M6A Methylase METTL3-mediated downregulation of TEP1 mRNA stability attenuates PDGF-BB-induced HASMC remodeling and inflammation via macrophage polarization.

BACKGROUND: Childhood asthma is a chronic inflammatory disease of the respiratory tract characterized by the contraction of smooth muscle, remodeling of the airway wall, bronchial inflammation, and obstruction, which is associated with increased airway smooth muscle mass. Telomerase Associated Protein 1 (TEP1) was reported to be aberrantly expressed in childhood asthma. Therefore, this study is designed to explore the role and mechanism of TEP1 on the pathogenesis of asthma. METHODS: Asthma cell models were established using Platelet-derived growth factor-BB (PDGF-BB) in Human airway smooth muscle cells (HASMCs). TEP1 and Methyltransferase-like 3 (METTL3) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). TEP1, autophagic markers (Beclin1, LC3II/LC3I, and P62), and contraction phenotypic markers (Calponin, SM22α, and α-SMA), M2-like macrophage markers (IRF4, CD206, and Arg-1), and METTL3 protein levels were examined by western blot assay. Cell viability and migration were assessed using CCK-8 and transwell assays. The proportion of iNOS and CD206 positive cells was detected using flow cytometry. The levels of IFN-γ, IL-4, and IL-10 were detected using ELISA. Interaction between METTL3 and TEP1 was verified using methylated RNA immunoprecipitation (MeRIP). RESULTS: TEP1 was highly expressed, and METTL3 was decreased in asthma patients and PDGF-BB-treated HASMCs. TEP1 knockdown relieved PDGF-BB-induced proliferation, migration, autophagy promotion, and contractile phenotype inhibition in HASMCs. Meanwhile, PDGF-BB-mediated M1-like macrophage polarization decrease and M2-like macrophage polarization increase were abolished by TEP1 silencing. Mechanistically, METTL3 could reduce the stability of TEP1 mRNA via m6A methylation. CONCLUSION: METTL3 destabilizes TEP1 mRNA in an m6A-dependent manner, thereby relieving PDGF-BB-triggered HASMC proliferation, migration, autophagy, loss of contractile phenotype, and M2-like macrophage activation. GRAPHICAL ABSTRACT: [Image: see text]