19, Number 3, February 2010
Mary Ann DeMichele-Sweet, Robert A. Sweet
Genetics of Psychosis in Alzheimer’s Disease: A Review
Abstract: In and of itself, late-onset Alzheimer’s disease (AD) can be a devastating illness. However, a sub-group of AD patients develop psychosis as the disease progresses. These patients have an added burden of greater cognitive impairment, higher rates of institutionalization, and higher mortality than AD patients without psychosis. While the etiopathogenesis of psychosis in AD (AD+P) is not known, mounting evidence accrued over the past ten years indicates that AD+P represents a distinct phenotype with a genetic basis. Elucidating the genetic mechanism of AD+P is crucial if better pharmaceutical treatments are to be developed for these patients. The goal of this review is to summarize what is currently known regarding the genetic basis of psychosis in AD. Specific attention is given to familial aggregation and heritability, linkage to chromosomal loci, and associations of candidate genes of APOE and the monoamine neurotransmitter system.
Liam D. Kaufman, Jay Pratt, Brian Levine, Sandra E. Black
Antisaccades: A Probe Into the Dorsolateral Prefrontal Cortex in Alzheimer’s Disease. A Critical Review
Abstract: The number of people living with Alzheimer’s disease (AD), the major cause of dementia, is projected to increase dramatically over the next few decades, making the search for treatments and tools to measure the progression of AD increasingly urgent. The antisaccade task, a hands- and language-free measure of inhibitory control, has been utilized in AD as a potential diagnostic test. While antisaccades do not appear to differentiate AD from healthy aging better than measures of episodic memory, they may still be beneficial. Specifically, antisaccades may provide not only a functional index of the Dorsolateral Prefrontal Cortex (DLPFC), which is damaged in the later stages of AD, but also a tool for monitoring the progression of AD. Further work is required to: 1) strengthen the link between antisaccade errors, in AD, with the DLPFC; 2) insure that antisaccade errors do not result from memory, visuospatial, or other deficits associated with AD; and 3) further validate the clinical analogue of the antisaccade task.
Roy C.Y. Choi, Judy T.T. Zhu, K. Wing Leung, Glanice K.Y. Chu, Heidi Q. Xie, Vicky P. Chen, Ken Y.Z. Zheng, David T.W. Lau, Tina T.X. Dong, Peter C.Y. Chow, Yi-Fan Han, Zheng-Tao Wang, Karl W.K. Tsim *contributed equally to the work
A Flavonol Glycoside, Isolated From Roots of Panax notoginseng, Reduces Amyloid-β-Induced Neurotoxicity in Cultured Neurons: Signaling Transduction and Drug Development for Alzheimer’s Disease
Abstract: A Radix Notoginseng flavonol glycoside (RNFG), quercetin 3-O-β-D-xylopyranosyl-β-D-galactopyranoside, was isolated from roots of Panax notoginseng. Among different biological properties being tested, RNFG possessed a strong activity in preventing amyloid-β (Aβ)-induced cell death. In an in vitro assay, RNFG inhibited the aggregation of Aβ in a dose-dependent manner. Moreover, application of RNFG in cultured cortical neurons, or PC12 cells, reduced the Aβ-induced cell death in time- and dose-dependent manners, with the suppression of Aβ-induced DNA fragmentation and caspase-3 activation. In cultured neurons, the pre-treatment of RNFG abolished the increase of Ca2+ mobilization triggered by the aged Aβ. The neuroprotective properties of RNFG required a specific sugar attachment within the main chemical backbone because the flavonol backbone by itself did not show any protective effect. In the memory impairment experiment using passive avoidance task, the administration of RNFG reduced the brain damage in scopolamine-treated rats. These results therefore reveal a novel function of Radix Notoginseng and its flavonol glycoside that could be very useful in developing food supplements for prevention, or potential drugs, for treating Alzheimer’s disease.
Yuen-Shan Ho, Man-Shan Yu, Xi-Fei Yang, Kwok-Fai So, Wai-Hung Yuen, Raymond Chuen-Chung Chang
Neuroprotective Effects of Polysaccharides from Wolfberry, the Fruits of Lycium barbarum, Against Homocysteine-induced Toxicity in Rat Cortical Neurons
Abstract: Previous clinical and epidemiological studies have suggested that elevated plasma homocysteine (Hcy) level increased the risk of Alzheimer’s disease (AD). Although the underlying mechanisms of its toxicity are elusive, it has been shown that Hcy damages neurons by inducing apoptosis, DNA fragmentation, and tau hyperphosphorylation. Wolfberry (Lycium barbarum) is a fruit that is known for its eye-protective and anti-aging properties in Asian countries. Previous studies from our laboratory have demonstrated that polysaccharides derived from wolfberry (LBA) have the ability to protect neurons from amyloid-β (Aβ) peptide neurotoxicity. We hypothesize that the neuroprotective effects of wolfberry is not limited to Aβ and can also provide protection against other AD risk factors. In this study, we aim to elucidate the neuroprotective effects of wolfberry against Hcy-induced neuronal damage. Our data showed that LBA treatment significantly attenuated Hcy-induced neuronal cell death and apoptosis in primary cortical neurons as demonstrated by LDH and caspase-3 like activity assay. LBA also significantly reduced Hcy-induced tau phosphorylation at tau-1 (Ser198/199/202), pS396 (Ser396), and pS214 (Ser214) epitopes as well as cleavage of tau. At the same time, we also found that the phosphorylation level of p-GSK3β (Ser9/Tyr 216) remained unchanged among different treatment groups at all detected time points. LBA treatment suppressed elevation of both p-ERK and p-JNK. In summary, our data demonstrated that LBA exerted neuroprotective effects on cortical neurons exposed to Hcy. Therefore, LBA has the potential to be a disease-modifying agent for the prevention of AD.
Lina Ji, Abha Chauhan and Ved Chauhan
Upregulation of Cytoplasmic Gelsolin, an Amyloid-β-Binding Protein, Under Oxidative Stress Conditions: Involvement of Protein Kinase C
Abstract: We have previously reported that gelsolin, an actin binding protein, regulates the fibrillization of amyloid-β protein. We report here that the expression of cytoplasmic gelsolin (c-gelsolin) was upregulated in a concentration-dependent manner when SH-SY5Y, PC-12, and HEK-293 cells were subjected to oxidative stress by treatment with hydrogen peroxide (H2O2). Further studies were done to elucidate the mechanism involved in the regulation of c-gelsolin expression in cells. Pretreatment of cells with cycloheximide (an inhibitor of protein synthesis) resulted in significant inhibition of H2O2-induced c-gelsolin expression, suggesting the possible de novo synthesis of c-gelsolin in cells. Staurosporine, a potent inhibitor of a variety of protein kinases including protein kinase C (PKC), also blocked the H2O2-induced expression of c-gelsolin. However, both H2O2 and staurosporine activated the mitogen-activated protein kinases (MAPKs), i.e., c-Jun N-terminal kinase, P38, and extracellular signal-regulated kinase. Pretreatment of cells with Calphostin C, an inhibitor of PKC, blocked the upregulation of c-gelsolin induced by H2O2, while specific inhibitors of MAPKs had no effect on c-gelsolin expression, suggesting that MAPKs may not be involved in H2O2-mediated upregulation of c-gelsolin. On the other hand, phorbol-12-myristate-13-acetate, an activator of PKC, induced the expression of c-gelsolin. Our studies indicate that c-gelsolin is upregulated in cells under oxidative stress, and PKC is involved in its upregulation. It is suggested that activators of PKC that induce gelsolin expression may have therapeutic significance in Alzheimer’s disease.
Juliana N. Souza-Talarico, Eliane C. Chaves, Sonia J. Lupien, Ricardo Nitrini, Paulo Caramelli
Relationship Between Cortisol Levels and Memory Performance may be Modulated by the Presence or Absence of Cognitive Impairment: Evidence from Healthy Elderly, Mild Cognitive Impairment and Alzheimer’s Disease Subjects
Abstract: An inverted U-shape function between cortisol levels and memory performance has been reported in studies on both young animals and humans. Yet little is known about this relationship in normal aging or in older subjects with cognitive impairment. This issue is particularly significant since increased levels of cortisol have been reported in Alzheimer’s disease (AD). The present study examined the association between cortisol levels and visual memory performance in healthy subjects as well as in individuals presenting mild cognitive impairment (MCI) or AD. Salivary cortisol was measured in 40 healthy elderly subjects, 31 individuals with amnestic MCI, and 40 subjects with mild probable AD. Memory performance was evaluated using the Brief Cognitive Screening Battery. Higher cortisol levels were associated with better memory performance in healthy elderly (p = 0.005), while higher cortisol levels were correlated with poorer memory performance in MCI subjects (p = 0.011). No correlation between cortisol and memory was found in the AD group (p > 0.05). These results suggest that the relationship between cortisol levels and memory performance in the aging process could vary according to the presence or absence of cognitive impairment.
Lan-Jian Zhang*, Yan Xiao*, Xiao-Lan Qi, Ke-Ren Shan, Jin-jing Pei, Shi-Xiang Kuang, Fang Liu, Zhi-Zhong Guan (Communicated by Chengxin Gong) *Contributed equally to this work.
Cholinesterase Activity and mRNA Level of Nicotinic Acetylcholine Receptors (α4 and β2 Subunits) in Blood of Elderly Chinese Diagnosed as Alzheimer’s Disease
Abstract: The aim of the study is to investigate the cholinergic deficit in Alzheimer’s disease (AD) and identify candidate blood biomarkers for the diagnosis of the disease. Twenty-nine elderly Chinese diagnosed with AD and 33 age-matched controls were selected. The activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in plasma were detected by a spectrophotometric method, and the mRNA levels of α4 and β2 nicotinic acetylcholine receptor (nAChR) subunits in blood leukocytes were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). The results showed that AChE activity in plasma was significantly lower in the AD group than in normal controls, while BuChE activity did not show any differences between AD and controls; mRNA levels of both α4 and β2 nAChR subunits in blood leukocytes were significantly lower in the AD group than in controls. The AChE activity and the mRNA levels of α4 and β2 nAChR subunits in the AD patients were also significantly correlated with cognitive test scores. No differences of AChE in plasma or α4 and β2 nAChR subunits in blood leukocytes were detected between smoking and non-smoking subjects. The results indicated that the decreases in the activity of AChE and in the mRNA levels of nAChR α4 and β2 subunits from the peripheral blood of patients with AD might serve as supplementary indicators for the clinical diagnosis of AD.
Claudio Babiloni, Giovanni B Frisoni, Fabrizio Vecchio, Michela Pievani, Cristina Geroldi, Charles De Carli, Raffaele Ferri, Fabrizio Vernieri, Roberta Lizio, Paolo M. Rossini (Communicated by Silvia Pellegrini)
Global Functional Coupling of Resting EEG Rhythms is Related to White-Matter Lesions Along the Cholinergic Tracts in Subjects with Amnesic Mild Cognitive Impairment
Abstract: We tested the hypothesis that global functional coupling of resting cortical electroencephalographic (EEG) rhythms is abnormal in amnesic mild cognitive impairment (MCI) patients with remarkable lesions along the cholinergic white-matter tracts. We used the eyes-closed resting EEG data (10-20 montage) of the same groups of 28 healthy elderly (Nold) and 57 MCI subjects of a previous reference study. The estimation of the cholinergic lesion was performed with a validated semi-automatic algorithm based on fluid-attenuated inversion recovery sequences on MRI. The MCI patients were divided into groups of high (MCI+; n=29) and low (MCI-; n=28) cholinergic damage. EEG rhythms of interest were delta (2-4Hz), theta (4-8Hz), alpha1 (8-10.5Hz), alpha2 (10.5-13Hz), beta1 (13-20Hz), beta2 (20-30Hz), and gamma (30-40Hz). The global functional coupling of the EEG rhythms was indexed computing the spectral coherence between each electrode and the other 18 electrodes (“electrode” coherence) and then averaging the “electrode” coherence of all 19 electrodes (total coherence). Total coherence of alpha1 rhythms was highest in the Nold, intermediate in the MCI-, and lowest in the MCI+ groups. Furthermore, the alpha1 total coherence was negatively correlated to (moderate to high) cholinergic lesion across the MCI subjects. In conclusion, damage to the cholinergic system is associated with alterations of the functional global coupling of resting alpha rhythms.
Estrella Gómez-Tortosa, Sagrario Barquero, Manuel Barón, Eulogio Gil-Neciga, Fernando Castellanos, Martín Zurdo, Sagrario Manzano, David G. Muñoz, Adolfo Jiménez-Huete, Alberto Rábano, M. José Sainz, Rosa Guerrero, Isabel Gobernado, Julián Pérez-Pérez, Adriano Jiménez-Escrig
Clinical-Genetic Correlations in Familial Alzheimer’s Disease Caused by Presenilin 1 Mutations
Abstract: We describe the clinical phenotype of nine kindred with presenile Alzheimer’s disease (AD) caused by different presenilin 1 (PS1) point mutations, and compare them with reported families with mutations in the same codons. Mutations were in exon 4 (Phe105Val), exon 5 (Pro117Arg, Glu120Gly), exon 6 (His163Arg), exon 7 (Leu226Phe), exon 8 (Val261Leu, Val272Ala, Leu282Arg), and exon 12 (Ile439Ser). Three of these amino acid changes (Phe105Val, Glu120Gly, and Ile439Ser) had not been previously reported in these positions. Distinct clinical features, including age of onset, symptoms and signs associated with the cortical-type dementia and aggressiveness of the disease, characterized the different mutations and were quite homogeneous across family members. Age of onset fell within a consistent range: some mutations caused the disease in the thirties (P117R, L226F, V272A), other in the forties (E120G, H163R, V261L, L282R), and other in the fifties (F105V, I439S). Associated features also segregated with specific mutations: early epileptic activity (E120G), spastic paraparesis (V261L), subcortical dementia and parkinsonism (V272A), early language impairment, frontal signs, and myoclonus (L226F), and late myoclonus and seizures (H163R, L282R). Neurological deterioration was particularly aggressive in PS1 mutations with earlier age of onset such as P117R, L226F, and E120G. With few exceptions, a similar clinical phenotype was found in families reported to have either the same mutation or different amino acid changes in the same codons. This series points to a strong influence of the specific genetic defect in the development of the clinical phenotype.
Belen Tizon, Elena M. Ribe, Weiqian Mi, Carol M. Troy, Efrat Levy (Communicated by Luciano D’Adamio) *Contributed equally to this work.
Cystatin C Protects Neuronal Cells from Amyloid-β-induced Toxicity
Abstract: Multiple studies suggest that cystatin C (CysC) has a role in Alzheimer’s disease (AD) and a decrease in CysC secretion is linked to the disease in patients with a polymorphism in the CysC gene. CysC binds amyloid-β (Aβ) and inhibits formation of Aβ fibrils and oligomers both in vitro and in mouse models of amyloid deposition. Here we studied the effect of CysC on cultured primary hippocampal neurons and a neuronal cell line exposed to either oligomeric or fibrillar cytotoxic forms of Aβ. The extracellular addition of the secreted human CysC together with preformed either oligomeric or fibrillar Aβ increased cell survival. While CysC inhibits Aβ aggregation, it does not dissolve preformed Aβ fibrils or oligomers. Thus, CysC has multiple protective effects in AD, by preventing the formation of the toxic forms of Aβ and by direct protection of neuronal cells from Aβ toxicity. Therapeutic manipulation of CysC levels, resulting in slightly higher concentrations than physiological could protect neuronal cells from cell death in AD.
Vincenzina Nicolia, Andrea Fuso, Rosaria A. Cavallaro, Andrea Di Luzio, Sigfrido Scarpa
B Vitamin Deficiency Promotes Tau Phosphorylation Through Regulation of GSK3β and PP2A
Abstract: Neurofibrillary tangles (NFTs), composed of intracellular filamentous aggregates of hyperphosphorylated protein tau, are one of the pathological hallmarks of Alzheimer’s disease (AD). Tau phosphorylation is regulated by the equilibrium between activities of its protein kinases and phosphatases; unbalance of these activities is proposed to be a reasonable causative factor to the disease process. Glycogen synthase kinase 3β (GSK3β) is one of the most important protein kinase in regulating tau phosphorylation; overexpression of active GSK3β causes AD-like hyperphosphorylation of tau. Protein phosphatase 2A (PP2A) is the major phosphatase that dephosphorylates tau; it was demonstrated that highly conserved carboxyl-terminal sequence of PP2A C-subunit is a focal point for phosphatase regulation. This is the site of a reversible methyl esterification reaction that controls ABαC heterotrimers formation. Here we demonstrate that GSK3β and PP2A genes were upregulated by inhibiting methylation reactions through by B vitamins deficiency. In this condition, methylated catalytic subunit PP2Ac was decreased, leading to reduced PP2A activity. By contrast, we observed GSK3β protein increase and a modulation in phosphorylation sites that regulate GSK3β activity. Therefore, one-carbon metabolism alteration seems to be a cause of deregulation of the equilibrium between GSK3β and PP2A, leading to abnormal hyperphosphorylated tau.
Emilio Di Maria, Sergio Cammarata, Maria Isola Parodi, Roberta Borghi, Luisa Benussi, Marialaura Galli, Daniela Galimberti, Roberta Ghidoni, Davide Gonella, Cristina Novello, Valeria Pollero, Lucia Perroni, Patrizio Odetti, Elio Scarpini, Giuliano Binetti, Massimo Tabaton
The H1 Haplotype of the Tau Gene (MAPT) is Associated with Mild Cognitive Impairment
Abstract: Mild cognitive impairment is often considered a transitional condition prodromal to Alzheimer’s disease. The dissection of genetic risk factors predisposing to mild cognitive impairment is paramount to assess the individual predisposition and reliably evaluate the effectiveness of early therapeutic interventions. We designed a cross-sectional analysis to test whether the occurrence of mild cognitive impairment is influenced by variations of the tau protein gene. The genotypes of seven polymorphisms tagging the major tau haplotypes were assayed on 186 patients with amnestic mild cognitive impairment and 191 unrelated controls. Association study was conducted by logistic regression including APOE genotype and age as covariates. Case-control analysis showed that the common H1 haplotype is significantly overrepresented in patients (OR, 95% CI: 2.31, 1.52-3.51; p<0.001), whereas did not provide positive signals for any of the H1 sub-haplotypes that had been described as associated with Alzheimer’s disease. This finding was confirmed when the ε4 allele of the APOE gene was taken into account (OR, 95% CI: 2.319, 1.492-3.603; p<0.001). These results firstly suggest that the risk of mild cognitive impairment is influenced by tau protein gene variations and that mild cognitive impairment shares a common genetic background with Alzheimer’s disease. They may help elucidating the genetic risk to cognitive decline and designing effective clinical trials.
Balu Chakravarthy, Chantal Gaudet, Michel Ménard, Trevor Atkinson, Leslie Brown, Frank M. LaFerla, Ubaldo Armato, James Whitfield
Amyloid-β Peptides Stimulate the Expression of the p75NTR Neurotrophin Receptor in SH-SY5Y Human Neuroblastoma Cells and AD Transgenic Mice
Abstract: The progression toward end-stage Alzheimer’s disease (AD) in the aging brain is driven by accumulating amyloid-β (Aβ)1-42 oligomers that is accompanied by the downregulation of the Trk A neurotrophin receptor and by either upregulation or at least maintenance of the p75 neurotrophin receptor (p75NTR), which can be stimulated by the accumulating Aβ1-42 peptides. Here we show that Aβ1-42 and its active fragment Aβ25-35, but not Aβ42-1, can at least double the level of p75NTR receptors in the membranes of model SH-SY5Y human neuroblastoma cells. We also show that p75NTR is upregulated in the hippocampi of two strains of AD transgenic mice. Specifically, the level of the p75NTR receptor in the hippocampal membranes from 12-15 month-old AD-triple transgenic mice (3xTg-AD) harboring PS1M146V, AβPPSwe, and tau P301L was nearly twice that in hippocampal membranes from age-matched wild-type mice. Similarly, the level of p75NTR receptor in 7 month-old B6.Cg-Tg AD mice harboring PSEN1dE9 and AβPPSwe was also increased above the level in the corresponding wild-type mice. This increase correlated with the age-dependent rise in Aβ1-42 levels in the AD mice. Thus, it appears that it could be the accumulating Aβ1-42 that increases or at least prevents the downregulation of p75NTR receptors in key parts of AD brains. It is possible that when the Aβ1-42 accumulation reaches a critical level in the brain on the way to late-onset AD, the Aβ1-42-induced p75NTR receptor signaling starts a vicious cycle that accelerates AD development because of the activated receptors’ recently shown ability to stimulate Aβ1-42 production.
Xiuli Yuan, Baoci Shan, Yunchuan Ma, Jiahe Tian, Kaida Jiang, Qiuyun Cao, Ruimin Wang (Communicated by Jianzhi Wang)
Multi-Center Study on Alzheimer’s Disease Using FDG PET: Group and Individual Analyses
Abstract: Using statistical parametric mapping (SPM), we evaluate the feasibility and accuracy of 18F -2-deoxy-2-fluoro-D-glucose (FDG) positron emission tomography (PET) for clinical diagnosis with characteristic hypo-metabolic regions, and examine the consistency of cerebral hypo-metabolism in Alzheimer’s disease (AD) cross multicenters at both the group and the individual levels. Four groups of scan data including 39 AD patients and 52 healthy control subjects derived from three centers were analyzed and comparisons between patient subgroups or individual patient and relevant control population were performed using Two Sample T-test. In the group analysis, the hypo-metabolic regions of AD patients obtained from different PET centers were similar and consistent. The common hypo-metabolic cerebral areas were located bilaterally in the posterior cingulate and medial parietal cortex, temporo-parietal cortex, prefrontal cortex, and the middle and inferior temporal gyrus (uncorrected, p<0.001). In the analysis of each individual subject, the location of declined posterior cingulate and medial parietal cortex, temporo-parietal cortex and temporal lobe were found highly consistent with relevant characteristic regions obtained in the group analysis and were selected for diagnosic purposes. Complete typical hypo-metabolic pattern was observed in 67% and 54% of AD patients in two sets of 3D scans, respectively. Only 27% and 33.3% patients showed full typical pattern in two sets of 2D scans. The results indicated that FDG PET measures and SPM can provide a valuable reference for clinical diagnosis of AD patients. The potential influence of acquisition mode on the clinical diagnosis of AD was suggested for further evaluation.
Walter Maetzler, Benjamin Schmid, Matthis Synofzik, Claudia Schulte, Karin Riester, Heiko Huber, Kathrin Brockmann, Thomas Gasser, Daniela Berg, Arthur Melms
The CST3 BB Genotype and Low Cystatin C Cerebrospinal Fluid Levels are Associated with Dementia in Lewy Body Disease
Abstract: A large proportion of demented Lewy body disease patients have Alzheimer’s disease (AD)-like pathology, in particular amyloid-β (Aβ) plaques. Cystatin C (CysC) is a carrier of soluble Aβ42 in the cerebrospinal fluid (CSF) and reduces Aβ plaque formation. The CST3 BB genotype leads to a reduced secretion of the protein in vitro and increases the risk for AD, suggesting that variability in the CST3 gene and CysC protein concentration may be associated with dementia in Lewy body disease. We therefore determined the CST3 genotype in 51 demented and 71 non-demented Lewy body disease patients, and in 52 controls, as well as CSF CysC and Aβ42 levels from 132 of these subjects. The CST3 BB genotype was associated with lowered CSF CysC levels and with dementia. Demented Lewy body disease patients had decreased CSF CysC levels. The correlation between CSF CysC and Aβ42 levels was high in non-demented subjects, but poor in demented patients. We conclude that, in Lewy body disease, the CST3 BB genotype and low CSF CysC levels are associated with dementia, possibly through a disturbed elimination of soluble Aβ42.
Zoë Hyde, Leon Flicker, Osvaldo P. Almeida, Kieran A. McCaul, Konrad Jamrozik, Graeme J. Hankey, S.A. Paul Chubb, Bu B. Yeap
Higher Luteinizing Hormone is Associated with Poor Memory Recall: The Health in Men Study
Abstract: Elevated levels of gonadotropins have been observed in patients with Alzheimer’s disease and have been associated with poorer cognition in women, but not men. The aim of this study was to explore the relationship between gonadotropins and cognition in a cohort of 585 healthy, community-dwelling men aged 70-87 years. Cognitive function was assessed with the California Verbal Learning Test Second Edition (CVLT-II) and the Standardized Mini-Mental State Examination (SMMSE). Testosterone, sex hormone binding globulin, and luteinizing hormone levels were assayed from early morning sera. Free testosterone was calculated using mass action equations. In linear regression analyses, neither total nor free testosterone levels were associated with measures of immediate or delayed recall. Higher levels of luteinizing hormone were associated with poorer performance on a measure of immediate recall (CVLT-II trials 1-5 total score) independent of total and free testosterone levels. The association remained after adjustment for age, educational attainment, and depression. In contrast, only total and free testosterone levels were associated with SMMSE score. These findings suggest a role for both androgens and gonadotropins in differing cognitive domains, and that gonadotropins may influence cognition independent of sex steroids.
Xin-An Liu, Kai Liao, Rong Liu, Hai-Hong Wang, Yao Zhang, Qi Zhang, Qun Wang, Hong-Lian Li, Qing Tian, Jian-Zhi Wang
Tau Dephosphorylation Potentiates Apoptosis with the Mechanisms Involving a Failed Dephosphorylation/Activation of Bcl-2
Abstract: Phosphorylation of tau, a major microtubule-associated protein, has been recently discovered to affect cell apoptosis. While the phosphorylation of tau is dynamically regulated, the role of tau dephosphorylation in cell viability is elusive. Here, we observed that the cells bearing high level of the dephosphorylated tau at Tau-1 epitope were more vulnerable to the apoptosis induced by staurosporine, camptothecin, and hydrogen peroxide, though the general outcome of tau expression was still anti-apoptotic. Further studies demonstrate that co-expression of tau and protein phosphatase 2A catalytic subunit (PP2Ac), the most active tau phosphatase, potentiates cell apoptosis with a correlatively increased dephosphorylation of tau and phosphorylation of Bcl-2 at Ser87 (pS87-Bcl2, the inactive form of the anti-apoptotic factor), whereas expression of PP2Ac alone in the absence of tau decreases the levels of pS87-Bcl2 and cleaved PARP, markers of early apoptosis. Finally, both tau and Bcl-2 were co-immunoprecipitated with PP2Ac, but the binding level of Bcl-2 with PP2Ac decreased prominently when tau was co-expressed. These data suggest that tau dephosphorylation by PP2Ac facilitates cell apoptosis with the mechanisms involving a failed dephosphorylation/activation of Bcl-2.
Elisa Canu, Donald G. McLaren, Michele E. Fitzgerald, Barbara B. Bendlin, Giada Zoccatelli, Franco Alessandrini, Francesca B. Pizzini, Giuseppe K. Ricciardi, Alberto Beltramello, Sterling C. Johnson, Giovanni B. Frisoni
Microstructural Diffusion Changes are Independent of Macrostructural Volume Loss in Moderate to Severe Alzheimer’s Disease
Abstract: Although it is established that Alzheimer’s disease (AD) leads to cerebral macrostructural atrophy, microstructural diffusion changes have also been observed, but it is not yet known whether these changes offer unique information about the disease pathology. Thus, a multi-modal imaging study was conducted to determine the independent contribution of each modality in moderate to severe AD. Seventeen patients with moderate-severe AD and 13 healthy volunteers underwent diffusion-weighted and T1-weighted MR scanning. Images were processed to obtain measures of macrostructural atrophy (gray and white matter volumes) and microstructural damage (fractional anisotropy and mean diffusivity). Microstructural diffusion changes independent of macrostructural loss were investigated using an ANCOVA where macrostructural maps were used as voxel-wise covariates. The reverse ANCOVA model was also assessed, where macrostructural loss was the dependent variable and microstructural diffusion tensor imaging maps were the imaging covariates. Diffusion differences between patients and controls were observed after controlling for volumetric differences in medial temporal, retrosplenial regions, anterior commissure, corona radiata, internal capsule, thalamus, corticopontine tracts, cerebral peduncle, striatum, and precentral gyrus. Independent volumetric differences were observed in the entorhinal cortex, inferior temporal lobe, posterior cingulate cortex, splenium and cerebellum. While it is well known that AD is associated with pronounced volumetric change, this study suggests that measures of microstructure provide unique information not obtainable with volumetric mapping in regions known to be pivotal in AD and in those thought to be spared. As such this work provides great understanding of the topography of pathological changes in AD that can be captured with imaging.
Yan-qing Shi, Tian-wen Huang, Li-Min Chen, Xiao-dong Pan, Jing Zhang, Yuan-gui Zhu, Xiao-chun Chen
Ginsenoside Rg1 Attenuates Amyloid-β Content, Regulates PKA/CREB Activity, and Improves Cognitive Performance in SAMP8 Mice
Abstract: It is well established that the presence of soluble amyloid-β protein (Aβ) correlates with the severity of dementia in Alzheimer’s disease (AD). Several lines of evidence indicate that cyclic AMP responsive element binding protein (CREB) and protein kinase A (PKA) are involved in soluble Aβ-trigged disruption of synaptic plasticity in early AD. Previously we have demonstrated the beneficial effects of ginsenoside Rg1 on Aβ-induced neuronal insult. Therefore, in the present study, we examined the effects of long-term consumption of Rg1 on the cerebral Aβ content and PKA/CREB signaling molecules, as well as cognitive performance in senescence-accelerated mouse prone 8 (SAMP8). Notably, a dose-dependent significant reduction of soluble Aβ1-40 was shown in the hippocampus of SAMP8 mice after administration with ginsenoside Rg1 for 3 months. Furthermore, Rg1 treatment resulted in a significant decrease of hippocampal PKA RIIα level (isoform IIα of the regulatory subunit of PKA). In contrast, phospho-CREB and brain derived neurotrophic factor (BDNF) levels were dramatically increased in the hippocampus of SAMP8 treated with Rg1. In a result, administration of ginsenoside Rg1 consequently improved learning and memory outcomes in SAMP8 mice. These data suggest that long-term consumption of ginsenoside Rg1 may delay cognitive decline, which is associated with its significant effects on Aβ generation and PKA/CREB activity, as well as BDNF content in the brain. These provide further support for the therapeutic or intervention potency of ginsenoside Rg1 in the early stage of AD.
Ivica Granic, Marcelo F. Masman, Kees C. Mulder, Ingrid M. Nijholt, Pieter J.W. Naude, Ammerins de Haan, Emőke Borbély, Botond Penke, Paul G.M. Luiten and Ulrich L.M. Eisel
LPYFDa Neutralizes Amyloid-β-Induced Memory Impairment and Toxicity
Abstract: Misfolding, oligomerization, and aggregation of the amyloid-β (Aβ) peptide is widely recognized as a central event in the pathogenesis of Alzheimer’s disease (AD). Recent studies have identified soluble Aβ oligomers as the main pathogenic agents and provided evidence that such oligomeric Aβ aggregates are neurotoxic, disrupt synaptic plasticity, and inhibit long-term potentiation. A promising therapeutic strategy in the battle against AD is the application of short synthetic peptides which are designed to bind to specific Aβ-regions thereby neutralizing or interfering with the devastating properties of oligomeric Aβ species. In the present study, we investigated the neuroprotective properties of the amyloid sequence derived pentapeptide LPYFDa in vitro as well as its memory preserving capacity against Aβ42-induced learning deficits in vivo. In vitro we showed that neurons in culture treated with LPYFDa are protected against Aβ42-induced cell death. Moreover, in vivo LPYFDa prevented memory impairment tested in a contextual fear conditioning paradigm in mice after bilateral intrahippocampal Aβ42 injections. We thus showed for the first time that an anti-amyloid peptide like LPYFDa can preserve memory by reverting Aβ42 oligomer-induced learning deficits.
Gurdeep Marwarha, Bhanu Dasari, Jaya R.P. Prasanthi, Jared Schommer and Othman Ghribi
Leptin is Involved in Accumulation of Amyloid-β and Tau Phosphorylation Induced by 27-Hydroxycholesterol in Organotypic Slices from Adult Rabbit Hippocampus
Abstract: Accumulation of amyloid-β (Aβ) peptide and deposition of hyperphosphorylated tau protein are two major pathological hallmarks of Alzheimer’s disease (AD). We have shown that cholesterol-enriched diets and its metabolite 27-hydroxycholesterol (27-OHC) increase Aβ and phosphorylated tau levels. However, the mechanisms by which cholesterol and 27-OHC regulate Aβ production and tau phosphorylation remain unclear. Leptin, an adipocytokine involved in cell survival and in learning, has been demonstrated to regulate Aβ production and tau hyperphosphorylationin transgenic mice for AD. However, the involvement of leptin signaling in cholesterol and cholesterol metabolites-induced Aβ accumulation and tau hyperphosphorylation are yet to be examined. In this study, we determined the effect of high cholesterol diet and 27-OHC on leptin expression levels and the extent to which leptin treatment affects 27-OHC-induced AD-like pathology. Our results show that feeding rabbits a 2% cholesterol-enriched diet for 12 weeks reduces the levels of leptin by ~80% and incubating organotypic slices from adult rabbit hippocampus with 27-OHC reduced leptin levels by ~30%. 27-OHC induces a 1.5-fold increase in Aβ40 and a 3-fold increase in Aβ42 and in phosphorylated tau. Treatment with leptin reversed the 27-OHC-induced increase in Aβ and phosphorylated tau by decreasing the levels of BACE-1 and GSK-3β respectively. Our results suggest that cholesterol-enriched diets and cholesterol metabolites induce AD-like pathology by altering leptin signaling. We propose that leptin administration may prevent the progression of sporadic forms of AD that are related to increased cholesterol and oxidized cholesterol metabolite levels.
Alexandra Auffret, Vanessa Gautheron, Mark P. Mattson, Jean Mariani, Catherine Rovira
Progressive Age-Related Impairment of the Late Long-Term Potentiation in Alzheimer’s Disease Presenilin-1 Mutant Knock-in Mice
Abstract: Presenilin 1 (PS1) mutations are responsible for many early-onset familial Alzheimer’s disease (FAD) cases. While increasing evidence points to impaired synaptic plasticity as an early event in AD, PS1 mutant mice exhibit a paradoxical increase in hippocampal long-term potentiation (LTP). Among PS1 mouse models, PS1 M146V mutant knock-in mice (PS1KI) are particularly interesting in that they exhibit memory impairment in spatial tasks. Here we investigated the effects of aging on two forms of LTP in PS1KI mice, the widely-studied early phase of LTP (E-LTP) and a particular form of LTP called late-LTP (L-LTP) which requires transcription and protein synthesis. L-LTP is thought to be critical for long-term memory. We found a lower L-LTP maintenance phase in PS1KI mice compared to wild type littermates at 3 months of age. As the mice age, they exhibit impairment of both the induction and maintenance phases of LTP. When E-LTP and NMDA receptor-mediated transmission were analyzed, PS1KI mice displayed an increase at 3 months compared to wild type littermates; this difference did not persist at older ages and finally decreased at 12 months. These results reveal an L-LTP decrease in PS1 mutant mice at an early stage, which occurs coincidently with a paradoxical enhancement of E-LTP. The observation of a decrease in both forms of LTP during aging supports the view that PS1KI mice are a valuable model for the study of age-dependent synaptic dysfunction and cognitive decline in AD.
Massimo Tabaton, Patrizio Odetti, Sergio Cammarata, Roberta Borghi, Fiammetta Monacelli, Carlo Caltagirone, Paola Bossù, Massimo Buscema, Enzo Grossi
Artificial Neural Networks Identify the Predictive Values of Risk Factors on the Conversion of Amnestic Mild Cognitive Impairment
Abstract: The search for markers that are able to predict the conversion of amnestic mild cognitive impairment (aMCI) to Alzheimer’s disease (AD) is crucial for early mechanistic therapies. Using artificial neural networks (ANNs), 22 variables that are known risk factors of AD were analyzed in 80 patients with aMCI, for a period spanning at least 2 years. The cases were chosen from 195 aMCI subjects recruited by four Italian Alzheimer’s disease units. The parameters of glucose metabolism disorder, female gender, and apolipoprotein E ε3/ε4 genotype were found to be the biological variables with high relevance for predicting the conversion of aMCI. The scores of attention and short term memory tests also were predictors. Surprisingly, the plasma concentration of amyloid-β42 had a low predictive value. The results support the utility of ANN analysis as a new tool in the interpretation of data from heterogeneous and distinct sources.
Elisa Mura*, Stefania Preda*, Stefano Govoni, Cristina Lanni, Luigia Trabace, Massimo Grilli, Federica Lagomarsino, Anna Pittaluga, Mario Marchi *Contributed equally to this work
Specific Neuromodulatory Actions of Amyloid-β on Dopamine Release in Rat Nucleus Accumbens and Caudate Putamen
Abstract: We previously demonstrated that amyloid-β (Aβ) has a neuromodulatory action in the nucleus accumbens (NAc). In this area of the brain, the peptide disrupts the cholinergic control of dopamine (DA) release both in vivo and in vitro. The aim of the present work was to extend the research on the neuromodulatory effect of Aβ1-40 on DA transmission to different release stimuli and to another dopaminergic brain area, the caudate putamen (CPu), in order to clarify whether the effect of the peptide is stimulus- or brain area-selective. We performed both in vivo (microdialysis associated to HPLC) and in vitro studies (synaptosomes in superfusion). Both in NAc and in CPu and both in vivo and in vitro, Aβ did not affect either basal or potassium-stimulated DA release. In CPu, the Aβ ability to impair the DA release evoked by the cholinergic agonist carbachol, observed in NAc, was confirmed only in vitro. Moreover, in vitro Aβ affected a specific component of the DA overflow evoked by the non-selective metabotropic glutamate receptors agonist t-ACPD. Altogether, the results show that Aβ may have different neuromodulatory actions depending upon the secretory stimulus and, in vivo, the brain area investigated.
Gábor Juhász, Balázs Barkóczi, Gabriella Vass, Zsolt Datki, Ákos Hunya, Lívia Fülöp, Dénes Budai, Botond Penke, Viktor Szegedi (Communicated by Ashley Bush)
Fibrillar Aβ1-42 Enhances NMDA Receptor Sensitivity via the Integrin Signaling Pathway
Abstract: The aggregated form of amyloid-β (Aβ)1-42 has been shown to increase N-methyl-D-aspartic acid (NMDA) evoked neuronal activity in vivo. Here we further characterized this phenomenon by investigating the role of integrin activation and downstream Src kinase activity using in vivo electrophysiology and in vitro intracellular Ca2+ measurements. Pretreatment of differentiated SH-SY5Y cells with fibrillar Aβ1-42 markedly enhanced the intracellular calcium increases caused by NMDA receptor (NMDA-R) stimulation. Function blocking antibody against β1 integrin depressed the facilitatory effects of Aβ1-42. Similarly, Aβ1-42 facilitated NMDA-R driven firing of hippocampal neurons in vivo, and this effect was reduced by neutralizing antibody against β1 integrins. The positive action of Aβ1-42 on NMDA-R dependent responses was also depressed by an inhibitor known to block Src kinase. These results support the hypothesis that aggregated Aβ1-42 is recognized by the β1 subunit containing integrins and may induce a Src kinase dependent NMDA receptor phosphorylation.
Liana Lisboa Fernandez, Marga Carmona, Manuel Portero-Otin, Alba Naudi, Reinald Pamplona, Nadja Schröder, Isidro Ferrer (Communicated by Sigfrido Scarpa)
Effects of Increased Iron Intake During the Neonatal Period on the Brain of Adult AβPP/PS1 Transgenic Mice
Abstract: The present study was aimed to investigate neuropathological changes in AβPP/PS1 transgenic mice (Tg), as a model of Alzheimer’s disease, subjected to supplementary iron administration in a critical postnatal period, in order to reveal the interaction of genetic and environmental risk factors in the pathogenesis of the disease. Twelve Tg and 10 ten wild-type (Wt) littermates were administered iron between the 12th and 14th post-natal days (TgFe, WtFe); 11 Tg and 15 Wt received vehicle (sorbitol 5%) alone in the same period (TgSb, WtSb). Mice were killed at the age of six months and processed for morphological and biochemical studies. No modifications in amyloid-β burden were seen in iron-treated and non-iron-treated AβPP/PS1 mice. No differences in microglial reactions were observed when comparing the four groups of mice. Yet increased astrocytosis, as revealed by densitometry of GFAP-immunoreactive astrocytes, and increased expression levels of GFAP, as revealed by gel electrophoresis and western blotting, were found in iron-treated mice (both Tg and Wt) when compared with TgSb and WtSb. This was accompanied by significant changes in brain fatty acid composition in AβPP/PS1 mice that led to a lower membrane peroxidizability index and to reduced protein oxidative damage, as revealed by reduced percentages of the oxidative stress markers: glutamic semialdehyde, aminoadipic semialdehyde, Nε-carboxymethyl-lysine, Nε-carboxyethyl-lysine, and Nε-malondialdehyde-lysine. These findings demonstrate that transient dietary iron supplementation during the neonatal period is associated with cellular and metabolic imprinting in the brain in adult life, but it does not interfere with the appearance of amyloid plaques in AβPP/PS1 transgenic mice.
Claudius Mueller, Weidong Zhou, Amy VanMeter, Michael Heiby, Shino Magaki, Mark M. Ross, Virginia Espina, Matthew Schrag, Cindy Dickson, Lance A. Liotta, Wolff M. Kirsch
The Heme Degradation Pathway is a Promising Serum Biomarker Source for the Early Detection of Alzheimer’s Disease
Abstract: One of the remaining challenges in Alzheimer's disease (AD) research is the establishment of biomarkers for early disease detection. As part of a prospective study spanning a period of five years, we have collected serial serum samples from cognitively normal, mild cognitively impaired (MCI), and mild AD participants, including same patient samples before and after cognitive decline. Using mass spectrometry we identified several promising leads for biomarker development, such as prosaposin, phospholipase D1, biliverdin reductase B, and S100 calcium binding protein A7. Selected candidate markers were verified using reverse phase protein microarray assays. Of 15 protein/protein abundance ratios that were significantly altered in sera from subjects with mild AD compared to Normal or MCI subjects, 14 were composed of ratios containing heme oxygenase-1, biliverdin reductase A, or biliverdin reductase B. Moreover, an increase in the protein abundance ratio of matrix metallopeptidase 9/biliverdin reductase differentiated stable MCI subjects from MCI subjects progressing into mild AD before the onset of cognitive decline. These findings strongly implicate the heme degradation pathway as a promising source of protein biomarkers for the early detection of AD.
Meeting Report from the Alzheimer Research Forum
The Society for Neuroscience 2009 Meeting Report, Part 1