Noninvasive mapping of the redox status in septic mouse by in vivo electron paramagnetic resonance imaging.
Increased reactive oxygen species (ROS) contribute to numerous brain disorders, and ROS generation has been examined in diverse experimental models of lipopolysaccharide (LPS)-induced inflammation. The in vivo electron paramagnetic resonance (EPR)/nitroxide spin probe method has been used to analyze the redox status in animal models modulated by ROS generation. In this study, a blood-brain barrier (BBB)-permeable nitroxide spin probe, 3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (HMP), was used as a redox-sensitive nitroxide probe. Magnetic resonance images of mouse head after the injection of HMP showed that HMP was distributed throughout all regions of the mouse head including the brain, suggesting that HMP can reveal redox information in all regions of the mouse head. After the injection of HMP through the mouse tail vein 6 h after the injection of LPS, three-dimensional (3D) EPR images were obtained each minute under a field scanning of 0.3 s and with 81 projections. The reduction reaction of HMP in septic mouse heads was remarkably accelerated compared to that in control mice, and this accelerated reaction was inhibited by aminoguanidine and allopurinol, which inhibit enzymatic activities of induced nitric oxide synthase and xanthine oxidase, respectively. Based on the pharmacokinetics of HMP in mouse heads, the half-life mapping of HMP was performed in LPS-treated mouse head. Half-life maps clearly show a difference in the redox status induced by ROS generation in the presence or absence of inhibitors of ROS-generating enzymes. The present results suggest that a 3D in vivo EPR imaging system combined with BBB-permeable HMP is a useful noninvasive tool for assessing changes in the redox status in rodent models of brain disease under oxidative stress.
Department of Liberal Arts and Sciences, Center for Medical Education, Sapporo Medical University, Sapporo, Hokkaido 060-8556, Japan. hgfujii@sapmed.ac.jp
Hirotada G
HG
Fujii
Hideo
H
Sato-Akaba
Miho C
MC
Emoto
Kouichi
K
Itoh
Yasuhiro
Y
Ishihara
Hiroshi
H
Hirata
D000818:Animals; D001921:Brain / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D004660:Encephalitis / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000378:metabolism*; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D008813:Mice, Inbred ICR; D010084:Oxidation-Reduction; D011743:Pyrimidines / Q000493:pharmacokinetics*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014018:Tissue Distribution
C101901:4-amino-5-hydroxymethyl-2-methylpyrimidine; D011743:Pyrimidines; D017382:Reactive Oxygen Species