Endometriosis is a chronic disorder characterized by the implantation of endometrial glands and stroma outside the uterus. However, the pathogenesis of endometriosis is still unclear. To date, there is no fully effective treatment without trauma because of various side effects. Recent data suggest that ferroptosis is a novel recognized form of nonapoptosis-regulated cell death characterized by iron-dependent and lethal lipid peroxidation accumulation, showing great promise in the treatment of many diseases. In the present study, we verified that erastin induced ferroptosis in ectopic endometrial stromal cells (EESCs). Furthermore, we found that the expression of metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) was decreased during erastin-induced ferroptosis. Knockdown of MALAT1 significantly aggravated the inhibition of cell viability and increased intracellular iron, Liperfluo, and MDA levels in EESCs upon erastin treatment. Mechanistically, we demonstrated that MALAT1 served as a competing endogenous RNA of miR-145-5p to regulate the expression of MUC1, a suppressor of ferroptosis. MALAT1 knockdown-mediated ferroptotic cell death and MUC1 downregulation could be abrogated by inhibition of miR-145-5p. In addition, miR-145-5p inhibition-mediated ferroptotic cell death could be abolished by MUC1 knockdown. Furthermore, erastin-induced ferroptosis shrunk endometriotic lesions via the MALAT1/miR-145-5p/MUC1 axis in vivo. Taken together, our data indicate that knockdown of MALAT1 facilitates ferroptosis upon erastin treatment via miR-145-5p/MUC1 signaling. The synergistic effect of MALAT1 knockdown and erastin induction in ferroptosis may be a new therapeutic strategy for endometriosis.

Background Endometriosis (EMs) is a common benign gynecological disease that affects approximately 10% of females of reproductive age. Endometriosis ectopic lesions could recruit macrophages, which in turn facilitates endometriosis progression. Several studies have indicated that CCL20 derived from macrophages activates the expression of CCR6 in several cells and induces cell proliferation and migration. However, the function of the CCL20/CCR6 axis in the interactions between macrophages and endometriotic stromal cells (ESCs) in EMs has yet to be elucidated. Methods Ectopic and normal endometrial tissues were collected from 35 ovarian endometriosis patients and 21 control participants for immunohistochemical staining. It was confirmed that macrophages secreted CCL20 to promote CCR6 activation of ESCs during co-culture by ELISA, qRT-PCR and western blot analysis. CCK8 and Edu assays were used to detect cell proliferation, and wound healing and Transwell assay were used to detect cell migration. Autophagic flux was detected by measuring the protein expression levels of LC3 and P62by western blot and analyzing the red/yellow puncta after ESCs were transfected with mRFP-GFP-LC3 double fluorescence adenovirus (Ad‐LC3). Lysosomal function was tested by quantifying the fluorescent intensities of Lyso-tracker and Gal3 and activity of acid phosphatase. In addition, co-IP experiments verified the binding relationship between CCR6 and TFEB. Finally, the suppressive effect of CCL20-NAb on endometriosis lesions in vivo was demonstrated in mice models. Results We demonstrated that macrophages secreted CCL20 to promote CCR6 activation of ESCs during co-culture, which further induced the proliferation and migration of ESCs. We observed that the CCL20/CCR6 axis impaired lysosomal function and then blocked the autolysosome degradation process of autophagic flux in ESCs. The combination of CCR6 and TFEB to inhibit TFEB nuclear translocation mediates the role of the CCL20/CCR6 axis in the above process. We also found that co-culture with ESCs upregulated the production and secretion of CCL20 by macrophages. The suppression effect of CCL20-NAb on endometriosis lesions in vivo was demonstrated in mice models. Conclusions Our data indicate that macrophages block TFEB-mediated autolysosome degradation process of autophagic flux in ESCs via the CCL20/CCR6 axis, thereby promoting ESC proliferation and migration.

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