Lewy Body Variant Research Articles

Role of Oxidative Damage in Protein Aggregation Associated with Parkinson's Disease and Related Disorders

Parkinson's disease, the most common movement disorder, is characterized by the loss of brainstem neurons, specifically dopaminergic neurons in the substantia nigra, as well as the accumulation of neuronal cytoplasmic filamentous proteinaceous inclusions comprised of polymerized alpha-synuclein. It was reported recently that alpha-synuclein can induce the formation of filamentous tau inclusions, which are characteristic of disorders like Alzheimer's disease and Lewy body variant of Alzheimer's disease, suggesting that a similar mechanism may exist between alpha-synuclein fibrillogenesis and tau polymerization. Pathological brain inclusions comprised of alpha-synuclein or tau proteins are associated with a spectrum of neurodegenerative disorders, and oxidative and nitrative injury has been implicated in all of these diseases. However, the role of oxidative damage in alpha-synuclein and tau polymerization and pathological inclusion formation is complex. Differences in the level, type, and temporal sequence of the oxidative alterations appear to result in both inhibitory and stimulatory effects on the fibrillogenesis of these proteins.

Genetic association between the APOE * 4 allele and Lewy bodies in Alzheimer disease

To explore the association between APOE*4 and pathologically confirmed cases of the Lewy body (LB) variant of Alzheimer disease (AD). With use of alpha-synuclein (AS) immunohistochemistry, LBs were detected in 74 of 131 (56.5%) of the AD + LB cases; the remaining 57 cases (43.5%) did not have LBs. There were no differences in gender or age between Caucasian subjects with AD + LB or AD alone or control subjects. The APOE*4 allele frequency was highest in the AD + LB group (47.3%; 95% CI = 37.8 to 57.0%), intermediate in the AD-alone group (35.1%; 95% CI = 25.3 to 46.3%), and lowest in the control group (14.2%; 95% CI = 10.5 to 18.9%). With use of logistic regression analysis, the odds of having AD + LB vs AD alone were 2.1-fold (95% CI = 1.0 to 4.5, p = 0.055) greater in persons with an APOE*4 allele than in those without an APOE*4 allele. The APOE*4 allele is associated with the presence of concomitant Lewy bodies in Alzheimer disease.

Structural Evidence for α-Synuclein Fibrils Using <italic>in Situ</italic> Atomic Force Microscopy

Human alpha-synuclein is a presynaptic terminal protein and can form insoluble fibrils that are believed to play an important role in the pathogenesis of several neurodegenerative diseases such as Parkinson's disease, dementia with Lewy bodies and Lewy body variant of Alzheimer's disease. In this paper, in situ atomic force microscopy has been used to study the structural properties of alpha-synuclein fibrils in solution using two different atomic force microscopy imaging modes: tapping mode and contact mode. In the in situ contact mode atomic force microscopy experiments alpha-synuclein fibrils quickly broke into fragments, and a similar phenomenon was found using tapping mode atomic force microscopy in which alpha-synuclein fibrils were incubated with guanidine hydrochloride (0.6 M). The alpha-synuclein fibrils kept their original filamentous topography for over 1 h in the in situ tapping mode atomic force microscopy experiments. The present results provide indirect evidence on how beta-sheets assemble into alpha-synuclein fibrils on a nanometer scale.

Differences in olfactory and visual memory in patients with pathologically confirmed Alzheimer's disease and the Lewy body variant of Alzheimer's disease

Recognition and remote memory for odors, faces, and symbols were assessed in patients with pathologically confirmed Lewy body variant of Alzheimer's disease (LBV), patients with pathologically confirmed Alzheimer's disease (AD), and healthy elderly controls. On recognition memory tasks, LBV and AD patients showed significantly lower discriminability (d') than controls, particularly for olfactory stimuli. However no significant differences were found in the bias measure (c). When participants rated familiarity (a proposed measure of remote memory) of olfactory stimuli LBV and AD patients reported significantly lower familiarity than controls. Familiarity ratings were significantly lower in LBV patients than in AD patients for olfactory, but not for visual stimuli. Consistent with prior reports, the LBV patients showed significantly poorer odor thresholds than AD patients. The results suggest that recognition memory for olfactory stimuli is impaired in LBV and AD. However, patients with LBV are more impaired than patients with AD on tasks requiring remote memory for olfactory but not visual stimuli. The findings suggest that odor memory tasks may be useful in the assessment of LBV and AD.

Degradative organelles containing mislocalized alpha-and beta-synuclein proliferate in presenilin-1 null neurons.

Presenilin-1 null mutation (PS1 −/−) in mice is associated with morphological alterations and defects in cleavage of transmembrane proteins. Here, we demonstrate that PS1 deficiency also leads to the formation of degradative vacuoles and to the aberrant translocation of presynaptic α- and β-synuclein proteins to these organelles in the perikarya of primary neurons, concomitant with significant increases in the levels of both synucleins. Stimulation of autophagy in control neurons produced a similar mislocalization of synucleins as genetic ablation of PS1. These effects were not the result of the loss of PS1 γ-secretase activity; however, dysregulation of calcium channels in PS1 −/− cells may be involved. Finally, colocalization of α-synuclein and degradative organelles was observed in brains from patients with the Lewy body variant of AD. Thus, aberrant accumulation of α- and β-synuclein in degradative organelles are novel features of PS1 −/− neurons, and similar events may promote the formation of α-synuclein inclusions associated with neurodegenerative diseases.

Septin 3 gene polymorphism in Alzheimer's disease.

Septin 3 is a novel member of the septin subfamily of GTPase domain proteins that was recently identified in human neuronal cells. These proteins are involved in vesicle trafficking, neurite outgrowth, and neurofibrillary tangle formation; however, the expression and functional role of septin 3 in normal neuronal tissues and as an etiological agent in neurological disorders is currently unclear. To further characterize these parameters, the present study analyzed the expression of three isoforms of septin 3 (A, B, and C) in fetal and adult human brains and polymorphism of the septin 3 exon 11 microsatellite in control, pure Alzheimer's disease (AD), Lewy body variant (LBV) of AD, and Parkinson's disease. Septin 3 mRNAs for isoforms A and B, but not C, were detected in the frontal cortex of fetus and adult human samples, as measured by reverse transcription-coupled polymerase chain reaction. Genotype analyses indicated that polymorphic septin 3 alleles were distributed in two peaks of frequency in both control and disease groups. Categorization of the alleles into short (S) and long (L) types revealed a significant difference between AD patients and controls (p = 0.034 by chi-square test). Furthermore, the S-allele homozygosity was significantly underrepresented in AD compared with control (p = 0.015 by chi-square test). These results suggest that polymorphism in exon 11 of septin 3 may have a determinative role in the pathogenesis of AD.

Age at onset is associated with disease severity in Lewy body variant and Alzheimer's disease.

This study investigated the influence of age at onset on cognitive performance, neuropathological and neurochemical features in autopsy-confirmed sporadic Lewy body variant (LBV) and in Alzheimer's disease (AD). We compared 28 early-onset (< or = 70 years) LBV subjects with 28 matched late-onset (> 70 years) subjects. Similarly, we examined the same features in 89 early onset AD and 89 matched late onset AD patients. Patients with early onset LBV and early onset AD declined more rapidly, had more neuritic plaques, and greater neocortical cholinergic loss compared to late onset LBV and late onset AD subjects. Taken together, these results suggest that for both LBV and AD, earlier age at onset may predict a more aggressive disease course.

Lewy bodies in patients presenting clinically with Alzheimer disease.

In a retrospective clinico-pathologic study of 37 demented and 13 nondemented aged subjects, SantaCruz et al. [1] found nigral Lewy bodies (LB) in 16/37 demented patients; (clinical diagnosis Parkinson disease (PD) in three, dementia with Lewy bodies (DLB) in two and Alzheimer disease (AD) in 10), ten of which qualified for the pathologic diagnosis of dementia with Lewy bodies (DLB). Five of them were diagnosed Lewy body variant of AD (LBV), while eight brains had few or no isocortical neuritic plaques. Most of them had clinically been indistiguishable from AD, although neucortical tangles (NFTs) were rare. Despite clinical similarities, Lewy body disease (LBD) could be distinguished morphologically from AD (no cortical LBs) by the presence of nigral LBs and the relative paucity of neocortical NFTs. Variable amounts of cortical LBs were seen in cases of both DLB and LBV but not in AD. Based on their limited number of cases, the authors distinguish 3 groups of disorders: AD without LBs, DLB with minimal neuritic AD pathology (Braak stages 0–4), and LBV with isocortical (stage 5 and 6) stages. Since there are only few data on prospective validation of consensus criteria for the diagnosis of DLB [2,3], we briefly present the results of a personal clinicopathologic cohort study of demented patients including

Dementias with Lewy bodies

Dementias with Lewy bodies are no rare cause of cognitive and motor impairments in old age. Neuropathologically, they must be distinguished into diffuse Lewy body disease resp. dementia with Lewy bodies, Parkinson's disease with concomitant Alzheimer's pathology, and the Lewy body variant of Alzheimer's disease according to extent and concomitant pathology. The most reliable diagnostic features of dementia with Lewy bodies are fluctuating disturbances of cognition and consciousness, visual disorders (hallucinations, visuoperceptive and visuoconstructive impairments), and early extrapyramidal signs of the hypokinetic-rigid type with a propensity to frequent falls. The pertinent diagnostic criteria are the consensus criteria according to McKeith et al. Additional contributions are to be expected by functional neuroimaging (SPECT, PET) and CSF examination (homovanillic acid). However, even assuming the most favorable conditions a diagnostic accuracy of 85 % is presently hard to achieve. Particularly, as is demonstrated using a case example, reliable antemortem diagnosis of Lewy body variant of Alzheimer's disease is hardly possible. Clinically, this group of diseases is important, since increased neuroleptic sensitivity must be taken into account and modern central cholinergic agents seem to be a promising therapeutic option.

Differential localization of α-, β- and γ-synucleins in the rat CNS

α-Synuclein is a presynaptic protein that normally participates in the homeostasis of synaptic vesicles. Missense mutations in its gene cause the protein to participate actively in the development of heritable forms of Parkinson’s disease. Moreover, its metabolism is perturbed in all cases of Parkinson’s disease where α-synuclein accumulates in a filamentous form in the Lewy body nerve cell lesion. Lewy bodies also develop in other common neurodegenerative disorders, like dementia with Lewy bodies and Lewy body variant of Alzheimer’s disease. In the present study, we have studied the detailed distribution of α-, β- and γ-synuclein in the rat CNS. α-Synuclein was not observed in perikarya, but was distributed with high intensity in nerve terminals in the caudate and putamen and ventral pallidum, where β-synuclein was much weaker and less densely distributed in the caudate and putamen. γ-Synuclein was not found in the caudate and putamen. α-Synuclein was robustly distributed in the substantia nigra pars reticulata, but was very weak or virtually absent from the perikarya of the neurons in the pars compacta. In contrast, β-synuclein was very weak or absent from the substantia nigra. γ-Synuclein was absent from the terminals of substantia nigra pars reticulata, but sparsely distributed γ-synuclein-containing neurons were detected in the substantia nigra pars compacta. In the brainstem, α-synuclein as well as γ-synuclein were present in the locus coeruleus with high intensity, while β-synuclein was very weak. In addition, α-synuclein was intense in the vagus nucleus, but weak in the oculomotor, facial, hypoglossal, accessory and ambiguous nuclei, where β-synuclein was very intensely present. Furthermore, γ-synuclein was localized in the terminals and in cell bodies of the Edinger–Westphal nucleus, the red nucleus, locus coeruleus, and most cranial nerve-related nuclei. In the spinal cord, α- and γ-synucleins were intensely present in laminae I and II and in the preganglionic sympathetic nuclei, whereas β-synuclein was very weak. These results indicate that α-synuclein is abundant in central catecholaminergic regions. β-Synuclein is more localized in the somatic cholinergic components, while it is particularly weak or absent from catecholaminergic neurons. γ-Synuclein appears to be present in both cholinergic and catecholaminergic regions, but very weak in the forebrain.

Amino acid determinants of α-synuclein aggregation: putting together pieces of the puzzle

Parkinson’s disease is the second most common neurodegenerative disease, and results from loss of dopaminergic neurons in the substantia nigra. The aggregation and fibrillation of α-synuclein in the form of intracellular proteinaceous aggregates (Lewy bodies and Lewy neurites) have been implicated as a causative factor in this disease, as well as in several other neurodegenerative disorders, including dementia with Lewy bodies, Lewy body variant of Alzheimer’s disease, multiple system atrophy and Hallervorden–Spatz disease. Thus, the aggregated forms of α-synuclein play a crucial role in the pathogenesis of the synucleinopathies. However, the molecular mechanisms underlying α-synuclein aggregation into specific filamentous inclusions remained unknown until recently. Data on the aggregation and fibrillation properties of human α-, β- and γ-synucleins, mouse α-synuclein and familial Parkinson’s disease mutants of human α-synuclein (A30P and A53T) are analyzed in order to shed light on the amino acid determinants of synuclein aggregation.

Characterization of α‐synuclein in immune system

Human α‐synuclein is a 140 amino acid protein with little or no secondary structure. α‐Synuclein is expressed at high levels in the brain and enriched in neural synaptic terminals but its physiological function remains largely unknown. More recently, α‐synuclein has been shown to be one of the principal components of Lewy bodies, neuronal inclusions that are found in diverse human neurodegenerative disorder including the Lewy body variant of Alzeheimer's disease, diffuse Lewy body disease, Parkinson's disease, multiple system atrophy. Therefore, α‐synuclein and its abnormal protein aggregation have been thought to play a role in the pathogenesis of these neurodegenerative diseases known as α‐synucleinopathies. In order to understand their etiology and pathogenesis, it is crucial to identify the normal function of ?α‐synuclein. It was previously reported that the splicing variant of ?α‐synuclein is expressed in heart, skeletal muscle, and pancreas. In our study, we identified the expression in spleen and also confirm the expression of α‐synuclein in isolated human lymphocytes. The physiological role in lymphocytes showed relationship with glucocorticoid‐induced apoptosis. This result suggests that the accumulated ?α‐synuclein might be involved in regulation of cell viability by the interaction with signal transduction proteins such as p38 MAP or JNK.

Association of monoamine oxidase A gene polymorphism with Alzheimer's disease and Lewy body variant

The association between (GT)n dinucleotide repeats in monoamine oxidase gene loci, monoamine oxidase A ( MAOA) and B ( MAOB), and Parkinson's disease (PD), Alzheimer's disease (AD), and Lewy body variant (LBV) of AD were determined. MAOA-GT polymorphisms were significantly associated with pure AD and LBV. MAOA-GT allele 113 was excessively represented in pure AD and LBV compared with controls. Furthermore, the frequency of females homozygous for MAOA-GT allele 113 was higher in pure AD and LBV than controls by 2.79- and 2.77-fold, respectively. In contrast, there was no association between MAOA-GT or MAOB-GT polymorphisms and PD. These results suggest that polymorphisms within the MAOA gene may have implication in AD pathology shared by pure AD and LBV.

THE CLINICAL BENEFITS OF RIVASTIGMINE MAY REFLECT ITS DUAL INHIBITORY MODE OF ACTION: AN HYPOTHESIS

SUMMARYRecent health technology assessments have given us the go‐ahead to use Cholinesterase inhibitors, which, in combination with community services, are currently the most appropriate treatment for patients with Alzheimer's disease (AD). Initial research focused upon acetylcholinesterase (AChE)‐selective agents, but it is now thought that dual inhibitors of AChE and butyrylcholinesterase (BuChE) may provide more sustained efficacy over the course of AD and may help to slow disease progression. Rivastigmine is a potent inhibitor of AChE and BuChE and has demonstrated broad benefits across the severity of AD and across the cognitive, functional and behavioural domains of AD. In addition, rivastigmine has shown cognitive and behavioural benefits in patients with dementia with the Lewy body variant of AD. These benefits may reflect the inhibition of both AChE and BuChE, as demonstrated by significant correlations between cognitive improvements and Cholinesterase inhibition in rivastigmine‐treated patients with AD. Rivastigmine shows a clear dose‐response relationship, and physicians should aim to maintain patients on doses of 6 mg/day or higher, to a maximum of 12 mg/day. As with all Cholinesterase inhibitors, rapid forced dose escalation may increase the incidence of typical cholinergic side‐effects, resulting in lower maintenance doses. In a chronic disease such as AD, there is time to implement slow dose escalation and higher final maintenance doses. If used appropriately, the benefits of rivastigmine seen in clinical practice may prove to be even greater than those reported in clinical trials.

Understanding and Managing Behavioural Symptoms in Alzheimer's Disease and Related Dementias: Focus on Rivastigmine

SummaryBehavioural and psychological symptoms of dementia (BPSD) are among the most distressing manifestations of dementia and result in considerable social and economic costs. Practical, non-pharmacological approaches such as environmental and behavioural changes may provide some benefit for patients in managing mild BPSD. In addition, various pharmacological approaches to treatment have been employed, such as neuroleptics and atypical antipsychotics, which differ in neurochemical target and clinical effectiveness. Growing evidence suggests that the neurobiological basis of BPSD in Alzheimer's disease (AD) and related dementias is a loss of cholinergic neurones and a resultant decline in acetylcholine (ACh) in brain regions which regulate behavioural and emotional responses, such as the limbic system. This cholinergic deficit can be partly corrected by inhibiting cholinesterase enzymes (ChEs). Studies of ChE inhibitors have shown positive effects to improve or stabilise existing BPSD and delay the emergence of new behavioural symptoms. In placebo-controlled studies, donepezil has reported efficacy in non-institutionalised moderate to moderately severe patients over a period of 24 weeks, but has failed to demonstrate efficacy in mild to moderate AD and in institutionalised patients with severe disease. Galantamine has been shown to delay the onset of BPSD in mild to moderate AD patients in one placebo-controlled study, and improve BPSD in a similar study of patients with cerebrovascular disease or probable vascular dementia. Studies with rivastigmine have shown efficacy in placebo-controlled studies of mild to moderately severe AD and in patients with Lewy body variant AD. Institutionalised patients with severe disease also show symptomatic benefits in BPSD with rivastigmine, resulting in a reduction in concomitant psychoactive medication use. Symptom complexes responding to ChE inhibitors appear to differ - all agents improve apathy, depression and anxiety, while rivastigmine additionally improves hallucinations and delusions, possibility as a result of dual inhibition of acetylcholinesterase and butyrylcholinesterase. The presence of hallucinations has been shown to predict response to rivastigmine. Accumulating data from studies of ChE inhibitors suggest that early intervention and long-term treatment, in addition to providing cognitive benefits, improves BPSD and offers potential to enhance quality of life. Differences seen between the agents in terms of efficacy in BPSD, tolerability and safety profiles may be the result of differences in neuropharmacological profiles.

Stabilization of Partially Folded Conformation during α-Synuclein Oligomerization in Both Purified and Cytosolic Preparations

Aggregation of alpha-synuclein is tightly associated with many neurodegenerative diseases, such as Parkinson's disease, dementia with Lewy body, Lewy body variant of Alzheimer's disease, multiple system atrophy, and Hallervorden-Spatz disease, implicating a crucial role of aggregated forms of alpha-synuclein in the pathogenesis. Here, we examined the effect of elevated temperature on the oligomerization and structural changes of alpha-synuclein in the early stage of aggregation and show that self-assembly is crucial for the stabilization of a partially folded conformation. The efficiency of alpha-synuclein oligomerization increased proportional to the temperature increase, both in purified form and in crude cytosolic preparation. This oligomerization coincided with a small but reproducible change in the circular dichroism spectrum and an increase in the 1-anilinonaphthalene-8-sulfonic acid binding. The hydrodynamic dimensions of the dimer measured by size exclusion chromatography suggest a pre-molten globule-like structure. These data suggest that partially folded alpha-synuclein, which is unstable in the monomeric form, is stabilized by self-assembly and that these oligomers may evolve into the fibril nucleus.

Characterization of the human alpha-synuclein gene: Genomic structure, transcription start site, promoter region and polymorphisms.

The human NACP/alpha-synuclein gene has been cloned. This gene consists of 6 exons ranging in size from 42 to 1110 bp. The translation start codon ATG is encoded by exon 2 and the stop codon TAA is encoded by exon 6. The non-Abeta component of Alzheimer's disease amyloid (NAC) is encoded by exon 4. The two previously reported minor isoforms of NACP/alpha-synuclein, NACP112 [29] and NACP126 [6], are alternatively spliced products, in which exon 5 and exon 3 are spliced out, respectively. Exon 1 was found to have different splicing sites, producing different 5'-untranslated sequences in the cDNAs. A previously reported dinucleotide repeat polymorphic marker has been mapped to 8kb upstream of the transcription start site. A highly TC-rich sequence in intron 4 was found to be polymorphic by length and four alleles, A0, A1, A2 and B have been identified in the Caucasian population. Genotyping this polymorphism among pure Alzheimer's, Lewy body variant and Parkinson's subjects and aged normal control subjects did not reveal any significant differences.

Metal-triggered structural transformations, aggregation, and fibrillation of human alpha-synuclein. A possible molecular NK between Parkinson's disease and heavy metal exposure.

Parkinson's disease involves the aggregation of alpha-synuclein to form fibrils, which are the major constituent of intracellular protein inclusions (Lewy bodies and Lewy neurites) in dopaminergic neurons of the substantia nigra. Occupational exposure to specific metals, especially manganese, copper, lead, iron, mercury, zinc, aluminum, appears to be a risk factor for Parkinson's disease based on epidemiological studies. Elevated levels of several of these metals have also been reported in the substantia nigra of Parkinson's disease subjects. We examined the effect of various metals on the kinetics of fibrillation of recombinant alpha-synuclein and in inducing conformational changes, as monitored by biophysical techniques. Several di- and trivalent metal ions caused significant accelerations in the rate of alpha-synuclein fibril formation. Aluminum was the most effective, along with copper(II), iron(III), cobalt(III), and manganese(II). The effectiveness correlated with increasing ion charge density. A correlation was noted between efficiency in stimulating fibrillation and inducing a conformational change, ascribed to formation of a partially folded intermediate. The potential for ligand bridging by polyvalent metal ions is proposed to be an important factor in the metal-induced conformational changes of alpha-synuclein. The results indicate that low concentrations of some metals can directly induce alpha-synuclein fibril formation.

Alzheimer's disease versus dementia with Lewy bodies: cerebral metabolic distinction with autopsy confirmation.

Seeking antemortem markers to distinguish Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD), we examined brain glucose metabolism of DLB and AD. Eleven DLB patients (7 Lewy body variant of AD [LBVAD] and 4 pure diffuse Lewy body disease [DLBD]) who had antemortem position emission tomography imaging and autopsy confirmation were compared to 10 autopsy-confirmed pure AD patients. In addition, 53 patients with clinically-diagnosed probable AD, 13 of whom later fulfilled clinical diagnoses of DLB, were examined. Autopsy-confirmed AD and DLB patients showed significant metabolic reductions involving parietotemporal association, posterior cingulate, and frontal association cortices. Only DLB patients showed significant metabolic reductions in the occipital cortex, particularly in the primary visual cortex (LBVAD -23% and DLBD -29% vs AD -8%), which distinguished DLB versus AD with 90% sensitivity and 80% specificity. Multivariate analysis revealed that occipital metabolic changes in DLB were independent from those in the adjacent parietotemporal cortices. Analysis of clinically diagnosed probable AD patients showed a significantly higher frequency of primary visual metabolic reduction among patients who fulfilled later dinical criteria for DLB. In these patients, occipital hypometabolism preceded some clinical features of DLB. Occipital hypometabolism is a potential antemortem marker to distinguish DLB versus AD.

Induction of Neuronal Cell Death by Rab5A-dependent Endocytosis of α-Synuclein

The presynaptic alpha-synuclein is a prime suspect for contributing to Lewy pathology and clinical aspects of diseases, including Parkinson's disease, dementia with Lewy bodies, and a Lewy body variant of Alzheimer's disease. Here we examined the pathogenic mechanism of neuronal cell death induced by alpha-synuclein. The exogenous addition of alpha-synuclein caused a marked decrease of cell viability in primary and immortalized neuronal cells. The neuronal cell death appeared to be correlated with the Rab5A-specific endocytosis of alpha-synuclein that subsequently caused the formation of Lewy body-like intracytoplasmic inclusions. This was further supported by the fact that the expression of GTPase-deficient Rab5A resulted in a significant decrease of its cytotoxicity as a result of incomplete endocytosis of alpha-synuclein.