RIFSP-3 Peptide from Pelophylax nigromaculatus Skin Attenuates Radiation-induced Skin Injury

Radiation-induced skin injury (RISI) remains a serious concern during cancer radiotherapy. Previous studies have shown that the skin of the black-spotted frog ( Pelophylax nigromaculatus ) exhibits pronounced radioprotective activity. This study investigated the radioprotective role and underlying mechanisms of a frog-derived peptide, RIFSP-3. WS1, HFF-1, and HaCaT cells treated with RIFSP-3 showed significantly higher viability, lower LDH release, and enhanced clonogenic survival than controls after radiation. RIFSP-3 also enhanced migration in cells exposed to 10 Gy and reduced expression of cell death-related proteins. In a mouse model of radiation-induced skin injury, RIFSP-3 alleviated erythema, edema, and ulceration while accelerating wound closure. RNA-Seq analysis revealed 97 commonly up-regulated and 129 commonly down-regulated genes across the 5 Gy ± RIFSP-3 and 10 Gy ± RIFSP-3 comparisons. KEGG pathway analysis showed enrichment of up-regulated DEGs in the cell cycle, oocyte meiosis, and p53 signaling, and enrichment of down-regulated DEGs in cytokine–cytokine receptor interaction, IL-17 signaling, and TNF signaling pathways. Protein-protein interaction analysis showed that upregulated genes were predominantly enriched in cell cycle and division pathways, whereas downregulated genes were central to inflammatory and immune signaling pathways. Taken together, these findings indicate that RIFSP-3 mitigates radiation-induced skin injury by modulating key cell-cycle pathways and associated inflammatory gene signatures, serving as a novel radioprotective agent.