Free radical imaging of endogenous redox molecules using dynamic nuclear polarization magnetic resonance imaging

Abstract

Redox reactions accompanied by the oxidation–reduction of endogenous molecules play important roles in maintaining homeostasis in living organisms. In humans, numerous endogenous molecules that contribute toward maintaining physiological conditions form free radicals via electron transfer. A typical example of this is the mitochondrial electron transport chain, which is involved in energy production. If free radicals derived from endogenous molecules could be visualized and exploited as biological and functional probes, redox reactions mediated by endogenous molecules could be detected non-invasively. We succeeded in visualizing the free radicals derived from endogenous molecules using an in vivo dynamic nuclear polarization (DNP) magnetic resonance imaging (MRI) system. In this review, we describe the visualization of endogenous redox molecules, such as flavins and ubiquinones, which are mitochondrial electron carriers, as well as vitamin E and vitamin C (ascorbate). In addition, we describe the application of melanin free radicals for the in vivo visualization of metabola without using probes via in vivo DNP-MRI.

Keywords:

• Redox imaging
• free radicals
• dynamic nuclear polarization MRI
• endogenous free radical intermediates

Acknowledgments

We thank Edanz Group (www.edanzediting.com/ac) for editing a draft of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Medical Research and Development Programs Focused on Technology Transfer, Development of Advanced Measurement and Analysis Systems (SENTAN) from the Japan Agency for Medical Research and Development, AMED Grant Number 162128; Health Labour Sciences Research Grant (Research on Publicly Essential Drugs and Medical Devices) from the Ministry of Health, Labour and Welfare of Japan; and Special Coordination Funds for Promoting Science and Technology (SCF funding program “Innovation Center for Medical Redox Navigation”). This work was also supported by JSPS KAKENHI (Grant Number 19H03358 and 16H05113).