amyloid-beta-peptides and Nerve-Degeneration

Presenilin-1 (PS1) mutations account for the greatest portion of early onset familial Alzheimer's disease (FAD) cases. The exact cellular function of PS1 is not known. To date, PS1 mutations have been shown to alter two potential biological roles of the protein, either of which could make neurons more susceptible to neurodegeneration. First, PS1 mutations result in elevated A beta 42/A beta 40 ratios in plasma of FAD patients, in transgenic mice and in transfected cell lines. A beta 42 is the more hydrophobic and most neurotoxic form of the peptide. A common molecular event that has been associated with all of the known early onset FAD genes is the excessive production or accumulation of the A beta peptide in the brain. PS1 mutations have also been found to alter the Notch signalling pathway, but the mechanism by which this may affect neurodegeneration remains to be determined. Future studies will be needed to elucidate whether PS1 mutations lead directly to neuronal dysfunction and degeneration or cause cell death by increasing A beta 42 generation and deposition.

Topics: Age of Onset; Alzheimer Disease; Amyloid beta-Peptides; Animals; Apolipoproteins E; Caenorhabditis elegans Proteins; Cell Line; Gene Expression; Helminth Proteins; Humans; Membrane Proteins; Mice; Mice, Transgenic; Middle Aged; Mutation; Nerve Degeneration; Peptide Fragments; Phenotype; Presenilin-1; Transfection

Topics: Amyloid beta-Peptides; Biomarkers; Brain Injuries; Glial Fibrillary Acidic Protein; Humans; Male; Middle Aged; Nerve Degeneration; Neurofilament Proteins; Peptide Fragments; Space Flight

A growing body of evidence suggests that the plasma concentration of the neurofilament light chain (NfL) might be considered a plasma biomarker for the screening of neurodegeneration in Alzheimer's disease (AD).. With a single molecule array method (Simoa, Quanterix), plasma NfL concentrations were measured in 99 subjects with AD at the stage of mild cognitive impairment (MCI-AD; n = 25) or at the stage of early dementia (ADD; n = 33), and in nondemented controls (n = 41); in all patients, the clinical diagnoses were in accordance with the results of the four core cerebrospinal fluid (CSF) biomarkers (amyloid β (Aβ)1-42, Aβ42/40, Tau, and pTau181), interpreted according to the Erlangen Score algorithm. The influence of preanalytical storage procedures on the NfL in plasma was tested on samples exposed to six different conditions.. NfL concentrations significantly increased in the samples exposed to more than one freezing/thawing cycle, and in those stored for 5 days at room temperature or at 4 °C. Compared with the control group of nondemented subjects (22.0 ± 12.4 pg/mL), the unadjusted plasma NfL concentration was highly significantly higher in the MCI-AD group (38.1 ± 15.9 pg/mL, p < 0.005) and even further elevated in the ADD group (49.1 ± 28.4 pg/mL; p < 0.001). A significant association between NfL and age (ρ = 0.65, p < 0.001) was observed; after correcting for age, the difference in NfL concentrations between AD and controls remained significant (p = 0.044). At the cutoff value of 25.7 pg/mL, unconditional sensitivity, specificity, and accuracy were 0.84, 0.78, and 0.82, respectively. Unadjusted correlation between plasma NfL and Mini Mental State Examination (MMSE) across all patients was moderate but significant (r = -0.49, p < 0.001). We observed an overall significant correlation between plasma NfL and the CSF biomarkers, but this correlation was not observed within the diagnostic groups.. This study confirms increased concentrations of plasma NfL in patients with Alzheimer's disease compared with nondemented controls.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Female; Humans; Male; Mental Status Schedule; Microarray Analysis; Middle Aged; Nerve Degeneration; Neurofilament Proteins; Peptide Fragments; ROC Curve

The dysregulation of posttranslational modifications of the microtubule-associated protein (MAP) tau plays a key role in Alzheimer's disease (AD) and related disorders. Thus, we have previously shown that beta amyloid (Aβ)-induced neurotoxicity was mediated, at least in part, by tau cleavage into the tau

Topics: Amyloid beta-Peptides; Animals; Astrocytes; Axonal Transport; Cells, Cultured; Cerebral Cortex; Cytoskeleton; Hippocampus; Humans; Mice, Inbred C57BL; Nerve Degeneration; Neurons; Octoxynol; Organelles; Peptide Fragments; Rats, Sprague-Dawley; tau Proteins; Transfection

MDMx/MDM4 is a negative regulator of the p53 tumor suppressor protein and is necessary for survival in dividing cells. MDMx is also expressed in postmitotic neurons, with prosurvival roles that are independent of its extensively described roles in carcinogenesis. We and others have shown a role for MDMx loss in neuronal death in vitro and in vivo in several neurodegenerative diseases. Further, we have recently shown that MDMx is targeted for proteolytic degradation by calcium-dependent proteases, calpains, in neurons in vitro, and that MDMx overexpression provided partial neuroprotection in a model of HIV-associated neurodegeneration. Here, we assessed whether amyloid β (Aβ)-induced MDMx degradation occurred in Alzheimer's Disease (AD) models. Our data shows an age-dependent reduction in MDMx levels in cholinergic neurons within the cortex of adult mice expressing the swedish mutant of the amyloid precursor protein, APP in the Tg2576 murine model of AD. In vitro, Aβ treatment of primary cortical neurons led to the caspase-dependent MDMx degradation. Our findings suggest that MDMx degradation associated with neuronal death occurs via caspase activation in neurons, and that the progressive loss of MDMx protein represents a potential mechanism of Aβ-induced neuronal death during disease progression in AD.

Topics: Aging; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Caspases; Cells, Cultured; Female; Mice; Mice, Mutant Strains; Nerve Degeneration; Neurons; Peptide Fragments; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-mdm2; Ubiquitin-Protein Ligases

Although the exact cause of Alzheimer's disease (AD) remains elusive, mounting evidence continues to support the involvement of neuroinflammation in the development of AD. Triptolide isolated from the herb Tripterygium wilfordii Hook F has anti-inflammatory and immunosuppressive activities. In this study, we observed the effects of triptolide on dendritic spines of hippocampal neurons in model rats with AD. Thirty male SD rats were randomly divided into control group, AD model group and triptolide-treated group. The AD model group was made with bilateral microinjection of aggregated beta-amyloid protein (Aβ)1-40 into hippocampus in rats and the control group rats were injected with normal saline in the same way. The triptolide-treated group rats were administered triptolide intraperitoneally for 30 days after microinjection of aggregated Aβ1-40 into hippocampus. Dendritic morphology of hippocampal neurons in each group was analyzed using Golgi staining and ImageJ software. Our data showed that the total number of intersection points of dendrites and spine density in hippocampal neurons in the AD model group were decreased as compared with the control group. However, the total number of intersection points of dendrites and spine density in hippocampal neurons in the triptolide-treated group were increased as compared with the AD model group. Our results indicate that triptolide can alleviate the degeneration of dendritic spines in hippocampal neurons in model rats with AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Dendritic Spines; Disease Models, Animal; Diterpenes; Epoxy Compounds; Hippocampus; Immunosuppressive Agents; Male; Nerve Degeneration; Peptide Fragments; Phenanthrenes; Rats; Rats, Sprague-Dawley

The objective of this study was to assess cerebrospinal fluid (CSF) β-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) activity in relation to Alzheimer's disease (AD) and to correlate the enzyme activity with protein markers of APP metabolism and axonal degeneration.. BACE1 activity and protein concentrations were measured and analyzed in 342 participants of the Alzheimer's Disease Neuroimaging Initiative, including 99 normal control, 75 stable mild cognitive impairment (MCI), 87 progressive MCI, and 79 AD dementia cases. All statistical analyses were Bonferroni corrected for multiple comparisons.. No significant differences between controls and any of the three patient groups were detected for BACE1 activity and soluble APPβ (sAPPβ) concentrations in CSF. Significant correlations with BACE1 activity were found for CSF APPβ and total tau in all four groups and for CSF phosphorylated tau181 in all groups but the progressive MCI group. There were no correlations for CSF amyloid β (Aβ)1-42 or for plasma Aβ1-42 and Aβ1-40.. The consistent correlation between BACE1 activity and sAPPβ supports their role as biomarkers of target engagement in clinical trials on BACE1 inhibition.

Topics: Aged; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Aspartic Acid Endopeptidases; Axons; Biomarkers; Clinical Trials as Topic; Cognitive Dysfunction; Databases, Factual; Female; Humans; Male; Nerve Degeneration; Peptide Fragments; Phosphorylation; tau Proteins

Abnormal accumulation of Aβ (amyloid β) within AEL (autophagy-endosomal-lysosomal) vesicles is a prominent neuropathological feature of AD (Alzheimer's disease), but the mechanism of accumulation within vesicles is not clear. We express secretory forms of human Aβ1-40 or Aβ1-42 in Drosophila neurons and observe preferential localization of Aβ1-42 within AEL vesicles. In young animals, Aβ1-42 appears to associate with plasma membrane, whereas Aβ1-40 does not, suggesting that recycling endocytosis may underlie its routing to AEL vesicles. Aβ1-40, in contrast, appears to partially localize in extracellular spaces in whole brain and is preferentially secreted by cultured neurons. As animals become older, AEL vesicles become dysfunctional, enlarge and their turnover appears delayed. Genetic inhibition of AEL function results in decreased Aβ1-42 accumulation. In samples from older animals, Aβ1-42 is broadly distributed within neurons, but only the Aβ1-42 within dysfunctional AEL vesicles appears to be in an amyloid-like state. Moreover, the Aβ1-42-containing AEL vesicles share properties with AD-like extracellular plaques. They appear to be able to relocate to extracellular spaces either as a consequence of age-dependent neurodegeneration or a non-neurodegenerative separation from host neurons by plasma membrane infolding. We propose that dysfunctional AEL vesicles may thus be the source of amyloid-like plaque accumulation in Aβ1-42-expressing Drosophila with potential relevance for AD.

Topics: Aging; Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Animals, Genetically Modified; Autophagy; Brain; Cell Membrane; Cells, Cultured; Cytoplasmic Vesicles; Drosophila melanogaster; Endocytosis; Endosomes; Extracellular Space; Humans; Lysosomes; Nerve Degeneration; Neurons; Peptide Fragments; Plaque, Amyloid

Melatonin plays an important role in aging and relevant neurodegeneration as an antioxidant and neuroprotector. It can interact with β-amyloid (Aβ) generation, inhibit formation of β-sheet and amyloid fibrils, modulate apoptosis, and protect cholinergic system function in Alzheimer's disease animal model. Recently, its effects on anesthetic-induced neurodegeneration have received more attention, and in this investigation, we explored whether melatonin can attenuate Aβ(1-40) generation and cholinergic dysfunction in the hippocampus of aged rats induced by isoflurane through enzyme-linked immunosorbent assay, Western blot, immunohistochemistry, and immunofluorescence. The results showed that isoflurane increased Aβ(1-40) generation and caused cholinergic dysfunction through decreasing choline acetyltransferase (ChAT) expression in the hippocampus in a dose-dependent way, and intraperitoneal melatonin premedication attenuated the neurodegeneration through inhibiting Aβ(1-40) generation and increasing ChAT expression, and its effects were more obvious in high-concentration isoflurane group. Collectively, our results provide evidence for the therapeutic value of melatonin on isoflurane-induced neurodegeneration, including Aβ(1-40) generation and cholinergic dysfunction, and further work is necessary to clarify its target sites and detailed mechanisms.

Topics: Amyloid beta-Peptides; Anesthetics, Inhalation; Animals; Antioxidants; Choline O-Acetyltransferase; Cholinergic Neurons; Dose-Response Relationship, Drug; Hippocampus; Isoflurane; Male; Melatonin; Nerve Degeneration; Peptide Fragments; Rats; Rats, Sprague-Dawley

Alzheimer disease (AD) is characterized by chronic neuroinflammation, which may lead to dysfunction in neuronal circuits. Although reactive microglia are found in association with accumulation of beta amyloid (Aβ) plaques in the AD brain, their contribution to neuronal cell loss remains speculative. A major genetic risk factor for sporadic AD is inheritance of the apolipoprotein (apo) E4 allele, which has been shown to contribute significantly to neurodegeneration in AD. Many studies have documented the ability of Aβ fibrils in vitro to induce microglia to undergo phenotypic activation, which results in the secretion and/or expression of a plethora of free radicals and pro-inflammatory mediators. These mediators, such as reactive nitrogen/oxygen species and IL-1β as well as cyclooxygenase-2 (COX-2) with associated prostaglandin E2 (PGE(2)), are believed to be neurotoxic and to contribute to the underlying cause of AD. We have used the human H4 neuroglioma cells as a model astroglial system to examine the interactions between IL-1β and nitric oxide (NO) as co-stimulators of Aβ(1-40) in enhancing the expression of COX-2 and production of PGE(2) in the presence of recombinant human apolipoprotein E4 (apoE4). Neither Aβ(1-40) nor its reverse sequence analog Aβ(40-1) alone had a significant effect on COX-2 expression and PGE(2) production in the cells. In contrast, after co-incubation with apoE4, Aβ(1-40) increased IL-1β-induced COX-2 expression and PGE(2) production. Aβ(12-28), which binds with high affinity to apoE4, blocked apoE4-mediated effects on Aβ(1-40). Furthermore, (±)-S-Nitroso-N-acetylpenicillamine (SNAP), an agent that releases nitric oxide (NO) in situ, alone did not affect IL-1β-induced COX-2 expression, but increased PGE(2) production only. Addition of Aβ(1-40) preincubated with apoE4 to H4 cells in the presence of SNAP led to an additive IL-1β-induced COX-2 expression and PGE(2) production. These observations indicate that increased PGE(2) resulted from increased nitrosative stress, which is enhanced by apoE4. Thus a molecular understanding of the interactions of apoE4 with Aβ, NO and IL-1β on the regulation of the COX-2/prostaglandin pathway may open new avenues in understanding the mechanism of development of neurodegenerative disease such as AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Apolipoprotein E4; Brain Neoplasms; Cell Line, Tumor; Cell Survival; Cyclooxygenase 2; Glioma; Humans; Interleukin-1beta; Nerve Degeneration; Nitric Oxide; Peptide Fragments

Growing evidence suggests that decreased brain-derived neurotrophic factor (BDNF) levels are associated with Alzheimer's disease (AD) pathogenesis. Therefore, BDNF gene therapy is considered to be a promising therapeutic strategy for treating AD. Sendai virus (SeV) is a type I parainfluenza virus that does not interact with host chromosomes because of its strict cytoplasmic life cycle. Although SeV is nonpathogenic in primates, including humans, its infectivity for neurons is strong. Here we demonstrate that SeV vectors effectively infected neurons, even though they were injected into subcortical white matter. Moreover, SeV vectors significantly induced BDNF expression, ameliorating synaptic degeneration and memory deficits in a transgenic mouse model of AD (Tg2576). This is the first study to demonstrate that viral vector administration in white matter is sufficient to restore cognitive function in vivo. These results also support the feasibility of using SeV vectors for gene therapy targeting the brain.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Brain-Derived Neurotrophic Factor; Cells, Cultured; Cerebral Cortex; Disease Models, Animal; Hippocampus; Humans; Male; Maze Learning; Memory Disorders; Mice; Mice, Transgenic; Nerve Degeneration; Neurons; Peptide Fragments; Sendai virus; Synapses

An early role of amyloid-β peptide (Aβ) aggregation in Alzheimer's disease pathogenesis is well established. However, the contribution of intracellular or extracellular forms of Aβ to the neurodegenerative process is a subject of considerable debate. We here describe transgenic mice expressing Aβ1-40 (APP47) and Aβ1-42 (APP48) with a cleaved signal sequence to insert both peptides during synthesis into the endoplasmic reticulum. Although lower in transgene mRNA, APP48 mice reach a higher brain Aβ concentration. The reduced solubility and increased aggregation of Aβ1-42 may impair its degradation. APP48 mice develop intracellular Aβ lesions in dendrites and lysosomes. The hippocampal neuron number is reduced already at young age. The brain weight decreases during aging in conjunction with severe white matter atrophy. The mice show a motor impairment. Only very few Aβ1-40 lesions are found in APP47 mice. Neither APP47 nor APP48 nor the bigenic mice develop extracellular amyloid plaques. While intracellular membrane expression of Aβ1-42 in APP48 mice does not lead to the AD-typical lesions, Aβ aggregates develop within cells accompanied by considerable neurodegeneration.

Topics: Age Factors; Alzheimer Disease; Amyloid beta-Peptides; Animals; Gene Expression Regulation; Humans; Intracellular Membranes; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nerve Degeneration; Neurons; Peptide Fragments; Rats

Degeneration of septal neurons in Alzheimer's disease (AD) results in abnormal information processing at cortical circuits and consequent brain dysfunction. The septum modulates the activity of hippocampal and cortical circuits and is crucial to the initiation and occurrence of oscillatory activities such as the hippocampal theta rhythm. Previous studies suggest that amyloid beta peptide (Abeta) accumulation may trigger degeneration in AD. This study evaluates the effects of single injections of Abeta 1-40 into the medial septum. Immunohistochemistry revealed a decrease in septal cholinergic (57%) and glutamatergic (53%) neurons in Abeta 1-40 treated tissue. Additionally, glutamatergic terminals were significantly less in Abeta treated tissue. In contrast, septal GABAergic neurons were spared. Unitary recordings from septal neurons and hippocampal field potentials revealed an approximately 50% increase in firing rates of slow firing septal neurons during theta rhythm and large irregular amplitude (LIA) hippocampal activities and a significantly reduced hippocampal theta rhythm power (49%) in Abeta 1-40 treated tissue. Abeta also markedly reduced the proportion of slow firing septal neurons correlated to the hippocampal theta rhythm by 96%. These results confirm that Abeta alters the anatomy and physiology of the medial septum contributing to septo-hippocampal dysfunction. The Abeta induced injury of septal cholinergic and glutamatergic networks may contribute to an altered hippocampal theta rhythm which may underlie the memory loss typically observed in AD patients.

Topics: Acetylcholine; Action Potentials; Alzheimer Disease; Amyloid beta-Peptides; Animals; Cholinergic Fibers; Disease Models, Animal; Glutamic Acid; Hippocampus; Male; Nerve Degeneration; Neural Pathways; Neurons; Peptide Fragments; Rats; Rats, Sprague-Dawley; Septal Nuclei; Theta Rhythm

Cdk5 dysregulation is a major event in the neurodegenerative process of Alzheimer's disease (AD). In vitro studies using differentiated neurons exposed to Abeta exhibit Cdk5-mediated tau hyperphosphorylation, cell cycle re-entry and neuronal loss. In this study we aimed to determine the role of Cdk5 in neuronal injury occurring in an AD mouse model obtained through the intracerebroventricular (icv) injection of the Abeta(1-40) synthetic peptide. In mice icv-injected with Abeta, Cdk5 activator p35 is cleaved by calpains, leading to p25 formation and Cdk5 overactivation. Subsequently, there was an increase in tau hyperphosphorylation, as well as decreased levels of synaptic markers. Cell cycle reactivation and a significant neuronal loss were also observed. These neurotoxic events in Abeta-injected mice were prevented by blocking calpain activation with MDL28170, which was administered intraperitoneally (ip). As MDL prevents p35 cleavage and subsequent Cdk5 overactivation, it is likely that this kinase is involved in tau hyperphosphorylation, cell cycle re-entry, synaptic loss and neuronal death triggered by Abeta. Altogether, these data demonstrate that Cdk5 plays a pivotal role in tau phosphorylation, cell cycle induction, synaptotoxicity, and apoptotic death in postmitotic neurons exposed to Abeta peptides in vivo, acting as a link between diverse neurotoxic pathways of AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Calpain; Cell Division; Cyclin-Dependent Kinase 5; Dipeptides; Disease Models, Animal; Female; G2 Phase; Injections, Intralesional; Injections, Intraperitoneal; Mice; Mice, Inbred C57BL; Nerve Degeneration; Peptide Fragments; Phosphorylation; Protease Inhibitors; tau Proteins

In an analysis of amyloid pathology in Alzheimer disease, we used an in situ approach to identify amyloid-beta (Abeta) accumulation and oxidative damage to nucleic acids in postmortem brain tissue of the hippocampal formation from subjects with Alzheimer disease. When carboxyl-terminal-specific antibodies directed against Abeta40 and Abeta42 were used for immunocytochemical analyses, Abeta42 was especially apparent within the neuronal cytoplasm, at sites not detected by the antibody specific to Abeta-oligomer. In comparison to the Abeta42-positive neurons, neurons bearing oxidative damage to nucleic acids were more widely distributed in the hippocampus. Comparative density measurements of the immunoreactivity revealed that levels of intraneuronal Abeta42 were inversely correlated with levels of intraneuronal 8-hydroxyguanosine, an oxidized nucleoside (r=- 0.61, p<0.02). Together with recent evidence that the Abeta peptide can act as an antioxidant, these results suggest that intraneuronal accumulation of non-oligomeric Abeta may be a compensatory response in neurons to oxidative stress in Alzheimer disease.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Brain; Cell Nucleus; Cytoplasm; Cytoprotection; Female; Guanosine; Humans; Immunohistochemistry; Male; Nerve Degeneration; Neurons; Nucleic Acids; Oxidative Stress; Peptide Fragments

Amyloid beta (Abeta)-containing plaques are surrounded by dystrophic neurites in the Alzheimer's disease (AD) brain, but whether and how plaques induce these neuritic abnormalities remain unknown. We tested the hypothesis that soluble oligomeric assemblies of Abeta, which surround plaques, induce calcium-mediated secondary cascades that lead to dystrophic changes in local neurites. We show that soluble Abeta oligomers lead to activation of the calcium-dependent phosphatase calcineurin (CaN) (PP2B), which in turn activates the transcriptional factor nuclear factor of activated T cells (NFAT). Activation of these signaling pathways, even in the absence of Abeta, is sufficient to produce a virtual phenocopy of Abeta-induced dystrophic neurites, dendritic simplification, and dendritic spine loss in both neurons in culture and in the adult mouse brain. Importantly, the morphological deficits in the vicinity of Abeta deposits in a mouse model of AD are ameliorated by CaN inhibition, supporting the hypothesis that CaN-NFAT are aberrantly activated by Abeta and that CaN-NFAT activation is responsible for disruption of neuronal structure near plaques. In accord with this, we also detect increased levels of an active form of CaN and NFATc4 in the nuclear fraction from the cortex of patients with AD. Thus, Abeta appears to mediate the neurodegeneration of AD, at least in part, by activation of CaN and subsequent NFAT-mediated downstream cascades.

Topics: Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Calcineurin; Calcium; Cells, Cultured; Cerebral Cortex; Culture Media, Conditioned; Dendritic Spines; Embryo, Mammalian; Enzyme-Linked Immunosorbent Assay; Green Fluorescent Proteins; Humans; Mice; Mice, Transgenic; Microtubule-Associated Proteins; Mutation; Nerve Degeneration; Neurites; Neurons; NFATC Transcription Factors; Oligopeptides; Peptide Fragments; Postmortem Changes; Protein Transport; Subcellular Fractions

The pathogenesis of Alzheimer's disease (AD) is associated with the accumulation of amyloid-β (Aβ) peptides and the loss of synapses. The addition of Aβ(1-42) reduced the amount of synaptophysin in cultured cortical neurons in a model of AD-induced synapse degeneration. Aβ(1-42) also reduced the uptake of the fluorescent dye FM1-43 into synaptic recycling vesicles, a measure of synaptic function. We report that pre-mixing Aβ(1-40) with Aβ(1-42) significantly reduced the effects of Aβ(1-42) on synapses; it increased both synaptic vesicle recycling and synaptophysin content. These results are consistent with reports that Aβ(1-40) forms oligomers with Aβ(1-42) and that these are less toxic than Aβ(1-42) alone. In contrast, the addition of Aβ(1-40) did not affect the synapse degeneration induced by the prion-derived peptide PrP82-146. The addition of Aβ(1-40) reduced Aβ(1-42) induced activation of cytoplasmic phospholipase A2 (cPLA2) within synapses consistent with the hypothesis that Aβ(1-42) induced synapse degeneration is mediated by aberrant activation of synaptic cPLA2. Such observations raise the possibility that the amount of Aβ(1-40) produced within the brain is critical in determining the synapse damaging effects of Aβ(1-42) and possibly the cognitive loss seen during the early stages of AD.

Topics: Amyloid beta-Peptides; Analysis of Variance; Animals; Cells, Cultured; Cerebral Cortex; Enzyme-Linked Immunosorbent Assay; Mice; Nerve Degeneration; Neurons; Peptide Fragments; Phospholipases A2; Synapses; Synaptic Vesicles; Synaptophysin

Galantamine, which is currently used in the treatment of patients with Alzheimer's disease (AD), has been shown to have a neuroprotective effect against beta-amyloid (Abeta) peptide-induced toxicity, which is involved in the pathogenesis of AD. In this study, we investigated the mechanism underlying the protective effect of galantamine on Abeta-induced toxicity in human neuroblastoma cells (SH-SY5Y). Using MTT and LDH leakage assays, we observed that galantamine pretreatment significantly prevented Abeta1-40-induced cell death. Abeta1-40-induced overexpression and increased cleavage of both calpain and calcineurin were observed by Western blotting and double immunofluorescent staining. Increased calcineurin phosphatase activity and decreased level of pSer112 BAD were also observed in Abeta1-40-damaged cells. However, all these alterations were found to be reversed by galantamine pretreatment. We also found that the neuroprotection of galantamine can be blocked by an alpha7 nAChR antagonist. Overall, our results suggest that galantamine may prevent the neuronal damage induced by Abeta1-40 through a mechanism related to the regulation of calpain-calcineurin activation and BAD phosphorylation, which may involve the participation of alpha7 nAChR.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Calcineurin; Calcineurin Inhibitors; Calpain; Cell Line, Tumor; Cholinesterase Inhibitors; Galantamine; Humans; Nerve Degeneration; Neuroblastoma; Peptide Fragments; Signal Transduction

Galantamine is currently used in the treatment of patients with mild-to-moderate Alzheimer's disease (AD). Although its action is mostly directed at the regulation of cholinergic transmission, galantamine can also afford neuroprotection against amyloid-beta peptide (Abeta), which is involved in AD pathogenesis. In this study, we used cultured rat cortical neurons treated with two forms of Abeta(1-40), fresh and previously aged (enriched in fibrils). First, we confirmed that galantamine prevented neurodegeneration induced by both peptide forms in a concentration-dependent manner. Moreover, we observed that when neurons were co-incubated with fresh Abeta(1-40) plus galantamine, the amount of amyloid aggregates was reduced. As oxidative conditions influence Abeta aggregation, we investigated whether galantamine prevents oxidative stress induced by this peptide. The data show that either fresh or aged Abeta(1-40) significantly increased the amount of reactive oxygen species and lipoperoxidation, these effects being prevented by galantamine. In Abeta(1-40)-treated neurons, the depletion of reduced glutathione (GSH) seems to be related to the decrease in glutathione peroxidase and glutathione reductase activities(.) These alterations in the GSH antioxidant system were prevented by galantamine. Overall, these results constitute the first evidence that galantamine can prevent the neuronal oxidative damage induced by Abeta, providing an in vitro basis for the beneficial actions of galantamine in the AD neurodegenerative process.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Antioxidants; Cells, Cultured; Cerebral Cortex; Cholinesterase Inhibitors; Cytoprotection; Dose-Response Relationship, Drug; Galantamine; Glutathione; Lipid Peroxidation; Nerve Degeneration; Neurons; Neuroprotective Agents; Oxidative Stress; Peptide Fragments; Plaque, Amyloid; Rats

Topics: Aged; Amyloid beta-Peptides; Biomarkers; Chromatography, High Pressure Liquid; Creatinine; Dementia; Enzyme-Linked Immunosorbent Assay; Female; Folic Acid; Germany; Homocysteine; Humans; Immunoassay; Linear Models; Male; Middle Aged; Nephelometry and Turbidimetry; Nerve Degeneration; Peptide Fragments; tau Proteins; Vitamin B 12

Neuropathological, epidemiological and experimental data indicate a potential interrelationship between Alzheimer's disease and prion diseases. Proteolytic processing of amyloid precursor protein (APP) by beta-secretase was recently suggested to be controlled by prion protein expression. Here, we characterized the prion infection of Tg2576 mice, which overexpress the human APP(Swe) protein. Prion infection of Tg2576-mice led to an early death of the animals, which was preceded by a relatively short symptomatic stage. However, disease-associated gliosis and deposition of misfolded prion protein PrP(Sc) were identical in infected Tg2576-mice and non-transgenic littermate controls. To analyze the effect of prion infection on APP processing and generation of beta-amyloid we determined cortical levels of SDS- and formic acid (FA)-extractable forms of beta-amyloid (1-40) and (1-42) by ELISA. Formic acid-extractable Abeta (1-42) levels were 10-fold higher in infected versus uninfected Tg2576 mice whereas other forms of Abeta were essentially unaffected by the prion infection. Hence, the experimental model demonstrates that a prion infection of the CNS promotes selectively formation of FA-extractable Abeta(1-42) in Tg2576 mice.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Cerebral Cortex; Formates; Gliosis; Humans; Mice; Mice, Transgenic; Nerve Degeneration; Neurochemistry; Peptide Fragments; Plaque, Amyloid; Prion Diseases; Prions; PrPSc Proteins; Scrapie; Survival Rate; Up-Regulation

Here, we examined whether amyloid-beta (Abeta) protein participates in cell death and retinal function using three types of transgenic (Tg) mice in vivo [human mutant amyloid precursor protein (APP) Tg (Tg 2576) mice, mutant presenilin-1 (PS-1) knock-in mice, and APP/PS-1 double Tg mice]. ELISA revealed that the insoluble form of Abeta(1-40) was markedly accumulated in the retinas of APP and APP/PS-1, but not PS-1 Tg, mice (vs. wild-type mice). In APP Tg and APP/PS-1 Tg mice, immunostaining revealed accumulations of intracellular Abeta(1-42) in retinal ganglion cells and in the inner and outer nuclear layers. APP Tg and APP/PS-1 Tg, but not PS-1 Tg, mice had less NMDA-induced retinal damage than wild-type mice, and the reduced damage in APP/PS-1 Tg mice was diminished by the pre-treatment of N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester, a gamma-secretase inhibitor. Furthermore, the number of TUNEL-positive cells was significantly less in ganglion cell layer of APP/PS-1 Tg mice than PS-1 Tg mice 24 h after NMDA injection. The phosphorylated form of calcium/calmodulin-dependent protein kinase IIalpha (CaMKIIalpha), but not total CaMKIIalpha or total NMDA receptor 1 (NR1) subunit, in total retinal extracts was decreased in non-treated retinas of APP/PS-1 Tg mice (vs. wild-type mice). CaMKIIalpha and NR2B proteins, but not NR1, in retinal membrane fraction were significantly decreased in APP/PS-1 Tg mice as compared with wild-type mice. The NMDA-induced increase in p-CaMKIIalpha in the retina was also lower in APP/PS-1 Tg mice than in wild-type mice. In electroretinogram and visual-evoked potential recordings, the implicit time to each peak from a light stimulus was prolonged in APP/PS-1 mice versus wild-type mice. Hence, Abeta may impair retinal function by reducing activation of NMDA-receptor signaling pathways.

Topics: Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Down-Regulation; Enzyme Inhibitors; Evoked Potentials, Visual; Glutamic Acid; Humans; Mice; Mice, Transgenic; Nerve Degeneration; Peptide Fragments; Presenilin-1; Receptors, N-Methyl-D-Aspartate; Retinal Diseases; Retinal Ganglion Cells; Signal Transduction; Vision, Ocular

A key role of mitotic activation in neuronal cell death in early stages of Alzheimer's disease (AD) has been suggested. Apparently, terminally differentiated neurons are precluded from mitotic division, yet some phenotypic markers of cell cycling are present in AD-vulnerable brain areas. In this paper, we investigated whether dividing human neuroblastoma cells are preferentially vulnerable to amyloid aggregate toxicity in some specific cell cycle stage(s). Our data indicate that Abeta1-40/42 aggregates added to the cell culture media bind to the plasma membrane and are internalized faster in the S than in the G2/M and G1 cells possibly as a result of a lower content in membrane cholesterol in the former. Earlier and sharper increases in reactive oxygen species production triggered a membrane oxidative injury and a significant impairment of antioxidant capacity, eventually culminating with apoptotic activation in S and, to a lesser extent, in G2/M exposed cells. G1 cells appeared more resistant to the amyloid-induced oxidative attack possibly because of their higher antioxidant capacity. The high vulnerability of S cells to aggregate toxicity extends previous data suggesting that neuronal loss in AD could result from mitotic reactivation of terminally differentiated neurons with arrest in the S phase.

Topics: Amyloid beta-Peptides; Apoptosis; Cell Cycle; Cell Line, Tumor; Cell Membrane; Cell Proliferation; Cholesterol; Endocytosis; Humans; Nerve Degeneration; Neuroblastoma; Oxidative Stress; Peptide Fragments; Phenotype; Reactive Oxygen Species; Time Factors

Activation of 5-HT4 receptors has been shown to improve memory processes in preclinical cognition models, suggesting potential utility of 5-HT4 agonists for the symptomatic treatment of Alzheimer's disease (AD). Recent studies have shown that 5-HT4 agonists also increase the secretion of the non-amyloidogenic soluble amyloid precursor protein-alpha (sAPPalpha). In the present study, we demonstrated that a selective 5-HT4 partial agonist, RS67333, inhibited the generation of beta-amyloid peptide (Abeta) in primary cortical cultures of Tg2576 transgenic mice expressing human APP(K670N/M671L). Furthermore, treatments with RS67333 selectively increased the survival of transgenic neurons in a dose-dependent manner, which was inhibited by 5-HT4 antagonists. These and previous data collectively suggest that the 5-HT4 receptor may be an effective therapeutic target for AD, providing both symptomatic improvements and neuroprotection.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Aniline Compounds; Animals; Cell Survival; Cells, Cultured; Cerebral Cortex; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Humans; Male; Mice; Mice, Transgenic; Nerve Degeneration; Neurons; Neuroprotective Agents; Peptide Fragments; Piperidines; Receptors, Serotonin, 5-HT4; Serotonin; Serotonin 5-HT4 Receptor Agonists; Serotonin Receptor Agonists; Synaptic Transmission; Treatment Outcome

Because senile plaques in Alzheimer's disease (AD) contain reactive microglia in addition to potentially neurotoxic aggregates of amyloid-beta (Abeta), we examined the influence of microglia on the viability of rodent neurons in culture exposed to aggregated Abeta 1-40. Microglia enhanced the toxicity of Abeta by releasing glutamate through the cystine-glutamate antiporter system Xc-. This may be relevant to Abeta toxicity in AD, because the system Xc(-)-specific xCT gene is expressed not only in cultured microglia but also in reactive microglia within or surrounding amyloid plaques in transgenic mice expressing mutant human amyloid precursor protein or in wild-type mice injected with Abeta. Inhibition of NMDA receptors or system Xc- prevented the microglia-enhanced neurotoxicity of Abeta but also unmasked a neuroprotective effect of microglia mediated by microglial secretion of apolipoprotein E (apoE) in the culture medium. Immunodepletion of apoE or targeted inactivation of the apoE gene in microglia abrogated neuroprotection by microglial conditioned medium, whereas supplementation by human apoE isoforms restored protection, which was potentiated by the presence of microglia-derived cofactors. These results suggest that inhibition of microglial system Xc- might be of therapeutic value in the treatment of AD. Its inhibition not only prevents glutamate excitotoxicity but also facilitates neuroprotection by apoE.

Topics: Alzheimer Disease; Amino Acid Transport System y+; Amyloid beta-Peptides; Animals; Apolipoproteins E; Cell Communication; Cell Death; Cell Survival; Cells, Cultured; Coculture Techniques; Female; Gene Expression Regulation; Glutamic Acid; Humans; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Microglia; Nerve Degeneration; Neurons; Peptide Fragments; Rats; Rats, Wistar

The purpose of this paper is to study the basic pharmacological action of sarsasapogenin, a sapogenin from the Chinese medicinal herb Rhizoma Anemarrhenae, (abbreviated as ZMS in this paper), on learning ability and memory of three animal models: aged rats and two neurodegeneration models produced either by single unilateral injection of beta-amyloid 1-40 (Abeta1-40) plus ibotenic acid (Ibot A) or by bilateral injection of Ibot A alone into nucleus basalis magnocellularis. Y-maze test and step-through test revealed that learning ability and memory were impaired in the three models and were improved by oral administration of ZMS. ZMS did not inhibit acetylcholinesterase nor did it occupy the binding sites of muscarinic acetylcholine receptor (M receptor), hence it is neither an cholinesterase inhibitor nor an agonist or antagonist of M receptors. On the other hand, the densities of total M receptor and its M1 subtype in the brain of the three models were significantly lower than control rats, and ZMS significantly raised the densities of total M receptors and its M1 subtype. Linear regression revealed significant correlation between the learning ability/memory and the density of either total M receptor or its M1 subtype. Autoradiographic study with 3H-pirenzipine showed that the M1 subtype density was significantly lowered in cortex, hippocampus and striatum of aged rats, and ZMS could reverse these changes towards normal control level. Interestingly, the M1 receptor density after ZMS administration only approached but did not exceed that of normal young control rats. Therefore, ZMS seems to represent a new approach to the pharmacological regulation of learning and memory and appears to be not simply palliative but may modify the progression of the disease.

Topics: Acetylcholinesterase; Age Factors; Amyloid beta-Peptides; Animals; Autoradiography; Brain; Disease Models, Animal; Excitatory Amino Acid Agonists; Female; Ibotenic Acid; Immunohistochemistry; Male; Maze Learning; Memory Disorders; Nerve Degeneration; Neurotoxins; Peptide Fragments; Rats; Rats, Sprague-Dawley; Receptors, Muscarinic; Spirostans

The present work shows that alpha-glycerylphosphorylethanolamine (alpha-GPE) is effective in recovering astrocytes from mitochondrial membrane integrity and potential derangement and cellular oxidative stress that occur under amyloid beta-peptides-induced reactive gliosis.alpha-Glycerylphosphorylethanolamine (alpha-GPE), a new compound with nootropic properties, known to improve in vivo the learning and memory processes, has been tested for its protective properties on an in vitro model of degeneration. Rat primary astrocytic cultures treated with two amyloid-derived peptides, Abeta((1-40)) and Abeta(3(pE)-42), showed a marked reduction of the mitochondrial redox activity and membrane potential, together with an increase of oxidative species production. Plasma membrane lipid peroxidation (LPO) as well as generation of peroxides is greatly increased under Abeta-peptides toxicity. These features, typical of the reactive gliosis that accompanies neuronal degeneration, were readily recovered by pretreatment with alpha-GPE. alpha-GPE, likely improving the fluidity of cell membrane, has the potential to recover astrocytes from the general redox derangement induced by different amyloid fragments and possibly to protect from inflammation, gliosis and neurodegeneration. This is the first evidence of an antioxidant effect of the ethanolamine derivative on a rat model of chronic gliosis.

Topics: Amyloid beta-Peptides; Animals; Astrocytes; Cell Membrane; Cells, Cultured; Gliosis; Lipid Peroxidation; Membrane Fluidity; Membrane Potentials; Microscopy, Confocal; Mitochondria; Nerve Degeneration; Oxidative Stress; Peptide Fragments; Phosphatidylethanolamines; Rats; Tetrazolium Salts; Thiazoles

Amyloid beta peptide (A beta) is widely believed to play a central and etiological role in Alzheimer disease (AD). A beta has been shown to have cytotoxic effects in neural cells, although the mechanism by which it does this is still unclear. To examine the involvement of the apoptotic cascade in A beta-induced cell death, we used mice deficient in caspase-3 (CPP 32), a key protease in this cascade. We microinjected A beta(1-40) into hippocampal regions of the brains of adult mice because AD is an adult-onset disease. We found significant cellular loss in the hippocampal regions of wild-type mice and dramatic rescue of neuronal cell death in caspase-3-deficient mice, with a gene dosage effect. In addition to adult mice, we observed little A beta-induced death of cultured neurons prepared from fetal brains of caspase-3-deficient mice but did observe death of such neurons from wild-type mice. The difference in A beta-induced neuronal death between wild-type and caspase-3-deficient mice was highly significant, indicating that A beta-induced neuronal death is mediated in vivo as well as in vitro by the caspase-3 apoptotic cascade.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Apoptosis; Caspase 3; Caspases; Cells, Cultured; Disease Models, Animal; Fetus; Gene Dosage; Hippocampus; Mice; Mice, Knockout; Nerve Degeneration; Neurons; Peptide Fragments; Signal Transduction

We wish to understand the normal function of amyloid-beta peptides (Abeta) and to see if they destabilize neuronal calcium homeostasis [Mattson et al., J. Neurosci. 12 (1992), 376-389]. We observed that a physiological concentration (10 nM) of Abeta1-42 increased both glutamate and noradrenaline exocytosis from rat cortical nerve endings at least in part by activation of N-type Ca2+ channels. Abeta oligomers rather than monomers or fibrils probably are the most active form. Three alternatively-proposed effects of Abeta (reactive oxygen species formation, membrane perforation, and disruption of Ca2+ stores) also were tested by incubating nerve endings with a relatively high (by this study's standards) concentration of Abeta1-42(100 nM). None of the three proposed effects were detected during these incubations. These results support the hypothesis that persistent elevations of Abeta, which normally operates as a modulator of N-type voltage gated calcium channels, could increase internal nerve ending Ca2+ and excitatory neurotransmitter release to produce the early neurotoxic effects that eventually lead to Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Cerebral Cortex; Female; Glutamic Acid; Hippocampus; Male; Nerve Degeneration; Nerve Endings; Nerve Tissue Proteins; Norepinephrine; Peptide Fragments; Plaque, Amyloid; Rats; Rats, Long-Evans; Rats, Sprague-Dawley; Rats, Wistar; Reactive Oxygen Species

We have previously shown that beta-amyloid (Abeta) increased the excitotoxicity of ibotenate, an N-methyl-D-aspartate (NMDA) receptor agonist, to hippocampal neurons of rats. In this report, non-toxic amounts of kainate were co-injected with Abeta into rat hippocampus. Nissl-stained brain sections revealed that Abeta/kainate co-injection exerted synergistic neuronal degeneration in the hippocampus as well as that by Abeta/ibotenate co-injection. MK-801, an NMDA receptor antagonist, blocked the neuronal loss induced by Abeta/ibotenate co-injection, but not by Abeta/kainate co-injection. On the other hand, 6-cyano-7-nitroquinoxaline-2, 3-dione, a kainate receptor antagonist, suppressed the neuronal loss induced by the Abeta/kainate co-injection, but not that by the Abeta/ibotenate co-injection. This suggests that Abeta increases the sensitivity of both the NMDA receptor and the kainate receptor.

Topics: Amyloid beta-Peptides; Animals; Drug Synergism; Hippocampus; Kainic Acid; Male; Nerve Degeneration; Peptide Fragments; Rats; Rats, Sprague-Dawley

It is unclear how and when insoluble beta-amyloid in senile plaques exerts degenerative effects on distant hippocampal neurons in Alzheimer's disease. Racemization of Ser and Asp residues of insoluble beta-amyloid is a typical age-dependent process. In this study, we investigated the fibril formation activity and cytotoxic activity of beta-amyloid 1-40 racemized at the Asp or Ser residue. In contrast to beta-amyloid 1-40 and its derivative substituted with the D-Asp(1, 7 or 23) or D-Ser(8) residue, [D-Ser(26)]beta-amyloid 1-40 was non-toxic to PC12 cells, and did not exhibit significant fibril formation activity making it soluble. However, [D-Ser(26)]beta-amyloid 1-40, but not beta-amyloid 1-40, was converted in vitro to a potent neurotoxic and truncated peptide, [D-Ser(26)]beta-amyloid 25-35 or [D-Ser(26)]beta-amyloid 25-40, by chymotrypsin-like enzymes and aminopeptidase M. Soluble [D-Ser(26)]beta-amyloid 1-40 was injected into rat hippocampus with a non-toxic dose of ibotenic acid, an excitatory amino acid. Nissl staining and microtubule-associated protein-2 immunostaining revealed that [D-Ser(26)]beta-amyloid 1-40, as well as [D-Ser(26)]beta-amyloid 25-35, produced a drastic degeneration of the CA1 neurons with ibotenic acid although [D-Ser(26)]beta-amyloid 1-40 alone or ibotenic acid alone did not exert neuronal damage. This suggests the in vivo conversion of non-toxic [D-Ser(26)]beta-amyloid 1-40 to the toxic and truncated peptides which enhance the susceptibility of neurons to the excitatory amino acid.These results and the presence of [D-Ser(26)]beta-amyloid 25-35-like antigens in Alzheimer's disease brains suggest that soluble [D-Ser(26)]beta-amyloid 1-40, possibly formed during the aging process, is released from senile plaques, and converted by brain proteinases to truncated [D-Ser(26)]beta-amyloid 25-35(40)-like peptides, which degenerate hippocampal neurons by enhancing the susceptibility to excitatory amino acids in Alzheimer's disease brains. These findings may provide the basis for a new therapeutic approach to prevent the neurodegeneration in Alzheimer's disease.

Topics: Alzheimer Disease; Amino Acid Isomerases; Amino Acid Sequence; Aminopeptidases; Amyloid beta-Peptides; Animals; Aspartic Acid; Chymotrypsin; Coloring Agents; Endopeptidases; Excitatory Amino Acid Agonists; Hippocampus; Ibotenic Acid; Male; Nerve Degeneration; Neurofibrillary Tangles; Neurons; PC12 Cells; Peptide Fragments; Plaque, Amyloid; Rats; Rats, Sprague-Dawley; Serine

Huperzine A, a promising therapeutic agent for Alzheimer's disease, was examined for its potential to antagonize the deleterious neurochemical, structural, and cognitive effects of infusing beta-amyloid protein-(1-40) into the cerebral ventricles of rats. Daily intraperitoneal administration of huperzine A for 12 consecutive days produced significant reversals of the beta-amyloid-induced deficit in learning a water maze task. This treatment also reduced the loss of choline acetyltransferase activity in cerebral cortex, and the neuronal degeneration induced by beta-amyloid protein-(1-40). In addition, huperzine A partly reversed the down-regulation of anti-apoptotic Bcl-2 and the up-regulation of pro-apoptotic Bax and P53 proteins and reduced the apoptosis that normally followed beta-amyloid injection. The present findings confirm that huperzine A can alleviate the cognitive dysfunction induced by intracerebroventricular infusion of beta-amyloid protein-(1-40) in rats. The beneficial effects are not confined to the cholinergic system, but also include favorable changes in the expression of apoptosis-related proteins and in the extent of apoptosis in widespread regions of the brain.

Topics: Alkaloids; Amyloid beta-Peptides; Animals; Apoptosis; bcl-2-Associated X Protein; Cerebral Cortex; Choline O-Acetyltransferase; Cognition Disorders; Dose-Response Relationship, Drug; Hippocampus; Humans; In Situ Nick-End Labeling; Infusion Pumps; Injections, Intraventricular; Male; Maze Learning; Memory Disorders; Microscopy, Electron; Nerve Degeneration; Neurons; Neuroprotective Agents; Peptide Fragments; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Psychomotor Performance; Rats; Rats, Sprague-Dawley; Sesquiterpenes; Tumor Suppressor Protein p53

JNPL3 transgenic mice expressing a mutant tau protein, which develop neurofibrillary tangles and progressive motor disturbance, were crossed with Tg2576 transgenic mice expressing mutant beta-amyloid precursor protein (APP), thus modulating the APP-Abeta (beta-amyloid peptide) environment. The resulting double mutant (tau/APP) progeny and the Tg2576 parental strain developed Abeta deposits at the same age; however, relative to JNPL3 mice, the double mutants exhibited neurofibrillary tangle pathology that was substantially enhanced in the limbic system and olfactory cortex. These results indicate that either APP or Abeta influences the formation of neurofibrillary tangles. The interaction between Abeta and tau pathologies in these mice supports the hypothesis that a similar interaction occurs in Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Brain; Crosses, Genetic; Disease Models, Animal; Female; Limbic System; Male; Mice; Mice, Transgenic; Mutation; Nerve Degeneration; Neurofibrillary Tangles; Neurons; Peptide Fragments; Plaque, Amyloid; RNA, Messenger; Sex Characteristics; Solubility; Spinal Cord; tau Proteins

The objective of this study was to investigate whether changes in Abeta and ERAB exist in the brain of diabetic mice, and to observe the effects of APP17 peptide. The numbers of neurons stained by APP17 peptide Abeta1-40 Abeta1-42 Abeta1-16 and ERAB antibodies in the brain of diabetic mice was increased compared with normal mice. Staining in APP17 peptide-protected mice was similar to normal mice. We conclude that increased Abeta1-42 and ERAB is an important cause of neuronal degeneration in diabetic encephalopathy. APP17 peptide retards neuronal degeneration by regulating the metabolism of Abeta.

Topics: 3-Hydroxyacyl CoA Dehydrogenases; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Brain Diseases, Metabolic; Carrier Proteins; Diabetes Mellitus, Experimental; Hippocampus; Immunohistochemistry; Male; Mice; Nerve Degeneration; Neurons; Neuroprotective Agents; Peptide Fragments

Neurotrophins, such as NGF, BDNF and NT-3 play a regulatory role on the function of microglial cells in vivo and in vitro, and the identification of new compounds with neurotrophic properties is becoming a new strategy for the prevention and/or treatment of neurodegenerative disorders. In this study we describe the use of two different models to demonstrate the ability of Cerebrolysin to reduce microglial activation. The results of these in vitro and in vivo studies indicate that Cerebrolysin might exert a neuroimmunotrophic activity reducing the extent of inflammation and accelerated neuronal death under pathological conditions such as those observed in neurodegenerative diseases.

Topics: Amino Acids; Amyloid beta-Peptides; Animals; Cells, Cultured; Cerebral Cortex; Female; Hippocampus; Interleukin-1; Lipopolysaccharides; Microglia; Nerve Degeneration; Neuroprotective Agents; Nootropic Agents; Peptide Fragments; Rats; Rats, Sprague-Dawley

A growing amount of evidence indicates the involvement of extracellular matrix components, especially laminins, in the development of Alzheimer's disease, although their role remains unclear. In this study, we clearly demonstrate that laminin 1 inhibits beta-amyloid peptide (Abeta)-induced neuronal cell death by preventing the fibril formation and interaction of the Abeta peptide with cell membranes. The presence of laminin at a laminin/Abeta peptide molar ratio of 1:800 significantly inhibits the Abeta-induced apoptotic events, together with inhibition of amyloid fibril formation. The inhibitory effects of laminin 1 were time- and dose-dependent, whereas laminin 2 had less effect on Abeta neurotoxicity. A preincubation of laminin and Abeta was not required to observe the protective effect of laminin, suggesting a direct interaction between laminin 1 and Abeta. Moreover, laminin had no effect on the toxicity of the fibrillar Abeta peptide, suggesting an interaction of laminin with nonfibrillar species of the Abeta peptide, sequestering the peptide in a soluble form. These data extend our understanding of laminin-dependent binding of Abeta and highlight the possible modulation role of laminin regarding Abeta aggregation and neurotoxicity in vivo.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Cell Membrane; Cell Survival; Cells, Cultured; Cerebral Cortex; Fetus; L-Lactate Dehydrogenase; Laminin; Nerve Degeneration; Neurofibrillary Tangles; Neurons; Neuroprotective Agents; Peptide Fragments; Rats; Rats, Wistar; Solubility

Small volumes of solutions injected into the hippocampus produce dramatic degeneration in dentate gyrus neurons, but not in neurons of the CA1 subfield. The aim of the present study was to ascertain whether solutions with different fragments of the beta-amyloid protein (Abeta) could produce further degeneration in areas beyond the dentate gyrus. It was found that 5 days after injection of an aqueous solution containing the Abeta 1-40 fragment into the hippocampus, long stretches of the CA1 subfield were either deprived of neurons or most of the neurons were degenerating. By contrast, in animals with deposits containing Abeta 1-28, Abeta 1-42 or water, neuronal degeneration or depletion only occurred in a reduced area around the place where the implant needle penetrated the CA1 subfield. In animals injected with Abeta 1-40, many profiles in the CA1 subfield and dentate gyrus were undergoing apoptosis, as seen using preparations processed by routine histology or the TUNEL technique for detection of fragmented DNA. In addition, there was higher infiltration by ED1-positive, activated microglia-macrophagic cells in Abeta 1-42 deposits than in deposits of Abeta 1-40. The present results suggest that the intrahippocampal injection of toxic Abeta fragments produces neuronal degeneration in the rat CA1 subfield when using the appropriate protocol, and, thus, can provide an in vivo model to investigate the neurotoxic effects of Abeta and for the evaluation of drugs with potential anti-neurodegenerative activity.

Topics: Amyloid beta-Peptides; Animals; Apoptosis; DNA Fragmentation; Female; Hippocampus; Immunohistochemistry; Macrophages; Nerve Degeneration; Neurons; Peptide Fragments; Rats; Rats, Sprague-Dawley

The beta-amyloid peptide (Abeta) is deposited in neuritic plaques which are characteristic features of Alzheimer's disease (AD). Prominent neurodegeneration and glial activation occurs around these plaques leading to the hypothesis that Abeta may play a causative role in the neuronal loss and the inflammatory response associated with AD. Here we show that Abeta-induced toxicity of cultured fetal rat cortical neurons is associated with internucleosomal DNA fragmentation beginning just 6 h after neurons are exposed to Abeta. Additionally, constitutive NF-kappaB activity readily measured in fetal rat cortical neurons decreases in a concentration- and time-dependent fashion following exposure to Abeta, but there is no corresponding decrease in NF-kappaB mRNA or protein (p65). An upregulation of both IkappaB alpha protein and mRNA which occurs in cortical neurons exposed to Abeta may be responsible for retaining NF-kappaB in the cytoplasm accounting for the observed decrease in activated NF-kappaB. The latter is supported by the observation that pretreatment of cortical cultures with an antisense oligonucleotide to IkappaBalpha mRNA is neuroprotective. In contrast to cortical neurons, exposure of rat primary astroglial cultures to Abeta results in a concentration- and time-dependent activation of NF-kappaB with subsequent upregulation of IL-1beta and IL-6. Our data suggest that Abeta-induced neurotoxicity as well as astrocyte activation may be medicated by the NF-kappaB/Rel family of proteins, and thus alterations in NF-kappaB-directed gene expression may contribute to both the neurodegeneration and inflammatory response which occur in AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Antisense Elements (Genetics); Astrocytes; Cells, Cultured; Cerebral Cortex; Gene Expression Regulation, Enzymologic; Interleukin-1; Interleukin-6; Nerve Degeneration; Neurons; Neurotoxins; NF-kappa B; Peptide Fragments; Polymerase Chain Reaction; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-rel; Rats

Recent evidence suggests that beta-amyloid peptide (beta-AP) may induce tau protein phosphorylation, resulting in loss of microtubule binding capacity and formation of paired helical filaments. The mechanism by which beta-AP increases tau phosphorylation, however, is unclear. Using a hybrid septal cell line, SN56, we demonstrate that aggregated beta-AP(1-40) treatment caused cell injury. Accompanying the cell injury, the levels of phosphorylated tau as well as total tau were enhanced as detected immunochemically by AT8, PHF-1, Tau-1, and Tau-5 antibodies. Alkaline phosphatase treatment abolished AT8 and PHF-1 immunoreactivity, confirming that the tau phosphorylation sites were at least at Ser(199/202) and Ser396. In association with the increase in tau phosphorylation, the immunoreactivity of cell-associated and secreted beta-amyloid precursor protein (beta-APP) was markedly elevated. Application of antisense oligonucleotide to beta-APP reduced expression of beta-APP and immunoreactivity of phosphorylated tau. Control peptide beta-AP(1-28) did not produce significant effects on tau phosphorylation, although it slightly increased cell-associated beta-APP. These results suggest that betaAP(1-40)-induced tau phosphorylation may be associated with increased beta-APP expression in degenerated neurons.

Topics: Alkaline Phosphatase; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Cell Survival; Hybrid Cells; Mice; Nerve Degeneration; Neuroblastoma; Neurotoxins; Oligonucleotides, Antisense; Peptide Fragments; Phosphorylation; tau Proteins

Two major C-terminal variants ending at Val40 and Ala42 constitute the majority of amyloid beta-protein (Abeta), which undergoes postsecretory aggregation and deposition in the Alzheimer disease (AD) brain. To probe the differential pathobiology of the two Abeta variants, we used an in vivo paradigm in which freshly solubilized Abeta1-40 or Abeta1-42 was injected into rat brains, followed by examination using Congo red birefringence, Abeta immunohistochemistry, and electron microscopy. In the rat brain, soluble Abeta 1-40 and Abeta1-42 formed aggregates, and the Abeta1-40 but not the Abeta1-42 aggregates showed Congo red birefringence. Electron microscopy revealed that the Abeta1-40 aggregates contained fibrillar structures similar to the amyloid fibrils of AD, whereas the Abeta1-42 aggregates contained nonfibrillar amorphous material. Preincubation of Abeta1-42 solution in vitro led to the formation of birefringent aggregates, and after injection of the preincubated Abeta1-42, the aggregates remained birefringent in the rat brain. Thus, a factor or factors might exist in the rat brain that inhibit the fibrillar assembly of soluble Abeta1-42. To analyze the postsecretory processing of Abeta, we used the same in vivo paradigm and showed that Abeta1-40 and Abeta1-42 were processed at their N termini to yield variants starting at pyroglutamate, and at their C termini to yield variants ending at Val40 and at Val39. Thus the normal rat brain could produce enzymes that mediate the conversion of Abeta 1-40/1-42 into processed variants similar to those in AD. This experimental paradigm may facilitate efforts to elucidate mechanisms of Abeta deposition evolving into amyloid plaques in AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Birefringence; Cerebral Cortex; Coloring Agents; Congo Red; Endopeptidases; Female; Hippocampus; Humans; Injections; Microscopy, Electron; Nerve Degeneration; Nerve Tissue Proteins; Peptide Fragments; Plaque, Amyloid; Rats; Rats, Sprague-Dawley

Amyloid beta protein (A beta) in neuritic plaques of Alzheimer's disease has been found to be racemized and/or isomerized at their Asp residues. To elucidate the effect of racemization on the aggregation properties of A beta, we synthesized three kinds of A beta peptides in which D-Asp was substituted for L-Asp residues, i.e, normal A beta 1-40, [D-Asp7]A beta 1-40 and [D-Asp23]A beta 1-40. The aggregation and fibril formation of each peptide was examined by means of spectrofluorometry and electron microscopy. Of the three peptides, normal A beta showed the gradual increase of aggregation while [D-Asp7]A beta 1-40 and [D-Asp23] A beta 1-40 showed more enhanced aggregation at the final stage when the fibril formations were detected in all peptides solutions by electron microscopy. A comparative immunohistochemical study by anti-racemized A beta antibody and anti-A beta 1-42/43 antibody further showed the in vivo incorporation of D-Asp in senile plaques of Alzheimer's disease brains, which may be involved in plaque formation at the later stage than the deposition of the longer form of A beta (A beta 1-42/43). Taken together with the recent accumulated evidence on the aggregation mechanisms of A beta, the data presented here suggest that racemization may occur after the amyloid fibril formation but enhance the aggregation process by shifting the equilibrium of A beta from the soluble form to the insoluble form in Alzheimer's disease.

Topics: Alzheimer Disease; Amino Acid Sequence; Amyloid beta-Peptides; Aspartic Acid; Biopolymers; Brain; Humans; Isomerism; Microscopy, Electron; Molecular Sequence Data; Nerve Degeneration; Nerve Tissue Proteins; Peptide Fragments; Protein Binding; Solubility; Spectrometry, Fluorescence; Stereoisomerism

The aggregation of amyloid beta-protein has been suggested to enhance its neurotoxicity in cultured hippocampal neurons. We found that aluminum, an epidemiologic risk factor for Alzheimer's disease, promoted the aggregation of synthetic amyloid beta-protein (beta 1-40) using immunoblotting and centrifugation. There were no significant changes by Ca or Mg. Other metals including Zn, Fe caused the small degree of aggregation compared to Al. Furthermore, beta 1-40 which was aggregated by aluminum was applied on cultured rat hippocampal neurons, and the characteristic deposition of amyloid fibrils was observed on cultured neurons. These results suggested that the degeneration of neurons and the deposition of amyloid beta-protein were enhanced by aluminum.

Topics: Aluminum; Alzheimer Disease; Amyloid beta-Peptides; Animals; Biopolymers; Calcium; Cell Death; Cells, Cultured; Drug Synergism; Hippocampus; Humans; Magnesium; Models, Neurological; Nerve Degeneration; Neurons; Peptide Fragments; Prealbumin; Protein Binding; Rats

To supplement the existing pharmacological evidence describing the effects of nimodipine, a 1,4-dihydropyridine with calcium channel blocking properties, our group has used a multidisciplinary approach. This work attempts to characterize the mechanism of action of nimodipine in neurons as well as investigate the effects of nimodipine in models of neurodegeneration and dementia. Patch voltage clamp studies demonstrated high-affinity nimodipine block of voltage-dependent L-type calcium channel activity in central neurons from primary cultures of neonatal rat hippocampus. Nimodipine potently blocks depolarization-induced increases in free calcium throughout the soma of these hippocampal neurons. In addition, somatic free calcium elevations induced by acute beta A4(25-35) exposure are also potently blocked by nimodipine. In behavioral studies, nimodipine produced enhanced retention in aging rabbits on eyeblink conditioning and also was shown to protect against medial septal lesion-induced retention deficits in a spatial learning task. These findings, from channel to behavioral effects, support the therapeutic usefulness of nimodipine in the treatment of aging and dementia and are consistent with the view that calcium regulation is important in disorders of neuronal degeneration.

Topics: Aging; Amyloid beta-Peptides; Animals; Behavior, Animal; Calcium; Cells, Cultured; Dementia; Female; In Vitro Techniques; Male; Nerve Degeneration; Neurons; Nimodipine; Peptide Fragments; Rabbits; Rats; Retention, Psychology