Neocortical morphometry and cholinergic neurochemistry in Pick''s disease.

With a computerized image-analysis apparatus for neocortical morphometry and chemical methods for evaluation of the cholinergic system, five brain specimens of Pick's disease (PD) were studied and the results compared to those from specimens of age-matched normal subjects and Alzheimer's disease (AD). The PD specimens showed major reductions in brain weight, frontal and temporal cortical thickness, and large neuron populations, compared with controls. Lesser reductions were seen in small neurons and thickness of the inferior parietal cortex. The authors found no relationship between age of onset or disease duration and either the degree of cortical thinning or neuron loss or the number of Pick bodies in the neocortex and hippocampus. PD specimens were more atrophic than AD brains, having lower brain weights and more fronto-temporal thinning. Large neurons were comparably reduced in the two conditions in the frontal and temporal lobes, but small neuron losses were greater in the PD midfrontal area. Only the AD cases showed loss of large neurons in the inferior parietal region. Levels of choline acetyltransferase were normal in PD and reduced in AD, whereas muscarinic receptor binding was decreased in both.     

Both plasma retinol-binding protein and haptoglobin precursor allele 1 in CSF: candidate biomarkers for the progression of normal to mild cognitive impairment to Alzheimer's disease

Cerebrospinal fluid (CSF) may be of valuable for exploring protein markers for the diagnosis of Alzheimer's disease (AD). The prospect of early detection and treatment, to slow progression, holds hope for aging populations with increased average lifespan. The aim of the present study was to investigate candidate CSF biological markers in patients with mild cognitive impairment (MCI) and AD and compare them with age-matched normal control subjects. In this report, we applied proteomics approaches to analyze 60 CSF samples derived from patients with neurodegenerative diseases such as MCI and AD. We classified patients by three groups: normal controls without cognitive dysfunction, MCI and AD. The AD group was subdivided into three groups by clinical severity according to clinical dementia rating (CDR), a well known clinical scale for dementia. We demonstrated a gradual decrease or absent of plasma retinol-binding protein (RBP) and haptoglobin precursor allele 1 in CSF from patients with MCI and AD compared to the age-matched normal subjects. Moreover, expression levels of both RBP and haptoglobin precursor allele 1 were observed to be very high in age-matched normal subjects. In contrast, the RBP and haptoglobin precursor allele 1 were much decreased in the MCI group; those expressions were more weak or absent in AD group, and correlated with disease severity and progression. These findings suggest that the CSF levels of both RBP and haptoglobin precursor allele 1 may be candidate biomarkers for the progression of normal to MCI to AD.     

Both plasma retinol-binding protein and haptoglobin precursor allele 1 in CSF: Candidate biomarkers for the progression of normal to mild cognitive impairment to Alzheimer's disease

Cerebrospinal fluid (CSF) may be of valuable for exploring protein markers for the diagnosis of Alzheimer's disease (AD). The prospect of early detection and treatment, to slow progression, holds hope for aging populations with increased average lifespan. The aim of the present study was to investigate candidate CSF biological markers in patients with mild cognitive impairment (MCI) and AD and compare them with age-matched normal control subjects. In this report, we applied proteomics approaches to analyze 60 CSF samples derived from patients with neurodegenerative diseases such as MCI and AD. We classified patients by three groups: normal controls without cognitive dysfunction, MCI and AD. The AD group was subdivided into three groups by clinical severity according to clinical dementia rating (CDR), a well known clinical scale for dementia. We demonstrated a gradual decrease or absent of plasma retinol-binding protein (RBP) and haptoglobin precursor allele 1 in CSF from patients with MCI and AD compared to the age-matched normal subjects. Moreover, expression levels of both RBP and haptoglobin precursor allele 1 were observed to be very high in age-matched normal subjects. In contrast, the RBP and haptoglobin precursor allele 1 were much decreased in the MCI group; those expressions were more weak or absent in AD group, and correlated with disease severity and progression. These findings suggest that the CSF levels of both RBP and haptoglobin precursor allele 1 may be candidate biomarkers for the progression of normal to MCI to AD.     

Early complement activation increases in the brain in some aged normal subjects

Complement activation is increased in Alzheimer's disease (AD) and may contribute to the development and progression of this disorder. To compare early complement activation between normal and AD brain specimens, C4d and iC3b concentrations were measured in hippocampus, entorhinal cortex, temporal cortex, parietal cortex, and cerebellum from aged normal and AD subjects n=10-14 for both), and in hippocampus and entorhinal cortex from younger normal subjects (n=5-6). C4d and iC3b levels increased 2.3- to 4.6-fold in AD versus aged normal specimens (all P <0.05), with lowest concentrations of these activation proteins generally in cerebellum. No significant differences were present between aged and younger normal C4d and iC3b levels in hippocampus or entorhinal cortex. However, the concentrations of these proteins were markedly increased in several aged normal specimens. Normal subject age was moderately associated with both C4d (r=0.49) and iC3b (r=0.53) concentrations in the hippocampus. Increased brain complement activation in some elderly individuals may promote the subsequent development of AD.     

β-Amyloid precursor protein and tau protein levels are differently regulated in human cerebellum compared to brain regions vulnerable to Alzheimer's type neurodegeneration

It is well established that the human brain exhibits regional variability in its vulnerability to Alzheimer's disease (AD) pathology. We set out to determine if this regional vulnerability is reflected in the expression pattern, or processing, of two key proteins involved in AD pathology, the β-amyloid precursor protein (APP) and tau, by immunoblotting. Our data demonstrate that APP processing and APP protein levels are not different between AD patients and healthy, age-matched subjects, but that levels of mature APP are greatly reduced in cerebellum compared to regions of the brain most vulnerable to AD, entorhinal cortex and hippocampus. In addition, protein levels of tau are significantly reduced in cerebellum compared to all other human brain regions examined. Unexpectedly, protein levels of glycogen synthase kinase 3 (GSK3), a major tau kinase, are at their lowest in hippocampus. The observations demonstrate that both mature APP as well as total APP and tau protein levels are greatly reduced in human cerebellum, a region of the human brain most resistant to AD pathology.     

Cellular distribution of insulin-like growth factor-II/mannose-6-phosphate receptor in normal human brain and its alteration in Alzheimer's disease pathology

The insulin-like growth factor-II/mannose-6-phosphate (IGF-II/M6P) receptor is a multifunctional membrane glycoprotein, which binds different classes of ligands including IGF-II and M6P-bearing lysosomal enzymes. Besides participating in the process of endocytosis this receptor functions in the trafficking of lysosomal enzymes from the trans-Glogi network (TGN) or the cell surface to lysosomes. In Alzheimer's disease (AD) brain, marked overexpression of certain lysosomal enzymes in vulnerable neuronal populations and their association to beta-amyloid (Abeta) containing neuritic plaques has been correlated to altered metabolic functions. In the present study, we measured the levels of IGF-II/M6P receptor and characterized its distribution profile in selected regions of AD and age-matched normal postmortem brains. Western blot analysis revealed no significant alteration in the levels of IGF-II/M6P receptor either in the hippocampus, frontal cortex or cerebellum between AD and age-matched control brains. However, a significant gene dose effect of apolipoprotein E (APOE) epsilon4 allele on IGF-II/M6P receptor levels was evident in the hippocampus of the AD brain. At the cellular level, immunoreactive IGF-II/M6P receptors were localized in the neurons of the frontal cortex, hippocampus and cerebellum of control brains. In AD brains, the labeling of the neurons was less intense in the frontal cortex and hippocampus than in the age-matched control brains. Additionally, IGF-II/M6P receptor immunoreactivity was observed in association with a subpopulation of Abeta-containing neuritic plaques as well as tau-positive neurofibrillary tangles both in the frontal cortex and the hippocampus. Reactive glial cells localized adjacent to the plaques also occasionally exhibited IGF-II/M6P receptor immunoreactivity. These results, when analyzed in context of the established role of the IGF-II/M6P receptor in the regulation of the intracellular trafficking of lysosomal enzymes, suggest that alterations in IGF-II/M6P receptor levels/distribution are possibly associated with altered functioning of the lysosomal enzymes and/or loss of neurons observed in AD brains, especially in patients carrying APOE epsilon4 alleles.     

Oxidative stress-mediated DHEA formation in Alzheimer's disease pathology

An alternative pathway for dehydroepiandrosterone (DHEA) synthesis has been suggested by treating rat and human brain cells with ferrous sulfate and beta-amyloid (Abeta). To determine if this pathway exists in human brain, levels of DHEA in hippocampus, hypothalamus and frontal cortex from Alzheimer's disease (AD) patients and age-matched controls were measured. DHEA is significantly higher in AD brain than control, and was highest in AD hippocampi. Cytochrome p450 17alpha-hydroxylase, responsible for peripheral DHEA synthesis, is not present in hippocampus. DHEA levels in AD cerebrospinal fluid (CSF) were significantly higher than age-matched controls. AD serum DHEA levels are lower than CSF, and not significantly different from controls. Treatment of control hippocampus, hypothalamus and serum with FeSO(4) increases DHEA, suggesting that levels of precursor are higher in control that in AD brain. This suggests that (i). an alternative precursor is present in control brain, (ii). AD brain DHEA is formed by oxidative stress metabolism of precursor, and (iii). CSF DHEA levels and serum DHEA formation in response to FeSO(4) may serve as an indicator of AD pathology.     

MicroRNAs in Alzheimer's disease: differential expression in hippocampus and cell-free cerebrospinal fluid

MicroRNAs (miRNAs) are small, noncoding RNAs that function in complex networks to regulate protein expression. In the brain, they are involved in development and synaptic plasticity. In this study, we aimed to identify miRNAs with a differential expression in either hippocampus or cerebrospinal fluid (CSF) from Alzheimer's disease (AD) patients and age-matched nondemented control subjects using quantitative polymerase chain reaction. In hippocampus, we also differentiated between AD patients with an intermediate stage, according to Braak III/IV stage, and a late stage, characterized according to Braak VI stage. Eight selected miRNAs were analyzed in hippocampus, and the expression of miR-16, miR-34c, miR-107, miR-128a, and miR-146a were differentially regulated. In CSF, out of 8 selected miRNAs only miR-16 and miR-146a could be reliably detected. In addition, we identified an effect of blood contamination on the CSF levels of miR-16, miR-24, and miR-146a. For group comparisons, we therefore selected CSF samples absent of, or containing only low numbers of blood cells. Levels of miR-146a were significantly decreased in CSF of AD patients. In conclusion, the abnormal expression of several miRNAs in hippocampus of intermediate- and late-stage AD patients suggests their involvement in AD pathogenesis, and low levels of miR-146a in CSF were associated with AD.     

Activation of brain regions vulnerable to Alzheimer's disease: the effect of mild cognitive impairment

This study examined the functionality of the medial temporal lobe (MTL) and posterior cingulate (PC) in mild cognitive impairment amnestic type (MCI), a syndrome that puts patients at greater risk for developing Alzheimer disease (AD). Functional MRI (fMRI) was used to identify regions normally active during encoding of novel items and recognition of previously learned items in a reference group of 77 healthy young and middle-aged adults. The pattern of activation in this group guided further comparisons between 14 MCI subjects and 14 age-matched controls. The MCI patients exhibited less activity in the PC during recognition of previously learned items, and in the right hippocampus during encoding of novel items, despite comparable task performance to the controls. Reduced fMRI signal change in the MTL supports prior studies implicating the hippocampus for encoding new information. Reduced signal change in the PC converges with recent research on its role in recognition in normal adults as well as metabolic decline in people with genetic or cognitive risk for AD. Our results suggest that a change in function in the PC may account, in part, for memory recollection failure in AD.     

聚腺苷二磷酸核糖糖苷水解酶调节癫痫大鼠海马组织凋亡诱导因子及炎症因子的研究

目的: 探讨聚腺苷二磷酸核糖糖苷水解酶(PARG)对癫痫大鼠海马神经元损伤的影响及其分子机制,探讨PARG抑制剂单宁酸对凋亡诱导因子(AIF)、白细胞介素1β(IL-1β)和肿瘤坏死因子α (TNF-α)的调节作用。方法: 应用Nissl染色方法检测海藻氨酸致痫大鼠海马神经元在单宁酸干预前后的变化;应用Western blotting检测单宁酸干预前后致痫大鼠海马组织聚腺苷二磷酸核糖、AIF、IL-1β和TNF-α表达的变化。结果: 单宁酸干预明显减少癫痫大鼠损伤海马神经元数目(P<0.05);增加致痫大鼠海马组织聚腺苷二磷酸核糖水平(P<0.05);增加致痫大鼠海马组织线粒体蛋白中AIF含量,降低核蛋白中AIF含量 (P<0.05);可显著降低致痫大鼠海马组织IL-1β和TNF-α蛋白表达(P<0.05)。结论: PARG抑制剂单宁酸可减轻癫痫大鼠海马神经元损伤,阻断线粒体AIF的核转位,抑制海马组织IL-1β和TNF-α的表达。     

Different patterns of gray matter atrophy in early- and late-onset Alzheimer’s disease

We assessed patterns of gray matter atrophy according to-age-at-onset in a large sample of 215 Alzheimer’s disease (AD) patients and 129 control subjects with voxel-based morphometry using 3-Tesla 3D T1-weighted magnetic resonance imaging. Local gray matter amounts were compared between late- and early-onset AD patients and older and younger control subjects, taking into account the effect of apolipoprotein E. Additionally, combined effects of age and diagnosis on volumes of hippocampus and precuneus were assessed. Compared with age-matched control subjects, late-onset AD patients exhibited atrophy of the hippocampus, right temporal lobe, and cerebellum, whereas early-onset AD patients showed gray matter atrophy in hippocampus, temporal lobes, precuneus, cingulate gyrus, and inferior frontal cortex. Direct comparisons between late- and early-onset AD patients revealed more pronounced atrophy of precuneus in early-onset AD patients and more severe atrophy in medial temporal lobe in late-onset AD patients. Age and diagnosis independently affected the hippocampus; moreover, the interaction between age and diagnosis showed that precuneus atrophy was most prominent in early-onset AD patients. Our results suggest that patterns of atrophy might vary in the spectrum of AD.     

Plasma levels of beta-amyloid (1-42) in Alzheimer's disease and mild cognitive impairment

We compared plasma levels of beta-amyloid 1-42 (pg/ml) found for 146 sporadic Alzheimer (AD) patients, 89 subjects with mild cognitive impairment (MCI) and 89 age-matched controls (CT). AD patients had significantly lower levels (38, 54, 52; p<0.01), unrelated to severity of the disease as assessed by MMSE score, age, sex or APOE4 status. Twenty cases investigated at two time points 18 months apart did not demonstrate further decreases. Thus, the reduction in beta-amyloid 1-42 may be a marker for AD status, specifically, a transition from normal status or MCI to AD, rather than a marker for neurodegenerative processes occurring in the disease.     

A cholinergic connection between normal aging and senile dementia in the human hippocampus

The cholinergic enzyme, choline acetyltransferase (CAT) has been estimated in autopsy brain tissue obtained from elderly, mentally normal and abnormal hospital patients, including those with senile dementia. In the normal subjects a substantial loss of cortical CAT occurred with increasing age and was most pronounced in the hippocampus. Of the age-matched abnormal groups investigated, significantly reduced enzyme activities were found in the group with senile dementia, in which the hippocampal loss was most extensive. These findings indicate a vulnerability of the hippocampal cholinergic system in old age and dementia which may be associated with memory derangement.     

Increased levels of 4-hydroxynonenal and acrolein, neurotoxic markers of lipid peroxidation, in the brain in Mild Cognitive Impairment and early Alzheimer's disease

Previous studies show increased levels of lipid peroxidation and neurotoxic by-products of lipid peroxidation including 4-hydroxynonenal (HNE) and acrolein in vulnerable regions of the Alzheimer's disease (AD) brain. To determine if lipid peroxidation occurs early in progression of AD, we analyzed levels of HNE and acrolein in the hippocampus/parahippocampal gyrus (HPG), superior and middle temporal gyrus (SMTG) and cerebellum (CER) of 7 subjects with Mild Cognitive Impairment (MCI), six subjects with early AD (EAD) and sevem age-matched control subjects using liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS). Our data show that there is a statistically significant (P<0.05) increase in HNE in HPG, SMTG and CER in MCI compared to age-matched control subjects. Specimens of SMTG also showed a significant increase in levels of acrolein in MCI. Comparison of EAD and control subjects showed a statistically significant increase in HNE in HPG and SMTG and a significant increase in acrolein in all three brain regions studied. We did not observe any statistically significant differences between MCI and EAD specimens. These results suggest that lipid peroxidation occurs early in the pathogenesis of AD.     

Differences in magnetization transfer ratios of the hippocampus between dementia with Lewy bodies and Alzheimer's disease

We compared magnetization transfer ratios (MTRs) in the brains of patients with dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) to determine whether regional differences in the brain structures between DLB and AD are detectable with magnetization transfer imaging. Seventeen patients with DLB, 31 patients with AD and 18 elderly normal controls were included. Although no significant differences were found in MTRs in the frontal white matter between the three groups, MTRs in the hippocampus, parahippocampus, and posterior cingulate white matter in both patients with DLB and AD were significantly lower than those in age-matched control subjects. However, MTRs in the hippocampus of patients with DLB were significantly higher than those in patients with AD. Logistic regression analysis revealed that hippocampal MTR yielded a sensitivity of 76% and a specificity of 71% in discriminating DLB from AD. These results may reflect underlying histopathological differences with less severe neuronal degeneration in the hippocampus of DLB. MTR measurement of the hippocampus may contribute to the clinical differentiation between DLB and AD.     

Hippocampus neuronal metabolic gene expression outperforms whole tissue data in accurately predicting Alzheimer's disease progression

Numerous metabolic alterations are associated with the impairment of brain cells in Alzheimer's disease (AD). Here we use gene expression microarrays of both whole hippocampus tissue and hippocampal neurons of AD patients to investigate the ability of metabolic gene expression to predict AD progression and its cognitive decline. We find that the prediction accuracy of different AD stages is markedly higher when using neuronal expression data (0.9) than when using whole tissue expression (0.76). Furthermore, the metabolic genes' expression is shown to be as effective in predicting AD severity as the entire gene list. Remarkably, a regression model from hippocampal metabolic gene expression leads to a marked correlation of 0.57 with the Mini-Mental State Examination cognitive score. Notably, the expression of top predictive neuronal genes in AD is significantly higher than that of other metabolic genes in the brains of healthy subjects. All together, the analyses point to a subset of metabolic genes that is strongly associated with normal brain functioning and whose disruption plays a major role in AD.     

Lymphocyte G-protein-coupled receptor kinase-2 is upregulated in patients with Alzheimer's disease

Alterations in signal transduction pathway of G-protein-coupled receptors (GPCRs) have been found in the cerebrocortex and in the peripheral cultured tissues of patients with Alzheimer's disease (AD). The G-protein-coupled receptor kinase-2 (GRK2) plays an important role in regulating the GPCRs signaling: its increased expression is associated with receptor desensitization. The aim of this study was to explore GRK2 levels in peripheral lymphocytes of AD patients and to establish a correlation between lymphocyte protein concentrations and the degree of cognitive impairment. GRK2 mRNA and protein expression were evaluated in the lymphocytes of AD patients with mild or moderate/severe cognitive impairment and in age-matched healthy subjects. Both GRK2 mRNA and protein expression were higher in AD patients lymphocytes compared to controls. Furthermore, lymphocyte GRK2 levels were significantly correlated to the degree of cognitive decline. Our preliminary data suggest that GRK2 is involved in GPCRs coupling dysfunction observed in AD patients. Further studies are needed in order to verify whether the lymphocyte GRK2 might be utilized as a novel biomarker in AD diagnosis and clinical monitoring.     

Age-dependent decline of neprilysin in Alzheimer's disease and normal brain: inverse correlation with A beta levels

Brain deposition of amyloid-beta (A beta) is a pathological hallmark of Alzheimer disease (AD) but A beta is also detected in non-demented elderly individuals. Neprilysin has been shown to be an important enzyme to degrade A beta in brain. We investigated whether decreased neprilysin levels contributes to the accumulation of A beta in AD and in normal aging. No difference in neprilysin protein and mRNA levels were found between AD subjects and age-matched controls. Protein levels of neprilysin were reduced with age in the temporal and frontal cortex of AD and normal brain. A significant positive correlation between insoluble A beta 40 and A beta 42 with age was found in cortex of normal brain whereas in AD brain the correlation between age and A beta was weaker. Our findings of an inverse correlation between neprilysin and insoluble A beta levels in both groups suggest that neprilysin is involved in the clearance of A beta. The observed age-dependent decline in neprilysin may be related to the increased A beta levels during normal aging. The similar rate of decline in neprilysin with age may not be the major cause of the high levels of A beta associated with AD but is likely to be a trigger of AD pathology.