Genotoxic Responses of Mitochondrial Oxygen Consumption Rate and Mitochondrial Semiquinone Radicals in Tumor Cells

Kumiko Yamamoto, Hironobu Yasui, Tomoki Bo, Tohru Yamamori, Wakako Hiraoka, Toshihide Yamasaki, Ken ichi Yamada, Osamu Inanami

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Our recent report demonstrated that genotoxic stimuli enhance mitochondrial energy metabolism in various tumor cell lines. However, the mitochondrial response against genotoxic stimuli has not been fully elucidated. In this study, to investigate mitochondrial functions in X-irradiated cells, the oxygen consumption rate (OCR) in human cervical adenocarcinoma HeLa cells was examined by electron spin resonance (ESR) spectroscopy with lithium 5,9,14,18,23,27,32,36-octa-n-butoxy-2,3-naphthalocyanine. ESR oximetry demonstrated that basal respiration, ATP-linked respiration, proton leak, maximal respiration, and reserve capacity increased in HeLa cells 24 h after X-irradiation. However, a flow cytometric analysis using MitoTracker Green showed that mitochondrial mass also increased following X-irradiation. When the OCR was standardized to the mitochondria membrane mass, the radiation-induced increases in the respiratory parameters disappeared. This finding indicated that the radiation-induced increase in cellular OCR was explained by an increase in mitochondrial mass but not by the activation of mitochondrial respiratory-related enzymes. In addition, mitochondrial semiquinone radicals at g = 2.004 were detected by low-temperature (110 K) ESR spectroscopy. The ESR signal intensity of semiquinone radicals was enhanced by X-irradiation, suggesting an increase in the electron flow in the electron transport chain. These data will be important to understand the mechanism of radio-sensitization by mitochondria-targeting reagents in tumor cells.

Original languageEnglish
Pages (from-to)837-851
Number of pages15
JournalApplied Magnetic Resonance
Issue number8
Publication statusPublished - Aug 1 2018

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics


Dive into the research topics of 'Genotoxic Responses of Mitochondrial Oxygen Consumption Rate and Mitochondrial Semiquinone Radicals in Tumor Cells'. Together they form a unique fingerprint.

Cite this