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Abstract
Inheritance of the apoE4 allele (epsilon4) increases the risk of developing Alzheimer's disease; however, the mechanisms underlying this association remain elusive. Recent data suggest that inheritance of epsilon4 may lead to reduced apoE protein levels in the CNS. We therefore examined apoE protein levels in the brains, CSF and plasma of epsilon2/2, epsilon3/3, and epsilon4/4 targeted replacement mice. These apoE mice showed a genotype-dependent decrease in apoE levels; epsilon2/2 >epsilon3/3 >epsilon4/4. Next, we sought to examine the relative contributions of apoE4 and apoE3 in the epsilon3/4 mouse brains. ApoE4 represented 30-40% of the total apoE. Moreover, the absolute amount of apoE3 per allele was similar between epsilon3/3 and epsilon3/4 mice, implying that the reduced levels of total apoE in epsilon3/4 mice can be explained by the reduction in apoE4 levels. In culture medium from epsilon3/4 human astrocytoma or epsilon3/3, epsilon4/4 and epsilon3/4 primary astrocytes, apoE4 levels were consistently lower than apoE3. Secreted cholesterol levels were also lower from epsilon4/4 astrocytes. Pulse-chase experiments showed an enhanced degradation and reduced half-life of newly synthesized apoE4 compared with apoE3. Together, these data suggest that astrocytes preferentially degrade apoE4, leading to reduced apoE4 secretion and ultimately to reduced brain apoE levels. Moreover, the genotype-dependent decrease in CNS apoE levels, mirror the relative risk of developing AD, and suggest that low levels of total apoE exhibited by epsilon4 carriers may directly contribute to the disease progression, perhaps by reducing the capacity of apoE to promote synaptic repair and/or Abeta clearance.
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52
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Götz J, Ittner LM, Schonrock N, Cappai R. An update on the toxicity of Abeta in Alzheimer's disease. Neuropsychiatr Dis Treat 2008; 4:1033-42. [PMID: 19337449 PMCID: PMC2646638 DOI: 10.2147/ndt.s3016] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Alzheimer's disease is characterized histopathologically by deposition of insoluble forms of the peptide Abeta and the protein tau in brain. Abeta is the principal component of amyloid plaques and tau of neurofibrillary tangles. Familial cases of AD are associated with causal mutations in the gene encoding the amyloid precursor protein, APP, from which the amyloidogenic Abeta peptide is derived, and this supports a role for Abeta in disease. Abeta can promote tau pathology and at the same time its toxicity is also tau-dependent. Abeta can adopt different conformations including soluble oligomers and insoluble fibrillar species present in plaques. We discuss which of these conformations exert toxicity, highlight molecular pathways involved and discuss what has been learned by applying functional genomics.
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Affiliation(s)
- Jürgen Götz
- Alzheimer's and Parkinson's Disease Laboratory, Brain and Mind Research Institute, University of Sydney, 100 Mallett St, Camperdown, NSW 2050, Australia.
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53
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Bour A, Grootendorst J, Vogel E, Kelche C, Dodart JC, Bales K, Moreau PH, Sullivan PM, Mathis C. Middle-aged human apoE4 targeted-replacement mice show retention deficits on a wide range of spatial memory tasks. Behav Brain Res 2008; 193:174-82. [PMID: 18572260 DOI: 10.1016/j.bbr.2008.05.008] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Accepted: 05/12/2008] [Indexed: 10/22/2022]
Abstract
Apolipoprotein (apo) E4, one of three human apoE (h-apoE) isoforms, has been identified as a major genetic risk factor for Alzheimer's disease and for cognitive deficits associated with aging. However, the biological mechanisms involving apoE in learning and memory processes are unclear. A potential isoform-dependent role of apoE in cognitive processes was studied in human apoE targeted-replacement (TR) mice. These mice express either the human apoE3 or apoE4 gene under the control of endogenous murine apoE regulatory sequences, resulting in physiological expression of h-apoE in both a temporal and spatial pattern similar to humans. Male and female apoE3-TR, apoE4-TR, apoE-knockout and C57BL/6J mice (15-18 months) were tested with spatial memory and avoidance conditioning tasks. Compared to apoE3-TR mice, spatial memory in female apoE4-TR mice was impaired based on their poor performances in; (i) the probe test of the water-maze reference memory task, (ii) the water-maze working memory task and (iii) an active avoidance Y-maze task. Retention performance on a passive avoidance task was also impaired in apoE4-TR mice, but not in other genotypes. These deficits in both spatial and avoidance memory tasks may be related to the anatomical and functional abnormalities previously reported in the hippocampus and the amygdala of apoE4-TR mice. We conclude that the apoE4-TR mice provide an excellent model for understanding the mechanisms underlying apoE4-dependent susceptibility to cognitive decline.
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Affiliation(s)
- Alexandra Bour
- Laboratoire de Neurosciences Comportementales et Cognitives, Université Louis Pasteur, CNRS-UMR 7191, IFR 37, GDR CNRS 2905, 12 rue Goethe, 67000 Strasbourg, France
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54
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Cappai R, Barnham KJ. Delineating the Mechanism of Alzheimer’s Disease Aβ Peptide Neurotoxicity. Neurochem Res 2007; 33:526-32. [PMID: 17762917 DOI: 10.1007/s11064-007-9469-8] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2007] [Accepted: 07/24/2007] [Indexed: 12/21/2022]
Abstract
The Alzheimer's disease neurotoxic amyloid-beta (A beta) peptide is derived from the larger amyloid precursor protein (APP) and is the principal component of the senile plaques in Alzheimer's disease (AD) brains. This mechanism by which A beta mediates neurotoxicity or neuronal dysfunction is not fully resolved. This review will outline some of the key determinants that modulate A beta's activity and the cellular pathways and mechanisms involved.
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Affiliation(s)
- Roberto Cappai
- Department of Pathology, The University of Melbourne, Melbourne, VIC 3010, Australia.
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55
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Cappai R, Barnham KJ. Molecular determinants of Alzheimer’s disease Aβ peptide neurotoxicity. FUTURE NEUROLOGY 2007. [DOI: 10.2217/14796708.2.4.397] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The Alzheimer’s disease amyloid precursor protein is sequentially processed to yield the neurotoxic amyloid-β (Aβ) peptide, which is the principal component of the senile plaques in Alzheimer’s disease brains. This review will outline the current thinking on how Aβ mediates neurotoxicity or neuronal dysfunction. In particular, this article will focus on the key residues that modulate Aβ’s activity and the cellular pathways and mechanisms involved. It will detail how Aβ–metal interactions are a key determinate in Alzheimer’s disease pathogenesis.
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Affiliation(s)
- Roberto Cappai
- The University of Melbourne, Department of Pathology, Bio21 Molecular Science & Biotechnology Institute, Victoria, 3010, Australia, and, The Mental Health Research Institute of Victoria, Parkville, Victoria, 3052, Australia
| | - Kevin J Barnham
- The University of Melbourne, Department of Pathology, Bio21 Molecular Science & Biotechnology Institute, Victoria, 3010, Australia, and, The Mental Health Research Institute of Victoria, Parkville, Victoria, 3052, Australia
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56
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Chan A, Shea TB. Folate deprivation increases presenilin expression, gamma-secretase activity, and Abeta levels in murine brain: potentiation by ApoE deficiency and alleviation by dietary S-adenosyl methionine. J Neurochem 2007; 102:753-60. [PMID: 17504266 DOI: 10.1111/j.1471-4159.2007.04589.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Folate deficiency has been associated with age-related neurodegeneration. One direct consequence of folate deficiency is a decline in the major methyl donor, S-adenosyl methionine (SAM). We demonstrate herein that dietary deficiency in folate and vitamin E, coupled pro-oxidant stress induced by dietary iron, increased presenilin-1 expression, gamma-secretase activity, and Abeta levels in normal adult mice. These increases were potentiated by apolipoprotein E deficiency as shown by treatment of transgenic mice homozygously lacking murine apolipoprotein E. Dietary supplementation with SAM in the absence of folate attenuated or alleviated these deleterious consequences. These findings link nutritional and genetic risk factors for age-related neurodegeneration and underscore that dietary supplementation with SAM may be useful to augment therapeutic approaches.
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Affiliation(s)
- Amy Chan
- Center for Cellular Neurobiology and Neurodegeneration Research, Department of Biological Sciences, University of Massachusetts Lowell, Lowell, Massachusetts 01854, USA
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57
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Riddell DR, Zhou H, Comery TA, Kouranova E, Lo CF, Warwick HK, Ring RH, Kirksey Y, Aschmies S, Xu J, Kubek K, Hirst WD, Gonzales C, Chen Y, Murphy E, Leonard S, Vasylyev D, Oganesian A, Martone RL, Pangalos MN, Reinhart PH, Jacobsen JS. The LXR agonist TO901317 selectively lowers hippocampal Abeta42 and improves memory in the Tg2576 mouse model of Alzheimer's disease. Mol Cell Neurosci 2007; 34:621-8. [PMID: 17336088 DOI: 10.1016/j.mcn.2007.01.011] [Citation(s) in RCA: 194] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Revised: 01/05/2007] [Accepted: 01/18/2007] [Indexed: 10/23/2022] Open
Abstract
Recent studies show that intracellular cholesterol levels can modulate the processing of amyloid precursor protein to Abeta peptide. Moreover, cholesterol-rich apoE-containing lipoproteins may also promote Abeta clearance. Agonists of the liver X receptor (LXR) transcriptionally induce genes involved in intracellular lipid efflux and transport, including apoE. Thus, LXR agonists have the potential to both inhibit APP processing and promote Abeta clearance. Here we show that LXR agonist, TO901317, increased hippocampal ABCA1 and apoE and decreased Abeta42 levels in APP transgenic mice. TO901317 had no significant effects on levels of Abeta40, full length APP, or the APP processing products. Next, we examined the effects of TO901317 in the contextual fear conditioning paradigm; TO901317 completely reversed the contextual memory deficit in these mice. These data demonstrate that LXR agonists do not directly inhibit APP processing but rather facilitate the clearance of Abeta42 and may represent a novel therapeutic approach to Alzheimer's disease.
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Affiliation(s)
- David R Riddell
- Discovery Neuroscience, Wyeth Research, CN8000, Princeton, NJ 08543, USA.
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58
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Molecules that Disrupt Memory Circuits in Alzheimer’s Disease: The Attack on Synapses by Aβ Oligomers (ADDLs). MEMORIES: MOLECULES AND CIRCUITS 2007. [DOI: 10.1007/978-3-540-45702-2_11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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59
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Yun SH, Park KA, Kwon S, Woolley CS, Sullivan PM, Pasternak JF, Trommer BL. Estradiol enhances long term potentiation in hippocampal slices from aged apoE4-TR mice. Hippocampus 2007; 17:1153-7. [PMID: 17696167 DOI: 10.1002/hipo.20357] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Hormone replacement therapy to treat or prevent Alzheimer Disease (AD) in postmenopausal women is controversial because it may pose other health risks such as cancer and thromboembolism. ApoE status is thought to influence the nootropic efficacy of hormone therapy, but findings are neither consistent nor well understood. We used a known in vitro memory model (long-term potentiation, LTP) in aged (24-27 month) female targeted replacement mice expressing human apoE3 or E4 to compare the effects of exogenous estradiol. Recording medial perforant path evoked field potentials in dentate gyrus of hippocampal slices, we found that both strains exhibited comparable basal synaptic transmission as assessed by input/output functions and paired pulse depression, and that these measures were not affected by estradiol. Vehicle-treated groups from both strains showed comparable LTP. Estradiol had no effect on LTP in apoE3-TR, but selectively increased LTP magnitude in apoE4-TR. The estradiol induced enhancement of LTP in aged female apoE4-TR is consistent with recent clinical observations that estrogen replacement decreases AD risk in some women with apoE4. Elucidating the mechanism of this selective enhancement may lead to more informed treatment decisions as well as to the development of safer alternatives to hormone therapy.
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Affiliation(s)
- Sung Hwan Yun
- Departments of Pediatrics and Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
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60
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Rebeck GW, LaDu MJ, Estus S, Bu G, Weeber EJ. The generation and function of soluble apoE receptors in the CNS. Mol Neurodegener 2006; 1:15. [PMID: 17062143 PMCID: PMC1635701 DOI: 10.1186/1750-1326-1-15] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Accepted: 10/24/2006] [Indexed: 01/11/2023] Open
Abstract
More than a decade has passed since apolipoprotein E4 (APOE-ε4) was identified as a primary risk factor for Alzheimer 's disease (AD), yet researchers are even now struggling to understand how the apolipoprotein system integrates into the puzzle of AD etiology. The specific pathological actions of apoE4, methods of modulating apolipoprotein E4-associated risk, and possible roles of apoE in normal synaptic function are still being debated. These critical questions will never be fully answered without a complete understanding of the life cycle of the apolipoprotein receptors that mediate the uptake, signaling, and degradation of apoE. The present review will focus on apoE receptors as modulators of apoE actions and, in particular, explore the functions of soluble apoE receptors, a field almost entirely overlooked until now.
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Affiliation(s)
- G William Rebeck
- Department of Neuroscience, Georgetown University, Washington DC, USA
| | - Mary Jo LaDu
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, USA
| | - Steven Estus
- Department of Physiology, University of Kentucky, Lexington, USA
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, USA
| | - Guojun Bu
- Department of Pediatrics, Washington University, St. Louis, USA
- Department of Cell Biology and Physiology, Washington University, St. Louis, USA
- Hope Center for Neurological Disorders, Washington University, St. Louis, USA
| | - Edwin J Weeber
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, USA
- Department of Pharmacology, Vanderbilt University, Nashville, USA
- Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, USA
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61
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Belinson H, Dolev I, Michaelson DM. Neuron-specific susceptibility to apolipoprotein E4. Neurobiol Aging 2006; 28:689-92; discussion 704-6. [PMID: 17023093 DOI: 10.1016/j.neurobiolaging.2006.06.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2006] [Accepted: 06/19/2006] [Indexed: 10/24/2022]
Affiliation(s)
- Haim Belinson
- Department of Neurobiochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel
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62
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Manelli AM, Bulfinch LC, Sullivan PM, LaDu MJ. Abeta42 neurotoxicity in primary co-cultures: effect of apoE isoform and Abeta conformation. Neurobiol Aging 2006; 28:1139-47. [PMID: 16837105 PMCID: PMC3752940 DOI: 10.1016/j.neurobiolaging.2006.05.024] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2006] [Revised: 05/18/2006] [Accepted: 05/19/2006] [Indexed: 11/16/2022]
Abstract
Autosomal dominant mutations that increase amyloid-beta(1-42) (Abeta42) cause familial Alzheimer's disease (AD), and the most common genetic risk factor for AD is the presence of the epsilon4 allele of apolipoprotein E (apoE). Previously, we characterized stable preparations of Abeta42 oligomers and fibrils and reported that oligomers induced a 10-fold greater increase in neurotoxicity than fibrils in Neuro-2A cells. To determine the effects of apoE genotype on Abeta42 oligomer- and fibril-induced neurotoxicity in vitro, we co-cultured wild type (WT) neurons with glia from WT, apoE-knockout (apoE-KO), and human apoE2-, E3-, and E4-targeted replacement (TR) mice. Dose-dependent neurotoxicity was induced by oligomeric Abeta42 with a ranking order of apoE4-TR>KO=apoE2-TR=apoE3-TR>WT. Neurotoxicity induced by staurosporine or glutamate were not affected by apoE genotype, indicating specificity for oligomeric Abeta42-induced neurotoxicity. These in vitro data demonstrate a gain of negative function for apoE4, synergistic with oligomeric Abeta42, in mediating neurotoxicity.
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Affiliation(s)
- Arlene M. Manelli
- Department of Medicine, Division of Geriatrics, Evanston Northwestern Healthcare Research Institute, Evanston, IL 60201, United States
| | - Lindsey C. Bulfinch
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, 808 S. Wood St., CME 578, M/C 512, Chicago, IL 60612, United States
| | - Patrick M. Sullivan
- Department of Medicine, Division of Neurology and Bryan ADRC, Duke University, Durham, NC 27710, United States
| | - Mary Jo LaDu
- Department of Medicine, Division of Geriatrics, Evanston Northwestern Healthcare Research Institute, Evanston, IL 60201, United States
- Corresponding author: Tel.: +1 312 355 4795; fax: +1 312 355 0386. (M.J. LaDu)
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63
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Yun SH, Gamkrelidze G, Stine WB, Sullivan PM, Pasternak JF, LaDu MJ, Trommer BL. Amyloid-beta1-42 reduces neuronal excitability in mouse dentate gyrus. Neurosci Lett 2006; 403:162-5. [PMID: 16765515 PMCID: PMC3752836 DOI: 10.1016/j.neulet.2006.04.065] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Revised: 04/10/2006] [Accepted: 04/24/2006] [Indexed: 11/17/2022]
Abstract
Amyloid-beta (Abeta) is causally implicated in Alzheimer's disease and neuroplasticity failure has acquired validity as a possible mechanism of early AD pathogenesis. We have previously demonstrated that oligomeric Abeta(1-42) inhibits LTP in the dentate gyrus of rat hippocampal slices. We now show, using whole cell recordings in hippocampal granule cells, that oligomeric Abeta(1-42) decreases neuronal excitability. In particular, Abeta(1-42) application was associated with a decrease in the number of action potentials fired in response to current injection, and with an increase in the amplitude of the afterhyperpolarization. Reduced excitability may underlie the Abeta-mediated impairment in neuroplasticity, and ultimately may contribute to the memory loss in Alzheimer disease.
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Affiliation(s)
- Sung Hwan Yun
- Departments of Pediatrics and Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60614, United States
- Department of Pediatrics, Division of Neurology, Evanston Northwestern Healthcare, 2650 Ridge Avenue, Evanston IL 60201, United States
- ENH Research Institute, 1001 University Place Evanston, IL 60202, United States
| | - Georgi Gamkrelidze
- Department of Physiology and Neuroscience, New York University School of Medicine, New York, NY 10016, United States
| | - W. Blaine Stine
- ENH Research Institute, 1001 University Place Evanston, IL 60202, United States
| | - Patrick M. Sullivan
- Department of Medicine, Division of Neurology, Duke University, Durham, NC 27710, United States
| | - Joseph F. Pasternak
- Departments of Pediatrics and Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60614, United States
- Department of Pediatrics, Division of Neurology, Evanston Northwestern Healthcare, 2650 Ridge Avenue, Evanston IL 60201, United States
- ENH Research Institute, 1001 University Place Evanston, IL 60202, United States
| | - Mary Jo LaDu
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612, United States
| | - Barbara L. Trommer
- Departments of Pediatrics and Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60614, United States
- Department of Pediatrics, Division of Neurology, Evanston Northwestern Healthcare, 2650 Ridge Avenue, Evanston IL 60201, United States
- ENH Research Institute, 1001 University Place Evanston, IL 60202, United States
- Corresponding author. Tel.: +1 847 570 2577; fax: +1 847 570 2073.
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64
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Szegedi V, Juhász G, Rózsa E, Juhász-Vedres G, Datki Z, Fülöp L, Bozsó Z, Lakatos A, Laczkó I, Farkas T, Kis Z, Tóth G, Soós K, Zarándi M, Budai D, Toldi J, Penke B. Endomorphin‐2, an endogenous tetrapeptide, protects against Aβ1‐42
in vitro
and
in vivo. FASEB J 2006; 20:1191-3. [PMID: 16636106 DOI: 10.1096/fj.05-4891fje] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The underlying cause of Alzheimer's disease (AD) is thought to be the beta-amyloid aggregates formed mainly by Abeta1-42 peptide. Protective pentapeptides [e.g., Leu-Pro-Phe-Phe-Asp (LPFFD)] have been shown to prevent neuronal toxicity of Abeta1-42 by arresting and reversing fibril formation. Here we report that an endogenous tetrapeptide, endomorphin-2 (End-2, amino acid sequence: YPFF), defends against Abeta1-42 induced neuromodulatory effects at the cellular level. Although End-2 does not interfere with the kinetics of Abeta fibrillogenesis according to transmission electron microscopic studies and quasielastic light scattering measurements, it binds to Abeta1-42 during aggregation, as revealed by tritium-labeled End-2 binding assay and circular dichroism measurements. The tetrapeptide attenuates the inhibitory effect on cellular redox activity of Abeta1-42 in a dose-dependent manner, as measured by 3-(4,5-dimethylthiazolyl-2)-2,-5-diphenyltetrazolium bromide (MTT) assay. In vitro and in vivo electrophysiological experiments show that End-2 also protects against the field excitatory postsynaptic potential attenuating and the NMDA-evoked response-enhancing effect of Abeta1-42. Studies using [D-Ala (2), N-Me-Phe (4), Gly (5)-ol]-enkephalin (DAMGO), a mu-opioid receptor agonist, show that the protective effects of the tetrapeptide are not mu-receptor modulated. The endogenous tetrapeptide End-2 may serve as a lead compound for the drug development in the treatment of AD.
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Affiliation(s)
- Viktor Szegedi
- Department of Medical Chemistry, University of Szeged, Dóm Square 8, Szeged 6720, Hungary.
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65
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Yun SH, Park KA, Sullivan P, Pasternak JF, Ladu MJ, Trommer BL. Blockade of nicotinic acetylcholine receptors suppresses hippocampal long-term potentiation in wild-type but not ApoE4 targeted replacement mice. J Neurosci Res 2006; 82:771-7. [PMID: 16273551 DOI: 10.1002/jnr.20684] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Both impaired nicotinic neurotransmission and the inheritance of apoE4 are associated with increased risk for Alzheimer disease (AD) as well as other deficiencies in memory-related behavior. Long-term potentiation (LTP), a cellular model of memory, is known to be altered by nicotinic agents. Recent studies also support an emergent role for apoE in LTP. We compared the effects of mecamylamine, a nonspecific antagonist of nicotinic acetylcholine receptors (nAChRs), on basal synaptic transmission and LTP in hippocampal slices from wild-type (wt) mice and targeted replacement mice expressing human apoE4 (apoE4-TR). Field excitatory postsynaptic potentials (EPSPs) were recorded in the dentate gyrus (DG) in response to medial perforant path activation, and theta burst stimulation was used to induce LTP. Bath application of mecamylamine (3 microM) did not alter input-output relationships or paired pulse depression in either mouse strain. Under control conditions, apoE4-TR mice showed significantly less LTP than wt mice (17.5% +/- 3.2%, n = 9, vs. 30.1% +/- 3.9%, n = 11, P < 0.02). Mecamylamine reduced LTP in wt mice to a level that was similar to control levels for apoE4-TR mice (15.7% +/- 3.4%, n = 9), whereas apoE4-TR showed no further reduction of LTP (16.6% +/- 3.7%, n = 8) by mecamylamine. Thus mice expressing human apoE4 differ from wt mice both in their capacity for LTP and in the effect on LTP of nicotinic cholinergic blockade. It is possible that nicotinic neurotransmission is already compromised in apoE4-TR mice and, hence, that interference with the integrity of this cholinergic system represents a mechanism by which inheritance of the apoE4 allele contributes to cognitive risk.
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Affiliation(s)
- Sung Hwan Yun
- Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
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66
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Klein WL. Synaptic targeting by Aβ oligomers (ADDLS) as a basis for memory loss in early Alzheimer's disease. Alzheimers Dement 2006; 2:43-55. [PMID: 19595855 DOI: 10.1016/j.jalz.2005.11.003] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Accepted: 11/23/2005] [Indexed: 01/19/2023]
Affiliation(s)
- William L. Klein
- Department of Neurobiology & Physiology, Cognitive Neurology and Alzehimer's Disease Center; Northwestern University Institute for Neuroscience, Northwestern University; Evanston IL 60208 USA
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