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PubMed2004

Biochemical and molecular studies of NMDA receptor subunits NR1/2A/2B in hippocampal subregions throughout progression of Alzheimer's disease pathology.

Alzheimer's disease (AD) is characterized by loss of specific cell populations within selective subregions of the hippocampus. Excitotoxicity, mediated via ionotropic glutamate receptors, may play a crucial role in this selective neuronal vulnerability. We investigated whether alterations in NMDA receptor subunits occurred during AD progression. Employing biochemical and in situ hybridization techniques in subjects with a broad range of AD pathology, protein levels, and mRNA expression of NR1/2A/2B subunits were assayed. With increasing AD neuropathology, protein levels and mRNA expression for NR1/2B subunits were significantly reduced, while the NR2A subunit mRNA expression and protein levels were unchanged. Cellular analysis of neuronal mRNA expression revealed a significant increase in the NR2A subunit in subjects with moderate neurofibrillary tangle neuropathology. This investigation supports the hypothesis that alterations occur in the expression of specific NMDA receptor subunits with increasing AD pathologic severity, which is hypothesized to contribute to the vulnerability of these neurons.

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PubMed2002

Alzheimer pathology in elderly patients with glioblastoma multiforme.

CONTEXT: Alzheimer disease (AD) and glioblastoma multiforme (GBM) have similar peak, age-specific incidence rates; however, to my knowledge, only 1 case of GBM associated with AD has been reported to date. The frequency of AD pathology, including neuritic plaques, diffuse plaques, neurofibrillary tangles, and cerebral amyloid angiopathy in patients with GBM is unknown. Studies of cancer occurrence in patients with AD are contradictory, with frequencies reported as equal to and as less than that in the general population. The GBM/AD nonconcordance may reflect underreporting of AD pathology or other factors. OBJECTIVE: To compare the frequency and extent of neocortical AD pathology in autopsy cases involving patients aged 60 to 82 years, both with and without GBM. Design.-Case-control study. Setting.-Pathology department of a university hospital. PATIENTS: Thirty-six autopsy cases of GBM patients aged 60 to 82 years; 54 cases of patients in the same age group without GBM or other primary brain tumors. METHODS: Examination of tumor sections for GBM and of neocortical sections for AD pathology according to Consortium to Establish a Registry for Alzheimer Disease (CERAD) guidelines. RESULTS: Glioblastoma multiforme was confirmed in all tumor cases. Alzheimer disease pathology was present in 42% of cases with GBM and in 48% of cases without GBM; 28% of GBM cases had CERAD age-related plaque scores indicative or suggestive of AD; 43% of cases without GBM had CERAD age-related plaque scores indicative or suggestive of AD. CONCLUSIONS: Alzheimer disease pathology was underreported in both GBM and non-GBM patients. The influence of neurodegenerative processes on GBM symptoms and therapy in elderly patients requires further study.

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PubMed2006

The significance of neuroinflammation in understanding Alzheimer's disease.

The interest of scientists in the involvement of inflammation-related mechanisms in the pathogenesis of Alzheimer's disease (AD) goes back to the work of one of the pioneers of the study of this disease. About hundred years ago Oskar Fischer stated that the crucial step in the plaque formation is the extracellular deposition of a foreign substance that provokes an inflammatory reaction followed by a regenerative response of the surrounding nerve fibers. Eighty years later immunohistochemical studies revealed that amyloid plaques are indeed co-localized with a broad variety of inflammation-related proteins (complement factors, acute-phase proteins, pro-inflammatory cytokines) and clusters of activated microglia. These findings have led to the view that the amyloid plaque is the nidus of a non-immune mediated chronic inflammatory response locally induced by fibrillar A beta deposits. Recent neuropathological studies show a close relationship between fibrillar A beta deposits, inflammation and neuroregeneration in relatively early stages of AD pathology preceding late AD stages characterized by extensive tau-related neurofibrillary changes. In the present work we will review the role of inflammation in the early stage of AD pathology and particularly the role of inflammation in A beta metabolism and deposition. We also discuss the possibilities of inflammation-based therapeutic strategies in AD.

Alzheimer Disease↗

PubMed2005

Mild cognitive impairment is related to Alzheimer disease pathology and cerebral infarctions.

OBJECTIVES: To examine the extent to which persons with mild cognitive impairment have intermediate levels of Alzheimer disease (AD) pathology, cerebral infarcts, and Lewy body disease. METHODS: A total of 180 Catholic clergy participating in the Religious Orders Study underwent annual detailed evaluation and brain autopsy. Blocks of midfrontal, superior temporal, medial temporal lobe, inferior parietal, entorhinal cortex, hippocampus, and substantia nigra were paraffin embedded, and sectioned at 6 mum. Cortical neuritic plaques, diffuse plaques, and neurofibrillary tangles were visualized with Bielschowsky silver stain, and counted and summarized to yield a Braak stage, Consortium to Establish a Registry for Alzheimer's Disease (CERAD) diagnosis, National Institute on Aging (NIA)-Reagan diagnosis, and composite measure of AD pathology. The authors recorded the number and location of all gross chronic cerebral infarctions. Lewy bodies were identified with antibodies to alpha-synuclein. Multiple regression analyses were used to examine the relation of AD pathology and cerebral infarctions to clinical diagnosis proximate to death, controlling for age, sex, and education. RESULTS: A total of 37 had mild cognitive impairment, 60 did not have cognitive impairment, and 83 had dementia proximate to death. Nearly all persons had at least some AD pathology. Cerebral infarctions were present in 35.2%, and 15.6% had Lewy body disease. Persons with mild cognitive impairment were intermediate in terms of Braak stage and CERAD and NIA-Reagan neuropathologic criteria for AD compared to the other two groups. In multiple regression analyses, persons with mild cognitive impairment had intermediate levels of AD pathology from those without cognitive impairment and those with dementia (test for trend, F = 45.2, p < 0.001). Further, the relation between cognition and AD pathology in persons with mild cognitive impairment did not differ significantly from the relation between cognition and AD pathology in persons with dementia or those without cognitive impairment. Persons with mild cognitive impairment also had intermediate levels of cerebral infarctions (test for trend, p = 0.04). Only 3 (8.1%) persons with mild cognitive impairment had Lewy body disease. CONCLUSION: These data suggest that mild cognitive impairment may be the earliest clinical manifestation of common age-related neurologic diseases.

Age Factors↗

PubMed2002

Impact of coexistent Alzheimer pathology on the natural history of Parkinson's disease.

OBJECTIVE: To assess the impact of coexisting Alzheimer (AD) pathology on the natural history of Parkinson's disease (PD). BACKGROUND: AD changes are frequently present in brains of demented PD patients. Assessing the relative contribution of AD pathology to the natural history of PD is difficult and the impact of both AD and cortical Lewy body (LB) pathologies on cognitive dysfunction is still under discussion. From clinical experience, dementia in PD patients, mainly related to AD pathology, is associated with a poor outcome, but the impact of AD pathology on the natural history of PD has not been studied systematically. MATERIAL AND METHODS: In 200 consecutive autopsy cases of PD (sex (m/f) ratio 1:1.1), age at death 58-98 (mean 77.0 +/- 9.5) years, from a specialized Austrian brain bank, retrospectively assessed major initial clinical symptoms (tremor, akinesia), moderate/severe dementia, and duration of illness were correlated with associated AD pathologies using CERAD, Braak and NIA-Reagan criteria. Mann-Whitney U-test, Cox-regression were used for statistical analysis. RESULTS: While gender had no influence on the clinical motor symptoms and outcome, tremor dominant type had a significantly better outcome than akinetic forms (p = 0.022), even after adjustment with age at onset and associated AD pathology (CERAD and Braak criteria). Patients with late onset showed significantly shorter duration of illness irrespective of dementia. Moderate to severe dementia, reported in 33% of the sample, was significantly correlated with AD pathology (all 3 criteria) that showed significantly negative correlation with survival: between CERAD 0-A vs. B and C there was a significant difference of odd ratios (p < 0.001), as was between Braak stages 0-2, 3-4.5, and 5, but not between Braak stages 3-4 and 5. CONCLUSIONS: The present data confirm previous studies suggesting better outcome of tremor-dominant than akinetic-rigid type of PD, significantly worse outcome in PD with late onset and dementia that is significantly correlated with coexistent neuritic Alzheimer pathology, particularly when using the CERAD and NIA-R criteria for the diagnosis of AD. Further studies are needed to elucidate the relative impact of cortical LB and AD pathologies on the natural history of PD.

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PubMed2005

Alzheimer's disease pathology influences severity and topographical distribution of cerebral amyloid angiopathy.

Cerebral amyloid angiopathy (CAA) is defined by beta-amyloid peptide (Abeta) depositions in cerebral vessels and is associated with Alzheimer's disease (AD). The relationship between sporadic CAA and AD, and the origin of Abeta in CAA are poorly understood. The aim of our study was to investigate the relationship between CAA and AD. Autopsy brains (n=113, 61.1% female, 55.8% clinically demented, age range 54-102 years, mean +/- SE 83.5+/-0.93 years) underwent standardized neuropathological assessment. CAA was evaluated in frontal, frontobasal, hippocampal, and occipital regions. Using immunohistochemistry, the severity of Abeta deposition in vessels was assessed semiquantitatively for each region separately. Evaluation of APOE genotype in 53 cases using real-time PCR showed significant correlations with severe AD pathology and CAA. CAA was present in 77 cases (68.1%), with the occipital region being affected significantly more often and more severely than other regions (P<0.01). Of brains without AD pathology 23.5% revealed CAA, whereas 24% with AD pathology showed no CAA. In concordance with other studies, the severity of both AD pathology and CAA showed a low, but significant correlation. This correlation, however, was only caused by the significant increase of occipital CAA with increasing AD pathology (P<0.01), and was independent of APOE genotype. Our results suggest that progressing AD pathology not only increases the severity of CAA, but also shifts its topographical distribution towards the occipital cortex.

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PubMed2006

Memory complaints are related to Alzheimer disease pathology in older persons.

OBJECTIVE: To study the relationship between Alzheimer disease (AD) pathology and memory complaints proximate to death. METHODS: A group of 90 older persons underwent detailed clinical evaluations and brain autopsy at death. The evaluations included administration of questions on subjective memory complaints and clinical classification of dementia and AD. On postmortem examination, neuritic plaques, diffuse plaques, and neurofibrillary tangles in tissue samples from five cortical regions were counted, and a summary measure of overall AD pathology was derived. In addition, amyloid load and tau tangles were quantified in eight regions. RESULTS: In multiple linear regression models adjusted for age, sex, and education, memory complaints were associated with AD pathology, including both amyloid and tau tangles. Subsequent analyses demonstrated that the relationship between memory complaints and AD pathology was present in those with and without dementia, and could not be explained by the potentially confounding effects of depressive symptoms or coexisting common chronic health problems. CONCLUSION: Memory complaints in older persons may indicate self awareness of a degenerative process.

Age Factors↗

PubMed1999

Rate of memory decline in AD is related to education and occupation: cognitive reserve?

OBJECTIVE: To determine whether the rate of decline in performance on a memory test is more rapid in AD patients with higher versus lower educational and occupational attainment. BACKGROUND: Epidemiologic and imaging studies have suggested that, given comparable clinical severity of dementia, AD pathology is more advanced in patients with higher educational and occupational attainment. Because educational and occupational attainment should not influence the progression of AD pathology, and because severe AD pathology will eventually produce a mortality-causing condition, people with higher attainment might experience clinical AD for a shorter time and have a more rapid clinical progression. METHODS: A total of 177 AD patients were tested yearly for up to four study visits with the Selective Reminding Test (a memory test). Analysis of prospective change in the total recall score was performed by applying generalized estimating equations to regression analyses with repeated measures. RESULTS: At the initial visit, scores were comparable in the high- and low-education and the high- and low-occupation groups. Overall, memory scores declined by approximately 1 point yearly (p<0.01). There was a more rapid decline in memory scores in patients with higher educational (p<0.057) and higher occupational attainment (p<0.02). The authors then stratified patients based on their initial memory scores. The more rapid decline in memory scores associated with higher educational and occupational attainment was noted only in the group with low initial scores (p<0.05 for both). The full group and stratified group analyses were also repeated controlling for other potentially relevant variables including age, gender, race, ethnicity, and the presence of extrapyramidal signs, stroke, or at least one apolipoprotein E-epsilon4 allele. The results remained unchanged. CONCLUSIONS: Memory declined more rapidly in AD patients with higher educational and occupational attainment. This adds support to the idea that the discontinuity between the degree of AD pathology and the observed clinical severity of AD is mediated through some form of reserve.

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PubMed1996

Long-term antipsychotic medication of schizophrenics does not promote the development of Alzheimer's disease brain pathology.

The present autopsy study was performed to examine whether long-term antipsychotic medication of schizophrenics promoted pathologic transition to Alzheimer's disease (AD) of the brain. Immunohistological staining of the hippocampal region with anti-human tau antibody was used to examine the degree of AD pathology in seven schizophrenic patients who had received long-term antipsychotic medication and in seven controls. The schizophrenic patients showed no significant difference from the controls for the number of tau-positive neurons. Additionally, the total amount of antipsychotic drugs for schizophrenic patients was calculated by using of chlorpromazine equivalents. No significant correlation between the total amount of antipsychotic drugs and the degree of AD pathology was observed. The long-term antipsychotic medication of these schizophrenics did not promote the development of AD pathology in the brain.

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PubMed2004

Effect of memantine on the levels of glial cells, neuropeptides, and peptide-degrading enzymes in rat brain regions of ibotenic acid-treated alzheimer's disease model.

It has been implicated that glia activation plays a critical role in the progression of Alzheimer's disease (AD). However, the precise mechanism of glia activation is not clearly understood yet. In our present studies, we confirmed our previous results where change the levels of neuropeptides and peptidases in ibotenic acid (IBO) infusion into the rat nucleus basalis magnocellularis, an animal model of AD. Furthermore, we extended our study to investigate a possible protection effect of co-administration on the changes of neuropeptides, and neuronal and glial cells in IBO-infused rat brain by memantine treatment. The levels of substance P and somatostatin were decreased in the striatum and frontal cortex 1 week after IBO infusion, and recovered to the control level by memantine treatment, indicating the involvement of neuropeptides in AD pathology. Furthermore, the immunohistochemical and enzymatic studies of GFAP and CD 11b, and peptidylarginine deiminase, markers of glia, in the striatum and frontal cortex showed the increase in IBO-treated rat brain as compared with controls, while co-administration of memantine and IBO no increase of astrocytes and microglia activation was observed. The present biochemical and immunohistochemical results suggest that glia activation might play an important role to the pathology of AD, and correlate with the changes of neuropeptide levels in AD brain that is recovered by memantine treatment.

Alzheimer Disease↗

PubMed1990

Alzheimer disease and the dementia of Parkinson disease: comparative investigations.

Intellectual abnormalities are common in Parkinson disease (PD), occurring in a majority of patients and exhibiting a spectrum of severity from mild to severe. Alzheimer disease (AD) has been posited as the cause of dementia in PD. Comparative neuropsychological studies, however, show differences in memory, language, and frontal lobe functions between AD and PD patients even when the two groups have comparably severe dementia syndromes. The AD-type neuropathology occurs in 10-60% of PD patients, and dementia is usually overt when AD pathology is identified at autopsy. The AD changes are less frequent than intellectual deterioration in PD, and dementia has been observed in PD patients without AD pathology. Therefore, concurrent AD cannot be the cause of all cases of dementia in PD. Cholinergic deficits occur in some PD patients, but cholinergic deficits have been described in patients without dementia and dementia has been documented in patients without cholinergic system abnormalities. Dopaminergic disturbances contribute to the dementia of PD. Differences in neuropeptide concentrations, electrophysiologic responses, and cerebral metabolism also support pathophysiologic distinctions between AD and the dementia of PD. Genetic investigations suggest a role for heredity in AD, whereas PD appears to be an acquired, nongenetic disorder. These studies indicate that despite areas of overlap in clinical symptoms and neuropathology, AD and the dementia of PD are largely distinct.

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PubMed2004

Atherosclerosis of cerebral arteries in Alzheimer disease.

A growing body of evidence suggests that vascular disease underlies Alzheimer dementia. Atherosclerotic lesions in the circle of Willis and large leptomeningeal vessels were quantified and found to correlate with Alzheimer disease (AD) clinical diagnosis and neuropathology. We hypothesize that AD pathology is the complex end result of slowly evolving vascular disease and parenchymal lesions. Confirmation of a central role for vascular pathology in AD will suggest important treatment options and directions for additional interventions to stave off this dementia.

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PubMed2003

Proneness to psychological distress is associated with risk of Alzheimer's disease.

BACKGROUND: Chronic stress is associated with hippocampal damage and impaired memory in animals and humans. OBJECTIVE: To examine this relationship with clinical and pathologic data from the Religious Orders Study. METHODS: Older Catholic clergy members underwent annual clinical evaluations, which included clinical classification of Alzheimer's disease (AD) and detailed cognitive function testing from which composite measures of global cognition and specific cognitive functions were derived. At the baseline evaluation, participants completed a measure of the tendency to experience psychological distress, a stable personality trait that served as an indicator of susceptibility to negative emotional states across the life span. More than 90% of participants who died underwent a uniform postmortem examination of the brain from which summary measures of AD pathology were derived. The association of distress proneness with incident AD and cognitive decline and with measures of AD pathology was examined in analyses adjusted for selected demographic and clinical variables. RESULTS: During a mean of 4.9 years of follow-up, 140 persons developed AD. Those high in distress proneness (90th percentile) had twice the risk of developing AD than those low in distress proneness (10th percentile). Distress proneness was related to decline in episodic memory but not in other cognitive domains, with a >10-fold increase in episodic memory decline in those high in distress proneness compared with those low in the trait. Among those who died, however, distress proneness was not related to common measures of AD pathology. CONCLUSION: Proneness to experience psychological distress is a risk factor for AD, an effect independent of AD pathologic markers such as cortical plaques and tangles.

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PubMed2004

Amyloid beta peptide 1-42 highly correlates with capillary cerebral amyloid angiopathy and Alzheimer disease pathology.

Recent studies reported both positive [Thal et al. (2003) J Neuropathol Exp Neurol 62:1287-1301] and negative [Tian et al. (2003) Neurosci Lett 352:137-140] correlations between cerebral amyloid angiopathy (CAA) and Alzheimer's disease (AD) pathology. We have recently shown high correlations between neuritic AD pathology and amyloid beta peptide (Abeta) deposits in the capillary/pericapillary compartment (CapCAA) with only low correlations to general CAA (non-capillary). We have now studied the relationship between CapCAA and AD pathology with respect to the distribution of Abeta40 and 42 in the frontal cortex of 100 human postmortem brains from both male and female, demented and non-demented patients (mean age +/- SD 84.3 +/- 9.3 years). Using polyclonal antibodies to Abeta40 and 42, capillary and plaques positivity were assessed semiquantiatively on a four-point scale. Abeta42 deposits in capillaries correlated highly with both Abeta42 deposits in plaques and morphological AD criteria (CERAD, Braak stages, and NIA-Reagan-Institute criteria), while only a low correlation with CAA was observed. Abeta40 deposits in capillaries differed morphologically from Abeta42 ones: they were limited to capillary walls, were significantly less frequent in both capillaries and plaques compared to Abeta42 ( P < 0.01), and showed a low correlation with morphological AD criteria ( P < 0.05) and general CAA ( P < 0.01). By contrast, Abeta42 deposits were seen in the glia limitans rather than in capillary walls themselves, and showed high correlation with morphological AD criteria ( P < 0.01). These data indicate that CapCAA is characterized by Abeta42 deposits in pericapillary spaces or in the glia limitans. A low correlation between CAA and CapCAA, but high correlations between morphological AD criteria and CapCAA suggest different pathomechanisms for both types of CAA, and a close relation between CapCAA and AD pathology (both neuritic and plaque type). These data support the concept of a neuronal origin of Abeta via drainage from interstitial fluid from the central nervous system along basement membranes to capillaries.

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PubMed2006

Chronic psychological distress and risk of Alzheimer's disease in old age.

Clinical and pathological data from the Rush Memory and Aging Project were used to test the hypothesis that distress proneness is associated with increased risk of Alzheimer's disease (AD). More than 600 older persons without dementia completed a 6-item measure of neuroticism, a stable indicator of proneness to psychological distress. At annual intervals thereafter, they underwent uniform evaluations that included clinical classification of AD and administration of 18 cognitive tests. Those who died underwent brain autopsy from which composite measures of AD pathology were derived. During a mean of about 3 years of follow-up, 55 people were clinically diagnosed with AD. In analyses that controlled for age, sex, and education, persons with a high level of distress proneness (score = 24, 90th percentile) were 2.7 times more likely to develop AD than those not prone to distress (score = 6, 10th percentile). Adjustment for depressive symptomatology or frequency of cognitive, social, and physical activity did not substantially change this effect. Distress proneness was also associated with more rapid cognitive decline. Among 45 participants who died and underwent brain autopsy, distress proneness was unrelated to diverse measures of AD pathology and was inversely related to cognition after controlling for AD pathology. The results support the hypothesis that distress proneness is associated with increased risk of dementia and suggest that neurobiologic mechanisms other than AD pathology may underlie the association.

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PubMed2003

Mitochondria and vascular lesions as a central target for the development of Alzheimer's disease and Alzheimer disease-like pathology in transgenic mice.

Accumulating evidence strongly suggests that the AD brain is characterized by impairments in energy metabolism, and vascular hypoperfusion, whereby oxidative stress appears to be an especially important contributor to neuronal death and development of AD pathology. We hypothesized that mitochondria play a key role in the generation of reactive oxygen species, resulting in oxidative damage to neuronal cell bodies, as well as other cellular compartments in the AD brain. All of these changes have been found to accompany AD pathology. In this review we have outlined recent evidence from the literature and our own original studies concerning the role of mitochondrial abnormalities and vascular damage in the pathogenesis of AD and AD-like pathology in transgenic mice (as a model for human AD). We examined ultrastructural features of vascular lesions and mitochondria from vascular wall cells in human AD brain biopsies, in human short post-mortem brain tissues and in yeast artificial chromosome (YAC) and C57B6/SJL transgenic positive (Tg+) mice overexpressing amyloid beta precursor protein (A beta PP). In situ hybridization using mitochondrial DNA (mtDNA) probes for human wild type, 5kb deleted and mouse mtDNA was performed along with immunocytochemistry using antibodies against amyloid beta precursor protein (A beta PP), 8-hydroxy-2'-guanosine (8OHG) and cytochrome C oxidase (COX) were studied at the electron microscopic levels. There was a higher degree of amyloid deposition in the vascular walls of the human AD, YAC and C57B6/SJL Tg(+) mice compared to aged-matched controls. In addition, vessels with more severe lesions showed immunopositive staining for APP and possessed large, lipid-laden vacuoles in the cytoplasm of endothelial cells (EC). Significantly more mitochondrial abnormalities were seen in human AD, YAC and C57B6/SJL Tg(+) mouse microvessels where lesions occurred. In situ hybridization using wild and chimera (5 kB) mtDNA probes revealed positive signals in damaged mitochondria from the vascular endothelium and in perivascular cells of lesioned microvessels close to regions of large amyloid deposition. These features were absent in undamaged regions of human AD tissues, YAC and C57B6/SJL Tg(+) mouse tissues and in aged-matched control subjects. In addition, vessels with atherosclerotic lesions revealed endothelium and perivascular cells possessing clusters of wild and deleted mtDNA positive probes. These mtDNA deletions were accompanied by increased amounts of immunoreactive APP, 8OHG and COX in the same cellular compartment. Our observations first time demonstrate that vascular wall cells, especially their mitochondria, appear to be a central target for oxidative stress induced damage.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2006

Phosphorylation of actin-depolymerizing factor/cofilin by LIM-kinase mediates amyloid beta-induced degeneration: a potential mechanism of neuronal dystrophy in Alzheimer's disease.

Deposition of fibrillar amyloid beta (fAbeta) plays a critical role in Alzheimer's disease (AD). We have shown recently that fAbeta-induced dystrophy requires the activation of focal adhesion proteins and the formation of aberrant focal adhesion structures, suggesting the activation of a mechanism of maladaptative plasticity in AD. Focal adhesions are actin-based structures that provide a structural link between the extracellular matrix and the cytoskeleton. To gain additional insight in the molecular mechanism of neuronal degeneration in AD, here we explored the involvement of LIM kinase 1 (LIMK1), actin-depolymerizing factor (ADF), and cofilin in Abeta-induced dystrophy. ADF/cofilin are actin-binding proteins that play a central role in actin filament dynamics, and LIMK1 is the kinase that phosphorylates and thereby inhibits ADF/cofilin. Our data indicate that treatment of hippocampal neurons with fAbeta increases the level of Ser3-phosphorylated ADF/cofilin and Thr508-phosphorylated LIMK1 (P-LIMK1), accompanied by a dramatic remodeling of actin filaments, neuritic dystrophy, and neuronal cell death. A synthetic peptide, S3 peptide, which acts as a specific competitor for ADF/cofilin phosphorylation by LIMK1, inhibited fAbeta-induced ADF/cofilin phosphorylation, preventing actin filament remodeling and neuronal degeneration, indicating the involvement of LIMK1 in Abeta-induced neuronal degeneration in vitro. Immunofluorescence analysis of AD brain showed a significant increase in the number of P-LIMK1-positive neurons in areas affected with AD pathology. P-LIMK1-positive neurons also showed early signs of AD pathology, such as intracellular Abeta and pretangle phosphorylated tau. Thus, LIMK1 activation may play a key role in AD pathology.

Actin Depolymerizing Factors↗

PubMed2006

Always around, never the same: pathways of amyloid beta induced neurodegeneration throughout the pathogenic cascade of Alzheimer's disease.

There is an increasing amount of evidence showing the importance of intermediate aggregation species of amyloid beta (Abeta) in the pathogenic cascade of Alzheimer's disease (AD). Different Abeta assembly forms may mediate diverse toxic effects at different stages of the disease. Mouse models for AD suggest that intraneuronal accumulation of Abeta oligomers might be involved in AD pathogenesis at a very early stage of the disease. The detrimental effect of oligomeric Abeta on synaptic efficacy is suggested to be an early event in the pathogenic cascade. Also early neuronal responses as activation of the unfolded protein response are processes likely to be associated with the increased occurrence of oligomeric or low fibrillar Abeta in AD pathology. In later stages of AD pathology, the fibrillarity of Abeta increases, concomitantly with a neuroinflammatory response, followed by tau related neurofibrillary changes in end stage pathology. We will review recent findings in in vitro cell models, in vivo mouse models, and post mortem AD brain tissue in view of the effects of different Abeta peptide species on neurodegeneration during AD pathogenesis. Insight into the role of different Abeta species during AD pathogenesis is essential for the development of disease modifying drugs and therapeutical strategies.

Alzheimer Disease↗