Emodin alleviates radiation-induced pulmonary fibrosis by targeting cellular senescence via the mtDNA-cGAS-STING axis.

Radiation-induced pulmonary fibrosis (RIPF) is a severe complication of thoracic radiotherapy with limited effective treatment options. Cellular senescence has emerged as a critical driver of age-related tissue fibrosis; however, its role in RIPF and potential as a therapeutic target are underexplored. In this study, we investigated whether emodin, a natural compound with known anti-aging properties, alleviates RIPF by suppressing radiation-induced cellular senescence. In a mouse model exposed to 16 Gy thoracic irradiation, emodin treatment significantly attenuated pulmonary fibrosis, reduced collagen deposition, and downregulated fibrotic markers. Notably, emodin markedly suppressed radiation-induced senescence in pulmonary epithelial cells, accompanied by reduced secretion of senescence-associated secretory phenotype (SASP) factors. Mechanistically, emodin preserved mitochondrial integrity, curbed mitochondrial reactive oxygen species (mtROS) accumulation, and prevented mitochondrial DNA (mtDNA) leakage into the cytoplasm, thereby inhibiting the cGAS-STING-NF-κB signaling pathway, a key pro-inflammatory axis in senescent cells. Importantly, knockdown of cGAS or treatment with the mitochondrial uncoupler CCCP attenuated the anti-senescent effects of emodin, underscoring the centrality of mitochondrial dysfunction and the mtDNA-cGAS-STING axis in senescence-driven fibrosis. Collectively, these findings identify emodin as a novel senescence-targeting agent that mitigates RIPF by alleviating mitochondrial dysfunction and disrupting the mtDNA-cGAS-STING pathway, highlighting its therapeutic potential in age-related fibrotic diseases.