P-337 Melatonin exerts a therapeutic effect on endometriosis by suppressing estrogen receptors mediated angiogenesis pathway

Abstract Study question What are the underlying mechanisms of melatonin to treat endometriosis? Summary answer Melatonin inhibited estrogen receptors/HIF1α/VEGF signaling pathway and limited the endometriotic lesions growth and angiogenesis. What is known already Currently, alternative pharmaceutical for endometriosis is needed urgently due to lack of satisfactory treatment option. The role of melatonin in inhibiting progression of endometriosis has attracted widespread attention in recent years. Several experimental animal studies showed melatonin decreased endometriotic lesion volume, albeit the exact mechanism is still unknown. As an estrogen-dependent disease, estrogen can not only stimulate the proliferation and growth of endometriotic lesions, but also stabilize HIF-1α and thus promote HIF-1α–induced VEGF via binding to estrogen receptors. Herein, estrogen receptors might be a therapeutic target to block the lesion growth and angiogenesis, subsequently inhibit the progression of endometriosis. Study design, size, duration We investigated the role of melatonin in endometriosis in vitro and in vivo. Endometriotic epithelial (12Z) and stromal (Hs 832(C).T) cell lines were cultured and treated with melatonin for 24 hours. Subcutaneous endometriotic model was surgically established in C57BL/6 mice, and randomly assigned to receive vehicle or melatonin for 21days. All experiments were performed 3-8 times for comparisons. Participants/materials, setting, methods The effect of melatonin on endometriotic cells was determined by MTT cell viability assay. Endometriotic lesion size and body weight were measured every 2-3 days after transplantation. RNA and protein expressions of estrogen receptors, HIF1α and VEGF were detected by qPCR and Western blotting and/or immunostaining in in vitro and in vivo experiments. In vivo imaging by Cellvizio was used to examine microvascular network of the developing endometriotic lesions. Main results and the role of chance Melatonin exerted inhibitory effects on cell growth in a dose and time-dependent manner in 12Z and Hs 832(C).T cell lines, and reduced the volume and weight of the ectopic endometriotic lesions without major change in body weight and behaviour. In addition, melatonin significantly decreased the percentage of area (48.41 vs 33.13%), average length (546.7 vs 240.9um) and total number of junctions (53.30 vs 26.68) of microvessels in the lesions. Melatonin also specially and significantly downregulated estrogen receptor β (ERβ) and G protein-coupled estrogen receptor 30 (GPR30) at RNA and protein levels while estrogen receptor α (ERα) was not significantly changed in both 12Z and Hs 832(C).T cells and endometriotic lesions. Furthermore, the expressions of downstream HIF1α and VEGF were significantly decreased after melatonin treatment. Limitations, reasons for caution Melatonin has been reported to employ a wide range of biological effects. Therefore, its suppressive effects on estrogen receptors/HIF1α/VEGF signaling pathway might be part of the pharmacological mechanisms to treat endometriosis. Further studies are also needed to explore the therapeutic mechanisms of melatonin from other perspectives. Wider implications of the findings Our findings add mechanistic insight in support of the use of melatonin as an adjuvant therapy in the management of endometriosis. Melatonin shows the potential to act as a novel alternative therapeutic drug to treat endometriosis with fewer side effects. Trial registration number NA