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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 85 (2003), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: JNK/SAPK has been implicated in the pathogenesis of Alzheimer's disease, but the upstream cascade leading to JNK/SAPK activation has not been elucidated in the disease. In this study, we focused on one of the physiological activators of JNK/SAPK, JNK kinase 1 (JKK1). Although there was no significant difference in the level and distribution of total JKK1 between Alzheimer's disease (AD) and age-matched control cases, increased levels of activated phospho-JKK1 were specifically localized to neurofibrillary pathology including neurofibrillary tangles, senile plaque neurites, granulovaualar degenerations and neuropil threads in severe AD (Braak stage V–VI), considerably overlapping with its downstream effector, phospho-JNK/SAPK, suggesting both a functional and mechanistic link. Nuclear localization of phospho-JKK1 was also found in mild (Braak stage III–IV) but not in severe AD cases (Braak stage V–VI), suggesting a possible re-distribution correlating with the progress of the disease. By immunoblot analyses, phospho-JKK1 was significantly increased in AD over control cases. Together, these findings lend further credence to the notion that the JNK/SAPK pathway is dysregulated in AD and also indicate an active role for this pathway in disease pathogenesis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Cellular responses to increased oxidative stress appear to be a mechanism that contributes to the varied cytopathology of Alzheimer's disease (AD). In this regard, we suspect that c-Jun N-terminal kinase/Stress activated protein kinase (JNK/SAPK), a major cellular stress response protein induced by oxidative stress, plays an important role in Alzheimer disease in susceptible neurons facing the dilemma of proliferation or death. We found that JNK2/SAPK-α and JNK3/SAPK-β were related to neurofibrillary pathology and JNK1/SAP-Kγ related to Hirano bodies in cases of AD but were only weakly diffuse in the cytoplasm in all neurons in control cases and in non-involved neurons in diseased brain. In this regard, in hippocampal and cortical regions of individuals with severe AD, the activated phospho-JNK/SAPK was localized exclusively in association with neurofibrillar alterations including neurofibrillary tangles, senile plaque neurites, neuropil threads and granulovacuolar degeneration structures (GVD), completely overlapping with τ-positive neurofibrillary pathology, but was virtually absent in these brain regions in younger and age-matched controls without pathology. However, in control patients with some pathology, as well as in mild AD cases, there was nuclear phospho-JNK/SAPK and translocation of phospho-JNK/SAPK from nuclei to cytoplasm, respectively, indicating that the activation and re-distribution of JNK/SAPK correlates with the progress of the disease. By immunoblot analysis, phospho-JNK/SAPK is significantly increased in AD over control cases. Together, these findings suggest that JNK/SAPK dysregulation, probably resulting from oxidative stress, plays an important role in the increased phosphorylation of cytoskeletal proteins found in AD.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: In this study, we compared the neuronal induction of the antioxidant heme oxygenase-1 (HO-1) in Alzheimer's disease with abnormalities in τ marked by antibodies recognizing either phosphorylation (AT8) or conformational change (Alz50). The epitope recognized by Alz50 shows a complete overlap with HO-1-containing neurons, but AT8 recognized these neurons as well as neurons not displaying HO-1. These findings suggest that τ phosphorylation precedes the HO-1 response and that HO-1 is coincident with the Alz50 epitope. This led us to consider whether oxidative damage plays a role in forming the Alz50 epitope. We found that 4-hydroxy-2-nonenal (HNE), a highly reactive product of lipid peroxidation, reacts with normal τ and induces the Alz50 epitope in τ. It is important that the ability of HNE to create the Alz50 epitope not only is dependent on lysine residues of τ but also requires τ phosphorylation because neither methylated, recombinant, nor dephosphorylated τ reacts with HNE to create the Alz50 epitope. Supporting the in vivo relevance of this observation, endogenous paired helical filament-τ isolated from subjects with Alzheimer's disease was immunoreactive with an antibody to a stable HNE-lysine adduct, as were all vulnerable neurons in subjects with Alzheimer's disease but not in control individuals. Together, these findings support the involvement of oxidative damage early in neurofibrillary tangle formation in Alzheimer's disease and also suggest that HNE modification contributes to the generation of the τ conformation defining the Alz50 epitope. These findings provide evidence that an interplay between phosphorylation of τ and neuronal oxidative stress-induced pathology is important in the formation of neurofibrillary tangles.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: While there is a host of pro-apoptotic stimuli that target neurons in Alzheimer disease (AD), given the chronicity of the disease and the survival of many neurons, those neurons must either avoid or, at minimum, delay apoptotic death signaling. In this study, we investigated Bcl-w, a novel member of the Bcl-2 family that promotes cell survival. In AD, we found increased levels of Bcl-w associated with neurofibrillary pathology and punctate intracytoplasmic structures whereas, in marked contrast, there are only low diffuse levels of Bcl-w in the neuronal cytoplasm of age-matched control cases. Immunoblot analysis confirmed that Bcl-w levels were significantly increased in AD. By electron microscopy, we determined that the increased Bcl-w expression in AD was ultrastructurally localized to mitochondria and neurofibrillary pathology. To investigate the cause and consequence of Bcl-w up-regulation in neurons, we found that fibrillized amyloid-β led to increased Bcl-w protein levels in M17 human neuroblastoma cells, and that overexpression of Bcl-w significantly protected neurons against staurosporine- and amyloid-β-induced apoptosis. Taken together, these series of results suggest that Bcl-w may play an important protective role in neurons in the diseased brain and that this aspect could be therapeutically harnessed to afford neuroprotection.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 86 (2003), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Extracellular-signal-regulated kinase (ERK) has been implicated in the pathogenesis of Alzheimer's disease (AD), but the upstream cascade leading to ERK activation has not been elucidated. In this study, we focused on one of the physiological activators of ERK, mitogen-activated protein kinase (MAPK)/ERK kinase 1 (MEK1). Although there was no significant difference in the level and distribution of total MEK1 between AD and age-matched control cases, increased levels of activated phospho-MEK1 were specifically localized to neuronal intracytoplasmic granular structures in severe AD (Braak stage V–VI). The considerable overlap between MEK1 and its downstream effector, phospho-ERK, suggests both a functional and mechanistic link. Nuclear localization of phospho-MEK1 was a prominent feature in both mild AD cases (Braak stage III–IV) and control cases with limited pathology (Braak stage I–II). Since MEK1 is normally cytoplasmic due to the active export from nucleus because of the presence of nuclear export signal in its amino-terminus, we suspect that the apparent nuclear accumulation of phospho-MEK1 in AD patients at early stages suggests that abnormal nuclear trafficking may contribute to the pathogenesis of AD. By immunoblot analyses, phospho-MEK1 was significantly increased in AD over control cases. Together, these findings lend further credence to the notion that the ERK pathway is dysregulated in AD and also indicate an active role for this pathway in disease pathogenesis.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Mitogen-activated protein kinase (MAPK) p38 has been implicated in the pathogenesis of Alzheimer's disease, but the upstream cascade leading to p38 activation has not been elucidated in the disease. In the present study, we focused on mitogen-activated protein kinase kinase 6 (MKK6), one of the upstream activators of p38 MAPK. We found that MKK6 was not only increased but also specifically associated with granular structures in the susceptible neurons in the hippocampus and cortex of Alzheimer's disease patients, but was only weakly diffuse in the cytoplasm in neurons in control cases. Immunoblot analysis demonstrated a significant increase of MKK6 level in Alzheimer's disease compared with age-matched controls. In this regard, in hippocampal and cortical regions of individuals with Alzheimer's disease, the activated phospho-MKK6 was localized exclusively in association with pathological alterations including neurofibrillary tangles, senile plaques, neuropil threads and granular structures, overlapping with activated p38 MAPK suggesting both a functional and mechanic link. By immunoblot analysis, phospho-MKK6 is also significantly increased in AD compared with control cases. Together, these findings lend further credence to the notion that the p38 MAPK pathway is dysregulated in Alzheimer's disease and also indicates an active role for this pathway in disease pathogenesis.
    Type of Medium: Electronic Resource
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