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Interaction of 1-hydroxyethyl radical with glutathione, ascorbic acid and alpha-tocopherol
D A Stoyanovsky1, D Wu, A I Cederbaum
1Department of Biochemistry, Mount Sinai School of Medicine, New York, NY 10029, USA.
Free Radical Biology & Medicine
|January 22, 1998
Summary
Ethanol metabolism generates the 1-hydroxyethyl radical (HER), which interacts with antioxidants like glutathione (GSH), ascorbate, and alpha-tocopherol. This study models HER generation and its antioxidant interactions, revealing how these antioxidants are consumed.
Area of Science:
- Biochemistry
- Free Radical Chemistry
- Cellular Metabolism
Background:
- Ethanol administration is known to deplete cellular antioxidants such as glutathione (GSH) and alpha-tocopherol.
- Ethanol is metabolized to the 1-hydroxyethyl radical (HER), a reactive species implicated in cellular damage.
- Understanding HER's interaction with antioxidants is crucial for elucidating ethanol's biological effects.
Purpose of the Study:
- To establish a reliable chemical model system for generating HER.
- To investigate the interactions between HER and key cellular antioxidants: GSH, ascorbic acid, and alpha-tocopherol.
- To validate the detection and quantification of HER using Electron Paramagnetic Resonance (EPR) spectrometry.
Main Methods:
- Synthesis of 1,1'-dihydroxyazoethane for controlled HER generation.
- Detection of HER using EPR spectrometry with spin traps PBN and DMPO.
- Computer simulation for validating EPR spectral data.
- In vitro experiments with GSH, ascorbic acid, and alpha-tocopherol.
- Cellular studies using HepG2 cells and redox cycling of 2,3-dimethoxy-1,4-naphthoquinone.
Main Results:
- Thermal decomposition of 1,1'-dihydroxyazoethane successfully generated HER, confirmed by EPR.
- GSH inhibited HER formation but did not degrade pre-formed HER adducts; GSH consumption was observed and partially reversed by NADPH/glutathione reductase.
- Ascorbic acid inhibited HER formation and reduced pre-formed HER adducts, with HER amplifying ascorbate oxidation.
- Alpha-tocopherol was consumed in the presence of HER.
- HER production in HepG2 cells correlated with GSH consumption.
Conclusions:
- A simple chemical system effectively generates HER for studying its reactivity.
- Cellular antioxidants (GSH, ascorbate, alpha-tocopherol) directly interact with HER.
- Ascorbate's ability to reduce HER adducts may complicate in vivo HER detection.
- These findings provide insights into the mechanisms underlying ethanol-induced oxidative stress and antioxidant depletion.