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Paramagnetic resonance in detecting carcinogenic risk from cytochrome P450 overexpression
M Paolini1, L Pozzetti, G F Pedulli
1Department of Pharmacology, Medical School, University of Bologna, Italy.
Background:
Despite the increasing interest in the role of oxygen radicals on human degenerative disorders including cancer, oxidative stress status is not yet measurable in vivo, largely precluding clinical application. Limited semi-quantitative assays of damage to broad classes of biomolecules such as lipids, proteins, and DNA are currently available. The detection of radicals in humans by a whole-body electron paramagnetic resonance (EPR) technique has not yet been developed, although this possibility has long fascinated free radical investigators.
Methods:
While the EPR spin trapping procedure can be used to detect carbon centered or hydroxyl radical in human tissues, the most common spin traps are much less useful for capturing the superoxide anion (O2). To overcome these limitations, we propose a whole-body-harvest approach that utilizes a highly lipophilic spin scavenger that when injected in the animal is capable of trapping the O2 generated in vivo throughout the body with formation of a stable nitroxide measurable by EPR in the urine. A process known to generate the O2 is the induction of certain cytochrome P450 (CYP) isozymes by drugs or environmental pollutants.
Results:
We report: 1) a correlation between the induction of each CYP gene family and the O2 yield; 2) support to an observation reported previously that the tumor promoting ability of CYP inducers is mainly mediated by the O2; and 3) the description of a method for nitroxide mediated O2 detection in vivo.
Conclusion:
These findings could open the way for using electron spin resonance in diagnostic practice.
Insights
Researchers developed a novel whole-body method to detect superoxide anion (O2) in vivo using electron paramagnetic resonance (EPR). This technique measures O2 generated by cytochrome P450 (CYP) enzymes, paving the way for in vivo oxidative stress diagnostics.
Area of Science:
- Biomedical Science
- Analytical Chemistry
- Free Radical Chemistry
Background:
- Oxidative stress from oxygen radicals is linked to degenerative diseases like cancer, but in vivo measurement remains a challenge.
- Current assays for oxidative damage are limited to semi-quantitative assessments of biomolecules.
- Direct in vivo detection of radicals in humans using electron paramagnetic resonance (EPR) has not been achieved.
Purpose of the Study:
- To develop a method for in vivo detection of superoxide anion (O2) using EPR.
- To overcome limitations of existing spin traps for O2 detection.
- To explore the role of O2 in drug- and pollutant-induced cytochrome P450 (CYP) activity.
Main Methods:
- A whole-body-harvest approach using a lipophilic spin scavenger was employed.
- The scavenger traps in vivo generated O2, forming a stable nitroxide.
- The nitroxide is measurable by EPR in urine, enabling O2 detection.
Main Results:
- A correlation was found between CYP gene family induction and O2 yield.
- Evidence supports O2 mediation in the tumor-promoting effects of CYP inducers.
- A method for nitroxide-mediated O2 detection in vivo was successfully described.
Conclusions:
- The developed method allows for in vivo O2 detection.
- Findings suggest a role for O2 in CYP-mediated tumor promotion.
- This research opens possibilities for EPR in clinical diagnostics.