Neurodegeneration最新文献

Recent studies have shown that cerebral beta amyloid (Aβ) protein deposition is a necessary, but not sufficient, factor to develop the pathology of Alzheimer's disease (AD). In the present immunohistochemical study, we have investigated in AD the distribution of Aβ associated proteins in the cerebral neocortex, in the cerebellar cortex where Aβ plaques are mainly of the diffuse type, and also in the cerebral neocortex of non-demented patients with Aβ plaques. Results show that immunolabeling for C1q, C4c, C3d, α1-ACT and Apolipoprotein E (ApoE) occurs in the great majority of Aβ plaques in all groups. ApoJ is present in Aβ plaques of the cerebral neocortex in AD and in non-demented elderly, but is almost absent from those of the AD cerebellar cortex. C4Bp and P-component, in contrast to AD, rarely occurs in Aβ plaques of the cerebral neocortex in the non-demented elderly. Heparan sulphate proteoglycan (HSPG) core protein and intercellular adhesion molecule-1 (ICAM-1) are absent in the diffuse Aβ plaques in the AD cerebellum. These differences in distribution and expression of Aβ associated proteins may be determined by brain region specific factors (cerebral cortex versus cerebellar cortex) and clinical state (demented versus non-demented cases). We suggest that, besides Aβ peptide, certain Aβ associated proteins are required for both amyloid plaque formation and for the induction of neurofibrillary changes.

Dithiocarbamates and CS₂ have been associated with neurobehavioural changes suggestive of central dopaminergic dysfunction. Diethyldithiocarbamate (DEDC), dimethyldithiocarbamate (DMDC), and methyldithiocarbamate (MDC) were examined for their ability to inhibit tyrosine hydroxylase (TH) activity in PC12 cells and transfected CHO fibroblasts that expressed TH ($\text{CHO}\text{TH}$) activity when tetrahydrobiopterin (BH₄) was added to medium. DEDC or DMDC did not significantly alter viability of PC12 cells or $\text{CHO}\text{TH}$ cells at ≤100 μM for 18 h; the EC50 for each compound was approximately 5 mM in both cell lines. In contrast, the EC50 for MDC was 41 or 74 μM in PC12 or $\text{CHO}\text{TH}$ cultures, respectively. There was no change in immunodetectable levels of TH in PC12 or $\text{CHO}\text{TH}$ cells following exposure to subcytotoxic concentrations of dithiocarbamates. DEDC and DMDC (5 to 100 μM) produced concentration-dependent reductions in PC12 cell dopamine and dopac levels as well as in dopa levels in $\text{CHO}\text{TH}$ cultures. Reduction of PC12 catechols was not due to altered vesicular storage. In vitro PC12 TH activity was 80.2 ± 3.4% or 82.4 ± 2.9% of control following exposure to 100 μM DEDC or DMDC, respectively, and was not fully restored by incubation with Fe²⁺. These results show that DEDC and DMDC, but not MDC, are low potency cytotoxins that decrease TH activity in cultured cells through mechanisms other than inhibition of BH₄ biosynthesis or iron chelation.

Fasting plasma and/or CSF amino acid levels have been measured in a group of 37 patients with motor neurone disease (MND) and in 35 neurological control patients undergoing lumbar puncture prior to myelography. There were no significant differences in the plasma levels of 22 amino acids between the two groups. In CSF, there was a significant elevation of the glutamate level in the MND patients (P=0.008). However, the MND group were heterogeneous with regard to CSF glutamate: 19/31 (61%) had levels within the normal range; eight (26%) had levels more than twice the upper limit of normal (≥10 μmol/l) and five (16%) had levels more than seven times normal (≥30 μmol/l). In a subset of seven MND patients there was a significant inverse correlation (r_s=−0.775,P<0.03) between CSF glutamate levels in life and the density of pre-synaptic glutamate re-uptake sites in the lumbar spinal cord measured in a post-mortem autoradiographic study. A possible interpretation of these findings is that an abnormality of glutamate transport may underlie the increase in CSF glutamate. The identification of a subgroup of MND patients with high CSF glutamate levels may be important in evaluating the clinical response to anti-glutamate therapeutic agents.

Recent reports have stressed an accumulation of iron and enhanced levels of lipid peroxides in the substantia nigra as essential factors in the pathogenesis of Parkinson's disease. Many investigators believe that tissue antioxidants, such as ascorbate, play a protective role. On the other hand, L-DOPA, which is used extensively to treat Parkinson's disease, undergoes autoxidation (as does dopamine), thus generating reactive oxygen species. We studied lipid peroxidation (LPO) in mouse brain homogenates and evaluated the effects of iron (5μM ferric-ADP), L-DOPA, dopamine and ascorbic acid, added either alone or in mixtures. Ascorbic acid was used at levels of 0.5 mM or 2.0 mM, approximating those present normally in brain. LPO in brain homogenates was stimulated by the addition of either ascorbic acid or iron, as well as by a combination of the two, in agreement with other reports. The effects of L-DOPA were complex: L-DOPA strongly suppressed LPO both with and without added iron-ADP. In sharp contrast, however, when ascorbic acid was also added, L-DOPA no longer suppressed LPO; indeed, L-DOPA stimulated LPO in the presence of added iron and ascorbic acid. Dopamine behaved similarly to L-DOPA. When ascorbic acid was studied over a concentration range, LPO was stimulated at 0.5, 1, 2 or 3 mM, with or without added iron and/or dopamine; 5 and 10 mM ascorbic acid were either not as effective or suppressed LPO below control levels. Deferoxamine, a powerful iron chelator, greatly suppressed LPO under all conditions, as did diethylenetriaminepentaacetate (DTPA). Added superoxide dismutase had no effect. These data illustrate: (a) the prominent pro-oxidant action of ascorbate, giving way to an antioxidant effect at high concentration (10 mM), and (b) the strong antioxidant effects of L-DOPA and dopamine, giving way to a milder pro-oxidant effect in the presence of added ascorbic acid.

The 6-hydroxydopamine (6-OHDA) model of nigral injury in rats has been in use as a standard animal model of parkinsonism for many years. While earlier studies established the time course for loss of catecholamine histofluorescence or tyrosine hydroxylase immunostaining in the cell bodies and terminals, these alterations in phenotypic expression do not define the time course of morphologic degeneration. We have therefore used a silver impregnation method to characterize the time course and morphology of the degeneration of neurons in the nigrostriatal system. Abundant neuronal death was observed in substantia nigra pars compacta (SNpc) as early as 12 hours after nigral 6-OHDA injection, and prior to any evidence of striatal terminal degeneration. From 1 to 7 days neuron death was accompanied by striatal fibre degeneration. After 7 days, fibre degeneration was no longer seen, but identifiable neuron death continued at low levels for as long as 31 days, and stained amorphous material was present at 60 days. The morphologic pattern of cell death in the early phase was similar to that in the late phase, and included cytoplasmic silver deposits and dark staining of the nucleolus. At no time was the morphology of apoptosis observed. We conclude that neuron death is a progressive process following 6-OHDA lesion, with similar morphology throughout the course of degeneration.

Magnetic resonance (MR) imaging in combination with gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) enhancement was used to investigate the integrity of the blood-brain barrier in a hamster model of scrapie (263K) during the clinical phase of the disease. The post Gd-DTPA images of the infected hamster brain showed marked enhancement, which was not present in control animals. These results suggest that blood-brain barrier function is disrupted in the clinically-affected animal.

Parkinson's disease is a neurodegenerative disorder, of which the most prominent morphological feature is the progressive loss of dopaminergic nigrostriatal neurons. Increased glutamatergic transmission in the basal ganglia has been implicated in the pathophysiology of Parkinson's disease (PD). This study investigated whether death of substantia nigra (SN) dopaminergic neurons could be caused by the hyperactivity of afferent pathways resulting in the release of a toxic dose of excitatory amino acids in the SN. Twice-daily unilateral stimulation of the subthalamic nucleus (STN) for 21 days, using two different pulse frequencies and current strengths, significantly increased amphetamine-induced rotation, whereas sham stimulated rats showed significantly reduced rotation. Striatal and SN dopamine (DA) levels were unaffected when compared to naı̈ve and sham stimulated rats. However, levels of the DA metabolite, homovanillic acid (HVA), were significantly higher in the ipsilateral anterior striata of rats that had been stimulated at high frequency (100 Hz) and low current (100 μA) as compared to sham treated animals. Stimulation of the pedunculopontine tegmentum (PPT), using a single kainic acid injection, did not affect DA concentration in the ipsilateral striatum and nucleus accumbens when compared to sham-treated rats. DA levels in the contralateral striatum and nucleus accumbens of lesioned rats were significantly higher than ipsilateral levels. DOPAC/DA ratios were lower in the contralateral striatum and nucleus accumbens, suggesting decreased DA turnover. Glutamic acid decarboxylase activity was significantly higher in the ipsilateral than the contralateral SN. The physical manifestations of PD require a large reduction in caudate and putamen DA levels and no such depletion was measured in this study. These results, therefore, do not support the hypothesis that Parkinson's disease may result from an overstimulation of substantia nigral DAneurons by glutamate afferents originating from the STN or PPT.

The influence of a single gene, engineered to be normally or abnormally expressed, can be evaluated in vivo through the development of transgenic animals. Application of this approach in the study of human neurological problems is contributing to an increased understanding of the pathogenic components operative in a variety of disorders. These include Alzheimer's disease, prion encephalopathies, motor neuron disease such as amyotrophic lateral sclerosis, and fragile X syndrome, as well as a number of viral-mediated neurological disorders. These transgenic animals can also serve as models to investigate the possible involvement of additional genetic and environmental factors on the disease state. Moreover, transgenic animals can be used in the development of intervention strategies. The application of this powerful and increasingly popular tool to investigate neurodegenerative disorders is reviewed.

Direct infusion of dopamine into the corpus striatum has been proposed as a potential approach for the treatment of Parkinson's disease. The present study examined the effect of intrastriatal dopamine infusion on D₂-dopamine receptors in the 6-hydroxydopamine (6-OHDA) lesioned rat brain. The completeness of the 6-OHDA-induced nigrostriatal injury was confirmed using [³H]-mazindol autoradiography and apomorphine-induced behaviour. Intrastriatal infusion of three different dopamine doses significantly reduced the apomorphine-induced behaviour. [³H]-spiperone autoradiography performed one day after the termination of dopamine infusion into the striatum revealed a dramatic reduction of D₂-dopamine receptor binding. The mean ± SEM percent reduction of D₂receptor binding in the affected areas of the striatum was 28.8±1.0% for 4.74 μg dopamine/h infusion rate, 35.0 ± 1.6% for 9.48 μg dopamine/h infusion rate and 33.3 ± 5.0% for 14.22 μg dopamine/h infusion rate when compared to the unlesioned side. Infusion of vehicle alone did not have any effect. The present results support the concept that intrastriatal dopamine infusion may be a useful therapeutic approach for the treatment of Parkinson's disease.

Cerebrospinal fluid (CSF) biochemical markers for Alzheimer's disease (AD) would be of great value, both to improve clinical diagnostic accuracy and to increase our knowledge of the pathogenesis of the disorder. An increase in the CSF-level of ‘neuronal thread protein’ (pancreatic thread protein (PTP) immunoreactive material in the brain) has been suggested to be just such a biochemical marker. We have studied CSF ‘neuronal thread protein’-like immunoreactivity (NTPLI) using a microparticle enzyme immunoassay. CSF-NTPLI did not differ significantly between AD type I (pure AD) and controls, but was significantly higher in AD type II (senile dementia) and vascular dementia (VAD) as compared with controls. Signs of blood-brain barrier (BBB) damage (elevated CSF/S albumin ratio) were found in both AD type II and in VAD, but not in AD type I. In a multiple ANOVA, with age and CSF/S albumin ratio as covariates, no significant difference in CSF-NTPLI between diagnostic groups was noted though both CSF/S albumin ratio and age (P<0.0001 andP<0.001 respectively) were found to influence the CSF-NTPLI level. Since BBB function was found to influence the CSF-NTPLI level, we examined whether NTPLI was present in serum. Indeed, serum NTPLI was about 40 times higher than CSF-NTPLI in neurological patients. Moreover, there was a statistically significant correlation between S-NTPLI and CSF-NTPLI. Taken together, present findings suggest that most of NTPLI in CSF comes from the serum, by passage over the BBB. As with the IgG index, we created a ‘NTPLI index’ (CSF/S NTPLI divided by CSF/S albumin ratio) to evaluate if there was an increase in NTPLI locally produced within the CNS in AD. However, there were no significant differences in NTPLI index between any of the groups. These findings suggest that, using these antibodies, CSF-NTPLI has no potential as a biochemical marker for AD, and that it is important to consider confounding factors, such as BBB function, in CSF studies.