ON101 counteracts oxidative stress and inflammation in radiation-induced dermatitis through Keap1/Nrf2 signaling.

Radiation-induced dermatitis (RID) remains a significant and challenging side effect of radiotherapy, with few effective topical interventions. This study investigates ON101 as a therapeutic candidate for RID, focusing on its modulation of the Keap1/Nrf2 signaling pathway. Using a murine model of radiation-induced skin injury, topical application of ON101 substantially reduced skin damage, as evidenced by decreased wound severity scores, preserved body weight, and improved histopathological outcomes. Histological analyses using H&E and Masson's trichrome staining revealed that ON101 and its active component, PA-F4, reversed radiation-associated dermal thickening and fibrosis, thus restoring skin architecture and elasticity. RNA sequencing demonstrated that ON101 treatment downregulated Keap1 expression, facilitating nuclear translocation and activation of Nrf2, a central regulator of antioxidant responses. Consistently, irradiated human keratinocytes (HaCaT) and dermal fibroblasts (HDFs) treated with ON101 exhibited significantly decreased levels of oxidative stress markers and pro-inflammatory cytokines, confirming its combined antioxidant and anti-inflammatory effects. Moreover, ON101 enhanced the expression of key genes involved in DNA damage repair and skin regeneration, including EGFR, VIM, and CTNNB1, highlighting its regenerative potential. Mechanistically, the study identified increased p62 and nuclear Nrf2 levels following ON101 treatment, confirming activation of the p62-Keap1-Nrf2 axis-a pivotal pathway governing cellular defense mechanisms against oxidative damage. Collectively, these results suggest that ON101 provides comprehensive protection against RID by modulating oxidative stress, reducing inflammation, and promoting tissue repair. Through these targeted molecular mechanisms, ON101 emerges as a promising topical therapeutic agent for managing radiation-induced cutaneous toxicity in clinical settings.