carbocyanines and Alzheimer-Disease

Despite the wide use of magnetic resonance imaging (MRI) as a clinical diagnostic tool, there are still no clinically approved MRI contrast agents that can be applied for cerebral Alzheimer's disease (AD) biomarker imaging. We report here the design and development of the first amyloid-β (Aβ)-targeted, blood-brain barrier (BBB) penetrable theranostic Gd(DOTA)-cyanine dyad, which was synthesized by the conjugation of Gd(DOTA) complex and carbazole-based cyanine dye by the copper(I)-catalyzed azide-alkyne cycloaddition click reaction for imaging of Aβ

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Carbocyanines; Coordination Complexes; Disease Models, Animal; Gadolinium; Magnetic Resonance Imaging; Mice

Most photoacoustic (PA) imaging agents are based on the repurposing of existing fluorescent dye platforms that exhibit non-optimal properties for PA applications. Herein, we introduce PA-HD, a new dye scaffold optimized for PA probe development that features a 4.8-fold increase in sensitivity and a red-shift of the λ

Topics: Alzheimer Disease; Animals; Brain; Carbocyanines; Disease Models, Animal; Fluorescent Dyes; Hydrogen Peroxide; Mice; Molecular Structure; Optical Imaging; Oxidative Stress; Photoacoustic Techniques

The core of the tau fibrils in Alzheimer disease is a hexapeptide sequence organized in paired helical filaments (PHF). This sequence AcPHF6 can be used as tau fibrils model for the fast screening of potential therapeutic inhibitors of fibril formation or their disruption. The assay is usually performed by monitoring the fluorescence increase of Thioflavin T (ThT), well-known reporter dye for fibrillation. However, the ThT assay is not faultless, and here we present novel fluorescent dye, cyanine attached to amino acid side-chain (Cy-aa) that shows several advantages over ThT. The fibrillation kinetics of AcPHF6 was monitored via Cy-aa at twenty times lower concentration compared to ThT and successfully reported the presence of fibrillation inhibitor by Cy-aa fluorescence decrease. Additionally, spectral properties of Cy-aa are red-shifted in comparison to ThT allowing screening of a wider range of potential fibrillation inhibitors. Moreover, in the mixture with the pre-formed fibrils, Cy-aa shows strong fluorescence light-up proportional to fibrils concentration. We also successfully coupled this fluorescent amino acid to PHF in order to completely avoid the possibility of dye displacement with screening compound, and this newly designed conjugate showed to be a reliable intrinsic fluorescent probe for monitoring fibrillation kinetics of amyloid peptides.

Topics: Alzheimer Disease; Amino Acids; Amyloid beta-Peptides; Benzothiazoles; Carbocyanines; Fluorescence; Fluorescent Dyes; Humans; Kinetics; Molecular Structure

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

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

The formation of amyloid-β (Aβ) plaques in the brain is one of the main pathological features of Alzheimer's disease (AD). The imaging probes, capable of detecting Aβ deposition, are important tools for early diagnosis of AD. In this article, we designed, synthesized and evaluated a cyanine-based near-infrared fluorescence (NIRF) probe ZT-1 for the detection of Aβ deposits in the brain. The probe had excellent fluorescent properties with an emission maximum above 720 nm upon binding to Aβ aggregates with affinity of 445.0 nM (K

Topics: Alzheimer Disease; Animals; Carbocyanines; Dose-Response Relationship, Drug; Infrared Rays; Male; Mice; Mice, Inbred C57BL; Mice, Inbred ICR; Molecular Structure; Optical Imaging; Plaque, Amyloid; Structure-Activity Relationship

Alzheimer's disease and other age-related neurodegenerative disorders are associated with deterioration of the noradrenergic locus coeruleus (LC), a probable trigger for mood and memory dysfunction. LC noradrenergic neurons exhibit particularly high levels of somatostatin binding sites. This is noteworthy since cortical and hypothalamic somatostatin content is reduced in neurodegenerative pathologies. Yet a possible role of a somatostatin signal deficit in the maintenance of noradrenergic projections remains unknown. Here, we deployed tissue microarrays, immunohistochemistry, quantitative morphometry and mRNA profiling in a cohort of Alzheimer's and age-matched control brains in combination with genetic models of somatostatin receptor deficiency to establish causality between defunct somatostatin signalling and noradrenergic neurodegeneration. In Alzheimer's disease, we found significantly reduced somatostatin protein expression in the temporal cortex, with aberrant clustering and bulging of tyrosine hydroxylase-immunoreactive afferents. As such, somatostatin receptor 2 (SSTR2) mRNA was highly expressed in the human LC, with its levels significantly decreasing from Braak stages III/IV and onwards, i.e., a process preceding advanced Alzheimer's pathology. The loss of SSTR2 transcripts in the LC neurons appeared selective, since tyrosine hydroxylase, dopamine β-hydroxylase, galanin or galanin receptor 3 mRNAs remained unchanged. We modeled these pathogenic changes in Sstr2(-/-) mice and, unlike in Sstr1(-/-) or Sstr4(-/-) genotypes, they showed selective, global and progressive degeneration of their central noradrenergic projections. However, neuronal perikarya in the LC were found intact until late adulthood (<8 months) in Sstr2(-/-) mice. In contrast, the noradrenergic neurons in the superior cervical ganglion lacked SSTR2 and, as expected, the sympathetic innervation of the head region did not show any signs of degeneration. Our results indicate that SSTR2-mediated signaling is integral to the maintenance of central noradrenergic projections at the system level, and that early loss of somatostatin receptor 2 function may be associated with the selective vulnerability of the noradrenergic system in Alzheimer's disease.

Topics: Age Factors; Aged; Alzheimer Disease; Amyloid beta-Peptides; Animals; Biogenic Monoamines; Carbocyanines; Case-Control Studies; Cohort Studies; Female; Gene Expression Regulation; Humans; Locus Coeruleus; Male; Mice; Mice, Transgenic; Middle Aged; Neurons; Norepinephrine; Receptors, Somatostatin; Signal Transduction; Somatostatin; tau Proteins; Temporal Lobe; Tyrosine 3-Monooxygenase

Some symmetrical and unsymmetrical thiacarbocyanines bearing NO-donor nitrooxy and furoxan moieties were synthesized and studied as candidate anti-Alzheimer's drugs. All products activated soluble guanylate cyclase (sGC) in a dose-dependent manner, depending on the presence in their structures of NO-donor groups. None displayed toxicity when tested at concentrations below 10 μM on human brain microvascular endothelial cells (hCMEC/D3). Some products were capable of inhibiting amyloid β-protein (Aβ) aggregation, with a potency in the low μM concentration range, and of inhibiting aggregation of human recombinant tau protein in amyloid fibrils when incubated with the protein at 1 μM concentration. Nitrooxy derivative 21 and furoxan derivative 22 were selected to investigate synaptic plasticity. Both products, tested at 2 μM concentration, counteracted the inhibition of long-term potentiation (LTP) induced by Aβ42 in hippocampal brain slices.

Topics: Alzheimer Disease; Carbocyanines; Humans; Nitric Oxide Donors

Shedding light on grey matter: Fluorescent trimethine cyanines were evaluated as imaging probes for neurofibrillary tangles in post-mortem brain sections of Alzheimer's disease patients. These probes bind to neurofibrillary tangles with high contrast and selectivity over amyloid β plaques.

Topics: Aged; Alzheimer Disease; Animals; Antineoplastic Agents; Brain; Carbocyanines; Cell Proliferation; Dose-Response Relationship, Drug; Drug Design; Drug Screening Assays, Antitumor; Fluorescent Dyes; Hep G2 Cells; Humans; Male; Molecular Structure; Olfactory Mucosa; Structure-Activity Relationship; tau Proteins; Zebrafish

The difficulty in developing a diagnostic assay for Creutzfeldt - Jakob disease (CJD) and other transmissible spongiform encephalopathies (TSEs) stems in part from the fact that the infectious agent is an aberrantly folded form of an endogenous cellular protein. This precludes the use of the powerful gene based technologies currently applied to the direct detection of other infectious agents. To circumvent this problem our research objective has been to identify a set of proteins exhibiting characteristic differential abundance in response to TSE infection. The objective of the present study was to assess the disease specificity of differentially abundant urine proteins able to identify scrapie infected mice. Two-dimensional differential gel electrophoresis was used to analyze longitudinal collections of urine samples from both prion-infected mice and a transgenic mouse model of Alzheimer's disease. The introduction of fluorescent dyes, that allow multiple samples to be co-resolved and visualized on one two dimensional gel, have increased the accuracy of this methodology for the discovery of robust protein biomarkers for disease. The accuracy of a small panel of differentially abundant proteins to correctly classify an independent naïve sample set was determined. The results demonstrated that at the time of clinical presentation the differential abundance of urine proteins were capable of identifying the prion infected mice with 87% sensitivity and 93% specificity. The identity of the diagnostic differentially abundant proteins was investigated by mass spectrometry.

Topics: Algorithms; Alzheimer Disease; Animals; Biomarkers; Carbocyanines; Diagnosis, Differential; Disease Models, Animal; Electrophoresis, Gel, Two-Dimensional; Female; Mass Spectrometry; Mice; Mice, Inbred C57BL; Mice, Transgenic; Principal Component Analysis; Proteins; Proteome; Reproducibility of Results; Scrapie

Beta-amyloid (Aβ) peptides are considered to play a major role in the pathogenesis of Alzheimer's disease (AD) and molecules that can prevent pathways of Aβ toxicity may be potential therapeutic agents for treatment of AD. We have previously reported that NK-4, a cyanine photosensitizing dye, displays neurotrophic and antioxidant activities. In this study, we report the effects of NK-4 on the toxicity of Aβ and on cognitive function and Aβ concentration in a transgenic mouse model of AD (Tg2576). In vitro, NK-4 effectively protected neuronal cells from toxicity induced by Aβ. In addition, it displayed profound inhibitory activities on Aβ fibril formation. In vivo, Tg2576 mice received an intraperitoneal injection at 100 or 500 µg/kg of NK-4 once a day, five times a week for 9 months. Administration of NK-4 to the mice attenuated impairment of recognition memory, associative memory, and learning ability, as assessed by a novel object recognition test, a passive avoidance test, and a water maze test, respectively. NK-4 decreased the brain Aβ concentration while increasing the plasma amyloid level in a dose-dependent manner. NK-4 also improved memory impairments of ICR mice induced by direct intracerebroventricular administration of Aβ. These lines of evidence suggest that NK-4 may affect multiple pathways of amyloid pathogenesis and could be useful for treatment of AD.

Topics: Alzheimer Disease; Animals; Carbocyanines; Central Nervous System Agents; Disease Models, Animal; Drug Evaluation, Preclinical; Female; Male; Maze Learning; Mice; Mice, Inbred ICR; Mice, Transgenic; PC12 Cells; Photosensitizing Agents; Quinolines; Rats; Recognition, Psychology; Swimming

Impairment of synaptic plasticity underlies memory dysfunction in Alzheimer's disease (AD). Molecules involved in this plasticity such as PSD-95, a major postsynaptic scaffold protein at excitatory synapses, may play an important role in AD pathogenesis. We examined the distribution of PSD-95 in transgenic mice of amyloidopathy (5XFAD) and tauopathy (JNPL3) as well as in AD brains using double-labeling immunofluorescence and confocal microscopy. In wild type control mice, PSD-95 primarily labeled neuropil with distinct distribution in hippocampal apical dendrites. In 3-month-old 5XFAD mice, PSD-95 distribution was similar to that of wild type mice despite significant Aβ deposition. However, in 6-month-old 5XFAD mice, PSD-95 immunoreactivity in apical dendrites markedly decreased and prominent immunoreactivity was noted in neuronal soma in CA1 neurons. Similarly, PSD-95 immunoreactivity disappeared from apical dendrites and accumulated in neuronal soma in 14-month-old, but not in 3-month-old, JNPL3 mice. In AD brains, PSD-95 accumulated in Hirano bodies in hippocampal neurons. Our findings support the notion that either Aβ or tau can induce reduction of PSD-95 in excitatory synapses in hippocampus. Furthermore, this PSD-95 reduction is not an early event but occurs as the pathologies advance. Thus, the time-dependent PSD-95 reduction from synapses and accumulation in neuronal soma in transgenic mice and Hirano bodies in AD may mark postsynaptic degeneration that underlies long-term functional deficits.

Topics: Age Factors; Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Analysis of Variance; Animals; Brain; Carbocyanines; Cell Count; Disease Models, Animal; Disks Large Homolog 4 Protein; Female; Gene Expression Regulation; Guanylate Kinases; Humans; Male; Membrane Proteins; Mice; Mice, Transgenic; Middle Aged; Synapses; tau Proteins; Tauopathies

To compare the fluorescence intensity and duration of qdots streptavidin conjugate (QDs-SA) with Cy3 as the molecular probe of β-amyloid precursor protein (APP), and to provide evidence for early molecular imaging and diagnosis of Alzheimer's disease (AD).. With the help of laser scanning confocal microscope and flow cytometry, the flurescence probe based on the QDs-SA was used to detect APP in HEK293 cells stably transfected pcDNA3.1/APP, and to compare with conventional fluroimmunoassay Cy3.. The immunofluorescence staining detection indicated APP expression was mainly located in the plasma membrane. The mean fluorescence intensity of QDs-SA (34.2336±4.2455) was greater than that of Cy3 (21.6023±3.0102)under the confocal fluorescence microscope (P<0.05). After persistent exciting for 12 min, the fluorescence intensity of APP stained by QDs-SA decreased by 27.87%. The other stained by Cy3 decreased by 79.60%. The positive rate of APP staining had no significant difference between the QDs-SA(54.4700±3.4433)% and Cy3 (54.3800±8.5229)% by flow cytometry, but the mean fluorescence intensity had statistical significance(P<0.05). The QDs-SA (1 045.4167±47.3623) was significantly higher than the mean fluorescence intensity of Cy3 (658.5467±55.0591).. QDs-SA fluorescence probes can effectively recognize APP and are sensitive and exceptionally photostable, suggesting that QDs-SA fluorescence probes could be a potential method in APP detection and offer a novel way for the diagnosis of Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Carbocyanines; Fluorescent Dyes; Gene Transfer Techniques; HEK293 Cells; Humans; Molecular Imaging; Quantum Dots

Triple transgenic (3xTg-AD) mice harboring the presenilin 1, amyloid precursor protein, and tau transgenes (Oddo et al., 2003b) display prominent levels of amyloid-beta (Abeta) immunoreactivity in forebrain regions. The Abeta immunoreactivity is first seen intracellularly in neurons and later as extracellular plaque deposits. The present study examined Abeta immunoreactivity that occurs in layer III of the granular division of retrosplenial cortex (RSg). This pattern of Abeta immunoreactivity in layer III of RSg develops relatively late, and is seen in animals older than 14 months. The appearance of the Abeta immunoreactivity is similar to an axonal terminal field and thus may offer a unique opportunity to study the relationship between afferent projections and the formation of Abeta deposits. Axonal tract tracing techniques demonstrated that the pattern of axon terminal labeling in layer III of RSg, following placement of DiI in medial septum, is remarkably similar to the pattern of cholinergic axons in RSg, as detected by acetylcholinesterase histochemical staining, choline acetyltransferase immunoreactivity, or p75 receptor immunoreactivity; this pattern also is strikingly similar to the band of Abeta immunoreactivity. In animals sustaining early damage to the medial septal nucleus (prior to the advent of Abeta immunoreactivity), the band of Abeta in layer III of RSg does not develop; the corresponding band of cholinergic markers also is eliminated. In older animals (after the appearance of the Abeta immunoreactivity) damage to cholinergic afferents by electrolytic lesions, immunotoxin lesions, or cutting the cingulate bundle, result in a rapid loss of the cholinergic markers and a slower reduction of Abeta immunoreactivity. These results suggest that the septal cholinergic axonal projections transport Abeta or amyloid precursor protein (APP) to layer III of RSg.

Topics: Acetylcholine; Afferent Pathways; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Carbocyanines; Cholinergic Fibers; Disease Models, Animal; Gyrus Cinguli; Humans; Immunohistochemistry; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neuroanatomical Tract-Tracing Techniques; Presenilin-1; Septal Nuclei; tau Proteins

Mitochondrial dysfunction may play an important role in the pathogenesis of ageing and age-neurodegenerative diseases such as Alzheimer's disease (AD). Platelet mitochondrial membrane potential (reflected by measurement of JC-1 fluorescence ratio) and adenosine 5'-triphosphate (ATP) contents of 24 moderate probable AD patients, 20 age-matched control subjects and 20 young control subjects were measured. Also, a beta-amyloid peptide (Abeta)-induced damage model of platelets was established. After the addition of Abeta, platelet JC-1 fluorescence ratio and ATP content of platelets were measured in 16 AD patients, 20 aged and 20 young control subjects. Young control subjects had higher JC-1 fluorescence ratio than both AD patients and aged control subjects. No significant differences in platelet ATP contents were found among AD patients, aged and young control subjects. After the addition of Abeta, platelet JC-1 fluorescence ratio and ATP content of aged and young control subjects lowered markedly, but no obvious decrease of platelet JC-1 fluorescence ratio of AD patients was found compared with those of aged and young control subjects. Decrease of platelet JC-1 fluorescence ratio of aged control subjects was lower than that of young control subjects following the addition of Abeta. These results indicated that mitochondrial dysfunction may occur during ageing and platelet mitochondria of AD patients and aged subjects showed a tolerance to Abeta-induced damage. Therefore, blood platelets might serve as a biomarker for detection of mitochondrial function and age-related disease.

Topics: Adenosine Triphosphate; Adolescent; Adult; Aged; Aged, 80 and over; Aging; Alzheimer Disease; Amyloid beta-Peptides; Analysis of Variance; Benzimidazoles; Biomarkers; Blood Platelets; Carbocyanines; Case-Control Studies; Cells, Cultured; Female; Humans; Male; Membrane Potential, Mitochondrial; Microscopy, Fluorescence; Middle Aged; Mitochondria; Peptide Fragments

Human recombinant tau can bind to the end of isolated human paired helical filaments (PHF). The sequential binding of tau protein to PHF could result in an elongation of the previously polymerized PHF. However, we have observed that the elongation takes place in a different way on different types of PHF. We have found that there are at least three populations of PHF. For one population, tau protein is able to bind to the ends of the filament and to elongate that filament. In the second PHF population, tau protein binds but does not elongates the filament. In the third, neither tau binding nor elongation was observed.

Topics: Alzheimer Disease; Binding Sites; Carbocyanines; Fluorescent Antibody Technique; Fluorescent Dyes; Humans; Intermediate Filament Proteins; Microscopy, Electron; Microtubules; Molecular Conformation; tau Proteins; Tubulin Modulators

Synaptic damage and loss are factors that affect the degree of dementia experienced in Alzheimer disease (AD) patients. Multicolor DiOlistic labeling of the hippocampus has been undertaken which allows the full dendritic arbor of targeted neurons to be imaged. Using this labeling technique the neuronal morphology of two transgenic mouse lines (J20 and APP/PS1) expressing mutant forms of the Amyloid Precursor Protein (APP), at various ages, have been visualized and compared to Wild Type (WT) littermate controls. Swollen bulbous dystrophic neurites with loss of spines were apparent in the transgenic animals. Upon quantification, statistically significant reductions in the number of spines and total dendrite area was observed in both transgenic mouse lines at 11 months of age. Similar morphological abnormalities were seen in human AD hippocampal tissue both qualitatively and quantitatively. Immunohistochemistry and DiOlistic labeling was combined so that Abeta plaques were imaged in relation to the dendritic trees. No preferential localization of these abnormal dystrophic neurites was seen in regions with plaques. DiI labeled reative astrocytes were often apparent in close proximity to A beta plaques.

Topics: Aging; Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Astrocytes; Biolistics; Carbocyanines; Dendrites; Dendritic Spines; Disease Models, Animal; Hippocampus; Humans; Immunohistochemistry; Mice; Mice, Transgenic; Mutation; Plaque, Amyloid; Pyramidal Cells; Staining and Labeling

Most Down's syndrome (DS) patients develop Alzheimer's disease (AD) neuropathology. Astrocyte and neuronal cultures derived from fetal DS brain show alterations in the processing of amyloid beta precursor protein (AbetaPP), including increased levels of AbetaPP and C99, reduced levels of secreted AbetaPP (AbetaPPs) and C83, and intracellular accumulation of insoluble Abeta42. This pattern of AbetaPP processing is recapitulated in normal astrocytes by inhibition of mitochondrial metabolism, consistent with impaired mitochondrial function in DS astrocytes. Intracellular Abeta42 and reduced AbetaPPs are also detected in DS and AD brains. The survival of DS neurons is markedly increased by recombinant or astrocyte-produced AbetaPPs, suggesting that AbetaPPs may be a neuronal survival factor. Thus, mitochondrial dysfunction in DS may lead to intracellular deposition of Abeta42, reduced levels of AbetaPPs, and a chronic state of increased neuronal vulnerability.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Apoptosis; Astrocytes; Benzimidazoles; Carbocyanines; Carbonyl Cyanide m-Chlorophenyl Hydrazone; Cell Survival; Cells, Cultured; Cerebral Cortex; Child; Child, Preschool; Down Syndrome; Fetus; Fluorescent Dyes; Hippocampus; Humans; Immunohistochemistry; In Situ Nick-End Labeling; Infant; Middle Aged; Mitochondria; Neurons; Peptide Fragments; Recombinant Proteins; Uncoupling Agents

Excitotoxic lesions in the magnocellular nucleus basalis (MBN) lead to a significant damage of cholinergic neurons concomitant with increased amyloid precursor protein (APP) expression in the cerebral cortex. However, the sensitivity of non-cholinergic neurons to excitotoxicity, and changes of APP expression in the damaged MBN are still elusive. Hence, we performed multiple-labeling immunocytochemistry for choline-acetyltransferase (ChAT), neuron-specific nuclear protein (NeuN) and APP 4, 24, and 48 h after NMDA infusion in the MBN. Whereas all cholinergic neurons were immunoreactive for NeuN, this neuronal marker also labeled a population of ChAT-immunonegative non-cholinergic neurons. Both neuron populations exhibited a similar degree of sensitivity to NMDA excitotoxicity that became evident as early as 4 h post-lesion. Cholinergic MBN neurons showed abundant APP immunoreactivity (approximately 90%), while only a fraction (approximately 20-30%) of non-cholinergic neurons expressed the protein. Remarkably, cholinergic but not non-cholinergic neurons retained their APP immunoreactivity after NMDA infusion. In conclusion, cholinergic MBN neurons are not preferentially sensitive to short-term excitotoxicity, but are one of the major sources of APP in the basal forebrain.

Topics: Acetylcholine; Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Basal Nucleus of Meynert; Biomarkers; Carbocyanines; Cell Count; Choline O-Acetyltransferase; Cholinergic Fibers; Down-Regulation; Fluorescent Dyes; Immunoglobulin G; Immunohistochemistry; Male; N-Methylaspartate; Neurons; Neurotoxins; Nuclear Proteins; Rats; Rats, Wistar; Receptor, Nerve Growth Factor

Class A scavenger receptors (SR-A) mediate microglial interaction with fibrillar beta-amyloid (fAbeta). We report here that neonatal microglia from SR-A knockout mice (SR-A-/-) adhere to surface-bound fAbeta, and produce reactive oxygen species (ROS) as efficiently as wildtype microglia; that both wildtype and SR-A-/- microglia express SR-BI; that antibodies against SR-BI do not affect adhesion or ROS production by wildtype microglia, but inhibit adhesion and ROS production of SR-A-/- microglia to immobilized fAbeta by approximately 40%. Adhesion to fAbeta-coated surfaces, and uptake of fAbeta by both wildtype and SR-A-/- microglia was almost completely inhibited by incubation with fucoidan. Thus SR-BI and SR-A mediate similar effector functions in neonatal microglia, which suggests that SR-BI plays as important a role as SR-A, and can maintain the wildtype phenotype in SR-A-/- microglia.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Animals, Newborn; Antineoplastic Agents; Brain; Carbocyanines; CD36 Antigens; Cell Adhesion; Cells, Cultured; Fluorescent Dyes; Gene Expression; Liver; Membrane Proteins; Mice; Mice, Inbred BALB C; Mice, Knockout; Microglia; Peptide Fragments; Polysaccharides; Reactive Oxygen Species; Receptors, Immunologic; Receptors, Lipoprotein; Receptors, Scavenger; Scavenger Receptors, Class A; Scavenger Receptors, Class B

Experiments were performed to determine if scavenger receptors (SRs) play a role in amyloid beta (Abeta) stimulation of peripheral blood monocyte (PBM) neurotoxicity. Results indicate that Abeta does not block binding of the SR ligand DiI-acetylated low density lipoprotein to PBM, nor does another SR ligand, fucoidin, inhibit Abeta-PBM binding. Moreover, neither of three SR ligands alone stimulates neurotoxicity in PBM, nor antagonizes the ability of Abeta to activate PBM to a neurocytopathic state. Such findings suggest that Abeta's action is not dependent upon engagement of the SR ligand binding domain and raise doubts about the role of SR in Abeta neurotoxicity.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Antineoplastic Agents; Binding Sites; Carbocyanines; Cells, Cultured; Cholesterol, LDL; Fluorescent Dyes; Humans; Membrane Proteins; Monocytes; Neurons; Peptide Fragments; Phagocytosis; Polysaccharides; Rats; Receptors, Immunologic; Receptors, Lipoprotein; Receptors, Scavenger; Scavenger Receptors, Class B; Signal Transduction

Diseases linked to defective mitochondrial function are characterized by morphologically abnormal, swollen mitochondria with distorted cristae. Several lines of evidence now suggest that sporadic forms of Parkinson's disease (PD) and Alzheimer's disease (AD) are linked to mitochondrial dysfunction arising from defects in mitochondrial DNA (mtDNA). Human neuroblastoma (SH-SY5Y) cells that are deficient in mtDNA (Rho(0)) were repopulated with mitochondria from AD or PD patients or age-matched controls. These cytoplasmic hybrid (cybrid) cell lines differ only in the source of their mtDNA. Differences between cybrid cell lines therefore arise from differences in mtDNA and provide a model for the study of how impaired mitochondrial function alters the mitochondria themselves and how these changes adversely affect the neuronal cells they occupy. Cybrid cell mitochondria were labeled with the mitochondrial membrane potential-sensitive dye, JC-1. Analysis of these JC-1 labeled mitochondria by confocal microscopy revealed that mitochondrial membrane potential was significantly reduced in both PD and AD cybrid cells when compared with controls. Ultrastructural examination showed that control cybrid cells contained small, morphologically normal, round or oval mitochondria with a dark matrix and regular distribution of cristae. PD cybrid cells contained a significant and increased percentage of mitochondria that were enlarged or swollen and had a pale matrix with few remaining cristae (0.26-0.65 microm(2)). AD cybrid cells also contained a significantly increased percentage of enlarged or swollen mitochondria (0.25-5.0 microm(2)) that had a pale matrix and few remaining cristae. Other pathological features such as crystal-like intramitochondrial inclusions and cytoplasmic inclusion bodies were also found in PD and AD cybrids. These observations suggest that transfer of PD or AD mtDNA into Rho(0) cells was sufficient to produce pathological changes in mitochondrial ultrastructure that are similar to those seen in other mitochondrial disorders. These data were reported in abstract form (Trimmer et al., 1998, Soc. Neurosci. Abstr. 24: 476).

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Benzimidazoles; Carbocyanines; Electron Transport Complex I; Female; Fluorescent Dyes; Humans; Hybrid Cells; Inclusion Bodies; Male; Microscopy, Confocal; Microscopy, Electron; Middle Aged; Mitochondria; NADH, NADPH Oxidoreductases; Neuroblastoma; Organic Chemicals; Parkinson Disease

Brain regional oxidative damage is thought to be a central mechanism in the pathogenesis of Alzheimer's disease (AD). Recent studies of cerebrospinal fluid (CSF) have suggested that increased lipid peroxidation of CSF and CSF lipoproteins also may occur in AD patients. In the present study, we determined the susceptibility of human CSF to ex vivo lipid peroxidation and tested the hypothesis that oxidized CSF lipoproteins may be neurotoxic. Whole CSF or a CSF lipoprotein fraction (d < 1.210 g/mL) was oxidized with 2,2'-azobis(2-amidino-propane)dihydrochloride (AAPH), a hydrophilic free-radical generator. Kinetics of CSF lipid peroxidation were followed by a standard fluorescence product accumulation assay. Oxidation of AD CSF yielded significantly shorter fluorescent lag times than controls, indicating reduced antioxidant capacity. Electrophoretic mobilities of CSF apolipoproteins were specifically reduced upon oxidation of CSF with AAPH, suggesting that lipoproteins are primary targets of CSF lipid peroxidation. Cultured neuronal cells were exposed to physiological concentrations of isolated CSF lipoproteins oxidized with increasing concentrations of AAPH; the resulting neurotoxicity showed a significant linear AAPH concentration-response relationship. These results suggest that oxidized CSF lipoproteins may contribute to the pathogenesis of neurodegeneration in AD.

Topics: Aged; Alzheimer Disease; Amidines; Animals; Carbocyanines; Cell Line; Electrophoresis, Polyacrylamide Gel; Fatty Acids; Female; Free Radicals; Humans; Kinetics; Lipid Peroxidation; Lipid Peroxides; Male; Mice; Microscopy, Fluorescence; Neurotoxins; Spectrometry, Fluorescence

The relationship of microglia to senile plaques was investigated by culturing glial cells derived from neonatal rat brain on cryostat sections of Alzheimer's disease (AD) or control brain. Rat microglia were identified by their uptake of DiI-acetylated LDL. Plaques were colocalized using Thioflavin-S staining. Although the number of microglia attached to AD tissue sections did not differ significantly from the number on control brain tissue, the density of microglia on senile plaques was significantly greater than on nonsenile plaque areas of the same sections. These results suggest that microglia may have a higher affinity for senile plaques than for nonsenile plaque regions of AD brain tissue and are consistent with the hypothesis that microglia respond to plaques.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Animals; Benzothiazoles; Brain; Carbocyanines; Cell Count; Cells, Cultured; Fluorescent Dyes; Humans; Lipoproteins, LDL; Microglia; Middle Aged; Plaque, Amyloid; Rats; Rats, Sprague-Dawley; Reference Values; Thiazoles

Microglia are immune system cells associated with Alzheimer's disease plaques containing beta-amyloid (A beta). Murine microglia internalize microaggregates of fluorescently labeled or radioiodinated A beta peptide 1-42. Uptake was confirmed using aggregates of unlabeled A beta detected by immunofluorescence. Uptake of A beta was reduced by coincubation with excess acetyl-low density lipoprotein (Ac-LDL) or other scavenger receptor (SR) ligands, and Dil-labeled Ac-LDL uptake by microglia was blocked by excess A beta. CHO cells transfected with class A or B SRs showed significantly enhanced uptake of A beta. These results show that microglia express SRs that may play a significant role in the clearance of A beta plaques. Binding to SRs could activate inflammation responses that contribute to the pathology of Alzheimer's disease.

Topics: alpha-Macroglobulins; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Antineoplastic Agents; Biological Transport; Brain Chemistry; Carbocyanines; Cholesterol, LDL; Fluorescent Dyes; Intracellular Membranes; Kinetics; Lipoproteins; Mice; Microglia; Mutation; Polysaccharides; Receptors, Cell Surface