Inhibitors for human glutaminyl cyclase by structure based design and bioisosteric replacement.

PubMed

Buchholz, Mirko; Hamann, Antje; Aust, Susanne; Brandt, Wolfgang; Böhme, Livia; Hoffmann, Torsten; Schilling, Stephan; Demuth, Hans-Ulrich; Heiser, Ulrich

2009-11-26

The inhibition of human glutaminyl cyclase (hQC) has come into focus as a new potential approach for the treatment of Alzheimer's disease. The hallmark of this principle is the prevention of the formation of Abeta(3,11(pE)-40,42), as these Abeta-species were shown to be of elevated neurotoxicity and likely to act as a seeding core leading to an accelerated formation of Abeta-oligomers and fibrils. Starting from 1-(3-(1H-imidazol-1-yl)propyl)-3-(3,4-dimethoxyphenyl)thiourea, bioisosteric replacements led to the development of new classes of inhibitors. The optimization of the metal-binding group was achieved by homology modeling and afforded a first insight into the probable binding mode of the inhibitors in the hQC active site. The efficacy assessment of the hQC inhibitors was performed in cell culture, directly monitoring the inhibition of Abeta(3,11(pE)-40,42) formation.

Developing novel immunogens for a safe and effective Alzheimer's disease vaccine.

PubMed

Lemere, Cynthia A

2009-01-01

Alzheimer's disease (AD) is the most prevalent form of neurodegeneration; however, therapies to prevent or treat AD are inadequate. Amyloid-beta (Abeta) protein accrues in cortical senile plaques, one of the key neuropathological hallmarks of AD, and is elevated in brains of early onset AD patients in a small number of families that bear certain genetic mutations, further implicating its role in this devastating neurological disease. In addition, soluble Abeta oligomers have been shown to be detrimental to neuronal function. Therapeutic strategies aimed at lowering cerebral Abeta levels are currently under development. One strategy is to immunize AD patients with Abeta peptides so that they will generate antibodies that bind to Abeta protein and enhance its clearance. As of 1999, Abeta immunotherapy, either through active immunization with Abeta peptides or through passive transfer of Abeta-specific antibodies, has been shown to reduce cerebral Abeta levels and improve cognitive deficits in AD mouse models and lower plaque load in nonhuman primates. However, a Phase II clinical trial of active immunization using full-length human Abeta1-42 peptide and a strong Th1-biased adjuvant, QS-21, ended prematurely in 2002 because of the onset of meningoencephalitis in approximately 6% of the AD patients enrolled in the study. It is possible that T cell recognition of the human full-length Abeta peptide as a self-protein may have induced an adverse autoimmune response in these patients. Although only approximately 20% of immunized patients generated anti-Abeta titers, responders showed some general slowing of cognitive decline. Focal cortical regions devoid of Abeta plaques were observed in brain tissues of several immunized patients who have since come to autopsy. In order to avoid a deleterious immune response, passive Abeta immunotherapy is under investigation by administering monthly intravenous injections of humanized Abeta monoclonal antibodies to AD patients. However, a safe and effective active Abeta vaccine would be more cost-effective and more readily available to a larger AD population. We have developed several novel short Abeta immunogens that target the Abeta N-terminus containing a strong B cell epitope while avoiding the Abeta mid-region and C-terminus containing T cell epitopes. These immunogens include dendrimeric Abeta1-15 (16 copies of Abeta1-15 on a lysine antigen tree), 2xAbeta1-15 (a tandem repeat of two lysine-linked Abeta1-15 peptides), and 2xAbeta1-15 with the addition of a three amino acid RGD motif (R-2xAbeta1-15). Intranasal immunization with our short Abeta fragment immunogens and a mucosal adjuvant, mutant Escherichia coli heat-labile enterotoxin LT(R192G), resulted in reduced cerebral Abeta levels, plaque deposition, and gliosis, as well as increased plasma Abeta levels and improved cognition in a transgenic mouse model of AD. Preclinical trials in nonhuman primates, and human clinical trials using similar Abeta immunogens, are now underway. Abeta immunotherapy looks promising but must be made safer and more effective at generating antibody titers in the elderly. It is hoped that these novel immunogens will enhance Abeta antibody generation across a broad population and avoid the adverse events seen in the earlier clinical trial.

Template-directed deposition of amyloid

NASA Astrophysics Data System (ADS)

Ha, Chanki

The formation of amyloid plaques in tissue is a pathological feature of many neurodegenerative diseases. Amyloid deposition, the process of amyloid plaque growth by the association of individual soluble amyloid molecules with a pre-existing amyloid template (i.e. plaque), is known to be critical for amyloid formation in vivo. In order to characterize amyloid deposition, we developed novel, synthetic amyloid templates like amyloid plaques in the human Alzheimer's brain by attaching amyloid seeds covalently onto an N-hydroxysuccinimide-activated surface. Amyloid plaques with a characteristic beta-sheet structure formed through a conformational rearrangement of soluble insulin or Abeta monomers upon interaction with the template. The amyloid deposition rate followed saturation kinetics with respect to insulin concentration in the solution. According to visualization of temporal evolution of Abeta plaque deposition on a template, it was found that mature amyloid plaques serve as a sink of soluble Abeta in a solution as well as a reservoir of small aggregates such as oligomers and protofibrils. Quantitative analysis of seeding efficiencies of three different Abeta species revealed that oligomeric forms of Abeta act more efficiently as seeds than monomers or fibrils do. Furthermore, studies on the interaction between Abeta40 and 42 showed an important role of Abeta42 in amyloid deposition. A slightly acidic condition was found to be unfavorable for amyloid plaque formation. Effects of metal ions on amyloid deposition indicated that Fe3+, but not Cu3 and Zn2+, is important for the deposition of amyloid plaques. The binding of Fe3+ to Abeta42 peptide was confirmed by using SIMS analysis. Zn2+ induced nonfibrillar amorphous aggregates, but the release of Zn2+ from Abeta42 deposits by Fe3+ triggered the formation of amyloid fibers. Effects or metal ion chelators such as ethylenediamine tetraacetic acid, deferoxamine, and clioquinol on amyloid deposition were tested to determine if they can be effective in preventing the deposition of amyloid plaques. The results may give insights into understanding the effects of environmental factors on amyloid plaque deposition and important information for therapeutic development for Alzheimer's disease.

Dual Targeting of Amyloid-beta Clearance and Neuroinflammation as a Novel Therapeutic Approach against Alzheimer's Disease

NASA Astrophysics Data System (ADS)

Batarseh, Yazan S.

Amyloid-beta (Abeta) cascade hypothesis suggests that Alzheimer's disease (AD) is related to an imbalance between the production and clearance of Abeta peptide. Sporadic AD has been related to faulty clearance of Abeta. Accumulation of Abeta oligomers (Abetao) has been linked to several downstream toxic effects including neuroinflammation, synaptic loss, and cellular death. Abeta transport across the blood-brain barrier (BBB) is one of the primary pathways for reducing Abeta load in the brain, which work hand in hand with other parenchymal mechanisms to reduce Abeta levels including intra and extracellular degradation by a family of Abeta degrading enzymes. Established AD drugs, such as the cholinesterase inhibitor donepezil, have been reported to have several additional non-cholinergic effects that alter Abeta pathology; reduce Abeta load, anti-inflammatory response, and attenuate synaptic loss. However, their limited effect only lead to minor improvements in AD symptoms without improving the prognosis of the disease. The lack of effective medical treatment for AD led to several studies focusing on establishing new therapeutic approaches to reduce Abeta pathology. We aimed to identify and characterize natural products that are capable of enhancing the BBB clearance of Abeta in addition to reducing neuroinflammation. Our first project was to investigate the role of oleocanthal (one of the active ingredients in extra-virgin olive oil; EVOO) on attenuating Abeta toxic effects on neurons and astrocytes. We developed Abeta oligomers (Abetao) induced inflammatory environment by exposing neurons and astrocytes to accumulative doses of Abetao to investigate oleocanthal effect on modulating Abetao pathological changes in neurons and astrocytes. Our findings demonstrated oleocanthal prevented Abetao-induced synaptic proteins, SNAP-25 and PSD-95, down-regulation in neurons, attenuated Abetao-induced inflammation, and restored glutamine transporter (GLT1) and glucose transporter (GLUT1) expressions in astrocytes. Results from this study support the protective effect of the EVOO-derived phenolic secoiridoid oleocanthal against AD pathology. Next, we evaluated the role of EVOO in enhancing donepezil's effect on increasing Abeta clearance and reducing neuroinflammation in AD transgenic model, namely 5XFAD mice. The long-term consumption of EVOO in combination with donepezil is expected to enhance and expand donepezil protective mechanisms against Abeta pathology. EVOO consumption in combination with donepezil treatment significantly reduced Abeta load and related pathology; EVOO consumption with donepezil up-regulated synaptic proteins, enhanced BBB tightness and reduced neuroinflammation associated with Abeta pathology. Long-term consumption of EVOO significantly reduced Abeta pathological manifestations in addition to enhancing and expanding donepezil protective mechanisms against Abeta pathology when given concomitantly. Therefore, EVOO consumption as a medical food combined with donepezil offers an effective therapeutic approach by enhancing the non-cholinergic mechanisms of donepezil and by providing additional mechanisms to attenuate Abeta related pathology in AD patients. In the third project, the effect of Crocus sativus extract on Abeta clearance across the BBB and related pathology were evaluated in vitro and in vivo in wild-type and AD transgenic models. Available studies reported Crocus sativus exerts a positive effect against AD, however, the mechanism(s) for such effect is unknown. Therefore, here, we investigated its effect on enhancing Abeta clearance and reducing neuroinflammation. Findings from in vitro studies demonstrated that Crocus sativus extract increased the tightness and enhanced Abeta transport in our cell-based BBB model. Followed in vivo studies confirmed the effect of Crocus sativus extract on the BBB integrity and function that was associated with reduced Abeta load and related pathology in 5XFAD mice. Furthermore, Crocus sativus extract up-regulated synaptic proteins and reduced neuroinflammation associated with Abeta pathology in the brains of 5XFAD mice. Crocin, one of the major active compounds in Crocus sativus, known for its antioxidant and anti-inflammatory effect, was also tested separately in vivo. Crocin was able to reduce Abeta load and related pathologies but to a lesser extent when compared to Crocus sativus extract, which could be explained, at least in part, by the lack of crocin's ability in enhancing Abeta clearance and reducing neuroinflammation. Findings from this project support the positive effect of Crocus sativus against AD by reducing Abeta pathological manifestations. In conclusion, in this work, the therapeutics potential of oleocanthal, EVOO, and Crocus sativus extracts was in vitro and in vivo evaluated for their effect on Abeta clearance, BBB integrity and function, neuroprotective and neuroinflammation. Oleocanthal, EVOO, and Crocus sativus extract enhanced the clearance of Abeta by inducing its transport across the BBB and enhancing its enzymatic degradation and reduced neuroinflammation, which collectively led to Abeta brain levels reduction associated with inflammation reduction and neuroprotection. Therefore, we suggest that natural products such as EVOO, oleocanthal, and Crocus sativus may have a high potential therapeutic role against AD pathology.

Activation of Wnt signaling by lithium and rosiglitazone reduced spatial memory impairment and neurodegeneration in brains of an APPswe/PSEN1DeltaE9 mouse model of Alzheimer's disease.

PubMed

Toledo, E M; Inestrosa, N C

2010-03-01

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a progressive deterioration of cognitive abilities, accumulation of the amyloid-beta-peptide (Abeta) and synaptic alterations. Treatment with lithium has been shown to provide neuroprotection against several insults, including protection against Abeta neurotoxicity in vitro. Rosiglitazone, a peroxisome proliferator activated receptor-gamma agonist, has been shown to attenuate Abeta-peptide neurotoxic effects, including the inflammatory response of microglia and astrocytes. Both types of drugs activate Wnt signaling, a pathway that has been shown to be related to AD. In this study, a double transgenic mouse model, which coexpresses APPswe and the exon 9 deletion of the presenilin 1 (PSEN1) gene, was used to examine, in vivo, the effect of lithium and rosiglitazone on Abeta neurotoxicity. Mice were tested for spatial memory, and their brain samples were used for histochemical and biochemical analysis. In this study, we report that both drugs significantly reduced (1) spatial memory impairment induced by amyloid burden; (2) Abeta aggregates and Abeta oligomers; and (3) astrocytic and microglia activation. They also prevented changes in presynaptic and postsynaptic marker proteins. Finally, both drugs activate Wnt signaling shown by the increase in beta-catenin and by the inhibition of the glycogen synthase kinase-3beta. We conclude that lithium and rosiglitazone, possibly by the activation of the Wnt signaling pathway, reduce various AD neuropathological markers and may be considered as potential therapeutic agents against the disease.

Abeta oligomers induce neuronal oxidative stress through an N-methyl-D-aspartate receptor-dependent mechanism that is blocked by the Alzheimer drug memantine.

PubMed

De Felice, Fernanda G; Velasco, Pauline T; Lambert, Mary P; Viola, Kirsten; Fernandez, Sara J; Ferreira, Sergio T; Klein, William L

2007-04-13

Oxidative stress is a major aspect of Alzheimer disease (AD) pathology. We have investigated the relationship between oxidative stress and neuronal binding of Abeta oligomers (also known as ADDLs). ADDLs are known to accumulate in brain tissue of AD patients and are considered centrally related to pathogenesis. Using hippocampal neuronal cultures, we found that ADDLs stimulated excessive formation of reactive oxygen species (ROS) through a mechanism requiring N-methyl-d-aspartate receptor (NMDA-R) activation. ADDL binding to neurons was reduced and ROS formation was completely blocked by an antibody to the extracellular domain of the NR1 subunit of NMDA-Rs. In harmony with a steric inhibition of ADDL binding by NR1 antibodies, ADDLs that were bound to detergent-extracted synaptosomal membranes co-immunoprecipitated with NMDA-R subunits. The NR1 antibody did not affect ROS formation induced by NMDA, showing that NMDA-Rs themselves remained functional. Memantine, an open channel NMDA-R antagonist prescribed as a memory-preserving drug for AD patients, completely protected against ADDL-induced ROS formation, as did other NMDA-R antagonists. Memantine and the anti-NR1 antibody also attenuated a rapid ADDL-induced increase in intraneuronal calcium, which was essential for stimulated ROS formation. These results show that ADDLs bind to or in close proximity to NMDA-Rs, triggering neuronal damage through NMDA-R-dependent calcium flux. This response provides a pathologically specific mechanism for the therapeutic action of memantine, indicates a role for ROS dysregulation in ADDL-induced cognitive impairment, and supports the unifying hypothesis that ADDLs play a central role in AD pathogenesis.

Abeta oligomer-induced aberrations in synapse composition, shape, and density provide a molecular basis for loss of connectivity in Alzheimer's disease.

PubMed

Lacor, Pascale N; Buniel, Maria C; Furlow, Paul W; Clemente, Antonio Sanz; Velasco, Pauline T; Wood, Margaret; Viola, Kirsten L; Klein, William L

2007-01-24

The basis for memory loss in early Alzheimer's disease (AD) seems likely to involve synaptic damage caused by soluble Abeta-derived oligomers (ADDLs). ADDLs have been shown to build up in the brain and CSF of AD patients and are known to interfere with mechanisms of synaptic plasticity, acting as gain-of-function ligands that attach to synapses. Because of the correlation between AD dementia and synaptic degeneration, we investigated here the ability of ADDLs to affect synapse composition, structure, and abundance. Using highly differentiated cultures of hippocampal neurons, a preferred model for studies of synapse cell biology, we found that ADDLs bound to neurons with specificity, attaching to presumed excitatory pyramidal neurons but not GABAergic neurons. Fractionation of ADDLs bound to forebrain synaptosomes showed association with postsynaptic density complexes containing NMDA receptors, consistent with observed attachment of ADDLs to dendritic spines. During binding to hippocampal neurons, ADDLs promoted a rapid decrease in membrane expression of memory-related receptors (NMDA and EphB2). Continued exposure resulted in abnormal spine morphology, with induction of long thin spines reminiscent of the morphology found in mental retardation, deafferentation, and prionoses. Ultimately, ADDLs caused a significant decrease in spine density. Synaptic deterioration, which was accompanied by decreased levels of the spine cytoskeletal protein drebrin, was blocked by the Alzheimer's therapeutic drug Namenda. The observed disruption of dendritic spines links ADDLs to a major facet of AD pathology, providing strong evidence that ADDLs in AD brain cause neuropil damage believed to underlie dementia.

The nootropic and neuroprotective proline-containing dipeptide noopept restores spatial memory and increases immunoreactivity to amyloid in an Alzheimer's disease model.

PubMed

Ostrovskaya, Rita U; Gruden, Marina A; Bobkova, Natalya A; Sewell, Robert D E; Gudasheva, Tatyana A; Samokhin, Alexander N; Seredinin, Sergey B; Noppe, Wim; Sherstnev, Vladimir V; Morozova-Roche, Ludmilla A

2007-08-01

The effects of the novel proline-containing nootropic and neuroprotective dipeptide, noopept (GVS-111, N-phenylacetyl-L-prolylglycine ethyl ester) were investigated in NMRI mice following olfactory bulbectomy. We have shown previously that these animals developed Alzheimer's disease (AD)-like behaviour, morphology and biochemistry including impairment of spatial memory, regional neuronal degeneration and elevated Abeta peptide brain levels. In the current investigation, spatial memory was assessed using the Morris water maze and serum antibodies to in vitro morphologically characterized amyloid structures of both Abeta((25-35)) peptide and equine lysozyme, as well as to neurotrophic glial factor S100b, were analyzed by enzyme-linked immunosorbent assay (ELISA). Noopept (administered at a dose of 0.01 mg/kg for a period of 21 days and during a further 5 days training) restored spatial memory and increased serum antibody levels to oligomers of Abeta((25-35)) peptide but not to equine lysozyme amyloid or S100b protein in bulbectomized animals. The positive immunotropic effect of noopept to Abeta((25-35)) peptide prefibrillar aggregates was more marked in sham-operated compared to the bulbectomized subjects which were characterized by an overall suppression of immunoreactivity. Enhancement of the immune response to Abeta((25-35)) peptide prefibrils caused by noopept may attenuate the neurotoxic consequences of amyloid fibrillization and also be associated with an improvement in spatial memory in bulbectomized mice. These actions of noopept, combined with its previously reported neuroprotective and cholinomimetic properties, suggests that this dipeptide may well be useful for improving cognitive deficits induced by neurodegenerative diseases.

Gene vaccination to bias the immune response to amyloid-beta peptide as therapy for Alzheimer disease.

PubMed

Qu, Baoxi; Rosenberg, Roger N; Li, Liping; Boyer, Philip J; Johnston, Stephen A

2004-12-01

The amyloid-beta (Abeta) peptide has a central role in the neurodegeneration of Alzheimer disease (AD). Immunization of AD transgenic mice with Abeta(1-42) (Abeta(42)) peptide reduces both the spatial memory impairments and AD-like neuropathologic changes in these mice. Therapeutic immunization with Abeta in patients with AD was shown to be effective in reducing Abeta deposition, but studies were discontinued owing to the development of an autoimmune, cell-mediated meningoencephalitis. We hypothesized that gene vaccination could be used to generate an immune response to Abeta(42) that produced antibody response but avoided an adverse cell-mediated immune effect. To develop an effective genetic immunization approach for treatment and prevention of AD without causing an autoimmune, cell-mediated meningoencephalitis. Mice were vaccinated with a plasmid that encodes Abeta(42), administered by gene gun. The immune response of the mice to Abeta(42) was monitored by measurement of (1) antibody levels by enzyme-linked immunosorbent assay (ELISA) and Western blot and (2) Abeta(42)-specific T-cell response as measured by interferon-gamma enzyme-linked immunospot (ELISPOT) assay. Gene-gun delivery of the mouse Abeta(42) dimer gene induced significant humoral immune responses in BALB/c wild-type mice after 3 vaccinations in 10-day intervals. All 3 mice in the treated group showed significant humoral immune responses. The ELISPOT assay for interferon-gamma release with mouse Abeta(42) peptide and Abeta(9-18) showed no evident cytotoxic T-lymphocyte response. We further tested the responses of wild-type BALB/c mice to the monomer Abeta(42) gene vaccine. Western blot evaluation showed both human and mouse Abeta monomer gene vaccine elicited detectable humoral immune responses. We also introduced the human Abeta(42) monomer gene vaccine into AD double transgenic mice APPswe/PSEN1(A246E). Mice were vaccinated with plasmids that encode Abeta(1-42) and Abeta(1-16), or with plasmid without the Abeta gene. Treated mice showed significant humoral immune responses as demonstrated by ELISA and by Western blot. These mice also showed no significant cellular immune response as tested by ELISPOT. One of the treated mice was killed at 7 months of age for histological observations, and scattered amyloid plaques were noted in all layers of the cerebral cortex and in the hippocampus in both Abeta(42)- and control-vaccinated mice. No definite difference was discerned between the experimental and control animals. Gene-gun-administered genetic immunization with the Abeta(42) gene in wild-type BALB/c and AD transgenic mice can effectively elicit humoral immune responses without a significant T-cell-mediated immune response to the Abeta peptide. This immunotherapeutic approach could provide an alternative active immunization method for therapy and prevention of AD.

Genetic cathepsin B deficiency reduces beta-amyloid in transgenic mice expressing human wild-type amyloid precursor protein.

PubMed

Hook, Vivian Y H; Kindy, Mark; Reinheckel, Thomas; Peters, Christoph; Hook, Gregory

2009-08-21

Neurotoxic beta-amyloid (Abeta) peptides participate in Alzheimer's disease (AD); therefore, reduction of Abeta generated from APP may provide a therapeutic approach for AD. Gene knockout studies in transgenic mice producing human Abeta may identify targets for reducing Abeta. This study shows that knockout of the cathepsin B gene in mice expressing human wild-type APP (hAPPwt) results in substantial decreases in brain Abeta40 and Abeta42 by 67% and decreases in levels of the C-terminal beta-secretase fragment (CTFbeta) derived from APP. In contrast, knockout of cathepsin B in mice expressing hAPP with the rare Swedish (Swe) and Indiana (Ind) mutations had no effect on Abeta. The difference in reduction of Abeta in hAPPwt mice, but not in hAPPSwe/Ind mice, shows that the transgenic model can affect cathepsin B gene knockout results. Since most AD patients express hAPPwt, these data validate cathepsin B as a target for development of inhibitors to lower Abeta in AD.

Molecular understanding of Abeta peptide interaction with isoflurane, propofol, and thiopental: NMR spectroscopic study.

PubMed

Mandal, Pravat K; Williams, John P; Mandal, Ratna

2007-01-23

Abeta peptide is the major component of senile plaques (SP), which accumulate in the brain of a patient with Alzheimer's disease (AD). A recent report indicated that isoflurane enhanced Abeta oligomerization (micro-aggregation) and subsequent cytotoxicity of the Abeta peptide. A separate study showed that a clinically relevant concentration of isoflurane induces apoptosis and increases Abeta production in a human neuroglioma cell line. In vitro studies have indicated that halothane interacts specifically with Abeta peptide to induce oligomerization and that Abeta42 oligomerizes faster than Abeta40. The specific interactions of isoflurane, propofol, and thiopental with uniformly 15N labeled Abeta40 and Abeta42 peptide were investigated using multidimensional nuclear magnetic resonance (NMR) experiments. We found that isoflurane and propofol (at higher concentration) interact with Abeta40 peptides and induce Abeta oligomerization. Thiopental does not interact with specific residues (G29, A30, and I31) of Abeta40; hence, the peptide remains in the monomeric form. On the basis of our NMR study, thiopental does not oligomerize Abeta40 even at higher concentrations.

LRP-mediated clearance of Abeta is inhibited by KPI-containing isoforms of APP.

PubMed

Moir, Robert D; Tanzi, Rudolph E

2005-04-01

The pathogenesis of Alzheimer's disease (AD) involves the abnormal accumulation and deposition of beta-amyloid in cerebral blood vessels and in the brain parenchyma. Critical in modulating beta-amyloid deposition in brain is the flux of Abeta across the blood brain barrier. The low-density lipoprotein receptor-related protein (LRP), is a large endocytic receptor that mediates the efflux of Abeta out of brain and into the periphery. The first step in the LRP-mediated clearance of Abeta involves the formation of a complex between Abeta and the LRP ligands apolipoprotein E (apoE) or alpha(2)-macroglobulin (alpha(2)M). The Abeta/chaperone complexes then bind to LRP via binding sites on apoE or alpha(2)M. The efflux of Abeta/chaperone complexes out of the neuropil and into the periphery may be attenuated by LRP-ligands that compete with apoE or alpha(2)M for LRP binding. LRP is also the cell surface receptor for Kunitz Protease Inhibitor (KPI) containing isoforms of Abeta's parent protein, the amyloid protein precursor (APP). Protein and mRNA levels of KPI-containing APP isoforms (APP-KPI) are elevated in AD brain and are associated with increased Abeta production. In this study we show that soluble non-amyloidogenic APP-KPI can also inhibit the uptake of Abeta/alpha(2)M in a cell culture model of LRP mediated Abeta clearance. Clearance of Abeta/apoE complexes was not inhibited by APP-KPI. Our findings are consistent with studies showing that apoE and alpha(2)M have discrete binding sites on LRP. Most significantly, our data suggests that the elevated levels of APP-KPI in AD brain may attenuate the clearance of Abeta, the proteins own amyloidogenic catabolic product.

Intravenous immunoglobulin and Alzheimer's disease immunotherapy.

PubMed

Solomon, Beka

2007-02-01

Amyloid-beta peptide (Abeta) contributes to the acute progression of Alzheimer's disease (AD) and has become the main target for therapeutics. Active immunization with Abeta in individuals with AD has been efficacious; however, some patients developed side effects, possibly related to an autoimmune response. Evidence that intravenous immunoglobulin (IVIg), an FDA-approved purified immunoglobulin fraction from normal human donor blood, shows promise of passive immunotherapy for AD is reviewed. Investigations into the molecular effects of IVIg on Abeta clearance, using the BV-2 cellular microglia line, demonstrate that IVIg dissolves Abeta fibrils in vitro, increases cellular tolerance to Abeta, enhances microglial migration toward Abeta deposits, and mediates phagocytosis of Abeta. Preliminary clinical results indicate that IVIg, which contains natural antibodies against the Abeta, warrants further study into its potential to deliver a controlled immune attack on the peptide, avoiding the immune toxicities that have had a negative impact on the first clinical trials of vaccine against Abeta.

AbetaPP/APLP2 family of Kunitz serine proteinase inhibitors regulate cerebral thrombosis.

PubMed

Xu, Feng; Previti, Mary Lou; Nieman, Marvin T; Davis, Judianne; Schmaier, Alvin H; Van Nostrand, William E

2009-04-29

The amyloid beta-protein precursor (AbetaPP) is best recognized as the precursor to the Abeta peptide that accumulates in the brains of patients with Alzheimer's disease, but less is known about its physiological functions. Isoforms of AbetaPP that contain a Kunitz-type serine proteinase inhibitor (KPI) domain are expressed in brain and, outside the CNS, in circulating blood platelets. Recently, we showed that KPI-containing forms of AbetaPP regulates cerebral thrombosis in vivo (Xu et al., 2005, 2007). Amyloid precursor like protein-2 (APLP2), a closely related homolog to AbetaPP, also possesses a highly conserved KPI domain. Virtually nothing is known of its function. Here, we show that APLP2 also regulates cerebral thrombosis risk. Recombinant purified KPI domains of AbetaPP and APLP2 both inhibit the plasma clotting in vitro. In a carotid artery thrombosis model, both AbetaPP(-/-) and APLP2(-/-) mice exhibit similar significantly shorter times to vessel occlusion compared with wild-type mice indicating a prothrombotic phenotype. Similarly, in an experimental model of intracerebral hemorrhage, both AbetaPP(-/-) and APLP2(-/-) mice produce significantly smaller hematomas with reduced brain hemoglobin content compared with wild-type mice. Together, these results indicate that AbetaPP and APLP2 share overlapping anticoagulant functions with regard to regulating thrombosis after cerebral vascular injury.

Alzheimer Abeta(1-42) monomer adsorbed on the self-assembled monolayers.

PubMed

Wang, Qiuming; Zhao, Jun; Yu, Xiang; Zhao, Chao; Li, Lingyan; Zheng, Jie

2010-08-03

Amyloid-beta (Abeta) peptide aggregation on the cell membranes is a key pathological event responsible for neuron cell death in Alzheimer's disease (AD). We present a collection of molecular docking and molecular dynamics simulations to study the conformational dynamics and adsorption behavior of Abeta monomer on the self-assembled monolayer (SAM), in comparison to Abeta structure in bulk solution. Two distinct Abeta conformations (i.e., alpha-helix and beta-hairpin) are selected as initial structures to mimic different adsorption states, whereas four SAM surfaces with different end groups in hydrophobicity and charge distribution are used to examine the effect of surface chemistry on Abeta structure and adsorption. Simulation results show that alpha-helical monomer displays higher structural stability than beta-hairpin monomer on all SAMs, suggesting that the preferential conformation of Abeta monomer could be alpha-helical or random structure when bound to surfaces. Structural stability and adsorption behavior of Abeta monomer on the SAMs originates from competitive interactions between Abeta and SAM and between SAM and interfacial water, which involve the conformation of Abeta, the surface chemistry of SAM, and the structure and dynamics of interfacial waters. The relative net binding affinity of Abeta with the SAMs is in the favorable order of COOH-SAM > NH(2)-SAM > CH(3)-SAM > OH-SAM, highlighting the importance of electrostatic and hydrophobic interactions for driving Abeta adsorption at the SAMs, but both interactions contribute differently to each Abeta-SAM complex. This work provides parallel insights into the understanding of Abeta structure and aggregation on cell membrane.

Serum amyloid beta peptides in patients with dementia and age-matched non-demented controls as detected by surface-enhanced laser desorption ionisation-time of flight mass spectrometry (SELDI-TOF MS).

PubMed

Frankfort, Suzanne V; van Campen, Jos P C M; Tulner, Linda R; Beijnen, Jos H

2008-09-01

By using surface enhanced laser desorption/ionisation- time of flight mass spectrometry (SELDI-TOF MS) an amyloid beta (Abeta) profile was shown in cerebrospinal fluid (CSF) of patients with dementia. To investigate the Abeta-profile in serum with SELDI-TOF MS, to evaluate if this profile resembles CSF profiles and to investigate the correlation between intensity of Abeta-peptide-peaks in serum and clinical, demographical and genetic variables. Duplicate profiling of Abeta by an SELDI-TOF MS immunocapture assay was performed in 106 patients, suffering from Alzheimer's Disease or Vascular Dementia and age-matched non-demented control patients. Linear regression analyses were performed to investigate the intensities of four selected Abeta peaks as dependent variables in relation to the independent clinical, demographic or genetic variables. Abeta37, Abeta38 and Abeta40 were found among additional unidentified Abeta peptides, with the most pronounced Abeta peak at a molecular mass of 7752. This profile partly resembled the CSF profile. The clinical diagnosis was not a predictive independent variable, however ABCB1 genotypes C1236T, G2677T/A, age and creatinine level showed to be related to Abeta peak intensities in multivariate analyses. We found an Abeta profile in serum that partly resembled the CSF profile in demented patients. Age, creatinine levels, presence of the APOE epsilon4 allele and ABCB1 genotypes (C1236T and G2677T/A) were correlated with the Abeta serum profile. The role of P-gp as an Abeta transporter and the role of ABCB1 genotypes deserves further research. The investigated serum Abeta profile is probably not useful in the diagnosis of dementia.

The role of mTOR signaling in Alzheimer disease.

PubMed

Oddo, Salvatore

2012-01-01

The buildup of Abeta and tau is believed to directly cause or contribute to the progressive cognitive deficits characteristic of Alzheimer disease. However, the molecular pathways linking Abeta and tau accumulation to learning and memory deficits remain elusive. There is growing evidence that soluble forms of Abeta and tau can obstruct learning and memory by interfering with several signaling cascades. In this review, I will present data showing that the mammalian target of rapamycin (mTOR) may play a role in Abeta and tau induced neurodegeneration.

Evidence for novel beta-sheet structures in Iowa mutant beta-amyloid fibrils.

PubMed

Tycko, Robert; Sciarretta, Kimberly L; Orgel, Joseph P R O; Meredith, Stephen C

2009-07-07

Asp23-to-Asn mutation within the coding sequence of beta-amyloid, called the Iowa mutation, is associated with early onset, familial Alzheimer's disease and cerebral amyloid angiopathy, in which patients develop neuritic plaques and massive vascular deposition predominantly of the mutant peptide. We examined the mutant peptide, D23N-Abeta40, by electron microscopy, X-ray diffraction, and solid-state NMR spectroscopy. D23N-Abeta40 forms fibrils considerably faster than the wild-type peptide (k = 3.77 x 10(-3) min(-1) and 1.07 x 10(-4) min(-1) for D23N-Abeta40 and the wild-type peptide WT-Abeta40, respectively) and without a lag phase. Electron microscopy shows that D23N-Abeta40 forms fibrils with multiple morphologies. X-ray fiber diffraction shows a cross-beta pattern, with a sharp reflection at 4.7 A and a broad reflection at 9.4 A, which is notably smaller than the value for WT-Abeta40 fibrils (10.4 A). Solid-state NMR measurements indicate molecular level polymorphism of the fibrils, with only a minority of D23N-Abeta40 fibrils containing the in-register, parallel beta-sheet structure commonly found in WT-Abeta40 fibrils and most other amyloid fibrils. Antiparallel beta-sheet structures in the majority of fibrils are indicated by measurements of intermolecular distances through (13)C-(13)C and (15)N-(13)C dipole-dipole couplings. An intriguing possibility exists that there is a relationship between the aberrant structure of D23N-Abeta40 fibrils and the unusual vasculotropic clinical picture in these patients.

How cholesterol constrains glycolipid conformation for optimal recognition of Alzheimer's beta amyloid peptide (Abeta1-40).

PubMed

Yahi, Nouara; Aulas, Anaïs; Fantini, Jacques

2010-02-05

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.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vitiello, Giuseppe; CSGI; Grimaldi, Manuela

Highlights: Black-Right-Pointing-Pointer iA{beta}5p shows a significant tendency to deeply penetrates the hydrophobic core of lipid membrane. Black-Right-Pointing-Pointer A{beta}(25-35) locates in the external region of the membrane causing a re-positioning of CHOL. Black-Right-Pointing-Pointer iA{beta}5p withholds cholesterol in the inner hydrophobic core of the lipid membrane. Black-Right-Pointing-Pointer iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane. -- Abstract: Alzheimer's disease is characterized by the deposition of aggregates of the {beta}-amyloid peptide (A{beta}) in the brain. A potential therapeutic strategy for Alzheimer's disease is the use of synthetic {beta}-sheet breaker peptides, which are capable of binding A{beta} but unable to become part ofmore » a {beta}-sheet structure, thus inhibiting the peptide aggregation. Many studies suggest that membranes play a key role in the A{beta} aggregation; consequently, it is strategic to investigate the interplay between {beta}-sheet breaker peptides and A{beta} in the presence of lipid bilayers. In this work, we focused on the effect of the {beta}-sheet breaker peptide acetyl-LPFFD-amide, iA{beta}5p, on the interaction of the A{beta}(25-35) fragment with lipid membranes, studied by Electron Spin Resonance spectroscopy, using spin-labeled membrane components (either phospholipids or cholesterol). The ESR results show that iA{beta}5p influences the A{beta}(25-35) interaction with the bilayer through a cholesterol-mediated mechanism: iA{beta}5p withholds cholesterol in the inner hydrophobic core of the bilayer, making the interfacial region more fluid and capable to accommodate A{beta}(25-35). As a consequence, iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane, which is the first step of the {beta}-amyloid aggregation process.« less

Minocycline prevents Abeta(25-35)-induced reduction of somatostatin and neprilysin content in rat temporal cortex.

PubMed

Burgos-Ramos, E; Puebla-Jiménez, L; Arilla-Ferreiro, E

2009-02-13

Tetracyclines have been demonstrated to inhibit formation of beta-amyloid (Abeta) aggregates and to disassemble preformed fibrils. Minocycline, a semi-synthetic second-generation tetracycline, can reverse Abeta-induced impairment of cognitive functions. Since somatostatin is involved in cognition and we recently showed that Abeta(25-35) lowers somatostatin expression in the rat temporal cortex, our aim here was to analyze the effects of minocycline on somatostatin immunoreactivity and mRNA levels in the temporal cortex of Abeta(25-35)-infused and healthy rats. Moreover, since brain levels of neprilysin, an Abeta-degrading enzyme, decrease with age, favoring the appearance of senile neuritic plaques, we tested whether minocyline could affect neprilysin expression. Wistar rats were thus injected with minocycline twice on the first day of treatment. On the following day, and during 14 days, Abeta(25-35) or vehicle were administered. Minocycline was injected once again on days 13 and 14. All animals were sacrificed 24 h after the last drug injection. Minocycline abrogated the Abeta(25-35)-induced decrease of somatostatin-like immunoreactive content, somatostatin mRNA levels, phosphorylated-CREB content and neprilysin levels. Minocycline alone enhanced these targets. Our findings indicate that minocycline prevents the deleterious effects of Abeta(25-35) on SRIF and neprilysin expression in the rat temporal cortex and that it has protective effects per se on these parameters.

Dietary fats, cerebrovasculature integrity and Alzheimer's disease risk.

PubMed

Takechi, R; Galloway, S; Pallebage-Gamarallage, M M S; Lam, V; Mamo, J C L

2010-04-01

An emerging body of evidence is consistent with the hypothesis that dietary fats influence Alzheimer's disease (AD) risk, but less clear is the mechanisms by which this occurs. Alzheimer's is an inflammatory disorder, many consider in response to fibrillar formation and extracellular deposition of amyloid-beta (Abeta). Alternatively, amyloidosis could notionally be a secondary phenomenon to inflammation, because some studies suggest that cerebrovascular disturbances precede amyloid plaque formation. Hence, dietary fats may influence AD risk by either modulating Abeta metabolism, or via Abeta independent pathways. This review explores these two possibilities taking into consideration; (i) the substantial affinity of Abeta for lipids and its ordinary metabolism as an apolipoprotein; (ii) evidence that Abeta has potent vasoactive properties and (iii) studies which show that dietary fats modulate Abeta biogenesis and secretion. We discuss accumulating evidence that dietary fats significantly influence cerebrovascular integrity and as a consequence altered Abeta kinetics across the blood-brain barrier (BBB). Specifically, chronic ingestion of saturated fats or cholesterol appears to results in BBB dysfunction and exaggerated delivery from blood-to-brain of peripheral Abeta associated with lipoproteins of intestinal and hepatic origin. Interestingly, the pattern of saturated fat/cholesterol induced cerebrovascular disturbances in otherwise normal wild-type animal strains is analogous to established models of AD genetically modified to overproduce Abeta, consistent with a causal association. Saturated fats and cholesterol may exacerbate Abeta induced cerebrovascular disturbances by enhancing exposure of vessels of circulating Abeta. However, presently there is no evidence to support this contention. Rather, SFA and cholesterol appear to more broadly compromise BBB integrity with the consequence of plasma protein leakage into brain, including lipoprotein associated Abeta. The latter findings are consistent with the concept that AD is a dietary-fat induced phenotype of vascular dementia, reflecting the extraordinary entrapment of peripherally derived lipoproteins endogenously enriched in Abeta. Rather than being the initiating trigger for inflammation in AD, accumulation of extracellular lipoprotein-Abeta may be a secondary amplifier of dietary induced inflammation, or possibly, simply be consequential. Clearly, delineating the mechanisms by which dietary fats increase AD risk may be informative in developing new strategies for prevention and treatment of AD. Copyright 2009 Elsevier Ltd. All rights reserved.

Switch-peptides: design and characterization of controllable super-amyloid-forming host-guest peptides as tools for identifying anti-amyloid agents.

PubMed

Camus, Marie-Stéphanie; Dos Santos, Sonia; Chandravarkar, Arunan; Mandal, Bhubaneswar; Schmid, Adrian W; Tuchscherer, Gabriele; Mutter, Manfred; Lashuel, Hilal A

2008-09-01

Several amyloid-forming proteins are characterized by the presence of hydrophobic and highly amyloidogenic core sequences that play critical roles in the initiation and progression of amyloid fibril formation. Therefore targeting these sequences represents a viable strategy for identifying candidate molecules that could interfere with amyloid formation and toxicity of the parent proteins. However, the highly amyloidogenic and insoluble nature of these sequences has hampered efforts to develop high-throughput fibrillization assays. Here we describe the design and characterization of host-guest switch peptides that can be used for in vitro mechanistic and screening studies that are aimed at discovering aggregation inhibitors that target highly amyloidogenic sequences. These model systems are based on a host-guest system where the amyloidogenic sequence (guest peptide) is flanked by two beta-sheet-promoting (Leu-Ser)(n) oligomers as host sequences. Two host-guest peptides were prepared by using the hydrophobic core of Abeta comprising residues 14-24 (HQKLVFFAEDV) as the guest peptide with switch elements inserted within (peptide 1) or at the N and C termini of the guest peptide (peptide 2). Both model peptides can be triggered to undergo rapid self-assembly and amyloid formation in a highly controllable manner and their fibrillization kinetics is tuneable by manipulating solution conditions (for example, peptide concentration and pH). The fibrillization of both peptides reproduces many features of the full-length Abeta peptides and can be inhibited by known inhibitors of Abeta fibril formation. Our results suggest that this approach can be extended to other amyloid proteins and should facilitate the discovery of small-molecule aggregation inhibitors and the development of more efficacious anti-amyloid agents to treat and/or reverse the pathogenesis of neurodegenerative and systemic amyloid diseases.

Zn(II)- and Cu(II)-induced non-fibrillar aggregates of amyloid-beta (1-42) peptide are transformed to amyloid fibrils, both spontaneously and under the influence of metal chelators.

PubMed

Tõugu, Vello; Karafin, Ann; Zovo, Kairit; Chung, Roger S; Howells, Claire; West, Adrian K; Palumaa, Peep

2009-09-01

Aggregation of amyloid-beta (Abeta) peptides is a central phenomenon in Alzheimer's disease. Zn(II) and Cu(II) have profound effects on Abeta aggregation; however, their impact on amyloidogenesis is unclear. Here we show that Zn(II) and Cu(II) inhibit Abeta(42) fibrillization and initiate formation of non-fibrillar Abeta(42) aggregates, and that the inhibitory effect of Zn(II) (IC(50) = 1.8 micromol/L) is three times stronger than that of Cu(II). Medium and high-affinity metal chelators including metallothioneins prevented metal-induced Abeta(42) aggregation. Moreover, their addition to preformed aggregates initiated fast Abeta(42) fibrillization. Upon prolonged incubation the metal-induced aggregates also transformed spontaneously into fibrils, that appear to represent the most stable state of Abeta(42). H13A and H14A mutations in Abeta(42) reduced the inhibitory effect of metal ions, whereas an H6A mutation had no significant impact. We suggest that metal binding by H13 and H14 prevents the formation of a cross-beta core structure within region 10-23 of the amyloid fibril. Cu(II)-Abeta(42) aggregates were neurotoxic to neurons in vitro only in the presence of ascorbate, whereas monomers and Zn(II)-Abeta(42) aggregates were non-toxic. Disturbed metal homeostasis in the vicinity of zinc-enriched neurons might pre-dispose formation of metal-induced Abeta aggregates, subsequent fibrillization of which can lead to amyloid formation. The molecular background underlying metal-chelating therapies for Alzheimer's disease is discussed in this light.

Beta-amyloid immunotherapy prevents synaptic degeneration in a mouse model of Alzheimer's disease.

PubMed

Buttini, Manuel; Masliah, Eliezer; Barbour, Robin; Grajeda, Henry; Motter, Ruth; Johnson-Wood, Kelly; Khan, Karen; Seubert, Peter; Freedman, Stephen; Schenk, Dale; Games, Dora

2005-10-05

Alzheimer's disease neuropathology is characterized by key features that include the deposition of the amyloid beta peptide (Abeta) into plaques, the formation of neurofibrillary tangles, and the loss of neurons and synapses in specific brain regions. The loss of synapses, and particularly the associated presynaptic vesicle protein synaptophysin in the hippocampus and association cortices, has been widely reported to be one of the most robust correlates of Alzheimer's disease-associated cognitive decline. The beta-amyloid hypothesis supports the idea that Abeta is the cause of these pathologies. However, the hypothesis is still controversial, in part because the direct role of Abeta in synaptic degeneration awaits confirmation. In this study, we show that Abeta reduction by active or passive Abeta immunization protects against the progressive loss of synaptophysin in the hippocampal molecular layer and frontal neocortex of a transgenic mouse model of Alzheimer's disease. These results, substantiated by quantitative electron microscopic analysis of synaptic densities, strongly support a direct causative role of Abeta in the synaptic degeneration seen in Alzheimer's disease and strengthen the potential of Abeta immunotherapy as a treatment approach for this disease.

The stability of monomeric intermediates controls amyloid formation: Abeta25-35 and its N27Q mutant.

PubMed

Ma, Buyong; Nussinov, Ruth

2006-05-15

The structure and stabilities of the intermediates affect protein folding as well as misfolding and amyloid formation. By applying Kramer's theory of barrier crossing and a Morse-function-like energy landscape, we show that intermediates with medium stability dramatically increase the rate of amyloid formation; on the other hand, very stable and very unstable intermediates sharply decrease amyloid formation. Remarkably, extensive molecular dynamics simulations and conformational energy landscape analysis of Abeta25-35 and its N27Q mutant corroborate the mathematical description. Both experimental and current simulation results indicate that the core of the amyloid structure of Abeta25-35 formed from residues 28-35. A single mutation of N27Q of Abeta25-35 makes the Abeta25-35 N27Q amyloid-free. Energy landscape calculations show that Abeta25-35 has extended intermediates with medium stability that are prone to form amyloids, whereas the extended intermediates for Abeta25-35 N27Q split into stable and very unstable species that are not disposed to form amyloids. The results explain the contribution of both alpha-helical and beta-strand intermediates to amyloid formation. The results also indicate that the structure and stability of the intermediates, as well as of the native folded and the amyloid states can be targeted in drug design. One conceivable approach is to stabilize the intermediates to deter amyloid formation.

A[Beta] Deposits in Older Non-Demented Individuals with Cognitive Decline Are Indicative of Preclinical Alzheimer's Disease

ERIC Educational Resources Information Center

Villemagne, V. L.; Pike, K. E.; Darby, D.; Maruff, P.; Savage, G.; Ng, S.; Ackermann, U.; Cowie, T. F.; Currie, J.; Chan, S. G.; Jones, G.; Tochon-Danguy, H.; O'Keefe, G.; Masters, C. L.; Rowe, C. C.

2008-01-01

Approximately 30% of healthy persons aged over 75 years show A[beta] deposition at autopsy. It is postulated that this represents preclinical Alzheimer's disease (AD). We evaluated the relationship between A[beta] burden as assessed by PiB PET and cognitive decline in a well-characterized, non-demented, elderly cohort. PiB PET studies and…

Amyloid beta peptide as a physiological modulator of neuronal 'A'-type K+ current.

PubMed

Plant, Leigh D; Webster, Nicola J; Boyle, John P; Ramsden, Martin; Freir, Darragh B; Peers, Chris; Pearson, Hugh A

2006-11-01

Control of neuronal spiking patterns resides, in part, in the type and degree of expression of voltage-gated K(+) channel subunits. Previous studies have revealed that soluble forms of the Alzheimer's disease associated amyloid beta protein (Abeta) can increase the 'A'-type current in neurones. In this study, we define the molecular basis for this increase and show that endogenous production of Abeta is important in the modulation of Kv4.2 and Kv4.3 subunit expression in central neurones. A-type K(+) currents, and Kv4.2 and Kv4.3 subunit expression, were transiently increased in cerebellar granule neurones by the 1-40 and 1-42 forms of Abeta (100nM, 2-24h). Currents through recombinant Kv4.2 channels expressed in HEK293 cells were increased in a similar fashion to those through the native channels. Increases in 'A'-type current could be prevented by the use of cycloheximide and brefeldin A, indicating that protein expression and trafficking processes were altered by Abeta, rather than protein degredation. Endogenous Abeta production in cerebellar granule neurones was blocked using inhibitors of either gamma- or beta-secretase and resulted in decreased K(+) current. Crucially this could be prevented by co-application of exogenous Abeta (1nM), however, no change in Kv4.2 or Kv4.3 subunit expression occurred. These data show that Abeta is a modulator of Kv4 subunit expression in neurones at both the functional and the molecular level. Thus Abeta is not only involved in Alzheimer pathology, but is also an important physiological regulator of ion channel expression and hence neuronal excitability.

Circulating neprilysin clears brain amyloid.

PubMed

Liu, Yinxing; Studzinski, Christa; Beckett, Tina; Murphy, M Paul; Klein, Ronald L; Hersh, Louis B

2010-10-01

The use of the peptidase neprilysin (NEP) as a therapeutic for lowering brain amyloid burden is receiving increasing attention. We have previously demonstrated that peripheral expression of NEP on the surface of hindlimb muscle lowers brain amyloid burden in a transgenic mouse model of Alzheimer's disease. In this study we now show that using adeno-associated virus expressing a soluble secreted form of NEP (secNEP-AAV8), NEP secreted into plasma is effective in clearing brain Abeta. Soluble NEP expression in plasma was sustained over the 3-month time period it was measured. Secreted NEP decreased plasma Abeta by 30%, soluble brain Abeta by approximately 28%, insoluble brain Abeta by approximately 55%, and Abeta oligomersby 12%. This secNEP did not change plasma levels of substance P or bradykinin, nor did it alter blood pressure. No NEP was detected in CSF, nor did the AAV virus produce brain expression of NEP. Thus the lowering of brain Abeta was due to plasma NEP which altered blood-brain Abeta transport dynamics. Expressing NEP in plasma provides a convenient way to monitor enzyme activity during the course of its therapeutic testing. Copyright 2010 Elsevier Inc. All rights reserved.

Reduction of aggregated Tau in neuronal processes but not in the cell bodies after Abeta42 immunisation in Alzheimer's disease.

PubMed

Boche, Delphine; Donald, Jane; Love, Seth; Harris, Scott; Neal, James W; Holmes, Clive; Nicoll, James A R

2010-07-01

Alzheimer's disease (AD) pathology is characterised by aggregation in the brain of amyloid-beta (Abeta) peptide and hyperphosphorylated tau (phospho-tau), although how these proteins interact in disease pathogenesis is unclear. Abeta immunisation results in removal of Abeta from the brain but cognitive decline continues to progress, possibly due to persistent phospho-tau. We quantified phospho-tau and Abeta42 in the brains of 10 AD patients (iAD) who were actively immunised with Abeta42 (AN1792, Elan Pharmaceuticals) compared with 28 unimmunised AD cases (cAD). The phospho-tau load was lower in the iAD than the cAD group in the cerebral cortex (cAD 1.08% vs. iAD 0.72%, P = 0.048), CA1 hippocampus (cAD 2.26% vs. iAD 1.05%; P = 0.001), subiculum (cAD 1.60% vs. iAD 0.31%; P = 0.001) and entorhinal cortex (cAD 1.10% vs. iAD 0.18%; P < 0.001). Assessment of the localisation within neurons of phospho-tau indicated that the Abeta immunotherapy-associated reduction was confined to neuronal processes, i.e. neuropil threads and dystrophic neurites. However, the phospho-tau accumulation in the neuronal cell bodies, contributing to neurofibrillary tangles, appeared not to be affected. In showing that Abeta immunisation can influence phospho-tau pathology, we confirm the position of Abeta as a target for modifying tau accumulation in AD and demonstrate a link between these proteins. However, the continuing progression of cognitive decline in AD patients after Abeta immunisation may be explained by its lack of apparent effect on tangles.

DNA beta-amyloid(1-42) trimer immunization for Alzheimer disease in a wild-type mouse model.

PubMed

Lambracht-Washington, Doris; Qu, Bao-Xi; Fu, Min; Eagar, Todd N; Stüve, Olaf; Rosenberg, Roger N

2009-10-28

DNA beta-amyloid(1-42) (Abeta42) trimer immunization was developed to produce specific T helper 2 cell (T(H)2)-type antibodies to provide an effective and safe therapy for Alzheimer disease (AD) by reducing elevated levels of Abeta42 peptide that occur in the brain of patients with AD. To compare the immune response in wild-type mice after immunization with DNA Abeta42 trimer and Abeta42 peptide. Wild-type mice received either 4 microg of DNA Abeta42 trimer immunization administered with gene gun (n = 8) or intraperitoneal injection of 100 microg of human Abeta42 peptide with the adjuvant Quil A (n = 8). Titers, epitope mapping, and isotypes of the Abeta42-specific antibodies were analyzed. Antibody titers, mapping of binding sites (epitopes), isotype profiles of the Abeta42-specific antibodies, and T-cell activation. DNA Abeta42 trimer immunization resulted in antibody titers with a mean of 15 microg per milliliter of plasma. The isotype profile of the antibodies differed markedly. A predominant IgG1 antibody response was found in the DNA-immunized mice, indicating a T(H)2 type of immune response (IgG1/IgG2a ratio of 10). The peptide-immunized mice showed a mixed T(H)1/T(H)2 immune response (IgG1/IgG2a ratio of 1) (P < .001). No increased T-cell proliferation was observed in the DNA-immunized mice (P = .03). In this preliminary study in a wild-type mouse model, DNA Abeta42 trimer immunization protocol produced a T(H)2 immune response and appeared to have low potential to cause an inflammatory T-cell response.

The second Cu(II)-binding site in a proton-rich environment interferes with the aggregation of amyloid-beta(1-40) into amyloid fibrils.

PubMed

Jun, Sangmi; Gillespie, Joel R; Shin, Byong-kyu; Saxena, Sunil

2009-11-17

The overall morphology and Cu(II) ion coordination for the aggregated amyloid-beta(1-40) [Abeta(1-40)] in N-ethylmorpholine (NEM) buffer are affected by Cu(II) ion concentration. This effect is investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM), and electron spin echo envelope modulation (ESEEM) spectroscopy. At lower than equimolar concentrations of Cu(II) ions, fibrillar aggregates of Abeta(1-40) are observed. At these concentrations of Cu(II), the monomeric and fibrillar Abeta(1-40) ESEEM data indicate that the Cu(II) ion is coordinated by histidine residues. For aggregated Abeta(1-40) at a Cu(II):Abeta molar ratio of 2:1, TEM and AFM images show both linear fibrils and granular amorphous aggregates. The ESEEM spectra show that the multi-histidine coordination for Cu(II) ion partially breaks up and becomes exposed to water or exchangeable protons of the peptide at a higher Cu(II) concentration. Since the continuous-wave electron spin resonance results also suggest two copper-binding sites in Abeta(1-40), the proton ESEEM peak may arise from the second copper-binding site, which may be significantly involved in the formation of granular amorphous aggregates. Thioflavin T fluorescence and circular dichroism experiments also show that Cu(II) inhibits the formation of fibrils and induces a nonfibrillar beta-sheet conformation. Therefore, we propose that Abeta(1-40) has a second copper-binding site in a proton-rich environment and the second binding Cu(II) ion interferes with a conformational transition into amyloid fibrils, inducing the formation of granular amorphous aggregates.

Amyloid-beta protofibrils differ from amyloid-beta aggregates induced in dilute hexafluoroisopropanol in stability and morphology.

PubMed

Nichols, Michael R; Moss, Melissa A; Reed, Dana Kim; Cratic-McDaniel, Stephanie; Hoh, Jan H; Rosenberry, Terrone L

2005-01-28

The brains of Alzheimer's disease (AD) patients contain large numbers of amyloid plaques that are rich in fibrils composed of 40- and 42-residue amyloid-beta (Abeta) peptides. Several lines of evidence indicate that fibrillar Abeta and especially soluble Abeta aggregates are important in the etiology of AD. Recent reports also stress that amyloid aggregates are polymorphic and that a single polypeptide can fold into multiple amyloid conformations. Here we demonstrate that Abeta-(1-40) can form soluble aggregates with predominant beta-structures that differ in stability and morphology. One class of aggregates involved soluble Abeta protofibrils, prepared by vigorous overnight agitation of monomeric Abeta-(1-40) at low ionic strength. Dilution of these aggregation reactions induced disaggregation to monomers as measured by size exclusion chromatography. Protofibril concentrations monitored by thioflavin T fluorescence decreased in at least two kinetic phases, with initial disaggregation (rate constant approximately 1 h(-1)) followed by a much slower secondary phase. Incubation of the reactions without agitation resulted in less disaggregation at slower rates, indicating that the protofibrils became progressively more stable over time. In fact, protofibrils isolated by size exclusion chromatography were completely stable and gave no disaggregation. A second class of soluble Abeta aggregates was generated rapidly (<10 min) in buffered 2% hexafluoroisopropanol (HFIP). These aggregates showed increased thioflavin T fluorescence and were rich in beta-structure by circular dichroism. Electron microscopy and atomic force microscopy revealed initial globular clusters that progressed over several days to soluble fibrous aggregates. When diluted out of HFIP, these aggregates initially were very unstable and disaggregated completely within 2 min. However, their stability increased as they progressed to fibers. Relative to Abeta protofibrils, the HFIP-induced aggregates seeded elongation by Abeta monomer deposition very poorly. The techniques used to distinguish these two classes of soluble Abeta aggregates may be useful in characterizing Abeta aggregates formed in vivo.

Enzymatic characteristics of I213T mutant presenilin-1/gamma-secretase in cell models and knock-in mouse brains: familial Alzheimer disease-linked mutation impairs gamma-site cleavage of amyloid precursor protein C-terminal fragment beta.

PubMed

Shimojo, Masafumi; Sahara, Naruhiko; Mizoroki, Tatsuya; Funamoto, Satoru; Morishima-Kawashima, Maho; Kudo, Takashi; Takeda, Masatoshi; Ihara, Yasuo; Ichinose, Hiroshi; Takashima, Akihiko

2008-06-13

Presenilin (PS)/gamma-secretase-mediated intramembranous proteolysis of amyloid precursor protein produces amyloid beta (Abeta) peptides in which Abeta species of different lengths are generated through multiple cleavages at the gamma-, zeta-, and epsilon-sites. An increased Abeta42/Abeta40 ratio is a common characteristic of most cases of familial Alzheimer disease (FAD)-linked PS mutations. However, the molecular mechanisms underlying amyloid precursor protein proteolysis leading to increased Abeta42/Abeta40 ratios still remain unclear. Here, we report our findings on the enzymatic analysis of gamma-secretase derived from I213T mutant PS1-expressing PS1/PS2-deficient (PS(-/-)) cells and from the brains of I213T mutant PS1 knock-in mice. Kinetics analyses revealed that the FAD mutation reduced de novo Abeta generation, suggesting that mutation impairs the total catalytic rate of gamma-secretase. Analysis of each Abeta species revealed that the FAD mutation specifically reduced Abeta40 levels more drastically than Abeta42 levels, leading to an increased Abeta42/Abeta40 ratio. By contrast, the FAD mutation increased the generation of longer Abeta species such as Abeta43, Abeta45, and >Abeta46. These results were confirmed by analyses of gamma-secretase derived from I213T knock-in mouse brains, in which the reduction of de novo Abeta generation was mutant allele dose-dependent. Our findings clearly indicate that the mechanism underlying the increased Abeta42/Abeta40 ratio observed in cases of FAD mutations is related to the differential inhibition of gamma-site cleavage reactions, in which the reaction producing Abeta40 is subject to more inhibition than that producing Abeta42. Our results also provide novel insight into how enhancing the generation of longer Abetas may contribute to Alzheimer disease onset.

Long-term soluble Abeta1-40 activates CaM kinase II in organotypic hippocampal cultures.

PubMed

Tardito, Daniela; Gennarelli, Massimo; Musazzi, Laura; Gesuete, Raffaella; Chiarini, Stefania; Barbiero, Valentina Sara; Rydel, Russell E; Racagni, Giorgio; Popoli, Maurizio

2007-09-01

Recent findings suggested a role for soluble amyloid-beta (Abeta) peptides in Alzheimer's disease associated cognitive decline. We investigated the action of soluble, monomeric Abeta(1-40) on CaM kinase II, a kinase involved in neuroplasticity and cognition. We treated organotypic hippocampal cultures short-term (up to 4h) and long-term (5 days) with Abeta(1-40) (1nM-5microM). Abeta did not induce cell damage, apoptosis or synaptic loss. Short-term treatment down-regulated enzymatic activity of the kinase, by reducing its Thr(286) phosphorylation. In contrast, long-term treatment (1nM-microM) markedly and significantly up-regulated enzymatic activity, with peak stimulation at 10nM (three-fold). Up-regulation of activity was associated with increased expression of the alpha-isoform of CaM kinase II, increased phosphorylation at Thr(286) (activator residue) and decreased phosphorylation at Thr(305-306) (inhibitory residues). We investigated the effect of glutamate on CaM kinase II following exposure to 1 or 10nM Abeta(1-40). As previously reported, glutamate increased CaM kinase II activity. However, the glutamate effect was not altered by pretreatment of slices with Abeta. Short- and long-term Abeta treatment showed opposite effects on CaM kinase II, suggesting that long-term changes are an adaptation to the kinase early down-regulation. The marked effect of Abeta(1-40) on the kinase suggests that semi-physiological and slowly raising peptide concentrations may have a significant impact on synaptic plasticity in the absence of synaptic loss or neuronal cell death.

Phosphate and HEPES buffers potently affect the fibrillation and oligomerization mechanism of Alzheimer's A{beta} peptide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garvey, Megan; Tepper, Katharina; Haupt, Caroline

Highlights: {yields} Sodium phosphate buffer accelerated A{beta}(1-40) nucleation relative to HEPES. {yields} A{beta}(1-40) fibrils formed in the two buffers show only minor structural differences. {yields} NMR revealed that A{beta}(1-40) histidine residues mediate buffer dependent changes. -- Abstract: The oligomerization of A{beta} peptide into amyloid fibrils is a hallmark of Alzheimer's disease. Due to its biological relevance, phosphate is the most commonly used buffer system for studying the formation of A{beta} and other amyloid fibrils. Investigation into the characteristics and formation of amyloid fibrils frequently relies upon material formed in vitro, predominantly in phosphate buffers. Herein, we examine the effects onmore » the fibrillation and oligomerization mechanism of A{beta} peptide that occur due solely to the influence of phosphate buffer. We reveal that significant differences in amyloid fibrillation are observed due to fibrillation being initiated in phosphate or HEPES buffer (at physiological pH and temperature). Except for the differing buffer ions, all experimental parameters were kept constant. Fibril formation was assessed using fluorescently monitored kinetic studies, microscopy, X-ray fiber diffraction and infrared and nuclear magnetic resonance spectroscopies. Based on this set up, we herein reveal profound effects on the mechanism and speed of A{beta} fibrillation. The three histidine residues at positions 6, 13 and 14 of A{beta}(1-40) are instrumental in these mechanistic changes. We conclude that buffer plays a more significant role in fibril formation than has been generally acknowledged.« less

Antagonist of peroxisome proliferator-activated receptor {gamma} induces cerebellar amyloid-{beta} levels and motor dysfunction in APP/PS1 transgenic mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Jing; Sun, Bing; Chen, Kui

2009-07-03

Recent evidences show that peroxisome proliferator-activated receptor {gamma} (PPAR{gamma}) is involved in the modulation of the amyloid-{beta} (A{beta}) cascade causing Alzheimer's disease (AD) and treatment with PPAR{gamma} agonists protects against AD pathology. However, the function of PPAR{gamma} steady-state activity in A{beta} cascade and AD pathology remains unclear. In this study, an antagonist of PPAR{gamma}, GW9662, was injected into the fourth ventricle of APP/PS1 transgenic mice to inhibit PPAR{gamma} activity in cerebellum. The results show that inhibition of PPAR{gamma} significantly induced A{beta} levels in cerebellum and caused cerebellar motor dysfunction in APP/PS1 transgenic mice. Moreover, GW9662 treatment markedly decreased the cerebellarmore » levels of insulin-degrading enzyme (IDE), which is responsible for the cellular degradation of A{beta}. Since cerebellum is spared from significant A{beta} accumulation and neurotoxicity in AD patients and animal models, these findings suggest a crucial role of PPAR{gamma} steady-state activity in protection of cerebellum against AD pathology.« less

Piracetam inhibits the lipid-destabilising effect of the amyloid peptide Abeta C-terminal fragment.

PubMed

Mingeot-Leclercq, Marie-Paule; Lins, Laurence; Bensliman, Mariam; Thomas, Annick; Van Bambeke, Françoise; Peuvot, Jacques; Schanck, André; Brasseur, Robert

2003-01-10

Amyloid peptide (Abeta) is a 40/42-residue proteolytic fragment of a precursor protein (APP), implicated in the pathogenesis of Alzheimer's disease. The hypothesis that interactions between Abeta aggregates and neuronal membranes play an important role in toxicity has gained some acceptance. Previously, we showed that the C-terminal domain (e.g. amino acids 29-42) of Abeta induces membrane permeabilisation and fusion, an effect which is related to the appearance of non-bilayer structures. Conformational studies showed that this peptide has properties similar to those of the fusion peptide of viral proteins i.e. a tilted penetration into membranes. Since piracetam interacts with lipids and has beneficial effects on several symptoms of Alzheimer's disease, we investigated in model membranes the ability of piracetam to hinder the destabilising effect of the Abeta 29-42 peptide. Using fluorescence studies and 31P and 2H NMR spectroscopy, we have shown that piracetam was able to significantly decrease the fusogenic and destabilising effect of Abeta 29-42, in a concentration-dependent manner. While the peptide induced lipid disorganisation and subsequent negative curvature at the membrane-water interface, the conformational analysis showed that piracetam, when preincubated with lipids, coats the phospholipid headgroups. Calculations suggest that this prevents appearance of the peptide-induced curvature. In addition, insertion of molecules with an inverted cone shape, like piracetam, into the outer membrane leaflet should make the formation of such structures energetically less favourable and therefore decrease the likelihood of membrane fusion.

Ten-year change in plasma amyloid beta levels and late-life cognitive decline.

PubMed

Okereke, Olivia I; Xia, Weiming; Selkoe, Dennis J; Grodstein, Francine

2009-10-01

Plasma levels of amyloid beta peptide (Abeta) are potential biomarkers of early cognitive impairment and decline and of Alzheimer disease risk. To relate midlife plasma Abeta measures and 10-year change in plasma Abeta measures since midlife to late-life cognitive decline. Prospective study of a population-based sample. Academic research. Plasma Abeta40 and Abeta42 levels were measured in 481 Nurses' Health Study participants in late midlife (mean age, 63.6 years) and again 10 years later (mean age, 74.6 years). Cognitive testing also began 10 years after the initial blood draw. Participants completed 3 repeated telephone-based assessments (mean span, 4.1 years). Multivariable linear mixed-effects models were used to estimate relations of midlife plasma Abeta40 to Abeta42 ratios and Abeta42 levels to late-life cognitive decline, as well as relations of 10-year change in Abeta40 to Abeta42 ratios and Abeta42 levels to cognitive decline. The 3 primary outcomes were the Telephone Interview for Cognitive Status (TICS) findings, a global score averaging the results of all tests (TICS, immediate and delayed verbal recall, category fluency, and attention), and a verbal memory score averaging the results of 4 tests of verbal recall. Higher midlife plasma Abeta40 to Abeta42 ratios were associated with worse late-life decline on the global score (P = .04 for trend). Furthermore, increase in Abeta40 to Abeta42 ratios since midlife predicted greater decline in the global score (P = .03 for trend) and in the TICS (P = .02 for trend). There was no association of cognitive decline with midlife plasma Abeta42 levels alone or with change in Abeta42 levels since midlife. In this large community-dwelling sample, higher plasma Abeta40 to Abeta42 ratios in late midlife and increases in Abeta40 to Abeta42 ratios 10 years later were significantly associated with greater decline in global cognition at late life.

Loss of function of ATXN1 increases amyloid beta-protein levels by potentiating beta-secretase processing of beta-amyloid precursor protein.

PubMed

Zhang, Can; Browne, Andrew; Child, Daniel; Divito, Jason R; Stevenson, Jesse A; Tanzi, Rudolph E

2010-03-19

Alzheimer disease (AD) is a devastating neurodegenerative disease with complex and strong genetic inheritance. Four genes have been established to either cause familial early onset AD (APP, PSEN1, and PSEN2) or to increase susceptibility for late onset AD (APOE). To date approximately 80% of the late onset AD genetic variance remains elusive. Recently our genome-wide association screen identified four novel late onset AD candidate genes. Ataxin 1 (ATXN1) is one of these four AD candidate genes and has been indicated to be the disease gene for spinocerebellar ataxia type 1, which is also a neurodegenerative disease. Mounting evidence suggests that the excessive accumulation of Abeta, the proteolytic product of beta-amyloid precursor protein (APP), is the primary AD pathological event. In this study, we ask whether ATXN1 may lead to AD pathogenesis by affecting Abeta and APP processing utilizing RNA interference in a human neuronal cell model and mouse primary cortical neurons. We show that knock-down of ATXN1 significantly increases the levels of both Abeta40 and Abeta42. This effect could be rescued with concurrent overexpression of ATXN1. Moreover, overexpression of ATXN1 decreased Abeta levels. Regarding the underlying molecular mechanism, we show that the effect of ATXN1 expression on Abeta levels is modulated via beta-secretase cleavage of APP. Taken together, ATXN1 functions as a genetic risk modifier that contributes to AD pathogenesis through a loss-of-function mechanism by regulating beta-secretase cleavage of APP and Abeta levels.

Islet immunity and beta cell reserve of indigenous Black South Africans with ketoacidosis at initial diagnosis of diabetes.

PubMed

Ekpebegh, Chukwuma; Longo-Mbenza, Benjamin; Blanco-Blanco, Ernesto

2013-01-01

Islet immunity and beta cell reserve status were utilized to classify persons with ketoacidosis as the initial manifestation of diabetes. The clinical features of the various diabetes classes were also characterized. Prospective cross sectional study. Nelson Mandela Academic Hospital, Mthatha, Eastern Cape Province, South Africa. Indigenous Black South Africans with ketoacidosis as the initial manifestation of diabetes. Islet immunity and beta cell reserve were respectively assessed using serum anti-glutamic acid decarboxylase 65 (GAD) antibody and serum C-peptide after 1 mg of intravenous glucagon. Serum anti-GAD 65 antibody > or = 5 units/L and < 5 units/L, respectively defined anti-GAD 65 positive (A+) and negative (A-). Replete (beta+) and deplete (beta-) beta cell reserve were serum C-peptide after glucagon injection of > or = 0.5 ng/mL and < 0.5 ng/mL, respectively. The proportions of patients with A+beta-, A+beta+, A-beta- and A-beta+ and their clinical characteristics were determined. Of the 38 males and 33 females who participated in the study, patients were categorized in various classes: A-beta+, 46.5% (n=33/ 71); A-beta-, 26.8% (n=19/71); A+beta-, 22.5% (n=16/71); and A+beta+, 4.2% (n=3/71). The ages of the various classes were: 41.8 +/- 13.8 years for A-beta+ (n=33); 36.5 +/- 14.6 years for A-beta- (n=19); and 20.6 +/- 7.1 years for the combination of A+beta- with A+beta+ (n=19) (P<.0001, P<.0001 for the combination of A+beta- and A+beta+ vs A-beta+, P=.001 for the combination of A+beta- and A+beta+ vs A-beta-and P=.2 for A-beta- vs A-beta+. The clinical features of type 2 diabetes were most prevalent in A-beta+ class while the A+beta- and A+beta+ groups had the clinical profile of type 1A diabetes. Most of the indigenous Black South African patients with ketoacidosis as the initial manifestation of diabetes had islet immunity, beta cell reserve status and clinical profiles of type 2 diabetes.

Plasma antibodies to Abeta40 and Abeta42 in patients with Alzheimer's disease and normal controls.

PubMed

Xu, Wuhua; Kawarabayashi, Takeshi; Matsubara, Etsuro; Deguchi, Kentaro; Murakami, Tetsuro; Harigaya, Yasuo; Ikeda, Masaki; Amari, Masakuni; Kuwano, Ryozo; Abe, Koji; Shoji, Mikio

2008-07-11

Antibodies to amyloid beta protein (Abeta) are present naturally or after Abeta vaccine therapy in human plasma. To clarify their clinical role, we examined plasma samples from 113 patients with Alzheimer's disease (AD) and 205 normal controls using the tissue amyloid plaque immunoreactivity (TAPIR) assay. A high positive rate of TAPIR was revealed in AD (45.1%) and age-matched controls (41.2%), however, no significance was observed. No significant difference was observed in the MMS score or disease duration between TAPIR-positive and negative samples. TAPIR-positive plasma reacted with the Abeta40 monomer and dimer, and the Abeta42 monomer weakly, but not with the Abeta42 dimer. TAPIR was even detected in samples from young normal subjects and young Tg2576 transgenic mice. Although the Abeta40 level and Abeta40/42 ratio increased, and Abeta42 was significantly decreased in plasma from AD groups when compared to controls, no significant correlations were revealed between plasma Abeta levels and TAPIR grading. Thus an immune response to Abeta40 and immune tolerance to Abeta42 occurred naturally in humans without a close relationship to the Abeta burden in the brain. Clarification of the mechanism of the immune response to Abeta42 is necessary for realization of an immunotherapy for AD.

Filamentous bacteriophage as a novel therapeutic tool for Alzheimer's disease treatment.

PubMed

Solomon, Beka

2008-10-01

Antibodies towards the N-terminal region of the amyloid-beta peptide (AbetaP) bind to Abeta fibrils, leading to their disaggregation. We developed an immunization procedure using filamentous phages displaying the only four amino acids EFRH encompassing amino acids 3-6 of the 42 residues of AbetaP, found to be the main regulatory site for Abeta formation. Phages displaying EFRH epitope are effective in eliciting humoral response against AbetaP which, in turn, relieves amyloid burden in brains of amyloid-beta protein precursor transgenic mice, improving their ability to perform cognitive tasks. In order to overcome the low permeability of the blood brain barrier for targeting 'anti-aggregating' monoclonal antibodies (mAbs) to Abeta plaques in the brain, we applied antibody engineering methods to minimize the size of mAbs while maintaining their biological activity. Single-chain antibodies displayed on the surface of filamentous phage showed the ability to enter the central nervous system (CNS). The genetically engineered filamentous bacteriophage proved to be an efficient, nontoxic viral delivery vector to the brain, offering an obvious advantage over other mammalian vectors. The feasibility of these novel strategies for production and targeting of anti-aggregating antibodies against Abeta plaques to disease affected regions in the CNS may have clinical potential for treatment of Alzheimer's disease.

Pregnenolone protects the PC-12 cell line against amyloid beta peptide toxicity but its sulfate ester does not.

PubMed

Akan, Pinar; Kizildag, Servet; Ormen, Murat; Genc, Sermin; Oktem, Mehmet Ali; Fadiloglu, Meral

2009-01-15

Pregnenolone (P), the main precursor of the steroids, and its sulfate ester, pregnenolone sulfate (PS), are the major neurosteroids produced in the neural tissue. Many neuroendocrinological studies stressed the neuroprotective role of neurosteroids although it has been suggested that the inhibition of P and PS synthesis can delay neuronal cell death. The potential roles of P and PS in vital neuronal functions and in amyloid beta peptide (Abeta) toxicity are not clearly identified. This work aims to investigate the effects of P and PS on cell viability and Abeta peptide toxicity in a concentration and exposure time-dependent manner in rat PC-12 cells. The cells were treated with 20muM Abeta peptide 25-35 and variable concentrations of P and PS ranging from 0.5muM to 100muM. To examine the effects of steroid treatment on Abeta peptide toxicity, 0.5muM (low) and 50muM (high) neurosteroids were used. The cell viability and lactate dehydrogenase release of cells were evaluated after 24, 48 and 72h. Morphological changes of cells were also examined. The treatment with higher than 1muM concentrations of P and PS significantly decreased the cell viability comparing to untreated cells. At lower concentrations, P and PS had no toxic actions until 72h. The Abeta treatment resulted in a significant decrease in cell viability comparing to untreated cells. P showed a dose-dependent protective effect against Abeta peptide in PC-12 cells. But its sulfate ester did not have the same effect on Abeta peptide toxicity, even it significantly decreased cell viability in Abeta-treated cells. Consequently, the discrepant effects of P and PS on Abeta peptide toxicity may provide insight on the pathogenesis of Alzheimer's disease.

Amyloid beta-Cu2+ complexes in both monomeric and fibrillar forms do not generate H2O2 catalytically but quench hydroxyl radicals.

PubMed

Nadal, Rebecca C; Rigby, Stephen E J; Viles, John H

2008-11-04

Oxidative stress plays a key role in Alzheimer's disease (AD). In addition, the abnormally high Cu(2+) ion concentrations present in senile plaques has provoked a substantial interest in the relationship between the amyloid beta peptide (Abeta) found within plaques and redox-active copper ions. There have been a number of studies monitoring reactive oxygen species (ROS) generation by copper and ascorbate that suggest that Abeta acts as a prooxidant producing H2O2. However, others have indicated Abeta acts as an antioxidant, but to date most cell-free studies directly monitoring ROS have not supported this hypothesis. We therefore chose to look again at ROS generation by both monomeric and fibrillar forms of Abeta under aerobic conditions in the presence of Cu(2+) with/without the biological reductant ascorbate in a cell-free system. We used a variety of fluorescence and absorption based assays to monitor the production of ROS, as well as Cu(2+) reduction. In contrast to previous studies, we show here that Abeta does not generate any more ROS than controls of Cu(2+) and ascorbate. Abeta does not silence the redox activity of Cu(2+/+) via chelation, but rather hydroxyl radicals produced as a result of Fenton-Haber Weiss reactions of ascorbate and Cu(2+) rapidly react with Abeta; thus the potentially harmful radicals are quenched. In support of this, chemical modification of the Abeta peptide was examined using (1)H NMR, and specific oxidation sites within the peptide were identified at the histidine and methionine residues. Our studies add significant weight to a modified amyloid cascade hypothesis in which sporadic AD is the result of Abeta being upregulated as a response to oxidative stress. However, our results do not preclude the possibility that Abeta in an oligomeric form may concentrate the redox-active copper at neuronal membranes and so cause lipid peroxidation.

Brain aging in the canine: a diet enriched in antioxidants reduces cognitive dysfunction.

PubMed

Cotman, Carl W; Head, Elizabeth; Muggenburg, Bruce A; Zicker, S; Milgram, Norton W

2002-01-01

Animal models that simulate various aspects of human brain aging are an essential step in the development of interventions to manage cognitive dysfunction in the elderly. Over the past several years we have been studying cognition and neuropathology in the aged-canine (dog). Like humans, canines naturally accumulate deposits of beta-amyloid (Abeta) in the brain with age. Further, canines and humans share the same Abeta sequence and also first show deposits of the longer Abeta1-42 species followed by the deposition of Abeta1-40. Aged canines like humans also show increased oxidative damage. As a function of age, canines show impaired learning and memory on tasks similar to those used in aged primates and humans. The extent of Abeta deposition correlates with the severity of cognitive dysfunction in canines. To test the hypothesis that a cascade of mechanisms centered on oxidative damage and Abeta results in cognitive dysfunction we have evaluated the cognitive effects of an antioxidant diet in aged canines. The diet resulted in a significant improvement in the ability of aged but not young animals to acquire progressively more difficult learning tasks (e.g. oddity discrimination learning). The canine represent a higher animal model to study the earliest declines in the cognitive continuum that includes age associated memory impairments (AAMI) and mild cognitive impairment (MCI) observed in human aging. Thus, studies in the canine model suggest that oxidative damage impairs cognitive function and that antioxidant treatment can result in significant improvements, supporting the need for further human studies. Copyright 2002 Elsevier Science Inc.

Cholesterol is necessary both for the toxic effect of Abeta peptides on vascular smooth muscle cells and for Abeta binding to vascular smooth muscle cell membranes.

PubMed

Subasinghe, Supundi; Unabia, Sharon; Barrow, Colin J; Mok, Su San; Aguilar, Marie-Isabel; Small, David H

2003-02-01

Accumulation of beta amyloid (Abeta) in the brain is central to the pathogenesis of Alzheimer's disease. Abeta can bind to membrane lipids and this binding may have detrimental effects on cell function. In this study, surface plasmon resonance technology was used to study Abeta binding to membranes. Abeta peptides bound to synthetic lipid mixtures and to an intact plasma membrane preparation isolated from vascular smooth muscle cells. Abeta peptides were also toxic to vascular smooth muscle cells. There was a good correlation between the toxic effect of Abeta peptides and their membrane binding. 'Ageing' the Abeta peptides by incubation for 5 days increased the proportion of oligomeric species, and also increased toxicity and the amount of binding to lipids. The toxicities of various Abeta analogs correlated with their lipid binding. Significantly, binding was influenced by the concentration of cholesterol in the lipid mixture. Reduction of cholesterol in vascular smooth muscle cells not only reduced the binding of Abeta to purified plasma membrane preparations but also reduced Abeta toxicity. The results support the view that Abeta toxicity is a direct consequence of binding to lipids in the membrane. Reduction of membrane cholesterol using cholesterol-lowering drugs may be of therapeutic benefit because it reduces Abeta-membrane binding.

Curcumin decreases amyloid-beta peptide levels by attenuating the maturation of amyloid-beta precursor protein.

PubMed

Zhang, Can; Browne, Andrew; Child, Daniel; Tanzi, Rudolph E

2010-09-10

Alzheimer disease (AD) is a devastating neurodegenerative disease with no cure. The pathogenesis of AD is believed to be driven primarily by amyloid-beta (Abeta), the principal component of senile plaques. Abeta is an approximately 4-kDa peptide generated via cleavage of the amyloid-beta precursor protein (APP). Curcumin is a compound in the widely used culinary spice, turmeric, which possesses potent and broad biological activities, including anti-inflammatory and antioxidant activities, chemopreventative effects, and effects on protein trafficking. Recent in vivo studies indicate that curcumin is able to reduce Abeta-related pathology in transgenic AD mouse models via unknown molecular mechanisms. Here, we investigated the effects of curcumin on Abeta levels and APP processing in various cell lines and mouse primary cortical neurons. We show for the first time that curcumin potently lowers Abeta levels by attenuating the maturation of APP in the secretory pathway. These data provide a mechanism of action for the ability of curcumin to attenuate amyloid-beta pathology.

Somatostatin regulates brain amyloid beta peptide Abeta42 through modulation of proteolytic degradation.

PubMed

Saito, Takashi; Iwata, Nobuhisa; Tsubuki, Satoshi; Takaki, Yoshie; Takano, Jiro; Huang, Shu-Ming; Suemoto, Takahiro; Higuchi, Makoto; Saido, Takaomi C

2005-04-01

Expression of somatostatin in the brain declines during aging in various mammals including apes and humans. A prominent decrease in this neuropeptide also represents a pathological characteristic of Alzheimer disease. Using in vitro and in vivo paradigms, we show that somatostatin regulates the metabolism of amyloid beta peptide (Abeta), the primary pathogenic agent of Alzheimer disease, in the brain through modulating proteolytic degradation catalyzed by neprilysin. Among various effector candidates, only somatostatin upregulated neprilysin activity in primary cortical neurons. A genetic deficiency of somatostatin altered hippocampal neprilysin activity and localization, and increased the quantity of a hydrophobic 42-mer form of Abeta, Abeta(42), in a manner similar to presenilin gene mutations that cause familial Alzheimer disease. These results indicate that the aging-induced downregulation of somatostatin expression may be a trigger for Abeta accumulation leading to late-onset sporadic Alzheimer disease, and suggest that somatostatin receptors may be pharmacological-target candidates for prevention and treatment of Alzheimer disease.

Surfaces modulate beta-amyloid peptide aggregation associated with Alzheimer's disease

NASA Astrophysics Data System (ADS)

Yates, Elizabeth Anne

A hallmark of Alzheimer's disease, a late onset neurodegenerative disease, is the presence of neuritic amyloid plaques deposited within the brain composed of beta-amyloid (Abeta) peptide aggregates. Abeta can aggregate into a variety of polymorphic aggregate structures under different chemical environments, specifically affected by the presence of differing surfaces. There are several point mutations clustered around the central hydrophobic core of Abeta (E22G Arctic mutation, E22K Italian mutation, D23N Iowa mutation, and A21G Flemish mutation). These mutations are associated with hereditary diseases ranging from almost pure cerebral amyloid angiopathy to typical Alzheimer's disease pathology with both plaques and tangles. To determine how these different point mutations, which modify both peptide charge and hydrophobic character, altered Abeta aggregation and morphology under free solution conditions, at an anionic surface/liquid interface and in the presence of supported lipid bilayers, atomic force microscopy was used. Additionally, the non-native conformation of Abeta leads to the formation of nanoscale, toxic aggregates which have been shown to strongly interact with supported lipid bilayers, which may represent a key step in potential toxic mechanisms. Understanding how specific regions of Abeta regulate its aggregation in the absence and presence of surfaces can provide insight into the fundamental interaction of Abeta with cellular surfaces. Specific fragments of Abeta (Abeta1-11, Abeta 1-28, Abeta10-26, Abeta12-24, Abeta 16-22, Abeta22-35, and Abeta1-40), represent a variety of chemically unique regions along Abeta, i.e., the extracellular domain, the central hydrophobic core, and transmembrane domain. Using various scanning probe microscopic techniques, the interaction of these Abeta sequences with lipid membranes was shown to alter aggregate morphology and induce mechanical changes of lipid bilayers compared to aggregates formed under free solution conditions. Lastly, in order to determine how chemical environment can lead to distinct polymorph fibril formation influencing disease pathology, various peptide preparation and fibril growth conditions of Abeta were studied in free solution and with a model lipid membrane.

Modulation of the humoral and cellular immune response in Abeta immunotherapy by the adjuvants monophosphoryl lipid A (MPL), cholera toxin B subunit (CTB) and E. coli enterotoxin LT(R192G).

PubMed

Maier, Marcel; Seabrook, Timothy J; Lemere, Cynthia A

2005-10-25

Abeta vaccination or passive transfer of human-specific anti-Abeta antibodies are approaches under investigation to prevent and/or treat Alzheimer's disease (AD). Successful active Abeta vaccination requires a strong and safe adjuvant to induce anti-Abeta antibody formation. We compared the adjuvants monophosphoryl lipid A (MPL)/trehalose dicorynomycolate (TDM), cholera toxin B subunit (CTB) and Escherichia coli heat-labile enterotoxin LT(R192G) for their ability to induce a humoral and cellular immune reaction, using fibrillar Abeta1-40/42 as a common immunogen in wildtype B6D2F1 mice. Subcutaneous (s.c.) administration with MPL/TDM resulted in anti-Abeta antibodies levels up to four times higher compared to s.c. LT(R192G). Using MPL/TDM, the anti-Abeta antibodies induced were mainly IgG2b, IgG1 and lower levels of IgG2a and IgM, with a moderate splenocyte proliferation and IFN-gamma production in vitro upon stimulation with Abeta1-40/42. LT(R192G), previously shown by us to induce robust titers of anti-Abeta antibodies, generated predominantly IgG2b and IgG1 anti-Abeta antibodies with very low splenocyte proliferation and IFN-gamma production. Weekly intranasal (i.n.) administration over 11 weeks of Abeta40/42 with CTB induced only moderate levels of antibodies. All immunogens generated antibodies that recognized mainly the Abeta1-7 epitope and specifically detected amyloid plaques on AD brain sections. In conclusion, MPL/TDM, in addition to LT(R192G), is an effective adjuvant when combined with Abeta40/42 and may aid in the design of Abeta immunotherapy.

Transthyretin Protects against A-Beta Peptide Toxicity by Proteolytic Cleavage of the Peptide: A Mechanism Sensitive to the Kunitz Protease Inhibitor

PubMed Central

Costa, Rita; Ferreira-da-Silva, Frederico; Saraiva, Maria J.; Cardoso, Isabel

2008-01-01

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the deposition of amyloid β-peptide (A-Beta) in the brain. Transthyretin (TTR) is a tetrameric protein of about 55 kDa mainly produced in the liver and choroid plexus of the brain. The known physiological functions of TTR are the transport of thyroid hormone T4 and retinol, through binding to the retinol binding protein. TTR has also been established as a cryptic protease able to cleave ApoA-I in vitro. It has been described that TTR is involved in preventing A-Beta fibrilization, both by inhibiting and disrupting A-Beta fibrils, with consequent abrogation of toxicity. We further characterized the nature of the TTR/A-Beta interaction and found that TTR, both recombinant or isolated from human sera, was able to proteolytically process A-Beta, cleaving the peptide after aminoacid residues 1, 2, 3, 10, 13, 14,16, 19 and 27, as determined by mass spectrometry, and reversed phase chromatography followed by N-terminal sequencing. A-Beta peptides (1–14) and (15–42) showed lower amyloidogenic potential than the full length counterpart, as assessed by thioflavin binding assay and ultrastructural analysis by transmission electron microscopy. A-Beta cleavage by TTR was inhibited in the presence of an αAPP peptide containing the Kunitz Protease Inhibitor (KPI) domain but not in the presence of the secreted αAPP derived from the APP isoform 695 without the KPI domain. TTR was also able to degrade aggregated forms of A-Beta peptide. Our results confirmed TTR as a protective molecule in AD, and prompted A-Beta proteolysis by TTR as a protective mechanism in this disease. TTR may prove to be a useful therapeutic agent for preventing or retarding the cerebral amyloid plaque formation implicated in AD pathology. PMID:18682830

Cholesterol accelerates the binding of Alzheimer's β-amyloid peptide to ganglioside GM1 through a universal hydrogen-bond-dependent sterol tuning of glycolipid conformation

PubMed Central

Fantini, Jacques; Yahi, Nouara; Garmy, Nicolas

2013-01-01

Age-related alterations of membrane lipids in brain cell membranes together with high blood cholesterol are considered as major risk factors for Alzheimer's disease. Yet the molecular mechanisms by which these factors increase Alzheimer's risk are mostly unknown. In lipid raft domains of the plasma membrane, neurotoxic Alzheimer's beta-amyloid (Abeta) peptides interact with both cholesterol and ganglioside GM1. Recent data also suggested that cholesterol could stimulate the binding of Abeta to GM1 through conformational modulation of the ganglioside headgroup. Here we used a combination of physicochemical and molecular modeling approaches to decipher the mechanisms of cholesterol-assisted binding of Abeta to GM1. With the aim of decoupling the effect of cholesterol on GM1 from direct Abeta-cholesterol interactions, we designed a minimal peptide (Abeta5-16) containing the GM1-binding domain but lacking the amino acid residues involved in cholesterol recognition. Using the Langmuir technique, we showed that cholesterol (but not phosphatidylcholine or sphingomyelin) significantly accelerates the interaction of Abeta5-16 with GM1. Molecular dynamics simulations suggested that Abeta5-16 interacts with a cholesterol-stabilized dimer of GM1. The main structural effect of cholesterol is to establish a hydrogen-bond between its own OH group and the glycosidic-bond linking ceramide to the glycone part of GM1, thereby inducing a tilt in the glycolipid headgroup. This fine conformational tuning stabilizes the active conformation of the GM1 dimer whose headgroups, oriented in two opposite directions, form a chalice-shaped receptacle for Abeta. These data give new mechanistic insights into the stimulatory effect of cholesterol on Abeta/GM1 interactions. They also support the emerging concept that cholesterol is a universal modulator of protein-glycolipid interactions in the broader context of membrane recognition processes. PMID:23772214

Identification of distinct physiochemical properties of toxic prefibrillar species formed by A{beta} peptide variants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goeransson, Anna-Lena, E-mail: anngo@ifm.liu.se; Nilsson, K. Peter R., E-mail: petni@ifm.liu.se; Kagedal, Katarina, E-mail: katarina.kagedal@liu.se

2012-04-20

Highlights: Black-Right-Pointing-Pointer Identification of toxic prefibrillar A{beta} species. Black-Right-Pointing-Pointer Fluorescence measurements using a combined set of fluorophores. Black-Right-Pointing-Pointer Morphology studies using transmission electron microscopy. -- Abstract: The formation of amyloid-{beta} peptide (A{beta}) aggregates at an early stage during the self-assembly process is an important factor in the development of Alzheimer's disease. The toxic effect is believed to be exerted by prefibrillar species of A{beta}. It is therefore important to identify which prefibrillar species are toxic and characterize their distinct properties. In the present study, we investigated the in vitro aggregation behavior of A{beta}-derived peptides possessing different levels of neurotoxic activity,more » using fluorescence spectroscopy in combination with transmission electron microscopy. The toxicity of various A{beta} aggregates was assessed by using cultures of human neuroblastoma cells. Through combined use of the fluorescence probe 8-anilino-1-napthalenesulfonate (ANS) and the novel luminescent probe pentamer formyl thiophene acetic acid (p-FTAA), we were able to identify those A{beta} peptide-derived prefibrillar species which exhibited cellular toxicity. In particular, species, which formed early during the aggregation process and showed strong p-FTAA and ANS fluorescence, were the species that possessed toxic activities. Moreover, by manipulating the aggregation conditions, it was possible to change the capacity of the A{beta} peptide to form nontoxic versus toxic species.« less

Detoxification depot for beta-amyloid peptides.

PubMed

Sundaram, Ranjini K; Kasinathan, Chinnaswamy; Stein, Stanley; Sundaram, Pazhani

2008-02-01

Alzheimer's Disease (AD) is caused by the deposition of insoluble and toxic amyloid peptides (Abeta) in the brain leading to memory loss and other associated neurodegenerative symptoms. To date there is limited treatment options and strategies for treating AD. Studies have shown that clearance of the amyloid plaques from the brain and thus from the blood could be effective in stopping and or delaying the progression of the disease. Small peptides derived from the Abeta-42 sequence, in particular KLVFF, have shown to be effective binders of Abeta peptides and thus could be useful in delaying progression of the disease. We have taken advantage of this property by generating the retro-inverso (RI) version of this peptide, ffvlk, in different formats. We are presenting a new detox gel system using poly ethylene glycol (PEG), polymerized and cross linked with the RI peptides. We hypothesize that detox gel incorporating RI peptides will act like a 'sink' to capture the Abeta peptides from the surrounding environment. We tested these detox gels for their ability to capture biotinylated Abeta-42 peptides in vitro. The results showed that the detox gels bound Abeta-42 peptides effectively and irreversibly. Gels incorporating the tetramer RI peptide exhibited maximum binding capacity. The detox gel could be a potential candidate for treatment strategies to deplete the brain of toxic amyloid peptides.

Uncaria rhynchophylla, a Chinese medicinal herb, has potent antiaggregation effects on Alzheimer's beta-amyloid proteins.

PubMed

Fujiwara, Hironori; Iwasaki, Koh; Furukawa, Katsutoshi; Seki, Takashi; He, Mei; Maruyama, Masahiro; Tomita, Naoki; Kudo, Yukitsuka; Higuchi, Makoto; Saido, Takaomi C; Maeda, Sumihiro; Takashima, Akihiko; Hara, Masahiko; Ohizumi, Yasushi; Arai, Hiroyuki

2006-08-01

Because the deposition of beta-amyloid protein (Abeta) is a consistent pathological hallmark of Alzheimer's disease (AD) brains, inhibition of Abeta generation, prevention of Abeta fibril formation, or destabilization of preformed Abeta fibrils would be attractive therapeutic strategies for the treatment of AD. We examined the effects of several medicinal herbs used in traditional Chinese medical formulae on the formation and destabilization of Abeta fibrils by using the thioflavin T binding assay, atomic force microscopic imaging, and electrophoresis. Our study demonstrates that several of these herbs have potent inhibitory effects on fibril formation of both Abeta(1-40) and Abeta(1-42) in concentration-dependent manners; in particular, Uncaria rhynchophylla inhibited Abeta aggregation most intensively. Significant destabilization of preformed Abeta(1-40) and Abeta(1-42) fibrils was also induced by Uncaria rhynchophylla as well as some other herb extracts. Three-dimensional HPLC analysis indicated that the water extract of this herb contains several different chemical compounds, including oxindole and indol alkaloids, which have been regarded as neuroprotective. Our results suggest that Uncaria rhynchophylla has remarkably inhibitory effects on the regulation of Abeta fibrils, and we conclude that this medicinal herb could have the potency to be a novel therapeutic agent to prevent and/or cure AD.

Non-fibrillar amyloid-{beta} peptide reduces NMDA-induced neurotoxicity, but not AMPA-induced neurotoxicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niidome, Tetsuhiro, E-mail: tniidome@pharm.kyoto-u.ac.jp; Goto, Yasuaki; Kato, Masaru

2009-09-04

Amyloid-{beta} peptide (A{beta}) is thought to be linked to the pathogenesis of Alzheimer's disease. Recent studies suggest that A{beta} has important physiological roles in addition to its pathological roles. We recently demonstrated that A{beta}42 protects hippocampal neurons from glutamate-induced neurotoxicity, but the relationship between A{beta}42 assemblies and their neuroprotective effects remains largely unknown. In this study, we prepared non-fibrillar and fibrillar A{beta}42 based on the results of the thioflavin T assay, Western blot analysis, and atomic force microscopy, and examined the effects of non-fibrillar and fibrillar A{beta}42 on glutamate-induced neurotoxicity. Non-fibrillar A{beta}42, but not fibrillar A{beta}42, protected hippocampal neurons frommore » glutamate-induced neurotoxicity. Furthermore, non-fibrillar A{beta}42 decreased both neurotoxicity and increases in the intracellular Ca{sup 2+} concentration induced by N-methyl-D-aspartate (NMDA), but not by {alpha}-amino-3-hydrozy-5-methyl-4-isoxazole propionic acid (AMPA). Our results suggest that non-fibrillar A{beta}42 protects hippocampal neurons from glutamate-induced neurotoxicity through regulation of the NMDA receptor.« less

Elucidation of interactions of Alzheimer amyloid beta peptides (Abeta40 and Abeta42) with insulin degrading enzyme: a molecular dynamics study.

PubMed

Bora, Ram Prasad; Prabhakar, Rajeev

2010-05-11

In this study, interactions of the two full-length Alzheimer amyloid beta peptides (Abeta40 and Abeta42) with the fully active form of insulin degrading enzyme (IDE) through unrestrained, all-atom MD simulations have been investigated. This enzyme is a Zn-containing metallopeptidase that catalyzes the degradation of the monomeric forms of these peptides, and this process is critical for preventing the progression of Alzheimer's disease (AD). The available X-ray structures of the free and small fragment-bound (Asp1-Glu3 and Lys16-Asp23 of Abeta40 and Asp1-Glu3 and Lys16-Glu22 of Abeta42) mutated forms of IDE and NMR structures of the full-length Abeta40 and Abeta42 have been used to build the starting structures for these simulations. The most representative structures derived from the Abeta40-IDE and Abeta42-IDE simulations accurately reproduced the locations of the active site Zn(2+) metal and small fragments of the substrates and their interactions with the enzyme from the X-ray structures. The remaining fragments of both the substrates were found to interact with IDE through several hydrogen bonding, pi-pi, CH-pi, and NH-pi interactions. In comparison to Abeta40, Abeta42 is more flexible and interacts through a smaller number (17-22) of hydrogen bonds in the catalytic chamber of IDE. Both the substrates adopted more beta-sheet character in the IDE environment, an observation that is in line with experiments. Their structural characteristics inside IDE are significantly different than the ones observed in aqueous solution. The atomistic level details provided by these simulations can help in the elucidation of binding and degrading mechanisms of the Abeta peptides by IDE.

Computational study of the binding of CuII to Alzheimer's amyloid-beta peptide: do Abeta42 and Abeta40 bind copper in identical fashion?

PubMed

Mantri, Yogita; Fioroni, Marco; Baik, Mu-Hyun

2008-11-01

One of the many hypotheses on the pathogenesis of Alzheimer's disease is that the amyloid-beta peptide (Abeta) binds CuII and can catalytically generate H2O2, leading to oxidative damage in brain tissues. For a molecular level understanding of such catalysis it is critical to know the structure of the Abeta-CuII complex precisely. Unfortunately, no high-resolution structure is available to date and there is considerable debate over the copper coordination environment with no clear consensus on which residues are directly bound to CuII. Considering all plausible isomers of the copper-bound Abeta42 and Abeta40 using a combination of density functional theory and classical molecular dynamics methods, we report an atomic resolution structure for each possible complex. We evaluated the relative energies of these isomeric structures and surprisingly found that Abeta42 and Abeta40 display very different binding modes, suggesting that shorter peptides that are truncated at the C-terminus may not be realistic models for understanding the chemistry of the most neurotoxic peptide, Abeta42.

Immunotherapy of Alzheimer's disease (AD): from murine models to anti-amyloid beta (Abeta) human monoclonal antibodies.

PubMed

Geylis, Valeria; Steinitz, Michael

2006-01-01

The deposition of amyloid beta (Abeta) protein is a key pathological feature in Alzheimer's disease (AD). In murine models of AD, both active and passive immunization against Abeta induce a marked reduction in amyloid brain burden and an improvement in cognitive functions. Preliminary results of a prematurely terminated clinical trial where AD patients were actively vaccinated with aggregated Abeta bear resemblance to those documented in murine models. Passive immunization of AD patients with anti-Abeta antibodies, in particular human antibodies, is a strategy that provides a more cautious management and control of any undesired side effects. Sera of all healthy adults contain anti-Abeta IgG autoimmune antibodies. Hence antigen-committed human B-cells are easily immortalized by Epstein-Barr virus (EBV) into anti-Abeta secreting cell lines. Two anti-Abeta human monoclonal antibodies which we recently prepared bind to the N-terminus of Abeta peptide and were shown to stain amyloid plaques in non-fixed brain sections from an AD patient. It is anticipated that specifically selected anti-Abeta human monoclonal antibodies could reduce and inhibit deposits of amyloid in brain while avoiding the cognitive decline that characterizes AD. In the future, this type of antibody may prove to be a promising immune therapy for the disease.

LRP in amyloid-beta production and metabolism.

PubMed

Bu, Guojun; Cam, Judy; Zerbinatti, Celina

2006-11-01

Amyloid-beta peptide (Abeta) production and accumulation in the brain is a central event in the pathogenesis of Alzheimer's disease (AD). Recent studies have shown that apolipoprotein E (apoE) receptors, members of the low-density lipoprotein receptor (LDLR) family, modulate Abeta production as well as Abeta cellular uptake. Abeta is derived from proteolytic processing of the amyloid precursor protein (APP), which interacts with several members of the LDLR family. Studies from our laboratory have focused on two members of the LDLR family, the LDLR-related protein (LRP) and LRP1B. Our in vitro studies have shown that while LRP's rapid endocytosis facilitates APP endocytic trafficking and processing to Abeta, LRP1B's slow endocytosis inhibits these processes. In addition to modulating APP endocytic trafficking, LRP's rapid endocytosis also facilitates Abeta cellular uptake by binding to Abeta either directly or via LRP ligands such as apoE. Our in vivo studies using transgenic mice have shown that overexpression of LRP in central nervous system (CNS) neurons increases soluble brain Abeta and this increase correlates with deficits in memory. Together our studies demonstrate that members of the LDLR family modulate APP processing and Abeta metabolism by several independent mechanisms. Understanding the pathways that modulate brain Abeta metabolism may enable the rational design of molecular medicine to treat AD.

M1 muscarinic agonists can modulate some of the hallmarks in Alzheimer's disease: implications in future therapy.

PubMed

Fisher, Abraham; Pittel, Zipora; Haring, Rachel; Bar-Ner, Nira; Kliger-Spatz, Michal; Natan, Niva; Egozi, Inbal; Sonego, Hagar; Marcovitch, Itzhak; Brandeis, Rachel

2003-01-01

M1 muscarinic receptors (M1 mAChRs) play a role in an apparent linkage of three major hallmarks of Alzheimer's disease (AD): beta-amyloid (Abeta) peptide; tau hyperphosphorylation and paired helical filaments (PHFs); and loss of cholinergic function conducive to cognitive impairments. We evaluated the M1 muscarinic agonists AF102B (Cevimeline, EVOXAC trade mark : prescribed for Sjøgren's syndrome), AF150(S), and AF267B on some of these hallmarks of AD. Activation of M1 mAChRs with these agonists leads, inter alia, to enhanced secretion of amyloid precursor protein (alpha-APP), (via alpha-secretase activation), to decreased Abeta (via gamma-secretase inhibition), and to inhibition of Abeta- and/or oxidative stress-induced cell death. In several animal models mimicking different aspects of AD, these drugs restored cognitive impairments, and in select cases induced a decrease in brain Abeta elevation, with a high safety margin, following po administration. Notably, in mice with small hippocampi, unlike rivastigmine and nicotine, AF150(S) and AF267B restored cognitive impairments also on escape latency in a Morris water maze paradigm, in reversal learning. Studies from other labs showed that AF102B and talsaclidine (another M1 agonist) decreased cerbrospinal fluid (CSF) Abeta in AD patients following chronic treatment, being the first reported drugs with such a profile. The clinical significance of these studies remains to be elucidated, yet based on in vivo (rabbits) and in vitro studies (cell cultures), our M1 agonists can decrease brain Abeta, owing to a novel and dual complementary effect (e.g., inhibition of gamma-secretase and activation of alpha-secretase). Remarkably, although M1 agonists can decrease CSF Abeta in AD patients, an increased AD-type pathology in Parkinson's disease was recently been associated with chronic antimuscarinic treatment. In another aspect, these agonists decreased tau hyperphosphorylation in vitro and in vivo. Notably, nicotinic agonists or cholinesterase inhibitors increased tau hyperphosphorylation. In summary, the M1 agonists tested are effective on cognition and behavior and show unique disease-modifying properties owing to beneficial effects on major hallmarks of AD. This may place such drugs in the first line of modern AD therapies (e.g., beta- or gamma-secretase inhibitors, vaccines against Abeta, statins, and inhibitors of tau hyperphosphorylation).

Review on the APP/PS1KI mouse model: intraneuronal Abeta accumulation triggers axonopathy, neuron loss and working memory impairment.

PubMed

Bayer, T A; Wirths, O

2008-02-01

Accumulating evidence points to an important role of intraneuronal Abeta as a trigger of the pathological cascade of events leading to neurodegeneration and eventually to Alzheimer's disease (AD) with its typical clinical symptoms, like memory impairment and change in personality. As a new concept, intraneuronal accumulation of Abeta instead of extracellular Abeta deposition has been introduced to be the disease-triggering event in AD. The present review compiles current knowledge on the amyloid precursor protein (APP)/PS1KI mouse model with early and massive intraneuronal Abeta42 accumulation: (1) The APP/PS1KI mouse model exhibits early robust brain and spinal cord axonal degeneration and hippocampal CA1 neuron loss. (2) At the same time-point, a dramatic, age-dependent reduced ability to perform working memory and motor tasks is observed. (3) The APP/PS1KI mice are smaller and show development of a thoracolumbar kyphosis, together with an incremental loss of body weight. (4) Onset of the observed behavioral alterations correlates well with robust axonal degeneration in brain and spinal cord and with abundant hippocampal CA1 neuron loss.

Syringin from stem bark of Fraxinus rhynchophylla protects Abeta(25-35)-induced toxicity in neuronal cells.

PubMed

Yang, Eun-Ju; Kim, Sang-In; Ku, Hyun-Yeong; Lee, Dong-Seok; Lee, Jong-Won; Kim, Yae-Sil; Seong, Yeon-Hee; Song, Kyung-Sik

2010-04-01

The medicinal herb Jinpi, derived from the dried stem barks of Fraxinus rhynchophylla belonging to Oleaceae is widely used as a variety of Korean folk remedies for anti-inflammatory, febricide, antidiarrhea, and antileukorrhea diseases. In the course of screening antidementia agents from natural products, F. rhynchophylla showed significant inhibitory activity toward Abeta(25-35)-induced neuronal cell death. An active principle was isolated and identified as syringin. When the neuroblastoma cells were exposed to 50 microM Abeta(25-35), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction rate (survival rate) decreased to 60.21 +/- 2.16% over control while syringin treated ones recovered cell viability up to 79.12 +/- 1.39% at 20 microM. In addition, 20 microM syringin almost completely removed Abeta(25-35)-induced reactive oxygen species. The neuroprotective effect of syringin seemed to be originated from the reduction of apoptosis since decrease in caspase-3 activity and expression, reduction in cleaved PARP, and DNA fragmentation were observed. These results suggest that F. rhynchophylla and syringin are expected to be useful for preventing Abeta(25-35)-induced neuronal cell damage.

Amyloid-beta aggregates formed at polar-nonpolar interfaces differ from amyloid-beta protofibrils produced in aqueous buffers.

PubMed

Nichols, Michael R; Moss, Melissa A; Reed, Dana Kim; Hoh, Jan H; Rosenberry, Terrone L

2005-07-01

The deposition of aggregated amyloid-beta (Abeta) peptides in the brain as senile plaques is a pathological hallmark of Alzheimer's disease (AD). Several lines of evidence indicate that fibrillar and, in particular, soluble aggregates of these 40- and 42-residue peptides are important in the etiology of AD. Recent studies also stress that amyloid aggregates are polymorphic and that a single polypeptide can fold into multiple amyloid conformations. Here we review our recent reports that Abeta(1-40) in vitro can form soluble aggregates with predominant beta-structures that differ in stability and morphology. One class of aggregates involved soluble Abeta protofibrils, prepared by vigorous overnight agitation of monomeric Abeta(1-40) in low ionic strength buffers. These aggregates were quite stable and disaggregated to only a limited extent on dilution. A second class of soluble Abeta aggregates was generated at polar-nonpolar interfaces. Aggregation in a two-phase system of buffer over chloroform occurred more rapidly than in buffer alone. In buffered 2% hexafluoroisopropanol (HFIP), microdroplets of HFIP were formed and the half-time for aggregation was less than 10 minutes. Like Abeta protofibrils, these interfacial aggregates showed increased thioflavin T fluorescence and were rich in beta-structure by circular dichroism. However, electron microscopy and atomic force microscopy revealed very different morphologies. The HFIP aggregates formed initial globular clusters that progressed over several days to soluble fibrous aggregates. When diluted out of HFIP these aggregates initially were very unstable and disaggregated completely within 2 minutes. However, their stability increased as they progressed to fibers. It is important to determine whether similar interfacial Abeta aggregates are produced in vivo.

A kinetic model for beta-amyloid adsorption at the air/solution interface and its implication to the beta-amyloid aggregation process.

PubMed

Jiang, Dianlu; Dinh, Kim Lien; Ruthenburg, Travis C; Zhang, Yi; Su, Lei; Land, Donald P; Zhou, Feimeng

2009-03-12

At the air/buffer solution interface the kinetics of adsorption of amyloid beta peptide, Abeta(1-42), whose bulk concentration (submicromolar) is more than 2 orders of magnitude lower than that typically used in other in vitro aggregation studies, has been studied using a Langmuir-Blodgett trough. The pressure-time curves exhibit a lag phase, wherein the surface pressure essentially remains at zero, and a rising phase, corresponding to the Abeta adsorption at the interface. The duration of the lag phase was found to be highly dependent on both the Abeta bulk concentration and the solution temperature. A large activation energy (62.2 +/- 4.1 KJ/mol) was determined and the apparent adsorption rate constant was found to be linearly dependent on the Abeta bulk concentration. Attenuated total reflection-IR spectra of the adsorbed Abeta transferred to a solid substrate and circular dichroism measurements of Abeta in the solution layer near the interface reveal that the natively unstructured Abeta in the bulk undergo a conformation change (folding) to mainly the alpha-helical structure. The results suggest that, prior to the adsorption step, an equilibrium between Abeta conformations is established within the subsurface. The kinetic equation derived from this model confirms that the overall Abeta adsorption is kinetically controlled and the apparent rate constant is proportional to the Abeta bulk concentration. This model also indicates that interfaces such as cell membranes and lipid bilayers may facilitate Abeta aggregation/ fibrillation by providing a thin hydrophobic layer adjacent to the interface for the initial A/beta conformation change (misfolding) and accumulation. Such a preconcentration effect offers a plausible explanation of the fact that Abeta fibrillation occurs in vivo at nanomolar concentrations. Another important biological implication from our work is that Abeta misfolding may occur before its adsorption onto a cell membrane. This general kinetic model should also find applications in adsorption studies of other types of biomolecules whose overall kinetics exhibits a lag phase that is dependent on the bulk concentration of the adsorbate.

Pathogenic prions deviate PrPC signaling in neuronal cells and impair A-beta clearance

PubMed Central

Pradines, E; Hernandez-Rapp, J; Villa-Diaz, A; Dakowski, C; Ardila-Osorio, H; Haik, S; Schneider, B; Launay, J-M; Kellermann, O; Torres, J-M; Mouillet-Richard, S

2013-01-01

The subversion of the normal function exerted by the cellular prion protein (PrPC) in neurons by pathogenic prions is assumed to have a central role in the pathogenesis of transmissible spongiform encephalopathies. Using two murine models of prion infection, the 1C11 neuronal cell line and neurospheres, we document that prion infection is associated with the constitutive activation of signaling targets normally coupled with PrPC, including the Fyn kinase, the mitogen-associated protein kinases ERK1/2 and the CREB transcription factor. PrPC-dependent signaling overactivation in infected cells is associated with the recruitment of p38 and JNK stress-associated kinases. Downstream from CREB, prion-infected cells exhibit reduced activity of the matrix metalloprotease (MMP)-9. As MMP-9 catalyzes the degradation of the amyloid A-beta peptide, the decrease in MMP-9 activity in prion-infected cells causes a significant impairment of the clearance of A-beta, leading to its accumulation. By exploiting two 1C11-infected clones accumulating high or moderate levels of prions, we show that the prion-induced changes are correlated with the level of infectivity. Of note, a dose-dependent increase in A-beta levels was also found in the cerebrospinal fluid of mice inoculated with these infected clones. By demonstrating that pathogenic prions trigger increases in A-beta levels through the deviation of PrPC signaling, our data argue that A-beta may exacerbate prion-induced toxicity. PMID:23303130

The metabolic enhancer piracetam ameliorates the impairment of mitochondrial function and neurite outgrowth induced by beta-amyloid peptide.

PubMed

Kurz, C; Ungerer, I; Lipka, U; Kirr, S; Schütt, T; Eckert, A; Leuner, K; Müller, W E

2010-05-01

beta-Amyloid peptide (Abeta) is implicated in the pathogenesis of Alzheimer's disease by initiating a cascade of events from mitochondrial dysfunction to neuronal death. The metabolic enhancer piracetam has been shown to improve mitochondrial dysfunction following brain aging and experimentally induced oxidative stress. We used cell lines (PC12 and HEK cells) and murine dissociated brain cells. The protective effects of piracetam in vitro and ex vivo on Abeta-induced impairment of mitochondrial function (as mitochondrial membrane potential and ATP production), on secretion of soluble Abeta and on neurite outgrowth in PC12 cells were investigated. Piracetam improves mitochondrial function of PC12 cells and acutely dissociated brain cells from young NMRI mice following exposure to extracellular Abeta(1-42). Similar protective effects against Abeta(1-42) were observed in dissociated brain cells from aged NMRI mice, or mice transgenic for mutant human amyloid precursor protein (APP) treated with piracetam for 14 days. Soluble Abeta load was markedly diminished in the brain of those animals after treatment with piracetam. Abeta production by HEK cells stably transfected with mutant human APP was elevated by oxidative stress and this was reduced by piracetam. Impairment of neuritogenesis is an important consequence of Abeta-induced mitochondrial dysfunction and Abeta-induced reduction of neurite growth in PC12 cells was substantially improved by piracetam. Our findings strongly support the concept of improving mitochondrial function as an approach to ameliorate the detrimental effects of Abeta on brain function.

Abeta1-42 Detection in CSF of Alzheimer's disease is influenced by temperature: indication of reversible Abeta1-42 aggregation?

PubMed

Sancesario, Giulia M; Esposito, Zaira; Nuccetelli, Marzia; Bernardini, Sergio; Sorge, Roberto; Martorana, Alessandro; Federici, Giorgio; Bernardi, Giorgio; Sancesario, Giuseppe

2010-06-01

Amyloid-beta 1-42 (Abeta1-42), peptide detectable in cerebrospinal fluid (CSF), has been extensively studied as diagnostic marker for Alzheimer's disease; however, results are variable. We investigated whether Abeta1-42 detection in CSF may be affected by handling temperature after lumbar puncture. CSF was collected from patients affected by probable AD (n=27), other dementias (OD) (n=24), or other neurological disorders without cognitive impairment (OND) (n=23). After lumbar puncture, CSF samples were either maintained at 37 degrees C, or handled according to standard procedures and centrifuged at 4 degrees C for 10 min; thereafter, one aliquot was further stored at 4 degrees C and another at 37 degrees C, before freezing all samples 90 min later at -80 degrees C, pending analysis. Abeta1-42 and total tau were determined using a commercially available sandwich enzyme-linked immunosorbent assay ELISA. Reduced Abeta1-42 and increased total tau CSF levels were confirmed as characteristic hallmarks of the OD and AD groups, providing standard measurement in samples stored at 4 degrees C before freezing. However, avoiding cooling or reheating CSF from 4 to 37 degrees C before freezing strikingly increased the Abeta1-42 concentration detectable in the AD group (P<0.01), but not in control groups. The results indicate that a pool of Abeta1-42 cannot be detectable in the CSF of AD patients, because standard preanalytical cooling masks in some ways the epitope recognized by Abeta1-42 specific antibodies. Moreover, our study suggests that low temperature could induce Abeta1-42 conformational changes and multimeric aggregates in probable AD, but, more importantly, Abeta1-42 aggregation could be reversible. Copyright (c) 2009 Elsevier Inc. All rights reserved.

Arginine vasopressin prevents against Abeta(25-35)-induced impairment of spatial learning and memory in rats.

PubMed

Pan, Yan-Fang; Chen, Xiao-Rong; Wu, Mei-Na; Ma, Cun-Gen; Qi, Jin-Shun

2010-04-01

Amyloid beta protein (Abeta) is thought to be responsible for loss of memory in Alzheimer's disease (AD). A significant decrease in [Arg(8)]-vasopressin (AVP) has been found in the AD brain and in plasma; however, it is unclear whether this decrease in AVP is involved in Abeta-induced impairment of spatial cognition and whether AVP can protect against Abeta-induced deficits in cognitive function. The present study examined the effects of intracerebroventricular (i.c.v.) injection of AVP on spatial learning and memory in the Morris water maze test and investigated the potential protective function of AVP against Abeta-induced impairment in spatial cognition. The results were as follows: (1) i.c.v. injection of 25 nmol Abeta(25-35) resulted in a significant decline in spatial learning and memory; (2) 1 nmol and 10 nmol, but not 0.1 nmol, AVP injections markedly improved learning and memory; (3) pretreatment with 1 nmol or 10 nmol, but not 0.1 nmol, AVP effectively reversed the impairment in spatial learning and memory induced by Abeta(25-35); and (4) none of the drugs, including Abeta(25-35) and different concentrations of AVP, affected the vision or swimming speed of the rats. These results indicate that Abeta(25-35) could significantly impair spatial learning and memory in rats, and pretreatment with AVP centrally can enhance spatial learning and effectively prevent the behavioral impairment induced by neurotoxic Abeta(25-35). Thus, the present study provides further insight into the mechanisms by which Abeta impairs spatial learning and memory, suggesting that up-regulation of central AVP might be beneficial in the prevention and treatment of AD. Copyright 2010 Elsevier Inc. All rights reserved.

Activation of mixed glia by Abeta-specific Th1 and Th17 cells and its regulation by Th2 cells.

PubMed

McQuillan, K; Lynch, Marina A; Mills, Kingston H G

2010-05-01

Microglia are innate immune cells of the CNS, that act as antigen-presenting cells (APC) for antigen-specific T cells and respond to inflammatory stimuli, such as amyloid-beta (Abeta), resulting in the release of neurotoxic factors and pro-inflammatory cytokines. Astrocytes can also act as APC and modulate the function of microglia. However, the role of distinct T cell subtypes, in particular Th17 cells, in glial activation and subsequent modulatory effects of Th2 cells are poorly understood. Here, we generated Abeta-specific Th1, Th2, and Th17 cells and examined their role in modulating Abeta-induced activation of microglia in a mixed glial culture, a preparation which mimics the complex APC types in the brain. We demonstrated that mixed glia acted as an effective APC for Abeta-specific Th1 and Th17 cells. Addition of Abeta-specific Th2 cells suppressed the Abeta-induced IFN-gamma production by Th1 cells and IL-17 production by Th17 cells with glia as the APC. Co-culture of Abeta-specific Th1 or Th17 cells with glia markedly enhanced Abeta-induced pro-inflammatory cytokine production and expression of MHC class II and co-stimulatory molecules on the microglia. Addition of Abeta-specific Th2 cells inhibited Th17 cell-induced IL-1beta and IL-6 production by mixed glia and attenuated Th1 cell-induced CD86 and CD40 expression on microglia. The modest enhancement of MHC class II and CD86 expression on astrocytes by Abeta-specific Th1 and Th17 was not attenuated by Th2 cells. These data indicate that Abeta-specific Th1 and Th17 cells induce inflammatory activation of glia, and that this is in part regulated by Th2 cells. Copyright 2010 Elsevier Inc. All rights reserved.

Dual response of BDNF to sublethal concentrations of beta-amyloid peptides in cultured cortical neurons.

PubMed

Aliaga, E; Silhol, M; Bonneau, N; Maurice, T; Arancibia, S; Tapia-Arancibia, L

2010-01-01

Beta-amyloid (Abeta) deposition is one important pathological hallmark in Alzheimer's disease (AD). However, low levels of Abeta may modify critical endogenous protection systems before neurodegeneration occurs. We examined the time-course effect of sublethal concentrations of Abeta on total BDNF (panBDNF), BDNF transcripts (I, II, IV and VI), trkB.FL, trkB.T1 and p75(NGFR) mRNA expression in cultured cortical neurons. We have shown that Abeta exhibited a dual response on BDNF mRNA, i.e. an increase at short times (3-5 h) and a dramatic decrease at longer times (24 or 48 h). The early increase in BDNF expression seems to be driven by increased expression of transcripts I and IV. The BDNF drop was specific since did not occur for other mRNAs examined. The BDNF protein content showed a similar profile but did not follow the dramatic reduction as its encoding mRNA. These observations may help to explain cognitive deficits observed at initial stages of AD.

Catalytic antibodies to amyloid beta peptide in defense against Alzheimer disease.

PubMed

Taguchi, Hiroaki; Planque, Stephanie; Nishiyama, Yasuhiro; Szabo, Paul; Weksler, Marc E; Friedland, Robert P; Paul, Sudhir

2008-05-01

Immunoglobulins (Igs) that bind amyloid beta peptide (Abeta) are under clinical trials for immunotherapy of Alzheimer disease (AD). We have identified IgMs and recombinant Ig fragments that hydrolyze Abeta. Hydrolysis of peripheral Abeta by the IgMs may induce increased Abeta release from the brain. The catalytic IgMs are increased in AD patients, presumably reflecting a protective autoimmune response. Reduced Abeta aggregation and neurotoxicity attributable to the catalytic function were evident. These findings provide a foundation for development of catalytic Igs for AD immunotherapy.

Gossypium herbaceam extracts inhibited NF-kappaB activation to attenuate spatial memory impairment and hippocampal neurodegeneration induced by amyloid-beta in rats.

PubMed

Ji, Chao; Aisa, Haji Akber; Yang, Nan; Li, Qing; Wang, Tao; Zhang, Ling; Qu, Kai; Zhu, Hai-Bo; Zuo, Ping-Ping

2008-07-01

Amyloid-beta (Abeta) is considered to be responsible for the pathogenesis of Alzheimer's disease. In the present study, the protective effect of Gossypium herbaceam extracts (GHE) on learning and memory impairment induced by Abeta were examined in vivo using Morris water maze and step through task. Furthermore, the antioxidant activity and neuroprotective effect of GHE was investigated with methods of histochemistry and biochemistry. These data showed that oral administration with GHE at the doses of 35, 70 and 140 mg/kg exerted an improved effect on the learning and memory impairment in rats induced by intracerebroventricular (i.c.v.) injection of 10 microg of Abeta(25-35). Subsequently, the GHE afforded a beneficial action on promotion on the activity of glutathione peroxidase and catalase, as well as inhibition on the NF-kappaB activation in the hippocampus followed by the presence of Abeta(25-35). Meanwhile, the number of degenerating neurons with an apoptotic feature was dramatically decreased in hippocampus after treatment with GHE, implicating that its antioxidant stress and inhibition of NF-kappaB activation could be involved in the mechanism underlying neuroprotection of GHE against Abeta-induced cell death. These findings suggested that GHE might be a potential agent for treatment of Alzheimer's disease.

Amyloid-beta aggregates cause alterations of astrocytic metabolic phenotype: impact on neuronal viability.

PubMed

Allaman, Igor; Gavillet, Mathilde; Bélanger, Mireille; Laroche, Thierry; Viertl, David; Lashuel, Hilal A; Magistretti, Pierre J

2010-03-03

Amyloid-beta (Abeta) peptides play a key role in the pathogenesis of Alzheimer's disease and exert various toxic effects on neurons; however, relatively little is known about their influence on glial cells. Astrocytes play a pivotal role in brain homeostasis, contributing to the regulation of local energy metabolism and oxidative stress defense, two aspects of importance for neuronal viability and function. In the present study, we explored the effects of Abeta peptides on glucose metabolism in cultured astrocytes. Following Abeta(25-35) exposure, we observed an increase in glucose uptake and its various metabolic fates, i.e., glycolysis (coupled to lactate release), tricarboxylic acid cycle, pentose phosphate pathway, and incorporation into glycogen. Abeta increased hydrogen peroxide production as well as glutathione release into the extracellular space without affecting intracellular glutathione content. A causal link between the effects of Abeta on glucose metabolism and its aggregation and internalization into astrocytes through binding to members of the class A scavenger receptor family could be demonstrated. Using astrocyte-neuron cocultures, we observed that the overall modifications of astrocyte metabolism induced by Abeta impair neuronal viability. The effects of the Abeta(25-35) fragment were reproduced by Abeta(1-42) but not by Abeta(1-40). Finally, the phosphoinositide 3-kinase (PI3-kinase) pathway appears to be crucial in these events since both the changes in glucose utilization and the decrease in neuronal viability are prevented by LY294002, a PI3-kinase inhibitor. This set of observations indicates that Abeta aggregation and internalization into astrocytes profoundly alter their metabolic phenotype with deleterious consequences for neuronal viability.

Probing energetics of Abeta fibril elongation by molecular dynamics simulations.

PubMed

Takeda, Takako; Klimov, Dmitri K

2009-06-03

Using replica exchange molecular dynamics simulations and an all-atom implicit solvent model, we probed the energetics of Abeta(10-40) fibril growth. The analysis of the interactions between incoming Abeta peptides and the fibril led us to two conclusions. First, considerable variations in fibril binding propensities are observed along the Abeta sequence. The peptides in the fibril and those binding to its edge interact primarily through their N-termini. Therefore, the mutations affecting the Abeta positions 10-23 are expected to have the largest impact on fibril elongation compared with those occurring in the C-terminus and turn. Second, we performed weak perturbations of the binding free energy landscape by scanning partial deletions of side-chain interactions at various Abeta sequence positions. The results imply that strong side-chain interactions--in particular, hydrophobic contacts--impede fibril growth by favoring disordered docking of incoming peptides. Therefore, fibril elongation may be promoted by moderate reduction of Abeta hydrophobicity. The comparison with available experimental data is presented.

Transgenic tomatoes expressing human beta-amyloid for use as a vaccine against Alzheimer's disease.

PubMed

Youm, Jung Won; Jeon, Jae Heung; Kim, Hee; Kim, Young Ho; Ko, Kisung; Joung, Hyouk; Kim, Hyunsoon

2008-10-01

Human beta-amyloid (Abeta) is believed to be one of the main components of Alzheimer's disease, so reduction of Abeta is considered a key therapeutic target. Using Agrobacterium-mediated nuclear transformation, we generated transgenic tomatoes for Abeta with tandem repeats. Integration of the human Abeta gene into the tomato genome and its transcription were detected by PCR and Northern blot, respectively. Expression of the Abeta protein was confirmed by western blot and ELISA, and then the transgenic tomato line expressing the highest protein level was selected for vaccination. Mice immunized orally with total soluble extracts from the transgenic tomato plants elicited an immune response after receiving a booster. The results indicate that tomato plants may provide a useful system for the production of human Abeta antigen.

Nanoparticle-mediated local and remote manipulation of protein aggregation.

PubMed

Kogan, Marcelo J; Bastus, Neus G; Amigo, Roger; Grillo-Bosch, Dolors; Araya, Eyleen; Turiel, Antonio; Labarta, Amilcar; Giralt, Ernest; Puntes, Victor F

2006-01-01

The local heat delivered by metallic nanoparticles selectively attached to their target can be used as a molecular surgery to safely remove toxic and clogging aggregates. We apply this principle to protein aggregates, in particular to the amyloid beta protein (Abeta) involved in Alzheimer's disease (AD), a neurodegenerative disease where unnaturally folded Abeta proteins self-assemble and deposit forming amyloid fibrils and plaques. We show the possibility to remotely redissolve these deposits and to interfere with their growth, using the local heat dissipated by gold nanoparticles (AuNP) selectively attached to the aggregates and irradiated with low gigahertz electromagnetic fields. Simultaneous tagging and manipulation by AuNP of Abeta at different stages of aggregation allow both, noninvasive exploration and dissolution of molecular aggregates.

Genetic variants in a haplotype block spanning IDE are significantly associated with plasma Abeta42 levels and risk for Alzheimer disease.

PubMed

Ertekin-Taner, Nilüfer; Allen, Mariet; Fadale, Daniel; Scanlin, Leah; Younkin, Linda; Petersen, Ronald C; Graff-Radford, Neill; Younkin, Steven G

2004-04-01

Risk for late onset Alzheimer disease (LOAD) and plasma amyloid beta levels (Abeta42; encoded by APP), an intermediate phenotype for LOAD, show linkage to chromosome 10q. Several strong candidate genes (VR22, PLAU, IDE) lie within the 1-lod support interval for linkage. Others have independently identified haplotypes in the chromosome 10q region harboring IDE that show highly significant association with intermediate AD phenotypes and with risk for AD. To pursue these associations, we analyzed the same haplotypes for association with plasma Abeta42 in 24 extended LOAD families and for association with LOAD in two independent case-control series. One series (MCR, 188 age-matched case-control pairs) did not show association (p=0.64) with the six haplotypes in the 276-kb region spanning three genes (IDE, KNSL1, and HHEX) previously shown to associate with LOAD. The other series (MCJ, 109 age-matched case-control pairs) showed significant (p=0.003) association with these haplotypes. In the MCJ series, the H4 (odds ratio [OR]=5.1, p=0.003) and H2(H7) haplotypes (OR=0.60, p=0.04) had the same effects previously reported. In this series, the H8 haplotype (OR=2.7, p=0.098) also had an effect similar as in one previous case control series but not in others. In the extended families, the H8 haplotype was associated with significantly elevated plasma Abeta42 (p=0.02). In addition, the H5(H10) haplotype, which is associated with reduced risk for AD in the other study is associated with reduced plasma Abeta42 (p=0.007) in our family series. These results provide strong evidence for pathogenic variant(s) in the 276-kb region harboring IDE that influence intermediate AD phenotypes and risk for AD. Copyright 2004 Wiley-Liss, Inc.

Chloride-dependency of amyloid beta protein-induced enhancement of glutamate neurotoxicity in cultured rat hippocampal neurons.

PubMed

Zhang, Nan-Yan; Kitagawa, Kaori; Wu, Bo; Xiong, Zheng-Mei; Otani, Hitomi; Inagaki, Chiyoko

2006-05-15

In our previous studies, pathophysiological concentrations of amyloid-beta (Abeta) proteins increased intracellular Cl(-) concentration ([Cl(-)]i) and enhanced glutamate neurotoxicity in primary cultured neurons, suggesting Cl(-)-dependent changes in glutamate signaling. To test this possibility, we examined the effects of isethionate-replaced low Cl(-) medium on the Abeta-induced enhancement of glutamate neurotoxicity in the primary cultured rat hippocampal neurons. In a normal Cl(-) (135 mM) medium, treatment with 10 nM Abeta25-35 for 2 days increased neuronal [Cl(-)]i to a level three times higher than that of control as assayed using a Cl(-)-sensitive fluorescent dye, while in a low Cl(-) (16 mM) medium such an Abeta25-35-induced increase in [Cl(-)]i was not observed. The Abeta treatment aggravated glutamate neurotoxicity in a normal Cl(-) medium as measured by mitochondrial reducing activity and lactate dehydrogenase (LDH) release, while in a low Cl(-) medium the Abeta treatment did not enhance glutamate toxicity. Upon such Abeta plus glutamate treatment under a normal Cl(-) condition, activated anti-apoptotic molecule Akt (Akt-pS473) level monitored by Western blot significantly decreased to 74% of control. Under a low Cl(-) condition, a resting Akt-pS473 level was higher than that under a normal Cl(-) condition and did not significantly change upon Abeta plus glutamate treatment. Tyrosine phosphorylation levels of 110 and 60 kDa proteins (pp110 and pp60) increased upon Abeta plus glutamate treatment under a normal Cl(-), but not low Cl(-), condition. These findings indicated that Abeta-induced enhancement of glutamate neurotoxicity is Cl(-)-dependent. Chloride-sensitive Akt pathway and tyrosine phosphorylation of proteins (pp110 and pp60) may be involved in this process.

New hydroxypyridinone iron-chelators as potential anti-neurodegenerative drugs.

PubMed

Arduino, Daniela; Silva, Daniel; Cardoso, Sandra M; Chaves, Silvia; Oliveira, Catarina R; Santos, M Amelia

2008-05-01

The neuroprotective action of a set of new hydroxypyridinone-based (3,4-HP) compounds (A, B and C), which are iron chelators extra-functionalized with a propargylamino group for potential MAO-B inhibition, was evaluated after cell treatment with MPP+ (an in vivo inducer of parkinsonism) and Abeta(1-40) and/or Abeta(1-42) peptides. Our results show that all these compounds improved cell viability in cells treated with MPP+ and Abeta(1-40) peptide or Abeta(1-42) peptide. In order to evaluate the cellular mechanisms underlying the activity of these compounds, we studied their protective role in caspase activation. All compounds tested were able to prevent MPP+ and Brefeldin A induced caspase-2 activation. They also showed quite effective in the inhibition of caspase-4 and caspase-3 activity, an effector caspase in the apoptotic process. Finally, detection of apoptotic-like cell death after cell exposure to MPP+ was also performed by TUNEL assay. Our results demonstrated that all tested compounds prevented DNA fragmentation by decreasing TUNEL positive cells. A, B and C were more effective than DFP (a 3,4-HP iron-chelating agent in clinical use) in MPP+ induced cell death. Therefore, these results evidenced a neuroprotective and antiapoptotic role for the compounds studied.

MALDI, AP/MALDI and ESI techniques for the MS detection of amyloid [beta]-peptides

NASA Astrophysics Data System (ADS)

Grasso, Giuseppe; Mineo, Placido; Rizzarelli, Enrico; Spoto, Giuseppe

2009-04-01

Amyloid [beta]-peptides (A[beta]s) are involved in several neuropathological conditions such as Alzheimer's disease and considerable experimental evidences have emerged indicating that different proteases play a major role in regulating the accumulation of A[beta]s in the brain. Particularly, insulin-degrading enzyme (IDE) has been shown to degrade A[beta]s at different cleavage sites, but the experimental results reported in the literature and obtained by mass spectrometry methods are somehow fragmentary. The detection of A[beta]s is often complicated by solubility issues, oxidation artifacts and spontaneous aggregation/cleavage and, in order to rationalize the different reported results, we analyzed A[beta]s solutions by three different MS approaches: matrix assisted laser desorption ionization-time of flight (MALDI-TOF), atmospheric pressure (AP) MALDI ion trap and electrospray ionization (ESI) ion trap. Differences in the obtained results are discussed and ESI is chosen as the most suitable MS method for A[beta]s detection. Finally, cleavage sites produced by interaction of A[beta]s with IDE are identified, two of which had never been reported in the literature.

False recognition correlates with amyloid-beta (1-42) but not with total tau in cerebrospinal fluid of patients with dementia and mild cognitive impairment.

PubMed

Hildebrandt, Helmut; Haldenwanger, Andreas; Eling, Paul

2009-01-01

Severe memory impairment forms the core symptom of Alzheimer's disease (AD), which is present early in the disease course. Recent studies show that AD patients not only suffer from forgetfulness, but also differ in their response bias, when having to decide whether information has been perceived recently, or whether it is only familiar or semantically related to perceived information. Changes in total tau-protein and amyloid-beta (Abeta) (1-42) concentration in cerebrospinal fluid are also features of AD, and they predict conversion from mild cognitive impairment to dementia. In this study we correlated recognition scores with total tau and Abeta (1-42) concentrations in patients with suggested dementia. We studied 40 patients and 21 healthy controls, using an incidental recognition memory task and a neuropsychological test battery. False recognition scores correlated with delayed recall and with Abeta(1-42), and Abeta (1-42) tended to correlate with delayed recall. Total tau, however, did not correlate with memory scores or with neuropsychological performance in general. We suggest that Abeta (1-42) may indicate a reduction in the specificity of the neuronal response in the limbic cortex, due to agglomeration of plaques. This process might be more specific for AD than the increase of tau, and therefore it is stronger correlated with recognition errors.

Increased T cell recruitment to the CNS after amyloid beta 1-42 immunization in Alzheimer's mice overproducing transforming growth factor-beta 1.

PubMed

Buckwalter, Marion S; Coleman, Bronwen S; Buttini, Manuel; Barbour, Robin; Schenk, Dale; Games, Dora; Seubert, Peter; Wyss-Coray, Tony

2006-11-01

Immunotherapy targeting the amyloid beta (Abeta) peptide is a novel therapy under investigation for the treatment of Alzheimer's disease (AD). A clinical trial using Abeta(1-42) (AN1792) as the immunogen was halted as a result of development of meningoencephalitis in a small number of patients. The cytokine TGF-beta1 is a key modulator of immune responses that is increased in the brain in AD. We show here that local overexpression of TGF-beta1 in the brain increases both meningeal and parenchymal T lymphocyte number. Furthermore, TGF-beta1 overexpression in a mouse model for AD [amyloid precursor protein (APP) mice] leads to development of additional T cell infiltrates when mice were immunized at a young but not old age with AN1792. Notably, only mice overproducing both Abeta (APP mice) and TGF-beta1 experienced a rise in T lymphocyte number after immunization. One-third of infiltrating T cells were CD4 positive. We did not observe significant differences in B lymphocyte numbers in any of the genotypes or treatment groups. These results demonstrate that TGF-beta1 overproduction in the brain can promote T cell infiltration, in particular after Abeta(1-42) immunization. Likewise, levels of TGF-beta1 or other immune factors in brains of AD patients may influence the response to Abeta(1-42) immunization.

Somatostatin, tau, and beta-amyloid within the anterior olfactory nucleus in Alzheimer disease.

PubMed

Saiz-Sanchez, D; Ubeda-Bañon, I; de la Rosa-Prieto, C; Argandoña-Palacios, L; Garcia-Muñozguren, S; Insausti, R; Martinez-Marcos, A

2010-06-01

Impaired olfaction is an early symptom of Alzheimer disease (AD). This likely to reflect neurodegenerative processes taking place in basal telencephalic structures that mediate olfactory processing, including the anterior olfactory nucleus. Betaeta-amyloid (Abeta) accumulation in AD brain may relate to decline in somatostatin levels: somatostatin induces the expression of the Abeta-degrading enzyme neprilysin and somatostatin deficiency in AD may therefore reduce Abeta clearance. We have investigated the expression of somatostatin in the anterior olfactory nucleus of AD and control brain. We report that somatostatin levels were reduced by approximately 50% in AD brain. Furthermore, triple-immunofluorescence revealed co-localization of somatostatin expression with Abeta (65.43%) with Abeta and tau (19.75%) and with tau (2.47%). These data indicate that somatostatin decreases in AD and its expression may be linked with Abeta deposition. Copyright (c) 2009 Elsevier Inc. All rights reserved.

IMPY: an improved thioflavin-T derivative for in vivo labeling of beta-amyloid plaques.

PubMed

Kung, Mei-Ping; Hou, Catherine; Zhuang, Zhi-Ping; Zhang, Bin; Skovronsky, Daniel; Trojanowski, John Q; Lee, Virginia M-Y; Kung, Hank F

2002-11-29

Development of small molecular probes for in vivo labeling and detection of beta-amyloid (Abeta) plaques in patients of Alzheimer's disease (AD) is of significant scientific interest, and it may also assist the development of drugs targeting Abeta plaques for treatment of AD. A novel probe, [123I/(125)I]IMPY, 6-iodo-2-(4'-dimethylamino-)phenyl-imidazo[1,2-a]pyridine, was successfully prepared with an iododestannylation reaction catalyzed by hydrogen peroxide. The modified thioflavin-T derivative displayed a good binding affinity for preformed synthetic Abeta40 aggregates in solution (K(i)=15+/-5 nM) and showed selective plaque labeling on postmortem AD brain sections. Biodistribution study in normal mice after an iv injection of [125I]IMPY exhibited excellent brain uptake (2.9% initial dose/brain at 2 min) and fast washout (0.2% initial dose/brain at 60 min). These properties are highly desirable for amyloid plaque imaging agents. In vivo plaque labeling was evaluated in a transgenic mouse model (Tg2576) engineered to produce excess amyloid plaques in the brain. Ex vivo autoradiograms of brain sections of the Tg 2576 mouse obtained at 4 h after an i.v. injection of [125I]IMPY clearly displayed a distinct plaque labeling with a low background activity. When the same brain section was stained with a fluorescent dye, thioflavin-S, the same Abeta plaques showed prominent fluorescent labeling consistent with the results of the autoradiogram. In conclusion, these findings clearly suggest that radioiodinated IMPY demonstrates desirable characteristics for in vivo labeling of Abeta plaques and it may be useful as a molecular imaging agent to study amyloidogenesis in the brain of living AD patients. Copyright 2002 Elsevier Science B.V.

Abnormality of G-protein-coupled receptor kinases at prodromal and early stages of Alzheimer's disease: an association with early beta-amyloid accumulation.

PubMed

Suo, Zhiming; Wu, Min; Citron, Bruce A; Wong, Gwendolyn T; Festoff, Barry W

2004-03-31

Overwhelming evidence indicates that the effects of beta-amyloid (Abeta) are dose dependent both in vitro and in vivo, which implies that Abeta is not directly detrimental to brain cells until it reaches a threshold concentration. In an effort to understand early Alzheimer's disease (AD) pathogenesis, this study focused on the effects of subthreshold soluble Abeta and the underlying molecular mechanisms in murine microglial cells and an AD transgenic mouse model. We found that there were two phases of dose-dependent Abeta effects on microglial cells: at the threshold of 5 microm and above, Abeta directly induced tumor necrosis factor-alpha (TNF-alpha) release, and at subthreshold doses, Abeta indirectly potentiated TNF-alpha release induced by certain G-protein-coupled receptor (GPCR) activators. Mechanistic studies revealed that subthreshold Abeta pretreatment in vitro reduced membrane GPCR kinase-2/5 (GRK2/5), which led to retarded GPCR desensitization, prolonged GPCR signaling, and cellular hyperactivity to GPCR agonists. Temporal analysis in an early-onset AD transgenic model, CRND8 mice, revealed that the membrane (functional) GRK2/5 in brain cortices were significantly reduced. More importantly, such a GRK abnormality took place before cognitive decline and changed in a manner corresponding with the mild to moderate soluble Abeta accumulation in these transgenic mice. Together, this study not only discovered a novel link between subthreshold Abeta and GRK dysfunction, it also demonstrated that the GRK abnormality in vivo occurs at prodromal and early stages of AD.

Zinc-Amyloid Interactions on a Millisecond Time-Scale Stabilize Non-Fibrillar Alzheimer Related Species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noy,D.; Solomonov, I.; Sinkevich, O.

2008-01-01

The role of zinc, an essential element for normal brain function, in the pathology of Alzheimer's disease (AD) is poorly understood. On one hand, physiological and genetic evidence from transgenic mouse models supports its pathogenic role in promoting the deposition of the amyloid {beta}-protein (A{beta}) in senile plaques. On the other hand, levels of extracellular ('free') zinc in the brain, as inferred by the levels of zinc in cerebrospinal fluid, were found to be too low for inducing A{beta} aggregation. Remarkably, the release of transient high local concentrations of zinc during rapid synaptic events was reported. The role of suchmore » free zinc pulses in promoting A{beta} aggregation has never been established. Using a range of time-resolved structural and spectroscopic techniques, we found that zinc, when introduced in millisecond pulses of micromolar concentrations, immediately interacts with A{beta} 1-40 and promotes its aggregation. These interactions specifically stabilize non-fibrillar pathogenic related aggregate forms and prevent the formation of A{beta} fibrils (more benign species) presumably by interfering with the self-assembly process of A{beta}. These in vitro results strongly suggest a significant role for zinc pulses in A{beta} pathology. We further propose that by interfering with A{beta} self-assembly, which leads to insoluble, non-pathological fibrillar forms, zinc stabilizes transient, harmful amyloid forms. This report argues that zinc represents a class of molecular pathogens that effectively perturb the self-assembly of benign A{beta} fibrils, and stabilize harmful non-fibrillar forms.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jiying; Ohno-Matsui, Kyoko, E-mail: k.ohno.oph@tmd.ac.jp; Morita, Ikuo

Highlights: Black-Right-Pointing-Pointer Cholesterol-treated RPE produces more A{beta} than non-treated RPE. Black-Right-Pointing-Pointer Neprilysin expression and activity decreased in cholesterol-treated RPE. Black-Right-Pointing-Pointer {alpha}-Secretase expression and activity decreased in cholesterol-treated RPE. Black-Right-Pointing-Pointer Cholesterol-enriched diet induced subRPE deposits in aged mice. Black-Right-Pointing-Pointer A{beta} were present in cholesterol-enriched-diet-induced subRPE deposits in aged mice. -- Abstract: Subretinally-deposited amyloid {beta} (A{beta}) is a main contributor of developing age-related macular degeneration (AMD). However, the mechanism causing A{beta} deposition in AMD eyes is unknown. Hypercholesterolemia is a significant risk for developing AMD. Thus, we investigated the effects of cholesterol on A{beta} production in retinal pigment epithelial (RPE) cells inmore » vitro and in the mouse retina in vivo. RPE cells isolated from senescent (12-month-old) C57BL/6 mice were treated with 10 {mu}g/ml cholesterol for 48 h. A{beta} amounts in culture supernatants were measured by ELISA. Activity and expression of enzymes and proteins that regulate A{beta} production were examined by activity assay and real time PCR. The retina of mice fed cholesterol-enriched diet was examined by transmission electron microscopy. Cholesterol significantly increased A{beta} production in cultured RPE cells. Activities of A{beta} degradation enzyme; neprilysin (NEP) and anti-amyloidogenic secretase; {alpha}-secretase were significantly decreased in cell lysates of cholesterol-treated RPE cells compared to non-treated cells, but there was no change in the activities of {beta}- or {gamma}-secretase. mRNA levels of NEP and {alpha}-secretase (ADAM10 and ADAM17) were significantly lower in cholesterol-treated RPE cells than non-treated cells. Senescent (12-month-old) mice fed cholesterol-enriched chow developed subRPE deposits containing A{beta}, whereas age-matched mice fed standard rodent chow diet did not. Activities and mRNA levels of NEP and {alpha}-secretase were significantly lower in native RPE cells freshly isolated from cholesterol-enriched chow fed mice compared to standard rodent chow fed mice. These findings suggest that cholesterol enhances subretinal A{beta} accumulation by modulating the activities of enzymes degrading and processing A{beta} in RPE cells in senescent subjects.« less

Abeta-degrading enzymes in Alzheimer's disease.

PubMed

Miners, James Scott; Baig, Shabnam; Palmer, Jennifer; Palmer, Laura E; Kehoe, Patrick G; Love, Seth

2008-04-01

In Alzheimer's disease (AD) Abeta accumulates because of imbalance between the production of Abeta and its removal from the brain. There is increasing evidence that in most sporadic forms of AD, the accumulation of Abeta is partly, if not in some cases solely, because of defects in its removal--mediated through a combination of diffusion along perivascular extracellular matrix, transport across vessel walls into the blood stream and enzymatic degradation. Multiple enzymes within the central nervous system (CNS) are capable of degrading Abeta. Most are produced by neurons or glia, but some are expressed in the cerebral vasculature, where reduced Abeta-degrading activity may contribute to the development of cerebral amyloid angiopathy (CAA). Neprilysin and insulin-degrading enzyme (IDE), which have been most extensively studied, are expressed both neuronally and within the vasculature. The levels of both of these enzymes are reduced in AD although the correlation with enzyme activity is still not entirely clear. Other enzymes shown capable of degrading Abetain vitro or in animal studies include plasmin; endothelin-converting enzymes ECE-1 and -2; matrix metalloproteinases MMP-2, -3 and -9; and angiotensin-converting enzyme (ACE). The levels of plasmin and plasminogen activators (uPA and tPA) and ECE-2 are reported to be reduced in AD. Reductions in neprilysin, IDE and plasmin in AD have been associated with possession of APOEepsilon4. We found no change in the level or activity of MMP-2, -3 or -9 in AD. The level and activity of ACE are increased, the level being directly related to Abeta plaque load. Up-regulation of some Abeta-degrading enzymes may initially compensate for declining activity of others, but as age, genetic factors and diseases such as hypertension and diabetes diminish the effectiveness of other Abeta-clearance pathways, reductions in the activity of particular Abeta-degrading enzymes may become critical, leading to the development of AD and CAA.

Cerebral amyloid-beta protein accumulation with aging in cotton-top tamarins: a model of early Alzheimer's disease?

PubMed

Lemere, Cynthia A; Oh, Jiwon; Stanish, Heather A; Peng, Ying; Pepivani, Imelda; Fagan, Anne M; Yamaguchi, Haruyasu; Westmoreland, Susan V; Mansfield, Keith G

2008-04-01

Alzheimer's disease (AD) is the most common progressive form of dementia in the elderly. Two major neuropathological hallmarks of AD include cerebral deposition of amyloid-beta protein (Abeta) into plaques and blood vessels, and the presence of neurofibrillary tangles in brain. In addition, activated microglia and reactive astrocytes are often associated with plaques and tangles. Numerous other proteins are associated with plaques in human AD brain, including Apo E and ubiquitin. The amyloid precursor protein and its shorter fragment, Abeta, are homologous between humans and non-human primates. Cerebral Abeta deposition has been reported previously for rhesus monkeys, vervets, squirrel monkeys, marmosets, lemurs, cynomologous monkeys, chimpanzees, and orangutans. Here we report, for the first time, age-related neuropathological changes in cotton-top tamarins (CTT, Saguinus oedipus), an endangered non-human primate native to the rainforests of Colombia and Costa Rica. Typical lifespan is 13-14 years of age in the wild and 15-20+ years in captivity. We performed detailed immunohistochemical analyses of Abeta deposition and associated pathogenesis in archived brain sections from 36 tamarins ranging in age from 6-21 years. Abeta plaque deposition was observed in 16 of the 20 oldest tamarins (>12 years). Plaques contained mainly Abeta42, and in the oldest animals, were associated with reactive astrocytes, activated microglia, Apo E, and ubiquitin-positive dystrophic neurites, similar to human plaques. Vascular Abeta was detected in 14 of the 20 aged tamarins; Abeta42 preceded Abeta40 deposition. Phospho-tau labeled dystrophic neurites and tangles, typically present in human AD, were absent in the tamarins. In conclusion, tamarins may represent a model of early AD pathology.

Mitochondria-targeted antioxidants protect against amyloid-beta toxicity in Alzheimer's disease neurons.

PubMed

Manczak, Maria; Mao, Peizhong; Calkins, Marcus J; Cornea, Anda; Reddy, Arubala P; Murphy, Michael P; Szeto, Hazel H; Park, Byung; Reddy, P Hemachandra

2010-01-01

The purpose of our study was to investigate the effects of the mitochondria-targeted antioxidants, MitoQ and SS31, and the anti-aging agent resveratrol on neurons from a mouse model (Tg2576 line) of Alzheimer's disease (AD) and on mouse neuroblastoma (N2a) cells incubated with the amyloid-beta (Abeta) peptide. Using electron and confocal microscopy, gene expression analysis, and biochemical methods, we studied mitochondrial structure and function and neurite outgrowth in N2a cells treated with MitoQ, SS31, and resveratrol, and then incubated with Abeta. In N2a cells only incubated with the Abeta, we found increased expressions of mitochondrial fission genes and decreased expression of fusion genes and also decreased expression of peroxiredoxins. Electron microscopy of the N2a cells incubated with Abeta revealed a significantly increased number of mitochondria, indicating that Abeta fragments mitochondria. Biochemical analysis revealed that function is defective in mitochondria. Neurite outgrowth was significantly decreased in Abeta-incubated N2a cells, indicating that Abeta affects neurite outgrowth. However, in N2a cells treated with MitoQ, SS31, and resveratrol, and then incubated with Abeta, abnormal expression of peroxiredoxins and mitochondrial structural genes were prevented and mitochondrial function was normal; intact mitochondria were present and neurite outgrowth was significantly increased. In primary neurons from amyloid-beta precursor protein transgenic mice that were treated with MitoQ and SS31, neurite outgrowth was significantly increased and cyclophilin D expression was significantly decreased. These findings suggest that MitoQ and SS31 prevent Abeta toxicity, which would warrant the study of MitoQ and SS31 as potential drugs to treat patients with AD.

Amyloid precursor protein-induced axonopathies are independent of amyloid-beta peptides.

PubMed

Stokin, Gorazd B; Almenar-Queralt, Angels; Gunawardena, Shermali; Rodrigues, Elizabeth M; Falzone, Tomás; Kim, Jungsu; Lillo, Concepción; Mount, Stephanie L; Roberts, Elizabeth A; McGowan, Eileen; Williams, David S; Goldstein, Lawrence S B

2008-11-15

Overexpression of amyloid precursor protein (APP), as well as mutations in the APP and presenilin genes, causes rare forms of Alzheimer's disease (AD). These genetic changes have been proposed to cause AD by elevating levels of amyloid-beta peptides (Abeta), which are thought to be neurotoxic. Since overexpression of APP also causes defects in axonal transport, we tested whether defects in axonal transport were the result of Abeta poisoning of the axonal transport machinery. Because directly varying APP levels also alters APP domains in addition to Abeta, we perturbed Abeta generation selectively by combining APP transgenes in Drosophila and mice with presenilin-1 (PS1) transgenes harboring mutations that cause familial AD (FAD). We found that combining FAD mutant PS1 with FAD mutant APP increased Abeta42/Abeta40 ratios and enhanced amyloid deposition as previously reported. Surprisingly, however, this combination suppressed rather than increased APP-induced axonal transport defects in both Drosophila and mice. In addition, neuronal apoptosis induced by expression of FAD mutant human APP in Drosophila was suppressed by co-expressing FAD mutant PS1. We also observed that directly elevating Abeta with fusions to the Familial British and Danish Dementia-related BRI protein did not enhance axonal transport phenotypes in APP transgenic mice. Finally, we observed that perturbing Abeta ratios in the mouse by combining FAD mutant PS1 with FAD mutant APP did not enhance APP-induced behavioral defects. A potential mechanism to explain these findings was suggested by direct analysis of axonal transport in the mouse, which revealed that axonal transport or entry of APP into axons is reduced by FAD mutant PS1. Thus, we suggest that APP-induced axonal defects are not caused by Abeta.

Adenosine A2A receptor blockade prevents synaptotoxicity and memory dysfunction caused by beta-amyloid peptides via p38 mitogen-activated protein kinase pathway.

PubMed

Canas, Paula M; Porciúncula, Lisiane O; Cunha, Geanne M A; Silva, Carla G; Machado, Nuno J; Oliveira, Jorge M A; Oliveira, Catarina R; Cunha, Rodrigo A

2009-11-25

Alzheimer's disease (AD) is characterized by memory impairment, neurochemically by accumulation of beta-amyloid peptide (namely Abeta(1-42)) and morphologically by an initial loss of nerve terminals. Caffeine consumption prevents memory dysfunction in different models, which is mimicked by antagonists of adenosine A(2A) receptors (A(2A)Rs), which are located in synapses. Thus, we now tested whether A(2A)R blockade prevents the early Abeta(1-42)-induced synaptotoxicity and memory dysfunction and what are the underlying signaling pathways. The intracerebral administration of soluble Abeta(1-42) (2 nmol) in rats or mice caused, 2 weeks later, memory impairment (decreased performance in the Y-maze and object recognition tests) and a loss of nerve terminal markers (synaptophysin, SNAP-25) without overt neuronal loss, astrogliosis, or microgliosis. These were prevented by pharmacological blockade [5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine (SCH58261); 0.05 mg . kg(-1) . d(-1), i.p.; for 15 d] in rats, and genetic inactivation of A(2A)Rs in mice. Moreover, these were synaptic events since purified nerve terminals acutely exposed to Abeta(1-42) (500 nm) displayed mitochondrial dysfunction, which was prevented by A(2A)R blockade. SCH58261 (50 nm) also prevented the initial synaptotoxicity (loss of MAP-2, synaptophysin, and SNAP-25 immunoreactivity) and subsequent loss of viability of cultured hippocampal neurons exposed to Abeta(1-42) (500 nm). This A(2A)R-mediated control of neurotoxicity involved the control of Abeta(1-42)-induced p38 phosphorylation and was independent from cAMP/PKA (protein kinase A) pathway. Together, these results show that A(2A)Rs play a crucial role in the development of Abeta-induced synaptotoxicity leading to memory dysfunction through a p38 MAPK (mitogen-activated protein kinase)-dependent pathway and provide a molecular basis for the benefits of caffeine consumption in AD.

Comorbid rat model of ischemia and β-amyloid toxicity: striatal and cortical degeneration.

PubMed

Amtul, Zareen; Whitehead, Shawn N; Keeley, Robin J; Bechberger, John; Fisher, Alicia L; McDonald, Robert J; Naus, Christian C; Munoz, David G; Cechetto, David F

2015-01-01

Levels of cerebral amyloid, presumably β-amyloid (Abeta), toxicity and the incidence of cortical and subcortical ischemia increases with age. However, little is known about the severe pathological condition and dementia that occur as a result of the comorbid occurrence of this vascular risk factor and Abeta toxicity. Clinical studies have indicated that small ischemic lesions in the striatum are particularly important in generating dementia in combination with minor amyloid lesions. These cognitive deficits are highly likely to be caused by changes in the cortex. In this study, we examined the viability and morphological changes in microglial and neuronal cells, gap junction proteins (connexin43) and neuritic/axonal retraction (Fer Kinase) in the striatum and cerebral cortex using a comorbid rat model of striatal injections of endothelin-1 (ET1) and Abeta toxicity. The results demonstrated ventricular enlargement, striatal atrophy, substantial increases in β-amyloid, ramified microglia and increases in neuritic retraction in the combined models of stroke and Abeta toxicity. Changes in connexin43 occurred equally in both groups of Abeta-treated rats, with and without focal ischemia. Although previous behavioral tests demonstrated impairment in memory and learning, the visual discrimination radial maze task did not show significant difference, suggesting the cognitive impairment in these models is not related to damage to the dorsolateral striatum. These results suggest an insight into the relationship between cortical/striatal atrophy, pathology and functional impairment. © 2014 International Society of Neuropathology.

Neuroprotective properties of Valeriana officinalis extracts.

PubMed

Malva, João O; Santos, Sandra; Macedo, Tice

2004-01-01

Valeriana officinalis have been used in traditional medicine for its sedative, hypnotic, and anticonvulsant effects. There are several reports in the literature supporting a GABAergic mechanism of action for valerian. The rationale of the present work is based on the concept that by decreasing neuronal network excitability valerian consumption may contribute to neuroprotection. The aim of our investigation was to evaluate the neuroprotective effects of V. officinalis against the toxicity induced by amyloid beta peptide 25-35 Abeta(25-35). Cultured rat hippocampal neurons were exposed to Abeta(25-35) (25 microM) for 24-48 h, after which morphological and biochemical properties were evaluated. The neuronal injury evoked by Abeta, which includes a decrease in cell reducing capacity and associated neuronal degeneration, was prevented by valerian extract. Analysis of intracellular free calcium (Ca(2+)i) indicated that the neuroprotective mechanisms may involve the inhibition of excess influx of Ca2+ following neuronal injury. Moreover, membrane peroxidation in rat hippocampal synaptosomes was evaluated, and our data indicate that valerian extract partially inhibited ascorbate/iron-induced peroxidation. In conclusion we show evidence that the signalling pathways involving Ca(2+)i and the redox state of the cells may play a central role in the neuroprotective properties of V. officinalis extract against Abeta toxicity. The novelty of the findings of the present work, indicating neuroprotective properties of valerian against Abeta toxicity may, at the long-term, contribute to introduction of a new relevant use of valerian alcoholic extract to prevent neuronal degeneration in aging or neurodegenerative disorders.

Neuropathological changes in brain cortex and hippocampus in a rat model of Alzheimer's disease.

PubMed

Nobakht, Maliheh; Hoseini, Seyed Mohammad; Mortazavi, Pejman; Sohrabi, Iraj; Esmailzade, Banafshe; Rahbar Rooshandel, Nahid; Omidzahir, Shila

2011-01-01

Alzheimer's disease (AD) is a neurodegenerative disorder with progressive loss of cognitive abilities and memory loss. The aim of this study was to compare neuropathological changes in hippocampus and brain cortex in a rat model of AD. Adult male Albino Wistar rats (weighing 250-300 g) were used for behavioral and histopathological studies. The rats were randomly assigned to three groups: control, sham and Beta amyloid (ABeta) injection. For behavioral analysis, Y-maze and shuttle box were used, respectively at 14 and 16 days post-lesion. For histological studies, Nissl, modified Bielschowsky and modified Congo red staining were performed. The lesion was induced by injection of 4 muL of ABeta (1-40) into the hippocampal fissure. In the present study, ABeta (1-40) injection into hippocampus could decrease the behavioral indexes and the number of CA1 neurons in hippocampus. ABeta injection CA1 caused ABeta deposition in the hippocampus and less than in cortex. We observed the loss of neurons in the hippocampus and cerebral cortex and certain subcortical regions. Y-maze test and single-trial passive avoidance test showed reduced memory retention in AD group. We found a significant decreased acquisition of passive avoidance and alternation behavior responses in AD group compared to control and sham group (P<0.0001). Compacted amyloid cores were present in the cerebral cortex, hippocampus and white matter, whereas, scattered amyloid cores were seen in cortex and hippocampus of AD group. Also, reduced neuronal density was indicated in AD group.

White matter lesion severity is associated with reduced cognitive performances in patients with normal CSF Abeta42 levels.

PubMed

Stenset, V; Hofoss, D; Johnsen, L; Skinningsrud, A; Berstad, A E; Negaard, A; Reinvang, I; Gjerstad, L; Fladby, T

2008-12-01

To identify possible associations between white matter lesions (WML) and cognition in patients with memory complaints, stratified in groups with normal and low cerebrospinal fluid (CSF) Abeta42 values. 215 consecutive patients with subjective memory complaints were retrospectively included. Patients were stratified into two groups with normal (n = 127) or low (n = 88) CSF Abeta42 levels (cut-off is 450 ng/l). Cognitive scores from the Mini-Mental State Examination (MMSE) and the Neurobehavioral Cognitive Status Examination (Cognistat) were used as continuous dependent variables in linear regression. WML load was used as a continuous independent variable and was scored with a visual rating scale. The regression model was corrected for possible confounding factors. WML were significantly associated with MMSE and all Cognistat subscores except language (repetition and naming) and attention in patients with normal CSF Abeta42 levels. No significant associations were observed in patients with low CSF Abeta42. WML were associated with affection of multiple cognitive domains, including delayed recall and executive functions, in patients with normal CSF Abeta42 levels. The lack of such associations for patients with low CSF Abeta42 (i.e. with evidence for amyloid deposition), suggests that amyloid pathology may obscure cognitive effects of WML.

The ACAT inhibitor CP-113,818 markedly reduces amyloid pathology in a mouse model of Alzheimer's disease.

PubMed

Hutter-Paier, Birgit; Huttunen, Henri J; Puglielli, Luigi; Eckman, Christopher B; Kim, Doo Yeon; Hofmeister, Alexander; Moir, Robert D; Domnitz, Sarah B; Frosch, Matthew P; Windisch, Manfred; Kovacs, Dora M

2004-10-14

Amyloid beta-peptide (Abeta) accumulation in specific brain regions is a pathological hallmark of Alzheimer's disease (AD). We have previously reported that a well-characterized acyl-coenzyme A: cholesterol acyltransferase (ACAT) inhibitor, CP-113,818, inhibits Abeta production in cell-based experiments. Here, we assessed the efficacy of CP-113,818 in reducing AD-like pathology in the brains of transgenic mice expressing human APP(751) containing the London (V717I) and Swedish (K670M/N671L) mutations. Two months of treatment with CP-113,818 reduced the accumulation of amyloid plaques by 88%-99% and membrane/insoluble Abeta levels by 83%-96%, while also decreasing brain cholesteryl-esters by 86%. Additionally, soluble Abeta(42) was reduced by 34% in brain homogenates. Spatial learning was slightly improved and correlated with decreased Abeta levels. In nontransgenic littermates, CP-113,818 also reduced ectodomain shedding of endogenous APP in the brain. Our results suggest that ACAT inhibition may be effective in the prevention and treatment of AD by inhibiting generation of the Abeta peptide.

Olfactory dysfunction correlates with amyloid-beta burden in an Alzheimer's disease mouse model.

PubMed

Wesson, Daniel W; Levy, Efrat; Nixon, Ralph A; Wilson, Donald A

2010-01-13

Alzheimer's disease often results in impaired olfactory perceptual acuity-a potential biomarker of the disorder. However, the usefulness of olfactory screens to serve as informative indicators of Alzheimer's is precluded by a lack of knowledge regarding why the disease impacts olfaction. We addressed this question by assaying olfactory perception and amyloid-beta (Abeta) deposition throughout the olfactory system in mice that overexpress a mutated form of the human amyloid-beta precursor protein. Such mice displayed progressive olfactory deficits that mimic those observed clinically-some evident at 3 months of age. Also, at 3 months of age, we observed nonfibrillar Abeta deposition within the olfactory bulb-earlier than deposition within any other brain region. There was also a correlation between olfactory deficits and the spatial-temporal pattern of Abeta deposition. Therefore, nonfibrillar, versus fibrillar, Abeta-related mechanisms likely contribute to early olfactory perceptual loss in Alzheimer's disease. Furthermore, these results present the odor cross-habituation test as a powerful behavioral assay, which reflects Abeta deposition and thus may serve to monitor the efficacy of therapies aimed at reducing Abeta.

Alzheimer Abeta peptide induces chromosome mis-segregation and aneuploidy, including trisomy 21: requirement for tau and APP.

PubMed

Granic, Antoneta; Padmanabhan, Jaya; Norden, Michelle; Potter, Huntington

2010-02-15

Both sporadic and familial Alzheimer's disease (AD) patients exhibit increased chromosome aneuploidy, particularly trisomy 21, in neurons and other cells. Significantly, trisomy 21/Down syndrome patients develop early onset AD pathology. We investigated the mechanism underlying mosaic chromosome aneuploidy in AD and report that FAD mutations in the Alzheimer Amyloid Precursor Protein gene, APP, induce chromosome mis-segregation and aneuploidy in transgenic mice and in transfected cells. Furthermore, adding synthetic Abeta peptide, the pathogenic product of APP, to cultured cells causes rapid and robust chromosome mis-segregation leading to aneuploid, including trisomy 21, daughters, which is prevented by LiCl addition or Ca(2+) chelation and is replicated in tau KO cells, implicating GSK-3beta, calpain, and Tau-dependent microtubule transport in the aneugenic activity of Abeta. Furthermore, APP KO cells are resistant to the aneugenic activity of Abeta, as they have been shown previously to be resistant to Abeta-induced tau phosphorylation and cell toxicity. These results indicate that Abeta-induced microtubule dysfunction leads to aneuploid neurons and may thereby contribute to the pathogenesis of AD.

Huperzine A protects isolated rat brain mitochondria against beta-amyloid peptide.

PubMed

Gao, Xin; Zheng, Chun Yan; Yang, Ling; Tang, Xi Can; Zhang, Hai Yan

2009-06-01

Our previous work in cells and animals showed that mitochondria are involved in the neuroprotective effect of huperzine A (HupA). In this study, the effects of HupA on isolated rat brain mitochondria were investigated. In addition to inhibiting the Abeta(25-35) (40 microM)-induced decrease in mitochondrial respiration, adenosine 5'-triphosphate (ATP) synthesis, enzyme activity, and transmembrane potential, HupA (0.01 or 0.1 microM) effectively prevented Abeta-induced mitochondrial swelling, reactive oxygen species increase, and cytochrome c release. More interestingly, administration of HupA to isolated mitochondria promoted the rate of ATP production and blocked mitochondrial swelling caused by normal osmosis. These results indicate that HupA protects mitochondria against Abeta at least in part by preserving membrane integrity and improving energy metabolism. These direct effects on mitochondria further extend the noncholinergic functions of HupA.

Acorus tatarinowii Schott extract protects PC12 cells from amyloid-beta induced neurotoxicity.

PubMed

An, Hong-Mei; Li, Guo-Wen; Lin, Chen; Gu, Chao; Jin, Miao; Sun, Wen-Xian; Qiu, Ming-Feng; Hu, Bing

2014-05-01

Amyloid-beta induced neurotoxicity has been identified as a major cause of Alzheimer's disease. Acorus tatarinowii Schott is one of the most frequently used Chinese herbs for Alzheimer's disease treatment. However, the effects of Acorus tatarinowii Schott on amyloid-beta mediated nerve cell damage remains unknown. In the present study, neuronal differentiated PC12 cells were used as a model to evaluate the effects of A. tatarinowii Schott extract (ATSE) against Abeta25-35 induced neurotoxicity. The results showed pretreatment with ATSE significantly protected PC12 cells from Abeta25-35 induced cell death, lactate dehydrogenase release, DNA damage, mitochondrial dysfunction and cytochrome c release from mitochondria. In addition, pretreatment with ATSE also significantly inhibited Abeta25-35 induced caspase-3 activation and reactive oxygen species generation in PC12 cells. These observations suggested that ATSE protects PC12 cells from amyloid-beta induced neurotoxicity.

Conformational changes of the amyloid beta-peptide (1-40) adsorbed on solid surfaces.

PubMed

Giacomelli, Carla E; Norde, Willem

2005-05-23

The conformational change of the 39-43 residues of the amyloid beta-peptide (Abeta) toward a beta-sheet enriched state promotes self-aggregation of the peptide molecules and constitutes the major peptide component of the amyloid plaques in Alzheimer patients. The crucial question behind the self-aggregation of Abeta is related to the different pathways the peptide may take after cleavage from the amyloid precursor proteins at cellular membranes. This work is aiming at determining the conformation of the Abeta (1-40) adsorbed on hydrophobic Teflon and hydrophilic silica particles, as model sorbent surfaces mimicking the apolar transmembrane environment and the polar, charged membrane surface, respectively. The mechanism by which the Abeta interacts with solid surfaces strongly depends on the hydrophobic/hydrophilic character of the particles. Hydrophobic and electrostatic interactions contribute differently in each case, causing a completely different conformational change of the adsorbed molecules on the two surfaces. When hydrophobic interactions between the peptide and the sorbent prevail, the adsorbed Abeta (1-40) mainly adopts an alpha-helix conformation due to H-bonding in the apolar part of the peptide that is oriented towards the surface. On the other hand, when the peptide adsorbs by electrostatic interactions beta-sheet formation is promoted due to intermolecular association between the apolar parts of the adsorbed peptide. Irrespective of the characteristics of the solid sorbent, crowding the surface results in intermolecular association between adsorbed molecules leading to a strong aggregation tendency of the Abeta (1-40). [Diagram: see text] CD spectra of Abeta (1-40) at pH 7: A) in solution ([Abeta]=0.2 mg.ml(-1)) freshly prepared (line) and after overnight incubation (symbols);B) on Teflon (Gamma=0.5 mg.m(-2)).

The amyloid cascade-inflammatory hypothesis of Alzheimer disease: implications for therapy.

PubMed

McGeer, Patrick L; McGeer, Edith G

2013-10-01

The amyloid cascade hypothesis is widely accepted as the centerpiece of Alzheimer disease (AD) pathogenesis. It proposes that abnormal production of beta amyloid protein (Abeta) is the cause of AD and that the neurotoxicity is due to Abeta itself or its oligomeric forms. We suggest that this, in itself, cannot be the cause of AD because demonstrating such toxicity requires micromolar concentrations of these Abeta forms, while their levels in brain are a million times lower in the picomolar range. AD probably results from the inflammatory response induced by extracellular Abeta deposits, which later become enhanced by aggregates of tau. The inflammatory response, which is driven by activated microglia, increases over time as the disease progresses. Disease-modifying therapeutic attempts to date have failed and may continue to do so as long as the central role of inflammation is not taken into account. Multiple epidemiological and animal model studies show that NSAIDs, the most widely used antiinflammatory agents, have a substantial sparing effect on AD. These studies provide a proof of concept regarding the anti-inflammatory approach to disease modification. Biomarker studies have indicated that early intervention may be necessary. They have established that disease onset occurs more than a decade before it becomes clinically evident. By combining biomarker and pathological data, it is possible to define six phases of disease development, each separated by about 5 years. Phase one can be identified by decreases in Abeta in the CSF, phase 2 by increases of tau in the CSF plus clear evidence of Abeta brain deposits by PET scanning, phase 3 by slight decreases in brain metabolic rate by PET-FDG scanning, phase 4 by slight decreases in brain volume by MRI scanning plus minimal cognitive impairment, phase 5 by increased scanning abnormalities plus clinical diagnosis of AD, and phase 6 by advanced AD requiring institutional care. Utilization of antiinflammatory agents early in the disease process remains an overlooked therapeutic opportunity. Such agents, while not preventative, have the advantage of being able to inhibit the consequences of both Abeta and tau aggregation. Since there is more than a decade between disease onset and cognitive decline, a window of opportunity exists to introduce truly effective disease-modifying regimens. Taking advantage of this opportunity is the challenge for the future.

Towards Alzheimer's beta-amyloid vaccination.

PubMed

Frenkel, D; Solomon, B

2001-01-01

Beta-amyloid pathology, the main hallmark of Alzheimer's disease (AD), has been linked to its conformational status and aggregation. We recently showed that site-directed monoclonal antibodies (mAbs) towards the N-terminal region of the human beta-amyloid peptide bind to preformed beta-amyloid fibrils (Abeta), leading to disaggregation and inhibition of their neurotoxic effect. Here we report the development of a novel immunization procedure to raise effective anti-aggregating amyloid beta-protein (AbetaP) antibodies, using as antigen filamentous phages displaying the only EFRH peptide found to be the epitope of these antibodies. Due to the high antigenicity of the phage no adjuvant is required to obtain high affinity anti-aggregating IgG antibodies in animals model, that exhibit identity to human AbetaP. Such antibodies are able to sequester peripheral AbetaP, thus avoiding passage through the blood brain barrier (BBB) and, as recently shown in a transgenic mouse model, to cross the BBB and dissolve already formed beta-amyloid plaques. To our knowledge, this is the first attempt to use as a vaccine a self-anti-aggregating epitope displayed on a phage, and this may pave the way to treat abnormal accumulation-peptide diseases, such as Alzheimer's disease or other amyloidogenic diseases. Copyright 2001 The International Association for Biologicals.

Hyposialylation of neprilysin possibly affects its expression and enzymatic activity in hereditary inclusion-body myopathy muscle.

PubMed

Broccolini, Aldobrando; Gidaro, Teresa; De Cristofaro, Raimondo; Morosetti, Roberta; Gliubizzi, Carla; Ricci, Enzo; Tonali, Pietro A; Mirabella, Massimiliano

2008-05-01

Autosomal recessive hereditary inclusion-body myopathy (h-IBM) is caused by mutations of the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase gene, a rate-limiting enzyme in the sialic acid metabolic pathway. Previous studies have demonstrated an abnormal sialylation of glycoproteins in h-IBM. h-IBM muscle shows the abnormal accumulation of proteins including amyloid-beta (Abeta). Neprilysin (NEP), a metallopeptidase that cleaves Abeta, is characterized by the presence of several N-glycosylation sites, and changes in these sugar moieties affect its stability and enzymatic activity. In the present study, we found that NEP is hyposialylated and its expression and enzymatic activity reduced in all h-IBM muscles analyzed. In vitro, the experimental removal of sialic acid by Vibrio Cholerae neuraminidase in cultured myotubes resulted in reduced expression of NEP. This was most likely because of a post-translational modification consisting in an abnormal sialylation of the protein that leads to its reduced stability. Moreover, treatment with Vibrio Cholerae neuraminidase was associated with an increased immunoreactivity for Abeta mainly in the form of distinct cytoplasmic foci within myotubes. We hypothesize that, in h-IBM muscle, hyposialylated NEP has a role in hampering the cellular Abeta clearing system, thus contributing to its abnormal accumulation within vulnerable fibers and possibly promoting muscle degeneration.

Fusion antibody for Alzheimer's disease with bidirectional transport across the blood-brain barrier and abeta fibril disaggregation.

PubMed

Boado, Ruben J; Zhang, Yufeng; Zhang, Yun; Xia, Chun-Fang; Pardridge, William M

2007-01-01

Delivery of monoclonal antibody therapeutics across the blood-brain barrier is an obstacle to the diagnosis or therapy of CNS disease with antibody drugs. The immune therapy of Alzheimer's disease attempts to disaggregate the amyloid plaque of Alzheimer's disease with an anti-Abeta monoclonal antibody. The present work is based on a three-step model of immune therapy of Alzheimer's disease: (1) influx of the anti-Abeta monoclonal antibody across the blood-brain barrier in the blood to brain direction, (2) binding and disaggregation of Abeta fibrils in brain, and (3) efflux of the anti-Abeta monoclonal antibody across the blood-brain barrier in the brain to blood direction. This is accomplished with the genetic engineering of a trifunctional fusion antibody that binds (1) the human insulin receptor, which mediates the influx from blood to brain across the blood-brain barrier, (2) the Abeta fibril to disaggregate amyloid plaque, and (3) the Fc receptor, which mediates the efflux from brain to blood across the blood-brain barrier. This fusion protein is a new antibody-based therapeutic for Alzheimer's disease that is specifically engineered to cross the human blood-brain barrier in both directions.

Testing the neurovascular hypothesis of Alzheimer's disease: LRP-1 antisense reduces blood-brain barrier clearance, increases brain levels of amyloid-beta protein, and impairs cognition.

PubMed

Jaeger, Laura B; Dohgu, Shinya; Hwang, Mark C; Farr, Susan A; Murphy, M Paul; Fleegal-DeMotta, Melissa A; Lynch, Jessica L; Robinson, Sandra M; Niehoff, Michael L; Johnson, Steven N; Kumar, Vijaya B; Banks, William A

2009-01-01

Decreased clearance is the main reason amyloid-beta protein (Abeta) is increased in the brains of patients with Alzheimer's disease (AD). The neurovascular hypothesis states that this decreased clearance is caused by impairment of low density lipoprotein receptor related protein-1 (LRP-1), the major brain-to-blood transporter of Abeta at the blood-brain barrier (BBB). As deletion of the LRP-1 gene is a lethal mutation, we tested the neurovascular hypothesis by developing a cocktail of phosphorothioate antisenses directed against LRP-1 mRNA. We found these antisenses in comparison to random antisense selectively decreased LRP-1 expression, reduced BBB clearance of Abeta42, increased brain levels of Abeta42, and impaired learning ability and recognition memory in mice. These results support dysfunction of LRP-1 at the BBB as a mechanism by which brain levels of Abeta could increase and AD would be promoted.

The marijuana component cannabidiol inhibits beta-amyloid-induced tau protein hyperphosphorylation through Wnt/beta-catenin pathway rescue in PC12 cells.

PubMed

Esposito, Giuseppe; De Filippis, Daniele; Carnuccio, Rosa; Izzo, Angelo A; Iuvone, Teresa

2006-03-01

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder. A massive accumulation of beta-amyloid (Abeta) peptide aggregates has been proposed as pivotal event in AD. Abeta-induced toxicity is accompanied by a variegated combination of events including oxidative stress. The Wnt pathway has multiple actions in the cascade of events triggered by Abeta, and drugs that rescue Wnt activity may be considered as novel therapeutics for AD treatment. Cannabidiol, a non-psychoactive marijuana component, has been recently proposed as an antioxidant neuroprotective agent in neurodegenerative diseases. Moreover, it has been shown to rescue PC12 cells from toxicity induced by Abeta peptide. However, the molecular mechanism of cannabidiol-induced neuroprotective effect is still unknown. Here, we report that cannabidiol inhibits hyperphosphorylation of tau protein in Abeta-stimulated PC12 neuronal cells, which is one of the most representative hallmarks in AD. The effect of cannabidiol is mediated through the Wnt/beta-catenin pathway rescue in Abeta-stimulated PC12 cells. These results provide new molecular insight regarding the neuroprotective effect of cannabidiol and suggest its possible role in the pharmacological management of AD, especially in view of its low toxicity in humans.

Intracellular Aß triggers neuron loss in the cholinergic system of the APP/PS1KI mouse model of Alzheimer's disease.

PubMed

Christensen, Ditte Z; Bayer, Thomas A; Wirths, Oliver

2010-07-01

Loss of cholinergic neurons in the Nucleus Basalis of Meynert in Alzheimer's disease (AD) patients was one of the first discoveries of neuron loss in AD. Despite an intense focus on the cholinergic system in AD, the reason for this cholinergic neuron loss is yet unknown. In the present study we examined Abeta-induced pathology and neuron loss in the cholinergic system of the bigenic APP/PS1KI mouse model. Expression of the APP transgene was found in ChAT-positive neurons of motor nuclei accompanied by robust intracellular Abeta accumulation, whereas no APP expressing neurons and thus no intracellular Abeta accumulation were found in neither the forebrain or pons complexes, nor in the caudate putamen. This expression pattern was used as a model system to study the effect of intra- and extracellular Abeta accumulation on neuron loss in the cholinergic system. Stereological quantification revealed a loss of ChAT-positive neurons in APP/PS1KI mice only in the motor nuclei Mo5 and 7N accumulating intracellular Abeta. This study supports the hypothesis of intracellular Abeta accumulation as an early pathological alteration contributing to cell death in AD. Copyright 2008 Elsevier Inc. All rights reserved.

A highly sensitive peptide substrate for detecting two Aß-degrading enzymes: neprilysin and insulin-degrading enzyme.

PubMed

Chen, Po-Ting; Liao, Tai-Yan; Hu, Chaur-Jong; Wu, Shu-Ting; Wang, Steven S-S; Chen, Rita P-Y

2010-06-30

Neprilysin has been singled out as the most promising candidate for use in the degradation of Abeta as a therapy for Alzheimer's disease. In this study, a quenched fluorogenic peptide substrate containing the first seven residues of the Abeta peptide plus a C-terminal Cysteine residue was synthesized to detect neprilysin activity. A fluorophore was attached to the C-terminal Cysteine and its fluorescence was quenched by a quencher linked to the N-terminus of the peptide. When this peptide substrate was degraded by an endopeptidase, fluorescence was produced and proved to be a sensitive detection system for endopeptidase activity. Our results showed that this assay system was extremely sensitive to neprilysin and insulin-degrading enzyme, but insensitive, or much less sensitive, to other Abeta-degrading enzymes. As low as 0.1 nM of neprilysin and 0.2 nM of insulin-degrading enzyme can be detected. Copyright 2010 Elsevier B.V. All rights reserved.

The common inhalation anesthetic isoflurane induces caspase activation and increases amyloid beta-protein level in vivo.

PubMed

Xie, Zhongcong; Culley, Deborah J; Dong, Yuanlin; Zhang, Guohua; Zhang, Bin; Moir, Robert D; Frosch, Matthew P; Crosby, Gregory; Tanzi, Rudolph E

2008-12-01

An estimated 200 million patients worldwide have surgery each year. Anesthesia and surgery have been reported to facilitate emergence of Alzheimer's disease. The commonly used inhalation anesthetic isoflurane has previously been reported to induce apoptosis, and to increase levels and aggregation of Alzheimer's disease-associated amyloid beta-protein (Abeta) in cultured cells. However, the in vivo relevance has not been addressed. We therefore set out to determine effects of isoflurane on caspase activation and levels of beta-site amyloid precursor protein-cleaving enzyme (BACE) and Abeta in naive mice, using Western blot, immunohistochemistry, and reverse transcriptase polymerase chain reaction. Here we show for the first time that a clinically relevant isoflurane anesthesia (1.4% isoflurane for 2 hours) leads to caspase activation and modest increases in levels of BACE 6 hours after anesthesia in mouse brain. Isoflurane anesthesia induces caspase activation, and increases levels of BACE and Abeta up to 24 hours after anesthesia. Isoflurane may increase BACE levels by reducing BACE degradation. Moreover, the Abeta aggregation inhibitor, clioquinol, was able to attenuate isoflurane-induced caspase-3 activation in vivo. Given that transient insults to brain may lead to long-term brain damage, these findings suggest that isoflurane may promote Alzheimer's disease neuropathogenesis and, as such, have implications for use of isoflurane in humans, pending human study confirmation.

Protective effect of stilbenes containing extract-fraction from Cajanus cajan L. on Abeta(25-35)-induced cognitive deficits in mice.

PubMed

Ruan, Can-Jun; Si, Jian-Yong; Zhang, Li; Chen, Di-Hua; Du, Guan-Hua; Su, Lan

2009-12-25

Cajanus cajan (L.) is a traditional Chinese herb medicine which contains a lot of potential active components. In the present study, we identified the effects of the stilbenes containing extract-fraction from C. cajan L. (sECC) on Abeta(25-35)-induced cognitive deficits, oxidative stress and cholinergic dysfunction in mice. Mice were treated with sECC (100 and 200mg/kg/d) for 1-week, and then received a single intracerebroventricular (i.c.v.) injection of Abeta(25-35) (5mug/mice). Behavioral changes and neuron apoptosis in mice were evaluated using Morris water maze and TUNEL tests. Furthermore, superoxide dismutase (SOD), choline acetyl transferase (ChAT) and acetylcholine esterase (AchE) activity in hippocampus and cortex were analyzed by spectrophotometric method. The data showed that consumption of sECC (200mg/kg) significantly ameliorated the cognitive deficits and neuron apoptosis caused by i.c.v. injection of Abeta(25-35). At the same time, the decreased SOD and ChAT activity in hippocampus and cortex were markedly increased by sECC (200mg/kg). sECC has no effect on AchE activity in hippocampus and cortex. These findings suggest that sECC may be a potential candidate for the development of therapeutic agents to manage cognitive impairment associated with Alzheimer's disease (AD) through increasing the activity of ChAT and anti-oxidative mechanism.

Abeta DNA vaccination for Alzheimer's disease: focus on disease prevention.

PubMed

Cribbs, David H

2010-04-01

Pre-clinical and clinical data suggest that the development of a safe and effective anti-amyloid-beta (Abeta) immunotherapy for Alzheimer's disease (AD) will require therapeutic levels of anti-Abeta antibodies, while avoiding proinflammatory adjuvants and autoreactive T cells which may increase the incidence of adverse events in the elderly population targeted to receive immunotherapy. The first active immunization clinical trial with AN1792 in AD patients was halted when a subset of patients developed meningoencephalitis. The first passive immunotherapy trial with bapineuzumab, a humanized monoclonal antibody against the end terminus of Abeta, also encountered some dose dependent adverse events during the Phase II portion of the study, vasogenic edema in 12 cases, which were significantly over represented in ApoE4 carriers. The proposed remedy is to treat future patients with lower doses, particularly in the ApoE4 carriers. Currently there are at least five ongoing anti-Abeta immunotherapy clinical trials. Three of the clinical trials use humanized monoclonal antibodies, which are expensive and require repeated dosing to maintain therapeutic levels of the antibodies in the patient. However in the event of an adverse response to the passive therapy antibody delivery can simply be halted, which may provide a resolution to the problem. Because at this point we cannot readily identify individuals in the preclinical or prodromal stages of AD pathogenesis, passive immunotherapy is reserved for those that already have clinical symptoms. Unfortunately those individuals have by that point accumulated substantial neuropathology in affected regions of the brain. Moreover, if Abeta pathology drives tau pathology as reported in several transgenic animal models, and once established if tau pathology can become self propagating, then early intervention with anti-Abeta immunotherapy may be critical for favorable clinical outcomes. On the other hand, active immunization has several significant advantages, including lower cost and the typical immunization protocol should be much less intrusive to the patient relative to passive therapy, in the advent of Abeta-antibody immune complex-induced adverse events the patients will have to receive immuno-supperssive therapy for an extended period until the anti Abeta antibody levels drop naturally as the effects of the vaccine decays over time. Obviously, improvements in vaccine design are needed to improve both the safety, as well as the efficacy of anti-Abeta immunotherapy. The focus of this review is on the advantages of DNA vaccination for anti-Abeta immunotherapy, and the major hurdles, such as immunosenescence, selection of appropriate molecular adjuvants, universal T cell epitopes, and possibly a polyepitope design based on utilizing existing memory T cells in the general population that were generated in response to childhood or seasonal vaccines, as well as various infections. Ultimately, we believe that the further refinement of our AD DNA epitope vaccines, possibly combined with a prime boost regime will facilitate translation to human clinical trials in either very early AD, or preferably in preclinical stage individuals identified by validated AD biomarkers.

The role of microglial cells and astrocytes in fibrillar plaque evolution in transgenic APP(SW) mice.

PubMed

Wegiel, J; Wang, K C; Imaki, H; Rubenstein, R; Wronska, A; Osuchowski, M; Lipinski, W J; Walker, L C; LeVine, H

2001-01-01

Ultrastructural reconstruction of 27 fibrillar plaques in different stages of formation and maturation was undertaken to characterize the development of fibrillar plaques in the brains of human APP(SW) transgenic mice (Tg2576). The study suggests that microglial cells are not engaged in Abeta removal and plaque degradation, but in contrast, are a driving force in plaque formation and development. Fibrillar Abeta deposition at the amyloid pole of microglial cells appears to initiate three types of neuropil response: degeneration of neurons, protective activation of astrocytes, and attraction and activation of microglial cells sustaining plaque growth. Enlargement of neuronal processes and synapses with accumulation of degenerated mitochondria, dense bodies, and Hirano-type bodies is the marker of toxic injury of neurons by fibrillar Abeta. Separation of amyloid cores from neurons and degradation of amyloid cores by cytoplasmic processes of hypertrophic astrocytes suggest the protective and defensive character of astrocytic response to fibrillar Abeta. The growth of cored plaque from a small plaque with one microglial cell with an amyloid star and a few dystrophic neurites to a large plaque formed by several dozen microglial cells seen in old mice is the effect of attraction and activation of microglial cells residing outside of the plaque perimeter. This mechanism of growth of plaques appears to be characteristic of cored plaques in transgenic mice. Other features in mouse microglial cells that are absent in human brain are clusters of vacuoles, probably of lysosomal origin. They evolve into circular cisternae and finally into large vacuoles filled with osmiophilic, amorphous material and bundles of fibrils that are poorly labeled with antibody to Abeta. Microglial cells appear to release large amounts of fibrillar Abeta and accumulate traces of fibrillar Abeta in a lysosomal pathway.

BACE1, a major determinant of selective vulnerability of the brain to amyloid-beta amyloidogenesis, is essential for cognitive, emotional, and synaptic functions.

PubMed

Laird, Fiona M; Cai, Huaibin; Savonenko, Alena V; Farah, Mohamed H; He, Kaiwen; Melnikova, Tatyana; Wen, Hongjin; Chiang, Hsueh-Cheng; Xu, Guilian; Koliatsos, Vassilis E; Borchelt, David R; Price, Donald L; Lee, Hey-Kyoung; Wong, Philip C

2005-12-14

A transmembrane aspartyl protease termed beta-site APP cleavage enzyme 1 (BACE1) that cleaves the amyloid-beta precursor protein (APP), which is abundant in neurons, is required for the generation of amyloid-beta (Abeta) peptides implicated in the pathogenesis of Alzheimer's disease (AD). We now demonstrate that BACE1, enriched in neurons of the CNS, is a major determinant that predisposes the brain to Abeta amyloidogenesis. The physiologically high levels of BACE1 activity coupled with low levels of BACE2 and alpha-secretase anti-amyloidogenic activities in neurons is a major contributor to the accumulation of Abeta in the CNS, whereas other organs are spared. Significantly, deletion of BACE1 in APPswe;PS1DeltaE9 mice prevents both Abeta deposition and age-associated cognitive abnormalities that occur in this model of Abeta amyloidosis. Moreover, Abeta deposits are sensitive to BACE1 dosage and can be efficiently cleared from the CNS when BACE1 is silenced. However, BACE1 null mice manifest alterations in hippocampal synaptic plasticity as well as in performance on tests of cognition and emotion. Importantly, memory deficits but not emotional alterations in BACE1(-/-) mice are prevented by coexpressing APPswe;PS1DeltaE9 transgenes, indicating that other potential substrates of BACE1 may affect neural circuits related to emotion. Our results establish BACE1 and APP processing pathways as critical for cognitive, emotional, and synaptic functions, and future studies should be alert to potential mechanism-based side effects that may occur with BACE1 inhibitors designed to ameliorate Abeta amyloidosis in AD.

Aniracetam restores the effects of amyloid-beta protein or ageing on membrane fluidity and intracellular calcium concentration in mice synaptosomes.

PubMed

Li, Y; Wang, J-J; Cai, J-X

2007-01-01

In the present study, we observed the in vitro effect of aniracetam on membrane fluidity and free calcium concentrations ([Ca(2+)]i) of frontal cortical (FC) and hippocampal (HP) synaptosomes of aged mice and young mice treated with amyloid-beta protein (Abeta) Membrane fluidity was measured by using fluorescence anisotropy of the lipophilic probe, 1,6-diphenyl-1,3,5-hexatriene (DPH). [Ca(2+)]i was measured by using Fura 2-AM fluorescent spectrophotometry. We found that membrane fluidity of the FC and HP synaptosomes was decreased in 14 months old mice compared with that in 3 months old mice. Similarly, Abeta25-35 (1 microM) decreased the membrane fluidity in 3 months old mice. These effects of ageing and Abeta25-35 on membrane fluidity were restored by aniracetam in a concentration-dependent manner. Furthermore, Abeta25-35 (1 microM) largely increased [Ca(2+)]i in FC and HP synaptosomes in 3 months old mice, but this effect on HP synaptosomes was effectively reversed by aniracetam (1-4 mM). The present findings suggest that aniracetam restores age- and Abeta-induced alterations in membrane fluidity or Abeta-induced increase in [Ca(2+)]i, demonstrating a possible beneficial role of aniracetam in the clinic treatment for senile dementia or Alzheimer's disease.

Cu(II) potentiation of Alzheimer Abeta1-40 cytotoxicity and transition on its secondary structure.

PubMed

Dai, Xue-Ling; Sun, Ya-Xuan; Jiang, Zhao-Feng

2006-11-01

Mounting evidence has shown that dyshomeostasis of the redox-active biometals such as Cu and Fe can lead to oxidative stress, which plays a key role in the neuropathology of Alzheimer' disease (AD). Here we demonstrate that with the formation of Cu(II).beta1-40 complexes, copper markedly potentiates the neurotoxicity exhibited by beta-amyloid peptide (Ab). A greater amount of hydrogen peroxide was released when Cu(II).beta1-40 complexes was added to the xanthine oxidase/xanthine system detected by potassium iodide spectrophotometry. Copper bound to Abeta1-40 was observed by electron paramagnetic resonance (EPR) spectroscopy. Circular dichroism (CD) studies indicated that copper chelation could cause a structural transition of Abeta. The addition of copper to Ab introduced an increase on beta-sheet as well as alpha-helix, which may be responsible for the aggregation of Abeta. We hypothesized that Abeta aggregation induced by copper may be responsible for local injury in AD. The interaction between Cu(2+) and Ab also provides a possible mechanism for the enrichment of metal ions in amyloid plaques in the AD brain.

Longitudinal cognitive decline is associated with fibrillar amyloid-beta measured by [11C]PiB.

PubMed

Resnick, S M; Sojkova, J; Zhou, Y; An, Y; Ye, W; Holt, D P; Dannals, R F; Mathis, C A; Klunk, W E; Ferrucci, L; Kraut, M A; Wong, D F

2010-03-09

To investigate whether longitudinal declines in cognition are associated with higher fibrillar amyloid-beta (Abeta) deposition in vivo in individuals without dementia. [(11)C]PiB images were obtained to measure fibrillar Abeta burden in 57 participants without dementia from the Baltimore Longitudinal Study of Aging. Participants (33 men, 24 women) had a mean (SD) age of 78.7 (6.2) years. Six participants (4 men, 2 women) had mild cognitive impairment defined as Clinical Dementia Rating = 0.5. To measure [(11)C]PiB retention, distribution volume ratios (DVR) for 15 regions of interest were estimated by fitting a simplified reference tissue model to the measured time activity curves. Mixed effects regression was used to predict cognitive trajectories over time using data before and including time of PiB (mean follow-up 10.8 years), with mean cortical DVR, age at baseline, sex, and education as independent predictors. Voxel-based analysis identified local associations. [(11)C]PiB retention was higher in older individuals. Greater declines over time in mental status and verbal learning and memory, but not visual memory, were associated significantly with higher PiB retention. Voxel-based analysis showed significant associations in frontal and lateral temporal regions. Higher Abeta deposition is associated with greater longitudinal decline in mental status and verbal memory in the preceding years. The differential association for verbal but not visual memory may reflect the greater reliance of verbal word list learning on prefrontal regions, which show early Abeta deposition. Prospective imaging may help distinguish between individuals with evolving neuropathology who develop accelerated cognitive decline vs those with normal aging.

PPARgamma agonist curcumin reduces the amyloid-beta-stimulated inflammatory responses in primary astrocytes.

PubMed

Wang, Hong-Mei; Zhao, Yan-Xin; Zhang, Shi; Liu, Gui-Dong; Kang, Wen-Yan; Tang, Hui-Dong; Ding, Jian-Qing; Chen, Sheng-Di

2010-01-01

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder. Accumulating data indicate that astrocytes play an important role in the neuroinflammation related to the pathogenesis of AD. It has been shown that microglia and astrocytes are activated in AD brain and amyloid-beta (Abeta) can increase the expression of cyclooxygenase 2 (COX-2), interleukin-1, and interleukin-6. Suppressing the inflammatory response caused by activated astrocytes may help to inhibit the development of AD. Curcumin is a major constituent of the yellow curry spice turmeric and proved to be a potential anti-inflammatory drug in arthritis and colitis. There is a low age-adjusted prevalence of AD in India, a country where turmeric powder is commonly used as a culinary compound. Curcumin has been shown to suppress activated astroglia in amyloid-beta protein precursor transgenic mice. The real mechanism by which curcumin inhibits activated astroglia is poorly understood. Here we report that the expression of COX-2 and glial fibrillary acidic protein were enhanced and that of peroxisome proliferator-activated receptor gamma (PPARgamma) was decreased in Abeta(25-35)-treated astrocytes. In line with these results, nuclear factor-kappaB translocation was increased in the presence of Abeta. All these can be reversed by the pretreatment of curcumin. Furthermore, GW9662, a PPARgamma antagonist, can abolish the anti-inflammatory effect of curcumin. These results show that curcumin might act as a PPARgamma agonist to inhibit the inflammation in Abeta-treated astrocytes.

Telmisartan prevented cognitive decline partly due to PPAR-{gamma} activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mogi, Masaki; Li Jianmei; Tsukuda, Kana

Telmisartan is a unique angiotensin receptor blocker (ARB) and partial agonist of peroxisome proliferator-activated receptor (PPAR)-{gamma}. Here, we investigated the preventive effect of telmisartan on cognitive decline in Alzheimer disease. In ddY mice, intracerebroventricular injection of A{beta} 1-40 significantly attenuated their cognitive function evaluated by shuttle avoidance test. Pretreatment with a non-hypotensive dose of telmisartan significantly inhibited such cognitive decline. Interestingly, co-treatment with GW9662, a PPAR-{gamma} antagonist, partially inhibited this improvement of cognitive decline. Another ARB, losartan, which has less PPAR-{gamma} agonistic effect, also inhibited A{beta}-injection-induced cognitive decline; however the effect was smaller than that of telmisartan and was notmore » affected by GW9662. Immunohistochemical staining for A{beta} showed the reduced A{beta} deposition in telmisartan-treated mice. However, this reduction was not observed in mice co-administered GW9662. These findings suggest that ARB has a preventive effect on cognitive impairment in Alzheimer disease, and telmisartan, with PPAR-{gamma} activation, could exert a stronger effect.« less

Beta amyloid and hyperphosphorylated tau deposits in the pancreas in type 2 diabetes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miklossy, J.; Miller, L.; Qing, H.

2008-08-25

Strong epidemiologic evidence suggests an association between Alzheimer disease (AD) and type 2 diabetes. To determine if amyloid beta (A{beta}) and hyperphosphorylated tau occurs in type 2 diabetes, pancreas tissues from 21 autopsy cases (10 type 2 diabetes and 11 controls) were analyzed. APP and tau mRNAs were identified in human pancreas and in cultured insulinoma beta cells (INS-1) by RT-PCR. Prominent APP and tau bands were detected by Western blotting in pancreatic extracts. Aggregated A{beta}, hyperphosphorylated tau, ubiquitin, apolipoprotein E, apolipoprotein(a), IB1/JIP-1 and JNK1 were detected in Langerhans islets in type 2 diabetic patients. A{beta} was co-localized with amylinmore » in islet amyloid deposits. In situ beta sheet formation of islet amyloid deposits was shown by infrared microspectroscopy (SIRMS). LPS increased APP in non-neuronal cells as well. We conclude that A{beta} deposits and hyperphosphorylated tau are also associated with type 2 diabetes, highlighting common pathogenetic features in neurodegenerative disorders, including AD and type 2 diabetes and suggesting that A{beta} deposits and hyperphosphorylated tau may also occur in other organs than the brain.« less

Expression of amyloid-beta 1-40 and 1-42 peptides in Capsicum annum var. angulosum for oral immunization.

PubMed

Szabó, Beáta; Hori, Koichi; Nakajima, Akiko; Sasagawa, Noboru; Watanabe, Yuichiro; Ishiura, Shoichi

2004-08-01

Alzheimer's disease (AD), the leading cause of dementia in the elderly population, still remains without an effective treatment. The accumulation and deposition of the amyloid-beta peptide (Abeta) in the brain is thought to be a key event in the pathogenesis of AD. Recently, a novel exciting technology has been investigated to combat AD: new immunotherapeutic approaches have been described that are based on vaccination with the Abeta peptide itself, and this has been shown to induce functionally beneficial anti-Abeta antibody responses in different transgenic animal models of AD. Here we report the high level expression of GFP-Abeta1-40 and 1-42 peptides in Capsicum annum var. angulosum (green pepper) using a new tomato mosaic tobamovirus-based hybrid replication vector. After preinoculation of Nicotiana benthamiana plants with the in vitro transcript of the vector, the isolated virions were used to inoculate green pepper, which accumulated the GFPAbeta1-40 or 1-42 fusion proteins to a level of 100 microg/g of leaves 7 days after inoculation. These results make it possible to test whether oral immunization by feeding plant samples could stimulate antibody production against Abeta peptides.

Lithium chloride increases the production of amyloid-beta peptide independently from its inhibition of glycogen synthase kinase 3.

PubMed

Feyt, Christine; Kienlen-Campard, Pascal; Leroy, Karelle; N'Kuli, Francisca; Courtoy, Pierre J; Brion, Jean-Pierre; Octave, Jean-Noël

2005-09-30

Glycogen synthase kinase 3 (GSK3) is able to phosphorylate tau at many sites that are found to be phosphorylated in paired helical filaments in Alzheimer disease. Lithium chloride (LiCl) efficiently inhibits GSK3 and was recently reported to also decrease the production of amyloid-beta peptide (Abeta) from its precursor, the amyloid precursor protein. Therefore, lithium has been proposed as a combined therapeutic agent, inhibiting both the hyperphosphorylation of tau and the production of Abeta. Here, we demonstrate that the inhibition of GSK3 by LiCl induced the nuclear translocation of beta-catenin in Chinese hamster ovary cells and rat cultured neurons, in which a decrease in tau phosphorylation was observed. In both cellular models, a nontoxic concentration of LiCl increased the production of Abeta by increasing the beta-cleavage of amyloid precursor protein, generating more substrate for an unmodified gamma-secretase activity. SB415286, another GSK3 inhibitor, induced the nuclear translocation of beta-catenin and slightly decreased Abeta production. It is concluded that the LiCl-mediated increase in Abeta production is not related to GSK3 inhibition.

Etiology of sporadic Alzheimer's disease: somatostatin, neprilysin, and amyloid beta peptide.

PubMed

Hama, E; Saido, T C

2005-01-01

We recently demonstrated that amyloid beta peptide (Abeta) is catabolized primarily by a neutral endopeptidase, neprilysin, in the brain and that a neuropeptide, somatostatin (SST), regulates brain Abeta level via modulation of neprilysin activity. Because SST expression in the brain declines upon aging in various mammals including rodents, apes and humans, we hypothesize that the aging-dependent reduction of SST triggers accumulation of Abeta in the brain by suppressing neprilysin action. This hypothesis accounts for the fact that aging is the predominant risk factor for Sporadic Alzheimer's disease.

Pathogenesis of A-beta+ ketosis-prone diabetes

USDA-ARS?s Scientific Manuscript database

A-beta+ ketosis-prone diabetes (KPD) is an emerging syndrome of obesity, unprovoked ketoacidosis, reversible beta-cell dysfunction, and near-normoglycemic remission. We combined metabolomics with targeted kinetic measurements to investigate its pathophysiology. Fasting plasma fatty acids, acylcarnit...

Disrupting beta-amyloid aggregation for Alzheimer disease treatment.

PubMed

Estrada, L D; Soto, C

2007-01-01

Alzheimer's disease is a devastating degenerative disorder for which there is no cure or effective treatment. Although the etiology of Alzheimer's disease is not fully understood, compelling evidence indicates that deposition of aggregates composed by a misfolded form of the amyloid beta peptide (Abeta) is the central event in the disease pathogenesis. Therefore, an attractive therapeutic strategy is to prevent or reverse Abeta misfolding and aggregation. Diverse strategies have been described to identify inhibitors of this process, including screening of libraries of small molecules chemical compounds, rational design of synthetic peptides, assessment of natural Abeta-binding proteins and stimulation of the immune system by vaccination. In this article we describe these different approaches, their principles and their potential strengths and weaknesses. Overall the available data suggest that the development of drugs to interfere with Abeta misfolding and aggregation is a feasible target that hold great promise for the treatment of Alzheimer's disease.

The pathogenic implication of abnormal interaction between apolipoprotein E isoforms, amyloid-beta peptides, and sulfatides in Alzheimer's disease.

PubMed

Han, Xianlin

2010-06-01

Alzheimer's disease (AD) is the most common cause of dementia in the aging population. Prior work has shown that the epsilon4 allele of apolipoprotein E (apoE4) is a major risk factor for "sporadic" AD, which accounts for >99% of AD cases without a defined underlying mechanism. Recently, we have demonstrated that sulfatides are substantially and specifically depleted at the very early stage of AD. To identify the mechanism(s) of sulfatide loss concurrent with AD onset, we have found that: (1) sulfatides are specifically associated with apoE-associated particles in cerebrospinal fluid (CSF); (2) apoE modulates cellular sulfatide levels; and (3) the modulation of sulfatide content is apoE isoform dependent. These findings not only lead to identification of the potential mechanisms underlying sulfatide depletion at the earliest stages of AD but also serve as mechanistic links to explain the genetic association of apoE4 with AD. Moreover, our recent studies further demonstrated that (1) apoE mediates sulfatide depletion in amyloid-beta precursor protein transgenic mice; (2) sulfatides enhance amyloid beta (Abeta) peptides binding to apoE-associated particles; (3) Abeta42 content notably correlates with sulfatide content in CSF; (4) sulfatides markedly enhance the uptake of Abeta peptides; and (5) abnormal sulfatide-facilitated Abeta uptake results in the accumulation of Abeta in lysosomes. Collectively, our studies clearly provide a link between apoE, Abeta, and sulfatides in AD and establish a foundation for the development of effective therapeutic interventions for AD.

Novel approaches for immunotherapeutic intervention in Alzheimer's disease.

PubMed

Vasilevko, Vitaly; Cribbs, David H

2006-07-01

Immunotherapy can attenuate amyloid neuropathology and improve cognitive function in transgenic models of Alzheimer's disease. However, the first clinical trial was halted when 6% of the Alzheimer's patients developed aseptic meningoencephalitis. Postmortem analysis of two cases with meningoencephalitis showed robust glial activation, T-cell infiltration and sporadic clearance of Abeta. Interestingly, transgenic mouse models of Alzheimer's disease failed as predictors of these adverse inflammatory events. However there are now several studies with amyloid precursor protein transgenic mice that have reported an increased risk of microhemorrhages at sites of cerebrovascular amyloid deposits and because approximately 80% of Alzheimer's patient's have cerebrovascular pathology, there is concern regarding clinical trials using passive administration of humanized anti-Abeta antibodies. Although many studies have now been published on immunotherapy in mouse models, the mechanism(s) of antibody-mediated clearance of beta-amyloid from the brain, and the cause of the antibody-induced microhemorrhages remain unclear. In this review, we will discuss the most recent results from the first clinical trial, offer speculation on possible causes for the failure of the trial, review data on antibody-mediated clearance mechanisms, explore the role of complement and inflammation in the clearance of beta-amyloid, and suggest novel strategies for avoiding problems in future clinical trials. The central hypothesis being proposed in this review is that anti-Abeta antibodies delivered directly to the CNS at the sites of amyloid deposits will be far more effective at clearing Abeta and safer than active or passive immunization strategies where the majority of the antibodies are in the periphery.

Curcumin-derived pyrazoles and isoxazoles: Swiss army knives or blunt tools for Alzheimer's disease?

PubMed

Narlawar, Rajeshwar; Pickhardt, Marcus; Leuchtenberger, Stefanie; Baumann, Karlheinz; Krause, Sabine; Dyrks, Thomas; Weggen, Sascha; Mandelkow, Eckhard; Schmidt, Boris

2008-01-01

Curcumin binds to the amyloid beta peptide (Abeta) and inhibits or modulates amyloid precursor protein (APP) metabolism. Therefore, curcumin-derived isoxazoles and pyrazoles were synthesized to minimize the metal chelation properties of curcumin. The decreased rotational freedom and absence of stereoisomers was predicted to enhance affinity toward Abeta(42) aggregates. Accordingly, replacement of the 1,3-dicarbonyl moiety with isosteric heterocycles turned curcumin analogue isoxazoles and pyrazoles into potent ligands of fibrillar Abeta(42) aggregates. Additionally, several compounds are potent inhibitors of tau protein aggregation and depolymerized tau protein aggregates at low micromolar concentrations.

Proteomic determination of widespread detergent-insolubility including Abeta but not tau early in the pathogenesis of Alzheimer's disease.

PubMed

Woltjer, Randall L; Cimino, P J; Boutté, Angela M; Schantz, Aimee M; Montine, Kathleen S; Larson, Eric B; Bird, Thomas; Quinn, Joseph F; Zhang, Jing; Montine, Thomas J

2005-11-01

Biochemical characterization of the major detergent-insoluble proteins that comprise hallmark histopathologic lesions initiated the molecular era of Alzheimer's disease (AD) research. Here, we reinvestigated detergent-insoluble proteins in AD using modern proteomic techniques. Using liquid chromatography (LC)-mass spectrometry (MS)-MS-based proteomics, we robustly identified 125 proteins in the detergent-insoluble fraction of late-onset AD (LOAD) temporal cortex that included several proteins critical to Abeta production, components of synaptic scaffolding, and products of genes linked to an increased risk of LOAD; we verified 15 of 15 of these proteins by Western blot. Following multiple analyses, we estimated that these represent ~80% of detergent-insoluble proteins in LOAD detectable by our method. Abeta, tau, and 7 of 8 other newly identified detergent-insoluble proteins were disproportionately increased in temporal cortex from patients with LOAD and AD derived from mutations in PSEN1 and PSEN2; all of these except tau were elevated in individuals with prodromal dementia, while none except Abeta were elevated in aged APPswe mice. These results are consistent with the amyloid hypothesis of AD and extend it to include widespread protein insolubility, not exclusively Abeta insolubility, early in AD pathogenesis even before the onset of clinical dementia.

Reductions in levels of the Alzheimer's amyloid beta peptide after oral administration of ginsenosides.

PubMed

Chen, Feng; Eckman, Elizabeth A; Eckman, Christopher B

2006-06-01

For millennia, ginseng and some of its components have been used to treat a wide variety of medical conditions, including age-related memory impairment. Because of its purported effects and apparently low rate of side effects, ginseng remains one of the top selling natural product remedies in the United States. Given its potential role for improving age-related memory impairments and its common use in China for the treatment of Alzheimer's disease-like symptoms, we analyzed the effects of commercially available preparations of ginseng on the accumulation of the Alzheimer's amyloid beta peptide (Abeta) in a cell-based model system. In this model system, ginseng treatment resulted in a significant reduction in the levels of Abeta in the conditioned medium. We next examined the effects of several compounds isolated from ginseng and found that certain ginsenosides lowered Abeta concentration in a dose-dependent manner with ginsenoside Rg3 having an approximate IC50 of under 25 microM against Abeta42. Furthermore, we found that three of these isolated components, ginsenoside Rg1, Rg3, and RE, resulted in significant reductions in the amount of Abeta detected in the brains of animals after single oral doses of these agents. The results indicate that ginseng itself, or purified ginsenosides, may have similarly useful effects in human disease.

Tyrosine gated electron transfer is key to the toxic mechanism of Alzheimer's disease beta-amyloid.

PubMed

Barnham, Kevin J; Haeffner, Fredrik; Ciccotosto, Giuseppe D; Curtain, Cyril C; Tew, Deborah; Mavros, Christine; Beyreuther, Konrad; Carrington, Darryl; Masters, Colin L; Cherny, Robert A; Cappai, Roberto; Bush, Ashley I

2004-09-01

Alzheimer's disease (AD) is characterized by the presence of neurofibrillary tangles and amyloid plaques, which are abnormal protein deposits. The major constituent of the plaques is the neurotoxic beta-amyloid peptide (Abeta); the genetics of familial AD support a direct role for this peptide in AD. Abeta neurotoxicity is linked to hydrogen peroxide formation. Abeta coordinates the redox active transition metals, copper and iron, to catalytically generate reactive oxygen species. The chemical mechanism underlying this process is not well defined. With the use of density functional theory calculations to delineate the chemical mechanisms that drive the catalytic production of H2O2 by Abeta/Cu, tyrosine10 (Y10) was identified as a pivotal residue for this reaction to proceed. The relative stability of tyrosyl radicals facilitates the electron transfers that are required to drive the reaction. Confirming the theoretical results, mutation of the tyrosine residue to alanine inhibited H2O2 production, Cu-induced radicalization, dityrosine cross-linking, and neurotoxicity.

Apolipoprotein E-mimetics inhibit neurodegeneration and restore cognitive functions in a transgenic Drosophila model of Alzheimer's disease.

PubMed

Sarantseva, Svetlana; Timoshenko, Svetlana; Bolshakova, Olga; Karaseva, Eugenia; Rodin, Dmitry; Schwarzman, Alexander L; Vitek, Michael P

2009-12-07

Mutations of the amyloid precursor protein gene (APP) are found in familial forms of Alzheimer's disease (AD) and some lead to the elevated production of amyloid-beta-protein (Abeta). While Abeta has been implicated in the causation of AD, the exact role played by Abeta and its APP precursor are still unclear. In our study, Drosophila melanogaster transgenics were established as a model to analyze AD-like pathology caused by APP overexpression. We demonstrated that age related changes in the levels and pattern of synaptic proteins accompanied progressive neurodegeneration and impairment of cognitive functions in APP transgenic flies, but that these changes may be independent from the generation of Abeta. Using novel peptide mimetics of Apolipoprotein-E, COG112 or COG133 proved to be neuroprotective and significantly improved the learning and memory of APP transgenic flies. The development of neurodegeneration and cognitive deficits was corrected by injections of COG112 or COG133, novel mimetics of apolipoprotein-E (apoE) with neuroprotective activities.

Capping of Aβ42 Oligomers by Small Molecule Inhibitors

PubMed Central

2015-01-01

Aβ42 peptides associate into soluble oligomers and protofibrils in the process of forming the amyloid fibrils associated with Alzheimer’s disease. The oligomers have been reported to be more toxic to neurons than fibrils, and have been targeted by a wide range of small molecule and peptide inhibitors. With single touch atomic force microscopy (AFM), we show that monomeric Aβ42 forms two distinct types of oligomers, low molecular weight (MW) oligomers with heights of 1–2 nm and high MW oligomers with heights of 3–5 nm. In both cases, the oligomers are disc-shaped with diameters of ∼10–15 nm. The similar diameters suggest that the low MW species stack to form the high MW oligomers. The ability of Aβ42 inhibitors to interact with these oligomers is probed using atomic force microscopy and NMR spectroscopy. We show that curcumin and resveratrol bind to the N-terminus (residues 5–20) of Aβ42 monomers and cap the height of the oligomers that are formed at 1–2 nm. A second class of inhibitors, which includes sulindac sulfide and indomethacin, exhibit very weak interactions across the Aβ42 sequence and do not block the formation of the high MW oligomers. The correlation between N-terminal interactions and capping of the height of the Aβ oligomers provides insights into the mechanism of inhibition and the pathway of Aβ aggregation. PMID:25422864

Defective lysosomal proteolysis and axonal transport are early pathogenic events that worsen with age leading to increased APP metabolism and synaptic Abeta in transgenic APP/PS1 hippocampus.

PubMed

Torres, Manuel; Jimenez, Sebastian; Sanchez-Varo, Raquel; Navarro, Victoria; Trujillo-Estrada, Laura; Sanchez-Mejias, Elisabeth; Carmona, Irene; Davila, Jose Carlos; Vizuete, Marisa; Gutierrez, Antonia; Vitorica, Javier

2012-11-22

Axonal pathology might constitute one of the earliest manifestations of Alzheimer disease. Axonal dystrophies were observed in Alzheimer's patients and transgenic models at early ages. These axonal dystrophies could reflect the disruption of axonal transport and the accumulation of multiple vesicles at local points. It has been also proposed that dystrophies might interfere with normal intracellular proteolysis. In this work, we have investigated the progression of the hippocampal pathology and the possible implication in Abeta production in young (6 months) and aged (18 months) PS1(M146L)/APP(751sl) transgenic mice. Our data demonstrated the existence of a progressive, age-dependent, formation of axonal dystrophies, mainly located in contact with congophilic Abeta deposition, which exhibited tau and neurofilament hyperphosphorylation. This progressive pathology was paralleled with decreased expression of the motor proteins kinesin and dynein. Furthermore, we also observed an early decrease in the activity of cathepsins B and D, progressing to a deep inhibition of these lysosomal proteases at late ages. This lysosomal impairment could be responsible for the accumulation of LC3-II and ubiquitinated proteins within axonal dystrophies. We have also investigated the repercussion of these deficiencies on the APP metabolism. Our data demonstrated the existence of an increase in the amyloidogenic pathway, which was reflected by the accumulation of hAPPfl, C99 fragment, intracellular Abeta in parallel with an increase in BACE and gamma-secretase activities. In vitro experiments, using APPswe transfected N2a cells, demonstrated that any imbalance on the proteolytic systems reproduced the in vivo alterations in APP metabolism. Finally, our data also demonstrated that Abeta peptides were preferentially accumulated in isolated synaptosomes. A progressive age-dependent cytoskeletal pathology along with a reduction of lysosomal and, in minor extent, proteasomal activity could be directly implicated in the progressive accumulation of APP derived fragments (and Abeta peptides) in parallel with the increase of BACE-1 and gamma-secretase activities. This retard in the APP metabolism seemed to be directly implicated in the synaptic Abeta accumulation and, in consequence, in the pathology progression between synaptically connected regions.

The Hb A variant (beta73 Asp-->Leu) disrupts Hb S polymerization by a novel mechanism.

PubMed

Adachi, Kazuhiko; Ding, Min; Surrey, Saul; Rotter, Maria; Aprelev, Alexey; Zakharov, Mikhail; Weng, Weijun; Ferrone, Frank A

2006-09-22

Polymerization of a 1:1 mixture of hemoglobin S (Hb S) and the artificial mutant HbAbeta73Leu produces a dramatic morphological change in the polymer domains in 1.0 M phosphate buffer that are a characteristic feature of polymer formation. Instead of feathery domains with quasi 2-fold symmetry that characterize polymerization of Hb S and all previously known mixtures such as Hb A/S and Hb F/S mixtures, these domains are compact structures of quasi-spherical symmetry. Solubility of Hb S/Abeta73Leu mixtures was similar to that of Hb S/F mixtures. Kinetics of polymerization indicated that homogeneous nucleation rates of Hb S/Abeta73Leu mixtures were the same as those of Hb S/F mixtures, while exponential polymer growth (B) of Hb S/Abeta73Leu mixtures were about three times slower than those of Hb S/F mixtures. Differential interference contrast (DIC) image analysis also showed that fibers in the mixture appear to elongate between three and five times more slowly than in equivalent Hb S/F mixtures by direct measurements of exponential growth of mass of polymer in a domain. We propose that these results of Hb S/Abeta73Leu mixtures arise from a non-productive binding of the hybrid species of this mixture to the end of the growing polymer. This "cap" prohibits growth of polymers, but by nature is temporary, so that the net effect is a lowered growth rate of polymers. Such a cap is consistent with known features of the structure of the Hb S polymer. Domains would be more spherulitic because slower growth provides more opportunity for fiber bending to spread domains from their initial 2-fold symmetry. Moreover, since monomer depletion proceeds more slowly in this mixture, more homogeneous nucleation events occur, and the resulting gel has a far more granular character than normally seen in mixtures of non-polymerizing hemoglobins with Hb S. This mixture is likely to be less stiff than polymerized mixtures of other hybrids such as Hb S with HbF, potentially providing a novel approach to therapy.

Pharmacological evidences for DFK167-sensitive presenilin-independent gamma-secretase-like activity.

PubMed

Sevalle, Jean; Ayral, Erwan; Hernandez, Jean-François; Martinez, Jean; Checler, Frédéric

2009-07-01

Amyloid-beta (Abeta) peptides production is thought to be a key event in the neurodegenerative process ultimately leading to Alzheimer's disease (AD) pathology. A bulk of studies concur to propose that the C-terminal moiety of Abeta is released from its precursor beta-amyloid precursor protein by a high molecular weight enzymatic complex referred to as gamma-secretase, that is composed of at least, nicastrin (NCT), Aph-1, Pen-2, and presenilins (PS) 1 or 2. They are thought to harbor the gamma-secretase catalytic activity. However, several lines of evidence suggest that additional gamma-secretase-like activities could potentially contribute to Abeta production. By means of a quenched fluorimetric substrate (JMV2660) mimicking the beta-amyloid precursor protein sequence targeted by gamma-secretase, we first show that as expected, this probe allows monitoring of an activity detectable in several cell systems including the neuronal cell line telencephalon specific murine neurons (TSM1). This activity is reduced by DFK167, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), and LY68458, three inhibitors known to functionally interact with PS. Interestingly, JMV2660 but not the unrelated peptide JMV2692, inhibits Abeta production in an in vitrogamma-secretase assay as expected from a putative substrate competitor. This activity is enhanced by PS1 and PS2 mutations known to be responsible for familial forms of AD and reduced by aspartyl mutations inactivating PS or in cells devoid of PS or NCT. However, we clearly establish that residual JMV2660-hydrolysing activity could be recovered in PS- and NCT-deficient fibroblasts and that this activity remained inhibited by DFK167. Overall, our study describes the presence of a proteolytic activity displaying gamma-secretase-like properties but independent of PS and still blocked by DFK167, suggesting that the PS-dependent complex could not be the unique gamma-secretase activity responsible for Abeta production and delineates PS-independent gamma-secretase activity as a potential additional therapeutic target to fight AD pathology.

Chitooligosaccharides suppress the level of protein expression and acetylcholinesterase activity induced by Abeta25-35 in PC12 cells.

PubMed

Lee, Sang-Hoon; Park, Jin-Sook; Kim, Se-Kwon; Ahn, Chang-Bum; Je, Jae-Young

2009-02-01

Clinical applications of acetylcholinesterase (AChE) inhibitors are widespread in Alzheimer's sufferers in order to activate central cholinergic system and alleviate cognitive deficits by inhibiting the hydrolysis of acetylcholine. In this study, six kinds of chitooligosaccharides (COSs) with different molecular weight and degree of deacetylation were examined for their inhibitory effects against AChE. The 90-COSs exhibited potent AChE inhibitory activities compared to 50-COSs, while 90-MMWCOS (1000-5000 Da) in the 90-COSs showed the highest activity. Cell culture experiment revealed that 90-MMWCOS suppressed the level of AChE protein expression and AChE activity induced by Abeta(25-35) in PC12 cell lines.

Influence of Aqueous-Salt Conditions on the Structure and Dynamics of the Monomeric and Novel Dimeric forms of the Alzheimer s ABeta21-30 protein fragment

NASA Astrophysics Data System (ADS)

Smith, Micholas Dean

The behavior of the Alzheimer's related peptide Abeta is the subject of much study. In typical computational studies the environment local to the peptide is assumed to be pure water; however, in vivo the peptide is found in the extracellular space near the plasma membrane which is rich in ionic species. In this thesis, the hypothesis that the presence of group I/IIA salts will result in increased sampling of disordered structures as well as modify the dynamics of meta-stable structural motifs in the small folding nucleus of the Abeta peptide (Abeta21-30) is examined under a variety of ionic environments and was shown that of the tested salts, CaCl2 (and MgCl2, to a much lesser degree) did increase the propensity for disordered states; while, the group IA salts, KCl and NaCl, had little effect on the secondary structure of the peptide. Further, study of three familial mutations of this peptide region is also performed under aqueous salt-environments to elucidate further mechanistic details of how aqueous salts modify the region's behavior. Finally, as experimental results have highlighted that aggregation rates of the full-length peptide are modified by the presence of CaCl2, this work examines novel dimers states of Abeta21-30 and their stabilities when exposed to CaCl2.

Lovastatin inhibits amyloid precursor protein (APP) beta-cleavage through reduction of APP distribution in Lubrol WX extractable low density lipid rafts.

PubMed

Won, Je-Seong; Im, Yeong-Bin; Khan, Mushfiquddin; Contreras, Miguel; Singh, Avtar K; Singh, Inderjit

2008-05-01

Previous studies have described that statins (inhibitors of cholesterol and isoprenoid biosynthesis) inhibit the output of amyloid-beta (Abeta) in the animal model and thus decrease risk of Alzheimer's disease. However, their action mechanism(s) in Abeta precursor protein (APP) processing and Abeta generation is not fully understood. In this study, we report that lovastatin treatment reduced Abeta output in cultured hippocampal neurons as a result of reduced APP levels and beta-secretase activities in low density Lubrol WX (non-ionic detergent) extractable lipid rafts (LDLR). Rather than altering cholesterol levels in lipid raft fractions and thus disrupting lipid raft structure, lovastatin decreased Abeta generation through down-regulating geranylgeranyl-pyrophosphate dependent endocytosis pathway. The inhibition of APP endocytosis by treatment with lovastatin and reduction of APP levels in LDLR fractions by treatment with phenylarsine oxide (a general endocytosis inhibitor) support the involvement of APP endocytosis in APP distribution in LDLR fractions and subsequent APP beta-cleavage. Moreover, lovastatin-mediated down-regulation of endocytosis regulators, such as early endosomal antigen 1, dynamin-1, and phosphatidylinositol 3-kinase activity, indicates that lovastatin modulates APP endocytosis possibly through its pleiotropic effects on endocytic regulators. Collectively, these data report that lovastatin mediates inhibition of LDLR distribution and beta-cleavage of APP in a geranylgeranyl-pyrophosphate and endocytosis-dependent manner.

Wild-type presenilin 1 protects against Alzheimer disease mutation-induced amyloid pathology.

PubMed

Wang, Runsheng; Wang, Baiping; He, Wanxia; Zheng, Hui

2006-06-02

Mutations in presenilin 1 (PS1) lead to dominant inheritance of early onset familial Alzheimer disease (FAD). These mutations are known to alter the gamma-secretase cleavage of the amyloid precursor protein, resulting in increased ratio of Abeta42/Abeta40 and accelerated amyloid plaque pathology in transgenic mouse models. To investigate the factors that drive the Abeta42/Abeta40 ratio and amyloid pathogenesis and to investigate the possible interactions between wild-type and FAD mutant PS1, which are co-expressed in transgenic animals, we expressed the PS1 M146V knock-in allele either on wild-type PS1 (PS1M146V/+) or PS1 null (PS1M146V/-) background and crossed these alleles with the Tg2576 APP transgenic mice. Introduction of the PS1 M146V mutation on Tg2576 background resulted in earlier onset of plaque pathology. Surprisingly, removing the wild-type PS1 in the presence of the PS1 M146V mutation (PS1M146V/-) greatly exacerbated the amyloid burden; and this was attributed to a reduction of gamma-secretase activity rather than an increase in Abeta42. Our findings establish a protective role of the wild-type PS1 against the FAD mutation-induced amyloid pathology through a partial loss-of-function mechanism.

The hyperforin derivative IDN5706 occludes spatial memory impairments and neuropathological changes in a double transgenic Alzheimer's mouse model.

PubMed

Cerpa, W; Hancke, J L; Morazzoni, P; Bombardelli, E; Riva, Antonella; Marin, P P; Inestrosa, Nibaldo C

2010-03-01

The use of natural compounds is an interesting stratagem in the search of drugs with therapeutic potential for the treatment of Alzheimer's disease (AD). We report here the effect of the hyperforin derivative (IDN5706, tetrahydrohyperforin), a semi-synthetic derivative of the St. John's Wort, on the brain neuropathology, learning and memory in a double transgenic (APPswe, PS-1dE9) mouse model of AD. Results indicate that, IDN5706 alleviates memory decline induced by amyloid-beta (Abeta) deposits as indicated by the Morris water maze paradigm. Moreover, the analysis of Abeta deposits by immunodetection and thioflavin-S staining of brain sections, only reveals a decrease in the frequency of the larger-size Abeta deposits, suggesting that IDN5706 affected the turnover of amyloid plaques. Immunohistochemical analysis, using GFAP and n-Tyrosine indicated that the hyperforin derivative prevents the inflammatory astrocytic reaction and the oxidative damage triggered by high Abeta deposit levels. We conclude that the hyperforin derivative, IDN5706, has therapeutic potential for prevention and treatment of AD.

Folding of the 25 residue Abeta(12-36) peptide in TFE/water: temperature-dependent transition from a funneled free-energy landscape to a rugged one.

PubMed

Kamiya, Narutoshi; Mitomo, Daisuke; Shea, Joan-Emma; Higo, Junichi

2007-05-17

The free-energy landscape of the Alzheimer beta-amyloid peptide Abeta(12-36) in a 40% (v/v) 2,2,2-trifluoroethanol (TFE)/water solution was determined by using multicanonical molecular dynamics simulations. Simulations using this enhanced conformational sampling technique were initiated from a random unfolded polypeptide conformation. Our simulations reliably folded the peptide to the experimental NMR structure, which consists of two linked helices. The shape of the free energy landscape for folding was found to be strongly dependent on temperature: Above 325 K, the overall shape was funnel-like, with the bottom of the funnel coinciding exactly with the NMR structure. Below 325 K, on the other hand, the landscape became increasingly rugged, with the emergence of new conformational clusters connected by low free-energy pathways. Finally, our simulations reveal that water and TFE solvate the polypeptide in different ways: The hydrogen bond formation between TFE and Abeta was enhanced with decreasing temperature, while that between water and Abeta was depressed.

A ketogenic diet reduces amyloid beta 40 and 42 in a mouse model of Alzheimer's disease.

PubMed

Van der Auwera, Ingrid; Wera, Stefaan; Van Leuven, Fred; Henderson, Samuel T

2005-10-17

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that primarily strikes the elderly. Studies in both humans and animal models have linked the consumption of cholesterol and saturated fats with amyloid-beta (Abeta) deposition and development of AD. Yet, these studies did not examine high fat diets in combination with reduced carbohydrate intake. Here we tested the effect of a high saturated fat/low carbohydrate diet on a transgenic mouse model of AD. Starting at three months of age, two groups of female transgenic mice carrying the "London" APP mutation (APP/V717I) were fed either, a standard diet (SD) composed of high carbohydrate/low fat chow, or a ketogenic diet (KD) composed of very low carbohydrate/high saturated fat chow for 43 days. Animals fed the KD exhibited greatly elevated serum ketone body levels, as measured by beta-hydroxybutyrate (3.85 +/- 2.6 mM), compared to SD fed animals (0.29 +/- 0.06 mM). In addition, animals fed the KD lost body weight (SD 22.2 +/- 0.6 g vs. KD 17.5 +/- 1.4 g, p = 0.0067). In contrast to earlier studies, the brief KD feeding regime significantly reduced total brain Abeta levels by approximately 25%. Despite changes in ketone levels, body weight, and Abeta levels, the KD diet did not alter behavioral measures. Previous studies have suggested that diets rich in cholesterol and saturated fats increased the deposition of Abeta and the risk of developing AD. Here we demonstrate that a diet rich in saturated fats and low in carbohydrates can actually reduce levels of Abeta. Therefore, dietary strategies aimed at reducing Abeta levels should take into account interactions of dietary components and the metabolic outcomes, in particular, levels of carbohydrates, total calories, and presence of ketone bodies should be considered.

In Situ FTIR Microspectroscopy of Brain Tissue from a Transgenic Mouse Model of Alzheimer Disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rak,M.; Del Bigio, M.; Mai, S.

2007-01-01

Plaques composed of the A{beta} peptide are the main pathological feature of Alzheimer's disease. Dense-core plaques are fibrillar deposits of A{beta}, showing all the classical properties of amyloid including {beta}-sheet secondary structure, while diffuse plaques are amorphous deposits. We studied both plaque types, using synchrotron infrared (IR) microspectroscopy, a technique that allows the chemical composition and average protein secondary structure to be investigated in situ. We examined plaques in hippocampal, cortical and caudal tissue from 5- to 21-month-old TgCRND8 mice, a transgenic model expressing doubly mutant amyloid precursor protein, and displaying impaired hippocampal function and robust pathology from an earlymore » age. Spectral analysis confirmed that the congophilic plaque cores were composed of protein in a {beta}-sheet conformation. The amide I maximum of plaque cores was at 1623 cm-1, and unlike for in vitro A{beta} fibrils, the high-frequency (1680-1690 cm-1) component attributed to antiparallel {beta}-sheet was not observed. A significant elevation in phospholipids was found around dense-core plaques in TgCRND8 mice ranging in age from 5 to 21 months. In contrast, diffuse plaques were not associated with IR detectable changes in protein secondary structure or relative concentrations of any other tissue components.« less

Defective lysosomal proteolysis and axonal transport are early pathogenic events that worsen with age leading to increased APP metabolism and synaptic Abeta in transgenic APP/PS1 hippocampus

PubMed Central

2012-01-01

Background Axonal pathology might constitute one of the earliest manifestations of Alzheimer disease. Axonal dystrophies were observed in Alzheimer’s patients and transgenic models at early ages. These axonal dystrophies could reflect the disruption of axonal transport and the accumulation of multiple vesicles at local points. It has been also proposed that dystrophies might interfere with normal intracellular proteolysis. In this work, we have investigated the progression of the hippocampal pathology and the possible implication in Abeta production in young (6 months) and aged (18 months) PS1(M146L)/APP(751sl) transgenic mice. Results Our data demonstrated the existence of a progressive, age-dependent, formation of axonal dystrophies, mainly located in contact with congophilic Abeta deposition, which exhibited tau and neurofilament hyperphosphorylation. This progressive pathology was paralleled with decreased expression of the motor proteins kinesin and dynein. Furthermore, we also observed an early decrease in the activity of cathepsins B and D, progressing to a deep inhibition of these lysosomal proteases at late ages. This lysosomal impairment could be responsible for the accumulation of LC3-II and ubiquitinated proteins within axonal dystrophies. We have also investigated the repercussion of these deficiencies on the APP metabolism. Our data demonstrated the existence of an increase in the amyloidogenic pathway, which was reflected by the accumulation of hAPPfl, C99 fragment, intracellular Abeta in parallel with an increase in BACE and gamma-secretase activities. In vitro experiments, using APPswe transfected N2a cells, demonstrated that any imbalance on the proteolytic systems reproduced the in vivo alterations in APP metabolism. Finally, our data also demonstrated that Abeta peptides were preferentially accumulated in isolated synaptosomes. Conclusion A progressive age-dependent cytoskeletal pathology along with a reduction of lysosomal and, in minor extent, proteasomal activity could be directly implicated in the progressive accumulation of APP derived fragments (and Abeta peptides) in parallel with the increase of BACE-1 and gamma-secretase activities. This retard in the APP metabolism seemed to be directly implicated in the synaptic Abeta accumulation and, in consequence, in the pathology progression between synaptically connected regions. PMID:23173743

Models of cooperative dynamics from biomolecules to magnets

NASA Astrophysics Data System (ADS)

Mobley, David Lowell

This work details application of computer models to several biological systems (prion diseases and Alzheimer's disease) and a magnetic system. These share some common themes, which are discussed. Here, simple lattice-based models are applied to aggregation of misfolded protein in prion diseases like Mad Cow disease. These can explain key features of the diseases. The modeling is based on aggregation being essential in establishing the time-course of infectivity. Growth of initial aggregates is assumed to dominate the experimentally observed lag phase. Subsequent fission, regrowth, and fission set apart the exponential doubling phase in disease progression. We explore several possible modes of growth for 2-D aggregates and suggest the model providing the best explanation for the experimental data. We develop testable predictions from this model. Like prion disease, Alzheimer's disease (AD) is an amyloid disease characterized by large aggregates in the brain. However, evidence increasingly points away from these as the toxic agent and towards oligomers of the Abeta peptide. We explore one possible toxicity mechanism---insertion of Abeta into cell membranes and formation of harmful ion channels. We find that mutations in this peptide which cause familial Alzheimer's disease (FAD) also affect the insertion of this peptide into membranes in a fairly consistent way, suggesting that this toxicity mechanism may be relevant biologically. We find a particular inserted configuration which may be especially harmful and develop testable predictions to verify whether or not this is the case. Nucleation is an essential feature of our models for prion disease, in that it protects normal, healthy individuals from getting prion disease. Nucleation is important in many other areas, and we modify our lattice-based nucleation model to apply to a hysteretic magnetic system where nucleation has been suggested to be important. From a simple model, we find qualitative agreement with experiment, and make testable experimental predictions concerning time-dependence and temperature-dependence of the major hysteresis loop and reversal curves which have been experimentally verified. We argue why this model may be suitable for systems like these and explain implications for Ising-like models. We suggest implications for future modeling work. Finally, we present suggestions for future work in all three areas.

Heat Resistant Characteristics of Major Royal Jelly Protein 1 (MRJP1) Oligomer

PubMed Central

Moriyama, Takanori; Ito, Aimi; Omote, Sumire; Miura, Yuri; Tsumoto, Hiroki

2015-01-01

Soluble royal jelly protein is a candidate factor responsible for mammiferous cell proliferation. Major royal jelly protein 1 (MRJP1), which consists of oligomeric and monomeric forms, is an abundant proliferative protein in royal jelly. We previously reported that MRJP1 oligomer has biochemical heat resistance. Therefore, in the present study, we investigated the effects of several heat treatments (56, 65 and 96°C) on the proliferative activity of MRJP1 oligomer. Heat resistance studies showed that the oligomer molecular forms were slightly maintained until 56℃, but the molecular forms were converted to macromolecular heat-aggregated MRJP1 oligomer at 65℃ and 96℃. But, the growth activity of MRJP1 oligomer treated with 96°C was slightly attenuated when compared to unheated MRJP1 oligomer. On the other hand, the cell proliferation activity was preserved until 96℃ by the cell culture analysis of Jurkat cells. In contrast, those of IEC-6 cells were not preserved even at 56°C. The present observations suggest that the bioactive heat-resistance properties were different by the origin of the cells. The cell proliferation analysis showed that MRJP1 oligomer, but not MRJP2 and MRJP3, significantly increased cell numbers, suggesting that MRJP1 oligomer is the predominant proliferation factor for mammiferous cells. PMID:26020775

Heat Resistant Characteristics of Major Royal Jelly Protein 1 (MRJP1) Oligomer.

PubMed

Moriyama, Takanori; Ito, Aimi; Omote, Sumire; Miura, Yuri; Tsumoto, Hiroki

2015-01-01

Soluble royal jelly protein is a candidate factor responsible for mammiferous cell proliferation. Major royal jelly protein 1 (MRJP1), which consists of oligomeric and monomeric forms, is an abundant proliferative protein in royal jelly. We previously reported that MRJP1 oligomer has biochemical heat resistance. Therefore, in the present study, we investigated the effects of several heat treatments (56, 65 and 96°C) on the proliferative activity of MRJP1 oligomer. Heat resistance studies showed that the oligomer molecular forms were slightly maintained until 56℃, but the molecular forms were converted to macromolecular heat-aggregated MRJP1 oligomer at 65℃ and 96℃. But, the growth activity of MRJP1 oligomer treated with 96°C was slightly attenuated when compared to unheated MRJP1 oligomer. On the other hand, the cell proliferation activity was preserved until 96℃ by the cell culture analysis of Jurkat cells. In contrast, those of IEC-6 cells were not preserved even at 56°C. The present observations suggest that the bioactive heat-resistance properties were different by the origin of the cells. The cell proliferation analysis showed that MRJP1 oligomer, but not MRJP2 and MRJP3, significantly increased cell numbers, suggesting that MRJP1 oligomer is the predominant proliferation factor for mammiferous cells.

Stabilization, Characterization, and Selective Removal of Cystatin C Amyloid Oligomers*

PubMed Central

Östner, Gustav; Lindström, Veronica; Hjort Christensen, Per; Kozak, Maciej; Abrahamson, Magnus; Grubb, Anders

2013-01-01

The pathophysiological process in amyloid disorders usually involves the transformation of a functional monomeric protein via potentially toxic oligomers into amyloid fibrils. The structure and properties of the intermediary oligomers have been difficult to study due to their instability and dynamic equilibrium with smaller and larger species. In hereditary cystatin C amyloid angiopathy, a cystatin C variant is deposited in arterial walls and cause brain hemorrhage in young adults. In the present investigation, we use redox experiments of monomeric cystatin C, stabilized against domain swapping by an intramolecular disulfide bond, to generate stable oligomers (dimers, trimers, tetramers, decamers, and high molecular weight oligomers). These oligomers were characterized concerning size by gel filtration, polyacrylamide gel electrophoresis, and mass spectrometry, shape by electron and atomic force microscopy, and, function by assays of their capacity to inhibit proteases. The results showed the oligomers to be highly ordered, domain-swapped assemblies of cystatin C and that the oligomers could not build larger oligomers, or fibrils, without domain swapping. The stabilized oligomers were used to induce antibody formation in rabbits. After immunosorption, using immobilized monomeric cystatin C, and elution from columns with immobilized cystatin C oligomers, oligomer-specific antibodies were obtained. These could be used to selectively remove cystatin C dimers from biological fluids containing both dimers and monomers. PMID:23629649

Hypoglycemic activities of A- and B-type procyanidin oligomer-rich extracts from different Cinnamon barks.

PubMed

Lu, Zhaolian; Jia, Qi; Wang, Rui; Wu, Ximin; Wu, Yingchun; Huang, Caiguo; Li, Yiming

2011-02-15

Procyanidin oligomers in Cinnamon are thought to be responsible for the biological activity in the treatment of diabetes mellitus (DM). To clarify types of procyanidin oligomers in different Cinnamon species and investigate their different effects, the present study investigated procyanidin oligomers in polyphenolic oligomer-rich extracts of three Cinnamon samples by LC-MS methods, and their hypoglycemic activities were detected in vivo and in vitro. The results showed that two of the three samples from Cinnamomum cassia were rich in B-type procyanidin oligomers, and the other sample was rich in A-type procyanidin oligomers. The Cinnamon extracts were administered at doses of 200 and 300 mg/kg body wt. in high-fat diet-fed and low-dose streptozotocin (STZ)-induced diabetic mice for 14 days. The results showed that blood glucose concentrations were significantly decreased in all Cinnamon extract groups compared with the control group (p<0.05). Administration of the Cinnamon extracts significantly increased the consumption of extracellular glucose in insulin-resistant HepG2 cells and normal HepG2 cells compared with the control group. These results suggest that both A- and B-type procyanidin oligomers in different Cinnamon species have hypoglycemic activities and may improve insulin sensitivity in type 2 DM. Copyright © 2010 Elsevier GmbH. All rights reserved.

Novel immunolocalization of alpha-synuclein in human muscle of inclusion-body myositis, regenerating and necrotic muscle fibers, and at neuromuscular junctions.

PubMed

Askanas, V; Engel, W K; Alvarez, R B; McFerrin, J; Broccolini, A

2000-07-01

Alpha-synuclein (alpha-syn) is an important component of neuronal and glial inclusions in brains of patients with several neurodegenerative disorders. Sporadic inclusion-body myositis (s-IBM) is the most common progressive muscle disease of older patients. Its muscle phenotype shows several similarities with Alzheimer disease brain. A distinct feature of s-IBM pathology is specific vacuolar degeneration of muscle fibers characterized by intracellular amyloid inclusions formed by both amyloid-beta (Abeta) and paired-helical filaments composed of phosphorylated tau. We immunostained alpha-syn in muscle biopsies of s-IBM, disease-control, and normal patients. Approximately 60% of Abeta-positive vacuolated muscle fibers (VMF) contained well-defined inclusions immunoreactive with antibodies against alpha-syn. In those fibers. alpha-syn co-localized with Abeta, both by light microscopy, and ultrastructurally. Paired-helical filaments did not contain alpha-syn immunoreactivity. In all muscle biopsies, alpha-syn was strongly immunoreactive at the postsynaptic region of the neuromuscular junctions. alpha-syn immunoreactivity also occurred diffusely in regenerating and necrotic muscle fibers. In cultured human muscle fibers, alpha-syn and its mRNA were expressed by immunocytochemistry, immunoblots, and Northern blots. Our study provides the first demonstration that alpha-syn participates in normal and pathologic processes of human muscle. Therefore. its function is not exclusive to the brain and neurodegenerative diseases.

An oligodeoxyribonucleotide that supports catalytic activity in the hammerhead ribozyme domain.

PubMed Central

Chartrand, P; Harvey, S C; Ferbeyre, G; Usman, N; Cedergren, R

1995-01-01

A study of the activity of deoxyribonucleotide-substituted analogs of the hammerhead domain of RNA catalysis has led to the design of a 14mer oligomer composed entirely of deoxyribonucleotides that promotes the cleavage of an RNA substrate. Characterization of this reaction with sequence variants and mixed DNA/RNA oligomers shows that, although the all-deoxyribonucleotide oligomer is less efficient in catalysis, the DNA/substrate complex shares many of the properties of the all-RNA hammerhead domain such as multiple turnover kinetics and dependence on Mg2+ concentration. On the other hand, the values of kinetic parameters distinguish the DNA oligomer from the all-RNA oligomer. In addition, an analog of the oligomer having a single ribonucleotide in a strongly conserved position of the hammerhead domain is associated with more efficient catalysis than the all-RNA oligomer. Images PMID:7479070

Laccase-Catalyzed Synthesis of Low-Molecular-Weight Lignin-Like Oligomers and their Application as UV-Blocking Materials.

PubMed

Lim, Jieyan; Sana, Barindra; Krishnan, Ranganathan; Seayad, Jayasree; Ghadessy, Farid J; Jana, Satyasankar; Ramalingam, Balamurugan

2018-02-02

The laccase-catalyzed oxidative polymerization of monomeric and dimeric lignin model compounds was carried out with oxygen as the oxidant in aqueous medium. The oligomers were characterized by using gel permeation chromatography (GPC) and matrix-assisted laser desorption ionization time-of-flight mass spectroscopy (MALDI-TOF MS) analysis. Oxidative polymerization led to the formation of oligomeric species with a number-average molecular weight (M n ) that ranged from 700 to 2300 Da with a low polydispersity index. Spectroscopic analysis provided insight into the possible modes of linkages present in the oligomers, and the oligomerization is likely to proceed through the formation of C-C linkages between phenolic aromatic rings. The oligomers were found to show good UV light absorption characteristics with high molar extinction coefficient (5000-38 000 m -1  cm -1 ) in the UV spectral region. The oligomers were blended independently with polyvinyl chloride (PVC) by using solution blending to evaluate the compatibility and UV protection ability of the oligomers. The UV/Vis transmittance spectra of the oligomer-embedded PVC films indicated that these lignin-like oligomers possessed a notable ability to block UV light. In particular, oligomers obtained from vanillyl alcohol and the dimeric lignin model were found to show good photostability in accelerated UV weathering experiments. The UV-blocking characteristics and photostability were finally compared with the commercial low-molecular-weight UV stabilizer 2,4-dihydroxybenzophenone. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anti-amyloid beta protein antibody passage across the blood-brain barrier in the SAMP8 mouse model of Alzheimer's disease: an age-related selective uptake with reversal of learning impairment.

PubMed

Banks, William A; Farr, Susan A; Morley, John E; Wolf, Kathy M; Geylis, Valeria; Steinitz, Michael

2007-08-01

Amyloid beta protein (Abeta) levels are elevated in the brain of Alzheimer's disease patients. Anti-Abeta antibodies can reverse the histologic and cognitive impairments in mice which overexpress Abeta. Passive immunization appears safer than vaccination and treatment of patients will likely require human rather than xenogenic antibodies. Effective treatment will likely require antibody to cross the blood-brain barrier (BBB). Unfortunately, antibodies typically cross the BBB very poorly and accumulate less well in brain than even albumin, a substance nearly totally excluded from the brain. We compared the ability of two anti-Abeta human monoclonal IgM antibodies, L11.3 and HyL5, to cross the BBB of young CD-1 mice to that of young and aged SAMP8 mice. The SAMP8 mouse has a spontaneous mutation that induces an age-related, Abeta-dependent cognitive deficit. There was preferential uptake of intravenously administered L11.3 in comparison to HyL5, albumin, and a control human monoclonal IgM (RF), especially by hippocampus and olfactory bulb in aged SAMP8 mice. Injection of L11.3 into the brains of aged SAMP8 mice reversed both learning and memory impairments in aged SAMP8 mice, whereas IgG and IgM controls were ineffective. Pharmacokinetic analysis predicted that an intravenous dose 1000 times higher than the brain injection dose would reverse cognitive impairments. This predicted intravenous dose reversed the impairment in learning, but not memory, in aged SAMP8 mice. In conclusion, an IgM antibody was produced that crosses the BBB to reverse cognitive impairment in a murine model of Alzheimer's disease.

Hypoxic augmentation of Ca2+ channel currents requires a functional electron transport chain.

PubMed

Brown, Stephen T; Scragg, Jason L; Boyle, John P; Hudasek, Kristin; Peers, Chris; Fearon, Ian M

2005-06-10

The incidence of Alzheimer disease is increased following ischemic episodes, and we previously demonstrated that following chronic hypoxia (CH), amyloid beta (Abeta) peptide-mediated increases in voltage-gated L-type Ca(2+) channel activity contribute to the Ca(2+) dyshomeostasis seen in Alzheimer disease. Because in certain cell types mitochondria are responsible for detecting altered O(2) levels we examined the role of mitochondrial oxidant production in the regulation of recombinant Ca(2+) channel alpha(1C) subunits during CH and exposure to Abeta-(1-40). In wild-type (rho(+)) HEK 293 cells expressing recombinant L-type alpha(1C) subunits, Ca(2+) currents were enhanced by prolonged (24 h) exposure to either CH (6% O(2)) or Abeta-(1-40) (50 nm). By contrast the response to CH was absent in rho(0) cells in which the mitochondrial electron transport chain (ETC) was depleted following long term treatment with ethidium bromide or in rho(+) cells cultured in the presence of 1 microm rotenone. CH was mimicked in rho(0) cells by the exogenous production of O2(-.). by xanthine/xanthine oxidase. Furthermore Abeta-(1-40) enhanced currents in rho(0) cells to a degree similar to that seen in cells with an intact ETC. The antioxidants ascorbate (200 microm) and Trolox (500 microm) ablated the effect of CH in rho(+) cells but were without effect on Abeta-(1-40)-mediated augmentation of Ca(2+) current in rho(0) cells. Thus oxidant production in the mitochondrial ETC is a critical factor, acting upstream of amyloid beta peptide production in the up-regulation of Ca(2+) channels in response to CH.

Donor-acceptor-donor thienyl/bithienyl-benzothiadiazole/quinoxaline model oligomers: experimental and theoretical studies.

PubMed

Pina, João; de Melo, J Seixas; Breusov, D; Scherf, Ullrich

2013-09-28

A comprehensive spectral and photophysical investigation of four donor-acceptor-donor (DAD) oligomers consisting of electron-deficient 2,1,3-benzothiadiazole or quinoxaline moieties linked to electron-rich thienyl or bithienyl units has been undertaken. Additionally, a bis(dithienyl) substituted naphthalene was also investigated. The D-A-D nature of these oligomers resulted in the presence of an intramolecular charge transfer (ICT) state, which was further substantiated by solvatochromism studies (analysis with the Lippert-Mataga formalism). Hereby, significant differences have been obtained for the fluorescence quantum yields of the oligomers in the non-polar solvent methylcyclohexane vs. the polar ethanol. The study was further complemented with the determination of the optimized ground-state molecular geometries for the oligomers together with the prediction of the lowest vertical one-electron excitation energy and the relevant molecular orbital contours using DFT calculations. The electronic transitions show a clear HOMO to LUMO charge-transfer character. In contrast to the thiophene oligomers (the oligothiophenes with n = 1-7), where the intersystem crossing (ISC) yield decreases with n, the studied DAD oligomers were found to show an increase in the ISC efficiency with the number of (donor) thienyl units.

Insulin regulates Presenilin 1 localization via PI3K/Akt signaling.

PubMed

Maesako, Masato; Uemura, Kengo; Kubota, Masakazu; Ando, Koichi; Kuzuya, Akira; Asada, Megumi; Kihara, Takeshi; Kinoshita, Ayae

2010-10-15

Recently, insulin signaling has been highlighted in the pathology of Alzheimer's disease (AD). Although the association between insulin signaling and Tau pathology has been investigated in several studies, the interaction between insulin signaling and Presenilin 1 (PS1), a key molecule of amyloid beta (Abeta) pathology, has not been elucidated so far. In this study, we demonstrated that insulin inhibited PS1 phosphorylation at serine residues (serine 353, 357) via phosphatidylinositol 3-kinase (PI3K)/Akt signal pathway and strengthened the trimeric complex of PS1/N-cadherin/beta-catenin, consequently relocalizing PS1 to the cell surface. Since our recent report suggests that PS1/N-cadherin/beta-catenin complex regulates Abeta production, it is likely that insulin signaling affects Abeta pathology by regulating PS1 localization. 2010 Elsevier Ireland Ltd. All rights reserved.

Differential protection among fractionated blueberry polyphenolic families against DA-, ABeta 42 and LPS-induced decrements in Ca2+ buffering in primary hippocampal cells

USDA-ARS?s Scientific Manuscript database

It has been postulated that at least part of the loss of cognitive function in aging may be the result of deficits in Ca2+ recovery (CAR) and increased oxidative/inflammatory (OX/INF) stress signaling. However, previous research showed that aged animals supplemented with blueberry (BB) extract, show...

Inflammation occurs early during the Abeta deposition process in TgCRND8 mice.

PubMed

Dudal, Sherri; Krzywkowski, Pascale; Paquette, Julie; Morissette, Céline; Lacombe, Diane; Tremblay, Patrick; Gervais, Francine

2004-08-01

Alzheimer's disease (AD) is characterized by a progressive cognitive decline leading to dementia and involves the deposition of amyloid-beta (Abeta) peptides into senile plaques. Other neuropathological features that accompany progression of the disease include a decrease in synaptic density, neurofibrillary tangles, dystrophic neurites, inflammation, and neuronal cell loss. In this study, we report the early kinetics of brain amyloid deposition and its associated inflammation in an early onset transgenic mouse model of AD (TgCRND8) harboring the human amyloid precursor protein gene with the Indiana and Swedish mutations. Both diffuse and compact plaques were detected as early as 9-10 weeks of age. Abeta-immunoreactive (Abeta-IR) plaques (4G8-positive) appeared first in the neocortex and amygdala, then in the hippocampal formation, and lastly in the thalamus. Compact plaques (ThioS-positive) with an amyloid core were observed as early as diffuse plaques were detected, but in lower numbers. Amyloid deposition increased progressively with age. The formation of plaques was concurrent with the appearance of activated microglial cells and shortly followed by the clustering of activated astrocytes around plaques at 13-14 weeks of age. This TgCRND8 mouse model allows for a rapid, time-dependent study of the relationship between the fibrillogenic process and the inflammatory response during the brain amyloidogenic process.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Streltsov, Victor A.; Titmuss, Stephen J.; Epa, V. Chandana

Neurodegeneration observed in Alzheimer disease (AD) is believed to be related to the toxicity from reactive oxygen species (ROS) produced in the brain by the amyloid-{beta} (A{beta}) protein bound primarily to copper ions. The evidence for an oxidative stress role of A{beta}-Cu redox chemistry is still incomplete. Details of the copper binding site in A{beta} may be critical to the etiology of AD. Here we present the structure determined by combining x-ray absorption spectroscopy (XAS) and density functional theory analysis of A{beta} peptides complexed with Cu{sup 2+} in solution under a range of buffer conditions. Phosphate-buffered saline buffer salt (NaCl)more » concentration does not affect the high-affinity copper binding mode but alters the second coordination sphere. The XAS spectra for truncated and full-length A{beta}-Cu{sup 2+} peptides are similar. The novel distorted six-coordinated (3N3O) geometry around copper in the A{beta}-Cu{sup 2+} complexes include three histidines: glutamic, or/and aspartic acid, and axial water. The structure of the high-affinity Cu{sup 2+} binding site is consistent with the hypothesis that the redox activity of the metal ion bound to A{beta} can lead to the formation of dityrosine-linked dimers found in AD.« less

The amyloid precursor protein and postnatal neurogenesis/neuroregeneration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Yanan; Tang, Bor Luen

2006-03-03

The amyloid precursor protein (APP) is the source of amyloid-beta (A{beta}) peptide, produced via its sequential cleavage {beta}- and {gamma}-secretases. Various biophysical forms of A{beta} (and the mutations of APP which results in their elevated levels) have been implicated in the etiology and early onset of Alzheimer's disease. APP's evolutionary conservation and the existence of APP-like isoforms (APLP1 and APLP2) which lack the A{beta} sequence, however, suggest that these might have important physiological functions that are unrelated to A{beta} production. Soluble N-terminal fragments of APP have been known to be neuroprotective, and the interaction of its cytoplasmic C-terminus with amore » myriad of proteins associates it with diverse processes such as axonal transport and transcriptional regulation. The notion for an essential postnatal function of APP has been demonstrated genetically, as mice deficient in both APP and APLP2 or all three APP isoforms exhibit early postnatal lethality and neuroanatomical abnormalities. Recent findings have also brought to light two possible functions of the APP family in Brain-regulation of neural progenitor cell proliferation and axonal outgrowth after injury. Interestingly, these two apparently related neurogenic/neuroregenerative functions of APP involve two separate domains of the molecule.« less

A cybernetic view on wind-up.

PubMed

Farajidavar, Aydin; Gharibzadeh, Shahriar; Towhidkhah, Farzad; Saeb, Sohrab

2006-01-01

Wind-up is described traditionally as a frequency dependent increase in the excitability of spinal cord neurons, evoked by electrical stimulation of afferent C-fibers. Different kinds of wind-up have been reported, but wind-up of Abeta fibers in hyperalgesic states has gained little attention. In this paper, we present a cybernetic view on Abeta fiber wind-up and consider the involved molecular mechanisms as feedback and feedforward processes. Furthermore, our previous hypothesis, the sprouting phenomenon, is included in this view. Considering the proposed model, wind-up in hyperalgesic states might leave out in three different ways: (1) blocking the NMDA receptors by increasing extracellular Mg2+, 2) blocking the receptors and channels that contribute to Ca2+ inward current, and 3) blocking the Abeta fibers by local anesthetics. It seems that wind-up may be inhibited more effectively by using these three blocking mechanisms simultaneously, because in this case, the feedback process (main controller), the feedforward process (trigger), and Abeta stimulation (trigger) would be inhibited concurrently. Wind up may aggravate the pain in clinical hyperalgesic situations such as post-surgical states, some neuropathic pains, fibromyalgia syndrome, and post-herpetic neuralgia. Surely, clinical studies are needed to validate the effectiveness of our abovementioned suggestions in relieving such clinical pains.

Determination of oligomers in virgin and recycled polyethylene terephthalate (PET) samples by UPLC-MS-QTOF.

PubMed

Ubeda, Sara; Aznar, Margarita; Nerín, Cristina

2018-03-01

An oligomer is a molecule that consists of a few monomer units. It can be formed during polymer manufacturing and also due to polymer degradation processes or even during use conditions. Since oligomers are not included in chemical databases, their identification is a complex process. In this work, the oligomers present in 20 different PET pellet samples have been determined. Two different sample treatment procedures, solvent extraction and total dissolution, were applied in order to select the most efficient one. The analyses were carried out by UPLC-MS-QTOF. The use of high resolution mass spectrometry allowed the structural elucidation of these compounds and their correct identification. The main oligomers identified were cyclic as well as lineal from the first, second, and third series. All of them were composed of terephthalic acid (TPA), diethylene glycol (DEG), and ethylene glycol (EG). Quantitative values were very different in both procedures. In total dissolution of PET samples, the concentration of oligomers was always, at least, 10 times higher than in solvent extraction; some of the compounds were only detected when total dissolution was used. Results showed that the oligomers with the highest concentration values were dimers and trimers, cyclic, as well as lineal, from the first and second series. The oligomer with the maximum concentration value was TPA 2 -EG-DEG that was found in all the samples in a concentration range from 2493 to 19,290 ng/g PET. No differences between virgin and recycled PET were found. Migration experiments were performed in two PET bottles, and results showed the transference of most of these oligomers to a fat food simulant (ethanol 95%). Graphical abstract Graphical abstract of the two procedures developd and optimized for identifying oligomers in PET pellets and in migration form PET bottles.

Tacripyrines, the first tacrine-dihydropyridine hybrids, as multitarget-directed ligands for the treatment of Alzheimer's disease.

PubMed

Marco-Contelles, José; León, Rafael; de los Ríos, Cristóbal; Samadi, Abdelouahid; Bartolini, Manuela; Andrisano, Vincenza; Huertas, Oscar; Barril, Xavier; Luque, F Javier; Rodríguez-Franco, María I; López, Beatriz; López, Manuela G; García, Antonio G; Carreiras, María do Carmo; Villarroya, Mercedes

2009-05-14

Tacripyrines (1-14) have been designed by combining an AChE inhibitor (tacrine) with a calcium antagonist such as nimodipine and are targeted to develop a multitarget therapeutic strategy to confront AD. Tacripyrines are selective and potent AChE inhibitors in the nanomolar range. The mixed type inhibition of hAChE activity of compound 11 (IC(50) 105 +/- 15 nM) is associated to a 30.7 +/- 8.6% inhibition of the proaggregating action of AChE on the Abeta and a moderate inhibition of Abeta self-aggregation (34.9 +/- 5.4%). Molecular modeling indicates that binding of compound 11 to the AChE PAS mainly involves the (R)-11 enantiomer, which also agrees with the noncompetitive inhibition mechanism exhibited by p-methoxytacripyrine 11. Tacripyrines are neuroprotective agents, show moderate Ca(2+) channel blocking effect, and cross the blood-brain barrier, emerging as lead candidates for treating AD.

Tau Oligomers Associate with Inflammation in the Brain and Retina of Tauopathy Mice and in Neurodegenerative Diseases

PubMed Central

Nilson, Ashley N.; English, Kelsey C.; Gerson, Julia E.; Barton Whittle, T.; Nicolas Crain, C.; Xue, Judy; Sengupta, Urmi; Castillo-Carranza, Diana L.; Zhang, Wenbo; Gupta, Praveena; Kayed, Rakez

2016-01-01

It is well-established that inflammation plays an important role in Alzheimer’s disease (AD) and frontotemporal lobar dementia (FTLD). Inflammation and synapse loss occur in disease prior to the formation of larger aggregates, but the contribution of tau to inflammation has not yet been thoroughly investigated. Tau pathologically aggregates to form large fibrillar structures known as tangles. However, evidence suggests that smaller soluble aggregates, called oligomers, are the most toxic species and form prior to tangles. Furthermore, tau oligomers can spread to neighboring cells and between anatomically connected brain regions. In addition, recent evidence suggests that inspecting the retina may be a window to brain pathology. We hypothesized that there is a relationship between tau oligomers and inflammation, which are hallmarks of early disease. We conducted immunofluorescence and biochemical analyses on tauopathy mice, FTLD, and AD subjects. We showed that oligomers co-localize with astrocytes, microglia, and HMGB1, a pro-inflammatory cytokine. Additionally, we show that tau oligomers are present in the retina and are associated with inflammatory cells suggesting that the retina may be a valid non-invasive biomarker for brain pathology. These results suggest that there may be a toxic relationship between tau oligomers and inflammation. Therefore, the ability of tau oligomers to spread may initiate a feed-forward cycle in which tau oligomers induce inflammation, leading to neuronal damage, and thus more inflammation. Further mechanistic studies are warranted in order to understand this relationship, which may have critical implications for improving the treatment of tauopathies. PMID:27716675

Effect of the electrostatic surface potential on the oligomerization of full-length human recombinant prion protein at single-molecule level

NASA Astrophysics Data System (ADS)

Wang, Bin; Lou, Zhichao; Zhang, Haiqian; Xu, Bingqian

2016-03-01

The electrostatic surface potential (ESP) of prion oligomers has critical influences on the aggregating processes of the prion molecules. The atomic force microscopy (AFM) and structural simulation were combined to investigate the molecular basis of the full-length human recombinant prion oligomerization on mica surfaces. The high resolution non-intrusive AFM images showed that the prion oligomers formed different patterns on mica surfaces at different buffer pH values. The basic binding units for the large oligomers were determined to be prion momoners (Ms), dimers (Ds), and trimers (Ts). The forming of the D and T units happened through the binding of hydrophobic β-sheets of the M units. In contrast, the α-helices of these M, D, and T units were the binding areas for the formation of large oligomers. At pH 4.5, the binding units M, D, and T showed clear polarized ESP distributions on the surface domains, while at pH 7.0, they showed more evenly distributed ESPs. Based on the conformations of oligomers observed from AFM images, the D and T units were more abundantly on mica surface at pH 4.5 because the ESP re-distribution of M units helped to stabilize these larger oligomers. The amino acid side chains involved in the binding interfaces were stabilized by hydrogen bonds and electrostatic interactions. The detailed analysis of the charged side chains at pH 4.5 indicated that the polarized ESPs induced the aggregations among M, D, and T to form larger oligomers. Therefore, the hydrogen bonds and electrostatic interactions worked together to form the stabilized prion oligomers.

Effect of the electrostatic surface potential on the oligomerization of full-length human recombinant prion protein at single-molecule level

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Bin; Xu, Bingqian, E-mail: bxu@engr.uga.edu; Lou, Zhichao

2016-03-21

The electrostatic surface potential (ESP) of prion oligomers has critical influences on the aggregating processes of the prion molecules. The atomic force microscopy (AFM) and structural simulation were combined to investigate the molecular basis of the full-length human recombinant prion oligomerization on mica surfaces. The high resolution non-intrusive AFM images showed that the prion oligomers formed different patterns on mica surfaces at different buffer pH values. The basic binding units for the large oligomers were determined to be prion momoners (Ms), dimers (Ds), and trimers (Ts). The forming of the D and T units happened through the binding of hydrophobicmore » β-sheets of the M units. In contrast, the α-helices of these M, D, and T units were the binding areas for the formation of large oligomers. At pH 4.5, the binding units M, D, and T showed clear polarized ESP distributions on the surface domains, while at pH 7.0, they showed more evenly distributed ESPs. Based on the conformations of oligomers observed from AFM images, the D and T units were more abundantly on mica surface at pH 4.5 because the ESP re-distribution of M units helped to stabilize these larger oligomers. The amino acid side chains involved in the binding interfaces were stabilized by hydrogen bonds and electrostatic interactions. The detailed analysis of the charged side chains at pH 4.5 indicated that the polarized ESPs induced the aggregations among M, D, and T to form larger oligomers. Therefore, the hydrogen bonds and electrostatic interactions worked together to form the stabilized prion oligomers.« less

Laser-induced propagation and destruction of amyloid beta fibrils.

PubMed

Yagi, Hisashi; Ozawa, Daisaku; Sakurai, Kazumasa; Kawakami, Toru; Kuyama, Hiroki; Nishimura, Osamu; Shimanouchi, Toshinori; Kuboi, Ryoichi; Naiki, Hironobu; Goto, Yuji

2010-06-18

The amyloid deposition of amyloid beta (Abeta) peptides is a critical pathological event in Alzheimer disease (AD). Preventing the formation of amyloid deposits and removing preformed fibrils in tissues are important therapeutic strategies against AD. Previously, we reported the destruction of amyloid fibrils of beta(2)-microglobulin K3 fragments by laser irradiation coupled with the binding of amyloid-specific thioflavin T. Here, we studied the effects of a laser beam on Abeta fibrils. As was the case for K3 fibrils, extensive irradiation destroyed the preformed Abeta fibrils. However, irradiation during spontaneous fibril formation resulted in only the partial destruction of growing fibrils and a subsequent explosive propagation of fibrils. The explosive propagation was caused by an increase in the number of active ends due to breakage. The results not only reveal a case of fragmentation-induced propagation of fibrils but also provide insights into therapeutic strategies for AD.

Decreased rhythmic GABAergic septal activity and memory-associated theta oscillations after hippocampal amyloid-beta pathology in the rat.

PubMed

Villette, Vincent; Poindessous-Jazat, Frédérique; Simon, Axelle; Léna, Clément; Roullot, Elodie; Bellessort, Brice; Epelbaum, Jacques; Dutar, Patrick; Stéphan, Aline

2010-08-18

The memory deficits associated with Alzheimer's disease result to a great extent from hippocampal network dysfunction. The coordination of this network relies on theta (symbol) oscillations generated in the medial septum. Here, we investigated in rats the impact of hippocampal amyloid beta (Abeta) injections on the physiological and cognitive functions that depend on the septohippocampal system. Hippocampal Abeta injections progressively impaired behavioral performances, the associated hippocampal theta power, and theta frequency response in a visuospatial recognition test. These alterations were associated with a specific reduction in the firing of the identified rhythmic bursting GABAergic neurons responsible for the propagation of the theta rhythm to the hippocampus, but without loss of medial septal neurons. Such results indicate that hippocampal Abeta treatment leads to a specific functional depression of inhibitory projection neurons of the medial septum, resulting in the functional impairment of the temporal network.

Protein kinase C involvement in the acetylcholine release reduction induced by amyloid-beta(25-35) aggregates on neuromuscular synapses.

PubMed

Tomàs, Marta; Garcia, Neus; Santafé, Manuel M; Lanuza, Maria; Tomàs, Josep

2009-01-01

Using intracellular recording of the diaphragm muscle of adult rats, we have investigated the short-term functional effects of amyloid-beta (Abeta(25-35) peptide aggregates on the modulation of acetylcholine (ACh) release and the involvement of protein kinase C (PKC). The non-aggregated form of this peptide does not change the evoked and spontaneous transmitter release parameters on the neuromuscular synapse. However, the aggregated form of Abeta(25-35) acutely interferes with evoked quantal ACh release (approximately 40% reduction) when synaptic activity in the ex vivo neuromuscular preparation is maintained by low frequency (1 Hz) electrical stimulation. This effect is partially dependent on the activity of PKC that may have a permissive action. The end result of Abeta(25-35) is in opposition to the PKC-dependent maintenance effect on ACh release manifested in active synapses.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Connor, D.M.; Miller, L.; Benveniste, H.

Our understanding of early development in Alzheimer's disease (AD) is clouded by the scale at which the disease progresses; amyloid beta (A{beta}) plaques, a hallmark feature of AD, are small ({approx} 50 {micro}m) and low contrast in diagnostic clinical imaging techniques. Diffraction enhanced imaging (DEI), a phase contrast x-ray imaging technique, has greater soft tissue contrast than conventional radiography and generates higher resolution images than magnetic resonance microimaging. Thus, in this proof of principle study, DEI in micro-CT mode was performed on the brains of AD-model mice to determine if DEI can visualize A{beta} plaques. Results revealed small nodules inmore » the cortex and hippocampus of the brain. Histology confirmed that the features seen in the DEI images of the brain were A{beta} plaques. Several anatomical structures, including hippocampal subregions and white matter tracks, were also observed. Thus, DEI has strong promise in early diagnosis of AD, as well as general studies of the mouse brain.« less

Relationship and significance between anti-beta2-glycoprotein I antibodies and platelet activation state in patients with ulcerative colitis.

PubMed

Gao, Yan-Hang; Gao, Pu-Jun; Wang, Chun-Guang; Wang, Xiao-Cong; Piao, Yun-Feng

2008-02-07

To study the relationship between anti-beta2-glycoprotein I (abeta2GPI) antibodies and platelet activation state in patients with ulcerative colitis (UC) and its significance. Peripheral blood samples were collected from 56 UC patients (34 males and 22 females, aged 43.5 years, range 21-66 years), including 36 at active stage and 20 at remission stage, and 25 sex-and age-matched controls. The level of abeta2GPI was measured by ELISA. The platelet activation markers, platelet activation complex-I (PAC-I) and P-selectin (CD62P) were detected by flow cytometry. The A value for IgG abeta2GPI in the active UC group was 0.61 +/- 0.13, significantly higher than that in the remittent UC and control groups (0.50 +/- 0.13 and 0.22 +/- 0.14, P < 0.01). There was a significant difference between the two groups (P < 0.01). The A value for IgM abeta2GPI in the active and remittent UC groups was 0.43 +/- 0.13 and 0.38 +/- 0.12, significantly higher than that in the control group (0.20 +/- 0.12, P < 0.01). However, there was no significant difference between the two groups (P > 0.05). The PAC-I positive rate for the active and remittent UC groups was 30.6% +/- 7.6% and 19.6% +/- 7.8% respectively, significantly higher than that for the control group (6.3% +/- 1.7%, P < 0.01). There was a significant difference between the two groups (P < 0.01). The CD62P positive rate for the active and remittent UC groups was 45.0% +/- 8.8% and 31.9% +/- 7.8% respectively, significantly higher than that for the control group (9.2% +/- 2.7%, P < 0.01). There was a significant difference between the two groups (P < 0.01). In the active UC group, the more severe the state of illness was, the higher the A value for IgG abeta2GPI was, and the positive rate for PAC-I and CD62P was positively correlated with the state of illness (Fabeta2GPI = 3.679, P < 0.05; FPAC-I (%) = 5.346, P < 0.01; and FCD62P (%) = 5. 418, P < 0.01). Meanwhile, in the same state of illness, the A value for IgG abeta2GPI was positively correlated to the positive rates for PAC-I and CD62P. abeta2GPI level, platelet activation state and their relationship of them are closely correlated with the pathogenesis and development of UC.

Structural and functional properties of prefibrillar α-synuclein oligomers.

PubMed

Pieri, Laura; Madiona, Karine; Melki, Ronald

2016-04-14

The deposition of fibrillar alpha-synuclein (α-syn) within inclusions (Lewy bodies and Lewy neurites) in neurons and glial cells is a hallmark of synucleinopathies. α-syn populates a variety of assemblies ranging from prefibrillar oligomeric species to fibrils whose specific contribution to neurodegeneration is still unclear. Here, we compare the specific structural and biological properties of distinct soluble prefibrillar α-syn oligomers formed either spontaneously or in the presence of dopamine and glutaraldehyde. We show that both on-fibrillar assembly pathway and distinct dopamine-mediated and glutaraldehyde-cross-linked α-syn oligomers are only slightly effective in perturbing cell membrane integrity and inducing cytotoxicity, while mature fibrils exhibit the highest toxicity. In contrast to low-molecular weight and unstable oligomers, large stable α-syn oligomers seed the aggregation of soluble α-syn within reporter cells although to a lesser extent than mature α-syn fibrils. These oligomers appear elongated in shape. Our findings suggest that α-syn oligomers represent a continuum of species ranging from unstable low molecular weight particles to mature fibrils via stable elongated oligomers composed of more than 15 α-syn monomers that possess seeding capacity.

Polymerization on the rocks: theoretical introduction

NASA Technical Reports Server (NTRS)

Orgel, L. E.; Bada, J. L. (Principal Investigator)

1998-01-01

It is difficult if not impossible to synthesize long polymers of amino acids, nucleotides, etc., in homogeneous aqueous solution. We suggest that long polymers were synthesized on the surface of minerals in a prebiotic process analogous to solid-phase synthesis. Provided that the affinity of a mineral for an oligomer increases with the length of the oligomer, adsorption must become essentially irreversible for sufficiently long oligomers. Irreversibly adsorbed oligomers may be elongated indefinitely by repeated cycles in which the mineral with its adsorbed oligomers is first incubated with activated monomers and then washed free of deactivated monomer and side-products. We discuss in some detail the formation of oligomers of negatively-charged amino acids such as glutamic acid on anion-exchange minerals such as hydroxylapatite or illite. We show that the average length of adsorbed oligomers at steady state, n, depends on the balance between the rate of chain elongation and the rate of hydrolysis, and we derive a very approximate formula for n.

The road to LOAD: late-onset Alzheimer's disease and a possible way to block it.

PubMed

Whitfield, James F

2007-10-01

The ageing brain becomes increasingly less able to destroy or eject toxic amyloid (A) beta42 peptide byproducts of normal neuronal activity that consequently accumulate to induce Alzheimer's disease (AD). Therefore, the various components of the Abeta-clearing machinery are prime targets for AD therapeutics. In this connection, there are reports that taking statins to lower circulating cholesterol to prevent cardiovascular disease can also prevent late-onset AD (LOAD) the most common form of the disease. However, it seems unlikely that statins would prevent LOAD by lowering the very long-lived brain cholesterol that is controlled independently from the very much shorter-lived circulating cholesterol. In fact, reducing the ability of the brain astrocytes to make cholesterol for their closely associated neuron clients' synaptogenesis could damage the brain rather than protect it. However, a plausible way statins might prevent LOAD is to target a main component of the clearance machinery, low-density lipoprotein receptor-related protein 1 (LRP1), the brain's powerful Abeta-efflux driver. This is indicated by a reported ability of micromolar concentrations of lovastatin and simvastatin to strongly stimulate brain vascular endothelial cells to make this Abeta ejector. Therefore, if this holds up, taking a statin over the years would prevent the normal decline of LRP1 in the ageing brain and a LOAD-driving accumulation of Abeta.

Brain inflammation and Alzheimer's-like pathology in individuals exposed to severe air pollution.

PubMed

Calderón-Garcidueñas, Lilian; Reed, William; Maronpot, Robert R; Henríquez-Roldán, Carlos; Delgado-Chavez, Ricardo; Calderón-Garcidueñas, Ana; Dragustinovis, Irma; Franco-Lira, Maricela; Aragón-Flores, Mariana; Solt, Anna C; Altenburg, Michael; Torres-Jardón, Ricardo; Swenberg, James A

2004-01-01

Air pollution is a complex mixture of gases (e.g., ozone), particulate matter, and organic compounds present in outdoor and indoor air. Dogs exposed to severe air pollution exhibit chronic inflammation and acceleration of Alzheimer's-like pathology, suggesting that the brain is adversely affected by pollutants. We investigated whether residency in cities with high levels of air pollution is associated with human brain inflammation. Expression of cyclooxygenase-2 (COX2), an inflammatory mediator, and accumulation of the 42-amino acid form of beta-amyloid (Abeta42), a cause of neuronal dysfunction, were measured in autopsy brain tissues of cognitively and neurologically intact lifelong residents of cities having low (n:9) or high (n:10) levels of air pollution. Genomic DNA apurinic/apyrimidinic sites, nuclear factor-kappaB activation and apolipoprotein E genotype were also evaluated. Residents of cities with severe air pollution had significantly higher COX2 expression in frontal cortex and hippocampus and greater neuronal and astrocytic accumulation of Abeta42 compared to residents in low air pollution cities. Increased COX2 expression and Abeta42 accumulation were also observed in the olfactory bulb. These findings suggest that exposure to severe air pollution is associated with brain inflammation and Abeta42 accumulation, two causes of neuronal dysfunction that precede the appearance of neuritic plaques and neurofibrillary tangles, hallmarks of Alzheimer's disease.

An unconventional hypothesis of oxidation in Alzheimer's disease: intersections with excitotoxicity.

PubMed

Barger, Steven W

2004-09-01

There are two major lines of investigation from which a connection has been traditionally drawn between chemical oxidation and Alzheimer's disease. First, a major risk factor for AD is age, and oxidative stress has long been a component of general hypotheses about biological aging. The second line of reasoning is a corollary of the Amyloid Hypothesis, the assumption that the amyloid beta-peptide (A-beta) which comprises AD's pathognomic plaques is a key mediator of the neurodegeneration occurring in this disorder. Under many experimental conditions, A-beta has been shown to evoke oxidative damage to tissues, cells, and biomolecules; even the redox properties of the peptide itself have been hotly debated. These two modalities of conjecture intersect under the Inflammatory Hypothesis of AD, as inflammation produces oxidation, old age is associated with elevation in inflammatory events, and A-beta can further exacerbate such inflammatory reactions in brain cells. This review discusses these arguments about the pathogenesis of AD and how they might be generalized to other neurodegenerative conditions. But, additional speculation is offered in the form of an inclusionary mechanism that may be specific and novel enough to qualify as a third line of theory; namely, the possibility that inflammatory reactions in microglia--activated by A-beta or other factors among the "usual suspects"--initiate programmed oxidation that is converted to the neuron-specific stress of excitotoxicity.

Exploring Beta-Amyloid Protein Transmembrane Insertion Behavior and Residue-Specific Lipid Interactions in Lipid Bilayers Using Multiscale MD Simulations

NASA Astrophysics Data System (ADS)

Qiu, Liming; Vaughn, Mark; Cheng, Kelvin

2013-03-01

Beta-amyloid (Abeta) interactions with neurons are linked to Alzheimer's. Using a multiscale MD simulation strategy that combines the high efficiency of phase space sampling of coarse-grained MD (CGD) and the high spatial resolution of Atomistic MD (AMD) simulations, we studied the Abeta insertion dynamics in cholesterol-enriched and -depleted lipid bilayers that mimic the neuronal membranes domains. Forward (AMD-CGD) and reverse (CGD-AMD) mappings were used. At the atomistic level, cholesterol promoted insertion of Abeta with high (folded) or low (unfolded) helical contents of the lipid insertion domain (Lys28-Ala42), and the insertions were stabilized by the Lys28 snorkeling and Ala42-anchoring to the polar lipid groups of the bilayer up to 200ns. After the forward mapping, the folded inserted state switched to a new extended inserted state with the Lys28 descended to the middle of the bilayer while the unfolded inserted state migrated to the membrane surface up to 4000ns. The two new states remained stable for 200ns at the atomistic scale after the reverse mapping. Our results suggested that different Abeta membrane-orientation states separated by free energy barriers can be explored by the multiscale MD more effectively than by Atomistic MD simulations alone. NIH RC1-GM090897-02

Long-term electromagnetic pulse exposure induces Abeta deposition and cognitive dysfunction through oxidative stress and overexpression of APP and BACE1.

PubMed

Jiang, Da-Peng; Li, Jin-Hui; Zhang, Jie; Xu, Sheng-Long; Kuang, Fang; Lang, Hai-Yang; Wang, Ya-Feng; An, Guang-Zhou; Li, Jing; Guo, Guo-Zhen

2016-07-01

A progressively expanded literature has been devoted in the past years to the noxious or beneficial effects of electromagnetic field (EMF) to Alzheimer׳s disease (AD). This study concerns the relationship between electromagnetic pulse (EMP) exposure and the occurrence of AD in rats and the underlying mechanisms, focusing on the role of oxidative stress (OS). 55 healthy male Sprague Dawley (SD) rats were used and received continuous exposure for 8 months. Morris water maze (MWM) test was conducted to test the ability of cognitive and memory. The level of OS was detected by superoxide dismutase (SOD) activity and glutathione (GSH) content. We found that long-term EMP exposure induced cognitive damage in rats. The content of β-amyloid (Aβ) protein in hippocampus was increased after long-term EMP exposure. OS of hippocampal neuron was detected. Western blotting and immunohistochemistry (IHC) assay showed that the content of Aβ protein and its oligomers in EMP-exposed rats were higher than that of sham-exposed rats. The content of Beta Site App Cleaving Enzyme (BACE1) and microtubule-associated protein 1 light chain 3-II (LC3-II) in EMP-exposed rats hippocampus were also higher than that of sham-exposed rats. SOD activity and GSH content in EMP-exposed rats were lower than sham-exposed rats (p<0.05). Several mechanisms were proposed based on EMP exposure-induced OS, including increased amyloid precursor protein (APP) aberrant cleavage. Although further study is needed, the present results suggest that long-term EMP exposure is harmful to cognitive ability in rats and could induce AD-like pathological manifestation. Copyright © 2016 Elsevier B.V. All rights reserved.

Biomarkers for early diagnosis of Alzheimer disease: 'ALZheimer ASsociated gene'--a new blood biomarker?

PubMed

Jellinger, Kurt A; Janetzky, Bernd; Attems, Johannes; Kienzl, Elisabeth

2008-08-01

Simple, non-invasive tests for an early detection of degenerative dementia by use of biomarkers are urgently required. However, up to the present, no validated extracerebral diagnostic markers (plasma/serum, platelets, urine, connective tissue) for the early diagnosis of Alzheimer disease (AD) are available. In disease stages with evident cognitive disturbances, the clinical diagnosis of probable AD is made with around 90% accuracy using modern clinical, neuropsychological and imaging methods. Diagnostic sensitivity and specificity even in early disease stages are improved by CSF markers, in particular combined tau and amyloid beta peptides (Abeta) and plasma markers (eg, Abeta-42/Abeta-40 ratio). Recently, a novel gene/protein--ALZAS (Alzheimer Associated Protein)--with a 79 amino acid sequence, containing the amyloid beta-42 fragment (Abeta-42), the amyloid precursor protein (APP) transmembrane signal and a 12 amino acid C-terminal, not present in any other known APP alleles, has been discovered on chromosome 21 within the APP region. Reverse transcriptase-PCR revealed the expression of the transcript of this protein in the cortex and hippocampal regions as well as in lymphocytes of human AD patients. The expression of ALZAS is mirrored by a specific autoimmune response in AD patients, directed against the ct-12 end of the ALZAS-peptide but not against the Abeta-sequence. ELISA studies of plasma detected highest titers of ALZAS in patients with mild cognitive impairment (presymptomatic AD), but only moderately increased titers in autopsy-confirmed AD, whereas low or undetectable ct-12 titers were found in cognitively intact age-matched subjects and young controls. The antigen, ALZAS protein, was detected in plasma in later clinical stages of AD. It is suggested that ALZAS represents an indicator in a dynamic equilibrium between both peripheral and brain degenerative changes in AD and may become a useful "non-invasive" diagnostic marker via a simple blood test.

Large α-synuclein oligomers inhibit neuronal SNARE-mediated vesicle docking

PubMed Central

Choi, Bong-Kyu; Choi, Mal-Gi; Kim, Jae-Yeol; Yang, Yoosoo; Lai, Ying; Kweon, Dae-Hyuk; Lee, Nam Ki; Shin, Yeon-Kyun

2013-01-01

Parkinson disease and dementia with Lewy bodies are featured with the formation of Lewy bodies composed mostly of α-synuclein (α-Syn) in the brain. Although evidence indicates that the large oligomeric or protofibril forms of α-Syn are neurotoxic agents, the detailed mechanisms of the toxic functions of the oligomers remain unclear. Here, we show that large α-Syn oligomers efficiently inhibit neuronal SNARE-mediated vesicle lipid mixing. Large α-Syn oligomers preferentially bind to the N-terminal domain of a vesicular SNARE protein, synaptobrevin-2, which blocks SNARE-mediated lipid mixing by preventing SNARE complex formation. In sharp contrast, the α-Syn monomer has a negligible effect on lipid mixing even with a 30-fold excess compared with the case of large α-Syn oligomers. Thus, the results suggest that large α-Syn oligomers function as inhibitors of dopamine release, which thus provides a clue, at the molecular level, to their neurotoxicity. PMID:23431141

Diverse mechanisms of antidiabetic effects of the different procyanidin oligomer types of two different cinnamon species on db/db mice.

PubMed

Chen, Liang; Sun, Peng; Wang, Ting; Chen, Kaixian; Jia, Qi; Wang, Heyao; Li, Yiming

2012-09-12

The procyanidin oligomers are thought to be responsible for the antidiabetic activity of cinnamon. To investigate the hypoglycemic effects of different procyanidin oligomer types, the procyanidin oligomer-rich extracts were prepared from two different cinnamon species. Using high-performance liquid chromatography with purified procyanidin oligomers as reference compounds, we found that the Cinnamomum cassia extract (CC-E) and Cinnamomum tamala extract (CT-E) were rich in B- and A-type procyanidin oligomers, respectively. In the experiment, 8-week-old diabetic (db/db) mice were gavaged with CC-E and CT-E (both 200 mg/kg per day) for 4 weeks. Both CC-E and CT-E exhibited antidiabetic effects. Moreover, histopathological studies of the pancreas, liver, and adipose tissue showed that CC-E promoted lipid accumulation in the adipose tissue and liver, whereas CT-E mainly improved the insulin concentration in the blood and pancreas.

Stabilization of neurotoxic Alzheimer amyloid-β oligomers by protein engineering

PubMed Central

Sandberg, Anders; Luheshi, Leila M.; Söllvander, Sofia; Pereira de Barros, Teresa; Macao, Bertil; Knowles, Tuomas P. J.; Biverstål, Henrik; Lendel, Christofer; Ekholm-Petterson, Frida; Dubnovitsky, Anatoly; Lannfelt, Lars; Dobson, Christopher M.; Härd, Torleif

2010-01-01

Soluble oligomeric aggregates of the amyloid-β peptide (Aβ) have been implicated in the pathogenesis of Alzheimer’s disease (AD). Although the conformation adopted by Aβ within these aggregates is not known, a β-hairpin conformation is known to be accessible to monomeric Aβ. Here we show that this β-hairpin is a building block of toxic Aβ oligomers by engineering a double-cysteine mutant (called Aβcc) in which the β-hairpin is stabilized by an intramolecular disulfide bond. Aβ40cc and Aβ42cc both spontaneously form stable oligomeric species with distinct molecular weights and secondary-structure content, but both are unable to convert into amyloid fibrils. Biochemical and biophysical experiments and assays with conformation-specific antibodies used to detect Aβ aggregates in vivo indicate that the wild-type oligomer structure is preserved and stabilized in Aβcc oligomers. Stable oligomers are expected to become highly toxic and, accordingly, we find that β-sheet-containing Aβ42cc oligomers or protofibrillar species formed by these oligomers are 50 times more potent inducers of neuronal apoptosis than amyloid fibrils or samples of monomeric wild-type Aβ42, in which toxic aggregates are only transiently formed. The possibility of obtaining completely stable and physiologically relevant neurotoxic Aβ oligomer preparations will facilitate studies of their structure and role in the pathogenesis of AD. For example, here we show how kinetic partitioning into different aggregation pathways can explain why Aβ42 is more toxic than the shorter Aβ40, and why certain inherited mutations are linked to protofibril formation and early-onset AD. PMID:20713699

Structural and functional properties of prefibrillar α-synuclein oligomers

PubMed Central

Pieri, Laura; Madiona, Karine; Melki, Ronald

2016-01-01

The deposition of fibrillar alpha-synuclein (α-syn) within inclusions (Lewy bodies and Lewy neurites) in neurons and glial cells is a hallmark of synucleinopathies. α-syn populates a variety of assemblies ranging from prefibrillar oligomeric species to fibrils whose specific contribution to neurodegeneration is still unclear. Here, we compare the specific structural and biological properties of distinct soluble prefibrillar α-syn oligomers formed either spontaneously or in the presence of dopamine and glutaraldehyde. We show that both on-fibrillar assembly pathway and distinct dopamine-mediated and glutaraldehyde-cross-linked α-syn oligomers are only slightly effective in perturbing cell membrane integrity and inducing cytotoxicity, while mature fibrils exhibit the highest toxicity. In contrast to low-molecular weight and unstable oligomers, large stable α-syn oligomers seed the aggregation of soluble α-syn within reporter cells although to a lesser extent than mature α-syn fibrils. These oligomers appear elongated in shape. Our findings suggest that α-syn oligomers represent a continuum of species ranging from unstable low molecular weight particles to mature fibrils via stable elongated oligomers composed of more than 15 α-syn monomers that possess seeding capacity. PMID:27075649

Antiparallel Triple-strand Architecture for Prefibrillar Aβ42 Oligomers*

PubMed Central

Gu, Lei; Liu, Cong; Stroud, James C.; Ngo, Sam; Jiang, Lin; Guo, Zhefeng

2014-01-01

Aβ42 oligomers play key roles in the pathogenesis of Alzheimer disease, but their structures remain elusive partly due to their transient nature. Here, we show that Aβ42 in a fusion construct can be trapped in a stable oligomer state, which recapitulates characteristics of prefibrillar Aβ42 oligomers and enables us to establish their detailed structures. Site-directed spin labeling and electron paramagnetic resonance studies provide structural restraints in terms of side chain mobility and intermolecular distances at all 42 residue positions. Using these restraints and other biophysical data, we present a novel atomic-level oligomer model. In our model, each Aβ42 protein forms a single β-sheet with three β-strands in an antiparallel arrangement. Each β-sheet consists of four Aβ42 molecules in a head-to-tail arrangement. Four β-sheets are packed together in a face-to-back fashion. The stacking of identical segments between different β-sheets within an oligomer suggests that prefibrillar oligomers may interconvert with fibrils via strand rotation, wherein β-strands undergo an ∼90° rotation along the strand direction. This work provides insights into rational design of therapeutics targeting the process of interconversion between toxic oligomers and non-toxic fibrils. PMID:25118290

Aβ42-oligomer Interacting Peptide (AIP) neutralizes toxic amyloid-β42 species and protects synaptic structure and function

NASA Astrophysics Data System (ADS)

Barucker, Christian; Bittner, Heiko J.; Chang, Philip K.-Y.; Cameron, Scott; Hancock, Mark A.; Liebsch, Filip; Hossain, Shireen; Harmeier, Anja; Shaw, Hunter; Charron, François M.; Gensler, Manuel; Dembny, Paul; Zhuang, Wei; Schmitz, Dietmar; Rabe, Jürgen P.; Rao, Yong; Lurz, Rudi; Hildebrand, Peter W.; McKinney, R. Anne; Multhaup, Gerhard

2015-10-01

The amyloid-β42 (Aβ42) peptide is believed to be the main culprit in the pathogenesis of Alzheimer disease (AD), impairing synaptic function and initiating neuronal degeneration. Soluble Aβ42 oligomers are highly toxic and contribute to progressive neuronal dysfunction, loss of synaptic spine density, and affect long-term potentiation (LTP). We have characterized a short, L-amino acid Aβ-oligomer Interacting Peptide (AIP) that targets a relatively well-defined population of low-n Aβ42 oligomers, rather than simply inhibiting the aggregation of Aβ monomers into oligomers. Our data show that AIP diminishes the loss of Aβ42-induced synaptic spine density and rescues LTP in organotypic hippocampal slice cultures. Notably, the AIP enantiomer (comprised of D-amino acids) attenuated the rough-eye phenotype in a transgenic Aβ42 fly model and significantly improved the function of photoreceptors of these flies in electroretinography tests. Overall, our results indicate that specifically “trapping” low-n oligomers provides a novel strategy for toxic Aβ42-oligomer recognition and removal.

Mechanisms to explain the reverse perivascular transport of solutes out of the brain.

PubMed

Schley, D; Carare-Nnadi, R; Please, C P; Perry, V H; Weller, R O

2006-02-21

Experimental studies and observations in the human brain indicate that interstitial fluid and solutes, such as amyloid-beta (Abeta), are eliminated from grey matter of the brain along pericapillary and periarterial pathways. It is unclear, however, what constitutes the motive force for such transport within blood vessel walls, which is in the opposite direction to blood flow. In this paper the potential for global pressure differences to achieve such transport are considered. A mathematical model is constructed in order to test the hypothesis that perivascular drainage of interstitial fluid and solutes out of brain tissue is driven by pulsations of the blood vessel walls. Here it is assumed that drainage occurs through a thin layer between astrocytes and endothelial cells or between smooth muscle cells. The model suggests that, during each pulse cycle, there are periods when fluid and solutes are driven along perivascular spaces in the reverse direction to the flow of blood. It is shown that successful drainage may depend upon some attachment of solutes to the lining of the perivascular space, in order to produce a valve-like effect, although an alternative without this requirement is also postulated. Reduction in pulse amplitude, as in ageing cerebral vessels, would prolong the attachment time, encourage precipitation of Abeta peptides in vessel walls, and impair elimination of Abeta from the brain. These factors may play a role in the pathogenesis of cerebral amyloid angiopathy and in the accumulation of Abeta in the brain in Alzheimer's disease.

Some photophysical properties of new oligomer obtained from anodic oxidation of 4,4‧-dimethoxychalcone

NASA Astrophysics Data System (ADS)

Ghomrasni, S.; Aribi, I.; Chemek, M.; Said, A. Haj; Alimi, K.

2018-04-01

Some photopysical properties of a new oligomer obtained from the anodic oxidation of the 4,4‧-dimethoxy-chalcone were investigated using different and complementary techniques. Firstly, TGA analysis and X-Ray diffraction experiments showed that the oligomer is thermally stable up to 500 K and partially organized at the solid state, respectively. Secondly, the optical properties of the oligomer were studied in solution and in the solid state. The optical band gap was estimated to be 3.17 eV in solution state and 2.70 eV in film state. What's more, the fluorescence decay is determined showing a considerably faster in the film state (0.183 ns) than in solution state (1.606 ns), due to the rapid non-radiative decay at inter-chain trap sites.

Amyloid Oligomers and Protofibrils, but Not Filaments, Self-Replicate from Native Lysozyme

PubMed Central

2015-01-01

Self-assembly of amyloid fibrils is the molecular mechanism best known for its connection with debilitating human disorders such as Alzheimer’s disease but is also associated with various functional cellular responses. There is increasing evidence that amyloid formation proceeds along two distinct assembly pathways involving either globular oligomers and protofibrils or rigid monomeric filaments. Oligomers, in particular, have been implicated as the dominant molecular species responsible for pathogenesis. Yet the molecular mechanisms regulating their self-assembly have remained elusive. Here we show that oligomers/protofibrils and monomeric filaments, formed along distinct assembly pathways, display critical differences in their ability to template amyloid growth at physiological vs denaturing temperatures. At physiological temperatures, amyloid filaments remained stable but could not seed growth of native monomers. In contrast, oligomers and protofibrils not only remained intact but were capable of self-replication using native monomers as the substrate. Kinetic data further suggested that this prion-like growth mode of oligomers/protofibrils involved two distinct activities operating orthogonal from each other: autocatalytic self-replication of oligomers from native monomers and nucleated polymerization of oligomers into protofibrils. The environmental changes to stability and templating competence of these different amyloid species in different environments are likely to be important for understanding the molecular mechanisms underlying both pathogenic and functional amyloid self-assembly. PMID:24884889

Amyloid oligomers and protofibrils, but not filaments, self-replicate from native lysozyme.

PubMed

Mulaj, Mentor; Foley, Joseph; Muschol, Martin

2014-06-25

Self-assembly of amyloid fibrils is the molecular mechanism best known for its connection with debilitating human disorders such as Alzheimer's disease but is also associated with various functional cellular responses. There is increasing evidence that amyloid formation proceeds along two distinct assembly pathways involving either globular oligomers and protofibrils or rigid monomeric filaments. Oligomers, in particular, have been implicated as the dominant molecular species responsible for pathogenesis. Yet the molecular mechanisms regulating their self-assembly have remained elusive. Here we show that oligomers/protofibrils and monomeric filaments, formed along distinct assembly pathways, display critical differences in their ability to template amyloid growth at physiological vs denaturing temperatures. At physiological temperatures, amyloid filaments remained stable but could not seed growth of native monomers. In contrast, oligomers and protofibrils not only remained intact but were capable of self-replication using native monomers as the substrate. Kinetic data further suggested that this prion-like growth mode of oligomers/protofibrils involved two distinct activities operating orthogonal from each other: autocatalytic self-replication of oligomers from native monomers and nucleated polymerization of oligomers into protofibrils. The environmental changes to stability and templating competence of these different amyloid species in different environments are likely to be important for understanding the molecular mechanisms underlying both pathogenic and functional amyloid self-assembly.

Towards non-invasive diagnostic imaging of early-stage Alzheimer's disease

NASA Astrophysics Data System (ADS)

Viola, Kirsten L.; Sbarboro, James; Sureka, Ruchi; de, Mrinmoy; Bicca, Maíra A.; Wang, Jane; Vasavada, Shaleen; Satpathy, Sreyesh; Wu, Summer; Joshi, Hrushikesh; Velasco, Pauline T.; Macrenaris, Keith; Waters, E. Alex; Lu, Chang; Phan, Joseph; Lacor, Pascale; Prasad, Pottumarthi; Dravid, Vinayak P.; Klein, William L.

2015-01-01

One way to image the molecular pathology in Alzheimer's disease is by positron emission tomography using probes that target amyloid fibrils. However, these fibrils are not closely linked to the development of the disease. It is now thought that early-stage biomarkers that instigate memory loss are composed of Aβ oligomers. Here, we report a sensitive molecular magnetic resonance imaging contrast probe that is specific for Aβ oligomers. We attach oligomer-specific antibodies onto magnetic nanostructures and show that the complex is stable and binds to Aβ oligomers on cells and brain tissues to give a magnetic resonance imaging signal. When intranasally administered to an Alzheimer's disease mouse model, the probe readily reached hippocampal Aβ oligomers. In isolated samples of human brain tissue, we observed a magnetic resonance imaging signal that distinguished Alzheimer's disease from controls. Such nanostructures that target neurotoxic Aβ oligomers are potentially useful for evaluating the efficacy of new drugs and ultimately for early-stage Alzheimer's disease diagnosis and disease management.

Increased aging in primary muscle cultures of sporadic inclusion-body myositis.

PubMed

Morosetti, Roberta; Broccolini, Aldobrando; Sancricca, Cristina; Gliubizzi, Carla; Gidaro, Teresa; Tonali, Pietro A; Ricci, Enzo; Mirabella, Massimiliano

2010-07-01

Ageing is thought to participate to the pathogenesis of sporadic inclusion-body myositis (s-IBM). Although the regenerative potential of s-IBM muscle is reduced in vivo, age-related abnormalities of satellite cells possibly accounting for the decline of muscle repair have not been demonstrated. Here we show that proliferation rate and clonogenicity of s-IBM myoblasts are significantly lower and doubling time is longer than normal age-matched controls, indicating that proliferative capacity of s-IBM muscles becomes exhausted earlier. Telomere shortening is detected in s-IBM cells suggesting premature senescence. Differently from controls, s-IBM myoblasts show increased active beta-catenin mainly localized within myonuclei, indicating active Wnt stimulation. After many rounds of muscle growth, only s-IBM myoblasts accumulate congophilic inclusions and immunoreactive Abeta(1-40) deposits. Therefore, s-IBM myoblasts seem to have a constitutively impaired regenerative capacity and the intrinsic property, upon sufficient aging in vitro, to accumulate Abeta. Our results might be valuable in understanding molecular mechanisms associated with muscle aging underlying the defective regeneration of s-IBM muscle and provide new clues for future therapeutic strategies. Copyright 2008 Elsevier Inc. All rights reserved.

NSAID-derived gamma-secretase modulators. Part III: Membrane anchoring.

PubMed

Baumann, Stefanie; Höttecke, Nicole; Schubenel, Robert; Baumann, Karlheinz; Schmidt, Boris

2009-12-15

Selective lowering of Abeta(42) levels with small-molecule substrate targeting gamma-secretase modulators (sGSMs), such as some non-steroidal anti-inflammatory drugs, is a promising therapeutic approach for Alzheimer's disease. Here we present N-substituted carbazole- and O-substituted fenofibrate-derived sGSMs and their activity data. Seven out of 19 screened compounds exhibited promising activity against Abeta(42) secretion at a low micromolar level. We presume that the sGSMs interact with lys624 at the membrane interface and that the lipophilic substituents anchor the compound orientation in the membrane.

Episodic memory loss is related to hippocampal-mediated beta-amyloid deposition in elderly subjects.

PubMed

Mormino, E C; Kluth, J T; Madison, C M; Rabinovici, G D; Baker, S L; Miller, B L; Koeppe, R A; Mathis, C A; Weiner, M W; Jagust, W J

2009-05-01

Although beta-amyloid (Abeta) plaques are a primary diagnostic criterion for Alzheimer's disease, this pathology is commonly observed in the brains of non-demented older individuals. To explore the importance of this pathology in the absence of dementia, we compared levels of amyloid deposition (via 'Pittsburgh Compound-B' (PIB) positron emission tomography (PET) imaging) to hippocampus volume (HV) and episodic memory (EM) in three groups: (i) normal controls (NC) from the Berkeley Aging Cohort (BAC NC, n = 20); (ii) normal controls (NC) from the Alzheimer's disease neuroimaging initiative (ADNI NC, n = 17); and (iii) PIB+ mild cognitive impairment subjects from the ADNI (ADNI PIB+ MCI, n = 39). Age, gender and education were controlled for in each statistical model, and HV was adjusted for intracranial volume (aHV). In BAC NC, elevated PIB uptake was significantly associated with smaller aHV (P = 0.0016) and worse EM (P = 0.0086). Within ADNI NC, elevated PIB uptake was significantly associated with smaller aHV (P = 0.047) but not EM (P = 0.60); within ADNI PIB+ MCI, elevated PIB uptake was significantly associated with both smaller aHV (P = 0.00070) and worse EM (P = 0.046). To further understand these relationships, a recursive regression procedure was conducted within all ADNI NC and PIB+ MCI subjects (n = 56) to test the hypothesis that HV mediates the relationship between Abeta and EM. Significant correlations were found between PIB index and EM (P = 0.0044), PIB index and aHV (P < 0.0001), as well as between aHV and EM (P < 0.0001). When both aHV and PIB were included in the same model to predict EM, aHV remained significant (P = 0.0015) whereas PIB index was no longer significantly associated with EM (P = 0.50). These results are consistent with a model in which Abeta deposition, hippocampal atrophy, and EM occur sequentially in elderly subjects, with Abeta deposition as the primary event in this cascade. This pattern suggests that declining EM in older individuals may be caused by Abeta-induced hippocampus atrophy.

Effects of memantine on soluble Alphabeta(25-35)-induced changes in peptidergic and glial cells in Alzheimer's disease model rat brain regions.

PubMed

Arif, M; Chikuma, T; Ahmed, Md M; Nakazato, M; Smith, M A; Kato, T

2009-12-15

Soluble forms of amyloid-beta (Abeta) have been considered responsible for cognitive dysfunction prior to senile plaque formation in Alzheimer's disease (AD). As its mechanism is not well understood, we examined the effects of repeated i.c.v. infusion of soluble Alphabeta(25-35) on peptidergic system and glial cells in the pathogenesis of AD. The present study aims to investigate the protective effects of memantine on Abeta(25-35)-induced changes in peptidergic and glial systems. Infusion of Alphabeta(25-35) decreased the level of immunoreactive somatostatin (SS) and substance P (SP) in the hippocampus prior to neuronal loss or caspase activation, which is correlated with the loss of spine density and activation of inducible nitric-oxide synthase (iNOS). Biochemical experiment with peptide-degrading enzymes, prolyl oligopeptidase (POP) and endopeptidase 24.15 (EP 24.15) activities demonstrated a concomitant increase with the activation of glial marker proteins, glial fibrillary acidic protein (GFAP) and CD11b in the Abeta-treated hippocampus. Double immunostaining experiments of EP 24.15 and GFAP/CD11b antibodies clearly demonstrated the co-localization of neuro peptidases with astrocytes and microglia. Treatment with memantine, a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist significantly attenuated Abeta(25-35)-induced changes of neuropeptides, their metabolizing enzymes, glial marker proteins, and activation of iNOS. Taken together, the data implies that memantine exerts its protective effects by modulating the neuropeptide system as a consequence of suppressing the glial cells and oxidative stress in AD model rat brain regions.

Synthesis and characterization of oligobenzimidazoles: Electrochemical, electrical, optical, thermal and rectification properties

NASA Astrophysics Data System (ADS)

Anand, Siddeswaran; Muthusamy, Athianna

2018-03-01

A series of benzimidazole monomers, (2-(2, 4-dihydroxyphenyl)-1H-benzimidazol-5-yl)(phenyl) methanone (BIKH), 2-(3-ethoxy-2-hydroxyphenyl)-1H-benzo [d]imidazole-5-yl) (phenyl) methanone (BIKE) and 2-(5-bromo-2-hydroxyphenyl)-1H-benzo [d]imidazole-5-yl) (phenyl) methanone (BIKB) were prepared by condensing three substituted aromatic aldehydes with 3, 4-diaminobenzophenone. In aqueous alkaline medium the benzimidazoles were converted in to oligomers by oxidative polycondensation using NaOCl as oxidant. The formation of monomers and oligomers were confirmed with 1H, 13C NMR, FT-IR, and UV-visible spectroscopic techniques. The oligomers were investigated for their optical, electrical, electrochemical and thermal properties. The electrochemical and optical band gaps of monomers and oligomers were calculated using both UV-visible spectroscopy and cyclic voltametry respectively. The band gap values of monomers are compared with band gap values obtained from quantum theoretical calculations with DFT. The electrical conductivity studies of iodine doped and undoped oligomers were done using two point probe technique. It is found that these values are showing good correlation with the charge densities on imidazole nitrogen obtained from Huckel method. The conductivity of oligomers increases with increase in iodine vapour contact time. The dielectric properties of oligomers have been investigated at different temperature and frequency. The dielectric measurement data were used to calculate the AC conductivity and activation energy of oligomers. Oligomer OBIKH is having greater thermal stability due to its number of chain propagation sites than other oligomers and is shown by its high carbines residue of around 60% at 600 °C in thermogravimetric analysis. I-V characteristics of oligobenzimidazole p-n diodes have shown good rectifying nature in the range -4 to 4 V.

Alzheimer's amyloid-β oligomers rescue cellular prion protein induced tau reduction via the Fyn pathway.

PubMed

Chen, Rong-Jie; Chang, Wei-Wei; Lin, Yu-Chun; Cheng, Pei-Lin; Chen, Yun-Ru

2013-09-18

Amyloid-β (Aβ) and tau are the pathogenic hallmarks in Alzheimer's disease (AD). Aβ oligomers are considered the actual toxic entities, and the toxicity relies on the presence of tau. Recently, Aβ oligomers have been shown to specifically interact with cellular prion protein (PrP(C)) where the role of PrP(C) in AD is still not fully understood. To investigate the downstream mechanism of PrP(C) and Aβ oligomer interaction and their possible relationships to tau, we examined tau expression in human neuroblastoma BE(2)-C cells transfected with murine PrP(C) and studied the effect under Aβ oligomer treatment. By Western blotting, we found that PrP(C) overexpression down-regulated tau protein and Aβ oligomer binding alleviated the tau reduction induced by wild type but not M128V PrP(C), the high AD risk polymorphic allele in human prion gene. PrP(C) lacking the Aβ oligomer binding site was incapable of rescuing the level of tau reduction. Quantitative RT-PCR showed the PrP(C) effect was attributed to tau reduction at the transcription level. Treatment with Fyn pathway inhibitors, Fyn kinase inhibitor PP2 and MEK inhibitor U0126, reversed the PrP(C)-induced tau reduction and Aβ oligomer treatment modulated Fyn kinase activity. The results suggested Fyn pathway regulated Aβ-PrP(C)-tau signaling. Overall, our results demonstrated that PrP(C) down-regulated tau via the Fyn pathway and the effect can be regulated by Aβ oligomers. Our study facilitated the understanding of molecular mechanisms among PrP(C), tau, and Aβ oligomers.

Single-molecule FRET studies on alpha-synuclein oligomerization of Parkinson’s disease genetically related mutants

NASA Astrophysics Data System (ADS)

Tosatto, Laura; Horrocks, Mathew H.; Dear, Alexander J.; Knowles, Tuomas P. J.; Dalla Serra, Mauro; Cremades, Nunilo; Dobson, Christopher M.; Klenerman, David

2015-11-01

Oligomers of alpha-synuclein are toxic to cells and have been proposed to play a key role in the etiopathogenesis of Parkinson’s disease. As certain missense mutations in the gene encoding for alpha-synuclein induce early-onset forms of the disease, it has been suggested that these variants might have an inherent tendency to produce high concentrations of oligomers during aggregation, although a direct experimental evidence for this is still missing. We used single-molecule Förster Resonance Energy Transfer to visualize directly the protein self-assembly process by wild-type alpha-synuclein and A53T, A30P and E46K mutants and to compare the structural properties of the ensemble of oligomers generated. We found that the kinetics of oligomer formation correlates with the natural tendency of each variant to acquire beta-sheet structure. Moreover, A53T and A30P showed significant differences in the averaged FRET efficiency of one of the two types of oligomers formed compared to the wild-type oligomers, indicating possible structural variety among the ensemble of species generated. Importantly, we found similar concentrations of oligomers during the lag-phase of the aggregation of wild-type and mutated alpha-synuclein, suggesting that the properties of the ensemble of oligomers generated during self-assembly might be more relevant than their absolute concentration for triggering neurodegeneration.

Modulation of beta-amyloid precursor protein trafficking and processing by the low density lipoprotein receptor family.

PubMed

Cam, Judy A; Bu, Guojun

2006-08-18

Amyloid-beta peptide (Abeta) accumulation in the brain is an early, toxic event in the pathogenesis of Alzheimer's disease (AD). Abeta is produced by proteolytic processing of a transmembrane protein, beta-amyloid precursor protein (APP), by beta- and gamma-secretases. Mounting evidence has demonstrated that alterations in APP cellular trafficking and localization directly impact its processing to Abeta. Recent studies have shown that members of the low-density lipoprotein receptor family, including LRP, LRP1B, SorLA/LR11, and apolipoprotein E (apoE) receptor 2, interact with APP and regulate its endocytic trafficking. Another common feature of these receptors is their ability to bind apoE, which exists in three isoforms in humans and the presence of the epsilon4 allele represents a genetic risk factor for AD. In this review, we summarize the current understanding of the function of these apoE receptors with a focus on their role in APP trafficking and processing. Knowledge of the interactions between these distinct low-density lipoprotein receptor family members and APP may ultimately influence future therapies for AD.

A thermodynamic study of Abeta(16-21) dissociation from a fibril using computer simulations

NASA Astrophysics Data System (ADS)

Dias, Cristiano; Mahmoudinobar, Farbod; Su, Zhaoqian

Here, I will discuss recent all-atom molecular dynamics simulations with explicit water in which we studied the thermodynamic properties of Abeta(16-21) dissociation from an amyloid fibril. Changes in thermodynamics quantities, e.g., entropy, enthalpy, and volume, are computed from the temperature dependence of the free-energy computed using the umbrella sampling method. We find similarities and differences between the thermodynamics of peptide dissociation and protein unfolding. Similarly to protein unfolding, Abeta(16-21) dissociation is characterized by an unfavorable change in enthalpy, a favorable change in the entropic energy, and an increase in the heat capacity. A main difference is that peptide dissociation is characterized by a weak enthalpy-entropy compensation. We characterize dock and lock states of the peptide based on the solvent accessible surface area. The Lennard-Jones energy of the system is observed to increase continuously in lock and dock states as the peptide dissociates. The electrostatic energy increases in the lock state and it decreases in the dock state as the peptide dissociates. These results will be discussed as well as their implication for fibril growth.

Effects of electronics, aromaticity, and solvent polarity on the rate of azaquinone-methide-mediated depolymerization of aromatic carbamate oligomers.

PubMed

Robbins, Jessica S; Schmid, Kyle M; Phillips, Scott T

2013-04-05

This paper uses physical-organic studies on well-defined oligomers to establish design principles for creating aromatic poly(carbamates) that depolymerize from head-to-tail in low dielectric constant environments when exposed to specific applied signals. We show that either increasing electron density or decreasing the aromaticity of aromatic repeating units in poly(carbamates) increase the overall depolymerization rate. For example, a methoxybenzene-based repeating unit provides depolymerization rates that are 143× faster than oligomers that contain a benzene-based repeating unit. Furthermore, the rate of depolymerization in the methoxybenzene-based system is tolerant to low dielectric environments, whereas the benzene-based oligomers are not.

Abiotic ligation of DNA oligomers templated by their liquid crystal ordering

NASA Astrophysics Data System (ADS)

Fraccia, Tommaso P.; Smith, Gregory P.; Zanchetta, Giuliano; Paraboschi, Elvezia; Yi, Yougwooo; Walba, David M.; Dieci, Giorgio; Clark, Noel A.; Bellini, Tommaso

2015-03-01

It has been observed that concentrated solutions of short DNA oligomers develop liquid crystal ordering as the result of a hierarchically structured supramolecular self-assembly. In mixtures of oligomers with various degree of complementarity, liquid crystal microdomains are formed via the selective aggregation of those oligomers that have a sufficient degree of duplexing and propensity for physical polymerization. Here we show that such domains act as fluid and permeable microreactors in which the order-stabilized molecular contacts between duplex terminals serve as physical templates for their chemical ligation. In the presence of abiotic condensing agents, liquid crystal ordering markedly enhances ligation efficacy, thereby enhancing its own phase stability. The coupling between order-templated ligation and selectivity provided by supramolecular ordering enables an autocatalytic cycle favouring the growth of DNA chains, up to biologically relevant lengths, from few-base long oligomers. This finding suggests a novel scenario for the abiotic origin of nucleic acids.

Esculin and its oligomer fractions inhibit adhesion and migration of U87 glioblastoma cells and in vitro angiogenesis.

PubMed

Mokdad-Bzeouich, Imen; Kovacic, Hervé; Ghedira, Kamel; Chebil, Latifa; Ghoul, Mohamed; Chekir-Ghedira, Leila; Luis, José

2016-03-01

Cancer metastasis is the major cause of cancer-related death. Chemoprevention is defined as the use of natural or synthetic substances to prevent cancer formation or cancer progress. In the present study, we investigate the antitumor activity of esculin and its oligomer fractions in U87 glioblastoma cells. We showed that esculin and its oligomers reduced U87 cell growth in a dose dependent manner. They also inhibited cell adhesion to collagen IV and vitronectin by interfering with the function of their respective receptors α2β1 and αvβ5 integrins. Furthermore, the tested samples were able to reduce migration of U87 cells towards another extracellular matrix fibronectin. Moreover, esculin and its oligomer fractions inhibited in vitro angiogenesis of endothelial cells (HMEC-1). In summary, our data provide the first evidence that esculin and its oligomer fractions are able to reduce adhesion, migration of glioblastoma cells and in vitro angiogenesis. Esculin and its oligomers may thus exert multi-target functions against cancer cells.

Morphine via nitric oxide modulates beta-amyloid metabolism: a novel protective mechanism for Alzheimer's disease.

PubMed

Pak, Theodore; Cadet, Patrick; Mantione, Kirk J; Stefano, George B

2005-10-01

The deposition of intracellular and extracellular beta-amyloid peptide (Abeta) in the brain is a pathologic feature of Alzheimer's disease (AD), a prevalent neurodegenerative disorder. However, the exact role of the Abeta peptide in causing AD's symptoms is unclear. CRL-2266 SH-SY5Y human neuroblastoma cells (ATCC, USA) and HTB-11 human neuroblastoma cells (ATCC, USA) were cultured. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to analyze the effects of beta25-35, morphine, and SNAP treatments upon BACE-1 and BACE-2 mRNA expression semi-quantitative RT-PCR. The production of NO in SH-SY5Y cells was detected using the Apollo 4000 Free Radical Analyzer (World Precision Instruments). Untreated HTB-11 neuroblastoma cells constitutively express BACE-1 and BACE-2 mRNA. Morphine down regulates the expression of BACE-1 and up regulates the expression of BACE-2 in a naloxone antagonizable manner. When HTB-11 cells were treated with L-NAME, a cNOS inhibitor; the effects of morphine were blocked. SNAP (a NO donor) mimicked the effect of morphine. In SH-SY5Y cells, Abeta treated cells show a dose-dependent decrease in NO release, demonstrating that Ab is dose-dependently inhibiting the release of constitutive NO. Ab and morphine/NO each inhibit the production of the other. This suggests that a deficiency of basal NO or endogenous morphine may trigger drastically reduced levels of basal NO. The outcome is chronic vasoconstriction and brain hypoperfusion and eventual neuronal death. This novel theorized mechanism for AD supports an increasingly-accepted vascular pathological hypothesis for the disease.

Herpes simplex virus interferes with amyloid precursor protein processing.

PubMed

Shipley, Suzanne J; Parkin, Edward T; Itzhaki, Ruth F; Dobson, Curtis B

2005-08-18

The early events underlying Alzheimer's disease (AD) remain uncertain, although environmental factors may be involved. Work in this laboratory has shown that the combination of herpes simplex virus type 1 (HSV1) in brain and carriage of the APOE-epsilon4 allele of the APOE gene strongly increases the risk of developing AD. The development of AD is thought to involve abnormal aggregation or deposition of a 39-43 amino acid protein--beta amyloid (Abeta)--within the brain. This is cleaved from the much larger transmembranal protein 'amyloid precursor protein' (APP). Any agent able to interfere directly with Abeta or APP metabolism may therefore have the capacity to contribute towards AD. One recent report showed that certain HSV1 glycoprotein peptides may aggregate like Abeta; a second study described a role for APP in transport of virus in squid axons. However to date the effects of acute herpesvirus infection on metabolism of APP in human neuronal-type cells have not been investigated. In order to find if HSV1 directly affects APP and its degradation, we have examined this protein from human neuroblastoma cells (normal and transfected with APP 695) infected with the virus, using Western blotting. We have found that acute HSV1 (and also HSV2) infection rapidly reduces full length APP levels--as might be expected--yet surprisingly markedly increases levels of a novel C-terminal fragment of APP of about 55 kDa. This band was not increased in cells treated with the protein synthesis inhibitor cycloheximide Herpes virus infection leads to rapid loss of full length APP from cells, yet also causes increased levels of a novel 55 kDa C-terminal APP fragment. These data suggest that infection can directly alter the processing of a transmembranal protein intimately linked to the aetiology of AD.

Hippocampal tau pathology is related to neuroanatomical connections: an ageing population-based study.

PubMed

Lace, G; Savva, G M; Forster, G; de Silva, R; Brayne, C; Matthews, F E; Barclay, J J; Dakin, L; Ince, P G; Wharton, S B

2009-05-01

Deposits of abnormally phosphorylated tau protein are found in numerous neurodegenerative disorders; the 'tauopathies', which include Alzheimer's and Pick's diseases, but tau pathology is also found in the ageing brain. Variation in tau pathology in brain ageing and its relationship to development of tauopathies and cognitive impairment remains unclear. We aimed to determine the extent and pattern of spread of tau pathology in the hippocampus, a susceptible region important in dementia and milder states of memory impairment, using hippocampal samples from the elderly population-based Medical Research Council Cognitive Function and Ageing Study neuropathology cohort. Tau deposition was assessed in hippocampal anatomical sub-regions using the AT8 antibody to phosphorylated tau and isoform-specific antibodies to 3 and 4-repeat tau (RD3 and RD4). Abeta pathology was also assessed. In this population sample, which includes the full ageing spectrum from individuals with no cognitive impairment to those with dementia satisfying clinico-pathology criteria for Alzheimer's disease, we have demonstrated a high prevalence at death of tau pathology. AT8, Abeta, RD3 and RD4 showed similar regional distribution and increased RD3 was noted in late-stage ghost tangles. Abeta was shown to be a poor explanatory variable for tau pathology. Tau deposition progressed in a hierarchical manner. Hippocampal input regions and projection zones (such as lateral entorhinal cortex, CA1/subiculum border and outer molecular layer of dentate) were initially affected, with anterograde progression though the hippocampal circuitry. Six hippocampal tau anatomical stages were defined, each linking projectionally to their adjacent stages, suggesting spread of tau malfunction through neuroanatomical pathways in hippocampal ageing. These stages were significantly associated with dementia, and may provide a clinically useful tool in the clinico-pathological assessment of dementia and mild cognitive impairment.

Rescue of Hypovitaminosis A Induces Non-Amyloidogenic Amyloid Precursor Protein (APP) Processing.

PubMed

Reinhardt, Sven; Grimm, Marcus O W; Stahlmann, Christoph; Hartmann, Tobias; Shudo, Koichi; Tomita, Taisuke; Endres, Kristina

2016-01-01

Retinoic acid, the bioactive metabolite of beta-carotene or vitamin A, plays a pleiotropic, multifunctional role in vertebrate development. Studies in rodents revealed that a diet deficient in vitamin A results in a complex neonatal syndrome (the VAD syndrome), manifested in many organs. In humans, the function of retinoic acid (RA) extends into adulthood, where it has important roles in fertility, vision, and suppression of neoplastic growth. In recent years, it has also been suggested that retinoic acid might potentially act as a therapeutically relevant drug in attenuating or even preventing neurodegenerative diseases such as Alzheimer's disease (AD). Here, we report that VAD leads to an increase in A-beta peptide levels while only minor effects were observed on expression levels of the amyloid precursor protein (APP) processing proteinases in wild type mice. In line with these findings, rescue of hypovitaminosis reduced A-beta amount to baseline and induced sApp-alpha secretion in combination with an increase of alpha-secretase Adam10. By comparing retinoic acid treatment starting from a full nutrition status and a "VAD" situation in human neuroblastoma cells, we show that while intensities of differential gene expression were higher in replenished cells, a large overlap in AD-related, regulated genes was observed. Our data suggest that hypovitaminosis A can contribute to onset or progression of AD by increasing synthesis of A-beta peptides and that several AD-related genes such as ADAM10 or BDNF are regulated by retinoic acid. We suggest that dietary supplementation with retinoic acid derivatives is likely to have a beneficial effect on AD-pathology in individuals with hypovitaminosis and patients with normal vitamin A status.

Large Soluble Oligomers of Amyloid β-Protein from Alzheimer Brain Are Far Less Neuroactive Than the Smaller Oligomers to Which They Dissociate

PubMed Central

Yang, Ting; Li, Shaomin; Xu, Huixin

2017-01-01

Soluble oligomers of amyloid β-protein (oAβ) isolated from the brains of Alzheimer's disease (AD) patients have been shown experimentally (in the absence of amyloid plaques) to impair hippocampal synaptic plasticity, decrease synapses, induce tau hyperphosphorylation and neuritic dystrophy, activate microglial inflammation, and impair memory in normal adult rodents. Nevertheless, there has been controversy about what types of oligomers actually confer these AD-like phenotypes. Here, we show that the vast majority of soluble Aβ species obtained from brains of humans who died with confirmed AD elute at high molecular weight (HMW) on nondenaturing size-exclusion chromatography. These species have little or no cytotoxic activity in several bioassays. However, incubation of HMW oAβ in mildly alkaline buffer led to their quantitative dissociation into low molecular weight oligomers (∼8–70 kDa), and these were now far more bioactive: they impaired hippocampal LTP, decreased neuronal levels of β2-adrenergic receptors, and activated microglia in wt mice in vivo. Thus, most soluble Aβ assemblies in AD cortex are large and inactive but under certain circumstances can dissociate into smaller, highly bioactive species. Insoluble amyloid plaques likely sequester soluble HMW oligomers, limiting their potential to dissociate. We conclude that conditions that destabilize HMW oligomers or retard the sequestration of their smaller, more bioactive components are important drivers of Aβ toxicity. Selectively targeting these small, cytotoxic forms should be therapeutically beneficial. SIGNIFICANCE STATEMENT Oligomers of amyloid β-protein (oAβ) are tought to play an important role in Alzheimer's disease (AD), but there is confusion and controversy about what types and sizes of oligomers have disease-relevant activity. Using size-exclusion chromatography and three distinct measures of bioactivity, we show that the predominant forms of Aβ in aqueous extracts of AD brain are high molecular weight (HMW) and relatively inactive. Importantly, under certain conditions, the abundant HMW oAβ can dissociate into low molecular weight species, and these low molecular weight oligomers are significantly more bioactive on synapses and microglia than the HMW species from which they are derived. We conclude that conditions that destabilize HMW oAβ or retard the sequestration of smaller, more bioactive components are important drivers of Aβ toxicity. PMID:28053038

Esters of oligo-(glycerol carbonate-glycerol): New biobased oligomeric surfactants.

PubMed

Holmiere, Sébastien; Valentin, Romain; Maréchal, Philippe; Mouloungui, Zéphirin

2017-02-01

Glycerol carbonate is one of the most potentially multifunction glycerol-derived compounds. Glycerol is an important by-product of the oleochemical industry. The oligomerization of glycerol carbonate, assisted by the glycerol, results in the production of polyhydroxylated oligomers rich in linear carbonate groups. The polar moieties of these oligomers (M w <1000Da) were supplied by glycerol and glycerol carbonate rather than ethylene oxide as in most commercial surfactants. The insertion of linear carbonate groups into the glycerol-based skeleton rendered the oligomers amphiphilic, resulting in a decrease in air/water surface tension to 57mN/m. We improved the physical and chemical properties of the oligomers, by altering the type of acylation reaction and the nature of the acyl donor. The polar head is constituted of homo-oligomers and hetero-oligomers. Homo-oligomers are oligoglycerol and/or oligocarbonate, hetero-oligomers are oligo(glycerol-glycerol carbonate). Coprah oligoesters had the best surfactant properties (CMC<1mg/mL, π cmc <30mN/m), outperforming molecules of fossil origin, such as ethylene glycol monododecyl ether, glycol ethers and fatty acid esters of sorbitan polyethoxylates. The self-assembling properties of oligocarbonate esters were highlighted by their ability to stabilize inverse and multiple emulsions. The oligo-(glycerol carbonate-glycerol ether) with relatively low molecular weights showed properties of relatively high-molecular weight molecules, and constitute a viable "green" alternative to ethoxylated surfactants. Copyright © 2016 Elsevier Inc. All rights reserved.

Expression of Somatostatin, cortistatin, and their receptors, as well as dopamine receptors, but not of neprilysin, are reduced in the temporal lobe of Alzheimer's disease patients.

PubMed

Gahete, Manuel D; Rubio, Alicia; Durán-Prado, Mario; Avila, Jesús; Luque, Raúl M; Castaño, Justo P

2010-01-01

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by severe cognitive deficit, wherein the impairment of episodic memory is the major hallmark. AD patients exhibit augmented accumulation of amyloid-beta (Abeta) and hyperphosphorylated tau protein in specific brain regions. In addition, several neuropeptides/neurotransmitter axes clearly associated with cognitive processes, Abeta turnover, and tau phosphorylation have also been found to be impaired in AD, such as somatostatin (SST)/cortistatin (CST) and dopamine (DA) systems. However, to date there is no precise quantitative data on the expression of these systems in the human brain of AD and normal patients. Here we measured by quantitative real-time PCR the mRNA levels of SST/CST, their receptors (sst1-5 and DA receptors (drd1-5) in addition to neprilysin (a SST-regulated enzyme involved in Abeta degradation) in three regions of the temporal lobe, one of the cortical regions most severely affected by AD. Our results reveal that some components of SST/CST- and DA-axes are divergently altered in the three areas of AD patients. Despite this region-specific regulation, an overall, common reduction of these systems was observed in the temporal lobe of AD patients. Conversely, neprilysin expression was not altered in AD, suggesting that Abeta accumulation observed in AD is due to a lack of neprilysin activation by SST rather than to a reduction of its expression. Collectively, our results define a comprehensive scenario wherein reduction of ssts, drds, and sst ligands SST and CST, could be involved, at least in part, in some of the more important defects observed in AD.

Adaptations in the structure and innervation of follicle-sinus complexes to an aquatic environment as seen in the Florida manatee (Trichechus manatus latirostris).

PubMed

Sarko, Diana K; Reep, Roger L; Mazurkiewicz, Joseph E; Rice, Frank L

2007-09-20

Florida manatees are large-bodied aquatic herbivores that use large tactile vibrissae for several purposes. Facial vibrissae are used to forage in a turbid water environment, and the largest perioral vibrissae can also grasp and manipulate objects. Other vibrissae distributed over the entire postfacial body appear to function as a lateral line system. All manatee vibrissae emanate from densely innervated follicle-sinus complexes (FSCs) like those in other mammals, although proportionately larger commensurate with the caliber of the vibrissae. As revealed by immunofluorescence, all manatee FSCs have many types of C, Adelta and Abeta innervation including Merkel, club, and longitudinal lanceolate endings at the level of the ring sinus, but they lack other types such as reticular and spiny endings at the level of the cavernous sinus. As in non-whisking terrestrial species, the inner conical bodies of facial FSCs are well innervated but lack Abeta-fiber terminals. Importantly, manatee FSCs have two unique types of Abeta-fiber endings. First, all of the FSCs have exceptionally large-caliber axons that branch to terminate as novel, gigantic spindle-like endings located at the upper ring sinus. Second, facial FSCs have smaller caliber Abeta fibers that terminate in the trabeculae of the cavernous sinus as an ending that resembles a Golgi tendon organ. In addition, the largest perioral vibrissae, which are used for grasping, have exceptionally well-developed medullary cores that have a structure and dense small-fiber innervation resembling that of tooth pulp. Other features of the epidermis and upper dermis structure and innervation differ from that seen in terrestrial mammals. Copyright (c) 2007 Wiley-Liss, Inc.

Synthesis and Electronic Properties of Length-Defined 9,10-Anthrylene-Butadiynylene Oligomers.

PubMed

Nagaoka, Maiko; Tsurumaki, Eiji; Nishiuchi, Mai; Iwanaga, Tetsuo; Toyota, Shinji

2018-05-18

Linear π-conjugated oligomers consisting of anthracene and diacetylene units were readily synthesized by a one-pot process that involved desilylation and oxidative coupling from appropriate building units. We were able to isolate length-defined oligomers ranging from 2-mer to 6-mer as stable and soluble solids. The bathochromic shifts in the UV-vis spectra suggested that the π-conjugation was extended with elongation of the linear chain. Cyclic voltammetric measurements showed characteristic reversible oxidation waves that were dependent on the number of anthracene units.

Single-Molecule Imaging Reveals that Small Amyloid-β1–42 Oligomers Interact with the Cellular Prion Protein (PrPC)

PubMed Central

Ganzinger, Kristina A; Narayan, Priyanka; Qamar, Seema S; Weimann, Laura; Ranasinghe, Rohan T; Aguzzi, Adriano; Dobson, Christopher M; McColl, James; St George-Hyslop, Peter; Klenerman, David

2014-01-01

Oligomers of the amyloid-β peptide (Aβ) play a central role in the pathogenesis of Alzheimer’s disease and have been suggested to induce neurotoxicity by binding to a plethora of cell-surface receptors. However, the heterogeneous mixtures of oligomers of varying sizes and conformations formed by Aβ42 have obscured the nature of the oligomeric species that bind to a given receptor. Here, we have used single-molecule imaging to characterize Aβ42 oligomers (oAβ42) and to confirm the controversial interaction of oAβ42 with the cellular prion protein (PrPC) on live neuronal cells. Our results show that, at nanomolar concentrations, oAβ42 interacts with PrPC and that the species bound to PrPC are predominantly small oligomers (dimers and trimers). Single-molecule biophysical studies can thus aid in deciphering the mechanisms that underlie receptor-mediated oAβ-induced neurotoxicity, and ultimately facilitate the discovery of novel inhibitors of these pathways. PMID:25294384

Cytotoxic Helix-Rich Oligomer Formation by Melittin and Pancreatic Polypeptide

PubMed Central

Singh, Pradeep K.; Ghosh, Dhiman; Tewari, Debanjan; Mohite, Ganesh M.; Carvalho, Edmund; Jha, Narendra Nath; Jacob, Reeba S.; Sahay, Shruti; Banerjee, Rinti; Bera, Amal K.; Maji, Samir K.

2015-01-01

Conversion of amyloid fibrils by many peptides/proteins involves cytotoxic helix-rich oligomers. However, their toxicity and biophysical studies remain largely unknown due to their highly dynamic nature. To address this, we chose two helical peptides (melittin, Mel and pancreatic polypeptide, PP) and studied their aggregation and toxicity. Mel converted its random coil structure to oligomeric helical structure upon binding to heparin; however, PP remained as helix after oligomerization. Interestingly, similar to Parkinson’s associated α-synuclein (AS) oligomers, Mel and PP also showed tinctorial properties, higher hydrophobic surface exposure, cellular toxicity and membrane pore formation after oligomerization in the presence of heparin. We suggest that helix-rich oligomers with exposed hydrophobic surface are highly cytotoxic to cells irrespective of their disease association. Moreover as Mel and PP (in the presence of heparin) instantly self-assemble into stable helix-rich amyloidogenic oligomers; they could be represented as models for understanding the biophysical and cytotoxic properties of helix-rich intermediates in detail. PMID:25803428

Laser-Induced Population Inversion in Rhodamine 6G for Lysozyme Oligomer Detection.

PubMed

Hanczyc, Piotr; Sznitko, Lech

2017-06-06

Fluorescence spectroscopy is a common method for detecting amyloid fibrils in which organic fluorophores are used as markers that exhibit an increase in quantum yield upon binding. However, most of the dyes exhibit enhanced emission only when bound to mature fibrils, and significantly weaker signals are obtained in the presence of amyloid oligomers. In the concept of population inversion, a laser is used as an excitation source to keep the major fraction of molecules in the excited state to create the pathways for the occurrence of stimulated emission. In the case of the proteins, the conformational changes lead to the self-ordering and thus different light scattering conditions that can influence the optical signatures of the generated light. Using this methodology, we show it is possible to optically detect amyloid oligomers using commonly available staining dyes in which population inversion can be induced. The results indicate that rhodamine 6G molecules are complexed with oligomers, and using a laser-assisted methodology, weakly emissive states can be detected. Significant spectral red-shifting of rhodamine 6G dispersed with amyloid oligomers and a notable difference determined by comparison of spectra of the fibrils suggest the existence of specific dye aggregates around the oligomer binding sites. This approach can provide new insights into intermediate oligomer states that are believed to be responsible for toxic seeding in neurodegeneration diseases.

Temporal requirements of insulin/IGF-1 signaling for proteotoxicity protection.

PubMed

Cohen, Ehud; Du, Deguo; Joyce, Derek; Kapernick, Erik A; Volovik, Yuli; Kelly, Jeffery W; Dillin, Andrew

2010-04-01

Toxic protein aggregation (proteotoxicity) is a unifying feature in the development of late-onset human neurodegenerative disorders. Reduction of insulin/IGF-1 signaling (IIS), a prominent lifespan, developmental and reproductive regulatory pathway, protects worms from proteotoxicity associated with the aggregation of the Alzheimer's disease-linked Abeta peptide. We utilized transgenic nematodes that express human Abeta and found that late life IIS reduction efficiently protects from Abeta toxicity without affecting development, reproduction or lifespan. To alleviate proteotoxic stress in the animal, the IIS requires heat shock factor (HSF)-1 to modulate a protein disaggregase, while DAF-16 regulates a presumptive active aggregase, raising the question of how these opposing activities could be co-regulated. One possibility is that HSF-1 and DAF-16 have distinct temporal requirements for protection from proteotoxicity. Using a conditional RNAi approach, we found an early requirement for HSF-1 that is distinct from the adult functions of DAF-16 for protection from proteotoxicity. Our data also indicate that late life IIS reduction can protect from proteotoxicity when it can no longer promote longevity, strengthening the prospect that IIS reduction might be a promising strategy for the treatment of neurodegenerative disorders caused by proteotoxicity.

Abeta42-driven cerebral amyloidosis in transgenic mice reveals early and robust pathology.

PubMed

Radde, Rebecca; Bolmont, Tristan; Kaeser, Stephan A; Coomaraswamy, Janaky; Lindau, Dennis; Stoltze, Lars; Calhoun, Michael E; Jäggi, Fabienne; Wolburg, Hartwig; Gengler, Simon; Haass, Christian; Ghetti, Bernardino; Czech, Christian; Hölscher, Christian; Mathews, Paul M; Jucker, Mathias

2006-09-01

We have generated a novel transgenic mouse model on a C57BL/6J genetic background that coexpresses KM670/671NL mutated amyloid precursor protein and L166P mutated presenilin 1 under the control of a neuron-specific Thy1 promoter element (APPPS1 mice). Cerebral amyloidosis starts at 6-8 weeks and the ratio of human amyloid (A)beta42 to Abeta40 is 1.5 and 5 in pre-depositing and amyloid-depositing mice, respectively. Consistent with this ratio, extensive congophilic parenchymal amyloid but minimal amyloid angiopathy is observed. Amyloid-associated pathologies include dystrophic synaptic boutons, hyperphosphorylated tau-positive neuritic structures and robust gliosis, with neocortical microglia number increasing threefold from 1 to 8 months of age. Global neocortical neuron loss is not apparent up to 8 months of age, but local neuron loss in the dentate gyrus is observed. Because of the early onset of amyloid lesions, the defined genetic background of the model and the facile breeding characteristics, APPPS1 mice are well suited for studying therapeutic strategies and the pathomechanism of amyloidosis by cross-breeding to other genetically engineered mouse models.

Development of micro immunosensors to study genomic and proteomic biomarkers related to cancer and Alzheimer's disease

NASA Astrophysics Data System (ADS)

Prabhulkar, Shradha

A report from the National Institutes of Health defines a disease biomarker as a "characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention." Early diagnosis is a crucial factor for incurable disease such as cancer and Alzheimer's disease (AD). During the last decade researchers have discovered that biochemical changes caused by a disease can be detected considerably earlier as compared to physical manifestations/symptoms. In this dissertation electrochemical detection was utilized as the detection strategy as it offers high sensitivity/specificity, ease of operation, and capability of miniaturization and multiplexed detection. Electrochemical detection of biological analytes is an established field, and has matured at a rapid pace during the last 50 years and adapted itself to advances in micro/nanofabrication procedures. Carbon fiber microelectrodes were utilized as the platform sensor due to their high signal to noise ratio, ease and low-cost of fabrication, biocompatibility, and active carbon surface which allows conjugation with biorecognition moieties. This dissertation specifically focuses on the detection of 3 extensively validated biomarkers for cancer and AD. Firstly, vascular endothelial growth factor (VEGF) a cancer biomarker was detected using a one-step, reagentless immunosensing strategy. The immunosensing strategy allowed a rapid and sensitive means of VEGF detection with a detection limit of about 38 pg/mL with a linear dynamic range of 0--100 pg/mL. Direct detection of AD-related biomarker amyloid beta (Abeta) was achieved by exploiting its inherent electroactivity. The quantification of the ratio of Abeta1-40/42 (or Abeta ratio) has been established as a reliable test to diagnose AD through human clinical trials. Triple barrel carbon fiber microelectrodes were used to simultaneously detect Abeta1-40 and Abeta1-42 in cerebrospinal fluid from rats within a detection range of 100nM to 1.2muM and 400nM to 1muM respectively. In addition, the release of DNA damage/repair biomarker 8-hydroxydeoxyguanine (8-OHdG) under the influence of reactive oxidative stress from single lung endothelial cell was monitored using an activated carbon fiber microelectrode. The sensor was used to test the influence of nicotine, which is one of the most biologically active chemicals present in cigarette smoke and smokeless tobacco.

Chemokines, macrophage inflammatory protein-2 and stromal cell-derived factor-1{alpha}, suppress amyloid {beta}-induced neurotoxicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raman, Dayanidhi; Milatovic, Snjezana-Zaja; Milatovic, Dejan

2011-11-15

Alzheimer's disease (AD) is characterized by a progressive cognitive decline and accumulation of neurotoxic oligomeric peptides amyloid-{beta} (A{beta}). Although the molecular events are not entirely known, it has become evident that inflammation, environmental and other risk factors may play a causal, disruptive and/or protective role in the development of AD. The present study investigated the ability of the chemokines, macrophage inflammatory protein-2 (MIP-2) and stromal cell-derived factor-1{alpha} (SDF-1{alpha}), the respective ligands for chemokine receptors CXCR2 and CXCR4, to suppress A{beta}-induced neurotoxicity in vitro and in vivo. Pretreatment with MIP-2 or SDF-1{alpha} significantly protected neurons from A{beta}-induced dendritic regression and apoptosismore » in vitro through activation of Akt, ERK1/2 and maintenance of metalloproteinase ADAM17 especially with SDF-1{alpha}. Intra-cerebroventricular (ICV) injection of A{beta} led to reduction in dendritic length and spine density of pyramidal neurons in the CA1 area of the hippocampus and increased oxidative damage 24 h following the exposure. The A{beta}-induced morphometric changes of neurons and increase in biomarkers of oxidative damage, F{sub 2}-isoprostanes, were significantly inhibited by pretreatment with the chemokines MIP-2 or SDF-1{alpha}. Additionally, MIP-2 or SDF-1{alpha} was able to suppress the aberrant mislocalization of p21-activated kinase (PAK), one of the proteins involved in the maintenance of dendritic spines. Furthermore, MIP-2 also protected neurons against A{beta} neurotoxicity in CXCR2-/- mice, potentially through observed up regulation of CXCR1 mRNA. Understanding the neuroprotective potential of chemokines is crucial in defining the role for their employment during the early stages of neurodegeneration. -- Research highlights: Black-Right-Pointing-Pointer Neuroprotective ability of the chemokines MIP2 and CXCL12 against A{beta} toxicity. Black-Right-Pointing-Pointer MIP-2 or CXCL12 prevented dendritic regression and apoptosis in vitro. Black-Right-Pointing-Pointer Neuroprotection through activation of Akt, ERK1/2 and maintenance of ADAM17. Black-Right-Pointing-Pointer Neuroprotection of hippocampal pyramidal neurons in vivo by MIP-2 or CXCL12. Black-Right-Pointing-Pointer MIP-2 or CXCL12 prevent elevation of F2-Isoprostanes against A{beta} treatment.« less

Chitovibrin: a chitin-binding lectin from Vibrio parahemolyticus.

PubMed

Gildemeister, O S; Zhu, B C; Laine, R A

1994-12-01

A novel 134 kDa, calcium-independent chitin-binding lectin, 'chitovibrin', is secreted by the marine bacterium Vibrio parahemolyticus, inducible with chitin or chitin-oligomers. Chitovibrin shows no apparent enzymatic activity but exhibits a strong affinity for chitin and chito-oligomers > dp9. The protein has an isoelectric pH of 3.6, shows thermal tolerance, binds chitin with an optimum at pH 6 and is active in 0-4 M NaCl. Chitovibrin appears to be completely different from other reported Vibrio lectins and may function to bind V. parahemolyticus to chitin substrates, or to capture or sequester chito-oligomers. It may be a member of a large group of recently described proteins in Vibrios related to a complex chitinoclastic (chitinivorous) system.

Association Thermodynamics and Conformational Stability of β-Sheet Amyloid β(17-42) Oligomers: Effects of E22Q (Dutch) Mutation and Charge Neutralization

PubMed Central

Blinov, Nikolay; Dorosh, Lyudmyla; Wishart, David; Kovalenko, Andriy

2010-01-01

Amyloid fibrils are associated with many neurodegenerative diseases. It was found that amyloidogenic oligomers, not mature fibrils, are neurotoxic agents related to these diseases. Molecular mechanisms of infectivity, pathways of aggregation, and molecular structure of these oligomers remain elusive. Here, we use all-atom molecular dynamics, molecular mechanics combined with solvation analysis by statistical-mechanical, three-dimensional molecular theory of solvation (also known as 3D-RISM-KH) in a new MM-3D-RISM-KH method to study conformational stability, and association thermodynamics of small wild-type Aβ17–42 oligomers with different protonation states of Glu22, as well the E22Q (Dutch) mutants. The association free energy of small β-sheet oligomers shows near-linear trend with the dimers being thermodynamically more stable relative to the larger constructs. The linear (within statistical uncertainty) dependence of the association free energy on complex size is a consequence of the unilateral stacking of monomers in the β-sheet oligomers. The charge reduction of the wild-type Aβ17–42 oligomers upon protonation of the solvent-exposed Glu22 at acidic conditions results in lowering the association free energy compared to the wild-type oligomers at neutral pH and the E22Q mutants. The neutralization of the peptides because of the E22Q mutation only marginally affects the association free energy, with the reduction of the direct electrostatic interactions mostly compensated by the unfavorable electrostatic solvation effects. For the wild-type oligomers at acidic conditions such compensation is not complete, and the electrostatic interactions, along with the gas-phase nonpolar energetic and the overall entropic effects, contribute to the lowering of the association free energy. The differences in the association thermodynamics between the wild-type Aβ17–42 oligomers at neutral pH and the Dutch mutants, on the one hand, and the Aβ17–42 oligomers with protonated Glu22, on the other, may be explained by destabilization of the inter- and intrapeptide salt bridges between Asp23 and Lys28. Peculiarities in the conformational stability and the association thermodynamics for the different models of the Aβ17–42 oligomers are rationalized based on the analysis of the local physical interactions and the microscopic solvation structure. PMID:20338850

Oil Palm Phenolics Inhibit the In Vitro Aggregation of β-Amyloid Peptide into Oligomeric Complexes

PubMed Central

Koledova, Vera V.; Shin, Hyeari; Park, Jennifer H.; Tan, Yew Ai; Sambanthamurthi, Ravigadevi

2018-01-01

Alzheimer's disease is a severe neurodegenerative disease characterized by the aggregation of amyloid-β peptide (Aβ) into toxic oligomers which activate microglia and astrocytes causing acute neuroinflammation. Multiple studies show that the soluble oligomers of Aβ42 are neurotoxic and proinflammatory, whereas the monomers and insoluble fibrils are relatively nontoxic. We show that Aβ42 aggregation is inhibited in vitro by oil palm phenolics (OPP), an aqueous extract from the oil palm tree (Elaeis guineensis). The data shows that OPP inhibits stacking of β-pleated sheets, which is essential for oligomerization. We demonstrate the inhibition of Aβ42 aggregation by (1) mass spectrometry; (2) Congo Red dye binding; (3) 2D-IR spectroscopy; (4) dynamic light scattering; (5) transmission electron microscopy; and (6) transgenic yeast rescue assay. In the yeast rescue assay, OPP significantly reduces the cytotoxicity of aggregating neuropeptides in yeast genetically engineered to overexpress these peptides. The data shows that OPP inhibits (1) the aggregation of Aβ into oligomers; (2) stacking of β-pleated sheets; and (3) fibrillar growth and coalescence. These inhibitory effects prevent the formation of neurotoxic oligomers and hold potential as a means to reduce neuroinflammation and neuronal death and thereby may play some role in the prevention or treatment of Alzheimer's disease. PMID:29666700

Wnt-related SynGAP1 is a neuroprotective factor of glutamatergic synapses against Aβ oligomers

PubMed Central

Codocedo, Juan F.; Montecinos-Oliva, Carla; Inestrosa, Nibaldo C.

2015-01-01

Wnt-5a is a synaptogenic factor that modulates glutamatergic synapses and generates neuroprotection against Aβ oligomers. It is known that Wnt-5a plays a key role in the adult nervous system and synaptic plasticity. Emerging evidence indicates that miRNAs are actively involved in the regulation of synaptic plasticity. Recently, we showed that Wnt-5a is able to control the expression of several miRNAs including miR-101b, which has been extensively studied in carcinogenesis. However, its role in brain is just beginning to be explored. That is why we aim to study the relationship between Wnt-5a and miRNAs in glutamatergic synapses. We performed in silico analysis which predicted that miR-101b may inhibit the expression of synaptic GTPase-Activating Protein (SynGAP1), a Ras GTPase-activating protein critical for the development of cognition and proper synaptic function. Through overexpression of miR-101b, we showed that miR-101b is able to regulate the expression of SynGAP1 in an hippocampal cell line. Moreover and consistent with a decrease of miR-101b, Wnt-5a enhances SynGAP expression in cultured hippocampal neurons. Additionally, Wnt-5a increases the activity of SynGAP in a time-dependent manner, with a similar kinetic to CaMKII phosphorylation. This also, correlates with a modulation in the SynGAP clusters density. On the other hand, Aβ oligomers permanently decrease the number of SynGAP clusters. Interestingly, when neurons are co-incubated with Wnt-5a and Aβ oligomers, we do not observe the detrimental effect of Aβ oligomers, indicating that, Wnt-5a protects neurons from the synaptic failure triggered by Aβ oligomers. Overall, our findings suggest that SynGAP1 is part of the signaling pathways induced by Wnt-5a. Therefore, possibility exists that SynGAP is involved in the synaptic protection against Aβ oligomers. PMID:26124704

Non-Traditional Aromatic Topologies and Biomimetic Assembly Motifs as Components of Functional Pi-Conjugated Oligomers

PubMed Central

Tovar, John D.; Diegelmann, Stephen R.; Peart, Patricia A.

2010-01-01

This article will highlight our recent work using conjugated oligomers as precursors to electroactive polymer films and self-assembling nanomaterials. One area of investigation has focused on nonbenzenoid aromaticity in the context of charge delocalization in conjugated polymers. In these studies, polymerizable pi-conjugated units were coupled onto unusual aromatic cores such as methano[10]annulene. This article will also show how biologically-inspired assembly of molecularly well-defined oligopeptides that flank pi-conjugated oligomers has resulted in the aqueous construction of 1-dimensional nanomaterials that encourage electronic delocalization among the pi-electron systems.

Change of electric dipole moment in charge transfer transitions of ferrocene oligomers studied by ultrafast two-photon absorption

NASA Astrophysics Data System (ADS)

Mikhaylov, Alexander; Arias, Eduardo; Moggio, Ivana; Ziolo, Ronald; Uudsemaa, Merle; Trummal, Aleksander; Cooper, Thomas; Rebane, Aleksander

2017-02-01

Change of permanent electric dipole moment in the lower-energy charge transfer transitions for a series of symmetrical and non-symmetrical ferrocene-phenyleneethynylene oligomers were studied by measuring the corresponding femtosecond two-photon absorption cross section spectra, and were determined to be in the range Δμ = 3 - 10 D. Quantum-chemical calculations of Δμ for the non-symmetrical oligomers show good quantitative agreement with the experimental results, thus validating two-photon absorption spectroscopy as a viable experimental approach to study electrostatic properties of organometallics and other charge transfer systems.

Concentration-dependent and configuration-dependent interactions of monovalent ions with an RNA tetraloop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miner, Jacob Carlson; Garcia, Angel Enrique

Monovalent salt solutions have strongly coupled interactions with biopolymers, from large polyelectrolytes to small RNA oligomers. High salt concentrations have been known to induce transitions in the structure of RNA, producing non-canonical configurations and even driving RNA to precipitate out of solution. Using all-atom molecular dynamics simulations, we model a monovalent salt species (KCL) at high concentrations (0.1–3m) and calculate the equilibrium distributions of water and ions around a small tetraloop-forming RNA oligomer in a variety of structural arrangements: folded A-RNA (canonical) and Z-RNA (non-canonical) tetraloops and unfolded configurations. From these data, we calculate the ion preferential binding coefficients andmore » Donnan coefficients for the RNA oligomer as a function of concentration and structure. We find that cation accumulation is highest around non-canonical Z-RNA configurations at concentrations below 0.5m, while unfolded configurations accumulate the most co-ions in all concentrations. By contrast, canonical A-RNA structures consistently show the lowest accumulations for all ion species. Water distributions vary markedly with RNA configuration but show little dependency on KCL concentration. Based on Donnan coefficient calculations, the net charge of the solution at the surface of the RNA decreases linearly as a function of salt concentration and becomes net-neutral near 2.5–3m KCL for folded configurations, while unfolded configurations still show a positive solution charge. Our findings show that all-atom molecular dynamics can describe the equilibrium distributions of monovalent salt in the presence of small RNA oligomers at KCL concentrations where ion correlation effects become important. Furthermore, these results provide valuable insights into the distributions of water and ions near the RNA oligomer surface as a function of structural configuration.« less

Concentration-dependent and configuration-dependent interactions of monovalent ions with an RNA tetraloop

DOE PAGES

Miner, Jacob Carlson; Garcia, Angel Enrique

2018-05-29

Monovalent salt solutions have strongly coupled interactions with biopolymers, from large polyelectrolytes to small RNA oligomers. High salt concentrations have been known to induce transitions in the structure of RNA, producing non-canonical configurations and even driving RNA to precipitate out of solution. Using all-atom molecular dynamics simulations, we model a monovalent salt species (KCL) at high concentrations (0.1–3m) and calculate the equilibrium distributions of water and ions around a small tetraloop-forming RNA oligomer in a variety of structural arrangements: folded A-RNA (canonical) and Z-RNA (non-canonical) tetraloops and unfolded configurations. From these data, we calculate the ion preferential binding coefficients andmore » Donnan coefficients for the RNA oligomer as a function of concentration and structure. We find that cation accumulation is highest around non-canonical Z-RNA configurations at concentrations below 0.5m, while unfolded configurations accumulate the most co-ions in all concentrations. By contrast, canonical A-RNA structures consistently show the lowest accumulations for all ion species. Water distributions vary markedly with RNA configuration but show little dependency on KCL concentration. Based on Donnan coefficient calculations, the net charge of the solution at the surface of the RNA decreases linearly as a function of salt concentration and becomes net-neutral near 2.5–3m KCL for folded configurations, while unfolded configurations still show a positive solution charge. Our findings show that all-atom molecular dynamics can describe the equilibrium distributions of monovalent salt in the presence of small RNA oligomers at KCL concentrations where ion correlation effects become important. Furthermore, these results provide valuable insights into the distributions of water and ions near the RNA oligomer surface as a function of structural configuration.« less

Concentration-dependent and configuration-dependent interactions of monovalent ions with an RNA tetraloop

NASA Astrophysics Data System (ADS)

Miner, Jacob Carlson; García, Angel Enrique

2018-06-01

Monovalent salt solutions have strongly coupled interactions with biopolymers, from large polyelectrolytes to small RNA oligomers. High salt concentrations have been known to induce transitions in the structure of RNA, producing non-canonical configurations and even driving RNA to precipitate out of solution. Using all-atom molecular dynamics simulations, we model a monovalent salt species (KCL) at high concentrations (0.1-3m) and calculate the equilibrium distributions of water and ions around a small tetraloop-forming RNA oligomer in a variety of structural arrangements: folded A-RNA (canonical) and Z-RNA (non-canonical) tetraloops and unfolded configurations. From these data, we calculate the ion preferential binding coefficients and Donnan coefficients for the RNA oligomer as a function of concentration and structure. We find that cation accumulation is highest around non-canonical Z-RNA configurations at concentrations below 0.5m, while unfolded configurations accumulate the most co-ions in all concentrations. By contrast, canonical A-RNA structures consistently show the lowest accumulations for all ion species. Water distributions vary markedly with RNA configuration but show little dependency on KCL concentration. Based on Donnan coefficient calculations, the net charge of the solution at the surface of the RNA decreases linearly as a function of salt concentration and becomes net-neutral near 2.5-3m KCL for folded configurations, while unfolded configurations still show a positive solution charge. Our findings show that all-atom molecular dynamics can describe the equilibrium distributions of monovalent salt in the presence of small RNA oligomers at KCL concentrations where ion correlation effects become important. Furthermore, these results provide valuable insights into the distributions of water and ions near the RNA oligomer surface as a function of structural configuration.

Concentration-dependent and configuration-dependent interactions of monovalent ions with an RNA tetraloop.

PubMed

Miner, Jacob Carlson; García, Angel Enrique

2018-06-14

Monovalent salt solutions have strongly coupled interactions with biopolymers, from large polyelectrolytes to small RNA oligomers. High salt concentrations have been known to induce transitions in the structure of RNA, producing non-canonical configurations and even driving RNA to precipitate out of solution. Using all-atom molecular dynamics simulations, we model a monovalent salt species (KCL) at high concentrations (0.1-3m) and calculate the equilibrium distributions of water and ions around a small tetraloop-forming RNA oligomer in a variety of structural arrangements: folded A-RNA (canonical) and Z-RNA (non-canonical) tetraloops and unfolded configurations. From these data, we calculate the ion preferential binding coefficients and Donnan coefficients for the RNA oligomer as a function of concentration and structure. We find that cation accumulation is highest around non-canonical Z-RNA configurations at concentrations below 0.5m, while unfolded configurations accumulate the most co-ions in all concentrations. By contrast, canonical A-RNA structures consistently show the lowest accumulations for all ion species. Water distributions vary markedly with RNA configuration but show little dependency on KCL concentration. Based on Donnan coefficient calculations, the net charge of the solution at the surface of the RNA decreases linearly as a function of salt concentration and becomes net-neutral near 2.5-3m KCL for folded configurations, while unfolded configurations still show a positive solution charge. Our findings show that all-atom molecular dynamics can describe the equilibrium distributions of monovalent salt in the presence of small RNA oligomers at KCL concentrations where ion correlation effects become important. Furthermore, these results provide valuable insights into the distributions of water and ions near the RNA oligomer surface as a function of structural configuration.

Molecular dynamics simulations of low-ordered alzheimer β-amyloid oligomers from dimer to hexamer on self-assembled monolayers.

PubMed

Zhao, Jun; Wang, Qiuming; Liang, Guizhao; Zheng, Jie

2011-12-20

Accumulation of small soluble oligomers of amyloid-β (Aβ) in the human brain is thought to play an important pathological role in Alzheimer's disease. The interaction of these Aβ oligomers with cell membrane and other artificial surfaces is important for the understanding of Aβ aggregation and toxicity mechanisms. Here, we present a series of exploratory molecular dynamics (MD) simulations to study the early adsorption and conformational change of Aβ oligomers from dimer to hexamer on three different self-assembled monolayers (SAMs) terminated with CH(3), OH, and COOH groups. Within the time scale of MD simulations, the conformation, orientation, and adsorption of Aβ oligomers on the SAMs is determined by complex interplay among the size of Aβ oligomers, the surface chemistry of the SAMs, and the structure and dynamics of interfacial waters. Energetic analysis of Aβ adsorption on the SAMs reveals that Aβ adsorption on the SAMs is a net outcome of different competitions between dominant hydrophobic Aβ-CH(3)-SAM interactions and weak CH(3)-SAM-water interactions, between dominant electrostatic Aβ-COOH-SAM interactions and strong COOH-SAM-water interactions, and between comparable hydrophobic and electrostatic Aβ-OH-SAM interactions and strong OH-SAM-water interactions. Atomic force microscopy images also confirm that all of three SAMs can induce the adsorption and polymerization of Aβ oligomers. Structural analysis of Aβ oligomers on the SAMs shows a dramatic increase in structural stability and β-sheet content from dimer to trimer, suggesting that Aβ trimer could act as seeds for Aβ polymerization on the SAMs. This work provides atomic-level understanding of Aβ peptides at interface. © 2011 American Chemical Society

Analysis of PEG oligomers in black gel inks: Discrimination and ink dating.

PubMed

Sun, Qiran; Luo, Yiwen; Xiang, Ping; Yang, Xu; Shen, Min

2017-08-01

Carbon-based black gel inks are common samples in forensic practice of questioned document examination in China, but there are few analytical methods for this type of ink. In this study, a liquid chromatography-.high resolution mass spectrometry (LC-HRMS) method was established for the analysis of PEG oligomers in carbon-based black gel ink entries. The coupled instruments achieve both the identification and quantification of PEG oligomers in ink entries with reproducible results. Twenty carbon-based black gel inks, whose Raman spectra appeared identical, were analyzed using the LC-HRMS method. As a result, the twenty gel inks were classified into four groups according to the distribution of PEG oligomers. Artificially aging of PEG 400 and a gel ink showed that as PEG degraded, the relative amounts of low molecular weight PEG oligomers increased, while those of high molecular weight decreased. The degradation of PEG oligomers in a naturally aged gel ink was consistent with those in the artificially aged samples, but occurred more slowly. This study not only provided a new method for discriminating carbon-based black gel ink entries, but also offered a new approach for studying the relative ink dating of carbon-based black gel ink entries. Copyright © 2017 Elsevier B.V. All rights reserved.

Selective amyloid β oligomer assay based on abasic site-containing molecular beacon and enzyme-free amplification.

PubMed

Zhu, Linling; Zhang, Junying; Wang, Fengyang; Wang, Ya; Lu, Linlin; Feng, Chongchong; Xu, Zhiai; Zhang, Wen

2016-04-15

Amyloid-beta (Aβ) oligomers are highly toxic species in the process of Aβ aggregation and are regarded as potent therapeutic targets and diagnostic markers for Alzheimer's disease (AD). Herein, a label-free molecular beacon (MB) system integrated with enzyme-free amplification strategy was developed for simple and highly selective assay of Aβ oligomers. The MB system was constructed with abasic site (AP site)-containing stem-loop DNA and a fluorescent ligand 2-amino-5,6,7-trimethyl-1,8-naphyridine (ATMND), of which the fluorescence was quenched upon binding to the AP site in DNA stem. Enzyme-free amplification was realized by target-triggered continuous opening of two delicately designed MBs (MB1 and MB2). Target DNA hybridization with MB1 and then MB2 resulted in the release of two ATMND molecules in one binding event. Subsequent target recycling could greatly amplify the detection sensitivity due to the greatly enhanced turn-on emission of ATMND fluorescence. Combining with Aβ oligomers aptamers, the strategy was applied to analyze Aβ oligomers and the results showed that it could quantify Aβ oligomers with high selectivity and monitor the Aβ aggregation process. This novel method may be conducive to improve the diagnosis and pathogenic study of Alzheimer's disease. Copyright © 2015 Elsevier B.V. All rights reserved.

Active Immunization Against hIAPP Oligomers Ameliorates the Diabetes- Associated Phenotype in a Transgenic Mice Model.

PubMed

Bram, Yaron; Peled, Sivan; Brahmachari, Sayanti; Harlev, Michael; Gazit, Ehud

2017-10-25

Type 2 diabetes is characterized by insulin tolerance in target cells followed by a reduction of pancreatic β-cell mass. Islet amyloid polypeptide oligomeric assemblies were shown to contribute to β-cell apoptosis by forming discrete pores that destabilize the cellular membrane. We previously characterized α-helical cytotoxic islet amyloid polypeptide oligomers which interact with cell membranes, following a complete internalization that leads to cellular apoptosis. Moreover, antibodies which bind the oligomers and neutralize the cytotoxicity were exclusively identified in the serum of type 2 diabetes patients. Here, we examined the usage of the newly characterized oligomers as an active immunization agent targeting amyloid self- assembly in a diabetes-associated phenotype transgenic mice model. Immunized transgenic mice showed an increase in hIAPP-antibody serum titer as well as improvement in diabetes-associated parameters. Lower fasting blood glucose levels, higher insulin, and lower islet amyloid polypeptide accumulation were observed. Furthermore, antibodies derived from the immunized mice reduced hIAPP oligomers cytotoxicity towards β-cells in a dose-dependent manner. This study highlights the significance of targeting the early amyloid self-assembly events for potential disease management. Furthermore, it demonstrates that α-helical oligomers conformers are valid epitope for the development of future immunization therapy.

Aqueous phase oligomerization of α,β-unsaturated carbonyls and acids investigated using ion mobility spectrometry coupled to mass spectrometry (IMS-MS)

NASA Astrophysics Data System (ADS)

Renard, Pascal; Tlili, Sabrine; Ravier, Sylvain; Quivet, Etienne; Monod, Anne

2016-04-01

One of the current essential issues to unravel our ability to forecast future climate change and air quality, implies a better understanding of natural processes leading to secondary organic aerosol (SOA) formation, and in particular the formation and fate of oligomers. The difficulty in characterizing macromolecules is to discern between large oxygenated molecules from series of oligomers containing repeated small monomers of diverse structures. In the present study, taking advantage from previously established radical vinyl oligomerization of methyl vinylketone (MVK) in the aqueous phase, where relatively simple oligomers containing up to 14 monomers were observed, we have investigated the same reactivity on several other unsaturated water soluble organic compounds (UWSOCs) and on a few mixtures of these precursor compounds. The technique used to characterize the formed oligomers was a traveling wave ion mobility spectrometry coupled to a hybrid quadrupole - time of flight mass spectrometer (IMS-MS) fitted with an electrospray source and ultra-high performance liquid chromatography (UPLC). The technique allows for an additional separation, especially for large ions, containing long carbon chains. We have shown the efficiency of the IMS-mass spectrometry technique to detect oligomers derived from MVK photooxidation in the aqueous phase. The results were then compared to other oligomers, derived from ten other individual biogenic UWSOCs. The technique allowed distinguishing between different oligomers arising from different precursors. It also clearly showed that compounds bearing a non-conjugated unsaturation did not provide oligomerization. Finally, it was shown that the IMS-mass spectrometry technique, applied to mixtures of unsaturated conjugated precursors, exhibited the ability of these precursors to co-oligomerize, i.e. forming only one complex oligomer system bearing monomers of different structures. The results are discussed in terms of atmospheric implications for the detection of oligomers in complex chamber and/or field samples.

Pathogenic Serum Amyloid A 1.1 Shows a Long Oligomer-rich Fibrillation Lag Phase Contrary to the Highly Amyloidogenic Non-pathogenic SAA2.2*

PubMed Central

Srinivasan, Saipraveen; Patke, Sanket; Wang, Yun; Ye, Zhuqiu; Litt, Jeffrey; Srivastava, Sunit K.; Lopez, Maria M.; Kurouski, Dmitry; Lednev, Igor K.; Kane, Ravi S.; Colón, Wilfredo

2013-01-01

Serum amyloid A (SAA) is best known for being the main component of amyloid in the inflammation-related disease amyloid A (AA) amyloidosis. Despite the high sequence identity among different SAA isoforms, not all SAA proteins are pathogenic. In most mouse strains, the AA deposits mostly consist of SAA1.1. Conversely, the CE/J type mouse expresses a single non-pathogenic SAA2.2 protein that is 94% identical to SAA1.1. Here we show that SAA1.1 and SAA2.2 differ in their quaternary structure, fibrillation kinetics, prefibrillar oligomers, and fibril morphology. At 37 °C and inflammation-related SAA concentrations, SAA1.1 exhibits an oligomer-rich fibrillation lag phase of a few days, whereas SAA2.2 shows virtually no lag phase and forms small fibrils within a few hours. Deep UV resonance Raman, far UV-circular dichroism, atomic force microscopy, and fibrillation cross-seeding experiments suggest that SAA1.1 and SAA2.2 fibrils possess different morphology. Both the long-lived oligomers of pathogenic SAA1.1 and the fleeting prefibrillar oligomers of non-pathogenic SAA2.2, but not their respective amyloid fibrils, permeabilized synthetic bilayer membranes in vitro. This study represents the first comprehensive comparison between the biophysical properties of SAA isoforms with distinct pathogenicities, and the results suggest that structural and kinetic differences in the oligomerization-fibrillation of SAA1.1 and SAA2.2, more than their intrinsic amyloidogenicity, may contribute to their diverse pathogenicity. PMID:23223242

Transient dichroism in photoreceptor membranes indicates that stable oligomers of rhodopsin do not form during excitation.

PubMed Central

Downer, N W; Cone, R A

1985-01-01

If a photoexcited rhodopsin molecule initiates the formation of rhodopsin oligomers during the process of visual excitation, the rate of rotational diffusion of the rhodopsin molecules involved should change markedly. Using microsecond-flash photometry, we have observed the rotational diffusion of rhodopsin throughout the time period of visual excitation and found that no detectable change occurs in its rotational diffusion rate. Partial chemical cross-linking of the retina yields oligomers of rhodopsin and causes a significant decrease in the rotational diffusion rate of rhodopsin even when as little as 20% of rhodopsin is dimeric. Moreover, the pattern of oligomers formed by cross-linking, taken together with the magnitude of decreases in rotational diffusion rate accompanying the cross-linking reaction, suggests that rhodopsin is a monomer in the dark-adapted state. The experiments reported here show that photoexcited rhodopsin molecules do not irreversibly associate with unbleached neighbors during the time course of the receptor response. Hence, it is not likely that stable oligomers of rhodopsin trigger the excitation of the photoreceptor cell. Images FIGURE 1 PMID:3919778

New oligomers containing pendant 4-aryl-7-phenylfluorene units as efficient charge transporting materials for OLEDs

NASA Astrophysics Data System (ADS)

Krucaite, G.; Baranauskyte, U.; Tavgeniene, D.; Andruleviciute, V.; Sutkuviene, S.; Yao, B.; Xie, Z.; Zhang, B.; Grigalevicius, S.

2017-10-01

Monomers and oligomers containing electronically isolated 4-aryl-7-phenylfluorene fragments have been synthesized by the multi-step synthetic route. The materials were characterized by thermo-gravimetric analysis, differential scanning calorimetry and electron photoemission technique. The oligomers represent materials of very high thermal stability having initial thermal degradation temperatures in the range of 402-412 °C. The glass transition temperatures of the amorphous oligomers were in the rage of 97-129 °C. The electron photoemission spectra of thin layers of the oligomeric materials showed ionization potentials in the range of 5.7-6.1 eV. Hole injecting/transporting properties of the electroactive oligomers were tested in the structures of organic light emitting diodes with tris(quinolin-8-olato)aluminium as a green emitter. The device containing hole-transporting material with 4-biphenyl-7-phenylfluorene electrophores exhibited the best overall performance with low turn on voltage of 4.4 V, high current efficiency exceeding 3.6 cd/A and maximum brightness exceeding 3200 cd/m2.

Low molecular weight oligomers of amyloid peptides display β-barrel conformations: A replica exchange molecular dynamics study in explicit solvent

NASA Astrophysics Data System (ADS)

De Simone, Alfonso; Derreumaux, Philippe

2010-04-01

The self-assembly of proteins and peptides into amyloid fibrils is connected to over 40 pathological conditions including neurodegenerative diseases and systemic amyloidosis. Diffusible, low molecular weight protein and peptide oligomers that form in the early steps of aggregation appear to be the harmful cytotoxic species in the molecular etiology of these diseases. So far, the structural characterization of these oligomers has remained elusive owing to their transient and dynamic features. We here address, by means of full atomistic replica exchange molecular dynamics simulations, the energy landscape of heptamers of the amyloidogenic peptide NHVTLSQ from the beta-2 microglobulin protein. The simulations totaling 5 μs show that low molecular weight oligomers in explicit solvent consist of β-barrels in equilibrium with amorphous states and fibril-like assemblies. The results, also accounting for the influence of the pH on the conformational properties, provide a strong evidence of the formation of transient β-barrel assemblies in the early aggregation steps of amyloid-forming systems. Our findings are discussed in terms of oligomers cytotoxicity.

Binding affinity of amyloid oligomers to cellular membranes is a generic indicator of cellular dysfunction in protein misfolding diseases

PubMed Central

Evangelisti, Elisa; Cascella, Roberta; Becatti, Matteo; Marrazza, Giovanna; Dobson, Christopher M.; Chiti, Fabrizio; Stefani, Massimo; Cecchi, Cristina

2016-01-01

The conversion of peptides or proteins from their soluble native states into intractable amyloid deposits is associated with a wide range of human disorders. Misfolded protein oligomers formed during the process of aggregation have been identified as the primary pathogenic agents in many such conditions. Here, we show the existence of a quantitative relationship between the degree of binding to neuronal cells of different types of oligomers formed from a model protein, HypF-N, and the GM1 content of the plasma membranes. In addition, remarkably similar behavior is observed for oligomers of the Aβ42 peptide associated with Alzheimer’s disease. Further analysis has revealed the existence of a linear correlation between the level of the influx of Ca2+ across neuronal membranes that triggers cellular damage, and the fraction of oligomeric species bound to the membrane. Our findings indicate that the susceptibility of neuronal cells to different types of misfolded oligomeric assemblies is directly related to the extent of binding of such oligomers to the cellular membrane. PMID:27619987

Selectivity in subunit composition of Ena/VASP tetramers

PubMed Central

Riquelme, Daisy N.; Meyer, Aaron S.; Barzik, Melanie; Keating, Amy; Gertler, Frank B.

2015-01-01

The members of the actin regulatory family of Ena/VASP proteins form stable tetramers. The vertebrate members of the Ena/VASP family, VASP, Mena and EVL, have many overlapping properties and expression patterns, but functional and regulatory differences between paralogues have been observed. The formation of mixed oligomers may serve a regulatory role to refine Ena/VASP activity. While it has been assumed that family members can form mixed oligomers, this possibility has not been investigated systematically. Using cells expressing controlled combinations of VASP, Mena and EVL, we evaluated the composition of Ena/VASP oligomers and found that VASP forms oligomers without apparent bias with itself, Mena or EVL. However, Mena and EVL showed only weak hetero-oligomerization, suggesting specificity in the association of Ena/VASP family members. Co-expression of VASP increased the ability of Mena and EVL to form mixed oligomers. Additionally, we found that the tetramerization domain (TD) at the C-termini of Ena/VASP proteins conferred the observed selectivity. Finally, we demonstrate that replacement of the TD with a synthetic tetramerizing coiled coil sequence supports homo-oligomerization and normal VASP subcellular localization. PMID:26221026

Synthesis of a new π-conjugated redox oligomer: Electrochemical and optical investigation

NASA Astrophysics Data System (ADS)

Blili, Saber; Zaâboub, Zouhour; Maaref, Hassen; Haj Said, Ayoub

2017-01-01

A new π-conjugated redox oligomer was prepared according a two-Step Synthesis. Firstly, an oligophenylene (OMPA) was obtained from the anodic oxidation of the (4-methoxyphenyl)acetonitrile. Then, the resulting material was chemically modified by the Knoevenagel condensation with the ferrocenecarboxaldehyde. This reaction led to a redox-conjugated oligomer the Fc-OMPA. The synthesized material was characterized using different spectroscopic techniques: NMR, FTIR, UV-vis and photoluminescence (PL) spectroscopy. The Fc-OMPA was used to modify a platinum electrode surface and the electrochemical response of the ferrocene redox-center was investigated by cyclic voltammetry. Moreover, the room temperature PL spectra of Fc-OMPA revealed that the ferrocene moiety, which acts as an electron donor, can effectively quench the oligomer luminescence. However, when ferrocene was oxidized to ferrocenium ion, the intramolecular charge transfer process was prevented which consequently enhanced the light emission. Thus, the oligomer light-emission can be, chemically or electrochemically tuned. The obtained results showed that the prepared material is a good candidate for the elaboration of electrochemical sensors and for the development of luminescent Redox-switchable devices.

Intracellular soluble α‐synuclein oligomers reduce pyramidal cell excitability

PubMed Central

Kaufmann, Timothy J.; Harrison, Paul M.; Richardson, Magnus J. E.; Pinheiro, Teresa J. T.

2016-01-01

Key points The presynaptic protein α‐synuclein forms aggregates during Parkinson's disease.Accumulating evidence suggests that the small soluble oligomers of α‐synuclein are more toxic than the larger aggregates appearing later in the disease.The link between oligomer toxicity and structure still remains unclear.In the present study, we have produced two structurally‐defined oligomers that have a similar morphology but differ in secondary structure.These oligomers were introduced into neocortical pyramidal cells during whole‐cell recording and, using a combination of experimentation and modelling, electrophysiological parameters were extracted.Both oligomeric species had similar effects on neuronal properties reducing input resistance, time constant and increasing capacitance. The net effect was a marked reduction in neuronal excitability that could impact on network activity. Abstract The presynaptic protein α‐synuclein (αSyn) aggregates during Parkinson's disease (PD) to form large proteinaceous amyloid plaques, the spread of which throughout the brain clinically defines the severity of the disease. During early stages of aggregation, αSyn forms soluble annular oligomers that show greater toxicity than much larger fibrils. These oligomers produce toxicity via a number of possible mechanisms, including the production of pore‐forming complexes that permeabilize membranes. In the present study, two well‐defined species of soluble αSyn oligomers were produced by different protocols: by polymerization of monomer and by sonication of fibrils. The two oligomeric species produced were morphologically similar, with both having an annular structure and consisting of approximately the same number of monomer subunits, although they differed in their secondary structure. Oligomeric and monomeric αSyn were injected directly into the soma of pyramidal neurons in mouse neocortical brain slices during whole‐cell patch clamp recording. Using a combined experimental and modelling approach, neuronal parameters were extracted to measure, for the first time in the neocortex, specific changes in neuronal electrophysiology. Both species of oligomer had similar effects: (i) a significant reduction in input resistance and the membrane time constant and (ii) an increase in the current required to trigger an action potential with a resultant reduction in the firing rate. Differences in oligomer secondary structure appeared to produce only subtle differences in the activity of the oligomers. Monomeric αSyn had no effect on neuronal parameters, even at high concentrations. The oligomer‐induced fall in neuronal excitability has the potential to impact both network activity and cognitive processing. PMID:26915902

The effect of polar end of long-chain fluorocarbon oligomers in promoting the superamphiphobic property over multi-scale rough Al alloy surfaces

NASA Astrophysics Data System (ADS)

Saifaldeen, Zubayda S.; Khedir, Khedir R.; Camci, Merve T.; Ucar, Ahmet; Suzer, Sefik; Karabacak, Tansel

2016-08-01

Rough structures with re-entrant property and their subsequent surface energy reduction with long-chain fluorocarbon oligomers are both critical in developing superamphiphobic (SAP, i.e. both super hydrophobic and superoleophobic) surfaces. However, morphology of the low-surface energy layer on a rough re-entrant substrate can strongly depend on the fluorocarbon oligomers used. In this study, the effect of polar end of different kinds of long-chain fluorocarbon oligomers in promoting a self-assembled monolayer with close packed molecules and robust adhesion on multi-scale rough Al alloy surfaces was investigated. Hierarchical Al alloy surfaces with microgrooves and nanograss structures were developed by a simple combination of one-directional mechanical sanding and post treatment in boiling de-ionized water (DIW). Three types of long-chain fluorocarbon oligomers of 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDTS), 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (PFDCS), and perfluorooctanoic acid (PFOA) were chemically vaporized onto these rough Al alloy surfaces. The PFDCS exhibited the lowest surface free energy of less than 10 mN/m. The contact angle and sliding angle measurements for water, ethylene glycol, and peanut oil verified the SAP property of hierarchical rough Al alloy surfaces treated with alkylsilane oligomers (PFDTS, PFDCS). However, the hierarchical surfaces treated with fluorocarbon oligomer with polar acidic tail (PFOA) showed highly amphiphobic properties but could not reach the threshold for SAP. Chemical stability of the hierarchical Al alloy surfaces treated with the fluorocarbon oligomers was tested under the harsh conditions of ultra-sonication in acetone and annealing at high temperature after different treatment times. Contact angle measurements revealed the robustness of the alkylsilane oligomers and deterioration of the PFOA coating particularly for low surface tension liquids. The robust adhesion and close-packing of the alkylsilane molecules as well as their vertical orientation with exposure of more CF3 groups instead of CF2 groups due to the polar silane-based tail are believed to be the main reasons behind their improved chemical stability. The selection of fluorocarbon oligomer with proper polar tail which can promote a self-assembled monolayer with close-packed molecules could make it possible for utilizing shorter fluorocarbon oligomers, which is environmentally favorable, to develop high surface energy materials with SAP properties.

Iron-induced oligomerization of human FXN81-210 and bacterial CyaY frataxin and the effect of iron chelators

PubMed Central

Ahlgren, Eva-Christina; Fekry, Mostafa; Wiemann, Mathias; Söderberg, Christopher A.; Bernfur, Katja; Gakh, Olex; Rasmussen, Morten; Højrup, Peter; Emanuelsson, Cecilia; Isaya, Grazia

2017-01-01

Patients suffering from the progressive neurodegenerative disease Friedreich’s ataxia have reduced expression levels of the protein frataxin. Three major isoforms of human frataxin have been identified, FXN42-210, FXN56-210 and FXN81-210, of which FXN81-210 is considered to be the mature form. Both long forms, FXN42-210 and FXN56-210, have been shown to spontaneously form oligomeric particles stabilized by the extended N-terminal sequence. The short variant FXN81-210, on other hand, has only been observed in the monomeric state. However, a highly homologous E. coli frataxin CyaY, which also lacks an N-terminal extension, has been shown to oligomerize in the presence of iron. To explore the mechanisms of stabilization of short variant frataxin oligomers we compare here the effect of iron on the oligomerization of CyaY and FXN81-210. Using dynamic light scattering, small-angle X-ray scattering, electron microscopy (EM) and cross linking mass spectrometry (MS), we show that at aerobic conditions in the presence of iron both FXN81-210 and CyaY form oligomers. However, while CyaY oligomers are stable over time, FXN81-210 oligomers are unstable and dissociate into monomers after about 24 h. EM and MS studies suggest that within the oligomers FXN81-210 and CyaY monomers are packed in a head-to-tail fashion in ring-shaped structures with potential iron-binding sites located at the interface between monomers. The higher stability of CyaY oligomers can be explained by a higher number of acidic residues at the interface between monomers, which may result in a more stable iron binding. We also show that CyaY oligomers may be dissociated by ferric iron chelators deferiprone and DFO, as well as by the ferrous iron chelator BIPY. Surprisingly, deferiprone and DFO stimulate FXN81-210 oligomerization, while BIPY does not show any effect on oligomerization in this case. The results suggest that FXN81-210 oligomerization is primarily driven by ferric iron, while both ferric and ferrous iron participate in CyaY oligomer stabilization. Analysis of the amino acid sequences of bacterial and eukaryotic frataxins suggests that variations in the position of the acidic residues in helix 1, β-strand 1 and the loop between them may control the mode of frataxin oligomerization. PMID:29200434

Tau Oligomers as Pathogenic Seeds: Preparation and Propagation In Vitro and In Vivo.

PubMed

Gerson, Julia E; Sengupta, Urmi; Kayed, Rakez

2017-01-01

Tau oligomers have been shown to be the main toxic tau species in a number of neurodegenerative disorders. In order to study tau oligomers both in vitro and in vivo, we have established methods for the reliable preparation, isolation, and detection of tau oligomers. Methods for the seeding of tau oligomers, isolation of tau oligomers from tissue, and detection of tau oligomers using tau oligomer-specific antibodies by biochemical and immunohistochemical methods are detailed below.

The dynamics of Alzheimer's disease biomarkers in the Alzheimer's Disease Neuroimaging Initiative cohort.

PubMed

Caroli, A; Frisoni, G B

2010-08-01

The aim of this study was to investigate the dynamics of four of the most validated biomarkers for Alzheimer's disease (AD), cerebro-spinal fluid (CSF) Abeta 1-42, tau, hippocampal volume, and FDG-PET, in patients at different stage of AD. Two hundred twenty-nine cognitively healthy subjects, 154 mild cognitive impairment (MCI) patients converted to AD, and 193 (95 early and 98 late) AD patients were selected from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. For each biomarker, individual values were Z-transformed and plotted against ADAS-cog scores, and sigmoid and linear fits were compared. For most biomarkers the sigmoid model fitted data significantly better than the linear model. Abeta 1-42 time course followed a steep curve, stabilizing early in the disease course. CSF tau and hippocampal volume changed later showing similar monotonous trends, reflecting disease progression. Hippocampal loss trend was steeper and occurred earlier in time in APOE epsilon4 carriers than in non-carriers. FDG-PET started changing early in time and likely followed a linear decline. In conclusion, this study provides the first evidence in favor of the dynamic biomarker model which has recently been proposed. 2010 Elsevier Inc. All rights reserved.

Alzheimer Disease Biomarkers as Outcome Measures for Clinical Trials in MCI.

PubMed

Caroli, Anna; Prestia, Annapaola; Wade, Sara; Chen, Kewei; Ayutyanont, Napatkamon; Landau, Susan M; Madison, Cindee M; Haense, Cathleen; Herholz, Karl; Reiman, Eric M; Jagust, William J; Frisoni, Giovanni B

2015-01-01

The aim of this study was to compare the performance and power of the best-established diagnostic biological markers as outcome measures for clinical trials in patients with mild cognitive impairment (MCI). Magnetic resonance imaging, F-18 fluorodeoxyglucose positron emission tomography markers, and Alzheimer's Disease Assessment Scale-cognitive subscale were compared in terms of effect size and statistical power over different follow-up periods in 2 MCI groups, selected from Alzheimer's Disease Neuroimaging Initiative data set based on cerebrospinal fluid (abnormal cerebrospinal fluid Aβ1-42 concentration-ABETA+) or magnetic resonance imaging evidence of Alzheimer disease (positivity to hippocampal atrophy-HIPPO+). Biomarkers progression was modeled through mixed effect models. Scaled slope was chosen as measure of effect size. Biomarkers power was estimated using simulation algorithms. Seventy-four ABETA+ and 51 HIPPO+ MCI patients were included in the study. Imaging biomarkers of neurodegeneration, especially MR measurements, showed highest performance. For all biomarkers and both MCI groups, power increased with increasing follow-up time, irrespective of biomarker assessment frequency. These findings provide information about biomarker enrichment and outcome measurements that could be employed to reduce MCI patient samples and treatment duration in future clinical trials.

Pathophysiology of pain in postherpetic neuralgia: a clinical and neurophysiological study.

PubMed

Truini, A; Galeotti, F; Haanpaa, M; Zucchi, R; Albanesi, A; Biasiotta, A; Gatti, A; Cruccu, G

2008-12-01

Postherpetic neuralgia is an exceptionally drug-resistant neuropathic pain. To investigate the pathophysiological mechanisms underlying postherpetic neuralgia we clinically investigated sensory disturbances, pains and itching, with an 11-point numerical rating scale in 41 patients with ophthalmic postherpetic neuralgia. In all the patients we recorded the blink reflex, mediated by non-nociceptive myelinated Abeta-fibers, and trigeminal laser evoked potentials (LEPs) related to nociceptive myelinated Adelta- and unmyelinated C-fiber activation. We also sought possible correlations between clinical sensory disturbances and neurophysiological data. Neurophysiological testing yielded significantly abnormal responses on the affected side compared with the normal side (P<0.001). The blink reflex delay correlated with the intensity of paroxysmal pain, whereas the Adelta- and C-LEP amplitude reduction correlated with the intensity of constant pain (P<0.01). Allodynia correlated with none of the neurophysiological data. Our study shows that postherpetic neuralgia impairs all sensory fiber groups. The neurophysiological-clinical correlations suggest that constant pain arises from a marked loss of nociceptive afferents, whereas paroxysmal pain is related to Abeta-fiber demyelination. These findings might be useful for a better understanding of pain mechanisms in postherpetic neuralgia.

ACE inhibition with captopril retards the development of signs of neurodegeneration in an animal model of Alzheimer's disease.

PubMed

AbdAlla, Said; Langer, Andreas; Fu, Xuebin; Quitterer, Ursula

2013-08-16

Increased generation of reactive oxygen species (ROS) is a significant pathological feature in the brains of patients with Alzheimer's disease (AD). Experimental evidence indicates that inhibition of brain ROS could be beneficial in slowing the neurodegenerative process triggered by amyloid-beta (Abeta) aggregates. The angiotensin II AT1 receptor is a significant source of brain ROS, and AD patients have an increased brain angiotensin-converting enzyme (ACE) level, which could account for an excessive angiotensin-dependent AT1-induced ROS generation. Therefore, we analyzed the impact of ACE inhibition on signs of neurodegeneration of aged Tg2576 mice as a transgenic animal model of AD. Whole genome microarray gene expression profiling and biochemical analyses demonstrated that the centrally active ACE inhibitor captopril normalized the excessive hippocampal ACE activity of AD mice. Concomitantly, the development of signs of neurodegeneration was retarded by six months of captopril treatment. The neuroprotective profile triggered by captopril was accompanied by reduced amyloidogenic processing of the amyloid precursor protein (APP), and decreased hippocampal ROS, which is known to enhance Abeta generation by increased activation of beta- and gamma-secretases. Taken together, our data present strong evidence that ACE inhibition with a widely used cardiovascular drug could interfere with Abeta-dependent neurodegeneration.

ACE Inhibition with Captopril Retards the Development of Signs of Neurodegeneration in an Animal Model of Alzheimer’s Disease

PubMed Central

AbdAlla, Said; Langer, Andreas; Fu, Xuebin; Quitterer, Ursula

2013-01-01

Increased generation of reactive oxygen species (ROS) is a significant pathological feature in the brains of patients with Alzheimer’s disease (AD). Experimental evidence indicates that inhibition of brain ROS could be beneficial in slowing the neurodegenerative process triggered by amyloid-beta (Abeta) aggregates. The angiotensin II AT1 receptor is a significant source of brain ROS, and AD patients have an increased brain angiotensin-converting enzyme (ACE) level, which could account for an excessive angiotensin-dependent AT1-induced ROS generation. Therefore, we analyzed the impact of ACE inhibition on signs of neurodegeneration of aged Tg2576 mice as a transgenic animal model of AD. Whole genome microarray gene expression profiling and biochemical analyses demonstrated that the centrally active ACE inhibitor captopril normalized the excessive hippocampal ACE activity of AD mice. Concomitantly, the development of signs of neurodegeneration was retarded by six months of captopril treatment. The neuroprotective profile triggered by captopril was accompanied by reduced amyloidogenic processing of the amyloid precursor protein (APP), and decreased hippocampal ROS, which is known to enhance Abeta generation by increased activation of beta- and gamma-secretases. Taken together, our data present strong evidence that ACE inhibition with a widely used cardiovascular drug could interfere with Abeta-dependent neurodegeneration. PMID:23959119

Effects of short-term Western diet on cerebral oxidative stress and diabetes related factors in APP x PS1 knock-in mice.

PubMed

Studzinski, Christa M; Li, Feng; Bruce-Keller, Annadora J; Fernandez-Kim, Sun Ok; Zhang, Le; Weidner, Adam M; Markesbery, William R; Murphy, M Paul; Keller, Jeffrey N

2009-02-01

A chronic high fat Western diet (WD) promotes a variety of morbidity factors although experimental evidence for short-term WD mediating brain dysfunction remains to be elucidated. The amyloid precursor protein and presenilin-1 (APP x PS1) knock-in mouse model has been demonstrated to recapitulate some key features of Alzheimer's disease pathology, including amyloid-beta (Abeta) pathogenesis. In this study, we placed 1-month-old APP x PS1 mice and non-transgenic littermates on a WD for 4 weeks. The WD resulted in a significant elevation in protein oxidation and lipid peroxidation in the brain of APP x PS1 mice relative to non-transgenic littermates, which occurred in the absence of increased Abeta levels. Altered adipokine levels were also observed in APP x PS1 mice placed on a short-term WD, relative to non-transgenic littermates. Taken together, these data indicate that short-term WD is sufficient to selectively promote cerebral oxidative stress and metabolic disturbances in APP x PS1 knock-in mice, with increased oxidative stress preceding alterations in Abeta. These data have important implications for understanding how WD may potentially contribute to brain dysfunction and the development of neurodegenerative disorders such as Alzheimer's disease.

Pediatric respiratory and systemic effects of chronic air pollution exposure: nose, lung, heart, and brain pathology.

PubMed

Calderón-Garcidueñas, Lilian; Franco-Lira, Maricela; Torres-Jardón, Ricardo; Henriquez-Roldán, Carlos; Barragán-Mejía, Gerardo; Valencia-Salazar, Gildardo; González-Maciel, Angelica; Reynoso-Robles, Rafael; Villarreal-Calderón, Rafael; Reed, William

2007-01-01

Exposures to particulate matter and gaseous air pollutants have been associated with respiratory tract inflammation, disruption of the nasal respiratory and olfactory barriers, systemic inflammation, production of mediators of inflammation capable of reaching the brain and systemic circulation of particulate matter. Mexico City (MC) residents are exposed to significant amounts of ozone, particulate matter and associated lipopolysaccharides. MC dogs exhibit brain inflammation and an acceleration of Alzheimer's-like pathology, suggesting that the brain is adversely affected by air pollutants. MC children, adolescents and adults have a significant upregulation of cyclooxygenase-2 (COX2) and interleukin-1beta (IL-1beta) in olfactory bulb and frontal cortex, as well as neuronal and astrocytic accumulation of the 42 amino acid form of beta -amyloid peptide (Abeta 42), including diffuse amyloid plaques in frontal cortex. The pathogenesis of Alzheimer's disease (AD) is characterized by brain inflammation and the accumulation of Abeta 42, which precede the appearance of neuritic plaques and neurofibrillary tangles, the pathological hallmarks of AD. Our findings of nasal barrier disruption, systemic inflammation, and the upregulation of COX2 and IL-1beta expression and Abeta 42 accumulation in brain suggests that sustained exposures to significant concentrations of air pollutants such as particulate matter could be a risk factor for AD and other neurodegenerative diseases.

The structure and function of Alzheimer's gamma secretase enzyme complex.

PubMed

Krishnaswamy, Sudarsan; Verdile, Giuseppe; Groth, David; Kanyenda, Limbikani; Martins, Ralph N

2009-01-01

The production and accumulation of the beta amyloid protein (Abeta) is a key event in the cascade of oxidative and inflammatory processes that characterizes Alzheimer's disease (AD). A multi-subunit enzyme complex, referred to as gamma (gamma) secretase, plays a pivotal role in the generation of Abeta from its parent molecule, the amyloid precursor protein (APP). Four core components (presenilin, nicastrin, aph-1, and pen-2) interact in a high-molecular-weight complex to perform intramembrane proteolysis on a number of membrane-bound proteins, including APP and Notch. Inhibitors and modulators of this enzyme have been assessed for their therapeutic benefit in AD. However, although these agents reduce Abeta levels, the majority have been shown to have severe side effects in pre-clinical animal studies, most likely due to the enzymes role in processing other proteins involved in normal cellular function. Current research is directed at understanding this enzyme and, in particular, at elucidating the roles that each of the core proteins plays in its function. In addition, a number of interacting proteins that are not components of gamma-secretase also appear to play important roles in modulating enzyme activity. This review will discuss the structural and functional complexity of the gamma-secretase enzyme and the effects of inhibiting its activity.

Docosahexaenoic acid provides protection from impairment of learning ability in Alzheimer's disease model rats.

PubMed

Hashimoto, Michio; Hossain, Shahdat; Shimada, Toshio; Sugioka, Kozo; Yamasaki, Hiroshi; Fujii, Yoshimi; Ishibashi, Yutaka; Oka, Jun-Ichiro; Shido, Osamu

2002-06-01

Docosahexaenoic acid (C22:6, n-3), a major n-3 fatty acid of the brain, has been implicated in restoration and enhancement of memory-related functions. Because Alzheimer's disease impairs memory, and infusion of amyloid-beta (Abeta) peptide (1-40) into the rat cerebral ventricle reduces learning ability, we investigated the effect of dietary pre-administration of docosahexaenoic acid on avoidance learning ability in Abeta peptide-produced Alzheimer's disease model rats. After a mini-osmotic pump filled with Abeta peptide or vehicle was implanted in docosahexaenoic acid-fed and control rats, they were subjected to an active avoidance task in a shuttle avoidance system apparatus. Pre-administration of docosahexaenoic acid had a profoundly beneficial effect on the decline in avoidance learning ability in the Alzheimer's disease model rats, associated with an increase in the cortico-hippocampal docosahexaenoic acid/arachidonic acid molar ratio, and a decrease in neuronal apoptotic products. Docosahexaenoic acid pre-administration furthermore increased cortico-hippocampal reduced glutathione levels and glutathione reductase activity, and suppressed the increase in lipid peroxide and reactive oxygen species levels in the cerebral cortex and hippocampus of the Alzheimer's disease model rats, suggesting an increase in antioxidative defence. Docosahexaenoic acid is thus a possible prophylactic means for preventing the learning deficiencies of Alzheimer's disease.

Expression of APP pathway mRNAs and proteins in Alzheimer's disease.

PubMed

Matsui, Toshifumi; Ingelsson, Martin; Fukumoto, Hiroaki; Ramasamy, Karunya; Kowa, Hisatomo; Frosch, Matthew P; Irizarry, Michael C; Hyman, Bradley T

2007-08-03

In both trisomy 21 and rare cases of triplication of amyloid precursor protein (APP) Alzheimer's disease (AD) pathological changes are believed to be secondary to increased expression of APP. We hypothesized that sporadic AD may also be associated with changes in transcription of APP or its metabolic partners. To address this issue, temporal neocortex of 27 AD and 21 non-demented control brains was examined to assess mRNA levels of APP isoforms (total APP, APP containing the Kunitz protease inhibitor domain [APP-KPI] and APP770) and APP metabolic enzymatic partners (the APP cleaving enzymes beta-secretase [BACE] and presenilin-1 [PS-1], and putative clearance molecules, low-density lipoprotein receptor protein [LRP] and apolipoprotein E [apoE]). Furthermore, we evaluated how changes in APP at the mRNA level affect the amount of Tris buffer extractable APP protein and Abeta40 and 42 peptides in AD and control brains. As assessed by quantitative PCR, APP-KPI (p=0.007), APP770 (p=0.004), PS-1 (p=0.004), LRP (p=0.003), apoE (p=0.0002) and GFAP (p<0.0001) mRNA levels all increased in AD, and there was a shift from APP695 (a neuronal isoform) towards KPI containing isoforms that are present in glia as well. APP-KPI mRNA levels correlated with soluble APPalpha-KPI protein (sAPPalpha-KPI) levels measured by ELISA (tau=0.33, p=0.015 by Kendall's rank correlation); in turn, soluble APPalpha-KPI protein levels positively correlated with Tris-extractable, soluble Abeta40 (p=0.046) and 42 levels (p=0.007). The ratio of soluble APPalpha-KPI protein levels to total APP protein increased in AD, and also correlated with GFAP protein levels in AD. These results suggest that altered transcription of APP in AD is proportionately associated with Abeta peptide, may occur in the context of gliosis, and may contribute to Abeta deposition in sporadic AD.

Pleomorphic copper coordination by Alzheimer's disease amyloid-beta peptide.

PubMed

Drew, Simon C; Noble, Christopher J; Masters, Colin L; Hanson, Graeme R; Barnham, Kevin J

2009-01-28

Numerous conflicting models have been proposed regarding the nature of the Cu(2+) coordination environment of the amyloid beta (Abeta) peptide, the causative agent of Alzheimer's disease. This study used multifrequency CW-EPR spectroscopy to directly resolve the superhyperfine interactions between Cu(2+) and the ligand nuclei of Abeta, thereby avoiding ambiguities associated with introducing point mutations. Using a library of Abeta16 analogues with site-specific (15)N-labeling at Asp1, His6, His13, and His14, numerical simulations of the superhyperfine resonances delineated two independent 3N1O Cu(2+) coordination modes, {N(a)(D1), O, N(epsilon)(H6), N(epsilon)(H13)} (component Ia) and {N(a)(D1), O, N(epsilon)(H6), N(epsilon)(H14)} (component Ib), between pH 6-7. A third coordination mode (component II) was identified at pH 8.0, and simulation of the superhyperfine resonances indicated a 3N1O coordination sphere involving nitrogen ligation by His6, His13, and His14. No differences were observed upon (17)O-labeling of the phenolic oxygen of Tyr10, confirming it is not a key oxygen ligand in the physiological pH range. Hyperfine sublevel correlation (HYSCORE) spectroscopy, in conjunction with site-specific (15)N-labeling, provided additional support for the common role of His6 in components Ia and Ib, and for the assignment of a {O, N(epsilon)(H6), N(epsilon)(H13), N(epsilon)(H14)} coordination sphere to component II. HYSCORE studies of a peptide analogue with selective (13)C-labeling of Asp1 revealed (13)C cross-peaks characteristic of equatorial coordination by the carboxylate oxygen of Asp1 in component Ia/b coordination. The direct resolution of Cu(2+) ligand interactions, together with the key finding that component I is composed of two distinct coordination modes, provides valuable insight into a range of conflicting ligand assignments and highlights the complexity of Cu(2+)/Abeta interactions.

Rhynchophylline Protects Against the Amyloid β-Induced Increase of Spontaneous Discharges in the Hippocampal CA1 Region of Rats.

PubMed

Shao, Hui; Mi, Ze; Ji, Wei-gang; Zhang, Cheng-huan; Zhang, Teng; Ren, Shuan-cheng; Zhu, Zhi-ru

2015-11-01

Accumulated soluble amyloid β (Aβ)-induced aberrant neuronal network activity has been recognized as a key causative factor leading to cognitive deficits which are the most outstanding characteristic of Alzheimer's disease (AD). As an important structure associated with learning and memory, the hippocampus is one of the brain regions that are impaired very early in AD, and the hippocampal CA1 region is selectively vulnerable to soluble Aβ oligomers. Our recent study showed that soluble Aβ1-42 oligomers induced hyperactivity and perturbed the firing patterns in hippocampal neurons. Rhynchophylline (RIN) is an important active tetracyclic oxindole alkaloid isolated from Uncaria rhynchophylla which is a traditional Chinese medicine and often used to treat central nervous system illnesses such as hypertension, convulsions, tremor, stroke etc. Previous evidence showed that RIN possessed neuroprotective effects of improving the cognitive function of mice with Alzheimer-like symptoms. In the present study, we aimed to investigate the protective effect of RIN against soluble Aβ1-42 oligomers-induced hippocampal hyperactivity. The results showed that (1) the mean frequency of spontaneous discharge was increased by the local application of 3 μM soluble Aβ1-42 oligomers; (2) 30 μM RIN did not exert any obvious effects on basal physiological discharges; and (3) treatment with RIN effectively inhibited the soluble Aβ1-42 oligomers-induced enhancement of spontaneous discharge, in a concentration-dependent manner with an IC50 = 9.0 μM. These in vivo electrophysiological results indicate that RIN can remold the spontaneous discharges disturbed by Aβ and counteract the deleterious effect of Aβ1-42 on neural circuit. The experimental findings provide further evidence to affirm the potential of RIN as a worthy candidate for further development into a therapeutic agent for AD.

Ultrafast Photoinduced Electron Transfer in a π-Conjugated Oligomer/Porphyrin Complex.

PubMed

Aly, Shawkat M; Goswami, Subhadip; Alsulami, Qana A; Schanze, Kirk S; Mohammed, Omar F

2014-10-02

Controlling charge transfer (CT), charge separation (CS), and charge recombination (CR) at the donor-acceptor interface is extremely important to optimize the conversion efficiency in solar cell devices. In general, ultrafast CT and slow CR are desirable for optimal device performance. In this Letter, the ultrafast excited-state CT between platinum oligomer (DPP-Pt(acac)) as a new electron donor and porphyrin as an electron acceptor is monitored for the first time using femtosecond (fs) transient absorption (TA) spectroscopy with broad-band capability and 120 fs temporal resolution. Turning the CT on/off has been shown to be possible either by switching from an organometallic oligomer to a metal-free oligomer or by controlling the charge density on the nitrogen atom of the porphyrin meso unit. Our time-resolved data show that the CT and CS between DPP-Pt(acac) and cationic porphyrin are ultrafast (approximately 1.5 ps), and the CR is slow (ns time scale), as inferred from the formation and the decay of the cationic and anionic species. We also found that the metallic center in the DPP-Pt(acac) oligomer and the positive charge on the porphyrin are the keys to switching on/off the ultrafast CT process.

Hydrolysis kinetics of secoisolariciresinol diglucoside oligomers from flaxseed.

PubMed

Yuan, Jian-Ping; Li, Xin; Xu, Shi-Ping; Wang, Jiang-Hai; Liu, Xin

2008-11-12

Flaxseed is the richest dietary source of the lignan secoisolariciresinol diglucoside (SDG) and contains the largest amount of SDG oligomers, which are often hydrolyzed to break the ester linkages for the release of SDG and the glycosidic bonds for the release of secoisolariciresinol (SECO). The alkaline hydrolysis reaction kinetics of SDG oligomers from flaxseed and the acid hydrolysis process of SDG and other glucosides were investigated. For the kinetic modeling, a pseudo-first-order reaction was assumed. The results showed that the alkaline hydrolysis of SDG oligomers followed first-order reaction kinetics under mild alkaline hydrolytic conditions and that the concentration of sodium hydroxide had a strong influence on the activation energy of the alkaline hydrolysis of SDG oligomers. The results also indicated that the main acid hydrolysates of SDG included secoisolariciresinol monoglucoside (SMG), SECO, and anhydrosecoisolariciresinol (anhydro-SECO) and that the extent and the main hydrolysates of the acid hydrolysis reaction depended on the acid concentration, hydrolysis temperature, and time. In addition, the production and change of p-coumaric acid glucoside, ferulic acid glucoside and their methyl esters and p-coumaric acid, ferulic acid, and their methyl esters during the process of hydrolysis was also investigated.

Functional Diversity of Isoamylase Oligomers: The ISA1 Homo-Oligomer Is Essential for Amylopectin Biosynthesis in Rice Endosperm1[W][OA

PubMed Central

Utsumi, Yoshinori; Utsumi, Chikako; Sawada, Takayuki; Fujita, Naoko; Nakamura, Yasunori

2011-01-01

Rice (Oryza sativa) endosperm has two isoamylase (ISA) oligomers, ISA1 homo-oligomer and ISA1-ISA2 hetero-oligomer. To examine their contribution to starch synthesis, expression of the ISA1 or ISA2 gene was differently regulated in various transgenic plants. Although suppression of ISA2 gene expression caused the endosperm to have only the homo-oligomer, no significant effects were detected on the starch phenotypes. In contrast, ISA2 overexpression led to endosperm having only the hetero-oligomer, and starch synthesis in the endosperm was drastically impaired, both quantitatively and qualitatively, because the starch was devoid of typical starch features, such as thermal and x-ray diffraction properties, and water-soluble highly branched maltodextrins were accumulated. In the ISA2 overexpressed line, about 60% to 70% of the ISA1-ISA2 hetero-oligomer was bound to starch, while the ISA homo- and hetero-oligomers from the wild type were mostly present in the soluble form at the early milking stage of the endosperm. Detailed analysis of the relative amounts of homo- and hetero-oligomers in various lines also led us to the conclusion that the ISA1 homo-oligomer is essential, but not the ISA1-ISA2 oligomer, for starch production in rice endosperm. The relative amounts of ISA1 and ISA2 proteins were shown to determine the ratio of both oligomers and the stoichiometry of both ISAs in the hetero-oligomer. It was noted when compared with the homo-oligomer that all the hetero-oligomers from rice endosperm and leaf and potato (Solanum tuberosum) tuber were much more stable at 40°C. This study provides substantial data on the structural and functional diversity of ISA oligomers between plant tissues and species. PMID:21436381

Separation of Uncharged Oligodeoxynucleotide Analogs by Anion-Exchange Chromatography at High pH

NASA Technical Reports Server (NTRS)

Schmidt, Jurgen G.; Nielsen, Peter E.; Orgel, Leslie

1996-01-01

Ion-exchange chromatography is a well-established method for the analysis and purification of phosphodiester-linked oligonucleotides. If elution is carried out under alkaline conditions, the secondary structure of G- and C-rich oligomers is disrupted. Furthermore, elution times become more sensitive to the G and T content of the oligomer, because G and T are deprotonated at pH 10. In recent work on peptide-nucleic acids (PNAs) we noted that mixtures of PNA oligomers G(sub 4), G(Sub 6), G(sub 8), and G(sub 10) are readily separated by elution at pH 12 on an RPC-5 column. Here we show that this separation method is more generally applicable.

Induction of Covalently Crosslinked p62 Oligomers with Reduced Binding to Polyubiquitinated Proteins by the Autophagy Inhibitor Verteporfin.

PubMed

Donohue, Elizabeth; Balgi, Aruna D; Komatsu, Masaaki; Roberge, Michel

2014-01-01

Autophagy is a cellular catabolic process responsible for the degradation of cytoplasmic constituents, including organelles and long-lived proteins, that helps maintain cellular homeostasis and protect against various cellular stresses. Verteporfin is a benzoporphyrin derivative used clinically in photodynamic therapy to treat macular degeneration. Verteporfin was recently found to inhibit autophagosome formation by an unknown mechanism that does not require exposure to light. We report that verteporfin directly targets and modifies p62, a scaffold and adaptor protein that binds both polyubiquitinated proteins destined for degradation and LC3 on autophagosomal membranes. Western blotting experiments revealed that exposure of cells or purified p62 to verteporfin causes the formation of covalently crosslinked p62 oligomers by a mechanism involving low-level singlet oxygen production. Rose bengal, a singlet oxygen producer structurally unrelated to verteporfin, also produced crosslinked p62 oligomers and inhibited autophagosome formation. Co-immunoprecipitation experiments demonstrated that crosslinked p62 oligomers retain their ability to bind to LC3 but show defective binding to polyubiquitinated proteins. Mutations in the p62 PB1 domain that abolish self-oligomerization also abolished crosslinked oligomer formation. Interestingly, small amounts of crosslinked p62 oligomers were detected in untreated cells, and other groups noted the accumulation of p62 forms with reduced SDS-PAGE mobility in cellular and animal models of oxidative stress and aging. These data indicate that p62 is particularly susceptible to oxidative crosslinking and lead us to propose a model whereby oxidized crosslinked p62 oligomers generated rapidly by drugs like verteporfin or over time during the aging process interfere with autophagy.

Induction of Covalently Crosslinked p62 Oligomers with Reduced Binding to Polyubiquitinated Proteins by the Autophagy Inhibitor Verteporfin

PubMed Central

Donohue, Elizabeth; Balgi, Aruna D.; Komatsu, Masaaki; Roberge, Michel

2014-01-01

Autophagy is a cellular catabolic process responsible for the degradation of cytoplasmic constituents, including organelles and long-lived proteins, that helps maintain cellular homeostasis and protect against various cellular stresses. Verteporfin is a benzoporphyrin derivative used clinically in photodynamic therapy to treat macular degeneration. Verteporfin was recently found to inhibit autophagosome formation by an unknown mechanism that does not require exposure to light. We report that verteporfin directly targets and modifies p62, a scaffold and adaptor protein that binds both polyubiquitinated proteins destined for degradation and LC3 on autophagosomal membranes. Western blotting experiments revealed that exposure of cells or purified p62 to verteporfin causes the formation of covalently crosslinked p62 oligomers by a mechanism involving low-level singlet oxygen production. Rose bengal, a singlet oxygen producer structurally unrelated to verteporfin, also produced crosslinked p62 oligomers and inhibited autophagosome formation. Co-immunoprecipitation experiments demonstrated that crosslinked p62 oligomers retain their ability to bind to LC3 but show defective binding to polyubiquitinated proteins. Mutations in the p62 PB1 domain that abolish self-oligomerization also abolished crosslinked oligomer formation. Interestingly, small amounts of crosslinked p62 oligomers were detected in untreated cells, and other groups noted the accumulation of p62 forms with reduced SDS-PAGE mobility in cellular and animal models of oxidative stress and aging. These data indicate that p62 is particularly susceptible to oxidative crosslinking and lead us to propose a model whereby oxidized crosslinked p62 oligomers generated rapidly by drugs like verteporfin or over time during the aging process interfere with autophagy. PMID:25494214

Somatostatin receptor subtype-4 agonist NNC 26-9100 mitigates the effect of soluble Aβ(42) oligomers via a metalloproteinase-dependent mechanism.

PubMed

Sandoval, Karin E; Farr, Susan A; Banks, William A; Crider, Albert M; Morley, John E; Witt, Ken A

2013-07-03

Soluble amyloid-β peptide (Aβ) oligomers have been hypothesized to be primary mediators of Alzheimer's disease progression. In this regard, reduction of soluble Aβ-oligomers levels within the brain may provide a viable means in which to treat the disease. Somatostatin receptor subtype-4 (SSTR4) agonists have been proposed to reduce Aβ levels in the brain via enhancement of enzymatic degradation. Herein we evaluated the effect of selective SSTR4 agonist NNC 26-9100 on the changes in learning and soluble Aβ42 oligomer brain content with and without co-administration of the M13-metalloproteinase family enzyme-inhibitor phosphoramidon, using the senescence-accelerated mouse prone-8 (SAMP8) model. NNC 26-9100 treatment (0.2 µg i.c.v. in 2 µL) improved learning, which was blocked by phosphoramidon (1 and 10mM, respectively). NNC 26-9100 decreased total soluble Aβ42, an effect which was blocked by phosphoramidon (10mM). Extracellular, intracellular, and membrane fractions were then isolated from cortical tissue and assessed for soluble oligomer alterations. NNC 26-9100 decreased the Aβ42 trimeric (12 kDa) form within the extracellular and intracellular fractions, and produced a band-split effect of the Aβ42 hexameric (25 kDa) form within the extracellular fraction. These effects were also blocked by phosphoramdon (1 and 10mM, respectively). Subsequent evaluation of NNC 26-9100 in APPswe Tg2576 transgenic mice showed a similar learning improvement and corresponding reduction in soluble Aβ42 oligomers within extracellular, intracellular, and membrane fractions. These data support the hypothesis that NNC 26-9100 reduces soluble Aβ42 oligomers and enhances learning through a phosphoramidon-sensitive metalloproteinase-dependent mechanism. Copyright © 2013 Elsevier B.V. All rights reserved.

Determinants of intention to change health-related behavior and actual change in patients with TIA or minor ischemic stroke.

PubMed

Brouwer-Goossensen, Dorien; Genugten, Lenneke van; Lingsma, Hester; Dippel, Diederik; Koudstaal, Peter; Hertog, Heleen den

2016-04-01

To assess determinants of intention to change health-related behavior and actual change in patients with TIA or ischemic stroke. In this prospective cohort study, 100 patients with TIA or minor ischemic stroke completed questionnaires on behavioral intention and sociocognitive factors including perception of severity, susceptibility, fear, response-efficacy and self-efficacy at baseline. Questionnaires on physical activity, diet and smoking were completed at baseline and at 3 months. Associations between sociocognitive factors and behavioral intention and actual change were studied with multivariable linear and logistic regression. Self-efficacy, response efficacy, and fear were independently associated with behavioral intention, with self-efficacy as the strongest determinant of intention to increase physical activity (aBeta 0.40; 95% CI 0.12-0.71), adapt a healthy diet (aBeta 0.49; 95% CI 0.23-0.75), and quit smoking (aBeta 0.51; 95% CI 0.13-0.88). Intention to change tended to be associated with actual health-related behavior change. Self-efficacy, fear, and response-efficacy were determinants of intention to change health-related behavior after TIA or ischemic stroke. These determinants of intention to change health-related behavior after TIA or ischemic stroke should be taken into account in the development of future interventions promoting health-related behavior change in these group of patients. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Neprilysin participates in skeletal muscle regeneration and is accumulated in abnormal muscle fibres of inclusion body myositis.

PubMed

Broccolini, Aldobrando; Gidaro, Teresa; Morosetti, Roberta; Gliubizzi, Carla; Servidei, Tiziana; Pescatori, Mario; Tonali, Pietro A; Ricci, Enzo; Mirabella, Massimiliano

2006-02-01

Neprilysin (NEP, EP24.11), a metallopeptidase originally shown to modulate signalling events by degrading small regulatory peptides, is also an amyloid-beta- (Abeta) degrading enzyme. We investigated a possible role of NEP in inclusion body myositis (IBM) and other acquired and hereditary muscle disorders and found that in all myopathies NEP expression was directly associated with the degree of muscle fibre regeneration. In IBM muscle, NEP protein was also strongly accumulated in Abeta-bearing abnormal fibres. In vitro, during the experimental differentiation of myoblasts, NEP protein expression was regulated at the post-transcriptional level with a rapid increase in the early stage of myoblast differentiation followed by a gradual reduction thereafter, coincident with the progression of the myogenic programme. Treatment of differentiating muscle cells with the NEP inhibitor dl-3-mercapto-2-benzylpropanoylglycine resulted in impaired differentiation that was mainly associated with an abnormal regulation of Akt activation. Therefore, NEP may play an important role during muscle cell differentiation, possibly through the regulation, either directly or indirectly, of the insulin-like growth factor I-driven myogenic programme. In IBM muscle increased NEP may be instrumental in (i) reducing the Abeta accumulation in vulnerable fibres and (ii) promoting a repair/regenerative attempt of muscle fibres possibly through the modulation of insulin-like growth factor I-dependent pathways.

Backbone conformation affects duplex initiation and duplex propagation in hybridisation of synthetic H-bonding oligomers.

PubMed

Iadevaia, Giulia; Núñez-Villanueva, Diego; Stross, Alexander E; Hunter, Christopher A

2018-06-06

Synthetic oligomers equipped with complementary H-bond donor and acceptor side chains form multiply H-bonded duplexes in organic solvents. Comparison of the duplex forming properties of four families of oligomers with different backbones shows that formation of an extended duplex with three or four inter-strand H-bonds is more challenging than formation of complexes that make only two H-bonds. The stabilities of 1 : 1 complexes formed between length complementary homo-oligomers equipped with either phosphine oxide or phenol recognition modules were measured in toluene. When the backbone is very flexible (pentane-1,5-diyl thioether), the stability increases uniformly by an order of magnitude for each additional base-pair added to the duplex: the effective molarities for formation of the first intramolecular H-bond (duplex initiation) and subsequent intramolecular H-bonds (duplex propagation) are similar. This flexible system is compared with three more rigid backbones that are isomeric combinations of an aromatic ring and methylene groups. One of the rigid systems behaves in exactly the same way as the flexible backbone, but the other two do not. For these systems, the effective molarity for formation of the first intramolecular H-bond is the same as that found for the other two backbones, but additional H-bonds are not formed between the longer oligomers. The effective molarities are too low for duplex propagation in these systems, because the oligomer backbones cannot adopt conformations compatible with formation of an extended duplex.

STEM/EELS Imaging of Magnetic Hybridization in Symmetric and Symmetry-Broken Plasmon Oligomer Dimers and All-Magnetic Fano Interference

DOE PAGES

Cherqui, Charles; Wu, Yueying; Li, Guoliang; ...

2016-09-27

Negative-index metamaterials composed of magnetic plasmon oligomers are actively being investigated for their potential role in optical cloaking, superlensing, and nanolithography applications. A significant improvement to their practicality lies in the ability to function at multiple distinct wavelengths in the visible part of spectrum. Here we utilize the nanometer spatial-resolving power of electron energy-loss spectroscopy to conclusively demonstrate hybridization of magnetic plasmons in oligomer dimers that can achieve this goal. We also show that breaking the dimer’s symmetry can induce all-magnetic Fano interferences based solely on the interplay of bright and dark magnetic modes, allowing us to further tailor themore » system’s optical responses. These features are engineered through the design of the oligomer’s underlying nanoparticle elements as elongated Ag nanodisks with spectrally isolated long-axis plasmon resonances. The resulting magnetic plasmon oligomers and their hybridized assemblies establish a new design paradigm for optical metamaterials with rich functionality.« less

High-molecular weight Aβ oligomers and protofibrils are the predominant Aβ species in the native soluble protein fraction of the AD brain.

PubMed

Upadhaya, Ajeet Rijal; Lungrin, Irina; Yamaguchi, Haruyasu; Fändrich, Marcus; Thal, Dietmar Rudolf

2012-02-01

Alzheimer's disease (AD) is characterized by the aggregation and deposition of amyloid β protein (Aβ) in the brain. Soluble Aβ oligomers are thought to be toxic. To investigate the predominant species of Aβ protein that may play a role in AD pathogenesis, we performed biochemical analysis of AD and control brains. Sucrose buffer-soluble brain lysates were characterized in native form using blue native (BN)-PAGE and also in denatured form using SDS-PAGE followed by Western blot analysis. BN-PAGE analysis revealed a high-molecular weight smear (>1000 kD) of Aβ(42) -positive material in the AD brain, whereas low-molecular weight and monomeric Aβ species were not detected. SDS-PAGE analysis, on the other hand, allowed the detection of prominent Aβ monomer and dimer bands in AD cases but not in controls. Immunoelectron microscopy of immunoprecipitated oligomers and protofibrils/fibrils showed spherical and protofibrillar Aβ-positive material, thereby confirming the presence of high-molecular weight Aβ (hiMWAβ) aggregates in the AD brain. In vitro analysis of synthetic Aβ(40) - and Aβ(42) preparations revealed Aβ fibrils, protofibrils, and hiMWAβ oligomers that were detectable at the electron microscopic level and after BN-PAGE. Further, BN-PAGE analysis exhibited a monomer band and less prominent low-molecular weight Aβ (loMWAβ) oligomers. In contrast, SDS-PAGE showed large amounts of loMWAβ but no hiMWAβ(40) and strikingly reduced levels of hiMWAβ(42) . These results indicate that hiMWAβ aggregates, particularly Aβ(42) species, are most prevalent in the soluble fraction of the AD brain. Thus, soluble hiMWAβ aggregates may play an important role in the pathogenesis of AD either independently or as a reservoir for release of loMWAβ oligomers. © 2011 The Authors Journal of Cellular and Molecular Medicine © 2011 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.

High-molecular weight Aβ oligomers and protofibrils are the predominant Aβ species in the native soluble protein fraction of the AD brain

PubMed Central

Upadhaya, Ajeet Rijal; Lungrin, Irina; Yamaguchi, Haruyasu; Fändrich, Marcus; Thal, Dietmar Rudolf

2012-01-01

Abstract Alzheimer’s disease (AD) is characterized by the aggregation and deposition of amyloid β protein (Aβ) in the brain. Soluble Aβ oligomers are thought to be toxic. To investigate the predominant species of Aβ protein that may play a role in AD pathogenesis, we performed biochemical analysis of AD and control brains. Sucrose buffer-soluble brain lysates were characterized in native form using blue native (BN)-PAGE and also in denatured form using SDS-PAGE followed by Western blot analysis. BN-PAGE analysis revealed a high-molecular weight smear (>1000 kD) of Aβ42-positive material in the AD brain, whereas low-molecular weight and monomeric Aβ species were not detected. SDS-PAGE analysis, on the other hand, allowed the detection of prominent Aβ monomer and dimer bands in AD cases but not in controls. Immunoelectron microscopy of immunoprecipitated oligomers and protofibrils/fibrils showed spherical and protofibrillar Aβ-positive material, thereby confirming the presence of high-molecular weight Aβ (hiMWAβ) aggregates in the AD brain. In vitro analysis of synthetic Aβ40- and Aβ42 preparations revealed Aβ fibrils, protofibrils, and hiMWAβ oligomers that were detectable at the electron microscopic level and after BN-PAGE. Further, BN-PAGE analysis exhibited a monomer band and less prominent low-molecular weight Aβ (loMWAβ) oligomers. In contrast, SDS-PAGE showed large amounts of loMWAβ but no hiMWAβ40 and strikingly reduced levels of hiMWAβ42. These results indicate that hiMWAβ aggregates, particularly Aβ42 species, are most prevalent in the soluble fraction of the AD brain. Thus, soluble hiMWAβ aggregates may play an important role in the pathogenesis of AD either independently or as a reservoir for release of loMWAβ oligomers. PMID:21418518

The Impact of HA Oligomer Content on Physical, Mechanical, and Biologic Properties of Divinyl Sulfone-Crosslinked HA Hydrogels

PubMed Central

Ibrahim, Samir; Kang, Qian K; Ramamurthi, Anand

2009-01-01

In recent studies, we showed that exogenous hyaluronic acid oligomers (HA-o) stimulate functional endothelialization, though native long-chain HA is more bioinert and possibly more biocompatible. Thus, in this study, hydrogels containing high molecular weight (HMW) HA (1×106 Da) and HA oligomer mixtures (HA-o: 0.75–10 kDa) were created by crosslinking with divinyl sulfone (DVS). The incorporation of HA oligomers was found to compromise the physical and mechanical properties of the gels (rheology, apparent crosslinking density, swelling ratio, degradation) and to very mildly enhance inflammatory cell recruitment in vivo; increasing the DVS crosslinker content within the gels in general, had the opposite effect, though the relatively high concentration of DVS within these gels (necessary to create a solid gel) also stimulated a mild sub-cutaneous inflammatory response in vivo and VCAM-1 expression by ECs cultured atop; ICAM-expression levels remained very low irrespective extent of DVS crosslinking or HA-o content. The greatest EC attachment and proliferation (MTT assay) was observed on gels that contained the highest amount of HA-o. The study shows that the beneficial EC response to HA oligomers and biocompatibility of HA is mostly unaltered by their chemical derivatization and crosslinking into a hydrogel. However, the study also demonstrates that the relatively high concentrations of DVS, necessary to create solid gels, compromises their biocompatibility. Moreover, the poor mechanics of even these heavily crosslinked gels, in the context of vascular implantation, necessitates the investigation of other, more appropriate crosslinking agents. Alternately, the outcomes of this study may be used to guide an approach based on chemical immobilization and controlled surface-presentation of both bioactive HA oligomers and more biocompatible HMW HAon synthetic or tissue engineered grafts already in use, without the use of a crosslinker, so that improved, predictable, and functional endothelialization can be achieved, and the need to create a mechanically compliant biomaterial for standalone use, circumvented. PMID:20186732

Single-molecule studies of oligomer extraction and uptake of dyes in poly(dimethylsiloxane) films.

PubMed

Lange, Jeffrey J; Collinson, Maryanne M; Culbertson, Christopher T; Higgins, Daniel A

2009-12-15

Single-molecule microscopic methods were used to probe the uptake, mobility, and entrapment of dye molecules in cured poly(dimethylsiloxane) (PDMS) films as a function of oligomer extraction. The results are relevant to the use of PDMS in microfluidic separations, pervaporation, solid-phase microextraction, and nanofiltration. PDMS films were prepared by spin-casting dilute solutions of Sylgard 184 onto glass coverslips, yielding approximately 1.4 microm thick films after curing. Residual oligomers were subsequently extracted from the films by "spin extraction". In this procedure, 200 microL aliquots of isopropyl alcohol were repeatedly dropped onto the film surface and spun off at 2000 rpm. Samples extracted 5, 10, 20, and 40 times were investigated. Dye molecules were loaded into these films by spin-casting nanomolar dye solutions onto the films. Both neutral perylene diimide (N,N'-bis(butoxypropyl)perylene-3,4,9,10-tetracarboxylic diimide) and cationic rhodamine 6G (R6G) dyes were employed. The films were imaged by confocal fluorescence microscopy. The images obtained depict nonzero populations of fixed and mobile molecules in all films. Cross-correlation methods were used to quantitatively determine the population of fixed molecules in a given region, while a Bayesian burst analysis was used to obtain the total population of molecules. The results show that the total amount of dye loaded increases with increased oligomer extraction, while the relative populations of fixed and mobile molecules decrease and increase, respectively. Bulk R6G data also show greater dye loading with increased oligomer extraction.

N-Substituted carbazolyloxyacetic acids modulate Alzheimer associated gamma-secretase.

PubMed

Narlawar, Rajeshwar; Pérez Revuelta, Blanca I; Baumann, Karlheinz; Schubenel, Robert; Haass, Christian; Steiner, Harald; Schmidt, Boris

2007-01-01

N-Sulfonylated and N-alkylated carbazolyloxyacetic acids were investigated for the inhibition and modulation of the Alzheimer's disease associated gamma-secretase. The introduction of a lipophilic substituent, which may vary from arylsulfone to alkyl, turned 2-carbazolyloxyacetic acids into potent gamma-secretase modulators. This resulted in the selective reduction of Abeta(42) and an increase of the less aggregatory Abeta(38) fragment by several compounds (e.g., 7d and 8c). Introduction of an electron donating group at position 6 and 8 of N-substituted carbazolyloxyacetic acids either decreased the activity or inversed modulation. The most active compounds displayed activity on amyloid precursor protein (APP) overexpressing cell lines in the low micromolar range and little or no effect on the gamma-secretase cleavage at the epsilon-site.

Dyslipidemia and dementia: current epidemiology, genetic evidence and mechanisms behind the associations

PubMed Central

Reitz, Christiane

2013-01-01

The role of cholesterol in the etiology of Alzheimer’s disease (AD) is still controversial. Some studies aiming to explore the association between lipids and/or lipid lowering treatment and AD indicate a harmful effect of dyslipidemia and a beneficial effect of statin therapy on AD risk. The findings are supported by genetic linkage and association studies that have clearly identified several genes involved in cholesterol metabolism or transport as AD susceptibility genes, including Apolipoprotein E (APOE), Apolipoprotein J (APOJ, CLU) and the sortilin-related receptor (SORL1). Functional cell biology studies support a critical involvement of lipid raft cholesterol in the modulation of AbetaPP processing by β- and γ-secretase resulting in altered Aβ production. Contradictory evidence comes from epidemiological studies showing no or controversial association between dyslipidemia and AD risk, cell biology studies suggesting that there is little exchange between circulating and brain cholesterol, that increased membrane cholesterol is protective by inhibiting loss of membrane integrity through amyloid cytotoxicity, and that cellular cholesterol inhibits co-localization of BACE1 and AbetaPP in non-raft membrane domains and thereby increasing generation of plasmin, an Aβ-degrading enzyme. The aim of this review is to summarize the findings of epidemiologic and cell biologic studies aiming to elucidate the role of cholesterol in AD etiology. PMID:21965313

Consensus report of the Working Group on: "Molecular and Biochemical Markers of Alzheimer's Disease". The Ronald and Nancy Reagan Research Institute of the Alzheimer's Association and the National Institute on Aging Working Group.

PubMed

1998-01-01

The ideal biomarker for Alzheimer's disease (AD) should detect a fundamental feature of neuropathology and be validated in neuropathologically-confirmed cases; it should have a sensitivity >80% for detecting AD and a specificity of >80% for distinguishing other dementias; it should be reliable, reproducible, non-invasive, simple to perform, and inexpensive. Recommended steps to establish a biomarker include confirmation by at least two independent studies conducted by qualified investigators with the results published in peer-reviewed journals. Our review of current candidate markers indicates that for suspected early-onset familial AD, it is appropriate to search for mutations in the presenilin 1, presenilin 2, and amyloid precursor protein genes. Individuals with these mutations typically have increased levels of the amyloid Abeta42 peptide in plasma and decreased levels of APPs in cerebrospinal fluid. In late-onset and sporadic AD, these measures are not useful, but detecting an apolipoprotein E e4 allele can add confidence to the clinical diagnosis. Among the other proposed molecular and biochemical markers for sporadic AD, cerebrospinal fluid assays showing low levels of Abeta42 and high levels of tau come closest to fulfilling criteria for a useful biomarker.

Direct Correlation Between Ligand-Induced α-Synuclein Oligomers and Amyloid-like Fibril Growth

PubMed Central

Nors Perdersen, Martin; Foderà, Vito; Horvath, Istvan; van Maarschalkerweerd, Andreas; Nørgaard Toft, Katrine; Weise, Christoph; Almqvist, Fredrik; Wolf-Watz, Magnus; Wittung-Stafshede, Pernilla; Vestergaard, Bente

2015-01-01

Aggregation of proteins into amyloid deposits is the hallmark of several neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. The suggestion that intermediate oligomeric species may be cytotoxic has led to intensified investigations of pre-fibrillar oligomers, which are complicated by their transient nature and low population. Here we investigate alpha-synuclein oligomers, enriched by a 2-pyridone molecule (FN075), and the conversion of oligomers into fibrils. As probed by leakage assays, the FN075 induced oligomers potently disrupt vesicles in vitro, suggesting a potential link to disease related degenerative activity. Fibrils formed in the presence and absence of FN075 are indistinguishable on microscopic and macroscopic levels. Using small angle X-ray scattering, we reveal that FN075 induced oligomers are similar, but not identical, to oligomers previously observed during alpha-synuclein fibrillation. Since the levels of FN075 induced oligomers correlate with the amounts of fibrils among different FN075:protein ratios, the oligomers appear to be on-pathway and modeling supports an ‘oligomer stacking model’ for alpha-synuclein fibril elongation. PMID:26020724

Amyloid β oligomers induce interleukin-1β production in primary microglia in a cathepsin B- and reactive oxygen species-dependent manner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taneo, Jun; Adachi, Takumi; Yoshida, Aiko

2015-03-13

Amyloid β (Aβ) peptide, a causative agent of Alzheimer's disease, forms two types of aggregates: oligomers and fibrils. These aggregates induce inflammatory responses, such as interleukin-1β (IL-1β) production by microglia, which are macrophage-like cells located in the brain. In this study, we examined the effect of the two forms of Aβ aggregates on IL-1β production in mouse primary microglia. We prepared Aβ oligomer and fibril from Aβ (1–42) peptide in vitro. We analyzed the characteristics of these oligomers and fibrils by electrophoresis and atomic force microscopy. Interestingly, Aβ oligomers but not Aβ monomers or fibrils induced robust IL-1β production in themore » presence of lipopolysaccharide. Moreover, Aβ oligomers induced endo/phagolysosome rupture, which released cathepsin B into the cytoplasm. Aβ oligomer-induced IL-1β production was inhibited not only by the cathepsin B inhibitor CA-074-Me but also by the reactive oxygen species (ROS) inhibitor N-acetylcysteine. Random chemical crosslinking abolished the ability of the oligomers to induce IL-1β. Thus, multimerization and fibrillization causes Aβ oligomers to lose the ability to induce IL-1β. These results indicate that Aβ oligomers, but not fibrils, induce IL-1β production in primary microglia in a cathepsin B- and ROS-dependent manner. - Highlights: • We prepared amyloid β (Aβ) fibrils with minimum contamination of Aβ oligomers. • Primary microglia (MG) produced IL-1β in response to Aβ oligomers, but not fibrils. • Only Aβ oligomers induced leakage of cathepsin B from endo/phagolysosomes. • IL-1β production in response to Aβ oligomers depended on both cathepsin B and ROS. • Crosslinking reduced the ability of the Aβ oligomers to induce IL-1β from MG.« less

Amyloid-like aggregates formation by bovine apo-carbonic anhydrase in various alcohols: A comparative study.

PubMed

Es-Haghi, Ali; Ebrahim-Habibi, Azadeh; Sabbaghian, Marjan; Nemat-Gorgani, Mohsen

2016-11-01

Peptides and proteins convert from their native states to amyloid fibrillar aggregates in a number of pathological conditions. Characterizing these species could provide useful information on their pathogenicity and the key factors involved in their generation. In this study, we have observed the ability of the model protein apo-bovine carbonic anhydrase (apo-BCA) to form amyloid-like aggregates in the presence of halogenated and non-halogenated alcohols. Far-UV circular dichroism, ThT fluorescence, atomic force microscopy and dynamic light scattering were used to characterize these structures. The concentration required for effective protein aggregation varied between the solvents, with non-halogenated alcohols acting in a wider range. These aggregates show amyloid-like structures as determined by specific techniques used for characterizing amyloid structures. Oligomers were obtained with various size distributions, but fibrillar structures were not observed. Use of halogenated alcohols resulted into smaller hydrodynamic radii, and most stable oligomers were formed in hexafluoropropan-2-ol (HFIP). At optimal concentrations used to generate these structures, the non-halogenated alcohols showed higher hydrophobicity, which may be related to the lower stability of the generated oligomers. These oligomers have the potential to be used as models in the search for effective treatments in proteinopathies. Copyright © 2016 Elsevier B.V. All rights reserved.

Phenylethynyl terminated imide oligomers

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Havens, Stephen J. (Inventor)

1994-01-01

Four phenylethynyl amine compounds - 3 and 4-aminophenoxy-4'-phenylethynylbenzophenone, and 3 and 4-amino-4'-phenylethynylbenzophenone - were readily prepared and were used to endcap imide oligomers. Phenylethynyl-terminated amide acid oligomers and phenylethynyl-terminated imide oligomers with various molecular weights and compositions were prepared and characterized. These oligomers were cured at 300 to 400 C to provide crosslinked polyimides with excellent solvent resistance, high strength and modulus, and good high temperature properties. Adhesive panels, composites, films, and moldings from these phenylethynyl terminated imide oligomers gave excellent mechanical performance.

Phenylethynyl terminated imide oligomers

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Havens, Stephen J. (Inventor)

1995-01-01

Four phenylethynyl amine compounds - 3 and 4-aminophenoxy-4'-phenylethynylbenzophenone, and 3 and 4-amino-4'-phenylethynylbenzophenone - were readily prepared and were used to endcap imide oligomers. Phenylethynyl-terminated amide acid oligomers and phenylethynyl-terminated imide oligomers with various molecular weights and compositions were prepared and characterized. These oligomers were cured at 300 to 400 C to provide crosslinked polyimides with excellent solvent resistance, high strength and modulus, and good high temperature properties. Adhesive panels, composites, films, and moldings from these phenylethynyl terminated imide oligomers gave excellent mechanical performance.

Distinct symmetry and limited peptide refolding activity of the thermosomes from the acidothermophilic archaea Acidianus tengchongensis S5{sup T}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Li; Hu, Zhong-jun; Luo, Yuan-ming

Recombinant thermosomes from the Acidianus tengchongensis strain S5{sup T} were purified to homogeneity and assembled in vitro into homo-oligomers (rATcpn{alpha} or rATcpn{beta}) and hetero-oligomers (rATcpn{alpha}{beta}). The symmetries of these complexes were determined by electron microscopy and image analysis. The rATcpn{alpha} homo-oligomer was shown to possess 8-fold symmetry while both rATcpn{beta} and rATcpn{alpha}{beta} oligomers adopted 9-fold symmetry. rATcpn{alpha}{beta} oligomers were shown to contain the {alpha} and {beta} subunits in a 1:2 ratio. All of the complexes prevented the irreversible inactivation of yeast alcohol dehydrogenase at 55 {sup o}C and completely prevented the formation of aggregates during thermal inactivation of citrate synthasemore » at 45 {sup o}C. All rATcpn complexes showed trace ATP hydrolysis activity. Furthermore, rATcpn{beta} sequestered fully chemically denatured substrates (GFP and thermophilic malic dehydrogenase) in vitro without refolding them in an ATP-dependent manner. This property is similar to previously reported properties of chaperonins from Sulfolobus tokodaii and Sulfolobus acidocaldarius. These features are consistent with the slow growth rates of these species of archaea in their native environment.« less

Separation of 'Uncharged' Oligodeoxynucleotide Analogs by Anion-Exchange Chromatography at High pH

NASA Technical Reports Server (NTRS)

Schmidt, Jurgen G.; Orgel, Leslie E.; Nielsen, Peter E.

1996-01-01

Ion-exchange chromatography is a well-established method for the analysis and purification of phosphodiester-linked oligonucleotides. If elution is carried out under alkaline conditions, the secondary structure of G- and C-rich oligomers is disrupted. Furthermore, elution times become more sensitive to the G and T content of the oligomer, because G and T are deprotonated at pH 10. In recent work on peptide-nucleic acids (PNAs) we noted that mixtures of PNA oligomers G(sub 4), G(sub 6), G(sub 8), and G9(sub 10) are readily separated by elution at pH 12 on an RPC-5 column. Here we show that this separation method is more generally applicable.

Anticoagulant flavonoid oligomers from the rhizomes of Alpinia platychilus.

PubMed

Shen, Chuan-Pu; Luo, Jian-Guang; Yang, Ming-Hua; Kong, Ling-Yi

2015-10-01

Two pairs of enantiomers of flavonoid oligomers (1a and 1b, 2a and 2b) along with one known chalcone (3) were isolated from the rhizomes of Alpinia platychilus. Their structures were elucidated on the basis of spectroscopic data (MS and 1D/2D NMR). The absolute configurations of the flavonoid oligomers were established by their ECD spectra. Separation of the enantiomeric mixtures (1a and 1b, 2a and 2b) was achieved on a chiral column using hexane:isopropyl alcohol:ethanol (7:2:1) as eluents. The anticoagulant assay showed that 2a, 2b and 3 exhibited potent activities to prolong the prothrombin times (PT) and the thrombin times (TT). Copyright © 2015 Elsevier B.V. All rights reserved.

Inhibition of Human Immunodeficiency Virus Replication by Antisense Oligodeoxynucleotides

NASA Astrophysics Data System (ADS)

Goodchild, John; Agrawal, Sudhir; Civeira, Maria P.; Sarin, Prem S.; Sun, Daisy; Zamecnik, Paul C.

1988-08-01

Twenty different target sites within human immunodeficiency virus (HIV) RNA were selected for studies of inhibition of HIV replication by antisense oligonucleotides. Target sites were selected based on their potential capacity to block recognition functions during viral replication. Antisense oligomers complementary to sites within or near the sequence repeated at the ends of retrovirus RNA (R region) and to certain splice sites were most effective. The effect of antisense oligomer length on inhibiting virus replication was also investigated, and preliminary toxicity studies in mice show that these compounds are toxic only at high levels. The results indicate potential usefulness for these oligomers in the treatment of patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex either alone or in combination with other drugs.

Synthesis and Characterization of Modified Phenylethynyl Terminated Polyimides

NASA Technical Reports Server (NTRS)

Chang, Alice C.

1998-01-01

As an ongoing effort to develop structural adhesives for high performance aerospace applications, recent work has focused on phenylethynyl terminated imide (PETI) oligomers. The work reported herein involves the synthesis and characterization of a series of phenylethynyl containing oligomers designated LARC (TM) MPEI (Modified Phenylethynyl Terminated Polyimide). These oligomers contain mixtures of linear, branched and star-shaped molecules. The fully imidized polymers exhibited minimum melt viscosity as low as 600 poise at 335 C. Ti/Ti lap shear specimens processed at 288 C under 15 psi showed tensile shear strength of approx. 6000 psi and 5200 psi at ambient and 350 F temperatures, respectively. The chemistry and properties of these new MPEIs are presented and compared to an optimized linear PETI, LaRC(Tm) -PETI-5.

Amyloid β-protein oligomers and Alzheimer’s disease

PubMed Central

2013-01-01

The oligomer cascade hypothesis, which states that oligomers are the initiating pathologic agents in Alzheimer’s disease, has all but supplanted the amyloid cascade hypothesis, which suggested that fibers were the key etiologic agents in Alzheimer’s disease. We review here the results of in vivo, in vitro and in silico studies of amyloid β-protein oligomers, and discuss important caveats that should be considered in the evaluation of these results. This article is divided into four sections that mirror the main approaches used in the field to better understand oligomers: (1) attempts to locate and examine oligomers in vivo in situ; that is, without removing these species from their environment; (2) studies involving oligomers extracted from human or animal tissues and the subsequent characterization of their properties ex vivo; (3) studies of oligomers that have been produced synthetically and studied using a reductionist approach in relatively simple in vitro biophysical systems; and (4) computational studies of oligomers in silico. These multiple orthogonal approaches have revealed much about the molecular and cell biology of amyloid β-protein. However, as informative as these approaches have been, the amyloid β-protein oligomer system remains enigmatic. PMID:24289820

Effect of curcumin analogs onα-synuclein aggregation and cytotoxicity

PubMed Central

Jha, Narendra Nath; Ghosh, Dhiman; Das, Subhadeep; Anoop, Arunagiri; Jacob, Reeba S.; Singh, Pradeep K.; Ayyagari, Narasimham; Namboothiri, Irishi N. N.; Maji, Samir K.

2016-01-01

Alpha-synuclein (α-Syn) aggregation into oligomers and fibrils is associated with dopaminergic neuron loss occurring in Parkinson’s disease (PD) pathogenesis. Compounds that modulate α-Syn aggregation and interact with preformed fibrils/oligomers and convert them to less toxic species could have promising applications in the drug development efforts against PD. Curcumin is one of the Asian food ingredient which showed promising role as therapeutic agent against many neurological disorders including PD. However, the instability and low solubility makes it less attractive for the drug development. In this work, we selected various curcumin analogs and studied their toxicity, stability and efficacy to interact with different α-Syn species and modulation of their toxicity. We found a subset of curcumin analogs with higher stability and showed that curcumin and its various analogs interact with preformed fibrils and oligomers and accelerate α-Syn aggregation to produce morphologically different amyloid fibrils in vitro. Furthermore, these curcumin analogs showed differential binding with the preformed α-Syn aggregates. The present data suggest the potential role of curcumin analogs in modulating α-Syn aggregation. PMID:27338805

Diamines Containing Pendent Phenylethynyl Groups

NASA Technical Reports Server (NTRS)

Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)

1997-01-01

Controlled molecular weight imide oligomers and co-oligomers containing pendent phenylethynyl groups (PEPIs) and endcapped with nonreactive or phenylethynyl groups have been prepared by the cyclodehydration of the precursor amide acid oligomers or co-oligomers containing pendent phenylethynyl groups and endcapped with nonreactive or phenylethynyl groups. The amine terminated amide acid oligomers or co-oligomers are prepared from the reaction of dianhydride(s) with an excess of diamine(s) and diamine containing pendent phenylethynyl groups and subsequently endcapped with a phenylethynyl phthalic anhydride or monofunctional anhydride. The anhydride terminated amide acid oligomers and co-oligomers are prepared from the reaction of diamine(s) and diamine containing pendent phenylethynyl group(s) with an excess of dianhydride(s) and subsequently endcapped with a phenylethynyl amine or monofunctional amine. The polymerizations are carried out in polar aprotic solvents such as and N,N-dimethylacetamide under nitrogen at room temperature. The amide acid oligomers or co-oligomers are subsequently cyclodehydrated either thermally or chemically to the corresponding imide oligomers. The polymers and copolymers prepared from these materials exhibit a unique and unexpected combination of properties that includes higher glass transition temperatures after curing and higher retention of neat resin, adhesive and carbon fiber reinforced mechanical properties at temperatures up to 204 C under wet conditions without sacrificing melt flow behavior and processability as compared to similar materials. These materials are useful as adhesives, coatings, films, moldings, and composite matrices.

Analysis of linear and cyclic oligomers in polyamide-6 without sample preparation by liquid chromatography using the sandwich injection method. II. Methods of detection and quantification and overall long-term performance.

PubMed

Mengerink, Y; Peters, R; Kerkhoff, M; Hellenbrand, J; Omloo, H; Andrien, J; Vestjens, M; van der Wal, S

2000-05-05

By separating the first six linear and cyclic oligomers of polyamide-6 on a reversed-phase high-performance liquid chromatographic system after sandwich injection, quantitative determination of these oligomers becomes feasible. Low-wavelength UV detection of the different oligomers and selective post-column reaction detection of the linear oligomers with o-phthalic dicarboxaldehyde (OPA) and 3-mercaptopropionic acid (3-MPA) are discussed. A general methodology for quantification of oligomers in polymers was developed. It is demonstrated that the empirically determined group-equivalent absorption coefficients and quench factors are a convenient way of quantifying linear and cyclic oligomers of nylon-6. The overall long-term performance of the method was studied by monitoring a reference sample and the calibration factors of the linear and cyclic oligomers.

Comparison of neurotoxicity of different aggregated forms of Aβ40, Aβ42 and Aβ43 in cell cultures.

PubMed

Fu, Lu; Sun, Yao; Guo, Yongqing; Chen, Yan; Yu, Bin; Zhang, Haihong; Wu, Jiaxin; Yu, Xianghui; Kong, Wei; Wu, Hui

2017-03-01

The abnormal deposition of amyloid-β (Aβ) peptides in the brain is the main neuropathological hallmark of Alzheimer's disease (AD). Amyloid deposits are formed by a heterogeneous mixture of Aβ peptides, among which the most studied are Aβ40 and Aβ42. Aβ40 is abundantly produced in the human brain, but the level of Aβ42 is remarkably increased in the brain of AD patients. Aside from Aβ40 and Aβ42, recent data have raised the possibility that Aβ43 peptides may be instrumental in AD pathogenesis. Besides its length, whether the Aβ aggregated form accounts for the neurotoxicity is also particularly controversial. Aβ fibrils are generally considered as key pathogenic substances in AD pathogenesis. Nevertheless, recent data implicated soluble Aβ oligomers as the main cause of synaptic dysfunction and memory loss in AD. To further address this uncertainty, we analyzed the neurotoxicity of different Aβ species and Aβ forms at the cellular level. The results showed that Aβ42 could form oligomers significantly faster than Aβ40 and Aβ43 and Aβ42 oligomers showed the greatest level of neurotoxicity. Regardless of the length of Aβ peptides, Aβ oligomers induced significantly higher cytotoxicity compared with the other two Aβ forms. Surprisingly, the neurotoxicity of fibrils in PC12 cells was only marginally but not significantly stronger than monomers, contrary to previous reports. Altogether, our findings demonstrate the high pathogenicity of Aβ42 among the three Aβ species and support the idea that Aβ42 oligomers contribute to the pathological events leading to neurodegeneration in AD. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Conformational alteration in alpha-toxin from Staphylococcus aureus concomitant with the transformation of the water-soluble monomer to the membrane oligomer.

PubMed

Ikigai, H; Nakae, T

1985-07-16

The membrane-damaging alpha-toxin aggregate of Staphylococcus aureus was characterized physicochemically. The aggregate weight of the toxin formed by various methods appeared to be 6 times higher than the molecular weight of the monomer as determined by the laser light scattering technique, suggesting the presence of a hexamer in the membrane. The aggregates fluoresced 20 to 50% more than the monomer at 336 nm. Circular dichroism measurements revealed that both the monomer and the oligomer showed essentially beta-sheet structure with the maximum ellipticity about -8,400 deg.cm2.dmol-1 at 215 nm. Circular dichroism spectrum of the oligomers showed ellipticity difference of -6,600, -44 and +84 deg.cm2.dmol-1, at 200, 250 and 280 nm, respectively, compared with the monomer. All these results suggest that the conformational change in the toxin molecule occurs concomitant with the transformation of the water-soluble monomer to the membrane-embedded hexamer.

Mitochondria, cognitive impairment, and Alzheimer's disease.

PubMed

Mancuso, M; Calsolaro, V; Orsucci, D; Carlesi, C; Choub, A; Piazza, S; Siciliano, G

2009-07-06

To date, the beta amyloid (Abeta) cascade hypothesis remains the main pathogenetic model of Alzheimer's disease (AD), but its role in the majority of sporadic AD cases is unclear. The "mitochondrial cascade hypothesis" could explain many of the biochemical, genetic, and pathological features of sporadic AD. Somatic mutations in mitochondrial DNA (mtDNA) could cause energy failure, increased oxidative stress, and accumulation of Abeta, which in a vicious cycle reinforce the mtDNA damage and the oxidative stress. Despite the evidence of mitochondrial dysfunction in AD, no causative mutations in the mtDNA have been detected so far. Indeed, results of studies on the role of mtDNA haplogroups in AD are controversial. In this review we discuss the role of the mitochondria, and especially of the mtDNA, in the cascade of events leading to neurodegeneration, dementia, and AD.

EFRH-phage immunization of Alzheimer's disease animal model improves behavioral performance in Morris water maze trials.

PubMed

Lavie, Vered; Becker, Maria; Cohen-Kupiec, Rachel; Yacoby, Iftach; Koppel, Rela; Wedenig, Manuela; Hutter-Paier, Birgit; Solomon, Beka

2004-01-01

We have developed an immunization procedure for the production of effective anti-beta-amyloid (anti-Abeta) antibodies, using filamentous phage displaying only 4 amino acids. The EFRH sequence, encompassing amino acids 3-6 of the 42 residues of Abeta peptide, was found previously to be the main regulatory site for amyloid modulation and the epitope of anti-aggregating antibodies. Engineered filamentous phage enable the display of various numbers of EFRH copies on the phage and serve as potent carriers of antigens. In the present study we have found that phage displaying high EFRH copy number are effective in eliciting humoral response against the EFRH sequence, which in turn relieves the amyloid burden in the brains of amyloid precursor protein Tg mice and improves their ability to perform cognitive tasks. Copyright 2004 Humana Press Inc.

Rapid endocytosis of the low density lipoprotein receptor-related protein modulates cell surface distribution and processing of the beta-amyloid precursor protein.

PubMed

Cam, Judy A; Zerbinatti, Celina V; Li, Yonghe; Bu, Guojun

2005-04-15

The low density lipoprotein receptor-related protein (LRP) is a approximately 600-kDa multifunctional endocytic receptor that is highly expressed in the brain. LRP and its ligands apolipoprotein E, alpha2-macroglobulin, and beta-amyloid precursor protein (APP), are genetically linked to Alzheimer disease and are found in characteristic plaque deposits in brains of patients with Alzheimer disease. To identify which extracellular domains of LRP interact with APP, we used minireceptors of each of the individual LRP ligand binding domains and assessed their ability to bind and degrade a soluble APP fragment. LRP minireceptors containing ligand binding domains II and IV, but not I or III, interacted with APP. To test whether APP trafficking is directly related to the rapid endocytosis of LRP, we generated stable Chinese hamster ovary cell lines expressing either a wild-type LRP minireceptor or its endocytosis mutants. Chinese hamster ovary cells stably expressing wild-type LRP minireceptor had less cell surface APP than pcDNA3 vector-transfected cells, whereas those stably expressing endocytosis-defective LRP minireceptors accumulated APP at the cell surface. We also found that the steady-state levels of the amyloid beta-peptides (Abeta) is dictated by the relative expression levels of APP and LRP, probably reflecting the dual roles of LRP in both Abeta production and clearance. Together, these data establish a relationship between LRP rapid endocytosis and APP trafficking and proteolytic processing to generate Abeta.

A sequence-dependent rigid-base model of DNA

NASA Astrophysics Data System (ADS)

Gonzalez, O.; Petkevičiutė, D.; Maddocks, J. H.

2013-02-01

A novel hierarchy of coarse-grain, sequence-dependent, rigid-base models of B-form DNA in solution is introduced. The hierarchy depends on both the assumed range of energetic couplings, and the extent of sequence dependence of the model parameters. A significant feature of the models is that they exhibit the phenomenon of frustration: each base cannot simultaneously minimize the energy of all of its interactions. As a consequence, an arbitrary DNA oligomer has an intrinsic or pre-existing stress, with the level of this frustration dependent on the particular sequence of the oligomer. Attention is focussed on the particular model in the hierarchy that has nearest-neighbor interactions and dimer sequence dependence of the model parameters. For a Gaussian version of this model, a complete coarse-grain parameter set is estimated. The parameterized model allows, for an oligomer of arbitrary length and sequence, a simple and explicit construction of an approximation to the configuration-space equilibrium probability density function for the oligomer in solution. The training set leading to the coarse-grain parameter set is itself extracted from a recent and extensive database of a large number of independent, atomic-resolution molecular dynamics (MD) simulations of short DNA oligomers immersed in explicit solvent. The Kullback-Leibler divergence between probability density functions is used to make several quantitative assessments of our nearest-neighbor, dimer-dependent model, which is compared against others in the hierarchy to assess various assumptions pertaining both to the locality of the energetic couplings and to the level of sequence dependence of its parameters. It is also compared directly against all-atom MD simulation to assess its predictive capabilities. The results show that the nearest-neighbor, dimer-dependent model can successfully resolve sequence effects both within and between oligomers. For example, due to the presence of frustration, the model can successfully predict the nonlocal changes in the minimum energy configuration of an oligomer that are consequent upon a local change of sequence at the level of a single point mutation.

High-order oligomers of intrinsically disordered brain proteins BASP1 and GAP-43 preserve the structural disorder.

PubMed

Forsova, Oksana S; Zakharov, Vladislav V

2016-04-01

Brain acid-soluble protein-1 (BASP1) and growth-associated protein-43 (GAP-43) are presynaptic membrane proteins participating in axon guidance, neuroregeneration and synaptic plasticity. They are presumed to sequester phosphatidylinositol-4,5-bisphosphate (PIP2 ) in lipid rafts. Previously we have shown that the proteins form heterogeneously sized oligomers in the presence of anionic phospholipids or SDS at submicellar concentration. BASP1 and GAP-43 are intrinsically disordered proteins (IDPs). In light of this, we investigated the structure of their oligomers. Using partial cross-linking of the oligomers with glutaraldehyde, the aggregation numbers of BASP1 and GAP-43 were estimated as 10-14 and 6-7 monomer subunits, respectively. The cross-linking pattern indicated that the subunits are circularly arranged. The circular dichroism (CD) spectra of the monomers were characteristic of coil-like IDPs showing unordered structure with a high population of polyproline-II conformation. The oligomerization was accompanied by a minor CD spectral change attributable to formation of a small amount of α-helix. The number of residues in the α-helical conformation was estimated as 13 in BASP1 and 18 in GAP-43. However, the overall structure of the oligomers remained disordered, indicating a high degree of 'fuzziness'. This was confirmed by measuring the hydrodynamic dimensions of the oligomers using polyacrylamide gradient gel electrophoresis and size-exclusion chromatography, and by assaying their sensitivity to proteolytic digestion. There is evidence that the observed α-helical folding occurs within the basic effector domains, which are presumably tethered together via anionic molecules of SDS or PIP2 . We conclude that BASP1 and GAP-43 oligomers preserve a mostly disordered structure, which may be of great importance for their function in PIP2 signaling pathway. © 2016 Federation of European Biochemical Societies.

A sequence-dependent rigid-base model of DNA.

PubMed

Gonzalez, O; Petkevičiūtė, D; Maddocks, J H

2013-02-07

A novel hierarchy of coarse-grain, sequence-dependent, rigid-base models of B-form DNA in solution is introduced. The hierarchy depends on both the assumed range of energetic couplings, and the extent of sequence dependence of the model parameters. A significant feature of the models is that they exhibit the phenomenon of frustration: each base cannot simultaneously minimize the energy of all of its interactions. As a consequence, an arbitrary DNA oligomer has an intrinsic or pre-existing stress, with the level of this frustration dependent on the particular sequence of the oligomer. Attention is focussed on the particular model in the hierarchy that has nearest-neighbor interactions and dimer sequence dependence of the model parameters. For a Gaussian version of this model, a complete coarse-grain parameter set is estimated. The parameterized model allows, for an oligomer of arbitrary length and sequence, a simple and explicit construction of an approximation to the configuration-space equilibrium probability density function for the oligomer in solution. The training set leading to the coarse-grain parameter set is itself extracted from a recent and extensive database of a large number of independent, atomic-resolution molecular dynamics (MD) simulations of short DNA oligomers immersed in explicit solvent. The Kullback-Leibler divergence between probability density functions is used to make several quantitative assessments of our nearest-neighbor, dimer-dependent model, which is compared against others in the hierarchy to assess various assumptions pertaining both to the locality of the energetic couplings and to the level of sequence dependence of its parameters. It is also compared directly against all-atom MD simulation to assess its predictive capabilities. The results show that the nearest-neighbor, dimer-dependent model can successfully resolve sequence effects both within and between oligomers. For example, due to the presence of frustration, the model can successfully predict the nonlocal changes in the minimum energy configuration of an oligomer that are consequent upon a local change of sequence at the level of a single point mutation.

Separation of a chemically modified DNA oligomer bound by the carcinogen 2-Amino-1-methy-6-phenylimidazo [4,5-{beta}]pyridine using capillary gel electrophoresis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, T.N.

1994-05-06

We have optimized the reaction conditions under which unactivated metabolite of the food borne carcinogen 2-amino-1-methyl-6-phenylimidazo [4,5-{beta}]pyridine (PhIP) is covalently bound to the oligodeoxynucleotide d(CCTACGCATCC). Capillary electrophoresis (CE) was used to separate and characterize this DNA oligomer bound by PhIP. We observed 2 major and several minor PhIP adduct species. The 2 major adducts had different absorbance maxima; the major adduct eluates with faster and slower mobilities had absorbance maxima of 360 and 340 nm, respectively. One of the two major PhIP adduct species was resolvable but the peak was broad. Using detection at 260 nm, the other major PhIPmore » adduct with fastest electrophoretic mobility was not resolvable, but coelute with the huge broad unmodified DNA oligomer peak. However, at higher wavelengths (>320 nm) where DNA does not absorb, electropherograms generated by detection at these higher wavelengths showed very heterogeneous binding by PhIP to the DNA oligomer with no interfering absorbance by the DNA.« less

Contact lines on silicone elastomers promote contamination

NASA Astrophysics Data System (ADS)

Hourlier-Fargette, Aurelie; Antkowiak, Arnaud; Neukirch, Sebastien

2017-11-01

Silicone elastomers are used in contact with aqueous liquids in a large range of applications. Due to numerous advantages such as its flexibility, optical transparency, or gas permeability, polydimethylsiloxane is widely spread in rapid prototyping for microfluidics or elastocapillarity experiments. However, silicone elastomers are known to contain a small fraction of uncrosslinked low-molecular-weight oligomers, the effects of which are not completely understood. We show that in various setups involving an air-water-silicone elastomer contact line, a capillarity-induced extraction of uncrosslinked oligomers occurs, leading to a contamination of water-air interfaces. We investigate the case of a static air-water-PDMS contact line, before focusing on moving contact lines. A water droplet sliding down on a PDMS inclined plane or an air bubble rising on an immersed PDMS plane exhibits two successive speed regimes: the second regime is reached only when a monolayer of oligomers completely covers the water-air interface. These experiments involve processes occurring at the polymer network scale that have significant macroscopic consequences, and therefore provide a simple test to evaluate the presence of uncrosslinked oligomers in an elastomer sample.

Stable, Metastable, and Kinetically Trapped Amyloid Aggregate Phases

PubMed Central

2015-01-01

Self-assembly of proteins into amyloid fibrils plays a key role in a multitude of human disorders that range from Alzheimer’s disease to type II diabetes. Compact oligomeric species, observed early during amyloid formation, are reported as the molecular entities responsible for the toxic effects of amyloid self-assembly. However, the relation between early-stage oligomeric aggregates and late-stage rigid fibrils, which are the hallmark structure of amyloid plaques, has remained unclear. We show that these different structures occupy well-defined regions in a peculiar phase diagram. Lysozyme amyloid oligomers and their curvilinear fibrils only form after they cross a salt and protein concentration-dependent threshold. We also determine a boundary for the onset of amyloid oligomer precipitation. The oligomeric aggregates are structurally distinct from rigid fibrils and are metastable against nucleation and growth of rigid fibrils. These experimentally determined boundaries match well with colloidal model predictions that account for salt-modulated charge repulsion. The model also incorporates the metastable and kinetic character of oligomer phases. Similarities and differences of amyloid oligomer assembly to metastable liquid–liquid phase separation of proteins and to surfactant aggregation are discussed. PMID:25469942

A quantitative evaluation of the iron-sulfur world and its relevance to life's origins.

PubMed

Ross, David S

2008-04-01

The significance of Wächtershäuser's iron-sulfur world to the origin of life and the limits to its notional autocatalytic cycles are examined in kinetic simulations of the chain polymerization sequence: primitive materials-->amino acids-->oligomers. The simulations were run for the formation of all oligomers up to the 20-mer over a 1 Gy interval from the end of the period of heavy bombardment, during which period life emerged. Upper-limit rate constant estimates developed from the studies of Huber and Wächtershäuser were employed. The simulations showed that oligomer production consistent with life's start within that interval emerges only with an autocatalyst exhibiting a catalytic proficiency comparable to that of contemporary enzymes. The simulations, moreover, ignored likely thermodynamic and statistical burdens which, if included, would have led to the need for catalytic capacities well in excess of those in present-day enzymes. Prebiotic oligomers with such levels of activity are clearly not likely, and it is apparent that the iron-sulfur scheme could not have played a role in life's beginnings.

Regulation of adhesion and growth of fibrosarcoma cells by NF-kappa B RelA involves transforming growth factor beta.

PubMed Central

Perez, J R; Higgins-Sochaski, K A; Maltese, J Y; Narayanan, R

1994-01-01

The NF-kappa B transcription factor is a pleiotropic activator that participates in the induction of a wide variety of cellular genes. Antisense oligomer inhibition of the RelA subunit of NF-kappa B results in a block of cellular adhesion and inhibition of tumor cell growth. Investigation of the molecular basis for these effects showed that in vitro inhibition of the growth of transformed fibroblasts by relA antisense oligonucleotides can be reversed by the parental-cell-conditioned medium. Cytokine profile analysis of these cells treated with relA antisense oligonucleotides revealed inhibition of transforming growth factor beta 1 (TGF-beta 1 to the transformed fibroblasts reversed the inhibitory effects of relA antisense oligomers on soft agar colony formation and cell adhesion to the substratum. Direct inhibition of TGF-beta 1 expression by antisense phosphorothioates to TGF-beta 1 mimicked the in vitro effects of blocking cell adhesion that are elicited by antisense relA oligomers. These results may explain the in vitro effects of relA antisense oligomers on fibrosarcoma cell growth and adhesion. Images PMID:8035811

Exciton–exciton annihilation as a probe of interchain interactions in PPV–oligomer aggregates

DOE PAGES

Peteanu, Linda A.; Chowdhury, Sanchari; Wildeman, Jurjen; ...

2017-01-20

One measure of exciton mobility in an aggregate is the efficiency of exciton–exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH–PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed frommore » the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. Furthermore, the wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.« less

Iterative divergent/convergent doubling approach to linear conjugated oligomers. A rapid route to a 128 A long potential molecular wire

NASA Astrophysics Data System (ADS)

Tour, James M.; Schumm, Jeffrey S.; Pearson, Darren L.

1994-06-01

Described is the synthesis of oligo (2-ethylphenylene ethynylene)s and oligo (2-(3'ethylheptyl) phenylene ethynylene)s via an iterative divergent convergent approach. Synthesized were the monomer, dimer, tetramer, and octamer of the ethyl derivative and the monomer, dimer, tetramer, octamer, and 16-mer of the ethylheptyl derivative. The 16-mer is 128 A long. At each stage in the iteration, the length of the framework doubles. Only three sets of reaction conditions are needed for the entire iterative synthetic sequence; an iodination, a protodesilylation, and a Pd/Cu-catalyzed cross coupling. The oligomers were characterized spectroscopically and by mass spectrometry. The optical properties are presented which show the stage of optical absorbance saturation. The size exclusion chromatography values for the number average weights, relative to polystyrene, illustrate the tremendous differences in the hydrodynamic volume of these rigid rod oligomers verses the random coils of polystyrene. These differences become quite apparent at the octamer stage. These oligomers may act as molecular wires in molecular electronic devices and they also serve as useful models for understanding related bulk polymers.

Stable, metastable, and kinetically trapped amyloid aggregate phases.

PubMed

Miti, Tatiana; Mulaj, Mentor; Schmit, Jeremy D; Muschol, Martin

2015-01-12

Self-assembly of proteins into amyloid fibrils plays a key role in a multitude of human disorders that range from Alzheimer's disease to type II diabetes. Compact oligomeric species, observed early during amyloid formation, are reported as the molecular entities responsible for the toxic effects of amyloid self-assembly. However, the relation between early-stage oligomeric aggregates and late-stage rigid fibrils, which are the hallmark structure of amyloid plaques, has remained unclear. We show that these different structures occupy well-defined regions in a peculiar phase diagram. Lysozyme amyloid oligomers and their curvilinear fibrils only form after they cross a salt and protein concentration-dependent threshold. We also determine a boundary for the onset of amyloid oligomer precipitation. The oligomeric aggregates are structurally distinct from rigid fibrils and are metastable against nucleation and growth of rigid fibrils. These experimentally determined boundaries match well with colloidal model predictions that account for salt-modulated charge repulsion. The model also incorporates the metastable and kinetic character of oligomer phases. Similarities and differences of amyloid oligomer assembly to metastable liquid-liquid phase separation of proteins and to surfactant aggregation are discussed.

Exciton-Exciton Annihilation as a Probe of Interchain Interactions in PPV-Oligomer Aggregates.

PubMed

Peteanu, Linda A; Chowdhury, Sanchari; Wildeman, Jurjen; Sfeir, Matthew Y

2017-02-23

One measure of exciton mobility in an aggregate is the efficiency of exciton-exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH-PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed from the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. The wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.

A quantitative evaluation of the iron-sulfur world and its relevance to life's origins

USGS Publications Warehouse

Ross, D.S.

2008-01-01

The significance of Wa??chtersha??user's iron-sulfur world to the origin of life and the limits to its notional autocatalytic cycles are examined in kinetic simulations of the chain polymerization sequence primitive materials ??? amino acids ??? oligomers The simulations were run for the formation of all oligomers up to the 20-mer over a 1 Gy interval from the end of the period of heavy bombardment, during which period life emerged. Upper-limit rate constant estimates developed from the studies of Huber and Wa??chtersha?? user were employed. The simulations showed that oligomer production consistent with life's start within that interval emerges only with an autocatalyst exhibiting a catalytic proficiency comparable to that of contemporary enzymes. The simulations, moreover, ignored likely thermodynamic and statistical burdens which, if included, would have led to the need for catalytic capacities well in excess of those in present-day enzymes. Prebiotic oligomers with such levels of activity are clearly not likely, and it is apparent that the iron-sulfur scheme could not have played a role in life's beginnings. ?? 2008 Mary Ann Liebert, Inc.

Structural Characteristics of the Alpha-Synuclein Oligomers Stabilized By the Flavonoid Baicalein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, D.-P.; Fink, A.L.; Uversky, V.N.

The flavonoid baicalein inhibits fibrillation of alpha-synuclein, which is a major component of Lewy bodies in Parkinson's disease. It has been known that baicalein induces the formation of alpha-synuclein oligomers and consequently prevents their fibrillation. In order to evaluate the structural properties of baicalein-stabilized oligomers, we purified oligomer species by HPLC and examined their stability and structure by CD, Fourier transform infrared spectroscopy, size exclusion chromatography HPLC, small-angle X-ray scattering, and atomic force microscopy. Baicalein-stabilized oligomers are beta-sheet-enriched according to CD and Fourier transform infrared spectroscopy analyses. They did not form fibrils even after very prolonged incubation. From small-angle X-raymore » scattering data and atomic force microscopy images, the oligomers were characterized as quite compact globular species. Oligomers were extremely stable, with a GdmCl C(m)=3.3 M. This high stability explains the previously observed inhibition properties of baicalein against alpha-synuclein fibrillation. These baicalein-stabilized oligomers, added to the solution of aggregating alpha-synuclein, were able to noticeably inhibit its fibrillation. After prolonged coincubation, short fibrils were formed, suggesting an effective interaction of oligomers with monomeric alpha-synuclein. Membrane permeability tests suggested that the baicalein-stabilized oligomers had a mild effect on the integrity of the membrane surface. This effect was rather similar to that of the monomeric protein, suggesting that targeted stabilization of certain alpha-synuclein oligomers might offer a potential strategy for the development of novel Parkinson's disease therapies.« less

Structural studies on HCN oligomers. [catalysts for prebiotic processes

NASA Technical Reports Server (NTRS)

Ferris, J. P.; Edelson, E. H.; Auyeung, J. M.; Joshi, P. C.

1981-01-01

NMR spectral studies on the HCN oligomers suggest the presence of carboxamide and urea groupings. The release of CO2, H2O, HCN, CH3CN, HCONH2 and pyridine on pyrolysis is consistent with the presence of these groupings as well as carboxylic acid groups. No basic primary amine groupings could be detected with fluorescamine. Hydrazinolysis of the HCN oligomers releases 10% of the amino acids normally released by acid hydrolysis. The oligomers give a positive biuret test but this is not due to the presence of peptide bonds. There is no conclusive evidence for the presence of peptide bonds in the HCN oligomers. No diglycine was detected on partial hydrolysis of the HCN oligomers at pH 8.5 suggesting that HCN oligomers were not a source of prebiotic peptides.

Prion Protein-mediated Toxicity of Amyloid-β Oligomers Requires Lipid Rafts and the Transmembrane LRP1*

PubMed Central

Rushworth, Jo V.; Griffiths, Heledd H.; Watt, Nicole T.; Hooper, Nigel M.

2013-01-01

Soluble oligomers of the amyloid-β (Aβ) peptide cause neurotoxicity, synaptic dysfunction, and memory impairments that underlie Alzheimer disease (AD). The cellular prion protein (PrPC) was recently identified as a high affinity neuronal receptor for Aβ oligomers. We report that fibrillar Aβ oligomers recognized by the OC antibody, which have been shown to correlate with the onset and severity of AD, bind preferentially to cells and neurons expressing PrPC. The binding of Aβ oligomers to cell surface PrPC, as well as their downstream activation of Fyn kinase, was dependent on the integrity of cholesterol-rich lipid rafts. In SH-SY5Y cells, fluorescence microscopy and co-localization with subcellular markers revealed that the Aβ oligomers co-internalized with PrPC, accumulated in endosomes, and subsequently trafficked to lysosomes. The cell surface binding, internalization, and downstream toxicity of Aβ oligomers was dependent on the transmembrane low density lipoprotein receptor-related protein-1 (LRP1). The binding of Aβ oligomers to cell surface PrPC impaired its ability to inhibit the activity of the β-secretase BACE1, which cleaves the amyloid precursor protein to produce Aβ. The green tea polyphenol (−)-epigallocatechin gallate and the red wine extract resveratrol both remodeled the fibrillar conformation of Aβ oligomers. The resulting nonfibrillar oligomers displayed significantly reduced binding to PrPC-expressing cells and were no longer cytotoxic. These data indicate that soluble, fibrillar Aβ oligomers bind to PrPC in a conformation-dependent manner and require the integrity of lipid rafts and the transmembrane LRP1 for their cytotoxicity, thus revealing potential targets to alleviate the neurotoxic properties of Aβ oligomers in AD. PMID:23386614

Antigenotoxic and free radical scavenging activities of extracts from Moricandia arvensis.

PubMed

Skandrani, I; Sghaier, M Ben; Neffati, A; Boubaker, J; Bouhlel, I; Kilani, S; Mahmoud, A; Ghedira, K; Chekir-Ghedira, L

2007-01-01

This study evaluates genotoxic and antigenotoxic effects of extracts from leaves of Moricandia arvensis, which are used in traditional cooking and medicines. Extracts showed no genotoxicity when tested with the SOS Chromotest using E. coli PQ37 and PQ35 strains, except for the total oligomers flavonoids enriched extract. Petroleum ether and methanol extracts are the most active in reducing nitrofurantoin genotoxicity, whereas methanol and total oligomers flavonoids enriched extracts showed the most important inhibitory effect of H2O2 genotoxicity. In addition, these two extracts showed important free radical scavenging activity toward the DPPH. radical, whereas the chloroform extract exhibited the highest value of TEAC against ABTS+. radical.

High-Capacity Conductive Nanocellulose Paper Sheets for Electrochemically Controlled Extraction of DNA Oligomers

PubMed Central

Razaq, Aamir; Nyström, Gustav; Strømme, Maria; Mihranyan, Albert; Nyholm, Leif

2011-01-01

Highly porous polypyrrole (PPy)-nanocellulose paper sheets have been evaluated as inexpensive and disposable electrochemically controlled three-dimensional solid phase extraction materials. The composites, which had a total anion exchange capacity of about 1.1 mol kg−1, were used for extraction and subsequent release of negatively charged fluorophore tagged DNA oligomers via galvanostatic oxidation and reduction of a 30–50 nm conformal PPy layer on the cellulose substrate. The ion exchange capacity, which was, at least, two orders of magnitude higher than those previously reached in electrochemically controlled extraction, originated from the high surface area (i.e. 80 m2 g−1) of the porous composites and the thin PPy layer which ensured excellent access to the ion exchange material. This enabled the extractions to be carried out faster and with better control of the PPy charge than with previously employed approaches. Experiments in equimolar mixtures of (dT)6, (dT)20, and (dT)40 DNA oligomers showed that all oligomers could be extracted, and that the smallest oligomer was preferentially released with an efficiency of up to 40% during the reduction of the PPy layer. These results indicate that the present material is very promising for the development of inexpensive and efficient electrochemically controlled ion-exchange membranes for batch-wise extraction of biomolecules. PMID:22195031

High-resolution NMR characterization of low abundance oligomers of amyloid-β without purification

NASA Astrophysics Data System (ADS)

Kotler, Samuel A.; Brender, Jeffrey R.; Vivekanandan, Subramanian; Suzuki, Yuta; Yamamoto, Kazutoshi; Monette, Martine; Krishnamoorthy, Janarthanan; Walsh, Patrick; Cauble, Meagan; Holl, Mark M. Banaszak; Marsh, E. Neil. G.; Ramamoorthy, Ayyalusamy

2015-07-01

Alzheimer’s disease is characterized by the misfolding and self-assembly of the amyloidogenic protein amyloid-β (Aβ). The aggregation of Aβ leads to diverse oligomeric states, each of which may be potential targets for intervention. Obtaining insight into Aβ oligomers at the atomic level has been a major challenge to most techniques. Here, we use magic angle spinning recoupling 1H-1H NMR experiments to overcome many of these limitations. Using 1H-1H dipolar couplings as a NMR spectral filter to remove both high and low molecular weight species, we provide atomic-level characterization of a non-fibrillar aggregation product of the Aβ1-40 peptide using non-frozen samples without isotopic labeling. Importantly, this spectral filter allows the detection of the specific oligomer signal without a separate purification procedure. In comparison to other solid-state NMR techniques, the experiment is extraordinarily selective and sensitive. A resolved 2D spectra could be acquired of a small population of oligomers (6 micrograms, 7% of the total) amongst a much larger population of monomers and fibers (93% of the total). By coupling real-time 1H-1H NMR experiments with other biophysical measurements, we show that a stable, primarily disordered Aβ1-40 oligomer 5-15 nm in diameter can form and coexist in parallel with the well-known cross-β-sheet fibrils.

Structural assemblies of the di- and oligomeric G-protein coupled receptor TGR5 in live cells: an MFIS-FRET and integrative modelling study

NASA Astrophysics Data System (ADS)

Greife, Annemarie; Felekyan, Suren; Ma, Qijun; Gertzen, Christoph G. W.; Spomer, Lina; Dimura, Mykola; Peulen, Thomas O.; Wöhler, Christina; Häussinger, Dieter; Gohlke, Holger; Keitel, Verena; Seidel, Claus A. M.

2016-11-01

TGR5 is the first identified bile acid-sensing G-protein coupled receptor, which has emerged as a potential therapeutic target for metabolic disorders. So far, structural and multimerization properties are largely unknown for TGR5. We used a combined strategy applying cellular biology, Multiparameter Image Fluorescence Spectroscopy (MFIS) for quantitative FRET analysis, and integrative modelling to obtain structural information about dimerization and higher-order oligomerization assemblies of TGR5 wildtype (wt) and Y111 variants fused to fluorescent proteins. Residue 111 is located in transmembrane helix 3 within the highly conserved ERY motif. Co-immunoprecipitation and MFIS-FRET measurements with gradually increasing acceptor to donor concentrations showed that TGR5 wt forms higher-order oligomers, a process disrupted in TGR5 Y111A variants. From the concentration dependence of the MFIS-FRET data we conclude that higher-order oligomers - likely with a tetramer organization - are formed from dimers, the smallest unit suggested for TGR5 Y111A variants. Higher-order oligomers likely have a linear arrangement with interaction sites involving transmembrane helix 1 and helix 8 as well as transmembrane helix 5. The latter interaction is suggested to be disrupted by the Y111A mutation. The proposed model of TGR5 oligomer assembly broadens our view of possible oligomer patterns and affinities of class A GPCRs.

High-resolution NMR characterization of low abundance oligomers of amyloid-β without purification

PubMed Central

Kotler, Samuel A.; Brender, Jeffrey R.; Vivekanandan, Subramanian; Suzuki, Yuta; Yamamoto, Kazutoshi; Monette, Martine; Krishnamoorthy, Janarthanan; Walsh, Patrick; Cauble, Meagan; Holl, Mark M. Banaszak; Marsh, E. Neil. G.; Ramamoorthy, Ayyalusamy

2015-01-01

Alzheimer’s disease is characterized by the misfolding and self-assembly of the amyloidogenic protein amyloid-β (Aβ). The aggregation of Aβ leads to diverse oligomeric states, each of which may be potential targets for intervention. Obtaining insight into Aβ oligomers at the atomic level has been a major challenge to most techniques. Here, we use magic angle spinning recoupling 1H-1H NMR experiments to overcome many of these limitations. Using 1H-1H dipolar couplings as a NMR spectral filter to remove both high and low molecular weight species, we provide atomic-level characterization of a non-fibrillar aggregation product of the Aβ1-40 peptide using non-frozen samples without isotopic labeling. Importantly, this spectral filter allows the detection of the specific oligomer signal without a separate purification procedure. In comparison to other solid-state NMR techniques, the experiment is extraordinarily selective and sensitive. A resolved 2D spectra could be acquired of a small population of oligomers (6 micrograms, 7% of the total) amongst a much larger population of monomers and fibers (93% of the total). By coupling real-time 1H-1H NMR experiments with other biophysical measurements, we show that a stable, primarily disordered Aβ1-40 oligomer 5–15 nm in diameter can form and coexist in parallel with the well-known cross-β-sheet fibrils. PMID:26138908

High-resolution NMR characterization of low abundance oligomers of amyloid-β without purification.

PubMed

Kotler, Samuel A; Brender, Jeffrey R; Vivekanandan, Subramanian; Suzuki, Yuta; Yamamoto, Kazutoshi; Monette, Martine; Krishnamoorthy, Janarthanan; Walsh, Patrick; Cauble, Meagan; Holl, Mark M Banaszak; Marsh, E Neil G; Ramamoorthy, Ayyalusamy

2015-07-03

Alzheimer's disease is characterized by the misfolding and self-assembly of the amyloidogenic protein amyloid-β (Aβ). The aggregation of Aβ leads to diverse oligomeric states, each of which may be potential targets for intervention. Obtaining insight into Aβ oligomers at the atomic level has been a major challenge to most techniques. Here, we use magic angle spinning recoupling (1)H-(1)H NMR experiments to overcome many of these limitations. Using (1)H-(1)H dipolar couplings as a NMR spectral filter to remove both high and low molecular weight species, we provide atomic-level characterization of a non-fibrillar aggregation product of the Aβ1-40 peptide using non-frozen samples without isotopic labeling. Importantly, this spectral filter allows the detection of the specific oligomer signal without a separate purification procedure. In comparison to other solid-state NMR techniques, the experiment is extraordinarily selective and sensitive. A resolved 2D spectra could be acquired of a small population of oligomers (6 micrograms, 7% of the total) amongst a much larger population of monomers and fibers (93% of the total). By coupling real-time (1)H-(1)H NMR experiments with other biophysical measurements, we show that a stable, primarily disordered Aβ1-40 oligomer 5-15 nm in diameter can form and coexist in parallel with the well-known cross-β-sheet fibrils.

Inhibition of Alzheimer’s Amyloid Toxicity with a Tricyclic Pyrone Molecule In Vitro and In Vivo

PubMed Central

Hong, Hyun-Seok; Rana, Sandeep; Barrigan, Lydia; Shi, Aibin; Zhang, Yi; Zhou, Feimeng; Jin, Lee-Way; Hua, Duy H.

2009-01-01

Small amyloid β 1–42 aggregates are toxic to neurons and may be the primary toxic species in Alzheimer’s disease (AD). Methods to reduce the level of Aβ, prevent Aβ aggregation, and eliminate existing Aβ aggregates have been proposed for treatment of AD. A tricyclic pyrone named CP2 is found to prevent cell death associated with Aβ oligomers. We studied the possible mechanisms of neuroprotection by CP2. Surface plasmon resonance spectroscopy shows a direct binding of CP2 with Aβ42 oligomer. Circular dichroism spectroscopy reveals monomeric Aβ42 peptide remains as a random coil/α-helix structure in the presence of CP2 over 48 h. Atomic force microscopy (AFM) studies show CP2 exhibits similar ability to inhibit Aβ42 aggregation as that of Congo Red and curcumin. AFM closed-fluid cell study demonstrates that CP2 disaggregates Aβ42 oligomers and protofibrils. CP2 also blocks Aβ fibrillations using a protein quantification method. Treatment of 5x FAD mice, a robust Aβ42-producing animal model of AD, with a two-week course of CP2 resulted in 40% and 50% decreases in non-fibrillar and fibrillar Aβ species, respectively. Our results suggest that CP2 might be beneficial to AD patients by preventing Aβ aggregation and disaggregating existing Aβ oligomers and protofibrils. PMID:19141069

Purified high molecular weight synthetic Aβ(1-42) and biological Aβ oligomers are equipotent in rapidly inducing MTT formazan exocytosis.

PubMed

Weidner, Adam M; Housley, Molly; Murphy, M Paul; Levine, Harry

2011-06-15

Synthetic soluble Aβ oligomers are often used as a surrogate for biologic material in a number of model systems. We compared the activity of Aβ oligomers (synthetic and cell culture media derived) on the human SH-SY5Y neuroblastoma and C2C12 mouse myoblast cell lines in a novel, modified MTT assay. Separating oligomers from monomeric peptide by size exclusion chromatography produced effects at peptide concentrations approaching physiologic levels (10-100 nM). Purified oligomers, but not monomers or fibrils, elicited an increase of a detergent-insoluble form of MTT formazan within 2h as opposed to a control toxin (H(2)O(2)). This effect was comparable for biological and synthetic peptide in both cell types. Monomeric Aβ attenuated the effect of soluble oligomers. This study suggests that the activities of biological and synthetic oligomers are indistinguishable during early stages of Aβ oligomer-cell interaction. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Amyloid-β oligomer detection by ELISA in cerebrospinal fluid and brain tissue.

PubMed

Bruggink, Kim A; Jongbloed, Wesley; Biemans, Elisanne A L M; Veerhuis, Rob; Claassen, Jurgen A H R; Kuiperij, H Bea; Verbeek, Marcel M

2013-02-15

Amyloid-β (Aβ) deposits are important pathological hallmarks of Alzheimer's disease (AD). Aβ aggregates into fibrils; however, the intermediate oligomers are believed to be the most neurotoxic species and, therefore, are of great interest as potential biomarkers. Here, we have developed an enzyme-linked immunosorbent assay (ELISA) specific for Aβ oligomers by using the same capture and (labeled) detection antibody. The ELISA predominantly recognizes relatively small oligomers (10-25 kDa) and not monomers. In brain tissue of APP/PS1 transgenic mice, we found that Aβ oligomer levels increase with age. However, for measurements in human samples, pretreatment to remove human anti-mouse antibodies (HAMAs) was required. In HAMA-depleted human hippocampal extracts, the Aβ oligomer concentration was significantly increased in AD compared with nondemented controls. Aβ oligomer levels could also be quantified in pretreated cerebrospinal fluid (CSF) samples; however, no difference was detected between AD and control groups. Our data suggest that levels of small oligomers might not be suitable as biomarkers for AD. In addition, we demonstrate the importance of avoiding HAMA interference in assays to quantify Aβ oligomers in human body fluids. Copyright © 2012 Elsevier Inc. All rights reserved.

Accumulation of oligomer-prone α-synuclein exacerbates synaptic and neuronal degeneration in vivo

PubMed Central

Rockenstein, Edward; Nuber, Silke; Overk, Cassia R.; Ubhi, Kiren; Mante, Michael; Patrick, Christina; Adame, Anthony; Trejo-Morales, Margarita; Gerez, Juan; Picotti, Paola; Jensen, Poul H.; Campioni, Silvia; Riek, Roland; Winkler, Jürgen; Gage, Fred H.; Winner, Beate

2014-01-01

In Parkinson’s disease and dementia with Lewy bodies, α-synuclein aggregates to form oligomers and fibrils; however, the precise nature of the toxic α-synuclein species remains unclear. A number of synthetic α-synuclein mutations were recently created (E57K and E35K) that produce species of α-synuclein that preferentially form oligomers and increase α-synuclein-mediated toxicity. We have shown that acute lentiviral expression of α-synuclein E57K leads to the degeneration of dopaminergic neurons; however, the effects of chronic expression of oligomer-prone α-synuclein in synapses throughout the brain have not been investigated. Such a study could provide insight into the possible mechanism(s) through which accumulation of α-synuclein oligomers in the synapse leads to neurodegeneration. For this purpose, we compared the patterns of neurodegeneration and synaptic damage between a newly generated mThy-1 α-synuclein E57K transgenic mouse model that is prone to forming oligomers and the mThy-1 α-synuclein wild-type mouse model (Line 61), which accumulates various forms of α-synuclein. Three lines of α-synuclein E57K (Lines 9, 16 and 54) were generated and compared with the wild-type. The α-synuclein E57K Lines 9 and 16 were higher expressings of α-synuclein, similar to α-synuclein wild-type Line 61, and Line 54 was a low expressing of α-synuclein compared to Line 61. By immunoblot analysis, the higher-expressing α-synuclein E57K transgenic mice showed abundant oligomeric, but not fibrillar, α-synuclein whereas lower-expressing mice accumulated monomeric α-synuclein. Monomers, oligomers, and fibrils were present in α-synuclein wild-type Line 61. Immunohistochemical and ultrastructural analyses demonstrated that α-synuclein accumulated in the synapses but not in the neuronal cells bodies, which was different from the α-synuclein wild-type Line 61, which accumulates α-synuclein in the soma. Compared to non-transgenic and lower-expressing mice, the higher-expressing α-synuclein E57K mice displayed synaptic and dendritic loss, reduced levels of synapsin 1 and synaptic vesicles, and behavioural deficits. Similar alterations, but to a lesser extent, were seen in the α-synuclein wild-type mice. Moreover, although the oligomer-prone α-synuclein mice displayed neurodegeneration in the frontal cortex and hippocampus, the α-synuclein wild-type only displayed neuronal loss in the hippocampus. These results support the hypothesis that accumulating oligomeric α-synuclein may mediate early synaptic pathology in Parkinson’s disease and dementia with Lewy bodies by disrupting synaptic vesicles. This oligomer-prone model might be useful for evaluating therapies directed at oligomer reduction. PMID:24662516

Accumulation of oligomer-prone α-synuclein exacerbates synaptic and neuronal degeneration in vivo.

PubMed

Rockenstein, Edward; Nuber, Silke; Overk, Cassia R; Ubhi, Kiren; Mante, Michael; Patrick, Christina; Adame, Anthony; Trejo-Morales, Margarita; Gerez, Juan; Picotti, Paola; Jensen, Poul H; Campioni, Silvia; Riek, Roland; Winkler, Jürgen; Gage, Fred H; Winner, Beate; Masliah, Eliezer

2014-05-01

In Parkinson's disease and dementia with Lewy bodies, α-synuclein aggregates to form oligomers and fibrils; however, the precise nature of the toxic α-synuclein species remains unclear. A number of synthetic α-synuclein mutations were recently created (E57K and E35K) that produce species of α-synuclein that preferentially form oligomers and increase α-synuclein-mediated toxicity. We have shown that acute lentiviral expression of α-synuclein E57K leads to the degeneration of dopaminergic neurons; however, the effects of chronic expression of oligomer-prone α-synuclein in synapses throughout the brain have not been investigated. Such a study could provide insight into the possible mechanism(s) through which accumulation of α-synuclein oligomers in the synapse leads to neurodegeneration. For this purpose, we compared the patterns of neurodegeneration and synaptic damage between a newly generated mThy-1 α-synuclein E57K transgenic mouse model that is prone to forming oligomers and the mThy-1 α-synuclein wild-type mouse model (Line 61), which accumulates various forms of α-synuclein. Three lines of α-synuclein E57K (Lines 9, 16 and 54) were generated and compared with the wild-type. The α-synuclein E57K Lines 9 and 16 were higher expressings of α-synuclein, similar to α-synuclein wild-type Line 61, and Line 54 was a low expressing of α-synuclein compared to Line 61. By immunoblot analysis, the higher-expressing α-synuclein E57K transgenic mice showed abundant oligomeric, but not fibrillar, α-synuclein whereas lower-expressing mice accumulated monomeric α-synuclein. Monomers, oligomers, and fibrils were present in α-synuclein wild-type Line 61. Immunohistochemical and ultrastructural analyses demonstrated that α-synuclein accumulated in the synapses but not in the neuronal cells bodies, which was different from the α-synuclein wild-type Line 61, which accumulates α-synuclein in the soma. Compared to non-transgenic and lower-expressing mice, the higher-expressing α-synuclein E57K mice displayed synaptic and dendritic loss, reduced levels of synapsin 1 and synaptic vesicles, and behavioural deficits. Similar alterations, but to a lesser extent, were seen in the α-synuclein wild-type mice. Moreover, although the oligomer-prone α-synuclein mice displayed neurodegeneration in the frontal cortex and hippocampus, the α-synuclein wild-type only displayed neuronal loss in the hippocampus. These results support the hypothesis that accumulating oligomeric α-synuclein may mediate early synaptic pathology in Parkinson's disease and dementia with Lewy bodies by disrupting synaptic vesicles. This oligomer-prone model might be useful for evaluating therapies directed at oligomer reduction.

Distinct Internalization Pathways of Human Amylin Monomers and Its Cytotoxic Oligomers in Pancreatic Cells

PubMed Central

Trikha, Saurabh; Jeremic, Aleksandar M.

2013-01-01

Toxic human amylin oligomers and aggregates are implicated in the pathogenesis of type 2 diabetes mellitus (TTDM). Although recent studies have shown that pancreatic cells can recycle amylin monomers and toxic oligomers, the exact uptake mechanism and trafficking routes of these molecular forms and their significance for amylin toxicity are yet to be determined. Using pancreatic rat insulinoma (RIN-m5F) beta (β)-cells and human islets as model systems we show that monomers and oligomers cross the plasma membrane (PM) through both endocytotic and non-endocytotic (translocation) mechanisms, the predominance of which is dependent on amylin concentrations and incubation times. At low (≤100 nM) concentrations, internalization of amylin monomers in pancreatic cells is completely blocked by the selective amylin-receptor (AM-R) antagonist, AC-187, indicating an AM-R dependent mechanism. In contrast at cytotoxic (µM) concentrations monomers initially (1 hour) enter pancreatic cells by two distinct mechanisms: translocation and macropinocytosis. However, during the late stage (24 hours) monomers internalize by a clathrin-dependent but AM-R and macropinocytotic independent pathway. Like monomers a small fraction of the oligomers initially enter cells by a non-endocytotic mechanism. In contrast a majority of the oligomers at both early (1 hour) and late times (24 hours) traffic with a fluid-phase marker, dextran, to the same endocytotic compartments, the uptake of which is blocked by potent macropinocytotic inhibitors. This led to a significant increase in extra-cellular PM accumulation, in turn potentiating amylin toxicity in pancreatic cells. Our studies suggest that macropinocytosis is a major but not the only clearance mechanism for both amylin’s molecular forms, thereby serving a cyto-protective role in these cells. PMID:24019897

Protection against the synaptic targeting and toxicity of Alzheimer's-associated Aβ oligomers by insulin mimetic chiro-inositols

PubMed Central

Pitt, Jason; Thorner, Michael; Brautigan, David; Larner, Joseph; Klein, William L.

2013-01-01

Alzheimer's disease (AD) is a progressive dementia that correlates highly with synapse loss. This loss appears due to the synaptic accumulation of toxic Aβ oligomers (ADDLs), which damages synapse structure and function. Although it has been reported that oligomer binding and toxicity can be prevented by stimulation of neuronal insulin signaling with PPARγ agonists, these agonists have problematic side effects. We therefore investigated the therapeutic potential of chiro-inositols, insulin-sensitizing compounds safe for human consumption. Chiro-inositols have been studied extensively for treatment of diseases associated with peripheral insulin resistance, but their insulin mimetic function in memory-relevant central nervous system (CNS) cells is unknown. Here we demonstrate that mature cultures of hippocampal neurons respond to d-chiro-inositol (DCI), pinitol (3-O-methyl DCI), and the inositol glycan INS-2 (pinitol β-1-4 galactosamine) with increased phosphorylation in key upstream components in the insulin-signaling pathway (insulin receptor, insulin receptor substrate-1, and Akt). Consistent with insulin stimulation, DCI treatment promotes rapid withdrawal of dendritic insulin receptors. With respect to neuroprotection, DCI greatly enhances the ability of insulin to prevent ADDL-induced synapse damage (EC50 of 90 nM). The mechanism comprises inhibition of oligomer binding at synapses and requires insulin/IGF signaling. DCI showed no effects on Aβ oligomerization. We propose that inositol glycans and DCI, a compound already established as safe for human consumption, have potential as AD therapeutics by protecting CNS synapses against Aβ oligomers through their insulin mimetic activity.—Pitt, J., Thorner, M., Brautigan, D., Larner, J., Klein, W. L. Protection against the synaptic targeting and toxicity of Alzheimer's-associated Aβ oligomers by insulin mimetic chiro-inositols. PMID:23073831

Comparative analyses of quaternary arrangements in homo-oligomeric proteins in superfamilies: Functional implications.

PubMed

Sudha, Govindarajan; Srinivasan, Narayanaswamy

2016-09-01

A comprehensive analysis of the quaternary features of distantly related homo-oligomeric proteins is the focus of the current study. This study has been performed at the levels of quaternary state, symmetry, and quaternary structure. Quaternary state and quaternary structure refers to the number of subunits and spatial arrangements of subunits, respectively. Using a large dataset of available 3D structures of biologically relevant assemblies, we show that only 53% of the distantly related homo-oligomeric proteins have the same quaternary state. Considering these homologous homo-oligomers with the same quaternary state, conservation of quaternary structures is observed only in 38% of the pairs. In 36% of the pairs of distantly related homo-oligomers with different quaternary states the larger assembly in a pair shows high structural similarity with the entire quaternary structure of the related protein with lower quaternary state and it is referred as "Russian doll effect." The differences in quaternary state and structure have been suggested to contribute to the functional diversity. Detailed investigations show that even though the gross functions of many distantly related homo-oligomers are the same, finer level differences in molecular functions are manifested by differences in quaternary states and structures. Comparison of structures of biological assemblies in distantly and closely related homo-oligomeric proteins throughout the study differentiates the effects of sequence divergence on the quaternary structures and function. Knowledge inferred from this study can provide insights for improved protein structure classification and function prediction of homo-oligomers. Proteins 2016; 84:1190-1202. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Oligomerisation of Synaptobrevin-2 Studied by Native Mass Spectrometry and Chemical Cross-Linking

NASA Astrophysics Data System (ADS)

Wittig, Sabine; Haupt, Caroline; Hoffmann, Waldemar; Kostmann, Susann; Pagel, Kevin; Schmidt, Carla

2018-06-01

Synaptobrevin-2 is a key player in signal transmission in neurons. It forms, together with SNAP25 and Syntaxin-1A, the neuronal soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex and mediates exocytosis of synaptic vesicles with the pre-synaptic membrane. While Synaptobrevin-2 is part of a four-helix bundle in this SNARE complex, it is natively unstructured in the absence of lipids or other SNARE proteins. Partially folded segments, presumably SNARE complex formation intermediates, as well as formation of Synaptobrevin-2 dimers and oligomers, were identified in previous studies. Here, we employ three Synaptobrevin-2 variants—the full-length protein Syb(1-116), the soluble, cytosolic variant Syb(1-96) as well as a shorter version Syb(49-96) containing structured segments but omitting a trigger site for SNARE complex formation—to study oligomerisation in the absence of interaction partners or when incorporated into the lipid bilayer of liposomes. Combining native mass spectrometry with chemical cross-linking, we find that the truncated versions show increased oligomerisation. Our findings from both techniques agree well and confirm the presence of oligomers in solution while membrane-bound Synaptobrevin-2 is mostly monomeric. Using ion mobility mass spectrometry, we could further show that lower charge states of Syb(49-96) oligomers, which most likely represent solution structures, follow an isotropic growth curve suggesting that they are intrinsically disordered. From a technical point of view, we show that the combination of native ion mobility mass spectrometry with chemical cross-linking is well-suited for the analysis of protein homo-oligomers. [Figure not available: see fulltext.

Tobacco class I cytosolic small heat shock proteins are under transcriptional and translational regulations in expression and heterocomplex prevails under the high-temperature stress condition in vitro.

PubMed

Park, Soo Min; Kim, Keun Pill; Joe, Myung Kuk; Lee, Mi Ok; Koo, Hyun Jo; Hong, Choo Bong

2015-04-01

Seven genomic clones of tobacco (Nicotiana tabacum W38) cytosolic class I small heat shock proteins (sHSPs), probably representing all members in the class, were isolated and found to have 66 to 92% homology between their nucleotide sequences. Even though all seven sHSP genes showed heat shock-responsive accumulation of their transcripts and proteins, each member showed discrepancies in abundance and timing of expression upon high-temperature stress. This was mainly the result of transcriptional regulation during mild stress conditions and transcriptional and translational regulation during strong stress conditions. Open reading frames (ORFs) of these genomic clones were expressed in Escherichia coli and the sHSPs were purified from E. coli. The purified tobacco sHSPs rendered citrate synthase and luciferase soluble under high temperatures. At room temperature, non-denaturing pore exclusion polyacrylamide gel electrophoresis on three sHSPs demonstrated that the sHSPs spontaneously formed homo-oligomeric complexes of 200 ∼ 240 kDa. However, under elevated temperatures, hetero-oligomeric complexes between the sHSPs gradually prevailed. Atomic force microscopy showed that the hetero-oligomer of NtHSP18.2/NtHSP18.3 formed a stable oligomeric particle similar to that of the NtHSP18.2 homo-oligomer. These hetero-oligomers positively influenced the revival of thermally inactivated luciferase. Amino acid residues mainly in the N-terminus are suggested for the exchange of the component sHSPs and the formation of dominant hetero-oligomers under high temperatures. © 2014 John Wiley & Sons Ltd.

[Effects of aluminium chloride on the methylation of app in hippocampal of rats].

PubMed

Yang, Xiaojuan; Yuan, Yuzhou; Niu, Qiao

2016-05-01

To study the effect of aluminum chloride on amyloid precursor protein ( APP ) promoter methylation and the content of amyloid beta-protein (Abeta) in hippocampus of rats. Forty male SPF grade SD rats were divided into four groups: control group (0.9% NaCl), 10 mg/kg AlCl3 group, 20 mg/kg AlCl3 group, and 30 mg/kg AlCl3 group, respectively. After treatment for 8 weeks, the APP methylation level and expressions of APP mRNA was detected by methylation specific PCR and quantitative real time PCR, respectively. The content of APP and Abeta were detected with enzym-linked immunosorbent assay (ELISA). With the increase of the content of aluminium chloride, the escape latency were significantly prolong (P < 0.05), numbers of traversing flat in AlCl3 20 mg/kg and AlCl3 30 mg/kg group high and were significantly decreased (P < 0.05), the methylation level of APP contaminated by AlCl3 were decreased (chi2 = 27.61, P < 0.05), the level of APP methylation in 30 mg/kg AlCl3 group was lower than three groups (P < 0.01). With the increase of aluminium chloride, the level of APP methylation were decreased (chi2 = 19.08, P < 0.01). With the increase of the content of aluminium chloride, the methylation level of APP treated with 20 mg/kg AlCl3 and 30 mg/kg AlCl3 were decreased compared with control group (P < 0.05), the level of APP methylation in 30 mg/kg AlCl3 group was lower than 10mg/kg AlCl3 group (P < 0.05), the APP mRNA expression level in AlCl3 group was of statistical significance compared to the control group (F = 8.973, P < 0.05), the level of APP mRNA in 30 mg/kg AlCl3 were higher than 10 mg/kg AlCl3 (P < 0.05). Compared with the control group, the content of APP and Abeta in hippocampus of AlCl3 group were increased (F = 11.14, P = 0. 032, F = 17.82, P = 0.018), and 30 mg/kg AlCl3 group were higher than 10 mg/kg AlCl3 (P < 0.05), the content of APP in 20 mg/kg AlCl3 group were higher than 10 mg/kg AlCl3 (P < 0.05). The result of immunohistochemistry revealed that the grey scale in hippocampus, which suggested that the deposition of Abeta was the most in 20 mg/kg AlCl3 group and 30 mg/kg AlCl3 group. Aluminium chloride might cause APP promoter methylation decline, affect the APP mRNA and APP expression increased and result in Abeta deposition in hippocampal.

Familial Danish dementia: a novel form of cerebral amyloidosis associated with deposition of both amyloid-Dan and amyloid-beta.

PubMed

Holton, Janice L; Lashley, Tammaryn; Ghiso, Jorge; Braendgaard, Hans; Vidal, Ruben; Guerin, Christopher J; Gibb, Graham; Hanger, Diane P; Rostagno, Agueda; Anderton, Brian H; Strand, Catherine; Ayling, Hilary; Plant, Gordon; Frangione, Blas; Bojsen-Møller, Marie; Revesz, Tamas

2002-03-01

Familial Danish dementia (FDD) is pathologically characterized by widespread cerebral amyloid angiopathy (CAA), parenchymal protein deposits, and neurofibrillary degeneration. FDD is associated with a mutation of the BRI2 gene located on chromosome 13. In FDD there is a decamer duplication, which abolishes the normal stop codon, resulting in an extended precursor protein and the release of an amyloidogenic fragment, ADan. The aim of this study was to describe the major neuropathological changes in FDD and to assess the distribution of ADan lesions, neurofibrillary pathology, glial, and microglial response using conventional techniques, immunohistochemistry, confocal microscopy, and immunoelectron microscopy. We showed that ADan is widely distributed in the central nervous system (CNS) in the leptomeninges, blood vessels, and parenchyma. A predominance of parenchymal pre-amyloid (non-fibrillary) lesions was found. Abeta was also present in a proportion of both vascular and parenchymal lesions. There was severe neurofibrillary pathology, and tau immunoblotting revealed a triplet electrophoretic migration pattern comparable with PHF-tau. FDD is a novel form of CNS amyloidosis with extensive neurofibrillary degeneration occurring with parenchymal, predominantly pre-amyloid rather than amyloid, deposition. These findings support the notion that parenchymal amyloid fibril formation is not a prerequisite for the development of neurofibrillary tangles. The significance of concurrent ADan and Abeta deposition in FDD is under further investigation.

Generation and initial characterization of FDD knock in mice.

PubMed

Giliberto, Luca; Matsuda, Shuji; Vidal, Ruben; D'Adamio, Luciano

2009-11-18

Mutations in the integral membrane protein 2B, also known as BRI(2), a type II trans-membrane domain protein cause two autosomal dominant neurodegenerative diseases, Familial British and Danish Dementia. In these conditions, accumulation of a C-terminal peptide (ABri and ADan) cleaved off from the mutated precursor protein by the pro-protein convertase furin, leads to amyloid deposition in the walls of blood vessels and parenchyma of the brain. Recent advances in the understanding of the generation of amyloid in Alzheimer's disease has lead to the finding that BRI(2) interacts with the Amyloid Precursor Protein (APP), decreasing the efficiency of APP processing to generate Abeta. The interaction between the two precursors, APP and BRI(2), and possibly between Abeta and ABri or ADan, could be important in influencing the rate of amyloid production or the tendency of these peptides to aggregate. We have generated the first BRI(2) Danish Knock-In (FDD(KI)) murine model of FDD, expressing the pathogenic decamer duplication in exon 6 of the BRI(2) gene. FDD(KI) mice do not show any evident abnormal phenotype, with normal brain histology and no detectable amyloid deposition in blood vessel walls or parenchyma. This new murine mouse model will be important to further understand the interaction between APP and BRI(2), and to provide insights into the molecular basis of FDD.

Phenylethynyl amine

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Havens, Stephen J. (Inventor)

1997-01-01

Four phenylethynyl amine compounds--3 and 4-aminophenoxy-4'-phenylethynylbenzophenone, and 3 and 4-amino-4'-phenylethynylbenzophenone--were readily prepared and were used to endcap imide oligomers. Phenylethynyl-terminated amide acid oligomers and phenylethynyl-terminated imide oligomers with various molecular weights and compositions were prepared and characterized. These oligomers were cured at 300.degree. C. to 400.degree. C. to provide crosslinked polyimides with excellent solvent resistance, high strength and modulus and good high temperature properties. Adhesive panels, composites, films and moldings from these phenylethynyl terminated imide oligomers gave excellent mechanical performance.

Preparation of Stable Amyloid-β Oligomers Without Perturbative Methods.

PubMed

Kotler, Samuel A; Ramamoorthy, Ayyalusamy

2018-01-01

Soluble amyloid-β (Aβ) oligomers have become a focal point in the study of Alzheimer's disease due to their ability to elicit cytotoxicity. A number of recent studies have concentrated on the structural characterization of soluble Aβ oligomers to gain insight into their mechanism of toxicity. Consequently, providing reproducible protocols for the preparation of such oligomers is of utmost importance. The method presented in this chapter details a protocol for preparing an Aβ oligomer, with a primarily disordered secondary structure, without the need for chemical modification or amino acid substitution. Due to the stability of these disordered Aβ oligomers and the reproducibility with which they form, they are amenable for biophysical and high-resolution structural characterization.

Electrophoretic studies of polygalacturonate oligomers and their interactions with metal ions.

PubMed

Wiedmer, S K; Cassely, A; Hong, M; Novotny, M V; Riekkola, M L

2000-09-01

Polygalacturonic acid, a linear homopolysaccharide, was investigated by capillary electrophoresis (CE) using linear polyacrylamide-coated capillaries and laser-induced fluorescence (LIF) detection. A successful separation of its fluorescently labeled oligomers was achieved through sieving in polyacrylamide entangled matrices. The reaction conditions for the derivatization of polygalacturonic acid were optimized. In studying the interactions between polygalacturonic acid and various metal ions, the end-label, free-solution electrophoretic (ELFSE) technique, developed earlier in our laboratory (Sudor, J., Novotny, M. V., Anal. Chem. 1995, 67, 4205-4209) was found preferable to the sieving method. ELFSE is fast and convenient in that no polymer solutions are needed for the separation. The investigation showed that for the moderately large oligomers, the strongest binding occurred with calcium and cadmium ions, while the smallest interaction was observed with magnesium ions.

Chemistry and technology of radiation processed composite materials

NASA Astrophysics Data System (ADS)

Czvikovszky, T.

Composite materials of synthetics (based on monomers, oligomers and thermoplastics) and of natural polymers (wood and other fibrous cellulosics) prepared by radiation processing, offer valuable structural materials with enhanced coupling forces between the components. The applied polymer chemistry of such composites shows several common features with that of radiation grafting. E.g. the polymerization rate of oligomer-monomer mixtures in wood remains in most cases proportional to the square-root of the initiating dose-rate, just as in the simultaneous grafting, demonstrating that the chain termination kinetics remain regularly bimolecular in the corresponding dose-rate ranges. In the processing experiences of such composites, low dose requirement, easy process-control, and good technical feasibility have been found for composites of wood with oligomer-monomer mixtures, for coconut fibres with unsaturated polyesters and for pretreated wood fibre with polypropylene.

Rapamycin-induced oligomer formation system of FRB-FKBP fusion proteins.

PubMed

Inobe, Tomonao; Nukina, Nobuyuki

2016-07-01

Most proteins form larger protein complexes and perform multiple functions in the cell. Thus, artificial regulation of protein complex formation controls the cellular functions that involve protein complexes. Although several artificial dimerization systems have already been used for numerous applications in biomedical research, cellular protein complexes form not only simple dimers but also larger oligomers. In this study, we showed that fusion proteins comprising the induced heterodimer formation proteins FRB and FKBP formed various oligomers upon addition of rapamycin. By adjusting the configuration of fusion proteins, we succeeded in generating an inducible tetramer formation system. Proteins of interest also formed tetramers by fusing to the inducible tetramer formation system, which exhibits its utility in a broad range of biological applications. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Effect of light chain V region duplication on IgG oligomerization and in vivo efficacy.

PubMed

Shuford, W; Raff, H V; Finley, J W; Esselstyn, J; Harris, L J

1991-05-03

A human immunoglobulin G1 (IgG1) antibody oligomer was isolated from a transfected myeloma cell line that produced a monoclonal antibody to group B streptococci. Compared to the IgG1 monomer, the oligomer was significantly more effective at protecting neonatal rats from infection in vivo. The oligomer was also shown to cross the placenta and to be stable in neonatal rats. Immunochemical analysis and complementary DNA sequencing showed that the transfected cell line produced two distinct kappa light chains: a normal light chain (Ln) with a molecular mass of 25 kilodaltons and a 37-kilodalton species (L37), the domain composition of which was variable-variable-constant (V-V-C). Cotransfection of vectors encoding the heavy chain and L37 resulted in production of oligomeric IgG.

Electrografting of conductive oligomers and polymers using diazonium electroreduction

NASA Astrophysics Data System (ADS)

Lacroix, Jean Christophe; Trippe-Allard, Gaelle; Ghilane, Jalal; Martin, Pascal

2014-03-01

This paper describes the attachment of conjugated oligomers onto electrode surface through the reduction of diazonium compounds. In this connection some properties of conjugated oligomers and of layers grafted through diazonium electroreduction will first be briefly presented. The electrochemical behavior of conjugated oligomers grafted on a surface using diazonium electroreduction will then be discussed.

Enzymatic production of defined chitosan oligomers with a specific pattern of acetylation using a combination of chitin oligosaccharide deacetylases

NASA Astrophysics Data System (ADS)

Hamer, Stefanie Nicole; Cord-Landwehr, Stefan; Biarnés, Xevi; Planas, Antoni; Waegeman, Hendrik; Moerschbacher, Bruno Maria; Kolkenbrock, Stephan

2015-03-01

Chitin and chitosan oligomers have diverse biological activities with potentially valuable applications in fields like medicine, cosmetics, or agriculture. These properties may depend not only on the degrees of polymerization and acetylation, but also on a specific pattern of acetylation (PA) that cannot be controlled when the oligomers are produced by chemical hydrolysis. To determine the influence of the PA on the biological activities, defined chitosan oligomers in sufficient amounts are needed. Chitosan oligomers with specific PA can be produced by enzymatic deacetylation of chitin oligomers, but the diversity is limited by the low number of chitin deacetylases available. We have produced specific chitosan oligomers which are deacetylated at the first two units starting from the non-reducing end by the combined use of two different chitin deacetylases, namely NodB from Rhizobium sp. GRH2 that deacetylates the first unit and COD from Vibrio cholerae that deacetylates the second unit starting from the non-reducing end. Both chitin deacetylases accept the product of each other resulting in production of chitosan oligomers with a novel and defined PA. When extended to further chitin deacetylases, this approach has the potential to yield a large range of novel chitosan oligomers with a fully defined architecture.

Montmorillonite Clay-Catalyzed Synthesis of RNA Oligomers

NASA Astrophysics Data System (ADS)

Ferris, J. P.; Miyakawa, S.; Huang, W.; Joshi, P.

2005-12-01

It is proposed that catalysis had a central role in the origins of life. This will be illustrated using the montmorillonite clay-catalyzed synthesis of oligomers of RNA from activated monomers, (Ferris and Ertem, 1993) a possible step in the origin of the RNA world (Ferris, 2005). Structural analysis of oligomers formed in the reaction of the activated monomer of 5'-AMP with that of 5'-CMP demonstrated that the oligomers formed were not produced by random synthesis but rather the sequences observed were directed by the montmorillonite catalyst (Miyakawa and Ferris, 2003). RNA oligomers containing up to 40 mers have been synthesized in reactions performed in water at 25 oC in the presence of montmorillonite (Huang and Ferris, 2003). Analysis of the structure elements in these oligomers from the 7 to 39 mers showed that they did not vary. Reaction of D, L-mixtures of the activated monomers of A and U resulted in the formation of greater amounts of the homochiral amounts of dimers and trimers of A than would be expected if there was no selectivity in the reaction. A limited number of the dimers and trimers of U were also formed but here the selectivity was for the formation of an excess of heterochiral products (Joshi et al., 2000). A postulate that explains why homochiral trimers of U are not formed and the significance of catalysis in prebiotic synthesis will be discussed. Ferris, J.P. (2005) Origins of life, molecular basis of. In R.A. Meyers, Ed. Encyclopedia of Molecular Cell Biology and Molecular Medicine, 10. Wiley-VCH Verlag, Weinheim, Germany. Ferris, J.P., and Ertem, G. (1993) Montmorillonite catalysis of RNA oligomer formation in aqueous solution. A model for the prebiotic formation of RNA. J. Am. Chem. Soc., 115, 12270-12275. Huang, W., and Ferris, J.P. (2003) Synthesis of 35-40 mers of RNA oligomers from unblocked monomers. A simple approach to the RNA world. Chem. Commun., 1458-1459. Joshi, P.C., Pitsch, S., and Ferris, J.P. (2000) Homochiral selection in the montmorillonite-catalyzed and uncatalyzed prebiotic synthesis of RNA. Chem. Commun., 2497-2498. Miyakawa, S., and Ferris, J.P. (2003) Sequence- and Regioselectivity in the montmorillonite-catalyzed synthesis of RNA. J. Am. Chem. Soc., 125, 8202-8208.

Glycyrrhiza and Uncaria Hook contribute to protective effect of traditional Japanese medicine yokukansan against amyloid β oligomer-induced neuronal death.

PubMed

Kanno, Hitomi; Kawakami, Zenji; Iizuka, Seiichi; Tabuchi, Masahiro; Mizoguchi, Kazushige; Ikarashi, Yasushi; Kase, Yoshio

2013-08-26

Yokukansan, a traditional Japanese (Kampo) medicine, composed of seven medicinal herbs has been traditionally used to treat neurosis, insomnia, and night crying and irritability in children. Recently, this medicine has been reported to improve the behavioral and psychological symptoms of dementia (BPSD) that often become problematic in patients with Alzheimer's disease (AD). Amyloid β (Aβ) oligomers, which are extremely toxic to neurons, are involved in neurodegeneration in AD. In animals, yokukansan has been proven to improve memory impairments and BPSD-like behavior in transgenic mice overexpressing amyloid precursor protein and mice intracerebroventricularly injected with Aβ oligomers. These results suggest that yokukansan is potentially able to reduce the neurotoxicity of Aβ oligomers. Therefore, the present study aimed to explore the improving effects brought by yokukansan that consists of seven herbs for Aβ oligomer-induced neurotoxicity in vitro and to identify the candidate herbs in yokukansan's action. Primary cultured rat cortical neurons were used. Neurotoxicity induced by Aβ oligomers (3µM) and improving effects of yokukansan (300-1000 µg/mL) and its constituent herbs were evaluated in MTT assay, DNA fragmentation analysis, and electron microscopic analysis at 48h after treatment with Aβ oligomers and drugs. Moreover, changes in expression of genes related to endoplasmic reticulum (ER) stress and in caspase-3 activity that is the enzyme closely related to apoptosis were analyzed to investigate the underlying mechanisms. Yokukansan ameliorated Aβ oligomer-induced neuronal damage in a dose-dependent manner in the MTT assay. This drug also suppressed DNA fragmentation caused by Aβ oligomers. Electron microscopic analysis suggested that yokukansan reduced karyopyknosis and the expansion of rough ER caused by Aβ oligomers. However, neither Aβ oligomers nor yokukansan affected the mRNA expression of any ER stress-related genes, including CHOP and GRP78. On the other hand, yokukansan dose-dependently suppressed Aβ oligomer-induced activation of caspase-3. Among the seven constituents of yokukansan, Glycyrrhiza and Uncaria Hook (60-200 µg/mL) suppressed Aβ oligomer-induced neuronal damage, DNA fragmentation, karyopyknosis, and caspase-3 activation to almost the same extent as yokukansan. The present results suggest that yokukansan possesses an ameliorative effect against Aβ oligomer-induced neuronal apoptosis through the suppression of caspase-3 activation. Glycyrrhiza and Uncaria Hook may, at least in part, contribute to the neuroprotective effect of yokukansan. These mechanisms may underlie the improving effects of yokukansan on memory impairment and BPSD-like behaviors induced by Aβ oligomers. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Curcumin inhibits aggregation of alpha-synuclein.

PubMed

Pandey, Neeraj; Strider, Jeffrey; Nolan, William C; Yan, Sherry X; Galvin, James E

2008-04-01

Aggregation of amyloid-beta protein (Abeta) is a key pathogenic event in Alzheimer's disease (AD). Curcumin, a constituent of the Indian spice Turmeric is structurally similar to Congo Red and has been demonstrated to bind Abeta amyloid and prevent further oligomerization of Abeta monomers onto growing amyloid beta-sheets. Reasoning that oligomerization kinetics and mechanism of amyloid formation are similar in Parkinson's disease (PD) and AD, we investigated the effect of curcumin on alpha-synuclein (AS) protein aggregation. In vitro model of AS aggregation was developed by treatment of purified AS protein (wild-type) with 1 mM Fe3+ (Fenton reaction). It was observed that the addition of curcumin inhibited aggregation in a dose-dependent manner and increased AS solubility. The aggregation-inhibiting effect of curcumin was next investigated in cell culture utilizing catecholaminergic SH-SY5Y cell line. A model system was developed in which the red fluorescent protein (DsRed2) was fused with A53T mutant of AS and its aggregation examined under different concentrations of curcumin. To estimate aggregation in an unbiased manner, a protocol was developed in which the images were captured automatically through a high-throughput cell-based screening microscope. The obtained images were processed automatically for aggregates within a defined dimension of 1-6 microm. Greater than 32% decrease in mutant alpha-synuclein aggregation was observed within 48 h subsequent to curcumin addition. Our data suggest that curcumin inhibits AS oligomerization into higher molecular weight aggregates and therefore should be further explored as a potential therapeutic compound for PD and related disorders.

The PDAPP mouse model of Alzheimer's disease: locus coeruleus neuronal shrinkage.

PubMed

German, Dwight C; Nelson, Omar; Liang, Fen; Liang, Chang-Lin; Games, Dora

2005-11-28

Alzheimer's disease is characterized by neuronal degeneration in the cerebral cortex and hippocampus and subcortical neuronal degeneration in such nuclei as the locus coeruleus (LC). Transgenic mice overexpressing mutant human amyloid precursor protein V717F, PDAPP mice, develop several Alzheimer's disease-like lesions. The present study sought to determine whether there is also loss of LC noradrenergic neurons or evidence of degenerative changes in these animals. PDAPP hemizygous and wild-type littermate control mice were examined at 23 months of age, at a time when there are numerous amyloid-beta (Abeta) plaques in the neocortex and hippocampus. Tissue sections were stained immunohistochemically with an antibody against tyrosine hydroxylase (TH) to identify LC neurons. Computer imaging procedures were used to count the TH-immunoreactive somata in sections through the rostral-caudal extent of the nucleus. There was no loss of LC neurons in the hemizygous mice. In a second experiment, homozygous PDAPP and wild-type mice were examined, at 2 months and 24 months of age. Again there was no age-related loss of neurons in the homozygous animals. In the portion of the LC where neurons reside that project to the cortex and hippocampus, however, the neurons were decreased in size selectively in the 24-month-old transgenic animals. These data indicate that overt LC cell loss does not occur following abundant overexpression of Abeta peptide. However, the selective size reduction of the LC neuronal population projecting to cortical and hippocampal regions containing Abeta-related neuropathology implies that these cells may be subjected to a retrograde-mediated stress. Copyright 2005 Wiley-Liss, Inc.

Survey of commercially available chocolate- and cocoa-containing products in the United States. 2. Comparison of flavan-3-ol content with nonfat cocoa solids, total polyphenols, and percent cacao.

PubMed

Miller, Kenneth B; Hurst, W Jeffrey; Flannigan, Nancy; Ou, Boxin; Lee, C Y; Smith, Nancy; Stuart, David A

2009-10-14

A survey of a broad range of chocolate- and cocoa-containing products marketed in the United States was conducted to provide a more detailed analysis of flavan-3-ol monomers, oligomers, and polymers, which can be grouped into a class of compounds called procyanidins. Samples consisted of the three or four top-selling products within the following six categories: natural cocoa powder, unsweetened baking chocolate, dark chocolate, semisweet baking chips, milk chocolate, and chocolate syrup. Composite samples were characterized for percent fat (% fat), percent nonfat cocoa solids (% NFCS), antioxidant level by ORAC, total polyphenols, epicatechin, catechin, total monomers, and flavan-3-ol oligomers and polymers (procyanidins). On a gram weight basis epicatechin and catechin content of the products follow in decreasing order: cocoa powder > baking chocolate > dark chocolate = baking chips > milk chocolate > chocolate syrup. Analysis of the monomer and oligomer profiles within product categories shows there are two types of profiles: (1) products that have high monomers with decreasing levels of oligomers and (2) products in which the level of dimers is equal to or greater than the monomers. Results show a strong correlation (R(2) = 0.834) of epicatechin to the level of % NFCS and also very good correlations for N = 2-5 oligomers to % NFCS. A weaker correlation was observed for catechin to % NFCS (R(2) = 0.680). Other analyses show a similar high degree of correlation with epicatechin and N = 2-5 oligomers to total polyphenols, with catechin being less well correlated to total polyphenols. A lesser but still good correlation exists between the calculated percent cacao (calcd % cacao) content, a proxy for percent cacao, and these same flavanol measures, with catechin again showing a lesser degree of correlation to calcd % cacao. Principal component analysis (PCA) shows that the products group discretely into five classes: (1) cocoa powder, (2) baking chocolate, (3) dark chocolate and semisweet chips, (4) milk chocolates, and (5) syrup. PCA also shows that most factors group closely together including the antioxidant activity, total polyphenols, and the flavan-3-ol measures with the exception of catechin and % fat in the product, which group separately. Because catechin distribution appears to be different from the other flavan-3-ol measures, an analysis of the epicatechin to catechin ratio was done, indicating there is a >5-fold variation in this measure across the products studied. The cocoa-containing products tested range from cocoa powder with 227.34 +/- 17.23 mg of procyanidins per serving to 25.75 +/- 9.91 mg of procyanidins per serving for chocolate syrup. These results are discussed with respect to other studies on commercial products, the bioavailability of the flavanols, and the possible role of processing on the amount of catechin in products.

Molecular size is important for the safety and selective inhibition of intrinsic factor Xase for fucosylated chondroitin sulfate.

PubMed

Yan, Lufeng; Li, Junhui; Wang, Danli; Ding, Tian; Hu, Yaqin; Ye, Xingqian; Linhardt, Robert J; Chen, Shiguo

2017-12-15

Fucosylated chondroitin sulfate from sea cucumber Isostichopus badionotus (FCS-Ib) showed potent anticoagulant activities without selectivity. The present study focused on developing safe FCS-Ib oligomers showing selective inhibition of intrinsic factor Xase (anti-FXase) prepared through partial N-deacetylation-deaminative cleavage. The N-deacetylation degree was regulated by reaction time, controlling the resulting oligomer distribution. Structure analysis confirmed the selectivity of degradation, and 12 high purity fractions with trisaccharide-repeating units were separated. In vitro anticoagulant assays indicated a decrease in molecular weight (Mw) dramatically reduced activated partial thromboplastin time (APTT), thrombin time (TT), AT-dependent anti-FIIa and anti-FXa activities, while the oligomers retained potent anti-FXase activity until they fell below 3kDa. Meanwhile, human FXII activation and platelet aggregation were markedly reduced with decreasing Mw and were moderate when under 12.0kDa. Thus, fragments of 3-12.0kDa should be safe and effective as selective inhibitors of intrinsic tenase complex for application as clinical anticoagulants. Copyright © 2017 Elsevier Ltd. All rights reserved.

Oligomer formation of Clostridium perfringens epsilon-toxin is induced by activation of neutral sphingomyelinase.

PubMed

Takagishi, Teruhisa; Oda, Masataka; Takehara, Masaya; Kobayashi, Keiko; Nagahama, Masahiro

2016-11-01

Clostridium perfringens epsilon-toxin is responsible for fatal enterotoxemia in ungulates. The toxin forms a heptamer in the lipid rafts of Madin-Darby Canine Kidney (MDCK) cells, leading to cell death. Here, we showed that epsilon-toxin requires neutral sphingomyelinase (nSMase) activity during oligomerization. We tested the role of nSMase in the oligomerization of epsilon-toxin using specific inhibitors, knockdown of nSMase, formation of ceramide, and localization of epsilon-toxin and ceramide by immunofluorescence staining. Epsilon-toxin induced the production of ceramide is a dose- and time-dependent manner in ACHN cells. GW4869, an inhibitor of nSMase, inhibited ceramide production induced by the toxin. GW4869 and knockdown of nSMase blocked toxin-induced cell death and oligomer formation of epsilon-toxin. Confocal microscopy images showed that the toxin induced ceramide clustering and colocalized with ceramide. These results demonstrated that oligomer formation of epsilon-toxin is facilitated by the production of ceramide through activation of nSMase caused by the toxin. Inhibitors of nSMase may confer protection against infection. Copyright © 2016 Elsevier B.V. All rights reserved.

Extracellular alpha-synuclein oligomers modulate synaptic transmission and impair LTP via NMDA-receptor activation.

PubMed

Diógenes, Maria José; Dias, Raquel B; Rombo, Diogo M; Vicente Miranda, Hugo; Maiolino, Francesca; Guerreiro, Patrícia; Näsström, Thomas; Franquelim, Henri G; Oliveira, Luís M A; Castanho, Miguel A R B; Lannfelt, Lars; Bergström, Joakim; Ingelsson, Martin; Quintas, Alexandre; Sebastião, Ana M; Lopes, Luísa V; Outeiro, Tiago Fleming

2012-08-22

Parkinson's disease (PD) is the most common representative of a group of disorders known as synucleinopathies, in which misfolding and aggregation of α-synuclein (a-syn) in various brain regions is the major pathological hallmark. Indeed, the motor symptoms in PD are caused by a heterogeneous degeneration of brain neurons not only in substantia nigra pars compacta but also in other extrastriatal areas of the brain. In addition to the well known motor dysfunction in PD patients, cognitive deficits and memory impairment are also an important part of the disorder, probably due to disruption of synaptic transmission and plasticity in extrastriatal areas, including the hippocampus. Here, we investigated the impact of a-syn aggregation on AMPA and NMDA receptor-mediated rat hippocampal (CA3-CA1) synaptic transmission and long-term potentiation (LTP), the neurophysiological basis for learning and memory. Our data show that prolonged exposure to a-syn oligomers, but not monomers or fibrils, increases basal synaptic transmission through NMDA receptor activation, triggering enhanced contribution of calcium-permeable AMPA receptors. Slices treated with a-syn oligomers were unable to respond with further potentiation to theta-burst stimulation, leading to impaired LTP. Prior delivery of a low-frequency train reinstated the ability to express LTP, implying that exposure to a-syn oligomers drives the increase of glutamatergic synaptic transmission, preventing further potentiation by physiological stimuli. Our novel findings provide mechanistic insight on how a-syn oligomers may trigger neuronal dysfunction and toxicity in PD and other synucleinopathies.

Enzyme-specific sensors via aggregation of charged p-phenylene ethynylenes.

PubMed

Hill, Eric H; Zhang, Yue; Evans, Deborah G; Whitten, David G

2015-03-11

Chemical and biological sensors are sought for their ability to detect enzymes as biomarkers for symptoms of various disorders, or the presence of chemical pollutants or poisons. p-Phenylene ethynylene oligomers with pendant charged groups have been recently shown to have ideal photophysical properties for sensing. In this study, one anionic and one cationic oligomer are combined with substrates that are susceptible to enzymatic degradation by phospholipases or acetylcholinesterases. The photophysical properties of the J-aggregated oligomers with the substrate are ideal for sensing, with fluorescence quantum yields of the sensors enhanced between 30 and 66 times compared to the oligomers without substrate. The phospholipase sensor was used to monitor the activity of phospholipase A1 and A2 and obtain kinetic information, though phospholipase C did not degrade the sensor. The acetylcholinesterase sensor was used to monitor enzyme activity and was also used to detect the inhibition of acetylcholinesterase by three different inhibitors. Phospholipase A2 is a biomarker for heart and circulatory disease, and acetylcholinesterase is a biomarker for Alzheimer's, and indicative of exposure to certain pesticides and nerve agents. This work shows that phenylene ethynylene oligomers can be tailored to enzyme-specific sensors by careful selection of substrates that induce formation of a molecular aggregate, and that the sensing of enzymes can be extended to enzyme kinetics and detection of inhibition. Furthermore, the aggregates were studied through all-atom molecular dynamics, providing a molecular-level view of the formation of the molecular aggregates and their structure.

The Volumetric Diversity of Misfolded Prion Protein Oligomers Revealed by Pressure Dissociation*

PubMed Central

Torrent, Joan; Lange, Reinhard; Rezaei, Human

2015-01-01

Protein oligomerization has been associated with a wide range of diseases. High pressure approaches offer a powerful tool for deciphering the underlying molecular mechanisms by revealing volume changes associated with the misfolding and assembly reactions. We applied high pressure to induce conformational changes in three distinct β-sheet-rich oligomers of the prion protein PrP, a protein characterized by a variety of infectious quaternary structures that can propagate stably and faithfully and cause diseases with specific phenotypic traits. We show that pressure induces dissociation of the oligomers and leads to a lower volume monomeric PrP state that refolds into the native conformation after pressure release. By measuring the different pressure and temperature sensitivity of the tested PrP oligomers, we demonstrate significantly different void volumes in their quaternary structure. In addition, by focusing on the kinetic and energetic behavior of the pressure-induced dissociation of one specific PrP oligomer, we reveal a large negative activation volume and an increase in both apparent activation enthalpy and entropy. This suggests a transition state ensemble that is less structured and significantly more hydrated than the oligomeric state. Finally, we found that site-specific fluorescent labeling allows monitoring of the transient population of a kinetic intermediate in the dissociation reaction. Our results indicate that defects in atomic packing may deserve consideration as a new factor that influences differences between PrP assemblies and that could be relevant also for explaining the origin of prion strains. PMID:26126829

Brain injury-associated biomarkers of TGF-beta1, S100B, GFAP, NF-L, tTG, AbetaPP, and tau were concomitantly enhanced and the UPS was impaired during acute brain injury caused by Toxocara canis in mice.

PubMed

Liao, Chien-Wei; Fan, Chia-Kwung; Kao, Ting-Chang; Ji, Dar-Der; Su, Kua-Eyre; Lin, Yun-Ho; Cho, Wen-Long

2008-06-24

Because the outcomes and sequelae after different types of brain injury (BI) are variable and difficult to predict, investigations on whether enhanced expressions of BI-associated biomarkers (BIABs), including transforming growth factor beta1 (TGF-beta1), S100B, glial fibrillary acidic protein (GFAP), neurofilament light chain (NF-L), tissue transglutaminases (tTGs), beta-amyloid precursor proteins (AbetaPP), and tau are present as well as whether impairment of the ubiquitin-proteasome system (UPS) is present have been widely used to help delineate pathophysiological mechanisms in various BIs. Larvae of Toxocara canis can invade the brain and cause BI in humans and mice, leading to cerebral toxocariasis (CT). Because the parasitic burden is light in CT, it may be too cryptic to be detected in humans, making it difficult to clearly understand the pathogenesis of subtle BI in CT. Since the pathogenesis of murine toxocariasis is very similar to that in humans, it appears appropriate to use a murine model to investigate the pathogenesis of CT. BIAB expressions and UPS function in the brains of mice inoculated with a single dose of 250 T. canis embryonated eggs was investigated from 3 days (dpi) to 8 weeks post-infection (wpi) by Western blotting and RT-PCR. Results revealed that at 4 and 8 wpi, T. canis larvae were found to have invaded areas around the choroid plexus but without eliciting leukocyte infiltration in brains of infected mice; nevertheless, astrogliosis, an indicator of BI, with 78.9~142.0-fold increases in GFAP expression was present. Meanwhile, markedly increased levels of other BIAB proteins including TGF-beta1, S100B, NF-L, tTG, AbetaPP, and tau, with increases ranging 2.0~12.0-fold were found, although their corresponding mRNA expressions were not found to be present at 8 wpi. Concomitantly, UPS impairment was evidenced by the overexpression of conjugated ubiquitin and ubiquitin in the brain. Further studies are needed to determine whether there is an increased risk of CT progression into neurodegenerative disease because neurodegeneration-associated AbetaPP and phosphorylated tau emerged in the brain.

Chronic Pharmacological mGluR5 Inhibition Prevents Cognitive Impairment and Reduces Pathogenesis in an Alzheimer Disease Mouse Model.

PubMed

Hamilton, Alison; Vasefi, Maryam; Vander Tuin, Cheryl; McQuaid, Robyn J; Anisman, Hymie; Ferguson, Stephen S G

2016-05-31

Beta-amyloid (Aβ) oligomers contribute to the pathophysiology of Alzheimer disease (AD), and metabotropic glutamate receptor 5 (mGluR5) has been shown to act as a receptor for both Aβ oligomers and cellular prion proteins. Furthermore, the genetic deletion of mGluR5 in an APPswe/PS1ΔE9 mouse model of AD improves cognitive function and reduces Aβ plaques and Aβ oligomer concentrations. Here, we show that chronic administration of the orally bioavailable mGluR5-selective negative allosteric modulator CTEP, which is similar in structure, potency, and selectivity to Basimglurant (RO4917523), which is currently in phase II clinical development for major depressive disorder and fragile X syndrome, reverses cognitive decline in APPswe/PS1ΔE9 mice and reduces Aβ plaque deposition and soluble Aβ oligomer concentrations in both APPswe/PS1ΔE9 and 3xTg-AD male mice. These findings suggest that CTEP or its analogue Basimglutant might potentially be an effective therapeutic for the treatment of AD patients. Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.

SERS Detection of Amyloid Oligomers on Metallorganic-Decorated Plasmonic Beads.

PubMed

Guerrini, Luca; Arenal, Raul; Mannini, Benedetta; Chiti, Fabrizio; Pini, Roberto; Matteini, Paolo; Alvarez-Puebla, Ramon A

2015-05-13

Protein misfolded proteins are among the most toxic endogenous species of macromolecules. These chemical entities are responsible for neurodegenerative disorders such as Alzheimer's, Parkinson's, Creutzfeldt-Jakob's and different non-neurophatic amyloidosis. Notably, these oligomers show a combination of marked heterogeneity and low abundance in body fluids, which have prevented a reliable detection by immunological methods so far. Herein we exploit the selectivity of proteins to react with metallic ions and the sensitivity of surface-enhanced Raman spectroscopy (SERS) toward small electronic changes in coordination compounds to design and engineer a reliable optical sensor for protein misfolded oligomers. Our strategy relies on the functionalization of Au nanoparticle-decorated polystyrene beads with an effective metallorganic Raman chemoreceptor, composed by Al(3+) ions coordinated to 4-mercaptobenzoic acid (MBA) with high Raman cross-section, that selectively binds aberrant protein oligomers. The mechanical deformations of the MBA phenyl ring upon complexation with the oligomeric species are registered in its SERS spectrum and can be quantitatively correlated with the concentration of the target biomolecule. The SERS platform used here appears promising for future implementation of diagnostic tools of aberrant species associated with protein deposition diseases, including those with a strong social and economic impact, such as Alzheimer's and Parkinson's diseases.

Driving Chemical Reactions in Plasmonic Nanogaps with Electrohydrodynamic Flow.

PubMed

Thrift, William J; Nguyen, Cuong Q; Darvishzadeh-Varcheie, Mahsa; Zare, Siavash; Sharac, Nicholas; Sanderson, Robert N; Dupper, Torin J; Hochbaum, Allon I; Capolino, Filippo; Abdolhosseini Qomi, Mohammad Javad; Ragan, Regina

2017-11-28

Nanoparticles from colloidal solution-with controlled composition, size, and shape-serve as excellent building blocks for plasmonic devices and metasurfaces. However, understanding hierarchical driving forces affecting the geometry of oligomers and interparticle gap spacings is still needed to fabricate high-density architectures over large areas. Here, electrohydrodynamic (EHD) flow is used as a long-range driving force to enable carbodiimide cross-linking between nanospheres and produces oligomers exhibiting sub-nanometer gap spacing over mm 2 areas. Anhydride linkers between nanospheres are observed via surface-enhanced Raman scattering (SERS) spectroscopy. The anhydride linkers are cleavable via nucleophilic substitution and enable placement of nucleophilic molecules in electromagnetic hotspots. Atomistic simulations elucidate that the transient attractive force provided by EHD flow is needed to provide a sufficient residence time for anhydride cross-linking to overcome slow reaction kinetics. This synergistic analysis shows assembly involves an interplay between long-range driving forces increasing nanoparticle-nanoparticle interactions and probability that ligands are in proximity to overcome activation energy barriers associated with short-range chemical reactions. Absorption spectroscopy and electromagnetic full-wave simulations show that variations in nanogap spacing have a greater influence on optical response than variations in close-packed oligomer geometry. The EHD flow-anhydride cross-linking assembly method enables close-packed oligomers with uniform gap spacings that produce uniform SERS enhancement factors. These results demonstrate the efficacy of colloidal driving forces to selectively enable chemical reactions leading to future assembly platforms for large-area nanodevices.

Green polymer chemistry: investigating the mechanism of radical ring-opening redox polymerization (R3P) of 3,6-dioxa-1,8-octanedithiol (DODT).

PubMed

Rosenthal-Kim, Emily Q; Puskas, Judit E

2015-04-13

The mechanism of the new Radical Ring-opening Redox Polymerization (R3P) of 3,6-dioxa-1,8-octanedithiol (DODT) by triethylamine (TEA) and dilute H2O2 was investigated. Scouting studies showed that the formation of high molecular weight polymers required a 1:2 molar ratio of DODT to TEA and of DODT to H2O2. Further investigation into the chemical composition of the organic and aqueous phases by 1H-NMR spectroscopy and mass spectrometry demonstrated that DODT is ionized by two TEA molecules (one for each thiol group) and thus transferred into the aqueous phase. The organic phase was found to have cyclic disulfide dimers, trimers and tetramers. Dissolving DODT and TEA in water before the addition of H2O2 yielded a polymer with Mn = 55,000 g/mol, in comparison with Mn = 92,000 g/mol when aqueous H2O2 was added to a DODT/TEA mixture. After polymer removal, MALDI-ToF MS analysis of the residual reaction mixtures showed only cyclic oligomers remaining. Below the LCST for TEA in water, 18.7 °C, the system yielded a stable emulsion, and only cyclic oligomers were found. Below DODT/TEA and H2O2 1:2 molar ratio mostly linear oligomers were formed, with <20% cyclic oligomers. The findings support the proposed mechanism of R3P.

[The effect of edaravone on MAPKs signal pathway associated with Abeta(25-35) treatment in PC12 cells].

PubMed

Zhang, Gui-lian; Guo, Ying-ying; Zhang, Lei; Li, Ting-ting; Du, Yun; Yao, Li; Zhang, Wang-gang; Wu, Hai-qin; Ma, Zhu-lin

2015-03-01

To explore whether edaravone protects cells damage via mitogen-activated protein kinases (MAPKs) signal pathway, and which procedure of p38 be affected so as to add theories for AD pathogenesis and treatments. According to different drugs treated, PC12 cells in vitro were divided into four groups. Negative control group: cells were treated with media alone. AD model group: cells were treated with 30 pmol/L Abeta(25-35). Inhibitor control group: cells were treated with 10 micromol/L SB203580 Cp38 mitogen-activated protein kinase (p38) inhibitor], 10 micromol/L SP600125 [c-Jun NH2 terminal kinase (JNK) inhibitor], or 10 micromol/L PD98059 extracelular signal regulated kinase (ERK) inhibitor]. Low-dose, middle-dose and high-dose edaravone group: cells plated for 24 hours treated with 30 micromol/L Abeta(25-35) and co-treated with 20, 40, 80 micromol/L edaravone 3 hours, respectively. The morphology of the treated cells were observed, the p-p38, p-JNK and p-ERK proteins in each group were tested by the Western blot. The p38 mRNA were tested in each group above (only add SB203580 10 micromol/L in third group) by the real time PCR. (1) The p-p38 protein was significantly increased in model control group compared with that in negative control group (P<0.05). The p-p38 protein in the inhibitor group and edaravone groups was decreased significantly (P<0.05) when compared with that in model control group. The p-p38 proteins were significantly increased in the three edaravone groups compared with that in inhibiter control group (P<0.05). The p-p38 protein in middle-dose edaravone group was decreased compared with that in low-dose edaravone group (P<0.05). There was no relationship in dose-dependent manner about edaravone. Compared with three edaravone groups, the p-p38 protein was lower than it in high-dose edaravone & inhibiter group (P<0.05). (2) The p-JNK protein was significantly increased in model control group compared with that in negative control group (P<0.05). The p-JNK protein in the inhibitor group was decreased compared with that in model control group (P<0.05). (3) No significantly difference of p-ERK protein concentration was observed in other groups when compared with that in negative control group (P>0.05 each). (4) Compared with negative control group, the p38 mRNA in model control group was significantly increased, and it was significantly decreased in inhibitor control group (P<0.05 each). In 40 micromol/L and 80 micromol/L edaravone groups, the p38 mRNA was significantly decreased compared with that in model control group, and it still was decreased compared with that in inhibitor control group (P<0.05). The p38 mRNA in 40 micromol/L edaravone group was the lowest among three edaravone groups, and it was obviously different from that in 20 micromol/L and 80 micromol/L edaravone groups (P<0.05). Abeta(25-35) could increase the p-p38 and p-JNK protein expression in cultured PC12 cells, but there was no obviously expression of p-ERK protein. These indicated that Abeta(25-35) might activate MAPKs signal pathway, especially p38 and JNK, and lead to PC12 cell damage. Edaravone could decrease p38 mRNA induced-Abeta(25-35), which indicated edaravone could protect PC12 cell damage via blocking p38 signal pathway in mRNA stage and protein stage simultaneously. Hence, it is promising that edaravone would be a new medicine for AD.

Lithium and memantine improve spatial memory impairment and neuroinflammation induced by β-amyloid 1-42 oligomers in rats.

PubMed

Budni, J; Feijó, D P; Batista-Silva, H; Garcez, M L; Mina, F; Belletini-Santos, T; Krasilchik, L R; Luz, A P; Schiavo, G L; Quevedo, J

2017-05-01

Alzheimer's disease (AD) is the most common cause of dementia in the elderly. The main hallmarks of this disease include progressive cognitive dysfunction and an accumulation of soluble oligomers of β-amyloid (Aβ) 1-42 peptide. In this research, we show the effects of lithium and memantine on spatial memory and neuroinflammation in an Aβ1-42 oligomers-induced animal model of dementia in rats. Aβ 1-42 oligomers were administered intrahippocampally to male wistar rats to induce dementia. Oral treatments with memantine (5mg/kg), lithium (5mg/kg), or both drugs in combination were performed over a period of 17days. 14days after the administration of the Aβ1-42 oligomers, the radial arm-maze task was performed. At the end of the test period, the animals were euthanized, and the frontal cortex and hippocampus were removed for use in our analysis. Our results showed that alone treatments with lithium or memantine ameliorate the spatial memory damage caused by Aβ1-42. The animals that received combined doses of lithium and memantine showed better cognitive performance in their latency time and total errors to find food when compared to the results from alone treatments. Moreover, in our study, lithium and/or memantine were able to reverse the decreases observed in the levels of interleukin (IL)-4 that were induced by Aβ1-42 in the frontal cortex. In the hippocampus, only memantine and the association of memantine and lithium were able to reverse this effect. Alone doses of lithium and memantine or the association of lithium and memantine caused reductions in the levels of IL-1β in the frontal cortex and hippocampus, and decreased the levels of TNF-α in the hippocampus. Taken together, these data suggest that lithium and memantine might be a potential therapy against cognitive impairment and neuroinflammation induced by Aβ1-42, and their association may be a promising alternative to be investigated in the treatment of AD-like dementia. Copyright © 2017 Elsevier Inc. All rights reserved.

Apoptosis induced by islet amyloid polypeptide soluble oligomers is neutralized by diabetes-associated specific antibodies

PubMed Central

Bram, Yaron; Frydman-Marom, Anat; Yanai, Inbal; Gilead, Sharon; Shaltiel-Karyo, Ronit; Amdursky, Nadav; Gazit, Ehud

2014-01-01

Soluble oligomeric assemblies of amyloidal proteins appear to act as major pathological agents in several degenerative disorders. Isolation and characterization of these oligomers is a pivotal step towards determination of their pathological relevance. Here we describe the isolation of Type 2 diabetes-associated islet amyloid polypeptide soluble cytotoxic oligomers; these oligomers induced apoptosis in cultured pancreatic cells, permeated model lipid vesicles and interacted with cell membranes following complete internalization. Moreover, antibodies which specifically recognized these assemblies, but not monomers or amyloid fibrils, were exclusively identified in diabetic patients and were shown to neutralize the apoptotic effect induced by these oligomers. Our findings support the notion that human IAPP peptide can form highly toxic oligomers. The presence of antibodies identified in the serum of diabetic patients confirms the pathological relevance of the oligomers. In addition, the newly identified structural epitopes may also provide new mechanistic insights and a molecular target for future therapy. PMID:24589570

A native interactor scaffolds and stabilizes toxic ATAXIN-1 oligomers in SCA1

PubMed Central

Lasagna-Reeves, Cristian A; Rousseaux, Maxime WC; Guerrero-Muñoz, Marcos J; Park, Jeehye; Jafar-Nejad, Paymaan; Richman, Ronald; Lu, Nan; Sengupta, Urmi; Litvinchuk, Alexandra; Orr, Harry T; Kayed, Rakez; Zoghbi, Huda Y

2015-01-01

Recent studies indicate that soluble oligomers drive pathogenesis in several neurodegenerative proteinopathies, including Alzheimer and Parkinson disease. Curiously, the same conformational antibody recognizes different disease-related oligomers, despite the variations in clinical presentation and brain regions affected, suggesting that the oligomer structure might be responsible for toxicity. We investigated whether polyglutamine-expanded ATAXIN-1, the protein that underlies spinocerebellar ataxia type 1, forms toxic oligomers and, if so, what underlies their toxicity. We found that mutant ATXN1 does form oligomers and that oligomer levels correlate with disease progression in the Atxn1154Q/+ mice. Moreover, oligomeric toxicity, stabilization and seeding require interaction with Capicua, which is expressed at greater ratios with respect to ATXN1 in the cerebellum than in less vulnerable brain regions. Thus, specific interactors, not merely oligomeric structure, drive pathogenesis and contribute to regional vulnerability. Identifying interactors that stabilize toxic oligomeric complexes could answer longstanding questions about the pathogenesis of other proteinopathies. DOI: http://dx.doi.org/10.7554/eLife.07558.001 PMID:25988806

Preparation of Chito-Oligomers by Hydrolysis of Chitosan in the Presence of Zeolite as Adsorbent

PubMed Central

Ibrahim, Khalid A.; El-Eswed, Bassam I.; Abu-Sbeih, Khaleel A.; Arafat, Tawfeeq A.; Al Omari, Mahmoud M. H.; Darras, Fouad H.; Badwan, Adnan A.

2016-01-01

An increasing interest has recently been shown to use chitin/chitosan oligomers (chito-oligomers) in medicine and food fields because they are not only water-soluble, nontoxic, and biocompatible materials, but they also exhibit numerous biological properties, including antibacterial, antifungal, and antitumor activities, as well as immuno-enhancing effects on animals. Conventional depolymerization methods of chitosan to chito-oligomers are either chemical by acid-hydrolysis under harsh conditions or by enzymatic degradation. In this work, hydrolysis of chitosan to chito-oligomers has been achieved by applying adsorption-separation technique using diluted HCl in the presence of different types of zeolite as adsorbents. The chito-oligomers were retrieved from adsorbents and characterized by differential scanning calorimetry (DSC), liquid chromatography/mass spectroscopy (LC/MS), and ninhydrin test. PMID:27455287

Polymerization on the rocks: negatively-charged alpha-amino acids

NASA Technical Reports Server (NTRS)

Hill, A. R. Jr; Bohler, C.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

1998-01-01

Oligomers of the negatively-charged amino acids, glutamic acid, aspartic acid, and O-phospho-L-serine are adsorbed by hydroxylapatite and illite with affinities that increase with oligomer length. In the case of oligo-glutamic acids adsorbed on hydroxylapatite, addition of an extra residue results in an approximately four-fold increase in the strength of adsorption. Oligomers much longer than the 7-mer are retained tenaciously by the mineral. Repeated incubation of short oligo-glutamic acids adsorbed on hydroxylapatite or illite with activated monomer leads to the accumulation of oligomers at least 45 units long. The corresponding reactions of aspartic acid and O-phospho-L-serine on hydroxylapatite are less effective in generating long oligomers, while illite fails to accumulate substantial amounts of long oligomers of aspartic acid or of O-phospho-L-serine.

Precise measurement of the self-diffusion coefficient for poly(ethylene glycol) in aqueous solution using uniform oligomers

NASA Astrophysics Data System (ADS)

Shimada, Kayori; Kato, Haruhisa; Saito, Takeshi; Matsuyama, Shigetomo; Kinugasa, Shinichi

2005-06-01

Uniform poly(ethylene glycol) (PEG) oligomers, with a degree of polymerization n =1-40, were separated by preparative supercritical fluid chromatography from commercial monodispersed samples. Diffusion coefficients, D, for separated uniform PEG oligomers were measured in dilute solutions of deuterium oxide (D2O) at 30 ° C, using pulsed-field gradient nuclear magnetic resonance. The measured D for each molecular weight was extrapolated to infinite dilution. Diffusion coefficients obtained at infinite dilution follow the scaling behavior of Zimm-type diffusion, even in the lower molecular weight range. Molecular-dynamics simulations for PEG in H2O also showed this scaling behavior, and reproduced close hydrodynamic interactions between PEG and water. These findings suggest that diffusion of PEG in water is dominated by hydrodynamic interaction over a wide molecular weight range, including at low molecular weights around 1000.

Relationship between population of the fibril-prone conformation in the monomeric state and oligomer formation times of peptides: Insights from all-atom simulations

NASA Astrophysics Data System (ADS)

Nam, Hoang Bao; Kouza, Maksim; Zung, Hoang; Li, Mai Suan

2010-04-01

Despite much progress in understanding the aggregation process of biomolecules, the factors that govern its rates have not been fully understood. This problem is of particular importance since many conformational diseases such as Alzheimer, Parkinson, and type-II diabetes are associated with the protein oligomerization. Having performed all-atom simulations with explicit water and various force fields for two short peptides KFFE and NNQQ, we show that their oligomer formation times are strongly correlated with the population of the fibril-prone conformation in the monomeric state. The larger the population the faster the aggregation process. Our result not only suggests that this quantity plays a key role in the self-assembly of polypeptide chains but also opens a new way to understand the fibrillogenesis of biomolecules at the monomeric level. The nature of oligomer ordering of NNQQ is studied in detail.

Soluble forms of polyQ-expanded huntingtin rather than large aggregates cause endoplasmic reticulum stress

NASA Astrophysics Data System (ADS)

Leitman, Julia; Ulrich Hartl, F.; Lederkremer, Gerardo Z.

2013-11-01

In Huntington’s disease, as in other neurodegenerative diseases, it was initially thought that insoluble protein aggregates are the toxic species. However, growing evidence implicates soluble oligomeric polyglutamine-expanded huntingtin in cytotoxicity. Here we show that pathogenic huntingtin inhibits endoplasmic reticulum (ER)-associated degradation and induces ER stress before its aggregation into visible inclusions. All three branches of the unfolded protein response are activated. ER stress can be compensated by overexpression of p97/VCP, suggesting its sequestration by pathogenic huntingtin as a main cause. Stress correlates with the presence of huntingtin oligomers and is independent of continual huntingtin synthesis. Stress levels, measured in striatal neurons, are stabilized but only slowly subside on huntingtin aggregation into inclusions. Our results can be explained by the constant conversion of huntingtin monomers to toxic oligomers; large aggregates sequester the former, precluding further conversion, whereas pre-existing toxic oligomers are only gradually depleted.

Repurposing doxycycline for synucleinopathies: remodelling of α-synuclein oligomers towards non-toxic parallel beta-sheet structured species

PubMed Central

González-Lizárraga, Florencia; Socías, Sergio B.; Ávila, César L.; Torres-Bugeau, Clarisa M.; Barbosa, Leandro R. S.; Binolfi, Andres; Sepúlveda-Díaz, Julia E.; Del-Bel, Elaine; Fernandez, Claudio O.; Papy-Garcia, Dulce; Itri, Rosangela; Raisman-Vozari, Rita; Chehín, Rosana N.

2017-01-01

Synucleinophaties are progressive neurodegenerative disorders with no cure to date. An attractive strategy to tackle this problem is repurposing already tested safe drugs against novel targets. In this way, doxycycline prevents neurodegeneration in Parkinson models by modulating neuroinflammation. However, anti-inflammatory therapy per se is insufficient to account for neuroprotection. Herein we characterise novel targets of doxycycline describing the structural background supporting its effectiveness as a neuroprotector at subantibiotic doses. Our results show that doxycycline reshapes α-synuclein oligomers into off-pathway, high-molecular-weight species that do not evolve into fibrils. Off-pathway species present less hydrophobic surface than on-pathway oligomers and display different β-sheet structural arrangement. These structural changes affect the α-synuclein ability to destabilize biological membranes, cell viability, and formation of additional toxic species. Altogether, these mechanisms could act synergically giving novel targets for repurposing this drug. PMID:28155912

Role of uncrosslinked chains in droplets dynamics on silicone elastomers.

PubMed

Hourlier-Fargette, Aurélie; Antkowiak, Arnaud; Chateauminois, Antoine; Neukirch, Sébastien

2017-05-21

We report an unexpected behavior in wetting dynamics on soft silicone substrates: the dynamics of aqueous droplets deposited on vertical plates of such elastomers exhibits two successive speed regimes. This macroscopic observation is found to be closely related to microscopic phenomena occurring at the scale of the polymer network: we show that uncrosslinked chains found in most widely used commercial silicone elastomers are responsible for this surprising behavior. A direct visualization of the uncrosslinked oligomers collected by water droplets is performed, evidencing that a capillarity-induced phase separation occurs: uncrosslinked oligomers are extracted from the silicone elastomer network by the water-glycerol mixture droplet. The sharp speed change is shown to coincide with an abrupt transition in surface tension of the droplets, when a critical surface concentration in uncrosslinked oligomer chains is reached. We infer that a droplet shifts to a second regime with a faster speed when it is completely covered with a homogeneous oil film.

Shaking Alone Induces De Novo Conversion of Recombinant Prion Proteins to β-Sheet Rich Oligomers and Fibrils

PubMed Central

Ladner-Keay, Carol L.; Griffith, Bethany J.; Wishart, David S.

2014-01-01

The formation of β-sheet rich prion oligomers and fibrils from native prion protein (PrP) is thought to be a key step in the development of prion diseases. Many methods are available to convert recombinant prion protein into β-sheet rich fibrils using various chemical denaturants (urea, SDS, GdnHCl), high temperature, phospholipids, or mildly acidic conditions (pH 4). Many of these methods also require shaking or another form of agitation to complete the conversion process. We have identified that shaking alone causes the conversion of recombinant PrP to β-sheet rich oligomers and fibrils at near physiological pH (pH 5.5 to pH 6.2) and temperature. This conversion does not require any denaturant, detergent, or any other chemical cofactor. Interestingly, this conversion does not occur when the water-air interface is eliminated in the shaken sample. We have analyzed shaking-induced conversion using circular dichroism, resolution enhanced native acidic gel electrophoresis (RENAGE), electron microscopy, Fourier transform infrared spectroscopy, thioflavin T fluorescence and proteinase K resistance. Our results show that shaking causes the formation of β-sheet rich oligomers with a population distribution ranging from octamers to dodecamers and that further shaking causes a transition to β-sheet fibrils. In addition, we show that shaking-induced conversion occurs for a wide range of full-length and truncated constructs of mouse, hamster and cervid prion proteins. We propose that this method of conversion provides a robust, reproducible and easily accessible model for scrapie-like amyloid formation, allowing the generation of milligram quantities of physiologically stable β-sheet rich oligomers and fibrils. These results may also have interesting implications regarding our understanding of prion conversion and propagation both within the brain and via techniques such as protein misfolding cyclic amplification (PMCA) and quaking induced conversion (QuIC). PMID:24892647

Bioluminescence Resonance Energy Transfer Studies Reveal Constitutive Dimerization of the Human Lutropin Receptor and a Lack of Correlation between Receptor Activation and the Propensity for Dimerization*

PubMed Central

Guan, Rongbin; Feng, Xiuyan; Wu, Xueqing; Zhang, Meilin; Zhang, Xuesen; Hébert, Terence E.; Segaloff, Deborah L.

2009-01-01

Previous studies from our laboratory using co-immunoprecipitation techniques suggested that the human lutropin receptor (hLHR) constitutively self-associates into dimers/oligomers and that agonist treatment of cells either increased hLHR dimerization/oligomerization and/or stabilized hLHR dimers/oligomers to detergent solubilization (Tao, Y. X., Johnson, N. B., and Segaloff, D. L. (2004) J. Biol. Chem. 279, 5904–5914). In this study, bioluminescence resonance energy transfer (BRET2) analyses confirmed that the hLHR constitutively self-associates in living cells. After subcellular fractionation, hLHR dimers/oligomers were detected in both the plasma membrane and endoplasmic reticulum (ER). Further evidence supporting the constitutive formation of hLHR dimer/oligomers in the ER is provided by data showing homodimerization of misfolded hLHR mutants that are retained in the ER. These mutants, when co-expressed with wild-type receptor, are shown by BRET2 to heterodimerize, accounting for their dominant-negative effects on cell surface receptor expression. Hormone desorption assays using intact cells demonstrate allosterism between hLHR protomers, indicating functional cell surface hLHR dimers. However, quantitative BRET2 analyses in intact cells indicate a lack of effect of agonist on the propensity of the hLHR to dimerize. Using purified plasma membranes, human chorionic gonadotropin was similarly observed to have no effect on the BRET2 signal. An examination of the propensity for constitutively active and signaling inactive hLHR mutants to dimerize further showed no correlation between dimerization and the activation state of the hLHR. Taken altogether, our data suggest that hLHR dimers/oligomers are formed early in the biosynthetic pathway in the ER, are constitutively expressed on the plasma membrane, and are not affected by the activation state of the hLHR. PMID:19147490

DNA sequence similarity recognition by hybridization to short oligomers

DOEpatents

Milosavljevic, Aleksandar

1999-01-01

Methods are disclosed for the comparison of nucleic acid sequences. Data is generated by hybridizing sets of oligomers with target nucleic acids. The data thus generated is manipulated simultaneously with respect to both (i) matching between oligomers and (ii) matching between oligomers and putative reference sequences available in databases. Using data compression methods to manipulate this mutual information, sequences for the target can be constructed.

Radiation inactivation method provides evidence that membrane-bound mitochondrial creatine kinase is an oligomer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quemeneur, E.; Eichenberger, D.; Goldschmidt, D.

1988-06-30

Lyophilized suspensions of rabbit heart mitochondria have been irradiated with varying doses of gamma rays. Mitochondrial creatine kinase activity was inactivated exponentially with a radiation inactivation size of 352 or 377 kDa depending upon the initial medium. These values are in good agreement with the molecular mass previously deduced from by permeation experiments: 357 kDa. This is the first direct evidence showing that the native form of mitochondrial creatine kinase is associated to the inner membrane as an oligomer, very likely an octamer.

Phase Separation During the Curing of a Cyanate Ester Oligomer

NASA Astrophysics Data System (ADS)

Gurov, D. A.; Novikov, G. F.

2018-07-01

It is found during the curing of a cyanate ester oligomer that there are such features as a step and a maximum in the frequency dependences (in a range of 10-2-105 Hz) of the real parts of the complex electric conductivity and loss tangent, respectively. In the frequency range where these features are observed, the diagrams of complex electric modulus are semicircles with centers near the abscissas. Subsequent analysis shows these features are due to the formation of the microphase of the intermediate product, carbamate.

Amplifying (Im)perfection: The Impact of Crystallinity in Discrete and Disperse Block Co-oligomers

PubMed Central

2017-01-01

Crystallinity is seldomly utilized as part of the microphase segregation process in ultralow-molecular-weight block copolymers. Here, we show the preparation of two types of discrete, semicrystalline block co-oligomers, comprising an amorphous oligodimethylsiloxane block and a crystalline oligo-l-lactic acid or oligomethylene block. The self-assembly of these discrete materials results in lamellar structures with unforeseen uniformity in the domain spacing. A systematic introduction of dispersity reveals the extreme sensitivity of the microphase segregation process toward chain length dispersity in the crystalline block. PMID:28994585

Siloxane containing addition polyimides. II - Acetylene terminated polyimides

NASA Technical Reports Server (NTRS)

Maudgal, S.; St. Clair, T. L.

1984-01-01

Acetylene terminated polyimide oligomers having a range of molecular weights have been synthesized by reacting bis (gamma-aminopropyl) tetramethyldisiloxane, aminophenylacetylene and 3, 3', 4, 4' benzophenonetetracarboxylic dianhydride in different molar ratios. The prepolymers were isolated and characterized for melt flow and cure properties. They show promise as adhesives for bonding titanium to titanium and as matrix resins for graphite cloth reinforced composites. The most promising system has been blended in varying proportions with Thermid 600, a commercially available acetylene terminated polyimide oligomer, and the mixtures have been tested for application as composite matrix resins.

Amplifying (Im)perfection: The Impact of Crystallinity in Discrete and Disperse Block Co-oligomers.

PubMed

van Genabeek, Bas; Lamers, Brigitte A G; de Waal, Bas F M; van Son, Martin H C; Palmans, Anja R A; Meijer, E W

2017-10-25

Crystallinity is seldomly utilized as part of the microphase segregation process in ultralow-molecular-weight block copolymers. Here, we show the preparation of two types of discrete, semicrystalline block co-oligomers, comprising an amorphous oligodimethylsiloxane block and a crystalline oligo-l-lactic acid or oligomethylene block. The self-assembly of these discrete materials results in lamellar structures with unforeseen uniformity in the domain spacing. A systematic introduction of dispersity reveals the extreme sensitivity of the microphase segregation process toward chain length dispersity in the crystalline block.

Targeting Cancer with Antisense Oligomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hnatowich, DJ

With financial assistance from the Department of Energy, we have shown definitively that radiolabeled antisense DNAs and other oligomers will accumulate in target cancer cells in vitro and in vivo by an antisense mechanism. We have also shown that the number of mRNA targets for our antisense oligomers in the cancer cell types that we have investigated so far is sufficient to provide and antisense image and/or radiotherapy of cancer in mice. These studies have been reported in about 10 publications. However our observation over the past several years has shown that radiolabeled antisense oligomers administered intravenously in their nativemore » and naked form will accumulate and be retained in target xenografts by an antisense mechanism but will also accumulate at high levels in normal organs such as liver, spleen and kidneys. We have investigated unsuccessfully several commercially available vectors. Thus the use of radiolabeled antisense oligomers for the imaging of cancer must await novel approaches to delivery. This laboratory has therefore pursued two new paths, optical imaging of tumor and Auger radiotherapy. We are developing a novel method of optical imaging tumor using antisense oligomers with a fluorophore is administered while hybridized with a shorter complementary oligomer with an inhibitor. In culture and in tumored mice that the duplex remains intact and thus nonfluorescent until it encounters its target mRNA at which time it dissociates and the antisense oligomer binds along with its fluorophore to the target. Simultaneous with the above, we have also observed, as have others, that antisense oligomers migrate rapidly and quantitatively to the nucleus upon crossing cell membranes. The Auger electron radiotherapy path results from this observation since the nuclear migration properties could be used effectively to bring and to retain in the nucleus an Auger emitting radionuclide such as 111In or 125I bound to the antisense oligomer. Since the object becomes radiotherapy rather than imaging, the delivery problem may be obviated by attaching the antisense oligomer to an antitumor antibody to improve delivery following intravenous administration. Since many antibodies are trapped in endosomes following internalization, a cell penetrating peptide such as tat will also be included to ensure transport of the complex without entrapment. Rather than covalent conjugation of the three entities, we are using streptavidin as linker after biotinylated each component. Our recent efforts have concentrated on establishing the influence of the streptavidin linker on the properties of each component within the delivery nanoparticle. Thus, we have shown that the Herceptin antibody, when linked to a labeled oligomer via streptavidin, remains capable of directing the label oligomer to Her2+ tumor cells in vitro and Her2+ tumor xenografts in mice. In addition, we have demonstrated that a labeled antisense oligomer within the nanoparticle remains capable of migrating to the nucleus and binding to its target mRNA in vitro and in vivo. We have shown that the tat peptide also preserves its properties of cell transport when incubated as one component of the nanoparticle. Most recently, we have addressed another of our concerns, namely whether the streptavidin would adversely effect the biodistribution of the antisense oligomer. We were pleased to find that the 99mTc-labeled antisense MORF within the Herceptin three component and two component nanoparticles accumulated and was retained in tumor in a manner suggestive of radiolabeled Herceptin itself. Thus the preserved properties within the streptavidin delivery nanoparticle of the Herceptin antibody, the tat peptide and the 111In labeled antisense MORF oligomer will explain why we have successfully demonstrated an Auger electron-mediated, antisense-mediated radiotherapy in cells in culture. One remaining concern is that the delivery nanoparticle may deliver the Auger electron emitting radionuclide to the nucleus of normal cells as well as tumor cells. We have now performed tumored mice studies of the three component delivery nanoparticle with the antisense MORF labeled with Cy3 so that tissue slices could be examined by immunohistology for evidence of MORF accumulations in the nuclei of both tumor and normal tissues. Microscopic examination shows nuclear staining in approximately 20% of the tumor cells in animals injected with the antisense nanoparticle and 10% of the tumor cells in animals receiving the sense nanoparticle, whereas no nuclear staining is seen in the tumor cells of mice given the PBS injection as another control. No nuclear staining was observed in all sections from all normal organs. Finally, my colleagues and I wish to express our gratitude to the DOE for their generous support of our research at a time when the NIH was unwilling to fund what they believed to be a risky« less

A quantification method for heat-decomposable methylglyoxal oligomers and its application on 1,3,5-trimethylbenzene SOA

NASA Astrophysics Data System (ADS)

Rodigast, Maria; Mutzel, Anke; Herrmann, Hartmut

2017-03-01

Methylglyoxal forms oligomeric compounds in the atmospheric aqueous particle phase, which could establish a significant contribution to the formation of aqueous secondary organic aerosol (aqSOA). Thus far, no suitable method for the quantification of methylglyoxal oligomers is available despite the great effort spent for structure elucidation. In the present study a simplified method was developed to quantify heat-decomposable methylglyoxal oligomers as a sum parameter. The method is based on the thermal decomposition of oligomers into methylglyoxal monomers. Formed methylglyoxal monomers were detected using PFBHA (o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride) derivatisation and gas chromatography-mass spectrometry (GC/MS) analysis. The method development was focused on the heating time (varied between 15 and 48 h), pH during the heating process (pH = 1-7), and heating temperature (50, 100 °C). The optimised values of these method parameters are presented. The developed method was applied to quantify heat-decomposable methylglyoxal oligomers formed during the OH-radical oxidation of 1,3,5-trimethylbenzene (TMB) in the Leipzig aerosol chamber (LEipziger AerosolKammer, LEAK). Oligomer formation was investigated as a function of seed particle acidity and relative humidity. A fraction of heat-decomposable methylglyoxal oligomers of up to 8 % in the produced organic particle mass was found, highlighting the importance of those oligomers formed solely by methylglyoxal for SOA formation. Overall, the present study provides a new and suitable method for quantification of heat-decomposable methylglyoxal oligomers in the aqueous particle phase.

Fluorene- and benzofluorene-cored oligomers as low threshold and high gain amplifying media

NASA Astrophysics Data System (ADS)

Kazlauskas, Karolis; Kreiza, Gediminas; Bobrovas, Olegas; AdomÄ--nienÄ--, Ona; AdomÄ--nas, Povilas; Jankauskas, Vygintas; JuršÄ--nas, Saulius

2015-07-01

Deliberate control of intermolecular interactions in fluorene- and benzofluorene-cored oligomers was attempted via introduction of different-length alkyl moieties to attain high emission amplification and low amplified spontaneous emission (ASE) threshold at high oligomer concentrations. Containing fluorenyl peripheral groups decorated with different-length alkyl moieties, the oligomers were found to express weak concentration quenching of emission, yet excellent carrier drift mobilities (close to 10-2 cm2/V/s) in the amorphous films. Owing to the larger radiative decay rates (>1.0 × 109 s-1) and smaller concentration quenching, fluorene-cored oligomers exhibited down to one order of magnitude lower ASE thresholds at higher concentrations as compared to those of benzofluorene counterparts. The lowest threshold (300 W/cm2) obtained for the fluorene-cored oligomers at the concentration of 50 wt % in polymer matrix is among the lowest reported for solution-processed amorphous films in ambient conditions, what makes the oligomers promising for lasing application. Great potential in emission amplification was confirmed by high maximum net gain (77 cm-1) revealed for these compounds. Although the photostability of the oligomers was affected by photo-oxidation, it was found to be comparable to that of various organic lasing materials including some commercial laser dyes evaluated under similar excitation conditions.

Over-expression of two different forms of the alpha-secretase ADAM10 affects learning and memory in mice.

PubMed

Schmitt, Ulrich; Hiemke, Christoph; Fahrenholz, Falk; Schroeder, Anja

2006-12-15

Members of the ADAM family (adisintegrin and metalloprotease) are the main candidates for physiologically relevant alpha-secretases. The alpha-secretase cleaves in the non-amyloidogenic pathway the amyloid precursor protein within the region of the Abeta peptides preventing their aggregation in the brain. The increase of alpha-secretase activity in the brain provides a plausible strategy to prevent Abeta formation. Concerning this possibility two transgenic mouse lines (FVB/N) have been created: mice over-expressing the bovine form of the alpha-secretase (ADAM10) and mice over-expressing an inactive form of the alpha-secretase (ADAM10-E348A-HA; ADAM10-dn). For behavioral examination a F1 generation of transgenic mice (C57Bl/6 x FVB/N (tg)) was generated and compared to wild type F1 generation (C57Bl/6 x FVB/N). Behavior was characterized in the following tasks: standard open field, enriched open field, elevated plus-maze, and the Morris water maze hidden platform task. Concerning basal activity, exploration, and anxiety, transgenic mice behaved similar to controls. With respect to learning and memory both transgenic lines showed a significant deficit compared to controls. ADAM10 mice however, showed thigmotaxis with passive floating behavior in the Morris water maze indicating differences in motivation, whereas, ADAM10-dn mice displayed an inconspicuous but limited goal-directed search pattern. Thus variation of the enzymatic activity of alpha-secretase ADAM10 alters learning and memory differentially. Nevertheless, it could be concluded that both, ADAM10 and ADAM10-dn mice are suitable control mice for the assessment of alpha-secretase-related effects in animal models of Alzheimer's disease.

Characterization of the oligomeric states of insulin in self-assembly and amyloid fibril formation by mass spectrometry.

PubMed Central

Nettleton, E J; Tito, P; Sunde, M; Bouchard, M; Dobson, C M; Robinson, C V

2000-01-01

The self-assembly and aggregation of insulin molecules has been investigated by means of nanoflow electrospray mass spectrometry. Hexamers of insulin containing predominantly two, but up to four, Zn(2+) ions were observed in the gas phase when solutions at pH 4.0 were examined. At pH 3.3, in the absence of Zn(2+), dimers and tetramers are observed. Spectra obtained from solutions of insulin at millimolar concentrations at pH 2.0, conditions under which insulin is known to aggregate in solution, showed signals from a range of higher oligomers. Clusters containing up to 12 molecules could be detected in the gas phase. Hydrogen exchange measurements show that in solution these higher oligomers are in rapid equilibrium with monomeric insulin. At elevated temperatures, under conditions where insulin rapidly forms amyloid fibrils, the concentration of soluble higher oligomers was found to decrease with time yielding insoluble high molecular weight aggregates and then fibrils. The fibrils formed were examined by electron microscopy and the results show that the amorphous aggregates formed initially are converted to twisted, unbranched fibrils containing several protofilaments. Fourier transform infrared spectroscopy shows that both the soluble form of insulin and the initial aggregates are predominantly helical, but that formation of beta-sheet structure occurs simultaneously with the appearance of well-defined fibrils. PMID:10920035

Aqueous phase oligomerization of methyl vinyl ketone through photooxidation - Part 1: Aging processes of oligomers

NASA Astrophysics Data System (ADS)

Renard, P.; Siekmann, F.; Salque, G.; Smaani, A.; Demelas, C.; Coulomb, B.; Vassalo, L.; Ravier, S.; Temime-Roussel, B.; Voisin, D.; Monod, A.

2014-06-01

Secondary organic aerosol (SOA) represents a substantial part of organic aerosol, which affects climate and human health. It is now accepted that one of the important pathways of SOA formation occurs via aqueous phase chemistry in the atmosphere. Recently, we have shown in a previous study (Renard et al., 2013) the mechanism of oligomerization of MVK (methyl vinyl ketone), and suggested that unsaturated water soluble organic compounds (UWSOC) might efficiently form SOA in wet aerosol particles, even for weakly soluble ones like MVK. The atmospheric relevance of these processes is explored by means of process model studies (in a companion paper). In the present study we investigate the aging of these aqueous phase MVK-oligomers (Part 1). We compared aqueous phase composition and SOA composition after nebulization, mainly by means of UPLC-ESI-MS and AMS, respectively. Both instruments match and show similar trend of oligomer formation and aging. The SMPS analysis performed on the nebulized solutions allow to quantify these SOA and to measure their mass yields. We have highlighted in the current study that MVK •OH-oxidation undergoes kinetic competition between functionalization and oligomerization. The SOA composition and its evolution highly depend on the precursor initial concentration. We determined the threshold of MVK concentration, i.e. 2 mM, from which oligomerization prevails over functionalization. Hence, at these concentrations, •OH-oxidation of MVK forms oligomers that are SV-OOA, with low O / C and high f43. Oligomers are then fragmented, via unidentified intermediates that have the properties of LV-OOA which then end into succinic, malonic and oxalic diacids. For lower initial MVK concentrations, the oligomerization is not the major process, and functionalization dominates, resulting in small carbonyls, dicarbonyls and mainly monoacids. The aging of these oligomers could be an explanation for the presence of a part of the diacids observed in aerosol.

A Combined Photochemical and Multicomponent Reaction Approach to Precision Oligomers.

PubMed

Konrad, Waldemar; Bloesser, Fabian R; Wetzel, Katharina S; Boukis, Andreas C; Meier, Michael A R; Barner-Kowollik, Christopher

2018-03-07

We introduce the convergent synthesis of linear monodisperse sequence-defined oligomers through a unique approach, combining the Passerini three-component reaction (P-3CR) and a Diels-Alder (DA) reaction based on photocaged dienes. A set of oligomers is prepared resting on a Passerini linker unit carrying an isocyano group for chain extension by P-3CR and a maleimide moiety for photoenol conjugation enabling a modular approach for chain growth. Monodisperse oligomers are accessible in a stepwise fashion by switching between both reaction types. Employing sebacic acid as a core unit allows the synthesis of a library of symmetric sequence-defined oligomers. The oligomers consist of alternating P-3CR and photoblocks with molecular weights up to 3532.16 g mol -1 , demonstrating the successful switching from P-3CR to photoenol conjugation. In-depth characterization was carried out including size-exclusion chromatography (SEC), high-resolution electrospray ionization mass spectrometry (ESI-MS) and NMR spectroscopy, evidencing the monodisperse nature of the precision oligomers. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

SDS-PAGE analysis of Aβ oligomers is disserving research into Alzheimer´s disease: appealing for ESI-IM-MS

NASA Astrophysics Data System (ADS)

Pujol-Pina, Rosa; Vilaprinyó-Pascual, Sílvia; Mazzucato, Roberta; Arcella, Annalisa; Vilaseca, Marta; Orozco, Modesto; Carulla, Natàlia

2015-10-01

The characterization of amyloid-beta peptide (Aβ) oligomer forms and structures is crucial to the advancement in the field of Alzheimer´s disease (AD). Here we report a critical evaluation of two methods used for this purpose, namely sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), extensively used in the field, and ion mobility coupled to electrospray ionization mass spectrometry (ESI-IM-MS), an emerging technique with great potential for oligomer characterization. To evaluate their performance, we first obtained pure cross-linked Aβ40 and Aβ42 oligomers of well-defined order. Analysis of these samples by SDS-PAGE revealed that SDS affects the oligomerization state of Aβ42 oligomers, thus providing flawed information on their order and distribution. In contrast, ESI-IM-MS provided accurate information, while also reported on the chemical nature and on the structure of the oligomers. Our findings have important implications as they challenge scientific paradigms in the AD field built upon SDS-PAGE characterization of Aβ oligomer samples.

Structure and function of small heat shock/alpha-crystallin proteins: established concepts and emerging ideas.

PubMed

MacRae, T H

2000-06-01

Small heat shock/alpha-crystallin proteins are defined by conserved sequence of approximately 90 amino acid residues, termed the alpha-crystallin domain, which is bounded by variable amino- and carboxy-terminal extensions. These proteins form oligomers, most of uncertain quaternary structure, and oligomerization is prerequisite to their function as molecular chaperones. Sequence modelling and physical analyses show that the secondary structure of small heat shock/alpha-crystallin proteins is predominately beta-pleated sheet. Crystallography, site-directed spin-labelling and yeast two-hybrid selection demonstrate regions of secondary structure within the alpha-crystallin domain that interact during oligomer assembly, a process also dependent on the amino terminus. Oligomers are dynamic, exhibiting subunit exchange and organizational plasticity, perhaps leading to functional diversity. Exposure of hydrophobic residues by structural modification facilitates chaperoning where denaturing proteins in the molten globule state associate with oligomers. The flexible carboxy-terminal extension contributes to chaperone activity by enhancing the solubility of small heat shock/alpha-crystallin proteins. Site-directed mutagenesis has yielded proteins where the effect of the change on structure and function depends upon the residue modified, the organism under study and the analytical techniques used. Most revealing, substitution of a conserved arginine residue within the alpha-crystallin domain has a major impact on quaternary structure and chaperone action probably through realignment of beta-sheets. These mutations are linked to inherited diseases. Oligomer size is regulated by a stress-responsive cascade including MAPKAP kinase 2/3 and p38. Phosphorylation of small heat shock/alpha-crystallin proteins has important consequences within stressed cells, especially for microfilaments.

Eckmaxol, a Phlorotannin Extracted from Ecklonia maxima, Produces Anti-β-amyloid Oligomer Neuroprotective Effects Possibly via Directly Acting on Glycogen Synthase Kinase 3β.

PubMed

Wang, Jialing; Zheng, Jiachen; Huang, Chunhui; Zhao, Jiaying; Lin, Jiajia; Zhou, Xuezhen; Naman, C Benjamin; Wang, Ning; Gerwick, William H; Wang, Qinwen; Yan, Xiaojun; Cui, Wei; He, Shan

2018-04-10

Alzheimer's disease is a progressive neurodegenerative disorder that mainly affects the elderly. Soluble β-amyloid oligomer, which can induce neurotoxicity, is generally regarded as the main neurotoxin in Alzheimer's disease. Here we report that eckmaxol, a phlorotannin extracted from the brown alga Ecklonia maxima, could produce neuroprotective effects in SH-SY5Y cells. Eckmaxol effectively prevented but did not rescue β-amyloid oligomer-induced neuronal apoptosis and increase of intracellular reactive oxygen species. Eckmaxol also significantly reversed the decreased expression of phospho-Ser9-glycogen synthase kinase 3β and increased expression of phospho-extracellular signal-regulated kinase, which was induced by Aβ oligomer. Moreover, both glycogen synthase kinase 3β and mitogen activated protein kinase inhibitors produced neuroprotective effects in SH-SY5Y cells. Furthermore, eckmaxol showed favorable interaction in the ATP binding site of glycogen synthase kinase 3β and mitogen activated protein kinase. These results suggested that eckmaxol might produce neuroprotective effects via concurrent inhibition of glycogen synthase kinase 3β and extracellular signal-regulated kinase pathways, possibly via directly acting on glycogen synthase kinase 3β and mitogen activated protein kinase. Based on the central role that β-amyloid oligomers play in the pathogenesis of Alzheimer's disease and the high annual production of Ecklonia maxima for alginate and other nutritional ingredients, this report represents a new candidate for the treatment of Alzheimer's disease, and also expands the potential application of Ecklonia maxima and its constituents in the field of pharmacology.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shanmugam, Ganesh; Polavarapu, Prasad L.; Hallgas, Balazs

The effects of D-amino acids at Asp{sup 23} and Ser{sup 26} residues on the conformational preference of {beta}-amyloid (A{beta}) peptide fragment (A{beta}{sub 20-29}) have been studied using different spectroscopic techniques, namely vibrational circular dichroism (VCD), vibrational absorption, and electronic circular dichroism. To study the structure of the A{beta}{sub 20-29}, [D-Asp{sup 23}]A{beta}{sub 20-29}, and [D-Ser{sup 26}]A{beta}{sub 20-29} peptides under different conditions, the spectra were measured in 10 mM acetate buffer (pH 3) and in 2,2,2-trifluoroethanol (TFE). The spectroscopic results indicated that at pH 3, A{beta}{sub 20-29} peptide takes random coil with {beta}-turn structure, while [D-Ser{sup 26}]A{beta}{sub 20-29} peptide adopts significant amountmore » of polyproline II (PPII) type structure along with {beta}-turn contribution and D-Asp-substituted peptide ([D-Asp{sup 23}]A{beta}{sub 20-29}) adopts predominantly PPII type structure. The increased propensity for PPII conformation upon D-amino acid substitution, in acidic medium, has important biological implications. In TFE, A{beta}{sub 20-29}, [D-Asp{sup 23}]A{beta}{sub 20-29}, and [D-Ser{sup 26}]A{beta}{sub 20-29} peptides adopt 3{sub 10}-helix, {alpha}-helix, and random coil with some {beta}-turn structures, respectively. The VCD data obtained for the A{beta} peptide films suggested that the secondary structures for the peptide films are not the same as those for corresponding solution and are also different among the A{beta} peptides studied here. This observation suggests that dehydration can have a significant influence on the structural preferences of these peptides.« less

The low density lipoprotein receptor-related protein 1B retains beta-amyloid precursor protein at the cell surface and reduces amyloid-beta peptide production.

PubMed

Cam, Judy A; Zerbinatti, Celina V; Knisely, Jane M; Hecimovic, Silva; Li, Yonghe; Bu, Guojun

2004-07-09

The low density lipoprotein (LDL) receptor-related protein 1B (LRP1B) is a newly identified member of the LDL receptor family that shares high homology with the LDL receptor-related protein (LRP). LRP1B was originally described as a putative tumor suppressor in lung cancer cells; however, its expression profile in several regions of adult human brain suggests it may have additional functions in the central nervous system. Since LRP1B has overlapping ligand binding properties with LRP, we investigated whether LRP1B, like LRP, could interact with the beta-amyloid precursor protein (APP) and modulate its processing to amyloid-beta peptides (Abetas). Using an LRP1B minireceptor (mLRP1B4) generated to study the trafficking of LRP1B, we found that mLRP1B4 and APP form an immunoprecipitable complex. Furthermore mLRP1B4 bound and facilitated the degradation of a soluble isoform of APP containing a Kunitz proteinase inhibitor domain but not soluble APP lacking a Kunitz proteinase inhibitor domain. A functional consequence of mLRP1B4 expression was a significant accumulation of APP at the cell surface, which is likely related to the slow endocytosis rate of LRP1B. More importantly, mLRP1B4-expressing cells that accumulated cell surface APP produced less Abeta and secreted more soluble APP. These findings reveal that LRP1B is a novel binding partner of APP that functions to decrease APP processing to Abeta. Consequently LRP1B expression could function to protect against the pathogenesis of Alzheimer's disease.

Mechanisms of pain in distal symmetric polyneuropathy: a combined clinical and neurophysiological study.

PubMed

Truini, A; Biasiotta, A; La Cesa, S; Di Stefano, G; Galeotti, F; Petrucci, M T; Inghilleri, M; Cartoni, C; Pergolini, M; Cruccu, G

2010-09-01

In patients with distal symmetric polyneuropathy we assessed non-nociceptive Abeta- and nociceptive Adelta-afferents to investigate their role in the development of neuropathic pain. We screened 2240 consecutive patients with sensory disturbances and collected 150 patients with distal symmetric polyneuropathy (68 with pain and 82 without). All patients underwent the Neuropathic Pain Symptom Inventory to rate ongoing, paroxysmal and provoked pains, a standard nerve conduction study (NCS) to assess Abeta-fibre function, and laser-evoked potentials (LEPs) to assess Adelta-fibre function. Patients with pain had the same age (P>0.50), but a longer delay since symptom onset than those without (P<0.01). Whereas the LEP amplitude was significantly lower in patients with pain than in those without (P<0.0001), NCS data did not differ between groups (P>0.50). LEPs were more severely affected in patients with ongoing pain than in those with provoked pain (P<0.0001). Our findings indicate that the impairment of Abeta-fibres has no role in the development of ongoing or provoked pain. In patients with ongoing pain the severe LEP suppression and the correlation between pain intensity and LEP attenuation may indicate that this type of pain reflects damage to nociceptive axons. The partially preserved LEPs in patients with provoked pain suggest that this type of pain is related to the abnormal activity arising from partially spared and sensitised nociceptive terminals. Because clinical and neurophysiological abnormalities followed similar patterns regardless of aetiology, pain should be classified and treated on mechanism-based grounds. Copyright (c) 2010 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Mechanisms of mononuclear phagocyte recruitment in Alzheimer's disease.

PubMed

Hickman, Suzanne E; El Khoury, Joseph

2010-04-01

Alzheimer's disease (AD) is associated with a significant neuroinflammatory component. Mononuclear phagocytes including monocytes and microglia are the principal cells involved, and they accumulate at perivascular sites of beta-amyloid (Abeta) deposition and in senile plaques. Recent evidence suggests that mononuclear phagocyte accumulation in the AD brain is dependent on chemokines. CCL2, a major monocyte chemokine, is upregulated in the AD brain. Interaction of CCL2 with its receptor CCR2 regulates mononuclear phagocyte accumulation in a mouse model of AD. CCR2 deficiency leads to lower mononuclear phagocyte accumulation and is associated with higher brain Abeta levels, specifically around blood vessels, suggesting that monocytes accumulate at sites of Abeta deposition in an initial attempt to clear these deposits and stop or delay their neurotoxic effects. Indeed, enhancing mononuclear phagocyte accumulation delays progression of AD. Here we review the mechanisms of mononuclear phagocyte accumulation in AD and discuss the potential roles of additional chemokines and their receptors in this process. We also propose a multi-step model for recruitment of mononuclear phagocytes into the brain. The first step involves egress of monocyte/microglial precursors from the bone marrow into the blood. The second step is crossing the blood-brain barrier to the perivascular areas and into the brain parenchyma. The final step includes movement of monocytes/microglia from areas of the brain that lack any amyloid deposition to senile plaques. Understanding the mechanism of recruitment of mononuclear phagocytes to the AD brain is necessary to further understand the role of these cells in the pathogenesis of AD and to identify any potential therapeutic use of these cells for the treatment of this disease.

Preparation of Imide Oligomers via Concurrent Reactive Extrusion

NASA Technical Reports Server (NTRS)

Avakian, Roger W. (Inventor); Hu, Ling (Inventor)

2018-01-01

Reactive extrusion can be used in a continuous, solvent-less preparation of imide oligomers involving two competing reactions among three ingredients, the first reaction between a dianhydride and a diamine and the second reaction between an endcap and the same diamine. The imide oligomer can form a composite via conventional production methods or via formation of a film from imide oligomer re-melted in an extruder before being impregnated into tape or fabric.

Imide Oligomers Endcapped with Phenylethynl Phthalic Anhydrides and Polymers Therefrom

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Smith, Joseph G., Jr. (Inventor)

1998-01-01

Controlled molecular weight phenylethynyl terminated imide oligomers (PETIs) have been prepared by the cyclodehydration of precursor phenylethynyl terminated amic acid oligomers. Amino terminated amic acid oligomers are prepared from the reaction of dianhydride(s) with an excess of diamine(s) and subsequently endcapped with phenylethynyl phthalic anhydride(s) (PEPA). The polymerizations are carried out in polar aprotic solvents such as N-methyl-2-pyrrolidinone or N.N-dimethylacetamide under nitrogen at room temperature. The amic acid oligomers are subsequently cyclodehydrated either thermally or cheznicauy to the corresponding imide oligomers. Direct preparation of PETIs from the reaction of dianhydxide(s) with an excess of diamine(s) and endcapped with phenylethynyl phthalic anhydride(s) has been performed in m-cresol. Phenylethynyl phthalic anhydrides are synthesized by the palladium catalyzed reaction of phenylacetylene with bromo substituted phthalic anhydrides in triethylamine. These new materials exhibit excellent properties and are potentially useful as adhesives, coatings, films, moldings and composite matrices.

Imide oligomers endcapped with phenylethynyl phthalic anhydrides and polymers therefrom

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Smith, Jr., Joseph G. (Inventor)

1996-01-01

Controlled molecular weight phenylethynyl terminated imide oligomers (PETIs) have been prepared by the cyclodehydration of precursor phenylethynyl terminated amic acid oligomers. Amino terminated amic acid oligomers are prepared from the reaction of dianhydride(s) with an excess of diamine(s) and subsequently endcapped with phenylethynyl phthalic anhydride(s) (PEPA). The polymerizations are carried out in polar aprotic solvents such as N-methyl-2-pyrrolidinone or N,N-dimethylacetamide under nitrogen at room temperature. The amic acid oligomers are subsequently cyclodehydrated either thermally or chemically to the corresponding imide oligomers. Direct preparation of PETIs from the reaction of dianhydride(s) with an excess of diamine(s) and endcapped with phenylethynyl phthalic anhydride(s) has been performed in m-cresol. Phenylethynyl phthalic anhydrides are synthesized by the palladium catalyzed reaction of phenylacetylene with bromo substituted phthalic anhydrides in triethylamine. These new materials exhibit excellent properties and are potentially useful as adhesives, coatings, films, moldings and composite matrices.

ER residency of the ceramide phosphoethanolamine synthase SMSr relies on homotypic oligomerization mediated by its SAM domain.

PubMed

Cabukusta, Birol; Kol, Matthijs; Kneller, Laura; Hilderink, Angelika; Bickert, Andreas; Mina, John G M; Korneev, Sergei; Holthuis, Joost C M

2017-01-25

SMSr/SAMD8 is an ER-resident ceramide phosphoethanolamine synthase with a critical role in controlling ER ceramides and suppressing ceramide-induced apoptosis in cultured cells. SMSr-mediated ceramide homeostasis relies on the enzyme's catalytic activity as well as on its N-terminal sterile α-motif or SAM domain. Here we report that SMSr-SAM is structurally and functionally related to the SAM domain of diacylglycerol kinase DGKδ, a central regulator of lipid signaling at the plasma membrane. Native gel electrophoresis indicates that both SAM domains form homotypic oligomers. Chemical crosslinking studies show that SMSr self-associates into ER-resident trimers and hexamers that resemble the helical oligomers formed by DGKδ-SAM. Residues critical for DGKδ-SAM oligomerization are conserved in SMSr-SAM and their substitution causes a dissociation of SMSr oligomers as well as a partial redistribution of the enzyme to the Golgi. Conversely, treatment of cells with curcumin, a drug disrupting ceramide and Ca 2+ homeostasis in the ER, stabilizes SMSr oligomers and promotes retention of the enzyme in the ER. Our data provide first demonstration of a multi-pass membrane protein that undergoes homotypic oligomerization via its SAM domain and indicate that SAM-mediated self-assembly of SMSr is required for efficient retention of the enzyme in the ER.

Dietary DHA supplementation in an APP/PS1 transgenic rat model of AD reduces behavioral and Aβ pathology and modulates Aβ oligomerization.

PubMed

Teng, Edmond; Taylor, Karen; Bilousova, Tina; Weiland, David; Pham, Thaidan; Zuo, Xiaohong; Yang, Fusheng; Chen, Ping-Ping; Glabe, Charles G; Takacs, Alison; Hoffman, Dennis R; Frautschy, Sally A; Cole, Gregory M

2015-10-01

Increased dietary consumption of docosahexaenoic acid (DHA) is associated with decreased risk for Alzheimer's disease (AD). These effects have been postulated to arise from DHA's pleiotropic effects on AD pathophysiology, including its effects on β-amyloid (Aβ) production, aggregation, and toxicity. While in vitro studies suggest that DHA may inhibit and reverse the formation of toxic Aβ oligomers, it remains uncertain whether these mechanisms operate in vivo at the physiological concentrations of DHA attainable through dietary supplementation. We sought to clarify the effects of dietary DHA supplementation on Aβ indices in a transgenic APP/PS1 rat model of AD. Animals maintained on a DHA-supplemented diet exhibited reductions in hippocampal Aβ plaque density and modest improvements on behavioral testing relative to those maintained on a DHA-depleted diet. However, DHA supplementation also increased overall soluble Aβ oligomer levels in the hippocampus. Further quantification of specific conformational populations of Aβ oligomers indicated that DHA supplementation increased fibrillar (i.e. putatively less toxic) Aβ oligomers and decreased prefibrillar (i.e. putatively more toxic) Aβ oligomers. These results provide in vivo evidence suggesting that DHA can modulate Aβ aggregation by stabilizing soluble fibrillar Aβ oligomers and thus reduce the formation of both Aβ plaques and prefibrillar Aβ oligomers. However, since fibrillar Aβ oligomers still retain inherent neurotoxicity, DHA may need to be combined with other interventions that can additionally reduce fibrillar Aβ oligomer levels for more effective prevention of AD in clinical settings. Published by Elsevier Inc.

Computer simulations and theoretical aspects of the depletion interaction in protein-oligomer mixtures.

PubMed

Boncina, M; Rescic, J; Kalyuzhnyi, Yu V; Vlachy, V

2007-07-21

The depletion interaction between proteins caused by addition of either uncharged or partially charged oligomers was studied using the canonical Monte Carlo simulation technique and the integral equation theory. A protein molecule was modeled in two different ways: either as (i) a hard sphere of diameter 30.0 A with net charge 0, or +5, or (ii) as a hard sphere with discrete charges (depending on the pH of solution) of diameter 45.4 A. The oligomers were pictured as tangentially jointed, uncharged, or partially charged, hard spheres. The ions of a simple electrolyte present in solution were represented by charged hard spheres distributed in the dielectric continuum. In this study we were particularly interested in changes of the protein-protein pair-distribution function, caused by addition of the oligomer component. In agreement with previous studies we found that addition of a nonadsorbing oligomer reduces the phase stability of solution, which is reflected in the shape of the protein-protein pair-distribution function. The value of this function in protein-protein contact increases with increasing oligomer concentration, and is larger for charged oligomers. The range of the depletion interaction and its strength also depend on the length (number of monomer units) of the oligomer chain. The integral equation theory, based on the Wertheim Ornstein-Zernike approach applied in this study, was found to be in fair agreement with Monte Carlo results only for very short oligomers. The computer simulations for a model mimicking the lysozyme molecule (ii) are in qualitative agreement with small-angle neutron experiments for lysozyme-dextran mixtures.

Alzheimer brain-derived tau oligomers propagate pathology from endogenous tau.

PubMed

Lasagna-Reeves, Cristian A; Castillo-Carranza, Diana L; Sengupta, Urmi; Guerrero-Munoz, Marcos J; Kiritoshi, Takaki; Neugebauer, Volker; Jackson, George R; Kayed, Rakez

2012-01-01

Intracerebral injection of brain extracts containing amyloid or tau aggregates in transgenic animals can induce cerebral amyloidosis and tau pathology. We extracted pure populations of tau oligomers directly from the cerebral cortex of Alzheimer disease (AD) brain. These oligomers are potent inhibitors of long term potentiation (LTP) in hippocampal brain slices and disrupt memory in wild type mice. We observed for the first time that these authentic brain-derived tau oligomers propagate abnormal tau conformation of endogenous murine tau after prolonged incubation. The conformation and hydrophobicity of tau oligomers play a critical role in the initiation and spread of tau pathology in the naïve host in a manner reminiscent of sporadic AD.

Charge transfer interactions in oligomer coated gold nanoclusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newmai, M. Boazbou; Kumar, Pandian Senthil, E-mail: duplasmonics@gmail.com

Gold nanoclusters were synthesized by a bottom-up synergistic approach of in-situ oligomerization of the monomer, N-vinyl pyrrolidone (NVP) and simultaneous weak reduction of Au-NVP complexes in the absence of any other external energy sources, thereby making these tiny gold clusters as the most elemental building blocks to construct further novel nano/microstructures with application potentials. It is well-known that metal clusters with less than 2 nm size do not show the usual surface plasmon band, because of the presence of a band-gap at the fermi level. Nevertheless, our present oligomer coated gold clusters show a discrete intense band at around 630 nm, whichmore » could very well be attributed to the charge transfer between the oligomer chain and the surface Au atoms. Such kind of sacrificial plasmon induced charge transfer interaction, observed for the very first time to the best of our knowledge, were also strongly corroborated through the enhancement / shifting of specific vibrational / rotational peaks as observed from the FTIR and Raman measurements as a function of the metal oxidation states, thus representing a new prototype for an efficient solar energy conversion probe.« less

Gelsolin as therapeutic target in Alzheimer's disease.

PubMed

Carro, Eva

2010-06-01

Fibrillar amyloid beta-protein (Abeta) is a major component of amyloid plaques in the brains of individuals with Alzheimer's disease (AD). However, a comprehensive explanation of the mechanisms leading to brain amyloidosis is still pending. Previous studies have identified the anti-amyloidogenic role of gelsolin in AD. Gelsolin can reduce amyloid burden by acting as an inhibitor of Abeta fibrillization, and as an antioxidant and anti-apoptotic protein. Recent evidence indicates reduced brain gelsolin levels in AD. Therefore, a better understanding of the roles of gelsolin in AD pathology, particularly those related with cognition, is required. Most of the information reviewed here relates to experimental studies. However, gelsolin may progress from the present evidence to preclinical and clinical applications. In addition, a greater insight into the environmental factors contributing to abnormally reduced gelsolin function in AD brains may become crucial for the development of much needed disease-modifying strategies. Because, the efficacy of available medicines is still poor, there is an urgent need for novel AD treatments. In this sense, gelsolin could play an important role.

Membrane microdomain switching: a regulatory mechanism of amyloid precursor protein processing.

PubMed

Sakurai, Takashi; Kaneko, Kumi; Okuno, Misako; Wada, Koji; Kashiyama, Taku; Shimizu, Hideaki; Akagi, Takumi; Hashikawa, Tsutomu; Nukina, Nobuyuki

2008-10-20

Neuronal activity has an impact on beta cleavage of amyloid precursor protein (APP) by BACE1 to generate amyloid-beta peptide (Abeta). However, the molecular mechanisms underlying this effect remain to be elucidated. Cholesterol dependency of beta cleavage prompted us to analyze immunoisolated APP-containing detergent-resistant membranes from rodent brains. We found syntaxin 1 as a key molecule for activity-dependent regulation of APP processing in cholesterol-dependent microdomains. In living cells, APP associates with syntaxin 1-containing microdomains through X11-Munc18, which inhibits the APP-BACE1 interaction and beta cleavage via microdomain segregation. Phosphorylation of Munc18 by cdk5 causes a shift of APP to BACE1-containing microdomains. Neuronal hyperactivity, implicated in Abeta overproduction, promotes the switching of APP microdomain association as well as beta cleavage in a partially cdk5-dependent manner. We propose that microdomain switching is a mechanism of cholesterol- and activity-dependent regulation of APP processing in neurons.

DFT Modeling of Cross-Linked Polyethylene: Role of Gold Atoms and Dispersion Interactions.

PubMed

Blaško, Martin; Mach, Pavel; Antušek, Andrej; Urban, Miroslav

2018-02-08

Using DFT modeling, we analyze the concerted action of gold atoms and dispersion interactions in cross-linked polyethylene. Our model consists of two oligomer chains (PEn) with 7, 11, 15, 19, or 23 carbon atoms in each oligomer cross-linked with one to three Au atoms through C-Au-C bonds. In structures with a single gold atom the C-Au-C bond is located in the central position of the oligomer. Binding energies (BEs) with respect to two oligomer radical fragments and Au are as high as 362-489 kJ/mol depending on the length of the oligomer chain. When the dispersion contribution in PEn-Au-PEn oligomers is omitted, BE is almost independent of the number of carbon atoms, lying between 293 and 296 kJ/mol. The dispersion energy contributions to BEs in PEn-Au-PEn rise nearly linearly with the number of carbon atoms in the PEn chain. The carbon-carbon distance in the C-Au-C moiety is around 4.1 Å, similar to the bond distance between saturated closed shell chains in the polyethylene crystal. BEs of pure saturated closed shell PEn-PEn oligomers are 51-187 kJ/mol. Both Au atoms and dispersion interactions contribute considerably to the creation of nearly parallel chains of oligomers with reasonably high binding energies.

Protection against β-amyloid-induced synaptic and memory impairments via altering β-amyloid assembly by bis(heptyl)-cognitin

PubMed Central

Chang, Lan; Cui, Wei; Yang, Yong; Xu, Shujun; Zhou, Wenhua; Fu, Hongjun; Hu, Shengquan; Mak, Shinghung; Hu, Juwei; Wang, Qin; Pui-Yan Ma, Victor; Chung-lit Choi, Tony; Dik-lung Ma, Edmond; Tao, Liang; Pang, Yuanping; Rowan, Michael J.; Anwyl, Roger; Han, Yifan; Wang, Qinwen

2015-01-01

β-amyloid (Aβ) oligomers have been closely implicated in the pathogenesis of Alzheimer’s disease (AD). We found, for the first time, that bis(heptyl)-cognitin, a novel dimeric acetylcholinesterase (AChE) inhibitor derived from tacrine, prevented Aβ oligomers-induced inhibition of long-term potentiation (LTP) at concentrations that did not interfere with normal LTP. Bis(heptyl)-cognitin also prevented Aβ oligomers-induced synaptotoxicity in primary hippocampal neurons. In contrast, tacrine and donepezil, typical AChE inhibitors, could not prevent synaptic impairments in these models, indicating that the modification of Aβ oligomers toxicity by bis(heptyl)-cognitin might be attributed to a mechanism other than AChE inhibition. Studies by using dot blotting, immunoblotting, circular dichroism spectroscopy, and transmission electron microscopy have shown that bis(heptyl)-cognitin altered Aβ assembly via directly inhibiting Aβ oligomers formation and reducing the amount of preformed Aβ oligomers. Molecular docking analysis further suggested that bis(heptyl)-cognitin presumably interacted with the hydrophobic pockets of Aβ, which confers stabilizing powers and assembly alteration effects on Aβ. Most importantly, bis(heptyl)-cognitin significantly reduced cognitive impairments induced by intra-hippocampal infusion of Aβ oligomers in mice. These results clearly demonstrated how dimeric agents prevent Aβ oligomers-induced synaptic and memory impairments, and offered a strong support for the beneficial therapeutic effects of bis(heptyl)-cognitin in the treatment of AD. PMID:26194093

Combined HILIC-ELSD/ESI-MS(n) enables the separation, identification and quantification of sugar beet pectin derived oligomers.

PubMed

Remoroza, C; Cord-Landwehr, S; Leijdekkers, A G M; Moerschbacher, B M; Schols, H A; Gruppen, H

2012-09-01

The combined action of endo-polygalacturonase (endo-PGII), pectin lyase (PL), pectin methyl esterase (fungal PME) and RG-I degrading enzymes enabled the extended degradation of methylesterified and acetylated sugar beet pectins (SBPs). The released oligomers were separated, identified and quantified using hydrophilic interaction liquid chromatography (HILIC) with online electrospray ionization ion trap mass spectrometry (ESI-IT-MS(n)) and evaporative light scattering detection (ELSD). By MS(n), the structures of galacturonic acid (GalA) oligomers having an acetyl group in the O-2 and/or O-3 positions eluting from the HILIC column were elucidated. The presence of methylesterified and/or acetylated galacturonic acid units within an oligomer reduced the interaction with the HILIC column significantly compared to the unsubstituted GalA oligomers. The HILIC column enables a good separation of most oligomers present in the digest. The use of ELSD to quantify oligogalacturonides was validated using pure GalA standards and the signal was found to be independent of the chemical structure of the oligomer being detected. The combination of chromatographic and enzymatic strategies enables to distinguish SBPs having different methylesters and acetyl group distribution. Copyright © 2012 Elsevier Ltd. All rights reserved.

The switching behaviors induced by torsion angle in a diblock co-oligomer molecule with tailoring graphene nanoribbon electrodes

NASA Astrophysics Data System (ADS)

Yang, Aiyun; Xia, Caijuan; Zhang, Boqun; Wang, Jun; Su, Yaoheng; Tu, Zheyan

2018-02-01

By applying first-principles method based on density functional theory combined with nonequilibrium Green’s function, we investigate the effect of torsion angle on the electronic transport properties in dipyrimidinyl-diphenyl co-oligomer molecular device with tailoring graphene nanoribbon electrodes. The results show that the torsion angle plays an important role on the electronic transport properties of the molecular device. When the torsion angle rotates from 0∘ to 90∘, the molecular devices exhibit very different current-voltage characteristics which can realize the on and off states of the molecular switch.

Montmorillonite catalysis of RNA oligomer formation in aqueous solution. A model for the prebiotic formation of RNA

NASA Technical Reports Server (NTRS)

Ferris, J. P.; Ertem, G.

1993-01-01

Oligomers of adenylic acid of up to the 11-mer in length are formed by the reaction of the phosphorimidazolide of adenosine (ImpA) in pH 8 aqueous solution at room temperature in the presence of Na(+)-montmorillonite. These oligomers are joined by phosphodiester bonds in which the 3',5'-linkage predominates over the 2',5'-linkage by a 2:1 ratio. Reaction of a 9:1 mixture of ImpA, A5'ppA results in the formation of oligomers with a 3:1 ratio of 3',5'- to 2',5'-linked phosphodiester bonds. A high proportion of these oligomers contain the A5'ppA grouping. A5'ppA reacts much more rapidly with ImpA than does 5'-ADP (ppA) or 5'-ATP (pppA). The exchangeable cation associated with the montmorillonite effects the observed catalysis with Li+, Na+, NH4+, and Ca2+ being the more effective while Mg2+ and Al3+ are almost ineffective catalysts. 2',5'-Linked oligomers, up to the tetramer in length, are formed using UO2(2+)-montmorillonite. The structure analysis of individual oligomer fractions was performed by selective enzymatic and KOH hydrolytic studies followed by HPLC analysis of the reaction products. It is concluded from the composition of the oligomers that the rate of addition ImpA to a 3'-terminus containing a 2',5'-linkage is slower than the addition to a nucleoside joined by a 3',5'-linked phosphodiester bond. The potential importance of mineral catalysis of the formation of RNA and other oligomers on primitive Earth is discussed.

Detergent-dispersant additives based on high-molecular-weight alkylphenols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulieva, K.N.; Namazova, I.I.; Ismailova, N.D.

1988-09-01

This article describes the synthesis and investigation of Mannich bases produced for alkylphenols, obtained in turn from ethylene oligomers. These oligomers are the still bottoms from distillation products of high-temperature oligomerization of ethylene in the presence of triethylaluminum. Two narrow cuts obtained from the distillation of oligomer fraction were used to study the influence of ethylene oligomer molecular weight on the properties of the additives. The additives were blended in DS-11 oil to evaluate their detergency-dispersancy and other properties. Comparison blends were made with succinimide additives based on the same ethylene oligomers. The Mannich bases give improvements in the oxidationmore » resistance, anticorrosion properties, and detergency-dispersancy of the DS-11 diesel oil.« less

Degradation of a Sodium Acrylate Oligomer by an Arthrobacter sp

PubMed Central

Hayashi, Takaya; Mukouyama, Masaharu; Sakano, Kouichi; Tani, Yoshiki

1993-01-01

Arthrobacter sp. strain NO-18 was first isolated from soil as a bacterium which could degrade the sodium acrylate oligomer and utilize it as the sole source of carbon. When 0.2% (wt/wt) oligomer was added to the culture medium, the acrylate oligomer was found to be degraded by 70 to 80% in 2 weeks, using gel permeation chromatography. To determine the maximum molecular weight for biodegradation, the degradation test was done with the hexamer, heptamer, and octamer, which were separated from the oligomer mixture by fractional gel permeation chromatography. The hexamer and heptamer were consumed to the extents of 58 and 36%, respectively, in 2 weeks, but the octamer was not degraded. Oligomers with three different terminal groups were synthesized to examine the effect of the different terminal groups on biodegradation, but few differences were found. Arthrobacter sp. NO-18 assimilated acrylic acid, propionic acid, glutaric acid, 2-methylglutaric acid, and 1,3,5-pentanetricarboxylic acid. Degradation of the acrylic unit structure by this strain is discussed. PMID:8517751

Effects of adding methacrylate monomers on viscosity and mechanical properties of experimental light-curing soft lining materials based on urethane (meth)acrylate oligomers.

PubMed

Kanie, Takahito; Kadokawa, Akihiko; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2008-11-01

We investigated the viscosity and mechanical properties of experimental light-curing soft lining materials based on six commercially available urethane (meth)acrylate oligomers. The viscosities of the six oligomers were 1.9, 20.6, 26.8, 144.0, 185.3, and 8803.4 Pa*s at 25 degrees C. Two monomers (ethyl- and butyl-methacrylate) were added at 20 wt% to these oligomers to decrease the viscosity, resulting in viscosity reductions of 0.2 to 13.6 Pa*s for the six oligomers. The mechanical properties (compressive modulus, Shore A hardness, and tensile strength) were measured after two times light-polymerization for 3 min. The addition of the monomers to the oligomers only slightly changed the mechanical properties, in contrast to the large viscosity changes. Based on these results, it appears that the addition of ethyl- or butyl-methacrylate monomers is useful for decreasing the viscosity of experimental light-curing soft lining materials without changing their mechanical properties.

Violation of the isolated square rule for group 13-15 oligomers: theoretical prediction of a new class of inorganic polymers.

PubMed

Timoshkin, Alexey Y; Schaefer, Henry F

2005-02-21

It is widely thought that the oligomer compounds [RMYR]n (M-group 13, Y-group 15 element) should obey the isolated square rule found for the boron-nitrogen cages. In contrast to these expectations, the needle-shaped oligomers, which violate this rule, are more stable compared to the cage (fullerene-like) oligomers for all MY pairs (M = B, Al, Ga, In; Y = N, P, As). The stability of the needle-shaped clusters improves with increasing oligomerization degree. Thus, the isolated square rule, which is analogous to the isolated pentagon rule widely applied for fullerenes, should not serve as the basis for searches for the most stable structures of the inorganic oligomers. Generation of the needle-shaped oligomers from the group 13 and 15 hydrides is thermodynamically favorable. A synthesis of novel inorganic polymers, formed by fusion of trimeric M3Y3 rings, is expected to be viable.

Transesterification of PHA to oligomers covalently bonded with (bio)active compounds containing either carboxyl or hydroxyl functionalities.

PubMed

Kwiecień, Iwona; Radecka, Iza; Kowalczuk, Marek; Adamus, Grażyna

2015-01-01

This manuscript presents the synthesis and structural characterisation of novel biodegradable polymeric controlled-release systems of pesticides with potentially higher resistance to weather conditions in comparison to conventional forms of pesticides. Two methods for the preparation of pesticide-oligomer conjugates using the transesterification reaction were developed. The first method of obtaining conjugates, which consist of bioactive compounds with the carboxyl group and polyhydroxyalkanoates (PHAs) oligomers, is "one-pot" transesterification. In the second method, conjugates of bioactive compounds with hydroxyl group and polyhydroxyalkanoates oligomers were obtained in two-step method, through cyclic poly(3-hydroxybutyrate) oligomers. The obtained pesticide-PHA conjugates were comprehensively characterised using GPC, 1H NMR and mass spectrometry techniques. The structural characterisation of the obtained products at the molecular level with the aid of mass spectrometry confirmed that both of the synthetic strategies employed led to the formation of conjugates in which selected pesticides were covalently bonded to PHA oligomers via a hydrolysable ester bond.

Bacoside-A, an Indian Traditional-Medicine Substance, Inhibits β-Amyloid Cytotoxicity, Fibrillation, and Membrane Interactions.

PubMed

Malishev, Ravit; Shaham-Niv, Shira; Nandi, Sukhendu; Kolusheva, Sofiya; Gazit, Ehud; Jelinek, Raz

2017-04-19

Bacoside-A, a family of compounds extracted from the Bacopa monniera plant, is a folk-medicinal substance believed to exhibit therapeutic properties, particularly enhancing cognitive functions and improving memory. We show that bacoside-A exerted significant inhibitory effects upon cytotoxicity, fibrillation, and particularly membrane interactions of amyloid-beta (1-42) (Aβ42), the peptide playing a prominent role in Alzeheimer's disease progression and toxicity. Specifically, preincubation of bacoside-A with Aβ42 significantly reduced cell toxicity and inhibited fibril formation both in buffer solution and, more significantly, in the presence of membrane vesicles. In parallel, spectroscopic and microscopic analyses reveal that bacoside-A blocked membrane interactions of Aβ42, while formation of Aβ42 oligomers was not disrupted. These interesting phenomena suggest that inhibition of Aβ42 oligomer assembly into mature fibrils, and blocking membrane interactions of the oligomers are likely the underlying factors for ameliorating amyloid toxicity by bacoside-A and its putative physiological benefits.

Interaction of arginine oligomer with model membrane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Dandan; Guoming, Li; Gao, Li

2007-08-10

Short oligomers of arginine (R8) have been shown to cross readily a variety of biological barriers. A hypothesis was put forward that inverted micelles form in biological membranes in the presence of arginine oligomer peptides, facilitating their transfer through the membranes. In order to define the role of peptide-lipid interaction in this mechanism, we prepared liposomes as the model membrane to study the ability of R8 inducing calcein release from liposomes, the fusion of liposomes, R8 binding to liposomes and membrane disturbing activity of the bound R8. The results show that R8 binding to liposome membrane depends on lipid compositions,more » negative surface charge density and interior water phase pH values of liposomes. R8 has no activity to induce the leakage of calcein from liposomes or improve liposome fusion. R8 does not permeabilize through the membrane spontaneously. These peptides delivering drugs through membranes may depend on receptors and energy.« less

Novel and economic acid-base indicator based on (p-toluidine) oligomer: Synthesis; characterization and solvatochromism applications

NASA Astrophysics Data System (ADS)

Zoromba, M. Sh.

2017-12-01

A new (p-toluidine) oligomer (PTO) was facile synthesized and economically routed via chemical oxidative polymerization by potassium dichromate as an initiator in an acidic aqueous medium at room temperature. The characterization of (p-toluidine) oligomer (PTO) has been described by various techniques including Fourier transform infra-red (FTIR), UV-Visible measurements, Mass spectra, H NMR, and thermal gravimetric analysis (TGA). Solvatochromism of PTO was studied in different polaritiy solvents such as acetic acid, acetone, dimethyl formamide, ethanol, isopropanol, chloroform, p-xylene, dichloromethane and carbon teterachloride. The absorption bands were bathochromically shifted with increased polarity of the solvent (positive solvatochromism). PTO shows three isosbestic points at 333, 388 and 472 nm in a binary mixture of acetone and chloroform. The deprotonation constants of PTO were found to be 3.1 and 5.8, based on spectrophotometric calculations. PTO was successfully used as an acid-base indicator; the acid solution color sharply turned from pink (acidic medium) to yellow (basic medium) at the end point.

An infrared spectroscopy approach to follow β-sheet formation in peptide amyloid assemblies

NASA Astrophysics Data System (ADS)

Seo, Jongcheol; Hoffmann, Waldemar; Warnke, Stephan; Huang, Xing; Gewinner, Sandy; Schöllkopf, Wieland; Bowers, Michael T.; von Helden, Gert; Pagel, Kevin

2017-01-01

Amyloidogenic peptides and proteins play a crucial role in a variety of neurodegenerative disorders such as Alzheimer's and Parkinson's disease. These proteins undergo a spontaneous transition from a soluble, often partially folded form, into insoluble amyloid fibrils that are rich in β-sheets. Increasing evidence suggests that highly dynamic, polydisperse folding intermediates, which occur during fibril formation, are the toxic species in the amyloid-related diseases. Traditional condensed-phase methods are of limited use for characterizing these states because they typically only provide ensemble averages rather than information about individual oligomers. Here we report the first direct secondary-structure analysis of individual amyloid intermediates using a combination of ion mobility spectrometry-mass spectrometry and gas-phase infrared spectroscopy. Our data reveal that oligomers of the fibril-forming peptide segments VEALYL and YVEALL, which consist of 4-9 peptide strands, can contain a significant amount of β-sheet. In addition, our data show that the more-extended variants of each oligomer generally exhibit increased β-sheet content.

Electrolytic conditioning of a magnesium aluminum chloride complex for reversible magnesium deposition

DOE PAGES

Barile, Christopher J.; Barile, Elizabeth C.; Zavadil, Kevin R.; ...

2014-12-04

We describe in this report the electrochemistry of Mg deposition and dissolution from the magnesium aluminum chloride complex (MACC). The results define the requirements for reversible Mg deposition and definitively establish that voltammetric cycling of the electrolyte significantly alters its composition and performance. Elemental analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDS) results demonstrate that irreversible Mg and Al deposits form during early cycles. Electrospray ionization-mass spectrometry (ESI-MS) data show that inhibitory oligomers develop in THF-based solutions. These oligomers form via the well-established mechanism of a cationic ring-opening polymerization of THF during the initial synthesis of the MACC andmore » under resting conditions. In contrast, MACC solutions in 1,2-dimethoxyethane (DME), an acyclic solvent, do not evolve as dramatically at open circuit potential. Furthermore, we propose a mechanism describing how the conditioning process of the MACC in THF improves its performance by both tuning the Mg:Al stoichiometry and eliminating oligomers.« less

Clay catalyzed RNA synthesis under Martian conditions: Application for Mars return samples.

PubMed

Joshi, Prakash C; Dubey, Krishna; Aldersley, Michael F; Sausville, Meaghen

2015-06-26

Catalysis by montmorillonites clay minerals is regarded as a feasible mechanism for the abiotic production and polymerization of key biomolecules on early Earth. We have investigated a montmorillonite-catalyzed reaction of the 5'-phosphorimidazolide of nucleosides as a model to probe prebiotic synthesis of RNA-type oligomers. Here we show that this model is specific for the generation of RNA oligomers despite deoxy-mononucleotides adsorbing equally well onto the montmorillonite catalytic surfaces. Optimum catalytic activity was observed over a range of pH (6-9) and salinity (1 ± 0.2 M NaCl). When the weathering steps of early Earth that generated catalytic montmorillonite were modified to meet Martian soil conditions, the catalytic activity remained intact without altering the surface layer charge. Additionally, the formation of oligomers up to tetramer was detected using as little as 0.1 mg of Na⁺-montmorillonite, suggesting that the catalytic activity of a Martian clay return sample can be investigated with sub-milligram scale samples. Copyright © 2015 Elsevier Inc. All rights reserved.

Effect of leaving group on the oligomerization of 5'-AMP on montmorillonite. [Abstract only

NASA Technical Reports Server (NTRS)

Prabahar, K. Joseph; Ferris, James P.

1994-01-01

The oligomerization of imidazole derivative of 5'-AMP (ImpA) in the presence of montmorillonite clay yields oligomers containing up to 10 monomer units. In these reactions, the heterocyclic base, imidazole is the leaving group. In our present study, we synthesized a series of activated nucleotides of 5'AMP using other leaving groups such as pyrazole, 1,2,4-triazole, piperidine, morpholine, 4-aminopyridine, 4-methylaminopyridine, 4-dimethylaminopyridine, 2-aminobenzimidazole etc. to determine the effect of amine leaving group on the products of the oligomerization reaction. Earlier results from our laboratory showed that the presence AppA in the clay reaction of ImpA enhances the oligomerization reaction to yield higher oligomers. We also studied the effect of AppA in the clay mediated oligomerization reaction of the activated nucleotides. Oligomerization of 2-amino-benzimidazole derivative of 5'-AMP gave higher oligomers containing up to nine monomer units in the presence of AppA.

Higher-order architecture of rhodopsin in intact photoreceptors and its implication for phototransduction kinetics.

PubMed

Gunkel, Monika; Schöneberg, Johannes; Alkhaldi, Weaam; Irsen, Stephan; Noé, Frank; Kaupp, U Benjamin; Al-Amoudi, Ashraf

2015-04-07

The visual pigment rhodopsin belongs to the family of G protein-coupled receptors that can form higher oligomers. It is controversial whether rhodopsin forms oligomers and whether oligomers are functionally relevant. Here, we study rhodopsin organization in cryosections of dark-adapted mouse rod photoreceptors by cryoelectron tomography. We identify four hierarchical levels of organization. Rhodopsin forms dimers; at least ten dimers form a row. Rows form pairs (tracks) that are aligned parallel to the disk incisures. Particle-based simulation shows that the combination of tracks with fast precomplex formation, i.e. rapid association and dissociation between inactive rhodopsin and the G protein transducin, leads to kinetic trapping: rhodopsin first activates transducin from its own track, whereas recruitment of transducin from other tracks proceeds more slowly. The trap mechanism could produce uniform single-photon responses independent of rhodopsin lifetime. In general, tracks might provide a platform that coordinates the spatiotemporal interaction of signaling molecules. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evidence that a synthetic amyloid-ß oligomer-binding peptide (ABP) targets amyloid-ß deposits in transgenic mouse brain and human Alzheimer's disease brain.

PubMed

Chakravarthy, Balu; Ito, Shingo; Atkinson, Trevor; Gaudet, Chantal; Ménard, Michel; Brown, Leslie; Whitfield, James

2014-03-14

The synthetic ~5 kDa ABP (amyloid-ß binding peptide) consists of a region of the 228 kDa human pericentrioloar material-1 (PCM-1) protein that selectively and avidly binds in vitro Aβ1-42 oligomers, believed to be key co-drivers of Alzheimer's disease (AD), but not monomers (Chakravarthy et al., (2013) [3]). ABP also prevents Aß1-42 from triggering the apoptotic death of cultured human SHSY5Y neuroblasts, likely by sequestering Aß oligomers, suggesting that it might be a potential AD therapeutic. Here we support this possibility by showing that ABP also recognizes and binds Aβ1-42 aggregates in sections of cortices and hippocampi from brains of AD transgenic mice and human AD patients. More importantly, ABP targets Aβ1-42 aggregates when microinjected into the hippocampi of the brains of live AD transgenic mice. Crown Copyright © 2014. Published by Elsevier Inc. All rights reserved.

Foldability of a Natural De Novo Evolved Protein.

PubMed

Bungard, Dixie; Copple, Jacob S; Yan, Jing; Chhun, Jimmy J; Kumirov, Vlad K; Foy, Scott G; Masel, Joanna; Wysocki, Vicki H; Cordes, Matthew H J

2017-11-07

The de novo evolution of protein-coding genes from noncoding DNA is emerging as a source of molecular innovation in biology. Studies of random sequence libraries, however, suggest that young de novo proteins will not fold into compact, specific structures typical of native globular proteins. Here we show that Bsc4, a functional, natural de novo protein encoded by a gene that evolved recently from noncoding DNA in the yeast S. cerevisiae, folds to a partially specific three-dimensional structure. Bsc4 forms soluble, compact oligomers with high β sheet content and a hydrophobic core, and undergoes cooperative, reversible denaturation. Bsc4 lacks a specific quaternary state, however, existing instead as a continuous distribution of oligomer sizes, and binds dyes indicative of amyloid oligomers or molten globules. The combination of native-like and non-native-like properties suggests a rudimentary fold that could potentially act as a functional intermediate in the emergence of new folded proteins de novo. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structural fingerprints and their evolution during oligomeric vs. oligomer-free amyloid fibril growth

PubMed Central

Foley, Joseph; Hill, Shannon E.; Miti, Tatiana; Mulaj, Mentor; Ciesla, Marissa; Robeel, Rhonda; Persichilli, Christopher; Raynes, Rachel; Westerheide, Sandy; Muschol, Martin

2013-01-01

Deposits of fibrils formed by disease-specific proteins are the molecular hallmark of such diverse human disorders as Alzheimer's disease, type II diabetes, or rheumatoid arthritis. Amyloid fibril formation by structurally and functionally unrelated proteins exhibits many generic characteristics, most prominently the cross β-sheet structure of their mature fibrils. At the same time, amyloid formation tends to proceed along one of two separate assembly pathways yielding either stiff monomeric filaments or globular oligomers and curvilinear protofibrils. Given the focus on oligomers as major toxic species, the very existence of an oligomer-free assembly pathway is significant. Little is known, though, about the structure of the various intermediates emerging along different pathways and whether the pathways converge towards a common or distinct fibril structures. Using infrared spectroscopy we probed the structural evolution of intermediates and late-stage fibrils formed during in vitro lysozyme amyloid assembly along an oligomeric and oligomer-free pathway. Infrared spectroscopy confirmed that both pathways produced amyloid-specific β-sheet peaks, but at pathway-specific wavenumbers. We further found that the amyloid-specific dye thioflavin T responded to all intermediates along either pathway. The relative amplitudes of thioflavin T fluorescence responses displayed pathway-specific differences and could be utilized for monitoring the structural evolution of intermediates. Pathway-specific structural features obtained from infrared spectroscopy and Thioflavin T responses were identical for fibrils grown at highly acidic or at physiological pH values and showed no discernible effects of protein hydrolysis. Our results suggest that late-stage fibrils formed along either pathway are amyloidogenic in nature, but have distinguishable structural fingerprints. These pathway-specific fingerprints emerge during the earliest aggregation events and persist throughout the entire cascade of aggregation intermediates formed along each pathway. PMID:24089713

Polydopamine and eumelanin molecular structures investigated with ab initio calculations† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc04692d Click here for additional data file.

PubMed Central

Chen, Chun-Teh; Martin-Martinez, Francisco J.; Jung, Gang Seob

2017-01-01

A set of computational methods that contains a brute-force algorithmic generation of chemical isomers, molecular dynamics (MD) simulations, and density functional theory (DFT) calculations is reported and applied to investigate nearly 3000 probable molecular structures of polydopamine (PDA) and eumelanin. All probable early-polymerized 5,6-dihydroxyindole (DHI) oligomers, ranging from dimers to tetramers, have been systematically analyzed to find the most stable geometry connections as well as to propose a set of molecular models that represents the chemically diverse nature of PDA and eumelanin. Our results indicate that more planar oligomers have a tendency to be more stable. This finding is in good agreement with recent experimental observations, which suggested that PDA and eumelanin are composed of nearly planar oligomers that appear to be stacked together via π–π interactions to form graphite-like layered aggregates. We also show that there is a group of tetramers notably more stable than the others, implying that even though there is an inherent chemical diversity in PDA and eumelanin, the molecular structures of the majority of the species are quite repetitive. Our results also suggest that larger oligomers are less likely to form. This observation is also consistent with experimental measurements, supporting the existence of small oligomers instead of large polymers as main components of PDA and eumelanin. In summary, this work brings an insight into the controversial structure of PDA and eumelanin, explaining some of the most important structural features, and providing a set of molecular models for more accurate modeling of eumelanin-like materials. PMID:28451292

β-Amyloid Oligomers Induce Phosphorylation of Tau and Inactivation of Insulin Receptor Substrate via c-Jun N-Terminal Kinase Signaling: Suppression by Omega-3 Fatty Acids and Curcumin

PubMed Central

Ma, Qiu-Lan; Yang, Fusheng; Rosario, Emily R.; Ubeda, Oliver J.; Beech, Walter; Gant, Dana J.; Chen, Ping Ping; Hudspeth, Beverly; Chen, Cory; Zhao, Yongle; Vinters, Harry V.; Frautschy, Sally A.

2009-01-01

Both insulin resistance (type II diabetes) and β-amyloid (Aβ) oligomers are implicated in Alzheimer's disease (AD). Here, we investigate the role of Aβ oligomer-induced c-Jun N-terminal kinase (JNK) activation leading to phosphorylation and degradation of the adaptor protein insulin receptor substrate-1 (IRS-1). IRS-1 couples insulin and other trophic factor receptors to downstream kinases and neuroprotective signaling. Increased phospho-IRS-1 is found in AD brain and insulin-resistant tissues from diabetics. Here, we report Aβ oligomers significantly increased active JNK and phosphorylation of IRS-1 (Ser616) and tau (Ser422) in cultured hippocampal neurons, whereas JNK inhibition blocked these responses. The omega-3 fatty acid docosahexaenoic acid (DHA) similarly inhibited JNK and the phosphorylation of IRS-1 and tau in cultured hippocampal neurons. Feeding 3xTg-AD transgenic mice a diet high in saturated and omega-6 fat increased active JNK and phosphorylated IRS-1 and tau. Treatment of the 3xTg-AD mice on high-fat diet with fish oil or curcumin or a combination of both for 4 months reduced phosphorylated JNK, IRS-1, and tau and prevented the degradation of total IRS-1. This was accompanied by improvement in Y-maze performance. Mice fed with fish oil and curcumin for 1 month had more significant effects on Y-maze, and the combination showed more significant inhibition of JNK, IRS-1, and tau phosphorylation. These data indicate JNK mediates Aβ oligomer inactivation of IRS-1 and phospho-tau pathology and that dietary treatment with fish oil/DHA, curcumin, or a combination of both has the potential to improve insulin/trophic signaling and cognitive deficits in AD. PMID:19605645

Structural fingerprints and their evolution during oligomeric vs. oligomer-free amyloid fibril growth

NASA Astrophysics Data System (ADS)

Foley, Joseph; Hill, Shannon E.; Miti, Tatiana; Mulaj, Mentor; Ciesla, Marissa; Robeel, Rhonda; Persichilli, Christopher; Raynes, Rachel; Westerheide, Sandy; Muschol, Martin

2013-09-01

Deposits of fibrils formed by disease-specific proteins are the molecular hallmark of such diverse human disorders as Alzheimer's disease, type II diabetes, or rheumatoid arthritis. Amyloid fibril formation by structurally and functionally unrelated proteins exhibits many generic characteristics, most prominently the cross β-sheet structure of their mature fibrils. At the same time, amyloid formation tends to proceed along one of two separate assembly pathways yielding either stiff monomeric filaments or globular oligomers and curvilinear protofibrils. Given the focus on oligomers as major toxic species, the very existence of an oligomer-free assembly pathway is significant. Little is known, though, about the structure of the various intermediates emerging along different pathways and whether the pathways converge towards a common or distinct fibril structures. Using infrared spectroscopy we probed the structural evolution of intermediates and late-stage fibrils formed during in vitro lysozyme amyloid assembly along an oligomeric and oligomer-free pathway. Infrared spectroscopy confirmed that both pathways produced amyloid-specific β-sheet peaks, but at pathway-specific wavenumbers. We further found that the amyloid-specific dye thioflavin T responded to all intermediates along either pathway. The relative amplitudes of thioflavin T fluorescence responses displayed pathway-specific differences and could be utilized for monitoring the structural evolution of intermediates. Pathway-specific structural features obtained from infrared spectroscopy and Thioflavin T responses were identical for fibrils grown at highly acidic or at physiological pH values and showed no discernible effects of protein hydrolysis. Our results suggest that late-stage fibrils formed along either pathway are amyloidogenic in nature, but have distinguishable structural fingerprints. These pathway-specific fingerprints emerge during the earliest aggregation events and persist throughout the entire cascade of aggregation intermediates formed along each pathway.

NADP+ Binding to the Regulatory Subunit of Methionine Adenosyltransferase II Increases Intersubunit Binding Affinity in the Hetero-Trimer

PubMed Central

Ortega, Rebeca; Martínez-Júlvez, Marta; Revilla-Guarinos, Ainhoa; Pérez-Pertejo, Yolanda; Velázquez-Campoy, Adrián; Sanz-Aparicio, Julia; Pajares, María A.

2012-01-01

Mammalian methionine adenosyltransferase II (MAT II) is the only hetero-oligomer in this family of enzymes that synthesize S-adenosylmethionine using methionine and ATP as substrates. Binding of regulatory β subunits and catalytic α2 dimers is known to increase the affinity for methionine, although scarce additional information about this interaction is available. This work reports the use of recombinant α2 and β subunits to produce oligomers showing kinetic parameters comparable to MAT II purified from several tissues. According to isothermal titration calorimetry data and densitometric scanning of the stained hetero-oligomer bands on denatured gels, the composition of these oligomers is that of a hetero-trimer with α2 dimers associated to single β subunits. Additionally, the regulatory subunit is able to bind NADP+ with a 1∶1 stoichiometry, the cofactor enhancing β to α2-dimer binding affinity. Mutants lacking residues involved in NADP+ binding and N-terminal truncations of the β subunit were able to oligomerize with α2-dimers, although the kinetic properties appeared altered. These data together suggest a role for both parts of the sequence in the regulatory role exerted by the β subunit on catalysis. Moreover, preparation of a structural model for the hetero-oligomer, using the available crystal data, allowed prediction of the regions involved in β to α2-dimer interaction. Finally, the implications that the presence of different N-terminals in the β subunit could have on MAT II behavior are discussed in light of the recent identification of several splicing forms of this subunit in hepatoma cells. PMID:23189196

Structural fingerprints and their evolution during oligomeric vs. oligomer-free amyloid fibril growth.

PubMed

Foley, Joseph; Hill, Shannon E; Miti, Tatiana; Mulaj, Mentor; Ciesla, Marissa; Robeel, Rhonda; Persichilli, Christopher; Raynes, Rachel; Westerheide, Sandy; Muschol, Martin

2013-09-28

Deposits of fibrils formed by disease-specific proteins are the molecular hallmark of such diverse human disorders as Alzheimer's disease, type II diabetes, or rheumatoid arthritis. Amyloid fibril formation by structurally and functionally unrelated proteins exhibits many generic characteristics, most prominently the cross β-sheet structure of their mature fibrils. At the same time, amyloid formation tends to proceed along one of two separate assembly pathways yielding either stiff monomeric filaments or globular oligomers and curvilinear protofibrils. Given the focus on oligomers as major toxic species, the very existence of an oligomer-free assembly pathway is significant. Little is known, though, about the structure of the various intermediates emerging along different pathways and whether the pathways converge towards a common or distinct fibril structures. Using infrared spectroscopy we probed the structural evolution of intermediates and late-stage fibrils formed during in vitro lysozyme amyloid assembly along an oligomeric and oligomer-free pathway. Infrared spectroscopy confirmed that both pathways produced amyloid-specific β-sheet peaks, but at pathway-specific wavenumbers. We further found that the amyloid-specific dye thioflavin T responded to all intermediates along either pathway. The relative amplitudes of thioflavin T fluorescence responses displayed pathway-specific differences and could be utilized for monitoring the structural evolution of intermediates. Pathway-specific structural features obtained from infrared spectroscopy and Thioflavin T responses were identical for fibrils grown at highly acidic or at physiological pH values and showed no discernible effects of protein hydrolysis. Our results suggest that late-stage fibrils formed along either pathway are amyloidogenic in nature, but have distinguishable structural fingerprints. These pathway-specific fingerprints emerge during the earliest aggregation events and persist throughout the entire cascade of aggregation intermediates formed along each pathway.

Modulation of LOX and COX pathways via inhibition of amyloidogenesis contributes to mitoprotection against β-amyloid oligomer-induced toxicity in an animal model of Alzheimer's disease in rats.

PubMed

Kalra, Jaspreet; Kumar, Puneet; Majeed, Abu Bakar Abdul; Prakash, Atish

2016-01-01

Several lines of evidence indicate that beta amyloid (β-A) production, neurofibrillary tangles and neuroinflammation are interrelated in the pathogenesis of Alzheimer's disease (AD). AD is associated with enhanced β-A production and accumulation resulting in neuroinflammation probably via activation of lipoxygenase (LOX) and cyclooxygenase (COX) pathways. Therefore, the present study was designed to investigate the role of LOX and COX inhibitors (zafirlukast and valdecoxib) in amyloidogenesis in β-A1-42 oligomer induced experimental AD in rats. The behavioral activities were assessed using actophotometer, novel object recognition test (ORT), Morris water maze (MWM) followed by biochemical assessments, determination of proinflammatory cytokines and mediators (TNF-α, IL-1β and PGE2), β-A1-42 levels and histopathological analysis. ICV administration of β-A1-42 oligomer produced significant impairment in memory consolidation. In addition to this significant increase in mito-oxidative stress, neuroinflammatory markers, acetylcholinesterase (AChE) toxicity, β-A1-42 level, neuronal cell death and neuroinflammation are more profound in β-A1-42 oligomer treated AD rats. Administration of zafirlukast (15 and 30mg/kg), and valdecoxib (5 and 10mg/kg) significantly improved the behavioral performances and showed significant reversal of mito-oxidative damage declining the neuroinflammation in β-A1-42 oligomer treated rats. Furthermore, more profound effects were observed at the sub-therapeutic dose combination of zafirlukast (15mg/kg) and valdecoxib (5mg/kg). The results of the present study indicate that protective effects of zafirlukast and valdecoxib are achieved through the blockade of release of LOX and COX metabolites therefore, representing a new therapeutic target for treating AD and other neurodegenerative disorders. Copyright © 2016 Elsevier Inc. All rights reserved.

Separation and determination of secoisolariciresinol diglucoside oligomers and their hydrolysates in the flaxseed extract by high-performance liquid chromatography.

PubMed

Li, Xin; Yuan, Jian-Ping; Xu, Shi-Ping; Wang, Jiang-Hai; Liu, Xin

2008-03-28

Flaxseed contains the largest amount of lignan secoisolariciresinol diglucoside (SDG) oligomers and is the richest dietary source of SDG. SDG oligomers in the flaxseed extract are often hydrolyzed to break the ester linkages for the release of SDG and the glycosidic bonds for the release of secoisolariciresinol (SECO). The hydrolysates of SDG oligomers are complicated because of the production of esters in an alcohol-containing medium. In this study, a new gradient reversed-phase high-performance liquid chromatography (HPLC) method has been developed to be suitable for the separation and determination of: (1) SDG oligomers extracted from the defatted flaxseed powder by a 70% aqueous methanol solution; (2) SDG oligomers and their alkaline hydrolysates, including SDG, p-coumaric acid glucoside and its methyl ester, ferulic acid glucoside and its methyl ester in an alkaline hydrolytic solution; and (3) the succedent acid hydrolysates, including secoisolariciresinol monoglucoside (SMG), SECO, anhydrosecoisolariciresinol (anhydro-SECO), p-coumaric acid and its methyl ester, ferulic acid and its methyl ester, 5-hydroxymethyl-2-furfural (HMF) and its degradation product in an acid hydrolytic solution. The content of SDG oligomers in a defatted flaxseed powder was found to be 38.5 mg/g on a dry matter basis, corresponding to a SDG content of 15.4 mg/g, which was determined after alkaline hydrolysis. Furthermore, this study presented a major reaction pathway for the hydrolysis of SDG oligomers.

Development of Processible Electroactive Oligomers and Polymers

DTIC Science & Technology

1991-10-01

of structure and electroactive properties. Electroactive molecules including fused ring (ladder oligomers) dyes , squarylium -heterocyclic moieties...Electroactive molecules including fused ring (ladder oligomers) dyes , squarylium -heterocyclic moieties, phenylpolyenes, thienylpolyenes, carbocyanine dyes ...phenylpolyenes, thienylpolyenes, carbocyanine dyes , and tetraazaannulenes have also been synthetically incorporated into a variety of traditional

Structure of Pseudoknot PK26 Shows 3D Domain Swapping in an RNA

NASA Technical Reports Server (NTRS)

Lietzke, Susan E; Barnes, Cindy L.

1998-01-01

3D domain swapping provides a facile pathway for the evolution of oligomeric proteins and allosteric mechanisms and a means for using monomer-oligomer equilibria to regulate biological activity. The term "3D domain swapping" describes the exchange of identical domains between two protein monomers to create an oligomer. 3D domain swapping has, so far, only been recognized in proteins. In this study, the structure of the pseudoknot PK26 is reported and it is a clear example of 3D domain swapping in RNA. PK26 was chosen for study because RNA pseudoknots are required structures in several biological processes and they arise frequently in in vitro selection experiments directed against protein targets. PK26 specifically inhibits HIV-1 reverse transcriptase with nanomolar affinity. We have now determined the 3.1 A resolution crystal structure of PK26 and find that it forms a 3D domain swapped dimer. PK26 shows extensive base pairing between and within strands. Formation of the dimer requires the linker region between the pseudoknot folds to adopt a unique conformation that allows a base within a helical stem to skip one base in the stacking register. Rearrangement of the linker would permit a monomeric pseudoknot to form. This structure shows how RNA can use 3D domain swapping to build large scale oligomers like the putative hexamer in the packaging RNA of bacteriophage Phi29.

Fluorescence of size-expanded DNA bases: reporting on DNA sequence and structure with an unnatural genetic set.

PubMed

Krueger, Andrew T; Kool, Eric T

2008-03-26

We recently described the synthesis and helix assembly properties of expanded DNA (xDNA), which contains base pairs 2.4 A larger than natural DNA pairs. This designed genetic set is under study with the goals of mimicking the functions of the natural DNA-based genetic system and of developing useful research tools. Here, we study the fluorescence properties of the four expanded bases of xDNA (xA, xC, xG, xT) and evaluate how their emission varies with changes in oligomer length, composition, and hybridization. Experiments were carried out with short oligomers of xDNA nucleosides conjugated to a DNA oligonucleotide, and we investigated the effects of hybridizing these fluorescent oligomers to short complementary DNAs with varied bases opposite the xDNA bases. As monomer nucleosides, the xDNA bases absorb light in two bands: one at approximately 260 nm (similar to DNA) and one at longer wavelength ( approximately 330 nm). All are efficient violet-blue fluorophores with emission maxima at approximately 380-410 nm and quantum yields (Phifl) of 0.30-0.52. Short homo-oligomers of the xDNA bases (length 1-4 monomers) showed moderate self-quenching except xC, which showed enhancement of Phifl with increasing length. Interestingly, multimers of xA emitted at longer wavelengths (520 nm) as an apparent excimer. Hybridization of an oligonucleotide to the DNA adjacent to the xDNA bases (with the xDNA portion overhanging) resulted in no change in fluorescence. However, addition of one, two, or more DNA bases in these duplexes opposite the xDNA portion resulted in a number of significant fluorescence responses, including wavelength shifts, enhancements, or quenching. The strongest responses were the enhancement of (xG)n emission by hybridization of one or more adenines opposite them, and the quenching of (xT)n and (xC)n emission by guanines opposite. The data suggest multiple ways in which the xDNA bases, both alone and in oligomers, may be useful as tools in biophysical analysis and biotechnological applications.

Isomer separation and effect of the degree of polymerization on the gas-phase structure of chondroitin sulfate oligosaccharides analyzed by ion mobility and tandem mass spectrometry.

PubMed

Poyer, Salomé; Lopin-Bon, Chrystel; Jacquinet, Jean-Claude; Salpin, Jean-Yves; Daniel, Régis

2017-12-15

Chondroitin sulfate (CS) glycosaminoglycans are bioactive sulfated polysaccharides comprising repeating units of uronic acid and N-acetyl galactose sulfated at various positions. The optimal length and sulfation pattern of the CS bioactive sequences remain elusive so that structure-activity relationships cannot be easily established. Development of efficient analytical methods allowing the differentiation of the various sulfation patterns of CS sequences is therefore of particular importance to correlate their biological functions to the sulfation pattern. Discrimination of different oligomers (dp2 to dp6) of synthetic chondroitin sulfate isomers was evaluated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in the negative-ion mode from deprotonated and alkali adduct species. In addition, ion mobility mass spectrometry (IMS-MS) was used to study the influence of both the degree of polymerization and sulfate group location on the gas-phase conformation of CS oligomers. ESI-MS/MS spectra of chondroitin sulfate isomers show characteristic product ions exclusively from alkali adduct species (Li, Na, K and Cs). Whatever the alkali adducts studied, MS/MS of chondroitin oligosaccharides sulfated at position 6 yields a specific product ion at m/z 139 while CS oligosaccharides sulfated at position 4 show a specific product ion at m/z 154. Being observed for the different CS oligomers di-, tetra- and hexasaccharides, these fragment ions are considered as diagnostic ions for chondroitin 6-O-sulfate and chondroitin 4-O-sulfate, respectively. IMS-MS experiments reveal that collision cross-sections (CCS) of CS oligomers with low charge states evolved linearly with degrees of polymerization indicating a similar gas-phase conformation. This study allows the fast and unambiguous differentiation of CS isomers sulfated at position 6 or 4 for both saturated and unsaturated analogues from MS/MS experiments. In addition, the CCS linear evolution of CS oligomers in function of the degree of polymerization indicates that no folding occurs even for hexasaccharides. Copyright © 2017 John Wiley & Sons, Ltd.

Amyloid Beta Mediates Memory Formation

ERIC Educational Resources Information Center

Garcia-Osta, Ana; Alberini, Cristina M.

2009-01-01

The amyloid precursor protein (APP) undergoes sequential cleavages to generate various polypeptides, including the amyloid [beta] (1-42) peptide (A[beta][1-42]), which is believed to play a major role in amyloid plaque formation in Alzheimer's disease (AD). Here we provide evidence that, in contrast with its pathological role when accumulated,…

Matrix effect in matrix-assisted laser desorption/ionization mass spectra of derivatized oligomeric polyols.

PubMed

Borisov, Roman S; Polovkov, Nikolai Yu; Zhilyaev, Dmitry I; Zaikin, Vladimir G

2013-01-30

Herein we describe a strong matrix effect observed in the matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectra of silylated glycerol alkoxylates and manifested in the loss of the silyl groups in the presence of carboxyl-containing matrices. Commercially available glycerol alkoxylates containing three end OH groups as well as three matrices - 2,5-dihydroxybenzoic acid (DHB), 3-indoleacrylic acid (IAA) and 1,8,9-anthracenetriol (dithranol) - were chosen for the investigation. N,O-Bis(trimethylsilyl)trifluoroacetamide containing 1% trimethylchlorosilane, acetic anhydride and a formylation mixture (formic acid/acetyl chloride) were used for derivatization. Initial oligomers and derivatized products were analyzed by MALDI-ToF-mass spectrometry (MS) on an Autoflex II instrument, equipped with a nitrogen laser (λ 337 nm), in positive ion reflectron mode. Only [M + Na](+) ions were observed for underivatized polymers and for completely derivatized polymers in the presence of DHB and dithranol, respectively. In the case of IAA the mass spectra revealed sets of peaks for underivatized, and for partially and completely derivatized oligomers. No similar 'matrix effect' was observed in the case of acylated glycerol alkoxylates (acyl = formyl, acetyl): only peaks for completely derivatized oligomers were obtained in all matrices: DHB, IAA and dithranol. Using 1,9-nonandiol, we showed that the 'matrix effect' was due to trans-silylation of carboxyl-containing matrices (DHB and IAA) during co-crystallization of silylated oligomers and matrices. The obtained results show that matrix molecules can participate as reactive species in MALDI-ToF-MS experiments. The matrix should be carefully chosen when a derivatization approach is applied because the analysis of spectra of the completely derivatized products is particularly desirable in the quantitative determination of functional end-groups. Copyright © 2012 John Wiley & Sons, Ltd.

Transgenic mice overexpressing tyrosine-to-cysteine mutant human alpha-synuclein: a progressive neurodegenerative model of diffuse Lewy body disease.

PubMed

Zhou, Wenbo; Milder, Julie B; Freed, Curt R

2008-04-11

Abnormal aggregation of human alpha-synuclein in Lewy bodies and Lewy neurites is a pathological hallmark of Parkinson disease and dementia with Lewy bodies. Studies have shown that oxidation and nitration of alpha-synuclein lead to the formation of stable dimers and oligomers through dityrosine cross-linking. Previously we have reported that tyrosine-to-cysteine mutations, particularly at the tyrosine 39 residue (Y39C), significantly enhanced alpha-synuclein fibril formation and neurotoxicity. In the current study, we have generated transgenic mice expressing the Y39C mutant human alpha-synuclein gene controlled by the mouse Thy1 promoter. Mutant human alpha-synuclein was widely expressed in transgenic mouse brain, resulting in 150% overexpression relative to endogenous mouse alpha-synuclein. At age 9-12 months, transgenic mice began to display motor dysfunction in rotarod testing. Older animals aged 15-18 months showed progressive accumulation of human alpha-synuclein oligomers, associated with worse motor function and cognitive impairment in the Morris water maze. By age 21-24 months, alpha-synuclein aggregates were further increased, accompanied by severe behavioral deficits. At this age, transgenic mice developed neuropathology, such as Lewy body-like alpha-synuclein and ubiquitin-positive inclusions, phosphorylation at Ser(129) of human alpha-synuclein, and increased apoptotic cell death. In summary, Y39C human alpha-synuclein transgenic mice show age-dependent, progressive neuronal degeneration with motor and cognitive deficits similar to diffuse Lewy body disease. The time course of alpha-synuclein oligomer accumulation coincided with behavioral and pathological changes, indicating that these oligomers may initiate protein aggregation, disrupt cellular function, and eventually lead to neuronal death.

Nitrogen-Containing, Light-Absorbing Oligomers Produced in Aerosol Particles Exposed to Methylglyoxal, Photolysis, and Cloud Cycling.

PubMed

De Haan, David O; Tapavicza, Enrico; Riva, Matthieu; Cui, Tianqu; Surratt, Jason D; Smith, Adam C; Jordan, Mary-Caitlin; Nilakantan, Shiva; Almodovar, Marisol; Stewart, Tiffany N; de Loera, Alexia; De Haan, Audrey C; Cazaunau, Mathieu; Gratien, Aline; Pangui, Edouard; Doussin, Jean-François

2018-04-03

Aqueous methylglyoxal chemistry has often been implicated as an important source of oligomers in atmospheric aerosol. Here we report on chemical analysis of brown carbon aerosol particles collected from cloud cycling/photolysis chamber experiments, where gaseous methylglyoxal and methylamine interacted with glycine, ammonium, or methylammonium sulfate seed particles. Eighteen N-containing oligomers were identified in the particulate phase by liquid chromatography/diode array detection/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry. Chemical formulas were determined and, for 6 major oligomer products, MS 2 fragmentation spectra were used to propose tentative structures and mechanisms. Electronic absorption spectra were calculated for six tentative product structures by an ab initio second order algebraic-diagrammatic-construction/density functional theory approach. For five structures, matching calculated and measured absorption spectra suggest that they are dominant light-absorbing species at their chromatographic retention times. Detected oligomers incorporated methylglyoxal and amines, as expected, but also pyruvic acid, hydroxyacetone, and significant quantities of acetaldehyde. The finding that ∼80% (by mass) of detected oligomers contained acetaldehyde, a methylglyoxal photolysis product, suggests that daytime methylglyoxal oligomer formation is dominated by radical addition mechanisms involving CH 3 CO*. These mechanisms are evidently responsible for enhanced browning observed during photolytic cloud events.

Liquid Crystalline Thermosets from Ester, Ester-Imide, and Ester-Amide Oligomers

NASA Technical Reports Server (NTRS)

Dingemans, Theodornus J. (Inventor); Weiser, Erik S. (Inventor); SaintClair, Terry L. (Inventor)

2005-01-01

Main chain thermotropic liquid crystal esters, ester-imides, and ester-amides were prepared from AA, BB, and AB type monomeric materials and were end-capped with phenylacetylene, phenylmaleimide, or nadimide reactive end-groups. The resulting reactive end-capped liquid crystal oligomers exhibit a variety of improved and preferred physical properties. The end-capped liquid crystal oligomers are thermotropic and have, preferably, molecular weights in the range of approximately 1000-15,OOO grams per mole. The end-capped liquid crystal oligomers have broad liquid crystalline melting ranges and exhibit high melt stability and very low melt viscosities at accessible temperatures. The end-capped liquid crystal oligomers are stable for up to an hour in the melt phase. These properties make the end-capped liquid crystal oligomers highly processable by a variety of melt process shape forming and blending techniques including film extrusion, fiber spinning, reactive injection molding (RIM), resin transfer molding (RTM), resin film injection (RFI), powder molding, pultrusion, injection molding, blow molding, plasma spraying and thermo-forming. Once processed and shaped, the end- capped liquid crystal oligomers were heated to further polymerize and form liquid crystalline thermosets (LCT). The fully cured products are rubbers above their glass transition temperatures. The resulting thermosets display many properties that are superior to their non-end-capped high molecular weight analogs.

Template-based modeling and ab initio refinement of protein oligomer structures using GALAXY in CAPRI round 30.

PubMed

Lee, Hasup; Baek, Minkyung; Lee, Gyu Rie; Park, Sangwoo; Seok, Chaok

2017-03-01

Many proteins function as homo- or hetero-oligomers; therefore, attempts to understand and regulate protein functions require knowledge of protein oligomer structures. The number of available experimental protein structures is increasing, and oligomer structures can be predicted using the experimental structures of related proteins as templates. However, template-based models may have errors due to sequence differences between the target and template proteins, which can lead to functional differences. Such structural differences may be predicted by loop modeling of local regions or refinement of the overall structure. In CAPRI (Critical Assessment of PRotein Interactions) round 30, we used recently developed features of the GALAXY protein modeling package, including template-based structure prediction, loop modeling, model refinement, and protein-protein docking to predict protein complex structures from amino acid sequences. Out of the 25 CAPRI targets, medium and acceptable quality models were obtained for 14 and 1 target(s), respectively, for which proper oligomer or monomer templates could be detected. Symmetric interface loop modeling on oligomer model structures successfully improved model quality, while loop modeling on monomer model structures failed. Overall refinement of the predicted oligomer structures consistently improved the model quality, in particular in interface contacts. Proteins 2017; 85:399-407. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Early and Selective Impairments in Axonal Transport Kinetics of Synaptic Cargoes Induced by Soluble Amyloid β-Protein Oligomers

PubMed Central

Tang, Yong; Scott, David A.; Das, Utpal; Edland, Steven D.; Radomski, Kryslaine; Koo, Edward H.; Roy, Subhojit

2013-01-01

The downstream targets of amyloid β (Aβ)-oligomers remain elusive. One hypothesis is that Aβ-oligomers interrupt axonal transport. Although previous studies have demonstrated Aβ-induced transport blockade, early effects of low-n soluble Aβ-oligomers on axonal transport remain unclear. Furthermore, the cargo selectivity for such deficits (if any) or the specific effects of Aβ on the motility kinetics of transported cargoes are also unknown. Toward this, we visualized axonal transport of vesicles in cultured hippocampal neurons treated with picomolar (pm) levels of cell-derived soluble Aβ-oligomers. We examined select cargoes thought to move as distinct organelles and established imaging parameters that allow organelle tracking with consistency and high fidelity – analyzing all data in a blinded fashion. Aβ-oligomers induced early and selective diminutions in velocities of synaptic cargoes but had no effect on mitochondrial motility, contrary to previous reports. These changes were N-methyl d-aspartate receptor/glycogen synthase kinase-3β dependent and reversible upon washout of the oligomers. Cluster-mode analyses reveal selective attenuations in faster-moving synaptic vesicles, suggesting possible decreases in cargo/motor associations, and biochemical experiments implicate tau phosphorylation in the process. Collectively, the data provide a biological basis for Aβ-induced axonal transport deficits. PMID:22309053

Liquid crystalline thermosets from ester, ester-imide, and ester-amide oligomers

NASA Technical Reports Server (NTRS)

Dingemans, Theodorous J. (Inventor); Weiser, Erik S. (Inventor); St. Clair, Terry L. (Inventor)

2005-01-01

Main chain thermotropic liquid crystal esters, ester-imides, and ester-amides were prepared from AA, BB, and AB type monomeric materials and were end-capped with phenylacetylene, phenylmaleimide, or nadimide reactive end-groups. The resulting reactive end-capped liquid crystal oligomers exhibit a variety of improved and preferred physical properties. The end-capped liquid crystal oligomers are thermotropic and have, preferably, molecular weights in the range of approximately 1000-15,000 grams per mole. The end-capped liquid crystal oligomers have broad liquid crystalline melting ranges and exhibit high melt stability and very low melt viscosities at accessible temperatures. The end-capped liquid crystal oligomers are stable for up to an hour in the melt phase. These properties make the end-capped liquid crystal oligomers highly processable by a variety of melt process shape forming and blending techniques including film extrusion, fiber spinning, reactive injection molding (RIM), resin transfer molding (RTM), resin film injection (RFI), powder molding, pultrusion, injection molding, blow molding, plasma spraying and thermo-forming. Once processed and shaped, the end-capped liquid crystal oligomers were heated to further polymerize and form liquid crystalline thermosets (LCT). The fully cured products are rubbers above their glass transition temperatures. The resulting thermosets display many properties that are superior to their non-end-capped high molecular weight analogs.

Adhesive Properties of Cured Phenylethynyl Containing Imides

NASA Technical Reports Server (NTRS)

Jensen, Brian J.; Chang, Alice C.

1997-01-01

Considerable attention has been directed towards acetylene terminated oligomers over the last 20 years' and recent work has focused on phenylethynyl terminated imide (PETI) oligomers. These reactive oligomers possess several features which make them attractive candidates for use as composite matrices and adhesives. The phenylethynyl group can be readily incorporated into many different functionalized oligomers. The reactive oligomers possess relatively low melt viscosities and thermally cure without the evolution of volatile by-products. Once cured, they typically display high glass transition temperatures (Tgs), excellent solvent resistance and high mechanical properties. new modified phenylethynyl-terminated imide (LaRC MPEI) oligomers were synthesized at various molecular weights utilizing a small amount of trifunctional amine. As long as the amount of triamine is relatively small, this approach produces a mixture of linear, star-shaped and branched polymer chains that has lower melt and solution viscosity than an equivalent molecular weight linear phenylethynyl terminated imide oligomers. The work reported herein involves the synthesis and characterization of a copolymer using this approach and the preparation of blends utilizing a phenylethynyl containing reactive plasticizer of lower molecular weight called LaRC LV-121. The chemistry and properties of this new MPEI as well as some blends of MPEI with LV-121, are presented and compared to the linear version, LARC-PETI-5.

Theoretical studies of optics and charge transport in organic conducting oligomers and polymers: Rational design of improved transparent and conducting polymers

NASA Astrophysics Data System (ADS)

Hutchison, Geoffrey Rogers

Theoretical studies on a variety of oligo- and polyheterocycles elucidate their optical and charge transport properties, suggesting new, improved transparent conductive polymers. First-principles calculations provide accurate methodologies for predicting both optical band gaps of neutral and cationic oligomers and intrinsic charge transfer rates. Multidimensional analysis reveals important motifs in chemical tailorability of oligoheterocycle optical and charge transport properties. The results suggest new directions for design of novel materials. Using both finite oligomer and infinite polymer calculations, the optical band gaps in polyheterocycles follow a modified particle-in-a-box formalism, scaling approximately as 1/N (where N is the number of monomer units) in short chains, saturating for long chains. Calculations demonstrate that band structure changes upon heteroatom substitution, (e.g., from polythiophene to polypyrrole) derive from heteroatom electron affinity. Further investigation of chemical variability in substituted oligoheterocycles using multidimensional statistics reveals the interplay between heteroatom and substituent in correlations between structure and redox/optical properties of neutral and cationic species. A linear correlation between band gaps of neutral and cationic species upon oxidation of conjugated oligomers, shows redshifts of optical absorption for most species and blueshifts for small band gap species. Interstrand charge-transport studies focus on two contributors to hopping-style charge transfer rates: internal reorganization energy and the electronic coupling matrix element. Statistical analysis of chemical variability of reorganization energies in oligoheterocycles proves the importance of reorganization energy in determining intrinsic charge transfer rates (e.g., charge mobility in unsubstituted oligothiophenes). Computed bandwidths across several oligothiophene crystal packing motifs show similar electron and hole bandwidths, and show that well-known tilted and herringbone motifs in oligothiophenes are driven by electrostatic repulsion. Tilted stacks exhibit intrinsic charge-transfer rates smaller than cofacial stacks, but with lower packing energy. Given similar electron and hole bandwidths, a charge injection model explains substitution-modulated majority carrier changes in n- and p-type oligothiophene field-effect transistors.

Development of dental restorative materials based on visible light-cured multi-methacrylates

NASA Astrophysics Data System (ADS)

Tiba, Amer

The studies described in this dissertation focus on new visible light-curing (VLC) oligomers exhibiting low shrinkage, low water sorption, and improved mechanical properties. A family of multi-methacrylates, based on poly(isopropylidenediphenol) resin (BPA), was synthesized, characterized, and evaluated. The commercial BPA resin is prepared from enzymatic polymerization (oligomerization) of bisphenol A. The BPA resin, having an average of eight phenolic hydroxyl groups per molecule, was treated with propylene carbonate, and the resultant product, i.e., propoxylated BPA (PEBPA) oligomer, was confirmed by Fourier transform infrared spectroscopy (FT-IR) and sp{13}C nuclear magnetic resonance (NMR). The propoxylated BPA was subsequently treated with methacryloyl chloride to produce the multi-methacrylates, identified by FT-IR and NMR. The PEBPA oligomer multimethacrylate: triethylene glycol dimethacrylate (TEGDMA) (50:50/wt:wt) blends were combined with 0.5 wt. % camphoroquinone (CQ) and 1.0 wt. % N,N-dimethylaminoethyl methacrylate (DMAEMA). The control polymers were 2,2-bis(4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl) propane (BisGMA): TEGDMA(50:50/wt:wt) blends having the same levels of CQ/DMAEMA. Differential photocalorimetry (DPC) and differential scanning calorimetry (DSC) showed these multimethacrylate/TEGDMA (neat resin) blends have polymerization characteristics comparable to the BisGMA/TEGDMA controls. These new multifunctional oligomers have lower polymerization shrinkage and lower uptake of water and other liquids, compared to BisGMA based materials. In addition, two experimental oligomers, PEBPA #2 and #3, have higher compressive strength than the BisGMA control. A biocompatibility test of the polymerized multi-methacrylate resins was performed and compared with the conventional BisGMA/TEGDMA resin and blank controls, using cell culture techniques. Human gingival fibroblasts were used for biocompatibility evaluation of these resins. The results revealed that the BPA oligomer (multi-methacrylate) based resin significantly favored the cell growth of the human gingival fibroblasts, compared to the control. An experimental composite was made from EPBPA oligomers (multi-methacrylates). The compressive strength of the experimental EPBPA containing composite was not significantly different than the commercial composite Herculite HXR. SEM photomicrographs revealed more voids in the experimental composites than the commercial composite on both the external surfaces of the prepared specimens and the subsequent fractured surfaces. This is due to the molding technique for specimen preparation and lack of good mechanical mixing for filler incorporation prior to placement of the resin in the mold for subsequent photopolymerization. However, the water sorption for the experimental EPBPA-based composite was significantly lower than the commercial Herculite (HXR) composite. This is most likely related to the hydrophobic nature of the experimental resin. These results suggest that the new type of polyfunctional methacrylate oligomers (PEBPA) have potential application in formulating dental composites as direct esthetic restorative materials with improved properties.

ER residency of the ceramide phosphoethanolamine synthase SMSr relies on homotypic oligomerization mediated by its SAM domain

PubMed Central

Cabukusta, Birol; Kol, Matthijs; Kneller, Laura; Hilderink, Angelika; Bickert, Andreas; Mina, John G. M.; Korneev, Sergei; Holthuis, Joost C. M.

2017-01-01

SMSr/SAMD8 is an ER-resident ceramide phosphoethanolamine synthase with a critical role in controlling ER ceramides and suppressing ceramide-induced apoptosis in cultured cells. SMSr-mediated ceramide homeostasis relies on the enzyme’s catalytic activity as well as on its N-terminal sterile α-motif or SAM domain. Here we report that SMSr-SAM is structurally and functionally related to the SAM domain of diacylglycerol kinase DGKδ, a central regulator of lipid signaling at the plasma membrane. Native gel electrophoresis indicates that both SAM domains form homotypic oligomers. Chemical crosslinking studies show that SMSr self-associates into ER-resident trimers and hexamers that resemble the helical oligomers formed by DGKδ-SAM. Residues critical for DGKδ-SAM oligomerization are conserved in SMSr-SAM and their substitution causes a dissociation of SMSr oligomers as well as a partial redistribution of the enzyme to the Golgi. Conversely, treatment of cells with curcumin, a drug disrupting ceramide and Ca2+ homeostasis in the ER, stabilizes SMSr oligomers and promotes retention of the enzyme in the ER. Our data provide first demonstration of a multi-pass membrane protein that undergoes homotypic oligomerization via its SAM domain and indicate that SAM-mediated self-assembly of SMSr is required for efficient retention of the enzyme in the ER. PMID:28120887

Electrostatic Forces as Dominant Interactions Between Proteins and Polyanions: an ESI MS Study of Fibroblast Growth Factor Binding to Heparin Oligomers

NASA Astrophysics Data System (ADS)

Minsky, Burcu Baykal; Dubin, Paul L.; Kaltashov, Igor A.

2017-04-01

The interactions between fibroblast growth factors (FGFs) and their receptors (FGFRs) are facilitated by heparan sulfate (HS) and heparin (Hp), highly sulfated biological polyelectrolytes. The molecular basis of FGF interactions with these polyelectrolytes is highly complex due to the structural heterogeneity of HS/Hp, and many details still remain elusive, especially the significance of charge density and minimal chain length of HS/Hp in growth factor recognition and multimerization. In this work, we use electrospray ionization mass spectrometry (ESI MS) to investigate the association of relatively homogeneous oligoheparins (octamer, dp8, and decamer, dp10) with acidic fibroblast growth factor (FGF-1). This growth factor forms 1:1, 2:1, and 3:1 protein/heparinoid complexes with both dp8 and dp10, and the fraction of bound protein is highly dependent on protein/heparinoid molar ratio. Multimeric complexes are preferentially formed on the highly sulfated Hp oligomers. Although a variety of oligomers appear to be binding-competent, there is a strong correlation between the affinity and the overall level of sulfation (the highest charge density polyanions binding FGF most strongly via multivalent interactions). These results show that the interactions between FGF-1 and Hp oligomers are primarily directed by electrostatics, and also demonstrate the power of ESI MS as a tool to study multiple binding equilibria between proteins and structurally heterogeneous polyanions.

Structure, wettability and thermal degradation of new fluoro-oligomer modified nanoclays.

PubMed

Valsecchi, R; Viganò, M; Levi, M; Turri, S

2008-04-01

Quaternary ammonium salts based on monofunctionalized Perfluoropolyether (PFPE) oligomers were synthesized and used for the cation exchange process of sodium Montmorillonite nanoclays. The new fluoromodified nanoclays were characterized through X-rays diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), termogravimetric analysis (TGA), differential scanning calorimetry (DSC), electronic microscopy (SEM-EDS), and contact angle measurements (CA). In particular XRD showed rather complex patterns (presence of higher order reflections) which allowed the calculation of basal spacings, regularly increasing with the molecular weight of the fluorinated macrocation. Both IR and SEM confirmed the presence of fluorinated segments at clays interface, while TGA showed a limited thermal stability with an onset of degradation temperature which seems not dependent on the molecular weight of the macrocation. CA measurements showed a peculiar behaviour, with evident dynamic hysteresis phenomena and surface tension components quite different from those of commercially available, organomodified clays.

Sequence space coverage, entropy of genomes and the potential to detect non-human DNA in human samples

PubMed Central

Liu, Zhandong; Venkatesh, Santosh S; Maley, Carlo C

2008-01-01

Background Genomes store information for building and maintaining organisms. Complete sequencing of many genomes provides the opportunity to study and compare global information properties of those genomes. Results We have analyzed aspects of the information content of Homo sapiens, Mus musculus, Drosophila melanogaster, Caenorhabditis elegans, Arabidopsis thaliana, Saccharomyces cerevisiae, and Escherichia coli (K-12) genomes. Virtually all possible (> 98%) 12 bp oligomers appear in vertebrate genomes while < 2% of 19 bp oligomers are present. Other species showed different ranges of > 98% to < 2% of possible oligomers in D. melanogaster (12–17 bp), C. elegans (11–17 bp), A. thaliana (11–17 bp), S. cerevisiae (10–16 bp) and E. coli (9–15 bp). Frequencies of unique oligomers in the genomes follow similar patterns. We identified a set of 2.6 M 15-mers that are more than 1 nucleotide different from all 15-mers in the human genome and so could be used as probes to detect microbes in human samples. In a human sample, these probes would detect 100% of the 433 currently fully sequenced prokaryotes and 75% of the 3065 fully sequenced viruses. The human genome is significantly more compact in sequence space than a random genome. We identified the most frequent 5- to 20-mers in the human genome, which may prove useful as PCR primers. We also identified a bacterium, Anaeromyxobacter dehalogenans, which has an exceptionally low diversity of oligomers given the size of its genome and its GC content. The entropy of coding regions in the human genome is significantly higher than non-coding regions and chromosomes. However chromosomes 1, 2, 9, 12 and 14 have a relatively high proportion of coding DNA without high entropy, and chromosome 20 is the opposite with a low frequency of coding regions but relatively high entropy. Conclusion Measures of the frequency of oligomers are useful for designing PCR assays and for identifying chromosomes and organisms with hidden structure that had not been previously recognized. This information may be used to detect novel microbes in human tissues. PMID:18973670

Sequence space coverage, entropy of genomes and the potential to detect non-human DNA in human samples.

PubMed

Liu, Zhandong; Venkatesh, Santosh S; Maley, Carlo C

2008-10-30

Genomes store information for building and maintaining organisms. Complete sequencing of many genomes provides the opportunity to study and compare global information properties of those genomes. We have analyzed aspects of the information content of Homo sapiens, Mus musculus, Drosophila melanogaster, Caenorhabditis elegans, Arabidopsis thaliana, Saccharomyces cerevisiae, and Escherichia coli (K-12) genomes. Virtually all possible (> 98%) 12 bp oligomers appear in vertebrate genomes while < 2% of 19 bp oligomers are present. Other species showed different ranges of > 98% to < 2% of possible oligomers in D. melanogaster (12-17 bp), C. elegans (11-17 bp), A. thaliana (11-17 bp), S. cerevisiae (10-16 bp) and E. coli (9-15 bp). Frequencies of unique oligomers in the genomes follow similar patterns. We identified a set of 2.6 M 15-mers that are more than 1 nucleotide different from all 15-mers in the human genome and so could be used as probes to detect microbes in human samples. In a human sample, these probes would detect 100% of the 433 currently fully sequenced prokaryotes and 75% of the 3065 fully sequenced viruses. The human genome is significantly more compact in sequence space than a random genome. We identified the most frequent 5- to 20-mers in the human genome, which may prove useful as PCR primers. We also identified a bacterium, Anaeromyxobacter dehalogenans, which has an exceptionally low diversity of oligomers given the size of its genome and its GC content. The entropy of coding regions in the human genome is significantly higher than non-coding regions and chromosomes. However chromosomes 1, 2, 9, 12 and 14 have a relatively high proportion of coding DNA without high entropy, and chromosome 20 is the opposite with a low frequency of coding regions but relatively high entropy. Measures of the frequency of oligomers are useful for designing PCR assays and for identifying chromosomes and organisms with hidden structure that had not been previously recognized. This information may be used to detect novel microbes in human tissues.

Binding of ATP by pertussis toxin and isolated toxin subunits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hausman, S.Z.; Manclark, C.R.; Burns, D.L.

1990-07-03

The binding of ATP to pertussis toxin and its components, the A subunit and B oligomer, was investigated. Whereas, radiolabeled ATP bound to the B oligomer and pertussis toxin, no binding to the A subunit was observed. The binding of ({sup 3}H)ATP to pertussis toxin and the B oligomer was inhibited by nucleotides. The relative effectiveness of the nucleotides was shown to be ATP > GTP > CTP > TTP for pertussis toxin and ATP > GTP > TTP > CTP for the B oligomer. Phosphate ions inhibited the binding of ({sup 3}H)ATP to pertussis toxin in a competitive manner;more » however, the presence of phosphate ions was essential for binding of ATP to the B oligomer. The toxin substrate, NAD, did not affect the binding of ({sup 3}H)ATP to pertussis toxin, although the glycoprotein fetuin significantly decreased binding. These results suggest that the binding site for ATP is located on the B oligomer and is distinct from the enzymatically active site but may be located near the eukaryotic receptor binding site.« less

[Differences in oligomerization of nucleocapsid protein of epidemic human influenza A(H1N1), A(H1N2) and B viruses].

PubMed

Prokudina, E N; Semenova, N P; Chumakov, V M; Burtseva, E I; Slepushkin, A N

2003-01-01

A comparative analysis of involving the nucleocapsid protein (NP) into shaping-up of SDS-resistant oligomers was carried out presently in circulating epidemic strains of human influenza, viruses A and B. The study results of viral isolates obtained from clinical samples and recent standard strains revealed that the involvement of NP in the SDS-resistant oligomers, which are different in various subtypes of influenza A viruses. According to this sign, the human viruses A(9H3N2) are close to the avian ones, in which, as proved by us previously, virtually the entire NP transforms itself into the oligomers resistant to SDS. About 10-20% of NP are involved in shaping-up the virus influenza A(H1N1) of SDS-resistant oligomers. No SDS-resistant NP-oligomers were detected in influenza of type B. It is suggested that the prevalence of human viruses A(H3N2) in NP-oligomers are the peculiarities of NP structure and of the presence of the PB1 protein from avian influenza virus.

Oligomer formation in the troposphere: from experimental knowledge to 3-D modeling

NASA Astrophysics Data System (ADS)

Lemaire, V.; Coll, I.; Couvidat, F.; Mouchel-Vallon, C.; Seigneur, C.; Siour, G.

2015-10-01

The organic fraction of atmospheric aerosols has proven to be a critical element of air quality and climate issues. However, its composition and the aging processes it undergoes remain insufficiently understood. This work builds on laboratory knowledge to simulate the formation of oligomers from biogenic secondary organic aerosol (BSOA) in the troposphere at the continental scale. We compare the results of two different modeling approaches, a 1st-order kinetic process and a pH-dependent parameterization, both implemented in the CHIMERE air quality model (AQM), to simulate the spatial and temporal distribution of oligomerized SOA over western Europe. Our results show that there is a strong dependence of the results on the selected modeling approach: while the irreversible kinetic process leads to the oligomerization of about 50 % of the total BSOA mass, the pH-dependent approach shows a broader range of impacts, with a strong dependency on environmental parameters (pH and nature of aerosol) and the possibility for the process to be reversible. In parallel, we investigated the sensitivity of each modeling approach to the representation of SOA precursor solubility (Henry's law constant values). Finally, the pros and cons of each approach for the representation of SOA aging are discussed and recommendations are provided to improve current representations of oligomer formation in AQMs.

Wheel-running in a transgenic mouse model of Alzheimer's disease: protection or symptom?

PubMed

Richter, Helene; Ambrée, Oliver; Lewejohann, Lars; Herring, Arne; Keyvani, Kathy; Paulus, Werner; Palme, Rupert; Touma, Chadi; Schäbitz, Wolf-Rüdiger; Sachser, Norbert

2008-06-26

Several studies on both humans and animals reveal benefits of physical exercise on brain function and health. A previous study on TgCRND8 mice, a transgenic model of Alzheimer's disease, reported beneficial effects of premorbid onset of long-term access to a running wheel on spatial learning and plaque deposition. Our study investigated the effects of access to a running wheel after the onset of Abeta pathology on behavioural, endocrinological, and neuropathological parameters. From day 80 of age, the time when Abeta deposition becomes apparent, TgCRND8 and wildtype mice were kept with or without running wheel. Home cage behaviour was analysed and cognitive abilities regarding object recognition memory and spatial learning in the Barnes maze were assessed. Our results show that, in comparison to Wt mice, Tg mice were characterised by impaired object recognition memory and spatial learning, increased glucocorticoid levels, hyperactivity in the home cage and high levels of stereotypic behaviour. Access to a running wheel had no effects on cognitive or neuropathological parameters, but reduced the amount of stereotypic behaviour in transgenics significantly. Furthermore, wheel-running was inversely correlated with stereotypic behaviour, suggesting that wheel-running may have stereotypic qualities. In addition, wheel-running positively correlated with plaque burden. Thus, in a phase when plaques are already present in the brain, it may be symptomatic of brain pathology, rather than protective. Whether or not access to a running wheel has beneficial effects on Alzheimer-like pathology and symptoms may therefore strongly depend on the exact time when the wheel is provided during development of the disease.

Investigation of ferroelectric domains in thin films of vinylidene fluoride oligomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Pankaj, E-mail: psharma@huskers.unl.edu; Poddar, Shashi; Ducharme, Stephen

2014-07-14

High-resolution vector piezoresponse force microscopy (PFM) has been used to investigate ferroelectric domains in thin vinylidene fluoride oligomer films fabricated by the Langmuir-Blodgett deposition technique. Molecular chains are found to be preferentially oriented normal to the substrate, and PFM imaging shows that the films are in ferroelectric β-phase with a predominantly in-plane polarization, in agreement with infrared spectroscopic ellipsometry and X-ray diffraction measurements. The fractal analysis of domain structure has yielded the Hausdorff dimension (D) in the range of ∼1.3–1.5 indicating a random-bond nature of the disorder potential, with domain size exhibiting Landau-Lifshitz-Kittel scaling.

Protection against peroxynitrite by cocoa polyphenol oligomers.

PubMed

Arteel, G E; Sies, H

1999-11-26

Flavonoids, natural plant constituents, protect against peroxynitrite and can thereby play a role in defense against this mediator of inflammation. Procyanidin oligomers of different size (monomer through nonamer), isolated from the seeds of Theobroma cacao, were examined for their ability to protect against peroxynitrite-dependent oxidation of dihydrorhodamine 123 and nitration of tyrosine. By molarity, oligomers were more effective than the monomeric epicatechin; the tetramer was particularly efficient at protecting against oxidation and nitration reactions. These results suggest that epicatechin oligomers found in cocoa powder and chocolate may be a potent dietary source for defense against peroxynitrite.

Oligomerization of mononucleotides on montmorillonite: A potential approach to the prebiotic synthesis of RNA. [Abstract only

NASA Technical Reports Server (NTRS)

Ferris, James P.; Ertem, Goezen; Ding, Zi Ping; Prabahar, Joseph

1994-01-01

The condensation of the 5'-phosphorimidazolide of adenosine (ImpA) on montmorillonite in a pH 8 aqueous solution yields oligomers containing up to 10 monomer units. The regiospecificity of 3',5'-phosphodiester bond formation is enhanced by addition of 10% diadenosine pyrophosphate (AppA) to the reaction mixture. A series of activated derivatives of 5'-AMP was prepared to investigate the effect of the leaving group on oligomer formation. The benzimidazole and p-dimethylamino-pyridine derivatives gave the best yields of oligomers. Factors important for oligomer formation is discussed.

Cholesterol ester hydrolase inhibitors reduce the production of synaptotoxic amyloid-β oligomers.

PubMed

McHale-Owen, Harriet; Bate, Clive

2018-03-01

The production of amyloid-β (Aβ) is the key factor driving pathogenesis in Alzheimer's disease (AD). Increasing concentrations of Aβ within the brain cause synapse degeneration and the dementia that is characteristic of AD. Here the factors that affect the release of disease-relevant forms Aβ were studied in a cell model. 7PA2 cells expressing the human amyloid precursor protein released soluble Aβ oligomers that caused synapse damage in cultured neurons. Supernatants from 7PA2 cells treated with the cholesterol synthesis inhibitor squalestatin contained similar concentrations of Aβ 42 to control cells but did not cause synapse damage in neuronal cultures. These supernatants contained reduced concentrations of Aβ 42 oligomers and increased concentrations of Aβ 42 monomers. Treatment of 7PA2 cells with platelet-activating factor (PAF) antagonists had similar effects; it reduced concentrations of Aβ 42 oligomers and increased concentrations of Aβ 42 monomers in cell supernatants. PAF activated cholesterol ester hydrolases (CEH), enzymes that released cholesterol from stores of cholesterol esters. Inhibition of CEH also reduced concentrations of Aβ 42 oligomers and increased concentrations of Aβ 42 monomers in cell supernatants. The Aβ monomers produced by treated cells protected neurons against Aβ oligomer-induced synapse damage. These studies indicate that pharmacological manipulation of cells can alter the ratio of Aβ monomer:oligomer released and consequently their effects on synapses. Copyright © 2017 Elsevier B.V. All rights reserved.

Properties of Poly- and Oligopentacenes Synthesized from Modular Building Blocks

DOE PAGES

Kumarasamy, Elango; Sanders, Samuel N.; Pun, Andrew B.; ...

2016-02-09

Here, we describe a facile route to well-defined, solution-processable pentacene oligomers (2 to 7) and homopolymer using Suzuki–Miyaura cross-coupling reactions. This synthetic strategy leads to regioisomers, regiopure syn- and anti-trimers were also synthesized, revealing minimal changes in solution properties but significant changes in the solid state arising from differing levels of crystallinity. The materials were characterized by steady state absorption spectroscopy and cyclic voltammetry to study their electronic structure. The steady state absorption spectra exhibit a new high-energy transition in the oligomers, which intensifies as a function of oligomer length, thus increasing the range of absorption to include the entiremore » visible spectrum. Density functional theory calculations indicate that the new peak results directly from the oligomerization. Solid state UV–vis suggests that while the monomer is amorphous, bricklayer packing in the higher oligomers significantly alters the solid state absorption relative to solution. The effect of oligomerization on packing was corroborated by GIWAXS analysis, which revealed crystalline domains in the oligomers. These domains, which are most evident in anti-trimer, become more pronounced upon thermal annealing. Photodegradation studies revealed considerable stability enhancement of oligomers toward oxygen and cycloaddition reactions relative to monomer. The synthesis and characterization of the first higher oligomers and homopolymer of pentacene should pave the way to applications in singlet fission, organic field-effect transistors, and organic photovoltaics.« less

Blood Ammonia as a Possible Etiological Agent for Alzheimer's Disease.

PubMed

Jin, Yan Yan; Singh, Parul; Chung, Hea-Jong; Hong, Seong-Tschool

2018-05-04

Alzheimer’s disease (AD), characterized by cognitive decline and devastating neurodegeneration, is the most common age-related dementia. Since AD is a typical example of a complex disease that is affected by various genetic and environmental factors, various factors could be involved in preventing and/or treating AD. Extracellular accumulation of beta-amyloid peptide (Aβ) and intracellular accumulation of tau undeniably play essential roles in the etiology of AD. However, interestingly enough, medications targeting Aβ or tau all failed and the only clinically efficient medications for AD are drugs targeting the cholinergic pathway. Also, a very intriguing discovery in AD is that the Mediterranean diet (MeDi), containing an unusually large quantity of Lactobacilli, is very effective in preventing AD. Based on recently emerging findings, it is our opinion that the reduction of blood ammonia levels by Lactobacilli in MeDi is the therapeutic agent of MeDi for AD. The recent evidence of Lactobacilli lowering blood ammonia level not only provides a link between AD and MeDi but also provides a foundation of pharmabiotics for hyperammonemia as well as various neurological diseases.

Aging Enables Ca2+ Overload and Apoptosis Induced by Amyloid-β Oligomers in Rat Hippocampal Neurons: Neuroprotection by Non-Steroidal Anti-Inflammatory Drugs and R-Flurbiprofen in Aging Neurons.

PubMed

Calvo-Rodríguez, María; García-Durillo, Mónica; Villalobos, Carlos; Núñez, Lucía

2016-07-22

The most important risk factor for Alzheimer's disease (AD) is aging. Neurotoxicity in AD has been linked to dyshomeostasis of intracellular Ca2+ induced by small aggregates of the amyloid-β peptide 1-42 (Aβ42 oligomers). However, how aging influences susceptibility to neurotoxicity induced by Aβ42 oligomers is unknown. In this study, we used long-term cultures of rat hippocampal neurons, a model of neuronal in vitro aging, to investigate the contribution of aging to Ca2+ dishomeostasis and neuron cell death induced by Aβ42 oligomers. In addition, we tested whether non-steroidal anti-inflammatory drugs (NSAIDs) and R-flurbiprofen prevent apoptosis acting on subcellular Ca2+ in aged neurons. We found that Aβ42 oligomers have no effect on young hippocampal neurons cultured for 2 days in vitro (2 DIV). However, they promoted apoptosis modestly in mature neurons (8 DIV) and these effects increased dramatically after 13 DIV, when neurons display many hallmarks of in vivo aging. Consistently, cytosolic and mitochondrial Ca2+ responses induced by Aβ42 oligomers increased dramatically with culture age. At low concentrations, NSAIDs and the enantiomer R-flurbiprofen lacking anti-inflammatory activity prevent Ca2+ overload and neuron cell death induced by Aβ42 oligomers in aged neurons. However, at high concentrations R-flurbiprofen induces apoptosis. Thus, Aβ42 oligomers promote Ca2+ overload and neuron cell death only in aged rat hippocampal neurons. These effects are prevented by low concentrations of NSAIDs and R-flurbiprofen acting on mitochondrial Ca2+ overload.

Structural requirements of cholesterol for binding to Vibrio cholerae hemolysin.

PubMed

Ikigai, Hajime; Otsuru, Hiroshi; Yamamoto, Koichiro; Shimamura, Tadakatsu

2006-01-01

Cholesterol is necessary for the conversion of Vibrio cholerae hemolysin (VCH) monomers into oligomers in liposome membranes. Using different sterols, we determined the stereochemical structures of the VCH-binding active groups present in cholesterol. The VCH monomers are bound to cholesterol, diosgenin, campesterol, and ergosterol, which have a hydroxyl group at position C-3 (3betaOH) in the A ring and a C-C double bond between positions C-5 and C-6 (C-C Delta(5)) in the B ring. They are not bound to epicholesterol and dihydrocholesterol, which form a covalent link with a 3alphaOH group and a C-C single bond between positions C-5 and C-6, respectively. This result suggests that the 3betaOH group and the C-CDelta(5) bond in cholesterol are required for VCH monomer binding. We further examined VCH oligomer binding to cholesterol. However, this oligomer did not bind to cholesterol, suggesting that the disappearance of the cholesterol-binding potential of the VCH oligomer might be a result of the conformational change caused by the conversion of the monomer into the oligomer. VCH oligomer formation was observed in liposomes containing sterols with the 3betaOH group and the C-C Delta(5) bond, and it correlated with the binding affinity of the monomer to each sterol. Therefore, it seems likely that monomer binding to membrane sterol leads to the assembly of the monomer. However, since oligomer formation was induced by liposomes containing either epicholesterol or dihydrocholesterol, the 3betaOH group and the C-C Delta(5) bond were not essential for conversion into the oligomer.

Solvent free low-melt viscosity imide oligomers and thermosetting polymide composites

NASA Technical Reports Server (NTRS)

Chuang, Chun-Hua (Inventor)

2012-01-01

.[.This invention relates to the composition and a solvent-free process for preparing novel imide oligomers and polymers specifically formulated with effective amounts of a dianhydride such as 2,3,3',4-biphenyltetra carboxylic dianydride (a-BPDA), at least one aromatic diamine and an endcapped of 4-phenylethynylphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260-280.degree. C. When the imide oligomer melt is cured at about 371.degree. C. in a press or autoclave under 100-500 psi, the melt resulted in a thermoset polyimide having a glass transition temperature (T.sub.g) equal to and above 310.degree. C. A novel feature of this process is that the monomers; namely the dianhydrides, diamines and the endcaps, are melt processable to form imide oligomers at temperatures ranging between 232-280.degree. C. (450-535.degree. F.) without any solvent. These low-melt imide oligomers can be easily processed by resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM) or the resin infusion process with fiber preforms e.g. carbon, glass or quartz preforms to produce polyimide matrix composites with 288-343.degree. C. (550-650.degree. F.) high temperature performance capability..]. .Iadd.This invention relates to compositions and a solvent-free reaction process for preparing imide oligomers and polymers specifically derived from effective amounts of dianhydrides such as 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), at least one aromatic polyamine and an end-cap such as 4-phenylethynyphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260.degree. C.-280.degree. C..Iaddend.

Montmorillonite-catalysed formation of RNA oligomers: the possible role of catalysis in the origins of life

PubMed Central

Ferris, James P

2006-01-01

Large deposits of montmorillonite are present on the Earth today and it is believed to have been present at the time of the origin of life and has recently been detected on Mars. It is formed by aqueous weathering of volcanic ash. It catalyses the formation of oligomers of RNA that contain monomer units from 2 to 30–50. Oligomers of this length are formed because this catalyst controls the structure of the oligomers formed and does not generate all possible isomers. Evidence of sequence-, regio- and homochiral selectivity in these oligomers has been obtained. Postulates on the role of selective versus specific catalysts on the origins of life are discussed. An introduction to the origin of life is given with an emphasis on reaction conditions based on the recent data obtained from zircons 4.0–4.5 Ga. PMID:17008218

Genotoxic and anti-genotoxic effects of esculin and its oligomer fractions against mitomycin C-induced DNA damages in mice.

PubMed

Mokdad Bzeouich, Imen; Mustapha, Nadia; Maatouk, Mouna; Ghedira, Kamel; Ghoul, Mohamed; Chekir-Ghedira, Leila

2016-12-01

Mitomycin C is one of the most effective chemotherapeutic drugs against various solid tumors. However, despite its wide spectrum of clinical benefits, this agent is capable of inducing various types of genotoxicity. In this study, we investigated the effect of esculin and its oligomer fractions (E1, E2 and E3) against mitomycin C induced genotoxicity in liver and kidney cells isolated from Balb/C mice using the comet assay. Esculin and its oligomer fractions were not genotoxic at the tested doses (20 mg/kg and 40 mg/kg b.w). A significant decrease in DNA damages was observed, suggesting a protective role of esculin and its oligomer fractions against the genotoxicity induced by mitomycin C on liver and kidney cells. Moreover, esculin and its oligomer fractions did not induce an increase of malondialdehyde levels. Copyright © 2016 Elsevier Inc. All rights reserved.

Phenylethynyl Phthalic Anhydride

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Smith, Joseph G., Jr. (Inventor)

1997-01-01

Controlled molecular weight PhenylEthynyl Terminated Imide oligomers (PETIs) have been prepared by the cyclodehydration of precursor phenylethynyl terminated amic acid oligomers. Amino terminated amic acid oligomers are prepared from the reaction of dianhydride(s) with an excess of diamine(s) and subsequently endcapped with PhenylEthynyl Phthalic Anhydride(s) (PEPA). The polymerizations are carried out in polar aprotic solvents such as N-methyl-2pyrrolidinone or N N-dimethylacetamide under nitrogen at room temperature. The amic acid oligomers are subsequently cyclodehydrated either thermally or chemically to the corresponding imide oligomers. Direct preparation of PETIs from the reaction of dianhydride(s) with an excess of diamine(s) and endcapped with phenylethynyl phthalic anhydride(s) has been performed in m-cresol. Phenylethynyl phthalic anhydrides are synthesized by the palladium catalyzed reaction of phenylacetylene with bromo substituted phthalic anhydrides in triethylamine. These new materials exhibit excellent properties and are potentially useful as adhesives, coatings, films, moldings and composite matrices.

Enhanced Circular Dichroism via Symmetry Breaking in a Chiral Plasmonic Nanoparticle Oligomer

NASA Astrophysics Data System (ADS)

Le, Khai Q.

2018-02-01

A chiral plasmonic nanoparticle oligomer, consisting of four symmetrically arranged nanodisks of different heights and having different optical absorption responses to left and right-handed circularly polarized light illumination, has been experimentally reported in the literature. The resulting circular dichroism (CD) signal was detectable with state of the art CD spectrometers but was much weaker than those of existing chiral nanostructures, i.e., three-dimensional (3-D) chiral metamaterials. In this letter, via symmetry breaking in such an oligomer, the author demonstrates that the CD can be enhanced up to six times compared to that of a symmetric oligomer, and is in the range of a relevant 3-D chiral metamolecule. Through investigation of geometrical parameters including particle size, asymmetric and symmetric gaps, the CD evolution was reported, which provides a useful guideline for design of two-dimensional chiral oligomers adopted as efficient probes for CD spectroscopic applications.

Effect of phosphate activating group on oligonucleotide formation on montmorillonite: the regioselective formation of 3',5'-linked oligoadenylates

NASA Technical Reports Server (NTRS)

Prabahar, K. J.; Cole, T. D.; Ferris, J. P.

1994-01-01

The effects of amine structure on the montmorillonite-catalyzed oligomerization of the 5'-phosphoramidates of adenosine are investigated. 4-Aminopyridine derivatives yielded oligoadenylates as long as dodecamers with a regioselectivity for 3',5'-phosphodiester bond formation averaging 88%. Linear and cyclic oligomers are obtained and no A5'ppA-containing products are detected. Oligomers as long as the hexanucleotide are obtained using 2-aminobenzimidazole as the activating group. A predominance of pA2'pA is detected in the dimer fraction along with cyclic 3',5'-trimer; no A5'ppA-containing oligomers were detected. Little or no oligomer formation was observed when morpholine, piperidine, pyrazole, 1,2,4-triazole, and 2-pyridone are used as phosphate-activating groups. The effects of the structure of the phosphate activating group on the oligomer structure and chain lengths are discussed.

Role of small oligomers on the amyloidogenic aggregation free-energy landscape.

PubMed

He, Xianglan; Giurleo, Jason T; Talaga, David S

2010-01-08

We combine atomic-force-microscopy particle-size-distribution measurements with earlier measurements on 1-anilino-8-naphthalene sulfonate, thioflavin T, and dynamic light scattering to develop a quantitative kinetic model for the aggregation of beta-lactoglobulin into amyloid. We directly compare our simulations to the population distributions provided by dynamic light scattering and atomic force microscopy. We combine species in the simulation according to structural type for comparison with fluorescence fingerprint results. The kinetic model of amyloidogenesis leads to an aggregation free-energy landscape. We define the roles of and propose a classification scheme for different oligomeric species based on their location in the aggregation free-energy landscape. We relate the different types of oligomers to the amyloid cascade hypothesis and the toxic oligomer hypothesis for amyloid-related diseases. We discuss existing kinetic mechanisms in terms of the different types of oligomers. We provide a possible resolution to the toxic oligomer-amyloid coincidence.

Enantiomers of Single-Wall Carbon Nanotubes Show Distinct Coating Displacement Kinetics.

PubMed

Zheng, Yu; Bachilo, Sergei M; Weisman, R Bruce

2018-06-27

It is known that specific oligomers of single-stranded DNA (ssDNA) can show remarkable selectivity when coating different structural species of single-wall carbon nanotubes (SWCNTs). We report that (ATT) 4 ssDNA coatings strongly distinguish between the two optical isomers of (7,5) SWCNTs. This causes resolvable shifts in their fluorescence spectra and differences of 2 orders of magnitude in the room temperature rates of coating displacement, as monitored through changes in nanotube fluorescence wavelength and intensity on exposure to sodium deoxycholate. During coating displacement, the enantiomer with high affinity for the ssDNA oligomer is deduced to form an intermediate hybrid that is not observed for the low affinity enantiomer. These results reveal that enantiomeric differences in SWCNTs complexed with ssDNA are more diverse and dramatic than previously recognized.

NMR, ESI/MS, and MALDI-TOF/MS analysis of pear juice polymeric proanthocyanidins with potent free radical scavenging activity.

PubMed

Es-Safi, Nour-Eddine; Guyot, Sylvain; Ducrot, Paul-Henri

2006-09-20

The structure of a polymeric proanthocyanidin fraction isolated from pear juice was characterized by NMR, ESI/MS, and MALDI-TOF/MS analyses, and its antioxidant activity was investigated using the DPPH free radical scavenging method. The results obtained from 13C NMR analysis showed the predominance of signals representative of procyanidins. Typical signals in the chemical shift region between 70 and 90 ppm demonstrated the exclusive presence of epicatechin units. The results obtained through negative ESI/MS analysis showed singly and doubly charged ions corresponding to the molecular mass of procyanidins with a degree of polymerization up to 22. The spectra obtained through MALDI-TOF/MS analysis revealed the presence of two series of tannin oligomers. Supporting the observations from NMR spectroscopy, the first series consists of well-resolved tannin identified as procyanidin polymers units with chain lengths of up to 25. A second series of monogalloyl flavan-3-ols polymers with polymerization degree up to 25 were also detected. This is the first mass spectrometric evidence confirming the existence of galloylated procyanidin oligomers in pear fruits. Within each of these oligomers, various signals exist suggesting the presence of several oligomeric tannins. The antioxidant properties of the polymeric fraction were investigated through reduction of the DPPH free radical, and the results obtained showed that the polymeric fraction exhibited a higher antioxidant power compared to those of (+)-catechin and B3 procyanidin dimer.

Numb endocytic adapter proteins regulate the transport and processing of the amyloid precursor protein in an isoform-dependent manner: implications for Alzheimer disease pathogenesis.

PubMed

Kyriazis, George A; Wei, Zelan; Vandermey, Miriam; Jo, Dong-Gyu; Xin, Ouyang; Mattson, Mark P; Chan, Sic L

2008-09-12

Central to the pathogenesis of Alzheimer disease is the aberrant processing of the amyloid precursor protein (APP) to generate amyloid beta-peptide (Abeta), the principle component of amyloid plaques. The cell fate determinant Numb is a phosphotyrosine binding domain (PTB)-containing endocytic adapter protein that interacts with the carboxyl-terminal domain of APP. The physiological relevance of this interaction is unknown. Mammals produce four alternatively spliced variants of Numb that differ in the length of their PTB and proline-rich region. In the current study, we determined the influence of the four human Numb isoforms on the intracellular trafficking and processing of APP. Stable expression of Numb isoforms that differ in the PTB but not in the proline-rich region results in marked differences in the sorting of APP to the recycling and degradative pathways. Neural cells expressing Numb isoforms that lack the insert in the PTB (short PTB (SPTB)) exhibited marked accumulation of APP in Rab5A-labeled early endosomal and recycling compartments, whereas those expressing isoforms with the insertion in the PTB (long PTB (LPTB)) exhibited reduced amounts of cellular APP and its proteolytic derivatives relative to parental control cells. Neither the activities of the beta- and gamma-secretases nor the expression of APP mRNA were significantly different in the stably transfected cells, suggesting that the differential effects of the Numb proteins on APP metabolism is likely to be secondary to altered APP trafficking. In addition, the expression of SPTB-Numb increases at the expense of LPTB-Numb in neuronal cultures subjected to stress, suggesting a role for Numb in stress-induced Abeta production. Taken together, these results suggest distinct roles for the human Numb isoforms in APP metabolism and may provide a novel potential link between altered Numb isoform expression and increased Abeta generation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peteanu, Linda A.; Chowdhury, Sanchari; Wildeman, Jurjen

One measure of exciton mobility in an aggregate is the efficiency of exciton–exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH–PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed frommore » the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. Furthermore, the wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.« less

Annotation of Different Dehydrocatechin Oligomers by MS/MS and Their Occurrence in Black Tea.

PubMed

Verloop, Annewieke J W; Gruppen, Harry; Vincken, Jean-Paul

2016-08-03

Dehydrocatechins (DhC's), oligomeric oxidation products of (epi)catechins, were formed in model incubations of epicatechin with mushroom tyrosinase. DhC oligomers up to tetramers were detected by reversed-phase ultrahigh-performance liquid chromatography mass spectrometry (RP-UHPLC-MS) analysis. Measurements with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) showed formation of oligomers up to at least 15 catechin subunits. Isomeric DhC's were obtained, and a method based on MS(2) fragment ratios was set up to distinguish between the different interflavanic configurations of the isomers. In the model incubation, 8 dehydrodicatechins (DhC2's) and 22 dehydrotricatechins (DhC3's) were tentatively annotated by their MS(2) signature fragments. Three different interflavanic configuration types were determined for the DhC2's. DhC2's and DhC3's were shown to occur in a black tea extract for the first time. For the DhC2's, at least two isomeric types, i.e., DhC β and DhC ε, could be annotated in black tea.

Detecting beta-amyloid aggregation from time-resolved emission spectra

NASA Astrophysics Data System (ADS)

Alghamdi, A.; Vyshemirsky, V.; Birch, D. J. S.; Rolinski, O. J.

2018-04-01

The aggregation of beta-amyloids is one of the key processes responsible for the development of Alzheimer’s disease. Early molecular-level detection of beta-amyloid oligomers may help in early diagnosis and in the development of new intervention therapies. Our previous studies on the changes in beta-amyloid’s single tyrosine intrinsic fluorescence response during aggregation demonstrated a four-exponential fluorescence intensity decay, and the ratio of the pre-exponential factors indicated the extent of the aggregation in the early stages of the process before the beta-sheets were formed. Here we present a complementary approach based on the time-resolved emission spectra (TRES) of amyloid’s tyrosine excited at 279 nm and fluorescence in the window 240-450 nm. TRES have been used to demonstrate sturctural changes occuring on the nanosecond time scale after excitation which has significant advantages over using steady-state spectra. We demonstrate this by resolving the fluorescent species and revealing that beta-amyloid’s monomers show very fast dielectric relaxation, and its oligomers display a substantial spectral shift due to dielectric relaxation, which gradually decreases when the oligomers become larger.

Na, K-ATPase α3 is a death target of Alzheimer patient amyloid-β assembly.

PubMed

Ohnishi, Takayuki; Yanazawa, Masako; Sasahara, Tomoya; Kitamura, Yasuki; Hiroaki, Hidekazu; Fukazawa, Yugo; Kii, Isao; Nishiyama, Takashi; Kakita, Akiyoshi; Takeda, Hiroyuki; Takeuchi, Akihide; Arai, Yoshie; Ito, Akane; Komura, Hitomi; Hirao, Hajime; Satomura, Kaori; Inoue, Masafumi; Muramatsu, Shin-ichi; Matsui, Ko; Tada, Mari; Sato, Michio; Saijo, Eri; Shigemitsu, Yoshiki; Sakai, Satoko; Umetsu, Yoshitaka; Goda, Natsuko; Takino, Naomi; Takahashi, Hitoshi; Hagiwara, Masatoshi; Sawasaki, Tatsuya; Iwasaki, Genji; Nakamura, Yu; Nabeshima, Yo-ichi; Teplow, David B; Hoshi, Minako

2015-08-11

Neurodegeneration correlates with Alzheimer's disease (AD) symptoms, but the molecular identities of pathogenic amyloid β-protein (Aβ) oligomers and their targets, leading to neurodegeneration, remain unclear. Amylospheroids (ASPD) are AD patient-derived 10- to 15-nm spherical Aβ oligomers that cause selective degeneration of mature neurons. Here, we show that the ASPD target is neuron-specific Na(+)/K(+)-ATPase α3 subunit (NAKα3). ASPD-binding to NAKα3 impaired NAKα3-specific activity, activated N-type voltage-gated calcium channels, and caused mitochondrial calcium dyshomeostasis, tau abnormalities, and neurodegeneration. NMR and molecular modeling studies suggested that spherical ASPD contain N-terminal-Aβ-derived "thorns" responsible for target binding, which are distinct from low molecular-weight oligomers and dodecamers. The fourth extracellular loop (Ex4) region of NAKα3 encompassing Asn(879) and Trp(880) is essential for ASPD-NAKα3 interaction, because tetrapeptides mimicking this Ex4 region bound to the ASPD surface and blocked ASPD neurotoxicity. Our findings open up new possibilities for knowledge-based design of peptidomimetics that inhibit neurodegeneration in AD by blocking aberrant ASPD-NAKα3 interaction.

Ring-like oligomers of Synaptotagmins and related C2 domain proteins

PubMed Central

Zanetti, Maria N; Bello, Oscar D; Wang, Jing; Coleman, Jeff; Cai, Yiying; Sindelar, Charles V; Rothman, James E; Krishnakumar, Shyam S

2016-01-01

We recently reported that the C2AB portion of Synaptotagmin 1 (Syt1) could self-assemble into Ca2+-sensitive ring-like oligomers on membranes, which could potentially regulate neurotransmitter release. Here we report that analogous ring-like oligomers assemble from the C2AB domains of other Syt isoforms (Syt2, Syt7, Syt9) as well as related C2 domain containing protein, Doc2B and extended Synaptotagmins (E-Syts). Evidently, circular oligomerization is a general and conserved structural aspect of many C2 domain proteins, including Synaptotagmins. Further, using electron microscopy combined with targeted mutations, we show that under physiologically relevant conditions, both the Syt1 ring assembly and its rapid disruption by Ca2+ involve the well-established functional surfaces on the C2B domain that are important for synaptic transmission. Our data suggests that ring formation may be triggered at an early step in synaptic vesicle docking and positions Syt1 to synchronize neurotransmitter release to Ca2+ influx. DOI: http://dx.doi.org/10.7554/eLife.17262.001 PMID:27434670

Self-Consistent Charge Density Functional Tight-Binding Study of Poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate) Ammonia Gas Sensor.

PubMed

Marutaphan, Ampaiwan; Seekaew, Yotsarayuth; Wongchoosuk, Chatchawal

2017-12-01

Geometric and electronic properties of 3,4-ethylenedioxythiophene (EDOT), styrene sulfonate (SS), and EDOT: SS oligomers up to 10 repeating units were studied by the self-consistent charge density functional tight-binding (SCC-DFTB) method. An application of PEDOT:PSS for ammonia (NH 3 ) detection was highlighted and investigated both experimentally and theoretically. The results showed an important role of H-bonds in EDOT:SS oligomers complex conformation. Electrical conductivity of EDOT increased with increasing oligomers and doping SS due to enhancement of π conjugation. Printed PEDOT:PSS gas sensor exhibited relatively high response and selectivity to NH 3 . The SCC-DFTB calculation suggested domination of direct charge transfer process in changing of PEDOT:PSS conductivity upon NH 3 exposure at room temperature. The NH 3 molecules preferred to bind with PEDOT:PSS via physisorption. The most favorable adsorption site for PEDOT:PSS-NH 3 interaction was found to be at the nitrogen atom of NH 3 and hydrogen atoms of SS with an average optimal binding distance of 2.00 Å.

Mechanical properties and cytotoxicity of experimental soft lining materials based on urethane acrylate oligomers.

PubMed

Kanie, Takahito; Tomita, Koichi; Tokuda, Masayuki; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2009-07-01

The purpose of this investigation was to determine whether experimental light-curing soft lining materials (ESLMs) based on commercially available urethane acrylate oligomers (UA-160TM, UV-3200B, UV-3500BA, and UV-3700B) are suitable for clinical use by measuring their viscosity, compressive modulus, Shore A hardness, tensile strength, adhesive strength, and cytotoxicity. The viscosities of the four ESLMs at 25 degrees C were 10.5 Pa.s, UV-3500BA; 144.0 Pa.s, UA-160TM; 328.8 Pa.s, UV-3700B; and 1079.7 Pa.s, UV-3200B. Polymerized UV-3700B was very soft, whereas the softness of the other ESLMs was similar to that of conventional soft lining materials. No significant difference in adhesive strength was observed between UV-3500BA and UV-3700B at 1 day and those at 12 months. Cytotoxicity was measured by a MTT-based assay using HeLa S3 and Ca9-22 cells. UV-3200B and UV-3700B oligomers and all four polymerized ESLMs showed cell viability over 95.2% (p < 0.05).

Self-Healable and Reprocessable Polysulfide Sealants Prepared from Liquid Polysulfide Oligomer and Epoxy Resin.

PubMed

Gao, Wentong; Bie, Mengyao; Liu, Fu; Chang, Pengshan; Quan, Yiwu

2017-05-10

Polysulfide sealants have been commercially applied in many industrial fields. In this article, we study the self-healing property of the epoxy resin-cured polysulfide sealants for the first time. The obtained sealants showed a flexible range of ultimate elongation of 157-478% and a tensile strength of 1.02-0.75 MPa corresponding to different polysulfide oligomers. By taking advantage of the dynamic reversible exchange of disulfide bonds, polysulfide sealants exhibited good self-healing ability under a moderate thermal stimulus. A higher molecular weight and a lower degree of cross-linking of polysulfide oligomer were helpful in improving the ultimate elongation and healing efficiency of the polysulfide sealants. After subjecting to a temperature of 75 °C for 60 min, both the tensile strength and ultimate elongation of a fully cut sample, LP55-F, were restored to 91% of the original values, without affecting the sealing property. Furthermore, the sample exhibited excellent reshaping and reprocessing abilities. These outcomes offer a paradigm toward sustainable industrial applications of the polysulfide-based sealants.

Oligomers and Polymers Based on Pentacene Building Blocks

PubMed Central

Lehnherr, Dan; Tykwinski, Rik R.

2010-01-01

Functionalized pentacene derivatives continue to provide unique materials for organic semiconductor applications. Although oligomers and polymers based on pentacene building blocks remain quite rare, recent synthetic achievements have provided a number of examples with varied structural motifs. This review highlights recent work in this area and, when possible, contrasts the properties of defined-length pentacene oligomers to those of mono- and polymeric systems.

Programmable Oligomers Targeting 5′-GGGG-3′ in the Minor Groove of DNA and NF-κB Binding Inhibition

PubMed Central

Chenoweth, David M.; Poposki, Julie A.; Marques, Michael A.; Dervan, Peter B.

2009-01-01

A series of hairpin oligomers containing benzimidazole (Bi) and imidazopyridine (Ip) rings were synthesized and screened to target 5′-WGGGGW-3′, a core sequence in the DNA binding site of NF-κB, a prolific transcription factor important in biology and disease. Five Bi and Ip containing oligomers bound to the 5′-WGGGGW-3′ site with high affinity. One of the oligomers (Im-Im-Im-Im-γ-PyBi-PyBi-β-Dp) was able to inhibit DNA binding by the transcription factor NF-κB. PMID:17095230

Nonenzymatic synthesis of RNA and DNA oligomers on hexitol nucleic acid templates: the importance of the A structure

NASA Technical Reports Server (NTRS)

Kozlov, I. A.; Politis, P. K.; Van Aerschot, A.; Busson, R.; Herdewijn, P.; Orgel, L. E.; Bada, J. L. (Principal Investigator); Dolan, M. (Principal Investigator)

1999-01-01

Hexitol nucleic acid (HNA) is an analogue of DNA containing the standard nucleoside bases, but with a phosphorylated 1,5-anhydrohexitol backbone. HNA oligomers form duplexes having the nucleic acid A structure with complementary DNA or RNA oligomers. The HNA decacytidylate oligomer is an efficient template for the oligomerization of the 5'-phosphoroimidazolides of guanosine or deoxyguanosine. Comparison of the oligomerization efficiencies on HNA, RNA, and DNA decacytidylate templates under various conditions suggests strongly that only nucleic acid double helices with the A structure support efficient template-directed synthesis when 5'-phosphoroimidazolides of nucleosides are used as substrates.

A chitin deacetylase from the endophytic fungus Pestalotiopsis sp. efficiently inactivates the elicitor activity of chitin oligomers in rice cells.

PubMed

Cord-Landwehr, Stefan; Melcher, Rebecca L J; Kolkenbrock, Stephan; Moerschbacher, Bruno M

2016-11-30

To successfully survive in plants, endophytes need strategies to avoid being detected by the plant immune system, as the cell walls of endophytes contain easily detectible chitin. It is possible that endophytes "hide" this chitin from the plant immune system by modifying it, or oligomers derived from it, using chitin deacetylases (CDA). To explore this hypothesis, we identified and expressed a CDA from Pestalotiopsis sp. (PesCDA), an endophytic fungus, in E. coli and characterized this enzyme and its chitosan oligomer products. We found that when PesCDA modifies chitin oligomers, the products are partially deacetylated chitosan oligomers with a specific acetylation pattern: GlcNAc-GlcNAc-(GlcN) n -GlcNAc (n ≥ 1). Then, in a bioactivity assay where suspension-cultured rice cells were incubated with the PesCDA products (processed chitin hexamers), we found that, unlike the substrate hexamers, chitosan oligomer products no longer elicited the plant immune system. Thus, this endophytic enzyme can prevent the endophyte from being recognized by the plant immune system; this might represent a more general hypothesis for how certain fungi are able to live in or on their hosts.