g(m1)-ganglioside and Alzheimer-Disease

It is widely accepted that the abnormal self-association of amyloid β-protein (Aβ) is central to the pathogenesis of Alzheimer's disease, the most common form of dementia. Accumulating evidence, both in vivo and in vitro, suggests that the binding of Aβ to gangliosides, especially monosialoganglioside GM1, plays an important role in the aggregation of Aβ. This review summarizes the molecular details of the binding of Aβ to ganglioside-containing membranes and subsequent structural changes, as revealed by liposomal and cellular studies. Furthermore, mechanisms of cytotoxicity by aggregated Aβ are also discussed.

Topics: Alzheimer Disease; Amyloid beta-Peptides; G(M1) Ganglioside; Humans; Liposomes; Membrane Microdomains; Protein Binding

Assembly and deposition of amyloid ß-protein (Aß) is an invariable and fundamental event in the pathological process of Alzheimer's disease (AD). To decipher the AD pathogenesis and also to develop disease-modifying drugs for AD, clarification of the molecular mechanism underlying the Aß assembly into amyloid fibrils in the brain has been a crucial issue. GM1-ganglioside-bound Aß (GAß), with unique molecular characteristics such as having an altered conformation and the capability to accelerate Aß assembly, was discovered in an autopsied brain showing early pathological changes of AD in 1995. On the basis of these findings, it was hypothesized that GAß is an endogenous seed for amyloid fibril formation in the AD brain. A body of evidence that supports this GAß hypothesis has been growing over this past 20 years. In this article, seminal GAß studies that have been carried out to date, including recent ones using unique animal models, are reviewed.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; Cell Membrane; G(M1) Ganglioside; Humans

The complex association of cholesterol metabolism and Alzheimer's disease is presented in depth, including the possible benefits to be gained from cholesterol-lowering statin therapy. Then follows a survey of the role of neuronal membrane cholesterol in Abeta pore formation and Abeta fibrillogenesis, together with the link with membrane raft domains and gangliosides. The contribution of structural studies to Abeta fibrillogenesis, using TEM and AFM, is given some emphasis. The role of apolipoprotein E and its isoforms, in particular ApoE4, in cholesterol and Abeta binding is presented, in relation to genetic risk factors for Alzheimer's disease. Increasing evidence suggests that cholesterol oxidation products are of importance in generation of Alzheimer's disease, possibly induced by Abeta-produced hydrogen peroxide. The body of evidence for a link between cholesterol in atherosclerosis and Alzheimer's disease is increasing, along with an associated inflammatory response. The possible role of cholesterol in tau fibrillization, tauopathies and in some other non-Abeta amyloidogenic disorders is surveyed.

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Apolipoproteins E; Atherosclerosis; Brain; Cholesterol; G(M1) Ganglioside; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Male; Neurons; Oxidative Stress; tau Proteins; Tauopathies

One of the fundamental questions regarding the pathogenesis of Alzheimer's disease (AD) is how the monomeric, nontoxic amyloid beta-protein (Abeta) is converted to its toxic assemblies in the brain. A unique Abeta species was identified previously in an AD brain, which is characterized by its binding to the GM1 ganglioside (GM1). On the basis of the molecular characteristics of this GM1-bound Abeta (GAbeta), it was hypothesized that Abeta adopts an altered conformation through its binding to GM1, and GAbeta acts as a seed for Abeta fibrillogenesis in an AD brain. To date, various in vitro and in vivo studies of GAbeta have been performed, and their results support the hypothesis. Using a novel monoclonal antibody specific to GAbeta, it was confirmed that GAbeta is endogenously generated in the brain. Regarding the role of gangliosides in the facilitation of Abeta assembly, it has recently been reported that region-specific deposition of hereditary variant-type Abetas is determined by local gangliosides in the brain. Furthermore, it is likely that risk factors for AD, including aging and the expression of apolipoprotein E4, alter GM1 distribution on the neuronal surface, leading to GAbeta generation.

Topics: Age Factors; Alzheimer Disease; Amyloid beta-Peptides; Animals; Apolipoprotein E4; Brain; Cell Membrane; G(M1) Ganglioside; Humans; Neurons; Protein Binding; Risk Factors

Evidence is accumulating to suggest that cholesterol is a potent risk factor for the development of Alzheimer's disease. An increase in cholesterol level in neuronal membranes may facilitate the generation and aggregation of the amyloid beta-protein (Abeta). Our results and those of other groups suggest that cholesterol has both direct and indirect effects of acceleration of Abeta fibrillogenesis. A novel concept of cholesterol neurobiology is necessary to elucidate the mechanism underlying cholesterol-dependent Abeta pathology.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Cholesterol; G(M1) Ganglioside; Humans; Macromolecular Substances; Neurofibrillary Tangles; Neurons; Plaque, Amyloid; Protein Binding; Risk Factors

A fundamental question about the pathogenesis of Alzheimer's disease (AD) is how monomeric, nontoxic amyloid beta-protein (Abeta) is converted to its toxic aggregates in the brain. The author previously identified a unique Abeta species in the AD brain, which is characterized by its binding to GM1 ganglioside (GM1). On the basis of the molecular characteristics of GM1-bound Abeta (GAbeta), the author hypothesized that GM1 plays a critical role in the process. The author recently examined this possibility using a novel monoclonal antibody raised against purified GAbeta and validated that GAbeta is endogenously generated in the brain and accelerates Abeta assembly by acting as a seed. Furthermore, the author provided a possibility that aging and the expression of apolipoprotein E4 facilitate Abeta assembly in the brain through an increase in the GM1 content in the neuronal membranes, which likely induces GAbeta generation. The author's results imply a mechanism underlying the onset of AD and also provide a new insight into development of novel therapeutic strategy.

Topics: Aging; Alzheimer Disease; Amyloid beta-Peptides; Animals; Antibodies; Brain; G(M1) Ganglioside; Humans; Liposomes; Protein Binding; Synaptosomes; Time Factors

Topics: Alzheimer Disease; Amyloid beta-Peptides; G(M1) Ganglioside; Genetic Variation; Humans; Membrane Microdomains; Nimodipine

Topics: Alzheimer Disease; Biomarkers; G(M1) Ganglioside; Guillain-Barre Syndrome; Hematologic Tests; Humans; Motor Neuron Disease; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Specimen Handling

Topics: Alzheimer Disease; Amyloid beta-Peptides; Brain; Cholesterol; G(M1) Ganglioside; Humans; Membrane Microdomains; Protein Binding; Solubility

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cell Death; Cholesterol; G(M1) Ganglioside; Humans; Membrane Microdomains; Neurons; Protein Binding

Gangliosides are glycosphingolipids localized to the outer leaflet of the plasma membrane of vertebrate cells. The highest ganglioside concentration of any organ is found in the mammalian brain, where the gangliosides are enriched in the neuronal membrane, particularly in the synapses. There are four major brain gangliosides with the same neutral tetrasaccharide core to which one to three sialic acids are linked--the simplest being the GM1-ganglioside. These gangliosides have been shown to have neuritogenic and neuronotrophic activity and to facilitate repair of neuronal tissue after mechanical, biochemical or toxic injuries. Mixtures of native bovine brain gangliosides were adopted for pharmacological use in the treatment of peripheral nerve damage, and GM1-ganglioside has been applied for the treatment of CNS injuries and diseases. Beneficial effects of GM1 have been documented in the treatment of stroke and spinal cord injuries, particularly when the treatment has been initiated within a few hours of the acute event. Continuous intraventricular infusion of GM1 has recently been shown to have a significant beneficial effect in Alzheimer disease of early onset (AD Type I).

Topics: Alzheimer Disease; Animals; Carbohydrate Sequence; Cerebrovascular Disorders; G(M1) Ganglioside; Humans; Molecular Sequence Data; Spinal Cord Injuries

A large body of experimental data suggests that neurotrophic molecules and/or substances that facilitate their action could be pharmaceutical agents for neurodegenerative pathologies. In particular, it has been demonstrated that nerve growth factor (NGF) exerts a physiological role for forebrain cholinergic neurons, while brain-derived neurotrophic factor (BDNF) seems to play a relevant role in rescuing dopaminergic neurons following damage. In addition, gangliosides are reported to potentiate neurotrophic factor effects in vitro as well as in vivo. In this study we examined the effects of the monosialoganglioside GM1 in different experimental models. The responsiveness of forebrain cholinergic neurons following NGF +/- GM1 was evaluated by assessing choline acetyltransferase (ChAT) activity in hippocampus, septal area and striatum of behaviorally impaired 24-month-old rats. NGF was intracerebroventricularly (i.c.v.) infused for 2 weeks while GM1 was given systemically for 3 weeks, starting from the beginning of NGF infusion. Moreover, the possible protective effects of GM1 were assessed following exposure of cultured cerebellar granule cells and dopaminergic mesencephalic neurons to different doses of 6-OH-DOPA, a metabolite of the dopamine pathway which has excitotoxic properties and has been hypothesized to participate in the pathology of Parkinson's disease. GM1 treatment to aged rats was seen to potentiate the NGF-induced increase of ChAT activity in the striatum ipsilateral to the NGF infusion. Moreover, in the striatum contralateral to the NGF infusion, GM1 increased ChAT activity above the control values, whereas NGF treatment alone did not affect enzymatic activity. GM1 treatment of cerebellar granule cells and mesencephalic neurons counteracted the dose- and time-dependent neurotoxicity of 6-OH-DOPA. These data support the notion that GM1 might prove useful in treating those pathological conditions where trophic factor deficits and/or excitotoxin-related toxicity play an important role.

Topics: Aging; Alzheimer Disease; Animals; Brain; Cerebral Ventricles; Choline O-Acetyltransferase; G(M1) Ganglioside; Humans; Injections, Intraventricular; Nerve Growth Factors; Organ Specificity; Parkinson Disease

Topics: Aged; Alzheimer Disease; Arginine Vasopressin; Cholinesterase Inhibitors; G(M1) Ganglioside; Humans; Mental Recall; Neuropsychological Tests; Physostigmine; Pilot Projects; Receptors, Cholinergic; Tacrine

Recent years have witnessed considerable change in the conceptualization of the pathophysiology of the cognitive impairments in dementing disorders, as a result of synaptic neurochemical analyses. Profound reductions in the forebrain cholinergic projections occur in Alzheimer's disease. In GM1 gangliosidosis, variable alterations in neurotransmitter related processes that are located in synaptic membranes have been described. Exploitation of animal models of human disorders resulting in dementia may further clarify the dynamic alterations in the biochemical processes required for effective neurotransmission in cortex.

Topics: Alzheimer Disease; Animals; Brain; Cats; Cerebral Cortex; Cholinergic Fibers; Dementia; Disease Models, Animal; Dopamine; G(M1) Ganglioside; gamma-Aminobutyric Acid; Gangliosidoses; Glutamates; Glutamic Acid; Humans; Neurotransmitter Agents; Norepinephrine; Rats; Serotonin; Synaptic Transmission

The metabolic processing of GM1 ganglioside, exogenously administered to cultured skin fibroblasts, was investigated on cells obtained from patients affected with Alzheimer disease, in comparison with age-matched control subjects. Cultured fibroblasts were incubated with GM1 ganglioside, [(3)H]-radiolabelled at the sphingosine moiety. It was observed that the extent of tritiated GM2 and GM3 ganglioside formation was higher in AD fibroblasts than in control cells. The activity of acidic beta-D-galactosidase, responsible of GM1 hydrolysis to GM2 within lysosomes, assayed in vitro on cell lysates, was increased in AD fibroblasts in comparison with control cells. These data suggest that up-regulation of lysosomal enzymes could be responsible of the enhanced GM1 catabolism in AD fibroblasts. Finally, it was found that the extent of GM1 hydrolysis in AD fibroblasts was inversely correlated with the mini-mental score index of patients. The increased hydrolysis rate of sphingolipids could be taken as peripheral hallmark of Alzheimer's disease patients.

Topics: Aged; Aged, 80 and over; Aging; Alzheimer Disease; Catalysis; Cells, Cultured; Female; Fibroblasts; G(M1) Ganglioside; Humans; Lysosomes; Male; Middle Aged; Severity of Illness Index; Skin; Statistics as Topic

Five patients with the early-onset form of Alzheimer disease (AD) received GM1 ganglioside by continuous injection into the frontal horns of the lateral ventricles for a period of 12 months. The optimal GM1 dose varied between 20 and 30 mg/24 h. The patients were trained twice a week for 4-5 h with an individually designed cognitive programme, which included the use of a word processor. Neurological, neuropsychological, psychiatric and neurochemical examinations were performed a week before surgery and on days 30, 90, 180, 270 and 365 after surgery. The cerebrospinal fluid levels of the monoamine metabolites homovanillic acid and 5-hydroxyindoleacetic acid and the neuropeptide somatostatin increased. The regional cerebral blood flow showed a tendency to increase. The progression of deterioration was stopped, and motor performance and neuropsychological assessments improved. The patients became more active and felt safer in relation to other people and performing various activities. They had improved reading comprehension and a better feeling for language. They were able to write reports and short letters on a word processor. When interviewed at the end of the study, all 5 patients stated that they felt better, and their relatives reported that they had regained integrity and their joie de vivre.

Topics: Aged; Alzheimer Disease; Cerebrovascular Circulation; Female; G(M1) Ganglioside; Homovanillic Acid; Humans; Hydroxyindoleacetic Acid; Injections, Intraventricular; Male; Middle Aged; Neuropsychological Tests; Somatostatin; Treatment Outcome

A double-blind, placebo-controlled pilot study was conducted to evaluate the safety and efficacy of treatment of patients with Alzheimer's disease using monosialoganglioside GM-1, a neurotrophic factor. Of 46 patients enrolled, 42 completed all study requirements. Nineteen patients received 100 mg of GM-1 by daily intramuscular injection for 12 weeks. Twenty-three patients received placebo. Case evaluations were done at baseline, week 12, and week 24 and included both cognitive and psychosocial scales. Study results suggested that the treatment was safe, yet offered no overall symptomatic benefit to patients with mild-to-moderate Alzheimer's disease. Whether or not GM-1 therapy may offer protective benefit by slowing or arresting the progression of the disease remains unclear, since the results of the cognitive evaluations suggested that neither the GM-1 group nor the placebo group declined significantly during the 24-week study.

Topics: Affect; Aged; Aged, 80 and over; Alzheimer Disease; Cognition; Double-Blind Method; Female; G(M1) Ganglioside; Humans; Male; Middle Aged; Neuropsychological Tests; Pilot Projects; Placebos; Psychiatric Status Rating Scales; Time Factors

The main purpose of this chapter is to summarize the chief findings on ganglioside changes/interactions with some of the neurodegenerative disorders. For the latter we have focused on three diseases that have seen especially intensive study in that regard: Parkinson's, Alzheimer's, and Huntington's diseases. Parkinson's disease (PD) has received the most intensive study with revelation of systemic deficiency of GM1 in brain and all peripheral tissues that have been analyzed to date; this pointed to GM1 replacement as a promising therapy which proved only partially successful when tried for reasons that are discussed. Huntington's disease resembles PD in also manifesting GM1 deficiency, which did, however, respond to GM1 replacement therapy - apparently due to GM1 being administered directly into the brain. Alzheimer's disease was more complex in relation to gangliosides, with b-series (GD1b, GT1b) apparently depressed along with a-series. GM1 administered in brain appeared to induce improvement, but in a limited number of patients. We summarize studies showing why GM1 is of critical importance in neuronal function, and we also briefly point to a few additional neurological disorders in which one or more ganglioside changes have been implicated.

Topics: Alzheimer Disease; G(M1) Ganglioside; Gangliosides; Humans; Neurodegenerative Diseases; Parkinson Disease

Monosialoganglioside GM1-bound amyloid β-peptides have been found in patients' brains exhibiting early pathological changes of Alzheimer's disease. Herein, we report the ability of non-micellar GM1 to modulate Aβ

Topics: Alzheimer Disease; Amyloid beta-Peptides; G(M1) Ganglioside; Humans; Peptide Fragments

Alzheimer's disease (AD) is associated with progressive accumulation of amyloid-β (Aβ) cross-β fibrils in the brain. Aβ species tightly associated with GM1 ganglioside, a glycosphingolipid abundant in neuronal membranes, promote amyloid fibril formation; therefore, they could be attractive clinical targets. However, the active conformational state of Aβ in GM1-containing lipid membranes is still unknown. The present solid-state nuclear magnetic resonance study revealed a nonfibrillar Aβ assemblage characterized by a double-layered antiparallel β-structure specifically formed on GM1 ganglioside clusters. Our data show that this unique assemblage was not transformed into fibrils on GM1-containing membranes but could promote conversion of monomeric Aβ into fibrils, suggesting that a solvent-exposed hydrophobic layer provides a catalytic surface evoking Aβ fibril formation. Our findings offer structural clues for designing drugs targeting catalytically active Aβ conformational species for the development of anti-AD therapeutics.

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; G(M1) Ganglioside; Humans; Neurons

Alzheimer's disease is a progressive degenerative condition that mainly affects cognition and memory. Recently, distinct clinical and neuropathological phenotypes have been identified in AD. Studies revealed that structural variation in Aβ fibrillar aggregates correlates with distinct disease phenotypes. Moreover, environmental surroundings, including other biomolecules such as proteins and lipids, have been shown to interact and modulate Aβ aggregation. Model membranes containing ganglioside (GM1) clusters are specifically known to promote Aβ fibrillogenesis. This study unravels the modulatory effect of non-micellar GM1, a glycosphingolipid frequently released from the damaged neuronal membranes, on Aβ

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; G(M1) Ganglioside; Humans; Neuroblastoma; Peptide Fragments

Alzheimer's disease is a progressive neurodegenerative disease and is the most common cause of dementia. It has been reported that the assembly of amyloid β-protein (Aβ) on the cell membrane is induced by the interaction of the Aβ monomer with gangliosides such as GM1. The ganglioside-bound Aβ (GAβ) complex acts as a seed to promote the toxic assembly of the Aβ fibrils. In a previous study, we found that a GM1 cluster-binding peptide (GCBP) specifically recognizes Aβ-sensitive ganglioside nanoclusters and inhibits the assembly of Aβ on a GM1-containing lipid membrane. In this study, cysteine-substituted double mutants of GCBP were designed and cyclized by intramolecular disulfide bond formation. Affinity assays indicated that one of the cyclic peptides had a higher affinity to a GM1-containing membrane compared to that of GCBP. Furthermore, surface topography analysis indicated that this peptide recognizes GM1 nanoclusters on the lipid membrane. An evaluation of the inhibitory kinetics indicated that the cyclic peptide could inhibit the formation of Aβ fibrils with an IC

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cyclization; G(M1) Ganglioside; Gangliosides; Humans; Neurodegenerative Diseases; Peptides, Cyclic

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Disease Models, Animal; G(M1) Ganglioside; Mice; Peptide Fragments

The amyloid cascade hypothesis states that senile plaques, composed of amyloid β (Aβ) fibrils, play a key role in Alzheimer's disease (AD). However, recent experiments have shown that Aβ oligomers are more toxic to neurons than highly ordered fibrils. The molecular mechanism underlying this observation remains largely unknown. One of the possible scenarios for neurotoxicity is that Aβ peptides create pores in the lipid membrane that allow Ca

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; G(M1) Ganglioside; Humans; Neurons; Peptide Fragments

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Antioxidant Response Elements; Antioxidants; G(M1) Ganglioside; Neuroprotective Agents; Oxidative Stress; PC12 Cells; Peptide Fragments; Rats; Signal Transduction

The aggregation of the amyloid beta (Aβ) peptide is associated with Alzheimer's disease (AD) pathogenesis. Cell membrane composition, especially monosialotetrahexosylganglioside (GM1), is known to promote the formation of Aβ fibrils, yet little is known about the roles of GM1 in the early steps of Aβ oligomer formation. Here, by using GM1-contained liposomes as a mimic of the neuronal cell membrane, we demonstrate that GM1 is a critical trigger of Aβ oligomerization and aggregation. We find that GM1 not only promotes the formation of Aβ fibrils but also facilitates the maintenance of Aβ42 oligomers on liposome membranes. We structurally characterize the Aβ42 oligomers formed on the membrane and find that GM1 captures Aβ by binding to its arginine-5 residue. To interrogate the mechanism of Aβ42 oligomer toxicity, we design a new liposome-based Ca

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; G(M1) Ganglioside; Humans; Liposomes; Peptide Fragments

A major hallmark of Alzheimer's disease (AD) is the accumulation of extracellular aggregates of amyloid-β (Aβ). Structural polymorphism observed among Aβ fibrils in AD brains seem to correlate with the clinical subtypes suggesting a link between fibril polymorphism and pathology. Since fibrils emerge from a templated growth of low-molecular-weight oligomers, understanding the factors affecting oligomer generation is important. Membrane lipids are key factors to influence early stages of Aβ aggregation and oligomer generation, which cause membrane disruption. We have previously demonstrated that conformationally discrete Aβ oligomers can be generated by modulating the charge, composition, and chain length of lipids and surfactants. Here, we extend our studies into liposomal models by investigating Aβ oligomerization on large unilamellar vesicles (LUVs) of total brain extracts (TBE), reconstituted lipid rafts (LRs), or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). Varying the vesicle composition by specifically increasing the amount of GM1 gangliosides as a constituent, we found that only GM1-enriched liposomes induce the formation of toxic, low-molecular-weight oligomers. Furthermore, we found that the aggregation on liposome surface and membrane disruption are highly cooperative and sensitive to membrane surface characteristics. Numerical simulations confirm such a cooperativity and reveal that GM1-enriched liposomes form twice as many pores as those formed in the absence GM1. Overall, this study uncovers mechanisms of cooperativity between oligomerization and membrane disruption under controlled lipid compositional bias, and refocuses the significance of the early stages of Aβ aggregation in polymorphism, propagation, and toxicity in AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Dimyristoylphosphatidylcholine; G(M1) Ganglioside; Gangliosides; Humans; Membrane Lipids; Phospholipids; Phosphorylcholine; Surface-Active Agents; Unilamellar Liposomes

A recently proposed lipid-chaperone hypothesis suggests that free lipid molecules, not bound to membranes, affect the aggregation of amyloidogenic peptides such as amyloid-β (Aβ) peptides, whose aggregates are the hallmarks of Alzheimer's disease. Here, we combine experiments with all-atom molecular dynamics simulations in explicit solvent to explore the effects of neuronal ganglioside GM1, abundant in mammalian brains, on the aggregation of two principal isoforms of Aβ, Aβ40 and Aβ42. Our simulations show that free GM1 forms stable, highly water-soluble complexes with both isoforms, and nuclear magnetic resonance experiments support the formation of well-ordered, structurally compact GM1+Aβ complexes. By simulation, we also show that Aβ40 monomers display a preference for binding to GM1-containing hetero-oligomers over GM1-lacking homo-oligomers, while Aβ42 monomers have the opposite preference. These observations explain why GM1 dose-dependently inhibits Aβ40 aggregation but has no effect on Aβ42 aggregation, as assessed by thioflavin T fluorescence.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; G(M1) Ganglioside; Gangliosides; Mammals; Molecular Dynamics Simulation; Peptide Fragments; Solvents; Water

The protracted preclinical stage of Alzheimer's disease (AD) provides the opportunity for early intervention to prevent the disease; however, the lack of minimally invasive and easily detectable biomarkers and their measurement technologies remain unresolved. Extracellular vesicles (EVs) are nanosized membrane vesicles released from a variety of cells and play important roles in cell-cell communication. Neuron-derived and ganglioside-enriched EVs capture amyloid-ß protein, a major AD agent, and transport it into glial cells for degradation; this suggests that EVs influence Aß accumulation in the brain. EV heterogeneity, however, requires the use of a highly sensitive technique for measuring specific EVs in biofluid. In this study, immuno-digital invasive cleavage assay (idICA) was developed for quantitating target-intact EVs.. EVs were captured onto ganglioside GM1-specific cholera toxin B subunit (CTB)-conjugated magnetic beads and detected with a DNA oligonucleotide-labeled Aß antibody. Fluorescence signals for individual EVs were then counted using an invasive cleavage assay (ICA). This idICA examines the Aß-bound and GM1-containing EVs isolated from the culture supernatant of human APP-overexpressing N2a (APP-N2a) cells and APP transgenic mice sera.. The idICA quantitatively detected Aß-bound and GM1-containing EVs isolated from culture supernatants of APP-N2a cells and sera of AD model mice. The idICA levels of Aß-associated EVs in blood gradually increased from 3- to 12-month-old mice, corresponding to the progression of Aß accumulations in the brain of AD model mice.. The present findings suggest that peripheral EVs harboring Aß and GM1 reflect Aß burden in mice. The idICA is a valuable tool for easy quantitative detection of EVs as an accessible biomarker for preclinical AD diagnosis.

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Amyloidogenic Proteins; Amyloidosis; Animals; Biomarkers; Cholera Toxin; Extracellular Vesicles; G(M1) Ganglioside; Gangliosides; Humans; Infant; Mice; Mice, Transgenic; Oligonucleotides

Neuroinflammation is involved in the pathology and progression of Alzheimer's disease (AD) and is closely related to microglial activation. We have previously reported that cattle encephalon glycoside and ignotin (CEGI) could inhibit the activation of microglia in APP/PS1 mice, a mouse model of familial AD. However, the anti-neuroinflammatory mechanisms of CEGI have not yet been fully elucidated. Here, we aimed to investigate the role of CEGI in microglia-mediated neuroinflammation in AD. APP/PS1 mice were treated with CEGI intraperitoneally for 30 days, and then their cognition was assessed. We showed that CEGI alleviated cognitive damage with higher nesting scores, preferential indices, and spontaneous alternation rates in APP/PS1 mice. Moreover, CEGI treatment effectively reduced microglial activation and Iba-1 levels in the cortex of APP/PS1 mice. Additionally, CEGI decreased pro-inflammatory factors production and neuroinflammation-mediated neuronal damage in vivo and in vitro. Finally, CEGI upregulated BDNF levels and downregulated TLR4 and p-NF-κB p65 levels in vivo and in vitro. Taken together, these findings indicated that CEGI could attenuate cognitive deficits in APP/PS1 mice and suppress microglia-induced neuroinflammation via increasing BDNF expression and inhibiting the TLR4/NF-κB pathway.

Topics: Alzheimer Disease; Animals; Brain-Derived Neurotrophic Factor; Carnosine; Cattle; Cell Line, Tumor; Cerebral Cortex; Cytokines; Female; G(M1) Ganglioside; Humans; Inflammation; Male; Mice, Inbred C57BL; Mice, Transgenic; Microglia; Neurons; Neuroprotective Agents; NF-kappa B p50 Subunit; Signal Transduction; Toll-Like Receptor 4

A major characteristic of Alzheimer's disease (AD) is the accumulation of misfolded amyloid-β (Aβ) peptide. Several studies linked AD with type 2 diabetes due to similarities between Aβ and human amylin. This study investigates the effect of amylin and pramlintide on Aβ pathogenesis and the predisposing molecular mechanism(s) behind the observed effects in TgSwDI mouse, a cerebral amyloid angiopathy (CAA) and AD model. Our findings showed that thirty days of intraperitoneal injection with amylin or pramlintide increased Aβ burden in mice brains. Mechanistic studies revealed both peptides altered the amyloidogenic pathway and increased Aβ production by modulating amyloid precursor protein (APP) and γ-secretase levels in lipid rafts. In addition, both peptides increased levels of B4GALNT1 enzyme and GM1 ganglioside, and only pramlintide increased the level of GM2 ganglioside. Increased levels of GM1 and GM2 gangliosides play an important role in regulating amyloidogenic pathway proteins in lipid rafts. Increased brain Aβ burden by amylin and pramlintide was associated with synaptic loss, apoptosis, and microglia activation. In conclusion, our findings showed amylin or pramlintide increase Aβ levels and related pathology in TgSwDI mice brains, and suggest that increased amylin levels or the therapeutic use of pramlintide could increase the risk of AD.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Cerebral Amyloid Angiopathy; G(M1) Ganglioside; G(M2) Ganglioside; Islet Amyloid Polypeptide; Membrane Microdomains; Mice; Mice, Transgenic; N-Acetylgalactosaminyltransferases; Protein Processing, Post-Translational

The abnormal aggregation of amyloid β-protein (Aβ) is considered central in the pathogenesis of Alzheimer's disease. We focused on membrane-mediated amyloidogenesis and found that amyloid fibrils formed on monosialoganglioside GM1 clusters were more toxic than those formed in aqueous solution. In this study, we investigated the structure of the toxic fibrils by Aβ-(1-40) in detail in comparison with less-toxic fibrils formed in aqueous solution. The less-toxic fibrils contain in-resister parallel β-sheets, whereas the structure of the toxic fibrils is unknown. Atomic force microscopy revealed that the toxic fibrils had a flat, tape-like morphology composed of a single β-sheet layer. Isotope-edited infrared spectroscopy indicated that almost the entire sequence of Aβ is included in the β-sheet. Chemical cross-linking experiments using Cys-substituted Aβs suggested that the fibrils mainly contained both in-resister parallel and two-residue-shifted antiparallel β-sheet structures. Solid-state NMR experiments also supported this conclusion. Thus, the toxic fibrils were found to possess a novel unique structure.

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Amyloidogenic Proteins; Amyloidosis; G(M1) Ganglioside; Humans; Peptide Fragments; Protein Structure, Secondary

Alzheimer's disease (AD) is an incurable neurodegenerative brain disorder that exhibits clear pathologic changes in the hippocampus. Traditional drug delivery systems are ineffective due to the existence of the blood-brain barrier (BBB). In this study, an efficient, stable, and easily constructed nanosystem (CB-Gd-Cy5.5) based on the cholera toxin B subunit (CB) is designed to improve the efficiency of drug delivery to the brain, especially the hippocampus. Through intranasal administration, CB-Gd-Cy5.5 is easily delivered to the brain without intervention by the BBB. The CB in CB-Gd-Cy5.5 is used for specifically combining with the monosialoganglioside GM1, which is widely found in the hippocampus. This nanosystem exhibits impressive performance in accumulating in the hippocampus. In addition, the good magnetic resonance imaging (MRI) capability of CB-Gd-Cy5.5 can satisfy the monitoring of AD in the different stages.

Topics: Administration, Intranasal; Alzheimer Disease; Animals; Blood-Brain Barrier; Carbocyanines; Cell Line; Cholera Toxin; Drug Carriers; G(M1) Ganglioside; Hippocampus; Magnetic Resonance Imaging; Male; Mice; Mice, Inbred BALB C; Nanoparticles

Due to an aging population, neurodegenerative diseases have become a major health issue, the most common being Alzheimer's disease. The mechanisms leading to neuronal loss still remain unclear but recent studies suggest that soluble Aβ oligomers have deleterious effects on neuronal membranes. Here, high-speed atomic force microscopy was used to assess the effect of oligomeric species of a variant of Aβ1-42 amyloid peptide on model membranes with various lipid compositions. Results showed that the peptide does not interact with membranes composed of phosphatidylcholine and sphingomyelin. Ganglioside GM1, but not cholesterol, is required for the peptide to interact with the membrane. Interestingly, when they are both present, a fast disruption of the membrane was observed. It suggests that the presence of ganglioside GM1 and cholesterol in membranes promotes the interaction of the oligomeric Aβ1-42 peptide with the membrane. This interaction leads to the membrane's destruction in a few seconds. This study highlights the power of high-speed atomic force microscopy to explore lipid-protein interactions with high spatio-temporal resolution.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cholesterol; G(M1) Ganglioside; Humans; Lipid Bilayers; Microscopy, Atomic Force; Peptide Fragments; Phosphatidylcholines

The assembly and deposition of amyloid β protein (Aβ) is a fundamental event during the early stages of Alzheimer's disease (AD) and cerebral amyloid angiopathy. A growing body of evidence indicates that gangliosides form a pathological platform for the generation of ganglioside-bound Aβ, which facilitates the assembly of soluble Aβs; however, the molecular mechanisms underlying the binding of Aβ to gangliosides in the brain remain unclear due to the lack of an in vivo system that may address this issue. In insects, including the fruit fly Drosophila melanogaster, gangliosides are not intrinsically present at a detectable level. We herein demonstrate that ganglioside expression is inducible in Drosophila via the expression of transgenes of ganglioside synthesis enzymes and the feeding of exogenous sialic acid, and also that the induction of ganglioside synthesis significantly accelerates Aβ assembly in vivo. Our results support the hypothesis that gangliosides are responsible for Aβ assembly in vivo and also provide an opportunity to develop a valuable model for basic research as well as a therapeutic strategy for AD.

Topics: Acetyltransferases; Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; Cell Membrane; Disease Models, Animal; Drosophila melanogaster; Drosophila Proteins; G(M1) Ganglioside; Galactosyltransferases; Gangliosides; Humans; N-Acetylneuraminic Acid; Protein Binding; Transgenes

Alzheimer's disease (AD) is characterized by the overproduction of the amyloid-β peptide (Aβ) which forms fibrils under the influence of raft microdomains containing the ganglioside GM1. Raft-mimicking artificial liquid ordered (Lo) domains containing GM1 enhance amyloid-β polymerization. Other experiments suggest that Aβ binds preferably to the non-raft liquid disordered (Ld) phase rather than to the Lo phase in the presence of GM1. Here, the interaction of Aβ(1-42) with GM1-containing biphasic Lo-Ld giant vesicles was investigated. Fluorescence colocalisation experiments confirm that Aβ(1-42) binds preferentially to the Ld phase. The effect of Aβ(1-42) on the Lo-Ld size dynamics was studied using photoinduced spinodal decomposition which mimics the nanodomain-microdomain raft coalescence. Aβ affects the kinetics of the coarsening phase and the size of the resulting microdomains. The effect depends on which phase is in a majority: when the Lo microdomains are formed inside an Ld phase, their growth rate becomes slower and their final size smaller in the presence of Aβ(1-42), whereas when the Ld microdomains are formed inside an Lo phase, the growth rate becomes faster and the final size larger. Fluorimetric measurements on large vesicles using the probe Laurdan indicate that Aβ(1-42) binding respectively increases or decreases the packing of the Ld phase in the presence or absence of GM1. The differential effects of Aβ on spinodal decomposition are accordingly interpreted as resulting from distinct effects of the peptide on the Lo-Ld line tension modulated by GM1. Such modulating effect of Aβ on domain dynamics could be important for lipid rafts in signaling disorders in AD as well as in Aβ fibrillation.

Topics: Alzheimer Disease; Amyloid beta-Peptides; G(M1) Ganglioside; Lipid Bilayers; Membrane Microdomains; Microscopy, Fluorescence

The ability of beta-amyloid peptide (Aβ) to disrupt the plasma membrane through formation of pores and membrane breakage has been previously described. However, the molecular determinants for these effects are largely unknown. In this study, we examined if the association and subsequent membrane perforation induced by Aβ was dependent on GM1 levels. Pretreatment of hippocampal neurons with D-PDMP decreased GM1 and Aβ clustering at the membrane (Aβ fluorescent-punctas/20μm, control=16.2±1.1 vs. D-PDMP=6.4±0.4, p<0.001). Interestingly, membrane perforation with Aβ occurred with a slower time course when the GM1 content was diminished (time to establish perforated configuration (TEPC) (min): control=7.8±2 vs. low GM1=12.1±0.5, p<0.01), suggesting that the presence of GM1 in the membrane can modulate the distribution and the membrane perforation by Aβ. On the other hand, increasing GM1 facilitated the membrane perforation (TEPC: control=7.8±2 vs. GM1=6.2±1min, p<0.05). Additionally, using Cholera Toxin Subunit-B (CTB) to block the interaction of Aβ with GM1 attenuated membrane perforation significantly. Furthermore, pretreatment with CTB decreased the membrane association of Aβ (fluorescent-punctas/20μm, Aβ: control=14.8±2.5 vs. CTB=8±1.4, p<0.05), suggesting that GM1 also plays a role in both association of Aβ with the membrane and in perforation. In addition, blockade of the Aβ association with CTB inhibited synaptotoxicity. Taken together, our results strongly suggest that membrane lipid composition can affect the ability of Aβ to associate and subsequently perforate the plasma membrane thereby modulating its neurotoxicity in hippocampal neurons.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cell Membrane; Cholera Toxin; G(M1) Ganglioside; HEK293 Cells; Hippocampus; Humans; Membrane Lipids; Neurons

Topics: Alzheimer Disease; Animals; Blood Platelets; Cell Membrane; Delayed-Action Preparations; Drug Delivery Systems; G(M1) Ganglioside; Humans; Magnets; Nanoparticles; Neoplasms; Neutrophils

RNA interference represents a novel therapeutic approach to modulate several neurodegenerative disease-related genes. However, exogenous delivery of siRNA restricts their transport into different tissues and specifically into the brain mainly due to its large size and the presence of the blood-brain barrier (BBB). To overcome these challenges, we developed here a strategy wherein a peptide known to target specific gangliosides was fused to a double-stranded RNA binding protein to deliver siRNA to the brain parenchyma. The designed fusion protein designated as TARBP-BTP consists of a double-stranded RNA-binding domain (dsRBD) of human Trans Activation response element (TAR) RNA Binding Protein (TARBP2) fused to a brain targeting peptide that binds to monosialoganglioside GM1. Conformation-specific binding of TARBP2 domain to siRNA led to the formation of homogenous serum-stable complex with targeting potential. Further, uptake of the complex in Neuro-2a, IMR32 and HepG2 cells analyzed by confocal microscopy and fluorescence activated cell sorting, revealed selective requirement of GM1 for entry. Remarkably, systemic delivery of the fluorescently labeled complex (TARBP-BTP:siRNA) in ΑβPP-PS1 mouse model of Alzheimer's disease (AD) led to distinctive localization in the cerebral hemisphere. Further, the delivery of siRNA mediated by TARBP-BTP led to significant knockdown of BACE1 in the brain, in both ΑβPP-PS1 mice and wild type C57BL/6. The study establishes the growing importance of fusion proteins in delivering therapeutic siRNA to brain tissues.

Topics: Alzheimer Disease; Amyloid Precursor Protein Secretases; Animals; Aspartic Acid Endopeptidases; Blood-Brain Barrier; Brain; Cell Line, Tumor; Drug Carriers; Drug Delivery Systems; G(M1) Ganglioside; Gene Transfer Techniques; Humans; Mice; Mice, Inbred C57BL; Peptides; Recombinant Fusion Proteins; RNA-Binding Proteins; RNA, Small Interfering; RNAi Therapeutics

The interaction of the amyloid-β protein (Aβ) with neuronal cell membranes plays a crucial role in Alzheimer's disease. Aβ undergoes structural changes upon binding to ganglioside GM1 containing membranes leading to altered molecular characteristics of the protein. The physiological role of the Aβ interaction with the ganglioside GM1 is still unclear. In order to further elucidate the molecular requirements of Aβ membrane binding, we tested different nanodiscs varying in their lipid composition, regarding the charge of the headgroups as well as ganglioside GM1 concentration. Nanodiscs are excellent model membrane systems for studying protein membrane interactions, and we show here their suitability to investigate the membrane interaction of Aβ. In particular, we set out to investigate whether the binding activity of GM1 to Aβ is specific for the assembly state of Aβ and compared the binding affinities of monomeric with oligomeric Aβ. Using fluorescence titration experiments, we demonstrate high-affinity binding of Aβ(1-40) to GM1 containing nanodiscs, with dissociation constants, K

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Binding, Competitive; Cell Membrane; Electrophoresis, Polyacrylamide Gel; G(M1) Ganglioside; Humans; Kinetics; Lipid Bilayers; Magnetic Resonance Spectroscopy; Nanostructures; Peptide Fragments; Phospholipids; Protein Binding; Protein Multimerization

Recent studies have suggested that a positive correlation exists between surgical interventions performed under general anesthesia and the risk of developing Alzheimer's disease (AD) in the late postoperative period. It has been reported that amyloid β-protein (Αβ) fibrillogenesis, which is closely related to AD, is accelerated by exposure to anesthetics. However, the mechanisms underlying these effects remain uncertain. This study was designed to investigate whether the anesthetic midazolam affects Αβ fibrillogenesis, and if so, whether it acts through GM1 ganglioside (GM1) on the neuronal surface. Midazolam treatment decreased GM1 expression in the detergent-resistant membrane microdomains of neurons, and these effects were regulated by the gamma-aminobutyric acid-A receptor. Midazolam inhibited Αβ fibril formation from soluble Αβ on the neuronal surface. In addition, midazolam suppressed GM1-induced fibril formation in a cell-free system. Moreover, midazolam inhibited the formation of Αβ assemblies in synaptosomes isolated from aged mouse brains. These finding suggested that midazolam has direct and indirect inhibitory effects on Αβ fibrillogenesis.

Topics: Alzheimer Disease; Amyloid; Anesthetics, Intravenous; Animals; Cells, Cultured; G(M1) Ganglioside; Male; Mice; Midazolam; Neurons; Protective Agents; Receptors, GABA; Synaptosomes

Growing evidence suggests that diabetes mellitus (DM) is one of the strongest risk factors for developing Alzheimer's disease (AD). However, it remains unclear why DM accelerates AD pathology. In cynomolgus monkeys older than 25 years, senile plaques (SPs) are spontaneously and consistently observed in their brains, and neurofibrillary tangles are present at 32 years of age and older. In laboratory-housed monkeys, obesity is occasionally observed and frequently leads to development of type 2 DM. In the present study, we performed histopathological and biochemical analyses of brain tissue in cynomolgus monkeys with type 2 DM to clarify the relationship between DM and AD pathology. Here, we provide the evidence that DM accelerates Aβ pathology in vivo in nonhuman primates who had not undergone any genetic manipulation. In DM-affected monkey brains, SPs were observed in frontal and temporal lobe cortices, even in monkeys younger than 20 years. Biochemical analyses of brain revealed that the amount of GM1-ganglioside-bound Aβ (GAβ)--the endogenous seed for Aβ fibril formation in the brain--was clearly elevated in DM-affected monkeys. Furthermore, the level of Rab GTPases was also significantly increased in the brains of adult monkeys with DM, almost to the same levels as in aged monkeys. Intraneuronal accumulation of enlarged endosomes was also observed in DM-affected monkeys, suggesting that exacerbated endocytic disturbance may underlie the acceleration of Aβ pathology due to DM.

Topics: Age Factors; Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Brain; Cathepsin D; Cerebral Amyloid Angiopathy; Diabetes Mellitus; Diabetes Mellitus, Type 2; Disease Models, Animal; Endocytosis; Female; G(M1) Ganglioside; Immunohistochemistry; Macaca fascicularis; Phagosomes; Plaque, Amyloid; rab GTP-Binding Proteins

Amyloid aggregation and deposition of amyloid β-peptide (Aβ) are pathologic characteristics of Alzheimer's disease (AD). Recent reports have shown that the association of Aβ with membranes containing ganglioside GM1 (GM1) plays a pivotal role in amyloid deposition and the pathogenesis of AD. However, the molecular interactions responsible for membrane damage associated with Aβ deposition are not fully understood. In this study, we microscopically observed amyloid aggregation of Aβ in the presence of lipid vesicles and on a substrate-supported planar membrane containing raft components and GM1. The experimental system enabled us to observe lipid-associated aggregation of Aβ, uptake of the raft components into Aβ aggregates, and relevant membrane damage. The results indicate that uptake of raft components from the membrane into Aβ deposits induces macroscopic heterogeneity of the membrane structure.

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Animals; Cell Membrane; G(M1) Ganglioside; Humans; Liposomes; Membrane Microdomains; Peptide Fragments; Protein Aggregation, Pathological

The aging brain is often characterized by the presence of multiple comorbidities resulting in synergistic damaging effects in the brain as demonstrated through the interaction of Alzheimer's disease (AD) and stroke. Gangliosides, a family of membrane lipids enriched in the central nervous system, may have a mechanistic role in mediating the brain's response to injury as their expression is altered in a number of disease and injury states. Matrix-Assisted Laser Desorption Ionization (MALDI) Imaging Mass Spectrometry (IMS) was used to study the expression of A-series ganglioside species GD1a, GM1, GM2, and GM3 to determine alteration of their expression profiles in the presence of beta-amyloid (Aβ) toxicity in addition to ischemic injury. To model a stroke, rats received a unilateral striatal injection of endothelin-1 (ET-1) (stroke alone group). To model Aβ toxicity, rats received intracerebralventricular (i.c.v.) injections of the toxic 25-35 fragment of the Aβ peptide (Aβ alone group). To model the combination of Aβ toxicity with stroke, rats received both the unilateral ET-1 injection and the bilateral icv injections of Aβ25-35 (combined Aβ/ET-1 group). By 3 d, a significant increase in the simple ganglioside species GM2 was observed in the ischemic brain region of rats who received a stroke (ET-1), with or without Aβ. By 21 d, GM2 levels only remained elevated in the combined Aβ/ET-1 group. GM3 levels however demonstrated a different pattern of expression. By 3 d GM3 was elevated in the ischemic brain region only in the combined Aβ/ET-1 group. By 21 d, GM3 was elevated in the ischemic brain region in both stroke alone and Aβ/ET-1 groups. Overall, results indicate that the accumulation of simple ganglioside species GM2 and GM3 may be indicative of a mechanism of interaction between AD and stroke.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; Brain Ischemia; G(M1) Ganglioside; G(M2) Ganglioside; G(M3) Ganglioside; Male; Peptide Fragments; Rats, Wistar; Reperfusion Injury; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Alzheimer's disease (AD) exerts a heavy health burden for modern society and has a complicated pathological background. The accumulation of extracellular β-amyloid (Aβ) is crucial in AD pathogenesis, and Aβ-initiated secondary pathological processes could independently lead to neuronal degeneration and pathogenesis in AD. Thus, the development of combination therapeutics that can not only accelerate Aβ clearance but also simultaneously protect neurons or inhibit other subsequent pathological cascade represents a promising strategy for AD intervention. Here, we designed a nanostructure, monosialotetrahexosylganglioside (GM1)-modified reconstituted high density lipoprotein (GM1-rHDL), that possesses antibody-like high binding affinity to Aβ, facilitates Aβ degradation by microglia, and Aβ efflux across the blood-brain barrier (BBB), displays high brain biodistribution efficiency following intranasal administration, and simultaneously allows the efficient loading of a neuroprotective peptide, NAP, as a nanoparticulate drug delivery system for the combination therapy of AD. The resulting multifunctional nanostructure, αNAP-GM1-rHDL, was found to be able to protect neurons from Aβ(1-42) oligomer/glutamic acid-induced cell toxicity better than GM1-rHDL in vitro and reduced Aβ deposition, ameliorated neurologic changes, and rescued memory loss more efficiently than both αNAP solution and GM1-rHDL in AD model mice following intranasal administration with no observable cytotoxicity noted. Taken together, this work presents direct experimental evidence of the rational design of a biomimetic nanostructure to serve as a safe and efficient multifunctional nanoplatform for the combination therapy of AD.

Topics: Administration, Intranasal; Alzheimer Disease; Amino Acid Sequence; Amyloid beta-Peptides; Animals; Apolipoproteins E; Brain; Combined Modality Therapy; Disease Models, Animal; Endocytosis; G(M1) Ganglioside; Glutamates; Lipoproteins, HDL; Memory Disorders; Mice, Inbred ICR; Microglia; Molecular Sequence Data; Nanoparticles; Neuroprotection; Neuroprotective Agents; Particle Size; Peptide Fragments; Peptides; Rats, Sprague-Dawley; Static Electricity; Tissue Distribution

Alzheimer's disease (AD) is a progressive dementia associated with loss of memory and cognitive dysfunction. In a previous study, we demonstrated a decrease in b-series gangliosides along with a change in ganglioside molecular species in the hippocampal grey matter of patients with AD. The present study demonstrates the use of imaging mass spectrometry for analyzing the spatial arrangement of ganglioside GM1 (GM1) molecular species in the hippocampus. In AD patients, we found a decrease in the ratio of GM1(d20:1/C18:0) to GM1 d18:1/C18:0) in the outer molecular layer (ML) of the dentate gyrus. Because the outer ML is the region of main input into the hippocampus, our findings may have a direct relationship to the mechanism of dysfunction in AD.

Topics: Aged, 80 and over; Alzheimer Disease; Biological Transport; Dentate Gyrus; Female; G(M1) Ganglioside; Humans; Male; Middle Aged

Soluble Aβ oligomers contribute importantly to synaptotoxicity in Alzheimer's disease, but their dynamics in vivo remain unclear. Here, we found that soluble Aβ oligomers were sequestered from brain interstitial fluid onto brain membranes much more rapidly than nontoxic monomers and were recovered in part as bound to GM1 ganglioside on membranes. Aβ oligomers bound strongly to GM1 ganglioside, and blocking the sialic acid residue on GM1 decreased oligomer-mediated LTP impairment in mouse hippocampal slices. In a hAPP transgenic mouse model, substantial levels of GM1-bound Aβ₄₂ were recovered from brain membrane fractions. We also detected GM1-bound Aβ in human CSF, and its levels correlated with Aβ₄₂, suggesting its potential as a biomarker of Aβ-related membrane dysfunction. Together, these findings highlight a mechanism whereby hydrophobic Aβ oligomers become sequestered onto GM1 ganglioside and presumably other lipids on neuronal membranes, where they may induce progressive functional and structural changes.

Topics: Age Factors; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Brain; Cell Membrane; Dose-Response Relationship, Drug; Embryo, Mammalian; Extracellular Fluid; G(M1) Ganglioside; Gangliosides; Hippocampus; Humans; In Vitro Techniques; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; Peptide Fragments

Increasing evidence suggests that gangliosides act as important mediators in both de- and remyelination. The scope of the present research was to investigate the presence of immunoglobulin (Ig) M antibodies against GM1, GD1b, and GQ1b gangliosides in the sera of patients with dementia and the possible connection with clinical parameters of the disease.. This research topic demonstrates the investigation of 103 patients with dementia and 60 healthy individuals using enzyme-linked immunosorbent assay for the presence of 3 antiganglioside antibodies in their sera.. The authors report a positive connection between IgM anti-GM1 and the age (P = .005) and the severity of dementia (P = .005). Most of the patients who revealed increased IgM anti-GD1b levels had Alzheimer's disease (AD; P = .002).. This study indicates that elevated IgM anti-GM1 may be connected with the neurodegeneration in older patients with severe dementia and that AD may also be associated with increased IgM anti-GD1b levels.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Autoantibodies; Case-Control Studies; Dementia; Enzyme-Linked Immunosorbent Assay; Female; G(M1) Ganglioside; Gangliosides; Humans; Immunoglobulin M; Male; Middle Aged

A few studies have reported the association of autoantibodies to GM1 or GQ1bα with Alzheimer's disease (AD) or vascular dementia. Here we investigated whether patients with AD or vascular dementia had high titers of the anti-ganglioside antibodies. Sera were obtained from patients with AD (n = 22), vascular dementia (n = 14), Guillain-Barré syndrome, and multifocal motor neuropathy as well as normal controls. Enzyme-linked immunosorbent assay showed titers of IgG and IgM anti-GM1, anti-GQ1bα, and anti-GT1aα antibodies did not differ among AD, vascular dementia, and normal controls, and being remarkably lower than those in Guillain-Barré syndrome and multifocal motor neuropathy. The anti-ganglioside antibodies are not biological markers of AD.

Topics: Adult; Aged; Aged, 80 and over; Alzheimer Disease; Autoantibodies; Biomarkers; Dementia, Vascular; Enzyme-Linked Immunosorbent Assay; Female; G(M1) Ganglioside; Gangliosides; Guillain-Barre Syndrome; Humans; Immunoglobulin G; Immunoglobulin M; Male; Middle Aged; Young Adult

Alzheimer's disease (AD), a severe neurodegenerative disorder, causes more than half of dementia cases. According to the popular "Aβ hypothesis" to explain the mechanism of this disease, amyloid β-peptides (Aβ) of 39-43 amino acid residues aggregate and deposit onto neurons, igniting the neurotoxic cascade of the disease. Therefore, researchers studying AD would like to elucidate the mechanisms by which essentially water-soluble but hydrophobic Aβ aggregates under pathological conditions. Most researchers have investigated the aggregation of Aβ in aqueous solution, and they concluded that the final aggregation product, the amyloid fibrils, were less toxic than the component peptide oligomers. They consequently shifted their interests to more toxic "soluble oligomers", structures that form as intermediates or off-pathway products during the aggregation process. Some researchers have also investigated artificial oligomers prepared under nonphysiological conditions. In contrast to these "in solution" studies, we have focused on "membrane-mediated" amyloidogenesis. In an earlier study, other researchers identified a specific form of Aβ that was bound to monosialoganglioside GM1, a sugar lipid, in brains of patients who exhibited the early pathological changes associated with AD. This Account summarizes 15 years of our research on this topic. We have found that Aβ specifically binds to GM1 that occurs in clusters, but not when it is uniformly distributed. Clustering is facilitated by cholesterol. Upon binding, Aβ changes its conformation from a random coil to an α-helix-rich structure. A CH-π interaction between the aromatic side chains of Aβ and carbohydrate moieties appended to GM1 appears to be important for binding. In addition, as Aβ accumulates and reaches its first threshold concentration (Aβ/GM1 = ∼0.013), aggregated β-sheets of ∼15 molecules appear and coexist with the helical form. However, this β-structure is stable and does not form larger aggregates. When the disease progresses further and the Aβ/GM1 ratio exceeds ∼0.044, the β-structure converts to a second β-structure that can seed aggregates. The seed recruits monomers from the aqueous phase to form toxic amyloid fibrils that have larger surface hydrophobicity and can contain antiparallel β-sheets. In contrast, amyloid fibrils formed in aqueous solution are less toxic and have parallel β-sheets. The less polar environments of GM1 clusters play an important role in the formation of these toxic f

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Animals; Apoptosis; Cell Line, Tumor; G(M1) Ganglioside; Humans; Molecular Dynamics Simulation; PC12 Cells; Protein Binding; Protein Structure, Secondary; Rats

The abnormal deposition of amyloids by amyloid-β protein (Aβ) is a pathological hallmark of Alzheimer's disease (AD). Aged rodents rarely develop the characteristic lesions of the disease, which is different from the case in humans. Rodent Aβ (rAβ) differs from human Aβ (hAβ) only in the three substitutions of Arg to Gly, Tyr to Phe, and His to Arg at positions 5, 10, and 13, respectively. Understanding the reason why rodent Aβ does not form amyloids is important to revealing factors that cause the abnormal aggregation of Aβ under pathologic conditions. We have proposed that the binding of Aβ to membranes with ganglioside clusters plays an important role in the abnormal aggregation of Aβ. In this study, we compared hAβ and rAβ in terms of aggregation on neuronal cells, on raftlike model membranes, and in buffer. We found that rAβ formed amyloid fibrils similar to those of hAβ in buffer solution. In contrast, on cell membranes and raftlike membranes, hAβ formed toxic, mature amyloid fibrils, whereas rAβ produced less toxic protofibrils that were not stained by the amyloid-specific dye Congo red. Thus, our ganglioside cluster-mediated amyloidogenesis hypothesis explains the immunity of rodents from cerebral Aβ amyloid deposition, strengthening the importance of ganglioside clusters as a platform of abnormal Aβ deposition in the pathology of AD.

Topics: Alzheimer Disease; Amino Acid Sequence; Amino Acid Substitution; Amyloid; Amyloid beta-Peptides; Animals; Cell Line; Cell Survival; G(M1) Ganglioside; Humans; Membrane Microdomains; Mice; Microscopy, Electron, Transmission; Models, Molecular; Molecular Sequence Data; Neurons; Protein Multimerization; Protein Structure, Secondary; Rats; Species Specificity; Spectroscopy, Fourier Transform Infrared

Alzheimer's disease (AD) is the most prevalent age-dependent form of dementia, characterized by extracellular amyloid deposits comprising amyloid β-peptide (Aβ) in the cerebral cortex. Increasing evidence has indicated that ganglioside GM1 (GM1) in lipid rafts plays a pivotal role in amyloid deposition of Aβ and the related cytotoxicity in AD. Despite recent efforts to characterize Aβ-lipid interactions, the effect of Aβ aggregation on dynamic properties and organization of lipid membranes is poorly understood. In this study, we examined the aggregation of Aβ on supported lipid bilayers containing raft components (i.e., cholesterol, sphingomyelin, and GM1) and its effects on the membrane properties. We showed that the lateral fluidity of membranes was significantly affected by membrane binding and subsequent aggregation of Aβ. Microscopic observations of the membrane surfaces demonstrated an enhancement in phase separation of lipids as a result of interactions between Aβ and GM1 during induced aggregation of Aβ. The uptake of GM1 into Aβ aggregates and the attendant membrane damage were also observed under a microscope when the membrane-anchored aggregates were formed. On the basis of these observations, we propose that Aβ aggregates formed in the presence of lipid membranes have a latent ability to trigger the uptake of raft components accompanied by phase separation of lipids.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cholesterol; G(M1) Ganglioside; Humans; Lipid Bilayers; Liposomes; Membrane Microdomains; Models, Molecular; Peptide Fragments; Phase Transition; Protein Binding; Sphingomyelins

GM-1 ganglioside (GM-1) has been proposed as a new therapeutic agent against Alzheimer's disease (AD). Therefore, in this study we aimed to investigate the effects of GM1 on memory deficits and oxidative stress in the hippocampus of rat model of AD. Wistar rats were randomly divided into three groups (n = 15): control group, model group, and treatment group, which were injected with vehicle, Aβ1-40, and Aβ1-40 together with GM-1, respectively. Morris water maze test was performed to evaluate spatial learning and memory of the rats. Brain malondialdehyde (MDA) content was detected by biochemical assay, and 4-hydroxynonenal (4-HNE) level in the hippocampus was examined by immunohistochemistry. The results showed that learning and memory deficits were improved in treatment group compared to model group. Brain MDA content and 4-HNE level in hippocampus CA1 were much lower in treatment group than in model group. In summary, we demonstrate that GM-1 could improve spatial learning and memory deficits in rat model of AD, and this may be mediated by the inhibition of oxidative stress and lipid peroxidation in the neurons. These data suggest that GM-1 is a potential agent for AD treatment.

Topics: Aldehydes; Alzheimer Disease; Animals; Disease Models, Animal; G(M1) Ganglioside; Hippocampus; Malondialdehyde; Maze Learning; Memory Disorders; Oxidative Stress; Rats; Rats, Wistar

Increasing evidence suggests that the interaction of misfolded protein oligomers with cell membranes is a primary event resulting in the cytotoxicity associated with many protein-misfolding diseases, including neurodegenerative disorders. We describe here the results of a study on the relative contributions to toxicity of the physicochemical properties of protein oligomers and the cell membrane with which they interact. We altered the amount of cholesterol and the ganglioside GM1 in membranes of SH-SY5Y cells. We then exposed the cells to two types of oligomers of the prokaryotic protein HypF-N with different ultrastructural and cytotoxicity properties, and to oligomers formed by the amyloid-β peptide associated with Alzheimer's disease. We identified that the degree of toxicity of the oligomeric species is the result of a complex interplay between the structural and physicochemical features of both the oligomers and the cell membrane.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cell Line, Tumor; Cell Membrane; Chemical Phenomena; Cholesterol; G(M1) Ganglioside; Humans; Membrane Lipids

Alzheimer's disease (AD) is a neurodegenerative disorder where β-amyloid tends to aggregate and form plaques. Lipid raft-associated ganglioside GM1 has been suggested to facilitate β-amyloid aggregation; furthermore, GM1 and GM2 are increased in lipid rafts isolated from cerebral cortex of AD cases.. The distribution of GM1 and GM2 was studied by immunohistochemistry in the frontal and temporal cortex of AD cases. Frontotemporal dementia (FTD) was included as a contrast group.. The distribution of GM1 and GM2 changes during the process of AD (n = 5) and FTD (n = 3) compared to controls (n = 5). Altered location of the GM1-positive small circular structures seems to be associated with myelin degradation. In the grey matter, the staining of GM1-positive plasma membranes might reflect neuronal loss in the AD/FTD tissue. The GM1-positive compact bundles were only visible in cells located in the AD frontal grey matter, possibly reflecting raft formation of GM1 and thus a pathological connection. Furthermore, our results suggest GM2 to be enriched within vesicles of pyramidal neurons of the AD/FTD brain.. Our study supports the biochemical finding of ganglioside accumulation in cellular membranes of AD patients and shows a redistribution of these molecules.

Topics: Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Female; Frontal Lobe; Frontotemporal Dementia; G(M1) Ganglioside; G(M2) Ganglioside; Humans; Immunohistochemistry; Male; Membrane Microdomains; Middle Aged; Myelin Sheath; Neurons; Research Design; Temporal Lobe

The behavior of the amyloid β-peptide (Aβ) within a membrane environment is integral to its toxicity and the progression of Alzheimer's disease. Ganglioside GM1 has been shown to enhance the aggregation of Aβ, but the underlying mechanism is unknown. Using atomistic molecular dynamics simulations, we explored the interactions between the 40-residue alloform of Aβ (Aβ(40) ) and several model membranes, including pure palmitoyloleoylphosphatidylcholine (POPC) and palmitoyloleoylphosphatidylserine (POPS), an equimolar mixture of POPC and palmitoyloleoylphosphatidylethanolamine (POPE), and lipid rafts, both with and without GM1, to understand the behavior of Aβ(40) in various membrane microenvironments. Aβ(40) remained inserted in POPC, POPS, POPC/POPE, and raft membranes, but in several instances exited the raft containing GM1. Aβ(40) interacted with GM1 largely through hydrogen bonding, producing configurations containing β-strands with C-termini that, in some cases, exited the membrane and became exposed to solvent. These observations provide insight into the release of Aβ from the membrane, a previously uncharacterized process of the Aβ aggregation pathway.

Topics: Alzheimer Disease; Amyloid beta-Peptides; G(M1) Ganglioside; Hydrogen Bonding; Membranes, Artificial; Molecular Dynamics Simulation; Phosphatidylcholines; Phosphatidylethanolamines; Phosphatidylserines

The loss of synapses and neurons in Alzheimer's disease (AD) is thought to be at least partly induced by toxic species formed by the amyloid beta (Aβ) peptide; therefore, therapeutics aimed at reducing Aβ toxicity could be of clinical use for treatment of AD. Liposomes are suitable vehicles for therapeutic agents and imaging probes, and a promising way of targeting the various Aβ forms. We tested liposomes functionalized with phosphatidic acid, cardiolipin, or GM1 ganglioside, previously shown to have high Aβ-binding capacity. Mimicking Aβ-induced toxicity in mouse neuroblastoma cell lines, combined with administration of cell viability-modulating agents, we observed that functionalized liposomes rescued cell viability to different extents. We also detected rescue of the imbalance of GSK-3β and PP2A activity, and reduction in tau phosphorylation. Thus, these liposomes appear particularly suitable for implementing further therapeutic strategies for AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Carboxylic Ester Hydrolases; Cardiolipins; Cell Line, Tumor; Cell Survival; G(M1) Ganglioside; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Liposomes; Mice; Phosphatidic Acids; Phosphorylation; tau Proteins

The effect of various types of nanoliposomes (associated with curcumin, phosphatidic acid, cardiolipin, or GM1 ganglioside) on the aggregation of the amyloid-β(1-42) (Aβ(1-42)) peptide was investigated. Nanoliposomes incorporating curcumin (curcumin-liposomes) were prepared by adding curcumin in the lipid phase during liposome preparation, whereas curcumin surface-decorated liposomes were prepared by using a curcumin-lipid conjugate (lipid-S-curcumin liposomes) or by attaching a curcumin derivative on preformed liposomes by click chemistry (click-curcumin liposomes). The lipid ligands (phosphatidic acid, cardiolipin, or GM1) were also incorporated into nanoliposomes during their formation. All nanoliposomes with curcumin, or the curcumin derivative, were able to inhibit the formation of fibrillar and/or oligomeric Aβ in vitro. Of the three forms of curcumin liposomes tested, the click-curcumin type was by far the most effective. Liposomes with lipid ligands only inhibited Aβ fibril and oligomer formation at a very high ratio of liposome to peptide. Curcumin-based liposomes could be further developed as a novel treatment for Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cardiolipins; Curcumin; G(M1) Ganglioside; Humans; Ligands; Liposomes; Nanoparticles; Peptide Fragments; Phosphatidic Acids

Gangliosides are targets for a variety of pathologically relevant proteins, including amyloid beta (Abeta), an important component implicated in Alzheimer's disease (AD). To provide a structural basis for this pathogenic interaction associated with AD, we conducted NMR analyses of the Abeta interactions with gangliosides using lyso-GM1 micelles as a model system. Our NMR data revealed that the sugar-lipid interface is primarily perturbed upon binding of Abeta to the micelles, underscoring the importance of the inner part of the ganglioside cluster for accommodating Abeta in comparison with the outer carbohydrate branches that provide microbial toxin- and virus-binding sites.

Topics: Algorithms; Alzheimer Disease; Amyloid beta-Peptides; Carbohydrate Sequence; Circular Dichroism; G(M1) Ganglioside; Humans; Kinetics; Magnetic Resonance Spectroscopy; Micelles; Models, Molecular; Molecular Sequence Data; Molecular Structure; Peptide Fragments; Protein Binding; Protein Structure, Tertiary; Water

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.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cholesterol; Crystallography, X-Ray; Fatty Acids; G(M1) Ganglioside; G(M3) Ganglioside; Glycolipids; Glycosphingolipids; Humans; Lipid Bilayers; Models, Molecular; Molecular Conformation; Molecular Dynamics Simulation; Molecular Structure; Peptide Fragments; Protein Binding; Sodium Chloride; Surface Properties

Ganglioside GM1 mediates the amyloid beta (Abeta) aggregation that is the hallmark of Alzheimer's disease (AD). To investigate how ganglioside-containing lipid bilayers interact with Abeta, we examined the interaction between Abeta40 and supported planar lipid bilayers (SPBs) on mica and SiO(2) substrates by using atomic force microscopy, fluorescence microscopy, and molecular dynamics computer simulations. These SPBs contained several compositions of sphingomyelin, cholesterol, and GM1 and were treated at physiological salt concentrations. Surprisingly high-speed Abeta aggregation of fibril formations occurred at all GM1 concentrations examined on the mica surface, but on the SiO(2) surface, only globular agglomerates formed and they formed slowly. At a GM1 concentration of 20mol%, unique triangular regions formed on the mica surface and the rapidly formed Abeta aggregations were observed only outside these regions. We have found that some unique surface-induced phase separations are induced by the GM1 clustering effects and the strong interactions between the GM1 head group and the water layer adsorbed in the ditrigonal cavities on the mica surface. The speed of Abeta40 aggregation and the shape of the agglomerates depend on the molecular conformation of GM1, which varies depending on the substrate materials. We identified the conformation that significantly accelerates Abeta40 aggregation, and we think that the detailed knowledge about the GM1 molecular conformation obtained in this work will be useful to those investigating Abeta-GM1 interactions.

Topics: Aluminum Silicates; Alzheimer Disease; Amyloid beta-Peptides; Animals; Cattle; Cholesterol; Computer Simulation; G(M1) Ganglioside; Humans; Membrane Microdomains; Protein Multimerization; Silicon Dioxide; Sphingomyelins; Swine

AD (Alzheimer's disease) is a neurodegenerative disease and the most common form of dementia. One of the pathological hallmarks of AD is the aggregation of extracellular Aβs (amyloid β-peptides) in senile plaques in the brain. The process could be initiated by seeding provided by an interaction between G(M1) ganglioside and Aβs. Several reports have documented the bifunctional roles of Aβs in NSCs (neural stem cells), but the precise effects of G(M1) and Aβ on NSCs have not yet been clarified. We evaluated the effect of G(M1) and Aβ-(1-40) on mouse NECs (neuroepithelial cells), which are known to be rich in NSCs. No change of cell number was detected in NECs cultured in the presence of either G(M1) or Aβ-(1-40). On the contrary, a decreased number of NECs were cultured in the presence of a combination of G(M1) and Aβ-(1-40). The exogenously added G(M1) and Aβ-(1-40) were confirmed to incorporate into NECs. The Ras-MAPK (mitogen-activated protein kinase) pathway, important for cell proliferation, was intact in NECs simultaneously treated with G(M1) and Aβ-(1-40), but caspase 3 was activated. NECs treated with G(M1) and Aβ-(1-40) were positive in the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) assay, an indicator of cell death. It was found that G(M1) and Aβ-(1-40) interacted in the presence of cholesterol and sphingomyelin, components of cell surface microdomains. The cytotoxic effect was found also in NSCs prepared via neurospheres. These results indicate that Aβ-(1-40) and G(M1) co-operatively exert a cytotoxic effect on NSCs, likely via incorporation into NEC membranes, where they form a complex for the activation of cell death signalling.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Biomarkers; Cell Lineage; Cell Proliferation; Cells, Cultured; G(M1) Ganglioside; Humans; Mice; Neural Stem Cells; Peptide Fragments

The assembly of amyloid beta-protein into fibrils is an initial event of Alzheimer's disease (AD). Previous studies suggest that ganglioside-bound amyloid beta-protein (Abeta), GAbeta, is an endogenous seed for amyloid in Alzheimer's disease (AD) brain and that GAbeta is generated in the membrane microdomains, comprising cholesterol, sphingomyelin (SM) and GM1 ganglioside. In this study, we showed that the GAbeta-dependent amyloidogenesis was accelerated on the surface of PC12 cells that had been pretreated with a sphingomyelinase inhibitor. Conversely, the enhanced GAbeta-dependent amyloidogenesis under the endocytic dysfunction, which is one of the cell-pathological features of AD, was suppressed by pretreatment with a SM synthase inhibitor. These suggest that SM is one of the key molecules for GAbeta generation and further imply that the interaction of Abeta with membrane lipids is critical in amyloid fibrillization in the brain.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Cell Line; Cell Membrane; Chromatography, Thin Layer; G(M1) Ganglioside; Membrane Microdomains; PC12 Cells; Rats; RNA Interference; Sphingomyelins

Gradual changes in steady-state levels of beta amyloid peptides (Abeta) in brain are considered an initial step in the amyloid cascade hypothesis of Alzheimer's disease. Abeta is a product of the secretase cleavage of amyloid precursor protein (APP). There is evidence that the membrane lipid environment may modulate secretase activity and alters its function. Cleavage of APP strongly depends on membrane properties. Since Abeta perturbs cell membrane fluidity, the cell membrane may be the location where the neurotoxic cascade of Abeta is initiated. Therefore, we tested effects of oligomeric Abeta on membrane fluidity of whole living cells, the impact of exogenous and cellular Abeta on the processing of APP and the role of GM-1 ganglioside. We present evidence that oligoAbeta((1-40)) stimulates the amyloidogenic processing of APP by reducing membrane fluidity and complexing with GM-1 ganglioside. This dynamic action of Abeta may start a vicious circle, where endogenous Abeta stimulates its own production. Based on our novel findings, we propose that oligoAbeta((1-40)) accelerates the proteolytic cleavage of APP by decreasing membrane fluidity.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Biophysical Phenomena; Cell Line; Cell Membrane; Cholesterol; G(M1) Ganglioside; Humans; Membrane Fluidity; Membrane Lipids; Mice; Microscopy, Confocal; Peptide Fragments; Protein Processing, Post-Translational; Protein Structure, Quaternary

Gangliosides, GM3 and GM1, are suggested to accelerate the deposition of the amyloid beta-protein as amyloid angiopathy and senile plaques, respectively, in the Alzheimer brain. We investigated the profile of amyloid deposition in the brains of transgenic mice expressing a mutant amyloid precursor protein with a disrupted GM2 synthase gene, in which GM3 accumulates whereas GM1 is lacking. These mice showed a significantly increased level of deposited amyloid beta-protein in the vascular tissues. Furthermore, formation of severe dyshoric-form amyloid angiopathy, in which amyloid extended from the blood vessel walls deeply into the surrounding parenchyma was observed. Our results indicate that the expression of gangliosides is a critical determinant for the amyloid pathology in the Alzheimer brain.

Topics: Aging; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Blood Vessels; Blotting, Western; Brain; Cerebral Amyloid Angiopathy; G(M1) Ganglioside; G(M3) Ganglioside; Humans; Immunohistochemistry; Mice; Mice, Transgenic; Mutation; N-Acetylgalactosaminyltransferases; Protease Nexins; Receptors, Cell Surface

The deposition of amyloid beta-protein (Abeta) is an invariable feature of Alzheimer's disease (AD); however, the biological mechanism underlying Abeta assembly into fibrils in the brain remains unclear. Here, we show that a high-density cluster of GM1 ganglioside (GM1), which was detected by the specific binding of a novel peptide (p3), appeared selectively on synaptosomes prepared from aged mouse brains. Notably, the synaptosomes bearing the high-density GM1 cluster showed extraordinary potency to induce Abeta assembly, which was suppressed by an antibody specific to GM1-bound Abeta, an endogenous seed for AD amyloid. Together with evidence that Abeta deposition starts at presynaptic terminals in the AD brain and that GM1 levels significantly increase in amyloid-positive synaptosomes prepared from the AD brain, our results suggest that the age-dependent high-density GM1 clustering at presynaptic neuritic terminals is a critical step for Abeta deposition in AD.

Topics: Aging; Alzheimer Disease; Amyloid beta-Peptides; Animals; Fluorescent Dyes; G(M1) Ganglioside; Mice; Models, Neurological; Neurites; PC12 Cells; Presynaptic Terminals; Rats; Synaptosomes

Although soluble oligomeric and protofibrillar assemblies of Abeta-amyloid peptide cause synaptotoxicity and potentially contribute to Alzheimer's disease (AD), the role of mature Abeta-fibrils in the amyloid plaques remains controversial. A widely held view in the field suggests that the fibrillization reaction proceeds 'forward' in a near-irreversible manner from the monomeric Abeta peptide through toxic protofibrillar intermediates, which subsequently mature into biologically inert amyloid fibrils that are found in plaques. Here, we show that natural lipids destabilize and rapidly resolubilize mature Abeta amyloid fibers. Interestingly, the equilibrium is not reversed toward monomeric Abeta but rather toward soluble amyloid protofibrils. We characterized these 'backward' Abeta protofibrils generated from mature Abeta fibers and compared them with previously identified 'forward' Abeta protofibrils obtained from the aggregation of fresh Abeta monomers. We find that backward protofibrils are biochemically and biophysically very similar to forward protofibrils: they consist of a wide range of molecular masses, are toxic to primary neurons and cause memory impairment and tau phosphorylation in mouse. In addition, they diffuse rapidly through the brain into areas relevant to AD. Our findings imply that amyloid plaques are potentially major sources of soluble toxic Abeta-aggregates that could readily be activated by exposure to biological lipids.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; Cells, Cultured; G(M1) Ganglioside; Injections, Intraventricular; Learning; Lipids; Mice; Neurotoxins; Peptide Fragments; Sphingolipids

The mechanism underlying plaque-independent neuronal death in Alzheimer disease (AD), which is probably responsible for early cognitive decline in AD patients, remains unclarified. Here, we show that a toxic soluble Abeta assembly (TAbeta) is formed in the presence of liposomes containing GM1 ganglioside more rapidly and to a greater extent from a hereditary variant-type ("Arctic") Abeta than from wild-type Abeta. TAbeta is also formed from soluble Abeta through incubation with natural neuronal membranes prepared from aged mouse brains in a GM1 ganglioside-dependent manner. An oligomer-specific antibody (anti-Oligo) significantly suppresses TAbeta toxicity. Biophysical and structural analyses by atomic force microscopy and size exclusion chromatography revealed that TAbeta is spherical with diameters of 10-20 nm and molecular masses of 200-300 kDa. TAbeta induces neuronal death, which is abrogated by the small interfering RNA-mediated knockdown of nerve growth factor receptors, including TrkA and p75 neurotrophin receptor. Our results suggest that soluble Abeta assemblies, such as TAbeta, can cause plaque-independent neuronal death that favorably occurs in nerve growth factor-dependent neurons in the cholinergic basal forebrain in AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Cell Death; Cells, Cultured; G(M1) Ganglioside; Humans; Liposomes; Mutation; Nerve Degeneration; Neurons; Rats; Rats, Sprague-Dawley; Receptor, Nerve Growth Factor; Receptor, trkA; RNA Interference

A pathological hallmark of Alzheimer's disease (AD) is the deposition of amyloid beta-protein (Abeta) in fibrillar form on neuronal cells. However, the role of Abeta fibrils in neuronal dysfunction is highly controversial. This study demonstrates that monosialoganglioside GM1 (GM1) released from damaged neurons catalyzes the formation of Abeta fibrils, the toxicity and the cell affinity of which are much stronger than those of Abeta fibrils formed in phosphate-buffered saline. Abeta-(1-40) was incubated with equimolar GM1 at 37 degrees C. After a lag period of 6-12 h, amyloid fibrils were formed, as confirmed by circular dichroism, thioflavin-T fluorescence, size-exclusion chromatography, and transmission electron microscopy. The fibrils showed significant cytotoxicity against PC12 cells differentiated with nerve growth factor. Trisialoganglioside GT1b also facilitated the fibrillization, although the effect was weaker than that of GM1. Our study suggests an exacerbation mechanism of AD and an importance of polymorphisms in Abeta fibrils during the pathogenesis of the disease.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Benzothiazoles; Cell Membrane; Chromatography, Gel; Circular Dichroism; G(M1) Ganglioside; Microscopy, Electron, Transmission; Neurons; PC12 Cells; Peptide Fragments; Protein Structure, Secondary; Rats; Thiazoles

We performed an immunohistochemical analysis of the GM1 ganglioside-bound amyloid beta-protein (GAbeta), an endogenous seed of Alzheimer amyloids, in sections of cerebral cortices of cynomolgus monkeys of different ages from 4 to 36 years old. Here, we show that neuronal GAbeta immunostaining significantly increases in the sections obtained from animals at ages below 19 years, even without senile plaque formation, and that GAbeta accumulation exclusively occurs in organelles involved in the endocytic pathway, including early, late, and recycling endosomes, not in those involved in the secretory pathway. Together with previous findings that Abeta generation likely occurs in early endosomes and that GM1 accumulation in early endosomes is induced by endocytic pathway abnormalities, our results provide further evidence that endosomes are intimately involved in the Abeta-associated pathology of Alzheimer's disease.

Topics: Aging; Alzheimer Disease; Amyloid beta-Peptides; Animals; Cerebral Cortex; Endocytosis; Endosomes; G(M1) Ganglioside; Immunohistochemistry; Macaca fascicularis; Neurons; Plaque, Amyloid; Protein Binding; Protein Transport; Signal Transduction

Endocytic pathway abnormalities were previously observed in brains affected with Alzheimer's disease (AD). To clarify the pathological relevance of these abnormalities to assembly of amyloid beta-protein (Abeta), we treated PC12 cells with chloroquine, which potently perturbs membrane trafficking from endosomes to lysosomes. Chloroquine treatment induced accumulation of GM1 ganglioside (GM1) in Rab5-positive enlarged early endosomes and on the cell surface. Notably, an increase in GM1 level on the cell surface was sufficient to induce Abeta assembly. Our results suggest that endocytic pathway abnormalities in AD brain induce GM1 accumulation on the cell surface, leading to amyloid fibril formation in brain.

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Animals; Chloroquine; Endocytosis; Endosomes; G(M1) Ganglioside; PC12 Cells; Protein Binding; rab5 GTP-Binding Proteins; Rats; Time Factors

Amyloid peptide (Abeta) is the major protein constituent of neuritic plaques in Alzheimer's disease (AD). This peptide is an amphipathic molecule that perturbs membranes and binds to raft-like membranes composed of gangliosides. Ganglioside GM1 binds tightly with Abeta and it is speculated that GM1 inhibits Abeta from undergoing alpha-helix to beta-sheet conformational changes. Although the role of gangliosides in conformational changes of Abeta have been studied, the specific nature of these interactions have not been reported. In the present report multidimensional NMR studies of ganglioside-Abeta interactions were conducted in sodium dodecyl sulphate (SDS) micelles, a membrane-mimicking environment. These studies reveal that asialoGM1 binds specifically with Abeta in a manner which could prevent beta-sheet formation. but that ganglioside GT1b does not bind Abeta. Plausible pathways for the involvement of gangliosides in amyloidogenesis are discussed.

Topics: Alzheimer Disease; Amyloid beta-Peptides; G(M1) Ganglioside; Gangliosides; Humans; Magnetic Resonance Spectroscopy; Micelles; Peptide Fragments; Sodium Dodecyl Sulfate

A fundamental question about the early pathogenesis of Alzheimer's disease (AD) concerns how toxic aggregates of amyloid beta protein (Abeta) are formed from its nontoxic soluble form. We hypothesized previously that GM1 ganglioside-bound Abeta (GAbeta) is involved in the process. We now examined this possibility using a novel monoclonal antibody raised against GAbeta purified from an AD brain. Here, we report that GAbeta has a conformation distinct from that of soluble Abeta and initiates Abeta aggregation by acting as a seed. Furthermore, GAbeta generation in the brain was validated by both immunohistochemical and immunoprecipitation studies. These results imply a mechanism underlying the onset of AD and suggest that an endogenous seed can be a target of therapeutic strategy.

Topics: Adult; Age Factors; Aged; Aged, 80 and over; Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Animals; Antibody Specificity; Benzothiazoles; Brain; Brain Chemistry; Cell Survival; Cells, Cultured; G(M1) Ganglioside; Humans; Liposomes; Macaca fascicularis; Macromolecular Substances; Microscopy, Immunoelectron; Middle Aged; Neurons; Peptide Fragments; Rats; Rats, Sprague-Dawley; Thiazoles; Time Factors

The deposition of amyloid beta-protein in the brain is a fundamental process in the development of Alzheimerís disease; however, the mechanism underlying aggregation of amyloid beta-protein remains to be determined. Here, we report that a membrane-mimicking environment, generated in the presence of detergents or a ganglioside, is sufficient per se for amyloid fibril formation from soluble amyloid beta-protein. Furthermore, hereditary variants of amyloid beta-protein, which are caused by amyloid precursor protein gene mutations, including the Dutch (E693Q), Flemish (A692G) and Arctic (E693G) types, show mutually different aggregation behavior in these environments. Notably, the Arctic-type amyloid beta-protein, in contrast to the wild-type and other variant forms, shows a markedly rapid and higher level of amyloid fibril formation in the presence of sodium dodecyl sulfate or GM1 ganglioside. These results suggest that there are favorable local environments for fibrillogenesis of amyloid beta-protein.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Circular Dichroism; Detergents; G(M1) Ganglioside; Humans; Kinetics; Macromolecular Substances; Membranes, Artificial; Microscopy, Electron; Mutation; Peptide Fragments; Protein Binding; Protein Structure, Secondary

The conversion of soluble, nontoxic amyloid beta-protein (Abeta) to aggregated, toxic Abeta rich in beta-sheet structures is considered to be the key step in the development of Alzheimer's disease. Therefore, extensive studies have been carried out on the mechanisms involved in Abeta aggregation and the characterization of Abeta aggregates formed in aqueous solutions mimicking biological fluids. On the other hand, several investigators pointed out that membranes play an important role in Abeta aggregation. However, it remains unclear whether Abeta aggregates formed in solution and membranes are identical and whether the former can bind to membranes. In this study, using a dye-labeled Abeta-(1-40) as well as native Abeta-(1-40), the properties of Abeta aggregates formed in buffer and raft-like membranes composed of monosialoganglioside GM1/cholesterol/sphingomyelin were compared. Fourier transform infrared spectroscopic measurements suggested that Abeta aggregates formed in buffer and in membranes have different beta-sheet structures. Fluorescence experiments revealed that Abeta aggregated in buffer did not show any affinity for membranes.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cholesterol; Dimerization; G(M1) Ganglioside; Humans; Liposomes; Models, Biological; Peptide Fragments; Protein Binding; Protein Structure, Secondary; Spectroscopy, Fourier Transform Infrared; Sphingomyelins

Plaques containing beta-amyloid (Abeta) peptides are one of the pathological features of Alzheimer's disease, and the reduction of Abeta is considered a primary therapeutic target. Amyloid clearance by anti-Abeta antibodies has been reported after immunization, and recent data have shown that the antibodies may act as a peripheral sink for Abeta, thus altering the periphery/brain dynamics. Here we show that peripheral treatment with an agent that has high affinity for Abeta (gelsolin or GM1) but that is unrelated to an antibody or immune modulator reduced the level of Abeta in the brain, most likely because of a peripherally acting effect. We propose that in general, compounds that sequester plasma Abeta could reduce or prevent brain amyloidosis, which would enable the development of new therapeutic agents that are not limited by the need to penetrate the brain or evoke an immune response.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Animals; Brain; Female; G(M1) Ganglioside; Gelsolin; Injections, Intraperitoneal; Male; Membrane Proteins; Mice; Mutation; Presenilin-1

The conversion of soluble, nontoxic amyloid beta-protein (A beta) to aggregated, toxic A beta rich in beta-sheet structures is considered to be the key step in the development of Alzheimer's disease. We have proposed that the aggregation proceeds in the lipid raft containing a ganglioside cluster, the formation of which is facilitated by cholesterol and for which A beta shows a specific affinity. In this study, using fluorescence resonance energy transfer, we found that after A beta binds to raft-like membranes composed of monosialoganglioside GM1/cholesterol/sphingomyelin (1/1/1), the protein can translocate to the phosphatidylcholine membranes to which soluble A beta does not bind. Furthermore, self-quenching experiments using fluorescein-labeled A beta revealed that the translocation process competes with the oligomerization of the protein in the raft-like membranes. These results suggest that the lipid raft containing a ganglioside cluster serves as a conformational catalyst or a chaperon generating a membrane-active form of A beta with seeding ability.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cholesterol; G(M1) Ganglioside; Humans; Kinetics; Membrane Microdomains; Membranes, Artificial; Models, Biological; Models, Molecular; Phosphatidylcholines; Protein Structure, Secondary; Protein Transport; Spectrometry, Fluorescence; Sphingomyelins

GM1 ganglioside-bound amyloid beta-protein (GM1-Abeta), found in brains exhibiting early pathological changes of Alzheimer's disease (AD) plaques, has been suggested to accelerate amyloid fibril formation by acting as a seed. We have previously found using dye-labeled Abeta that Abeta recognizes a GM1 cluster, the formation of which is facilitated by cholesterol [Kakio, A., Nishimoto, S., Yanagisawa, K., Kozutsumi, Y., and Matsuzaki, K. (2001) J. Biol. Chem. 276, 24985-24990]. In this study, we investigated the ganglioside species-specificity in its potency to induce a conformational change of Abeta, by which ganglioside-bound Abeta acts as a seed for Abeta fibrillogenesis, using a major ganglioside occurring in brains (GM1, GD1a, GD1b, and GT1b) in raft-like membranes composed of cholesterol and sphingomyelin. Abeta recognized ganglioside clusters, the density of which increased with the number of sialic acid residues. Interestingly, however, mixing of gangliosides inhibited cluster formation. In contrast, the affinities of the protein for the clusters were similar irrespective of lipid composition and of the order of 10(6) M(-)(1) at 37 degrees C. Abeta underwent a conformational transition from an alpha-helix-rich structure to a beta-sheet-rich structure with the increase in protein density on the membrane. Ganglioside-bound Abeta proteins exhibited seeding abilities for amyloid formation. GM1-Abeta exhibited the strongest seeding potential, especially under beta-sheet-forming conditions. This study suggested that lipid composition including gangliosides and cholesterol strictly controls amyloid formation.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Binding Sites; Boron Compounds; Cattle; Coumarins; Fluorescent Dyes; G(M1) Ganglioside; Humans; Liposomes; Membrane Microdomains; Peptide Fragments; Protein Structure, Secondary

GM1 ganglioside-bound amyloid beta-protein (GM1/Abeta), found in brains exhibiting early pathological changes of Alzheimer's disease (AD) including diffuse plaques, has been suggested to be involved in the initiation of amyloid fibril formation in vivo by acting as a seed. To elucidate the molecular mechanism underlying GM1/Abeta formation, the effects of lipid composition on the binding of Abeta to GM1-containing lipid bilayers were examined in detail using fluorescent dye-labeled human Abeta-(1-40). Increases in not only GM1 but also cholesterol contents in the lipid bilayers facilitated the binding of Abeta to the membranes by altering the binding capacity but not the binding affinity. An increase in membrane-bound Abeta concentration triggered its conformational transition from helix-rich to beta-sheet-rich structures. Excimer formation of fluorescent dye-labeled GM1 suggested that Abeta recognizes a GM1 "cluster" in membranes, the formation of which is facilitated by cholesterol. The results of the present study strongly suggested that increases in intramembrane cholesterol content, which are likely to occur during aging, appear to be a risk factor for amyloid fibril formation.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Binding Sites; Binding, Competitive; Boron Compounds; Cell Line; Cholesterol; Coumarins; Fluorescent Dyes; G(M1) Ganglioside; Humans; Lipid Bilayers; Protein Binding; Protein Conformation; Spectrometry, Fluorescence

The proteolytic processing of amyloid precursor protein (APP) has been linked to sphingolipid-cholesterol microdomains (rafts). However, the raft proteases that may be involved in APP cleavage have not yet been identified. In this work we present evidence that the protease plasmin is restricted to rafts of cultured hippocampal neurons. We also show that plasmin increases the processing of human APP preferentially at the alpha-cleavage site, and efficiently degrades secreted amyloidogenic and non-amyloidogenic APP fragments. These results suggest that brain plasmin plays a preventive role in APP amyloidogenesis. Consistently, we show that brain tissue from Alzheimer's disease patients contains reduced levels of plasmin, implying that plasmin downregulation may cause amyloid plaque deposition accompanying sporadic Alzheimer's disease.

Topics: Adult; Age Factors; Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Blotting, Western; Brain; Caveolin 1; Caveolins; Cell Line; Cells, Cultured; Fibrinolysin; G(M1) Ganglioside; Hippocampus; Humans; Membrane Microdomains; Microscopy, Fluorescence; Middle Aged; Neurons; Plasminogen; Rats; Time Factors; Tissue Plasminogen Activator; Transfection

To study the effect of GM1 ganglioside interfering the metabolism of amyloid beta-protein precursor (APP) on cells for exploring the relationship between GM1 and development of Alzheimer senile plaques and the other amyloidoses.. GM1 influencing the metabolism of APP and the release of its metabolite secretory APP on human APP695 cDNA transfected cells were detected by metabolic radiolabeling. The affinity of GM1 and recombinant secretory APP was analyzed by Western blot and dot blot.. GM1 specifically bound APP, and interfered the proteolysis of APP and inhibited the release of secretory APP on cells.. The abnormal metabolism of GM1 may contribute to the aggregation and deposition of amyloid beta-protein in Alzheimer brains.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; G(M1) Ganglioside; Humans

We previously identified a novel amyloid beta-protein (A beta), that binds to GM1 ganglioside, in brains exhibiting the early pathological changes of AD. In this study, we raised monoclonal antibodies, using membrane fractions containing abundant GM1 ganglioside-bound A beta as antigens. Monoclonal antibody 4396, produced in this study, immunoprecipitates A beta42 in the membrane fractions of brains with diffuse plaques, but does not react with soluble A beta42 or GM1 ganglioside. Furthermore, this antibody recognizes the A beta bound to lipid vesicles containing GM1 ganglioside, and unexpectedly, phosphatidylinositol. In contrast, a control anti-A beta monoclonal antibody does not recognize the A beta bound to these lipid vesicles. These results indicate that A beta associated with lipids has an immunoreactivity distinct from that of soluble A.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Antibodies, Monoclonal; Antibody Specificity; Cell Membrane; Cerebral Cortex; Female; G(M1) Ganglioside; Humans; Lipid Metabolism; Mice; Mice, Inbred BALB C; Solubility

Serum antibodies against a series of antigens, including an organ-specific central nervous system (CNS) antigen and the neurotransmitter serotonin, were investigated in 22 patients with Alzheimer's Disease (n=15) and other age-related dementias (n=7) by indirect immunofluorescence assay and enzyme-linked immunosorbent assay. Patients with dementia showed an increase of antibody-positive sera against nuclear antigen, gastric parietal cells, CNS antigen, gangliosides (Gm1), laminin, and keratin. Alzheimer's Disease patients alone exhibited antibodies against CNS antigen. However, the results do not show sufficient specificity and sensitivity for use as a diagnostic indicator.

Topics: Aged; Alzheimer Disease; Autoantibodies; Dementia, Multi-Infarct; Enzyme-Linked Immunosorbent Assay; Female; Fluorescent Antibody Technique, Direct; G(M1) Ganglioside; History, Ancient; Humans; Keratins; Laminin; Male; Serotonin

The earliest event so far known that occurs in the brain affected with Alzheimer's disease (AD) is the deposition and fibril formation of amyloid beta-protein (A beta). A beta is cleaved from a glycosylated membrane protein, called beta-amyloid protein precursor, and normally secreted into the extracellular space. Here we report on the presence of membrane-bound A beta that tightly binds GM1 ganglioside. This suggests that this novel A beta species, rather than secreted A beta, may act as a 'seed' for amyloid and further that intracellular abnormalities in the membrane recycling already exist at the stage of amyloidogenesis.

Topics: Adult; Aging; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Cerebral Cortex; Down Syndrome; G(M1) Ganglioside; Humans; Membrane Glycoproteins; Middle Aged; Neurofibrillary Tangles; Peptide Fragments

Topics: Alzheimer Disease; Bone Regeneration; Brain Tissue Transplantation; Coronary Circulation; G(M1) Ganglioside; Humans; Hyaluronic Acid; Models, Cardiovascular; Parkinson Disease; Publishing; Research; Sweden

During a study evaluating GM1 ganglioside as a possible treatment for Alzheimer's disease, two patients suffered immune responses that appeared to be limited to localized inflammation at the sites of the intramuscular GM1 injections. We determined that one patient's anti-GM1 IgM antibody titer rose from 1:400 to 1:3200 and her anti-GM1 IgG titer from < 1:50 to 1:400,000 during the immune response. The second patient's titer rose from < 1:50 to 1:3200 IgM and from 1:3200 to 1:400,000 IgG. These findings document that patients may experience acute rises in their anti-GM1 antibody levels in response to GM1 and that such rises may not necessarily cause significant acute clinical neuronal injury.

Topics: Aged; Alzheimer Disease; Antibodies; Female; G(M1) Ganglioside; Humans; Immunoglobulin M; Motor Neuron Disease; Peripheral Nervous System Diseases

Topics: Alzheimer Disease; Autoantibodies; G(M1) Ganglioside; Humans; Immunoglobulin G

The four major brain gangliosides, GM1, GD1a, GD1b, and GT1b, were determined in cerebrospinal fluid (CSF) of 43 patients with "probable Alzheimer's disease (AD)" and 40 healthy controls without psychiatric or neurological disorders. The total concentration of the four gangliosides did not differ significantly between "probable AD" group (116 +/- 58 nmol/L) and controls (92 +/- 31 nmol/L), but the proportion between the gangliosides was changed. In the "probable AD" group compared with the age-matched control group, there was an increase in both the GM1 (22.6 +/- 9.3% vs 12.6 +/- 4.1%; p < 0.0001) and GD1a (32.1 +/- 9.8% vs 23.3 +/- 5.7%; p < 0.0005) proportion, and a decrease in the GD1b (20.0 +/- 6.6% vs 23.8 +/- 6.0%; p < 0.05) and GT1b (25.3 +/- 7.9 vs 40.3 +/- 9.3%; p < 0.0001) proportion. The proportion of GM1 showed a positive correlation with age in the control group (r = 0.45; p < 0.01), but a negative correlation with age in the "probable AD" group (r = -0.37; p < 0.05). Thus, although the increase in proportion GM1 in the "probable AD" group was preferentially found in younger "probable AD" patients, it was not caused by age differences. While the pathogenetic mechanism for these changes in CSF-gangliosides in "probable AD" remains to be established, it may reflect the degeneration of nerve cells and synapses.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Aging; Alzheimer Disease; Female; G(M1) Ganglioside; Gangliosides; Humans; Male; Middle Aged; Reference Values

To investigate structural changes in cell membranes of the Alzheimer-type dementia (ATD) brain, we immunostained for GM1 ganglioside which is a major component of the cell membrane. Our results have shown that astrocytic membranes and senile plaques (SPs) have the same immunoreactivity against the monoclonal anti-ganglioside GM1 antibody. Moreover, the astrocytic processes within the SPs were altered and their abnormal membranes seemed to contribute to the formation of SPs.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Antibodies, Monoclonal; Antibody Specificity; Astrocytes; Brain; Cell Membrane; G(M1) Ganglioside; Humans; Immunohistochemistry; Middle Aged; Staining and Labeling

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Brain; Cerebral Cortex; Cerebrosides; G(M1) Ganglioside; Gangliosides; Humans; Nerve Growth Factors

The pharmacokinetic parameters of GM1 ganglioside were examined in 16 patients (mean age 64 +/- 5 years) with Alzheimer's disease. The ganglioside was given intramuscularly and subcutaneously. The maximum GM1 blood level was reached after 48-72 h, the subcutaneous route leading to the highest blood levels, but the individual variability was relatively large. When 100 mg GM1 ganglioside was given daily for a week, maximum serum values of 15 to 20 mumol/l were found in 3 patients. The elimination half-life from serum was 60-75 h.

Topics: Aged; Alzheimer Disease; G(M1) Ganglioside; Humans; Injections, Intramuscular; Injections, Subcutaneous; Middle Aged

Topics: Alzheimer Disease; Animals; Antibodies; Brain; G(M1) Ganglioside; Glycosphingolipids; Humans; Lymphocyte Activation; Lymphocytes; T-Lymphocytes

Gangliosides are thought to have a role in neuronal development and regeneration while anti-ganglioside antibodies have been shown to impair these processes. In the present work we examined whether the neuronal degeneration in Alzheimer's disease is associated with the presence of anti-ganglioside antibodies. A significant level of antibodies specific to ganglioside GM1 but not to other gangliosides (GD1a, GD1b, GT1b and GQ1b) was found in patients with Alzheimer's disease as compared to normal age matched controls. A high level of antibodies to GM1 was also found in patients with multi-infarct dementia and Parkinson's disease with dementia but not in non-demented patients with other neurodegenerative diseases. These results may reflect a specific change in ganglioside metabolism which is associated with the neurodegenerative processes underlying Alzheimer's disease and other causes of dementia.

Topics: Adult; Aged; Aged, 80 and over; Alzheimer Disease; Autoantibodies; Female; G(M1) Ganglioside; Humans; Male; Middle Aged; Nervous System Diseases

In rats with extensive unilateral cortical damage, retrograde effects upon the cholinergic cells of the basal nucleus were observed. Cells of the basal nucleus stained immunocytochemically for choline acetyltransferase were shrunken and choline acetyltransferase enzymatic activity in that region was reduced. Both these effects could be prevented by the administration of the ganglioside GM1.

Topics: Alzheimer Disease; Animals; Basal Ganglia; Brain Diseases; Cerebral Cortex; Choline O-Acetyltransferase; G(M1) Ganglioside; Male; Rats; Rats, Inbred Strains; Substantia Innominata