NAT10 accelerates pulmonary fibrosis through N4-acetylated TGFB1-initiated epithelial-to-mesenchymal transition upon ambient fine particulate matter exposure

Exposure to ambient fine particulate matter (PM_2.5) has been linked to a higher pulmonary fibrosis risk. Dysregulation of the epitranscriptome results in abnormal expression of mRNAs during fibrosis development. N4-acetylcytidine (ac4C) is one of the most frequent RNA epigenetic alterations, however, its function in PM_2.5-triggered fibrosis is yet unknown. In this study, lung epithelial and murine models were established and exposed to PM_2.5 to analyze the function of ac4C alteration in pulmonary fibrosis and underlying mechanisms. Meanwhile, the expression levels of only known ac4C "writer" protein, N-acetyltransferase 10 (NAT10), were significantly induced in pulmonary epithelia, relative to the control. Subsequently, NAT10 enhanced the stability of transforming growth factor beta 1 (TGFB1) mRNA as well as protein levels. As an up-stream driver, TGFB1 accelerated EMT and fibrosis process. Inhibition of NAT10 significantly protected against pulmonary EMT and fibrosis driven by PM_2.5 exposure, whereas TGFB1 overexpression reversed the protective effects of NAT10 inhibition. Thus, NAT10 accelerated PM_2.5-triggered pulmonary fibrosis via increasing TGFB1 mRNA stability in an ac4C-dependent manner. Our results reveal a pivotal role of NAT10-regulated mRNA ac4C acetylation in PM_2.5-triggered pulmonary fibrosis and uncover the potential epitranscriptional mechanism.