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1.
PLoS One ; 13(3): e0194896, 2018.
Article in English | MEDLINE | ID: mdl-29566083

ABSTRACT

More than 90% of the cases of Parkinson's disease have unknown etiology. Gradual loss of dopaminergic neurons of substantia nigra is the main cause of morbidity in this disease. External factors such as environmental toxins are believed to play a role in the cell loss, although the cause of the selective vulnerability of dopaminergic neurons remains unknown. We have previously shown that aquaglyceroporin AQP9 is expressed in dopaminergic neurons and astrocytes of rodent brain. AQP9 is permeable to a broad spectrum of substrates including purines, pyrimidines, and lactate, in addition to water and glycerol. Here we test our hypothesis that AQP9 serves as an influx route for exogenous toxins and, hence, may contribute to the selective vulnerability of nigral dopaminergic (tyrosine hydroxylase-positive) neurons. Using Xenopus oocytes injected with Aqp9 cRNA, we show that AQP9 is permeable to the parkinsonogenic toxin 1-methyl-4-phenylpyridinium (MPP+). Stable expression of AQP9 in HEK cells increases their vulnerability to MPP+ and to arsenite-another parkinsonogenic toxin. Conversely, targeted deletion of Aqp9 in mice protects nigral dopaminergic neurons against MPP+ toxicity. A protective effect of Aqp9 deletion was demonstrated in organotypic slice cultures of mouse midbrain exposed to MPP+ in vitro and in mice subjected to intrastriatal injections of MPP+ in vivo. Seven days after intrastriatal MPP+ injections, the population of tyrosine hydroxylase-positive cells in substantia nigra is reduced by 48% in Aqp9 knockout mice compared with 67% in WT littermates. Our results show that AQP9 -selectively expressed in catecholaminergic neurons-is permeable to MPP+ and suggest that this aquaglyceroporin contributes to the selective vulnerability of nigral dopaminergic neurons by providing an entry route for parkinsonogenic toxins. To our knowledge this is the first evidence implicating a toxin permeable membrane channel in the pathophysiology of Parkinson's disease.


Subject(s)
Aquaporins/genetics , Neuroprotection/genetics , Parkinson Disease/genetics , Parkinson Disease/pathology , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Animals , Disease Models, Animal , Dopaminergic Neurons/drug effects , Dopaminergic Neurons/metabolism , Female , Gene Deletion , HEK293 Cells , Humans , MPTP Poisoning/genetics , MPTP Poisoning/metabolism , MPTP Poisoning/pathology , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Mutagenesis, Site-Directed , Neuroprotective Agents/metabolism , Parkinson Disease, Secondary/chemically induced , Parkinson Disease, Secondary/genetics , Parkinson Disease, Secondary/metabolism , Parkinson Disease, Secondary/pathology , Substantia Nigra/drug effects , Substantia Nigra/metabolism , Xenopus laevis
2.
Neurotox Res ; 34(1): 47-61, 2018 07.
Article in English | MEDLINE | ID: mdl-29460114

ABSTRACT

Several studies have shown that intrastriatal application of 1-methyl-4-phenylpyridinium (MPP+) produces similar biochemical changes in rat to those seen in Parkinson's disease (PD), such as dopaminergic terminal degeneration and consequent appearance of motor deficits, making the MPP+ lesion a widely used model of parkinsonism in rodents. Previous results from our group have shown a neuroprotective effect of the carboxyl-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) under different types of stress. In the present study, pretreatment with the intraperitoneal injection of Hc-TeTx in rats prevents the decrease of tyrosine hydroxylase immunoreactivity in the striatum due to injury with MPP+, when applied stereotaxically in the striatum. Similarly, striatal catecholamine contents are restored, as well as the levels of two other dopaminergic markers, the dopamine transporter (DAT) and the vesicular monoamine transporter-2 (VMAT-2). Additionally, uptake studies of [3H]-dopamine and [3H]-MPP+ reveal that DAT action is not affected by Hc-TeTx, discarding a protective effect due to a reduced entry of MPP+ into nerve terminals. Behavioral assessments show that Hc-TeTx pretreatment improves the motor skills (amphetamine-induced rotation, forelimb use, and adjusting steps) of MPP+-treated rats. Our results lead us to consider Hc-TeTx as a potential therapeutic tool in pathologies caused by impairment of dopaminergic innervation in the striatum, as is the case of PD.


Subject(s)
MPTP Poisoning/prevention & control , Neuroprotective Agents/administration & dosage , Peptide Fragments/administration & dosage , Tetanus Toxin/administration & dosage , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , 3,4-Dihydroxyphenylacetic Acid/metabolism , Analysis of Variance , Animals , Corpus Striatum/drug effects , Corpus Striatum/metabolism , Corpus Striatum/ultrastructure , Disease Models, Animal , Dopamine/metabolism , Dopamine/pharmacokinetics , Dopamine Plasma Membrane Transport Proteins/metabolism , Dose-Response Relationship, Drug , Drug Administration Routes , Drug Administration Schedule , Functional Laterality/drug effects , Homovanillic Acid/metabolism , MPTP Poisoning/pathology , Male , Movement/drug effects , Peptide Fragments/therapeutic use , Rats , Rats, Sprague-Dawley , Substantia Nigra/drug effects , Substantia Nigra/pathology , Synaptosomes/drug effects , Synaptosomes/metabolism , Tetanus Toxin/therapeutic use , Time Factors , Tritium/pharmacokinetics , Tyrosine 3-Monooxygenase/metabolism
3.
Trends Pharmacol Sci ; 38(6): 541-555, 2017 06.
Article in English | MEDLINE | ID: mdl-28442167

ABSTRACT

The neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes a Parkinson's disease (PD)-like syndrome by inducing degeneration of nigrostriatal dopaminergic neurons. Studies of the MPTP model have revealed the pathomechanisms underlying dopaminergic neurodegeneration and facilitated the development of drug treatments for PD. In this review, we provide an update on MPTP bioactivation and biodistribution, reconcile the distinct views on energetic failure versus reactive oxygen species (ROS) formation as main drivers of MPTP-induced neurodegeneration, and describe recently identified intrinsic features of the nigrostriatal system that make it particularly vulnerable to MPTP. We discuss these new perspectives on the endogenous tipping points of tissue homeostasis and the drivers responsible for vicious cycles in relation to their relevance for the development of novel intervention strategies for PD.


Subject(s)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacology , MPTP Poisoning/chemically induced , Neurodegenerative Diseases/chemically induced , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Animals , Astrocytes/drug effects , Astrocytes/metabolism , Astrocytes/pathology , Dopaminergic Neurons/drug effects , Dopaminergic Neurons/metabolism , Dopaminergic Neurons/pathology , Humans , MPTP Poisoning/metabolism , MPTP Poisoning/pathology , Neostriatum/drug effects , Neostriatum/metabolism , Neostriatum/pathology , Neurodegenerative Diseases/metabolism , Neurodegenerative Diseases/pathology
4.
Biochemistry (Mosc) ; 82(3): 330-339, 2017 Mar.
Article in English | MEDLINE | ID: mdl-28320274

ABSTRACT

Mitochondria play an important role in molecular mechanisms of neuroplasticity, adaptive changes of the brain that occur in the structure and function of its cells in response to altered physiological conditions or development of pathological disorders. Mitochondria are a crucial target for actions of neurotoxins, causing symptoms of Parkinson's disease in various experimental animal models, and also neuroprotectors. Good evidence exists in the literature that mitochondrial dysfunction induced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) influences functioning of the ubiquitin-proteasomal system (UPS) responsible for selective proteolytic degradation of proteins from various intracellular compartments (including mitochondria), and neuroprotective effects of certain antiparkinsonian agents (monoamine oxidase inhibitors) may be associated with their effects on UPS. The 19S proteasomal Rpn10 subunit is considered as a ubiquitin receptor responsible for delivery of ubiquitinated proteins to the proteasome proteolytic machinery. In this study, we investigated proteomic profiles of mouse brain mitochondrial Rpn10-binding proteins, brain monoamine oxidase B (MAO B) activity, and their changes induced by a single-dose administration of the neurotoxin MPTP and the neuroprotector isatin. Administration of isatin to mice prevented MPTP-induced inactivation of MAO B and influenced the profile of brain mitochondrial Rpn10-binding proteins, in which two pools of proteins were clearly recognized. The constitutive pool was insensitive to neurotoxic/neuroprotective treatments, while the variable pool was specifically influenced by MPTP and the neuroprotector isatin. Taking into consideration that the neuroprotective dose of isatin used in this study can result in brain isatin concentrations that are proapoptotic for cells in vitro, the altered repertoire of mitochondrial Rpn10-binding proteins may thus represent a part of a switch mechanism from targeted elimination of individual (damaged) proteins to more efficient ("global") elimination of damaged organelles and whole damaged cells.


Subject(s)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Brain/metabolism , Carrier Proteins/metabolism , Isatin , MPTP Poisoning/metabolism , Mitochondria/metabolism , Nerve Tissue Proteins/metabolism , Neuroprotective Agents , Neurotoxins , Animals , Brain/pathology , Isatin/pharmacokinetics , Isatin/pharmacology , MPTP Poisoning/pathology , Male , Mice , Monoamine Oxidase/metabolism , Neuroprotective Agents/pharmacokinetics , Neuroprotective Agents/pharmacology , Neurotoxins/pharmacokinetics , Neurotoxins/toxicity , RNA-Binding Proteins
5.
J Cereb Blood Flow Metab ; 35(1): 37-47, 2015 Jan.
Article in English | MEDLINE | ID: mdl-25248837

ABSTRACT

This study was to investigate the influence of age on the expression of organic cation transporters (OCTs) that belong to the SLC22 family in brain microvessels (BMVs) and its implications for 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic toxicity in mice. Here, we showed that Oct1 and Oct2, but not Oct3, mRNAs were detected and enriched (compared with cerebral cortex) in BMVs of C57BL/6 (B6) mice using reverse transcription-quantitative PCR (RT-qPCR), and immunofluorescence analysis further revealed that Oct1 and Oct2 proteins were colocalized with endothelial markers. Both the mRNA and protein levels of Oct1 and Oct2 were reduced in aged mice. After an intraperitoneal administration of MPTP, brain extracellular levels of MPTP and 1-methyl-4-phenyl-pyridinium (MPP(+)) were much lower in aged mice and in Oct1/2(-/-) mice compared with younger mice and wild-type control mice, respectively. Knockout of Oct1/Oct2 protected Oct1/2(-/-) mice from MPTP-induced neurotoxicity, whereas the loss of tyrosine hydroxylase (TH)-positive neurons was slightly greater in aged than in younger mice. However, intrastriatal infusion of low-dose MPTP caused more severe dopaminergic toxicity in the substantia nigra of both aged mice and Oct1/2(-/-) mice. These findings show that age-dependent downregulation or knockout of Oct1/Oct2 in BMVs may reduce the transport of MPTP, which, in part, affects its dopaminergic toxicity.


Subject(s)
Aging/metabolism , Brain/blood supply , Dopamine/metabolism , MPTP Poisoning/metabolism , Microvessels/metabolism , Octamer Transcription Factor-1/genetics , Organic Cation Transport Proteins/genetics , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , 1-Methyl-4-phenylpyridinium/metabolism , Animals , Blood-Brain Barrier/metabolism , Brain/metabolism , Corpus Striatum/drug effects , Corpus Striatum/metabolism , Dogs , Dose-Response Relationship, Drug , Down-Regulation , Injections, Intraperitoneal , Madin Darby Canine Kidney Cells , Male , Mice, Inbred C57BL , Mice, Knockout , Microdialysis , Organic Cation Transporter 2 , RNA, Messenger/genetics , Reverse Transcriptase Polymerase Chain Reaction , Transfection
6.
Int J Toxicol ; 33(6): 482-9, 2014.
Article in English | MEDLINE | ID: mdl-25381089

ABSTRACT

Allometric scaling between metabolic rate, size, body temperature, and other biological traits has found broad applications in ecology, physiology, and particularly in toxicology and pharmacology. Basal metabolic rate (BMR) was observed to scale with body size and temperature. However, the mass scaling exponent was increasingly debated whether it should be 2/3, 3/4, or neither, and scaling with body temperature also attracted recent attention. Based on thermodynamic principles, this work reports 2 new scaling relationships between BMR, size, temperature, and biological time. Good correlations were found with the new scaling relationships, and no universal scaling exponent can be obtained. The new scaling relationships were successfully validated with external toxicological and pharmacological studies. Results also demonstrated that individual extrapolation models can be built to obtain scaling exponent specific to the interested group, which can be practically applied for dose and toxicity extrapolations.


Subject(s)
Basal Metabolism , Body Size , Body Temperature , Pharmacology/methods , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/analogs & derivatives , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Amphibians , Animals , Arachnida , Azetidines/pharmacokinetics , Birds , Fishes , Fluoroquinolones/pharmacokinetics , Humans , Insecta , Linear Models , Mammals , Maximum Tolerated Dose , Piperazines/pharmacokinetics , Prokaryotic Cells , Reptiles , Toxicity Tests/methods
7.
Neurotoxicology ; 37: 1-14, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23523781

ABSTRACT

The pharmacokinetics and neurotoxicity of paraquat dichloride (PQ) were assessed following once weekly administration to C57BL/6J male mice by intraperitoneal injection for 1, 2 or 3 weeks at doses of 10, 15 or 25 mg/kg/week. Approximately 0.3% of the administered dose was taken up by the brain and was slowly eliminated, with a half-life of approximately 3 weeks. PQ did not alter the concentration of dopamine (DA), homovanillic acid (HVA) or 3,4-dihydroxyphenylacetic acid (DOPAC), or increase dopamine turnover in the striatum. There was inconsistent stereological evidence of a loss of DA neurons, as identified by chromogenic or fluorescent-tagged antibodies to tyrosine hydroxylase in the substantia nigra pars compacta (SNpc). There was no evidence that PQ induced neuronal degeneration in the SNpc or degenerating neuronal processes in the striatum, as indicated by the absence of uptake of silver stain or reduced immunolabeling of tyrosine-hydroxylase-positive (TH(+)) neurons. There was no evidence of apoptotic cell death, which was evaluated using TUNEL or caspase 3 assays. Microglia (IBA-1 immunoreactivity) and astrocytes (GFAP immunoreactivity) were not activated in PQ-treated mice 4, 8, 16, 24, 48, 96 or 168 h after 1, 2 or 3 doses of PQ. In contrast, mice dosed with the positive control substance, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 10mg/kg/dose×4 doses, 2 h apart), displayed significantly reduced DA and DOPAC concentrations and increased DA turnover in the striatum 7 days after dosing. The number of TH(+) neurons in the SNpc was reduced, and there were increased numbers of degenerating neurons and neuronal processes in the SNpc and striatum. MPTP-mediated cell death was not attributed to apoptosis. MPTP activated microglia and astrocytes within 4 h of the last dose, reaching a peak within 48 h. The microglial response ended by 96 h in the SNpc, but the astrocytic response continued through 168 h in the striatum. These results bring into question previous published stereological studies that report loss of TH(+) neurons in the SNpc of PQ-treated mice. This study also suggests that even if the reduction in TH(+) neurons reported by others occurs in PQ-treated mice, this apparent phenotypic change is unaccompanied by neuronal cell death or by modification of dopamine levels in the striatum.


Subject(s)
Basal Ganglia/drug effects , Herbicides/pharmacokinetics , Herbicides/toxicity , Paraquat/pharmacokinetics , Paraquat/toxicity , Substantia Nigra/drug effects , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , 3,4-Dihydroxyphenylacetic Acid/metabolism , Animals , Astrocytes/drug effects , Astrocytes/metabolism , Astrocytes/pathology , Basal Ganglia/metabolism , Basal Ganglia/pathology , Cell Death/drug effects , Dopamine/metabolism , Dopaminergic Neurons/drug effects , Dopaminergic Neurons/metabolism , Dopaminergic Neurons/pathology , Dose-Response Relationship, Drug , Drug Administration Schedule , Half-Life , Herbicides/administration & dosage , Homovanillic Acid/metabolism , Injections, Intraperitoneal , MPTP Poisoning/metabolism , MPTP Poisoning/pathology , Male , Metabolic Clearance Rate , Mice , Mice, Inbred C57BL , Microglia/drug effects , Microglia/metabolism , Microglia/pathology , Nerve Degeneration , Paraquat/administration & dosage , Substantia Nigra/metabolism , Substantia Nigra/pathology , Tyrosine 3-Monooxygenase/metabolism
8.
J Biol Chem ; 288(6): 4436-51, 2013 Feb 08.
Article in English | MEDLINE | ID: mdl-23258538

ABSTRACT

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxic side product formed in the chemical synthesis of desmethylprodine opioid analgesic, which induces Parkinson disease. Monoamine oxidase B, present in the mitochondrial outer membrane of glial cells, catalyzes the oxidation of MPTP to the toxic 1-methyl-4-phenylpyridinium ion (MPP(+)), which then targets the dopaminergic neurons causing neuronal death. Here, we demonstrate that mitochondrion-targeted human cytochrome P450 2D6 (CYP2D6), supported by mitochondrial adrenodoxin and adrenodoxin reductase, can efficiently catalyze the metabolism of MPTP to MPP(+), as shown with purified enzymes and also in cells expressing mitochondrial CYP2D6. Neuro-2A cells stably expressing predominantly mitochondrion-targeted CYP2D6 were more sensitive to MPTP-mediated mitochondrial respiratory dysfunction and complex I inhibition than cells expressing predominantly endoplasmic reticulum-targeted CYP2D6. Mitochondrial CYP2D6 expressing Neuro-2A cells produced higher levels of reactive oxygen species and showed abnormal mitochondrial structures. MPTP treatment also induced mitochondrial translocation of an autophagic marker, Parkin, and a mitochondrial fission marker, Drp1, in differentiated neurons expressing mitochondrial CYP2D6. MPTP-mediated toxicity in primary dopaminergic neurons was attenuated by CYP2D6 inhibitor, quinidine, and also partly by monoamine oxidase B inhibitors deprenyl and pargyline. These studies show for the first time that dopaminergic neurons expressing mitochondrial CYP2D6 are fully capable of activating the pro-neurotoxin MPTP and inducing neuronal damage, which is effectively prevented by the CYP2D6 inhibitor quinidine.


Subject(s)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Cytochrome P-450 CYP2D6/metabolism , Dopamine Agents/pharmacokinetics , Dopaminergic Neurons/enzymology , Mitochondria/metabolism , Mitochondrial Proteins/metabolism , Parkinsonian Disorders/enzymology , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/adverse effects , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacology , Adrenergic alpha-Antagonists/pharmacology , Animals , Cell Line , Cytochrome P-450 CYP2D6/genetics , Dopamine Agents/adverse effects , Dopamine Agents/pharmacology , Dopaminergic Neurons/pathology , Dynamins/genetics , Dynamins/metabolism , Humans , Mice , Mitochondria/genetics , Mitochondrial Proteins/genetics , Parkinsonian Disorders/drug therapy , Parkinsonian Disorders/genetics , Parkinsonian Disorders/pathology , Quinidine/pharmacology , Reactive Oxygen Species/metabolism , Ubiquitin-Protein Ligases/genetics , Ubiquitin-Protein Ligases/metabolism
9.
Neuropharmacology ; 60(6): 963-74, 2011 May.
Article in English | MEDLINE | ID: mdl-21288472

ABSTRACT

Parkinson's disease (PD) is characterized by degeneration of nigrostriatal dopaminergic (DA) neurons. Mice treated with MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) exhibit microglial activation-induced oxidative stress and inflammation, and nigrostriatal DA neuronal damage, and thus serve as an experimental model of PD. Here, we report that fluoxetine, one of the most commonly prescribed antidepressants, prevents MPTP-induced degeneration of nigrostriatal DA neurons and increases striatal dopamine levels with the partial motor recovery. This was accompanied by inhibiting transient expression of proinflammatory cytokines and inducible nitric oxide synthase; and attenuating microglial NADPH oxidase activation, reactive oxygen species/reactive nitrogen species production, and consequent oxidative damage. Interestingly, fluoxetine was found to protect DA neuronal damage from 1-methyl-4-phenyl-pyridinium (MPP(+)) neurotoxicity in co-cultures of mesencephalic neurons and microglia but not in neuron-enriched mesencephalic cultures devoid of microglia. The present in vivo and in vitro findings show that fluoxetine may possess anti-inflammatory properties and inhibit glial activation-mediated oxidative stress. Therefore, we carefully propose that neuroprotection of fluoxetine might be associated with its anti-inflammatory properties and could be employed as novel therapeutic agents for PD and other disorders associated with neuroinflammation and microglia-derived oxidative damage.


Subject(s)
Dopamine/metabolism , Fluoxetine/therapeutic use , MPTP Poisoning/prevention & control , Microglia/metabolism , Nerve Degeneration/prevention & control , Neurons/pathology , Recovery of Function/drug effects , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , 1-Methyl-4-phenylpyridinium/antagonists & inhibitors , 1-Methyl-4-phenylpyridinium/pharmacology , Animals , Cell Count/methods , Coculture Techniques/methods , Corpus Striatum/drug effects , Corpus Striatum/metabolism , Cytokines/metabolism , Fluoxetine/pharmacology , MPTP Poisoning/metabolism , Male , Mice , Mice, Inbred C57BL , Microglia/immunology , NADPH Oxidases/antagonists & inhibitors , NADPH Oxidases/metabolism , Nerve Degeneration/chemically induced , Neurons/metabolism , Neuroprotective Agents/pharmacology , Neuroprotective Agents/therapeutic use , Nitric Oxide Synthase Type II/metabolism , Oxidative Stress/drug effects , Rotarod Performance Test/methods , Substantia Nigra
10.
J Neurochem ; 114(3): 717-27, 2010 Aug.
Article in English | MEDLINE | ID: mdl-20477935

ABSTRACT

The cellular localization of organic cation transporter (OCT) 1 and OCT2 in isolated brain microvessel endothelial cells from humans, rats, and mice and in cultured adult rat brain endothelial cells was examined by confocal microscopy and in isolated luminal and abluminal membrane fractions by Western blot analysis. Cellular uptake of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was measured with or without OCT1/OCT2 silencing. The interaction between MPTP and amantadine was studied by in vitro kinetic analysis and in vivo brain microdialysis. MPTP-induced dopaminergic toxicity was examined by measuring dopamine levels in the brain striatum and by positron emission tomography scanning. The results showed that both OCT1 and OCT2 were mainly expressed on the luminal side of brain microvessel endothelial cells and adult rat brain endothelial cells. Cellular uptake of MPTP was significantly (p < 0.05) decreased by about 53%, 60%, or 91% following silencing of OCT1, OCT2, or both, respectively. Amantadine competitively inhibited MPTP uptake in vitro and significantly (p < 0.05) reduced the area under the time-concentration curve for MPTP and MPP(+) in the brain extracellular fluid in rats and mice by 65-70% and 35-85%, respectively. MPTP-induced dopaminergic toxicity in mice was ameliorated by amantadine without stimulating dopamine turnover. In conclusion, OCT1 and OCT2 are important for MPTP transfer across the blood-brain barrier and amantadine reduces the blood-brain barrier transfer of MPTP and MPTP-induced dopaminergic toxicity in rodents.


Subject(s)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Blood-Brain Barrier/metabolism , Dopamine/physiology , Endothelial Cells/metabolism , Octamer Transcription Factor-1/metabolism , Organic Cation Transport Proteins/metabolism , Animals , Binding, Competitive/physiology , Biological Transport, Active , Capillaries/cytology , Capillaries/metabolism , Cells, Cultured , Dopamine/toxicity , Humans , Male , Mice , Mice, Inbred C57BL , Neurotoxins/pharmacokinetics , Organic Cation Transporter 2 , Parkinsonian Disorders/metabolism , Parkinsonian Disorders/physiopathology , Rats , Rats, Wistar
11.
Neuropharmacology ; 56(8): 1075-81, 2009 Jun.
Article in English | MEDLINE | ID: mdl-19298832

ABSTRACT

Evidence for involvement of cytochrome P450 2E1 in the MPTP-induced mouse model of PD has been reported [Vaglini, F., Pardini, C., Viaggi, C., Bartoli, C., Dinucci, D., Corsini, G.U., 2004. Involvement of cytochrome P450 2E1 in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse model of Parkinson's disease. J. Neurochem. 91, 285-298]. We studied the sensitivity of Cyp2e1(-/-) mice to the acute administration of MPTP in comparison with their wild-type counterparts. In Cyp2e1(-/-) mice, the reduction of striatal DA content was less pronounced 7 days after MPTP treatment compared to treated wild-type mice. Similarly, TH immunoreactivity analysis of the substantia nigra of Cyp2e1(-/-) mice did not show any neuronal lesions after MPTP treatment. In contrast to this, wild-type animals showed a minimal but significant lesioning by the toxin as evaluated also by means of non-stereologic computerized assisted analysis of this brain area. Striatal levels of DA metabolites after 7 days were variably affected by the toxin, but consistent differences between the two animal strains were not observed. We evaluated short-term changes in the levels of striatal DA and its metabolites, and we monitored striatal MPP(+) levels. Striatal MPP(+) was cleared more rapidly in Cyp2e1(-/-) mice than in wild-type animals and, consistently, striatal DA content decreased faster in Cyp2e1(-/-) mice than in wild-type animals, and 3-methoxytyramine and HVA levels showed an early and sharp rise. Our findings suggest that Cyp2e1(-/-) mice are weakly sensitive to MPTP-induced brain lesions, markedly in contrast with a protective role of the enzyme as suggested previously. The differences observed between the knockout mice and their wild-type counterparts are modest and may be due to an efficient compensatory mechanism or genetic drift in the colonies.


Subject(s)
Corpus Striatum/drug effects , Cytochrome P-450 CYP2E1/deficiency , MPTP Poisoning/metabolism , Parkinsonian Disorders/metabolism , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , 1-Methyl-4-phenylpyridinium/metabolism , Animals , Corpus Striatum/chemistry , Cytochrome P-450 CYP2E1/genetics , Cytochrome P-450 CYP2E1/physiology , Dopamine/analogs & derivatives , Dopamine/analysis , Dopamine/deficiency , Homovanillic Acid/analysis , Male , Mice , Mice, Knockout , Nerve Tissue Proteins/analysis , Neurons/drug effects , Neurons/enzymology , Prodrugs/pharmacokinetics , Prodrugs/toxicity , Substantia Nigra/drug effects , Substantia Nigra/metabolism , Tyrosine 3-Monooxygenase/analysis
12.
Life Sci ; 81(8): 664-72, 2007 Aug 02.
Article in English | MEDLINE | ID: mdl-17689566

ABSTRACT

To examine the interaction between nicotine and MPTP/MPP+ in the blood-brain barrier, cellular uptake of MPTP and MPP+ was studied in the presence of nicotine and several compounds, including MPTP/MPP+ analogs and a specific inhibitor of organic cation transporter (OCT) in an adult rat brain microvascular endothelial cell line (ARBEC). The kinetic properties of the uptake of MPTP, MPP+, and nicotine were also examined. In addition, a microdialysis study was performed to evaluate the in vivo effect of nicotine (i.p.) on extracellular levels of MPTP and MPP+ in the brain after intravenous administration of MPTP. The results showed that uptake of MPTP, MPP+, and nicotine was partly mediated by a carrier system that was sensitive to decynium22, a specific OCT inhibitor. RT-PCR showed the presence of OCT1 mRNA in ARBEC. Capacity for uptake of MPTP and nicotine was much higher than that for MPP+ (Km and Vm values of 10.94+/-1.44 microM and 0.049+/-0.007 pmol/mg s, respectively, for MPP+, compared to values of 35.75+/-0.85 microM and 40.95+/-3.56 pmol/mg s for MPTP and 25.29+/-6.44 microM and 51.15+/-14.18 pmol/mg s for nicotine). In addition, nicotine competitively inhibited the uptake of both MPTP and MPP+, with inhibition constants (Ki) of 328 microM and 210 microM, respectively. In vivo microdialysis results showed that nicotine significantly reduced brain extracellular levels of MPTP in the first 30 min (507.4+/-8.5 ng/ml vs. 637.9+/-30.8 ng/ml with and without nicotine pre-treatment, respectively), but did not have significant effect on those of MPP+. In conclusion, nicotine can inhibit in vitro cellular uptake and in vivo transfer of MPTP across the blood-brain barrier, which can be mediated by multiple pathways including OCT1.


Subject(s)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/antagonists & inhibitors , Brain/pathology , Dopamine Antagonists/pharmacology , Endothelial Cells/drug effects , MPTP Poisoning/prevention & control , Nicotine/pharmacology , Nicotinic Agonists/pharmacology , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Algorithms , Animals , Blood-Brain Barrier , Cells, Cultured , Cotinine/metabolism , Data Interpretation, Statistical , Dopamine Agents/metabolism , Dopamine Agents/pharmacokinetics , Endothelial Cells/pathology , Extracellular Space/drug effects , Extracellular Space/metabolism , MPTP Poisoning/pathology , MPTP Poisoning/physiopathology , Male , Microdialysis , Nonlinear Dynamics , Rats , Rats, Wistar , Reverse Transcriptase Polymerase Chain Reaction
13.
FASEB J ; 21(9): 2226-36, 2007 Jul.
Article in English | MEDLINE | ID: mdl-17369508

ABSTRACT

Parkinson's disease (PD), a neurodegenerative disorder, causes severe motor impairment due to loss of dopaminergic neurons in substantia nigra pars compacta (SNpc). MPTP, a neurotoxin that causes dopaminergic cell loss in mice, was used in an animal model to study the pathogenic mechanisms leading to neurodegeneration. We observed the activation of apoptosis signal regulating kinase (ASK1, MAPKKK) and phosphorylation of its downstream targets MKK4 and JNK, 12 h after administration of a single dose of MPTP. Further, Daxx, the death-associated protein, translocated to the cytosol selectively in SNpc neurons seemingly due to MPTP mediated down-regulation of DJ-1, the redox-sensitive protein that binds Daxx in the nucleus. Coadministration of alpha-lipoic acid (ALA), a thiol antioxidant, abolished the activation of ASK1 and phosphorylation of downstream kinases, MKK4, and JNK and prevented the down-regulation of DJ-1 and translocation of Daxx to the cytosol seen after MPTP. ALA also attenuated dopaminergic cell loss in SNpc seen after subchronic MPTP treatment. Our studies demonstrate for the first time that MPTP triggers death signaling pathway by activating ASK1 and translocating Daxx, in vivo, in dopaminergic neurons in SNpc of mice and thiol antioxidants, such as ALA terminate this cascade and afford neuroprotection.


Subject(s)
Antioxidants/therapeutic use , Antiparkinson Agents/therapeutic use , Carrier Proteins/metabolism , Intracellular Signaling Peptides and Proteins/metabolism , MAP Kinase Kinase Kinase 5/metabolism , MAP Kinase Signaling System/drug effects , MPTP Poisoning/drug therapy , Nerve Tissue Proteins/metabolism , Neuroprotective Agents/therapeutic use , Nuclear Proteins/metabolism , Parkinsonian Disorders/drug therapy , Substantia Nigra/drug effects , Thioctic Acid/therapeutic use , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Acetylcysteine/pharmacology , Alkynes/pharmacology , Animals , Antioxidants/pharmacology , Antiparkinson Agents/pharmacology , Biotransformation , Cell Nucleus/metabolism , Co-Repressor Proteins , Cystathionine gamma-Lyase/antagonists & inhibitors , Cytosol/metabolism , Dopamine/analysis , Drug Evaluation, Preclinical , Electron Transport Complex I/drug effects , Enzyme Activation/drug effects , Glutathione/analysis , Glycine/analogs & derivatives , Glycine/pharmacology , JNK Mitogen-Activated Protein Kinases/metabolism , MAP Kinase Kinase 4/metabolism , MPTP Poisoning/metabolism , Male , Mesencephalon/chemistry , Mice , Mice, Inbred C57BL , Molecular Chaperones , Neurons/chemistry , Neurons/pathology , Neuroprotective Agents/pharmacology , Oncogene Proteins/biosynthesis , Oncogene Proteins/genetics , Parkinsonian Disorders/metabolism , Peroxiredoxins , Phosphorylation , Protein Deglycase DJ-1 , Protein Processing, Post-Translational/drug effects , Protein Transport/drug effects , Substantia Nigra/metabolism , Thioctic Acid/pharmacology
14.
J Mass Spectrom ; 41(12): 1643-53, 2006 Dec.
Article in English | MEDLINE | ID: mdl-17136767

ABSTRACT

Examination of the electrospray ionization product ion spectra of 1,2-dihydropyridinyl and 4-aryl-1,2-dihydropyridinyl derivatives bearing a 1-cyclopropyl or 1-trans-2-phenylcyclopropyl group has led to the characterization of unexpected fragment ions. For example, the base peak at m/z 156 present in the product ion spectrum of trans-1-(2-phenylcyclopropyl)-4-phenyl-1,2-dihydropyridine proved not to be the expected 4-phenylpyridinium species but rather the isomeric 3-phenyl-5-azoniafulvenyl species. The results of studies with a series of structural and isotopically labeled analogs require a novel fragmentation pathway to account for the formation of this and related fragment ions. One possible pathway is based on an initial 1,5-sigmatropic shift of a cyclopropylmethylene hydrogen atom that is accompanied by opening of the cyclopropyl ring. The resulting eniminium intermediates then fragment to yield the 5-azoniafulvenyl species.


Subject(s)
Dihydropyridines/chemistry , Neurotoxins/chemistry , Spectrometry, Mass, Electrospray Ionization , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/chemistry , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Cations/chemistry , Dihydropyridines/analysis , Enzymes/metabolism , Hydrogen/chemistry , Isomerism , Isotopes , Neurotoxins/analysis
15.
Toxicol Appl Pharmacol ; 216(3): 387-98, 2006 Nov 01.
Article in English | MEDLINE | ID: mdl-16870220

ABSTRACT

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxin is a chemical inducer of Parkinson's disease (PD) whereas N-methylated beta-carbolines and isoquinolines are naturally occurring analogues of MPTP involved in PD. This research has studied the oxidation of MPTP by human CYP2D6 (CYP2D6*1 and CYP2D6*10 allelic variants) as well as by a mixture of cytochrome P450s-resembling HLM, and the products generated compared with those afforded by human monoamine oxidase (MAO-B). MPTP was efficiently oxidized by CYP2D6 to two main products: MPTP-OH (p-hydroxylation) and PTP (N-demethylation), with turnover numbers of 10.09 min-1 and Km of 79.36+/-3 microM (formation of MPTP-OH) and 18.95 min-1 and Km 69.6+/-2.2 microM (PTP). Small amounts of dehydrogenated toxins MPDP+ and MPP+ were also detected. CYP2D6 competed with MAO-B for the oxidation of MPTP. MPTP oxidation by MAO-B to MPDP+ and MPP+ toxins (bioactivation) was up to 3-fold higher than CYP2D6 detoxification to PTP and MPTP-OH. Several N-methylated beta-carbolines and isoquinolines were screened for N-demethylation (detoxification) that was not significantly catalyzed by CYP2D6 or the P450s mixture. In contrast, various beta-carbolines were efficiently hydroxylated to hydroxy-beta-carbolines by CYP2D6. Thus, N(2)-methyl-1,2,3,4-tetrahydro-beta-carboline (a close MPTP analog) was highly hydroxylated to 6-hydroxy-N(2)-methyl-1,2,3,4-tetrahydro-beta-carboline and a corresponding 7-hydroxy-derivative. Thus, CYP2D6 could participate in the bioactivation and/or detoxification of these neuroactive compounds by an active hydroxylation pathway. The CYP2D6*1 enzymatic variant exhibited much higher metabolism of both MPTP and N(2)-methyl-1,2,3,4-tetrahydro-beta-carboline than the CYP2D6*10 variant, highlighting the importance of CYP2D6 polymorphism in the oxidation of these toxins. Altogether, these results suggest that CYP2D6 can play an important role in the metabolic outcome of both MPTP and beta-carbolines.


Subject(s)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/metabolism , Alkaloids/metabolism , Cytochrome P-450 CYP2D6/metabolism , Dopamine Agents/metabolism , Harmine/analogs & derivatives , Isoquinolines/metabolism , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Biotransformation , Catalysis , Chromatography, High Pressure Liquid , Dealkylation , Dopamine Agents/pharmacokinetics , Harmine/metabolism , Humans , Hydroxylation , Indicators and Reagents , Kinetics , Microsomes, Liver/enzymology , Microsomes, Liver/metabolism , Monoamine Oxidase/metabolism , Oxidation-Reduction , Spectrometry, Mass, Electrospray Ionization
16.
J Neurosci ; 25(28): 6594-600, 2005 Jul 13.
Article in English | MEDLINE | ID: mdl-16014720

ABSTRACT

Parkinson's disease (PD) is characterized by a loss of ventral midbrain dopaminergic neurons, which can be modeled by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Inflammatory oxidants have emerged as key contributors to PD- and MPTP-related neurodegeneration. Here, we show that myeloperoxidase (MPO), a key oxidant-producing enzyme during inflammation, is upregulated in the ventral midbrain of human PD and MPTP mice. We also show that ventral midbrain dopaminergic neurons of mutant mice deficient in MPO are more resistant to MPTP-induced cytotoxicity than their wild-type littermates. Supporting the oxidative damaging role of MPO in this PD model are the demonstrations that MPO-specific biomarkers 3-chlorotyrosine and hypochlorous acid-modified proteins increase in the brains of MPTP-injected mice. This study demonstrates that MPO participates in the MPTP neurotoxic process and suggests that inhibitors of MPO may provide a protective benefit in PD.


Subject(s)
Brain/enzymology , Parkinsonian Disorders/enzymology , Peroxidase/physiology , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Amyotrophic Lateral Sclerosis/enzymology , Animals , Corpus Striatum/enzymology , Dopamine/analysis , Drug Evaluation, Preclinical , Enzyme Induction , Humans , Huntington Disease/enzymology , Hypochlorous Acid/analysis , Male , Mesencephalon/enzymology , Mice , Mice, Inbred C57BL , Mice, Knockout , Nerve Tissue Proteins/chemistry , Neurons/drug effects , Neurons/enzymology , Oxidative Stress , Parkinson Disease/enzymology , Peroxidase/biosynthesis , Peroxidase/deficiency , Peroxidase/genetics , RNA, Messenger/biosynthesis , Reverse Transcriptase Polymerase Chain Reaction , Tyrosine/analogs & derivatives , Tyrosine/analysis
17.
Neuromolecular Med ; 6(2-3): 87-92, 2004.
Article in English | MEDLINE | ID: mdl-15970626

ABSTRACT

Administration of triacetyluridine (TAU) is a means of delivering exogenous pyrimidines to the brain, which may help to compensate for bioenergetic defects. TAU has previously been shown to be neuroprotective in animal models of Huntington's and Alzheimer's diseases. We examined whether oral administration of TAU in the diet could exert significant neuroprotective effects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity model of Parkinson's disease. Administration of TAU significantly attenuated MPTP-induced depletion of striatal dopamine and loss of tyrosine-hydroxylase-positive neurons in the substantia nigra. These findings suggest that administration of TAU may be a novel approach for treating neurodegenerative diseases associated with impaired mitochondrial function.


Subject(s)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacology , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Neuroprotective Agents/pharmacology , Neurotoxins/toxicity , Uridine/analogs & derivatives , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/antagonists & inhibitors , 3,4-Dihydroxyphenylacetic Acid/metabolism , Acetates , Animals , Dietary Supplements , Disease Models, Animal , Dopamine/metabolism , Homovanillic Acid/metabolism , MPTP Poisoning/prevention & control , Mice , Neurotoxins/antagonists & inhibitors , Uridine/administration & dosage , Uridine/pharmacology
18.
Nervenarzt ; 73(10): 982-9, 2002 Oct.
Article in German | MEDLINE | ID: mdl-12376887

ABSTRACT

Retrospective case-control studies among patients with idiopathic Parkinson's syndrome (IPS) show a positive association to the existence of a - mostly premorbid - exposure to pesticides. In acute pesticide intoxications, usually symptoms other than parkinsonism are found. Therefore, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) continues to be the agent best documented both experimentally and clinically to cause a clinical syndrome comparable to IPS. It is debated whether still unknown effects between exogenous pesticide exposure and the xenobiotic enzyme system may lead to IPS in single genetically susceptible individuals. In practice, the present data on the problem of pesticide exposure in IPS are irrelevant for medicolegal considerations.


Subject(s)
Parkinson Disease, Secondary/chemically induced , Pesticides/adverse effects , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/adverse effects , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Aryl Hydrocarbon Hydroxylases/genetics , Basal Ganglia/drug effects , Basal Ganglia/pathology , Case-Control Studies , Disease Susceptibility , Humans , Parkinson Disease, Secondary/epidemiology , Parkinson Disease, Secondary/genetics , Parkinsonian Disorders/chemically induced , Pesticides/pharmacokinetics , Polymorphism, Genetic , Retrospective Studies , Risk Factors
19.
Pharmacol Toxicol ; 90(4): 203-7, 2002 Apr.
Article in English | MEDLINE | ID: mdl-12076315

ABSTRACT

Idiopathic Parkinson's disease may be caused by environmental neurotoxins such as pesticides, however the major risk factor is old age. We postulated that the high incidence of Parkinson's disease in older people is secondary to age-related impairment of the hepatic detoxification of xenobiotics. Previously, we have shown that there are significant differences between the hepatic disposition of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and pesticides. Here, we investigated whether there are age-related differences in the hepatic disposition of MPTP and pesticides, putatively associated with the pathogenesis of Parkinson's disease. We measured the hepatic disposition of paraquat, dichlorodiphenyltrichloroethane (DDT), malathion and MPTP using the multiple indicator dilution technique in the perfused livers of Fischer F344 rats aged 3 and 18 months. The recoveries of MPTP, DDT and malathion were increased from the livers of the older rats (by 258%, 253% and 134% compared with young rats, respectively). The hepatic transport of DDT and malathion into hepatocytes was reduced with age suggesting that part of the impaired uptake of neurotoxins may be secondary to an age-related barrier to influx. Ageing may increase risk of Parkinson's disease by altering hepatic detoxification and increasing systemic bioavailability of neurotoxins.


Subject(s)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Aging/metabolism , Dopamine Agents/pharmacokinetics , Liver/metabolism , Pesticides/pharmacokinetics , Animals , DDT/pharmacokinetics , Malathion/pharmacokinetics , Male , Paraquat/pharmacokinetics , Perfusion , Rats , Rats, Inbred F344
20.
Biochem Biophys Res Commun ; 289(1): 130-6, 2001 Nov 23.
Article in English | MEDLINE | ID: mdl-11708789

ABSTRACT

Modulation of hepatic disposition of MPTP could influence susceptibility to its neurotoxicity. Therefore, we studied hepatocellular transport of MPTP in the perfused rat liver and isolated rat hepatocytes. The perfused liver extensively extracted MPTP. Amiloride and tubocurarine, inhibitors of OCT1, increased MPTP recovery (253 +/- 78 and 283 +/- 64%, respectively) and reduced PS(influx) (0.69 +/- 0.36 to 0.27 +/- 0.11, and 0.97 +/- 0.50 to 0.23 +/- 0.05 ml/s/g, respectively). P-glycoprotein inhibitor, daunomycin, and Oatp 1 & 2 inhibitor, rifamycin, had no effect. In isolated hepatocytes, amiloride and tubocurarine increased hepatic uptake of MPTP (23 +/- 12 and 6 +/- 2%, respectively). Daunomycin reduced MPTP uptake by 22 +/- 8% and rifamycin had no effect. Only a small proportion of MPTP is taken up into hepatocytes by transporters; however, modulation of these transport mechanisms will influence systemic bioavailability.


Subject(s)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacokinetics , Liver/metabolism , Amiloride/pharmacology , Animals , Biological Availability , Biological Transport, Active/drug effects , Cell Membrane/drug effects , Cell Membrane/metabolism , Daunorubicin/pharmacology , Hepatocytes/drug effects , Hepatocytes/metabolism , In Vitro Techniques , Liver/drug effects , MPTP Poisoning/etiology , MPTP Poisoning/metabolism , Male , Neurotoxins/pharmacokinetics , Neurotoxins/toxicity , Organic Cation Transporter 1/metabolism , Perfusion , Rats , Rats, Wistar , Rifamycins/pharmacology , Tubocurarine/pharmacology
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