Synergy between Th1 and Th2 responses during endometriosis: A review of current understanding.

Endometriosis is widely perceived as an estrogen-dependent chronic disorder with infertility and pelvic pain. Although the etiology of endometriosis has remained elusive, many studies have proclaimed the relevance of immune system disorders with endometriosis. With the discovery that the dysregulation of multiple biological functions in endometriosis is caused by the aberrant differentiation of T helper cells, a shift towards Th2 immune response may account for the disease progression. This review attempts to present mechanisms of cytokines, chemokines, signal pathways, transcription factors and some other factors related with the derivation of Th1/Th2 immune response involved in the development of endometriosis. The current understanding of treatment approaches and potential therapeutic targets will also be outlined with brief discussion.

DNA damage and effects on antioxidative enzymes in zebra fish (Danio rerio) induced by atrazine.

The effect of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1, 3, 5-triazine) on the activity of some antioxidative enzymes (superoxide dismutase, SOD; catalase, CAT; and guaiacol peroxidase, POD) and DNA damage induced by atrazine were investigated in zebra fish (Danio rerio). Zebra fish were exposed to four different concentrations of atrazine (0, 2.5, 5, and 10 mg/L) for 7, 14, and 21 days, with three replicates of 10 fishes per treatment. Compared to the controls, the SOD activity in the 2.5 mg/L treatment was markedly stimulated in 21 days, while the SOD activities in the 5 mg/L treatment was stimulated at first and then inhibited. The change of CAT activity at 2.5 mg/L was similar to the SOD activity at 2.5 mg/L. The POD activities in the 2.5, 5, and 10 mg/L treatment were markedly higher on days 14 and 21 compared with the controls. The olive tail moments of single-cell gel electrophoresis (SCGE) of zebra fish enhanced after treatment of different doses on days 7, 14, and 21, and significant differences were found compared to the controls. In conclusion, these findings showed the effect regularity of atrazine to zebra fish, and also provide the basis for the future research of adverse effects induced by atrazine in aquatic ecosystems.

Regulatory T cells induce polarization of pro-repair macrophages by secreting sFGL2 into the endometriotic milieu.

An increased number of highly active regulatory T cells (Tregs) and macrophages has been found in peritoneal fluid from women with endometriosis. Here, we show that the level of Tregs-derived soluble fibrinogen-like protein 2 (sFGL2) increases in the peritoneal fluid of women with endometriosis. Higher expression of FGL2 and its receptor CD32B is observed in eutopic endometrium and ectopic tissues. The production of sFGL2 in Tregs may be enhanced by several cytokines. sFGL2 selectively induces pro-repair macrophage polarization mainly through the activation of the SHP2-ERK1/2-STAT3 signaling pathway, and the suppression of the NF-κB signaling pathway. Furthermore, sFGL2 induces a much higher level of metallothionein (MT) expression that in turn facilitates pro-repair macrophages polarization. sFGL2-induced pro-repair macrophages promote Th2 and Tregs differentiation, creating a positive feedback loop. These findings suggest that sFGL2 secreted by Tregs skews macrophages toward a pro-repair phenotype via SHP2-ERK1/2-STAT3 signaling pathway, which is involved in the progression of endometriosis.

Correction: Trophoblast-derived CXCL16 induces M2 macrophage polarization that in turn inactivates NK cells at the maternal-fetal interface.

In this article, published online 27 March 2018, in the "ACKNOWLEDGEMENTS", it should be supplemented as follows: "This study was funded by a grant from the National Natural Science Foundation of China, number 81490744, awarded to Da-Jin Li." The authors regret the omission.

Trophoblast-derived CXCL16 induces M2 macrophage polarization that in turn inactivates NK cells at the maternal-fetal interface.

Decidual macrophages (dMΦ) are distinct from the conventional macrophages present in other tissues and express M2 macrophage markers, but the molecular mechanisms of formation and the roles of M2 MΦ during pregnancy have not been completely elucidated. The crosstalk between decidual natural killer cells (dNK) and dMΦ plays an important role in the maintenance of maternal-fetal immune tolerance. Here, CXCL16 derived from first-trimester trophoblast cells induces the polarization of human M2 macrophages. The M2 MΦ polarized by CXCL16 exhibit decreased interleukin-15 production, which facilitates the inactivation of NK cells. The cytotoxicity of NK cells is attenuated by the CXCL16-polarized M2 MΦ. The data shown in the present study provide evidence to support the hypothesis that CXCL16 secreted by trophoblast cells is a key molecule involved in decidual M2 MΦ polarization, which in turn regulates the killing ability of NK cells, thereby contributing to the homeostatic and immune-tolerant milieu required for successful fetal development.

Fibroblast Growth Factor 7 Regulates Proliferation and Decidualization of Human Endometrial Stromal Cells via ERK and JNK Pathway in an Autocrine Manner.

Decidualization is an essential activity of the endometrium in pregnancy, but the molecular mechanisms involving the initiation and maintenance have not yet been clarified. In the present study, we examined the expression of fibroblast growth factor 7 (FGF7) in endometria, normal decidua, and abortion decidua from miscarriage by immunohistochemistry. We analyzed the expression of FGF7 and FGFR2 and the levels of phosphorylated extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinase (JNK) in endometrial stromal cells (ESCs), and decidual stromal cells (DSCs) from early pregnancy or miscarriage by In-Cell Western assay. The effect of FGF7 on the proliferation of decidualized ESCs was determined by bromodeoxyuridine proliferation assay. Our results show that the expression of FGF7 protein in the normal decidua is obviously higher than that of the endometrium and the abortion decidua, and the expression of FGF7 in the abortion decidua was still higher than that in the endometrium. The FGF7 expression in ESCs is significantly increased after stimulation with a combination of progesterone and 17ß-estradiol or 8-bromoadenosine 3',5'-cyclic monophosphate for 12 days. The expression of FGF7 and FGFR2 and the levels of phosphorylated ERK and JNK in DSCs from normal decidua are markedly higher compared with that in ESCs from the endometrium, and the DSCs from abortion decidua had lower expression than DSCs from normal decidua but still higher than ESCs from the endometrium. Our results suggest that FGF7 may stimulate ESCs proliferation and insulin-like growth factor-binding protein 1 and prolactin expressions through ERK and JNK signal pathways in an autocrine manner.

The CCL17-CCR4 axis between endometrial stromal cells and macrophages contributes to the high levels of IL-6 in ectopic milieu.

Endometriosis is a chronic inflammatory disease characterized by the elevation of proinflammatory cytokines, such as IL-6, in the peritoneal fluid. However, the precise mechanism of the highly elevated IL-6 levels in ectopic milieu remains unclear. The aim of this study was to investigate whether the cross talk between endometrial stromal cells (ESCs) and macrophages contributes to the elevated IL-6 production. Samples of endometrium and ectopic tissues were obtained from patients with or without endometriosis. The peripheral blood samples were collected from healthy volunteers. Enzyme-linked immunosorbent assay (ELISA) was for IL-6 levels in peritoneal fluid and cell culture supernatant. In-Cell Western assay was used for protein expression of CCL17 and phosphorylation levels of ERK, JNK, and P38. Immunohistochemistry was performed on normal, eutopic endometrium and ectopic tissues to analyze CCL17 expression. Flow cytometry was applied to detect the expression of CCR4, IL-6, and the phosphorylation levels of NF-κB. Patients with endometriosis have higher levels of IL-6 in peritoneal fluid compared to the control. The co-culture of ESCs and macrophages produce more IL-6 than cultured alone, respectively. The eutopic endometrium had significantly higher expression of CCL17 compared to normal endometrium, and the ectopic tissues had the highest expression. IL-6 induced CCL17 secretion in ESCs via activating JNK signaling pathway, CCL17 upregulated the expression of its receptor CCR4 on macrophages. Furthermore, CCL17-CCR4 axis subsequently led to excessive IL-6 production in macrophages by activating NF-κB. These findings suggest that the cross talk between ESCs and macrophages promotes the expression of CCL17 in ESCs and CCR4 on macrophages, which contributes to the high levels of IL-6 in ectopic milieu.

Fractalkine/CX3CR1 is involved in the pathogenesis of endometriosis by regulating endometrial stromal cell proliferation and invasion.

PROBLEM: Chemokines have been reported to play a sovereign role in the establishment and progression of endometriosis. Fractalkine is a chemokine that is upregulated in many inflammatory diseases including endometriosis. Fractalkine functions as a chemotactic role for lymphocytes and monocytes. In this study, we investigated the role of fractalkine/CX3CR1 in the pathogenesis of endometriosis. METHOD OF STUDY: In this study, immunohistochemistry was performed on normal endometrium (taken from controls), eutopic endometrium (taken from patients with endometriosis), and ectopic tissues to analyze fractalkine/CX3CR1 expression. The levels of fractalkine in peritoneal fluid and the cell culture supernatant were examined by enzyme-linked immunosorbent assay (ELISA). Bromodeoxyuridine (BrdU) cell proliferation assay was applied to detect the proliferation of endometrial stromal cells (ESCs). The invasion of ESCs was measured by transwell invasion assay. The protein levels of Bcl2, MMP2, MMP9, p-AKT/AKT, p-p38/p38, p-JNK/JNK, and p-ERK/ERK were analyzed by Western blot. RESULTS: We found that the eutopic endometrium had significantly higher expression of fractalkine and CX3CR1 compared to normal endometrium, and the ectopic tissues had the highest expression. The concentrations of fractalkine in peritoneal fluid of endometriosis patients were obviously higher than that of the control and correlate very well with the severity of endometriosis. Fractalkine enhanced ESCs proliferation and invasion via activating AKT and p38 signal pathways. Moreover, high concentration of estradiol (10(-7) , 10(-6)  mol L(-1) ) induced fractalkine expression while high concentration of progesterone (10(-6) , 10(-5)  mol L(-1) ) inhibited fractalkine expression in ESCs. CONCLUSION: The results revealed that the high levels of fractalkine in ectopic milieu promoted proliferation and invasion of ESCs through activating AKT and p38 signal pathways. Estradiol has a stimulating effect on the expression of fractalkine. The present results increase our understanding of the significance of fractalkine in the progression of endometriosis and shed some lights on the targeted fractalkine/CX3CR1 therapies.