Familial Alzheimer's Disease Patients Research Articles

Alzheimer Aβ Peptide Induces Chromosome Mis-Segregation and Aneuploidy, Including Trisomy 21: Requirement for Tau and APP

Both sporadic and familial Alzheimer's disease (AD) patients exhibit increased chromosome aneuploidy, particularly trisomy 21, in neurons and other cells. Significantly, trisomy 21/Down syndrome patients develop early onset AD pathology. We investigated the mechanism underlying mosaic chromosome aneuploidy in AD and report that FAD mutations in the Alzheimer Amyloid Precursor Protein gene, APP, induce chromosome mis-segregation and aneuploidy in transgenic mice and in transfected cells. Furthermore, adding synthetic Abeta peptide, the pathogenic product of APP, to cultured cells causes rapid and robust chromosome mis-segregation leading to aneuploid, including trisomy 21, daughters, which is prevented by LiCl addition or Ca(2+) chelation and is replicated in tau KO cells, implicating GSK-3beta, calpain, and Tau-dependent microtubule transport in the aneugenic activity of Abeta. Furthermore, APP KO cells are resistant to the aneugenic activity of Abeta, as they have been shown previously to be resistant to Abeta-induced tau phosphorylation and cell toxicity. These results indicate that Abeta-induced microtubule dysfunction leads to aneuploid neurons and may thereby contribute to the pathogenesis of AD.

Fractal analysis of amyloid plaques in Alzheimer's disease patients and mouse models

The varied morphological and biochemical forms in which amyloid deposits in brain of Alzheimer's disease (AD) patients are complex and their mechanisms of formation are not completely understood. Here we investigated the ability of fractal dimension (FD) to differentiate between the textures of commonly observed amyloid plaques in sporadic and familial AD patients and aged-control individuals as well as in transgenic mouse models of amyloidosis. Studying more than 6000 amyloid plaques immunostained for total Aβ (Aβt), Aβ40 or Aβ42, we show here that Aβ40 FD could efficiently differentiate between (i) AD patients and aged-control individuals (P<0.001); (ii) sporadic and familial AD due to presenilin-1 or APP (A692G) mutations (P<0.001); and (iii) three transgenic mouse models of different genotypes (P<0.001). Furthermore, while diffuse and dense-core plaques present in humans and transgenic mice had comparable FDs, both Aβt and Aβ42 FD could also differentiate diffuse plaques from other plaque types in both species (P<0.001). Our data suggest that plaque FD could be a valuable tool for objective, computer-oriented AD diagnosis as well as for genotype-phenotype correlations of AD.

PIN1 gene variants in Alzheimer's disease

BackgroundPeptidyl-prolyl isomerase, NIMA-interacting 1 (PIN1) plays a significant role in the brain and is implicated in numerous cellular processes related to Alzheimer's disease (AD) and other neurodegenerative conditions. There are confounding results concerning PIN1 activity in AD brains. Also PIN1 genetic variation was inconsistently associated with AD risk.MethodsWe performed analysis of coding and promoter regions of PIN1 in early- and late-onset AD and frontotemporal dementia (FTD) patients in comparison with healthy controls.ResultsAnalysis of eighteen PIN1 common polymorphisms and their haplotypes in EOAD, LOAD and FTD individuals in comparison with the control group did not reveal their contribution to disease risk.In six unrelated familial AD patients four novel PIN1 sequence variants were detected. c.58+64C>T substitution that was identified in three patients, was located in an alternative exon. In silico analysis suggested that this variant highly increases a potential affinity for a splicing factor and introduces two intronic splicing enhancers. In the peripheral leukocytes of one living patient carrying the variant, a 2.82 fold decrease in PIN1 expression was observed.ConclusionOur data does not support the role of PIN1 common polymorphisms as AD risk factor. However, we suggest that the identified rare sequence variants could be directly connected with AD pathology, influencing PIN1 splicing and/or expression.

Microsomal prostaglandin E synthase-2: Cellular distribution and expression in Alzheimer's disease

Nonsteroidal anti-inflammatory drugs, such as cyclooxygenase (COX)-2 inhibitors, have been unsuccessful in slowing or reversing Alzheimer's disease (AD). Thus, understanding the expression patterns of the downstream effectors for the regulation of prostaglandin synthesis may be important for understanding the pathological processes involved in AD and formulating more effective pharmacotherapeutics for this disease. In this study, we used immunofluorescence, immunohistochemistry, and Western blot analysis to compare patterns of microsomal prostaglandin E synthase (mPGES)-2 expression in the middle frontal gyrus (MFG) of AD patients and age-matched controls. In control human brain sections, mPGES-2 immunoreactivity was observed in neurons, activated microglia, and endothelium, but not in resting microglia, astrocytes, or smooth muscle cells. Microsomal PGES-2 immunoreactivity was particularly elevated in the pyramidal neurons of brains from three of five sporadic and four of five familial AD patients compared with four of five age-matched control brains that showed minimal immunoreactivity. In contrast, Western blot analysis revealed no difference in mPGES-2 levels between end-stage AD brain tissue and control brain tissue. These results suggest that in human cortex, mPGES-2 is constitutive in neurons and endothelium and induced in activated microglia. Furthermore, the high immunoreactivity of mPGES-2 in pyramidal neurons of AD brains indicates that it might have a potential role in the functional replacement of cytosolic PGES or inactive mPGES-1 in later stages of AD.

Membrane cholesterol enrichment prevents Aβ-induced oxidative stress in Alzheimer's fibroblasts

A growing body of evidence implicates low membrane cholesterol in the pathogenesis of Alzheimer's disease (AD). Here we show that Aβ42 soluble oligomers accumulate more slowly and in reduced amount at the plasma membranes of PS-1L392V and APPV717I fibroblasts from familial AD (FAD) patients enriched in cholesterol content than at the counterpart membranes. The Aβ42-induced production of reactive oxygen species (ROS) and the increase in membrane lipoperoxidation were also prevented by high membrane cholesterol, thus resulting in a higher resistance to amyloid toxicity with respect to control fibroblasts. On the other hand, the recruitment of amyloid assemblies to the plasma membrane of cholesterol-depleted fibroblasts was significantly increased, thus triggering an earlier and sharper production of ROS and a higher membrane oxidative injury. These results identify membrane cholesterol as being key to Aβ42 oligomer accumulation at the cell surfaces and to the following Aβ42-induced cell death in AD neurons.

Changes in adhesion efficiency and vimentin distribution of fibroblasts from familial Alzheimer's disease patients

Cultured fibroblasts from familial Alzheimer's disease patients were characterized. Familial Alzheimer fibroblasts showed the same appearance by phase microscopy and the same growth rate with the control fibroblasts cultured from the age-matched healthy control subjects. Fibroblasts cultured from familial Alzheimer's disease patients showed decreased efficiency in adhesion to substrata in limited periods. While 80% of the control fibroblasts finished adhesion within 30 minutes incubation, only 30% of Alzheimer fibroblasts completed adhesion within the same period. When fibroblasts from familial Alzheimer's disease were kept under serum-free media more than ten days, they showed a unique aberration of vimentin fiber distribution, while other cytoskeletal fibers were remained intact. It is indicated that fibroblasts cultured from patients with familial Alzheimer's disease can be used to study pathological processes which affect the cytoskeletal organization in the fibroblasts as well as in the cells of the central nervous system.

Gamma-Secretase-Dependent and -Independent Effects of Presenilin1 on β-Catenin·Tcf-4 Transcriptional Activity

Presenilin1 (PS1) is a component of the γ-secretase complex mutated in cases of Familial Alzheimer's disease (FAD). PS1 is synthesized as a 50 kDa peptide subsequently processed to two 29 and 20 kDa subunits that remain associated. Processing of PS1 is inhibited by several mutations detected in FAD patients. PS1 acts as negative modulator of β-catenin·Tcf-4 transcriptional activity. In this article we show that in murine embryonic fibroblasts (MEFs) the mechanisms of action of the processed and non-processed forms of PS1 on β-catenin·Tcf-4 transcription are different. Whereas non-processed PS1 inhibits β-catenin·Tcf-4 activity through a mechanism independent of γ-secretase and associated with the interaction of this protein with plakoglobin and Tcf-4, the effect of processed PS1 is prevented by γ-secretase inhibitors, and requires its interaction with E- or N-cadherin and the generation of cytosolic terminal fragments of these two cadherins, which in turn destabilize the β-catenin transcriptional cofactor CBP. Accordingly, the two forms of PS1 interact differently with E-cadherin or β-catenin and plakoglobin: whereas processed PS1 binds E-cadherin with high affinity and β-catenin or plakoglobin weakly, the non-processed form behaves inversely. Moreover, contrarily to processed PS1, that decreases the levels of c-fos RNA, non-processed PS1 inhibits the expression c-myc, a known target of β-catenin·Tcf-4, and does not block the activity of other transcriptional factors requiring CBP. These results indicate that prevention of PS1 processing in FAD affects the mechanism of repression of the transcriptional activity dependent on β-catenin.

Association between HFE 187 C&gt;G (H63D) mutation and early-onset familial Alzheimer’s disease PSEN-1 839A&gt;C (E280A) mutation

Dear Editor, Alzheimer’s disease (AD, OMIM#104300) is a progressive neurodegenerative disorder characterized by memory loss and cognitive and behavioral abilities impairment. At least three genes have consistently been associated with familial AD (FAD): Aβ precursor protein (APP, OMIM#104760), presenilin-1 (PSEN-1, OMIM#104311) and presenilin-2 (PSN2, OMIM#600759). Noticeably, a single base pair change from A to C (c.839A>C) at codon 280 (gAa-gCa) which results in a Glu-to-Ala substitution in PSEN-1 causes FAD in a large Colombian population in Antioquia region, northwest Colombia [1]. Given that this community is a genetic isolate population [2], this population is a unique resource for the study of modifier genes. Hereditary hemochromatosis (HH, OMIM#235200) is an autosomal recessive disorder of excessive iron uptake and deposition and damage to several organs of the body. HH is most often caused by at least two missense mutations in the gene HFE (chromosome 6p21.3): the c.C187G mutation of exon 2, which results in H63D change at protein translation; and the c.G845A mutation of exon 4, which results in C282Y. Interestingly, brains from AD patients have shown accumulation of iron [3]. Consequently, it is reasonable to think that HFE mutations may be pathological mediator of AD by contributing to brain iron deposition and/or earlier manifestation of dementia symptoms in AD patients. The aim of this study was to examine the allele frequencies of HFE mutations (H63D, C282Y) and their influence on the age of disease onset in a group of patients affected by FAD bearing the E280A mutation in PSEN-1 gene. This investigation was approved by the Ethical Committee of the University of Antioquia (Colombia), and it was supported by Colciencias grants #1115-041-8113 to CVP. A total of 105 individuals (67 women, 38 men) previously genotyped as E280A in PSEN-1 and 220 (117 women, 103 men, range age 18–65 years) non-demented controls, not relatives of FAD patients, were screened for H63D and C282Y in HFE gene by polymerase chain reaction method using the primers sequences reported elsewhere. Amplification mixtures were digested with Mbo I (exon 2) and Rsa I (exon 4) and subsequently analyzed by restriction fragment length polymorphism. Given that the age at onset FAD data (defined as the age at which the patient presented with memory impairment that interferes notably with daily activities) was only available from 75 individuals (52 women, 23 men; mean age of onset at 44.30±5.13; range 33–55 years), they were selected for associative studies between FAD PSN-1 and HH mutations. Tables 1 and 2 show the results of genotype and allelic analysis, respectively. Of notice, the H63D genotype frequencies of healthy normal individuals and FAD patients displayed almost identical distributions for the wild-type, heterozygous, and homozygous conditions [χ(2)=0.43, p=0.8061]. This genotype in both cohorts was at Hardy–Weinberg equilibrium. Similarly, there were no statistically significant differences in the allele frequencies between FAD patients and controls who were wild-type, heterozygous, and homozygous for the H63D alteration [χ(1)=0.39, p=0.5319]. In contrast, there were neither homozygote nor heterozygous for the C282Y mutation in the cohort of FAD patients, and one heterozygote was found among the control group. Given that neither the genotype nor the allelic frequencies of Ann Hematol (2008) 87:671–673 DOI 10.1007/s00277-008-0467-y

Protective effect of new S-acylglutathione derivatives against amyloid-induced oxidative stress

Recent data support the role of oxidative stress in the pathogenesis of Alzheimer disease (AD). In particular, glutathione (GSH) metabolism is altered and its levels are decreased in affected brain regions and peripheral cells from AD patients and in experimental models of AD. In the past decade, interest in the protective effects of various antioxidants aimed at increasing intracellular GSH content has been growing. Because much experimental evidence suggests a possible protective role of unsaturated fatty acids in age-related diseases, we designed the synthesis of new S-acylglutathione (acyl-SG) thioesters. S-Lauroylglutathione (lauroyl-SG) and S-palmitoleoylglutathione (palmitoleoyl-SG) were easily internalized into the cells and they significantly reduced Aβ42-induced oxidative stress in human neurotypic SH-SY5Y cells. In particular, acyl-SG thioesters can prevent the impairment of intracellular ROS scavengers, intracellular ROS accumulation, lipid peroxidation, and apoptotic pathway activation. Palmitoleoyl-SG seemed more effective in cellular protection against Aβ-induced oxidative damage than lauroyl-SG, suggesting a valuable role for the monounsaturated fatty acid. In this study, we demonstrate that acyl-SG derivatives completely avoid the sharp lipoperoxidation in primary fibroblasts from familial AD patients occurring after exposure to Aβ42 aggregates. Hence, we put forward these derivatives as new antioxidant compounds which could be excellent candidates for therapeutic treatment of AD and other oxidative stress-related diseases.

Wild-Type But Not FAD Mutant Presenilin-1 Prevents Neuronal Degeneration by Promoting Phosphatidylinositol 3-Kinase Neuroprotective Signaling

The role of presenilin-1 (PS1) in neuronal phosphatidylinositol 3-kinase (PI3K)/Akt signaling was investigated in primary neuronal cultures from wild-type (WT) and PS1 null (PS1-/-) embryonic mouse brains. Here we show that in PS1-/- cultures, the onset of neuronal maturation coincides with a decrease in the PI3K-dependent phosphorylation-activation of Akt and phosphorylation-inactivation of glycogen synthase kinase-3 (GSK-3). Mature PS1-/- neurons show increased activation of apoptotic caspase-3 and progressive degeneration preceded by dendritic retraction. Expression of exogenous WT PS1 or constitutively active Akt in PS1-/- neurons stimulates PI3K signaling and suppresses both caspase-3 activity and dendrite retraction. The survival effects of PS1 are sensitive to inhibitors of PI3K kinase but insensitive to gamma-secretase inhibitors. Familial Alzheimer disease (FAD) mutations suppress the ability of PS1 to promote PI3K/AKT signaling, prevent phosphorylation/inactivation of GSK-3 and promote activation of caspase-3. These mutation effects are reversed upon coexpression of constitutively active Akt. Together, our data indicate that the neuroprotective role of PS1 depends on its ability to activate the PI3K/Akt signaling pathway and that PS1 FAD mutations increase GSK-3 activity and promote neuronal apoptosis by inhibiting the function of PS1 in this pathway. These observations suggest that stimulation of PI3K/Akt signaling may be beneficial to FAD patients.

Enhanced Accumulation of Phosphorylated α-Synuclein and Elevated β-Amyloid 42/40 Ratio Caused by Expression of the Presenilin-1 ΔT440 Mutant Associated with Familial Lewy Body Disease and Variant Alzheimer's Disease

Mutations in the PSEN1 gene encoding presenilin 1 (PS1) are linked to a vast majority of pedigrees with early-onset, autosomal dominant forms of familial Alzheimer's disease (FAD). Lewy body (LB) pathology is frequently found in the brains of FAD patients harboring PSEN1 mutations. We recently reported on a novel PS1 mutation with the deletion of threonine at codon 440 (deltaT440) in a familial case diagnosed as having the neocortical type of dementia with LBs (DLB) and variant AD. In this report, we investigated the possible involvement of PS1 deltaT440 mutation in aberrant alpha-synuclein accumulation. We established cell lines that stably express either wild-type (WT) PS1 or the FAD-linked PS1 H163R, E280A, deltaE9, and PS1 deltaT440 mutants and now demonstrate that the expression of the PS1 deltaT440 mutant led to a marked elevation in the ratio of beta-amyloid (Abeta) 42/40 peptides in a conditioned medium. More importantly, we report here that the levels of phosphorylated alpha-synuclein increase in neuronal and non-neuronal cells expressing the PS1 deltaT440 mutant compared with cells that express WT PS1 or the PS1 H163R and E280A variants that are not associated with LB pathology. This finding is consistent with our demonstration of elevated levels of phosphorylated alpha-synuclein in the detergent-resistant fraction prepared from a patient's brain with PS1 deltaT440 mutation. These observations raise the intriguing suggestion that the mechanism(s) by which the PS1 deltaT440 mutant causes DLB and variant AD are by enhancing the phosphorylation of alpha-synuclein and the ratio of Abeta(42/40) peptides, respectively, in the brain.

Familial Alzheimer disease–linked mutations specifically disrupt Ca2+ leak function of presenilin 1

Mutations in presenilins are responsible for approximately 40% of all early-onset familial Alzheimer disease (FAD) cases in which a genetic cause has been identified. In addition, a number of mutations in presenilin-1 (PS1) have been suggested to be associated with the occurrence of frontal temporal dementia (FTD). Presenilins are highly conserved transmembrane proteins that support cleavage of the amyloid precursor protein by gamma-secretase. Recently, we discovered that presenilins also function as passive ER Ca(2+) leak channels. Here we used planar lipid bilayer reconstitution assays and Ca(2+) imaging experiments with presenilin-null mouse embryonic fibroblasts to analyze ER Ca(2+) leak function of 6 FAD-linked PS1 mutants and 3 known FTD-associated PS1 mutants. We discovered that L166P, A246E, E273A, G384A, and P436Q FAD mutations in PS1 abolished ER Ca(2+) leak function of PS1. In contrast, A79V FAD mutation or FTD-associated mutations (L113P, G183V, and Rins352) did not appear to affect ER Ca(2+) leak function of PS1 in our experiments. We validated our findings in Ca(2+) imaging experiments with primary fibroblasts obtained from an FAD patient possessing mutant PS1-A246E. Our results indicate that many FAD mutations in presenilins are loss-of-function mutations affecting ER Ca(2+) leak activity. In contrast, none of the FTD-associated mutations affected ER Ca(2+) leak function of PS1, indicating that the observed effects are disease specific. Our observations are consistent with the potential role of disturbed Ca(2+) homeostasis in Alzheimer disease pathogenesis.

Increased susceptibility to amyloid toxicity in familial Alzheimer's fibroblasts

Much experimental evidence suggests that an imbalance in cellular redox status is a major factor in the pathogenesis of Alzheimer's disease (AD). Our previous data showed a marked increase in membrane lipoperoxidation in primary fibroblasts from familial AD (FAD) patients. In the present study, we demonstrate that when oligomeric structures of Aβ 1-40 and Aβ 1-42 are added to the culture media, they accumulate quicker near the plasma membrane, and are internalized faster and mostly in APPV717I fibroblasts than in age-matched healthy cells; this results in an earlier and sharper increase in the production of reactive oxygen species (ROS). Higher ROS production leads in turn to an increase in membrane oxidative-injury and significant impairment of cellular antioxidant capacity, giving rise to apoptotic cascade activation and finally to a necrotic outcome. In contrast, healthy fibroblasts appear more resistant to amyloid oxidative-attack, possibly as a result of their plasma membrane integrity and powerful antioxidant capacity. Our data are consistent with increasing evidence that prefibrillar aggregates, compared to mature fibrils, are likely the more toxic species of the peptides. These findings provide compelling evidence that cells bearing increased membrane lipoperoxidation are more susceptible to aggregate toxicity as a result of their reduced ability to counteract amyloid oligomeric attack.

Wild-type Presenilin 1 Protects against Alzheimer Disease Mutation-induced Amyloid Pathology

Mutations in presenilin 1 (PS1) lead to dominant inheritance of early onset familial Alzheimer disease (FAD). These mutations are known to alter the gamma-secretase cleavage of the amyloid precursor protein, resulting in increased ratio of Abeta42/Abeta40 and accelerated amyloid plaque pathology in transgenic mouse models. To investigate the factors that drive the Abeta42/Abeta40 ratio and amyloid pathogenesis and to investigate the possible interactions between wild-type and FAD mutant PS1, which are co-expressed in transgenic animals, we expressed the PS1 M146V knock-in allele either on wild-type PS1 (PS1M146V/+) or PS1 null (PS1M146V/-) background and crossed these alleles with the Tg2576 APP transgenic mice. Introduction of the PS1 M146V mutation on Tg2576 background resulted in earlier onset of plaque pathology. Surprisingly, removing the wild-type PS1 in the presence of the PS1 M146V mutation (PS1M146V/-) greatly exacerbated the amyloid burden; and this was attributed to a reduction of gamma-secretase activity rather than an increase in Abeta42. Our findings establish a protective role of the wild-type PS1 against the FAD mutation-induced amyloid pathology through a partial loss-of-function mechanism.

Presenilin mutations linked to familial Alzheimer's disease reduce endoplasmic reticulum and Golgi apparatus calcium levels

Presenilin-1 and -2 (PS1 and PS2) mutations, the major cause of familial Alzheimer's disease (FAD), have been causally implicated in the pathogenesis of neuronal cell death through a perturbation of cellular Ca 2+ homeostasis. We have recently shown that, at variance with previous suggestions obtained in cells expressing other FAD-linked PS mutations, PS2-M239I and PS2-T122R cause a reduction and not an increase in cytosolic Ca 2+ rises induced by Ca 2+ release from stores. In this contribution we have used different cell models: human fibroblasts from controls and FAD patients, cell lines (SH-SY5Y, HeLa, HEK293, MEFs) and rat primary neurons expressing a number of PS mutations, e.g. P117L, M146L, L286V, and A246E in PS1 and M239I, T122R, and N141I in PS2. The effects of FAD-linked PS mutations on cytosolic Ca 2+ changes have been monitored either by using fura-2 or recombinant cytosolic aequorin as the probe. Independently of the cell model or the employed probe, the cytosolic Ca 2+ increases, caused by agonist stimulation or full store depletion by drug treatment, were reduced or unchanged in cells expressing the PS mutations. Using aequorins, targeted to the endoplasmic reticulum or the Golgi apparatus, we here show that FAD-linked PS mutants lower the Ca 2+ content of intracellular stores. The phenomenon was most prominent in cells expressing PS2 mutants, and was observed also in cells expressing the non-pathogenic, “loss-of-function” PS2-D366A mutation. Taken as a whole, our findings, while confirming the capability of presenilins to modify Ca 2+ homeostasis, suggest a re-evaluation of the “Ca 2+ overload” hypothesis in AD and a new working hypothesis is presented.

Differential Regional Atrophy of the Cingulate Gyrus in Alzheimer Disease: A Volumetric MRI Study

Magnetic resonance imaging-based volumetric measurements provide a useful technique for quantifying in vivo regional cerebral atrophy in Alzheimer disease (AD). Histopathological studies have shown the cingulate cortex, a cytoarchitectonically heterogeneous region, to be severely affected in AD. In this study, we developed and validated a manual segmentation protocol, based on macroscopic characteristics such as gyri and sulci patterns, in order to assess volumetric changes in 4 cingulate regions of interest. Cingulate cortical volumes of 10 familial AD patients were compared with 10 age- and sex-matched controls. Inter- and intrarater reliability coefficients were high for all cingulate regions (91.9-99.4%). All 4 cingulate regions were significantly smaller (P < 0.05) in AD cases compared with controls: rostral anterior cingulate gyrus (22.5% smaller), caudal anterior cingulate gyrus (20.7% smaller), posterior cingulate gyrus (44.1% smaller), and retrosplenial cortex (21.5% smaller). The atrophy in the posterior cingulate region was significantly greater than that in other cingulate regions (P < 0.001), suggesting a higher vulnerability for this region in familial AD. Considering the functional and connectional differences of these 4 cingulate regions, detection and monitoring of their atrophy may provide insights into the natural history of AD and may help in the search for diagnostic markers for early AD.

Aging sensitizes toward ROS formation and lipid peroxidation in PS1M146L transgenic mice

Mutations in the presenilins (PS) account for the majority of familial Alzheimer disease (FAD) cases. To test the hypothesis that oxidative stress can underlie the deleterious effects of presenilin mutations, we analyzed lipid peroxidation products (4-hydroxynonenal (HNE) and malondialdehyde) and antioxidant defenses in brain tissue and levels of reactive oxygen species (ROS) in splenic lymphocytes from transgenic mice bearing human PS1 with the M146L mutation (PS1M146L) compared to those from mice transgenic for wild-type human PS1 (PS1wt) and nontransgenic littermate control mice. In brain tissue, HNE levels were increased only in aged (19–22 months) PS1M146L transgenic animals compared to PS1wt mice and not in young (3–4 months) or middle-aged mice (13–15 months). Similarly, in splenic lymphocytes expressing the transgenic PS1 proteins, mitochondrial and cytosolic ROS levels were elevated to 142.1 and 120.5% relative to controls only in cells from aged PS1M146L animals. Additionally, brain tissue HNE levels were positively correlated with mitochondrial ROS levels in splenic lymphocytes, indicating that oxidative stress can be detected in different tissues of PS1 transgenic mice. Antioxidant defenses (activities of antioxidant enzymes Cu/Zn-SOD, GPx, or GR) or susceptibility to in vitro oxidative stimulation was unaltered. In summary, these results demonstrate that the PS1M146L mutation increases mitochondrial ROS formation and oxidative damage in aged mice. Hence, oxidative stress caused by the combined effects of aging and PS1 mutations may be causative for triggering neurodegenerative events in FAD patients.

Chronically increased oxidative stress in fibroblasts from Alzheimer's disease patients causes early senescence and renders resistance to apoptosis by oxidative stress

It is well established that oxidative stress is involved in several neurodegenerative disorders, including Alzheimer's disease (AD). Study of the induction and consequences of oxidative stress in the peripheral tissues of the familial AD patients can help to elucidate the inherent abnormalities and the mechanism of pathogenesis of this disease. AD fibroblasts have been used as a model to investigate the underlying mechanisms of oxidative stress. In our study, we used AD fibroblasts from six different donors who are either at high risk of developing AD or have already been diagnosed with AD to study the effect of oxidative stress in comparison with the effect on non-AD normal human fibroblast. Oxidative stress was induced by a brief exposure of the cells to 250 μM H 2O 2 followed by incubation in normal conditions. Neuronal loss due to oxidative stress is a characteristic of Alzheimer's patients; however, our results showed that AD fibroblasts were more resistant to oxidative stress compared to non-AD fibroblasts. Measurement of reactive oxygen species (ROS) indicated that AD fibroblasts produced more ROS than did non-AD NHF cells either in basal conditions or after induction of oxidative stress. Furthermore, we found that expression of p21 was significantly higher in AD cells than in non-AD cells and expression of Bax, a pro-apoptotic protein was downregulated/absent in AD cells during normal or under conditions of external oxidative stress. Further experiments revealed that mitochondria in AD cells moved to the peri-nuclear region following induction of oxidative stress. Thus, these results suggest that AD fibroblasts are chronically exposed to oxidative stress that may trigger senescent phenotype, making AD cell resistant to apoptosis by external oxidative stress.

Cortical and subcortical diseases: Do true neuropsychological differences exist?

Previous work examining the cortical-subcortical distinction as it relates to cognitive patterns has not typically used genetic confirmation to identify these groups, controlled for age, or used a comprehensive battery to assess specific cognitive abilities. The present study is the first to include only genetically confirmed Familial Alzheimer's disease (FAD) and Huntington's disease (HD) patients to evaluate this distinction. Ten patients with FAD, 11 patients with HD, and 17 matched healthy individuals were compared on a comprehensive neuropsychological battery that included tasks of language, memory, attention, visual-spatial, and executive function. The only neuropsychological measures to differentiate the two clinical groups were Animal Fluency and Letter Fluency; performance on all other measures did not differ. Although the neuropsychological battery adequately distinguished between clinical and healthy individuals, it was not useful to further differentiate the cortical or subcortical nature of the disease. FAD and HD appear to have similar neuropsychological profiles; therefore the cortical versus subcortical cognitive distinction may not be clinically meaningful.

PEN–2 gene mutation in a familial Alzheimer’s disease case

Genetic evidence indicates a central role of cerebral accumulation of beta-amyloid (Abeta) in the pathogenesis of Alzheimer's disease (AD). Beside presenilin 1 and 2, three other recently discovered proteins (Aph 1, PEN 2 and nicastrin) are associated with gamma-secretase activity, the enzymatic complex generating Abeta. Alterations in genes encoding these proteins were candidates for a role in AD. The PEN 2 gene was examined for unknown mutations and polymorphisms in sporadic and familial Alzheimer patients. Samples from age-matched controls (n=253), sporadic AD (SAD, n=256) and familial AD (FAD, n=140) were screened with DHPLC methodology followed by sequencing. Scanning the gene identified for the first time a missense mutation (D90N) in a patient with FAD. Three intronic polymorphisms were also identified, one of which had a higher presence of the mutated allele in AD subjects carrying the allele epsilon4 of apolipoprotein E than controls. The pathogenic role of the PEN-2 D90N mutation in AD is not clear, but the findings might lead to new studies on its functional and genetic role.