Selective nigral toxicity after systemic administration of 1-methyl-4-phenyl-1,2,5,6-tetrahydropyrine (MPTP) in the squirrel monkey

1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) was administered via the intraperitoneal route to squirrel monkeys. Akinesia, rigidity and hypophonia were seen after repeated doses of 2 mg/kg. Postural tremor was present in one animal. Neuropathologic examination revealed cell loss restricted to the zona compacta of the substantia nigra. MPTP appears effective in producing an animal model for Parkinson's disease in the squirrel monkey, and may be one of the more selective neurotoxins described to date.     

Presence of reactive microglia in monkey substantia nigra years after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine administration

This report describes the presence of reactive microglia, the accumulation of extracellular melanin, and the extensive loss of dopaminergic neurons in the substantia nigra of monkeys administered 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) 5 to 14 years before death. This evidence of chronic neuroinflammation years after MPTP exposure is similar to that previously reported in humans. The monkeys were drug free for at least 3 years before death, indicating that a brief exposure to MPTP had instituted an ongoing inflammatory process. The mechanism is unknown but could have important implications regarding the cause of Parkinson's disease and possible approaches to therapy.     

偏侧PD猴模型黑质和纹状体GFAP表达的变化

目的探讨偏侧帕金森病（PD）猴模型黑质和纹状体胶质原纤维酸性蛋白（GFAP）表达的变化。方法向3只恒河猴经单侧颈内动脉注射1-甲基4-苯基1，2，3，6-四氢吡啶（MPTP）制备偏侧PD猴模型，应用免疫组化染色方法观察3只偏侧PD猴模型和1只正常猴黑质和纹状体GFAP表达变化。结果偏侧PD模型猴MPTP毁损侧的黑质和纹状体GFAP免疫阳性细胞数目较对侧和正常对照猴明显增加，但MPTP毁损侧对侧的黑质和纹状体GFAP免疫阳性细胞数目未发现明显变化。结论偏侧PD猴模型MPTP毁损侧黑质和纹状体GFAP的表达增加，推测星形胶质细胞可能在黑质和纹状体神经元变性和死亡过程中起一定作用。     

Protective action of recombinant neurturin on dopaminergic neurons in substantia nigra in a rhesus monkey model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by muscular trembling palsy due to lack of dopamine (DA) in the substantia nigra-striatum (nigrostriatal) system resulting from the degeneration and necrosis of dopaminergic neurons. No effective cure has been found. Neurturin (NTN) has been demonstrated to act specifically on midbrain (mesencephalic) dopaminergic neurons with protective actions specifically. In the present study, we induced rhesus monkey model of Parkinson's disease by injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Rhesus monkeys were randomly divided into a PD model group, NTN treatment group and normal control groups. In the NTN treatment group, 1 mg of E. coli-derived recombinant human NTN was injected into the cerebral ventricles 48 h before the injection of MPTP. Results indicated that Rhesus monkeys in the PD model group acquired PD symptoms that increasingly aggravated over time, while monkeys treated with NTN had less apparent or no symptoms. Using fluorospectrophotometry, the dopamine (DA), 5, 5-hydroxytrytamine (5-HT) and the 5-hydroxyindoleacetic acid (5-HIAA) contents of DA, 5-HT and 5-HIAA in substantia nigra, putamen and caudate nucleus in monkeys from the model group was found to be significantly lower than in the normal control group. While no significant differences were found between monkeys treated with NTN and normal control groups, the contents of DA, 5-HT and 5-HIAA in the NTN treatment group were higher than those observed in the PD model group. A dramatic loss of neurons in the substantia nigra in monkeys in the PD model group was observed by light microscopy, while no obvious loss was observed in the NTN treatment group in which the numbers of neurons were similar to those in normal controls. These results indicate that recombinant human NTN can prevent PD symptoms as well as protect dopaminergic neurons and preserve DA content in midbrain substantia nigra in rhesus monkeys exposed to MPTP.     

Intracerebroventricularly-administered 1-methyl-4-phenylpyridinium ion and brain-derived neurotrophic factor affect catecholaminergic nerve terminals and neurogenesis in the hippocampus,striatum and substantia nigra

Parkinson's disease is a progressive neurological disease characterized by the degeneration of dopaminergic neurons in the substantia nigra.A highly similar pattern of neurodegeneration can be induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP) or 1-methyl-4-phenylpyridinium ion(MPP+),which cause the death of dopaminergic neurons.Administration of MPTP or MPP+ results in Parkinson's disease-like symptoms in rodents.However,it remains unclear whether intracerebroventricular MPP+ administration affects neurogenesis in the substantia nigra and subgranular zone or whether brain-derived neurotrophic factor alters the effects of MPP+.In this study,MPP+(100 nmol) was intracerebroventricularly injected into mice to model Parkinson's disease.At 7 days after administration,the number of bromodeoxyuridine(Brd U)-positive cells in the subgranular zone of the hippocampal dentate gyrus increased,indicating enhanced neurogenesis.In contrast,a reduction in Brd U-positive cells was detected in the substantia nigra.Administration of brain-derived neurotrophic factor(100 ng) 1 day after MPP+ administration attenuated the effect of MPP+ in the subgranular zone and the substantia nigra.These findings reveal the complex interaction between neurotrophic factors and neurotoxins in the Parkinsonian model that result in distinct effects on the catecholaminergic system and on neurogenesis in different brain regions.     

MPTP对褐鼠黑质纤连蛋白基因表达的影响

目的研究腹腔注射1-甲基-4-苯基-1，2，3，6-四氢吡啶(MPTP)对褐鼠黑质纤连蛋白基因表达的影响，初步探讨其参与注射MPTP后的免疫机制。方法通过腹腔注射MPTP建立帕金森病(PD)褐鼠模型，采用逆转录(RT)．聚合酶链反应(PCR)方法研究纤连蛋白在黑质的表达情况。结果经MPTP腹腔注射后褐鼠模型出现典型PD症状，黑质酪氨酸羟化酶表达水平明显降低，黑质纤连蛋白基因表达明显上调。结论纤连蛋白在PD鼠黑质高表达可能促使T淋巴细胞透过血．脑屏障(BBB)进入脑组织，参与PD鼠的免疫反应。     

COX-2-deficient mice are less prone to MPTP-neurotoxicity than wild-type mice

The primary lesion in Parkinson's disease is the death of dopaminergic neurons in the substantia nigra. The role of cyclooxygenase (COX)-2 in the etiology of Parkinson's disease was explored using COX-2 gene knockout mice. Mortality after injection of 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP, a chemical known to cause parkinsonism in humans) in heterozygous COX-2-deficient mice was lower than that in wild-type mice. The number of tyrosine hydroxylase immunoreactive neurons in the substantia nigra pars compacta of MPTP-treated wild-type mice declined to a greater extent than in heterozygous mice. Inhibition of COX-2 protein expression decreased the lesion caused by MPTP and protected the dopaminergic neurons in substantia nigra pars compacta. This result suggested that inhibition of COX-2 has potential therapeutic implications.     

Systemic administration of rotenone produces selective damage in the striatum and globus pallidus, but not in the substantia nigra

Complex I dysfunction has been implicated in the pathogenesis of Parkinson's disease and in the neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which produces a Parkinsonian syndrome in experimental animals and humans. Rotenone is an insecticide which is a specific inhibitor of complex I. We examined the pattern of central nervous system damage produced by i.v. systemic administration of rotenone in rats. Rotenone produced selective damage in the striatum and the globus pallidus, but the substantia nigra was spared. These results are consistent with prior reports suggesting that the selective vulnerability of the substantia nigra to MPTP involves both uptake by the dopamine transporter as well as complex I inhibition, and they show that rotenone produces a unique pattern of central nervous system damage. © 1997 Elsevier Science B.V. All rights reserved.     

Isatin decreases Bax protein expression in the substantia nigra of a mouse model of Parkinson’s disease

The present study observed the action of 1H-indole-2, 3-dione (isatin) on Bax protein expression in the substantia nigra of a Parkinson’s disease animal model. Parkinson’s disease-like behaviors were induced in C57BL/6J mice treated with 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). Bax protein expression was significantly reduced in isatin (100, 200 mg/kg)-pretreated mice. Results demonstrate that isatin plays a neuroprotective role in mice treated with MPTP by down-regulating Bax protein express...     

Parkinson's disease: pathological mechanisms and actions of piribedil

The cause of the degeneration of dopamine-containing cells in the zona compacta of the substantia nigra in Parkinson's disease remains unknown. The ability of the selective nigral toxin 1-methyl-4-phenyl-1,2,3,6tetrahydropyridine (MPTP) (via its metabolite MPP⁺) to destroy nigral dopamine cells selectively by inhibiting complex I of the mitochondrial energy chain may provide a clue. Indeed, recent studies of post-mortem brain tissue have suggested the presence of an on-going toxic process in the substantia nigra in Parkinson's disease leading to excess lipid peroxidation. This appears also to involve a disruption of mitochondrial function since mitochondrial superoxide dismutase activity is increased and there is impairment of complex I. These changes may in turn relate to a selective increase in the total iron content of substantia nigra coupled to a generalised decrease in brain ferritin content. Piribedil is used in the symptomatic treatment of Parkinson's disease and is particularly effective against tremor. Piribedil (and its metabolites) acts as a dopamine D-2 receptor agonist. However, in our studies in contrast to other dopamine agonists, in vivo piribedil interacts with dopamine receptors in the substantia nigra and nucleus accumbens but not those in the striatum. In patients with Parkinson's disease the beneficial effects of piribedil may be limited by nausea and drowsiness. Indeed, in MPTP-treated primates piribedil reverses motor deficits but marked side-effects occur. However, pre-treatment with the peripheral dopamine receptor antagonist domperidone prevents the unwanted effects and piribedil produces a profound and longer-lasting reversal of all components of the motor syndrome. These results suggest that combined with domperidone piribedil could be used as an effective monotherapy in the treatment of Parkinson's disease.     

Locus ceruleus lesions and eosinophilic inclusions in MPTP-treated monkeys

Systemic administration of the recently discovered neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces severe clinical parkinsonism and degeneration of the substantia nigra in humans and monkeys. In previous studies, no convincing structural damage to nerve cells outside the substantia nigra could be demonstrated in subhuman primates. Using a protracted MPTP regimen and older animals, we now report locus ceruleus lesions and eosinophilic inclusion bodies in squirrel monkeys. The inclusions were seen only in areas where Lewy bodies are found in human Parkinson's disease. No such abnormalities were seen in control animals. These findings suggest that similarities between the neuropathology of MPTP-induced parkinsonism in the monkey and human Parkinson's disease are greater than first thought and increase the usefulness of the MPTP monkey model for research in Parkinson's disease.     

Down-regulation of metabotropic glutamate receptor 1alpha in globus pallidus and substantia nigra of parkinsonian monkeys

Enhanced glutamatergic neurotransmission via the subthalamopallidal or subthalamonigral projection seems crucial for developing parkinsonian motor signs. In the present study, the possible changes in the expression of metabotropic glutamate receptors (mGluRs) were examined in the basal ganglia of a primate model for Parkinson's disease. When the patterns of immunohistochemical localization of mGluRs in monkeys administered systemically with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were analysed in comparison with normal controls, we found that expression of mGluR1alpha, but not of other subtypes, was significantly reduced in the internal and external segments of the globus pallidus and the substantia nigra pars reticulata. To elucidate the functional role of mGluR1 in the control of pallidal neuron activity, extracellular unit recordings combined with intrapallidal microinjections of mGluR1-related agents were then performed in normal and parkinsonian monkeys. In normal awake conditions, the spontaneous firing rates of neurons in the pallidal complex were increased by DHPG, a selective agonist of group I mGluRs, whereas they were decreased by AIDA, a selective antagonist of group I mGluRs, or LY367385, a selective antagonist of mGluR1. These electrophysiological data strongly indicate that the excitatory mechanism of pallidal neurons by glutamate is mediated at least partly through mGluR1. The effects of the mGluR1-related agents on neuronal firing in the internal pallidal segment became rather obscure after MPTP treatment. Our results suggest that the specific down-regulation of pallidal and nigral mGluR1alpha in the parkinsonian state may exert a compensatory action to reverse the overactivity of the subthalamic nucleus-derived glutamatergic input that is generated in the disease.     

Mitochondrial DNA analysis in Parkinson's disease

The reduced form of nicotinamide adenine dinucleotide coenzyme Q reductase (complex I) activity has recently been shown to be deficient in the substantia nigra of patients dying with Parkinson's disease. This biochemical defect is identical to that produced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which also produces parkinsonism in humans. Complex I comprises 25 polypeptides, seven of which are encoded by mitochondrial DNA. Restriction fragment analysis of substantia nigra DNA from six patients with Parkinson's disease did not show any major deletion. In two cases, there were different novel polymorphisms that were not observed in control brain (n = 6) or blood (n = 34) samples.     

Impaired glutamate homeostasis and programmed cell death in a chronic MPTP mouse model of Parkinson's disease

The pathogenesis of Parkinson's disease is not fully understood, but there is evidence that excitotoxic mechanisms contribute to the pathology. However, data supporting a role for excitotoxicity in the pathophysiology of the disease are controversial and sparse. The goal of this study was to determine whether changes in glutamate signaling and uptake contribute to the demise of dopaminergic neurons in the substantia nigra. Mice were treated chronically with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and probenecid or vehicle (probenecid or saline alone). Extracellular levels of glutamate in the substantia nigra were substantially increased, and there was an increase in the affinity, but no change in the velocity, of glutamate transport after MPTP/probenecid treatment compared to vehicle controls. In addition, the substantia nigra showed two types of programmed death, apoptosis (type I) and autophagic (type II) cell death. These data suggest that increased glutamate signaling could be an important mechanism for the death of dopaminergic neurons and trigger the induction of programmed cell death in the chronic MPTP/probenecid model.     

Novel mitochondrial DNA mutations in Parkinson's disease

Summary. Despite the recent discovery of several chromosomal gene mutations in familial Parkinson's disease (PD) the genetic background for idiopathic PD remains to be elusive. Since the discovery of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) action on dopaminergic neuronal cells and the specific decrease of mitochondrial complex I activity in substantia nigra of PD patients mitochondrial biochemistry and genetics emerged to become Pandora's box in the pathogenesis of PD. One approach was to establish the potential role of defective mitochondrial DNA (mtDNA). As complex I genes are the most vulnerable part of mtDNA we analyzed the mitochondrial MTND1 and MTND2 genes of 10 substantia nigra and 85 platelet samples from PD patients. We were uneventful to detect heteroplasmic base changes even applying techniques able to visualize mutations with low percentage of heteroplasmy but here we report novel homoplasmic base changes. These results add further evidence that there are no inherited disease specific mtDNA mutations, hence individual homoplasmic mutations or very low grade heteroplasmic mutations in the vicinity of mitochondrial metabolism and oxidative stress may contribute to selective neuronal vulnerability in PD. Received February 4, 2002; accepted February 27, 2002     

Development of a stable, early stage unilateral model of Parkinson's disease in middle-aged rhesus monkeys

An important issue raised in testing new neuroprotective/restorative treatments for Parkinson's disease (PD) is the optimal stage in the disease process to initiate therapy. Current palliative treatments are effective in the early disease stages raising ethical concerns about substituting an experimental treatment for a proven therapy. Thus, we have endeavored to create a stable 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) nonhuman primate model of early PD. The new model was created by controlling for dose and route administration of MPTP (unilateral intracarotid infusion), and age of the animals (middleaged, 16–19 years old) in 27 female rhesus monkeys. All animals showed stable parkinsonian features lasting for up to 12-month as per behavioral evaluation. Compared with late-stage PD animals, postmortem analysis demonstrated that more dopaminergic neurons remained in the substantia nigra pars compacta, and more fibers were found in the striatum. In addition, tissue levels of striatal dopamine and its metabolites were also higher. Our results support that a milder but stable PD model can be produced in middle-aged rhesus monkeys.     

Aging and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced degeneration of dopaminergic neurons in the substantia nigra

This study assessed the influence of aging on substantia nigra degeneration induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Extensive neuronal degeneration was found in the substantia nigra of older (8–12 months of age) but not younger (6–8 weeks of age) mice given MPTP. Older mice did not have higher brain concentrations of either MPTP or 1-methyl-4-phenylpyridinium (MPP⁺), the putative toxic metabolite of MPTP, to account for the greater toxicity. In fact, older mice metabolized MPTP more rapidly than younger mice, probably because of the increase in monoamine oxidase activity that occurs with aging. Striatal synaptosomes from older mice did not accumulate more [³H]MPP⁺ than synaptosomes from younger mice. Thus, it is concluded that the greater neurodegenerative effect of MPTP in older animals is not due to greater levels or uptake of MPP⁺, but rather is related to a true increase in sensitivity of older dopaminergic cells to MPTP. For comparative purposes, the toxic effect of another dopaminergic neurotoxin, methamphetamine, was tested. Older animals were not more sensitive than young mature animals to the toxic effect of methamphetamine. This finding indicates that the increased sensitivity of older dopaminergic neurons to MPTP is selective. The link established here between aging and the neurodegenerative effect of MPTP, a toxin which produces parkinsonism in humans, provides a mechanism by which an age-related neurodegenerative disorder such as Parkinson's disease could be caused by an MPTP-like toxin in the environment.     

Expression of S-100 protein is related to neuronal damage in MPTP-treated mice

S-100beta is a calcium-binding protein expressed at high levels in brain and is known as a marker of brain damage. However, little is known about the role of S-100beta protein during neuronal damage caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). To determine whether S-100beta protein is induced in glial cells after MPTP treatment, we investigated the expression of S-100 protein immunohistochemically, using MPTP-treated mice. We also examined the change of neurons and glial cells in mice after MPTP treatment. The present study shows that tyrosine hydroxylase (TH) immunoreactivity decreased gradually in the striatum and substantia nigra from 1 day after MPTP treatment. Thereafter, TH-immunopositive cells and fibers decreased in the striatum and substantia nigra at 3 days after MPTP treatment. In contrast, S-100-immunopositive cells and glial fibrillary acidic protein (GFAP)-immunopositive cells increased markedly in the striatum and substantia nigra at 3 days after MPTP treatment. Seven days after MPTP treatment, S-100-immunopositive cells decreased in the striatum and substantia nigra. However, the number of GFAP-immunopositive cells increased in these regions. In double-labeled immunostaining with anti-S-100 and anti-GFAP antibodies, S-100 immunoreactivity was observed only in the GFAP-positive astrocytes. These results provide evidence that astrocytic activation may play a role in the pathogenesis of MPTP-induced degeneration of dopaminergic neurons. Furthermore, the present study demonstrates that S-100 protein is expressed selectively by astrocytes, but not by microglia, after MPTP treatment. These results provide valuable information for the pathogenesis of the acute stage of Parkinson's disease.     

MPTP对褐鼠黑质NAPOR基因表达的影响

目的 研究腹腔注射1—甲基—4—苯基—1，2，3，6—四氢吡啶(MPTP)对褐鼠黑质神经母细胞瘤凋亡相关的RNA结合蛋白(NAPOR)基因表达的影响，为阐明帕金森病(PD)的分子机制提供线索。方法 通过腹腔注射MPTP建立褐鼠PD模型，采用逆转录PCR方法研究NAPOR在黑质的表达情况。结果 通过MPTP腹腔注射后褐鼠模型出现典型PD症状、黑质酪氨酸羟化酶表达水平明显降低验证PD模型成功，PD鼠黑质NAPOR基因表达明显上调。结论 NAPOR为RNA结合蛋白，其表达的模式与神经元凋亡密切相关。提示MPTP对黑质神经元的毒性可能通过改变NAPOR基因的表达，促进神经元凋亡而实现。     

帕金森病临床前期小鼠模型的建立

目的建立帕金森病临床前期的小鼠动物模型,了解帕金森病发病前的组织病理学改变,特别是小鼠中脑黑质、纹状体的超微病理及突触数量的变化。方法60只C57Bl/6j小鼠,采用小剂量MPTP多次慢性给药方法(4mg/kg.d)建立帕金森病临床前期小鼠动物模型。通过光学显微镜及电子显微镜观察小鼠黑质及纹状体的超微病理变化;利用色谱分析测定模型小鼠纹状体的多巴胺含量;通过动物爬杆试验(pole test)检测小鼠肢体运动协调的行为学改变。结果鼠脑黑质部分神经细胞变性及纹状体内突触数量减少;各给药组小鼠纹状体内多巴胺的含量均有不同程度的下降,同时各实验组小鼠行为学的定量及定性观察均未出现明显的行为学改变。结论低剂量MPTP慢性给药方式可以建立帕金森病临床前期的小鼠动物模型。该模型的超微形态学、生物化学及动物的行为学等结果可以作为研究帕金森病发病早期的参考指标。