Dementia, parkinsonism, and motor neuron disease: neurochemical and neuropathological correlates

Ubiquitin ligase HMG-CoA reductase degradation 1 (HRD1) prevents cell death in a cellular model of Parkinson's disease

Endoplasmic reticulum (ER) stress may play a role in the etiology of Parkinson's disease (PD). We have previously reported that ubiquitin ligase 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase degradation 1 (HRD1) involved in ER stress degrades unfolded protein that accumulates in the ER due to loss of function of Parkin, which is a causative factor in familial PD. We have also demonstrated that cell death is suppressed by the degradation of unfolded proteins. These findings indicate that HRD1 may serve as a compensatory mechanism for the loss of function of Parkin in familial PD patients. However, the role of HRD1 in sporadic PD has not yet been identified. This study aimed to reveal the roles of HRD1 and associated molecules in a cellular model of PD. We demonstrated that expressions of HRD1 and Suppressor/Enhancer Lin12 1-like (SEL1L: a HRD1 stabilizer) increased in SH-SY5Y human neuroblastoma cells upon exposure to 6-hydroxydopamine (6-OHDA). The 6-OHDA-induced cell death was suppressed in cells overexpressing wt-HRD1, whereas cell death was enhanced in cells with knockdown of HRD1 expression. These results suggest that HRD1 is a key molecule involved in 6-OHDA-induced cell death. By contrast, suppression of SEL1L expression decreased the amount of HRD1 protein. As a result, 6-OHDA-induced cell death was enhanced in cells suppressing SEL1L expression, and this cell death was much more evident than that in cells with suppression of HRD1 expression. These findings strongly indicate that SEL1L is necessary for maintaining and stabilizing the amount of HRD1 protein, and stabilizing the amount of HRD1 protein through SEL1L may serve to protect against 6-OHDA-induced cell death. Furthermore, the expression of Parkin was reinforced when HRD1 mRNA had been suppressed in cells, but was not observed when SEL1L mRNA had been restrained. It is possible that Parkin expression is induced as a compensatory mechanism when HRD1 mRNA decreases. This intracellular transduction may suppress the enhancement of 6-OHDA-induced cell death caused by the loss of HRD1. Taken together with these results, it is suggested that HRD1 and its stabilizer (SEL1L) are key molecules for elucidating the pathogenesis and treatment of PD.

Endoplasmic reticulum stress and Parkinson's disease: the role of HRD1 in averting apoptosis in neurodegenerative disease

Endoplasmic reticulum (ER) stress has been known to be involved in the pathogenesis of various diseases, particularly neurodegenerative disorders such as Parkinson's disease (PD). We previously identified the human ubiquitin ligase HRD1 that is associated with protection against ER stress and its associated apoptosis. HRD1 promotes the ubiquitination and degradation of Parkin-associated endothelin receptor-like receptor (Pael-R), an ER stress inducer and causative factor of familial PD, thereby preventing Pael-R-induced neuronal cell death. Moreover, upregulation of HRD1 by the antiepileptic drug zonisamide suppresses 6-hydroxydopamine-induced neuronal cell death. We review recent progress in the studies on the mechanism of ER stress-induced neuronal death related to PD, particularly focusing on the involvement of HRD1 in the prevention of neuronal death as well as a potential therapeutic approach for PD based on the upregulation of HRD1.

Clinical aspects of familial forms of frontotemporal dementia associated with parkinsonism

Frontotemporal dementia is the second most common dementia among people under the age of 65. Fifty percent of affected patients have an associated family history. Several pathogenic genes have been identified for frontotemporal dementia associated with parkinsonism, including microtubule-associated protein tau, progranulin, and chromatin modifying protein 2B, and fused in sarcoma. It has also been reported that frontotemporal dementia associated with parkinsonism can be linked to chromosome 9p. In addition, there are families with frontotemporal dementia associated with a parkinsonian phenotype but unknown genetic status. Some of these kindreds have been diagnosed clinically as familial progressive supranuclear palsy, hereditary diffuse leukoencephalopathy with axonal spheroids, "overlap" syndrome, and others. Clinical presentation of frontotemporal dementia associated with parkinsonism is variable at age of symptomatic disease onset, disease duration, symptoms, and their occurrence during the disease course. Clinically, it is often difficult to sort out the different genetic forms of frontotemporal dementia associated with parkinsonism. However, with available clinical genetic testing for known genes, the precise diagnosis can be accomplished in some cases.

Cell transplantation and gene therapy in Parkinson's disease

Parkinson's disease is a progressive neurodegenerative disorder affecting, in part, dopaminergic motor neurons of the ventral midbrain and their terminal projections that course to the striatum. Symptomatic strategies focused on dopamine replacement have proven effective at remediating some motor symptoms during the course of disease but ultimately fail to deliver long-term disease modification and lose effectiveness due to the emergence of side effects. Several strategies have been experimentally tested as alternatives for Parkinson's disease, including direct cell replacement and gene transfer through viral vectors. Cellular transplantation of dopamine-secreting cells was hypothesized as a substitute for pharmacotherapy to directly provide dopamine, whereas gene therapy has primarily focused on restoration of dopamine synthesis or neuroprotection and restoration of spared host dopaminergic circuitry through trophic factors as a means to enhance sustained controlled dopamine transmission. This seems now to have been verified in numerous studies in rodents and nonhuman primates, which have shown that grafts of fetal dopamine neurons or gene transfer through viral vector delivery can lead to improvements in biochemical and behavioral indices of dopamine deficiency. However, in clinical studies, the improvements in parkinsonism have been rather modest and variable and have been plagued by graft-induced dyskinesias. New developments in stem-cell transplantation and induced patient-derived cells have opened the doors for the advancement of cell-based therapeutics. In addition, viral-vector-derived therapies have been developed preclinically with excellent safety and efficacy profiles, showing promise in clinical trials thus far. Further progress and optimization of these therapies will be necessary to ensure safety and efficacy before widespread clinical use is deemed appropriate.

Involvement of endoplasmic reticulum stress on the cell death induced by 6-hydroxydopamine in human neuroblastoma SH-SY5Y cells

Endoplasmic reticulum (ER) dysfunction is known to activate the unfolded protein response, which is characterized by the activation of two divergent processes, i.e., suppression of the initiation process in global protein synthesis and expression of glucose-regulated protein 78 (Bip/Grp78) and the C/EBP homologous transcription factor CHOP/Gadd153. In this study, we examined the expression of CHOP/Gadd153 and Bip/Grp78 in human neuroblastoma SH-SY5Y cells treated with 6-hydroxydopamine (6-OHDA), which is used to prepare animal models of Parkinson's disease. 6-OHDA treatment induced cell death, in a concentration-dependent manner, which was inhibited by co-treatment with an antioxidant N-acetylcysteine. 6-OHDA was also effective in decreasing proteasome activity and in increasing the levels of high molecular ubiquitin-conjugated proteins. Furthermore, 6-OHDA induced a marked increase in the expression of both CHOP/Gadd153 and Bip/Grp78. This increase was prevented by N-acetylcysteine. Taken together, our data indicate that ER dysfunction is at least in part involved in the mechanisms underlying cell death induced by 6-OHDA in SH-SY5Y cells.

Methylphenidate ('Ritalin') can ameliorate abnormal risk-taking behavior in the frontal variant of frontotemporal dementia

The frontal variant of frontotemporal dementia is a significant neurological condition worldwide. There exist few treatments available for the cognitive and behavioural sequelae of fvFTD. Previous research has shown that these patients display risky decision-making, and numerous studies have now demonstrated pathology affecting the orbitofrontal cortex. The present study uses a within-subjects, double-blind, placebo-controlled procedure to investigate the effects of a single dose of methylphenidate (40 mg) upon a range of different cognitive processes including those assessing prefrontal cortex integrity. Methylphenidate was effective in 'normalizing' the decision-making behavior of patients, such that they became less risk taking on medication, although there were no significant effects on other aspects of cognitive function, including working memory, attentional set shifting, and reversal learning. Moreover, there was an absence of the normal subjective and autonomic responses to methylphenidate seen in elderly subjects. The results are discussed in terms of the 'somatic marker' hypothesis of impaired decision-making following orbitofrontal dysfunction.

Ubiquitin-only intraneuronal inclusion in the substantia nigra is a characteristic feature of motor neurone disease with dementia

Two types of ubiquitinated inclusions have been described in motor neurone disease (MND). (1) Skein or globular ubiquitinated inclusions in the motor neurones (more frequently in the lower motor neurones). This is a characteristic feature of all motor neurone disease categories. (2) Dot-shape or crescentric ubiquitinated inclusions in the upper layers of cortex and dentate gyrus described in cases of motor neurone disease with dementia (DMND). We investigated the substantia nigra (SN) in MND cases; two cases of motor neurone disease inclusion body (MND-IB) dementia, six cases of DMND, 14 cases of MND (including one case from Guam and two cases of familial SOD1 mutation), four cases of Parkinson's disease (PD), and 10 cases of age-matched normal controls. SN and spinal cord sections were stained with ubiquitin (alpha-synuclein, tau, PGM1, SMI-31 and SOD1 antibodies). The neuronal density in SN was quantified by using a computer-based image analysis system. Four out of six DMND cases showed rounded ubiquitin positive inclusions with irregular frayed edges, associated with neuronal loss, reactive astrocytosis and a large number of activated microglia cells. These inclusions are negative with antibodies to (alpha-synuclein, tau, SMI-31 and SOD1). The SN in cases from MND-IB dementia and MND showed occasional neuronal loss and no inclusions. The ubiquitin-only inclusions in SN of DMND cases are similar (but not identical) to the ubiquitinated inclusions described previously in the spinal cord of MND cases and are distinct from Lewy bodies (LBs). The degeneration of SN is most likely a primary neurodegenerative process of motor neurone disease type frequently involving the DMND cases. MND disease is a spectrum and multisystem disorder with DMND located at the extreme end of a spectrum affecting the CNS more widely than just the motor system.

Other Parkinson syndromes

The etiology of parkinsonism is varied. Symptomatic parkinsonism is seen in the setting of genetic disorders, infectious processes, structural lesions, and as a result of concomitant medications. A thorough history and good examination will differentiate PD from the diverse group of conditions that can mimic it.

The neurochemistry of Alzheimer type, vascular type and mixed type dementias compared

We present the results of a meta-analysis of neurochemical changes in human post mortem brains of Alzheimer type (AD), vascular type (VD) and mixed type (MF) dementias, and matched controls based on 275 articles published between January 1980 and February 1994. Severity of degeneration between the different neurochemical systems is as follows, although ranking is difficult with regard to limited numbers of investigations in some neurochemical systems: Cholinergic system > serotonergic system > excitatory amino acids > GABAergic system > energy metabolism > NA > oxidative stress parameters > neuropeptides > DA. But, within a neurochemical system, degeneration is not evenly distributed. Spared parameters, e.g. muscarinic receptors and MAO-B, allow to make some suggestions for future therapeutic strategies.

Parkinsonism in motor neuron disease: case report and literature review

This report describes a patient who had clinical features of both motor neuron disease and Parkinson's disease. Neuropathological examination and immunocytochemical studies showed that he had motor neuron disease of the progressive muscular atrophy type, and Lewy body Parkinson's disease, with intracytoplasmic inclusion bodies characteristic of both conditions. This is the first detailed description of these two diseases occurring concurrently in the same patient. A review of all previously reported cases of combined motor neuron disease and parkinsonism has led to the following conclusions: (1) that these two neuropathologically defined diseases occur together very infrequently, but (2) that parkinsonism and substantia nigra degeneration are not uncommon as part of the multi-system disease process underlying motor neuron disease.

Neuropsychiatric disorders, myoclonus, and dystonia in calcification of basal ganglia pathways

Two cases of basal ganglia calcification involving the globus pallidus are presented. Both patients had cognitive dysfunction, temporal lobe-like symptoms (including amnestic state, perceptual distortions, or complex visual hallucinations), and myoclonus. Patient 1 manifested depression, auditory hallucinations, anxiety, paranoia, and postural tremor; patient 2 manifested multifocal dystonia with dystonic tremor. These cases supplement other reports of psychotic features and dementia associated with pallidal pathology. Additionally, the phenomena encountered in these cases are considered in light of recent advances in our understanding of basal ganglia functional pathways. These cases afford a potential pathophysiological window to the possible role of the globus pallidus in these neuropsychiatric conditions. In concert with other recent findings, these cases suggest specific pathway involvement in hallucinations, paranoia, depression, myoclonus, and dystonia. Further research will indicate if these pathways play a role in schizophrenia, mood disorders, and anxiety disorders.

Diminution of dopaminergic neurons in the substantia nigra of sporadic amyotrophic lateral sclerosis

The substantia nigra was examined immunohistochemically using the antibody to tyrosine hydroxylase in 15 patients with sporadic amyotrophic lateral sclerosis (ALS). The number of dopaminergic neurons was diminished in the substantia nigra of seven cases. The diminution was not related to the age, duration of the illness or use of respirators. Supranuclear ophthalmoplegia developed in four and dementia in three out of seven patients with reduction of nigral dopaminergic neurons. In addition, five out of the seven patients developed respiratory failure within 2 years after the onset of the illness. The nigral dopaminergic system may be involved in rapidly progressive ALS patients with supranuclear ophthalmoplegia and/or dementia.

Calbindin D-28k and parvalbumin immunoreactivity in the frontal cortex in patients with frontal lobe dementia of non-Alzheimer type associated with amyotrophic lateral sclerosis

The morphology and distribution of local-circuit neurons (interneurons) were examined, by calbindin D-28k and parvalbumin immunocytochemistry, in the frontal cortex (area 8) in two patients with frontal lobe dementia of non-Alzheimer type associated with classical amyotrophic lateral sclerosis (ALS), and in seven normal cases. The density of calbindin D-28k immunoreactive cells was dramatically reduced in ALS patients, but the density of parvalbumin-immunoreactive neurons was preserved. Decreased density of calbindin D-28k-immunoreactive neurons, which are mainly located in the upper cortical layers, may interfere with the normal processing of cortico-cortical connections, whereas integrity of parvalbumin-immunoreactive cells may be associated with the preservation of the major inhibitory intracortical circuits in patients with frontal lobe dementia.

Rapidly progressive aphasic dementia and motor neuron disease

Articulatory and language impairment heralded rapidly progressive motor neuron disease in 7 patients aged 54 to 77 years. One patient had a family history of a similar disorder. Severe nonfluent aphasia developed in all 7 patients and 4 were anarthric within a year. Other cognitive domains were impaired, yet 2 patients lived alone until 1 month before their deaths. Four died within 2 years. Abnormalities were found on electromyography, computed tomography, magnetic resonance imaging, single-photon emission computed tomography, and electroencephalography. Neuropathological examination in 3 patients showed bilateral hemispheric atrophy with neuronal loss and gliosis predominantly of superficial cortical layers. Pigmented and hypoglossal nuclei were relatively preserved. At all spinal levels there was degeneration of corticospinal tracts and loss of anterior horn cells with gliosis. Rapidly progressive aphasic dementia and motor neuron disease are a distinctive clinical entity whose nosology is poorly understood.

Dementia and Amyotrophic Lateral Sclerosis

Dementia and Amyotrophic Lateral Sclerosis The case-histories of two patients are presented with Amyo-trofic Lateral Sclerosis and dementia (ALS-D), followed by a discussion of recent literature on this topic. This condition can be considered as the interface between non-Alzheimer frontal lobe dementia and amyotrophic lateral sclerosis. The nosological classification of the ALS-D complex has not been established yet.

Aging produces a specific pattern of striatal dopamine loss: implications for the etiology of idiopathic Parkinson's disease

To examine the possible causal contribution of normal or accelerated aging to the neurodegenerative process of Parkinson's disease, we measured the influence of aging on subregional striatal dopamine and homovanillic acid levels in postmortem brain of 23 neurologically and psychiatrically normal human subjects 14-92 years old. We observed a significant decline in striatal dopamine levels and increase in the homovanillic acid/dopamine molar ratios with increasing age. The dopamine loss, on average, was of the same magnitude in the caudate nucleus and the putamen (-60% in the 84-year-old group as compared with the 22-year-old group), with the caudal component of both nuclei being more affected than the rostral subdivisions. The level of subregional dopamine metabolism, as measured by the homovanillic acid/dopamine ratio, in our young individuals (mean age, 22 years) was found to be inversely correlated to the degree of subregional dopamine loss suffered by the individuals in the older age groups. We conclude the following: (a) Striatal subdivisions with physiologically higher dopamine metabolism are not at a greater risk of suffering dopamine neuronal damage with advancing age, as would seem to be implied by the oxidative stress hypothesis; thus, formation of dopamine-derived oxy radicals in the human striatum appears unlikely to be a primary factor responsible for the age-related striatal dopamine loss. (b) The regional and subregional pattern of striatal dopamine loss in normal aging differs substantially from the pattern typically observed in idiopathic Parkinson's disease; therefore, the cause of idiopathic Parkinson's disease cannot be primarily an age-dependent neurodegenerative process.

Dementia of frontal lobe type and motor neuron disease. A Golgi study of the frontal cortex

Neuropathological findings in a 38 year old patient with dementia of frontal lobe type and motor neuron disease included pyramidal tracts, myelin pallor and neuron loss, gliosis and chromatolysis in the hypoglossal nucleus, together with frontal atrophy, neuron loss, gliosis and spongiosis in the upper cortical layers of the frontal (and temporal) lobes. Most remaining pyramidal and non-pyramidal neurons (multipolar, bitufted and bipolar cells) in the upper layers (layers II and III) of the frontal cortex (area B) had reduced dendritic arbors, proximal dendritic varicosities and amputation of dendrites as revealed in optimally stained rapid Golgi sections. Pyramidal cells in these layers also showed depletion of dendritic spines. Neurons in the inner layers were preserved. Loss of receptive surfaces in neurons of the upper cortical layers in the frontal cortex are indicative of neuronal disconnection, and are "hidden" contributory morphological substrates for the development of dementia.