20, Number 1, April 2010
George Perry and Mark A. Smith
William R. Markesbery, M.D.: A Tribute
D. Allan Butterfield
William R. Markesbery, M.D.: A Legacy of Excellence in Alzheimer’s Disease Research and a Life Well-Lived
Yuri I. Arshavsky
Why Alzheimer’s Disease Starts with a Memory Impairment: Neurophysiological Insight
Abstract: Alzheimer’s disease is a neurodegenerative disease whose sole initial symptom is memory impairment. However, the mechanisms which make the neurons involved in learning and memory particularly vulnerable to the formation of amyloid plaques and neurofibrillary tangles remain completely unknown. Here, I propose a hypothesis that may resolve this puzzle. A growing body of evidence suggests that memory formation involves epigenetic mechanisms that regulate patterns of gene expression. Therefore, it is conceivable that the process of memory consolidation may include the synthesis of novelproteins that are recognized by the immune system as “non-self” antigens. Normally, neurons involved in formation and storage of memory are isolated from the organism’s immune system by the blood-brain barrier. Since all known genetic and environmental risk factors for Alzheimer’s disease can compromise this barrier, I hypothesize that the disease is initiated as an autoimmune reaction against the memory-bearing neurons. This reaction gradually makes these neurons vulnerable to the subsequent formation of amyloid plaques and neurofibrillary tangles. This hypothesis suggests that early therapy of Alzheimer’s disease could be devoted to preventing impairments in the blood-brain barrier. Recent evidence that formation of the blood-brain barrier is controlled via the Wnt/β-catenin signaling pathway may suggest potential directions to addressing this problem.
Vincenza Frisardi, Vincenzo Solfrizzi, Cristiano Capurso, Patrick G Kehoe, Bruno P. Imbimbo, Andrea Santamato, Flora Dellegrazie, Davide Seripa, Alberto Pilotto, Antonio Capurso, Francesco Panza
Aluminum in the Diet and Alzheimer’s Disease: From Current Epidemiology to Possible Disease-Modifying Treatment
Abstract: In recent years, interest in the potential role of metals in the pathogenesis of Alzheimer’s disease (AD) has grown considerably. In particular, aluminum (Al) neurotoxicity was suggested after its discovery in the senile plaques and neurofibrillary tangles that represent the principal neuropathological hallmarks of AD. Al is omnipresent in everyday life and can enter the human body from several sources, most notably from drinking water and food consumption. The evidence supporting association from ingestion of Al from drinking water is somewhat stronger than for its ingestion from food. However, other elements present in drinking water, such as fluoride, copper, zinc, or iron could also have an effect on cognitive impairment or modify any Al neurotoxicity. Some epidemiological studies, but not all, suggested that silica could be protective against Al damage, because it reduced oral absorption of Al and/or enhanced Al excretion. Some epidemiological investigations suggested an association between chronic exposure to Al and risk of AD, although this relationship falls short of all the criteria generally attributed to causation. Future studies need to be more rigorous to truly test the validity of previous findings and in doing so attempt to identify dose-response relationships between Al and AD risk which may provide new routes to disease-modifying treatment of AD or possibly some lifestyle modification, to supplement existing symptomatic approaches.
Jacqueline C. Mitchell, Michael S. Perkinton, Darran M. Yates, Kwok-Fai Lau, Boris Rogelj, Christopher C.J. Miller*, Declan M. McLoughlin* (Handling Associate Editor: Thomas Shea) *These authors contributed equally.
Expression of the Neuronal Adaptor Protein X11α Protects Against Memory Dysfunction in a Transgenic Mouse Model of Alzheimer’s Disease
Abstract: X11α is a neuronal-specific adaptor protein that binds to the amyloid-β protein precursor (AβPP). Overexpression of X11α reduces Aβ production but whether X11α also protects against Aβ-related memory dysfunction is not known. To test this possibility, we crossed X11α transgenic mice with AβPP-Tg2576 mice. AβPP-Tg2576 mice produce high levels of brain Aβ and develop age-related defects in memory function that correlate with increasing Aβ load. Overexpression of X11α alone had no detectable adverse effect upon behavior. However, X11α reduced brain Aβ levels and corrected spatial reference memory defects in aged X11α/AβPP double transgenics. Thus, X11α may be a therapeutic target for Alzheimer’s disease.
Benedetta Nacmias, Andrea Tedde, Silvia Bagnoli, Ersilia Lucenteforte, Elena Cellini, Irene Piaceri, Bianca Maria Guarnieri, Valentina Bessi, Laura Bracco, Sandro Sorbi
Lack of Implication for CALHM1 P86L Common Variation in Italian Patients with Early and Late Onset Alzheimer’s Disease
Abstract: A recent study identified a polymorphism (Pro86Leu) in the Calcium homeostasis modulator 1 (CALHM1) gene whose minor Leucine allele showed a higher frequency in Alzheimer’s disease (AD) patients compared to controls (29% in AD and 22% in controls). Further studies provided conflicting results in different ethnic groups. In order to assess the involvement of the CALHM1 genetic variant on the risk of developing AD, we analyzed the genotype and allele distributions of the Pro86Leu polymorphism in 758 Italian subjects. Our results did not confirm an association between the CALHM1 variation and AD, thus suggesting a genetic heterogeneity among the various populations.
Paola Piscopo, Giuseppina Talarico, Alessio Crestini, Marina Gasparini, Lorenzo Malvezzi-Campeggi, Elisa Piacentini, Gian Luigi Lenzi, Giuseppe Bruno, Annamaria Confaloni (Handling Associate Editor: Amalia Bruni)
A Novel Mutation in the Predicted TM3 Domain of the PSEN2 Gene in an Italian Pedigree with Atypical Alzheimer’s Disease
Abstract: Alzheimer’s disease (AD) is characterized by accumulation of toxic amyloid-β (Aβ) in the brain, with neuronal death, and an associated increased Aβ42/40 ratio. Several mutations in presenilin1 (PSEN1), presenilin 2 (PSEN2), and amyloid-β protein precursor are involved in the etiology of familial AD (FAD); these mutations alter the Aβ42/40 ratio and promote apoptosis. We describe an Italian pedigree linked to a novel mutation (S175C) at the third transmembrane domain of PSEN2. Clinical phenotype in these individuals is characterized by fast cognitive decline with progressive memory impairment, early involvement of executive functions, behavioral disturbances, and extrapyramidal signs.
Michelle T. Fodero-Tavoletti, Victor L.Villemagne, Brett M. Paterson, Anthony R. White, Qiao-Xin Li, James Camakaris, Graeme O’Keefe, Roberto Cappai, Kevin J. Barnham, Paul S. Donnelly
Bis(thiosemicarbazonato) Cu-64 Complexes for Positron Emission Tomography Imaging of Alzheimer’s Disease
Abstract: A bis(thiosemicarbazonato) complex radiolabeled with positron emitting Cu-64 can be used for a new and alternative method for the non-invasive diagnosis of Alzheimer’s disease using positron emission tomography (PET). Most imaging agents being investigated for the diagnosis of Alzheimer’s disease target plaque burden but our new approach highlights altered copper homeostasis. This approach has the potential to offer complementary information to other diagnostic procedures that elucidate plaque burden.
Nanditha G. Nair, George Perry, Mark A. Smith, V. Prakash Reddy (Handling Editor: Jesus Avila)
NMR Studies of Zinc, Copper, and Iron Binding to Histidine, the Principal Metal Ion Complexing Site of Amyloid-β Peptide
Abstract: Amyloid-β (Aβ), the major component of senile plaques in Alzheimer’s disease, is known to complex transition metal ions mainly through histidine residues. In this study, using 1H NMR titration experiments, we show that histidine binds strongly to Zn(II), Cu(II), and Fe(III) ions at a biologically relevant pH (pH 7.4), with a stoichiometry of Zn(II):histidine binding of 1:2. The observed deshielding of the chemical shifts and relative line broadening indicate that Fenton-active Cu(II) and Fe(III) bind to histidine relatively more efficiently as compared to Zn(II). Parallel studies showed that glutamic acid and aspartic acid are relatively inefficient in metal ion binding. From these studies, we suggest that Aβ-chelated Zn(II) is readily displaced by Cu(II) and Fe(III) ions and leads to a propagation of oxidative stress.
Margherita Di Paola, Gianfranco Spalletta, Carlo Caltagirone (Handling Associate Editor: Cindy Carlsson)
In Vivo Structural Neuroanatomy of Corpus Callosum in Alzheimer’s Disease and Mild Cognitive Impairment Using Different MRI Techniques: A Review
Abstract: The corpus callosum (CC), which connects the two cerebral hemispheres, is the largest white matter fiber bundle in the human brain. This structure presents a peculiar myelination pattern; it has small diameter fibers, located in the genu, which myelinate much later in normal development, and large diameter fibers of the splenium, which myelinate early in development. Although the pathology of AD mainly involves the cerebral gray matter structure, there is evidence that white matter may also be involved. To illustrate callosal white matter changes in AD pathology, in this review we summarize in vivo imaging studies in humans, focusing on region of interest, voxel-based morphometry, diffusion-weighted imaging, and diffusion tensor imaging techniques. Our aims were to identify where in the CC, when in the different stages of AD, and how callosal changes can be detected with different MRI techniques. Results showed that changes in the anterior (genu and anterior body) as well as in the posterior (isthmus and splenum) portions of the CC might already be present in the early stages of AD. These findings support the hypothesis that two mechanisms, Wallerian degeneration and myelin breakdown, might be responsible for the region-specific changes detected in AD patients. Wallerian degeneration affects the posterior CC subregion, which receives axons directly from those brain areas (temporo-parietal lobe regions) primarily affected by the AD pathology. Instead, the myelin breakdown process affects the later-myelinating CC subregion and explains the earlier involvement of the genu in CC atrophy.
Cristina Lanni, Marco Racchi, Serena Stanga, Giuliano Mazzini, Alberto Ranzenigo, Renzo Polotti, Maurizio Memo, Stefano Govoni, Daniela Uberti
Unfolded Blood p53 as Predictive Signature from Mild Cognitive Impairment to Alzheimer’s Disease
Abstract: Mild cognitive impairment (MCI) is a syndrome defined as cognitive decline, but not sufficient to meet the criteria for any specific dementia. Although subjects with MCI may have an increased risk to develop AD, this clinical state encompasses several subtypes of cognitive dysfunction of different etiologies, none of which necessarily progresses to AD. The current inability of clinical criteria to accurately identify this at-risk group for AD development is fuelling the interest in biomarkers able to supplement clinical approaches. We recently described a blood-based cytofluorimetric method for conformationally altered p53 protein detection that allows the discrimination of AD patients from control subjects and patients affected by other dementias. The same protein also predicted progression to AD in preclinical patients with MCI two years before clinical diagnosis of AD was made. Herein, we describe these findings and discuss the potential of the test in diagnosing AD.
Matthew J. Sharman*, Guanghou Shui*, Aaron Z. Fernandis, Wei Ling F. Lim, Tamar Berger, Eugene Hone, Kevin Taddei, Ian J. Martins, Jorge Ghiso, Joseph D. Buxbaum, Sam Gandy, Markus R. Wenk, Ralph N. Martins *Authors contributed equally to this work.
Profiling Brain and Plasma Lipids in Human APOE ε2, ε3, and ε4 Knock-in Mice Using Electrospray Ionization Mass Spectrometry
Abstract: It is known that apolipoprotein E (ApoE) is essential for normal lipid metabolism. ApoE is the major apolipoprotein in the central nervous system and plays a key role in neurobiology by mediating the transport of cholesterol, phospholipids, and sulfatides. We therefore examined APOE ε2, ε3, and ε4 knock-in mice, using electrospray ionization mass spectrometry to determine if APOE genotype or age leads to altered levels in the brain of a number of glycerophospholipids (phosphatidylinositol, PI; phosphatidylethanolamine, PE; phosphatidic acid, PA, phosphatidylserine, PS; phosphatidylcholine, PC), sphingolipids (sphingomyelin, SM; ceramide, Cer), cholesterol, and triacylglycerols. We observed slight changes within individual PI, PE, PC, Cer, and SM lipid levels in APOE ε2 and ε4 mice compared to APOE ε3 mice. However, overall, we did not observe any major effects in APOE ε4 knock-in mice for the levels of the glycerophospholipids measured, as compared to APOE ε2 and ε3 mice. Our findings indicate that variations in ApoE isoforms do not per se affect bulk lipid homeostasis in the brain. These findings indicate that APOE ε4 is not associated with disturbances in brain sterol or sphingolipids in the absence of environmental factors.
Wanda Carolina Leon*, Fabio Canneva*, Vanessa Partridge, Simon Allard, Maria Teresa Ferretti, Arald DeWilde, Freya Vercauteren, Ramtin Atifeh, Adriana Ducatenzeiler, William Klein, Moshe Szyf, Leena Alhonen, A. Claudio Cuello *equally contributed to the experimental work
A Novel Transgenic Rat Model with a Full Alzheimer’s-Like Amyloid Pathology Displays Pre-Plaque Intracellular Amyloid-β-Associated Cognitive Impairment
Abstract: Alzheimer’s disease (AD) is a neurodegenerative pathology in which amyloid-β (Aβ) peptide accumulates in different brain areas leading to deposition of plaques and a progressive decline of cognitive functions. After a decade in which a number of transgenic (Tg) mouse models mimicking AD-like amyloid-deposition pathology have been successfully generated, few rat models have been reported that develop intracellular and extracellular Aβ accumulation, together with impairment of cognition. The generation of a Tg rat reproducing the full AD-like amyloid pathology has been elusive. Here we describe the generation and characterization of a new transgenic rat line, coded McGill-R-Thy1-APP, developed to express the human amyloid-β precursor protein (AβPP) carrying both the Swedish and Indiana mutations under the control of the murine Thy1.2 promoter. The selected mono-transgenic line displays an extended phase of intraneuronal Aβ accumulation, already apparent at 1 week after birth, which is widespread throughout different cortical areas and the hippocampus (CA1, CA2, CA3, and dentate gyrus). Homozygous Tg animals eventually produce extracellular Aβ deposits and, by 6 months of age, dense, thioflavine S-positive, amyloid plaques are detected, associated with glial activation and surrounding dystrophic neurites. The cognitive functions in transgenic McGill-R-Thy1-APP rats, as assessed using the Morris water maze task, were found already altered as early as at 3 months of age, when no CNS plaques are yet present. The spatial cognitive impairment becomes more prominent in older animals (13 months), where the behavioral performance of Tg rats positively correlates with the levels of soluble Aβ (trimers) measured in the cortex.
Supplementary Data for Leon et al. article (PDF)
Pravat K Mandal, Virgil Simplaceanu, Vincenzo Fodale
Intravenous Anesthetic Diazepam Does Not Induce Amyloid-β Peptide Oligomerization but Diazepam Co-administered with Halothane Oligomerizes Amyloid-β Peptide: An NMR Study
Abstract: Amyloid-β peptide (Aβ) oligomerization has a profound role in Alzheimer’s disease pathophysiology. Biophysical studies have shown that smaller sized inhaled anesthetics promote oligomerization by inducing perturbation of three critical amino acid residues (G29, A30, and I31) located in the helix-loop-helix domain of Aβ. In this present experimental study, using state-of-the-art nuclear magnetic resonance, we have monitored the influence of a larger sized intravenous anesthetic, diazepam, as well as diazepam co-administered with halothane, on Aβ. It was concluded that diazepam (in isolation) does not interact with the G29, A30, and I31 residues, and no Aβ oligomerization occurs in the presence of 0.101 mM diazepam, even after 63 days. However, when diazepam was co-administered with halothane, profound Aβ oligomerization is observed. These results strengthen the hypothesis that the presence of smaller molecular sized anesthetic is instrumental in promoting Aβ oligomerization even when co-administered with a larger sized anesthetic, namely diazepam.
Karthikeyan Balakrishnan, Luminita-Cornelia Andrei-Selmer, Thorsten Selmer, Michael Bacher, Richard Dodel
Comparison of Intravenous Immunoglobulins for Naturally Occurring Autoantibodies against Amyloid-β
Abstract: Intravenous immunoglobulins (IVIG) are currently used for therapeutic purposes in autoimmune disorders. Recently, we demonstrated the presence of naturally occurring antibodies against amyloid-β (nAbs-Aβ) within the pool of IVIG. In this study, we compared different brands of IVIG for nAbs-Aβ and have found differences in the specificity of the nAbs-Aβ towards Aβ1-40 and Aβ1-42. We analyzed the influence of a pH-shift over the course of antibody storage using ELISA and investigated antibody dimerization at acidic and neutral pH as well as differences in the IgG subclass distributions among the IVIG using both HPLC and a nephelometric assay. Furthermore, we investigated the epitope region of purified nAbs-Aβ. The differences found in Aβ specificity are not directly proportionate to the binding nature of these antibodies when administered in vivo. This information, however, may serve as a guide when choosing the commercial source of IVIG for therapeutic applications in Alzheimer’s disease.
Ze-Fen Wang, Jun Yin, Yao Zhang, Ling-Qiang Zhu, Qing Tian, Xiao-Chuan Wang, Hong-Lian Li and Jian-Zhi Wang (Handling Associate Editor: Xiongwei Zhu)
Overexpression of Tau Proteins Antagonizes Amyloid-β-Potentiated Apoptosis Through Mitochondria-Caspase-3 Pathway in N2a Cells
Abstract: It has been a puzzle why the tangle-bearing neurons in Alzheimer’s disease (AD) brain do not die preferentially of apoptosis even though they are actually challenged by multiple proapoptotic factors. Recently, we have reported that phosphorylation of tau can antagonize apoptosis induced by exogenous apoptotic inducers. Amyloid-β (Aβ), a recognized endogenous proapoptotic factor, is significantly increased in the AD brains, however, it is not known whether tau could abate the Aβ-potentiated apoptosis. Here, we observed that the cells bearing high level of Aβ were more vulnerable than the controls to H2O2-induced apoptosis, and this effect of Aβ was associated with decrease of Bcl-2, elevation of Bax and cytosolic cytochrome-c, as well as activation of caspase-3, suggesting that Aβ could potentiate the oxidant-induced cell apoptosis with involvement of mitochondria-caspase-3 pathway. More importantly, we also found that expression of tau that became hyperphosphorylated could reduce the Aβ-potentiated apoptosis with simultaneous preservation of Bcl-2 and suppression of Bax, cytosolic cytochrome-c, and caspase-3 activity, implying that overexpression of tau that became hyperphosphorylated can attenuate the Aβ-potentiated cell apoptosis through mitochondria-caspase-3 pathway. These findings provide an explanation of the chronic nature of neurodegeneration of neurons with neurofibrillary pathology of abnormal hyperphosphorylated tau in AD and related tauopathies.
Bruno P. Imbimbo, Luciana Giardino, Sandra Sivilia, Alessandro Giuliani, Marco Gusciglio, Vladimiro Pietrini, Elda Del Giudice, Antonello D'Arrigo, Alberta Leon, Gino Villetti, Laura Calzà (Handling Associate Editor: Patrizia Mecocci)
CHF5074, a Novel γ-Secretase Modulator, Restores Hippocampal Neurogenesis Potential and Reverses Contextual Memory Deficit in a Transgenic Mouse Model of Alzheimer’s Disease
Abstract: The effects of compounds interfering with γ-secretase, the enzymatic complex responsible of the formation of the amyloid-β (Aβ) peptide from amyloid-β protein precursor (AβPP), on plaque deposition in transgenic mouse models of Alzheimer’s disease are known but scanty data are available on the effects of these drugs on brain plasticity. We evaluated the effects of long-term treatment with CHF5074, a new γ-secretase modulator, on hippocampal neurogenesis, cortical synaptophysin levels, and contextual memory in transgenic mice carrying the double Swedish mutation of AβPP (Tg2576). Six-month old Tg2576 mice were treated with CHF5074 (375 ppm in the diet) up to 15 months of age. Age-matched control transgenic and wild-type mice received standard diet. Compared to wild-type animals, transgenic controls showed a significant decrease in the number of doublecortin-positive neuroblasts in dentate gyrus, synaptophysin intensity in the cortex, freezing to context in the contextual fear conditioning test. Compared to transgenic controls, CHF5074 treatment of Tg2576 mice resulted in a significant attenuation of the neurogenesis impairment in hippocampus (p=0.036), normalization of synaptophysin levels in cortex (p<0.001), attenuation of plaque burden in the cortex (p=0.033), increases astroglial reaction around plaques (p=0.001), and attenuation of activated microglia (p=0.040). These effects were associated to a complete reversal of contextual memory deficit (p=0.006). Contextual memory significantly correlated with synaptophysin immunoreactivity in the cortex (r=0.548, p=0.0038).
Katie Palmer, Fulvia Di Iulio, Ambra Erika Varsi, Walter Gianni, Giuseppe Sancesario, Carlo Caltagirone, Gianfranco Spalletta
Neuropsychiatric Predictors of Progression from Amnestic-Mild Cognitive Impairment to Alzheimer’s Disease: The Role of Depression and Apathy
Abstract: The aim of the study is to evaluate whether depression or apathy in patients with amnestic-mild cognitive impairment (MCI) increases the risk of progressing to Alzheimer’s disease (AD). We investigated 131 consecutive memory-clinic outpatients with newly-diagnosed amnestic-MCI (mean age 70.8, SD=6.5). Psychiatric disorders were diagnosed at baseline according to the criteria for depression and apathy in AD. Neuropsychiatric symptoms were assessed with the Neuropsychiatric Inventory (NPI). Follow-up examinations were conducted after six months and annually for four years. Neurologists diagnosed AD at follow-up using NINCDS-ADRDA criteria. Cox proportional hazard models with 95% confidence intervals were used to test the hypothesis that apathy or depression increases the risk of developing AD. At baseline, 36.6% amnestic-MCI patients had a diagnosis of depression and 10.7% had apathy. Patients with both amnestic-MCI and an apathy diagnosis had an almost sevenfold risk of AD progression compared to amnestic-MCI patients without apathy (HR=6.9; 2.3-20.6), after adjustment for age, gender, education, baseline global cognitive and functional status, and depression. Furthermore, the risk of developing AD increased 30% per point on the NPI apathy item (HR=1.3; 1.1-1.4). There was no increased risk of developing AD in amnestic-MCI patients with either a diagnosis or symptoms of depression. In conclusion, apathy, but not depression, predicts which patients with amnestic-MCI will progress to AD. Thus, apathy has an important impact on amnestic-MCI and should be considered a mixed cognitive/psychiatric disturbance related to ongoing AD neurodegeneration.
John H. Dougherty Jr., Rex L. Cannon, Christopher R. Nicholas, Lorin Hall, Felicia Hare, Erika Carr, Andrew Dougherty, Jennifer Janowitz, Justin Arunthamakun
The Computerized Self Test (CST): An Interactive, Internet Accessible Cognitive Screening Test For Dementia
Abstract: The computer self test (CST) is an interactive, internet-based instrument designed to assess functional cognitive domains impaired by Alzheimer’s disease (AD) and mild cognitive impairment (MCI). This study consisted of 215 total subjects with a mean age of 75.24. The 84 cognitively impaired patients (excluding patients diagnosed as MCI) met all criteria set forth by NINCDS/ADRDA for the diagnosis of AD. Control participants consisted of 104 age-matched individuals who were cognitively unimpaired. All patients completed the CST prior to other routine neurocognitive procedures. The CST accurately classified 96% of the cognitively impaired individuals as compared to controls, while the Mini-Mental Status Examination (MMSE) accurately classified 71% and the Mini-Cog 69% in the same respect. In addition, the CST accurately classified 91% of the six experimental groups (control, MCI, early AD, mild to moderate, moderate to severe, and severe) as compared to 54% for the MMSE and 48% for the Mini-Cog. In conclusions, the CST demonstrates a high degree of sensitivity and specificity and is capable of accurately identifying cognitive impairment in patients with variable degrees of cognitive abnormality. This interactive internet-based cognitive screening tool may aid in early detection of cognitive impairment in the primary care setting. The ease of use and interpretation may also provide the means to obtain an accurate baseline from which to monitor cognitive changes over time.
Bram Meeus, Karen Nuytemans, David Crosiers, Sebastiaan Engelborghs, Karin Peeters, Maria Mattheijssens, Ellen Elinck, Ellen Corsmit, Peter Paul De Deyn, Christine Van Broeckhoven, Jessie Theuns
Comprehensive Genetic and Mutation Analysis of Familial Dementia with Lewy Bodies Linked to 2q35-q36
Abstract: The second most frequent form of neurodegenerative dementia after Alzheimer’s disease is dementia with Lewy bodies (DLB). Since informative DLB families are scarce, little is presently known about the molecular genetic etiology of DLB. We recently mapped the first locus for DLB on chromosome 2q35-q36 in a multiplex Belgian family, DR246, with autopsy-proven DLB pathology in a region of 9.2 Mb. Here, we describe the ascertainment of additional DR246 family members and significant finemapping of the DLB locus to 3.3 Mb based on informative meiotic recombinants. Extensive sequencing of the 42 positional candidate genes within the DLB region did not identify a simple pathogenic mutation that co-segregated with disease in family DR246. Also high resolution analysis of copy number variations in the DLB locus did not provide evidence for a complex mutation. In conclusion, we confirmed the DLB locus at 2q35-q36 as a genetic entity but candidate gene-based sequencing and copy number variation analysis did not identify the pathogenic mutation in family DR246. Other detection strategies will be needed to reveal the underlying mutation explaining the linkage of DLB to 2q35-q26. Possibly the disease mutation in this family acts through a more complex mechanism than generally envisaged for monogenic disorders. Nevertheless, identifying the first familial DLB gene is likely to contribute an entry point into the pathogenic cascades underlying DLB pathology.
Supplementary Data for Meeus et al. article (PDF)
Paola De Bartolo*, Debora Cutuli*, Laura Ricceri, Francesca Gelfo, Francesca Foti, Daniela Laricchiuta, Maria Luisa Scattoni, Gemma Calamandrei, Laura Petrosini *contributed equally to this work. (Handling Associate Editor: Sigfrido Scarpa)
Does Age Matter? Behavioral and Neuro-anatomical Effects of Neonatal and Adult Basal Forebrain Cholinergic Lesions
Abstract: The “cholinergic hypothesis” of dementia posits that progressive loss of basal forebrain cholinergic neurons and consequent decrease of acetylcholine levels in the deafferented projection sites are correlated with degree of cognitive decline in dementia. It has also been proposed that early dysfunction of the basal forebrain (BF) cholinergic system may be a risk factor for subsequent cognitive decline and possibly dementia. To characterize how age when BF cholinergic system is lesioned affects behavioral performances and morphology of neocortical neurons, seven-day-old rats were bilaterally i.c.v. injected with 192 IgG-saporin. In adulthood, these animals were subjected to spatial and associative tests. Subsequently, the morphology of parietal pyramidal neurons was assessed. The same behavioral and morphological evaluations were made in 80-day-old rats tested three weeks after bilateral i.c.v. injections of 192 IgG-saporin. The behavioral consequences of both cholinergic depletions were markedly similar. While both groups of lesioned animals exhibited very subtle deficits in the Morris water maze, they were significantly impaired in spatial discrimination in the open field and the radial maze. Paralleling behavioral data, the results of the morphological analysis revealed comparable increases in number and density of spines in apical and basal dendrites in layer-III parietal pyramidal neurons following both neonatal and adult cholinergic depletions. The present results demonstrate that the consequences of abnormal maturation of the cholinergic system are not substantially different from those evoked by cholinergic dysfunction in adulthood and provide a developmental psychobiological perspective of the neuronal foundations of the impaired cognitive functions.
Silvia García-Matas, Núria de Vera, Arantxa Ortega Aznar, Josep M. Marimon, Albert Adell, Anna M. Planas, Rosa Cristòfol, Coral Sanfeliu (Handling Associate Editor: Gemma Casadesus)
In Vitro and In Vivo Activation of Astrocytes by Amyloid-β is Potentiated by Pro-Oxidant Agents
Abstract: Alzheimer’s disease (AD) is a devastating age-related neurodegenerative disease. Age is main risk factor for sporadic AD, which is the most prevalent type. Amyloid-β peptide (Aβ) neurotoxicity is the proposed first step in a cascade of deleterious events leading to AD pathology and dementia. Glial cells play an important role in these changes. Astrocytes provide vital support to neurons and modulate functional synapses. Therefore, the toxic effects of Aβ on astrocytes promote neurodegenerative changes that might lead to AD. Aging reduces astrocyte antioxidant defense and induces oxidative stress. We studied the effects of Aβ42 on cultures of human astrocytes in the presence or absence of the following pro-oxidant agents: buthionine sulfoximine (BSO), a glutathione synthesis inhibitor, and FeSO4, which liberates redox active iron. Pro-oxidant conditions potentiated Aβ toxicity, as shown by the generation of free radicals, inflammatory changes, and apoptosis. A similar treatment was assayed in rats in vivo. A combination of Aβ40 and Aβ42 or Aβ42 alone was infused intracerebroventricularly for 4 weeks. Other animal groups were also infused with BSO and FeSO4. A long-term analysis that ended 4 months later showed higher cognitive impairment in the Morris water maze task, which was induced by Aβ plus pro-oxidant agent treatments. Pro-oxidant agents also potentiate brain tissue pathology. This was demonstrated in histological studies that showed highly increased astrocyte reactivity in AD-vulnerable areas, Aβ deposits, and oxidative damage of AD-sensitive hippocampal neurons. To increase understanding of AD, experimental models should be used that mimic age-related brain changes, in which age-related oxidative stress potentiates the effects of Aβ.
Mercè Boada, Carmen Antúnez, Jesús López-Arrieta, José Jorge Galán, Francisco J. Morón, Isabel Hernández, Juan Marín, Pablo Martínez-Lage, Montserrat Alegret, Jose M. Carrasco, Concha Moreno, Luis M. Real, Antonio González-Pérez, Lluís Tárraga, Agustín Ruiz (Handling Associate Editor: Weixiong Zhang)
CALHM1 P86L Polymorphism is Associated with Late-Onset Alzheimer’s Disease in a Recessive Model
Abstract: CALHM1 gene coding non-synonymous SNP P86L (rs2986017) was reported to increase the risk of Alzheimer’s disease (AD) in a recent study. We have investigated this genetic variant in 2470 individuals from Spain to conduct an independent replication study of the proposed SNP marker. By applying a recessive model, we observed weak evidence of an association between P86L mutation and late-onset AD (LOAD) susceptibility in our case-control study (OR=1.38 C.I.=[1.01-1.89]). Meta-analysis of available studies also supports a recessive model for CALHM1 P86L variant and provides evidence of between study heterogeneity. Importantly, we found that adjusted mean age at AD onset in P86L homozygous LOAD patients was significantly earlier that in the rest of patients (77.06 ± 6 for P86L homozygous carriers versus 79.03 ± 6 for the rest of patients, p=0.002). We concluded that the CALMH1 gene may contribute to AD risk in our study population. The observed genetic model (recessive) and the estimated magnitude of the effect both imply that virtually all studies performed to date were markedly underpowered to detect this effect and underscore the importance of follow up, replication, and meta-analyses of promising genetic signals.
Sandra D. Mulder, Wiesje M. van der Flier, Jan H. Verheijen, Cees Mulder, Philip Scheltens, Marinus A. Blankenstein, C. Erik Hack, Robert Veerhuis (Handling Associate Editor: Henrik Zetterberg)
BACE1 Activity in Cerebrospinal Fluid and Its Relation to Markers of AD Pathology
Abstract: Several studies have shown that reduced amyloid-β 1-42 (Aβ42) and increased tau levels in cerebrospinal fluid (CSF) reflect increased Alzheimer’s disease (AD) pathology in the brain. β-site AβPP cleaving enzyme (BACE1) is thought to be the major β-secretase involved in Aβ production in the brain, and therefore we investigated the relation between BACE1 activity and CSF markers Aβ40, Aβ42, total tau (t-tau), and tau phosphorylated at threonine 181 (p-tau) in CSF of control (n=12), mild cognitive impairment (n=18), and AD (n=17) subjects. Patients were classified according to their Aβ42, t-tau, and p-tau CSF biomarker levels, with either an AD-like biomarker profile (two or three biomarkers abnormal: Aβ42 < 495 pg/ml in combination with t-tau > 356 pg/ml, and/or p-tau > 54 pg/ml) or a normal biomarker profile (≤ one biomarker abnormal). This resulted in 19 subjects with an AD-like biomarker profile (66 ± 6 years, 53% female, and Mini-Mental Status Examination (MMSE) score: 23 ± 5) and 28 subjects with a normal biomarker profile (62 ± 11 years, 43% female, and MMSE score: 27 ± 4). Subjects with an AD-like biomarker profile had higher CSF BACE1 activity levels, compared to patients with a normal biomarker profile (20 pg/ml and 16 pg/ml respectively; p=0.01), when controlled for age and gender. In the whole sample, BACE1 activity correlated with CSF levels of Aβ40, t-tau, and p-tau (r=0.38, r=0.63, and r=0.65; all p<0.05), but not with Aβ42. These data suggest that increased BACE1 activity in CSF relates to AD pathology in the brain.
Haifeng Jin, Nobuo Sanjo, Toshiki Uchihara, Kazuhiko Watabe, Peter St. George-Hyslop, Paul E. Fraser, Hidehiro Mizusawa
Presenilin-1 Holoprotein is an Interacting Partner of Sarco Endoplasmic Reticulum Calcium-ATPase and Confers Resistance to Endoplasmic Reticulum Stress
Abstract: Presenilin-1 (PSEN1) is a primary component of the γ-secretase complex, and total levels of its holoprotein and endoproteolytic fragments are tightly regulated. We examined the effects of several types of endoplasmic reticulum (ER) stress on quantitative changes in the levels of PSEN1 mRNA, holoprotein, and fragments. The ER stress-inducing chemical compounds tunicamycin, brefeldin-A, thapsigargin, and staurosporine were added to the culture media of various human cell lines. Tunicamycin treatment caused a doubling of PSEN1 holoprotein production in HEK293 cells and an increase in holoprotein production to approximately 180% in GOTO human neuroblastoma and KNS-42 human glioma cell lines, without changing the amounts of PSEN1 N- or C-terminal fragments. The elevated holoprotein level in HEK293 cells was accompanied by an increase in PSEN1 mRNA expression. HEK293 cells that stably overexpressed PSEN1 holoprotein showed increased resistance to ER stress induced by tunicamycin, but they did not show resistance to ER stress caused by thapsigargin, a specific inhibitor of sarco ER calcium-ATPase (SERCA). In wild-type HEK293 cells under ER stress induced by tunicamycin, an increased amount of SERCA interacted with PSEN1 holoprotein. PSEN1 production varied among cell types and circumstances. The results suggested that the holoprotein forms a complex with the SERCA channel and participates in the regulation of intracellular calcium homeostasis. These findings provide support for the calcium hypothesis of Alzheimer’s disease.
Supplementary Data for Jin et al. article (PDF)
Mithu Raychaudhuri and Debashis Mukhopadhyay
Grb2-Mediated Alteration in the Trafficking of AβPP: Insights from Grb2-AICD Interaction
Abstract: The amyloid-β protein precursor (AβPP) is processed by various proteases located along the endosomal lysosomal pathway and any alteration in its trafficking would be important in the pathogenesis of Alzheimer’s disease (AD). Our current study is based on the clinical evidence that an AβPP intracellular domain (AICD) “adaptor” protein, growth factor receptor protein binding protein 2 (Grb2), gets concentrated in neuronal cell bodies in AD patients. Here we show that both endogenous and exogenously transfected Grb2 interact with AβPP in Neuro 2A cells. Endogenous Grb2 partially co-localizes to late endosomal compartments along with AβPP and AICD. Increase in the concentration of Grb2 confines it in enlarged late endosomes leading to more sequestration of AβPP and AICD within these compartments. This confinement of AβPP due to Grb2 overexpression affects its turnover by inhibiting its release via exosomal vesicles. As a consequence, the level of intracellular AβPP and AICD increases. The effect of Grb2 overexpression has been verified by knocking down Grb2 as well as by overexpressing Grb2 in Grb2 knocked down cells. Having established the Grb2-mediated trafficking of AICD and its impairment, the significance of its consequence has now become apparent in the downstream events of AD pathogenesis.
Supplementary Data for Raychaudhuri and Mukhopadhyay article (PDF)
Chengxuan Qiu, Weili Xu, Bengt Winblad, Laura Fratiglioni
Vascular Risk Profiles for Dementia and Alzheimer’s Disease in Very Old People: A Population-Based Longitudinal Study
Abstract: Numerous studies have linked individual vascular factors to dementia including Alzheimer’s disease (AD). We investigated different vascular risk profiles in relation to dementia and AD among very old people. A standardized follow-up procedure was applied three times to a dementia-free cohort (n=1270, age ≥ 75) over a nine-year period to detect dementia and AD cases using the DSM-III-R criteria. We examined two vascular risk profiles, which were scored by counting the number of corresponding vascular factors: 1) atherosclerotic profile included systolic pressure ≥160 mmHg, diabetes/prediabetes, and stroke; and 2) cerebral hypoperfusion profile constituted diastolic pressure <70 mmHg, pulse pressure <70 mmHg, and heart failure. Data were analyzed with Cox proportional-hazards models controlling for major potential confounders. During the 6406 person-years of follow-up, 428 subjects developed dementia, including 328 AD cases. All components of vascular profiles were significantly or marginally associated with increased dementia risk. The risk of dementias was increased with increasing score of both risk profiles (p for trend ≤0.001); subjects with a score ≥2 in either profile had an approximately twofold-increased risk for dementia and AD. These data suggest that aggregation of atherosclerotic- and hypoperfusion-related vascular factors increases the risk of dementia in very old people. Severe cerebral atherosclerosis and insufficient perfusion are involved in the development of dementia including AD.
Jeffrey Cummings, Murat Emre, Dag Aarsland, Sibel Tekin, Nalina Dronamraju, Roger Lane (Handling Associate Editor: Sandrine Andrieu)
Effects of rivastigmine in Alzheimer’s disease patients with and without hallucinations
Abstract: Hallucinations in Alzheimer’s disease (AD) may indicate greater cortical cholinergic deficits. Rivastigmine has shown larger treatment benefits versus placebo in dementia with Lewy bodies and Parkinson’s disease dementia patients with hallucinations. In this retrospective, hypothesis-generating analysis, we investigated whether hallucinations in AD were associated with greater treatment benefits with rivastigmine. Data were pooled from two randomized, double-blind, 6-month, mild-to-moderate AD trials comparing rivastigmine with placebo. Co-primary efficacy parameters were the Alzheimer Disease Assessment Scale-cognitive subscale (ADAS-cog) and Clinician’s Interview-Based Impression of Change plus Caregiver Input (CIBIC-plus). Efficacy data were analyzed for two subpopulations: those with and those without hallucinations at baseline. Of 927 patients, 194 (21%) reported hallucinations at baseline. Hallucinators tended to have greater decline on placebo on all outcome measures. On the ADAS-cog, mean rivastigmine–placebo differences of 3.7 points in hallucinators and 2.2 points in non-hallucinators were reported at 6 months (both p<0.001). In hallucinators, a significant rivastigmine–placebo difference of -1.0 points (a beneficial effect) was seen on the CIBIC-plus at 6 months (p<0.001). Non-hallucinators showed a smaller significant treatment difference of -0.3 points (p<0.05). Interaction testing suggested that differences in treatment effects were significant between hallucinators and non-hallucinators. Hallucinations predicted greater treatment responses to oral rivastigmine.
Natalia Loskutova, Robyn A. Honea, William M. Brooks, Jeffrey M. Burns
Low Volumes of Limbic Grey Matter and the Hypothalamus Correlate with Low Bone Density in Early Alzheimer’s Disease
Abstract: Accelerated bone loss is associated with Alzheimer’s disease (AD). Although the central nervous system plays a direct role in regulating bone mass, primarily through the actions of the hypothalamus, there is little work investigating the possible role of neurodegeneration in bone loss. In this cross-sectional study, we examined the association between bone mineral density (BMD) and neuroimaging markers of neurodegeneration (i.e., global and regional measures of brain volume) in early AD and non-demented aging. Fifty-five non-demented and 63 early AD participants underwent standard neurological and neuropsychological assessment, structural MRI scanning, and dual energy x-ray absorptiometry. In early AD, voxel-based morphometry analyses demonstrated that low BMD was associated with low volume in limbic grey matter (GM) including the hypothalamus, cingulate, and parahippocampal gyri and in the left superior temporal gyrus and left inferior parietal cortex. No relationship between BMD and regional GM volume was found in non-demented controls. The hypothesis-driven region of interest analysis further isolating the hypothalamus demonstrated a positive relationship between BMD and hypothalamic volume after controlling for age and gender in the early AD group but not in non-demented controls. These results demonstrate that lower BMD is associated with lower hypothalamic volume in early AD, suggesting that central mechanisms of bone remodeling may be disrupted by neurodegeneration.
Wei Zheng, Tao Wang, Dan Yu, Wan-Yu Feng, Ying-Xue Nie, Meredin Stoltenberg, Gorm Danscher, Zhan-You Wang (Handling Associate Editor: Ashley Bush)
Elevation of Zinc Transporter ZnT3 Protein in the Cerebellar Cortex of the AβPP/PS1 Transgenic Mouse
Abstract: The presence of senile plaques containing abundant amyloid-β (Aβ) peptide is one of the major pathological hallmarks of Alzheimer’s disease (AD). Recent studies support the notion that overexpression of zinc transporters (ZnT) is involved in zinc metabolic disturbances and Aβ aggregation in AD brains. Here we present data showing an elevated expression of zinc transporter 3 (ZnT3) protein, revealed by immunoblotting assay, in the cerebellum of the amyloid-β protein precursor (AβPP)/presenilin 1 (PS1) transgenic mouse. Confocal microscopic and autometallographic results showed that ZnT3 immunofluorescence and zinc ions were predominantly located in the amyloid plaques. ZnT3 protein was abundantly distributed throughout the plaques, whereas zinc ions were mainly located in the peripheral parts of rosette-shaped plaques with a lightly stained center. Collectively, our results suggest that ZnT3 protein is involved in the Aβ aggregation in the cerebellum of the AβPP/PS1 mouse.
George Bartzokis, Po H. Lu, Todd A. Tishler, Douglas G. Peters, Anastasia Kosenko, Katherine A. Barrall, J. Paul Finn, Pablo Villablanca, Gerhard Laub, Lori L. Altshuler, Daniel H. Geschwind, Jim Mintz, Elizabeth Neely, James R. Connor (Handling Associate Editor: Christopher Exley)
Prevalent Iron Metabolism Gene Variants Associated with Increased Brain Ferritin Iron in Healthy Older Men
Abstract: Prevalent gene variants involved in iron metabolism [hemochromatosis (HFE) H63D and transferrin C2 (TfC2)] have been associated with higher risk and earlier age at onset of Alzheimer’s disease (AD), especially in men. Brain iron increases with age, is higher in men, and is abnormally elevated in several neurodegenerative diseases, including AD and Parkinson’s disease, where it has been reported to contribute to younger age at onset in men. The effects of the common genetic variants (HFE H63D and/or TfC2) on brain iron were studied across eight brain regions (caudate, putamen, globus pallidus, thalamus, hippocampus, white matter of frontal lobe, genu, and splenium of corpus callosum) in 66 healthy adults (35 men, 31 women) aged 55 to 76. The iron content of ferritin molecules (ferritin iron) in the brain was measured with MRI utilizing the Field Dependent Relaxation Rate Increase (FDRI) method. 47% of the sample carried neither genetic variant (IRON-) and 53% carried one and/or the other (IRON+). IRON+ men had significantly higher FDRI compared to IRON- men (p=0.013). This genotype effect was not observed in women who, as expected, had lower FDRI than men. This is the first published evidence that these highly prevalent genetic variants in iron metabolism genes can influence brain iron levels in men. Clinical phenomena such as differential gender-associated risks of developing neurodegenerative diseases and age at onset may be associated with interactions between iron genes and brain iron accumulation. Clarifying mechanisms of brain iron accumulation may help identify novel interventions for age-related neurodegenerative diseases.
Meeting Report from the Alzheimer Research Forum
The Society for Neuroscience 2009 Meeting Report, Part 3