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

## TL;DR

X-rays increase Fe2+-caused oxidative damage to cell membranes in fibroblasts, suggesting a link to ferroptosis and tissue repair.

## Contribution

Demonstrates that X-rays enhance Fe2+-mediated oxidative membrane damage, supported by a liposome model.

## Key findings

- Fe2+ at 40 µM caused sublethal oxidative stress without membrane rupture in fibroblasts.
- X-ray irradiation increased Fe2+-induced membrane damage and lipid peroxidation.
- Citric acid and glutathione reduced the observed effects, indicating redox-dependent processes.

## Abstract

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.