Melatonin Suppresses NLRP3 Inflammasome Activation via SIRT1-Mediated ETS1 Deacetylation to Attenuate LPS-Induced Pyroptosis in Alveolar Epithelial Cells

Fan He, Chunzi Liu, Yun Yu, Qiaofang Wang, Lin Li, Xiaoyun Chao, Liping Chen, Cong Yu Neonatal Intensive Care Unit, Jiangxi Provincial Children’s Hospital, Nanchang, Jiangxi, 330038, People’s Republic of ChinaCorrespondence: Liping Chen, Neonatal Intensive Care Unit, Jiangxi Provincial Children’s Hospital, No. 1666, DieziHu Road, Honggutan District, Nanchang, Jiangxi, 330038, People’s Republic of China, Tel + 86 13627918180, Email ccllpp88@qq.com Cong Yu, Neonatal Intensive Care Unit, Jiangxi Provincial Children’s Hospital, No. 1666, DieziHu Road, Honggutan District, Nanchang, Jiangxi, 330038, People’s Republic of China, Tel + 86 13627918180, Email yucong@ncmc.edu.cnPurpose: While melatonin is known to suppress pyroptosis in various cell types, its role and mechanisms in alveolar epithelial cells are not fully understood. Using lipopolysaccharide (LPS)-treated human pulmonary alveolar epithelial cells (HPAEpiC) as an in vitro model, this study aimed to investigate the anti-pyroptotic mechanism of melatonin.Methods: HPAEpiC cells were treated with LPS to induce pyroptosis. Cell death was assessed by propidium iodide staining, and morphological changes were examined using transmission electron microscopy (TEM). Pyroptosis-related markers were analyzed by Western blot and immunofluorescence, while inflammatory factors were measured by enzyme-linked immunosorbent assay (ELISA). Chromatin immunoprecipitation (ChIP) assay and siRNA knockdown were performed to identify key targets and mechanisms involved in melatonin-mediated inhibition of pyroptosis.Results: Melatonin significantly reduced LPS-induced pyroptosis in HPAEpiC cells. It downregulated the expression of E26 oncogene homolog 1 (ETS1), and overexpression of ETS1 reversed the anti-pyroptotic effect of melatonin. ChIP assays confirmed that ETS1 binds to the NLRP3 promoter, an interaction inhibited by melatonin. Additionally, melatonin upregulated sirtuin 1 (SIRT1), leading to ETS1 deacetylation. Knockdown of SIRT1 abolished the protective effect of melatonin against pyroptosis. Furthermore, siRNA targeting melatonin receptor 2 (MT2) attenuated melatonin-induced SIRT1 upregulation, ETS1 deacetylation, and pyroptosis inhibition.Conclusion: Our findings indicate that melatonin alleviates LPS-induced pyroptosis in alveolar epithelial cells through the MT2/SIRT1/ETS1/NLRP3 signaling pathway.Keywords: melatonin, LPS, ETS1, SIRT1, pyroptosis, pulmonary alveolar epithelial cells