31, Number 4, September 2012
Weiming Xia, Stephen T Wong, Eugene Hanlon, Peter Morin
γ-Secretase Modulator in Alzheimer’s Disease: Shifting the End
Abstract: The outcomes of the clinical trials of the γ-secretase inhibitor Semagacestat (LY-450139) and the γ-secretase modulator (GSM) Tarenflurbil were disappointing, but may not represent the end of the γ-secretase era. γ-Secretase modulators, by definition, only block the γ-secretase cleavage of amyloid-β protein precursor (AβPP) to generate the longer, 42-residue amyloid-β (Aβ42) without changing the production of total Aβ. The first generation GSMs were shown to block Aβ42 generation while increasing Aβ38. The non-steroidal anti-inflammatory drug, Tarenflurbil, binds to AβPP and shifts the cleavage site from Aβ42 to Aβ38. In addition, Tarenflurbil does not affect the γ-secretase cleavage of Notch. Even before the failed clinical trials of Tarenflurbil, second generation GSMs had emerged, and some of these GSMs interact with presenilin, which carries the active site of the γ-secretase. While second generation GSMs are pharmacologically superior to first generation GSMs, in vivo Aβ profiles (decreased levels of Aβ38, Aβ40, and Aβ42) in animals treated with potent GSMs are strikingly different from those in cultured cells. Thus, the unique pharmacologic properties of new GSMs and their mechanisms of action need to be elucidated in order to avoid the fate of Tarenflurbil. It is critical to understand how GSMs shift the “end” in vivo, i.e., shifting the γ-secretase cleavage at the C-terminal end of Aβ. In view of the myriad effects of candidate GSMs on Aβ production in cells and animals, drug development would benefit from better definition of the target-GSM interaction and physiological function of shorter Aβ peptides.
Francisco C. Pérez-Martínez, Blanca Carrión, Valentín Ceña
The Use of Nanoparticles for Gene Therapy in the Nervous System
Abstract: Nanoparticles represent an alternative to viral vectors for genetic material transfer to the nervous system. However, to increase transfection efficiency in the central nervous system and to decrease toxicity, the design of nanoparticles needs to be improved to enhance blood-brain barrier crossing and endosomal escape. This paper reviews the strategies used to solve these difficulties and covers the use of various nanoparticles including natural inorganic particles, natural polymers, cationic lipids, polyethylenimine derivatives, dendrimers, and carbon-based nanoparticles. The effectiveness, both in vivo and in vitro, of each method to deliver genetic material to neural tissue is discussed.
Mariana G. Figueiro, Robert Hamner, Patricia Higgins, Thomas Hornick, Mark S. Rea (Handling Associate Editor: Verena Buschert)
Field Measurements of Light Exposures and Circadian Disruption in Two Populations of Older Adults
Abstract: The absence of daily robust light-dark exposure patterns may contribute to sleep disturbances in persons with Alzheimer’s disease and related dementias (ADRD). Personal light-dark and activity-rest patterns were measured for healthy older adults and for persons with ADRD. Persons with ADRD experienced lower light levels, exhibited lower activity levels, and had greater levels of circadian disruption than healthy older adults during winter. Seasonal differences were observed for persons with ADRD; lower levels of light exposure and greater levels of circadian disruption were seen during the winter than during the summer, although activity levels did not differ for the two seasons.
Christine A.F. von Arnim, Florian Herbolsheimer, Thorsten Nikolaus, Richard Peter, Hans K. Biesalski, Albert C. Ludolph, Matthias Riepe, Gabriele Nagel, the ActiFE Ulm study group
Dietary Antioxidants and Dementia in a Population-Based Case-Control Study among Older People in South Germany
Abstract: Oxidative stress is believed to play a central role in the pathogenesis of Alzheimer’s disease (AD), a neurodegenerative disease. Antioxidants may prevent the onset AD as high dietary intake of vitamin C and E were reported to be associated with lower risk of the disease. The objective of this study was to evaluate the serum levels of antioxidants in persons with mild dementia to test whether it is associated with lower levels of antioxidants in a cross-sectional study in the population of the “Activity and Function in the Ederly in Ulm” (ActiFE) study. Main exposure measures were vitamin C, vitamin E, β-carotene, lycopene, and coenzyme Q10 as analyzed by HPLC. Main outcome measures were mild cognitive impairment among 74 mildly demented compared to 158 age- and gender-matched controls. We found that blood vitamin C and β-carotene concentrations were significantly lower in demented than in control persons even after adjusting for school education, intake of dietary supplements, smoking habits, body mass index, and alcohol consumption (3rd versus 1st tertile: OR: 0.29, 95%CI, 0.09-0.96 and 0.13, 95%CI, 0.03-0.55, respectively). No associations were found for vitamin E, lycopene, and coenzyme Q10. Our findings suggest an association of vitamin C and β-carotene with dementia. However this is limited to the cross-sectional character of our study and longitudinal data will give further insight into this association.
Supplementary Data for von Arnim et al. article (PDF)
Christopher Exley, Emily House, Anthony Polwart, Margaret M. Esiri
Brain Burdens of Aluminum, Iron, and Copper and their Relationships with Amyloid-β Pathology in 60 Human Brains
Abstract: The deposition in the brain of amyloid-β as beta sheet conformers associated with senile plaques and vasculature is frequently observed in Alzheimer’s disease. While metals, primarily aluminum, iron, zinc, and copper, have been implicated in amyloidβ deposition in vivo, there are few data specifically relating brain metal burden with extent of amyloid pathologies in human brains. Herein brain tissue content of aluminum, iron, and copper are compared with burdens of amyloid-β, as senile plaques and as congophilic amyloid angiopathy, in 60 aged human brains. Significant observations were strong negative correlations between brain copper burden and the degree of severity of both senile plaque and congophilic amyloid angiopathy pathologies with the relationship with the former reaching statistical significance. While we did not have access to the dementia status of the majority of the 60 brain donors, this knowledge for just 4 donors allowed us to speculate that diagnosis of dementia might be predicted by a combination of amyloid pathology and a ratio of the brain burden of copper to the brain burden of aluminum. Taking into account only those donor brains with either senile plaque scores ³4 and/or congophilic amyloid angiopathy scores ³12, a Cu:Al ratio of <20 would predict that at least 39 of the 60 donors would have been diagnosed as suffering from dementia. Future research should test the hypothesis that in individuals with moderate to severe amyloid pathology low brain copper is a predisposition to developing dementia.
Davide Seripa, Alessandra Bizzarro, Andrea Pilotto, Orazio Palmieri, Francesco Panza, Grazia D’Onofrio, Carolina Gravina, Silvana Archetti, Antonio Daniele, Barbara Borroni, Alessandro Padovani, Carlo Masullo (Handling Associate Editor: Daniela Galimberti)
TOMM40, APOE, and APOC1 in Primary Progressive Aphasia and Frontotemporal Dementia
Abstract: The aim of this study was to investigate the apolipoprotein E (APOE) chromosomal region in frontotemporal lobar degeneration (FTLD), and in particular in primary progressive aphasia (PPA) and the behavioral variant frontotemporal dementia (bvFTD). To this aim, we selected three single-nucleotide polymorphisms (SNPs) rs2075650 and rs157590 (TOMM40), and rs1064725 (APOC1), representative of the linkage disequilibrium (LD) blocks at the 19q13-q13.2 chromosomal region. The SNPs rs429358 and rs7412 forming the APOE polymorphism were also included in the study. The analysis was made in 282 patients with a clinical diagnosis of sporadic FTLD, namely 207 bvFTD and 75 PPA, and 296 cognitively healthy control subjects in blinded fashion. LD (r2=0.35) between TOMM40 (rs2075650) and APOC1 (rs1064725) was observed in PPA, but not in controls and in bvFTD. Inside this region of 26.9kb, LD (r2≥0.50) between TOMM40 (rs2075650) and APOE (rs429358) was observed in bvFTD and in controls, but not in PPA. Inside this region of 16.3kb, LD (r2=0.14) between TOMM40 (rs157590) and APOE (rs429358) was observed in PPA, but not in bvFTD and in controls. Although the genetics of PPA and bvFTD needs further investigation, our results suggested the presence of a different genetic background underlying PPA and bvFTD at the 19q13-q13.2 chromosomal region.
Supplementary Data for Seripa et al. article (PDF)
Vincent Deramecourt, Florence Lebert, Claude-Alain Maurage, Francisco-Jose Fernandez-Gomez, Simon Dujardin, Morvane Colin, Nicolas Sergeant, Valérie Buée-Scherrer, Fabienne Clot, Isabelle Le Ber, Alexis Brice, Florence Pasquier, Luc Buée
Clinical, Neuropathological, and Biochemical Characterization of the Novel Tau Mutation P332S
Abstract: MAPT mutations cause autosomal dominant frontotemporal lobar degeneration. These diseases are characterized by considerable heterogeneity in their clinical, neuropathological, and biochemical presentations. We describe the full characterization of a family with autosomal dominant frontotemporal lobar degeneration caused by a novel MAPT mutation. Clinical, imaging, neuropathological, and biochemical data are presented. The proband was a woman who died at 85 years old, 25 years after the onset of a slowly progressive and isolated anarthria and opercular syndrome. The pathological examination of her brain showed marked atrophy of primary motor and premotor cortices, associated with predominant neuronal tau-positive lesions mimicking Pick bodies. At the biochemical level, the six tau isoforms aggregate to display a pathological triplet at 60, 64, and 69 kDa. Two of her sons presented at 48 and 50 years old with a right temporal variant of frontotemporal degeneration characterized by severe prosopagnosia, semantic impairment, and behavioral modifications. In these three patients, the molecular analysis of MAPT showed the c.1945C>T mutation on exon 11 resulting in the P332S substitution in tau sequence. This mutation changes the PGGG motif of the third repeat domain of the protein and therefore reduces the ability of tau to bind microtubule. From a clinical point of view, this mutation is associated with considerable intrafamilial phenotypic variation.
Sönke Arlt, Edzard Schwedhelm, Heike Kölsch, Holger Jahn, Michael Linnebank, Yvo Smulders, Frank Jessen, Rainer H. Böger, Julius Popp
Dimethylarginines, Homocysteine Metabolism, and Cerebrospinal Fluid Markers for Alzheimer’s Disease
Abstract: Dimethylarginine and homocysteine metabolism are closely linked and alterations of both were observed in plasma and cerebrospinal fluid (CSF) of patients with Alzheimer’s disease (AD). CSF parameters of homocysteine metabolism have recently found to be associated with the CSF level of the AD biomarker phosphorylated tau (ptau) in AD patients. To investigate possible relationships between homocysteine and dimethylarginine metabolism and the AD CSF biomarkers ptau181 and amyloid-β 1-42 (Aβ42), we assessed parameters of homocysteine metabolism (CSF homocysteine, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), 5-methyltetrahydrofolate (5-MTHF)) and dimethylarginine metabolism (plasma and CSF asymmetric dimethylarginine (ADMA), symmetric dimethylarginine, L-arginine) as well as CSF Aβ42 and ptau181 in 98 controls and 51 AD patients. Multivariate linear regression analyses were performed to assess associations between the considered parameters. SAH concentrations show significant associations to CSF ADMA levels, and CSF ADMA and L-arginine to ptau181, but not to Aβ42 concentrations in AD patients. When including concentrations of homocysteine, 5-MTHF, SAM, and SAH into the analysis, CSF ADMA concentrations independently predicted ptau181 levels in AD patients but homocysteine-related metabolites were associated with ptau181 only when ADMA was removed from the analysis model. These results suggest that CSF ADMA may interact with CNS homocysteine metabolism and may contribute to neurodegeneration and accumulation of phosphorylated tau in AD. Functional and interventional studies are needed to further proof this hypothesis.
Tiina Laakso, Pranuthi Muggalla, Kai Kysenius, Juha Lauren, Anja Paatero, Henri J. Huttunen, Matti S. Airaksinen (Handling Associate Editor: Annakaisa Haapasalo)
LRRTM3 is Dispensable for Amyloid-β Production in Mice
Abstract: Neuronal LRRTM3 (leucine-rich repeat transmembrane 3) protein has been reported to promote amyloid-β protein precursor (AβPP) processing and LRRTM3 is a candidate gene in late-onset Alzheimer’s disease. To address the role of LRRTM3 in AβPP processing and amyloid-β (Aβ) production in vivo, we analyzed amyloidogenic processing of AβPP in the brains of LRRTM3-deficient mice and transgenic AβPP/PS1 mice with or without LRRTM3. We did not find differences between the genotypes in the levels of Aβ or AβPP C-terminal fragments indicating that LRRTM3 is not an essential regulator of Aβ production in adult mice. Moreover, Aβ levels in primary cortical neurons were similar between the genotypes, indicating that LRRTM3 is not required for Aβ generation in developing mice.
Supplementary Data for Laakso et al. article (PDF)
Yan Zeng, Yakun Liu, Mianyun Wu, Jun Liu, Qi Hu
Activation of TrkB by 7,8-Dihydroxyﬂavone Prevents Fear Memory Defects and Facilitates Amygdalar Synaptic Plasticity in Aging
Abstract: 7,8-dihydroxyflavone (7,8-DHF) has recently been identified as a brain-derived neurotrophic factor (BDNF) mimetic to selectively activate the tropomyosin-related kinase B (TrkB) with high affinity. We have previously demonstrated that 7,8-DHF in vitro rescues long-term synaptic plasticity in the hippocampus of aged rats. The present study assessed the effectiveness of 7,8-DHF on age-related declines in fear memories and amygdalar synaptic plasticity. We found that Sprague Dawley male rats began to show significant deficits in the acquisition and retention of memories for contextual and cued fear conditioning, as well as the reduction of BDNF, TrkB, and phosphorylated TrkB at the age of 25 months. Therefore, rats at 24 months old received intraperitoneal administration of either 7,8-DHF (5mg/kg, i.p.) or vehicle once daily for a consecutive 4 weeks. At the end of treatment period, cognitive performance, amygdalar synaptic plasticity, synaptogenesis, and the phosphorylation of several proteins crucial to synaptic plasticity were evaluated. The results show that chronic 7,8-DHF treatments significantly enhanced the activation of phosphorylated TrkB at the Y515 and Y816 sites, increased spine density and number in several brain regions that process fear memory including the amygdala, hippocampus, and prefrontal cortex, facilitated basolateral amygdalar synaptic plasticity, and in turn prevented performance in fear conditioning tasks from declining. Our results thus confirm a critical role for TrkB signaling activation by 7,8-DHF in preventing age-related declines in fear learning and memory and strongly suggest a potential usefulness for 7,8-DHF or a TrkB agonist in reversing age-related memory impairment.
Aysegul Yildiz-Unal, Sirin Korulu, Arzu Karabay (Handling Associate Editor: Selma Yilmazer)
Q111qc vSpeedyRINGO Inhibits Calpain-Directed Apoptosis in Neurons
Abstract: The calcium-activated proteolytic enzyme calpain is one of the key proteins that can directly or indirectly drive neurons into apoptosis. The indirect way is through cyclin dependent kinase 5 (CDK5), a non-mitotic kinase, which is upregulated through calpain overactivation and followed by a subsequent increase in p53 and active caspase-3 levels under neurodegenerative conditions. The direct way is the upregulation of p53 by calpain itself, since p53 is a substrate for it. SpeedyRINGO is an atypical cell cycle regulator that has been shown to have protective effects in mitotic cells against apoptosis by inhibiting caspase-3 activation when p53 is present. Our aim was to reveal possible protective effects of SpeedyRINGO against calpain-induced caspase-3 activation in neurons which is crucial in terms of providing novel insights in preventing the caspase-3 activation cascade in neurodegeneration. For this reason, mRNA and protein levels were analyzed by qRT-PCR, western blotting, and immunofluorescence. We show that calpain overactivation leads to the upregulation of p53 and a subsequent increase in active caspase-3 level, indicating activation of apoptotic machinery in neurons. This calpain-directed caspase-3 activation upon upregulation of p53 is inhibited by the expression of SpeedyRINGO in rat hippocampal neurons. Therefore, SpeedyRINGO acts as a savior for neurons that are under apoptotisis due to caspase-3 activation.
Daan van Abel, Omar Michel, Rob Veerhuis, Marlies Jacobs, Marie van Dijk, Cees B.M. Oudejans
Direct Downregulation of CNTNAP2 by STOX1A is Associated with Alzheimer’s Disease
Abstract: STOX1A is a transcription factor which is functionally and structurally similar to the forkhead box protein family. STOX1A has been shown to be associated with pre-eclampsia, a pregnancy associated disease, and to have potential implications in late onset Alzheimer’s disease. However, the exact function of STOX1A and its target genes are still largely unknown. Therefore, in this study we performed chromatin immunoprecipitation coupled to shotgun cloning to discover novel STOX1A target genes. Our results show that CNTNAP2, a member of the neurexin family, is directly downregulated by STOX1A. Additionally, we show that CNTNAP2 expression is downregulated in the hippocampus of Alzheimer’s disease patients where STOX1A expression has been shown to be upregulated. In conclusion, these results further indicate the potential involvement of STOX1A and its target genes in the etiology of Alzheimer’s disease.
Supplementary Data for van Abel et al. article (PDF)
Ru Zhang*, Guizhen Xue*, Shaodeng Wang, Lihong Zhang, Changjie Shi, Xin Xie (Handling Associate Editor: Zhi-Ying Wu) *These authors contributed equally to this study.
Novel Object Recognition as a Facile Behavior Test for Evaluating Drug Effects in AβPP/PS1 Alzheimer’s Disease Mouse Model
Abstract: Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the AβPP/PS1 transgenic mouse model is a commonly used experimental model to mimic the pathological and cognitive impairments in AD. A classic method to evaluate spatial learning and memory, the Morris water maze is widely applied to study the cognitive deficits in rodent AD models. However, the assay procedure is relatively complicated and requires a properly equipped environment. The novel object recognition test is a relatively simple and straightforward method to test working memory in rodents. However, whether the latter can be used as a common tool for evaluating the therapeutic effects of drugs in the AβPP/PS1 transgenic AD mouse model remain unclear. In the present study, we assessed the cognitive impairment of AβPP/PS1 AD mice with the novel object recognition test. In parallel, Morris water maze was performed and compared with the novel object recognition study. Both assays worked equally well in evaluating the cognitive defect of AβPP/PS1 mice. Furthermore, we drew similar conclusions from the novel object recognition assay as from the Morris water maze in assessing the therapeutic effects of two previously reported compounds, donepezil and naltrindole, on AD. We found the novel object recognition to be a facile assay with almost no stress to mice and think it could be used as an ideal primary screening assay to evaluate drug effects on AβPP/PS1 AD model.
Diane Jansen, Carola I.F. Janssen, Tim Vanmierlo, Pieter J. Dederen, Daan van Rooij, Bastian Zinnhardt, Cindy L.M. Nobelen, Anna-Lena Janssen, Anne Hafkemeijer, Martina P.C. Mutsaers, Anne M.C.M. Doedée, Almar A.M. Kuipers, Laus M. Broersen, Monique Mulder, Amanda J. Kiliaan (Handling Associate Editor: Gary Arendash)
Cholesterol and Synaptic Compensatory Mechanisms in Alzheimer’s Disease Mice Brain During Aging
Abstract: Research into the development of Alzheimer’s disease (AD) provides increasing evidence that vascular risk factors, including high serum cholesterol, might influence the progression of cognitive impairment and neural degeneration. In this study, we investigated the effects of high dietary cholesterol intake and the cholesterol-lowering liver X receptor-agonist T0901317 on capillary density, amyloid-β deposition, and presynaptic boutons in the hippocampus of adult (8 months) and aged (15 months) AβPPswe-PS1dE9 and wild-type mice to elucidate how cholesterol may affect neurodegenerative processes in aging and AD. Our results show increased number of presynaptic boutons in 15-month-old AβPP-PS1 mice compared to age-matched wild-type animals, but no difference at 8 months of age. High cholesterol intake accelerated this response by increasing the amount of presynaptic boutons at 8 and 15 months of age, while T0901317 intake decreased the amount of presynaptic boutons in 15-month-old AβPP-PS1 mice. These findings suggest a synaptic compensatory response to maintain connectivity during aging. We hypothesize that high cholesterol intake may cause impaired cerebral blood flow inducing ischemia, fortifying the above mentioned hypothesis of a compensatory mechanism. Contrarily, cholesterol-lowering agents may positively influence cerebral circulation, thereby diminishing aggravation of AD-like pathology.
Jing Yang, PingLei Pan, Wei Song, Hui-Fang Shang
Quantitative Meta-Analysis of Gray Matter Abnormalities in Semantic Dementia
Abstract: Cumulative evidence of gray matter abnormalities in semantic dementia (SD) has been reported using voxel-based morphometry (VBM). However, these studies have not been reviewed quantitatively. To estimate gray matter changes in SD quantitatively, we systematically searched whole-brain VBM studies comparing SD patients with healthy controls in the PubMed, ISI Web of Science, and EMABSE databases from January 1990 to August 2011. Coordinates with significant differences between the gray matter volumes of SD patients and healthy controls were extracted from clusters. Meta-analysis was performed using anatomic likelihood estimation. Seven studies, with 68 SD patients and 167 healthy controls, were included. Gray matter volume reductions were found in bilateral fusiform and inferior temporal gyri, extending to the medial portion of the temporal lobes (including amygdala and parahippocampal gyri), left temporal pole, middle temporal gyrus, and caudate. No significant increase in gray matter volume was found. Our findings provide strong evidence of atrophy in bilateral temporal lobes with predominate impairment on the left side, parahippocampal gyrus/amygdala, and left caudate, representing the pathophysiology of SD.
Stéphanie Paillard-Borg, Laura Fratiglioni, Weili Xu, Bengt Winblad, Hui-Xin Wang
An Active Lifestyle Postpones Dementia Onset by More than One Year in Very Old Adults
Abstract: The purpose of this study was to test the hypothesis that an active lifestyle delays age at dementia onset. This study included 388 incident dementia cases (DSM-III-R criteria) that developed over a 9-year follow-up period among 1,375 baseline dementia-free community dwellers with good cognitive function (MMSE>23) (mean age=81.2) from the Kungsholmen Project. An active lifestyle was defined as participation in mental, physical, or social activity. We used linear regression models to estimate influence of baseline active lifestyle on age at onset of incident dementia and general linear models to estimate mean age at dementia onset. Age at onset of dementia was significantly older in persons who had higher levels of participation in mental, physical, or social activity (β: 0.18, 0.29 and 0.23 respectively, p <0.001 for all the activities) independent of education, medical condition, functional status, and other confounders including APOE. When the three types of activities were integrated into an index, we found that the broader the spectrum of participation in the activities, the later the onset of disease (β=0.93, p=0.01 for participating in two activities, and β=1.42, p<0.001 for three activities). There were 17 months difference in mean age at dementia onset between the inactive group and the most active group. An active lifestyle operates as a protective factor for dementia by delaying the clinical onset of the disease. These findings highlight the relevance of encouraging old adults to have active lifestyles, which could have a great impact on public health.
Juan Sanchez-Ramos, Cynthia Cimino, Ross Avila, Amanda Rowe, Ren Chen, Glenn Whelan, Xiaoyang Lin, Chuanhai Cao, Raj Ashok
Pilot Study of Granulocyte-Colony Stimulating Factor for Treatment of Alzheimer’s Disease
Abstract: Human granulocyte colony-stimulating-factor (G-CSF) is widely used for treatment of neutropenia and to mobilize stem/progenitor cells for bone marrow transplantation. In studies of thousands of healthy donor subjects treated with G-CSF to mobilize stem/progenitor cells, the side-effect profile has been reported to be mild and reversible. In pre-clinical studies, G-CSF was reported to improve spatial learning performance and to markedly reduce amyloid deposition in hippocampus and entorhinal cortex in a murine model of Alzheimer’s disease (AD). The present study investigated the effects of a five day schedule of G-CSF administration on tolerability, safety, and cognition in eight patients with mild to moderate stage AD. A double-blind placebo control, cross-over design was implemented. Treatment with G-CSF did not result in serious adverse events. The most common and expected side effects were transient increases in white blood cell count, myalgias and diffuse aching that improved with non-steroidal anti-inflammatory medications. Of a battery of cognitive tests administered using the CANTAB computerized system, only the mean paired associate learning (PAL total trials adjusted) was significantly improved at the final visit of the study compared to baseline values (p<0.05). There were no significant differences in amyloid-β1-42 levels in cerebrospinal fluid measured two weeks after G-CSF and two weeks after placebo treatments. In conclusion, administration of G-CSF in a dosage regimen commonly used for bone marrow donors was well tolerated and safe, and provided a signal of positive change in a hippocampal-dependent task of cognitive performance.
Mei-Chuan Chou, Chun-Hung Chen, Ching-Kuan Liu, Su-Hwei Chen, Shyh-Jong Wu, Yuan-Han Yang
Concentrations of Rivastigmine and NAP 226-90 and the Cognitive Response in Taiwanese Alzheimer’s Disease Patients
Abstract: The aim of this small pilot study was to evaluate the association between plasma concentrations of rivastigmine and its metabolite, NAP 226-90, and cognitive function in patients with Alzheimer’s disease (AD). Rivastigmine-treated AD patients, who had been maintained on a fixed regimen of twice daily rivastigmine (6 to 12 mg/d) for ≥ 6 months, were eligible for evaluation. The assessments included Cognitive Assessment Screening Instrument (CASI) and Clinical Dementia Rating scale, conducted at baseline and at 6-month follow-up. The 9 subdomains of CASI at baseline and follow-up were analyzed in relation to the plasma concentrations of rivastigmine and NAP 226-90, as measured by capillary electrophoresis. Logistic regression was performed to adjust for age, gender, education level, apolipoprotein E ε4 genotype status, and baseline CASI score to investigate the association between plasma rivastigmine and NAP 226-90 concentrations and the cognitive response. The total sample consisted of 53 clinically diagnosed AD patientstaking rivastigmine only at doses of 6 mg to 9 mg/d because of intolerability at 12 mg/d. Higher rivastigmine concentration was significantly associated with improved or preserved short-term memory and worsened abstraction/judgment (p < 0.05), but not with changes in other domains (p> 0.05). Higher NAP 226-90 concentration was significantly associated with worsened abstraction/judgment (p < 0.05), but not with changes in other domains. Higher plasma rivastigmine concentration was significantly associated with improved or preserved short-term memory but worsened abstraction/judgment. An optimal concentration of rivastigmine should be quantified for each patient because of differential cognitive responses.
Giulia M. Sancesario, Maria T. Cencioni, Zaira Esposito, Giovanna Borsellino, Marzia Nuccetelli, Alessandro Martorana, Luca Battistini, Roberto Sorge, Gianfranco Spalletta, Davide Ferrazzoli, Giorgio Bernardi, Sergio Bernardini, Giuseppe Sancesario
The Load of Amyloid-β Oligomers is Decreased in the Cerebrospinal Fluid of Alzheimer’s Disease Patients
Abstract: Amyloid-β (Aβ) oligomers are heterogeneous and instable compounds of variable molecular weight. Flow cytometry and fluorescence resonance energy transfer (FRET)-based methods allow the simultaneous detection of Aβ oligomers with low and high molecular weight in their native form. We evaluated whether an estimate of different species of Aβ oligomers in the cerebrospinal fluid (CSF) with or without dilution with RIPA buffer could be more useful in the diagnosis of Alzheimer’s disease (AD) than the measurement of Aβ42 monomers, total tau (t-tau), and phosphorylated tau (p-tau). Increased t-tau (p<0.01) and p-tau (p<0.01), and decreased Aβ42 (p<0.01), were detected in the CSF of patients with AD (n = 46), compared to patients with other dementia (OD) (n = 35) or with other neurological disorders (OND) (n = 56). In native CSF (n = 137), the levels of Aβ oligomers were lower (p< 0.05) in AD than in OD and OND patients; in addition, the ratio Aβ oligomers/p-tau was lower in AD than in OD (p<0.01) and OND (p<0.05) patients, yielding a sensitivity of 75% and a specificity of 64%. However, in CSF diluted with RIPA (n = 30), Aβ oligomers appeared higher (p< 0.05) in AD than in OND patients, suggesting they become partially disaggregated and more easily detectable after RIPA. In conclusion, FRET analysis in native CSF is essential to correctly determine the composition of Aβ oligomers. In this experimental setting, the simultaneous estimate of low and high molecular weight Aβ oligomers is as useful as the other biomarkers in the diagnosis of AD. The low amount of Aβ oligomers detected in native CSF of AD may be inversely related to their levels in the brain, as occurs for Aβ monomers, representing a biomarker for the amyloid pathogenic cascade.
Jorge Fuentealba, Andrea Dibarrart, Francisco Saez-Orellana, María Cecilia Fuentes-Fuentes, Carlos N. Oyanedel, José Guzmán, Claudia Perez, José Becerra, Luis G. Aguayo
Synaptic Silencing and Plasma Membrane Dyshomeostasis Induced by Amyloid-β Peptide are Prevented by Aristotelia Chilensis Enriched Extract
Abstract: Alzheimer’s disease (AD) is characterized by the presence of different types of extracellular and neurotoxic aggregates of amyloid-β (Aβ). Recently, bioactive compounds extracted from natural sources showing neuroprotective properties have become of interest in brain neurodegeneration. We have purified, characterized, and evaluated the protective potential of one extract enriched in polyphenols obtained from Aristotelia chilensis (MQ), a Chilean berry fruit, in neuronal models of AD induced by soluble oligomers of Aβ1-40. For example, using primary hippocampal cultures from rats (E18), we observed neuroprotection when the neurons were co-incubated with Aβ (0.5 μM) plus MQ for 24 h (Aβ=23±2%; Aβ+MQ=3±1%; n=3). In parallel, co-incubation of Aβ with MQ recovered the frequency of Ca2+ transient oscillations when compared to neurons treated with Aβ alone (Aβ=72±3%; Aβ+MQ=86±2%; n=5), correlating with the changes observed in spontaneous synaptic activity. Additionally, MAP-2 immunostaining showed a preservation of the dendritic tree, suggesting that the toxic effect of Aβ is prevented in the presence of MQ. A new complex mechanism is proposed by which MQ induces neuroprotective effects including antioxidant properties, modulation of cell survival pathways, and/or direct interaction with the Aβ aggregates. Our results suggest that MQ induces changes in the aggregation kinetics of Aβ producing variations in the nucleation phase (Aβ: k1=2.7±0.4x10-3 s-1; MQ: k1 = 8.3 ±0.6x10-3 s-1) and altering Thioflavin T insertion in β-sheets. In conclusion, MQ induces a potent neuroprotection by direct interaction with the Aβ aggregates, generating far less toxic species and in this way protecting the neuronal network.