Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.64 (MPP)
 1,876 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In vivo administration of either 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or methamphetamine (MA) produces damage to the dopaminergic nervous system which may be due in part to the generation of reactive oxygen species (ROS). The resistance of superoxide dismutase (SOD) over-expressing transgenic mice to the effects of both MPTP and MA suggests the involvement of superoxide in the resulting neurotoxicity of both compounds. Superoxide can be converted by SOD to hydrogen peroxide, which itself can cause cellular degeneration by reacting with free iron to produce highly reactive hydroxyl radicals resulting in damage to proteins, nucleic acids and membrane phospholipids. Hydrogen peroxide has also been reported to be produced via inhibition of NADH dehydrogenase by MPP + formed during oxidation of MPTP by MAO-B and by dopamine auto-oxidation following MA-induced dopamine release from synaptic vesicles within nerve terminals. To test whether hydrogen peroxide is an important factor in the toxicity of either of these two neurotoxins, we created clonal PC12 lines expressing elevated levels of the hydrogen peroxide-reducing enzyme glutathione peroxidase (GSHPx). Elevation of GSHPx levels in PC12 was found to diminish the rise in ROS levels and lipid peroxidation resulting from MA but not MPTP treatment. Elevated levels of GSHPx also appeared to prevent decreases in transport-mediated dopamine uptake produced via MA administration as well as to attenuate toxin-induced cell loss as measured by either MTT reduction or LDH release. Our data, therefore, suggest that hydrogen peroxide production likely contributes to MA toxicity in dopaminergic neurons.
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PMID:Elevated expression of glutathione peroxidase in PC12 cells results in protection against methamphetamine but not MPTP toxicity. 919 Oct 89

The present study elucidated the protective effect of beta-carbolines (harmaline, harmalol, and harmine) on oxidative neuronal damage. MPTP treatment increased activities of total superoxide dismutase, catalase, and glutathione peroxidase and levels of malondialdehyde and carbonyls in the basal ganglia, diencephalon plus midbrain of brain compared with control mouse brain. Coadministration of harmalol (48 mg/kg) attenuated the MPTP effect on the enzyme activities and formation of tissue peroxidation products. Harmaline, harmalol, and harmine attenuated both the 500 microM MPP(+)-induced inhibition of electron flow and membrane potential formation and the 100 microM dopamine-induced thiol oxidation and carbonyl formation in mitochondria. The scavenging action of beta-carbolines on hydroxyl radicals was represented by inhibition of 2-deoxy-D-ribose degradation. Harmaline and harmalol (100 microM) attenuated 200 microM dopamine-induced viability loss in PC12 cells. The beta-carbolines (50 microM) attenuated 50 microM dopamine-induced apoptosis in PC12 cells. The compounds alone did not exhibit significant cytotoxic effects. The results indicate that beta-carbolines attenuate brain damage in mice treated with MPTP and MPP(+)-induced mitochondrial damage. The compounds may prevent dopamine-induced mitochondrial damage and PC12 cell death through a scavenging action on reactive oxygen species and inhibition of monoamine oxidase and thiol oxidation.
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PMID:Protective effect of harmalol and harmaline on MPTP neurotoxicity in the mouse and dopamine-induced damage of brain mitochondria and PC12 cells. 1089 27

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), via its major metabolite 1-methyl-4-phenylpyridinium (MPP(+)), produces in primates including humans clinical, biochemical, and neuropathological changes similar to those which occur in idiopathic Parkinson's disease. Ebselen is an antioxidant drug with glutathione peroxidase-like activity and a proven neuroprotective action in stroke patients. Here we show that Ebselen, when administered before, during, and after MPTP injections, prevents both neuronal loss and clinical symptoms in a primate MPTP model of Parkinson's disease. Ebselen also prevents peroxide radical overproduction induced by serum withdrawal in cultured PC12 cells and hydroxyl radical generation induced by the mitochondrial toxin, MPP(+), in vivo in rat brain. Moreover, Ebselen inhibits MPP(+)-induced toxicity in PC12 cells, without interacting with the dopamine uptake system. Our results demonstrate that compounds which prevent mitochondrial dysfunction and free radical production may be useful as preventive treatment of Parkinson's disease.
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PMID:The antioxidant ebselen prevents neurotoxicity and clinical symptoms in a primate model of Parkinson's disease. 1108 89

1-Methyl-4-phenylpyridinium (MPP(+)) is a neurotoxin used in cellular models of Parkinson's Disease. Although intracellular iron plays a crucial role in MPP(+)-induced apoptosis, the molecular signalling mechanisms linking iron, reactive oxygen species (ROS) and apoptosis are still unknown. We investigated these aspects using cerebellar granule neurons (CGNs) and human SH-SY5Y neuroblastoma cells. MPP(+) enhanced caspase 3 activity after 24 h with significant increases as early as 12 h after treatment of cells. Pre-treatment of CGNs and neuroblastoma cells with the metalloporphyrin antioxidant enzyme mimic, Fe(III)tetrakis(4-benzoic acid)porphyrin (FeTBAP), completely prevented the MPP(+)-induced caspase 3 activity as did overexpression of glutathione peroxidase (GPx1) and pre-treatment with a lipophilic, cell-permeable iron chelator [N, N '-bis-(2-hydroxybenzyl)ethylenediamine-N, N '-diacetic acid, HBED]. MPP(+) treatment increased the number of TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labelling)-positive cells which was completely blocked by pre-treatment with FeTBAP. MPP(+) treatment significantly decreased the aconitase and mitochondrial complex I activities; pre-treatment with FeTBAP, HBED and GPx1 overexpression reversed this effect. MPP(+) treatment increased the intracellular oxidative stress by 2-3-fold, as determined by oxidation of dichlorodihydrofluorescein and dihydroethidium (hydroethidine). These effects were reversed by pre-treatment of cells with FeTBAP and HBED and by GPx1 overexpression. MPP(+)-treatment enhanced the cell-surface transferrin receptor (TfR) expression, suggesting a role for TfR-induced iron uptake in MPP(+) toxicity. Treatment of cells with anti-TfR antibody (IgA class) inhibited MPP(+)-induced caspase activation. Inhibition of nitric oxide synthase activity did not affect caspase 3 activity, apoptotic cell death or ROS generation by MPP(+). Overall, these results suggest that MPP(+)-induced cell death in CGNs and neuroblastoma cells proceeds via apoptosis and involves mitochondrial release of ROS and TfR-dependent iron.
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PMID:1-Methyl-4-phenylpyridinium (MPP+)-induced apoptosis and mitochondrial oxidant generation: role of transferrin-receptor-dependent iron and hydrogen peroxide. 1252 38

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.
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PMID:Alpha-synuclein up-regulation and aggregation during MPP+-induced apoptosis in neuroblastoma cells: intermediacy of transferrin receptor iron and hydrogen peroxide. 1474 48

The neuropathology associated with Parkinson's disease (PD) is thought to involve excessive production of free radicals, dopamine autoxidation, defects in glutathione peroxidase expression, attenuated levels of reduced glutathione, altered calcium homeostasis, excitotoxicity and genetic defects in mitochondrial complex I activity. While the neurotoxic mechanisms are vastly different for excitotoxins and 1-methyl-4-phenylpyridinium ion (MPP(+)), both are thought to involve free radical production, compromised mitochondrial activity and excessive lipid peroxidation. We show here that the levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) increased significantly after treatment of cultured cerebellar granule cells (CGCs) with 50 microM MPP(+). Co-treatment with antioxidants such as ascorbate (ASC), catalase, alpha-tocopherol (alpha-TOH), coenzyme Q(10) (CoQ(10)) or superoxide dismutase (SOD) rescued the cells from MPP(+)-induced death. MPP(+)-induced cell death was also abolished by co-treatment with nitric oxide synthase (NOS) inhibitors such as 7-nitroindazole (7-NI), 2-ethyl-2-thiopseudourea hydrobromide (EPTU) or S-methylisothiourea sulphate (MPTU). We also tested the protective effects of an iron chelator (deferoxamine mesylate, DFx) and a peroxynitrite scavenger (FeTTPS) and the results lend further support to the view that the free radical cytotoxicity plays an essential role in MPP(+)-induced death in primary cultures of CGC.
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PMID:Protection against MPP+ neurotoxicity in cerebellar granule cells by antioxidants. 1519 80

Decreased glutathione levels associated with increased oxidative stress are a hallmark of numerous neurodegenerative diseases, including Parkinson's disease. GSH is an important molecule that serves as an anti-oxidant and is also a major determinant of cellular redox environment. Previous studies have demonstrated that neurotoxins can cause changes in reduced and oxidized GSH levels; however, information regarding steady state levels remains unexplored. The goal of this study was to characterize changes in cellular GSH levels and its regulatory enzymes in a dopaminergic cell line (N27) following treatment with the Parkinsonian toxin, 1-methyl-4-phenylpyridinium (MPP(+)). Cellular GSH levels were initially significantly decreased 12 h after treatment, but subsequently recovered to values greater than controls by 24 h. However, oxidized glutathione (GSSG) levels were increased 24 h following treatment, concomitant with a decrease in GSH/GSSG ratio prior to cell death. In accordance with these changes, ROS levels were also increased, confirming the presence of oxidative stress. Decreased enzymatic activities of glutathione reductase and glutamate-cysteine ligase by 20-25% were observed at early time points and partly account for changes in GSH levels after MPP(+) exposure. Additionally, glutathione peroxidase activity was increased 24 h following treatment. MPP(+) treatment was not associated with increased efflux of glutathione to the medium. These data further elucidate the mechanisms underlying GSH depletion in response to the Parkinsonian toxin, MPP(+).
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PMID:1-methyl-4-phenylpyridinium-induced alterations of glutathione status in immortalized rat dopaminergic neurons. 1739 26

The neuroprotective effects of catalpol, an iridoid glycoside present in the roots of Rehmannia glutinosa, on 1-methyl-4-phenylpyridinium (MPP(+))-induced oxidative stress in cultured mesencephalic neurons, especially dopaminergic neurons, were investigated. Exposure of mesencephalic neurons to 10microM MPP(+) induced a leakage of lactate dehydrogenase (LDH) and decreased cell viability, measured with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Catalpol increased neuron viability and markedly attenuated MPP(+)-induced dopaminergic neuron death in a dose-dependent manner. In order to clarify the neuroprotective mechanism of catalpol, mitochondrial function, the activities of endogenous antioxidants and the lipid peroxide content were measured. The results indicated that catalpol prevented the MPP(+)-induced inhibition of complex I activity and the loss of mitochondrial membrane potential. In addition, catalpol reduced the content of lipid peroxide and increased the activity of glutathione peroxidase and superoxide dismutase. Taken together, the above results suggest that catalpol may be a candidate drug for the treatment of oxidative stress-induced neurodegenerative disease.
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PMID:Neuroprotective effect of catalpol against MPP(+)-induced oxidative stress in mesencephalic neurons. 1751 20

PC12 cells were used to examine the in vitro antioxidative and anti-inflammatory effects of oleanolic acid (OA) and ursolic acid (UA). PC12 cells were pretreated with OA or UA at 20 and 40 microM and followed by exposure of hydrogen peroxide (H(2)O(2)) or 1-methyl-4-phenylpyridinium ion (MPP(+)) to induce cell injury. Results showed that H(2)O(2)- or MPP(+)-treatment significantly decreased cell viability and increased lactate dehydrogenase (LDH) release (P < 0.05). The pretreatment from OA or UA significantly and concentration-dependently reduced subsequent H(2)O(2)- or MPP(+)-induced cell death and LDH release (P < 0.05). Either H(2)O(2)- or MPP(+)-treatment significantly increased malonyldialdehyde (MDA) formation, decreased glutathione (GSH) content, and diminished glutathione peroxidase (GPX), catalase, and superoxide dismutase (SOD) activities (P < 0.05). The pretreatment from OA or UA significantly retained GSH, and reversed H(2)O(2)- and MPP(+)-induced impairment in catalase and SOD activities (P < 0.05), and decreased MDA formation (P < 0.05). Either H(2)O(2)- or MPP(+)-treatment significantly elevated interleukin-6 (IL-6) and tumor necrosis factor (TNF)-alpha levels (P < 0.05). The pretreatments from OA or UA significantly attenuated subsequent H(2)O(2)- or MPP(+)-induced release of IL-6 and TNF-alpha (P < 0.05). Based on the observed antioxidative and anti-inflammatory activities from OA and UA, these 2 compounds were potent agents against neurodegenerative disorder.
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PMID:Antioxidative and anti-inflammatory protection of oleanolic acid and ursolic acid in PC12 cells. 1880 14

Nerve growth factor differentiated PC12 cells were used to examine the antioxidative and anti-inflammatory effects of astaxanthin (AX) and canthaxanthin (CX). PC12 cells were pretreated with AX or CX at 10 or 20 muM, and followed by exposure of hydrogen peroxide (H(2)O(2)) or 1-methyl-4-phenylpyridinium ion (MPP(+)) to induce cell injury. H(2)O(2) or MPP(+) treatment significantly decreased cell viability, increased lactate dehydrogenase (LDH) release, enhanced DNA fragmentation, and lowered mitochondrial membrane potential (MMP) (P < 0.05). The pretreatments from AX or CX concentration-dependently alleviated H(2)O(2) or MPP(+)-induced cell death, LDH release, DNA fragmentation, and MMP reduction (P < 0.05). Either H(2)O(2) or MPP(+) treatment significantly increased malonyldialdehyde (MDA) and reactive oxygen species (ROS) formations, decreased glutathione content, and lowered glutathione peroxidase (GPX) and catalase activities (P < 0.05). The pretreatments from AX or CX significantly retained GPX and catalase activities, and decreased MDA and ROS formations (P < 0.05). H(2)O(2) or MPP(+) treatment significantly decreased Na(+)-K(+)-ATPase activity, elevated caspase-3 activity and levels of interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-alpha (P < 0.05); and the pretreatments from these agents significantly restored Na(+)-K(+)-ATPase activity, suppressed caspase-3 activity and release of IL-1, IL-6, and TNF-alpha (P < 0.05). Based on the observed antioxidative and anti-inflammatory protection from AX and CX, these 2 compounds were potent agents against neurodegenerative disorder.
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PMID:Antioxidative and anti-inflammatory neuroprotective effects of astaxanthin and canthaxanthin in nerve growth factor differentiated PC12 cells. 1989 74


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