Katsunori Nishi

Retrograde dopaminergic neuron degeneration following intrastriatal proteasome inhibition

Recent studies have suggested that defects in the ubiquitin-proteasome system (UPS) contribute to the etiopathogenetic mechanisms underlying dopaminergic neuronal degeneration in Parkinsons disease. The present study aims to study the effects of proteasome inhibition in the nerve terminals of nigrostriatal dopaminergic neurons in the substantia nigra pars compacta (SNpc). Following a unilaterally intrastriatal injection of lactacystin, a selective proteasome inhibitor, dopaminergic neurons in the ipsilateral SNpc progressively degenerated with alpha-synuclein-immunopositive intracytoplasmic inclusions. When lactacystin was administered at a high concentration, the striatum was simultaneously involved, and alpha-synuclein-immunopositive extracytoplasmic granules appeared extensively within the SN pars reticulata (SNpr). In addition, during the retrograde neuron degeneration in SN, the level of heme oxygenase-1 immunopositivity, an oxidative stress marker, was markedly increased in SNpc neurons. These results reveal that intrastriatal proteasome inhibition sufficiently induces retrograde dopaminergic neuronal degeneration with abundant accumulation of alpha-synuclein in the SN.

Magnesium exerts both preventive and ameliorating effects in an in vitro rat Parkinson disease model involving 1-methyl-4-phenylpyridinium (MPP+) toxicity in dopaminergic neurons.

A study was conducted to clarify the effects of magnesium (Mg) administration in a rat Parkinson disease (PD) model involving culture of ventral mesencephalic-striatal cells with 1-methyl-4-phenylpyridinium (MPP+), based on recent evidence for significant loss of dopaminergic neurons exclusively in the substantia nigra of 1-year-old rats after exposure to low Mg intake over generations [Oyanagi, K., Kawakami, E., Kikuchi-Horie, K., Ohara, K., Ogata, K., Takahama, S., Wada, M., Kihira, T., Yasui, M., 2006. Magnesium deficiency over generations in rats with special references to the pathogenesis of the parkinsonism-dementia complex and amyotrophic lateral sclerosis of Guam. Neuropathology 26, 115-128.]. The results indicated that Mg might protect dopaminergic neurons in the substantia nigra from degeneration. The concentration of Mg in the culture medium varied from 0.8 mM, corresponding to the control condition, to 4.0 mM. Effects were estimated by counting the number of surviving dopaminergic neurons immunopositive for tyrosine hydroxylase and measuring the length of dopaminergic neurites. An increase in the concentration of Mg to 1.2 mM significantly inhibited the toxicity of MPP+, and a concentration of 4.0 mM completely prevented any decrease in the number of dopaminergic neurons. The length of dopaminergic neurites was significantly preserved in the presence of Mg at 1.2 and 4.0 mM. An increase in the concentration of Mg to 1.2 and 4.0 mM led to a significant amelioration in the length of dopaminergic neurites after MPP+ toxicity. This is the first report to document a significant and striking effect of Mg for prevention of neurite and neuron pathology, and also amelioration of neurite pathology in a PD model.

Destruction of norepinephrine terminals in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice reduces locomotor activity induced by L-dopa.

There is little information concerning the effects of norepinephrine (NE) depletion on clinical features of patients with Parkinsons disease. By inducing two types of experimental parkinsonism, one with a dopamine (DA) deficiency alone and the other with both a DA and NE deficiency, we attempted to evaluate the differences in locomotor activity and behavioral responses between the two groups after L-DOPA administration. The results of the study revealed that increases in locomotor activity were markedly suppressed in the DA and NE deficient group. This may suggest that with striatal DA deficiency the central NE terminals play a significant role in the increase in locomotor activity after L-DOPA administration.

Differential expression of c-Fos following administration of two tremorgenic agents : harmaline and oxotremorine

The regional distribution of c-Fos expression in the brain after the administration of two tremorgenic agents was studied. In both the harmaline- and oxotremorin-treated rats, c-Fos-positive neurons were extensively distributed in the basal ganglia nuclei and the cerebellum. Additionally, in the harmalinetreated rats, numerous c-Fos-positive neurons were also distributed throughout the inferior olivary nucleus. In the oxotremorine-treated rats, while the inferior olive was not involved, c-Fos was strongly expressed in the neurons of the reticular thalamic nucleus, possibly due to the muscarinic effects of oxotremorine. The present study revealed that the inferior olive is selectively activated in the harmaline-administered animals and that the basal ganglia are involved in both harmaline- and oxotremorine-induced tremors.

Significance of CSF total neopterin and biopterin in inflammatory neurological diseases

Total neopterin (T-N), a by-product in the biopterin biosynthesis and an indicator of activation of the cellular immune system, and total biopterin (T-B) levels in cerebrospinal fluid (CSF), were measured in patients with various inflammatory neurological diseases and Parkinsons disease, and the following results were obtained. (1) In patients with neuro-sarcoidosis, neuro-Behçets disease and meningitis, CSF T-N levels were markedly elevated in the exacerbation or acute stages of their neurological symptoms and remarkably decreased in the remission or chronic stages. In the neuro-sarcoidosis and neuro-Behçets disease patients, however, CSF T-B levels showed no substantial change. (2) There was a significant positive correlation between CSF T-N levels and CSF/serum albumin ratios only in the meningitis patients. However, increases of CSF T-N levels were not associated with those of plasma T-N levels. (3) In the Parkinsons disease patients, CSF T-N levels remained normal, although CSF T-B levels significantly decreased. (4) A gradient for the CSF T-N value (lumbar greater than ventricular CSF), being reverse to the CSF T-B value, was observed. These results indicate that the significance of CSF T-N is quite different from CSF T-B, and that CSF T-N appears to be a valuable biochemical marker for evaluating the activity of inflammation within the central nervous system. Its measurement seems useful for therapeutic monitoring, especially of patients showing the chronic exacerbating-remitting course.

Expression of c-Jun in dopaminergic neurons of the substantia nigra in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice

The expression of c-Jun in the brains of young (8-week-old) and older (52-week-old) mice following administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was investigated immunocytochemically. Both age groups exhibited reduction in the number of dopaminergic neurons in the substantia nigra after administration of MPTP. There was a significant difference in the magnitude of decrease in the number of dopaminergic neurons between the two groups, as has previously been reported, and the older mice exhibited more extensive loss of dopaminergic neurons in the substantia nigra after MPTP administration than did the young mice. Prolonged c-Jun expression was induced in the substantia nigra following administration of MPTP, and this induction was more prominent in the older mice than in the young mice. Maximum expression of c-Jun occurred on day 7 after the administration of MPTP in both groups. Double staining for tyrosine hydroxylase (TH; a dopaminergic neuron marker) and c-Jun revealed their co-localization indicating that the cells expressing c-Jun were dopaminergic neurons. Cytoplasmic volumes of strongly c-Jun positive cells were reduced, suggesting that they may have been degenerating. In situ end labeling revealed no apoptotic neurons after MPTP administration. These results suggest the existence of some cascade mechanism of nonapoptotic death of dopaminergic neurons following administration of MPTP.

Difference in recovery patterns of striatal dopamine content, tyrosine hydroxylase activity and total biopterin content after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration: a comparison of young and older mice

Striatal dopamine (DA) content, tyrosine hydroxylase (TH) activity, and total biopterin content were measured as parameters of recovery, after administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in 7-week-old (young) and 28-week-old (older) C57 BL/6 mice. After 10 consecutive days of injection of MPTP (30 mg/kg/day) young mice were sacrificed at one day and 2, 4, 8, 12 and 20 weeks; older mice (20 mg/kg/day) at one day and 4, 8, and 12 weeks. All 3 parameters were markedly reduced one day after the last injection of MPTP. During the observation period, the parameters showed a gradual and partial recovery. The recovery rates of the 3 parameters differed significantly, especially during the early phases of 2-8 weeks. Total biopterin content showed a greater rate of recovery than TH activity and TH activity, a greater rate of recovery than DA content. In the older mice group, the recovery of all 3 parameters was retarded significantly, and dissociation of the recovery rates between the 3 parameters was more prominent. The results of our present study suggest that, following neurotoxic injury, the recovery of biopterin may play a significant role in dopaminergic terminal regeneration.

Total biopterin levels in the ventricular CSF of patients with Parkinson's disease: A comparison between akineto-rigid and tremor types

Total L-erythro-biopterin (T-BP) levels in the ventricular cerebrospinal fluid (CSF) were measured in 43 patients with Parkinsons disease (PD) and 12 age-matched neurological controls. In 5 of the PD patients and 1 control, lumbar CSF T-BP values were also measured. The mean ventricular CSF T-BP level in the PD patients, 15.6 +/- 0.5 pmol/ml (mean +/- SE), was significantly lower than that in the controls (21.3 +/- 1.4 pmol/ml, P less than 0.0001). The mean T-BP concentration in the ventricular CSF was 1.9 times higher than that in the lumbar CSF (P less than 0.0005), indicating a rostrocaudal gradient for the T-BP value in the CSF. When the PD patients were classified according to their predominant clinical features into 24 akineto-rigid (A-R) type and 19 tremor (T) type, there was a significant negative correlation between the T-BP levels and duration of illness only for the A-R type patients (rho = -0.605, P less than 0.005). No such significant correlation was found in the T type patients. These results may indicate a difference of pathophysiological changes in the brain between the 2 types of PD.

Effects of blockade of metabotropic glutamate receptors in the subthalamic nucleus on haloperidol-induced Parkinsonism in rats

The present study examined the postural effects of unilaterally local injection of metabotropic glutamate receptor (mGluR) antagonists into the subthalamic nucleus (STN), in rats with haloperidol-induced parkinsonism. In rats which received unilateral microinjections of (+)-alpha-methyl-4-carboxyphenylglycine (MCPG), a selective, subtype-non-specific antagonist of mGluR, but not the vehicle, into the STN, systemic administration of haloperidol induced ipsiversive dystonic posturing. The severity of the dystonic posturing was dose-dependent. However, subtype-specific antagonists of group I, II, or III mGluRs induced no dystonic posturing. The present findings suggest that the activity of the STN under conditions of dopamine blockade is facilitated by blockade of mGluRs in the STN, suggesting that mGluRs exert inhibitory influence on glutamate release in the STN.

Effects of the globus pallidus lesion on the induction of c-Fos by dopaminergic drugs in the striatum possibly via pallidostriatal feedback loops

c-Fos is one of the transcription factors contributing to the regulation of the downstream gene expression. Administration of dopamine D1 receptor agonist or D2 receptor antagonist have been known to induce c-Fos expressions in striatal projection neurons. We examined the effects of unilateral ablation of the globus pallidus (GP) on apomorphine- or haloperidol-induced expression of c-Fos in the striatum. Haloperidol induced a high level of c-Fos expression in the striatal neurons, predominantly those in the dorsal part, and the unilateral GP lesion caused by ibotenic acid increased the number of neurons exhibiting haloperidol-induced c-Fos expression in the striatum on the side with the GP lesion by about 2- or 3-fold. On the other hand, the unilateral GP lesion had no significant effect on the apomorphine-induced c-Fos expression in the striatal neurons. The present study provides evidence indicating that the activity of GP neurons may have an inhibitory influence on the induction of the immediate early genes by haloperidol in the striatal neurons, suggesting a function of the pallido-striatal feedback loops which have been identified anatomically.