Antioxidant defence system and stabilized level of reactive oxygen species (ROS) protect organisms against various diseases such as stroke or inflammation. In order to create an effective therapy for such diseases, the in vivo redox status map may be useful. The fact is that EPR imaging, with a suitable external imaging probe, is a great tool for monitoring the balance or imbalance between oxidation and reduction reactions and assessing the redox state of the brain.
That issue was considered by Hirotada Fujii and his research group in the paper “Mapping of Redox Status in a Brain-Disease Mouse Model by Three-Dimensional EPR Imaging”.
Control mice and transient middle cerebral artery occlusion (MCAO) mice were used as the subjects in this experiment. The in vivo redox state in the brains of control and MCAO mice was measured by improved EPR imager that enabled rapid data acquisition, engineered by Fuji and colleagues. Reduction of the acquisition time has allowed to obtain high-quality 3D images in a very short time. A nitroxide, 3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidine-1-oxy (HMP), was used as a redox-sensitive spin probe. HMP has passed freely through the brain-blood barrier, which was also confirmed by MRI examination.
The redox status of MCAO mice was visualized as 3D maps, where each voxel represents half-live of HMP in the difference part of brain. The half-life mapping of HMP has shown a significant heterogeneity of the redox state in brain of MCAO mice. It was also revealed that there is an increase of HMP in the brain of ischemia-reperfusion-treated mice, and consequently, the reduction rate of nitroxide is slower in MCAO mice.
This study confirmed that with the use of an EPR scanner and given an appropriate time of data acquisition, is it possible to provide a 3D map of the in vivo redox state in the mouse brain . Therefore, the role of EPR imaging systems in the research on redox status is significant.
Fujii H, Sato-Akaba H, Kawanishi K, Hirata H.; Mapping of redox status in a brain-disease mouse model by three-dimensional EPR imaging; Magn Reson Med. 2011 Jan;65(1):295-303; DOI: 10.1002/mrm.22598.