AD Hippocampus Research Articles

Visual deep learning of unprocessed neuroimaging characterises dementia subtypes and generalises across non-stereotypic samples.

Dementia's diagnostic protocols are mostly based on standardised neuroimaging data collected in the Global North from homogeneous samples. In other non-stereotypical samples (participants with diverse admixture, genetics, demographics, MRI signals, or cultural origins), classifications of disease are difficult due to demographic and region-specific sample heterogeneities, lower quality scanners, and non-harmonised pipelines. We implemented a fully automatic computer-vision classifier using deep learning neural networks. A DenseNet was applied on raw (unpreprocessed) data from 3000 participants (behavioural variant frontotemporal dementia-bvFTD, Alzheimer's disease-AD, and healthy controls; both male and female as self-reported by participants). We tested our results in demographically matched and unmatched samples to discard possible biases and performed multiple out-of-sample validations. Robust classification results across all groups were achieved from standardised 3T neuroimaging data from the Global North, which also generalised to standardised 3T neuroimaging data from Latin America. Moreover, DenseNetalso generalised to non-standardised, routine 1.5T clinical images from Latin America. These generalisations were robust in samples with heterogenous MRI recordings and were not confounded by demographics (i.e., were robust in both matched and unmatched samples, and when incorporating demographic variables in a multifeatured model). Model interpretability analysis using occlusion sensitivity evidenced core pathophysiological regions for each disease (mainly the hippocampus in AD, and the insula in bvFTD) demonstrating biological specificity and plausibility. The generalisable approach outlined here could be used in the future to aid clinician decision-making in diverse samples. The specific funding of this article is provided in the acknowledgements section.

Fingolimod Affects Transcription of Genes Encoding Enzymes of Ceramide Metabolism in Animal Model of Alzheimer\u2019s Disease

The imbalance in sphingolipid signaling may be critically linked to the upstream events in the neurodegenerative cascade of Alzheimer’s disease (AD). We analyzed the influence of mutant (V717I) amyloid β precursor protein (AβPP) transgene on sphingolipid metabolism enzymes in mouse hippocampus. At 3 months of age AβPP/Aβ presence upregulated enzymes of ceramide turnover on the salvage pathway: ceramide synthases (CERS2, CERS4, CERS6) and also ceramidase ACER3. At 6 months, only CERS6 was elevated, and no ceramide synthase was increased at 12 months. However, sphingomyelin synthases, which utilize ceramide on the sphingomyelinase pathway, were reduced (SGMS1 at 12 and SGMS2 at 6 months). mRNAs for sphingomyelin synthases SGMS1 and SGMS2 were also significantly downregulated in human AD hippocampus and neocortex when compared with age-matched controls. Our findings suggest early-phase deregulation of sphingolipid homeostasis in favor of ceramide signaling. Fingolimod (FTY720), a modulator of sphingosine-1-phosphate receptors countered the AβPP-dependent upregulation of hippocampal ceramide synthase CERS2 at 3 months. Moreover, at 12 months, FTY720 increased enzymes of ceramide-sphingosine turnover: CERS4, ASAH1, and ACER3. We also observed influence of fingolimod on the expression of the sphingomyelinase pathway enzymes. FTY720 counteracted the AβPP-linked reduction of sphingomyelin synthases SGMS1/2 (at 12 and 6 months, respectively) and led to elevation of sphingomyelinase SMPD2 (at 6 and 12 months). Therefore, our results demonstrate potentially beneficial, age-specific effects of fingolimod on transcription of sphingolipid metabolism enzymes in an animal model of AD.

Multiparametric imaging hippocampal neurodegeneration and functional connectivity with simultaneous PET/MRI in Alzheimer\u2019s disease

PurposeThe objective of this study is to investigate the hippocampal neurodegeneration and its associated aberrant functions in mild cognitive impairment (MCI) and Alzheimer’s disease (AD) patients using simultaneous PET/MRI.MethodsForty-two cognitively normal controls (NC), 38 MCI, and 22 AD patients were enrolled in this study. All subjects underwent 18F-FDG PET/functional MRI (fMRI) and high-resolution T1-weighted MRI scans on a hybrid GE Signa PET/MRI scanner. Neurodegeneration in hippocampus and its subregions was quantified by regional gray matter volume and 18F-FDG standardized uptake value ratio (SUVR) relative to cerebellum. An iterative reblurred Van Cittert iteration method was used for voxelwise partial volume correction on 18F-FDG PET images. Regional gray matter volume was estimated from voxel-based morphometric analysis with MRI. fMRI data were analyzed after slice time correction and head motion correction using statistical parametric mapping (SPM12) with DPARSF toolbox. The regions of interest including hippocampus, cornu ammonis (CA1), CA2/3/dentate gyrus (DG), and subiculum were defined in the standard MNI space.ResultsPatient groups had reduced SUVR, gray matter volume, and functional connectivity compared to NC in CA1, CA2/3/DG, and subiculum (AD < MCI < NC). There was a linear correlation between the left CA2/3DG gray matter volume and 18F-FDG SUVR in AD patients (P < 0.001, r = 0.737). Significant correlation was also found between left CA2/3/DG-superior medial frontal gyrus functional connectivity and left CA2/3/DG hypometabolism in patients with AD. The functional connectivity of right CA1-precuneus in patients with MCI and right subiculum-superior frontal gyrus in patients with AD was positively correlated with mini mental status examination scores (P < 0.05).ConclusionOur findings demonstrate that the associations existed at subregional hippocampal level between the functional connectivity measured by fMRI and neurodegeneration measured by structural MRI and 18F-FDG PET. Our results may provide a basis for precision neuroimaging of hippocampus in AD.

Contactin-2, a synaptic and axonal protein, is reduced in cerebrospinal fluid and brain tissue in Alzheimer\u2019s disease

BackgroundSynaptic and axonal loss are two major mechanisms underlying Alzheimer’s disease (AD) pathogenesis, and biomarkers reflecting changes in these cellular processes are needed for early diagnosis and monitoring the progression of AD. Contactin-2 is a synaptic and axonal membrane protein that interacts with proteins involved in the pathology of AD such as amyloid precursor protein (APP) and beta-secretase 1 (BACE1). We hypothesized that AD might be characterized by changes in contactin-2 levels in the cerebrospinal fluid (CSF) and brain tissue. Therefore, we aimed to investigate the levels of contactin-2 in the CSF and evaluate its relationship with disease pathology.MethodsContactin-2 was measured in CSF from two cohorts (selected from the Amsterdam Dementia Cohort), comprising samples from controls (cohort 1, n = 28; cohort 2, n = 20) and AD (cohort 1, n = 36; cohort 2, n = 70) using an analytically validated commercial enzyme-linked immunosorbent assay (ELISA). The relationship of contactin-2 with cognitive decline (Mini-Mental State Examination (MMSE)) and other CSF biomarkers reflecting AD pathology were analyzed. We further characterized the expression of contactin-2 in postmortem AD human brain (n = 14) versus nondemented controls (n = 9).ResultsCSF contactin-2 was approximately 1.3-fold reduced in AD patients compared with controls (p < 0.0001). Overall, contactin-2 levels correlated with MMSE scores (r = 0.35, p = 0.004). We observed that CSF contactin-2 correlated with the levels of phosphorylated tau within the control (r = 0.46, p < 0.05) and AD groups (r = 0.31, p < 0.05). Contactin-2 also correlated strongly with another synaptic biomarker, neurogranin (control: r = 0.62, p < 0.05; AD: r = 0.60, p < 0.01), and BACE1, a contactin-2 processing enzyme (control: r = 0.64, p < 0.01; AD: r = 0.46, p < 0.05). Results were further validated in a second cohort (p < 0.01). Immunohistochemical analysis revealed that contactin-2 is expressed in the extracellular matrix. Lower levels of contactin-2 were specifically found in and around amyloid plaques in AD hippocampus and temporal cortex.ConclusionsTaken together, these data reveal that the contactin-2 changes observed in tissues are reflected in CSF, suggesting that decreased contactin-2 CSF levels might be a biomarker reflecting synaptic or axonal loss.

Modulatory Effects of Fingolimod (FTY720) on the Expression of Sphingolipid Metabolism-Related Genes in an Animal Model of Alzheimer\u2019s Disease

Sphingolipid signaling disturbances correlate with Alzheimer’s disease (AD) progression. We examined the influence of FTY720/fingolimod, a sphingosine analog and sphingosine-1-phosphate (S1P) receptor modulator, on the expression of sphingolipid metabolism and signaling genes in a mouse transgenic AD model. Our results demonstrated that AβPP (V717I) transgene led with age to reduced mRNA expression of S1P receptors (S1PRs), sphingosine kinase SPHK2, ceramide kinase CERK, and the anti-apoptotic Bcl2 in the cerebral cortex and hippocampus, suggesting a pro-apoptotic shift in 12-month old mice. These changes largely emulated alterations we observed in the human sporadic AD hippocampus: reduced SPHK1, SPHK2, CERK, S1PR1, and BCL2. We observed that the responses to FTY720 treatment were modified by age and notably differed between control (APP−) and AD transgenic (APP+) animals. AβPP (V717I)-expressing 12-month-old animals reacted to fingolimod with wide changes in the gene expression program in cortex and hippocampus, including increased pro-survival SPHKs and CERK. Moreover, BCL2 was elevated by FTY720 in the cortex at all ages (3, 6, 12 months) while in hippocampus this increase was observed at 12 months only. In APP− mice, fingolimod did not induce any significant mRNA changes at 12 months. Our results indicate significant effect of FTY720 on the age-dependent transcription of genes involved in sphingolipid metabolism and pro-survival signaling, suggesting its neuroprotective role in AD animal model.

Aβ-dependent reduction of NCAM2-mediated synaptic adhesion contributes to synapse loss in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by synapse loss due to mechanisms that remain poorly understood. We show that the neural cell adhesion molecule 2 (NCAM2) is enriched in synapses in the human hippocampus. This enrichment is abolished in the hippocampus of AD patients and in brains of mice overexpressing the human amyloid-β (Aβ) precursor protein carrying the pathogenic Swedish mutation. Aβ binds to NCAM2 at the cell surface of cultured hippocampal neurons and induces removal of NCAM2 from synapses. In AD hippocampus, cleavage of the membrane proximal external region of NCAM2 is increased and soluble extracellular fragments of NCAM2 (NCAM2-ED) accumulate. Knockdown of NCAM2 expression or incubation with NCAM2-ED induces disassembly of GluR1-containing glutamatergic synapses in cultured hippocampal neurons. Aβ-dependent disassembly of GluR1-containing synapses is inhibited in neurons overexpressing a cleavage-resistant mutant of NCAM2. Our data indicate that Aβ-dependent disruption of NCAM2 functions in AD hippocampus contributes to synapse loss.

A High-sugar High-fat Diet Induced Metabolic Syndrome Shows some Symptoms of Alzheimer's Disease in Rats.

Cases of sporadic Alzheimer's disease (SAD) are the predominant form of the age-related dementia. New evidence suggests that metabolic syndrome (MS), a metabolic disorder, is an initiating factor of some SAD cases. A high-sugar high-fat diet could cause MS, we aimed to investigate whether it could directly lead to SAD. The characteristic molecules of AD (hippocampus Aβ and Tau) were tested by using ELISA and western blotting to confirm the happening hallmarks of AD in brain. MS and inflammation related biochemical indicators were measured using immunological method. Proteins associated with the insulin resistance signal pathway (JNK, PI-3K, AKT, GSK-3β, GLUT3) were evaluated using western blotting method. The levels of reactive oxygen species (ROS) were measured by immunofluorescence method. Expressions of hippocampus Aβ, phosphorylation-Tau (p-Tau), inflammatory factors and p-JNK, Gsk-3βwere higher in the model rats than those in the control rats and expressions of p-PI3K, p-AKT and GLUT3 were reversed. The MS model animals, which can induce the characteristics symptoms of AD, and therefore it may be preliminarily considered that the AD pertains to the MS-related diseases.

SWATH analysis of the synaptic proteome in Alzheimer's disease

Brain tissue from Alzheimer's disease patients exhibits synaptic degeneration in selected regions. Synaptic dysfunction occurs early in the disease and is a primary pathological target for treatment. The molecular mechanisms underlying this degeneration remain unknown. Quantifying the synaptic proteome in autopsy brain and comparing tissue from Alzheimer's disease cases and subjects with normal aging are critical to understanding the molecular mechanisms associated with Alzheimer pathology. We isolated synaptosomes from hippocampus and motor cortex so as to reduce sample complexity relative to whole-tissue homogenates. Synaptosomal extracts were subjected to strong cation exchange (SCX) fractionation to further partition sample complexity; each fraction received SWATH-based information-dependent acquisition to generate a comprehensive peptide-ion library. The expression of synaptic proteins from AD hippocampus and motor cortex was then compared between groups. A total of 2077 unique proteins were identified at a critical local false discovery rate <5%. Thirty of these, including 17 novel proteins, exhibited significant expression differences between cases and controls; these proteins are involved in cellular functions including structural maintenance, signal transduction, autophagy, oxidative stress, and proteasome activity, or they have synaptic-vesicle related or energy-related functions. Differentially expressed proteins were subjected to pathway analysis to identify protein–protein interactions. This revealed that the most perturbed molecular and cellular functions were cellular assembly and organization. Core analysis revealed RhoA signaling to be the top canonical pathway. Network analysis showed that differentially expressed proteins were related to cellular assembly and organization, and cellular function and maintenance. This is the first study to combine SCX fractionation with SWATH analysis. SWATH is a promising new technique that can greatly enhance protein identification in any proteome, and has many other benefits; however, there are limitations yet to be resolved.

Accumulation of BRI2-BRICHOS ectodomain correlates with a decreased clearance of Aβ by insulin degrading enzyme (IDE) in Alzheimer’s disease

The precursor protein BRI2 that in its mutated form is associated with British and Danish dementia, can regulate critical processes involved in AD pathogenesis including not only the metabolism of amyloid precursor protein (APP) and formation of Aβ, but also the levels of secreted insulin degrading enzyme (IDE), an enzyme involved in Aβ clearance. We recently observed increased levels of a 45kDa BRI2 form as well as BRI2 ectodomain deposits in Aβ plaques in human AD hippocampus, which may affect BRI2 functional activity. Since BRI2 regulated the levels of secreted IDE and subsequent degradation of Aβ in human cell culture models, we explored if BRI2 changes could affect the Aβ degradation capacity of IDE in human hippocampus (n=28). We observed that IDE is the main enzyme involved in Aβ degradation, and both IDE levels as well as Aβ degradation tend to be decreased in AD. Interestingly, the levels of the 45kDa BRI2 form and BRI2 deposits in hippocampal tissue were inversely correlated with IDE protein levels (r=−0.52, p=0.005; r=−0.4, p=0.045) and IDE activity (r=−0.5935, p=0.0004; r=−0.4, p=0.03). Taken together, the current results suggest a relationship between BRI2 protein changes, IDE activity and Aβ levels in human hippocampus. Thus, the formation and accumulation high of molecular weight BRI2 forms observed in AD may impair IDE functioning and consequently lead to impaired Aβ clearance and to the accumulation of Aβ.

P4‐160: Automated hippocampal shape analysis in normal aging, mild cognitive impairment and Alzheimer's disease

MRI-based volumetric assessment of brain structure has been widely employed in the studies of AD, MCI, and healthy aging and consistent findings of the studies include volume loss in the hippocampus and entorhinal cortex. In this study, we assessed surface shape differences of the hippocampus, which reflect regional volume changes, through automated hippocampal segmentation in subjects of healthy aging, MCI, and AD. Same number of healthy control (n = 25), MCI subjects (n = 25), and patients with probable AD (n = 25) were included. The automated hippocampal segmentation method with group specific template was used for reconstruction of three dimensional hippocampal shapes in each subject. In each subject, the locations of the hippocampal surface were registered on an age-matched neuroanatomical template and variations in hippocampal diameter were calculated. To validate the accuracy of the automated methods, one reader manually outlined the boundary of the hippocampus and the results were compared with those of automated methods. Significant surface shape differences were observed between normal aging and AD in the lateral zone of the body of both hippocampi and the inferior-medial zone of the left hippocampal body, which are proximal to the cornu ammonis (CA)1 subfield and the subiculum. Between amnestic MCI and AD, there were also significant shape differences in the lateral and inferior-medial zones of the left hippocampal body and lateral surface of the hippocampal tail of the right hippocampus. However, a comparison of amnestic MCI and normal control did not reveal significant differences. In AD, atrophic changes appear in the hippocampus; however, this is not a unique finding of AD without specification of sub-regions and can also be seen in other types of dementia, MCI, and healthy aging. In this study, hippocampal surface deformation was most pronounced in areas covering the CA1 subfield and the subiculum in AD compared to normal control and MCI. The automated surface analysis used in this study is easier to use than the manual-drawing method and displays specific deformational changes of the hippocampus in AD, which could be a useful tool for group-level studies.

Biliverdin reductase-A protein levels and activity in the brains of subjects with Alzheimer disease and mild cognitive impairment

Biliverdin reductase-A is a pleiotropic enzyme involved not only in the reduction of biliverdin-IX-alpha into bilirubin-IX-alpha, but also in the regulation of glucose metabolism and cell growth secondary to its serine/threonine/tyrosine kinase activity. Together with heme oxygenase, whose metabolic role is to degrade heme into biliverdin-IX-alpha, it forms a powerful system involved in the cell stress response during neurodegenerative disorders. In this paper, an up-regulation of the biliverdin reductase-A protein levels was found in the hippocampus of the subjects with Alzheimer disease and arguably its earliest form, mild cognitive impairment. Moreover a significant reduction in the phosphorylation of serine, threonine and tyrosine residues of biliverdin reductase-A was found, and this was paralleled by a marked reduction in its reductase activity. Interestingly, the levels of both total and phosphorylated biliverdin reductase-A were unchanged as well as its enzymatic activity in the cerebella. These results demonstrated a dichotomy between biliverdin reductase-A protein levels and activity in the hippocampus of subjects affected by Alzheimer disease and mild cognitive impairment, and this effect likely is attributable to a reduction in the phosphorylation of serine, threonine and tyrosine residues of biliverdin reductase-A. Consequently, not just the increased levels of biliverdin reductase-A, but also its changed activity and phosphorylation state, should be taken into account when considering potential biomarkers for Alzheimer disease and mild cognitive impairment.

Increased expression of cholesterol transporter ABCA1 is highly correlated with severity of dementia in AD hippocampus

To gain insight into ATP-binding cassette transporter A1 ( ABCA1) function and its potential role in AD pathology, we analyzed the expression of the cholesterol transporter ABCA1 in postmortem hippocampus from persons at different stages of dementia and AD associated neuropathology relative to cognitively intact normal donors by quantitative polymerase chain reaction (qPCR) and Western blot. In this study clinical dementia rating (CDR) scores were used as a measure of dementia severity, whereas, Braak neuropathological staging and neuritic plaque density were used as an index of the neuropathological progression of AD. Correlation analysis showed that ABCA1 mRNA expression was significantly elevated at the earliest recognizable stage of dementia compared to persons with intact cognition. ABCA1 mRNA was also positively correlated with Braak neuropathological stages and neuritic plaque density counts. Additionally, ABCA1 mRNA levels showed robust correlation with dementia severity even after controlling for the confounding contribution of accompanying neuropathological parameters to ABCA1 mRNA expression. Western blot analyses showed that the differential expression observed at the transcriptional level is also reflected at the protein level. Thus, our study provides transcriptional and translational evidence that the expression of ABCA1, a key modulator of cholesterol transport across the plasma membrane, is dysregulated in the AD brain and that this dysregulation is associated with increasing severity of AD, whether measured functionally as dementia severity or neuropathologically as increased neuritic plaque and neurofibrillary tangle density.

Under-expression of Kalirin-7 Increases iNOS Activity in Cultured Cells and Correlates to Elevated iNOS Activity in Alzheimer's Disease Hippocampus1

Recently, it has been reported that Kalirin gene transcripts are under-expressed in AD hippocampal specimens compared to the controls. The Kalirin gene generates a dozen Kalirin isoforms. Kalirin-7 is the predominant protein expressed in the adult brain and plays crucial roles in growth and maintenance of neurons. Yet its role in human diseases is unknown. We report that Kalirin-7 is significantly diminished both at the mRNA and protein levels in the hippocampus specimens from 19 AD patients compared to the specimens from 15 controls. Kalirin-7 associates with iNOS in the hippocampus, and therefore, Kalirin-7 is complexed with iNOS less in AD hippocampus extracts than in control hippocampus extracts. In cultured cells, Kalirin-7 associates with iNOS and down-regulates the enzyme activity. The down-regulation is attributed to the highly conserved 33 amino acid sequence, K(617) -H(649), of the 1,663 amino acids long Kalirin-7. Remarkably, the iNOS activity is considerably higher in the hippocampus specimens from AD patients than the specimens from 15 controls. These observations suggest that the under-expression of Kalirin-7 in AD hippocampus correlates to the elevated iNOS activity.

Brain tissue microarrays in neurodegenerative diseases: Validation of methodology and immunohistochemical study of growth‐associated protein‐43 and calretinin

A tissue microarray (TMA) was constructed using 47 neurodegenerative diseases (NDD), including Alzheimer's disease (AD; n = 30) and non-AD NDD (n = 17), and from seven controls. For validation of the methodology, the following three immunostains were used. Tau and beta-amyloid-related pathologies were more significantly recognized in tauopathies/AD compared to non-tauopathies/controls, and these results were comparable to the assessment of the whole brain sections. But no alpha-synuclein pathologies were observed despite five cases of dementia with Lewy bodies. It was concluded that the TMA technique is useful for NDD with diffuse pathological processes but not for those with patchy and occasional lesions or in early stages. Growth-associated protein (GAP)-43 and calretinin were also immunostained. A significant reduction in GAP-43 expression was seen in the frontal lobe and hippocampus in AD compared to non-AD cases, but not in other areas. No significant difference in number of anticalretinin immunoreactive neurons or in density of immunoreactive neurites was observed between any of the NDD and controls, which may indicate that calretinin-positive neurons are spared in the degenerative process. These results are compatible with the previous studies. These analyses were performed rapidly in a large number of cases using a single slide under uniform staining conditions.

O1-01-02: Mitochondrial alterations in relation to synaptic pathology in Alzheimer’s disease

hippocampus in AD. Individuals with MCI, lacking a clinical diagnosis of AD, manifest a decline in synapse numbers in the hippocampus. It is unclear whether areas of neocortex also affected in AD display synaptic loss during this prodromal transitional stage. The inferior temporal gyrus (ITG) is considered tertiary association cortex with a special role in higher order visual function. It is an integral part of the visual association pathway that provides the anatomical substrate for the perception and memory of shapes and objects. Objective: To assess total synaptic numbers in lamina III of the ITG during the progression of AD. Methods: Tissue was examined from the Rush Religious Orders Study and from the AD Center at the University of Kentucky. All cases had detailed clinical evaluation within 12 months prior to death and were categorized as AD, MCI, or no cognitive impairment (NCI). Systematic random samples throughout the entire extent of the ITG were obtained at autopsy and processed for standard transmission electron microscopy. Unbiased stereological techniques employing the physical disector were used to estimate the total number of synapses in lamina III. Results: Preliminary results revealed that the AD group had significantly fewer synapses than NCI. The mean number of synapses in the MCI group was also lower compared to NCI but higher than the AD subjects. The total volume of the ITG appeared the same for both the NCI and MCI cases; and substantially greater than the AD group volume. There was a highly significant association between the total number of synapses in the ITG and the subject’s score on the mini mental status exam (MMSE). Conclusions: This is the first study to estimate the total number of synapses in a specific region of the human neocortex. These results suggest that the ITG in individuals with MCI manifest synaptic loss that may be equivalent to some AD subjects, supporting the idea that significant synaptic loss occurs early in the progression to AD.

Decreased phosphatidylethanolamine binding protein expression correlates with Aβ accumulation in the Tg2576 mouse model of Alzheimer's disease

Phosphatidylethanolamine binding protein (PEBP) is a multifunctional protein, with proposed roles as the precursor protein of hippocampal cholinergic neurostimulating peptide (HCNP), and as the Raf kinase inhibitor protein (RKIP). Previous studies have demonstrated a decrease in PEBP mRNA in CA1 region of AD hippocampus. The current study demonstrates that PEBP is decreased in the hippocampus of 11 month Tg2576 mice, in the absence of change in mRNA levels compared to non-transgenic littermates. The level of PEBP in transgenic mouse hippocampus significantly decreases at 11 months (a time point when Aβ begins accumulating) and 15 months (when Aβ plaques have formed). There was a significant correlation between decreased PEBP expression and accumulation of Aβ. Immunohistochemical studies on Tg2576 and AD brain sections demonstrate that PEBP immunoreactivities are present at the periphery of dense multicore Aβ plaques, and in selective astrocytes, primarily surrounding plaques. These findings suggest that PEBP expression may be influenced by accumulation of Aβ. Down-regulation of PEBP may result in lower levels of HCNP or altered coordination of signal transduction pathways that may contribute to neuronal dysfunction and pathogenesis in AD.

Hippocampal neurons in pre-clinical Alzheimer’s disease

In a previous study of hippocampal neurons in aging and AD [Lancet 344 (1994) 769], we demonstrated that the loss of neurons in the CA1 region was disease-specific and not related to aging. In the present study, we examined for loss of hippocampal neurons in preclinical AD, a period during which there are abundant amyloid deposits in the brain but no evidence of cognitive decline. We examined the postmortem brains of 33 subjects from the Baltimore Longitudinal Study of Aging and the Johns Hopkins Alzheimer’s Disease Research Center. Using unbiased stereology, we estimated the total number of neurons in the granule cell layer, hilus, CA3-2, CA1, and subiculum of AD ( n=14), preclinical AD ( n=8), and age-matched control subjects ( n=11). The results from the present study confirm our previous finding of significant neuronal losses in the CA1 (48%), hilus (14%), and subiculum (24%) in AD [Lancet 344 (1994) 769]. However, we did not observe a significant loss of neurons in CA1 or any of the other subdivisions of the hippocampus in preclinical AD.

Usefulness of MRI measures of entorhinal cortex versus hippocampus in AD

MRI-based measurements of hippocampal atrophy are a sensitive indicator of the early pathologic degeneration of the medial temporal lobe in AD. However, AD pathology appears first in the transentorhinal/entorhinal cortex, not the hippocampus. The authors tested the hypothesis that MRI-based measurements of the entorhinal cortex are more sensitive than measurements of hippocampal volume in discriminating among three clinical groups; controls, patients with a mild cognitive impairment (MCI), and patients with mild probable AD. The authors studied 30 controls, 30 patients with MCI, and 30 patients with AD who were matched among clinical groups on age, gender, and education. All underwent a standardized MRI protocol from which the authors made measurements of hippocampal volume, entorhinal cortex volume, and the cumulative length of the medial border of the entorhinal cortex. Pairwise intergroup differences (p < 0.01) were found for all MRI measurements with the exception of the cumulative length of the entorhinal cortex, which did not differentiate controls from MCI patients. Whereas the hippocampal and entorhinal cortex volume measurements provided slightly better intergroup discrimination than the entorhinal distance measurement, overall differences in discriminating ability among the three MRI measurements were minor. Despite the theoretical rationale for the superiority of entorhinal measurements in early AD, the authors found MRI measurements of the hippocampus and entorhinal cortex were approximately equivalent at intergroup discrimination. Measurements of the hippocampus may be preferable because MRI depiction of the boundaries of the entorhinal cortex can be obscured by anatomic ambiguity, image artifact, or both.

Inducible nitric oxide synthase immunoreactivity in the Alzheimer disease hippocampus: association with Hirano bodies, neurofibrillary tangles, and senile plaques.

Inducible nitric oxide synthase (iNOS) is involved in the generation of nitric oxide, a molecule with multiple biological activities. Although iNOS expression may be part of antimicrobial armamentarium, inappropriate expression of iNOS can potentially lead to damage to the host. In this report, we determined the expression of iNOS by immunocytochemistry in the hippocampus of the Alzheimer brains (AD) as well as in young and old normal brains. The results showed localization of iNOS immunoreactivity to Hirano bodies of the AD hippocampus. In addition, small granular iNOS immunoreactive profiles were detected associated with senile plaques and extracellular neurofibrillary tangles. In the hippocampus of control brains, morphologically similar profiles were immunoreactive for iNOS, but in far fewer numbers than in AD hippocampus. The results suggest that iNOS is expressed in a subset of pyramidal neurons in the AD hippocampus, and that iNOS may be involved in the pathogenesis of neuronal degeneration in AD.

Increased regional brain concentrations of ceruloplasmin in neurodegenerative disorders

Ceruloplasmin (CP), the major plasma anti-oxidant and copper transport protein, is synthesized in several tissues, including the brain. We compared regional brain concentrations of CP and copper between subjects with Alzheimer's disease (AD, n = 12), Parkinson's disease (PD, n = 14), Huntington's disease (HD, n = 11), progressive supranuclear palsy (PSP, n = 11), young adult normal controls (YC, n = 6) and elderly normal controls (EC, n = 7). Mean CP concentrations were significantly increased vs. EC ( P < 0.05) in AD hippocampus, entorhinal cortex, frontal cortex, and putamen, PD hippocampus, frontal, temporal, and parietal cortices, and HD hippocampus, parietal cortex, and substantia nigra. lmmunocytochemical staining for CP in AD hippocampus revealed marked staining within neurons, astrocytes, and neuritic plaques. Increased CP concentrations in brain in these disorders may indicate a localized acute phase-type response and/or a compensatory increase to oxidative stress.