8-hydroxyguanine and Parkinsonian-Disorders

We previously reported that 8-oxoguanine (8-oxoG) accumulates in the cytoplasm of dopamine neurons in the substantia nigra of patients with Parkinson's disease and the expression of MTH1 carrying an oxidized purine nucleoside triphosphatase activity increases in these neurons, thus suggesting that oxidative damage in nucleic acids is involved in dopamine neuron loss. In the present study, we found that levels of 8-oxoG in cellular DNA and RNA increased in the mouse nigrostriatal system during the tyrosine hydroxylase (TH)-positive dopamine neuron loss induced by the administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MTH1-null mice exhibited a greater accumulation of 8-oxoG in mitochondrial DNA accompanied by a more significant decrease in TH and dopamine transporter immunoreactivities in the striatum after MPTP administration, than in wild-type mice. We thus demonstrated that MTH1 protects the dopamine neurons from oxidative damage in the nucleic acids, especially in the mitochondrial DNA of striatal nerve terminals of dopamine neurons.

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; Animals; Corpus Striatum; Disease Models, Animal; DNA Repair Enzymes; DNA, Mitochondrial; Dopamine; Dopamine Plasma Membrane Transport Proteins; Guanine; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Neurons; Oxidative Stress; Parkinsonian Disorders; Phosphoric Monoester Hydrolases; RNA; Substantia Nigra; Tyrosine 3-Monooxygenase

Mutations in parkin are involved in some cases of autosomal recessive juvenile parkinsonism (AR-JP), but it is not known how they result in nigral cell death. We examined the effect of parkin overexpression on the response of cells to various insults. Wild-type and AR-JP-associated mutant parkins (Del3-5, T240R, and Q311X) were overexpressed in NT-2 and SK-N-MC cells. Overexpressed wild-type parkin delayed cell death induced by serum withdrawal, H(2)O(2), 1-methyl-4-phenylpyridinium (MPP(+)), or 4-hydroxy-2-trans-nonenal (HNE) but did not delay cell death caused by the proteasome inhibitor lactacystin. Increases in damage to proteins (protein carbonyls and 3-nitrotyrosine) were attenuated by wild-type parkin after serum withdrawal or exposure to H(2)O(2), MPP(+), or HNE but not after exposure to lactacystin. The mutant parkins (of all types) markedly accelerated cell death in response to all the insults, accompanied by increased levels of 8-hydroxyguanine, protein carbonyls, lipid peroxidation, and 3-nitrotyrosine and decreased levels of GSH. The viability loss induced by all the insults showed apoptotic features. The presence of parkin mutations in substantia nigra in Parkinson's disease may increase neuronal vulnerability to a range of toxic insults.

Topics: 1-Methyl-4-phenylpyridinium; Acetylcysteine; Aldehydes; Apoptosis; Cell Death; Cell Line, Tumor; Drug Resistance; Enzyme Inhibitors; Genetic Predisposition to Disease; Glutamic Acid; Guanine; Humans; Hydrogen Peroxide; Mutation; Nerve Degeneration; Neurons; Neurotoxins; Oxidative Stress; Parkinsonian Disorders; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Substantia Nigra; Tyrosine; Ubiquitin-Protein Ligases

Mutations in alpha-synuclein (A30P and A53T) are involved in some cases of familial Parkinson's disease (FPD), but it is not known how they result in nigral cell death. We examined the effect of alpha-synuclein overexpression on the response of cells to various insults. Wild-type alpha-synuclein and alpha-synuclein mutations associated with FPD were overexpressed in NT-2/D1 and SK-N-MC cells. Overexpression of wild-type alpha-synuclein delayed cell death induced by serum withdrawal or H(2)O(2), but did not delay cell death induced by 1-methyl-4-phenylpyridinium ion (MPP(+)). By contrast, wild-type alpha-synuclein transfectants were sensitive to viability loss induced by staurosporine, lactacystin or 4-hydroxy-2-trans-nonenal (HNE). Decreases in glutathione (GSH) levels were attenuated by wild-type alpha-synuclein after serum deprivation, but were aggravated following lactacystin or staurosporine treatment. Mutant alpha-synucleins increased levels of 8-hydroxyguanine, protein carbonyls, lipid peroxidation and 3-nitrotyrosine, and markedly accelerated cell death in response to all the insults examined. The decrease in GSH levels was enhanced in mutant alpha-synuclein transfectants. The loss of viability induced by toxic insults was by apoptosic mechanism. The presence of abnormal alpha-synucleins in substantia nigra in PD may increase neuronal vulnerability to a range of toxic agents.

Topics: 1-Methyl-4-phenylpyridinium; Aldehydes; alpha-Synuclein; Cell Division; Cell Line; Cell Survival; Clone Cells; Culture Media, Serum-Free; Enzyme Inhibitors; Gene Expression; Glutathione; Guanine; Humans; Hydrogen Peroxide; Ketones; Lipid Peroxidation; Mitochondria; Mutation; Nerve Tissue Proteins; Neuroblastoma; Oxidants; Oxidative Stress; Parkinsonian Disorders; Synucleins; Teratocarcinoma; Transfection; Tyrosine