Nicotinic receptor subtypes in human brain ageing, Alzheimer and Lewy body diseases

Human brain ageing is associated with reductions in a variety of nicotinic receptors subtypes, whereas changes in age-related disorders including Alzheimer's disease or Parkinson's disease are more selective. In Alzheimer's disease, in the cortex there is a selective loss of the alpha4 (but not alpha3 or 7) subunit immunoreactivity and of nicotine or epibatidine binding but not alpha-bungarotoxin binding. Epibatidine binding is inversely correlated with clinical dementia ratings and with the level of Abeta1-42, but not related to plaque or tangle densities. In contrast, alpha-bungarotoxin binding is positively correlated with plaque densities in the entorhinal cortex. In human temporal cortex loss of acetylcholinesterase catalytic activity is positively correlated with decreased epibatidine binding and in a transgenic mouse model over expressing acetylcholinesterase, epibatidine binding is elevated. In Parkinson's disease, loss of striatal nicotine binding appears to occur early but is not associated with a loss of alpha4 subunit immunoreactivity. Tobacco use in normal elderly individuals is associated with increased alpha4 immunoreactivity in the cortex and lower densities of amyloid-beta plaques, and with greater numbers of dopaminergic neurons in the substantia nigra pars compacta. These findings indicate an early involvement of the alpha4 subunit in beta-amyloidosis but not in nigro-striatal dopaminergic degeneration.     

α-Synuclein phosphorylation at serine 129 occurs after initial protein deposition and inhibits seeded fibril formation and toxicity

α-Synuclein (α-syn) phosphorylation at serine 129 (pS129–α-syn) is substantially increased in Lewy body disease, such as Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). However, the pathogenic relevance of pS129–α-syn remains controversial, so we sought to identify when pS129 modification occurs during α-syn aggregation and its role in initiation, progression and cellular toxicity of disease. Using diverse aggregation assays, including real-time quaking-induced conversion (RT-QuIC) on brain homogenates from PD and DLB cases, we demonstrated that pS129–α-syn inhibits α-syn fibril formation and seeded aggregation. We also identified lower seeding propensity of pS129–α-syn in cultured cells and correspondingly attenuated cellular toxicity. To build upon these findings, we developed a monoclonal antibody (4B1) specifically recognizing nonphosphorylated S129–α-syn (WT–α-syn) and noted that S129 residue is more efficiently phosphorylated when the protein is aggregated. Using this antibody, we characterized the time-course of α-syn phosphorylation in organotypic mouse hippocampal cultures and mice injected with α-syn preformed fibrils, and we observed aggregation of nonphosphorylated α-syn followed by later pS129–α-syn. Furthermore, in postmortem brain tissue from PD and DLB patients, we observed an inverse relationship between relative abundance of nonphosphorylated α-syn and disease duration. These findings suggest that pS129–α-syn occurs subsequent to initial protein aggregation and apparently inhibits further aggregation. This could possibly imply a potential protective role for pS129–α-syn, which has major implications for understanding the pathobiology of Lewy body disease and the continued use of reduced pS129–α-syn as a measure of efficacy in clinical trials.

Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) are both associated with underlying Lewy body disease, which represents the second most common neurodegenerative disorder after Alzheimer’s disease (1, 2). The neuropathological hallmark of Lewy body disease is the intracellular aggregation of the protein α-synuclein (α-syn) into spherical cytoplasmic inclusions, termed Lewy bodies, but are also observed in neuronal processes as Lewy neurites (LNs) (3).α-Syn is thought to play a central role in the pathobiology of Lewy body disease. Single-point mutations and genetic modifications affecting α-syn expression—through duplications, triplications, or polymorphisms in its promoter—have been linked to both idiopathic and familial forms of Lewy body disease (4–6). Nevertheless, neuropathological studies utilizing pan–α-syn antibodies, recognizing both physiological and pathological forms of the protein, do not consistently report a relationship between the load of Lewy body pathology and clinical disease severity (2). To reconcile the apparent importance of α-syn in Lewy body disease with the difficulty relating Lewy body burdens in the brain to phenotypic severity, continued research has focused on the identification of particularly disease-relevant forms of α-syn. α-Syn undergoes various posttranslational modifications (PTMs)—including acetylation, nitration, ubiquitination, and glycosylation and phosphorylation at serine 129 (pS129)—increases from ∼4% under physiological conditions to 90% in Lewy body disease, suggesting it is associated with the disease state (7–9).Previous studies have reported that pS129 enhances intracellular aggregate formation in SH-SY5Y cells (10), and mediates cell death through activation of the unfolded protein response pathway (11). Furthermore, studies in rodent models have suggested that pS129 exacerbates the rate of pathological protein aggregation and deposition, with subsequent negative effects on neuronal functioning (12). However, these studies are counterbalanced by others reporting a potentially neuroprotective function of phosphorylation in animal models (13, 14) and cellular model systems (15). Additionally, studies have reported neutral findings regarding pS129 modification as neither enhancing nor diminishing cellular toxicity and α-syn aggregation (16, 17). Despite the uncertain pathogenic role of pS129 in Lewy body disease, antibodies against pS129 are widely used, based on the putative view that they label a species of α-syn that is particularly disease-relevant. These studies often employ pS129–α-syn as a marker of the abundance of protein inclusions to stage disease severity and evaluate the relationship between its abundance and important clinical or pathological variables, such as disease duration, phenotypic severity, or cell loss (18). Such studies typically identify that pS129 abundance throughout the brain correlates with disease severity (19–21), though it remains uncertain whether phosphorylation precedes protein aggregation or occurs secondarily to deposition of nonphosphorylated α-syn, and whether pS129 is a key driver of pathogenicity or simply a useful marker of a neurodegenerative process (22, 23). Therefore, although there is a substantial literature on pS129 in Lewy body disease, there is continued controversy regarding its potential contribution to disease states, with numerous studies reporting discordant findings. Despite contradictory findings regarding the disease-relevance of pS129, it is widely viewed as a particularly disease-associated modification, thus necessitating further research to address its importance for Lewy body disease.To address the key questions regarding the pathogenic relevance of pS129–α-syn, the present study aimed to undertake a comprehensive and multidisciplinary project to address this important and pressing question. The key aim of the study was to better understand the role of pS129 in the natural history of Lewy body disease, by determining when pS129 occurs in the development of α-syn aggregates and how it affects the aggregation-propensity and cytotoxicity of α-syn     

Longitudinal study of cerebral blood flow SPECT in Parkinson's disease with dementia, and dementia with Lewy bodies

BACKGROUND: People with Parkinson's disease (PD) have an increased risk of developing dementia (PDD), which often has clinical features similar to dementia with Lewy bodies (DLB). Whilst perfusion studies have shown parieto-occipital hypoperfusion in DLB and PDD relative to controls, there have not been any longitudinal studies of perfusion changes in PDD and DLB. METHODS: In this study, we measured brain perfusion using Tc99m HMPAO SPECT over one year in 17 PDD, 18 DLB and 34 healthy subjects. We used SPM99 to compare perfusion changes in the two dementia groups against the control group. RESULTS: We did not see any reductions in perfusion in either of the dementia groups. However, in the DLB, but not PDD group, there was a significant increase in putamen perfusion relative to controls over the year. In both DLB and PDD groups, there was a correlation between striatal perfusion increase over the year, and worsening of parkinsonism. Perfusion changes were not secondary to changes in antiparkinsonian medication. CONCLUSION: The increase in striatal perfusion may be a compensatory change related to decreasing striatal dopaminergic input from the substantia nigra in PDD and DLB, consistent with the increased predominance of rigidity over tremor symptoms in these groups compared with non-demented PD.     

Socio-demographic factors and self-reported funtional status: the significance of social support

Background  

The aim of the present work was to investigate the relative importance of socio-demographic and physical health status factors for subjective functioning, as well as to examine the role of social support.     

In vitro and in vivo activity of murine lymphokine-activated killer cells after cryopreservation

The in vitro and in vivo effects of cryopreservation on the cytotoxic activity of murine lymphokine-activated killer (LAK) cells were studied. LAK cells were generated by incubation of spleen lymphocytes of BALB/c mice for 3 days with recombinant interleukin-2 (rIL-2) and subsequent cryopreservation. Cytotoxicity was determined in a 51Cr release assay. After thawing, cytotoxic activity was reduced (40.4% 51Cr release at an effector:target cell ratio of 40:1 as compared to 68.5% 51Cr release before freezing) and could be restored to precryopreserved levels by reincubation with rIL-2 for 2 days after thawing (78.8% 51Cr release). These cells were then tested in BALB/c mice injected with RAW 112 cells, a pre-B-cell lymphoma line. The results demonstrate that the survival rate of mice injected with cryopreserved and restimulated LAK cells (50% survival greater than 180 days after injection) did not differ significantly from that of mice injected with fresh unfrozen LAK cells (60% survival greater than 120 days, 50% survival greater than 180 days). Cryopreserved LAK cells have potential use in adoptive immunotherapy.     

Cholinesterase inhibitors in dementia with Lewy bodies: a comparative analysis

OBJECTIVE: To compare efficacy of different cholinesterase inhibitors (ChEIs) for treating patients with dementia with Lewy bodies (DLB). DESIGN: Retrospective comparison of three independent clinical studies of ChEI treatment using donepezil, galantamine or rivastigmine in patients with DLB. METHOD: Data was obtained from open label trials of donepezil and galantamine and a placebo controlled randomized trial of rivastigmine in DLB. Changes in Mini Mental State Examination (MMSE), Neuropsychiatric Inventory (NPI) and United Parkinson's Disease Rating Scale (UPDRS-III) scores were compared between the three treatments at 12 and 20 weeks. RESULTS: All ChEIs significantly improved cognitive and neuropsychiatric measures. Reduction in the total NPI score appeared significantly greater after donepezil treatment. There was no significant increase in UPDRS-III scores. CONCLUSIONS: It is unclear to what extent these findings reflect true differences between ChEIs or are due to methodological artefacts of comparing different studies. There is so far no compelling evidence that any one ChEI is better than the other in treating DLB but head to head comparative studies of different ChEIs are warranted to clarify this.     

Early Cognitive Change in the General Population: How Do Different Definitions Work?

OBJECTIVES: To explore the application of existing classifications of mild cognitive impairment (MCI) and associated states in a large population sample. DESIGN: Prospective cohort study, baseline phase (cross-sectional analysis). SETTING: Large-scale multicenter study in the United Kingdom. PARTICIPANTS: Thirteen thousand four individuals aged 65 and older from the Medical Research Council Cognitive Function and Aging Study. From this, a subsample of 2,640 individuals was selected and completed a more-detailed cognitive assessment. MEASUREMENTS: Information on sociodemographic status, general health, cognitive impairment (measured using the Mini-Mental State Examination), and functional ability was collected in a structured interview at baseline. The Geriatric Mental State Automated Geriatric Examination for Computer-Assisted Taxonomy and the Cambridge Cognitive Examination were used in assessment to determine cognitive status. Using a systematic literature review to collect all symptom classifications for nonnormal dementia states, these were then operationalized retrospectively. Each participant was classified according to each. RESULTS: Population prevalence estimates were variable (range 0.1-42%), reflecting differences in the focus and content of each state. Limited overlap existed between states such that many individuals were concurrently classified as normal and impaired. This highlights the heterogeneity in classification as captured using different definitions. CONCLUSION: Classification of cognitively impaired and cognitively normal individuals is dependent on the way criteria are defined and operationalized. Each classification captures a unique group of individuals, with little concordance. Given the importance of early detection of dementia and the calls for screening, and recruitment into pharmacological trials of cognitively impaired individuals, there is an urgent need for an agreed-upon standard MCI case definition to use as a criterion standard.     

A semi-structured interview to assess visual hallucinations in older people

OBJECTIVE: Visual hallucinations are under-reported by patients and are often undiscovered by health professionals. There is no gold standard available to assess hallucinations. Our objective was to develop a reliable, valid, semi-structured interview for identifying and assessing visual hallucinations in older people with eye disease and cognitive impairment. METHODS: We piloted the North-East Visual Hallucinations Interview (NEVHI) in 80 older people with visual and/or cognitive impairment (patient group) and 34 older people without known risks of hallucinations (control group). The informants of 11 patients were interviewed separately. We established face validity, content validity, criterion validity, inter-rater agreement and the internal consistency of the NEVHI, and assessed the factor structure for questions evaluating emotions, cognitions, and behaviours associated with hallucinations. RESULTS: Recurrent visual hallucinations were common in the patient group (68.8%) and absent in controls (0%). The criterion, face and content validities were good and the internal consistency of screening questions for hallucinations was high (Cronbach alpha: 0.71). The inter-rater agreements for simple and complex hallucinations were good (Kappa 0.72 and 0.83, respectively). Four factors associated with experiencing hallucinations (perceived control, pleasantness, distress and awareness) were identified and explained a total variance of 73%. Informants gave more 'don't know answers' than patients throughout the interview (p = 0.008), especially to questions evaluating cognitions and emotions associated with hallucinations (p = 0.02). CONCLUSIONS: NEVHI is a comprehensive assessment tool, helpful to identify the presence of visual hallucinations and to quantify cognitions, emotions and behaviours associated with hallucinations.     

Dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is the second commonest cause of neurodegenerative dementia in older people. It is part of the range of clinical presentations that share a neuritic pathology based on abnormal aggregation of the synaptic protein alpha-synuclein. DLB has many of the clinical and pathological characteristics of the dementia that occurs during the course of Parkinson's disease. Here we review the current state of scientific knowledge on DLB. Accurate identification of patients is important because they have specific symptoms, impairments, and functional disabilities that differ from those of other common types of dementia. Severe neuroleptic sensitivity reactions are associated with significantly increased morbidity and mortality. Treatment with cholinesterase inhibitors is well tolerated by most patients and substantially improves cognitive and neuropsychiatric symptoms. Clear guidance on the management of DLB is urgently needed. Virtually unrecognised 20 years ago, DLB could within this decade be one of the most treatable neurodegenerative disorders of late life.