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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 82 (2002), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Epidemiologic evidence implicates cyclooxygenase activity in the pathogenesis of Alzheimer's disease, in which amyloid plaques have been found to contain increased levels of dimers and higher multimers of the amyloid β peptide. The product of the oxygenation of arachidonic acid by the cyclooxygenases, prostaglandin H2 (PGH2), rearranges non-enzymatically to several prostaglandins, including the highly reactive γ-keto aldehydes, levuglandins E2 and D2. We demonstrate that PGH2 markedly accelerates the formation of dimers and higher oligomers of amyloid β1−42. This is associated with the formation of levuglandin adducts of the peptide. These findings provide the molecular basis for a hypothesis linking cyclooxygenase activity to the formation of oligomers of amyloid β.
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Manganese ethylene-bis-dithiocarbamate (Mn-EBDC) is the major active element of maneb, a pesticide linked to parkinsonism in certain individuals upon chronic exposure. Additionally, it has been shown to produce dopaminergic neurodegeneration in mice systemically coexposed to another pesticide, 1,1′-dimethyl-4,4′-bipyridinium (paraquat). Here, we described a rat model in which selective dopaminergic neurodegeneration was produced by delivering Mn-EBDC directly to the lateral ventricles. After establishing this model, we tested whether Mn-EBDC provoked dopamine efflux in the striatum, a well-known phenomenon produced by the mitochondrial inhibitor 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) that causes parkinsonism in humans, as well as in some animals. Finally, we investigated whether Mn-EBDC directly inhibited mitochondrial function in vitro using isolated brain mitochondria. Our data demonstrated that Mn-EBDC induced extensive striatal dopamine efflux that was comparable with that induced by MPP+, and that Mn-EBDC preferentially inhibited mitochondrial complex III. As mitochondrial dysfunction is pivotal in the pathogenesis of Parkinson's disease (PD), our results support the proposal that exposure to pesticides such as maneb, or other naturally occurring compounds that inhibit mitochondrial function, may contribute to PD development.
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Increase in prostaglandin (PG) E2 levels and oxidative damage are associated with diseases of brain that involve activation of innate immunity. We tested the hypothesis that cerebral oxidative damage resulting from activation of innate immunity with intracerebroventricular (icv) lipopolysaccharide (LPS) is dependent on PGE2-mediated signaling. We measured two quantitative in vivo biomarkers of lipid peroxidation: F2-isoprostanes (IsoPs) that derive from arachidonic acid (AA) that is uniformly distributed in all cell types in brain, and F4-neuroprostanes (NeuroPs) that derive from docosahexaenoic acid (DHA) that is highly concentrated in neuronal membranes. LPS stimulated delayed elevations in cerebral F2-IsoPs and F4-NeuroPs that were completely suppressed by indomethacin or ibuprofen pre-treatment. LPS-induced cerebral oxidative damage was abolished by disruption of subtype 2 receptor for PGE2 (EP2). In contrast, initial oxidative damage from icv kainic acid (KA) was more rapid than with LPS also was completely suppressed by indomethacin or ibuprofen pre-treatment but was independent of EP2 receptor activation. The protective effect of deleting the EP2 receptor was not associated with changes in cerebral eicosaniod production, but was partially related to reduced induction of nitric oxide synthase (NOS) activity. These results suggest the EP2 receptor as a therapeutic target to limit oxidative damage from activation of innate immunity in cerebrum.
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  • 4
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The mechanisms that underlie dopaminergic neurodegeneration in Parkinson's disease (PD) are not known but have been proposed to involve oxidation of dopamine and related catechols. In other organ systems, cytotoxicity from catechol oxidation is profoundly influenced by mercapturate metabolism. Here we have tested the hypothesis that catechol thioethers produced in the mercapturic acid pathway may act as dopaminergic neurotoxins. A rat mesencephalic/neuroblastoma hybrid (MES) cell line was exposed to dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), or eight different catechol thioethers for up to 24 h, and the extent of apoptosis was quantified by a microculture kinetic assay. Apoptosis also was confirmed morphologically with Giemsa-stained cultures and by demonstration of internucleosomal DNA fragmentation. The results showed that dopamine at 5-50 μM produced concentration-dependent increases in the percentage of apoptotic MES cells. At 25 and 50 μM dopamine, the maximal proportions of apoptotic cells were detected at ∼ 19 (20.7 ± 2.0%) and 14 h (30.3 ± 3.5%), respectively. None of the catechol thioethers (up to 5 μM) alone induced significant apoptosis in MES cells. However, when MES cells were incubated with dopamine (25 μM) and catechol thioethers (5 μM) to mimic pathological conditions, 5-S-N-acetylcysteinyldopamine, 5-S-homocysteinyldopamine, and 5-S-homocysteinyl-DOPAC significantly increased the percentage of apoptotic cells compared with dopamine alone. These results suggest that mercapturate metabolism of endogenous catechols may yield products that facilitate dopaminergic neurodegeneration.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford UK : Blackwell Science Ltd
    Journal of neurochemistry 72 (1999), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A destructive cycle of oxidative stress and mitochondrial dysfunction is proposed in neurodegenerative disease. Lipid peroxidation, one outcome of oxidative challenge, can lead to the formation of 4-hydroxy-2(E)-nonenal (HNE), a lipophilic alkenal that forms stable adducts on mitochondrial proteins. In this study, we characterized the effects of HNE on brain mitochondrial respiration. We used whole rat brain mitochondria and concentrations of HNE comparable to those measured in patients with Alzheimer’s disease. Our results showed that HNE inhibited respiration at multiple sites. Complex I-linked and complex II-linked state 3 respirations were inhibited by HNE with IC50 values of ∼200 μM HNE. Respiration was apparently diminished owing to the inhibition of complex III activity. In addition, complex II activity was reduced slightly. The lipophilicity and adduction characteristics of HNE were responsible for the effects of HNE on respiration. The inhibition of respiration was not prevented by N-acetylcysteine or aminoguanidine. Studies using mitochondria isolated from porcine cerebral cortex also demonstrated an inhibition of complex I- and complex II-linked respiration. Thus, in neurodegenerative disease, oxidative stress may impair mitochondrial respiration through the production of HNE.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The formation of cyclooxygenase-derived lipid adducts of protein in brains of patients who had Alzheimer's disease has been investigated. The enzymatic product of the cyclooxygenases, prostaglandin H2, rearranges in part to highly reactive γ-ketoaldehydes, levuglandin (LG) E2 and LGD2. These γ-ketoaldehydes react with free amines on proteins to yield a covalent adduct. Utilizing analysis of the levuglandinyl-lysine adducts by liquid chromatography-tandem mass spectrometry, we now find that this post-translational modification is increased significantly in the hippocampus in Alzheimer's disease. The magnitude of the increase correlates with the pathological evidence of severity.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Alterations in glutathione (GSH) metabolism are associated with neurodegeneration in Alzheimer's disease (AD), and GSH depletion follows application of exogenous fibrillar amyloid β (Aβ) peptides in experimental systems; these results are commonly cited as evidence of oxidative damage in AD. We used MC65 human neuroblastoma cells that conditionally express carboxy-terminal fragments of the Aβ precursor protein (Aβ/CTFs) to directly test the hypothesis that GSH is part of the cellular response to stressors associated with Aβ/CTF accumulation and not simply a marker of oxidative damage. Our data showed that Aβ/CTFs accumulated by post-translational processes and were associated with progressive increases in oxidative damage and cytotoxicity. Ethycrinic acid (EA) or diethyl maleate (DEM), reagents that deplete GSH through non-specific thiol adduction, gave rise to dose-dependent cytotoxicity that was independent of Aβ/CTF expression and minimally responsive to α-tocopherol (AT). In contrast, buthionine sulfoximine (BSO), a selective inhibitor of GSH synthase, not only augmented Aβ/CTF-associated cell death but unexpectedly potentiated Aβ/CTF accumulation; both outcomes were completely suppressed by AT. These data suggest that antioxidants may serve as ‘Aβ targeting’ therapies that suppress toxic protein aggregation rather than simply acting as downstream radical scavengers.
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  • 8
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Activation of glial innate immunity is widely proposed to contribute to a number of degenerative and destructive diseases of brain. However, the precise role of activated innate immunity has been difficult to define in vivo because of multiple simultaneous pathogenic processes and responses to injury that confound interpretation of results from complex models of disease. Here, we used the model of intracerebroventricular (ICV) injection of lipopolysaccharide (LPS) to test the hypothesis that directly activated glial innate immunity leads to neurodegeneration in cerebrum and to establish the molecular determinants of and neuroprotectants from such innate immunity-mediated neuronal damage. Our results showed that ICV LPS induced delayed, reversible oxidative damage to cerebral neuronal membranes as measured by F4-neuroprostanes that was coincident with degeneration of the hippocampal pyramidal neuron dendritic system, but not neuron death, in adult mice. Both neuronal oxidative damage and dendritic degeneration were NF-κB and iNOS dependent and were completely suppressed by ibuprofen and α-tocopherol, but not naproxen or γ-tocopherol. These results prove that activation of glial innate immunity can lead to neurodegeneration independent of other pathologic processes, closely associate oxidative damage to neuronal membranes with degeneration of the dendritic system, and provide a possible explanation for the varying efficacy of neuroprotectants that have been suggested in observational studies of dementia.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Aging and apolipoprotein E (APOE) isoform are among the most consistent risks for the development of Alzheimer's disease (AD). Metabolic factors that modulate risk have been elusive, though oxidative reactions and their by-products have been implicated in human AD and in transgenic mice with overt histological amyloidosis. We investigated the relationship between the levels of endogenous murine amyloid β (Aβ) peptides and the levels of a marker of oxidation in mice that never develop histological amyloidosis [i.e. APOE knockout (KO) mice with or without transgenic human APOEɛ3 or human APOEɛ4 alleles]. Aging-, gender-, and APOE-genotype-dependent changes were observed for endogenous mouse brain Aβ40 and Aβ42 peptides. Levels of the oxidized lipid F2-isoprostane (F2-isoPs) in the brains of the same animals as those used for the Aβ analyses revealed aging- and gender-dependent changes in APOE KO and in human APOEɛ4 transgenic KO mice. Human APOEɛ3 transgenic KO mice did not exhibit aging- or gender-dependent increases in F2-isoPs. In general, the changes in the levels of brain F2-isoPs in mice according to age, gender, and APOE genotype mirrored the changes in brain Aβ levels, which, in turn, paralleled known trends in the risk for human AD. These data indicate that there exists an aging-dependent, APOE-genotype-sensitive rise in murine brain Aβ levels despite the apparent inability of the peptide to form histologically detectable amyloid. Human APOEɛ3, but not human APOEɛ4, can apparently prevent the aging-dependent rise in murine brain Aβ levels, consistent with the relative risk for AD associated with these genotypes. The fidelity of the brain Aβ/F2-isoP relationship across multiple relevant variables supports the hypothesis that oxidized lipids play a role in AD pathogenesis, as has been suggested by recent evidence that F2-isoPs can stimulate Aβ generation and aggregation.
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  • 10
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Inheritance of the apolipoprotein (APO) E gene ɛ4 or ɛ2 allele alters the risk of developing Alzheimer disease (AD), while increased alpha-tocopherol (AT) intake appears to lower the risk of AD. As APOE is a major apolipoprotein in the CNS and AT in vivo is transported in lipoproteins, we tested the hypothesis that CNS lipoproteins, as modeled by relevant concentrations of high density lipoprotein (HDL), and AT would interact to suppress neurotoxicity in a cell culture model of amyloid beta (Aβ)- related toxicity. These cells conditionally express C99-derived peptides, proposed to be a key step in AD pathogenesis; this expression is closely associated with subsequent cell death. We found that physiologic concentrations of lipoproteins present in the CNS protected from C99-associated toxicity and provided evidence for two mechanisms of protection. The first was AT-independent, APOE isoform-dependent, and most potent for the APOE2 isoform. The second was a synergistic protection afforded by a combination of APOAI, or less so APOE, and AT. These data provide a novel explanation for the apparent AD-protective effect of inheriting an ɛ2 APOE allele, and suggest that optimizing AT enrichment of CNS lipoproteins or devising APOAI mimetics may augment AT efficacy in treating AD.
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