RESUMEN
The risk of Alzheimer's disease (AD) is strongly determined by genetic factors and recent genome-wide association studies (GWAS) have identified several genes for the disease risk. In addition to the disease risk, age-at-onset (AAO) of AD has also strong genetic component with an estimated heritability of 42%. Identification of AAO genes may help to understand the biological mechanisms that regulate the onset of the disease. Here we report the first GWAS focused on identifying genes for the AAO of AD. We performed a genome-wide meta-analysis on three samples comprising a total of 2222 AD cases. A total of ~2.5 million directly genotyped or imputed single-nucleotide polymorphisms (SNPs) were analyzed in relation to AAO of AD. As expected, the most significant associations were observed in the apolipoprotein E (APOE) region on chromosome 19 where several SNPs surpassed the conservative genome-wide significant threshold (P<5E-08). The most significant SNP outside the APOE region was located in the DCHS2 gene on chromosome 4q31.3 (rs1466662; P=4.95E-07). There were 19 additional significant SNPs in this region at P<1E-04 and the DCHS2 gene is expressed in the cerebral cortex and thus is a potential candidate for affecting AAO in AD. These findings need to be confirmed in additional well-powered samples.
Asunto(s)
Edad de Inicio , Enfermedad de Alzheimer/epidemiología , Enfermedad de Alzheimer/genética , Cadherinas/genética , Estudio de Asociación del Genoma Completo/estadística & datos numéricos , Anciano , Apolipoproteínas E/genética , Femenino , Predisposición Genética a la Enfermedad/genética , Estudio de Asociación del Genoma Completo/métodos , Humanos , Masculino , Polimorfismo de Nucleótido Simple/genética , Población Blanca/genéticaRESUMEN
Studies in three different transgenic mouse models suggest that the amyloid beta-protein contributes to memory loss in Alzheimer disease. Immunization with an amyloid beta-peptide fragment reduces learning and memory impairments in mice, and this approach may eventually be used to prevent and/or treat this disease in people.
Asunto(s)
Enfermedad de Alzheimer/terapia , Péptidos beta-Amiloides/inmunología , Trastornos del Conocimiento/terapia , Ovillos Neurofibrilares , Vacunas/administración & dosificación , Animales , Modelos Animales de Enfermedad , Ratones , Ratones TransgénicosRESUMEN
Substances which have an innervation-like effect on the cholinesterase activity of organ-cultured rat extensor digitorum longus muscles are moved in nerve by axonal transport, are released from nerve by stimulation, and are present in innervated muscle but apparently absent from denervated muscle. Substances which increase the acetylcholine sensitivity of cultured muscles behave similarly.
Asunto(s)
Transporte Axonal , Músculos/inervación , Neuronas/fisiología , Acetilcolina/farmacología , Animales , Colinesterasas/metabolismo , Estimulación Eléctrica , Masculino , Potenciales de la Membrana/efectos de los fármacos , Desnervación Muscular , Músculos/fisiología , RatasRESUMEN
The 4-kilodalton amyloid beta protein (A beta), which forms fibrillar deposits in Alzheimer's disease (AD), is derived from a large protein referred to as the amyloid beta protein precursor (beta APP). Human neuroblastoma (M17) cells transfected with constructs expressing wild-type beta APP or a mutant, beta APP delta NL, recently linked to familial AD were compared. After continuous metabolic labeling for 8 hours, cells expressing beta APP delta NL had five times more of an A beta-bearing, carboxyl terminal, beta APP derivative than cells expressing wild-type beta APP and they released six times more A beta into the medium. Thus this mutant beta APP may cause AD because its processing is altered in a way that releases increased amounts of A beta.
Asunto(s)
Péptidos beta-Amiloides/biosíntesis , Precursor de Proteína beta-Amiloide/genética , Mutagénesis Sitio-Dirigida , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Secuencia de Aminoácidos , Péptidos beta-Amiloides/genética , Precursor de Proteína beta-Amiloide/metabolismo , Secuencia de Bases , Clonación Molecular , Humanos , Datos de Secuencia Molecular , Neuroblastoma , Oligodesoxirribonucleótidos , Reacción en Cadena de la Polimerasa/métodos , Transfección , Células Tumorales CultivadasRESUMEN
The approximately 120-kilodalton amyloid beta protein precursor (beta APP) is processed into a complex set of 8- to 12-kilodalton carboxyl-terminal derivatives that includes potentially amyloidogenic forms with the approximately 4-kilodalton amyloid beta protein (beta AP) at or near their amino terminus. In order to determine if these derivatives are processed in a secretory pathway or by the endosomal-lysosomal system, (i) deletion mutants that produce the normal set of carboxyl-terminal derivatives and shortened secreted derivatives were analyzed and (ii) the effect of inhibitors of endosomal-lysosomal processing was examined. In the secretory pathway, cleavage of the beta APP occurs at a single site within the beta AP to generate one secreted derivative and one nonamyloidogenic carboxyl-terminal fragment, whereas, in the endosomal-lysosomal system, a complex set of carboxyl-terminal derivatives is produced that includes the potentially amyloidogenic forms.
Asunto(s)
Precursor de Proteína beta-Amiloide/metabolismo , Amiloide/biosíntesis , Fragmentos de Péptidos/metabolismo , Cloruro de Amonio/farmacología , Precursor de Proteína beta-Amiloide/genética , Secuencia de Bases , Línea Celular , Endopeptidasas/metabolismo , Humanos , Leupeptinas/farmacología , Lisosomas/metabolismo , Datos de Secuencia Molecular , Mutagénesis , TransfecciónRESUMEN
Normal processing of the amyloid beta protein precursor (beta APP) results in secretion of a soluble 4-kilodalton protein essentially identical to the amyloid beta protein (A beta) that forms insoluble fibrillar deposits in Alzheimer's disease. Human neuroblastoma (M17) cells transfected with constructs expressing wild-type beta APP or the beta APP717 mutants linked to familial Alzheimer's disease were compared by (i) isolation of metabolically labeled 4-kilodalton A beta from conditioned medium, digestion with cyanogen bromide, and analysis of the carboxyl-terminal peptides released, or (ii) analysis of the A beta in conditioned medium with sandwich enzyme-linked immunosorbent assays that discriminate A beta 1-40 from the longer A beta 1-42. Both methods demonstrated that the 4-kilodalton A beta released from wild-type beta APP is primarily but not exclusively A beta 1-40. The beta APP717 mutations, which are located three residues carboxyl to A beta 43, consistently caused a 1.5- to 1.9-fold increase in the percentage of longer A beta generated. Long A beta (for example, A beta 1-42) forms insoluble amyloid fibrils more rapidly than A beta 1-40. Thus, the beta APP717 mutants may cause Alzheimer's disease because they secrete increased amounts of long A beta, thereby fostering amyloid deposition.
Asunto(s)
Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Mutación , Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/química , Precursor de Proteína beta-Amiloide/química , Precursor de Proteína beta-Amiloide/genética , Medios de Cultivo Condicionados , Ensayo de Inmunoadsorción Enzimática , Humanos , Neuroblastoma , Transfección , Células Tumorales CultivadasRESUMEN
In situ hybridization was used to assess total amyloid protein precursor (APP) messenger RNA and the subset of APP mRNA containing the Kunitz protease inhibitor (KPI) insert in 11 Alzheimer's disease (AD) and 7 control brains. In AD, a significant twofold increase was observed in total APP mRNA in nucleus basalis and locus ceruleus neurons but not in hippocampal subicular neurons, neurons of the basis pontis, or occipital cortical neurons. The increase in total APP mRNA in locus ceruleus and nucleus basalis neurons was due exclusively to an increase in APP mRNA lacking the KPI domain. These findings suggest that increased production of APP lacking the KPI domain in nucleus basalis and locus ceruleus neurons may play an important role in the deposition of cerebral amyloid that occurs in AD.
Asunto(s)
Enfermedad de Alzheimer/genética , Amiloide/genética , Regulación de la Expresión Génica , Precursores de Proteínas/genética , ARN Mensajero/genética , Bacteriófago lambda/genética , Encéfalo/metabolismo , Corteza Cerebral/metabolismo , Humanos , Locus Coeruleus/metabolismo , Neuronas/metabolismo , Hibridación de Ácido Nucleico , Regiones Operadoras Genéticas , Plásmidos , ARN/genética , ARN Complementario , ARN Mensajero/metabolismo , Proteínas Represoras/metabolismo , Transcripción Genética , Inhibidores de Tripsina/genéticaRESUMEN
Plasma Abeta42 (amyloid beta42 peptide) is invariably elevated in early-onset familial Alzheimer's disease (AD), and it is also increased in the first-degree relatives of patients with typical late-onset AD (LOAD). To detect LOAD loci that increase Abeta42, we used plasma Abeta42 as a surrogate trait and performed linkage analysis on extended AD pedigrees identified through a LOAD patient with extremely high plasma Abeta. Here, we report linkage to chromosome 10 with a maximal lod score of 3.93 at 81 centimorgans close to D10S1225. Remarkably, linkage to the same region was obtained independently in a genome-wide screen of LOAD sibling pairs. These results provide strong evidence for a novel LOAD locus on chromosome 10 that acts to increase Abeta.
Asunto(s)
Enfermedad de Alzheimer/sangre , Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/sangre , Cromosomas Humanos Par 10/genética , Ligamiento Genético , Fragmentos de Péptidos/sangre , Carácter Cuantitativo Heredable , Adulto , Edad de Inicio , Anciano , Anciano de 80 o más Años , Péptidos beta-Amiloides/genética , Femenino , Marcadores Genéticos , Predisposición Genética a la Enfermedad , Humanos , Escala de Lod , Masculino , Persona de Mediana Edad , Linaje , Fragmentos de Péptidos/genética , FenotipoRESUMEN
We have analyzed alternatively spliced beta amyloid protein precursor (beta APP) mRNAs by using the polymerase chain reaction to amplify beta APP cDNAs produced by reverse transcription. With this approach the three previously characterized beta APP mRNAs (beta APP695, beta APP751, and beta APP770) are readily detected and compared in RNA samples extracted from specimens as small as a single cryostat section. We show that the results obtained with this method are not affected by partial RNA degradation and use it to identify a novel alternatively spliced beta APP714 mRNA that is present at low abundance in each of the many human brain regions, peripheral tissues, and cell lines that we have examined; demonstrate that nonneuronal cells in the adult human brain and meninges produce appreciable beta APP695, beta APP751, and beta APP770 mRNA; and identify changes in beta APP gene expression in the AD brain and meninges that may contribute to amyloid deposition.
Asunto(s)
Enfermedad de Alzheimer/genética , Amiloide/genética , Precursores de Proteínas/genética , ARN Mensajero/genética , Secuencia de Aminoácidos , Precursor de Proteína beta-Amiloide , Secuencia de Bases , Encéfalo/metabolismo , Línea Celular , ADN/genética , Expresión Génica , Humanos , Inmunohistoquímica , Datos de Secuencia Molecular , Neuronas/metabolismo , Reacción en Cadena de la Polimerasa , Empalme del ARN , ARN Mensajero/análisisRESUMEN
Mutations in the presenilin 1 (PS1) and presenilin 2 genes cosegregate with the majority of early-onset familial Alzheimer's disease (FAD) pedigrees. We now document that the Abeta1-42(43)/Abeta1-40 ratio in the conditioned media of independent N2a cell lines expressing three FAD-linked PS1 variants is uniformly elevated relative to cells expressing similar levels of wild-type PS1. Similarly, the Abeta1-42(43)/Abeta1-40 ratio is elevated in the brains of young transgenic animals coexpressing a chimeric amyloid precursor protein (APP) and an FAD-linked PS1 variant compared with brains of transgenic mice expressing APP alone or transgenic mice coexpressing wild-type human PS1 and APP. These studies provide compelling support for the view that one mechanism by which these mutant PS1 cause AD is by increasing the extracellular concentration of Abeta peptides terminating at 42(43), species that foster Abeta deposition.
Asunto(s)
Enfermedad de Alzheimer/genética , Precursor de Proteína beta-Amiloide/genética , Proteínas de la Membrana/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Química Encefálica/genética , Medios de Cultivo Condicionados , Expresión Génica/fisiología , Humanos , Ratones , Ratones Transgénicos , Mutación/fisiología , Neuroblastoma , Presenilina-1 , Proteínas Recombinantes de Fusión/fisiología , Transfección , Células Tumorales Cultivadas/química , Células Tumorales Cultivadas/fisiologíaRESUMEN
Several pathogenic Alzheimer's disease (AD) mutations have been described, all of which cause increased amyloid beta-protein (Abeta) levels. Here we present studies of a pathogenic amyloid precursor protein (APP) mutation, located within the Abeta sequence at codon 693 (E693G), that causes AD in a Swedish family. Carriers of this 'Arctic' mutation showed decreased Abeta42 and Abeta40 levels in plasma. Additionally, low levels of Abeta42 were detected in conditioned media from cells transfected with APPE693G. Fibrillization studies demonstrated no difference in fibrillization rate, but Abeta with the Arctic mutation formed protofibrils at a much higher rate and in larger quantities than wild-type (wt) Abeta. The finding of increased protofibril formation and decreased Abeta plasma levels in the Arctic AD may reflect an alternative pathogenic mechanism for AD involving rapid Abeta protofibril formation leading to accelerated buildup of insoluble Abeta intra- and/or extracellularly.
Asunto(s)
Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/fisiología , Precursor de Proteína beta-Amiloide/genética , Mutación/fisiología , Péptidos beta-Amiloides/sangre , Péptidos beta-Amiloides/química , Línea Celular/metabolismo , Medios de Cultivo/metabolismo , Heterocigoto , Humanos , Persona de Mediana Edad , Linaje , Fragmentos de Péptidos/fisiología , SueciaRESUMEN
We investigated synaptic communication and plasticity in hippocampal slices from mice overexpressing mutated 695-amino-acid human amyloid precursor protein (APP695SWE), which show behavioral and histopathological abnormalities simulating Alzheimer's disease. Although aged APP transgenic mice exhibit normal fast synaptic transmission and short term plasticity, they are severely impaired in in-vitro and in-vivo long-term potentiation (LTP) in both the CA1 and dentate gyrus regions of the hippocampus. The LTP deficit was correlated with impaired performance in a spatial working memory task in aged transgenics. These deficits are accompanied by minimal or no loss of presynaptic or postsynaptic elementary structural elements in the hippocampus, suggesting that impairments in functional synaptic plasticity may underlie some of the cognitive deficits in these mice and, possibly, in Alzheimer's patients.
Asunto(s)
Envejecimiento/fisiología , Envejecimiento/psicología , Precursor de Proteína beta-Amiloide/metabolismo , Aprendizaje/fisiología , Plasticidad Neuronal/fisiología , Sinapsis/fisiología , Precursor de Proteína beta-Amiloide/genética , Animales , Giro Dentado/fisiología , Hipocampo/fisiología , Humanos , Potenciación a Largo Plazo/fisiología , Memoria/fisiología , Ratones , Ratones Transgénicos/genética , Percepción Espacial/fisiologíaRESUMEN
The accumulation of amyloid beta protein (Abeta) in the Tg2576 mouse model of Alzheimer's disease (AD) was evaluated by ELISA, immunoblotting, and immunocytochemistry. Changes in Abeta begin at 6-7 months as SDS-insoluble forms of Abeta42 and Abeta40 that require formic acid for solubilization appear. From 6 to 10 months, these insoluble forms increase exponentially. As insoluble Abeta appears, SDS-soluble Abeta decreases slightly, suggesting that it may be converting to an insoluble form. Our data indicate that it is full-length unmodified Abeta that accumulates initially in Tg2576 brain. SDS-resistant Abeta oligomers and most Abeta species that are N-terminally truncated or modified develop only in older Tg2576 mice, in which they are present at levels far lower than in human AD brain. Between 6 and 10 months, when SDS-insoluble Abeta42 and Abeta40 are easily detected in every animal, histopathology is minimal because only isolated Abeta cores can be identified. By 12 months, diffuse plaques are evident. From 12 to 23 months, diffuse plaques, neuritic plaques with amyloid cores, and biochemically extracted Abeta42 and Abeta40 increase to levels like those observed in AD brains. Coincident with the marked deposition of Abeta in brain, there is a decrease in CSF Abeta and a substantial, highly significant decrease in plasma Abeta. If a similar decline occurs in human plasma, it is possible that measurement of plasma Abeta may be useful as a premorbid biomarker for AD.
Asunto(s)
Envejecimiento/metabolismo , Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Enfermedad de Alzheimer/patología , Péptidos beta-Amiloides/sangre , Péptidos beta-Amiloides/líquido cefalorraquídeo , Precursor de Proteína beta-Amiloide/análisis , Precursor de Proteína beta-Amiloide/sangre , Precursor de Proteína beta-Amiloide/líquido cefalorraquídeo , Animales , Biomarcadores/análisis , Biomarcadores/sangre , Biomarcadores/líquido cefalorraquídeo , Encéfalo/patología , Química Encefálica , Modelos Animales de Enfermedad , Ensayo de Inmunoadsorción Enzimática , Femenino , Formiatos/química , Humanos , Immunoblotting , Inmunohistoquímica , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Especificidad de Órganos , Placa Amiloide/metabolismo , Placa Amiloide/patología , Dodecil Sulfato de Sodio/químicaRESUMEN
Prior to the identification of the various abnormal proteins deposited as fibrillar aggregates in the Alzheimer's disease (AD) brain, there was tremendous controversy over the importance of the various lesions with respect to primacy in the pathology of AD. Nevertheless, based on analogy to systemic amyloidosis, many investigators believed that the amyloid deposits in AD played a causal role and that characterization of these deposits would hold the key to understanding this complex disease. Indeed, in retrospect, it was the initial biochemical purifications of the approximately 4 kDa amyloid beta-peptide (Abeta) from amyloid deposits in the mid 1980s that launched a new era of AD research (Glenner and Wong, Biochem. Biophys. Res. Commun. 122 (1984) 1121-1135; Wong et al., Proc. Natl. Acad Sci. USA 82 (1985) 8729 8732; and Masters et al., Proc. Natl. Acad Sci. USA 82 (1985) 4245-4249). Subsequent studies of the biology of Abeta together with genetic studies of AD have all supported the hypothesis that altered Abeta metabolism leading to aggregation plays a causal role in AD. Although there remains controversy as to whether Abeta deposited as classic amyloid or a smaller, aggregated, form causes AD, the relevance of studying the amyloid deposits has certainly been proven. Despite the significant advances in our understanding of the role of Abeta in AD pathogenesis, many important aspects of Abeta biology remain a mystery. This review will highlight those aspects of Abeta biology that have led to our increased understanding of the pathogenesis of AD as well as areas which warrant additional study.
Asunto(s)
Enfermedad de Alzheimer/etiología , Péptidos beta-Amiloides/análisis , Química Encefálica , Encéfalo/metabolismo , Enfermedad de Alzheimer/diagnóstico , Enfermedad de Alzheimer/terapia , Secuencia de Aminoácidos , Péptidos beta-Amiloides/genética , Péptidos beta-Amiloides/metabolismo , Animales , Biomarcadores/análisis , Línea Celular , Electroforesis en Gel de Poliacrilamida , Ensayo de Inmunoadsorción Enzimática , Humanos , Espectrometría de Masas , Proteínas de la Membrana/análisis , Proteínas de la Membrana/genética , Datos de Secuencia Molecular , Mutación , Fragmentos de Péptidos/análisis , Fragmentos de Péptidos/genética , Presenilina-1 , Presenilina-2 , Isoformas de Proteínas/análisisRESUMEN
Studies demonstrating that accumulation and aggregation of the amyloid beta protein (Abeta) within the brain is likely to cause Alzheimer's disease (AD) have provided the rationale for therapeutic strategies aimed at influencing Abeta production, aggregation and clearance. gamma-secretase catalyzes the final cleavage that releases the Abeta from its precursor; therefore, it is a potential therapeutic target for the treatment of AD. Recent data show that the polytopic membrane proteins presenilin 1 and presenilin 2 are either catalytic components or essential co-factors of a membrane-bound proteolytic complex that possesses gamma-secretase activity. Although recent findings demonstrating that gamma-secretase inhibitors bind directly to presenilins (PSs) further support a catalytic role for PSs in gamma-secretase cleavage, additional studies are still needed to clarify the role of PSs in gamma-secretase cleavage and the use of targeting PSs to reduce Abeta production.
Asunto(s)
Enfermedad de Alzheimer/terapia , Proteínas de la Membrana/metabolismo , Secretasas de la Proteína Precursora del Amiloide , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Ácido Aspártico Endopeptidasas , Catálisis , Endopeptidasas/metabolismo , Humanos , Proteínas de la Membrana/genética , Proteínas de la Membrana/inmunología , Modelos Biológicos , Presenilina-1 , Presenilina-2RESUMEN
Vaccinations with Abeta1-42 have been shown to reduce amyloid burden in transgenic models of Alzheimer's disease (AD). We have further tested the efficacy of Abeta1-42 immunization in the Tg2576 mouse model of AD by immunizing one group of mice with minimal Abeta deposition, one group of mice with modest Abeta deposition, and one group with significant Abeta deposition. The effects of immunization on Abeta deposition were examined using biochemical and immunohistochemical methods. In Tg2576 mice immunized prior to significant amyloid deposition, Abeta1-42 immunization was highly effective. Biochemically extracted Abeta40 and Abeta42 levels were significantly reduced and immunohistochemical plaque load was also reduced. Immunization of mice with modest amounts of pre-existing Abeta deposits selectively reduced Abeta42 without altering Abeta40, although plaque load was reduced. In contrast, in Tg2576 mice with significant pre-existing Abeta loads, Abeta1-42 immunization only minimally decreased Abeta42 levels, whereas no alteration in Abeta40 levels or in plaque load was observed. These results indicate that in Tg2576 mice, Abeta1-42 immunization is more effective at preventing additional Abeta accumulation and does not result in significant clearance of pre-existing Abeta deposits.
Asunto(s)
Enfermedad de Alzheimer/prevención & control , Péptidos beta-Amiloides/inmunología , Precursor de Proteína beta-Amiloide/genética , Amiloidosis/prevención & control , Fragmentos de Péptidos/inmunología , Factores de Edad , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/patología , Amiloidosis/patología , Animales , Encéfalo/patología , Modelos Animales de Enfermedad , Humanos , Inmunización , Ratones , Ratones Transgénicos , Placa Amiloide/patologíaRESUMEN
Because the mechanisms of A beta degradation in normal and Alzheimer's disease brain are poorly understood, we have examined whether various cortical cells are capable of processing this peptide. Rat microglia and astrocytes, as well as the human THP-1 monocyte cell line, degraded A beta 1-42 added to culture medium. In contrast, neither rat cortical neurons or meningeal fibroblasts effectively catabolized this peptide. When A beta fibrils were immobilized as plaque-like deposits on culture dishes, both microglia and THP-1 cells removed the peptide. Astrocytes were incapable of processing the A beta deposits, but these cells released glycosaminoglycase-sensitive molecules that inhibited the subsequent removal of A beta by microglia. This implied that astrocyte-derived proteoglycans associated with the amyloid peptide and slowed its degradation. The addition of purified proteoglycan to A beta that was in medium or focally deposited also resulted in significant inhibition of peptide removal by microglia. These data suggest that A beta can be catabolized by microglia and proteoglycans which co-localize with senile plaques may slow the degradation of A beta within these pathologic bodies.
Asunto(s)
Péptidos beta-Amiloides/metabolismo , Neuroglía/metabolismo , Animales , Astrocitos/citología , Astrocitos/metabolismo , Células Cultivadas , Humanos , Microglía/citología , Microglía/metabolismo , Monocitos/citología , Monocitos/metabolismo , Neuroglía/citología , Proteoglicanos/metabolismo , Ratas , Ratas Sprague-DawleyRESUMEN
Chronic expression of inflammatory cytokines, including interleukin-1beta, tumor necrosis factor alpha, and interleukin-6, by glia may underlie the neurodegenerative events that occur within the brains of patients with Alzheimer's disease (AD). The present study determined whether these markers of inflammation could be observed within the brains of Tg(HuAPP695.K670N/M671L)2576 transgenic mice (Tg2576) that have recently been shown to mimic many features of AD. Interleukin-1beta- and tumor necrosis factor alpha-immunopositive microglia were localized with thioflavine-positive (fibrillar) Abeta deposits. Moreover, interleukin-6 immunoreactive astrocytes surrounded fibrillar Abeta deposits. These findings provide evidence that Tg2576 mice exhibit features of the inflammatory pathology seen in AD and suggest that these mice are a useful animal model for studying the role inflammation may play in this disease.
Asunto(s)
Envejecimiento/patología , Enfermedad de Alzheimer/patología , Interleucina-1/análisis , Neuroglía/patología , Factor de Necrosis Tumoral alfa/análisis , Animales , Biomarcadores , Modelos Animales de Enfermedad , Inmunohistoquímica , Inflamación/patología , Ratones , Ratones TransgénicosRESUMEN
Some forms of familial Alzheimer's disease are caused by mutations in the amyloid beta protein precursor (beta APP), and there is excellent evidence that these mutations foster amyloid deposition by increasing secretion of total amyloid beta protein (A beta) or the highly amyloidogenic A beta 1-42 form. These observations provide a powerful rationale for developing an animal model of AD by generating transgenic mice in which cerebral amyloid deposition is induced by A beta overproduction. To produce substantial A beta in vivo, we generated mice expressing the transgene of signal peptide and 99 residues of carboxyl-terminal fragment (CTF) of beta APP under control of the cytomegalovirus enhancer/chicken beta-actin promoter. The transgenic mRNA was detected in many tissues of these mice, but the levels of transgenic mRNA, CTF, and A beta did not correlate well indicating that tissue-specific posttranslational processing may play an important role in determining the amount of A beta that accumulates in various tissues. A beta was detected biochemically in brain, kidney, and pancreas with the largest amount present in pancreas. In transgenic plasma, there was a marked accumulation of human A beta 1-40 and A beta 1-42(43) to levels over 30-times those observed in normal human plasma. Thus, the transgenic mice produce and secrete considerable A beta. Despite this increase in A beta secretion and the elevated A beta in brain, immunohistochemistry revealed no consistent cerebral A beta deposition. In pancreas, however, intracellular A beta deposits were detected immunohistochemically in acinar cells and interstitial macrophages, some of which showed severe degeneration. In addition, examination of these cells by immunoelectron microscopy revealed many putative amyloid fibrils (7-12 nm) that were stained by anti-A beta antibodies. Overall, our findings indicate that tissue-specific posttranslational processing may play a pivotal role in A beta production and amyloid fibril formation in vivo. By carefully analyzing the changes that occur in the transgenic mice described here as compared to the transgenic line that has recently been shown to form extracellular amyloid plaques in brain, it may be possible to gain considerable insight into the factors that determine the location and amount of A beta that accumulates as amyloid.
Asunto(s)
Péptidos beta-Amiloides/metabolismo , Neurofibrillas/metabolismo , Páncreas/metabolismo , Péptidos beta-Amiloides/genética , Animales , Secuencia de Bases , Northern Blotting , Western Blotting , Citomegalovirus/genética , Ensayo de Inmunoadsorción Enzimática , Humanos , Inmunohistoquímica , Ratones , Ratones Transgénicos , Microscopía Electrónica , Datos de Secuencia Molecular , Neurofibrillas/ultraestructura , Páncreas/ultraestructura , Reacción en Cadena de la Polimerasa , TransgenesRESUMEN
We isolated and sequenced a soluble approximately 25 kDa amino-terminal derivative of the beta amyloid protein precursor (beta APP) that is readily detected in human cerebrospinal fluid (CSF). In CSF samples from 24 Alzheimer's disease (AD) patients and 12 controls, we then quantitated this approximately 25 kDa form as well as the approximately 125 and approximately 105 kDa derivatives that we previously identified. Our analysis shows (1) that, in AD, there is a significant decrease in the relative amount of the approximately 105 kDa form and a corresponding significant increase in the relative amount of the approximately 25 kDa form; (2) that these changes correlate with the mental status of the AD patients; and (3) that the same changes occur to a lesser extent in elderly as compared with young control patients. These observations indicate that processing of the beta APP changes in normal individuals as they age and to a greater extent in those who develop AD. The changes in beta APP derivatives that we have observed in CSF could have major implications because they may reflect fundamental mechanisms responsible for amyloid deposition and can be measured in living patients.