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

Purpose: 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