The Role And Mechanism Of CXCL16/CXCR6 Chemokine Axis In The Pathogenesis Of Endometriosis

BackgroundEndometriosis(EMs)referred to the growth of endometrial glands and stroma outside the uterine cavity,with repeated recurrent bleeding,formation of diseases and symptoms.The incidence of endometriosis in women of reproductive age is about 10%to 15%,and the main clinical symptoms include pain and infertility.A variety of hypotheses have been put forward for the etiology of endometriosis,including the theory of meristematic reflux,the theory of coelomic metaplasia,the theory of hematocele and lymphatic metastasis,but its pathogenesis is still unclear,which severely restricting its clinical treatment.Therefore,it is necessary to further explore the pathogenesis of endometriosis and find the key therapeutic targets with small adverse reactions among the pathogenic factors,so as to effectively improve the therapeutic effect.CXC chemokine ligand 16(CXCL16)is a newly discovered chemokine belonging to the CXC family of chemokines,with two forms of existence,membrane-bound type and secretory type.CXCL16 have both characteristics of the chemokines of the CC family and the CX3C family,with transmembrane structures and mucoprotein-like structures.The chemokine receptor CXCR6 is the only receptor of CXCL16,also known as the orphan receptor Benzo or STRL33 receptor,and is a G-protein coupled receptor which across membranes seven times.CXCL16/CXCR6 chemokine axis has a variety of biological functions,and previous reports of it on human diseases mainly focus on atherosclerosis,rheumatic immunity,hepatitis,and other immune and inflammatory diseases.In recent years,abnormal expression of CXCL16/CXCR6 in malignant tumors of various human systems has been gradually recognized.The expression of CXCL16/CXCR6 was significantly increased in various tumors,including prostate cancer,breast cancer,lung cancer and colorectal cancer,and was positively correlated with the degree of malignancy of tumors.Further studies have found that the expression and function of CXCL16/CXCR6 have certain tissue specificity,and it plays an important role in the development of tumors through the fine regulation of epigenetics and the involvement of malignant biological behaviors such as cell migration and metastasis.Although endometriosis is a benign disease,it has biological behaviors similar to malignant tumors,such as invasion,distant metastasis and recurrence.Previous studies have shown that CXCL16/CXCR6 is expressed in ovarian ectopic endometrial tissue and that CXCL16 induces the production of IL-8 in ectopic endometrial stromal cells,suggesting that it may be involved in the regulation of the inflammatory response of endometriosis.However,the specific pathogenesis of CXCL16/CXCR6 axis in endometriosis remains unclear.The aim of this study was to examine and compare the expression of CXCL16/CXCR6 in patients with or without endometriosis.Study the effect of CXCL16/CXCR6 on ectopic endometrial stromal cell proliferation,migration and invasion.Further explore the relevant cellular and molecular mechanism of CXCL16/CXCR6 in endometriosis and to provide new ideas for the treatment of the disease.ObjectiveTo clarify the effect of CXCL16/CXCR6 chemokine axis on migration and proliferation of endometrial stromal cells and related signaling pathway molecules,and explore possible clinical intervention targets for endometriosis.Materials and methodsPreoperative serum of women with non-endometriosis and patients with endometriosis was collected,and the expression level of secretory CXCL16 in the two groups was detected by ELISA.Endometrium sample from non-endometriosis women and ovarian endometriosis sample from patients with endometriosis were collected.mRNA and protein expression of CXCL16/CXCR6 were detected by RT-qPCR and Western Blot.Primary cells were cultured and ectopic endometrial stromal cells(EESCs)were purified from fresh ovarian endometrium tissue.Small interfering RNA(siRNA-CXCR6)were constructed and transient transfection of EESCs with siRNA-CXCR6 to inhibit the expression of CXCR6.Changes in cell proliferation after treatment were detected by CCK8,cell migration and invasion activity were detected by transwell,and activation of the ERK signal pathway was detected by Western Blot.Treat of EESCs with TNF-a in vitro,the expression of CXCL16 and CXCR6 in the EESCs of the treatment group and the non-treatment group were detected by ELISA and Western Blot.Results1.The expression levels of secretory CXCL16 and membrane-bound CXCL16 in serum and endometriosis tissues were significantly higher in endometriosis group than that in the non-endometriosis group,while the expression levels of CXCR6 have no significantly different between the two groups.2.Successfully purified and cultured primary ectopic endometrial stromal cells with high purity,long fusiform and stable state,which can be passed on.3.After siRNA-CXCR6 transfection inhibited the expression of CXCR6 in EESCs,the proliferation capacity of EESCs remained unchanged,while the cell migration and invasion capacity decreased.4.After the inhibition of CXCR6 expression in EESCs,the phosphorylation level of ERK signaling pathway significantly decreased.5.After the treatment of EESCs with TNF-a in vitro,the expression levels of secretory CXCL16 and membrane-bound CXCL16 were increased,while the expression of CXCR6 was not significantly changed.Conclusion1.Abnormal regulation of CXCL16/CXCR6 chemokine axis may be correlated with the occurrence and development of endometriosis.2.CXCL16/CXCR6 may affect the migration and invasion ability of ectopic endoplasmic cells(EESCs)through the ERK signaling pathway.3.TNF-a may be involved in the abnormal expression of CXCL16 in patients with endometriosis.