receptor expression and function in human endometrial stromal cells

STUDY QUESTION How does hCG signal in human endometrial stromal cells (ESCs) and what is its role in regulating ESC function? SUMMARY ANSWER hCG signaling in ESCs activates the extracellular signal-regulated protein kinases 1 and 2 (Erk1/2) pathway through exchange protein activated by cyclic AMP (cAMP) (Epac) and transiently increases progesterone receptor (PR) transcript and protein expression and its transcriptional function. WHAT IS KNOWN ALREADY hCG is one of the earliest embryo-derived secreted signals in the endometrium, which abundantly expresses LH/hCG receptors. hCG signals through cAMP/protein kinase A (PKA) in gonadal cells, but in endometrial epithelial cells, hCG induces Erk1/2 activation independent of the cAMP/PKA pathway. Few data exist concerning the signal transduction pathways triggered by hCG in ESCs and their role in regulation of ESC function. STUDY DESIGN, SIZE, DURATION This is an in vitro study comprising patients undergoing benign gynecological surgery (n = 46). PARTICIPANTS/MATERIALS, SETTING, METHODS Endometrial samples were collected from normal cycling women during the mid-secretory phase for ESCs isolation. The study conducted in an academic research laboratory within a tertiary-care hospital. The activation of the Erk1/2 signal transduction pathway elicited by hCG was evaluated in ESC. Signaling pathway inhibitors were used to examine the roles of PKA, PI3K, PKC, adenylyl cyclase and Epac on the hCG-stimulated up-regulation of phospho-Erk1/2 (pErk1/2). Erk1/2 phosphorylation was determined by immunoblot. siRNA targeting Epac was used to investigate the molecular mechanisms. To assess the role of Erk1/2 signaling induced by hCG on ESC function, gene expression regulation was examined by immunofluorescence and real-time quantitative PCR. The role of PR on the regulation of transcript levels was studied using progesterone and the PR antagonist RU486. All experiments were conducted using at least three different cell culture preparations in triplicate. MAIN RESULTS AND THE ROLE OF CHANCE Addition of hCG to ESCs in vitro induced the phosphorylation of Erk1/2 through cAMP accumulation. Such induction could not be blocked by inhibitors for PKA, PKC and PI3K. Epac inhibition and knockdown with siRNA prevented pErk1/2 induction by hCG. ESCs stimulated with hCG for up to 72 h showed a significant increase in PR mRNA and immunofluorescent label at 48 h only; an effect that was abrogated with the mitogen-activated protein kinase kinase inhibitor UO126. In addition, the hCG-activated Erk1/2 pathway significantly decreased the mRNA levels for secreted frizzled-related protein 4 (SFRP4) at 24 h, whereas it increased those for homeobox A10 (HOXA10) at 48 h (P = 0.041 and P = 0.022 versus control, respectively). Prolactin mRNA levels were not significantly modified. HOXA10 mRNA up-regulation by hCG was not enhanced by co-stimulation with progesterone; however, it was completely abolished in the presence of RU486 (P = 0.036 hCG versus hCG + RU486). LARGE SCALE DATA N/A. LIMITATIONS, REASONS FOR CAUTION This is an in vitro study utilizing stromal cell cultures from human endometrial tissues. Furthermore, results obtained should also be confirmed in vivo in the context of the whole human endometrial tissue and hormonal milieu. The in vitro experiments using hCG have been conducted without other hormones/factors that may also modulate the ESCs response to hCG. WIDER IMPLICATIONS OF THE FINDINGS We have determined that hCG induces the PR through the Erk1/2 pathway in ESCs which may render them more sensitive to progesterone, increasing our understanding about the effects of hCG at the embryo-maternal interface. The activation of such a pathway in the context of the hormonal milieu during the window of implantation might contribute to a successful dialog between the embryo and the uterus, leading to appropriate endometrial function. Defective hCG signaling in the endometrial stromal tissue may lead to an incomplete uterine response, compromising embryo implantation and early pregnancy. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the National Fund for Scientific and Technological Development, Government of Chile (FONDECYT) grants 11100443 and 1140614 (A.T.-P.). The authors have no conflicts of interest to declare.

Expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in human endometrial stromal and epithelial cells is regulated by interferon-gamma but not iron.

Background/Aims: Endometrial cells are chronically exposed to iron due to cyclic menstrual bleeding. Iron induces expression of adhesion molecules in endothelial cells. The purpose of this study was to investigate iron incorporation by human endometrial cells and to test whether iron may stimulate expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1. Methods: Endometrial stromal and epithelial cells were cultured in medium alone or supplemented with INF-γ or transferrin (Tf). Iron incorporation by cells was quantified by densitometry of ferritin immunostaining. ICAM-1 and VCAM-1 expression were evaluated at the transcriptional level by real-time RT-PCR. Membrane-bound and soluble protein levels of ICAM-1 were measured by quantitative immunohistochemistry and ELISA, respectively. Results: Tf induced a significant increase in ferritin immunostaining in both endometrial cell types. Endometrial cells treated with INF-γ expressed more ICAM-1 and VCAM-1 than untreated cells. By contrast, Tf treatment did not alter ICAM-1 and VCAM-1 expression in cultured endometrial cells. Conclusions: Endometrial cells are able to incorporate iron from Tf and to metabolize it to ferritin. Iron, unlike interferon-γ, does not appear to be involved in the regulation of ICAM-1 and VCAM-1 expression in cultured endometrial cells.

Iron overload-modulated nuclear factor kappa-B activation in human endometrial stromal cells as a mechanism postulated in endometriosis pathogenesis.

OBJECTIVE To evaluate the effect of iron overload on nuclear factor kappa-B (NF-κB) activation in human endometrial stromal cells (ESCs). DESIGN Experimental study. SETTING University hospital research laboratory. PATIENT(S) Ten healthy women. INTERVENTION(S) Isolated ESCs from endometrial biopsies were incubated with 50 μM FeSO(4) or vehicle. The NF-κB inhibitor [5-(p-fluorophenyl)-2-ureido] thiophene-3-carboxamide (TPCA-1), which inhibits IKKβ, the kinase of IκBα (inhibitory protein of NF-κB), was used to prevent iron overload-stimulated NF-κB changes in ESCs. MAIN OUTCOME MEASURE(S) NF-κB activation was assessed by p65:DNA-binding activity immunodetection assay. IκBα, p65, and intercellular adhesion molecule (ICAM)-1 proteins expression was evaluated by Western blots. ESC soluble ICAM (sICAM)-1 secretion was measured by ELISA using conditioned medium. RESULT(S) Iron overload increased p65:DNA-binding activity and decreased IκBα and p65 cytoplasmic expression in ESCs after 30 minutes of incubation as compared with the basal condition. ESC ICAM-1 expression and sICAM-1 secretion were higher after 24 hours of iron overload treatment than in the absence of treatment. TPCA-1 prevented the iron overload-induced increase of p65:DNA binding and IκBα degradation. CONCLUSION(S) Iron overload activates IKKβ in ESCs, stimulating the NF-κB pathway and increasing ICAM-1 expression and sICAM-1 secretion. These results suggest that iron overload induces a proendometriotic phenotype on healthy ESCs, which could participate in endometriosis pathogenesis and development.

Unsuccessful Induction of Endometriosis in Female Rhesus Macaques (Macaca mulatta)

Background/Aims: The aim of this study was to induce endometriosis in female rhesus macaques (Macaca mulatta) for research purposes. Methods: Three female monkeys from 4 to 4.5 years of age underwent three consecutive attempts at endometriosis induction over an 8-month period: (i) the first attempt involved intravaginal sampling of endometrial tissue and transplantation into the intrapelvic cavity; (ii) the second entailed surgical removal of endometrium after hysterotomy and intra-abdominal placement, and (iii) the third used endometrial mucosa obtained by scraping the uterus after hysterectomy, placed in a surgical pouch created in the retrovesical space (Retzius). In each case, the pelvic cavity was closely inspected after 7, 9, and 6 weeks respectively for the presence of endometriotic lesions, and peritoneal biopsies were performed. Results: Neither macroscopic observation nor histological analysis revealed any endometriotic lesions. Conclusion: This failure to induce endometriosis in female rhesus macaques suggests that this species is not the most efficient experimental model among primates to investigate endometriosis development or treatment.