GDF15 drives epithelial cell senescence in radiation-induced lung injury via `ERK1/2-p16` pathway

Radiation-induced lung injury (RILI) is a debilitating complication of thoracic radiotherapy, significantly impacting cancer treatment outcomes and patient quality of life. Current management primarily focuses on supportive care, with limited specific therapeutic options. Cellular senescence, a state of irreversible cell cycle arrest, is increasingly recognized as a key pathological process in RILI development, contributing to inflammation and fibrosis. Identifying specific senescence-associated molecules and their mechanisms in RILI is crucial for developing targeted interventions to mitigate this severe side effect.

Researchers performed bioinformatics analysis, integrating RILI-related gene expression data with senescence-related gene sets, to identify candidate molecules. This led to the identification of Growth Differentiation Factor 15 (GDF15). A rat model of RILI was established via thoracic irradiation. Inflammatory injury and fibrosis were assessed using hematoxylin and eosin (HE) and Masson's trichrome staining. DNA damage was evaluated by γH2AX immunofluorescence. Senescence was quantified via senescence-associated β-galactosidase (SA-β-gal) staining and Western blot for p53, p21, p16, and GDF15 expression. Further in vivo and in vitro experiments in irradiated BEAS-2B cells explored the mechanism of GDF15 in epithelial senescence, including GDF15 knockdown and ERK1/2 inhibition.

Bioinformatics analysis prominently identified GDF15 as an upregulated senescence-related gene in RILI. In irradiated rat lungs, γH2AX expression was significantly increased, accompanied by notable inflammatory infiltration, fibrotic changes, and upregulation of senescence-associated markers like p53, p21, and p16. SA-β-gal staining further confirmed the presence of radiation-induced senescence in vivo. Similar findings were observed in irradiated BEAS-2B cells, reinforcing the cellular senescence response. Mechanistic experiments revealed that:

GDF15 knockdown significantly attenuated radiation-induced senescence and downregulated the expression of p-ERK1/2 and its downstream target p16. Furthermore, pharmacological ERK1/2 inhibition independently reduced SA-β-gal staining and p16 expression in irradiated cells, confirming the involvement of the ERK1/2-p16 signaling pathway in GDF15-mediated senescence.