title: Alpha-synuclein up-regulation and aggregation during MPP+-induced apoptosis in neuroblastoma cells: intermediacy of transferrin receptor iron and hydrogen peroxide.
abstract: 1-Methyl-4-phenylpyridinium (MPP(+)) is a neurotoxin that causes Parkinson's disease in experimental animals and humans. Despite the fact that intracellular iron was shown to be crucial for MPP(+)-induced apoptotic cell death, the molecular mechanisms for the iron requirement remain unclear. We investigated the role of transferrin receptor (TfR) and iron in modulating the expression of alpha-synuclein (alpha-syn) in MPP(+)-induced oxidative stress and apoptosis. Results show that MPP(+) inhibits mitochondrial complex-1 and aconitase activities leading to enhanced H(2)O(2) generation, TfR expression and alpha-syn expression/aggregation. Pretreatment with cell-permeable iron chelators, TfR antibody (that inhibits TfR-mediated iron uptake), or transfection with glutathione peroxidase (GPx1) enzyme inhibits intracellular oxidant generation, alpha-syn expression/aggregation, and apoptotic signaling as measured by caspase-3 activation. Cells overexpressing alpha-syn exacerbated MPP(+) toxicity, whereas antisense alpha-syn treatment totally abrogated MPP(+)-induced apoptosis in neuroblastoma cells without affecting oxidant generation. The increased cytotoxic effects of alpha-syn in MPP(+)-treated cells were attributed to inhibition of mitogen-activated protein kinase and proteasomal function. We conclude that MPP(+)-induced iron signaling is responsible for intracellular oxidant generation, alpha-syn expression, proteasomal dysfunction, and apoptosis. Relevance to Parkinson's disease is discussed.
authors.affiliation: Department of Biophysics and Free Radical Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: Shasi V
authors.initials: SV
authors.lastname: Kalivendi
authors.forename: Sonya
authors.initials: S
authors.lastname: Cunningham
authors.forename: Srigiridhar
authors.initials: S
authors.lastname: Kotamraju
authors.forename: Joy
authors.initials: J
authors.lastname: Joseph
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 / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D003546:Cysteine Endopeptidases / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D006540:Herbicides / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D020935:MAP Kinase Signaling System; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009447:Neuroblastoma / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D016877:Oxidants / Q000378:metabolism; D018384:Oxidative Stress; D046988:Proteasome Endopeptidase Complex; D011990:Receptors, Transferrin / Q000096:biosynthesis / Q000378:metabolism* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051843:Synucleins; D013997:Time Factors; D014162:Transfection; D015854:Up-Regulation; D051844:alpha-Synuclein
chemical_list: D000975:Antioxidants; D002614:Chelating Agents; D006540:Herbicides; D009097:Multienzyme Complexes; D009419:Nerve Tissue Proteins; D016376:Oligonucleotides, Antisense; D016877:Oxidants; D011990:Receptors, Transferrin; C497604:SNCA protein, human; D051843:Synucleins; D051844:alpha-Synuclein; D006861:Hydrogen Peroxide; D007501:Iron; D005979:Glutathione Peroxidase; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D015655:1-Methyl-4-phenylpyridinium