Rosmarinic acid alleviates radiation-induced pulmonary fibrosis by downregulating tRNA N7-Methylguanosine modification-regulated fibroblast to myofibroblast transition through the exosomes pathway [m7G-tRNA MeRIP-Seq]

Radiation-induced pulmonary fibrosis (RIPF) is a common complication after radiotherapy in thoracic cancer patients, and there is a lack of effective treatment methods. The aim of this study was to explore the protective effect of rosmarinic acid (RA) on RIPF in mice as well as the underlying mechanism.We found that RA exerted an antifibrotic effect on lung tissues of RIPF mouse models and inhibited the progression of FMT through exosomes derived from lung epithelial cells. Mechanistically, RA reduced the transcription and translation efficiency of SPHK1 in lung fibroblasts by decreasing the tRNA N7-methylguanosine modification and downregulating the expression of tRNAs in lung epithelial cell-derived exosomes after irradiation, as well as inhibiting the interaction of SPHK1 with the NAT10 protein in fibroblasts. Furthermore, exosomes derived from irradiated lung epithelial cells after RA intervention decreased the acetylation and cytoplasmic translocation of PFKFB3, suppressing the FMT process triggered by glycolysis, and ultimately decelerating the progression of RIPF. In this study, m7G-tRNA-seq and tRNA-seq analysis were conducted to identify the m7G modified tRNAs. Western blotting, immunohistochemistry, northwestern blotting, northern blotting, immunofluorescence, wound-healing assays and Edu experiments were performed to explore the molecular mechanism by which RA regulated fibroblast to myofibroblast transformation (FMT) by affecting the exosomes of lung epithelial cells. Ribo-seq and mRNA-seq analysis were used to explore the underlying target mRNA. Seahorse assays and immunoprecipitation were carried out to elucidate the effects of RA on glycolysis and FMT processes via the regulation of PFKFB3 acetylation.