title: Magnetic Resonance Imaging of Mitochondrial Dysfunction and Metabolic Activity, Accompanied by Overproduction of Superoxide.
abstract: This study shows that a mitochondria-penetrating nitroxide probe (mito-TEMPO) allows detection of superoxide and visualization of mitochondrial dysfunction in living cells due to the effect of T1 shortening in MRI. Mitochondrial dysfunction was induced by treatment of cells with rotenone and 2-methoxyestradiol (2-ME/Rot). The MRI measurements were performed on 7T MRI. The 2-ME/Rot-treated cells were characterized by overproduction of superoxide, which was confirmed by a conventional dihydroethidium test. In the presence of mito-TEMPO, the intensity of MRI signal in 2-ME/Rot-treated cells was ∼30-40% higher, in comparison with that in untreated cells or culture media. In model (cell-free) systems, we observed that superoxide, but not hydrogen peroxide, increased the intensity of T1-weighted MRI signal of mito-TEMPO. Moreover, the superoxide restores the T1-weighted MRI contrast of mito-TEMPOH, a noncontrast (diamagnetic) analogue of mito-TEMPO. This was also confirmed by using EPR spectroscopy. The results demonstrate that superoxide radical is involved in the enhancement of T1-weighted MRI contrast in living cells, in the absence and presence of mito-TEMPO. This report gives a direction for discovering new opportunities for functional MRI, for detection of metabolic activity, accompanied by overproduction of superoxide, as well as by disturbance of the balance between superoxide and hydrogen peroxide, a very important approach to clarify the fine molecular mechanisms in the regulation of many pathologies. The visualization of mitochondrial activity in real-time can be crucial to clarify the molecular mechanism of the functional MRI in its commonly accepted definition, as a method for detection of neurovascular coupling.
authors.affiliation: Molecular Imaging Center, National Institute of Radiological Science , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Rumiana
authors.initials: R
authors.lastname: Bakalova
authors.affiliation: Medical Faculty, Trakia University , 11 Armejska Str., Stara Zagora 6000, Bulgaria.
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Georgieva
authors.affiliation: Medical Faculty, Trakia University , 11 Armejska Str., Stara Zagora 6000, Bulgaria.
authors.forename: Donika
authors.initials: D
authors.lastname: Ivanova
authors.affiliation: Medical Faculty, Trakia University , 11 Armejska Str., Stara Zagora 6000, Bulgaria.|Institute of Biophysics & Biomedical Engineering, Bulgarian Academy of Sciences , 21 Acad. G. Bonchev Str., Sofia 1114, Bulgaria.
authors.forename: Zhivko
authors.initials: Z
authors.lastname: Zhelev
authors.affiliation: Molecular Imaging Center, National Institute of Radiological Science , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Ichio
authors.initials: I
authors.lastname: Aoki
authors.affiliation: Molecular Imaging Center, National Institute of Radiological Science , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Saga
mesh_terms: D000077584:2-Methoxyestradiol; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003497:Cyclic N-Oxides / Q000494:pharmacology; D058266:Dielectric Spectroscopy; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D019169:Jurkat Cells / Q000378:metabolism* / Q000473:pathology; D020014:K562 Cells / Q000378:metabolism* / Q000473:pathology; D007938:Leukemia / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008928:Mitochondria / Q000187:drug effects*; D016877:Oxidants / Q000494:pharmacology; D013113:Spin Labels; D013481:Superoxides / Q000378:metabolism*; D013997:Time Factors; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D003497:Cyclic N-Oxides; D016877:Oxidants; D013113:Spin Labels; D050257:Tubulin Modulators; D013481:Superoxides; D004958:Estradiol; D000077584:2-Methoxyestradiol; D006861:Hydrogen Peroxide
keywords: Nitroxides; hydrogen peroxide; magnetic resonance imaging; mitochondrial dysfunction; superoxide