beta-Amyloid (A beta) deposition in elderly non-demented patients and patients with Alzheimer's disease

Exploring the Pattern Associated With Longitudinal Changes of β-Amyloid Deposition During Cognitively Normal Healthy Aging

The aim of this study was to determine a pattern associated with longitudinal changes of β-amyloid (Aβ) deposition during cognitively normal(CN) healthy aging. We used ¹⁸F-florbetapir (AV-45) PET images of the brains of 207 cognitively normal subjects (CN1), obtained through the Alzheimer's Disease Neuroimaging Initiative (ADNI), to identify the healthy aging pattern and 76 cognitively normal healthy subjects (CN2), obtained through the Xuanwu Hospital of Capital Medical University, Beijing, China, to verify it. A voxel-based correlation analysis of standardized uptake value ratio (SUVR) map image and age was conducted using the DPABI (Data Processing & Analysis of Brain Imaging) software to identify the pattern. The sum of squares due to errors (SSE), R-square (R²) and the root-mean-square error (RMSE) were calculated to assess the quality of curve fitting. Among them, R² was proposed as the coherence coefficient, which was as an index to assess the correlation between SUVR value of the pattern and subjects' age. The pattern characterized by age-associated longitudinal changes of Aβ deposition was mainly distributed in the right middle and inferior temporal gyrus, the right temporal pole: middle temporal gyrus, the right inferior occipital gyrus, the right inferior frontal gyrus (triangular portion), and the right precentral gyrus. There were a significant positive correlation between the SUVR value of the pattern and age for each CN group (CN1: R² = 0.120, p < 0.001 for quadratic model; CN2: R² = 0.152, p = 0.002 for quadratic model). These findings suggest a pattern of changes in Aβ deposition that can be used to distinguish physiological changes from pathophysiological changes, constituting a new method for elucidating the neuropathological mechanism of Alzheimer's disease.

Intermittent hypoxia improves cognition and reduces anxiety-related behavior in APP/PS1 mice

INTRODUCTION

Although hypoxia can exacerbate symptoms of various neurological disorders, accumulating evidence has indicated that intermittent hypoxia (IH) may exert protective effects against brain diseases. In the present study, we aimed to determine whether exposure to IH exerts beneficial effects in a transgenic murine model of Alzheimer's disease (AD). Because comorbid anxiety is prevalent among patients with AD, we explored the effects of IH on anxiety-like behaviors and associated factors in APP/PS1 mice.

METHODS

APP/PS1 mice were subjected to IH for two weeks. We assessed cognitive performance and anxiety-related behavior using standard behavioral assessments. Amyloid beta (Aβ) levels in the hippocampus were assessed using immunofluorescence and enzyme-linked immunosorbent assays (ELISA). We also assessed cell morphology and brain-derived neurotrophic factor (BDNF) expression in the hippocampus.

RESULTS

Exposure to IH significantly increased cognitive performance and decreased anxiety-related behaviors in APP/PS1 mice. Immunofluorescence and ELISA results revealed that IH pretreatment significantly lowered Aβ levels in the cortex and hippocampus. Morphological studies validated the neuroprotective effect of IH exposure on hippocampal neurogenesis. Molecular studies revealed IH-enhanced BDNF expression and inhibition of apoptosis-related protein expression in the hippocampus of APP/PS1 mice.

CONCLUSIONS

Our study demonstrates that IH improves cognition and reduces anxiety in a murine model of AD. Thus, further studies are required to determine whether IH can be used as a preventive/adjuvant therapy in patients with AD.

Effect of Aggregated β-Amyloid (1-42) on Synaptic Plasticity of Hippocampal Dentate Gyrus Granule Cells in Vivo

INTRODUCTION

Alzheimer's disease (AD) is a common neurodegenerative disorder in elderly people with an impairment of cognitive decline and memory loss. β-amyloid (Aβ) as a potent neurotoxic peptide has a pivotal role in the pathogenesis of AD. This disease begins with impairment in synaptic functions before developing into later neuro¬degeneration and neuronal loss. The aim of this study was to evaluate the synaptic plasticity and electrophysiological function of granule cells in hippocampal dentate gyrus (DG) after intracerebroventricular (i.c.v.) administration of aggregated Aβ (1-42) peptide in vivo.

METHODS

Animals were divided to control and Aβ (1-42) groups. Long-term potentia¬tion (LTP) in perforant path-DG synapses was assessed in order to investigate the effect of aggregated Aβ (1-42) on synaptic plasticity. Field excitatory post-synaptic potential (fEPSP) slope and population spike (PS) amplitude were measured.

RESULTS

Administration of Aβ (1-42) significantly decreased fEPSP slope and PS amplitude in Aβ (1-42) group comparing with the control group and had no effect on baseline activity of neurons.

CONCLUSION

The present study indicates that administration of aggregated form of Aβ (1-42) into the lateral ventricle effectively inhibits LTP in granular cells of the DG in hippocampus in vivo.

Prolongation of T2 relaxation times of hippocampus and amygdala in Alzheimer's disease

There exists controversy on the MR T(2) relaxometry of hippocampus in Alzheimer's disease (AD). The aim of our study was to examine whether there was a prolonged T(2) relaxation time (T(2)) in hippocampus and amygdala in AD, and whether in AD, the relaxometry data correlated to cognitive performance. In a 1.5 T MR scanner, T(2) of hippocampus and amygdala was measured from 51 patients with AD, 23 subjects with vascular dementia (VaD) and 31 healthy elderly controls. The cognitive performance was assessed with the Alzheimer's Disease Assessment Scale - Cognitive Subscale (ADAS-Cog). The AD patients had longer T(2) in hippocampus and amygdala than VaD subjects and healthy elderly controls. In AD, the right hippocampal T(2) was correlated with ADAS-Cog scores, whereas amygdaloid T(2) was not.

Quantifying the pathology of neurodegenerative disorders: quantitative measurements, sampling strategies and data analysis

The use of quantitative methods has become increasingly important in the study of neurodegenerative disease. Disorders such as Alzheimer's disease (AD) are characterized by the formation of discrete, microscopic, pathological lesions which play an important role in pathological diagnosis. This article reviews the advantages and limitations of the different methods of quantifying the abundance of pathological lesions in histological sections, including estimates of density, frequency, coverage, and the use of semiquantitative scores. The major sampling methods by which these quantitative measures can be obtained from histological sections, including plot or quadrat sampling, transect sampling, and point-quarter sampling, are also described. In addition, the data analysis methods commonly used to analyse quantitative data in neuropathology, including analyses of variance (anova) and principal components analysis (PCA), are discussed. These methods are illustrated with reference to particular problems in the pathological diagnosis of AD and dementia with Lewy bodies (DLB).

Overexpression of full-length but not N-terminal truncated isoform of microtubule-associated protein (MAP) 1B accelerates apoptosis of cultured cortical neurons

beta-amyloid (Abeta) is presumed to play a pathogenic role in Alzheimer's disease (AD). However, there is an imperfect correlation between Abeta deposition and neuronal loss or dementia. To clarify neuronal responses to Abeta, Abeta-induced gene expression in cultured cortical neurons was analyzed by differential display followed by Northern blotting. Here we report that nonaggregated or aggregated Abeta induced microtubule-associated protein 1B (MAP1B) mRNA, especially the alternative transcript containing exon 3U, before disruption of the cell membrane by Abeta. An alternative transcript containing exon 3U is translated into an N-terminal truncated shorter isoform of MAP1B. Transfection experiments reveal that overexpression of this isoform does not accelerate neurite outgrowth or apoptosis of cortical neurons. In contrast, overexpression of MAP1B fragments containing the N-terminal 126 amino acids promoted neurite outgrowth and neuronal apoptosis. These results suggest that Abeta does not induce deleterious full-length MAP1B directly, but overexpression of full-length MAP1B might act as an effector of cell death in neurodegenerative disorders related to cytoskeletal abnormalities.

Beta-amyloid deposition in the temporal lobe of patients with dementia with Lewy bodies: comparison with non-demented cases and Alzheimer's disease

beta-Amyloid (Abeta) deposition in regions of the temporal lobe in patients with dementia with Lewy bodies (DLB) was compared with elderly, non-demented (ND) cases and with Alzheimer's disease (AD). The distribution, density and clustering patterns of diffuse, primitive and classic Abeta deposits were similar in 'pure' DLB and ND cases. The distribution of Abeta deposits and the densities of the diffuse and primitive deposits were similar in 'mixed' DLB/AD cases compared with AD. However, the density of the classic deposits was significantly lower in DLB/AD compared with AD. In addition, the primitive Abeta deposits occurred more often in small, regularly spaced clusters in the tissue and less often in a single large cluster in DLB/AD compared with 'pure' AD. These results suggest that pure DLB and AD are distinct disorders which can coexist in some patients. However, the Abeta pathology of DLB/AD cases is not identical to that observed in patients with AD alone.

Low amyloid (Abeta) plaque load and relative predominance of diffuse plaques distinguish argyrophilic grain disease from Alzheimer's disease

Argyrophilic grain disease constitutes one cause of late-onset dementia. Its classification among dementia disorders is still unclear because most of the reported argyrophilic grain disease cases are associated with neurofibrillary lesions (e.g. neurofibrillary tangles) which are also typical of Alzheimer's disease. In the present study we determine whether argyrophilic grain disease is associated with the senile plaques of Alzheimer's disease. The distribution and density of senile plaques was systematically investigated in 11 demented argyrophilic grain disease cases using Abeta immunohistochemistry and stereological techniques, and the results were compared with 11 Alzheimer's disease cases. All subjects with argyrophilic grain disease exhibited neurofibrillary changes corresponding to Braak stages I-III. Three of the 11 argyrophilic grain disease cases (27%) were completely devoid of Abeta deposits. In argyrophilic grain disease cases with senile plaques, the average total plaque-load was significantly lower (1%) than in Alzheimer's disease (3.1%) (P<0. 005). The regional distribution of the senile plaques and the proportion of diffuse vs. primitive or mature plaques in argyrophilic grain disease resembled values of senile plaques reported in non-demented elderly subjects, and was significantly different from Alzheimer's disease. Similarly the immunocytochemical profile of the Abeta deposition in argyrophilic grain disease resembled that of non-demented elderly subjects rather than that of subjects with Alzheimer's disease. As all argyrophilic grain disease cases under investigation were demented, including those devoid of senile plaques, the present study further supports the thesis that dementia in argyrophilic grain disease correlates more with the density and distribution of argyrophilic grains than with associated lesions of the Alzheimer-type.

beta-Amyloid (A beta) deposition in the medial temporal lobe of patients with dementia with Lewy bodies

The distribution and density of diffuse, primitive and classic beta-amyloid (A beta) deposits in the medial temporal lobe (MTL) was studied in cases of dementia with Lewy bodies (DLB) with and without associated Alzheimer's disease (AD) and 15 cases of sporadic AD. In the 'pure' DLB cases, virtually no A beta deposits were observed in the CA regions of the hippocampus or dentate gyrus whereas deposits were distributed throughout the MTL in DLB/AD and AD cases. Densities of diffuse and primitive A beta deposits were similar in AD and DLB/AD cases but density was significantly reduced in the 'pure' DLB cases. The density of the classic deposits was significantly reduced in DLB cases with or without associated AD compared with AD cases. These results suggest that A beta deposition in the MTL in 'pure' DLB cases is similar to that of elderly non-demented patients while, with the exception of the classic deposits, A beta deposition in DLB/AD cases is similar to that in cases of AD alone.