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Mitochondrial electron transport-linked tocopheroxyl radical reduction
J J Maguire1, D S Wilson, L Packer
1Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
The Journal of Biological Chemistry
|December 25, 1989
Summary
Vitamin E (alpha-tocopherol) acts as an antioxidant in mitochondria. The electron transport chain can regenerate vitamin E by reducing its oxidized form, suggesting a key role in vitamin E recycling.
Area of Science:
- Biochemistry
- Mitochondrial Biology
- Antioxidant Research
Background:
- Alpha-tocopherol (vitamin E) is a crucial lipophilic antioxidant protecting mitochondrial membranes from oxidative damage by inhibiting lipid peroxidation.
- The primary oxidation product, the tocopheroxyl radical, can be recycled by water-soluble antioxidants like ascorbate or glutathione.
- Physiological vitamin E levels are too low for direct detection of the tocopheroxyl radical using electron spin resonance (ESR).
Purpose of the Study:
- To investigate the detectability and potential recycling mechanisms of the tocopheroxyl radical in mitochondrial membranes.
- To explore the role of the mitochondrial electron transport chain in the redox cycling of vitamin E.
Main Methods:
- Dietary supplementation with vitamin E to increase its concentration in rat liver mitochondrial membranes.
- Induction of tocopheroxyl radical formation using a lipoxygenase and arachidonic acid oxidizing system.
- Detection of the tocopheroxyl radical using ESR spectroscopy.
- Assessment of tocopheroxyl radical reduction by mitochondrial electron transport chain components (NADH, succinate, reduced cytochrome c) in submitochondrial particles.
Main Results:
- Dietary vitamin E supplementation significantly increased vitamin E content in mitochondrial membranes, enabling direct ESR detection of the tocopheroxyl radical.
- The electron transport chain components, including NADH, succinate, and reduced cytochrome c, were shown to effectively reduce the tocopheroxyl radical.
- This reduction by the electron transport chain prevented the accumulation of the tocopheroxyl radical and subsequent vitamin E consumption.
Conclusions:
- The mitochondrial electron transport chain possesses the capability to reduce the tocopheroxyl radical, thereby regenerating vitamin E.
- This redox cycling mechanism mediated by the electron transport chain likely plays a significant physiological role in maintaining vitamin E levels within mitochondria.
- The findings provide direct evidence for an endogenous pathway for vitamin E recycling within the cell.