Lipoxin A4 Suppresses Estrogen-Induced Epithelial-Mesenchymal Transition via ALXR-Dependent Manner in Endometriosis

Objective: Epithelial-mesenchymal transition (EMT) is essential for embryogenesis, fibrosis, and tumor metastasis. Aberrant EMT phenomenon has been reported in endometriotic tissues of patients with endometriosis (EM). In this study, we further investigated the molecular mechanism of which lipoxin A(4) (LXA(4)) suppresses estrogen (E-2)-induced EMT in EM. Study Design: The EMT markers were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot in eutopic endometrial epithelial cells (EECs) or investigated by immunohistochemistry and qRT-PCR in endometriotic lesion of EM mice. The invasion and migration under different treatments were assessed by transwell assays with or without Matrigel. The messenger RNA (mRNA) and activities of matrix metalloproteinase 2 (MMP-2) and MMP-9 were determined by qRT-PCR and gelatin zymography, respectively. Luciferase reporter assay was used to measure the activity of zinc finger E-box binding homeobox 1(ZEB1) promoter. The level of E-2 in endometriotic tissues was assessed by enzyme-linked immunosorbent assay. Results: In eutopic EECs, stimulatory effects of E-2 on EMT progress, migration, and invasion were all diminished by LXA(4). Lipoxin A(4) reduced E-2-induced ZEB1 promoter activity. Lipoxin A(4) also attenuated the phosphorylation of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase induced by E-2. Co-incubation with Boc-2 rather than DMF antagonized the influence of LXA(4). Animal experiments showed that LXA(4) inhibited the EMT progress, MMP expression, and proteinase activities of endometriotic lesion in an LXA(4) receptor (ALXR) manner, which suppressed the progression of EM. ZEB1 mRNA expression was upregulated and well correlated with E-2 level in human endometrium. Conclusion: Lipoxin A(4) suppresses E-2-induced EMT via ALXR-dependent manner in eutopic EECs, which reveals a novel biological effect of LXA(4) in EM.