Previous Article |
Table of Contents
| Next Article 
MEDICAL SCIENCES
Simultaneous molecular imaging of redox reactions monitored by Overhauser-enhanced MRI with 14N- and 15N-labeled nitroxyl radicals
Department of Bio-Functional Science, Graduate School of Pharmaceutical Sciences, Kyushu University, Higashi-ku, Fukuoka 812-8582, Japan
Communicated by Albert W. Overhauser, Purdue University, West Lafayette, IN, December 13, 2005 (received for review September 16, 2005)
MRI has provided significant clinical utility in the diagnosis of diseases and will become a powerful tool to assess phenotypic changes in genetically engineered animals. Overhauser enhanced MRI (OMRI), which is a double resonance technique, creates images of free radical distributions in small animals by enhancing the water proton signal intensity by means of the Overhauser effect. Several studies have demonstrated noninvasive assessment of reactive oxygen species generation in small animals by using low frequency electron spin resonance (ESR) spectroscopy/imaging and nitroxyl radicals. In vivo ESR signal intensities of nitroxyl radicals decrease with time after injection; and the decreases are enhanced by reactive oxygen species, generated in oxidative disease models in a site-specific manner. In this study, we show images of nitroxyl radicals with different isotopes by changing the external magnetic field for ESR irradiation between 14N and 15N nuclei in field-cycled OMRI. OMRI simultaneously obtained dual images of two individual chemical processes. Oxidation and reduction were monitored in a rate-dependent manner at nanometer scale by labeling membrane-permeable and -impermeable nitroxyl radicals with 14N and 15N nuclei. Phantom objects containing ascorbic acid-encapsulated liposomes with membrane-permeable radicals but not membrane-impermeable ones show a time-dependent decrease of the OMRI image intensity. The pharmacokinetics in mice was assessed with OMRI after radical administration. This OMRI technique with dual probes should offer significant applicability to nanometer scale molecular imaging and simultaneous assessment of independent processes in gene-modified animals. Thus, it may become a powerful tool to clarify mechanisms of disease and to monitor pharmaceutical therapy.
ESR | reactive oxygen species | oxidative disease | nanometer
Conflict of interest statement: No conflicts declared.
Freely available online through the PNAS open access option.
Abbreviations: AsA, ascorbic acid; 
, ESR magnetic field; 
, NMR magnetic field; carboxy-PROXYL, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl; carbamoyl-PROXYL, 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl; DNP, dynamic nuclear polarization; ESR, electron spin resonance; HRP, horseradish peroxidase; MC-PROXYL, 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl; OMRI, Overhauser-enhanced MRI; oxo-TEMPO, 4-oxo-2,2,6,6-tetramethyl-piperidine-1-oxyl; ROS, reactive oxygen species; TE, echo time; TESR, ESR irradiation time; TR, repetition time; FOV, field of view.
* To whom correspondence should be addressed. E-mail: utsumi{at}pch.phar.kyushu-u.ac.jp.
© 2006 by The National Academy of Sciences of the USA
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg What's this?
This article has been cited by other articles in HighWire Press-hosted journals:
|
|
 |
|
  V. Shulaev and D. J. Oliver Metabolic and Proteomic Markers for Oxidative Stress. New Tools for Reactive Oxygen Species Research Plant Physiology, June 1, 2006; 141(2): 367 - 372. [Full Text] [PDF]
|
|
