chondroitin-sulfates and Alzheimer-Disease

In this report we focus on the characterization of appican, the chondroitin sulfate proteoglycan form of amyloid precursor protein (APP), and the role that it and other proteoglycans may play in AD. Appican is expressed by certain transformed cell lines of neural origin, namely C6 cells and N2a neuroblastomas. It is detected in both human and rat brain and in primary cultures is expressed by astrocytes, but not neurons. The core protein of appican has been shown to be an alternatively spliced isoform of APP, lacking exon 15 of the APP gene, originally identified in leukocytes (L-APP). Splicing out of exon 15 results in the joining of exons 14 and 16, and formation of an Asp-Xaa-Ser-Gly consensus sequence for chondroitin sulfate chain attachment to serine 619 of L-APP, which lies 16 amino acids upstream of the A beta peptide sequence. Mutation of this serine residue to an alanine prevented chondroitin sulfate chain addition to the core protein. Levels of appican expression could be regulated by growth conditions independently of APP, suggesting that these molecules may serve distinct physiological roles within the cell. Morphological changes were also observed in both astrocytic and transformed cell cultures, that appeared to reflect changes in levels of appican expression. Preliminary data suggest that appican may be a strong cell adhesion molecule. Transfected C6 glioma cells overexpressing appican remained attached to tissue culture dishes markedly better than either C6 cells over-expressing exon-15 containing APP or WT C6 cells. Appican-enriched extracellular matrix (ECM) was also observed to serve as a much better substrate for attachment of N2a neuroblastomas, pheocromocytoma PC12 cells and primary astrocytes compared to APP enriched ECM.

Topics: Alzheimer Disease; Amino Acid Sequence; Amyloid beta-Protein Precursor; Animals; Chondroitin Sulfate Proteoglycans; Chondroitin Sulfates; Humans; Molecular Sequence Data; Proteoglycans

The purpose of this study was to construct a transmembrane peptide-chondroitin sulphate‑gold nanoparticle (TAT-CS@Au) delivery system and investigate its activity as an anti-Alzheimer's disease (AD) drug. We successfully prepared TAT-CS@Au nanoparticles, investigated their anti-AD effects, and explored the possible mechanisms in in vitro models. TAT-CS@Au exhibited excellent cellular uptake and transport capacity, effectively inhibited the accumulation of Aβ

Topics: Alzheimer Disease; Amyloid beta-Peptides; Chondroitin Sulfates; Gold; Humans; Metal Nanoparticles; Neuroblastoma; Oxidative Stress; Peptide Fragments; Pharmaceutical Preparations

Chondroitin sulfate E (CS-E), which is characterized by oversulfated disaccharide units, has been shown to regulate neuronal adhesion, neurite outgrowth and exert neuroprotective effects. In view of these findings, here we investigated the anti-Alzheimer's disease (AD) activities of CSE by using transgenic Caenorhabditis elegans model of Alzheimer's disease. The behavioral experiments demonstrated that CSE at the concentration of 1 mg/mL significantly delayed the worm paralysis caused by Aβ aggregation as compared with control group. Western blot analysis revealed that the level of small oligomers in the transgenic C. elegans was significantly reduced upon treatment with CSE. The number of Aβ plaque deposits in transgenic worm was significantly decreased. In addition, CSE also protected the worms from oxidative stress and rescued chemotaxis dysfunction in transgenic strain CL2355. Taken together, these data suggested that CSE could protect against Aβ-induced toxicity in C. elegans. These results offer valuable evidence for the future use of CSE in the development of agents for the treatment of AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Animals, Genetically Modified; Caenorhabditis elegans; Chondroitin Sulfates; Disease Models, Animal

Our previous study found that low molecular weight chondroitin sulfate (LMWCS) had neuroprotective effects against the toxicity of amyloid-β (Aβ) peptides both in vitro and in vivo, and we speculated that the effects might be related with its anti-oxidative activities. In this study, the anti-Alzheimer's disease (AD) activity of LMWCS was further studied in 5XFAD transgenic mice. After 4-month gavage, the levels of Aβ

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Behavior, Animal; Chondroitin Sulfates; Cytokines; Disease Models, Animal; Mice; Mice, Transgenic; Molecular Weight; Neuroinflammatory Diseases; Neuroprotective Agents; Oxidative Stress; Presenilin-1; tau Proteins

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Cell Line, Tumor; Cell Survival; Chemical Phenomena; Chondroitin Sulfates; Drug Discovery; Glutathione; Humans; Metal Nanoparticles; Molecular Targeted Therapy; Oxidation-Reduction; Oxidative Stress; Reactive Oxygen Species; Selenium; Spectrum Analysis

Glycosaminoglycans (GAGs), including heparan sulfates and chondroitin sulfates, are major components of the extracellular matrix. Upon interacting with heparin binding growth factors (HBGF), GAGs participate to the maintaintenance of tissue homeostasis and contribute to self-healing. Although several processes regulated by HBGF are altered in Alzheimer's disease, it is unknown whether the brain GAG capacities to bind and regulate the function of HBGF or of other heparin binding proteins, as tau, are modified in this disease. Here, we show that total sulfated GAGs from hippocampus of Alzheimer's disease have altered capacities to bind and potentiate the activities of growth factors including FGF-2, VEGF, and BDNF while their capacity to bind to tau is remarkable increased. Alterations of GAG structures and capacities to interact with and regulate the activity of heparin binding proteins might contribute to impaired tissue homeostasis in the Alzheimer's disease brain.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Brain; Brain-Derived Neurotrophic Factor; Brazil; Chondroitin Sulfates; Extracellular Matrix; Female; Fibroblast Growth Factor 2; Glycosaminoglycans; Heparin; Heparitin Sulfate; Hippocampus; Humans; Male; Middle Aged; Protein Binding; tau Proteins; Temporal Lobe; Vascular Endothelial Growth Factor A

Alzheimer's disease (AD) is a progressive disorder leading to cognitive impairment and neuronal loss. Cerebral extracellular accumulation and deposition of amyloid ß plaques is a pathological hallmark of AD. Chondroitin sulfate (CS) is an extracellular component abundant in the brain. CS is a sulfated glycosaminoglycan covalently attached to a core protein, forming chondroitin sulfate proteoglycan. The structure of CS is heterogeneous with sulfation modification and elongation of the chain. The structural diversity of CS allows it to play various roles in the brain. Increasing evidence has shown that CS promotes aggregation of amyloid ß peptides into higher-order species such as insoluble amyloid ß fibrils. Difficulties in the structural analysis of brain CS, as well as its heterogeneity, limit the study of potential roles of CS in AD pathology. Here we established a microanalysis method with reversed-phase ion-pair high performance liquid chromatography and found that CS in the brains of Tg2576 AD model mice show a lower molecular size and an increased ratio of CS-B motif di-sulfated disaccharide. Our findings provide insight into the structural changes of cerebral CS upon Alzheimer's pathogenesis.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Chondroitin Sulfates; Disaccharides; Mice; Mice, Inbred C57BL; Plaque, Amyloid

In the present study, we investigated the effects of low molecular weight chondroitin sulfate (LMWCS) on amyloid beta (Aβ)-induced neurotoxicity in vitro and in vivo. The in vitro results showed that LMWCS blocked Aβ25-35-induced cell viability loss and apoptosis, decreased intracellular calcium concentration, reactive oxygen species (ROS) levels, the mitochondrial membrane potential (MMP) depolarization, and the protein expression of Caspase-3. During in vivo experiments, LMWCS improved the cognitive impairment induced by Aβ1-40, increased the level of choline acetyltransferase (ChAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and decreased the level of malondialdehyde (MDA) and acetylcholinesterase (AChE) in the mouse brain. Moreover, LMWCS decreased the density of pyramidal cells of CA1 regions, and suppressed the protein expression of Bax/Bcl-2 and Caspase-3, -9 in the hippocampus of mice. In conclusion, LMWCS possessed neuroprotective properties against toxic effects induced by Aβ peptides both in vitro and in vivo, which might be related to anti-apoptotic activity. LMWCS might be a useful preventive and therapeutic compound for Alzheimer's disease.

Topics: Acetylcholinesterase; Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain Injuries; Calcium; Caspase 3; Cell Line; Choline O-Acetyltransferase; Chondroitin Sulfates; Disease Models, Animal; Exploratory Behavior; Male; Maze Learning; Membrane Potentials; Mice; Mice, Inbred BALB C; Neuroblastoma; Neuroprotective Agents; Peptide Fragments; Rats; Reactive Oxygen Species

Glycosaminoglycans (GAGs), in particular as part of heparan sulfate proteoglycans, are associated with cerebral amyloid angiopathy (CAA). Similarly, GAGs are also associated with the severe CAA found in patients suffering from hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), where the amyloid beta (Abeta) peptide contains the Dutch mutation (DAbeta(1-40)). This suggests a role for GAGs in vascular Abeta aggregation. It was the aim of this study to investigate the effect of different GAGs (heparin, chondroitin sulfate, heparan sulfate), the macromolecule dextran sulfate and, using desulfated heparins, the role of GAG sulfate moieties on the in vitro aggregation of CAA-associated DAbeta(1-40) and on DAbeta(1-40)-induced toxicity of cultured cerebrovascular cells. We also aimed to study the in vivo distribution of various sulfated heparan sulfate GAG epitopes in CAA. Of all GAGs tested, heparin was the strongest inducer of aggregation of DAbeta(1-40) in the different aggregation assays, with both heparin and heparan sulfate reducing Abeta-induced cellular toxicity. Furthermore, (partial) removal of the sulfate moieties of heparin partially abolished the effects of heparin on aggregation and cellular toxicity, suggesting an essential role for the sulfate moieties in heparin. Finally, we demonstrated the in vivo association of sulfated heparan sulfate (HS) GAGs with CAA. We conclude that sulfate moieties within GAGs, like heparin and HS, have an important role in Abeta aggregation in CAA and in Abeta-mediated toxicity of cerebrovascular cells.

Topics: Aged; Alzheimer Disease; Amyloid beta-Peptides; Cell Death; Cells, Cultured; Cerebral Amyloid Angiopathy; Chondroitin Sulfates; Female; Heparin; Heparitin Sulfate; Humans; Mutation; Occipital Lobe; Peptide Fragments; Pericytes

One mechanism leading to neurodegeneration during Alzheimer's disease (AD) is amyloid beta peptide (Abeta)-induced neurotoxicity. Among the factors proposed to potentiate Abeta toxicity is its covalent modification through carbohydrate-derived advanced glycation endproducts (AGEs). Other experimental evidence, though, indicates that certain polymeric carbohydrates like the glycosaminoglycan (GAG) chains found in proteoglycan molecules attenuate the neurotoxic effect of Abeta in primary neuronal cultures. Pretreatment of the 42-residue Abeta fragment (Abeta1-42) with the ubiquitous brain carbohydrates, glucose, fructose, and the GAG chondroitin sulfate B (CSB) inhibits Abeta1-42-induced apoptosis and reduces the peptide neurotoxicity on neuroblastoma cells, a cytoprotective effect that is partially reverted by AGE inhibitors such as pyridoxamine and L-carnosine. Thioflavin T fluorescence measurements indicate that at concentrations close to physiological, only CSB promotes the formation of Abeta amyloid fibril structure. Atomic force microscopy imaging and Western blot analysis suggest that glucose favours the formation of globular oligomeric structures derived from aggregated species. Our data suggest that at short times carbohydrates reduce Abeta1-42 toxicity through different mechanisms both dependent and independent of AGE formation.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Cell Death; Cell Line, Tumor; Chondroitin Sulfates; Dose-Response Relationship, Drug; Glucose; Glycation End Products, Advanced; Humans; Peptide Fragments

Aggregation of amyloid-beta (Abeta) in the forebrain of Alzheimer's disease (AD) subjects may disturb the molecular organization of the extracellular microenvironment that modulates neural and synaptic plasticity. Proteoglycans are major components of this extracellular environment. To test the hypothesis that Abeta, or another amyloid precursor protein (APP) dependent mechanism modifies the accumulation and/or turnover of extracellular proteoglycans, we examined whether the expression and processing of brevican, an abundant extracellular, chondroitin sulfate (CS)-bearing proteoglycan, were altered in brains of Abeta-depositing transgenic mice (APPsw - APP gene bearing the Swedish mutation) as a model of AD. The molecular size of CS chains attached to brevican was smaller in hippocampal tissue from APPsw mice bearing Abeta deposits compared to non-transgenic mice, likely because of changes in the CS chains. Also, the abundance of the major proteolytic fragment of brevican was markedly diminished in extracts from several telencephalic regions of APPsw mice compared to non-transgenic mice, yet these immunoreactive fragments appeared to accumulate adjacent to the plaque edge. These results suggest that Abeta or APP exert inhibitory effects on proteolytic cleavage mechanisms responsible for synthesis and turnover of proteoglycans. As proteoglycans stabilize synaptic structure and inhibit molecular plasticity, defective brevican processing observed in Abeta-bearing mice and potentially end-stage human AD, may contribute to deficient neural plasticity.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Blotting, Western; Brain Chemistry; Brevican; Cell Line; Chondroitin Sulfate Proteoglycans; Chondroitin Sulfates; Culture Media; Extracellular Space; Humans; Image Processing, Computer-Assisted; Immunohistochemistry; Lectins, C-Type; Mice; Mice, Transgenic; Nerve Tissue Proteins; Plaque, Amyloid; Protein Processing, Post-Translational; Reverse Transcriptase Polymerase Chain Reaction

Progressive cerebral deposition of beta-amyloid peptide either in blood vessels or around neurites is one of the most important features of Alzheimer's disease (AD). The beta-peptide, known as Abeta or A4, is produced by proteolytic cleavage of the amyloid precursor protein (APP). Two APP processing pathways have been proposed as physiological alternatives; only one of which leads to the production of Abeta or amyloidogenic peptides. However, we have little information regarding these processing pathways in the brain, or on whether posttranslational modifications such as glycosylation affect APP processing in vivo. Furthermore, the physiological function(s) of this protein in nervous tissue remains unclear, although modulatory roles in cell adhesion and neuritic extension have been suggested. It has been reported that APP may be glycosylated as a proteoglycan. We purified this APP population from human brain, and our data indicate that PG-APP supports neurite extension of hippocampal neurons. Neurons grown on this substratum showed an increased capacity to elongate neurites and increased neuritic "branching" compared to culture on laminin. These effects were enhanced with PG-APP samples obtained from AD brains. Our results suggest that this APP population may act as a neurite outgrowth and branching promoter and may thus play a role in some pathological conditions. These findings may have significant implications in understanding normal brain development and pathological situations (such as AD).

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Antibodies; Blotting, Western; Cell Adhesion; Chondroitin Sulfates; Hippocampus; Humans; Middle Aged; Neurites; Neurons; Rats

One of the major clinical features of Alzheimer's disease is the presence of extracellular amyloid plaques that are associated with glycosaminoglycan-containing proteoglycans. It has been proposed that proteoglycans and glycosaminoglycans facilitate amyloid fibril formation and/or stabilize these aggregates. Characterization of proteoglycan-protein interactions has suggested that basic amino acids in a specific conformation are necessary for glycosaminoglycan binding. Amyloid-beta peptide (Abeta) has a cluster of basic amino acids at the N-terminus (residues 13-16, His-His-Gln-Lys), which are considered critical for glycosaminoglycan interactions. To understand the molecular recognition of glycosaminoglycans by Abeta, we have examined a series of synthetic peptides with systematic alanine substitutions. These include: His13-->Ala, His14-->Ala, Lys16-->Ala, His13His14Lys16-->Ala and Arg5His6-->Ala. Alanine substitutions result in differences in both the secondary and fibrous structure of Abeta1-28 as determined by circular dichroism spectroscopy and electron microscopy. The results demonstrate that the His-His-Gln-Lys region of Abeta, and in particular His13, is an important structural domain, as Ala substitution produces a dysfunctional folding mutant. Interaction of the substituted peptides with heparin and chondroitin sulfate glycosaminoglycans demonstrate that although electrostatic interactions contribute to binding, nonionic interactions such as hydrogen bonding and van der Waals packing play a role in glycosaminoglycan-induced Abeta folding and aggregation.

Topics: Alanine; Alzheimer Disease; Amino Acid Sequence; Amino Acid Substitution; Amyloid beta-Peptides; Chondroitin Sulfates; Circular Dichroism; Dermatan Sulfate; Glycosaminoglycans; Heparin; Humans; Hydrogen Bonding; Microscopy, Electron; Molecular Sequence Data; Mutation; Peptide Fragments; Protein Binding; Protein Folding; Protein Structure, Quaternary; Protein Structure, Secondary; Static Electricity

The mechanism of metal ion-catalyzed oxidative modification of apolipoprotein E (apoE) in human very-low-density lipoprotein (VLDL) and its inhibition by glycosaminoglycan (GAG) was investigated in vitro. The VLDL oxidation catalyzed by Cu2+ led to the lipid peroxidation, the formation of aggregates, and covalent modification of apoE. The modified apoE lost heparin-binding activity. These results suggest that the lipid peroxidation of VLDL and modification of apoE cause impairment of lipid uptake by cells and deposit the oxidized lipids in the tissues. The lipid peroxidation and oxidative modification of apoE in VLDL mediated by Cu2+ and an aqueous radical generator were suppressed by GAG, heparan sulfate, heparin, and chondroitin sulfate A, even though GAGs demonstrated no ability to scavenge alpha,alpha-diphenyl-beta-picrylhydrazyl radical. There were no relationships between inhibitory activity of GAGs in the VLDL oxidation and their number of sulfate groups which possess chelating activity of metal ion. Therefore, it can be considered that the inhibition of VLDL oxidation by GAGs is possibly due to the interaction between GAG and VLDL which bring about the steric hindrance, interference with the reaction between VLDL particle and the reactive oxygen species. These studies suggest that GAGs preserve the biological functions of apoE from oxidative stress.

Topics: Adult; Aldehydes; Alzheimer Disease; Amidines; Apolipoproteins E; Bepridil; Biphenyl Compounds; Chelating Agents; Cholesterol Esters; Chondroitin Sulfates; Copper Sulfate; Dextrans; Free Radical Scavengers; Glutathione; Glycosaminoglycans; Heparin; Hippocampus; Humans; Hydrogen-Ion Concentration; Lipid Peroxidation; Lipoproteins, VLDL; Male; Picrates; Reactive Oxygen Species; Thiobarbituric Acid Reactive Substances

Previous studies have established that in response to wounding, the expression of amyloid precursor-like protein 2 (APLP2) in the basal cells of migrating corneal epithelium is greatly up-regulated. To further our understanding of the functional significance of APLP2 in wound healing, we have measured the migratory response of transfected Chinese hamster ovary (CHO) cells expressing APLP2 isoforms to a variety of extracellular matrix components including laminin, collagen types I, IV, and VII, fibronectin, and heparan sulfate proteoglycans (HSPGs). CHO cells overexpressing either of two APLP2 variants, differing in chondroitin sulfate (CS) attachment, exhibit a marked increase in chemotaxis toward type IV collagen and fibronectin but not to laminin, collagen types I and VII, and HSPGs. Cells overexpressing APLP2-751 (CS-modified) exhibited a greater migratory response to fibronectin and type IV collagen than their non-CS-attached counterparts (APLP2-763), suggesting that CS modification enhanced APLP2 effects on cell migration. Moreover, in the presence of chondroitin sulfate, transfectants overexpressing APLP2-751 failed to exhibit this enhanced migration toward fibronectin. The APLP2-ECM interactions were also explored by solid phase adhesion assays. While overexpression of APLP2 isoforms moderately enhanced CHO adhesion to laminin, collagen types I and VII, and HSPGs lines, especially those overexpressing APLP2-751, exhibited greatly increased adhesion to type IV collagen and fibronectin. These observations suggest that APLP2 contributes to re-epithelialization during wound healing by supporting epithelial cell adhesion to fibronectin and collagen IV, thus influencing their capacity to migrate over the wound bed. Furthermore, APLP2 interactions with fibronectin and collagen IV appear to be potentiated by the addition of a CS chain to the core proteins.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Cell Adhesion; Cell Movement; CHO Cells; Chondroitin Sulfates; Collagen; Cricetinae; Fibronectins; Nerve Tissue Proteins

Alzheimer's beta-amyloid precursor related proteins bearing chondroitin sulfate chains were detected in the conditioned media of primary cultured astrocytes obtained from fetal rat brains by Western blotting using the monoclonal antibody 22C11 against Alzheimer's beta-amyloid precursor protein (APP), but not in the media of cortical neurons. The chondroitin sulfate proteoglycan form of APP was also detectable in a soluble proteoglycan fraction prepared from 10-day-old rat brains. However, the amount of proteoglycan form of APP in the brain was very small compared to non-proteoglycan forms at all the developmental stages from embryonic day 14 to 2 years. These observations suggest that astrocytes are one cellular source of the proteoglycan form of APP in the brain.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Astrocytes; Blotting, Western; Brain; Cells, Cultured; Chondroitin Sulfate Proteoglycans; Chondroitin Sulfates; Rats; Rats, Sprague-Dawley; Solubility

beta-Amyloid, the principal component of senile plaques in individuals with Alzheimer's disease, is derived from larger integral membrane glycoproteins, termed amyloid precursor proteins (APP). APP is a member of a family of proteins that includes the amyloid precursor-like proteins APLP1 and APLP2. The present study examines the metabolism of mouse APLP2 in cultured mammalian cells. We report that in stably transfected Chinese hamster ovary and transiently transfected African green monkey kidney (COS-1) cells, APLP2 is modified by glycosaminoglycan (GAG) addition. The sensitivity of GAG-modified APLP2 to digestion with chondroitinase AC indicates that chondroitin sulfate (CS) chains are the preponderant GAG on APLP2. CS GAG modification of APLP2 occurs in a region with little homology to APP. Contained within this heterologous region is a predicted CS modification site, ENEGSGMAEQ (APLP2 residues 610-619); APLP2 polypeptides harboring a serine-to-alanine substitution at position 614 fail to undergo CS GAG modification. Our observation that APLP2 is modified by a pathway distinct from APP suggests that the two molecules may be functionally divergent.

Topics: Alzheimer Disease; Amino Acid Sequence; Amyloid beta-Protein Precursor; Animals; Base Sequence; Cell Line; CHO Cells; Chondroitin Sulfates; Cricetinae; Glycosaminoglycans; Molecular Sequence Data; Nerve Tissue Proteins; Oligonucleotides, Antisense; Protein Processing, Post-Translational; Transfection

Each of the known classes of mammalian glycosaminoglycans, with the exception of keratan sulphate, was found in cerebral cortex samples from patients with Alzheimer-type dementia and age-matched controls. These molecules were quantitated, after electrophoresis and staining with Alcian Blue dye, by scanning densitometry. No significant differences were found between the mean levels of each of the above glycosaminoglycans in frontal cortex from patients with dementia compared with controls. An increase (26%; p less than 0.05) in the mean level of hyaluronate, but not of other glycosaminoglycans, was found in temporal cortex samples. On the other hand, the uronic acid content of hyaluronate degradation products following Streptomyces hyaluronidase treatment of brain glycosaminoglycans did not reveal any statistically significant changes in Alzheimer's disease. HPLC of disaccharide products from Arthrobacter chondroitinase AC digests did not reveal any significant changes in sulphate substitution of chondroitin sulphate in Alzheimer brain.

Topics: Alzheimer Disease; Cerebral Cortex; Chondroitin Sulfates; Chromatography, High Pressure Liquid; Disaccharides; Frontal Lobe; Glycosaminoglycans; Humans; Hyaluronic Acid; Temporal Lobe; Uronic Acids