ac4C modification of PDK4 by NAT10 promotes pulmonary fibrosis by reprogramming mitochondrial dynamics in fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disorder with limited therapeutic options, necessitating the identification of novel pathogenic mechanisms and therapeutic targets. Here, we report a critical role for the RNA acetyltransferase NAT10 in driving pulmonary fibrosis through epitranscriptomic regulation of mitochondrial metabolism. We found that NAT10 and its catalyzed N4-acetylcytidine (ac4C) modification were significantly upregulated in fibrotic lungs from IPF patients and bleomycin-challenged mice, particularly within activated fibroblasts. Genetic ablation of NAT10 in fibroblasts markedly attenuated fibrotic progression, whereas its overexpression exacerbated the pathology. Mechanistically, integrated transcriptomic and biochemical analyses identified pyruvate dehydrogenase kinase 4 (PDK4) as a key downstream target whose mRNA stability was enhanced by NAT10-mediated ac4C modification. This post-transcriptional regulation led to PDK4 upregulation, which in turn promoted mitochondrial fission and reactive oxygen species production, thereby facilitating fibroblast-to-myofibroblast transition and excessive extracellular matrix deposition. Furthermore, we delineated the upstream regulation of NAT10, demonstrating that TGF-β1 transcriptionally induces NAT10 expression via direct Smad3 binding to its promoter, forming a positive feedback loop that sustains fibrotic activation. Our study unveils the NAT10-ac4C-PDK4 axis as a central regulator of mitochondrial dynamics in pulmonary fibrosis and highlights NAT10 as a promising therapeutic target for restoring metabolic homeostasis and ameliorating fibrotic lung remodeling.