Peritoneal fluid interleukin-6 in women with chronic pelvic pain

Interleukin in endometriosis-associated infertility-pelvic pain: systematic review and meta-analysis

The objective is to study the significance of altered interleukin levels in endometriosis-related infertility or pelvic pain. The present systematic review and meta-analysis includes a discussion on the roles of interleukin in the physiopathology of endometriosis-associated infertility and/or pelvic pain. We included all studies in which interleukins in peritoneal fluid, follicular fluid or serum from patients were measured and that correlated the findings with either peritoneal or deep endometriosis-associated infertility or pelvic pain. For the meta-analysis, we selected studies on the following cytokines: interleukin-1 (IL-1), interleukin-6 (IL-6) and interleukin-8 (IL-8). Endometriosis is a chronic inflammatory disease. Inflammatory processes clearly participate in the etiology of endometriosis. Cytokines are mediators of inflammation, and increase in their concentration in plasma or other body fluids signals the presence and extent of tissue lesions. A number of studies have reported on the association between higher cytokine levels and progression or maintenance of endometriosis and coexisting infertility or pelvic pain. The results of the analyses support that an association exists between elevated serum IL-6 and/or IL-8 concentrations and the occurrence of endometriosis-associated infertility. Such association was not found for endometriosis-associated pain. In spite of accumulated evidence on the association of pro-inflammatory cytokines and endometriosis, it still is not clear if and how these mediators participate in the physiopathology of endometriosis-associated infertility or pelvic pain, in part due to poor quality of the evidence established in the vast majority of interleukins and challenges in endometriosis research reproducibility. In summary, the results of the analyses support that an association exists between elevated serum IL-6 and/or IL-8 concentrations and the occurrence of endometriosis-associated infertility.

Endometriosis and the Fallopian Tubes: Theories of Origin and Clinical Implications

Endometriosis is a common, oestrogen driven chronic condition, where endometrium-like epithelial and stromal cells exist in ectopic sites. At present, no curative treatments are available and the existing evidence for disease progression is conflicting. The pathogenesis is still unknown and evidently complex, as mechanisms of initiation may depend on the anatomical distribution of endometriotic lesions. However, amongst the numerous theories and plethora of mechanisms, contributions of the fallopian tubes (FT) to endometriosis are rarely discussed. The FT are implicated in all endometriosis associated symptomatology and clinical consequences; they may contribute to the origin of endometriotic tissue, determine the sites for ectopic lesion establishment and act as conduits for the spread of proinflammatory media. Here, we examine the available evidence for the contribution of the human FT to the origin, pathogenesis and symptoms/clinical consequences of endometriosis. We also examine the broader topic linking endometriosis and the FT epithelium to the genesis of ovarian epithelial cancers. Further studies elucidating the distinct functional and phenotypical characteristics of FT mucosa may allow the development of novel treatment strategies for endometriosis that are potentially curative.

Cellular Components Contributing to Fibrosis in Endometriosis: A Literature Review

Endometriosis-related fibrosis represents a complex phenomenon with underlying mechanisms yet to be clarified. Fibrosis is consistently present in all disease forms and contributes to classic endometriosis-related symptoms of pain and infertility. The purpose of this literature review was to examine the role of various cellular populations and biologic mechanisms and signaling pathways in inducing fibrogenesis of endometriotic lesions. A search was performed through PubMed and MEDLINE for animal and human studies published in English in the last 23 years that examined fibrosis in superficial, ovarian, and deep infiltrating endometriosis. The main cell types found to be involved in the development of fibrosis were platelets, macrophages, ectopic endometrial cells, and sensory nerve fibers. Interactions among each of the cell types contribute to the production of fibrosis through the production of soluble factors, mostly transforming growth factor-β but also other cytokines and neuropeptides. Cell types known to be critical to the pathophysiology of endometriosis also contribute to fibrogenesis, thus supporting the theory that fibrosis is an inherent part of endometriosis.

The Relationship Between Plasma Inflammatory Cytokines and Labor Pain

BACKGROUND

Proinflammatory cytokines are increased in maternal blood at term pregnancy and are associated with cervical ripening and the initiation of labor. We hypothesize that maternal plasma cytokines also affect the sensitivity to labor pain.

METHODS

By using a previously validated model describing labor pain, we used a deidentified database derived from healthy nulliparous parturients who delivered singleton pregnancies at term. Numerical rating scores for pain were recorded after the onset of regular contractions using an 11-point scale. Maternal blood was drawn for the measurement of interleukin (IL)-1β, IL-4, IL-6, IL-8, and IL-10; interferon-γ; and tumor necrosis factor-α on admission or at the onset of painful contractions, whichever occurred later. Individual demographic, physiognomic, and cytokine variables that significantly affected labor pain at P < 0.05 were reported and included stepwise into a multivariable model.

RESULTS

One hundred sixty parturients provided 411 numerical analog scores for pain that were evaluated with our model. The relationship between numerical analog scores and cervical dilation was significantly affected by the type of membrane rupture, membrane status, induction, oxytocin administration, maternal race, and plasma IL-1β concentration as individual variables. Only the association between the highest IL-1β quartile and slower acceleration of pain during labor remained significant in the multivariate model (P = 0.0003). Women with IL-1β concentration in the highest quartile arrived at the labor room with a more dilated cervix than those with lower plasma concentrations of IL-1β (5.1 ± 3.0 vs 4.1 ± 2.6 cm; P < 0.02) and had faster labor progress.

CONCLUSIONS

Inflammatory cytokines including IL-1β play a role in cervical ripening. High maternal plasma concentrations of IL-1β may serve as a marker of advanced cervical ripening and readiness for labor that proceeds with less pain.

Distinct peritoneal fluid ghrelin and leptin in infertile women with endometriosis and their correlation with interleukin-6 and vascular endothelial growth factor

OBJECTIVE

The objective of the present study was to evaluate the levels of leptin, ghrelin, interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) in peritoneal fluid in patients with endometriosis and infertility, and study their correlation.

DESIGN AND SETTING

This cross-sectional study included women undergoing diagnostic and/or therapeutic laparoscopy for endometriosis with chief complaint of infertility and/or pain at a tertiary care hospital. Based upon laparoscopic and histopathological findings, patients were categorized as with endometriosis and no endometriosis. Of the 50 patients with infertility (age 23-41 years), 19 had endometriosis while 31 had no endometriosis. The markers were assessed using ELISA kits.

RESULTS

The median levels of leptin in patients with endometriosis (10.20 ng/mL) were higher (p = 0.04) and median levels of ghrelin in patients with endometriosis (150.4 pg/mL) were lower (p = 0.037) versus patients with no endometriosis (5.07 ng/mL and 229.6 pg/mL, respectively). The median levels of IL-6 and VEGF in patients with endometriosis were not different between the groups. The correlation analyses showed that leptin levels and IL-6 were positively correlated (p = 0.0001).

CONCLUSIONS

The results suggest that ghrelin and leptin might play a key role in pathophysiology of endometriosis, and leptin is associated with inflammation in endometriosis.

Enhanced inflammatory activity of endometriotic lesions from the rectovaginal septum

Endometriosis is characterised by the growth of ectopic lesions at multiple locations outside the uterine cavity and may be considered a collection of distinct but related conditions. The exact aetiology of endometriosis is still not clear although a role for inflammation is increasingly accepted. We therefore investigated the inflammatory activity of eutopic tissue and that of the matching ectopic lesions from different locations by measuring the genetic expression of inflammatory chemokines and cytokines. The gene expression in matching eutopic and ectopic tissue was compared, as was the gene expression in lesions from different locations. A significantly higher mRNA expression of the chemokines ENA-78 and RANTES and the cytokines IL-6 and TNFα was observed in endometriotic lesions of the rectovaginal septum (RVS) compared to that of matching eutopic tissue. Comparisons across lesion locations showed a significantly higher expression of IL-6 and TNFα in the RVS compared to lesions from either the ovaries or the peritoneum. These results show that the production of some inflammatory chemokines and cytokines is significantly increased in the ectopic endometrial tissue compared to matching eutopic tissue. Furthermore, IL-6 and TNFα are produced in significantly higher quantities in RVS lesions compared to other lesions.

In vitro model of stromal and epithelial immortalized endometriotic cells

Endometriosis is a relatively common chronic gynecologic disorder that usually presents with chronic pelvic pain or infertility. It results from implantation of endometrial tissue outside the uterine cavity. Despite its frequency and its impact on quality of life, the understanding of pathogenesis of endometriosis remains incomplete and its treatment remains controversial. In this work, we established a suitable in vitro model system of immortalized human endometriotic cell line taking advantage of the human telomerase reverse transcriptase. The results demonstrate that these cells retain the natural characteristics of endometrial cells in term of phenotype and of functional expression of estrogen and progesterone receptors, without chromosomal abnormalities. In conclusion, these cells are potentially useful as an experimental model to investigate endometriosis biology.

Analysis of cytokines in the peritoneal fluid of endometriosis patients as a function of the menstrual cycle stage using the Bio-Plex® platform

OBJECTIVE

Endometriosis is a painful disease affecting 10-15% of reproductive-age women. Concentrations of several cytokines and angiogenic factors in peritoneal fluid (PF) have been found to correlate with the severity of the disease. However, levels of some analytes vary across the menstrual cycle, and an ideal biomarker of endometriosis has not yet been identified. We have compared the PF concentrations of different cytokines in proliferative and secretory phases in women with and without the disease using the Bio-Plex platform.

METHODS

PF was aspirated during laparoscopy (N = 133) and the PF concentrations of 18 cytokines from Bio-Plex panels I and II determined with the serum protocol.

RESULTS

Increased PF concentrations of IL-6, IL-18, eotaxin, and MCP-1 were found in endometriosis with no changes with menstrual cycle. Levels of IL-12(p70), ICAM-1, and GRO-α were higher in the secretory phase, while eotaxin concentrations were lower.

CONCLUSION

Of the 18 cytokines tested, IL-6, IL-18 and MCP-1 were the best PF markers of endometriosis.

Peritoneal cytokines and adhesion formation in endometriosis: an inverse association with vascular endothelial growth factor concentration

OBJECTIVE

To evaluate inflammatory/angiogenic cytokines-interleukin-1β (IL-1β), IL-6, IL-8, IL-12, interferon-γ (IFN-γ), tumor necrosis factor (TNF), and vascular endothelial growth factor A (VEGF-A)-in the peritoneal fluid of patients with endometriosis in relation to the occurrence and severity of pelvic adhesions and in control women without pelvic pathology.

DESIGN

Case-control study.

SETTING

University research institution and hospital.

PATIENT(S)

Sixty-five women with laparoscopically and histopathologically confirmed endometriosis, including 40 women with pelvic adhesions, and 37 control women without pelvic pathology.

INTERVENTION(S)

Peritoneal fluid aspirated during routine diagnostic laparoscopic examination.

MAIN OUTCOME MEASURE(S)

Cytokines evaluated in the peritoneal fluid via specific enzyme-linked immunosorbent assays.

RESULT(S)

Endometriosis and the revised American Fertility Society score of this disease were associated with statistically significantly increased levels of peritoneal IL-6 and IL-8 whereas the incidence and score of endometriosis-related pelvic adhesions were negatively associated with increased levels of VEGF-A. Notably, the concentration of VEGF-A predicted adhesion development and severity after adjustment for endometriosis severity. The adhesion score also correlated with increased levels of IL-6; however, after adjustment for endometriosis severity, the effect of this cytokine was no longer statistically significant.

CONCLUSION(S)

Increased levels of VEGF-A may be associated with a decreased rate of pelvic adhesion formation in the course of endometriosis.

Endometriosis and mechanisms of pelvic pain

Endometriosis remains an enigmatic disorder in that the cause, the natural history, and the precise mechanisms by which it causes pain are not completely understood. The pain symptoms most commonly attributed to endometriosis are dysmenorrhea, dyspareunia, and chronic pelvic pain. Pain may be due to nociceptive, inflammatory, or neuropathic mechanisms, and there is evidence that all 3 of these mechanisms are relevant to endometriosis-associated pelvic pain. It is proposed that the clinically observed inconsistencies of the relationships of endometriosis severity and the presence or severity of pain are likely due to variable roles of different pain mechanisms in endometriosis. A better understanding of the roles of nociceptive, inflammatory, and neuropathic pain in endometriosis is likely to improve the treatment of women with endometriosis-associated pelvic pain.

Is There a Role for Acupuncture in Endometriosis Pain, Or ‘endometrialgia’?

Endometriosis is a common cause of pelvic pain in women, many of whom suffer a progression of symptoms over their menstrual life. Symptoms may include combinations of abnormal visceral sensations and emotional distress. Endometriosis pain, or ‘endometrialgia’ often has a negative influence on the ability to work, on family relationships and sense of worth.

Endometrialgia is often considered to be a homogeneous sensory entity, mediated by a specialised high threshold sensory system, which extends from the periphery through the spinal cord, brain stem and thalamus to the cerebral cortex. However, multiple mechanisms have been detected in the nervous system responsible for the pain including peripheral sensitisation, phenotypic switches, central sensitisation, ectopic excitability, structural reorganisation, decreased inhibition and increased facilitation, all of which may contribute to the pain.

Although the causes of endometrialgia can differ (eg inflammatory, neuropathic and functional), they share some characteristics. Endometrialgia may be evoked by a low intensity, normally innocuous stimulus (allodynia), or it may be an exaggerated and prolonged response to a noxious stimulus (hyperalgesia). The pain may also be spontaneous in the absence of any apparent peripheral stimulus.

Oestrogens and prostaglandins probably play key modulatory roles in endometriosis and endometrialgia. Consequently many of the current medical treatments for the condition include oral drugs, like non-steroid anti-inflammatory drugs, contraceptives, progestogens, androgenic agents, gonadotrophin releasing hormone analogues, as well as laparoscopic surgical excision of the endometriosis lesions. However, management of pain in women with endometriosis is currently inadequate for many. Possibly acupuncture and cognitive therapy may be used as an adjunct.

Endometriosis and tissue factor

Tissue factor (TF), is a cellular receptor that binds the ligand factor VII/VIIa to initiate the blood coagulation cascade. In addition to its role as the initiator of the hemostatic cascade, TF is known to be involved in angiogenesis via an interaction with factor VIIa and protease-activated receptor-2 (PAR-2). In this article we review previous studies from our laboratory demonstrating that the pattern and level of TF expression is altered in multiple cell types derived from eutopic and ectopic endometrium from women with endometriosis compared with normal endometrium. We posit that the inflammatory environment that occurs in ectopic and eutopic endometrium from patients with disease results in high TF expression that in turn, signals via PAR-2 to further produce inflammatory cytokine or chemokine production and macrophage recruitment. Thus, our studies suggest that TF might be an ideal target for therapeutic intervention in endometriosis.

Is Endometriosis Associated with Systemic Subclinical Inflammation?

Endometriosis is a pelvic inflammatory process with altered function of immune-related cells and increased number of activated macrophages in the peritoneal environment that secrete various local products, such as growth factors and cytokines. The elevation of cytokines and other factors in the peritoneal fluid is accompanied by the elevation of similar factors, such as CRP, SAA, TNF-alpha, MCP-1, IL-6, IL-8 and CCR1, in the peripheral blood of patients with endometriosis. CD44+ and CD14+ monocytes are significantly increased, while CD3+ T lymphocytes and CD20+ B lymphocytes show modest, but significant decrease in peripheral blood of women with endometriosis. This indicates that endometriosis could be viewed as a local disease with systemic subclinical manifestations. This review provides an overview of data on the changes of various factors in peripheral blood and their potential use as diagnostic tools in patients with endometriosis.

Higher activity by opaque endometriotic lesions than nonopaque lesions

BACKGROUND

Higher activity by early endometriosis than advanced endometriosis has been reported. However, the pattern of activity in individual colored endometriotic lesions in pelvic cavity is unknown. We investigated the variation in activity of the different colored morphologic lesions as proposed by the current revised American Society of Reproductive Medicine (ASRM) classification in women with endometriosis.

METHODS

Peritoneal fluid (PF) and biopsies were collected during laparoscopy from 45 infertile women with pelvic endometriosis and 15 women without endometriosis. PF concentrations of hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), interleukin-6 (IL-6) and monocyte chemotactic protein-1 (MCP-1) were measured by enzyme-linked immunosorbent assay (ELISA). The immunohistochemical staining of HGF and proliferating cell nuclear antigen (PCNA) in opaque and nonopaque endometriotic lesions was examined using respective antibodies, and a computer-analyzed modified quantitative-histogram score (Q-H score) was used to quantify the immunoreaction.

RESULTS

Opaque red lesions were defined as nontransparent lesions, including polypoid excrescence, blood bleb or ecchymosis, and nonopaque lesions were defined as translucent or transparent lesions, including vesicular bleb or clear papule. The women with endometriosis containing dominant opaque red lesions showed significantly higher PF concentrations of HGF, VEGF, IL-6 or MCP-1 than those with either nonopaque lesions or black lesions or control women. There was no difference in any of these cytokine or chemokine levels between women harboring nonopaque lesions and black lesions. Interestingly, PF concentrations of all these markers were significantly reduced in women containing true black lesions and true white lesions after excluding the presence of coexisting red spot from dominant black or white lesions. In a parallel fashion, the immunoexpressions of HGF and PCNA in intact tissue as shown by the Q-H score were significantly stronger in the opaque red lesions than in the nonopaque lesions or black lesions.

CONCLUSIONS

Opaque red lesions display a higher activity than with nonopaque red lesions in both PF and intact tissue. This indicates different histogenesis in their generation in the pelvic cavity.

Association of interleukin-6 and estradiol with hepatocyte growth factor in peritoneal fluid of women with endometriosis

BACKGROUND

Different cytokines and ovarian steroid hormones have been reported to regulate the growth and maintenance of endometriosis. We determined the relationship between peritoneal fluid concentrations of interleukin-6, ovarian steroids and hepatocyte growth factor in different revised American Fertility Society (AFS) staging and morphologic appearances of endometriosis.

METHODS

Peritoneal fluid was collected from 30 women with endometriosis and 20 women without endometriosis during laparoscopy, and hepatocyte growth factor, interleukin(IL)-6 and ovarian steroids were measured in peritoneal fluid. The concentrations of hepatocyte growth factor and IL-6 in peritoneal fluid were measured by ELISA, and that of estradiol and progesterone by using the immulyze-enzyme amplified luminescence system. Changes in peritoneal fluid concentrations of hepatocyte growth factor, IL-6, estradiol and progesterone in different stages and morphologic appearances of endometriosis were examined to demonstrate their differences in early and advanced endometriosis.

RESULTS

Peritoneal fluid levels of hepatocyte growth factor in women with stage I-II endometriosis were significantly higher than in both women with stage III-IV endometriosis and without endometriosis. A similar significant increase in stage I-II endometriosis was also observed for IL-6 and estradiol. When we divided the women according to different morphologic appearances of endometriosis, we found significantly higher concentrations of hepatocyte growth factor (HGF), IL-6, estradiol and progesterone in women containing red lesions compared with other pigments or without endometriosis. A positive correlation was observed between peritoneal fluid levels of IL-6 and hepatocyte growth factor only but not between other markers. Although estradiol levels in peritoneal fluid showed an increased tendency to elevate in the proliferative phase of endometriosis women, hepatocyte growth factor and progesterone displayed higher concentrations in the secretory phase of the menstrual cycle. After adjusting different variables in peritoneal fluid, multiple analysis of covariance indicated that hepatocyte growth factor levels in peritoneal fluid were independently involved in the red morphologic activity of endometriosis.

CONCLUSIONS

Early staging and red color appearance of endometriosis are associated with the elevation in peritoneal fluid concentrations of hepatocyte growth factor, IL-6 and estradiol, demonstrating the combined effect of these cytokines and ovarian steroids in the production of hepatocyte growth factor from endometrial tissues in active endometriosis.