RESUMEN
Oxidative stress is a major pathogenic mechanism in Parkinson's disease (PD). As an important cellular antioxidant, glutathione (GSH) balances the production and incorporation of free radicals to protect neurons from oxidative damage. GSH level is decreased in the brains of PD patients. Hence, clarifying the molecular mechanism of GSH deficiency may help deepen our knowledge of PD pathogenesis. Here we report that the astrocytic dopamine D2 receptor (DRD2) regulates GSH synthesis via PKM2-mediated Nrf2 transactivation. In addition we find that pyridoxine can dimerize PKM2 to promote GSH biosynthesis. Further experiments show that pyridoxine supplementation increases the resistance of nigral dopaminergic neurons to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity in wild-type mice as well as in astrocytic Drd2 conditional knockout mice. We conclude that dimerizing PKM2 may be a potential target for PD treatment.
Asunto(s)
Glutatión/biosíntesis , Intoxicación por MPTP/patología , Factor 2 Relacionado con NF-E2/genética , Fármacos Neuroprotectores/administración & dosificación , Piruvato Quinasa/metabolismo , Receptores de Dopamina D2/metabolismo , Animales , Astrocitos , Técnicas de Observación Conductual , Conducta Animal/efectos de los fármacos , Células Cultivadas , Dopamina/metabolismo , Neuronas Dopaminérgicas , Intoxicación por MPTP/diagnóstico , Intoxicación por MPTP/tratamiento farmacológico , Ratones Noqueados , Factor 2 Relacionado con NF-E2/metabolismo , Estrés Oxidativo/efectos de los fármacos , Cultivo Primario de Células , Multimerización de Proteína/efectos de los fármacos , Piridoxina/administración & dosificación , Especies Reactivas de Oxígeno/metabolismo , Receptores de Dopamina D2/genética , Sustancia Negra/citología , Sustancia Negra/efectos de los fármacos , Sustancia Negra/patología , Activación TranscripcionalRESUMEN
Parkinson's disease (PD) is a movement-associated disorder that specifically affects dopamine-producing neurons. The disease causes demyelation that adversely impacts upon the motor activity of the brain. Currently there are no promising biomarkers for PD; improved understanding of the molecular mechanisms underlying the different pathological stages of PD are required to enable identification of a novel biomarker. The present study successfully established a PD mouse model via nasal injection of 1methyl-4phenyl-1,2,3,6-tetrahydropyridine. The expression of cJun Ntermal kinase 3 (JNK3) and caspase3 in two different pathological stages of PD were analysed using immunohistochemistry and western blot analysis. The results inidcated that the initial PD pathogenesis recovers on response to rasagiline. Immunohistochemistry and western blot analysis revealed that treatment with rasagiline positively regulated earlystage PD pathogenesis by downregulating the expression of JNK3 and upregulating caspase3; however, there was no positive effect on the advanced stages of PD. Overall, these results concluded that rasagiline has the ability to inhibit the expression of JNK3 and upregulate caspase3 in early stages of PD; however, rasagline appears to have no impact on JNK3 and caspase3 levels in the advanced stages of PD.
Asunto(s)
Biomarcadores/metabolismo , Intoxicación por MPTP/diagnóstico , Proteína Quinasa 10 Activada por Mitógenos/metabolismo , Animales , Caspasa 3/metabolismo , Modelos Animales de Enfermedad , Regulación hacia Abajo/efectos de los fármacos , Inmunohistoquímica , Indanos/farmacología , Indanos/uso terapéutico , Intoxicación por MPTP/tratamiento farmacológico , Intoxicación por MPTP/patología , Masculino , Ratones , Ratones Endogámicos BALB C , Índice de Severidad de la Enfermedad , Regulación hacia Arriba/efectos de los fármacosAsunto(s)
Inhibidores Enzimáticos/farmacología , Locomoción/efectos de los fármacos , Intoxicación por MPTP/metabolismo , alfa-Metiltirosina/farmacología , Animales , Dopamina/biosíntesis , Dopamina/metabolismo , Diagnóstico Precoz , Intoxicación por MPTP/diagnóstico , Intoxicación por MPTP/fisiopatología , Masculino , Ratones , Ratones Endogámicos C57BL , Sustancia Negra/efectos de los fármacos , Sustancia Negra/metabolismo , Sustancia Negra/fisiopatología , Tirosina 3-Monooxigenasa/antagonistas & inhibidoresRESUMEN
BACKGROUND: Mirtazapine, a noradrenergic and specific serotonergic antidepressant (NaSSA), shows multiple pharmacological actions such as inhibiting presynaptic α2 noradrenaline receptor (NAR) and selectively activating 5-hydroxytriptamine (5-HT) 1A receptor (5-HT1AR). Mirtazapine was also reported to increase dopamine release in the cortical neurons with 5-HT dependent manner. To examine whether mirtazapine has a therapeutic potency in Parkinson's disease (PD), we examined this compound in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice model of PD. RESULTS: Male C57BL/6 mice were subjected to MPTP treatment to establish a PD model. Mirtazapine was administered once a day for 3 days after MPTP treatment. MPTP-induced motor dysfunction, assessed by beam-walking and rota-rod tests, was significantly improved by administration of mirtazapine. Biochemical examinations by high performance liquid chromatography and western blot analysis suggested mirtazapine facilitated utilization of dopamine by increasing turnover and protein expression of transporters, without affecting on neurodegenerative process by MPTP. These therapeutic effects of mirtazapine were reduced by administration of WAY100635, an inhibitor for 5HT1AR, or of clonidine, a selective agonist for α2-NAR, or of prazosin, an inhibitor for α1-NAR, respectively. CONCLUSION: Our results showed mirtazapine had a therapeutic potency against PD in a mouse model. Because PD patients sometimes show depression together, it will be a useful drug for a future PD treatment.
Asunto(s)
Encéfalo/fisiopatología , Modelos Animales de Enfermedad , Intoxicación por MPTP/tratamiento farmacológico , Intoxicación por MPTP/fisiopatología , Mianserina/análogos & derivados , Animales , Antidepresivos Tricíclicos/uso terapéutico , Encéfalo/efectos de los fármacos , Estudios de Factibilidad , Intoxicación por MPTP/diagnóstico , Masculino , Mianserina/uso terapéutico , Ratones , Ratones Endogámicos C57BL , Mirtazapina , Resultado del TratamientoRESUMEN
Parkinson's disease (PD) is characterized by the loss of dopamine-producing neurons in the nigrostriatal system. Numerous researchers in the past have attempted to track the progression of dopaminergic depletion in PD. We applied a quantitative non-invasive PET imaging technique to follow this degeneration process in an MPTP-induced mouse model of PD. The VMAT2 ligand (18)F-DTBZ (AV-133) was used as a radioactive tracer in our imaging experiments to monitor the changes of the dopaminergic system. Intraperitoneal administrations of MPTP (a neurotoxin) were delivered to mice at regular intervals to induce lesions consistent with PD. Our results indicate a significant decline in the levels of striatal dopamine and its metabolites (DOPAC and HVA) following MPTP treatment as determined by HPLC method. Images obtained by positron emission tomography revealed uptake of (18)F-DTBZ analog in the mouse striatum. However, reduction in radioligand binding was evident in the striatum of MPTP lesioned animals as compared with the control group. Immunohistochemical analysis further confirmed PET imaging results and indicated the progressive loss of dopaminergic neurons in treated animals compared with the control counterparts. In conclusion, our findings suggest that MPTP induced PD in mouse model is appropriate to follow the degeneration of dopaminergic system and that (18)F-DTBZ analog is a potentially sensitive radiotracer that can used to diagnose changes associated with PD by PET imaging modality.
Asunto(s)
Intoxicación por MPTP/diagnóstico , Tomografía de Emisión de Positrones , Tetrabenazina/análogos & derivados , Animales , Cuerpo Estriado/metabolismo , Modelos Animales de Enfermedad , Dopamina/metabolismo , Radioisótopos de Flúor , Masculino , Ratones , Ratones Endogámicos C57BL , Norepinefrina/metabolismoRESUMEN
The positron emission tomography (PET) tracer 2ß-carbomethoxy-3ß-(4-chlorophenyl)-8-(2-[18F]-fluoroethyl)-nortropane ((18)F-FECNT) is a highly specific ligand for dopamine transporter (DAT) that yields higher peak striatum-to-cerebellum ratios and offers more favorable kinetics than most (18)F-radiolabeled DAT ligands currently available. The goal of this study is to validate the use of (18)F-FECNT as a PET radiotracer to assess the degree of striatal dopamine terminals denervation and midbrain dopaminergic cell loss in MPTP-treated parkinsonian monkeys. Three rhesus monkeys received weekly injections of MPTP (0.2-0.5 mg/kg) for 21 weeks, which resulted in the progressive development of a moderate level of parkinsonism. We carried out (18)F-FECNT PET at baseline (twice; 10 weeks apart) and at week 21 post-MPTP injections. Postmortem stereological cell counts of dopaminergic neurons in the ventral midbrain, and intensity measurements of DAT and tyrosine hydroxylase (TH) immunoreactivity in the striatum were performed and correlated with striatal and ventral midbrain PET data. Three additional monkeys were used as controls for midbrain dopaminergic cell counts, and striatal DAT or TH immunoreactivity measurements. The correlation and coefficient of variance between (18)F-FECNT test-retest specific uptake ratios were 0.99 (R²) and 2.65%, respectively. The (18)F-FECNT binding potential of the ventral midbrain and striatal regions was tightly correlated with postmortem stereological cell counts of nigral dopaminergic neurons (R²=0.91), and striatal DAT (R²=0.83) or TH (R²=0.88) immunoreactivity intensity measurements. These findings demonstrate that (18)F-FECNT is a highly sensitive PET imaging ligand to quantify both striatal dopamine denervation and midbrain dopaminergic cell loss associated with parkinsonism.
Asunto(s)
Proteínas de Transporte de Dopamina a través de la Membrana Plasmática/metabolismo , Radioisótopos de Flúor , Intoxicación por MPTP/diagnóstico por imagen , Nortropanos , Tomografía de Emisión de Positrones , Animales , Autorradiografía , Síntomas Conductuales/etiología , Encéfalo/diagnóstico por imagen , Encéfalo/patología , Calbindinas , Femenino , Ligandos , Intoxicación por MPTP/complicaciones , Intoxicación por MPTP/diagnóstico , Macaca mulatta , Tomografía de Emisión de Positrones/métodos , Reproducibilidad de los Resultados , Proteína G de Unión al Calcio S100/metabolismo , Factores de Tiempo , Tirosina 3-Monooxigenasa/metabolismoRESUMEN
Parkinsonism caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) exposure was first identified in intravenous drug users. This neurotoxicant has since been used extensively in nonhuman primates to induce an experimental model of Parkinson disease (PD). In this study, the authors examined the intraoperative physiological characteristics and efficacy of subthalamic nucleus deep brain stimulation (DBS) in 1 of only 4 known living patients with MPTP-induced parkinsonism. The physiological recordings were consistent with recordings from MPTP-treated primates and humans with PD, thus providing further validation for the MPTP model in the study of the neurophysiology of the nigrostriatal dopaminergic deficit in PD. Furthermore, DBS produced a significant clinical improvement in this patient similar to the improvement seen after DBS in patients with idiopathic PD. This unique case has important implications for translational research that employs the MPTP-primate model for symptomatic therapy in PD.
Asunto(s)
Estimulación Encefálica Profunda/métodos , Intoxicación por MPTP/complicaciones , Intoxicación por MPTP/fisiopatología , Trastornos Parkinsonianos/inducido químicamente , Trastornos Parkinsonianos/fisiopatología , Trastornos Parkinsonianos/terapia , Núcleo Subtalámico/fisiopatología , 1-Metil-4-fenil-1,2,3,6-Tetrahidropiridina/administración & dosificación , 1-Metil-4-fenil-1,2,3,6-Tetrahidropiridina/efectos adversos , Adulto , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/fisiopatología , Dopamina/metabolismo , Estudios de Seguimiento , Humanos , Intoxicación por MPTP/diagnóstico , Intoxicación por MPTP/terapia , Masculino , Neuronas/efectos de los fármacos , Neuronas/fisiología , Trastornos Parkinsonianos/diagnóstico , Abuso de Sustancias por Vía Intravenosa/complicaciones , Sustancia Negra/efectos de los fármacos , Sustancia Negra/fisiopatologíaRESUMEN
The most valuable model of Parkinson's disease available at present is the primate model treated with 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine (MPTP), frequently used to study response to new drugs or surgical treatments. The evaluation of such therapies requires clinical rating scales which measure precisely motor behaviour in both normal and parkinsonian monkeys. It is obvious that such evaluation can only be valid if parallel studies are carried out under similar experimental conditions with well-defined objective criteria. Hence the need to compare and assess the different rating scales in use if we want to be able to compare the results of clinical studies. In order to give rise to some fresh thinking on the necessity of a certain uniformity of assessment, this study compares eight clinical rating scales and considers their capacity to express in quantitative terms both the severity of MPTP intoxication in five cynomolgus monkeys and the alleviation afforded by levodopa. None of the eight scales reaches all the criteria despite the Kurlan scale would appear as an interesting working basis for a further consensual definition of a worldwide used parkinsonian monkey clinical rating scale