RESUMO
INTRODUCTION: Primary age-related tauopathy (PART) is a recently described entity that can cause cognitive impairment in the absence of Alzheimer's disease (AD). Here, we compared neuropathological features, tau haplotypes, apolipoprotein E (APOE) genotypes, and cognitive profiles in age-matched subjects with PART and AD pathology. METHODS: Brain autopsies (n = 183) were conducted on participants 85 years and older from the Baltimore Longitudinal Study of Aging and Johns Hopkins Alzheimer's Disease Research Center. Participants, normal at enrollment, were followed with periodic cognitive evaluations until death. RESULTS: Compared with AD, PART subjects showed significantly slower rates of decline on measures of memory, language, and visuospatial performance. They also showed lower APOE ε4 allele frequency (4.1% vs. 17.6%, P = .0046). DISCUSSION: Our observations suggest that PART is separate from AD and its distinction will be important for the clinical management of patients with cognitive impairment and for public health care planning.
Assuntos
Envelhecimento/patologia , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Disfunção Cognitiva/genética , Neuropatologia , Tauopatias/genética , Idoso de 80 Anos ou mais , Apolipoproteína E4/genética , Autopsia , Baltimore , Encéfalo , Genótipo , Humanos , Estudos Longitudinais , Memória , Testes NeuropsicológicosRESUMO
In addition to motor function, the cerebellum has been implicated in cognitive and social behaviors. Various structural and functional abnormalities of Purkinje cells (PCs) have been observed in schizophrenia and autism. As PCs express the gene Disrupted-In-Schizophrenia-1 (DISC1), and DISC1 variants have been associated with neurodevelopmental disorders, we evaluated the role of DISC1 in cerebellar physiology and associated behaviors using a mouse model of inducible and selective expression of a dominant-negative, C-terminus truncated human DISC1 (mutant DISC1) in PCs. Mutant DISC1 male mice demonstrated impaired social and novel placement recognition. No group differences were found in novelty-induced hyperactivity, elevated plus maze test, spontaneous alternation, spatial recognition in Y maze, sociability or accelerated rotarod. Expression of mutant DISC1 was associated with a decreased number of large somata PCs (volume: 3000-5000µm3) and an increased number of smaller somata PCs (volume: 750-1000µm3) without affecting the total number of PCs or the volume of the cerebellum. Compared to control mice, attached loose patch recordings of PCs in mutant DISC1 mice revealed increased spontaneous firing of PCs; and whole cell recordings showed increased amplitude and frequency of mEPSCs without significant changes in either Rinput or parallel fiber EPSC paired-pulse ratio. Our findings indicate that mutant DISC1 alters the physiology of PCs, possibly leading to abnormal recognition memory in mice.
Assuntos
Disfunção Cognitiva/metabolismo , Potenciais Pós-Sinápticos Excitadores/fisiologia , Locomoção/fisiologia , Proteínas do Tecido Nervoso/biossíntese , Células de Purkinje/metabolismo , Comportamento Social , Animais , Disfunção Cognitiva/genética , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas do Tecido Nervoso/genéticaRESUMO
OBJECTIVE: To test the hypothesis that asymptomatic Alzheimer disease lesions may appear before 50 years of age. BACKGROUND: Alzheimer disease has an asymptomatic stage during which people are cognitively intact despite having substantial pathologic changes in the brain. While this asymptomatic stage is common in older people, how early in life it may develop has been unknown. METHODS: We microscopically examined the postmortem brains of 154 people aged 30 to 39 years (n=59) and 40 to 50 years (n=95) for specific Alzheimer lesions: beta-amyloid plaques, neurofibrillary tangles, and tau-positive neurites. We genotyped DNA samples for the apolipoprotein E gene (APOE). RESULTS: We found beta-amyloid lesions in 13 brains, all of them from people aged 40 to 49 with no history of dementia. These plaques were of the diffuse type only and appeared throughout the neocortex. Among these 13 brains, five had very subtle tau lesions in the entorhinal cortex and/or hippocampus. All individuals with beta-amyloid deposits carried one or two APOE4 alleles. Among the individuals aged 40 to 50 with genotype APOE3/4, 10 (36%) had beta-amyloid deposits but 18 (64%) had none. CONCLUSIONS: Our study demonstrates that beta-amyloid deposits in the cerebral cortex appear as early as 40 years of age in APOE4 carriers, suggesting that these lesions may constitute a very early stage of Alzheimer disease. Future preventive and therapeutic measures for this disease may have to be stratified by risk factors like APOE genotype and may need to target people in their 40s or even earlier.
Assuntos
Doença de Alzheimer/patologia , Encéfalo/patologia , Emaranhados Neurofibrilares/patologia , Placa Amiloide/patologia , Adulto , Doença de Alzheimer/mortalidade , Autopsia , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Huntington's disease (HD) is a devastating genetic neurodegenerative disease caused by CAG trinucleotide expansion in the exon-1 region of the huntingtin gene. Currently, no cure is available. It is becoming increasingly apparent that mutant Huntingtin (HTT) impairs metabolic homeostasis and causes transcriptional dysregulation. The peroxisome proliferator-activated receptor gamma (PPAR-γ) is a transcriptional factor that plays a key role in regulating genes involved in energy metabolism; recent studies demonstrated that PPAR-γ activation prevented mitochondrial depolarization in cells expressing mutant HTT and attenuated neurodegeneration in various models of neurodegenerative diseases. PPAR-γ-coactivator 1α (PGC-1 α) transcription activity is also impaired by mutant HTT. We now report that the PPAR-γ agonist, rosiglitazone (RSG), significantly attenuated mutant HTT-induced toxicity in striatal cells and that the protective effect of RSG is mediated by activation of PPAR-γ. Moreover, chronic administration of RSG (10 mg/kg/day, i.p) significantly improved motor function and attenuated hyperglycemia in N171-82Q HD mice. RSG administration rescued brain derived neurotrophic factor(BDNF) deficiency in the cerebral cortex, and prevented loss of orexin-A-immunopositive neurons in the hypothalamus of N171-82Q HD mice. RSG also prevented PGC-1α reduction and increased Sirt6 protein levels in HD mouse brain. Our results suggest that modifying the PPAR-γ pathway plays a beneficial role in rescuing motor function as well as glucose metabolic abnormalities in HD.
Assuntos
Doença de Huntington/tratamento farmacológico , Neurônios/efeitos dos fármacos , Fármacos Neuroprotetores/uso terapêutico , Tiazolidinedionas/uso terapêutico , Trifosfato de Adenosina/metabolismo , Anilidas/farmacologia , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/enzimologia , Encéfalo/patologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Linhagem Celular , Modelos Animais de Doenças , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/genética , Glutamatos/genética , Humanos , Proteína Huntingtina , Doença de Huntington/complicações , Doença de Huntington/genética , Doença de Huntington/patologia , Hiperglicemia/tratamento farmacológico , Hiperglicemia/etiologia , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , L-Lactato Desidrogenase/metabolismo , Masculino , Camundongos , Camundongos Transgênicos , Transtornos dos Movimentos/tratamento farmacológico , Transtornos dos Movimentos/etiologia , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Neuropeptídeos/metabolismo , Fármacos Neuroprotetores/farmacologia , Orexinas , PPAR gama/antagonistas & inibidores , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , RNA Mensageiro/metabolismo , Rosiglitazona , Sirtuínas/metabolismo , Tiazolidinedionas/farmacologia , Transativadores/genética , Transativadores/metabolismo , Fatores de Transcrição , Transfecção , Expansão das Repetições de Trinucleotídeos/genéticaRESUMO
The definitive Alzheimer's disease (AD) diagnosis requires postmortem confirmation of neuropathological hallmarks-amyloid-ß (Aß) plaques and neurofibrillary tangles (NFTs). The advent of radiotracers for amyloid imaging presents an opportunity to investigate amyloid deposition in vivo. The (11)C-Pittsburgh compound-B (PiB)-PET ligand remains the most widely studied to date; however, regional variations in (11)C-PiB binding and the extent of agreement with neuropathological assessment have not been thoroughly investigated. Sojkova and colleagues [35] reported variable agreement between CERAD-based neuropathologic diagnosis of AD lesions and mean cortical PiB, suggesting the need for a more direct quantification of regional Aß in relation to in vivo imaging. In the present study, we extend these findings by examining the correspondence among regional (11)C-PiB load, region-matched quantitative immunohistological assessments of Aß and NFTs, and brain atrophy (MRI) in six older Baltimore Longitudinal Study of Aging participants who came to autopsy (imaging-autopsy interval range 0.2-2.4 years). The total number of Aß plaques (6E10) and NFTs (PHF1) in paraffin sections from hippocampus, orbito-frontal cortex, anterior and posterior cingulate gyrus, precuneus and cerebellum was quantified using a technique guided by unbiased stereological principles. We report a general agreement between the regional measures of amyloid obtained via stereological assessment and imaging, with significant relationships evident for the anterior (r = 0.83; p = 0.04) and posterior (r = 0.94; p = 0.005) cingulate gyri, and the precuneus (r = 0.94; p = 0.005). No associations were observed between (11)C-PiB load and NFT count for any of the regions examined (p > 0.2 in all regions), or between regional Aß or NFT counts and corresponding brain volumes. The strong associations of PiB retention with region-matched, quantitative analyses of Aß in postmortem tissue offer support for the validity of (11)C-PiB-PET imaging as a method for evaluation of plaque burden in vivo.
Assuntos
Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Emaranhados Neurofibrilares/patologia , Placa Amiloide/patologia , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/diagnóstico por imagem , Doença de Alzheimer/metabolismo , Compostos de Anilina , Autopsia/métodos , Benzotiazóis/metabolismo , Feminino , Humanos , Masculino , Emaranhados Neurofibrilares/diagnóstico por imagem , Emaranhados Neurofibrilares/metabolismo , Neuroimagem/métodos , Placa Amiloide/diagnóstico por imagem , Placa Amiloide/metabolismo , Tomografia por Emissão de Pósitrons , TiazóisRESUMO
Huntington's disease (HD) is characterized clinically by chorea, motor impairment, psychiatric manifestations, and dementia. Atrophy of the striatum is the neuropathological hallmark of HD, and previous studies have suggested that striatal atrophy correlates more closely with motor impairment than with chorea. Motor impairment, as measured by motor impairment score, correlates with functional disability in HD patients, but chorea does not. In this study, we investigated the relation between neuronal loss and these motor features. We conducted neuropathological and stereologic assessments of neurons in putamen and subthalamic nuclei in HD patients and age-matched controls. In putamen, we estimated the total number and volume of medium spiny neurons labeled with dopamine- and cAMP-regulated phosphoprotein 32 kDa (DARPP-32). In subthalamic nuclei, we estimated the total number of neurons on hematoxylin & eosin/luxol fast blue stains. In putamen of HD, immunohistochemistry showed DARPP-32 neuronal atrophy with extensive disruption of neurites and neuropil; stereologic studies found significant decreases in both the number and size of DARPP-32 neurons; we also detected a significant reduction of overall putamen volume in HD patients, compared to controls. In subthalamic nuclei, there was a mild, but significant, neuronal loss in the HD group. The loss of neurons in putamen and subthalamic nuclei as well as putaminal atrophy were significantly correlated with severity of motor impairment, but not with chorea. Our findings suggest that neuronal loss and atrophy in striatum and neuronal loss in subthalamic nuclei contribute specifically to the motor impairment of HD, but not to chorea.
Assuntos
Corpo Estriado/patologia , Doença de Huntington/patologia , Doença de Huntington/fisiopatologia , Atividade Motora/fisiologia , Neurônios/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Análise de Variância , Autopsia , Estudos de Casos e Controles , Morte Celular , Tamanho Celular , Avaliação da Deficiência , Fosfoproteína 32 Regulada por cAMP e Dopamina/metabolismo , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neurônios/metabolismo , Neurônios/fisiologia , Escalas de Graduação Psiquiátrica , Estatística como AssuntoRESUMO
Molecular genetic research provides unprecedented opportunities to examine genotype-phenotype correlations underlying complex syndromes. To investigate pathogenic mutations and genotype-phenotype relationships in diverse neurodegenerative conditions, we performed a rare variant analysis of damaging mutations in autopsy-confirmed neurodegenerative cases from the Johns Hopkins Brain Resource Center (n = 1243 patients). We used NeuroChip genotyping and C9orf72 hexanucleotide repeat analysis to rapidly screen our cohort for disease-causing mutations. In total, we identified 42 individuals who carried a pathogenic mutation in LRRK2, GBA, APP, PSEN1, MAPT, GRN, C9orf72, SETX, SPAST, or CSF1R, and we provide a comprehensive description of the diverse clinicopathological features of these well-characterized cases. Our study highlights the utility of high-throughput genetic screening arrays to establish a molecular diagnosis in individuals with complex neurodegenerative syndromes, to broaden disease phenotypes and to provide insights into unexpected disease associations.
Assuntos
Estudos de Associação Genética , Ensaios de Triagem em Larga Escala/métodos , Mutação , Doenças Neurodegenerativas/diagnóstico , Doenças Neurodegenerativas/genética , Idoso , Idoso de 80 Anos ou mais , Proteína C9orf72/genética , Estudos de Coortes , Expansão das Repetições de DNA , Feminino , Técnicas de Genotipagem , Humanos , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina/genética , Masculino , Pessoa de Meia-Idade , Técnicas de Diagnóstico Molecular/métodosRESUMO
The pathologic changes of Alzheimer disease (AD) evolve very gradually over decades before the disease becomes clinically manifest. Thus, it is not uncommon to find substantial numbers of Abeta plaques and neurofibrillary tangles in autopsy brains of older subjects with documented normal cognition, a state that we define as asymptomatic AD (ASYMAD). The goal of this study is to understand the morphometric substrate of ASYMAD subjects compared with mild cognitive impairment and definite AD cases. We used designed-based stereology to measure the volumes of neuronal cell bodies, nuclei, and nucleoli in 4 cerebral regions: anterior cingulate gyrus, posterior cingulate gyrus, primary visual cortex, and CA1 of hippocampus. We examined and compared autopsy brains from 4 groups (n = 15 each) of participants in the Baltimore Longitudinal Study of Aging: ASYMAD, mild cognitive impairment, AD, and age-matched controls. We found significant hypertrophy of the neuronal cell bodies, nuclei, and nucleoli of CA1 of hippocampus and anterior cingulate gyrus neurons in ASYMAD subjects compared with control and mild cognitive impairment cases. In the posterior cingulate gyrus and primary visual cortex, the hypertrophy was limited to the nuclei and nucleoli. The hypertrophy of cortical neurons and their nuclei and nucleoli in ASYMAD may represent an early reaction to the presence of neurotoxic Abeta or tau, or a compensatory mechanism that prevents the progression of the disease into dementia.
Assuntos
Doença de Alzheimer/patologia , Encéfalo/patologia , Neurônios/patologia , Idoso , Idoso de 80 Anos ou mais , Transtornos Cognitivos/patologia , Humanos , HipertrofiaRESUMO
Sporadic Alzheimer's disease (AD) usually presents clinically after 65 years of age, but its pathological changes begin decades earlier. We examined for AD pathology in the postmortem brains of 431 of subjects aged 30-65 years not clinically characterized. Among 40-49 year olds, 15% showed diffuse amyloid ß (Aß) plaques, with a prevalence of 80% in ApoE4/E4, 42% in E4/E3, and <1% in E3/E3 subjects. Aß deposits appeared after age 49 years in subjects with E3/E3 genotypes. Neuritic plaques first appeared after age 50 years and increased steadily with age in all genotypes. Insoluble Aß42 levels were highest in parietal, temporal, and frontal lobes, but barely detectable in precuneus. Tau lesions were present in the hippocampus and entorhinal cortex in 7% of subjects aged <40 years and increased steadily with age reaching near 70% in the 60- to 65-year age group. In the locus coeruleus, tau lesions were present in 72% of subjects aged 31-40 years and 94% in the 41- to 50-year age group. Both Aß and tau lesions are present in the brains of young individuals decades before the age of clinical onset of AD. Aß lesions closely correlate with the ApoE4 allele and appear as the earliest event in the development of senile plaques.
Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Apolipoproteínas E/genética , Encéfalo/fisiologia , Adulto , Idoso , Doença de Alzheimer/metabolismo , Encéfalo/metabolismo , Feminino , Predisposição Genética para Doença , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Emaranhados Neurofibrilares/patologia , Placa Amiloide/patologia , Proteínas tau/metabolismoRESUMO
Amyloid ß (Aß) plays a critical role in the pathogenesis of Alzheimer's disease. Nevertheless, its distribution and clearance before Aß plaque formation needs to be elucidated. Using an optimized immunofluorescent staining method, we examined the distribution of Aß in the post-mortem parietal cortex of 35 subjects, 30 to 65 years of age, APOE ε3/ε3, without AD lesions. We used 11A1, an antibody against an Aß conformer which forms neurotoxic oligomers. 11A1 immunoreactivity (IR) was present in cortical neurons, pericapillary spaces, astrocytes and the extracellular compartment at 30 years of age. The percentage of neurons with 11A1 IR did not change with age, but the number and percentage of astrocytes with 11A1 IR gradually increased. Notably, the percentage of pericapillary spaces labeled with 11A1 IR declined significantly in the 5th decade of the life, at the same time that 11A1 IR increased in the extracellular space. Our findings indicate that the Aß toxic conformer is normally present in various cell types and brain parenchyma, and appears to be constitutively produced, degraded, and cleared from the inferior parietal cortex. The decrease in pericapillary Aß and the concomitant increase of extracellular Aß may reflect an age-associated impairment in Aß clearance from the brain.
Assuntos
Peptídeos beta-Amiloides/toxicidade , Lobo Parietal/metabolismo , Placa Amiloide/patologia , Adulto , Idoso , Anticorpos/metabolismo , Astrócitos/metabolismo , Feminino , Humanos , Masculino , Microglia/metabolismo , Pessoa de Meia-Idade , Neurônios/metabolismo , Placa Amiloide/metabolismoRESUMO
Alzheimer disease is the most common dementia in older Americans, but its impact on blacks is not clearly understood. We examined prospectively 200 autopsy brains at the Office of the Chief Medical Examiner in Maryland and compared the frequency and severity of Alzheimer lesions in blacks and whites. Histologic sections of the hippocampus and entorhinal and neocortices were immunostained for Abeta and tau proteins. Subjects were genotyped for ApoE. Abeta deposits were rated as none, sparse, moderate, or frequent; tau lesions were rated into 4 groups corresponding to Braak scores; and Abeta angiopathy was classified as present or absent. Outcome scores were treated as ordinal variables and analyzed by proportional odds logistic regression. Abeta plaques were present in 60% of black males, 58% of white males, 74% of black females, and 74% of white females. Tau lesions were present in 96% of black males, 88% of white males, 96% of black females, and 96% of white females. Neither race nor gender was a significant factor in the frequency or severity of Alzheimer lesions, and ApoE4 increased the risk for Alzheimer lesions similarly in blacks and whites.
Assuntos
Doença de Alzheimer/patologia , População Negra/genética , Encéfalo/patologia , Emaranhados Neurofibrilares/patologia , Placa Amiloide/patologia , População Branca/genética , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/epidemiologia , Doença de Alzheimer/genética , Peptídeos beta-Amiloides/metabolismo , Apolipoproteína E4/genética , Encéfalo/fisiopatologia , Córtex Entorrinal/patologia , Córtex Entorrinal/fisiopatologia , Feminino , Predisposição Genética para Doença/genética , Genótipo , Hipocampo/patologia , Hipocampo/fisiopatologia , Humanos , Imuno-Histoquímica , Masculino , Neocórtex/patologia , Neocórtex/fisiopatologia , Prevalência , Distribuição por Sexo , Proteínas tau/metabolismoRESUMO
In order to understand better the neuropathological substrate of dementia in Parkinson's disease (PD) and to examine its interactions with Alzheimer's disease (AD), we examined autopsy brains from 21 cases of PD and Lewy body disease (LBD) with dementia. We separated brains in two groups according to the presence of Abeta deposits. In brains without Abeta, we found few or no Lewy bodies (LB) in the cerebral cortex. By contrast, in brains with Abeta, we observed significant increases in LB in the cerebral cortex (p < 0.01) and alpha-synuclein immunoreactive lesions in the cingulate cortex (p < 0.01). Immunoblots of alpha-synuclein from cingulate cortex in brains with Abeta showed significantly higher levels of insoluble alpha-synuclein compared to brains without Abeta. Our observations indicate that in cases of PD with dementia, the neocortex is not necessarily involved by LB. Furthermore, the presence of Abeta deposits in the cerebral cortex was associated with extensive alpha-synuclein lesions and higher levels of insoluble alpha-synuclein. This suggests that Abeta enhances the development of cortical alpha-synuclein lesions in cases of PD.
Assuntos
Doença de Alzheimer/metabolismo , Córtex Cerebral/metabolismo , Doença por Corpos de Lewy/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Doença de Parkinson/metabolismo , Placa Amiloide/metabolismo , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Córtex Cerebral/patologia , Córtex Cerebral/fisiopatologia , Diagnóstico Diferencial , Feminino , Formiatos/química , Humanos , Imuno-Histoquímica/métodos , Corpos de Lewy/metabolismo , Corpos de Lewy/patologia , Doença por Corpos de Lewy/patologia , Doença por Corpos de Lewy/fisiopatologia , Masculino , Pessoa de Meia-Idade , Doença de Parkinson/patologia , Doença de Parkinson/fisiopatologia , Placa Amiloide/patologia , Sinucleínas , alfa-Sinucleína , Proteínas tau/metabolismoRESUMO
Asymptomatic Alzheimer's disease (ASYMAD) subjects are individuals characterized by preserved cognition before death despite substantial AD pathology at autopsy. ASYMAD subjects show comparable levels of AD pathology, i.e. ß-amyloid neuritic plaques (Aß-NP) and tau-neurofibrillary tangles (NFT), to those observed in mild cognitive impairment (MCI) and some definite AD cases. Previous clinicopathologic studies on ASYMAD subjects have shown specific phenomena of hypertrophy in the cell bodies, nuclei, and nucleoli of hippocampal pyramidal neurons and other cerebral areas. Since it is well established that the allele APOε4 is a major genetic risk factor for AD, we examined whether specific alleles of APOE could be associated with the different clinical outcomes between ASYMAD and MCI subjects despite equivalent AD pathology. A total of 523 brains from the Nun Study were screened for this investigation. The results showed higher APOε2 frequency (p < 0.001) in ASYMAD (19.2%) vs. MCI (0%) and vs. AD (4.7%). Furthermore, higher education in ASYMAD vs. MCI and AD (p < 0.05) was found. These novel autopsy-verified findings support the hypothesis of the beneficial effect of APOε2 and education, both which seem to act as contributing factors in delaying or forestalling the clinical manifestations of AD despite consistent levels of AD pathology.
Assuntos
Doença de Alzheimer/patologia , Doença de Alzheimer/psicologia , Apolipoproteína E2/metabolismo , Cognição/fisiologia , Idoso de 80 Anos ou mais , Alelos , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Apolipoproteína E2/genética , Autopsia , Feminino , Humanos , MasculinoRESUMO
In a previous study of hippocampal neurons in aging and AD [Lancet 344 (1994) 769], we demonstrated that the loss of neurons in the CA1 region was disease-specific and not related to aging. In the present study, we examined for loss of hippocampal neurons in preclinical AD, a period during which there are abundant amyloid deposits in the brain but no evidence of cognitive decline. We examined the postmortem brains of 33 subjects from the Baltimore Longitudinal Study of Aging and the Johns Hopkins Alzheimer's Disease Research Center. Using unbiased stereology, we estimated the total number of neurons in the granule cell layer, hilus, CA3-2, CA1, and subiculum of AD (n = 14) preclinical AD (n = 8), and age-matched control subjects (n = 11). The results from the present study confirm our previous finding of significant neuronal losses in the CA1 (48%), hilus (14%), and subiculum (24%) in AD [Lancet 344 (1994) 769]. However, we did not observe a significant loss of neurons in CA1 or any of the other subdivisions of the hippocampus in preclinical AD.
Assuntos
Doença de Alzheimer/patologia , Hipocampo/patologia , Degeneração Neural/patologia , Neurônios/patologia , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/fisiopatologia , Contagem de Células , Morte Celular/fisiologia , Giro Denteado/patologia , Giro Denteado/fisiopatologia , Progressão da Doença , Feminino , Hipocampo/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Degeneração Neural/fisiopatologiaRESUMO
Subpopulations of dopaminergic (DA) neurons within the substantia nigra pars compacta (SNpc) display a differential vulnerability to loss in Parkinson's disease (PD); however, it is not clear why these subsets are preferentially selected in PD-associated neurodegeneration. In rodent SNpc, DA neurons can be divided into two subpopulations based on the expression of aldehyde dehydrogenase 1 (ALDH1A1). Here, we have shown that, in α-synuclein transgenic mice, a murine model of PD-related disease, DA neurodegeneration occurs mainly in a dorsomedial ALDH1A1-negative subpopulation that is also prone to cytotoxic aggregation of α-synuclein. Notably, the topographic ALDH1A1 pattern observed in α-synuclein transgenic mice was conserved in human SNpc. Postmortem evaluation of brains of patients with PD revealed a severe reduction of ALDH1A1 expression and neurodegeneration in the ventral ALDH1A1-positive DA subpopulations. ALDH1A1 expression was also suppressed in α-synuclein transgenic mice. Deletion of Aldh1a1 exacerbated α-synuclein-mediated DA neurodegeneration and α-synuclein aggregation, whereas Aldh1a1-null and control DA neurons were comparably susceptible to 1-methyl-4-phenylpyridinium-, glutamate-, or camptothecin-induced cell death. ALDH1A1 overexpression appeared to preferentially protect against α-synuclein-mediated DA neurodegeneration but did not rescue α-synuclein-induced loss of cortical neurons. Together, our findings suggest that ALDH1A1 protects subpopulations of SNpc DA neurons by preventing the accumulation of dopamine aldehyde intermediates and formation of cytotoxic α-synuclein oligomers.
Assuntos
Aldeído Desidrogenase/metabolismo , Neurônios Dopaminérgicos/metabolismo , Neurônios Dopaminérgicos/patologia , Doença de Parkinson/metabolismo , Doença de Parkinson/patologia , Substância Negra/metabolismo , Substância Negra/patologia , alfa-Sinucleína/metabolismo , Aldeído Desidrogenase/deficiência , Aldeído Desidrogenase/genética , Família Aldeído Desidrogenase 1 , Animais , Modelos Animais de Doenças , Neurônios Dopaminérgicos/classificação , Feminino , Humanos , Masculino , Camundongos , Camundongos Knockout , Camundongos Mutantes , Camundongos Transgênicos , Proteínas Mutantes/química , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Mutação de Sentido Incorreto , Degeneração Neural/genética , Degeneração Neural/metabolismo , Degeneração Neural/patologia , Doença de Parkinson/genética , Multimerização Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Retinal Desidrogenase , alfa-Sinucleína/química , alfa-Sinucleína/genéticaRESUMO
Older adults with intact cognition before death and substantial Alzheimer disease (AD) lesions at autopsy have been termed "asymptomatic AD subjects" (ASYMAD). We previously reported hypertrophy of neuronal cell bodies, nuclei, and nucleoli in the CA1 of the hippocampus (CA1), anterior cingulate gyrus, posterior cingulate gyrus, and primary visual cortex of ASYMAD versus age-matched Control and mild cognitive impairment (MCI) subjects. However, it was unclear whether the neuronal hypertrophy could be attributed to differences in the severity of AD pathology. Here, we performed quantitative analyses of the severity of ß-amyloid (Aß) and phosphorylated tau (tau) loads in the brains of ASYMAD, Control, MCI, and AD subjects (n = 15 per group) from the Baltimore Longitudinal Study of Aging. Tissue sections from CA1, anterior cingulate gyrus, posterior cingulate gyrus, and primary visual cortex were immunostained for Aß and tau; the respective loads were assessed using unbiased stereology by measuring the fractional areas of immunoreactivity for each protein in each region. The ASYMAD and MCI groups did not differ in Aß and tau loads. These data confirm that ASYMAD and MCI subjects have comparable loads of insoluble Aß and tau in regions vulnerable to AD pathology despite divergent cognitive outcomes. These findings imply that cognitive impairment in AD may be caused or modulated by factors other than insoluble forms of Aß and tau.
Assuntos
Doença de Alzheimer , Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Disfunção Cognitiva/patologia , Disfunção Cognitiva/fisiopatologia , Proteínas tau/metabolismo , Idoso de 80 Anos ou mais , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Autopsia , Encéfalo/patologia , Feminino , Humanos , Masculino , Testes Neuropsicológicos , Mudanças Depois da Morte , Técnicas EstereotáxicasRESUMO
Asymptomatic Alzheimer disease (ASYMAD) is characterized by normal cognition despite substantial AD pathology. To identify factors contributing to cognitive resilience, we compared early changes in regional cerebral blood flow (rCBF) in individuals subsequently diagnosed as ASYMAD with changes in cognitively impaired (CI) and normal older participants from the Baltimore Longitudinal Study of Aging. Participants underwent annual positron emission tomography (PET) rCBF measurements beginning 10.0 (SD 3.6) years before death and while cognitively intact. Based on clinical and autopsy information, subjects were grouped as cognitively normal (CN = 7), ASYMAD (n= 6), and CI (=6). Autopsy material was analyzed using CERAD and Braak scores and quantitative stereologic measures of tau and amyloid. ASYMAD and CI groups had similar CERAD and Braak scores, similar amounts of ß-amyloid and tau in middle frontal (MFG), middle temporal (MTG), and inferior parietal (IP) regions, and more ß-amyloid than CN in precuneus, MFG, and IP areas. Voxel-based PET analysis identified similarities and differences in longitudinal rCBF change among groups across a 7.2-year interval. Both ASYMAD and CI groups showed similar longitudinal rCBF declines in precuneus, lingual, and MTG regions relative to CN. The CI also showed greater rCBF decreases in anterior and posterior cingulate, cuneus, and brainstem regions relative to ASYMAD and CN, whereas ASYMAD showed greater relative rCBF increases over time in medial temporal and thalamic regions relative to CI and CN. Our findings provide evidence of early functional alterations that may contribute to cognitive resilience in those who accumulate AD pathology but maintain normal cognition.
RESUMO
The amyloid precursor protein (APP) is the source of beta-amyloid, a pivotal peptide in the pathogenesis of Alzheimer's disease (AD). This study examines the possible effect of APP transgene expression on neuronal size by measuring the volumes of cortical neurons (microm(3)) in transgenic mouse models with familial AD Swedish mutation (APPswe), with or without mutated presenilin1 (PS1dE9), as well as in mice carrying wild-type APP (APPwt). Overexpression of APPswe and APPwt protein, but not of PS1dE9 alone, resulted in a greater percentage of medium-sized neurons and a proportionate decrease in the percentage of small-sized neurons. Our observations indicate that the overexpression of mutant (APPswe) or wild-type APP in transgenic mice is necessary and sufficient for hypertrophy of cortical neurons. This is highly suggestive of a neurotrophic effect and also raises the possibility that the lack of neuronal loss in transgenic mouse models of AD may be attributed to overexpression of APP.
Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Tamanho Celular , Córtex Cerebral/citologia , Neurônios/citologia , Receptores de Superfície Celular/metabolismo , Precursor de Proteína beta-Amiloide/genética , Análise de Variância , Animais , Córtex Cerebral/metabolismo , Feminino , Masculino , Camundongos , Camundongos Transgênicos , Mutação , Neurônios/metabolismo , Presenilina-1/genética , Presenilina-1/metabolismo , Nexinas de Proteases , Receptores de Superfície Celular/genética , Caracteres SexuaisRESUMO
Mutations in alpha-synuclein and Leucine-rich repeat kinase 2 (LRRK2) are linked to autosomal dominant forms of Parkinson's disease (PD). However, little is known about any potential pathophysiological interplay between these two PD-related genes. Here we show in transgenic mice that although overexpression of LRRK2 alone did not cause neurodegeneration, the presence of excess LRRK2 greatly accelerated the progression of neuropathological abnormalities developed in PD-related A53T alpha-synuclein transgenic mice. Moreover, we found that LRRK2 promoted the abnormal aggregation and somatic accumulation of alpha-synuclein in A53T mice, which likely resulted from the impairment of microtubule dynamics, Golgi organization, and the ubiquitin-proteasome pathway. Conversely, genetic ablation of LRRK2 preserved the Golgi structure and suppressed the aggregation and somatic accumulation of alpha-synuclein, and thereby delayed the progression of neuropathology in A53T mice. These findings demonstrate that overexpression of LRRK2 enhances alpha-synuclein-mediated cytotoxicity and suggest inhibition of LRRK2 expression as a potential therapeutic option for ameliorating alpha-synuclein-induced neurodegeneration.