Sepiapterin attenuates 1-methyl-4-phenylpyridinium-induced apoptosis in neuroblastoma cells transfected with neuronal NOS: role of tetrahydrobiopterin, nitric oxide, and proteasome activation

Free Radic Biol Med. 2005 Oct 15;39(8):1059-74. doi: 10.1016/j.freeradbiomed.2005.05.022.

Abstract

In this study, we investigated the molecular mechanism of toxicity of 1-methyl-4-phenylpyridinium (MPP+), an ultimate toxic metabolite of a mitochondrial neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, that causes parkinsonism in experimental animals and humans. Using wild-type and human neuronal nitric oxide synthase (nNOS) stably transfected neuroblastoma cells (SH-SY5Y), we showed that nNOS overexpression in SH-SY5Y cells greatly enhanced proteasome activity and mitigated MPP+-induced apoptosis. During MPP+-induced oxidative stress, intracellular BH4 levels decreased, resulting in nNOS "uncoupling" (i.e., switching from nitric oxide to superoxide generation). Increasing the intracellular BH4 levels by sepiapterin supplementation restored the nNOS activity, inhibited superoxide formation, increased proteasome activity, decreased protein ubiquitination, and attenuated apoptosis in MPP+-treated cells. Implications of BH4 depletion in dopaminergic cells and sepiapterin supplementation to augment the striatal nNOS activity in the pathogenesis mechanism and treatment of Parkinson disease are discussed.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Methyl-4-phenylpyridinium / toxicity*
  • Aconitate Hydratase / antagonists & inhibitors
  • Apoptosis / drug effects*
  • Biopterins / analogs & derivatives
  • Biopterins / analysis
  • Biopterins / metabolism
  • Dimerization
  • Electron Transport Complex I / antagonists & inhibitors
  • Enzyme Activation
  • Humans
  • Neuroblastoma
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase Type I / genetics
  • Nitric Oxide Synthase Type I / metabolism*
  • Proteasome Endopeptidase Complex / metabolism*
  • Pterins / pharmacology*
  • Superoxides / metabolism
  • Transfection
  • Tumor Cells, Cultured

Substances

  • Pterins
  • Superoxides
  • Biopterins
  • Nitric Oxide
  • sepiapterin
  • Nitric Oxide Synthase Type I
  • Proteasome Endopeptidase Complex
  • Aconitate Hydratase
  • Electron Transport Complex I
  • sapropterin
  • 1-Methyl-4-phenylpyridinium