Partial protection from the dopaminergic neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine by four different antioxidants in the mouse

C57 black mice given a single injection of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 40 mg/kg, developed marked reduction of striatal dopamine content and loss of dopaminergic neurons in the zona compacta of the substantia nigra. However, pretreatment with any one of four different antioxidants, alpha-tocopherol, beta-carotene, ascorbic acid or N-acetylcysteine, significantly decreased MPTP-induced striatal dopamine loss, and alpha-tocopherol prevented neuronal loss in the substantia nigra. Four chemical analogues of MPTP (cinnamaldehyde, N,N-dimethylcinnamylamine, arecoline and 2-methyl-1,2,3,4-tetrahydro-6,7-isoquinolinediol) were all found to lack dopaminergic nigrostriatal neurotoxicity in the mouse.     

Tetrodotoxin elevates arterial pressure but not plasma vasopressin when injected into the caudal ventrolateral medulla of the rabbit

When tetrodotoxin (TTS) is microinjected into the caudal ventrolateral medulla it elevates arterial pressure. This is consistent with previous microinjection experiments which show that the injected region contains neurons whose activity inhibits peripheral sympathetic vasomotor tone. However, TTX does not alter plasma vasopressin and this suggests that increases in plasma vasopressin which follow electrolytic lesions may result from excitatory effects of the lesions.     

The importance of the ‘4–5’ double bond for neurotoxicity in primates of the pyridine derivative MPTP

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a newly recognized neurotoxin which selectively damages the cells of the substantia nigra in primates. It has been effective in producing an animal model for Parkinson's disease. We now report that saturating the ‘4–5’ double bond in the tetrahydropyridine ring of MPTP prevents its metabolic oxidation to 1-methyl-4-phenylpyridinium ion (MPP⁺) and removes its behavioral and neurotoxic effects. We believe that this represents an important step towards elucidating the mechanism of action of this compound.     

Dopaminergic toxicity after the stereotaxic administration of the 1-methyl-4-phenylpyridinium ion (MPP+) to rats

The administration of the 1-methyl-4-phenylpyridinium ion (MPP+) stereotaxically into the left neostriatum or left median forebrain bundle of female rats resulted in a very large and highly significant loss of dopamine and of its metabolites in the left neostriatum. The effect of MPP+ on neostriatal dopamine content was in general considerably greater than its effect on serotonin or on several amino acids. These results are consistent with the premise that MPP+, formed from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) by the enzyme monoamine oxidase B, may be responsible for the toxicity observed after MPTP administration.     

Neuroprotective effects of rotigotine in the acute MPTP-lesioned mouse model of Parkinson's disease

Dopamine agonists used to manage Parkinsonian motor symptoms have been suggested to be neuroprotective. The study was designed to assess the neuroprotective potential of the D(3)/D(2)/D(1) dopamine receptor agonist rotigotine in the acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned (MPTP) mouse model of Parkinson's disease by measuring mesencephalic degenerating neurons using FluoroJade staining and the remaining dopaminergic nerve endings in the striatum using dopamine transporter binding. Continuous administration of rotigotine at a dose of 3mg/kg significantly attenuated MPTP-induced acute cell degeneration in the FluoroJade-staining paradigm. Rotigotine (0.3-3mg/kg) partially protected dopamine nerve endings from MPTP-induced degeneration in a dose-dependent manner. These data suggest that rotigotine, at the doses employed, significantly protected dopamine neurons from degeneration in an acute mouse model of MPTP intoxication.     

Participation of brain monoamine oxidase B form in the neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine: relationship between the enzyme inhibition and the neurotoxicity

A neurotoxin for nigrostriatal dopaminergic neurons, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its oxidized metabolite, 1-methyl-4-phenylpyridine (MPP+), both dose-dependently inhibited rat striatal and forebrain monoamine oxidase (MAO) activity with monoamine oxidase A (MAO-A) selectively reversible (competitive, Ki = 4.5 and 2.0 microM) inhibition. A comparison of the Ki values indicated the affinity of MPP+ for MAO-A to be greater than that of MPTP. MPTP inhibited monoamine oxidase B (MAO-B) with both a reversible (competitive, Ki = 116 microM) and an irreversible time-dependent component, but inhibition by MPP+ was reversible and competitive (Ki = 180 microM). These results, together with previous findings on metabolism of MPTP to MPP+ by brain MAO-B, suggest that MPP+ is a simple inhibitor of MAO-A and MAO-B, but MPTP might be a 'suicide substrate' inhibitor for MAO-B.     

Neuroprotective effect of baicalein against MPTP neurotoxicity: behavioral, biochemical and immunohistochemical profile

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes the damage of dopaminergic neurons as seen in Parkinson's disease (PD). Oxidative stress has been implicated in the pathogenesis of PD. Baicalein, isolated from the traditional Chinese herbal medicine Huangqin (Scutellaria baicalensis Georgi), has been shown to have antioxidant effects. Here we investigated the effect of baicalein on MPTP-induced neurotoxicity in mice. Pretreatment with baicalein for a week was followed by challenge with MPTP for 4 consecutive days; the subsequent behavioral, biochemical and immunohistochemical manifestations in mice were determined and compared to those in untreated mice and mice challenged only with MPTP. The present study showed that baicalein could improve the abnormal behavior in MPTP-treated mice. The protective effect may be caused by increasing the levels of DA and 5-HT in the striatum, increasing the counts of dopaminergic neurons, inhibiting oxidative stress and the astroglia response. These results suggest that baicalein possesses potent neuroprotective activity and may be a potential anti-Parkinson's disease drug that is worthy of further study.     

Modeling a sensitization stage and a precipitation stage for Parkinson's disease using prenatal and postnatal 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine administration

Idiopathic Parkinson's disease (PD) is a neurodegenerative disorder of mature and older individuals. Since all aged individuals do not develop PD, predisposing conditions may exist that pair with the stress placed on the basal ganglia during aging to produce the symptoms of PD. In this project we used 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to test the hypothesis that a sensitization stage and a precipitating stage underlie idiopathic PD. To induce the sensitization stage, pregnant C57BL/6J mice were treated with MPTP (10 mg/kg/day) during gestation days 8–12 to target the emerging fetal nigrostriatal dopamine neurons. For the precipitating stage, the 3-months old offspring were administered MPTP for 7 days, to simulate the changes that occur during aging. The weights and motor activity of the offspring, high performance liquid chromatography (HPLC) striatal dopamine and its metabolites and Western blot for tyrosine hydroxylase (TH) were determined. Offspring exposed to prenatal MPTP showed lower birth weights that eventually recovered. Prenatal MPTP also reduced motor activity by 10–30%, striatal TH by 38%, dopamine by 14%, homovanillic acid by 16.5% and 3-methoxytyramine by 66%. The postnatal MPTP was more potent in the prenatal MPTP-exposed offspring. MPTP at 10, 20 and 30 mg/kg, dose-relatedly, reduced striatal TH by 9.4%, 48.6% and 82.4% in the prenatal-phosphate buffered saline (PBS) mice and by 48%, 78.7% and 92.7% in the prenatal-MPTP groups. More importantly, postnatal MPTP at 10 mg/kg that showed slight effects on DA, DOPAC, HVA and 3-MT in the prenatal-PBS offspring, showed 69.9%, 80.0%, 48.4% and 65.4% reductions in the prenatal-MPTP mice. The study may identify a new model for PD, and the outcome suggests that some cases of idiopathic PD may have a fetal basis in which early subtle nigrostriatal impairments occurred and PD symptoms are precipitated later by deteriorating changes in the nigrostriatum, that would not caused symptoms in individuals with normal nigrostriatal system.     

Acute administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine affects the adrenal glands as well as the brain in the marmoset

A parkinsonian syndrome was induced in marmosets by administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) for 4 days. Ten days following the onset of drug administration, brainstem and adrenal tissues were assayed for levels of monoamines and their metabolites. In the brainstem tegmentum, dopamine, its metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC), and noradrenaline were reduced, whereas 5-hydroxytryptamine (5-HT) levels were elevated, in comparison with untreated controls. In the adrenal gland, 5-HT and adrenaline levels were unchanged, but dopamine and noradrenaline were substantially elevated.     

Effects of acidic fibroblast growth factor on the development of experimental parkinsonism and striatal level of dopamine and its metabolites in mice of different ages

Intranasal administration of acidic fibroblast growth factor suppressed the development of oligokinesia and muscular rigidity and elevated the content of dopamine and its metabolites (dihydroxyphenylacetic acid and homovanillic acid) in the striatum of 7-month-old mice with MPTP-induced Parkinsonian syndrome. In 14-month-old mice the antiparkinsonic effect of acidic fibroblast growth factor was weakened or absent. It is suggested that this factor is able to attenuate or postpone degeneration and death of nigral dopaminergic neurons. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 5, pp. 502–505, May, 1999     

Autoradiographic localization of binding sites for the arginine-vasopressin (VP) metabolite, VP4-9, in rat brain

A discrete neuro-anatomical pattern of binding sites was observed for a principal metabolite of arginine-vasopressin (VP4-9) after incubation of tissue sections with [35S]VP4-9 and autoradiography. [35S]VP4-9-labeled binding sites were highly concentrated in the pineal gland, the nucleus tractus solitarii (nts), the arcuate nucleus region (an) and the organum vasculosum lamina terminalis (ovlt). The distribution of these sites is distinctly different from the putative VP and oxytocin receptor systems in rat brain. It is possible that the VP4-9 binding sites are also involved in memory processes and/or that the VP metabolite exerts additional effects on the brain.     

Alterations of the expression and activity of midbrain nitric oxide synthase and soluble guanylyl cyclase in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinsonism in mice

The study was aimed at investigating the expression and the activity of neuronal nitric oxide synthase, and of soluble guanylyl cyclase and phosphodiesterase activities that regulate guanosine 3',5'-cyclic monophosphate level in the midbrain, in a mouse model of PD using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine injections. Adult male mice of the C57/BL strain were given three i.p. injections of physiological saline or three i.p. injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine solution in physiological saline at 2 h intervals (summary 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine dose: 40 mg/kg), and were killed 3, 7, or 14 days later. mRNA, protein level, and/or activities of neuronal nitric oxide synthase, soluble guanylyl cyclase, phosphodiesterase and guanosine 3',5'-cyclic monophosphate were determined. Immunohistochemistry showed about 75% decrease in the number of tyrosine hydroxylase-positive neurons in the substantia nigra pars compacta. Mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine showed increased midbrain guanylyl cyclase and total nitric oxide synthase activities at 3, 7, and 14 days post-treatment. The specific neuronal nitric oxide synthase inhibitor 7-nitroindazole (10 microM) and the specific inducible nitric oxide synthase inhibitor 1400W (10 microM) inhibited the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced excess in nitric oxide synthase activity by 63-70 and 13-25%, respectively. The increases in total midbrain nitric oxide synthase activity were accompanied by elevated guanosine 3',5'-cyclic monophosphate, enhanced expression of neuronal nitric oxide synthase and of the beta1 subunit of guanylyl cyclase at both mRNA and protein levels that persisted up to the end of the observation period, and by enhanced neuronal nitric oxide synthase and guanylyl cyclase beta1 immunoreactivities in substantia nigra pars compacta 7 and 14 days after the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treatment. The increases in guanylyl cyclase activity were found to occur exclusively due to increased maximal enzyme activity. No 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced change in phosphodiesterase activity has been detected in any brain region studied. 7-Nitroindazole prevented a significant increase in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced midbrain guanosine 3',5'-cyclic monophosphate level and neurodegeneration of dopaminergic neurons. These results raise the possibility that the nitric oxide/guanylyl cyclase/guanosine 3',5'-cyclic monophosphate signaling pathway may play a role in maintaining dopaminergic neurons function in substantia nigra pars compacta.     

Neurometabolic profiles of the substantia nigra and striatum of MPTP‐intoxicated common marmosets: An in vivo proton MRS study at 9.4 T

Given the strong coupling between the substantia nigra (SN) and striatum (STR) in the early stage of Parkinson's disease (PD), yet only a few studies reported to date that have simultaneously investigated the neurochemistry of these two brain regions in vivo, we performed longitudinal metabolic profiling in the SN and STR of 1‐methyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐intoxicated common marmoset monkey models of PD (n = 10) by using proton MRS (¹H–MRS) at 9.4 T. T₂ relaxometry was also performed in the SN by using MRI. Data were classified into control, MPTP_2weeks, and MPTP_6‐10 weeks groups according to the treatment duration. In the SN, T₂ of the MPTP_6‐10 weeks group was lower than that of the control group (44.33 ± 1.75 versus 47.21 ± 2.47 ms, p < 0.05). The N‐acetylaspartate to total creatine ratio (NAA/tCr) and γ‐aminobutyric acid to tCr ratio (GABA/tCr) of the MPTP_6‐10 weeks group were lower than those of the control group (0.41 ± 0.04 versus 0.54 ± 0.08 (p < 0.01) and 0.19 ± 0.03 versus 0.30 ± 0.09 (p < 0.05), respectively). The glutathione to tCr ratio (GSH/tCr) was correlated with T₂ for the MPTP_6‐10 weeks group (r = 0.83, p = 0.04). In the STR, however, GABA/tCr of the MPTP_6‐10 weeks group was higher than that of the control group (0.25 ± 0.10 versus 0.16 ± 0.05, p < 0.05). These findings may be an in vivo depiction of the altered basal ganglion circuit in PD brain resulting from the degeneration of nigral dopaminergic neurons and disruption of nigrostriatal dopaminergic projections. Given the important role of non‐human primates in translational studies, our findings provide better understanding of the complicated evolution of PD.     

Conversion of the neurotoxic precursor 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine into its pyridinium metabolite by human platelet monoamine oxidase type B

MPTP (1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine) causes selective and irreversible degeneration of the substantia nigra of human and non-human primates. In the central nervous system, the oxidative metabolism of MPTP to 1-methyl-4-phenyl-pyridinium (MPP+) by monoamine oxidase type B (MAO-B) seems to be a critical feature in the neurotoxic process. We now report that [3H]MPTP is rapidly converted in vitro into [3H]MPP+ by human platelet MAO-B. The formation of [3H]MPP+ in human platelets is prevented by specific MAO-B but not by MAO-A or by 5-hydroxytryptamine uptake inhibitors.     

Genotype-phenotype correlation for non-HLA disease associated risk alleles in multiple sclerosis

A series of oxicam non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to be neuroprotective against 1-methyl-4-phenyl pyridinium in human neuroblastoma SH-SY5Y cells via the phosphatidylinositol 3-kinase (PI3K)/Akt pathway independent of cyclooxygenase (COX) inhibition. The present study endeavored to establish this novel effect of meloxicam (MLX), an oxicam NSAID, in a mouse Parkinson's disease (PD) model using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Male C57BL/6 mice, which received MPTP (30 mg/kg/day; s.c.) for 5 consecutive days (chronic model) with 10-day follow-up saline administrations, showed significant motor dysfunction in the pole test due to reduced tyrosine hydroxylase (TH) protein levels in the brain on day 16 after MPTP/saline treatment. Daily coadministrations of MLX (10mg/kg/day; i.p.) and MPTP for the first 5 days and follow-up 10 days with MLX administrations alone (MPTP/MLX treatment) significantly ameliorated MPTP-induced behavioral abnormalities in mice. Concomitant decreases of TH protein levels in the striatum and midbrain of MPTP/MLX-treated mice were not only significantly (p<0.01 and p<0.05, respectively) ameliorated but phosphorylated Akt (pAkt473) expression in the midbrain was also significantly (p<0.01) increased in the midbrain when compared with MPTP/saline-treated mice. These results suggest that MLX, an oxicam NSAID, attenuated dopaminergic neuronal death in the experimental MPTP-PD model by maintenance of the Akt-signaling. Oxicam NSAIDs may serve as potential drugs for PD treatment via a novel mechanism of action.     

阻断Notch信号通路降低1-甲基-4苯基-1,2,3,6-四氢吡啶诱导的多巴胺能神经元损伤

目的探讨Notch信号通路的缺失对1-甲基-4苯基-1,2,3,6-四氢吡啶(MPTP)诱导的中脑多巴胺能神经元损伤的影响。方法选用5月龄TH-Cre Rbpj基因敲除小鼠及野生型小鼠共48只,腹腔注射MPTP建立帕金森病(PD)模型,通过行为学、免疫组织化学和Western blotting等方法研究阻断Notch信号通路对MPTP诱导的中脑黑质多巴胺能神经元损伤的影响。结果 MPTP处理的Rbpj CKO小鼠运动能力强于MPTP处理的野生型小鼠;Rbpj CKO小鼠黑质致密部神经元数目较野生型小鼠减少;MPTP处理后,野生型小鼠多巴胺能神经元数目明显下降,而Rbpj CKO小鼠多巴胺能神经元数目无明显改变;Western blotting结果显示,MPTP处理后Rbpj CKO小鼠和野生型小鼠Notch-1胞内结构域(NICD-1)的表达均明显增加,且Rbpj CKO小鼠表达量增加更为显著。结论Notch信号通路缺失导致多巴胺能神经元数量减少,阻断Notch信号通路可以降低MPTP诱导的多巴胺能神经元损伤。     

Potentiation by reserpine and tetrabenazine of brain catecholamine depletions by MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) in the mouse; evidence for subcellular sequestration as basis for cellular resistance to the toxicant

Administration to mice of the neurotoxicant MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) decreased striatal dopamine and, to a lesser extent, hippocampal noradrenaline levels when measured 2 weeks after the last dose of MPTP. Reserpine and tetrabenazine, inhibitors of the catecholamine vesicular transporter, potentiated the catecholamine depletions produced by MPTP in the hippocampus and striatum, respectively. These results are compatible with our hypothesis that sequestration of the toxic MPTP metabolite MPP⁺ (1-methyl-4-phenylpyridinium) in the catecholamine storage vesicle retards the catecholaminergic toxicity of MPTP.     

线粒体转录终止因子蛋白家族的表达以及在MPTP/MPP~+诱导下的表达变化

目的探讨线粒体转录终止因子(MTERFs)蛋白家族在组织和细胞中的表达以及在神经毒素MPTP/MPP+诱导下的表达变化。方法取正常C57BL小黑鼠的脑、肝、肾组织,以及人神经母细胞瘤细胞SH-SY5Y、人心肌细胞HCM、人肝细胞L-02,检测MTERFs的蛋白表达情况;通过MPTP/MPP+构建帕金森病(PD)动物/细胞模型,检测MTERFs的蛋白表达变化情况。结果 MTERFs在小鼠脑中和SH-SY5Y细胞中蛋白表达水平较高;MPTP/MPP+诱导的PD模型中,MTERF3蛋白表达水平明显降低。结论在小鼠脑和SH-SY5Y细胞中,MTERFs表达较高;MPTP/MPP+诱导下MTERF3蛋白表达明显降低,影响了线粒体转录水平,这可能参与了帕金森病发生的过程。     

Septohippocampal connections to field CA1 of the rat identified with field potential analysis and retrograde labeling by horseradish peroxidase

Electrical stimulation of the medial septal nucleus produced field potentials in the hippocampal CA1 region of the rat. The laminar field-potential analysis suggested that the electromotive force of the septum-induced responses might be attributable mainly to excitatory postsynaptic potential currents generated in the stratum oriens (layer of distribution of basal dendrites of hippocampal pyramidal cells). Neural cell bodies in the medial septum-diagonal band complex were retrogradely labeled with horseradish peroxidase (HRP) injected into the stratum oriens of CA1, but not with HRP injected into other CA1 strata. Thus the medial septal nucleus was indicated to send excitatory inputs to basal dendrites of CA1 pyramidal cells.