Relationship between 17-beta-estradiol and prolactin in the regulation of natural killer cell activity during progression of endometriosis

Prolactin and pain of endometriosis

Women experience chronic pain more often than men with some pain conditions being specific to women while others are more prevalent in women. Prolactin, a neuropeptide hormone with higher serum levels in women, has recently been demonstrated in preclinical studies to sensitize nociceptive sensory neurons in a sexually dimorphic manner. Dysregulation of prolactin and prolactin receptors may be responsible for increased pain especially in female predominant conditions such as migraine, fibromyalgia, and pelvic pain. In this review, we focus on the role of prolactin in endometriosis, a condition characterized by pelvic pain and infertility that affects a large proportion of women during their reproductive age. We discuss the symptoms and pathology of endometriosis and discuss how different sources of prolactin secretion may contribute to this disease. We highlight our current understanding of prolactin-mediated mechanisms of nociceptor sensitization in females and how this mechanism may apply to endometriosis. Lastly, we report the results of a systematic review of clinical studies conducted by searching the PubMed and EMBASE databases to identify association between endometriosis and blood levels of prolactin. The results of this search strongly indicate that serum prolactin levels are increased in patients with endometriosis and support the possibility that high levels of prolactin may promote pelvic pain in these patients and increase vulnerability to other comorbid pain conditions likely by dysregulating prolactin receptor expression. Targeting of prolactin and prolactin receptors may improve management of pain associated with endometriosis.

The pathogenesis of endometriosis: clues from the immunological evidence

INTRODUCTION

Endometriosis pathogenesis is still a matter of debate. It is now agreed that a complex cooperation of genetic, hormonal, immune and environmental factors is implicated. However, no consensus has been reached yet on what firstly is responsible for the initiation, promotion and survival of endometrial-like tissue outside the uterine cavity. Since consistent evidence have found immunological alterations in women with the disease, the impairment of immune system has been considered for decades one of the possible causes of endometriosis. The aim of this literature review is to summarize the available findings on a particular aspect of this topic represented by the inhibition of natural killer (NK) cell activity in women affected as a paradigmatic example of the complexity in studying the pathogenesis of endometriosis.

EVIDENCE ACQUISITION

Advanced search of PubMed for English articles published between 1990 and September 2020 using the keywords "endometriosis" or "endometrioma" or "endometriotic" or "ectopic endometrium" in combination with "natural killer cells" (NK).

EVIDENCE SYNTHESIS

Consistent studies have found an impairment in NK cell activity in women with endometriosis especially in advanced stages of disease (stage III/IV). Reports to explain these findings support the phenomenon as a consequence of the disease establishment. Evidence from genetic studies have questioned the role of these dysfunctions in the pathogenesis of the disease.

CONCLUSIONS

Immunological dysfunctions and the decreased NK cell cytotoxicity may only represent consequence of endometriosis, although the underlining mechanisms still need to be elucidated.

Sex dichotomy in the course of experimental latent toxoplasmosis

Toxoplasma gondii is an opportunistic zoonotic protozoan that exceeds neurological and congenital impact sequence to reactivating latent toxoplasmosis especially under immunosuppression. Sex-associated hormones influence the severity of Toxoplasma infection. Thus, our study aimed to compare toxoplasmosis associated morbidity in both male and female mice and to monitor the response to anti-Toxoplasma therapeutics fortified with sex hormones in comparison to presently used drugs. Twenty male and 20 female mice were infected with ME49 Toxoplasma strain. The morbidity was assessed in the chronic stage in both sexes by estimating brain cyst burden, brain histopathological examination and monitoring serum anti-Toxoplasma IL-12 using ELISA method. Another 40 male and 40 female mice were infected with ME49 Toxoplasma strain then after 6 weeks received different treatment regimens including Atovaquone, Spiramycin, Metronidazole, Estradiol benzoate and Testoserone propionate either as a monotherapy or as a combination. Treatment response was monitored by scoring mice activity and brain cyst burden. This study showed that female mice demonstrated higher cyst burden and manifested more pathological reactions than male mice. While, the IL-12 serum level was significantly higher in male than female mice. Also, it is proved that the Toxoplasma cyst number was reduced significantly when used testosterone/atovaquone, or testosterone/spiramycin/metronidazole combined regimen in female mice groups. While for male mice, the combined therapy of spiramycin/metronidazole was the superior one. Accordingly, combined therapy with sex hormones is a promising strategy for discovering new therapeutic regimens for treating latent toxoplasmosis especially in female.

Toxoplasma gondii: One Organism, Multiple Models

Toxoplasma gondii is an intensely studied protozoan parasite. It is also used as a model organism to research additional clinically relevant human and veterinary parasites due to ease of in vitro culture and genetic manipulation. Recently, it has been developed as a model of inflammatory bowel disease, due to their similar pathologies. However, researchers vary widely in how they use T. gondii, which makes study comparisons and interpretation difficult. The aim of this review is to provide researchers with a tool to: (i) determine the appropriateness of the different T. gondii models to their research, (ii) interpret results from the wide range of study conditions, and (iii) consider new advances in technology which could improve or refine their experimental setup.

Correlation between aromatase expression in the eutopic endometrium of symptomatic patients and the presence of endometriosis

Objective

To investigate whether aromatase expression in the eutopic endometrium correlates with the presence and severity of endometriosis in patients with infertility and/or dysmenorrhea undergoing laparoscopy and hysteroscopy.

Patients

The study involved 106 patients of reproductive age with symptoms of dysmenorrhea and infertility. Sixteen endometriosis-free asymptomatic patients were used as a control group.

Methods

Concomitant laparoscopy and hysteroscopy was carried out in all cases. An endometrial biopsy was taken to determine aromatase p450 expression by immunohistochemistry. Endometriosis was staged according to the American Society of Reproductive Medicine classification.

Results

Endometriosis was diagnosed by laparoscopy in 92/106 symptomatic patients. In this group, aromatase expression was detected in the eutopic endometrium of 66/92 patients with endometriosis (72%) and in 13/14 (95%) patients in the symptomatic, endometriosis-free group (P = 0.09). Aromatase expression was not detected in any patients from the control group. In the endometriosis group, aromatase expression was detected in the eutopic endometrium of 28/45 patients (62%) with American Society of Reproductive Medicine classification stage 1 of the disease, in 11/14 patients (78%) with stage II, 14/20 patients (70%) with stage III, and in 12/13 patients (92%) with stage IV; however, the difference was only statistically significant between stages I and IV (P = 0.04).

Conclusion

Aromatase expression in the endometrium was associated with the presence of dysmenorrhea and infertility irrespective of the presence of endometriosis. When endometriosis was present, however, there was a tendency for aromatase expression to be positively correlated with dysmenorrhea severity.

Patients with endometriosis of the rectosigmoid have a higher percentage of natural killer cells in peripheral blood

STUDY OBJECTIVE

To estimate the concentration of natural killer (NK) cells in the peripheral blood in patients with and without endometriosis.

DESIGN

Case-control study (Canadian Task Force classification II-2).

SETTING

Tertiary referral hospital.

PATIENTS

One hundred fifty-five patients who had undergone videolaparoscopy were divided into 2 groups: those with endometriosis (n = 100) and those without endometriosis (n = 55).

INTERVENTIONS

The percentage of NK cells relative to peripheral lymphocytes was quantified at flow cytometry in 155 patients who had undergone laparoscopy. In addition to verifying the presence of endometriosis, stage of disease and the sites affected were also evaluated.

MEASUREMENTS AND MAIN RESULTS

The mean (SD) percentage of NK cells was higher (15.3% [9.8%]) in patients with endometriosis than in the group without the disease (10.6% [5.8%]) (p < .001). The percentage of NK cells was highest (19.8 [10.3%]) in patients with advanced stages of endometriosis and in those in whom the rectosigmoid colon was affected. In a statistical model of probability, the association of this marker (NK cells ≥11%) with the presence of symptoms such as pain and intestinal bleeding during menstruation and the absence of previous pregnancy yielded a 78% likelihood of the rectosigmoid colon being affected.

CONCLUSION

Compared with patients without endometriosis, those with endometriosis demonstrate a higher concentration of peripheral NK cells. The percentage of NK cells is greater, primarily in patients with advanced stages of endometriosis involving the rectosigmoid colon. Therefore, it may serve as a diagnostic marker for this type of severe endometriosis, in particular if considered in conjunction with the symptoms.

Immune interactions in endometriosis

Endometriosis is a common, complex gynecologic disorder characterized by the presence of endometrial glands and stroma at extrauterine (ectopic) sites. In women who develop this disease, alterations in specific biological processes involving both the endocrine and immune systems have been observed, which may explain the survival and growth of displaced endometrial tissue in affected women. In the past decade, a considerable amount of research has implicated a role for alterations in progesterone action at both eutopic and ectopic sites of endometrial growth which may contribute to the excessive inflammation associated with progression of endometriosis; however, it remains unclear whether these anomalies induce the condition or are simply a consequence of the disease process. In this article, we summarize current knowledge of alterations within the immune system of endometriosis patients and discuss how endometrial cells from women with this disease not only have the capacity to escape immunosurveillance, but also use inflammatory mechanisms to promote their growth within the peritoneal cavity. Finally, we discuss evidence that exposure to an environmental endocrine disruptor, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin, can mediate the development of an endometrial phenotype that exhibits both reduced progesterone responsiveness and hypersensitivity to proinflammatory stimuli mimicking the endometriosis phenotype. Future studies in women with endometriosis should consider whether a heightened inflammatory response within the peritoneal microenvironment contributes to the development and persistence of this disease.

Trafficking of peripheral blood CD56(bright) cells to the decidualizing uterus--new tricks for old dogmas?

CD56(bright) lymphocytes become abundant in the human uterus during every menstrual cycle, following the surge in pituitary-derived luteinizing hormone (LH), which initiates final oocyte maturation. While the uterus is host to some CD56(bright) cells prior to ovulation, the rapid increase is thought to be due to proliferation of the resident population, accompanied by recruitment of CD56(bright) lymphocytes from the circulation. The rapid increase in CD56(bright) cells is concurrent with the onset of decidualization, the transformation of uterine stromal cells into secretory decidual cells. Uterine CD56(bright) cells proliferate and differentiate to become the predominant lymphocytes of the post-ovulatory uterus. These distinct, tissue-specific natural killer (NK) cells either die prior to menses or increase in number during early pregnancy, and then decline toward the end of the first trimester. Since lymphocytes home to tissues from the circulation, we investigated mechanisms of NK cell traffic over the course of natural menstrual cycles by measuring functional interactions between CD56+ cells from blood and endothelial cells using the Stamper-Woodruff assay of lymphocyte adhesion to frozen tissue sections. While a baseline level of adhesion was maintained throughout the cycle, elevated l-selectin-dependent adhesion of peripheral blood CD56(bright) cells occurred during a peri-ovulatory window. However, there were no significant menstrual cycle-induced changes in the transcription of l-selectin, alpha 4 integrin or LFA-1, or in expression of these proteins by NK cells, suggesting that the enhanced adhesion was due to post-translational modifications of these molecules. Quantitative RT-PCR failed to amplify the message for LH receptor or the alpha or beta forms of progesterone or estrogen receptors from blood NK cell subsets. Thus, we conclude that the actions of LH, E(2,) and P(4) on NK cells that promote interactions with endothelium and potential uterine homing are indirectly mediated through the responsiveness of other cell types.

Antitumor effects of recombinant human prolactin in human adenocarcinoma-bearing SCID mice with human NK cell xenograft

To survey the immune regulatory function of recombinant human prolactin (rhPRL) and its potential application in adoptive immunotherapy, CB17-SCID mice were loaded with human colon adenocarcinoma HT-29 cells (5 x 10(5) cells/mouse, i.p.) 24 h before adoptive transfer with the purified human NK cells followed by rhPRL injection (10 mug/mouse, every other day for a total of 10 injections). Upon analysis, rhPRL did not exert any direct inhibitory effects on HT-29 cells but slightly improved the tumor cell growth both in vitro and in vivo. After SCID mice were reconstituted with human NK cells, rhPRL improved the antitumor effects of human NK cells in HT-29-bearing SCID mice, showing a prolonged survival from 70.4 to 112.1 days, and the increased survival rate from all died to 40% survival for more than 160 days. rhPRL improved the proliferation of human NK cells with or without PHA stimulation. rhPRL also directly enhanced the cytotoxicity of human NK cells against HT-29 tumor cells in 4-h coculture. The supernatant of rhPRL-stimulating NK cells inhibited the proliferation of HT-29 cells through, at least partly, the interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) in the supernatant. Thus, rhPRL administration in HT-29 tumor-bearing SCID mice promotes the antitumor effects of adoptively transferred NK cells.

Decidualization of the human endometrial stromal cell: an enigmatic transformation

Changes in human endometrium are essential to allow the establishment of pregnancy. These changes are induced in vivo by progesterone, and include appearance within the tissue of a specific uterine natural killer cell, characterized by an abundant expression of CD56. Changes also occur in the stromal cells, which undergo a characteristic decidualization reaction. Decidualized stromal cells are derived from the fibroblast-like cells within the endometrium, which maintain their progesterone receptors in the presence of progesterone. Prolonged exposure to progesterone induces a rounded cell characterized by release of prolactin and insulin-like growth factor binding protein-1 (IGFBP-1), and expression of tissue factor. Additional changes include the secretion of interleukin (IL)-15, vascular endothelial growth factor, and surface expression of zinc dependent metalloproteinases such as CD10 and CD13. In vitro, elevated intracellular cAMP as well as progesterone is necessary for decidualization. In vivo, these conditions may be provided by progesterone from the corpus luteum, by prostaglandin E, a stimulator of adenyl cyclase, and relaxin, which has recently been shown to be a phosphodiesterase inhibitor. Given the co-distribution of uterine natural killer cells and decidualized stromal cells, a mutual interaction might provide the correct regulatory environment for successful implantation, and penetration of the maternal blood vessels by trophoblastic cells.

Interleukin-6 (IL-6) expression and natural killer (NK) cell dysfunction and anergy in heart failure

Immune dysfunction has been postulated to play a role in the pathophysiology of chronic heart failure. We examined the relation between interleukin-6 (IL-6) production and natural killer (NK) cell dysfunction in patients with chronic heart failure. Sera and peripheral blood mononuclear cells (PBMCs) were collected from 82 patients with advanced heart failure. Levels of circulating NK cells and T cells were determined by flow cytometry. NK cell function was measured by standard cytotoxicity assays. IL-6 in supernatants of PBMC cultured in vitro was quantitated by an enzyme-linked immunosorbent assay. The levels of circulating NK cells were lower in patients with heart failure than in normal controls (p = 0.0037). NK cells from patients with heart failure also exhibited impaired cytolytic functions in the absence of stimuli and in response to IL-2 and IL-12 (p <0.0001 for all conditions). PBMCs from patients with heart failure produced higher levels of IL-6 in response to a T-cell stimulus than did PBMCs from healthy controls (p = 0.0012). The level of IL-6 produced by unstimulated PBMCs in patients with heart failure correlated with NK cell cytolytic impairment (p = 0.0012). These results demonstrated that PBMCs are a source of IL-6 in patients with heart failure. Production of IL-6 by PBMCs correlated with NK cell anergy to other cytokines that use signal transduction pathways that may be regulated by IL-6. These results support a model of cytokine-induced anergy in conditions that result in high systemic levels of IL-6.

Stress, stress response, and health

Components of stress and the stress response differ between men and women. The tend-and-befriend response, mediated by oxytocin and endogenous opioids, may be more applicable to women than the fight-or-flight response, which was based largely on studies of men. Even within the flight-or-flight response pattern there are sex-based differences. The HPA axis interacts with reproductive function, such as menstruation. For immune function there are sex differences as well as differences within the menstrual phase. Inclusion of men and women in stress response studies is critical. Further study is needed to clarify the influence of ovarian hormones on the stress and immune responses during the reproductive stages in women's lives, including menarche. pregnancy, and perimenopause.

Sex-associated hormones and immunity to protozoan parasites

Numerous epidemiological and clinical studies have noted differences in the incidence and severity of parasitic diseases between males and females. Although in some instances this may be due to gender-associated differences in behavior, there is overwhelming evidence that sex-associated hormones can also modulate immune responses and consequently directly influence the outcome of parasitic infection. Animal models of disease can often recreate the gender-dependent differences observed in humans, and the role of sex-associated hormones can be confirmed by experimentally altering their levels. Under normal circumstances, levels of sex hormones not only differ between males and females but vary according to age. Furthermore, not only are females of reproductive age subject to the regular hormonal cycles which control ovulation, they are also exposed to dramatically altered levels during pregnancy. It is thus not surprising that the severity of many diseases, including those caused by parasites, has been shown to be affected by one or more of these circumstances. In addition, infection with many pathogens has been shown to have an adverse influence on pregnancy. In this article we review the impact of sex-associated hormones on the immune system and the development and maintenance of immunity to the intracellular protozoan parasites Toxoplasma gondii, Plasmodium spp., and Leishmania spp.

Theories of endometriosis

Endometriosis is characterised by the presence of abnormally located tissue resembling the endometrium with glands and stroma. Several hypotheses have attempted to explain the development of such tissue. The oldest theory, that of metaplasia, suggests that under diverse influences coelomic tissue could be transformed into endometrium. The most often cited theory, that of implantation, proposes that the physiological phenomenon of endometrial reflux in the fallopian tubes during menstruation may, in certain conditions, overcome local defense mechanisms, implant, and proliferate. The peritoneal fluid in unaffected women possesses the capacity to prevent endometriotic tissue from becoming established. The reasons for the occurrence of endometriosis and its consequences (pain, sterility, adhesions) are probably numerous and involve the endometrium, the immune system (macrophages, natural killer cells), the peritoneum, and fallopian tubes. The failure to clear the peritoneal cavity of fragments of endometrium could cause a state of local inflammation with hyperactivation of macrophages secreting a variety of different compounds. Some of these compounds may bring about metaplasia of the peritoneum or the development of Mullerian residues.

Is endometriosis an endometrial disease?

Endometriosis is characterised by the presence of abnormally located tissue resembling the endometrium with glands and stroma. Several hypotheses have attempted to explain the development of such tissue. The most often cited theory, that of implantation, proposes that the physiological phenomenon of endometrial reflux in the fallopian tubes during menstruation may, in certain conditions, overcome local defense mechanisms, implant, and proliferate. The implantation theory does not explain why endometriosis will develop only in approximately 10-15% of women, while the reflux of endometrial tissue via the fallopian tubes during menstruation is a quasi-universal phenomenon. The endometrium of women affected by endometriosis could be abnormal compared with endometrium of healthy women. The abnormal endometrium could be able to protect itself from harmful effects of immune cells by expressing specific antigens, by harbouring a different immune cell population and by synthetizing and secreting immunosuppressive factors. Several others characteristic features of endometrium have been described in women with endometriosis: (1) production of its own estrogens in too heavy amount; (2) aptitude for setting up on peritoneum; (3) tendencies to proliferate and to invade tissue; (4) aggressiveness for the peritoneum; (5) auto-protection from physiological apoptosis; (6) abnormal expression of heat shock proteins; and (7) excessive angiogenesis.

Menopause and estrogen deficiency as a risk factor in dementing illness: hypothesis on the biological basis

The positive efficacy of estrogen replacement therapy (ERT) in the treatment of neurodegenerative disorders such as Alzheimer's disease (AD) is a matter of intense debate among clinicians and neuroscientists. The experimental and preliminary clinical evidence supporting the use of ERT are based on epidemiological data and on the study of the effect of estrogens on several aspects of brain homeostasis, including the modulation of neurotransmitters and vascular changes. In spite of numerous data available the mechanisms underlying the putative estrogen effects in neurodegenerative diseases are largely unknown. The aim of this paper is to discuss and elaborate on some of the hypotheses and controversial findings currently present in this field.

Innate immunity to Toxoplasma gondii is influenced by gender and is associated with differences in interleukin-12 and gamma interferon production

Given that differences between the sexes in relative susceptibility to parasitic infections have been noted, this study further elucidates the mechanisms responsible by demonstrating that male SCID mice are more resistant than female mice to infection with Toxoplasma gondii and that this difference correlates with enhanced innate immune responses in these animals. Male SCID mice exhibited longer survival times, lower parasite burdens, and less severe pathological changes postinfection. An immunological basis for these differences is demonstrated in that these animals produced interleukin-12 more rapidly and exhibited higher levels of gamma interferon earlier postinfection.