Experimental parkinsonism modulates multiple genes involved in the transduction of dopaminergic signals in the striatum

The irreversible loss of the dopamine-mediated control of striatal function is considered the functional substrate of the motor symptoms of Parkinson's disease. This pathological event causes a complex rearrangement of neuronal activity which involves specific dopamine-regulated cellular functions and, secondarily, several other cellular properties and transmitter systems. In the present study, we applied recently developed cDNA microarray technology to investigate the genetic correlates of the alterations produced by 6-hydroxydopamine-induced dopamine denervation in the nucleus striatum. We found that chronic dopamine denervation caused the modulation of 50 different genes involved in several cellular functions. In particular, products of the genes modulated by this experimental manipulation are involved both in the intracellular transduction of dopamine signal and in the regulation of glutamate transmission in striatal neurons, providing some information on the possible neuronal events which lead to the reorganization of glutamate transmission in the striatum of parkinsonian rats.     

Striatal dopaminergic loss without parkinsonism in a case of corticobasal degeneration

Neurochemical analyses of post-mortem brain from cases of corticobasal degeneration are extremely rare although nearly 100 cases have been reported in the literature. We detail findings of neurotransmitter derangement in the basal ganglia of a case of neuropathologically confirmed corticobasal degeneration, who presented with dementia. The implications of severe neuronal loss in the substantia nigra and extremely low levels of dopamine and its metabolites in the striatum are considered in relation to the absence of an intrinsic extrapyramidal syndrome.     

Proton magnetic resonance imaging and spectroscopy identify metabolic changes in the striatum in the MPTP feline model of parkinsonism

We administered 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to adult, male cats to model Parkinson's disease (PD), and utilized proton magnetic resonance imaging (MRI) and spectroscopy (MRS) at a field strength of 1.5 T to identify metabolic degenerative changes in the striatum in vivo. Neurologic status and somatosensory-evoked potentials in vivo, as well as postmortem striatal histopathological and immunohistochemical parameters, were examined. Nine cats were equally divided into three groups and treated daily for 10 days as follows: saline, MPTP, and pargyline (a monoamine oxidase inhibitor) plus MPTP. The MPTP-treated cats displayed bradykinesia, head tremor, and reduced oculovestibular reflex activity. MRI showed a diffuse increase of the T2-weighted signal in the striatum of two MPTP-treated cats. Analysis of the MRS spectra indicated significantly lower N-acetylaspartate/creatine (CR) and glutamine-glutamate complex/CR ratios than the control baseline. Two MPTP-treated cats had low choline-containing compounds/CR ratio, whereas a lactate peak was present in all MPTP-treated cats. In the striatum of the MPTP-treated cats, there was a significant decline of tyrosine hydroxylase immunoreactivity and histological evidence for a diffuse cytotoxic reaction. Pretreatment with pargyline attenuated the MPTP-induced clinical signs, MRI and MRS changes, and the histopathological and immunoreactivity alterations. We conclude that proton MRI/MRS is a sensitive, noninvasive measure of neural toxicity and biochemical alteration of the striatum in a feline model of PD.     

Profound astrogenesis in the striatum of adult mice following nigrostriatal dopaminergic lesion by repeated MPTP administration.

Neural progenitor cells are present in the rodent brain throughout adulthood, and can proliferate and differentiate into new neurons and/or glia to repair injury. To explore the repair processes mediated by brain progenitor cells, a selective lesion of the nigrostriatal dopaminergic pathway was induced in young adult mice by repeated administration of the neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). A thymidine analog, bromodeoxyuridine (BrdU), was used as a tracer for DNA synthesis to label the dividing cells and their terminal progeny following injury. Three days after MPTP treatments (25 mg/kg, once daily for 5 days), an 8-fold increase in the number of BrdU-labeled newborn cells was observed in the dorsal striatum. A 5-fold increase was also seen in the substantia nigra (SN). Newborn cells in the striatum survived beyond 60 days after their birth whereas newborn cells in the SN survived for less than 31 days. The vast majority of newborn cells in the striatum differentiated into astroglia according to their radial morphology and co-expression with an astroglial marker, S100beta, within 10 days after birth. In contrast, most BrdU-positive cells in the SN failed to co-express S100beta. Little or none of BrdU-labeled cells in both the striatum and SN were found to co-localize with a neuronal marker, neuronal nuclear antigen, or tyrosine hydroxylase during the full course of survival days surveyed (3 to 60 days). Repeated MPTP also decreased dopamine content and uptake in the striatum, which showed a significant recovery 31 days after MPTP lesion. These results demonstrate a rapid and profound astrogenesis in the striatum of young adult mice in response to toxic dopaminergic insult. The lack of neurogenesis in the two affected brain areas indicates the relative importance of glial cell regeneration in repairing MPTP injury.     

Selective loss of subpopulations of ventral mesencephalic dopaminergic neurons in the monkey following exposure to MPTP

Tyrosine hydroxylase immunohistochemical examination of the mesencephalon of severely parkinsonian MPTP-treated macaque fascicularis monkeys revealed a marked loss of substantia nigra pars compacta (SNc) neurons in both medial and central portions of the nucleus with a relative sparing of neurons in the dorsal-most portions of the substantia nigra. These animals also sustained 20–65% loss of neurons in the substantia nigra pars lateralis area, ventral tegmental area (A-10), and the retrorubral area (A-8 cell group, and the parabrachialis pigmentosus region). These animals all had extreme striatal dopamine depletions. A monkey which received several small doses of MPTP and yet remained asypptomatic for a motor disorder (although it had demonstrable behavioral performance deficits) had only a loss only ventral SNc neurons, with no appreciable cells in associated ventral mesencephalic dopamine areas and no loss of striatal dopamine. These data suggest that the effects of MPTP are not as selective as originally thought and, more importantly, indicate that MPTP-induced parkinsonism in the primate may be more analogous to idiopathic Parkinson's disease, where cells other than SNc cells are affected. Furthermore, the present findings suggest that only certain mesencephalic dopamine neurons are susceptible to MPTP-induced damage. The unique characteristics of these neurons need to be elucidated.     

Association of vascular parkinsonism with impaired neuronal integrity in the striatum

Summary. The purpose of this study is to identify the underlying differences between patients with white matter lesions (WMLs) who manifested gait disturbance suggestive of vascular parkinsonism (VaP) and those who did not, using the PET scan. Fourteen patients with extensive WMLs, as determined by MRI, were divided into two groups – 7 with gait disturbance and 7 without it. Neuronal integrity was evaluated with a PET scan using [¹¹C]flumazenil (FMZ) by calculating the distribution volume of FMZ (FMZ-V_d) in various regions of interest by non-linear curve fitting. Additionally, tracer kinetic analysis was applied for voxel-by-voxel quantification of FMZ-V_d and data analysis was performed using statistical parametric mapping. The striatal FMZ-V_d values were inversely correlated with the motor UPDRS scores (r = 0.70, p < 0.005), and their reductions were associated with the presence of gait disturbance. Therefore, differences in neuronal integrity in the striatum may determine whether patients with WMLs develop VaP or not.     

Spontaneous functional recovery from parkinsonism is not due to reinnervation of the dorsal striatum by residual dopaminergic neurons

Cats exposed to MPTP experience severe motor deficits that spontaneously recover after 4–6 weeks. This recovery occurs despite a persistent deficit (approximately 95%) in dorsal striatal DA levels. To determine whether residual DA neurons that previously did not innervate the dorsal caudate nucleus (CD) have innervated this area in recovered MPTP-treated animals, HRP was injected into the dorsal lateral and dorsal medial CD and the locations of retrogradely labeled neurons in ventral mesencephalon were mapped in normal and recovered MPTP-treated cats. Tyrosine hydroxylase (TH) positive cells were also counted in ventral mesencephalic DA-containing cell groups in normal, symptomatic, and recovered MPTP-treated cats. Results showed no difference in the pattern of HRP labeling in normal and recovered cats except for the loss of labeled substantia-nigra pars compacta (SNc) cells in MPTP-treated cats. Cell counts revealed no significant difference in the degree of TH-positive cell loss in all ventral mesencephalic areas studied in both symptomatic and recovered cats. The results suggest that spontaneous recovery of gross motor function in MPTP-treated cats is most likely not dependent upon reinnervation of the dorsal striatum from residual DAergic neurons.     

Correlation of striatal fluorodopa uptake in the MPTP Monkey with dopaminergic indices

Striatal ¹⁸F-6-fluorodopa (FD) uptake constants were measured by positron emission tomography in (1) normal cynomolgus monkeys and (2) a series of cynomolgus and rhesus monkeys that had received intracarotid infusions of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). After the animals were killed, the number and average size of dopaminergic neurons in the substantia nigra pars compacta were measured. Striatal levels of dopamine and its metabolites, and the striatal activities of the dopaminergic synthetic enzymes, were also determined. The striatal FD uptake constants showed highly significant positive correlations with both number and size of dopaminergic neurons, indicating atrophy of surviving neurons in MPTP-treated animals. The uptake constants also showed significant positive correlations with striatal levels of dopamine, total catecholamines, and the activities of the synthetic enzymes. Both histochemical and biochemical data on tyrosine hydroxylase suggested some contralateral enzyme loss in these MPTP-treated monkeys, as well as decreased enzyme activity in surviving neurons on the lesioned side. However, residual enzyme activities were apparently not rate limiting to striatal FD uptake. It is concluded that PET-FD measurements by positron emission tomography provide a good index of the integrity of the nigrostriatal pathway.     

Tyrosine hydroxylase-immunohistochemical study in the midbrain of experimental MPTP parkinsonism]

We have performed tyrosine hydroxylase (TH)-immunohistochemical study in the midbrain of experimental MPTP parkinsonism. Eight female adult crab-eating monkeys (macaca fascicularis) were subjected to the experiment and divided into four groups. In the acute experimental parkinsonism (group A), a daily dose of 1.3 mg/kg MPTP was given intravenously for 7 days. Monkeys in the subacute group B were injected every other day a dose of 1.0 mg/kg MPTP intravenously for 7-14 days. Chronic experimental parkinsonism group C was induced by administration of a dose of 0.5 mg/kg twice a week intravenously for 120 days. Group D served as a control. TH-immunoreactive cells were counted in substantia nigra pars compacta (SNc: consisting of lateral, intermediate, medial regions) and paramedian region of midbrain. The remaining TH-immunoreactive cells in group A,B and C were approximately 65.1%, 46.6% and 32.1% of the control group D. The ratio of TH-immunoreactive cells in the lateral region of group A, B and C was lower than in group D. The TH-immunoreactive ratio in the intermediate and medial region of group B and C was lower than in group D. In the medial region of group C, the TH-immunoreactive ratio was increased than in group B. In the paramedian region of all groups, there was no significant differences in the ratio of TH-immunoreactive cells, but many more TH-immunoreactive nerve fibers were observed in group B and C than in group A and D. From the 90th day after MPTP treatment, monkeys in group C began to show a gradual recovery from the flexed posture and hypokinesia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reduced MPTP neurotoxicity in striatum of the mutant mouse tottering

The effects of MPTP treatment (4 × 10 mg/kg, 2-h intervals) on in vivo striatal binding of (+)-α-[³H]dihydrotetrabenazine ((+)-[³H]DTBZ) to the vesicular monoamine transporter type 2 (VMAT2) were examined in wild type (+,+) and tottering (tg/tg) mice of the C57BL/6J strain. The tottering mutant has been previously characterized as having hyperinnervation of noradrenergic terminals in the brain, with increased concentrations of norepinephrine and increased numbers of VMAT2 binding sites. In wild-type mice, MPTP caused a significant decrease in specific striatal (+)-[³H]DTBZ binding in both males (-71%) and females (-57%), consistent with dopaminergic terminal losses. In the tottering mice, the neurotoxic effects of MPTP were diminished, with smaller losses of (+)-[³H]DTBZ binding observed both in males (-45%) and females (-26%). These results are consistent with the hypothesis that vesicular storage (as a result of hyperinnervation) offers neuroprotection toward MPTP toxicity, although the confounding effects of increases in norepinephrine concentrations or changes in calcium ion channel function (both also characteristics of the tottering mutant) cannot be ruled out. The tottering mutant does, however, offer another animal model to examine the biochemical features responsible for MPTP toxicity. Synapse 30:205–210, 1998. © 1998 Wiley-Liss, Inc.     

Paradoxial response to dopaminergic agents in parkinsonism

A patient with the classical stigmata of parkinsonism was treated on three separate occasions with levodopa, a combination of levodopa and carbidopa, and lergotrile mesylate, a direct-acting dopamine-receptor agonist. All three treatment regimens resulted in dose-related increases in parkinsonian features. To our knowledge, this response has not been previously described. Lergotrile did not alter CSF homovanillic acid concentration. It is suggested that this rare paradoxical motor response to dopaminergic agents may be associated with dysfunction of the postsynaptic dopamine receptor site.     

Damage to oligodendrocytes in the striatum after MPTP neurotoxicity in mice

Summary We investigated the alteration of oligodendrocytes in comparison with that of astrocytes and microglia in the mouse striatum after MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropridine) treatment under the same conditions using Western blot analysis and Immunohistochemistry. In our Western blot analysis, four administrations of MPTP at 2-h intervals to mice produced the remarkable loss of TH (tyrosine hydroxylase) protein levels in the striatum after 3 and 7 days. In contrast, GFAP (glial fibrillary acidic protein) and Iba-1 protein in the striatum showed a significant increase of GFAP and Iba-1 protein levels 3 and 7 days after MPTP treatment. On the other hand, the levels of CNPase (2′, 3′-cyclic nucleotide 3′-phosphodiesterase) protein were decreased significantly in the striatum 3 and 7 days after MPTP treatment. In our immunohistochemical study, a significant decrease in the area of expression of CNPase-positive profiles was observed in the striatum 3 and 7 days after MPTP treatment. These results demonstrate that oligodendrocytes in the striatum are damaged after MPTP treatment. Thus our present findings provide valuable information for the pathogenesis of Parkinson’s disease.     

Zebrafish embryos are susceptible to the dopaminergic neurotoxin MPTP

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces selective loss of dopaminergic neurons in the mammalian midbrain, eliciting symptoms characteristic of Parkinson's disease. By exploiting the advantages of zebrafish embryos, we report here that dopaminergic neurons in this species are specifically perturbed when exposed to MPTP. In contrast to mammals, the zebrafish does not possess a midbrain dopaminergic system. Instead, the main population of neurons expressing the dopamine transporter is located in the posterior tuberculum of the diencephalon. Exposure of embryos to MPTP led to a pronounced reduction in the number of dopaminergic cells in the diencephalon. This effect can be reversed by deprenyl, a specific inhibitor of monoamine oxidase B that catalyses the conversion of MPTP to its active metabolite, MPP+. Similarly, direct treatment of embryos with MPP+ abolished the diencephalic dopaminergic neurons. These larvae also demonstrated behavioural defects in swimming responses. Thus, dopaminergic neurons in the posterior tuberculum of the zebrafish may be homologous to the midbrain dopaminergic system of mammals. In addition, the mechanism behind the loss of dopaminergic neurons following pharmacological perturbation may be conserved among vertebrates and suggest that the zebrafish can be used as a convenient and economical system to study the pathogenesis of Parkinson's disease and for testing potential therapeutic strategies.     

Pramipexole attenuates the dopaminergic cell loss induced by intraventricular 6-hydroxydopamine

Summary. The D₃ preferring dopamine agonist pramipexole has been shown to attenuate the cell loss induced by levodopa in vitro. Pramipexole was herein evaluated in the 6-hydroxydopamine lesion model to determine its in vivo effect. Rats were treated with pramipexole or saline before and after an intracerebroventricular 6-hydroxydopamine injection. In the preliminary study, 6-hydroxydopamine produced a 68% reduction in striatal dopamine and a 62% loss in tyrosine hydroxylase immunoreactive (THir) cell counts in the substantia nigra. Pramipexole treated animals exhibited a 29% and a 27% reduction in striatal dopamine and THir cell counts, respectively. THir cell counts and striatal dopamine were significantly correlated. In the stereological study, 6-hydroxydopamine reduced THir cell counts by 47% in saline treated animals and 26% in pramipexole treated animals. These data demonstrate that pramipexole attenuates the biochemical and THir cell changes normally produced by 6-hydroxydopamine consistent with its neuroprotective actions in vitro. Received May 17, 1999; accepted August 3, 1999     

Relatively spared mesocorticolimbic dopaminergic system in juvenile parkinsonism

This study aims to examine the function of the mesocorticolimbic dopaminergic system, including the amygdala, in recognizing emotions in juvenile parkinsonism (JP). Eleven patients with JP and 16 age-matched controls selected one basic emotion (happiness, sadness, anger, fear, surprise, or disgust) that best described the emotional state represented by visual and auditory stimuli. There was no significant difference between the patients and normal controls in their recognition of emotions. The spared emotion recognition in JP could be attributed to the absence of any pathological changes or the normal dopamine concentrations in the mesocorticolimbic system in this condition.     

Exploring pre-degenerative alterations in humans using induced pluripotent stem cell-derived dopaminergic neurons

<正>Understanding the cellular and molecular mechanisms underlying human neurological disorders is hindered by both the complexity of the disorders and the lack of suitable experimental models recapitulating key pathological features of the disease.This is a crucial issue since a limited understanding of pathogenic mechanisms precludes the development of drugs counteracting the progression of the disease.Among neurological disorders,Parkinson’s disease(PD)is likely caused by a variable