RESUMO
Recent data suggest that intraneuronal accumulation of metabolites of the amyloid-ß-precursor protein (APP) is neurotoxic. We observed that transgenic mice overexpressing in neurons a human APP gene harboring the APPE693Q (Dutch) mutation have intraneuronal lysosomal accumulation of APP carboxylterminal fragments (APP-CTFs) and oligomeric amyloid ß (oAß) but no histological evidence of amyloid deposition. Morphometric quantification using the lysosomal marker protein 2 (LAMP-2) immunolabeling showed higher neuronal lysosomal counts in brain of 12-months-old APPE693Q as compared with age-matched non-transgenic littermates, and western blots showed increased lysosomal proteins including LAMP-2, cathepsin D and LC3. At 24 months of age, these mice also exhibited an accumulation of α-synuclein in the brain, along with increased conversion of LC3-I to LC3-II, an autophagosomal/autolysosomal marker. In addition to lysosomal changes at 12 months of age, these mice developed cholinergic neuronal loss in the basal forebrain, GABAergic neuronal loss in the cortex, hippocampus and basal forebrain and gliosis and microgliosis in the hippocampus. These findings suggest a role for the intraneuronal accumulation of oAß and APP-CTFs and resultant lysosomal pathology at early stages of Alzheimer's disease-related pathology.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Proteína 2 de Membrana Associada ao Lisossomo/metabolismo , Proteínas/metabolismo , Doença de Alzheimer/genética , Precursor de Proteína beta-Amiloide/genética , Animais , Encéfalo/metabolismo , Córtex Cerebral/metabolismo , Modelos Animais de Doenças , Hipocampo/metabolismo , Humanos , Proteína 2 de Membrana Associada ao Lisossomo/genética , Camundongos , Camundongos Transgênicos , Neurônios/metabolismo , Fragmentos de Peptídeos/metabolismo , alfa-Sinucleína/metabolismoRESUMO
The presence of olfactory dysfunction in individuals at higher risk of Alzheimer's disease has significant diagnostic and screening implications for preventive and ameliorative drug trials. Olfactory threshold, discrimination and identification can be reliably recorded in the early stages of neurodegenerative diseases. The current study has examined the ability of various olfactory functions in predicting cognitive decline in a community-dwelling sample. A group of 308 participants, aged 46-86 years old, were recruited for this study. After 3 years of follow-up, participants were divided into cognitively declined and non-declined groups based on their performance on a neuropsychological battery. Assessment of olfactory functions using the Sniffin' Sticks battery indicated that, contrary to previous findings, olfactory discrimination, but not olfactory identification, significantly predicted subsequent cognitive decline (odds ratio = 0.869; P<0.05; 95% confidence interval = 0.764-0.988). The current study findings confirm previously reported associations between olfactory and cognitive functions, and indicate that impairment in olfactory discrimination can predict future cognitive decline. These findings further our current understanding of the association between cognition and olfaction, and support olfactory assessment in screening those at higher risk of dementia.
Assuntos
Doença de Alzheimer/diagnóstico , Discriminação Psicológica , Transtornos do Olfato/diagnóstico , Olfato , Idoso , Idoso de 80 Anos ou mais , Agnosia/diagnóstico , Agnosia/psicologia , Doença de Alzheimer/genética , Doença de Alzheimer/psicologia , Apolipoproteína E4/genética , Apolipoproteínas E/genética , Estudos de Coortes , Progressão da Doença , Feminino , Genótipo , Humanos , Vida Independente/psicologia , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Testes Neuropsicológicos/estatística & dados numéricos , Odorantes , Transtornos do Olfato/psicologia , Valor Preditivo dos Testes , Psicometria , Reconhecimento Psicológico , Limiar SensorialRESUMO
Despite apolipoprotein E's important role in cholesterol transport and metabolism in the brain as well as its influence on Alzheimer's disease, the impact of the human APOE genotype on cholesterol metabolism in brain has not been fully examined. This study was carried out to investigate APOE genotype effects on oxysterols measured. In this study the measurement of cholesterol and several oxysterols in the brains of human APOE epsilon2, epsilon3 and epsilon4 knock-in mice at 8 weeks and 1 year of age using gas chromatography mass spectrometry (GC-MS) demonstrated no APOE genotype or age effect on total brain cholesterol and the oxysterol 24-hydroxycholesterol. The level of 27-hydroxycholesterol was elevated in 1 year old animals for all APOE genotypes. Interestingly, lathosterol an indicator of cholesterol synthesis was significantly reduced in the 1 year old animals for all APOE genotypes. APOE epsilon4 expressing mice exhibited statistically lower levels of lathosterol compared to APOE epsilon2 in both the young and old mice. Oxidized cholesterol metabolites were significantly lower in APOE epsilon2 mice compared to other genotypes at 8 weeks old. Although minimal differences were observed between APOE E3 and E4 knock-in (KI) mice, these findings indicate that there are some clear APOE genotype specific effects on brain cholesterol synthesis and associated metabolic pathways, particularly in APOE epsilon2 KI mice.
Assuntos
Envelhecimento/metabolismo , Apolipoproteína E2/fisiologia , Apolipoproteína E3/fisiologia , Apolipoproteína E4/fisiologia , Química Encefálica , Colesterol/metabolismo , Hidroxicolesteróis/metabolismo , Animais , Apolipoproteína E2/genética , Apolipoproteína E3/genética , Apolipoproteína E4/genética , Cromatografia Gasosa-Espectrometria de Massas , Técnicas de Introdução de Genes , Genótipo , Humanos , Cetocolesteróis/metabolismo , Masculino , Camundongos , Oxirredução , Especificidade da EspécieRESUMO
High fat diets and sedentary lifestyles are becoming major concerns for Western countries. They have led to a growing incidence of obesity, dyslipidemia, high blood pressure, and a condition known as the insulin-resistance syndrome or metabolic syndrome. These health conditions are well known to develop along with, or be precursors to atherosclerosis, cardiovascular disease, and diabetes. Recent studies have found that most of these disorders can also be linked to an increased risk of Alzheimer's disease (AD). To complicate matters, possession of one or more apolipoprotein E epsilon4 (APOE epsilon4) alleles further increases the risk or severity of many of these conditions, including AD. ApoE has roles in cholesterol metabolism and Abeta clearance, both of which are thought to be significant in AD pathogenesis. The apparent inadequacies of ApoE epsilon4 in these roles may explain the increased risk of AD in subjects carrying one or more APOE epsilon4 alleles. This review describes some of the physiological and biochemical changes that the above conditions cause, and how they are related to the risk of AD. A diversity of topics is covered, including cholesterol metabolism, glucose regulation, diabetes, insulin, ApoE function, amyloid precursor protein metabolism, and in particular their relevance to AD. It can be seen that abnormal lipid, cholesterol and glucose metabolism are consistently indicated as central in the pathophysiology, and possibly the pathogenesis of AD. As diagnosis of mild cognitive impairment and early AD are becoming more reliable, and as evidence is accumulating that health conditions such as diabetes, obesity, and coronary artery disease are risk factors for AD, appropriate changes to diets and lifestyles will likely reduce AD risk, and also improve the prognosis for people already suffering from such conditions.
Assuntos
Doença de Alzheimer/epidemiologia , Apolipoproteínas E/metabolismo , Doenças Cardiovasculares/epidemiologia , Colesterol/metabolismo , Diabetes Mellitus/epidemiologia , Doença de Alzheimer/metabolismo , Doenças Cardiovasculares/metabolismo , Diabetes Mellitus/metabolismo , Humanos , Fatores de RiscoRESUMO
The major protein component of the extracellular deposits in Alzheimer's disease (AD) is a 4 kDa peptide termed amyloid-beta (Abeta). This peptide is known to bind apolipoprotein E (apoE), a key mediator of lipoprotein transport, in an isoform specific manner. Whilst these isoform specific effects on apoE are well recognized, the functional significance of this interaction is poorly understood. Here, we investigated the influence of Abeta on apoE-mediated lipoprotein binding to cells using fluorescently tagged lipoprotein-like emulsions. Using this approach, we demonstrate that Abeta enhanced the normally poor binding of apoE2 lipoprotein-like particles to fibroblasts in culture, whilst markedly reducing the binding of apoE3 and apoE4. This suggests that the action of apoE isoforms on cellular lipoprotein or cholesterol metabolism is differentially modulated by Abeta. This also suggests that Abeta may also compromise apoE function in the Alzheimer disease affected brain.
Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Apolipoproteínas E/metabolismo , Apolipoproteína E2 , Apolipoproteína E3 , Apolipoproteína E4 , Sítios de Ligação/fisiologia , Técnicas de Cultura de Células , Linhagem Celular , Dimerização , Fibroblastos/citologia , Fibroblastos/metabolismo , Humanos , Imuno-Histoquímica , Pele/citologiaRESUMO
Neurodegeneration is associated with increased frequency of neurological soft signs (NSS). We designed the present study to investigate the association between NSS and subjective memory complaints, cognitive function and apolipoprotein E genotype in a community-dwelling sample of volunteers participating in an ongoing longitudinal program investigating predictors of cognitive decline. NSS were found to be associated with apolipoprotein E (APOE) epsilon4 genotype (p = 0.015), age (p = 0.012) and poor cognitive performance, as assessed by the Mini Mental State Examination (p = 0.053). There was no significant difference between subjects with and without memory complaints in relation to the frequency of NSS (p = 0.130). The association with age and the APOE epsilon4 genotype suggests that the systematic investigation of NSS may contribute to identify subjects at risk of clinically significant cognitive decline in later life.
Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/fisiopatologia , Apolipoproteínas E/genética , Transtornos Cognitivos/diagnóstico , Adulto , Idoso , Idoso de 80 Anos ou mais , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Testes Neuropsicológicos , Polimorfismo Genético/genéticaRESUMO
There is currently intense controversy regarding the use of hormone replacement therapy (HRT) in postmenopausal women, in relation to its therapeutic efficacy in Alzheimer's disease (AD). It has been suggested that the benefits of HRT may be modified by apolipoprotein E (APOE) genotype (the major genetic risk factor for AD). Here we report the findings of the first study designed to systematically explore the interaction of (a) oestrogen replacement therapy (ERT) and (b) possession of an epsilon4 allele of APOE on specific elements of episodic learning and memory that are commonly used indices of age-related cognitive decline. This data represents a cross-sectional analysis of the interaction of ERT and APOE genotype on learning and memory in a cohort of 181 healthy postmenopausal women [ERT users (n = 101, mean age 65.40 +/- 6.34); ERT non-users (n = 80, mean age 67.03 +/- 6.80)] residing in Perth, Western Australia. The highest level of learning (trials 2-5; P < 0.05) and memory (e.g. total number of items recalled; P < 0.05) performance was observed in women taking ERT who were not carriers of the APOE epsilon4 allele. APOEepsilon4 carriers receiving ERT performed no better on episodic memory testing than APOE epsilon4 carriers who were not receiving ERT. These cognitive differences related to genetic profile, were noted on both recall and recognition (P = 0.005) tests of memory. The findings have significance for evaluating whether and when ERT may be clinically indicated. Specifically, ERT may benefit the cognitive functioning of women not carrying the APOE epsilon4 allele.
Assuntos
Alelos , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/metabolismo , Apolipoproteínas E/metabolismo , Terapia de Reposição de Estrogênios/métodos , Transtornos da Memória/tratamento farmacológico , Idoso , Doença de Alzheimer/complicações , Cognição/efeitos dos fármacos , Estudos Transversais , Estrogênios/administração & dosagem , Estrogênios/farmacologia , Feminino , Genótipo , Humanos , Transtornos da Memória/complicações , Transtornos da Memória/diagnóstico , Testes Neuropsicológicos , Pós-Menopausa , Reconhecimento PsicológicoRESUMO
The apolipoprotein E (APOE, gene; apoE, protein) type 4 isoform is a well-established risk factor for late-onset Alzheimer's disease (AD), and new data suggest that APOE promoter polymorphisms might also modulate AD risk, perhaps by altering transcription of the APOE gene. The current study was undertaken to determine whether the presence of the APOE promoter -491AA genotype (that appears to increase the risk for AD) is associated with an increase in the levels of apoE in brain tissue. Among 40 control and 20 autopsy-confirmed AD brain samples, levels of apoE were increased in the frontal cortex of AD cases (P < 0.001), consistent with the well-recognized up-regulation of APOE expression in reactive astrocytes. Among controls, the -491A allele appeared to impart a gene dose-dependent effect on the levels of apoE in frontal cortex. The levels of apoE in the brains of AD patients with the -491AA genotype were increased as compared to control subjects with the same genotype (P< 0.001). These data support the notion that the -491AA APOE promoter genotype is associated with elevated brain apolipoprotein E levels, suggesting that the risk for AD may be modulated by the apoE protein level as well as by the apoE protein isoform.
Assuntos
Apolipoproteínas E/genética , Apolipoproteínas E/metabolismo , Lobo Frontal/metabolismo , Idade de Início , Idoso , Doença de Alzheimer/epidemiologia , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Feminino , Predisposição Genética para Doença/epidemiologia , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Regiões Promotoras Genéticas/genética , Fatores de RiscoRESUMO
The accurate clinical diagnosis of Alzheimer's disease can only be made with a high degree of certainty in specialized centres. The identification of predictive or diagnostic genetic factors may improve accuracy of disease prediction or diagnosis. One major genetic risk factor, the epsilon4 allele of the apolipoprotein E gene, is universally recognised. We have recently shown that the A allele of the apolipoprotein E, -491A/T promoter polymorphism is also an important risk factor for Alzheimer's disease in an Australian population. We designed the present study to investigate the association between apolipoprotein E genotype, -491A/T polymorphism, plasma apoE levels and the subjective experience of memory decline among 98 subjects and 49 age, gender and education-matched normal controls. An increased frequency of the epsilon4 allele of apolipoprotein E was significantly associated with the 'memory complainers' group (OR = 2.35, P = 0.02) as was the A allele of the -491A/T polymorphism (OR = 2, P = 0.02). Among all subjects, only seven individuals were homozygous for both of these alleles, and six of these seven individuals belonged to the 'memory complainers' group. This sub-group also had relatively elevated plasma apolipoprotein E levels (P < 0.01) and tended to score lower on the Mini-Mental State Examination (MMSE) and Cambridge Cognition Test. These data suggest that the epsilon4 allele of apolipoprotein E and the -491A allele are over-represented among individuals who complain of memory difficulties. Follow-up studies should clarify whether these genotypes and phenotypes are useful in the prediction and/or diagnosis of Alzheimer's disease.
Assuntos
Apolipoproteínas E/genética , Transtornos da Memória/genética , Polimorfismo Genético , Doença de Alzheimer/diagnóstico , Doença de Alzheimer/epidemiologia , Doença de Alzheimer/genética , Apolipoproteína E4 , Predisposição Genética para Doença/epidemiologia , Genótipo , Humanos , Transtornos da Memória/diagnóstico , Transtornos da Memória/epidemiologia , Valor Preditivo dos Testes , Regiões Promotoras Genéticas/genética , Fatores de RiscoRESUMO
Mutations in the presenilin-1 (PS-1) gene on chromosome 14 account for the majority of early-onset familial Alzheimer's disease (FAD) cases. To date, more than 90 mutations have been identified and, while most of these mutations are completely penetrant, the Glu318Gly mutation has been suggested to be partially penetrant. These findings indicate that it may play a similar role to apolipoprotein E (APOE)-epsilon4 by acting as a genetic risk factor for AD. In the current study, a total of 682 subjects were tested to assess the frequency of the Glu318Gly mutation in AD in the Australian population. The Glu318Gly mutation was identified in six sporadic late-onset AD patients, four FAD patients (unrelated) and in nine control subjects. The frequency of this mutation was highest in the familial AD group (8.7%) and lowest in control subjects (2.2%). When the mutation frequencies were compared, we found a statistically significant difference between the latter two groups (Fisher's exact test, P < 0.05). The genotype frequency of the Glu318Gly mutation in all AD cases and controls in the Australian population was 2.8%. This frequency is comparable to that observed for the Dutch population (3.2%), but not for the Finnish population (6.8% and 6.0%) or the Spanish population (5.3%). These findings show that the frequency of the Glu318Gly mutation is increased in FAD patients, suggesting a potential role as a genetic risk factor contributing to the pathogenesis of familial AD.
Assuntos
Doença de Alzheimer/genética , Proteínas de Membrana/genética , Mutação Puntual , Adulto , Idade de Início , Idoso , Doença de Alzheimer/epidemiologia , Austrália , Saúde da Família , Feminino , Predisposição Genética para Doença/epidemiologia , Humanos , Masculino , Pessoa de Meia-Idade , Presenilina-1 , Fatores de RiscoRESUMO
The deposition of beta amyloid is a critical event in the pathogenesis of Alzheimer's disease. This peptide is a metabolite of the amyloid precursor protein. Recent research suggests that there is a correlation between plasma insulin and glucose concentrations and memory performance in Alzheimer's disease sufferers. Additionally, in vitro evidence suggests that both insulin and glucose may affect the metabolism of amyloid precursor protein and therefore the production of beta amyloid--however, to our knowledge no in vivo data have yet been published. We investigated the effect of elevated plasma levels of glucose and insulin on the plasma concentration of amyloid precursor protein in non-Alzheimer's disease subjects. As would be expected following ingestion of a glucose drink, blood insulin and glucose levels significantly increased. Interestingly, however, plasma amyloid precursor protein concentration decreased. Whilst no correlation was observed between insulin or glucose levels and plasma amyloid precursor protein concentration, the decrease in plasma amyloid precursor protein concentration was affected by the apolipoprotein E genotype of the subject. Possession of an epsilon4 allele resulted in a reduced decrease in plasma amyloid precursor protein in response to glucose ingestion when compared to non-epsilon4 subjects. We conclude that glucose ingestion, and the subsequent elevation of plasma levels of glucose and insulin leads to a decrease in plasma amyloid precursor protein concentration. Further studies are required to determine the clinical significance of these physiological changes in plasma amyloid precursor protein and the implications for Alzheimer's disease pathogenesis.
Assuntos
Precursor de Proteína beta-Amiloide/sangue , Glicemia/fisiologia , Insulina/sangue , Administração Oral , Adulto , Alelos , Apolipoproteína E4 , Apolipoproteínas E/genética , Glucose/farmacologia , Humanos , Pessoa de Meia-Idade , Concentração Osmolar , Valores de ReferênciaRESUMO
The epsilon4 allele of apolipoprotein E gene is a major risk factor for Alzheimer's disease. However, the mechanism by which the E4 isoform of apolipoprotein E increases the risk of Alzheimer's disease is poorly understood. To determine whether the isoform-specific effects of apolipoprotein E may be mediated via clearance of bound beta-amyloid, we examined the uptake of beta-amyloid 1-40 into Chinese hamster ovary cells in the presence or absence of the apolipoprotein E isoforms E2, E3 and E4. Apolipoprotein E2 and E3 treatments were associated with higher association of beta-amyloid with cells as compared to treatment with E4. Heparin blocked the association of beta-amyloid with cells, as did an antibody to one of the apolipoprotein E receptors (the low-density lipoprotein receptor-related protein). Thus, the apolipoproteins E2 and E3, but not E4, may play important roles in the clearance of beta-amyloid from the extracellular space via the low-density lipoprotein receptor-related protein.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Apolipoproteínas E/farmacologia , Células CHO/metabolismo , Fragmentos de Peptídeos/metabolismo , Peptídeos beta-Amiloides/antagonistas & inibidores , Peptídeos beta-Amiloides/farmacocinética , Animais , Anticorpos/farmacologia , Apolipoproteína E2 , Apolipoproteína E3 , Apolipoproteína E4 , Cricetinae , Heparina/farmacologia , Fragmentos de Peptídeos/antagonistas & inibidores , Fragmentos de Peptídeos/farmacocinética , Receptores de LDL/imunologiaRESUMO
Recent evidence suggests that a polymorphism in the regulatory region of the apolipoprotein E gene (APOE) is associated with an increased risk for developing Alzheimer's disease (AD) independent of that conveyed by the epsilon4 allele of APOE. Previous work by our group indicated that plasma apolipoprotein E (apoE) levels were elevated in AD, raising the possibility that the -491 genotype might modify AD risk by increasing expression of the APOE gene. In a total of 638 individuals the -491AA genotype was significantly associated with AD (P < 0.005) while the TT genotype was associated with controls (P < 0.005). In 138 individuals the AA genotype showed significantly higher plasma apoE levels, independent of epsilon4 and AD status (P < 0.01) as well as within control and AD groups (P < 0.05). Within the AD group the AA genotype showed increased apoE levels when compared to AA controls (P < 0.0001). These results suggest that the -491 AA genotype is associated with increased plasma apoE levels, providing a potential basis for elucidating how that genotype increases the risk for developing AD.
Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Apolipoproteínas E/sangue , Apolipoproteínas E/genética , Apolipoproteína E4 , DNA/genética , Genótipo , Humanos , Polimorfismo Genético/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Generalized oxidative deficits associated with experimental thiamine deficiency (TD) lead to selective neurodegeneration. In mouse brain, TD produces region-specific breach of the blood-brain barrier (BBB), neuronal loss and an accumulation of amyloid precursor protein (APP) in abnormal neurites. The APP-laden abnormal neurites within the damaged areas of mouse brain aggregate into neuritic clusters which strikingly resemble the neuritic component of Alzheimer amyloid plaques. However, amyloid beta-peptide (Abeta) immunoreactivity has not been demonstrated in these neuritic clusters, possibly because the Abeta region of APP in mice contains three amino acid substitutions as compared with the amino acid sequence of human Abeta. In contrast, the guinea pig nucleic acid sequence is more related to the human sequence and the Abeta region is identical in sequence to that of human APP. Thus, the current studies tested whether the presence of an authentic Abeta fragment of APP (i.e., identical to that of man) might make guinea pigs more vulnerable to the development of Abeta-containing neuritic clusters following TD. During late stages of TD, BBB abnormalities, manifested by immunoglobulin G (IgG) extravasation and increased NADPH diaphorase reactivity in microvessels, occurred in brain areas known to be damaged by TD in mice. However, despite the prolonged thiamine deprivation and the advanced neurological symptoms of guinea pigs, no significant neuronal loss or altered APP/Abeta immunostaining occurred in any brain region. Microglial activation, another early marker of damage in mice, was not evident in thiamine-deficient guinea pig brain. Ferritin immunoreactivity and iron deposition in oligodendrocytes within areas of BBB abnormalities were either slightly enhanced or unchanged as compared to controls. This is the first report of brain abnormalities in the guinea pig model of dietary and pyrithiamine-induced TD. The results demonstrate species differences in the response to TD-induced damage, and further support the role of BBB and nitric oxide in the initial events in TD pathology.
Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Barreira Hematoencefálica/fisiologia , Neuritos/metabolismo , Neurônios/patologia , Deficiência de Tiamina/metabolismo , Deficiência de Tiamina/patologia , Peptídeos beta-Amiloides/metabolismo , Animais , Comportamento Animal/fisiologia , Encéfalo/patologia , Contagem de Células , Ferritinas/metabolismo , Cobaias , Histocitoquímica , Imuno-Histoquímica , Ferro/metabolismo , Masculino , NADPH Desidrogenase/metabolismo , Neurônios/metabolismoRESUMO
We screened 703 Australian subjects for an intronic polymorphism in the presenilin-1 (PS-1) gene. PS-1 intronic allele 1 homozygosity was not associated with individuals with early- or late-onset sporadic Alzheimer's disease (EOAD or LOAD). Carriers for the PS-1 intronic allele 1 were also not associated with significantly increased risk for AD regardless of gender. Our results for the Australian population are consistent with those of recent reports for other populations and do not support the conclusion that the PS-1 intronic polymorphism is associated with AD.
Assuntos
Doença de Alzheimer/genética , Íntrons/genética , Proteínas de Membrana/genética , Polimorfismo Genético , Adulto , Idoso , Idoso de 80 Anos ou mais , Alelos , Apolipoproteína E4 , Apolipoproteínas E/genética , Austrália , DNA/análise , Análise Mutacional de DNA/estatística & dados numéricos , Feminino , Frequência do Gene , Ligação Genética , Testes Genéticos , Genótipo , Humanos , Leucócitos/química , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Presenilina-1RESUMO
Abnormal oxidative processes including a reduction in thiamine-dependent enzymes accompany many neurodegenerative diseases. Thiamine deficiency (TD) models the cellular and molecular mechanisms by which chronic oxidative aberrations associated with thiamine-dependent enzyme deficits cause selective neurodegeneration. The mechanisms underlying selective cell death in TD are unknown. In rodent TD, the earliest region-specific pathological change is breakdown of the blood-brain barrier (BBB). The current studies tested whether nitric oxide and microglia are important in the initial events that couple BBB breakdown to selective neuronal loss. Enhanced expression of endothelial nitric oxide synthase and nicotinamide adenine dinucleotide phosphate diaphorase reactivity in microvessels, as well as the presence of numerous inducible nitric oxide synthase-immunoreactive microglia, accompanied the increases in BBB permeability. Nitric oxide synthase induction appears critical to TD pathology, because immunoreactivity for nitrotyrosine, a specific nitration product of peroxynitrite, also increased in axons of susceptible regions. In addition, TD elevated iron and the antioxidant protein ferritin in microvessels and in activated microglia, suggesting that these cells are responding to an oxidative challenge. All of these changes occurred in selectively vulnerable regions, preceding neuronal death. These findings are consistent with the hypothesis that the free radical-mediated BBB alterations permit entry of iron and extraneuronal proteins that set in motion a cascade of inflammatory responses culminating in selective neuronal loss. Thus, the TD model should help elucidate the relationship between oxidative deficits, BBB abnormalities, the inflammatory response, ferritin and iron elevation, and selective neurodegeneration.
Assuntos
Morte Celular , Microglia/fisiologia , Óxido Nítrico Sintase/metabolismo , Deficiência de Tiamina/fisiopatologia , Animais , Barreira Hematoencefálica , Encéfalo/enzimologia , Encéfalo/patologia , Indução Enzimática , Ferritinas/análise , Histocitoquímica , Técnicas Imunoenzimáticas , Ferro/análise , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microglia/química , Microglia/enzimologia , NADPH Desidrogenase/metabolismo , Estresse Oxidativo , Ratos , Ratos Endogâmicos F344 , Deficiência de Tiamina/patologia , Fatores de Tempo , Tirosina/análogos & derivados , Tirosina/análiseRESUMO
The metabolic pathways governing the turnover of presenilin 1 (PS1) have been incompletely worked out. The PS1 holoprotein has low abundance in many cells and appears to undergo endoproteolytic cleavage near residue 298. We provide evidence that one mechanism by which the PS1 holoprotein is degraded is through the action of the 26S proteasome. We also show that the proteasome does not participate in the endoproteolytic cleavage.
Assuntos
Doença de Alzheimer/metabolismo , Proteínas de Membrana/metabolismo , Peptídeo Hidrolases/metabolismo , Complexo de Endopeptidases do Proteassoma , Animais , Western Blotting , Células CACO-2 , Hipocampo/metabolismo , Humanos , Técnicas In Vitro , Camundongos , NF-kappa B/metabolismo , Presenilina-1 , Ratos , Ratos WistarRESUMO
To assess the influence of age and diet on cerebral pathology in mice lacking apolipoprotein E (apoE), four male apoE knockout mice (epsilon -/-), and five male wild-type (epsilon +/+) littermate controls were placed on a high-fat/high-cholesterol diet for 7 weeks beginning at 17 months of age. All four aged knockout mice developed xanthomatous lesions in the brain consisting mostly of crystalline cholesterol clefts, lipid globules, and foam cells. Smaller xanthomas were confined mainly to the choroid plexus and ventral fornix in the roof of the third ventricle, occasionally extending subpially along the choroidal fissure and into the adjacent parenchyma. More advanced xanthomas disrupted adjoining neural tissue in the fornix, hippocampus, and dorsal diencephalon; in one case, over 60% of one telencephalic hemisphere, including nearly the entire neocortex, was obliterated by the lesion. No xanthomas were observed in aged wild-type controls fed the high-fat/high-cholesterol diet. Brains from 42 additional animals, fed only conventional chow, were examined; 3 of 15 aged (15- to 23-month-old) apoE knockout mice developed small choroidal xanthomas. In contrast, no lesions were observed in five young (2- to 4-month-old) apoE knockout mice or in any wild-type controls between the ages of 2 and 23 months. Our findings indicate that disorders of lipid metabolism can induce significant pathological changes in the central nervous system of aged apoE knockout mice, particularly those on a high-fat/high-cholesterol diet. It may be fruitful to seek potential interactions between genetic factors and diet in modulating the risk of Alzheimer's disease and other neurodegenerative disorders in aged humans.
Assuntos
Envelhecimento/metabolismo , Apolipoproteínas E/deficiência , Encéfalo/metabolismo , Metabolismo dos Lipídeos , Animais , Apolipoproteínas E/genética , Apolipoproteínas E/fisiologia , Encefalopatias/etiologia , Encefalopatias/patologia , Colesterol na Dieta/administração & dosagem , Gorduras na Dieta/administração & dosagem , Feminino , Masculino , Camundongos , Camundongos Knockout/genética , Valores de Referência , Xantomatose/etiologia , Xantomatose/patologiaRESUMO
Presenilin-1 (PS-1) and amyloid precursor protein (APP) have been linked to the pathogenesis of Alzheimer's disease. While APP accumulation is well documented in several models of brain injury, the role of PS-1 levels in neurodegeneration, if any, remains to be elucidated. The current studies examined PS-1 and APP expression in brain following thiamine deficiency (TD), a nutritional model associated with impaired oxidation and selective neurodegeneration. TD did not alter PS-1 immunoreactivity in any region of rodent brain before or after cell loss. In contrast, APP immunoreactivity accumulated in swollen neurites within, or around lesions in rats, or in abnormal clusters in mice. Thus, alterations in APP but not PS-1 levels are involved in TD-induced neurodegeneration.
Assuntos
Precursor de Proteína beta-Amiloide/biossíntese , Encéfalo/metabolismo , Proteínas de Membrana/biossíntese , Deficiência de Tiamina/metabolismo , Precursor de Proteína beta-Amiloide/análise , Animais , Encéfalo/patologia , Modelos Animais de Doenças , Imuno-Histoquímica , Proteínas de Membrana/análise , Camundongos , Camundongos Endogâmicos C57BL , Neuritos/metabolismo , Neuritos/patologia , Presenilina-1 , Ratos , Ratos Endogâmicos F344 , Deficiência de Tiamina/patologiaRESUMO
Amyloid precursor-like proteins (APLPs), APLP1 and APLP2, are members of a gene family which include the Alzheimer beta-amyloid precursor protein (APP). APLP1, APLP2, and APP contain highly homologous amino acid sequences, especially in their cytoplasmic domains, although APLPs lack the beta-amyloid domain derived by proteolytic processing from APP. APP is phosphorylated at three sites in the cytoplasmic domain in cultured cells and adult rat brain [Suzuki et al. (1994) EMBO J. 13, 1114-1122; Oishi, et al. (1997) Mol. Med. 3, 109-121] and at sites in the extracellular domain in cultured cells [Knops et al. (1993) Biochem. Biophys. Res. Commun. 197, 380-385; Hung & Selkoe (1994) EMBO J. 13, 534-542; Walter et al. (1997) J. Biol. Chem. 272, 1896-1903]. We report here that a cytoplasmic domain peptide from APLP1 is phosphorylated in vitro by protein kinase C and that a cytoplasmic domain peptide from APLP2 is phosphorylated in vitro by protein kinase C and cdc2 kinase. APLP2 is phosphorylated by cdc2 kinase at a site homologous to the cdc2 kinase site phosphorylated in APP. Furthermore, phosphorylation of this site occurs in a cell cycle-dependent manner in cultured cells. These findings indicate that in intact cells the phosphorylation of APLP2 appears to be regulated in a similar fashion to that of APP.