Expression Of Interleukin-6 And Its Receptors In Endometriosis

BACKGROUNDEndometriosis (EMs) is a common gynecologic problem with a multidimensional etiology, including hereditary, hormonal and immunologic factors. The exactly etiology is still unknown, but a local pelvic inflammatory process with altered function of immune-related cells and altered levels of cytokines in the peritoneal cavity has been detected and involved in the development and progression of EMs.Interleukin-6 (IL-6) was a multiple bioactive cytokine, elevated in peritoneal fluid (PF) of women with EMs. The action mechanism of IL-6 was complicated and the association with the grade of EMs was still indefinite. Macrophages were the predominant cell type in PF. Many investigations showed activated macrophages in PF of women with EMs significantly increased and secreted more cytokines include IL-6 . In the meanwhile, the adhesive function of macrophages were reduced. Increased PF concentrations and in vitro macrophage production of IL-6 have been reported in patients with EMs, suggesting that peritoneal macrophages are the major source of IL-6.IL-6 exerts multiple bioactivities through its receptor (IL-6R). IL-6R is belongto immunprotein superfamily receptor, combining the characteristics of hemopoiesis superfamily receptor. It consists of two components: subunit A (ligand-binding subunit, IL-6Ra, or CD126) and subunit B (the signal transducer subunit, glycoprotein, gp130). CD126 is specific for IL-6 but gp130 is a signal transduction molecule common to the receptor complexes of IL-6,IL-10,IL-11, leucocyte inhibitory factor(LIF), and ciliary neurotrophic factor(CNTF). IL-6 first binds to IL-6Ra and the combination of IL-6-IL-6Ra induces the structure changes of gpl30 and then couples with gp130, the complex formation activates PTK and NF-IL6, resulting in cellular functional response.Membrane binding receptor (mIL-6R) and soluble receptor (sIL-6R) are two forms of IL-6R. Extensively expression of mIL-6R in multiple cells and extensively existing of sIL-6R in kinds of body fluid were observed. Production of sIL-6R were considered by two ways: hydrolysis of mIL-6R by protease and synthesis from mRNA that encodes sIL-6R existing in body fluids. Complex of SIL-6R-IL-6 acts as an agonist of IL-6. Widespread expression of gp130 enlarged effect spectra of tissues and cells, thus more extensively educed the multifunctional biological effects of IL-6. The unique property of sIL-6R that mediates and enhances the biological purpose of IL-6 plays an important role in human disorders.Limit literatures reported in the past years about the role of IL-6R in EMs. IL-6 and sIL-6R act as a growth-regulatory signal for human endometrial stromal cells in a dose- and cell-density-dependent inhibition. Endometrial stromal cells resisted to IL-6 and sIL-6R correlating with weak expression of IL-6R. Dysregulation of IL-6 response plays a role in EMs. A few studies showed discordant expression of sIL-6R in EMs.OBJECTIVESIn the present study, we detected the number of activated macrophages and their expression of mIL-6R in PF with or without EMs and also the levels of IL-6 and sIL-6R in PF and plasma were detected, in order to evaluate the roles of IL-6R (mIL-6R and sIL-6R ) and the potential mechanism of IL-6 in the pathogenesis of EMs.MATERIALS AND METHODS1. SubjectsThe study group comprised women with EMs confirmed by laparoscopy and histologic examination, staged into two groups according to the r-AFS, group A(stage I-II:19 cases ) and group B(stage III-IV:28 cases). The control group comprised women with benign ovarian cystic tumours, uterine malformation confirmed by laparoscopy or histologic examination.2. SamplesPlasma samples: Peripheral blood was collected in EDTA tube before laparoscopy and plasma was stored in - 70℃ for ELISA detection.PF samples: PF was collected at the start of laparoscopy, the supernatant fluid was stored in -℃ for ELISA detection and the macrophages were isolated for flow cytometry test(FCM).3. MethodsFCM: The double staining of PF samples with CD14-FITC and CD126-PE-labeled monoclonal antibody were evaluated by FCM. ELISA: double antibody sandwiched ELISA kits were used to detect the levels of IL-6 and sIL-6R in PF and plasma.4. Statistics analysisDates were presented as mean ±SEM and the levels of IL-6 in PF were dealed with LOG. ANOVA test, Student-Newman-Keuls test and linear correlation test were used for Statistical analysis. Two tails test with P < 0.05 was considered statistically significant. All data were managed with SPSS 13.0 software packageRESULTS1. Advanced expression of CD14+,CD126+ and CD14+/CD126+ in two EMs groups (P < 0.05)compared with control group but no difference between these two EMs groups (P>0.05) .2. Linear correlation between CD14+and CD126+ , CD14+and CD14+/CD126+, CD126+ and CD14+/CD126 , r=0.657, 0.698, 0.991 (P < 0.05)3. Ascendant tendency of the ratios of CD126+ /CD14+ cells in CD14+ cells, but nearly 99% CD126+ cells expressed on CD14+ cells4. Elevated levels of IL-6 in two EMs groups (P < 0.05 )but elevated levels of SIL-6R only in group B in PF (P<0.05 ).5. Increased levels of IL-6(P<0.05 ) and decreased levels of sIL-6R in group B in plasma(P<0.05).6. No definite correlation between IL-6 concentration in PF and the expression of CD14+, CD126+ and CD14+/ CD126+.7. Different tendency of the elevated IL-6 level and sIL-6R level in PF8. Elevated levels of IL-6 accompanied by reduced concentration of sIL-6R in PF.CONCLUSIONS1. Peritoneal macrophages were obviously increased in PF with EMs and mayinvolved in the pathogenesis of EMs.2. IL-6 may exerts its biological effect mainly through binding to the mIL-6R ofmacrophages in PF.3. Peritoneal macrophages were not only the main original cells but also the major target cells of IL-6, and may promoted the development of EMs by autocrine loop of IL-6.4. Increased sIL-6R concentration in PF involved in EMs, and may correlated to the severity of EMs.5. Increased level of sIL-6R in PF was companied by decreased level in PB, butdid not correlate to increased IL-6 level in PF..6. Increased levels of IL-6 in PF plays more important role in EMs than that in PB, but shows no correlation to the grades of EMs.