title: Sepiapterin attenuates 1-methyl-4-phenylpyridinium-induced apoptosis in neuroblastoma cells transfected with neuronal NOS: role of tetrahydrobiopterin, nitric oxide, and proteasome activation.
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.
authors.affiliation: Department of Biophysics and Free Radical Research Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
authors.forename: Tiesong
authors.initials: T
authors.lastname: Shang
authors.forename: Srigiridhar
authors.initials: S
authors.lastname: Kotamraju
authors.forename: Hongtao
authors.initials: H
authors.lastname: Zhao
authors.forename: Shasi V
authors.initials: SV
authors.lastname: Kalivendi
authors.forename: Cecilia J
authors.initials: CJ
authors.lastname: Hillard
authors.forename: B
authors.initials: B
authors.lastname: Kalyanaraman
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000633:toxicity*; D000154:Aconitate Hydratase / Q000037:antagonists & inhibitors; D017209:Apoptosis / Q000187:drug effects*; D001708:Biopterins / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism; D019281:Dimerization; D042967:Electron Transport Complex I / Q000037:antagonists & inhibitors; D004789:Enzyme Activation; D006801:Humans; D009447:Neuroblastoma; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011622:Pterins / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D011622:Pterins; D013481:Superoxides; D001708:Biopterins; D009569:Nitric Oxide; C016727:sepiapterin; D052248:Nitric Oxide Synthase Type I; D046988:Proteasome Endopeptidase Complex; D000154:Aconitate Hydratase; D042967:Electron Transport Complex I; C003402:sapropterin; D015655:1-Methyl-4-phenylpyridinium