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Secondary inhibition of 2-ketoglutarate dehydrogenase complex by MPTP

G T Joffe1, J K Parks, W D Parker

  • 1Department of Neurology, University of Virginia School of Medicine, Charlottesville 22901, USA.

Neuroreport
|October 6, 1998
PubMed

Insights

The neurotoxin 1-methyl-4-phenylpyridine (MPP+) may inhibit 2-ketoglutarate dehydrogenase complex (KDHC) via a radical-mediated process. Cysteine prevents this inhibition, suggesting MPP+ does not directly interact with KDHC.

Area of Science:

  • Neuroscience
  • Biochemistry
  • Toxicology

Background:

  • 1-methyl-4-phenylpyridine (MPP+) is a neurotoxin linked to parkinsonism.
  • MPP+ is known to inhibit complex I of the electron transport chain.
  • Emerging evidence suggests MPP+ may also inhibit 2-ketoglutarate dehydrogenase complex (KDHC).

Purpose of the Study:

  • To investigate the mechanism by which MPP+ inhibits KDHC.
  • To determine if MPP+ directly interacts with KDHC or acts indirectly.
  • To explore the role of radical-mediated events in MPP+-induced KDHC inhibition.

Main Methods:

  • Experiments were conducted using isolated rat liver mitochondria.
  • Inhibition of KDHC by MPP+ and S-nitroso-N-acetyl-penicillamine (SNAP) was assessed.
  • The effect of the radical quencher cysteine (Cys) on MPP+ and SNAP-induced inhibition was evaluated.

Main Results:

  • MPP+ was confirmed to inhibit KDHC in isolated rat liver mitochondria.
  • Preincubation with cysteine prevented the inhibition of KDHC by MPP+.
  • Cysteine also blocked the inhibition of KDHC by SNAP, a nitric oxide generator.

Conclusions:

  • MPP+ likely inhibits KDHC through a radical-mediated mechanism, not direct interaction.
  • The findings suggest a novel pathway for MPP+ neurotoxicity involving oxidative stress.
  • Cysteine's protective effect highlights the role of free radicals in KDHC dysfunction induced by MPP+.

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