21, Number 1, July 2010
Kenneth Hensley (Handling Associate Editor: Patrizia Mecocci)
Neuroinflammation in Alzheimer's Disease: Mechanisms, Pathologic Consequences, and Potential for Therapeutic Manipulation
Abstract: The concept of neuroinflammation has evolved over the past two decades from an initially controversial viewpoint to its present status as a generally accepted idea whose mechanisms and consequences are still actively under research and debate, particularly with regard to Alzheimer’s disease (AD). This review summarizes the current status of neuroinflammation research as it specifically relates to AD. Neuroinflammation is discussed mechanistically with emphasis on the role of redox signal transduction linked to the activation of central nervous system-relevant innate immune pathways. Redox signaling is presented both as a causal factor and a consequence of sustained neuroinflammation. Functional relationships are discussed that connect distinct neuroinflammatory components such as cytokines, eicosanoids, classic AD pathology (amyloid plaques and neurofibrillary tangles), and the recently emergent notion of “damage-associated molecular patterns”. The interaction of these paracrine factors likely can produce positive as well as negative effects on the AD brain, ranging from plaque clearance by microglia in the short term to glial dysfunction and neuronal compromise if the neuroinflammation is chronically sustained and unmitigated. Recent disappointments in AD clinical trials of anti-inflammatory drugs are discussed with reference to possible explanations and potential avenues for future pharmacological approaches to the disease.
Elizabeth Kirby, Stephan Bandelow and Eef Hogervorst
Visual Impairment in Alzheimer’s Disease: A Critical Review
Abstract: Visual impairment is a common symptom of Alzheimer’s disease (AD). Recent studies have demonstrated the potential of visual interventions to improve the functioning of AD patients. Therefore, clarification of the profile of visual deficits in AD and possible mechanisms underlying these deficits are needed. This review focuses on three areas as mechanisms for the visual impairment in AD: 1) the broad-band pathway deficit; 2) glaucoma; and 3) the relative dysfunction of the ventral and dorsal streams of vision. While much research has been produced with regard to these areas, methodological flaws and lack of continuity between studies has led to conflicting findings. Nevertheless, recent imaging research suggests that the loss of retinal ganglion cells in AD may play an important role in the visual deficit in AD. This review looks to critically evaluate current research and highlight the need to investigate recent significant findings in primary vision research in understanding the impairment of vision in AD.
Sandra Iurescia*, Daniela Fioretti*, Francesca Mangialasche, Monica Rinaldi (Handling Associate Editor: Patrizia Mecocci) *contributed equally
The Pathological Cross Talk Between Apolipoprotein E and Amyloid-β Peptide in Alzheimer’s Disease: Emerging Gene-Based Therapeutic Approaches
Abstract: Apolipoprotein E (ApoE) plays a key role in lipid transport in the plasma and in the central nervous system through its interaction with members of the low-density lipoprotein receptor family. The three common isoforms of ApoE (ApoE2, ApoE3, and ApoE4) differ in their ability to perform neuronal maintenance and repair functions and differentially affect the risk of developing neurodegenerative disorders. The ApoE4 isoform is a strong genetic risk factor for Alzheimer’s disease. Up-to-date knowledge about the structural and biophysical features of ApoE4 shed light on the molecular basis underlying the isoform-specific pathogenic role of ApoE4 and its contribution to AD pathology through several different mechanisms. ApoE4 impacts on amyloid-β (Aβ) production, Aβ clearance, Aβ fibrillation, and tangle formation as well as on mitochondrial functions leading to neuronal toxicity and synaptic damage. This review summarizes the pathological cross talk between ApoE and Aβ peptide in Alzheimer’s disease. Lastly, we examine emerging gene-based therapeutic approaches encompassing the use of ApoE and their potential opportunities to preventing or treating Alzheimer’s disease.
Amy Chan and Thomas B. Shea
Apolipoprotein E3 as a Risk Factor for Alzheimer’s Disease Under Conditions of Nutritional Imbalance
Abstract: The presence of one or more copies of the E4 allele of apolipoprotein E (ApoE) is strongly associated with of Alzheimer’s disease (AD). The impact of E4 on neurodegeneration is potentiated by dietary oxidative challenge. Our prior studies in transgenic mice demonstrate that, in the face of dietary oxidative challenge, E3 does not provide any further protection than E4 or lack of murine ApoE for aggression, oxidative damage, presenilin-1 expression, and γ-secretase activity, and provides only partial reduction in phospho-tau levels. Extrapolation of these findings to the human condition leads us to hypothesize that the E3 allele may not provide sufficient neuroprotection under conditions of dietary compromise and/or oxidative challenge. Epidemiological evidence is consistent with this possibility. The E3 allele is approximately half as effective compared to E2 at buffering the impact of a single E4 allele. In addition, the risk of AD increases linearly for the genotypes E2/2, E2/3, and E3/3. It has been proposed that that clinical manifestation of AD may in some cases require the convergence of 2 or more risk factors. We hypothesize that the combined impact of dietary oxidative stress and either the ApoE3 or E4 genotype represents one such condition.
Vincenza Frisardi, Vincenzo Solfrizzi, Cristiano Capurso, Bruno P. Imbimbo, Gianluigi Vendemiale, Davide Seripa, Alberto Pilotto, Francesco Panza
Is Insulin Resistant Brain State a Central Feature of the Metabolic-Cognitive Syndrome?
Abstract: Cumulative evidence suggests that metabolic syndrome (MetS) may be important in the development of mild cognitive impairment, vascular dementia, and Alzheimer’s disease (AD). As such, these patients might be described as having “metabolic-cognitive syndrome”—MetS plus cognitive impairment of degenerative or vascular origin. While peripheral insulin resistance appears to be of primary pathophysiological importance in MetS, the definitions of MetS and its components do not include any reference to insulin resistance or hyperinsulinemia. In the present article, we discuss the role of these factors in the development of cognitive decline and dementia, including underlying mechanisms that influence amyloid-β (Aβ) peptide metabolism and tau protein hyperphosphorylation, the principal neuropathological hallmarks of AD. In AD, an age-related desynchronization of biological systems results, involving stress components, cortisol and noradrenaline, reactive oxygen species, and membrane damage as major candidates that precipitates an insulin resistant brain state (IRBS) with decreased glucose/energy metabolism and the increased formation of hyperphosphorylated tau protein and Aβ. Unfortunately, it is very difficult to include the measurement of peripheral insulin resistance in the current MetS criteria or the identification of IRBS for the metabolic-cognitive syndrome. However, since inflammation has been suggested among the MetS components, we propose IRBS as an additional feature of the metabolic-cognitive syndrome to also identify a molecular profile in patients at high risk of developing predementia or dementia syndromes.
Po-Yuan Chang, Shao-Chun Lu, Chu-Huang Chen
S-Adenosylhomocysteine: A Better Marker of the Development of Alzheimer’s Disease than Homocysteine?
William C. Herz, Jesus I. Grave de Peralta
Use of Primary Data Leads to Unsupportable Conclusions and Policy Options
Suzanne M. de la Monte
Ignoring the Evidence Will Not Stop the Alzheimer’s Disease/Diabetes Pandemic
Peter T. Nelson and Wang-Xia Wang (Handling Associate Editor: Thomas Montine)
MiR-107 is Reduced in Alzheimer’s Disease Brain Neocortex: Validation Study
Abstract: MiR-107 is a microRNA (miRNA) that we reported previously to have decreased expression in the temporal cortical gray matter early in the progression of Alzheimer’s disease (AD). Here we study a new group of well-characterized human temporal cortex samples (N=19). MiR-107 expression was assessed, normalized to miR-124 and let-7a. Correlation was observed between decreased miR-107 expression and increased neuritic plaque counts (P<0.05) and neurofibrillary tangle counts (P<0.02) in adjacent brain tissue. Adjusted miR-107 and BACE1 mRNA levels tended to correlate negatively (trend with regression P<0.07). In sum, miR-107 expression tends to be lower relative to other miRNAs as AD progresses.
Tokuhei Ikeda, Kenjiro Ono, David Elashoff, Margaret M. Condron, Moeko Noguchi-Shinohara, Mitsuhiro Yoshita, David B. Teplow, Masahito Yamada (Handling Associate Editor: Robert Friedland)
Cerebrospinal Fluid from Alzheimer’s Disease Patients Promotes Amyloid β-Protein Oligomerization
Abstract: Oligomers of the amyloid β-protein (Aβ) play an important role in Alzheimer’s disease (AD). We hypothesized that AD patients have a central nervous system environment that promotes Aβ oligomerization. We investigated the effect of cerebrospinal fluid (CSF) from 33 patients with AD and 33 age-matched, non-demented controls on oligomerization of Aβ1-40 and Aβ1-42 using the technique of photo-induced cross-linking of unmodified proteins. CSF inhibited oligomerization of both Aβ1-40 and Aβ1-42. This inhibitory effect was significantly weaker in AD patients than in non-demented controls. Our results indicate that AD patients have a CSF environment favorable for Aβ oligomerization.
Barbara Borroni, Roberto Del Bo, Stefano Goldwurm, Silvana Archetti, Cristian Bonvicini, Chiara Agosti, Barbara Bigni, Alice Papetti, Simona Ghezzi, Giacomo Sacilotto, Giovanni Pezzoli, Massimo Gennarelli, Nereo Bresolin, Gian Pietro Comi, Alessandro Padovani (Handling Associate Editor: Amalia Bruni)
VEGF Haplotypes are Associated with Increased Risk to Progressive Supranuclear Palsy and Corticobasal Syndrome
Abstract: Progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) are in the spectrum of tauopathies and recognized to have a strong genetic background. It has been widely reported that MAPT tau haplotype H1 is a genetic risk factor in both conditions, but no other genetic determinants have so far been proposed. Recently, vascular endothelial growth factor (VEGF) haplotypes were reported to confer risk to frontotemporal dementia (FTD). The aim of this study was to evaluate the role of VEGF genetic determinants in PSP and CBS susceptibility. We evaluated a cohort of 687 unrelated Italian subjects, including 117 PSP, 108 CBS, 199 FTD, and 263 healthy controls. Genotype and allele frequencies of three well-known polymorphisms located within the VEGF promoter (-2578C/A, -1190G/A, and -1154G/A) were carried out. Genetic analysis revealed the presence of significant changes in terms of genotype and allele distributions in patients compared to healthy controls. A-G-G haplotype (-2578C/A, 1190G/A, -1154G/A) was overrepresented in both PSP (OR=6.64, 95%CI=2.3-19.6, P=0.0003, CGG=reference) and CBS (OR=5.20,95%CI=1.70-15.9, P=0.003, CGG=reference) compared to healthy subjects. No differences between PSP and CBS and FTD were found, and the A-G-G haplotype was also overrepresented in FTD. Overall, these data suggest that VEGF gene variability represents a susceptibility factor for PSP and CBS. These data argue that additional genes may confer disease risk to PSP and CBS, and to FTD as well, beyond the MAPT tau haplotype. Further studies are warranted.
Julián Benito-León, Elan D. Louis, Saturio Vega, Félix Bermejo-Pareja
Statins and Cognitive Functioning in the Elderly: A Population-Based Study
Abstract: In a 2009 Cochrane review, the authors concluded that there is good evidence that statins, given in late life to people at risk of vascular disease, have no effect in preventing Alzheimer’s disease or dementia. A related issue, which remains unclear, is whether statins improve cognitive function. While some studies have shown a beneficial effect of statins on cognitive function, others have observed mild detrimental effects on cognition. Our aim was to assess cognitive function in community-dwelling elderly participants treated with statins compared with their untreated counterparts (i.e., controls) living in the same population. 137 population-dwelling participants who were receiving statins and 411 matched controls age ≥ 65 years (median = 72 years) in central Spain (the Neurological Diseases in Central Spain study [NEDICES]) underwent a neuropsychological assessment, including tests of global cognitive performance, frontal-executive function, verbal fluency, and memory. Median duration of statin treatment was 2 years. Of 137 participants receiving statins, 53 (38.7%) were taking pravastatin, 38 (27.7%) simvastatin, 37 (27.0%) lovastatin, 6 (4.4%) fluvastatin, and 3 (2.2%) atorvastatin. Although initial univariate analyses indicated some differences, after adjusting for age, gender, education, depressive symptoms, premorbid intelligence, medications that potentially affect cognitive function, and blood cholesterol levels, statin users and controls performed similarly on all neuropsychological tests. In this population-based sample, elderly participants treated with statins and untreated controls performed similarly in all tested cognitive areas. These results do not support a positive benefit of statins on cognition.
Arun L.W. Bokde, Michaela Karmann, Christine Born, Stefan J. Teipel, Muamer Omerovic, Michael Ewers, Thomas Frodl, Eva Meisenzahl, Maximilian Reiser, Hans-Jürgen Möller, Harald Hampel
Altered Brain Activation During a Verbal Working Memory Task in Subjects with Amnestic Mild Cognitive Impairment
Abstract: In subjects with mild cognitive impairment (MCI), memory disorders indicate a high risk for conversion to Alzheimer’s disease (AD). The objective of this study was to delineate the differences in brain activation between amnestic MCI and age-matched healthy controls (HC) during a verbal working memory task. The verbal working memory task was a delay match to sample design. Brain activation was measured using functional magnetic resonance imaging. There were 8 subjects in each group and were matched for performance. The task was analyzed as an event-related design. Group differences were calculated using Analysis of Covariance (ANCOVA) with statistical significance at p<0.05 corrected. Both groups activated a wide network in the posterior and frontal areas of the brain. There was higher activation in the parietal and frontal lobes in the MCI compared to the HC during the maintenance phase. There were no areas in the HC that activated higher than the MCI subjects. Response time in the task in the HC group was correlated to the left hippocampus during encoding phase and to the parietal and frontal areas during the recall phase. In the MCI group, there was strong correlation to the inferior and middle temporal gyrii during encoding, the middle frontal gyrus during the maintenance phase, and hippocampus during recall phase. The activation differences between groups may be compensatory mechanisms within the MCI group for the effects of the putative AD neuropathology. This has been the first study that has examined verbal working memory in MCI.
David Baglietto-Vargas, Ines Moreno-Gonzalez, Raquel Sanchez-Varo, Sebastian Jimenez, Laura Trujillo-Estrada, Elisabeth Sanchez-Mejias, Manuel Torres, Manuel Romero-Acebal, Diego Ruano, Marisa Vizuete, Javier Vitorica, Antonia Gutierrez (Handling Associate Editor: Justo Garcia de Yebenes)
Calretinin Interneurons are Early Targets of Extracellular Amyloid-β Pathology in PS1/AβPP Alzheimer Mice Hippocampus
Abstract: Specific neuronal networks are preferentially affected in the early stages of Alzheimer's disease (AD). The distinct subpopulations of hippocampal inhibitory GABAergic system have been shown to display differential vulnerability to neurodegeneration in AD. We have previously reported a substantial loss of SOM/NPY interneurons, whereas those expressing parvalbumin were unaltered, in the hippocampus of 6 month-old PS1/AβPP transgenic mice. In the present study, we now investigated the pathological changes of hippocampal calretinin (CR) interneurons in this PS1/AβPP model from 2 to 12 months of age. The total number of CR-immunoreactive inhibitory cells was determined by stereology in CA1 and CA2/3 subfields. Our findings show a substantial decrease (35%-45%) of CR-positive interneurons in both hippocampal subfields of PS1/AβPP mice at very early age (4 months) compared to age-matched control mice. This decrease was accompanied by a reduced CR mRNA content as determined by quantitative RT-PCR. However, the number of another hippocampal CR-positive population (belonging to Cajal-Retzius cells) was not affected. The selective early loss of CR-interneurons was parallel to the appearance of extracellular Aβ deposits, preferentially in CR-axonal fields, and the formation of dystrophic neurites. This specific GABAergic subpopulation plays a crucial role in the generation of synchronous rhythmic activity in hippocampus by controlling other interneurons. Therefore, early alterations of hippocampal inhibitory functionality in AD, caused by select CR-cells neurodegeneration, could result in cognitive impairments seen in initial stages of the disease.
Jia-Min Zhuo and Domenico Praticò (Handling Associate Editor: M. Cristina Polidori)
Severe In Vivo Hyper-Homocysteinemia is not Associated with Amyloid-β Peptides Elevation in the Tg2576 Mice
Abstract: Since hyper-homocysteinemia (HHcy) was recognized as a risk factor for Alzheimer’s disease (AD), many studies tried to induce HHcy in animal models to investigate its effect on amyloid-β protein precursor (AβPP) metabolism. Previous reports found that HHcy induced in AD transgenic mouse models, by either methionine-enriched diet or vitamin Bs deficient diet feeding, is associated with elevation of amyloid-β (Aβ) levels. However, there is no data available on the effect of dietary intervention which combines both excessive methionine and low levels of vitamin Bs on amyloidogenesis in any of these models. In the current study, we investigated the effect of a combination diet, which was both enriched in methionine and deficient in folate, vitamin B6 and B12, in an AD mouse model, the Tg2576. We found that 7 months treatment of this diet induced severe HHcy in these mice with plasma homocysteine level higher than 150 μM. However, no difference was detected in brain Aβ levels or deposition between the diet-treated and control group. As shown by western blot, severe HHcy did not alter the steady state levels of proteins involved in AβPP metabolism, either. These results demonstrate that this combination diet-induced severe HHcy does not influence amyloidogenesis in vivo.
Jianghua Lu, Kaixuan Wang, Mariana Rodova, Raquel Esteves, Diana Berry, E. Lezi, Adam Crafter, Matthew Barrett, Sandra M. Cardoso, Isaac Onyango, W. Davis Parker, Joseph Fontes, Jeffrey M. Burns, Russell H. Swerdlow
Polymorphic Variation in Cytochrome Oxidase Subunit Genes
Abstract: Cytochrome oxidase (COX) activity varies between individuals and low activities associate with Alzheimer’s disease. Whether genetic heterogeneity influences function of this multimeric enzyme is unknown. To explore this we sequenced three mitochondrial DNA (mtDNA) and ten nuclear COX subunit genes from at least 50 individuals. 20% had non-synonymous mtDNA COX gene polymorphisms, 12% had a COX4I1 non-synonymous G to A transition, and other genes rarely contained non-synonymous polymorphisms. Frequent untranslated region (UTR) polymorphisms were seen in COX6A1, COX6B1, COX6C, and COX7A1; heterogeneity in a COX7A1 5` UTR Sp1 site was extensive. Synonymous polymorphisms were common and less frequent in the more conserved COX1 than the less conserved COX3, suggesting at least in mtDNA synonymous polymorphisms experience selection pressure and are not functionally silent. Compound gene variations occurred within individuals. To test whether variations could have functional consequences, we studied the COX4I1 G to A transition and an AGCCCC deletion in the COX7A1 5` UTR Sp1 site. Cells expressing the COX4I1 polymorphism had reduced COX Vmax activity. In reporter construct-transduced cells where green fluorescent protein expression depended on the COX7A1 Sp1 site, AGCCCC deletion reduced fluorescence. Our findings indicate COX subunit gene heterogeneity is pervasive and may mediate COX functional variation.
Lucrezia Hausner, Lutz Frölich, Virginie Gardette, Emma Reynish, Pierre-Jean Ousset, Sandrine Andrieu, Bruno Vellas, on behalf of the ICTUS-EADC study group
Regional Variation on the Presentation of Alzheimer’s Disease Patients in Memory Clinics within Europe: Data from the ICTUS Study
Abstract: This study set out to describe the variations within Europe for Alzheimer’s disease (AD) patients with regards to clinical and socio-demographic features, co-morbidities, drug treatment, and psychosocial care. 1,379 mild to moderate AD subjects from the ICTUS study were clustered into four geographic regions according to WHO-classification of European countries. Northern patients showed the mildest severity of dementia (MMSE: 21.6 ± 3.7, p<0.001), received the lowest rate of concomitant psychotropic drug treatment (24.3%, p<0.001), and appeared to be healthier than patients in the rest of Europe. Western subjects were diagnosed earliest (0.5 ± 0.9 month, p<0.001), received the highest rate of formal care (45.0%, p<0.001), and had the highest rates of antidementia drug treatment (60.4%, p<0.001). Southern subjects had the shortest education period (5.6 ± 4.0, p<0.001), the most severe cognitive decline in MMSE: 19.8 ± 4.0, p<0.001 and ADAScog: 24.2 ± 9.6, p<0.001 and received less antidementia drug treatment (37.6%; p<0.001), lived more often with their caregivers (74.4%, p<0.001), and had the highest caregiver burden (22.6 ± 15.2, p=0.049). Eastern AD subjects received more concomitant psychopharmacological drugs (68.6%, p<0.001), caregivers were more often different (18.6%, p<0.001) from spouse or offspring, caregiver burden was lowest (18.7 ± 12.4, p=0.049), nearly all subjects received only informal care (95.7%, p<0.001) and were affected more by co-morbidities. Overall, these data show differences in socio-demographic and clinical characteristics between AD patients from four European geographical regions. The presentation and management of AD in Europe appears to differ according to European regions and likely reflects differences in cultural factors and health politics.
Hai-Hong Wang, Hong-Lian Li, Rong Liu, Yao Zhang, Kai Liao, Qun Wang, Jian-Zhi Wang, Shi-Jie Liu (Handling Associate Editor: Xiongwei Zhu)
Tau Overexpression Inhibits Cell Apoptosis with the Mechanisms Involving Multiple Viability-Related Factors
Abstract: The formation of neurofibrillary tangles, mainly composed of hyperphosphorylated tau protein, is a hallmark in the brain of human tauopathies, including Alzheimer’s disease (AD). Although neurons bearing neurofibrillary tangles are constantly exposed to various apoptotic stimuli, they do not appear to preferentially die by apoptosis. The underlying mechanism for such resistance to apoptosis remains elusive. Previously, we studied the role of tau phosphorylation in apoptosis and found that tau hyperphosphorylation by glycogen synthase kinase-3 (GSK-3) rendered cells more resistant to apoptosis. In this study, we show that the overexpression of tau without any exogenous activation of kinases also confers increased resistance to apoptosis in both N2a cells and in a tau transgenic mouse model. Mechanistically, the overexpression of tau was associated with a reduced p53 level, decreased release of cytochrome C from mitochondria, and inhibition of caspases-9/-3. Additionally, a decreased phosphorylation and increased nuclear translocation of β-catenin were also detected in N2a/tau cells, and knockdown of β-catenin eliminated the anti-apoptotic effect of tau. Furthermore, tau was spontaneously hyperphosphorylated upon overexpression and by staurosporine treatment. The phosphorylation level of p53 decreased upon tau overexpression, and a more profound reduction of the phosphorylated p53 was detected when the cells were treated with lithium and roscovitine, inhibitors of GSK-3 and cyclin-dependent kinase-5 (Cdk-5). These results suggest that the overexpression of tau, which may be hyperphosphorylated by endogenous GSK-3 and Cdk-5, is anti-apoptotic by mechanisms involving modulation of multiple anti-apoptotic factors, including β-catenin and p53-mitochondria-caspase-mediated apoptotic pathways.
Mariavaleria Pellicanò, Matteo Bulati, Silvio Buffa, Mario Barbagallo, Anna Di Prima, Gabriella Misiano, Pasquale Picone, Marta Di Carlo, Domenico Nuzzo, Giuseppina Candore, Sonya Vasto, Domenico Lio, Calogero Caruso, Giuseppina Colonna Romano
Systemic Immune Responses in Alzheimer’s Disease: In Vitro Mononuclear Cell Activation and Cytokine Production
Abstract: To investigate the systemic signs of immune-inflammatory responses in Alzheimer’s disease (AD), in the present study we have analyzed blood lymphocyte subsets and the expression of activation markers on peripheral blood mononuclear cells (PBMCs) from AD patients and age-matched healthy controls (HC) activated in vitro by recombinant amyloid-β peptide (rAβ42). Our study of AD lymphocyte subpopulations confirms the already described decrease of the absolute number and percentage of B cells when compared to HC lymphocytes, whereas the other subsets are not significantly different in patients and controls. We report the increased expression of the activation marker CD69 and of the chemokine receptors CCR2 and CCR5 on T cells but no changes of CD25 after activation. B cells are also activated by rAβ42 as demonstrated by the enhanced expression of CCR5. Moreover, rAβ42 induces an increased expression of the scavenger receptor CD36 on monocytes. Some activation markers and chemokine receptors are overexpressed in unstimulated AD cells when compared to controls. This is evidence of the pro-inflammatory status of AD. Stimulation by rAβ42 also induces the production of the pro-inflammatory cytokines IL-1β, IL-6, IFN-g, and TNF-α, and of the anti-inflammatory cytokines IL-10 and IL-1Ra. The chemokines RANTES, MIP-1β, and eotaxin as well as some growth factors (GM-CSF, G-CSF) are also overproduced by AD-derived PBMC activated by rAβ42. These results support the involvement of systemic immunity in AD patients. However, our study is an observational one so we cannot draw a conclusion about its contribution to the pathophysiology of the disease.
Woojin Scott Kim, Surabhi Bhatia, David A. Elliott, Lotta Agholme, Katarina Kågedal, Heather McCann, Glenda M. Halliday, Kevin J. Barnham, Brett Garner
Increased ATP-Binding Cassette Transporter A1 Expression in Alzheimer’s Disease Hippocampal Neurons
Abstract: ATP-binding cassette transporter A1 (ABCA1) reduces amyloid-β burden in transgenic mouse models of Alzheimer’s disease (AD). Associations between ABCA1 polymorphisms and AD risk are also established. Little is known regarding the regulation of ABCA1 expression in the brain and how this may be affected by AD. In the present study we assessed ABCA1 mRNA and protein expression in the hippocampus of AD cases compared to controls. ABCA1 was clearly expressed in hippocampal neurons and expression was increased two- to three-fold in AD cases. The increased hippocampal ABCA1 expression was associated with increased APOE and PUMA gene expression, implying an association with neuronal stress. Consistent with this, treatment of SK-N-SH neurons with amyloid-β peptide resulted in a 48% loss in survival and a significant upregulation of ABCA1, APOE, and PUMA gene expression. Studies in young (2 month) and old (12 month) transgenic mice expressing a familial AD form of human amyloid-β protein precursor and presenilin-1 revealed a significant age-dependent upregulation of hippocampal Abca1 compared to wild-type control mice. However, hippocampal Apoe and Puma gene expression were not correlated with increased Abca1 expression in mice. Our data indicate that ABCA1 is upregulated in AD hippocampal neurons potentially via an amyloid-β-mediated pathway.
Scott E. Kanoski, Yanshu Zhang, Wei Zheng, Terry L. Davidson
The Effects of a High-Energy Diet on Hippocampal Function and Blood-Brain Barrier Integrity in the Rat
Abstract: Cognitive impairment and Alzheimer’s disease are linked with intake of a Western diet, characterized by high levels of saturated fats and simple carbohydrates. In rats, these dietary components have been shown to disrupt hippocampal-dependent learning and memory processes, particularly those involving spatial memory. Using a rat model, the present research assessed the degree to which consumption of a high-energy (HE) diet, similar to those found in modern Western cultures, produces a selective impairment in hippocampal function as opposed to a more global cognitive disruption. Learning and memory performance was examined following 90-day consumption of an HE-diet in three nonspatial discrimination learning problems that differed with respect to their dependence on the integrity of the hippocampus. The results showed that consumption of the HE-diet impaired performance in a hippocampal-dependent feature negative discrimination problem relative to chow-fed controls, whereas performance was spared on two discrimination problems that do not rely on the hippocampus. To explore the mechanism whereby consuming HE-diets impairs cognitive function, we investigated the effect of HE-diets on the integrity of the blood-brain barrier (BBB). We found that HE-diet consumption produced a decrease in mRNA expression of tight junction proteins, particularly Claudin-5 and -12, in the choroid plexus and the BBB. Consequently, an increased blood-to-brain permeability of sodium fluorescein was observed in the hippocampus, but not in the striatum and prefrontal cortex following HE-diet access. There results indicate that hippocampal function may be particularly vulnerable to disruption by HE-diets, and this disruption may be related to impaired BBB integrity.
Sindre Rolstad, Arto Nordlund, Carl Eckerström, Marie H. Gustavsson, Kaj Blennow, Pernille J. Olesen, Henrik Zetterberg, Anders Wallin
High Education May Offer Protection Against Tauopathy in Patients with Mild Cognitive Impairment
Abstract: The concepts of brain and cognitive reserve stem from the observation that premorbid factors (e.g., education) result in variation in the response to brain pathology. Potential early influence of reserve on pathology, as assessed using the cerebrospinal fluid biomarkers total tau and amyloid-β42, and cognition was explored in mild cognitive impairment (MCI) patients who remained stable over a two-year period. A total of 102 patients with stable MCI grouped on the basis of educational level were compared with regard to biomarker concentrations and cognitive performance. Stable MCI patients with higher education had lower concentrations of t-tau as compared to those with lower education. Also, educational level predicted a significant proportion of the total variance in t-tau concentrations. Our results suggest that higher education may offer protection against tauopathy.
Manjeet Singh, Ven Murthy, Charles Ramassamy
Modulation of Hydrogen Peroxide and Acrolein-Induced Oxidative Stress, Mitochondrial Dysfunctions and Redox Regulated Pathways by the Bacopa Monniera Extract: Potential Implication in Alzheimer’s Disease
Abstract: Acrolein is one of the by-products of lipid peroxidation. Due to its high reactivity, it is not only a marker of lipid peroxidation but could also be an initiator of oxidative stress by adducting cellular nucleophilic groups. In brains of Alzheimer’s disease (AD) patients, levels of acrolein are significantly higher in vulnerable brain region and, on primary hippocampal culture, it is more toxic than 4-hydroxyl-nonenal. The toxicity of the amyloid-β peptide is mediated through the generation of hydrogen peroxide (H2O2). The actions of H2O2 include oxidative modifications of proteins, lipids, and DNA as observed in AD. Bacopa monniera (BM) has a long history of use in India as a memory-enhancing therapy. The objective of our study was to investigate the neuroprotective effects of the standardized extracts of BM against acrolein and H2O2 and to elucidate the mechanisms underlying this protection. Our results show that a pre-treatment with the BM extract protected the human neuroblastoma cell line SK-N-SH against H2O2 and acrolein. We demonstrated that BM pre-treatment significantly inhibited the generation of intracellular reactive oxygen species in addition to preserving the mitochondrial membrane potential. BM pre-treatment also prevented the modifications of the activity of several redox regulated proteins, i.e., NF-κB, Sirt1, ERK1/2, and p66Shc, so as to favor cell survival in response to oxidative stress. Thus, our findings demonstrate that BM can protect human neuroblastoma cells against H2O2 and acrolein through different mechanisms involved in the pathophysiology of AD and could have a therapeutic application in the prevention of AD.
Anna V. Kamynina, Olga M. Volpina, Natalya I. Medvinskaya, Irina Ju. Aleksandrova, Tatyana D. Volkova, Dmitriy O. Koroev, Aleksandr N. Samokhin, Inna V. Nesterova, Irina V. Shelukhina, Elena V. Kryukova, Viktor I. Tsetlin, Vadim T. Ivanov, Natalya V. Bobkova
Vaccination with Peptide 173-193 of Acetylcholine Receptor α7-Subunit Prevents Memory Loss in Olfactory Bulbectomized Mice
Abstract: We studied the ability of four non-conjugated α7-subunit fragments of the nicotinic acetylcholine receptor to induce an immune response and to protect memory in olfactory bulbectomized mice which demonstrate abnormalities similar to Alzheimer’s disease (AD). Vaccination only with the α7-subunit fragment 173-193 was shown to rescue spatial memory, to restore the level of α7 acetylcholine receptors in the cortex, and to prevent an increase in the amyloid-β (Aβ) level in brain tissue in these animals. Antibodies against the peptide 173-193 were revealed in blood serum and cerebrospinal liquid in the bulbectomized mice. Passive immunization with mouse blood sera containing antibodies to the peptide 173-193 also restored memory in bulbectomized animals. The observed positive effect of both active and passive immunization with the fragment of α7-subunit on memory of bulbectomized mice provides a new insight into an anti-AD drug design.
Ji-Seon Seo, Yea-Hyun Leem, Kang-Woo Lee, Seung-Woo Kim, Ja-Kyeong Lee, Pyung-Lim Han
Severe Motor Neuron Degeneration in the Spinal Cord of the Tg2576 Mouse Model of Alzheimer Disease
Abstract: The transgenic mouse Tg2576 is widely used as a murine model of Alzheimer’s disease (AD) and exhibits plaque pathogenesis in the brain and progressive memory impairments. Here we report that Tg2576 mice also have severe spinal cord deficits. At 10 months of age, Tg2576 mice showed a severe defect in the hindlimb extension reflex test and abnormal body trembling and hindlimb tremors when suspended by the tail. The frequency and severity of these abnormalities were overt at 10 months of age and became gradually worsened. On the foot-printing analysis, Tg2576 mice had shorter and narrower strides than the non-transgenic control. Histological analyses showed that neuronal cells including cholinergic neurons in the lumbar cord of Tg2576 mice were severely reduced in number. At 16 months of age, Tg2576 mice showed high levels of amyloid-β accumulation in the spinal cord. Consistent with this, Tg2576 mice showed that lipid peroxidation levels were increased and mitochondrial metabolic activity were significantly reduced in the spinal cord. Administration of curcumin, a natural compound that has antioxidant properties, notably reversed motor function deficits of Tg2576 mice. The enhanced lipid peroxidation and neuronal loss in the lumbar cord was also partially suppressed by curcumin. Electron microscopic analysis revealed that the sciatic nerve fibers were severely reduced in number and were demyelinated in Tg2576 mice, which were partially rescued by curcumin. These results showed that Tg2576 mice display severe degeneration of motor neurons in the spinal cord and associated motor function deficits.
Supplementary Data for Seo et al. article (PDF)
Noemí Rueda, María Llorens-Martín, Jesús Flórez, Elsa Valdizán, Pradeep Banerjee, Jose Luis Trejo, Carmen Martínez-Cué
Memantine Normalizes Several Phenotypic Features in the Ts65Dn Mouse Model of Down Syndrome
Abstract: Ts65Dn (TS) mice exhibit several phenotypic characteristics of human Down syndrome, including an increased brain expression of amyloid-β protein precursor (AβPP) and cognitive disturbances. Aberrant N-methyl-D-aspartate (NMDA) receptor signaling has been suspected in TS mice, due to an impaired generation of hippocampal long-term potentiation (LTP). Memantine, an uncompetitive NMDA receptor antagonist approved for the treatment of moderate to severe Alzheimer’s disease, is known to normalize LTP and improve cognition in transgenic mice with high brain levels of AβPP and amyloid-β protein. It has recently been demonstrated that acute injections of memantine rescue performance deficits of TS mice on a fear conditioning test. Here we show that oral treatment of aged TS mice with a clinically relevant dose of memantine (30 mg/kg/day for 9 weeks) improved spatial learning in the water maze task and slightly reduced brain AβPP levels. We also found that TS mice exhibited a significantly reduced granule cell count and vesicular glutamate transporter-1 (VGLUT1) labeling compared to disomic control mice. After memantine treatment, the levels of hippocampal VGLUT1 were significantly increased, reaching the levels observed in vehicle treated-control animals. Memantine did not significantly affect granule cell density. These data indicate that memantine may normalize several phenotypic abnormalities in TS mice, many of which—such as impaired cognition—are also associated with Down syndrome and Alzheimer’s disease.
Nathalie Le Bastard, Judith Leurs, Walter Blomme, Peter Paul De Deyn, Sebastiaan Engelborghs (Handling Associate Editor: Sanna-Kaisa Herukka)
Plasma Amyloid-β Forms in Alzheimer’s Disease and Non-Alzheimer’s Disease Patients
Abstract: The objective of this study was to evaluate the diagnostic performance of full-length and N-truncated plasma amyloid-β (Aβ) forms in patients with Alzheimer’s disease (AD) and non-Alzheimer’s disease dementia (non-AD) as compared to healthy control subjects. Plasma samples from 50 AD, 50 non-AD, and 47 control subjects were included and analyzed using a multiparameter fluorimetric bead-based immunoassay for the simultaneous quantification of different Aβ forms. No significant differences in Aβ isoforms were detected between dementia and controls; or AD, non-AD, and controls. Compared to control subjects, pooled dementia patients (AD and non-AD) and AD patients alone had significantly lower plasma Aβ1-42/AβN-42 ratios. In each diagnostic group, all plasma Aβ concentrations were significantly correlated. No significant correlations between plasma Aβ forms and age were found. The low diagnostic performance of cross-sectional plasma Aβ measurements hampers future application as diagnostic markers or screening tools for dementia. CSF biomarker analysis remains superior, although the possible application of longitudinal plasma Aβ measurements as screening tools for dementia remains to be elucidated.
Verena Poetsch, Winfried Neuhaus, Christian Roland Noe (Handling Associate Editor: William Banks)
Serum-Derived Immunoglobulins Neutralize Adverse Effects of Amyloid-β Peptide on the Integrity of a Blood-Brain Barrier In Vitro Model
Abstract: A disrupted blood-brain barrier (BBB) might have major effects on the progression of Alzheimer’s disease (AD). This supports the theory of blood as a chronic source of exogenous amyloid-β (Aβ) peptide as well as other neurotoxic substances in the brain, which would normally be excluded by an intact BBB. In addition to Aβ, neuroinflammation is suggested to contribute to the pathological conditions in AD and is a known disruptor of BBB integrity. Consequently, new therapeutic approaches to stabilize the BBB should be developed. Serum derived immunoglobulins, also called intravenous immunoglobulins (IVIG), are gained from plasma of healthy individuals and were found to induce positive effects in some patients with AD, but mechanisms of action are unclear by now. Moreover, there are no data on how IVIG affects the BBB itself. Therefore, we examined the potency of Aβ peptides as well as neuroinflammatory mediators (TNF-α and LPS) either alone or after simultaneous application of IVIG to disintegrate the BBB by evaluating the transport rate of Carboxyfluorescein, a marker of paracellular leakage. Our results showed beneficial effects of IVIG on a disrupted BBB, which could positively influence diseases outcome in AD. With a stabilized BBB, systemic Aβ, as well as from other toxic substances from the blood, are prevented from entering the brain.
Meeting Report from the Alzheimer Research Forum
The 7th Leonard Berg Symposium, Part 3