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Rosales-Corral SA, Acuña-Castroviejo D, Coto-Montes A, Boga JA, Manchester LC, Fuentes-Broto L, Korkmaz A, Ma S, Tan DX, Reiter RJ. Alzheimer's disease: pathological mechanisms and the beneficial role of melatonin. J Pineal Res 2012; 52:167-202. [PMID: 22107053 DOI: 10.1111/j.1600-079x.2011.00937.x] [Citation(s) in RCA: 218] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Alzheimer's disease (AD) is a highly complex neurodegenerative disorder of the aged that has multiple factors which contribute to its etiology in terms of initiation and progression. This review summarizes these diverse aspects of this form of dementia. Several hypotheses, often with overlapping features, have been formulated to explain this debilitating condition. Perhaps the best-known hypothesis to explain AD is that which involves the role of the accumulation of amyloid-β peptide in the brain. Other theories that have been invoked to explain AD and summarized in this review include the cholinergic hypothesis, the role of neuroinflammation, the calcium hypothesis, the insulin resistance hypothesis, and the association of AD with peroxidation of brain lipids. In addition to summarizing each of the theories that have been used to explain the structural neural changes and the pathophysiology of AD, the potential role of melatonin in influencing each of the theoretical processes involved is discussed. Melatonin is an endogenously produced and multifunctioning molecule that could theoretically intervene at any of a number of sites to abate the changes associated with the development of AD. Production of this indoleamine diminishes with increasing age, coincident with the onset of AD. In addition to its potent antioxidant and anti-inflammatory activities, melatonin has a multitude of other functions that could assist in explaining each of the hypotheses summarized above. The intent of this review is to stimulate interest in melatonin as a potentially useful agent in attenuating and/or delaying AD.
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Affiliation(s)
- Sergio A Rosales-Corral
- Centro de Investigación Biomédica de Occidente del Instituto Mexicano del Seguro Social, Guadalajara, Jalisco, México.
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102
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The role of APP proteolytic processing in lipid metabolism. Exp Brain Res 2011; 217:365-75. [DOI: 10.1007/s00221-011-2975-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 12/01/2011] [Indexed: 12/14/2022]
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103
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Orešič M, Hyötyläinen T, Herukka SK, Sysi-Aho M, Mattila I, Seppänan-Laakso T, Julkunen V, Gopalacharyulu PV, Hallikainen M, Koikkalainen J, Kivipelto M, Helisalmi S, Lötjönen J, Soininen H. Metabolome in progression to Alzheimer's disease. Transl Psychiatry 2011; 1:e57. [PMID: 22832349 PMCID: PMC3309497 DOI: 10.1038/tp.2011.55] [Citation(s) in RCA: 197] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Mild cognitive impairment (MCI) is considered as a transition phase between normal aging and Alzheimer's disease (AD). MCI confers an increased risk of developing AD, although the state is heterogeneous with several possible outcomes, including even improvement back to normal cognition. We sought to determine the serum metabolomic profiles associated with progression to and diagnosis of AD in a prospective study. At the baseline assessment, the subjects enrolled in the study were classified into three diagnostic groups: healthy controls (n=46), MCI (n=143) and AD (n=47). Among the MCI subjects, 52 progressed to AD in the follow-up. Comprehensive metabolomics approach was applied to analyze baseline serum samples and to associate the metabolite profiles with the diagnosis at baseline and in the follow-up. At baseline, AD patients were characterized by diminished ether phospholipids, phosphatidylcholines, sphingomyelins and sterols. A molecular signature comprising three metabolites was identified, which was predictive of progression to AD in the follow-up. The major contributor to the predictive model was 2,4-dihydroxybutanoic acid, which was upregulated in AD progressors (P=0.0048), indicating potential involvement of hypoxia in the early AD pathogenesis. This was supported by the pathway analysis of metabolomics data, which identified upregulation of pentose phosphate pathway in patients who later progressed to AD. Together, our findings primarily implicate hypoxia, oxidative stress, as well as membrane lipid remodeling in progression to AD. Establishment of pathogenic relevance of predictive biomarkers such as ours may not only facilitate early diagnosis, but may also help identify new therapeutic avenues.
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Affiliation(s)
- M Orešič
- VTT Technical Research Centre of Finland, Espoo, Finland.
| | - T Hyötyläinen
- VTT Technical Research Centre of Finland, Espoo, Finland
| | - S-K Herukka
- Department of Neurology, Kuopio University Hospital and University of Eastern Finland, Kuopio, Finland
| | - M Sysi-Aho
- VTT Technical Research Centre of Finland, Espoo, Finland
| | - I Mattila
- VTT Technical Research Centre of Finland, Espoo, Finland
| | | | - V Julkunen
- Department of Neurology, Kuopio University Hospital and University of Eastern Finland, Kuopio, Finland
| | | | - M Hallikainen
- Department of Neurology, Kuopio University Hospital and University of Eastern Finland, Kuopio, Finland
| | - J Koikkalainen
- VTT Technical Research Centre of Finland, Tampere, Finland
| | - M Kivipelto
- Aging Research Center, Karolinska Institute, Stockholm, Sweden
| | - S Helisalmi
- Department of Neurology, Kuopio University Hospital and University of Eastern Finland, Kuopio, Finland
| | - J Lötjönen
- VTT Technical Research Centre of Finland, Tampere, Finland
| | - H Soininen
- Department of Neurology, Kuopio University Hospital and University of Eastern Finland, Kuopio, Finland
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104
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Hartmann T, Prinetti A. Going the wrong road: Fyn and targeting of amyloid precursor protein to lipid rafts. J Neurochem 2011; 118:677-9. [PMID: 21689102 DOI: 10.1111/j.1471-4159.2011.07353.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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105
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Sano M, Bell KL, Galasko D, Galvin JE, Thomas RG, van Dyck CH, Aisen PS. A randomized, double-blind, placebo-controlled trial of simvastatin to treat Alzheimer disease. Neurology 2011; 77:556-63. [PMID: 21795660 PMCID: PMC3149154 DOI: 10.1212/wnl.0b013e318228bf11] [Citation(s) in RCA: 209] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 04/05/2011] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Lowering cholesterol is associated with reduced CNS amyloid deposition and increased dietary cholesterol increases amyloid accumulation in animal studies. Epidemiologic data suggest that use of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) may decrease the risk of Alzheimer disease (AD) and a single-site trial suggested possible benefit in cognition with statin treatment in AD, supporting the hypothesis that statin therapy is useful in the treatment of AD. OBJECTIVE To determine if the lipid-lowering agent simvastatin slows the progression of symptoms in AD. METHODS This randomized, double-blind, placebo-controlled trial of simvastatin was conducted in individuals with mild to moderate AD and normal lipid levels. Participants were randomly assigned to receive simvastatin, 20 mg/day, for 6 weeks then 40 mg per day for the remainder of 18 months or identical placebo. The primary outcome was the rate of change in the Alzheimer's Disease Assessment Scale-cognitive portion (ADAS-Cog). Secondary outcomes measured clinical global change, cognition, function, and behavior. RESULTS A total of 406 individuals were randomized: 204 to simvastatin and 202 to placebo. Simvastatin lowered lipid levels but had no effect on change in ADAS-Cog score or the secondary outcome measures. There was no evidence of increased adverse events with simvastatin treatment. CONCLUSION Simvastatin had no benefit on the progression of symptoms in individuals with mild to moderate AD despite significant lowering of cholesterol. CLASSIFICATION OF EVIDENCE This study provides Class I evidence that simvastatin 40 mg/day does not slow decline on the ADAS-Cog.
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Affiliation(s)
- M Sano
- Mount Sinai School of Medicine, Bronx, NY 10468, USA.
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106
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Mathew A, Yoshida Y, Maekawa T, Sakthi Kumar D. Alzheimer's disease: Cholesterol a menace? Brain Res Bull 2011; 86:1-12. [DOI: 10.1016/j.brainresbull.2011.06.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Revised: 06/17/2011] [Accepted: 06/19/2011] [Indexed: 12/20/2022]
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107
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Amaya KR, Sweedler JV, Clayton DF. Small molecule analysis and imaging of fatty acids in the zebra finch song system using time-of-flight-secondary ion mass spectrometry. J Neurochem 2011; 118:499-511. [PMID: 21496023 PMCID: PMC3137756 DOI: 10.1111/j.1471-4159.2011.07274.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fatty acids are central to brain metabolism and signaling, but their distributions within complex brain circuits have been difficult to study. Here we applied an emerging technique, time-of-flight secondary ion mass spectrometry (ToF-SIMS), to image specific fatty acids in a favorable model system for chemical analyses of brain circuits, the zebra finch (Taeniopygia guttata). The zebra finch, a songbird, produces complex learned vocalizations under the control of an interconnected set of discrete, dedicated brain nuclei 'song nuclei'. Using ToF-SIMS, the major song nuclei were visualized by virtue of differences in their content of essential and non-essential fatty acids. Essential fatty acids (arachidonic acid and docosahexaenoic acid) showed distinctive distributions across the song nuclei, and the 18-carbon fatty acids stearate and oleate discriminated the different core and shell subregions of the lateral magnocellular nucleus of the anterior nidopallium. Principal component analysis of the spectral data set provided further evidence of chemical distinctions between the song nuclei. By analyzing the robust nucleus of the arcopallium at three different ages during juvenile song learning, we obtain the first direct evidence of changes in lipid content that correlate with progression of song learning. The results demonstrate the value of ToF-SIMS to study lipids in a favorable model system for probing the function of lipids in brain organization, development and function.
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Affiliation(s)
- Kensey R Amaya
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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108
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Kawaguchi M, Okabe T, Okudaira S, Hanaoka K, Fujikawa Y, Terai T, Komatsu T, Kojima H, Aoki J, Nagano T. Fluorescence probe for lysophospholipase C/NPP6 activity and a potent NPP6 inhibitor. J Am Chem Soc 2011; 133:12021-30. [PMID: 21721554 DOI: 10.1021/ja201028t] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Nucleotide pyrophosphatases/phosphodiesterases (NPPs) are ubiquitous membrane-associated or secreted ectoenzymes that have a role in regulating extracellular nucleotide and phospholipid metabolism. Among the members of the NPP family, NPP1 and -3 act on nucleotides such as ATP, while NPP2, -6, and -7 act on phospholipids such as lysophosphatidylcholine and sphingomyelin. NPP6, a recently characterized NPP family member, is a choline-specific glycerophosphodiester phosphodiesterase, but its functions remain to be analyzed, partly due to the lack of highly sensitive activity assay systems and practical inhibitors. Here we report synthesis of novel NPP6 fluorescence probes, TG-mPC and its analogues TG-mPC(3)C, TG-mPC(5)C, TG-mPENE, TG-mPEA, TG-mPhos, TG-mPA, TG-mPMe, and TG-mPPr. Among the seven NPPs, only NPP6 hydrolyzed TG-mPC, TG-mPC(3)C, and TG-mPENE. TG-mPC was hydrolyzed in the cell lysate from NPP6-transfected cells, but not control cells, showing that it is suitable for use in cell-based NPP6 assays. We also examined the usefulness of TG-mPC as a fluorescence imaging probe. We further applied TG-mPC to carry out high-throughput NPP6 inhibitor screening and found several NPP6-selective inhibitors in a library of about 80,000 compounds. Through structure-activity relationship (SAR) analysis, we identified a potent and selective NPP6 inhibitor with an IC(50) value of 0.21 μM. Our NPP6-selective fluorescence probe, TG-mPC, and the inhibitor are expected to be useful to elucidate the biological function of NPP6.
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Affiliation(s)
- Mitsuyasu Kawaguchi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan
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109
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Moser AB, Steinberg SJ, Watkins PA, Moser HW, Ramaswamy K, Siegmund KD, Lee DR, Ely JJ, Ryder OA, Hacia JG. Human and great ape red blood cells differ in plasmalogen levels and composition. Lipids Health Dis 2011; 10:101. [PMID: 21679470 PMCID: PMC3129581 DOI: 10.1186/1476-511x-10-101] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 06/17/2011] [Indexed: 02/06/2023] Open
Abstract
Background Plasmalogens are ether phospholipids required for normal mammalian developmental, physiological, and cognitive functions. They have been proposed to act as membrane antioxidants and reservoirs of polyunsaturated fatty acids as well as influence intracellular signaling and membrane dynamics. Plasmalogens are particularly enriched in cells and tissues of the human nervous, immune, and cardiovascular systems. Humans with severely reduced plasmalogen levels have reduced life spans, abnormal neurological development, skeletal dysplasia, impaired respiration, and cataracts. Plasmalogen deficiency is also found in the brain tissue of individuals with Alzheimer disease. Results In a human and great ape cohort, we measured the red blood cell (RBC) levels of the most abundant types of plasmalogens. Total RBC plasmalogen levels were lower in humans than bonobos, chimpanzees, and gorillas, but higher than orangutans. There were especially pronounced cross-species differences in the levels of plasmalogens with a C16:0 moiety at the sn-1 position. Humans on Western or vegan diets had comparable total RBC plasmalogen levels, but the latter group showed moderately higher levels of plasmalogens with a C18:1 moiety at the sn-1 position. We did not find robust sex-specific differences in human or chimpanzee RBC plasmalogen levels or composition. Furthermore, human and great ape skin fibroblasts showed only modest differences in peroxisomal plasmalogen biosynthetic activity. Human and chimpanzee microarray data indicated that genes involved in plasmalogen biosynthesis show cross-species differential expression in multiple tissues. Conclusion We propose that the observed differences in human and great ape RBC plasmalogens are primarily caused by their rates of biosynthesis and/or turnover. Gene expression data raise the possibility that other human and great ape cells and tissues differ in plasmalogen levels. Based on the phenotypes of humans and rodents with plasmalogen disorders, we propose that cross-species differences in tissue plasmalogen levels could influence organ functions and processes ranging from cognition to reproduction to aging.
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Affiliation(s)
- Ann B Moser
- Hugo W. Moser Research Institute at Kennedy Krieger, and Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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110
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Lu JX, Yau WM, Tycko R. Evidence from solid-state NMR for nonhelical conformations in the transmembrane domain of the amyloid precursor protein. Biophys J 2011; 100:711-719. [PMID: 21281586 DOI: 10.1016/j.bpj.2010.12.3696] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Revised: 10/22/2010] [Accepted: 12/08/2010] [Indexed: 02/03/2023] Open
Abstract
The amyloid precursor protein (APP) is subject to proteolytic processing by γ-secretase within neuronal membranes, leading to Alzheimer's disease-associated β-amyloid peptide production by cleavage near the midpoint of the single transmembrane (TM) segment of APP. Conformational properties of the TM segment may affect its susceptibility to γ-secretase cleavage, but these properties have not been established definitively, especially in bilayer membranes with physiologically relevant lipid compositions. In this article, we report an investigation of the APP-TM conformation, using (13)C chemical shifts obtained with two-dimensional solid-state NMR spectroscopy as site-specific conformational probes. We find that the APP-TM conformation is not a simple α-helix, particularly at 37°C in multilamellar vesicles with compositions that mimic the composition of neuronal cell membranes. Instead, we observe a mixture of helical and nonhelical conformations at the N- and C-termini and in the vicinity of the γ-cleavage site. Conformational plasticity of the TM segment of APP may be an important factor in the γ-secretase cleavage mechanism.
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Affiliation(s)
- Jun-Xia Lu
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Wai-Ming Yau
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Robert Tycko
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland.
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Abstract
Lipid-mediated signalling regulates a plethora of physiological processes, including crucial aspects of brain function. In addition, dysregulation of lipid pathways has been implicated in a growing number of neurodegenerative disorders, such as Alzheimer's disease (AD). Although much attention has been given to the link between cholesterol and AD pathogenesis, growing evidence suggests that other lipids, such as phosphoinositides and phosphatidic acid, have an important role. Regulators of lipid metabolism (for example, statins) are a highly successful class of marketed drugs, and exploration of lipid dysregulation in AD and identification of novel therapeutic agents acting through relevant lipid pathways offers new and effective options for the treatment of this devastating disorder.
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112
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Phospholipase d2 ablation ameliorates Alzheimer's disease-linked synaptic dysfunction and cognitive deficits. J Neurosci 2011; 30:16419-28. [PMID: 21147981 DOI: 10.1523/jneurosci.3317-10.2010] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Growing evidence implicates aberrant lipid signaling in Alzheimer's disease (AD). While phospholipases A2 and C have been recently shown to mediate key actions of amyloid β-peptide (Aβ) through a dysregulation of arachidonic acid and phosphatidylinositol-4,5-bisphosphate metabolism, respectively, the role of phospholipase D (PLD) has so far remained elusive. PLD produces phosphatidic acid (PA), a bioactive lipid involved in multiple aspects of cell physiology, including signaling and membrane trafficking processes. Here we show that oligomeric Aβ enhances PLD activity in cultured neurons and that this stimulatory effect does not occur upon ablation of PLD2 via gene targeting. Aβ fails to suppress long-term potentiation in PLD2-deficient hippocampal slices, suggesting that PLD2 is required for the synaptotoxic action of this peptide. In vivo PLD activity, as assessed by detection of phosphatidylethanol levels using mass spectrometry (MS) following ethanol injection, is also increased in the brain of a transgenic mouse model of AD (SwAPP). Furthermore, Pld2 ablation rescues memory deficits and confers synaptic protection in SwAPP mice despite a significant Aβ load. MS-based lipid analysis of Pld2 mutant brains in the presence or absence of the SwAPP transgene unmasks striking crosstalks between different PA species. This lipid analysis shows an exquisite acyl chain specificity and plasticity in the perturbation of PA metabolism. Collectively, our results point to specific molecular species of PA as key modulators of AD pathogenesis and identify PLD2 as a novel potential target for therapeutics.
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113
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Sterol chemical configuration and conformation influence the thermotropic phase behaviour of dipalmitoylphosphatidylcholine mixtures containing 5β-cholestan-3β- and -3α-ol. Chem Phys Lipids 2011; 164:70-7. [DOI: 10.1016/j.chemphyslip.2010.10.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2010] [Revised: 10/20/2010] [Accepted: 10/27/2010] [Indexed: 01/27/2023]
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114
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Barrier L, Fauconneau B, Noël A, Ingrand S. Ceramide and Related-Sphingolipid Levels Are Not Altered in Disease-Associated Brain Regions of APP and APP/PS1 Mouse Models of Alzheimer's Disease: Relationship with the Lack of Neurodegeneration? Int J Alzheimers Dis 2010; 2011:920958. [PMID: 21234372 PMCID: PMC3014734 DOI: 10.4061/2011/920958] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 11/16/2010] [Indexed: 02/06/2023] Open
Abstract
There is evidence linking sphingolipid abnormalities, APP processing, and neuronal death in Alzheimer's disease (AD). We previously reported a strong elevation of ceramide levels in the brain of the APP(SL)/PS1Ki mouse model of AD, preceding the neuronal death. To extend these findings, we analyzed ceramide and related-sphingolipid contents in brain from two other mouse models (i.e., APP(SL) and APP(SL)/PS1(M146L)) in which the time-course of pathology is closer to that seen in most currently available models. Conversely to our previous work, ceramides did not accumulate in disease-associated brain regions (cortex and hippocampus) from both models. However, the APP(SL)/PS1Ki model is unique for its drastic neuronal loss coinciding with strong accumulation of neurotoxic Aβ isoforms, not observed in other animal models of AD. Since there are neither neuronal loss nor toxic Aβ species accumulation in APP(SL) mice, we hypothesized that it might explain the lack of ceramide accumulation, at least in this model.
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Affiliation(s)
- Laurence Barrier
- Groupe de Recherche sur le Vieillissement Cérébral, GreViC EA 3808, Faculté de Médecine et de Pharmacie, 6 rue de la Milétrie, BP 199, 86034 Poitiers Cedex, France
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115
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Designed fluorescent probes reveal interactions between amyloid-beta(1-40) peptides and GM1 gangliosides in micelles and lipid vesicles. Biophys J 2010; 99:1510-9. [PMID: 20816063 DOI: 10.1016/j.bpj.2010.06.043] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Revised: 06/16/2010] [Accepted: 06/17/2010] [Indexed: 12/20/2022] Open
Abstract
A hallmark of the common Alzheimer's disease (AD) is the pathological conversion of its amphiphatic amyloid-beta (Abeta) peptide into neurotoxic aggregates. In AD patients, these aggregates are often found to be tightly associated with neuronal G(M1) ganglioside lipids, suggesting an involvement of G(M1) not only in aggregate formation but also in neurotoxic events. Significant interactions were found between micelles made of newly synthesized fluorescent G(M1) gangliosides labeled in the polar headgroup or the hydrophobic chain and Abeta(1-40) peptide labeled with a BODIPY-FL-C1 fluorophore at positions 12 and 26, respectively. From an analysis of energy transfer between the different fluorescence labels and their location in the molecules, we were able to place the Abeta peptide inside G(M1) micelles, close to the hydrophobic-hydrophilic interface. Large unilamellar vesicles composed of a raftlike G(M1)/bSM/cholesterol lipid composition doped with labeled G(M1) at various positions also interact with labeled Abeta peptide tagged to amino acids 2 or 26. A faster energy transfer was observed from the Abeta peptide to bilayers doped with 581/591-BODIPY-C(11)-G(M1) in the nonpolar part of the lipid compared with 581/591-BODIPY-C(5)-G(M1) residing in the polar headgroup. These data are compatible with a clustering process of G(M1) molecules, an effect that not only increases the Abeta peptide affinity, but also causes a pronounced Abeta peptide penetration deeper into the lipid membrane; all these factors are potentially involved in Abeta peptide aggregate formation due to an altered ganglioside metabolism found in AD patients.
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116
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Nano-HPLC–MS analysis of phospholipids in cerebrospinal fluid of Alzheimer’s disease patients—a pilot study. Anal Bioanal Chem 2010; 398:2929-37. [DOI: 10.1007/s00216-010-4273-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 09/09/2010] [Accepted: 09/18/2010] [Indexed: 12/14/2022]
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117
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Hasegawa H, Liu L, Nishimura M. Dilysine retrieval signal-containing p24 proteins collaborate in inhibiting γ-cleavage of amyloid precursor protein. J Neurochem 2010; 115:771-81. [PMID: 20807314 DOI: 10.1111/j.1471-4159.2010.06977.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
γ-Secretase mediates intramembranous γ-cleavage and ε-cleavage of β-amyloid precursor protein (APP) to liberate β-amyloid peptide (Aβ) and APP intracellular domain respectively from the membrane. Although the regulatory mechanism of γ-secretase cleavage remains unresolved, a member of the p24 cargo protein family, named p24δ(1) or TMP21, has been identified as an activity-modulating component. The p24 family proteins are divided into four subfamilies (p24α, β, δ and γ). In contrast to p24δ(1), p24β(1) has reportedly no effect on γ-cleavage. In this study, we determined whether p24α(2), p24γ(3) or p24γ(4) modulates APP processing. Knockdown of cellular p24α(2) induced a significant increase in Aβ generation but not in APP intracellular domain production in cell-based and cell-free assays, whereas p24α(2) over-expression suppressed Aβ secretion. By contrast, Aβ secretion was not altered by p24γ(3) or p24γ(4) knockdown. Endogenous p24α(2) co-immunoprecipitated with core components of the γ-secretase complex, and the anti-p24α(2) immunoprecipitate exhibited γ-secretase activity. Mutational disruption of the conserved dilysine ER-retrieval motifs of p24α(2) and p24δ(1) perturbed inhibition of γ-cleavage. Simultaneous knockdown, or co-over-expression, of these proteins had no additive or synergistic effect on Aβ generation. Our findings suggest that dilysine ER-retrieval signal-containing p24 proteins, p24α(2) and p24δ(1), bind with γ-secretase complexes and collaborate in attenuating γ-cleavage of APP.
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Affiliation(s)
- Hiroshi Hasegawa
- Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu, Shiga, Japan.
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118
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Boland B, Smith DA, Mooney D, Jung SS, Walsh DM, Platt FM. Macroautophagy is not directly involved in the metabolism of amyloid precursor protein. J Biol Chem 2010; 285:37415-26. [PMID: 20864542 PMCID: PMC2988347 DOI: 10.1074/jbc.m110.186411] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Alterations in the metabolism of amyloid precursor protein (APP) are believed to
play a central role in Alzheimer disease pathogenesis. Burgeoning data indicate
that APP is proteolytically processed in endosomal-autophagic-lysosomal
compartments. In this study, we used both in vivo and
in vitro paradigms to determine whether alterations in
macroautophagy affect APP metabolism. Three mouse models of glycosphingolipid
storage diseases, namely Niemann-Pick type C1, GM1 gangliosidosis, and Sandhoff
disease, had mTOR-independent increases in the autophagic vacuole
(AV)-associated protein, LC3-II, indicative of impaired lysosomal flux. APP
C-terminal fragments (APP-CTFs) were also increased in brains of the three mouse
models; however, discrepancies between LC3-II and APP-CTFs were seen between
primary (GM1 gangliosidosis and Sandhoff disease) and secondary (Niemann-Pick
type C1) lysosomal storage models. APP-CTFs were proportionately higher than
LC3-II in cerebellar regions of GM1 gangliosidosis and Sandhoff disease,
although LC3-II increased before APP-CTFs in brains of NPC1 mice. Endogenous
murine Aβ40 from RIPA-soluble extracts was increased in brains of all
three mice. The in vivo relationship between AV and APP-CTF
accumulation was also seen in cultured neurons treated with agents that impair
primary (chloroquine and leupeptin + pepstatin) and secondary (U18666A
and vinblastine) lysosomal flux. However, Aβ secretion was unaffected by
agents that induced autophagy (rapamycin) or impaired AV clearance, and
LC3-II-positive AVs predominantly co-localized with degradative LAMP-1-positive
lysosomes. These data suggest that neuronal macroautophagy does not directly
regulate APP metabolism but highlights the important anti-amyloidogenic role of
lysosomal proteolysis in post-secretase APP-CTF catabolism.
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Affiliation(s)
- Barry Boland
- Laboratory for Neurodegenerative Research, School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Dublin 4, Ireland.
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119
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Molecular insights into amyloid regulation by membrane cholesterol and sphingolipids: common mechanisms in neurodegenerative diseases. Expert Rev Mol Med 2010; 12:e27. [PMID: 20807455 PMCID: PMC2931503 DOI: 10.1017/s1462399410001602] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Alzheimer, Parkinson and other neurodegenerative diseases involve a series of brain
proteins, referred to as ‘amyloidogenic proteins’, with exceptional
conformational plasticity and a high propensity for self-aggregation. Although the
mechanisms by which amyloidogenic proteins kill neural cells are not fully understood, a
common feature is the concentration of unstructured amyloidogenic monomers on
bidimensional membrane lattices. Membrane-bound monomers undergo a series of
lipid-dependent conformational changes, leading to the formation of oligomers of varying
toxicity rich in β-sheet structures (annular pores, amyloid fibrils) or in
α-helix structures (transmembrane channels). Condensed membrane nano- or
microdomains formed by sphingolipids and cholesterol are privileged sites for the binding
and oligomerisation of amyloidogenic proteins. By controlling the balance between
unstructured monomers and α or β conformers (the chaperone effect),
sphingolipids can either inhibit or stimulate the oligomerisation of amyloidogenic
proteins. Cholesterol has a dual role: regulation of protein–sphingolipid
interactions through a fine tuning of sphingolipid conformation (indirect effect), and
facilitation of pore (or channel) formation through direct binding to amyloidogenic
proteins. Deciphering this complex network of molecular interactions in the context of
age- and disease-related evolution of brain lipid expression will help understanding of
how amyloidogenic proteins induce neural toxicity and will stimulate the development of
innovative therapies for neurodegenerative diseases.
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120
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Abstract
AD (Alzheimer's disease) is a progressive neurodegenerative disease of unknown origin. Despite questions as to the underlying cause(s) of this disease, shared risk factors for both AD and atherosclerotic cardiovascular disease indicate that vascular mechanisms may critically contribute to the development and progression of both AD and atherosclerosis. An increased risk of developing AD is linked to the presence of the apoE4 (apolipoprotein E4) allele, which is also strongly associated with increased risk of developing atherosclerotic cardiovascular disease. Recent studies also indicate that cardiovascular risk factors, including elevated blood cholesterol and triacylglycerol (triglyceride), increase the likelihood of AD and vascular dementia. Lipids and lipoproteins in the circulation interact intimately with the cerebrovasculature, and may have important effects on its constituent brain microvascular endothelial cells and the adjoining astrocytes, which are components of the neurovascular unit. The present review will examine the potential mechanisms for understanding the contributions of vascular factors, including lipids, lipoproteins and cerebrovascular Abeta (amyloid beta), to AD, and suggest therapeutic strategies for the attenuation of this devastating disease process. Specifically, we will focus on the actions of apoE, TGRLs (triacylglycerol-rich lipoproteins) and TGRL lipolysis products on injury of the neurovascular unit and increases in blood-brain barrier permeability.
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121
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Thal DR, Papassotiropoulos A, Saido TC, Griffin WST, Mrak RE, Kölsch H, Del Tredici K, Attems J, Ghebremedhin E. Capillary cerebral amyloid angiopathy identifies a distinct APOE epsilon4-associated subtype of sporadic Alzheimer's disease. Acta Neuropathol 2010; 120:169-83. [PMID: 20535486 DOI: 10.1007/s00401-010-0707-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2010] [Revised: 05/27/2010] [Accepted: 05/29/2010] [Indexed: 01/01/2023]
Abstract
The deposition of amyloid beta-protein (Abeta) in the vessel wall, i.e., cerebral amyloid angiopathy (CAA), is associated with Alzheimer's disease (AD). Two types of CAA can be differentiated by the presence or absence of capillary Abeta-deposits. In addition, as in Alzheimer's disease, risk for capillary CAA is associated with the apolipoprotein E (APOE) epsilon4-allele. Because these morphological and genetic differences between the two types of AD-related CAA exist, the question arises as to whether there exist further differences between AD cases with and without capillary CAA and, if so, whether capillary CAA can be employed to distinguish and define specific subtypes of AD. To address this question, we studied AD and control cases both with and without capillary CAA to identify the following: (1) distinguishing neuropathological features; (2) alterations in perivascular protein expression; and (3) genotype-specific associations. More widespread Abeta-plaque pathology was observed in AD cases with capillary CAA than in those without. Expression of perivascular excitatory amino acid transporter 2 (EAAT-2/GLT-1) was reduced in cortical astrocytes of AD cases with capillary CAA in contrast to those lacking capillary Abeta-deposition and controls. Genetically, AD cases with capillary CAA were strongly associated with the APOE epsilon4 allele compared to those lacking capillary CAA and to controls. To further validate the existence of distinct types of AD we analyzed polymorphisms in additional apoE- and cholesterol-related candidate genes. Our results revealed an association between AD cases without capillary CAA (i.e., AD cases with CAA but lacking capillary CAA and AD cases without CAA) and the T-allele of the alpha(2)macroglobulin receptor/low-density lipoprotein receptor-related protein-1 (LRP-1) C766T polymorphism as opposed to AD cases with capillary CAA and non-AD controls. Taken together, these results indicate that AD cases with capillary CAA differ significantly from other AD cases both genetically and morphologically, thereby pointing to a specific capillary CAA-related and APOE epsilon4-associated subtype of AD.
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Affiliation(s)
- Dietmar Rudolf Thal
- Institute of Pathology, University of Ulm, Albert Einstein Allee 11, Ulm, Germany.
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122
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Etgen T, Sander D, Bickel H, Sander K, Förstl H. Cognitive decline: the relevance of diabetes, hyperlipidaemia and hypertension. ACTA ACUST UNITED AC 2010. [DOI: 10.1177/1474651410368408] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Cognitive decline including mild cognitive impairment describes a heterogeneous condition with cognitive changes between normal ageing and dementia. Cognitive impairment can be promoted or caused by treatable somatic factors. In this review, three important cardiovascular risk factors, diabetes mellitus, hypercholesterolaemia and hypertension, and their association with cognitive decline, are assessed. Though there are many hints of a causal association between diabetes mellitus and the development of cognitive decline, definitive proof of a protective effect of antidiabetic treatment by controlled or randomised placebo-controlled studies is needed. In midlife, elevated cholesterol levels comprise a risk factor for cognitive decline. In elderly subjects, cholesterol levels decline and are not clearly associated with cognitive impairment. The evidence for treatment of hypercholesterolaemia by statins solely for prevention of cognitive decline remains unclear. There is an age-dependent relationship between blood pressure and cognitive impairment. Midlife hypertension is associated with an increased risk of developing cognitive decline and antihypertensive treatment may therefore be beneficial, whereas hypertension later in life does not carry the same risk of cognitive dysfunction. Diagnosis of these somatic factors is essential in cognitive impairment, as diligent treatment may improve cognitive performance and postpone the manifestation of dementia.
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Affiliation(s)
- Thorleif Etgen
- Department of Psychiatry and Psychotherapy, Technische Universität München, Munich, Germany, Department of Neurology, Klinikum Traunstein, Traunstein, Germany,
| | - Dirk Sander
- Department of Neurology, Medical Park Loipl, Bischofswiesen, Germany, Department of Neurology, Technische Universität München, Munich, Germany
| | - Horst Bickel
- Department of Psychiatry and Psychotherapy, Technische Universität München, Munich, Germany
| | - Kerstin Sander
- Department of Neurology, Medical Park Loipl, Bischofswiesen, Germany, Department of Neurology, Technische Universität München, Munich, Germany
| | - Hans Förstl
- Department of Psychiatry and Psychotherapy, Technische Universität München, Munich, Germany
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123
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Simi L, Malentacchi F, Luciani P, Gelmini S, Deledda C, Arvia R, Mannelli M, Peri A, Orlando C. Seladin-1 expression is regulated by promoter methylation in adrenal cancer. BMC Cancer 2010; 10:201. [PMID: 20465827 PMCID: PMC2875219 DOI: 10.1186/1471-2407-10-201] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 05/13/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Seladin-1 overexpression exerts a protective mechanism against apoptosis. Seladin-1 mRNA is variably expressed in normal human tissues. Adrenal glands show the highest levels of seladin-1 expression, which are significantly reduced in adrenal carcinomas (ACC). Since up to now seladin-1 mutations were not described, we investigated whether promoter methylation could account for the down-regulation of seladin-1 expression in ACC. METHODS A methylation sensitive site was identified in the seladin-1 gene. We treated DNA extracted from two ACC cell lines (H295R and SW13) with the demethylating agent 5-Aza-2-deoxycytidine (5-Aza). Furthermore, to evaluate the presence of an epigenetic regulation also 'in vivo', seladin-1 methylation and its mRNA expression were measured in 9 ACC and in 5 normal adrenal glands. RESULTS The treatment of cell lines with 5-Aza induced a significant increase of seladin-1 mRNA expression in H295R (fold increase, F.I. = 1.8; p = 0.02) and SW13 (F.I. = 2.9; p = 0.03). In ACC, methylation density of seladin-1 promoter was higher (2682 +/- 686) than in normal adrenal glands (362 +/- 97; p = 0.02). Seladin-1 mRNA expression in ACC (1452 +/- 196) was significantly lower than in normal adrenal glands (3614 +/- 949; p = 0.01). CONCLUSION On this basis, methylation could be involved in the altered pattern of seladin-1 gene expression in ACC.
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Affiliation(s)
- Lisa Simi
- Clinical Biochemistry, Department of Clinical Physiopathology, University of Florence, viale Pieraccini 6, Florence, 50139 Italy
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124
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A functional polymorphism in the HMGCR promoter affects transcriptional activity but not the risk for Alzheimer disease in Swedish populations. Brain Res 2010; 1344:185-91. [PMID: 20450896 DOI: 10.1016/j.brainres.2010.04.073] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Revised: 04/26/2010] [Accepted: 04/27/2010] [Indexed: 01/13/2023]
Abstract
Variations in genes associated with cholesterol homeostasis have been reported to modify the risk of developing Alzheimer disease (AD). To date there have been few investigations into variations in genes directly involved in cholesterol biosynthesis and AD. We investigated the influence of the -911C>A polymorphism (rs3761740) in the hydroxy-methyl-glutaryl CoA reductase (HMGCR) gene promoter on basal and regulated transcription, plasma cholesterol levels and the association with AD. Under in vitro conditions the A allele was found to be significantly more responsive to SREBP-2 mediated regulation than the C allele. In an age and sex matched case-control study, the genotype distribution and allele frequency of this polymorphism were not associated with AD (OR=1.03; 95% CI=0.72-1.48). However, we did find evidence supporting an interaction between the HMGCR A allele, the APOE E4 allele and an altered risk of AD (OR=2.41; 95% CI=0.93-6.22).
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125
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Gulati S, Liu Y, Munkacsi AB, Wilcox L, Sturley SL. Sterols and sphingolipids: dynamic duo or partners in crime? Prog Lipid Res 2010; 49:353-65. [PMID: 20362613 DOI: 10.1016/j.plipres.2010.03.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
One manner in which eukaryotic cells respond to their environments is by optimizing the composition and proportions of sterols and sphingolipids in membranes. The physical association of the planar ring of sterols with the acyl chains of phospholipids, particularly sphingolipids, produces membrane micro-heterogeneity that is exploited to coordinate several crucial pathways. We hypothesize that these lipid molecules play an integrated role in human disease; when one of the partners is mis-regulated, pathology frequently ensues. Sterols and sphingolipid levels are not coordinated by the action of a single master regulator, however the cross-talk between their metabolic pathways is considerable. We describe our perspectives on the key components of synthesis, catabolism and transport of these lipid partners with an emphasis on evolutionarily conserved reactions that produce disease states when defective.
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Affiliation(s)
- Sonia Gulati
- Institute of Human Nutrition, Columbia University Medical Center, 630 W. 168th St., New York, NY 10032, USA
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126
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Braverman N, Zhang R, Chen L, Nimmo G, Scheper S, Tran T, Chaudhury R, Moser A, Steinberg S. A Pex7 hypomorphic mouse model for plasmalogen deficiency affecting the lens and skeleton. Mol Genet Metab 2010; 99:408-16. [PMID: 20060764 PMCID: PMC2839039 DOI: 10.1016/j.ymgme.2009.12.005] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 12/04/2009] [Accepted: 12/04/2009] [Indexed: 02/01/2023]
Abstract
Rhizomelic chondrodysplasia punctata type 1 is a peroxisome biogenesis disorder with the clinical features of rhizomelia, abnormal epiphyseal calcifications, congenital cataracts, and profound growth and developmental delays. It is a rare autosomal recessive disorder, caused by defects in the peroxisome receptor, PEX7. The pathology results from a deficiency of plasmalogens, a critical class of ether phospholipids whose functions are largely unknown. To study plasmalogens in an animal model, avoid early mortality and facilitate therapeutic investigations in this disease, we engineered a hypomorphic mouse model in which Pex7 transcript levels are reduced to less than 5% of wild type. These mice are born in expected ratios, are fertile and have a normal life span. However, they are petite and develop early cataracts. Further investigations showed delayed endochondral ossification and abnormalities in lens fibers. The biochemical features of reduced Pex7 function were reproduced in this model, including tissue plasmalogen deficiency, phytanic acid accumulation, reduced import of Pex7 ligands and consequent defects in plasmalogen biosynthesis and phytanic acid oxidation. Dietary supplementation with batyl alcohol, a plasmalogen precursor, recovered ether phospholipids in blood, but did not alter the clinical phenotype. The relatively mild phenotype of these mice mimics patients with milder PEX7 defects, and highlights the skeleton and lens as sensitive markers of plasmalogen deficiency. The role of plasmalogens in the normal function of these tissues at various ages can now be studied and additional therapeutic interventions tested in this model.
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Affiliation(s)
- Nancy Braverman
- Department of Human Genetics and Pediatrics, Montreal Children's Hospital Research Institute, McGill University, Montreal, QC, Canada.
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127
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Kumari U, Heese K. Cardiovascular dementia - a different perspective. Open Biochem J 2010; 4:29-52. [PMID: 20448820 PMCID: PMC2864432 DOI: 10.2174/1874091x01004010029] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2009] [Revised: 01/12/2010] [Accepted: 01/22/2010] [Indexed: 02/08/2023] Open
Abstract
The number of dementia patients has been growing in recent years and dementia represents a significant threat to aging people all over the world. Recent research has shown that the number of people affected by Alzheimer's disease (AD) and dementia is growing at an epidemic pace. The rapidly increasing financial and personal costs will affect the world's economies, health care systems, and many families. Researchers are now exploring a possible connection among AD, vascular dementia (VD), diabetes mellitus (type 2, T2DM) and cardiovascular diseases (CD). This correlation may be due to a strong association of cardiovascular risk factors with AD and VD, suggesting that these diseases share some biologic pathways. Since heart failure is associated with an increased risk of AD and VD, keeping the heart healthy may prove to keep the brain healthy as well. The risk for dementia is especially high when diabetes mellitus is comorbid with severe systolic hypertension or heart disease. In addition, the degree of coronary artery disease (CAD) is independently associated with cardinal neuropathological lesions of AD. Thus, the contribution of T2DM and CD to AD and VD implies that cardiovascular therapies may prove useful in preventing AD and dementia.
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Affiliation(s)
- Udhaya Kumari
- Division of Cell and Molecular Biology, School of Biological Sciences, College of Science, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
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128
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Yahi N, Aulas A, Fantini J. How cholesterol constrains glycolipid conformation for optimal recognition of Alzheimer's beta amyloid peptide (Abeta1-40). PLoS One 2010; 5:e9079. [PMID: 20140095 PMCID: PMC2816720 DOI: 10.1371/journal.pone.0009079] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Accepted: 01/20/2010] [Indexed: 11/21/2022] Open
Abstract
Membrane lipids play a pivotal role in the pathogenesis of Alzheimer's disease, which is associated with conformational changes, oligomerization and/or aggregation of Alzheimer's beta-amyloid (Abeta) peptides. Yet conflicting data have been reported on the respective effect of cholesterol and glycosphingolipids (GSLs) on the supramolecular assembly of Abeta peptides. The aim of the present study was to unravel the molecular mechanisms by which cholesterol modulates the interaction between Abeta(1-40) and chemically defined GSLs (GalCer, LacCer, GM1, GM3). Using the Langmuir monolayer technique, we show that Abeta(1-40) selectively binds to GSLs containing a 2-OH group in the acyl chain of the ceramide backbone (HFA-GSLs). In contrast, Abeta(1-40) did not interact with GSLs containing a nonhydroxylated fatty acid (NFA-GSLs). Cholesterol inhibited the interaction of Abeta(1-40) with HFA-GSLs, through dilution of the GSL in the monolayer, but rendered the initially inactive NFA-GSLs competent for Abeta(1-40) binding. Both crystallographic data and molecular dynamics simulations suggested that the active conformation of HFA-GSL involves a H-bond network that restricts the orientation of the sugar group of GSLs in a parallel orientation with respect to the membrane. This particular conformation is stabilized by the 2-OH group of the GSL. Correspondingly, the interaction of Abeta(1-40) with HFA-GSLs is strongly inhibited by NaF, an efficient competitor of H-bond formation. For NFA-GSLs, this is the OH group of cholesterol that constrains the glycolipid to adopt the active L-shape conformation compatible with sugar-aromatic CH-pi stacking interactions involving residue Y10 of Abeta(1-40). We conclude that cholesterol can either inhibit or facilitate membrane-Abeta interactions through fine tuning of glycosphingolipid conformation. These data shed some light on the complex molecular interplay between cell surface GSLs, cholesterol and Abeta peptides, and on the influence of this molecular ballet on Abeta-membrane interactions.
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Affiliation(s)
- Nouara Yahi
- Université Paul Cézanne (Aix-Marseille 3), Université de la Méditerranée (Aix-Marseille 2), Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille, CNRS UMR 6231, INRA USC 2027, Interactions Moléculaires et Systèmes Membranaires, Faculté des Sciences Saint-Jérôme, Marseille, France
| | - Anaïs Aulas
- Université Paul Cézanne (Aix-Marseille 3), Université de la Méditerranée (Aix-Marseille 2), Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille, CNRS UMR 6231, INRA USC 2027, Interactions Moléculaires et Systèmes Membranaires, Faculté des Sciences Saint-Jérôme, Marseille, France
| | - Jacques Fantini
- Université Paul Cézanne (Aix-Marseille 3), Université de la Méditerranée (Aix-Marseille 2), Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille, CNRS UMR 6231, INRA USC 2027, Interactions Moléculaires et Systèmes Membranaires, Faculté des Sciences Saint-Jérôme, Marseille, France
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129
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Adibhatla RM, Hatcher JF. Lipid oxidation and peroxidation in CNS health and disease: from molecular mechanisms to therapeutic opportunities. Antioxid Redox Signal 2010; 12:125-69. [PMID: 19624272 DOI: 10.1089/ars.2009.2668] [Citation(s) in RCA: 317] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Reactive oxygen species (ROS) are produced at low levels in mammalian cells by various metabolic processes, such as oxidative phosphorylation by the mitochondrial respiratory chain, NAD(P)H oxidases, and arachidonic acid oxidative metabolism. To maintain physiological redox balance, cells have endogenous antioxidant defenses regulated at the transcriptional level by Nrf2/ARE. Oxidative stress results when ROS production exceeds the cell's ability to detoxify ROS. Overproduction of ROS damages cellular components, including lipids, leading to decline in physiological function and cell death. Reaction of ROS with lipids produces oxidized phospholipids, which give rise to 4-hydroxynonenal, 4-oxo-2-nonenal, and acrolein. The brain is susceptible to oxidative damage due to its high lipid content and oxygen consumption. Neurodegenerative diseases (AD, ALS, bipolar disorder, epilepsy, Friedreich's ataxia, HD, MS, NBIA, NPC, PD, peroxisomal disorders, schizophrenia, Wallerian degeneration, Zellweger syndrome) and CNS traumas (stroke, TBI, SCI) are problems of vast clinical importance. Free iron can react with H(2)O(2) via the Fenton reaction, a primary cause of lipid peroxidation, and may be of particular importance for these CNS injuries and disorders. Cholesterol is an important regulator of lipid organization and the precursor for neurosteroid biosynthesis. Atherosclerosis, the major risk factor for ischemic stroke, involves accumulation of oxidized LDL in the arteries, leading to foam cell formation and plaque development. This review will discuss the role of lipid oxidation/peroxidation in various CNS injuries/disorders.
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Affiliation(s)
- Rao Muralikrishna Adibhatla
- Department of Neurological Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53792-3232, USA.
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130
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Oresic M. Metabolomics, a novel tool for studies of nutrition, metabolism and lipid dysfunction. Nutr Metab Cardiovasc Dis 2009; 19:816-824. [PMID: 19692215 DOI: 10.1016/j.numecd.2009.04.018] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Revised: 04/20/2009] [Accepted: 04/29/2009] [Indexed: 12/28/2022]
Abstract
AIMS In this review metabolomics is introduced in historic perspective, with key platforms and bioinformatics methodologies described. An overview is provided covering recent applications of metabolomics and lipidomics in the context of human physiology, lipid metabolism and nutrition. DATA SYNTHESIS Global coverage of human metabolome requires application of multiple analytical platforms. The choice of a particular targeted or non-targeted analytical strategy depends on the hypothesis tested, state-of-the-art in the field, as well as on sample availability. Human metabolome has been shown to be sensitive to age, gut microbial composition, and lifestyle. Several studies have shown that, given the appropriate experimental design, subtle effects of interventions such as change of diet or weight loss can be detected by metabolomics and studied in the context of human physiology and health status. CONCLUSION Metabolome provides a sensitive intermediate phenotype linking the genotype, gut microbial composition and personal health status. Innovative experimental designs combined with novel computational tools for handling metabolomics data offer new opportunities for early disease detection as well as for characterization of dietary and therapeutic interventions in the context of human physiology.
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Affiliation(s)
- M Oresic
- VTT Technical Research Centre of Finland, FIN-02044 VTT, Espoo, Finland.
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131
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Lessig J, Fuchs B. HOCl-mediated glycerophosphocholine and glycerophosphoethanolamine generation from plasmalogens in phospholipid mixtures. Lipids 2009; 45:37-51. [PMID: 19937395 DOI: 10.1007/s11745-009-3365-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Accepted: 07/03/2009] [Indexed: 11/30/2022]
Abstract
Many mammalian tissues and cells contain, in addition to (diacyl) phospholipids, considerable amounts of plasmalogens, which may function as important antioxidants. Apart from the "scavenger" function mediated by the high sensitivity of the vinyl-ether bond, the functional role of plasmalogens is so far widely unknown. Furthermore, there is increasing evidence that plasmalogen degradation products have harmful effects in inflammatory processes. In a previous investigation glycerophosphocholine (GPC) formation was verified as a novel plasmalogen degradation pathway upon oxidation with hypochlorous acid (HOCl), however these investigations were performed in simple model systems. Herein, we examine plasmalogen degradation in a more complex system in order to evaluate if GPC generation is also a major pathway in the presence of other highly unsaturated glycerophospholipids (GPL) representing an additional reaction site of HOCl targets. Using MALDI-TOF mass spectrometry and (31)P NMR spectroscopy, we confirmed that the first step of the HOCl-induced degradation of GPL mixtures containing plasmalogens is the attack of the vinyl-ether bond resulting in the generation of 1-lysophosphatidylcholine (lysoPtdCho) or 1-lysophosphatidylethanolamine. In the second step HOCl reacts with the fatty acyl residue in the sn-2 position of 1-lysoPtdCho. This reaction is about three times faster in comparison to comparable diacyl-GPL. Thus, the generation of GPC and glycerophosphoethanolamine (GPE) from plasmalogens are relevant products formed from HOCl attack on the vinyl-ether bond of plasmalogens under pathological conditions.
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Affiliation(s)
- Jacqueline Lessig
- Medical Faculty, Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstrasse 16-18, 04107 Leipzig, Germany
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132
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Mutka AL, Haapanen A, Käkelä R, Lindfors M, Wright AK, Inkinen T, Hermansson M, Rokka A, Corthals G, Jauhiainen M, Gillingwater TH, Ikonen E, Tyynelä J. Murine cathepsin D deficiency is associated with dysmyelination/myelin disruption and accumulation of cholesteryl esters in the brain. J Neurochem 2009; 112:193-203. [PMID: 19845830 DOI: 10.1111/j.1471-4159.2009.06440.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cathepsin D (CTSD) deficiencies are fatal neurological diseases that in human infants and in sheep are characterized by extreme loss of neurons and myelin. To date, similar morphological evidence for myelin disruption in CTSD knockout mice has not been reported. Here, we show that CTSD deficiency leads to pronounced myelin changes in the murine brain: myelin-related proteolipid protein and myelin basic protein were both markedly reduced at postnatal day 24, and the amount of lipids characteristically high in myelin (e.g. plasmalogen-derived alkenyl chains and glycosphingolipid-derived 20- and 24-carbon acyl chains) were significantly lowered compared with controls. These changes were accompanied by ultrastructural alterations of myelin, including significant thinning of myelin sheaths. Furthermore, in CTSD knockout brains there was a pronounced accumulation of cholesteryl esters and abnormal levels of proteins related to cholesterol transport, with an increased content of apolipoprotein E and a reduced content of ATP-binding cassette transporter A1. These results provide evidence for dysmyelination and altered trafficking of cholesterol in brains of CTSD knockout mice, and warrant further studies on the role of lipid metabolism in the pathogenesis of CTSD deficiencies.
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Affiliation(s)
- Aino-Liisa Mutka
- Institute of Biomedicine/Anatomy, Biomedicum, University of Helsinki, Helsinki, Finland
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133
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Hanuš LO, Levitsky DO, Shkrob I, Dembitsky VM. Plasmalogens, fatty acids and alkyl glyceryl ethers of marine and freshwater clams and mussels. Food Chem 2009. [DOI: 10.1016/j.foodchem.2009.03.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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134
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Thakur G, Micic M, Leblanc RM. Surface chemistry of Alzheimer's disease: a Langmuir monolayer approach. Colloids Surf B Biointerfaces 2009; 74:436-56. [PMID: 19726167 DOI: 10.1016/j.colsurfb.2009.07.043] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 07/28/2009] [Accepted: 07/29/2009] [Indexed: 12/14/2022]
Abstract
Amyloid beta (1-40) and (1-42) peptides are the major constituents of hallmark senile plaques found in Alzheimer's disease (AD) patients. Study of aggregation of Abeta (1-40) and (1-42) peptides and the truncated Abeta fragments could lead towards the mechanism of AD. Langmuir monolayer approach is one of the excellent methods to investigate the mechanism and origin of AD. Particularly, to study the steps involved in the formation and assembly of beta-sheet structures leading to formation of amyloid fibrils. Surface pressure- and surface potential-area isotherms provide information regarding the nature of short-range and long-range interactions between the molecules especially the lipids and the Abeta peptides. Spectroscopic methods like IRRAS, PM-IRRAS, FTIR-ATR, and GIXD at the air-water interface provide insight into the structural characterization, and orientation of the molecules in the Langmuir monolayer.
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Affiliation(s)
- Garima Thakur
- Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146, United States
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135
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Nuutinen T, Suuronen T, Kauppinen A, Salminen A. Clusterin: a forgotten player in Alzheimer's disease. ACTA ACUST UNITED AC 2009; 61:89-104. [PMID: 19651157 DOI: 10.1016/j.brainresrev.2009.05.007] [Citation(s) in RCA: 207] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 05/13/2009] [Accepted: 05/14/2009] [Indexed: 11/16/2022]
Abstract
Clusterin, also known as apolipoprotein J, is a versatile chaperone molecule which contains several amphipathic and coiled-coil alpha-helices, typical characteristics of small heat shock proteins. In addition, clusterin has three large intrinsic disordered regions, so-called molten globule domains, which can stabilize stressed protein structures. Twenty years ago, it was demonstrated that the expression of clusterin was clearly increased in Alzheimer's disease (AD). Later it was observed that clusterin can bind amyloid-beta peptides and prevent their fibrillization. Clusterin is also involved in the clearance of amyloid-beta peptides and fibrils by binding to megalin receptors and enhancing their endocytosis within glial cells. Clusterin is a complement inhibitor and can suppress complement activation observed in AD. Clusterin is also present in lipoprotein particles and regulates cholesterol and lipid metabolism of brain which is disturbed in AD. Clusterin is a stress-induced chaperone which is normally secreted but in conditions of cellular stress, it can be transported to cytoplasm where it can bind to Bax protein and inhibit neuronal apoptosis. Clusterin can also bind to Smad2/3 proteins and potentiate the neuroprotective TGFbeta signaling. An alternative splicing can produce a variant isoform of clusterin which can be translocated to nuclei where it induces apoptosis. The role of nuclear clusterin in AD needs to be elucidated. We will review here the extensive literature linking clusterin to AD and examine the recent progress in clusterin research with the respect to AD pathology. Though clusterin can be viewed as a multipotent guardian of brain, it is unable to prevent the progressive neuropathology in chronic AD.
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Affiliation(s)
- Tapio Nuutinen
- Department of Neuroscience and Neurology, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio, Finland
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136
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Sannerud R, Annaert W. Trafficking, a key player in regulated intramembrane proteolysis. Semin Cell Dev Biol 2009; 20:183-90. [DOI: 10.1016/j.semcdb.2008.11.004] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Revised: 11/05/2008] [Accepted: 11/07/2008] [Indexed: 01/03/2023]
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137
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Kim JH, Ong WY. Localization of the transcription factor, sterol regulatory element binding protein-2 (SREBP-2) in the normal rat brain and changes after kainate-induced excitotoxic injury. J Chem Neuroanat 2009; 37:71-7. [DOI: 10.1016/j.jchemneu.2008.12.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 12/05/2008] [Accepted: 12/05/2008] [Indexed: 10/21/2022]
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138
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Membrane cholesterol content influences binding properties of muscarinic M2 receptors and differentially impacts activation of second messenger pathways. Eur J Pharmacol 2009; 606:50-60. [PMID: 19374848 DOI: 10.1016/j.ejphar.2009.01.028] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 01/06/2009] [Accepted: 01/19/2009] [Indexed: 11/22/2022]
Abstract
We investigated the influence of membrane cholesterol content on preferential and non-preferential signaling through the M(2) muscarinic acetylcholine receptor expressed in CHO cells. Cholesterol depletion by 39% significantly decreased the affinity of M(2) receptors for [(3)H]-N-methylscopolamine ([(3)H]-NMS) binding and increased B(max) in intact cells and membranes. Membranes displayed two-affinity agonist binding sites for carbachol and cholesterol depletion doubled the fraction of high-affinity binding sites. In intact cells it also reduced the rate of agonist-induced receptor internalization and changed the profile of agonist binding from a single site to two affinity states. Cholesterol enrichment by 137% had no effects on carbachol E(max) of cAMP synthesis inhibition and on cAMP synthesis stimulation and inositolphosphates (IP) accumulation at higher agonist concentrations (non-preferred pathways). On the other hand, cholesterol depletion significantly increased E(max) of cAMP synthesis inhibition or stimulation without change in potency, and decreased E(max) of IP accumulation. Noteworthy, modifications of membrane cholesterol had no effect on membrane permeability, oxidative activity, protein content, or relative expression of G(s), G(i/o), and G(q/11) alpha subunits. These results demonstrate distinct changes of M(2) receptor signaling through both preferential and non-preferential G-proteins consequent to membrane cholesterol depletion that occur at the level of receptor/G-protein/effector protein interactions in the cell membrane. The significant decrease of IP accumulation by cholesterol depletion was also observed in cells expressing M(3) receptors and by both cholesterol depletion and enrichment in cells expressing M(1) receptors indicating relevance of reduced G(q/11) signaling for the pathogenesis of Alzheimer's disease.
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139
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140
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Electron tomography of early melanosomes: implications for melanogenesis and the generation of fibrillar amyloid sheets. Proc Natl Acad Sci U S A 2008; 105:19726-31. [PMID: 19033461 DOI: 10.1073/pnas.0803488105] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Melanosomes are lysosome-related organelles (LROs) in which melanins are synthesized and stored. Early stage melanosomes are characterized morphologically by intralumenal fibrils upon which melanins are deposited in later stages. The integral membrane protein Pmel17 is a component of the fibrils, can nucleate fibril formation in the absence of other pigment cell-specific proteins, and forms amyloid-like fibrils in vitro. Before fibril formation Pmel17 traffics through multivesicular endosomal compartments, but how these compartments participate in downstream events leading to fibril formation is not fully known. By using high-pressure freezing of MNT-1 melanoma cells and freeze substitution to optimize ultrastructural preservation followed by double tilt 3D electron tomography, we show that the amyloid-like fibrils begin to form in multivesicular compartments, where they radiate from the luminal side of intralumenal membrane vesicles. The fibrils in fully formed stage II premelanosomes organize into sheet-like arrays and exclude the remaining intralumenal vesicles, which are smaller and often in continuity with the limiting membrane. These observations indicate that premelanosome fibrils form in association with intralumenal endosomal membranes. We suggest that similar processes regulate amyloid formation in pathological models.
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141
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Lipidomics: a new window to biomedical frontiers. Trends Biotechnol 2008; 26:647-52. [PMID: 18951641 DOI: 10.1016/j.tibtech.2008.09.001] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2008] [Revised: 09/01/2008] [Accepted: 09/02/2008] [Indexed: 12/17/2022]
Abstract
Lipids are a highly diverse class of molecules with crucial roles in cellular energy storage, structure and signaling. Lipid homeostasis is fundamental to maintain health, and lipid defects are central to the pathogenesis of important and devastating diseases. Newly emerging advances have facilitated the development of so-called lipidomics technologies and offer an opportunity to elucidate the mechanisms leading to disease. Furthermore, these advances also provide the tools to unravel the complexity of the 'allostatic forces' that allow maintenance of normal cellular/tissue phenotypes through the application of bioenergetically inefficient adaptive mechanisms. An alternative strategy is to focus on tissues with limited allostatic capacity, such as the eye, that could be used as readouts of metabolic stress over time. Identification of these allostatic mechanisms and pathological 'scares' might provide a window to unknown pathogenic mechanisms, as well as facilitate identification of early biomarkers of disease.
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142
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Skaff O, Pattison DI, Davies MJ. The vinyl ether linkages of plasmalogens are favored targets for myeloperoxidase-derived oxidants: a kinetic study. Biochemistry 2008; 47:8237-45. [PMID: 18605737 DOI: 10.1021/bi800786q] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Plasmalogens, which contain a vinyl ether bond, are major phospholipids of the plasma membranes of endothelial and vascular smooth muscle cells and cardiac myocytes. These lipids, in contrast to other phospholipids, have been reported to be targets of HOCl/HOBr generated by myeloperoxidase, with elevated levels of the products of these reactions (alpha-chloro/alpha-bromo aldehydes and unsaturated lysophospholipids) having been detected in human atherosclerotic lesions. The reason(s) for the targeting of this lipid class, over other phospholipids, is poorly understood, and is examined here. It is shown that HOCl and HOBr react with a model vinyl ether (ethylene glycol vinyl ether) 200-300-fold faster ( k = 1.6 x 10 (3) and 3.5 x 10 (6) M (-1) s (-1), respectively) than with aliphatic alkenes (models of phospholipids). True plasmalogens react ca. 20-fold slower than the models. Chloramines and bromamines (from reaction of HOCl/HOBr with primary amines and alpha-amino groups) also react with vinyl ethers, unlike aliphatic alkenes, with k = 10 (-3)-10 (2) M (-1) s (-1) for chloramines (with the His side chain chloramine being the most reactive, k = 172 M (-1) s (-1)) and k = 10 (3)-10 (4) M (-1) s (-1) for bromamines. The bromamine rate constants are typically 10 (5)-10 (6) larger than those of the chloramines. Intermolecular vinyl ether oxidation by phospholipid headgroup bromamines can also occur. These kinetic data indicate that plasmalogens are significantly more susceptible to oxidation than the aliphatic alkenes of phospholipids, thereby rationalizing the detection of products from the former, but not the latter, in human atherosclerotic lesions.
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Affiliation(s)
- Ojia Skaff
- The Heart Research Institute, 114 Pyrmont Bridge Road, Camperdown, Sydney, NSW 2050, Australia
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143
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He X, Huang Y, Li B, Gong CX, Schuchman EH. Deregulation of sphingolipid metabolism in Alzheimer's disease. Neurobiol Aging 2008; 31:398-408. [PMID: 18547682 DOI: 10.1016/j.neurobiolaging.2008.05.010] [Citation(s) in RCA: 366] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 04/07/2008] [Accepted: 05/06/2008] [Indexed: 12/14/2022]
Abstract
Abnormal sphingolipid metabolism has been previously reported in Alzheimer's disease (AD). To extend these findings, several sphingolipids and sphingolipid hydrolases were analyzed in brain samples from AD patients and age-matched normal individuals. We found a pattern of elevated acid sphingomyelinase (ASM) and acid ceramidase (AC) expression in AD, leading to a reduction in sphingomyelin and elevation of ceramide. More sphingosine also was found in the AD brains, although sphingosine-1-phosphate (S1P) levels were reduced. Notably, significant correlations were observed between the brain ASM and S1P levels and the levels of amyloid beta (Abeta) peptide and hyperphosphorylated tau protein. Based on these findings, neuronal cell cultures were treated with Abeta oligomers, which were found to activate ASM, increase ceramide, and induce apoptosis. Pre-treatment of the neurons with purified, recombinant AC prevented the cells from undergoing Abeta-induced apoptosis. We propose that ASM activation is an important pathological event leading to AD, perhaps due to Abeta deposition. The downstream consequences of ASM activation are elevated ceramide, activation of ceramidases, and production of sphingosine. The reduced levels of S1P in the AD brain, together with elevated ceramide, likely contribute to the disease pathogenesis.
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Affiliation(s)
- Xingxuan He
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, NY 10029, USA
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144
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Osenkowski P, Ye W, Wang R, Wolfe MS, Selkoe DJ. Direct and potent regulation of gamma-secretase by its lipid microenvironment. J Biol Chem 2008; 283:22529-40. [PMID: 18539594 DOI: 10.1074/jbc.m801925200] [Citation(s) in RCA: 216] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
gamma-Secretase is an unusual and ubiquitous aspartyl protease with an intramembrane catalytic site that cleaves many type-I integral membrane proteins, most notably APP and Notch. Several reports suggest that cleavage of APP to produce the Abeta peptide is regulated in part by lipids. As gamma-secretase is a multipass protein complex with 19 transmembrane domains, it is likely that the local lipid composition of the membrane can regulate gamma-activity. To determine the direct contribution of the lipid microenvironment to gamma-secretase activity, we purified the human protease from overexpressing mammalian cells, reconstituted it in vesicles of varying lipid composition, and examined the effects of individual phospholipids, sphingolipids, cholesterol, and complex lipid mixtures on substrate cleavage. A conventional gamma-activity assay was modified to include a detergent-removal step to facilitate proteoliposome formation, and this increased baseline activity over 2-fold. Proteoliposomes containing sphingolipids significantly increased gamma-secretase activity over a phosphatidylcholine-only baseline, whereas the addition of phosphatidylinositol significantly decreased activity. Addition of soluble cholesterol in the presence of phospholipids and sphingolipids robustly increased the cleavage of APP- and Notch-like substrates in a dose-dependent manner. Reconstitution of gamma-secretase in complex lipid mixtures revealed that a lipid raft-like composition supported the highest level of activity compared with other membrane compositions. Taken together, these results demonstrate that membrane lipid composition is a direct and potent modulator of gamma-secretase and that cholesterol, in particular, plays a major regulatory role.
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Affiliation(s)
- Pamela Osenkowski
- Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
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145
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Venugopal C, Demos CM, Rao KSJ, Pappolla MA, Sambamurti K. Beta-secretase: structure, function, and evolution. CNS & NEUROLOGICAL DISORDERS DRUG TARGETS 2008; 7:278-94. [PMID: 18673212 PMCID: PMC2921875 DOI: 10.2174/187152708784936626] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The most popular current hypothesis is that Alzheimer's disease (AD) is caused by aggregates of the amyloid peptide (Abeta), which is generated by cleavage of the Abeta protein precursor (APP) by beta-secretase (BACE-1) followed by gamma-secretase. BACE-1 cleavage is limiting for the production of Abeta, making it a particularly good drug target for the generation of inhibitors that lower Abeta. A landmark discovery in AD was the identification of BACE-1 (a.k.a. Memapsin-2) as a novel class of type I transmembrane aspartic protease. Although BACE-2, a homologue of BACE-1, was quickly identified, follow up studies using knockout mice demonstrated that BACE-1 was necessary and sufficient for most neuronal Abeta generation. Despite the importance of BACE-1 as a drug target, development has been slow due to the incomplete understanding of its function and regulation and the difficulties in developing a brain penetrant drug that can specifically block its large catalytic pocket. This review summarizes the biological properties of BACE-1 and attempts to use phylogenetic perspectives to understand its function. The article also addresses the challenges in discovering a selective drug-like molecule targeting novel mechanisms of BACE-1 regulation.
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Affiliation(s)
| | | | | | | | - Kumar Sambamurti
- Medical University of South Carolina, Charleston, South Carolina
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146
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Rebollo A, Pou J, Alegret M. Cholesterol lowering and beyond: role of statins in Alzheimer’s disease. ACTA ACUST UNITED AC 2008. [DOI: 10.2217/1745509x.4.2.171] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Alzheimer’s disease (AD), the most common form of dementia, is a major health problem with increasing prevalence associated with the increase in life span. Unfortunately, drugs currently used to treat this disorder have only modest therapeutic efficacy. Therefore, there is an urgent need to develop new pharmacological strategies to prevent or delay the onset of AD. As it has been suggested that there is a link between cholesterol and the development of AD, one such strategy could be the inhibition of cholesterol synthesis using HMG-CoA reductase inhibitors (statins). In addition to their cholesterol-lowering properties, statins exert multiple lipid-independent (pleiotropic) effects that may explain some of their beneficial actions. The aim of this article is to summarize the current knowledge on the effects of statins on AD and the mechanisms involved, based on data from in vitro, in vivo and clinical studies, and to provide an overview of the future perspectives in this field.
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Affiliation(s)
- Alba Rebollo
- University of Barcelona & Ciber Diabetes y Enfermedades Metabólicas asociadas (CIBERDEM), Pharmacology Department, Faculty of Pharmacy & Biomedicine Institute (IBUB), Instituto de Salud Carlos III, Spain
| | - Jordi Pou
- University of Barcelona & Ciber Diabetes y Enfermedades Metabólicas asociadas (CIBERDEM), Pharmacology Department, Faculty of Pharmacy & Biomedicine Institute (IBUB), Instituto de Salud Carlos III, Spain
| | - Marta Alegret
- University of Barcelona & Ciber Diabetes y Enfermedades Metabólicas asociadas (CIBERDEM), Pharmacology Department, Faculty of Pharmacy & Biomedicine Institute (IBUB), Instituto de Salud Carlos III, Spain
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147
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Abstract
Deregulated lipid metabolism may be of particular importance for CNS injuries and disorders, as this organ has the highest lipid concentration next to adipose tissue. Atherosclerosis (a risk factor for ischemic stroke) results from accumulation of LDL-derived lipids in the arterial wall. Pro-inflammatory cytokines (TNF-alpha and IL-1), secretory phospholipase A2 IIA and lipoprotein-PLA2 are implicated in vascular inflammation. These inflammatory responses promote atherosclerotic plaques, formation and release of the blood clot that can induce ischemic stroke. TNF-alpha and IL-1 alter lipid metabolism and stimulate production of eicosanoids, ceramide, and reactive oxygen species that potentiate CNS injuries and certain neurological disorders. Cholesterol is an important regulator of lipid organization and the precursor for neurosteroid biosynthesis. Low levels of neurosteroids were related to poor outcome in many brain pathologies. Apolipoprotein E is the principal cholesterol carrier protein in the brain, and the gene encoding the variant Apolipoprotein E4 is a significant risk factor for Alzheimer's disease. Parkinson's disease is to some degree caused by lipid peroxidation due to phospholipases activation. Niemann-Pick diseases A and B are due to acidic sphingomyelinase deficiency, resulting in sphingomyelin accumulation, while Niemann-Pick disease C is due to mutations in either the NPC1 or NPC2 genes, resulting in defective cholesterol transport and cholesterol accumulation. Multiple sclerosis is an autoimmune inflammatory demyelinating condition of the CNS. Inhibiting phospholipase A2 attenuated the onset and progression of experimental autoimmune encephalomyelitis. The endocannabinoid system is hypoactive in Huntington's disease. Ethyl-eicosapetaenoate showed promise in clinical trials. Amyotrophic lateral sclerosis causes loss of motorneurons. Cyclooxygenase-2 inhibition reduced spinal neurodegeneration in amyotrophic lateral sclerosis transgenic mice. Eicosapentaenoic acid supplementation provided improvement in schizophrenia patients, while the combination of (eicosapentaenoic acid + docosahexaenoic acid) provided benefit in bipolar disorders. The ketogenic diet where >90% of calories are derived from fat is an effective treatment for epilepsy. Understanding cytokine-induced changes in lipid metabolism will promote novel concepts and steer towards bench-to-bedside transition for therapies.
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Affiliation(s)
- Rao Muralikrishna Adibhatla
- Department of Neurological Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI
- Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, Madison, WI
- Neuroscience Training Program, University of Wisconsin School of Medicine and Public Health, Madison, WI
- William S. Middleton Veterans Affairs Hospital, Madison, WI
| | - J. F. Hatcher
- Department of Neurological Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI
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