Importance of Locations of Iron Ions to Elicit Cytotoxicity Induced by a Fenton-Type Reaction

Kintaro Igarashi; Yoshimi Shoji; Emiko Sekine-Suzuki; Megumi Ueno; Ken-Ichiro Matsumoto; Ikuo Nakanishi; Koji Fukui

doi:10.3390/cancers14153642

Importance of Locations of Iron Ions to Elicit Cytotoxicity Induced by a Fenton-Type Reaction

Cancers (Basel). 2022 Jul 27;14(15):3642. doi: 10.3390/cancers14153642.

Authors

Kintaro Igarashi^{1

2}, Yoshimi Shoji^{2

3}, Emiko Sekine-Suzuki⁴, Megumi Ueno², Ken-Ichiro Matsumoto², Ikuo Nakanishi³, Koji Fukui¹

Affiliations

¹ Molecular Cell Biology Laboratory, Department of Bioscience and Engineering, College of Systems Engineering and Science, Shibaura Institute of Technology, Fukasaku 307, Minuma-ku, Saitama 337-8570, Japan.
² Quantitative RedOx Sensing Group, Department of Radiation Regulatory Science Research, National Institute of Radiological Sciences, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba-shi 263-8555, Japan.
³ Quantum RedOx Chemistry Team, Institute for Quantum Life Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba-shi 263-8555, Japan.
⁴ Human Resources Development Center, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba-shi 263-8555, Japan.

Abstract

The impact of the site of the Fenton reaction, i.e., hydroxyl radical (^•OH) generation, on cytotoxicity was investigated by estimating cell lethality in rat thymocytes. Cells were incubated with ferrous sulfate (FeSO₄) and hydrogen peroxide (H₂O₂), or pre-incubated with FeSO₄ and then H₂O₂ was added after medium was replaced to remove iron ions or after the medium was not replaced. Cell lethality in rat thymocytes was estimated by measuring cell sizes using flow cytometry. High extracellular concentrations of FeSO₄ exerted protective effects against H₂O₂-induced cell death instead of enhancing cell lethality. The pre-incubation of cells with FeSO₄ enhanced cell lethality induced by H₂O₂, whereas a pre-incubation with a high concentration of FeSO₄ exerted protective effects. FeSO₄ distributed extracellularly or on the surface of cells neutralized H₂O₂ outside cells. Cytotoxicity was only enhanced when the Fenton reaction, i.e., the generation of ^•OH, occurred inside cells. An assessment of plasmid DNA breakage showed that ^•OH induced by the Fenton reaction system did not break DNA. Therefore, the main target of intracellularly generated ^•OH does not appear to be DNA.

Keywords: Fenton reaction; cytotoxicity; hydrogen peroxide; hydroxyl radical; iron ion; molecular distribution; oxidative stress; plasmid DNA; rat thymocyte; reactive oxygen species.

Grants and funding

This research received no external funding.