Monitoring of biological one-electron reduction by (19)F NMR using hypoxia selective activation of an (19)F-labeled indolequinone derivative.
Biological reduction of fluorine-labeled indolequinone derivative (IQ-F) was characterized by (19)F NMR for quantitative molecular understanding. The chemical shift change in (19)F NMR allowed monitoring of the enzymatic reduction of IQ-F. Upon hypoxic treatment of IQ-F with NADPH:cytochrome P450 reductase, IQ-F was activated via catalytic one-electron reduction to release nonafluoro-tert-butyl alcohol (F-OH), while the formation of F-OH was significantly suppressed under aerobic conditions. Similar hypoxia-selective reduction of IQ-F occurred within A549 cells, which expresses NADPH:cytochrome P450 reductase. The kinetic analysis was also performed to propose a reaction mechanism. The molecular oxygen slightly prevents the binding of IQ-F to reductase, while the rate of net reaction was decreased due to oxidation of a semiquinone anion radical intermediate generated by one-electron reduction of IQ-F. The disappearance of IQ-F and appearance of F-OH were imaged by (19)F fast spin echo, thus visualizing the hypoxia-selective reduction of IQ-F by means of MR imaging.
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510, Japan. tanabeka@scl.kyoto-u.ac.jp
Kazuhito
K
Tanabe
Hiroshi
H
Harada
Michiko
M
Narazaki
Kazuo
K
Tanaka
Kenichi
K
Inafuku
Hirokazu
H
Komatsu
Takeo
T
Ito
Hisatsugu
H
Yamada
Yoshiki
Y
Chujo
Tetsuya
T
Matsuda
Masahiro
M
Hiraoka
Sei-ichi
S
Nishimoto
D002460:Cell Line; D005462:Fluorine Radioisotopes; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D045563:Indolequinones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010084:Oxidation-Reduction
D005462:Fluorine Radioisotopes; D045563:Indolequinones