X-rays enhance Fe²⁺-mediated oxidative membrane damage in OUMS-36T-1 fibroblasts, supported by the liposome model

Ferroptosis is a regulated form of cell death driven by iron-dependent membrane lipid peroxidation, with ferrous ions (Fe²⁺) and reactive oxygen species playing central roles. Although X-rays are known to generate free radicals via water radiolysis, their role in ferroptosis-related oxidative membrane injury remains unclear. The present study investigated the effects of Fe²⁺ on membrane damage in OUMS-36T-1 human fibroblasts under X-ray irradiation. DOPC/DOPS (8:2 mol/mol) liposomes were employed as a simplified membrane model to explore the underlying mechanisms. In vitro, Fe²⁺ at 1-40 µM promoted cell proliferation up to 10 µM, whereas higher concentrations of Fe²⁺ reduced cell viability. At 40 µM Fe²⁺, intracellular reactive oxygen species and lipid peroxidation levels were elevated; however, lactate dehydrogenase leakage was not observed, suggesting sublethal oxidative stress without overt membrane rupture. However, following 4 Gy X-ray irradiation, cell proliferation at 40 µM Fe²⁺ significantly decreased, accompanied by increased oxidative stress, lipid peroxidation and lactate dehydrogenase leakage, indicating enhanced membrane damage rather than definitive ferroptotic cell death. These effects were mitigated by citric acid, an iron chelator, or reduced glutathione, suggesting the involvement of redox-dependent processes at or near the membrane surface. Experiments with DOPC/DOPS (8:2 mol/mol) liposomes revealed that Fe²⁺-induced lipid peroxidation was significantly enhanced by X-rays. Furthermore, the combination of liposomes and X-rays appeared to accelerate the oxidation of Fe²⁺. These findings suggest that Fe²⁺ interacts with cell membranes to promote lipid peroxidation and impair proliferation, and that X-rays amplify these effects by exacerbating Fe²⁺-mediated oxidative membrane damage. Given the critical role of fibroblasts in post-irradiation tissue repair, the present study highlights the synergistic impact of Fe²⁺ and X-rays on ferroptosis-associated oxidative membrane injury, underscoring their biological significance.