What is the oxidation hypothesis of the etiology of Parkinson disease (PD)?

Updated: Jan 24, 2019
  • Author: Robert A Hauser, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
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Answer

The oxidation hypothesis suggests that free radical damage, resulting from dopamine's oxidative metabolism, plays a role in the development or progression of Parkinson disease. The oxidative metabolism of dopamine by MAO leads to the formation of hydrogen peroxide. Normally, hydrogen peroxide is cleared rapidly by glutathione, but if hydrogen peroxide is not cleared adequately, it may lead to the formation of highly reactive hydroxyl radicals that can react with cell membrane lipids to cause lipid peroxidation and cell damage. In Parkinson disease, levels of reduced glutathione are decreased, suggesting a loss of protection against formation of free radicals. Iron is increased in the substantia nigra and may serve as a source of donor electrons, thereby promoting the formation of free radicals.

Parkinson disease is associated with increased dopamine turnover, decreased protective mechanisms (glutathione), increased iron (a pro-oxidation molecule), and evidence of increased lipid peroxidation. This hypothesis has raised concern that increased dopamine turnover due to levodopa administration could increase oxidative damage and accelerate loss of dopamine neurons. However, there is no clear evidence that levodopa accelerates disease progression.


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